Exhaust gas purification device for an engine

An exhaust gas purification device for an engine having an exhaust passage, said device comprising:

• an NO.sub.x absorbent arranged in the exhaust passage and absorbing NO.sub.x when an air-fuel ratio of exhaust gas flowing into the NO.sub.x absorbent is lean, said NO.sub.x absorbent releasing absorbed NO.sub.x when said air-fuel ratio of exhaust gas becomes rich;
• an air-fuel ratio control means for controlling said air-fuel ratio of exhaust gas to make said air-fuel ratio of exhaust gas lean when NO.sub.x is to be absorbed in said NO.sub.x absorbent, said air-fuel ratio control means changing over said air-fuel ratio of exhaust gas from a lean air-fuel ratio to a rich air-fuel ratio and increasing a richness of exhaust gas flowing into said NO.sub.x absorbent to a predetermined richness in which the exhaust gas flowing into said NO.sub.x absorbent contains therein an excessive amount of unburned components relative to an amount necessary to reduce all of the NO.sub.x when NO.sub.x is to be released from said NO.sub.x absorbent;
• and
• unburned component oxidizing means for oxidizing the unburned components of the exhaust gas discharged from said NO.sub.x absorbent.