Patent ID: 8390163

Claim:
An electric rotating machine comprising: a stator; a rotor having a rotor core and inserted in a bore formed in the stator such that an air gap is formed between the stator and the rotor; and magnetic poles circumferentially arranged in a peripheral portion of the rotor core of the rotor; wherein the rotor further comprises slits formed in the rotor core and extending between adjacent ones of the magnetic poles, wherein magnetic gap is formed between the magnetic poles and the rotor core, wherein the rotor core has portions, each extending between the slit and the magnetic pole, in which compressive stress is induced when stress is induced in the portions of the rotor core between the slit and the magnetic pole by centrifugal force produced when the rotor rotates and acting on the magnetic pole and a portion of the rotor core on the radially outer side of each magnetic pole, wherein a radial length from an outer surface of the rotor to a bottom of the slit is longer than a radial length from the outer surface of the rotor to an inner edge of the magnetic gap, wherein the slit has an open end to the surface of the rotor core, and the bottom of the slit swells circumferentially toward a center of the magnetic pole.