| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately perform NOx reduction treatment by controlling the way of the dispersion of a reducer in an NOx catalyst in an exhaust emission control system in which the amount of exhaust gas flowing in the storage/reduction type NOx catalyst is reduced and NOx stored in the NOx catalyst is reduced by supplying the reducer into the NOx catalyst. <P>SOLUTION: Air-fuel ratio detection means are disposed on the upstream side and downstream side of the storage/reduction type NOx catalyst. The adding time of the reducer is changed so that a difference between an air-fuel ratio detected by an air-fuel ratio detection means disposed on the upstream side of the NOx catalyst and an air-fuel ratio detected by an air-fuel ratio detection means disposed on the downstream thereof becomes an aimed value in a prescribed period after the amount of the exhaust gas flowing into the NOx catalyst is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
