Alternating-Tooth Bicycle Chainring for Rough-Terrain Chain Retention
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Solution Overview
Problem
Managing chain engagement and preventing frame damage in bicycles, especially when riding over rough terrain, is challenging due to severe chain tension changes and potential contact between the chainring and the chain stay, leading to frame and chainring deformation.
Innovation Solution
A solitary chainring design with alternating groups of teeth, featuring protrusions and recesses to guide the chain effectively, and a crankset configuration that includes a bicycle crank arm attached to the chainring, ensuring reliable chain management and preventing frame deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional chainring design is used, then the structure is simple, but the chain engagement is unreliable under severe tension changes and rough terrain conditions
Solution Approach 1:
The chainring teeth are segmented into two distinct groups: first group teeth with protrusions on the outboard side and second group teeth with recesses on the inboard side. This segmentation allows different tooth configurations to handle different phases of chain engagement, improving reliability under varying tension conditions while maintaining a relatively simple overall structure.
Solution Approach 2:
Different regions of the chainring teeth are given different local qualities through the alternating pattern of protrusions and recesses. The protrusions on first group teeth provide enhanced engagement on the outboard side, while the recesses on second group teeth create corresponding engagement features on the inboard side, allowing the chainring to adapt to severe tension changes and rough terrain conditions.
2Ease of operation
If the chainring teeth are designed with protrusions and recesses to guide the chain, then chain management is improved, but the manufacturing complexity increases
Solution Approach 1:
The tooth configuration is segmented into two alternating groups with distinct features. First group teeth have protrusions on the outboard side while second group teeth have recesses on the inboard side. This segmentation simplifies the manufacturing process by allowing standardized production of each tooth type, which can then be alternately arranged to achieve the desired chain guidance function.
Solution Approach 2:
The tooth design employs asymmetry by placing protrusions on the outboard side of first group teeth and recesses on the inboard side of second group teeth. This asymmetric configuration optimizes chain guidance in the direction of chain movement while maintaining manufacturing simplicity through repetitive alternating patterns.
3Strength
If the chainring and crankset are rigid to prevent deformation, then structural strength is improved, but the frame may still contact the chain stay under high loads
Solution Approach 1:
The alternating pattern of protrusions and recesses in the tooth configuration creates a more distributed load path through the chainring and crankset. This segmentation of load paths reduces stress concentrations that could lead to elastic deformation and contact between the chainring and chain stay under high loads, thereby preventing frame damage while maintaining overall structural strength.
Data Source
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AI summary
A chainring (50) of a bicycle front crankset for engaging a drive chain (10), including a plurality of teeth (52) formed about a periphery of the chainring (50), the plurality of teeth (52) consisting of an even number. The plurality of teeth includes a first group of teeth (58) and a second group of teeth (60) arranged alternatingly between the first group of teeth (58). The first group of teeth (58) and the second group of teeth (60) are equal in number. Each of the first and second group of teeth include an outboard side (54) and an inboard side (56) opposite the outboard side (54) and each tooth of the first group of teeth (58) includes at least a first protrusion on the outboard side (54) thereof and each tooth of the second group of teeth (60) are free of the first protrusions on the outboard side (54) and the inboard side (56).