WO2023171704A1

WO2023171704A1 - Drive mechanism, and robot arm

Info

Publication number: WO2023171704A1
Application number: PCT/JP2023/008775
Authority: WO
Inventors: 光樹土屋
Original assignee: 住友重機械工業株式会社
Priority date: 2022-03-11
Filing date: 2023-03-08
Publication date: 2023-09-14

Abstract

A drive mechanism according to the present disclosure comprises a drive portion A, a driven portion 52 configured to be capable of rotating about a first axis of rotation 21 on the basis of a driving force transmitted from the drive portion A, and an engagement structure 40 that engages the drive portion A and the driven portion 52 in such a way as to be capable of transmitting power, wherein the engagement structure 40 comprises an engaging portion 22 which is coupled to the drive portion A and which is configured to be capable of rotating about a second axis of rotation 31 extending parallel to the first axis of rotation 21, an engaged portion 41 which engages with the engaging portion 22, and resilient portions 42A, 42B which urge the engaged portion 41 toward the engaging portion 22, and wherein an engaging surface of the engaging portion 22 that engages with the engaged portion 41 includes: a first surface part 23Ba of which, when the engaging portion 22 is positioned in a first rotational position rotated a first amount of rotation relative to the driven portion 52 about the second axis of rotation 31, an amount of change of rotational torque acting on the drive portion A, based on a load acting on the engaging portion 41 from the engaged portion 23 with respect to a change in rotational position, is a first amount of change; and a second surface part 23Bb of which, when the engaging portion 22 is positioned in a second rotational position rotated a second amount of rotation, greater than the first amount of rotation, about the second axis of rotation 31, the amount of change of rotational torque acting on the drive portion A, based on the load acting on the engaging portion 41 from the engaged portion 23 with respect to a change in rotational position, is a second amount of change, smaller than the first amount of change.

Description

Drive mechanism and robot arm

The present invention relates to a drive mechanism and a robot arm.

Conventionally, technology has been proposed in which when a robot arm collides with an obstacle such as a person, workpiece, or equipment, the rigidity of the robot arm is changed to absorb the impact and suppress damage caused by the collision. For example, in Patent Document 1, as the three-dimensional cam is rotated by an ultrasonic motor, the inclination angle of the contact surface between the cam follower connected to the output arm and the cam groove of the three-dimensional cam is changed, and the cam groove of the three-dimensional cam is changed. A configuration is described in which the rigidity of the output arm is changed by changing the force acting on the cam follower.

JP2014-97548A

However, in the configuration described in Patent Document 1, when the robot arm collides with an obstacle, the impact applied to the robot arm from the obstacle is accurately absorbed and suppressed due to the delay in response of the ultrasonic motor. There was a possibility that I would not be able to do so.

The present invention has been made in view of these circumstances, and aims to increase the effect of mitigating impact force by passively changing the rigidity, and to achieve nonlinear elasticity while maintaining rigidity above a certain level. An object of the present invention is to provide a drive mechanism that can improve back drivability and that does not require the addition of an external drive system, and a robot arm equipped with the drive mechanism.

The present application provides a drive unit, a driven unit configured to be rotatable about a first rotation axis based on a driving force transmitted from the drive unit, and a link between the drive unit and the driven unit. an engagement structure that engages to enable power transmission, the engagement structure being connected to the drive unit and configured to be rotatable about a second rotation axis extending parallel to the first rotation axis. an engaged portion that engages with the engaging portion; and an elastic portion that biases the engaged portion toward the engaging portion; The engagement surface that engages with the engaged part has a rotational position when the engagement part is located at a first rotational position where the engagement part is rotated by a first rotation amount with respect to the driven part about the second rotation axis. a first surface portion in which an amount of change in the rotational torque acting on the driving portion based on a load acting on the engaging portion from the engaged portion in response to a change is a first amount of change; When located at a second rotational position rotated by a second rotational amount, which is larger than the first rotational amount, about the rotational axis, the drive unit may A drive mechanism is disclosed that includes a second surface portion in which the amount of change in the applied rotational torque is a second amount of change that is smaller than the first amount of change.

The engagement surface may be a convex curved surface, and the curvature of the second surface portion may be smaller than the curvature of the first surface portion.

The first surface portion and the second surface portion may be continuous surface portions in a circumferential direction centered on the first rotation axis.

The engagement surface includes a first engagement surface that engages the engagement section when the drive section rotates in a first rotation direction about the first rotation axis, and a first engagement surface that engages the engagement section when the drive section rotates in the first rotation direction. It may also include a second engagement surface that engages with the engagement portion when rotating in a second rotation direction opposite to the first rotation direction about the axis.

The adjustment section may include a spacer interposed between a support section that supports the elastic section and the elastic section.

The engagement structure may further include a restriction part that restricts the moving direction of the engagement part.

The present application discloses a robot arm that includes a drive mechanism, a first link in which the drive part of the drive mechanism is provided, and a second link in which the driven part of the drive mechanism is provided.

According to the present invention, the effect of mitigating impact force can be enhanced by passively changing the rigidity, and back drivability can be improved by achieving nonlinear elasticity while maintaining torsional rigidity above a certain level. Accordingly, it is possible to provide a drive mechanism that is capable of providing a drive mechanism that does not require the addition of an external drive system, and a robot arm that includes the drive mechanism.

FIG. 1 is a schematic diagram of a robot arm according to an embodiment. FIG. 2 is a schematic cross-sectional view of a drive mechanism according to an embodiment taken along a plane perpendicular to a rotation axis. FIG. 2A is an enlarged view of the main part of FIG. 2A. FIG. 1 is a functional block diagram of a robot system according to an embodiment. FIG. 3 is a schematic diagram showing a method for driving a drive mechanism according to an embodiment. FIG. 3 is a schematic diagram showing a method for driving a drive mechanism according to an embodiment. FIG. 3 is a schematic diagram showing a method for driving a drive mechanism according to an embodiment. FIG. 3 is a diagram for explaining the function of a drive mechanism according to an embodiment. FIG. 3 is a schematic diagram showing characteristics of a drive mechanism according to an embodiment. FIG. 3 is a schematic diagram showing characteristics of a drive mechanism according to an embodiment. FIG. 7 is a schematic cross-sectional view of a drive mechanism according to another embodiment taken along a plane perpendicular to the rotation axis.

As shown in FIG. 1, the robot arm 20 is a vertical multi-joint robot arm consisting of multiple joints (for example, 6 axes), and includes a base (not shown) and a plurality of links L1 to L3 connected to the base. We are prepared. Each of the plurality of links L1 and L2 includes a drive mechanism 30. A link L3 provided at the tip of the robot arm 20 is equipped with a holding portion LA for holding an object to be held.

Next, the configuration of the drive mechanism 30 according to this embodiment will be described. Hereinafter, for convenience of understanding the description of the specification, the description will focus on the drive mechanism 30 provided in the link L2.

As shown in FIGS. 2A and 2B, the drive mechanism 30 includes a rotating body 52 configured to be rotatable about the rotating shaft 21 based on the driving force transmitted from the actuator A provided in the link L1; An engagement structure 40 that engages between the actuator A and the rotating body 52 to enable power transmission is provided. The actuator A is an example of a driving part, the rotating body 52 is an example of a driven part, the cam member 22 is an example of an engaging part, and the rotating shaft 31 is an example of a second rotation axis. .

A cam member 22 is connected to the rotating shaft 21 of the actuator A. The cam member 22 is configured to be rotatable about the rotating shaft 21. The rotation axis 21 is an example of a first rotation axis. The cam member 22 has a flat plate shape, and four recesses 23 are provided on the outer peripheral surface of the cam member 22. The four recesses 23 are provided at equal angular intervals in the circumferential direction around the rotating shaft 21 . Each recess 23 has a line-symmetric shape with respect to a perpendicular to the bottom surface 23A, and includes a bottom surface 23A, a first cam curved surface 23B, and a second cam curved surface 23C. The first cam curved surface 23B and the second cam curved surface 23C are examples of engagement surfaces. The first cam curved surface 23B extends from the bottom surface 23A in a first direction along the circumferential direction around the rotating shaft 21. The second cam curved surface 23C extends from the bottom surface 23A in a second direction that is opposite to the first direction along the circumferential direction around the rotating shaft 21.

The first cam curved surface 23B is a surface that engages with the engagement structure 40 when the cam member 22 rotates in the first rotation direction about the rotation shaft 21, and is a surface that engages with the engagement structure 40. and a surface portion 23Bb. The first surface portion 23Ba and the second surface portion 23Bb are continuous surface portions in the circumferential direction centered on the rotating shaft 21, the first surface portion 23Ba is adjacent to the bottom surface 23A, and the second surface portion 23Bb is the first surface portion 23Bb. Adjacent to the surface portion 23Ba on the opposite side to the bottom surface 23A. The first surface portion 23Ba changes the rotational torque based on the load acting on the actuator A from the link L2 in response to a change in rotational position when the cam member 22 is located at a first rotational position rotated by a first rotational amount with respect to the link L2. The amount becomes the first amount of change. The second surface portion 23Bb is configured to rotate the actuator from the link L2 in response to a change in rotational position when the actuator A is located at a second rotational position where the actuator A has rotated by a second rotational amount larger than the first rotational amount with respect to the link L2 around the rotational axis 21. The amount of change in the rotational torque acting on actuator A based on the load acting on A is a second amount of change that is smaller than the first amount of change. The first surface portion 23Ba and the second surface portion 23Bb are convex curved surfaces, and the curvature of the second surface portion 23Bb is larger than the curvature of the first surface portion 23Ba.

The second cam curved surface 23C is a surface that engages with the engagement structure 40 when the cam member 22 rotates about the rotation shaft 21 in a second rotation direction opposite to the first rotation direction. It includes a surface portion 23Ca and a second surface portion 23Cb. The first surface portion 23Ca and the second surface portion 23Cb are continuous surface portions in the circumferential direction around the rotating shaft 21, the first surface portion 23Ca is adjacent to the bottom surface 23A, and the second surface portion 23Cb is the first surface portion 23Cb. Adjacent to the surface portion 23Ca on the opposite side to the bottom surface 23A. The first surface portion 23Ca is the amount of change in rotational torque based on the load acting on the actuator A from the link L2 in response to a change in rotational position when the actuator A is located at a first rotational position rotated by a first rotational amount with respect to the link L2. is the first amount of change. When the cam member 22 is located at a second rotation position where the cam member 22 rotates by a second rotation amount larger than the first rotation amount with respect to the link L2 around the rotation shaft 21, the second surface portion 23Cb is rotated from the link L2 in response to a change in rotational position. The amount of change in the rotational torque acting on actuator A based on the load acting on actuator A is a second amount of change that is smaller than the first amount of change. The first surface portion 23Ca and the second surface portion 23Cb are convex curved surfaces, and the curvature of the second surface portion 23Cb is larger than the curvature of the first surface portion 23Ca.

The contour shapes of the first cam curved surface 23B and the second cam curved surface 23C are expressed by the following equations.
(Number 1)
S(T)=anTn+...+a1T
Here, S indicates a dimensionless displacement and is calculated as the ratio of the displacement s of the driven joint to the stroke range h. T indicates dimensionless time and is calculated as the ratio of the rotation angle θ of the cam to the allocation angle θh. ak (k=1 to n) is a coefficient that defines the contour shape of the first cam curved surface 23B and the second cam curved surface 23C, and is a coefficient that defines the contour shape of the first cam curved surface 23B and the second cam curved surface 23C, and the characteristics of the first surface portions 23Ba, 23Ca and the second surface portions 23Bb, 23Cb described above. determined to satisfy.

The link L2 includes, for example, a cylindrical housing 50 and a rotating body 52 rotatably supported by the housing 50 via a bearing 51. The rotating body 52 has an annular shape, and the center of the rotating body 52 coincides with the axis of the rotating shaft 21 . The rotating body 52 is configured to be rotatable about the rotating shaft 21 based on the driving force transmitted from the actuator A via the engagement structure 40.

The engagement structure 40 includes, for example, a cam follower 41 as an example of an engaged part, a pair of

springs

42A and 42B, a holding member 43, and a linear guide 44. The cam follower 41 has a spherical shape and is rotatably held by a holding member 43. The holding member 43 includes a flat plate portion 43A, a bearing portion 43B that rotatably holds the cam follower 41, and a bearing portion 43B that is provided at a central position in the longitudinal direction of the flat plate portion 43A, and a bearing portion 43B that extends from the bearing portion 43B toward the outside in the radial direction of the rotating shaft. It includes a columnar portion 43C that extends linearly. The movement direction of the columnar portion 43C is regulated by a linear motion guide 44 fixed to the rotating body 52 in a direction along the longitudinal direction of the columnar portion 43C. The linear guide 44 restricts the movement direction of the cam follower 41 supported by the holding member 43 in the radial direction of the rotating shaft. The linear guide 44 is an example of a regulating section. The rotating body 52 includes a recessed portion 52A that constitutes a movable range of the columnar portion 43C of the holding member 43. A pair of

springs

42A and 42B are provided on both sides of the flat plate portion 43A of the holding member 43 in the longitudinal direction. The pair of

springs

42A and 42B are arranged between the flat plate portion 43A of the holding member 43 and the inner peripheral surface of the rotating body 52. The rotating body 52 is an example of a support section. The pair of

springs

42A, 42B biases the cam follower 41 against the cam member 22 by pressing the holding member 43 in a direction toward the cam member 22. The pair of

springs

42A and 42B are an example of a biasing section. A spacer 45 is provided between each of the pair of

springs

42A, 42B and the inner peripheral surface of the rotating body 52. The rotating body 52 is an example of a support section. The spacer 45 adjusts the magnitude of the force with which the pair of

springs

42A, 42B urges the cam follower 41 against the cam member 22 by adjusting the elastic force of each of the pair of

springs

42A, 42B. The spacer 45 is an example of an adjustment section.

Next, the control configuration of the robot system according to this embodiment will be explained.

As shown in FIG. 3, the control device 10 controls the robot arm 20. The control device 10 according to the present embodiment is configured to control the starting position of the reference position of the robot arm 20 (for example, the center point of a link corresponding to the hand position; hereinafter referred to as the "reference position" or "reference part") and its timing. A start position acquisition unit 10A that acquires the attitude of It includes a control command acquisition unit 10D that acquires a control command for controlling a servo motor corresponding to a drive unit of each actuator A according to the acquired route, and a storage unit 10E.

The starting position acquisition unit 10A acquires, for example, the starting position input from a teaching device (not shown) connectable to the control device 10 and the posture of the robot arm 20 at that time. The teaching device may be a teaching device that follows online teaching that actually moves the robot arm 20 at the site and teaches the reference position and posture at that time as the starting position, or it may teach the position and posture of the reference position as the starting position by a computer program. , a text type, a simulator type, an emulator type, or an automatic teaching type teaching device that follows offline teaching.

The target position acquisition unit 10B acquires, for example, the target position input from the teaching device and the posture at that time, similarly to the starting position. The target position acquisition unit 10B is capable of acquiring a plurality of target positions and postures at those positions.

The route acquisition unit 10C acquires a route (planned trajectory) connecting the starting position and the target position through calculation processing or the like.

The control command acquisition unit 10D acquires, through arithmetic processing, a control command for controlling each motor mounted on the drive unit of each actuator A in order to move the reference position along the path, and supplies it to the robot arm 20. . For example, the control command acquisition unit 10D uses inverse kinematics to calculate the rotation angle of each motor for positioning the reference position on the path, generates a control command based on this, and It is possible to store it in the storage unit 10E.

The storage unit 10E stores computer programs (including route generation algorithms) and necessary data and other information for executing each process shown in each embodiment.

Regarding the hardware configuration of the control device 10 described above, the control device 10 includes, for example, arithmetic elements that are processors such as a CPU (Central Processing Unit) and a GPU (Graphical Processing Unit), an SRAM (Static Random Access Memory), and a DRAM. Consists of a computer equipped with volatile memory elements such as (Dynamic Random Access Memory), non-volatile memory elements such as NOR flash memory, NAND flash memory, and HDD (Hard Disc Drive), and communication means such as a bus that connects them. It is possible to do so. A nonvolatile memory element is a storage medium that stores information non-transitory. The volatile memory element temporarily stores at least a portion of these computer programs, arithmetic processing results, and the like. The storage unit 10E is composed of these storage elements. Further, when the arithmetic element executes a computer program stored in the storage unit 10E, it functions as a start position acquisition unit 10A, a target position acquisition unit 10B, a route acquisition unit 10C, and a control command acquisition unit 10D. However, at least some of these arithmetic elements, nonvolatile memory elements, etc. may be installed in a remote location connected to a communication network such as the Internet. For example, the computing element may be configured to obtain a computer program or necessary data via a communication network. Further, the control device 10 may include two or more processors as arithmetic elements. Furthermore, the control device 10 may be configured to be able to execute a plurality of computer programs, and control by the control device 10 may be realized based on a first computer program. The first computer program may be non-transitory stored in a non-volatile storage element of the storage unit 10E.

The control device 10 and the robot arm 20 are configured to be able to send and receive information through wireless or wired communication means.

Note that the control device 10 may be connected to or integrally provided with a teaching device for teaching the robot system 100 to operate. Further, the teaching device may be provided on the robot arm 20, and for example, input/output means including a display may be used as part of the teaching device. The teaching device includes, for example, a portable teaching pendant. Like the control device 10, the teaching device includes an arithmetic element, a volatile memory element, and a nonvolatile memory element, and further includes a display means having a display and an input means having a plurality of operation keys and levers. The input means may include a touch panel type input means that performs input by pressing the display.

Next, the operation of the drive mechanism 30 according to this embodiment will be explained.

As shown in FIG. 4, before the actuator A drives the cam member 22, the cam follower 41 is pressed against the recess 23 of the cam member 22 based on the elastic force of the

springs

42A and 42B. In this case, the cam follower 41 is engaged with both the first cam curved surface 23B and the second cam curved surface 23C of the recess 23. The cam follower 41 restricts the rotation of the cam member 22 in both the first direction and the second direction along the circumferential direction around the rotating shaft 21 .

Next, as shown in FIG. 5, when the actuator A rotates the cam member 22 in the first rotational direction about the rotation shaft 21, the cam follower 41 resists the elastic force of the

springs

42A and 42B and rotates the cam member 22. 22 rides on the first surface portion 23Ba of the first cam curved surface 23B of the recess 23. In this case, the cam follower 41 is pressed against the first surface portion 23Ba of the first cam curved surface 23B based on the reaction force from the

springs

42A and 42B. The cam member 22 applies rotational torque to the rotation of the cam member 22 by the actuator A in the first rotation direction based on the pressing force from the cam member 22 . In this case, since the first surface portion 23Ba of the first cam curved surface 23B has a relatively large curvature, the amount of change in rotational torque with respect to a change in the rotational position of the cam member 22 is Becomes relatively large.

Next, as shown in FIG. 6, when the actuator A further rotates the cam member 22 in the first rotation direction about the rotation shaft 21, the cam follower 41 resists the elastic force of the

springs

42A and 42B to cam the cam member 22. It rides on the second surface portion 23Bb of the first cam curved surface 23B of the recess 23 of the member 22. In this case, the cam follower 41 is pressed against the second surface portion 23Bb of the first cam curved surface 23B based on the reaction force from the

springs

42A and 42B. The cam member 22 applies rotational torque to the rotation of the cam member 22 by the actuator A in the first rotation direction based on the pressing force from the cam member 22 . In this case, since the second surface portion 23Bb of the first cam curved surface 23B has a relatively small curvature, the amount of change in rotational torque with respect to a change in the rotational position of the cam member 22 is Becomes relatively small.

As described above, as shown in FIG. 7, in the linear elastic mechanism in which the torsion angle of the robot arm and the torsion torque show a linear relationship, the rotation of the cam member due to changes in the rotational position is independent of the rotation angle of the cam member. The amount of increase in torque remains constant. The rotation angle of the cam member corresponds to the twist angle of the robot arm, and the rotation torque of the cam member corresponds to the twist torque of the robot arm. In contrast, in the drive mechanism 30 of the present embodiment, the rotation angle of the cam member 22 is relatively small, and while the cam follower 41 rides on the first surface portion 23Ba of the first cam curved surface 23B, the rotation of the cam member 22 is The amount of increase in rotational torque with respect to a change in position is relatively large. On the other hand, while the rotation angle of the cam member 22 is relatively large and the cam follower 41 rides on the second surface portion 23Bb of the first cam curved surface 23B, the amount of increase in rotational torque with respect to a change in the rotational position of the cam member 22 is Becomes relatively small. That is, in the drive mechanism 30 of the present embodiment, as the cam member 22 rotates, the cam follower 41 moves from the first surface portion 23Ba of the first cam curved surface 23B to the second surface portion 23Bb. The amount of increase in rotational torque with respect to a change in rotational position is reduced. In this case, the rotational torque changes continuously with respect to the rotational position change of the cam member 22.

Further, as shown in FIG. 8A, in the drive mechanism 30 of this embodiment, when the spacer 45 is provided, the cam follower 41 exerts more force on the cam member 22 than when the spacer 45 is not provided. The pressure increases, and as a result, the rotational torque when the cam member 22 rotates also increases. Further, in the case where the drive mechanism 30 of the present embodiment is provided with the spacer 45, even before the actuator A drives the cam member 22, the cam follower 41 is moved based on the elastic force of the springs 45A and 45B. is pressed against the cam member 22 to apply rotational torque to the cam member 22. This restricts the rotation of the cam member 22 in both the first direction and the second direction along the circumferential direction around the rotating shaft 21 .

Furthermore, as shown in FIG. 8B, in the drive mechanism 30 of this embodiment, the torsional rigidity of the cam member 22 decreases as the rotation angle of the cam member 22 increases. The torsional rigidity indicates the rate of change of torsional torque with respect to the torsional angle of the robot arm 20. Therefore, even if a large external force is applied to the robot arm, such as when an operator unexpectedly collides with the robot arm, by reducing the torsional rigidity of the robot arm 20, the cam member 22 may rotate significantly. In addition, reaction force from the robot arm 20 is suppressed from acting on the operator.

Note that the above embodiment can also be implemented in the following forms.

In the above embodiment, the engagement structure 40 has been described using coil springs as the

springs

42A and 42B, but as shown in FIG. 9, the engagement structure 40A uses a plate spring as the spring 42C. May be used.

[Additional notes]
The technical idea that can be understood from the above embodiments will be described below.

[Appendix 1]
A drive unit;
a driven part configured to be rotatable about a first rotation axis based on the driving force transmitted from the driving part;
an engagement structure that engages the driving part and the driven part to enable power transmission;
Equipped with
The engagement structure is
an engagement part connected to the drive part and configured to be rotatable about a second rotation axis extending in parallel with the first rotation axis;
an engaged part that engages with the engaging part;
an elastic part that urges the engaged part toward the engaging part;
The engagement surface of the engagement portion that engages with the engaged portion is
When the engaging part is located at the first rotational position rotated by the first rotation amount with respect to the driven part about the second rotational axis, it is based on the load acting on the engaging part from the engaged part in response to a change in rotational position. a first surface portion where the amount of change in the rotational torque acting on the drive portion is a first amount of change;
When the engaging part is located at a second rotational position rotated by a second rotational amount that is larger than the first rotational amount about the second rotational axis, the method is based on the load acting on the engaging part from the engaged part in response to a change in rotational position. a second surface portion in which the amount of change in the rotational torque acting on the drive portion is a second amount of change smaller than the first amount of change;
including,
Drive mechanism.

[Appendix 2]
The engagement surface is a convex curved surface,
The curvature of the second surface portion is smaller than the curvature of the first surface portion.
The drive mechanism described in Supplementary Note 1.

[Appendix 3]
The first surface portion and the second surface portion are continuous surface portions in the circumferential direction centered on the first rotation axis,
The drive mechanism according to supplementary note 1 or 2.

[Appendix 4]
The engagement structure further includes an adjustment section that adjusts the magnitude of the elastic force of the elastic section.
The drive mechanism according to any one of Supplementary Notes 1 to 3.

[Appendix 5]
The adjustment section includes a spacer interposed between the support section that supports the elastic section and the elastic section.
The drive mechanism described in Appendix 4.

[Appendix 6]
The engagement structure further includes a regulating part that regulates the moving direction of the engaging part.
The drive mechanism according to any one of Supplementary Notes 1 to 5.

[Appendix 7]
The drive mechanism described in any one of Supplementary Notes 1 to 6,
a first link provided with a drive part of the drive mechanism;
a second link provided with a driven portion of the drive mechanism;
A robot arm equipped with.

Note that each of the embodiments described above is intended to facilitate understanding of the present invention, and is not intended to be interpreted as limiting the present invention. The present invention may be modified/improved without departing from its spirit, and the present invention also includes equivalents thereof. In other words, the scope of the present invention includes modifications to each embodiment by those skilled in the art as long as they have the characteristics of the present invention. For example, each element provided in each embodiment, its arrangement, material, conditions, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. Further, each embodiment is an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the characteristics of the present invention. .

DESCRIPTION OF SYMBOLS 10... Control device, 20... Robot arm, 21... Rotating shaft, 22... Cam member, 23... Recessed part, 23B... First cam curved surface, 23C... Second cam curved surface, 30... Drive mechanism, 40, 40A... Engagement structure , 41... Cam follower, 42A, 42B... Spring, 43... Holding member, 43A... Flat plate part, 43B... Bearing part, 43C... Column part, 44... Linear motion guide, 45... Spacer, A... Actuator.

Claims

A drive unit;
a driven part configured to be rotatable about a first rotation axis based on the driving force transmitted from the driving part;
an engagement structure that engages the driving part and the driven part to enable power transmission;
Equipped with
The engagement structure is
an engagement part connected to the drive part and configured to be rotatable about a second rotation axis extending in parallel with the first rotation axis;
an engaged part that engages with the engaging part;
an elastic part that urges the engaged part toward the engaging part,
The engagement surface of the engagement portion that engages with the engaged portion is
When the engaging part is located at a first rotational position rotated by a first rotation amount with respect to the driven part about the second rotation axis, the engagement part changes from the engaged part to the engaging part in response to a change in rotational position. a first surface portion in which the amount of change in the rotational torque acting on the drive unit based on the applied load is a first amount of change;
When the engaging portion is located at a second rotational position rotated by a second rotational amount that is greater than the first rotational amount about the second rotational axis, the engaged portion acts on the engaging portion in response to a change in rotational position. a second surface portion in which the amount of change in the rotational torque acting on the drive unit based on the load is a second amount of change smaller than the first amount of change;
including,
Drive mechanism.
The engagement surface is a convex curved surface,
The curvature of the second surface portion is smaller than the curvature of the first surface portion.
The drive mechanism according to claim 1.
The first surface portion and the second surface portion are continuous surface portions in a circumferential direction centered on the first rotation axis,
The drive mechanism according to claim 1.
The engagement structure further includes an adjustment section that adjusts the magnitude of the elastic force of the elastic section.
The drive mechanism according to claim 1.
The adjustment section includes a spacer interposed between a support section that supports the elastic section and the elastic section.
The drive mechanism according to claim 4.
The engagement structure further includes a regulating part that regulates a moving direction of the engaging part.
The drive mechanism according to claim 1.
The drive mechanism according to any one of claims 1 to 6,
a first link provided with the drive section of the drive mechanism;
a second link on which the driven portion of the drive mechanism is provided;
A robot arm equipped with.