JP7768095B2 - Control device for internal combustion engine - Google Patents

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, an exhaust purification member, installed in the exhaust passage. When the amount of particulate matter trapped on the filter exceeds a threshold, temperature control is performed to raise the temperature of the filter.

Japanese Patent Application Laid-Open No. 2022-77242

One type of temperature rise control involves increasing the load on the internal combustion engine to raise the temperature of the exhaust gas. However, depending on the state of the internal combustion engine, an increase in the amount of fuel injected when the load on the internal combustion engine increases may increase the amount of particulate matter emitted from the combustion chamber. In this case, for example, there is a possibility that the amount of particulate matter trapped in the exhaust purification component may increase.

A 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 increase the engine load to raise the temperature of an exhaust purification element provided in an exhaust passage and remove the particulate matter from the exhaust purification element when the amount of deposition, which is the amount of particulate matter trapped in the element, is equal to or greater than a regeneration execution value.The control device executes a process to calculate the temperature of a piston top surface of the internal combustion engine based on a coolant temperature, an intake air amount, and an ignition timing , and includes, as a condition for permitting execution of the temperature rise control, a condition that the temperature of the piston top surface of the internal combustion engine is equal to or greater 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 factors such as fuel that comes into contact with the piston top surface not vaporizing and burning incompletely. In consideration of this, this configuration executes temperature rise control 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 prevent an increase in particulate matter emissions due to the execution of temperature rise control.

1 is a schematic diagram showing the configuration of an internal combustion engine, a drive system, and a control device according to an embodiment. 4 is a flowchart showing the 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 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 located downstream of the intake passage 12, is provided in the intake port 12a. 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. The air-fuel mixture 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 rotational energy of a crankshaft 26.

When the exhaust valve 28 opens, the air-fuel mixture burned in the combustion chamber 20 is discharged as exhaust gas into the exhaust passage 30. 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 traps PM and supports a three-way catalyst. The three-way catalyst and GPF are exhaust purification components that purify the exhaust gas.

The crankshaft 26 is mechanically connected to the carrier C of the planetary gear mechanism 50, which 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. 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 an inverter 56. An AC voltage is applied to the terminals of the second motor-generator 54 by an inverter 58.

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

To control the control variables of the internal combustion engine 10, the control device 70 references the intake air volume GA detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82. The control device 70 also references the coolant temperature THW, which is the temperature of the coolant for 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 references the output signal Sp of the output side rotational angle sensor 89, which detects the rotational angle of the ring gear R. To control the control variables of the first motor-generator 52, the control device 70 also references the output signal Sm1 of the first rotational angle sensor 90, which detects the rotational angle of the first motor-generator 52. To control the control variables of the second motor-generator 54, the control device 70 also references the output signal Sm2 of the second rotational angle sensor 92, which detects the rotational angle of the second motor-generator 54. The control device 70 also references the accelerator pedal depression amount ACCP, which is the amount of accelerator pedal depression 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, ROM 74, storage device 75, and peripheral circuits 76, which are capable of communicating via a communication line 78. Here, the peripheral circuits 76 include circuits that generate clock signals that regulate internal operation, power supply circuits, reset circuits, etc. The control device 70 controls the control variables by having the CPU 72 execute programs stored in the ROM 74.

For example, the control device 70 controls the fuel injection of the port injection valves 16 and the in-cylinder injection valves 22. The control device 70 also controls the ignition timing of the spark plugs 24. The control device 70 also controls the air-fuel ratio to maintain the air-fuel ratio of the mixture at a target air-fuel ratio AFt, which is set based on the engine operating state. The control device 70 also calculates the required torque required for vehicle travel based on the accelerator depression amount ACCP and the vehicle speed SP. The control device 70 also controls the required output power 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, charging efficiency η, coolant temperature THW, and other factors. 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 has increased and it is desirable to remove the particulate matter. If it determines that the deposition amount DPM is equal to or greater than the regeneration execution value DPMH, the control device 70 issues a temperature increase request, which requests 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.

<Process for calculating the temperature of the piston top surface>
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 processing procedure for calculating the piston top temperature THp. The processing shown in Figure 2 is realized by the CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined interval. Note that, below, the step number of each process will be represented by a number preceded by an "S."

In the series of processes shown in FIG. 2, the CPU 72 first obtains the coolant 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 used to correct the deviation between the base temperature THpb and the actual piston top surface temperature. In the processing of S120, the CPU 72 calculates the temperature correction value THh using a pre-prepared map or model formula.

Next, the CPU 72 calculates the piston top temperature THp (S130). In the processing of S130, the CPU 72 adds the temperature correction value THh to the base temperature THpb and assigns the result 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 determines whether the conditions for permitting execution of the temperature rise control described above are met. If the conditions for permitting execution are met, the control device 70 executes the temperature rise control. The processing procedure for determining whether or not to execute the temperature rise control is shown in Figure 3. The processing shown in Figure 3 is also implemented 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 there is a request to increase the temperature of the GPF 34 (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 reference value THpref (S220). The reference value THpref is the lowest piston top surface temperature THp at which an increase in particulate matter emissions due to the execution of temperature rise control can be suppressed, and is set in advance.

If the processing of S220 determines that the piston top surface temperature THp is equal to or greater than the determination 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 predetermined reference value AFtref (S240). The reference value AFtref is a preset 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.

If the CPU 72 determines in S240 that the target air-fuel ratio AFt is equal to or greater than the predetermined reference value AFtref (S240: YES), it executes temperature rise control (S250). As temperature rise control, the CPU 72 performs, for example, a process to increase the exhaust gas temperature by retarding the ignition timing, and an increase process to increase the engine load to compensate for the reduction in engine output due to the ignition timing retard. Furthermore, as temperature rise control, the CPU 72 performs, for example, a process to reduce the output torque of the first motor-generator 52 and the second motor-generator 54, while increasing the required output power Pe of the internal combustion engine 10 to compensate for the torque reduction. Both of these processes increase the engine load to increase the temperature of the exhaust purification components provided in the exhaust passage.

If the processing of S220 above returns a negative determination, or if the processing of S240 above returns a negative determination, the CPU 72 performs reduction control (S260). Reduction control is a process for reducing the number and amount of particulate matter emitted from the combustion chambers 20 of the internal combustion engine 10. As reduction control, the CPU 72, for example, prohibits retarding the ignition timing. When retarding the ignition timing is prohibited in this manner, the process for increasing the engine load to compensate for the reduction in engine output due to the retard is no longer performed. Furthermore, 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 reducing the required output Pe of the internal combustion engine 10 by the amount of that torque increase. Both of these processes are processes for reducing particulate matter emitted from the combustion chambers 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 effect>
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 emitted from the combustion chamber 20 tends to increase due to reasons such as fuel in contact with the piston top surface not vaporizing and burning incompletely. In consideration of this, in this embodiment, the piston top surface temperature THp, which is the temperature of the piston top surface, is calculated based on the coolant temperature THW, the intake air amount GA, and the ignition timing AOP. The conditions for permitting the execution of temperature rise control include the temperature of the piston top surface of the internal combustion engine 10 being equal to or greater than a predetermined reference value THpref. Therefore, temperature rise control is executed when the piston top surface temperature THp is equal to or greater than the reference value THpref (S220: YES in Figure 3). Therefore, because temperature rise control is not executed when the piston top surface temperature is low, an increase in particulate matter emissions due to the execution of temperature rise control can be suppressed.

(2) When the air-fuel ratio of the air-fuel mixture is rich, the amount of unburned fuel during combustion increases, which tends to increase the amount of particulate matter emitted from the combustion chamber 20. In consideration of this, 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 reference value AFtref. Therefore, when the target air-fuel ratio AFt is equal to or greater than the reference value AFtref and there is little unburned fuel, temperature rise control is executed (S240: YES in Figure 3). Therefore, by executing temperature rise control when there is a lot of unburned fuel during combustion, it is possible to prevent an increase in particulate matter emissions.

(3) When the piston top surface temperature is lower than the predetermined judgment value THpref, the amount of particulate matter emitted from the combustion chamber 20 tends to increase. Furthermore, when the target air-fuel ratio of the mixture is lower than the predetermined judgment value AFtref, the amount of particulate matter emitted from the combustion chamber 20 also tends to increase. In this regard, in this embodiment, when the conditions for allowing the execution of temperature increase control are not met, reduction control is executed to reduce the particulate matter emitted 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 lower than the judgment value AFtref. Therefore, an increase in the amount of particulate matter emitted from the combustion chamber 20 can be suppressed.

The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

The piston top surface temperature THp may be calculated in a different manner or 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 effects and advantages other than those of (2) above can be obtained.

The process of S260 shown in Fig. 3 may be omitted. Even in this case, the effects and advantages other than those of (3) above can be obtained.
The temperature increase control is performed to remove 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 increase 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 purification member by injecting fuel during a fuel cut.

(b) A process of stopping fuel supply to some of the multiple 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 is made richer than the stoichiometric 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 stoichiometric air-fuel ratio. In lean cylinders, combustion occurs at an air-fuel ratio higher than the stoichiometric air-fuel ratio.

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

The control device is not limited to one equipped with a CPU 72 and 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 on at least a portion of what was software processed in the above embodiments. 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 in accordance with a program, and a program storage device, such as a ROM, that stores the program. (b) A processing device and program storage device that executes part of the above processing in accordance with 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, 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
50... Planetary gear mechanism 52... First motor generator 52a... Rotating shaft 54... Second motor generator 54a... Rotating shaft 56... Inverter 58... Inverter 60... Driving wheel 70... Control device 72... CPU
74...ROM

Claims (3)

A control device for an internal combustion engine, in which, when a deposition amount, which is the amount of particulate matter trapped in an exhaust purification element provided in an exhaust passage, is equal to or greater than a regeneration execution value, a temperature rise control is executed to increase an engine load to raise the temperature of the exhaust purification element and remove the particulate matter from the exhaust purification element ,
Execute a process of calculating a temperature of a piston top surface of the internal combustion engine based on a cooling water temperature, an intake air amount, and an ignition timing;
The control device for an internal combustion engine, wherein a condition for permitting execution of the temperature increase control includes a condition that the temperature of the piston top surface is equal to or higher than a predetermined judgment value. The control device for an internal combustion engine according to claim 1, wherein the conditions for permitting execution of the temperature increase control include a condition that a target air-fuel ratio of the air-fuel mixture is equal to or greater than a predetermined judgment value. 3. The control device for an internal combustion engine according to claim 1, wherein when the condition for permitting execution of the temperature increase control is not satisfied, reduction control is executed to reduce particulate matter emitted from the combustion chamber.