Patent Document ID: 20040003804
Application ID: 10600515
Patent Flag: 0

Claim One:
1. An air-fuel ratio control apparatus for controlling an air-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine having a plurality of cylinders so that the air-fuel ratio coincides with a target air-fuel ratio, said air-fuel ratio control apparatus comprising: an air-fuel ratio sensor provided at a position downstream of a joining portion of an exhaust manifold connected to said plurality of cylinders, said air-fuel ratio sensor for detecting an air-fuel ratio in exhaust; identifying means for identifying at least one model parameter of a controlled object model defined by a relation between the air-fuel ratio detected by said air-fuel ratio sensor and a fuel supply amount parameter that specifies a fuel supply amount to each cylinder of said engine, the at least one model parameter being identified corresponding to each cylinder of said engine; and air-fuel ratio difference determining means for determining a degree of differences between air-fuel ratios of air-fuel mixtures to be supplied to said plurality of cylinders, according to the at least one model parameter identified by said identifying means.