Torque restriction mechanism, drive device, and robot device

Patent metadata

Field	Value
Publication number	US-11148304-B2
Application number	US-201716318956-A
Country	US
Kind code	B2
Filing date	Jul 5, 2017
Priority date	Aug 2, 2016
Publication date	Oct 19, 2021
Grant date	Oct 19, 2021

Abstract

A torque restriction mechanism is provided by which torque cutoff and torque transmission can be reliably performed without being affected by a rotation state of the drive unit, and damage to a collision object can be reduced even with a simple configuration. The torque restriction mechanism includes a first clutch and a second clutch. The first clutch cuts off torque to a driven unit when reaction torque at a stationary portion of a motor equals or exceeds a first value. The second clutch that transmits torque in accordance with a rotation state of a rotor of the motor, cuts off torque to the driven unit when the reaction torque equals or exceeds a second value larger than the first value.

First claim

The invention claimed is:

1. A torque restriction mechanism to be connected to a housing and a stationary portion that includes a stator of a motor for rotating a driven unit with respect to the housing of a drive device for housing the motor, and to transmit or cut off torque from the housing to the stationary portion, the torque restriction mechanism comprising:
a first clutch to cut off the torque to the driven unit when reaction torque generated in the stationary portion due to rotation of the driven unit equals or exceeds a predetermined first value; and
a second clutch to transmit the torque based on a rotation state of a rotor of the motor to be connected to the driven unit,
wherein the second clutch cuts off the torque to the driven unit when the reaction torque equals or exceeds a second value larger than the first value.

2. The torque restriction mechanism according to claim 1 , wherein the second clutch is driven when angular acceleration of the rotor equals or exceeds a predetermined value and is not driven when the angular acceleration of the rotor is smaller than the predetermined value.

3. The torque restriction mechanism according to claim 2 ,
wherein the second clutch comprises:
a clutch driven part fixed to the housing at a first end thereof;
a clutch driver to move a second end of the clutch driven part at an inner side in a radial direction of the motor; and
a clutch locking part fixed to the stationary portion,

and wherein, the clutch driver locks the second end of the clutch driven part in the clutch locking part when the angular acceleration equals or exceeds the predetermined value.

4. The torque restriction mechanism according to claim 3 , wherein the clutch driven part is made of material to be broken when stress being equal to or exceeding a predetermined value is applied.

5. The torque restriction mechanism according to claim 3 , further comprising a rectifier circuit to output current value corresponding to the angular acceleration of the rotor, wherein the clutch driver locks the second end of the clutch driven part in the clutch locking part when the current value outputted from the rectifier circuit equals or exceeds a predetermined value.

6. The torque restriction mechanism according to claim 1 ,
wherein, the housing supports the stationary portion so as to be freely rotatable in a circumferential direction thereof,
the second clutch comprises:
one or more inner rings each connected to a drive rotation shaft of the rotor and to move radially outward in the motor owing to rotation of the drive rotation shaft;
a ring receptor disposed in the stationary portion radially outward with respect to the one or more inner rings, having a notch on one side that is opposite to the other side facing the one or more inner rings; and
an outer ring provided radially outward with respect to the ring receptor in a place facing the notch, and fixed to the housing,

wherein, when an angular velocity of the drive rotation shaft exceeds a predetermined value, the one or more inner rings move the ring receptor radially outward to lock the notch of the ring receptor in the outer ring.

7. The torque restriction mechanism according to claim 1 , wherein the first clutch includes a spring for return to a position before the torque is cut off in a case where the torque to the driven unit is cut off.

8. The torque restriction mechanism according to claim 1 , wherein the first clutch further includes a resilient member having initial reaction force to restrict circumferential movement of the motor.

9. A drive device comprising the motor and the torque restriction mechanism according to claim 1 .

10. A robot device comprising the drive device according to claim 9 and the driven unit rotated by the motor.

11. A drive device comprising:
an electric motor that includes a stator and a rotating rotor;
a housing that houses the electric motor and that transfers torque generated by the electric motor;
a magnetic clutch that magnetically attaches the electric motor to the housing, the magnetic clutch disengages the electric motor from the housing in response to receiving a reaction torque greater than the magnetic force holding the electric motor to the housing;
a locking clutch that attaches the electric motor to the housing, the locking clutch includes an actuator that engages the locking clutch with the electric motor to enable and disable torque control by the locking clutch, the locking clutch disengages the electric motor from the housing in response to receiving a reaction torque that exceeds a locking force holding the actuator of the locking clutch to the electric motor;
a controller configured to control the electric motor, compute an angular acceleration of the electric motor based on the control of the electric motor, and operate the actuator of the locking clutch to enable the locking clutch in response to determining that the angular acceleration of the electric motor is equal to, or greater than, a predetermined threshold, wherein
the magnetic clutch and the locking clutch are configured to disengage the electric motor from the housing without receiving a command from the controller to disengage the housing.

12. The drive device according to claim 11 , wherein
the controller is configured to disable the locking clutch in response to determining that the angular acceleration of the electric motor is below the predetermined threshold.

13. The drive device according to claim 11 , further comprising:
a torque cutoff detection sensor that outputs a torque cutoff signal in response to the magnetic clutch disengaging the housing from the electric motor fixing plate, wherein
the controller is configured to stop supplying current to the electric motor in response to receiving the torque cutoff signal from the torque cutoff detection sensor.

14. The drive device according to claim 11 , wherein the housing further comprises
a support flange that extends toward the electric motor,
an electric motor fixing plate that is located above the support flange and that attaches the electric motor to the magnetic clutch and the locking clutch, and
a sliding plate that is located between the support flange and the electric motor fixing plate and that allows the electric motor to rotate freely without transferring torque to the housing when the electric motor is disconnected from the magnetic clutch and the locking clutch.

15. The drive device according to claim 14 , wherein the magnetic clutch further comprises
a magnet support that is attached to the electric motor fixing plate and that includes a support surface,
a fixed permanent magnet that includes a first end and a second end opposite to the first end in a circumferential direction of the electric motor, the fixed permanent magnet includes an outer surface and an inner surface opposite to the outer surface in a radial direction of the electric motor, the inner surface of the fixed permanent magnet is attached to the support surface of the magnetic support,
a first detachable permanent magnet magnetically attached to the first end of the fixed permanent magnet, the first detachable magnet includes a surface that extends beyond the outer surface of the fixed permanent magnet in the radial direction of the electric motor,
a second detachable permanent magnet magnetically attached to the second end of the fixed permanent magnet, the second detachable permanent magnet includes a surface that extends beyond the outer surface of the fixed permanent magnet in the radial direction of the electric motor, and
a magnet holder that restricts circumfe

Assignees

• Mitsubishi Electric Corp

Inventors

• Hamada Akiko

Classifications

• F16D43/30

  Systems of a plurality of automatic clutches · CPC title

• F16D1/00

  Couplings for rigidly connecting two coaxial shafts or other movable machine elements (attachment of wheels to axles for railway carriages B60B; for attachment of cranks to their shafts F16C3/10) · CPC title

• F16D2011/006

  Locking or detent means, i.e. means to keep the clutch in engaged condition · CPC title

• B25J19/06 Primary

  Safety devices · CPC title

• H02K7/11

  with dynamo-electric clutches · CPC title