| 摘要 |
<p>PROBLEM TO BE SOLVED: To precisely diagnose deterioration of a catalyst due to smoke and to restore catalyst performance by increasing a catalyst inlet temperature when smoke deterioration occurs, in an engine to effect stratification combustion. SOLUTION: A decision value to indicate the degree of deterioration due to smoke of a catalyst according to an engine load, an engine rotation speed, or a catalyst inlet temperature is set, and the decision value is integrated in order, (S3). A fluctuation frequency of oxygen concentrations in upper stream and downstream of the catalyst is compared to diagnose the deterioration of the catalyst (S1). When deterioration of the catalyst is diagnosed through the diagnosis, by comparing an integrated value Re of a decision value and a given value with each other, the deterioration of the catalyst is diagnosed to be caused by accumulation of smoke or not (S4). When smoke deterioration is diagnosed, stratification combustion and uniform lean combustion are prohibited and a catalyst inlet temperature is increased and catalyst performance is restored (S6) through separation and burning of smoke accumulated on the catalyst.</p> |
