Abstract: A selective catalytic reduction system includes a selective catalytic reduction device on an exhaust pipe of an engine, a urea solution tank that stores a urea solution, a float-type urea solution level sensor in the urea solution tank, a dosing valve on the exhaust pipe upstream of the selective catalytic reduction device, a urea solution injection control section that controls an amount of urea solution to be injected through the dosing valve in accordance with an amount of NOx discharged from the engine, an inclination sensor that detects an inclination angle of the urea solution tank relative to horizontal, and an inclination angle correcting section that corrects a liquid level of the urea solution, the liquid level being detected by a detection unit from the position of a float, with the inclination angle detected by the inclination sensor.

Abstract: A selective catalytic reduction system includes a selective catalytic reduction device on an exhaust pipe of an engine, a urea solution tank that stores a urea solution, a float-type urea solution level sensor in the urea solution tank, a dosing valve on the exhaust pipe upstream of the selective catalytic reduction device, a urea solution injection control section that controls an amount of urea solution to be injected through the dosing valve in accordance with an amount of NOx discharged from the engine, an inclination sensor that detects an inclination angle of the urea solution tank relative to horizontal, and an inclination angle correcting section that corrects a liquid level of the urea solution, the liquid level being detected by a detection unit from the position of a float, with the inclination angle detected by the inclination sensor.

Abstract: A urea water consumption diagnostic device includes a sensor which detects a level of urea water in a urea water tank, a calculation unit which calculates a cumulative consumed amount based on a detection value entered from the sensor and calculating a replenishment amount based on a change in the detected level of the urea water after a replenishment of the urea water, and a unit which, when a cumulative instructed injection amount of the urea water injected from a dosing valve has become greater than or equal to a determination amount, determines whether or not there is clogging of the urea water by comparing the cumulative consumed amount to the cumulative instructed injection amount. The calculation unit subtracts a level from the changed level of the urea water detected by the sensor upon replenishment to the urea water tank, and stores the resulting level as the replenishment amount.

Abstract: A urea quality diagnosis system capable of accurately diagnosing the quality of an aqueous urea solution in a urea tank. A concentration and a level (L) of an aqueous urea solution inside a urea tank 16 are detected, and the quality of the aqueous urea solution is diagnosed based on a detected value of the concentration of the aqueous urea solution when the level L is equal to or higher than a predetermined value.

Abstract: A selective catalytic reduction (SCR) system that can detect whether or not a float is stuck even where a water level sensor that detects a liquid level in a stepwise manner is used, including: an urea injection quantity integrating unit that integrates an injected quantity of urea to calculate an urea injection quantity integrated value; an integrated value resetting unit that, if a detected value from detection means changes, resets the urea injection quantity integrated value; and an abnormality determination unit that, if the urea injection quantity integrated value exceeds a predetermined threshold value for determination, determines a level sensor as having an abnormality.

Abstract: A selective catalytic reduction (SCR) system that can detect whether or not a float is stuck even where a water level sensor that detects a liquid level in a stepwise manner is used, including: an urea injection quantity integrating unit that integrates an injected quantity of urea to calculate an urea injection quantity integrated value; an integrated value resetting unit that, if a detected value from detection means changes, resets the urea injection quantity integrated value; and an abnormality determination unit that, if the urea injection quantity integrated value exceeds a predetermined threshold value for determination, determines a level sensor as having an abnormality.

Abstract: A urea quality diagnosis system capable of accurately diagnosing a quality of an aqueous urea solution in a urea tank. A concentration and a level L of an aqueous urea solution inside a urea tank 16 are detected, and the quality of the aqueous urea solution is diagnosed based on a detected value of the concentration of the aqueous urea solution when the level L is equal to or higher than a predetermined value.