EXHAUST PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

In an exhaust passageway upstream of an exhaust purification apparatus, there is provided a pre-stage catalyst of heat capacity smaller than that of the exhaust purification apparatus, and it is intended to, even when a reducing agent is added from a reducing agent addition valve toward the upstream side end face of the pre-stage catalyst, inhibit any excess temperature rise of the pre-stage catalyst. The reducing agent addition valve is disposed at a location where the added reducing agent in liquid form reaches the pre-stage catalyst. At the performing of the addition of the reducing agent by the reducing agent addition valve so as to feed the reducing agent to the pre-stage catalyst and the exhaust purification apparatus, when the degree of activation of the pre-stage catalyst is higher than a given level, there is carried out enhanced focused addition of the reducing agent as compared with the addition when the degree of activation of the pre-stage catalyst is not higher than the given level.