Method for detecting incorrect filling of a storage container in a motor vehicle

Abstract

The invention relates to a method for detecting a filling error for a storage container of a liquid, in particular a urea-water solution, in a motor vehicle. The speed of sound in the liquid is determined and a filling error is detected if the speed of sound deviates from an expected value.

Description

Technical Field

[0001] The invention relates to a method for detecting filling errors in a storage container in a motor vehicle. Background Art

[0002] In the field of automotive technology, selective catalytic converters, hereinafter referred to as SCR converters, are known for reducing nitrogen oxides by means of the dosing of an aqueous urea solution.

[0003] This aqueous solution of urea is pre-stored in a storage tank and metered into the exhaust gas line of the internal combustion engine by means of a metering system. After being converted into NH3, the urea contained in the solution reacts with nitrogen oxides in the catalytic converter and reduces them to nitrogen. For this selective catalytic reduction, a sufficient supply of NH3 to the catalytic converter is required in order to comply with predefined exhaust gas limit values.

[0004] Current exhaust gas legislation therefore requires monitoring of the quality and quantity of the reducing agent.

[0005] Usually, the filling nozzles for urea-water solution and diesel fuel are arranged close to each other. In the case of driver error, the following situation may occur, that is, the driver fills the fuel liquid into the storage container for urea-water solution during the filling process.

[0006] There is also the risk that the driver fills the tank with a low-quality urea-water solution. In particular, filling the tank with a urea-water solution having a concentration lower than that specified is problematic.

[0007] Furthermore, methods and devices are known in which the quality of a urea-water solution is monitored by means of an ultrasonic sensor. The ultrasonic sensor measures the propagation time of an ultrasonic wave over a defined measuring path. The speed of sound is calculated in the sensor from the measured propagation time and the known measuring path. In conjunction with the currently prevailing medium temperature, the urea concentration can be inferred. Summary of the invention

[0008] In contrast, the method according to the invention with the features of the independent claim has the advantage that an incorrect refill of a tank of liquid, such as diesel fuel, can be reliably and simply detected. In particular, all liquids whose sound velocity is significantly lower or higher than that of a urea-water solution can be reliably detected.

[0009] This is achieved in that in a method for detecting a filling error of a storage container for a liquid, in particular for a urea-water solution, in a motor vehicle, the speed of sound in the liquid is determined and a filling error is detected if the speed of sound deviates from an expected value.

[0010] When the speed of sound is between the first threshold value and the second threshold value, a particularly reliable identification of a filling error is obtained. In this case, it is assumed that a filling with a poor-quality urea-water solution has been carried out.

[0011] If a sound velocity below a second threshold value is detected, a filling error with diesel fuel is detected.

[0012] By checking the value range of the speed of sound, the type of tank filling error can be identified. In other words, it can be distinguished whether the tank is filled with diesel fuel or a urea solution with too low a concentration.

[0013] It is particularly advantageous to perform a check for a filling error when the temperature is above a threshold value. The threshold value is selected such that the speed of sound of diesel fuel is less than the speed of sound of water. The temperature of the urea-water solution is preferably used for this purpose. Alternatively, a temperature can also be measured and used, which characterizes the temperature of the urea-water solution.

[0014] In another aspect, the invention relates to a novel program code together with processing instructions for creating a computer program executable on a controller, in particular a source code with compiling and / or linking instructions, wherein when the program code is converted, i.e., in particular compiled and / or linked, into an executable computer program according to the processing instructions, the program code generates a computer program for implementing all the steps of one of the described methods. The program code can be given in particular by a source code, which can be downloaded, for example, from a server on the Internet. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 shows a schematic diagram of a metering device for an SCR catalyst system,

[0016] Figure 2 shows different signals plotted over time, and

[0017] Figure 3 A flow chart is shown for explaining the method of operation according to the present invention. DETAILED DESCRIPTION

[0018] Figure 1 1 shows the main components of an SCR catalytic converter system for dosing urea-water solution. The urea-water solution is located in a storage container 100 and from there reaches the exhaust gas line 120 of the internal combustion engine via a dosing device 110. In the exhaust gas line, the exhaust gas preferably reaches the SRC catalytic converter directly or reaches the exhaust gas pipeline that leads to the SRC catalytic converter. The SRC catalytic converter system is used to reduce nitrogen oxides in the exhaust gas of the internal combustion engine by means of selective catalytic reduction (SCR). For reduction, the reducing agent for the dosing device 110 is sprayed into the exhaust gas line 120 upstream of the SRC catalytic converter.

[0019] The urea-water solution is stored in a storage container 100. An ultrasonic sensor 130 is arranged in the storage container. The ultrasonic sensor 130 can be used to measure the sound velocity of the urea-water solution. The output signal of the ultrasonic sensor 130 reaches a controller 140. The controller in particular controls the metering device 110. In addition, the controller can also control other elements of the exhaust system and the internal combustion engine. In addition, other sensors for forming control signals can also be evaluated.

[0020] In particular, a temperature sensor is provided, which detects a temperature value. Here, the temperature in the exhaust gas line is preferably used. For this purpose, a sensor 150 is particularly provided. It also provides a signal to the controller 140.

[0021] Furthermore, it is provided that a temperature value T is detected which corresponds to the temperature of the urea-water solution.

[0022] exist Figure 2 In the diagram, the speed of sound SG of different liquids is plotted as a function of the temperature T of the liquid. The values ​​for the urea-water solution are plotted with a dotted line, the values ​​for almost pure water with a dashed line, and the values ​​for diesel fuel with a solid line. The urea-water solution has the highest speed of sound. It increases with increasing temperature T. The speed of sound of water is significantly lower, but also increases with increasing temperature. In contrast, diesel has a significantly lower speed of sound. It decreases with increasing temperature. For low temperature values, the speed of sound of diesel fuel is equal to or even greater than the speed of sound of pure water. Starting from temperature TS, the speed of sound of diesel fuel becomes less than the speed of sound of water.

[0023] Due to an unexpected or unintentional filling error, on the one hand, a urea-water solution with a lower concentration or even pure water or diesel fuel may be refilled. This is reliably detected by the method described below. According to the invention, the speed of sound SG is measured for this purpose.

[0024] If the sound velocity is in the region between the dotted line and the dashed line, an error is detected as follows, i.e. the refill tank is filled with a urea-water solution with insufficient concentration. In this case, it is preferred to continue to operate the metering system, because a certain reduction of nitrogen oxides also occurs with a lower metered urea-water solution.

[0025] If, on the other hand, a sound velocity significantly below the speed of water is measured, an error bit is set, which causes the system to shut down for component protection reasons. This prevents damage to other components due to the metering of diesel into the exhaust gas line.

[0026] For example, refilling of the fuel tank can be detected and the system can be placed in a safe state. By expanding this function with additional queries, other liquids can also be detected that have a higher speed of sound than the urea-water solution.

[0027] exist Figure 3 1 shows an exemplary embodiment of the method of operation according to the invention with the aid of a flow chart. In a first step 300, the sound velocity SG and the temperature T of the liquid in the storage container 100 are measured. A subsequent query 310 checks whether the temperature T is greater than a set value TS. This query 310 ensures that measurements are only carried out in a temperature range greater than TS in which the sound velocity of the diesel fuel is less than the sound velocity of water.

[0028] If query 310 detects that temperature T is less than or equal to TS, the program ends in step 315. If query 310 detects that temperature T is greater than TS, query 320 checks whether the sound speed SG is less than a first threshold value S1. If this is not the case, the program ends in step 315 as well. If the sound speed is less than the first threshold value S1, query 330 checks whether the sound speed SG is also less than a threshold value S2. The second threshold value S2 is significantly less than the first threshold value S1. The threshold values ​​S1 and S2 define a range in which a urea-water solution with an impermissible urea concentration is detected. This is detected when query 320 detects that the sound speed is less than the first threshold value S1 and second query 330 detects that the sound speed is greater than the threshold value S2. If this is the case, a urea-water solution with insufficient properties is detected in step 340. In this case, this is indicated to the driver, a corresponding entry is made in the fault memory, and an emergency driving operation is started if necessary.

[0029] If query 330 detects that the speed of sound is also less than the second threshold value S2, filling with diesel fuel is detected in step 350. In this case, the exhaust gas aftertreatment system is immediately shut down. If necessary, this can also be displayed to the driver and a corresponding entry can be made in the fault memory.

[0030] This means that an insufficient concentration of the urea-water solution is detected in the sound velocity value range between the first threshold value S1 and the second threshold value S2. Filling with fuel is detected in the value range below the threshold value S2.

[0031] In an advantageous embodiment, the measurement is carried out at a temperature below the freezing point of the urea-water solution. Here, the ultrasonic sensor cannot provide a signal because it is not working. If the ultrasonic sensor still provides a signal, it is assumed that there is a filling error.

Claims

1. A method for detecting a filling error of a storage container for a liquid in a motor vehicle, characterized in that The speed of sound and the temperature of the liquid are known, a check for the presence of a tanking error is performed only when the temperature of the liquid is above a threshold value, from which the speed of sound of diesel fuel becomes less than the speed of sound of water, and a tanking error is identified when the speed of sound of the liquid deviates from an expected value.

2. The method according to claim 1, characterized in that The method is used to detect a filling error of a supply container for urea-water solution.

3. The method according to claim 1 or 2, characterized in that: Filling with poor-quality urea-water solution is detected when the sound velocity of the liquid is between a first threshold value and a second threshold value.

4. The method according to claim 3, characterized in that: Filling of the tank with diesel fuel is detected when the speed of sound of the liquid is below a second threshold value. 5 . A computer program product, which is designed to implement the method according to claim 1 .

6. A machine-readable storage medium on which the computer program product according to claim 5 is stored.

7. A controller configured to implement the method according to any one of claims 1 to 4.

8. Program code means for creating a computer program product executable on a controller, wherein: When the program code is converted into an executable computer program product according to processing instructions, the program code produces a computer program product according to claim 5.

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