Bicycle Derailleur Guide Wheel with Variable Tooth Width
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Solution Overview
Problem
Conventional bicycle chain guide arrangements with constant tooth widths suffer from poor guiding properties, leading to chain slippage, vibrations, jamming, and increased wear, especially during gear changes and when encountering strong inclines due to the limited lateral support provided by inner chain links.
Innovation Solution
The guide wheel features radially projecting gear teeth with wider guide segments at the tooth gap base and along the tooth flanks, supporting both inner and outer chain links, and alternating tooth widths to improve guiding, and can include axially projecting ring segments or local projections for enhanced support and self-cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all gear teeth are embodied with essentially constant thickness matched to smaller link spacing between inner chain links, then inner chain links are properly guided, but outer chain links engage with substantial lateral clearance resulting in poor guiding properties
Solution Approach 1:
The patent applies local quality by providing different tooth widths at different locations around the guide wheel. Specifically, teeth have alternating widths: narrower teeth (matching inner chain link spacing) and wider teeth (matching outer chain link spacing). This local variation in tooth geometry allows proper engagement and guiding for both inner and outer chain links, resolving the contradiction between manufacturing simplicity and guiding reliability.
2Ease of manufacture
If guide wheels have constant tooth width, then manufacturing is simplified, but chain guiding reliability deteriorates during strong inclines and gear changing
Solution Approach 1:
The patent implements local quality by varying tooth width locally around the guide wheel circumference. Narrower teeth are positioned to engage with inner chain links while wider teeth engage with outer chain links. This localized geometric variation maintains manufacturing feasibility while significantly improving chain engagement stability during challenging riding conditions such as strong inclines and gear changes.
Solution Approach 2:
The patent applies segmentation by dividing the guide wheel teeth into distinct segments with different widths. Rather than a uniform tooth structure, the teeth are segmented into alternating narrow and wide configurations, each optimized for specific chain link types. This segmentation allows the guide wheel to handle both inner and outer chain links effectively, improving reliability without excessive manufacturing complexity.
3Device complexity
If only inner chain links provide lateral guidance, then structure is simpler, but chain stability deteriorates leading to vibrations and slippage
Solution Approach 1:
The patent resolves this contradiction by applying local quality to the tooth width configuration. Instead of a uniform guiding mechanism, the teeth have locally varied widths that provide appropriate lateral support for both inner and outer chain links. This localized differentiation in tooth geometry enables dual-chain-link guidance without increasing overall device complexity, thereby improving chain stability and preventing vibrations and slippage.
Data Source
AI summary
The invention relates to a guide wheel for a rear derailleur in a bicycle gear system for guiding a chain, including an annular wheel body with a central opening for rotatable bearing about a rotational axis of the guide wheel. The guide wheel includes a plurality of radially projecting teeth that are arranged on an outer circumferential surface of the wheel body. A tooth gap is arranged between each adjacent pair of teeth, individual teeth in the area of a root circle of the gear teeth having a predetermined tooth width matched to the chain. For improving the guiding properties, it is provided that the guide wheel has on at least some of the tooth gaps in the area near a tooth gap base and/or on at least some of the teeth at least one guide segment with a greater width than the tooth width of at least one of the adjacent teeth.