CN112405511A - Mechanical arm - Google Patents

Abstract

The invention aims to provide a manipulator capable of reducing the influence caused by reverse driving. A robot (100) has a joint (40) to which a motor (38) and a speed reducer (6) are assembled, and the robot has: an acquisition mechanism that acquires information relating to rotation of the motor (38); and a control mechanism for detecting the external force applied to the part according to the information acquired by the acquisition mechanism and executing the retreat action. The speed reducer (6) has a parallel axis gear mechanism (8) and an eccentric oscillating gear mechanism (10), and the output rotation of the parallel axis gear mechanism (8) is input to the eccentric oscillating gear mechanism (10). The eccentric oscillating type gear mechanism (10) is of a central crank type in which an eccentric body shaft (12) is disposed on the axis of an internal gear (16), and the reduction ratio thereof is 35 or less.

Description

Mechanical arm

The present application claims priority based on japanese patent application No. 2019-151531, applied on 8/21/2019. The entire contents of this japanese application are incorporated by reference into this specification.

Technical Field

The present invention relates to a manipulator.

Background

A robot having a plurality of joints is known. Patent document 1 describes a robot hand that performs a retracting operation in response to an external force. The robot described in patent document 1 detects an external force acting on the robot, and causes the robot to perform a retracting operation when the detected external force is larger than a 1 st threshold, and stops the retracting operation when a variation in the detected external force after the retracting operation is smaller than a 2 nd threshold.

Patent document 1: japanese patent No. 6034895

When an external force sensor is provided on the output side of the reduction gear as in patent document 1, the external force sensor is expensive and disadvantageous in terms of cost.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a robot hand capable of coping with an external force without depending on an external force sensor on the output side of a reduction gear.

In order to solve the above problem, a robot according to an embodiment of the present invention includes a joint in which a motor and a speed reducer are assembled, and includes: an acquisition mechanism that acquires information relating to rotation of the motor; and a control mechanism for detecting the external force applied to the part according to the information acquired by the acquisition mechanism and executing the retreat action. The speed reducer has a parallel axis gear mechanism and an eccentric oscillating gear mechanism, and output rotation of the parallel axis gear mechanism is input to the eccentric oscillating gear mechanism. The eccentric oscillating type gear mechanism is of a central crank type in which an eccentric body shaft is disposed on the axis of an internal gear, and the reduction ratio thereof is 35 or less.

Any combination of the above-described constituent elements or a mode in which the constituent elements or expressions of the present invention are replaced with each other in a method, a system, or the like is also effective as an aspect of the present invention.

According to the present invention, it is possible to provide a robot hand that can cope with an external force without depending on an external force sensor on the output side of a reduction gear.

Drawings

Fig. 1 is a side view schematically showing a robot according to an embodiment.

Fig. 2 is a side sectional view showing a speed reducer of the robot hand of fig. 1.

Fig. 3 is a block diagram schematically showing the robot hand of fig. 1.

Fig. 4 is a graph showing a relationship between the reduction ratio and the efficiency of the eccentric oscillating type gear mechanism.

In the figure: 6-speed reducer, 8-parallel shaft gear mechanism, 10-eccentric swinging gear mechanism, 12-eccentric body shaft, 14-external gear, 14 a-external gear, 16-internal gear, 16 a-internal gear, 38-motor, 40-joint, 42-arm, 52-acquisition part, 54-control part, 54 c-external force detection part and 100-manipulator.

Detailed Description

The present inventors have studied a robot having a joint in which a motor and a reduction gear are incorporated, and have obtained the following findings.

In the joint of the manipulator, when a rotational driving force of a motor is input to an input shaft of a speed reducer, an output member of the speed reducer rotates at a reduced speed at a predetermined reduction ratio, and an arm connected to the output member rotates about the axis of the joint. When an external force is applied from the arm to the joint by direct teaching or the like, the reduction gear of the joint is driven in the reverse direction. When the vehicle is driven in the reverse direction, the reverse drive torque is transmitted from the output side to the input side of the reduction gear. This reverse drive torque applies excessive stress (load) to the internal mechanism of the reduction gear, and may damage the internal mechanism. As a result of the study, it has been found that, if the transmission efficiency of the reduction gear is high, stress (load) applied to the internal mechanism of the reduction gear is small, and the reverse drive is less likely to cause damage.

As a result of research on reduction gears of various configurations from the viewpoint of improving transmission efficiency, it has been found that transmission efficiency can be improved particularly by arranging a parallel-axis gear mechanism and a center crank type eccentric oscillating gear mechanism (hereinafter, sometimes referred to as "oscillating gear mechanism") in this order and appropriately selecting a reduction ratio of the eccentric oscillating gear mechanism. Fig. 4 is a graph g1 showing a relationship between a reduction ratio Rg (a speed ratio obtained by dividing an input rotation speed by an output rotation speed) and a transmission efficiency Eg of the swing type gear mechanism. From this data, it is understood that when the reduction gear ratio Rg is 35 or less, the transmission efficiency is high, and when the reduction gear ratio Rg exceeds 35, the transmission efficiency is significantly reduced. Further, it has been found that the transmission efficiency is further improved when the reduction gear ratio Rg is 17 or less. In addition, in this reduction gear, the reduction ratio of the parallel-axis gear mechanism has less influence on the transmission efficiency. Here, the transmission efficiency is a ratio of the output torque to the input torque, and is obtained by (output torque) ÷ (input torque × reduction ratio) × 100%.

In the robot hand, in order to prevent damage due to the reverse driving, a configuration in which the motor is retreated by an external force has been studied. For example, it is conceivable to provide a torque sensor on the output side of the reduction gear and cause the motor to perform a retraction operation based on the detection result. However, in this structure, there is a possibility that the torque sensor is broken by an external force, and a space for providing the torque sensor and its wiring is additionally required, which is disadvantageous in terms of cost. Therefore, a structure for recognizing the state of the external force from information on the rotation of the motor such as the motor current without using a torque sensor has been studied. As a result, it was found that the retraction operation can be performed without using the torque sensor.

As described above, it is considered that a robot arm capable of coping with an external force (reverse drive) at low cost can be provided by combining a parallel-axis gear mechanism and a center crank type eccentric oscillating gear mechanism, using a reduction gear mechanism having a reduction gear ratio Rg of 35 or less, and causing a motor to perform a retracting operation based on information on the rotation of the motor. Hereinafter, a robot based on these findings will be described with reference to the embodiments.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the embodiment and the modifications, the same or equivalent constituent elements and components are denoted by the same reference numerals, and overlapping description is appropriately omitted. In the drawings, the dimensions of the components are shown enlarged or reduced as appropriate for the convenience of understanding. In the drawings, parts that are not essential to the description of the embodiments are omitted.

Further, the terms including the numbers 1, 2, and the like are used for describing various constituent elements, and the terms are used only for the purpose of distinguishing one constituent element from other constituent elements, and the constituent elements are not limited by the terms.

[ embodiment ]

Hereinafter, the structure of the robot 100 according to the embodiment will be described with reference to the drawings. Fig. 1 is a side view schematically showing a robot hand 100 according to the present embodiment. The robot 100 is a multi-joint robot having a plurality of arms connected together via a plurality of joints from a distal end side to a proximal end side. The robot 100 of the present embodiment includes a joint 40 and an arm 42. The robot 100 further includes an acquisition unit 52 for acquiring information on the rotation of the motor in order to perform the retracting operation based on the external force, and a control unit 54 for detecting the external force applied thereto based on the information and performing the retracting operation. First, the joint 40 and the arm 42 will be described, and the acquisition unit 52 and the control unit 54 will be described later.

The joint 40 includes a 1 st joint 40a, a 2 nd joint 40b, a 3 rd joint 40c, a 4 th joint 40d, a 5 th joint 40e, and a 6 th joint 40f in this order from the distal end side. The arm 42 includes a 1 st arm 42a, a 2 nd arm 42b, a 3 rd arm 42c, a 4 th arm 42d, a 5 th arm 42e, and a 6 th arm 42 f. The 1 st arm 42a is connected to the leading end side (output side) of the 1 st joint 40 a. The 2 nd to 6 th arms 42b to 42f are connected between the 1 st to 6 th joints 40a to 40 f. The base end side of the 6 th joint 40f is connected to a base 42g, and the base 42g is fixedly connected to the installation surface Gf.

The motor 38 and the speed reducer 6 are assembled to the joint 40. When the rotational driving force is input from the motor 38 to the reduction gear 6, the output member of the reduction gear 6 rotates at a reduced speed so that the arm 42 rotates about the axial center of the joint 40. In the robot 100, the rotation of each motor 38 is controlled so that the tool 42h attached to the output side of the 1 st arm 42a moves along a predetermined trajectory. In the case where the robot arm 100 of the present embodiment has a plurality of joints 40, it is not necessary to assemble the object of the present invention (i.e., the speed reducer) to all the joints, and the object of the present invention (i.e., the speed reducer) may be assembled to at least one of the joints. In particular, it is preferable to incorporate the object of the present invention (i.e., a reduction gear) in the joint on the distal end side.

The motor 38 may be any motor capable of inputting a rotational driving force to the reduction gear 6, and a motor based on various principles may be used. The motor 38 of the present embodiment is a servomotor. In this case, there are advantages of small size, large output, long life, and almost no need for maintenance.

Next, the speed reducer 6 will be described. Fig. 2 is a side sectional view showing the speed reducer 6. The speed reducer 6 includes a parallel axis gear mechanism 8 and an eccentric oscillating gear mechanism 10, and the output rotation of the parallel axis gear mechanism 8 is input to the eccentric oscillating gear mechanism 10. The eccentric rocking type gear mechanism 10 is a central crank type gear mechanism in which an eccentric body shaft 12 described later is disposed on the shaft center of an internal gear. In the present embodiment, the parallel shaft gear mechanism 8 and the eccentric oscillating gear mechanism 10 are housed in a housing 20 described later.

Hereinafter, a direction along a central axis La of an internal gear 16 (described later) of the eccentric oscillating type gear mechanism 10 is referred to as an "axial direction", and a circumferential direction and a radial direction of a circle centered on the central axis La are referred to as a "circumferential direction" and a "radial direction", respectively. For convenience of explanation, hereinafter, one side (right side in the drawing) in the axial direction is referred to as an input side, and the other side (left side in the drawing) is referred to as an opposite-to-input side.

The parallel shaft gear mechanism 8 includes a drive shaft 8a, a drive gear 8b, and a driven gear 8 c. In this example, the drive shaft 8a is an output shaft of the motor 38. The drive shaft 8a extends in parallel with the central axis La at a position deviated from the central axis La. The drive shaft 8a enters the housing 20 from a motor mounting hole 20h provided in the input-side surface portion 20c of the housing 20 toward the opposite input side of the housing 20 together with the motor 38. The drive gear 8b is fixed to the outer periphery of the drive shaft 8 a. The driven gear 8c is fixed to the outer periphery of the eccentric body shaft 12 extending in parallel with the drive shaft 8a, and meshes with the drive gear 8 b. The drive gear 8b and the driven gear 8c may be spur gears or other gears such as helical gears.

The eccentric oscillating gear mechanism 10 is an eccentric oscillating gear device that oscillates an external gear meshing with an internal gear, rotates one of the internal gear and the external gear, and outputs the generated motion component from an output member to a driving member. In the eccentric oscillating type gear mechanism 10 of this example, the rotation of the external gear is restricted to rotate the internal gear, and rotation is output from the internal gear.

The eccentric oscillating type gear mechanism 10 of the present embodiment includes an eccentric body shaft 12, an external gear 14, an internal gear 16, a transmission member 18, a housing 20, a bearing support 22, an eccentric body shaft bearing 24, a center bearing 26, an eccentric bearing 28, an inner pin 30, a flange member 32, an output member 34, and a main bearing 36.

(outer cover)

The outer case 20 has a cylindrical portion 20b surrounding the internal gear 16 and an input side surface portion 20c provided on an input side portion of the internal gear 16. The bearing support 22 is a portion extending from the center of the input-side surface portion 20c toward the input-opposite side, and in this example, the bearing support 22 and the input-side surface portion 20c are integrally formed of a single material. The bearing support portion 22 has a hollow cylindrical shape surrounding the center axis La. The flange member 32 is a hollow circular member, and is fixed to the input-side opposite end of the cylindrical portion 20B of the housing 20 by a bolt B4. The inner peripheral side of the flange member 32 extends radially inward of the cylindrical portion 20b and covers a part of the main bearing 36 on the opposite side to the input side. The flange member 32 projects radially outward from the tube portion 20 b. The flange member 32 is fixed to a frame (not shown) of the joint 40.

The internal gear 16 and the external gear 14 mesh with each other. The output member 34 is synchronized with the rotation of the internal gear 16. The housing 20 is synchronized with the rotation of the external gear 14. The main bearing 36 is disposed between the output member 34 and the tube portion 20 b. An eccentric body shaft bearing 24 for supporting the eccentric body shaft 12 is disposed on the outer periphery of the bearing support 22.

(eccentric body axis)

The eccentric body shaft 12 rotates around the rotation center line by the rotational power input from the driven gear 8c of the parallel shaft gear mechanism 8. The eccentric body shaft 12 is supported by a bearing support 22 of the housing 20 via an eccentric body shaft bearing 24, and is rotatably supported by the housing 20.

As shown in fig. 2, the input-side end of the eccentric body shaft 12 is positioned closer to the input side than the input-opposite-side end of the drive shaft 8 a. That is, the eccentric body shaft 12 partially overlaps the drive shaft 8a as viewed in the radial direction. The parallel axis gear mechanism 8 is included in the axial range of the eccentric oscillating type gear mechanism 10. The drive shaft 8a overlaps the external gear 14 when viewed in the axial direction. The input-opposite-side end of the drive shaft 8a is axially opposed to the external gear 14.

The eccentric oscillating gear mechanism 10 is a central crank type eccentric oscillating gear device in which the eccentric body shaft 12 is disposed on the central axis La of the internal gear 16. The eccentric body shaft 12 has a plurality of eccentric portions 12a for oscillating the external gear 14. The axis of the eccentric portion 12a is eccentric with respect to the rotation center line of the eccentric body shaft 12. In the present embodiment, two eccentric portions 12a are provided, and the eccentric phases of the adjacent eccentric portions 12a are deviated from each other by 180 °.

(outer gear)

The external gears 14 are provided individually corresponding to the plurality of eccentric portions 12a, and perform an oscillating rotation in accordance with the rotation of the eccentric body shaft 12. The external gear 14 is rotatably supported by the corresponding eccentric portion 12a via an eccentric bearing 28. Outer teeth 14a are formed on the outer periphery of the outer gear 14. The external gear 14 moves while meshing with the internal teeth of the internal gear 16 to oscillate.

A plurality of inner pin holes 14h are provided in the outer gear 14 at positions offset from the axial center thereof. An inner pin 30 is inserted through each inner pin hole 14 h. A play (i.e., a clearance) for absorbing a wobbling component of the external gear 14 is provided between the inner pin 30 and the inner pin hole 14 h. The inner pin 30 partially contacts the inner wall surface of the inner pin hole 14 h.

(internal Gear)

The internal gear 16 is a hollow cylindrical member having internal teeth 16a on an inner peripheral portion thereof, which mesh with the external gear 14. In the present embodiment, the number of the internal teeth 16a of the internal gear 16 is one more than the number of the external teeth of the external gear 14. The internal gear 16 rotates relative to the external gear 14 in accordance with the swing rotation of the external gear 14.

(transmitting member)

The transmission member 18 is a hollow circular member disposed between the internal gear 16 and the output member 34. The transmission member 18 in this example is disposed on the side portion on the input-side opposite side of the external gear 14. The transmission member 18 transmits power from the internal gear 16 to the output member 34. The transmission member 18 is fixed to the non-input side portion of the internal gear 16 by a bolt B1. A center bearing 26 is provided between the inner peripheral surface of the transmission member 18 and the outer peripheral surface of the bearing support portion 22. The transmission member 18 is rotatably supported by the bearing support portion 22 via a center bearing 26.

The eccentric body shaft bearing 24 is disposed between the eccentric body shaft 12 and the bearing support 22 to support the eccentric body shaft 12. The eccentric bearing 28 is disposed between the eccentric portion 12a and the external gear 14 to transmit eccentric motion to the external gear 14. The center bearing 26 is disposed between the transmission member 18 and the bearing support portion 22 to support the transmission member 18. The center bearing 26 is disposed adjacent to the input-side opposite side portion of the eccentric body shaft bearing 24.

The main bearing 36 is disposed between the output member 34 and the cylindrical portion 20b of the housing 20 to support the output member 34. In the present embodiment, the eccentric body shaft bearing 24, the center bearing 26, and the eccentric bearing 28 are ball bearings having spherical rolling elements, and the main bearing 36 is a cross roller bearing having cylindrical rollers as the rolling elements. These bearings may also take other forms of bearing.

(inner sales)

The inner pins 30 are rod-shaped members that transmit power between the outer gear 14 and the output member 34, and are provided in plurality at intervals in the circumferential direction. The inner pin 30 of this example is press-fitted and fixed to the input side face portion 20c, and extends from the input side face portion 20c through the inner pin hole 14h of the external gear 14 toward the input-side opposite side. The inner pin 30 abuts a part of the inner pin hole 14h to restrict the rotation of the external gear 14 and allow only the oscillation thereof.

(output member)

The output member 34 is a circular member, and power from the internal gear 16 is transmitted to the output member 34 via the transmission member 18. The output member 34 rotates integrally with the internal gear 16 and the transmission member 18. The output member 34 is disposed on a side portion on the opposite side to the input side in the axial direction of the external gear 14, and is disposed radially inward of the main bearing 36. The output member 34 is fixed to the input-side portion of the transmission member 18 by a bolt B2. The output member 34 is rotatably supported by the cylindrical portion 20b of the housing 20 via a main bearing 36. The driven member 46 is fixed to the non-input side portion of the output member 34 by a bolt B5. The output member 34 outputs a rotational driving force to the driven member 46. The driven member 46 is coupled to the arm 42 supported by the joint 40.

Next, the operation of the speed reducer 6 configured as described above will be described. When the motor 38 rotates, the drive gear 8b, the driven gear 8c meshing with the drive gear, and the eccentric body shaft 12 rotate integrally. When the eccentric body shaft 12 rotates, the eccentric portion 12a of the eccentric body shaft 12 rotates eccentrically. When the eccentric portion 12a eccentrically rotates, it oscillates the external gear 14 via the eccentric bearing 28. At this time, the external gear 14 oscillates so that its axis rotates around the rotation center line of the eccentric body shaft 12.

When the external gear 14 oscillates, the meshing positions of the external gear 14 and the internal gear 16 sequentially deviate. As a result, one of the external gear 14 and the internal gear 16 rotates by the number of teeth difference between the external gear 14 and the internal gear 16 every time the eccentric body shaft 12 rotates once. In the present embodiment, the internal gear 16 rotates on its own axis, and the decelerated rotation is output from the output member 34 via the transmission member 18. When the output member 34 rotates, the driven member 46 fixed to the output member 34 rotates. When the driven member 46 rotates, the arm 42 coupled to the driven member 46 rotates.

Next, the acquisition unit 52 and the control unit 54 will be described. Fig. 3 is a block diagram schematically showing the robot 100. The functional blocks shown in fig. 3 are implemented by elements or mechanical devices including a CPU (Central processing Unit) of a computer in terms of hardware, and by computer programs or the like in terms of software. Accordingly, those skilled in the art who have the benefit of this description will appreciate that the functional blocks can be implemented in a variety of ways through a combination of hardware and software.

The acquisition unit 52 and the control unit 54 control the motor 38 to perform a retraction operation (hereinafter referred to as "retraction control") according to an external force in order to prevent the reduction gear 6 from being damaged by the reverse driving. As described above, the acquisition unit 52 functions as an acquisition means for acquiring information relating to the rotation of the motor 38. The control unit 54 functions as a control means for detecting an external force and executing the retraction operation based on the acquisition result of the acquisition unit 52.

The information on the rotation of the motor 38 includes the torque of the output shaft of the motor, the rotation speed of the motor, the driving voltage of the motor (the duty ratio of the PWM driving signal), the current of the motor, and the like. In the present embodiment, the information on the rotation of the motor 38 is the drive current Im of the motor 38, and the acquisition unit 52 includes a current sensor 52s that detects the drive current Im. The current sensor 52s of the present embodiment is a series resistor having a small resistance value and connected in series with the motor 38. The acquisition unit 52 can detect the drive current Im as a voltage drop of the series resistor.

The control unit 54 of the present embodiment mainly includes a 1 st receiving unit 54a, a 2 nd receiving unit 54b, an external force detecting unit 54c, a motor driving unit 54d, and a retraction control unit 54 e. The 1 st receiving unit 54a receives information on the difference between the position command information from the upper control system 4 and the position information of each arm 42 from the position sensor 4 s. The upper control system 4 may be, for example, a main system that controls the operation of each joint 40 of the robot 100. The 1 st receiving unit 54a generates the position command signal Ps based on the reception result.

The 2 nd receiving unit 54b receives the drive current Im from the current sensor 52s of the acquiring unit 52. For example, the 2 nd receiving unit 54b may be configured to include a DA converter that converts the driving current Im into a digital signal.

The external force detection unit 54c detects the external force acting on the joint 40 based on the acquisition result of the acquisition unit 52. For example, the external force detection unit 54c may detect the external force from the driving voltage Vd and the driving current Im of the driving motor 38. For example, the external force detection unit 54c may store information on the relationship between the driving voltage Vd and the driving current Im in the absence of the external force in advance, and estimate the external force from the newly detected driving voltage Vd and driving current Im and the stored information. For example, a regression line (including linear regression and polynomial regression) may be obtained from the stored information, and the external force may be estimated from the magnitude of deviation from the regression line.

The retraction control unit 54e determines the retraction operation based on the external force estimated by the external force detection unit 54 c. For example, the retraction control unit 54e may generate the retraction information Pc such as no retraction, deceleration, stop, and inversion according to the magnitude of the external force.

The motor drive unit 54d supplies the motor 38 with a drive voltage Vd whose magnitude is determined based on the position command signal Ps and the retraction information Pc. The motor drive unit 54d may be configured to include a PWM inverter. The magnitude of the driving voltage Vd depends on the duty ratio of the PWM driving signal. When the retraction information Pc is "not retracted", the motor drive unit 54d supplies the drive voltage Vd corresponding to the position command signal Ps. When the backoff information Pc is "decelerated", the motor drive unit 54d supplies the drive voltage Vd with a reduced duty ratio. When the backoff information Pc is "stopped", the motor drive unit 54d sets the duty ratio of the drive voltage Vd to zero%. When the retraction information Pc is "reverse", the motor drive unit 54d supplies the reverse drive voltage Vd.

According to the acquisition unit 52 and the control unit 54 configured as described above, since the retraction control of the motor 38 can be performed in accordance with the external force, it is possible to prevent the reduction gear unit 6 from being damaged by the reverse driving, and to alleviate the impact when a person comes into contact with the robot. Further, compared to a configuration in which the torque sensor is provided on the output side of the reduction gear, the possibility of damage to the torque sensor due to external force can be reduced, which is advantageous in terms of space and cost for providing the torque sensor.

Next, the reduction ratio Rs of the reduction gear 6 will be described. The reduction ratio Rs is a product of the reduction ratio Rg of the eccentric rocking type gear mechanism 10 and the reduction ratio Rp of the parallel-axis gear mechanism 8. A graph g1 of fig. 4 shows a relationship between the reduction gear ratio Rg of the eccentric swing type gear mechanism 10 and the transmission efficiency Eg. As shown in the graph g1, when the reduction gear ratio Rg is 35 or less, the transmission efficiency Eg is high, and when the reduction gear ratio Rg exceeds 35, the transmission efficiency Eg rapidly decreases. When the reduction gear ratio Rg is 17 or less, the transmission efficiency Eg is further improved. The reduction gear ratio Rg may be set to 35 or less from the viewpoint of improving the transmission efficiency Eg.

When the eccentric rocking type gear mechanism 10 is manufactured, manufacturing errors inevitably occur in the tooth shapes of the internal teeth 16a and the external teeth 14 a. This manufacturing error may cause variation in the gap between the teeth and variation in the timing of contact, and may adversely affect the transmission efficiency of the eccentric oscillating type gear mechanism 10. In order to secure a margin against this manufacturing error, the reduction gear ratio Rg is preferably 17 or less. It is understood that if the amount is within this range, the effect of manufacturing errors on the transmission efficiency can be maintained at a level that is practically free from problems. The reduction ratio Rg of the present embodiment is set to 15, and the transmission efficiency of the eccentric oscillating type gear mechanism 10 is 95%.

The reduction gear ratio Rp of the parallel-axis gear mechanism 8 can be set to the desired reduction gear ratio Rs of the reduction gear 6 divided by the reduction gear ratio Rg of the eccentric rocking type gear mechanism 10. If the reduction ratio Rp is too large, the diameter ratio of the drive gear 8b to the driven gear 8c becomes large, and backlash increases, which may result in a decrease in transmission accuracy. To ensure the transmission accuracy, the reduction ratio Rp is preferably 5 or less. It is understood that if the transmission accuracy is within this range, the transmission accuracy can be secured at a level that is practically free from problems. The reduction ratio Rp in the present embodiment is set to 5.

In order to enable accurate retraction control, the reduction ratio Rs of the speed reducer 6 is preferably 175 or less, and more preferably 85 or less. When the reduction ratio Rs of the reduction gear 6 is too small, the driving force of the arm 42 is reduced. The reduction ratio Rs of the speed reducer 6 is preferably 50 or more in order to ensure the driving force of the arm 42. It is understood that if the reduction ratio Rs of the reduction gear 6 is within a range of 50 to 175 (more preferably, within a range of 50 to 85), the accuracy of the retraction control and the driving force of the arm 42 can be maintained at a level that does not cause any practical problem. The reduction ratio Rs of the present embodiment is set to 75.

If the efficiency of the speed reducer 6 is too low, a time lag between the transmission of the external force from the output side of the speed reducer to the motor side becomes large, and the speed reducer 6 may be damaged until the retraction control is performed by detecting the external force. In order to detect an external force on the motor side and perform retraction control before the reduction gear 6 is damaged, the efficiency of the reduction gear 6 is preferably 80% or more. It is understood that if the amount is within this range, the backoff control can be performed at a level that does not cause practical problems. The transmission efficiency of the speed reducer 6 of the present embodiment is 90%.

According to the robot 100 having the above configuration, it is possible to provide a robot capable of coping with an external force without providing a torque sensor on the output side of the reduction gear 6.

The above description explains an example of the embodiment of the present invention in detail. The above embodiments are merely specific examples for carrying out the present invention. The contents of the embodiments are not intended to limit the technical scope of the present invention, and various design changes such as changes, additions, deletions, and the like of the constituent elements can be made without departing from the scope of the inventive concept defined in the claims. In the above-described embodiments, the terms "in the embodiments", "in the embodiments" and the like are given to the contents in which such a design change is possible, but the contents without such a sign do not mean that the design change is not permitted. The hatching in the drawings does not limit the material of the object to be hatched.

[ modified examples ]

Hereinafter, a modified example will be described. In the drawings and the description of the modified examples, the same or equivalent constituent elements and components as those of the embodiments are denoted by the same reference numerals. The description overlapping with the embodiment is appropriately omitted, and the description is repeated for the configuration different from the embodiment.

In the description of the embodiment, the example of decelerating, stopping, and reversing the motor has been described for the retracting operation, but the present invention is not limited to this. For example, the retraction operation may be any one of deceleration, stop, and reverse rotation of the motor, or may be other operations.

In the description of the embodiment, the external force is estimated from the driving voltage Vd and the driving current Im by regression analysis, but the present invention is not limited to this. For example, the external force may be estimated by using an external force estimation model generated by known machine learning (including supervised learning) based on information on the rotation of the motor such as the driving voltage Vd and the driving current Im and data of the external force. In this case, the control unit 54 may further include a storage unit for storing the external force estimation model. The control unit 54 may further include a model generation unit that generates an external force estimation model by machine learning.

In the description of the embodiment, the example in which the rotation is output from the internal gear 16 is shown for the eccentric oscillating type gear mechanism 10, but the present invention is not limited to this. The eccentric oscillating type gear mechanism may be configured such that the internal gear is fixed and rotation is output from the external gear.

In the description of the embodiment, the robot is an example of a multi-joint robot having six joints, but the present invention is not limited to this. For example, the robot may be a horizontal multiaxial robot (SC ARA robot). Also, the number of joints is not limited. The manipulator of the present invention is suitably applied to a cooperative robot, a service robot, a robot cart, and the like that operate in the vicinity of a human without being separated from the human, but is not limited thereto.

In the description of the embodiment, the cylindrical portion 20b, the input-side surface portion 20c, and the bearing support portion 22 are integrally formed of a single material, but may be formed separately and then joined together.

In the description of the embodiment, the example in which two external gears 14 are provided is shown, but the present invention is not limited to this. The outer gear 14 may also be provided with one or more than three.

In the description of the embodiment, the example in which only the input side of the inner pin 30 is supported is shown, but the present invention is not limited to this. A carrier may be provided on the opposite input side of the external gear, and the opposite input side of the inner pin may be fixed to the carrier.

The above modifications also exhibit the same operational advantages as the embodiment.

Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. The new embodiment which is produced by the combination has the effects of the combined embodiments and the modifications.

Claims (5)

1. A robot having a joint in which a motor and a speed reducer are incorporated, the robot comprising:

an acquisition mechanism that acquires information relating to rotation of the motor; and

a control means for detecting the application of an external force based on the information acquired by the acquisition means and executing a retraction operation,

the speed reducer has a parallel axis gear mechanism and an eccentric oscillating gear mechanism, the output rotation of the parallel axis gear mechanism is input to the eccentric oscillating gear mechanism,

the eccentric oscillating gear mechanism is a central crank gear mechanism in which an eccentric body shaft is disposed on the axis of an internal gear, and the reduction ratio is 35 or less.

2. The robot hand of claim 1,

the reduction ratio of the eccentric oscillating gear mechanism is 17 or less.

3. The robot hand according to claim 1 or 2,

the reduction ratio of the parallel shaft gear mechanism is 5 or less.

4. The robot hand according to any one of claims 1 to 3,

the reduction ratio of the reduction gear is 50 to 175 inclusive.

5. The robot hand according to any one of claims 1 to 4,

the transmission efficiency of the speed reducer is more than 80%.

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