| 摘要 |
<P>PROBLEM TO BE SOLVED: To increase an NOx cleaning rate. <P>SOLUTION: In an exhaust emission control device, a catalyst 22 suitable for reducing NOx in exhaust gas by ammonia in excessive oxygen are disposed in exhaust passages 18, 21 of an internal combustion engine, and urea solution is supplied in the exhaust passage 21 upstream of the catalyst 22 through a flow control valve 33. When a temperature of the catalyst 22 is low, an amount of supplied urea has an equivalent ratio of one or more with respect to an NOx amount, and the urea contained in the urea solution is stored in the catalyst 22. In acceleration operation of the engine, when the temperature of the catalyst is within an ammonia discharge area, the amount of supplied urea is decreased to be the equivalent ratio of one or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
