Exhaust gas purification apparatus for an internal combustion engine

摘要

An NOx absorbent is installed in an exhaust conduit of an internal combustion engine capable of fuel combustion at lean air-fuel ratios. An oxygen concentration is repeatedly or continuously decreased by, for example, switching the air-fuel from the lean air-fuel ratio to a stoichiometric or rich air fuel ratio when the exhaust gas temperature is higher than 550 DEG C. or when NOx absorbent temperature is higher than 500 DEG C. As a result, the SOx absorbed in the NOx absorbent during lean air-fuel ratio, low temperature operation is released from the NOx absorbent, and the SOx-poisoned NOx absorbent is recovered.