Patent ID: 7832202
Filing Date: 2010-11-16
Classification: F01N

Abstract:
1. An exhaust gas purification device for an internal combustion engine, the exhaust gas purification device comprising: an injector that injects fuel of an amount corresponding to an injection amount command value into a cylinder of the engine; a NOx catalyst provided in an exhaust system of the engine for occluding nitrogen oxides when an air-fuel ratio is lean and for reducing and releasing the occluded nitrogen oxides when the air-fuel ratio is rich; an A/F sensor provided upstream of the NOx catalyst in the exhaust system for sensing the air-fuel ratio; a fresh air amount sensor that senses an amount of a fresh air supplied to the engine; a rich purge controller that performs rich purge control of setting the injection amount command value to make the air-fuel ratio rich, whereby supplying the fuel for reduction to the NOx catalyst; a total reducing agent amount calculation device that calculates a total reducing agent amount as a sum of the fuel consumed for the reduction in the rich purge control based on the air-fuel ratio as of the rich purge control sensed with the A/F sensor and the fresh air amount as of the rich purge control sensed with the fresh air amount sensor; a state setting device that sets a specified air-fuel ratio state, in which the air-fuel ratio is controlled in a certain air-fuel ratio range enabling more precise measurement of the air-fuel ratio than in the rich purge control; and a total reducing agent amount correction device that corrects a value of the total reducing agent amount based on an injection amount command value difference, which is a difference between the injection amount command value in the rich purge control and the injection amount command value in the specified air-fuel ratio state, and the air-fuel ratio in the specified air-fuel ratio state sensed with the A/F sensor.