| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the deterioration in cleaning efficiency following switching for recovery by changing over an air-fuel ratio in consideration of a catalyst temperature when the air-fuel ratio is switched for recovery of the cleaning rate of an NOx catalyst. SOLUTION: A catalyst temperature is estimated based on a driving state (an engine speed, a fuel injection amount or the like). The estimated catalyst temperature is corrected based on A/F, and fuel injection or ignition timing so as to increase estimation accuracy. This corrected estimated temperature is compared with a temperature necessary at the time of rich switching, and the operation of switching to rich is determined.</p> |
