Patent ID: 7409284

Claim:
An individual-cylinder air-fuel ratio estimation apparatus for an internal combustion engine, comprising: an air-fuel ratio sensor which is installed in a confluent exhaust pipe with exhaust manifolds of a plurality of cylinders of the internal combustion engine connected thereto, and which detects an air-fuel ratio of gases exhausted from the individual cylinders; and an individual-cylinder air-fuel ratio estimation means for estimating air-fuel ratios of the individual cylinders on the basis of the air-fuel ratio of the gases as detected by the air-fuel, ratio sensor; and a means for creating a plurality of individual-cylinder air-fuel ratio estimation models by modeling relations between air-fuel ratios of the individual cylinders and detection values of the air-fuel ratio sensor, separately for the respective cylinders, the individual-cylinder air-fuel ratio estimation means estimating the air-fuel ratios of the individual cylinders by employing the individual-cylinder air-fuel ratio estimation models which are different for the respective cylinders.