| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas emission control system capable of improving a NOx purification rate and suppressing ammonia slip even if the operating condition of an internal combustion engine is a high load.SOLUTION: During the operation of a diesel engine 1, an ECU 14 calculates a flow volume of NOx from a detection value of an air-intake sensor 21 and a detection value of a NOx sensor 13, compares this calculated value with a threshold, and detects whether an operating condition of the diesel engine is a low load or a high load. If the operating condition of the diesel engine 1 is the low load, the ECU 14 controls a supply quantity of urea water supplied from an injection nozzle 7 to a supply quantity for achieving a target air-intake preset in the ECU 14. If it is detected that the operating condition of the diesel engine 1 is the high load and a ratio of NO in NOx is higher than a ratio of NO, the supply quantity of the urea water supplied from the injection nozzle 7 is set greater than the supply quantity for achieving the target air-intake. |
