| 摘要 |
PROBLEM TO BE SOLVED: To improve the elimination rate of a NOx catalyst.SOLUTION: An exhaust emission control system, which includes a selective reduction type NOx catalyst provided in an exhaust passage of an engine, calculates a basic injection timing θb on the basis of the operating condition of the engine (S101), estimates a NOx elimination rate η on the basis of the inlet gas temperature of the NOx catalyst, the ammonia adsorption amount of the NOx catalyst, a NOx mass flow amount in the NOx catalyst, and a NO2/NOx rate in exhaust gas supplied to the NOx catalyst (S102), calculates a reference NOx elimination rate η0 on the basis of the operating condition of the engine (S103), calculates an injection timing correction amount Δθ on the basis of a difference Δη between the NOx elimination rate η and the reference NOx elimination rate η0 (S104, S105), and corrects the basic injection timing θb using the injection timing correction amount Δθ (S106).SELECTED DRAWING: Figure 2 |
