| 摘要 |
PURPOSE:To reduce cost by mounting tabular conductors as a rotor and a stator, forming a capacitor between the rotor and the stator and obtaining the signal of electric-capacity change proportional to the number of revolutions. CONSTITUTION:A driver circuit for a bipolar type brushless DC motor is shaped by a three-phase driving coil 6, and a first drive transistor (Tr) group and a second drive Tr group forming current paths to the three-phase coil 6 from a DC power. The position of a rotor 1 is detected by Hall elements 4, and switching is conducted by a changeover controller. A capacitor is used for detecting frequency, and electric capacity varies by frequency proportional to the number of revolutions of the motor. The capacitor is constituted by utilizing a gap between the rotor 1 and a stator 5'. Accordingly, speed can be detected without fitting a magnetic pole section to the outer circumferential section of the rotor. |
