Centrally Mounted Bicycle Drive with Radial Planetary-Bevel Structure
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Solution Overview
Problem
Conventional centrally mounted driving mechanisms for power-assisted bicycles have a large axial length due to sequentially arranged and positioned connecting members, limiting the space for mounting larger capacity batteries.
Innovation Solution
A centrally mounted driving mechanism with a reduced axial length, featuring a planetary gear mechanism connected via a clutch to a bevel gear support, and a compact structure with fewer positioning parts, allowing for a larger battery capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adjacent connecting members are sequentially arranged and respectively positioned in the axial direction of the motor, then the positioning structures can be properly provided, but the axial length of the driving mechanism becomes large
Solution Approach 1:
The patent changes the arrangement dimension from axial direction to radial direction. The planetary gear output bracket and bevel gear support are positioned side by side in the radial direction, with the planetary gear output bracket extending radially outward from the motor output shaft, and the bevel gear support positioned adjacent to it, thereby reducing the axial length while maintaining proper positioning structures.
Solution Approach 2:
The patent employs a nested arrangement where the planetary gear output bracket is positioned inside the bevel gear support in the axial direction, with the planetary gear output bracket extending radially outward from the motor output shaft and the bevel gear support surrounding it. This nesting configuration allows both components to be properly positioned while minimizing the overall axial length.
2Length of moving object
If the axial length of the driving mechanism is reduced, then the available mounting space on the seat tube is increased, but the positioning structures may become insufficient
Solution Approach 1:
The patent compensates for reduced axial length by utilizing the radial dimension for positioning. The planetary gear output bracket is positioned with its outer end against the inner wall of the bevel gear support, and the bevel gear support is positioned with its inner end against the outer end of the planetary gear output bracket. This radial positioning arrangement provides stable positioning structures while maintaining a compact axial length.
3Manufacturing precision
If a double row bearing positioning structure is employed for the planetary gear output bracket, then the positioning precision is improved, but the axial length increases
Solution Approach 1:
The patent extracts the positioning function from the axial direction and relocates it to the radial direction. Instead of using a double row bearing structure in the axial direction, the positioning is achieved through the radial arrangement where the planetary gear output bracket is positioned against the bevel gear support and the bevel gear support is positioned against the planetary gear output bracket. This extraction of the positioning function from the axial dimension reduces the axial length while maintaining positioning precision.
Data Source
AI summary
A centrally-mounted drive mechanism used for a power-assisted bicycle, and a power-assisted bicycle are provided. The centrally-mounted drive mechanism includes an outer casing, an electric motor, a planetary gear mechanism in a transmission connection with an output shaft of the electric motor, a bevel gear driving end, and a bevel gear driven end that meshes with the bevel gear driving end, said bevel gear driven end being connected to a crankset. The planetary gear mechanism includes a planetary gear and a planetary gear output bracket, and a bevel gear support base that is sleeved on the outer part of the planetary gear output bracket. A clutch is disposed between the planetary gear output bracket and the bevel gear support base, and a transmission connection is formed via the clutch between the planetary gear output bracket and the bevel gear support base.