| 摘要 |
PURPOSE:To reduce the irregular torque by composing a current flowed to the stator coil of a brushless DC motor to cancel the variation in a magnetic flux density. CONSTITUTION:A current converter 7 controls transistors 14-19 on the basis of a rotor magnet magnetism variation detection signal detected from Hall elements 1, 2, 3, flows a current to stator coils 20, 21, 22 to generate a torque. In this case, an additional impedance 55 is added to an impedance formed by the coils 20, 21, 22, and a control transistor 54 for controlling ON, OFF the impedance 55 is further provided. The output signals of drivers 8-13 are input through a differentiator made of a capacitor 23, a resistor 24, a waveform shaper 51, a delay circuit 52 and a monostable multivibrator 53 to the transistor 53 to turn it ON or OFF. In this case, a ripple of the torque generated by the variation in the magnetic flux density is cancelled by suitably setting the delay time of the circuit 52 and the duty given by the multivibrator 53. |
