Patent ID: 7181904
Filing Date: 2007-02-27
Classification: B01D,F01N,F02B,F02D,F02M,Y02A,Y02T

Abstract:
1. An exhaust purification device for a compression ignition type internal combustion engine having an SO x trap catalyst arranged in an engine exhaust passage and adapted for trapping SO x contained in exhaust gas and having an NO x storing catalyst arranged in the exhaust passage downstream of the SO x trap catalyst, the NO x storing catalyst storing NO x contained in exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lean and releasing the stored NO x when the air-fuel ratio of the exhaust gas flowing in becomes the stoichiometric air-fuel ratio or rich, wherein said SO x trap catalyst traps SO x contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the SO x trap catalyst is lean, has the property that the trapped SO x gradually diffuses inside the SO x trap catalyst when the temperature of the SO x trap catalyst rises under a lean air-fuel ratio of the exhaust gas, and has the property of releasing the trapped SO x when the air-fuel ratio of the exhaust gas flowing into the SO x trap catalyst becomes rich if the temperature of the SO x trap catalyst is the SO x release temperature or more; said device is provided with air-fuel ratio control means continuing to maintain the air-fuel ratio of the exhaust gas flowing into the SO x trap catalyst lean, without allowing said exhaust gas to become rich, during engine operation and estimating means for estimating an SO x trap rate showing a ratio of SO x trapped and the SO x trap catalyst in the SO x contained in the exhaust gas; and said device makes the temperature of the SO x trap catalyst rise under a lean air-fuel ratio of the exhaust gas when the SO x trap rate falls below a predetermined rate so as to thereby restore the SO x trap rate.