Combined RFeB Magnet with Rare Earth Interface
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Solution Overview
Problem
RFeB-based magnets face challenges with low coercive force at elevated temperatures, leading to magnetization inversion, and existing methods for improving coercive force either compromise residual magnetic flux density or lack sufficient heat resistance for high-temperature applications.
Innovation Solution
A combined type RFeB-based magnet is created by bonding a first unit magnet with a higher content of light rare earth elements and a second unit magnet with a higher content of heavy rare earth elements, using an interface material containing carbides, hydroxides, or oxides of light rare earth elements to enhance coercive force and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth element RH is added to improve coercive force, then coercive force Hcj is improved, but residual magnetic flux density Br decreases
Solution Approach 1:
The patent applies local quality by creating a composite magnet structure where different regions have different compositions: the first unit magnet contains light rare earth elements (Nd, Pr) for high residual magnetic flux density, while the second unit magnet contains heavy rare earth elements (Dy, Tb, Ho) for high coercive force. This allows each region to optimize its properties locally rather than requiring the entire magnet to have uniform composition.
Solution Approach 2:
The patent segments the magnet into multiple unit magnets with different functional characteristics. By dividing the magnet into a first unit magnet (light rare earth element-based) and a second unit magnet (heavy rare earth element-based), the system can simultaneously achieve high residual magnetic flux density and high coercive force through the combined effect of segmented units.
2Reliability
If heavy rare earth element RH is added to prevent magnetization inversion at high temperature, then heat resistance is improved, but the amount of RH increases causing cost and resource issues
Solution Approach 1:
The patent concentrates heavy rare earth elements specifically in the second unit magnet where they are most needed for high-temperature stability, rather than distributing them uniformly throughout the entire magnet. This localized approach maximizes heat resistance where required while minimizing the total amount of expensive heavy rare earth elements used.
Solution Approach 2:
By segmenting the magnet into functional units, the patent can assign the heat resistance function specifically to the second unit magnet containing heavy rare earth elements, while the first unit magnet maintains high residual flux density. This segmentation allows optimized resource allocation for thermal stability.
3Force
If grain boundary diffusion method is used to improve coercive force, then coercive force Hcj is improved with less RH, but the method is complex and requires additional processing steps
Solution Approach 1:
The patent simplifies manufacturing by segmenting the magnet into pre-formed unit magnets with different compositions, which can then be bonded together using conventional techniques. This avoids the complex grain boundary diffusion process while still achieving the benefit of having both light and heavy rare earth element regions in the final magnet assembly.
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 solution effectively increases coercive force while maintaining residual magnetic flux density, providing high heat resistance suitable for high-temperature applications such as vehicle drive motors, and reduces the occurrence of eddy currents due to the insulating nature of the interface materials.
Implementation Method 1
the interface material contains at least one compound selected from the group consisting of a carbide, a hydroxide, and an oxide of the light rare earth element RL... providing high heat resistance
Implementation Method 2
reduces the occurrence of eddy currents due to the insulating nature of the interface materials
Implementation Method 3
the heavy rare earth element RH has an effect of hindering the above-described magnetization inversion... coercive force Hcj is improved
Implementation Method 4
the coercive force is improved by making at least one element selected from the group consisting of Dy, Tb and Ho... be present inside the RFeB-based magnet
Implementation Method 5
the RFeB-based magnet is heated, thereby penetrating the RH to the inside of the magnet through a grain boundary of the RFeB-based magnet... atoms of the RH diffuse only to the vicinity of the surface of respective crystal grains
Data Source
AI summary
Provided is a combined type RFeB-based magnet, including: a first unit magnet; a second unit magnet; and an interface material that bonds the first unit magnet and the second unit magnet, in which the first unit magnet and the second unit magnet are RFeB-based magnets containing a light rare earth element RL that is at least one element selected from the group consisting of Nd and Pr, Fe, and B, in which the interface material contains at least one compound selected from the group consisting of a carbide, a hydroxide, and an oxide of the light rare earth element RL, and in which an amount of a heavy rare earth element RH that is at least one element selected from the group consisting of Dy, Tb and Ho in the second unit magnet is more than that in the first unit magnet.