Control device and control method for internal combustion engine

Abstract

An engine control device and a control method of an internal combustion engine, the engine control device configured to execute a determination process and an abnormality diagnosis process, the determination process being a process of determining whether a deviation of a first change amount from a second change amount at the time of fuel cut operation is equal to or below a threshold value, the abnormality diagnosis process being a process of determining that an exhaust purification device is detached when it is determined in the determination process that the deviation is equal to or below the threshold value. The first change amount and the second change amount are each a change amount per unit time of a temperature of exhaust gas on an upstream side and a downstream side of the exhaust purification device, respectively. The control device is configured to interrupt the determination process when the temperature on the upstream side rises during a determination period.

Description

Technical Field

[0001] This disclosure relates to a control device and control method for an internal combustion engine. Background Technology

[0002] The exhaust gas purification device installed in the exhaust passage has a heat capacity. Therefore, the heat of the exhaust gas introduced into the exhaust gas purification device is consumed through heat exchange with the exhaust gas purification device. As a result, a difference arises 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 Publication No. 2020-106028 discloses a control device for an internal combustion engine that detects when a filter for capturing particulate matter in exhaust gas detaches from the exhaust passage. The control device disclosed in the aforementioned publication compares changes in exhaust temperature upstream of the filter with changes in exhaust temperature downstream of the filter. Then, the control device determines that the filter has detached based on the difference between the changes in exhaust temperature upstream and downstream of the filter. Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] The control device disclosed in the aforementioned announcement performs anomaly detection when the exhaust purification device, such as a filter, is disconnected. Such a control device requires high precision in anomaly detection.

[0006] Technical solutions for solving the problem

[0007] This disclosure discloses a control device for an internal combustion engine, applicable to an internal combustion engine with an exhaust purification device installed in the exhaust passage. The control device is configured to perform a fuel cut-off operation that rotates the output shaft of the internal combustion engine when fuel supply is stopped. The control device is configured to perform a first change-of-time calculation process, a second change-of-time calculation process, a determination process, and an anomaly diagnosis process. The first change-of-time calculation process calculates a first change-of-time as the change in upstream temperature, where upstream temperature is the exhaust temperature upstream of the exhaust purification device. The second change-of-time calculation process calculates a second change-of-time as the change in downstream temperature, where downstream temperature is the exhaust temperature downstream of the exhaust purification device. The determination process determines if the deviation between the first change-of-time and the second change-of-time during the fuel cut-off operation is below a threshold value. The anomaly diagnosis process determines that the exhaust purification device is disengaged if the deviation is determined to be below the threshold value during the determination process. The control device is configured to interrupt the determination process if the upstream temperature rises during the determination period. The determination period is the period from the start of the determination process until the upstream temperature decreases from its value at the start of the determination process by a predetermined temperature.

[0008] The control method for an internal combustion engine disclosed herein is applicable to an internal combustion engine equipped with an exhaust purification device in the exhaust passage. The control device is configured to perform a fuel cut-off operation that rotates the output shaft of the internal combustion engine when fuel supply is stopped. The control method includes: calculating a first change in temperature per unit time as the change in upstream temperature, the upstream temperature being the temperature of the exhaust gas upstream of the exhaust purification device; calculating a second change in temperature per unit time as the change in downstream temperature, the downstream temperature being the temperature of the exhaust gas downstream of the exhaust purification device; performing a determination process that determines if the deviation between the first change and the second change during the fuel cut-off operation is below a threshold; determining that the exhaust purification device is disengaged when the deviation is below the threshold; and interrupting the determination process if the upstream temperature rises during the determination period, the determination period being from the start of the determination process until the upstream temperature decreases from its value at the start of the determination process by a predetermined temperature. Attached Figure Description

[0009] Figure 1This is a schematic diagram showing an engine control unit as one embodiment of an internal combustion engine control device, an engine controlled by the engine control unit, and a hybrid vehicle equipped with the engine.

[0010] Figure 2 It is shown Figure 1 A flowchart of the process flow for the regeneration process performed by the engine control unit.

[0011] Figure 3 It is shown Figure 1 The flowchart shows the main routine for abnormal diagnosis and handling executed by the engine control unit.

[0012] Figure 4 It is shown Figure 1 A flowchart of the process flow for the routine of handling fuel cut-off requests executed by the engine control unit.

[0013] Figure 5 It is shown Figure 1 The flowchart shows the process flow of the routine for determining the regeneration execution conditions executed by the engine control unit.

[0014] Figure 6 It is shown Figure 1 The flowchart shows the processing flow of the subroutine for abnormal diagnosis and handling executed by the engine control unit. Detailed Implementation

[0015] The following is for reference Figures 1-6 An engine control unit 110, which is one embodiment of a control device for an internal combustion engine, will be described.

[0016] <Regarding the composition of vehicles>

[0017] like Figure 1 As shown, the engine 10 has four cylinders, #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the engine 10. At the four intake ports 12a downstream of the intake passage 12, there are port injection valves 16 that 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 also has in-cylinder injection valves 22 that inject fuel into cylinders #1 to #4 respectively. Sometimes, fuel is also injected into the combustion chamber 20 from the in-cylinder injection valves 22. The air-fuel mixture in the combustion chamber 20 is used for combustion with the spark discharge of the spark plug 24. The combustion energy generated is converted into the rotational energy of the crankshaft 26.

[0018] The air-fuel mixture after combustion in the combustion chamber 20 is discharged as exhaust gas into the exhaust passage 30 as the exhaust valve 28 opens. The exhaust passage 30 is equipped with a three-way catalytic converter 32 with oxygen-absorbing capacity and a gasoline particulate filter (GPF) 34 as an exhaust purification device. The GPF 34 is a device that integrates the three-way catalytic converter into a filter that captures particulate matter (hereinafter referred to as PM) contained in the exhaust gas.

[0019] The crankshaft rotor 40, which has teeth 42, is coupled to the crankshaft 26. The crankshaft rotor 40 has 32 teeth 42, spaced approximately every 10°CA. Therefore, the crankshaft rotor 40 has a missing tooth 44 where the spacing between adjacent teeth 42 is greater than 10°CA. This is used to indicate the rotation angle that serves as a reference for the crankshaft 26.

[0020] The crankshaft 26 is mechanically connected to the planet carrier C of the planetary gear mechanism 50, which constitutes the power distribution device. The rotating shaft 52a of the first electric generator 52 is mechanically connected to the sun gear S of the planetary gear mechanism 50. The rotating shaft 54a and drive wheel 60 of the second electric generator 54 are mechanically connected to the ring gear R of the planetary gear mechanism 50. An AC voltage is applied to the terminals of the first electric generator 52 via a converter 56. An AC voltage is applied to the terminals of the second electric generator 54 via a converter 58.

[0021] <Regarding Control Device 500>

[0022] The control unit 500 controls the engine 10, the first electric generator 52, and the second electric generator 54. The control unit 500 includes an engine control unit 110 that controls the engine 10. Additionally, the control unit 500 includes a motor control unit 130 that controls the first electric generator 52 and the second electric generator 54. Furthermore, the control unit 500 includes a general control unit 100 that oversees the control of the vehicle. The general control unit 100 is connected to the engine control unit 110 and the motor control unit 130. The aforementioned control units consist of processing circuitry and a memory storing programs executed by the processing circuitry.

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

[0024] The engine control unit 110 operates the engine 10's operating parts, such as the throttle valve 14, the port injection valve 16, the cylinder injection valve 22, and the spark plug 24, in order to control the torque, exhaust component ratio, and other control quantities of the engine 10.

[0025] The motor control unit 130 operates the converter 56 to control the speed, which is a control quantity for the first electric generator 52. Additionally, the motor control unit 130 operates the converter 58 to control the torque, which is a control quantity for the second electric generator 54.

[0026] exist Figure 1 The document records the operating signals MS1 to MS6 for the throttle body 14, the port injection valve 16, the cylinder injection valve 22, the spark plug 24, and the converters 56 and 58. The engine control unit 110, in order to control the engine 10, refers to the intake air volume Ga detected by the air flow meter 80. Additionally, the engine control unit 110 also refers to the output signal Scr of the crankshaft angle sensor 82, the coolant temperature THW detected by the coolant 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, in order to control the first electric generator 52, refers to the output signal Sm1 of the first rotation angle sensor 90. The first rotation angle sensor 90 detects the rotation angle of the first electric generator 52. The motor control unit 130, in order to control the second electric generator 54, refers to the output signal Sm2 of the second rotation angle sensor 92. The second rotation angle sensor 92 detects the rotation angle of the second electric generator 54.

[0027] The engine control unit 110 and the motor control unit 130 are connected to the overall control unit 100 via communication lines. The overall control unit 100, the motor control unit 130, and the engine control unit 110 communicate via CAN, exchanging information based on detection signals input from sensors and their respective calculated information, thereby sharing this information.

[0028] The control unit 100 is connected to an accelerator position sensor 101, a brake sensor 102, and a vehicle speed sensor 103. 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 installed 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 to detect the 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. Additionally, a downstream temperature sensor 89 is also connected to the engine control unit 110 to detect the 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 GPF temperature based on the internal combustion engine load rate KL, the internal combustion engine speed NE, and the exhaust temperature 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 the count CNT by counting the number of times the output signal Scr from the input crankshaft angle sensor 82 is received. The value of the count CNT corresponds to the crankshaft angle; a larger value indicates a larger crankshaft angle. When the count CNT reaches a value equivalent to 720°CA, or 0°CA, it is reset to "0". The crankshaft angle corresponding to the state where the count CNT is "0" is the crankshaft angle at top dead center of compression.

[0033] <Regarding fuel injection methods>

[0034] The engine control unit 110 modifies the fuel injection method of the engine 10 based on the engine load rate KL and the engine speed NE. For example, in the high-load region, the engine 10 supplies fuel only through in-cylinder injection based on the in-cylinder injection valve 22. In the low-load region, the engine 10 supplies fuel only through port injection based on the port injection valve 16. Additionally, the engine 10 sometimes supplies fuel through both port injection and in-cylinder injection. In this case, the engine control unit 110 modifies the ratio of port injection to in-cylinder injection based on the engine load rate KL and the engine speed NE. The engine 10 thus achieves the formation of a suitable air-fuel mixture for combustion.

[0035] The internal combustion engine speed NE is calculated by the engine control unit 110 based on the output signal Scr. Additionally, the internal combustion engine load rate KL is calculated by the engine control unit 110 based on the intake air volume Ga and the internal combustion engine speed NE.

[0036] <About Recycling Process>

[0037] Figure 2 The processing steps of the routine regeneration process performed by the engine control unit 110 are shown. Figure 2The routine shown is implemented by processing circuitry that repeatedly executes a program stored in memory at predetermined intervals. Hereinafter, the step numbers of each process are indicated by numbers beginning with "S".

[0038] exist Figure 2 In the illustrated routine, the engine control unit 110 first obtains the internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW (S10). Next, the engine control unit 110 calculates the updated amount ΔDPM of the accumulated amount DPM based on the internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW (S12). Here, the accumulated amount DPM is the amount of PM captured 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 internal combustion engine speed NE, the internal combustion engine load rate KL, and the coolant temperature THW. Then, the engine control unit 110 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 adds the updated amount ΔDPM to the accumulated amount DPM and sets the new accumulated amount DPM as the sum. The engine control unit 110 updates the accumulated amount DPM in this way (S14). Next, the engine control unit 110 determines whether the flag F is "1" (S16). If the flag F is "1", it indicates that a regeneration process for burning off PM from GPF34 is being performed. On the other hand, if the flag F is "0", it indicates that no regeneration process is being performed. If the engine control unit 110 determines that the flag F is "0" (S16: No), it determines whether the accumulated amount DPM is above the regeneration execution value DPMH (S18). The regeneration execution value DPMH is a threshold used by the engine control unit 110 to determine whether PM removal is necessary based on the accumulated amount DPM being above the regeneration execution value DPMH.

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

[0041] Condition (1): The command value of the torque of the engine 10, i.e. the internal combustion engine torque command value Te*, is above the predetermined value Teth.

[0042] Condition (2): The internal combustion engine speed NE is above the predetermined speed.

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

[0044] When the engine control unit 110 determines that the logical AND operation is true (S20: Yes), it performs a regeneration process, substituting "1" into flag F (S22). That is, the engine control unit 110 stops injecting fuel from the port injection valve 16 and the in-cylinder injection valve 22 of cylinder #1. Then, the engine control unit 110 sets the air-fuel ratio of the mixture in the combustion chamber 20 of cylinders #2 to #4 to be richer than the stoichiometric air-fuel ratio. That is, the regeneration process is a stop process that stops the fuel supply to one of the multiple cylinders and supplies fuel to the remaining cylinders. This process is used to burn off the PM trapped in the GPF34 by increasing the temperature of the GPF34 by discharging oxygen and unburned fuel into the exhaust passage 30. That is, the engine control unit 110 increases the exhaust temperature by discharging oxygen and unburned fuel into the exhaust passage 30, causing the unburned fuel to burn in the three-way catalyst 32, etc. This allows the temperature of the GPF34 to rise. In addition, the engine control unit 110 can burn off the PM captured by the GPF34 by supplying oxygen to the GPF34.

[0045] Furthermore, the cylinder that stops the fuel supply is not limited to cylinder #1. For example, the cylinders that stop the fuel supply can be switched sequentially in a manner that makes the number of times the fuel supply is stopped uniform (without bias).

[0046] The engine control unit 110 requests the motor control unit 130 to perform a process (S24) to compensate for the torque variation of the crankshaft 26 of the engine 10 caused by the cessation of combustion control in cylinder #1. Upon receiving this request, the motor control unit 130 adds a compensating torque to the requested torque. The requested torque is the torque required to generate by the second electric generator 54 for vehicle operation. Furthermore, the motor control unit 130 operates the converter 58 based on the requested torque with the added compensating torque.

[0047] As a specific example of the conditions under which the torque compensation process can be performed, one could cite the following: the second electric generator 54 is not malfunctioning, and the battery has the power required to perform the torque compensation process.

[0048] On the other hand, when the engine control unit 110 determines that the flag F is "1" (S16: Yes), it determines whether the accumulated amount DPM is below the stop threshold DPML (S26). The stop threshold DPML is a threshold used by the engine control unit 110 to determine whether the regeneration process can be stopped based on the condition that the accumulated amount DPM is below the stop threshold DPML. When the accumulated amount DPM is below the stop threshold DPML (S26: Yes), the engine control unit 110 stops the regeneration process and substitutes "0" into the flag F (S28).

[0049] If the engine control unit 110 has completed the processing of S24 and S28, and if the determination in the processing of S18 and S20 is negative, it temporarily terminates the process. Figure 2 The example shown.

[0050] <Regarding the Diagnosis and Handling of Abnormalities>

[0051] If the exhaust purification device detaches from the exhaust passage 30, the exhaust cannot be purified. Therefore, the engine control unit 110 performs abnormal diagnostic processing to determine the state of the exhaust purification device detachment.

[0052] Figure 3 The main routine for abnormal diagnostic processing executed by the engine control unit 110 is shown. 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 if the fault diagnosis process is not completed even once during one stroke of the vehicle's main switch from being turned on to off. That is, the fault diagnosis process is executed once per stroke. Hereinafter, the step numbers of each process are indicated by numbers beginning with "S".

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

[0054] Thus, in the processing of S30, the engine control unit 110 performs the calculation of the first change ΔTin of the change in temperature of the exhaust gas on the upstream side of the exhaust purification device, i.e., the upstream side temperature Tin, per unit time.

[0055] In addition, during the processing in S30, the engine control unit 110 performs a second change of ΔTout, which is the change of the temperature of the exhaust gas downstream of the exhaust purification device, i.e., the downstream temperature Tout, per unit time.

[0056] The engine control unit 110 executes this routine at regular intervals, for example, 65 milliseconds, sampling the upstream temperature Tin and the downstream temperature Tou. In the first change calculation process of S30, the engine control unit 110 calculates the difference by subtracting the previously sampled upstream temperature Tin from the currently sampled upstream temperature Tin. The calculated difference is then stored in memory as the first change amount ΔTin. Similarly, in the second change calculation process of S30, the engine control unit 110 calculates the difference by subtracting the previously sampled downstream temperature Tou from the currently sampled downstream temperature Tou. The calculated difference is then stored in memory as the second change amount ΔTout.

[0057] Next, the engine control unit 110 calculates the moving average of the first change ΔTin (S32). Specifically, in the processing of S32, the engine control unit 110 calculates the long-term moving average and the 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 smoothed moving average is calculated based on the following equation (1).

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

[0060] In equation (1), “α” is the smoothing coefficient. The smoothing coefficient α is calculated based on equation (2).

[0061]

[0062] In equation (2), “N” represents the sample size. When calculating the long-term moving average, the number of times the first change ΔTin is obtained within a 10-second period is “N”. Conversely, when calculating the short-term moving average, the number of times the first change ΔTin is obtained within a 3-second period is “N”. Since the first change ΔTin is calculated every 65 milliseconds, 153 instances of the first change ΔTin are calculated within a 10-second period. That is, when calculating the long-term moving average, the sample size is 153, therefore, the smoothing coefficient α is “0.013”. Furthermore, within a 3-second period, 46 instances of the first change ΔTin are calculated. That is, when calculating the short-term moving average, the sample size is 46, therefore, the smoothing coefficient α is “0.0426”.

[0063] In equation (1), “S” is the exponentially smoothed moving average of the first change ΔTin. In equation (1), “Y” is the first change ΔTin. The subscripts “t” and “t-1” indicate different calculation periods. That is, the subscript “t-1” indicates the value calculated last time. The initial value of “S” is “0”.

[0064] As shown in equation (1), the long-term moving average and short-term moving average, which are exponential 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 exponential moving average S by the difference obtained by subtracting the smoothing coefficient α from 1.

[0065] As mentioned 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] In the process of S32, the engine control unit 110 performs a first average value calculation process and a second average value calculation process. The first average value calculation process is the process of calculating the short-term moving average of the upstream temperature Tin. The second average value calculation process is the process of calculating the long-term moving average, which is an exponential smoothed moving average with a period longer than the short-term moving average.

[0067] When calculating the long-term moving average and 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 the portion of the GPF 34 10 mm from the front end as the front-side temperature TFr. Additionally, the engine control unit 110 calculates the temperature of the portion of the GPF 34 10 mm from the rear end as the rear-side temperature TRr. That is, in the processing of S34, the engine control unit 110 performs front-side temperature estimation processing for estimating the front-side temperature TFr and rear-side temperature estimation processing for estimating the rear-side temperature TRr. The front-side temperature TFr is the temperature of the portion of the GPF 34 closer to the front end than the center. The rear-side temperature TRr is the temperature of the 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 equation (3).

[0069]

[0070] In equation (3), “ofs1” is the offset value used at the front end. Additionally, “KFr” in equation (3) is the passivation coefficient used at the front end. The subscripts “t” and “t-1” in equation (3) indicate different calculation periods. That is, the subscript “t-1” represents the previously calculated value. The initial value of the front-end temperature TFr is the upstream temperature Tin.

[0071] In addition, the back-end temperature TRr is calculated based on the following equation (4).

[0072]

[0073] In Equation (4), “ofs2” represents the offset value used at the back end. Additionally, “KRr” in Equation (4) represents the passivation coefficient used at the back end. The subscripts “t” and “t-1” in Equation (4) also indicate different calculation periods. That is, the subscript “t-1” represents the previously calculated value. The initial value of the back end temperature TRr is the upstream temperature Tin.

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

[0075] The offset value ofs1 for the front end is set so that the temperature of the part 10 mm from the front end of the GPF34 can be calculated based on equation (3). Similarly, the offset value ofs2 for the rear end is set so that the temperature of the part 10 mm from the rear end of the GPF34 can be calculated based on equation (4). In other words, the passivation coefficient and offset value in equations (3) and (4) are adjusted through matching to minimize the deviation between the results of the preliminary experiments and simulations and the calculated results.

[0076] When the front-side temperature TFr and rear-side temperature TRr are calculated through the processing in S34, the engine control unit 110 determines whether the preconditions for performing abnormal diagnostic processing are met (S40). The preconditions here are set to the condition that the logical AND of the following conditions (4) and (5) is true.

[0077] Condition (4): The various sensors connected to the engine control unit 110 do not produce any abnormalities, that is, all sensors are normal.

[0078] Condition (5): The condition of not completing the abnormal diagnosis and treatment has not been met.

[0079] If the prerequisite condition is met (S40: Yes), the engine control unit 110 determines whether it is in fuel cut-off operation (S42). Fuel cut-off operation is an operation mode in which the output shaft of the internal combustion engine, i.e., the crankshaft 26, is rotated while the fuel supply is stopped. This vehicle is a hybrid vehicle; therefore, when it is not necessary to run the engine 10, the internal combustion engine is usually stopped, and the crankshaft 26 is stopped immediately. Therefore, in this vehicle, in order to perform abnormal diagnosis processing, in a state where the internal combustion engine would normally be stopped, the crankshaft 26 is rotated while the first electric generator 52 drives the crankshaft 26 and the fuel supply is stopped. This achieves fuel cut-off operation.

[0080] Figure 4 The flowchart shown illustrates a routine for handling FC requests, which switches between ON and OFF states. An FC request is an instruction to perform fuel cut-off operation. This routine is repeatedly executed by the control unit 100. As described later, this routine enables the FC request, thereby performing fuel cut-off operation.

[0081] When this routine begins, the control unit 100 determines whether the preconditions required for operating the FC are met (S90). The preconditions here are set to the condition that the logical AND of the following conditions (6) and (7) is true.

[0082] Condition (6): The various sensors connected to the control device 500 do not produce any abnormalities.

[0083] Condition (7): The battery stores the power required to rotate the crankshaft 26 to achieve fuel cut-off operation.

[0084] If the precondition is met (S90: Yes), the control unit 100 determines whether the throttle valve 14 is closed (S92). That is, the control unit 100 determines whether the accelerator operation is released and the throttle valve 14 is closed (OFF).

[0085] If it is determined that the throttle valve 14 is closed (S92: Yes), the control unit 100 enables the FC (fuel ignition) demand and resets the FC counter FCcnt to "0" (S94). When the FC demand is enabled through the processing of S94, the engine control unit 110 stops the fuel supply to the engine 10. At this time, the motor control unit 130 drives the crankshaft 26 via the first electric generator 52. Thus, fuel cut-off operation is performed.

[0086] Next, the control unit 100 determines whether the fuel cut-off operation is in progress (S96). Furthermore, if it is determined that the throttle valve 14 is not closed (S92: No), the control unit 100 does not perform the processing in S94 and moves the processing to S96.

[0087] In the processing of S96, if it is determined that the system is in fuel cut-off operation (S96: Yes), the control unit 100 determines whether the abnormal diagnosis process has been completed (S98). The abnormal diagnosis process determination is either an abnormal determination or a normal determination, as described later.

[0088] If the system determines in S98 that the abnormality diagnosis has been completed (S98: Yes), the control unit 100 requests the FC to shut down (S100). This terminates the fuel cut-off operation. When the fuel cut-off operation ends in this manner, the control unit 100 terminates the entire series of routines.

[0089] If it is determined in S98 that the determination has not been completed (S98: No), the control unit 100 increments the FC count FCcnt (S102). Then, the control unit 100 determines whether the FC count FCcnt is above the threshold FCth (S104).

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

[0091] On the other hand, if it is determined in S104 that the FC count FCcnt is above the threshold FCth (S104: Yes), the control unit 100 requests the FC to be turned off (S100). Thus, if the FC count FCcnt reaches the threshold FCth before the abnormal diagnosis process is completed, the fuel cut-off operation ends. When the fuel cut-off operation ends in this way, the control unit 100 terminates this series of routines.

[0092] When the fuel cut-off operation is continuously performed for an extended period, the temperature of the exhaust gas purification device decreases, making it impossible to properly perform abnormal diagnostic processing. Therefore, when the control unit 100 determines that the FC count FCcnt is above the threshold FCth (S104: Yes), it terminates the fuel cut-off operation, thereby interrupting the abnormal diagnostic processing.

[0093] If the precondition is determined not to be met in the processing of S90 (S90: No), the overall control unit 100 does not execute the processing of S92 to S104, but directly terminates the series of routines. Furthermore, if the fuel cut-off operation is not in progress in the processing of S96 (S96: No), the overall control unit 100 does not execute the processing of S98 to S104, but directly terminates the series of routines. In this way, the fuel cut-off operation is performed through the FC request processing executed by the overall control unit 100.

[0094] return Figure 3 If the process in S42 determines that the engine is in fuel cut-off operation (S42: Yes), the engine control unit 110 determines whether the execution condition is met (S44). The execution condition here is set to the following condition (8) to condition (11) being true.

[0095] Condition (8): The preheating condition has been met.

[0096] Condition (9): The upstream temperature Tin tends to rise and the front-end temperature TFr is above 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 representing the operation of the engine 10 at the stoichiometric air-fuel ratio.

[0098] Condition (11): The condition is to determine the effect of no regeneration treatment.

[0099] The upward trend of the upstream temperature Tin is determined based on the fact that both the derivative of the short-term moving average and the derivative of the long-term moving average, calculated through the process in S32, are above a predetermined value. The predetermined value is set such that the magnitude of the upward trend of the upstream temperature Tin can be determined based on the condition that the derivative is above the predetermined value. The predetermined value is not necessarily positive.

[0100] The determination of the impact of no regeneration treatment was passed. Figure 5 Perform the routine shown. Figure 5 This is a flowchart illustrating the process of determining the execution conditions after regeneration.

[0101] This routine is repeatedly executed by the engine control unit 110 during the operation of engine 10. For example... Figure 5As shown, when this routine begins, the engine control unit 110 determines whether regeneration processing is in progress (S70). During the processing of S70, if it is determined that regeneration processing is in progress (S70: Yes), the engine control unit 110 determines whether there is an effect of regeneration processing (S74). Then, the engine control unit 110 temporarily terminates this routine.

[0102] On the other hand, in the processing of S70, if it is determined that the regeneration process is not in progress (S70: No), the engine control unit 110 determines whether the regeneration process was in progress last time (S72). In the processing of S72, if it is determined that the regeneration process was not in progress 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 terminates this routine.

[0103] In the process of S72, if it is determined that the previous regeneration process was in progress (S72: Yes), the engine control unit 110 determines whether the intake air quantity Ga is greater than or equal to the predetermined quantity Gath (S76). In the process of S76, if it is determined that the intake air quantity Ga is greater than or equal to the predetermined quantity Gath (S76: Yes), the engine control unit 110 increments the timing counter Tcnt (S78). Then, the engine control unit 110 determines whether the timing counter Tcnt is greater than or equal to the threshold Tth (S80).

[0104] In the processing of S80, if it is determined that the timing count Tcnt is above the threshold Tth (S80: Yes), the engine control unit 110 resets the timing count 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 terminates this routine.

[0105] On the other hand, in the processing of S80, if the timing count Tcnt is lower than the threshold Tth (S80: No), the engine control unit 110 returns to the processing of S76. Furthermore, in the processing of S76, if it is determined that the intake air volume Ga is lower than the predetermined amount Gath (S76: No), the engine control unit 110 resets the timing count Tcnt to "0" (S84). Then, the engine control unit 110 returns to the processing of S76.

[0106] Thus, after performing the regeneration process (S72: Yes), the engine control unit 110 performs the processes S76 to S84. Then, if the intake air volume Ga is at or above a predetermined amount Gath (S76: Yes) for a predetermined period or longer (S80: Yes), it is determined that there is no effect from the regeneration process (S86).

[0107] The threshold Tth and the predetermined Gath are set to be such that the temperature of the exhaust gas purification device can be determined through the processing of S76 to S84 to reach a level that will not adversely affect the abnormal diagnosis and processing.

[0108] As described above, the execution condition includes the condition that the regeneration process has no impact. That is, "the determination that the process of S86 has no impact" is the post-regeneration execution condition. The post-regeneration execution condition is the execution condition for the abnormal diagnosis process after the regeneration process has been performed.

[0109] return Figure 3 In the process of S44, if the condition for execution is determined to be met (S44: Yes), the engine control unit 110 performs abnormal diagnosis processing (S50). On the other hand, if the condition is determined to be no in the processes of S40 to S44, the engine control unit 110 does not perform abnormal diagnosis processing but temporarily terminates the routine.

[0110] <Regarding the Diagnosis and Handling of Abnormalities>

[0111] Next, refer to Figure 6 The content of abnormal diagnosis and handling is explained. Figure 6 This is a flowchart illustrating the processing flow of the routine for abnormal diagnosis and handling. The engine control unit 110 repeatedly executes this routine when abnormal diagnosis and handling begins.

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

[0113] If the termination 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 previously calculated cumulative value ΣDif is added to the difference Dif calculated through this process of S56. Then, the cumulative value ΣDif is updated by setting their sum as the new cumulative value ΣDif. The calculation of ΣDif begins in this way through S56 and S58, thereby the engine control unit 110 begins the determination process. The determination period is the period from when the upstream temperature Tin drops to a predetermined temperature, for example, 25°C, from the time the determination process begins.

[0114] When the cumulative value ΣDif is calculated through processing S58, the engine control unit 110 temporarily terminates this routine. By repeatedly executing this routine, the cumulative value ΣDif is updated by accumulating the differences Dif calculated during the decision period.

[0115] As shown Figure 3 As explained, the anomaly diagnosis process is performed under the condition that the fuel cut-off operation is in progress (S42: Yes). Therefore, during the anomaly diagnosis process, the upstream temperature Tin gradually decreases. When the upstream temperature Tin drops to a predetermined temperature, a determination that is not within the determination period is performed in the process of S54 (S54: No).

[0116] Therefore, the engine control unit 110 calculates the decision parameter Xd (S60). The engine control unit 110 divides the cumulative value ΣDif by the number of times the difference Dif is accumulated. The engine control unit 110 sets the quotient calculated in this way as the decision parameter Xd. That is, the decision parameter Xd is the average value of the difference Dif obtained by subtracting the first change ΔTin from the second change ΔTout during the decision 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 in the processing of S62 (S62: No), the engine control unit 110 performs an anomaly determination (S66).

[0118] More specifically, in the processing of S66, the engine control unit 110, based on the determination result in S62, determines that the deviation between the first change amount ΔTin and the second change amount ΔTout during fuel cutoff operation is below a threshold. Then, based on this determination result, the engine control unit 110 performs an anomaly determination indicating that the GPF34, as an exhaust purification device, has disengaged from the exhaust passage 30. When an anomaly determination is performed, the engine control unit 110 terminates this routine. Thus, the anomaly diagnosis process is completed.

[0119] If, in the processing of S62, it is determined that the determination parameter Xd is greater than the predetermined value Xth (S62: Yes), the engine control unit 110 performs a normal determination (S64). That is, based on the determination result in S62, the engine control unit 110 determines that the deviation between the first change amount ΔTin and the second change amount ΔTout during fuel cut-off operation is greater than a threshold. Then, based on this determination result, the engine control unit 110 performs a normal determination indicating that the GPF34, as an exhaust purification device, has not disengaged from the exhaust passage 30. If a normal determination is performed, the engine control unit 110 also terminates this routine. Thus, the abnormal diagnosis process is completed.

[0120] The processing of S54 to S66 in the abnormal diagnosis process is equivalent to determining that the deviation between the first change ΔTin and the second change ΔTout during the fuel cut-off operation is below a threshold.

[0121] On the other hand, if the termination condition is determined to be met during the processing of S52 before the abnormality diagnosis process is completed (S52: Yes), the engine control unit 110 will not perform the processing of S54 to S66 but will terminate the current routine. That is, in this case, the engine control unit 110 will interrupt the determination process and terminate the abnormality processing.

[0122] <The function of this implementation method>

[0123] When the exhaust gas purification device is disconnected, there is no 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 ΔTin and the second change ΔTout is small.

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

[0125] Therefore, anomaly detection can be performed based on the deviation between the first change amount ΔTin and the second change amount ΔTout being below a threshold.

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

[0127] During fuel cut-off operation, air passing through combustion chamber 20 is introduced into the exhaust gas purification device. This air is at a lower temperature than the exhaust gas. Therefore, during fuel cut-off operation, the temperature deviation between the air introduced into the exhaust gas purification device and the temperature of the exhaust gas purification device is greater than the temperature deviation between the exhaust gas and the exhaust gas purification device.

[0128] The engine control unit 110 performs anomaly diagnosis processing when it is in fuel cut-off operation (S42: Yes). Furthermore, in its determination process, the engine control unit 110 determines if the deviation between the first change amount ΔTin during fuel cut-off operation and the second change amount ΔTout during fuel cut-off operation is below a threshold. If the deviation is determined to be below the threshold, an anomaly determination is performed (S62: Yes, S66).

[0129] That is, according to the engine control unit 110, the determination process is performed when the deviation between the first change amount ΔTin and the second change amount ΔTout is significantly different between the case where the exhaust purification device is installed and the case where the exhaust purification device is disconnected.

[0130] Furthermore, during fuel cut-off operation, air with a temperature lower than the exhaust gas temperature and lower than the exhaust gas purification device temperature is introduced into the exhaust gas purification device. During fuel cut-off operation, the temperature of the air introduced into the exhaust gas purification device, i.e., the upstream temperature Tin, gradually decreases. During fuel cut-off operation, the air introduced into the exhaust gas purification device is heated through heat exchange with the exhaust gas purification device. Therefore, during fuel cut-off operation, the downstream temperature Tout decreases slowly compared to the upstream temperature Tin. Therefore, the second change ΔTout during fuel cut-off operation is a negative value with an absolute value smaller than the first change ΔTin. Therefore, if an exhaust gas purification device is installed, the average value of the difference between the second change ΔTout and the first change ΔTin during the determination period, i.e., the determination parameter Xd, is a positive value.

[0131] When the exhaust purification device is disconnected, no heat exchange occurs between the air and the device. Therefore, the second change, ΔTout, is also a negative value with a large absolute value. Thus, the determination parameter Xd is either a positive or negative value smaller than when the exhaust purification device is installed.

[0132] Therefore, it is possible to perform anomaly diagnosis based on the judgment parameter Xd being below a predetermined value Xth.

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

[0134] Furthermore, as the upstream temperature Tin rises, the decision period becomes longer. The first change ΔTin and the second change ΔTout gradually decrease. Therefore, as the decision period lengthens, the decision parameter Xd decreases.

[0135] In this way, when the upstream temperature Tin rises during the judgment period, it is easy to make an anomaly judgment even if an exhaust purification device is installed.

[0136] In contrast, if the engine control unit 110 determines that the upstream temperature Tin has risen during the determination period, it determines that the abort condition has been met (S54: Yes) and interrupts the determination process. Thus, the abnormality determination is not performed and the abnormality diagnosis process ends.

[0137] After regeneration, the exhaust purification unit reaches a high temperature. Additionally, oxidation reactions of particulate matter may continue. When the judgment process is performed under these conditions, the second change, ΔTout, is unstable, potentially making accurate anomaly detection impossible.

[0138] After performing the regeneration process, the engine control unit 110, as referred to Figure 5 As explained, no decision-making process is performed during the period from the end of the regeneration process until the post-regeneration execution conditions are met. That is, the engine control unit 110 does not perform decision-making process or perform anomaly determination during the period immediately after the regeneration process ends, when it is susceptible to the effects of the regeneration process.

[0139] <Effects of this implementation method>

[0140] (1) The engine control unit 110 performs abnormal diagnosis processing under the condition that it is in fuel cut-off operation. As a result, the determination processing is performed when the deviation between the first change amount ΔTin and the second change amount ΔTout is significantly different between the case where the exhaust purification device is installed and the case where the exhaust purification device is disconnected. Therefore, the engine control unit 110 can achieve more accurate abnormal determination.

[0141] (2) The determination execution conditions include "condition (9): the upstream side temperature Tin shows an upward trend and the front end temperature TFr is higher than the rear end temperature TRr". That is, the engine control unit 110 starts the determination process based on the condition that the upstream side temperature Tin shows an upward trend.

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

[0143] As the upstream temperature Tin rises, the exhaust gas purification device is heated by the exhaust gas introduced from the front end. Therefore, in the exhaust gas purification device, there is a high probability that a temperature gradient will be generated that is higher towards the front end and lower towards the rear end.

[0144] When a temperature gradient occurs in the exhaust gas purification device, with the temperature decreasing towards the rear end, the air introduced into the device is less likely to heat up compared to a temperature gradient with increasing temperature towards the rear end or no temperature gradient at all. In other words, when a temperature gradient occurs in the exhaust gas purification device, the downstream temperature Tout is inherently lower compared to a temperature gradient with increasing temperature towards the rear end or no temperature gradient at all. Therefore, the second change ΔTout is small. On the other hand, during fuel cut-off operation, the upstream temperature Tin gradually decreases towards atmospheric temperature. Therefore, the first change ΔTin during fuel cut-off operation is large.

[0145] As mentioned above, when the exhaust purification device is disconnected, there is no heat exchange between the gas and the exhaust purification device. Therefore, the deviation between the first change ΔTin and the second change ΔTout is small.

[0146] That is, the engine control unit 110 begins the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout tends to increase when an exhaust purification device is installed. Furthermore, the engine control unit 110 performs the determination process when the deviation between the first change amount ΔTin and the second change amount ΔTout differs significantly between the situation where an exhaust purification device is installed and the situation where the exhaust purification device is not installed. Therefore, the engine control unit 110 can achieve more accurate anomaly detection.

[0147] (3) As described above, the determination execution condition includes "condition (9): the upstream side temperature Tin tends to rise and the front side temperature TFr is higher than the rear side temperature TRr". That is, the engine control unit 110 starts the determination process with the condition that the front side temperature TFr is higher than the rear side temperature TRr.

[0148] Therefore, the engine control unit 110 can also begin processing when the deviation between the first change ΔTin and the second change ΔTout tends to increase when an exhaust purification device is installed. Thus, the engine control unit 110 can achieve highly accurate anomaly detection.

[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 that indicates the engine 10 is operating at a stoichiometric air-fuel ratio". That is, the engine control unit 110 starts the determination process with the condition that the air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range.

[0150] It is possible that when the gas introduced into the exhaust gas purification device contains fuel components, these fuel components may undergo an oxidation reaction within the device, causing the downstream temperature Tout to change due to the heat of reaction. When there are fluctuations in the downstream temperature Tout caused by such reasons, accurate anomaly detection is impossible.

[0151] Therefore, the engine control unit 110 does not perform the determination process if the air-fuel ratio detected by the air-fuel ratio sensor 81 is outside the predetermined range.

[0152] Therefore, the engine control unit 110 can suppress situations where judgment processing may not be performed accurately.

[0153] (5) As mentioned above, when the upstream temperature Tin rises during the determination period, it is easy to make an abnormality determination even if an exhaust purification device is installed.

[0154] In contrast, if the upstream temperature Tin rises during the determination period, the engine control unit 110 interrupts the determination process. Therefore, the engine control unit 110 can suppress the occurrence of erroneous determinations.

[0155] (6) As described above, the determination execution condition includes "Condition (11): The condition that a determination has been made without the influence of regeneration processing." That is, after the engine control unit 110 performs regeneration processing, it does not perform determination processing during the period from the end of regeneration processing until the regeneration execution condition is met. In this way, the engine control unit 110 does not perform determination processing during the period immediately after the regeneration processing, which is susceptible to the influence of regeneration processing. As a result, the engine control unit 110 does not perform abnormal determination during the period immediately after the regeneration processing. Therefore, the engine control unit 110 is able to suppress the situation of making incorrect abnormal diagnosis.

[0156] (7) If the internal combustion engine continues to operate for a certain period of time after the regeneration process ends, the temperature of the exhaust purification device and the exhaust passage 30 will converge to a temperature close to the exhaust temperature. In addition, the oxidation reaction of particulate matter in the exhaust purification device will also converge. That is, the effect of the regeneration process will not affect the judgment process.

[0157] Therefore, as described above, if the internal combustion engine has been running for a predetermined period of time or more since the end of the regeneration process, with the intake air quantity Ga being at or above a predetermined amount Gath (S76: Yes) (S80: Yes), the engine control unit 110 determines that the post-regeneration execution condition has been met. According to this technical solution, the engine control unit 110 can begin the determination process when the effect of the regeneration process does not affect the determination process.

[0158] <Example of Change>

[0159] This embodiment can be modified as follows. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0160] An example is shown where the decision execution condition includes an upward trend in the upstream temperature Tin, but the decision execution condition is not limited to the conditions illustrated in the above embodiment. For example, the upward trend in the upstream temperature Tin may not be set as the decision execution condition.

[0161] Furthermore, the criteria for determining that the upstream temperature Tin is trending upward are not limited to using long-term and short-term moving averages. For example, instead of using two moving averages, only one moving average can be used, and the trend can be determined based on the positive derivative of that moving average.

[0162] • An example is shown in which the front-side temperature TFr is compared with the back-side temperature TRr and the case where the front-side temperature TFr is higher is set as one of the decision execution conditions, but it can also be omitted.

[0163] This example illustrates setting the logic and conditions for determining execution conditions as follows: the upstream temperature Tin tends to rise, and the front-end temperature TFr is higher than the rear-end temperature TRr. Conversely, either the upstream temperature Tin tends to rise, or the front-end temperature TFr is higher than the rear-end temperature TRr, can be set as one of the determination execution conditions.

[0164] • An example is shown in which one of the determination execution conditions is "Condition (10): The air-fuel ratio detected by the air-fuel ratio sensor 81 is within a predetermined range representing the operation of the engine 10 at the stoichiometric air-fuel ratio". The determination execution conditions can be changed appropriately. For example, condition (10) can also be omitted.

[0165] The example shown illustrates a scenario where the upstream temperature Tin has increased, and the decision process is interrupted because the first change ΔTin calculated during the decision period is not negative. However, this is not the only possibility. For instance, the upstream temperature Tin could also be determined to have increased when the first change ΔTin is positive.

[0166] • After performing the regeneration process, the decision-making process is not performed until the post-regeneration execution condition is met, but it can also be omitted.

[0167] The example shown illustrates a scenario where the internal combustion engine has been running for a predetermined period of time since the end of the regeneration process, with the intake air quantity Ga being a predetermined amount of Gath or higher. However, this is not the only possibility. For instance, it could also be determined that the regeneration execution condition is met if a certain amount of time has elapsed since the end of the regeneration process.

[0168] • The predetermined conditions for allowing the regeneration process to be performed are not limited to the conditions exemplified in the above embodiments. For example, regarding the three conditions (1) to (3) above, only two of them may be included, or for example, only one of them may be included. The predetermined conditions may include conditions other than the three conditions above, or they may not include any of the three conditions above.

[0169] The estimated treatment of DPM (decisive mass per unit area) is not limited to... Figure 2 The process is illustrated in the example. For instance, the buildup amount DPM can also be estimated based on the pressure difference between the upstream and downstream sides of the GPF34 and the intake air volume Ga. Specifically, when the pressure difference is large, the buildup amount DPM can be estimated to be a larger value compared to when the pressure difference is small. Moreover, even if the pressure difference is the same, when the intake air volume Ga is small, the buildup amount DPM can be estimated to be a larger value compared to when the intake air volume Ga is large. Here, if the pressure on the downstream side of the GPF34 is considered a constant value, the aforementioned pressure Pex can be used instead of the pressure difference.

[0170] • The layout of the three-way catalyst 32 and GPF34 in the exhaust passage 30 can also be such that the GPF34 is located on the upstream side of the three-way catalyst 32.

[0171] • The GPF34 is not limited to a filter carrying a three-way catalyst; it may be simply a filter. Furthermore, the GPF34 is not limited to being located downstream of the three-way catalyst 32 in the exhaust passage 30. Moreover, the presence of a GPF34 in the vehicle is not essential. For example, even if the exhaust purification device only includes the three-way catalyst 32, a shutdown procedure can be performed to preheat the three-way catalyst 32, as described above. The engine control unit 110 can determine whether the exhaust purification device is disengaged through abnormal diagnostic processing.

[0172] • The vehicle may also be a vehicle that does not perform the torque compensation process of S24.

[0173] • The regeneration process of S22, i.e., the shutdown process, may not include enriching the air-fuel ratio in cylinders other than the shutdown cylinder. For example, in the case of GPF34 regeneration process, if the GPF temperature is high enough that particulate matter will burn as long as oxygen is supplied, then even without enrichment, the combustion of particulate matter can continue to regenerate GPF34.

[0174] The engine control unit 110 is not limited to having processing circuitry and memory, and using them to perform software processing. For example, the engine control unit 110 may also have dedicated hardware circuitry, such as an ASIC, that performs hardware processing on at least a portion of the software processing performed in the above embodiments. That is, the engine control unit 110 may include processing circuitry having any of the following configurations (a) to (c).

[0175] (a) A processing circuit that includes all the processing devices that perform the above-mentioned processing according to the program, and a program storage device such as a ROM that stores the program.

[0176] (b) A processing circuit having a processing device for performing a portion of the above-described processing according to a program, a program storage device, and dedicated hardware circuitry for performing the remaining processing.

[0177] (c) A processing circuit that has all the dedicated hardware circuits to perform the above processing.

[0178] Here, there may be multiple software execution devices and dedicated hardware circuits equipped with processing devices and program storage devices.

[0179] • The vehicle is not limited to a series-parallel hybrid vehicle; for example, it could also be a parallel hybrid vehicle or a series hybrid vehicle. Moreover, the vehicle is not limited to a hybrid vehicle; for example, it could also be a vehicle whose power generation device is only the engine 10.

[0180] The example shown is an inline 4-cylinder engine with four cylinders, but 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 can also be a V-type engine, a horizontally opposed engine, or a W-type engine, each with an exhaust gas purification device for each cylinder bank. In this case, the stopping process can be configured to stop fuel supply to at least one cylinder in each cylinder bank during one cycle. This allows sufficient oxygen to be supplied to the exhaust gas purification devices of each cylinder bank in the V-type engine, etc.

[0181] Furthermore, the expression "at least one" as used in this specification means "more than one" of the desired options. For example, if the number of options is two, "at least one" means "only one option" or "both options". As another example, if the number of options is three or more, "at least one" means "only one option" or "any combination of two or more options".

Claims

1. A control device for an internal combustion engine, wherein an exhaust purification device is provided in the exhaust passage of the internal combustion engine, and the internal combustion mechanism is configured to perform a fuel cut-off operation that causes the output shaft of the internal combustion engine to rotate when the fuel supply is stopped. The control device is configured to perform a first change calculation process, a second change calculation process, a judgment process, and an anomaly diagnosis process. The first change calculation process is the process of calculating the first change as the change in upstream temperature per unit time, where upstream temperature is the temperature of the exhaust gas on the upstream side of the exhaust purification device. The second change calculation process is the process of calculating the second change as the change in downstream temperature per unit time, where downstream temperature is the temperature of the exhaust gas downstream of the exhaust purification device. The determination process is a process that determines if the deviation between the first change amount and the second change amount during the fuel cut-off operation is below a threshold. The abnormality diagnosis process is a process in which, if the deviation is determined to be below the threshold during the determination process, it is determined that the exhaust purification device has disengaged. The control device is configured to interrupt the determination process if the upstream temperature rises during the determination period. The determination period is the period from the start of the determination process until the upstream temperature decreases from its initial value at the start of the determination process to a predetermined temperature. The determination process is the process performed when the determination execution condition is met. The determination execution condition includes the condition that the air-fuel ratio detected by the air-fuel ratio sensor installed in the exhaust passage is within a predetermined range representing the operation of the internal combustion engine at the stoichiometric air-fuel ratio.

2. The control device for an internal combustion engine according to claim 1, The control device is configured to determine that the upstream temperature has risen if the first change calculated during the determination period is not negative, and then interrupt the determination process.

3. A control method for an internal combustion engine, wherein an exhaust purification device is provided in the exhaust passage of the internal combustion engine, and the internal combustion mechanism is configured to perform a fuel cut-off operation that causes the output shaft of the internal combustion engine to rotate when the fuel supply is stopped. The control method includes: Calculate the first change as the change in upstream temperature per unit time, where upstream temperature is the temperature of the exhaust gas on the upstream side of the exhaust purification device; Calculate the second change as the change in downstream temperature per unit time, where the downstream temperature is the temperature of the exhaust gas on the downstream side of the exhaust purification device. A determination process is performed to determine if the deviation between the first change amount during the fuel cut-off operation and the second change amount during the fuel cut-off operation is below a threshold. If the deviation is determined to be below the threshold, it is determined that the exhaust purification device is disconnected. as well as If the upstream temperature rises during the determination period, the determination process is interrupted. The determination period is the period from the start of the determination process until the upstream temperature decreases from its initial value at the start of the determination process to a predetermined temperature. The determination process is the process performed when the determination execution condition is met. The determination execution condition includes the condition that the air-fuel ratio detected by the air-fuel ratio sensor installed in the exhaust passage is within a predetermined range representing the operation of the internal combustion engine at the stoichiometric air-fuel ratio.

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