Exhaust Gas Purifying Device for Internal Combustion Engine

An exhaust gas purifying device for an internal combustion engine comprising an NOX occluding and reducing catalyst disposed in an exhaust passage of an internal combustion engine, the NOX occluding and reducing catalyst occluding NOX contained in exhaust gas by one of the absorption and the adsorption or by both the absorption and the adsorption when an air-fuel ratio of the exhaust gas flowing into the catalyst is lean and reducing and purifying the occluded NOX with a reducing component contained in the exhaust gas when an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio or a rich air-fuel ratio,

• the exhaust gas purifying device for an internal combustion engine further comprising:
• NOX occluding and reducing catalysts arranged in series to each other on the upstream side and the downstream side of the exhaust gas passage of the internal combustion engine;
• and an H2 sensor, which is arranged in series to each other in the exhaust gas passage between the upstream side NOX occluding and reducing catalyst and the downstream side NOX occluding and reducing catalyst, for detecting a hydrogen component concentration in the exhaust gas, wherein
• when the NOX occluding and reducing catalyst is to reduce and purify NOX occluded during a lean air-fuel ratio operation of the engine, at the time of executing a regenerating operation in which the exhaust gas of a rich air-fuel ratio or a stoichiometric air-fuel ratio is supplied to the NOX occluding and reducing catalyst for a predetermined period of time, according to the hydrogen component concentration in the exhaust gas detected by the H2 sensor, an air-fuel ratio of the exhaust gas flowing into the upstream side NOX occluding and reducing catalyst is controlled.