Internal combustion engine control device and method

Abstract

The present invention relates to a control device and method for an internal combustion engine. The control device for an internal combustion engine is configured to perform a temperature increase process, a misfire detection process for detecting misfires, a determination process, and a reduction process. The temperature increase process includes increasing the temperature of a catalyst by a partial cylinder fuel cut process. The determination process includes determining whether the number of misfires detected by the misfire detection process among the number of times combustion control is performed in each cylinder is greater than a prescribed value. The reduction process includes reducing the amount of temperature increase of the catalyst when the number of misfires is greater than a prescribed value compared to when the number of misfires is less than a prescribed value.

Description

Technical Field

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

[0002] For example, Japanese Patent Publication No. 2018-162721 discloses a device for performing a temperature increase process to increase the temperature of a catalyst for purifying exhaust gas. In this device, when misfire is detected during the execution of the temperature increase process, the device changes the threshold for terminating the temperature increase process and terminates the temperature increase process at an earlier stage.

[0003] The present inventors have studied the following: when the shaft torque of the internal combustion engine is not zero, as a heating process for heating the catalyst, the fuel supply to some cylinders is stopped and the fuel supply to the remaining cylinders is performed. Here, if misfire occurs during the execution of such a heating process, the amount of fuel supplied to the catalyst increases, so there is a risk of overheating the catalyst. Summary of the invention

[0004] A control device for an internal combustion engine of one embodiment is configured to control an internal combustion engine having a catalyst for purifying exhaust gas in an exhaust passage and having a plurality of cylinders. The control device for the internal combustion engine is configured to perform: a temperature increase process for stopping fuel supply to a portion of the plurality of cylinders and performing fuel supply to the remaining cylinders other than the portion of the cylinders, thereby increasing the temperature of the catalyst; a misfire detection process for detecting misfire; a determination process for determining whether the number of misfires detected by the misfire detection process among the number of times combustion control is performed in each cylinder is greater than a prescribed value; and a reduction process for reducing the amount of temperature increase of the catalyst when the number of misfires is greater than the prescribed value compared to when the number of misfires is less than the prescribed value.

[0005] According to this configuration, when the number of misfires is equal to or greater than a predetermined value, the amount of catalyst temperature increase is reduced by reducing the number of processes executed, so that excessive catalyst temperature increase when misfires occur can be suppressed.

[0006] Furthermore, in the above control device, the reduction process may include terminating the stop of the fuel supply to the part of the cylinders and starting the fuel supply to the part of the cylinders.

[0007] According to this configuration, by executing the reduction process, fuel supply to a part of the cylinders to which fuel supply has been stopped is started, so the amount of air in the exhaust gas discharged from the cylinder is reduced. Therefore, although the unburned fuel supplied to the catalyst increases due to the occurrence of misfire, the amount of air supplied to the catalyst is reduced, so that overheating of the catalyst can be suppressed.

[0008] Furthermore, in the above control device, the reduction process may include adjusting the amount of fuel supplied to the part of cylinders to start fuel supply so that the air-fuel ratio of the mixture in the cylinder becomes leaner than the theoretical air-fuel ratio.

[0009] According to this configuration, the amount of air in the exhaust gas discharged from the cylinder increases compared to the case where the air-fuel ratio of the mixture of the cylinder at the start of fuel supply is set to the chemical equivalent ratio, so the catalyst temperature increase effect can be obtained to a certain extent. Therefore, the catalyst temperature increase can be implemented while suppressing the overheating of the catalyst.

[0010] Furthermore, in the above-mentioned control device, the reduction process may include a process of reducing the number of cylinders to which fuel supply is stopped for a predetermined period when the temperature raising process is executed.

[0011] According to this configuration, since the amount of air supplied to the catalyst during a predetermined period is reduced by executing the reduction process, it is possible to suppress excessive temperature rise of the catalyst.

[0012] Furthermore, in the above control device, the reduction process may include a process of reducing the amount of fuel supplied to the remaining cylinders.

[0013] According to this configuration, by executing the reduction process, the amount of fuel supplied to other cylinders to which fuel is supplied is reduced, so the amount of unburned fuel in the exhaust gas discharged from these cylinders is reduced. Therefore, although the amount of unburned fuel supplied to the catalyst increases due to the occurrence of misfire, the amount of unburned fuel supplied to the catalyst is reduced, so that overheating of the catalyst can be suppressed.

[0014] In another embodiment, a method for controlling an internal combustion engine is provided, the internal combustion engine having a catalyst for purifying exhaust gas in an exhaust passage and having a plurality of cylinders. The method includes: stopping fuel supply to a portion of the plurality of cylinders and supplying fuel to the remaining cylinders other than the portion of the cylinders, thereby raising the temperature of the catalyst; detecting misfire; determining whether the number of misfires detected among the number of times combustion control is executed in each cylinder is greater than a prescribed value; and when the number of misfires is greater than the prescribed value, reducing the amount of temperature increase of the catalyst compared to when the number of misfires is less than the prescribed value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing the configuration of a drive system and a control device according to the first embodiment.

[0016] Figure 2 This is a flowchart showing a procedure related to the regeneration process performed by the control device in this embodiment.

[0017] Figure 3 This is a flowchart showing a procedure related to the misfire detection process executed by the control device in this embodiment.

[0018] Figure 4 This is a flowchart showing a procedure related to processing executed by the control device in this embodiment.

[0019] Figure 5 This is a flowchart showing a procedure related to processing executed by the control device according to the second embodiment.

[0020] Figure 6 This is a flowchart showing a procedure related to processing executed by the control device according to the third embodiment.

[0021] Figure 7 This is a flowchart showing a procedure related to processing executed by a control device according to the fourth embodiment.

[0022] Figure 8 This is a flowchart showing a procedure related to a process executed by a control device according to another embodiment.

[0023] Fig. 9 This is a flowchart showing a procedure related to a process executed by a control device according to another embodiment.

[0024] Fig.10 This is a flowchart showing a procedure related to a process executed by a control device according to another embodiment. DETAILED DESCRIPTION

[0025] <First embodiment>

[0026] Hereinafter, a first embodiment of a control device for an internal combustion engine will be described with reference to the drawings.

[0027] like Figure 1 As shown, the internal combustion engine 10 has four cylinders, cylinder #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10. In the intake port (intake passage) 12a, which is the downstream portion of the intake passage 12, a port injection valve 16 is provided for injecting fuel into the intake port 12a. The air sucked into the intake passage 12 and / or the fuel injected from the port injection valve 16 flows into the combustion chamber 20 as the intake valve 18 opens. Fuel is injected into the combustion chamber 20 from the in-cylinder injection valve 22. In addition, the mixture of air and fuel in the combustion chamber 20 is supplied to combustion as the spark discharge of the spark plug 24. The combustion energy generated at this time is converted into the rotational energy of the crankshaft 26.

[0028] The mixture that has been combusted in the combustion chamber 20 is discharged as exhaust gas to the exhaust passage 30 as the exhaust valve 28 opens. A three-way catalyst 32 having oxygen storage capacity and a gasoline particulate filter (GPF) 34 are provided in the exhaust passage 30. In addition, in the present embodiment, as the GPF 34, a GPF in which a three-way catalyst is supported on a filter for collecting particulate matter (PM) is assumed.

[0029] The crankshaft 26 is coupled to a crank rotor 40 having teeth 42. The teeth 42 indicate a plurality of rotation angles of the crankshaft 26. The teeth 42 are provided at intervals of 10° CA on the crank rotor 40, but a toothless portion 44 is provided at one location where the intervals between adjacent teeth 42 are 30° CA. This is to indicate a rotation angle that serves as a reference for the crankshaft 26.

[0030] The crankshaft 26 is mechanically connected to the planetary carrier C of the planetary gear mechanism 50 constituting the power distribution device. The rotating shaft 52a of the first motor generator 52 is mechanically connected to the sun gear S of the planetary gear mechanism 50. In addition, the rotating shaft 54a of the second motor generator 54 and the drive wheel 60 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 motor generator 52 by an inverter 56. In addition, an AC voltage is applied to the terminals of the second motor generator 54 by an inverter 58.

[0031] The control device 70 is configured to control the internal combustion engine 10. The control device 70 is configured to operate various operation parts of the internal combustion engine 10, such as the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24, in order to control the control amount such as the torque and exhaust component ratio of the internal combustion engine 10. For example, the control device 70 calculates the required torque Tr* for the vehicle based on parameters such as the accelerator pedal operation amount ACCP detected by the accelerator sensor 83 and the vehicle speed SP detected by the vehicle speed sensor 84. Then, the control device 70 calculates the required output Pe* for the internal combustion engine 10 based on the required torque Tr* and the like. Then, the control device 70 calculates the target rotation speed Ne* and the internal combustion engine torque command value Te* that enable the required output Pe* to be efficiently output from the internal combustion engine 10. Then, the control device 70 controls the intake air amount, the fuel injection amount of the port injection valve 16 and the in-cylinder injection valve 22, and the ignition timing of the mixture to obtain the internal combustion engine torque command value Te*. In addition, the control device 70 performs incremental correction based on various requirements when setting the fuel injection amount. For example, the control device 70 implements control such as the startup incremental amount implemented when the internal combustion engine 10 is started, the warm-up incremental amount implemented when the internal combustion engine 10 is cold started, and the recovery incremental amount implemented when recovering from a fuel cut.

[0032] The control device 70 is configured to control the first motor generator 52. The control device 70 operates the inverter 56 so as to control the rotation speed as a control variable of the first motor generator 52.

[0033] The control device 70 is configured to control the second motor generator 54. The control device 70 operates the inverter 58 to control the torque as the control amount of the second motor generator 54. Figure 1 Operation signals MS1 to MS6 of the throttle valve 14 , the port injection valve 16 , the in-cylinder injection valve 22 , the spark plug 24 , and the inverters 56 and 58 are shown.

[0034] The control device 70 refers to the intake air amount Ga detected by the air flow meter 80, the output signal Scr of the crank angle sensor 82, and the water temperature THW detected by the water temperature sensor 86 in order to control the control amount of the internal combustion engine 10. In addition, the control device 70 refers to the pressure Pex of the exhaust gas flowing into the GPF 34 detected by the exhaust pressure sensor 88, and the air-fuel ratio AFf detected by the air-fuel ratio sensor 89 on the upstream side of the three-way catalyst 32. In addition, the control device 70 refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52, and the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54 in order to control the control amount of the first motor generator 52 and the second motor generator 54.

[0035] The control device 70 includes a CPU 72 (processor), a ROM 74, a storage device 75, and a peripheral circuit 76. The CPU 72, the ROM 74, the storage device 75, and the peripheral circuit 76 can communicate via a communication line 78. Here, the peripheral circuit 76 includes a circuit for generating a clock signal for defining internal operations, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control amount by the CPU 72 executing a program stored in the ROM 74.

[0036] Figure 2 The following shows the procedure of processing executed by the control device 70 according to the present embodiment. Figure 2 The processing shown is realized by the CPU 72 repeatedly executing, for example, a program stored in the ROM 74 in a predetermined cycle. In the following, the step number of each process is represented by a number with "S" added at the beginning.

[0037] exist Figure 2 In the series of processing shown, the CPU 72 first obtains the engine rotation speed NE, the charging efficiency η and the water temperature THW (S10). The engine rotation speed NE is calculated by the CPU 72 based on the output signal Scr. In addition, the charging efficiency η is calculated by the CPU 72 based on the intake air amount Ga and the engine rotation speed NE.

[0038] Then, the CPU 72 calculates the update amount ΔDPM of the accumulation amount DPM based on the engine rotation speed NE, the charging efficiency η and the water temperature THW (S12). Here, the accumulation amount DPM is the amount of PM trapped by the GPF 34. In detail, the CPU 72 calculates the amount of PM in the exhaust gas discharged to the exhaust passage 30 based on the engine rotation speed NE, the charging efficiency η and the water temperature THW. In addition, the CPU 72 calculates the temperature of the GPF 34 based on the engine rotation speed NE and the charging efficiency η. Then, the CPU 72 calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and / or the temperature of the GPF 34.

[0039] Then, the CPU 72 updates the deposition amount DPM based on the update amount ΔDPM ( S14 ).

[0040] Then, the CPU 72 determines whether the flag F is "1" (S16). If the flag F is "1", it indicates that the temperature raising process for removing the PM in the GPF 34 by combustion is being executed, and if the flag F is "0", it indicates that it is not.

[0041] When the CPU 72 determines that the flag F is "0" (S16: NO), it determines whether the deposition amount DPM is equal to or greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value at which the amount of PM trapped by the GPF 34 increases and PM removal is desired.

[0042] When the CPU 72 determines that the accumulation amount DPM is greater than the regeneration execution value DPMH (S18: Yes), it determines whether the execution condition of the temperature increase process is satisfied (S20). Here, the execution condition is, for example, a condition in which the logical AND of the following conditions (A) and (B) is true. In other words, the execution condition satisfies both conditions (A) and (B).

[0043] Condition (A): The internal combustion engine torque command value Te*, which is a command value of the torque to the internal combustion engine 10, is equal to or greater than a predetermined value Teth.

[0044] Condition (B): The engine rotation speed NE of the internal combustion engine 10 is equal to or higher than a predetermined speed.

[0045] When the CPU 72 determines that the execution condition of the temperature increase process is satisfied (S20: YES), the CPU 72 executes the temperature increase process and substitutes "1" into the flag F (S22). As the temperature increase process, the CPU 72 executes a partial cylinder fuel cut process.

[0046] The partial cylinder fuel cut process is a process of stopping the fuel supply to a part of the cylinders among the plurality of cylinders and performing the fuel supply to the remaining cylinders other than the part of the cylinders. The partial cylinder fuel cut process includes a stop process and an increase process.

[0047] The stop process is a process of stopping the fuel supply to the cylinder #1 by stopping the fuel injection from the port injection valve 16 and the in-cylinder injection valve 22 of the cylinder #1. In addition, hereinafter, the cylinder that implements the stop process is referred to as the fuel cut cylinder, and the remaining cylinders other than the fuel cut cylinder, that is, the cylinders to which fuel is supplied to perform the combustion of the mixture, are referred to as combustion cylinders. In addition, in the present embodiment, the above-mentioned stop process is performed once per one combustion cycle.

[0048] The increase process is a process that increases the amount of air and fuel supplied to each combustion cylinder of cylinder #2, cylinder #3, and cylinder #4 compared to when the above-mentioned stop process is not executed in order to supply unburned fuel to the exhaust system and compensate for the reduction in the output of the internal combustion engine accompanying the above-mentioned stop process. When the increase process is executed, the amount of intake air of the combustion cylinder is increased by adjusting the opening of the throttle valve 14. In addition, when the increase process is executed, the amount of fuel injection injected from the port injection valve 16 and / or the in-cylinder injection valve 22 is increased so that the air-fuel ratio of the mixture in the combustion cylinder is richer than the theoretical air-fuel ratio.

[0049] This partial cylinder fuel cut process is a process for increasing the temperature of GPF 34 by discharging oxygen and unburned fuel into the exhaust passage 30, thereby removing PM trapped by GPF 34 through combustion. That is, by discharging oxygen and unburned fuel into the exhaust passage 30, the unburned fuel is burned in the three-way catalyst 32 to increase the temperature of the exhaust gas, thereby increasing the temperature of GPF 34. In addition, by supplying oxygen to GPF 34, PM trapped by GPF 34 can be removed through combustion.

[0050] On the other hand, in the process of S16, when the CPU 72 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 set to a value at which the amount of PM trapped by the GPF 34 becomes small enough to stop the temperature increase process. When the CPU 72 determines that the accumulation amount DPM is less than the stop threshold DPML (S26: Yes), it stops the temperature increase process by stopping the execution of the partial cylinder fuel cut process and substitutes "0" for the flag F (S28).

[0051] When the CPU 72 completes the processing of S22 and S28 and makes a negative determination in the processing of S18 and S20, the CPU 72 once terminates the processing. Figure 2 A series of processing is shown.

[0052] Figure 3 The following is a diagram showing the sequence of the misfire detection process executed by the control device 70 . Figure 3The processing shown is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined cycle, for example.

[0053] exist Figure 3 In the series of processing shown, the CPU 72 first obtains the time T30 required for the crankshaft 26 to rotate 30° CA (S30). The time T30 is calculated by the CPU 72 by measuring the time required for the crankshaft 24 to rotate 30° CA based on the output signal Scr.

[0054] Then, the CPU 72 sets m=0, 1, 2, 3, ..., substitutes the time T30[m] into the time T30[m+1], substitutes the time T30 newly acquired in the process of S30 into the time T30[0], and stores them in the storage device 75 (S32). The process of S32 is a process for making the variable in the brackets after the time T30 become a larger number as the time goes by. When the value of the variable in the brackets is increased by 1 by this process, the time T30 is the time T30 counted before 30° CA.

[0055] Then, the CPU 72 determines whether the current rotation angle of the crankshaft 26 is ATDC 150°CA based on the compression top dead center of any one of the cylinders #1 to #4 (S34).

[0056] When the CPU 72 determines that the current rotation angle of the crankshaft 26 is ATDC150°CA based on the compression top dead center of any one of the cylinders #1 to #4 (S34: Yes), it determines whether the combustion control is executed in the cylinder determined to be ATDC150°CA, that is, whether the fuel injection and ignition for burning the air-fuel mixture are executed (S36). In other words, the CPU 72 determines whether the determination target cylinder is a cylinder whose combustion control is stopped due to the above-mentioned regeneration process, that is, it is not a fuel cut cylinder.

[0057] When the CPU 72 determines that the combustion control is executed (S36: Yes), it regards one of the above cylinders as a determination target for the presence or absence of misfire, and calculates the rotational variation ΔT30[0] of the cylinder as the determination target (S38). Specifically, the CPU 72 subtracts the time T30[4] from the latest time T30[0]. Here, T30[4] is the time required for the cylinder as the determination target to rotate 30°CA from TDC. Therefore, when misfire does not occur, the time T30[0] is smaller than the time T30[4], so the rotational variation ΔT30[0] is negative. On the other hand, when misfire occurs, the rotational variation ΔT30[0] is positive.

[0058] Then, CPU72 determines whether the rotational variation ΔT30[0] is greater than the variation threshold Δth (S40). This process is to determine whether misfire has occurred in the cylinder that is the subject of determination. For example, CPU72 can variably set the variation threshold Δth according to the engine rotation speed NE and the filling efficiency η. However, the parameters that determine the variation threshold Δth are not limited to variables representing the load such as the filling efficiency η and the engine rotation speed NE. The parameters that determine the variation threshold Δth can also be, for example, the sum of the past rotational variation ΔT30 and a predetermined value. Here, the past rotational variation ΔT30 is the amount in the cylinder that is an integer multiple of 360° past the timing of the occurrence of the compression top dead center and the combustion control has not been stopped. In addition, the predetermined value at this time can also be variably set according to the variable representing the load and / or the engine rotation speed NE.

[0059] When the CPU 72 determines that the rotation variation ΔT30[0] is equal to or greater than the variation threshold Δth (S40: YES), it determines that a misfire has occurred and detects the misfire (S42). Then, the CPU 72 increases (adds 1) the misfire counter Cmf (S44).

[0060] When the CPU 72 completes the processing of S44 and makes a negative determination in the processing of S34, S36, and S40, the CPU 72 once terminates the processing of S44. Figure 3 A series of processing is shown.

[0061] Figure 4 The following shows the procedure of the misfire rate calculation process executed by the control device 70 . Figure 4 The processing shown is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined cycle, for example.

[0062] exist Figure 4 In the series of processes shown, CPU72 first determines whether one of cylinders #1 to #4 is at the compression top dead center (S50). When CPU72 determines that one of cylinders #1 to #4 is at the compression top dead center (S50: Yes), it determines whether the combustion control is stopped in the cylinder #1 to #4 due to the regeneration process (S52). In other words, CPU72 determines whether the fuel cut-off process is being performed in the cylinder. In other words, CPU72 determines whether the stop process of the combustion control is being performed. Then, when CPU72 determines that the combustion control is being performed (S52: No), it increases the effective count Ce (S54). The value of the effective count Ce represents the number of times the combustion control is performed, that is, the number of times fuel injection and ignition are performed in the cylinder to burn the mixture. Then, CPU72 determines whether the effective count Ce is greater than the specified value Ceth (S56).

[0063] When the CPU 72 determines that the effective count Ce is equal to or greater than the predetermined value Ceth ( S56 : Yes), it now acquires the current misfire count Cmf ( S58 ).

[0064] Then, the CPU 72 calculates the misfire rate Cr (S60). The misfire rate Cr is a value indicating the ratio of the number of misfires detected in the misfire detection process to the number of times the combustion control is executed in each cylinder, and in the present embodiment, is a value obtained by dividing the value of the misfire count Cmf obtained in S58 by the value of the effective count Ce at the time when the affirmative determination is made in S56 (Cr = Cmf / Ce).

[0065] Then, the CPU 72 sets the determination threshold value Crth ( S62 ).

[0066] The determination threshold Crth is a value for determining whether the three-way catalyst 32 has become overheated due to the occurrence of misfire during the execution of the temperature increase process. Regarding the determination threshold Crth, the lowest value of the misfire rate at which the three-way catalyst 32 may become overheated in such a state is set based on the engine rotation speed NE and the charging efficiency η indicating the load of the internal combustion engine 10. In addition, the higher the internal combustion engine rotation speed NE is or the larger the value of the charging efficiency η is, the higher the temperature of the exhaust gas is, so the three-way catalyst 32 is likely to become overheated. Therefore, in the present embodiment, the value of the determination threshold Crth is changed to be smaller as the internal combustion engine rotation speed NE is higher or the value of the charging efficiency η is larger, but for greater simplicity, the determination threshold Crth may also be a fixed value.

[0067] After setting the determination threshold Crth in this way, the CPU 72 determines whether the misfire rate Cr obtained in S60 is greater than or equal to the determination threshold Crth (S64). The determination process in S64 is a process for determining whether the number of misfires detected in the above-mentioned misfire detection process among the number of times the combustion control is executed in each cylinder is greater than or equal to a predetermined value Sth. In addition, the predetermined value Sth can be appropriately set to a value greater than "1".

[0068] Then, when it is determined that the misfire rate Cr is equal to or higher than the determination threshold value Crth (S64: YES), the CPU 72 determines whether the current flag F is "1", that is, whether the temperature increase process is being executed (S66).

[0069] Then, when it is determined that the current flag F is "1" (S66: Yes), the CPU72 executes a reduction process (S68) to reduce the temperature increase of the three-way catalyst 32. As the reduction process, the CPU72 executes a process to stop the temperature increase process. That is, the CPU72 executes a process to stop the execution of the partial cylinder fuel cut-off process. If the execution of the partial cylinder fuel cut-off process is stopped in this way, the stop of the fuel supply to the fuel cut-off cylinder is stopped and the fuel supply to the fuel cut-off cylinder is started. At the start of the fuel supply, the fuel injection amount is adjusted so that the air-fuel ratio of the mixture of the cylinder that previously became the fuel cut-off cylinder becomes a chemical equivalent ratio. In addition, if the execution of the partial cylinder fuel cut-off process is stopped, the increase in the amount of air and the amount of fuel supplied to the combustion cylinder is stopped, and the fuel injection amount is reduced so that the air-fuel ratio of the mixture of the combustion cylinder becomes a chemical equivalent ratio or slightly lean.

[0070] On the other hand, when it is determined in the process of S64 that the misfire rate Cr is less than the determination threshold value Crth (S64: No), and when it is determined in the process of S66 that the flag F is not "1" (S66: No), CPU72 initializes the misfire count Cmf, the effective count Ce and the misfire rate Cr (S70).

[0071] When the CPU 72 completes the processing of S68 and S70, makes a negative determination in the processing of S50 and S56, and makes a positive determination in the processing of S52, the CPU 72 once terminates the processing. Figure 4 A series of processing is shown.

[0072] Next, the operation and effects of this embodiment will be described.

[0073] (1) When the misfire rate Cr is equal to or higher than the judgment threshold Crth ( Figure 4 S64: Yes), when the number of misfires is greater than a predetermined value, the above-mentioned reduction process is executed ( Figure 4 The temperature rise amount of the three-way catalyst 32 is reduced by performing S68. Therefore, it is possible to suppress the overheating of the three-way catalyst 32 when misfire occurs.

[0074] (2) As the above-mentioned reduction process, a process of terminating the above-mentioned temperature increase process is executed. The process of terminating the temperature increase process is a process of terminating the stop of the fuel supply to the fuel cut-off cylinder and starting the fuel supply to the fuel cut-off cylinder. If the fuel supply to the fuel cut-off cylinder to which the fuel supply is stopped is started in this way, the combustion of the air-fuel mixture in the cylinder is started. Therefore, the amount of air in the exhaust gas discharged from the cylinder is reduced. Therefore, although the unburned fuel supplied to the three-way catalyst 32 increases due to the occurrence of misfire, the amount of air supplied to the three-way catalyst 32 is reduced. Therefore, the overheating of the three-way catalyst 32 can be suppressed.

[0075] (3) As the above-mentioned reduction process, a process of stopping the above-mentioned temperature increase process is performed. The process of stopping the temperature increase process is a process of reducing the amount of fuel supplied to the combustion cylinder. If the amount of fuel supplied to the combustion cylinder is reduced in this way, the amount of unburned fuel in the exhaust gas discharged from the combustion cylinder is reduced. Therefore, although the unburned fuel supplied to the three-way catalyst 32 increases due to the occurrence of misfire, the amount of unburned fuel supplied to the three-way catalyst 32 is reduced. Therefore, it is possible to suppress the overheating of the three-way catalyst 32.

[0076] (4) When the accumulation amount DPM is greater than the threshold value DPMth, the CPU 72 performs a temperature increase process. As a result, the air sucked in during the intake stroke of the cylinder #1 is not supplied for combustion but flows out to the exhaust passage during the exhaust stroke of the cylinder #1. In addition, the mixed gas of the cylinders #2 to #4 becomes richer than the theoretical air-fuel ratio, so a large amount of unburned fuel is included in the exhaust gas discharged from the cylinders #2 to #4 to the exhaust passage 30. The oxygen and unburned fuel discharged to the exhaust passage 30 are supplied for combustion at the three-way catalyst 32 and the like, thereby increasing the temperature of the GPF 34. In addition, the oxygen in the air flowing out to the exhaust passage 30 oxidizes the PM in the GPF 34. As a result, the PM can be removed by combustion.

[0077] <Second embodiment>

[0078] Hereinafter, the second embodiment will be described focusing on the differences from the first embodiment.

[0079] Figure 5 The following shows the processing sequence of this embodiment. Figure 5 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Figure 5 For convenience, Figure 4 The same step numbers are given to corresponding processes shown.

[0080] exist Figure 5 In the series of processes shown, the CPU 72 sequentially executes the processes from S50 to S66 described above.

[0081] Then, when it is determined in the process of S66 that the flag F is "1" (S66: Yes), the CPU 72 executes a reduction process (S68a) to reduce the temperature increase amount of the three-way catalyst 32. As the reduction process, the CPU 72 executes a process of stopping the stop of the fuel supply to the fuel cut cylinder and starting the fuel supply to the fuel cut cylinder. At the start of the fuel supply, the fuel injection amount is adjusted so that the air-fuel ratio of the mixture of the cylinder that has previously become the fuel cut cylinder becomes the chemical equivalent ratio.

[0082] Then, when the CPU 72 completes the processing of S68a and S70, when a negative determination is made in the processing of S50 and S56, and when a positive determination is made in the processing of S52, the CPU 72 once ends the processing. Figure 5 A series of processing is shown.

[0083] Thus, in this embodiment, as the reduction process in S68a, the fuel supply to the fuel cut cylinder is stopped and the fuel supply to the fuel cut cylinder is started. Therefore, even if misfire occurs during the execution of the temperature increase process, effects other than the above (3) can be obtained.

[0084] <Third embodiment>

[0085] Hereinafter, the third embodiment will be described focusing on the differences from the first embodiment.

[0086] Figure 6 The following shows the processing sequence of this embodiment. Figure 6 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Figure 6 For convenience, Figure 4 The same step numbers are given to corresponding processes shown.

[0087] exist Figure 6 In the series of processes shown, the CPU 72 sequentially executes the processes from S50 to S66 described above.

[0088] Then, when it is determined in the process of S66 that the flag F is "1" (S66: Yes), the CPU 72 executes a reduction process (S68b) to reduce the temperature increase amount of the three-way catalyst 32. As this reduction process, the CPU 72 executes a process to reduce the fuel supply amount to the combustion cylinder. In other words, the CPU 72 stops increasing the amount of air and fuel supplied to the combustion cylinder and reduces the amount of fuel injection so that the air-fuel ratio of the mixture in the combustion cylinder becomes a chemical equivalent ratio or slightly lean.

[0089] Then, when the CPU 72 completes the processing of S68b and S70, when a negative determination is made in the processing of S50 and S56, and when a positive determination is made in the processing of S52, the CPU 72 once ends the processing. Figure 6 A series of processing is shown.

[0090] Thus, in the present embodiment, as the reduction process in S68b, a process of reducing the amount of fuel supplied to the combustion cylinder is performed. Therefore, even if misfire occurs during the execution of the temperature increase process, effects other than the above (2) can be obtained.

[0091] <Fourth embodiment>

[0092] Hereinafter, the fourth embodiment will be described focusing on the differences from the first embodiment.

[0093] Figure 7 The following shows the processing sequence of this embodiment. Figure 7 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Figure 7 For convenience, Figure 4 The same step numbers are given to corresponding processes shown.

[0094] exist Figure 7 In the series of processes shown, the CPU 72 sequentially executes the processes from S50 to S66 described above.

[0095] Then, when it is determined in the process of S66 that the flag F is "1" (S66: Yes), the CPU 72 executes a reduction process (S68c) to reduce the temperature increase of the three-way catalyst 32. As the reduction process, the CPU 72 executes a process to reduce the execution frequency of the above-mentioned stop process. In other words, a process is executed to reduce the number of cylinders to which fuel supply is stopped within a predetermined period when the temperature increase process is executed. For example, in the present embodiment, a process is executed to change the repetition period of the combustion cycle in which the above-mentioned stop process is executed once from every 1 combustion cycle to every 2 combustion cycles. In addition, the changed repetition period may also be a period other than "every 2 combustion cycles".

[0096] Then, when the CPU 72 completes the processing of S68c and S70, when a negative determination is made in the processing of S50 and S56, and when a positive determination is made in the processing of S52, the CPU 72 once ends the processing. Figure 7 A series of processing is shown.

[0097] Thus, in the present embodiment, as the reduction process in the above-mentioned S68c, a process of reducing the number of cylinders to which fuel supply is stopped within a predetermined period when the temperature increase process is executed is performed. Therefore, the amount of air supplied to the three-way catalyst 32 within the predetermined period is reduced. Therefore, although the unburned fuel supplied to the three-way catalyst 32 increases due to the occurrence of misfire, the amount of air supplied to the three-way catalyst 32 is reduced. Therefore, the overheating of the three-way catalyst 32 can be suppressed. Therefore, in the present embodiment as well, the same effects as those of the above-mentioned second embodiment can be obtained.

[0098] In addition, each of the above-mentioned embodiments can be implemented by changing as follows. Each of the embodiments and the following modified examples can be implemented in combination with each other within the range that there is no technical contradiction.

[0099] In the reduction process, in order to reduce the amount of air supplied to the three-way catalyst 32, the fuel supply to the fuel cut cylinder is stopped and the fuel supply to the fuel cut cylinder is started, but the amount of air supplied to the three-way catalyst 32 may be reduced in other ways. Such examples are shown below in (A) and (B).

[0100] (A) When the fuel supply to the fuel cut cylinder is started by the reduction process, the fuel supply amount to the cylinder that becomes the fuel cut cylinder may be adjusted so that the air-fuel ratio of the mixture of the cylinder becomes lean. In this case, the amount of air in the exhaust gas discharged from the cylinder becomes larger than the case where the air-fuel ratio of the mixture of the fuel cut cylinder that starts the fuel supply is made the chemical equivalent ratio. Therefore, the temperature increase effect of the three-way catalyst 32 can be obtained to a certain extent. Therefore, the temperature increase of the three-way catalyst 32 can be implemented while suppressing the overheating of the three-way catalyst 32. In addition, in the case of this modified example, it is desirable to perform the reduction process in such a way that the temperature increase amount of the three-way catalyst 32 is smaller as the amount of unburned fuel supplied to the three-way catalyst 32 is larger. For example, the larger the difference between the misfire rate Cr and the determination threshold Crth, the smaller the leanness of the air-fuel ratio is and the smaller the amount of air supplied to the three-way catalyst 32 is.

[0101] (B) The throttle opening may be reduced to reduce the intake air amount. This may be realized, for example, by reducing the required output Pe* of the internal combustion engine 10 or reducing the upper limit protection value of the required output Pe*. In addition, such a reduction in the required output Pe* may be compensated by the output of the above-mentioned electric generator.

[0102] In the reduction process, in order to reduce the amount of fuel supplied to the combustion cylinder, the amount of fuel injection is reduced so that the air-fuel ratio of the mixture in the combustion cylinder becomes a chemical equivalent ratio or slightly lean, but the amount of fuel supplied can also be reduced in other ways. Such examples are shown below in (C) to (E).

[0103] (C) When the reduction process is executed, the degree of richness when the temperature increase process is executed may be reduced so that the air-fuel ratio of the mixture is rich while the amount of fuel supplied to the combustion cylinder is reduced. In addition, in the case of this modified example, it is also desirable to execute the reduction process in such a manner that the amount of temperature increase of the three-way catalyst 32 decreases as the amount of unburned fuel supplied to the three-way catalyst 32 increases. For example, the greater the difference between the misfire rate Cr and the determination threshold Crth, the greater the degree of richness of the air-fuel ratio is, and the less the amount of unburned fuel supplied to the three-way catalyst 32 is.

[0104] (D) The amount of intake air may be reduced by reducing the throttle opening, thereby reducing the amount of fuel injection. This may be realized, for example, by reducing the required output Pe* of the internal combustion engine 10 or reducing the upper limit protection value of the required output Pe*. In addition, such a reduction in the required output Pe* may be compensated by the output of the above-mentioned motor generator.

[0105] (E) When executing the above-mentioned increment processing such as the increment at startup, the increment at warm-up, and the increment at recovery, these increment values ​​may be reduced. In addition, these increment values ​​gradually decay with the passage of time and / or the increase in the temperature of the internal combustion engine, and such decay speed may be accelerated.

[0106] The overheating of the three-way catalyst 32 due to the increase of unburned fuel may occur due to reasons other than misfire, for example, when the temperature of the internal combustion engine 10 is low. Here, the control device 70 may execute the following process to suppress the overheating of the three-way catalyst 32 when the internal combustion engine is low temperature.

[0107] Figure 8 The following shows the sequence of processing executed by the control device 70 . Figure 8 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Figure 8 For convenience, Figure 4 The same step numbers are given to corresponding processes shown.

[0108] exist Figure 8 In the series of processing shown, the CPU 72 first determines whether the internal combustion engine 10 is in an operating state with increased unburned fuel (S80). In this S80, the CPU 72 determines that the internal combustion engine 10 is in an operating state with increased unburned fuel when any one of the following conditions (a) to (f) shown as an example is satisfied.

[0109] (a) The cooling water temperature of the internal combustion engine 10 detected by the sensor is equal to or lower than a predetermined value.

[0110] (b) The oil temperature of the internal combustion engine 10 detected by the sensor is equal to or lower than a predetermined value.

[0111] (c) The time elapsed after the internal combustion engine was started is equal to or less than a prescribed value.

[0112] (d) The most recent internal combustion engine stop time is equal to or longer than a prescribed value.

[0113] (e) The time elapsed from the fuel cut recovery is less than a prescribed value.

[0114] (f) The fuel cut execution time most recently is equal to or longer than a prescribed value.

[0115] It should be noted that the above-mentioned respective predetermined values ​​are appropriate values ​​set for determining that the internal combustion engine 10 is in an operating state where the amount of unburned fuel increases.

[0116] Then, when it is determined that the internal combustion engine 10 is in an operating state where the unburned fuel increases (S80: Yes), the CPU 72 determines whether the flag F is "1", that is, whether the temperature increase process is being performed (S82). Then, when it is determined that the flag F is "1" (S82: Yes), the CPU 72 performs the above-mentioned process of S68, that is, the above-mentioned reduction process, and once ends this process. In addition, as the reduction process, the above-mentioned process of S68a, the process of S68b, and / or the process of S68c may also be performed.

[0117] If the CPU 72 makes a negative determination in the processing of S80 and S82, the CPU 72 ends the processing of S80 and S82. Figure 8 A series of processing is shown.

[0118] According to such a modification, it is possible to suppress an overheating of the three-way catalyst 32 when the engine temperature is low.

[0119] If unburned fuel increases when misfire occurs and / or when the engine is cold, the air-fuel ratio AFf becomes richer than the stoichiometric air-fuel ratio. Here, the control device 70 may execute the following processing to suppress overheating of the three-way catalyst 32 due to the increase in unburned fuel.

[0120] Fig. 9 The following shows the sequence of processing executed by the control device 70 . Fig. 9 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Fig. 9 For convenience, Figure 8 The same step numbers are given to corresponding processes shown.

[0121] exist Fig. 9In the series of processes shown, the CPU 72 first determines whether the current air-fuel ratio AFf is less than the prescribed value AFfref (S90). That is, the CPU 72 determines whether the current air-fuel ratio AFf is the same as the prescribed value AFfref or a value richer than the prescribed value AFfref. The prescribed value AFfref is a value richer than the theoretical air-fuel ratio, and is a value used to determine whether the three-way catalyst 32 is overheated when the temperature increase process is performed without performing the reduction process. For example, as the prescribed value AFfref, the air-fuel ratio AFf in the case where the unburned fuel is supplied to the three-way catalyst 32 in an amount obtained by subtracting the maximum amount of unburned fuel supplied to the three-way catalyst 32 when the temperature increase process is performed from the minimum amount of unburned fuel in which the three-way catalyst 32 is likely to be overheated can be set. Then, when the air-fuel ratio AFf is less than the prescribed value AFfref, it is determined that the three-way catalyst 32 is likely to be overheated when the temperature increase process is performed without performing the reduction process.

[0122] When the CPU 72 determines that the air-fuel ratio AFf is less than or equal to the predetermined value AFfref (S90: Yes), it then determines whether the flag F is "1", that is, whether the temperature increase process is being performed (S82). Then, when it is determined that the flag F is "1" (S82: Yes), the CPU 72 performs the process of S68, that is, the above-mentioned reduction process, and ends the present process. In addition, as the reduction process, the above-mentioned process of S68a, the process of S68b, and / or the process of S68c may be performed.

[0123] If the CPU 72 makes a negative determination in the processing of S90 or S82, the CPU 72 ends the processing of S90 or S82. Fig. 9 A series of processing is shown.

[0124] According to such a modification, it is possible to suppress an over-temperature increase of the three-way catalyst 32 due to an increase in unburned fuel.

[0125] In order to suppress the overheating of the three-way catalyst 32, the control device 70 may execute the following processing.

[0126] Fig.10 The following shows the sequence of processing executed by the control device 70 . Fig.10 The processing shown is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined cycle, for example.

[0127] exist Fig.10In the series of processes shown, the CPU 72 first determines whether the increment value is less than a predetermined value α (S100). The increment value is the sum of the increment correction values ​​of the fuel injection amount obtained by the process other than the temperature increase process, for example, the sum of various increment values ​​such as the increment at startup, the warm-up increment, and the recovery increment. In addition, the predetermined value α is a value used to determine whether the three-way catalyst 32 is overheated when such various increment corrections and temperature increase processes are performed. For example, as the predetermined value α, a value obtained by subtracting the maximum amount of unburned fuel supplied to the three-way catalyst 32 when the temperature increase process is performed from the minimum amount of unburned fuel at which the three-way catalyst 32 is likely to be overheated can be set.

[0128] Then, when it is determined that the increase value is smaller than the predetermined value α (S100: YES), the CPU 72 permits execution of the temperature increase process (S102) and ends the present process once because the unburned fuel amount is sufficient to suppress overheating of the three-way catalyst 32 even if the temperature increase process is executed.

[0129] On the other hand, when it is determined that the increase value is greater than the specified value α (S100: No), if the temperature increase process is executed, the amount of unburned fuel may exceed the amount causing the three-way catalyst 32 to overheat, so the CPU 72 prohibits the execution of the temperature increase process (S104) and ends the present process.

[0130] According to such a modification, it is possible to suppress the overheating of the three-way catalyst 32 caused by the increase of unburned fuel. In addition, in the case where the execution of the temperature increase process is changed from prohibition to permission in this modification, the temperature increase amount of the temperature increase process may be gradually increased. In this case, it is possible to suppress the surge in the amount of air and fuel supplied to the three-way catalyst 32, so it is possible to more appropriately suppress the overheating of the three-way catalyst 32.

[0131] In addition, the process of S100 in this modified example is changed to the process of S90 described above. Then, if a negative determination is made in the process of S90, the process of S102 may be executed, and if a positive determination is made in the process of S90, the process of S104 may be executed. In this case, the same effect can be obtained.

[0132] In the misfire detection process, the rotation variation ΔT30 is set to a value obtained by subtracting the time T30[4] required for rotation in the interval of TDC to 30ATDC from the time T30[0] required for rotation in the interval of 120ATDC to 150ATDC, but the present invention is not limited thereto. For example, the rotation variation ΔT30 may be set to a value obtained by subtracting the time T30 required for rotation in the interval of TDC to 30ATDC of the cylinder that is the target of misfire determination from the time T30 required for rotation in the interval of TDC to 30ATDC of the cylinder that is the previous compression top dead center.

[0133] In the misfire detection process, the amount of change in the rotation speed of the crankshaft 26 in the rotation angle interval below the compression top dead center occurrence interval, i.e., the rotational variation, is quantified based on the difference between the times required for rotation in the rotation angle interval, but the present invention is not limited to this and may be quantified based on a ratio.

[0134] In the misfire detection process, the amount of change in rotation speed, that is, the amount of rotation change, is quantified by time, but the present invention is not limited thereto and may be quantified by angular velocity.

[0135] In the misfire detection process, misfire is detected based on the variation in the rotation speed of the crankshaft 26. In addition to this, for example, a cylinder pressure sensor is provided to detect the pressure in the combustion chamber 20 and misfire is detected based on the behavior of the detection value, or the axial torque of the crankshaft 26 is calculated or detected and misfire is detected based on the behavior of the axial torque.

[0136] ·exist Figure 3 In the misfire detection process shown, the process of S42 may be omitted, and when an affirmative determination is made in S40 , the process of S44 may be subsequently executed.

[0137] The predetermined conditions for allowing the execution of the temperature increase treatment are not limited to those exemplified in the above embodiment. For example, only one of the above two conditions (A) and (B) may be included. In addition, the predetermined conditions may also include conditions other than the above two conditions.

[0138] In the increase process, in order to compensate for the decrease in the output of the internal combustion engine accompanying the stop process, the amount of air and the amount of fuel supplied to the combustion chamber 20 when the combustion control of the air-fuel mixture in the cylinders other than the fuel cut cylinder is executed is increased compared to when the stop process is not executed. In addition, in the case where the decrease in the output of the internal combustion engine accompanying the stop process can be compensated by the output of the motor generator described above, for example, only the amount of fuel may be increased in the increase process.

[0139] The process for executing the partial cylinder fuel cut-off process is not limited to the above-mentioned regeneration process. For example, it may be a process for stopping the supply of fuel to a part of the cylinders in order to adjust the output of the internal combustion engine 10. In addition, for example, it may be a process for stopping the combustion control in a part of the cylinders when an abnormality occurs in the cylinders. In addition, for example, it may be a process for stopping the combustion control of only a part of the cylinders when the oxygen storage amount of the three-way catalyst 32 is below a specified value and executing a control process for making the air-fuel ratio of the mixture in the remaining cylinders become the theoretical air-fuel ratio.

[0140] · As the estimation process of the accumulation amount DPM, it is not limited to Figure 2As shown in the example. For example, the accumulation amount DPM can also be estimated based on the pressure difference between the upstream side and the downstream side of GPF34 and the intake air amount Ga. Specifically, when the pressure difference is large, the accumulation amount DPM is estimated to be a larger value than when the pressure difference is small; even if the pressure difference is the same, when the intake air amount Ga is small, the accumulation amount DPM is estimated to be a larger value than when the intake air amount Ga is large. Here, when the pressure on the downstream side of GPF34 is regarded as a constant value, the above-mentioned pressure Pex can be used instead of the pressure difference.

[0141] When the above-mentioned partial cylinder fuel cut-off process is executed, the number of cylinders for which combustion control is stopped is "1", but the number of cylinders for which combustion control is stopped can be appropriately changed with "the number of cylinders - 1" as the maximum value. In addition, the cylinders for which combustion control is stopped do not need to be fixed to a predetermined cylinder. For example, the cylinders for which combustion control is stopped may be changed for each combustion cycle.

[0142] · The GPF 34 is not limited to a filter carrying a three-way catalyst, but may be only a filter. In addition, the GPF 34 is not limited to being disposed downstream of the three-way catalyst 32 in the exhaust passage 30. In addition, the three-way catalyst 32 may be replaced by an oxidation catalyst that oxidizes the components contained in the exhaust gas. In addition, the exhaust purification device does not necessarily have the GPF 34. For example, even in the case where the exhaust purification device is composed of only the three-way catalyst 32, when oxygen is supplied to the three-way catalyst 32 whose oxygen storage amount becomes less than a specified value by stopping combustion control in a part of the cylinders, it is also effective to perform the processing illustrated in the above-mentioned embodiments and these modified examples.

[0143] ·The control device 70 is not limited to a device having a CPU 72 and a ROM 74 to execute software processing. For example, it may also have a dedicated hardware circuit such as an ASIC that performs hardware processing on at least a part of the software processing performed in the above-mentioned embodiment. That is, the control device 70 only needs to be configured as any one of the following (a) to (c). (a) A processing device that executes all the above-mentioned processing in accordance with a program and a program storage device such as a ROM that stores the program. (b) A processing device and a program storage device that execute a part of the above-mentioned processing in accordance with a program, as well as a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all the above-mentioned processing. Here, there may be multiple software execution devices and dedicated hardware circuits having a processing device and a program storage device.

[0144] 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. However, it is not limited to a hybrid vehicle, and may be, for example, a vehicle in which the power generation device of the vehicle is only the internal combustion engine 10 .

Claims

1. A control device for an internal combustion engine, the internal combustion engine having a catalyst for purifying exhaust gas in an exhaust passage and having a plurality of cylinders, The control device of the internal combustion engine is configured to execute: a temperature raising process of stopping the supply of fuel to some of the plurality of cylinders and performing the supply of fuel to the remaining cylinders other than the some of the cylinders, thereby raising the temperature of the catalyst; Misfire detection processing to detect misfires; a determination process of determining whether the number of misfires detected by the misfire detection process among the number of times combustion control is executed in each cylinder is equal to or greater than a predetermined value; as well as The reduction process reduces the amount of temperature increase of the catalyst when the number of misfires is equal to or greater than the predetermined value, compared to when the number of misfires is less than the predetermined value.

2. The control device for an internal combustion engine according to claim 1, wherein: The reduction process includes terminating the stop of the fuel supply to the part of the cylinders and starting the fuel supply to the part of the cylinders.

3. The control device for an internal combustion engine according to claim 2, wherein: The reduction process includes adjusting the amount of fuel supplied to the cylinders so that the air-fuel ratio of the mixture of the part of cylinders to start the fuel supply becomes leaner than the theoretical air-fuel ratio.

4. The control device for an internal combustion engine according to claim 1, wherein: The reduction process includes reducing the number of cylinders to which fuel supply is stopped for a predetermined period while the temperature raising process is being executed.

5. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein: The reduction process includes reducing the amount of fuel supplied to the remaining cylinders.

6. A method of controlling an internal combustion engine, the internal combustion engine having a catalyst for purifying exhaust gas in an exhaust passage and having a plurality of cylinders, The method includes: stopping fuel supply to some of the plurality of cylinders and performing fuel supply to the remaining cylinders other than the some of the cylinders, thereby raising the temperature of the catalyst; The test does not fire; determining whether the number of misfires detected among the number of times combustion control is executed in each cylinder is equal to or greater than a predetermined value; as well as When the number of misfires is equal to or greater than the predetermined value, the amount of temperature increase of the catalyst is reduced compared to when the number of misfires is less than the predetermined value.

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