Patent ID: 6920388

Claim:
An apparatus for controlling the air-fuel ratio of an internal combustion engine having an exhaust gas sensor disposed downstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine, for detecting the concentration of a particular component in an exhaust gas which has passed through the catalytic converter, estimating means for sequentially generating data representative of an estimated value of an output of said exhaust gas sensor after a set dead time, using the set dead time which is set as a dead time of an exhaust system ranging from a position upstream of said catalytic converter to said exhaust gas sensor and including said catalytic converter, manipulated variable generating means for generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter to converge the output of said exhaust gas sensor to a predetermined target value, using the data generated by said estimating means, and air-fuel ratio manipulating means for manipulating the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine depending on the manipulated variable, comprising: flow rate data generating means for sequentially generating data representative of a flow rate of the exhaust gas supplied to the catalytic converter, and dead time setting means for variably setting a value of said set dead time depending on the value of the data generated by said flow rate data generating means; wherein a predetermined model of said exhaust system is established for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor via a dead time element and a response delay element of said set dead time from the air-fuel ratio of the exhaust gas which enters said catalytic converter, further comprising identifying means for sequentially identifying the value of a predetermined parameter of said model using the value of the set dead time set by said dead time setting means; wherein said estimating means generates the data representative of the estimated value of the output of said exhaust gas sensor using the identified value of said parameter determined by said identifying means, according to a predetermined estimating algorithm which is constructed based on the model of said exhaust system; and wherein said identifying means determines the identified value of the parameter of the model of said exhaust system for limiting the identified value to a value within a predetermined range depending on the value of the data generated by said flow rate data generating means.