Patent ID: 6644017
Filing Date: 2003-11-11
Classification: F02D

Abstract:
A device for controlling an air-fuel ratio of an internal combustion engine comprising;a fuel injection valve for injecting fuel to said engine; a catalytic converter disposed in an exhaust pipe of said engine; an exhaust gas quantity sensor for detecting an exhaust gas quantity of said engine; an oxygen sensor disposed in the exhaust pipe on the upstream side of said catalytic converter for detecting an oxygen concentration in the exhaust gas; an oxygen quantity estimating unit that estimates an oxygen quantity stored in said catalytic converter based on said exhaust gas quantity and said oxygen concentration; a feedback control unit that feedback controls a fuel injection quantity by said fuel injection valve, so that said oxygen quantity approaches a target quantity; a misfire detecting unit that detects a misfire in said engine; a misfire period control prohibiting unit that, when an occurrence of misfire is detected, prohibits said fuel injection quantity control based on the oxygen concentration detected at that moment; a post misfire control prohibiting unit that prohibits said fuel injection quantity control based on the oxygen concentration detected at that moment, for a predetermined period of time from the end of misfire; a decreasing correction unit that forcibly corrects the fuel injection quantity to be decreased for said predetermined period of time from the end of misfire; and a control starting unit that starts the fuel injection quantity control based on said oxygen quantity at the end of the forcible decreasing correction of said fuel injection quantity.