Rotor Magnet Dysprosium Diffusion for Demagnetization
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Solution Overview
Problem
Permanent magnets in drive motors suffer from demagnetization due to high temperatures, particularly at the central portion where heat is not dissipated, leading to increased costs when enhancing coercivity with dysprosium (Dy) as it reduces magnetic flux density across the magnet.
Innovation Solution
A grain boundary diffusion process (GBDP) is applied to diffuse dysprosium (Dy) on the surface of neodymium (Nd) magnets based on temperature distribution, increasing coercivity at high-temperature areas and maintaining magnetic flux density by reducing Dy content at lower-temperature areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dysprosium (Dy) is mixed with neodymium (Nd) magnet to increase Dy content, then coercivity is enhanced, but magnetic flux density Br decreases
Solution Approach 1:
The patent applies local quality by concentrating Dy diffusion specifically at the central portion of the permanent magnet where temperature is highest and demagnetization risk is greatest, rather than uniformly distributing Dy throughout the entire magnet. This localized approach enhances coercivity only where needed, preserving magnetic flux density in other regions.
Solution Approach 2:
The patent segments the Dy distribution according to temperature zones within the permanent magnet, applying different Dy concentrations to different regions - higher concentration at the hot central portion and lower or no concentration at cooler end portions - thereby optimizing the balance between coercivity enhancement and magnetic flux density maintenance.
2Reliability
If Dy content is increased to enhance coercivity, then demagnetization resistance improves, but overall cost increases
Solution Approach 1:
The patent reduces cost by applying Dy only locally at the central portion of the permanent magnet rather than throughout the entire magnet. Since Dy is an expensive rare earth element, this localized diffusion strategy significantly reduces material cost while still providing sufficient demagnetization resistance at the critical high-temperature region.
Solution Approach 2:
The patent applies partial action by using Dy diffusion only at the central portion rather than uniformly across the entire magnet. This partial application is sufficient to prevent demagnetization at the critical high-temperature zone without incurring the full cost of universal Dy incorporation.
3Reliability
If Dy is uniformly applied to the entire permanent magnet, then coercivity is enhanced throughout, but magnetic flux density is reduced across all regions
Solution Approach 1:
The patent resolves this contradiction by making coercivity enhancement local rather than universal - Dy is diffused specifically at the central portion where temperature causes coercivity degradation, while end portions maintain their original high magnetic flux density characteristics without Dy-induced reduction.
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 enhances coercivity at high-temperature regions to prevent demagnetization while maintaining or increasing average magnetic flux density, reducing the overall cost by optimizing Dy distribution without mixing it with the Nd magnet.
Implementation Method 1
a grain boundary diffusion process (GBDP) of diffusing Dy on the surface of a permanent magnet according to temperature distribution of the permanent magnet
Data Source
AI summary
Disclosed herein is a rotor permanent magnet apparatus for a drive motor based on temperature distribution. The permanent magnet may enhance coercivity without a substantial decrease in magnetic flux density Br by applying a grain boundary diffusion process of diffusing dysprosium on the surface of the permanent magnet based on the temperature distribution of the permanent magnet.