METHOD FOR DETERMINING THE DEGREE OF AGEING OF AN NO SB X /SB -STORAGE CATALYST OF AN INTERNAL COMBUSTION ENGINE, ESPECIALLY IN A MOTOR VEHICLE

摘要

The invention relates to a method for determining the degree of ageing of an NOx-storage catalyst of an internal combustion engine, especially in a motor vehicle. According to the inventive method, a switching operating point (U) is determined as a function of a momentary operating temperature at the time of switching in order to determine the moment of switching from the storage phase to the discharge phase at least on the basis of the integral value of the NOx mass flow in front of and/or after the storage catalyst and/or the respective moment of switching during the fulfillment of a predefinable switching condition so as to determine the degree of ageing of the storage catalyst. Said swiching operating point is compared in a second step with a storage catalyst capacity field which extends over a temperature window, which is predefinable and optimized, especially with regard to fuel consumption, and which is formed by a plurality of individual operating points for a new and an aged storage catalyst such that a switching operating point located within the capacity field represents a modification in relation to the previous operating point as an indication of the ageing of the storage catalyst,as opposed to a fall below the the minimum NOx storage capacity, while the switching operating point departing from the capacity field represents a fall below the minium NOx storage capacity.