Patent ID: 8183722

Claim:
An accessory drive system that is connected to a prime mover having an output shaft for outputting mechanical power, and drives an accessory, comprising: a rotating machine including a first rotor that is connected to one of the output shaft of the prime mover and the accessory and is rotatable in a circumferential direction, and a second rotor that is connected to the other of the output shaft of the prime mover and the accessory and is rotatable in the circumferential direction, and a stator that is unmovable, wherein said first rotor has a magnetic pole row that is formed by a predetermined plurality of magnetic poles arranged in the circumferential direction, and has each two adjacent magnetic poles so disposed as to have polarities different from each other; wherein said stator has an armature row that is formed by a plurality of armatures arranged in the circumferential direction, and is disposed in a manner opposed to said magnetic pole row, for generating a rotating magnetic field rotating in the circumferential direction between said armature row and said magnetic pole row by a predetermined plurality of armature magnetic poles generated at said plurality of armatures; wherein said second rotor has a soft magnetic material element row that is formed by a predetermined plurality of soft magnetic material elements arranged in the circumferential direction in a manner spaced from each other, and is disposed such that said soft magnetic material element row is positioned between said magnetic pole row and said armature row, and wherein a ratio between a number of the armature magnetic poles, a number of the magnetic poles, and a number of said soft magnetic material elements is set to 1:m:(1+m)/2(m≠1.0).