Outer-Rotor Magnet Holding Structure for Secure Fixation and Torque
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Solution Overview
Problem
Existing rotating electric machines face challenges in effectively fixing magnets during rotation, leading to potential detachment and reduced performance, particularly in slot-less motor designs with outer-rotor structures.
Innovation Solution
A rotating electric machine design featuring a circular annular magnet portion with alternating magnetic poles and a cylindrical magnet holding portion, where the magnet portion is arranged on the inner side of the armature, forming an arch structure to ensure uniform compression and improved frictional locking, and the magnet holding portion is reduced in size to enhance fixation and torque performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnets are fixed in a conventional manner in slot-less motor designs, then the structure is simple, but magnet detachment occurs during rotation
Solution Approach 1:
The magnet holding portion is designed with a curved inner circumferential surface that matches the outer circumferential surface of the magnet portion. This curved geometry creates continuous contact between the magnets and the holding portion, generating frictional forces that prevent magnet detachment during rotation without requiring additional complex fixation mechanisms
Solution Approach 2:
The magnet holding portion is designed with a reduced outer circumference compared to the magnet portion, creating a pre-compression effect. This prior cushioning ensures that magnets are continuously pressed against the holding portion, maintaining reliable fixation throughout operation without requiring additional active fixation systems
2Power
If the magnet holding portion is reduced in size, then fixation and torque performance are enhanced, but the space for magnet arrangement is reduced
Solution Approach 1:
The magnet holding portion is selectively reduced in size only in the radial direction where it contacts the magnets, while maintaining sufficient volume in other dimensions to accommodate the magnet arrangement. This localized dimensioning approach enhances fixation and torque performance through increased contact pressure and friction, while preserving the necessary space for magnet placement
3Reliability
If magnets are arranged in an array with reduced outer circumference, then frictional locking is improved, but manufacturing precision requirements increase
Solution Approach 1:
The curved inner circumferential surface of the magnet holding portion naturally guides and accommodates the circular-arc-shaped magnets during assembly. This curved geometry provides form closure that tolerates minor manufacturing variations, reducing the stringency of precision requirements while maintaining effective frictional locking through continuous contact
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 design effectively prevents magnet detachment during rotation, enhances torque by strengthening magnetic flux on the d-axis, and reduces eddy current losses, while maintaining efficient magnetic flux distribution and torque density.
Implementation Method 1
the plurality of magnets are arrayed in the circumferential direction, an outer circumference of the magnets is reduced from an outer side toward an inner side in the radial direction
Implementation Method 2
a magnet portion that is formed into a circular annular shape and includes a plurality of magnetic poles of which polarities alternate in a circumferential direction
Data Source
AI summary
In a rotating electric machine, a field element includes: a circular annular magnet portion that includes magnetic poles of which polarities alternate in a circumferential direction; and a cylindrical magnet holding portion where the magnet portion is fixed on an inner circumferential surface of the magnet portion. An armature is arranged to oppose the magnet portion on an inner side in a radial direction of the magnet portion. The magnet portion includes circular-arc-shaped magnets arranged in an array in the circumferential direction. In each magnet, both end surfaces in the circumferential direction are along the radial direction and in contact with a magnet adjacent in the circumferential direction. The magnet holding portion is reduced in size such that, in a state where the magnets are arrayed in the circumferential direction, an outer circumference of the magnets is reduced from an outer side toward an inner side in the radial direction.