Halbach Magnet Array Grain Boundary Diffusion for Demagnetization
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Solution Overview
Problem
Magnetic field generators with Halbach magnet arrays face demagnetization issues due to the use of expensive and unevenly distributed dysprosium (Dy) and terbium (Tb) in grain boundary diffusion magnets, which also hinder high-precision assembly.
Innovation Solution
A magnetic field generator with a grain boundary diffusion layer of Dy or Tb compounds on the contact surfaces of main and secondary magnets, reducing the amount of Dy and Tb used and improving assembly precision by forming these layers through coating and heating, allowing for a linear Halbach magnet array without gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grain boundary diffusion treatment is performed to diffuse Dy and/or Tb into grain boundaries near the surfaces of permanent magnets, then coercive force is increased and demagnetization resistance is improved, but the amount of Dy and/or Tb used increases and cost increases
Solution Approach 1:
The patent applies grain boundary diffusion treatment only to specific contact surfaces of the permanent magnets where demagnetization occurs, rather than treating the entire magnet. This localized approach concentrates the Dy/Tb diffusion precisely where needed (at the contact surfaces exposed to opposite magnetic fields) while minimizing the total amount of heavy rare earth elements required, thus resolving the contradiction between improving demagnetization resistance and reducing material cost.
2Reliability
If grain boundary diffusion treatment is performed on permanent magnets, then coercive force is increased, but the magnets expand and assembly precision is reduced
Solution Approach 1:
The patent divides the permanent magnets into multiple pieces and performs grain boundary diffusion treatment on only specific contact surfaces of selected magnets, rather than treating entire magnets uniformly. This segmentation approach limits the expansion effect to localized regions, allowing the overall magnet array to maintain dimensional stability and assembly precision while still achieving the desired coercive force enhancement at critical locations.
3Reliability
If neodymium sintered magnets with high contents of Dy and/or Tb are used, then coercive force is increased and demagnetization resistance is improved, but residual magnetic flux density is reduced and thrust is reduced
Solution Approach 1:
The patent creates a local quality gradient by concentrating Dy/Tb enrichment specifically at the contact surfaces through grain boundary diffusion treatment, while the bulk magnet material maintains its original composition with high residual magnetic flux density. This localized treatment approach allows the magnets to achieve high coercive force at critical surfaces without sacrificing the overall residual magnetic flux density, thereby maintaining thrust performance while improving demagnetization resistance.
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 solution enhances demagnetization resistance, reduces the use of expensive Dy and Tb, and improves the thrust characteristics of linear motors by maintaining the size of magnets during assembly and preventing demagnetization.
Implementation Method 1
a grain boundary diffusion layer is formed in which at least one of Dy or Tb being heavy rare earth elements or a compound of at least one of the Dy or the Tb is diffused into internal grain boundaries from the contact surfaces
Implementation Method 2
heating at least either the main magnetic pole magnets or the secondary magnetic pole magnets applied with the coating material to form a grain boundary diffusion layer
Data Source
AI summary
A magnetic field generator including: a yoke; and a plurality of main magnetic pole magnets and a plurality of secondary magnetic pole magnets, the main magnetic pole magnets and the secondary magnetic pole magnets comprising a rare earth sintered magnet, having magnetic pole orientations different from each other by substantially 90°, and being alternately arranged in a linear Halbach magnet array without gaps and fixed to the yoke, wherein near contact surfaces of the main magnetic pole magnets and the secondary magnetic pole magnets, a grain boundary diffusion layer is formed in which at least one of Dy or Tb being heavy rare earth elements or a compound of at least one of the Dy or the Tb is diffused into internal grain boundaries from the contact surfaces.