DC MOTOR

PROBLEM TO BE SOLVED: To provide a DC motor with motor rated power smaller than that of a normal field coil field motor, in which the frictional torque and cogging torque are substantially zero during non-energization. SOLUTION: A magnet 12 is arranged in a tubular yoke 11 and a stator 2 is arranged on the inner circumferential side of the magnet 12. The stator 2 has a field pole portion 14 connected magnetically with the magnet 12, and a coupling core portion 15 for connecting between the field pole portions 14 magnetically and applied with a field coil 16. On the inner circumferential side of the stator 2, a rotor 3, having a plurality of teeth 25 applied with an armature coil 23, is arranged rotatably. When the field coil 16 is nonconducting, a magnetic circuit X passing through adjacent field pole portions 14, the coupling core portion 15 and the yoke 11 is formed between adjacent magnets 12. Since the magnetic flux of the magnet 12 is bypassed by the coupling core portion 15 and does not to pass through the rotor 3, magneto-frictional torque and cogging torque will not be generated during energization. COPYRIGHT: (C)2007,JPO&INPIT