Electric Bicycle Driving Unit Bearing Positioning
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Solution Overview
Problem
Existing electric assist bicycle driving units face challenges in space utilization due to the requirement for bearings, which can limit the placement of other components and efficiency in using available space.
Innovation Solution
The driving unit design includes a crankshaft, motor, and transmission shaft with strategically positioned bearings and gears, allowing for effective use of space by placing the first bearing adjacent to the output gear opposite the rotor, enabling the use of space between the bearing and rotor for additional components and optimizing the transmission of driving forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bearings are provided in certain positions to support the motor output shaft, then the motor can be properly supported and rotated, but space for other components near the bearings is reduced
Solution Approach 1:
The patent positions the first bearing in the axial direction at the same location as the second transmission gear, and the second bearing in the axial direction at the same location as the first transmission gear. This dimensional arrangement allows bearings to be placed in previously unavailable spaces along the axial direction, supporting the motor output shaft while maintaining space for other components in the radial direction.
2Area of stationary object
If the first bearing is positioned adjacent to the output gear opposite the rotor, then space between the bearing and rotor can be used effectively, but the bearing support structure becomes more complex
Solution Approach 1:
The bearing support structure serves multiple functions: it supports the motor output shaft for rotation, provides a foundation for mounting transmission gears, and enables effective space utilization between the bearing and rotor. By making the bearing structure multi-functional, the patent achieves space efficiency without proportionally increasing structural complexity.
Data Source
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AI summary
A driving unit for use in an electric assist bicycle is provided where space can be used effectively. The driving unit 50 includes a motor 60. The motor 60 includes a rotor 72, an output shaft 74 and an output gear 76. The output shaft 74 rotates together with the rotor 72 and extends parallel to the central axis L1 of the crankshaft 54. The output gear 76 is located on the output shaft 74. A plurality of bearings 78L and 78R support the output shaft 74, the output shaft being rotatable around the central axis L2 of the output shaft 74. The plurality of bearings 78L and 78R include a first bearing 78R located at the same position as the second transmission gear 86 as measured in an axial direction of the crankshaft 54.