Motor with permanent magnet

A motor of an inner-rotor type comprising:

• a stator including a plurality of teeth for receiving windings, and a yoke connected to each tooth;
• and
• a rotor having permanent magnets facing said stator;
• wherein an inner wall surface of each tooth faces said rotor with an air-gap therebetween,
• wherein each tooth is separated from an adjacent tooth by a slot-open-section extending between a tailing end of the tooth and a leading end of the adjacent tooth,
• wherein the inner wall surface of each tooth has an arc extending 90/N degrees from a center of the slot-open-section toward the tailing end, N representing an integer not less than 1,
• wherein the air-gap at the tailing end of each tooth is greater than the air-gap at the leading end of each tooth,
• wherein the inner wall surface of each tooth includes a straight-line tailing section extending 30/N degrees from the center of the slot-open-section toward the leading end, and
• wherein the straight-line tailing section extends tangentially from the arc.