Patent ID: 8970080
Filing Date: 2015-03-03
Classification: H02K

Abstract:
1. An electric motor comprising: a stator including a yoke, a stator core having a plurality of inside teeth projecting in the inside direction of the yoke forming a plurality of inside slot open angles and a plurality of outside teeth projecting in the outside direction of the yoke forming a plurality of outside slot open angles, and a winding wound on the stator core; an inside rotor opposite to the end face of leading ends of the inside teeth across a gap, including an inside rotor core rotatably held on the stator, and a plurality of poles held on the inside rotor core forming a plurality of inside pole angles; and an outside rotor opposite to the end face of leading ends of the outside teeth across a gap, including an outside rotor core rotatably held on the stator, and a plurality of poles held on the outside rotor core forming a plurality of outside pole angles, wherein the inside rotor generates an induced voltage at a predetermined speed and causes an inside cogging torque dependent on a ratio of the inside slot open angle to the inside pole angle, and the outside rotor generates another induced voltage at the predetermined speed and causes an outside cogging torque dependent on a ratio of the outside slot open angle to the outside pole angle, wherein the ratios are adjusted so that (i) the inside cogging torque and the outside cogging torque substantially cancel each other in inverted phases and (ii) the sum of the induced voltage due to the inside rotor at the predetermined speed and the induced voltage due to the outside rotor at the predetermined speed is maximized.