| 摘要 |
A urea spray SCR control system is provided to control the amount of urea spray appropriate for an engine-out NOx discharge amount in a period in which pre-heating control is performed. The urea spray SCR control system includes an SCR catalyst 23 provided in a discharge pipe 14 of an engine 10, a dosing valve 41 for injecting urea water at an upstream side of the SCR catalyst 23, and NOx sensors 46, 47 for measuring the amount of NOx in exhaust gas, wherein the urea spray SCR control system controls injection of the urea water from the dosing valve 41. The urea spray SCR control system includes a plurality of NOx model maps 60 corresponding to an atmospheric pressure condition, an outdoor air temperature, and an engine water temperature, and determines the amount of NOx from each NOx model map 60 on the basis of detection values of atmospheric pressure detection means, outdoor air temperature detection means, and engine water temperature detection means, and controls the amount of injection of the urea water from the dosing valve 41 on the basis of the amount of NOx thus determined. |
