Control device for internal combustion engine

Abstract

To suppress the occurrence of preignition in an internal combustion engine using hydrogen as fuel.SOLUTION: A control device 100 controls a fuel injection amount of an in-cylinder injection valve 35 arranged at an internal combustion engine 1 which uses hydrogen as fuel. When setting a quantity of a fuel gas which flows back to the in-cylinder injection valve 35 by the occurrence of preignition as a reverse flow rate, and setting one combustion cycle with a cylinder in which fuel injection is performed succeeding to a cylinder in which the preignition occurs as a starting point as a succeeding cycle, when the reverse flow rate is low, the control device 100 performs processing for reducing the fuel injection amount at the succeeding cycle compared with the case that the reverse flow rate is high.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] When pre-ignition occurs in an internal combustion engine, the pressure inside the cylinder becomes excessively high, which may cause high-temperature combustion gas to flow back into the fuel injection valve, damaging the fuel injection valve. Therefore, for example, in the internal combustion engine described in Patent Document 1, when the occurrence of pre-ignition is predicted, the occurrence of pre-ignition is suppressed by cooling the inside of the cylinder using the latent heat of vaporization of the fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-189062 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an internal combustion engine that uses hydrogen as fuel, it is difficult to cool the inside of the cylinder using the latent heat of vaporization of the fuel, and therefore the occurrence of pre-ignition cannot be suppressed using the method described in the above document. [Means for solving the problem]

[0005] A control device for an internal combustion engine that solves the above problem controls the fuel injection amount of a fuel injection valve provided in an internal combustion engine that uses hydrogen as fuel. When the amount of combustion gas that flows back into the fuel injection valve due to pre-ignition is defined as the backflow amount, and the next cycle is defined as one combustion cycle starting from the cylinder in which fuel injection is performed next to the cylinder in which pre-ignition occurred, the control device executes processing to reduce the fuel injection amount in the next cycle when the backflow amount is small compared to when the backflow amount is large. [Effects of the Invention]

[0006] This control device for an internal combustion engine can suppress the occurrence of pre-ignition in an internal combustion engine that uses hydrogen as fuel. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of the process executed by the control device. [Figure 3] FIG. 3 is a flowchart showing a procedure of a process executed by the control device in the modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Configuration of an internal combustion engine> As shown in Fig. 1, a cylinder 4 is provided in a cylinder block 2 of an internal combustion engine 1. A piston 5 is provided in the cylinder 4, and the piston 5 is connected to a crankshaft 7 via a connecting rod 6.

[0009] A cylinder head 3 is attached to the top of the cylinder block 2. A combustion chamber 8 is formed in each cylinder 4 between the top surface of the piston 5 and the cylinder head 3. The cylinder head 3 is also provided with an in-cylinder injection valve 35, which is a fuel injection valve that directly injects hydrogen gas, the fuel for the internal combustion engine 1, into each cylinder, and a spark plug 11 that spark-ignites the air-fuel mixture in the combustion chamber 8, for each cylinder of the internal combustion engine 1.

[0010] The cylinder head 3 is also provided with an intake port 9 and an exhaust port 10 connected to the combustion chamber 8. The intake port 9 constitutes a part of an intake passage through which intake air flows. The intake port 9 is connected to an intake passage 20 provided with a throttle valve 14 for adjusting the amount of intake air. The intake port 9 is also provided with an intake valve 12 for opening and closing the intake port 9.

[0011] The exhaust port 10 is provided with an exhaust valve 13 that opens and closes the exhaust port 10. The exhaust port 10 is connected to an exhaust passage 30. <About the control device> The control device 100 includes a CPU 110, a memory 120 in which control programs and data are stored, etc. The CPU 110 executes the programs stored in the memory 120 to perform various engine controls and the like.

[0012] Various sensors are connected to the control device 100. For example, the control device 100 is connected to a crank angle sensor 41 that detects the rotation angle of the crankshaft 7, an air flow meter 44 that detects the intake air amount GA, and a water temperature sensor 45 that detects the coolant temperature TW, which is the temperature of the coolant for the internal combustion engine 1. The control device 100 is also connected to a fuel pressure sensor 46 that detects the fuel pressure PF, which is the pressure of the fuel supplied to the direct injection valve 35. The control device 100 is also connected to a knocking sensor 48, which is a vibration sensor that outputs an output signal KN corresponding to the magnitude of vibration of the cylinder 4, and an accelerator sensor 49 that detects the accelerator operation amount ACCP, which is the amount of operation of the accelerator pedal.

[0013] The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 41. The control device 100 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 cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 1 is operating steadily at the current engine speed NE with the throttle valve 14 fully open. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

[0014] The control device 100 performs various engine controls, such as opening control of the throttle valve 14, injection control of fuel injected from the in-cylinder injection valve 35, and ignition control of the spark plug 11. For example, the control device 100 calculates the required output of the internal combustion engine 1 based on the accelerator operation amount ACCP, etc. Then, the control device 100 calculates the required injection amount Qd that will achieve the required output and substitutes it for the fuel injection amount Qa of the in-cylinder injection valve 35. Then, the control device 100 controls the driving of the in-cylinder injection valve 35 so that fuel is injected from the in-cylinder injection valve 35 in the fuel injection amount Qa.

[0015] The control device 100 also executes a process for determining the occurrence of pre-ignition based on the output signal KN of the knocking sensor 48. Note that such a process for determining pre-ignition is well known, and it can be determined that pre-ignition has occurred, for example, when a value generated from the output signal KN is equal to or greater than a predetermined threshold value. In the following, "pre-ignition" will be referred to as "plague."

[0016] <Regarding Plague Suppression> The control device 100 executes the following process to suppress the occurrence of plague. Fig. 2 shows the procedure of the process executed by the control device 100. The process shown in Fig. 2 is realized by the CPU 110 executing a program stored in the memory 120. The process shown in Fig. 3 is repeatedly executed at predetermined intervals. In the following, the step number of each process is represented by a number preceded by "S."

[0017] 2 starts, the control device 100 determines whether or not a pre-ignition has occurred (S100). In the process of S100, the control device 100 refers to the result of the above-described pre-ignition determination process.

[0018] If it is determined in the process of S100 that a plague has occurred (S100), the control device 100 calculates the in-cylinder pressure PP at the time of the plague occurrence in the cylinder in which the plague occurred (S110). In the process of S110, the control device 100 calculates the in-cylinder pressure PP, for example, as follows. That is, the control device 100 acquires the engine speed NE and engine load factor KL stored in advance from the memory 120. Note that it is desirable to store the values ​​of the engine speed NE and the fuel pressure PF at the time of the plague occurrence. Then, in order to calculate the in-cylinder pressure PP based on the engine speed NE and the engine load factor KL at the time of the plague occurrence, the control device 100 calculates the in-cylinder pressure PP by referring to a two-dimensional map stored in the memory 120. Note that, basically, the higher the engine speed NE, the higher the calculated in-cylinder pressure PP will be, and the higher the engine load factor KL, the higher the calculated in-cylinder pressure PP will be.

[0019] Next, the control device 100 calculates the backflow amount BFA (S120). The backflow amount BFA is the amount of combustion gas that flows back to the direct injection valve 35 due to the occurrence of plague. In the process of S120, the control device 100 calculates the backflow amount BFA, for example, as follows. That is, the control device 100 acquires the engine speed NE and fuel pressure PF stored in advance from the memory 120. It is desirable to store the values ​​of the engine speed NE and fuel pressure PF when a plague occurs. Then, to calculate the backflow amount BFA based on the engine speed NE, fuel pressure PF, and the calculated in-cylinder pressure PP, the control device 100 references a three-dimensional map stored in the memory 120. Basically, the higher the engine speed NE, the shorter the time the nozzle of the direct injection valve 35 is exposed to high pressure, and therefore the backflow amount BFA tends to be smaller. Furthermore, the higher the fuel pressure PF, the stronger the closing force of the valve element of the direct injection valve 35, and therefore the backflow amount BFA tends to be smaller. Furthermore, the higher the in-cylinder pressure PP, the stronger the opening force of the valve element of the direct injection valve 35, and therefore the backflow amount BFA tends to be larger. Therefore, the three-dimensional map for calculating the backflow amount BFA is adapted to match these trends in the backflow amount BFA.

[0020] Next, the control device 100 determines whether the calculated backflow amount BFA is "0" or whether the calculated backflow amount BFA is equal to or greater than a predetermined first threshold value R1 (S130). The magnitude of the value of the first threshold value R1 is set so that, based on the backflow amount BFA being equal to or greater than the first threshold value R1, it can be accurately determined that the backflow amount BFA is large enough to require sufficient scavenging of the direct injection valve 35.

[0021] If the determination in S130 is affirmative (S130: YES), the control device 100 executes a process of substituting the required injection amount Qd described above for the fuel injection amount Qa in order to set the fuel injection amount Qa in the next cycle (S150). The next cycle is one combustion cycle starting from the cylinder in which fuel injection is performed next after the cylinder in which the pre-ignition occurred.

[0022] If the determination in the process of S130 is negative (S130: NO), that is, if the backflow amount BFA is greater than "0" and less than the first threshold value R1, the control device 100 executes the process of S140.

[0023] In the process of S140, the control device 100 determines whether the calculated backflow amount BFA is equal to or greater than a second threshold value R2. The second threshold value R2 is a value greater than 0 and less than the first threshold value R1. The magnitude of the value of the second threshold value R2 is set so that, based on the backflow amount BFA being equal to or greater than the second threshold value R2, it can be accurately determined that the backflow amount BFA is an amount that requires scavenging of the direct injection valve 35.

[0024] If the determination in the process of S140 is affirmative (S140: YES), that is, if the backflow amount BFA is less than the first threshold value R1 and is equal to or greater than the second threshold value R2, the control device 100 executes the process of S160.

[0025] In the process of S160, the control device 100 executes a process of substituting the small injection amount Qs for the fuel injection amount Qa as the setting of the fuel injection amount Qa for the next cycle. The small injection amount Qs is the fuel injection amount that makes the hydrogen concentration of the air-fuel mixture less than the flammable concentration.

[0026] If the determination in the process of S140 is negative (S140: NO), that is, if the backflow amount BFA is less than the second threshold value R2 and greater than "0", the control device 100 executes the process of S170.

[0027] In the process of S170, the control device 100 executes a process of substituting "0" for the fuel injection amount Qa as the setting of the fuel injection amount Qa in the next cycle. That is, a process for executing a fuel cut in the next cycle is executed.

[0028] If a negative determination is made in S100 (S100: NO), the control device 100 executes a process of substituting the required injection amount Qd described above for the fuel injection amount Qa in order to set the fuel injection amount Qa in the next cycle (S180).

[0029] Then, when any one of the processes of S150, S160, S170, and S180 has been executed, the control device 100 ends this process in the current execution cycle. <Operation of this embodiment> If the backflow amount BFA is "0" and it is estimated that no backflow of combustion gas into the direct injection valve 35 is occurring, an affirmative determination is made in the processing of S130. If an affirmative determination is made in the processing of S130, the control device 100 executes processing to substitute the required injection amount Qd for the fuel injection amount Qa as the setting of the fuel injection amount Qa in the next cycle (S150). In other words, normal fuel injection control is executed.

[0030] Furthermore, if it is determined that the amount of combustion gas that has flowed back into the direct injection valve 35 is equal to or greater than the first threshold value R1, that is, if a positive determination is made in the processing of S130, the control device 100 executes the processing of S150. In the processing of S150, the control device 100 executes processing to substitute the required injection amount Qd for the fuel injection amount Qa as the setting of the fuel injection amount Qa for the next cycle. In other words, normal fuel injection control is executed. Such normal fuel injection control causes the direct injection valve 35 to inject fuel equivalent to the required injection amount Qd. Therefore, even if combustion gas has flowed back and remained inside the direct injection valve 35 of the cylinder where bleed has occurred, the combustion gas is scavenged by fuel injection in the next cycle.

[0031] Furthermore, when the backflow amount BFA is less than the first threshold value R1 and greater than "0," that is, when the backflow amount BFA is less than the first threshold value R1 and a negative determination is made in the process of S130, the control device 100 executes the process of S160 or the process of S170. In the process of S160, the fuel injection amount Qa in the next cycle is set to the small amount injection amount Qs. Therefore, when the backflow amount BFA is less than the first threshold value R1, the fuel injection amount Qa in the next cycle is reduced compared to when the backflow amount BFA is greater than or equal to the first threshold value R1.

[0032] Furthermore, in the process of S170, the fuel injection amount Qa in the next cycle is set to "0." Therefore, even by the process of S170, when the backflow amount BFA is smaller than the first threshold value R1, the fuel injection amount Qa in the next cycle is reduced compared to when the backflow amount BFA is equal to or greater than the first threshold value R1.

[0033] <Effects of this embodiment> (1) The control device 100 controls the fuel injection amount Qa of the direct injection valve 35 provided in the internal combustion engine 1 that uses hydrogen as fuel. The amount of combustion gas that flows back to the direct injection valve 35 due to the occurrence of plague is defined as the backflow amount BFA, and the next cycle is defined as one combustion cycle starting from the cylinder in which fuel injection is performed next to the cylinder in which plague occurred. When the backflow amount BFA is small, processing is executed to reduce the fuel injection amount Qa in the next cycle compared to when the backflow amount BFA is large.

[0034] As described above, in this embodiment, when the backflow amount BFA of the combustion gas is small and the possibility of damage to the direct injection valve 35 is relatively low, the fuel injection amount Qa in the next cycle is reduced. Therefore, the occurrence of plague in the next cycle can be suppressed.

[0035] (2) Since the occurrence of plague in the next cycle can be suppressed, damage to the direct injection valve 35 due to the backflow of combustion gas resulting from the occurrence of plague can be suppressed. (3) The occurrence of plagues in the next cycle can be suppressed, thereby preventing the occurrence of consecutive plagues.

[0036] (4) When the backflow amount BFA is equal to or greater than the first threshold R1, normal fuel injection control is executed. Therefore, even if combustion gas flows back and remains in the in-cylinder injection valve 35 of the cylinder where bleed has occurred, the combustion gas can be scavenged by fuel injection in the next cycle.

[0037] (5) If the determination in S140 is affirmative, that is, if the backflow amount BFA is less than the first threshold value R1 and equal to or greater than the second threshold value R2, the control device 100 sets the fuel injection amount Qa so that the hydrogen concentration of the air-fuel mixture is less than the flammable concentration (S160). This ensures that plague is prevented from occurring in the next cycle. Even if combustion gas flows back and remains in the direct injection valve 35 of the cylinder where plague occurred, fuel injection is performed in the next cycle, so that the combustion gas can be scavenged from the direct injection valve 35.

[0038] (6) If the determination in S140 is negative, that is, if the backflow amount BFA is less than the second threshold value R2 and greater than "0," the control device 100 sets the fuel injection amount Qa to "0" (S170). This reliably prevents plague from occurring in the next cycle. Furthermore, because the fuel injection amount is set to "0," it is possible to prevent unburned hydrogen from being discharged into the exhaust passage 30, unlike, for example, when the fuel injection amount Qa is set so that the hydrogen concentration in the air-fuel mixture is less than the flammable concentration.

[0039] (7) The backflow amount BFA of combustion gas changes depending on the in-cylinder pressure PP of the cylinder where plague has occurred. Therefore, in the process of S120, the control device 100 calculates the backflow amount BFA based on the in-cylinder pressure PP of the cylinder where plague has occurred. Therefore, the backflow amount BFA can be calculated appropriately.

[0040] <Example of change> 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.

[0041] The parameters for calculating the backflow amount BFA are the engine speed NE, the fuel pressure PF, and the in-cylinder pressure PP, but it is also possible to omit either the engine speed NE or the fuel pressure PF as the parameters, or to omit both the engine speed NE and the fuel pressure PF.

[0042] The process of S140 shown in Fig. 2 is omitted. If a negative determination is made in the process of S130, the process of S160 may be executed. The process of S140 shown in Fig. 2 is omitted. If a negative determination is made in the process of S130, the process of S170 may be executed.

[0043] The backflow amount BFA of combustion gas changes depending on the cylinder pressure PP of the cylinder where plague occurs. Therefore, the cylinder pressure PP may be used as a substitute for the backflow amount BFA. 3 shows a processing procedure when the in-cylinder pressure PP is used as a substitute value for the backflow amount BFA. Note that the same steps as those shown in FIG. 2 are denoted by the same step numbers in FIG. 3.

[0044] As shown in FIG. 3, after calculating the in-cylinder pressure PP in the process of S110, the control device 100 executes the process of S200. In the processing of S200, the control device 100 determines whether the in-cylinder pressure PP is equal to or less than a third threshold value Rp3 or equal to or greater than a first threshold value Rp1. The third threshold value Rp3 is the in-cylinder pressure PP when the backflow amount BFA is "0" and is determined in advance. The first threshold value Rp1 is the in-cylinder pressure PP when the backflow amount BFA is equal to the first threshold value R1 and is determined in advance. The first threshold value Rp1 is a value greater than the third threshold value Rp3.

[0045] If the determination in the process of S200 is affirmative (S200: YES), the control device 100 executes the process of S150. On the other hand, if a negative determination is made in the process of S200 (S200: NO), the control device 100 executes the process of S210.

[0046] In the process of S210, the control device 100 determines whether the in-cylinder pressure PP is equal to or greater than a second threshold value Rp2. The second threshold value Rp2 is the in-cylinder pressure PP when the backflow amount BFA is equal to the second threshold value Rp2, and is determined in advance. The second threshold value Rp2 is greater than the third threshold value Rp3 and less than the first threshold value Rp1.

[0047] If the determination in the process of S210 is affirmative (S210: YES), the control device 100 executes the process of S160. On the other hand, if a negative determination is made in the process of S210 (S210: NO), the control device 100 executes the process of S170.

[0048] According to this modified example, the accuracy of the determination when selecting one of the processes S150, S160, and S170 to switch the fuel injection amount Qa according to the backflow amount of combustion gas is lower than in the above embodiment, but the same effect as in the above embodiment can be obtained.

[0049] The control device 100 includes a CPU 110 and a memory 120 and executes software processing. However, this is merely an example. The control device 100 may also include a dedicated hardware circuit (e.g., an ASIC) that processes at least part of the software processing executed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c): (a) a processing device that executes all of the above processing according to a program and a program storage device such as a memory that stores the program; (b) a processing device and program storage device that executes part of the above processing according to a program and a dedicated hardware circuit that executes the remaining processing; or (c) a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software circuits and dedicated hardware circuits that include a processing device and a program storage device. That is, the above processing may be executed by a processing circuit that includes at least one software circuit and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0050] 1...Internal combustion engine 2...Cylinder block 3...Cylinder head 4...Cylinder 5...Piston 6...Connecting rod 7...Crankshaft 8...Combustion chamber 9...Intake port 10...Exhaust port 12...Intake valve 13...Exhaust valve 14...Throttle valve 20...Intake passage 30...Exhaust passage 35...In-cylinder injection valve 41...Crank angle sensor 44...Air flow meter 45...Water temperature sensor 46...Fuel pressure sensor 48...Knocking sensor 49...Accelerator sensor 100...Control device

Claims

1. A control device for controlling a fuel injection amount of a fuel injection valve provided in an internal combustion engine that uses hydrogen as fuel, The amount of combustion gas that flows back to the fuel injection valve due to the occurrence of pre-ignition is defined as the backflow amount, and when one combustion cycle starting from the cylinder in which fuel injection is executed next to the cylinder in which pre-ignition occurred is defined as the next cycle, if the backflow amount is small, processing is executed to reduce the fuel injection amount in the next cycle compared to when the backflow amount is large. Control device for internal combustion engines.

2. When the backflow amount is less than a first threshold value and is equal to or greater than a second threshold value that is smaller than the first threshold value, the fuel injection amount is set so that the hydrogen concentration of the air-fuel mixture becomes less than a flammable concentration. The control device for an internal combustion engine according to claim 1.

3. If the backflow amount is less than the second threshold value and greater than "0", the fuel injection amount is set to "0". The control device for an internal combustion engine according to claim 2.

4. A process for calculating the backflow amount is executed based on the in-cylinder pressure of the cylinder in which pre-ignition occurred. The control device for an internal combustion engine according to claim 1.

5. The cylinder pressure of the cylinder in which pre-ignition occurred is used as a substitute for the backflow amount. The control device for an internal combustion engine according to claim 1.

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