Wave Generator Bearing Groove Pattern for Stable Lubrication
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Solution Overview
Problem
In strain wave gearing devices, the wave generator bearing flexes into an ellipsoidal shape, leading to uneven lubrication between rolling elements and raceway surfaces, resulting in increased friction and instability, especially under high load or low-viscosity lubrication conditions.
Innovation Solution
The wave generator features an inner-race and outer-race lubrication groove pattern with fine, linear or curved grooves that guide and hold lubricant efficiently, ensuring adequate lubrication at both tightly and loosely contacted areas, reducing friction and preventing oil film tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wave generator bearing is operated under high load or low-viscosity lubrication conditions, then the device can operate in diverse environments, but the lubrication state deteriorates leading to increased friction and instability
Solution Approach 1:
The invention applies different groove patterns to different regions of the raceway surface. The first groove pattern is formed in short-axis-side portions where rolling elements are loosely held, while the second groove pattern is formed in long-axis-side portions where rolling elements are tightly held. This local differentiation optimizes lubrication for each specific contact condition, maintaining reliable lubrication across diverse operating environments.
2Reliability
If fine recessed grooves are formed in raceway surfaces to enhance oil film formation, then lubrication is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention divides the raceway surface into multiple regions with different groove patterns. The first groove pattern with grooves extending in the circumferential direction is applied to short-axis-side portions, while the second groove pattern is applied to long-axis-side portions. This segmentation allows each region to be optimized for its specific lubrication needs while maintaining manufacturability through standardized groove formation processes.
3Force
If the rolling elements are tightly held between inner and outer races at long-axis-side portions, then load bearing capacity is improved, but lubrication becomes insufficient leading to increased friction
Solution Approach 1:
The invention addresses this contradiction by forming a second groove pattern specifically in the long-axis-side portions where rolling elements are tightly held. This local groove formation provides dedicated lubrication pathways in the high-load contact zones, ensuring that the tightly held rolling elements receive adequate lubrication while maintaining their load-bearing function.
4Reliability
If lubrication grooves are formed to guide and hold lubricant, then oil film holding capability is improved, but the device complexity increases
Solution Approach 1:
The invention segments the raceway surface into distinct zones with different groove patterns. The first groove pattern in short-axis-side portions and the second groove pattern in long-axis-side portions are both relatively simple linear groove configurations. This segmentation approach maintains overall device simplicity while providing targeted lubrication enhancement where needed, avoiding excessive complexity.
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 design maintains a stable lubrication state along the circumferential direction, reducing friction, preventing lubricant leakage, and enhancing oil film holding capability, thereby ensuring smooth operation and reducing the risk of irregular rotation.
Implementation Method 1
fine recessed grooves are formed in raceway surfaces in order to increase the potential for an oil film to be formed between rolling elements and the raceway surfaces
Implementation Method 2
Balls inserted between the inner and outer races roll along raceway surfaces of the outer race and the inner race, whereby the wave generator plug and the externally toothed gear can smoothly rotate relative to each other with a small amount of torque
Implementation Method 3
the state of contact between the balls and the raceway surfaces of the inner and outer races is a state of mixed lubrication
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 2(c)
AI summary
An outer-ring lubrication groove pattern (6) formed in an outer-race raceway surface (47a) and an inner-race lubrication groove pattern 5(5) formed in an inner-race raceway surface (46a) of a wave generator bearing (45) of a strain wave gearing device (1) are patterns in which linear lubrication grooves (53, 54, 60) having very small widths and depths of several micrometers or less are arranged at fine pitches of several micrometers or less. The inner-race lubrication groove pattern 10(5) includes a second groove pattern (52) formed in long-axis-side inner-race raceway surface portions (46B1, 46B2) to hold the lubricant, and a first groove pattern (51) formed in short-axis-side inner-race raceway surface portions (46A1, 46A2) to hold the lubricant and guide the lubricant to the second groove pattern (52). This configuration 15 improves the contact state between balls (48) and the inner-race and outer-race raceway surfaces (46a, 47a) of the wave generator bearing (45), thus reducing the coefficient of friction therebetween.