Fuel supply device

Abstract

To inhibit gas in a cylinder from flowing into a cylinder injection valve when preignition occurs in the cylinder.SOLUTION: A control device 60 for an internal combustion engine 10 controls a pressure regulating device 23 for regulating supply fuel pressure to a cylinder injection valve 16. The control device 60 executes: fuel pressure retention processing for controlling the pressure regulating device 23 so that the supply fuel pressure is retained at base fuel pressure when an operating state of the internal combustion engine 10 is not a predetermined operating state; and fuel pressure increase processing for controlling the pressure regulating device 23 so that the supply fuel pressure becomes higher than the base fuel pressure after injection of fuel by the cylinder injection valve 16 when the operating state of the internal combustion engine 10 is the predetermined operating state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel supply device provided in an internal combustion engine having a cylinder and an in-cylinder injection valve that injects fuel into the cylinder. [Background technology]

[0002] Patent Document 1 discloses a control device applied to an internal combustion engine that uses hydrogen as fuel. The internal combustion engine has multiple cylinders. When the control device detects the occurrence of pre-ignition in one of the multiple cylinders, it performs control to increase the combustion speed of fuel in the cylinder where the occurrence of pre-ignition has been detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-130473 Summary of the Invention [Problem to be solved by the invention]

[0004] When pre-ignition occurs in a cylinder, the internal pressure of that cylinder increases. Therefore, in an internal combustion engine equipped with an in-cylinder injection valve as a fuel injection valve that injects fuel into the cylinder, when pre-ignition occurs in a cylinder, the internal pressure of that cylinder increases, causing the in-cylinder injection valve to open. When the in-cylinder injection valve opens in this way, the internal pressure of the cylinder is high, causing gas inside the cylinder to flow into the in-cylinder injection valve. [Means for solving the problem]

[0005] A fuel supply device for solving the above problem is provided in an internal combustion engine including a cylinder and an in-cylinder injection valve that injects fuel into the cylinder. The fuel supply device includes a fuel pressure regulating device that regulates the supply fuel pressure, which is the pressure of fuel supplied to the in-cylinder injection valve, and a control device that controls the fuel pressure regulating device. The control device executes a fuel pressure maintaining process that controls the fuel pressure regulating device to maintain the supply fuel pressure at a base fuel pressure when the operating state of the internal combustion engine is not a predetermined operating state, and a fuel pressure increasing process that controls the fuel pressure regulating device to make the supply fuel pressure higher than the base fuel pressure after fuel injection from the in-cylinder injection valve when the operating state of the internal combustion engine is the predetermined operating state.

[0006] The higher the pressure of fuel supplied to the in-cylinder injection valve, the less likely the in-cylinder injection valve will open even if the internal pressure of the cylinder increases. Therefore, in the fuel supply device described above, when the internal combustion engine is operating in a predetermined operating state, the supplied fuel pressure after fuel injection from the in-cylinder injection valve becomes higher than the base fuel pressure. This makes it less likely that the in-cylinder injection valve will open even if pre-ignition occurs in a cylinder and the internal pressure of that cylinder increases. As a result, when pre-ignition occurs in a cylinder, gas in that cylinder can be prevented from flowing into the in-cylinder injection valve.

[0007] In one example of the above fuel supply device, when the operating state of the internal combustion engine is the specified operating state, the control device executes a fuel pressure reduction process that controls the fuel pressure adjustment device so that the supply fuel pressure is reduced before the start of fuel injection from the in-cylinder injection valve.

[0008] If the fuel supply pressure is too high, it becomes difficult to finely adjust the fuel injection amount of the direct injection valve. In this regard, in the fuel supply device described above, the fuel supply pressure is reduced before the direct injection valve starts fuel injection. Therefore, it is possible to prevent a decrease in the controllability of the fuel injection amount of the direct injection valve when the internal combustion engine is operating in a predetermined operating state.

[0009] In one example of the fuel supply device, the control device controls the fuel pressure adjustment device in the fuel pressure reduction process so that the supply fuel pressure is reduced to the base fuel pressure before the start of fuel injection from the direct injection valve.

[0010] In the fuel supply device, when the internal combustion engine is operating in a predetermined operating state, the supply fuel pressure is reduced to the base fuel pressure before fuel injection from the direct injection valve is started. Therefore, the controllability of the fuel injection amount from the direct injection valve when the internal combustion engine is operating in the predetermined operating state can be made to the same level as when the internal combustion engine is not operating in the predetermined operating state.

[0011] When the internal combustion engine has a plurality of the cylinders, one example of the fuel supply device includes a plurality of the in-cylinder injection valves corresponding to the plurality of cylinders. When the in-cylinder injection valve corresponding to the cylinder among the plurality of cylinders having the highest probability of pre-ignition is set as the specified in-cylinder injection valve, it is preferable that the control device controls the fuel pressure adjustment device in the fuel pressure increasing process so that the supply fuel pressure after fuel injection from the specified in-cylinder injection valve is higher than the base fuel pressure.

[0012] In an internal combustion engine with multiple cylinders, the probability of pre-ignition varies from cylinder to cylinder. Therefore, in the fuel supply device, when the internal combustion engine is operating in a predetermined operating state, the supply fuel pressure after fuel injection from the in-cylinder injection valve corresponding to the cylinder with the highest probability of pre-ignition is set to be higher than the base fuel pressure. This makes it possible to prevent gas from inside the cylinder from flowing into the in-cylinder injection valve. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine system equipped with a fuel supply device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a direct injection valve provided in the internal combustion engine system. [Figure 3]FIG. 3 is a flowchart showing a processing routine executed by the control device in the fuel supply device of the first embodiment. [Figure 4] FIG. 4 is a timing chart for explaining the operation of the fuel supply device of the first embodiment. [Figure 5] FIG. 5 is a flowchart showing a processing routine executed by the control device in the fuel supply device of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) A first embodiment of a fuel supply device will be described below with reference to FIGS. 1 shows an internal combustion engine system mounted on a vehicle and equipped with a fuel supply device according to this embodiment. The internal combustion engine system includes an internal combustion engine 10, a detection system for detecting the state of the internal combustion engine 10, and a control device 60 for controlling the internal combustion engine 10.

[0015] <Internal combustion engine> The internal combustion engine 10 is an internal combustion engine that uses hydrogen gas as fuel. The internal combustion engine 10 includes a plurality of cylinders 11, a crankshaft 12, an intake passage 13, a throttle valve 14, and an exhaust passage 15. In the example shown in FIG. 1, the internal combustion engine 10 includes four cylinders 11. In this specification, when the four cylinders are described collectively, they are referred to as "cylinders 11," and when they are described separately, they are referred to as cylinder #1, cylinder #2, cylinder #3, and cylinder #4.

[0016] The intake passage 13 is a passage through which air flows to be introduced into the multiple cylinders 11. A throttle valve 14 is installed in the intake passage 13. The amount of intake air, which is the amount of air flowing through the intake passage 13, is adjusted by adjusting the throttle opening, which is the opening degree of the throttle valve 14.

[0017] The internal combustion engine 10 is equipped with a plurality of in-cylinder injection valves 16 and a plurality of ignition devices 17. One in-cylinder injection valve 16 and one ignition device 17 are provided for each cylinder 11. The in-cylinder injection valve 16 is a fuel injection valve that injects fuel into the cylinder 11. The configuration of the in-cylinder injection valve 16 will be described later. In the plurality of cylinders 11, an air-fuel mixture containing air and fuel is burned by the discharge of the ignition device 17. The power obtained by the combustion of the air-fuel mixture is transmitted to the crankshaft 12, causing the crankshaft 12 to rotate. Exhaust gas is generated by the combustion of the air-fuel mixture in the plurality of cylinders 11. This exhaust gas is discharged from the plurality of cylinders 11 to the exhaust passage 15.

[0018] The internal combustion engine 10 includes a fuel tank 21, a fuel supply passage 22, a pressure regulating device 23, a delivery pipe 24, and a pressure reducing mechanism 25. The fuel tank 21, the fuel supply passage 22, the pressure regulating device 23, the delivery pipe 24, and the pressure reducing mechanism 25 constitute an example of a "fuel supply device" provided in the internal combustion engine 10.

[0019] Fuel tank 21 stores high-pressure fuel. Fuel supply passage 22 is a passage that supplies the fuel stored in fuel tank 21 to delivery pipe 24. Pressure regulator 23 is installed in fuel supply passage 22. Pressure regulator 23 reduces the pressure of the fuel flowing through fuel supply passage 22 under the control of control device 60. Therefore, the pressure of the fuel flowing in the portion of fuel supply passage 22 that is closer to delivery pipe 24 than pressure regulator 23 is lower than the pressure of the fuel flowing in the portion of fuel supply passage 22 that is closer to fuel tank 21 than pressure regulator 23.

[0020] A plurality of in-cylinder injection valves 16 are connected to the delivery pipe 24. That is, the delivery pipe 24 temporarily stores fuel to be supplied to the plurality of in-cylinder injection valves 16. In the following description, the pressure of the fuel inside the delivery pipe 24 will be referred to as the "supply fuel pressure."

[0021] The pressure reducing mechanism 25 is a mechanism that reduces the pressure of fuel supplied to the delivery pipe 24. The pressure reducing mechanism 25 has a first purge passage 26, a first purge valve 27, a reservoir chamber 28, a second purge passage 29, and a second purge valve 30.

[0022] The first purge passage 26 is a passage that connects the delivery pipe 24 and the storage chamber 28. The first purge valve 27 is an electronically controlled valve. The first purge valve 27 is installed in the first purge passage 26. The storage chamber 28 temporarily stores the fuel that has flowed in from the first purge passage 26. When the first purge valve 27 is closed, the outflow of fuel from the delivery pipe 24 to the storage chamber 28 via the first purge passage 26 is restricted. On the other hand, when the first purge valve 27 is open, the fuel flows out from the delivery pipe 24 to the storage chamber 28 via the first purge passage 26.

[0023] The second purge passage 29 is a passage that connects the storage chamber 28 and the intake passage 13. More specifically, the second purge passage 29 is connected to a portion of the intake passage 13 that is downstream of the throttle valve 14. The second purge valve 30 is an electronically controlled valve. The second purge valve 30 is installed in the second purge passage 29. When the second purge valve 30 is closed, fuel is not supplied from the storage chamber 28 to the intake passage 13 via the second purge passage 29. On the other hand, when the second purge valve 30 is open, fuel is supplied from the storage chamber 28 to the intake passage 13 via the second purge passage 29.

[0024] The configuration of the direct injection valve 16 will be described with reference to FIG. The direct injection valve 16 has a cylindrical body 41, a seat member 42, a needle 43, a valve-closing spring 44, and an electromagnetic coil 45. The seat member 42 is held at a tip end 411 of the body 41. An injection port 46 that injects fuel into the cylinder 11 is formed in the seat member 42.

[0025] The needle 43 is housed within the body 41 in a state in which it can move toward and away from the seat member 42. When the needle 43 is seated on the valve seat of the seat member 42, the injection port 46 is closed. This state of the in-cylinder injection valve 16 in which the injection port 46 is closed is referred to as "the in-cylinder injection valve 16 is closed." On the other hand, when the needle 43 is away from the valve seat of the seat member 42, the injection port 46 is open. This state of the in-cylinder injection valve 16 in which the injection port 46 is open is referred to as "the in-cylinder injection valve 16 is open."

[0026] An internal fuel passage 47 through which fuel flows is formed between the inner circumferential surface of the body 41 and the needle 43. The internal fuel passage 47 is connected to the delivery pipe 24. Therefore, when the direct injection valve 16 is opened, the internal fuel passage 47 is connected to the injection port 46. At this time, if the pressure in the internal fuel passage 47 is higher than the internal pressure of the cylinder 11, fuel is injected from the injection port 46 into the cylinder 11.

[0027] The valve-closing spring 44 biases the needle 43 in a direction that presses the needle 43 against the seat member 42. When current flows through the electromagnetic coil 45, an electromagnetic force is generated in a direction that moves the needle 43 away from the seat member 42. Therefore, when current flows through the electromagnetic coil 45, the needle 43 moves away from the seat member 42 against the biasing force of the valve-closing spring 44. This opens the direct injection valve 16. On the other hand, when current is stopped from flowing through the electromagnetic coil 45, the needle 43 is pressed against the seat member 42 by the biasing force of the valve-closing spring 44. This closes the direct injection valve 16.

[0028] <Detection system> 1, the detection system includes a plurality of sensors that output signals according to the detection results to the control device 60. The detection system includes the following sensors: a crank angle sensor 51, an air flow meter 52, an oil temperature sensor 53, a water temperature sensor 54, an intake air temperature sensor 55, and a fuel pressure sensor 56.

[0029] The crank angle sensor 51 detects the rotation angle of the crankshaft 12. The rotation speed of the crankshaft 12 based on the detected value of the crank angle sensor 51 is referred to as the "engine speed NE." The air flow meter 52 detects the intake air amount. The intake air amount based on the detected value of the air flow meter 52 is referred to as the "intake air amount GA." The oil temperature sensor 53 detects the temperature of the oil circulating within the internal combustion engine 10. The oil temperature based on the detected value of the oil temperature sensor 53 is referred to as the "oil temperature TPo." The water temperature sensor 54 detects the temperature of the coolant circulating within the internal combustion engine 10. The coolant temperature based on the detected value of the water temperature sensor 54 is referred to as the "coolant temperature TPw." The intake air temperature sensor 55 detects the temperature of the air that has passed through the throttle valve 14 in the intake passage 13. The air temperature based on the detected value of the intake air temperature sensor 55 is referred to as the "intake air temperature TPa." The fuel pressure sensor 56 detects the supply fuel pressure. The supply fuel pressure based on the detected value of the fuel pressure sensor 56 is referred to as the "supply fuel pressure FP."

[0030] <Control device> 1, the control device 60 has a CPU 61 and a memory 62. The memory 62 stores various control programs executed by the CPU 61. The CPU 61 executes the control programs to control the opening of the throttle valve 14, the fuel injection amount of the direct injection valve 16, and the ignition timing of the ignition device 17 based on signals from a plurality of sensors. The control device 60 also controls the pressure regulator 23, the first purge valve 27, and the second purge valve 30 that constitute the fuel supply device. In other words, the control device 60 constitutes an example of a "fuel supply device."

[0031] <Control to adjust fuel supply pressure> The control for adjusting the fuel supply pressure FP will be described with reference to Fig. 3. Fig. 3 shows the processing routine for this control. The CPU 61 executes a control program, causing the control device 60 to execute this processing routine at each predetermined control cycle.

[0032] In step S11 of this processing routine, the control device 60 acquires the engine speed NE, intake air amount GA, engine load factor KL, oil temperature TPo, water temperature TPw, intake air temperature TPa, and supply fuel pressure FP as state quantities of the internal combustion engine 10.

[0033] Here, the engine load factor KL can be derived based on the engine speed NE and the intake air amount GA. The engine load factor KL is an index value of the air filling rate in the cylinder 11. Specifically, the engine load factor KL is the ratio of the amount of inflow air per combustion cycle of one cylinder to a reference inflow air amount. Note that the reference inflow air amount changes depending on the engine speed NE.

[0034] In step S13, the control device 60 determines whether the operating state of the internal combustion engine 10 is a predetermined operating state. The operating state of the internal combustion engine 10 is the operating state of the internal combustion engine 10 indicated by the engine speed NE and the engine load factor KL. The predetermined operating state is used to determine whether pre-ignition is likely to occur in the cylinder 11. The predetermined operating state is set through experiments, simulations, etc. If the operating state of the internal combustion engine 10 is a predetermined operating state, it is deemed that pre-ignition is likely to occur in the cylinder 11. If the operating state of the internal combustion engine 10 is not a predetermined operating state, it is deemed that pre-ignition is unlikely to occur in the cylinder 11.

[0035] The predetermined operating state varies depending on the oil temperature TPo, the water temperature TPw, and the intake air temperature TPa. This is because the higher the temperature inside the cylinder 11, the higher the probability of pre-ignition occurring. Therefore, when the control device 60 estimates that the temperature inside the cylinder 11 is high based on the oil temperature TPo, the water temperature TPw, and the intake air temperature TPa, it appropriately changes the predetermined operating state so that the operating state of the internal combustion engine 10 is more likely to be determined to be the predetermined operating state compared to when it estimates that the temperature inside the cylinder 11 is not high.

[0036] When the control device 60 determines that the operating state of the internal combustion engine 10 is not a predetermined operating state (S13: NO), the process proceeds to step S15. When the target value of the supply fuel pressure FP is set to the supply fuel pressure target value FPTr, in step S15, the control device 60 sets a base fuel pressure FPb as the supply fuel pressure target value FPTr. The base fuel pressure FPb is the supply fuel pressure FP that corresponds to the current operating state of the internal combustion engine 10. Then, in step S17, the control device 60 operates the fuel pressure regulator based on the supply fuel pressure target value FPTr. For example, when the supply fuel pressure FP is lower than the supply fuel pressure target value FPTr, the control device 60 operates the pressure regulator 23 to increase the amount of fuel supplied to the delivery pipe 24 via the fuel supply passage 22. This increases the supply fuel pressure FP. On the other hand, when the supply fuel pressure FP is higher than the supply fuel pressure target value FPTr, the control device 60 operates the pressure regulator 23 to decrease the amount of fuel supplied to the delivery pipe 24 via the fuel supply passage 22. This limits the increase in the supply fuel pressure FP. That is, when the operating state of the internal combustion engine 10 is not a predetermined operating state, the control device 60 controls the fuel pressure regulator so that the supply fuel pressure FP is maintained at the base fuel pressure FPb. Therefore, steps S15 and S17 correspond to the "fuel pressure maintenance process." After that, the control device 60 temporarily ends this process routine.

[0037] On the other hand, in step S13, if the control device 60 determines that the operating state of the internal combustion engine 10 is a predetermined operating state (YES), the process proceeds to step S19. In step S19, the control device 60 determines whether or not the timing has come when fuel injection from a specified in-cylinder injection valve among the multiple in-cylinder injection valves 16 has been completed.

[0038] Here, the probability that pre-ignition will occur in each cylinder 11 differs for each cylinder 11. For example, among the multiple cylinders 11, pre-ignition is more likely to occur in a cylinder whose internal temperature is more likely to become high. Therefore, in this embodiment, based on specifications such as the shape of the coolant flow path in the internal combustion engine 10, the shape of the flow path for oil circulating through the internal combustion engine 10, and the installation position and orientation of the internal combustion engine 10 in the engine compartment of the vehicle, the cylinder among the multiple cylinders 11 that is assumed to be most likely to experience pre-ignition is set as the specified cylinder. Then, among the multiple in-cylinder injection valves 16, the in-cylinder injection valve 16 that injects fuel into the specified cylinder is set as the specified in-cylinder injection valve.

[0039] In step S19, if the control device 60 determines that the fuel injection of the specified in-cylinder injection valve has been completed (YES), the process proceeds to step S23. On the other hand, if the control device 60 determines that the fuel injection of the specified in-cylinder injection valve has not been completed (S19: NO), the process proceeds to step S21.

[0040] In step S21, the control device 60 determines whether or not at least one of the following conditions (A1) and (A2) is met. (A1) The specified cylinder stroke is the intake stroke. (A2) The specified cylinder injection valve is injecting fuel.

[0041] If at least one of the two conditions (A1) and (A2) is satisfied (S21: YES), the control device 60 proceeds to step S27. On the other hand, if neither of the two conditions (A1) nor (A2) is satisfied (S21: NO), the control device 60 proceeds to step S23.

[0042] In step S23, the control device 60 sets an increased fuel pressure FPup as the supply fuel pressure target value FPTr. The increased fuel pressure FPup is a fuel pressure higher than the base fuel pressure FPb. Then, in step S25, the control device 60 operates the fuel pressure regulator based on the supply fuel pressure target value FPTr. For example, when the supply fuel pressure FP is lower than the supply fuel pressure target value FPTr, the control device 60 operates the pressure regulator 23 to increase the amount of fuel supplied to the delivery pipe 24 via the fuel supply passage 22. On the other hand, when the supply fuel pressure FP is higher than the supply fuel pressure target value FPTr, the control device 60 operates the pressure regulator 23 to decrease the amount of fuel supplied to the delivery pipe 24 via the fuel supply passage 22. In other words, when the internal combustion engine 10 is operating in a predetermined operating state, the control device 60 controls the fuel pressure regulator so that the supply fuel pressure FP is higher than the base fuel pressure FPb. Therefore, steps S23 and S25 correspond to the "fuel pressure increase process." After that, the control device 60 temporarily ends this process routine.

[0043] Here, the increased fuel pressure FPup will be explained. The increased fuel pressure FPup is a fuel pressure that prevents the direct injection valve 16 corresponding to the cylinder 11 from opening even if pre-ignition occurs in the cylinder 11 and the internal pressure of the cylinder 11 increases. The increased fuel pressure FPup is set to satisfy the following relational expression (Equation 1). In the relational expression (Equation 1), "Fs" is the biasing force that the valve-closing spring 44 of the direct injection valve 16 applies to the needle 43. "Ph" is the fuel pressure in the internal fuel passage 47. "Pp" is the expected value of the internal pressure of the cylinder 11 when pre-ignition occurs. When the direct injection valve 16 is closed, if the sum of the biasing force Fs of the valve-closing spring 44 and the fuel pressure Ph in the internal fuel passage 47 is equal to or greater than the expected internal pressure value Pp, the direct injection valve 16 will not open even if pre-ignition occurs in the cylinder 11. The fuel pressure Ph in the internal fuel passage 47 is approximately equal to the supply fuel pressure FP. Therefore, for example, the sum of the value obtained by subtracting the biasing force Fs from the assumed internal pressure Pp and a predetermined offset value α is set as the increased fuel pressure FPup.

[0044] Fs+Ph≧Pp (Formula 1) In step S27, the control device 60 sets the base fuel pressure FPb as the supply fuel pressure target value FPTr. Then, in step S29, the control device 60 operates the fuel pressure regulator based on the supply fuel pressure target value FPTr. For example, when the supply fuel pressure FP is lower than the supply fuel pressure target value FPTr, the control device 60 operates the pressure regulator 23 to increase the amount of fuel supplied to the delivery pipe 24 via the fuel supply device. This increases the supply fuel pressure FP. On the other hand, when the supply fuel pressure FP is higher than the supply fuel pressure target value FPTr, the control device 60 opens the first purge valve 27 to allow the fuel in the delivery pipe 24 to flow into the storage chamber 28. This reduces the supply fuel pressure FP toward the base fuel pressure FPb. That is, when the internal combustion engine 10 is operating in a predetermined operating state, the control device 60 controls the fuel pressure regulator so that the supply fuel pressure FP is reduced before the start of fuel injection from the specified direct injection valve. Specifically, the control device 60 controls the fuel pressure regulator so that the supply fuel pressure FP is reduced to the base fuel pressure FPb before the start of fuel injection from the specified direct injection valve. Therefore, steps S27 and S29 correspond to the "fuel pressure reduction process." After that, the control device 60 temporarily ends this process routine.

[0045] <Operation of this embodiment> The operation when the internal combustion engine 10 is in a predetermined operating state will be described with reference to Fig. 4. Fig. 4(A) shows the transition of the opening and closing of the intake valve of a predetermined cylinder, Fig. 4(B) shows the timing of fuel injection from a predetermined direct injection valve, and Fig. 4(C) shows the transition of the supply fuel pressure FP.

[0046] In the example shown in Figure 4, the intake valve opens at timing t11. That is, the intake stroke begins in a specific cylinder. At timing t11, the increased fuel pressure FPup is set as the target fuel supply pressure FPTr.

[0047] At timing t12 during the intake stroke, the supply fuel pressure target value FPTr is changed from the increased fuel pressure FPup to the base fuel pressure FPb. The base fuel pressure FPb is lower than the increased fuel pressure FPup. Therefore, the pressure reducing mechanism 25 is activated so that the supply fuel pressure FP is reduced to the base fuel pressure FPb. Specifically, the first purge valve 27 is opened, and fuel in the delivery pipe 24 flows into the storage chamber 28. As a result, the supply fuel pressure FP is reduced toward the base fuel pressure FPb, as indicated by the two-dot chain line in FIG. 4C. In this example, the supply fuel pressure FP has been reduced to the base fuel pressure FPb at timing t13, when fuel injection from the specified direct injection valve is started.

[0048] The fuel stored in the storage chamber 28 is supplied to the intake passage 13 via a second purge passage 29 by opening a second purge valve 30 . During the period when fuel is injected by the specified in-cylinder injection valve, the supply fuel pressure target value FPTr is maintained at the base fuel pressure FPb, and therefore, during this period, the supply and discharge of fuel through the delivery pipe 24 is adjusted so that the supply fuel pressure FP becomes the base fuel pressure FPb.

[0049] At timing t14, fuel injection from the specified direct-cylinder injection valve is terminated. Then, the supply fuel pressure target value FPTr is changed from the base fuel pressure FPb to the increased fuel pressure FPup. When the supply fuel pressure target value FPTr is increased in this manner, the supply fuel pressure FP is also increased toward the increased fuel pressure FPup. That is, after fuel injection from the specified direct-cylinder injection valve, the supply fuel pressure FP becomes higher than the base fuel pressure FPb.

[0050] <Effects of this embodiment> (1-1) When the internal combustion engine 10 is in a predetermined operating state, the supply fuel pressure FP becomes higher than the base fuel pressure FPb after fuel injection from a specified in-cylinder injection valve. This makes it difficult for the specified in-cylinder injection valve to open even if pre-ignition occurs in the specified cylinder and the internal pressure of the specified cylinder increases. As a result, when pre-ignition occurs in the specified cylinder, gas in the specified cylinder can be prevented from flowing into the specified in-cylinder injection valve.

[0051] (1-2) Even if the supply fuel pressure FP is made higher than the base fuel pressure FPb after fuel injection from the specified in-cylinder injection valve, the supply fuel pressure FP is reduced to the base fuel pressure FPb before the start of the next fuel injection from the specified in-cylinder injection valve. Therefore, it is possible to prevent a decrease in the controllability of the fuel injection amount from the specified in-cylinder injection valve when the operating state of the internal combustion engine 10 is a specified operating state. More specifically, it is possible to maintain the controllability of the fuel injection amount from the specified in-cylinder injection valve when the operating state of the internal combustion engine 10 is a specified operating state at the same level as when the operating state of the internal combustion engine 10 is not a specified operating state.

[0052] (Second embodiment) A second embodiment of the fuel supply device will be described with reference to Fig. 5. The second embodiment differs from the first embodiment in that a processing routine for estimating a specified cylinder is executed. In the following description, differences from the first embodiment will be mainly described, and the same reference numerals will be used to designate the same members as those in the first embodiment, and redundant description will be omitted.

[0053] The estimation of the specified cylinder will be described with reference to Fig. 5. Fig. 5 shows a processing routine for estimating the specified cylinder. The CPU 61 executes a control program, and the control device 60 executes this processing routine at each predetermined control cycle.

[0054] In step S31 of this processing routine, the control device 60 determines whether or not pre-ignition has occurred in any of the plurality of cylinders 11. If the control device 60 detects pre-ignition (S31: YES), the control device 60 proceeds to step S33. On the other hand, if the control device 60 does not detect pre-ignition (S31: NO), the control device 60 temporarily ends this processing routine.

[0055] In step S33, the control device 60 identifies the cylinder in which pre-ignition occurred from among the multiple cylinders 11. Then, the control device 60 increments the counter Cnt(#N) of the cylinder 11 in which pre-ignition occurred by 1. For example, if the cylinder 11 in which pre-ignition occurred is cylinder #1, the control device 60 increments the counter Cnt(#1) by 1. After updating the counter Cnt(#N) in this way, the control device 60 proceeds to step S35.

[0056] In step S35, the control device 60 increments the total value CntA of the number of times pre-ignition has occurred in the internal combustion engine 10 by 1. That is, the total value CntA is equal to the sum of the counter Cnt(#1) of cylinder #1, the counter Cnt(#2) of cylinder #2, the counter Cnt(#3) of cylinder #3, and the counter Cnt(#4) of cylinder #4. After updating the total value CntA in this way, the control device 60 proceeds to step S37.

[0057] In step S37, the control device 60 determines whether the total value CntA of the occurrence counts is equal to or greater than the determination value CntAth. A value required to identify the cylinder with the highest probability of pre-ignition occurrence is set as the determination value CntAth. For example, the determination value CntAth is set to a value greater than the number of cylinders of the internal combustion engine 10. If the total value CntA is equal to or greater than the determination value CntAth (S37: YES), the control device 60 proceeds to step S39. On the other hand, if the total value CntA is less than the determination value CntAth (S37: NO), the control device 60 temporarily ends this processing routine.

[0058] In step S39, the control device 60 selects the cylinder with the largest corresponding counter Cnt(#N) from among the plurality of cylinders 11. Then, the control device 60 sets the selected cylinder as the specified cylinder. After setting the specified cylinder in this way, the control device 60 temporarily ends this processing routine.

[0059] If the total value CntA is less than the judgment value CntAth, the control device 60 sets the cylinder that is assumed to be most susceptible to pre-ignition based on the specifications of the internal combustion engine 10 to the specified specification, as described in the first embodiment above.

[0060] <Effects of this embodiment> In this embodiment, in addition to the effects (1-1) and (1-2) of the first embodiment, the following effects can be further obtained.

[0061] (2-1) Even for the same model of internal combustion engine 10, the cylinder in which pre-ignition is most likely to occur may differ depending on the model. Therefore, in this embodiment, when the internal combustion engine 10 is operating, the cylinder 11 in which pre-ignition actually occurred is identified, thereby ascertaining the cylinder in which pre-ignition is most likely to occur. As a result, if pre-ignition actually occurs in the cylinder in which pre-ignition is most likely to occur, the in-cylinder injection valve 16 corresponding to that cylinder is opened, and gas in the cylinder can be prevented from flowing into the in-cylinder injection valve 16.

[0062] (Example of change) The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0063] In the fuel pressure reduction process, if the supply fuel pressure FP can be made lower than the increased fuel pressure FPup, a fuel pressure different from the base fuel pressure FPb may be set as the supply fuel pressure target value FPTr. For example, a fuel pressure between the increased fuel pressure FPup and the base fuel pressure FPb may be set as the supply fuel pressure target value FPTr.

[0064] - It is not necessary to perform the fuel pressure reduction process. In the fuel pressure increasing process, if the supply fuel pressure FP can be made higher than the base fuel pressure FPb, it is not essential to set the target supply fuel pressure FPTr so as to satisfy the above relational expression (Equation 1).

[0065] The number of cylinders in the internal combustion engine does not have to be four. For example, the number of cylinders in the internal combustion engine may be one, three, five or more. The fuel supplied to the direct injection valve 16 by the fuel supply device may be a gaseous fuel other than hydrogen gas.

[0066] The fuel supplied to the direct injection valve 16 by the fuel supply device does not have to be gaseous fuel. The control device 60 is not limited to a device that includes a CPU and a ROM and executes software processing. In other words, the control device 60 may have any one of the following configurations (a) to (c).

[0067] (a) The control device 60 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions that cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0068] (b) The control device 60 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application specific integrated circuits (ASICs) or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array."

[0069] (c) The control device 60 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes of the various processes. [Explanation of symbols]

[0070] 10...Internal combustion engine 11, #1~#4...cylinder 16...In-cylinder injection valve 21...Fuel tank 22…Fuel supply passage 23...Pressure regulator 25...Decompression mechanism 60...Control device

Claims

1. A fuel supply device provided in an internal combustion engine having a plurality of cylinders and a plurality of in-cylinder injection valves provided corresponding to the plurality of cylinders and injecting fuel into the cylinders, a fuel pressure adjusting device that adjusts a supply fuel pressure, which is the pressure of fuel supplied to the cylinder injection valve; and a control device that controls the fuel pressure adjusting device, When the in-cylinder injection valve corresponding to the cylinder with the highest probability of pre-ignition occurring among the plurality of cylinders is defined as the specified in-cylinder injection valve, The control device a fuel pressure maintaining process for controlling the fuel pressure adjusting device so that the supply fuel pressure is maintained at a base fuel pressure when the operating state of the internal combustion engine is not a predetermined operating state; and executing a fuel pressure increasing process for controlling the fuel pressure adjusting device so that the supply fuel pressure after fuel injection from the specified in-cylinder injection valve becomes higher than the base fuel pressure when the operating state of the internal combustion engine is the predetermined operating state. Fuel supply device.

2. When the operating state of the internal combustion engine is the predetermined operating state, the control device executes a fuel pressure reduction process to control the fuel pressure adjustment device so that the supply fuel pressure is reduced before the start of fuel injection from the specified direct injection valve.

2. The fuel supply system of claim 1.

3. In the fuel pressure reduction process, the control device controls the fuel pressure adjustment device so that the supply fuel pressure is reduced to the base fuel pressure before the start of fuel injection from the specified direct injection valve.

3. The fuel supply system according to claim 2.

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