Bicycle Sprocket with Alternating Teeth for Chain Wear Reduction
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Solution Overview
Problem
Current bicycle sprockets face challenges in efficiently engaging with bicycle chains due to mismatched tooth widths and orientations, leading to excessive contact and wear, which affects shifting performance and durability.
Innovation Solution
The design features a bicycle sprocket with alternating first and second teeth of varying axial widths and orientations, including leading and trailing recesses, to optimize chain engagement and reduce wear by matching tooth dimensions with inner and outer link spaces of the chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sprocket teeth with uniform width and orientation are used, then manufacturing is simple, but chain engagement is inefficient leading to excessive wear
Solution Approach 1:
The sprocket employs two distinct tooth types (first teeth and second teeth) with different axial widths and orientations. First teeth have a first axial width and non-parallel tooth tops, while second teeth have a second axial width and parallel tooth tops. This local differentiation optimizes chain engagement at specific regions, improving reliability without requiring complete redesign of all teeth.
Solution Approach 2:
The sprocket teeth are segmented into alternating first teeth and second teeth around the circumference. This segmentation allows different portions of the chain engagement path to be optimized independently, with first teeth engaging inner link plates and second teeth engaging outer link plates, thereby resolving the contradiction between engagement efficiency and manufacturing simplicity.
2Reliability
If sprocket teeth are designed with varying axial widths, then chain wear is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the axial width parameter of sprocket teeth by defining two distinct types: first teeth with a first axial width and second teeth with a second axial width. This parameter variation is designed to match the different link plate dimensions in the chain, reducing wear through proper fit. The leading and trailing recesses further refine the engagement geometry, ensuring precise contact points while maintaining manufacturability through clear geometric definitions.
3Reliability
If tooth tops are oriented non-parallel to sprocket plane, then chain contact is optimized, but excessive contact occurs without recesses
Solution Approach 1:
Leading recesses and trailing recesses are introduced at specific locations on the first teeth to locally modify contact characteristics. These recesses prevent excessive contact between the tooth tops and inner link plates while maintaining optimized chain retention through the non-parallel tooth top orientation. The recesses are positioned to engage with specific chain link plates during rotation, creating controlled contact zones.
4Productivity
If alternating first and second teeth are used, then shifting performance improves, but device complexity increases
Solution Approach 1:
The sprocket circumference is segmented into alternating first teeth and second teeth, where first teeth have non-parallel tops for engaging inner link plates and second teeth have parallel tops for engaging outer link plates. This segmentation enables smooth chain shifting by providing appropriately shaped contact surfaces for different chain positions, improving productivity through enhanced shifting performance while maintaining a relatively simple alternating pattern.
Data Source
AI summary
A bicycle sprocket comprises a sprocket body and a chain engagement structure. The chain engagement structure includes a plurality of sprocket teeth. The plurality of sprocket teeth include at least one first tooth and at least one second tooth. The at least one first tooth has a first tooth top extending non-parallel to a sprocket-plane perpendicular to a rotational center axis when viewed from a radial direction of the bicycle sprocket. The at least one first tooth has a first axial chain-engagement width that is larger than an inner link space defined between a pair of inner link plates of a bicycle chain and smaller than an outer link space defined between a pair of outer link plates of the bicycle chain. The at least one second tooth has a second axial chain-engagement width that is smaller than the inner link space.