| 简介 |
PROBLEM TO BE SOLVED : To reduce the strain of distribution of magnetization in rotating direction and, further, reduce cogging torque by forming recessed and projected part in the direction of outer diametral circumference and skewing the recessed and projected part into the axial direction thereof, in an ring type sintered magnet constituted of a rare earth or the like having a powerful magnetic force.
SOLUTION : In the ring type sintered magnet manufactured by orienting magnetic power in a magnetic field, then, compressing and forming through sintering process, periodical recessed and projected configurations 21, 22 are formed at least in one region in the axial direction of ring in the outer diametral circumference of the ring, while the recessed and projected configurations 21, 22 are changed in accordance with the axial position thereof, the magnetic poles are formed periodically along the recessed and projected configurations 21, 22, and the boundary of the magnetic poles is provided in the recessed part 21. Especially, the recessed and projected configurations 21, 22 are formed obliquely by rotating in the axial direction. Further, the recessed and projected configurations 21, 22 are formed so as to be approached to the wave forms of absolute value of a sine wave.
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