Patent ID: 8132402

Claim:
An exhaust purification device of an internal combustion engine, the exhaust purification device comprising: an NO x selective reduction catalyst disposed in an engine exhaust passage of the internal combustion engine, a urea aqueous solution feed system including a urea aqueous solution feed valve disposed in the engine exhaust passage upstream of the NO x selective reduction catalyst, ammonia produced from the urea aqueous solution fed from the urea aqueous solution feed valve selectively reducing NO x contained in an exhaust gas output by the NO x selective reduction catalyst, a NO x purification amount detector that detects a NO x purification amount achieved by the NO x selective reduction catalyst, a urea aqueous solution feed amount detector that detects a feed amount of the urea aqueous solution, a urea aqueous solution concentration detector that detects a concentration of the urea aqueous solution, and a control unit that judges whether abnormalities exist in the NO x selective reduction catalyst, the urea aqueous solution feed system, and the urea aqueous solution concentration based on detection results of the NO x purification amount detector, the urea aqueous solution feed amount detector and the urea aqueous solution concentration detector, wherein when the control unit judges that the NO x purification amount is abnormal and that the urea aqueous solution feed system and the urea aqueous solution concentration are not abnormal, the control unit judges that the NO x selective reduction catalyst is abnormal.