Wave Generator Bearing Shoulder Layout for Coning Deformation
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Solution Overview
Problem
The coning deformation in gear devices causes ball impact issues at the bearing raceway surfaces, leading to potential deterioration or damage due to reduced torsional stiffness and altered ball trajectories.
Innovation Solution
The gear device incorporates a wave generator with an elliptical cam and a bearing having inner and outer ring shoulder parts with varying heights along the major and minor axes, strategically positioned to manage ball stress and prevent edge contact, thereby reducing the likelihood of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the gap between the inner circumferential surface of the external gear and the outer ring of the bearing is reduced to solve torsional stiffness issues, then the torsional stiffness is improved, but the ball may hit the edge of the raceway surface causing deterioration or damage
Solution Approach 1:
The inner ring shoulder parts are designed with different heights at different locations (major axis vs minor axis) to provide localized support. The first inner ring shoulder part has a greater height than the second inner ring shoulder part, creating asymmetric local geometry that prevents ball edge contact while maintaining the required gap reduction for torsional stiffness.
Solution Approach 2:
The bearing structure introduces asymmetric features through the unequal heights of the inner ring shoulder parts positioned at major and minor axes. This asymmetric design allows the bearing to differently constrain the ball at opposite sides, preventing the ball from hitting the raceway surface edge while maintaining compact dimensions for stiffness.
2Productivity
If the wave generator is fitted into the external gear, then the gear device achieves its speed reduction function, but coning deformation occurs causing ball trajectory alteration and raceway surface damage
Solution Approach 1:
The inner ring shoulder parts are pre-positioned to counteract the coning deformation effects before they can cause ball trajectory alteration. By having the first inner ring shoulder part (at minor axis) taller than the second (at major axis), the structure preemptively compensates for the opening/narrowing deformation, keeping the ball centered on the raceway surface throughout operation.
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 effectively reduces the stress on the bearing surfaces, minimizing the risk of deterioration and damage by ensuring proper alignment and support for the balls, thus enhancing the gear device's operational reliability.
Implementation Method 1
The bearing has an inner ring, an outer ring, and a plurality of balls arranged between the inner ring and the outer ring
Data Source
AI summary
A gear device includes an internal gear, a flexible external gear, and a wave generator. The wave generator has an elliptic cam and a bearing. An inner ring has an inner ring raceway surface which a plurality of balls are in contact with, and a pair of inner ring shoulder parts. At a position of a minor axis, a first inner ring shoulder part has a greater height than a second inner ring shoulder part. At a position of a major axis, the second inner ring shoulder part has a greater height than the first inner ring shoulder part.