Exhaust treatment system for a motor vehicle

Abstract

The present invention relates to an exhaust gas treatment system for a motor vehicle, the exhaust gas treatment system having: a first catalytic converter for selective catalytic reduction; a second catalytic converter for selective catalytic reduction; a first nitrogen oxide sensor located before the first catalytic converter and used to detect a first nitrogen oxide value; a second nitrogen oxide sensor located between the first and second catalytic converters and used to detect a second nitrogen oxide value; a third nitrogen oxide sensor located after the second catalytic converter and used to detect a third nitrogen oxide value; an electronic analysis device for: calculating a first efficiency of the first catalytic converter based on the first and second nitrogen oxide values, calculating a second efficiency of the second catalytic converter based on the second and third nitrogen oxide values, and calculating a total efficiency of the exhaust gas treatment system based on the first and third nitrogen oxide values; and a fault determination unit for obtaining a fault cause based on an allocation matrix, the allocation matrix allocating the fault cause based on the first efficiency, the second efficiency and the total efficiency.

Description

Technical Field

[0001] The invention relates to an exhaust gas treatment system for a motor vehicle and to a method for determining the cause of a fault in an exhaust gas treatment system. Background Art

[0002] In the case of catalytic converters for selective catalytic reduction (SCR), it is legally necessary to monitor whether the catalytic converters have the required nitrogen oxide reduction capacity. In addition, it is necessary to monitor whether the nitrogen oxide sensors in the exhaust system are functioning properly. It is technically difficult to distinguish between a defective catalytic converter, a defective nitrogen oxide sensor and a defective metering system for the reducing agent, because the same conditions, such as a low nitrogen oxide conversion rate, occur here. This challenge is particularly great in diesel exhaust systems, which include two actively metered catalytic converters and three nitrogen oxide sensors that are arranged one after the other. Summary of the invention

[0003] The object of the present invention is to determine the cause of a fault in an exhaust gas treatment system in a technically simple manner and with a high degree of accuracy.

[0004] According to a first aspect, the object is achieved by an exhaust gas treatment system for a motor vehicle, the exhaust gas treatment system having: a first catalytic converter for selective catalytic reduction; a second catalytic converter for selective catalytic reduction; a first nitrogen oxide sensor located before the first catalytic converter for detecting a first nitrogen oxide value; a second nitrogen oxide sensor located between the first and second catalytic converters for detecting a second nitrogen oxide value; a third nitrogen oxide sensor located after the second catalytic converter for detecting a third nitrogen oxide value; and an electronic analysis device for calculating a first efficiency of the first catalytic converter based on the first and second nitrogen oxide values, a second efficiency of the second catalytic converter based on the second and third nitrogen oxide values, and a total efficiency of the exhaust gas treatment system based on the first and third nitrogen oxide values; and a fault determination unit for determining a fault cause based on an assignment matrix, the assignment matrix assigning a fault cause based on the first efficiency, the second efficiency and the total efficiency. A technical advantage is achieved in that possible fault causes or defects of individual components of the exhaust gas treatment system can be determined quickly, in a simple manner and reliably. Failed components of the exhaust gas treatment system can be easily identified. These components include the catalytic converter or an injection system for injecting an aqueous urea solution into the catalytic converter.

[0005] In a technically advantageous embodiment of the exhaust gas treatment system, the electronic evaluation device comprises a data memory for storing the assignment matrix. This achieves the technical advantage that, for example, the assignment matrix can be stored permanently.

[0006] In another technically advantageous embodiment of the exhaust gas treatment system, the electronic evaluation device comprises a data interface for updating the assignment matrix. This achieves the technical advantage that, for example, changes and adaptations can be made at a later time.

[0007] In another technically advantageous embodiment of the exhaust gas treatment system, the exhaust gas treatment system comprises a first temperature sensor for detecting a first temperature of the first catalytic converter and a second temperature sensor for detecting a second temperature of the second catalytic converter. This achieves technical advantages, for example, in order to obtain further data for detecting the cause of the fault.

[0008] In another technically advantageous embodiment of the exhaust gas treatment system, the electronic evaluation device is designed to determine the cause of the fault additionally based on the first and second temperatures. This achieves technical advantages, for example, such that individual defective components of the exhaust gas treatment system can be identified more accurately.

[0009] In another technically advantageous embodiment of the exhaust gas treatment system, the allocation matrix is ​​used to determine the cause of the fault based on the first and second temperatures. This also achieves the technical advantage that the cause of the fault can be determined quickly and in a few steps, for example.

[0010] In another technically advantageous embodiment of the exhaust gas treatment system, the electronic evaluation device is formed by a digital electronic circuit or by a software module, thereby achieving technical advantages such as enabling rapid processing of the output information.

[0011] According to a second aspect, the object is achieved by a method for determining a cause of a fault in an exhaust gas treatment system, the method comprising the following steps: detecting a first nitrogen oxide value located before a first catalyst for selective catalytic reduction; detecting a second nitrogen oxide value located between the first catalyst for selective catalytic reduction and the second catalyst; detecting a third nitrogen oxide value located after the second catalyst for selective catalytic reduction; calculating a first efficiency of the first catalyst based on the first and second nitrogen oxide values, calculating a second efficiency of the second catalyst based on the second and third nitrogen oxide values, and calculating a total efficiency of the exhaust gas treatment system based on the first and third nitrogen oxide values; and obtaining a cause of the fault based on an allocation matrix, the allocation matrix allocating the cause of the fault based on the first efficiency, the second efficiency and the total efficiency. The same technical advantages as the exhaust gas treatment system according to the first aspect are thereby achieved.

[0012] In a technically advantageous embodiment of the method, the cause of the fault is additionally determined based on the temperature of the first catalytic converter and / or the second catalytic converter. This also achieves technical advantages, for example, in order to obtain further data for determining the cause of the fault.

[0013] In another technically advantageous embodiment of the method, an assignment matrix is ​​used to determine the assignment matrix based on the first and second temperatures. This also achieves the technical advantage that the cause of the fault can be detected quickly and in a few steps, for example.

[0014] In another technically advantageous embodiment of the method, the assignment matrix is ​​updated via a data interface, thereby achieving the technical advantage that, for example, changes and adaptations can be made at a later time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Several exemplary embodiments of the invention are shown in the drawings and will be described in more detail below.

[0016] The accompanying drawings show:

[0017] Figure 1 shows a schematic diagram of an exhaust treatment system;

[0018] Figure 2 shows an allocation matrix for obtaining fault causes; and

[0019] Figure 3 A block diagram of a method for determining the cause of a fault in an exhaust gas treatment system is shown. DETAILED DESCRIPTION

[0020] Figure 1 A schematic diagram of an exhaust gas treatment system 100 is shown. The exhaust gas treatment system 100 is integrated in a diesel exhaust system 109 of a vehicle and is used to clean exhaust gas. The exhaust gas treatment system 100 includes a first catalyst 101-1 for selective catalytic reduction and a second catalyst 101-2 for selective catalytic reduction. The two catalysts 101-1 and 101-2 are arranged successively in the diesel exhaust system 109, so that a dual selective catalytic reaction for the exhaust gas can be performed.

[0021] The nitrogen oxides NOx in the exhaust gas are reduced by selective catalytic reduction. For this purpose, an aqueous urea solution is used. The urea solution is injected into the exhaust gas flow at system pressure in a metered manner by an injector. In the titanium-coated SCR catalyst, ammonia reduces nitrogen monoxide and nitrogen dioxide to nitrogen and water vapor starting from an exhaust gas temperature of 170 degrees.

[0022] The chemical reactions on the catalysts 101 - 1 and 101 - 2 are selective, so that nitrogen oxides NO, NO 2 are preferentially reduced, while undesirable side reactions such as oxidation of sulfur dioxide to sulfur trioxide are largely suppressed.

[0023] To determine the nitrogen oxide value before and after exhaust gas treatment, the exhaust gas treatment system 100 includes a plurality of nitrogen oxide sensors 103-1, ..., 103-3. The nitrogen oxide sensors 103-1, ..., 103-3 include metal oxides such as ceramics, which can withstand the temperature in the exhaust gas flow. The nitrogen oxide sensors 103-1, ..., 103-3 obtain nitrogen oxide values, such as NO values ​​or NO2 values, in the exhaust gas flow.

[0024] The first nitrogen oxide sensor 103-1 is arranged in front of the first catalyst 101-1 and is used to detect a first nitrogen oxide value NOx-1 in the exhaust gas flow before exhaust treatment. The second nitrogen oxide sensor 103-2 is arranged between the first and second catalysts 101-1 and 101-2 and is used to detect a second nitrogen oxide value NOx-2 in the exhaust gas flow between the catalysts 101-1 and 101-2. The third nitrogen oxide sensor 103-3 is arranged after the second catalyst 101-2 and is used to detect a third nitrogen oxide value NOx-3 in the exhaust gas flow after being treated by the exhaust gas treatment system 100.

[0025] The nitrogen oxide sensors 103-1, ..., 103-3 are electrically connected to the electronic analysis device 105 via data lines so that the measured nitrogen oxide values ​​can be transmitted to the electronic analysis device. The electronic analysis device 105 analyzes the nitrogen oxide values ​​and uses them to determine possible fault causes. To this end, the electronic analysis device 105 can calculate the efficiency of the first catalytic converter 101-1, the efficiency of the second catalytic converter 101-2, or the overall efficiency of the exhaust gas treatment system 100.

[0026] For example, the efficiency of the first catalyst 101-1 can be obtained by dividing the first nitrogen oxide value by the second nitrogen oxide value. For example, the efficiency of the second catalyst 101-2 can be obtained by dividing the second nitrogen oxide value by the third nitrogen oxide value. For example, the overall efficiency of the exhaust gas treatment system 100 can be obtained by dividing the first nitrogen oxide value by the third nitrogen oxide value. The electronic analysis device 105 is, for example, composed of a digital electronic circuit or a software module.

[0027] The analysis device 105 comprises an electronic fault determination unit 113 for determining the cause of the fault based on the assignment matrix 200. The electronic fault determination unit 113 is likewise formed by a digital electronic circuit or a software module, for example.

[0028] Furthermore, the evaluation device 105 comprises a data interface 115 via which the stored assignment matrix can be changed or updated. The data interface 115 is, for example, a wireless interface such as a WLAN interface or a GSM interface or a wired interface such as a CAN bus.

[0029] In addition, the exhaust gas treatment system 100 includes a first temperature sensor 107-1 for detecting a first temperature of the first catalyst 101-1 and a second temperature sensor 107-2 for detecting a second temperature of the second catalyst 101-2. The temperature sensors 107-1 and 107-2 are electronic components that provide an electrical signal as a measure of temperature. The temperature sensors 107-1 and 107-2 are also electrically connected to the electronic analysis device 105 via a data line so that the measured temperature values ​​can be transmitted to the electronic analysis device.

[0030] In addition to the nitrogen oxide values, the temperatures of the catalytic converters 101 - 1 and 101 - 2 can also be analyzed to determine the cause of the fault. For this purpose, the cause of the fault is determined with the aid of an assignment matrix that assigns the cause of the fault to the corresponding nitrogen oxide values ​​and temperature values.

[0031] The assignment matrix is ​​stored, for example, in an electronic data memory such as a ROM memory or a flash memory in the electronic analysis device 105. The assignment matrix and the nitrogen oxide values ​​and the temperature values ​​can be processed by a processor for data processing. In this way, the corresponding fault causes in the exhaust gas treatment system 100 can be obtained.

[0032] Figure 2 A possible assignment matrix 200 (fingerprint matrix) for obtaining fault causes is shown. The assignment matrix 200 assigns corresponding fault causes based on the respective efficiencies of the first catalytic converter 101-1, the second catalytic converter 101-2 and the entire exhaust gas treatment system 100 and the temperatures of the first catalytic converter 101-1 and the second catalytic converter 101-2. Therefore, it is possible to obtain based on the assignment matrix 200: which fault cause exists when the efficiencies of the first catalytic converter 101-1, the second catalytic converter 101-2 and the exhaust gas treatment system and the temperatures of the first catalytic converter 101-1 and the second catalytic converter 101-2 are known. Through the assignment matrix 200, individual defective components of the exhaust gas treatment system 100 can be obtained in a simple and fast manner based on the respective efficiencies and temperatures.

[0033] For example, if the efficiency and temperature of the first catalyst 101 - 1 are high, the efficiency and temperature of the second catalyst 101 - 2 are high, and the overall efficiency of the exhaust treatment system 100 is high, the exhaust treatment system 100 is in a normal state (OK).

[0034] In contrast, if the first catalyst 101 - 1 is inefficient at high temperatures, and the efficiency and temperature of the second catalyst 101 - 2 are high, and the overall efficiency of the exhaust treatment system 100 is high, then the catalyst 101 - 1 is defective.

[0035] By means of the assignment matrix 200, the corresponding fault cause can be determined for all operating states of the exhaust gas treatment system 100. By using the assignment matrix 200, the fault cause can be reliably determined in a simple and fast manner.

[0036] Figure 3 A block diagram of a method for determining a fault cause in an exhaust gas treatment system 100 is shown. The method includes: a first step S101 of detecting a first nitrogen oxide value NOx-1 located before a first catalyst 101-1 for selective catalytic reduction; a step S102 of detecting a second nitrogen oxide value NOx-2 located between the first catalyst 101-1 and the second catalyst 101-2 for selective catalytic reduction; and a step S103 of detecting a third nitrogen oxide value NOx-2 located after the second catalyst 101-1 for selective catalytic reduction. Subsequently, in step S104, a first efficiency of the first catalyst is calculated based on the first and second nitrogen oxide values, a second efficiency of the second catalyst is calculated based on the second and third nitrogen oxide values, and a total efficiency of the exhaust gas treatment system is calculated based on the first and third nitrogen oxide values. In step S105, a fault cause is obtained based on an allocation matrix, and the allocation matrix allocates the fault cause based on the first efficiency, the second efficiency, and the total efficiency.

[0037] By determining the efficiency of the first and second catalysts 101 - 1 and 101 - 2 under various conditions (eg, the temperature of the catalysts), output information is collected that can more accurately determine the cause of the fault.

[0038] In particular, the conditions are preferred wherein:

[0039] - the first and second catalysts 101 - 1 and 101 - 2 are both at operating temperature,

[0040] - both the first and second catalysts 101-1 and 101-2 are below the operating temperature,

[0041] - Only the first catalyst 101 - 1 is at operating temperature, or

[0042] Only the second catalytic converter 101 - 2 is at operating temperature.

[0043] The output information collected in this way can be used to determine the source of the fault with the aid of the assignment matrix 200 .

[0044] The distribution matrix is ​​used to determine the source of the fault by means of the efficiency of the first catalyst 101-1, the efficiency of the second catalyst 101-2, and the overall efficiency of the exhaust treatment system 100. In addition, the operating temperature of the first catalyst 101-1 and the operating temperature of the second catalyst 101-2 are determined. The NOx conversion rates of the individual catalysts and the entire exhaust treatment system are monitored to collect output information of the distribution matrix.

[0045] All features which have been described and illustrated in connection with individual embodiments of the invention can be provided in various combinations in the subject matter of the invention in order to achieve their advantageous effects simultaneously.

[0046] All method steps can be implemented by means suitable for carrying out the respective method steps.All functions implemented by the features of the present subject matter can be method steps of a method.

[0047] The scope of protection of the present invention is given by the claims and is not limited to the features described in the description or shown in the drawings.

[0048] List of Reference Numerals

[0049] 100 Exhaust treatment system

[0050] 101 Catalyst

[0051] 103 NOx sensor

[0052] 105 Analysis device

[0053] 107 Temperature sensor

[0054] 109 Diesel engine exhaust system

[0055] 111 Data storage

[0056] 113 Fault determination unit

[0057] 115 Data Interface

[0058] 200 Allocation Matrix

Claims

1. An exhaust gas treatment system (100) for a motor vehicle, the exhaust gas treatment system having: A first catalyst (101-1) for selective catalytic reduction; A second catalyst (101-2) for selective catalytic reduction; a first nitrogen oxide sensor (103-1) located before the first catalyst (101-1) and used for detecting a first nitrogen oxide value (NOx-1); A second nitrogen oxide sensor (103-2) located between the first and second catalysts (101-1; 101-2) for detecting a second nitrogen oxide value (NOx-2); a third nitrogen oxide sensor (103-3) for detecting a third nitrogen oxide value (NOx-3) after the second catalyst (101-2), wherein the second catalyst is arranged downstream of the first catalyst; and an electronic analysis device (105) for calculating a first efficiency of the first catalyst (101-1) based on the first and second nitrogen oxide values ​​(NOx-1; NOx-2), calculating a second efficiency of the second catalyst (101-2) based on the second and third nitrogen oxide values ​​(NOx-2; NOx-3), and calculating an overall efficiency of the exhaust gas treatment system (100) based on the first and third nitrogen oxide values ​​(NOx-1; NOx-3); and A fault determination unit (113) is used to obtain the cause of a fault in at least one of the first, second or third nitrogen oxide sensors, or in one of the first and / or second catalysts, or in all of the first, second or third nitrogen oxide sensors and the first and / or second catalysts based on an allocation matrix (200), wherein the allocation matrix allocates the cause of the fault based on the first efficiency, the second efficiency and the total efficiency.

2. The exhaust gas treatment system (100) according to claim 1, wherein the electronic analysis device (105) comprises a data memory (111) for storing the allocation matrix (200).

3. The exhaust gas treatment system (100) according to claim 2, wherein the exhaust gas treatment system (100) comprises a first temperature sensor (107-1) for detecting a first temperature of the first catalyst (101-1) and a second temperature sensor (107-2) for detecting a second temperature of the second catalyst (101-2).

4. The exhaust gas treatment system (100) according to claim 3, wherein the electronic evaluation device (105) is designed to determine the cause of the fault additionally based on the first and second temperatures.

5. The exhaust gas treatment system (100) of claim 4, wherein the allocation matrix (200) is used to determine the fault cause based on the first and second temperatures.

6. The exhaust gas treatment system (100) according to one of the preceding claims, wherein the electronic analysis device (105) is formed by a digital electronic circuit or by a software module.

7. A method for determining the cause of a fault in an exhaust gas treatment system, the method comprising the following steps: Detecting (S101) a first nitrogen oxide value (NOx-1) located before a first catalyst (101-1) for selective catalytic reduction; Detecting (S102) a second nitrogen oxide value (NOx-2) between the first catalyst (101-1) and the second catalyst (101-2) for selective catalytic reduction; detecting (S103) a third nitrogen oxide value (NOx-3) after the second catalyst (101-2) for selective catalytic reduction, wherein the second catalyst is arranged downstream of the first catalyst; as well as Calculating (S104) a first efficiency of the first catalyst (101-1) based on the first and second nitrogen oxide values ​​(NOx-1; NOx-2), calculating a second efficiency of the second catalyst (101-2) based on the second and third nitrogen oxide values ​​(NOx-2; NOx-3), and calculating a total efficiency of the exhaust gas treatment system (100) based on the first and third nitrogen oxide values ​​(NOx-1; NOx-3); as well as The cause of a fault in at least one of the first, second or third nitrogen oxide sensors, or in one of the first and / or second catalysts, or in all of the first, second or third nitrogen oxide sensors and the first and / or second catalysts is obtained (S105) based on an allocation matrix (200), wherein the allocation matrix allocates the cause of the fault based on the first efficiency, the second efficiency and the total efficiency.

8. The method according to claim 7, wherein: The cause of the fault is additionally determined based on a temperature of the first catalytic converter (101-1) and / or the second catalytic converter (101-2).

9. The method according to claim 8, wherein: The allocation matrix (200) is used to determine the fault cause based on the first and second temperatures.

10. The method according to claim 7, wherein the allocation matrix (200) is updated via a data interface (115).

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