Patent ID: 8134266

Claim:
An electric motor comprising: a stator including a stator core having a yoke and a plurality of teeth protruded from the yoke, which is formed with slots between the teeth being adjacent to each other, and winding wound around the stator core; and a rotor rotatably held against the stator, having a rotor core and a plurality of magnetic poles held by the rotor core and confronting tip ends of the teeth via gaps, wherein the rotor core is formed by rotor core materials circumferentially equally divided into a predetermined number of divisions greater than one; and the least common multiple being N for the number of slots and the number of magnetic poles, and the least common multiple being M for the number of the slots and the number of the divisions, then N is equal to M, wherein the stator core includes: a plurality of outer teeth protruded outward of the yoke, and a plurality of inner teeth protruded inward of the yoke, which is formed with outer slots between the outer teeth being adjacent to each other and with inner slots between the inner teeth being adjacent to each other; the rotor comprises: an outer rotor rotatably held against the stator, having an outer rotor core and a plurality of magnetic poles held by the outer rotor core, and confronting tip ends of the outer teeth via gaps outside the stator; an inner rotor rotatably held against the stator, having an inner rotor core and a plurality of magnetic poles held by the inner rotor core, and confronting tip ends of the inner teeth via gaps inside the stator; the outer rotor core is formed by outer rotor core materials circumferentially equally divided into the predetermined number of divisions, the inner rotor core is formed by inner rotor core materials circumferentially equally divided into the predetermined number of divisions, and the least common multiple being Nout for the number of the outer slots and the number of the magnetic poles of the outer rotor, and the least common multiple being Mout for the number of the outer slots and the number of divisions of the outer rotor core, the least common multiple being Nin for the number of the inner slots and the number of the magnetic poles of the inner rotor, and the least common multiple being Min for the number of the inner slots and the number of divisions of the inner rotor core, then at least Nout is equal to Mout, or Nin is equal to Min.