| abstract |
(57) Abstract: The present invention provides an N-type internal combustion engine capable of preventing ammonia slip by accurately performing ammonia addition control. An object of the present invention is to provide an Ox purification device. SOLUTION: An N disposed in an exhaust passage E of an engine 1 is provided. The NOx purification rate η is calculated from the information of the Ox catalyst 14, the urea water supply device 15 for supplying ammonia to the exhaust passage E, the NOx sensors 22 and 23 disposed in the exhaust passage E, and the NOx sensor, and the purification is performed. From the rate of ammonia consumption C NH3 A1 for calculating the ammonia adsorption amount ANH3 based on the ammonia consumption amount, an ammonia adsorption amount estimation unit A2 for estimating the ammonia adsorption amount ANH3 based on the ammonia consumption amount. A correction means A3 is provided for calculating a difference Δη in the NOx purification rate at the time of supply ηb, estimating the current ammonia adsorption amount Am NH3 based on the difference Δη, and correcting the ammonia adsorption amount A NH3 based on the adsorption amount. |