WO2023115848A1 - 谐波齿轮装置以及机器人用关节装置 - Google Patents

谐波齿轮装置以及机器人用关节装置 Download PDF

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Publication number
WO2023115848A1
WO2023115848A1 PCT/CN2022/099435 CN2022099435W WO2023115848A1 WO 2023115848 A1 WO2023115848 A1 WO 2023115848A1 CN 2022099435 W CN2022099435 W CN 2022099435W WO 2023115848 A1 WO2023115848 A1 WO 2023115848A1
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Prior art keywords
gear
flexible external
external gear
teeth
wave generator
Prior art date
Application number
PCT/CN2022/099435
Other languages
English (en)
French (fr)
Inventor
王刚
林文捷
峯岸清次
伊佐地毅
郭子铭
Original Assignee
美的集团股份有限公司
广东极亚精机科技有限公司
广东美的制冷设备有限公司
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Priority claimed from JP2021210602A external-priority patent/JP7518811B2/ja
Application filed by 美的集团股份有限公司, 广东极亚精机科技有限公司, 广东美的制冷设备有限公司 filed Critical 美的集团股份有限公司
Priority to CN202280076192.7A priority Critical patent/CN118284757A/zh
Publication of WO2023115848A1 publication Critical patent/WO2023115848A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J17/00—Joints
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H1/00—Toothed gearings for conveying rotary motion
    • F16H1/28—Toothed gearings for conveying rotary motion with gears having orbital motion
    • F16H1/32—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H49/00—Other gearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H57/00—General details of gearing
    • F16H57/04—Features relating to lubrication or cooling or heating

Definitions

  • Embodiments of the present disclosure generally relate to a harmonic gear device and a joint device for a robot, and more specifically, relate to a harmonic gear device and a joint device for a robot including a rigid internal gear, a flexible external gear, and a wave generator.
  • Patent Document 1 discloses that the surface treatment of a flexible external gear in a harmonic gear device (flexural mesh gear device) is carried out by nitriding treatment.
  • the harmonic gear unit has a ring-shaped rigid internal gear, a cup-shaped flexible external gear arranged inside, and an elliptical wave generator embedded in the inside.
  • the flexible external gear includes a cylindrical body and external teeth formed on the outer peripheral surface of the body.
  • the flexible external gear is bent into an ellipse by the action of the wave generator, and the external teeth of the flexible external gear located at both ends of the ellipse in the direction of the major axis mesh with internal teeth formed on the inner peripheral surface of the rigid internal gear.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2001-59153
  • Embodiments of the present disclosure have been made in view of the above-mentioned circumstances, and an object of the present disclosure is to provide a harmonic gear device and a robot joint device that are unlikely to cause a decrease in reliability.
  • a harmonic gear device includes a rigid internal gear, a flexible external gear, and a wave generator.
  • the rigid internal gear is an annular member having internal teeth.
  • the flexible external gear is an annular member having external teeth and arranged inside the rigid internal gear.
  • the wave generator has a non-circular cam driven to rotate about a rotation axis, and a bearing mounted on the outside of the cam. The wave generator is disposed inside the flexible external gear and causes the flexible external gear to bend.
  • the flexible external gear is deformed as the cam rotates, a part of the external teeth meshes with a part of the internal teeth, and the flexible external gear Relative rotation is performed with respect to the rigid internal gear according to the difference in the number of teeth of the flexible external gear and the rigid internal gear.
  • a chemical conversion treatment coating is provided on a target surface constituted by at least one of the outer peripheral surface of the wave generator and the inner peripheral surface of the flexible external gear.
  • a joint device for a robot includes the harmonic gear device, a first member fixed to the rigid internal gear, and a second member fixed to the flexible external gear.
  • FIG. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to Embodiment 1.
  • FIG. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to Embodiment 1.
  • FIG. 1B is an enlarged view of area Z1 of FIG. 1A .
  • FIG. 2A is a schematic view of the above-mentioned harmonic gear device viewed from the input side of the rotary shaft.
  • FIG. 2B is an enlarged view of area Z1 of FIG. 2A .
  • 3A is a schematic exploded perspective view of the harmonic gear device viewed from the output side of the rotary shaft.
  • 3B is a schematic exploded perspective view of the harmonic gear device viewed from the input side of the rotary shaft.
  • FIG. 4 is a cross-sectional view showing a schematic structure of an actuator including the above-mentioned harmonic gear device.
  • FIG. 5 is an enlarged schematic cross-sectional view of a main part of a range corresponding to FIG. 1B .
  • FIG. 6 is a schematic diagram of the inner peripheral surface of the flexible external gear viewed from the bearing side of the harmonic gear device.
  • Fig. 7A is a schematic view showing the surface state of the inner peripheral surface of the flexible external gear and the outer peripheral surface of the wave generator in the section along line A1-A1 in Fig. 6 .
  • FIG. 7B is an enlarged schematic view of the region Z1 in FIG. 7A .
  • 8A is a schematic view showing the surface state of the inner peripheral surface of the flexible external gear and the outer peripheral surface of the wave generator in the cross section of line A2-A2 in FIG. 6 .
  • FIG. 8B is an enlarged schematic diagram of the area Z1 in FIG. 8A .
  • FIG. 9 is a schematic diagram schematically showing changes in the state of the target surface of the above-mentioned harmonic gear device, which is a schematic diagram showing the surface state of the external teeth in the area Z1 of FIG. A schematic diagram of the surface state of an external tooth.
  • FIG. 10 is a conceptual explanatory view for illustrating the operation of the long-axis side and the short-axis side of the tapered surface of the harmonic gear device.
  • Fig. 11 is a cross-sectional view showing an example of a robot using the above-mentioned harmonic gear device.
  • FIG. 12A is a cross-sectional view illustrating a schematic configuration of a harmonic gear device according to a modified example of the first embodiment.
  • FIG. 12B is an enlarged view of the area Z1 of FIG. 12A .
  • 13A is a schematic view showing the surface state of the inner peripheral surface of the flexible external gear and the outer peripheral surface of the wave generator in the section along line A1-A1 of FIG. 6 in the harmonic gear device according to the second embodiment.
  • FIG. 13B is an enlarged schematic view of the region Z1 in FIG. 13A .
  • FIGS. 1A to 5 The drawings referred to in the embodiments of the present disclosure are all schematic drawings, and the size and thickness ratios of the structural elements in the drawings do not necessarily reflect the actual size ratios.
  • the tooth shape, size, and number of teeth of the internal teeth 21 and the external teeth 31 in FIGS. 2A to 3B are only schematically shown for illustration, and are not intended to be limited to the illustrated shapes.
  • the harmonic gear device 1 of the present embodiment is a gear device including a rigid internal gear 2 , a flexible external gear 3 , and a wave generator 4 .
  • an annular flexible external gear 3 is arranged inside an annular rigid internal gear 2
  • a wave generator 4 is arranged inside the flexible external gear 3 .
  • the wave generator 4 partially meshes the external teeth 31 of the flexible external gear 3 with the internal teeth 21 of the rigid internal gear 2 by flexing the flexible external gear 3 into a non-circular shape.
  • the wave generator 4 rotates, the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the rigid internal gear 2, and a flexible force is generated between the two gears (the rigid internal gear 2 and the flexible external gear 3).
  • the external gear 3 rotates relative to the tooth number difference between the flexible external gear 3 and the rigid internal gear 2 .
  • the rigid internal gear 2 is fixed, the flexible external gear 3 rotates with the relative rotation of both gears.
  • a rotational output decelerated at a relatively high reduction ratio according to the difference in the number of teeth of both gears can be obtained from the flexible external gear 3 .
  • the wave generator 4 that flexes the flexible external gear 3 has a non-circular cam 41 and a bearing 42 that are driven to rotate around the input side rotation axis Ax1 (see FIG. 1A ).
  • the bearing 42 is arranged between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the inner ring 422 of the bearing 42 is fixed to the outer peripheral surface 411 of the cam 41 , and the outer ring 421 of the bearing 42 is elastically deformed by being pressed by the cam 41 via a ball-shaped rolling element 423 .
  • the rolling elements 423 roll so that the outer ring 421 can rotate relative to the inner ring 422.
  • the wave generator 4 having the bearing 42 transmits power by meshing the internal teeth 21 and the external teeth 31 while flexing the flexible external gear 3 .
  • the contact portion between the flexible external gear 3 and the wave generator 4 may Fretting wear occurs. If fretting wear occurs, it may cause roughness of the surface, rust caused by wear powder, and damage to the wave generator 4 (bearing 42) caused by the wear powder entering the inside of the wave generator 4, etc., affecting Reliability of the harmonic gear unit 1.
  • the rotation of the wave generator 4 requires excess energy, resulting in a decrease in power transmission efficiency, or by the force applied to the bearing 42. Life shortening due to increased load, etc.
  • the wear powder enters the bearing 42, starting from the indentation formed by the bite of the wear powder between the outer ring 421 or the inner ring 422 and the rolling element 423 of the bearing 42, the outer ring 421, the inner ring 422 and the The surface of any of the rolling elements 423 may be damaged.
  • the harmonic gear device 1 suppresses the occurrence of fretting wear by the following configuration, and makes it less likely to cause a decrease in reliability.
  • the harmonic gear device 1 of the present embodiment includes an annular rigid internal gear 2 having internal teeth 21 , an annular flexible external gear 3 having external teeth 31 , and a wave harmonic gear. generator 4.
  • the flexible external gear 3 is disposed inside the rigid internal gear 2 .
  • the wave generator 4 is disposed inside the flexible external gear 3 and causes the flexible external gear 3 to bend.
  • the wave generator 4 has a non-circular cam 41 driven to rotate around the rotation axis Ax1 , and a bearing 42 attached to the outside of the cam 41 .
  • the flexible external gear 3 is deformed with the rotation of the cam 41, a part of the external teeth 31 meshes with a part of the internal teeth 21, and the flexible external gear 3 follows the shape of the flexible external gear 3.
  • the difference in the number of teeth from the rigid internal gear 2 makes relative rotation with respect to the rigid internal gear 2 .
  • the chemical conversion treatment coating C1 is provided on the target surface S1 constituted by at least one of the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the contact portion of the flexible external gear 3 with the wave generator 4 (bearing 42 ) has a surface state that is easily maintained covered with the lubricant Lb1 (see FIG. 4 ).
  • the lubricant Lb1 is held (soaked) in the chemical conversion treatment coating C1, and the position is easily maintained lubricated. The state covered by agent Lb1.
  • fretting wear is suppressed by preventing "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion of the outer ring 421 and the flexible external gear 3 generation.
  • a relatively soft chemical conversion treatment coating C1 such as a phosphate coating is provided on the outer peripheral surface 424 of the wave generator 4 and/or the inner peripheral surface 301 of the flexible external gear 3, thereby The contact portion between the external gear 3 and the wave generator 4 maintains sufficient lubricant Lb1.
  • the harmonic gear device 1 of the present embodiment As a result, the surface of the contact portion of the flexible external gear 3 with the bearing 42 (the outer ring 421 ) is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. Therefore, in the harmonic gear device 1 of the present embodiment, troubles caused by fretting wear between (the outer ring 421 of) the bearing 42 and the flexible external gear 3 are less likely to occur, and reliability reduction is less likely to occur.
  • the harmonic gear device 1 of the present embodiment is less prone to decrease in reliability especially when used for a long period of time, so that the transmission efficiency of the harmonic gear device 1 is further improved, its life is increased, and its performance is improved. .
  • the chemical conversion treatment coating C1 may be provided on at least one of the outer peripheral surface 424 of (the bearing 42 of) the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the chemical conversion treatment coating C1 provided on the flexible external gear 3 is called
  • the chemical conversion treatment coating C2 (see FIG. 13A ) provided on the wave generator 4 is referred to as the "first chemical conversion treatment coating” and the "second chemical conversion treatment coating”.
  • the chemical conversion treatment coating C1 is provided only on the inner peripheral surface 301 of the flexible external gear 3 among the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the chemical conversion treatment coating C1 includes the “first chemical conversion treatment coating” provided on the target surface S1 constituted by the inner peripheral surface 301 of the flexible external gear 3 .
  • the chemical conversion treatment coating (second chemical conversion treatment coating) on the wave generator 4 side will be described in the second embodiment.
  • the harmonic gear device 1 of the present embodiment constitutes an actuator 100 together with a drive source 101 and an output unit 102 as shown in FIG. 4 .
  • the actuator 100 of this embodiment includes the harmonic gear device 1 , the driving source 101 and the output unit 102 .
  • the drive source 101 rotates the wave generator 4 .
  • the output unit 102 takes out the rotational force of either one of the rigid internal gear 2 and the flexible external gear 3 as an output.
  • the harmonic gear device 1 of the present embodiment constitutes a robot joint device 130 together with a first member 131 and a second member 132 as shown in FIG. 4 .
  • the robot joint device 130 of this embodiment includes the harmonic gear device 1 , the first member 131 and the second member 132 .
  • the first member 131 is fixed to the rigid internal gear 2 .
  • the second member 132 is fixed to the flexible external gear 3 . Accordingly, relative rotation occurs between the flexible external gear 3 and the rigid internal gear 2 in the harmonic gear device 1, so that the first member 131 and the second member 132 in the robot joint device 130 are relatively rotated.
  • annulus refers to a shape such as a circle (ring) that forms a space (region) surrounded on the inside at least when viewed from above, and is not limited to a circular shape (annular shape) that is a perfect circle when viewed from above. ), may also be, for example, an ellipse shape, a polygonal shape, and the like. Also, for example, even if it has a bottom portion 322 like the cup-shaped flexible external gear 3 , as long as the trunk portion 321 is ring-shaped, it is called a “ring-shaped” flexible external gear 3 .
  • the "rigidity” mentioned in the embodiments of the present disclosure refers to the property that an object resists the deformation when an external force is applied to the object and the object is about to be deformed. In other words, a rigid object is difficult to deform even when an external force is applied.
  • the "flexibility” mentioned in the embodiments of the present disclosure refers to the property of an object elastically deforming (flexing) when an external force is applied to the object. In other words, a flexible object is easily deformed elastically when an external force is applied. Therefore, "rigid” and “flexible” are opposite meanings.
  • the "rigidity" of the rigid internal gear 2 and the “flexibility” of the flexible external gear 3 are used in opposite meanings. That is, the “rigidity” of the rigid internal gear 2 means that the rigid internal gear 2 has relatively higher rigidity than at least the flexible external gear 3 , that is, the rigid internal gear 2 is hardly deformed even if an external force is applied thereto. Similarly, the “flexibility” of the flexible external gear 3 means that the flexible external gear 3 has relatively higher flexibility than the rigid internal gear 2 at least, that is, it is easily elastically deformed when an external force is applied.
  • one side of the rotation axis Ax1 (right side in FIG. 1A ) is sometimes referred to as “input side”, and the other side of the rotation axis Ax1 (left side in FIG. 1A ) is sometimes referred to as “input side”.
  • output side That is, in the example of FIG. 1A , the flexible external gear 3 has the opening surface 35 on the "input side” of the rotation axis Ax1.
  • input side and “output side” are merely labels added for explanation, and are not intended to limit the positional relationship between the input and the output when viewed from the harmonic gear device 1 .
  • non-circular shape refers to a shape that is not a perfect circle, including, for example, an elliptical shape and an oblong shape.
  • the non-circular cam 41 of the wave generator 4 has an elliptical shape. That is, in the present embodiment, the wave generator 4 bends the flexible external gear 3 into an elliptical shape.
  • the "elliptical shape” mentioned in the embodiments of the present disclosure refers to the overall shape in which the perfect circle is flattened and the intersection point of the major axis and the minor axis orthogonal to each other is located in the center, and it is not limited to the distance between two fixed points on a plane.
  • the curve formed by the set of points where the sum of the distances is constant is the "ellipse” in mathematics. That is to say, the cam 41 in the present embodiment may be a curved line formed by a collection of points whose distances from two fixed points on a plane are constant as the mathematical "ellipse", or may not be
  • the "ellipse” in mathematics is an ellipse like a long circle.
  • the drawings referred to in the embodiments of the present disclosure are all schematic drawings, and the ratios of the sizes and thicknesses of the structural elements in the drawings do not necessarily reflect the actual size ratios. Therefore, for example, in FIG. 2A , the shape of the cam 41 of the wave generator 4 is a slightly exaggerated elliptical shape, but it is not intended to limit the actual shape of the cam 41 .
  • the “rotational axis” mentioned in the embodiments of the present disclosure refers to an imaginary axis (straight line) that is the center of the rotational motion of the rotating body. That is, the rotation axis Ax1 is a virtual axis without a real body.
  • the wave generator 4 rotates around the rotation axis Ax1.
  • the internal teeth 21 of the rigid internal gear 2 are composed of a set of teeth formed on the inner peripheral surface of the rigid internal gear 2 .
  • the external teeth 31 of the flexible external gear 3 are composed of a set of teeth formed on the outer peripheral surface of the flexible external gear 3 .
  • the “chemical conversion treatment coating” mentioned in the embodiments of the present disclosure is a coating formed by chemical treatment (chemical treatment), which is formed by performing chemical conversion treatment on an object surface to cover the object surface.
  • Chemical conversion treatment is one of the forms of surface treatment, which causes a chemical reaction by causing a treatment agent to act on the surface of a material (especially a metal), thereby imparting corrosion resistance and affinity with paint, etc. Different properties are handled. Therefore, properties different from those of the target surface S1 before the chemical conversion treatment are imparted to the chemical conversion treatment coating C1 .
  • the chemical conversion treatment include electrochemical oxidation or sulfurization, chemical oxidation or reduction, and film formation using oxides or phosphates of aluminum, chromium, or zinc, and the like.
  • the chemical conversion treatment using phosphate for iron when the iron is immersed in the treatment solution, the iron dissolves and the pH of the solution near the iron rises, whereby the metal ions in the solution become insoluble salts and Precipitation, thereby forming a chemical conversion treatment film covering iron.
  • the "parallel” mentioned in the embodiments of the present disclosure refers to the situation that two straight lines on a plane are extended to any position and do not intersect, that is, the angle between the two is strictly 0 degrees (or 180 degrees) Except for the case of , the angle between the two is in a relationship within an error range that converges to a few degrees (for example, less than 10 degrees) relative to 0 degrees.
  • the "orthogonal" mentioned in the embodiments of the present disclosure means that, except for the case where the angle between the two intersects strictly at 90 degrees, the angle between the two is within a few degrees relative to 90 degrees. (for example, less than 10 degrees) degree of error range relationship.
  • FIG. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device 1
  • FIG. 1B is an enlarged view of a region Z1 in FIG. 1A
  • 2A is a schematic view of the harmonic gear device 1 viewed from the input side of the rotation axis Ax1 (the right side of FIG. 1A )
  • FIG. 2B is an enlarged view of a region Z1 in FIG. 2A
  • FIG. 3A is a schematic exploded perspective view of the harmonic gear device 1 viewed from the output side of the rotation axis Ax1 (the left side in FIG. 1A ).
  • 3B is a schematic exploded perspective view of the harmonic gear device 1 viewed from the input side of the rotation axis Ax1.
  • FIG. 4 is a cross-sectional view showing a schematic configuration of the actuator 100 including the harmonic gear device 1 and the robot joint device 130 .
  • the harmonic gear device 1 of this embodiment includes the rigid internal gear 2, the flexible external gear 3, and the wave generator 4 as described above.
  • the materials of the rigid internal gear 2, the flexible external gear 3, and the wave generator 4, which are the structural elements of the harmonic gear device 1 are stainless steel, cast iron, carbon steel for mechanical structure, chrome-molybdenum steel, or phosphor bronze. or metals such as aluminum bronze.
  • the metal mentioned here includes metals subjected to surface treatment such as nitriding treatment.
  • a cup-shaped harmonic gear device is illustrated as an example of the harmonic gear device 1 . That is, the cup-shaped flexible external gear 3 is used in the harmonic gear device 1 of the present embodiment.
  • the wave generator 4 is combined with the flexible external gear 3 so as to be accommodated in the cup-shaped flexible external gear 3 .
  • the harmonic gear unit 1 is used in a state where the rigid internal gear 2 is fixed to the input side case 111 (see FIG. 4 ) and the output side case 112 (see FIG. 4 ). . Accordingly, the flexible external gear 3 relatively rotates with respect to the fixed member (input-side housing 111 and the like) in association with the relative rotation of the rigid internal gear 2 and the flexible external gear 3 .
  • the harmonic gear device 1 when the harmonic gear device 1 is used for the actuator 100, by applying a rotational force as an input to the wave generator 4, the rotation as an output is taken out from the flexible external gear 3. force. That is, the harmonic gear device 1 operates so as to take the rotation of the wave generator 4 as an input rotation and the rotation of the flexible external gear 3 as an output rotation. Accordingly, in the harmonic gear unit 1 , it is possible to obtain an output rotation decelerated at a relatively high reduction ratio relative to the input rotation.
  • the input-side rotational axis Ax1 and the output-side rotational axis Ax2 are located on the same straight line.
  • the rotation axis Ax1 on the input side and the rotation axis Ax2 on the output side are coaxial.
  • the rotation axis Ax1 on the input side is the rotation center of the wave generator 4 to which the input rotation is applied
  • the rotation axis Ax1 on the output side is the rotation center of the flexible external gear 3 which generates the output rotation. That is, in the harmonic gear unit 1 , the output rotation can be coaxially reduced by a relatively high reduction ratio relative to the input rotation.
  • the rigid internal gear 2 is also called a circular spline and is an annular member having internal teeth 21 .
  • the rigid internal gear 2 has an annular shape in which at least the inner peripheral surface is a perfect circle in plan view.
  • the internal teeth 21 are formed on the inner peripheral surface of the annular rigid internal gear 2 along the circumferential direction of the rigid internal gear 2 . All the plurality of teeth constituting the internal teeth 21 have the same shape and are provided at equal intervals over the entire area in the circumferential direction of the inner peripheral surface of the rigid internal gear 2 . That is, the pitch circle of the internal teeth 21 is a perfect circle in plan view.
  • the rigid internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1.
  • the internal teeth 21 are all formed over the entire length of the rigid internal gear 2 in the thickness direction.
  • the tooth lines of the internal teeth 21 are all parallel to the rotation axis Ax1.
  • the rigid internal gear 2 is fixed to the input-side housing 111 (see FIG. 4 ), the output-side housing 112 (see FIG. 4 ), and the like. Therefore, a plurality of fixing holes 22 for fixing are formed in the rigid internal gear 2 (see FIGS. 3A and 3B ).
  • the flexible external gear 3 is also called a flex spline and is an annular member having external teeth 31 .
  • the flexible external gear 3 is a cup-shaped member formed of a relatively thin metal elastic body (metal plate). That is, the flexible external gear 3 has flexibility because its thickness is relatively small (thin).
  • the flexible external gear 3 has a cup-shaped body portion 32 .
  • the main body part 32 has a body part 321 and a bottom part 322 .
  • the body portion 321 has a cylindrical shape in which at least the inner peripheral surface 301 is a perfect circle in plan view in a state where the flexible external gear 3 is not elastically deformed.
  • the central axis of the body part 321 coincides with the rotation axis Ax1.
  • the bottom portion 322 is disposed on one opening surface of the trunk portion 321 and has a disc shape that is a perfect circle in plan view.
  • the bottom portion 322 is arranged on the opening surface on the output side of the rotation axis Ax1 among the pair of opening surfaces of the trunk portion 321 .
  • the body part 32 has a bottomed cylindrical shape, that is, a cup shape that is open to the input side of the rotation axis Ax1 in the whole body part 321 and the bottom part 322 .
  • the opening surface 35 is formed on the end surface on the opposite side to the bottom portion 322 in the direction of the rotation axis Ax1 of the flexible external gear 3 .
  • the flexible external gear 3 has a cylindrical shape having an opening surface 35 on one side in the tooth line direction D1 (here, the input side of the rotation axis Ax1).
  • the body part 321 and the bottom part 322 are integrally formed by one metal member, thereby realizing the seamless body part 32 .
  • the wave generator 4 having a non-circular shape (elliptical shape) is fitted inside the body part 321 with respect to the flexible external gear 3 , and the wave generator 4 is combined.
  • the flexible external gear 3 is elastically deformed into a non-circular shape by receiving an external force from the wave generator 4 in the radial direction (direction perpendicular to the rotation axis Ax1) from the inside toward the outside.
  • the body portion 321 of the flexible external gear 3 is elastically deformed into an elliptical shape. That is, the state where the flexible external gear 3 is not elastically deformed refers to the state where the wave generator 4 is not combined with the flexible external gear 3 .
  • the elastically deformed state of the flexible external gear 3 refers to the state in which the wave generator 4 is combined with the flexible external gear 3 .
  • the wave generator 4 is fitted into an end portion of the inner peripheral surface 301 of the trunk portion 321 on the side opposite to the bottom portion 322 (the input side of the rotation axis Ax1 ).
  • the wave generator 4 is fitted into the end portion on the opening surface 35 side in the direction of the rotation axis Ax1 of the body portion 321 of the flexible external gear 3 . Therefore, in the state where the flexible external gear 3 is elastically deformed, the end portion of the flexible external gear 3 on the opening surface 35 side in the direction of the rotation axis Ax1 is deformed more than the end portion on the bottom 322 side, Becomes a shape closer to an elliptical shape.
  • the inner peripheral surface 301 of the body portion 321 of the flexible external gear 3 includes a portion inclined with respect to the rotation axis Ax1.
  • the tapered surface 302 (see Figure 9).
  • external teeth 31 are formed along the circumferential direction of the body portion 321 at an end portion of at least the side opposite to the bottom portion 322 (input side of the rotation axis Ax1 ) in the outer peripheral surface of the body portion 321 .
  • the external teeth 31 are provided at least at the end portion on the opening surface 35 side in the direction of the rotation axis Ax1 of the body portion 321 of the flexible external gear 3 .
  • All the plurality of teeth constituting the external teeth 31 have the same shape and are provided at equal intervals over the entire area of the outer peripheral surface of the flexible external gear 3 in the circumferential direction. That is, the pitch circles of the external teeth 31 are perfect circles in plan view when the flexible external gear 3 is not elastically deformed.
  • the external teeth 31 are formed only within a constant width from the end edge of the trunk portion 321 on the opening surface 35 side (the input side of the rotation axis Ax1 ). Specifically, the external teeth 31 are formed on the outer peripheral surface of at least the part where the wave generator 4 is fitted in the direction of the rotation axis Ax1 in the trunk part 321 (the end part on the side of the opening surface 35 ). The tooth lines of the external teeth 31 are all parallel to the rotation axis Ax1.
  • the tooth line of any one of the internal teeth 21 of the rigid internal gear 2 and the external teeth 31 of the flexible external gear 3 is parallel to the rotation axis Ax1 . Therefore, in the present embodiment, the "tooth line direction D1" is a direction parallel to the rotation axis Ax1. Moreover, the size of the tooth line direction D1 of the internal teeth 21 is the tooth width of the internal teeth 21. Similarly, the size of the tooth line direction D1 of the external teeth 31 is the tooth width of the external teeth 31. Therefore, the tooth line direction D1 and the tooth width direction mean the same.
  • the rotation of the flexible external gear 3 is taken out as the output rotation. Therefore, the output unit 102 of the actuator 100 is attached to the flexible external gear 3 (see FIG. 4 ).
  • a plurality of mounting holes 33 for mounting a shaft serving as the output unit 102 are formed in the bottom portion 322 of the flexible external gear 3 .
  • a through hole 34 is formed in the central portion of the bottom portion 322 . The periphery of the through hole 34 in the bottom 322 is thicker than other parts of the bottom 322 .
  • the flexible external gear 3 configured in this way is disposed inside the rigid internal gear 2 .
  • the flexible external gear 3 is connected to the rigid internal gear 2 so that only the end portion on the side opposite to the bottom 322 (the input side of the rotation axis Ax1 ) of the outer peripheral surface of the body portion 321 is inserted into the inside of the rigid internal gear 2 .
  • Gear 2 combo That is, the portion (the end portion on the side of the opening surface 35 ) into which the wave generator 4 is fitted in the direction of the rotation axis Ax1 of the body portion 321 of the flexible external gear 3 is inserted inside the rigid internal gear 2 .
  • external teeth 31 are formed on the outer peripheral surface of the flexible external gear 3
  • internal teeth 21 are formed on the inner peripheral surface of the rigid internal gear 2 . Therefore, in a state where the flexible external gear 3 is disposed inside the rigid internal gear 2 , the external teeth 31 and the internal teeth 21 face each other.
  • the number of internal teeth 21 of the rigid internal gear 2 is greater than the number of external teeth 31 of the flexible external gear 3 by 2N (N is a positive integer).
  • N is "1" as an example, and the number of teeth of the flexible external gear 3 (of the external teeth 31 ) is "2" larger than the number of teeth of the rigid internal gear 2 (of the internal teeth 21 ).
  • Such a difference in the number of teeth of the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation relative to the input rotation in the harmonic gear device 1 .
  • the rotation is set so that the center of the outer tooth 31 in the tooth line direction D1 faces the center of the inner tooth 21 in the tooth line direction D1.
  • the dimension (tooth width) of the external teeth 31 in the tooth line direction D1 is larger than the dimension (tooth width) of the internal teeth 21 in the tooth line direction D1. Therefore, in the direction parallel to the rotation axis Ax1 , the internal teeth 21 are accommodated within the range of the tooth line of the external teeth 31 .
  • the external teeth 31 protrude in at least one of the tooth line directions D1 with respect to the internal teeth 21 .
  • the external teeth 31 protrude toward both sides (the input side and the output side of the rotation axis Ax1 ) in the tooth line direction D1 with respect to the internal teeth 21 .
  • the pitch circles of the external teeth 31 that draw a perfect circle are set to be larger than those drawn in the same manner.
  • the pitch circle of the perfect circle internal teeth 21 is one circle smaller. That is, in a state where the flexible external gear 3 is not elastically deformed, the external teeth 31 and the internal teeth 21 are opposed to each other with gaps therebetween and do not mesh with each other.
  • the trunk portion 321 is bent into an elliptical shape (non-circular shape)
  • the The external teeth 31 of the flexible external gear 3 partially mesh with the internal teeth 21 of the rigid internal gear 2 . That is, the body portion 321 (at least the end portion on the opening surface 35 side) of the flexible external gear 3 is elastically deformed into an elliptical shape, thereby, as shown in FIG.
  • the teeth 31 mesh with the internal teeth 21 .
  • the major diameter of the pitch circle of the external teeth 31 that draws an ellipse coincides with the diameter of the pitch circle of the inner teeth 21 that draws a perfect circle
  • the minor diameter of the pitch circle of the outer teeth 31 that draws an ellipse is smaller than that of the inner teeth 21 that draws a perfect circle.
  • the diameter of the pitch circle is small.
  • the wave generator 4 is also called a wave generator (wave generator), and is a component that causes the flexible external gear 3 to flex to cause the external teeth 31 of the flexible external gear 3 to produce wave motion.
  • the wave generator 4 has a non-circular outer peripheral shape, specifically an elliptical shape in plan view.
  • the wave generator 4 has a cam 41 having a non-circular shape (here, an ellipse) and a bearing 42 mounted on the outer periphery of the cam 41 . That is, with respect to the bearing 42 , the cam 41 having a non-circular shape (elliptical shape) is fitted inside the inner ring 422 of the bearing 42 to combine the cam 41 . Accordingly, the bearing 42 is elastically deformed into a non-circular shape by receiving an external force from the cam 41 in the radial direction (direction perpendicular to the rotation axis Ax1 ) from the inner side toward the outer side of the inner ring 422 .
  • the state where the bearing 42 is not elastically deformed refers to the state where the cam 41 is not combined with the bearing 42 .
  • the state where the bearing 42 is elastically deformed refers to the state where the cam 41 is combined with the bearing 42 .
  • the cam 41 is a member having a non-circular shape (here, an elliptical shape) driven to rotate around the rotation axis Ax1 on the input side.
  • the cam 41 has an outer peripheral surface 411 (see FIG. 1B ), and at least the outer peripheral surface 411 is formed of an elliptical metal plate in plan view.
  • the cam 41 has a predetermined thickness in the direction of the rotation axis Ax1 (that is, the tooth line direction D1).
  • the cam 41 has the same level of rigidity as the rigid internal gear 2 .
  • the thickness of the cam 41 is smaller (thinner) than that of the rigid internal gear 2 .
  • the rotation of the wave generator 4 is used as the input rotation. Therefore, the input unit 103 of the actuator 100 is attached to the wave generator 4 (see FIG. 4 ).
  • a cam hole 43 for attaching a shaft serving as the input unit 103 is formed at the center of the cam 41 of the wave generator 4 .
  • the bearing 42 has an outer ring 421 , an inner ring 422 and a plurality of rolling elements 423 .
  • the bearing 42 is constituted by a deep groove ball bearing using spherical balls as the rolling elements 423 .
  • Both the outer ring 421 and the inner ring 422 are annular members. Both the outer ring 421 and the inner ring 422 are annular members formed of a relatively thin metal elastic body (metal plate). That is, the outer ring 421 and the inner ring 422 have flexibility because they are relatively thin (thin). In the present embodiment, both the outer ring 421 and the inner ring 422 have a perfect circular ring shape in plan view when the bearing 42 is not elastically deformed (the cam 41 is not combined with the bearing 42 ). The inner ring 422 is one turn smaller than the outer ring 421 and is disposed inside the outer ring 421 .
  • the inner diameter of the outer ring 421 is larger than the outer diameter of the inner ring 422 , a gap is formed between the inner peripheral surface 425 of the outer ring 421 and the outer peripheral surface of the inner ring 422 .
  • a plurality of rolling elements 423 is disposed in a gap between the outer ring 421 and the inner ring 422 .
  • the plurality of rolling elements 423 are arranged in line in the circumferential direction of the outer ring 421 .
  • All the plurality of rolling elements 423 are metal balls (balls) of the same shape, and are arranged at equal intervals over the entire area of the outer ring 421 in the circumferential direction.
  • the bearing 42 further has a cage, and a plurality of rolling elements 423 are held between the outer ring 421 and the inner ring 422 by the cage, although not shown in particular.
  • the dimension in the width direction (direction parallel to the rotation axis Ax1 ) of the outer ring 421 and the inner ring 422 is the same as the thickness of the cam 41 . That is, the dimension in the width direction of the outer ring 421 and the inner ring 422 is smaller than the thickness of the rigid internal gear 2 .
  • the cam 41 and the bearing 42 are combined, the inner ring 422 of the bearing 42 is fixed to the cam 41 , and the inner ring 422 is elastically deformed into an elliptical shape following the outer peripheral shape of the cam 41 .
  • the outer ring 421 of the bearing 42 is elastically deformed into an elliptical shape by being pressed by the inner ring 422 via the plurality of rolling elements 423 . Therefore, both the outer ring 421 and the inner ring 422 of the bearing 42 are elastically deformed into an elliptical shape. In this way, in the state where the bearing 42 is elastically deformed (the state where the cam 41 is combined with the bearing 42 ), the outer ring 421 and the inner ring 422 form elliptical shapes that are similar to each other.
  • the outer peripheral shape of the wave generator 4 having an ellipse shape rotates around the rotation axis Ax1 as its major axis, following the cam. 41 rotations vary.
  • the wave generator 4 configured in this way is disposed inside the flexible external gear 3 .
  • the flexible external gear 3 is connected to the wave generator 4 in such a manner that only the end portion of the inner peripheral surface 301 of the trunk portion 321 on the side opposite to the bottom 322 (opening surface 35 side) is fitted to the wave generator 4 . combination.
  • the bearing 42 of the wave generator 4 is arranged between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the outer diameter of the outer ring 421 in the state where the bearing 42 is not elastically deformed is the same as the outer diameter of the flexible external gear 3 (the body part 321 ) in the state where the elastic deformation is not generated. ) have the same inner diameter. Therefore, the outer peripheral surface 424 (see FIG. 5 ) of the outer ring 421 in the wave generator 4 is in contact with the inner peripheral surface 301 of the flexible external gear 3 over the entire circumference of the bearing 42 in the circumferential direction.
  • the trunk portion 321 bends into an elliptical shape (non-circular shape).
  • the flexible external gear 3 is fixed to the outer ring 421 of the bearing 42 .
  • the "gap" mentioned in the embodiments of the present disclosure means a space that may be generated between opposing surfaces of two objects, and a gap may be generated between the two objects even if the two objects are not separated. That is, even if two objects are in contact, a gap may be slightly generated between the two objects.
  • a gap is generated between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 , which are opposed to each other. X1.
  • the outer peripheral surface 424 of the outer ring 421 is in contact with the inner peripheral surface 301 of the flexible external gear 3, there is no large gap X1 therebetween.
  • the gap X1 between the outer ring 421 and the flexible external gear 3 is a small gap that can be locally generated between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 .
  • a microscopic gap X1 is formed between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 such that the lubricant Lb1 can penetrate.
  • the harmonic gear device 1 having the above-mentioned structure, as shown in FIG. 2A , by flexing the body part 321 of the flexible external gear 3 into an elliptical shape (non-circular shape), the external teeth 31 of the flexible external gear 3 are relatively The internal teeth 21 of the rigid internal gear 2 are partially meshed. That is, when (the trunk portion 321 of) the flexible external gear 3 is elastically deformed into an elliptical shape, two external teeth 31 corresponding to both ends of the elliptical shape in the long-axis direction mesh with the internal teeth 21 .
  • a wave motion occurs in the external teeth 31 formed on the outer peripheral surface of the flexible external gear 3 .
  • the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the rigid internal gear 2 and generates relative rotation between the flexible external gear 3 and the rigid internal gear 2 . That is, the external teeth 31 mesh with the internal teeth 21 at both ends in the direction of the major axis of the elliptical shape formed by the flexible external gear 3 (the body portion 321 of the flexible external gear 3 ), so that the rotation axis passes through the major axis of the ellipse.
  • Ax1 rotates as a center, the meshing position of the internal teeth 21 and the external teeth 31 moves.
  • the flexible external gear 3 is deformed as the wave generator 4 rotates about the rotation axis Ax1, and a part of the external teeth 31 and a part of the internal teeth 21 are separated. Mesh, and make the flexible external gear 3 rotate according to the tooth number difference between the flexible external gear 3 and the rigid internal gear 2.
  • the difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the harmonic gear device 1 . That is, when the number of teeth of the rigid internal gear 2 is "V1" and the number of teeth of the flexible external gear 3 is "V2", the speed reduction ratio R1 is expressed by the following formula 1.
  • the deceleration The ratio R1 is "35".
  • the cam 41 rotates clockwise around the rotation axis Ax1 once (360 degrees) when viewed from the input side of the rotation axis Ax1
  • the flexible external gear 3 rotates counterclockwise around the rotation axis Ax1.
  • the amount corresponding to the tooth number difference "2" that is, 10.3 degrees).
  • such a high reduction ratio R1 can be realized by combining the first-stage gears (the rigid internal gear 2 and the flexible external gear 3 ).
  • the harmonic gear device 1 only needs to include at least a rigid internal gear 2, a flexible external gear 3, and a wave generator 4, and may further include, for example, the spline described in the column of "(3.2) Actuator".
  • the bushing 113 and the like are used as structural elements.
  • the actuator 100 of the present embodiment includes the harmonic gear device 1 of the present embodiment, a drive source 101 , and an output unit 102 . That is, the actuator 100 includes a drive source 101 and an output unit 102 in addition to the rigid internal gear 2 , the flexible external gear 3 , and the wave generator 4 constituting the harmonic gear device 1 .
  • the actuator 100 includes an input unit 103 , an input side case 111 , an output side case 112 , a spline bush 113 , and a spacer 114 in addition to the harmonic gear unit 1 , the drive source 101 , and the output unit 102 . , the first stopper 115 , the second stopper 116 and the mounting plate 117 .
  • the actuator 100 further includes input side bearings 118 , 119 , an input side oil seal 120 , output side bearings 121 , 122 , and an output side oil seal 123 .
  • the materials of the actuator 100 other than the driving source 101, the input side oil seal 120 and the output side oil seal 123 are stainless steel, cast iron, carbon steel for mechanical structure, chromium molybdenum steel, phosphor bronze or aluminum bronze. and other metals.
  • the driving source 101 is a power generation source such as a motor (electric motor). Power generated by drive source 101 is transmitted to cam 41 of wave generator 4 in harmonic gear unit 1 . Specifically, the drive source 101 is connected to a shaft as the input unit 103 , and power generated by the drive source 101 is transmitted to the cam 41 via the input unit 103 . Thereby, the drive source 101 can rotate the cam 41 .
  • the output unit 102 is a cylindrical shaft arranged along the rotation axis Ax2 on the output side.
  • the central axis which is the axis of the output unit 102 coincides with the rotation axis Ax2.
  • the output unit 102 is held by the output-side housing 112 so as to be rotatable about the rotation axis Ax2.
  • the output part 102 is fixed to the bottom 322 of the main body part 32 of the flexible external gear 3 , and rotates together with the flexible external gear 3 around the rotation axis Ax2 . That is, the output unit 102 takes out the rotational force of the flexible external gear 3 as an output.
  • the input unit 103 is a cylindrical shaft arranged along the rotation axis Ax1 on the input side.
  • the central axis that is the axis of the input unit 103 coincides with the rotation axis Ax1.
  • the input unit 103 is held by the input-side housing 111 so as to be rotatable about the rotation axis Ax1.
  • the input unit 103 is attached to the cam 41 of the wave generator 4, and rotates together with the cam 41 around the rotation axis Ax1. That is, the input unit 103 transmits power (rotational force) generated by the drive source 101 as an input to the cam 41 .
  • the input side rotation axis Ax1 and the output side rotation axis Ax2 are on the same straight line, so the input unit 103 and the output unit 102 are coaxially located.
  • the input side housing 111 holds the input unit 103 rotatably via input side bearings 118 and 119 .
  • a pair of input-side bearings 118 and 119 are arranged along the rotation axis Ax1 at intervals.
  • the shaft serving as the input part 103 passes through the input side housing 111, and the front end of the input part 103 extends from the input side end surface (the right end surface in FIG. 4 ) of the rotation axis Ax1 in the input side housing 111. protrude.
  • the input side oil seal 120 closes the gap between the input side end surface of the rotation shaft Ax1 of the input side housing 111 and the input portion 103 .
  • the output side housing 112 holds the output unit 102 rotatably via output side bearings 121 and 122 .
  • a pair of output-side bearings 121 and 122 are arranged along the rotation axis Ax2 at intervals.
  • the output side oil seal 123 closes the gap between the output side end surface of the output side housing 112 on the output side of the rotation shaft Ax1 and the output portion 102 .
  • the input-side housing 111 and the output-side housing 112 sandwich the rigid internal gear of the harmonic gear unit 1 from both sides in the direction parallel to the rotation axis Ax1, that is, the tooth line direction D1. 2 combined with each other.
  • the input-side housing 111 contacts the rigid internal gear 2 from the input side of the rotation axis Ax1
  • the output-side housing 112 contacts the rigid internal gear 2 from the output side of the rotation axis Ax1 .
  • the input-side housing 111 passes through the plurality of fixing holes 22 in a state where the rigid internal gear 2 is sandwiched between the output-side housing 112 and is fastened and fixed to the output-side housing 112 by screws (bolts). .
  • the input-side housing 111 , the output-side housing 112 , and the rigid internal gear 2 are joined together and integrated.
  • the rigid internal gear 2 constitutes the outer contour of the actuator 100 together with the input side housing 111 and the output side housing 112 .
  • the spline bushing 113 is a cylindrical member for coupling the shaft serving as the input unit 103 to the cam 41 .
  • the spline bushing 113 is inserted into the cam hole 43 formed in the cam 41 , and the shaft serving as the input unit 103 is inserted into the spline bushing 113 so as to pass through the spline bushing 113 .
  • the movement of the spline bush 113 relative to both the cam 41 and the input unit 103 is restricted in the rotational direction centering on the rotational axis Ax1, and the spline bush 113 can at least move in a direction parallel to the rotational axis Ax1. Move relative to the input unit 103 .
  • a spline connection structure is realized as a connection structure between the input unit 103 and the cam 41 . Therefore, the cam 41 is movable along the rotation axis Ax1 relative to the input unit 103 and rotates together with the input unit 103 around the rotation axis Ax1.
  • the spacer 114 fills the gap between the spline bushing 113 and the cam 41 .
  • the first stopper 115 is a component that prevents the spline bushing 113 from coming off the cam 41 .
  • the first stopper 115 is constituted by, for example, an E-ring, and is attached at a position on the input side of the rotation shaft Ax1 when viewed from the cam 41 in the spline bush 113 .
  • the second stopper 116 is a member that prevents the input portion 103 from coming off the spline bush 113 .
  • the second stopper 116 is formed of, for example, an E-ring, and is attached to the input portion 103 so as to come into contact with the spline bush 113 from the output side of the rotation axis Ax1 .
  • the mounting plate 117 is a member for mounting the shaft as the output unit 102 on the bottom 322 of the flexible external gear 3 .
  • the mounting plate 117 passes through the plurality of mounting holes 33 while sandwiching the peripheral portion of the through hole 34 in the bottom 322 with the flange portion of the output unit 102, and is screwed relative to the flange portion. (Bolts) are fastened.
  • the shaft serving as the output unit 102 is fixed to the bottom portion 322 of the flexible external gear 3 .
  • the lubricant Lb1 is sealed inside the outer contour of the actuator 100 constituted by the input-side housing 111 , the output-side housing 112 , and the rigid internal gear 2 . That is, in the space surrounded by the input-side case 111 , the output-side case 112 , and the rigid internal gear 2 , there is a “lubricant reservoir” capable of storing the liquid or gel-like lubricant Lb1 .
  • the meshing portion of the internal teeth 21 and the external teeth 31, and between the outer ring 421 and the inner ring 422 of the bearing 42, etc. are injected with a liquid or a gel.
  • the lubricant Lb1 is liquid lubricating oil (oil).
  • the lubricant Lb1 also enters the gap X1 between the outer ring 421 (outer peripheral surface 424 ) of the bearing 42 and the flexible external gear 3 .
  • the liquid level of lubricant Lb1 is located below the lower ends of output side bearings 121 and 122 , only in the lower part of the outer contour of actuator 100 ( The lower part in the vertical direction) stores the lubricant Lb1. Therefore, only a part in the rotation direction of the external teeth 31 and the outer ring 421 of the bearing 42 and the like are immersed in the lubricant Lb1 in the state of FIG. 4 . From this state, when the output unit 102 rotates with the rotation of the input unit 103, the outer ring 421 and the flexible external gear 3 also rotate around the rotation axis Ax1. As a result, the outer teeth 31 and the outer ring 421 of the bearing 42 The entirety of the rotation direction of etc. is immersed in the lubricant Lb1.
  • the robot joint device 130 of the present embodiment includes the harmonic gear device 1 of the present embodiment, a first member 131 , and a second member 132 as shown in FIG. 4 . That is, the robot joint device 130 includes a first member 131 and a second member 132 in addition to the rigid internal gear 2 , the flexible external gear 3 , and the wave generator 4 constituting the harmonic gear device 1 .
  • the first member 131 is a member fixed to the rigid internal gear 2
  • the second member 132 is a member fixed to the flexible external gear 3 . Therefore, relative rotation occurs between the flexible external gear 3 and the rigid internal gear 2 in the harmonic gear device 1 , thereby generating relative rotation between the first member 131 and the second member 132 .
  • the joint device 130 for a robot constitutes a connection point when two or more members (the first member 131 and the second member 132 ) are connected (movably connected) in a mutually movable state via the harmonic gear device 1 .
  • first member 131 and the second member 132 may be directly or indirectly fixed to the rigid internal gear 2 and the flexible external gear 3 , respectively.
  • first member 131 is indirectly coupled (fixed) to the rigid internal gear 2 by being coupled to the output side case 112 .
  • the second member 132 is indirectly coupled (fixed) to the flexible external gear 3 by being coupled to the output portion 102 .
  • robot joint device 130 configured in this way, for example, when cam 41 of wave generator 4 is rotated by power generated by drive source 101 , relative rotation occurs between flexible external gear 3 and rigid internal gear 2 . Then, along with the relative rotation of the flexible external gear 3 and the rigid internal gear 2 , between the first member 131 and the second member 132 centering on the output side rotation axis Ax2 (coaxial with the input side rotation axis Ax1 ) produce relative rotation. As a result, according to the joint device 130 for a robot, the first member 131 and the second member 132 connected via the harmonic gear device 1 can be driven so as to relatively rotate about the rotation axis Ax1. Thus, the robot joint device 130 can realize joint mechanisms of various robots.
  • FIG. 5 is an enlarged schematic cross-sectional view of a main part of a range corresponding to FIG. 1B .
  • FIG. 6 is a schematic view of the inner peripheral surface 301 of the flexible external gear 3 viewed from the bearing 42 side of FIG. 5 .
  • the cylindrical inner peripheral surface 301 is actually developed along the circumferential direction D2 of the harmonic gear device 1, and is shown as a plan view in the tooth line direction D1 and the circumferential direction D2 orthogonal to each other.
  • the "circumferential direction D2" mentioned here is the circumferential direction centering on the rotation axis Ax1.
  • the outer ring 421 of the bearing 42 and the through-hole H1 are shown by imaginary lines (two-dot chain line).
  • FIG. 7A is a schematic diagram showing the surface state of the inner peripheral surface 301 of the flexible external gear 3 and the outer peripheral surface 424 of the wave generator 4 (the outer ring 421) in the cross section of the A1-A1 line in FIG. An enlarged schematic view of area Z1 in FIG. 7A .
  • FIG. 7A is a cross section taken along the tooth line direction D1 of the harmonic gear device 1 , and thus corresponds to an enlarged view of a region Z1 in FIG. 5 .
  • 8A is a schematic diagram showing the surface state of the inner peripheral surface 301 of the flexible external gear 3 and the outer peripheral surface 424 of the wave generator 4 (the outer ring 421) in the cross section of the A2-A2 line in FIG.
  • An enlarged schematic diagram of area Z1 in FIG. 8A is a schematic diagram schematically showing changes in the state of the target surface S1 (inner peripheral surface 301 of the flexible external gear 3 ).
  • At least one of the outer ring 421 of the bearing 42 and the external teeth 31 of the flexible external gear 3 is provided with a through hole H1 along the radial direction. It passes through in the direction and is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 . That is, the inner peripheral surface 425 (refer to FIG. 5 ) that is the rolling surface of the plurality of rolling elements 423 in the outer ring 421 of the bearing 42 and the inner peripheral surface 425 (see FIG. 5 ) that is the contact with the internal teeth 21 of the external teeth 31 of the flexible external gear 3 At least one of the outer peripheral surfaces of the engaging surfaces communicates with the gap X1 via the through-hole H1. Therefore, the lubricant Lb1 can be supplied through the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1 .
  • the harmonic gear device 1 of the present embodiment can supply the lubricant Lb1 to the contact portion of the flexible external gear 3 and the wave generator 4 through the through hole H1 by providing the through hole H1, thereby, the contact portion Sufficient lubricant Lb1 is maintained.
  • "lubricant depletion" is prevented, the surface of the contact portion between the outer ring 421 and the flexible external gear 3 is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. Therefore, in the harmonic gear device 1 of the present embodiment, troubles caused by fretting wear between the outer ring 421 and the flexible external gear 3 are less likely to occur, and a harmonic gear device that is less likely to cause a decrease in reliability can be provided. 1.
  • the through hole H1 may be provided in at least one of the outer ring 421 and the external teeth 31 of the flexible external gear 3 .
  • the through-holes H1 provided in the outer ring 421 are referred to as "the second The first through hole” and the through hole H2 (see FIG. 12B ) provided in the external teeth 31 of the flexible external gear 3 are called “second through hole”.
  • the through-hole H1 is provided only in the outer ring 421 and the outer ring 421 of the external teeth 31 in the flexible external gear 3 .
  • the through hole H1 includes the “first through hole” provided in the outer ring 421 .
  • the through-hole H2 (second through-hole) on the side of the external teeth 31 of the flexible external gear 3 will be described in "(8) Modification".
  • the “passing through in the radial direction” mentioned in the embodiments of the present disclosure refers to passing through in the radial direction, that is, the direction perpendicular to the rotation axis Ax1 , that is, the radial direction. That is, as long as it is the through-hole H1 provided in the outer ring 421 as in this embodiment, the through-hole H1 may pass through between the inner peripheral surface 425 and the outer peripheral surface 424, which are two surfaces in the radial direction of the outer ring 421, or may be Tilted with respect to, for example, a radial direction.
  • the through hole H1 (first through hole) provided in the outer ring 421 penetrates through the outer ring 421 in the radial direction.
  • one opening surface of the through hole H1 faces the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other opening surface of the through hole H1 opens to the inner peripheral surface 425 of the outer ring 421 . Therefore, one end of the through hole H1 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other end is connected to the space between the inner peripheral surface 425 of the outer ring 421 and the outer peripheral surface of the inner ring 422 .
  • the through hole H1 is a circular hole having a circular (perfect circle) cross-sectional shape perpendicular to the radial direction.
  • the center line of the through hole H1 is parallel to the radial direction. That is, the through hole H1 is a hole extending straight in the radial direction from the inner peripheral surface 425 to the outer peripheral surface 424 of the outer ring 421 .
  • the cross-sectional shape of the through hole H1 perpendicular to the radial direction is the same shape over the entire length of the through hole H1 in the radial direction. That is, a cylindrical space is formed inside the through-hole H1.
  • the diameter ⁇ 1 (see FIG. 5 ) of the through hole H1 is the smaller of 0.1 times or less than the diameter ⁇ 2 (see FIG. 5 ) of each of the plurality of rolling elements 423 or 1.0 mm or less.
  • the diameter ⁇ 1 of the through-hole H1 referred to here refers to its diameter when the cross-sectional shape of the through-hole H1 is a perfect circle, and refers to its short diameter when the cross-sectional shape of the through-hole H1 is a non-circular shape (such as an elliptical shape). Axial dimension.
  • the diameter ⁇ 1 of the through hole H1 is not more than 0.1 times the diameter ⁇ 2 of the rolling element 423 and not more than 1.0 mm. According to such a diameter ⁇ 1 of the through hole H1, the lubricant Lb1 can be efficiently supplied to the gap X1 between the H1 outer ring 421 and the flexible external gear 3 through the through hole.
  • the space between the outer ring 421 and the inner ring 422 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1, therefore, the space between the outer ring 421 and the inner ring 422
  • the lubricant Lb1 is supplied to the gap X1 through the through hole H1.
  • the flow of the lubricant Lb1 in the through hole H1 is schematically indicated by dotted arrows.
  • the rolling elements 423 function as a pump and can send the lubricant Lb1 between the outer ring 421 and the inner ring 422 into the gap X1 through the through hole H1 .
  • “lubricant depletion” in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3 is prevented, and the occurrence of fretting wear is easily suppressed.
  • the harmonic gear device 1 of the present embodiment includes a pump structure for supplying the lubricant Lb1 to the gap X1 through the through hole H1 when the flexible external gear 3 rotates relative to the rigid internal gear 2 .
  • the plurality of rolling elements 423 of the bearing 42 roll in the circumferential direction of the outer ring 421 , so the plurality of rolling elements 423 function as a pump as described above. That is, a plurality of rolling elements 423 constitute a pump structure.
  • the rolling element 423 rolls in the space between the outer ring 421 and the inner ring 422, thereby increasing the pressure in the space between the outer ring 421 and the inner ring 422, so that the outer ring The lubricant Lb1 between 421 and the inner ring 422 is extruded to the side of the gap X1 through the through hole H1.
  • the rolling elements 423 constitute a positive displacement pump such as a vane pump, and squeeze out the lubricant Lb1 to the gap X1 side with sufficient pressure, so that a sufficient amount of the lubricant Lb1 can be easily supplied into the gap X1.
  • the opening surface of the through hole H1 on the inner peripheral surface 425 side of the outer ring 421 opens on the bottom surface of the rolling groove 426 formed in the inner peripheral surface 425 of the outer ring 421 . That is, a rolling groove 426 extending in the circumferential direction over the entire circumference of the outer ring 421 is formed at the center of the inner peripheral surface 425 of the outer ring 421 in the width direction (tooth line direction D1). scroll.
  • the same rolling groove 427 is also formed on the outer peripheral surface of the inner ring 422 , and a plurality of rolling elements 423 are held between these rolling grooves 426 , 427 facing each other so as to be sandwiched.
  • the through holes H1 are arranged in the range where the rolling grooves 426 are formed in the width direction (tooth line direction D1 ) of the outer ring 421 so as to open to the bottom surface of the rolling grooves 426 of the outer ring 421 .
  • the through-hole H1 is arrange
  • the through hole H1 is arranged at the center of the rolling groove 426 in the width direction (tooth line direction D1 ) of the outer ring 421 .
  • the centers of the plurality of rolling elements 423 pass through the opening surface of the through hole H1, so that when the rolling elements 423 rotate, the rolling elements 423 effectively function as pumps, and it is easy to pass through the through hole H1 to the gap X1.
  • the outer ring 421 and the flexible external gear 3 are in contact mainly at both ends of the outer ring 421 in the width direction (tooth line direction D1 ). Therefore, the through-hole H1 is formed at the center of the outer ring 421 in the width direction (tooth line direction D1), so that when the outer ring 421 comes into contact with the flexible external gear 3, the outer ring 421 is less likely to be damaged due to the through-hole H1. reduction in strength.
  • the cross-sectional shape of the rolling grooves 426 and 427 perpendicular to the circumferential direction of the outer ring 421 is formed in an arc shape.
  • the curvature of the circular arc in the cross-sectional shape of the rolling grooves 426 and 427 is larger than the curvature of each of the plurality of rolling elements 423 .
  • the radius of curvature of the arc in the cross-sectional shape of the rolling grooves 426 and 427 is smaller than the radius of curvature of the rolling element 423 .
  • each rolling element 423 is supported at four points in total, which are both end edges of the rolling groove 426 in the outer ring 421 in the width direction (tooth line direction D1 ) and the inner ring 422 . Both ends of the rolling groove 427 in the width direction (tooth line direction D1).
  • the rolling elements 423 are supported by a pair of end edges that are diagonally opposed to each other.
  • the opening surface of the through-hole H1 formed in the bottom surface of the rolling groove 426 faces the surface of the rolling element 423 with the above-mentioned gap therebetween.
  • the opening surface of the through-hole H1 formed in the bottom surface of the rolling groove 426 faces the surface of the rolling element 423 with the above-mentioned gap therebetween.
  • a distance (gap) equal to or greater than a predetermined value is ensured between the opening surface of the through-hole H1 and the rolling element 423, so that the through-hole H1 will not be blocked by rolling elements 423 . Accordingly, even when the plurality of rolling elements 423 pass through the through-hole H1 while rolling, the plurality of rolling elements 423 do not collide with the opening edge of the through-hole H1. As a result, when the rolling elements 423 pass through the through-hole H1, the impact caused by the rolling elements 423 colliding with the opening edge of the through-hole H1 can be avoided, and the outer ring 421, the rolling elements 423, etc. can be easily protected from the impact. .
  • the through hole H1 includes a plurality of first through holes provided in the outer ring 421 so as to be aligned in the circumferential direction of the outer ring 421 .
  • the through-holes H1 are composed only of the first through-holes provided in the outer ring 421 , and therefore, all of the plurality of through-holes H1 are aligned in the circumferential direction of the outer ring 421 .
  • three through-holes H1 are provided in the outer ring 421 .
  • the lubricant Lb1 can be supplied through the gap X1 between the outer ring 421 and the flexible external gear 3 at a plurality of places (three places in the present embodiment) in the circumferential direction of the outer ring 421 through the through hole H1 .
  • the interval P1 of the plurality of through holes H1 is a value other than a multiple of the interval P2 of the plurality of rolling elements 423 .
  • the bearing 42 has 26 rolling elements 423 and the outer ring 421 has three through holes H1.
  • the 26 rolling elements 423 and the three through-holes H1 are respectively provided at equal intervals (equal intervals) in the circumferential direction of the outer ring 421 .
  • the interval P1 is a value expressed by the distance between the centers of two through-holes H1 adjacent in the circumferential direction of the outer ring 421 by an angle around the rotation axis Ax1.
  • the distance between the centers of two adjacent rolling elements 423 is a value represented by an angle around the rotation axis Ax1.
  • the rolling elements 423 do not exist at positions corresponding to all the through holes H1 at the same time. That is, in a state where one rolling element 423 is located at a position corresponding to one through-hole H1, the rolling element 423 is not located at a position corresponding to the other two through-holes H1. Therefore, in the harmonic gear device 1 of the present embodiment, it is possible to avoid a relatively large impact that may occur when a plurality of rolling elements 423 are simultaneously fitted (or pulled out) into a plurality of through-holes H1, and it is easy to protect the outer ring 421. And the rolling elements 423 etc. are protected from impact. In addition, the pumping action by the rolling of the rolling elements 423 is also more efficient than when the rolling elements 423 are positioned on all the through holes H1 at the same time.
  • the chemical conversion treatment coating C1 is provided on the target surface S1 constituted by the inner peripheral surface 301 of the flexible external gear 3 . That is, by subjecting the inner peripheral surface 301 of the flexible external gear 3 as the target surface S1 to chemical conversion treatment, chemical conversion is formed so as to cover the target surface S1 (the inner peripheral surface 301 of the flexible external gear 3 ).
  • the chemical conversion treatment coating C1 is a phosphate coating formed by chemical conversion treatment (Parkerizing treatment) using phosphate.
  • Such a chemical conversion treatment coating C1 is formed on the outermost surface of the target surface S1 (the inner peripheral surface 301 of the flexible external gear 3 in this embodiment).
  • the chemical conversion treatment coating C1 is made of a material softer than at least the target surface S1 itself. That is, the hardness of the chemical conversion coating C1 is lower than the hardness of parts of the target surface S1 other than the chemical conversion coating C1 .
  • the surface hardness of the chemical conversion coating C1 is lower (softer) than that of the flexible external gear 3 and the outer ring 421 of the bearing 42 of the wave generator 4 .
  • the chemical conversion treatment coating C1 interposed therebetween serves as a buffer, and damage to the flexible external gear 3 and the wave generator 4 can be suppressed.
  • the flexible external gear 3 and the wave generator 4 are assembled or when the harmonic gear device 1 is initially used, etc., at the contact portion of the flexible external gear 3 and the wave generator 4, there is a phenomenon called "bite". In the case of local adhesive wear of "connection" (galling).
  • the relatively low-hardness chemical conversion treatment coating C1 is peeled (peeled off) from the target surface S1, so that the flexible external gear 3 And the growth of wear of the wave generator 4 is suppressed, which is beneficial to the protection of the flexible external gear 3 and the wave generator 4 .
  • the chemical conversion treatment coating C1 is a porous coating having many fine pores (microscopic pores) during its formation (chemical conversion treatment). Therefore, the chemical conversion treatment coating C1 can soak the lubricant Lb1 like a sponge by introducing the lubricant Lb1 (see FIG. 4 ) into the pores. Then, the lubricant Lb1 soaked in the chemical conversion treatment coating C1 seeps out from the chemical conversion treatment coating C1 appropriately according to temperature, pressure, and the like. In this way, the chemical conversion treatment coating C1 is configured to be able to hold the lubricant Lb1. Therefore, the lubricant is likely to remain in the contact portion of the Lb1 flexible external gear 3 with the wave generator 4 , and sufficient lubricant Lb1 can be maintained at the contact portion.
  • the inner peripheral surface 301 of the flexible external gear 3 on which the chemical conversion treatment coating C1 is formed is always maintained with lubricating performance by the lubricant Lb1.
  • the chemical conversion treatment film C1 is different from a self-low-friction film such as diamond-like carbon (DLC: Diamond-Like Carbon), and realizes the flexible external gear 3 and the wave generator 4 by holding the lubricant Lb1. low-friction contact between them. Therefore, as long as the chemical conversion treatment coating C1 in the state of holding the lubricant Lb1 exists in the gap X1 between the flexible external gear 3 and the wave generator 4, the flexible external gear 3 can be realized for a long period of time using the lubricant Lb1. Low-friction contact with the wave generator 4.
  • DLC Diamond-Like Carbon
  • the chemical conversion treatment coating C1 may peel (peel off) from the target surface S1 due to abrasion such as "seizing". Therefore, in the harmonic gear device 1 in which contamination of foreign matter (contamination) may be a problem, the chemical conversion treatment coating C1 cannot generally be employed.
  • the chemical conversion treatment coating after peeling (peeling) is adopted. C1 leaves the following structure in the gap X1 (between the flexible external gear 3 and the wave generator 4 ).
  • the groove 303 capable of holding at least the chemical conversion treatment coating C1 is formed on the target surface S1 .
  • a plurality of grooves 303 are formed on the inner peripheral surface 301 (target surface S1 ) facing the gap X1 in the flexible external gear 3 .
  • Concavities and convexities are formed on the target surface S1 by the plurality of grooves 303 . That is, the portion of the target surface S1 where the groove 303 is formed becomes a relatively concave recess, and the portion where the groove 303 is not formed becomes a relatively protruding protrusion 304 (see FIG. 7A ).
  • the target surface S1 can hold the chemical conversion treatment coating C1 (after peeling off) in the groove 303 which is a concave portion.
  • the groove 303 is formed by utilizing the processing marks generated on the inner peripheral surface 301 of the flexible external gear 3 by honing. That is, in the honing process, mesh-shaped (twill-shaped) scratch marks called "cross-hatching" remain on the polished surface.
  • the cross hatching is composed of a plurality of first grooves 303 a and a plurality of second grooves 303 b intersecting at an intersection angle of 20 degrees or more and 60 degrees or less, and is formed on the inner peripheral surface of the honed flexible external gear 3 Roughly the entire area of the 301.
  • the plurality of grooves 303 extend in both the tooth line direction D1 and the circumferential direction D2 on the inner peripheral surface 301 of the flexible external gear 3 , and define a plurality of convex portions 304 that are rhombus-shaped in plan view. That is, the slots 303 include first slots 303 a and second slots 303 b intersecting each other.
  • the lubricant Lb1 can easily spread over a relatively wide range in the gap X1. That is, the lubricant Lb1 infiltrated into the chemical conversion treatment coating C1 easily diffuses in both the tooth line direction D1 and the circumferential direction D2 in the gap X1 through the groove 303 .
  • the lubricant Lb1 can be expected to diffuse in the tooth line direction D1 and the circumferential direction D2 due to, for example, capillarity.
  • the mesh-like groove 303 includes the first groove 303a and the second groove 303b intersecting each other as cross-hatched, the lubricant Lb1 not only easily spreads in either the tooth line direction D1 or the circumferential direction D2, but also And it is easy to spread to both of them.
  • the target surface S1 (the inner periphery of the flexible external gear 3 in this embodiment) formed by shearing metal crystal grains such as cutting, grinding, or honing, surface 301), producing a plurality of grooves 303.
  • scaly "burrs" protrusions
  • the boundary between the concavo-convex (groove 303 and convex portion 304 ) has a rounded shape, so that, for example, “snitching” is less likely to occur at the initial stage of use of the harmonic gear device 1 .
  • the chemical conversion treatment coating C1 is formed so as to cover the entire area of the target surface S1 on the target surface S1 subjected to shot peening, barrel grinding, or the like in this way. That is, the chemical conversion treatment coating C1 is seamlessly formed on both the inner surface of the groove 303 and the surface of the convex portion 304 as shown in FIGS. 7A to 8B .
  • the thickness L2 of the chemical conversion treatment coating C1 is smaller than the depth L1 of the groove 303 .
  • the depth L1 of the groove 303 referred to here is the distance from the convex portion 304 to the bottom of the groove 303 .
  • the depth L1 of the groove 303 is not less than 2 ⁇ m and not more than 8 ⁇ m, and the thickness L2 of the chemical conversion treatment film C1 is not less than 1 ⁇ m and not more than 5 ⁇ m.
  • the thickness L2 of the chemical conversion treatment coating C1 is 3 ⁇ m.
  • the thickness L2 of the chemical conversion coating C1 smaller than the depth L1 of the groove 303, the entire thickness of the chemical conversion coating C1 is accommodated in the groove 303, and the outer peripheral surface 424 of the wave generator 4 and the groove 303 are suppressed.
  • the chemical conversion treatment film C1 in the tank 303 contacts.
  • the thickness L2 of the chemical conversion coating C1 is greater than that of the flexible external gear 3 when the wave generator 4 is combined with the flexible external gear 3 in the state where the chemical conversion coating C1 is removed.
  • the gap generated between the wave generator 4 is small. That is, the thickness L2 of the chemical conversion treatment coating C1 is smaller than the distance between the flexible external gear 3 and the wave generator 4 in the state P11 of FIG. 9 .
  • the chemical conversion treatment coating C1 is less likely to be compressed. Damaged under action.
  • the surface state of the inner peripheral surface 301 of the flexible external gear 3 changes as shown in FIG. 9 as the harmonic gear device 1 is used.
  • 9 shows the state P11 before the chemical conversion coating C1 is formed, the state P12 after the chemical conversion coating C1 is formed and before the use of the harmonic gear device 1 starts, and the state where the chemical conversion coating C1 is partially worn. P13, and a state P14 in which the chemical conversion treatment coating C1 is further worn.
  • the chemical conversion treatment coating C1 is uniformly provided on the target surface S1 (in this embodiment, the inner circumference of the flexible external gear 3). Both the groove 303 and the protrusion 304 in the surface 301).
  • the cam 41 of the wave generator 4 rotates to elastically deform the outer ring 421 and the flexible external gear 3, and along with this, the outer ring 421 and the flexible external gear 3 are elastically deformed. Relative rotation may occur between the external gears 3 . This relative rotation is, for example, about a few thousandths or a few hundredths of the rotation speed of the cam 41.
  • the peeled chemical conversion treatment coating C10 remains between the wave generator 4 (outer ring 421) and the flexible external gear 3 by being held in the groove 303.
  • the hardness of the chemical conversion treatment film C1 is lower than the hardness of either the flexible external gear 3 or the outer ring 421 of the bearing 42 of the wave generator 4 as described above. Therefore, even if the peeled chemical conversion treatment coating C1 leaks (overflows) from the gap X1 between the flexible external gear 3 and the wave generator 4, the foreign matter made of the chemical conversion treatment coating C1 is relatively soft. In short, by using the foreign matter caused by abrasion that tends to occur at the initial stage of use of the harmonic gear device 1 as the soft foreign matter coming out of the relatively soft chemical conversion treatment coating C1, for example, even if the foreign matter enters the bearing 42, it is possible to suppress damage to the bearing 42. Damage to bearing 42. As a result, for example, the amount of generation of hard foreign matter that damages the bearing 42 and the like is suppressed.
  • the surface hardness of the internal teeth 21 is lower than that of the external teeth 31 . That is, the hardness of the surface of the external teeth 31 is higher (harder) than that of the internal teeth 21 .
  • the "hardness” mentioned in the embodiments of the present disclosure refers to the degree of hardness of an object, for example, the hardness of a metal is represented by the size of a depression formed by pushing a steel ball with a certain pressure.
  • examples of the hardness of metals include Rockwell hardness (HRC), Brinell hardness (HB), Vickers hardness (HV), and Shore hardness (Hs).
  • HRC Rockwell hardness
  • HB Brinell hardness
  • HV Vickers hardness
  • Hs Shore hardness
  • hardness is represented by Vickers hardness (HV).
  • As a method of increasing (hardening) the hardness of a metal member there are, for example, alloying or heat treatment.
  • the surface of the external teeth 31 of the flexible external gear 3 is made of a material with high hardness and high toughness (toughness), and the internal teeth 21 of the rigid internal gear 2 are made of a material with a hardness lower than that of the external teeth 31 .
  • the following material is used for the external teeth 31, that is, a material obtained by heat-treating (quenching and tempering) nickel-chromium-molybdenum steel specified as "SNCM439" in Japanese Industrial Standards (JIS: Japanese Industrial Standards) .
  • Spherical graphite cast iron specified as "FCD800-2" in Japanese Industrial Standards (JIS) is used for the internal teeth 21 .
  • the surface hardness of the internal teeth 21 which is relatively low in hardness compared with the external teeth 31 , is preferably HV350 or less.
  • the surface hardness of the internal teeth 21 is selected within the range of HV250 or more and less than HV350.
  • the lower limit of the surface hardness of the internal teeth 21 is not limited to HV250, and may be, for example, HV150, HV160, HV170, HV180, HV190, HV200, HV210, HV220, HV230, or HV240.
  • the upper limit of the surface hardness of the internal teeth 21 is not limited to HV350, and may be, for example, HV360, HV370, HV380, HV390, HV400, HV410, HV420, HV430, HV440, or HV450.
  • the surface hardness of the external teeth 31 which is relatively harder than the internal teeth 21 , is preferably HV380 or higher.
  • the surface hardness of the external teeth 31 is selected within the range of not less than HV380 and not more than HV450.
  • the lower limit of the surface hardness of the external teeth 31 is not limited to HV380, and may be, for example, HV280, HV290, HV300, HV310, HV320, HV330, HV340, HV350, HV360, or HV370.
  • the upper limit of the surface hardness of the internal teeth 21 is not limited to HV450, and may be, for example, HV460, HV470, HV480, HV490, HV500, HV510, HV520, HV530, HV540, or HV550.
  • the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is HV50 or more. That is, the surface hardness of the external teeth 31 is set to be higher than the surface hardness of the internal teeth 21 by HV50 or more. In short, for example, if the surface hardness of the internal teeth 21 is HV350, the surface hardness of the external teeth 31 is HV400 or more. In addition, if the surface hardness of the external teeth 31 is HV380, the surface hardness of the internal teeth 21 is HV330 or less.
  • the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is not limited to HV50 or greater, and may be, for example, HV20 or greater, HV30 or greater, or HV40 or greater. Furthermore, the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is preferably large, for example, more preferably HV60 or higher, HV70 or higher, HV80 or higher, HV90 or higher, or HV100 or higher. If the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is HV100 or more, when the surface hardness of the internal teeth 21 is HV350, the surface hardness of the external teeth 31 is HV450 or more.
  • the surface hardness of the internal teeth 21 is set lower than the surface hardness of the external teeth 31 . Therefore, when the internal teeth 21 contact the external teeth 31 during operation of the harmonic gear device 1 , the internal teeth 21 having a relatively lower surface hardness than the external teeth 31 are actively worn. When two members (the inner teeth 21 and the outer teeth 31 ) having different surface hardnesses contact each other, the wear of the relatively soft inner teeth 21 is accelerated, and the wear of the relatively hard outer teeth 31 is suppressed.
  • the tooth surfaces of the internal teeth 21 are moderately worn, thereby increasing the actual contact area between the internal teeth 21 and the external teeth 31 and reducing the surface pressure, making it difficult to Wear of the external teeth 31 occurs.
  • the surface hardness of the internal teeth 21 is HV350 or less as in the present embodiment, even if foreign matter occurs due to chipping or wear of the internal teeth 21 due to the contact between the internal teeth 21 and the external teeth 31, the foreign matter is relatively soft. quality.
  • the harmonic gear device 1 by using the foreign matter caused by wear that is likely to occur at the initial stage of use of the harmonic gear device 1 as a soft foreign matter that comes out of the relatively soft internal teeth 21, for example, even if the foreign matter enters the bearing 42, it is possible to suppress damage to the bearing 42. damage. As a result, for example, the amount of generation of hard foreign matter that greatly damages the bearing 42 is suppressed. Especially when the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is a relatively large value such as HV50 or more, the above-mentioned effect is remarkable.
  • the surface hardness of the internal teeth 21 and the external teeth 31 does not have to be specified by Vickers hardness (HV), and can also be specified by other hardness, such as Rockwell hardness (HRC), Brinell hardness (HB) or Shore hardness (Hs).
  • HV Vickers hardness
  • HRC Rockwell hardness
  • HB Brinell hardness
  • Hs Shore hardness
  • the surface hardness of the internal teeth 21 is preferably HRC30 or less.
  • the surface hardness of the internal teeth 21 is selected within a range of not less than HRC20 and less than HRC30.
  • the lower limit of the surface hardness of the internal teeth 21 is not limited to HRC20, and may be, for example, HRC10, HRC15, or HRC25.
  • the upper limit of the surface hardness of the internal teeth 21 is not limited to HRC30, and may be, for example, HRC35, HRC40, or HRC45.
  • the surface hardness of the external teeth 31 is preferably HRC40 or higher.
  • the surface hardness of the external teeth 31 is selected within the range of not less than HRC40 and not more than HRC60.
  • the lower limit of the surface hardness of the external teeth 31 is not limited to HRC40, and may be, for example, HRC30, HRC35, or the like.
  • the upper limit of the surface hardness of the external teeth 31 is not limited to HRC60, and may be, for example, HRC50, HRC55, HRC65, HRC70, or HRC75.
  • the target surface S1 constituted by at least one of the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 is provided with a By chemically converting the coating C1, a sufficient lubricant Lb1 can be maintained at the contact portion between the flexible external gear 3 and the wave generator 4. Therefore, the surface of the contact portion of the flexible external gear 3 with the bearing 42 (the outer ring 421 ) is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. The generation of hard foreign matter coming out of the gear 3 or the outer ring 421.
  • the damage caused by relatively hard foreign matter entering the bearing 42 is less likely to occur, and the reduction in reliability is less likely to occur especially during long-term use, so that the transmission efficiency of the harmonic gear device 1 is further improved. Improvement, long life and high performance.
  • the internal teeth 21 have a dedendum 212 and a dedendum 213 as shown in FIG. 1B .
  • the internal teeth 21 are provided on the inner peripheral surface of the rigid internal gear 2, so the dedendum 212 of the internal teeth 21 corresponds to the inner peripheral surface of the rigid internal gear 2, and the addendum 213 faces inward from the inner peripheral surface of the rigid internal gear 2 (the rigid internal gear 2 center of gear 2) protrudes.
  • the external tooth 31 has a dedendum 312 and a dedendum 313 as shown in FIG. 1B .
  • the external teeth 31 are arranged on the outer peripheral surface of the flexible external gear 3 (the body part 321), so the dedendum 312 of the external teeth 31 is equivalent to the outer peripheral surface of the flexible external gear 3 (the body part 321), and the addendum 313 is from the flexible external gear 3 (the body part 321).
  • the outer peripheral surface of (the body part 321 of) the external gear 3 protrudes outward.
  • the crests 313 of the external teeth 31 are inserted between adjacent pairs of crests 213 of the internal teeth 21 , so that the internal teeth 21 and the external teeth 31 are meshed.
  • the dedendum 313 of the external tooth 31 is opposed to the dedendum 212 of the internal tooth 21
  • the dedendum 213 of the internal tooth 21 is opposed to the dedendum 312 of the external tooth 31 .
  • the internal teeth 21 have chamfered portions 211 at both end portions in the tooth line direction D1.
  • the chamfered portion 211 is a C surface obtained by reducing the protruding amount of the internal teeth 21 toward both sides in the tooth line direction D1 , and is basically a portion that does not contribute to the meshing of the internal teeth 21 and the external teeth 31 . That is, the chamfered portion 211 of the internal tooth 21 does not contact the external tooth 31 even at the meshing position of the internal tooth 21 and the external tooth 31 .
  • the external teeth 31 have chamfered portions 311 at both end portions in the tooth line direction D1.
  • the chamfered portion 311 is a C surface obtained by reducing the protruding amount of the internal teeth 21 toward both sides in the tooth line direction D1 , and is basically a portion that does not contribute to the meshing of the internal teeth 21 and the external teeth 31 . That is, the chamfered portion 311 of the external tooth 31 does not contact the internal tooth 21 even at the meshing position between the internal tooth 21 and the external tooth 31 .
  • the internal teeth 21 of the rigid internal gear 2 have tooth line trimming portions 210 . That is, in the harmonic gear device 1 , at least the internal teeth 21 are subjected to tooth line dressing.
  • the tooth line trimming portion 210 of the internal teeth 21 is provided at at least one end in the tooth line direction D1.
  • the inner tooth 21 has the tooth line trimming portion 210 at least one end portion of the internal tooth 21 in the tooth line direction D1.
  • the tooth line trimming portion 210 is provided at both ends of the internal tooth 21 in the tooth line direction D1.
  • the external teeth 31 of the flexible external gear 3 also have tooth line trimming portions 310 . That is, in the harmonic gear device 1 , not only the internal teeth 21 but also the external teeth 31 are subjected to tooth line dressing.
  • the tooth line trimming portion 210 of the external teeth is provided at at least one end portion in the tooth line direction D1.
  • the external teeth 31 have the tooth line trimming portion 310 on at least one end portion of the external teeth 31 in the tooth line direction D1.
  • the tooth line trimming portion 310 is provided at both ends of the external teeth 31 in the tooth line direction D1.
  • the harmonic gear device 1 of the present embodiment at least one of the internal teeth 21 and the external teeth 31 has the tooth line trimming portion 210 , 310 .
  • the tooth line trimmers 210 and 310 make it difficult to generate stress concentration due to excessive tooth contact between the internal teeth 21 and the external teeth 31 , and as a result, the tooth contact between the internal teeth 21 and the external teeth 31 can be improved. Therefore, foreign matter due to chipping or abrasion due to contact between the internal teeth 21 and the external teeth 31 is less likely to occur, and it is possible to realize the harmonic gear device 1 that is less likely to decrease in reliability.
  • the contact between the flexible external gear 3 and the wave generator 4 Parts may experience fretting wear. Moreover, if fretting wear occurs, it may cause roughness of the surface, rust caused by abrasive powder, and damage to the wave generator 4 (the bearing 42) caused by the abrasive powder entering the inside of the wave generator 4, etc. This affects the reliability of the harmonic gear device 1 .
  • the cause of such fretting wear is considered to be "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the flexible external gear 3 and the wave generator 4 . That is, it can be estimated that the contact portion between the flexible external gear 3 and the wave generator 4 is originally in an environment where fretting wear is likely to occur due to microvibration between the contact surfaces in a state where the lubricant Lb1 is insufficient. environment. Specifically, the following two reasons can be considered as the reason why such fretting wear is likely to occur in an environment.
  • the first reason is that the flexible external gear 3 frequently repeats elastic deformation. That is to say, during one rotation of the cam 41 of the wave generator 4, the flexible external gear 3 repeats two elastic deformations with the long axis of the ellipse in one direction (for example, the vertical direction in FIG. 2A ). Therefore, when the cam 41 rotates at high speed, the flexible external gear 3 is elastically deformed repeatedly at high speed, and vibrations are likely to be generated at the contact portion between the flexible external gear 3 and the wave generator 4 as the elastic deformation is repeated. As a result, microvibration occurs in a state where the lubricant Lb1 is insufficient at the contact portion between the flexible external gear 3 and the wave generator 4 .
  • the end of the flexible external gear 3 on the opening surface 35 side in the direction of the rotation axis Ax1 deforms more than the end on the bottom 322 side. , and become a shape closer to an ellipse shape. Therefore, in the state where the flexible external gear 3 is elastically deformed, the inner peripheral surface 301 of the body portion 321 of the flexible external gear 3 includes a tapered surface inclined by an inclination angle ⁇ 1 with respect to the rotation axis Ax1 as shown in FIG. 10 . 302. Furthermore, the inclination angle ⁇ 1 of the tapered surface 302 changes with the elastic deformation of the flexible external gear 3 .
  • the inclination angle ⁇ 1 of the tapered surface 302 is the largest at both ends of the ellipse in the major axis direction ("major axis side" in FIG. 10 ),
  • the inclination angle ⁇ 1 of the tapered surface 302 is the smallest at both ends in the minor axis direction of the ellipse ("minor axis side” in FIG. 10 ). Therefore, the inclination angle ⁇ 1 of the tapered surface 302 also changes at high speed due to the frequent and repeated elastic deformation of the flexible external gear 3, whereby the inner peripheral surface 301 (tapered surface 302) of the flexible external gear 3 repeatedly impacts the outer ring.
  • the outer peripheral surface 424 of 421 vibrates. As described above, microvibrations accompanying impacts are generated, and as a result, fretting wear is likely to occur at the contact portion between the flexible external gear 3 and the wave generator 4 .
  • the second reason is that the relative rotation between the outer ring 421 and the flexible external gear 3 is at a low speed. That is to say, under the influence of the gap X1 between the outer ring 421 and the flexible external gear 3, the cam 41 of the wave generator 4 rotates and the outer ring 421 and the flexible external gear 3 elastically deform. Relative rotation may occur between the ring 421 and the flexible external gear 3 . However, this relative rotation is, for example, a low-speed rotation of about a few thousandths or a few hundredths of the rotation speed of the cam 41 .
  • the lubricant Lb1 cannot be expected to flow due to the relative rotation, and it is disadvantageous to form a film (oil film) of the lubricant Lb1 at the contact portion. environment of. However, since relative rotation may occur between the outer ring 421 and the flexible external gear 3 , the outer ring 421 and the flexible external gear 3 rub against each other, creating an environment where fretting wear easily occurs.
  • the lubricant Lb1 can be forcibly supplied to the contact portion between the outer ring 421 and the flexible external gear 3 in an environment where fretting wear is likely to occur. That is, the harmonic gear device 1 can supply the lubricant Lb1 to the contact portion of the flexible external gear 3 and the wave generator 4 through the through hole H1 , thereby maintaining sufficient lubricant Lb1 at the contact portion. In this way, occurrence of fretting wear is suppressed by preventing "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3 .
  • the target surface S1 constituted by at least one of the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 is provided with a chemical conversion treatment coating.
  • the harmonic gear device 1 of the present embodiment As a result, the surface of the contact portion between the outer ring 421 and the flexible external gear 3 is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. Therefore, in the harmonic gear device 1 of the present embodiment, troubles caused by fretting wear between the outer ring 421 and the flexible external gear 3 are less likely to occur, and a harmonic gear device that is less likely to cause a decrease in reliability can be provided. 1. In addition, the harmonic gear device 1 of the present embodiment is less prone to reliability degradation, especially during long-term use, so that the transmission efficiency, longer life, and higher performance of the harmonic gear device 1 are further brought about.
  • the harmonic gear device 1 since the lubricant Lb1 is supplied to the contact portion between the outer ring 421 and the flexible external gear 3, it is difficult to hinder the deformation followability of the flexible external gear 3, resulting in improvement of power transmission efficiency, Longer life due to reduction of the load applied to the bearing 42 and the like. Moreover, since the wear powder generated by fretting wear is also prevented from entering the bearing 42, etc., the occurrence of damage starting from the indentation formed by the bite of the wear powder (flaking of the surface origin type) is also reduced. . Therefore, as the harmonic gear device 1 , a longer life and higher performance can be expected.
  • the through-hole H1 is provided so that when the eye-catching portion of the outer ring 421 passes through the lubricant reservoir, lubrication is replenished only through the gap between the outer ring 421 and the inner ring 422 .
  • lubricant Lb1 the lubricant Lb1 can also be supplied to the gap X1. That is, since the lubricant Lb1 replenished between the outer ring 421 and the inner ring 422 is supplied to the gap X1 through the through hole H1, friction at the contact portion with the flexible external gear 3 is less likely to occur on the entire circumference of the outer ring 421. "Lubricant exhausted".
  • the rolling elements 423 when the bearing 42 operates to rotate the plurality of rolling elements 423 , the rolling elements 423 function as a pump, whereby the lubricant Lb1 can be forcibly sent into the gap X1 through the through hole H1 .
  • the chemical conversion treatment coating C1 is provided on the target surface S1 constituted by at least one of the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 . According to these configurations, the lubricant Lb1 supplied to the gap X1 via the through hole H1 is likely to remain on the inner peripheral surface 301 of the flexible external gear 3, and the depletion of the lubricant in the gap X1 can be efficiently eliminated.
  • the rapid change of the inclination angle ⁇ 1 of the tapered surface 302 due to repeated elastic deformation of the flexible external gear 3 also contributes to the diffusion of the lubricant Lb1 in the gap X1.
  • the startability of the harmonic gear device 1 can be improved in a low-temperature environment where the lubricant Lb1 is likely to solidify, for example.
  • FIG. 11 is a cross-sectional view showing an example of a robot 9 using the harmonic gear device 1 according to this embodiment.
  • the robot 9 is a horizontal multi-joint robot, a so-called SCARA (Selective Compliance Assembly Robot Arm) type robot.
  • SCARA Selective Compliance Assembly Robot Arm
  • the robot 9 includes two robot joint devices 130 (including the harmonic gear device 1 ) and a link 91 .
  • the two robot joint devices 130 are respectively provided at the joints of two places in the robot 9 .
  • the link 91 connects the two robot joint devices 130 .
  • the harmonic gear unit 1 is not a cup-shaped harmonic gear unit but a hat-shaped harmonic gear unit. That is, in the harmonic gear device 1 illustrated in FIG. 11 , the flexible external gear 3 formed in the shape of a top hat is used.
  • a surface processing step of processing the surface of the outer ring 421 (in particular, the inner peripheral surface 425 serving as the rolling surface) after the drilling step of forming the through-hole H1. That is, it is preferable that compressive residual stress remains around the through-hole H1 in the outer ring 421 so that the through-hole H1 does not become a starting point of cracking of the outer ring 421 . For this reason, it is preferable to form the through-hole H1 before performing a surface processing step such as quenching on the outer ring 421 so that compressive residual stress due to heat treatment remains.
  • the periphery of the through hole H1 in the outer ring 421 may be subjected to processing such as shot peening in which the surface is modified and solidified by projecting a small spherical projection, thereby improving the appearance. Fatigue strength of ring 421.
  • Embodiment 1 is just one of various implementations of the embodiments of the present disclosure. Embodiment 1 Various changes can be made according to the design, as long as the purpose of the embodiments of the present disclosure can be achieved.
  • the drawings referred to in the embodiments of the present disclosure are all schematic drawings, and the size and thickness ratios of the structural elements in the drawings do not necessarily reflect the actual size ratio. Modified examples of the first embodiment are listed below. Modifications described below can be applied in combination as appropriate.
  • the through hole H1 may be at a position deviated from the center of the plurality of rolling elements 423 in the direction parallel to the rotation axis Ax1 (tooth line direction D1).
  • the through hole H1 is disposed at a position deviated from the center of the rolling element 423 toward the opening surface 35 , that is, at a position between the center of the rolling element 423 and the opening surface 35 in the tooth line direction D1 .
  • the through-hole H1 may be provided in a plurality of places in the direction (tooth line direction D1) parallel to the rotation axis Ax1.
  • the opening area of the through hole H1 on the side of the gap X1 may be smaller than the opening area of the through hole H1 on the side opposite to the gap X1. That is, in the (first) through-hole H1 provided in the outer ring 421 , the opening area of the through-hole H1 on the side of the gap X1 , that is, the outer peripheral surface 424 , is larger than that of the through-hole H1 on the side opposite to the gap X1 , that is, the inner peripheral surface 425 .
  • the side opening area is small. Thereby, the pressure of the lubricant Lb1 supplied to the gap X1 through the through hole H1 can be increased.
  • FIGS. 12A and 12B are cross-sectional views showing modifications of the first embodiment, and corresponding to FIGS. 1A and 1B .
  • (second) through holes H2 are provided in the external teeth 31 of the flexible external gear 3 .
  • the through-holes H include "second through-holes" provided in the external teeth 31 of the flexible external gear 3.
  • the through-hole H2 provided in the part of the external teeth 31 of the flexible external gear 3, that is, the through-hole H2 provided in the position corresponding to the bearing 42 in the direction of the rotation axis Ax1, passes the flexible external gear 3 in the radial direction. .
  • one opening surface of the through hole H2 faces the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other opening surface of the through hole H2 becomes the same as that of the external teeth 31 of the flexible external gear 3 .
  • the outer peripheral surfaces of the meshing surfaces of the internal teeth 21 are open. Therefore, one end of the through hole H2 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other end is connected to the space between the outer teeth 31 and the inner teeth 21 . Therefore, the space between the external teeth 31 and the internal teeth 21 communicates with the gap X1 between the outer ring 421 and the flexible external gear 3 via the through hole H2. Therefore, the lubricant Lb1 in the space between the external teeth 31 and the internal teeth 21 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H2.
  • the external teeth 31 and the internal teeth 21 constitute a positive displacement pump such as a vane pump, and squeeze out the lubricant Lb1 to the gap X1 side with sufficient pressure, so that sufficient lubricant Lb1 can be easily supplied into the gap X1.
  • the (second) through hole H2 is located between the center of the external teeth 31 and the end on the opening surface 35 side in a direction parallel to the rotation axis Ax1 (tooth line direction D1 ).
  • the (second) through hole H2 is arranged at the dedendum 312 and the dedendum 313 of the dedendum 313 of the external teeth 31 .
  • the through holes H1 and H2 may be provided on both the outer ring 421 and the external teeth 31 of the flexible external gear 3 .
  • the lubricant Lb1 in the space between the outer ring 421 and the inner ring 422 of the bearing 42 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1.
  • the lubricant Lb1 in the space between the external teeth 31 and the internal teeth 21 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through-hole H2. Therefore, the lubricant Lb1 can be supplied to the gap X1 from both sides (inside and outside) in the radial direction.
  • the (first) through hole H1 and the (second) through hole H2 preferably have different positions in the tooth line direction D1 of the inner teeth 21 .
  • the harmonic gear device 1 it is not an essential configuration of the harmonic gear device 1 to perform tooth profile modification on the internal teeth 21 and the external teeth 31 .
  • at least one of the internal teeth 21 and the external teeth 31 may not be profiled.
  • ensuring a distance equal to or greater than a predetermined value in the radial direction between the tracks of the plurality of rolling elements 423 and the opening surface of the (first) through-hole H1 provided in the outer ring 421 is very important for the harmonic gear device 1 .
  • Language is not a necessary structure. That is, in a state where the rolling elements 423 are present at positions corresponding to the through-holes H1, no gap is generated between the opening surface of the through-holes H1 and the rolling elements 423, and the rolling elements 423 may close the through-holes H1. .
  • each rolling element 423 is not an essential structure of the harmonic gear device 1, and each rolling element 423 may be supported by two points, for example.
  • the harmonic gear device 1 is not limited to the cup type described in the first embodiment, and may be, for example, a top hat type, a ring type, a differential type, a flat type (doughnut type), or a shield type.
  • a top-hat type harmonic gear device 1 as illustrated in FIG. 10 has a cylindrical flexible external gear 3 similar to the cup type. It has an open face 35 . That is, the hat-shaped flexible external gear 3 has a flange portion at one end of the rotation axis Ax1 and has an opening surface 35 at an end opposite to the flange portion. Even the top-hat-shaped flexible external gear 3 has external teeth 31 at the end on the opening surface 35 side, into which the wave generator 4 is fitted.
  • the structure of the actuator 100 is not limited to the structure described in Embodiment 1, and can be appropriately changed.
  • the connection structure between the input unit 103 and the cam 41 is not limited to a spline connection structure, and a cross joint or the like may be used.
  • the Oldham joint as the connection structure between the input part 103 and the cam 41, the eccentricity between the input side rotation axis Ax1 and the wave generator 4 (cam 41) can be canceled out, and thus the rigid internal gear 2 and the flexible external gear 3 can be cancelled. of eccentricity.
  • the cam 41 does not have to be movable along the rotation axis Ax1 relative to the input portion 103 .
  • the application examples of the harmonic gear device 1, the actuator 100, and the robot joint device 130 of this embodiment are not limited to the above-mentioned horizontal articulated robot, and may be industrial robots or industrial robots other than the horizontal articulated robot, for example. Use other than robots etc. Examples of industrial robots other than horizontal articulated robots include vertical articulated robots, parallel link robots, and the like. Examples of robots other than industrial use include home-use robots, care-use robots, and medical-use robots.
  • the bearing 42 is not limited to a deep groove ball bearing, For example, an angular contact ball bearing etc. may be sufficient.
  • the bearing 42 is not limited to a ball bearing, and may be a cylindrical roller bearing, a needle roller bearing, or a tapered roller bearing such as a roller bearing such as a "roller" in which the rolling elements 423 are not ball-shaped. Even with the rolling elements 423 other than the ball shape (spherical body shape), a pressure difference is generated by the rolling elements 423 rolling, whereby the rolling elements 423 function as a pump structure.
  • each component of the harmonic gear device 1 , the actuator 100 , or the robot joint device 130 is not limited to metal, and may be resin such as engineering plastic, for example.
  • the lubricant Lb1 is not limited to a liquid substance such as lubricating oil (oil), but may be a gel-like substance such as grease.
  • the number and arrangement of the through holes H1 are not limited to those described in the first embodiment.
  • one, two, or four through holes H1 may be provided.
  • the interval P1 of the plurality of through-holes H1 may be a multiple of the interval P2 of the plurality of rolling elements 423, and the plurality of through-holes H1 are not necessarily arranged at equal intervals. .
  • the chemical conversion treatment coating C1 is not limited to a phosphate coating formed by a chemical conversion treatment using phosphate, and may be another chemical conversion treatment coating.
  • the plurality of grooves 303 may be formed not only on the inner peripheral surface 301 of the flexible external gear 3 but also on the outer peripheral surface 424 of the wave generator 4 .
  • the peeled chemical conversion treatment film C10 may also be held in the groove on the outer peripheral surface 424 side of the wave generator 4 .
  • FIG. 13A is a schematic diagram showing the surface state of the inner peripheral surface 301 of the flexible external gear 3 and the outer peripheral surface 424 of the wave generator 4 (outer ring 421) in the A1-A1 line section of FIG.
  • FIG. 13B is an enlarged schematic view of the region Z1 in FIG. 13A .
  • the chemical conversion coatings C1 and C2 are provided on both the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 .
  • the chemical conversion coatings C1 and C2 include the "first chemical conversion coating” provided on the target surface S1 constituted by the inner peripheral surface 301 of the flexible external gear 3, and the "first chemical conversion coating” provided on The “second chemical conversion treatment coating” of the target surface S2 constituted by the outer peripheral surface 424 of the wave generator 4 .
  • the (second) chemical conversion treatment coating C2 is also constituted by a phosphate coating as an example, similarly to the (first) chemical conversion treatment coating C1 .
  • both the chemical conversion coating C1 of the inner peripheral surface 301 of the flexible external gear 3 and the chemical conversion coating C2 of the outer peripheral surface 424 of the wave generator 4 can hold (wet) the lubricant Lb1. Therefore, the lubricant Lb1 is more likely to remain in the contact portion of the flexible external gear 3 with the wave generator 4, and more sufficient lubricant Lb1 can be maintained at the contact portion.
  • the compositions of the chemical conversion coatings C1 and C2 are the same on the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 . That is, both the (first) chemical conversion treatment coating C1 and the (second) chemical conversion treatment coating C2 are phosphate coatings and are composed of coatings with the same composition. Therefore, it is difficult for the (first) chemical conversion treatment film C1 and the (second) chemical conversion treatment film C2 to have a variation in peeling amount, and both the chemical conversion treatment films C1 and C2 are easily peeled off in a balanced manner.
  • a "groove” may be formed on the target surface S2 constituted by the outer peripheral surface 424 of the wave generator 4, similarly to the groove 303 on the target surface S1 (inner peripheral surface 301 of the flexible external gear 3).
  • the peeled chemical conversion treatment coatings C1 and C2 can also be held in the grooves of the target surface S2.
  • the chemical conversion treatment coating C2 may be provided only on the outer peripheral surface 424 of the wave generator 4 among the outer peripheral surface 424 of the wave generator 4 and the inner peripheral surface 301 of the flexible external gear 3 .
  • Embodiment 2 can be applied in combination with the configuration (including modifications) described in Embodiment 1 as appropriate.
  • the harmonic gear unit (1, 1A, 1B) of the first aspect includes a rigid internal gear (2), a flexible external gear (3), and a wave generator (4).
  • the rigid internal gear (2) is an annular member having internal teeth (21).
  • the flexible external gear (3) is an annular member having external teeth (31) and arranged inside the rigid internal gear (2).
  • the wave generator (4) has a non-circular cam (41) that is driven to rotate around the rotation axis (Ax1), and a bearing (42) mounted on the outside of the cam (41).
  • the wave generator (4) is arranged inside the flexible external gear (3), and causes the flexible external gear (3) to bend.
  • the flexible external gear (3) is deformed with the rotation of the cam (41), and a part of the external teeth (31) meshes with a part of the internal teeth (21) , and make the flexible external gear (3) relatively rotate relative to the rigid internal gear (2) according to the tooth number difference between the flexible external gear (3) and the rigid internal gear (2).
  • a chemical conversion treatment film ( C1, C2, C10).
  • occurrence of fretting wear is suppressed by preventing "lubricant depletion” in which the lubricant (Lb1) is insufficient or exhausted at the contact portion of the wave generator (4) and the flexible external gear (3).
  • the conversion coatings (C1, C2, C10) can maintain sufficient lubricant (Lb1) at the contact portion of the flexible external gear (3) and the wave generator (4).
  • the surface of the contact portion of the flexible external gear (3) with the wave generator (4) is covered with the lubricant (Lb1), and the occurrence of fretting wear is suppressed. Therefore, troubles caused by fretting wear between the wave generator (4) and the flexible external gear (3) are less likely to occur, and it is possible to provide a harmonic gear device (1, 1A, 1B) that is less likely to cause a decrease in reliability. .
  • the target surface (S1, S2) is formed with a film (C1, C2, C10) capable of holding at least the chemical conversion treatment. ) slot (303).
  • the chemical conversion treatment coatings (C1, C2, C10) can be left in the wave generator ( 4) Between the flexible external gear (3).
  • the slots (303) include first slots (303a) and second slots (303b) intersecting each other.
  • the lubricant (Lb1) easily spreads over a relatively large range in the gap (X1) between the wave generator (4) and the flexible external gear (3).
  • the thickness (L2) of the chemical conversion treatment film (C1, C2, C10) is smaller than that of the groove ( 303) has a small depth (L1).
  • the chemical conversion treatment coatings (C1, C2, C10) are accommodated in the tank (303), and the chemical conversion treatment coatings (C1, C2, C10) are hardly exposed from the tank (303).
  • the hardness ratio of the chemical conversion treatment film (C1, C2, C10) is The hardness of the parts other than the chemical conversion treatment coating (C1, C2, C10) among the surfaces (S1, S2) is low.
  • the chemical conversion treatment film (C1, C2, C10) sandwiched between the two serves as a buffer, which can suppress the flexibility. Damage to the external gear (3) and the wave generator (4).
  • the chemical conversion treatment film (C1, C2, C10) is configured to maintain Lubricant (Lb1).
  • the lubricant (Lb1) is likely to remain in the contact portion between the flexible external gear (3) and the wave generator (4), and sufficient lubricant (Lb1) can be maintained at the contact portion.
  • the chemical conversion treatment film (C1, C2, C10) is arranged on the wave generator Both the outer peripheral surface (424) of (4) and the inner peripheral surface (301) of the flexible external gear (3).
  • the chemical conversion treatment coatings (C1, C2, C10) have the same composition.
  • the chemical conversion treatment film (C1) on the side of the flexible external gear (3) and the chemical conversion treatment film (C2) on the side of the wave generator (4) are less likely to produce deviations in the peeling amount, and the chemical conversion treatment Both the films (C1, C2) are easily peeled off in a balanced manner.
  • the outer ring (421) of the bearing (42) and the flexible external gear At least one of the external teeth (31) in (3) is provided with a through hole (H1, H2), the through hole (H1, H2) passes through in the radial direction, and is connected with the outer ring (421) and the flexible
  • the gap (X1) between the external gears (3) is connected.
  • the lubricant (Lb1) can be supplied through the gap (X1) between the outer ring (421) and the flexible external gear (3) through the through holes (H1, H2). Accordingly, occurrence of fretting wear can be further suppressed by preventing "lubricant depletion" in which the lubricant (Lb1) is insufficient or exhausted at the contact portion between the outer ring (421) and the flexible external gear (3).
  • the robot joint device (130) of the ninth aspect includes the harmonic gear device (1, 1A, 1B) of any one of the first to eighth aspects, and a first member (131) fixed to the rigid internal gear (2). ), and a second member (132) fixed to the flexible external gear (3).
  • the structures of the second to eighth solutions are not necessary for the harmonic gear device (1, 1A, 1B) and can be appropriately omitted.

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Abstract

提供了一种不易产生可靠性降低的谐波齿轮装置以及机器人用关节装置。谐波齿轮装置（1）包括刚性内齿轮（2）、挠性外齿轮（3）及波发生器（4），波发生器（4）具有以旋转轴（Ax1）为中心被驱动旋转的非圆形状的凸轮（41）、以及装配在凸轮（41）的外侧的轴承（42），伴随于凸轮（41）的旋转而使挠性外齿轮（3）变形，使外齿（31）的一部分与内齿（21）的一部分啮合，并使挠性外齿轮（3）按照其与刚性内齿轮（2）的齿数差相对于刚性内齿轮（2）进行相对旋转，在由波发生器（4）的外周面（424）和挠性外齿轮（3）的内周面（301）中的至少一方构成的对象面（S1）设有化学转化处理覆膜（C1）。

Description

谐波齿轮装置以及机器人用关节装置
相关申请的交叉引用
本申请基于申请号为特愿2021-210602、申请日为2021年12月24日的日本专利申请提出，并要求该日本专利申请的优先权，该日本专利申请的全部内容在此引入本申请作为参考。
技术领域
本公开实施例一般性地涉及谐波齿轮装置以及机器人用关节装置，更详细而言，涉及包括刚性内齿轮、挠性外齿轮以及波发生器的谐波齿轮装置以及机器人用关节装置。
背景技术
在专利文献1中公开了通过氮化处理来进行谐波齿轮装置(挠曲啮合式齿轮装置)中的挠性外齿轮的表面处理。
谐波齿轮装置具有环状的刚性内齿轮、配置于其内侧的杯形的挠性外齿轮、以及嵌入至其内侧的椭圆形的波发生器。挠性外齿轮包括圆筒状的躯体部、以及在躯体部的外周面形成的外齿。挠性外齿轮在波发生器的作用下挠曲成椭圆形，挠性外齿轮的位于椭圆形状的长轴方向的两端的外齿部分与形成于刚性内齿轮的内周面的内齿啮合。
当波发生器利用马达等旋转时，两齿轮的啮合位置在圆周方向上移动，在两齿轮之间产生与内齿和外齿的齿数差(2N(N为正整数))相应的相对旋转。在此，当刚性内齿轮侧被固定时，可从挠性外齿轮侧得到与两齿轮的齿数差相应地被大幅减速了的旋转输出。
现有技术文献
专利文献
专利文献1：日本特开2001-59153号公报
发明内容
发明要解决的课题
然而，在上述那样的谐波齿轮装置中，由于嵌入至挠性外齿轮的内侧的波发生器旋转，因此特别是如果长期使用，则在挠性外齿轮与波发生器的接触部位可能产生微动磨损(fretting wear)。若产生微动磨损，则有可能导致表面的粗糙、由磨损粉引起的生锈、以及由磨损粉进入波发生器的内侧引起的波发生器(的轴承)的损伤等，从而影响谐波齿轮装置的可靠性。
本公开实施例是鉴于上述情况而完成的，其目的在于提供不易产生可靠性的降低的谐波齿轮装置以及机器人用关节装置。
用于解决课题的方案
本公开实施例的一方案的谐波齿轮装置包括刚性内齿轮、挠性外齿轮以及波发生器。所述刚性内齿轮是具有内齿的环状的部件。所述挠性外齿轮是具有外齿，且配置于所述刚性内齿轮的内侧的环状的部件。所述波发生器具有以旋转轴为中心被驱动旋转的非圆形状的凸轮，以及装配于所述凸轮的外侧的轴承。所述波发生器配置于所述挠性外齿轮的内侧，并使所述挠性外齿轮产生挠曲。在所述谐波齿轮装置中，伴随于所述凸轮的旋转而使所述挠性外齿轮变形，使所述外齿的一部分与所述内齿的一部分啮合，并使所述挠性外齿轮按照所述挠性外齿轮与所述刚性内齿轮的齿数差相对于所述刚性内齿轮进行相对旋转。在由所述波发生器的外周面和所述挠性外齿轮的内周面中的至少一方构成的对象面设置有化学转化处理覆膜。
本公开实施例的一方案的机器人用关节装置包括所述谐波齿轮装置、固定于所述刚性内齿轮的第一构件、以及固定于所述挠性外齿轮的第二构件。
发明效果
根据本公开实施例，具有可以提供能够不易产生可靠性的降低的谐波齿轮装置以及机器人用关节装置这样的优点。
附图说明
图1A是示出实施方式一的谐波齿轮装置的概要结构的剖视图。
图1B是图1A的区域Z1的放大图。
图2A是从旋转轴的输入侧观察上述谐波齿轮装置时的概要图。
图2B是图2A的区域Z1的放大图。
图3A是从旋转轴的输出侧观察上述谐波齿轮装置时的概要分解立体图。
图3B是从旋转轴的输入侧观察上述谐波齿轮装置时的概要分解立体图。
图4是示出包括上述谐波齿轮装置在内的致动器的概要结构的剖视图。
图5是对相当于图1B的范围将主要部分放大后的概要剖视图。
图6是上述谐波齿轮装置的从轴承侧观察时的挠性外齿轮的内周面的示意图。
图7A是表示图6的A1-A1线剖面中的挠性外齿轮的内周面以及波发生器的外周面的表面状态的概要图。
图7B是将图7A的区域Z1放大后的概要图。
图8A是表示图6的A2-A2线剖面中的挠性外齿轮的内周面以及波发生器的外周面的表面状态的概要图。
图8B是将图8A的区域Z1放大后的概要图。
图9是示意性地表示上述谐波齿轮装置的对象面的状态的变化的概要图，是表示图7的区域Z1中的外齿的表面状态的概要图，是表示图7的区域Z2中的外齿的表面状态的概要图。
图10是用于示出上述谐波齿轮装置的锥面的长轴侧以及短轴侧的动作的概念性的说明图。
图11是示出使用上述谐波齿轮装置的机器人的一例的剖视图。
图12A是示出实施方式一的变形例的谐波齿轮装置的概要结构的剖视图。
图12B是图12A的区域Z1的放大图。
图13A是关于实施方式二的谐波齿轮装置，表示图6的A1-A1线剖面中的挠性外齿轮的内周面以及波发生器的外周面的表面状态的概要图。
图13B是将图13A的区域Z1放大后的概要图。
具体实施方式
(实施方式一)
(1)概要
以下，参照图1A至图5对本实施方式的谐波齿轮装置1的概要进行说明。本公开实施例中参照的附图均是示意性的图，图中的各结构要件的大小以及厚度各自的比并不一定反映实际的尺寸比。例如，图2A至图3B中的内齿21及外齿31的齿形、尺寸及齿数等都只不过是为了说明而示意性地表示，并不旨在限定于图示的形状。
本实施方式的谐波齿轮装置1是包括刚性内齿轮2、挠性外齿轮3及波发生器4的齿轮装置。该谐波齿轮装置1中，在环状的刚性内齿轮2的内侧配置环状的挠性外齿轮3，而且在挠性外齿轮3的内侧配置波发生器4。波发生器4通过使挠性外齿轮3挠曲成非圆形状，从而使挠性外齿轮3的外齿31相对于刚性内齿轮2的内齿21局部地啮合。当波发生器4旋转时，内齿21与外齿31的啮合位置在刚性内齿轮2的圆周方向上移动，在两齿轮(刚性内齿轮2以及挠性外齿轮3)之间产生使挠性外齿轮3按照挠性外齿轮3与刚性内齿轮2的齿数差进行的相对旋转。在此，如果刚性内齿轮2 被固定，则挠性外齿轮3会伴随于两齿轮的相对旋转而旋转。其结果是，可从挠性外齿轮3得到与两齿轮的齿数差相应地以比较高的减速比被减速了的旋转输出。
另外，使挠性外齿轮3产生挠曲的波发生器4具有以输入侧的旋转轴Ax1(参照图1A)为中心被驱动旋转的非圆形状的凸轮41、以及轴承42。轴承42配置在凸轮41的外周面411与挠性外齿轮3的内周面301之间。轴承42的内圈422固定于凸轮41的外周面411，轴承42的外圈421经由滚珠状的滚动体423被凸轮41按压而弹性变形。在此，滚动体423进行滚动，由此外圈421能够相对于内圈422相对旋转，因此，当非圆形状的凸轮41旋转时，内圈422的旋转不会向外圈421传递，而在被凸轮41按压的挠性外齿轮3的外齿31产生波动运动。通过产生外齿31的波动运动，从而如上述那样内齿21与外齿31的啮合位置沿刚性内齿轮2的圆周方向上移动，并在挠性外齿轮3与刚性内齿轮2之间产生相对旋转。
总之，在这种谐波齿轮装置1中，具有轴承42的波发生器4一边使挠性外齿轮3挠曲，一边利用内齿21与外齿31的啮合实现动力的传递。
在这种谐波齿轮装置1中，特别是如果长期使用，伴随于嵌入至挠性外齿轮3的内侧的波发生器4的旋转，在挠性外齿轮3与波发生器4的接触部位可能产生微动磨损(fretting wear)。若产生微动磨损，则有可能导致表面的粗糙、由磨损粉引起的生锈、以及由磨损粉进入波发生器4的内侧引起的波发生器4(的轴承42)的损伤等，而影响谐波齿轮装置1的可靠性。
作为一例，当由于表面的粗糙或锈的产生而阻碍挠性外齿轮3的变形跟随性时，波发生器4的旋转需要多余的能量，导致动力传递效率的降低、或由施加于轴承42的载荷增加而造成的寿命缩短等。另外，当磨损粉进入轴承42时，以由磨损粉向轴承42的外圈421或内圈422与滚动体423之间的咬入而形成的压痕为起点，在外圈421、内圈422以及滚动体423中的 任一个的表面可能产生损伤。由于这样的损伤(表面起点型的剥落)导致谐波齿轮装置1的品质及特性等的劣化，结果导致谐波齿轮装置1的可靠性降低。因此，本实施方式的谐波齿轮装置1利用以下的结构抑制微动磨损的产生，而不易产生可靠性降低。
即，本实施方式的谐波齿轮装置1如图1A至图3B所示，包括具有内齿21的环状的刚性内齿轮2、具有外齿31的环状的挠性外齿轮3、以及波发生器4。挠性外齿轮3配置于刚性内齿轮2的内侧。波发生器4配置于挠性外齿轮3的内侧，并使挠性外齿轮3产生挠曲。波发生器4具有以旋转轴Ax1为中心被驱动旋转的非圆形状的凸轮41、以及装配于凸轮41的外侧的轴承42。在谐波齿轮装置1中，伴随于凸轮41的旋转而使挠性外齿轮3变形，使外齿31的一部分与内齿21的一部分啮合，并使挠性外齿轮3按照挠性外齿轮3与刚性内齿轮2的齿数差相对于刚性内齿轮2进行相对旋转。在此，如图5所示，在由波发生器4的外周面424和挠性外齿轮3的内周面301中的至少一方构成的对象面S1设置有化学转化处理覆膜C1。
根据该方案，挠性外齿轮3中与波发生器4(轴承42)接触的接触部位成为容易维持被润滑剂Lb1(参照图4)覆盖的状态的表面状态。总之，由于在挠性外齿轮3与波发生器4的接触部位设置有化学转化处理覆膜C1，因此通过使润滑剂Lb1保持(浸润)于化学转化处理覆膜C1，该部位容易维持被润滑剂Lb1覆盖的状态。
也就是说，在本实施方式的谐波齿轮装置1中，通过防止在外圈421与挠性外齿轮3的接触部位处润滑剂Lb1不足或枯竭的“润滑剂耗尽”，来抑制微动磨损的产生。进一步而言，作为一例，将磷酸盐覆膜等比较软的化学转化处理覆膜C1设置于波发生器4的外周面424以及/或挠性外齿轮3的内周面301，由此，在挠性外齿轮3与波发生器4的接触部位维持充分的润滑剂Lb1。其结果是，挠性外齿轮3中与轴承42(的外圈421)接触的接触部位的表面成为被润滑剂Lb1覆盖的状态，微动磨损的产生受到抑 制。因此，在本实施方式的谐波齿轮装置1中，不易产生由轴承42(的外圈421)与挠性外齿轮3之间的微动磨损引起的不良状况，而能够提供不易产生可靠性降低的谐波齿轮装置1。并且，本实施方式的谐波齿轮装置1特别是在长期使用时也不易产生可靠性的降低，因此，还进一步带来了谐波齿轮装置1的传递效率的改善、长寿命化以及高性能化。
然而，化学转化处理覆膜C1设置于波发生器4(的轴承42)的外周面424和挠性外齿轮3的内周面301中的至少一方即可。在本公开实施例中，在对分别设置于波发生器4和挠性外齿轮3的化学转化处理覆膜C1进行区分的情况下，将设置于挠性外齿轮3的化学转化处理覆膜C1称为“第一化学转化处理覆膜”，并将设置于波发生器4的化学转化处理覆膜C2(参照图13A)称为“第二化学转化处理覆膜”。在本实施方式中，作为一例，化学转化处理覆膜C1仅设置于波发生器4的外周面424和挠性外齿轮3的内周面301中的挠性外齿轮3的内周面301。换言之，在本实施方式中，化学转化处理覆膜C1包括设置于由挠性外齿轮3的内周面301构成的对象面S1的“第一化学转化处理覆膜”。另一方面，对于波发生器4侧的化学转化处理覆膜(第二化学转化处理覆膜)，将在实施方式二中进行说明。
另外，本实施方式的谐波齿轮装置1如图4所示，与驱动源101以及输出部102一起构成致动器100。换言之，本实施方式的致动器100包括谐波齿轮装置1、驱动源101及输出部102。驱动源101使波发生器4旋转。输出部102将刚性内齿轮2和挠性外齿轮3中的任一方的旋转力作为输出而取出。
另外，本实施方式的谐波齿轮装置1如图4所示，与第一构件131以及第二构件132一起构成机器人用关节装置130。换言之，本实施方式的机器人用关节装置130包括谐波齿轮装置1、第一构件131及第二构件132。第一构件131固定于刚性内齿轮2。第二构件132固定于挠性外齿轮3。由此，通过在谐波齿轮装置1中挠性外齿轮3与刚性内齿轮2之间产生相对 旋转，使得机器人用关节装置130中的第一构件131与第二构件132相对旋转。
根据本实施方式的机器人用关节装置130，具有谐波齿轮装置1的不易产生可靠性降低这样的优点。
(2)定义
本公开实施例中提及“环状”是指至少在俯视时在内侧形成包围的空间(区域)的圈(环)那样的形状，不限于在俯视时为正圆的圆形状(圆环状)，也可以是例如椭圆形状以及多边形状等。而且，例如，即使是如杯状的挠性外齿轮3那样具有底部322的形状，只要其躯体部321为环状，就称为“环状”的挠性外齿轮3。
本公开实施例中提及的“刚性”是指在对物体施加外力且物体欲变形时，物体抵抗该变形的性质。换言之，具有刚性的物体即使施加外力也难以变形。另外，本公开实施例中提及的“挠性”是指在对物体施加了外力时，物体弹性变形的(挠曲)性质。换言之，具有挠性的物体在被施加了外力时容易弹性变形。因此，“刚性”与”挠性”是相反的意思。
特别是，在本公开实施例中，刚性内齿轮2的“刚性”与挠性外齿轮3的“挠性”以相对的意思来使用。即，刚性内齿轮2的“刚性”是指至少与挠性外齿轮3相比，相对地刚性内齿轮2具有较高的刚性，也就是说即使刚性内齿轮2被施加外力也难以变形。同样，挠性外齿轮3的“挠性”是指至少与刚性内齿轮2相比，相对地挠性外齿轮3具有较高的挠性，也就是说在被施加了外力时容易弹性变形。
另外，在本公开实施例中，有时将旋转轴Ax1的一侧(图1A的右侧)称为“输入侧”，并将旋转轴Ax1的另一侧(图1A的左侧)称为“输出侧”。也就是说，在图1A的例子中，挠性外齿轮3在旋转轴Ax1的“输入侧”具有开口面35。但是，“输入侧”及“输出侧”只不过是为了说明而附加的标签，并不旨在限定从谐波齿轮装置1观察时的输入以及输出的 位置关系。
本公开实施例中提及的“非圆形状”是指不是正圆的形状，包括例如椭圆形状以及长圆形状等。在本实施方式中，作为一例，波发生器4的非圆形状的凸轮41为椭圆形状。也就是说，在本实施方式中，波发生器4使挠性外齿轮3挠曲成椭圆形状。
本公开实施例中提及的“椭圆形状”是指正圆被压扁而相互正交的长轴与短轴的交点位于中心的这样的形状整体，不限于由一平面上的距某两个定点的距离的和为恒定的点的集合构成的曲线即数学上的“椭圆”。也就是说，本实施方式中的凸轮41既可以是如数学上的“椭圆”那样由一平面上的距某两个定点的距离的和为恒定的点的集合构成的曲线状，也可以不是数学上的“椭圆”而是长圆那样的椭圆形状。如上所述，本公开实施例中参照的附图均是示意性的图，图中的各结构要件的大小及厚度各自的比不一定反映实际的尺寸比。因此，例如在图2A中，使波发生器4的凸轮41的形状为稍微夸大的椭圆形状，但并不旨在限定实际的凸轮41的形状。
本公开实施例中提及的“旋转轴”是指作为旋转体的旋转运动的中心的假想的轴(直线)。也就是说，旋转轴Ax1是不伴有实体的假想轴。波发生器4以旋转轴Ax1为中心进行旋转运动。
本公开实施例中提及的“内齿”以及“外齿”分别不是指单体的“齿”，而是指多个“齿”的集合(组)。也就是说，刚性内齿轮2的内齿21由在刚性内齿轮2的内周面形成的多个齿的集合构成。同样，挠性外齿轮3的外齿31由在挠性外齿轮3的外周面形成的多个齿的集合构成。
本公开实施例中提及的“化学转化处理覆膜”是通过化学转化处理(chemical treatment)形成的覆膜，是通过对某对象面实施化学转化处理而以包覆该对象面的方式形成的膜(覆膜)。“化学转化处理”是表面处理的形式之一，是通过使处理剂作用于材料(特别是金属)的表面而引起化学反应，从而施加耐腐蚀性以及与涂料的亲和性等与原来的材料不同的性 质的处理。因此，对化学转化处理覆膜C1赋予与实施化学转化处理前的对象面S1不同的性质。作为化学转化处理的具体例，有利用电化学实施的氧化或硫化、利用化学药品实施的氧化或还元、以及利用铝、铬或锌等的氧化物或磷酸盐实施的覆膜形成等。例如，在利用以铁为对象的磷酸盐进行的化学转化处理中，在将铁浸渍于处理液时，铁溶解，铁附近的溶液pH上升，由此，溶液中的金属离子成为不溶性的盐并析出，从而形成覆盖铁的化学转化处理覆膜。
本公开实施例中提及的“平行”是指，除了一平面上的两条直线延长到任何位置也不相交的情况，即，两者之间的角度严格地为0度(或180度)的情况之外，两者之间的角度处于相对于0度收敛在几度(例如小于10度)程度的误差范围内的关系。同样，本公开实施例中提及的“正交”是指，除了两者之间的角度严格地以90度相交的情况之外，两者之间的角度处于相对于90度收敛在几度(例如小于10度)程度的误差范围内的关系。
(3)构成
以下，参照图1A至图4对本实施方式的谐波齿轮装置1、致动器100以及机器人用关节装置130的详细结构进行说明。
图1A是示出谐波齿轮装置1的概要结构的剖视图，图1B是图1A的区域Z1的放大图。图2A是从旋转轴Ax1的输入侧(图1A的右侧)观察谐波齿轮装置1时的概要图，图2B是图2A的区域Z1的放大图。图3A是从旋转轴Ax1的输出侧(图1A的左侧)观察谐波齿轮装置1时的概要分解立体图。图3B是从旋转轴Ax1的输入侧观察谐波齿轮装置1时的概要分解立体图。图4是示出包括谐波齿轮装置1在内的致动器100以及机器人用关节装置130的概要结构的剖视图。
(3.1)谐波齿轮装置
本实施方式的谐波齿轮装置1如上所述，包括刚性内齿轮2、挠性外齿 轮3及波发生器4。在本实施方式中，作为谐波齿轮装置1的结构要件的刚性内齿轮2、挠性外齿轮3以及波发生器4的材质为不锈钢、铸铁、机械结构用碳钢、铬钼钢，磷青铜或铝青铜等金属。这里所说的金属包括实施了氮化处理等表面处理的金属。
另外，在本实施方式中，作为谐波齿轮装置1的一例，例示杯型的谐波齿轮装置。也就是说，在本实施方式的谐波齿轮装置1中使用形成为杯状的挠性外齿轮3。波发生器4以收容在杯状的挠性外齿轮3内的方式与挠性外齿轮3组合。
另外，在本实施方式中，作为一例，在将刚性内齿轮2固定于输入侧壳体111(参照图4)以及输出侧壳体112(参照图4)等的状态下使用谐波齿轮装置1。由此，伴随于刚性内齿轮2与挠性外齿轮3的相对旋转，挠性外齿轮3相对于固定构件(输入侧壳体111等)进行相对旋转。
而且，在本实施方式中，在将谐波齿轮装置1用于致动器100的情况下，通过对波发生器4施加作为输入的旋转力，从而从挠性外齿轮3取出作为输出的旋转力。也就是说，谐波齿轮装置1以将波发生器4的旋转作为输入旋转并将挠性外齿轮3的旋转作为输出旋转的方式动作。由此，在谐波齿轮装置1中，能够得到相对于输入旋转以比较高的减速比减速的输出旋转。
而且，在本实施方式的谐波齿轮装置1中，输入侧的旋转轴Ax1和输出侧的旋转轴Ax2位于同一直线上。换言之，输入侧的旋转轴Ax1与输出侧的旋转轴Ax2是同轴的。在此，输入侧的旋转轴Ax1是被施加输入旋转的波发生器4的旋转中心，输出侧的旋转轴Ax1是产生输出旋转的挠性外齿轮3的旋转中心。也就是说，在谐波齿轮装置1中，在同轴上能够得到相对于输入旋转以比较高的减速比减速的输出旋转。
刚性内齿轮2也称为圆花键(circular spline)且是具有内齿21的环状的部件。在本实施方式中，刚性内齿轮2具有至少内周面在俯视时为正圆 的圆环状。内齿21在圆环状的刚性内齿轮2的内周面沿着刚性内齿轮2的圆周方向形成。构成内齿21的多个齿全部为同一形状，且在刚性内齿轮2的内周面中的圆周方向的整个区域等间距地设置。也就是说，内齿21的节圆在俯视时为正圆。另外，刚性内齿轮2在旋转轴Ax1的方向上具有规定的厚度。内齿21均形成在刚性内齿轮2的厚度方向的全长上。内齿21的齿线均与旋转轴Ax1平行。
如上所述，刚性内齿轮2固定于输入侧壳体111(参照图4)以及输出侧壳体112(参照图4)等。因此，在刚性内齿轮2形成有固定用的多个固定孔22(参照图3A以及图3B)。
挠性外齿轮3也称为柔性花键(flex spline)且是具有外齿31的环状的部件。在本实施方式中，挠性外齿轮3是由比较薄的金属弹性体(金属板)形成为杯状的部件。也就是说，挠性外齿轮3通过其厚度比较小(薄)而具有挠性。挠性外齿轮3具有杯状的主体部32。主体部32具有躯体部321以及底部322。躯体部321在挠性外齿轮3未产生弹性变形的状态下，具有至少内周面301在俯视时为正圆的圆筒状。躯体部321的中心轴与旋转轴Ax1一致。底部322配置于躯体部321的一方的开口面，且具有在俯视时为正圆的圆盘状。底部322配置于躯体部321的一对开口面中的、旋转轴Ax1的输出侧的开口面。根据上述内容，主体部32在躯体部321以及底部322的整体上实现了向旋转轴Ax1的输入侧开放的有底的圆筒状即杯状的形状。换言之，在挠性外齿轮3的旋转轴Ax1的方向上的与底部322相反的一侧的端面形成有开口面35。也就是说，挠性外齿轮3是在齿线方向D1的一方(在此为旋转轴Ax1的输入侧)具有开口面35的筒状。在本实施方式中，躯体部321以及底部322由一个金属构件形成为一体，由此实现无缝的主体部32。
在此，将非圆形状(椭圆形状)的波发生器4相对于挠性外齿轮3嵌入至躯体部321的内侧，从而组合波发生器4。由此，挠性外齿轮3通过从 内侧朝向外侧受到来自波发生器4的径向方向(与旋转轴Ax1正交的方向)的外力，而弹性变形为非圆形状。在本实施方式中，通过将波发生器4组合于挠性外齿轮3，从而挠性外齿轮3的躯体部321弹性变形为椭圆形状。也就是说，挠性外齿轮3未产生弹性变形的状态是指未将波发生器4组合于挠性外齿轮3的状态。相反，挠性外齿轮3产生了弹性变形的状态是指将波发生器4组合于挠性外齿轮3的状态。
更详细而言，波发生器4嵌入至躯体部321的内周面301中与底部322相反的一侧(旋转轴Ax1的输入侧)的端部。换言之，波发生器4嵌入至挠性外齿轮3的躯体部321中的、旋转轴Ax1的方向上的开口面35侧的端部。因此，在挠性外齿轮3产生了弹性变形的状态下，与底部322侧的端部相比，挠性外齿轮3在旋转轴Ax1的方向上的开口面35侧的端部更大地变形，成为更接近椭圆形状的形状。根据这样的旋转轴Ax1的方向上的变形量的差异，在挠性外齿轮3产生了弹性变形的状态下，挠性外齿轮3的躯体部321的内周面301包括相对于旋转轴Ax1倾斜的锥面302(参照图9)。
另外，在躯体部321的外周面中的至少与底部322相反的一侧(旋转轴Ax1的输入侧)的端部处，外齿31沿着躯体部321的圆周方向形成。换言之，外齿31设置于挠性外齿轮3的躯体部321中的至少旋转轴Ax1的方向上的开口面35侧的端部。构成外齿31的多个齿全部为同一形状，且在挠性外齿轮3的外周面中的圆周方向的整个区域等间距地设置。也就是说，外齿31的节圆在挠性外齿轮3未产生弹性变形的状态下，在俯视时正圆。外齿31仅形成在距躯体部321的开口面35侧(旋转轴Ax1的输入侧)的端缘恒定宽度的范围内。具体而言，在躯体部321中的旋转轴Ax1的方向上至少供波发生器4嵌入的部分(开口面35侧的端部)，在外周面形成有外齿31。外齿31的齿线均与旋转轴Ax1平行。
总之，在本实施方式的谐波齿轮装置1中，刚性内齿轮2的内齿21以及挠性外齿轮3的外齿31中任一个的齿线均与旋转轴Ax1平行。因此，在 本实施方式中，“齿线方向D1”是与旋转轴Ax1平行的方向。并且，内齿21的齿线方向D1的尺寸是内齿21的齿宽，同样，外齿31的齿线方向D1的尺寸是外齿31的齿宽，因此，齿线方向D1与齿宽方向意思相同。
在本实施方式中，如上所述，将挠性外齿轮3的旋转作为输出旋转取出。因此，在挠性外齿轮3安装有致动器100的输出部102(参照图4)。在挠性外齿轮3的底部322形成有用于安装作为输出部102的轴的多个安装孔33。而且，在底部322的中央部形成有透孔34。底部322中的透孔34的周围比底部322的其他部位厚。
这样构成的挠性外齿轮3配置于刚性内齿轮2的内侧。在此，挠性外齿轮3以仅躯体部321的外周面中的与底部322相反的一侧(旋转轴Ax1的输入侧)的端部***至刚性内齿轮2的内侧的方式，与刚性内齿轮2组合。也就是说，挠性外齿轮3的躯体部321中的在旋转轴Ax1的方向上供波发生器4嵌入的部分(开口面35侧的端部)***至刚性内齿轮2的内侧。在此，在挠性外齿轮3的外周面形成有外齿31，在刚性内齿轮2的内周面形成有内齿21。因此，在将挠性外齿轮3配置于刚性内齿轮2的内侧的状态下，外齿31与内齿21相互对置。
在此，刚性内齿轮2中的内齿21的齿数比挠性外齿轮3的外齿31的齿数多2N(N为正整数)。在本实施方式中，作为一例，N为“1”，挠性外齿轮3的(外齿31的)齿数比刚性内齿轮2的(内齿21的)齿数多“2”。这样的挠性外齿轮3与刚性内齿轮2的齿数差规定谐波齿轮装置1中输出旋转相对于输入旋转的减速比。
在此，在本实施方式中，作为一例，如图1A以及图1B所示，以外齿31的齿线方向D1的中心与内齿21的齿线方向D1的中心相对的方式，来设定旋转轴Ax1的方向上的挠性外齿轮3与刚性内齿轮2的相对位置。也就是说，对于挠性外齿轮3的外齿31和刚性内齿轮2的内齿21而言，齿线方向D1上的中心的位置对准旋转轴Ax1的方向的同一位置。另外，在 本实施方式中，外齿31的齿线方向D1的尺寸(齿宽)比内齿21的齿线方向D1的尺寸(齿宽)大。因此，在与旋转轴Ax1平行的方向上，内齿21收纳在外齿31的齿线的范围内。换言之，外齿31相对于内齿21向齿线方向D1的至少一方突出。在本实施方式中，外齿31相对于内齿21向齿线方向D1的双方(旋转轴Ax1的输入侧以及输出侧)突出。
在此，在挠性外齿轮3未产生弹性变形的状态(未将波发生器4组合于挠性外齿轮3的状态)下，描绘正圆的外齿31的节圆设定为比同样描绘正圆的内齿21的节圆小一圈。也就是说，在挠性外齿轮3未产生弹性变形的状态下，外齿31与内齿21通过隔着间隙对置而没有相互啮合。
另一方面，在挠性外齿轮3产生了弹性变形的状态(将波发生器4组合于挠性外齿轮3的状态)下，由于躯体部321挠曲成椭圆形状(非圆形状)，因此挠性外齿轮3的外齿31相对于刚性内齿轮2的内齿21局部地啮合。也就是说，挠性外齿轮3的躯体部321(的至少开口面35侧的端部)弹性变形为椭圆形状，由此，如图2A所示，位于椭圆形状的长轴方向的两端的外齿31与内齿21啮合。换言之，描绘椭圆的外齿31的节圆的长径与描绘正圆的内齿21的节圆的直径一致，描绘椭圆的外齿31的节圆的短径比描绘正圆的内齿21的节圆的直径小。这样，当挠性外齿轮3弹性变形时，构成外齿31的多个齿中的一部分齿与构成内齿21的多个齿中的一部分齿啮合。结果是，在谐波齿轮装置1中，能够使外齿31的一部分与内齿21的一部分啮合。
波发生器4也称为波产生器(wave generator)，是使挠性外齿轮3产生挠曲而使挠性外齿轮3的外齿31产生波动运动的部件。在本实施方式中，波发生器4是在俯视时外周形状为非圆形状、具体而言为椭圆形状的部件。
波发生器4具有非圆形状(在此为椭圆形状)的凸轮41和在凸轮41的外周装配的轴承42。也就是说，相对于轴承42，在轴承42的内圈422的内侧嵌入有非圆形状(椭圆形状)的凸轮41，从而组合凸轮41。由此， 轴承42通过从内圈422的内侧朝向外侧受到来自凸轮41的径向方向(与旋转轴Ax1正交的方向)的外力，而弹性变形为非圆形状。也就是说，轴承42未产生弹性变形的状态是指未将凸轮41组合于轴承42的状态。相反，轴承42产生了弹性变形的状态是指将凸轮41组合于轴承42的状态。
凸轮41是以输入侧的旋转轴Ax1为中心被驱动旋转的非圆形状(在此为椭圆形状)的部件。凸轮41具有外周面411(参照图1B)，且至少外周面411由在俯视时为椭圆形状的金属板构成。凸轮41在旋转轴Ax1的方向(即齿线方向D1)上具有规定的厚度。由此，凸轮41具有与刚性内齿轮2相同程度的刚性。但是，凸轮41的厚度比刚性内齿轮2的厚度小(薄)。在本实施方式中，如上所述，将波发生器4的旋转作为输入旋转。因此，在波发生器4安装有致动器100的输入部103(参照图4)。在波发生器4的凸轮41的中央部形成有用于安装作为输入部103的轴的凸轮孔43。
轴承42具有外圈421、内圈422及多个滚动体423。在本实施方式中，作为一例，轴承42使用球体状的滚珠作为滚动体423，由深沟球轴承构成。
外圈421以及内圈422均是环状的部件。外圈421以及内圈422均是由比较薄的金属弹性体(金属板)形成为环状的部件。也就是说，外圈421以及内圈422分别通过厚度比较小(薄)而具有挠性。在本实施方式中，外圈421以及内圈422在轴承42未产生弹性变形的状态(未将凸轮41组合于轴承42的状态)下，均具有在俯视时为正圆的圆环状。内圈422比外圈421小一圈并配置于外圈421的内侧。在此，外圈421的内径比内圈422的外径大，因此在外圈421的内周面425与内圈422的外周面之间产生间隙。
多个滚动体423配置在外圈421与内圈422之间的间隙。多个滚动体423在外圈421的圆周方向上排列配置。多个滚动体423全部为同一形状的金属球(滚珠)，且在外圈421的圆周方向的整个区域等间距地设置。在此，轴承42还具有保持器，多个滚动体423由保持器保持在外圈421与内 圈422之间，但未特别地进行图示。
另外，在本实施方式中，作为一例，外圈421以及内圈422的宽度方向(与旋转轴Ax1平行的方向)的尺寸与凸轮41的厚度相同。也就是说，外圈421以及内圈422的宽度方向的尺寸比刚性内齿轮2的厚度小。
通过这样的轴承42的结构，凸轮41与轴承42组合，由此轴承42的内圈422固定于凸轮41，内圈422弹性变形为仿效与凸轮41的外周形状的椭圆形状。此时，轴承42的外圈421经由多个滚动体423被内圈422按压而弹性变形为椭圆形状。因此，轴承42的外圈421及内圈422均弹性变形为椭圆形状。这样，在轴承42产生了弹性变形的状态(将凸轮41组合于轴承42的状态)下，外圈421及内圈422形成相互为相似形状的椭圆形状。
即使在轴承42产生了弹性变形的状态下，由于在外圈421与内圈422之间夹有多个滚动体423，因此外圈421与内圈422之间的间隙在外圈421的整周上被维持为大致恒定。然后，在该状态下，外圈421与内圈422之间的多个滚动体423进行滚动，由此，外圈421能够相对于内圈422相对旋转。因此，在轴承42产生了弹性变形的状态下，当凸轮41以旋转轴Ax1为中心旋转时，凸轮41的旋转不会传递至外圈421、内圈422的弹性变形经由多个滚动体423传递至外圈421。也就是说，在波发生器4中，当凸轮41以旋转轴Ax1为中心旋转时，外圈421以由外圈421所仿照的椭圆形状的长轴以旋转轴Ax1为中心旋转的方式弹性变形。因此，作为波发生器4整体而言，从旋转轴Ax1的输入侧观察时的、呈椭圆形状的波发生器4的外周形状以其长轴以旋转轴Ax1为中心旋转的方式，伴随于凸轮41的旋转而变化。
这样构成的波发生器4配置在挠性外齿轮3的内侧。在此，挠性外齿轮3以仅躯体部321的内周面301中与底部322相反的一侧(开口面35侧)的端部与波发生器4嵌合的方式，与波发生器4组合。此时，波发生器4的轴承42配置于凸轮41的外周面411与挠性外齿轮3的内周面301之间。 在此，轴承42未产生弹性变形的状态(未将凸轮41组合于轴承42的状态)下的外圈421的外径与同样未产生弹性变形的状态下的挠性外齿轮3(躯体部321)的内径相同。因此，波发生器4中的外圈421的外周面424(参照图5)在轴承42的圆周方向的整周上与挠性外齿轮3的内周面301相接。因此，在挠性外齿轮3产生了弹性变形的状态(将波发生器4组合于挠性外齿轮3的状态)下，躯体部321挠曲为椭圆形状(非圆形状)。在该状态下，挠性外齿轮3相对于轴承42的外圈421被固定。
但是，由于挠性外齿轮3与波发生器4仅嵌合，因此，挠性外齿轮3和轴承42的外圈421并不是完全固定。因此，如上所述，在挠性外齿轮3与嵌入至挠性外齿轮3的内侧的外圈421之间会产生微小的间隙X1(参照图1B)。严格来说，由于外圈421的外周面424的直径比挠性外齿轮3的内周面301的直径稍小，因此，外圈421与挠性外齿轮3之间的间隙X1不会被完全填埋，至少局部地产生间隙X1。而且，也存在这样的间隙X1的影响，波发生器4的凸轮41旋转且外圈421以及挠性外齿轮3弹性变形，伴随于此，在外圈421与挠性外齿轮3之间可能产生相对旋转。该相对旋转例如是凸轮41的转速的几千分之一或几百分之一程度的旋转，但由于这样的相对旋转而使得外圈421与挠性外齿轮3相对地相互摩擦的现象是微动磨损的一个成因。
本公开实施例中提及的“间隙”表示在两个物体的对置面间可能产生的空间，即使该两个物体不分离在两者之间也可能产生间隙。也就是说，即使两个物体接触，在该两个物体之间也可能稍微产生间隙。在挠性外齿轮3与嵌入至挠性外齿轮3的内侧的外圈421之间，在相互对置的外圈421的外周面424与挠性外齿轮3的内周面301之间产生间隙X1。但是，基本上由于外圈421的外周面424与挠性外齿轮3的内周面301接触，因此在两者间不会产生大的间隙X1。因此，外圈421与挠性外齿轮3之间的间隙X1是在外圈421的外周面424与挠性外齿轮3的内周面301之间可局部产 生的微小间隙。作为一例，在外圈421的外周面424和挠性外齿轮3的内周面301产生润滑剂Lb1能够浸透的程度的微观的间隙X1。
在上述结构的在谐波齿轮装置1中，如图2A所示，通过挠性外齿轮3的躯体部321挠曲为椭圆形状(非圆形状)，挠性外齿轮3的外齿31相对于刚性内齿轮2的内齿21局部地啮合。也就是说，通过挠性外齿轮3(的躯体部321)弹性变形为椭圆形状，从而与该椭圆形状的长轴方向的两端相当的两个部位的外齿31相对于内齿21啮合。而且，当凸轮41以旋转轴Ax1为中心旋转时，凸轮41的旋转不会传递至外圈421以及挠性外齿轮3，内圈422的弹性变形经由多个滚动体423传递至外圈421以及挠性外齿轮3。因此，从旋转轴Ax1的输入侧观察时的呈椭圆形状的挠性外齿轮3的外周形状以其长轴以旋转轴Ax1为中心旋转的方式，伴随于凸轮41的旋转而变化。
其结果是，在形成于挠性外齿轮3的外周面的外齿31产生波动运动。通过产生外齿31的波动运动，内齿21与外齿31的啮合位置在刚性内齿轮2的圆周方向上移动，并在挠性外齿轮3与刚性内齿轮2之间产生相对旋转。也就是说，外齿31在挠性外齿轮3(的躯体部321)所形成的椭圆形状的长轴方向的两端处与内齿21啮合，因此，通过该椭圆形状的长轴以旋转轴Ax1为中心旋转，从而内齿21与外齿31的啮合位置移动。这样，在本实施方式的谐波齿轮装置1中，伴随于以旋转轴Ax1为中心的波发生器4的旋转而使挠性外齿轮3变形，使外齿31的一部分与内齿21的一部分啮合，并使挠性外齿轮3按照挠性外齿轮3与刚性内齿轮2的齿数差进行旋转。
然而，谐波齿轮装置1中，如上所述，挠性外齿轮3与刚性内齿轮2的齿数差规定谐波齿轮装置1中的输出旋转相对于输入旋转的减速比。也就是说，在将刚性内齿轮2的齿数设为“V1”，并将挠性外齿轮3的齿数设为“V2”的情况下，减速比R1由下述式1表示。
R1＝V2/(V1-V2)···(式1)
总之，刚性内齿轮2与挠性外齿轮3的齿数差(V1-V2)越小，则减速比R1越大。作为一例，当刚性内齿轮2的齿数V1为“72”，挠性外齿轮3的齿数V2为“70”，它们的齿数差(V1-V2)为“2”时，根据上述式1，减速比R1为“35”。在该情况下，当从旋转轴Ax1的输入侧观察时，若凸轮41以旋转轴Ax1为中心顺时针旋转1周(360度)，则挠性外齿轮3以旋转轴Ax1为中心逆时针旋转与齿数差“2”相应的量(也就是10.3度)。
根据本实施方式的谐波齿轮装置1，这样高的减速比R1能够通过一级齿轮(刚性内齿轮2以及挠性外齿轮3)的组合来实现。
另外，谐波齿轮装置1至少包括刚性内齿轮2、挠性外齿轮3及波发生器4即可，例如，也可以是进一步包括“(3.2)致动器”的栏中所说明的花键衬套113等作为结构要件。
(3.2)致动器
接下来，对本实施方式的致动器100的结构更详细地进行说明。
本实施方式的致动器100如图4所示，包括本实施方式的谐波齿轮装置1、驱动源101及输出部102。也就是说，致动器100除了构成谐波齿轮装置1的刚性内齿轮2、挠性外齿轮3以及波发生器4之外，还包括驱动源101以及输出部102。另外，致动器100除了谐波齿轮装置1、驱动源101以及输出部102之外，还包括输入部103、输入侧壳体111、输出侧壳体112、花键衬套113、间隔件114、第一止挡件115、第二止挡件116以及安装板117。另外，在本实施方式中，致动器100还包括输入侧轴承118、119、输入侧油封120、输出侧轴承121、122以及输出侧油封123。
在本实施方式中，致动器100中的驱动源101、输入侧油封120以及输出侧油封123以外的部件的材质是不锈钢、铸铁、机械结构用碳钢、铬钼钢、磷青铜或铝青铜等金属。
驱动源101是马达(电动机)等动力的产生源。由驱动源101产生的动力向谐波齿轮装置1中的波发生器4的凸轮41传递。具体而言，驱动源101与作为输入部103的轴连接，由驱动源101产生的动力经由输入部103传递至凸轮41。由此，驱动源101能够使凸轮41旋转。
输出部102是沿着输出侧的旋转轴Ax2配置的圆柱状的轴。作为输出部102的轴的中心轴与旋转轴Ax2一致。输出部102被输出侧壳体112保持为能够以旋转轴Ax2为中心旋转。输出部102固定于挠性外齿轮3中的主体部32的底部322，并以旋转轴Ax2为中心与挠性外齿轮3一起旋转。也就是说，输出部102将挠性外齿轮3的旋转力作为输出而取出。
输入部103是沿着输入侧的旋转轴Ax1配置的圆柱状的轴。作为输入部103的轴的中心轴与旋转轴Ax1一致。输入部103被输入侧壳体111保持为能够以旋转轴Ax1为中心旋转。输入部103安装于波发生器4的凸轮41，并以旋转轴Ax1为中心与凸轮41一起旋转。也就是说，输入部103将由驱动源101产生的动力(旋转力)作为输入向凸轮41传递。在本实施方式中，如上所述，输入侧的旋转轴Ax1与输出侧的旋转轴Ax2处于同一直线上，因此，输入部103与输出部102位于同轴上。
输入侧壳体111经由输入侧轴承118、119将输入部103保持为输入部103能够旋转。一对输入侧轴承118、119沿着旋转轴Ax1隔开间隔地排列配置。在本实施方式中，作为输入部103的轴贯穿通过输入侧壳体111，且输入部103的前端部从输入侧壳体111中的旋转轴Ax1的输入侧的端面(图4的右端面)突出。输入侧壳体111的旋转轴Ax1的输入侧的端面中的与输入部103之间的间隙被输入侧油封120堵塞。
输出侧壳体112经由输出侧轴承121、122将输出部102保持为输出部102能够旋转。一对输出侧轴承121、122沿着旋转轴Ax2隔开间隔地排列配置。在本实施方式中，作为输出部102的轴贯穿通过输出侧壳体112，且输出部102的前端部从输出侧壳体112中的旋转轴Ax1的输出侧的端面(图 4的左端面)突出。输出侧壳体112的旋转轴Ax1的输出侧的端面中的与输出部102之间的间隙被输出侧油封123堵塞。
在此，如图4所示，输入侧壳体111与输出侧壳体112在从平行于旋转轴Ax1的方向、也就是齿线方向D1的两侧夹着谐波齿轮装置1的刚性内齿轮2的状态下相互结合。具体而言，输入侧壳体111相对于刚性内齿轮2从旋转轴Ax1的输入侧接触，输出侧壳体112相对于刚性内齿轮2从旋转轴Ax1的输出侧接触。这样，输入侧壳体111在与输出侧壳体112之间夹着刚性内齿轮2的状态下，穿过多个固定孔22，而相对于输出侧壳体112被螺钉(螺栓)紧固固定。由此，输入侧壳体111、输出侧壳体112以及刚性内齿轮2相互结合而一体化。换言之，刚性内齿轮2与输入侧壳体111以及输出侧壳体112一起构成致动器100的外轮廓。
花键衬套113是用于将作为输入部103的轴相对于凸轮41进行连结的筒状的部件。花键衬套113***至形成于凸轮41的凸轮孔43，作为输入部103的轴以贯穿通过花键衬套113的方式***至花键衬套113。在此，花键衬套113在以旋转轴Ax1为中心的旋转方向上相对于凸轮41以及输入部103双方的移动被限制，且花键衬套113在与旋转轴Ax1平行的方向上至少能够相对于输入部103移动。由此，作为输入部103与凸轮41的连结结构，实现了花键连结结构。因此，凸轮41能够相对于输入部103沿着旋转轴Ax1移动，并以旋转轴Ax1为中心与输入部103一起旋转。
间隔件114是填埋花键衬套113与凸轮41的间隙的部件。第一止挡件115是防止花键衬套113从凸轮41脱落的部件。第一止挡件115例如由E形环构成，且在从花键衬套113中的凸轮41观察时安装于旋转轴Ax1的输入侧的位置。第二止挡件116是防止输入部103从花键衬套113脱落的部件。第二止挡件116例如由E形环构成，且以相对于花键衬套113从旋转轴Ax1的输出侧接触的方式安装于输入部103。
安装板117是用于在挠性外齿轮3的底部322安装作为输出部102的 轴的部件。具体而言，安装板117在与输出部102的凸缘部之间夹着底部322中的透孔34的周围部分的状态下，穿过多个安装孔33，而相对于凸缘部被螺钉(螺栓)紧固固定。由此，在挠性外齿轮3的底部322固定作为输出部102的轴。
然而，在本实施方式中，在由输入侧壳体111、输出侧壳体112以及刚性内齿轮2构成的致动器100的外轮廓的内侧封入有润滑剂Lb1。也就是说，在由输入侧壳体111、输出侧壳体112以及刚性内齿轮2包围的空间内存在能够贮存液状或凝胶状的润滑剂Lb1的“润滑剂储存处”。
即，本实施方式的谐波齿轮装置1中，例如，在内齿21与外齿31的啮合部分、以及轴承42的外圈421与内圈422之间等，注入有液状或凝胶状的润滑剂Lb1。作为一例，润滑剂Lb1是液状的润滑油(油)。并且，在谐波齿轮装置1使用时，润滑剂Lb1也进入轴承42的外圈421(外周面424)与挠性外齿轮3之间的间隙X1。
在本实施方式中，作为一例，如图4所示，以润滑剂Lb1的液面位于比输出侧轴承121、122的下端更靠下方的方式，仅在致动器100的外轮廓的下部(铅垂方向的下部)贮存有润滑剂Lb1。因此，对于外齿31以及轴承42的外圈421等，在图4的状态下，仅旋转方向上的一部分浸渍于润滑剂Lb1。从该状态开始，当输出部102伴随于输入部103的旋转而旋转时，外圈421以及挠性外齿轮3也绕旋转轴Ax1旋转，其结果是，外齿31以及轴承42的外圈421等的旋转方向的整体浸渍于润滑剂Lb1。
(3.3)机器人用关节装置
接下来，对本实施方式的机器人用关节装置130的结构更详细地进行说明。
本实施方式的机器人用关节装置130如图4所示，包括本实施方式的谐波齿轮装置1、第一构件131及第二构件132。也就是说，机器人用关节装置130除了构成谐波齿轮装置1的刚性内齿轮2、挠性外齿轮3以及波发 生器4之外，包括第一构件131以及第二构件132。
第一构件131是固定于刚性内齿轮2的构件，第二构件132是固定于挠性外齿轮3的构件。因此，通过在谐波齿轮装置1中在挠性外齿轮3与刚性内齿轮2之间产生相对旋转，从而在第一构件131与第二构件132之间也产生相对旋转。这样，机器人用关节装置130经由谐波齿轮装置1构成将两个以上的构件(第一构件131以及第二构件132)以相互活动的状态连结(可动连结)时的结合部位。
在此，第一构件131以及第二构件132分别相对于刚性内齿轮2以及挠性外齿轮3直接或间接地固定即可。在图4的例子中，第一构件131通过与输出侧壳体112结合，而相对于刚性内齿轮2间接地结合(固定)。同样，第二构件132通过与输出部102结合，而相对于挠性外齿轮3间接地结合(固定)。
在这样构成的机器人用关节装置130中，例如，当利用由驱动源101产生的动力使得波发生器4的凸轮41旋转时，在挠性外齿轮3与刚性内齿轮2之间产生相对旋转。然后，伴随于挠性外齿轮3与刚性内齿轮2的相对旋转，在第一构件131与第二构件132之间以输出侧的旋转轴Ax2(与输入侧的旋转轴Ax1同轴)为中心产生相对旋转。结果是，根据机器人用关节装置130，能够驱动经由谐波齿轮装置1而连结的第一构件131以及第二构件132，以使它们以旋转轴Ax1为中心相对旋转。由此，机器人用关节装置130能够实现各种机器人的关节机构。
(4)各部的详细结构
接下来，参照图1A至图2B、图5至图9对本实施方式的谐波齿轮装置1的各部的更详细的结构更详细地进行说明。
图5是对相当于图1B的范围将主要部分放大后的概要剖视图。图6是从图5的轴承42侧观察时的挠性外齿轮3的内周面301的示意图。在图6中，实际上将圆筒状的内周面301沿谐波齿轮装置1的周向D2展开，并作 为相互正交的齿线方向D1以及周向D2的俯视图进行表示。这里所说的“周向D2”是以旋转轴Ax1为中心的圆周方向。在图6中，用想像线(双点划线)示出轴承42的外圈421以及贯通孔H1。图7A是表示图6的A1-A1线剖面中的挠性外齿轮3的内周面301以及波发生器4(的外圈421)的外周面424的表面状态的概要图，图7B是将图7A的区域Z1放大后的概要图。图7A由于是沿着谐波齿轮装置1的齿线方向D1而得的剖面，因此相当于图5的区域Z1的放大图。图8A是表示图6的A2-A2线剖面中的挠性外齿轮3的内周面301以及波发生器4(的外圈421)的外周面424的表面状态的概要图，图8B是将图8A的区域Z1放大后的概要图。图9是示意性地表示对象面S1(挠性外齿轮3的内周面301)的状态的变化的概要图。
(4.1)贯通孔
在本实施方式中，如图1A以及图1B所示，在轴承42的外圈421与挠性外齿轮3中的外齿31中的至少一方设置有贯通孔H1，该贯通孔H1沿着径向方向贯穿通过，并连结于外圈421与挠性外齿轮3之间的间隙X1。也就是说，轴承42的外圈421中的作为多个滚动体423的滚动面的内周面425(参照图5)、以及挠性外齿轮3的外齿31中的作为与内齿21的啮合面的外周面中的至少一方借助贯通孔H1与间隙X1连通。因此，能够通过贯通孔H1对外圈421与挠性外齿轮3之间的间隙X1供给润滑剂Lb1。
也就是说，本实施方式的谐波齿轮装置1通过设置贯通孔H1，而能够经由贯通孔H1对挠性外齿轮3与波发生器4的接触部位供给润滑剂Lb1，由此，在接触部位维持充分的润滑剂Lb1。其结果是，防止了“润滑剂耗尽”，外圈421与挠性外齿轮3的接触部位的表面成为被润滑剂Lb1覆盖的状态，微动磨损的产生受到抑制。因此，在本实施方式的谐波齿轮装置1中，不易产生由外圈421与挠性外齿轮3之间的微动磨损引起的不良状况，而能够提供不易产生可靠性降低的谐波齿轮装置1。
然而，贯通孔H1设置于外圈421和挠性外齿轮3中的外齿31中的至 少一方即可。在本公开实施例中，在对分别设置于外圈421和挠性外齿轮3中的外齿31的贯通孔H1进行区分的情况下，将设置于外圈421的贯通孔H1称为“第一贯通孔”，并将设置于挠性外齿轮3的外齿31的贯通孔H2(参照图12B)称为“第二贯通孔”。在本实施方式中，作为一例，贯通孔H1仅设置于外圈421和挠性外齿轮3中的外齿31中的外圈421一方。换言之，在本实施方式中，贯通孔H1包括设置于外圈421的“第一贯通孔”。另一方面，在“(8)变形例”中对挠性外齿轮3的外齿31侧的贯通孔H2(第二贯通孔)进行说明。
另外，本公开实施例中提及的“沿着径向方向贯穿通过”是指沿着径向方向、也就是与旋转轴Ax1正交的方向即径向贯穿通过。即，只要如本实施方式那样是设置于外圈421的贯通孔H1，则贯通孔H1贯穿通过外圈421的径向方向的两面即内周面425及外周面424之间即可，也可以相对于例如径向方向倾斜。
在此，首先参照图5以及图6对本实施方式中的贯通孔H1的形状以及尺寸进行说明。
设置于外圈421的贯通孔H1(第一贯通孔)沿着径向方向贯穿通过外圈421。由此，贯通孔H1的一方的开口面面向外圈421与挠性外齿轮3之间的间隙X1，贯通孔H1的另一方的开口面在外圈421的内周面425开口。因此，贯通孔H1的一端与外圈421与挠性外齿轮3之间的间隙X1相连，另一端与外圈421的内周面425与内圈422的外周面之间的空间相连。因此，配置有多个滚动体423的外圈421的内周面425与内圈422的外周面之间的空间经由贯通孔H1，而与外圈421与挠性外齿轮3之间的间隙X1连通。
另外，贯通孔H1是与径向方向正交的剖面形状为圆形(正圆)状的圆孔。在本实施方式中，作为一例，贯通孔H1的中心线与径向方向平行。也就是说，贯通孔H1是从外圈421的内周面425到外周面424沿径向方向笔 直地延伸的孔。而且，贯通孔H1的与径向方向正交的剖面形状在贯通孔H1的径向方向上的全长上为同一形状。也就是说，在贯通孔H1的内部形成圆柱状的空间。
在此，贯通孔H1的径φ1(参照图5)是多个滚动体423各自的径φ2(参照图5)的0.1倍以下或1.0mm以下中的较小的一方。这里所说的贯通孔H1的径φ1在贯通孔H1的剖面形状为正圆的情况下为其直径，在贯通孔H1的剖面形状为非圆形状(例如椭圆形状)的情况下是指其短轴方向的尺寸。在本实施方式中，作为一例，贯通孔H1的径φ1为滚动体423的径φ2的0.1倍以下且1.0mm以下。根据这样的贯通孔H1的径φ1，能够通过贯通孔而高效地对H1外圈421与挠性外齿轮3之间的间隙X1供给润滑剂Lb1。
根据以上说明的结构，外圈421与内圈422之间的空间经由贯通孔H1而与外圈421与挠性外齿轮3之间的间隙X1相连，因此，外圈421与内圈422之间的润滑剂Lb1通过贯通孔H1而向间隙X1供给。在图5中，用虚线箭头示意性地表示贯通孔H1内的润滑剂Lb1的流动。特别是，当轴承42动作而使得多个滚动体423旋转时，滚动体423作为泵发挥功能，而能够将外圈421与内圈422之间的润滑剂Lb1经由贯通孔H1送入间隙X1。其结果是，防止在外圈421与挠性外齿轮3的接触部位处润滑剂Lb1不足或枯竭的“润滑剂耗尽”，从而容易抑制微动磨损的产生。
总之，本实施方式的谐波齿轮装置1包括泵结构，该泵结构在挠性外齿轮3相对于刚性内齿轮2相对旋转时，通过贯通孔H1对间隙X1供给润滑剂Lb1。在挠性外齿轮3相对于刚性内齿轮2相对旋转时，轴承42的多个滚动体423在外圈421的周向上滚动，因此，如上述那样多个滚动体423作为泵发挥功能。也就是说，多个滚动体423构成泵结构。特别是，在本实施方式中，滚动体423在外圈421与内圈422之间的空间内滚动，由此，提高外圈421与内圈422之间的空间内的压力，因此，处于外圈421与内 圈422之间的润滑剂Lb1通过贯通孔H1而被挤出至间隙X1侧。这样，滚动体423构成叶片泵那样的容积型的泵，以充分的压力将润滑剂Lb1挤出至间隙X1侧，因此，容易向间隙X1内供给充分的润滑剂Lb1。
另外，贯通孔H1中的、外圈421的内周面425侧的开口面在形成于外圈421的内周面425的滚动槽426的底面开口。也就是说，在外圈421的内周面425的宽度方向(齿线方向D1)的中央部形成有在外圈421的整周上沿周向延伸的滚动槽426，多个滚动体423沿着滚动槽426滚动。在内圈422的外周面也形成有同样的滚动槽427，多个滚动体423以被夹入的方式保持在这些相互对置的滚动槽426、427之间。并且，贯通孔H1以在外圈421的滚动槽426的底面开口的方式配置在外圈421的宽度方向(齿线方向D1)上的形成有滚动槽426的范围内。
而且，在本实施方式中，贯通孔H1在与旋转轴Ax1平行的方向(齿线方向D1)上，配置在与多个滚动体423的中心相同的位置。换言之，贯通孔H1配置在外圈421的宽度方向(齿线方向D1)上的滚动槽426的中心。根据该结构，多个滚动体423的中心在贯通孔H1的开口面上通过，由此，在滚动体423旋转时，滚动体423作为泵高效地起作用，而容易经由贯通孔H1向间隙X1送入润滑剂Lb1。而且，可知外圈421与挠性外齿轮3主要在外圈421的宽度方向(齿线方向D1)的两端部进行接触。因此，贯通孔H1形成于外圈421的宽度方向(齿线方向D1)上的中心，由此，在外圈421与挠性外齿轮3的接触时，不易产生由贯通孔H1引起的外圈421的强度的降低。
在此，如图5所示，滚动槽426、427的与外圈421的周向正交的剖面形状形成为圆弧状。并且，滚动槽426、427的剖面形状中的圆弧的曲率比多个滚动体423各自的曲率大。换言之，滚动槽426、427的剖面形状中的圆弧的曲率半径比滚动体423的曲率半径小。因此，在多个滚动体423以被夹入的方式保持在滚动槽426、427之间的状态下，在滚动槽426、427 的底面与各滚动体423的表面之间确保一定程度的间隙。也就是说，如图5所示，各滚动体423在合计四处被4点支承，该四处为外圈421中的滚动槽426的宽度方向(齿线方向D1)的两端缘和内圈422中的滚动槽427的宽度方向(齿线方向D1)的两端缘。但是，实际上在外圈421与内圈422之间相对地施加推力方向(与旋转轴Ax1平行的方向)的载荷，因此，滚动体423被成为相互斜对关系的一对端缘支承。
因此，形成于滚动槽426的底面的贯通孔H1的开口面隔着上述间隙相对于滚动体423的表面对置。总之，在本实施方式中，在径向方向上，在多个滚动体423的轨道与设置于外圈421的(第一)贯通孔H1的外圈421的内周面425侧的开口面之间确保规定值以上的距离。也就是说，即使在滚动体423存在于与贯通孔H1对应的位置的状态下，也会在贯通孔H1的开口面与滚动体423之间确保规定值以上的距离(间隙)，从而贯通孔H1不会被滚动体423闭塞。由此，多个滚动体423即使在滚动时通过贯通孔H1上，多个滚动体423也不会与贯通孔H1的开口缘碰撞。其结果是，在滚动体423通过贯通孔H1上时，能够避免由滚动体423与贯通孔H1的开口缘碰撞而引起的冲击的产生，而容易保护外圈421以及滚动体423等免受冲击。
(4.2)贯通孔的数量以及配置
接下来，参照图2A以及图2B对本实施方式中的贯通孔H1的数量以及配置进行说明。
如图2A所示，贯通孔H1包括以在外圈421的周向上排列的方式设置于外圈421的多个第一贯通孔。在本实施方式中，贯通孔H1仅由设置于外圈421的第一贯通孔的构成，因此，多个贯通孔H1全部在外圈421的周向上排列配置。在本实施方式中，作为一例，在外圈421设置有3个贯通孔H1。因此，能够在外圈421的周向的多个部位(在本实施方式中为三处)通过贯通孔H1对外圈421与挠性外齿轮3之间的间隙X1供给润滑剂Lb1。 其结果是，与贯通孔H1在外圈421的周向上仅设置于一处的情况相比，容易在间隙X1中的外圈421的周向的整个区域的范围内供给润滑剂Lb1。
在此，如图2A所示，多个贯通孔H1(第一贯通孔)的间隔P1是多个滚动体423的间隔P2的倍数以外的值。在本实施方式中，作为一例，轴承42具有26个滚动体423，在外圈421具有3个贯通孔H1。并且，26个滚动体423以及3个贯通孔H1分别在外圈421的周向上等间距(等间隔)地设置。因此，3个贯通孔H1在外圈421的周向上的间隔P1成为120度(＝360度÷3)，26个滚动体423在外圈421的周向上的间隔P2成为13.85度(＝360度÷26)。在此，间隔P1是将在外圈421的周向上相邻的两个贯通孔H1的中心间距离用绕旋转轴Ax1的角度来表示的值，同样，间隔P2是将在外圈421的周向上相邻的两个滚动体423的中心间距离用绕旋转轴Ax1的角度来表示的值。在本实施方式中，为了即使这样对多个滚动体423的间隔P2(13.85度)乘以任何整数也不与多个贯通孔H1的间隔P1(120度)一致，将间隔P1设为不能被间隔P2整除那样的值。
由此，滚动体423不会同时存在于与全部贯通孔H1对应的位置。也就是说，在一个滚动体423位于与一个贯通孔H1对应的位置的状态下，滚动体423不会位于与其他两个贯通孔H1对应的位置。因此，在本实施方式的谐波齿轮装置1中，能够避免在多个滚动体423同时嵌入(或拔出)多个贯通孔H1时产生可能产生的比较大的冲击，而容易保护外圈421以及滚动体423等免受冲击。另外，与滚动体423同时位于全部贯通孔H1上的情况相比，基于滚动体423的滚动的泵作用也变得高效。
(4.3)挠性外齿轮的内周面的表面状态
接下来，参照图5至图9对本实施方式中的挠性外齿轮3的内周面301的表面状态进行说明。
在本实施方式中，如上所述，在由挠性外齿轮3的内周面301构成的对象面S1设置有化学转化处理覆膜C1。也就是说，通过对作为对象面S1 的挠性外齿轮3的内周面301实施化学转化处理，以包覆对象面S1(挠性外齿轮3的内周面301)的方式形成有化学转化处理覆膜C1。在本实施方式中，作为一例，化学转化处理覆膜C1是通过使用磷酸盐的化学转化处理(磷化(Parkerizing)处理)而形成的磷酸盐覆膜。
这种化学转化处理覆膜C1形成于对象面S1(本实施方式中为挠性外齿轮3的内周面301)的最外表面。化学转化处理覆膜C1是至少比对象面S1自身软的材质。也就是说，化学转化处理覆膜C1的硬度比对象面S1中除化学转化处理覆膜C1以外的部位的硬度低。在本实施方式中，特别是化学转化处理覆膜C1的表面硬度比挠性外齿轮3、以及波发生器4的轴承42的外圈421中任一个的表面硬度低(软)。因此，在挠性外齿轮3与波发生器4接触时，夹设在两者之间的化学转化处理覆膜C1成为缓冲部，能够抑制挠性外齿轮3以及波发生器4的损伤。具体地，在将挠性外齿轮3与波发生器4组装时或者谐波齿轮装置1使用初期等中，在挠性外齿轮3与波发生器4的接触部位，存在产生被称为“咬接”(galling)的局部粘付磨损的情况。根据本实施方式的谐波齿轮装置1，在产生这样的“咬接”的壳体中，通过比较低硬度的化学转化处理覆膜C1从对象面S1剥离(剥落)，从而挠性外齿轮3以及波发生器4的磨损的成长被抑制，有利于挠性外齿轮3以及波发生器4的保护。
另外，化学转化处理覆膜C1是在其形成过程(化学转化处理)中多个细孔(微观孔)的多孔质覆膜。因此，化学转化处理覆膜C1通过在这些多个细孔内引入润滑剂Lb1(参照图4)，而能够宛如海绵那样浸润润滑剂Lb1。然后，浸润于化学转化处理覆膜C1的润滑剂Lb1根据温度以及压力等适当地从化学转化处理覆膜C1渗出。这样，化学转化处理覆膜C1构成为能够保持润滑剂Lb1。因此，润滑剂容易留在Lb1挠性外齿轮3中的与波发生器4的接触部位，而能够在接触部位维持充分的润滑剂Lb1。
结果是，形成有化学转化处理覆膜C1的挠性外齿轮3的内周面301始 终由润滑剂Lb1维持润滑性能。由此，特别是能够使谐波齿轮装置1从静止状态向旋转状态转移时的起动效率动态效率化及高效率化。也就是说，根据本实施方式的谐波齿轮装置1，不仅能够抑制润滑剂耗尽，而且还能够实现例如谐波齿轮装置1在润滑剂Lb1容易固化的低温环境下的起动性的改善。
这样，化学转化处理覆膜C1例如与如类金刚石碳(DLC：Diamond-Like Carbon)那样自身为低摩擦的覆膜不同，其通过保持润滑剂Lb1来实现挠性外齿轮3与波发生器4之间的低摩擦的接触。因此，只要在挠性外齿轮3与波发生器4之间的间隙X1存在保持有润滑剂Lb1的状态下的化学转化处理覆膜C1，则能够利用润滑剂Lb1长期地实现挠性外齿轮3与波发生器4之间的低摩擦的接触。
然而，如上所述，有时化学转化处理覆膜C1例如由于“咬接”等磨损而从对象面S1剥离(剥落)。因此，在产生异物混入(污染(contamination))可成为问题的谐波齿轮装置1中，通常不能采用化学转化处理覆膜C1。在本实施方式中，为了将这样的化学转化处理覆膜C1不仅能够用于润滑(润滑剂Lb1的保持)而且能够应对异物混入的问题，而采用将剥离(剥落)后的化学转化处理覆膜C1留在(挠性外齿轮3与波发生器4之间的)间隙X1的下述结构。
即，在本实施方式的谐波齿轮装置1中，如图6所示，在对象面S1形成有至少能够保持化学转化处理覆膜C1的槽303。在本实施方式中，作为一例，在挠性外齿轮3中面向间隙X1的内周面301(对象面S1)形成有多条槽303。利用这些多条槽303在对象面S1形成凹凸。也就是说，对象面S1中的形成有槽303的部分成为相对凹陷的凹部，未形成有槽303的部分成为相对突出的凸部304(参照图7A)。通过形成这样的凹凸，对象面S1能够在作为凹部的槽303内保持(剥离后的)化学转化处理覆膜C1。
在此，利用在挠性外齿轮3的内周面301上因珩磨加工而产生加工痕 来形成槽303。即，在珩磨加工中，在研磨后的表面残留被称为“交叉阴影”的网眼状(斜纹状)的刻痕痕迹。作为一例，交叉阴影由以20度以上且60度以下的交叉角度交叉的多条第一槽303a以及多条第二槽303b构成，且形成于被珩磨加工的挠性外齿轮3的内周面301的大致整个区域。这些多条槽303在挠性外齿轮3的内周面301沿齿线方向D1和周向D2双方延伸，划分出俯视时呈菱形的多个凸部304。即，槽303包括相互交叉的第一槽303a以及第二槽303b。
通过在包括第一槽303a以及第二槽303b的这些多条槽303中保持(剥离后的)化学转化处理覆膜C1，润滑剂Lb1容易遍及间隙X1中的比较大的范围。也就是说，浸润于化学转化处理覆膜C1的润滑剂Lb1容易通过槽303内在间隙X1内向齿线方向D1以及周向D2双方扩散。特别是，如果是通过珩磨加工等而产生的微细的槽303，则可以期待润滑剂Lb1由于例如毛细管现象，而向齿线方向D1以及周向D2扩散。而且，由于是如交叉阴影那样包括相互交叉的第一槽303a以及第二槽303b的网眼状的槽303，因此润滑剂Lb1不仅容易向齿线方向D1和周向D2中的任一个方向扩散，而且容易向它们双方扩散。
更详细而言，例如像切削加工、磨削加工或珩磨加工那样，在利用对金属的晶粒进行剪切的加工而形成的对象面S1(本实施方式中为挠性外齿轮3的内周面301)，产生多条槽303。在该状态下，虽然在晶界产生鳞状的“毛刺”(凸部)，但通过对该状态的对象面S1进一步实施喷丸硬化加工或滚磨加工等，从而除去磨削加工痕迹。由此，如图7A至图8B所示，凹凸(槽303和凸部304)的边界部位成为带有圆角的形状，例如，在谐波齿轮装置1的使用初期不易产生“咬接”。在本实施方式中，对于这样实施了喷丸硬化加工或滚磨加工等后的对象面S1，以覆盖对象面S1的整个区域的方式形成化学转化处理覆膜C1。也就是说，化学转化处理覆膜C1如图7A至图8B所示，无缝地形成于槽303的内表面和凸部304的表面双方。
另外，在本实施方式中，如图7B所示，化学转化处理覆膜C1的厚度L2比槽303的深度L1小。这里所说的槽303的深度L1是凸部304到槽303的底部的距离。例如，槽303的深度L1为2μm以上且8μm以下，化学转化处理覆膜C1的厚度L2为1μm以上且5μm以下。作为一例，在槽303的深度L1为5μm的情况下，化学转化处理覆膜C1的厚度L2为3μm。这样，通过使化学转化处理覆膜C1的厚度L2比槽303的深度L1小，整个化学转化处理覆膜C1的厚度部分收纳在槽303内，而抑制波发生器4的外周面424与形成在槽303内的化学转化处理覆膜C1接触。
而且，在本实施方式中，化学转化处理覆膜C1的厚度L2比在将波发生器4组合于除去了化学转化处理覆膜C1的状态下的挠性外齿轮3时在挠性外齿轮3与波发生器4之间产生的间隙小。也就是说，化学转化处理覆膜C1的厚度L2比图9的状态P11下的挠性外齿轮3与波发生器4之间的距离小。由此，即使将波发生器4组合于在内周面301(对象面S1)形成有化学转化处理覆膜C1的状态下的挠性外齿轮3，化学转化处理覆膜C1也不易在压缩的作用下损坏。
并且，挠性外齿轮3的内周面301的表面状态伴随于谐波齿轮装置1的使用而如图9所示那样变化。在图9中，示出化学转化处理覆膜C1形成前的状态P11、化学转化处理覆膜C1形成后且谐波齿轮装置1使用开始前的状态P12、化学转化处理覆膜C1局部磨损的状态P13、以及化学转化处理覆膜C1进一步磨损的状态P14。
从图9可以明确的是，在谐波齿轮装置1的使用开始前(状态P12)，化学转化处理覆膜C1均匀地设置于对象面S1(本实施方式中为挠性外齿轮3的内周面301)中的槽303和凸部304双方。另一方面，当谐波齿轮装置1被驱动时，如上所述，波发生器4的凸轮41旋转而使外圈421以及挠性外齿轮3弹性变形，伴随于此，在外圈421与挠性外齿轮3之间可能产生相对旋转。该相对旋转例如是凸轮41的转速的几千分之一或几百分之一 程度的旋转，但由于这样的相对旋转，外圈421可能会与挠性外齿轮3相对地相互摩擦。而且，即使在与旋转轴Ax1平行的方向(齿线方向D1)上，在外圈421与挠性外齿轮3之间也可能产生相对滑动。其结果是，如图9的状态P13所示，首先，形成于凸部304的化学转化处理覆膜C1逐渐剥离(剥落)，剥离后的化学转化处理覆膜C10保持在槽303内。当进一步进行磨损时，如图9的状态P14所示，形成于凸部304的化学转化处理覆膜C1大致剥离(剥落)，剥离后的化学转化处理覆膜C10保持在槽303内。
这样，即使化学转化处理覆膜C1从对象面S1剥离，剥离后的化学转化处理覆膜C10通过保持在槽303内而留在波发生器4(外圈421)与挠性外齿轮3之间的间隙X1。因此，浸润于化学转化处理覆膜C1、C10的润滑剂Lb1适当渗出，由此，润滑剂Lb1容易留在挠性外齿轮3中的与波发生器4的接触部位，而能够在接触部位维持充分的润滑剂Lb1。
而且，化学转化处理覆膜C1的硬度如上述那样比挠性外齿轮3、以及波发生器4的轴承42的外圈421中任一个的硬度低。因此，即使剥离后的化学转化处理覆膜C1从挠性外齿轮3与波发生器4之间的间隙X1漏出(溢出)，由化学转化处理覆膜C1构成的异物也比较软质。总之，通过将在谐波齿轮装置1的使用初期容易产生的磨损所引起的异物作为从比较软质的化学转化处理覆膜C1出来的软质的异物，例如即使异物进入轴承42也能够抑制对轴承42的损害。结果是，抑制例如对轴承42的损害变大的硬质的异物的产生量等。
(4.4)表面硬度
接下来，对本实施方式中的内齿21以及外齿31的表面硬度进行说明。
在本实施方式中，如上所述，内齿21的表面硬度比外齿31的表面硬度低。也就是说，外齿31的表面的硬度比内齿21的表面硬度高(硬)。本公开实施例中提及的“硬度”表示物体的硬度的程度，金属的硬度例如用以一定的压力推压钢球而形成的凹陷的大小来表示。具体而言，作为金 属的硬度的一例，有洛氏硬度(HRC)、布氏硬度(HB)，维氏硬度(HV)或肖氏硬度(Hs)等。在本实施方式中，只要没有特别限定，则通过维氏硬度(HV)来表示硬度。作为提高(加硬)金属部件的硬度的方法，例如有合金化或热处理等。
在本实施方式中，挠性外齿轮3的外齿31的表面由高硬度且高韧性(强韧)的材质构成，刚性内齿轮2的内齿21由硬度比外齿31低地材质构成。在本实施方式中，作为一例，外齿31使用以下材料，即，对日本工业规格(JIS：Japanese Industrial Standards)中规定为“SNCM439”的镍铬钼钢实施了热处理(淬火回火)的材料。内齿21使用在日本工业规格(JIS)中规定为“FCD800-2”的球状石墨铸铁。
而且，与外齿31相比相对低硬度的内齿21的表面硬度优选为HV350以下。在本实施方式中，作为一例，内齿21的表面硬度在HV250以上且小于HV350的范围内选择。内齿21的表面硬度的下限值不限于HV250，例如也可以是HV150、HV160、HV170、HV180、HV190、HV200、HV210、HV220、HV230或HV240等也可以是。同样，内齿21的表面硬度的上限值不限于HV350，例如也可以是HV360、HV370、HV380、HV390、HV400、HV410、HV420、HV430、HV440或HV450等。
相对于此，与内齿21相比相对高硬度的外齿31的表面硬度优选为HV380以上。在本实施方式中，作为一例，外齿31的表面硬度在HV380以上且HV450以下的范围内选择。外齿31的表面硬度的下限值不限于HV380，例如也可以是HV280、HV290、HV300、HV310、HV320、HV330、HV340、HV350、HV360或HV370等。同样，内齿21的表面硬度的上限值不限于HV450，例如也可以是HV460、HV470、HV480、HV490、HV500、HV510、HV520、HV530，HV540或HV550等。
另外，在本实施方式中，内齿21的表面硬度与外齿31的表面硬度的差为HV50以上。也就是说，外齿31的表面硬度设定得比内齿21的表面 硬度高HV50以上。总之，例如，如果内齿21的表面硬度为HV350，则外齿31的表面硬度为HV400以上。另外，如果外齿31的表面硬度为HV380，则内齿21的表面硬度为HV330以下。内齿21的表面硬度与外齿31的表面硬度的差不限于HV50以上，例如也可以是HV20以上、HV30以上或HV40以上。而且，内齿21的表面硬度与外齿31的表面硬度的差优选较大，例如进一步优选为HV60以上、HV70以上、HV80以上、HV90以上或HV100以上。如果内齿21的表面硬度与外齿31的表面硬度的差设为HV100以上，则当内齿21的表面硬度为HV350时，外齿31的表面硬度为HV450以上。
如同上述，在本实施方式中，内齿21的表面硬度设定得比外齿31的表面硬度低。因此，在谐波齿轮装置1工作时，若内齿21与外齿31接触，则与外齿31相比，表面硬度相对低的内齿21积极地磨损。当表面硬度不同的两个部件(内齿21以及外齿31)接触时，相对软质的内齿21的磨损加剧，相对硬质的外齿31的磨损被抑制。也就是说，在谐波齿轮装置1的使用的初期阶段，内齿21的齿面适度地磨损，由此，内齿21与外齿31之间的真实接触面积扩大，面压降低，从而不易产生外齿31的磨损。并且，在如本实施方式那样内齿21的表面硬度为HV350以下的情况下，由于内齿21与外齿31的接触，即使因内齿21的缺损或磨损等产生异物，该异物也比较软质。总之，通过将在谐波齿轮装置1的使用初期容易产生的磨损所引起的异物作为从比较软质的内齿21出来的软质的异物，例如，即使异物进入轴承42也能够抑制对轴承42的损害。结果是，例如，抑制对轴承42的损害变大的硬质的异物的产生量等。特别是当内齿21的表面硬度与外齿31的表面硬度的差为如HV50以上那样的比较大的值时，上述效果显著。
而且，通过使用球状石墨铸铁作为内齿21的材料，在内齿21的初期磨损时，能够期待抑制内齿21与外齿31的齿面的烧结的效果。由此，能够得到内齿21与外齿31的啮合部位处的润滑效果，且能够提高谐波齿轮装置1中的动力传递效率。
内齿21以及外齿31的表面硬度并非必须用维氏硬度(HV)来规定，也可以用其他硬度、例如洛氏硬度(HRC)、布氏硬度(HB)或肖氏硬度(Hs)来规定内齿21以及外齿31的表面硬度。
具体地，在用洛氏硬度规定表面硬度的情况下，内齿21的表面硬度优选为HRC30以下。作为一例，内齿21的表面硬度在HRC20以上且小于HRC30的范围内选择。内齿21的表面硬度的下限值不限于HRC20、例如也可以是HRC10、HRC15或HRC25等。同样，内齿21的表面硬度的上限值不限于HRC30，例如也可以是HRC35、HRC40或HRC45等。
相对于此，外齿31的表面硬度优选为HRC40以上。作为一例，外齿31的表面硬度在HRC40以上且HRC60以下的范围内选择。外齿31的表面硬度的下限值不限于HRC40，例如也可以是HRC30或HRC35等。同样，外齿31的表面硬度的上限值不限于HRC60，例如也可以是HRC50、HRC55，HRC65，HRC70或HRC75等。
然而，由于挠性外齿轮3与波发生器4(轴承42的外圈421)之间的微动磨损，因缺损或磨损等而产生的异物比较硬质。也就是说，由于表面硬度比较高的挠性外齿轮3与轴承42的外圈421的接触而产生的异物比如上述那样从内齿21出来的软质的异物硬质。当从挠性外齿轮3或外圈421出来的硬质的异物进入轴承42时，以由异物向外圈421或内圈422与滚动体423之间的咬入而形成的压痕为起点，在外圈421、内圈422以及滚动体423中任一个的表面可能产生损伤。由于这样的损伤(表面起点型的剥落)导致谐波齿轮装置1的品质以及特性等的劣化，结果导致谐波齿轮装置1的可靠性降低。
但是，在本实施方式的谐波齿轮装置1中，如上所述，在由波发生器4的外周面424和挠性外齿轮3的内周面301中的至少一方构成的对象面S1设置有化学转化处理覆膜C1，由此，能够在挠性外齿轮3与波发生器4的接触部位维持充分的润滑剂Lb1。因此，挠性外齿轮3中与轴承42(的外 圈421)接触的接触部位的表面成为被润滑剂Lb1覆盖的状态，微动磨损的产生受到抑制，因此，原本就抑制了从挠性外齿轮3或外圈421出来的硬质的异物的产生。结果是，例如，不易产生由比较硬质的异物进入轴承42而引起的损伤，特别是在长期使用时也不易产生可靠性的降低，因此还进一步带来了谐波齿轮装置1的传递效率的改善、长寿命化以及高性能化。
(4.5)齿线修整
接下来，对本实施方式中的内齿21以及外齿31的齿线修整进行说明。
作为前提，内齿21如图1B所示，具有齿根212以及齿顶213。内齿21设置于刚性内齿轮2的内周面，因此内齿21的齿根212相当于刚性内齿轮2的内周面，齿顶213从刚性内齿轮2的内周面朝向内侧(刚性内齿轮2的中心)突出。
另一方面，外齿31如图1B所示，具有齿根312以及齿顶313。外齿31设置于挠性外齿轮3(的躯体部321)的外周面，因此外齿31的齿根312相当于挠性外齿轮3(的躯体部321)的外周面，齿顶313从挠性外齿轮3(的躯体部321)的外周面朝向外侧突出。
在内齿21与外齿31的啮合位置处，外齿31的齿顶313***内齿21的相邻的一对齿顶213之间，从而内齿21与外齿31啮合。此时，外齿31的齿顶313与内齿21的齿根212对置，内齿21的齿顶213与外齿31的齿根312对置。并且，理想的是，在内齿21的齿根212与外齿31的齿顶313之间、及在外齿31的齿根312与内齿21的齿顶213之间，确保微小的间隙。在该状态下，内齿21和外齿31的在齿厚方向上对置的齿面彼此接触，而进行刚性内齿轮2与挠性外齿轮3之间的动力传递。
而且，内齿21在齿线方向D1的两端部具有倒角部211。倒角部211是朝向齿线方向D1的两侧减小内齿21的突出量而得到的C面，基本上是对内齿21与外齿31的啮合没有帮助的部位。也就是说，内齿21的倒角部211即使在内齿21与外齿31的啮合位置处也不与外齿31相接。同样，外 齿31在齿线方向D1的两端部具有倒角部311。倒角部311是朝向齿线方向D1的两侧减小内齿21的突出量而得到的C面，基本上是对内齿21与外齿31的啮合没有帮助的部位。也就是说，外齿31的倒角部311即使在内齿21与外齿31的啮合位置处也不与内齿21相接。
在此，在本实施方式中，刚性内齿轮2的内齿21具有齿线修整部210。也就是说，在谐波齿轮装置1中，至少对内齿21实施齿线修整。内齿21的齿线修整部210设置于齿线方向D1的至少一方的端部。换言之，内齿21在内齿21的齿线方向D1的至少一方的端部具有齿线修整部210。在本实施方式中，齿线修整部210设置于内齿21的齿线方向D1的两端部。
另外，在本实施方式中，挠性外齿轮3的外齿31也具有齿线修整部310。也就是说，谐波齿轮装置1中，不仅对内齿21实施齿线修整，而且对外齿31也实施齿线修整。外齿的齿线修整部210设置于齿线方向D1的至少一方的端部。换言之，外齿31在外齿31的齿线方向D1的至少一方的端部具有齿线修整部310。在本实施方式中，齿线修整部310设置于外齿31的齿线方向D1的两端部。
这样，在本实施方式的谐波齿轮装置1中，内齿21和外齿31中的至少一方具有齿线修整部210、310。利用齿线修整部210、310，能够不易产生由内齿21与外齿31的过度的齿接触引起的应力集中，结果是，能够改善该内齿21与外齿31的齿接触。因此，不易产生由内齿21与外齿31的接触所造成的缺损或磨损等而引起的异物，能够实现不易产生可靠性降低的谐波齿轮装置1。
(5)作用
接下来，对本实施方式的谐波齿轮装置1的作用更详细地进行说明。
如上所述，在谐波齿轮装置1中，特别是如果长期使用，伴随于嵌入至挠性外齿轮3的内侧的波发生器4的旋转，在挠性外齿轮3与波发生器4的接触部位可能产生微动磨损。并且，若产生微动磨损，则有可能导致表 面的粗糙、由磨损粉引起的生锈、以及由磨损粉进入波发生器4的内侧引起的波发生器4(的轴承42)的损伤等，而影响谐波齿轮装置1的可靠性。
作为产生这样的微动磨损的原因，可以考虑是在挠性外齿轮3与波发生器4的接触部位产生了润滑剂Lb1不足或枯竭的“润滑剂耗尽”。即，可以推定原本挠性外齿轮3与波发生器4的接触部位处于以下环境，即，由于在润滑剂Lb1不充分的状态下产生接触面之间的微振动，而容易产生微动磨损的环境。作为成为容易产生这样的微动磨损的环境的理由，具体可以考虑下述两个理由。
第一个理由是挠性外齿轮3频繁地反复进行弹性变形。也就是说，在波发生器4的凸轮41旋转一周的期间，挠性外齿轮3反复进行两次一方向(例如图2A的上下方向)为椭圆形状的长轴的弹性变形。因此，通过凸轮41高速旋转，挠性外齿轮3高速地反复进行弹性变形，伴随于该弹性变形的反复进行，容易在挠性外齿轮3与波发生器4的接触部位产生振动。结果是，在挠性外齿轮3与波发生器4的接触部位，在润滑剂Lb1不充分的状态下产生微振动。
更详细而言，在挠性外齿轮3产生了弹性变形的状态下，挠性外齿轮3在旋转轴Ax1的方向上的开口面35侧的端部比在底部322侧的端部变形更大，而成为更接近椭圆形状的形状。因此，在挠性外齿轮3产生了弹性变形的状态下，挠性外齿轮3的躯体部321的内周面301如图10所示，包括相对于旋转轴Ax1倾斜了倾斜角度θ1的锥面302。并且，锥面302的倾斜角度θ1伴随于挠性外齿轮3的弹性变形而变化。也就是说，在从开口面35侧观察挠性外齿轮3时，在椭圆形状的长轴方向的两端部，锥面302的倾斜角度θ1为最大(图10的“长轴侧”)，在椭圆形状的短轴方向的两端部，锥面302的倾斜角度θ1为最小(图10的“短轴侧”)。因此，通过挠性外齿轮3频繁地反复进行弹性变形，锥面302的倾斜角度θ1也高速地变化，由此，挠性外齿轮3的内周面301(锥面302)以反复冲击外圈421 的外周面424的方式振动。这样，通过产生伴随冲击的微振动，结果是，在挠性外齿轮3与波发生器4的接触部位容易产生微动磨损。
第二个理由是外圈421与挠性外齿轮3之间的相对旋转为低速。也就是说，在外圈421与挠性外齿轮3之间的间隙X1的影响的作用下，波发生器4的凸轮41旋转且外圈421以及挠性外齿轮3弹性变形，伴随于此，在外圈421与挠性外齿轮3之间可能产生相对旋转。然而，该相对旋转例如是凸轮41的转速的几千分之一或几百分之一程度的低速旋转。因此，在外圈421与挠性外齿轮3之间的间隙X1中，无法期待利用该相对旋转来使润滑剂Lb1流动，而处于不利于在其接触部位形成由润滑剂Lb1形成的膜(油膜)的环境。但是，由于在外圈421与挠性外齿轮3之间可能产生相对旋转，因此，外圈421与挠性外齿轮3相对地相互摩擦，而成为容易产生微动磨损的环境。
在本实施方式的谐波齿轮装置1中，根据上述那样的理由，能够对处于容易产生微动磨损的环境的外圈421与挠性外齿轮3之间的接触部位强制地供给润滑剂Lb1。即，谐波齿轮装置1能够经由贯通孔H1对挠性外齿轮3与波发生器4的接触部位供给润滑剂Lb1，由此，在接触部位维持充分的润滑剂Lb1。这样，通过防止在外圈421与挠性外齿轮3的接触部位处润滑剂Lb1不足或枯竭的“润滑剂耗尽”，来抑制微动磨损的产生。
另外，在本实施方式的谐波齿轮装置1中，在由波发生器4的外周面424和挠性外齿轮3的内周面301中的至少一方构成的对象面S1设置有化学转化处理覆膜C1。因此，通过化学转化处理覆膜C1浸润润滑剂Lb1，润滑剂Lb1容易留在挠性外齿轮3中的与波发生器4的接触部位，而能够在接触部位维持充分的润滑剂Lb1。由此，能够进一步防止在外圈421与挠性外齿轮3的接触部位处润滑剂Lb1不足或枯竭的“润滑剂耗尽”，抑制微动磨损的产生。
其结果是，外圈421与挠性外齿轮3的接触部位的表面成为被润滑剂 Lb1覆盖的状态，微动磨损的产生受到抑制。因此，在本实施方式的谐波齿轮装置1中，不易产生由外圈421与挠性外齿轮3之间的微动磨损引起的不良状况，而能够提供不易产生可靠性降低的谐波齿轮装置1。并且，本实施方式的谐波齿轮装置1特别是在长期使用时也不易产生可靠性的降低，因此还进一步带来了谐波齿轮装置1的传递效率的改善、长寿命化以及高性能化。
即，在谐波齿轮装置1中，由于对外圈421与挠性外齿轮3的接触部位供给润滑剂Lb1，因此难以阻碍挠性外齿轮3的变形跟随性，从而带来动力传递效率的提高、由施加于轴承42的载荷减少而引起的长寿命化等。而且，由于也防止了因微动磨损而产生的磨损粉进入轴承42等，因此，也减少了以由磨损粉的咬入而形成的压痕为起点的损伤(表面起点型的剥落)的产生。因此，作为谐波齿轮装置1，可期待长寿命化以及高性能化。
特别是，在着眼于外圈421的周向的一部分的情况下，在仅在致动器100的外轮廓的下部存在润滑剂储存处的结构中(参照图4)，如果没有贯通孔H1，则仅在该着眼部位通过润滑剂储存处时，润滑剂Lb1能够浸入间隙X1。并且，由于外圈421的旋转与内圈422的旋转相比为低速，因此，润滑剂Lb1能够浸入间隙X1的频率变低。相对于此，在本实施方式的谐波齿轮装置1中，通过设置有贯通孔H1，从而在外圈421的着眼部位通过润滑剂储存处时，仅通过对外圈421与内圈422之间补充润滑剂Lb1，就能够对间隙X1也供给润滑剂Lb1。也就是说，由于补充到外圈421与内圈422之间的润滑剂Lb1通过贯通孔H1向间隙X1供给，因此在外圈421的整周上不易产生与挠性外齿轮3的接触部位处的“润滑剂耗尽”。
另外，在本实施方式中，当轴承42动作而使多个滚动体423旋转时，滚动体423作为泵发挥功能，由此，能够将润滑剂Lb1经由贯通孔H1强制地送入间隙X1。而且，在由波发生器4的外周面424和挠性外齿轮3的内周面301中的至少一方构成的对象面S1设置有化学转化处理覆膜C1。根 据这些结构，经由贯通孔H1向间隙X1供给的润滑剂Lb1容易留在挠性外齿轮3的内周面301，能够高效地消除在该间隙X1处的润滑剂耗尽。而且，通过挠性外齿轮3反复进行弹性变形，锥面302的倾斜角度θ1高速地变化也有助于润滑剂Lb1在该间隙X1扩散。并且，不仅能够抑制润滑剂耗尽，而且还能够实现例如谐波齿轮装置1在润滑剂Lb1容易固化的低温环境下的起动性的改善。
(6)应用例
接下来，参照图11对本实施方式的谐波齿轮装置1、致动器100以及机器人用关节装置130的应用例进行说明。
图11是示出本实施方式的使用谐波齿轮装置1的机器人9的一例的剖视图。该机器人9是水平多关节机器人，即所谓的斯卡拉(SCARA：Selective Compliance Assembly Robot Arm)型机器人。
如图11所示，机器人9包括两个机器人用关节装置130(包括谐波齿轮装置1)和连杆91。两个机器人用关节装置130分别设置于机器人9中的两个部位的关节部。连杆91连结两个部位的机器人用关节装置130。在图11的例子中，谐波齿轮装置1由不是杯型而是由礼帽型的谐波齿轮装置构成。也就是说，在图11所例示的在谐波齿轮装置1中，使用形成为礼帽状的挠性外齿轮3。
(7)制造方法
在制造本实施方式的谐波齿轮装置1时，特别是在制造外圈421时，优选实施避免因设置贯通孔H1而导致强度降低的对策。
作为一例，优选在形成贯通孔H1的开孔工序后，进行外圈421的(特别是成为滚动面的内周面425)的表面加工的表面加工工序。也就是说，优选在外圈421中的贯通孔H1周边残留压缩残留应力，以免贯通孔H1成为外圈421的破裂的起点。为此，优选在对外圈421进行淬火等表面加工工序之前，形成贯通孔H1，残留由热处理引起的压缩残留应力。或者，也可 以在热处理后，对外圈421中的贯通孔H1周边实施以下加工，即，通过投射较小的球状投射件而对表面赋予改性固化的喷丸硬化加工等，由此，提高外圈421的疲劳强度。
(8)变形例
实施方式一只不过是本公开实施例的各种实施方式之一。实施方式一可以根据设计等进行各种变更，只要能够达成本公开实施例的目的即可。另外，本公开实施例参照的附图均是示意性的图，图中的各结构要件的大小以及厚度各自的比不一定反映实际的尺寸比。以下，列举实施方式一的变形例。以下说明的变形例能够适当组合来应用。
贯通孔H1也可以在与旋转轴Ax1平行的方向(齿线方向D1)上处于相对多个滚动体423的中心偏离的位置。作为一例，贯通孔H1配置于相对滚动体423的中心向开口面35侧偏离的位置、也就是在齿线方向D1上滚动体423的中心与开口面35之间的位置。根据该结构，具有如下优点：即使从滚动体423对形成有贯通孔H1的构件(此处为外圈421)沿径向方向上施加较大的载荷，该载荷也难以作用于贯通孔H1的周边，而不易产生以贯通孔H1为起点的破裂等。
另外，贯通孔H1也可以在与旋转轴Ax1平行的方向(齿线方向D1)上设置在多个部位。另外，也可以是，在径向方向上，贯通孔H1在间隙X1侧的开口面积比贯通孔H1在与间隙X1相反的一侧的开口面积小。即，在设置于外圈421的(第一)贯通孔H1中，贯通孔H1在间隙X1侧即外周面424侧的开口面积比贯通孔H1在与间隙X1相反的一侧即内周面425侧的开口面积小。由此，能够提高通过贯通孔H1向间隙X1供给的润滑剂Lb1的压力。
图12A以及图12B是示出实施方式一的变形例，且相当于图1A以及图1B的剖视图。在图12A以及图12B所示的谐波齿轮装置1A中，(第二)贯通孔H2设置于挠性外齿轮3的外齿31。换言之，在本变形例中，贯通 孔H包括设置于挠性外齿轮3的外齿31的“第二贯通孔”。设置于挠性外齿轮3的外齿31部分的贯通孔H2，也就是在旋转轴Ax1方向上设置在与轴承42对应的部位的贯通孔H2将挠性外齿轮3沿着径向方向贯穿通过。由此，贯通孔H2的一方的开口面面向外圈421与挠性外齿轮3之间的间隙X1，贯通孔H2的另一方的开口面在挠性外齿轮3的外齿31中的成为与内齿21的啮合面的外周面开口。因此，贯通孔H2的一端与外圈421与挠性外齿轮3之间的间隙X1相连，另一端与外齿31与内齿21之间的空间相连。因此，外齿31与内齿21之间的空间经由贯通孔H2，而与外圈421与挠性外齿轮3之间的间隙X1连通。因此，处于外齿31与内齿21之间的空间的润滑剂Lb1能够通过贯通孔H2向外圈421与挠性外齿轮3之间的间隙X1供给。
在挠性外齿轮3相对于刚性内齿轮2相对旋转时，外齿31的一部分与内齿21啮合，因此外齿31以及内齿21作为泵发挥功能。也就是说，外齿31以及内齿21构成泵结构。在本变形例中，通过外齿31与内齿21啮合，而提高外齿31与内齿21之间的空间内的压力，因此，处于外齿31与内齿21之间的润滑剂Lb1通过贯通孔H2而被挤出至间隙X1侧。这样，外齿31以及内齿21构成叶片泵那样的容积型的泵，并以充分的压力将润滑剂Lb1挤出至间隙X1侧，因此容易向间隙X1内供给充分的润滑剂Lb1。
在此，如图12B所示，(第二)贯通孔H2在与旋转轴Ax1平行的方向(齿线方向D1)上，位于外齿31中的中心与开口面35侧的端部之间。另外，(第二)贯通孔H2配置于外齿31的齿根312以及齿顶313中的齿顶313。由此，若与在齿根312形成贯通孔H2的情况相比，则通过将贯通孔H2形成于齿顶313，而不易产生以贯通孔H2为起点的破裂等。
另外，贯通孔H1、H2也可以设置在外圈421以及挠性外齿轮3的外齿31双方。在该情况下，处于轴承42的外圈421与内圈422之间的空间的润滑剂Lb1能够通过贯通孔H1向外圈421与挠性外齿轮3之间的间隙 X1供给。而且，处于外齿31与内齿21之间的空间的润滑剂Lb1能够通过贯通孔H2向外圈421与挠性外齿轮3之间的间隙X1供给。因此，能够从径向方向的两侧(内侧以及外侧)对间隙X1供给润滑剂Lb1。在此，对于(第一)贯通孔H1和(第二)贯通孔H2而言，优选在内齿21的齿线方向D1上的位置不同。
另外，对内齿21以及外齿31实施齿形修整并非谐波齿轮装置1所必须的结构。例如，也可以对内齿21和外齿31中的至少一方不实施齿形修整。
另外，在径向方向上，在多个滚动体423的轨道与设置于外圈421的(第一)贯通孔H1的开口面之间确保规定值以上的距离，这对于谐波齿轮装置1而言并非必须的结构。也就是说，也可以是在滚动体423存在于与贯通孔H1对应的位置的状态下，在贯通孔H1的开口面与滚动体423之间不产生间隙，而由滚动体423闭塞贯通孔H1。
另外，在轴承42中各滚动体423被4点支承也并非谐波齿轮装置1所必须的结构，例如，各滚动体423也可以是被两点支承的结构。
另外，谐波齿轮装置1不限于实施方式一中说明的杯型，例如也可以是礼帽型、环型、差速器型、扁平型(圆饼型)或屏蔽型等。例如，即使是图10所例示那样的礼帽型的谐波齿轮装置1，也与杯型同样具有筒状的挠性外齿轮3，该筒状的挠性外齿轮3在齿线方向D1的一方具有开口面35。也就是说，礼帽状的挠性外齿轮3在旋转轴Ax1的一侧的端部具有凸缘部，在与凸缘部相反的一侧的端部具有开口面35。即使是礼帽状的挠性外齿轮3，也在开口面35侧的端部具有外齿31且供波发生器4嵌入。
另外，对于致动器100的结构，也不限于实施方式一中说明的结构，能够进行适当的变更。例如，对于输入部103与凸轮41的连结结构，不限于花键连结结构，也可以使用十字接头等。通过使用十字接头作为输入部103与凸轮41的连结结构，能够抵消输入侧的旋转轴Ax1与波发生器4(凸 轮41)之间的偏心，进而能够抵消刚性内齿轮2与挠性外齿轮3的偏心。而且，凸轮41不必能够相对于输入部103沿着旋转轴Ax1移动。
另外，本实施方式的谐波齿轮装置1、致动器100以及机器人用关节装置130的应用例不限于上述那样的水平多关节机器人，例如也可以是水平多关节机器人以外的工业用机器人或工业用以外的机器人等。对于水平多关节机器人以外的工业用机器人，作为一例，有垂直多关节型机器人或并联连杆型机器人等。对于工业用以外的机器人，作为一例，有家庭用机器人、护理用机器人或医疗用机器人等。
另外，轴承42不限于深沟球轴承，例如也可以是角接触球轴承等。而且，轴承42不限于球轴承，例如也可以是由滚动体423不为滚珠状的“滚子”构成的圆筒滚子轴承、针状滚子轴承或圆锥滚子轴承等滚子轴承。即使是这样的滚珠状(球体状)以外的滚动体423，也通过滚动体423滚动而产生压力差，由此，滚动体423作为泵结构发挥功能。
另外，谐波齿轮装置1、致动器100或机器人用关节装置130的各结构要件的材质不限于金属，例如也可以是工程塑料等树脂。
另外，润滑剂Lb1不限于润滑油(油)等液状的物质，也可以是润滑脂等凝胶状的物质。
另外，贯通孔H1的数量以及配置不限于实施方式一中说明的数量以及配置。例如，贯通孔H1也可以设置1个、2个或4个以。而且，在设置有多个贯通孔H1的情况下，多个贯通孔H1的间隔P1也可以是多个滚动体423的间隔P2的倍数，多个贯通孔H1等间距地进行配置也不是必须的。
另外，化学转化处理覆膜C1不限于通过使用磷酸盐的化学转化处理而形成的磷酸盐覆膜，也可以是其他的化学转化处理覆膜。
另外，多条槽303不仅可以形成于挠性外齿轮3的内周面301，还可以形成于波发生器4的外周面424。在该情况下，剥离后的化学转化处理覆膜C10也可以保持在波发生器4的外周面424侧的槽内。
(实施方式二)
如图13A以及图13B所示，本实施方式的谐波齿轮装置1B与实施方式一的谐波齿轮装置1的不同点在于，化学转化处理覆膜C2设置于波发生器4(的轴承42)的外周面424。以下，对于与实施方式一同样的结构，标注共同的附图标记并适当省略说明。图13A与图7A同样是表示图6的A1-A1线剖面中的挠性外齿轮3的内周面301以及波发生器4(的外圈421)的外周面424的表面状态的概要图，图13B是将图13A的区域Z1放大后的概要图。
在本实施方式中，化学转化处理覆膜C1、C2设置于波发生器4的外周面424和挠性外齿轮3的内周面301双方。换言之，在本实施方式中，化学转化处理覆膜C1、C2包括设置于由挠性外齿轮3的内周面301构成的对象面S1的“第一化学转化处理覆膜”、以及设置于由波发生器4的外周面424构成的对象面S2的“第二化学转化处理覆膜”。对于(第二)化学转化处理覆膜C2，也与(第一)化学转化处理覆膜C1同样，作为一例由磷酸盐覆膜构成。
根据该结构，挠性外齿轮3的内周面301的化学转化处理覆膜C1和波发生器4的外周面424的化学转化处理覆膜C2双方能够保持(浸润)润滑剂Lb1。因此，润滑剂Lb1更容易留在挠性外齿轮3中的与波发生器4的接触部位，而能够在接触部位维持更充分的润滑剂Lb1。
并且，在本实施方式中，在波发生器4的外周面424和挠性外齿轮3的内周面301，化学转化处理覆膜C1、C2的组成相同。也就是说，(第一)化学转化处理覆膜C1以及(第二)化学转化处理覆膜C2均是磷酸盐覆膜，由相同组成的覆膜构成。因此，在(第一)化学转化处理覆膜C1和(第二)化学转化处理覆膜C2不易产生剥离量的偏差，化学转化处理覆膜C1、C2双方容易均衡地剥离。
另外，也可以与对象面S1(挠性外齿轮3的内周面301)的槽303同 样地，在由波发生器4的外周面424构成的对象面S2形成有“槽”。由此，在对象面S2的槽内也能够保持剥离后的化学转化处理覆膜C1、C2。
作为实施方式二的变形例，化学转化处理覆膜C2也可以仅设置于波发生器4的外周面424和挠性外齿轮3的内周面301中的、波发生器4的外周面424。
实施方式二的结构(包括变形例)能够与实施方式一中说明的结构(包括变形例)适当组合来应用。
(总结)
如以上说明的那样，第一方案的谐波齿轮装置(1、1A、1B)包括刚性内齿轮(2)、挠性外齿轮(3)及波发生器(4)。刚性内齿轮(2)是具有内齿(21)的环状的部件。挠性外齿轮(3)是具有外齿(31)，且配置在刚性内齿轮(2)的内侧的环状的部件。波发生器(4)具有以旋转轴(Ax1)为中心被驱动旋转的非圆形状的凸轮(41)、以及装配于凸轮(41)的外侧的轴承(42)。波发生器(4)配置在挠性外齿轮(3)的内侧，并使挠性外齿轮(3)产生挠曲。在谐波齿轮装置(1、1A、1B)中，伴随于凸轮(41)的旋转而使挠性外齿轮(3)变形，使外齿(31)的一部分与内齿(21)的一部分啮合，并使挠性外齿轮(3)按照挠性外齿轮(3)与刚性内齿轮(2)的齿数差相对于刚性内齿轮(2)相对旋转。在由波发生器(4)的外周面(424)和挠性外齿轮(3)的内周面(301)中的至少一方构成的对象面(S1、S2)设置有化学转化处理覆膜(C1、C2、C10)。
根据该方案，通过防止在波发生器(4)与挠性外齿轮(3)的接触部位处润滑剂(Lb1)不足或枯竭的“润滑剂耗尽”，来抑制微动磨损的产生。进一步而言，通过在由波发生器(4)的外周面(424)和挠性外齿轮(3)的内周面(301)中的至少一方构成的对象面(S1、S2)设置有化学转化处理覆膜(C1、C2、C10)，能够在挠性外齿轮(3)与波发生器(4)的接触部位维持充分的润滑剂(Lb1)。其结果是，挠性外齿轮(3)中的与波 发生器(4)的接触部位的表面成为被润滑剂(Lb1)覆盖的状态，微动磨损的产生受到抑制。因此，不易产生由波发生器(4)与挠性外齿轮(3)之间的微动磨损引起的不良状况，而能够提供不易产生可靠性降低的谐波齿轮装置(1、1A、1B)。
在第二方案的谐波齿轮装置(1、1A、1B)中，在第一方案的基础上，在对象面(S1、S2)形成有至少能够保持化学转化处理覆膜(C1、C2、C10)的槽(303)。
根据该方案，通过将剥离后的化学转化处理覆膜(C1、C2、C10)保持在槽(303)内，而能够将化学转化处理覆膜(C1、C2、C10)留在波发生器(4)与挠性外齿轮(3)之间。
在第三方案的谐波齿轮装置(1、1A、1B)中，在第二方案的基础上，槽(303)包括相互交叉的第一槽(303a)以及第二槽(303b)。
根据该方案，润滑剂(Lb1)容易遍及波发生器(4)与挠性外齿轮(3)之间的间隙(X1)中的比较大的范围。
在第四方案的谐波齿轮装置(1、1A、1B)中，在第二方案或第三方案的基础上，化学转化处理覆膜(C1、C2、C10)的厚度(L2)比槽(303)的深度(L1)小。
根据该方案，化学转化处理覆膜(C1、C2、C10)收纳在槽(303)内，化学转化处理覆膜(C1、C2、C10)难以从槽(303)露出。
在第五方案的谐波齿轮装置(1、1A、1B)中，在第一方案至第四方案中任一个方案的基础上，化学转化处理覆膜(C1、C2、C10)的硬度比对象面(S1、S2)中除化学转化处理覆膜(C1、C2、C10)以外的部位的硬度低。
根据该方案，在挠性外齿轮(3)与波发生器(4)接触时，夹设在两者之间的化学转化处理覆膜(C1、C2、C10)成为缓冲部，能够抑制挠性外齿轮(3)以及波发生器(4)的损伤。
在第六方案的谐波齿轮装置(1、1A、1B)中，在第一方案至第五方案中任一个方案的基础上，化学转化处理覆膜(C1、C2、C10)构成为能够保持润滑剂(Lb1)。
根据该方案，润滑剂(Lb1)容易留在挠性外齿轮(3)与波发生器(4)的接触部位，能够在接触部位维持充分的润滑剂(Lb1)。
在第七方案的谐波齿轮装置(1、1A、1B)中，在第一方案至第六方案中任一个方案的基础上，化学转化处理覆膜(C1、C2、C10)设置于波发生器(4)的外周面(424)和挠性外齿轮(3)的内周面(301)双方。在波发生器(4)的外周面(424)和挠性外齿轮(3)的内周面(301)，化学转化处理覆膜(C1、C2、C10)的组成相同。
根据该方案，在挠性外齿轮(3)侧的化学转化处理覆膜(C1)和波发生器(4)侧的化学转化处理覆膜(C2)，不易产生剥离量的偏差，化学转化处理覆膜(C1、C2)双方容易均衡地剥离。
在第八方案的谐波齿轮装置(1、1A、1B)中，在第一方案至第七方案中任一个方案的基础上，在轴承(42)的外圈(421)和挠性外齿轮(3)中的外齿(31)中的至少一方设置有贯通孔(H1、H2)，该贯通孔(H1、H2)沿着径向方向贯穿通过，并与外圈(421)与挠性外齿轮(3)之间的间隙(X1)相连。
根据该方案，能够通过贯通孔(H1、H2)对外圈(421)与挠性外齿轮(3)之间的间隙(X1)供给润滑剂(Lb1)。由此，通过防止在外圈(421)与挠性外齿轮(3)的接触部位处润滑剂(Lb1)不足或枯竭的“润滑剂耗尽”，而能够进一步抑制微动磨损的产生。
第九方案的机器人用关节装置(130)包括第一方案至第八方案中任一个方案的谐波齿轮装置(1、1A、1B)、固定于刚性内齿轮(2)的第一构件(131)、以及固定于挠性外齿轮(3)的第二构件(132)。
根据该方案，不易产生由轴承(42)与挠性外齿轮(3)之间的微动磨 损引起的不良状况，而能够提供不易产生可靠性降低的机器人用关节装置(130)。
对于第二方案至第八方案的结构，并非谐波齿轮装置(1、1A、1B)所必须的结构，可以适当省略。
附图标记说明：
1、1A、1B谐波齿轮装置
2刚性内齿轮
3挠性外齿轮
4波发生器
21内齿
31外齿
41凸轮
42轴承
130机器人用关节装置
131第一构件
132第二构件
301(挠性外齿轮的)内周面
303槽
303a第一槽
303b第二槽
421外圈
424(波发生器的)外周面
Ax1旋转轴
C1、C2、C10化学转化处理覆膜
H1(第一)贯通孔
H2(第二)贯通孔
L1(槽的)深度
L2(化学转化处理覆膜的)厚度
Lb1润滑剂
S1、S2对象面
X1间隙。
工业实用性
根据本公开实施例，能够提供一种可靠性高的谐波齿轮装置以及机器人用关节装置。

Claims (9)

  1. 一种谐波齿轮装置，其中，
    所述谐波齿轮装置包括：
    环状的刚性内齿轮，具有内齿；
    环状的挠性外齿轮，具有外齿，且配置于所述刚性内齿轮的内侧；以及
    波发生器，具有以旋转轴为中心被驱动旋转的非圆形状的凸轮、以及装配于所述凸轮的外侧的轴承，所述波发生器配置于所述挠性外齿轮的内侧，并使所述挠性外齿轮产生挠曲，
    在所述谐波齿轮装置中，伴随于所述凸轮的旋转而使所述挠性外齿轮变形，使所述外齿的一部分与所述内齿的一部分啮合，并使所述挠性外齿轮按照所述挠性外齿轮与所述刚性内齿轮的齿数差相对于所述刚性内齿轮进行相对旋转，
    在由所述波发生器的外周面和所述挠性外齿轮的内周面中的至少一方构成的对象面设置有化学转化处理覆膜。
  2. 根据权利要求1所述的谐波齿轮装置，其中，
    在所述对象面形成有至少能够保持所述化学转化处理覆膜的槽。
  3. 根据权利要求2所述的谐波齿轮装置，其中，
    所述槽包括相互交叉的第一槽以及第二槽。
  4. 根据权利要求2或3所述的谐波齿轮装置，其中，
    所述化学转化处理覆膜的厚度比所述槽的深度小。
  5. 根据权利要求1至4中任一项所述的谐波齿轮装置，其中，
    所述化学转化处理覆膜的硬度比所述对象面中除所述化学转化处理覆膜以外的部位的硬度低。
  6. 根据权利要求1至5中任一项所述的谐波齿轮装置，其中，
    所述化学转化处理覆膜构成为能够保持润滑剂。
  7. 根据权利要求1至6中任一项所述的谐波齿轮装置，其中，
    所述化学转化处理覆膜设置于所述波发生器的外周面和所述挠性外齿轮的内周面双方，
    在所述波发生器的外周面和所述挠性外齿轮的内周面，所述化学转化处理覆膜的组成相同。
  8. 根据权利要求1至7中任一项所述的谐波齿轮装置，其中，
    在所述轴承的外圈和所述挠性外齿轮的所述外齿中的至少一方设置有贯通孔，该贯通孔沿着径向方向贯穿通过，并与所述外圈与所述挠性外齿轮之间的间隙相连。
  9. 一种机器人用关节装置，其中，
    所述机器人用关节装置包括：
    权利要求1至8中任一项所述的谐波齿轮装置；
    固定于所述刚性内齿轮的第一构件；以及
    固定于所述挠性外齿轮的第二构件。
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