| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent generation of white smoke and deterioration of fuel economy by appropriately correcting an interval time of NOx purge in accordance with NOx occlusion amount when a catalyst is in an inactive state.SOLUTION: An exhaust emission control system includes: a NOx occlusion reduction type catalyst 32; a catalyst temperature estimation section 115; a NOx storage amount estimation section 113; a regeneration control section 100 for executing catalyst regeneration for recovering NOx occlusion capacity of the NOx occlusion reduction type catalyst 32 by making exhaust gas rich; an interval setting section 118 for setting a target interval time from completion of catalyst regeneration to start of next catalyst regeneration; a catalyst regeneration start processing section 110 for starting the next catalyst regeneration when the NOx occlusion amount reaches a threshold value or more and elapsed time from the completion of the catalyst regeneration reaches the target interval time; and an interval target value correction section 119 for elongating the target interval time for correction on the basis of the NOx occlusion amount when the catalyst temperature is lower than a predetermined catalyst active temperature.SELECTED DRAWING: Figure 4 |
