Method For Determining a Quality of a Reducing Agent Solution Containing Ammonia Used to Reduce Nitrite Oxide
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Abstract
A determination of a quality of a reducing agent solution containing ammonia used to reduce nitrogen oxides involves actuating a metering unit that delivers metered quantities of reducing agent solution into an engine'"'"'s discharged exhaust gas and determining an efficiency value that is at least correlated with the efficiency of the SCR catalytic converter and comparing the efficiency value to a predefinable limit value. If an efficiency value not corresponding to proper functioning of the SCR exhaust emission control system is identified by the comparison, a switch is made to a diagnostic mode in a second method step. If a predefinable deviation of the efficiency value from a limit value is identified after expiration of the second method step time period, a third method step is performed for conditioning the SCR catalytic converter. A fourth step involves an adaptation mode in which a deviation from the efficiency value is determined.
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Citations
28 Claims
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1-8. -8. (canceled)
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9. A method for determining a quality of a reducing agent solution containing ammonia used to reduce nitrogen oxides in an SCR exhaust emission control system of an internal combustion engine, the method comprising:
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a first method step that is a normal metering mode, which comprises actuating a metering unit to deliver a first target metering quantity of the reducing agent solution into exhaust gas of the internal combustion engine exhaust gas; determining, using a NOx sensor situated downstream from an SCR catalytic converter of the SCR exhaust emission control system and which has a cross-sensitivity to ammonia, a first efficiency value that is at least correlated with the efficiency of the SCR catalytic converter; comparing the determined efficiency value to a first limit value; wherein when the comparison indicates that the SCR exhaust emission control system is not functioning properly, the normal metering mode is terminated and a switch is made to a diagnostic mode in a second method step, wherein the second method step involves actuating the metering unit to deliver a second target metering quantity of reducing agent solution, which is greater than the first metering quantity, for a first time period, determining a second efficiency value, and comparing the determined second efficiency value with a second limit value; wherein when, after the first time period has elapsed, the comparison of the second efficiency value to the second limit value indicates a deviation of the second efficiency value and the second limit value, a third method step is performed in which the SCR catalytic converter is conditioned in such a way that a quantity of ammonia stored in the SCR catalytic converter falls below a predefined storage quantity limit value, and wherein an adaptation mode is switched to in a fourth method step, wherein the fourth method step involves actuating the metering unit to deliver a third target metering quantity of reducing agent solution for a second predefined period of time, determining a third efficiency value, and comparing the third efficiency value with a third limit value, wherein if the comparison of the third efficiency value and third limit value indicates a deviation of the third efficiency value and the third limit value, it is determined that there is a deficient quality reducing agent solution. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification