Exhaust gas monitoring device and exhaust gas monitoring method

Abstract

The present application provides an exhaust gas monitoring device and an exhaust gas monitoring method. The exhaust gas monitoring device includes: an exhaust gas purification device that removes nitrogen oxides; and a nitrogen oxide sensor that is disposed in an exhaust pipe at a position downstream of the exhaust gas purification device and measures a concentration of nitrogen oxides contained in exhaust gas that has passed through the exhaust gas purification device. The exhaust gas monitoring device acquires an upstream concentration and a downstream concentration. The upstream concentration is a concentration of nitrogen oxides contained in exhaust gas that flows into the exhaust gas purification device. The downstream concentration is an output value of the sensor. The exhaust gas monitoring device outputs, in a case where the downstream concentration exceeds an upper limit value that is calculated based on the upstream concentration, a processed concentration after the downstream concentration is replaced by the upper limit value as a value that represents the concentration of nitrogen oxides contained in exhaust gas that has passed through the exhaust gas purification device.

Description

Technical Field

[0001] This disclosure relates to exhaust gas monitoring devices and exhaust gas monitoring methods. Background Technology

[0002] Japanese Patent Application Publication No. 2023-8849 discloses an exhaust system. This exhaust system includes a nitrogen oxide sensor installed in the exhaust pipe. This sensor measures the nitrogen oxides (NOx) contained in the engine exhaust. x The concentration of ). Summary of the Invention

[0003] [The problem the invention aims to solve]

[0004] In exhaust systems, ammonia (NH3) is sometimes present in the exhaust gas. Nitrogen oxide sensors, in addition to NO... x In addition, it also reacts with NH3. Therefore, the output value of the nitrogen oxide sensor sometimes becomes less accurate than it reflects the actual amount of NO in the exhaust gas. x The concentration value is too high.

[0005] In one aspect of this disclosure, an exhaust monitoring device for an exhaust system is provided. The exhaust system includes: an exhaust purification device disposed in the exhaust pipe of an engine to remove nitrogen oxides (NOx) contained in the exhaust; and a NOx sensor disposed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of NOx contained in the exhaust that has passed through the exhaust purification device. The exhaust monitoring device is configured to obtain an upstream concentration and a downstream concentration, the upstream concentration being the concentration of NOx contained in the exhaust flowing into the exhaust purification device, and the downstream concentration being the output value of the NOx sensor. The exhaust monitoring device includes a processing circuit. The processing circuit is configured to perform the following processing: if the downstream concentration is below an upper limit calculated based on the upstream concentration, outputting the downstream concentration as a value representing the concentration of NOx contained in the exhaust that has passed through the exhaust purification device; and if the downstream concentration exceeds the upper limit, outputting a processed concentration after replacing the downstream concentration with the upper limit as a value representing the concentration of NOx contained in the exhaust that has passed through the exhaust purification device.

[0006] In another aspect of this disclosure, an exhaust monitoring device for an exhaust system is provided. The exhaust system includes: an exhaust purification device disposed in the exhaust pipe of an engine to remove nitrogen oxides contained in the exhaust; and a nitrogen oxide sensor disposed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of nitrogen oxides contained in the exhaust that has passed through the exhaust purification device. The exhaust monitoring device is configured to acquire the output value of the nitrogen oxide sensor, i.e., the downstream concentration. The exhaust monitoring device includes a processing circuit. The processing circuit is configured to perform the following processing: if the downstream concentration is below an upper limit calculated based on the purification rate of the exhaust purification device, outputting the downstream concentration as a value representing the concentration of nitrogen oxides contained in the exhaust that has passed through the exhaust purification device; and if the downstream concentration exceeds the upper limit, outputting a processed concentration after replacing the downstream concentration with the upper limit as a value representing the concentration of nitrogen oxides contained in the exhaust that has passed through the exhaust purification device.

[0007] In yet another aspect of this disclosure, an exhaust monitoring method is provided in an exhaust system. The exhaust system includes: an exhaust purification device disposed in the exhaust pipe of an engine to remove nitrogen oxides (NOx) contained in the exhaust; and a NOx sensor disposed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of NOx contained in the exhaust passing through the exhaust purification device. The exhaust monitoring method includes the following processing: obtaining the concentration of NOx contained in the exhaust flowing into the exhaust purification device, i.e., an upstream concentration; obtaining the output value of the NOx sensor, i.e., a downstream concentration; if the downstream concentration is below an upper limit calculated based on the upstream concentration, outputting the downstream concentration as a value representing the concentration of NOx contained in the exhaust passing through the exhaust purification device; and if the downstream concentration exceeds the upper limit, outputting a processed concentration after replacing the downstream concentration with the upper limit as a value representing the concentration of NOx contained in the exhaust passing through the exhaust purification device. Attached Figure Description

[0008] Figure 1 This is a schematic diagram showing the structure of the vehicle according to the first embodiment.

[0009] Figure 2 This is a time series diagram showing the shifts in upstream and downstream concentrations in the first case.

[0010] Figure 3 This is a time series diagram showing the shifts in upstream and downstream concentrations in the second case.

[0011] Figure 4 It means Figure 1The exhaust monitoring device is used to calculate downstream NO x A flowchart of a series of processes performed based on concentration.

[0012] Figure 5 This refers to the upstream concentration, downstream concentration, and downstream NO concentration in the second example. x A time series diagram showing the concentration shift.

[0013] Figure 6 It means Figure 1 The exhaust monitoring device is used to calculate NO. x A flowchart of a series of processes executed based on quantity.

[0014] Figure 7 This refers to the exhaust monitoring device of the second embodiment, used to calculate downstream NO. x A flowchart of a series of processes performed based on concentration.

[0015] Figure 8 This is a diagram illustrating how the exhaust monitoring device of the second embodiment estimates the purification rate of the exhaust purification device.

[0016] Figure 9 This is a timeline diagram illustrating an example of the shifts in upstream concentration, upper limit, and downstream concentration in the second embodiment.

[0017] Figure 10 This refers to the exhaust monitoring device of the third embodiment, used to calculate downstream NO. x A flowchart of a series of processes performed based on concentration.

[0018] Figure 11 This is a diagram illustrating how the exhaust monitoring device of the third embodiment calculates the estimated value.

[0019] Figure 12 This refers to the exhaust monitoring device of the fourth embodiment, used to calculate downstream NO. x A flowchart of a series of processes performed based on concentration.

[0020] Figure 13 This is a schematic diagram showing the structure of the vehicle according to the fifth embodiment.

[0021] Figure 14 This is a time series diagram showing the shifts in upstream concentration, downstream concentration, and subsequent downstream concentration in the third case.

[0022] Figure 15 This is a time series diagram showing the shifts in upstream concentration, downstream concentration, and subsequent downstream concentration in the fourth case.

[0023] Figure 16 This refers to the exhaust monitoring device of the fifth embodiment, used to calculate the NO in the downstream stage.x A flowchart of a series of processes performed based on concentration.

[0024] Figure 17 This is a time series diagram showing the shifts in upstream concentration, downstream concentration, and subsequent downstream concentration in the fourth case.

[0025] Figure 18 This is a time series diagram showing the shifts in upstream concentration, downstream concentration, and subsequent downstream concentration in the fourth case.

[0026] Figure 19 This refers to the exhaust monitoring device of the sixth embodiment, used to calculate the NO in the downstream stage. x A flowchart of a series of processes performed based on concentration. Detailed Implementation

[0027] (First Implementation)

[0028] The following is for reference Figures 1-6 The exhaust monitoring device of the first embodiment will be described.

[0029] <Structure of Vehicle 50>

[0030] like Figure 1 As shown, vehicle 50 is equipped with exhaust system 40. Exhaust system 40 includes diesel engine 10, SCR (Selective Catalytic Reduction) 11, exhaust pipe 13, injector 14, first nitrogen oxide sensor 21, second nitrogen oxide sensor 22 and exhaust monitoring device 30.

[0031] The exhaust pipe 13 is connected to the diesel engine 10. The exhaust gas discharged from the diesel engine 10 is discharged to the outside of the vehicle 50 through the exhaust pipe 13.

[0032] An SCR catalyst 11 is installed midway through the exhaust pipe 13. The SCR catalyst 11 removes nitrogen oxides (NOx) contained in the exhaust gas. x The SCR catalyst 11 is an exhaust gas purification device. It adsorbs ammonia (NH3) generated from the hydrolysis of urea. The SCR catalyst 11 uses NH3 as a reducing agent to reduce NO in the exhaust gas. x .

[0033] The first nitrogen oxide sensor 21 is disposed upstream of the SCR catalyst 11 in the exhaust pipe 13. The first nitrogen oxide sensor 21 measures the NO content in the exhaust gas flowing into the SCR catalyst 11. x The concentration.

[0034] In the following description, the first nitrogen oxide sensor 21 located upstream of the SCR catalyst 11 will be referred to as the upstream nitrogen oxide sensor. In the following description, the NOx content in the exhaust gas flowing into the SCR catalyst 11 will be referred to as the upstream nitrogen oxide sensor. x The concentration of nitrogen oxides is called the upstream concentration. The first nitrogen oxide sensor 21 outputs the upstream concentration.

[0035] Injector 14 is positioned downstream of the first nitrogen oxide sensor 21 and upstream of the SCR catalyst 11 in the exhaust pipe 13. Injector 14 adds urea to the SCR catalyst 11 by injecting urea water into the SCR catalyst 11.

[0036] A second nitrogen oxide sensor 22 is disposed downstream of the SCR catalyst 11 in the exhaust pipe 13. The second nitrogen oxide sensor 22 measures the NO content in the exhaust gas that has passed through the SCR catalyst 11. x The concentration of nitrogen oxides. Hereinafter, in the description, the concentration output by the second nitrogen oxide sensor 22 will be referred to as the downstream concentration.

[0037] The exhaust monitoring device 30 includes a processing circuit 31 and a storage device 32. The storage device 32 stores programs. The processing circuit 31 performs various processes by executing the programs stored in the storage device 32. The processing circuit 31 includes a processor.

[0038] The exhaust monitoring device 30 is communicatively connected to the first nitrogen oxide sensor 21. The exhaust monitoring device 30 periodically obtains the output value of the first nitrogen oxide sensor 21, i.e., the upstream concentration, by communicating with the first nitrogen oxide sensor 21.

[0039] The exhaust monitoring device 30 is communicatively connected to the second nitrogen oxide sensor 22. The exhaust monitoring device 30 periodically obtains the output value of the second nitrogen oxide sensor 22, i.e., the downstream concentration, by communicating with the second nitrogen oxide sensor 22.

[0040] <Shifts in upstream and downstream concentrations>

[0041] Figure 2 and Figure 3 Specific examples illustrating the shifts in upstream and downstream concentrations. In Figure 2 and Figure 3 In the middle, the vertical axis represents NO. x The concentration. In Figure 2 and Figure 3 In the diagram, the horizontal axis represents time. The following will... Figure 2 The shift shown is called the first case. Figure 3 The shift shown is called the second example. In Figure 2 and Figure 3 In the diagram, the upstream concentration is represented by a dashed line, and the downstream concentration is represented by a single-dot dashed line.

[0042] like Figure 2 As shown, in the first case, the upstream concentration consistently remained higher than the downstream concentration.

[0043] like Figure 1 As illustrated, the upstream concentration is the NO concentration contained in the exhaust gas flowing into the SCR catalyst 11, as output by the first NOx sensor 21. x The concentration of NO. On the other hand, the downstream concentration is the NO concentration in the exhaust gas that has passed through the SCR catalyst 11, as output by the second nitrogen oxide sensor 22. x The concentration.

[0044] When the exhaust gas flowing into the SCR catalyst 11 passes through the SCR catalyst 11, NO... x The amount of NO flowing into the SCR catalyst 11 is reduced. x The amount of NO contained in the exhaust gas of SCR catalyst 11 was compared with that of SCR catalyst 11. x The amount is large. Therefore, as shown in the first example, the upstream concentration always tends to be higher than the downstream concentration.

[0045] like Figure 3 As shown, in the second case, the downstream concentration value was temporarily greater than the upstream concentration value.

[0046] For reference Figure 1 NH3 is adsorbed onto the SCR catalyst 11. When the temperature of the SCR catalyst 11 increases, the NH3 adsorbed onto the SCR catalyst 11 is released from the SCR catalyst 11. In this case, the exhaust gas passing through the SCR catalyst 11 contains NH3 released from the SCR catalyst 11.

[0047] Nitrogen oxide sensor in addition to NO x In addition, it also reacts with NH3 to produce an output value. Therefore, if NH3 is released from the SCR catalyst 11, the second nitrogen oxide sensor 22 will react with NO contained in the exhaust gas. x In addition to the reaction, it also reacts with NH3. Therefore, as shown in the second example, sometimes the downstream concentration is greater than the upstream concentration.

[0048] In this case, the second nitrogen oxide sensor 22 measures the amount of NH3 reacted with the NO contained in the exhaust gas passing through the exhaust purification device. x Compared to the concentration, the output value becomes too large.

[0049] <Exhaust monitoring device 30 is for outputting downstream NO x A series of processing steps performed based on concentration >

[0050] As described above, the exhaust monitoring device 30 outputs downstream NO considering the possibility that the value output by the second nitrogen oxide sensor 22 may become excessive. x Concentration. Downstream NO x The concentration is indicated by the exhaust monitoring device 30 as the amount of NO contained in the exhaust gas that has passed through the SCR catalyst 11. x The output value is the concentration value.

[0051] Figure 4 This indicates that the exhaust monitoring device 30 outputs downstream NO. x A series of processing steps performed at a given concentration. Figure 4 The series of processes shown are executed by the processing circuit 31 when the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations. Hereinafter, S refers to a step.

[0052] Processing circuit 31 at the beginning Figure 4 During the series of processes shown, process S11 is executed first. In process S11, processing circuit 31 determines whether the obtained downstream concentration is below the upper limit value.

[0053] Exhaust monitoring device 30 calculates downstream NO x When the concentration is determined, if the downstream concentration exceeds the upper limit, the downstream concentration is replaced with the upper limit. In the first embodiment, the upper limit is the upstream concentration obtained at the same time interval as the downstream concentration.

[0054] If, during processing S11, processing circuit 31 determines that the downstream concentration is below the upper limit (S11: Yes), it proceeds to processing S12. In processing S12, processing circuit 31 uses the downstream concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 4 The series of processes shown.

[0055] Thus, when the downstream concentration obtained by the exhaust monitoring device 30 is below the upper limit, the downstream concentration will be used as the downstream NO concentration. x Concentration output.

[0056] If, during processing S11, processing circuit 31 determines that the downstream concentration is greater than the upper limit (S11: No), it proceeds to processing S13. In processing S13, processing circuit 31 uses the processed concentration as the downstream NO concentration. x Concentration output. In the first embodiment, the processed concentration is the value of the downstream concentration replaced by the upstream concentration. That is, in S13, the processing circuit 31 uses the upstream concentration as the downstream NO value. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 4 The series of processes shown.

[0057] Thus, if the downstream concentration obtained by the exhaust monitoring device 30 exceeds the upper limit, the downstream concentration will be replaced with the treated concentration after the upper limit is obtained, and this will be used as the downstream NO concentration. x Concentration output.

[0058] Downstream NO x Concentration shift >

[0059] Figure 5 Indicates downstream NO x An example of concentration shift. In Figure 5 In the middle, the vertical axis represents NO. x The concentration. In Figure 5 In the middle, the horizontal axis represents time.

[0060] exist Figure 5 It shows Figure 3 The upstream and downstream concentration shifts are illustrated in the second example. Figure 5 In the diagram, the upstream concentration is represented by a dashed line, and the downstream concentration is represented by a single-dot dashed line.

[0061] Figure 5 This indicates the downstream NO output of the exhaust monitoring device 30 in the second case. x The shift in concentration. Figure 5 In the middle, the downstream NO output of the exhaust monitoring device 30 x Concentration is represented by a solid line.

[0062] exist Figure 5 During the period up to time T1, the downstream concentration is lower than the upstream concentration. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations during the period up to time T1, it determines that the downstream concentration is lower than the upper limit (S11: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration as the downstream NO concentration. x Concentration output (S12). Therefore, in Figure 5 In the middle, it indicates downstream NO x The solid line representing the concentration overlaps with the dashed line representing the downstream concentration shift during the period up to time T1.

[0063] exist Figure 5 During the period from time T1 to time T2, the downstream concentration is greater than the upstream concentration. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations during the period from time T1 to time T2, it determines that the downstream concentration is greater than the upper limit (S11: No). Then, the exhaust gas monitoring device 30 uses the processed concentration as the downstream NO concentration. x Concentration output (S13). As described above, the processed concentration is the value of the upstream concentration, which is the upper limit, replacing the downstream concentration. Therefore, in Figure 5 In the middle, it indicates downstream NO xThe solid line representing the concentration overlaps with the dashed line representing the shift in upstream concentration during the period from time T1 to time T2.

[0064] exist Figure 5 After time T2, the downstream concentration is below the upstream concentration. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations after time T2, it determines that the downstream concentration is below the upper limit (S11: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration as the downstream NO concentration. x Concentration output (S12). Therefore, in Figure 5 In the middle, it indicates downstream NO x The solid line representing concentration overlaps with the dashed line representing the downstream concentration shift after time T2.

[0065] <Exhaust monitoring device 30 for calculating NO x A series of processes executed based on quantity >

[0066] Exhaust monitoring device 30 calculates the NO contained in the exhaust gas. x Quantity. NO x The amount is the NO contained in the exhaust gas. x The quality.

[0067] Figure 6 This indicates that the exhaust monitoring device 30 is used to calculate the NO content in the exhaust gas. x A series of processing steps executed based on quantity. Figure 6 The series of processes shown are performed by the exhaust monitoring device 30. Figure 4 The series of processes shown calculates downstream NO x After concentration, the process is executed by the processing circuit 31.

[0068] Processing circuit 31 at the beginning Figure 6 In the series of processes shown, process S21 is executed first. In process S21, processing circuit 31 calculates the NO content in the exhaust gas. x The processing circuit 31 calculates the exhaust flow rate, for example, based on the output value of an air flow meter. The exhaust flow rate is a mass flow rate. Then, the processing circuit 31 calculates the exhaust flow rate based on the downstream NO... x Calculate NO concentration and exhaust flow rate. x Quantity. For example, processing circuit 31 calculates downstream NO. x The product of concentration and exhaust flow rate is taken as the NO content in the exhaust. x quantity.

[0069] Next, processing circuit 31 executes process S22. In process S22, processing circuit 31 calculates NO. x The cumulative value of the amount. Exhaust monitoring device 30 whenever NO is calculated. xWhen calculating the cumulative value of the quantity, the calculated cumulative value is stored in storage device 32. In the processing of S22, processing circuit 31 processes the previously calculated NO stored in storage device 32. x The cumulative value of the quantity plus the NO calculated in the S21 process. x Quantity, to calculate NO at the current moment. x The cumulative value of the quantity. Then, the processing circuit 31 causes the processing to enter S23.

[0070] In the processing of S23, the processing circuit 31 will calculate the NO at the current time in the processing of S22. x The accumulated value is stored in storage device 32. Afterwards, processing circuit 31 terminates. Figure 6 The series of processes shown.

[0071] Thus, whenever the processing circuit 31 calculates the downstream NO x Calculating NO concentration x Quantity, and NO x The cumulative value of the amount is stored in storage device 32. For example, after the vehicle 50 has finished driving, the exhaust monitoring device 30 stores the calculated NO... x Dividing the cumulative value of the quantity by the vehicle's travel distance of 50 allows us to calculate the NO for each certain travel distance. x quantity.

[0072] <The Role of the First Implementation Method>

[0073] Through the SCR catalyst 11, which serves as an exhaust purification device, NO in the exhaust gas is... x The amount of nitrogen oxides decreases, so the downstream concentration becomes lower than the upstream concentration. The exhaust monitoring device 30 uses the value calculated based on the upstream concentration as an upper limit to correct the output value of the second nitrogen oxide sensor 22.

[0074] <Effects of this implementation method>

[0075] (1-1) The exhaust monitoring device 30 can suppress the acquisition of excessively large output values ​​of the second nitrogen oxide sensor 22.

[0076] (1-2) The upstream concentration is the output value of the first nitrogen oxide sensor 21, which is installed in the exhaust pipe 13 upstream of the SCR catalyst 11, which is an exhaust purification device, to measure the concentration of nitrogen oxides contained in the exhaust gas flowing into the SCR catalyst 11. Thus, the exhaust monitoring device 30 can obtain the upstream concentration.

[0077] (Second Implementation)

[0078] Hereinafter, a vehicle 50 including the exhaust monitoring device 30 of the second embodiment will be described with reference to the accompanying drawings. In the second embodiment, the difference from the first embodiment is that the exhaust monitoring device 30 calculates the upper limit value taking into account the purification rate of the exhaust purification device. Hereinafter, the description will focus on the differences from the first embodiment; for similarities, the description will be simplified or omitted.

[0079] <Exhaust monitoring device 30 is for outputting downstream NO x A series of processing steps performed based on concentration >

[0080] Figure 7 The exhaust monitoring device 30 of the second embodiment outputs downstream NO. x A series of processing steps performed at a given concentration. Figure 7 The series of processes shown are executed by the processing circuit 31 when the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations. In the second embodiment, the exhaust gas monitoring device 30, upon obtaining the upstream and downstream concentrations, replaces... Figure 4 The series of processes shown are executed Figure 7 The series of processes shown.

[0081] Processing circuit 31 at the beginning Figure 7 In the series of processes shown, process S31 is executed first. In process S31, the processing circuit 31 calculates the purification rate of the SCR catalyst 11.

[0082] Figure 8 This illustrates how the processing circuit 31 calculates the purification rate of the SCR catalyst 11. For example... Figure 8 As shown, the processing circuit 31 estimates the purification rate of the SCR catalyst 11 based on the catalyst temperature and the exhaust flow rate.

[0083] The catalyst temperature is the temperature of the SCR catalyst 11. The exhaust monitoring device 30 stores a constant map in the storage device 32, which outputs the catalyst temperature when the intake air volume and the coolant temperature of the diesel engine 10 at the start of vehicle 50 operation are input. The processing circuit 31 obtains the intake air volume, for example, by acquiring the output value of the air flow meter. The processing circuit 31 obtains the coolant temperature, for example, from a temperature sensor installed in the diesel engine 10. Then, the processing circuit 31 outputs the catalyst temperature by inputting the acquired intake air volume and coolant temperature into the constant map.

[0084] The exhaust monitoring device 30 stores a constant table in the storage device 32 that outputs the exhaust flow rate if the intake air volume is input. The processing circuit 31 outputs the exhaust flow rate by inputting the obtained intake air volume into the constant table.

[0085] The exhaust monitoring device 30 stores a constant mapping of the purification rate of the SCR catalyst 11 when the catalyst temperature and exhaust flow rate are input in the storage device 32. The processing circuit 31 calculates the purification rate of the SCR catalyst 11 by inputting the catalyst temperature and exhaust flow rate into the constant mapping.

[0086] like Figure 7 As shown, after calculating the purification rate of the SCR catalyst 11, the processing circuit 31 performs the processing step S32. In S32, the processing circuit 31 calculates the upper limit value.

[0087] In the second embodiment, the exhaust monitoring device 30 uses the upstream concentration value output by the first nitrogen oxide sensor 21, which reflects the purification rate of the SCR catalyst 11, as the upper limit value. In process S32, the processing circuit 31 calculates the upper limit value by subtracting the product of the upstream concentration and the purification rate of the SCR catalyst 11 from the upstream concentration output by the first nitrogen oxide sensor 21. Then, the processing circuit 31 proceeds to process S33.

[0088] In the process of S33, the processing circuit 31 determines whether the obtained downstream concentration is below the upper limit value calculated in the process of S32.

[0089] If, during processing S33, processing circuit 31 determines that the downstream concentration is below the upper limit (S33: Yes), processing proceeds to S34. In processing S34, processing circuit 31 uses the downstream concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 7 The series of processes shown.

[0090] Thus, when the downstream concentration obtained by the exhaust monitoring device 30 is below the upper limit, the downstream concentration will be used as the downstream NO concentration. x Concentration output.

[0091] If, during processing S33, processing circuit 31 determines that the downstream concentration is greater than the upper limit (S33: No), it proceeds to processing S35. In processing S35, processing circuit 31 uses the processed concentration as the downstream NO concentration. x Concentration output. The processed concentration is the value of the upper limit, which replaces the downstream concentration. In S35, the processing circuit 31 uses the upper limit calculated in the processing of S32 as the downstream NO. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 7 The series of processes shown.

[0092] Thus, if the downstream concentration obtained by the exhaust monitoring device 30 exceeds the upper limit, the downstream concentration will be replaced with the treated concentration after the upper limit is obtained, and this will be used as the downstream NO concentration. x Concentration output.

[0093] Downstream NO x Concentration shift >

[0094] Figure 9 Indicates the downstream NO in the second embodiment x An example of concentration shift. In Figure 9 In the middle, the vertical axis represents NO. x The concentration. In Figure 9 In the middle, the horizontal axis represents time.

[0095] exist Figure 9 The diagram shows the shifts in upstream and downstream concentrations. Figure 9 In the diagram, the upstream concentration is represented by a dashed line, and the downstream concentration is represented by a single-dot dashed line.

[0096] exist Figure 9 The diagram shows the shift in the upper limit value. Figure 9 The upper limit shown is based on the upstream concentration and the NO concentration of the exhaust gas monitoring device 30 and the SCR catalyst 11. x The purification rate is the upper limit calculated in the S32 process. Figure 9 In the diagram, the upper limit value calculated by the exhaust monitoring device 30 is represented by a double-dotted line. Figure 9 In the middle, the downstream NO output of the exhaust monitoring device 30 x Concentration is represented by a solid line.

[0097] exist Figure 9 During the period up to time T1, the downstream concentration is below the upper limit. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations during the period up to time T1, it determines that the downstream concentration is below the upper limit (S33: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration as the downstream NO concentration. x Concentration output (S34). Therefore, in Figure 9 In the middle, it indicates downstream NO x The solid line representing the concentration overlaps with the dashed line representing the downstream concentration shift during the period up to time T1.

[0098] exist Figure 9 During the period from time T1 to time T2, the downstream concentration is greater than the upper limit. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations during the period from time T1 to time T2, it determines that the downstream concentration is greater than the upper limit (S33: No). Then, the exhaust gas monitoring device 30 uses the treated concentration as the downstream NO concentration. x Concentration output (S35). As described above, the processed concentration is the value with the downstream concentration replaced by the upper limit value. Therefore, in Figure 9 In the middle, it indicates downstream NO xThe solid line representing the concentration overlaps with the double-dotted line representing the shift in the upper limit value during the period from time T1 to time T2.

[0099] exist Figure 9 After time T2, the downstream concentration is below the upper limit. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations after time T2, it determines that the downstream concentration is below the upper limit (S33: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration as the downstream NO concentration. x Concentration output (S34). Therefore, in Figure 9 In the middle, it indicates downstream NO x The solid line representing concentration overlaps with the dashed line representing the downstream concentration shift after time T2.

[0100] In the first embodiment, the upstream concentration is set as an upper limit. On the other hand, in the second embodiment, the value that reflects the purification rate of the SCR catalyst 11 in relation to the upstream concentration is set as an upper limit. Therefore, the upper limit in the second embodiment is lower than the upper limit in the first embodiment.

[0101] Downstream NO x The concentration is output in such a way that the value does not exceed the upper limit. Therefore, in the second embodiment, the downstream NO is calculated... x Concentration ratio of downstream NO calculated in the first embodiment x The concentration decreases.

[0102] <Function and Effects of the Second Embodiment>

[0103] (2-1) The exhaust monitoring device 30 of the second embodiment has the same effect as (1-1) and (1-2) in the first embodiment.

[0104] (2-2) In the exhaust monitoring device 30 of the second embodiment, the processing circuit 31 performs calculation of the upper limit value based on the purification rate of nitrogen oxides by the SCR catalyst 11, which is an exhaust purification device, and the upstream concentration.

[0105] The exhaust monitoring device 30 of the second embodiment reflects the purification rate of the SCR catalyst 11, which is an exhaust purification device, to an upper limit value. As a result, the exhaust monitoring device 30 can suppress the acquisition of excessively high output values ​​of the second nitrogen oxide sensor 22.

[0106] (2-3) The exhaust monitoring device 30 uses a value calculated based on the purification rate of the SCR catalyst 11, which is an exhaust purification device, as an upper limit to correct the output value of the second nitrogen oxide sensor 22. As a result, the exhaust monitoring device 30 can suppress the acquisition of an excessively high output value of the second nitrogen oxide sensor 22.

[0107] (Third Implementation)

[0108] Hereinafter, a vehicle 50 including the exhaust monitoring device 30 of the third embodiment will be described with reference to the accompanying drawings. In the third embodiment, the difference from the first embodiment is that the exhaust monitoring device 30 uses an estimated value, rather than the output value of the first nitrogen oxide sensor 21, as the upper limit value. The following description focuses on the differences from the first embodiment; for similarities, the description is simplified or omitted.

[0109] <Exhaust monitoring device 30 is for outputting downstream NO x A series of processing steps performed based on concentration >

[0110] Figure 10 The exhaust monitoring device 30 of the third embodiment outputs downstream NO. x A series of processing steps performed at a given concentration. Figure 10 The series of processes shown are executed by the processing circuit 31 when the exhaust gas monitoring device 30 obtains the downstream concentration. In the third embodiment, the exhaust gas monitoring device 30, upon obtaining the downstream concentration, replaces... Figure 4 The series of processes shown are executed Figure 10 The series of processes shown.

[0111] Processing circuit 31 at the beginning Figure 10 During the series of processes shown, process S41 is executed first. In process S41, processing circuit 31 calculates an estimated value. This estimated value is the NO content contained in the exhaust gas flowing into the SCR catalyst 11. x The estimated concentration.

[0112] Figure 11 This indicates the method by which the processing circuit 31 calculates the estimated value. For example... Figure 11 As shown, the processing circuit 31 calculates the estimated value based on the engine speed and fuel injection quantity.

[0113] The engine speed is the rotational speed of the diesel engine 10 per unit time. The processing circuit 31, for example, obtains the output value of a crankshaft angle sensor that measures the angle of the crankshaft of the diesel engine 10, and outputs the engine speed based on the time required for the crankshaft to rotate a predetermined angle.

[0114] The fuel injection quantity is the amount of fuel injected by the fuel injection valve in the diesel engine 10 each time it injects fuel. The processing circuit 31 obtains information about the fuel injection quantity, for example, from a control device that controls the fuel injection valve.

[0115] When the engine speed and fuel injection quantity are input, the exhaust monitoring device 30 stores a constant mapping of the estimated output value in the storage device 32. The processing circuit 31 calculates the estimated value by inputting the obtained engine speed and fuel injection quantity into the constant mapping.

[0116] The exhaust monitoring device 30 in the third embodiment uses the estimated value output in the processing of S41 instead of the output value of the first nitrogen oxide sensor 21 as the upstream concentration. Therefore, in the third embodiment, the exhaust system 40 may also be without the first nitrogen oxide sensor 21.

[0117] like Figure 10 As shown, after calculating the estimated value, processing circuit 31 executes process S42. In process S42, processing circuit 31 determines whether the obtained downstream concentration is below the upper limit value. In other words, in process S42, processing circuit 31 determines whether the obtained downstream concentration is below the estimated value calculated in process S41.

[0118] If, during processing S42, processing circuit 31 determines that the downstream concentration is below the upper limit (S42: Yes), it proceeds to processing S43. In processing S43, processing circuit 31 uses the downstream concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 10 The series of processes shown.

[0119] Thus, when the downstream concentration obtained by the exhaust monitoring device 30 is below the upper limit, the downstream concentration will be used as the downstream NO concentration. x Concentration output.

[0120] If, during processing S42, processing circuit 31 determines that the downstream concentration is greater than the upper limit (S42: No), it proceeds to processing S44. In processing S44, processing circuit 31 uses the processed concentration as the downstream NO concentration. x Concentration output. The processed concentration is the value with the downstream concentration replaced by the upper limit value. In the processing of S44, the processing circuit 31 uses the estimated value calculated in the processing of S41 as the downstream NO. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 10 The series of processes shown.

[0121] Thus, if the downstream concentration obtained by the exhaust monitoring device 30 exceeds the estimated upper limit, the treated concentration after replacing the downstream concentration with the upper limit will be used as the downstream NO concentration. x Concentration output.

[0122] <Function and Effects of the Third Implementation Method>

[0123] (3-1) The exhaust monitoring device 30 of the third embodiment has the same effect as (1-1) in the first embodiment.

[0124] (3-2) The upstream concentration is an estimated value calculated based on the rotational speed and fuel injection quantity of the diesel engine 10, which is the engine. Thus, the exhaust monitoring device 30 of the third embodiment can obtain the upstream concentration.

[0125] (Fourth Implementation)

[0126] Hereinafter, a vehicle 50 including the exhaust monitoring device 30 of the fourth embodiment will be described with reference to the accompanying drawings. In the fourth embodiment, the difference from the third embodiment is that the value that reflects the purification rate of the exhaust purification device to an estimated value is used as an upper limit value. Hereinafter, the description will focus on the differences from the third embodiment; for similarities, the description will be simplified or omitted.

[0127] <Exhaust monitoring device 30 is for outputting downstream NO x A series of processing steps performed based on concentration >

[0128] Figure 12 The exhaust monitoring device 30 of the fourth embodiment outputs downstream NO. x A series of processing steps performed at a given concentration. Figure 12 The series of processes shown are executed by the processing circuit 31 when the exhaust gas monitoring device 30 obtains the downstream concentration. In the fourth embodiment, the exhaust gas monitoring device 30, upon obtaining the downstream concentration, replaces... Figure 4 The series of processes shown are executed Figure 12 The series of processes shown.

[0129] Processing circuit 31 at the beginning Figure 12 During the series of processes shown, the process S51 is executed first. In the process S51, the processing circuit 31 calculates an estimated value. The estimated value referred to here is the NO content contained in the exhaust gas flowing into the SCR catalyst 11. x The estimated concentration. At this time, the processing circuit 31 uses... Figure 11 The estimated value is calculated in the manner illustrated. Then, the processing circuit 31 initiates processing in step S52.

[0130] The exhaust monitoring device 30 in the fourth embodiment uses a value reflecting an estimated value as the upstream concentration. Therefore, in the fourth embodiment, similar to the third embodiment, the exhaust system 40 may not include the first nitrogen oxide sensor 21.

[0131] In the S52 process, the processing circuit 31 calculates the purification rate of the SCR catalyst 11. At this time, the processing circuit 31 uses... Figure 8 The purification rate of the SCR catalyst 11 is calculated in the manner illustrated. Then, the processing circuit 31 initiates processing in step S53.

[0132] In the process of S53, the processing circuit 31 calculates an upper limit value. In the fourth embodiment, the exhaust monitoring device 30 uses the value reflecting the purification rate of the SCR catalyst 11 in the estimated value as the upper limit value. In the process of S53, the processing circuit 31 calculates the upper limit value as the value obtained by subtracting the product of the estimated value and the purification rate of the SCR catalyst 11 from the estimated value. After that, the processing circuit 31 causes the process to proceed to S54.

[0133] In the process of S54, the processing circuit 31 determines whether the obtained downstream concentration is below the upper limit value calculated in the process of S53.

[0134] If, during processing S54, processing circuit 31 determines that the downstream concentration is below the upper limit (S54: Yes), it proceeds to processing S55. In processing S55, processing circuit 31 uses the downstream concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 12 The series of processes shown.

[0135] Thus, when the downstream concentration obtained by the exhaust monitoring device 30 is below the upper limit, the downstream concentration will be used as the downstream NO concentration. x Concentration output.

[0136] If, during processing S54, processing circuit 31 determines that the downstream concentration is greater than the upper limit (S54: No), it proceeds to processing S56. In processing S56, processing circuit 31 uses the processed concentration as the downstream NO concentration. x Concentration output. The processed concentration is the value of the upper limit, which replaces the downstream concentration. In S56, the processing circuit 31 uses the upper limit calculated in the processing of S53 as the downstream NO. x The output is determined by the concentration. Afterwards, processing circuit 31 terminates. Figure 12 The series of processes shown.

[0137] Thus, if the downstream concentration obtained by the exhaust monitoring device 30 exceeds the upper limit, the downstream concentration will be replaced with the treated concentration after the upper limit is obtained, and this will be used as the downstream NO concentration. x Concentration output.

[0138] <Function and Effects of the Fourth Implementation Method>

[0139] (4-1) The exhaust monitoring device 30 of the fourth embodiment has the same effect as (1-1) in the first embodiment.

[0140] (4-2) The exhaust monitoring device 30 of the fourth embodiment has the same effect as (2-2) and (2-3) in the second embodiment.

[0141] (4-3) The exhaust monitoring device 30 of the fourth embodiment has the same effect as (3-2) in the third embodiment.

[0142] (Fifth Implementation)

[0143] Hereinafter, a vehicle 50 including the exhaust monitoring device 30 of the fifth embodiment will be described with reference to the accompanying drawings. In the fifth embodiment, the difference from the first embodiment is that the exhaust system 40 includes a downstream exhaust purification device. The description will focus on the differences from the first embodiment; for similarities, the description will be simplified or omitted.

[0144] <Structure of vehicle 50 according to the fifth embodiment>

[0145] like Figure 13 As shown, in the vehicle 50 of the fifth embodiment, the exhaust system 40 includes a second SCR catalyst 12, a second injector 15, and a third nitrogen oxide sensor 23.

[0146] like Figure 13 As shown, in the exhaust pipe 13, a second SCR catalyst 12 is disposed downstream of the SCR catalyst 11 and the second nitrogen oxide sensor 22. In the second SCR catalyst 12, the meaning of SCR is the same as that of the SCR catalyst 11. The second SCR catalyst 12 is used to remove NO contained in the exhaust gas after it has passed through the exhaust purification device. x The exhaust gas purification device is removed. The second SCR catalyst 12 adsorbs NH3 generated from the hydrolysis of urea. The second SCR catalyst 12 uses NH3 as a reducing agent to reduce NO in the exhaust gas. x .

[0147] like Figure 13 As shown, the second injector 15 is positioned in the exhaust pipe 13 downstream of the second nitrogen oxide sensor 22 and upstream of the second SCR catalyst 12. The second injector 15 adds urea to the second SCR catalyst 12 by injecting urea water toward the second SCR catalyst 12.

[0148] like Figure 13 As shown, a third nitrogen oxide sensor 23 is disposed in the exhaust pipe 13 downstream of the second SCR catalyst 12. The third nitrogen oxide sensor 23 measures the NOx content in the exhaust gas passing through the second SCR catalyst 12, which serves as a downstream exhaust purification device. x The concentration. Hereinafter, in the description, the concentration output by the third nitrogen oxide sensor 23 will be referred to as the downstream concentration.

[0149] The exhaust monitoring device 30 is communicatively connected to the third nitrogen oxide sensor 23. The exhaust monitoring device 30 periodically obtains the output value of the third nitrogen oxide sensor 23, i.e., the downstream concentration, by communicating with the third nitrogen oxide sensor 23.

[0150] <Shifts in upstream and downstream concentrations>

[0151] Figure 14 and Figure 15 Specific examples illustrating the shifts in upstream concentration, downstream concentration, and subsequent downstream concentration. In Figure 14 and Figure 15 In the middle, the vertical axis represents NO. x The concentration. In Figure 14 and Figure 15 In the diagram, the horizontal axis represents time. The following will... Figure 14 The shift shown is called the third case. Figure 15 The shift shown is called the fourth case. Figure 14 and Figure 15 In the diagram, upstream concentration is represented by a dashed line, downstream concentration by a single-dotted line, and subsequent downstream concentration by a double-dotted line.

[0152] like Figure 14 As shown, in the third case, the upstream concentration consistently shifted towards a value higher than the downstream concentration. Furthermore, in the third case, the downstream concentration consistently shifted towards a value higher than the concentration of the subsequent downstream stage.

[0153] Originally, using Figure 2 The first example illustrates a situation where the upstream concentration consistently exceeds the downstream concentration. The downstream concentration is the NO content in the exhaust gas that has passed through the SCR catalyst 11, as output by the second NOx sensor 22. x The concentration of NO in the exhaust gas flowing through the SCR catalyst 11 into the second SCR catalyst 12 is [missing information]. Therefore, the downstream concentration is the NO concentration contained in the exhaust gas flowing into the second SCR catalyst 12. x The concentration of NO in the exhaust gas after passing through the second SCR catalyst 12 is the output of the third nitrogen oxide sensor 23. x The concentration.

[0154] The exhaust gas flowing into the second SCR catalyst 12, upon passing through the second SCR catalyst 12, NO x The amount of NO decreases. In other words, the amount of NO in the exhaust gas flowing into the second SCR catalyst 12 decreases. x The amount of NO contained in the exhaust gas passed through the second SCR catalyst 12 was compared to that of the second SCR catalyst 12. x The amount is large. Therefore, as shown in the third example, the order from largest to smallest should be upstream concentration, downstream concentration, and subsequent downstream concentration.

[0155] like Figure 15 As shown, in the fourth case, the downstream concentration value is temporarily higher than the upstream concentration value. The rationale has already been used. Figure 3 The second example shown illustrates this.

[0156] like Figure 15 As shown, in the fourth case, the downstream concentration value is temporarily greater than the upstream and downstream concentration values.

[0157] Similar to SCR catalyst 11, NH3 is adsorbed onto the second SCR catalyst 12. When the temperature of the second SCR catalyst 12 increases, the NH3 adsorbed onto the second SCR catalyst 12 is released from it. In this case, the exhaust gas passing through the second SCR catalyst 12 contains NH3 released from the second SCR catalyst 12.

[0158] Furthermore, if NH3 is released from SCR catalyst 11 at a high temperature in the second SCR catalyst 12, the NH3 released from SCR catalyst 11 cannot be adsorbed onto the second SCR catalyst 12 and will pass through the second SCR catalyst 12. Therefore, the exhaust gas that has passed through the second SCR catalyst 12 contains not only the NH3 released from the second SCR catalyst 12 but also the NH3 released from the SCR catalyst 11.

[0159] Therefore, when the NH3 released from the second SCR catalyst 12 and the NH3 released from the SCR catalyst 11 react with the third nitrogen oxide sensor 23, the downstream concentration value is sometimes larger than the upstream and downstream concentration values.

[0160] In this case, the amount of NH3 reacted in the third nitrogen oxide sensor 23 is compared with the amount of NO contained in the exhaust gas passing through the downstream exhaust purification device. x Compared to the concentration, the output value becomes too large.

[0161] <Exhaust monitoring device 30 is for outputting NO downstream of the after-stage> x A series of processing steps performed based on concentration >

[0162] As described above, the exhaust monitoring device 30 takes into account that sometimes the value output by the third nitrogen oxide sensor 23 becomes too high, and outputs NO to the downstream stage. x Concentration. Downstream NO x The concentration is indicated by the exhaust monitoring device 30 as the amount of NO contained in the exhaust gas that has passed through the second SCR catalyst 12. x The output value is the concentration value.

[0163] Figure 16 This indicates that the exhaust monitoring device 30 outputs NO downstream of the afterstage. xThe process involves a series of treatments performed at a given concentration. In the fifth embodiment, the exhaust monitoring device 30 outputs the concentration of nitrogen oxides (NOx) in the exhaust gas that has passed through the SCR catalyst 11, i.e., the downstream NO, in the manner shown in the first to fourth embodiments. x concentration. Figure 16 The series of processes shown obtains the downstream concentration of NO after the exhaust monitoring device 30 and outputs the downstream NO. x After concentration, the process is executed by the processing circuit 31.

[0164] Processing circuit 31 at the beginning Figure 16 During the series of processes shown, the process S61 is executed first. In the process S61, the processing circuit 31 determines whether the obtained downstream concentration of the subsequent stage is below the upper limit value of the subsequent stage.

[0165] The exhaust monitoring device 30 of the fifth embodiment calculates the NO downstream of the downstream stage. x When the concentration of downstream components exceeds the upper limit of the downstream component, the downstream concentration is replaced with the upper limit of the downstream component. In the fifth embodiment, the upper limit of the downstream component is the downstream NO concentration. x concentration.

[0166] If, during processing S61, processing circuit 31 determines that the downstream concentration is below the upper limit of the downstream stage (S61: Yes), processing proceeds to S62. In processing S62, processing circuit 31 uses the downstream NO concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 16 The series of processes shown.

[0167] Thus, when the exhaust gas monitoring device 30 obtains a downstream concentration below the upper limit of the downstream stage, it will use the downstream NO concentration as the downstream NO concentration. x Concentration output.

[0168] If, during processing S61, the processing circuit 31 determines that the downstream concentration of the subsequent stage is greater than the upper limit value of the subsequent stage (S61: No), the processing proceeds to S63. In processing S63, the processing circuit 31 uses the concentration after the subsequent stage processing as the downstream NO concentration. x Concentration output. The concentration after post-processing is the value of the downstream concentration replaced by the upper limit value of the downstream stage. In the fifth embodiment, the concentration after post-processing is the value of the downstream NO replaced by the downstream NO concentration. x The concentration value. That is, in S63, the processing circuit 31 will process the downstream NO... x Concentration as downstream NO x Concentration output. Afterwards, processing circuit 31 terminates. Figure 16 The series of processes shown.

[0169] Thus, if the downstream concentration of the exhaust gas monitoring device 30 exceeds the upper limit of the downstream concentration, the downstream concentration will be replaced with the post-treatment concentration of the downstream gas after the upper limit is reached, and this will be used as the downstream NO concentration. x Concentration output.

[0170] Downstream NO x Concentration and downstream NO x Concentration shift >

[0171] Figure 17 Indicates downstream NO x An example of concentration shift. Figure 18 Indicates downstream NO x The shift in concentration. Figure 17 and Figure 18 In the middle, the vertical axis represents NO. x The concentration. In Figure 17 and Figure 18 In the middle, the horizontal axis represents time.

[0172] exist Figure 17 as well as Figure 18 It shows Figure 15 The upstream concentration, downstream concentration, and subsequent downstream NO concentration in the fourth case shown and illustrated x The shift in concentration. Figure 17 and Figure 18 In the diagram, upstream concentration is represented by a dashed line, downstream concentration by a single-dotted line, and subsequent downstream concentration by a double-dotted line.

[0173] Figure 17 This indicates that in the fourth case, the downstream NO output of the exhaust monitoring device 30... x The shift in concentration. Figure 17 In the middle, the downstream NO output of the exhaust monitoring device 30 x Concentration is represented by a solid line. Furthermore, in Figure 17 In the process, exhaust monitoring device 30 outputs downstream NO in the same manner as in the first embodiment. x Concentration. That is, in Figure 17 In the process, the exhaust monitoring device 30 uses the upstream concentration output by the first nitrogen oxide sensor 21 as the upper limit and outputs the downstream NO concentration. x concentration.

[0174] exist Figure 17 During the period up to time T1, the downstream concentration was lower than the upstream concentration. Therefore, if the exhaust gas monitoring device 30 has obtained the upstream and downstream concentrations during the period up to time T1, it determines that the downstream concentration is lower than the upstream concentration. Figure 4 S11 shown: Yes). Then, the exhaust monitoring device 30 will use the downstream concentration as the downstream NO concentration. x Concentration output ( Figure 4As shown in S12). Therefore, in Figure 17 In the middle, it indicates downstream NO x The solid line representing the concentration overlaps with the dashed line representing the downstream concentration shift during the period up to time T1.

[0175] exist Figure 17 During the period from time T1 to time T2, the downstream concentration is greater than the upstream concentration. Therefore, when the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations during the period from time T1 to time T2, it determines that the downstream concentration is greater than the upstream concentration. Figure 4 S11 shown: No). Then, the exhaust monitoring device 30 will use the treated concentration as the downstream NO concentration. x Concentration output ( Figure 4 As shown in S13). As mentioned above, the post-treatment concentration is the value of the upstream concentration, which is the upper limit, replacing the downstream concentration. Therefore, in Figure 17 In the middle, it indicates downstream NO x The solid line representing the concentration overlaps with the dashed line representing the shift in upstream concentration from time T1 to time T2.

[0176] exist Figure 17 After time T2, the downstream concentration is lower than the upstream concentration. Therefore, if the exhaust gas monitoring device 30 obtains the upstream and downstream concentrations after time T2, it determines that the downstream concentration is lower than the upstream concentration. Figure 4 S11 shown: Yes). Then, the exhaust monitoring device 30 will use the downstream concentration as the downstream NO concentration. x Concentration output ( Figure 4 As shown in S12). Therefore, in Figure 17 In the middle, it indicates downstream NO x The solid line representing concentration overlaps with the dashed line representing the downstream concentration shift after time T2.

[0177] Figure 18 This indicates the shift in downstream concentration output from exhaust gas monitoring device 30 in the fourth case. Figure 18 In the figure, the downstream concentration output by the exhaust monitoring device 30 is represented by a solid line.

[0178] exist Figure 18 During the period up to time T1, the downstream concentration was below the upstream concentration. Additionally, in Figure 18 During the period up to time T1, the downstream concentration of the subsequent stage is below the downstream concentration. That is, in Figure 18 During the period up to time T1, the downstream concentration was... Figure 17 The downstream NO shown x The concentration is below [a certain level]. Therefore, the exhaust gas monitoring device 30 calculates the downstream NO concentration during the period up to time T1. xIf the concentration of the exhaust gas is measured and the downstream concentration of the next stage is obtained, it is determined that the downstream concentration of the next stage is below the upper limit of the next stage (S61: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration of the next stage as the downstream NO concentration of the next stage. x Concentration output (S62). Therefore, in Figure 18 In the middle, it indicates the downstream NO x The solid line representing concentration overlaps with the double-dotted line representing the shift in concentration downstream of the next stage during the period up to time T1.

[0179] exist Figure 18 During the period from time T1 to time T2, the downstream concentration was higher than the upstream concentration. Therefore, in Figure 18 During the period from time T1 to time T2, downstream NO x The concentration is equal to the upstream concentration. Figure 18 During the period from time T1 to time T2, the downstream concentration is higher than the upstream concentration. That is, in Figure 18 During the period from time T1 to time T2, the downstream concentration of the subsequent stage was higher than that of the previous stage. Figure 17 The downstream NO shown x The concentration is high. Therefore, the exhaust gas monitoring device 30 calculates the downstream NO concentration during the period from time T1 to time T2. x If the concentration of the downstream stage is obtained, it is determined that the downstream concentration is greater than the upper limit of the downstream stage (S61: No). Then, the exhaust gas monitoring device 30 uses the concentration after downstream treatment as the downstream NO concentration. x Concentration output (S63). As described above, the concentration after subsequent processing is obtained by replacing the downstream concentration of the subsequent stage with the downstream NO concentration as the upper limit of the subsequent stage. x The concentration value. Therefore, in Figure 18 In the middle, it indicates the downstream NO x The solid line representing concentration overlaps with the dashed line representing the shift in upstream concentration during the period from time T1 to time T2.

[0180] exist Figure 18 During the period from time T2 to time T3, the downstream concentration was lower than the upstream concentration. Therefore, in Figure 18 During the period from time T2 to time T3, downstream NO x The concentration is equal to the downstream concentration. Figure 18 During the period from time T2 to time T3, the concentration of the subsequent downstream stage is higher than that of the downstream stage. That is, in Figure 18 During the period from time T2 to time T3, the downstream concentration of the subsequent stage was higher than that of the previous stage. Figure 17 The downstream NO shown x The concentration is high. Therefore, the exhaust gas monitoring device 30 calculates the downstream NO concentration during the period from time T2 to time T3. xIf the concentration of the downstream stage is obtained, it is determined that the downstream concentration is greater than the upper limit of the downstream stage (S61: No). Then, the exhaust gas monitoring device 30 uses the concentration after downstream treatment as the downstream NO concentration. x Concentration output (S63). As described above, the concentration after subsequent processing is obtained by replacing the downstream concentration of the subsequent stage with the downstream NO concentration as the upper limit of the subsequent stage. x The concentration value. Therefore, in Figure 18 In the middle, it indicates the downstream NO x The solid line representing concentration overlaps with the dashed line representing the downstream concentration shift during the period from time T2 to time T3.

[0181] exist Figure 18 After time T3, the downstream concentration of the subsequent stage is lower than the upstream concentration, and also lower than the downstream concentration. That is, at... Figure 18 After time T3, the downstream concentration is Figure 17 The downstream NO shown x The concentration is below [a certain level]. Therefore, the exhaust gas monitoring device 30 calculates the downstream NO concentration after time T3. x If the concentration of the exhaust gas is measured and the downstream concentration of the next stage is obtained, it is determined that the downstream concentration of the next stage is below the upper limit of the next stage (S61: Yes). Then, the exhaust gas monitoring device 30 uses the downstream concentration of the next stage as the downstream NO concentration of the next stage. x Concentration output (S62). Therefore, in Figure 18 In the middle, it indicates the downstream NO x The solid line representing concentration overlaps with the double-dotted line representing the shift in concentration downstream of the subsequent stage after time T3.

[0182] <Function and Effects of the Fifth Implementation Method>

[0183] (5-1) The exhaust monitoring device 30 of the fifth embodiment has the same effect as (1-1) and (1-2) in the first embodiment.

[0184] (5-2) The exhaust system 40 includes a downstream exhaust purification device, namely a second SCR catalyst 12, which is disposed in the exhaust pipe 13 downstream of the SCR catalyst 11 serving as the exhaust purification device, and removes nitrogen oxides contained in the exhaust gas that has passed through the SCR catalyst 11. The exhaust system 40 includes a third nitrogen oxide sensor 23 serving as a downstream nitrogen oxide sensor, which is disposed in the exhaust pipe 13 downstream of the second SCR catalyst 12 serving as the downstream exhaust purification device, and measures the concentration of nitrogen oxides contained in the exhaust gas that has passed through the second SCR catalyst 12. The exhaust monitoring device 30 can obtain the output value of the third nitrogen oxide sensor 23, i.e., the downstream concentration. The processing circuit 31 outputs the downstream concentration based on the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust purification device, i.e., the downstream NO. x If the concentration calculation is below the upper limit of the downstream stage, the downstream concentration is used as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the downstream exhaust purification device. If the downstream concentration exceeds the upper limit of the downstream stage, the processing circuit 31 performs a calculation that replaces the downstream concentration with the upper limit of the downstream stage and uses the post-processed concentration as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the downstream exhaust purification device.

[0185] The concentration of nitrogen oxides in the exhaust gas passing through the second SCR catalyst 12, which serves as a downstream exhaust gas purification device, is lower than the treated concentration in an exhaust gas purification device upstream of the downstream device. The exhaust monitoring device 30 uses the value calculated based on the treated concentration as the downstream upper limit value to correct the output value of the third nitrogen oxide sensor 23, which serves as a downstream nitrogen oxide sensor. As a result, the exhaust monitoring device 30 can suppress the acquisition of excessively high output values ​​from the downstream nitrogen oxide sensor.

[0186] (Sixth Implementation Method)

[0187] Hereinafter, a vehicle 50 including the exhaust monitoring device 30 of the sixth embodiment will be described with reference to the accompanying drawings. In the sixth embodiment, the difference from the first embodiment is that the exhaust system 40 includes a downstream exhaust purification device. Furthermore, in the sixth embodiment, the difference from the fifth embodiment is that the exhaust monitoring device 30 reflects the purification rate of the downstream exhaust purification device in the downstream NO... x The concentration value is used as an upper limit, rather than downstream NO. x Concentration is used as an upper limit. The following description focuses on the differences from the fifth embodiment; for points of similarity, the description is simplified or omitted.

[0188] <Exhaust monitoring device 30 is for outputting NO downstream of the after-stage> x A series of processing steps performed based on concentration >

[0189] Figure 19 This indicates that the exhaust monitoring device 30 outputs NO downstream of the afterstage. x The process involves a series of treatments performed at a given concentration. In the sixth embodiment, the exhaust monitoring device 30 outputs the concentration of nitrogen oxides (NOx) in the exhaust gas that has passed through the SCR catalyst 11, i.e., the downstream NO, in the manner shown in the first to fourth embodiments. x concentration. Figure 19 The series of processes shown obtains the downstream concentration of NO after the exhaust monitoring device 30 and outputs the downstream NO. x The concentration is then determined by the processing circuit 31.

[0190] Processing circuit 31 at the beginning Figure 19 In the series of processes shown, process S71 is executed first. In process S71, processing circuit 31 calculates the purification rate of the second SCR catalyst 12. At this time, processing circuit 31... Figure 8 The purification rate of the second SCR catalyst 12 is calculated in the manner illustrated in the figure.

[0191] Then, the processing circuit 31 executes the processing in S72. In the processing in S72, the processing circuit 31 calculates the upper limit value of the subsequent stage.

[0192] In the sixth embodiment, the exhaust monitoring device 30 will reflect the purification rate of the second SCR catalyst 12 in the downstream NO. x The concentration value is used as the upper limit value for the subsequent stage. Processing circuit 31 calculates the concentration from downstream NO in the S72 processing. x Concentration minus downstream NO x The value obtained by multiplying the concentration by the purification rate of the second SCR catalyst 12 is used as the upper limit value of the subsequent stage. Then, the processing circuit 31 causes the processing to enter S73.

[0193] In the processing of S73, the processing circuit 31 determines whether the obtained downstream concentration of the subsequent stage is below the upper limit value of the subsequent stage calculated in the processing of S72.

[0194] If, during processing S73, processing circuit 31 determines that the downstream concentration is below the upper limit of the downstream stage (S73: Yes), processing proceeds to S74. In processing S74, processing circuit 31 uses the downstream NO concentration as the downstream NO concentration. x Concentration output. Afterwards, processing circuit 31 terminates. Figure 19 The series of processes shown.

[0195] Thus, when the exhaust gas monitoring device 30 obtains a downstream concentration below the upper limit of the downstream stage, it will use the downstream NO concentration as the downstream NO concentration. x Concentration output.

[0196] If, during processing S73, processing circuit 31 determines that the downstream concentration of the subsequent stage is greater than the upper limit value of the subsequent stage (S73: No), it proceeds to processing S75. In processing S75, processing circuit 31 uses the concentration after subsequent processing as the downstream NO concentration. x Concentration output. The concentration after post-processing is the value of replacing the downstream concentration with the upper limit value of the post-processing stage. In the sixth embodiment, the concentration after post-processing is the value of replacing the downstream concentration with the upper limit value of the post-processing stage calculated in the processing of S72. Afterwards, the processing circuit 31 ends. Figure 19 The series of processes shown.

[0197] Thus, if the downstream concentration of the exhaust gas monitoring device 30 exceeds the upper limit of the downstream concentration, the downstream concentration will be replaced with the post-treatment concentration of the downstream gas after the upper limit is reached, and this will be used as the downstream NO concentration. x Concentration output.

[0198] <Function and Effects of the Sixth Implementation Method>

[0199] (6-1) The exhaust monitoring device 30 of the sixth embodiment has the same effect as (1-1) and (1-2) in the first embodiment.

[0200] (6-2) The exhaust monitoring device 30 of the sixth embodiment has the same effect as (5-2) in the fifth embodiment.

[0201] (6-3) In the exhaust monitoring device 30 of the sixth embodiment, the processing circuit 31 performs the following: It outputs downstream NO based on the purification rate of nitrogen oxides by the second SCR catalyst 12, which is a downstream exhaust purification device, and a value representing the concentration of nitrogen oxides contained in the exhaust gas passing through the exhaust purification device, i.e., the SCR catalyst 11. x Concentration is used to calculate the upper limit value of the subsequent stage.

[0202] The exhaust monitoring device 30 reflects the purification rate of the downstream exhaust purification device to the upper limit of the downstream stage. As a result, the exhaust monitoring device 30 can suppress the acquisition of excessively high output values ​​from the downstream nitrogen oxide sensor.

[0203] (Other implementation methods)

[0204] The above embodiments can be implemented by modification in the following ways. The embodiments and the following modifications can be combined with each other within a technically compatible framework.

[0205] In the first and second embodiments, the exhaust monitoring device 30 sets the output value of the first nitrogen oxide sensor 21, which is the upstream nitrogen oxide, as the upstream concentration. In the third and fourth embodiments, the exhaust monitoring device 30 sets an estimated value as the upstream concentration.

[0206] The value used by the exhaust monitoring device 30 for the upstream concentration is not limited to the embodiments described above. For example, the exhaust monitoring device 30 may also use a constant value as the upstream concentration. For example, the exhaust monitoring device 30 may also use NO that may be contained in the exhaust gas emitted by the diesel engine 10. x The maximum concentration is taken as the upstream concentration.

[0207] In the second, fourth, and sixth embodiments, the exhaust monitoring device 30 is... Figure 8 The purification rate of SCR catalyst 11 or second SCR catalyst 12 is calculated in the manner shown. The method by which the exhaust monitoring device 30 calculates the purification rate is not limited to the embodiments described above. For example, the exhaust monitoring device 30 may also use a constant value as the purification rate. In addition, the exhaust monitoring device 30 may also use other methods besides… Figure 8 In addition to the catalyst temperature and exhaust flow rate shown, the degradation rate of SCR catalyst 11 and second SCR catalyst 12 can also be used as parameters to calculate the purification rate.

[0208] In the fifth and sixth embodiments, the exhaust monitoring device 30 uses downstream NO-based... x The upper limit of the concentration calculation is used to output the downstream NO concentration. x Concentration. The exhaust gas monitoring device 30 outputs NO downstream of the stage. x The concentration method is not limited to the above-described embodiments. For example, the exhaust monitoring device 30 may also use the product of the upstream concentration, the value obtained by subtracting the purification rate of SCR catalyst 11 from 1, and the value obtained by subtracting the purification rate of second SCR catalyst 12 from 1 as the downstream NO concentration. x Calculated by concentration.

[0209] In the first to sixth embodiments, the exhaust purification device and the subsequent exhaust purification device are SCRs. The exhaust purification device and the subsequent exhaust purification device may also be three-way catalytic converters. Furthermore, the vehicle 50 may not have a diesel engine 10, but instead have a gasoline engine.

[0210] When the exhaust purification device is a three-way catalytic converter, if the air-fuel ratio of the exhaust is rich, NH3 will be generated on the catalytic converter. Therefore, even with a three-way catalytic converter, NH3 may still be produced. Figure 3 or Figure 15 The upstream concentration, downstream concentration, and subsequent downstream concentration shifts are shown in the manner described.

Claims

1. An exhaust monitoring device, which is an exhaust monitoring device in an exhaust system, wherein, The exhaust system includes: An exhaust purification device, installed in the engine's exhaust pipe, removes nitrogen oxides contained in the exhaust; and A nitrogen oxide sensor is installed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of nitrogen oxides in the exhaust gas that has passed through the exhaust purification device. The exhaust monitoring device is configured to obtain upstream and downstream concentrations, wherein the upstream concentration is the concentration of nitrogen oxides contained in the exhaust gas flowing into the exhaust purification device, and the downstream concentration is the output value of the nitrogen oxide sensor. The exhaust monitoring device includes a processing circuit. The processing circuit is configured to perform the following processing: If the downstream concentration is below an upper limit calculated based on the upstream concentration, the downstream concentration is output as a value representing the concentration of nitrogen oxides in the exhaust gas that has passed through the exhaust gas purification device; and If the downstream concentration exceeds the upper limit, the output concentration after replacing the downstream concentration with the upper limit is used as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device.

2. The exhaust monitoring device according to claim 1, wherein, The processing circuit is configured to perform a process that calculates the upper limit value based on the purification rate of nitrogen oxides by the exhaust gas purification device and the upstream concentration.

3. An exhaust monitoring device, which is an exhaust monitoring device in an exhaust system, wherein, The exhaust system includes: An exhaust purification device, installed in the engine's exhaust pipe, removes nitrogen oxides contained in the exhaust; and A nitrogen oxide sensor is installed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of nitrogen oxides in the exhaust gas that has passed through the exhaust purification device. The exhaust monitoring device is configured to obtain the output value of the nitrogen oxide sensor, i.e., the downstream concentration. The exhaust monitoring device includes a processing circuit. The processing circuit is configured to perform the following processing: If the downstream concentration is below an upper limit calculated based on the purification rate of the exhaust gas purification device, the downstream concentration is output as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device; and If the downstream concentration exceeds the upper limit, the output concentration after replacing the downstream concentration with the upper limit is used as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device.

4. The exhaust monitoring device according to any one of claims 1 to 3, wherein, The exhaust system also includes: A downstream exhaust gas purification device, located downstream of the exhaust gas purification device in the exhaust pipe, removes nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device; and A downstream nitrogen oxide sensor is installed in the exhaust pipe, positioned downstream of the downstream exhaust purification device, to measure the concentration of nitrogen oxides in the exhaust gas that has passed through the downstream exhaust purification device. The exhaust monitoring device is configured to obtain the output value of the downstream nitrogen oxide sensor, i.e., the downstream concentration. The processing circuit is configured to perform the following processing: When the downstream concentration is below the upper limit value of the downstream stage calculated based on the output value of the concentration of nitrogen oxides contained in the exhaust gas passing through the exhaust gas purification device, the downstream concentration is output as a value representing the concentration of nitrogen oxides contained in the exhaust gas passing through the exhaust gas purification device; and If the downstream concentration exceeds the upper limit of the downstream stage, the output is the post-treatment concentration after replacing the downstream concentration with the upper limit of the downstream stage as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device.

5. The exhaust monitoring device according to claim 4, wherein, The processing circuit is configured to perform the following processing: calculate the upper limit value of the downstream exhaust purification device based on the purification rate of nitrogen oxides by the downstream exhaust purification device and the output value of the concentration of nitrogen oxides contained in the exhaust gas passing through the exhaust purification device.

6. The exhaust monitoring device according to any one of claims 1 to 5, wherein, The upstream concentration is the output value of the upstream nitrogen oxide sensor, which is located in the exhaust pipe upstream of the exhaust purification device and measures the concentration of nitrogen oxides contained in the exhaust gas flowing into the exhaust purification device.

7. The exhaust monitoring device according to any one of claims 1 to 6, wherein, The upstream concentration is an estimated value calculated based on the engine speed and fuel injection quantity.

8. An exhaust monitoring method, which is an exhaust monitoring method in an exhaust system, wherein, The exhaust system includes: An exhaust purification device, installed in the engine's exhaust pipe, removes nitrogen oxides contained in the exhaust; and A nitrogen oxide sensor is installed in the exhaust pipe downstream of the exhaust purification device to measure the concentration of nitrogen oxides in the exhaust gas that has passed through the exhaust purification device. The exhaust monitoring method includes the following processing: The concentration of nitrogen oxides contained in the exhaust gas flowing into the exhaust purification device is obtained, i.e., the upstream concentration. Obtain the output value of the nitrogen oxide sensor, i.e., the downstream concentration; If the downstream concentration is below an upper limit calculated based on the upstream concentration, the downstream concentration is output as a value representing the concentration of nitrogen oxides in the exhaust gas that has passed through the exhaust gas purification device; and If the downstream concentration exceeds the upper limit, the output concentration after replacing the downstream concentration with the upper limit is used as a value representing the concentration of nitrogen oxides contained in the exhaust gas that has passed through the exhaust gas purification device.

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