Patent ID: 7742870

Claim:
An air-fuel ratio control device of an internal combustion engine, the air-fuel ratio control device comprising: an air-fuel ratio feedback control means for performing feedback control of a fuel quantity injected into the internal combustion engine based on a sensing value of an air-fuel ratio sensor sensing an air-fuel ratio of exhaust gas of the internal combustion engine; a storage means for storing data of past feedback correction amounts calculated by the air-fuel ratio feedback control means in a chronological order; a dead time sensing means for sensing a dead time necessary for change in the fuel quantity injected into the internal combustion engine to appear as change in an output of the air-fuel ratio sensor; a response time sensing means for sensing a response time of the air-fuel ratio sensor; and a control gain correcting means for correcting a control gain of the feedback control performed by the air-fuel ratio feedback control means in accordance with the response time sensed by the response time sensing means, wherein the air-fuel ratio feedback control means calculates a present feedback correction amount by using the data of the past feedback correction amounts stored in the storage means, the sensing value of the air-fuel ratio sensor and a target air-fuel ratio, the air-fuel ratio feedback control means includes a changing means for changing the number of elements constituting the data of the past feedback correction amounts used for calculating the present feedback correction amount in accordance with the dead time sensed by the dead time sensing means, the response time sensing means senses a lean direction response time, which is a response time in the case where the output of the air-fuel ratio sensor changes from a rich side to a lean side, and a rich direction response time, which is a response time in the case where the output of the air-fuel ratio sensor changes from the lean side to the rich side, respectively, and the control gain correcting means corrects the control gain in accordance with the lean direction response time when the output of the air-fuel ratio sensor changes from the rich side to the lean side and corrects the control gain in accordance with the rich direction response time when the output of the air-fuel ratio sensor changes from the lean side to the rich side.