SYSTEM FOR DETERMINING DETERIORATION OF EXHAUST PURIFICATION DEVICE

摘要

The objective of the present invention is, in a system for determining the deterioration of an exhaust purification device having a selective reduction NOx catalyst, to further increase the precision of the deterioration determination by suppressing determination errors during the deterioration determination. The present invention is provided with a catalyst having an oxidizing ability downstream of the NOx catalyst that has ammonia as a reducing agent, and when the amount of ammonia adsorbed to the NOx catalyst becomes greater than an equilibrium adsorption amount, of the amount of ammonia flowing into the catalyst having an oxidizing ability, at least one or the total value of the amount of ammonia flowing out of the catalyst having an oxidizing ability and the amount of ammonia converted to NOx at the catalyst having an oxidizing ability is calculated, and when the value exceeds a threshold, the use of the detection value of an NOx sensor in the deterioration determination is limited or the deterioration determination itself is prohibited.