Air-fuel ratio control system for internal combustion engines

摘要

An air-fuel ratio control system for internal combustion engines has an air-fuel ratio sensor mounted in an exhaust pipe of an internal combustion engine and is adapted to produce an output indicative of the air-fuel ratio of a mixture supplied to the engine, on the basis of the composition of exhaust gases in the exhaust pipe. The air-fuel ratio sensor is provided with an electric heater for heating the air-fuel ratio sensor. The system further has an engine operation sensor adapted to sense, through detection of the state of the ignition switch, whether the engine has been stopped. When the engine operation sensor has sensed that the engine has been stopped, the electric heater is supplied with power for a predetermined time after the stop of the engine so as to evaporate any water content clinging to the air-fuel ratio sensor.