Exhaust purification device for internal combustion engine

摘要

In order to prevent a decrease in the accuracy with which filter malfunctions are determined due to a decrease in the detection accuracy of a PM sensor, the present invention is equipped with: a selective reduction NOx catalyst that is provided in the exhaust passage of an internal combustion engine, and reduces NOx by means of a supplied reduction agent; a supply device that supplies a urea aqueous solution as the reduction agent from the upstream side of the selective reduction NOx catalyst; a PM sensor that is downstream from the selective reduction NOx catalyst, and that detects the amount of particulate matter in the exhaust; and a control unit that reduces the amount of intermediate products generated from the urea aqueous solution supplied from the supply device until becoming ammonia, when an amount of particulate matter is detected by the PM sensor. The amount of generated intermediate products is reduced to an amount that is less than when particulate matter is not detected.