Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of highly accurately determining an abnormal state where an exhaust emission control device is not mounted.SOLUTION: An engine control unit that is a control device for an internal combustion engine executes determination processing for determining a difference between first change amount that is change amount of an upstream side temperature that is a temperature of exhaust gas on the upstream side of an exhaust emission control device when a fuel cut operation is being performed and second change amount that is change amount of a downstream side temperature that is a temperature of exhaust gas on the downstream side of the exhaust emission control device when the fuel cut operation is being performed is a threshold value or smaller (S54-S66). When a determination that the difference is the threshold value or smaller is made in the determination processing (No in S62), the engine control unit makes an abnormality determination that the exhaust emission control device is in the detached state (S66). When the upstream side temperature rises in a determination period (Yes in S52), the engine control unit interrupts the determination processing.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] Since the exhaust gas purification device provided in the exhaust passage has a heat capacity, the heat of the exhaust gas introduced into the exhaust gas purification device is consumed by heat exchange with the exhaust gas purification device. As a result, a difference occurs between the change in the exhaust gas temperature upstream of the exhaust gas purification device and the change in the exhaust gas temperature downstream of the exhaust gas purification device.

[0003] Patent Document 1 discloses a control device for an internal combustion engine that detects whether a filter that captures particulate matter in the exhaust gas has been removed from an exhaust passage. The control device disclosed in Patent Document 1 compares the change in exhaust gas temperature upstream of the filter with the change in exhaust gas temperature downstream of the filter. Then, it is determined that the filter has been removed based on the difference between the change in exhaust gas temperature upstream and the change in exhaust gas temperature downstream of the filter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-106028 A Summary of the Invention [Problem to be solved by the invention]

[0005] A control device for an internal combustion engine that detects a state in which an exhaust purification device that treats exhaust gas has been removed and determines whether or not there is an abnormality is required to perform the determination with high accuracy. [Means for solving the problem]

[0006] The means for solving the above problems and their effects will be described below. A control device for an internal combustion engine for solving the above problems is applied to an internal combustion engine having an exhaust purification device provided in an exhaust passage. The control device for an internal combustion engine is a control device that may perform a fuel cut operation in which an engine output shaft is rotated with fuel supply stopped. The control device executes a first change amount calculation process that calculates a first change amount that is a change amount per unit time of an upstream temperature that is the temperature of exhaust gas upstream of the exhaust purification device, a second change amount calculation process that calculates a second change amount that is a change amount per unit time of a downstream temperature that is the temperature of exhaust gas downstream of the exhaust purification device, a determination process that determines whether a deviation between the first change amount when the fuel cut operation is being performed and the second change amount when the fuel cut operation is being performed is equal to or less than a threshold value, and an abnormality diagnosis process that performs an abnormality determination that the exhaust purification device is in a removed state when it is determined in the determination process that the deviation is equal to or less than the threshold value. This control device interrupts the determination process if the upstream temperature increases within a determination period from the upstream temperature at the start of the determination process until the upstream temperature decreases by a predetermined temperature.

[0007] During fuel cut operation, air that is lower in temperature than the exhaust gas and lower in temperature than the exhaust purification device is introduced into the exhaust purification device. The air introduced into the exhaust purification device during fuel cut operation is warmed by heat exchange with the exhaust purification device. Therefore, during fuel cut operation, the downstream temperature decreases gradually. Therefore, the second change amount during fuel cut operation becomes a negative value with an absolute value smaller than that of the first change amount.

[0008] When the exhaust gas purification device is removed, heat exchange between the air and the exhaust gas purification device does not occur, so the second amount of change also becomes a negative value with a large absolute value. This allows abnormality diagnosis to be performed based on the difference between the first amount of change and the second amount of change being equal to or smaller than the threshold value.

[0009] However, if the upstream temperature rises during the determination period for some reason, the first change amount becomes a positive value, and the deviation becomes smaller. Furthermore, when the upstream temperature rises, the determination period becomes longer. The first change amount and the second change amount become gradually smaller. Therefore, when the determination period becomes longer, the deviation becomes smaller.

[0010] In this way, if the upstream temperature rises within the determination period, an abnormality determination is likely to be made even if an exhaust purification device is installed. In contrast, if the upstream temperature rises within the determination period, the control device suspends the determination process, thereby making it possible to prevent erroneous abnormality determinations.

[0011] One aspect of the control device for an internal combustion engine determines that the upstream temperature is increasing based on the first amount of change calculated within the determination period being not a negative value, and interrupts the determination process.

[0012] In this manner, it is possible to determine that the upstream temperature is increasing. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an engine control unit, which is one embodiment of a control device for an internal combustion engine, an engine controlled by the engine control unit, and a hybrid vehicle equipped with the engine. [Diagram 2] FIG. 2 is a flowchart showing the flow of processing in a routine related to the playback process. [Diagram 3] FIG. 3 is a flowchart showing a process flow of a main routine for the abnormality diagnosis process executed by the engine control unit. [Figure 4] FIG. 4 is a flowchart showing a process flow in a routine related to a fuel cut request process executed by the engine control unit. [Diagram 5] FIG. 5 is a flowchart showing a process flow in a routine for determining whether or not a post-regeneration execution condition is satisfied, which is executed by the engine control unit. [Figure 6] FIG. 6 is a flowchart showing the flow of processing in a subroutine related to the abnormality diagnosis processing executed by the engine control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An engine control unit 110, which is a control device for an internal combustion engine according to one embodiment, will be described below with reference to FIGS. <Vehicle configuration> As shown in FIG. 1, the engine 10 has four cylinders, namely, cylinders #1 to #4. A throttle valve 14 is provided in an intake passage 12 of the engine 10. A port injection valve 16 that injects fuel into the intake port 12a is provided in an intake port 12a, which is a downstream portion of the intake passage 12. Air drawn into the intake passage 12 and fuel injected from the port injection valve 16 flow into a combustion chamber 20 when an intake valve 18 opens. The engine 10 is also provided with an in-cylinder injection valve 22 that injects fuel into the cylinders #1 to #4. Fuel may also be injected from the in-cylinder injection valve 22 into the combustion chamber 20. The mixture of air and fuel in the combustion chamber 20 is combusted in response to a spark discharge from an ignition plug 24. The combustion energy generated at this time is converted into the rotational energy of a crankshaft 26.

[0015] The air-fuel mixture burned in the combustion chamber 20 is discharged as exhaust gas into an exhaust passage 30 when an exhaust valve 28 opens. A three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34) are provided in the exhaust passage 30 as exhaust purification devices. The GPF 34 is a filter that collects particulate matter (hereinafter referred to as PM) contained in the exhaust gas and supports the three-way catalyst.

[0016] A crank rotor 40 having teeth 42 is coupled to the crankshaft 26. The crank rotor 40 is basically provided with 32 teeth 42 at every 10° CA. Therefore, the crank rotor 40 is provided with one missing tooth portion 44 where the spacing between adjacent teeth 42 is wider to compensate for the lack of two teeth 42. This is to indicate the reference rotation angle of the crankshaft 26.

[0017] The crankshaft 26 is mechanically connected to a carrier C of a planetary gear mechanism 50 constituting a power split device. A rotating shaft 52a of a first motor generator 52 is mechanically connected to a sun gear S of the planetary gear mechanism 50. A rotating shaft 54a of a second motor generator 54 and a driving wheel 60 are mechanically connected to a ring gear R of the planetary gear mechanism 50. An AC voltage is applied to terminals of the first motor generator 52 by an inverter 56. An AC voltage is applied to terminals of the second motor generator 54 by an inverter 58.

[0018] <Regarding the control device 500> The control device 500 controls the engine 10, the first motor generator 52, and the second motor generator 54. The control device 500 includes an engine control unit 110 that controls the engine 10. The control device 500 also includes a motor control unit 130 that controls the first motor generator 52 and the second motor generator 54. The control device 500 also includes an overall control unit 100 that is connected to the engine control unit 110 and the motor control unit 130 and that overall controls the vehicle. These control units are configured with a processing circuit and a memory that stores programs executed by the processing circuit, etc.

[0019] The control device 500 controls the engine 10, the first motor generator 52, and the second motor generator 54. In other words, the control device 500 controls the power train of the vehicle. Detection signals of sensors provided in various parts of the vehicle are input to the control device 500.

[0020] The engine control unit 110 operates operating parts of the engine 10, such as the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24, in order to control the control variables of the engine 10, such as the torque and the exhaust component ratio.

[0021] In addition, the motor control unit 130 operates the inverter 56 to control the rotation speed, which is the control variable of the first motor generator 52. In addition, the motor control unit 130 operates the inverter 58 to control the torque, which is the control variable of the second motor generator 54.

[0022] 1 shows operation signals MS1 to MS6 of the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the spark plug 24, and the inverters 56 and 58. The engine control unit 110 refers to the intake air amount Ga detected by the air flow meter 80 in order to control the control amount of the engine 10. The engine control unit 110 also refers to the output signal Scr of the crank angle sensor 82, the water temperature THW detected by the water temperature sensor 86, and the exhaust pressure Pex flowing into the GPF 34 detected by the exhaust pressure sensor 88. The motor control unit 130 also refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52 in order to control the control amount of the first motor generator 52. The motor control unit 130 refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54 in order to control the control amount of the second motor generator 54.

[0023] The engine control unit 110 and the motor control unit 130 are each connected to the overall control unit 100 via a communication line. The overall control unit 100, the motor control unit 130, and the engine control unit 110 mutually exchange and share information based on detection signals input from sensors and calculated information via CAN communication.

[0024] An accelerator position sensor 101, a brake sensor 102, and a vehicle speed sensor 103 are connected to the integrated control unit 100. The accelerator position sensor 101 detects the accelerator opening. The brake sensor 102 detects the amount of brake operation. The vehicle speed sensor 103 detects the vehicle speed.

[0025] Further, an air-fuel ratio sensor 81 is provided in the exhaust passage 30. The air-fuel ratio sensor 81 is connected to the engine control unit 110. The air-fuel ratio sensor 81 detects the air-fuel ratio.

[0026] In addition, an upstream temperature sensor 87 is connected to the engine control unit 110 to detect an upstream temperature Tin, which is the temperature of the exhaust gas between the three-way catalyst 32 and the GPF 34 in the exhaust passage 30. In addition, a downstream temperature sensor 89 is also connected to the engine control unit 110 to detect a downstream temperature Tout, which is the temperature of the exhaust gas downstream of the GPF 34.

[0027] The engine control unit 110 estimates the catalyst temperature and the GPF temperature based on the engine load ratio KL, the engine speed NE, and the exhaust gas temperatures detected by the upstream temperature sensor 87 and the downstream temperature sensor 89. The catalyst temperature is the temperature of the three-way catalyst 32. On the other hand, the GPF temperature is the temperature of the GPF 34.

[0028] Furthermore, the engine control unit 110 counts the number of times the output signal Scr of the crank angle sensor 82 is input to calculate a counter CNT, which is a value corresponding to the crank angle. The value of the counter CNT corresponds to the crank angle, and the larger the value, the larger the crank angle. When the counter CNT reaches a value corresponding to 720° CA, i.e., 0° CA, it is reset to "0" again. The crank angle when the counter CNT is "0" is the crank angle at the compression top dead center.

[0029] <Fuel injection mode> The engine control unit 110 changes the fuel injection mode in the engine 10 according to the engine load factor KL and the engine speed NE. For example, in the high load region, the engine 10 supplies fuel only by in-cylinder injection, which is fuel injection by the in-cylinder injection valve 22. In the low load region, the engine 10 supplies fuel only by port injection, which is fuel injection by the port injection valve 16. The engine 10 may also supply fuel by port injection and in-cylinder injection. In this case, the engine control unit 110 changes the ratio of port injection and in-cylinder injection according to the engine load factor KL and the engine speed NE. In this way, the engine 10 forms an air-fuel mixture suitable for combustion.

[0030] The engine speed NE is calculated based on the output signal Scr by the engine control unit 110. The engine load factor KL is calculated by the engine control unit 110 based on the intake air amount Ga and the engine speed NE.

[0031] <About recycling> Fig. 2 shows the processing procedure of the routine for the regeneration process executed by the engine control unit 110. The routine shown in Fig. 2 is realized by the processing circuit repeatedly executing a program stored in memory, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

[0032] In the routine shown in Fig. 2, the engine control unit 110 first acquires the engine speed NE, the engine load factor KL, and the water temperature THW (S10). Next, the engine control unit 110 calculates an update amount ΔDPM for the accumulation amount DPM based on the engine speed NE, the engine load factor KL, and the water temperature THW (S12). Here, the accumulation amount DPM is the amount of PM trapped in the GPF 34. In detail, the engine control unit 110 calculates the amount of PM in the exhaust gas discharged into the exhaust passage 30 based on the engine speed NE, the engine load factor KL, and the water temperature THW. Then, the engine control unit 110 calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the GPF temperature.

[0033] Next, the engine control unit 110 sets the new accumulation amount DPM to the sum of the accumulation amount DPM and the update amount ΔDPM. In this way, the accumulation amount DPM is updated (S14). Next, the engine control unit 110 judges whether or not the flag F is "1" (S16). When the flag F is "1", it indicates that a regeneration process for burning and removing PM in the GPF 34 is being executed. On the other hand, when the flag F is "0", it indicates that a regeneration process is not being executed. When the engine control unit 110 judges that the flag F is "0" (S16: NO), it judges whether or not the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is a threshold value for judging that it is necessary to remove PM based on the accumulation amount DPM being equal to or greater than the regeneration execution value DPMH.

[0034] When it is determined that the regeneration execution value DPMH is equal to or greater than the regeneration execution value DPMH (S18: YES), the engine control unit 110 determines whether or not the execution condition for the regeneration process is satisfied (S20). Here, the execution condition may be a condition that the logical product of the following conditions (1) to (3) is true.

[0035] Condition (1): An engine torque command value Te*, which is a command value of torque for the engine 10, is equal to or greater than a predetermined value Teth. Condition (2): The engine speed NE is equal to or higher than a predetermined speed.

[0036] Condition (3): A condition that enables the torque compensation process of S24 to be executed. When the engine control unit 110 judges that the logical product is true (S20: YES), it executes the regeneration process and assigns "1" to the flag F (S22). That is, the engine control unit 110 stops the injection of fuel from the port injection valve 16 and the in-cylinder injection valve 22 of the cylinder #1. Then, the engine control unit 110 makes the air-fuel ratio of the mixture in the combustion chamber 20 of the cylinders #2 to #4 richer than the theoretical air-fuel ratio. That is, the regeneration process is a process of stopping the fuel supply to one of the cylinders and supplying fuel to the remaining cylinders. This process is a process for burning and removing the PM captured by the GPF 34 by discharging oxygen and unburned fuel into the exhaust passage 30 to raise the temperature of the GPF 34. That is, the engine control unit 110 burns the unburned fuel in the three-way catalyst 32 or the like by discharging oxygen and unburned fuel into the exhaust passage 30, and raises the temperature of the exhaust gas. This makes it possible to raise the temperature of the GPF 34. In addition, by supplying oxygen to the GPF 34, the PM trapped by the GPF 34 can be burned and removed.

[0037] Note that the cylinder to which the fuel supply is stopped is not limited to cylinder #1. For example, the cylinders to which the fuel supply is stopped may be switched in order so that there is no bias in the number of times the fuel supply is stopped.

[0038] The engine control unit 110 requests the motor control unit 130 to perform a process for compensating for torque fluctuations in the crankshaft 26 of the engine 10 caused by the stop of the combustion control of cylinder #1 (S24). Upon receiving this request, the motor control unit 130 superimposes a compensation torque on the torque required for running for the second motor generator 54. Then, the motor control unit 130 operates the inverter 58 based on the required torque on which the compensation torque has been superimposed.

[0039] The conditions for the torque compensation process to be executed include that no abnormality occurs in the second motor generator 54, and that the power required to execute the torque compensation process is stored in the battery.

[0040] On the other hand, when the engine control unit 110 determines that the flag F is "1" (S16: YES), it determines whether the accumulation amount DPM is equal to or less than the stop threshold value DPML (S26). The stop threshold value DPML is a threshold value for determining whether the regeneration process may be stopped based on the accumulation amount DPM being equal to or less than the stop threshold value DPML. When the accumulation amount DPM is equal to or less than the stop threshold value DPML (S26: YES), the engine control unit 110 stops the regeneration process and assigns "0" to the flag F (S28).

[0041] When the engine control unit 110 completes the processes of S24 and S28, or when a negative determination is made in the processes of S18 and S20, the engine control unit 110 temporarily ends the routine shown in FIG.

[0042] <About abnormality diagnosis processing> However, it becomes impossible to purify the exhaust gas if the exhaust purification device is removed from the exhaust passage 30. Therefore, the engine control unit 110 executes an abnormality diagnosis process to detect that the exhaust purification device has been removed and to make an abnormality determination that the exhaust purification device has been removed.

[0043] FIG. 3 shows the processing procedure of the main routine for the abnormality diagnosis processing executed by the engine control unit 110. The routine shown in FIG. 3 is realized by a processing circuit executing a program stored in memory. The engine control unit 110 repeatedly executes this routine when the abnormality diagnosis processing has not been completed even once during one trip from when the vehicle's main switch is turned ON to when it is turned OFF. In other words, the abnormality diagnosis processing is executed once per trip. In the following, the step number of each process is represented by a number preceded by "S."

[0044] In the routine shown in Fig. 3, the engine control unit 110 first calculates the amount of temperature change (S30). The amount of temperature change is the amount of change in the upstream temperature Tin detected by the upstream temperature sensor 87 and the amount of change in the downstream temperature Tout detected by the downstream temperature sensor 89. That is, the engine control unit 110 calculates the amount of change in the upstream temperature Tin, which is the temperature of the exhaust gas flowing into the GPF 34, which is an exhaust purification device, and the amount of change in the downstream temperature Tout, which is the temperature of the exhaust gas flowing out from the GPF 34. Hereinafter, the amount of change in the upstream temperature Tin will be referred to as a first amount of change ΔTin. Also, below, the amount of change in the downstream temperature Tout will be referred to as a second amount of change ΔTout.

[0045] In this way, in the processing of S30, the engine control unit 110 executes a first change amount calculation process to calculate a first change amount ΔTin, which is the amount of change per unit time of the upstream temperature Tin, which is the temperature of the exhaust gas upstream of the exhaust purification device.

[0046] In addition, in the processing of S30, the engine control unit 110 executes a second change amount calculation process to calculate a second change amount ΔTout, which is the amount of change per unit time of the downstream temperature Tout, which is the temperature of the exhaust downstream of the exhaust purification device.

[0047] The engine control unit 110 executes this routine at regular intervals, for example every 65 milliseconds, to sample the upstream temperature Tin and the downstream temperature Tout. In a first change amount calculation process in S30, the engine control unit 110 calculates the difference between the currently sampled upstream temperature Tin and the previously sampled upstream temperature Tin. Then, the engine control unit 110 stores the calculated difference in memory as a first change amount ΔTin. Similarly, in a second change amount calculation process in S30, the engine control unit 110 calculates the difference between the currently sampled downstream temperature Tout and the previously sampled downstream temperature Tout. Then, the engine control unit 110 stores the calculated difference in memory as a second change amount ΔTout.

[0048] Next, the engine control unit 110 calculates a moving average value of the first change amount ΔTin (S32). Specifically, in the process of S32, the engine control unit 110 calculates a long-term moving average value of the first change amount ΔTin and a short-term moving average value of the first change amount ΔTin. The long-term moving average value is an exponentially smoothed moving average, for example, a 10-second moving average. The short-term moving average value is also an exponentially smoothed moving average, for example, a 3-second moving average.

[0049] The exponential moving average is calculated based on the following formula (1).

[0050]

number

[0051] In addition, "α" in formula (1) is a smoothing coefficient. The smoothing coefficient α is calculated based on the following formula (2).

[0052]

number

[0053] In formula (2), "N" is the number of samples. When calculating a long-term moving average, the number of times the first change amount ΔTin is acquired during 10 seconds is "N". On the other hand, when calculating a short-term moving average, the number of times the first change amount ΔTin is acquired during 3 seconds is "N". Since the first change amount ΔTin is calculated every 65 milliseconds, the first change amount ΔTin is calculated 153 times during 10 seconds. In other words, when calculating a long-term moving average, the number of samples is 153, so the smoothing coefficient α is "0.013". Also, during 3 seconds, the first change amount ΔTin is calculated 46 times. In other words, when calculating a short-term moving average, the number of samples is 46, so the smoothing coefficient α is "0.0426".

[0054] "S" in formula (1) is the exponentially smoothed moving average of the first change amount ΔTin. "Y" in formula (1) is the first change amount ΔTin. The subscript "t" and the subscript "t-1" indicate the difference in the time of calculation. In other words, the subscript "t-1" indicates the value calculated previously. The initial value of "S" is "0".

[0055] As shown in equation (1), the long-term moving average value and the short-term moving average value, which are exponentially smoothed moving averages, are the sum of the product of the first change amount ΔTin multiplied by the smoothing coefficient α and the product of the previously calculated exponentially smoothed moving average S multiplied by the difference between 1 and the smoothing coefficient α.

[0056] When calculating a long-term moving average, the smoothing coefficient α is set to "0.013." On the other hand, when calculating a short-term moving average, the smoothing coefficient α is set to "0.0426." Thus, in the processing of S32, the engine control unit 110 executes a first average value calculation process that calculates a short-term moving average value of the upstream temperature Tin, and a second average value calculation process that calculates a long-term moving average value, which is an exponentially smoothed moving average over a longer period than the short-term moving average value.

[0057] After calculating the long-term moving average value and the short-term moving average value in this way, the engine control unit 110 next calculates the filter temperature (S34). Here, the temperature of a portion 10 millimeters from the front end of the GPF 34 is calculated as the front-end temperature TFr. Also, here, the temperature of a portion 10 millimeters from the rear end of the GPF 34 is calculated as the rear-end temperature TRr. That is, in the process of S34, a front-end temperature estimation process is executed to estimate the front-end temperature TFr, which is the temperature of a portion of the GPF 34 that is further forward than the center, and a rear-end temperature estimation process is executed to estimate the rear-end temperature TRr, which is the temperature of a portion of the GPF 34 that is further rear than the center.

[0058] The front end temperature TFr is calculated based on the following formula (3).

[0059]

number

[0060] In equation (3), "ofs1" is the offset value for the front end. Also, in equation (3), "KFr" is the smoothing coefficient for the front end. The subscripts "t" and "t-1" in equation (3) indicate the difference in the time of calculation. In other words, the subscript "t-1" indicates the value calculated previously. The initial value of the front end temperature TFr is the upstream temperature Tin.

[0061] The rear end temperature TRr is calculated based on the following formula (4).

[0062]

number

[0063] In equation (4), "ofs2" is the rear end offset value. Also, in equation (4), "KRr" is the rear end smoothing coefficient. The subscripts "t" and "t-1" in equation (4) also indicate the difference in the time of calculation. In other words, the subscript "t-1" indicates the value calculated previously. The initial value of the rear end temperature TRr is the upstream temperature Tin.

[0064] The front end smoothing coefficient KFr and the rear end smoothing coefficient KRr are determined based on the intake air amount Ga. The front end smoothing coefficient KFr and the rear end smoothing coefficient KRr become smaller as the intake air amount Ga increases. The rear end smoothing coefficient KRr becomes smaller than the front end smoothing coefficient KFr.

[0065] The magnitude of the front end offset value ofs1 is set so that the temperature of a portion 10 mm from the front end of the GPF 34 can be calculated based on equation (3). The magnitude of the rear end offset value ofs2 is set so that the temperature of a portion 10 mm from the rear end of the GPF 34 can be calculated based on equation (4). In other words, the smoothing coefficients and offset values ​​in equations (3) and (2) are values ​​that have been adjusted by adaptation so that the deviation between the results of experiments and simulations performed in advance and the calculated results is minimized.

[0066] After calculating the front end temperature TFr and the rear end temperature TRr through the process of S34, the engine control unit 110 determines whether or not the preconditions for executing the abnormality diagnosis process are satisfied (S40). The preconditions here may be a condition that the logical product of the following conditions (4) and (5) is true.

[0067] Condition (4): No abnormality has occurred in the various sensors connected to the engine control unit 110, that is, all the sensors are normal. Condition (5): The abnormality diagnosis process has not been completed.

[0068] If the precondition is met (S40: YES), the engine control unit 110 determines whether or not the vehicle is in a fuel-cut operation (S42). The fuel-cut operation is an operation mode in which the crankshaft 26, which is the engine output shaft, is rotated with the fuel supply stopped. Since this vehicle is a hybrid vehicle, when it is not necessary to operate the engine 10, the crankshaft 26 is usually stopped as soon as the engine operation is stopped. Therefore, in this vehicle, in order to perform an abnormality diagnosis process, when the engine operation is normally stopped, the crankshaft 26 is driven by the first motor generator 52 to rotate the crankshaft 26 with the fuel supply stopped. This realizes the fuel-cut operation.

[0069] The flowchart shown in Fig. 4 shows a routine for FC request processing that switches between ON and OFF an FC request, which is a command that requests the execution of fuel cut operation. This routine is repeatedly executed by the general control unit 100. As will be described later, the fuel cut operation is executed by turning the FC request ON through this routine.

[0070] When this routine starts, the overall control unit 100 determines whether or not the preconditions for operating the FC request are met (S90). The preconditions here may be a condition that the logical product of the following conditions (6) and (7) is true.

[0071] Condition (6): No abnormality is occurring in any of the various sensors connected to the control device 500. Condition (7): The electric power required to rotate the crankshaft 26 and achieve fuel cut operation is stored in the battery.

[0072] If the precondition is met (S90: YES), the overall control unit 100 determines whether the throttle valve 14 has been turned OFF (S92). That is, it determines whether the accelerator operation has been released and the throttle valve 14 has been closed.

[0073] When it is determined that the throttle valve 14 is turned OFF (S92: YES), the overall control unit 100 turns the FC request ON and resets the FC counter FCcnt to "0" (S94). When the FC request is turned ON through the processing of S94, the engine control unit 110 stops the fuel supply to the engine 10. In addition, the motor control unit 130 drives the crankshaft 26 by the first motor generator 52. This executes the fuel cut operation.

[0074] Next, the overall control unit 100 judges whether or not the fuel cut operation is in progress (S96). If it is not judged that the throttle valve 14 is turned OFF (S92: NO), the overall control unit 100 advances the process to S96 without executing the process of S94.

[0075] When it is determined in the process of S96 that the fuel cut operation is in progress (S96: YES), the overall control unit 100 determines whether the determination in the abnormality diagnosis process is completed (S98). Note that the determination in the abnormality diagnosis process is an abnormality determination or a normality determination, which will be described later.

[0076] When it is determined in S98 that the abnormality diagnosis has already been completed (S98: YES), the overall control unit 100 turns off the FC request (S100). This ends the fuel cut operation. When the fuel cut operation is thus ended, the overall control unit 100 ends this series of routines.

[0077] When it is determined in S98 that the determination is not completed (S98: NO), the overall control unit 100 increments the FC counter FCcnt (S102). Then, the overall control unit 100 determines whether the FC counter FCcnt is equal to or greater than a threshold value FCth (S104).

[0078] When it is determined in S104 that the FC counter FCcnt is less than the threshold value FCth (S104: NO), the overall control unit 100 ends this routine once. In this case, the fuel cut operation is continued.

[0079] On the other hand, when it is determined in S104 that the FC counter FCcnt is equal to or greater than the threshold value FCth (S104: YES), the overall control unit 100 turns off the FC request (S100). As a result, if the FC counter FCcnt reaches the threshold value FCth before the determination by the abnormality diagnosis process is completed, the fuel cut operation is terminated. When the fuel cut operation is terminated in this manner, the overall control unit 100 terminates this series of routines.

[0080] If the fuel cut operation continues for a long time, the temperature of the exhaust purification device will drop and the abnormality diagnosis process cannot be performed properly. Therefore, when the overall control unit 100 determines that the FC counter FCcnt is equal to or greater than the threshold value FCth (S104: YES), the fuel cut operation is ended and the abnormality diagnosis process is interrupted.

[0081] If it is determined in the process of S90 that the precondition is not satisfied (S90: NO), the overall control unit 100 does not execute the processes of S92 to S104 and ends this series of routines. If it is determined in the process of S96 that the fuel cut operation is not in progress (S96: NO), the overall control unit 100 does not execute the processes of S98 to S104 and ends this series of routines. The fuel cut operation is thus executed through the FC request process executed by the overall control unit 100.

[0082] 3, when it is determined in the process of S42 that the fuel cut operation is in progress (S42: YES), the engine control unit 110 determines whether or not a determination execution condition is satisfied (S44). The determination execution condition here may be a condition that the logical product of the following conditions (8) to (11) is true.

[0083] Condition (8): Warm-up is complete. Condition (9): The upstream temperature Tin has an increasing tendency and the front end temperature TFr is equal to or higher than the rear end temperature TRr.

[0084] Condition (10): The condition that the air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range which indicates that operation is performed at the stoichiometric air-fuel ratio. Condition (11): A condition that indicates that a determination has been made that there is no effect of the regeneration process.

[0085] The upstream temperature Tin is determined to be on an upward trend based on both the differential value of the short-term moving average value and the differential value of the long-term moving average value calculated through the process of S32 being equal to or greater than a preset value. The preset value may be set to a value that allows determination that the upstream temperature Tin is on an upward trend based on these differential values ​​being equal to or greater than the preset value. The preset value does not necessarily have to be a positive value.

[0086] Furthermore, the determination that there is no effect of the regeneration process is performed through a routine shown in Fig. 5. Fig. 5 is a flowchart showing the flow of the process for determining whether or not the execution condition after regeneration is satisfied. This routine is repeatedly executed by the engine control unit 110 while the engine 10 is operating. As shown in Fig. 5, when this routine is started, the engine control unit 110 judges whether or not the regeneration process is being executed (S70). If it is judged in the process of S70 that the regeneration process is being executed (S70: YES), the engine control unit 110 judges that there is an effect of the regeneration process (S74). Then, the engine control unit 110 temporarily ends this routine.

[0087] On the other hand, if it is determined in the process of S70 that the regeneration process is not being executed (S70: NO), the engine control unit 110 determines whether or not the regeneration process was executed last time (S72). If it is determined in the process of S72 that the regeneration process was not executed last time either (S72: NO), the engine control unit 110 determines that there is no effect of the regeneration process (S86). Then, the engine control unit 110 temporarily ends this routine.

[0088] If it is determined in the process of S72 that the regeneration process was being performed last time (S72: YES), the engine control unit 110 determines whether the intake air amount Ga is equal to or greater than a preset amount Gath (S76). If it is determined in the process of S76 that the intake air amount Ga is equal to or greater than the preset amount Gath (S76: YES), the engine control unit 110 increments the time counter Tcnt (S78). Then, the engine control unit 110 determines whether the time counter Tcnt is equal to or greater than a threshold value Tth (S80).

[0089] In the process of S80, when it is determined that the time counter Tcnt is equal to or greater than the threshold value Tth (S80: YES), the engine control unit 110 resets the time counter Tcnt to "0" (S82). Then, the engine control unit 110 determines that there is no effect of the regeneration process (S86). Then, the engine control unit 110 temporarily ends this routine.

[0090] On the other hand, when it is determined in the process of S80 that the time counter Tcnt is less than the threshold value Tth (S80: NO), the engine control unit 110 returns to the process of S76. When it is determined in the process of S76 that the intake air amount Ga is less than the preset amount Gath (S76: NO), the engine control unit 110 resets the time counter Tcnt to "0" (S84). Then, the engine control unit 110 returns to the process of S76.

[0091] In this way, after executing the regeneration process (S72: YES), the engine control unit 110 executes the processes of S76 to S84. Then, if the state in which the intake air amount Ga is equal to or greater than the preset amount Gath (S76: YES) continues for a preset period or longer (S80: YES), it is determined that the effect of the regeneration process has disappeared (S86).

[0092] The magnitude of the threshold value Tth and the magnitude of the preset amount Gath may be set so as to be able to determine through the processes of S76 to S84 that the temperature of the exhaust purification device has dropped to a level that does not adversely affect the abnormality diagnosis process.

[0093] As described above, the judgment execution condition includes a condition that it has been determined that there is no influence of the regeneration process. In other words, the determination that there is no influence of the process of S86 is the post-regeneration execution condition, which is the execution condition for the abnormality diagnosis process after the regeneration process is executed.

[0094] 3, when it is determined in the process of S44 that the determination execution condition is satisfied (S44: YES), the engine control unit 110 executes the abnormality diagnosis process (S50). On the other hand, when a negative determination is made in the processes of S40 to S44, the engine control unit 110 temporarily ends this routine without executing the abnormality diagnosis process.

[0095] <About abnormality diagnosis processing> Next, the contents of the abnormality diagnosis process will be described with reference to Fig. 6. Fig. 6 is a flow chart showing the flow of the process routine for the abnormality diagnosis process. When the abnormality diagnosis process is started, the engine control unit 110 repeatedly executes this routine.

[0096] When this routine is started, the engine control unit 110 judges whether or not a stop condition is satisfied (S52). The stop condition is a condition that the upstream temperature Tin has increased during execution of the abnormality diagnosis process. The abnormality diagnosis process is repeatedly executed during a judgment period, which will be described later. Therefore, the stop condition is a condition that the upstream temperature Tin has increased during the judgment period. Note that the engine control unit 110 judges that the upstream temperature Tin has increased based on the fact that the first change amount ΔTin calculated during the judgment period is not a negative value.

[0097] When it is determined that the stop condition is not satisfied (S52: NO), the engine control unit 110 determines whether or not it is within the determination period (S54). When it is determined in the process of S54 that it is within the determination period (S54: YES), the engine control unit 110 calculates the difference Dif, which is the difference obtained by subtracting the first change amount ΔTin from the second change amount ΔTout (S56). Then, the engine control unit 110 calculates an integrated value ΣDif of the difference Dif. Specifically, the engine control unit 110 adds the difference Dif calculated through the process of S56 this time to the integrated value ΣDif calculated last time. Then, the integrated value ΣDif is updated by making the sum a new integrated value ΣDif. By starting the calculation of ΣDif through S56 and S58 in this way, the engine control unit 110 starts the determination process. The determination period is a period from the upstream temperature Tin at the time when the determination process is started in this way until the upstream temperature Tin drops by a predetermined temperature, for example, 25°C.

[0098] When the integrated value ΣDif is calculated through the process of S58, the engine control unit 110 temporarily ends this routine. By repeatedly executing this routine, the differences Dif calculated during the determination period are integrated and the integrated value ΣDif is updated.

[0099] As described with reference to Fig. 3, the abnormality diagnosis process is executed under the condition that the fuel cut operation is in progress (S42: YES). Therefore, the upstream temperature Tin gradually decreases while the abnormality diagnosis process is being performed. When the upstream temperature Tin decreases by the predetermined temperature, it is determined in the process of S54 that the determination period is not in progress (S54: NO).

[0100] Then, the engine control unit 110 calculates a judgment parameter Xd (S60). The engine control unit 110 divides the integrated value ΣDif by the number of times the difference Dif has been integrated. The engine control unit 110 sets the quotient thus calculated as the judgment parameter Xd. In other words, the judgment parameter Xd is the average value of the difference Dif, which is the difference obtained by subtracting the first change amount ΔTin from the second change amount ΔTout during the judgment period.

[0101] Next, the engine control unit 110 judges whether the judgment parameter Xd is greater than a preset value Xth (S62). If it is judged that the judgment parameter Xd is equal to or less than the preset value Xth in the process of S62 (S62: NO), the engine control unit 110 performs an abnormality judgment (S66).

[0102] More specifically, in the process of S66, the engine control unit 110 determines that the deviation between the first change amount ΔTin and the second change amount ΔTout when the fuel cut operation is being performed is equal to or smaller than a threshold value based on the determination result of S62. Then, based on this determination result, the engine control unit 110 performs an abnormality determination to the effect that the GPF 34, which is an exhaust purification device, is in a state of being removed from the exhaust passage 30. When the abnormality determination is performed, the engine control unit 110 ends this routine. In this manner, the abnormality diagnosis process is completed.

[0103] Furthermore, when it is determined in the process of S62 that the determination parameter Xd is greater than the preset value Xth (S62: YES), the engine control unit 110 performs a normal determination (S64). That is, the engine control unit 110 determines that the deviation between the first change amount ΔTin and the second change amount ΔTout when the fuel cut operation is being performed based on the determination result in S62 is greater than the threshold value. Then, based on this determination result, the engine control unit 110 performs a normal determination that the GPF 34, which is an exhaust purification device, has not been removed from the exhaust passage 30. Even when a normal determination is performed, the engine control unit 110 ends this routine. In this manner, the abnormality diagnosis process is completed.

[0104] The processing from S54 to S66 in the abnormality diagnosis processing corresponds to a judgment process that determines whether the deviation between the first change amount ΔTin when fuel cut operation is being performed and the second change amount ΔTout when fuel cut operation is being performed is equal to or less than a threshold value.

[0105] On the other hand, if it is determined that the abort condition is satisfied in the process of S52 before the abnormality diagnosis process is completed (S52: YES), the engine control unit 110 ends this routine without performing the processes of S54 to S66. That is, in this case, the engine control unit 110 interrupts the determination process and ends the abnormality process.

[0106] <Action of this embodiment> When the exhaust purification device is detached, heat exchange does not take place between the gas introduced into the exhaust purification device and the exhaust purification device, so the difference between the first change amount ΔTin and the second change amount ΔTout is small.

[0107] In contrast, when an exhaust purification device is installed, the downstream temperature Tout changes due to heat exchange between the gas introduced into the exhaust purification device and the exhaust purification device, resulting in a large deviation between the first change amount ΔTin and the second change amount ΔTout.

[0108] Therefore, an abnormality can be determined based on whether the deviation between the first change amount ΔTin and the second change amount ΔTout is equal to or smaller than a threshold value. In addition, the greater the difference between the temperature of the gas introduced into the exhaust purification device and the temperature of the exhaust purification device, the easier it is for heat exchange to occur between the gas and the exhaust purification device. Therefore, if the exhaust purification device is installed, the greater the difference between the temperature of the gas introduced into the exhaust purification device and the temperature of the exhaust purification device, the greater the difference between the first change amount ΔTin and the second change amount ΔTout.

[0109] During fuel cut operation, air that has passed through the combustion chamber 20 is introduced into the exhaust purification device. This air has a lower temperature than the exhaust gas. Therefore, the difference between the temperature of the air introduced into the exhaust purification device during fuel cut operation and the temperature of the exhaust purification device is greater than the difference between the temperature of the exhaust gas and the temperature of the exhaust purification device.

[0110] The engine control unit 110 executes the abnormality diagnosis process under the condition that the fuel cut operation is in progress (S42: YES). Then, the engine control unit 110 determines in the determination process whether the difference between the first change amount ΔTin when the fuel cut operation is in progress and the second change amount ΔTout when the fuel cut operation is in progress is equal to or smaller than a threshold value. Then, when it is determined that the difference is equal to or smaller than the threshold value, an abnormality determination is performed (S62: YES, S66).

[0111] In other words, according to the engine control unit 110, the judgment process is performed in a state in which the magnitude of deviation between the first change amount ΔTin and the second change amount ΔTout is significantly different between when the exhaust purification device is installed and when it is removed.

[0112] During fuel cut operation, air that is lower in temperature than the exhaust gas and lower in temperature than the exhaust purification device is introduced into the exhaust purification device. The air introduced into the exhaust purification device during fuel cut operation is warmed by heat exchange with the exhaust purification device. Therefore, during fuel cut operation, the downstream temperature Tout gradually decreases. Therefore, the second change amount ΔTout during fuel cut operation becomes a negative value with an absolute value smaller than that of the first change amount ΔTin. Therefore, if an exhaust purification device is installed, the judgment parameter Xd, which is the average value of the difference obtained by subtracting the first change amount ΔTin from the second change amount ΔTout during the judgment period, becomes a positive value.

[0113] When the exhaust gas purification device is removed, there is no heat exchange between the air and the exhaust gas purification device, so the second change amount ΔTout also becomes a large negative value with a large absolute value, and the determination parameter Xd therefore becomes a smaller positive value or a negative value than when the exhaust gas purification device is installed.

[0114] This allows abnormality diagnosis to be performed based on whether the determination parameter Xd is equal to or smaller than the preset value Xth. However, if the upstream temperature Tin rises during the judgment period for some reason, the first change amount ΔTin becomes a positive value. In this case, the difference between the second change amount ΔTout and the first change amount ΔTin becomes a large negative value, so the judgment parameter Xd becomes small.

[0115] Furthermore, when the upstream temperature Tin rises, the judgment period becomes longer. The first change amount ΔTin and the second change amount ΔTout gradually become smaller. Therefore, when the judgment period becomes longer, the judgment parameter Xd becomes smaller.

[0116] In this way, if the upstream temperature Tin rises within the determination period, an abnormality determination is likely to be made even if an exhaust purification device is installed. On the other hand, if the engine control unit 110 determines that the upstream temperature Tin has increased within the determination period, it determines that the stop condition is satisfied (S54: YES) and interrupts the determination process. As a result, the abnormality diagnosis process ends without performing an abnormality determination.

[0117] After the regeneration process is performed, the exhaust gas purification device is at a high temperature. In addition, the oxidation reaction of particulate matter may continue. If the determination process is performed in such a state, the second change amount ΔTout may become unstable, and an accurate abnormality determination may not be possible.

[0118] After executing the regeneration process, the engine control unit 110 does not execute the determination process during the period from the end of the regeneration process until the post-regeneration execution condition is satisfied, as described with reference to Fig. 5. In other words, the engine control unit 110 does not execute the determination process and does not perform abnormality determination during the period immediately after the end of the regeneration process, which is susceptible to the effects of the regeneration process.

[0119] <Effects of this embodiment> (1) The engine control unit 110 executes the abnormality diagnosis process under the condition that the fuel cut operation is in progress. As a result, the determination process is executed in a state in which the magnitude of the difference between the first change amount ΔTin and the second change amount ΔTout is significantly different between a case in which the exhaust purification device is installed and a case in which the exhaust purification device is removed. Therefore, the engine control unit 110 can realize a more accurate abnormality determination.

[0120] (2) The determination execution conditions include "Condition (9): the upstream temperature Tin is increasing and the front end temperature TFr is equal to or higher than the rear end temperature TRr." In other words, the engine control unit 110 starts the determination process on the condition that the upstream temperature Tin is increasing.

[0121] The air introduced into the exhaust purification device during fuel cut operation is warmed by heat exchange with the exhaust purification device. Furthermore, when the upstream temperature Tin is rising, the exhaust purification device is warmed by the exhaust gas introduced from the front end, so there is a high probability that a temperature gradient occurs in the exhaust purification device in which the temperature is higher toward the front end and lower toward the rear end.

[0122] When such a temperature gradient occurs in which the temperature is lower toward the rear end, the air introduced into the exhaust purification device is less likely to be warmed up than when a temperature gradient occurs in which the temperature is higher toward the rear end, or when no temperature gradient occurs. In other words, when a temperature gradient occurs in which the temperature is lower toward the rear end, the downstream temperature Tout is lower to begin with, compared to when a temperature gradient occurs in which the temperature is higher toward the rear end, or when no temperature gradient occurs. Therefore, the second change amount ΔTout is small. On the other hand, during fuel cut operation, the upstream temperature Tin gradually decreases toward the atmospheric temperature. Therefore, the first change amount ΔTin during fuel cut operation is large.

[0123] As described above, when the exhaust purification device is removed, such heat exchange between the gas and the exhaust purification device does not take place, so the difference between the first change amount ΔTin and the second change amount ΔTout is small.

[0124] That is, the engine control unit 110 starts the determination process in a state where the magnitude of deviation between the first change amount ΔTin and the second change amount ΔTout is likely to become large when an exhaust purification device is installed. In addition, the engine control unit 110 executes the determination process in a state where the magnitude of deviation between the first change amount ΔTin and the second change amount ΔTout is significantly different when an exhaust purification device is installed and when the exhaust purification device is removed. Therefore, the engine control unit 110 can realize anomaly determination with higher accuracy.

[0125] (3) As described above, the conditions for executing the determination include "Condition (9): the upstream temperature Tin is on an increasing trend and the front end temperature TFr is equal to or higher than the rear end temperature TRr." In other words, the engine control unit 110 starts the determination process on the condition that the front end temperature TFr is equal to or higher than the rear end temperature TRr.

[0126] This also allows the engine control unit 110 to start the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout is likely to become large when an exhaust gas purification device is installed. Therefore, the engine control unit 110 can realize highly accurate abnormality determination.

[0127] (4) As described above, the conditions for executing the determination include "Condition (10): the air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range indicating that operation has been performed at the stoichiometric air-fuel ratio." In other words, the engine control unit 110 starts the determination process on the condition that the air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range.

[0128] If the gas introduced into the exhaust gas purification device contains fuel components, the fuel components may cause an oxidation reaction in the exhaust gas purification device, and the downstream temperature Tout may change due to the heat of the reaction. If the downstream temperature Tout varies due to such factors, it is not possible to accurately determine whether an abnormality has occurred.

[0129] Therefore, the engine control unit 110 does not execute the determination process when the air-fuel ratio detected by the air-fuel ratio sensor 81 is outside a predetermined range. This makes it possible for the engine control unit 110 to suppress execution of the determination process when there is a risk that an accurate abnormality determination cannot be made.

[0130] (5) As described above, if the upstream temperature Tin rises within the determination period, an abnormality determination is likely to be made even if an exhaust purification device is installed. On the other hand, if the upstream temperature Tin rises within the determination period, the engine control unit 110 suspends the determination process, thereby making it possible for the engine control unit 110 to prevent erroneous abnormality determinations from being made.

[0131] (6) As described above, the judgment execution conditions include "Condition (11): a condition that a judgment is made that there is no influence of the regeneration process." In other words, after executing the regeneration process, the engine control unit 110 does not execute the judgment process during the period from the end of the regeneration process until the post-regeneration execution condition is satisfied. In this way, the engine control unit 110 does not execute the judgment process during the period immediately after the end of the regeneration process, when it is likely to be influenced by the regeneration process. As a result, no abnormality judgment is made. Therefore, the engine control unit 110 can prevent erroneous abnormality diagnosis from being made.

[0132] (7) If the engine operation continues for a certain period of time after the regeneration process is completed, the temperatures of the exhaust gas purification device and the exhaust passage 30 will converge to a temperature close to the exhaust gas temperature. Also, the oxidation reaction of particulate matter in the exhaust gas purification device will converge. In other words, the influence of the regeneration process will no longer affect the determination process.

[0133] Therefore, as described above, the engine control unit 110 determines that the post-regeneration execution condition is satisfied when the engine operation continues for a predetermined period or more (S80: YES) with the intake air amount Ga being equal to or greater than the predetermined amount Gath (S76: YES) after the end of the regeneration process. In this manner, the determination process can be started when the effect of the regeneration process is no longer exerted on the determination process.

[0134] <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.

[0135] Although the judgment execution condition includes the upstream temperature Tin tending to rise in the example shown, the judgment execution condition is not limited to the example shown in the above embodiment. For example, the judgment execution condition does not have to be the upstream temperature Tin tending to rise.

[0136] Furthermore, the condition for determining that the upstream temperature Tin is on an upward trend is not limited to the method using the long-term moving average value and the short-term moving average value. For example, instead of using two types of moving average values, only one type of moving average value may be used, and the upward trend may be determined based on whether the differential value of that moving average value is positive.

[0137] In the above example, the front end temperature TFr is compared with the rear end temperature TRr, and the front end temperature TFr being higher is set as one of the conditions for executing the judgment. However, this may be omitted. In the above example, the logical OR condition between the upstream temperature Tin tending to rise and the leading end temperature TFr being higher than the trailing end temperature TRr is used as one of the conditions for executing the judgment. However, the judgment may be performed under the condition that either the upstream temperature Tin tending to rise or the leading end temperature TFr being higher than the trailing end temperature TRr is used as one of the conditions for executing the judgment.

[0138] An example has been shown in which one of the conditions for executing the judgment includes "Condition (10): the condition that the air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range indicating that operation has been performed at the stoichiometric air-fuel ratio." The conditions for executing the judgment can be changed as appropriate. For example, the condition (10) may be omitted.

[0139] Although an example has been shown in which it is determined that the upstream temperature Tin is rising and the determination process is interrupted based on the fact that the first change amount ΔTin calculated within the determination period is not a negative value, this is not limiting. For example, it may be determined that the upstream temperature Tin is rising when the first change amount ΔTin becomes a positive value.

[0140] After the playback process is executed, the judgment process is not executed until the post-playback execution condition is met, but this may be omitted. Although an example has been given in which it is determined that the post-regeneration execution condition is satisfied when engine operation continues for a predetermined period of time or longer with the intake air amount Ga being equal to or greater than a predetermined amount Gath after the regeneration process is completed, this is not limiting. For example, it may be determined that the post-regeneration execution condition is satisfied when a certain amount of time has elapsed after the regeneration process is completed.

[0141] The predetermined conditions for permitting the execution of the playback process are not limited to those exemplified in the above embodiment. For example, with regard to the three conditions (1) to (3) above, only two of them may be included, or only one of them may be included. Note that the predetermined conditions may include conditions other than the above three conditions, or may not include any of the above three conditions.

[0142] The process of estimating the deposition amount DPM is not limited to the example shown in Fig. 2. For example, the deposition amount DPM may be estimated based on the intake air amount Ga and the pressure difference between the upstream and downstream sides of the GPF 34. Specifically, the deposition amount DPM may be estimated to be a larger value when the pressure difference is large than when it is small, and even if the pressure difference is the same, the deposition amount DPM may be estimated to be a larger value when the intake air amount Ga is small than when it is large. Here, when the pressure downstream of the GPF 34 is regarded as a constant value, the pressure Pex can be used instead of the pressure difference.

[0143] The layout of the three-way catalyst 32 and the GPF 34 in the exhaust passage 30 may be such that the GPF 34 is provided upstream of the three-way catalyst 32. The GPF 34 is not limited to a filter carrying a three-way catalyst, and may be a filter alone. Furthermore, the GPF 34 is not limited to one provided downstream of the three-way catalyst 32 in the exhaust passage 30. Furthermore, the provision of the GPF 34 itself is not essential. For example, even if the exhaust purification device is composed of only the three-way catalyst 32, as described above, a stop process may be executed to warm up the three-way catalyst 32. It is sufficient that the abnormality diagnosis process is used to determine whether the exhaust purification device is removed.

[0144] The vehicle may not execute the torque compensation process in S24. The stop process of S22 does not have to include enriching the air-fuel ratio in cylinders other than the stopped cylinder. For example, in the case of the regeneration process of the GPF 34, if the GPF temperature becomes high enough and oxygen is supplied to cause combustion of particulate matter, the combustion can be continued and regeneration can proceed without enriching the air-fuel ratio in the stop process.

[0145] The engine control unit 110 is not limited to a unit equipped with a processing circuit and a memory and executing software processing. For example, the engine control unit 110 may be equipped with a dedicated hardware circuit such as an ASIC that performs hardware processing of at least a part of what was processed by software in the above embodiment. That is, the engine control unit 110 may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a ROM that stores the program. (b) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, there may be a plurality of software execution devices equipped with a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0146] The vehicle is not limited to a series-parallel hybrid vehicle, but may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle, and may be, for example, a vehicle in which the power generating device of the vehicle is only the engine 10.

[0147] Although the engine 10 is an in-line four-cylinder engine having four cylinders, the engine 10 controlled by the engine control unit 110 is not limited to this. That is, the engine 10 is not limited to a four-cylinder engine. The engine 10 may also be a V-type engine, a horizontally opposed engine, or a W-type engine in which an exhaust purification device is provided for each bank. In this case, the stop process may be configured so that fuel supply to at least one cylinder in each bank is stopped during one cycle. This makes it possible to send sufficient oxygen to the exhaust purification device of each bank of a V-type engine, etc.

[0148] Note that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more. [Explanation of symbols]

[0149] 10…Engine 12…Intake passage 14...Throttle valve 16...Port injection valve 20…Combustion chamber 22...In-cylinder injection valve 26…Crankshaft 30…Exhaust passage 32...Three-way catalyst 34…GPF 52…First motor generator 54…Second motor generator 60…Drive wheel 80…Air flow meter 81...Air-fuel ratio sensor 82...Crank angle sensor 87…Upstream temperature sensor 89…Downstream temperature sensor 90…1st rotation angle sensor 92…2nd rotation angle sensor 100…General control unit 101...Accelerator position sensor 110…Engine control unit 130...Motor control unit 500...Control device

Claims

1. The present invention is applied to an internal combustion engine having an exhaust purification device provided in an exhaust passage, A control device for an internal combustion engine that may execute a fuel cut operation in which an engine output shaft is rotated in a state where fuel supply is stopped, a first change amount calculation process for calculating a first change amount, which is an amount of change per unit time of an upstream temperature, which is the temperature of the exhaust gas upstream of the exhaust purification device; a second change amount calculation process for calculating a second change amount, which is an amount of change per unit time of a downstream temperature, which is the temperature of the exhaust gas downstream of the exhaust purification device; a determination process for determining whether a deviation between the first change amount when the fuel cut operation is being performed and the second change amount when the fuel cut operation is being performed is equal to or smaller than a threshold value when a determination execution condition is satisfied; an abnormality diagnosis process for performing an abnormality determination that the exhaust purification device is in a detached state when the deviation is determined to be equal to or less than the threshold value in the determination process; interrupting the determination process when the upstream temperature increases within a determination period from the upstream temperature at the start of the determination process until the upstream temperature decreases by a predetermined temperature; The condition for making the determination includes that an air-fuel ratio detected by an air-fuel ratio sensor provided in the exhaust passage is within a predetermined range indicating that operation is performed at a stoichiometric air-fuel ratio. A control device for an internal combustion engine.

2. The upstream temperature is determined to be increasing based on the first change amount calculated within the determination period being not a negative value, and the determination process is interrupted. The control device for an internal combustion engine according to claim 1.

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