Bicycle Drive Unit Housing Force Transmission
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Solution Overview
Problem
Bicycle drive units face challenges in maintaining strength while minimizing size and weight, and in efficiently transmitting upward forces without increasing wear or impact on components.
Innovation Solution
The bicycle drive unit design includes a housing with a transmitting surface positioned below the crank rotational axis, allowing for efficient force transmission to a base member, with optional intermediate members to reduce wear and impact, and made from resin materials to save weight, while securing elements like fasteners and side surfaces for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the housing size is reduced to minimize overall drive unit size, then the compactness is improved, but the strength and ability to transmit upward force deteriorates
Solution Approach 1:
The transmitting surface is positioned below the crank rotational axis, utilizing the vertical space dimension that would otherwise be unused. This allows the housing to transmit upward forces effectively without increasing the horizontal footprint or overall volume of the drive unit.
Solution Approach 2:
The housing is made from resin material, which provides a favorable strength-to-weight ratio. This allows the housing to maintain adequate strength for force transmission while keeping the overall volume and weight minimized.
2Volume of moving object
If the transmitting surface is positioned below the crank rotational axis to utilize space, then the compactness is improved, but the risk of impact and wear increases
Solution Approach 1:
A fastener is introduced as an intermediary element between the transmitting surface and the base member. This fastener absorbs and distributes the impact forces, protecting the transmitting surface from direct impact and reducing wear while maintaining the compact configuration.
Solution Approach 2:
The fastener serves as a cushioning element that is pre-installed to absorb upcoming impact forces before they reach the transmitting surface. This beforehand protection reduces wear on the transmitting surface while maintaining the space-efficient design.
3Weight of moving object
If resin material is used for the housing to save weight, then the weight is reduced, but the durability and impact resistance may deteriorate
Solution Approach 1:
The use of resin material provides a favorable strength-to-weight ratio. The resin housing achieves adequate impact resistance for the application while significantly reducing weight compared to metal alternatives.
Solution Approach 2:
The fastener acts as a protective intermediary that shields the resin housing from direct high-impact forces. This allows the use of lighter resin material while the fastener compensates for any不足 in impact resistance.
Data Source
AI summary
A bicycle drive unit comprises a housing configured to be mounted to a first base member. The housing includes a first wall at least partly defining an internal space to at least partly accommodate a bicycle crank having a crank rotational axis. The first wall includes a first transmitting surface disposed to at least partly face upward in a bicycle upright state where the crank rotational axis horizontally extends and the housing is mounted on the first base member. The first transmitting surface is configured to face a first receiving surface of the first base member to transmit an upward force from the housing to the first base member. The first transmitting surface being at least partly disposed below the crank rotational axis in the bicycle upright state.