Abnormality determination device for internal combustion engine

Abstract

To accurately determine whether or not an exhaust emission control device is detached from an exhaust passage.SOLUTION: An abnormality determination device for an internal combustion engine acquires an upstream temperature that is a temperature of exhaust gas upstream of an exhaust emission control device in an exhaust passage. The abnormality determination device acquires a downstream temperature that is a temperature of exhaust gas downstream of the exhaust emission control device in the exhaust passage. The abnormality determination device calculates an index value having a positive correlation with an absolute value of a difference between the upstream temperature and the downstream temperature (S71). When the index value is smaller than a predetermined diagnosis threshold value, the abnormality determination device determines that the exhaust emission control device has been detached from the exhaust passage (S82). The abnormality determination device acquires a moisture level having a positive correlation with an amount of condensation water present in the exhaust emission control device. When the moisture level is low, the abnormality determination device corrects the diagnosis threshold value so that the index value is likely to be determined to be the diagnosis threshold value or higher, compared to when the moisture level is high (S72).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an abnormality determination device for an internal combustion engine. [Background technology]

[0002] The internal combustion engine disclosed in Patent Document 1 includes multiple cylinders, an exhaust passage, and a PM trapping device. The cylinders are spaces in which fuel is burned. The exhaust passage is a passage for exhaust gas discharged from each cylinder. The PM trapping device is attached midway through the exhaust passage. The PM trapping device traps particulate matter in the exhaust gas. The abnormality determination device disclosed in Patent Document 1 also determines whether the PM trapping device has been removed from the exhaust passage.

[0003] Here, in the internal combustion engine disclosed in Patent Document 1, immediately after the internal combustion engine starts to operate, the heat of the exhaust gas flowing through the exhaust passage is absorbed by the PM trapping device. As a result, immediately after the internal combustion engine starts to operate, the temperature rise rate downstream of the PM trapping device in the exhaust passage is smaller than the temperature rise rate upstream of the PM trapping device in the exhaust passage. On the other hand, if the PM trapping device is removed from the exhaust passage, the heat of the exhaust gas flowing through the exhaust passage is not absorbed by the PM trapping device. Therefore, in this case, even immediately after the internal combustion engine starts to operate, the difference between the temperature rise rate upstream of the PM trapping device in the exhaust passage and the temperature rise rate downstream of the PM trapping device in the exhaust passage is small.

[0004] Therefore, the abnormality determination device disclosed in Patent Document 1 obtains an upstream temperature, which is the temperature of the exhaust gas upstream of the exhaust purification device in the exhaust passage. The abnormality determination device also obtains a downstream temperature, which is the temperature of the exhaust gas downstream of the exhaust purification device in the exhaust passage. The abnormality determination device then determines that the exhaust purification device has been removed from the exhaust passage when the absolute value of the difference between the upstream temperature and the downstream temperature becomes small. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-106028 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an internal combustion engine such as that disclosed in Patent Document 1, condensed water is generally present in the PM trapping device when the internal combustion engine starts to operate. If condensed water is present in this way, immediately after the internal combustion engine starts to operate, the heat of the exhaust gas flowing through the exhaust passage is consumed as heat of vaporization for evaporating the condensed water in the PM trapping device. However, the abnormality determination device of Patent Document 1 does not take into consideration the influence of the amount of condensed water in the PM trapping device, etc. Therefore, the abnormality determination device of Patent Document 1 may not be able to accurately determine whether the PM trapping device has been removed, depending on, for example, the amount of condensed water. [Means for solving the problem]

[0007] The abnormality determination device for an internal combustion engine to solve the above problem is applied to an internal combustion engine that has a cylinder that combusts fuel, an exhaust passage through which exhaust gas discharged from the cylinder flows, and an exhaust purification device located midway through the exhaust passage to purify the exhaust gas, and executes the following processes: a first process of acquiring an upstream temperature, which is the temperature of the exhaust gas upstream of the exhaust purification device in the exhaust passage; a second process of acquiring a downstream temperature, which is the temperature of the exhaust gas downstream of the exhaust purification device in the exhaust passage; a third process of calculating an index value that has a positive correlation with the absolute value of the difference between the upstream temperature and the downstream temperature; a fourth process of determining that the exhaust purification device has been removed from the exhaust passage if the index value is smaller than a predetermined diagnostic threshold value; a fifth process of acquiring a humidity level that has a positive correlation with the amount of condensed water present in the exhaust purification device; and a sixth process of correcting one or more of the index value and the diagnostic threshold value so that the index value is more likely to be determined to be equal to or greater than the diagnostic threshold value when the humidity level is low, compared to when the humidity level is high. Effect of the Invention

[0008] According to the above configuration, in a situation where the wetness level is low, in other words, in a situation where the index value calculated in the third process is likely to be small due to condensed water, the sixth process, for example, increases the index value or decreases the diagnostic threshold value. As a result, in a situation where the index value calculated in the third process is low due to a low wetness level, it is more likely to be determined that the exhaust purification device has not been removed. As a result, it is possible to suppress an erroneous determination in the fourth process that the exhaust purification device has been removed from the exhaust passage due to the influence of condensed water, even when the exhaust purification device is attached to the exhaust passage. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Diagram 2] FIG. 2 is a flowchart showing the wetness level acquisition control. [Diagram 3] FIG. 3 is a flowchart showing the first determination control. [Figure 4] FIG. 4 is a flowchart showing the second determination control. [Diagram 5] FIG. 5 is an explanatory diagram regarding condensed water in the GPF. [Figure 6] FIG. 6 is an explanatory diagram regarding condensed water in the GPF. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Vehicle Overview> An embodiment of the present invention will now be described with reference to Figures 1 to 6. First, a schematic configuration of a vehicle 100 will be described.

[0011] 1, a vehicle 100 is equipped with a spark ignition type internal combustion engine 10. The internal combustion engine 10 is equipped with a plurality of cylinders 11, an intake passage 21, a throttle valve 22, and a plurality of fuel injection valves 23. The internal combustion engine 10 also is equipped with a plurality of ignition devices 24, an exhaust passage 26, a three-way catalyst 27, and a GPF 28.

[0012] The cylinders 11 are spaces for burning a mixture of fuel and intake air. A crankshaft (not shown) rotates due to the combustion of the mixture of fuel and intake air in the cylinders 11. An example of the fuel is gasoline. In this embodiment, the internal combustion engine 10 has four cylinders 11. Note that FIG. 1 shows only one representative cylinder 11.

[0013] The intake passage 21 is connected to the cylinders 11. The intake passage 21 introduces intake air from outside the internal combustion engine 10 to each cylinder 11. The exhaust passage 26 is connected to the cylinders 11. The exhaust passage 26 discharges exhaust gas from each cylinder 11 to outside the internal combustion engine 10. In this embodiment, the exhaust passage 26 extends generally from the front of the vehicle 100 to the rear of the vehicle 100.

[0014] The throttle valve 22 is located in the middle of the intake passage 21. The throttle valve 22 adjusts the amount of intake air flowing through the intake passage 21. The fuel injection valve 23 is located near the downstream end of the intake passage 21. The internal combustion engine 10 has four fuel injection valves 23 corresponding to the four cylinders 11. The fuel injection valves 23 inject fuel supplied from a fuel tank (not shown) into the intake passage 21. As a result, fuel from the fuel injection valves 23 is supplied to the cylinders 11. The ignition devices 24 are located in the cylinders 11. The internal combustion engine 10 has four ignition devices 24 corresponding to the four cylinders 11. The ignition devices 24 ignite a mixture of fuel and intake air by spark discharge. Note that FIG. 1 shows only one fuel injection valve 23 and one ignition device 24 as representatives.

[0015] The three-way catalyst 27 is located in the exhaust passage 26. The three-way catalyst 27 purifies the exhaust gas flowing through the exhaust passage 26. Specifically, the three-way catalyst 27 has a function of purifying hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas. The three-way catalyst 27 also has a function of storing oxygen in the exhaust gas.

[0016] The GPF 28 is located downstream of the three-way catalyst 27 in the exhaust passage 26. In this embodiment, the GPF 28 is a filter carrying a three-way catalyst. Therefore, the GPF 28 is capable of collecting particulate matter contained in the exhaust flowing through the exhaust passage 26. Note that "GPF" is an abbreviation for Gasoline Particulate Filter. In this embodiment, the GPF 28 is an example of an exhaust purification device that is located in the exhaust passage 26 and purifies the exhaust.

[0017] 1, the vehicle 100 is equipped with an air flow meter 81, a water temperature sensor 82, an intake air temperature sensor 83, and a crank angle sensor 84. The vehicle 100 also is equipped with an accelerator operation amount sensor 85, a vehicle speed sensor 86, an upstream temperature sensor 87, a downstream temperature sensor 88, and an acceleration sensor 89.

[0018] The air flow meter 81 detects the intake air amount GA, which is the amount of intake air flowing through the intake passage 21 per unit time. The water temperature sensor 82 detects the coolant temperature THW, which is the temperature of the coolant flowing through each part of the internal combustion engine 10. The intake air temperature sensor 83 detects the intake air temperature THA, which is the temperature of the intake air flowing through the intake passage 21. The crank angle sensor 84 detects the crank angle SC, which is the rotational position of the crankshaft of the internal combustion engine 10. The accelerator operation amount sensor 85 detects the accelerator operation amount ACC, which is the amount of operation of the accelerator pedal operated by the driver. The vehicle speed sensor 86 detects the vehicle speed SP, which is the speed of the vehicle 100.

[0019] The upstream temperature sensor 87 is located in the exhaust passage 26, downstream of the three-way catalyst 27 and upstream of the GPF 28. The upstream temperature sensor 87 detects an upstream temperature Tin, which is the temperature of the exhaust gas upstream of the GPF 28 in the exhaust passage 26. The downstream temperature sensor 88 is located in the exhaust passage 26, downstream of the GPF 28. The downstream temperature sensor 88 detects a downstream temperature Tout, which is the temperature of the exhaust gas downstream of the GPF 28 in the exhaust passage 26.

[0020] The acceleration sensor 89 is a so-called three-axis sensor. That is, the acceleration sensor 89 can detect longitudinal acceleration GX, lateral acceleration GY, and vertical acceleration GZ. The longitudinal acceleration GX is acceleration along the longitudinal axis of the vehicle 100. The lateral acceleration GY is acceleration along the lateral axis of the vehicle 100. The vertical acceleration GZ is acceleration along the vertical axis of the vehicle 100.

[0021] As shown in Fig. 1, the vehicle 100 includes a control device 90. The control device 90 acquires signals indicating various values ​​from various sensors. That is, the control device 90 can execute a first process for acquiring an upstream temperature Tin. The control device 90 can also execute a second process for acquiring a downstream temperature Tout.

[0022] The control device 90 includes an execution unit 91 and a storage unit 92. An example of the execution unit 91 is a CPU. The storage unit 92 includes a read-only ROM, a readable and writable volatile RAM, and a readable and writable non-volatile storage. The storage unit 92 prestores a control program 92A as one of various programs. The execution unit 91 executes the control program 92A to realize various processes described below. In other words, the execution unit 91 executes the control program 92A to realize various processes related to abnormality determination of the internal combustion engine 10. In this embodiment, the control device 90 is an example of an abnormality determination device for the internal combustion engine 10.

[0023] The control device 90 calculates the road surface gradient AR, which is the gradient of the road surface at the point where the vehicle 100 is located, for each predetermined control cycle based on the longitudinal acceleration GX, the lateral acceleration GY, and the vertical acceleration GZ. In this embodiment, when the vehicle 100 is located on a level road surface, the road surface gradient AR is zero. When the vehicle 100 is located on an uphill road, the road surface gradient AR is a positive value. When the vehicle 100 is located on a downhill road, the road surface gradient AR is a negative value.

[0024] <Moisture level acquisition control> Next, the wetness level acquisition control executed by the control device 90 will be described with reference to Fig. 2. This wetness level acquisition control is a control for acquiring the wetness level LW. Here, the wetness level LW has a positive correlation with the amount of condensed water present in the GPF 28. In this embodiment, the control device 90 starts the wetness level acquisition control when the internal combustion engine 10 is operating.

[0025] As shown in FIG. 2, when the execution unit 91 of the control device 90 starts the wetness level acquisition control, it executes the process of step S21. In step S21, the execution unit 91 calculates an upstream reference amount WSin, which is a reference amount of condensed water present in the upstream portion of the exhaust passage 26 with respect to the GPF 28. In this embodiment, the upstream reference amount WSin is the amount of condensed water present in the upstream portion with respect to the GPF 28 at the time when the internal combustion engine 10 starts operating, assuming that the road surface gradient AR is zero, that is, assuming that the vehicle 100 is located on a horizontal road surface. For example, the execution unit 91 calculates the upstream reference amount WSin based on the soak time Tsoak and the upstream temperature Tin. Specifically, the execution unit 91 calculates a larger value of the upstream reference amount WSin as the soak time Tsoak is longer and the upstream temperature Tin is lower. Here, the soak time Tsoak is the period from the end of the previous operation of the internal combustion engine 10 to the start of the current operation of the internal combustion engine 10. After step S21, the execution section 91 advances the process to step S22.

[0026] In step S22, the execution unit 91 calculates a GPF reference amount WSG, which is a reference amount of condensed water present in the GPF 28. In this embodiment, the GPF reference amount WSG is the amount of condensed water present in the GPF 28 at the time when the internal combustion engine 10 starts operating, assuming that the road surface gradient AR is zero, that is, assuming that the vehicle 100 is located on a level road surface. For example, the execution unit 91 calculates the GPF reference amount WSG based on the soak time Tsoak, the upstream temperature Tin, and the downstream temperature Tout. Specifically, the execution unit 91 calculates a larger value of the GPF reference amount WSG as the soak time Tsoak is longer, the upstream temperature Tin is lower, and the downstream temperature Tout is lower. After step S22, the execution unit 91 advances the process to step S23.

[0027] In step S23, the execution unit 91 calculates a downstream reference amount WSout, which is a reference amount of condensed water present in a portion of the exhaust passage 26 downstream of the GPF 28. In this embodiment, the downstream reference amount WSout is the amount of condensed water present in a portion downstream of the GPF 28 at the time when the internal combustion engine 10 starts operating, assuming that the road surface gradient AR is zero, that is, assuming that the vehicle 100 is located on a level road surface. For example, the execution unit 91 calculates the downstream reference amount WSout based on the soak time Tsoak and the downstream temperature Tout. Specifically, the execution unit 91 calculates a downstream reference amount WSout with a larger value as the soak time Tsoak is longer and the downstream temperature Tout is lower. After step S23, the execution unit 91 advances the process to step S24.

[0028] In step S24, the execution unit 91 calculates the GPF water amount WG, which is the total amount of condensed water present in the GPF 28 at the time of processing in step S24. For example, the execution unit 91 calculates the GPF water amount WG based on the upstream reference amount WSin, the GPF reference amount WSG, the downstream reference amount WSout, the road surface gradient AR, the intake air amount GA, and the upstream temperature Tin.

[0029] Here, when the internal combustion engine 10 is operating, the amount of condensed water in the GPF 28 may increase as the exhaust gas flowing through the exhaust passage 26 moves the condensed water present in the upstream portion of the exhaust passage 26 with respect to the GPF 28 to the GPF 28. Therefore, the execution unit 91 calculates the increase amount of condensed water in the GPF 28, for example, by applying the upstream reference amount WSin and the integrated value of the intake air amount GA to a first map. Note that the above relationship is determined in advance in the first map through experiments, simulations, etc. Also, when the internal combustion engine 10 is operating, the amount of condensed water in the GPF 28 may decrease as the condensed water in the GPF 28 evaporates due to the exhaust gas flowing through the exhaust passage 26. Therefore, the execution unit 91 calculates the decrease amount of condensed water in the GPF 28, for example, by applying the GPF reference amount WSG, the integrated value of the intake air amount GA, and the integrated value of the upstream temperature Tin to a second map. Note that the above relationship is determined in advance in the second map through experiments, simulations, etc.

[0030] As described above, the exhaust passage 26 generally extends from the front of the vehicle 100 to the rear of the vehicle 100. Therefore, for example, when the road surface gradient AR is a positive value, that is, when the vehicle 100 is located on an uphill road, the condensed water present in the upstream portion of the exhaust passage 26 with respect to the GPF 28 is likely to move to the GPF 28. Therefore, when the road surface gradient AR is a positive value, the execution unit 91 corrects the GPF reference amount WSG to a larger value as the upstream reference amount WSin and the road surface gradient AR are larger. On the other hand, for example, when the road surface gradient AR is a negative value, that is, when the vehicle 100 is located on a downhill road, the condensed water present in the downstream portion of the exhaust passage 26 with respect to the GPF 28 is likely to move to the GPF 28. Therefore, when the road surface gradient AR is a negative value, the execution unit 91 corrects the GPF reference amount WSG to a larger value as the downstream reference amount WSout is larger and the road surface gradient AR is smaller.

[0031] Then, the execution unit 91 calculates the GPF water amount WG based on the increase in the amount of condensed water in the GPF 28, the decrease in the amount of condensed water in the GPF 28, and the corrected GPF reference amount WSG. After step S24, the execution unit 91 advances the process to step S31.

[0032] In step S31, the execution unit 91 calculates a specific ratio RI, which is a ratio of an area where condensed water exists in an orthogonal cross section, which is a cross section perpendicular to the direction in which the exhaust gas flows, of the GPF 28. Specifically, the execution unit 91 calculates the specific ratio RI based on the GPF water amount WG and the road surface gradient AR. For example, as shown in FIG. 5, the condensed water existing in the GPF 28 generally tends to exist in an area in the vertically downward direction of the GPF 28. In this embodiment, if it is assumed that the road surface gradient AR is zero, that is, if it is assumed that the vehicle 100 is located on a horizontal road surface, the ratio of the area where condensed water exists in all orthogonal cross sections that can be taken by the GPF 28 is approximately constant. In this case, the execution unit 91 calculates the above ratio as the specific ratio RI. On the other hand, as shown in FIG. 6, if it is assumed that the road surface gradient AR is a positive value, that is, if it is assumed that the vehicle 100 is located on an uphill slope, the condensed water moves to the rear of the vehicle 100 in the GPF 28, in other words, downstream of the GPF 28. As a result, the proportion of the area where condensed water exists in the orthogonal cross section at the upstream end of the GPF 28 is minimized, while the proportion of the area where condensed water exists in the orthogonal cross section at the downstream end of the GPF 28 is maximized. In this case, the execution unit 91 calculates the proportion of the area where condensed water exists in the orthogonal cross section at the downstream end of the GPF 28 as the specific proportion RI. That is, in this embodiment, the specific proportion RI is the maximum value of the proportions of the area where condensed water exists in the orthogonal cross section of the GPF 28. As shown in FIG. 2, after step S31, the execution unit 91 advances the process to step S32.

[0033] In step S32, the execution unit 91 calculates the wetness level LW based on the GPF water volume WG and the specific ratio RI. For example, the execution unit 91 calculates a higher value of the wetness level LW as the GPF water volume WG increases and as the specific ratio RI increases. In other words, when the GPF water volume WG is large, the execution unit 91 acquires a higher value of the wetness level LW compared to when the GPF water volume WG is small. Also, when the specific ratio RI is large, the execution unit 91 acquires a higher value of the wetness level LW compared to when the specific ratio RI is small. Note that the wetness level LW can take a number of stages, such as "0", "1", "2", etc. In this embodiment, the processing of steps S21 to S32 is an example of a fifth processing. After step S32, the execution unit 91 ends the current wetness level acquisition control. Then, the execution unit 91 advances the processing to step S21 again.

[0034] <First judgment control> Next, the first determination control executed by the control device 90 will be described with reference to Fig. 3. This first determination control is the first control for determining whether or not the GPF 28 has been removed from the exhaust passage 26. In this embodiment, the control device 90 starts the first determination control every time the internal combustion engine 10 operates, on the condition that the processing of step S81 or step S82 in the second determination control described later has not been executed in the current trip. Note that a trip refers to a period from when the system of the vehicle 100 is started to when the system of the vehicle 100 is shut down.

[0035] 3, when the execution unit 91 of the control device 90 starts the first determination control, it executes the process of step S41. In step S41, the execution unit 91 determines whether or not a predetermined precondition is satisfied. For example, the execution unit 91 determines that the precondition is satisfied when all of the following requirements (1) to (3) are satisfied.

[0036] Requirement (1): All sensors must be functioning normally. Requirement (2): The coolant temperature THW is equal to or higher than a predetermined first low temperature threshold. Requirement (3): The intake air temperature THA is equal to or higher than a predetermined second low temperature threshold.

[0037] Here, an example of the first low temperature threshold is "-15° C." Moreover, an example of the second low temperature threshold is "-15° C." In step S41, if the execution unit 91 determines that the precondition is satisfied (S41: YES), the execution unit 91 advances the process to step S42.

[0038] In step S42, the execution unit 91 determines whether or not a predetermined cooling condition is satisfied. For example, the execution unit 91 determines that the cooling condition is satisfied when all of the following requirements (4) to (6) are satisfied.

[0039] Requirement (4): The soak time Tsoak must be equal to or greater than a predetermined specified period. Requirement (5): The upstream temperature Tin is equal to or lower than a predetermined first permitted temperature. Requirement (6): The downstream temperature Tout is equal to or lower than a predetermined second permissible temperature.

[0040] Here, the specified period is determined as a threshold for determining whether or not a soak time Tsoak has elapsed long enough for the GPF 28 to be sufficiently cooled. An example of the specified period is about several hours to a dozen hours. The first permitted temperature is a threshold for determining whether or not the upstream temperature Tin is sufficiently low. An example of the first permitted temperature is several tens of degrees Celsius. The second permitted temperature is a threshold for determining whether or not the downstream temperature Tout is sufficiently low. An example of the second permitted temperature is several tens of degrees Celsius. If the execution unit 91 determines in step S42 that the cooling condition is satisfied (S42: YES), the execution unit 91 advances the process to step S46.

[0041] In step S46, the execution unit 91 sets the upstream temperature Tin at the time of the processing of step S46 as the start upstream temperature TSin. After step S46, the execution unit 91 advances the process to step S47.

[0042] In step S47, the execution unit 91 sets the downstream temperature Tout at the time of the processing of step S47 as the start downstream temperature TSout. After step S47, the execution unit 91 ends the current first determination control.

[0043] On the other hand, if the execution unit 91 determines in the above-mentioned step S41 that the prerequisite is not satisfied (S41: NO), the execution unit 91 ends the current first determination control. Similarly, if the execution unit 91 determines in the above-mentioned step S42 that the cooling condition is not satisfied (S42: NO), the execution unit 91 ends the current first determination control.

[0044] <Second judgment control> Next, the second determination control executed by the control device 90 will be described with reference to Fig. 4. This second determination control is a second control for determining whether or not the GPF 28 has been removed from the exhaust passage 26. In this embodiment, the control device 90 starts the second determination control every time the start upstream temperature TSin and the start downstream temperature TSout are set by the first determination control in a state in which the wetness level LW has been acquired by the wetness level acquisition control.

[0045] As shown in Fig. 4, when the execution unit 91 of the control device 90 starts the second determination control, it executes the process of step S51. In step S51, the execution unit 91 sets the allowable value A based on the wetness level LW. Specifically, the execution unit 91 sets a larger allowable value A as the wetness level LW is higher. In this embodiment, the process of step S51 is an example of a seventh process in which the allowable value A is made larger when the wetness level LW is high compared to when the wetness level LW is low. After step S51, the execution unit 91 advances the process to step S52.

[0046] In step S52, the execution unit 91 determines whether the intake air amount GA is equal to or less than a predetermined allowable value A. Here, the intake air amount GA is approximately equal to the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time. Therefore, in this embodiment, the intake air amount GA corresponds to the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time. In step S52, if the execution unit 91 determines that the intake air amount GA is greater than the allowable value A (S52: NO), the execution unit 91 ends the current second determination control. On the other hand, in step S52, if the execution unit 91 determines that the intake air amount GA is equal to or less than the allowable value A (S52: YES), the execution unit 91 advances the process to step S61. In other words, the execution unit 91 advances the process to step S61, assuming that the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time is equal to or less than the predetermined allowable value A as a necessary condition.

[0047] In step S61, the execution unit 91 calculates an upstream change amount ΔTin, which is a value obtained by subtracting the start upstream temperature TSin from the upstream temperature Tin at the time of the processing of step S61. After step S61, the execution unit 91 advances the processing to step S62.

[0048] In step S62, the execution unit 91 calculates an upstream integral value ΣΔTin, which is a value obtained by integrating the upstream change amount ΔTin from the start point of the second determination control to the processing point of step S62. That is, in this step S62, the execution unit 91 calculates a new upstream integral value ΣΔTin by adding the upstream change amount ΔTin to the upstream integral value ΣΔTin calculated in the previous step S62. In this embodiment, the upstream integral value ΣΔTin is an example of an integral value of the upstream temperature Tin. After step S62, the execution unit 91 advances the process to step S63.

[0049] In step S63, the execution unit 91 calculates a downstream change amount ΔTout, which is a value obtained by subtracting the start downstream temperature TSout from the downstream temperature Tout at the time of the processing of step S63. After step S63, the execution unit 91 advances the processing to step S64.

[0050] In step S64, the execution unit 91 calculates a downstream integral value ΣΔTout, which is a value obtained by integrating the downstream change amount ΔTout from the start point of the second determination control to the processing point of step S64. That is, in this step S64, the execution unit 91 calculates a new downstream integral value ΣΔTout by adding the downstream change amount ΔTout to the downstream integral value ΣΔTout calculated in the previous step S64. In this embodiment, the downstream integral value ΣΔTout is an example of the integral value of the downstream temperature Tout. After step S64, the execution unit 91 advances the process to step S65.

[0051] In step S65, the execution unit 91 sets a judgment temperature TF based on the start downstream temperature TSout and the wetness level LW. Specifically, the execution unit 91 sets a value obtained by adding a specified value to the start downstream temperature TSout as the judgment temperature TF. At this time, the execution unit 91 increases the specified value as the wetness level LW is lower. In other words, the execution unit 91 sets a higher value of the judgment temperature TF as the wetness level LW is lower. Note that the specified value is a positive value. After step S65, the execution unit 91 advances the process to step S66.

[0052] In step S66, the execution unit 91 determines whether the downstream temperature Tout is equal to or higher than a predetermined judgment temperature TF. If the execution unit 91 determines in step S66 that the downstream temperature Tout is lower than the judgment temperature TF (S66: NO), the execution unit 91 ends the current second judgment control. Then, the execution unit 91 advances the process to step S51 again. On the other hand, if the execution unit 91 determines in step S66 that the downstream temperature Tout is equal to or higher than the judgment temperature TF (S66: YES), the execution unit 91 advances the process to step S71.

[0053] In step S71, the execution unit 91 calculates a quotient Q by dividing the upstream integral value ΣΔTin by the downstream integral value ΣΔTout. In this embodiment, the quotient Q is an index value indicating the difference between the integral value of the upstream temperature Tin during the period from when the internal combustion engine 10 starts operating until the downstream temperature Tout becomes equal to or higher than a predetermined judgment temperature TF, and the integral value of the downstream temperature Tout during the same period. In other words, the quotient Q is an index value that has a positive correlation with the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout. In this embodiment, the processes of steps S61 to S71 are an example of a third process. After step S71, the execution unit 91 advances the process to step S72.

[0054] In step S72, the execution unit 91 sets the diagnostic threshold QA based on the wetness level LW. Specifically, the execution unit 91 sets the diagnostic threshold QA to a smaller value as the wetness level LW is lower. In this embodiment, the process of step S72 is a process of correcting the diagnostic threshold QA so that, when the wetness level LW is low, a positive determination is more likely to be made in the process of step S73 described later than when the wetness level LW is high. That is, the process of step S72 is an example of the sixth process. The diagnostic threshold QA is set to a value that is a certain value smaller than the minimum value of the quotient Q calculated in step S71 when the GPF 28 is attached to the exhaust passage 26. After step S72, the execution unit 91 advances the process to step S73.

[0055] In step S73, the execution unit 91 determines whether the quotient Q is equal to or greater than a predetermined diagnostic threshold QA. If the execution unit 91 determines in step S73 that the quotient Q is equal to or greater than the diagnostic threshold QA (S73: YES), the execution unit 91 advances the process to step S81.

[0056] In step S81, the execution unit 91 determines that the GPF 28 is attached to the exhaust passage 26. That is, the execution unit 91 determines that the internal combustion engine 10 is normal. After step S81, the execution unit 91 ends the current second determination control.

[0057] On the other hand, in the above-mentioned step S73, when the execution unit 91 determines that the quotient Q is less than the diagnostic threshold QA (S73: NO), the execution unit 91 advances the process to step S82. In other words, when the index value is less than the diagnostic threshold QA, the execution unit 91 advances the process to step S82.

[0058] In step S82, the execution unit 91 determines that the GPF 28 has been removed from the exhaust passage 26. That is, the execution unit 91 determines that the internal combustion engine 10 is abnormal. At this time, the execution unit 91 outputs a control signal to a display (not shown) to notify the driver of the vehicle 100, etc., that the GPF 28 has been removed from the exhaust passage 26 on the display. In this embodiment, the processes of steps S73 to S82 are an example of a fourth process for determining whether or not the GPF 28 has been removed from the exhaust passage 26 based on the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout. After step S82, the execution unit 91 ends this second determination control.

[0059] <Action of this embodiment> In the vehicle 100, when the internal combustion engine 10 stops after it has been operating, condensed water is generated in the exhaust passage 26. When the condensed water is generated in this manner, the condensed water is present in the GPF 28 when the internal combustion engine 10 subsequently starts operating. Therefore, immediately after the internal combustion engine 10 starts operating, the heat of the exhaust gas flowing through the exhaust passage 26 is consumed as heat of vaporization for evaporating the condensed water in the GPF 28. Thereafter, when the amount of condensed water in the GPF 28 decreases, the downstream temperature Tout increases. Here, for example, in a situation where the amount of condensed water in the GPF 28 is relatively small when the internal combustion engine 10 starts operating, the timing at which the downstream temperature Tout increases is early. Then, immediately after the internal combustion engine 10 starts operating, the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout tends to be small. As a result, the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout becomes small, which may result in an erroneous determination that the GPF 28 has been removed from the exhaust passage 26 even though the GPF 28 is actually attached to the exhaust passage 26.

[0060] In this regard, in the wetness level acquisition control, the execution unit 91 of the control device 90 acquires a wetness level LW that has a positive correlation with the amount of condensed water present in the GPF 28. In addition, in steps S61 to S71 of the second determination control, the execution unit 91 calculates a quotient Q as an index value that has a positive correlation with the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout. Furthermore, in step S72, the execution unit 91 sets a smaller value of the diagnostic threshold QA as the wetness level LW is lower. Then, in step S73, if the quotient Q is equal to or greater than the diagnostic threshold QA, the execution unit 91 determines in step S81 that the GPF 28 is attached to the exhaust passage 26. On the other hand, in step S73, if the quotient Q is smaller than the diagnostic threshold QA, the execution unit 91 determines in step S82 that the GPF 28 is removed from the exhaust passage 26.

[0061] <Effects of this embodiment> (1) According to this embodiment, the execution unit 91 reduces the diagnostic threshold value QA in a situation where the wetness level LW is low, in other words, in a situation where the quotient Q calculated in steps S61 to S71 is likely to be small due to condensed water. As a result, in a situation where the quotient Q is small due to the low wetness level LW, a positive determination is more likely to be made in step S73. In other words, it is more likely to be determined that the GPF 28 is attached to the exhaust passage 26. As a result, it is possible to suppress an erroneous determination that the GPF 28 is removed from the exhaust passage 26 due to the influence of condensed water, even when the GPF 28 is attached to the exhaust passage 26.

[0062] (2) In the internal combustion engine 10, when the specific ratio RI, which is the ratio of the area where condensed water exists in the orthogonal cross section of the GPF 28, is small, the downstream temperature Tout tends to increase because the exhaust gas flows through a portion of the orthogonal cross section of the GPF 28 where condensed water does not exist. Then, the increase in the downstream temperature Tout tends to decrease the quotient Q calculated in steps S61 to S71.

[0063] In this regard, in step S32, the execution unit 91 calculates a higher value of the wetness level LW as the specific ratio RI increases. As a result, when the specific ratio RI is small, the wetness level LW is low, so that the wetness level LW that more accurately takes into account the influence of condensed water can be obtained.

[0064] (3) In the internal combustion engine 10, when the GPF water amount WG, which is the total amount of condensed water present in the GPF 28, is small, the heat of vaporization consumed to evaporate the condensed water in the GPF 28 is small, and the downstream temperature Tout is likely to become high. In this regard, in step S32, the execution unit 91 calculates a higher value of the wetness level LW as the GPF water amount WG increases. As a result, by taking the GPF water amount WG into account, a more accurate wetness level LW can be obtained.

[0065] (4) In the internal combustion engine 10, the downstream temperature Tout tends to be higher when the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time is high, compared to when the flow rate is low. In this regard, the execution unit 91 executes the processes from step S61 onwards, with the prerequisite that the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time in step S52 is equal to or less than a predetermined allowable value A. As a result, it is possible to suppress an erroneous determination that the GPF 28 has been removed from the exhaust passage 26, despite the fact that the GPF 28 is attached to the exhaust passage 26, due to an excessively high flow rate of exhaust gas flowing through the exhaust passage 26 per unit time.

[0066] (5) In step S51, the execution unit 91 sets a larger permissible value A as the wetness level LW increases. As a result, the permissible value A is increased in a situation where the wetness level LW is high, in other words, in a situation where the downstream temperature Tout is unlikely to increase even if the flow rate of exhaust gas flowing through the exhaust passage 26 per unit time is high. As a result, the processing from step S61 onwards can be performed more frequently than in a case where the permissible value A is not large.

[0067] (6) For example, the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout may change temporarily depending on the operating conditions of the internal combustion engine 10. Therefore, in a configuration in which it is determined whether or not the GPF 28 is attached to the exhaust passage 26 by simply comparing the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout with the diagnostic threshold value QA, the above determination result is likely to change depending on the operating conditions of the internal combustion engine 10, etc.

[0068] In this regard, the execution unit 91 calculates a quotient Q as an index value from an upstream integral value ΣΔTin based on the upstream temperature Tin and a downstream integral value ΣΔTout based on the downstream temperature Tout. Then, the execution unit 91 compares the magnitude of the quotient Q as the index value with the diagnostic threshold value QA to determine whether or not the GPF 28 is attached to the exhaust passage 26. Therefore, even if the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout temporarily changes due to the operating conditions of the internal combustion engine 10, it is possible to reduce the possibility that the determination result of whether or not the GPF 28 is attached to the exhaust passage 26 will change.

[0069] (7) In step S65, the execution unit 91 sets a higher value of the judgment temperature TF as the wetness level LW is lower. Therefore, in a situation where the wetness level LW is low, in other words, in a situation where the downstream temperature Tout is likely to be high, the judgment temperature TF becomes high. This lengthens the period from the start of the second judgment control until the processing of step S66 makes a positive judgment, thereby lengthening the period for calculating the upstream integral value ΣΔTin and the downstream integral value ΣΔTout. As a result, the influence of a temporary change in the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout on the quotient Q as an index value can be reduced.

[0070] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0071] In the above embodiment, the wetness level acquisition control may be changed. For example, the method of calculating the GPF water volume WG in steps S21 to S24 may be changed. As a specific example, the condensed water in the exhaust passage 26 may move depending on the acceleration acting on the vehicle 100. Therefore, the execution unit 91 may calculate the GPF water volume WG by taking into account the longitudinal acceleration GX, etc. As another specific example, the ease of movement of the condensed water in the exhaust passage 26 varies depending on the inclination of the exhaust passage 26 when the vehicle 100 is located on a level road surface. Therefore, the execution unit 91 may calculate the GPF water volume WG by taking into account the structure of the exhaust passage 26, including the inclination of the exhaust passage 26.

[0072] For example, the calculation configuration of the wetness level LW in step S32 may be changed. As a specific example, in step S32, the execution unit 91 may calculate the wetness level LW based only on the specific ratio RI, regardless of the GPF water volume WG. Also, as a specific example, in step S32, the execution unit 91 may calculate the wetness level LW based only on the GPF water volume WG, regardless of the specific ratio RI. In this case, the processing of step S31 may be omitted.

[0073] In the above embodiment, the first determination control and the second determination control may be changed. For example, the way in which the tolerance A is set in step S51 may be changed. As a specific example, in step S51, the execution unit 91 may set a constant tolerance A regardless of the wetness level LW.

[0074] For example, the processes of steps S51 and S52 may be omitted. As a specific example, if the flow rate of exhaust gas passing through the exhaust passage 26 per unit time is unlikely to become excessively high, the effects of omitting the processes of steps S51 and S52 are small.

[0075] For example, the way in which the determination temperature TF is set in step S65 may be changed. As a specific example, in step S65, the execution unit 91 may set the determination temperature TF to a value obtained by adding a certain specified value to the start downstream temperature TSout, regardless of the wetness level LW.

[0076] For example, the process of step S71 may be changed. As a specific example, in step S71, the execution unit 91 may calculate, as the index value, a value obtained by subtracting the downstream integral value ΣΔTout from the upstream integral value ΣΔTin, instead of the quotient Q. Also, as a specific example, in step S71, the execution unit 91 may calculate, as the index value, the absolute value of the difference between the upstream temperature Tin and the downstream temperature Tout, instead of the quotient Q.

[0077] For example, the way in which the diagnostic threshold QA is set in step S72 may be changed. As a specific example, when the wetness level LW is lower than a predetermined threshold, the execution unit 91 may set the diagnostic threshold QA to a smaller value than when the wetness level LW is equal to or higher than the threshold.

[0078] As a specific example, the execution unit 91 may set a constant diagnostic threshold value QA regardless of the wetness level LW. In this case, the execution unit 91 may correct the quotient Q, which is an index value, so that a positive determination is more likely to be made in the process of step S73 when the wetness level LW is low than when the wetness level LW is high. For example, the execution unit 91 may increase the quotient Q as the wetness level LW decreases. Also, for example, the execution unit 91 may increase the quotient Q when the wetness level LW is lower than a predetermined threshold value, compared to when the wetness level LW is equal to or higher than the threshold value. Note that the execution unit 91 may correct both the quotient Q, which is an index value, and the diagnostic threshold value QA so that a positive determination is more likely to be made in the process of step S73 when the wetness level LW is low than when the wetness level LW is high.

[0079] In the above embodiment, the configuration of the vehicle 100 may be changed. For example, the exhaust purification device may be changed. As a specific example, the GPF 28 may include one of a filter and a three-way catalyst. In this case, one of the filter and the three-way catalyst in the GPF 28 is the exhaust purification device. As a specific example, the exhaust purification device may be a three-way catalyst 27 instead of the GPF 28. In this case, the upstream temperature sensor 87 may be located upstream of the three-way catalyst 27 in the exhaust passage 26. Also, the downstream temperature sensor 88 may be located downstream of the three-way catalyst 27 in the exhaust passage 26. [Explanation of symbols]

[0080] 10... internal combustion engine 11... cylinder 21... intake passage 22... throttle valve 23... fuel injection valve 24... ignition device 26... exhaust passage 27... three-way catalyst 28... GPF 81... air flow meter 82... water temperature sensor 83... intake air temperature sensor 84... crank angle sensor 85... accelerator operation amount sensor 86... vehicle speed sensor 87... upstream temperature sensor 88... downstream temperature sensor 89... acceleration sensor 90... control device 91... execution unit 92... memory unit 92A... control program 100... vehicle

Claims

1. The present invention is applied to an internal combustion engine including a cylinder for burning fuel, an exhaust passage through which exhaust gas discharged from the cylinder flows, and an exhaust purification device located in the exhaust passage for purifying the exhaust gas, a first process of acquiring an upstream temperature, which is a temperature of exhaust gas upstream of the exhaust purification device in the exhaust passage; a second process of acquiring a downstream temperature, which is a temperature of the exhaust gas downstream of the exhaust purification device in the exhaust passage; a third process of calculating an index value having a positive correlation with an absolute value of a difference between the upstream temperature and the downstream temperature; a fourth process of determining that the exhaust purification device is removed from the exhaust passage when the index value is smaller than a predetermined diagnosis threshold value; A fifth process of obtaining a wetness level that is positively correlated with an amount of condensed water present in the exhaust gas purification device; a sixth process of correcting one or more of the index value and the diagnostic threshold value so that, when the wetness level is low, the index value is more likely to be determined to be equal to or greater than the diagnostic threshold value than when the wetness level is high; Run An abnormality determination device for an internal combustion engine.

2. When a cross section of the exhaust purification device perpendicular to the direction in which the exhaust gas flows is defined as an orthogonal cross section, In the fifth process, Calculating a specific ratio, which is a ratio of an area where condensed water exists, on the orthogonal cross section; When the specific ratio is small, a lower value of the wetness level is obtained compared to when the specific ratio is large; and Run 2. The abnormality determination device for an internal combustion engine according to claim 1.

3. In the fifth process, Calculating a total amount of condensed water present in the exhaust purification device; obtaining a lower value of the wetness level when the total amount is low compared to when the total amount is high; Run 3. The abnormality determination device for an internal combustion engine according to claim 1.

4. executing the fourth process under the condition that a flow rate of the exhaust gas flowing through the exhaust passage per unit time is equal to or less than a predetermined allowable value; When the wetness level is high, a seventh process is further executed to increase the allowable value compared to when the wetness level is low.

3. The abnormality determination device for an internal combustion engine according to claim 1.

5. In the third process, Calculating, as the index value, an integral value of the upstream temperature during a period from when the internal combustion engine starts operating until when the downstream temperature becomes equal to or higher than a predetermined judgment temperature, and a difference between the integral value of the downstream temperature during the same period; When the wetness level is low, the determination temperature is set higher than when the wetness level is high; Run 3. The abnormality determination device for an internal combustion engine according to claim 1.

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