Bicycle Drive Unit Coaxial Motor Bottom Bracket Integration
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Solution Overview
Problem
Conventional bicycle drive units with motors often fail to provide a sufficient assisting force, as the motor output is not effectively combined with pedaling force to enhance riding efficiency, and the design can be cumbersome for installation and maintenance.
Innovation Solution
A bicycle drive unit featuring a motor configuration with a rotor and stator arrangement that includes a first and second casing, where the rotor has magnets attached to the casing and the stator is non-rotatably coupled to the bottom bracket, allowing for a larger assisting force and easier installation by being threadedly coupled to the bottom bracket shell, with a sealed space to protect components and a compact coaxial design for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a motor is integrated into the bicycle bottom bracket to provide assisting force, then the riding efficiency is improved, but the device complexity and installation difficulty increase
Solution Approach 1:
The motor is merged with the bottom bracket assembly, integrating the drive unit directly into the bicycle's existing bottom bracket interface. This consolidation reduces the number of separate components and simplifies installation while maintaining the assisting function
Solution Approach 2:
The bottom bracket assembly serves dual functions: traditional crank support and motor housing. The same structural elements that support the crank also house the motor components, allowing one assembly to perform multiple functions and reduce overall system complexity
2Productivity
If a motor is integrated into the bicycle bottom bracket to provide assisting force, then the riding efficiency is improved, but the ease of operation and maintenance deteriorate
Solution Approach 1:
The drive unit is segmented into modular components that can be independently accessed and serviced. The motor housing is designed as a separate assembly that can be removed from the bottom bracket shell, allowing maintenance without disassembling the entire bottom bracket structure
Solution Approach 2:
A removable motor housing acts as an intermediary between the motor components and the bottom bracket shell. This housing can be detached to provide access to internal components for maintenance while maintaining the integrated appearance when assembled
3Reliability
If magnets are fixedly attached to the rotor casing with adhesive, then the motor reliability is improved, but the ease of repair deteriorates
Solution Approach 1:
The magnetic attachment system transitions from a static permanent bond to a dynamic, reversible connection. Magnets provide strong holding force during operation (reliability) but can be easily separated with simple tools for repair (ease of repair), adapting the connection strength to the operational context
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
The solution enhances the assisting power by effectively combining pedaling force with motor output, providing a more efficient and compact bicycle drive unit that is easier to install and maintain, with improved torque generation and reduced weight.
Implementation Method 1
The first motor includes a first rotor having a first magnet disposed on the first casing, and a first stator non-rotatably coupled to the first bottom bracket. The first magnet and the first stator radially face with each other with respect to the rotational axis of the crank axle.
Data Source
AI summary
In accordance with a first aspect, a bicycle drive unit includes a first bottom bracket, a crank axle, and a first motor. The first bottom bracket is configured to be coupled to a first axial end of a bottom bracket shell of a bicycle. The crank axle is rotatably supported by the first bottom bracket with respect to a rotational axis. The crank axle has a first end portion and a second end portion. The first motor includes a first casing non-rotatably coupled to the crank axle, a second casing non-rotatably coupled to the bottom bracket shell, a first rotor having a first magnet disposed on the first casing, and a first stator non-rotatably coupled to the first bottom bracket. The first magnet and the first stator radially face with each other with respect to the rotational axis of the crank axle.