| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device for effectively suppressing NHslip while improving the NOx eliminating rate.SOLUTION: The exhaust emission control device having an LNT 31 and an SCR 32 arranged in an exhaust passage 12 of an internal combustion engine 10 starting from the exhaust upstream side, includes an NHgeneration amount estimating part 41 for estimating the generation amount of ammonia generated by the LNT 31 under a rich atmosphere, an NHconsumption amount estimating part 42 for estimating the consumption amount of the ammonia required for reducing NOx flowing from the LNT 31 into the SCR 32 under a lean atmosphere, an NHadsorption amount estimating part 43 for estimating the adsorption amount of the ammonia adsorbed by the SCR 32 from a difference between the generation amount of the ammonia and the consumption amount of the ammonia, and an NHgeneration control part 44 for controlling an exhaust air-fuel ratio to meet the rich atmosphere to the extent that the adsorption amount of the ammonia is the predetermined upper-limit adsorption amount of the ammonia or lower so that the LNT 31 generates the ammonia. |
