Development of Rare Earth Saving Magnet by Partial Diffusion Method

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Masashi Inoue, Honda R&D Co.,Ltd.

Abstract

Nd2Fe14B sintered magnets used in HEV, EV drive/power-generating motors have high magnetic flux density, which contributes to higher torque and miniaturization of the motors. Nd2Fe14B sintered magnets have Dy added to them to raise coercive force but in addition to being scarce rare-earth elements, production sites are limited so prices have risen in recent years. Therefore, technology is required that maintains demagnetization characteristics even if the amount of Dy used is reduced.
This time, in order to reduce the amount of Dy used even a little, JMAG’s electromagnetic field analysis identified the demagnetization region of a motor targeted for development and quantified the expected coercive force to the magnet. As a result of this, a magnet with reduced rare earth was developed with the partial diffusion method which had as its concept of minimizing the amount of Dy used on the required locations and motor characteristic evaluations proved that the developed magnet’s demagnetization characteristics are equivalent to that of traditional magnets.

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