Wave Generator Roller Support Bearing Sizing for Fatigue Life
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Solution Overview
Problem
The service life of roller-type wave generators in wave gear devices is limited by rolling fatigue, with no prior solutions addressing this issue effectively, particularly at high reduction ratios where dynamic load rating and rotation speed play a crucial role.
Innovation Solution
The size of roller support bearings is tailored to match the load distribution in the wave generator, with larger bearings for rollers on the long axis to manage higher loads, extending the service life by distributing load more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rollers of the same size are used in all positions, then the device complexity is reduced and manufacturing is simplified, but the rolling fatigue life is limited due to uneven load distribution
Solution Approach 1:
The patent applies local quality by specifying different roller support bearing sizes for different positions based on load distribution. Rollers on the long axis (first and second rollers) use larger support bearings (outer diameter D1) while rollers on other positions (third to sixth rollers) use smaller support bearings (outer diameter D2). This localized differentiation optimizes reliability where loads are highest without unnecessarily increasing complexity elsewhere.
Solution Approach 2:
The patent changes the parameter of support bearing outer diameter based on position and load characteristics. By setting D1 > D2, the invention creates a parameter gradient that matches the load distribution pattern in wave gear devices, particularly at high reduction ratios where long-axis rollers experience significantly higher loads.
2Duration of action of stationary object
If larger support bearings are used for rollers on the long axis, then the rolling fatigue life is extended, but the device complexity and manufacturing cost increase
Solution Approach 1:
The invention implements local quality by applying larger support bearings (D1) only to the first and second rollers on the long axis where loads are highest, while using smaller bearings (D2) for the third to sixth rollers. This targeted approach extends service life where needed without uniformly increasing manufacturing complexity across all components.
Solution Approach 2:
The patent segments the roller support bearing system into two groups based on load characteristics: high-load rollers (first and second) receiving larger bearings, and lower-load rollers (third to sixth) receiving smaller bearings. This segmentation allows differentiated service life optimization without requiring complete redesign of all bearing components.
3Productivity
If uniform roller sizes are used, then the manufacturing precision requirements are simplified, but the load distribution efficiency is suboptimal leading to reduced service life
Solution Approach 1:
The patent applies local quality by matching support bearing size to local load conditions. The first and second rollers on the long axis receive larger bearings (D1) to handle higher loads, while the third to sixth rollers use smaller bearings (D2). This improves load carrying efficiency without requiring complex precision manufacturing across all components uniformly.
Data Source
AI summary
A wave generator for a wave gear device is provided with a pair of first rollers arranged in a position that is point-symmetric in relation to the center of a flexible externally toothed gear, a pair of second rollers, and a pair of third rollers. The first rollers are located on a long axis of the flexible externally toothed gear that is being flex into an ellipsoidal shape, and the second and third rollers are located in positions that are linearly symmetric in relation to the long axis between the long axis and a short axis. Support bearings of the first rollers are larger than those of the second and third rollers. The rolling fatigue life of a roller-type of the wave generator can be to be enhanced.