Control device for internal combustion engine

Abstract

To suppress increase in an amount of particulate matter emitted from an internal combustion engine due to temperature rise control.SOLUTION: A control device 70 executes temperature rise control of causing temperature of GPF34 installed in an exhaust passage 30 to rise by increasing engine load. A condition of permitting execution of temperature rise control is that the temperature of a piston-top surface of an internal combustion engine 10 is equal to or higher than a predetermined determination value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] For example, the internal combustion engine described in Patent Document 1 is provided with a filter, which is an exhaust purification member, in an exhaust passage. When the amount of particulate matter trapped on the filter reaches or exceeds a threshold, temperature control is performed to increase the temperature of the filter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-77242 Summary of the Invention [Problem to be solved by the invention]

[0004] One type of temperature increase 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, an increase in the fuel injection amount 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, the amount of particulate matter trapped in the exhaust purification member may increase. [Means for solving the problem]

[0005] The control device for an internal combustion engine that solves the above problem comprises: When the amount of particulate matter trapped in the exhaust gas purification member provided in the exhaust passage is equal to or greater than the regeneration execution value, By increasing the engine load The aforementioned Increase the temperature of the exhaust purification components and remove the particulate matter from the exhaust purification member. The control device for an internal combustion engine in which temperature rise control is executed. 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 conditions for permitting execution of the temperature increase control include the temperature of the piston top surface of the internal combustion engine being equal to or higher than a predetermined judgment value.

[0006] 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 that comes into contact with 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. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing the configuration of an internal combustion engine, a drive system, and a control device according to an embodiment. [Figure 2] 4 is a flowchart showing the procedure of a piston temperature calculation process executed by the control device of the embodiment. [Figure 3] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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 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.

[0009] The air-fuel mixture burned in the combustion chamber 20 is discharged as exhaust gas into an exhaust passage 30 when an exhaust valve 28 opens. A three-way catalyst 32 with oxygen storage capacity and a gasoline particulate filter (GPF 34) are provided in the exhaust passage 30. 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.

[0010] The crankshaft 26 is mechanically connected to a carrier C of a planetary gear mechanism 50 that constitutes a power split device. A rotating shaft 52a of a first motor generator 52 is mechanically connected to a sun gear S of the planetary gear mechanism 50. A rotating shaft 54a of a second motor generator 54 and drive wheels 60 are mechanically connected to a ring gear R of the planetary gear mechanism 50. An AC voltage is applied to terminals of the first motor generator 52 by an inverter 56. An AC voltage is applied to terminals of the second motor generator 54 by an inverter 58.

[0011] The control device 70 controls the internal combustion engine 10, and operates 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, exhaust gas component ratio, and other control 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 control variable. The control device 70 also controls the second motor-generator 54, and operates the inverter 58 to control the torque, which is the control variable. Figure 1 shows 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, 58, respectively.

[0012] The control device 70 references the intake air amount GA detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82 to control the control variable of the internal combustion engine 10. The control device 70 also references a coolant temperature THW, which is the temperature of the coolant for the internal combustion engine 10 detected by a water temperature sensor 86, and an air-fuel ratio AF, which is detected by an air-fuel ratio sensor 88. The control device 70 also references an output signal Sp of an output-side rotation angle sensor 89, which detects the rotation angle of the ring gear R. The control device 70 also references an output signal Sm1 of a first rotation angle sensor 90, which detects the rotation angle of the first motor-generator 52, to control the control variable of the first motor-generator 52. The control device 70 also references an output signal Sm2 of a second rotation angle sensor 92, which detects the rotation angle of the second motor-generator 54, to control the control variable of the second motor-generator 54. The control device 70 also references an accelerator operation amount ACCP, which is the amount of depression of the accelerator pedal, detected by an 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.

[0013] The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and a peripheral circuit 76, which are capable of communicating with each other via a 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, etc. The control device 70 controls the control amount by the CPU 72 executing a program stored in the ROM 74.

[0014] 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 adjust 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 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.

[0015] 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 coolant temperature THW, and the like. Then, it 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 in the GPF 34 is large and it is desirable 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 issues a temperature increase request, which requests the execution of temperature increase control to remove the trapped particulate matter from the GPF 34. Then, if a condition permitting the execution of temperature increase control is met, the control device 70 executes temperature increase control.

[0016] <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.

[0017] Fig. 2 shows the procedure for calculating the piston top surface temperature THp. The process shown in Fig. 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."

[0018] 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 surface temperature THp, based on the coolant 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.

[0019] 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 difference 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 prepared map or model formula.

[0020] Next, the CPU 72 calculates the piston top surface temperature THp (S130). In the process of S130, the CPU 72 adds the temperature correction value THh to the base temperature THpb and assigns the result to the piston top surface temperature THp.

[0021] 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.

[0022] 3, the CPU 72 determines whether or not there is a request to increase the temperature of the GPF 34 (S200). If it determines that there is a request to increase the temperature of the GPF 34 (S200: YES), the CPU 72 acquires the piston top surface temperature THp (S210).

[0023] Next, the CPU 72 determines whether the piston top temperature THp is equal to or higher than a predetermined determination value THpref (S220). The determination value THpref is a preset minimum piston top temperature THp that can suppress an increase in particulate matter emissions due to the execution of temperature rise control.

[0024] When it is determined in the process of S220 that the piston top surface temperature THp is equal to or higher than the determination value THpre (S220: YES), the CPU 72 acquires the current target air-fuel ratio AFt (S230).

[0025] 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 value (e.g., 14.0) of the air-fuel ratio that can suppress an increase in particulate matter emissions due to an increase in unburned fuel.

[0026] If 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, 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 decrease in engine output caused by the ignition timing retardation. As temperature rise control, the CPU 72 also 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 decrease. Both of these processes increase the engine load to increase the temperature of the exhaust gas purification members provided in the exhaust passage.

[0027] If the determination in the processing of S220 above is negative, or if the determination in the processing of S240 above is negative, the CPU 72 performs reduction control (S260). Reduction control is a process for reducing the number or 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 of the ignition timing. When retarding of 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 not 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 the torque increase. Both of these processes are processes for reducing the particulate matter emitted from the combustion chambers 20 through control of the engine load.

[0028] 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.

[0029] (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 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 piston top surface temperature is low, it is possible to suppress an increase in the amount of particulate matter emitted due to the execution of temperature rise control.

[0030] (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 permitting the execution of temperature rise control include the target air-fuel ratio AFt of the air-fuel 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 the amount of unburned fuel is small, the temperature rise control is executed (YES in S240 of FIG. 3). Therefore, by executing temperature rise control when the amount of unburned fuel is large during combustion, it is possible to suppress an increase in the amount of particulate matter emitted.

[0031] (3) When the temperature of the piston top surface is lower than the predetermined judgment value THpref, the amount of particulate matter emitted from the combustion chamber 20 tends to increase. Also, when the target air-fuel ratio of the air-fuel mixture is smaller than the predetermined judgment value AFtref, the amount of particulate matter emitted from the combustion chamber 20 tends to increase. In this regard, in this embodiment, when the condition for permitting execution of temperature increase control is 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 smaller than the judgment value AFtref. Therefore, it is possible to suppress an increase in the amount of particulate matter emitted from the combustion chamber 20.

[0032] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0033] The piston top surface temperature THp may be calculated in another 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, functions and effects other than (2) above can be obtained.

[0034] The process of S260 shown in Fig. 3 may be omitted. Even in this case, functions and effects other than (3) above can be obtained. The temperature rise control is for removing particulate matter trapped in the GPF 34, but it may be performed for other purposes. For example, it may be performed to warm up the catalyst.

[0035] 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 element by injecting fuel during a fuel cut.

[0036] (b) A process of stopping fuel supply to some of the cylinders of the internal combustion engine 10 and supplying fuel to the remaining cylinders. At this time, the air-fuel ratio in the cylinders to which fuel is supplied is made richer than the stoichiometric air-fuel ratio.

[0037] (c) Dither control, in which some of the cylinders are set to rich cylinders and the remaining cylinders are set to 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.

[0038] The GPF 34 is not limited to a filter carrying a three-way catalyst, but may be a filter alone. Also, the GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30.

[0039] The control device is not limited to one 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 on at least a portion of the software processing performed in the above embodiments. That is, the control device may have any of the following configurations (a) to (c): (a) equipped with 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) equipped with 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; or (c) equipped with 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 a program storage device, and multiple dedicated hardware circuits.

[0040] 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. [Explanation of symbols]

[0041] 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...Rotation axis 54...Second motor generator 54a...Rotation axis 56...Inverter 58...Inverter 60...Drive wheels 70...Control device 72...CPU 74...ROM

Claims

1. 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 performed to increase the 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 condition for permitting execution of the temperature increase control includes that the temperature of the piston top surface is equal to or higher than a predetermined judgment value. Control device for internal combustion engines.

2. The condition for permitting execution of the temperature increase control includes that the target air-fuel ratio of the mixture is equal to or greater than a predetermined judgment value. The control device for an internal combustion engine according to claim 1.

3. When the condition for permitting execution of the temperature increase control is not satisfied, a reduction control for reducing particulate matter emitted from the combustion chamber is executed. The control device for an internal combustion engine according to claim 1 or 2.

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