| 摘要 |
<p>PROBLEM TO BE SOLVED: To keep satisfactory NOx purification function and reduce catalyst temperature to a specified temperature range fast, when a shift to a lean operation range is made in a condition where the temperature of an NOx catalyst is higher than the specific temperature range with high NOx absorption performance. SOLUTION: In an engine equipped with an NOx catalyst 35 that absorbs NOx in an oxygen excess atmosphere and an injector 22 that directly injects the fuel in a combustion chamber, this controller comprises delay means 51, by which a change to a lean air-fuel ratio when a shift to a lean operation range is made with the temperature of the NOx catalyst not less than the predetermined value. Also, the controller is provided with an air-fuel ratio control means 52, which makes the air-fuel ratio approximately theoretical one by adjusting the amount of intake air during the delay time, fuel injection control means 53 which injects the fuel from an injector on intake stroke during the delay time, and exhaust emission temperature reducing means 54, which lowers the temperature of the exhaust emission by EGR and the like during the delay time.</p> |
