Exhaust purification device of internal combustion engine

摘要

In an internal combustion engine, an NOx selective reduction catalyst is arranged in the engine exhaust passage and a urea aqueous solution stored in a urea aqueous solution tank is fed to the NOx selective reduction catalyst where the NOx is selectively reduced. Opening and closing of the urea aqueous solution refill port of the urea aqueous solution tank are detected and it is judged if the urea aqueous solution is refilled in the urea aqueous solution tank. When it is judged that the NOx purification rate has fallen to an allowable level or less at the time of engine operation right after the urea aqueous solution is refilled in the urea aqueous solution tank, it is judged that the refilled urea aqueous solution is abnormal.