PURPOSE: To increase safety in a combustion apparatus, by forcibly closing an open/close valve for fuel after a delay time, which starts from the time when no signal is detected, and is determined by the opening of a proportional valve at that time, has passed, in case that a combustion detecting signal does not come out through a fuel opening signal is outputted.
CONSTITUTION: When a fuel valve is opened by a command from a microcomputer 1 and a fuel opening signal S2 is output, a capacitor 62 starts discharging by a transistor 64 being turned OFF, in the same manner as an ignition behavior starts in the normal state. But if the fuel is not ignited within a specified time, the potentials E+ on both sides of a capacitor 62 gradually drop. At the last step, a comparator 61 inverts the logic of its output signal Sr, changing it into an abnormal sensing signal Sr of significant logic "L". When this signal is outputted, a switching means 6 shown as a pnp transistor is turned ON, forcibly dropping a command signal S1 for a fuel valve opening to the ground, oututting a valve closing command to a fuel valve open/close circuit 4, forcibly closing the fuel valve.
TAKAMI SATORU
UCHISE YOSHIBUMI
