| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for making fine cogging torque which may occur in a nine-slot eight-pole brushless DC motor, into stable fine cogging torque.SOLUTION: A polar tooth 10 around which a stator coil 3 is wound is provided in an outer circumferential part of a stator core 4, and a polar tooth surface 6 is provided at a position of the polar tooth 10 facing an inner circumferential surface of a rotor 2. On the polar tooth surface 6, a recess 5 is provided and width of the recess 5 in a circumference direction is settled within an angle range 1.5 to 2 times as large as an angle range in a circumference direction of a gap between neighboring polar teeth 10. A depth dimension D of the recess 5 in a diameter direction is 0.6% or more in an inner diameter of a permanent magnet 8, and an angle range watching the polar tooth 10 from a rotation shaft is 0.65 to 0.8 times as large as an angle obtained by dividing 360 degrees with the number of magnetic poles of the permanent magnet 8 of the rotor 2. |
