Exhaust Purification Device of Compression Ignition Type Internal Combustion Engine

摘要

An internal combustion engine in which an SOx trap catalyst able to trap SOx contained in exhaust gas is arranged in an engine exhaust passage upstream of an NOx storing catalyst. The SOx trap catalyst is strengthened in basicity compared with the NOx storing catalyst to an extent so that when the temperature of the SOx trap catalyst is in the temperature range at the time of ordinary operation, that is, substantially 150° C. to substantially 400° C., the NOx purification rate by the SOx trap catalyst becomes less than substantially 10 percent of the NOx purification rate by the NOx storing catalyst. When NOx should be released from the NOx storing catalyst, the air-fuel ratio of the exhaust gas flowing into the SOx trap catalyst is temporarily switched from lean to rich.