Abnormality determination device

Abstract

Provided is an abnormality determination device capable of ensuring an opportunity for abnormality determination and determining whether an exhaust purification device is abnormal. A control device as the abnormality determination device is applied to an intake and exhaust system. The exhaust purification device reduces nitrogen oxides in exhaust gas using ammonia as a reducing agent. An injector injects urea water. A first sensor is a nitrogen oxide sensor disposed at a position upstream of the injector. A second sensor is a nitrogen oxide sensor disposed at a position downstream of the exhaust purification device. When a purification rate of nitrogen oxides based on the exhaust purification device is low, the control device, during fuel cut, causes the injector to inject an amount of urea water that produces an amount of ammonia capable of being adsorbed in the absence of an abnormality in the exhaust purification device, and then determines that an abnormality is present in the exhaust purification device when the output of the nitrogen oxide sensor is a value equal to or higher than a predetermined value.

Description

Technical Field

[0001] This invention relates to an anomaly detection device. Background Technology

[0002] Patent Document 1 describes an anomaly detection device for an exhaust gas purification device. The exhaust gas purification device uses ammonia as a reducing agent to reduce nitrogen oxides (NOx) in the exhaust gas. The anomaly detection device observes the NOx purification rate based on the values ​​measured by a NOx sensor located upstream and a NOx sensor located downstream of the exhaust gas purification device. Furthermore, the anomaly detection device determines that the exhaust gas purification device is malfunctioning when the NOx purification rate based on the exhaust gas purification device is low.

[0003] When a large amount of ammonia is adsorbed in the exhaust gas purification device, if the temperature of the device increases, the ammonia will detach from it. Furthermore, the NOx sensor located downstream of the exhaust gas purification device reacts with the ammonia detached from it, sometimes outputting a value higher than the actual amount of NOx in the exhaust gas. In such cases, even if the exhaust gas purification device is not malfunctioning, the anomaly detection device may mistakenly determine that it is malfunctioning. Therefore, the anomaly detection device described in Patent Document 1 does not determine whether the exhaust gas purification device is malfunctioning when it is estimated that a large amount of ammonia has detached from it.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-109224 Summary of the Invention

[0005] The above-mentioned anomaly detection device has less chance of determining whether there is an anomaly in the exhaust purification device.

[0006] The anomaly detection device for solving the above-mentioned problem is an anomaly detection device that determines whether there is an anomaly in the exhaust purification device in the exhaust system. The exhaust system includes: the exhaust purification device, which is located midway in the exhaust pipe of the engine and uses ammonia as a reducing agent to reduce nitrogen oxides in the exhaust. The exhaust system includes: an injector, which is located upstream of the exhaust purification device and injects urea solution into the exhaust pipe. The exhaust system includes: a first sensor, which is a nitrogen oxide sensor that measures the amount of nitrogen oxides contained in the exhaust, and is located upstream of the injector. The exhaust system includes: a second sensor, which is a nitrogen oxide sensor, and is located downstream of the exhaust purification device. The anomaly detection device includes a processing circuit. In the anomaly detection device, when the nitrogen oxide purification rate of the exhaust purification device is low, the processing circuit, during fuel cut-off, causes the injector to inject urea solution in an amount that can adsorb the amount of ammonia required to remove the exhaust purification device in the absence of an anomaly, and if the nitrogen oxide sensor outputs a value above a predetermined value, it determines that there is an anomaly in the exhaust purification device.

[0007] Invention Effects

[0008] The aforementioned anomaly detection device can ensure the opportunity for anomaly detection and determine whether the exhaust purification device is malfunctioning. Attached Figure Description

[0009] Figure 1 This is a schematic diagram showing the structure of an intake and exhaust system equipped with an abnormality detection device according to one embodiment.

[0010] Figure 2 It means Figure 1 The flowchart shows the abnormality determination process performed by the abnormality determination device.

[0011] Figure 3 It is used for explanation Figure 1 The diagram shows how the abnormality detection device estimates the amount of ammonia adsorbed in the exhaust gas purification device.

[0012] Figure 4 It means Figure 1 A graph showing the relationship between the temperature of the exhaust gas purification device and the amount of ammonia adsorbed in the exhaust gas purification device.

[0013] Figure 5 It is used for explanation Figure 1 The diagram shows how the abnormality detection device determines the amount of urea water injected into the exhaust pipe. Detailed Implementation

[0014] The following is for reference. Figures 1-5 One embodiment of the anomaly detection device will be described.

[0015] <Structure of intake and exhaust system 100>

[0016] The intake and exhaust system 100 is applied to the engine 12 mounted on the vehicle. The intake and exhaust system 100 consists of an intake system that supplies air from outside the vehicle to the engine 12 and an exhaust system that discharges exhaust from the engine 12 to outside the vehicle.

[0017] The intake and exhaust system 100 includes an upstream intake pipe 17, a turbocharger 18, a downstream intake pipe 19, a throttle valve 20, and an air flow meter 27 as the intake system.

[0018] The upstream air intake pipe 17 is connected to the outside of the vehicle. Figure 1 The arrows represented by dashed lines in the diagram indicate that air is drawn from outside the vehicle into the upstream intake pipe 17.

[0019] Air flow meter 27 is located midway in the upstream intake pipe 17. Air flow meter 27 measures the amount of air drawn in from outside the vehicle.

[0020] The turbocharger 18 is connected to the upstream intake pipe 17, the downstream intake pipe 19, and the exhaust pipe 13. The turbocharger 18 includes a turbine and a compressor. The turbine is located within the exhaust pipe 13. The compressor is located across the upstream intake pipe 17 and the downstream intake pipe 19. In the turbocharger 18, the turbine rotates by receiving exhaust gas flowing within the exhaust pipe 13, thereby activating the compressor. As a result, air passing through the upstream intake pipe 17 is compressed. The air compressed by the turbocharger 18 is delivered to the downstream intake pipe 19.

[0021] like Figure 1 As shown, the downstream intake pipe 19 is connected to the engine 12. The downstream intake pipe 19 supplies air compressed by the turbocharger 18 to the engine 12.

[0022] Throttle valve 20 is located midway down the downstream intake manifold 19. Throttle valve 20 controls the amount of air drawn into engine 12.

[0023] The intake and exhaust system 100 includes an exhaust pipe 13, an exhaust purification device 14, a return path piping 15, a return path valve 16, a first sensor 21, a second sensor 22, a temperature sensor 23, and an injector 24 as the exhaust system. The intake and exhaust system 100 also includes a high-pressure return path piping 25 and a high-pressure return path valve 26 as the exhaust system.

[0024] The exhaust pipe 13 is connected to the outside of the vehicle. Exhaust from the engine 12 flows inside the exhaust pipe 13. Figure 1 The arrow in the solid line indicates that the exhaust of engine 12 is discharged to the outside of the vehicle.

[0025] like Figure 1 As shown, the exhaust purification device 14 is located midway through the exhaust pipe 13. The exhaust purification device 14 is a selective reduction catalyst (SCR) that uses ammonia (NH3) as a reducing agent to reduce nitrogen oxides (NOx) in the exhaust gas. NH3 generated from the hydrolysis of urea is adsorbed in the exhaust purification device 14.

[0026] like Figure 1 As shown, an injector 24 is disposed upstream of the exhaust purification device 14 in the exhaust pipe 13. The injector 24 sprays urea water into the exhaust pipe 13.

[0027] like Figure 1 As shown, a first sensor 21 is disposed upstream of the injector 24 in the exhaust pipe 13. The first sensor 21 is a nitrogen oxide sensor that measures the amount of NOx contained in the exhaust.

[0028] like Figure 1 As shown, a second sensor 22 is disposed downstream of the exhaust purification device 14 in the exhaust pipe 13. The second sensor 22 is also a nitrogen oxide sensor, just like the first sensor 21.

[0029] In the intake and exhaust system 100, the first sensor 21 measures the amount of NOx contained in the exhaust gas before passing through the exhaust purification device 14. The second sensor 22 measures the amount of NOx contained in the exhaust gas after passing through the exhaust purification device 14.

[0030] like Figure 1 As shown, a temperature sensor 23 is installed in the exhaust pipe 13 downstream of the exhaust purification device 14. The temperature sensor 23 measures the temperature of the exhaust gas passing through the exhaust purification device 14.

[0031] like Figure 1 As shown, the return path pipe 15 connects to a portion of the exhaust pipe 13 downstream of the exhaust purification device 14 and a portion of the upstream intake pipe 17 downstream of the air flow meter 27. In the exhaust pipe 13, a portion of the exhaust gas passing through the exhaust purification device 14 flows into the return path pipe 15. Furthermore, the exhaust gas passing through the return path pipe 15 flows into the upstream intake pipe 17, merging with air flowing into the upstream intake pipe 17 from outside the vehicle. Thus, the return path pipe 15 allows the exhaust gas passing through the exhaust purification device 14 to return to the engine 12.

[0032] The return path valve 16 is located midway through the return path pipe 15. The return path valve 16 adjusts the amount of exhaust gas returning to the engine 12 through the return path pipe 15.

[0033] The high-pressure return path piping 25 is connected to the exhaust manifold and downstream intake manifold 19 of the engine 12. A portion of the exhaust gas passing through the exhaust manifold flows into the high-pressure return path piping 25. Furthermore, the exhaust gas passing through the high-pressure return path piping 25 flows into the downstream intake manifold 19, merging with the air supplied to the engine 12. Thus, the high-pressure return path piping 25 causes a portion of the exhaust gas passing through the exhaust manifold to return to the engine 12.

[0034] The high-pressure return path valve 26 is located midway through the high-pressure return path piping 25. The high-pressure return path valve 26 adjusts the amount of exhaust gas returning to the engine 12 through the high-pressure return path piping 25.

[0035] <Structure and Function of Control Device 10>

[0036] like Figure 1 As shown, the intake and exhaust system 100 includes a control device 10.

[0037] like Figure 1 As shown, the control device 10 includes a processing circuit 11 and a storage device 28. The processing circuit 11 performs various processes by executing programs stored in the storage device 28. The processing circuit 11 includes a processor.

[0038] like Figure 1 As shown, the control device 10 is communicatively connected to the first sensor 21, the second sensor 22, and the temperature sensor 23. The control device 10 communicates with each sensor to acquire measured values. The control device 10 can estimate the temperature of the exhaust gas purification device 14 based on the output value of the temperature sensor 23.

[0039] like Figure 1 As shown, the control device 10 is communicatively connected to the injector 24. After determining the amount of urea solution to be injected by the injector 24, the control device 10 is able to inject the determined amount of urea solution.

[0040] like Figure 1As shown, the control device 10 is communicatively connected to the air flow meter 27. The control device 10 acquires the output value of the air flow meter 27. The air flow meter 27 detects the amount of air flowing in the upstream intake manifold 17. The amount of air drawn into the engine 12 can be estimated using the engine speed and the opening of the throttle valve 20. The air flowing into the upstream intake manifold 17 from outside the vehicle merges with the exhaust gas flowing through the return path pipe 15 downstream of the air flow meter 27. Therefore, when the exhaust gas flows through the return path pipe 15, the output value of the air flow meter 27 is less than the estimated amount of air drawn into the engine 12. The control device 10 can compare the output value of the air flow meter 27 with the estimated air volume to estimate the amount of exhaust gas returning to the engine 12 through the return path pipe 15. Hereinafter, the amount of exhaust gas returning to the engine 12 through the return path pipe 15, estimated based on the output value of the air flow meter 27, will be recorded as an estimated amount.

[0041] like Figure 1 As shown, the control device 10 is communicatively connected to the return path valve 16. The control device 10 controls the return path valve 16 based on an estimated quantity. When the estimated quantity is less than the amount of exhaust gas to be returned to the engine 12, the control device 10 increases the opening of the return path valve 16. On the other hand, when the estimated quantity is greater than the amount of exhaust gas to be returned to the engine 12, the control device 10 decreases the opening of the return path valve 16. Furthermore, when the control device 10 does not want the exhaust gas to return to the engine 12, it closes the return path valve 16 to block the exhaust gas from returning to the engine 12.

[0042] <Abnormal determination of exhaust purification device 14 based on control device 10>

[0043] The control device 10 functions as an abnormality determination device to determine whether there is any abnormality in the exhaust purification device 14. Figure 2 This describes the series of processes performed by the control device 10 when determining whether there is an abnormality in the exhaust gas purification device 14. The abnormality in the exhaust gas purification device 14 referred to here means that the exhaust gas purification device 14 has deteriorated and its NH3 adsorption capacity has decreased.

[0044] Figure 2 The series of processes shown are executed by the processing circuit 11. Upon acquiring the output values ​​of the first sensor 21 and the second sensor 22, the processing circuit 11 executes... Figure 2 The series of processes shown.

[0045] <Processing of steps S11 to S13>

[0046] In step S11, the processing circuit 11 calculates the NOx purification rate based on the exhaust gas purification device 14. At this time, the processing circuit 11 calculates the NOx purification rate based on the exhaust gas purification device 14 according to the output value of the first sensor 21 and the output value of the second sensor 22.

[0047] In the next step S12, the processing circuit 11 determines whether the calculated purification rate is below a predetermined value N1. The predetermined value N1 is a threshold preset for determining whether the NOx purification rate based on the exhaust gas purification device 14 is low.

[0048] A purification rate higher than the predetermined value N1 indicates that the exhaust gas purification device 14 is functioning correctly and can effectively purify NOx. If the processing circuit 11 determines that the purification rate is not below the predetermined value N1 (step S12: No), the process proceeds to step S22. The processing in step S22 will be described later.

[0049] A purification rate below a predetermined value N1 indicates a low NOx purification rate based on the exhaust gas purification device 14. If the processing circuit 11 determines that the purification rate is below the predetermined value N1 (step S12: Yes), the processing is advanced to step S13.

[0050] In step S13, the processing circuit 11 determines whether the engine 12 is in a fuel cut-off period. If the processing circuit 11 determines in step S13 that the engine 12 is not in a fuel cut-off period (step S13: No), the processing in step S13 is executed again. On the other hand, if in step S13 it is determined that the engine 12 is in a fuel cut-off period (step S13: Yes), the process proceeds to step S14.

[0051] <Processing method in step S14>

[0052] In step S14, the processing circuit 11 performs an adsorption amount estimation process. The adsorption amount estimation process is a process of estimating the amount of NH3 adsorbed on the exhaust gas purification device 14.

[0053] Figure 3 This indicates the method by which the anomaly detection device estimates the amount of NH3 adsorbed on the exhaust gas purification device 14. For example... Figure 3 As shown, the amount of NH3 adsorbed in the exhaust gas purification device 14 can be estimated by subtracting the amount of NH3 consumed in the exhaust gas purification device 14 and the amount of NH3 removed from the exhaust gas purification device 14 from the amount of NH3 supplied to the exhaust gas purification device 14 and then summing the results.

[0054] The amount of NH3 supplied to the exhaust purification device 14 can be estimated based on the amount of urea water injected by the injector 24.

[0055] like Figure 3 As shown, the amount of NH3 consumed in the exhaust gas purification device 14 can be estimated by multiplying the amount of NOx added to the exhaust gas purification device 14 by an estimated NOx purification rate. This is because NH3 is consumed through a reaction with NOx.

[0056] The NOx purification rate is affected by the amount of NH3 adsorbed in the exhaust gas purification device 14. For example, when the amount of NH3 adsorbed in the exhaust gas purification device 14 is less than the amount of NOx added to the exhaust gas purification device 14, the NOx purification rate decreases.

[0057] The NOx purification rate is affected by the temperature of the exhaust gas purification device 14. This is because the degree of reaction between NOx and NH3 changes depending on the temperature of the exhaust gas purification device 14.

[0058] The NOx purification rate is affected by the intake air volume (Ga). For example, with a large intake air volume, the amount of NH3 reacting with NOx decreases because the exhaust flow rate is faster.

[0059] like Figure 3 As shown, the control device 10 estimates the NOx purification rate based on the amount of NH3 adsorbed in the exhaust gas purification device 14, the temperature of the exhaust gas purification device 14, and the intake air volume. At this time, the control device 10 uses the air that has just passed through… Figure 3 The amount estimated in this way is used as the amount of NH3 adsorbed on the exhaust purification device 14.

[0060] The amount of NH3 that can be adsorbed by the exhaust gas purification device 14 is affected by the temperature of the exhaust gas purification device 14. Figure 4 This indicates the relationship between the temperature of the exhaust gas purification device 14 and the amount of NH3 that can be adsorbed onto the exhaust gas purification device 14. Figure 4 In the process, when the temperature of the exhaust purification device 14 is T1, the amount of NH3 that can be adsorbed by the exhaust purification device 14 is A1. Figure 4 In the process, when the temperature of the exhaust purification device 14 is T2, the amount of NH3 that can be adsorbed by the exhaust purification device 14 is A2.

[0061] like Figure 4 As shown, as the temperature of the exhaust gas purification device 14 increases, the amount of NH3 that can be adsorbed onto the exhaust gas purification device 14 decreases. Therefore, when the temperature of the exhaust gas purification device 14 rises while NH3 is adsorbed, the NH3 that cannot be adsorbed onto the exhaust gas purification device 14 will detach. For example, if the exhaust gas purification device 14 has an adsorbed amount of NH3 of A1 at a temperature of T1, and if the temperature of the exhaust gas purification device 14 rises to T2, the amount of NH3 detached will be the difference between A1 and A2.

[0062] The control device 10 stores in the storage device 28 a maximum adsorption capacity mapping table, which represents the amount of NH3 that can be adsorbed relative to the temperature of the exhaust gas purification device 14. The control device 10 refers to the maximum adsorption capacity mapping table and compares the maximum adsorption capacity of NH3 at the current temperature of the exhaust gas purification device 14 with the maximum adsorption capacity at the temperature just passed through the exhaust gas purification device 14. Figure 3 The amount of NH3 adsorbed on the exhaust gas purification device 14 is estimated by the method described above. If the amount of NH3 adsorbed on the exhaust gas purification device 14 exceeds the maximum adsorption capacity, the control device 10 calculates the difference as the amount of NH3 removed.

[0063] The processing circuit 11 estimates the amount of NH3 adsorbed in the exhaust gas purification device 14 based on the calculated amount of NH3 supplied to the exhaust gas purification device 14, the amount of NH3 consumed in the exhaust gas purification device 14, and the amount of NH3 removed from the exhaust gas purification device 14. Having estimated the amount of NH3 adsorbed in the exhaust gas purification device 14, the processing circuit 11 proceeds to step S15.

[0064] <Processing steps S15 to S22>

[0065] In step S15, the processing circuit 11 determines whether NH3 can be sufficiently adsorbed onto the exhaust gas purification device 14 after urea solution has been sprayed. If the amount of NH3 adsorbed onto the exhaust gas purification device 14 is large, further adsorption of NH3 onto the exhaust gas purification device 14 is not possible. For example, if the amount of NH3 estimated by the processing circuit 11 in step S14 is below a threshold, it determines that NH3 can be sufficiently adsorbed onto the exhaust gas purification device 14.

[0066] In step S15, if the processing circuit 11 determines that NH3 cannot be sufficiently adsorbed by the exhaust purification device 14 (step S15: No), the process ends. Figure 2 The process described is as follows: When the amount of NH3 adsorbed on the exhaust gas purification device 14 is high, the processing circuit 11 terminates without determining whether the exhaust gas purification device 14 is malfunctioning. Figure 2 The series of processes shown.

[0067] In step S15, if the processing circuit 11 determines that NH3 can be sufficiently adsorbed by the exhaust purification device 14 (step S15: Yes), the processing will proceed to step S16. In step S16, the processing circuit 11 will perform an injection quantity calculation.

[0068] The injection quantity calculation process is used to determine the amount of urea water injected from the injector 24 into the exhaust pipe 13. Figure 5 This indicates the method by which the processing circuit 11 determines the amount of urea water injected from the injector 24 in the injection quantity calculation process.

[0069] As described above, the control device 10 can estimate the temperature of the exhaust gas purification device 14 based on the output value of the temperature sensor 23. In the injection quantity calculation process, the processing circuit 11 calculates the maximum amount of NH3 that can be adsorbed onto the exhaust gas purification device 14 based on the estimated temperature of the exhaust gas purification device 14 and the maximum adsorption capacity mapping table stored in the storage device 28. Then, the processing circuit 11 determines the amount of urea water to be injected into the exhaust pipe 13 by subtracting the amount of NH3 adsorbed onto the exhaust gas purification device 14 calculated in step S14 from the maximum amount of NH3 that can be adsorbed onto the exhaust gas purification device 14.

[0070] Thus, the processing circuit 11 determines the amount of urea solution that can be adsorbed by the exhaust purification device 14 under normal conditions as the amount of NH3 to be sprayed. Having determined the amount of sprayed urea solution, the processing circuit 11 proceeds to step S17.

[0071] At the moment the processing in step S17 is performed, the engine 12 is in a fuel cut-off period. During the fuel cut-off period, since it is not necessary to return exhaust gas to the engine 12, the return path valve 16 is closed. In the processing of step S17, the processing circuit 11 opens the return path valve 16. Then, the processing circuit 11 proceeds the processing to step S18.

[0072] In step S18, the processing circuit 11 causes the injector 24 to spray urea solution. At this time, the processing circuit 11 causes the injector 24 to spray the amount of urea solution determined in step S16. Then, the processing circuit 11 proceeds to step S19.

[0073] In step S19, the processing circuit 11 obtains the output value of the first sensor 21 by communicating with the first sensor 21. Then, the processing circuit 11 proceeds to step S20.

[0074] In step S20, the processing circuit 11 determines whether the output value of the first sensor 21 is greater than or equal to a predetermined value N2.

[0075] During fuel cut-off, NH3 is less likely to escape from exhaust gas purification device 14 due to the lower temperature. Furthermore, NOx is not supplied to exhaust pipe 13 during fuel cut-off because combustion does not occur.

[0076] Therefore, when there is no malfunction in the exhaust purification device 14, the NH3 generated by the urea water injected during fuel cut-off is adsorbed into the exhaust purification device 14. That is, when there is no malfunction in the exhaust purification device 14, the amount of NH3 flowing downstream from the exhaust purification device 14 is reduced.

[0077] On the other hand, if the injector 24 sprays urea water when the exhaust purification device 14 is malfunctioning, even if the amount of NH3 that could be adsorbed when the exhaust purification device 14 is not malfunctioning, it will still pass through the exhaust purification device 14.

[0078] NH3 passing through the exhaust purification device 14, after passing through the return path pipe 15 and the engine 12, enters the upstream portion of the exhaust pipe 13 through the exhaust purification device 14. If an oxidation reaction occurs on the electrodes of the nitrogen oxide sensor, the nitrogen oxide sensor reacts and outputs a value. Therefore, in the event of an abnormality in the exhaust purification device 14, the first sensor 21 can detect the NH3 passing through the exhaust purification device 14.

[0079] Thus, if the first sensor 21 outputs a large value when the injector 24 sprays urea water during fuel cutoff, it can be assumed that a large amount of NH3 is passing through due to an abnormality in the exhaust purification device 14. The predetermined value N2 is a pre-determined threshold used to determine whether the output value of the first sensor 21 is large.

[0080] If the processing circuit 11 determines that the output value of the first sensor 21 is greater than or equal to a predetermined value N2 (step S20: Yes), the processing proceeds to step S21. In step S21, the processing circuit 11 determines that the exhaust purification device 14 is malfunctioning. Then, the processing circuit 11 terminates. Figure 2 The series of processes shown.

[0081] If the processing circuit 11 determines that the output value of the first sensor 21 is not greater than the predetermined value N2 (step S20: No), the processing proceeds to step S22. In step S22, the processing circuit 11 determines that the exhaust purification device 14 is not malfunctioning. Then, the processing circuit 11 terminates. Figure 2 The series of processes shown.

[0082] <The function of this implementation method>

[0083] The control device 10, which serves as an anomaly detection device, checks whether the nitrogen oxide sensor detects NH3 generated by the urea water injected by the injector 24 during fuel cut-off. Thus, the anomaly detection device determines whether the anomaly in the purification rate is caused by the removal of NH3 from the exhaust gas purification device 14.

[0084] <Effects of this implementation method>

[0085] (1) The control device 10 can ensure the opportunity for abnormality determination and determine whether the exhaust purification device 14 is abnormal.

[0086] (2) The intake and exhaust system 100, including the exhaust system, includes a return path pipe 15 and a return path valve 16. The return path pipe 15 allows exhaust gas passing through the exhaust purification device 14 to flow back to the engine 12. The return path valve 16 is located midway through the return path pipe 15 and blocks the exhaust gas flowing back to the engine 12. In the control device 10, when the purification rate is low, during fuel cut-off, with the return path valve 16 open and the injector 24 injecting urea water, if the first sensor 21 outputs a value greater than or equal to a predetermined value N2, the processing circuit 11 determines that the exhaust purification device 14 is malfunctioning.

[0087] When determining whether there is an abnormality in the exhaust purification device 14, the control device 10 makes a determination based on the output value of the first sensor 21. Therefore, even if the second sensor 22 malfunctions, the control device 10 can still determine whether there is an abnormality in the exhaust purification device 14.

[0088] (3) The processing circuit 11 estimates the temperature of the exhaust gas purification device 14 during the fuel cut-off period. The processing circuit 11 causes the injector 24 to inject urea water that produces an amount of ammonia below the maximum amount of ammonia that the exhaust gas purification device 14 can adsorb at the estimated temperature.

[0089] Even when there is no malfunction in the exhaust gas purification device 14, ammonia will still pass through it if the amount of ammonia supplied to it exceeds its capacity to adsorb. There is a correlation between the temperature of the exhaust gas purification device 14 and the amount of ammonia it can adsorb. The control device 10 determines the amount of urea solution injected into the exhaust pipe 13 based on the temperature of the exhaust gas purification device 14. Therefore, the control device 10 can reduce the amount of ammonia passing through the exhaust gas purification device 14 when there is no malfunction.

[0090] (4) The processing circuit 11 estimates the amount of ammonia adsorbed on the exhaust purification device 14 during the fuel cut-off period. The processing circuit 11 causes the injector 24 to inject urea water into the exhaust pipe 13 to produce an amount of ammonia obtained by subtracting the amount of ammonia adsorbed on the exhaust purification device 14 from the maximum amount.

[0091] Even if the exhaust purification device 14 malfunctions, ammonia may not pass through the exhaust purification device 14 if the amount of urea solution sprayed by the injector 24 is low. The control device 10 causes the injector 24 to spray an amount of urea solution determined by subtracting the amount of ammonia currently adsorbed by the exhaust purification device 14 from the maximum amount of ammonia that can be adsorbed by the exhaust purification device 14. Thus, the control device 10 can suppress ammonia from passing through the exhaust purification device 14 when there is no malfunction, and can facilitate the passage of ammonia through the exhaust purification device 14 when there is a malfunction.

[0092] (5) The processing circuit 11 estimates the amount of ammonia adsorbed on the exhaust gas purification device 14 during the fuel cut-off period. The processing circuit 11 does not determine whether there is any abnormality in the exhaust gas purification device 14 when the amount of ammonia adsorbed on the exhaust gas purification device 14 is large.

[0093] Even when there is no abnormality in the exhaust purification device 14, if the amount of ammonia supplied to the exhaust purification device 14 is large, the ammonia will pass through the exhaust purification device 14. The control device 10 does not determine whether there is an abnormality in the exhaust purification device 14 when the amount of ammonia adsorbed on the exhaust purification device 14 is large. Therefore, the control device 10 can more accurately determine whether there is an abnormality in the exhaust purification device 14.

[0094] <Example of Change>

[0095] The above-described embodiments can be modified to be implemented in the manner described above. The above-described embodiments and the following modifications can be combined with each other to implement them within the scope of technical inconsistency.

[0096] In step S19, the processing circuit 11 acquires the output value of the first sensor 21. Furthermore, in steps S20 to S22, the processing circuit 11 determines whether the exhaust purification device 14 is malfunctioning based on the output value of the first sensor 21. Alternatively, the processing circuit 11 can also determine whether the exhaust purification device 14 is malfunctioning based on the output value of the second sensor 22. In this case, the intake and exhaust system 100 may not include the return path piping 15 and the return path valve 16.

[0097] ·like Figure 5 As shown and explained, the processing circuit 11 determines the amount of urea solution by including the amount of NH3 obtained by subtracting the amount of NH3 adsorbed by the exhaust gas purification device 14 from the maximum amount of NH3 that can be adsorbed by the exhaust gas purification device 14. The method by which the processing circuit 11 determines the amount of urea solution injected in the injection quantity calculation process is not limited to... Figure 5 In this way, for example, the processing circuit 11 may also determine the amount of urea water to be sprayed in a manner that includes the maximum amount of NH3 that can be adsorbed onto the exhaust gas purification device 14 based on the temperature of the exhaust gas purification device 14.

[0098] Even when the amount of NH3 adsorbed on the exhaust purification device 14 is large, the processing circuit 11 can determine whether there is any abnormality in the exhaust purification device 14.

[0099] Symbol Explanation

[0100] 10-Control device, 11-Processing circuit, 12-Engine, 13-Exhaust pipe, 14-Exhaust purification device, 15-Return path piping, 16-Return path valve, 17-Upstream intake pipe, 18-Turbocharger, 19-Downstream intake pipe, 20-Throttle valve, 21-First sensor, 22-Second sensor, 23-Temperature sensor, 24-Injector, 25-High-pressure return path piping, 26-High-pressure return path valve, 100-Intake and exhaust system.

Claims

1. An anomaly detection device, characterized in that, The system for determining whether there is any abnormality in the exhaust purification device within the exhaust system, wherein the exhaust system comprises: The exhaust purification device is installed in the middle of the engine's exhaust pipe and uses ammonia as a reducing agent to reduce nitrogen oxides in the exhaust. An injector, positioned upstream of the exhaust purification device, sprays urea solution into the exhaust pipe. The first sensor, which is a nitrogen oxide sensor for measuring the amount of nitrogen oxides contained in the exhaust gas, is positioned upstream of the injector; and The second sensor, which is the nitrogen oxide sensor, is located further downstream than the exhaust purification device. The anomaly detection device includes a processing circuit. When the nitrogen oxide purification rate of the exhaust purification device is low, the processing circuit, during fuel cut-off, causes the injector to spray urea water in an amount that can adsorb the amount of ammonia that is not present in the exhaust purification device. If the nitrogen oxide sensor outputs a value above a predetermined value, it determines that there is an abnormality in the exhaust purification device.

2. The anomaly determination device according to claim 1, characterized in that, The exhaust system includes: A return path piping that allows exhaust gas passing through the exhaust purification device to return to the engine; and A return path valve is located midway through the return path piping and blocks the return of exhaust gas to the engine. When the purification rate is low, during the fuel cut-off period, when the return path valve is open and the injector is spraying the urea water, if the first sensor outputs a value above the predetermined value, the processing circuit determines that there is an abnormality in the exhaust purification device.

3. The anomaly determination device according to claim 1 or 2, characterized in that, The processing circuit estimates the temperature of the exhaust gas purification device during the fuel cut-off period. The processing circuit causes the injector to spray urea water in an amount of ammonia below the maximum amount of ammonia that the exhaust purification device can adsorb at the estimated temperature.

4. The anomaly determination device according to claim 3, characterized in that, The processing circuit estimates the amount of ammonia adsorbed on the exhaust gas purification device during the fuel cut-off period. The processing circuit causes the injector to inject urea water into the exhaust pipe, producing an amount equal to the maximum amount minus the amount of ammonia adsorbed by the exhaust purification device.

5. The anomaly determination device according to claim 1 or 2, characterized in that, The processing circuit estimates the amount of ammonia adsorbed on the exhaust gas purification device during the fuel cut-off period. When the amount of ammonia adsorbed in the exhaust purification device is large, the processing circuit does not determine whether there is any abnormality in the exhaust purification device.

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