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Title:
METHOD FOR IDENTIFYING INSTALLATION POSITIONS OF NITROGEN OXIDE SENSORS, STORAGE MEDIUM, AND ELECTRONIC CONTROL UNIT
Document Type and Number:
WIPO Patent Application WO/2020/074446
Kind Code:
A1
Abstract:
The present invention relates to a method for identifying installation positions of nitrogen oxide sensors of an exhaust gas aftertreatment system for a diesel engine, the method comprising the following steps: controlling at least one metering and injection unit to inject an exhaust gas treatment liquid into an exhaust pipe; obtaining the concentrations of nitrogen oxides detected by a plurality of nitrogen oxide sensors and corresponding identification codes; comparing the concentrations of nitrogen oxides detected by the plurality of nitrogen oxide sensors; and designating, based on the comparison result, the identification codes to characterize the installation positions of the corresponding nitrogen oxide sensors in the exhaust gas aftertreatment system. The present invention further relates to a machine-readable non-volatile storage medium and an electronic control unit. According to the present invention, the installation positions of the nitrogen oxide sensors in the exhaust gas aftertreatment system for the diesel engine can be identified such that the concentrations of nitrogen oxides detected by the nitrogen oxide sensors correctly correspond to the installation positions thereof in the exhaust gas aftertreatment system.

Inventors:
LIU YI (CN)
XU YUJIANG (CN)
Application Number:
PCT/EP2019/077088
Publication Date:
April 16, 2020
Filing Date:
October 07, 2019
Export Citation:
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Assignee:
BOSCH GMBH ROBERT (DE)
International Classes:
F01N3/20; F01N11/00
Domestic Patent References:
WO2017138873A12017-08-17
WO2016010558A12016-01-21
Foreign References:
EP1247966A22002-10-09
US20090107114A12009-04-30
EP1333170A22003-08-06
DE102008042289A12010-03-25
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Claims:
Claims

1. A method for identifying installation positions of nitrogen oxide sensors of an exhaust gas aftertreatment system (100, 200, 300) for a diesel engine, the exhaust gas aftertreatment system (100, 200, 300) for the diesel engine being provided with at least one metering and injection unit (107, 109, 207, 307) for metering and injecting an exhaust gas treatment liquid into an exhaust pipe (11), and a plurality of nitrogen oxide sensors (101, 103, 105, 201, 203, 205, 301, 303) which are installed inside the exhaust pipe (11) along an exhaust gas flow direction (17) and which are used for detecting concentrations of nitrogen oxides in the exhaust gas inside the exhaust pipe (11), the plurality of nitrogen oxide sensors (101, 103, 105, 201, 203, 205,

301, 303) being respectively assigned identification codes ;

characterized in that the method comprises the following steps:

controlling the at least one metering and injection unit (107, 109, 207, 307) to inject the exhaust gas treatment liquid into the exhaust pipe (11);

obtaining the concentrations of nitrogen oxides detected by the plurality of nitrogen oxide sensors (101, 103, 105, 201, 203, 205, 301, 303) and corresponding identification codes;

comparing the concentrations of nitrogen oxides detected by the plurality of nitrogen oxide sensors (101, 103, 105, 201, 203, 205, 301, 303); and

designating, based on the comparison result, the identification codes to characterize the installation positions of the corresponding nitrogen oxide sensors in the exhaust gas aftertreatment system (100, 200, 300).

2. The method of claim 1, characterized in that the exhaust gas aftertreatment system (100) for the diesel engine is provided with three nitrogen oxide sensors (101, 103, 105) and two metering and injection units (107, 109) .

3. The method of claim 2, characterized by comprising the following steps:

controlling the two metering and injection units (107, 109) respectively to inject the exhaust gas treatment liquid into the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the highest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed the most upstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the lowest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed the most downstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11); and

designating the identification code of the remaining nitrogen oxide sensor in the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed between the nitrogen oxide sensor the most upstream and the nitrogen oxide sensor the most downstream inside the exhaust pipe (11) .

4. The method of claim 2, characterized by comprising the following steps:

controlling the upstream one (107) of the two metering and injection units (107, 109) to inject the exhaust gas treatment liquid into the exhaust pipe (11); designating the identification code of the nitrogen oxide sensor having the highest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed the most upstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the lowest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed the most downstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11); and

designating the identification code of the remaining nitrogen oxide sensor in the three nitrogen oxide sensors (101, 103, 105) to characterize that this nitrogen oxide sensor is installed between the nitrogen oxide sensor the most upstream and the nitrogen oxide sensor the most downstream inside the exhaust pipe (11) .

5. The method of claim 1, characterized in that the exhaust gas aftertreatment system (200) for the diesel engine is provided with three nitrogen oxide sensors (201, 203, 205) and one metering and injection unit (207), and the method comprises the following steps: controlling the metering and injection unit (207) to inject the exhaust gas treatment liquid into the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the highest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (201, 203, 205) to characterize that this nitrogen oxide sensor is installed the most upstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the lowest one of the concentrations of nitrogen oxides detected by the three nitrogen oxide sensors (201, 203, 205) to characterize that this nitrogen oxide sensor is installed the most downstream with respect to the other two nitrogen oxide sensors inside the exhaust pipe (11); and designating the identification code of the remaining nitrogen oxide sensor in the three nitrogen oxide sensors (201, 203, 205) to characterize that this nitrogen oxide sensor is installed between the nitrogen oxide sensor the most upstream and the nitrogen oxide sensor the most downstream inside the exhaust pipe (11) .

6. The method of claim 1, characterized in that the exhaust gas aftertreatment system (300) for the diesel engine is provided with two nitrogen oxide sensors (301, 303) and one metering and injection unit (307), and the method comprises the following steps:

controlling the metering and injection unit (307) to inject the exhaust gas treatment liquid into the exhaust pipe (11);

designating the identification code of the nitrogen oxide sensor having the higher one of the concentrations of nitrogen oxides detected by the two nitrogen oxide sensors (301, 303) to characterize that this nitrogen oxide sensor is installed upstream of the other nitrogen oxide sensor in the exhaust pipe (11), and/or the identification code of the nitrogen oxide sensor having the lower one of the concentrations of nitrogen oxides detected by the two nitrogen oxide sensors (301, 303) to characterize that this nitrogen oxide sensor is installed downstream of the other nitrogen oxide sensor in the exhaust pipe (11) .

7. The method of any one of claims 1 to 6, characterized in that the exhaust gas treatment liquid is an aqueous urea solution.

8. A machine-readable non-volatile storage medium on which program instructions for implementing a method of any one of claims 1 to 7 are stored.

9. An electronic control unit (7), the electronic control unit (7) having a memory and a processor, wherein the memory stores executable program instructions which, when executed, cause the processor to implement a method of any one of claims 1 to 7.

Description:
Description

Method for identifying installation positions of nitrogen oxide sensors, storage medium, and electronic control unit

Technical Field

The present invention relates to a method for identifying installation positions of nitrogen oxide sensors of an exhaust gas aftertreatment system for a diesel engine. The present invention further relates to a machine-readable non-volatile storage medium on which program instructions for implementing the method are stored. The present invention further relates to an electronic control unit having a memory and a processor, wherein the memory stores executable program instructions which, when executed, cause the processor to implement the method. Background Art

Diesel engines produce exhaust gas with a higher concentration of nitrogen oxides after combustion, and this exhaust gas cannot be directly discharged into the air, but needs to be treated by exhaust gas aftertreatment systems before being discharged into the atmosphere. Selective catalytic reduction (SCR) is a technique widely used for reducing the concentration of nitrogen oxides in the exhaust gas discharged from the diesel engine. The selective catalytic reduction method treats the exhaust gas discharged from the diesel engine by using an exhaust gas treatment liquid (usually an aqueous urea solution) in the exhaust gas after-treatment system to convert harmful nitrogen oxides in the exhaust gas into harmless nitrogen and water vapor, to reduce harmful gas emissions from the diesel engine.

To this end, the exhaust gas aftertreatment system generally comprises a storage tank for storing the exhaust gas treatment liquid, a metering and injection unit for metering and injecting the exhaust gas treatment liquid into an exhaust gas pipe, and a supply unit which is connected between the storage tank and the metering and injection unit and which is used for supplying the exhaust gas treatment liquid to the metering and injection unit, an exhaust gas filter for filtering the exhaust gas, a catalytic converter for selectively catalytically reducing nitrogen oxides in the exhaust gas by using the exhaust gas treatment liquid, and various sensors for detecting the exhaust gas. An electronic control unit (ECU) is used for control and diagnostic purposes, which communicates with the various sensors disposed in the exhaust gas aftertreatment system via a CAN bus. When the exhaust gas aftertreatment system is in operation, the electronic control unit calculates the injection amount of the exhaust gas treatment liquid based on data collected by the various sensors. Under the control of the electronic control unit, a pump in the supply unit extracts the exhaust gas treatment liquid from the storage tank through a liquid suction pipeline and delivers the exhaust gas treatment liquid to the metering and injection unit through a pressure pipeline at a certain pressure, and then the metering and injection unit atomizes and injects, according to a predetermined injection amount, the exhaust gas treatment liquid into an exhaust pipe, thereby prompting the nitrogen oxides in the exhaust gas to be reduced inside the exhaust pipe. Among the various sensors disposed in the exhaust gas aftertreatment system, a nitrogen oxide (NO c ) sensor is used to detect the concentration of nitrogen oxides such as NO and NO 2 in the exhaust gas inside the exhaust pipe and feed back the detected concentration of nitrogen oxides via the CAN bus to the electronic control unit to achieve a closed-loop control over nitrogen oxide emissions.

In conventional exhaust gas aftertreatment systems, the nitrogen oxide sensor is typically provided only at the last segment of the exhaust gas aftertreatment system to detect the concentration of nitrogen oxides in the exhaust gas discharged from the exhaust gas aftertreatment system. However, due to the introduction of more strict emission regulations and higher requirements for the performance of on-board diagnostic systems, more than one nitrogen oxide sensor is disposed in the exhaust gas aftertreatment system to achieve more accurate emission control and on-board diagnostics. In the case where more than one nitrogen oxide sensor is provided, these nitrogen oxide sensors need to be distinguished when the nitrogen oxide sensors communicate with the electronic control unit via the CAN bus, in order to make the concentrations of nitrogen oxides detected by the nitrogen oxide sensors correctly correspond to the installation positions of the nitrogen oxide sensors in the exhaust gas aftertreatment system.

For an exhaust gas aftertreatment system for a diesel engine that is provided with a plurality of nitrogen oxide sensors, it is desirable to automatically identify the installation positions of the nitrogen oxide sensors in the exhaust gas aftertreatment system.

Summary of the Invention

An object of the present invention is to provide a method of identifying installation positions of nitrogen oxide sensors of an exhaust gas aftertreatment system for an diesel engine, which method is capable of identifying the installation positions of the nitrogen oxide sensors in the exhaust gas aftertreatment system for the diesel engine .

According to an aspect of the present invention, there is provided a method for identifying installation positions of nitrogen oxide sensors of an exhaust gas aftertreatment system for a diesel engine, the exhaust gas aftertreatment system for the diesel engine being provided with at least one metering and injection unit for metering and injecting an exhaust gas treatment liquid into an exhaust pipe, and a plurality of nitrogen oxide sensors which are installed inside the exhaust pipe along an exhaust gas flow direction and which are used for detecting concentrations of nitrogen oxides in the exhaust gas inside the exhaust pipe, the plurality of nitrogen oxide sensors being respectively assigned identification codes;

characterized in that the method comprises the following steps:

controlling the at least one metering and injection unit to inject an exhaust gas treatment liquid into the exhaust pipe;

obtaining the concentrations of nitrogen oxides detected by the plurality of nitrogen oxide sensors and corresponding identification codes;

comparing the concentrations of nitrogen oxides detected by the plurality of nitrogen oxide sensors; and designating, based on the comparison result, the identification codes to characterize the installation positions of the corresponding nitrogen oxide sensors in the exhaust gas aftertreatment system.

According to another aspect of the present invention, there is provided a machine-readable non volatile storage medium on which program instructions for implementing the above method are stored.

According to still another aspect of the present invention, there is provided an electronic control unit having a memory and a processor, wherein the memory stores executable program instructions which, when executed, cause the processor to implement the above method .

According to the present invention, the installation positions of the corresponding nitrogen oxide sensors in the exhaust gas aftertreatment system for the diesel engine can be identified based on the concentrations of nitrogen oxides detected by the nitrogen oxide sensors. In this way, the installation positions of the nitrogen oxide sensors in the exhaust gas aftertreatment system for the diesel engine can be identified such that the concentrations of nitrogen oxides detected by the nitrogen oxide sensors correctly correspond to the installation positions thereof in the exhaust gas aftertreatment system.

Brief Description of the Drawings

Fig. 1 is a schematic view of the working principle of a nitrogen oxide sensor;

Fig. 2A schematically shows an exhaust gas aftertreatment system, which is provided with three nitrogen oxide sensors and two metering and injection units ;

Fig. 2B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe in an exhaust gas flow direction and the injection of the exhaust gas treatment liquid into the exhaust pipe by the metering and injection units during operation of the exhaust gas aftertreatment system of Fig. 2A;

Fig. 2C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors of the exhaust gas aftertreatment system for the diesel engine of Fig. 2A, in accordance with one embodiment of the present invention ;

Fig. 3A schematically shows another exhaust gas aftertreatment system similar to the exhaust gas aftertreatment system shown in Fig. 2A, but being provided with only one metering and injection unit;

Fig. 3B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe in an exhaust gas flow direction and the injection of the exhaust gas treatment liquid into the exhaust pipe by the metering and injection unit during operation of the exhaust gas aftertreatment system of Fig. 3A;

Fig. 3C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors of the exhaust gas aftertreatment system for the diesel engine of Fig. 3A, in accordance with another embodiment of the present invention ;

Fig. 4A schematically shows still another exhaust gas aftertreatment system similar to the exhaust gas aftertreatment system of Fig. 2A, but being provided with only two nitrogen oxide sensors and one metering and injection unit;

Fig. 4B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe in an exhaust gas flow direction and the injection of the exhaust gas treatment liquid into the exhaust pipe by the metering and injection unit during operation of the exhaust gas aftertreatment system of Fig. 4A; and

Fig. 4C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors of the exhaust gas aftertreatment system for the diesel engine of Fig. 4A, in accordance with still another embodiment of the present invention.

Detailed Description of Embodiments

Preferred embodiments of the present invention are described in detail below with reference to examples. It should be understood by those skilled in the art that these exemplary embodiments are not intended to limit the present invention in any way.

Fig. 1 is a schematic view of the working principle of a nitrogen oxide sensor. The nitrogen oxide sensor 1 comprises a nitrogen oxide sensing element 3 and a sensor control unit 5. When the nitrogen oxide sensor 1 is in operation, the nitrogen oxide sensing element 3 detects the concentration of nitrogen oxides in exhaust gas and transmits the detected concentration of nitrogen oxides in the form of an electrical signal to the sensor control unit 5, and the electrical signal is then encoded by the sensor control unit 5 and transmitted to an electronic control unit (ECU) 7 via a CAN bus 9 in the form of a CAN message along with an identification code indicating the installation position of the nitrogen oxide sensor 1 in the exhaust gas aftertreatment system. This identification code is assigned to the nitrogen oxide sensor 1 at the time of manufacture, and corresponds to the installation position of the nitrogen oxide sensor 1 in the exhaust gas aftertreatment system. The electronic control unit 7 receives the CAN message transmitted by the nitrogen oxide sensor 1 and obtains the concentration of nitrogen oxides detected by the nitrogen oxide sensor 1 and the corresponding installation position from the CAN message, whereby the electronic control unit 7 controls the injection of the exhaust gas treatment liquid and determines an input to an on-board diagnostic system (OBD) .

Fig. 2A schematically shows an exhaust gas aftertreatment system 100, which is provided with three nitrogen oxide sensors 101, 103, 105 and two metering and injection units 107, 109. The three nitrogen oxide sensors 101, 103, 105 communicate with the electronic control unit 7 via the CAN bus. The first nitrogen oxide sensor 101, the second nitrogen oxide sensor 103, and the third nitrogen oxide sensor 105 have been respectively assigned identification codes corresponding to the positions where they are to be installed in the exhaust gas aftertreatment system 100 at the time of manufacture. The first nitrogen oxide sensor 101, the second nitrogen oxide sensor 103, and the third nitrogen oxide sensor 105 are arranged inside an exhaust pipe 11 along an exhaust gas flow direction 17 (indicated by the arrow) . Specifically, the first nitrogen oxide sensor 101 is disposed near an inlet of the exhaust gas aftertreatment system 100 inside the exhaust pipe 11 to measure the concentration of nitrogen oxides in the exhaust gas discharged from a diesel engine. The second nitrogen oxide sensor 103 is disposed between an exhaust gas filter 13 and a catalytic converter 15 inside the exhaust pipe 11 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the exhaust gas filter 13 and before passing through the catalytic converter 15. The third nitrogen oxide sensor 105 is disposed downstream of the catalytic converter 15 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the catalytic converter 15. The first metering and injection unit 107 and the second metering and injection unit 109 are hard-wired to the electronic control unit 7 and inject the exhaust gas treatment liquid into the exhaust pipe 11 under the control of the electronic control unit 7. Specifically, the first metering and injection unit 107 is disposed between the first nitrogen oxide sensor 101 and the second nitrogen oxide sensor 103 and upstream of the exhaust gas filter 13 for injecting the exhaust gas treatment liquid into the exhaust pipe 11. The second metering and injection unit 109 is disposed between the second nitrogen oxide sensor 103 and the third nitrogen oxide sensor 105 and upstream of the catalytic converter 15 for injecting the exhaust gas treatment liquid into the exhaust pipe 11. The exhaust gas filter 13 is, for example, SDPF or CDPF, which may be coated with a catalyst for selective catalytic reduction of the nitrogen oxides, and when the first metering and injection unit 107 injects the exhaust gas treatment liquid into the exhaust pipe 11, the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 can react with the exhaust gas treatment liquid in the exhaust gas filter 13 and are converted into harmless nitrogen and water vapor. In addition, the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 can also react with the exhaust gas treatment liquid in the catalytic converter 15 and are converted into harmless nitrogen and water vapor.

Fig. 2B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17 and the injection of the exhaust gas treatment liquid into the exhaust pipe 11 by the metering and injection units 107, 109 during operation of the exhaust gas aftertreatment system 100 of Fig. 2A. In Fig. 2B, the triangles represent the operation of the metering and injection units 107, 109 to inject the exhaust gas treatment liquid into the exhaust pipe 11, and the dashed lines 111, 113, 115 represent the change of the concentration of the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17 under the operation of the different metering and injection units. When both the first metering and injection unit 107 and the second metering and injection unit 109 inject the exhaust gas treatment liquid into the exhaust pipe 11, since the nitrogen oxides in the exhaust gas react with the exhaust gas treatment liquid in the exhaust gas filter 13 and the catalytic converter 15 respectively as described above, and are converted into harmless nitrogen and water vapor, the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 is lowered in the exhaust gas flow direction 17 as indicated by the dashed line 111. That is, in this case, the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 101 is the highest, the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 105 is the lowest, and the concentration of nitrogen oxides detected by the second nitrogen oxide sensor 103 is between the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 101 and the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 105. When only the second metering and injection unit 109 injects the exhaust gas treatment liquid into the exhaust pipe 11, since the nitrogen oxides in the exhaust gas react with the exhaust gas treatment liquid only in the catalytic converter 15, the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 is lowered in the exhaust gas flow direction 17 as indicated by the dashed line 113. That is, in this case, the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 105 is the lowest, and the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 101 is approximately equal to that detected by the second nitrogen oxide sensor 103. When only the first metering and injection unit 107 injects the exhaust gas treatment liquid into the exhaust pipe 11, although the exhaust gas treatment liquid injected by the metering and injection unit 107 in the exhaust gas filter 13 reacts with the nitrogen oxides in the exhaust gas, this reaction is incomplete, and some of the exhaust gas treatment liquid and the nitrogen oxides remain, and then the remaining exhaust gas treatment liquid and nitrogen oxides react in the catalytic converter 15 to further lower the concentration of nitrogen oxides in the exhaust gas. Consequently, the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 is lowered in the exhaust gas flow direction 17 as indicated by the dashed line 115. That is, in this case, the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 101 is the highest, the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 105 is the lowest, and the concentration of nitrogen oxides detected by the second nitrogen oxide sensor 103 is still between the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 101 and the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 105. According to the relationship shown in Fig. 2B between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17 and the injection of the exhaust gas treatment liquid by the metering and injection units 107, 109 in the exhaust gas aftertreatment system 100 during operation of the exhaust gas aftertreatment system 100 of Fig. 2A, a method for identifying the installation positions of the nitrogen oxide sensors 101, 103, 105 of the exhaust gas aftertreatment system 100 for the diesel engine of Fig. 2A is conceivable.

Fig. 2C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors 101, 103, 105 of the exhaust gas aftertreatment system 100 for the diesel engine of Fig. 2A, in accordance with one embodiment of the present invention. The nitrogen oxide sensors 101, 103, 105 are randomly installed in the exhaust gas aftertreatment system 100 during vehicle assembly or during vehicle maintenance. In step S101, the first metering and injection unit 107 is controlled to inject the exhaust gas treatment liquid into the exhaust pipe 11. In step S103, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 101, 103, 105 and the corresponding identification codes are obtained. In step S105, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 101, 103, 105 are compared. In step S107, based on the comparison result, the identification code of the nitrogen oxide sensor having the highest detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed the most upstream with respect to the remaining two nitrogen oxide sensors inside the exhaust pipe 11. In step S109, the second metering and injection unit 109 is controlled to inject the exhaust gas treatment liquid into the exhaust pipe 11. In step Sill, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 101, 103, 105 and the identification codes are obtained again. In step S113, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 101, 103, 105 are compared again. In step S115, the identification code of the nitrogen oxide sensor having the lowest detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed the most downstream with respect to the remaining two nitrogen oxide sensors inside the exhaust pipe 11, and the identification code of the remaining nitrogen oxide sensor (the identification code being not designated) is designated to characterize that this nitrogen oxide sensor is installed between the nitrogen oxide sensor the most upstream and the nitrogen oxide sensor the most downstream inside the exhaust pipe 11. In this way, the installation positions of the three nitrogen oxide sensors 101, 103, 105 in the exhaust gas aftertreatment system 100 can be correctly identified, and the concentrations of nitrogen oxides detected by these nitrogen oxide sensors correspond correctly to the installation positions of the nitrogen oxide sensors. It should be understood that by simply controlling the first metering and injection unit 107 to inject the exhaust gas treatment liquid into the exhaust pipe 11, it is also possible to identify (i.e., based on the dashed line 115 in Fig. 2B) the installation positions of the three nitrogen oxide sensors 101, 103, 105 in the exhaust gas aftertreatment system 100, but the method shown in Fig. 2C is more accurate.

Fig. 3A schematically shows another exhaust gas aftertreatment system 200 similar to the exhaust gas aftertreatment system 100 shown in Fig. 2A, but being provided with only one metering and injection unit 207. The three nitrogen oxide sensors 201, 203, 205 communicate with the electronic control unit 7 via the CAN bus. The first nitrogen oxide sensor 201, the second nitrogen oxide sensor 203, and the third nitrogen oxide sensor 205 have been respectively assigned identification codes corresponding to the positions where they are to be installed in the exhaust gas aftertreatment system 200 at the time of manufacture. The first nitrogen oxide sensor 201, the second nitrogen oxide sensor 203, and the third nitrogen oxide sensor 205 are arranged inside an exhaust pipe 11 along the exhaust gas flow direction 17 (indicated by the arrow) . Specifically, the first nitrogen oxide sensor 201 is disposed near an inlet of the exhaust gas aftertreatment system 200 inside the exhaust pipe 11 to measure the concentration of nitrogen oxides in the exhaust gas discharged from the diesel engine. The second nitrogen oxide sensor 203 is disposed between an exhaust gas filter 13 and a catalytic converter 15 inside the exhaust pipe 11 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the exhaust gas filter 13 and before passing through the catalytic converter 15. The third nitrogen oxide sensor 205 is disposed downstream of the catalytic converter 15 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the catalytic converter 15. The metering and injection unit 207 is hard-wired to the electronic control unit 7 and injects the exhaust gas treatment liquid into the exhaust pipe 11 under the control of the electronic control unit 7. Specifically, the metering and injection unit 207 is disposed between the first nitrogen oxide sensor 201 and the second nitrogen oxide sensor 203 and upstream of the exhaust gas filter 13 for injecting the exhaust gas treatment liquid into the exhaust pipe 11. As described above with reference to the exhaust gas aftertreatment system 100 of Fig. 2A, the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 can react with the exhaust gas treatment liquid in the exhaust gas filter 13 and the catalytic converter 15 respectively and are converted into harmless nitrogen and water vapor.

Fig. 3B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17 and the injection of the exhaust gas treatment liquid into the exhaust pipe 11 by the metering and injection unit 207 during operation of the exhaust gas aftertreatment system 200 of Fig. 3A. In Fig. 3B, the triangle represents the operation of the metering and injection unit 207 to inject the exhaust gas treatment liquid into the exhaust pipe 11, and the dashed line 211 represents the change in the concentration of the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 along the exhaust gas flow direction 17 under the operation of the metering and injection unit. When the metering and injection unit 207 injects the exhaust gas treatment liquid into the exhaust pipe 11, similarly to the case shown by the dashed line 115 in Fig. 2B, the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 is lowered in the exhaust gas flow direction 17 as indicated by the dashed line 211. That is, in this case, the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 201 is the highest, the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 205 is the lowest, and the concentration of nitrogen oxides detected by the second nitrogen oxide sensor 203 is between the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 201 and the concentration of nitrogen oxides detected by the third nitrogen oxide sensor 205. Similarly, a method for identifying the installation positions of the nitrogen oxide sensors 201, 203, 205 of the exhaust gas aftertreatment system 200 for the diesel engine of Fig. 3A is also conceivable.

Fig. 3C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors 201, 203, 205 of the exhaust gas aftertreatment system 200 for the diesel engine of Fig. 3A, in accordance with one embodiment of the present invention. The nitrogen oxide sensors 201, 203, 205 are randomly installed in the exhaust gas aftertreatment system 200 during vehicle assembly or during vehicle maintenance. In step S201, the metering and injection unit 207 is controlled to inject the exhaust gas treatment liquid into the exhaust pipe 11. In step S203, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 201, 203, 205 and the corresponding identification codes are obtained. In step S205, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 201, 203, 205 are compared. In step S207, the identification code of the nitrogen oxide sensor having the highest detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed the most upstream with respect to the remaining two nitrogen oxide sensors inside the exhaust pipe 11, the identification code of the nitrogen oxide sensor having the lowest detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed the most downstream with respect to the remaining two nitrogen oxide sensors inside the exhaust pipe 11, and the identification code of the remaining nitrogen oxide sensor is designated to characterize that this nitrogen oxide sensor is installed between the nitrogen oxide sensor the most upstream and the nitrogen oxide sensor the most downstream inside the exhaust pipe 11. In this way, the installation positions of the three nitrogen oxide sensors 201, 203, 205 in the exhaust gas aftertreatment system 200 can be correctly identified, and the concentrations of nitrogen oxides detected by these nitrogen oxide sensors correspond correctly to the installation positions of the nitrogen oxide sensors.

Fig. 4A schematically shows still another exhaust gas aftertreatment system 300 similar to the exhaust gas aftertreatment system 100 shown in Fig. 2A and the exhaust gas aftertreatment system 200 shown in Fig. 3A, but being provided with two nitrogen oxide sensors 301, 303 and one metering and injection unit 307. The two nitrogen oxide sensors 301, 303 communicate with the electronic control unit 7 via the CAN bus. The first nitrogen oxide sensor 301 and the second nitrogen oxide sensor 303 have been respectively assigned identification codes corresponding to the positions where they are to be installed in the exhaust gas aftertreatment system 300 at the time of manufacture. The first nitrogen oxide sensor 301 and the second nitrogen oxide sensor 303 are arranged inside the exhaust pipe 11 along the exhaust gas flow direction 17 (indicated by the arrow) . Specifically, the first nitrogen oxide sensor 301 is disposed between the exhaust gas filter 13 and the catalytic converter 15 inside the exhaust pipe 11 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the exhaust gas filter 13 and before passing through the catalytic converter 15. The second nitrogen oxide sensor 303 is disposed downstream of the catalytic converter 15 to measure the concentration of nitrogen oxides in the exhaust gas after passing through the catalytic converter 15. The metering and injection unit 307 is hard-wired to the electronic control unit 7 and injects the exhaust gas treatment liquid into the exhaust pipe 11 under the control of the electronic control unit 7. The metering and injection unit 307 is disposed between the first nitrogen oxide sensor 301 and the second nitrogen oxide sensor 303 and upstream of the catalytic converter 15 for injecting the exhaust gas treatment liquid into the exhaust pipe 11. In this embodiment, since the metering and injection unit 307 is disposed downstream of the exhaust gas filter 13 inside the exhaust pipe 11, the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 can only react with the exhaust gas treatment liquid in the catalytic converter 15 and are converted into harmless nitrogen and water vapor .

Fig. 4B schematically shows the relationship between the change in the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17 and the injection of the exhaust gas treatment liquid into the exhaust pipe 11 by the metering and injection unit 307 during operation of the exhaust gas aftertreatment system 300 of Fig. 4A. In Fig. 4B, the triangle represents the operation of the metering and injection unit 307 to inject the exhaust gas treatment liquid into the exhaust pipe 11, and the dashed line 311 represents the change in the concentration of the nitrogen oxides in the exhaust gas inside the exhaust pipe 11 along the exhaust gas flow direction 17 under the operation of the metering and injection unit. When the metering and injection unit 307 injects the exhaust gas treatment liquid into the exhaust pipe 11, similarly to the case shown by the dashed line 113 in Fig. 2B, the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 is lowered in the exhaust gas flow direction 17 as indicated by the dashed line 311. That is, in this case, the concentration of nitrogen oxides detected by the first nitrogen oxide sensor 301 is the highest, and the concentration of nitrogen oxides detected by the second nitrogen oxide sensor 303 is the lowest. Similarly, a method for identifying the installation positions of the nitrogen oxide sensors 301, 303 of the exhaust gas aftertreatment system 300 for the diesel engine of Fig. 4A is also conceivable.

Fig. 4C schematically shows a logic flow diagram of a method for identifying the installation positions of the nitrogen oxide sensors 301, 303 of the exhaust gas aftertreatment system 300 for the diesel engine of Fig. 4A, in accordance with still another embodiment of the present invention. The nitrogen oxide sensors 301, 303 are randomly installed in the exhaust gas aftertreatment system 300 during vehicle assembly or during vehicle maintenance. In step S301, the metering and injection unit 307 is controlled to inject the exhaust gas treatment liquid into the exhaust pipe 11. In step S303, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 301, 303 and the corresponding identification codes are obtained. In step S305, the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 301, 303 are compared. In step S307, the identification code of the nitrogen oxide sensor having the higher detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed upstream of the other nitrogen oxide sensor inside the exhaust pipe 11, and/or the identification code of the nitrogen oxide sensor having the lower detected concentration of nitrogen oxides is designated to characterize that this nitrogen oxide sensor is installed downstream of the other nitrogen oxide sensor inside the exhaust pipe 11. In this way, the installation positions of the two nitrogen oxide sensors 301, 303 in the exhaust gas aftertreatment system 300 can be correctly identified, and the concentrations of nitrogen oxides detected by these nitrogen oxide sensors correspond correctly to the installation positions of the nitrogen oxide sensors.

According to the methods shown in Figs. 2C, 3C and 4C, the installation positions of the nitrogen oxide sensors 101, 103, 105, 201, 203, 205, 301, 303 in the exhaust gas aftertreatment system 100, 200, 300 can be identified, such that the concentrations of nitrogen oxides detected by the nitrogen oxide sensors 101, 103, 105, 201, 203, 205, 301, 303 correspond correctly to their installation positions thereof in the exhaust gas aftertreatment system 100, 200, 300.

It should be understood that although not shown in the drawings, the exhaust gas aftertreatment system 100, 200, 300 may also comprise other structures or components needed to perform the exhaust gas aftertreatment. For example, the exhaust gas aftertreatment system 100, 200, 300 may further comprise a storage tank for storing the exhaust gas treatment liquid, a supply unit which is connected between the storage tank and the metering and injection unit and which is used for supplying the exhaust gas treatment liquid to the metering and injection unit, etc.

It should also be understood that the dashed line 111, 113, 115, 211, 311 only schematically shows the tendency of the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 in the exhaust gas flow direction 17, and should not be understood as indicating a gradient of the concentration of nitrogen oxides in the exhaust gas inside the exhaust pipe 11 along the exhaust gas flow direction 17. These dashed lines for representing tendency can be pre-calibrated by the skilled person through experimentation and will vary depending on the type of the catalyst and the specific configuration of the exhaust gas aftertreatment system.

It should be further understood that the methods shown in Figs. 2C, 3C, and 4C may be executable program instructions which are stored on a machine-readable non volatile storage medium. It should also be understood that the electronic control unit 7 may have a memory and a processor, wherein the memory can store executable program instructions which, when executed, cause the processor to implement the method shown in Figs. 2C, 3C, and 4C.

An exhaust gas aftertreatment system provided with more than three nitrogen oxide sensors is also conceivable, in which the installation positions of the corresponding nitrogen oxide sensors in the exhaust gas aftertreatment system for the diesel engine can be identified based on the concentrations of nitrogen oxides detected by the nitrogen oxide sensors.

The present invention has been described in detail above with reference to the specific embodiments. It is apparent that the above description and the embodiments shown in the accompany drawings should be understood as exemplary and not limiting the present invention. For those skilled in the art, various variants or modifications can be made to the present invention without departing from the spirit of the present invention, and none of these variants or modifications departs from the scope of the present invention.