E-Bike Motor Rotor Structure for Compact Axial Gear Engagement
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Solution Overview
Problem
Existing motor units for electric bicycles face challenges in minimizing their size in the axial direction due to the protruding parts of the rotary shaft, which can increase the overall size of the motor drive unit.
Innovation Solution
The motor unit design incorporates a rotor with a first and second portion, where the second portion has a larger inner diameter, allowing the rotary shaft's projection to protrude while keeping the rotary shaft's length constant, thus preventing an increase in the motor unit's size in the axial direction, and includes a gear mechanism with teeth on the projection for engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the rotary shaft has a protruding part with toothing part formed on it, then the gear mechanism can be engaged, but the rotary shaft length increases and the motor drive unit size increases in the axial direction
Solution Approach 1:
The invention moves the toothing part from the rotary shaft to the rotor's end surface, changing the spatial dimension where the gear engagement occurs. This allows the gear mechanism to engage with the rotor rather than requiring the rotary shaft to protrude, thereby resolving the contradiction between gear engagement capability and rotary shaft length.
Solution Approach 2:
The rotor is given multiple functions: it not only generates rotational motion through electromagnetic interaction but also provides the toothing part for gear engagement. By making the rotor multi-functional, the invention eliminates the need for a separate protruding structure on the rotary shaft, thus reducing axial length while maintaining gear engagement capability.
2Reliability
If the protruding part length is increased to ensure proper gear engagement, then the gear mechanism engagement is improved, but the motor drive unit size increases in the axial direction
Solution Approach 1:
The toothing part is relocated from the axial dimension (protruding from rotary shaft) to the radial dimension (formed on rotor end surface), allowing gear engagement without increasing axial protrusion length. This dimensional change ensures reliable gear engagement while maintaining compact motor drive unit volume.
Solution Approach 2:
The toothing part is formed locally on the end surface of the rotor where it is most effective for gear engagement, rather than requiring extended protrusion from the rotary shaft. This localized approach ensures proper gear engagement while minimizing the overall volume of the motor drive unit.
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
This design effectively suppresses the axial growth of the motor unit, allowing for a more compact size while maintaining the necessary protrusion length for the gear engagement, thereby optimizing the motor unit's dimensions without compromising functionality.
Implementation Method 1
The motor includes a rotary shaft, a rotor, and a stator. The stator is configured to rotate the rotor.
Data Source
AI summary
A rotary shaft includes a projection protruding from a rotor along an axial direction of the rotary shaft. The projection has an outer peripheral surface provided with teeth engaged with a gear. The rotor has a first portion which is located around the rotary shaft and which is fixed to the rotary shaft. The rotor has a second portion which is located at an end of the rotor, the end facing the projection. The second portion has an inner diameter larger than an inner diameter of the first portion.