Strain Wave Gear Release Groove for Uniform Tooth Loading
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Solution Overview
Problem
In strain wave gearing, the stress distribution in the tooth trace direction of the external gear is uneven, leading to reduced tooth bottom fatigue strength and transmission torque capacity, due to the non-uniform pressing force from the wave generator.
Innovation Solution
A release groove is formed in the surface contact portion between the flexible gear and the wave generator, with a width equal to or greater than the ball raceway groove and a gradually increasing depth, to alleviate stress and improve torque transmission by smoothing the pressing force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pressing force of the wave generator is increased to enhance tooth bottom fatigue strength, then the transmission torque capacity is improved, but the stress concentration at the ball center position in the tooth trace direction increases
Solution Approach 1:
The invention introduces a release groove at the specific location where the ball center position contacts the flexible gear (the most stressed region), creating a localized stress relief zone. This allows the pressing force to be distributed more evenly across the contact surface, reducing peak stress concentration while maintaining overall tooth bottom fatigue strength enhancement
Solution Approach 2:
The release groove segments the continuous contact surface between the wave generator and flexible gear, creating distinct contact and non-contact zones. This segmentation allows the pressing force to be applied more uniformly across the remaining contact areas, preventing stress concentration at any single point while maintaining sufficient total contact area for torque transmission
2Strength
If the pressing force distribution in the tooth trace direction is made smooth, then tooth bottom fatigue strength is improved, but the complexity of the wave generator structure increases
Solution Approach 1:
Instead of redesigning the entire wave generator structure to achieve smooth pressing force distribution, the invention applies a localized modification (release groove) only at the critical contact region. This maintains the simplicity of the overall wave generator structure while achieving the desired smooth force distribution effect where it matters most
Solution Approach 2:
Rather than trying to make the pressing force distribution smooth through complex wave generator design, the invention inverts the approach by introducing a release groove that removes material from the contact surface. This negative approach (removing rather than adding) simplifies the structure while achieving the smoothing effect on force distribution
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The release groove reduces maximum stress at the tooth bottom, enhances tooth bottom fatigue strength, and increases the transmission torque capacity of the flexible gear by ensuring a uniform pressing force distribution, thereby improving the overall performance of the strain wave gearing.
Implementation Method 1
The external gear is partially meshed with the internal gear by being flexed in the radial direction by the wave generator
Implementation Method 2
The balls inserted between the inner and outer rings roll along the raceway surfaces of the outer ring and the inner ring
Implementation Method 3
The release groove reduces maximum stress at the tooth bottom, enhances tooth bottom fatigue strength, and increases the transmission torque capacity
Data Source
AI summary
A strain wave gearing wherein the outer circumferential surface of an outer ring of a wave generator is in contact with an inner-circumferential-surface portion of a flexible externally toothed gear, and a release groove, which is not in contact with the outer circumferential surface, is formed in the inner-circumferential-surface portion. The release groove is formed in a region containing a ball raceway groove. The groove depth of the release groove gradually increases from both sides of the groove in the groove width direction toward a deepest portion of the groove provided at an intermediate portion in the groove width direction. By providing the release groove, it is possible to smooth the distribution of pressing force of the wave generator acting on the externally toothed gear in the tooth-trace direction. In addition, the tooth root fatigue strength and the transmission torque capacity of the externally toothed gear can be improved.