Abstract: A method for operating an NOx trap for an internal combustion engine includes measuring parameters that influence the delay between the metering of a regenerating agent and its becoming effective in regenerating the NOx trap. Such parameters include the fuel film on an intake wall and the quantity of oxygen bonded in the catalytic converters upstream of the NOx trap. Measuring these parameters helps determine the quantity of regenerating agent or the number of working cycles required for regeneration of the NOx trap.

Abstract: The invention provides the replacing of the known "macroscopic" processes by a "microscopic" approach control strategy for an NOx accumulator. The regeneration phases after approximately 30 seconds of a lean operation, which last approximately one second in the state of the art, is replaced by a rich operating cycle after a sequence of lean ones. The number of lean operating cycles which can be carried out before a regenerating operating cycle depends on the combustion process of the internal-combustion engine as well as on the construction and the volume of the catalyst.