EXHAUST POST-TREATMENT DEVICE OF DIESEL ENGINE

摘要

PROBLEM TO BE SOLVED: To provide a device which can suppress the deterioration of a NOx purification rate even if a load is varied immediately after the start of rich spike treatment.SOLUTION: The exhaust post-treatment device of a diesel engine comprises: means (21) for setting an air excess rate of exhaust in initial treatment to a rich-side first fundamental air excess rate when a regeneration time of a NOx trap catalyst (15) comes; means (21) for setting an air excess rate of exhaust in post-treatment to a second fundamental air excess rate in the vicinity of 1.0 when the air excess rate of the exhaust is set to the first fundamental air excess rate; means (21) for predicting a remaining oxygen amount of the NOx trap catalyst by using a change speed of the second air excess rate when the second air excess rate detected by second air excess rate detection means crosses the vicinity of 1.0 from a lean side while the air excess rate of the exhaust is set to the first fundamental air excess rate; and means (21) for controlling a supply amount of a reducer in the post-treatment on the basis of the remaining oxygen amount which is predicted by the remaining oxygen amount prediction means.