| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent degradation in fuel economy of internal combustion engines, resulting from rich spike control. SOLUTION: During lean combustion, NOx in the exhaust of an engine 11 is trapped on a catalyst 33b, and an amount of NOx thus adsorbed equaling or exceeding an allowable value triggers rich spike control that offers temporary rich combustion. The rich combustion of the rich spike control reduce NOx thus adsorbed on the catalyst 33b into N2 with the aid of HC and the like, or removes the NOx from the catalyst 33b. Although the NOx reduction efficiency by the rich combustion is lowered as the amount of NOx trapped on the catalyst 33b falls close to zero, the rich spike control is finished, when the amount of trapped NOx dips to a preset value over zero.</p> |
