ELECTRIC MOTOR

PROBLEM TO BE SOLVED: To reduce torque ripple in a motor which is provided with magnets in the radial direction of an armature core while facing the same poles each other. SOLUTION: A pair of magnets 12 are arranged on the inner circumferential surface of a cylindrical yoke 3 incorporating a rotor 4 while facing the same poles each other, an iron pole portion 3a is formed between the magnets of the yoke, and the iron pole portion is formed with a radius of curvature larger than that of the magnet 12. Although an attraction torque tends to rise abruptly when teeth forming the surface of revolution of an armature core move from a magnet to an iron pole portion, but since a corresponding portion of the iron pole portion is remote from the teeth, abrupt rise of attraction torque is controlled and subsequent abrupt fall of attraction torque is also controlled. Consequently, rising and falling of attraction torque can be changed gently and torque ripple is reduced. COPYRIGHT: (C)2009,JPO&INPIT