To prevent the failure in operation of a solenoid by comprising an accumulation amount detecting means for detecting an accumulation amount of an accumulator, and forbidding the energization of the solenoid when the output of this accumulation amount detecting means is below a predetermined value.

The voltage necessary for the close energization without recharging after the termination of the open energization is determined on the basis of the capacity of a capacitor 4 and the resistance value of a solenoid 10. The open energization is forbidden until the predetermined voltage is obtained. Whereby the voltage of the capacitor 4 is sufficient in the open energization, and the close energization can be executed with the remained charge of the capacitor 4 even when the close energization is required immediately after the open energization. That is, an open state is not continued regardless of a time when a battery is demounted. In a case when the accumulation amount is not satisfied, the solenoid is not energized, so that the lowering of the accumulation amount caused by the frequent energization of solenoid can be prevented, which prevents the failure in operation of the solenoid 10.