Optimized harmonic drive

Patent metadata

Field	Value
Publication number	US-10975947-B2
Application number	US-201815907281-A
Country	US
Kind code	B2
Filing date	Feb 27, 2018
Priority date	Feb 27, 2018
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

An optimized harmonic drive (“OHD”) includes a wave generator, a flex spline, and a circular rigid spline. The wave generator includes a wave generator contour that minimizes a velocity profile of the wave generator during a high load condition. The flex spline is attached to the wave generator and the circular rigid spline is mechanically engaged to the flex spline. The flex spline includes a plurality of flex spline teeth and the circular rigid spline includes a plurality of rigid spline teeth. The plurality of rigid spline teeth is greater than the plurality of flex spline teeth and the high load condition exists when the rigid spline teeth of the plurality of rigid spline teeth are fully engaged with flex spline teeth of the plurality of flex spline teeth.

First claim

What is claimed is:

1. A harmonic drive comprising:
a wave generator having a wave generator contour;
a flex spline coupled to the wave generator, wherein the flex spline includes a plurality of flex spline teeth; and
a circular rigid spline mechanically engaged to the flex spline, wherein the circular rigid spline includes a plurality of rigid spline teeth,
wherein a number of rigid spline teeth of the plurality of rigid spline teeth is greater than a number of flex spline teeth of the plurality of flex spline teeth and
wherein the wave generator contour is configured so that rotation of the wave generator causes a portion of the flex spline teeth to engage and disengage with tooth cavities formed by a portion of the plurality of rigid spline teeth, wherein the wave generator contour is configured to result in a velocity profile during use with substantially zero velocity for a first tooth of the plurality of flex spline teeth when the first tooth is fully engaged in a tooth cavity formed by a first tooth and a second tooth of the plurality of rigid spline teeth, and wherein the velocity profile corresponds to a movement locus of the first tooth of the plurality of flex spline teeth relative to the tooth cavity.

2. The harmonic drive of claim 1 , wherein the first tooth is in a high load condition when fully engaged in any tooth cavity of the tooth cavities.

3. The harmonic drive of claim 2 , wherein each flex spline tooth of the plurality of flex spline teeth has a flex tooth contour based on a set of parameters used to generate the wave generator contour.

4. The harmonic drive of claim 1 , wherein each rigid spline tooth of the plurality of rigid spline teeth has a rigid tooth contour based on a set of parameters used to generate the wave generator contour.

5. The harmonic drive of claim 1 ,
wherein the wave generator contour is defined by a radius vector that has a parametric relationship with an angle θ,
wherein the radius vector is equal to R M −H(sin|θ|−|θ|cos θ) x ,
wherein x is greater than 0 and less than 1,
wherein H is a tooth height of a flex spline tooth of the plurality of flex spline teeth,
wherein R M is a length of a semi-major axis of the wave generator, and
wherein θ is between

-

π
2

⁢

⁢
to
⁢

⁢

π
2

.

6. The harmonic drive of claim 5 , wherein a difference between the length of the semi-major axis of the wave generator and a length of a semi-minor axis of the wave generator is approximately equal to the tooth height.

7. The harmonic drive of claim 1 ,
wherein a flex tooth contour of the plurality of flex spline teeth is defined by a parametric relationship with an angle φ that is defined as H(sin|φ|−|φ|cos φ) a ,
wherein a is greater than 0 and less than 1,
wherein H is a tooth height of a flex spline tooth of the plurality of flex spline teeth, and
wherein φ is between

-

π
2

⁢

⁢
to
⁢

⁢

π
2

.

8. The harmonic drive of, claim 1 ,
wherein a rigid tooth contour of the plurality of rigid spline teeth is defined by a parametric relationship with an angle ϕ that is defined as H(sin|ϕ|−|ϕ|cos ϕ) b ,
wherein b is greater than 0 and less than 1,
wherein H is a tooth height of a flex spline tooth of the plurality of flex spline teeth, and
wherein ϕ is between

-

π
2

⁢

⁢
to
⁢

⁢

π
2

.

9. The harmonic drive of claim 8 , wherein a flex tooth contour of teeth of the plurality of flex spline teeth is the same as the rigid tooth contour.

10. A method for producing a harmonic drive the method comprising:
coupling a flex spline to a wave generator, wherein the wave generator has a particular wave generator contour, and wherein the flex spline includes a first number of flex spline teeth; and
positioning a first portion of the flex spline teeth in tooth cavities of a circular rigid spline, wherein the tooth cavities are formed between rigid spline teeth of the circular rigid spline, wherein a second number of rigid spline teeth is greater than the first number, wherein the particular wave generator contour is configured so that rotation of the wave generator causes a portion of the flex spline teeth to engage and disengage with the tooth cavities, wherein the particular wave generator contour is configured to result in a velocity profile during use with substantially zero velocity for a first tooth of the flex spline teeth when the first tooth is fully engaged in a tooth cavity formed by a first tooth and a second tooth of the rigid spline teeth, and wherein the velocity profile corresponds to a movement locus of the first tooth of the plurality of flex spline teeth relative to the tooth cavity.

11. The method of claim 10 , wherein the first tooth is in a high load condition when fully engaged in any rigid tooth cavity of the rigid tooth cavities.

12. The method of claim 11 , further comprising determining the particular wave generator contour,
wherein determining the particular wave generator contour includes determining a radius vector that has a parametric relationship with an angle θ,
wherein the radius vector is equal to R M −H(sin|θ|−|θ|cos θ) x ,
wherein x is greater than 0 and less than 1,
wherein H is a tooth height of a flex spline tooth of the flex spline teeth,
wherein R M is a length a semi-major axis of the wave generator, and
wherein θ is between

-

π
2

⁢

⁢
to
⁢

⁢

π
2

.

13. The method of claim 12 , further including determining H, wherein H is approximately equal to a flex spline tooth width.

14. The method of claim 10 , further comprising producing a flex tooth contour for the flex spline teeth, wherein the flex tooth contour is based on a

Assignees

• Boeing Co

Inventors

• Atmur Robert J
• Sargent William Patrick

Classifications

• F16H55/08

  Profiling · CPC title

• F16H55/17

  Toothed wheels (worm wheels F16H55/22; chain wheels F16H55/30) · CPC title

• F16H55/0833

  Flexible toothed member, e.g. harmonic drive · CPC title

• F16H49/001 Primary

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

• F16H2049/003

  Features of the flexsplines therefor · CPC title