Patent ID: 6615579
Filing Date: 2003-09-09
Classification: B01D,F01N,F02B,F02D,Y02T

Abstract:
An exhaust gas purification system for an internal combustion engine equipped with an NOx adsorber catalyst which absorbs, for deposition, NOx when exhaust gas lean in its air fuel ratio flows in, and releases deposited NOx when an oxygen concentration of exhaust gas inflow is reduced, comprising:a NOx deposition calculating means for calculating the amount of NOx deposited on the NOx adsorber catalyst; a first air fuel ratio controlling means which, when the NOx deposition calculated by the NOx deposition calculating means reaches a predetermined reference level, alters an air fuel ratio of exhaust gas discharged from the internal combustion engine to come into contact with the NOx adsorber catalyst to stoichiometric air fuel ratio, so as to cause the NOx adsorber catalyst to release NOx deposited thereupon; and a reference NOx level setting means which changes a reference NOx level in accordance with a driving condition defined by a load range with which the internal combustion engine runs, or by a load and engine speed with which the internal combustion engine run, wherein the reference NOx level is set as a ratio relative to a maximum attainable NOx deposition on the NOx absorber catalyst.