Patent ID: 7204079

Claim:
A device for determining the mass of NOx stored in a NOx trap in an exhaust line of a motor vehicle engine, which device comprises means for acquiring the richness of the exhaust gases, the flowrate of NOx on the upstream side of the NOx trap, and the temperature of the NOx trap, and further comprises: means for comparing the richness of the exhaust gases on the upstream side of the NOx trap to a predetermined value to determine if the exhaust gases on the upstream side of the NOx trap are lean or rich; first determination means for determining, when the exhaust gases are lean, the increase per unit of time of the mass of NOx stored in the NOx trap as a function of the mass of NOx already stored in the NOx trap, the temperature of the NOx trap, and the flowrate of the NOx on the upstream side of the NOx trap; and second determination means for determining, when the exhaust gases are rich, the reduction per unit of time of the mass of NOx stored in the NOx trap as a function of the temperature of the NOx trap and the richness of the exhaust gases on the upstream side of the NOx trap.