METHOD FOR CONTROLLING SUPPLY OF CURRENT TO RESISTANCE HEAT GENERATION TYPE ELECTRIC HEATER OF OXYGEN SENSOR

摘要

PURPOSE:To effectively avoid the lowering in the durability of a heater, by controlling power supplied to the heater so as to limit the current supplied to the heater to a predetermined value or less by detecting said current supplied to the heater. CONSTITUTION:A microcomputer 50 is operated upon the reception of the supply of the current from a battery power source 17 and determines the fuel jet amount per one cycle corresponding to the sucking quantity of air per one cycle according to the output of a crank angle sensor 19 and that of a suction pipe pressure sensor 20 and further corrects the fuel jet amount on the basis of the oxygen concn. of exhaust gas detected by an oxygen sensor 21 so as to bring the air/fuel ratio of the gaseous mixture supplied to a combustion chamber to the predetermined objective air/fuel ratio. An electric heater 28 is provided to the oxygen sensor 21 to hold the same to a predetermined value equal to or higher than the active temp. thereof. In addition, power to the electric heater 28 is controlled by the switching action of a transistor 54 so that the current supplied to the heater 28 is limited to a predetermined value or less.