Bicycle Crank Assembly Axial Torque Transmission
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Solution Overview
Problem
Current bicycle crank assemblies face complexity in structurally integrating torque transmission and bearing structures, leading to increased design and assembly challenges.
Innovation Solution
The bicycle crank assembly incorporates a torque transmitting member that is stationary with respect to the crank axle and movable with respect to the movable member, utilizing a bearing structure and groove configuration to simplify the structure and facilitate easy assembly, while also reducing friction and air resistance through a sliding structure and biasing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the torque transmitting member and bearing structure are integrated in a complex manner, then the structural stability is improved, but the device complexity increases
Solution Approach 1:
The crank assembly is divided into distinct functional components: a crank arm, a movable member that moves axially, a torque transmitting member, and a bearing structure. Each component performs a specific function and can be independently designed and manufactured, reducing overall device complexity while maintaining structural stability through their coordinated arrangement.
Solution Approach 2:
The movable member acts as an intermediary between the crank arm and the torque transmitting member. It receives the pedaling force from the crank arm and transfers it to the torque transmitting member through axial movement, enabling torque transmission without direct complex integration between the crank arm and torque transmitting member.
2Ease of manufacture
If the torque transmitting member is stationary with respect to the crank axle, then the ease of manufacture is improved, but the ease of operation deteriorates
Solution Approach 1:
The torque transmitting member is designed to be stationary with respect to the crank axle in the axial direction, simplifying its manufacturing and assembly. However, it is configured to rotate relative to the crank axle, enabling it to transmit torque effectively. This combination of axial stationarity and rotational mobility resolves the contradiction between ease of manufacture and ease of operation.
3Device complexity
If the bearing structure is disposed at the same location as the torque transmitting member, then the device complexity is reduced, but the manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The bearing structure is disposed at a location different from the torque transmitting member in the axial direction, separating their functions along the axial dimension. This spatial separation allows each component to be manufactured and positioned independently with standard tolerances, avoiding the need for high-precision co-location while maintaining device functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration simplifies the crank assembly structure, enhances pedaling torque transmission efficiency, and reduces assembly complexity, while minimizing friction and air resistance, resulting in a more compact and efficient design.
Implementation Method 1
The bearing structure is disposed between the movable member and the crank axle to slidably support the movable member in the axial direction
Data Source
AI summary
A bicycle crank assembly comprises a sprocket, a crank axle, a movable member, a torque transmitting member, and a bearing structure. The sprocket has a rotational center axis. The crank axle extends along the rotational center axis. The crank axle includes an internal space. The movable member is movably provided in the internal space to move the sprocket in an axial direction of the rotational center axis. The torque transmitting member is to transmit a pedaling torque from the crank axle to the sprocket. The bearing structure is disposed between the movable member and the crank axle to slidably support the movable member in the axial direction. The bearing structure is disposed at a location different from a location of the torque transmitting member in the axial direction.