Strain Wave Gear Coupling and Bearing Layout for Low Backlash
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Solution Overview
Problem
Strain wave gear systems face challenges in precise wave generator positioning, radial over-constraint leading to eccentric loading, length and backlash issues due to compliance devices, and inefficient lubrication and sealing methods, which increase costs and user complexity.
Innovation Solution
A strain wave gear system with a ring gear and wave generator, featuring a non-circular flexspline, strategically located bearings for axial constraint without radial movement, and a sealing system using a cap and housing with a protrusion and cavity for consistent sealant distribution, along with a lubricating system using plungers to precisely deliver grease to bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ball bearings are used to constrain the wave generator, then the manufacturer can properly position the wave generator, but the system becomes radially over-constrained causing eccentric loading on the bearings
Solution Approach 1:
The patent removes the radial constraint function from the bearing system, extracting only the axial positioning function. The wave generator is positioned axially using a simplified mechanism without radial constraining bearings, eliminating the source of eccentric loading while maintaining positioning capability.
Solution Approach 2:
Instead of using bearings to constrain the wave generator radially (traditional approach), the patent inverts the approach by allowing radial movement and using a different mechanism for axial positioning. This reverses the constraint strategy from radial to axial only, avoiding the harmful eccentric loads.
2Adaptability or versatility
If an Oldham style coupling is used for input connection, then compliance with misalignment is achieved, but the system length increases and backlash is introduced
Solution Approach 1:
The patent extracts the compliance function from a separate Oldham coupling component and integrates it directly into the input connection mechanism. This eliminates the need for an additional axial coupling component, reducing overall system length while maintaining misalignment compensation capability.
Solution Approach 2:
The patent merges the compliance function with the input connection function into a single integrated mechanism. The input connection structure itself provides misalignment compensation through built-in flexibility, combining two functions that were previously separate into one compact component.
3Reliability
If traditional sealing methods are used, then sealing is provided, but significant space is required resulting in larger product size
Solution Approach 1:
The patent uses thin film seals instead of bulky traditional sealing methods. The sealant is applied as a thin conformal coating that provides effective sealing while occupying minimal space, dramatically reducing the volume required for sealing components.
4Reliability
If manual grease application is used for bearing lubrication, then lubrication is provided, but user complexity increases and consistent lubrication is difficult to achieve
Solution Approach 1:
The patent implements a self-lubrication system where the bearing contains an internal grease reservoir and distribution mechanism that automatically delivers lubrication without user intervention. The bearing serves itself by internally managing the lubrication function, eliminating the need for manual grease application by the user.
Data Source
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).