| 摘要 |
PURPOSE:To prevent chattering noise in a driving device due to drag torque, by flowing a reverse excitation current in a coil and removing its residual magnetism. CONSTITUTION:If car speed becomes not higher than preset car speed, a buffer 47 outputs a signal of high level, then an NOR gate 48 outputs a signal of low level to turn off transistors 40, 41 and flow a current by the order of a c b e. Accordingly, a current of reverse polarity, smaller than a rated current at a clutch directly coupled condition, flows in a coil 7, and a reverse excitation current flows to remove residual magnetism due to the hysteresis of a magnetic material in a drive member 8 and driven member 10 of an electromagnetic clutch 1. Drag torque of the driven member, so-called drag, due to the drive member 8 is not caused by said reverse excitation, then a noise of chattering sound or the like in a driving device is not caused in the condition of a car not in motion. |
