EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of improving NOx conversion performance in a rich air-fuel ratio area and making an actual air-fuel ratio coincide with a target air-fuel ratio even if a large quantity of hydrogen is formed caused by reaction characteristics of an exhaust emission control catalyst and error occurs on output of an air-fuel ratio sensor due to influence of the hydrogen. SOLUTION: This exhaust emission control device for the internal combustion engine is provided with an exhaust emission control catalyst provided with a lower layer and an upper layer covering the lower layer, storing oxygen when oxygen concentration in exhaust gas is high and discharging oxygen when oxygen concentration in exhaust gas is low, and having oxygen storage material having oxygen storing capacity contained in the upper layer; an air-fuel ratio sensor provided in the downstream of the exhaust emission control catalyst; and an air-fuel ratio control means making the actual air-fuel ratio coincide with the target air-fuel ratio based on the output from the air-fuel ratio sensor and error of the output of the air-fuel ratio sensor caused by hydrogen formed by the exhaust emission control catalyst. COPYRIGHT: (C)2008,JPO&INPIT