# US 11,441,650 B2 · Rotation transmission mechanism provided with strain wave gearing

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- Number: US 11,441,650 B2
- Document ID: US11441650B2
- Status: Granted
- Kind: B2
- Application number: 17/076,194
- Filed: 2020-10-21
- Published: 2021-02-04
- Granted: 2022-09-13
- Earliest claimed: 2020-10-21
- Assignees: Harmonic Drive Systems Inc.
- Applicants: Harmonic Drive Systems Inc.
- Inventors: Jun Handa; Hiroaki Kimura; Sotaro Miyake
- Web page: https://patentgrep.com/patent/US11441650B2

## CPC

- F16H 35/10: Arrangements or devices for absorbing overload or preventing damage by overload
- F16H 49/001: {Wave gearings, e.g. harmonic drive transmissions}
- F16H 2049/003: {Features of the flexsplines therefor}
- F16H: GEARING

## Abstract

In a rotation transmission mechanism that transmits the rotational driving force of a motor to a load-side member via a speed reducer, a strain wave gearing is used as the speed reducer, and the allowable load torque of members in the powertrain other than the strain wave gearing is greater than a predetermined upper-limit load torque. The allowable load torque of the strain wave gearing is dictated by the ratcheting torque, which is set so as not to exceed the upper-limit load torque. In an overload state, ratcheting is generated in the strain wave gearing, so that the strain wave gearing functions as a mechanical fuse. Other power transmission members can be protected from an overload state without adding a separate member such as a torque limiter.

## Claims

### Claim 1

A rotation transmission mechanism that transmits rotational driving force outputted from a rotation drive source to a load-side member via a speed reducer, the rotation transmission mechanism comprising:
a powertrain configured from a plurality of power-transmitting members including the speed reducer;
the speed reducer being a strain wave gearing;
an allowable load torque of the power-transmitting members other than the strain wave gearing being greater than a predetermined upper-limit load torque;
an allowable load torque of the strain wave gearing being prescribed by a ratcheting torque set to a value equal to or lower than the upper-limit load torque; and
the strain wave gearing functioning as a mechanical fuse;
wherein a rigid internally toothed gear in the strain wave gearing is fixed and fastened to a fixed-side member of the strain wave gearing by means of a plurality of fastening bolts;
the fastening bolts are respectively inserted into bolt holes formed at a constant pitch in a circumferential direction of the rigid internally toothed gear; and
slits, which extend outward in the radial direction from the bolt holes to an external peripheral surface of the rigid internally toothed gear, are provided to a portion of the internally toothed gear fastened by some of the fastening bolts in the circumferential direction and rigidity in a radial direction is made less than in other portions, so that
a fastening force by which the rigid internally toothed gear is fixed by being fastened to the fixed-side member is set to a lesser fastening force in one portion of the internally toothed gear in a circumferential direction than a case in which the allowable load torque of the strain wave gearing is greater than the upper-limit load torque, whereby the ratcheting torque is set to be equal to or lower than the upper-limit load torque.