Permanent magnet type rotary electric machine and electric power steering apparatus using the same

Abstract

Not less than two regions different in magnetic circuit design are provided in a rotational axis direction of the rotor ( 30 ), the regions being different by changing a cross-sectional shape in the rotational axis direction in a cross-section perpendicular to a rotational shaft ( 10 ) of the rotor ( 30 ) having the permanent magnets ( 1 ) and the rotor core ( 2 ); the supplemental grooves ( 5 ) are provided in axial partial regions of each of the teeth ( 7 ) of the stator core ( 3 ); and the region in which the supplemental groove ( 5 ) is provided is each partial region for each region facing a region same in magnetic circuit design of the rotor ( 30 ). This enables to reduce cogging torque generated by variations on the rotor side.

1 . A permanent magnet type rotary electric machine comprising:
 a rotor having a plurality of magnetic poles composed of permanent magnets and a rotor core; and   a stator including armature windings and a stator core which is provided with slots for incorporating said armature windings and has a plurality of teeth facing said rotor,   each of said teeth of said stator core being provided with supplemental grooves at portions facing said rotor,   wherein not less than two regions different in magnetic circuit design are provided in a rotational axis direction of said rotor, the regions being different by changing a cross-sectional shape in the rotational axis direction in a cross-section perpendicular to a rotational shaft of said rotor having said permanent magnets and said rotor core;   the supplemental grooves are provided in axial partial regions of said tooth of said stator core;   the region in which the supplemental groove is provided is each partial region for each region facing a same region in magnetic circuit design of the rotor; and   an axial end face of the supplemental groove is located in an end face perpendicular to the rotational shaft between the regions different in magnetic circuit design of said rotor.   
     
     
         2 . The permanent magnet type rotary electric machine according to  claim 1 , wherein the region in which the supplemental groove is provided is a region half of each axial length for each region facing a same region in magnetic circuit design of the rotor. 
     
     
         3 . The permanent magnet type rotary electric machine according to  claim 1 , wherein a width Wd of the supplemental groove is larger than an opening width Ws of the slot. 
     
     
         4 . The permanent magnet type rotary electric machine according to  claim 1 , wherein a depth Hd of the supplemental groove is larger than a thickness Hs of an end portion of said tooth. 
     
     
         5 . The permanent magnet type rotary electric machine according to  claim 1 , wherein the supplemental groove is not provided in an axial end portion of said stator core. 
     
     
         6 . The permanent magnet type rotary electric machine according to  claim 1 , wherein the supplemental groove is provided at one place in a circumferential center portion of said stator core at a portion in which the tooth faces said rotor. 
     
     
         7 . The permanent magnet type rotary electric machine according to  claim 1 , wherein when the number of poles of said magnetic poles of said rotor is P and the number of the slots of said stator is S, the following relationship is established: 0.75<S/P<1.5. 
     
     
         8 . The permanent magnet type rotary electric machine according to  claim 1 , wherein the number of poles P of said magnetic pole of said rotor is 12n±2n and the number of the slots S of said stator is 12n, n being natural number. 
     
     
         9 . The permanent magnet type rotary electric machine according to  claim 1 , wherein the number of poles P of said magnetic pole of said rotor is 9n±n and the number of the slots S of said stator is 9n, n being natural number. 
     
     
         10 . A permanent magnet type rotary electric machine comprising:
 a rotor having a plurality of magnetic poles composed of permanent magnets and a rotor core; and   a stator including armature windings and a stator core which is provided with slots for incorporating said armature windings and has a plurality of teeth facing said rotor,   each of said teeth of said stator core being provided with supplemental grooves at portions facing said rotor,   wherein the plurality of said magnetic poles of said rotor are configured by arranging not less than two groups of permanent magnets in a rotational axis direction, respectively;   the supplemental grooves are provided in axial partial regions of said tooth of said stator core;   the region in which the supplemental groove is provided is each partial region for each region facing not less than two groups of said permanent magnets arranged in the rotational axis direction; and   an axial end face of the supplemental groove is located in an end face perpendicular to the rotational shaft between not less than two groups of said permanent magnets arranged in the rotational axis direction.   
     
     
         11 . The permanent magnet type rotary electric machine according to  claim 10 , wherein the region in which the supplemental groove is provided is a region half of each axial length for each region facing not less than two groups of said permanent magnets arranged in the rotational axis direction. 
     
     
         12 . An electric power steering apparatus using the permanent magnet type rotary electric machine as set forth in  claim 1  as a driving motor.