AIR-FUEL RATIO CONTROL APPARATUS AND AIR-FUEL RATIO CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE

摘要

An amount of fuel injected into an internal combustion engine is controlled to adjust an air-fuel ratio. An air-fuel ratio sensor is disposed upstream of a three-way catalyst. An ammonia sensor is disposed downstream of the three-way catalyst. Main feedback control based on the air-fuel ratio sensor is performed such that the air-fuel ratio of exhaust gas becomes close to a target air-fuel ratio in the neighborhood of a stoichiometric air-fuel ratio. Sub-feedback control is performed on the basis of an output value of the ammonia sensor.