| 摘要 |
<P>PROBLEM TO BE SOLVED: To calculate the supplied amount of urea while taking release of NOx while the temperature of an NOx storage catalyst is increased into consideration. <P>SOLUTION: An NOx selective reduction catalyst 14 is disposed in an engine exhaust passage, and the NOx storage catalyst 12 is disposed in the engine exhaust passage on the upstream side of the NOx selective reduction catalyst 14. When the stored NOx amount of the NOx storage catalyst 12 exceeds a predetermined allowable value, the NOx storage catalyst 12 is heated to release NOx from the NOx storage catalyst 12. The supplied amount of urea is reduced by the reduced amount of the stored NOx amount calculated for the supplied amount of urea determined by the operating state of the engine, and increased by the reduced amount of the released NOx amount calculated for the supplied amount of urea determined by the operating state of the engine. <P>COPYRIGHT: (C)2009,JPO&INPIT |
