| 摘要 |
A control unit calculates the amount of ammonia to be generated, from the amount of a urea solution added, according to an engine operation state and calculates a NOx purification rate when the amount of a urea solution according to the engine operation state is added on an exhaust upstream side of an SCR catalyst. Also, the control unit calculates the assumed adsorption amount of ammonia adsorbed by the SCR catalyst, on the basis of the amount of ammonia generated and the NOx purification rate. The control unit performs a correction by subtracting the amount of a urea solution corresponding to the adsorption amount of ammonia from the amount of a urea solution added, according to the engine operation state and controls the addition of the urea solution on the basis of the corrected amount of a urea solution added. |
