EXHAUST EMISSION CONTROL DEVICE FOR AN INTERNAL COMBUSTION ENGINE

摘要

An exhaust emission control device of an internal combustion engine, comprising an NOx catalyst (17) installed in the exhaust gas passage of a le an burnable internal combustion engine and discharging the NOx absorbed therein with reducing agent for reducing, a reducing agent feeding means (19) installed in the exhaust gas passage on the upstream side of the NOx catalys t (17), a load detection means for detecting a load on the internal combustion engine (1), and a reducing agent addition control means for controlling a reducing agent adding time and a reducing agent adding interval based on the load on the internal combustion engine (1), wherein the adding time and addi ng interval for the reducing agent are controlled in consideration of the degre e of adherence of the reducing agent on the wall surface in the exhaust gas passage varying according to the flow velocity and temperature of exhaust ga s of the internal combustion engine (1) to supply sufficient amount of reducin g agent to the NOx catalyst side irrespective of the operating conditions, whereby a proper amount of reducing agent can always be supplied to the Nox catalyst even if the operating conditions of the internal combustion engine vary.