Multi-Sprocket Chain Shift Geometry for High-Load Gear Changes
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Solution Overview
Problem
Conventional multi-sprocket arrangements for bicycle rear wheel hubs face challenges in precise chain changeover under high operating loads, leading to vibrations, wear, and potential damage due to large transmission ratio steps causing deviations from tangential conditions, resulting in inefficient gearshift and increased risk of chain slippage or breakage.
Innovation Solution
A multi-sprocket arrangement with sprockets of different diameters featuring corrective features such as riding-up teeth and projections, and optimized gearshift channels, which ensure precise chain link plate orientation and engagement, reducing the deviation from tangential conditions and enhancing wear resistance and vibration reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional multi-sprocket arrangements are used with large transmission ratio steps, then a wide gear range is achieved, but deviations from tangential conditions occur causing vibrations and wear
Solution Approach 1:
The sprocket features non-uniform tooth geometry where specific teeth have modified dimensions and positions. The first tooth has a reduced tooth height and modified profile compared to other teeth, creating localized quality changes that enable precise chain engagement during gearshift while maintaining standard teeth elsewhere for normal operation
Solution Approach 2:
The first tooth is pre-positioned and pre-shaped to facilitate the chain's transition from one sprocket to another. This preliminary configuration of the tooth geometry anticipates the chain's path during gearshift, ensuring proper engagement before the chain actually contacts the tooth, thereby preventing vibrations and wear
2Ease of manufacture
If standard sprocket teeth are used, then manufacturing is simple, but precise chain link plate orientation during gearshift cannot be achieved
Solution Approach 1:
Only specific critical teeth (the first tooth and subsequent teeth in the sequence) require modified geometry to achieve proper chain orientation. The majority of teeth on the sprocket can be manufactured using standard processes, thereby maintaining ease of manufacture while achieving precision where needed
Solution Approach 2:
The first tooth has an asymmetric profile with reduced height and modified dimensions compared to other teeth. This asymmetric design is intentionally applied only to the critical gearshift tooth, allowing precise chain link plate orientation during transition while keeping the rest of the sprocket symmetric and easy to manufacture
3Volume of moving object
If large transmission ratio steps are used between adjacent sprockets, then a compact design is achieved, but chain slippage and breakage risk increase
Solution Approach 1:
The first tooth with its modified geometry is positioned in advance to guide the chain through the large transmission ratio step. This preliminary configuration ensures the chain maintains proper orientation and engagement throughout the transition, preventing slippage and breakage even in compact arrangements with large gear ratio steps
Data Source
AI summary
A drive arrangement for a bicycle has a multi-sprocket arrangement for a rear wheel hub of the bicycle. The multi-sprocket arrangement comprises a plurality of sprockets with different diameters, wherein the sprockets each have a plurality of teeth which are separated by tooth spaces, and which can be placed in engagement with a drive chain with wide and narrow chain links which follow one another alternatively in succession. On a circumference of at least a starting sprocket of the plurality of sprockets, at least one sequence of teeth is provided at a location where a changeover of the drive chain from the starting sprocket to a selected sprocket occurs. The sequence of teeth comprises a first tooth having a tooth base that is tangent to a root circle of the starting sprocket or lies radially outside of the root circle, and at least one additional tooth which follows the first tooth lies with its tooth base radially within the root circle of the starting sprocket.