# US 2017/0254403 A1 · Wave generator and strain wave gearing

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- Number: US 2017/0254403 A1
- Document ID: US20170254403A1
- Status: Published application
- Kind: A1
- Application number: 15/519,677
- Filed: 2014-11-21
- Published: 2017-09-07
- Earliest claimed: 2014-11-21
- Assignees: Harmonic Drive Systems Inc.
- Applicants: Harmonic Drive Systems Inc.
- Inventors: Masaru KOBAYASHI
- Web page: https://patentgrep.com/patent/US20170254403A1

## CPC

- F16H 49/001: {Wave gearings, e.g. harmonic drive transmissions}
- F16C 19/364: {with tapered rollers, i.e. rollers having essentially the shape of a truncated cone}
- F16C 33/588: {Races of sheet metal}
- F16C 2361/61: Toothed gear systems, e.g. support of pinion shafts
- F16H 2049/003: {Features of the flexsplines therefor}
- F16H: GEARING
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS

## Abstract

A wave generator of a strain wave gearing has a rigid plug provided with an elliptical outer peripheral surface, and a roller bearing. The outer peripheral surface of the plug is provided with a major-axis-side outer-peripheral surface portion formed at a major axis position L1, and a minor-axis-side outer-peripheral surface portion formed at a minor axis position L2. The major-axis-side outer-peripheral surface portion is a tapered surface that is tapered along a center axis line, and the minor-axis-side outer-peripheral surface portion is an inverted tapered surface that is tapered in the opposite direction. An externally toothed gear can be supported and flexed into an elliptical shape without partial contact by using the wave generator in which the roller bearing is used.

## Claims

### Claim 1

A wave generator of a strain wave gearing, which makes a cup-shaped or silk-hat-shaped externally toothed gear to flex into an elliptical shape and partially mesh with a rigid internally toothed gear, the wave generator comprising:
a rigid plug having an elliptical outer peripheral surface; and
a roller bearing mounted on the outer peripheral surface of the plug,
wherein the outer peripheral surface of the plug has:
a tapered surface that is tapered toward a first direction along a center axis line of the plug on a major axis position of the outer peripheral surface; and
an inverted tapered surface that is tapered toward a second direction opposite to the first direction along the center axis line on a minor axis position of the outer peripheral surface.

### Claim 2 (depends on 1)

The wave generator of the strain wave gearing according to claim 1, wherein the outer peripheral surface of the plug is formed so that an elliptical outline in each axis-perpendicular section in the center axis direction has a same circumferential length.

### Claim 3 (depends on 1)

The wave generator of the strain wave gearing according to claim 1,
wherein the outer peripheral surface of the plug is tapered so as to have a different taper angle on each position in the circumferential direction thereof, and
each taper angle corresponds to a coring angle on each corresponding position in the circumferential direction of the external-tooth forming portion, in which the corning angle is obtained when the external-tooth forming portion of the externally toothed gear is flexed at a predetermined position in a tooth trace direction into a predetermined elliptical shape.

### Claim 4 (depends on 1)

The wave generator of the strain wave gearing according to claim 1,
wherein an inner race of the roller bearing is integrally formed in the plug, and
the outer peripheral surface is an inner-race raceway.

### Claim 5 (depends on 1)

A strain wave gearing comprising:
a rigid internally toothed gear;
a cup-shaped or a silk-hat-shaped flexible externally toothed gear; and
a wave generator for flexing the externally toothed gear into an elliptical shape and meshing with the internally toothed gear, and for moving meshing positions between the both gears in a circumferential direction,
wherein the wave generator is one that is defined in claim 1.

### Claim 6 (depends on 5)

The strain wave gearing according to claim 5, wherein an outer race of the roller bearing of the wave generator is integrally formed in the external-tooth forming portion of the externally toothed gear.