| 摘要 |
<P>PROBLEM TO BE SOLVED: To highly accurately detect a rotation state of a DC motor regardless of the rotation speed while preventing torque fluctuation without providing a sensor such as an encoder. <P>SOLUTION: A soft magnetic protrusion 13 is provided on the inner peripheral face of a housing 10 of a motor 2. An air gap between a rotor core 20 and the housing 10 (including the protrusion 13) is changed by the protrusion 13 along with the rotation of the rotor core 20. Therefore, the magnetic resistance of the motor 2 is also changed, thereby changing an inductance between brushes 18, 19 of the motor 2 along with the rotation. On the other hand, a driving DC voltage is applied to the motor 2 from a DC power supply 6, however, an AC voltage from an AC component generating part 7 is superposed on the DC voltage. Consequently, the amplitude of an AC component included in a current flowing in the motor 2 is changed along with the rotation of the motor 2. A rotation-signal detecting part 4 generates a rotation pulse on the basis of amplitude changes of the AC component included in a conduction current. <P>COPYRIGHT: (C)2011,JPO&INPIT |
