Air/fuel ratio control apparatus for an internal combustion engine

摘要

Achieved is an air/fuel ratio control apparatus for an internal combustion engine where the purification ability of a three-way catalyst is brought back to an optimal state immediately after a fuel cut by expelling oxygen absorbed by the three-way catalyst due to the fuel cut without being affected by the oxygen absorption amount of the three-way catalyst before the fuel cut. The air/fuel ratio control apparatus for an internal combustion engine includes: a three-way catalyst that is provided in an exhaust system of the internal combustion engine and removes poisonous substances present in an exhaust gas; an oxygen concentration sensor that detects an oxygen concentration of the exhaust gas passed through the three-way catalyst; a fuel injection valve that injects fuel into the internal combustion engine; an injection amount adjusting means for adjusting an amount of the injected fuel so that an air/fuel ratio becomes a predetermined air/fuel ratio; an fuel injection suspending means for suspending the fuel injection; and a correction factor setting means for setting an air/fuel ratio enrich correction factor according to a difference between an output voltage of the oxygen concentration sensor and a predetermined target voltage set for the oxygen concentration sensor, where the injection amount adjusting means performs air/fuel ratio enrich processing.