PURPOSE: To realize a clean firing by a method wherein an electromagnetic pump is controlled, so that an oil feeding amount of liquid fuel from a firing start to finish may be decreased steppingly through at least two steps, and finally the oil feeding amount becomes ordinary after the firing is completed.
CONSTITUTION: After an operation switch is turned ON, heating of an evaporator 11 by an electric heater 13 reaches a prescribed temperature, and a prepurge is done by an ignition device IG. Next, an oil feeding amount which is set to an amount twice as much as the ordinary one, and an electromagnetic pump 16 is driven at a pulse frequency corresponding to the oil feeding amount (at 200% driving). When the 200% driving of the electromagnetic pump 16 continues for 0.5 second, the pump driving is switched to 110% driving, which corresponds to more than ordinary by 10%. The oil feeding is continued and a finish of firing is waited. When the firing finish is determined by a current flowing to a flame rod FL, the ignition device IG is stopped, and the pump driving is switched to 100% driving. By this, an oil feeding amount to the evaporator 11 is set to the one for ordinary operation. As a result, red fire or bad smell does not occur at the time of firing.
ARAKI TAKASHI
NEMOTO TAKUO
