| 摘要 |
<p>PROBLEM TO BE SOLVED: To accurately detect that the amount of oxygen stored in an exhaust emission control catalyst reaches zero while suppressing the worsening of exhaust emission associated with an error even if occurring in the detection.SOLUTION: A control device for an internal combustion engine includes an exhaust emission control catalyst 20, and a downstream side air-fuel ratio sensor 41. The control device further includes feedback control means for feedback controlling the supply amount of fuel to be supplied to a combustion chamber of the internal combustion engine so that the air-fuel ratio of exhaust gas to flow into the exhaust emission control catalyst is a target air-fuel ratio, target air-fuel ratio setting means for setting the target air-fuel ratio, and deterioration degree detecting means for detecting the deterioration degree of the exhaust emission control catalyst. In the case that the target air-fuel ratio is set to be a rich air-fuel ratio, when the air-fuel ratio output by the downstream side air-fuel ratio sensor is a rich determined air-fuel ratio or lower, the target air-fuel ratio setting means changes over the target air-fuel ratio into a lean air-fuel ratio. The rich determined air-fuel ratio is set to be less different from a theoretical air-fuel ratio as the deterioration degree detected by the deterioration degree detecting means is higher.</p> |
