Strain Wave Gear Meshing Geometry for Higher Torsional Rigidity
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Solution Overview
Problem
Conventional strain wave gear devices with meshing parts at three or more positions experience significant deformation, limiting their power transmission efficiency despite increased rigidity.
Innovation Solution
A strain wave gear device design where the external gear is configured with a wave generator to form meshing parts at three or more positions, with specific diameter and tooth number ratios to minimize deformation and enhance rigidity, using materials like resin for weight savings and friction reduction treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the meshing part is provided at three or more positions in the circumferential direction, then the rigidity against torsion is improved, but large deformation occurs at the external gear and elastically deforming bearing, reducing power transmission efficiency
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between the working pitch diameter and number of teeth for the external gear and internal gear. By controlling the ratio (DpF/ZF) > (DpR/ZR) and satisfying the inequality relation involving tip diameters, root diameters, and lift amount, the deformation required for meshing is reduced while maintaining three or more meshing positions, thus improving power transmission efficiency without sacrificing rigidity
Solution Approach 2:
The patent utilizes the flexibility of the external gear and elastically deforming bearing to enable dynamic noncircular deflection. The wave generator causes the external gear to deflect into a noncircular shape that forms meshing parts with the internal gear at three or more positions, allowing the system to adapt its shape dynamically while maintaining efficient power transmission through controlled deformation
2Stability of the object's composition
If the external gear is made flexible to form meshing parts at three or more positions, then the rigidity of the strain wave gear device is increased, but the deformation amount required for meshing increases, limiting power transmission efficiency
Solution Approach 1:
The patent resolves this contradiction by changing the geometric parameters of the gear system. By establishing that (DpF/ZF) > (DpR/ZR) and satisfying the inequality relation involving tip diameters, root diameters, and lift amount, the required deformation amount is reduced while maintaining the flexibility needed for three or more meshing positions, thus achieving both rigidity and manufacturing precision
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
This configuration improves power transmission efficiency while maintaining increased rigidity, reducing deformation and enhancing angular transmission accuracy and impact resistance.
Implementation Method 1
an external gear (3) that has flexibility and is arranged at an inner circumference side of the internal gear (2)... a wave generator (4) that is assembled to an inner circumference of the external gear (3) to cause the external gear (3) to noncircularly deflect
Data Source
AI summary
It is included an internal gear (2), an external gear (3) having flexibility, and a wave generator (4) that forms a meshing part (P) with the internal gear (2) in the external gear (3) and moves the meshing part (P) in a circumferential direction of the internal gear (2). The wave generator (4) is configured such that the meshing part (P) is formed at three or more positions in a circumferential direction of the external gear (3). A value (DpF/ZF) obtained by dividing a working pitch diameter DpF of the external gear (3) by the number of teeth ZF is greater than a value (DpR/ZR) obtained by dividing a working pitch diameter DpR of the internal gear (2) by the number of teeth ZR.