Patent ID: 6347513
Filing Date: 2002-02-19
Classification: B01D,F01N,F02D

Abstract:
In a method for regenerating a NOx storage catalytic converter disposed in an exhaust gas stream of an internal combustion engine operating with air excess, at least in certain operating ranges, the engine having an overrun fuel cut-off, the improvement which comprises:storing NOx contained in the exhaust gas of the internal combustion engine in the catalytic converter in a storage phase; catalytically converting the stored NOx in the catalytic converter in a regeneration phase; placing a NOx sensor downstream of the NOx storage catalytic converter for evaluating a signal of the NOx sensor; detecting the signal of the Nox sensor in the operating range of the overrun fuel cut-off of the engine; forming at least one of an average value and a minimum value from individual measured values of the signal and storing the at least one of the average value and the minimum value as an offset value of the signal; detecting the signal of the NOx sensor in operating ranges of the engine beyond the overrun fuel cut-off, and taking the offset value into account when the signal is processed further; comparing an offset-corrected signal with a threshold value; and emptying the NOx storage catalytic converter by catalytically converting stored NOx through addition of a reducing agent in a regeneration phase in the event that the threshold value is exceeded.