| 摘要 |
PROBLEM TO BE SOLVED: To reduce the weight of a motor by establishing a specific relation between the radial distances from the internal surface of a rotor core to the inter-pole side end sections of the inner peripheral surfaces of permanent magnets and the peripheral lengths of the permanent magnets. SOLUTION: The magnetic fluxes flowing out of a circumferential length portion 2w of a permanent magnet 8 is absorbed to the adjacent magnets 8 having different polarities on both sides of the magnet 8, in such a way that the magnetic fluxes from the two half-length portions (w) on both sides of the center of the magnet 8 are separately absorbed to the adjacent magnets 8. When the distance (r) from the internal surface of a rotor 7 to the inter-pole side end section of the inner peripheral surface of the magnet 8 meets r/w>1, the magnetic fluxes flow smoothly, but, when the distance (r) meets r/w<1, the magnetic fluxes do not flow smoothly and the magnetic flux density in a gap 5 drops. When r/w>0.8, the magnetic flux density hardly changes, but, when r/w<0.8, the density abruptly drops. When the magnetic flux density drops, the output of a motor drops. When the output of the motor is fixed, the weight of the motor increases, because the thickness of coil of the motor must be increased. When r/w=0.6±0.1, the weight of the motor can be reduced without decreasing the output of the motor.
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