| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a rich spike control performing good reduction of an NO<SB>x</SB>trap catalyst without deteriorating exhaust performance. <P>SOLUTION: In an internal combustion engine 1 having the NO<SB>x</SB>trap catalyst 11 in an exhaust passage, first enriching by decreasing an air excess ratio to a first target air excess ratio λ1 within a desorption range where NO<SB>x</SB>is desorbed from the NO<SB>x</SB>trap catalyst 11, and second enriching by decreasing the air excess ratio to be lower than the first target air excess ratio λ1 so as to reduce the NO<SB>x</SB>desorbed by the first enriching, are performed. When regeneration request is made, the first enriching is performed and start of the second enriching is prohibited until it is determined that the air excess ratio is shifted to the first target air excess ratio λ1 by the first enriching. On the other hand, when it is determined that the air excess ratio is shifted to the first target air excess ratio λ1, a control for starting the second enriching is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT |
