| 摘要 |
<p>PROBLEM TO BE SOLVED: To rapidly recover temporary deterioration of a catalyst by controlling an air-fuel ratio to a rich air-fuel ratio of a lean side more than a stoichiometric air-fuel ratio and a prescribed rich air-fuel ratio, when a detected operating condition is in a deterioration recover treatment region which is set in a high load region, and a deterioration degree of a detected catalyst is a prescribed value or more. SOLUTION: In the case where deterioration of a catalyst is recover-treated on an operation, fuel cut control is stopped at the time of deceleration so as to prevent advance of temporary deterioration (S11). On the basis of a reversal frequency Fr, a deterioration degree Rm and a deterioration recover treatment temperature Ta in several steps of a catalyst 1 are read out from a table (S12), (S13). The treatment temperature Ta is set higher toward that the deterioration degree Rm of the catalyst 1 is increased, and the deterioration recover treatment is set in such a way that it is treated in a same time regardless of the deterioration degree Rm. It is thus possible to prevent deterioration recover treatment control from continuing more than necessary, and it is also possible to precisely control an exhaust temperature at the time of deterioration recover treatment.</p> |
