Rear-Wheel Sprocket Pairing With Release Teeth for Chain Wear Control
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Solution Overview
Problem
Bicycle rear-wheel sprocket cassettes with odd tooth counts face issues due to varying engagement with chain links, leading to physical weakening and increased wear, especially with the introduction of electric motor-assisted cycling which demands higher torque transmission and smaller gear leaps.
Innovation Solution
A bicycle rear-wheel sprocket pairing with even tooth counts of 22 or less, featuring specific upshift and downshift recess formations and single release and catch teeth to ensure consistent chain engagement and reduced structural weakening, allowing for stable operation under increased mechanical stress without increased installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If odd tooth count sprockets are used, then the sprocket can engage with alternating chain links (inner and outer link plates), but the sprocket experiences varying engagement conditions leading to physical weakening and increased wear
Solution Approach 1:
The sprocket teeth are designed with differentiated local properties: release teeth have modified geometry (reduced thickness, inclined surfaces) compared to regular teeth. This local differentiation allows specific teeth to handle the demanding release function while other teeth maintain standard robust geometry for normal power transmission, resolving the contradiction between engagement versatility and wear resistance
Solution Approach 2:
The sprocket is segmented into functionally distinct tooth zones: regular teeth for standard engagement and specialized release teeth for chain release operations. This segmentation allows each tooth type to be optimized for its specific function, with release teeth experiencing controlled weakening only where necessary while the majority of teeth maintain full strength
2Reliability
If multiple release teeth are provided on the sprocket, then the chain can be released more reliably, but the structural strength of the sprocket is reduced due to multiple weakened tooth regions
Solution Approach 1:
The release function is extracted from all teeth and concentrated in specific designated release teeth. Only these extracted teeth are weakened through geometric modification, while the remaining teeth retain full structural integrity. This selective extraction resolves the contradiction by localizing the functional requirement to specific elements rather than compromising the entire sprocket structure
3Power
If electric motor-assisted cycling is implemented, then higher torque transmission is achieved, but the sprocket experiences increased mechanical stress and wear
Solution Approach 1:
The sprocket design incorporates local quality differentiation where release teeth have modified geometry optimized for their specific function, while the majority of teeth maintain standard robust construction. This allows the sprocket to handle high torque loads through the strong regular teeth while the specialized release teeth manage the additional stress from motor-assisted cycling during chain release operations
Data Source
AI summary
A bicycle rear-wheel sprocket pairing for engaging in a meshing, force-transmitting and form-fitting manner with a bicycle roller chain, wherein the rear-wheel sprocket pairing is rotatable about a sprocket axis. The sprocket axis defines an axial direction running along the sprocket axis, a radial direction running so as to be orthogonal to the sprocket axis, and a circumferential direction encircling the sprocket axis. The rear-wheel sprocket pairing comprises a larger sprocket and a smaller sprocket which for rotating conjointly with the larger sprocket in a slip-free manner about the sprocket axis is connected to the larger sprocket so as to be coaxial with and axially directly adjacent to the latter. The larger sprocket has an even tooth count of equal to or less than twenty-two teeth, and the difference in the tooth count between the larger and the smaller sprocket is exactly two teeth.