WO2023189389A1 - Oil-impregnated sintered bearing and fluid dynamic bearing device including same - Google Patents

Oil-impregnated sintered bearing and fluid dynamic bearing device including same Download PDF

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Publication number
WO2023189389A1
WO2023189389A1 PCT/JP2023/009160 JP2023009160W WO2023189389A1 WO 2023189389 A1 WO2023189389 A1 WO 2023189389A1 JP 2023009160 W JP2023009160 W JP 2023009160W WO 2023189389 A1 WO2023189389 A1 WO 2023189389A1
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Prior art keywords
dynamic pressure
bearing
radial
axial
oil
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PCT/JP2023/009160
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French (fr)
Japanese (ja)
Inventor
正志 山郷
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Ntn株式会社
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Publication of WO2023189389A1 publication Critical patent/WO2023189389A1/en

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    • 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
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C17/00—Sliding-contact bearings for exclusively rotary movement
    • F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
    • 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
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/10—Construction relative to lubrication
    • 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
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • 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
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/72—Sealings
    • F16C33/74—Sealings of sliding-contact bearings

Definitions

  • the present invention relates to a sintered oil-impregnated bearing and a fluid dynamic bearing device equipped with this bearing, and more particularly to a sintered oil-impregnated bearing having a radial dynamic pressure generating section and a fluid dynamic pressure bearing device equipped with this bearing.
  • a sintered oil-impregnated bearing is a bearing formed of sintered metal, and is used with the internal pores of a porous body impregnated with lubricating oil. Specifically, in this bearing, as the shaft inserted into the inner periphery of the sintered oil-impregnated bearing rotates relative to each other, lubricating oil impregnated into the internal hole oozes out onto the sliding part with the shaft, forming an oil film. The shaft is rotatably supported via this oil film. Due to its excellent rotational precision and quietness, such bearings are used as bearing devices for motors installed in various electrical devices including information equipment, and more specifically, in HDDs, CDs, DVDs, and Blu-ray discs. It is suitably used as a bearing device for a spindle motor in a disk drive device, a fan motor built into these disk drive devices, a PC, etc., or a polygon scanner motor built into a laser beam printer (LBP).
  • LBP laser beam printer
  • a dynamic pressure generating section such as a dynamic pressure groove may be formed on the inner circumferential surface of the sintered oil-impregnated bearing with the aim of further improving quietness and extending the service life.
  • a radial dynamic pressure generating section for example, a so-called herringbone shape is known, which is formed by arranging a plurality of dynamic pressure grooves that are inclined in different directions with respect to the circumferential direction of the inner circumferential surface of the bearing. (For example, see Patent Document 1).
  • each inclined dynamic pressure groove with a relatively large longitudinal dimension is arranged on the external communication side of the fluid dynamic pressure bearing device (the axial opening side of the housing).
  • the fluid dynamic pressure bearing device aims to generate a flow of lubricating oil from the axially open side of the housing toward the closed side by the differential pressure of the above-mentioned pulling force, and to prevent lubricating oil from leaking. It has been proposed (for example, see Patent Document 2).
  • the longitudinal dimension of the inclined dynamic pressure groove is increased, the axial dimension of the sintered oil-impregnated bearing and thus of the fluid dynamic pressure bearing device increases.
  • the center of gravity of the rotating body is often located relatively upward, so that the upper portion of the sintered oil-impregnated bearing is likely to wear out.
  • the technical problem to be solved by the present invention is to avoid increasing the size of the bearing device while ensuring the drawing force of the lubricating oil to the center of the bearing by the dynamic pressure groove, so that the lubricating oil is not drawn to the outside of the bearing.
  • the purpose of the present invention is to enable mass production of sintered oil-impregnated bearings that can prevent oil leakage.
  • this bearing is a sintered metal bearing obtained by compression-molding metal powder into a cylindrical shape to form a compact, and then sintering the formed compact, and the internal cavity is lubricated.
  • the radial dynamic pressure generating section has a plurality of inclined dynamic pressure grooves that are inclined with respect to the circumferential direction of the inner circumferential surface.
  • a plurality of ridges provided between the inclined dynamic pressure grooves, and the ridges have a contraction whose inner diameter decreases from the axial center of the inner circumferential surface toward the axial end. It is characterized by the fact that it has a diameter section.
  • the present inventor focused on the shape of the hill between the inclined dynamic pressure grooves, which was conventionally assumed to have a constant inner diameter in the axial direction, and discovered that the inner diameter of the hill is at the axial center of the inner peripheral surface of the bearing. It has been found that the drawing force of lubricating oil by the inclined dynamic pressure grooves between the hill portions is improved when the pressure decreases from the side toward the end in the axial direction.
  • the present invention has been made based on the above findings, and by providing the above-mentioned reduced diameter portion in the hill portion between the inclined dynamic pressure grooves, it is possible to increase the drawing force of lubricating oil by the inclined dynamic pressure groove between the hill portions. can.
  • the value obtained by subtracting the inner diameter dimension at the second end portion on the axial end side from the inner diameter dimension at the first end portion on the axial center side of the reduced diameter portion is 0 ⁇ m. It may be more than 1.5 ⁇ m or less.
  • the inner diameter dimension of the reduced diameter portion may be tapered from the axial center side toward the axial end side.
  • the groove depth of the inclined dynamic pressure groove may increase from the axial center side toward the axial end side.
  • the inner diameter dimension of the inclined dynamic pressure groove may be constant in the axial direction.
  • the inner diameter of the inclined dynamic pressure groove is constant in the axial direction, by reducing the inner diameter of the hill portion toward the end in the axial direction (by providing a reduced diameter portion), the diameter of the inclined dynamic pressure groove can be reduced.
  • the groove depth can be increased from the axial center side toward the axial end sides.
  • the formability of the inclined dynamic pressure groove is stabilized. If the formability of the inclined dynamic pressure groove is stable, the formability of the hill part will also be stable, especially when the forming mold bites into the inner circumferential surface of the bearing and the hill part bulges and deforms inward. , it becomes possible to stably form a highly accurate radial dynamic pressure generating section with little variation in dimensions.
  • the radial dynamic pressure generating section includes a plurality of first inclined dynamic pressure grooves which are inclined in different directions with respect to the circumferential direction and which are adjacent in the axial direction. It may have a groove and a second inclined dynamic pressure groove, and a hill portion may be provided between the first inclined dynamic pressure groove and between the second inclined dynamic pressure groove. Additionally, in this case, a diameter-reduced portion is provided in the hill between the first inclined dynamic pressure grooves, the first inclined dynamic pressure grooves are located on the axial end side, and the second inclined dynamic pressure grooves are located on the axial center side. , and the longitudinal dimension of the first inclined dynamic pressure groove may be larger than the longitudinal dimension of the second inclined dynamic pressure groove.
  • the inclined dynamic pressure groove (the first inclined dynamic pressure groove) located on the axial end side
  • lubrication from the axial end side to the axial center side can be increased.
  • the drawing force of oil becomes dominant, and the differential pressure of the drawing force in this direction can be increased.
  • the reduced diameter portion is provided in the hill portion between the first inclined dynamic pressure grooves having a relatively large longitudinal dimension, it is possible to further increase the pulling force in the above-mentioned direction. Therefore, even if the pulling force in each direction varies due to various factors such as variations in dimensional accuracy and shape accuracy, the lubricating oil can be drawn (flow) from the axial end toward the center. It is possible to generate this stably and more reliably prevent leakage to the outside of the bearing.
  • the sintered oil-impregnated bearing includes, for example, the sintered oil-impregnated bearing, a housing having a configuration in which one axial end is open and the other end is closed, and the sintered oil-impregnated bearing is fixed to the inner periphery.
  • a radial bearing is formed between the inner circumferential surface of the sintered oil-impregnated bearing and the outer circumferential surface of the shaft by the dynamic pressure action of the rotating body, which has a shaft inserted into the inner circumference of the sintered oil-impregnated bearing, and the radial dynamic pressure generating section.
  • the present invention can suitably be provided as a fluid dynamic pressure bearing device including a radial bearing portion that supports the shaft portion in a radial direction in a non-contact manner with a film of lubricating oil formed in the gap.
  • the radial dynamic pressure generating portions are provided at two locations separated in the axial direction on the inner circumferential surface of the sintered oil-impregnated bearing, and each radial dynamic pressure generating portion is a plurality of first inclined dynamic pressure grooves and second inclined dynamic pressure grooves which are inclined in different directions with respect to the direction and which are adjacent in the axial direction, and between the first inclined dynamic pressure grooves;
  • a plurality of hill portions may be provided between the second inclined dynamic pressure groove and the second inclined dynamic pressure groove.
  • the first inclined dynamic pressure groove is located on the axial end side
  • the second radial dynamic pressure groove is located on the axial end side.
  • the inclined dynamic pressure grooves may be located on the central side in the axial direction, and a reduced diameter portion may be provided at the hill portion between the first inclined dynamic pressure grooves.
  • the radial dynamic pressure generating parts each having a set of inclined dynamic pressure grooves and a hill part are provided at two locations separated in the axial direction, and the inclined dynamic pressure generating part is arranged at the position closest to the opening side of the housing.
  • the dynamic pressure of the lubricating oil can be increased at two locations separated in the axial direction, and the drawing force of the lubricating oil can be increased. Therefore, for example, even if the first inclined dynamic pressure groove and the second inclined dynamic pressure groove have the same longitudinal dimension, it is possible to create a flow of lubricating oil from the housing opening side to the closed side. Therefore, in this case, it is possible to reduce the axial dimension of the sintered oil-impregnated bearing, which in turn makes it possible to downsize the fluid dynamic bearing device.
  • the fluid dynamic pressure bearing device secures the lubricating oil drawing force by the dynamic pressure groove while avoiding the increase in the size of the bearing device, and prevents the lubricating oil from leaking to the outside of the bearing. Since this can be prevented, it can be suitably provided, for example, as a motor equipped with this fluid dynamic pressure bearing device.
  • FIG. 1 is a sectional view of a motor according to an embodiment of the present invention.
  • 2 is a sectional view of the fluid dynamic bearing device shown in FIG. 1.
  • FIG. 3 is a cross-sectional view of the sintered oil-impregnated bearing shown in FIG. 2.
  • FIG. 4 is a cross-sectional view taken along line XX of the sintered oil-impregnated bearing shown in FIG. 3.
  • FIG. 4 is a YY cross-sectional view of the sintered oil-impregnated bearing shown in FIG. 3.
  • FIG. FIG. 4 is an axial end view of the sintered oil-impregnated bearing shown in FIG. 3 when viewed from the direction of arrow Z.
  • FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG.
  • FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view of the sintered body at the time of starting press-fitting of the sintered body into the die.
  • FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view at the time when the press-fitting operation into the sintered body is completed.
  • FIG. 4 is a diagram for explaining the process of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view at the time when the sintered body is removed from the die.
  • FIG. 3 is a sectional view of a fluid dynamic bearing device according to another embodiment of the present invention.
  • FIG. 1 shows an example of the configuration of a spindle motor according to this embodiment.
  • This spindle motor M is used, for example, in a disk drive device of an HDD, and is connected to a fluid dynamic pressure bearing device 1, a disk hub 3 fixed to a shaft member 2 of the fluid dynamic pressure bearing device 1, and a gap in the radial direction, for example.
  • the drive unit 4 includes a bracket 5 and a drive unit 4 consisting of a stator coil 4a and a rotor magnet 4b facing each other via a stator coil 4a and a rotor magnet 4b.
  • the stator coil 4a is fixed to the bracket 5, and the rotor magnet 4b is fixed to the disk hub 3.
  • the fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 5.
  • the disk hub 3 holds a predetermined number of disks 6 (two in FIG. 1). When the stator coil 4a is energized, the rotor magnet 4b rotates, and accordingly, the disk 6 held by the disk
  • FIG. 2 shows a cross-sectional view of a fluid dynamic bearing device 1 according to an embodiment of the present invention.
  • This fluid dynamic bearing device 1 includes a housing 7, a sintered oil-impregnated bearing 8 disposed on the inner periphery of the housing 7, a shaft member 2 inserted into the inner periphery of the sintered oil-impregnated bearing 8, and a sintered oil-impregnated bearing 8 arranged on the inner periphery of the housing 7. It includes a seal member 9 that seals one end in the axial direction, and a lid member 10 that closes the other end in the axial direction of the housing 7. The internal space of the housing 7 is filled with lubricating oil.
  • the side on which the seal member 9 is provided is assumed to be the upper side, and the opposite side in the axial direction is assumed to be the lower side.
  • this vertical direction does not limit the actual manufacturing manner and usage manner of the fluid dynamic bearing device 1 in any way.
  • the housing 7 has an overall cylindrical shape and is open at least at one end in the axial direction.
  • the housing 7 has a configuration in which both ends in the axial direction are open, and a seal member 9 is disposed on the upper end side in the axial direction of the housing 7, and a lid member 10 is disposed on the lower end side in the axial direction. There is.
  • a first inner circumferential surface 7a having a predetermined inner diameter is provided on the inner circumference of the housing 7.
  • the first inner circumferential surface 7a is disposed at the center of the housing 7 in the axial direction.
  • the inner diameter dimension of the first inner circumferential surface 7a is constant in the axial direction.
  • the outer circumferential surface 8d of the sintered oil-impregnated bearing 8 is fixed to the first inner circumferential surface 7a by appropriate means.
  • a second inner circumferential surface 7b is provided on the upper end side of the inner circumference of the housing 7 to form a second seal space S2, which will be described later, between the housing 7 and the seal member 9.
  • the inner diameter dimension of the second inner circumferential surface 7b is larger than the inner diameter dimension of the first inner circumferential surface 7a.
  • the second inner circumferential surface 7b has a tapered shape in which the inner diameter increases from the lower end in the axial direction toward the upper end in the axial direction.
  • a third inner circumferential surface 7c for fixing the lid member 10 is provided on the lower end side of the inner circumference of the housing 7.
  • the inner diameter dimension of the third inner circumferential surface 7c is larger than the inner diameter dimension of the first inner circumferential surface 7a.
  • the seal member 9 integrally includes a cylindrical portion 9a and an inner flange portion 9b extending radially inward from the axially upper end of the cylindrical portion 9a.
  • a seal member 9 is fixed to the sintered oil-impregnated bearing 8.
  • the means for fixing the seal member 9 and the sintered oil-impregnated bearing 8 is arbitrary, and the seal member 9 is fixed to the sintered oil-impregnated bearing 8 by, for example, adhesion.
  • the inner circumferential surface 9c of the sealing member 9 (the inner circumferential surface of the inner flange portion 9b) has a tapered shape in which the inner diameter increases from the lower end toward the upper end in the axial direction, and is in contact with the outer circumferential surface 2a1 of the opposing shaft portion 2a.
  • a first seal space S1 is formed in which the radial clearance decreases from the upper end side to the lower end side in the axial direction (see FIG. 2).
  • the first seal space S1 acts to draw in the lubricating oil from the upper end side to the lower end side in the axial direction, so that the oil level of the lubricating oil can always be maintained within the axial range of the first seal space S1.
  • the outer circumferential surface 9d of the seal member 9 (the outer circumferential surface of the cylindrical portion 9a) is formed so that the outer diameter dimension is constant in the axial direction, and is spaced between the second inner circumferential surface 7b of the opposing housing 7. , forming a second seal space S2 in which the size of the radial gap decreases from the upper end side to the lower end side in the axial direction (see FIG. 2). Since the second seal space S2 has a larger axial dimension than the first seal space S1, it has a buffer function to absorb the volume change due to the temperature change of the lubricating oil filled in the internal space of the housing 7. The lubricating oil level can always be maintained within the axial range of the second seal space S2 within the expected temperature change range.
  • the shaft member 2 includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a.
  • the portion of the outer circumferential surface 2a1 of the shaft portion 2a that faces the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 is free of unevenness, except that a hollow portion 2c in the form of a cylindrical surface with a relatively small diameter is provided. It is formed with no smooth cylindrical surface. Further, the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b are formed into smooth flat surfaces.
  • the lid member 10 is fixed to the third inner circumferential surface 7c of the housing 7 by appropriate means.
  • the upper end surface 10a of the lid member 10 is provided with an annular thrust bearing surface that forms a thrust bearing gap of the thrust bearing portion T2 between the lower end surface 2b2 of the flange portion 2b of the opposing shaft member 2.
  • This thrust bearing surface is provided with a dynamic pressure generating section (thrust dynamic pressure generating section) for generating a dynamic pressure effect on the lubricating oil within the thrust bearing gap of the thrust bearing portion T2.
  • this thrust dynamic pressure generating section like the thrust dynamic pressure generating section 14 of the sintered oil-impregnated bearing 8 described later, includes, for example, a spiral-shaped dynamic pressure groove and a convex part that partitions this dynamic pressure groove. It is constructed by alternately arranging shaped hill portions in the circumferential direction (see FIG. 5).
  • the sintered oil-impregnated bearing 8 is made of a porous body of sintered metal and is formed into a cylindrical shape.
  • the metal structure constituting this porous body is basically arbitrary, and for example, the metal structure of pure copper (including industrial pure copper) or copper alloy, and the metal structure of pure iron (including industrial pure iron) or stainless steel.
  • a metal structure mainly containing at least one of the metal structures of iron alloys can be adopted.
  • the internal pores of the sintered oil-impregnated bearing 8 are impregnated with lubricating oil.
  • the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 has a cylindrical radial bearing surface that forms radial bearing gaps of the radial bearing sections R1 and R2 between the outer circumferential surface 2a1 of the opposing shaft section 2a. They are placed at separate locations. As shown in FIG. 3, radial dynamic pressure generating portions 11 and 12 are formed on the two radial bearing surfaces, respectively, for generating a dynamic pressure effect on the lubricating oil within the radial bearing gap.
  • the first radial dynamic pressure generating section 11 located above the inner circumferential surface 8a in the axial direction includes a plurality of first inclined dynamic pressure grooves 11a arranged along the circumferential direction of the inner circumferential surface 8a, It has a plurality of first hill portions 11b formed between one inclined dynamic pressure groove 11a.
  • the first inclined dynamic pressure groove 11a is inclined at a predetermined angle with respect to the circumferential direction of the inner peripheral surface 8a, and provides lubrication between the shaft member 2 and the sintered oil-impregnated bearing 8 when the shaft member 2 rotates, which will be described later. It has the effect of drawing oil toward the center of the bearing to increase dynamic pressure (the effect of generating a drawing force in the direction indicated by arrow F1 in FIG. 2).
  • the first radial dynamic pressure generating section 11 includes a plurality of second inclined dynamic pressure grooves 11c and a plurality of second inclined dynamic pressure grooves 11c, in addition to the first inclined dynamic pressure grooves 11a and the first hill portions 11b. It has a hill portion 11d.
  • the plurality of first inclined dynamic pressure grooves 11a and the plurality of second inclined dynamic pressure grooves 11c are arranged in a herringbone shape.
  • the second inclined dynamic pressure groove 11c is inclined in the opposite direction and at the same angle as the first inclined dynamic pressure groove 11a with respect to the circumferential direction of the inner circumferential surface 8a, and the second inclined dynamic pressure groove 11c is inclined in the opposite direction and at the same angle as the first inclined dynamic pressure groove 11a.
  • the lubricating oil between the shaft member 2 and the sintered oil-impregnated bearing 8 is drawn toward the end of the bearing to increase the dynamic pressure (an action that generates a pulling force in the direction indicated by arrow F2 in FIG. 2). play.
  • the longitudinal dimension of the first inclined dynamic pressure groove 11a is larger than the longitudinal dimension of the second inclined dynamic pressure groove 11c.
  • the longitudinal dimension of the first inclined dynamic pressure groove 11a is equal to the longitudinal direction of the second inclined dynamic pressure groove 11c.
  • the axial dimension L1 of the first inclined dynamic pressure groove 11a becomes larger than the axial dimension L2 of the second inclined dynamic pressure groove 11c (see FIG. 3).
  • the first inclined dynamic pressure groove 11a located at the uppermost side of the inner circumferential surface 8a is formed up to the upper end of the inner circumferential surface 8a (the chamfered portion between the inner circumferential surface 8a and the upper end surface 8c).
  • the upper end of the first inclined dynamic pressure groove 11a is open).
  • the lower end of the first inclined dynamic pressure groove 12a located on the axial end side (lowest end side) of the inner circumferential surface 8a is located closer to the center in the axial direction than the lower end of the inner circumferential surface 8a (see FIG. 3).
  • a perfectly circular band portion 11e extending along the circumferential direction of the inner circumferential surface 8a is provided between the first inclined dynamic pressure groove 11a and the second inclined dynamic pressure groove 11c.
  • This band portion 11e defines a first inclined dynamic pressure groove 11a and a second inclined dynamic pressure groove 11c.
  • the lower end of the first hill portion 11b in the axial direction and the band portion 11e are continuous, and the upper end of the second hill portion 11d in the axial direction and the band portion 11e are continuous.
  • the inner diameter dimension at the lower end in the axial direction of the first hill portion 11b is equal to the inner diameter dimension of the band portion 11e.
  • the inner diameter dimension at the upper end in the axial direction of the second hill portion 11d is equal to the inner diameter dimension of the band portion 11e.
  • the first hill portion 11b located on the axial end side of the sintered oil-impregnated bearing 8 has an inner diameter dimension closer to the axial center of the inner circumferential surface 8a.
  • a reduced diameter portion 13 is provided that decreases in diameter toward the end in the axial direction. This reduced diameter portion 13 is provided in at least a portion of the first hill portion 11b in the longitudinal direction. In this embodiment, the reduced diameter portion 13 is provided over the entire first hill portion 11b. Further, the reduced diameter portion 13 has a tapered shape in which the inner diameter is reduced.
  • the inner diameter dimension D1 at the first end portion 11b1 on the axial center side of the first hill portion 11b is larger than the inner diameter dimension D2 at the second end portion 11b2 on the axial end side of the first hill portion 11b, and the difference D1 -D2 is set to, for example, 1.5 ⁇ m or less.
  • the inner diameter dimension of the second hill portion 11d is constant over the entire area (see FIGS. 3 and 4A).
  • the groove depth of the first inclined dynamic pressure groove 11a increases from the axial center side toward the axial end side.
  • the amount of increase in the groove depth is the amount of increase in the inner diameter dimension of the first hill portion 11b (in this case, the inner diameter dimension equal to the difference D1-D2).
  • the groove depth d1 at the first end portion 11a1 on the axial center side of the first inclined dynamic pressure groove 11a is 2.5 ⁇ m or more and 5.0 ⁇ m or less.
  • the groove depth d2 at the second end portion 11a2 on the axial end side of the first inclined dynamic pressure groove 11a is more than 2.5 ⁇ m and less than 6.5 ⁇ m.
  • the groove depth of the second inclined dynamic pressure groove 11c is constant over the entire area (see FIGS. 3 and 4A).
  • the second radial dynamic pressure generating section 12 located on the lower side of the inner circumferential surface 8a in the axial direction includes a plurality of first inclined dynamic pressure grooves 12a and a plurality of first hill sections. 12b, a plurality of second inclined dynamic pressure grooves 12c, a plurality of second hill portions 12d, and a band portion 12e.
  • the longitudinal dimension of the first inclined dynamic pressure groove 12a and the longitudinal dimension of the second inclined dynamic pressure groove 12c are equal.
  • the longitudinal dimension of the first inclined dynamic pressure groove 12a is the same as that of the second inclined dynamic pressure groove 12c.
  • the axial dimension L3 of the first inclined dynamic pressure groove 12a becomes equal to the axial dimension L4 of the second inclined dynamic pressure groove 12c (see FIG. 3).
  • the groove depth of each inclined dynamic pressure groove 12a, 12c is constant over the entire area.
  • the inner diameter dimensions of the first hill portion 12b and the second hill portion 12d are both constant over the entire area (see FIG. 4B). That is, the reduced diameter portion 13 is not provided in the hill portions 12b and 12d of the second radial dynamic pressure generating portion 12.
  • the above-described dimensional relationship between the inclined dynamic pressure grooves 12a, 12c and the hill portions 12b, 12d is merely an example.
  • the inner diameter dimension of the first inclined dynamic pressure groove 12a located at the lowest end of the inner circumferential surface 8a may vary in the axial direction (eg, decrease toward the lower end).
  • the groove depth of the first inclined dynamic pressure groove 12a may similarly vary in the axial direction (decreasing toward the lower end side).
  • the radial bearing gap G1 between the shaft portion 2a and the sintered oil-impregnated bearing 8 in the first radial dynamic pressure generating portion 11 is defined as the distance from the axial lower end to the axial center (strictly speaking, the axial center) as shown in FIG. It is constant up to the first end 11b1 of the first hill 11b, and decreases from the center in the axial direction toward the upper end in the axial direction (the second end 11b2 of the first hill 11b).
  • the radial bearing gap G2 in the second radial dynamic pressure generating section 12 is constant over the entire axial direction, as shown in FIG. 4B.
  • the radial bearing gap G1 in the reduced diameter portion 13 is desirably equal to or larger than the above-mentioned inner diameter difference D1-D2 (maximum 1.5 ⁇ m).
  • the lower end surface 8b of the sintered oil-impregnated bearing 8 is provided with an annular thrust bearing surface that forms a thrust bearing gap of the thrust bearing portion T1 between the upper end surface 2b1 of the opposing flange portion 2b.
  • a dynamic pressure generating section (thrust dynamic pressure generating section) 14 is formed on this thrust bearing surface to generate a dynamic pressure effect on the lubricating oil in the thrust bearing gap of the thrust bearing section T1.
  • the illustrated thrust dynamic pressure generation section 14 is configured by alternately arranging spiral-shaped thrust dynamic pressure grooves 14a and convex hill portions 14b that partition the thrust dynamic pressure grooves 14a in the circumferential direction. .
  • the height dimension of the hill portion 14b is constant over the entire area.
  • the upper end surface 2b1 and the groove bottom surface of the thrust dynamic pressure groove 14a are on the same plane.
  • annular groove 8c1 having a wedge-shaped cross section is formed at a radially intermediate position of the upper end surface 8c of the sintered oil-impregnated bearing 8. Further, radial grooves 8c2 connecting the annular groove 8c1 and the inner circumferential surface 8a are formed at a plurality of locations in the circumferential direction on the radially inner side of the annular groove 8c1 of the upper end surface 8c.
  • a plurality of (for example, three) axial grooves 8d1 extending in the axial direction are formed on the outer peripheral surface 8d of the sintered oil-impregnated bearing 8.
  • the plurality of axial grooves 8d1 are formed at equal intervals apart from each other in the circumferential direction.
  • the sintered oil-impregnated bearing 8 includes a powder compacting step (s1) in which raw powder is compression-molded to obtain a compact, and a sintering step (s1) in which the compact is sintered to obtain a sintered compact 8S. s2) and sizing the sintered body 8S to form inclined dynamic pressure grooves 11a, 11c, 12a, 12c forming the radial dynamic pressure generating parts 11, 12 on at least the inner circumferential surface 8Sa of the sintered body 8S. It mainly includes a pressure groove sizing step (s3).
  • a dimensional sizing process is performed in which the sintered body 8S is sized, and the inner peripheral surface 8Sa of the sintered body 8S is A rotational sizing process for performing rotational sizing may also be provided.
  • a raw material powder that will be the material of the sintered oil-impregnated bearing 8 that will be the final product is prepared, and this is compression-molded into a predetermined shape by die press molding.
  • compression molding of the raw material powder is performed using a molding die composed of a die and an upper punch configured to be movable relative to both the lower punch (elevating and lowering).
  • the space defined by the inner peripheral surface of the die, the outer peripheral surface of the core pin, and the upper end surface of the lower punch is filled with raw material powder, and then the upper punch is lowered with the lower punch fixed. and pressurizes the packed raw material powder in the axial direction. Then, the upper punch is lowered to a predetermined position while applying pressure, and the raw powder is compressed to a predetermined axial dimension, thereby forming a green compact.
  • the raw material powder used includes one or more types of arbitrary metal powders.
  • a raw material powder mainly containing pure copper powder and stainless steel powder as an iron alloy powder is used.
  • pure iron powder may be used instead of stainless steel powder, or iron alloy powder other than stainless steel may be used.
  • a mixed powder of iron alloy powder such as stainless steel powder and pure iron powder may be added to pure copper powder and used as the raw material powder.
  • the composition of the raw material powder may be set so that the sintered oil-impregnated bearing 8 obtained by sintering has the above-mentioned metal structure.
  • substances other than the above-mentioned metal powders can also be blended into the raw material powder, such as graphite or amide wax-based solid lubricant powder.
  • the green compact is sintered at a temperature that corresponds to the composition of the raw powder, especially the metal powder contained in the raw powder.
  • a concrete 8S is obtained (see Figure 6A).
  • the temperature during sintering is set to 750° C. or higher and lower than the melting point of copper.
  • the molding device 20 used here includes a die 21 having a press-fit hole 21a of the sintered body 8S, a sizing pin 22 arranged so as to be insertable into the press-fit hole 21a of the die 21, and a die 21 having a press-fit hole 21a of the sintered body 8S.
  • the lower punch 23 is configured to be movable up and down relative to the die 21, and the lower punch 23 is configured to be movable up and down relative to both the die 21 and the lower punch 23. It has an upper punch 24.
  • the inner diameter of the press-fit hole 21a of the die 21 is appropriately set according to the press-fit allowance of the sintered body 8S to be sized.
  • a first mold 22a having a shape corresponding to the dynamic pressure grooves 11a, 11c, 12a, 12c to be molded is provided on the outer peripheral surface of the sizing pin 22 (see FIG. 6A), and a first mold 22a is provided on the outer peripheral surface of the upper punch 24.
  • a second molding die having a shape corresponding to the thrust dynamic pressure groove 14a of the lower end surface 8b to be molded is provided on the end surface 24a (not shown).
  • the first mold 22a has a convex molding part 22a1 for molding the first inclined dynamic pressure grooves 11a, 12a and the second inclined dynamic pressure grooves 11c, 12c, the first hill parts 11b, 12b, and the second inclined dynamic pressure grooves 11b, 12b. It is composed of hill portions 11d and 12d, and a concave molding portion 22a2 for molding the band portions 11e and 12e.
  • the outer diameter dimension and sizing of the convex molded part 22a1 are excluded from the concave molded part 22a2, except for the part corresponding to the first hill part 11b of the first radial dynamic pressure generating part 11 (the reduced diameter part molded part 22a3).
  • the outer diameter of the outer peripheral surface of the pin 22 in a region other than the first mold 22a is set to be the same.
  • the axial dimension H1 of the reduced diameter portion forming portion 22a3 is set larger than the axial dimension H2 of the reduced diameter portion 13 (first hill portion 11b) to be formed (see FIG. 7(a) and (see (b)).
  • half of the difference in outer diameter between the convex molded part 22a1 and the concave molded part 22a2 is set to be larger than the target value of the groove depth of the inclined dynamic pressure grooves 11a, 11c, 12a, 12c to be molded, for example.
  • the outer diameter of the convex molded portion 22a1 and the outer diameter of the concave molded portion 22a2 are set respectively.
  • the inner circumferential surface 8Sa further bites into the first mold 22a (see FIG. 7A). Note that the sizing pin 22 descends as the sintered body 8S descends as the inner circumferential surface 8Sa of the sintered body 8S bites into the first mold 22a.
  • the shape of the first mold 22a specifically the shape of the convex molded part 22a1, the concave molded part 22a2, and the reduced diameter part molded part 22a3, are each transferred to the inner peripheral surface 8Sa,
  • the first inclined dynamic pressure grooves 11a, 12a, the second inclined dynamic pressure grooves 11c, 12c, the first hill portions 11b, 12b, the second hill portions 11d, 12d, the band portions 11e, 12e, and the reduced diameter portion 13 are formed. (See Figure 7B).
  • the second mold provided on the lower end surface 24a of the upper punch 24 bites into the lower end surface 8Sb of the sintered body 8S, so that the shape of the second mold is transferred to the lower end surface 8Sb, and the corresponding thrust Dynamic pressure grooves 14a and hill portions 14b are formed.
  • the die 21 After forming the predetermined radial dynamic pressure generating parts 11, 12 and thrust dynamic pressure generating part on the inner peripheral surface 8Sa and lower end surface 8Sb of the sintered body 8S in this way, the die 21 is moved relative to the lower punch 23. to release the restraint of the sintered body 8S by the die 21 (see FIG. 7B). As a result, the sintered body 8S springs back in the outer diameter direction, and the outer diameter dimension of the outer circumferential surface 8Sd and the inner diameter dimension of the inner circumferential surface 8Sa increase. In addition, by raising the upper punch 24 and releasing the axial restraint of the sintered body 8S by the upper punch 24 and the lower punch 23 (see FIG.
  • the sintered body 8S is moved in the axial direction. Springback occurs, and the axial dimensions of the outer circumferential surface 8Sd and the inner circumferential surface 8Sa increase. In this way, after the die 21 is lowered, the sintered body 8S springs back in the outer diameter direction, and the inner circumferential surface 8Sa expands in diameter, so that the hill portions 11b and 11d formed to protrude inwardly. , 12b, 12d and the convex molded portion 22a1 as much as possible, and the sizing pin 22 can be extracted from the sintered body 8S.
  • the sintered body 8S in which the radial dynamic pressure generating parts 11, 12 and the reduced diameter part 13 are formed on the inner peripheral surface 8a, that is, the sintered oil-impregnated bearing 8 in the form shown in FIGS. 3 to 5 is obtained. I can do it.
  • the sintered oil-impregnated bearing 8 manufactured through the above sizing process has, for example, an inner diameter of 1 to 5 mm, an outer diameter of 3 to 8 mm, and an axial dimension of 2 to 15 mm.
  • the internal pores are impregnated with lubricating oil to complete the sintered oil-impregnated bearing 8.
  • the sintered oil-impregnated bearing 8 may be impregnated with lubricating oil.
  • various types of lubricating oil can be used, but when provided for disk drive devices such as HDDs, oils with low evaporation rate and low viscosity are required, taking into account temperature changes during use or transportation. Ester-based lubricating oils with excellent properties, such as dioctyl sebacate (DOS) and dioctyl azelate (DOZ), can be suitably used.
  • DOS dioctyl sebacate
  • DOZ dioctyl azelate
  • the lower end surface 8b of the sintered oil-impregnated bearing 8 faces the thrust bearing surface due to the dynamic pressure action of the thrust dynamic pressure generating section 14 provided on the lower end surface 8b.
  • a lubricating oil film is formed between the upper end surface 2b1 of the flange portion 2b and the pressure of the oil film is increased.
  • a gap is created between the upper end surface 10a of the lid member 10 and the lower end surface 2b2 of the flange portion 2b facing the upper end surface 10a.
  • a lubricating oil film is formed (a thrust bearing gap is formed), and the pressure of the oil film is increased.
  • thrust bearing portions T1 and T2 are formed that support the shaft member 2 in a non-contact manner so as to be relatively rotatable in one thrust direction and the other thrust direction.
  • the longitudinal dimension L1 of the first inclined dynamic pressure groove 11a forming the first radial dynamic pressure generating section 11 provided on the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 is the longitudinal direction dimension L1 of the second inclined dynamic pressure groove 11c. larger than dimension L2 (see Figure 3). Therefore, when the shaft member 2 rotates, the drawing force F1 of the lubricating oil toward the bearing center side by the first inclined dynamic pressure groove 11a is increased by the drawing force F2 of lubricating oil toward the bearing end side by the second inclined dynamic pressure groove 11c. exceed.
  • the lubricating oil filling the radial bearing gap G1 causes a flow toward the axially downward side of the sintered oil-impregnated bearing 8 as a whole, and from the thrust bearing gap of the first thrust bearing portion T1, Following the path 15 consisting of the axial groove 8d1, the gap between the lower end surface of the inner flange 9b of the seal member 9 and the upper end surface 8c of the sintered oil-impregnated bearing 8, the annular groove 8c1, and the radial groove 8c2, the first radial bearing section It is drawn into the radial bearing gap of R1 again. That is, a lubricating oil circulation path 15 including radial bearing gaps G1 and G2 is formed in the bearing internal space.
  • the radial bearing clearance G1 is reduced at the bearing end. There is a risk of it spreading on the side.
  • the radial bearing gap G1 widens, the dynamic pressure action of the lubricating oil by the first inclined dynamic pressure groove 11a decreases, so the pulling force by the second inclined dynamic pressure groove 11c is greater than the pulling force F1 by the first inclined dynamic pressure groove 11a.
  • the force F2 becomes dominant, and there is a concern that in some cases, the lubricating oil may flow backward from the axial center side of the inner circumferential surface 8a to the axially upper end side.
  • the reduced diameter portion 13 is formed in the first inclined dynamic pressure groove 11a, and the diameter decreases from the axial center side to the axially upper end side of the inner circumferential surface 8a. It was provided in the first hill part 11b between (see FIG. 4A). Thereby, it is possible to increase the drawing force F1 of the lubricating oil toward the center in the axial direction, which is generated in the radial bearing gap G1 by the first inclined dynamic pressure groove 11a between the first hill portions 11b.
  • the radial bearing gap G1 The axial dimension of the first seal space S1 directly connected to can be reduced.
  • the seal member 9 having the form shown in FIG. 2, the increase in the axial dimension of the fluid dynamic bearing device 1 due to the provision of the seal member 9 is suppressed to substantially the axial dimension of the inner flange portion 9b. Therefore, it can also contribute to making the fluid dynamic bearing device 1 thinner (smaller).
  • the sintered oil-impregnated bearing according to the present invention and the fluid dynamic pressure bearing device equipped with this bearing are not limited to the above-mentioned exemplary embodiments, and can be used within the scope of the present invention. It can take any form.
  • FIG. 8 shows a cross-sectional view of a fluid dynamic bearing device 31 according to another embodiment of the present invention.
  • the fluid dynamic bearing device 31 in this embodiment differs from the fluid dynamic bearing device 1 shown in FIG. 2 in that it has only the first seal space S1.
  • the seal member 32 is integrated with the upper end portion of the housing 7, and the inner circumferential surface 32a of the seal member 32 and the inner circumferential surface 32a are connected to each other.
  • a first seal space S1 is formed between the outer peripheral surfaces two a1 of the opposing shaft portions 2a.
  • the axial dimension of the first seal space S1 adjacent to the radial bearing gap G1 can be made larger compared to the fluid dynamic pressure bearing device 1 shown in FIG. Therefore, by providing the sintered oil-impregnated bearing 33 of the fluid dynamic pressure bearing device 31 with a reduced diameter portion 13 similar to that shown in FIG. It is possible to create a flow of lubricating oil from the radial bearing gap G1 to the radial bearing gap G2 on the lower side in the axial direction. With this configuration, it is possible to provide the fluid dynamic pressure bearing device 31 with a sufficient effect of preventing leakage of lubricating oil.
  • the longitudinal dimension of the first inclined dynamic pressure groove in the first radial dynamic pressure generating section 34 on the axially upper side of the oil-impregnated bearing 33 can be made the same as the longitudinal dimension of the second inclined dynamic pressure groove. Therefore, the axial dimension of the sintered oil-impregnated bearing 33 can be made smaller than that of the sintered oil-impregnated bearing 8 shown in FIG.
  • the present invention is applied to the fluid dynamic bearing device 1, 31 that includes the shaft member 2 (rotating body) to which the disk hub 3 is fixed.
  • the present invention can also be preferably applied to a fluid dynamic bearing device equipped with a shaft member 2 (rotating body) to which a fan or a polygon mirror is fixed. That is, the present invention applies not only to a spindle motor M for driving a disk as shown in FIG. It can also be preferably applied to bearing devices.
  • Fluid dynamic pressure bearing device 2 Shaft member 2a Shaft portion 2a1 Outer peripheral surface 2b Flange portion 2c Center relief portion 3 Disc hub 4 Drive portion 4a Stator coil 4b Rotor magnet 5 Bracket 6 Disk 7 Housing 7a First inner peripheral surface 7b Second inner surface Circumferential surface 7c Third inner circumferential surface 8 Sintered oil-impregnated bearing 8S Sintered body 8a, 8Sa Inner circumferential surface 8b, 8Sb Lower end surface 8c, 8Sc Upper end surface 8c1 Annular groove 8c2 Radial groove 8d, 8Sd Outer circumferential surface 8d1 Axial groove 9 Seal member 9a Cylindrical portion 9b Inner flange portion 9c Inner circumferential surface 9d Outer circumferential surface 10 Lid member 10a Upper end surface 11 First radial dynamic pressure generating portion 11a First inclined dynamic pressure groove 11b First hill portion 11c Second inclined dynamic pressure groove 11d Second hill portion 11e Band portion 12 Second radial dynamic pressure generating portions 12a, 12c Inclined dynamic

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  • General Engineering & Computer Science (AREA)
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Abstract

A radial dynamic pressure generation unit 11 is formed on an inner circumferential surface 8a of an oil-impregnated sintered bearing 8. The radial dynamic pressure generation unit 11 includes a plurality of inclined dynamic pressure grooves 11a inclined with respect to the circumferential direction of the inner circumferential surface 8a, and a plurality of ridges 11b provided between the inclined dynamic pressure grooves 11a. The ridge 11b includes a diameter reduction portion 13 where the inner diameter dimension of the ridge 11b decreases in the direction from the axial center side toward the axial end side of the inner circumferential surface 8a.

Description

焼結含油軸受とこの軸受を備えた流体動圧軸受装置Sintered oil-impregnated bearing and fluid dynamic bearing device equipped with this bearing
　本発明は、焼結含油軸受とこの軸受を備えた流体動圧軸受装置に関し、特にラジアル動圧発生部を有する焼結含油軸受とこの軸受を備えた流体動圧軸受装置に関する。 The present invention relates to a sintered oil-impregnated bearing and a fluid dynamic bearing device equipped with this bearing, and more particularly to a sintered oil-impregnated bearing having a radial dynamic pressure generating section and a fluid dynamic pressure bearing device equipped with this bearing.
　焼結含油軸受は、焼結金属で形成される軸受であって、多孔質体の内部空孔に潤滑油を含浸させた状態で使用される。具体的には、この軸受は、焼結含油軸受の内周に挿入された軸部の相対回転に伴い内部空孔に含浸させた潤滑油が軸部との摺動部に滲み出して油膜を形成し、この油膜を介して軸部を回転支持する。このような軸受は、その優れた回転精度及び静粛性から、情報機器をはじめ種々の電気機器に搭載されるモータ用の軸受装置として、より具体的には、ＨＤＤや、ＣＤ、ＤＶＤ、ブルーレイディスク用のディスク駆動装置におけるスピンドルモータ用、これらディスク駆動装置やＰＣ等に組み込まれるファンモータ用、あるいは、レーザビームプリンタ（ＬＢＰ）に組み込まれるポリゴンスキャナモータ用の軸受装置として好適に使用されている。 A sintered oil-impregnated bearing is a bearing formed of sintered metal, and is used with the internal pores of a porous body impregnated with lubricating oil. Specifically, in this bearing, as the shaft inserted into the inner periphery of the sintered oil-impregnated bearing rotates relative to each other, lubricating oil impregnated into the internal hole oozes out onto the sliding part with the shaft, forming an oil film. The shaft is rotatably supported via this oil film. Due to its excellent rotational precision and quietness, such bearings are used as bearing devices for motors installed in various electrical devices including information equipment, and more specifically, in HDDs, CDs, DVDs, and Blu-ray discs. It is suitably used as a bearing device for a spindle motor in a disk drive device, a fan motor built into these disk drive devices, a PC, etc., or a polygon scanner motor built into a laser beam printer (LBP).
　また、焼結含油軸受の内周面には、更なる静音性向上並びに高寿命化を狙って、動圧溝などの動圧発生部（ラジアル動圧発生部）を形成することがある。ラジアル動圧発生部としては、例えば軸受内周面の円周方向に対して互いに異なる向きに傾斜した複数の動圧溝を配列してなる、いわゆるへリングボーン形状と呼ばれるものが知られている（例えば、特許文献１を参照）。また、ラジアル動圧発生部が上述の如き構成をとる場合、例えば一方の傾斜動圧溝の長手方向寸法を、他方の傾斜動圧溝の長手方向寸法よりも大きくすることで、各傾斜動圧溝による潤滑油の引き込み力の差圧を発生させると共に、相対的に長手方向寸法の大きな一方の傾斜動圧溝を流体動圧軸受装置の外部連通側（ハウジングの軸方向開口側）に配置することで、上記引き込み力の差圧により、全体としてハウジングの軸方向開口側から閉塞側に向かう潤滑油の流れを発生させ、潤滑油の漏れ出しを防止することを狙った流体動圧軸受装置が提案されている（例えば、特許文献２を参照）。 Additionally, a dynamic pressure generating section (radial dynamic pressure generating section) such as a dynamic pressure groove may be formed on the inner circumferential surface of the sintered oil-impregnated bearing with the aim of further improving quietness and extending the service life. As a radial dynamic pressure generating section, for example, a so-called herringbone shape is known, which is formed by arranging a plurality of dynamic pressure grooves that are inclined in different directions with respect to the circumferential direction of the inner circumferential surface of the bearing. (For example, see Patent Document 1). In addition, when the radial dynamic pressure generating section has the above-described configuration, for example, by making the longitudinal dimension of one inclined dynamic pressure groove larger than the longitudinal dimension of the other inclined dynamic pressure groove, each inclined dynamic pressure In addition to generating a differential pressure in the lubricating oil drawing force between the grooves, one inclined dynamic pressure groove with a relatively large longitudinal dimension is arranged on the external communication side of the fluid dynamic pressure bearing device (the axial opening side of the housing). As a result, the fluid dynamic pressure bearing device aims to generate a flow of lubricating oil from the axially open side of the housing toward the closed side by the differential pressure of the above-mentioned pulling force, and to prevent lubricating oil from leaking. It has been proposed (for example, see Patent Document 2).
特開２０００－３０６０３６号公報Japanese Patent Application Publication No. 2000-306036 特開２００７－１４７０８２号公報Japanese Patent Application Publication No. 2007-147082
　特許文献１に記載の流体動圧軸受装置では、傾斜動圧溝の長手方向寸法を異ならせることにより発生する差圧により、潤滑油の漏れ出し防止を図っている。一方で、この種の軸受装置において、上記差圧の大きさは、傾斜動圧溝の長手方向寸法だけでなく、傾斜動圧溝の溝深さのばらつきや、軸受内周面の形状精度（真直度など）、軸部外周面の形状精度（真直度など）、あるいは軸受内周面と軸部外周面との間の軸受隙間の寸法精度（軸方向でのばらつきなど）など、量産品にとって避けることが難しい寸法、形状のばらつきによっても左右される。 In the fluid dynamic pressure bearing device described in Patent Document 1, leakage of lubricating oil is prevented by differential pressure generated by varying the longitudinal dimensions of the inclined dynamic pressure grooves. On the other hand, in this type of bearing device, the magnitude of the differential pressure is determined not only by the longitudinal dimension of the inclined dynamic pressure grooves, but also by variations in the groove depth of the inclined dynamic pressure grooves, and by the shape accuracy of the inner peripheral surface of the bearing. For mass-produced products, there are important issues such as the shape accuracy (straightness, etc.) of the outer circumferential surface of the shaft, or the dimensional accuracy of the bearing gap between the inner circumferential surface of the bearing and the outer circumferential surface of the shaft (variation in the axial direction, etc.). It also depends on variations in size and shape that are difficult to avoid.
　また、ハウジングの軸方向開口側に位置する傾斜動圧溝の長手方向寸法と、ハウジングの軸方向閉塞側に位置する傾斜動圧溝の長手方向寸法との差が大きいほど、潤滑油の引き込み力は大きくなるが、傾斜動圧溝の長手方向寸法を大きくするほど、焼結含油軸受ひいては流体動圧軸受装置の軸方向寸法が増大する。また、この種の軸受装置を搭載したスピンドルモータにおいては、回転体の重心が相対的に上方に位置することが多いため、焼結含油軸受の上方部位が摩耗し易い。焼結含油軸受の摩耗と共に軸受隙間が大きくなり、上記差圧が低下した結果、ハウジングの軸方向中央側に向けた潤滑油の引き込み力を満足に得ることが難しくなり、潤滑油の漏れ出しを招くおそれが高まる。 Furthermore, the larger the difference between the longitudinal dimension of the inclined dynamic pressure groove located on the axially open side of the housing and the longitudinal dimension of the inclined dynamic pressure groove located on the axially closed side of the housing, the greater the lubricating oil drawing force. However, as the longitudinal dimension of the inclined dynamic pressure groove is increased, the axial dimension of the sintered oil-impregnated bearing and thus of the fluid dynamic pressure bearing device increases. Furthermore, in a spindle motor equipped with this type of bearing device, the center of gravity of the rotating body is often located relatively upward, so that the upper portion of the sintered oil-impregnated bearing is likely to wear out. As the sintered oil-impregnated bearing wears, the bearing gap increases and the above differential pressure decreases, making it difficult to obtain a satisfactory lubricating oil drawing force toward the axial center of the housing, which prevents lubricating oil from leaking. There is an increased risk of inviting
　以上の実情に鑑み、本発明により解決すべき技術課題は、軸受装置の大型化を避けつつも動圧溝による潤滑油の軸受中央側への引き込み力を確保して、軸受外部への潤滑油の漏れ出しを防止することのできる焼結含油軸受の量産を可能にすることである。 In view of the above circumstances, the technical problem to be solved by the present invention is to avoid increasing the size of the bearing device while ensuring the drawing force of the lubricating oil to the center of the bearing by the dynamic pressure groove, so that the lubricating oil is not drawn to the outside of the bearing. The purpose of the present invention is to enable mass production of sintered oil-impregnated bearings that can prevent oil leakage.
　前記課題の解決は、本発明に係る焼結含油軸受によって達成される。すなわち、この軸受は、金属粉末を筒状に圧縮成形して圧粉体を形成し、形成した圧粉体を焼結して得られる焼結金属製の軸受であって、内部空孔に潤滑油が含浸され、内周面にラジアル動圧発生部が形成される焼結含油軸受において、ラジアル動圧発生部は、内周面の円周方向に対して傾斜した複数の傾斜動圧溝と、傾斜動圧溝の間に設けられる複数の丘部とを有し、丘部には、丘部の内径寸法が内周面の軸方向中央側から軸方向端部側に向かうにつれて減少する縮径部が設けられている点をもって特徴付けられる。 The solution to the above problem is achieved by the sintered oil-impregnated bearing according to the present invention. In other words, this bearing is a sintered metal bearing obtained by compression-molding metal powder into a cylindrical shape to form a compact, and then sintering the formed compact, and the internal cavity is lubricated. In a sintered oil-impregnated bearing that is impregnated with oil and has a radial dynamic pressure generating section formed on its inner circumferential surface, the radial dynamic pressure generating section has a plurality of inclined dynamic pressure grooves that are inclined with respect to the circumferential direction of the inner circumferential surface. , a plurality of ridges provided between the inclined dynamic pressure grooves, and the ridges have a contraction whose inner diameter decreases from the axial center of the inner circumferential surface toward the axial end. It is characterized by the fact that it has a diameter section.
　本発明者は、従来、内径寸法が軸方向で一定であることが前提であった傾斜動圧溝間の丘部の形状に着目し、丘部の内径寸法が軸受内周面の軸方向中央側から軸方向端部側に向かうにつれて減少する形態をなす場合に、丘部の間の傾斜動圧溝による潤滑油の引き込み力が向上することを見出した。本発明は上記知見に基づきなされたもので、上述した縮径部を傾斜動圧溝間の丘部に設けることによって、丘部の間の傾斜動圧溝による潤滑油の引き込み力を高めることができる。そのため、上述した精度上の理由で潤滑油の軸受中央側への引き込み力が不足する場合、もしくは軸受の損耗に伴い上記引き込み力が低下する場合においても、軸受中央側に向けた潤滑油の引き込み作用を担う傾斜動圧溝間の丘部に縮径部を設けることで、上記引き込み力の不足分又は低下分を補って、必要な大きさの引き込み力を得ることが可能となる。従って、本発明の如き焼結含油軸受を量産して使用する場合に、潤滑油の軸受外部への漏れ出しを長期にわたって防止することが可能となる。 The present inventor focused on the shape of the hill between the inclined dynamic pressure grooves, which was conventionally assumed to have a constant inner diameter in the axial direction, and discovered that the inner diameter of the hill is at the axial center of the inner peripheral surface of the bearing. It has been found that the drawing force of lubricating oil by the inclined dynamic pressure grooves between the hill portions is improved when the pressure decreases from the side toward the end in the axial direction. The present invention has been made based on the above findings, and by providing the above-mentioned reduced diameter portion in the hill portion between the inclined dynamic pressure grooves, it is possible to increase the drawing force of lubricating oil by the inclined dynamic pressure groove between the hill portions. can. Therefore, even if the force to draw the lubricating oil toward the center of the bearing is insufficient due to the accuracy reasons mentioned above, or if the force to draw the lubricant decreases due to wear and tear on the bearing, the lubricant will still be drawn toward the center of the bearing. By providing a diameter-reduced portion in the hill portion between the inclined dynamic pressure grooves that play a role, it is possible to compensate for the shortage or decrease in the pulling force and obtain the necessary amount of pulling force. Therefore, when the sintered oil-impregnated bearing of the present invention is mass-produced and used, it is possible to prevent lubricating oil from leaking out of the bearing for a long period of time.
　また、本発明に係る焼結含油軸受において、縮径部の軸方向中央側の第一端部における内径寸法から、軸方向端部側の第二端部における内径寸法を減じた値が、０μｍを超えかつ１．５μｍ以下であってもよい。 Further, in the sintered oil-impregnated bearing according to the present invention, the value obtained by subtracting the inner diameter dimension at the second end portion on the axial end side from the inner diameter dimension at the first end portion on the axial center side of the reduced diameter portion is 0 μm. It may be more than 1.5 μm or less.
　このように、丘部に設けた縮径部の軸方向両端部間での内径寸法差を最大で１．５μｍ以下とすることで、軸部外周面と軸受内周面との間に形成され、通常数μｍの幅で管理される軸受隙間（ラジアル軸受隙間）の軸方向の変動を許容範囲内に収めることができる。これより、縮径部を設けたことが軸受隙間に及ぼす悪影響を最小限に抑えつつ、上記引き込み力を増大させることができるので、十分な大きさの引き込み力を安定的に発揮させることが可能となる。 In this way, by setting the inner diameter dimension difference between both axial ends of the reduced diameter section provided on the hill to a maximum of 1.5 μm or less, the diameter difference formed between the outer circumferential surface of the shaft and the inner circumferential surface of the bearing is reduced. , it is possible to keep fluctuations in the axial direction of the bearing clearance (radial bearing clearance), which is normally controlled to a width of several μm, within an allowable range. This makes it possible to increase the above-mentioned pulling force while minimizing the negative effect that the provision of the reduced diameter part has on the bearing clearance, making it possible to stably exert a sufficient pulling force. becomes.
　また、本発明に係る焼結含油軸受において、縮径部の内径寸法が、軸方向中央側から軸方向端部側に向かうにつれてテーパ状に減少していてもよい。 Furthermore, in the sintered oil-impregnated bearing according to the present invention, the inner diameter dimension of the reduced diameter portion may be tapered from the axial center side toward the axial end side.
　このように、縮径部の形状をテーパ状にすることによっても、縮径部を設けたことがラジアル軸受隙間に及ぼす悪影響を抑えることができる。よって、本構成によっても、十分な大きさの引き込み力を安定的に発揮させることが可能となる。 In this way, by tapering the shape of the reduced diameter portion, it is possible to suppress the adverse effect that the provision of the reduced diameter portion has on the radial bearing clearance. Therefore, this configuration also makes it possible to stably exert a sufficient pulling force.
　また、本発明に係る焼結含油軸受において、傾斜動圧溝の溝深さが、軸方向中央側から軸方向端部側に向かうにつれて増大していてもよい。 Furthermore, in the sintered oil-impregnated bearing according to the present invention, the groove depth of the inclined dynamic pressure groove may increase from the axial center side toward the axial end side.
　このように、傾斜動圧溝の溝深さを変化させることで、軸受の継続使用により丘部が摩耗した場合であっても、初期の溝深さが十分な大きさを有しているため、摩耗後も必要な溝深さを維持することができる。従って、長期にわたって所要の動圧作用ひいては軸受性能を発揮することが可能となる。 In this way, by changing the groove depth of the inclined dynamic pressure groove, even if the hill portion wears out due to continued use of the bearing, the initial groove depth is large enough. , the required groove depth can be maintained even after wear. Therefore, it becomes possible to exhibit the required dynamic pressure action and thus the bearing performance over a long period of time.
　また、本発明に係る焼結含油軸受において、傾斜動圧溝の内径寸法が軸方向で一定であってもよい。 Furthermore, in the sintered oil-impregnated bearing according to the present invention, the inner diameter dimension of the inclined dynamic pressure groove may be constant in the axial direction.
　傾斜動圧溝の内径寸法を軸方向で一定とした場合でも、丘部の内径寸法を軸方向端部側に向けて縮小させることにより（縮径部を設けることにより）、傾斜動圧溝の溝深さを、軸方向中央側から軸方向端部側に向かうにつれて増大させることができる。また、上述のように傾斜動圧溝の内径寸法を軸方向で一定にすることにより、傾斜動圧溝の成形性が安定する。傾斜動圧溝の成形性が安定すれば、特に成形型を軸受内周面に食い込ませて丘部を内径側に膨出変形させる成形態様をとる場合、丘部の成形性についても安定するので、寸法のばらつきの少ない高精度なラジアル動圧発生部を安定的に形成することが可能となる。 Even if the inner diameter of the inclined dynamic pressure groove is constant in the axial direction, by reducing the inner diameter of the hill portion toward the end in the axial direction (by providing a reduced diameter portion), the diameter of the inclined dynamic pressure groove can be reduced. The groove depth can be increased from the axial center side toward the axial end sides. Furthermore, by making the inner diameter of the inclined dynamic pressure groove constant in the axial direction as described above, the formability of the inclined dynamic pressure groove is stabilized. If the formability of the inclined dynamic pressure groove is stable, the formability of the hill part will also be stable, especially when the forming mold bites into the inner circumferential surface of the bearing and the hill part bulges and deforms inward. , it becomes possible to stably form a highly accurate radial dynamic pressure generating section with little variation in dimensions.
　また、本発明に係る焼結含油軸受において、ラジアル動圧発生部は、円周方向に対して互いに異なる向きに傾斜しかつ軸方向で隣接する傾斜動圧溝としての複数の第一傾斜動圧溝と第二傾斜動圧溝とを有し、第一傾斜動圧溝の間及び第二傾斜動圧溝の間に丘部がそれぞれ設けられてもよい。また、この場合、第一傾斜動圧溝間の丘部に縮径部が設けられ、第一傾斜動圧溝は軸方向端部側に位置し、第二傾斜動圧溝は軸方向中央側に位置し、かつ　第一傾斜動圧溝の長手方向寸法が、第二傾斜動圧溝の長手方向寸法よりも大きくてもよい。 Further, in the sintered oil-impregnated bearing according to the present invention, the radial dynamic pressure generating section includes a plurality of first inclined dynamic pressure grooves which are inclined in different directions with respect to the circumferential direction and which are adjacent in the axial direction. It may have a groove and a second inclined dynamic pressure groove, and a hill portion may be provided between the first inclined dynamic pressure groove and between the second inclined dynamic pressure groove. Additionally, in this case, a diameter-reduced portion is provided in the hill between the first inclined dynamic pressure grooves, the first inclined dynamic pressure grooves are located on the axial end side, and the second inclined dynamic pressure grooves are located on the axial center side. , and the longitudinal dimension of the first inclined dynamic pressure groove may be larger than the longitudinal dimension of the second inclined dynamic pressure groove.
　このように、軸方向端部側に位置する傾斜動圧溝（第一傾斜動圧溝）の長手方向寸法を相対的に大きくすることによって、軸方向端部側から軸方向中央側に向かう潤滑油の引き込み力が優勢となり、当該方向への引き込み力の差圧を大きくすることができる。加えて本構成では、相対的に長手方向寸法の大きな第一傾斜動圧溝間の丘部に縮径部を設けたので、上述した方向への引き込み力をさらに高めることができる。よって、寸法精度や形状精度のばらつき等、種々の要因により各方向への引き込み力に変動が生じた場合であっても、軸方向端部側から中央側に向かう潤滑油の引き込み（流れ）を安定的に発生させて、軸受外部への漏れ出しをより確実に防止することが可能となる。 In this way, by relatively increasing the longitudinal dimension of the inclined dynamic pressure groove (the first inclined dynamic pressure groove) located on the axial end side, lubrication from the axial end side to the axial center side can be increased. The drawing force of oil becomes dominant, and the differential pressure of the drawing force in this direction can be increased. In addition, in this configuration, since the reduced diameter portion is provided in the hill portion between the first inclined dynamic pressure grooves having a relatively large longitudinal dimension, it is possible to further increase the pulling force in the above-mentioned direction. Therefore, even if the pulling force in each direction varies due to various factors such as variations in dimensional accuracy and shape accuracy, the lubricating oil can be drawn (flow) from the axial end toward the center. It is possible to generate this stably and more reliably prevent leakage to the outside of the bearing.
　また、以上の説明に係る焼結含油軸受は、例えば当該焼結含油軸受と、軸方向一端側が開口し他端側が閉塞された形態をなし焼結含油軸受が内周に固定されるハウジングと、焼結含油軸受の内周に挿入される軸部を有する回転体と、ラジアル動圧発生部の動圧作用により、焼結含油軸受の内周面と軸部の外周面との間のラジアル軸受隙間に形成される潤滑油の膜で軸部をラジアル方向に非接触支持するラジアル軸受部とを備えた流体動圧軸受装置として好適に提供可能である。 Further, the sintered oil-impregnated bearing according to the above description includes, for example, the sintered oil-impregnated bearing, a housing having a configuration in which one axial end is open and the other end is closed, and the sintered oil-impregnated bearing is fixed to the inner periphery. A radial bearing is formed between the inner circumferential surface of the sintered oil-impregnated bearing and the outer circumferential surface of the shaft by the dynamic pressure action of the rotating body, which has a shaft inserted into the inner circumference of the sintered oil-impregnated bearing, and the radial dynamic pressure generating section. The present invention can suitably be provided as a fluid dynamic pressure bearing device including a radial bearing portion that supports the shaft portion in a radial direction in a non-contact manner with a film of lubricating oil formed in the gap.
　また、本発明に係る流体動圧軸受装置において、焼結含油軸受の内周面のうち軸方向に離れた二ヶ所にラジアル動圧発生部が設けられ、各ラジアル動圧発生部は、円周方向に対して互いに異なる向きに傾斜しかつ軸方向で隣接する傾斜動圧溝としての複数の第一傾斜動圧溝と第二傾斜動圧溝とを有し、第一傾斜動圧溝の間及び第二傾斜動圧溝の間には複数の丘部がそれぞれ設けられてもよい。また、この場合、二つのラジアル動圧軸受部のうちハウジングの軸方向開口側に位置する一方のラジアル動圧発生部において、第一傾斜動圧溝は軸方向端部側に位置し、第二傾斜動圧溝は軸方向中央側に位置すると共に、第一傾斜動圧溝間の丘部に縮径部が設けられていてもよい。 Further, in the fluid dynamic pressure bearing device according to the present invention, the radial dynamic pressure generating portions are provided at two locations separated in the axial direction on the inner circumferential surface of the sintered oil-impregnated bearing, and each radial dynamic pressure generating portion is a plurality of first inclined dynamic pressure grooves and second inclined dynamic pressure grooves which are inclined in different directions with respect to the direction and which are adjacent in the axial direction, and between the first inclined dynamic pressure grooves; A plurality of hill portions may be provided between the second inclined dynamic pressure groove and the second inclined dynamic pressure groove. Further, in this case, in one of the two radial dynamic pressure bearing parts, which is located on the axial opening side of the housing, the first inclined dynamic pressure groove is located on the axial end side, and the second radial dynamic pressure groove is located on the axial end side. The inclined dynamic pressure grooves may be located on the central side in the axial direction, and a reduced diameter portion may be provided at the hill portion between the first inclined dynamic pressure grooves.
　このように、各一組の傾斜動圧溝と丘部とを有するラジアル動圧発生部を軸方向に離れた二ヶ所に設けて、かつ最もハウジングの開口側に近い位置に配置された傾斜動圧溝間の丘部に縮径部を設けることによって、潤滑油の動圧を軸方向に離れた二ヶ所で高めつつ、潤滑油の引き込み力を高めることができる。従って、例えば第一傾斜動圧溝と第二傾斜動圧溝とで長手方向寸法を同じ大きさとした場合であっても、ハウジング開口側から閉塞側に向かう潤滑油の流れを作り出すことができる。よって、この場合には焼結含油軸受の軸方向寸法を小さくすることができ、ひいては流体動圧軸受装置の小型化を図ることが可能となる。 In this way, the radial dynamic pressure generating parts each having a set of inclined dynamic pressure grooves and a hill part are provided at two locations separated in the axial direction, and the inclined dynamic pressure generating part is arranged at the position closest to the opening side of the housing. By providing a diameter-reduced portion in the hill portion between the pressure grooves, the dynamic pressure of the lubricating oil can be increased at two locations separated in the axial direction, and the drawing force of the lubricating oil can be increased. Therefore, for example, even if the first inclined dynamic pressure groove and the second inclined dynamic pressure groove have the same longitudinal dimension, it is possible to create a flow of lubricating oil from the housing opening side to the closed side. Therefore, in this case, it is possible to reduce the axial dimension of the sintered oil-impregnated bearing, which in turn makes it possible to downsize the fluid dynamic bearing device.
　以上の説明に係る流体動圧軸受装置は、上述のように、軸受装置の大型化を避けつつも動圧溝による潤滑油の引き込み力を確保して、軸受外部への潤滑油の漏れ出しを防止可能とするものであるから、例えばこの流体動圧軸受装置を備えたモータとして好適に提供可能である。 As mentioned above, the fluid dynamic pressure bearing device according to the above explanation secures the lubricating oil drawing force by the dynamic pressure groove while avoiding the increase in the size of the bearing device, and prevents the lubricating oil from leaking to the outside of the bearing. Since this can be prevented, it can be suitably provided, for example, as a motor equipped with this fluid dynamic pressure bearing device.
　以上より、本発明によれば、軸受装置の大型化を避けつつも動圧溝による軸受中央側への潤滑油の引き込み力を確保して、軸受外部への潤滑油の漏れ出しを防止可能な焼結含油軸受を量産することが可能となる。 As described above, according to the present invention, it is possible to prevent the leakage of lubricating oil to the outside of the bearing by ensuring the drawing force of the lubricating oil to the center side of the bearing by the dynamic pressure groove while avoiding an increase in the size of the bearing device. It becomes possible to mass produce sintered oil-impregnated bearings.
本発明の一実施形態に係るモータの断面図である。FIG. 1 is a sectional view of a motor according to an embodiment of the present invention. 図１に示す流体動圧軸受装置の断面図である。2 is a sectional view of the fluid dynamic bearing device shown in FIG. 1. FIG. 図２に示す焼結含油軸受の断面図である。3 is a cross-sectional view of the sintered oil-impregnated bearing shown in FIG. 2. FIG. 図３に示す焼結含油軸受のＸ－Ｘ断面図である。4 is a cross-sectional view taken along line XX of the sintered oil-impregnated bearing shown in FIG. 3. FIG. 図３に示す焼結含油軸受のＹ－Ｙ断面図である。4 is a YY cross-sectional view of the sintered oil-impregnated bearing shown in FIG. 3. FIG. 図３に示す焼結含油軸受を矢印Ｚの向きから見た軸方向端面図である。FIG. 4 is an axial end view of the sintered oil-impregnated bearing shown in FIG. 3 when viewed from the direction of arrow Z. 図３に示すラジアル動圧溝を型成形する工程を説明するための図で、サインジングピンを挿入する前における焼結体の断面図である。FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view of the sintered body before inserting the signing pin. 図３に示すラジアル動圧溝を型成形する工程を説明するための図で、焼結体のダイへの圧入開始時における焼結体の断面図である。FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view of the sintered body at the time of starting press-fitting of the sintered body into the die. 図３に示すラジアル動圧溝を型成形する工程を説明するための図で、焼結体への圧入動作が完了した時点における断面図である。FIG. 4 is a diagram for explaining the step of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view at the time when the press-fitting operation into the sintered body is completed. 図３に示すラジアル動圧溝を型成形する工程を説明するための図で、焼結体をダイから脱型した時点における断面図である。FIG. 4 is a diagram for explaining the process of molding the radial dynamic pressure groove shown in FIG. 3, and is a cross-sectional view at the time when the sintered body is removed from the die. 本発明の他の実施形態に係る流体動圧軸受装置の断面図である。FIG. 3 is a sectional view of a fluid dynamic bearing device according to another embodiment of the present invention.
　以下、本発明の一実施形態を図面に基づき説明する。 Hereinafter, one embodiment of the present invention will be described based on the drawings.
　図１は、本実施形態に係るスピンドルモータの一構成例を示している。このスピンドルモータＭは、例えばＨＤＤのディスク駆動装置に用いられるもので、流体動圧軸受装置１と、流体動圧軸受装置１の軸部材２に固定されたディスクハブ３と、例えば半径方向のギャップを介して対向しているステータコイル４ａ及びロータマグネット４ｂとからなる駆動部４と、ブラケット５とを備えている。ステータコイル４ａはブラケット５に固定され、ロータマグネット４ｂはディスクハブ３に固定される。流体動圧軸受装置１は、ブラケット５の内周に固定される。ディスクハブ３には、所定枚数（図１では２枚）のディスク６が保持される。ステータコイル４ａに通電すると、ロータマグネット４ｂが回転し、これに伴って、ディスクハブ３に保持されたディスク６が軸部材２と一体に回転する。 FIG. 1 shows an example of the configuration of a spindle motor according to this embodiment. This spindle motor M is used, for example, in a disk drive device of an HDD, and is connected to a fluid dynamic pressure bearing device 1, a disk hub 3 fixed to a shaft member 2 of the fluid dynamic pressure bearing device 1, and a gap in the radial direction, for example. The drive unit 4 includes a bracket 5 and a drive unit 4 consisting of a stator coil 4a and a rotor magnet 4b facing each other via a stator coil 4a and a rotor magnet 4b. The stator coil 4a is fixed to the bracket 5, and the rotor magnet 4b is fixed to the disk hub 3. The fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 5. The disk hub 3 holds a predetermined number of disks 6 (two in FIG. 1). When the stator coil 4a is energized, the rotor magnet 4b rotates, and accordingly, the disk 6 held by the disk hub 3 rotates together with the shaft member 2.
　図２は、本発明の一実施形態に係る流体動圧軸受装置１の断面図を示している。この流体動圧軸受装置１は、ハウジング７と、ハウジング７の内周に配設される焼結含油軸受８と、焼結含油軸受８の内周に挿入される軸部材２と、ハウジング７の軸方向一端側をシールするシール部材９と、ハウジング７の軸方向他端側を閉塞する蓋部材１０とを備える。ハウジング７の内部空間には、潤滑油が充填されている。以下の説明においては、便宜上、シール部材９が設けられた側を上側、その軸方向反対側を下側として説明を行う。もちろん、この上下方向は、実際の流体動圧軸受装置１の製造態様及び使用態様を何ら限定しない。 FIG. 2 shows a cross-sectional view of a fluid dynamic bearing device 1 according to an embodiment of the present invention. This fluid dynamic bearing device 1 includes a housing 7, a sintered oil-impregnated bearing 8 disposed on the inner periphery of the housing 7, a shaft member 2 inserted into the inner periphery of the sintered oil-impregnated bearing 8, and a sintered oil-impregnated bearing 8 arranged on the inner periphery of the housing 7. It includes a seal member 9 that seals one end in the axial direction, and a lid member 10 that closes the other end in the axial direction of the housing 7. The internal space of the housing 7 is filled with lubricating oil. In the following description, for convenience, the side on which the seal member 9 is provided is assumed to be the upper side, and the opposite side in the axial direction is assumed to be the lower side. Of course, this vertical direction does not limit the actual manufacturing manner and usage manner of the fluid dynamic bearing device 1 in any way.
　ハウジング７は、全体として円筒状をなし、少なくとも軸方向一端側を開口した形態をなす。本実施形態では、ハウジング７は軸方向両端側を開口した形態をなし、ハウジング７の軸方向上端側にシール部材９が配設されると共に、軸方向下端側に蓋部材１０が配設されている。 The housing 7 has an overall cylindrical shape and is open at least at one end in the axial direction. In this embodiment, the housing 7 has a configuration in which both ends in the axial direction are open, and a seal member 9 is disposed on the upper end side in the axial direction of the housing 7, and a lid member 10 is disposed on the lower end side in the axial direction. There is.
　ハウジング７の内周には、所定の内径寸法を有する第一内周面７ａが設けられる。本実施形態では、第一内周面７ａは、ハウジング７の軸方向中央側に配設されている。第一内周面７ａの内径寸法は軸方向で一定である。この第一内周面７ａには焼結含油軸受８の外周面８ｄが適宜の手段で固定される。 A first inner circumferential surface 7a having a predetermined inner diameter is provided on the inner circumference of the housing 7. In this embodiment, the first inner circumferential surface 7a is disposed at the center of the housing 7 in the axial direction. The inner diameter dimension of the first inner circumferential surface 7a is constant in the axial direction. The outer circumferential surface 8d of the sintered oil-impregnated bearing 8 is fixed to the first inner circumferential surface 7a by appropriate means.
　ハウジング７の内周上端側には、シール部材９との間に後述する第二シール空間Ｓ２を形成するための第二内周面７ｂが設けられる。第二内周面７ｂの内径寸法は、第一内周面７ａの内径寸法よりも大きい。また、本実施形態では、第二内周面７ｂは、軸方向下端側から軸方向上端側に向かうにつれて内径寸法が増大するテーパ形状をなしている。 A second inner circumferential surface 7b is provided on the upper end side of the inner circumference of the housing 7 to form a second seal space S2, which will be described later, between the housing 7 and the seal member 9. The inner diameter dimension of the second inner circumferential surface 7b is larger than the inner diameter dimension of the first inner circumferential surface 7a. Furthermore, in this embodiment, the second inner circumferential surface 7b has a tapered shape in which the inner diameter increases from the lower end in the axial direction toward the upper end in the axial direction.
　ハウジング７の内周下端側には、蓋部材１０を固定するための第三内周面７ｃが設けられる。本実施形態では、第三内周面７ｃの内径寸法は、第一内周面７ａの内径寸法よりも大きい。 A third inner circumferential surface 7c for fixing the lid member 10 is provided on the lower end side of the inner circumference of the housing 7. In this embodiment, the inner diameter dimension of the third inner circumferential surface 7c is larger than the inner diameter dimension of the first inner circumferential surface 7a.
　シール部材９は、本実施形態では、筒状部９ａと、筒状部９ａの軸方向上端から半径方向内側に延びる内鍔部９ｂとを一体に有する。この場合、例えば内鍔部９ｂの下端面が焼結含油軸受８の上端面８ｃに当接し、筒状部９ａの内周面が焼結含油軸受８の外周面８ｄに当接した状態で、シール部材９が焼結含油軸受８に固定される。なお、シール部材９と焼結含油軸受８との固定手段は任意であり、例えば接着によりシール部材９が焼結含油軸受８に固定される。 In this embodiment, the seal member 9 integrally includes a cylindrical portion 9a and an inner flange portion 9b extending radially inward from the axially upper end of the cylindrical portion 9a. In this case, for example, with the lower end surface of the inner flange portion 9b in contact with the upper end surface 8c of the sintered oil-impregnated bearing 8, and the inner peripheral surface of the cylindrical portion 9a in contact with the outer peripheral surface 8d of the sintered oil-impregnated bearing 8, A seal member 9 is fixed to the sintered oil-impregnated bearing 8. Note that the means for fixing the seal member 9 and the sintered oil-impregnated bearing 8 is arbitrary, and the seal member 9 is fixed to the sintered oil-impregnated bearing 8 by, for example, adhesion.
　シール部材９の内周面９ｃ（内鍔部９ｂの内周面）は、内径寸法が軸方向下端側から上端側に向かうにつれて増大するテーパ形状をなし、対向する軸部２ａの外周面２ａ１との間に、軸方向上端側から下端側に向かうにつれて径方向隙間が縮小する第一シール空間Ｓ１を形成する（図２を参照）。第一シール空間Ｓ１は、軸方向上端側から下端側に向けて潤滑油の引き込み作用を奏し、これにより潤滑油の油面を常に第一シール空間Ｓ１の軸方向範囲内に保持し得る。 The inner circumferential surface 9c of the sealing member 9 (the inner circumferential surface of the inner flange portion 9b) has a tapered shape in which the inner diameter increases from the lower end toward the upper end in the axial direction, and is in contact with the outer circumferential surface 2a1 of the opposing shaft portion 2a. In between, a first seal space S1 is formed in which the radial clearance decreases from the upper end side to the lower end side in the axial direction (see FIG. 2). The first seal space S1 acts to draw in the lubricating oil from the upper end side to the lower end side in the axial direction, so that the oil level of the lubricating oil can always be maintained within the axial range of the first seal space S1.
　また、シール部材９の外周面９ｄ（筒状部９ａの外周面）は、外径寸法が軸方向で一定となるように形成され、対向するハウジング７の第二内周面７ｂとの間に、軸方向上端側から下端側に向かうにつれて径方向隙間の大きさが縮小する第二シール空間Ｓ２を形成する（図２を参照）。第二シール空間Ｓ２は、第一シール空間Ｓ１に比べて軸方向寸法が大きいことから、ハウジング７の内部空間に充填された潤滑油の温度変化に伴う容積変化量を吸収するバッファ機能を有し、想定される温度変化の範囲内で潤滑油の油面を常に第二シール空間Ｓ２の軸方向範囲内に保持し得る。 Further, the outer circumferential surface 9d of the seal member 9 (the outer circumferential surface of the cylindrical portion 9a) is formed so that the outer diameter dimension is constant in the axial direction, and is spaced between the second inner circumferential surface 7b of the opposing housing 7. , forming a second seal space S2 in which the size of the radial gap decreases from the upper end side to the lower end side in the axial direction (see FIG. 2). Since the second seal space S2 has a larger axial dimension than the first seal space S1, it has a buffer function to absorb the volume change due to the temperature change of the lubricating oil filled in the internal space of the housing 7. The lubricating oil level can always be maintained within the axial range of the second seal space S2 within the expected temperature change range.
　軸部材２は、軸部２ａと、軸部２ａの下端に一体又は別体に設けられたフランジ部２ｂとを備える。軸部２ａの外周面２ａ１のうち、焼結含油軸受８の内周面８ａと対向する部分は、相対的に小径な円筒面状の中逃げ部２ｃが設けられている点を除いて凹凸のない平滑な円筒面に形成されている。また、フランジ部２ｂの上端面２ｂ１及び下端面２ｂ２は平滑な平坦面状に形成されている。 The shaft member 2 includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. The portion of the outer circumferential surface 2a1 of the shaft portion 2a that faces the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 is free of unevenness, except that a hollow portion 2c in the form of a cylindrical surface with a relatively small diameter is provided. It is formed with no smooth cylindrical surface. Further, the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b are formed into smooth flat surfaces.
　蓋部材１０はハウジング７の第三内周面７ｃに適宜の手段で固定される。蓋部材１０の上端面１０ａには、対向する軸部材２のフランジ部２ｂの下端面２ｂ２との間にスラスト軸受部Ｔ２のスラスト軸受隙間を形成する円環状のスラスト軸受面が設けられている。このスラスト軸受面には、スラスト軸受部Ｔ２のスラスト軸受隙間内の潤滑油に動圧作用を発生させるための動圧発生部（スラスト動圧発生部）が設けられている。図示は省略するが、このスラスト動圧発生部は、後述する焼結含油軸受８のスラスト動圧発生部１４と同様に、例えば、スパイラル形状の動圧溝と、この動圧溝を区画する凸状の丘部とを円周方向に交互に配置することで構成される（図５を参照）。 The lid member 10 is fixed to the third inner circumferential surface 7c of the housing 7 by appropriate means. The upper end surface 10a of the lid member 10 is provided with an annular thrust bearing surface that forms a thrust bearing gap of the thrust bearing portion T2 between the lower end surface 2b2 of the flange portion 2b of the opposing shaft member 2. This thrust bearing surface is provided with a dynamic pressure generating section (thrust dynamic pressure generating section) for generating a dynamic pressure effect on the lubricating oil within the thrust bearing gap of the thrust bearing portion T2. Although not shown in the drawings, this thrust dynamic pressure generating section, like the thrust dynamic pressure generating section 14 of the sintered oil-impregnated bearing 8 described later, includes, for example, a spiral-shaped dynamic pressure groove and a convex part that partitions this dynamic pressure groove. It is constructed by alternately arranging shaped hill portions in the circumferential direction (see FIG. 5).
　焼結含油軸受８は、焼結金属の多孔質体で円筒状に形成される。この多孔質体を構成する金属組織は、原則として任意であり、例えば、純銅（工業用純銅を含む）又は銅合金の金属組織と、純鉄（工業用純鉄を含む）又はステンレス鋼などの鉄合金の金属組織のうち少なくとも一方を主に含む金属組織が採用可能である。また、焼結含油軸受８の内部空孔には、潤滑油が含浸される。 The sintered oil-impregnated bearing 8 is made of a porous body of sintered metal and is formed into a cylindrical shape. The metal structure constituting this porous body is basically arbitrary, and for example, the metal structure of pure copper (including industrial pure copper) or copper alloy, and the metal structure of pure iron (including industrial pure iron) or stainless steel. A metal structure mainly containing at least one of the metal structures of iron alloys can be adopted. Further, the internal pores of the sintered oil-impregnated bearing 8 are impregnated with lubricating oil.
　焼結含油軸受８の内周面８ａには、対向する軸部２ａの外周面２ａ１との間にラジアル軸受部Ｒ１，Ｒ２のラジアル軸受隙間を形成する円筒状のラジアル軸受面が軸方向の二箇所に離間して設けられている。２つのラジアル軸受面には、図３に示すように、ラジアル軸受隙間内の潤滑油に動圧作用を発生させるためのラジアル動圧発生部１１，１２がそれぞれ形成されている。 The inner circumferential surface 8a of the sintered oil-impregnated bearing 8 has a cylindrical radial bearing surface that forms radial bearing gaps of the radial bearing sections R1 and R2 between the outer circumferential surface 2a1 of the opposing shaft section 2a. They are placed at separate locations. As shown in FIG. 3, radial dynamic pressure generating portions 11 and 12 are formed on the two radial bearing surfaces, respectively, for generating a dynamic pressure effect on the lubricating oil within the radial bearing gap.
　ここで、内周面８ａの軸方向上側に位置する第一ラジアル動圧発生部１１は、内周面８ａの円周方向に沿って配列される複数の第一傾斜動圧溝１１ａと、第一傾斜動圧溝１１ａの間に形成される複数の第一丘部１１ｂとを有する。第一傾斜動圧溝１１ａは、内周面８ａの円周方向に対して所定角度傾斜しており、後述する軸部材２の回転時、軸部材２と焼結含油軸受８との間の潤滑油を軸受中央側に向けて引き込んで動圧を高める作用（図２中、矢印Ｆ１で示す向きの引き込み力を発生させる作用）を奏する。 Here, the first radial dynamic pressure generating section 11 located above the inner circumferential surface 8a in the axial direction includes a plurality of first inclined dynamic pressure grooves 11a arranged along the circumferential direction of the inner circumferential surface 8a, It has a plurality of first hill portions 11b formed between one inclined dynamic pressure groove 11a. The first inclined dynamic pressure groove 11a is inclined at a predetermined angle with respect to the circumferential direction of the inner peripheral surface 8a, and provides lubrication between the shaft member 2 and the sintered oil-impregnated bearing 8 when the shaft member 2 rotates, which will be described later. It has the effect of drawing oil toward the center of the bearing to increase dynamic pressure (the effect of generating a drawing force in the direction indicated by arrow F1 in FIG. 2).
　また、本実施形態では、第一ラジアル動圧発生部１１は、第一傾斜動圧溝１１ａと第一丘部１１ｂとに加えて、複数の第二傾斜動圧溝１１ｃと、複数の第二丘部１１ｄとを有する。この場合、複数の第一傾斜動圧溝１１ａ及び複数の第二傾斜動圧溝１１ｃはへリングボーン形状に配列されている。すなわち、第二傾斜動圧溝１１ｃは、内周面８ａの円周方向に対して第一傾斜動圧溝１１ａとは逆向きにかつ同じ角度だけ傾斜しており、後述する軸部材２の回転時、軸部材２と焼結含油軸受８との間の潤滑油を軸受端部側に向けて引き込んで動圧を高める作用（図２中、矢印Ｆ２で示す向きの引き込み力を発生させる作用）を奏する。 Further, in the present embodiment, the first radial dynamic pressure generating section 11 includes a plurality of second inclined dynamic pressure grooves 11c and a plurality of second inclined dynamic pressure grooves 11c, in addition to the first inclined dynamic pressure grooves 11a and the first hill portions 11b. It has a hill portion 11d. In this case, the plurality of first inclined dynamic pressure grooves 11a and the plurality of second inclined dynamic pressure grooves 11c are arranged in a herringbone shape. That is, the second inclined dynamic pressure groove 11c is inclined in the opposite direction and at the same angle as the first inclined dynamic pressure groove 11a with respect to the circumferential direction of the inner circumferential surface 8a, and the second inclined dynamic pressure groove 11c is inclined in the opposite direction and at the same angle as the first inclined dynamic pressure groove 11a. At this time, the lubricating oil between the shaft member 2 and the sintered oil-impregnated bearing 8 is drawn toward the end of the bearing to increase the dynamic pressure (an action that generates a pulling force in the direction indicated by arrow F2 in FIG. 2). play.
　本実施形態では、第一傾斜動圧溝１１ａの長手方向寸法は、第二傾斜動圧溝１１ｃの長手方向寸法よりも大きい。ここで、第一傾斜動圧溝１１ａと第二傾斜動圧溝１１ｃの傾斜角度の大きさは等しいため、第一傾斜動圧溝１１ａの長手方向寸法が第二傾斜動圧溝１１ｃの長手方向寸法より大きい場合、第一傾斜動圧溝１１ａの軸方向寸法Ｌ１は、第二傾斜動圧溝１１ｃの軸方向寸法Ｌ２よりも大きくなる（図３を参照）。また、内周面８ａの最も上端側に位置する第一傾斜動圧溝１１ａは、内周面８ａの上端部にまで形成されている（内周面８ａと上端面８ｃとの間の面取り部に第一傾斜動圧溝１１ａの上端部が開口している）。一方、第二ラジアル動圧発生部１２を構成する傾斜動圧溝１２ａ，１２ｃのうち、内周面８ａの軸方向端部側（最も下端側）に位置する第一傾斜動圧溝１２ａの下端部は、内周面８ａの下端部よりも軸方向中央側に位置している（図３を参照）。 In this embodiment, the longitudinal dimension of the first inclined dynamic pressure groove 11a is larger than the longitudinal dimension of the second inclined dynamic pressure groove 11c. Here, since the magnitude of the inclination angle of the first inclined dynamic pressure groove 11a and the second inclined dynamic pressure groove 11c is equal, the longitudinal dimension of the first inclined dynamic pressure groove 11a is equal to the longitudinal direction of the second inclined dynamic pressure groove 11c. In this case, the axial dimension L1 of the first inclined dynamic pressure groove 11a becomes larger than the axial dimension L2 of the second inclined dynamic pressure groove 11c (see FIG. 3). Furthermore, the first inclined dynamic pressure groove 11a located at the uppermost side of the inner circumferential surface 8a is formed up to the upper end of the inner circumferential surface 8a (the chamfered portion between the inner circumferential surface 8a and the upper end surface 8c). The upper end of the first inclined dynamic pressure groove 11a is open). On the other hand, among the inclined dynamic pressure grooves 12a and 12c constituting the second radial dynamic pressure generation section 12, the lower end of the first inclined dynamic pressure groove 12a located on the axial end side (lowest end side) of the inner circumferential surface 8a is located closer to the center in the axial direction than the lower end of the inner circumferential surface 8a (see FIG. 3).
　第一傾斜動圧溝１１ａと第二傾斜動圧溝１１ｃとの間には、内周面８ａの円周方向に沿って延びる真円形状の帯部１１ｅが設けられている。この帯部１１ｅによって、第一傾斜動圧溝１１ａと第二傾斜動圧溝１１ｃとが区画されている。また、第一丘部１１ｂの軸方向下端と帯部１１ｅとは連続しており、かつ、第二丘部１１ｄの軸方向上端と帯部１１ｅとは連続している。ここで、第一丘部１１ｂの軸方向下端における内径寸法と、帯部１１ｅの内径寸法とは等しい。また、第二丘部１１ｄの軸方向上端における内径寸法と、帯部１１ｅの内径寸法とは等しい。 A perfectly circular band portion 11e extending along the circumferential direction of the inner circumferential surface 8a is provided between the first inclined dynamic pressure groove 11a and the second inclined dynamic pressure groove 11c. This band portion 11e defines a first inclined dynamic pressure groove 11a and a second inclined dynamic pressure groove 11c. Further, the lower end of the first hill portion 11b in the axial direction and the band portion 11e are continuous, and the upper end of the second hill portion 11d in the axial direction and the band portion 11e are continuous. Here, the inner diameter dimension at the lower end in the axial direction of the first hill portion 11b is equal to the inner diameter dimension of the band portion 11e. Further, the inner diameter dimension at the upper end in the axial direction of the second hill portion 11d is equal to the inner diameter dimension of the band portion 11e.
　ここで、焼結含油軸受８の軸方向端部側に位置する第一丘部１１ｂには、図４Ａに示すように、第一丘部１１ｂの内径寸法が内周面８ａの軸方向中央側から軸方向端部側に向かうにつれて減少する縮径部１３が設けられている。この縮径部１３は、第一丘部１１ｂの少なくとも長手方向の一部に設けられている。本実施形態では、縮径部１３は、第一丘部１１ｂの全域にわたって設けられている。また、この縮径部１３は、テーパ状に内径寸法が縮小する形態をなしている。第一丘部１１ｂの軸方向中央側の第一端部１１ｂ１における内径寸法Ｄ１は、第一丘部１１ｂの軸方向端部側の第二端部１１ｂ２における内径寸法Ｄ２よりも大きく、その差Ｄ１－Ｄ２は、例えば１．５μｍ以下に設定される。一方、第二丘部１１ｄの内径寸法は全域にわたって一定である（図３及び図４Ａを参照）。 Here, as shown in FIG. 4A, the first hill portion 11b located on the axial end side of the sintered oil-impregnated bearing 8 has an inner diameter dimension closer to the axial center of the inner circumferential surface 8a. A reduced diameter portion 13 is provided that decreases in diameter toward the end in the axial direction. This reduced diameter portion 13 is provided in at least a portion of the first hill portion 11b in the longitudinal direction. In this embodiment, the reduced diameter portion 13 is provided over the entire first hill portion 11b. Further, the reduced diameter portion 13 has a tapered shape in which the inner diameter is reduced. The inner diameter dimension D1 at the first end portion 11b1 on the axial center side of the first hill portion 11b is larger than the inner diameter dimension D2 at the second end portion 11b2 on the axial end side of the first hill portion 11b, and the difference D1 -D2 is set to, for example, 1.5 μm or less. On the other hand, the inner diameter dimension of the second hill portion 11d is constant over the entire area (see FIGS. 3 and 4A).
　第一傾斜動圧溝１１ａの溝深さは、軸方向中央側から軸方向端部側に向かうにつれて増大している。本実施形態では、第一傾斜動圧溝１１ａの内径寸法は一定であるから（図４Ａを参照）、溝深さの増大量は第一丘部１１ｂの内径寸法の増大量（ここでは内径寸法差Ｄ１－Ｄ２）に等しい。一例として、第一傾斜動圧溝１１ａの軸方向中央側の第一端部１１ａ１における溝深さｄ１は、２．５μｍ以上でかつ５．０μｍ以下である。また、第一傾斜動圧溝１１ａの軸方向端部側の第二端部１１ａ２における溝深さｄ２は、２．５μｍを超えかつ６．５μｍ以下である。一方、第二傾斜動圧溝１１ｃの溝深さは全域にわたって一定である（図３及び図４Ａを参照）。 The groove depth of the first inclined dynamic pressure groove 11a increases from the axial center side toward the axial end side. In this embodiment, since the inner diameter dimension of the first inclined dynamic pressure groove 11a is constant (see FIG. 4A), the amount of increase in the groove depth is the amount of increase in the inner diameter dimension of the first hill portion 11b (in this case, the inner diameter dimension equal to the difference D1-D2). As an example, the groove depth d1 at the first end portion 11a1 on the axial center side of the first inclined dynamic pressure groove 11a is 2.5 μm or more and 5.0 μm or less. Further, the groove depth d2 at the second end portion 11a2 on the axial end side of the first inclined dynamic pressure groove 11a is more than 2.5 μm and less than 6.5 μm. On the other hand, the groove depth of the second inclined dynamic pressure groove 11c is constant over the entire area (see FIGS. 3 and 4A).
　内周面８ａの軸方向下側に位置する第二ラジアル動圧発生部１２は、第一ラジアル動圧発生部１１と同様、複数の第一傾斜動圧溝１２ａと、複数の第一丘部１２ｂと、複数の第二傾斜動圧溝１２ｃと、複数の第二丘部１２ｄと、帯部１２ｅとを有する。ここで、第一傾斜動圧溝１２ａの長手方向寸法と、第二傾斜動圧溝１２ｃの長手方向寸法とは等しい。本実施形態では、第一傾斜動圧溝１２ａと第二傾斜動圧溝１２ｃの傾斜角度の大きさは等しいため、第一傾斜動圧溝１２ａの長手方向寸法が第二傾斜動圧溝１２ｃの長手方向寸法と等しい場合、第一傾斜動圧溝１２ａの軸方向寸法Ｌ３は、第二傾斜動圧溝１２ｃの軸方向寸法Ｌ４に等しくなる（図３を参照）。各傾斜動圧溝１２ａ，１２ｃの溝深さは全域にわたって一定である。第一丘部１２ｂ及び第二丘部１２ｄの内径寸法はともに全域にわたって一定である（図４Ｂを参照）。すなわち、第二ラジアル動圧発生部１２の丘部１２ｂ，１２ｄには縮径部１３は設けられていない。もちろん、上述した各傾斜動圧溝１２ａ，１２ｃ及び各丘部１２ｂ，１２ｄの寸法関係は一例に過ぎない。例えば、内周面８ａの最も下端側に位置する第一傾斜動圧溝１２ａの内径寸法が軸方向で変動（例えば下端側に向かうにつれて減少）してもよい。第一傾斜動圧溝１２ａの溝深さについても同様に軸方向で変動（下端側に向かうにつれて減少）してもよい。 Like the first radial dynamic pressure generating section 11, the second radial dynamic pressure generating section 12 located on the lower side of the inner circumferential surface 8a in the axial direction includes a plurality of first inclined dynamic pressure grooves 12a and a plurality of first hill sections. 12b, a plurality of second inclined dynamic pressure grooves 12c, a plurality of second hill portions 12d, and a band portion 12e. Here, the longitudinal dimension of the first inclined dynamic pressure groove 12a and the longitudinal dimension of the second inclined dynamic pressure groove 12c are equal. In this embodiment, since the first inclined dynamic pressure groove 12a and the second inclined dynamic pressure groove 12c have the same inclination angle, the longitudinal dimension of the first inclined dynamic pressure groove 12a is the same as that of the second inclined dynamic pressure groove 12c. When equal to the longitudinal dimension, the axial dimension L3 of the first inclined dynamic pressure groove 12a becomes equal to the axial dimension L4 of the second inclined dynamic pressure groove 12c (see FIG. 3). The groove depth of each inclined dynamic pressure groove 12a, 12c is constant over the entire area. The inner diameter dimensions of the first hill portion 12b and the second hill portion 12d are both constant over the entire area (see FIG. 4B). That is, the reduced diameter portion 13 is not provided in the hill portions 12b and 12d of the second radial dynamic pressure generating portion 12. Of course, the above-described dimensional relationship between the inclined dynamic pressure grooves 12a, 12c and the hill portions 12b, 12d is merely an example. For example, the inner diameter dimension of the first inclined dynamic pressure groove 12a located at the lowest end of the inner circumferential surface 8a may vary in the axial direction (eg, decrease toward the lower end). The groove depth of the first inclined dynamic pressure groove 12a may similarly vary in the axial direction (decreasing toward the lower end side).
　この場合、第一ラジアル動圧発生部１１における軸部２ａと焼結含油軸受８との間のラジアル軸受隙間Ｇ１は、図４Ａに示すように、軸方向下端から軸方向中央（厳密には第一丘部１１ｂの第一端部１１ｂ１）まで一定で、軸方向中央から軸方向上端（第一丘部１１ｂの第二端部１１ｂ２）に向かうにつれて減少する。一方、第二ラジアル動圧発生部１２におけるラジアル軸受隙間Ｇ２は、図４Ｂに示すように、その軸方向全域にわたって一定である。なお、縮径部１３におけるラジアル軸受隙間Ｇ１は、上述した内径寸法差Ｄ１－Ｄ２（最大で１．５μｍ）以上であることが望ましい。 In this case, the radial bearing gap G1 between the shaft portion 2a and the sintered oil-impregnated bearing 8 in the first radial dynamic pressure generating portion 11 is defined as the distance from the axial lower end to the axial center (strictly speaking, the axial center) as shown in FIG. It is constant up to the first end 11b1 of the first hill 11b, and decreases from the center in the axial direction toward the upper end in the axial direction (the second end 11b2 of the first hill 11b). On the other hand, the radial bearing gap G2 in the second radial dynamic pressure generating section 12 is constant over the entire axial direction, as shown in FIG. 4B. The radial bearing gap G1 in the reduced diameter portion 13 is desirably equal to or larger than the above-mentioned inner diameter difference D1-D2 (maximum 1.5 μm).
　焼結含油軸受８の下端面８ｂには、対向するフランジ部２ｂの上端面２ｂ１との間にスラスト軸受部Ｔ１のスラスト軸受隙間を形成する円環状のスラスト軸受面が設けられている。このスラスト軸受面には、図５に示すように、スラスト軸受部Ｔ１のスラスト軸受隙間内の潤滑油に動圧作用を発生させるための動圧発生部（スラスト動圧発生部）１４が形成されている。図示例のスラスト動圧発生部１４は、スパイラル形状のスラスト動圧溝１４ａと、スラスト動圧溝１４ａを区画する凸状の丘部１４ｂとを円周方向に交互に配列することで構成される。丘部１４ｂの高さ寸法は全域にわたって一定である。また、上端面２ｂ１とスラスト動圧溝１４ａの溝底面とは同一平面上にある。 The lower end surface 8b of the sintered oil-impregnated bearing 8 is provided with an annular thrust bearing surface that forms a thrust bearing gap of the thrust bearing portion T1 between the upper end surface 2b1 of the opposing flange portion 2b. As shown in FIG. 5, a dynamic pressure generating section (thrust dynamic pressure generating section) 14 is formed on this thrust bearing surface to generate a dynamic pressure effect on the lubricating oil in the thrust bearing gap of the thrust bearing section T1. ing. The illustrated thrust dynamic pressure generation section 14 is configured by alternately arranging spiral-shaped thrust dynamic pressure grooves 14a and convex hill portions 14b that partition the thrust dynamic pressure grooves 14a in the circumferential direction. . The height dimension of the hill portion 14b is constant over the entire area. Further, the upper end surface 2b1 and the groove bottom surface of the thrust dynamic pressure groove 14a are on the same plane.
　焼結含油軸受８の上端面８ｃの半径方向中間位置には、図３に示すように、断面楔状の環状溝８ｃ１が形成される。また、上端面８ｃの環状溝８ｃ１より半径方向内側には、環状溝８ｃ１と内周面８ａとをつなぐ半径方向溝８ｃ２が円周方向複数箇所に形成される。 As shown in FIG. 3, an annular groove 8c1 having a wedge-shaped cross section is formed at a radially intermediate position of the upper end surface 8c of the sintered oil-impregnated bearing 8. Further, radial grooves 8c2 connecting the annular groove 8c1 and the inner circumferential surface 8a are formed at a plurality of locations in the circumferential direction on the radially inner side of the annular groove 8c1 of the upper end surface 8c.
　焼結含油軸受８の外周面８ｄには、軸方向に伸びる複数本（例えば３本）の軸方向溝８ｄ１が形成される。本実施形態では、複数の軸方向溝８ｄ１は、相互に円周方向で等間隔だけ離れた位置に形成されている。これら軸方向溝８ｄ１は、上述した環状溝８ｃ１及び半径方向溝８ｃ２と共に軸受内部空間における潤滑油の循環路を形成し、これにより円滑な潤滑油の供給状態を確保可能としている（詳細は後述する）。 A plurality of (for example, three) axial grooves 8d1 extending in the axial direction are formed on the outer peripheral surface 8d of the sintered oil-impregnated bearing 8. In this embodiment, the plurality of axial grooves 8d1 are formed at equal intervals apart from each other in the circumferential direction. These axial grooves 8d1, together with the annular groove 8c1 and the radial groove 8c2, form a circulation path for lubricating oil in the bearing internal space, thereby making it possible to ensure a smooth lubricating oil supply state (details will be described later). ).
　以下、上記構成の焼結含油軸受８の製造方法の一例を説明する。 Hereinafter, an example of a method for manufacturing the sintered oil-impregnated bearing 8 having the above structure will be described.
　本発明に係る焼結含油軸受８は、原料粉末を圧縮成形して圧粉体を得る圧粉成形工程（ｓ１）と、圧粉体を焼結して焼結体８Ｓを得る焼結工程（ｓ２）と、焼結体８Ｓにサイジングを施して、焼結体８Ｓの少なくとも内周面８Ｓａにラジアル動圧発生部１１，１２をなす傾斜動圧溝１１ａ，１１ｃ，１２ａ，１２ｃを成形する動圧溝サイジング工程（ｓ３）とを主に備える。必要に応じて、焼結工程（ｓ２）の後で動圧溝サイジング工程（ｓ３）の前に、焼結体８Ｓに寸法サイジングを施す寸法サイジング工程と、焼結体８Ｓの内周面８Ｓａに回転サイジングを施す回転サイジング工程とを設けてもよい。 The sintered oil-impregnated bearing 8 according to the present invention includes a powder compacting step (s1) in which raw powder is compression-molded to obtain a compact, and a sintering step (s1) in which the compact is sintered to obtain a sintered compact 8S. s2) and sizing the sintered body 8S to form inclined dynamic pressure grooves 11a, 11c, 12a, 12c forming the radial dynamic pressure generating parts 11, 12 on at least the inner circumferential surface 8Sa of the sintered body 8S. It mainly includes a pressure groove sizing step (s3). If necessary, after the sintering process (s2) and before the dynamic pressure groove sizing process (s3), a dimensional sizing process is performed in which the sintered body 8S is sized, and the inner peripheral surface 8Sa of the sintered body 8S is A rotational sizing process for performing rotational sizing may also be provided.
（ｓ１）圧粉成形工程
　まず、最終的な製品となる焼結含油軸受８の材料となる原料粉末を用意し、これを金型プレス成形により所定の形状に圧縮成形する。具体的には、図示は省略するが、ダイと、ダイの孔内に挿入配置されるコアピンと、ダイとコアピンとの間に配設され、ダイに対して昇降可能に構成された下パンチ、および、ダイと下パンチの何れに対しても相対変位（昇降）可能に構成された上パンチとで構成される成形金型を用いて原料粉末の圧縮成形を行う。この場合、ダイの内周面とコアピンの外周面、および、下パンチの上端面とで区画形成される空間に原料粉末を充填し、然る後、下パンチを固定した状態で上パンチを下降させ、充填状態の原料粉末を軸方向に加圧する。そして、加圧しながら所定の位置まで上パンチを下降させ、原料粉末を所定の軸方向寸法にまで圧縮することで、圧粉体が成形される。 (s1) Powder compacting process First, a raw material powder that will be the material of the sintered oil-impregnated bearing 8 that will be the final product is prepared, and this is compression-molded into a predetermined shape by die press molding. Specifically, although not shown, a die, a core pin inserted into a hole of the die, a lower punch disposed between the die and the core pin and configured to be movable up and down with respect to the die; Then, compression molding of the raw material powder is performed using a molding die composed of a die and an upper punch configured to be movable relative to both the lower punch (elevating and lowering). In this case, the space defined by the inner peripheral surface of the die, the outer peripheral surface of the core pin, and the upper end surface of the lower punch is filled with raw material powder, and then the upper punch is lowered with the lower punch fixed. and pressurizes the packed raw material powder in the axial direction. Then, the upper punch is lowered to a predetermined position while applying pressure, and the raw powder is compressed to a predetermined axial dimension, thereby forming a green compact.
　ここで、原料粉末には、任意の金属粉末を一種類又は二種類以上含むものが使用される。本実施形態では、純銅粉末と、鉄合金粉末としてのステンレス鋼粉末とを主に含む原料粉末が使用される。もちろん、ステンレス鋼粉末に代えて純鉄粉末を使用してもよいし、ステンレス鋼以外の鉄合金粉末を使用してもよい。あるいは、ステンレス鋼粉末等の鉄合金粉末と純鉄粉末との混合粉末を、純銅粉末に加えたものを原料粉末として使用してもよい。要は、焼結して得らえる焼結含油軸受８が上述した金属組織を有するように原料粉末の組成を設定すればよい。もちろん、原料粉末には、上述した金属粉末以外の物質を配合することもでき、例えば黒鉛や、アミドワックス系の固体潤滑剤粉末などを配合してもよい。 Here, the raw material powder used includes one or more types of arbitrary metal powders. In this embodiment, a raw material powder mainly containing pure copper powder and stainless steel powder as an iron alloy powder is used. Of course, pure iron powder may be used instead of stainless steel powder, or iron alloy powder other than stainless steel may be used. Alternatively, a mixed powder of iron alloy powder such as stainless steel powder and pure iron powder may be added to pure copper powder and used as the raw material powder. In short, the composition of the raw material powder may be set so that the sintered oil-impregnated bearing 8 obtained by sintering has the above-mentioned metal structure. Of course, substances other than the above-mentioned metal powders can also be blended into the raw material powder, such as graphite or amide wax-based solid lubricant powder.
（ｓ２）焼結工程
　上述のようにして、圧粉体を得た後、この圧粉体を原料粉末、特に原料粉末に含まれる金属粉末の組成に応じた温度で焼結することにより、焼結体８Ｓを得る（図６Ａを参照）。例えば、上述のように原料粉末が純銅粉末を含む場合、焼結時の温度は７５０℃以上でかつ銅の融点未満の温度に設定される。 (s2) Sintering process After obtaining the green compact as described above, the green compact is sintered at a temperature that corresponds to the composition of the raw powder, especially the metal powder contained in the raw powder. A concrete 8S is obtained (see Figure 6A). For example, when the raw material powder contains pure copper powder as described above, the temperature during sintering is set to 750° C. or higher and lower than the melting point of copper.
（ｓ３）動圧溝サイジング工程
　上記工程ｓ１，ｓ２を経て得られた焼結体８Ｓに対して所定の型成形（動圧溝サイジング）を施すことで、焼結体８Ｓの内周面８Ｓａにラジアル動圧発生部１１，１２をなす傾斜動圧溝１１ａ，１１ｃ，１２ａ，１２ｃを形成する。ここで使用する成形装置２０は、図６Ａに示すように、焼結体８Ｓの圧入穴２１ａを有するダイ２１と、ダイ２１の圧入穴２１ａに挿入可能に配置されるサイジングピン２２と、ダイ２１とサイジングピン２２との間に配設され、ダイ２１に対して相対的に昇降可能に構成された下パンチ２３、および、ダイ２１と下パンチ２３の何れに対しても昇降可能に構成された上パンチ２４とを有する。この場合、ダイ２１の圧入穴２１ａの内径寸法は、サイジングすべき焼結体８Ｓの圧入代に応じて適宜設定される。また、サイジングピン２２の外周面には、成形すべき動圧溝１１ａ，１１ｃ，１２ａ，１２ｃに対応する形状の第１成形型２２ａが設けられると共に（図６Ａを参照）、上パンチ２４の上端面２４ａには、成形すべき下端面８ｂのスラスト動圧溝１４ａに対応する形状の第２成形型が設けられる（図示は省略）。 (s3) Dynamic pressure groove sizing process By performing predetermined mold forming (dynamic pressure groove sizing) on the sintered body 8S obtained through the above steps s1 and s2, the inner circumferential surface 8Sa of the sintered body 8S is Inclined dynamic pressure grooves 11a, 11c, 12a, and 12c forming radial dynamic pressure generating portions 11 and 12 are formed. As shown in FIG. 6A, the molding device 20 used here includes a die 21 having a press-fit hole 21a of the sintered body 8S, a sizing pin 22 arranged so as to be insertable into the press-fit hole 21a of the die 21, and a die 21 having a press-fit hole 21a of the sintered body 8S. and the sizing pin 22, the lower punch 23 is configured to be movable up and down relative to the die 21, and the lower punch 23 is configured to be movable up and down relative to both the die 21 and the lower punch 23. It has an upper punch 24. In this case, the inner diameter of the press-fit hole 21a of the die 21 is appropriately set according to the press-fit allowance of the sintered body 8S to be sized. Further, a first mold 22a having a shape corresponding to the dynamic pressure grooves 11a, 11c, 12a, 12c to be molded is provided on the outer peripheral surface of the sizing pin 22 (see FIG. 6A), and a first mold 22a is provided on the outer peripheral surface of the upper punch 24. A second molding die having a shape corresponding to the thrust dynamic pressure groove 14a of the lower end surface 8b to be molded is provided on the end surface 24a (not shown).
　ここで、第１成形型２２ａは、第一傾斜動圧溝１１ａ，１２ａ及び第二傾斜動圧溝１１ｃ，１２ｃを型成形する凸状成形部２２ａ１と、第一丘部１１ｂ，１２ｂと第二丘部１１ｄ，１２ｄ、及び帯部１１ｅ，１２ｅを型成形する凹状成形部２２ａ２とで構成される。 Here, the first mold 22a has a convex molding part 22a1 for molding the first inclined dynamic pressure grooves 11a, 12a and the second inclined dynamic pressure grooves 11c, 12c, the first hill parts 11b, 12b, and the second inclined dynamic pressure grooves 11b, 12b. It is composed of hill portions 11d and 12d, and a concave molding portion 22a2 for molding the band portions 11e and 12e.
　この場合、凹状成形部２２ａ２のうち第一ラジアル動圧発生部１１の第一丘部１１ｂに対応する部分（縮径部成形部２２ａ３）を除き、凸状成形部２２ａ１の外径寸法と、サイジングピン２２の外周面のうち第１成形型２２ａ以外の領域の外径寸法とは同一に設定される。また、縮径部成形部２２ａ３の軸方向寸法Ｈ１は、成形すべき縮径部１３（第一丘部１１ｂ）の軸方向寸法Ｈ２よりも大きく設定されている（後述する図７（ａ）及び（ｂ）を参照）。 In this case, the outer diameter dimension and sizing of the convex molded part 22a1 are excluded from the concave molded part 22a2, except for the part corresponding to the first hill part 11b of the first radial dynamic pressure generating part 11 (the reduced diameter part molded part 22a3). The outer diameter of the outer peripheral surface of the pin 22 in a region other than the first mold 22a is set to be the same. Further, the axial dimension H1 of the reduced diameter portion forming portion 22a3 is set larger than the axial dimension H2 of the reduced diameter portion 13 (first hill portion 11b) to be formed (see FIG. 7(a) and (see (b)).
　また、凸状成形部２２ａ１と凹状成形部２２ａ２の外径寸法差の半分の値が、例えば成形すべき傾斜動圧溝１１ａ，１１ｃ，１２ａ，１２ｃの溝深さの狙い値よりも大きくなるように、凸状成形部２２ａ１の外径寸法と凹状成形部２２ａ２の外径寸法がそれぞれ設定される。 Also, half of the difference in outer diameter between the convex molded part 22a1 and the concave molded part 22a2 is set to be larger than the target value of the groove depth of the inclined dynamic pressure grooves 11a, 11c, 12a, 12c to be molded, for example. The outer diameter of the convex molded portion 22a1 and the outer diameter of the concave molded portion 22a2 are set respectively.
　次に、上記構成の成形装置２０を用いた動圧溝サイジングの一態様を説明する。まず、図６Ａに示すように、ダイ２１の上端面２１ｂに焼結体８Ｓを配置した状態で、その上方から上パンチ２４とサイジングピン２２を下降させる。これにより、焼結体８Ｓの内周にサイジングピン２２を挿入し、サイジングピン２２の外周に設けておいた第１成形型２２ａを内周面８Ｓａと半径方向で対向させる。この時点で、第１成形型２２ａの縮径部成形部２２ａ３の上端部と、成形すべき縮径部１３（第一丘部１１ｂ）の上端部とが同一の軸方向位置となるように、第一成形型２２ａが配置される（図６Ｂを参照）。 Next, one aspect of dynamic pressure groove sizing using the molding apparatus 20 having the above configuration will be described. First, as shown in FIG. 6A, with the sintered body 8S placed on the upper end surface 21b of the die 21, the upper punch 24 and the sizing pin 22 are lowered from above. Thereby, the sizing pin 22 is inserted into the inner circumference of the sintered body 8S, and the first mold 22a provided on the outer circumference of the sizing pin 22 is made to face the inner circumferential surface 8Sa in the radial direction. At this point, the upper end of the reduced diameter part forming part 22a3 of the first mold 22a and the upper end of the reduced diameter part 13 (first hill part 11b) to be formed are at the same axial position. A first mold 22a is placed (see FIG. 6B).
　そして、図６Ｂに示す状態から、上パンチ２４のみを引き続き下降させて焼結体８Ｓの上端面８Ｓｃを押圧する。これにより、焼結体８Ｓがダイ２１の圧入穴２１ａに押込まれ、焼結体８Ｓの外周面８Ｓｄが圧迫されると共に、予め内周に挿入したサイジングピン２２の第１成形型２２ａに内周面８Ｓａが食い付く。また、この状態から、さらに上パンチ２４を下降させて、焼結体８Ｓを上パンチ２４と下パンチ２３とで挟持し、外径方向への変形をダイ２１により拘束された状態の焼結体８Ｓを軸方向に圧迫することで、さらに内周面８Ｓａが第１成形型２２ａに食い付く（図７Ａを参照）。なお、サイジングピン２２は第１成形型２２ａに焼結体８Ｓの内周面８Ｓａが食い付くことで、焼結体８Ｓの下降に伴って下降する。このようにして、第１成形型２２ａの形状、具体的には凸状成形部２２ａ１と凹状成形部２２ａ２、及び縮径部成形部２２ａ３の形状がそれぞれ内周面８Ｓａに転写されることで、第一傾斜動圧溝１１ａ，１２ａと第二傾斜動圧溝１１ｃ，１２ｃ、第一丘部１１ｂ，１２ｂと第二丘部１１ｄ，１２ｄ、帯部１１ｅ，１２ｅ、及び縮径部１３が成形される（図７Ｂを参照）。また、この際、上パンチ２４の下端面２４ａに設けた第２成形型が焼結体８Ｓの下端面８Ｓｂに食い込むことで、下端面８Ｓｂに第２成形型の形状が転写され、対応するスラスト動圧溝１４ａと丘部１４ｂとが成形される。 Then, from the state shown in FIG. 6B, only the upper punch 24 is continuously lowered to press the upper end surface 8Sc of the sintered body 8S. As a result, the sintered body 8S is pushed into the press-fit hole 21a of the die 21, the outer peripheral surface 8Sd of the sintered body 8S is pressed, and the inner periphery is inserted into the first mold 22a of the sizing pin 22 inserted into the inner periphery in advance. Surface 8Sa bites. Further, from this state, the upper punch 24 is further lowered to sandwich the sintered body 8S between the upper punch 24 and the lower punch 23, and the sintered body is restrained from being deformed in the outer radial direction by the die 21. By pressing 8S in the axial direction, the inner circumferential surface 8Sa further bites into the first mold 22a (see FIG. 7A). Note that the sizing pin 22 descends as the sintered body 8S descends as the inner circumferential surface 8Sa of the sintered body 8S bites into the first mold 22a. In this way, the shape of the first mold 22a, specifically the shape of the convex molded part 22a1, the concave molded part 22a2, and the reduced diameter part molded part 22a3, are each transferred to the inner peripheral surface 8Sa, The first inclined dynamic pressure grooves 11a, 12a, the second inclined dynamic pressure grooves 11c, 12c, the first hill portions 11b, 12b, the second hill portions 11d, 12d, the band portions 11e, 12e, and the reduced diameter portion 13 are formed. (See Figure 7B). At this time, the second mold provided on the lower end surface 24a of the upper punch 24 bites into the lower end surface 8Sb of the sintered body 8S, so that the shape of the second mold is transferred to the lower end surface 8Sb, and the corresponding thrust Dynamic pressure grooves 14a and hill portions 14b are formed.
　このようにして焼結体８Ｓの内周面８Ｓａ及び下端面８Ｓｂに所定のラジアル動圧発生部１１，１２とスラスト動圧発生部を成形した後、ダイ２１を下パンチ２３に対して相対的に下降させて、ダイ２１による焼結体８Ｓの拘束状態を解除する（図７Ｂを参照）。これにより、焼結体８Ｓは外径方向へのスプリングバックを生じ、外周面８Ｓｄの外径寸法及び内周面８Ｓａの内径寸法が増加する。また、上パンチ２４を上昇させて、上パンチ２４と下パンチ２３とによる焼結体８Ｓの軸方向の拘束状態を解除することで（図７Ｂを参照）、焼結体８Ｓは軸方向へのスプリングバックを生じ、外周面８Ｓｄ及び内周面８Ｓａの軸方向寸法が増加する。このように、ダイ２１の下降後、焼結体８Ｓが外径方向へのスプリングバックを生じることで、内周面８Ｓａが拡径するので、内径側に突出して成形される丘部１１ｂ，１１ｄ，１２ｂ，１２ｄと凸状成形部２２ａ１との干渉を可及的に回避して、サイジングピン２２を焼結体８Ｓから抜き取ることができる。また、この際、スプリングバックの量を調整することで、第一丘部１１ｂに設けられる縮径部１３と凸状成形部２２ａ１との干渉についても可及的に回避して、サイジングピン２２を焼結体８Ｓから抜き取ることができる。これにより、内周面８ａにラジアル動圧発生部１１，１２、及び縮径部１３が形成された焼結体８Ｓ、すなわち、図３～図５に示す形態の焼結含油軸受８を得ることができる。なお、上記サイジングを経て製造される焼結含油軸受８の内径寸法は例えば１～５ｍｍ、外径寸法は３～８ｍｍ、軸方向寸法は２～１５ｍｍである。 After forming the predetermined radial dynamic pressure generating parts 11, 12 and thrust dynamic pressure generating part on the inner peripheral surface 8Sa and lower end surface 8Sb of the sintered body 8S in this way, the die 21 is moved relative to the lower punch 23. to release the restraint of the sintered body 8S by the die 21 (see FIG. 7B). As a result, the sintered body 8S springs back in the outer diameter direction, and the outer diameter dimension of the outer circumferential surface 8Sd and the inner diameter dimension of the inner circumferential surface 8Sa increase. In addition, by raising the upper punch 24 and releasing the axial restraint of the sintered body 8S by the upper punch 24 and the lower punch 23 (see FIG. 7B), the sintered body 8S is moved in the axial direction. Springback occurs, and the axial dimensions of the outer circumferential surface 8Sd and the inner circumferential surface 8Sa increase. In this way, after the die 21 is lowered, the sintered body 8S springs back in the outer diameter direction, and the inner circumferential surface 8Sa expands in diameter, so that the hill portions 11b and 11d formed to protrude inwardly. , 12b, 12d and the convex molded portion 22a1 as much as possible, and the sizing pin 22 can be extracted from the sintered body 8S. In addition, at this time, by adjusting the amount of springback, interference between the reduced diameter portion 13 provided on the first hill portion 11b and the convex molded portion 22a1 is avoided as much as possible, and the sizing pin 22 is It can be extracted from the sintered body 8S. As a result, the sintered body 8S in which the radial dynamic pressure generating parts 11, 12 and the reduced diameter part 13 are formed on the inner peripheral surface 8a, that is, the sintered oil-impregnated bearing 8 in the form shown in FIGS. 3 to 5 is obtained. I can do it. The sintered oil-impregnated bearing 8 manufactured through the above sizing process has, for example, an inner diameter of 1 to 5 mm, an outer diameter of 3 to 8 mm, and an axial dimension of 2 to 15 mm.
　然る後、潤滑油を内部空孔に含浸させることで、焼結含油軸受８が完成する。なお、焼結含油軸受８をハウジング７に組付けた後に、焼結含油軸受８に潤滑油を含浸させてもよい。要は、図２に示す流体動圧軸受装置１が完成した時点で、焼結含油軸受８の内部空孔を含む軸受内部空間が潤滑油で満たされた状態であれば、含浸手段やそのタイミングは任意である。また、潤滑油としては、種々の油が使用可能であるが、ＨＤＤ等のディスク駆動装置用に提供される場合、その使用時あるいは輸送時における温度変化を考慮して、低蒸発率及び低粘度性に優れたエステル系潤滑油、例えばジオクチルセバケート（ＤＯＳ）、ジオクチルアゼレート（ＤＯＺ）等が好適に使用可能である。 After that, the internal pores are impregnated with lubricating oil to complete the sintered oil-impregnated bearing 8. Note that after the sintered oil-impregnated bearing 8 is assembled into the housing 7, the sintered oil-impregnated bearing 8 may be impregnated with lubricating oil. In short, if the internal space of the sintered oil-impregnated bearing 8 including the internal cavity is filled with lubricating oil when the fluid dynamic bearing device 1 shown in FIG. is optional. In addition, various types of lubricating oil can be used, but when provided for disk drive devices such as HDDs, oils with low evaporation rate and low viscosity are required, taking into account temperature changes during use or transportation. Ester-based lubricating oils with excellent properties, such as dioctyl sebacate (DOS) and dioctyl azelate (DOZ), can be suitably used.
　以上の構成を有する流体動圧軸受装置１において、軸部材２と焼結含油軸受８との相対回転開始前、焼結含油軸受８の内周面８ａに設けた二つのラジアル軸受面と、これらに対向する軸部２ａの外周面２ａ１との間にはラジアル軸受隙間Ｇ１，Ｇ２がそれぞれ形成された状態にある（図４Ａ及び図４Ｂを参照）。そして軸部材２と焼結含油軸受８の相対回転が開始されるのに伴い、両ラジアル軸受隙間Ｇ１，Ｇ２に形成される油膜の圧力がラジアル動圧発生部１１，１２（傾斜動圧溝１１ａ，１１ｃ，１２ａ，１２ｃ）の動圧作用によって高められ、その結果、軸部材２をラジアル方向に相対回転自在に非接触支持するラジアル軸受部Ｒ１，Ｒ２が軸方向に離間した二箇所に形成される（図２を参照）。このとき、軸部２ａの外周面２ａ１に中逃げ部２ｃを設けたことにより、二つのラジアル軸受隙間Ｇ１，Ｇ２間には円筒状の潤滑油溜りが形成される。そのため、各ラジアル軸受隙間Ｇ１，Ｇ２における油膜切れ、すなわちラジアル軸受部Ｒ１，Ｒ２の軸受性能低下を可及的に防止することができる。 In the fluid dynamic bearing device 1 having the above configuration, before the relative rotation between the shaft member 2 and the sintered oil-impregnated bearing 8 starts, two radial bearing surfaces provided on the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 and Radial bearing gaps G1 and G2 are respectively formed between the outer circumferential surface 2a1 of the shaft portion 2a facing the shaft portion 2a (see FIGS. 4A and 4B). Then, as the relative rotation between the shaft member 2 and the sintered oil-impregnated bearing 8 starts, the pressure of the oil film formed in the gaps G1 and G2 of both radial bearings increases , 11c, 12a, 12c), and as a result, radial bearing portions R1 and R2 that support the shaft member 2 relatively rotatably in the radial direction in a non-contact manner are formed at two locations spaced apart in the axial direction. (See Figure 2). At this time, a cylindrical lubricating oil reservoir is formed between the two radial bearing gaps G1 and G2 by providing the hollow part 2c on the outer circumferential surface 2a1 of the shaft part 2a. Therefore, it is possible to prevent the oil film from running out in each of the radial bearing gaps G1 and G2, that is, from deteriorating the bearing performance of the radial bearing portions R1 and R2 as much as possible.
　また、軸部材２と焼結含油軸受８の相対回転時、下端面８ｂに設けたスラスト動圧発生部１４の動圧作用により、焼結含油軸受８の下端面８ｂと、スラスト軸受面に対向するフランジ部２ｂの上端面２ｂ１との間に潤滑油膜が形成され、当該油膜の圧力が高められる。また、蓋部材１０の上端面１０ａに設けられたスラスト動圧発生部の動圧作用により、蓋部材１０の上端面１０ａと、上端面１０ａに対向するフランジ部２ｂの下端面２ｂ２との間に潤滑油膜が形成され（スラスト軸受隙間が形成され）、当該油膜の圧力が高められる。この結果、軸部材２をスラスト一方向及び他方向に相対回転自在に非接触支持するスラスト軸受部Ｔ１，Ｔ２が形成される。 In addition, when the shaft member 2 and the sintered oil-impregnated bearing 8 rotate relative to each other, the lower end surface 8b of the sintered oil-impregnated bearing 8 faces the thrust bearing surface due to the dynamic pressure action of the thrust dynamic pressure generating section 14 provided on the lower end surface 8b. A lubricating oil film is formed between the upper end surface 2b1 of the flange portion 2b and the pressure of the oil film is increased. Further, due to the dynamic pressure action of the thrust dynamic pressure generation section provided on the upper end surface 10a of the lid member 10, a gap is created between the upper end surface 10a of the lid member 10 and the lower end surface 2b2 of the flange portion 2b facing the upper end surface 10a. A lubricating oil film is formed (a thrust bearing gap is formed), and the pressure of the oil film is increased. As a result, thrust bearing portions T1 and T2 are formed that support the shaft member 2 in a non-contact manner so as to be relatively rotatable in one thrust direction and the other thrust direction.
　また、焼結含油軸受８の内周面８ａに設けられた第一ラジアル動圧発生部１１をなす第一傾斜動圧溝１１ａの長手方向寸法Ｌ１は、第二傾斜動圧溝１１ｃの長手方向寸法Ｌ２よりも大きい（図３を参照）。そのため、軸部材２の回転時、第一傾斜動圧溝１１ａによる潤滑油の軸受中心側への引き込み力Ｆ１が、第二傾斜動圧溝１１ｃによる潤滑油の軸受端部側への引き込み力Ｆ２を上回る。この引き込み力の差により、ラジアル軸受隙間Ｇ１に満たされた潤滑油は、全体として焼結含油軸受８の軸方向下側に向けた流れを生じ、第１スラスト軸受部Ｔ１のスラスト軸受隙間から、軸方向溝８ｄ１、シール部材９の内鍔部９ｂの下端面と焼結含油軸受８の上端面８ｃとの隙間、環状溝８ｃ１、半径方向溝８ｃ２という経路１５を辿って、第１ラジアル軸受部Ｒ１のラジアル軸受隙間に再び引き込まれる。すなわち、軸受内部空間に、ラジアル軸受隙間Ｇ１，Ｇ２を含む潤滑油の循環路１５が形成される。これにより、軸受内部空間内の潤滑油の圧力が局部的に負圧になる現象を防止して、負圧発生に伴う気泡の生成、気泡の生成に起因する潤滑油の漏れや軸受性能の劣化、振動の発生等の問題が回避される。また、何らかの理由で潤滑油中に気泡が混入した場合、気泡が潤滑油に伴って循環する際に各シール空間Ｓ１，Ｓ２内の潤滑油の油面（気液界面）から外気に排出されるので、気泡による悪影響が効果的に防止される。 Further, the longitudinal dimension L1 of the first inclined dynamic pressure groove 11a forming the first radial dynamic pressure generating section 11 provided on the inner circumferential surface 8a of the sintered oil-impregnated bearing 8 is the longitudinal direction dimension L1 of the second inclined dynamic pressure groove 11c. larger than dimension L2 (see Figure 3). Therefore, when the shaft member 2 rotates, the drawing force F1 of the lubricating oil toward the bearing center side by the first inclined dynamic pressure groove 11a is increased by the drawing force F2 of lubricating oil toward the bearing end side by the second inclined dynamic pressure groove 11c. exceed. Due to this difference in pulling force, the lubricating oil filling the radial bearing gap G1 causes a flow toward the axially downward side of the sintered oil-impregnated bearing 8 as a whole, and from the thrust bearing gap of the first thrust bearing portion T1, Following the path 15 consisting of the axial groove 8d1, the gap between the lower end surface of the inner flange 9b of the seal member 9 and the upper end surface 8c of the sintered oil-impregnated bearing 8, the annular groove 8c1, and the radial groove 8c2, the first radial bearing section It is drawn into the radial bearing gap of R1 again. That is, a lubricating oil circulation path 15 including radial bearing gaps G1 and G2 is formed in the bearing internal space. This prevents the lubricating oil pressure in the bearing internal space from becoming locally negative, causing the generation of air bubbles due to the generation of negative pressure, and the leakage of lubricating oil and deterioration of bearing performance due to the generation of air bubbles. , problems such as generation of vibrations are avoided. In addition, if air bubbles are mixed into the lubricating oil for some reason, they will be discharged to the outside air from the oil surface (air-liquid interface) of the lubricating oil in each seal space S1, S2 as the air bubbles circulate with the lubricating oil. Therefore, the adverse effects of air bubbles are effectively prevented.
　一方、上述した寸法精度ないし形状精度上の問題により、あるいは継続使用に伴って第一ラジアル動圧発生部１１の第一丘部１１ｂが上端部において損耗することにより、ラジアル軸受隙間Ｇ１が軸受端部側で広がるおそれがある。ラジアル軸受隙間Ｇ１が広がると、第一傾斜動圧溝１１ａによる潤滑油の動圧作用が低下するので、第一傾斜動圧溝１１ａによる引き込み力Ｆ１に比べて第二傾斜動圧溝１１ｃによる引き込み力Ｆ２が優勢となり、場合によっては、内周面８ａの軸方向中央側から軸方向上端側に潤滑油が逆流する事態が懸念される。 On the other hand, due to the above-mentioned problems with dimensional accuracy or shape accuracy, or due to wear and tear of the first hill portion 11b of the first radial dynamic pressure generating portion 11 at the upper end due to continued use, the radial bearing clearance G1 is reduced at the bearing end. There is a risk of it spreading on the side. When the radial bearing gap G1 widens, the dynamic pressure action of the lubricating oil by the first inclined dynamic pressure groove 11a decreases, so the pulling force by the second inclined dynamic pressure groove 11c is greater than the pulling force F1 by the first inclined dynamic pressure groove 11a. The force F2 becomes dominant, and there is a concern that in some cases, the lubricating oil may flow backward from the axial center side of the inner circumferential surface 8a to the axially upper end side.
　本実施形態に係る焼結含油軸受８では、内径寸法が内周面８ａの軸方向中央側から軸方向上端部側に向かうにつれて減少する形態をなす縮径部１３を第一傾斜動圧溝１１ａ間の第一丘部１１ｂに設けた（図４Ａを参照）。これにより、第一丘部１１ｂの間の第一傾斜動圧溝１１ａによるラジアル軸受隙間Ｇ１に発生する潤滑油の軸方向中央側への引き込み力Ｆ１を高めることができる。そのため、上述した寸法精度上の理由で潤滑油の軸受軸方向中央側への引き込み力Ｆ１が不足する場合、もしくは焼結含油軸受８の損耗に伴い上記引き込み力Ｆ１が低下する場合においても、上記引き込み力Ｆ１の不足分又は低下分を補って、必要な大きさの引き込み力Ｆ１を得ることが可能となる。従って、本実施形態に記載の焼結含油軸受８を量産して使用する場合においても、潤滑油の軸受外部への漏れ出し、本実施形態では各シール空間Ｓ１，Ｓ２を通じた流体動圧軸受装置１外への漏れ出しを長期にわたって防止することが可能となる。 In the sintered oil-impregnated bearing 8 according to the present embodiment, the reduced diameter portion 13 is formed in the first inclined dynamic pressure groove 11a, and the diameter decreases from the axial center side to the axially upper end side of the inner circumferential surface 8a. It was provided in the first hill part 11b between (see FIG. 4A). Thereby, it is possible to increase the drawing force F1 of the lubricating oil toward the center in the axial direction, which is generated in the radial bearing gap G1 by the first inclined dynamic pressure groove 11a between the first hill portions 11b. Therefore, even if the drawing force F1 of lubricating oil toward the center in the bearing axial direction is insufficient due to the above-mentioned dimensional accuracy reason, or if the drawing force F1 decreases due to wear and tear of the sintered oil-impregnated bearing 8, the above-mentioned It becomes possible to obtain a necessary magnitude of the pulling force F1 by compensating for the shortage or decrease in the pulling force F1. Therefore, even when the sintered oil-impregnated bearing 8 described in this embodiment is mass-produced and used, the lubricating oil may leak to the outside of the bearing, and in this embodiment, the fluid dynamic bearing device It becomes possible to prevent leakage to the outside for a long period of time.
　また、本実施形態のように、潤滑油の軸方向中央側への引き込み力Ｆ１を高めて、潤滑油の流体動圧軸受け装置１外への漏れ出しを防止できるのであれば、ラジアル軸受隙間Ｇ１に直結する第一シール空間Ｓ１の軸方向寸法を縮小できる。この場合、第一シール空間Ｓ１よりも半径方向外側に第二シール空間Ｓ２を設けることで、潤滑油のバッファ機能を確保しつつ、所要のシール性能を維持することが可能となる。また、図２に示す形態のシール部材９であれば、シール部材９を設けることによる流体動圧軸受装置１の軸方向寸法の増加を、実質的に内鍔部９ｂの軸方向寸法分に抑えることができるので、流体動圧軸受装置１の薄肉化（小型化）にも寄与し得る。 Furthermore, as in the present embodiment, if it is possible to prevent the lubricating oil from leaking out of the fluid dynamic bearing device 1 by increasing the force F1 that draws the lubricating oil toward the center in the axial direction, the radial bearing gap G1 The axial dimension of the first seal space S1 directly connected to can be reduced. In this case, by providing the second seal space S2 outside the first seal space S1 in the radial direction, it is possible to maintain the required sealing performance while ensuring the buffer function of the lubricating oil. Furthermore, with the seal member 9 having the form shown in FIG. 2, the increase in the axial dimension of the fluid dynamic bearing device 1 due to the provision of the seal member 9 is suppressed to substantially the axial dimension of the inner flange portion 9b. Therefore, it can also contribute to making the fluid dynamic bearing device 1 thinner (smaller).
　以上、本発明の一実施形態を説明したが、本発明に係る焼結含油軸受及びこの軸受を備えた流体動圧軸受装置は上記例示の形態に限定されることなく、本発明の範囲内において任意の形態を採り得る。 Although one embodiment of the present invention has been described above, the sintered oil-impregnated bearing according to the present invention and the fluid dynamic pressure bearing device equipped with this bearing are not limited to the above-mentioned exemplary embodiments, and can be used within the scope of the present invention. It can take any form.
　図８は、本発明の他の実施形態に係る流体動圧軸受装置３１の断面図を示している。図８に示すように、本実施形態における流体動圧軸受装置３１は、第一シール空間Ｓ１のみを有する点で、図２に示す流体動圧軸受装置１と相違する。詳述すると、本実施形態に係る流体動圧軸受装置３１において、シール部材３２は、ハウジング７の上端部と一体化されており、シール部材３２の内周面３２ａと、この内周面３２ａに対向する軸部２ａの外周面２ａ１との間に、第一シール空間Ｓ１が形成される。 FIG. 8 shows a cross-sectional view of a fluid dynamic bearing device 31 according to another embodiment of the present invention. As shown in FIG. 8, the fluid dynamic bearing device 31 in this embodiment differs from the fluid dynamic bearing device 1 shown in FIG. 2 in that it has only the first seal space S1. Specifically, in the fluid dynamic bearing device 31 according to the present embodiment, the seal member 32 is integrated with the upper end portion of the housing 7, and the inner circumferential surface 32a of the seal member 32 and the inner circumferential surface 32a are connected to each other. A first seal space S1 is formed between the outer peripheral surfaces two a1 of the opposing shaft portions 2a.
　流体動圧軸受装置３１が上記構成をなす場合、図２に示す流体動圧軸受装置１に比べて、ラジアル軸受隙間Ｇ１に隣接する第一シール空間Ｓ１の軸方向寸法を大きくとることができる。そのため、流体動圧軸受装置３１の焼結含油軸受３３にも、図４Ａと同様の縮径部１３を設けることで、潤滑油の軸受中央側への引き込み力を大きくして、軸方向上側のラジアル軸受隙間Ｇ１から軸方向下側のラジアル軸受隙間Ｇ２への潤滑油の流れを作り出すことができる。このように構成することで、流体動圧軸受装置３１に十分な潤滑油の漏れ出し防止効果を付与することができるので、例えば図３に示す焼結含油軸受８の場合と同様に、焼結含油軸受３３の軸方向上側の第一ラジアル動圧発生部３４における第一傾斜動圧溝の長手方向寸法を、第二傾斜動圧溝の長手方向寸法と同じ大きさにすることができる。よって、焼結含油軸受３３の軸方向寸法を図２に示す焼結含油軸受８よりも小さくすることが可能となる。 When the fluid dynamic pressure bearing device 31 has the above configuration, the axial dimension of the first seal space S1 adjacent to the radial bearing gap G1 can be made larger compared to the fluid dynamic pressure bearing device 1 shown in FIG. Therefore, by providing the sintered oil-impregnated bearing 33 of the fluid dynamic pressure bearing device 31 with a reduced diameter portion 13 similar to that shown in FIG. It is possible to create a flow of lubricating oil from the radial bearing gap G1 to the radial bearing gap G2 on the lower side in the axial direction. With this configuration, it is possible to provide the fluid dynamic pressure bearing device 31 with a sufficient effect of preventing leakage of lubricating oil. The longitudinal dimension of the first inclined dynamic pressure groove in the first radial dynamic pressure generating section 34 on the axially upper side of the oil-impregnated bearing 33 can be made the same as the longitudinal dimension of the second inclined dynamic pressure groove. Therefore, the axial dimension of the sintered oil-impregnated bearing 33 can be made smaller than that of the sintered oil-impregnated bearing 8 shown in FIG.
　また、以上の説明では、ディスクハブ３が固定された軸部材２（回転体）を備えた流体動圧軸受装置１，３１に本発明を適用した場合について説明を行ったが、本発明は、ファン、あるいはポリゴンミラーが固定された軸部材２（回転体）を備えた流体動圧軸受装置にも好ましく適用することができる。すなわち、本発明は、図１に示すようなディスク駆動用のスピンドルモータＭのみならず、ファンモータや、レーザビームプリンタ（ＬＢＰ）用のポリゴンスキャナモータ等、その他の電気機器に組み込まれる流体動圧軸受装置にも好ましく適用することが可能である。 Furthermore, in the above description, the present invention is applied to the fluid dynamic bearing device 1, 31 that includes the shaft member 2 (rotating body) to which the disk hub 3 is fixed. The present invention can also be preferably applied to a fluid dynamic bearing device equipped with a shaft member 2 (rotating body) to which a fan or a polygon mirror is fixed. That is, the present invention applies not only to a spindle motor M for driving a disk as shown in FIG. It can also be preferably applied to bearing devices.
１　　　流体動圧軸受装置
２　　　軸部材
２ａ　　軸部
２ａ１　外周面
２ｂ　　フランジ部
２ｃ　　中逃げ部
３　　　ディスクハブ
４　　　駆動部
４ａ　　ステータコイル
４ｂ　　ロータマグネット
５　　　ブラケット
６　　　ディスク
７　　　ハウジング
７ａ　　第一内周面
７ｂ　　第二内周面
７ｃ　　第三内周面
８　　　焼結含油軸受
８Ｓ　　焼結体
８ａ，８Ｓａ　内周面
８ｂ，８Ｓｂ　下端面
８ｃ，８Ｓｃ　上端面
８ｃ１　環状溝
８ｃ２　半径方向溝
８ｄ，８Ｓｄ　外周面
８ｄ１　軸方向溝
９　　　シール部材
９ａ　　筒状部
９ｂ　　内鍔部
９ｃ　　内周面
９ｄ　　外周面
１０　　蓋部材
１０ａ　上端面
１１　　第一ラジアル動圧発生部
１１ａ　第一傾斜動圧溝
１１ｂ　第一丘部
１１ｃ　第二傾斜動圧溝
１１ｄ　第二丘部
１１ｅ　帯部
１２　　第二ラジアル動圧発生部
１２ａ，１２ｃ　傾斜動圧溝
１２ｂ，１２ｄ　丘部
１２ｅ　帯部
１３　　縮径部
１４　　スラスト動圧発生部
１４ａ　スラスト動圧溝
１４ｂ　丘部
１５　　循環路
２０　　成形装置
２１　　ダイ
２２　　サイジングピン
２２ａ　第一成形型
２２ａ１　凸状成形部
２２ａ２　凹状成形部
２２ａ３　縮径部成形部
２３　　下パンチ
２４　　上パンチ
３１　　流体動圧軸受装置
３２　　シール部材
３２ａ　内周面
３３　　焼結含油軸受
３４　　第一ラジアル動圧発生部
Ｄ１，Ｄ２　内径寸法
Ｆ１　　引き込み力（軸受中央側）
Ｆ２　　引き込み力（軸受端部側）
Ｇ１，Ｇ２　ラジアル軸受隙間
Ｈ１　　軸方向寸法（縮径部成形部）
Ｈ２　　軸方向寸法（縮径部）
Ｌ１，Ｌ２，Ｌ３，Ｌ４　軸方向寸法（傾斜動圧溝）
Ｍ　　　スピンドルモータ
Ｒ１，Ｒ２　ラジアル軸受部
Ｓ１　　第一シール空間
Ｓ２　　第二シール空間
Ｔ１，Ｔ２　スラスト軸受部 1 Fluid dynamic pressure bearing device 2 Shaft member 2a Shaft portion 2a1 Outer peripheral surface 2b Flange portion 2c Center relief portion 3 Disc hub 4 Drive portion 4a Stator coil 4b Rotor magnet 5 Bracket 6 Disk 7 Housing 7a First inner peripheral surface 7b Second inner surface Circumferential surface 7c Third inner circumferential surface 8 Sintered oil-impregnated bearing 8S Sintered body 8a, 8Sa Inner circumferential surface 8b, 8Sb Lower end surface 8c, 8Sc Upper end surface 8c1 Annular groove 8c2 Radial groove 8d, 8Sd Outer circumferential surface 8d1 Axial groove 9 Seal member 9a Cylindrical portion 9b Inner flange portion 9c Inner circumferential surface 9d Outer circumferential surface 10 Lid member 10a Upper end surface 11 First radial dynamic pressure generating portion 11a First inclined dynamic pressure groove 11b First hill portion 11c Second inclined dynamic pressure groove 11d Second hill portion 11e Band portion 12 Second radial dynamic pressure generating portions 12a, 12c Inclined dynamic pressure grooves 12b, 12d Hill portion 12e Band portion 13 Reduced diameter portion 14 Thrust dynamic pressure generating portion 14a Thrust dynamic pressure groove 14b Hill portion 15 Circulation path 20 Molding device 21 Die 22 Sizing pin 22a First mold 22a1 Convex molded portion 22a2 Concave molded portion 22a3 Reduced diameter portion molded portion 23 Lower punch 24 Upper punch 31 Fluid dynamic pressure bearing device 32 Seal member 32a Inner peripheral surface 33 Sintered oil-impregnated bearing 34 First radial dynamic pressure generating portion D1, D2 Inner diameter dimension F1 Pulling force (bearing center side)
F2 Retraction force (bearing end side)
G1, G2 Radial bearing clearance H1 Axial dimension (reduced diameter part molded part)
H2 Axial dimension (reduced diameter part)
L1, L2, L3, L4 Axial dimension (inclined dynamic pressure groove)
M Spindle motor R1, R2 Radial bearing part S1 First seal space S2 Second seal space T1, T2 Thrust bearing part

Claims (9)

  1. 　金属粉末を筒状に圧縮成形して圧粉体を形成し、形成した前記圧粉体を焼結して得られる焼結金属製の軸受であって、内部空孔に潤滑油が含浸され、内周面にラジアル動圧発生部が形成される焼結含油軸受において、
    　前記ラジアル動圧発生部は、前記内周面の円周方向に対して傾斜した複数の傾斜動圧溝と、前記傾斜動圧溝の間に設けられる複数の丘部とを有し、
    　前記丘部には、前記丘部の内径寸法が前記内周面の軸方向中央側から軸方向端部側に向かうにつれて減少する縮径部が設けられていることを特徴とする焼結含油軸受。     A sintered metal bearing obtained by compression-molding metal powder into a cylindrical shape to form a compact, and sintering the formed compact, the internal cavity being impregnated with lubricating oil, In sintered oil-impregnated bearings in which a radial dynamic pressure generating section is formed on the inner peripheral surface,
    The radial dynamic pressure generating section has a plurality of inclined dynamic pressure grooves inclined with respect to the circumferential direction of the inner peripheral surface, and a plurality of hill portions provided between the inclined dynamic pressure grooves,
    A sintered oil-impregnated bearing characterized in that the hill portion is provided with a reduced diameter portion in which the inner diameter dimension of the hill portion decreases from the axial center side of the inner circumferential surface toward the axial end side. .
  2. 　前記縮径部の前記軸方向中央側の第一端部における内径寸法から、前記軸方向端部側の第二端部における内径寸法を減じた値が、０μｍを超えかつ１．５μｍ以下である請求項１に記載の焼結含油軸受。 The value obtained by subtracting the inner diameter dimension at the second end portion on the axial end side from the inner diameter dimension at the first end portion on the axial center side of the reduced diameter portion is greater than 0 μm and 1.5 μm or less. The sintered oil-impregnated bearing according to claim 1.
  3. 　前記縮径部の内径寸法が、前記軸方向中央側から前記軸方向端部側に向かうにつれてテーパ状に減少している請求項１又は２に記載の焼結含油軸受。 The sintered oil-impregnated bearing according to claim 1 or 2, wherein the inner diameter dimension of the reduced diameter portion decreases in a tapered shape from the axial center side toward the axial end side.
  4. 　前記傾斜動圧溝の溝深さが、前記軸方向中央側から前記軸方向端部側に向かうにつれて増大している請求項１～３に記載の焼結含油軸受。 The sintered oil-impregnated bearing according to claim 1, wherein the groove depth of the inclined dynamic pressure groove increases from the axial center side toward the axial end side.
  5. 　前記傾斜動圧溝の内径寸法が前記軸方向で一定である請求項４に記載の焼結含油軸受。 The sintered oil-impregnated bearing according to claim 4, wherein the inner diameter dimension of the inclined dynamic pressure groove is constant in the axial direction.
  6. 　前記ラジアル動圧発生部は、前記円周方向に対して互いに異なる向きに傾斜しかつ前記軸方向で隣接する前記傾斜動圧溝としての複数の第一傾斜動圧溝と第二傾斜動圧溝とを有し、
    　前記第一傾斜動圧溝の間及び第二傾斜動圧溝の間には前記丘部がそれぞれ設けられ、前記第二傾斜動圧溝間の丘部には前記縮径部が設けられ、
    　前記第一傾斜動圧溝は前記軸方向中央側に位置し、前記第二傾斜動圧溝は前記軸方向端部側に位置し、かつ
    　前記第二傾斜動圧溝の長手方向寸法が、前記第一傾斜動圧溝の長手方向寸法よりも大きい請求項１～５の何れか一項に記載の焼結含油軸受。     The radial dynamic pressure generating section includes a plurality of first inclined dynamic pressure grooves and second inclined dynamic pressure grooves, which are inclined in different directions with respect to the circumferential direction and are adjacent to each other in the axial direction. and has
    The hill portions are provided between the first inclined dynamic pressure grooves and the second inclined dynamic pressure grooves, and the reduced diameter portion is provided in the hill portion between the second inclined dynamic pressure grooves,
    The first inclined dynamic pressure groove is located on the central side in the axial direction, the second inclined dynamic pressure groove is located on the end side in the axial direction, and the longitudinal dimension of the second inclined dynamic pressure groove is The sintered oil-impregnated bearing according to claim 1, which is larger than the longitudinal dimension of the first inclined dynamic pressure groove.
  7. 　請求項１に記載された焼結含油軸受と、軸方向一端側が開口し他端側が閉塞された形態をなし前記焼結含油軸受が内周に固定されるハウジングと、前記焼結含油軸受の内周に挿入される軸部を有する回転体と、前記ラジアル動圧発生部の動圧作用により、前記焼結含油軸受の内周面と前記軸部の外周面との間のラジアル軸受隙間に形成される潤滑油の膜で前記軸部をラジアル方向に非接触支持するラジアル軸受部とを備えた流体動圧軸受装置。 A sintered oil-impregnated bearing according to claim 1, a housing having a configuration in which one axial end side is open and the other end side is closed, and the sintered oil-impregnated bearing is fixed to the inner periphery; A radial bearing gap is formed between the inner peripheral surface of the sintered oil-impregnated bearing and the outer peripheral surface of the shaft by the dynamic pressure action of a rotating body having a shaft inserted into the circumference and the radial dynamic pressure generating section. a radial bearing section that supports the shaft section in a radial direction in a non-contact manner with a film of lubricating oil.
  8. 　前記焼結含油軸受の内周面のうち軸方向に離れた二ヶ所に前記ラジアル動圧発生部が設けられ、前記各ラジアル動圧発生部は、前記円周方向に対して互いに異なる向きに傾斜しかつ前記軸方向で隣接する前記傾斜動圧溝としての複数の第一傾斜動圧溝と第二傾斜動圧溝とを有し、前記第一傾斜動圧溝の間及び第二傾斜動圧溝の間には複数の前記丘部がそれぞれ設けられ、
    　前記二つのラジアル動圧軸受部のうち前記ハウジングの軸方向開口側に位置する一方のラジアル動圧発生部において、前記第一傾斜動圧溝は前記軸方向中央側に位置し、前記第二傾斜動圧溝は前記軸方向端部側に位置すると共に、前記第二傾斜動圧溝間の丘部に前記縮径部が設けられている請求項７に記載の流体動圧軸受装置。     The radial dynamic pressure generating portions are provided at two locations separated in the axial direction on the inner peripheral surface of the sintered oil-impregnated bearing, and each of the radial dynamic pressure generating portions is inclined in different directions with respect to the circumferential direction. and a plurality of first inclined dynamic pressure grooves and second inclined dynamic pressure grooves adjacent to each other in the axial direction, and between the first inclined dynamic pressure grooves and the second inclined dynamic pressure groove. Each of the plurality of hill portions is provided between the grooves,
    In one of the two radial dynamic pressure bearing sections located on the axial opening side of the housing, the first inclined dynamic pressure groove is located on the axial center side, and the second inclined dynamic pressure groove is located on the axial center side. 8. The fluid dynamic bearing device according to claim 7, wherein the dynamic pressure groove is located on the axial end side, and the reduced diameter portion is provided on a hill between the second inclined dynamic pressure grooves.
  9. 　請求項１～８の何れか一項に記載の流体動圧軸受装置を備えたモータ。 A motor comprising the fluid dynamic bearing device according to any one of claims 1 to 8.
PCT/JP2023/009160 2022-03-28 2023-03-09 Oil-impregnated sintered bearing and fluid dynamic bearing device including same WO2023189389A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000155284A (en) * 1998-11-19 2000-06-06 Canon Inc Deflection scanner
JP2006105237A (en) * 2004-10-04 2006-04-20 Nippon Densan Corp Fluid dynamic pressure bearing, spindle motor provided with the fluid dynamic pressure bearing, and recording disc drive provided with the spindle motor
WO2018037822A1 (en) * 2016-08-26 2018-03-01 Ntn株式会社 Dynamic pressure bearing and method for manufacturing same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000155284A (en) * 1998-11-19 2000-06-06 Canon Inc Deflection scanner
JP2006105237A (en) * 2004-10-04 2006-04-20 Nippon Densan Corp Fluid dynamic pressure bearing, spindle motor provided with the fluid dynamic pressure bearing, and recording disc drive provided with the spindle motor
WO2018037822A1 (en) * 2016-08-26 2018-03-01 Ntn株式会社 Dynamic pressure bearing and method for manufacturing same

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