AIR-FUEL RATIO CONTROLLER FOR INTERNAL COMBUSTION ENGINES

摘要

An air-fuel ratio controller for internal combustion engines capable of properly rating the deteriorated conditions of a catalyst device while ensuring a required purifying performance of the catalyst device provided in an exhaust passage of the internal combustion engine, wherein a target air-fuel ratio KCMD of an exhaust gas on the upstream side of the catalyst device (3) is sequentially determined so that outputs VO2/OUT from an O2 sensor (6) downstream the catalyst device (3) converge to a preset target value VO2/TARGET, and a fuel supply amount to the engine (1) is controlled so that outputs KACT from an air-fuel sensor (5) converge to this target air-fuel ratio KCMD. While thus controlling, a deterioration rating linear function DOLLAR G(s) value using as a variable component time-series data of outputs VO2/OUT from the O2 sensor (6) is determined, and the central value of the square sigma <2> of the value is determined as a deterioration rating parameter, the deteriorated conditions of the catalyst device (3) being rated based on this deterioration rating parameter.