Hub Motor Assembly with Cycloidal Speed Reducer
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Solution Overview
Problem
Conventional electrically driven hub motors with planetary gear systems have a low torque-to-volume ratio and uneven force distribution due to non-concentric shafts, leading to inefficient torque transmission and potential durability issues.
Innovation Solution
A hub motor assembly incorporating a cycloidal speed reducer and one-way clutch unit, featuring an eccentric cam, cycloidal wheel, positioning plate, carrier pins, annular force-transmitting member, and roller units, which enables high torque-to-volume ratio and even force distribution by allowing eccentric cycloidal motion and directional rotation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a planetary gear system is used in the hub motor assembly, then the structure can transmit torque, but the torque-to-volume ratio becomes low
Solution Approach 1:
The gear system is segmented into a cycloidal wheel with multiple lobes and a positioning plate with corresponding carrier pins, allowing distributed contact points that reduce the overall volume required for torque transmission while maintaining high torque density
Solution Approach 2:
The cycloidal wheel employs a curved cycloidal profile instead of straight gear teeth, enabling more efficient torque transmission through rolling contact and reducing the radial space required for the gear system, thereby improving the torque-to-volume ratio
2Reliability
If conventional shaft alignment is used, then the structure is simple, but force distribution on the hub becomes uneven
Solution Approach 1:
The positioning plate is designed with an asymmetric geometry relative to the hub center, with carrier pins positioned at specific non-uniform intervals. This asymmetric configuration compensates for potential shaft misalignment and ensures even force distribution across the hub surface during operation
Solution Approach 2:
The positioning plate acts as an intermediary element between the cycloidal wheel and the hub, distributing the forces from the cycloidal wheel's lobes evenly across multiple carrier pins to the hub, thereby ensuring uniform force distribution even with minor shaft alignment variations
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 achieves a high torque-to-volume ratio, ensuring efficient and durable operation with even force distribution, reducing noise and manufacturing costs through modular design.
Implementation Method 1
The cycloidal speed reducer includes an eccentric cam, at least one cycloidal wheel... The eccentric cam is mounted on and rotates with the output shaft. The cycloidal wheel is coupled to be driven by the eccentric cam such that when the output shaft outputs the rotational force, the cycloidal wheel is permitted to move about the axial line.
Implementation Method 2
The roller unit includes a plurality of contact rollers, and is coupled between the cycloidal wheel and the annular force-transmitting member.
Data Source
AI summary
A hub motor assembly includes a hub axle, a hub shell, a motor unit, a cycloidal speed reducer, and a one-way clutch unit. When an output shaft of the motor unit rotates in a first direction about an axial line, a cycloidal wheel of the cycloidal speed reducer is driven to produce an eccentric cycloidal motion relative to the axial line, to thereby drive rotation of the hub shell in the first direction. When the output shaft rotates in a second direction opposite to the first direction, the hub shell is prevented from rotating with the output shaft.