Patent ID: 7694512

Claim:
An exhaust gas purification apparatus for an internal combustion engine, comprising: a NO x occlusion and reduction catalyst arranged in the exhaust path of the internal combustion engine for occluding by absorbing and/or adsorbing NO x in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the catalyst is lean, and purifying by reducing the occluded NO x when the air-fuel ratio of the exhaust gas flowing into the catalyst is a stoichiometric air-fuel ratio or a rich air-fuel ratio; and a H 2 sensor arranged in the exhaust path upstream of the NO x occlusion and reduction catalyst for detecting the concentration of the hydrogen component in the exhaust gas; wherein the SO x poisoning restoration process in which the temperature of the exhaust gas is increased while the air-fuel ratio of the exhaust gas flowing into the NO x occlusion and reduction catalyst is held at a rich air-fuel ratio in order to release the sulfur oxide occluded together with NO x by the NO x occlusion and reduction catalyst from the NO x occlusion and reduction catalyst, wherein, based on the hydrogen component concentration in the exhaust gas upstream of the NO x reduction catalyst detected by the H 2 sensor, at least one of the air-fuel ratio of the exhaust gas flowing into the NO x occlusion and reduction catalyst during the SO x poisoning restoration process and the duration of the SO x poisoning restoration process is controlled; wherein the air-fuel ratio of the exhaust gas flowing into the NO x occlusion and reduction catalyst is controlled during the execution of the SO x poisoning restoration process in such a manner that the concentration of the hydrogen component in the exhaust gas detected by the H 2 sensor is between 0.1% and 2.0%.