Wave Gear Tooth Profile Shifting for Coning Compensation
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Solution Overview
Problem
Current wave gear devices face challenges in enhancing load torque performance and preventing ratcheting, requiring a rational tooth profile that accounts for coning and ensures continuous meshing.
Innovation Solution
A wave gear device with a tooth profile that applies necessary profile shifting to the flexible externally toothed gear, defining deflection changes along the tooth trace, using similarity curves derived from movement trajectories to achieve three-dimensional contact and increased torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flexible externally toothed gear is deflected into an ellipsoidal shape by the wave generator, then meshing occurs at both end parts in the direction of the major axis of the ellipse, but the amount of deflection increases from the diaphragm side to the front-end opening, causing coning that affects meshing quality
Solution Approach 1:
The patent applies different profile shifting amounts to different axial positions of the flexible externally toothed gear. Specifically, the profile shifting amount varies along the tooth trace direction, with larger shifting amounts applied to regions with greater deflection (front-end opening side) and smaller shifting amounts to regions with less deflection (diaphragm side). This local differentiation compensates for the coning effect and ensures uniform meshing quality across the entire gear width.
Solution Approach 2:
The patent changes the profile shifting parameter as a function of axial position. The profile shifting amount is calculated based on the deflection amount at each axial position, creating a continuous variation of the profile shifting parameter along the tooth trace direction. This parameter change approach transforms the uniform tooth profile into a position-dependent profile that compensates for deflection-induced coning.
2Reliability
If a conventional tooth profile is used without considering coning, then manufacturing is simpler, but effective meshing cannot be maintained along the entire tooth trace due to deflection variations
Solution Approach 1:
The patent applies profile shifting as a preliminary design action to compensate for the anticipated coning effect before the gear operates. By pre-calculating and pre-applying the appropriate profile shifting amounts at different axial positions, the design ensures that the tooth profiles are already optimized for continuous meshing under deflected conditions, eliminating the need for complex real-time adjustments or post-manufacturing modifications.
3Power
If the tooth profile does not account for deflection variations, then design is simpler, but torque transmission capability is reduced due to limited effective meshing range
Solution Approach 1:
The patent utilizes parameter changes by varying the profile shifting amount as a function of axial position and deflection magnitude. This systematic parameter variation enables the tooth profile to adapt to local deflection conditions, ensuring optimal meshing and torque transmission across the entire gear width. The method transforms a single-parameter design into a multi-parameter design that captures the spatial variation of deflection effects.
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 approach enables effective meshing along the entire tooth trace, enhancing torque transmission and ratcheting performance by accounting for coning and ensuring high gear teeth engagement.
Implementation Method 1
The flexible externally toothed gear is deflected into an ellipsoidal shape by the wave generator, and caused to mesh with the rigid internally toothed gear at both end parts in the direction of the major axis of the ellipse. The amount of deflection of the external teeth of the flexible externally toothed gear deflected into an ellipsoidal shape increases from a side towards the diaphragm to the front-end opening along the tooth trace direction of the external teeth, the amount of deflection being substantially proportional with respect to the distance from the diaphragm.
Data Source
AI summary
In a wave gear device, similarity curve tooth profiles for defining the tooth-face tooth profile of each of a flexible externally toothed gear and a rigid internally toothed gear is determined from the movement trajectory, relative to a tooth of the rigid internally toothed gear, of a tooth of the flexible externally toothed gear at a main cross-section at which the deflection factor is κ=1. Tooth profile curves, which have been subjected to profile shifting corresponding to the difference between the deflection factor κo (>1) of the opening-end cross-section of the flexible externally toothed gear and the deflection factor κ of the main cross-section, are determined from the similarity curves; and the tooth profile curves are used to form the tooth-face tooth profile portions of the two gears. High-gear-tooth compound tooth profiles, defined from the tooth-face tooth profile portions, straight-line tooth profile portions continuing from the tooth-face tooth profile portions, and appropriate tooth-flank tooth profile portions for avoiding interference are used as tooth profiles of the internal teeth and the external teeth. Also, taking coning of the flexible externally toothed gear into account, negative profile shifting is applied from an opening-end cross-section to an inner-end cross-section of the flexible externally toothed gear, and rational meshing between the two gears is obtained along the entire tooth trace.