Bicycle Sprocket Tooth Layout for Lightweight Smooth Gearshifting
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Solution Overview
Problem
Existing bicycle sprocket designs face challenges in reducing weight without compromising structural strength or obstructing gearshifting, as they often require tooth removal which can lead to stress concentration and inefficient energy transfer during gear changes.
Innovation Solution
The design incorporates spurs instead of teeth in specific areas, allowing the chain to engage with multiple teeth during gearshifting, distributing the load and reducing the risk of chain fall, while maintaining structural integrity and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If teeth are removed from the sprocket to reduce weight, then the weight of the sprocket is reduced, but the structural strength is compromised and stress concentration occurs
Solution Approach 1:
The sprocket is divided into functional zones: full teeth in the gearshifting area for strength and engagement, and spurs in non-gearshifting areas for weight reduction. This segmentation allows different parts to serve different purposes optimally.
Solution Approach 2:
Different structural characteristics are applied to different locations: full teeth with complete structural integrity are placed where chain engagement occurs (gearshifting area), while spurs with reduced material are placed where they don't engage the chain, optimizing both strength and weight locally.
2Weight of moving object
If teeth are removed from the sprocket to reduce weight, then the weight of the sprocket is reduced, but gearshifting becomes obstructed and less efficient
Solution Approach 1:
The sprocket circumference is segmented into a gearshifting area with full teeth for efficient chain engagement and non-gearshifting areas with spurs for weight reduction, ensuring gearshifting performance is maintained where needed.
Solution Approach 2:
Full teeth with complete engagement surfaces are localized to the gearshifting area to ensure proper chain interaction, while spurs are localized to non-critical areas, optimizing gearshifting efficiency without unnecessary weight.
3Device complexity
If the chain engages with a single tooth during gearshifting, then the gearshifting process is simpler, but the load is not distributed and wear increases
Solution Approach 1:
The sprocket design preliminarily positions multiple teeth (including spurs) in the gearshifting path so that the chain naturally engages with multiple teeth simultaneously during gearshifting, distributing the load before any single tooth is fully loaded.
Solution Approach 2:
The effective number of engaging teeth is changed from one to multiple by modifying the sprocket geometry, which changes the load distribution parameter and reduces stress on individual teeth, improving wear resistance.
Data Source
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AI summary
A bicycle sprocket (P13) is described, comprising a plurality of teeth arranged one after the other along a circumferential direction and a plurality of spaces each of which being arranged between two of said teeth. Said plurality of teeth includes at least one first gearshifting tooth (10) and at least one second tooth (20) arranged immediately downstream of said at least one first gearshifting tooth (10) with reference to a rotation direction (R) of the sprocket during pedaling. Said plurality of spaces includes at least one first space (15) defined between said at least one first gearshifting tooth (10) and said at least one second tooth (20) and having a predetermined circumferential extension and at least one second space (25) arranged downstream of said at least one second tooth (20) with reference to said rotation direction (R) and having a circumferential extension greater than that of said at least one first space (15). A sprocket assembly comprising the aforementioned sprocket (P13) is also described.