Strain wave gearing and actuator

Patent metadata

Field	Value
Publication number	US-12234903-B2
Application number	US-202118576392-A
Country	US
Kind code	B2
Filing date	Sep 21, 2021
Priority date	Sep 21, 2021
Publication date	Feb 25, 2025
Grant date	Feb 25, 2025

Abstract

In the interior of a device housing of a strain wave gearing, a detection mechanism is incorporated at a site on the outer peripheral side of a hub of a wave generator. The hub of the wave generator is linked to a motor shaft so that axial force does not act thereon. The detection mechanism detects minute displacements in the axial direction that occur in the hub of the wave generator due to thrust acting on the wave generator. Thrust acting on the wave generator is obtained on the basis of the detected minute displacements. With this strain wave gearing in which the detection mechanism is incorporated, operation control that is responsive to sensed thrust is possible through the use of thrust information during operation.

First claim

The invention claimed is:

1. A strain wave gearing comprising:
a rigid internally toothed gear;
a flexible externally toothed gear that is disposed inside the internally toothed gear;
a wave generator that is disposed inside the externally toothed gear, the wave generator causing the externally toothed gear to flex into a non-circular shape and partially mesh with the internally toothed gear;
a device housing that rotatably supports the wave generator; and
a detection mechanism that, in order to calculate thrust generated between the wave generator and the externally toothed gear, detects displacement produced in the wave generator in the direction of an axis by the thrust,
wherein
the wave generator is provided with a cylindrical hub that is linked to an external rotating shaft so as to rotate integrally with the rotating shaft while being capable of moving relatively in the direction of the axis,
the device housing is provided with a cylindrical housing portion that surrounds the hub, and
the detection mechanism is disposed between the hub and the cylindrical housing and detects the displacement produced in the hub in the direction of the axis.

2. The strain wave gearing according to claim 1 ,
wherein
the wave generator is provided with a rigid wave plug provided with a non-circular outer peripheral surface;
the hub is formed integrally with or fixed to one plug end surface of the wave plug in the direction of the axis;
the detection mechanism is provided with a laser light source, a reflection part that reflects laser light from the laser light source, and a light-receiving part that receives the laser light reflected by the reflection part;
a detection unit, which is provided with the laser light source and the light-receiving part, is attached to the device housing; and
the reflection part is provided to the plug end surface.

3. The strain wave gearing according to claim 2 ,
wherein
the reflection part is provided with a ring-shaped reflective surface that is centered on the axis on the plug end surface; and
at least a pair of the detection units are provided, the detection units being disposed at symmetrical angular positions that are offset by 180 degrees centered on the axis.

4. The strain wave gearing according to claim 1 ,
wherein
the detection mechanism is provided with:
a detection pattern that is disposed on an outer peripheral surface of the hub, the detection pattern being capable of expanding and contracting in a manner that follows displacement of the hub in the direction of the axis; and
a detection unit that is attached to the device housing, the detection unit optically or magnetically detecting expansion and contraction of the detection pattern.

5. The strain wave gearing according to claim 4 ,
wherein
the detection pattern includes light-reflective parts and non-reflective parts that are formed alternatingly at regular intervals along the direction of the axis; and
the detection unit is an optical detection unit provided with a fixed slit plate in which are formed light-transmitting parts that are formed at regular intervals along the direction of the axis, a light-emitting part that emits detection light toward the detection pattern via the light-transmitting parts, and a light-receiving part that receives, via the light-transmitting parts, the detection light reflected by the reflection part.

6. The strain wave gearing according to claim 5 ,
wherein
at least a pair of the detection units are provided, the detection units being disposed at symmetrical angular positions that are offset by 180 degrees centered on the axis.

7. The strain wave gearing according to claim 6 ,
wherein
the detection pattern is formed over the entire circumference of the hub, and
the detection units are provided with a ring-shaped light-emitting part and a ring-shaped light-receiving part that coaxially surround the detection pattern.

8. The strain wave gearing according to claim 5 ,
wherein
the detection pattern is formed directly on the outer peripheral surface of the hub, or is formed on a film that is affixed to the outer peripheral surface of the hub.

9. The strain wave gearing according to claim 4 ,
wherein
the detection pattern includes magnetic parts and non-magnetic parts that are formed alternatingly at regular intervals along the direction of the axis; and
the detection unit is a magnetic detection unit provided with magnets that face the detection pattern such that the intensity of a magnetic field changes in association with expansion and contraction of the detection pattern in the direction of the axis, and a magnetic detection element that detects any change in the intensity of the magnetic field.

10. The strain wave gearing according to claim 9 ,
wherein
at least a pair of the detection units are provided, the detection units being disposed at symmetrical angular positions that are offset by 180 degrees centered on the axis.

11. The strain wave gearing according to claim 9 ,
wherein
the detection pattern is formed over the entire circumference of the hub, and
the detection unit is provided with a ring-shaped magnet and a ring-shaped magnetic detection element that coaxially surround the detection pattern.

12. The strain wave gearing according to claim 9 ,
wherein
the detection pattern is formed directly on the outer peripheral surface of the hub, or is formed on a film that is affixed to the outer peripheral surface of the hub.

13. The strain wave gearing according to claim 1 , further comprising:
a temperature sensor for performing temperature correction for the displacement detected by the detection mechanism, the temperature sensor being disposed near the hub.

14. The strain wave gearing according to claim 1 , furthermore comprising:
a calculation unit that calculates at least one of whether or not thrust has been generated, the direction of the thrust, the magnitude of the thrust, and any change over time in the thrust on the basis of the detection result from the detection mechanism; and
an operation state determination unit that determines the operation state of the strain wave gearing on the basis of the calculation result from the calculation unit.

15. The strain wave gearing according to claim 14 , furthermore comprising:
an operation control unit that performs operation control for the strain wave gearing on the basis of the detection result from the detection mechanism or the determination result from the operation state determination unit.

16. An actuator comprising:
the strain wave gearing according to claim 15 , and
a motor in which a motor shaft is linked to the hub of the wave generator,
wherein
the operation control unit controlling rotation inputted from the motor to the strain wave gearing to thereby perform the operation control for the strain wave gearing.

17. The actuator according to claim 16 , furthermore comprising:
a brake mechanism that controls the rotation inputted to the strain wave gearing,
wherein
the operation control unit controls the brake mechanism to thereby perform the operation control for the strain wave gearing.

Assignees

• Harmonic Drive Systems

Inventors

• Kobayashi Masaru

Classifications

• F16H57/01

  Monitoring wear or stress of gearing elements, e.g. for triggering maintenance · CPC title

• F16H49/001 Primary

  Wave gearings, e.g. harmonic drive transmissions · CPC title

• G01L5/12

  for measuring axial thrust in a rotary shaft, e.g. of propulsion plants · CPC title

• F16H2049/003

  Features of the flexsplines therefor · CPC title

• F16H57/02

  Gearboxes; Mounting gearing therein · CPC title