Fuel pressure control device of internal combustion engine

Abstract

To rapidly reduce pressure of fuel supplied to a fuel injection valve and also suppress pressure fluctuation.SOLUTION: A control device 100 executes a first process, a second process and a third process as a fuel pressure reduction control. The first process includes closing both a pressure reducing valve 30 being a first electromagnetic valve and a second shutoff valve 22 being a second electromagnetic valve when execution request of the fuel pressure reduction control is made. The second process includes adjusting the fuel pressure of fuel supplied to a fuel injection valve 15 by repeatedly performing opening / closing drive of the second shutoff valve 22 after execution of the first process. The third process includes, when, after execution of the second process, the fuel pressure in a fuel piping 40 between the pressure reducing valve 30 and the second shutoff valve 22 becomes a predetermined pressure, adjusting the fuel pressure of the fuel supplied to the fuel injection valve 15 by stopping the opening / closing drive of the second shutoff valve 22 to maintain the second shutoff valve 22 in a valve open state, and repeatedly performing opening / closing drive of the pressure reducing valve 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, the internal combustion engine described in Patent Document 1 reduces the pressure of gaseous fuel stored in a tank and supplies the fuel to a fuel injection valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-182969 Summary of the Invention [Problem to be solved by the invention]

[0004] As the fuel pressure reduction control as described above, the following control may be performed. That is, a solenoid valve is provided in a fuel passage connecting a fuel tank and a fuel injection valve that supplies fuel to a cylinder, and opens and closes the fuel passage. Allowable upper and lower limits are set for a target fuel pressure. When fuel is injected from the fuel injection valve with the solenoid valve closed, fuel flows out of the fuel passage downstream of the solenoid valve, causing the fuel pressure downstream of the solenoid valve to drop. When this downstream fuel pressure reaches the lower limit, the solenoid valve is opened. This opening of the solenoid valve supplies fuel to the fuel passage downstream of the solenoid valve, causing the fuel pressure downstream of the solenoid valve to rise. When this downstream fuel pressure reaches the upper limit, the solenoid valve is closed. By repeatedly opening and closing the solenoid valve in this way, the fuel pressure downstream of the solenoid valve, which is the pressure of fuel supplied to the fuel injection valve, is adjusted to be within a predetermined control range between the upper and lower limits.

[0005] When the fuel pressure reduction control is executed, the time it takes for the actual fuel pressure to drop to within the control range becomes shorter as the volume of the fuel passage from the solenoid valve to the fuel injection valve becomes smaller. However, the smaller the volume of the fuel passage, the more significant the pressure fluctuations that accompany the opening and closing of the solenoid valve.

[0006] Therefore, when fuel pressure reduction control is executed, it is desirable to quickly reduce the pressure of the fuel supplied to the fuel injection valve and suppress pressure fluctuations in the fuel passage. [Means for solving the problem]

[0007] A fuel pressure control device for an internal combustion engine that solves the above-mentioned problems is applied to an internal combustion engine having a tank that stores fuel, a fuel injection valve that supplies fuel to a cylinder, a fuel passage connecting the tank and the fuel injection valve, a first solenoid valve provided in the fuel passage for opening and closing the fuel passage, and a second solenoid valve provided in the fuel passage downstream of the first solenoid valve in the fuel flow direction through the fuel passage for opening and closing the fuel passage, and the fuel pressure control device performs fuel pressure reduction control and has a processing circuit. The fuel pressure reduction control adjusts the fuel pressure of the fuel supplied to the fuel injection valve so that the fuel pressure is lower than before the fuel pressure reduction control is performed. The processing circuit is configured to perform first, second, and third processes as the fuel pressure reduction control. The first process closes both the first and second solenoid valves when a request to perform the fuel pressure reduction control is issued. The second process adjusts the fuel pressure of the fuel supplied to the fuel injection valve by repeatedly opening and closing the second solenoid valve after performing the first process. The third process is a process in which, when the fuel pressure in the fuel passage between the first solenoid valve and the second solenoid valve reaches a predetermined pressure after the second process is executed, the opening and closing drive of the second solenoid valve is stopped to maintain the second solenoid valve in an open state, and the fuel pressure of the fuel supplied to the fuel injection valve is adjusted by repeatedly opening and closing the first solenoid valve. [Effects of the Invention]

[0008] This fuel pressure control device for an internal combustion engine can quickly reduce the pressure of the fuel supplied to the fuel injection valve and suppress pressure fluctuations in the fuel passage. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an internal combustion engine and a control device according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 3] 3A and 3B are timing charts showing the fuel pressure reduction control of the embodiment, in which Fig. 3A shows the change in fuel pressure, Fig. 3B shows the operating state of the pressure reducing valve, and Fig. 3C shows the operating state of the second shutoff valve. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a fuel pressure control device for an internal combustion engine according to one embodiment will be described with reference to FIGS. <About internal combustion engines> An internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle and is an internal combustion engine that uses hydrogen gas as a gaseous fuel.

[0011] An intake passage 11 of the internal combustion engine 10 is provided with a throttle valve 12 for adjusting the amount of intake air. The fuel supply device 200 provided in the internal combustion engine 10 includes a fuel injection valve 15, a tank 20, a fuel pipe 40, a first shutoff valve 21, a second shutoff valve 22, a pressure reducing valve 30, and a delivery pipe 60.

[0012] The fuel injection valve 15 supplies fuel to the cylinder 10 a of the internal combustion engine 10 . The tank 20 stores hydrogen gas, which is a gaseous fuel, in a highly compressed state. The fuel pipe 40 connects the tank 20 and the delivery pipe 60 .

[0013] The fuel injection valve 15 is connected to the delivery pipe 60. The fuel piping 40 and the delivery pipe 60 are a fuel passage connecting the tank 20 and the fuel injection valve 15. The hydrogen gas stored in the tank 20 is supplied to the fuel injection valve 15 via the fuel piping 40 and the delivery pipe 60.

[0014] In the fuel pipe 40, a first shutoff valve 21, a pressure reducing valve 30, and a second shutoff valve 22 are arranged in this order in the direction of fuel flow. The first shutoff valve 21 is an electromagnetic valve and is disposed near the outlet of the tank 20. When the first shutoff valve 21 is open, fuel is supplied from the tank 20 to the fuel pipe 40. When the first shutoff valve 21 is closed, fuel supply from the tank 20 to the fuel pipe 40 is stopped.

[0015] The pressure reducing valve 30 is an electromagnetic valve that reduces the fuel pressure of the hydrogen gas stored in the tank 20 under high pressure to a specified pressure (for example, about 4 MPa) and supplies the fuel to the fuel injection valve 15. The pressure reducing valve 30 is a first electromagnetic valve that is provided in the fuel passage and opens and closes the fuel passage.

[0016] The second shutoff valve 22 is a solenoid valve and is disposed near the delivery pipe 60. When the second shutoff valve 22 is open due to energization, fuel is supplied to the delivery pipe 60. When the second shutoff valve 22 is closed due to de-energization, fuel supply to the delivery pipe 60 is stopped. The second shutoff valve 22 is a second solenoid valve that is provided in the fuel passage downstream of the first solenoid valve in the flow direction of fuel in the fuel passage and opens and closes the fuel passage.

[0017] The first shutoff valve 21 and the second shutoff valve 22 are closed when the internal combustion engine 10 is not operating. On the other hand, the first shutoff valve 21 and the second shutoff valve 22 are basically open when the internal combustion engine 10 is operating.

[0018] A first pressure sensor 81 provided in the fuel pipe 40 between the first shutoff valve 21 and the pressure reducing valve 30 detects a first pressure P1, which is the fuel pressure in the fuel pipe 40 between the first shutoff valve 21 and the pressure reducing valve 30.

[0019] A second pressure sensor 82 provided in the fuel pipe 40 between the pressure reducing valve 30 and the second shutoff valve 22 detects a second pressure P2, which is the fuel pressure in the fuel pipe 40 between the pressure reducing valve 30 and the second shutoff valve 22.

[0020] A third pressure sensor 83 provided in the delivery pipe 60 detects a third pressure P3, which is the fuel pressure in the delivery pipe 60. A temperature sensor 84 provided in the delivery pipe 60 detects a fuel temperature THF, which is the temperature of the fuel in the delivery pipe 60.

[0021] The control device 100 performs various controls such as fuel injection for the internal combustion engine 10 by controlling various control objects such as the throttle valve 12, the fuel injection valve 15, the first shutoff valve 21, the second shutoff valve 22, and the pressure reducing valve 30. The control device 100 includes a CPU 110 and a memory 120 configured from a ROM, a RAM, etc., and performs various controls by the CPU 110 executing programs stored in the memory 120.

[0022] The control device 100 refers to various values required for controlling the internal combustion engine 10. For example, the control device 100 refers to the detection values of the first pressure sensor 81, the second pressure sensor 82, the third pressure sensor 83, and the temperature sensor 84. The control device 100 also refers to a detection signal from an accelerator position sensor 71 that detects an accelerator operation amount ACCP, which is an operation amount of an accelerator pedal 27 operated by a driver of a vehicle equipped with the internal combustion engine 10. The control device 100 also refers to a detection signal from a speed sensor 72 that detects a vehicle speed SP of the vehicle equipped with the internal combustion engine 10. The control device 100 also refers to a detection signal from an air flow meter 73 that detects an intake air amount GA of the internal combustion engine 10, and a detection signal Scr from a crank angle sensor 74 that detects a rotation angle of a crankshaft of the internal combustion engine 10.

[0023] The control device 100 calculates the engine speed NE based on the detection signal Scr from the crank angle sensor 74. 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 10 is steadily operated at the current engine speed NE under full load. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

[0024] Hydrogen gas, which is the engine fuel, has a wider range of combustible mixtures than gasoline, and can be combusted even in lean mixtures. Therefore, the control device 100 adjusts the output of the internal combustion engine 10 through the following combustion control.

[0025] That is, the control device 100 calculates a required output Pe, which is a required value of the engine output of the internal combustion engine 10, based on the accelerator operation amount ACCP and the like. The control device 100 sets a required injection amount Qd based on the required output Pe. The required injection amount Qd is a target value of fuel injected from one fuel injection valve 15 in one combustion cycle. The control device 100 calculates a required air amount GAd, which is a target value of the intake air amount required to achieve the target air-fuel ratio AFt, based on the target air-fuel ratio AFt and the required injection amount Qd. In this embodiment, the target air-fuel ratio AFt is a lean air-fuel ratio, for example, an excess air ratio λ = 2.5 to 3.0. The control device 100 then controls the fuel injection valve 15 so that an amount of fuel corresponding to the required injection amount Qd is injected. The control device 100 also controls the opening of the throttle valve 12 so that an amount of air corresponding to the required air amount GAd is introduced into the cylinder. In this way, in the internal combustion engine 10, output adjustment is performed by changing the air-fuel ratio of the mixture through adjustment of the fuel injection amount and the intake air amount.

[0026] <Fuel pressure control> The control device 100 is a fuel pressure control device that adjusts the pressure of fuel supplied to the fuel injection valve 15. That is, an upper limit value PNU and a lower limit value PNL that are allowable for a first target pressure PNt1 (for example, a pressure of about 4 MPa), which is a target value of the fuel pressure, are set. Then, with the first shutoff valve 21 and the second shutoff valve 22 maintained in an open state, the control device 100 drives the pressure reducing valve 30 to open when a third pressure P3, which is the fuel pressure in the delivery pipe 60, reaches the lower limit value PNL. By driving the pressure reducing valve 30 to open, fuel is supplied to the fuel passage downstream of the pressure reducing valve 30, and the fuel pressure downstream of the pressure reducing valve 30 increases. Then, when the third pressure P3 reaches the upper limit value PNU, the control device 100 drives the pressure reducing valve 30 to close. By repeatedly driving the pressure reducing valve 30 to open and close in this manner, the fuel pressure downstream of the pressure reducing valve 30, that is, the pressure of the fuel supplied to the fuel injection valve 15, is adjusted to be within a predetermined control range CRN between an upper limit value PNU and a lower limit value PNL.

[0027] <Fuel pressure drop control> On the other hand, when the fuel injection amount of the fuel injection valve 15 is reduced, such as during idling, the control device 100 performs fuel pressure reduction control to maintain the third pressure P3, which is the fuel pressure in the delivery pipe 60, at a pressure lower than the first target pressure PNt1. The fuel pressure reduction control adjusts the fuel pressure so that the fuel pressure of the fuel supplied to the fuel injection valve 15 is lower than before the fuel pressure reduction control is performed. By performing this fuel pressure reduction control, a small amount of fuel is injected from the fuel injection valve 15 with high precision. When performing this fuel pressure reduction control, a second target pressure PNt2 (e.g., a pressure of approximately 1 MPa) lower than the first target pressure PNt1 is set, and an upper limit value PLU and a lower limit value PLL that are allowable for this second target pressure PNt2 are set. The upper limit value PLU is a pressure lower than the above-mentioned lower limit value PNL. Then, the control device 100 executes the processing described below to adjust the pressure of the fuel supplied to the fuel injection valve 15 to be within a predetermined control range CRL sandwiched between an upper limit value PLU and a lower limit value PLL.

[0028] The control device 100 executes the process shown in FIG. 2 to perform the fuel pressure reduction control. Fig. 2 shows the procedure of the process executed by the control device 100. The process shown in Fig. 2 is implemented by the CPU 110 executing a program stored in the memory 120 of the control device 100. The process shown in Fig. 2 is started when there is a request to execute fuel pressure reduction control. For example, the control device 100 requests the execution of fuel pressure reduction control when the operating state of the internal combustion engine 10 transitions to an idle operating state. Hereinafter, step numbers are represented by numbers preceded by "S."

[0029] When this process starts, the control device 100 closes both the pressure reducing valve 30 and the second shutoff valve 22 (S100). The process of S100 is a first process for closing both the first solenoid valve and the second solenoid valve when a request to execute fuel pressure reduction control is made.

[0030] Next, the control device 100 determines whether the third pressure P3 is equal to or less than the lower limit value PLL (S110).The control device 100 then repeatedly executes the process of S110 until it is determined that the third pressure P3 is equal to or less than the lower limit value PLL.

[0031] If it is determined in the process of S110 that the third pressure P3 is equal to or less than the lower limit value PLL, the control device 100 performs fuel pressure adjustment using the second shutoff valve 22 (S120). The fuel pressure adjustment in S120 is performed by repeatedly driving the second shutoff valve 22 to open and close so that the third pressure P3 is within the above-mentioned control range CRL. The process of S120 is a second process that adjusts the fuel pressure of the fuel supplied to the fuel injection valve by repeatedly driving the second solenoid valve to open and close after the first process is performed. The driving of the second solenoid valve to open and close by this second process is started when the fuel pressure of the fuel supplied to the fuel injection valve reaches a predetermined pressure after the first process is performed. In other words, when the third pressure P3 becomes equal to or less than the above-mentioned lower limit value PLL, the driving of the second solenoid valve to open and close by the second process is started.

[0032] Next, the control device 100 determines whether the absolute value of the difference between the second pressure P2 and the third pressure P3 is equal to or less than a predetermined judgment value ΔPref (S130). The judgment value ΔPref is an adaptive value for determining whether the second pressure P2 is close to the third pressure P3.

[0033] Then, the control device 100 repeatedly executes the process of S130 until it is determined that the absolute value of the difference between the second pressure P2 and the third pressure P3 is equal to or smaller than the reference value ΔPref. If it is determined in the process of S130 that the absolute value of the difference between the second pressure P2 and the third pressure P3 is equal to or less than the reference value ΔPref, the control device 100 closes the second shutoff valve 22 (140). Then, the control device 100 executes fuel pressure adjustment using the pressure reducing valve 30 (S150). The fuel pressure adjustment in S150 is performed by repeatedly driving the pressure reducing valve 30 to open and close so that the third pressure P3 falls within the control range CRL described above. The processes of S140 and S150 constitute a third process. This third process is executed when the fuel pressure in the fuel passage between the first solenoid valve and the second solenoid valve reaches a predetermined pressure after the second process is executed. That is, the third process is a process in which the opening and closing drive of the second solenoid valve is stopped to keep the second solenoid valve open, and the first solenoid valve is repeatedly opened and closed to adjust the fuel pressure of the fuel supplied to the fuel injection valve.

[0034] Next, the control device 100 determines whether or not there is currently a request to execute fuel pressure reduction control (S160), and the control device 100 repeatedly executes the process of S160 until it is determined that there is no request to execute the control.

[0035] If it is determined in the processing of S160 that there is no request to execute fuel pressure reduction control, the control device 100 opens both the pressure reducing valve 30 and the second shutoff valve 22 (S170). The control device 100 determines that there is no request to execute fuel pressure reduction control when, for example, the operating state of the internal combustion engine 10 transitions to a state where the engine load is higher than the idle operating state. The processing of S170 is a fourth processing that opens both the first solenoid valve and the second solenoid valve when there is no longer a request to execute fuel pressure reduction control during the execution of the third processing.

[0036] Next, the control device 100 determines whether the third pressure P3 is equal to or greater than the upper limit value PNU (S180). The control device 100 then repeatedly executes the process of S180 until it is determined that the third pressure P3 is equal to or greater than the upper limit value PNU.

[0037] If it is determined in the processing of S180 that the third pressure P3 is equal to or greater than the upper limit value PNU, the control device 100 performs fuel pressure adjustment using the pressure reducing valve 30 (S190). The fuel pressure adjustment in S190 is performed by repeatedly driving the pressure reducing valve 30 to open and close so that the third pressure P3 falls within the above-mentioned control range CRN.

[0038] After executing the process of S190, the control device 100 ends this process. <Operation of this embodiment> An example of fuel pressure reduction control is shown in Figure 3. Figure 3(a) shows the changes in the second pressure P2 and the third pressure P3, Figure 3(b) shows the operating state of the pressure reducing valve 30, and Figure 3(c) shows the operating state of the second shutoff valve 22.

[0039] Before time t1, the vehicle is running normally, and the second shutoff valve 22 is maintained in an open state. The pressure reducing valve 30 is repeatedly opened and closed, thereby adjusting the second pressure P2 and the third pressure P3 to fuel pressures within the control range CRN.

[0040] At time t1, when an idle operation is requested of the internal combustion engine 10, execution of fuel pressure reduction control is requested, and first, both the pressure reducing valve 30 and the second shutoff valve 22 are closed and maintained in that state. While the pressure reducing valve 30 and the second shutoff valve 22 are closed, the fuel in the delivery pipe 60 decreases each time fuel is injected from the fuel injection valve 15, so the third pressure P3 indicated by the solid line gradually decreases, while the second pressure P2 indicated by the two-dot chain line is maintained at the pressure at time t1.

[0041] At time t2, when the third pressure P3 drops to the lower limit value PLL, the process of S120 is started, thereby starting fuel pressure regulation that repeatedly opens and closes the second shutoff valve 22. By this fuel pressure regulation, the third pressure P3 is regulated to a fuel pressure within the control range CRL.

[0042] At time t2, when fuel pressure adjustment by the second shut-off valve 22 begins, the fuel that was present in the fuel piping 40 between the second shut-off valve 22 and the pressure reducing valve 30 flows into the delivery pipe 60, and the second pressure P2 gradually decreases.

[0043] At time t3, when the absolute value of the difference between the third pressure P3, which is adjusted to a fuel pressure within the control range CRL, and the reduced second pressure P2 becomes equal to or less than the determination value ΔPref, the processing of S140 and the processing of S150 are started. Therefore, the second shutoff valve 22 is maintained in an open state, and fuel pressure adjustment is started by repeatedly driving the pressure reducing valve 30 to open and close. This fuel pressure adjustment continuously maintains the third pressure P3 at a fuel pressure within the control range CRL.

[0044] At time t4, when the request to execute the fuel pressure reduction control is released, the process of S170 is executed, and the pressure reducing valve 30 and the second shutoff valve 22 are both opened and maintained in that state. While the pressure reducing valve 30 and the second shutoff valve 22 are open, fuel is supplied from the tank 20 toward the delivery pipe 60, so the second pressure P2 and the third pressure P3 gradually increase.

[0045] At time t5, when the third pressure P3 increases to the upper limit value PNU, the process of S190 is started, thereby starting fuel pressure regulation that repeatedly opens and closes the pressure reducing valve 30. By this fuel pressure regulation, the third pressure P3 is regulated to a fuel pressure within the control range CRN.

[0046] <Effects of this embodiment> (1) The control device 100 executes a first process, a second process, and a third process as fuel pressure reduction control.

[0047] The first process is a process for closing both the pressure reducing valve 30 and the second shutoff valve 22 when a request to execute fuel pressure reduction control is made. When the first process is executed, the second shutoff valve 22 is closed. Here, the second shutoff valve 22 is provided downstream of the pressure reducing valve 30 in the fuel pipe 40. Therefore, compared to when the pressure reducing valve 30 is closed and the second shutoff valve 22 is open, the volume inside the fuel pipe 40 from the closed solenoid valve to the fuel injection valve 15 is smaller. When the volume inside the fuel pipe 40 is smaller, the rate at which the fuel pressure in the fuel pipe 40 decreases due to fuel injection from the fuel injection valve 15 increases. Therefore, when the fuel pressure reduction control is executed, the fuel pressure of the fuel supplied to the fuel injection valve 15 can be quickly reduced.

[0048] The second process is a process for adjusting the fuel pressure of the fuel supplied to the fuel injection valve 15 by repeatedly driving the second shutoff valve 22 to open and close after the first process is executed. In the second process, the second shutoff valve 22 is repeatedly driven to open and close, thereby maintaining the fuel pressure that was reduced by the execution of the first process.

[0049] Furthermore, the third process is a process for stopping the opening and closing of the second shutoff valve 22 and maintaining the second shutoff valve 22 in an open state when the second pressure P2, which is the fuel pressure in the fuel pipe 40 between the pressure reducing valve 30 and the second shutoff valve 22, reaches a predetermined pressure after the second process is executed. The third process is a process for adjusting the fuel pressure of the fuel supplied to the fuel injection valve 15 by repeatedly opening and closing the pressure reducing valve 30. Therefore, compared to a case in which the fuel pressure of the fuel supplied to the fuel injection valve 15 is adjusted by repeatedly opening and closing the second shutoff valve 22, the volume inside the fuel pipe 40 from the solenoid valve being opened and closed and the fuel injection valve 15 becomes larger. When the volume inside the fuel pipe 40 becomes larger, the increase in fuel pressure that occurs when the fuel consumed by fuel injection is replenished into the fuel pipe 40 and the decrease in fuel pressure that occurs due to fuel consumption in the fuel pipe 40 due to fuel injection are slowed down. Therefore, fluctuations in the fuel pressure in the fuel pipe 40 can be suppressed. More specifically, the fluctuation period of the fuel pressure in the fuel pipe 40 becomes longer, and therefore the pressure fluctuation becomes gentler.

[0050] Furthermore, as described above, when the fuel pressure of the fuel supplied to the fuel injection valve 15 is adjusted by repeatedly driving the pressure reducing valve 30 to open and close, changes in the fuel pressure due to fuel replenishment to the fuel pipe 40 and fuel consumption in the fuel pipe 40 are gradual. Therefore, when the fuel pressure is adjusted to be within a predetermined control range by repeatedly driving the solenoid valve to open and close, the opening and closing times of the solenoid valve become longer, and the number of times the solenoid valve is opened and closed within a certain period of time decreases. Therefore, in the third process, the number of times the solenoid valve provided in the fuel pipe 40 of the internal combustion engine 10 is opened and closed can be reduced compared to when the fuel pressure of the fuel supplied to the fuel injection valve 15 is adjusted by repeatedly driving the second shutoff valve 22 to open and close.

[0051] (2) The control device 100 executes a fourth process. The fourth process is a process for opening both the pressure reducing valve 30 and the second shutoff valve 22 when the request to execute the fuel pressure reduction control is no longer present during execution of the third process. According to this fourth process, when the request to execute the fuel pressure reduction control is no longer present, both the pressure reducing valve 30 and the second shutoff valve 22 are opened. Therefore, the fuel pressure of the fuel supplied to the fuel injector 15 can be quickly increased.

[0052] (3) The fuel of the internal combustion engine 10 is gaseous fuel. Unlike liquid fuels such as gasoline, gaseous fuel has poor lubricity. Therefore, the solenoid valve, which repeatedly opens and closes, is prone to wear due to sliding. In this regard, according to the fuel pressure control device of this embodiment, as described above, the number of times the solenoid valve provided in the fuel pipe 40 operates can be reduced. Therefore, wear on the solenoid valve provided in the fuel pipe 40 of the internal combustion engine 10 that uses gaseous fuel can be suppressed.

[0053] <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.

[0054] In the process of S110 shown in Fig. 2, it is determined whether the third pressure P3 is equal to or less than the lower limit value PLL. Alternatively, in the process of S110, it is determined by another method whether the third pressure P3 is within the control range CRL. If the third pressure P3 is within the control range CRL, the processes from S120 onward may be similarly performed.

[0055] In the process of S130 shown in Fig. 2, it is determined whether the absolute value of the difference between the second pressure P2 and the third pressure P3 is equal to or less than the reference value ΔPref. Alternatively, in the process of S130, it may be determined by another method whether the second pressure P2 is within the control range CRL. If the second pressure P2 is within the control range CRL, the processes from S140 onward may be similarly performed.

[0056] 2, it is determined whether the third pressure P3 is equal to or greater than the upper limit value PNU. Alternatively, in the process of S180, it may be determined by another method whether the third pressure P3 is within the control range CRN. If the third pressure P3 is within the control range CRN, the process of S190 may be similarly performed.

[0057] Furthermore, in the process of S180, it is determined whether the second pressure P2 is equal to or greater than the upper limit value PNU. If the second pressure P2 is equal to or greater than the upper limit value PNU, the process of S190 may be similarly performed. Furthermore, in the process of S180, it is determined by another method whether the second pressure P2 is within the control range CRN. If the second pressure P2 is within the control range CRN, the process of S190 may be similarly performed.

[0058] The fuel for the internal combustion engine 10 is hydrogen gas, which is a gaseous fuel, but other gaseous fuels, such as compressed natural gas, may also be used. The fuel used in the internal combustion engine 10 is gaseous fuel, but it may be liquid fuel.

[0059] The control device 100 is not limited to a device equipped with a CPU and memory and executing software processing. For example, the control device 100 may be equipped with a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of the software processing performed in the above embodiments. That is, the control device 100 may include a processing circuit having any of the following configurations (a) to (c): (a) a processing circuit equipped with one or more processing devices that execute all of the above processing according to a program and one or more program storage devices, such as ROM, that store the program; (b) a processing circuit equipped with one or more processing devices and one or more program storage devices that execute part of the above processing according to a program, and one or more dedicated hardware circuits that execute the remaining processing; (c) a processing circuit equipped with one or more dedicated hardware circuits that execute all of the above processing. Program storage devices, i.e., computer-readable media, include any available media that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0060] 10...Internal combustion engine 10a...cylinder 11...Intake passage 12...Throttle valve 12...Throttle valve passage 15...Fuel injection valve 20...Tank 21...First shutoff valve 22...Second shutoff valve 27...Accelerator pedal 30...Reducing valve 40…Fuel piping 60...Delivery pipe 71...Accelerator position sensor 72...Speed sensor 73...Air flow meter 74...Crank angle sensor 81...First pressure sensor 82...Second pressure sensor 83...Third pressure sensor 84...Temperature sensor 100...Control device 110...CPU 120...Memory 200…Fuel supply device

Claims

1. a fuel pressure control device adapted to an internal combustion engine having a tank for storing fuel, a fuel injection valve for supplying fuel to a cylinder, a fuel passage connecting the tank and the fuel injection valve, a first electromagnetic valve provided in the fuel passage for opening and closing the fuel passage, and a second electromagnetic valve provided in the fuel passage downstream of the first electromagnetic valve in a fuel flow direction in the fuel passage for opening and closing the fuel passage, the fuel pressure control device performing fuel pressure reduction control and having a processing circuit, the fuel pressure reduction control is control for adjusting the fuel pressure so that the fuel pressure of the fuel supplied to the fuel injection valve is reduced compared to before the fuel pressure reduction control was performed, the processing circuit is configured to execute a first process, a second process, and a third process as the fuel pressure reduction control, the first process is a process for closing both the first solenoid valve and the second solenoid valve when a request for execution of the fuel pressure reduction control is issued, the second process is a process for adjusting a fuel pressure of fuel supplied to the fuel injection valve by repeatedly driving the second solenoid valve to open and close after the first process is executed, The third process is a process in which, when the fuel pressure in the fuel passage between the first solenoid valve and the second solenoid valve reaches a predetermined pressure after the second process is executed, the opening and closing drive of the second solenoid valve is stopped to maintain the second solenoid valve in an open state, and the opening and closing drive of the first solenoid valve is repeatedly performed to adjust the fuel pressure of the fuel supplied to the fuel injection valve. Fuel pressure control device for internal combustion engines.

2. The opening and closing drive of the second solenoid valve by the second process is started when the fuel pressure of the fuel supplied to the fuel injection valve reaches a predetermined pressure after the first process is executed.

2. The fuel pressure control device for an internal combustion engine according to claim 1.

3. the processing circuitry is configured to perform a fourth operation; The fourth process is a process for opening both the first solenoid valve and the second solenoid valve when the request for execution of the fuel pressure reduction control is no longer present during execution of the third process.

2. The fuel pressure control device for an internal combustion engine according to claim 1.

4. The fuel is a gaseous fuel 2. The fuel pressure control device for an internal combustion engine according to claim 1.

5. The request to execute the fuel pressure reduction control is a request that occurs when the operating state of the internal combustion engine transitions to an idle operating state.

2. The fuel pressure control device for an internal combustion engine according to claim 1.

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