JP2024050159A - Control device for internal combustion engine - Google Patents

Abstract

[Problem] To suppress deterioration of a catalyst while suppressing deterioration of fuel efficiency. [Solution] A control device (70) executes a deterioration determination process to determine whether or not a three-way catalyst (32) has deteriorated, a stop process to stop fuel injection when the engine rotation speed falls below a determination value when there is a stop request to stop operation of an internal combustion engine (10), and a change process to reduce the determination value for determining the engine rotation speed when it is determined that the three-way catalyst (32) has deteriorated compared to when it is determined that the three-way catalyst (32) has not deteriorated. [Selected Figure] Figure 1

Description

The present invention relates to a control device for an internal combustion engine.

When the operation of an internal combustion engine is stopped, oxygen is supplied to the catalyst between the time when fuel injection is stopped and the time when the crankshaft stops rotating, which may cause the catalyst to deteriorate. Therefore, for example, in the internal combustion engine described in Patent Document 1, even in a situation where there is no demand for output from the internal combustion engine and the operation of the internal combustion engine can be stopped, fuel injection in the internal combustion engine is continued to burn the mixture. In this way, when the combustion of the mixture continues, the supply of oxygen to the catalyst is suppressed, and deterioration of the catalyst is suppressed.

JP 2013-163393 A

However, in the internal combustion engine described in Patent Document 1, even in situations where the operation of the internal combustion engine can be stopped, fuel injection in the internal combustion engine continues to burn the mixture in order to prevent deterioration of the catalyst, which results in a deterioration of fuel efficiency.

The control device for an internal combustion engine that solves the above problem is a control device for an internal combustion engine that has a catalyst in an exhaust passage. This control device executes a deterioration determination process that determines whether or not the catalyst has deteriorated, a stop process that stops fuel injection in the internal combustion engine when the engine speed of the internal combustion engine falls below a determination value when there is a stop request to stop the operation of the internal combustion engine, and a change process that reduces the determination value when it is determined that the catalyst has deteriorated compared to when it is determined that the catalyst has not deteriorated.

According to this configuration, when it is determined that the catalyst has deteriorated, the engine speed at which fuel injection is stopped is lower than when it is determined that the catalyst has not deteriorated, and the time between when fuel injection is stopped and when the crankshaft stops rotating is shorter. Therefore, the amount of oxygen supplied to the catalyst between when fuel injection is stopped and when the crankshaft stops rotating is reduced. Therefore, by stopping fuel injection, it is possible to suppress deterioration of the catalyst while suppressing deterioration of fuel economy.

1 is a diagram showing a configuration of a drive system and a control device for a vehicle according to an embodiment; 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. 4 is a timing chart showing the operation of the embodiment, in which Fig. 4(A) shows the accelerator operation amount, Fig. 4(B) shows the engine rotation speed, Fig. 4(C) shows the direct injection flag, Fig. 4(D) shows the stop execution flag, and Fig. 4(E) shows the first MG torque over time.

Hereinafter, a specific embodiment of a control device for an internal combustion engine will be described.
<Configuration of vehicle equipped with internal combustion engine and control device>
As shown in FIG. 1, an internal combustion engine 10 mounted on a vehicle VC includes, for example, four cylinders #1 to #4.

A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10. A port injection valve 16 that injects fuel into the intake port 12a, which is the downstream portion of the intake passage 12, is provided. This port injection valve 16 is a fuel injection valve that supplies fuel to the cylinders of the internal combustion engine 10.

Air drawn into the intake passage 12 and fuel injected from the port injection valve 16 flow into the combustion chamber 20 when the intake valve 18 opens, and are supplied to each cylinder. Fuel is also directly injected into the combustion chamber 20 from the in-cylinder injection valve 22. This in-cylinder injection valve 22 is also a fuel injection valve that supplies fuel to the cylinders of the internal combustion engine 10. The mixture of air and fuel in the combustion chamber 20 is combusted with the spark discharge of the ignition device 24. The combustion energy generated at that time is converted into the rotational energy of the crankshaft 26.

The air-fuel mixture burned in the combustion chamber 20 is discharged as exhaust gas into the exhaust passage 30 when the exhaust valve 28 opens. The exhaust passage 30 is provided with a three-way catalyst 32 with oxygen storage capacity and a gasoline particulate filter (GPF 34). The GPF 34 is a filter that collects PM and is supported by a three-way catalyst.

The crankshaft 26 is mechanically connected to the carrier C of the planetary gear mechanism 50 that constitutes the power split device. The sun gear S of the planetary gear mechanism 50 is mechanically connected to the rotating shaft 52a of the first motor generator 52 (hereinafter referred to as the first MG 52). In addition, the ring gear R of the planetary gear mechanism 50 is mechanically connected to the rotating shaft 54a of the second motor generator 54 (hereinafter referred to as the second MG 54) and the drive wheels 60.

The first MG 52 functions as a generator that generates electricity using the engine output, and also functions as a starting starter (electric motor) that cranks the crankshaft 26 when starting the internal combustion engine 10. This first MG 52 is a motor that can apply torque to the crankshaft 26.

The second MG 54 functions as an electric motor that generates driving force for the drive wheels 60, and also functions as a generator that generates electricity through regenerative braking when the vehicle VC is decelerating.
An AC voltage is applied to the terminals of the first MG 52 by a first inverter 56. Also, an AC voltage is applied to the terminals of the second MG 54 by a second inverter 58. Both the first inverter 56 and the second inverter 58 are power conversion circuits that convert the terminal voltage of a battery 59, which serves as a DC voltage source, into an AC voltage and output it.

The control device 70 operates the operating 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 ignition device 24, in order to control the torque, exhaust gas component ratio, and other control variables of the internal combustion engine 10 as the controlled object.

The control device 70 also operates the first inverter 56 to control the torque, which is the control variable of the first MG 52, which is the control object. The control device 70 also operates the second inverter 58 to control the torque, which is the control variable of the second MG 54, which is the control object.

Figure 1 shows the operation signals MS1 to MS6 of the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the ignition device 24, the first inverter 56, and the second inverter 58.

In order to control the control amount of the internal combustion engine 10, the control device 70 refers to the intake air amount GA detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82. The control device 70 also refers to the water temperature THW detected by the water temperature sensor 84 and the output signal Sp of the output side rotation angle sensor 86 that detects the rotation angle of the ring gear R. The control device 70 also refers to the temperature Tb of the battery 59 detected by the temperature sensor 87, the charge/discharge current I of the battery 59 detected by the current sensor 88, and the terminal voltage Vb of the battery 59 detected by the voltage sensor 89. In order to control the control amount of the first MG 52, the control device 70 also refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first MG 52. The control device 70 calculates the first rotation speed Nmg1, which is the rotation speed of the rotating shaft 52a of the first MG 52, based on the output signal Sm1. In addition, the control device 70 refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second MG 54 in order to control the control amount of the second MG 54. The control device 70 calculates the second rotation speed Nmg2, which is the rotation speed of the rotary shaft 54a of the second MG 54, based on the output signal Sm2. The control device 70 also refers to the accelerator operation amount ACCP, which is the amount of depression of the accelerator pedal detected by the accelerator sensor 94. The control device 70 calculates the engine rotation speed NE based on the output signal Scr of the crank angle sensor 82. The control device 70 also calculates the engine load factor KL based on the engine rotation speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is operated steadily under a full load state. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

The control device 70 includes a CPU 72, a ROM 74, a peripheral circuit 76, and a communication line 78. The CPU 72, the ROM 74, and the peripheral circuit 76 are capable of communicating with each other via the communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal that regulates 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.

For example, the control device 70 calculates the required torque required for the vehicle VC to travel based on the accelerator operation amount ACCP and the vehicle speed SP. The control device 70 also controls the required output Pe of the internal combustion engine 10 and the output torque of the first MG 52 and the second MG 54 to satisfy the required torque of the vehicle VC.

Furthermore, when the required output Pe becomes "0", the control device 70 automatically stops the operation of the internal combustion engine 10 if there is a request to stop the operation of the internal combustion engine 10, and performs intermittent operation to automatically start the internal combustion engine 10 when the required output Pe becomes greater than "0". Examples of when the required output Pe becomes "0" include when the accelerator operation amount ACCP becomes "0" or when the required torque of the vehicle VC can be satisfied by the output torque of the second MG 54 alone. Examples of when the required output Pe becomes greater than "0" include when the required torque of the vehicle VC can no longer be satisfied by the output torque of the second MG 54 alone.

<Processing Executed by the Control Device>
Fig. 2 shows the procedure of the process executed by the control device 70. The process shown in Fig. 2 is started when the required output Pe of the internal combustion engine 10 becomes "0" and a stop request is generated to stop the operation of the internal combustion engine 10. Note that, hereinafter, the step number of each process is represented by a number preceded by "S".

In the series of processes shown in FIG. 2, first, the control device 70 judges whether the current catalyst temperature Tc1 is equal to or higher than the threshold value Tc1ref (S100). The catalyst temperature Tc1 is the temperature of the three-way catalyst 32, and is calculated by the control device 70 based on the engine rotation speed NE, the engine load factor KL, the vehicle speed SP, etc. The threshold value Tc1ref is, for example, the minimum temperature at which the deterioration of the three-way catalyst 32 progresses. The process of S100 is a process for judging whether the three-way catalyst 32 is in a state where deterioration is likely to progress. When the catalyst temperature Tc1 is equal to or higher than the threshold value Tc1ref and the three-way catalyst 32 is in a state where deterioration is likely to progress, a positive judgment is made, whereas when the catalyst temperature Tc1 is less than the threshold value Tc1ref and the three-way catalyst 32 is in a state where deterioration is unlikely to progress, a negative judgment is made.

If the determination in S100 is positive, the control device 70 determines whether the deterioration level R is equal to or greater than the threshold value Rref (S110). The deterioration level R is a value indicating the degree of deterioration of the three-way catalyst 32. The control device 70 calculates the deterioration level R so that the value of the deterioration level R increases as the accumulated mileage of the vehicle VC increases. Note that the deterioration level R may be calculated based on other parameters. For example, the accumulated value of the amount of heat received by the three-way catalyst 32 may be calculated, and the deterioration level R may be calculated so that the value of the deterioration level R increases as the accumulated value increases.

The threshold value Rref is a preset adaptation value for determining whether or not the three-way catalyst 32 has deteriorated. If the deterioration level R is equal to or greater than the threshold value Rref, it is determined that there is deterioration, whereas if the deterioration level R is less than the threshold value Rref, it is determined that there is no deterioration. In this way, the process of S110 is a deterioration determination process for determining whether or not there is deterioration of the catalyst.

When the determination in S110 is positive, the control device 70 assigns the second speed NEref2, which is the second determination value, to the determination value NEref (S120). When a stop request is issued, the control device 70 executes a stop process to stop fuel injection in the internal combustion engine 10 when the engine speed NE falls below the determination value NEref. The second speed NEref2 is a preset value, and is a rotation speed lower than the first speed NEref1 described below. The process of S120 is a change process that reduces the determination value NEref when it is determined that there is catalyst deterioration compared to when it is determined that there is no catalyst deterioration, and is a process that is performed to suppress catalyst deterioration.

After executing the process of S120, the control device 70 next determines whether the engine rotation speed NE is equal to or lower than a first speed NEref1 (S130).
When it is determined that the engine speed NE exceeds the first speed NEref1 (S130: NO), the control device 70 repeatedly executes the process of S130 until it determines that the engine speed NE is equal to or lower than the first speed NEref1.

If the determination in S130 is affirmative, the control device 70 sets the in-cylinder injection flag Fd to "ON" (S140). When the in-cylinder injection flag Fd is set to "ON", fuel injection is started only from the in-cylinder injection valve 22. Note that when the stop execution flag Fs, which will be described later, becomes "ON", the in-cylinder injection flag Fd is set to "OFF".

If a negative judgment is made in the process of S100 or the process of S110, the control device 70 assigns the first speed NEref1, which is the first judgment value, to the judgment value NEref (S150). The first speed NEref1 is a preset value and is a rotation speed higher than the second speed NEref2.

After performing the process of S140 or the process of S150, the control device 70 next determines whether the current engine speed NE is equal to or lower than a reference value NEref (S160).
When it is determined that the engine speed NE exceeds the reference value NEref (S160: NO), the control device 70 repeatedly executes the process of S160 until it determines that the engine speed NE is equal to or lower than the reference value NEref.

If the determination in the process of S160 is affirmative, the control device 70 sets the stop execution flag Fs to "ON" (S170). Next, the control device 70 executes a stop process (S180). As part of this stop process, the control device 70 executes a process to stop fuel injection into the internal combustion engine 10. Then, this process ends.

Fig. 3 shows the procedure of another process executed by the control device 70. The process shown in Fig. 3 is started when the stop execution flag Fs is set to "ON" in the process of S170 described above, for example.
3, first, the control device 70 determines whether the current catalyst temperature Tc1 is equal to or higher than the threshold value Tc1ref (S200). The process of S200 is the same as the process of S100 described above.

In the process of S200, if it is determined that the catalyst temperature Tc1 is equal to or higher than the threshold value Tc1ref and that the three-way catalyst 32 is in a state where deterioration is likely to progress (S200: YES), the control device 70 determines whether the current vehicle speed SP is equal to or higher than the reference value SPref (S210). The reference value SPref is a vehicle speed at which the increase in vehicle vibration due to the execution of the torque increase process described below can be masked by the vibration caused by the vehicle's running, and is a predetermined suitable value.

If the vehicle speed SP is determined to be equal to or greater than the reference value SPref (S210: YES), the control device 70 substitutes the second torque T2 for the first MG torque Tm1, which is the required value of the output torque of the first MG 52, to control the torque of the first MG 52 (S220). The second torque T2 is a torque that resists the rotation of the crankshaft 26, and has a greater force resisting the rotation of the crankshaft 26 than the first torque T1 described below. The absolute value of the output torque of the first MG 52 indicates the magnitude of the torque. In addition, the output torque of the first MG 52 indicates a torque acting in the same direction as the rotation direction of the crankshaft 26 with a positive value. On the other hand, the output torque of the first MG 52 indicates a torque acting in the opposite direction to the rotation direction of the crankshaft 26, that is, a torque that resists the rotation of the crankshaft 26 with a negative value. Then, when the second torque T2 is substituted for the first MG torque Tm1 in the process of S220, the control device 70 executes a torque application process that controls the torque of the first MG 52 so that the second torque T2 is applied from the first MG 52 to the crankshaft 26. This torque application process is performed to suppress deterioration of the catalyst. The process of S220 corresponds to a torque increase process that increases the torque applied from the motor and resists the rotation of the crankshaft when the catalyst is in a state where deterioration is likely to progress, compared to when the catalyst is in a state where deterioration is unlikely to progress.

If a negative judgment is made in the process of S200 or the process of S210, the control device 70 substitutes the first torque T1 for the first MG torque Tm1 to control the torque of the first MG 52 (S230). The first torque T1 is a preset negative value, and has an absolute value smaller than that of the second torque T2. Then, when the first torque T1 is substituted for the first MG torque Tm1 in the process of S230, the control device 70 executes a torque application process to control the torque of the first MG 52 so that the first torque T1 is applied from the first MG 52 to the crankshaft 26. This torque application process is also performed to suppress deterioration of the catalyst.

After performing the process of S220 or the process of S230, the control device 70 then determines whether the rotation of the crankshaft 26 has stopped based on the current engine speed NE (S240).

If it is determined that the rotation of the crankshaft 26 has not stopped (S240: NO), the control device 70 repeatedly executes the process of S240 until it determines that the rotation of the crankshaft 26 has stopped.

If a positive determination is made in the process of S240, the control device 70 assigns the first required torque T1* to the first MG torque Tm1 and performs torque control of the first MG 52, thereby terminating the torque application process (S250). The first required torque T1* is a value calculated based on the vehicle's driving requirements, etc., and is set to "0" when the vehicle is driven only by the output torque of the second MG 54, for example. The control device 70 then terminates this process.

<Action>
4 shows, by solid lines, the transition of each value when the second speed NEref2 is set as the reference value NEref and the second torque T2 is set to the first MG torque Tm1 in the torque application process. Note that Fig. 4A shows the transition of the accelerator operation amount, Fig. 4B shows the transition of the engine rotation speed, Fig. 4C shows the transition of the direct injection flag, Fig. 4D shows the transition of the stop execution flag, and Fig. 4E shows the transition of the first MG torque.

When the accelerator pedal is released at time t1, the accelerator depression amount ACCP decreases toward "0", and the engine speed NE also decreases.
Then, at time t2, when the engine speed NE drops to a first speed NEref1, the direct injection flag Fd is set to "ON" and fuel injection from only the direct injection valve is started.

Furthermore, at time t3, when the engine speed NE drops to the second speed NEref2, the stop execution flag Fs is set to "ON", and the stop process is executed to end the combustion of the mixture. Also, at time t3, the torque application process is started, and the second torque T2, which has an absolute value greater than the first torque T1, is applied from the first MG 52 to the crankshaft 26. As a result, as shown by the two-dot chain line, the engine speed NE decreases at a faster rate than the rate at which the engine speed NE decreases when the first torque T1 is applied from the first MG 52. Then, at time t4, when the rotation of the crankshaft 26 stops, the torque application process is ended, and the first MG torque Tm1 is changed from the second torque T2 to the first required torque T1* (for example, "0").

＜Effects＞
The effects of this embodiment will be described.
(1) In the process of S110 shown in FIG. 2, when it is determined that the three-way catalyst 32 is deteriorated, the second speed NEref2, which is lower than the first speed NEref1, is set as the above-mentioned determination value NEref. Therefore, when it is determined that the three-way catalyst 32 is deteriorated, the engine rotation speed NE at which fuel injection is stopped is lower than when it is determined that the three-way catalyst 32 is not deteriorated. Therefore, when the second speed NEref2 is set as the determination value NEref, the time from when fuel injection is stopped to when the rotation of the crankshaft 26 stops is shorter by the period from time t2 to time t3 shown in FIG. 4 compared to when the first speed NEref1 is set. Therefore, the amount of oxygen supplied to the three-way catalyst 32 from when fuel injection is stopped to when the rotation of the crankshaft 26 stops is reduced. Therefore, by stopping fuel injection, it is possible to suppress deterioration of the three-way catalyst 32 while suppressing deterioration of fuel efficiency.

(2) When the second speed NEref2 is set as the judgment value NEref, the mixture is burned at lower revolutions than when the first speed NEref1 is set, which makes it easier for fuel economy to deteriorate. Therefore, in this configuration, when it is determined that the three-way catalyst 32 has deteriorated, the second speed NEref2 is set as the judgment value NEref. Therefore, it is possible to suppress deterioration of fuel economy compared to when the second speed NEref2 is set as the judgment value NEref, regardless of whether the three-way catalyst 32 has deteriorated or not.

(3) If the engine speed at which fuel injection is stopped is lowered, the mixture may be insufficiently mixed, which may cause unstable combustion. Here, fuel injection using the in-cylinder injection valve 22 has the characteristic that the combustion is less likely to become unstable due to insufficient mixing of the mixture than fuel injection using the port injection valve 16, and the combustion is stable even at low rotation speeds. Therefore, in this embodiment, when the engine speed NE is between the first speed NEref1 and the second speed NEref2 and the speed range is such that the combustion may become unstable, fuel injection is performed only from the in-cylinder injection valve 22. Therefore, when it is determined that the three-way catalyst 32 has deteriorated, the mixture can be properly combusted even if the engine speed at which fuel injection is stopped is lowered.

(4) After fuel injection in the internal combustion engine 10 is stopped, the torque application process is executed. Therefore, the time from stopping fuel injection to stopping the rotation of the crankshaft 26 is shortened. Therefore, the amount of oxygen supplied to the three-way catalyst 32 during the period from stopping fuel injection to stopping the rotation of the crankshaft 26 is reduced, which also suppresses the deterioration of the three-way catalyst 32. Here, in this embodiment, when it is determined in the process of S200 shown in FIG. 3 that the three-way catalyst 32 is in a state in which deterioration is likely to progress, a second torque T2 larger than the first torque T1 is set as the torque against the rotation of the crankshaft 26. Therefore, when the three-way catalyst 32 is in a state in which deterioration is likely to progress, the torque against the rotation of the crankshaft 26 is increased compared to when the three-way catalyst 32 is in a state in which deterioration is unlikely to progress. Therefore, when the three-way catalyst 32 is in a state in which deterioration is likely to progress, the time from stopping fuel injection to stopping the rotation of the crankshaft 26 is further shortened. Therefore, the amount of oxygen supplied to the three-way catalyst 32 between the time fuel injection is stopped and the time the crankshaft 26 stops rotating is further reduced, which makes it possible to suppress deterioration of the three-way catalyst 32 even in a state in which deterioration of the three-way catalyst 32 is likely to progress.

(5) When the torque increase process described above is performed, the rotational speed of the crankshaft 26 decreases, which may increase vehicle vibration and cause discomfort to vehicle occupants. When the vehicle speed is relatively high, the vibration caused by the vehicle traveling increases, and the increase in vehicle vibration caused by the torque increase process is masked. Therefore, in this embodiment, the torque increase process is performed when the vehicle speed SP is equal to or greater than the predetermined judgment value SPref. Therefore, it is possible to suppress discomfort caused to vehicle occupants by the increase in vehicle vibration caused by the execution of the torque increase process.

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

The processes of S130 and S140 shown in Fig. 2 may be omitted. Even in this case, effects other than the above effect (3) can be obtained.
The process of S210 shown in Fig. 3 may be omitted. Even in this case, effects other than the above (5) can be obtained.

The series of processes shown in Fig. 3 may be omitted. Even in this case, effects other than those of (4) and (5) above can be obtained.
The GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30. Furthermore, it is not essential to provide the GPF 34 in the exhaust passage. The GPF 34 is not limited to being a filter carrying a three-way catalyst. For example, if a three-way catalyst is provided upstream, the GPF 34 may be a filter alone.

The hybrid vehicle is not limited to a series-parallel hybrid vehicle. For example, it may be a parallel hybrid vehicle.
The number of motor generators provided in the vehicle VC may be changed as appropriate.

The series of processes shown in FIG. 2 may be executed in a vehicle that has only an internal combustion engine as a prime mover.
The control device 70 is not limited to a device having a CPU 72 and a ROM 74 and executing software processing. For example, a dedicated hardware circuit such as an ASIC may be provided to perform hardware processing of at least a part of what is processed by software in the above embodiment. That is, the control device may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a ROM that stores the program. (b) A processing device and a program storage device that execute part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, the software execution device having a processing device and a program storage device, and the dedicated hardware circuit may be one or any multiple number.

10: internal combustion engine 16: port injection valve 20: combustion chamber 22: in-cylinder injection valve 26: crankshaft 32: three-way catalyst 34: GPF
50... Planetary gear mechanism 52... First motor generator (first MG)
52a...rotating shaft 54...second motor generator (second MG)
54a: Rotating shaft 56: First inverter 58: Second inverter 59: Battery 60: Driving wheel 70: Control device

Claims (4)

A control device for an internal combustion engine having a catalyst in an exhaust passage,
a deterioration determination process for determining whether or not the catalyst has deteriorated;
a stop process for stopping fuel injection in the internal combustion engine when an engine speed of the internal combustion engine becomes equal to or lower than a determination value when there is a stop request for stopping the operation of the internal combustion engine;
and when it is determined that the catalyst has deteriorated, executing a change process to make the determination value smaller than when it is determined that the catalyst has not deteriorated. the internal combustion engine includes a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that injects fuel into a combustion chamber,
2. The control device for an internal combustion engine according to claim 1, wherein when the judgment value that is set when it is determined that there is no deterioration of the catalyst is a first judgment value, and the judgment value that is set when it is determined that there is deterioration of the catalyst is a second judgment value, and when the engine rotation speed is between the first judgment value and the second judgment value, fuel injection is performed only from the in-cylinder injection valve. a motor capable of applying torque to a crankshaft of the internal combustion engine is connected to the crankshaft;
a torque application process of applying a torque from the motor against the rotation of the crankshaft after stopping fuel injection in the internal combustion engine;
The control device for an internal combustion engine according to claim 1 , further comprising: a torque increasing process for increasing the torque when the catalyst is in a state in which deterioration is likely to progress, compared to when the catalyst is in a state in which deterioration is unlikely to progress. The control device for an internal combustion engine according to claim 3 , wherein the torque increasing process is executed when a vehicle speed of the vehicle mounting the internal combustion engine is equal to or greater than a predetermined determination value.

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