Patent ID: 7703275

Claim:
An exhaust purification device for a compression ignition type internal combustion engine comprising: a combustion chamber; an engine exhaust passage separate from the combustion chamber; fuel adding means for injecting particulate fuel into the engine exhaust passage; an HC adsorbing and oxidation catalyst arranged in the engine exhaust passage downstream of the fuel adding means for adsorbing and oxidizing hydrocarbons contained in exhaust gas; and an NO x storing catalyst arranged in the engine exhaust passage downstream of the HC adsorbing and oxidation catalyst for storing NO x contained in the exhaust gas when an air-fuel ratio of the inflowing exhaust gas is lean and releasing the stored NO x when the air-fuel ratio of the inflowing exhaust gas becomes a stoichiometric air-fuel ratio or rich, wherein particulate fuel is added from the fuel adding means when making the air-fuel ratio of the exhaust gas flowing into the NO x storing catalyst rich to make the NO x storing catalyst release NO x , the amount of addition of particulate fuel at this time is set to an amount whereby the air-fuel ratio of the exhaust gas flowing into the HC absorbing and oxidation catalyst becomes a rich air-fuel ratio smaller than the rich air-fuel ratio when flowing into the NO x storing catalyst, and after the added particulate fuel is adsorbed at the HC adsorbing and oxidation catalyst, and the majority of the adsorbed fuel is oxidized in the HC adsorbing and oxidation catalyst and the air-fuel ratio of the exhaust gas flowing into the NO x storing catalyst is made rich over a longer period than when the air-fuel ratio of the exhaust gas flowing into the HC adsorbing and oxidation catalyst is made rich.