Patent ID: 7356985

Claim:
A cylinder-by-cylinder air-fuel ratio controller for an internal combustion engine comprising: an air-fuel ratio sensor for detecting an air-fuel ratio of an exhaust gas of cylinders of the internal combustion engine, the air-fuel ratio sensor being mounted in an exhaust collection part in which the exhaust gas gathers and flows; cylinder-by-cylinder air-fuel ratio estimating means for estimating the air-fuel ratio of each cylinder on the basis of a detection value of the air-fuel ratio sensor at each of air-fuel ratio detection timings of the cylinders; and cylinder-by-cylinder air-fuel ratio control means for performing a control to make the air-fuel ratio of each cylinder coincide with a target air-fuel ratio on the basis of the estimated air-fuel ratio of each cylinder, and correcting means for correcting the air-fuel ratio detection timing in accordance with the target air-fuel ratio or the detected air-fuel ratio, wherein the correcting means corrects the air-fuel ratio detection timing so as to be retarded with respect to the air-fuel ratio detection timing at the stoichiometric air-fuel ratio when the target air-fuel ratio or the detected air-fuel ratio is lean, and the correcting means corrects the air-fuel ratio detection timing so as to be advanced with respect to the air-fuel ratio detection timing at the stoichiometric air-fuel ratio when the target air-fuel ratio or the detected air-fuel ratio is rich.