PURPOSE: To prevent the danger of explosive ignition and improve safety and ignition characteristics by providing a suction quantity adjusting means which regulates a suction quantity to minimum and constructing this suction quantity adjusting means so as to be released at a level lower than an ignition detecting level, a blow out detecting level, etc.
CONSTITUTION: In a state in which a solenoid damper 10a closes the hole of a solenoid damper 10b but does not close entirely, a small amount of combustion air flows in through small holes 10c around the main hole of the solenoid damper 10a. In such a state of insufficient air, gas mixture of vaporized fuel and a small amount of combustion air is ignited by an igniter 7. When ignited, a combustion flame is detected by a flame rod 9 and a flame current is detected by a resistor 19. If the level of a flame voltage detected by the resistor 19 becomes lower than the standard voltage of a comparator 29, the solenoid damper 10a becomes off and normal combustion air is supplied.
MAEHARA NAOYOSHI
UNO TAKASHI
