Radial-Direction Gap Magnet Motor Cogging Torque Reduction
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Solution Overview
Problem
Radial-direction gap type magnet motors face challenges in reducing cogging torque while maintaining high torque density, as increasing energy density leads to increased cogging torque, and existing methods to reduce cogging torque either compromise torque density or are difficult to manufacture and economically inefficient.
Innovation Solution
A magnetic anisotropic magnetic pole with a specific configuration, where the magnetization vector angle Mθ is controlled to be between 75 to 90° and the change in this angle with respect to the mechanic angle φp is minimized, using a deformed magnetic pole with a circular arc shape and a thermosetting resin composite, to achieve high energy density and reduced cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the energy density (BH) max of the magnet is increased to achieve higher torque density, then the torque density is improved, but the cogging torque increases causing disturbance in smooth rotation, increased vibration or noise, and deterioration in rotation control performance
Solution Approach 1:
The magnetic pole is designed with non-uniform thickness in the radial direction, creating local quality variations. The thickness is greater at the center and smaller at the ends, which locally adjusts the magnetic flux distribution to reduce cogging torque while maintaining high torque density through optimized energy density (BH) max of the magnet material
Solution Approach 2:
The invention changes the geometric parameter of the magnetic pole from uniform to non-uniform thickness distribution. By adjusting the radial thickness profile (greater at center, smaller at ends), the magnetic circuit parameters are optimized to achieve low cogging torque while maintaining high torque density through increased energy density (BH) max
2Object-generated harmful factors
If the thickness of the magnetic pole is reduced to minimize cogging torque, then the cogging torque is reduced, but the magnetic pole becomes mechanically weak and processing becomes difficult
Solution Approach 1:
Instead of uniformly reducing thickness, the invention applies local quality variation by making the magnetic pole thicker at the center and thinner at the ends. This local thickness optimization reduces cogging torque through improved magnetic flux distribution while the central thickness provides sufficient mechanical strength and ease of processing
3Object-generated harmful factors
If the magnetic pole thickness is made non-uniform to reduce cogging torque, then the cogging torque is minimized, but the manufacturing complexity increases
Solution Approach 1:
The non-uniform thickness profile is designed to be manufacturable by controlling the radial thickness distribution. The gradual variation from center to end allows for practical manufacturing processes while achieving the desired cogging torque reduction through optimized magnetic flux distribution
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 approach effectively increases torque density by approximately 1.36 times while keeping cogging torque lower than isotropic magnets, enhancing power saving, resource efficiency, size reduction, and silencing in small motors.
Implementation Method 1
a magnet is different from other magnetic materials in that an effective magnetization remains even after removing an external magnetic field
Implementation Method 2
uses a magnet capable of attracting or repelling other magnetic materials and of permanently generating a static magnetic field without an external energy
Implementation Method 3
a magnetic anisotropic magnetic pole having a non-radial magnetic anisotropic region provided at a magnetic pole end
Implementation Method 4
the increase in energy density (BH) max of the magnet induces a higher torque density in the radial-direction gap type magnet motor
Data Source
AI summary
In a radial-direction gap type magnet motor, when an energy density increases, a direction change Mθ/φp of a static magnetic field with respect to a mechanic angle between different poles increases in an exponential manner and thus to decrease a cogging torque of the motor is not compatible to increase a torque density. In order to solve the problem, assuming that φt denotes a mechanic angle of a stator iron core teeth, φp denotes a mechanical angle of a magnetic pole, and Mθ denotes an angle of a static magnetic field with respect to a circumferential tangential line of a radial magnetic pole center, a radial-direction type magnet motor in which φt<φp, Mθ in a magnetic pole center region is 75 to 90°, and Mθ/φp≦7 is satisfied in the magnetic pole end region of φp×0.1°, and further, a static magnetic field generating source is configured as a magnetic anisotropic magnetic pole having an energy density (BH) max≧150 kJ/m3 is provided.