Control device for engine compartment cooling

Claim 1

A control device for an automobile comprising: a first switching circuit for permitting and inhibiting power supply to an engine compartment exhaust fan for exhausting air from an engine compartment; a processing block for controlling ON and OFF states of the first switching circuit; a power source circuit for producing a source voltage to the processing block from electric power of an on-vehicle battery supplied through a key switch; a temperature sensor for detecting an air temperature level in the engine compartment; a power source sensor for generating an output corresponding to one of ON and OFF states of the key switch; and a second switching circuit provided between the on-vehicle battery and the power source circuit, for permitting power supply through a by-pass line to the power source circuit in response to a command from the processing block; wherein said processing block includes first means for turning on the second switching circuit before the key switch is turned off, second means for turning on and off the first switching circuit on the basis of an output of the air temperature sensor, third means for determining the ON and OFF states of the key switch on the basis of an output of the power source sensor, and fourth means for turning off the second switching circuit after the engine compartment exhaust fan is kept controlled for a predetermined time period when the key switch is determined to be in the OFF state; and wherein said fourth means comprises means for starting a cooling timer when the key switch is determined in the OFF state, means for turning off the second switching circuit if control of the engine compartment exhaust fan to cool the engine compartment to a desired temperature is completed upon timeout of the cooling timer, and for starting an extended timer if control of the engine compartment exhaust fan to cool the engine compartment to the desired temperature has not been completed, means for turning off the second switching circuit immediately after the control of the exhaust fan to cool the engine compartment to the desired temperature is completed during counting of the extended timer, and means for turning off the second switching circuit upon timeout of the extended timer even if the control of the engine compartment exhaust fan to cool the engine compartment to the desired temperature has not been completed.