Device for purifying the exhaust gas of an internal combustion engine

A device for purifying the exhaust gas of an internal combustion engine comprising:

• a particulate trap disposed in the engine exhaust system;
• an exhaust gas recirculation passage communicating the upstream of said particulate trap in said engine exhaust system with the engine intake system;
• a control valve for controlling the amount of exhaust gas recirculated through said exhaust gas recirculation passage to be an optimum amount in accordance with the engine operating condition;
• a pressure differential detection means for detecting directly or indirectly a pressure differential between the upstream side and the downstream side of said particulate trap during a fuel-cut after said control valve is fully closed and after a throttle valve disposed on said engine intake system is fully opened;
• and
• an estimation means for estimating an amount of particulate trapped by said particulate trap on the basis of said pressure differential detected by said pressure differential detection means.