Bicycle Chainwheel Tooth Profile for Wear-Resistant Chain Release
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Solution Overview
Problem
Individual chain wheels for bicycle front crank arrangements experience material abrasion in load flanks due to the drive chain rollers, leading to edge formation that impedes chain slipping and potential jumping, especially under heavy load conditions.
Innovation Solution
The design incorporates teeth with a first and second group, where the first group's teeth have profiles with openings for inner link plates to engage, ensuring unobstructed disengagement even under wear, and features shallow load flank angles to reduce contact forces and wear, along with projections to prevent jumping, and recesses to prevent edge formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If teeth have steep load flanks to prevent chain jumping, then chain security is improved, but material abrasion increases leading to edge formation that blocks chain slipping
Solution Approach 1:
The patent changes the geometric parameters of the tooth profiles, specifically using shallower load flank angles instead of steep angles. This parameter modification reduces the contact pressure and abrasion between the chain rollers and tooth flanks, preventing edge formation while maintaining chain security through alternative profile designs.
Solution Approach 2:
The patent introduces additional geometric dimensions and features to the tooth profiles, including specific curvature radii, profile shapes, and dimensional relationships between different tooth elements. These dimensional changes allow the teeth to maintain security function while reducing harmful abrasion through optimized geometry.
2Reliability
If teeth have steep load flanks to prevent chain jumping, then chain security is improved, but chain slipping becomes impeded due to edge formation
Solution Approach 1:
The patent modifies the geometric parameters of the tooth load flanks to shallower angles, which reduces the digging-in effect of chain rollers and prevents edge formation. This maintains smooth chain slipping while alternative profile geometries ensure chain security without the harmful steep angle characteristics.
3Device complexity
If individual chain wheel is used to reduce components, then device complexity is reduced, but wear-induced blocking occurs more readily due to continuous loading
Solution Approach 1:
The patent optimizes the geometric parameters of the tooth profiles with shallower load flanks and specific dimensional relationships. This reduces the intensity of wear during continuous operation of the individual chain wheel, preventing edge formation and maintaining reliable chain engagement throughout the service life.
Solution Approach 2:
The patent introduces additional geometric dimensions and profile features to the teeth, creating a more complex tooth geometry that distributes loading more favorably and reduces wear intensity, thereby improving wear resistance while maintaining the simple single-chain-wheel configuration.
Data Source
AI summary
An individual chain wheel for a bicycle front crank arrangement for engaging in a drive chain includes a plurality of teeth formed on a circumference of the chain wheel and having a first and a second group of teeth. The teeth of the second group of teeth are arranged in an alternating manner between the teeth of the first group of teeth. Each tooth has a load flank via which force is transmitted between an adjacent roller of the drive chain and the respective tooth. Each tooth of the first group may also have at least one profile with an opening in the vicinity of the flank, in which a portion of an inner link plate of the drive chain, which portion protrudes beyond the roller, engages.