Patent ID: 8256211

Claim:
An aqueous urea solution feed device of an internal combustion engine provided with an aqueous urea solution feed valve arranged in an engine exhaust passage upstream of an NO x selective reducing catalyst, an aqueous urea solution tank, and a feed pump for feeding an aqueous urea solution stored in the aqueous urea solution tank to the aqueous urea solution feed valve, the feed pump being operated forward to feed the aqueous urea solution in the aqueous urea solution tank to the aqueous urea solution feed valve when the aqueous urea solution is in a condition to be fed from the aqueous urea solution feed valve, wherein an ammonia gas feed pipe for feeding ammonia gas generated in the aqueous urea solution tank is connected to an end of an aqueous urea solution feed passage extending from the feed pump to the aqueous urea solution feed valve, said end being on the aqueous urea solution feed valve side, and the ammonia gas generated in the aqueous urea solution tank is drawn into the aqueous urea solution feed passage via the ammonia gas feed pipe by operating the feed pump in reverse when the supply of the aqueous urea solution from the aqueous urea solution feed valve is stopped, the ammonia gas drawn into the aqueous urea solution feed passage being ejected from the aqueous urea solution feed valve when operating the feed pump forward.