RING MAGNET AND APPARATUS AND METHOD FOR MANUFACTURING RING MAGNET

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PROBLEM TO BE SOLVED : To manufacture a ring magnet of rare earth or the like having strong magnetic force, which magnet makes it possible to reduce distortion in magnetization distribution in the direction of rotation and reduce cogging torque. SOLUTION : An apparatus for manufacturing the ring magnet includes an annular die 80 constructed of multiple arch-shaped members 81 to 84, cylinders 81A to 84A that move the multiple arch-shaped members 81 to 84 in the radial direction and hold them under pressure, a lower punch 91 that closes the lower part of the die 80, and an upper punch 92 that applies pressure to magnet material 118 supplied into the cavity 90 formed by the die 80 and the lower punch 91. The die 80 has such a portion that the sectional shape of its inner circumferential surface perpendicular to its axis varies depending on its position in the axial direction. A ring magnet is extrusion molded using this apparatus, and then the arch-shaped members 81 to 84 are moved outward in the radial direction to release the ring magnet. COPYRIGHT : (C)2006, JPO&NCIPI