Patent ID: 7162359

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, identifying means for sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of said catalytic converter to said exhaust gas sensor and including said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor via at least a dead time element from the air-fuel ratio of the exhaust gas which enters said catalytic converter, manipulated variable generating means for sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model to converge the output of said exhaust gas sensor to a predetermined target value, 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, said apparatus comprising: flow rate data generating means for sequentially generating data representative of a flow rate of the exhaust gas flowing through the catalytic converter; and dead time selling means for variably selling a set dead time as the dead time of a dead time element of the model of said exhaust system depending on the value of the data generated by said flow rate data generating means, wherein said identifying means identifies the value of said parameter according to an algorithm for minimizing an error between the output of said exhaust gas sensor in the model of said exhaust system and an actual output of said exhaust gas sensor, using the value of the set dead time set by said dead time setting means, said apparatus further comprising: means for variably setting the value of a weighted parameter of said algorithm depending on the value of the data generated by said flow rate data generating means.