Patent ID: 7127881
Filing Date: 2006-10-31
Classification: F01N,F02D,Y02T

Abstract:
1. Method for operating a nitrogen oxide storage-type catalytic converter of an internal combustion engine comprising: storing nitrogen oxides in a nitrogen oxide storage catalytic converter in a first operating phase (lean phase) as a storage phase for a specific storage time, after expiration of the storage time at a specific switching instant for a specific discharge time, switching to a second operating phase as the discharge phase takes place, in which the nitrogen oxides which were stored during the storage time are discharged from the nitrogen oxide storage catalytic converter, determining the switching instant in the storage phase as a function of the nitrogen oxide slip as the difference between the nitrogen oxide mass flow which has flowed into the nitrogen oxide storage catalytic converter and the nitrogen oxide mass flow which has flowed out of the nitrogen oxide storage catalytic converter, each relative to the storage time, establishing the switching instant from the storage phase to the discharge phase in which a relative nitrogen oxide slip is determined such that the nitrogen oxide mass flow upstream of the nitrogen oxide storage catalytic converter and the nitrogen oxide mass flow downstream of the nitrogen oxide storage catalytic converter are each integrated over the time interval of the lean phase and the quotient of the integral values are brought into a relative relationship with a predeterminable degree of conversion of the nitrogen oxide which has been derived from the exhaust gas limit value, such that when this predetermined switching condition is present, switching from the storage phase to the discharge phase is carried out at the switching instant which has been optimized with respect to fuel consumption and storage potential.