Patent ID: 6172439
Filing Date: 2001-01-09
Classification: H02K

Abstract:
A motor comprising:a rotor case having a cylindrical portion;a cylindrical yoke fixed to an inner surface of said cylindrical portion, said yoke being made of a magnetic material;said rotor case and said cylindrical yoke having different coefficients of thermal expansion;a cylindrical rotor magnet fixed to an inner surface of said yoke;a frame for rotatively supporting said rotor case;an armature fixed to said frame, said armature being opposite to said rotor magnet;a yoke separating slit for permitting enlargement of a diameter of said yoke by expansion of said slit in a circumferential direction of said yoke, said enlargement and expansion being caused by rotation of the rotor and by heat generated during rotation;a plurality of yoke bonding portions where an outer surface of said yoke is bonded to the inner surface of said cylindrical portion, said yoke bonding portions being apart from one another in the circumferential direction; andthe inner surface of said cylindrical portion and the outer surface of said yoke being permitted to separate from and contact one another between adjoining yoke bonding portions, wherein said yoke separating slit is formed at a position between said adjoining yoke bonding portions and at a position corresponding to an inflection point of a magnetic pole of said rotor magnet.