Continuous Anisotropy Ring Magnet Manufacturing for Low Cogging Torque
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Solution Overview
Problem
Existing methods for manufacturing rare-earth/iron-based ring magnets struggle to balance high energy density with low cogging torque, especially in small-sized motors, leading to increased noise and vibration due to radial anisotropic magnet characteristics that deteriorate at smaller diameters.
Innovation Solution
A method of manufacturing rare-earth/iron-based ring magnets with controlled continuous anisotropy by molding segments with varying circumferential sections under a uniform external magnetic field, then extruding and compression-molding them into a ring shape to maintain high energy density while minimizing cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If radial anisotropic magnet characteristics are used to increase energy density, then torque density increases, but cogging torque increases causing noise and vibration
Solution Approach 1:
The patent applies local quality by creating different anisotropic characteristics in different regions of the magnet. The magnetic pole has a radial anisotropic region at the center and non-radial anisotropic regions at the ends, allowing each region to contribute differently to torque generation while minimizing cogging torque through the non-radial orientation at the pole ends.
2Volume of moving object
If magnet diameter is reduced for downsizing, then motor size decreases, but energy density deteriorates
Solution Approach 1:
The patent changes the anisotropic direction parameter from purely radial to a continuous distribution including non-radial orientations. This parameter change allows the magnet to maintain high energy density even at small diameters by optimizing the magnetic field distribution and reducing leakage flux through the non-radial anisotropic regions.
3Ease of manufacture
If uniform anisotropy is used for simple manufacturing, then manufacturing complexity decreases, but magnetic field distribution becomes suboptimal
Solution Approach 1:
The patent segments the magnetic pole into distinct regions (radial anisotropic region at the center and non-radial anisotropic regions at the ends) with different anisotropic characteristics. This segmentation allows optimization of magnetic field distribution in each region while maintaining a manufacturable structure through the extrusion and compression molding process.
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 increases energy density by two times or more, enhancing torque density without increasing cogging torque, and maintains magnetic field stability even at small diameters, reducing noise and improving motor efficiency.
Implementation Method 1
magnetized under a uniform external magnetic field to align magnetic domains
Implementation Method 2
controlled continuous anisotropy by molding segments with varying circumferential sections
Implementation Method 3
extruding and compression-molding them into a ring shape
Implementation Method 4
compression-molding from both thrust-direction end surfaces
Data Source
AI summary
A process of manufacturing segments, an anisotropic direction of which is continuously changed in a plane vertically by a uniform magnetic field maintained in a constant direction and a process of arranging a plurality of segments on a circumference, extruding the segments in a ring shape by rheology based on the viscous deformation of the segments, from one thrust-direction end surface of the segments, and subsequently compressing the segments from both thrust-direction end surfaces of the segments are necessarily included. A ring magnet, anisotropy of which is controlled in a continuous direction, is provided, and a source for generating a static magnetic field has energy density (BH) max≧160 to 180 kJ/m3.