Rare-earth permanent magnet

Abstract

There is provided a rare-earth permanent magnet optimized to an IPM type motor for a car, capable of improving corrosion resistance, abrasion resistance, and impact resistance. The rare-earth permanent magnet 16 is configured by forming an electroplated Ni coating film 21, of which thickness is 15 [mu]m or more and 30 [mu]m or less and of which shape is a columnar crystal structure, on a surface of a R-Fe-B system permanent magnet (R is a rare-earth element) 22. The electroplated Ni coating film 21 has a high hardness region, where the Vickers hardness is 300 or more and 600 or less, and a low hardness region, where the Vickers hardness is 150 or more and 300 or less. The rare-earth permanent magnet 16 is used in a state where the rare-earth permanent magnet 16 is inserted into a slot of a yoke in a rotor of an IPM type motor for a car.

Description

technical field [0001] The present invention relates to a rare earth permanent magnet inserted into a slot in a rotor yoke of an IPM type motor for automobiles. Background technique [0002] As rare earth permanent magnets, R—Fe—B based rare earth permanent magnets (R is a rare earth element) are known. As high-quality permanent magnets, R-Fe-B series rare-earth permanent magnets are used in electric vehicles or hybrid vehicles that require such high quality. However, since R—Fe—B based rare earth permanent magnets contain easily oxidized rare earth elements and iron as main components, there are problems in that their corrosion resistance is relatively low and that they cause deterioration and deviation of magnetic properties due to corrosion. [0003] In addition, since electric motors of electric vehicles or hybrid vehicles require high performance, internal permanent magnet (IPM) type motors are used in many cases. The IPM type motor has a rotor structure in which magn...

AI Technical Summary

Problems solved by technology

However, since R-Fe-B based rare earth permanent magnets contain easily oxidized rare earth elements and iron as main components, there are problems in that their corrosion resistance is relatively low and that they cause deterioration and deviation in magnetic properties due to corrosion.

As a result, there are also problems that the coating is scratched or worn, and cracks appear in the coating

[0007] However, the rare-earth permanent magnets disclosed in JP-A No. 9-7810 and JP-A No. 2003-97429 cannot satisfy all requirements of corrosion resistance, wear resistance and impact resistance at the same time.

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