Bicycle Sprocket Structure With Shared Shift Facilitation Projection
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Solution Overview
Problem
Existing bicycle sprockets require separate projections for upshifting and downshifting operations, which complicates the structure and can lead to inefficient chain engagement and derailing during shifting processes.
Innovation Solution
A bicycle sprocket design featuring a common shifting facilitation projection, upshifting facilitation teeth, and downshifting facilitation teeth arranged in a specific configuration to facilitate both upshifting and downshifting operations, with chamfered teeth for smooth derailing and engagement, reducing the area required for these features and improving chain-holding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate projections are used for upshifting and downshifting operations, then the shifting facilitation function is provided, but the structure of the bicycle sprocket becomes complicated
Solution Approach 1:
The patent combines separate upshifting facilitation projection and downshifting facilitation projection into a single integrated shifting facilitation projection. This projection has different functional surfaces: an inclined surface for upshifting operation and another inclined surface for downshifting operation. By merging two separate components into one, the structure is simplified while maintaining both shifting facilitation functions.
Solution Approach 2:
The shifting facilitation projection serves multiple functions: it facilitates upshifting operations through its first inclined surface, facilitates downshifting operations through its second inclined surface, and can also serve as a chain-retaining feature. This multi-functional design eliminates the need for separate dedicated projections for each shifting direction, reducing overall structural complexity.
2Ease of operation
If separate projections for upshifting and downshifting are provided, then shifting facilitation is achieved, but the area required for these features increases
Solution Approach 1:
By consolidating upshifting and downshifting facilitation features into a single projection rather than using two separate projections, the total area occupied by shifting features is reduced. The integrated projection occupies less radial and circumferential space compared to two separate projections that would need to be distributed around the sprocket.
3Device complexity
If a common shifting facilitation projection is used for both upshifting and downshifting, then the structure is simplified and area is reduced, but chain engagement and derailing efficiency must be maintained
Solution Approach 1:
The shifting facilitation projection has different local qualities on different surfaces: the first inclined surface is optimized for upshifting engagement with specific geometry and orientation, while the second inclined surface is optimized for downshifting engagement. Each surface has tailored characteristics that ensure reliable chain interaction for its specific function, maintaining high reliability despite the integrated design.
Solution Approach 2:
The single shifting facilitation projection is segmented into distinct functional zones: an upshifting facilitation area with specific geometry for receiving the chain during upshifting, and a downshifting facilitation area with different geometry for engaging the chain during downshifting. This segmentation of function within a unified structure allows each operation to be optimized independently while maintaining overall simplicity.
Data Source
AI summary
A bicycle sprocket having a rotational center axis, the bicycle sprocket comprises a sprocket body, a chain engagement structure, and a shifting facilitation projection. The chain engagement structure is arranged on a radially outer periphery of the sprocket body. The chain engagement structure includes a plurality of chain-driving teeth to engage with a bicycle chain to transmit a rotational driving force to the bicycle chain. The shifting facilitation projection is to facilitate an upshifting operation of the bicycle chain and to facilitate a downshifting operation of the bicycle chain.