| 摘要 |
PROBLEM TO BE SOLVED: To reduce torque ripple and cogging torque by defining the amount of eccentricity which is a difference in a distance between the inner diameter of a stator corresponding to such a point that a gap length between a magnetic field permanent magnet and an armature is minimized, the center of the stator, and the center of the inner diameter curvature of the center of the magnetic field permanent magnet. SOLUTION: The thickness of a magnetic field permanent magnet 20 is formed so as to be the thickest at a center and get thinner gradually toward both ends. When the distance between the magnetic field permanent magnet 20 at a position where a gap length is minimized and a rotational center is Rsi, the inner side curvature of the magnetic field permanent magnet 20 is Rmi, and the offset of the inner diameter side curvature center of the magnetic field permanent magnet 20 and the rotational center is (d), the amount of eccentricity is defined asδ=d/Rsi withδ>0.09. When the value of the amount of eccentricityδis larger than a specific point, the value of cogging torque and irregularity high volume production can be reduced. It is thus possible to reduce torque ripple and cogging torque in a four-pole, multi-winding, 22-plot, and four-brush type.
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