E-Bike Drive Unit Bulging Cover for Speed Reducer Layout
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Solution Overview
Problem
Existing drive units for electrically assisted bicycles lack efficient use of space and structural elements, leading to potential wire entanglement and reduced design freedom for components like speed reducers and torque sensors.
Innovation Solution
A drive unit design featuring a cover with a bulging portion that extends outward from the motor, supporting speed reducers and providing a wiring space, while also serving as a reinforcing structure, allowing for improved layout and integration of torque sensors and circuit substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner lid is made small and does not extend toward the pedal crank shaft to increase stiffness, then the stiffness of the inner lid is improved, but the space utilization and layout freedom are worsened
Solution Approach 1:
The patent extends the inner lid in the axial direction (another dimension) to create a bulging portion that protrudes from the motor circumference. This dimensional extension provides additional space for positioning the speed reducer's rotational axis away from the motor axis, thereby improving layout freedom without compromising the radial stiffness of the inner lid structure.
2Volume of moving object
If the speed reducer rotational axis is positioned close to the motor for compact design, then the device size is reduced, but wire entanglement and operational interference increase
Solution Approach 1:
The bulging portion of the inner lid creates additional axial space that allows the speed reducer rotational axis to be positioned at the bulging portion rather than close to the motor. This spatial separation in the axial dimension prevents wire entanglement between the motor and speed reducer while maintaining a compact overall drive unit design.
Solution Approach 2:
The bulging portion of the inner lid acts as an intermediary structure between the motor and the speed reducer. It provides a dedicated mounting location for the speed reducer that is spatially separated from the motor, thereby mediating the spatial relationship and preventing harmful wire entanglement while maintaining compact integration.
3Adaptability or versatility
If additional structural elements are added to provide wiring space and support components, then the functionality is improved, but the device complexity increases
Solution Approach 1:
The inner lid is designed with multi-functionality: it serves as the housing cover, provides structural reinforcement, creates the bulging portion for speed reducer mounting, and defines the wiring space. By making the inner lid perform multiple functions, the patent avoids adding separate structural elements, thereby reducing device complexity while improving component integration capability.
Solution Approach 2:
The patent merges the functions of the inner lid with the speed reducer support structure and wiring space definition. Instead of having separate components for these functions, they are combined into the inner lid itself, reducing the total number of parts and simplifying the overall device structure.
Data Source
AI summary
A drive unit of an electrically assisted bicycle includes a housing, a crank shaft extending through a first wall and a second wall of the housing and rotatably supported by the housing, a motor inside the housing, a cover inside and attached to the housing to cover at least a portion of the motor, and a speed reducing mechanism between the cover and the second wall inside the housing. The cover includes a bulging portion bulging outward from the motor when viewed from an axial direction of the crank shaft. The speed reducing mechanism includes a first speed reducer rotatably supported by the cover and the second wall so that a rotational axis center of the first speed reducer is located at the bulging portion when viewed from the axial direction of the crank shaft.