EXHAUST GAS PURIFICATION APPARATUS FOR AN INTERNAL COMBUSTION ENGINE

摘要

A reduction in the accuracy of a failure determination of a filter due to a reduction in the detection accuracy of a PM sensor is suppressed. To this end, provision is made for an NOx selective reduction catalyst arranged in an exhaust passage of the internal combustion engine to reduce NOx by means of a reducing agent supplied thereto, a supply device to supply urea water as the reducing agent from an upstream side of the NOx selective reduction catalyst, a PM sensor to detect an amount of particulate matter in an exhaust gas at the downstream side of the NOx selective reduction catalyst, and a control unit to make an amount of production of intermediate products from the urea water supplied from the supply device to ammonia smaller when an amount of particulate matter is detected by the PM sensor than when not detected.