EXHAUST PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

A construction in which a reducing agent is added to exhaust gas in an exhaust path on the upstream side of a pre-catalyst and in which a reducing agent addition valve is placed at a position at which at least a part of the reducing agent can arrive in a liquid state at the pre-catalyst. In the construction, the reducing agent can be supplied in a preferable condition by the exhaust purification device provided in an exhaust path on the downstream side of the pre-catalyst. When the reducing agent is added by the reducing agent addition valve (S107), the flow rate of exhaust gas entering the pre-catalyst is reduced so that at least a part of the reducing agent having arrived at and vaporized by the pre-catalyst flows back (S106).