US Patent 7362031 Electric motor

An electric motor has an armature rotatably accommodated inside a motor housing and a pair of magnets fixed to an inner surface of the motor housing so as to face the armature. The armature has an armature core 17 fixed to a rotating shaft 16, and ten slots S1 to S10 formed on the armature core accommodate coils. These slots S1 to S10 are of four types that are different in shape, thereby enhancing a lamination factor of each coil. Also, these slots S1 to S10 are formed so as to be tilted in a rotating direction with respect to an axial direction of the rotating shaft 16. Therefore, a magnetic imbalance caused by the slots S1 to S10 being formed in varying shapes is uniformized.