ESTIMATION METHOD OF NOX OCCLUSION AMOUNT IN RELATION TO METHOD OF ESTIMATING NOX OCCLUSION AMOUNT OF NOX OCCLUSION CATALYST INTERPOSED IN EXHAUST PASSAGE OF ENGINE

摘要

PURPOSE: An estimation method of the NOx occlusion amount is provided to estimate the NOx occlusion amount of a NOx occlusion catalyst with high accuracy by reflecting the newest state in the model of a catalyst. CONSTITUTION: An estimation method of the NOx occlusion amount comprises steps of compensating for each modulus by sequentially correcting for each modulus of a polynomial expression in lean operation(S1); maintaining each modulus if start of rich operation is determined(S2,S3); comparing an actually measured value and an estimated value of a NOx purification rate and determining the difference is over a limit value if rich operation is finished(S4,S5); and continuing renewal of each modulus in lean operation if the difference between the actually measured value and estimated value of the NOx purification rate is under the limit value, and correcting the NOx occlusion amount to a value calculated from a formula if the difference is over the limit value and returning(S6).