Control device for internal combustion engine

Abstract

To suppress an excessive rise in temperature of a catalyst.SOLUTION: A control device 70 executes specific cylinder stop processing of stopping fuel supply to some of a plurality of cylinders provided in an internal combustion engine 10 and performing fuel supply to the remaining cylinders other than the some of the cylinders. The control device 70 stops feedback control of an air-fuel ratio while executing the specific cylinder stopping processing. Then, setting the cylinders to which fuel supply is performed during execution of the specific cylinder stop processing as combustion cylinders, the control device 70 executes processing of reducing and correcting the amount of fuel supplied to the combustion cylinders on the basis of the amount of volatile fuel contained in the blow-by gas introduced into an intake passage 12 while the specific cylinder stop processing is executed.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, Patent Document 1 describes a control device for an internal combustion engine that executes a specific cylinder stop process to stop fuel supply to some of the multiple cylinders in the internal combustion engine, and to supply fuel to the remaining cylinders other than the some of the cylinders. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-60027 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if feedback control of the air-fuel ratio is performed while the specific cylinder stop process is being executed, there is a risk that the controllability of the air-fuel ratio will decrease. Therefore, it is considered to stop the feedback control of the air-fuel ratio while the specific cylinder stop process is being executed.

[0005] On the other hand, the blow-by gas introduced into the intake passage may contain volatile fuel. In a stopped cylinder where combustion is stopped by stopping the fuel supply due to the execution of the specific cylinder stop process, such volatile fuel flows into the cylinder and then flows out into the exhaust passage without being burned. Therefore, there is a risk that the catalyst installed in the exhaust passage may be overheated if more fuel than the target amount is supplied to the catalyst. [Means for solving the problem]

[0006] The control device for an internal combustion engine that solves the above problem is applied to an internal combustion engine that includes a plurality of cylinders, a catalyst provided in an exhaust passage, and a blow-by gas passage that introduces blow-by gas in a crankcase into an intake passage, and executes a specific cylinder stop process that stops fuel supply to some of the plurality of cylinders and supplies fuel to the remaining cylinders other than the some of the cylinders. This control device stops feedback control of the air-fuel ratio during the execution of the specific cylinder stop process, and executes a process of reducing and correcting the amount of fuel supplied to the combustion cylinder based on the amount of volatile fuel contained in the blow-by gas introduced into the intake passage when the cylinder to which fuel is supplied during the execution of the specific cylinder stop process is set as a combustion cylinder during the execution of the specific cylinder stop process. Effect of the Invention

[0007] This control device for an internal combustion engine can prevent an excessive rise in temperature of a catalyst provided in the exhaust passage. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine according to one embodiment. [Diagram 2] FIG. 2 is a flowchart showing a procedure of a process executed by the control device of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of a control device for an internal combustion engine will be described with reference to FIGS. <Configuration of the internal combustion engine and control device> 1, the internal combustion engine 10 has four cylinders, for example, cylinder #1 to cylinder #4. The internal combustion engine 10 is an engine mounted on a vehicle.

[0010] A throttle valve 14 is provided in an intake passage 12 of the internal combustion engine 10. The internal combustion engine 10 also has a port injection valve 16 that injects fuel into an intake port. 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. In addition, a cylinder head of the internal combustion engine 10 is provided with an in-cylinder injection valve 22 that directly injects fuel into the combustion chamber 20. The mixture of air and fuel in the combustion chamber 20 is combusted in response to spark discharge from an ignition plug 24.

[0011] The air-fuel mixture burned in the combustion chamber 20 of each cylinder is discharged as exhaust gas into an exhaust passage 30 when the exhaust valve 28 opens. The exhaust passage 30 is provided with an oxidation catalyst 32 and a gasoline particulate filter (hereinafter referred to as GPF) 34 that collects particulate matter (hereinafter referred to as PM) in the exhaust gas. The GPF 34 supports a three-way catalyst.

[0012] The internal combustion engine 10 is provided with a blow-by gas processing device that processes blow-by gas. The blow-by gas processing device is a device that introduces blow-by gas in the crankcase of the internal combustion engine 10 into the intake passage 12, and is provided with a PCV valve 50. The PCV valve 50 is a valve that adjusts the flow rate of blow-by gas introduced into the intake passage 12, and the opening degree of the valve is changed by utilizing the pressure difference between the crankcase and the intake passage 12. The PCV valve 50 and a portion of the intake passage 12 downstream of the throttle valve 14 are connected via a blow-by gas passage 51. The blow-by gas in the crankcase is introduced into the intake passage 12 via the blow-by gas passage 51.

[0013] The control device 70 operates various 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 spark plug 24, to control the torque, exhaust component ratio, and the like as control variables of the internal combustion engine 10. Fig. 1 shows operation signals MS1 to MS4 for the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24, respectively.

[0014] In order to control the control amount of the internal combustion engine 10, the control device 70 refers to the output signal Scr from the crank angle sensor 83, the intake air amount GA detected by the air flow meter 84, and the water temperature THW which is the temperature of the cooling water of the internal combustion engine 10 detected by the water temperature sensor 85. The control device 70 also refers to the oil temperature THO which is the temperature of the lubricating oil of the internal combustion engine 10 detected by the oil temperature sensor 86. The control device 70 also refers to the intake pressure PM which is a value detected by the pressure sensor 87 and which is the pressure of the intake passage 12 at a location downstream of the throttle valve 14. The control device 70 also refers to the accelerator operation amount ACCP which is the operation amount of the accelerator pedal detected by the accelerator sensor 88. The control device 70 also refers to the vehicle speed SP of the vehicle detected by the vehicle speed sensor 89. In addition, the control device 70 refers to a first air-fuel ratio AF1 detected by a first air-fuel ratio sensor 81 provided upstream of the oxidation catalyst 32, and a second air-fuel ratio AF2 detected by a second air-fuel ratio sensor 82 provided downstream of the oxidation catalyst 32.

[0015] The control device 70 includes a CPU 72, a ROM 74, 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 the internal operation, a power supply circuit, a reset circuit, etc. The control device 70 performs various controls by the CPU 72 executing a program stored in the ROM 74.

[0016] As one of various controls, the control device 70 executes a well-known air-fuel ratio feedback control. In the air-fuel ratio feedback control, an air-fuel ratio correction value FH, which is a feedback value for making the actual air-fuel ratio match the target air-fuel ratio AFt, is calculated based on the first air-fuel ratio AF1, the second air-fuel ratio AF2, and the target air-fuel ratio AFt of the air-fuel mixture. This air-fuel ratio correction value FH is updated at any time during the execution of the air-fuel ratio feedback control, while the update stops when the execution of the air-fuel ratio feedback control is stopped. Then, the amount of fuel injected from the port injection valve 16 and the in-cylinder injection valve 22 is feedback-corrected by the air-fuel ratio correction value FH, so that the actual air-fuel ratio converges to the target air-fuel ratio AFt.

[0017] <Regeneration process of GPF> The control device 70 executes a regeneration process of the GPF 34. Fig. 2 shows the procedure of the regeneration process. The process shown in Fig. 2 is realized by the CPU 72 repeatedly executing the program stored in the ROM 74 at a predetermined cycle. In the following, the step numbers of each process are represented by numbers preceded by "S".

[0018] In the series of processes shown in Fig. 2, the CPU 72 first acquires the engine rotational speed NE, the filling efficiency η, and the water temperature THW (S10). The engine rotational speed NE is calculated by the CPU 72 based on the output signal Scr. The filling efficiency η is calculated by the CPU 72 based on the engine rotational speed NE and the intake air amount GA.

[0019] Next, the CPU 72 calculates an update amount ΔDPM of the accumulation amount DPM based on the engine speed NE, the charging efficiency η, and the water temperature THW (S12). Here, the accumulation amount DPM is the amount of PM trapped in the GPF 34. More specifically, the CPU 72 calculates the amount of PM in the exhaust gas discharged into the exhaust passage 30 based on the engine speed NE, the charging efficiency η, and the water temperature THW. The CPU 72 also calculates the temperature of the GPF 34 based on the engine speed NE and the charging efficiency η. The CPU 72 then calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of the GPF 34. Note that when the process of S20 described below is executed, the temperature of the GPF 34 and the update amount ΔDPM may be calculated based on the increase coefficient K.

[0020] Next, the CPU 72 updates the accumulation amount DPM in accordance with the update amount ΔDPM (S14). Next, the CPU 72 determines whether or not an execution flag Fc is "1" (S16). When the execution flag Fc is "1", it indicates that a regeneration process for burning and removing PM from the GPF 34 is being executed, and when the execution flag Fc is "0", it indicates that the regeneration process is not being executed.

[0021] When the CPU 72 determines that the execution flag Fc is "0" (S16: NO), it determines whether the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value at which the amount of PM trapped by the GPF 34 is large and it is desired to remove the PM.

[0022] When the CPU 72 determines that the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18: YES), it executes the regeneration process and sets the execution flag Fc to "1" (S20). In addition, as the process in S20, it stops the above-mentioned air-fuel ratio feedback control. More specifically, it holds the above-mentioned air-fuel ratio correction value FH at the current value and stops updating it.

[0023] As the regeneration process according to this embodiment, the CPU 72 executes a specific cylinder stopping process. The specific cylinder stopping process is a process for stopping the fuel supply to some of the cylinders among a plurality of cylinders and supplying fuel to the remaining cylinders other than the some of the cylinders, and includes a stopping process and an increasing process.

[0024] The stop process is a process for stopping fuel injection from the port injection valve 16 and the direct injection valve 22 of cylinder #1, that is, for stopping the fuel supply to cylinder #1 by performing a fuel cut. Note that, hereinafter, the cylinder for which this stop process is performed is referred to as a stopped cylinder, and the remaining cylinders other than the stopped cylinder, that is, the cylinders to which fuel is supplied and the air-fuel mixture is burned, are referred to as combustion cylinders.

[0025] The amount-increasing process is a process for increasing the amount of fuel supplied to each of the combustion cylinders, namely, cylinders #2, #3, and #4, compared to when the stop process is not executed, in order to supply unburned fuel to the exhaust passage 30. When the amount-increasing process is executed, the amount of fuel injected from the port injection valve 16 and the in-cylinder injection valve 22 is increased so that the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the stoichiometric air-fuel ratio.

[0026] This specific cylinder stop process performs a regeneration process in which oxygen and unburned fuel are supplied to the exhaust passage 30 to raise the temperature of the GPF 34, thereby burning and removing the PM trapped in the GPF 34. That is, oxygen and unburned fuel are discharged into the exhaust passage 30, and the unburned fuel is burned in the oxidation catalyst 32 or the like to raise the temperature of the exhaust gas, thereby raising the temperature of the GPF 34. Then, oxygen is supplied to the GPF 34, whereby the PM trapped by the GPF 34 is burned and removed.

[0027] Specifically, the CPU 72 assigns "0" to the required injection amount Qd for the port injector 16 and the in-cylinder injection valve 22 of the cylinder #1. The required injection amount Qd is a target value for the total amount of fuel injected from the port injector 16 and the in-cylinder injection valve 22 in one combustion cycle.

[0028] On the other hand, the CPU 72 calculates the required injection amount Qd for each of the cylinders #2, #3, and #4 based on the increase coefficient K, the base injection amount Qb, the air-fuel ratio correction value FH, and the decrease correction value α using the following equation (1).

[0029] Qd = K Qb FH-α…(1) The increase coefficient K is a value set by the CPU 72 so that the amount of unburned fuel in the exhaust discharged from cylinders #2, #3, and #4 into the exhaust passage 30 is equal to or less than the amount that reacts just right with the oxygen discharged from cylinder #1. For example, in the early stage of the regeneration process of the GPF 34, the CPU 72 sets the air-fuel ratio of the mixture in cylinders #2, #3, and #4 to a value as close as possible to the amount that reacts just right in order to raise the temperature of the oxidation catalyst 32 early. By multiplying by this increase coefficient K, the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the theoretical air-fuel ratio.

[0030] The base injection amount Qb is an injection amount for making the air-fuel ratio of the mixture the stoichiometric air-fuel ratio. The CPU 72 calculates the base injection amount Qb based on, for example, the charging efficiency η and the engine rotation speed NE.

[0031] The reduction correction value α is a value calculated by the CPU 72 as follows. First, the CPU 72 calculates the amount of volatile fuel VF in the blow-by gas introduced into the intake passage 12 based on the engine operating state. The calculation of this amount of volatile fuel VF is the same as the calculation of the outflow fuel amount Qout described in, for example, JP 2006-177288 A. Then, the CPU 72 calculates the amount of volatile fuel VFs per cylinder, which is the amount of volatile fuel in the blow-by gas sucked into the combustion chamber 20 of one cylinder in the intake stroke, based on the calculated amount of volatile fuel VF and the engine rotation speed NE. Then, the CPU 72 multiplies the amount of volatile fuel VFs per cylinder by the value obtained by dividing the number A of stopped cylinders in one combustion cycle by the number B of burning cylinders in one combustion cycle, and assigns the result to the reduction correction value α. For example, in the case of this embodiment, since number A is "1" and number B is "3", the reduction correction value α is "1 / 3 × cylinder-specific volatile fuel amount VFs", that is, "VFS / 3". When calculating the required injection amount Qd of each cylinder #2, #3, and #4, this reduction correction value α is subtracted, so that the amount of fuel supplied to the combustion cylinders from the fuel injection valves such as the port injection valve 16 and the direct injection valve 22 is reduced by the amount of volatile fuel flowing into the stopped cylinders.

[0032] The amount of volatile fuel flowing into the cylinder rarely changes suddenly. Therefore, the portion of the fuel supplied to the combustion cylinder that corresponds to the volatile fuel in the blow-by gas is almost offset by the air-fuel ratio correction value FH when the required injection amount Qd is calculated, even though the update is stopped.

[0033] On the other hand, when the CPU 72 determines that the execution flag Fc is "1" in the process of S16 (S16: YES), the CPU 72 determines whether the accumulation amount DPM is equal to or smaller than the stop threshold value DPML (S22). The stop threshold value DPML is set to a value at which the amount of PM trapped in the GPF 34 becomes small enough to allow the regeneration process to be stopped.

[0034] When the CPU 72 determines that the accumulation amount DPM is greater than the stop threshold value DPML (S22: NO), the CPU 72 continues the process of S20. On the other hand, when it is determined that the accumulation amount DPM is equal to or less than the stop threshold value DPML (S22: YES), the CPU 72 assigns "0" to the execution flag Fc (S28). When the execution flag Fc becomes "0", each process performed in the process of S20 is stopped. That is, the regeneration process is stopped, and the air-fuel ratio feedback control is resumed, thereby resuming the update of the air-fuel ratio correction value FH.

[0035] It should be noted that when the CPU 72 has completed the process of S20 or S28, or when a negative determination is made in the process of S18, the CPU 72 temporarily ends the series of processes shown in FIG. <Action and Effects> The operation and effects of this embodiment will be described.

[0036] In this embodiment, the air-fuel ratio feedback control is stopped during the execution of the specific cylinder stop process described above, that is, during the execution of the regeneration process of the GPF 34. During the execution of the specific cylinder stop process, a process is executed to reduce the amount of fuel supplied to the combustion cylinder based on the volatile fuel amount VF contained in the blow-by gas introduced into the intake passage 12. More specifically, when calculating the required injection amount Qd of the combustion cylinder, the fuel amount is reduced by the reduction correction value α calculated based on the volatile fuel amount VF. Therefore, the amount of fuel that reaches the oxidation catalyst 32 during the execution of the specific cylinder stop process is reduced, so that the excessive temperature rise of the oxidation catalyst 32 can be suppressed.

[0037] <Example of change> 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.

[0038] The process for executing the specific cylinder stop process is not limited to the regeneration process described above. For example, the specific cylinder stop process may be executed for catalyst warm-up or sulfur poisoning recovery. Also, for example, the specific cylinder stop process may be executed to increase the amount of oxygen stored in the oxidation catalyst 32.

[0039] The number of cylinders to be stopped for fuel supply to be stopped in one combustion cycle when the specific cylinder stopping process is being executed is "1". However, the number of cylinders to be stopped can be changed as appropriate with the maximum value being "total number of cylinders - 1". Also, it is not essential to fix the cylinders to be stopped to predetermined cylinders. For example, the cylinders to be stopped for fuel supply to be stopped may be changed for each combustion cycle.

[0040] The GPF 34 is not limited to a filter carrying a three-way catalyst, and may be a filter alone. Furthermore, the GPF 34 is not limited to being provided downstream of the oxidation catalyst 32 in the exhaust passage 30. Furthermore, the oxidation catalyst 32 may be replaced with a three-way catalyst that purifies components contained in the exhaust gas. [Explanation of symbols]

[0041] 10... internal combustion engine, 12... intake passage, 30... exhaust passage, 32... oxidation catalyst, 34... GPF, 50... PCV valve, 51... blow-by gas passage, 70... control device

Claims

[Claim 1] A control device is applied to an internal combustion engine including a plurality of cylinders, a catalyst provided in an exhaust passage, and a blow-by gas passage that introduces blow-by gas in a crankcase into an intake passage, and executes a specific cylinder stop process to stop fuel supply to some of the plurality of cylinders and to supply fuel to the remaining cylinders other than the some of the cylinders, During the execution of the specific cylinder stop process, a feedback control of an air-fuel ratio is stopped, When a cylinder to which fuel is supplied during the execution of the specific cylinder stop process is defined as a combustion cylinder, during the execution of the specific cylinder stop process, a process for reducing and correcting the amount of fuel supplied to the combustion cylinder based on the amount of volatile fuel contained in the blow-by gas introduced into the intake passage is performed. A control device for an internal combustion engine.

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