Wave Gear Bearing Clearance for Lubrication and Load Distribution
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Solution Overview
Problem
Wave gearing in robots experiences reduced reliability and life due to inappropriate engagement between the external gear and wave generator, leading to excessive load application and stress concentration, resulting from insufficient lubrication or excessive stress on the external teeth.
Innovation Solution
A gearing design with an internal gear, a flexible external gear, and a wave generator where the outer diameter of the bearing and inner diameter of the external gear satisfy specific diameter differences to ensure proper engagement, preventing excessive tightening or loosening, thus maintaining adequate lubrication and reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the engagement between the external gear and wave generator is tight (small difference between inner diameter of external gear and outer diameter of wave generator), then the contact area is increased, but the lubrication supply is insufficient and excessive load is applied
Solution Approach 1:
The patent introduces a bearing as an intermediary component between the wave generator and the external gear. The bearing's outer circumferential surface contacts the inner circumferential surface of the external gear, while the wave generator contacts the bearing's inner circumferential surface through a cam mechanism. This intermediary bearing ensures adequate lubrication supply to the contact interface and distributes the load, preventing the problems of insufficient lubrication and excessive stress concentration that occur when the wave generator directly engages with the external gear.
2Reliability
If the engagement between the external gear and wave generator is loose (large difference between inner diameter of external gear and outer diameter of wave generator), then the lubrication supply is improved, but the contact area is reduced and stress is concentrated on the bottom of external teeth
Solution Approach 1:
The bearing serves as a mediator that maintains optimal engagement between the wave generator and external gear. By introducing this intermediate component, the system achieves both adequate lubrication supply (as the bearing can be properly lubricated) and sufficient contact area (through the bearing's outer surface contacting the external gear), thereby avoiding stress concentration on the external teeth while maintaining good lubrication performance.
3Volume of moving object
If the difference between inner diameter of external gear and outer diameter of wave generator is excessively small, then the structural compactness is improved, but the load distribution is poor and excessive load is applied
Solution Approach 1:
The bearing acts as an intermediary that enables better load distribution while maintaining compact design. The bearing's outer circumferential surface provides a distributed contact interface with the external gear, preventing stress concentration on individual teeth. The cam mechanism on the wave generator controls the bearing's deformation to achieve the desired engagement, thus maintaining structural compactness while improving load distribution and strength.
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 proposed gearing design enhances the mechanical characteristics, reliability, and life of the wave gearing by ensuring sufficient lubrication and distributing the load effectively, preventing premature failure.
Implementation Method 1
a bearing 42 contacting an inner circumferential surface 311 of the external gear 3 and a cam 41 contacting an inner circumferential surface of the bearing 42
Data Source
AI summary
A gearing includes an internal gear, a flexible external gear partially meshing with the internal gear and relatively rotating about a rotation axis to the internal gear, and a wave generator including a bearing contacting an inner circumferential surface of the external gear and a cam contacting an inner circumferential surface of the bearing and moving a mesh position between the internal gear and the external gear in a circumferential direction about the rotation axis, wherein an outer circumferential surface of the bearing forms a circular shape without contact with the cam, the inner circumferential surface of the external gear forms a circular shape without contact with the wave generator, andd12-d22≦-0.003[mm]and-6×10-4≦(d12-d22)/d22where an outer diameter of the bearing without contact with the cam is d1 [mm] and an inner diameter of the external gear without contact with the wave generator is d2 [mm].