Patent ID: 7647157

Claim:
A control device for an internal combustion engine having a catalyst arranged in an exhaust passage thereof, the control device comprising: a downstream air-fuel ratio sensor for outputting a detection signal indicative of an air-fuel ratio of exhaust gases on a downstream side of the catalyst arranged in the exhaust passage; deviation-calculating means for calculating a deviation between an output from said downstream air-fuel ratio sensor and a predetermined target value at a predetermined deviation calculation period; air-fuel ratio-calculating means for calculating a target air-fuel ratio of a mixture to be supplied to the engine so as to converge the output from said downstream air-fuel ratio sensor to the predetermined target value, according to the calculated deviation, based on any one of a Δ modulation algorithm, a ΔΣ modulation algorithm, and a ΣΔ modulation algorithm, at a predetermined air-fuel ratio calculation period shorter than the predetermined deviation calculation period; and air-fuel ratio control means for controlling an air-fuel ratio of the mixture to be supplied to the engine, according to the calculated target air-fuel ratio.