| 摘要 |
<P>PROBLEM TO BE SOLVED: To approximate a ratio of NO to NO<SB>2</SB>in exhaust gas 1:1. <P>SOLUTION: A NOx selective reduction catalyst 15 is disposed in an engine exhaust passage, an oxidation catalyst 12 is disposed in the engine exhaust passage upstream of the NOx selective reduction catalyst 15, and urea water is supplied to the NOx selective reduction catalyst 15 to reduce NOx. In an engine operation state where a conversion ratio from NO to NOx in the oxidation catalyst 12 suffers a loss, combustion is controlled so that the ratio of NO<SB>2</SB>to NOx in exhaust gas delivered from a combustion chamber 2 becomes 50% or more. <P>COPYRIGHT: (C)2009,JPO&INPIT |
