JP2024065320A - Control device for internal combustion engine - Google Patents

Abstract

[Problem] To suppress an increase in the amount of particulate matter emitted from an internal combustion engine due to temperature rise control. [Solution] A control device (70) executes temperature rise control to increase the temperature of a GPF (34) provided in an exhaust passage (30) by increasing the engine load. Conditions for allowing the execution of temperature rise control include the temperature of the piston top surface of an internal combustion engine (10) being equal to or higher than a predetermined judgment value. [Selected Figure] Figure 1

Description

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

For example, the internal combustion engine described in Patent Document 1 has a filter, which is an exhaust purification member, in the exhaust passage. When the amount of particulate matter trapped in the filter reaches or exceeds a threshold value, temperature control is performed to increase the temperature of the filter.

JP 2022-77242 A

One type of temperature rise control is to increase the exhaust temperature by increasing the load on the internal combustion engine. However, depending on the state of the internal combustion engine, the amount of particulate matter emitted from the combustion chamber may increase due to an increase in the fuel injection amount when the load on the internal combustion engine increases. In this case, for example, the amount of particulate matter captured by the exhaust purification member may increase.

The control device for an internal combustion engine that solves the above problem is a control device for an internal combustion engine that executes temperature rise control to raise the temperature of an exhaust purification member provided in an exhaust passage by increasing the engine load. The conditions for allowing the execution of the temperature rise control include the temperature of the piston top surface of the internal combustion engine being equal to or higher than a predetermined judgment value.

When the temperature of the piston top surface is low, the amount of particulate matter emitted from the combustion chamber tends to increase due to reasons such as fuel touching the piston top surface not vaporizing and burning incompletely. In consideration of this, in this configuration, temperature rise control is executed when the temperature of the piston top surface is equal to or higher than a predetermined judgment value. Therefore, since temperature rise control is not executed when the temperature of the piston top surface is low, it is possible to suppress an increase in particulate matter emissions due to the execution of temperature rise control.

1 is a schematic diagram showing a configuration of an internal combustion engine, a drive system, and a control device according to an embodiment; 4 is a flowchart showing a procedure of a piston temperature calculation 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.

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

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). In this embodiment, the GPF 34 is assumed to be a filter that collects PM and supports a three-way catalyst. The three-way catalyst and the GPF are exhaust purification members that purify the exhaust gas.

The crankshaft 26 is mechanically connected to the carrier C of the planetary gear mechanism 50 that constitutes the power split device. The rotating shaft 52a of the first motor generator 52 is mechanically 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 wheels 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 the inverter 56. In addition, an AC voltage is applied to the terminals of the second motor generator 54 by the inverter 58.

The control device 70 controls the internal combustion engine 10, and operates the operating parts of the internal combustion engine 10, such as the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, and spark plug 24, to control the torque and exhaust component ratio as the controlled variables. The control device 70 also controls the first motor generator 52, and operates the inverter 56 to control the rotation speed, which is the controlled variable. The control device 70 also controls the second motor generator 54, and operates the inverter 58 to control the torque, which is the controlled variable. Figure 1 shows the operation signals MS1 to MS6 of the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, spark plug 24, and inverters 56 and 58.

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 in order to control the control amount of the internal combustion engine 10. The control device 70 also refers to the coolant temperature THW, which is the temperature of the coolant of the internal combustion engine 10 detected by the water temperature sensor 86, and the air-fuel ratio AF, which is detected by the air-fuel ratio sensor 88. The control device 70 also refers to the output signal Sp of the output side rotation angle sensor 89, which detects the rotation angle of the ring gear R. The control device 70 also refers to the output signal Sm1 of the first rotation angle sensor 90, which detects the rotation angle of the first motor generator 52, in order to control the control amount of the first motor generator 52. The control device 70 also refers to the output signal Sm2 of the second rotation angle sensor 92, which detects the rotation angle of the second motor generator 54, in order to control the control amount of the second motor generator 54. 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 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 speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current amount of air flowing into the cylinder to the amount of air flowing into the cylinder when the internal combustion engine 10 is operating steadily under full load. The amount of air flowing into the cylinder is the amount of air flowing into each cylinder during the intake stroke. The control device 70 also calculates the vehicle speed SP of the vehicle equipped with the internal combustion engine 10 based on the output signal Sp of the output side rotation angle sensor 89.

The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and peripheral circuits 76, which are capable of communicating with each other via a communication line 78. Here, the peripheral circuits 76 include a circuit that generates a clock signal that regulates the internal operation, a power supply circuit, a reset circuit, etc. 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 performs fuel injection control of the port injection valve 16 and the in-cylinder injection valve 22. The control device 70 also performs ignition timing control of the spark plug 24. The control device 70 also performs air-fuel ratio control to control the air-fuel ratio of the mixture to a target air-fuel ratio AFt that is set based on the engine operating state. The control device 70 also calculates the required torque required for the vehicle 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 motor generator 52 and the second motor generator 54 to satisfy the required torque of the vehicle.

The control device 70 also calculates the deposition amount DPM, which is the amount of particulate matter trapped in the GPF 34, based on the engine speed NE, the charging efficiency η, the cooling water temperature THW, and the like. It then determines whether the deposition amount DPM is equal to or greater than the regeneration execution value DPMH. The regeneration execution value DPMH is set to a value at which the amount of particulate matter trapped by the GPF 34 is large and it is desired to remove the particulate matter. If it is determined that the deposition amount DPM is equal to or greater than the regeneration execution value DPMH, the control device 70 makes a temperature increase request to request the execution of temperature increase control to remove the trapped particulate matter from the GPF 34. If the conditions permitting the execution of temperature increase control are met, the control device 70 executes temperature increase control.

<Calculating the piston top temperature>
The control device 70 calculates a piston top temperature THp, which is the temperature of the piston top surface of the internal combustion engine 10 .

Figure 2 shows the process for calculating the piston top temperature THp. The process shown in Figure 2 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

In the series of processes shown in FIG. 2, the CPU 72 first obtains the cooling water temperature THW, the intake air amount GA, and the ignition timing AOP (S100).
Next, the CPU 72 calculates a base temperature THpb, which is a basic value of the piston top temperature THp, based on the cooling water temperature THW (S110). In the process of S110, the CPU 72 calculates the base temperature THpb using a map or model formula prepared in advance.

Next, the CPU 72 calculates a temperature correction value THh based on the intake air amount GA and the ignition timing AOP (S120). The temperature correction value THh is a value for correcting the deviation between the base temperature THpb and the actual piston top surface temperature. In the process of S120, the CPU 72 calculates the temperature correction value THh using a map or model formula prepared in advance.

Next, the CPU 72 calculates the piston top temperature THp (S130). In the process of S130, the CPU 72 assigns the value obtained by adding the temperature correction value THh to the base temperature THpb to the piston top temperature THp.

Then, the CPU 72 temporarily ends this process.
<Regarding the process for determining whether or not to execute temperature rise control>
The control device 70 judges whether or not the conditions for permitting execution of the above-mentioned temperature rise control are satisfied. If the conditions for permitting execution are satisfied, the control device 70 executes the temperature rise control. The procedure for judging whether or not the temperature rise control can be executed is shown in Fig. 3. The process shown in Fig. 3 is also realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined interval.

In the series of processes shown in FIG. 3, the CPU 72 determines whether or not there is a request to increase the temperature of the GPF 34 described above (S200). If the CPU 72 determines that there is a request to increase the temperature of the GPF 34 (S200: YES), it acquires the piston top surface temperature THp (S210).

Next, the CPU 72 determines whether the piston top surface temperature THp is equal to or greater than a predetermined judgment value THpref (S220). The judgment value THpref is the lowest piston top surface temperature THp that can suppress an increase in particulate matter emissions due to the execution of temperature rise control, and is preset.

If the processing of S220 determines that the piston top surface temperature THp is equal to or higher than the judgment value THpre (S220: YES), the CPU 72 obtains the current target air-fuel ratio AFt (S230).

Next, the CPU 72 determines whether the target air-fuel ratio AFt is equal to or greater than a preset reference value AFtref (S240). The reference value AFtref is the minimum air-fuel ratio value (e.g., 14.0) that can suppress an increase in particulate matter emissions due to an increase in unburned fuel, and is preset.

When it is determined in the process of S240 that the target air-fuel ratio AFt is equal to or greater than the predetermined reference value AFtref (S240: YES), the CPU 72 executes temperature rise control (S250). As temperature rise control, the CPU 72 performs a process of increasing the exhaust temperature by, for example, retarding the ignition timing, and an increase process of increasing the engine load to compensate for the decrease in engine output due to the retardation of the ignition timing. As temperature rise control, the CPU 72 performs a process of decreasing the output torque of the first motor generator 52 and the second motor generator 54, while increasing the required output Pe of the internal combustion engine 10 to compensate for the decrease in torque. All of these processes are processes of increasing the engine load to increase the temperature of the exhaust purification member provided in the exhaust passage.

When the above-mentioned S220 processing makes a negative judgment, or when the above-mentioned S240 processing makes a negative judgment, the CPU 72 performs reduction control (S260). Reduction control is a process for reducing the number and amount of particulate matter discharged from the combustion chamber 20 of the internal combustion engine 10. As reduction control, the CPU 72, for example, prohibits retardation of the ignition timing. When retardation of the ignition timing is prohibited in this way, the process for increasing the engine load to compensate for the decrease in engine output due to the retardation is not performed. As reduction control, the CPU 72, for example, performs a process for increasing the output torque of the first motor generator 52 and the second motor generator 54 while decreasing the required output Pe of the internal combustion engine 10 by the amount of the increase in torque. All of these processes are processes for reducing the particulate matter discharged from the combustion chamber 20 through control of the engine load.

If a negative determination is made in the process of S200, or after the process of S250 or the process of S260 is executed, the CPU 72 ends this process.
<Action and Effects>
The operation and effects of this embodiment will be described.

(1) When the temperature of the piston top surface is low, the amount of particulate matter discharged from the combustion chamber 20 tends to increase due to reasons such as fuel touching the piston top surface not vaporizing and burning incompletely. In consideration of this point, in this embodiment, the piston top surface temperature THp, which is the temperature of the piston top surface, is calculated based on the cooling water temperature THW, the intake air amount GA, and the ignition timing AOP. The conditions for allowing the execution of the temperature rise control include that the temperature of the piston top surface of the internal combustion engine 10 is equal to or higher than a predetermined judgment value THpref. Therefore, when the piston top surface temperature THp is equal to or higher than the judgment value THpref, the temperature rise control is executed (S220: YES in FIG. 3). Therefore, since the temperature rise control is not executed when the temperature of the piston top surface is low, it is possible to suppress an increase in the amount of particulate matter emitted due to the execution of the temperature rise control.

(2) When the air-fuel ratio of the mixture is rich, the amount of particulate matter emitted from the combustion chamber 20 tends to increase due to the increase in unburned fuel during combustion. In consideration of this point, in this embodiment, the conditions for allowing the execution of temperature rise control include the target air-fuel ratio AFt of the mixture being equal to or greater than a predetermined judgment value AFtref. Therefore, when the target air-fuel ratio AFt is equal to or greater than the judgment value AFtref and there is little unburned fuel, temperature rise control is executed (S240: YES in FIG. 3). Therefore, by executing temperature rise control when there is a lot of unburned fuel during combustion, it is possible to suppress an increase in the amount of particulate matter emissions.

(3) When the temperature of the piston top surface is lower than the predetermined judgment value THpref, the amount of particulate matter discharged from the combustion chamber 20 tends to increase. Also, when the target air-fuel ratio of the mixture is smaller than the predetermined judgment value AFtref, the amount of particulate matter discharged from the combustion chamber 20 tends to increase. In this regard, in this embodiment, when the conditions for allowing the execution of the temperature increase control are not met, reduction control is executed to reduce the particulate matter discharged from the combustion chamber 20. In other words, reduction control is executed when the piston top surface temperature THp is lower than the judgment value THpref or when the target air-fuel ratio AFt is smaller than the judgment value AFtref. Therefore, it is possible to suppress an increase in the amount of particulate matter discharged from the combustion chamber 20.

The above embodiment can be modified as follows. The above embodiment and the following modified examples can be combined together to the extent that no technical contradiction exists.

The piston top temperature THp may be calculated in a different manner or may be detected by a sensor or the like.
The processes of S230 and S240 shown in Fig. 3 may be omitted. Even in this case, the same effects and advantages as those described above in (2) can be obtained.

The process of S260 shown in Fig. 3 may be omitted. Even in this case, the effects and advantages other than the above item (3) can be obtained.
The temperature increase control is performed to remove the particulate matter trapped in the GPF 34, but may be performed for another purpose. For example, the temperature increase control may be performed to warm up the catalyst.

The temperature rise control performed in the process of S250 shown in FIG. 3 may include the following processes (a) and (b) and the control (c), as appropriate.
(a) A process of introducing unburned fuel into an exhaust gas purification member by injecting fuel during a fuel cut.

(b) A process for stopping fuel supply to some of the cylinders of the internal combustion engine 10 and supplying fuel to the remaining cylinders. Note that the air-fuel ratio in the cylinders to which fuel is supplied at this time is made richer than the theoretical air-fuel ratio.

(c) Dither control in which some of the cylinders are set as rich cylinders and the remaining cylinders are set as lean cylinders. In rich cylinders, combustion occurs at an air-fuel ratio lower than the theoretical air-fuel ratio. In lean cylinders, combustion occurs at an air-fuel ratio higher than the theoretical air-fuel ratio.

The GPF 34 is not limited to a filter carrying a three-way catalyst, but may be a filter only. Also, the GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30.

The control device is not limited to a device equipped with a CPU 72 and a ROM 74 and executing software processing. For example, it may be equipped with a dedicated hardware circuit such as an ASIC that performs hardware processing of at least a portion of what was processed by software in the above embodiment. That is, the control device may have any of the following configurations (a) to (c). (a) It includes 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) It includes a processing device and program storage device that executes a portion of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with a processing device and program storage device, and multiple dedicated hardware circuits.

The vehicle is not limited to a series-parallel hybrid vehicle, but may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle, and may be, for example, a vehicle whose prime mover is only an internal combustion engine 10.

Reference Signs List 10 internal combustion engine 12 intake passage 12a intake port 14 throttle valve 16 port injection valve 18 intake valve 20 combustion chamber 22 in-cylinder injection valve 24 spark plug 26 crankshaft 28 exhaust valve 30 exhaust passage 32 three-way catalyst 34 GPF
Reference Signs List 50: Planetary gear mechanism 52: First motor generator 52a: Rotating shaft 54: Second motor generator 54a: Rotating shaft 56: Inverter 58: Inverter 60: Drive wheels 70: Control device 72: CPU
74...ROM

Claims (4)

A control device for an internal combustion engine in which a temperature rise control is performed to raise a temperature of an exhaust purification member provided in an exhaust passage by increasing an engine load,
A control device for an internal combustion engine, wherein a condition for permitting execution of the temperature increase control includes a temperature of a piston top surface of the internal combustion engine being equal to or higher than a predetermined judgment value. The control device for an internal combustion engine according to claim 1 , wherein the condition for permitting execution of the temperature increase control includes a target air-fuel ratio of the mixture being equal to or greater than a predetermined judgment value. 3. The control device for an internal combustion engine according to claim 1, further comprising a process for calculating the temperature of the piston top surface based on a cooling water temperature, an intake air amount, and an ignition timing. 3. The control device for an internal combustion engine according to claim 1, further comprising: a control for reducing particulate matter emitted from a combustion chamber when the condition for permitting execution of the temperature increase control is not satisfied.

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