Fuel supply system for internal combustion engines

Abstract

The valve element of the solenoid valve provided in the fuel passage is quickly opened. [Solution] The fuel supply device 300 includes a second shut-off valve 22 that is provided in a fuel pipe 40 of an internal combustion engine and has a valve body that opens when the pressure difference between the upstream and downstream sides of the valve body in the fuel flow direction in the fuel pipe 40 falls below a predetermined value, a bypass pipe 400 that is connected to the fuel pipe 40 upstream of the second shut-off valve 22 and the fuel pipe 40 downstream of the second shut-off valve 22 in the fuel flow direction, and a bypass valve 410 that is provided in the bypass pipe 400 and opens when there is a request to open the valve body of the second shut-off valve 22.

Description

[Technical Field]

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

[0002] For example, a fuel supply device for an internal combustion engine described in Patent Document 1 has a shutoff valve, which is an electromagnetic valve, in a fuel passage connecting a fuel tank and a fuel injection valve. When starting the internal combustion engine, the opening timing of the shutoff valve is appropriately controlled to supply gas fuel at the required pressure to the fuel injection valve, thereby improving startability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-118842 Summary of the Invention [Problem to be solved by the invention]

[0004] By configuring a solenoid valve so that it opens when the pressure difference between the upstream and downstream sides of the valve element of the solenoid valve falls below a predetermined value, the magnetic force required to open the solenoid valve can be reduced. Reducing the magnetic force required to open the valve can, for example, make the solenoid valve more compact and reduce power consumption. However, when using such a pressure difference, the pressure difference exceeds the predetermined value when the valve is closed. Therefore, it takes time for the pressure difference to fall below the predetermined value when the valve is opened, which can make it difficult to quickly open the valve element of the solenoid valve. [Means for solving the problem]

[0005] A fuel supply device for an internal combustion engine that solves the above problem includes a solenoid valve that is provided in a fuel passage of the internal combustion engine and has a valve body, and that opens when the pressure difference between the upstream and downstream sides of the valve body in the flow direction of fuel in the fuel passage becomes equal to or less than a predetermined value, a bypass flow passage that is connected upstream and downstream of the solenoid valve in the flow direction of fuel in the fuel passage, and a bypass valve that is provided in the bypass flow passage and opens when there is a request to open the valve body. [Effects of the Invention]

[0006] This fuel supply device for an internal combustion engine can quickly open the valve body of the electromagnetic valve provided in the fuel passage. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an internal combustion engine to which a fuel supply device for an internal combustion engine according to one embodiment is applied, a fuel supply system, and a control device. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of the second shutoff valve of the same embodiment. [Figure 3] FIG. 3 is a flowchart showing the procedure of the process executed by the control device in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a specific embodiment of a fuel supply device for an internal combustion engine will be described with reference to FIGS. <Internal combustion engine, fuel supply device and control device> An internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle and uses hydrogen gas, which is a fluid gaseous fuel, as fuel.

[0009] An intake passage 11 of an internal combustion engine 10 is provided with a throttle valve 12 for adjusting the amount of intake air. The fuel supply device 300 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, a delivery pipe 60, a bypass pipe 400, and a bypass valve 410.

[0010] The fuel injection valve 15 supplies fuel to the cylinder 10a 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 to a delivery pipe 60. The fuel injection valve 15 is connected to the delivery pipe 60. The fuel pipe 40 and the delivery pipe 60 are fuel passages connecting the tank 20 to the fuel injection valve 15. The hydrogen gas stored in the tank 20 is supplied to the fuel injection valve 15 via the fuel pipe 40 and the delivery pipe 60.

[0011] 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. The pressure reducing valve 30 is a valve for reducing the fuel pressure of hydrogen gas stored in a high pressure state in the tank 20 to a specified pressure (for example, about 4 MPa) and supplying the fuel to the fuel injection valve 15. The second shutoff valve 22 is an electromagnetic valve and is disposed in the fuel pipe 40 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.

[0012] 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.

[0013] 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. 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. 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.

[0014] The bypass pipe 400 constitutes a bypass flow path that connects the fuel pipe 40 upstream of the second shutoff valve 22 and the fuel pipe 40 downstream of the second shutoff valve 22 in the fuel flow direction.

[0015] The bypass valve 410 is an electromagnetic valve and is provided in the bypass pipe 400. When the bypass valve 410 is opened, fuel flows through the bypass pipe 400. When the bypass valve 410 is closed, the flow of fuel through the bypass pipe 400 is blocked.

[0016] 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 bypass valve 410. 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.

[0017] 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.

[0018] <Fuel pressure control> The control device 100 executes fuel pressure control to control the pressure of fuel supplied to the fuel injection valve 15, i.e., the fuel pressure in the fuel passage connected downstream of the second shutoff valve 22 in the direction of fuel flow in the fuel passage. This fuel pressure control repeatedly opens and closes the second shutoff valve 22 so that the fuel pressure in the fuel passage connected downstream of the second shutoff valve 22 falls within a control range CR defined by a predetermined upper limit value PtU and a predetermined lower limit value PtL. The target pressure Pt of the fuel pressure in the fuel pressure control is a preset pressure lower than the second pressure P2, which is the fuel pressure after being reduced by the pressure reducing valve 30. For example, the target pressure Pt is approximately 1 MPa. The upper limit value PtU of the fuel pressure that is allowable for the target pressure Pt is set to the lower limit value PtL.

[0019] The fuel pressure control is executed, for example, when the operating state of the internal combustion engine 10 transitions to an idling state. When the injection amount of the fuel injection valve 15 decreases, such as during idling, the fuel pressure control is executed to maintain the third pressure P3, which is the fuel pressure in the delivery pipe 60, at a pressure lower than the second pressure P2, thereby allowing a small amount of fuel to be injected from the fuel injection valve 15 with high precision.

[0020] On the other hand, when the operating state of the internal combustion engine 10 transitions to a normal operating state where the engine load is higher than in the idle operating state, fuel pressure control of the second shutoff valve 22 is stopped. This stops the periodic opening and closing drive of the second shutoff valve 22, and the second shutoff valve 22 is maintained in an open state. While the second shutoff valve 22 is open, fuel is supplied from the tank 20 to the delivery pipe 60, so that the third pressure P3 gradually increases toward the second pressure P2, which is the pressure during normal operation.

[0021] <Structure of the second shutoff valve> 2 shows the structure of second shutoff valve 22. In the following, the direction along the central axis L of plunger 211 provided in second shutoff valve 22 will be referred to as the axial direction. Also, the direction perpendicular to the axial direction will be referred to as the radial direction.

[0022] The second shutoff valve 22 includes a housing 200, a stator 230, an electromagnetic coil 240, a first valve 210, a holder 250, a second valve 220, and the like. The housing 200 has an inlet port 201 to which the fuel pipe 40 connected to the pressure reducing valve 30 is connected, and an outlet port 203 to which the fuel pipe 40 connected to the delivery pipe 60 is connected.

[0023] The inlet port 201 and the outlet port 203 communicate with each other via a first chamber 202 which is a space formed inside the housing 200 . The stator 230 is cylindrical and is provided within the housing 200 .

[0024] The electromagnetic coil 240 is provided on the outer periphery of the stator 230. The electromagnetic coil 240 opens the valve element when energized. First valve 210, which is a first valve body, includes plunger 211 that moves in the axial direction within stator 230, and first seal member 213 that opens and closes first fuel passage 222 as plunger 211 moves.

[0025] One end of plunger 211 forms protrusion 212 that protrudes from stator 230. The first seal member 213 is provided at the tip of protrusion 212. Protrusion 212 also includes pin 214 that extends radially. Both ends of pin 214 protrude from the outer circumferential surface of protrusion 212.

[0026] The holder 250 has a cylindrical portion 251 that is coaxial with the central axis L. The inner peripheral surface of the cylindrical portion 251 faces the outer peripheral surface of the protruding portion 212 and is spaced apart from it. Second valve 220, which is a second valve body, is slidably housed on the inner circumferential surface of cylindrical portion 251. Second valve 220 is formed with hole 221, through which the outer circumferential surface of protrusion 212 of first valve 210 slides. Second valve 220 is formed with elongated hole 225, into which pin 214 is inserted and which allows movement of pin 214 in the axial direction.

[0027] The first fuel passage 222 extending in the axial direction is formed at the tip of the second valve 220. The first fuel passage 222 is connected to the outlet port 203 that constitutes the second fuel passage. The outlet port 203 is a fuel passage with a flow path cross-sectional area larger than that of the first fuel passage 222.

[0028] A second seal member 224 that opens and closes the outlet port 203 is provided at the tip of the second valve 220. More specifically, the second seal member 224 opens and closes a second valve seat 204 provided at one end of the outlet port 203.

[0029] A first valve seat 223 protruding toward the protrusion 212 is formed at the tip of the second valve 220, in which the first fuel passage 222 is formed. The first valve seat 223 is opened and closed by a first seal member 213, thereby opening and closing the first fuel passage 222. The first fuel passage 222 serves as a communication passage that connects a flow passage upstream of the second valve 220, which serves as a second valve body, with a flow passage downstream of the second valve 220. The flow passage upstream of the second valve 220 includes a pressure chamber 227 (described below), a communication passage 226 (described below), the first chamber 202, and the inlet port 201. The flow passage downstream of the second valve 220 is the outlet port 203. The first valve 210 serves as a first valve body that opens before the second valve 220 opens and closes the first fuel passage 222.

[0030] In the hole 221, the space surrounded by the wall surface around the first valve seat 223 and the tip surface of the protrusion 212 serves as a pressure chamber 227 to which pressure acts to urge the second valve 220 in the valve closing direction. This pressure chamber 227 is connected to the first chamber 202 via a communication passage 226.

[0031] A second chamber 255 is formed on the inner peripheral surface side of a cylindrical portion 251 of the holder 250, and is a space for ensuring the stroke amount of the second valve 220 in the axial direction. End face 228 of second valve 220 opposite the side on which second seal member 224 is disposed and restriction portion 253, which is formed by the surface of holder 250 facing end face 228, come into contact with each other when second valve 220 is in the fully open state. By maintaining the abutting state between end face 228 and restriction portion 253, the position of the valve element when second valve 220 is in the fully open state is stabilized.

[0032] An end cap 280 that closes the end opposite to the side where plunger 211 is inserted is provided inside stator 230. A third chamber 257, which is a space, is formed between end cap 280 and plunger 211. In addition, a spring 215 that urges plunger 211 in a direction away from end cap 280 is provided between end cap 280 and plunger 211.

[0033] <Opening and closing operation of the second shutoff valve> When the electromagnetic coil 240 is energized, the plunger 211 is drawn into the stator 230, and the first valve 210 moves in a direction in which the first seal member 213 moves away from the first valve seat 223, thereby opening the first valve 210. When the first seal member 213 moves away from the first valve seat 223, the fuel that has flowed in from the inlet port 201 flows into the outlet port 203 via the first chamber 202, the communication passage 226, the pressure chamber 227, and the first fuel passage 222.

[0034] As a result of first valve 210 moving in a direction in which first seal member 213 moves away from first valve seat 223, pin 214 of first valve 210 comes into contact with wall surface 229 that is located in the valve opening direction of first valve 210 in the axial direction of elongated hole 225 of second valve 220. Therefore, a valve opening force Fop acting in the same direction as the movement direction of first valve 210 is applied to second valve 220. This valve opening force Fop is an attractive force generated by the magnetic force of electromagnetic coil 240, and acts in the direction in which second valve 220 opens.

[0035] When first valve 210 opens, pressure chamber 227 and outlet port 203 communicate with each other, reducing the pressure difference between pressure chamber 227 and outlet port 203. This reduces drag Fcl, which is a force resisting the opening of second valve 220. Note that drag Fcl includes a force acting in the closing direction of second valve 220, the sliding resistance of second valve 220 and holder 250, and the like. The force acting in the closing direction of second valve 220 includes a differential pressure load generated by the pressure difference between pressure chamber 227 and outlet port 203, and the biasing force of spring 215.

[0036] When the opening of first valve 210 reduces the differential pressure load, causing the valve-opening force Fop to become greater than the resistance Fcl, second valve 220 moves in a direction in which second seal member 224 moves away from second valve seat 204. This movement of second valve 220 opens second valve 220. When second seal member 224 moves away from second valve seat 204, fuel that has flowed in from inlet port 201 flows mainly into outlet port 203 via first chamber 202.

[0037] When the second valve 220 is in a fully open state, the end face 228 and the restricting portion 253 come into contact with each other, thereby stopping the movement of the second valve 220 in the axial direction. The fuel that has flowed into the outlet port 203 is sent to the fuel injection valve 15 via the fuel pipe 40 and the delivery pipe 60 .

[0038] When the supply of electricity to the electromagnetic coil 240 is stopped, the biasing force of the spring 215 or the like moves the first valve 210 in a direction in which the first seal member 213 abuts against the first valve seat 223. This causes the first valve 210 to close.

[0039] When first seal member 213 abuts against first valve seat 223, the biasing force of spring 215 acts on second valve 220. As a result, second valve 220 moves in the direction in which second seal member 224 abuts against second valve seat 204. This causes second valve 220 to close.

[0040] In this way, in the second shutoff valve 22, the second valve 220, which opens and closes the outlet port 203 having a larger cross-sectional area than the first fuel passage 222, is opened using the pressure in the pressure chamber 227. That is, the second valve 220 opens when the pressure difference between the pressure chamber 227 and the outlet port 203, which is the pressure difference between the upstream and downstream sides of the second valve 220, decreases to a predetermined value or less. Therefore, the magnetic force required to open the second valve 220 can be reduced compared to when the magnetic force of an electromagnetic coil is directly used to open the second valve 220. Therefore, the electromagnetic coil 240 can be made smaller. In this embodiment, the attractive force of the electromagnetic coil 240 is set so that the second valve 220 opens when the pressure difference becomes approximately zero. That is, the attractive force is set to be the force of the sliding resistance between the second valve 220 and the holder 250 and the force of the spring 215, which are part of the resistance Fcl.

[0041] Furthermore, in the second shutoff valve 22, a small flow rate of fuel is adjusted using the first valve 210. Therefore, the above-described fuel pressure control is performed by driving the first valve 210 to open and close. Furthermore, in an operating state where the engine load is higher than in an idling operating state, the second valve 220 is opened.

[0042] <Bypass valve opening / closing control> 3 shows the procedure of the process executed by the control device 100 to control the opening and closing of the bypass valve 410. In the following, step numbers are represented by numbers preceded by "S."

[0043] When this process starts, the control device 100 determines (S100) whether or not there is a request to open the second valve 220. A request to open the second valve 220 is made, for example, when the engine is started or when the fuel pressure control is completed.

[0044] When it is determined that there is a request to open the second valve 220 (S100: YES), the control device 100 opens the bypass valve 410 (S110). Next, the control device 100 determines whether the second valve 220 is fully open (S120). The full-open determination in the processing of S120 can be performed as appropriate. For example, when the second valve 220 is fully open, the actual current flowing through the electromagnetic coil 240 temporarily decreases. Therefore, if a temporary decrease in the actual current is detected, it can be determined that the second valve 220 is fully open. Furthermore, when the second valve 220 is fully open, the third pressure P3 becomes equal to the second pressure P2 and remains the same. Therefore, if such behavior of the third pressure P3 is detected, it can be determined that the second valve 220 is fully open.

[0045] Then, the control device 100 repeatedly executes the processes of S110 and S120 until a positive determination is made in the process of S120. If the determination in the process of S120 is affirmative, the control device 100 closes the bypass valve 410 (S130).

[0046] When the process of S130 has been executed, or when a negative determination is made in the process of S100, the control device 100 ends this process. <Actions and Effects of This Embodiment> (1) When there is a request to open the second valve 220 of the second shutoff valve 22 provided in the fuel pipe 40, the bypass valve 410 provided in the bypass pipe 400 opens. When the bypass valve 410 opens, the upstream and downstream sides of the second valve 220 communicate with each other via the bypass pipe 400. Therefore, fuel flows from the upstream side to the downstream side of the second valve 220. When fuel flows in in this manner, the pressure on the downstream side of the second valve 220 quickly rises toward the pressure on the upstream side of the second valve 220, and the pressure difference between the upstream side and the downstream side of the second valve 220 quickly decreases. Therefore, when there is a request to open the second valve 220, the second valve 220 quickly opens.

[0047] (2) If there is a delay in opening the second valve 220 during engine start, the fuel flow rate required for engine start cannot be sufficiently ensured, which may result in a longer engine start time, for example. In this regard, in the present embodiment, the request to open the second valve 220 described above is issued during engine start. Therefore, the second valve 220 opens quickly during engine start. This makes it possible to prevent the engine start time from becoming longer.

[0048] (3) The request to open the second valve 220 is made when the fuel pressure control ends. Therefore, the second valve 220 opens quickly when the fuel pressure control ends. Therefore, the third pressure P3, which has become lower than the second pressure P2 due to the execution of the fuel pressure control, can be quickly restored to the second pressure P2. Therefore, for example, a return from idling to normal operation can be quickly performed.

[0049] <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.

[0050] The bypass pipe 400 may be configured as a bypass flow path that connects the fuel pipe 40 upstream of the second shutoff valve 22 to the delivery pipe 60 . The second shutoff valve 22 does not have to include the first valve 210. In this case, the second valve 220 may be directly driven to open and close by the electromagnetic coil 240. Even in this modification, when a request is made to open the second valve 220, the bypass valve 410 opens, so that the pressure difference between the upstream and downstream sides of the second valve 220 quickly becomes equal to or less than the predetermined value. Therefore, the second valve 220 quickly opens.

[0051] When the above-described fuel pressure control is not being executed, the bypass valve 410 may be maintained in an open state. 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.

[0052] The fuel used in the internal combustion engine 10 is gaseous fuel, but it may be liquid fuel. The fluid flow path is the fuel passage of the internal combustion engine 10, but may be another flow path. [Explanation of symbols]

[0053] 10...internal combustion engine 20...tank 21...first shutoff valve 22...second shutoff valve 22...second valve 30...pressure reducing valve 40...fuel piping 60...delivery pipe 100...control device 210...first valve 220...second valve 300...fuel supply device 400...bypass piping 410...bypass valve

Claims

[Claim 1] a solenoid valve provided in a fuel passage of an internal combustion engine, the solenoid valve having a valve body, the solenoid valve opening when a pressure difference between an upstream side and a downstream side of the valve body in a fuel flow direction in the fuel passage becomes equal to or less than a predetermined value; a bypass flow path connected to the fuel passage upstream of the solenoid valve and the fuel passage downstream of the solenoid valve in a fuel flow direction; a bypass valve that is provided in the bypass flow path and opens when there is a request to open the valve body. Fuel supply system for internal combustion engines.

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