Crankshaft Positioning for Human-Powered Vehicle Components
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Solution Overview
Problem
Existing human-powered vehicle components, such as bicycle assist units, lack a specific structure to easily determine the relative position of the crank arm and sprocket, leading to inefficiencies in operation.
Innovation Solution
A human-powered vehicle component featuring a crankshaft with coupling portions that include positioning elements, such as recesses and projections, and marks, to predetermine the relative phase positions of the crank arm and sprocket, ensuring proper alignment and preventing relative rotation, thereby simplifying the coupling process and enhancing operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If no specific positioning structure is provided, then the coupling process becomes complex and time-consuming, but adding positioning structures increases device complexity
Solution Approach 1:
The positioning portions (protrusions and recesses) are pre-formed on the crank arm and crankshaft during manufacturing. This preliminary action ensures that when the components are assembled, the relative positions are automatically determined without requiring additional adjustment or complex coupling procedures, thus improving ease of operation while maintaining simple structure.
Solution Approach 2:
The positioning portions are designed to automatically align and secure the crank arm and crankshaft in the correct relative positions during assembly. The protrusions and recesses engage with each other self-aligning, eliminating the need for external positioning tools or complex alignment procedures, thereby improving ease of coupling without increasing device complexity.
2Measurement precision
If positioning portions are added to determine relative phase positions, then the relative position of crank arm and sprocket is precisely determined, but the device structure becomes more complex
Solution Approach 1:
The positioning portions utilize asymmetric geometric features (protrusions and recesses with specific shapes and orientations) that naturally guide the crank arm and crankshaft into the correct relative phase position. This asymmetric design provides precise positioning through the inherent geometry of the components themselves, achieving measurement precision without adding complex positioning mechanisms.
3Reliability
If multiple coupling portions are provided on the crankshaft, then the crank arm and sprocket can be securely coupled, but the crankshaft structure becomes more complex
Solution Approach 1:
The coupling function is segmented into distinct positioning portions located at different axial positions on the crankshaft. Each positioning portion (first positioning portion for the crank arm, second positioning portion for the sprocket) handles a specific coupling task independently. This segmentation provides reliable coupling for each component while keeping the overall crankshaft structure simple and modular.
Data Source
AI summary
A human-powered vehicle component includes a crankshaft including a rotational center axis and a first coupling portion that allows a crank arm to be coupled and a transmission provided on the crankshaft and including a second coupling portion that allows a sprocket to be coupled. The first coupling portion includes a first positioning portion that determines a first predetermined relative phase position of the crank arm with respect to the crankshaft in a circumferential direction about the rotational center axis. The second coupling portion includes a second positioning portion that determines a second predetermined relative phase position of the sprocket with respect to the crankshaft in the circumferential direction about the rotational center axis.