US 12,074,475 B2
Rare earth permanent magnet and rotating electric machine including the same
Takuma Hayakawa, Tokyo (JP)
Assigned to TDK Corporation, Tokyo (JP)
Filed by TDK Corporation, Tokyo (JP)
Filed on Mar. 22, 2021, as Appl. No. 17/208,185.
Claims priority of application No. 2020-054504 (JP), filed on Mar. 25, 2020.
Prior Publication US 2021/0305852 A1, Sep. 30, 2021
Int. Cl. H02K 1/02 (2006.01); H01F 1/057 (2006.01); H01F 7/02 (2006.01); H01F 41/02 (2006.01)
CPC H02K 1/02 (2013.01) [H01F 1/0577 (2013.01); H01F 7/0205 (2013.01); H01F 41/0293 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A rare earth permanent magnet having a first surface and satisfying A1<B1, A1>C1, A1>D1, A1−C1≥10 kA/m, A1−D1≥10 kA/m, and B1−A1≥10 kA/m, where
A1 is a coercive force of a portion a1 including a center of gravity of the first surface, and a surface of the portion a1 being the same surface as the first surface of the magnet,
B1 is a coercive force of a portion b1 including an end of the first surface, the end being distant from the portion a1 in a Y direction perpendicular to a normal direction at the center of gravity of the first surface, and a surface of the portion b1 being the same surface as the first surface of the magnet,
C1 is a coercive force of a portion c1 including an end of the first surface, the end being distant from the portion a1 in a X direction perpendicular to the normal direction at the center of gravity of the first surface, the X direction perpendicular to the Y direction, and a surface of the portion c1 being the same surface as the first surface of the magnet, and
D1 is a coercive force of a portion d1 including an end of the first surface, the end being distant from the portion a1 in the −X direction opposite to the X direction, and a surface of the portion d1 being the same surface as the first surface of the magnet, wherein
a heavy rare earth element is present on a top layer of the first surface, and
a size of each of the portion a1, the portion b1, the portion c1, and the portion d1 is 0.5 to 10 mm×0.5 to 10 mm×0.5 to 10 mm.