Patent ID: 8132401

Claim:
An exhaust purification device of an internal combustion engine, the exhaust purification device comprising: an engine exhaust passage; an SO x trap catalyst arranged in the engine exhaust passage, the SO x trap catalyst is capable of trapping SO x contained in exhaust gas; an NO x storage catalyst arranged in the engine exhaust passage downstream of the SO x trap catalyst, the NO x storage catalyst is capable storing NO x contained in the exhaust gas when an air-fuel ratio of an inflowing exhaust gas is lean and capable of releasing a stored NO x when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich; a fuel addition valve arranged in the engine exhaust passage upstream of the NO x storage catalyst; and a control unit that is programmed such that, when making the air-fuel ratio of the exhaust gas flowing into the NO x storage catalyst the stoichiometric air-fuel ratio or rich to make the NOx storage catalyst release the NOx, an additional fuel is fed into the combustion chamber and a fuel is added from the fuel addition valve, and at this time: the amount of additional fuel to the combustion chamber and the amount of added fuel from the fuel addition valve are controlled so that the air-fuel ratio of the exhaust gas exhausted from the combustion chamber becomes the smallest in the range where the SO x trap catalyst does not release SO x ; and when a SO x trap amount of the SO x trap catalyst is below a predetermined value, the air-fuel ratio of the exhaust gas exhausted from the combustion chamber is made slightly rich.