Strain Wave Gear System Radial Constraint and Lubrication Design
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Solution Overview
Problem
Strain wave gear systems face challenges such as high customization costs, user risk in positioning critical components, radial over-constraint leading to undesirable loads, length and backlash addition from compliance devices, and messy lubrication methods that can result in leakage.
Innovation Solution
A strain wave gear system design featuring a housing with a ring gear and annular bearing cap for precise wave generator positioning, using ball bearings constrained within grooves to prevent radial movement, and a grease distribution mechanism with plungers for controlled re-greasing, eliminating the need for external lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ball bearings are used to constrain the wave generator, then the manufacturer can properly position the wave generator, but the bearings over-constrain the system radially and create undesirable loads
Solution Approach 1:
The patent removes the wave generator from the bearing's radial constraint system. Instead of having the bearing support the wave generator radially, the wave generator is positioned and retained only axially by the bearing races, eliminating the harmful radial loads while preserving positioning precision
Solution Approach 2:
The patent inverts the traditional constraint approach by using the bearing races to retain the wave generator axially rather than radially. The wave generator passes through the bearing assembly, with the races providing axial retention while allowing free radial movement, reversing the conventional constraint direction
2Adaptability or versatility
If an Oldham style coupling is used for input connection, then misalignment compensation is achieved, but length and backlash are added to the system
Solution Approach 1:
The patent extracts and eliminates the Oldham coupling from the system entirely. Instead of using a separate misalignment compensation device, the design allows direct connection of the input shaft to the wave generator, accepting minor misalignments without adding length or backlash
Solution Approach 2:
The patent merges the input connection function with the wave generator positioning function. The input shaft is directly coupled to the wave generator through a simplified connection mechanism that combines alignment tolerance with the positioning system, eliminating the need for separate compliance devices
3Reliability
If traditional lubrication methods are used, then bearings can be lubricated, but the process is messy and can result in leakage
Solution Approach 1:
The patent implements a self-lubricating system where the bearing races are provided with lubricant reservoirs and distribution mechanisms that automatically deliver lubricant to the bearing contacts during operation, eliminating the need for external lubrication applications and preventing leakage
Solution Approach 2:
The patent utilizes porous materials or lubricant-impregnated components within the bearing races that continuously supply lubricant through capillary action, ensuring consistent lubrication without requiring external application and preventing leakage
Data Source
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AI summary
A strain wave gear system (10) includes first and second sets of ball bearings (80, 82) located intermediate a flange (84) and a retainer plate (88) rotatable with an output (54) and a radially oriented flat disc (74) of the input including strain relief (76). Strain relief (76) is a helical slot in a coupling (70) located radially within the wave generator (94) and the ring gear (22). The ring gear (22) is sealed by a sealing system including sealant (42) forced by a protrusion (34) of the cap (24) entering into a cavity (36) through a channel (40) into a relief volume (38) of the housing (12). The bearing (48) rotatably mounting the housing (12) to the output (54) is lubricated by a lubricating system including plungers (110) threadably received in axial bores (102) intersecting with radial bores (104) in communication with radial holes (47) of the bearing (48).