Controlling rich regeneration of NOx storage unit of lean burn engine, determines oxygen storage during first regeneration, regenerates at rate related to NOx stored, and desulfurizes when regeneration interval is slight

摘要

The quantity of oxygen in the unit is determined from the oxygen sensor peak signal amplitude, during a first regeneration process. NOx is removed from the unit at a frequency related inversely to the quantity of NOx stored in it. Desulfurization is carried out to restore the capacity of the unit, once regeneration time falls below a minimal value. An Independent claim is included for the corresponding regeneration control system. It includes an oxygen sensor for the exhaust gases flowing through the unit and a control/regulation module programmed to carry out the method. Preferred features: Deterioration of the unit is indicated, when a predetermined number of desulfurization processes have been carried out, without increase in regeneration interval. A regeneration adjustment factor is related to the capacity of the unit, and filling time is also adjusted in accordance with the factor. NOx storage quantity is adjusted, to saturate a predetermined fraction of the capacity of the unit. The initial value of filling time of the unit, is determined from a reference table, as a function of engine speed and loading, and/or from the mass air flow rate. It is determined as an inverse power of the product of engine load and engine speed. A related process for filling and regenerating a lean burn NOx storage unit (34) is described, based on the foregoing principles.