Verfahren zur Erkennung der Betriebsbereitschaft eines Katalysator für den Auspuff einer Brennkraftmaschine

摘要

Detecting the condition of NOx catalyst in an engine exhaust pipe includes supplying an engine with a lean air fuel mixture and recirculating some exhaust gas. The NOx output of the engine is increased to saturate the catalyst, the state of the catalyst is modeled and the level of saturation detected. The air fuel mixture is made rich to regenerate the catalyst and the richness of the gas leaving the catalyst is detected. The mixture is made lean to stop catalyst regeneration. The NOx output may be increased by reducing the exhaust gas recirculation. Saturation is determined from the catalyst temperature, the NOx concentration in the exhaust and the engine load at saturation. Completion of catalyst regeneration is determined from the engine load and switching of an oxygen sensor detecting the richness of the exhaust gas. There is a time lapse after detecting complete regeneration before the mixture is made lean.