Floating Sprocket Bicycle Drive Train Shifting
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Solution Overview
Problem
Bicycle drive trains face challenges in smooth shifting operations, particularly when sprockets with axially displaceable teeth are used, leading to complex structures and potential chain sag issues.
Innovation Solution
The introduction of a floating sprocket assembly with axially displaceable teeth and an actuator, such as an electric motor, to simplify the sprocket structure, improve shifting smoothness, and reduce chain sag through a chain tensioner that moves in tandem with the floating sprocket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If axially displaceable teeth are used on the sprocket to improve shifting performance, then shifting smoothness is improved, but the structure becomes more complex
Solution Approach 1:
The sprocket is divided into two independent parts: a fixed sprocket and a floating sprocket with axially displaceable teeth. The floating sprocket can move independently along the chain to absorb axial movements during shifting, while the fixed sprocket remains stationary. This segmentation allows the shifting smoothness function to be isolated to the floating sprocket, preventing the entire drive train structure from becoming complex.
Solution Approach 2:
The floating sprocket acts as an intermediary element between the fixed sprocket and the chain. It mediates the interaction by absorbing axial movements through its ability to move along the chain, thereby smoothing the shifting operation without requiring complex mechanisms in the fixed sprocket or chain itself.
2Ease of operation
If a floating sprocket with axially displaceable teeth is introduced to smooth shifting, then shifting performance is improved, but the device complexity increases
Solution Approach 1:
The drive train is segmented into a fixed sprocket assembly and a separate floating sprocket assembly. The floating sprocket is positioned between the fixed sprocket and the chain, creating a modular structure where each component has a specific function. This segmentation prevents the need for complex integration mechanisms while achieving smooth shifting.
3Reliability
If the chain tensioner is made movable to follow floating sprocket movement, then chain sag is reduced, but the structure becomes more complex
Solution Approach 1:
The chain tensioner is designed with movable elements that can dynamically adjust their position to follow the movement of the floating sprocket. This dynamic adjustment allows the tensioner to maintain optimal chain tension throughout the shifting range, preventing chain sag without requiring a completely rigid or fixed structure.
Data Source
AI summary
A bicycle drive train comprises a sprocket assembly and a floating sprocket. The sprocket assembly comprises a first rotational center axis, a first sprocket, and a second sprocket. The first sprocket includes at least one first sprocket tooth and at least one first axially displaceable tooth with respect to the first rotational center axis. The second sprocket includes at least one second sprocket tooth. The at least one first axially displaceable tooth is displaceable relative to the at least one first sprocket tooth toward the at least one second sprocket tooth. The floating sprocket comprises a second rotational center axis and an axially sliding surface. The axially sliding surface is to support the floating sprocket movably relative to the sprocket assembly in an axial direction with respect to the second rotational center axis.