Exhaust emission control system for internal combustion engine, and control method for exhaust emission control system

摘要

An exhaust emission control system is applied to an internal combustion engine in which an automatic stop and automatic restart of engine operation are carried out, includes an urea aqueous solution addition valve that supplies urea aqueous solution to an exhaust passage and an urea aqueous solution supply tube that supplies urea aqueous solution to the urea aqueous solution addition valve, and recovers urea aqueous solution in the urea aqueous solution supply tube at the time of a manual stop of engine operation as a result of off operation of an ignition switch. At the time of the automatic stop, urea aqueous solution (solid line A) in an amount that is smaller than a recovery amount (broken line B) of urea aqueous solution at the time of the manual stop is recovered from the urea aqueous solution supply tube.