Fuel supply system for internal combustion engines

Abstract

To properly detect hydrogen gas leaks. [Solution] The control device 100 of the fuel supply device 300 includes a processing circuit 110 that performs a process to determine whether or not there is a fuel leak in the fuel passage downstream of the second shut-off valve 22, which is provided in the fuel passage and opens and closes the fuel passage. When the mass of the fuel in the fuel passage downstream of the second shut-off valve 22 is defined as the hydrogen mass, the processing circuit 110 performs the following processes: calculate a first hydrogen mass based on the fuel pressure and fuel temperature when the second shut-off valve 22 is closed due to engine shutdown; calculate a second hydrogen mass based on the fuel pressure and fuel temperature immediately before the second shut-off valve 22 opens due to engine startup after engine shutdown; calculate the difference between the first hydrogen mass and the second hydrogen mass; and determine whether or not there is a fuel leak based on the difference.

Description

Technical Field

[0001] The present invention relates to a fuel supply device for an internal combustion engine.

Background Art

[0002] Internal combustion engines using hydrogen gas as fuel are known. When such an internal combustion engine is stopped, fuel leakage occurs if, for example, poor closing of a fuel injection valve occurs. Therefore, it is necessary to detect fuel leakage from a fuel passage including the fuel injection valve. Accordingly, for example, in the internal combustion engine described in Patent Document 1, a hydrogen detection sensor that detects hydrogen gas leaking from a fuel system is provided in an upper cover mounted on a head cover.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] When fuel leakage is detected using the above hydrogen detection sensor, fuel leakage may not be properly detected unless the hydrogen gas detection portion of the hydrogen detection sensor is installed at an appropriate position. On the other hand, when there is fuel leakage from the fuel passage, the fuel pressure in the fuel passage gradually decreases when the fuel passage is sealed. Therefore, it is possible to detect leakage of hydrogen gas based on such a change in fuel pressure.

[0005] However, when the fuel temperature in the fuel passage rises due to heat transferred from the internal combustion engine, the density of the fuel changes and the change in fuel pressure becomes small, so there is a risk that leakage of hydrogen gas cannot be properly detected.

Means for Solving the Problem

[0006] A fuel supply device for an internal combustion engine that solves the above problems includes a tank for storing hydrogen gas, which is the fuel for the internal combustion engine; a fuel injection valve for supplying the fuel to the cylinders; a fuel passage for supplying the fuel in the tank to the fuel injection valve; a solenoid valve provided in the fuel passage for opening and closing the fuel passage; a pressure sensor for detecting the fuel pressure in the fuel passage downstream of the solenoid valve when viewed in the direction of fuel flow; a temperature sensor for detecting the fuel temperature in the downstream fuel passage; and a control device equipped with a processing circuit that performs a process to determine whether or not there is a fuel leak in the downstream fuel passage. When the mass of the fuel in the downstream fuel passage is defined as the hydrogen mass, the processing circuit performs a process to calculate a first hydrogen mass based on the fuel pressure and fuel temperature when the solenoid valve is closed due to engine shutdown; a process to calculate a second hydrogen mass based on the fuel pressure and fuel temperature immediately before the solenoid valve opens due to engine startup after the engine shutdown has been performed; a process to calculate the difference between the first hydrogen mass and the second hydrogen mass; and a process to determine whether or not there is a fuel leak based on the difference. [Effects of the Invention]

[0007] This internal combustion engine's fuel supply system can properly detect hydrogen gas leaks. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a fuel supply system for an internal combustion engine in one embodiment. [Figure 2] Figure 2 is a timing chart showing the changes in each value when there is a hydrogen gas leak, where (A) shows the changes in the operating state of the internal combustion engine, (B) shows the changes in the open / closed state of the second shut-off valve, (C) shows the changes in fuel temperature, (D) shows the changes in the third pressure, and (E) shows the magnitude of the calculated hydrogen mass. [Modes for carrying out the invention]

[0009] Below, one embodiment of a fuel supply system for an internal combustion engine will be described with reference to Figures 1 and 2. <Configuration of the fuel supply system for an internal combustion engine> The internal combustion engine 10 shown in Figure 1 is mounted on a vehicle and uses hydrogen gas, a fluid gaseous fuel, as its fuel. The vehicle is, for example, a hybrid vehicle equipped with the internal combustion engine 10 and an electric motor as prime movers. In such a hybrid vehicle, the internal combustion engine 10 is operated intermittently.

[0010] The 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 system 300 provided by the internal combustion engine 10 includes a fuel injection valve 15, a tank 20, fuel piping 40, a first shut-off valve 21, a second shut-off valve 22, a pressure reducing valve 30, and a delivery pipe 60.

[0011] The fuel injector 15 supplies fuel to the cylinder 10a of the internal combustion engine 10. The tank 20 stores hydrogen gas, a gaseous fuel, in a compressed state. The fuel piping 40 connects the tank 20 to the delivery pipe 60. The fuel injector 15 is connected to the delivery pipe 60. The fuel piping 40 and the delivery pipe 60 are fuel passages connecting the tank 20 and the fuel injector 15. The hydrogen gas stored in the tank 20 is supplied to the fuel injector 15 via the fuel piping 40 and the delivery pipe 60.

[0012] In the fuel piping 40, a first shut-off valve 21, a pressure reducing valve 30, and a second shut-off valve 22 are arranged in order in the direction of fuel flow. The first shut-off valve 21 is a solenoid valve and is located near the outlet of the tank 20. When the first shut-off valve 21 is open, fuel is supplied from the tank 20 to the fuel piping 40. When the first shut-off valve 21 is closed, the fuel supply from the tank 20 to the fuel piping 40 is stopped.

[0013] The pressure reducing valve 30 is a valve for reducing the fuel pressure, which is the fuel pressure of hydrogen gas stored in a high-pressure state in the tank 20, to a prescribed pressure (for example, approximately 4 MPa) and supplying the pressure-reduced hydrogen gas to the fuel injection valves 15.

[0014] The second shut-off valve 22 is a solenoid valve, and is disposed near the delivery pipe 60 in the fuel pipe 40. When the second shut-off valve 22 is opened by energization, fuel is supplied to the delivery pipe 60. When the second shut-off valve 22 is closed by stopping energization, the fuel supply to the delivery pipe 60 is stopped.

[0015] The first shut-off valve 21 and the second shut-off valve 22 are closed when the operation of the internal combustion engine 10 is stopped. On the other hand, the first shut-off valve 21 and the second shut-off valve 22 are basically open during the operation of the internal combustion engine 10.

[0016] The first pressure sensor 81 provided on the fuel pipe 40 between the first shut-off valve 21 and the pressure reducing valve 30 detects a first pressure P1, which is the fuel pressure inside the fuel pipe 40 between the first shut-off valve 21 and the pressure reducing valve 30.

[0017] The second pressure sensor 82 provided on the fuel pipe 40 between the pressure reducing valve 30 and the second shut-off valve 22 detects a second pressure P2, which is the fuel pressure inside the fuel pipe 40 between the pressure reducing valve 30 and the second shut-off valve 22.

[0018] The third pressure sensor 83 provided on the delivery pipe 60 detects a third pressure P3, which is the fuel pressure of the delivery pipe 60. The third pressure sensor 83 is a pressure sensor that detects the fuel pressure in the fuel passage downstream of the solenoid valve as viewed in the fuel flow direction.

[0019] The temperature sensor 84 provided on the delivery pipe 60 detects a fuel temperature THF, which is the temperature of the fuel inside the delivery pipe 60. The temperature sensor 84 is a pressure sensor that detects the fuel pressure in the fuel passage downstream of the solenoid valve as viewed in the fuel flow direction.

[0020] The control device 100 implements various controls such as fuel injection for an internal combustion engine 10 by controlling various controlled objects including a throttle valve 12, a fuel injection valve 15, a first shutoff valve 21, and a second shutoff valve 22. This control device 100 includes a processing circuit 110 configured by a CPU and a memory. In the processing circuit 110, various controls are implemented when a program stored in the memory is executed by the CPU.

[0021] The control device 100 references various values required for controlling the internal combustion engine 10. For example, the control device 100 references detection values from a first pressure sensor 81, a second pressure sensor 82, a third pressure sensor 83, and a temperature sensor 84. The control device 100 also references a detection signal from an accelerator position sensor 71 that detects an accelerator operation amount ACCP, which is the 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 further references a detection signal from a vehicle speed sensor 72 that detects a vehicle speed SP of the vehicle equipped with the internal combustion engine 10. In addition, the control device 100 references 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.

[0022] The control device 100 calculates an engine rotational speed NE based on the detection signal Scr from the crank angle sensor 74. The control device 100 also calculates an engine load factor KL based on the engine rotational 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 operated steadily at a full load condition at the current engine rotational speed NE. Note that the cylinder inflow air amount is the amount of air that flows into each cylinder during an intake stroke.

[0023] When an engine stop request is generated due to a predetermined stop condition being satisfied, the control device 100 stops the operation of the internal combustion engine 10. When an engine start request is generated due to a predetermined start condition being satisfied, the control device 100 starts the internal combustion engine 10 that has been stopped. In this manner, intermittent stopping and starting of the internal combustion engine 10 is repeated.

[0024] <Regarding hydrogen gas leak detection> The processing circuit 110 determines whether or not there is a fuel leak in the fuel passage downstream of the second shut-off valve 22 when viewed in the direction of fuel flow by executing the process described below. Fuel leaks in the fuel passage downstream of the second shut-off valve 22 include, for example, fuel leaks from the fuel injector 15 due to a malfunction of the fuel injector 15, or fuel leaks from the delivery pipe 60. Fuel leaks in the fuel passage downstream of the second shut-off valve 22 also include, for example, fuel leaks from the fuel piping 40 connecting the second shut-off valve 22 and the delivery pipe 60.

[0025] Figure 2 shows the changes in various values ​​when fuel leakage occurs in the fuel passage downstream of the second shut-off valve 22. Figure 2(A) shows the changes in the operating state of the internal combustion engine. Figure 2(B) shows the changes in the open / closed state of the second shut-off valve 22. Figure 2(C) shows the changes in the fuel temperature THF. Figure 2(D) shows the changes in the third pressure P3. Figure 2(E) shows the magnitude of the calculated hydrogen mass MH.

[0026] The hydrogen mass MH referred to here is the mass of fuel present in the fuel passage downstream of the second shut-off valve 22, viewed in the direction of fuel flow. In other words, it is a value that includes at least the sum of the fuel mass in the fuel piping 40 connecting the second shut-off valve 22 and the delivery pipe 60, the fuel mass in the delivery pipe 60, and the fuel mass in the fuel injector 15. Here, the volume of the fuel passage downstream of the second shut-off valve 22 is known. Therefore, the hydrogen mass MH in such a downstream fuel passage is calculated based on the third pressure P3 and the fuel temperature THF, which is related to density.

[0027] As shown in Figure 2, at time t1, the processing circuit 110 determines that the engine shutdown is complete. For example, the processing circuit 110 determines that the engine shutdown is complete when the engine rotation speed NE has been at "0" for a predetermined period of time due to the shutdown in response to the engine shutdown request.

[0028] As a result of this engine shutdown, the processing circuit 110 closes the second shut-off valve 22, which had been open until then. The processing circuit 110 then performs the process of acquiring the third pressure P3c, which is the fuel pressure when the second shut-off valve 22 closes due to engine shutdown, and the fuel temperature THFc, which is also the fuel temperature when the second shut-off valve 22 closes due to engine shutdown.

[0029] Next, the processing circuit 110 performs a process to calculate the first hydrogen mass MH1 based on the acquired third pressure P3c and fuel temperature THFc. If a fuel leak occurs in the fuel passage downstream of the second shut-off valve 22, the third pressure P3 will gradually decrease after the second shut-off valve 22 is closed.

[0030] Meanwhile, the fuel temperature THF gradually rises due to heat received from the internal combustion engine 10. At time t2, the processing circuit 110 determines that engine starting has begun. For example, the processing circuit 110 determines that engine starting has begun when an engine starting request is made.

[0031] As the engine starts up, the processing circuit 110 opens the second shut-off valve 22, which had been closed until then. The processing circuit 110 then executes a process to acquire the third pressure P3o, which is the fuel pressure immediately before the second shut-off valve 22 opens, and the fuel temperature THFo, which is also immediately before the second shut-off valve 22 opens.

[0032] Next, the processing circuit 110 performs a process to calculate the second hydrogen mass MH2 based on the acquired third pressure P3o and fuel temperature THFo. If fuel leakage occurs in the fuel passage downstream of the second shut-off valve 22, the amount of hydrogen gas in that fuel passage decreases, and therefore the second hydrogen mass MH2 will be smaller than the first hydrogen mass MH1.

[0033] Next, the processing circuit 110 calculates the difference ΔMH between the first hydrogen mass MH1 and the second hydrogen mass MH2 by subtracting the first hydrogen mass MH1 from the second hydrogen mass MH2.

[0034] Next, the processing circuit 110 obtains the intermittent stop time Tst, which is the time from when the engine is stopped at time t1 until when the engine starts up at time t2. Next, the processing circuit 110 calculates the fuel leakage rate N per unit time by dividing the difference ΔMH by the intermittent stop time Tst.

[0035] Then, if the acquired intermittent stop time Tst is greater than or equal to a predetermined threshold Tstref, a determination process is executed to determine whether or not there is a fuel leak based on the difference ΔMH. For example, as part of this determination process, the processing circuit 110 performs the following: That is, the processing circuit 110 determines that there is a fuel leak if the amount of leak N calculated based on the difference ΔMH is greater than or equal to a predetermined threshold Nref, while determining that there is no fuel leak if the amount of leak N is less than the threshold Nref.

[0036] Furthermore, the threshold value Tstref mentioned above has a preset suitable value for appropriately determining fuel leakage. In this embodiment, the threshold value Nref is set variably according to the intermittent stop time Tst, the coolant temperature THW, and the vehicle speed SP, but the threshold value Nref may also be set to a fixed value.

[0037] Furthermore, the fuel leak detection described above may be performed once per trip, or each time the internal combustion engine 10 intermittently stops. <Operation and Effects of This Embodiment> (1) The processing circuit 110 performs a process to calculate the first hydrogen mass MH1 based on the third pressure P3c and fuel temperature THFc when the second shut-off valve 22 is closed due to engine shutdown. The processing circuit 110 performs a process to calculate the second hydrogen mass MH2 based on the third pressure P3o and fuel temperature THFo just before the second shut-off valve 22 opens due to engine startup after engine shutdown. The processing circuit 110 performs a process to calculate the difference ΔMH between the first hydrogen mass MH1 and the second hydrogen mass MH2. The processing circuit 110 performs a process to determine whether or not there is a fuel leak based on the difference ΔMH.

[0038] Thus, the hydrogen mass MH in the fuel passage is calculated based on the fuel pressure (third pressure P3) and fuel temperature (THF), and the calculated hydrogen mass MH takes into account the density change due to engine heat. Furthermore, the presence or absence of fuel leakage is determined based on the difference ΔMH, which represents the change in hydrogen mass MH when the second shut-off valve 22 is open, so the determination is made with the influence of engine heat during engine shutdown suppressed. Therefore, hydrogen gas leaks can be appropriately detected.

[0039] (2) When fuel leakage occurs from the fuel passage, if the intermittent stop time Tst, which is the time from when the engine is stopped until it is started, is short, the difference ΔMH will be smaller compared to when the intermittent stop time Tst is long. Therefore, there is a risk of a false determination that there is no fuel leakage even though there is. In this embodiment, however, when the intermittent stop time Tst, which is the time from when the engine is stopped until it is started, is greater than or equal to a predetermined threshold Tstref, a determination process is executed to determine whether or not there is a leak based on the difference ΔMH, so such false determinations can be suppressed.

[0040] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0041] The calculation of the leakage amount N is omitted. Then, if the difference ΔMH is greater than or equal to a predetermined threshold, it may be determined that there is a fuel leak. Regardless of the length of the intermittent stop time Tst, a determination process may be performed to determine the presence or absence of leakage based on the difference ΔMH. In this case as well, effects other than those described in (2) above can be obtained. [Explanation of Symbols]

[0042] 10...Internal combustion engine 10a...Cylinder 11...Intake passage 12...Throttle valve 15...Fuel injection valve 20...Tank 21...First shut-off valve 22...Second shut-off valve 27...Accelerator pedal 30...Pressure 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...Processing circuit 300...Fuel supply device

Claims

1. A fuel supply system for an internal combustion engine, The fuel supply device is The internal combustion engine comprises a tank for storing hydrogen gas, which is the fuel for the internal combustion engine; a fuel injection valve for supplying the fuel to the cylinders; a fuel passage for supplying the fuel from the tank to the fuel injection valve; a solenoid valve provided in the fuel passage for opening and closing the fuel passage; a pressure sensor for detecting the fuel pressure in the fuel passage downstream of the solenoid valve in the direction of fuel flow; a temperature sensor for detecting the fuel temperature in the downstream fuel passage; and a control device comprising a processing circuit for performing a process to determine whether or not there is a fuel leak in the downstream fuel passage. When the mass of the fuel in the downstream fuel passage is defined as the mass of hydrogen, The aforementioned processing circuit is A process for calculating the first hydrogen mass based on the fuel pressure and fuel temperature when the solenoid valve closes due to engine shutdown, A process for calculating the second hydrogen mass based on the fuel pressure and fuel temperature immediately before the solenoid valve opens upon engine restart after the aforementioned engine shutdown, A process for calculating the difference between the first hydrogen mass and the second hydrogen mass, The process of determining whether or not there is a fuel leak based on the difference is executed. A fuel supply system for an internal combustion engine.

2. The processing circuit executes a process to determine whether or not there is a fuel leak based on the difference if the time from when the engine is stopped until it is started is greater than or equal to a predetermined threshold. A fuel supply device for an internal combustion engine according to claim 1.

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