Patent ID: 6316851
Filing Date: 2001-11-13
Classification: H02K

Abstract:
A motor comprising:a rotor magnet having a cylindrical shape at least an outer peripheral surface of which is alternately magnetized to different poles along a circumferential direction to define magnetic poles;a rotary shaft secured to said rotor magnet;a coil disposed in an axial direction of said rotor magnet and with said rotor magnet side by side;an outer yoke magnetized by said coil and having a first portion comprising outer magnetized portions opposed to the outer peripheral surface of said rotor magnet and a second portion, wherein said outer magnetized portions are constituted by notches and teeth extending in parallel with said rotary shaft, and said coil is mounted in said second portion of said outer yoke;an inner yoke magnetized by said coil and having a first portion comprising inner magnetized portions opposed to an inner peripheral surface of said rotor magnet and a second portion, wherein said inner magnetized portions are opposed to said outer magnetized portions, the diameter of said second portion of said inner yoke is smaller than the distance between said inner magnetized portions, and said coil is mounted on said second portion of said inner yoke, wherein magnetic flux generated by said coil traverses across said rotor magnet between said inner magnetized portions and said outer magnetized portions; andholding means for holding said rotor magnet at a position where centers of said magnetic poles of said rotor magnet deviate from a straight line connecting centers of said outer magnetized portions and a rotational center of said rotor magnet when said outer and inner magnetized portions are not magnetized by said coil.