| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that NOx reduction rate is deteriorated when addition of reducing agent is started when a NOx storage reduction catalyst is regenerated with shutting off flow of exhaust gas. <P>SOLUTION: An exhaust emission control device comprises a pair of NOx storage reduction catalysts 4, 4 installed in the middle of an exhaust pipe 3 in parallel, exhaust change over valves 6, 7 distributing exhaust gas 2 to either of NOx storage reduction catalysts 4, 4, a reducing agent adding means (fuel reforming device 9) individually adding reducing agent (reformed gas 10) to each inlet side of the NOx storage reduction catalysts 4, 4, and a valve open close control means (control device 13) inhibiting a rapid increase of desorbing NOx by variably controlling open close speed of the exhaust change over valves 6, 7 according to operation states. <P>COPYRIGHT: (C)2009,JPO&INPIT |
