EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To effectively prevent deterioration of fuel economy by prohibiting execution of NOx purge in a state where an exhaust lambda value is hard to lower.SOLUTION: An exhaust emission control system includes: an NOx occlusion and reduction type catalyst 32 that occludes NOx in exhaust gas in an exhaust lean state and reduces the occluded NOx for purification in an exhaust rich state; an NOx purge control section 60 for executing NOx purge for reducing the NOx occluded in the NOx occlusion and reduction type catalyst 32 for purification by causing exhaust gas to become a rich state; and an NOx purge prohibiting processing section 70 for prohibiting the execution of the NOx purge by the NOx purge control section 60 when fuel injection amount of an internal combustion engine 10 is smaller than a predetermined lower limit injection amount threshold value.SELECTED DRAWING: Figure 1