Exhaust gas purification apparatus for an internal combustion engine

An exhaust gas purification apparatus for an internal combustion engine comprising:

• an internal combustion engine capable of fuel combustion at lean air-fuel ratios and an exhaust conduit connected to the engine;
• an NOx absorbent installed in the exhaust conduit and including at least one element selected from the group consisting of alkaline earth, rare-earth, alkaline metals, and oxides of alkaline earth, rare-earth, and alkaline metals, the NOx absorbent absorbing NOx included in exhaust gas having excess oxygen therein and releasing the NOx which the NOx absorbent has absorbed when an oxygen concentration of the exhaust gas decreases;
• operating condition detecting means for detecting an operating condition of the engine;
• operating condition determining means for determining whether the exhaust gas includes excess oxygen and for determining whether one of an exhaust gas temperature and an NOx absorbent temperature is high;
• and
• exhaust gas oxygen concentration control means for decreasing the oxygen concentration of the exhaust gas flowing into the NOx absorbent when the operating condition determining means determines that the exhaust gas includes excess oxygen and that one of an exhaust gas temperature and an NOx absorbent temperature is high.