| 摘要 |
PURPOSE:To enhance the operating speed of a hammer, by providing a recirculating circuit with another loop form circuit comprising a transistor. CONSTITUTION:When a hammer current reaches a preset value, a main transistor 6 is turned OFF under the function of a comparator 4. With the transistor 6 turned OFF, a counter-electromotive force is induced in a solenoid 1, and when the voltage applied between both ends of a Zener diode 3 by the counter- electromotive force exceeds the Zener voltage Vzd, a recirculating current flows. After the recirculating current is increased and the potential of a resistor 9 connected to the base of a transistor 10 reaches 0.7V (a preset voltage of the transistor 10), the transistor 10 conducts, and the recirculating current is permitted to flow through a main recirculating circuit. When a voltage inputted to the comparator 4 reaches a predetermined value, the main transistor 6 is turned ON, and the hammer current flows to the solenoid 1. Accordingly, the hammer current can be maintained to be substantially constant through switching of the main transistor 6.
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