Breakdown determination system for exhaust purification device

摘要

In this breakdown determination system, which performs a breakdown determination with respect to an exhaust purification device having a selective reduction NOx catalyst (NOx catalyst) using ammonia as a reducing agent and provided to the exhaust pathway of an internal combustin engine, the breakdown determination of the exhaust purification device is performed by means of a breakdown determination unit on the basis of the detection value of an NOx sensor that detects NOx in exhaust. Also, on the basis of the adsorption quantity difference that is of a hypothetical breakdown case and that is the difference between the actual ammonia adsorption quantity at the NOx catalyst and the ammonia equilibrium adsorption quantity when the ammonia adsorption to the NOx catalyst is in an equilibrium state in the case supposing that the exhaust purification device is in a predetermined breakdown state, the actual breakdown determination by the breakdown determination unit is prohibited, or the use of the NOx sensor in the breakdown determination is limited. As a result, in the breakdown determination system for an exhaust purification device having a selective reduction NOx catalyst, the precision of the breakdown determination is increased by suppressing determination errors during the breakdown determination.