Sliding Contact Wave Generator Bearing for Lower Rotational Torque
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Solution Overview
Problem
Sliding contact-type wave generators experience increased rotational torque due to coning in cup-shaped or top-hat-shaped strain wave gearing, leading to inefficiencies during high-speed rotation.
Innovation Solution
A wave generator with an ellipsoidal external peripheral surface and a wave generator bearing composed of an endless coil spring, allowing the annular body to flex into an ellipsoidal shape, reducing frictional resistance and minimizing one-sided contact, thereby reducing rotational torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a sliding contact-type wave generator is used, then efficiency during high-speed rotation is improved due to less viscous resistance, but rotational torque increases due to one-sided contact caused by coning
Solution Approach 1:
A wave generator bearing is introduced as an intermediary component between the wave generator plug and the externally toothed gear. The bearing includes an inner race, outer race, and annular body that distributes contact pressure, converting the one-sided contact problem into multi-point contact while maintaining the sliding contact mechanism's low viscous resistance advantage
Solution Approach 2:
The contact parameters are changed by transitioning from direct sliding contact between the plug and gear to sliding contact through a bearing with an annular body. This changes the contact distribution from concentrated one-sided contact to distributed multi-point contact, reducing rotational torque while preserving the sliding contact efficiency
2Ease of operation
If the ellipsoidal external peripheral surface of the plug is in one-sided contact with the internal peripheral surface of the externally toothed gear, then wave generation is achieved, but rotational torque increases
Solution Approach 1:
The wave generator bearing acts as a mediator that maintains the wave generation function while distributing the contact load. The annular body of the bearing makes contact at multiple points on the internal peripheral surface of the externally toothed gear, eliminating one-sided contact and reducing rotational torque
Solution Approach 2:
The contact interaction is extended from a single-point or one-sided contact in one dimension to multi-point contact distributed across different angular positions. The annular body of the bearing contacts the gear at multiple locations around its circumference, transforming the contact geometry to reduce torque
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 solution effectively generates waves in the externally toothed gear with reduced rotational torque, improving efficiency and minimizing torque increases caused by coning, especially in cup-shaped or top-hat-shaped strain wave gearing.
Implementation Method 1
an annular body composed of an endless coil spring, and provided with rigidity capable of maintaining a fixed gap between the inner race and outer race, and flexibility in a radial direction of the annular body so as to be capable of flexing into a non-circular shape
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(d)
Figure 3(a)~3(b)
AI summary
The wave generator (4) of a strain wave gearing (1) is provided with an ellipsoidally contoured wave generator plug (21) and a wave generator bearing (23). The wave generator bearing (23) is provided with an annular body (26) fitted between inner and outer races (24, 25) in a sliding contact state. The annular body (26) is composed of an endless coil spring and has a rigidity that is able to maintain a constant gap between the inner and outer races (24, 25). The annular body also has a specified overall flexibility in the radial direction so that the annular body can be flexed into an ellipsoidal shape by the wave generator plug (11). Since sliding occurs between the annular body (26) and the inner race (24) when the wave generator plug (21) rotates, it is possible to generate a wave motion in an externally toothed gear (3) with a small rotational torque.