| 摘要 |
PURPOSE:To realize burn-out when there is no input signal, by applying DC voltage having negative polarity to a piezoelectric element flapper from a separate DC voltage source when an input electric signal is not applied. CONSTITUTION:A series circuit consisting of a resistor RA and a condenser CA is connected to a full wave rectifier circuit 10 in place of the discharge resistor Ra thereof. When an input current Ii is flowed and a power source is normal, constant DC voltage E1 is obtained in the output of the circuit 10 while DC voltage E2 corresponding to the current Ii is obtained in the output of the full wave rectifier circuit 10 and voltage E2-E1 is applied to a piezoelectric element flapper 2 to obtain the output pressure corresponding to the current Ii. In this operative state, when the capacitor CA is charged so as to reach voltage E1 through the resistor RA and current Ii is cut off, the charge voltage E1 of the capacitor CA is supplied to the flapper 2 in place of the circuit 10. On the other hand, because voltage E2 comes to zero, voltage -E1 is applied to the flapper 2 to displace the same so as to keep away from the nozzle 3 to lower back pressure and output pressure is fallen to 0kg/cm<2> by this method, burn-out can be realized. |
