EXHAUST GAS PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

The present invention resides in an exhaust gas purification system for an internal combustion engine provided with an addition valve for adding an oxidizing agent or a reducing agent into an exhaust gas, an object of which is to suppress the occurrence or the deterioration of the foreign matter malfunction in the addition valve caused by the suck back of the oxidizing agent or the reducing agent from the inside of the addition valve. In the present invention, the suck back control is executed such that the oxidizing agent or the reducing agent, which stays in the addition valve, is sucked back after the stop of the operation of the internal combustion engine (S110). Further, the addition of the oxidizing agent or the reducing agent is executed at a predetermined timing before the execution of the suck back control in order to blow off any foreign matter existing in the addition valve or in the vicinity of an injection port of the addition valve (S107).