Rear Sprocket Tooth Chamfers for Quiet Shifting and Chain Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bicycle rear sprockets face challenges in reducing noise and ensuring smooth shifting operations due to the contact between the bicycle chain and the sprocket, particularly when the chain is inclined relative to the center plane of the bicycle frame, leading to increased noise and potential chain drop during reverse rotation.
Innovation Solution
The bicycle rear sprocket design incorporates driving-noise reduction teeth with chamfers and chain-drop reduction teeth, which include upstream and downstream circumferential surfaces, chamfers, and axially recessed teeth to facilitate smooth shifting, reduce noise, and prevent chain drop by adjusting the distance between the chain and the center plane, thereby enhancing the operational efficiency and reliability of the sprocket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional sprocket teeth are used, then the structure is simple, but noise is generated during chain contact and shifting operations
Solution Approach 1:
The invention applies local quality by introducing chamfers only at specific locations on the sprocket teeth (upstream and downstream sides) rather than changing the entire tooth structure. The chamfers are positioned at the corners where the chain contacts the tooth during engagement and disengagement, locally modifying the geometry to reduce noise-generating impacts while maintaining the overall simple sprocket design.
Solution Approach 2:
The invention employs asymmetry by designing different chamfer configurations on the upstream and downstream sides of the sprocket teeth. The upstream chamfer and downstream chamfer have different orientations and positions relative to the tooth geometry, creating an asymmetric tooth profile that optimizes chain engagement characteristics and reduces noise during the asymmetric chain-sprocket interaction cycle.
2Adaptability or versatility
If the chain is inclined relative to the center plane during reverse rotation, then reverse pedaling is enabled, but chain drop and increased noise occur
Solution Approach 1:
The invention applies preliminary action by pre-configuring the chamfers on the sprocket teeth before the chain engages during reverse rotation. The upstream and downstream chamfers are positioned to proactively guide the chain onto the tooth flanks at appropriate angles, preventing chain drop and reducing noise before the harmful contact occurs. This preliminary geometric preparation ensures stable chain engagement during the vulnerable reverse rotation phase.
Solution Approach 2:
The chamfers act as intermediary elements between the chain and the sprocket tooth flanks during reverse rotation. Instead of the chain directly impacting the tooth corners (which causes noise and instability), the chamfers serve as mediating surfaces that guide and cushion the chain's engagement, particularly when the chain is inclined relative to the center plane during reverse pedaling.
3Ease of operation
If smooth shifting is achieved through chamfer design, then noise is reduced, but manufacturing complexity increases
Solution Approach 1:
The invention applies parameter changes by modifying only specific geometric parameters of the sprocket teeth (the addition of chamfer angles and dimensions at upstream and downstream corners) rather than redesigning the entire tooth profile. This localized parameter modification achieves smooth chain shifting and noise reduction while maintaining compatibility with conventional sprocket manufacturing processes, minimizing the increase in manufacturing complexity.
Data Source
AI summary
A bicycle rear sprocket comprises a sprocket body and a plurality of sprocket teeth including a plurality of driving-noise reduction teeth. Each of the plurality of driving-noise reduction teeth comprises an upstream circumferential surface, a downstream circumferential surface, a first chamfer, and a second chamfer. The first chamfer has a first borderline relative to the bicycle outward surface. The second chamfer has a second borderline relative to the bicycle outward surface. A first opposite end of the first borderline and a second opposite end of the second borderline are disposed radially outwardly from each of a first end of the first borderline and a second end of the second borderline with respect to the rotational center axis. A total number of the plurality of driving-noise reduction teeth is equal to or larger than one-third of a total tooth-space number of the plurality of sprocket teeth.