Control device and control method for internal combustion engine

Abstract

A control device and control method for an internal combustion engine, the control device being configured to execute a regeneration process, a determination process, and an abnormality diagnosis process. The regeneration process is a process for burning and removing particulate matter accumulated on an exhaust gas purification device. The determination process is a process for determining whether a deviation between a first variation and a second variation per unit time, representing the variation in exhaust gas temperature on the upstream and downstream sides of the exhaust gas purification device, is below a threshold value. The abnormality diagnosis process is a process for determining that the exhaust gas purification device has disengaged if the deviation is determined to be below the threshold value in the determination process. The control device is configured not to execute the determination process during the period from the end of the regeneration process until a condition for executing the regeneration process is satisfied.

Description

Technical Field

[0001] The present disclosure relates to a control device and a control method for an internal combustion engine. Background Art

[0002] The exhaust gas purification device, located in the exhaust passage, has a heat capacity. Therefore, the heat of the exhaust gas introduced into the exhaust gas purification device is dissipated through heat exchange with the exhaust gas purification device. As a result, a difference occurs between the change in exhaust gas temperature upstream of the exhaust gas purification device and the change in exhaust gas temperature downstream of the exhaust gas purification device.

[0003] Japanese Patent Application Laid-Open No. 2020-106028 discloses a control device for an internal combustion engine that detects when a filter that captures particulate matter in the exhaust gas has detached from the exhaust passage. The control device disclosed in this publication compares changes in the exhaust temperature upstream of the filter with changes in the exhaust temperature downstream of the filter. The control device then determines that the filter has detached based on the difference between the changes in the exhaust temperature upstream and downstream of the filter. Summary of the Invention

[0004] Problems to be solved by the invention

[0005] The control device disclosed in the above publication performs abnormality determination that the exhaust gas purification device such as a filter is disconnected. Such a control device is required to perform abnormality determination with high accuracy.

[0006] Technical solutions to problems

[0007] A control device for an internal combustion engine according to one technical solution of the present disclosure is applicable to an internal combustion engine having an exhaust gas purification device installed in its exhaust passage. The control device is configured to execute a regeneration process, a first variation calculation process, a second variation calculation process, a determination process, and an abnormality diagnosis process. The regeneration process is a process for burning and removing particulate matter accumulated on the exhaust gas purification device. The first variation calculation process is a process for calculating a first variation as the variation per unit time of the upstream temperature, which is the temperature of the exhaust gas on the upstream side of the exhaust gas purification device. The second variation calculation process is a process for calculating a second variation as the variation per unit time of the downstream temperature, which is the temperature of the exhaust gas on the downstream side of the exhaust gas purification device. The determination process is a process for determining whether a deviation between the first variation and the second variation is below a threshold value. The abnormality diagnosis process is a process for determining that the exhaust gas purification device is disengaged if the deviation is determined to be below the threshold value in the determination process. The control device is configured not to execute the determination process after the regeneration process is executed, during a period from when the regeneration process is terminated until a post-regeneration execution condition is satisfied.

[0008] A control method for an internal combustion engine according to a technical solution of the present disclosure is applicable to an internal combustion engine having an exhaust gas purification device installed in an exhaust passage. The control method includes: performing a regeneration process to burn and remove particulate matter accumulated in the exhaust gas purification device; calculating a first variation per unit time of an upstream temperature, the upstream temperature being the temperature of the exhaust gas upstream of the exhaust gas purification device; calculating a second variation per unit time of a downstream temperature, the downstream temperature being the temperature of the exhaust gas downstream of the exhaust gas purification device; performing a determination process to determine whether a deviation between the first variation and the second variation is below a threshold value; determining that the exhaust gas purification device is disengaged if the deviation is determined to be below the threshold value; and, after performing the regeneration process, not performing the determination process from the end of the regeneration process until a post-regeneration execution condition is satisfied. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram showing the configuration of an engine control unit as 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.

[0010] Figure 2 It shows Figure 1 Flowchart of the processing flow of a regeneration processing routine executed by the engine control unit.

[0011] Figure 3 It shows Figure 1 Flowchart of the processing flow of the main routine of the abnormality diagnosis processing executed by the engine control unit.

[0012] Figure 4 It shows Figure 1 Flowchart of the processing flow of a routine for fuel cut request processing executed by an engine control unit.

[0013] Figure 5 It shows Figure 1 Flowchart of the processing flow of a routine for determining a post-regeneration execution condition executed by an engine control unit.

[0014] Figure 6 It shows Figure 1 Flowchart of the processing flow of a subroutine of abnormality diagnosis processing executed by an engine control unit. DETAILED DESCRIPTION

[0015] Below, refer to Figures 1 to 6 An engine control unit 110 as one embodiment of a control device for an internal combustion engine will be described.

[0016] <About the vehicle's structure>

[0017] like Figure 1 As shown, the engine 10 has four cylinders, cylinders #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the engine 10. Port injection valves 16 are provided in each of the four intake ports 12a, which are located in the downstream portion of the intake passage 12, to inject fuel into the intake ports 12a. Air drawn into the intake passage 12 and fuel injected from the port injection valves 16 flow into the combustion chamber 20 as the intake valve 18 opens. The engine 10 is also provided with in-cylinder injection valves 22 that inject fuel into cylinders #1 to #4, respectively. Fuel may also be injected into the combustion chamber 20 from the in-cylinder injection valves 22. The mixture of air and fuel in the combustion chamber 20 is combusted as spark discharge is generated by the spark plug 24. The combustion energy generated at this time is converted into rotational energy of the crankshaft 26.

[0018] The mixture after combustion in the combustion chamber 20 is discharged as exhaust gas into the exhaust passage 30 as the exhaust valve 28 opens. A three-way catalyst 32 with 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 captures particulate matter (hereinafter referred to as PM) contained in the exhaust gas and carries a three-way catalyst.

[0019] A crank rotor 40, equipped with teeth 42, is coupled to the crankshaft 26. The crank rotor 40 has 32 teeth 42, which are arranged substantially every 10° CA. Therefore, the crank rotor 40 has a tooth-missing portion 44, where the interval between adjacent teeth 42 is greater than 10° CA. This represents the reference rotation angle of the crankshaft 26.

[0020] The crankshaft 26 is mechanically coupled to the planetary carrier C of the planetary gear mechanism 50 that constitutes the power split device. The rotating shaft 52a of the first motor generator 52 is mechanically coupled to the sun gear S of the planetary gear mechanism 50. The rotating shaft 54a of the second motor generator 54 and the drive wheel 60 are mechanically coupled to the ring gear R of the planetary gear mechanism 50. An AC voltage is applied to the terminals of the first motor generator 52 via the inverter 56. An AC voltage is applied to the terminals of the second motor generator 54 via the inverter 58.

[0021] <Regarding Control Device 500>

[0022] 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. Furthermore, the control device 500 includes a motor control unit 130 that controls the first motor generator 52 and the second motor generator 54. Furthermore, the control device 500 includes an overall control unit 100 that oversees vehicle control. The overall control unit 100 is connected to the engine control unit 110 and the motor control unit 130. These control units are comprised of a processing circuit and a memory that stores programs executed by the processing circuit.

[0023] The control device 500 controls the engine 10, the first motor generator 52, and the second motor generator 54. That is, the control device 500 controls the powertrain of the vehicle. Detection signals from sensors installed in various parts of the vehicle are input to the control device 500.

[0024] The engine control unit 110 operates operating components 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 torque, exhaust component ratio, and other control variables of the engine 10 .

[0025] Motor control unit 130 operates inverter 56 to control the rotational speed as a control variable of first motor generator 52 . Motor control unit 130 also operates inverter 58 to control the torque as a control variable of second motor generator 54 .

[0026] exist Figure 1, describes operation signals MS1 to MS6 for the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, spark plug 24, and inverters 56 and 58. Engine control unit 110 refers to intake air amount Ga detected by air flow meter 80 to control the controlled variable of engine 10. Engine control unit 110 also refers to output signal Scr from crank angle sensor 82, water temperature THW detected by water temperature sensor 86, and exhaust pressure Pex flowing into GPF 34 detected by exhaust pressure sensor 88. Motor control unit 130 refers to output signal Sm1 from first rotation angle sensor 90 to control the controlled variable of first motor generator 52. First rotation angle sensor 90 detects the rotation angle of first motor generator 52. Motor control unit 130 refers to output signal Sm2 from second rotation angle sensor 92 to control the controlled variable of second motor generator 54. Second rotation angle sensor 92 detects the rotation angle of second motor generator 54.

[0027] The engine control unit 110 and the motor control unit 130 are each connected to the unified control unit 100 via a communication line. The unified control unit 100, the motor control unit 130, and the engine control unit 110 communicate via CAN to exchange information based on detection signals input from sensors and information calculated by each, thereby sharing this information.

[0028] 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 amount of accelerator operation. The brake sensor 102 detects the amount of brake operation. The vehicle speed sensor 103 detects the vehicle speed.

[0029] 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.

[0030] An upstream temperature sensor 87 is connected to the engine control unit 110 for detecting an upstream temperature Tin. The upstream temperature Tin is the temperature of the exhaust gas between the three-way catalyst 32 and the GPF 34 in the exhaust passage 30. Furthermore, a downstream temperature sensor 89 is connected to the engine control unit 110 for detecting a downstream temperature Tout. The downstream temperature Tout is the temperature of the exhaust gas downstream of the GPF 34.

[0031] The engine control unit 110 estimates the catalyst temperature and the GPF temperature based on the engine load factor 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.

[0032] The engine control unit 110 calculates a counter CNT by counting the number of times the output signal Scr of the crank angle sensor 82 is input. The value of the counter CNT corresponds to the crank angle, with a larger value indicating a larger crank angle. The counter CNT is reset to "0" when it reaches a value equivalent to 720°CA, or 0°CA. The crank angle corresponding to the counter CNT being "0" is the crank angle at compression top dead center.

[0033] <About fuel injection method>

[0034] Engine control unit 110 changes the fuel injection method of engine 10 based on engine load factor KL and engine speed NE. For example, in the high-load range, engine 10 supplies fuel only through fuel injection using in-cylinder injection valve 22, i.e., in-cylinder injection. In the low-load range, engine 10 supplies fuel only through fuel injection using port injection valve 16, i.e., port injection. In addition, engine 10 sometimes supplies fuel through both port injection and in-cylinder injection. In this case, engine control unit 110 changes the ratio of port injection to in-cylinder injection based on engine load factor KL and engine speed NE. In this way, engine 10 forms a mixture suitable for combustion.

[0035] The engine speed NE is calculated based on the output signal Scr by the engine control unit 110. The engine load factor KL is also calculated by the engine control unit 110 based on the intake air amount Ga and the engine speed NE.

[0036] <About Recycling>

[0037] Figure 2 The following shows the processing steps of a regeneration processing routine executed by the engine control unit 110. Figure 2 The routine shown is implemented by the processing circuit repeatedly executing a program stored in a memory at a predetermined cycle, for example.

[0038] exist Figure 2In the routine shown, the engine control unit 110 first obtains the engine speed NE, the engine load factor KL, and the water temperature THW (S10). Next, the engine control unit 110 calculates an updated amount ΔDPM of 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 refers to the amount of PM trapped by the GPF 34. Specifically, 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. The engine control unit 110 then calculates the updated amount ΔDPM based on the amount of PM in the exhaust gas and the GPF temperature.

[0039] Next, the engine control unit 110 sets the sum of the accumulation amount DPM and the update amount ΔDPM as the new accumulation amount DPM. In this way, the engine control unit 110 updates the accumulation amount DPM (S14). Next, the engine control unit 110 determines whether the flag F is "1" (S16). When the flag F is "1", it indicates that the regeneration process for burning and removing the PM of the GPF 34 is being performed. On the other hand, when the flag F is "0", it indicates that the regeneration process is not being performed. When the engine control unit 110 determines that the flag F is "0" (S16: No), it determines whether the accumulation amount DPM is greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is a threshold value used by the engine control unit 110 to determine that the state requires PM removal based on the fact that the accumulation amount DPM is greater than the regeneration execution value DPMH.

[0040] When the engine control unit 110 determines that the accumulation amount DPM is greater than the regeneration execution value DPMH (S18: YES), it determines whether the execution condition of the regeneration process is met (S20). Here, the execution condition is set to the condition that the logical sum of the following conditions (1) to (3) is true.

[0041] Condition (1): The internal combustion engine torque command value Te*, which is a torque command value for the engine 10, is equal to or greater than a predetermined value Teth.

[0042] Condition (2): The internal combustion engine speed NE is equal to or higher than a predetermined speed.

[0043] Condition (3): The condition that the torque compensation process of S24 can be executed.

[0044] If the engine control unit 110 determines that the logical AND is true (S20: YES), it executes the regeneration process and sets "1" to flag F (S22). Specifically, the engine control unit 110 stops fuel injection from the port injection valve 16 and the in-cylinder injection valve 22 of cylinder #1. The engine control unit 110 then enriches the air-fuel ratio of the mixture within the combustion chambers 20 of cylinders #2 through #4 to a value richer than the stoichiometric air-fuel ratio. In other words, the regeneration process stops fuel supply to one of the multiple cylinders and supplies fuel to the remaining cylinders. This process increases the temperature of the GPF 34 by discharging oxygen and unburned fuel into the exhaust passage 30, thereby burning and removing PM trapped by the GPF 34. Specifically, the engine control unit 110 discharges oxygen and unburned fuel into the exhaust passage 30, causing the unburned fuel to combust in the three-way catalyst 32 and other components, thereby increasing the temperature of the exhaust gas. This increases the temperature of the GPF 34. Furthermore, the engine control unit 110 can burn and remove PM trapped by the GPF 34 by supplying oxygen to the GPF 34 .

[0045] The cylinder to which fuel supply is stopped is not limited to cylinder # 1. For example, the cylinder to which fuel supply is stopped may be switched sequentially so that the number of times fuel supply is stopped is uniform (no bias occurs).

[0046] Engine control unit 110 requests motor control unit 130 to perform processing to compensate for torque fluctuations on crankshaft 26 of engine 10 caused by the cessation of combustion control for cylinder #1 (S24). Receiving this request, motor control unit 130 superimposes the compensation torque on the requested torque. The requested torque is the torque required to be generated by second motor generator 54 for vehicle travel. Motor control unit 130 then operates inverter 58 based on the requested torque to which the compensation torque has been superimposed.

[0047] Specific examples of the conditions under which the torque compensation process can be executed include that the second motor generator 54 has no abnormality and that the battery has stored electric power required for executing the torque compensation process.

[0048] On the other hand, if the engine control unit 110 determines that the flag F is "1" (S16: YES), it determines whether the accumulation amount DPM is less than the stop threshold DPML (S26). The stop threshold DPML is a threshold used by the engine control unit 110 to determine that the regeneration process can be stopped based on the accumulation amount DPM being less than the stop threshold DPML. If the accumulation amount DPM is less than the stop threshold DPML (S26: YES), the engine control unit 110 stops the regeneration process and sets "0" to flag F (S28).

[0049] The engine control unit 110 temporarily ends the process when the process of S24 and S28 is completed and the result of the process of S18 and S20 is negative. Figure 2 The routine shown.

[0050] <About abnormality diagnosis and processing>

[0051] The exhaust gas purification device cannot be purified if it is detached from the exhaust passage 30. Therefore, the engine control unit 110 executes an abnormality diagnosis process to determine the detached state of the exhaust gas purification device.

[0052] Figure 3 The following shows the processing steps of the main routine of the abnormality diagnosis process executed by the engine control unit 110. Figure 3 The routine shown is implemented by the processing circuit executing a program stored in memory. The engine control unit 110 repeatedly executes this routine until the abnormality diagnosis process is completed once during a single trip (when the vehicle's main switch is turned on and off). In other words, the abnormality diagnosis process is executed once per trip. Below, the step numbers of each process are indicated by a number prefixed with "S."

[0053] exist Figure 3 In the routine shown, the engine control unit 110 first calculates the temperature change (S30). The temperature change includes the change in the upstream temperature Tin detected by the upstream temperature sensor 87 and the change in the downstream temperature Tout detected by the downstream temperature sensor 89. That is, the engine control unit 110 calculates the change in the upstream temperature Tin and the change in the downstream temperature Tout, respectively. The upstream temperature Tin is the temperature of the exhaust gas flowing into the GPF 34, which serves as the exhaust purification device. The downstream temperature Tout is the temperature of the exhaust gas flowing out of the GPF 34. Hereinafter, the change in the upstream temperature Tin will be referred to as the first change ΔTin. Furthermore, the change in the downstream temperature Tout will be referred to as the second change ΔTout.

[0054] Thus, in the process of S30 , the engine control unit 110 executes the first variation calculation process of calculating the first variation ΔTin, which is the variation per unit time of the upstream temperature Tin, the temperature of the exhaust gas on the upstream side of the exhaust purification device.

[0055] Furthermore, in the process of S30 , the engine control unit 110 executes a second variation calculation process of calculating a second variation ΔTout which is a variation per unit time of the downstream temperature Tout, the temperature of the exhaust gas on the downstream side of the exhaust purification device.

[0056] The engine control unit 110 executes this routine at a predetermined interval, for example, every 65 milliseconds, sampling the upstream temperature Tin and the downstream temperature Tout. In the first variation calculation process at S30, the engine control unit 110 calculates a difference by subtracting the previously sampled upstream temperature Tin from the currently sampled upstream temperature Tin. This difference is then stored in the memory as the first variation ΔTin. Similarly, in the second variation calculation process at S30, the engine control unit 110 calculates a difference by subtracting the previously sampled downstream temperature Tout from the currently sampled downstream temperature Tout. This difference is then stored in the memory as the second variation ΔTout.

[0057] Next, the engine control unit 110 calculates a moving average of the first change ΔTin (S32). Specifically, in S32, the engine control unit 110 calculates a long-term moving average of the first change ΔTin and a short-term moving average of the first change ΔTin. The long-term moving average is an exponentially smoothed moving average, for example, a 10-second moving average. The short-term moving average is also an exponentially smoothed moving average, for example, a 3-second moving average.

[0058] The exponential moving average is calculated based on the following formula (1).

[0059] S t =α×Y t +(1-α)×S t-1 …Formula (1)

[0060] "α" in the formula (1) is a smoothing coefficient. The smoothing coefficient α is calculated based on the following formula (2).

[0061]

[0062] "N" in formula (2) is the number of samples. When calculating the long-term moving average, the number of times the first change ΔTin is obtained during a 10-second period is "N." On the other hand, when calculating the short-term moving average, the number of times the first change ΔTin is obtained during a 3-second period is "N." Since the first change ΔTin is calculated every 65 milliseconds, the first change ΔTin is calculated 153 times during a 10-second period. That is, when calculating the long-term moving average, the number of samples is 153, so the smoothing coefficient α is "0.013." Furthermore, the first change ΔTin is calculated 46 times during a 3-second period. That is, when calculating the short-term moving average, the number of samples is 46, so the smoothing coefficient α is "0.0426."

[0063] "S" in equation (1) is the exponentially smoothed moving average of the first change ΔTin. "Y" in equation (1) is the first change ΔTin. The subscripts "t" and "t-1" indicate the difference in calculation period. That is, the subscript "t-1" indicates the value calculated last. The initial value of "S" is "0."

[0064] As shown in formula (1), the long-term moving average and short-term moving average, which are exponentially smoothed moving averages, are the sum of the product of multiplying the first change ΔTin by the smoothing coefficient α and the product of multiplying the previously calculated exponentially smoothed moving average S by the difference obtained by subtracting the smoothing coefficient α from 1.

[0065] As described above, when calculating the long-term moving average, the smoothing coefficient α is set to “0.013.” On the other hand, when calculating the short-term moving average, the smoothing coefficient α is set to “0.0426.”

[0066] Thus, in the process of S32, the engine control unit 110 executes the first average value calculation process and the second average value calculation process. The first average value calculation process calculates the short-term moving average value of the upstream temperature Tin. The second average value calculation process calculates the long-term moving average value, which is an exponentially smoothed moving average with a longer period than the short-term moving average value.

[0067] After calculating the long-term moving average and the short-term moving average, the engine control unit 110 then calculates the filter temperature (S34). Here, the engine control unit 110 calculates the temperature of a portion of the GPF 34 10 mm from the front end as the front-end temperature TFr. Furthermore, the engine control unit 110 calculates the temperature of a portion of the GPF 34 10 mm from the rear end as the rear-end temperature TRr. Specifically, in S34, the engine control unit 110 performs a front-end temperature estimation process to estimate the front-end temperature TFr and a rear-end temperature estimation process to estimate the rear-end temperature TRr. The front-end temperature TFr is the temperature of a portion of the GPF 34 closer to the front end than the center. The rear-end temperature TRr is the temperature of a portion of the GPF 34 closer to the rear end than the center.

[0068] The front end temperature TFr is calculated based on the following formula (3).

[0069]

[0070] In equation (3), "ofs1" is the front-end offset value. Furthermore, "KFr" in equation (3) is the front-end passivation coefficient. The subscripts "t" and "t-1" in equation (3) indicate the difference in calculation period. That is, the subscript "t-1" indicates the value calculated last. The initial value of the front-end temperature TFr is the upstream temperature Tin.

[0071] In addition, the rear end side temperature TRr is calculated based on the following formula (4).

[0072]

[0073] In equation (4), "ofs2" is the rear-end offset value. Furthermore, "KRr" in equation (4) is the rear-end passivation coefficient. The subscripts "t" and "t-1" in equation (4) also indicate the difference in calculation time. That is, the subscript "t-1" indicates the value calculated last. The initial value of the rear-end temperature TRr is the upstream temperature Tin.

[0074] The front-end passivation coefficient KFr and the rear-end passivation coefficient KRr are determined based on the intake air amount Ga. The front-end passivation coefficient KFr and the rear-end passivation coefficient KRr decrease as the intake air amount Ga increases. The rear-end passivation coefficient KRr is smaller than the front-end passivation coefficient KFr.

[0075] The magnitude of the front-end offset value ofs1 is set so that the temperature of the portion 10 mm from the front end of the GPF 34 can be calculated based on equation (3). Furthermore, the magnitude of the rear-end offset value ofs2 is set so that the temperature of the portion 10 mm from the rear end of the GPF 34 can be calculated based on equation (4). Specifically, the inactivation coefficients and offset values ​​in equations (3) and (4) are adjusted by matching to minimize the deviation between the results of the previously conducted experiments and simulations and the calculated results.

[0076] After calculating the front-end temperature TFr and the rear-end temperature TRr in step S34, the engine control unit 110 determines whether a prerequisite for executing the abnormality diagnosis process is satisfied (step S40). The prerequisite is simply that the logical sum of the following conditions (4) and (5) is true.

[0077] Condition (4): There is no abnormality in the various sensors connected to the engine control unit 110, that is, all the sensors are normal.

[0078] Condition (5): The abnormality diagnosis process has not been completed.

[0079] If the prerequisites are met (S40: YES), the engine control unit 110 determines whether fuel-cut operation is in progress (S42). Fuel-cut operation is an operation mode in which the crankshaft 26, the output shaft of the internal combustion engine, is rotated while the fuel supply is stopped. This vehicle is a hybrid vehicle, and therefore, when it is not necessary to operate the engine 10, the internal combustion engine is normally stopped, and the crankshaft 26 is immediately stopped. Therefore, in this vehicle, in order to perform abnormality diagnosis, the crankshaft 26 is rotated while the first motor generator 52 is driving the crankshaft 26 and the fuel supply is stopped, while the internal combustion engine would normally be stopped. This achieves fuel-cut operation.

[0080] Figure 4 The flowchart shown shows the FC request processing routine, which switches the FC request on and off. The FC request is an instruction requesting the execution of a fuel-cut operation. This routine is repeatedly executed by the unified control unit 100. As described later, this routine turns on the FC request, thereby executing a fuel-cut operation.

[0081] When this routine is started, the overall control unit 100 determines whether the precondition for operating the FC request is satisfied (S90). The precondition here is that the logical sum of the following conditions (6) and (7) is true.

[0082] Condition (6): The condition that no abnormality occurs in the various sensors connected to the control device 500.

[0083] Condition (7): The battery stores electric power required to rotate the crankshaft 26 and realize the fuel cut operation.

[0084] If the precondition is met (S90: YES), the overall control unit 100 determines whether the throttle valve 14 is closed (S92). In other words, the overall control unit 100 determines whether the throttle valve 14 is closed (OFF) due to the release of the accelerator operation.

[0085] If it is determined that the throttle valve 14 is closed (S92: YES), the unified control unit 100 turns on the FC request and resets the FC counter FCcnt to "0" (S94). When the FC request is turned on by the process in S94, the engine control unit 110 stops the fuel supply to the engine 10. Furthermore, at this time, the motor control unit 130 drives the crankshaft 26 via the first motor generator 52. This executes the fuel-cut operation.

[0086] Next, the overall control unit 100 determines whether the fuel cut operation is in progress (S96). If it is determined that the throttle valve 14 is not closed (S92: No), the overall control unit 100 does not execute the process of S94 and proceeds to S96.

[0087] If 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 abnormality diagnosis process is completed (S98). The abnormality diagnosis process is an abnormality determination or a normal determination described later.

[0088] If it is determined in S98 that the abnormality diagnosis has been completed (S98: YES), the integrated control unit 100 turns off the FC request (S100). This terminates the fuel cut operation. When the fuel cut operation is terminated in this manner, the integrated control unit 100 terminates the series of routines.

[0089] If it is determined in S98 that the determination is not completed (S98: No), the overall control unit 100 increments the FC count FCcnt (S102). The overall control unit 100 then determines whether the FC count FCcnt is equal to or greater than the threshold value FCth (S104).

[0090] If it is determined in S104 that the FC count FCcnt is lower than the threshold value FCth (S104: No), the overall control unit 100 immediately temporarily terminates this routine. In this case, the fuel cut operation continues.

[0091] On the other hand, if it is determined in S104 that the FC count FCcnt is greater than the threshold value FCth (S104: YES), the unified control unit 100 requests FC OFF (S100). Thus, if the FC count FCcnt reaches the threshold value FCth before the abnormality diagnosis process is completed, the fuel cut operation is terminated. Upon terminating the fuel cut operation in this manner, the unified control unit 100 terminates this series of routines.

[0092] If the fuel cut operation is continued for a long time, the temperature of the exhaust gas purification system will decrease, and the abnormality diagnosis process cannot be properly performed. Therefore, if the overall control unit 100 determines that the FC count FCcnt is greater than the threshold value FCth (S104: YES), it ends the fuel cut operation and interrupts the abnormality diagnosis process.

[0093] If the precondition is determined not to be met during S90 (S90: No), the integrated control unit 100 terminates the series of routines without executing S92-S104. Furthermore, if the fuel-cut operation is not in progress during S96 (S96: No), the integrated control unit 100 terminates the series of routines without executing S98-S104. In this manner, fuel-cut operation is executed through the FC request processing executed by the integrated control unit 100.

[0094] return Figure 3 If 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 the determination execution condition is satisfied (S44). The determination execution condition here can be the condition that the logical sum of the following conditions (8) to (11) is true.

[0095] Condition (8): The preheating condition is completed.

[0096] Condition (9): The upstream temperature Tin shows an upward trend and the front end temperature TFr is equal to or higher than the rear end temperature TRr.

[0097] Condition (10): The air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range indicating that the engine 10 is operated at the stoichiometric air-fuel ratio.

[0098] Condition (11): The condition that it was determined that there was no influence of the regeneration process was performed.

[0099] The upstream temperature Tin is determined to be on an upward trend based on the fact that both the differential value of the short-term moving average and the differential value of the long-term moving average calculated in step S32 are greater than or equal to a predetermined value. The predetermined value can be set to a value that indicates an upward trend in the upstream temperature Tin based on the differential value being greater than or equal to the predetermined value. The predetermined value does not necessarily have to be positive.

[0100] The judgment that there is no influence of regeneration treatment is passed Figure 5 The routine shown is carried out. Figure 5 This is a flowchart showing the flow of a process for determining post-regeneration execution conditions.

[0101] This routine is repeatedly executed by the engine control unit 110 during the operation of the engine 10. Figure 5As shown, when this routine starts, the engine control unit 110 determines whether the regeneration process is being executed (S70). If it is determined that the regeneration process is being executed (S70: Yes), the engine control unit 110 determines whether there is any influence from the regeneration process (S74). The engine control unit 110 then temporarily ends this routine.

[0102] 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 the regeneration process was being executed last time (S72). If it is determined in the process of S72 that the regeneration process was not being executed last time (S72: No), the engine control unit 110 determines that there is no influence of the regeneration process (S86). The engine control unit 110 then temporarily ends this routine.

[0103] If, in the process of S72, it is determined that the regeneration process was being executed last time (S72: YES), the engine control unit 110 determines whether the intake air amount Ga is equal to or greater than the predetermined amount Gath (S76). If, in the process of S76, it is determined that the intake air amount Ga is equal to or greater than the predetermined amount Gath (S76: YES), the engine control unit 110 increments the timer counter Tcnt (S78). The engine control unit 110 then determines whether the timer counter Tcnt is equal to or greater than the threshold value Tth (S80).

[0104] If, during the process of S80, it is determined that the timer counter Tcnt is greater than the threshold value Tth (S80: YES), the engine control unit 110 resets the timer counter Tcnt to "0" (S82). The engine control unit 110 then determines that there is no influence from the regeneration process (S86). The engine control unit 110 then temporarily terminates this routine.

[0105] On the other hand, if the timer counter Tcnt is lower than the threshold value Tth in the process of S80 (S80: NO), the engine control unit 110 returns to the process of S76. Furthermore, if the intake air amount Ga is determined to be lower than the predetermined amount Gath in the process of S76 (S76: NO), the engine control unit 110 resets the timer counter Tcnt to "0" (S84). The engine control unit 110 then returns to the process of S76.

[0106] Thus, after executing the regeneration process (S72: YES), the engine control unit 110 executes the processes of S76 to S84. Then, if the state where the intake air amount Ga is equal to or greater than the predetermined amount Gath (S76: YES) continues for a predetermined period or longer (S80: YES), it is determined that there is no influence of the regeneration process (S86).

[0107] The magnitude of the threshold value Tth and the magnitude of the predetermined amount Gath may be set so that it can be determined through the processes of S76 to S84 that the temperature of the exhaust gas purification device has dropped to a level that does not adversely affect the abnormality diagnosis process.

[0108] As described above, the determination execution condition includes the condition that the regeneration process has not been affected. In other words, "determination of no impact through the process of S86" is a post-regeneration execution condition. The post-regeneration execution condition is the execution condition for the abnormality diagnosis process after the regeneration process has been executed.

[0109] return Figure 3 In the process of S44, if it is determined that the determination execution condition is met (S44: Yes), the engine control unit 110 executes the abnormality diagnosis process (S50). On the other hand, if it is determined that it is not in the process of S40 to S44, the engine control unit 110 does not execute the abnormality diagnosis process and temporarily terminates this routine.

[0110] <About abnormality diagnosis and processing>

[0111] Next, refer to Figure 6 The contents of abnormality diagnosis processing are explained. Figure 6 1 is a flowchart showing the processing flow of the abnormality diagnosis processing routine. When the engine control unit 110 starts the abnormality diagnosis processing, it repeatedly executes this routine.

[0112] When this routine begins, the engine control unit 110 determines whether a termination condition has been met (S52). The termination condition is that the upstream temperature Tin has increased during the execution of the abnormality diagnosis process. The abnormality diagnosis process is repeatedly executed within a determination period, described later. Therefore, the termination condition is that the upstream temperature Tin has increased during the determination period. The engine control unit 110 determines that the upstream temperature Tin has increased based on the fact that the first change ΔTin calculated during the determination period is not a negative value.

[0113] If it is determined that the suspension condition is not met (S52: No), the engine control unit 110 determines whether it is within the determination period (S54). In the process of S54, if it is determined that it is within the determination period (S54: Yes), the engine control unit 110 calculates the difference Dif (S56). The difference Dif can be obtained by subtracting the first change ΔTin from the second change ΔTout. Then, the engine control unit 110 calculates the cumulative value ΣDif of the difference Dif. Specifically, the difference Dif calculated by the process of S56 is added to the cumulative value ΣDif calculated last time. Then, the cumulative value ΣDif is updated by setting the sum of these as the new cumulative value ΣDif. The calculation of ΣDif is started through S56 and S58 in this way, and thus the engine control unit 110 starts the determination process. The determination period is the period from the upstream side temperature Tin at the time of starting the determination process in this way until the upstream side temperature Tin drops by a predetermined temperature, for example, 25°C.

[0114] When the integrated value ΣDif is calculated by 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 to update the integrated value ΣDif.

[0115] As shown Figure 3 As described above, the abnormality diagnosis process is executed under the condition that fuel-cut operation is in progress (S42: Yes). Therefore, the upstream temperature Tin gradually decreases during the abnormality diagnosis process. If the upstream temperature Tin drops by a predetermined temperature, the process in S54 determines that the determination period is not within the determination period (S54: No).

[0116] The engine control unit 110 then calculates a determination parameter Xd (S60). The engine control unit 110 divides the accumulated value ΣDif by the number of times the difference Dif has been accumulated. The engine control unit 110 sets the quotient thus calculated as the determination parameter Xd. Specifically, the determination parameter Xd is the average value of the difference Dif obtained by subtracting the first change ΔTin from the second change ΔTout during the determination period.

[0117] Next, the engine control unit 110 determines whether the determination parameter Xd is greater than the predetermined value Xth (S62). If the determination parameter Xd is determined to be less than the predetermined value Xth (S62: No), the engine control unit 110 performs an abnormality determination (S66).

[0118] More specifically, in S66, the engine control unit 110 determines, based on the determination result in S62, that the deviation between the first change amount ΔTin and the second change amount ΔTout during the fuel-cut operation is below a threshold value. Based on this determination result, the engine control unit 110 then performs an abnormality determination, indicating that the GPF 34, serving as the exhaust purification device, is disengaged from the exhaust passage 30. Upon making this abnormality determination, the engine control unit 110 terminates this routine. This completes the abnormality diagnosis process.

[0119] If, during the process of S62, the determination parameter Xd is greater than the predetermined value Xth (S62: YES), the engine control unit 110 performs a normal determination (S64). Specifically, based on the determination result of S62, the engine control unit 110 determines that the deviation between the first change amount ΔTin and the second change amount ΔTout during the fuel-cut operation is greater than the threshold value. Based on this determination result, the engine control unit 110 then performs a normal determination, indicating that the GPF 34, serving as the exhaust purification device, has not been disengaged from the exhaust passage 30. Even if the normal determination is made, the engine control unit 110 terminates this routine. This completes the abnormality diagnosis process.

[0120] The processes of S54 to S66 in the abnormality diagnosis process correspond to a determination process for determining whether the deviation between the first change amount ΔTin during the fuel cut operation and the second change amount ΔTout during the fuel cut operation is equal to or smaller than a threshold value.

[0121] On the other hand, if the abort condition is determined to be met in S52 before the abnormality diagnosis process is completed (S52: YES), the engine control unit 110 terminates this routine without performing S54 to S66. In other words, in this case, the engine control unit 110 interrupts the determination process and terminates the abnormality process.

[0122] <Function of this embodiment>

[0123] When the exhaust gas purification device is disconnected, heat exchange between the gas introduced into the exhaust gas purification device and the exhaust gas purification device is not performed. Therefore, the deviation between the first change amount ΔTin and the second change amount ΔTout is small.

[0124] In contrast, when the exhaust gas purification device is installed, the downstream temperature Tout changes due to heat exchange between the gas introduced into the exhaust gas purification device and the exhaust gas purification device. Therefore, the deviation between the first change amount ΔTin and the second change amount ΔTout is large.

[0125] Therefore, abnormality determination can be performed based on the fact that the deviation between the first change amount ΔTin and the second change amount ΔTout is equal to or smaller than the threshold value.

[0126] Furthermore, the greater the deviation between the temperature of the gas introduced into the exhaust purification device and the temperature of the exhaust purification device, the easier it is to exchange heat between the gas and the exhaust purification device. Therefore, if the exhaust purification device is installed, the greater the deviation between the temperature of the gas introduced into the exhaust purification device and the temperature of the exhaust purification device, the greater the deviation between the first change ΔTin and the second change ΔTout.

[0127] During fuel-cut operation, air that has passed through the combustion chamber 20 is introduced into the exhaust gas purification system. This air is cooler than the exhaust gas. Therefore, during fuel-cut operation, the difference between the temperature of the air introduced into the exhaust gas purification system and the temperature of the exhaust gas purification system is greater than the difference between the temperature of the exhaust gas and the exhaust gas purification system.

[0128] The engine control unit 110 executes abnormality diagnosis processing under the condition that the fuel cut operation is in progress (S42: YES). Furthermore, during the determination process, the engine control unit 110 determines whether the deviation between the first change amount ΔTin during the fuel cut operation and the second change amount ΔTout during the fuel cut operation is less than a threshold value. If the deviation is determined to be less than the threshold value, an abnormality determination is performed (S62: YES, S66).

[0129] That is, the engine control unit 110 executes the determination process in a state where the magnitude of the deviation between the first change amount ΔTin and the second change amount ΔTout differs significantly between when the exhaust gas purification device is installed and when the exhaust gas purification device is removed.

[0130] Furthermore, during fuel-cut operation, air with a lower temperature than both the exhaust gas and the exhaust gas purification device is introduced into the exhaust gas purification device. During fuel-cut operation, the temperature of the air introduced into the exhaust gas purification device, namely, the upstream temperature Tin, gradually decreases. During fuel-cut operation, the air introduced into the exhaust gas purification device is heated by heat exchange with the exhaust gas purification device. Therefore, during fuel-cut operation, the downstream temperature Tout decreases more slowly than the upstream temperature Tin. Therefore, the second change ΔTout during fuel-cut operation is a negative value smaller in absolute value than the first change ΔTin. Therefore, if the exhaust gas purification device is installed, the judgment parameter Xd, which is the average value of the difference between the first change ΔTin and the second change ΔTout during the judgment period, is a positive value.

[0131] When the exhaust gas purification device is removed, heat exchange between the air and the exhaust gas purification device does not occur. Therefore, the second change ΔTout also has a large negative absolute value. Therefore, the judgment parameter Xd has a smaller positive or negative value than when the exhaust gas purification device is installed.

[0132] Thus, abnormality diagnosis can be performed based on the determination parameter Xd being equal to or less than the predetermined value Xth.

[0133] However, if the upstream temperature Tin rises for some reason during the determination period, the first change ΔTin will be a positive value. In this case, the difference obtained by subtracting the first change ΔTin from the second change ΔTout will be a large negative value. Therefore, the determination parameter Xd will become smaller.

[0134] Furthermore, as the upstream temperature Tin increases, the determination period becomes longer. The first change ΔTin and the second change ΔTout gradually decrease. Therefore, as the determination period becomes longer, the determination parameter Xd becomes smaller.

[0135] In this way, when the upstream temperature Tin rises during the determination period, abnormality determination can be easily performed even if the exhaust gas purification device is installed.

[0136] On the other hand, if the engine control unit 110 determines that the upstream temperature Tin has increased during the determination period, it determines that the suspension condition is satisfied (S54: YES) and interrupts the determination process. Thus, the abnormality diagnosis process ends without performing an abnormality determination.

[0137] After the regeneration process is performed, the exhaust gas purification device reaches a high temperature. In addition, the oxidation reaction of particulate matter may continue. If the determination process is performed under such conditions, the second variation ΔTout becomes unstable, and accurate abnormality determination may not be possible.

[0138] After the engine control unit 110 executes the regeneration process, Figure 5 As described above, the determination process is not executed from the end of the regeneration process until the post-regeneration execution condition is satisfied. That is, the engine control unit 110 does not execute the determination process and does not perform abnormality determination in the period immediately after the end of the regeneration process, which is easily affected by the regeneration process.

[0139] <Effects of this embodiment>

[0140] (1) The engine control unit 110 executes abnormality diagnosis processing under the condition that the engine is in fuel-cut operation. Consequently, the engine control unit 110 executes the diagnosis processing when the magnitude of the difference between the first change amount ΔTin and the second change amount ΔTout differs significantly between when the exhaust gas purification device is installed and when the exhaust gas purification device is removed. Consequently, the engine control unit 110 can achieve more accurate abnormality determination.

[0141] (2) The determination execution condition includes "Condition (9): the upstream temperature Tin is increasing and the front temperature TFr is equal to or greater than the rear temperature TRr." That is, the engine control unit 110 starts the determination process under the condition that the upstream temperature Tin is increasing.

[0142] During the fuel-cut operation, the air introduced into the exhaust gas purification device is heated by heat exchange with the exhaust gas purification device.

[0143] When the upstream temperature Tin rises, the exhaust gas purification device is heated by the exhaust gas introduced from the front end. Therefore, the exhaust gas purification device is likely to generate a temperature gradient in which the temperature increases toward the front end and decreases toward the rear end.

[0144] When such a temperature gradient, where the temperature decreases toward the rear end, is generated in the exhaust gas purification device, the air introduced into the device is less likely to heat up compared to when a temperature gradient increases toward the rear end or when no temperature gradient is generated. In other words, when a temperature gradient decreases toward the rear end of the exhaust gas purification device is generated, the downstream temperature Tout is inherently lower than when a temperature gradient increases toward the rear end or when no temperature gradient is generated. Therefore, the second variation ΔTout is small. Meanwhile, during fuel-cut operation, the upstream temperature Tin gradually decreases toward the ambient air temperature. Therefore, the first variation ΔTin during fuel-cut operation is large.

[0145] As described above, when the exhaust gas purification device is disconnected, such heat exchange between the gas and the exhaust gas purification device does not occur. Therefore, the deviation between the first change amount ΔTin and the second change amount ΔTout is small.

[0146] Specifically, the engine control unit 110 initiates the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout tends to increase when the exhaust gas purification device is installed. Furthermore, the engine control unit 110 executes the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout significantly differs between when the exhaust gas purification device is installed and when the exhaust gas purification device is removed. Consequently, the engine control unit 110 can achieve more accurate abnormality determination.

[0147] (3) As described above, the determination execution condition includes "Condition (9): the upstream temperature Tin is increasing and the front-end temperature TFr is equal to or greater than the rear-end temperature TRr." That is, the engine control unit 110 starts the determination process when the front-end temperature TFr is equal to or greater than the rear-end temperature TRr.

[0148] Thus, the engine control unit 110 also starts the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout tends to increase when the exhaust gas purification device is installed.

[0149] (4) As described above, the determination execution condition includes "Condition (10): The air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range indicating that the engine 10 is operating at the stoichiometric air-fuel ratio." That is, 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 the predetermined range.

[0150] When the gas introduced into the exhaust gas purification system contains fuel, there is a possibility that the fuel will undergo an oxidation reaction within the exhaust gas purification system, causing the downstream temperature Tout to vary due to the heat of the reaction. If the downstream temperature Tout fluctuates due to such factors, accurate abnormality determination cannot be performed.

[0151] 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.

[0152] This allows the engine control unit 110 to avoid executing the determination process when there is a possibility that accurate abnormality determination cannot be made.

[0153] (5) As described above, when the upstream temperature Tin rises during the determination period, abnormality determination is easily performed even if the exhaust gas purification device is installed.

[0154] On the other hand, if the upstream temperature Tin rises during the determination period, the engine control unit 110 interrupts the determination process. This can prevent the engine control unit 110 from making an erroneous abnormality determination.

[0155] (6) As described above, the determination execution condition includes "condition (11): the condition that a determination is made that there is no influence of the regeneration process." That is, after the engine control unit 110 has executed the regeneration process, it does not execute the determination process during the period from the end of the regeneration process to the satisfaction of the post-regeneration execution condition. In this way, the engine control unit 110 does not execute the determination process during the period immediately after the regeneration process, which is susceptible to the influence of the regeneration process. Thus, the engine control unit 110 does not perform an abnormality determination during the period immediately after the regeneration process. Therefore, the engine control unit 110 can prevent the situation where an erroneous abnormality diagnosis is made.

[0156] (7) If the engine continues to operate for a certain period of time after the regeneration process is completed, the temperature of the exhaust gas purification device and the exhaust passage 30 will converge to a temperature close to the exhaust gas temperature. In addition, the oxidation reaction of the particulate matter in the exhaust gas purification device will also converge. In other words, the influence of the regeneration process will not affect the determination process.

[0157] Therefore, as described above, the engine control unit 110 determines that the post-regeneration execution condition is satisfied when the engine continues to operate for a predetermined period or longer (S80: Yes) while the intake air amount Ga is equal to or greater than the predetermined amount Gath (S76: Yes) after the regeneration process ends. This allows the engine control unit 110 to start the determination process without being affected by the regeneration process.

[0158] <Change Example>

[0159] This embodiment can be implemented by modifying as follows: This embodiment and the following modifications can be implemented in combination with each other within a range that does not technically conflict.

[0160] While the example in which the abnormality diagnosis process is executed under the condition that the fuel cut operation is in progress has been shown, the condition for executing the abnormality diagnosis process does not necessarily need to include the fuel cut operation being in progress.

[0161] In the example shown, the average value calculated by dividing the cumulative value ΣDif by the number of times the difference Dif is calculated is used as the judgment parameter Xd. Alternatively, a value calculated by another method may be used as the judgment parameter Xd. The judgment parameter Xd may simply be an indicator indicating the magnitude of the deviation between the first change ΔTin and the second change ΔTout. For example, the judgment parameter Xd may be the cumulative value ΣDif itself.

[0162] While the example in which the determination execution condition includes the upstream temperature Tin showing an upward trend is shown, the determination execution condition is not limited to the conditions exemplified in the above embodiment. For example, the upstream temperature Tin showing an upward trend may not be set as the determination execution condition.

[0163] Furthermore, the condition for determining that the upstream temperature Tin is increasing is not limited to using both the long-term and short-term moving averages. For example, instead of using two moving averages, only one moving average may be used, and an increasing trend may be determined based on a positive differential value of the moving average.

[0164] Although the example in which the front end temperature TFr and the rear end temperature TRr are compared and the front end temperature TFr is higher is set as one of the determination execution conditions is shown, this may be omitted.

[0165] An example is shown in which a logical AND condition of the upstream temperature Tin showing an upward trend and the front-end temperature TFr being higher than the rear-end temperature TRr is set as one of the determination execution conditions. Alternatively, either the upstream temperature Tin showing an upward trend or the front-end temperature TFr being higher than the rear-end temperature TRr may be set as one of the determination execution conditions.

[0166] An example is shown in which one of the determination execution conditions includes "Condition (10): The air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range indicating that the engine 10 is operating at the stoichiometric air-fuel ratio." The determination execution conditions can be modified as appropriate. For example, condition (10) may be omitted.

[0167] During the determination period, if the upstream temperature Tin rises, the determination process is interrupted. However, such an interruption condition may be omitted.

[0168] While the example shows a case where the upstream temperature Tin is determined to have increased and the determination process is interrupted based on the fact that the first change ΔTin calculated during the determination period is not a negative value, the present invention is not limited to this. For example, the upstream temperature Tin may be determined to have increased when the first change ΔTin is a positive value.

[0169] The example in which the post-regeneration execution condition is determined to be satisfied when the engine continues to operate for a predetermined period or longer while the intake air amount Ga is equal to or greater than a predetermined amount Gath after the regeneration process has ended is shown, but the present invention is not limited thereto. For example, the post-regeneration execution condition may be determined to be satisfied when a predetermined period of time has elapsed since the regeneration process ended.

[0170] The predetermined conditions for allowing the execution of the regeneration process are not limited to the conditions exemplified in the above embodiment. For example, of the three conditions (1) to (3), only two may be included, or only one may be included. The predetermined conditions may include conditions other than the three conditions described above, or may not include any of the three conditions described above.

[0171] The estimation of the accumulation amount DPM is not limited to Figure 2 The process illustrated in . For example, the accumulation amount DPM can also be estimated based on the pressure difference between the upstream and downstream sides of GPF 34 and the intake air amount Ga. Specifically, when the pressure difference is large, the accumulation amount DPM can be estimated to be larger than when the pressure difference is small. Furthermore, even if the pressure difference is the same, when the intake air amount Ga is small, the accumulation amount DPM can be estimated to be larger than when the intake air amount Ga is large. Here, when the pressure on the downstream side of GPF 34 is assumed to be constant, the pressure Pex described above can be used instead of the pressure difference.

[0172] The layout of the three-way catalyst 32 and the GPF 34 in the exhaust passage 30 may be a layout in which the GPF 34 is provided on the upstream side of the three-way catalyst 32 .

[0173] The GPF 34 is not limited to a filter carrying a three-way catalyst and may be simply a filter. Furthermore, the GPF 34 is not limited to being located downstream of the three-way catalyst 32 in the exhaust passage 30. Furthermore, the vehicle's inclusion of the GPF 34 is not essential. For example, even when the exhaust purification system includes only the three-way catalyst 32, the shutdown process may be executed to warm up the three-way catalyst 32 as described above. The engine control unit 110 may simply determine whether the exhaust purification system is disengaged through abnormality diagnosis processing.

[0174] The vehicle may not execute the torque compensation process of S24.

[0175] The regeneration process in S22, i.e., the deactivation process, does not necessarily need to include enriching the air-fuel ratio in cylinders other than the deactivated cylinder. For example, in the case of regeneration of the GPF 34, if the GPF temperature is sufficiently high such that combustion of particulate matter occurs simply by supplying oxygen, the GPF 34 can be regenerated while combustion of particulate matter continues even without enrichment.

[0176] The engine control unit 110 is not limited to a configuration that includes processing circuitry and memory and uses these to execute software processing. For example, the engine control unit 110 may also include dedicated hardware circuitry, such as an ASIC, that performs hardware processing for at least a portion of the software processing executed in the above-described embodiments. Specifically, the engine control unit 110 may include a processing circuit having any of the following configurations (a) to (c).

[0177] (a) A processing circuit including a processing device for executing all the above-mentioned processes according to a program and a program storage device such as a ROM for storing the program.

[0178] (b) A processing circuit including a processing device and a program storage device for executing part of the above-mentioned processing according to a program, and a dedicated hardware circuit for executing the remaining processing.

[0179] (c) A processing circuit including dedicated hardware circuits for executing all of the above-mentioned processes.

[0180] Here, the number of software execution devices or dedicated hardware circuits including the processing device and the program storage device may be plural.

[0181] The vehicle is not limited to a series-parallel hybrid vehicle, and may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. Furthermore, the vehicle is not limited to a hybrid vehicle, and may be, for example, a vehicle in which the power generation device is only the engine 10 .

[0182] While an example of an inline 4-cylinder engine with four cylinders is shown, 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 4-cylinder engine. Alternatively, the engine 10 may be a V-type engine, a horizontally opposed engine, or a W-type engine, each with an exhaust gas purification device installed in each cylinder group. In this case, the shutdown process can be configured to stop fuel supply to at least one cylinder in each cylinder group during a single cycle. This allows sufficient oxygen to be supplied to the exhaust gas purification device in each cylinder group of a V-type engine or the like.

[0183] Furthermore, the expression "at least one" as used in this specification means "one or more" of the desired options. For example, when there are two options, the expression "at least one" as used in this specification means "only one option" or "both options." For another example, when there are three or more options, the expression "at least one" as used in this specification means "only one option" or "a combination of two or more options."

Claims

1. A control device for an internal combustion engine, wherein an exhaust gas purification device is provided in an exhaust passage of the internal combustion engine, The control device is configured to execute a regeneration process, a first change amount calculation process, a second change amount calculation process, a determination process, and an abnormality diagnosis process. The regeneration process is a process for burning and removing particulate matter accumulated on the exhaust purification device. The first variation calculation process is a process of calculating a first variation as a variation per unit time of an upstream temperature, the upstream temperature being a temperature of exhaust gas on the upstream side of the exhaust gas purification device. The second variation calculation process is a process for calculating a second variation as a variation per unit time of a downstream temperature, the downstream temperature being a temperature of the exhaust gas on the downstream side of the exhaust gas purification device. The determination process is a process for determining whether the deviation between the first change amount and the second change amount is equal to or smaller than a threshold value. The abnormality diagnosis process is a process of determining that the exhaust gas purification device is in a disengaged state when the deviation is determined to be equal to or less than the threshold value in the determination process. The control device is configured not to execute the determination process after the regeneration process is executed, during a period from when the regeneration process is terminated until a post-regeneration execution condition is satisfied.

2. The control device for an internal combustion engine according to claim 1, The control device is configured to determine that the post-regeneration execution condition is satisfied when the internal combustion engine continues to operate in a state where the intake air amount is equal to or greater than a predetermined amount for a predetermined period or longer after the regeneration process is completed.

3. A control method for an internal combustion engine, wherein an exhaust gas purification device is provided in an exhaust passage of the internal combustion engine, the control method comprising: performing a regeneration process for burning and removing particulate matter accumulated on the exhaust purification device; calculating a first variation amount as a variation amount per unit time of an upstream temperature, the upstream temperature being a temperature of exhaust gas on an upstream side of the exhaust gas purification device; calculating a second variation amount as a variation amount per unit time of a downstream side temperature, the downstream side temperature being a temperature of the exhaust gas on the downstream side of the exhaust gas purification device; executing a determination process of determining whether a deviation between the first change amount and the second change amount is equal to or smaller than a threshold value; When it is determined that the deviation is equal to or smaller than the threshold value, it is determined that the exhaust gas purification device is in a disengaged state; as well as After the regeneration process is executed, the determination process is not executed during a period from when the regeneration process is completed until a post-regeneration execution condition is satisfied.

Images