| 摘要 |
An air-fuel ratio control apparatus of an internal combustion engine according to the present invention is provided with an oxygen storage amount estimator for estimating an oxygen storage amount of an exhaust purifying catalyst and air-fuel ratio control means for controlling an air-fuel ratio, based on the oxygen storage amount. An upper threshold and a lower threshold are set for the oxygen storage amount, and the air-fuel ratio controller performs such control that, when the oxygen storage amount is larger than the upper threshold, the controller controls the air-fuel ratio to a rich region and that, when the oxygen storage amount is smaller than the lower threshold, the controller controls the air-fuel ratio to a lean region. Since this control makes the oxygen storage amount vary between the upper threshold and the lower threshold (within a predetermined range), it is feasible to promote activation of the exhaust purifying catalyst, so as to keep purification performance of the exhaust purifying catalyst high, and to implement stable control of air-fuel ratio.
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