Asymmetric Chain Ring Teeth for Secure Chain Engagement
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Solution Overview
Problem
Conventional chain rings with uniform teeth can lead to gaps that increase the risk of chain disengagement and may result in increased weight, entanglement of debris, and damage due to larger teeth sizes, which are undesirable for vehicle performance and safety.
Innovation Solution
A chain ring design featuring teeth with identical thickness at their thickest point, with alternating rectangular and non-rectangular cross-sectional shapes to fit within inner and outer links of a drive chain, applying lateral pressure in specific directions and offsetting top surfaces asymmetrically to improve interfitting and reduce entanglement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If teeth of larger size are used to reduce gaps and improve chain engagement, then chain disengagement risk is reduced, but weight of the chain ring increases
Solution Approach 1:
The patent applies different tooth configurations to different subsets of teeth around the chain ring. First subset teeth have a first cross-sectional shape optimized for engaging inner links, while second subset teeth have a second cross-sectional shape optimized for engaging outer links. This local differentiation allows each tooth to be precisely sized for its specific engagement task, reducing overall weight while maintaining reliable chain engagement without requiring all teeth to be uniformly large.
2Reliability
If teeth of larger size are used to reduce gaps and improve chain engagement, then chain disengagement risk is reduced, but risk of tooth catching on chain portions increases
Solution Approach 1:
Different subsets of teeth have different cross-sectional shapes tailored to their specific engagement requirements. This local optimization ensures that each tooth's size and shape are precisely matched to the chain link it engages, preventing excessive size that would cause catching while maintaining sufficient engagement reliability.
3Reliability
If teeth of larger size are used to reduce gaps and improve chain engagement, then chain disengagement risk is reduced, but likelihood of debris entanglement increases
Solution Approach 1:
The patent employs different cross-sectional shapes for different tooth subsets, allowing precise optimization of each tooth's dimensions. This prevents unnecessary material accumulation between teeth that would occur with uniformly large teeth, thereby reducing debris entanglement while maintaining reliable chain engagement through locally optimized tooth geometries.
4Ease of manufacture
If uniform teeth are used in chain ring, then manufacturing is simplified, but gaps between tooth and chain increase
Solution Approach 1:
The patent differentiates teeth into subsets with different cross-sectional shapes, where first subset teeth are optimized for inner link engagement and second subset teeth for outer link engagement. This local differentiation eliminates gaps between teeth and chain links by tailoring each tooth's geometry to its specific engagement target, while the systematic subset approach keeps manufacturing complexity manageable.
Solution Approach 2:
The chain ring teeth are segmented into distinct subsets with different configurations. This segmentation allows each subset to be independently optimized for its specific function (engaging inner vs. outer links), resolving the gap issue without requiring complete redesign of all teeth, thus balancing manufacturing feasibility with engagement reliability.
5Reliability
If alternating narrow and wide teeth are used to match chain link widths, then chain engagement is improved, but weight of the chain ring increases
Solution Approach 1:
The patent applies different cross-sectional shapes to different tooth subsets rather than alternating narrow and wide teeth throughout. This allows precise local optimization where each tooth subset is sized appropriately for its specific engagement task, avoiding the weight penalty of uniformly larger alternating teeth while maintaining reliable engagement with both inner and outer links.
Data Source
AI summary
A drive system for a vehicle includes a chain ring and a drive chain. The chain ring has a plurality of teeth serially arranged and joined to one another. A first subset of teeth has a first outer face that applies a lateral pressure to a link of a drive chain in a first direction. A second subset of teeth has a second outer face that applies a lateral pressure to another link of a drive chain in a second direction. The teeth all have substantially the same width. The top surfaces of the teeth are offset from the centerline of the drive chain. The centerlines of the top surfaces of the teeth are arranged asymmetrically on one side of the centerline of the drive chain.