Fuel supply system for internal combustion engines

Abstract

To provide a fuel supply device for an internal combustion engine, capable of making a fuel pressure variable without increasing the opening / closing drive frequency of a valve.SOLUTION: A shut-off valve 6 arranged in a fuel supply pipe is provided with a pilot valve 82 and a main valve 83 for making the opening of the pilot valve 82 only by relatively reducing the electromagnetic force of an electromagnetic solenoid and the opening of the main valve 83 by relatively increasing the electromagnetic force of the electromagnetic solenoid switchable. Namely, a supply fuel pressure can be changed in at least two stages. Thus, the supply fuel pressure is variable without increasing the opening / closing drive frequencies of the valves 82, 83 to achieve the appropriate fuel supply amount for the operating condition of the internal combustion engine.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a fuel supply device provided in an internal combustion engine typified by a gas engine. In particular, the present invention relates to improvements for making the supply fuel pressure variable.

Background Art

[0002] Conventionally, as disclosed in Patent Document 1 and Patent Document 2, in a gas engine that uses a gas such as hydrogen as fuel, an openable and closable valve is provided in a fuel supply pipe that extends from a fuel tank to a delivery pipe in the fuel supply system. Patent Document 1 discloses a configuration in which a shut-off valve that is closed when the supply of fuel (hydrogen gas) toward the fuel injection valve is stopped is provided in the fuel supply pipe. Further, Patent Document 2 discloses a configuration in which a pressure reducing valve for reducing the pressure of the fuel supplied toward the fuel injection valve (hereinafter, may also be referred to as supply fuel pressure) is provided in the fuel supply pipe. Generally, this pressure reducing valve is mechanical, and the supply fuel pressure is fixed at a constant value.

Prior Art Documents

Patent Documents

[0003] [[ID=并21]]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the fuel supply pressure is fixed to a constant value by a pressure reducing valve, the following problems arise. Specifically, if the fuel supply pressure fixed by the pressure reducing valve is set to a pressure suitable for when the fuel injection amount into the combustion chamber is at its maximum (so-called WOT), (a relatively high pressure), it becomes difficult to sufficiently improve the accuracy of the fuel injection amount when the minimum injection amount is reached (so-called idling). On the other hand, if the fuel supply pressure fixed by the pressure reducing valve is set to a pressure suitable for when the minimum injection amount is reached, (a relatively low pressure), there is a risk that the fuel injection amount when the maximum injection amount is required may not be obtained sufficiently. For this reason, it is preferable to make the fuel supply pressure variable in order to obtain the appropriate fuel injection amount for both when the fuel injection amount into the combustion chamber is at its maximum and at its minimum.

[0005] One way to satisfy this requirement is to equip the fuel supply piping with a solenoid valve and adjust the supplied fuel pressure by switching the opening and closing of this solenoid valve (alternating between a fully open state and a fully closed state). Figure 5(b) shows an example of the change in the supply current to the electromagnetic solenoid (excitation current for switching the opening and closing of the solenoid valve) and the resulting change in the internal pressure of the delivery pipe (hereinafter referred to as the delivery pressure) when this solenoid valve is used. Specifically, Figure 5(b) shows an example where the vehicle goes from normal driving (period T1 in the figure) through a deceleration period (period T2 in the figure), then transitions to idling (period T3 in the figure), and then, after an acceleration period (period T4 in the figure), returns to normal driving (period T5 in the figure).

[0006] In the configuration equipped with the aforementioned solenoid valve, during idling operation, the solenoid valve is switched alternately between a fully open state and a fully closed state in a short period of time to adjust the delivery pressure to a predetermined range (a delivery pressure suitable for idling operation, which is P1 in the figure).

[0007] In the case where a solenoid valve is installed in this way, not only does the number of times the solenoid valve is opened and closed per unit time (the number of times it is repeatedly switched between fully open and fully closed) increase, but it also becomes difficult to adjust the fuel flow rate, so there was room for improvement.

[0008] The present invention has been made in view of the above, and its object is to provide a fuel supply device for an internal combustion engine that can vary the supplied fuel pressure without increasing the number of times the valve is opened and closed. [Means for solving the problem]

[0009] The present invention provides a solution for achieving the above objective, which involves a fuel supply device that reduces the pressure of fuel in a high-pressure tank using a pressure reduction means, and then supplies this fuel to a fuel injector of an internal combustion engine via a fuel supply pipe. This fuel supply device is provided with a pressure variable device in the fuel supply pipe that varies the pressure of the fuel supplied to the fuel injector. The pressure variable device includes a pilot valve that opens due to an electromagnetic force generated by energizing a built-in electromagnetic solenoid, and in the open state supplies the fuel to the fuel injector, and a main valve that opens in conjunction with the movement of the pilot valve when an electromagnetic force greater than the electromagnetic force that opens the pilot valve is generated from the electromagnetic solenoid, and in the open state increases the amount of fuel supplied to the fuel injector compared to when only the pilot valve is open. Furthermore, the variable pressure device includes a fuel introduction space connected to an upstream fuel supply pipe connected to the high-pressure tank, and a fuel outlet space connected to a downstream fuel supply pipe extending toward the fuel injection valve. The main valve includes a pilot valve insertion portion into which the tip of the pilot valve is inserted, and a fuel passage having one end communicating with the space inside the pilot valve insertion portion and the other end communicating with the fuel outlet space. The pilot valve insertion portion has a passage that penetrates radially through the pilot valve insertion portion and connects the fuel introduction space and the pilot valve. A through hole is formed that communicates with the inner space of the valve insertion portion, and when the main valve is closed, the tip of the main valve abuts against the opening edge of the fuel outlet space, thereby blocking the fuel inlet space and the fuel outlet space, and when the pilot valve is closed, the tip of the pilot valve inserted into the pilot valve insertion portion abuts against the opening edge of the fuel passage of the main valve, thereby blocking the inner space of the pilot valve insertion portion and the fuel passage, and the pilot of the main valve A pin insertion hole is provided on the base end side of the main valve, which is on the side of movement in the valve opening direction of the main valve, rather than the position where the through hole is formed in the pilot valve insertion portion, and a pin is inserted into the tip of the pilot valve, and the inner diameter dimension of the pin insertion hole in the direction along the direction of movement is set to be larger than the outer diameter dimension of the pin in the direction along the direction of movement, and when both the main valve and the pilot valve are in the closed state, the pin A predetermined gap is provided between the outer surface of the main valve, which faces the direction of movement of the pilot valve when the electromagnetic solenoid is energized, and the inner surface of the pin insertion hole facing the outer surface. The main valve is configured such that when the pilot valve moves beyond the predetermined amount in the valve opening direction, the pin contacts the inner surface of the pin insertion hole, thereby receiving an operating force from the pilot valve in the valve opening direction and starting to open. The casing that movably supports the main valve is provided with a support portion that contacts the outer surface of the pilot valve insertion portion.The length of the support portion in the direction along the movement direction of the main valve is set to cover the outer opening of the pin insertion hole at the positions in which the main valve is closed and open, and to not close the through hole of the pilot valve insertion portion at the position in which the main valve is closed. It is characterized by the following:

[0010] This specific feature allows for switching between supplying fuel to the fuel injector at a relatively low flow rate by controlling the energization of the electromagnetic solenoid, and supplying fuel to the fuel injector at a relatively high flow rate by opening only the pilot valve. In other words, the fuel supply pressure can be varied in at least two stages: a state where the fuel supply pressure is relatively low by supplying a relatively low flow rate, and a state where the fuel supply pressure is relatively high by supplying a relatively high flow rate. Therefore, compared to the case where the aforementioned electromagnetic valve is installed, the fuel supply pressure can be varied without increasing the number of valve opening and closing operations, and a fuel supply amount suitable for the operating conditions of the internal combustion engine can be obtained.

[0012] Also, By adjusting the electromagnetic force through the control of current supply to a single electromagnetic solenoid, it is possible to switch between a state in which only the pilot valve is open by limiting the movement of the pilot valve to a predetermined amount or less, and a state in which the main valve is open by exceeding the predetermined amount of movement of the pilot valve.

[0014] AlsoWhen the main valve is in a closed state, with its tip in contact with the opening edge of the fuel outlet space, and the pilot valve is in a closed state, with its tip in contact with the opening edge of the fuel passage of the main valve, if the pilot valve moves due to the electromagnetic force of the electromagnetic solenoid, and the amount of movement is less than or equal to a predetermined amount, the pin integrally provided on the tip of the pilot valve will not impart any operating force (an operating force in the opening direction to the main valve) to the inner surface of the pin insertion hole of the main valve. As a result, only the pilot valve will be open (a state in which the fuel supply pressure is relatively low by making the fuel supply amount relatively small). Then, if the electromagnetic force of the electromagnetic solenoid increases and the amount of movement of the pilot valve exceeds the predetermined amount, the pin will impart an operating force to the inner surface of the pin insertion hole, and the electromagnetic force of the electromagnetic solenoid will be transmitted to the main valve as well, resulting in the main valve being open (a state in which the fuel supply pressure is relatively high by making the fuel supply amount relatively large). In this way, by employing a connection structure between the pilot valve and the main valve using a pin, it becomes possible to switch between a state where only the pilot valve is open and a state where the main valve is also open.

[0015] Also ,before The tip of the main valve and the tip of the pilot valve are both equipped with a rubber sealing material.

[0016] According to this, when the internal combustion engine is stopped and each valve is closed, the sealing material can reliably prevent fuel leakage (fuel leakage into the combustion chamber). For example, even if the fuel injection valve that injects fuel into the combustion chamber of the internal combustion engine does not have sufficient fuel leak prevention performance, the variable pressure device can prevent fuel leakage, thus reliably preventing fuel leakage from the fuel supply device to the internal combustion engine when the internal combustion engine is stopped. [Effects of the Invention]

[0017] In the present invention, a pilot valve and a main valve are provided in a pressure variable device disposed in a fuel supply pipe, and it is possible to switch between opening only the pilot valve by making the electromagnetic force of an electromagnetic solenoid relatively small and opening the main valve by making the electromagnetic force of the electromagnetic solenoid relatively large. That is, the supply fuel pressure can be changed in at least two stages. For this reason, the supply fuel pressure can be made variable without increasing the number of valve opening and closing driving operations, and a fuel supply amount suitable for the operating state of the internal combustion engine can be obtained.

Brief Description of the Drawings

[0018] [Figure 1] It is a diagram showing a schematic configuration of a hydrogen engine system. [Figure 2] It is a cross-sectional view of a shut-off valve. [Figure 3] It is a cross-sectional view showing the periphery of each valve of the shut-off valve. FIG. 3(a) shows the closed state of each valve, FIG. 3(b) shows the open state of the pilot valve, and FIG. 3(c) shows the open state of the main valve. [Figure 4] It is a diagram for explaining the closing force and opening force acting on each valve. [Figure 5] It is a diagram showing an example of the change in the excitation current with respect to the electromagnetic solenoid and the accompanying change in the delivery pressure. FIG. 5(a) is a diagram according to an embodiment, and FIG. 5(b) is a diagram according to the prior art. [Figure 6] It is a diagram showing an example of the temporal change of the pilot pressure, main pressure, valve stroke, and inrush current in the embodiment.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings. This embodiment will describe the case where the present invention is applied to a system equipped with a 4-cylinder hydrogen engine (an internal combustion engine using hydrogen gas as fuel) mounted on a vehicle.

[0020] - Schematic Configuration of Hydrogen Engine System - First, before explaining the shut-off valve (the pressure variable device in the present invention) provided in the fuel supply system, a schematic configuration of the hydrogen engine system according to the present embodiment will be briefly described.

[0021] FIG. 1 is a diagram showing a schematic configuration of a hydrogen engine system 1 according to the present embodiment. As shown in this FIG. 1, the hydrogen engine system 1 according to the present embodiment includes an intake system 3, an exhaust system 4, and a fuel supply system (the fuel supply device according to the present invention) 5 connected to an engine body (internal combustion engine) 2. Each will be briefly described below.

[0022] The engine body 2 includes four cylinders #1 to #4 of the first to fourth, and a rotational driving force is obtained by the reciprocating movement of a piston (not shown) accompanying the combustion of an air-fuel mixture (a mixture of hydrogen gas and air) in the combustion chambers (inside the cylinders) of these cylinders #1 to #4. A cylinder head (not shown) is assembled to the upper end of a cylinder block 21 in the engine body 2, and an ignition plug 22 is disposed on the cylinder head so as to face the combustion chambers of each of the cylinders #1 to #4. Further, an injector (direct injection injector: fuel injection valve) 54 for injecting hydrogen gas (fuel) supplied from the fuel supply system 5 into the combustion chamber is disposed in each of the cylinders #1 to #4. A water temperature sensor 23 for detecting the water temperature of engine cooling water, a crank angle sensor 24 for detecting the crank angle, etc. are arranged in the cylinder block 21. The configuration of the engine body 2 is not limited to this.

[0023] The intake system 3 includes an intake passage 31, a surge tank 32, and an intake manifold 33 for supplying intake air to the combustion chambers of cylinders #1 to #4. Upstream of the intake passage 31 (upstream of the intake air flow), there is an air cleaner 34, an air flow meter 35, an intake air temperature sensor 36 (built into the air flow meter 35), and an electronically controlled throttle valve 37. The throttle valve 37 is driven by a throttle motor 38. An intake valve (not shown) is provided at the downstream end of the intake port formed in the cylinder head, and intake air is supplied to the combustion chamber when this intake valve opens. The configuration of the intake system 3 is not limited to this. For example, it may be configured without a surge tank 32.

[0024] The exhaust system 4 comprises an exhaust manifold 41 and an exhaust passage 42. A catalytic converter 43 for purifying exhaust gas (mainly NOx in the exhaust) is located in the middle of the exhaust passage 42. An exhaust valve (not shown) is located at the upstream end of the exhaust port formed in the cylinder head, and exhaust gas is discharged from the combustion chamber when this exhaust valve opens. The configuration of the exhaust system 4 is not limited to this.

[0025] The fuel supply system 5 includes a hydrogen storage tank (high-pressure tank) 51, fuel supply piping 52, a delivery pipe 53, and an injector 54 for each cylinder. The hydrogen storage tank 51 is a tank that stores hydrogen under high pressure. The fuel supply piping 52 is equipped with a pressure reducing valve (pressure reducing means) 55 for reducing the pressure of the hydrogen gas supplied to the delivery pipe 53, a relief valve 56 that opens when the fuel pressure inside the fuel supply piping 52 exceeds a predetermined value, and a shut-off valve 6 for adjusting the supply fuel pressure supplied toward the delivery pipe 53. Hereinafter, the fuel supply piping 52 upstream of the shut-off valve 6 (towards the hydrogen storage tank 51) will be referred to as the upstream fuel supply piping 52a, and the fuel supply piping 52 downstream of the shut-off valve 6 (towards the delivery pipe 53) will be referred to as the downstream fuel supply piping 52b. Furthermore, the delivery pipe 53 is equipped with a pressure sensor 57 for detecting the pressure of the hydrogen gas inside the delivery pipe 53, and a temperature sensor 58 for detecting the temperature of the hydrogen gas inside the delivery pipe 53.

[0026] Each injector 54 injects hydrogen gas supplied via the delivery pipe 53 into the combustion chamber at a predetermined timing. The hydrogen gas injected into the combustion chamber from the injector 54 mixes with the air supplied from the intake system 3 to form a fuel-air mixture in the combustion chamber. This mixture is ignited by the spark plug 22 and burns. The resulting high-temperature, high-pressure combustion gas pushes the pistons down from top dead center during the expansion stroke of each cylinder #1 to #4, causing the crankshaft to rotate and generating rotational driving force (output torque).

[0027] The ECU (Electronic Control Unit) 100 is a well-known unit equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and backup RAM. The CPU performs various calculations based on various control programs and maps stored in the ROM. The RAM temporarily stores the calculation results from the CPU and data input from various sensors, while the backup RAM stores data that should be saved, for example, when the engine is stopped.

[0028] The ECU100 is connected to the aforementioned water temperature sensor 23, crank angle sensor 24, air flow meter 35, intake air temperature sensor 36, pressure sensor 57, temperature sensor 58, etc. The ECU100 is also connected to an accelerator position sensor 101 (not shown) that outputs a detection signal corresponding to the amount the accelerator pedal is pressed. Furthermore, the ECU100 is connected to a spark plug 22 (more specifically, an igniter), throttle motor 38, injector 54, etc.

[0029] The ECU 100 then performs various controls based on signals from the various sensors, including drive control of the injector 54 (control of fuel injection amount), control of ignition timing by the spark plug 22, and drive control of the throttle motor 38 (control of intake air amount).

[0030] -Configuration of the shut-off valve- Next, the shut-off valve 6, a component that is a feature of this embodiment, will be described. Figure 2 is a cross-sectional view of the shut-off valve 6. In the following description, the left side of Figure 2 will be referred to as the base end side, and the right side as the tip side. As shown in Figure 2, the shut-off valve 6 includes an electromagnetic solenoid 71 and a drive unit 7 disposed on the base end side, and a pressure regulating unit 8 disposed on the tip side that can regulate the supplied fuel pressure by being driven by the drive unit 7.

[0031] The drive unit 7 has a configuration in which an electromagnetic solenoid 71 is housed within the drive unit side casing 72.

[0032] The drive unit side casing 72 comprises a casing body 73 formed by integrally assembling multiple members, and a spring receiving member 74 bolted to the base end side (left side in Figure 2) of the casing body 73.

[0033] The electromagnetic solenoid 71 comprises a core material 71a and a solenoid coil 71b consisting of a wire wound around the outer circumference of the core material 71a, and generates an electromagnetic force when current is passed through the solenoid coil 71b. The magnitude of this electromagnetic force can be adjusted according to the current value passed through the solenoid coil 71b.

[0034] The pressure regulating unit 8 comprises a pressure regulating unit side casing 81, a pilot valve 82, and a main valve 83.

[0035] The pressure regulating section side casing 81 is integrally assembled to the drive section side casing 72 via a sealing material 61, and a hydrogen gas flow space is formed inside. This hydrogen gas flow space has a fuel introduction space 81a connected to the upstream fuel supply pipe 52a (upstream fuel supply pipe 52a connected to the hydrogen storage tank 51: see Figure 1) and a fuel outlet space 81b connected to the downstream fuel supply pipe 52b (downstream fuel supply pipe 52b extending toward the delivery pipe 53 and injector 54). Therefore, when at least one of the pilot valve 82 and the main valve 83 is open, the fuel introduction space 81a and the fuel outlet space 81b are in communication, and hydrogen gas supplied from the hydrogen storage tank 51 and depressurized by the pressure reducing valve 55 passes through the shut-off valve 6 and is introduced into the delivery pipe 53.

[0036] The pilot valve 82 is a valve that can be moved by the electromagnetic force of the electromagnetic solenoid 71, and a part of it is inserted inside the core material 71a of the electromagnetic solenoid 71. A spring housing recess 82a is formed at the base end of the pilot valve 82. The spring 82b housed in this spring housing recess 82a is compressed between the bottom surface of the spring housing recess 82a and the spring receiving member 74, and applies a biasing force to the pilot valve 82 in the closing direction (towards the tip). In other words, when the solenoid coil 71b of the electromagnetic solenoid 71 is not energized and no electromagnetic force is generated, the pilot valve 82 moves in the closing direction (towards the tip) due to the biasing force of the spring 82b. However, when the solenoid coil 71b of the electromagnetic solenoid 71 is energized and an electromagnetic force is generated, the pilot valve 82 moves in the opening direction (towards the base end) against the biasing force of the spring 82b. The amount of movement of the pilot valve 82 in the opening direction is adjusted by the magnitude of the electromagnetic force, that is, the magnitude of the current supplied to the solenoid coil 71b.

[0037] The tip 82g of the pilot valve 82 is inserted into the base portion of the main valve 83, allowing for relative movement with respect to the main valve 83 within a predetermined range of motion. The configuration of the tip 82g of the pilot valve 82 and the main valve 83, as well as the assembly state of these valves 82 and 83, will be described below.

[0038] The main valve 83 has a substantially disc-shaped tip portion 83a and a pilot valve insertion portion 83b that extends cylindrically from the outer edge of the tip portion 83a toward the base end. The outer diameter of the tip portion 82g of the pilot valve 82 is substantially the same as the inner diameter of the pilot valve insertion portion 83b, and the tip portion 82g of the pilot valve 82 is inserted into the pilot valve insertion portion 83b.

[0039] The tip 83a of the main valve 83 is provided with a fuel passage 83c that extends in a direction along the axis of the main valve 83. One end of this fuel passage 83c (the base end of the main valve 83) is open to the space inside the pilot valve insertion portion 83b, and the other end (the tip of the main valve 83) is open to the fuel outlet space 81b. In addition, the pilot valve insertion portion 83b of the main valve 83 has a through hole 83d that penetrates through the pilot valve insertion portion 83b in the radial direction. As a result, the space inside the pilot valve insertion portion 83b and the fuel introduction space 81a are in communication through the through hole 83d. In other words, one end of the fuel passage 83c can communicate with the fuel introduction space 81a via the through hole 83d. These fuel passage 83c and through hole 83d serve as passages for hydrogen gas when the pilot valve 82 is opened, as will be described later. Therefore, the inner diameter dimensions of these fuel passages 83c and through-holes 83d are specified according to the required fuel supply pressure when the pilot valve 82 is open.

[0040] An annular recess 83e is formed on the tip end face of the tip portion 83a of the main valve 83, and an annular rubber first sealing material 83f is fitted into this recess 83e. As shown in Figures 2 and 3(a) (cross-sectional views showing the area around each valve 82, 83 of the shut-off valve 6, showing each valve 82, 83 in the closed state), when the main valve 83 is in the closed state, the first sealing material 83f of the main valve 83 abuts against the opening edge of the fuel outlet space 81b, thereby blocking the fuel inlet space 81a and the fuel outlet space 81b. In other words, the fuel inlet space 81a and the fuel outlet space 81b are blocked by the high sealing performance accompanied by elastic deformation of the first sealing material 83f.

[0041] A recess 82c is formed at the tip 82g of the pilot valve 82, and a cylindrical, rubber second sealing material 82d is fitted into this recess 82c. As shown in Figures 2 and 3(a), when the pilot valve 82 is in the closed position, the second sealing material 82d of the pilot valve 82 abuts against the opening edge of the fuel passage 83c of the main valve 83, thereby blocking the space inside the pilot valve insertion portion 83b from the fuel passage 83c. In other words, the space inside the pilot valve insertion portion 83b and the fuel passage 83c are blocked by the high sealing performance accompanied by elastic deformation of the second sealing material 82d.

[0042] Furthermore, the pilot valve insertion portion 83b of the main valve 83 has pin insertion holes 83g, 83g formed on opposite surfaces. In Figure 2, pin insertion holes 83g, 83g are formed on the upper and lower surfaces of the pilot valve insertion portion 83b, respectively. These pin insertion holes 83g may be circular or rectangular. Also, as shown in Figure 2, these pin insertion holes 83g may be through holes that extend to the outer surface of the pilot valve insertion portion 83b, or they may be closed holes that do not reach the outer surface of the pilot valve insertion portion 83b.

[0043] A pin 82e is attached to the tip 82g of the pilot valve 82, extending in a direction perpendicular to the axis of the pilot valve 82. Specifically, a through hole is formed in the tip 82g of the pilot valve 82, and the pin 82e is inserted into this through hole. The inner diameter of the through hole and the outer diameter of the pin 82e are approximately the same. The length of the pin 82e is set to be slightly longer than the outer diameter of the tip 82g of the pilot valve 82. The ends of the pin 82e (the parts that protrude from the outer surface of the pilot valve 82) are inserted into a pin insertion hole 83g. The outer diameter of the pin 82e is set to be smaller than the inner diameter of the pin insertion hole 83g. Therefore, the relative movement of the pilot valve 82 with respect to the main valve 83 (relative movement in the direction along the axis) is limited by the difference between the outer diameter of the pin 82e and the inner diameter of the pin insertion hole 83g.

[0044] Specifically, as shown in Figure 2, when both the main valve 83 and the pilot valve 82 are in the closed state, a predetermined gap is provided between the outer surface of the pin 82e facing the base end and the inner surface of the pin insertion hole 83g opposite this surface. Therefore, when the pilot valve 82 moves due to the electromagnetic force of the electromagnetic solenoid 71, if the amount of movement is less than or equal to the aforementioned predetermined amount, the pin 82e will not impart any operating force (an operating force in the opening direction to the main valve 83) to the inner surface of the pin insertion hole 83g. As a result, as shown in Figure 3(b), only the pilot valve 82 will be open. In this state, the hydrogen gas flow will be as indicated by the arrows in the figure. In other words, the hydrogen gas that flows from the upstream fuel supply pipe 52a into the fuel introduction space 81a will be led out to the downstream fuel supply pipe 52b via the through hole 83d, the space inside the pilot valve insertion part 83b, the fuel passage 83c, and the fuel outlet space 81b. As mentioned above, the inner diameter dimensions of the fuel passage 83c and the through-hole 83d are specified according to the required fuel supply pressure (a relatively low required pressure) when the pilot valve 82 is open. Therefore, by making the amount of fuel supplied to the delivery pipe 53 a relatively small flow rate, the supplied fuel pressure is kept relatively low.

[0045] On the other hand, if the electromagnetic force of the electromagnetic solenoid 71 becomes large and the amount of movement of the pilot valve 82 exceeds the predetermined amount mentioned above, the pin 82e will apply an operating force to the inner surface of the pin insertion hole 83g, and the electromagnetic force of the electromagnetic solenoid 71 will be transmitted to the main valve 83. As a result, the main valve 83 will be in an open state (the main valve 83 will be pulled up) as shown in Figure 3(c). In the stage before the main valve 83 opens, the pilot valve 82 is already in an open state, and the pressure difference between the fuel inlet space 81a and the fuel outlet space 81b (the differential pressure across the main valve 83) is small, so it is possible to open the main valve 83 with a relatively small electromagnetic force. In this state, the hydrogen gas flow is as shown by the arrows in the figure. In other words, the hydrogen gas that flows from the upstream fuel supply pipe 52a into the fuel inlet space 81a passes through the gap formed between the main valve 83 and the pressure regulating section side casing 81, goes through the fuel outlet space 81b, and is led out to the downstream fuel supply pipe 52b. In this case, the cross-sectional area of ​​the gap formed between the main valve 83 and the pressure regulating casing 81 is larger than the cross-sectional area of ​​the hydrogen gas flow path (for example, the cross-sectional area of ​​the fuel passage 83c) in the state shown in Figure 3(b) above. Therefore, by increasing the fuel supply rate to the delivery pipe 53 to a relatively large flow rate, the supplied fuel pressure is made relatively high.

[0046] Here, we will explain the closing and opening forces acting on each valve 82 and 83. Figure 4 is a diagram illustrating these closing and opening forces. As shown in Figure 4, the closing forces acting on each valve 82 and 83 include the biasing force (spring force) from the spring 82b, as well as the upstream-downstream differential pressure acting on the pilot valve 82 (the differential pressure between the fuel inlet space 81a and the fuel outlet space 81b: the front-to-back differential pressure) and the upstream-downstream differential pressure acting on the main valve 83. As shown in Figure 2, when comparing the area of ​​the main valve 83 facing the base end with the area facing the fuel outlet space 81b, the former area is larger, and therefore, when the main valve 83 is in the closed state, a large upstream-downstream differential pressure is applied in the closing direction.

[0047] On the other hand, when only the pilot valve 82 is open, the pressure acting on the pilot valve 82 includes the spring force and the differential pressure between the upstream and downstream sides of the pilot valve 82. By adjusting the electromagnetic force within the range of X in the figure, a state in which only the pilot valve 82 is open can be obtained. Furthermore, when the main valve 83 is open, there is almost no differential pressure between the upstream and downstream sides of each valve 82 and 83, so the electromagnetic force required to open the main valve 83 against the spring force becomes the opening force. For this reason, this electromagnetic force can be relatively small, and as a result, the diameter of the solenoid coil 71b can be reduced.

[0048] -Explanation of the operation of the shut-off valve- Next, the operation of the shut-off valve 6, configured as described above, will be explained.

[0049] As mentioned above, in a hydrogen engine, it is preferable to vary the fuel supply pressure in order to obtain an appropriate fuel injection amount for both the maximum and minimum fuel injection amounts into the combustion chamber. In this embodiment, the shut-off valve 6 varies the fuel supply pressure by controlling the excitation current to the electromagnetic solenoid 71, switching between a state in which only the pilot valve 82 is open (see Figure 3(b)) and a state in which the main valve 83 is open (see Figure 3(c)). For example, when the accelerator pedal depression amount detected by the accelerator opening sensor 101 is zero and the engine is idling, the excitation current is set relatively low to open only the pilot valve 82 and set the fuel supply pressure low, thereby improving the accuracy of the fuel injection amount. On the other hand, when the accelerator pedal depression amount detected by the accelerator opening sensor 101 is large, for example, when the engine is in WOT mode, the excitation current is set relatively high to open the main valve 83 and set the fuel supply pressure high, thereby ensuring that a sufficient fuel injection amount is obtained.

[0050] Figure 5(a) shows an example of the change in the supply current (excitation current for switching the opening and closing of the pilot valve 82 and the main valve 83) to the electromagnetic solenoid 71 of the shut-off valve 6 according to this embodiment, and the resulting change in the delivery pressure. Specifically, Figure 5(a) shows an example where, similar to the case of Figure 5(b) described above, the vehicle transitions from normal driving (period T1 in the figure) to a deceleration period (period T2 in the figure), then to idling (period T3 in the figure), and then, after an acceleration period (period T4 in the figure), returns to normal driving (period T5 in the figure).

[0051] During idling, the excitation current is kept relatively low, and only the pilot valve 82 is opened, as shown in Figure 3(b). This allows for fuel to be supplied to the delivery pipe 53 at a relatively low flow rate, resulting in a low fuel supply pressure, which improves the accuracy of fuel injection. More specifically, feedback control of the excitation current is performed based on the hydrogen gas pressure detected by the pressure sensor 57 installed in the delivery pipe 53, so that the hydrogen gas pressure in the delivery pipe 53 is adjusted to within a predetermined range P1. In the excitation current waveform shown in Figure 5(a), with only the pilot valve 82 open, the excitation current is reduced to zero and the pilot valve 82 is closed when the delivery pressure reaches the upper limit of the range P1, and the excitation current is increased when the delivery pressure reaches the lower limit of the range P1, thereby opening the pilot valve 82. This operation is repeated.

[0052] On the other hand, during WOT (Wash Over Time), the excitation current is set relatively high to open the main valve 83 as shown in Figure 3(c). This allows fuel to be supplied to the delivery pipe 53 with a relatively large flow rate, resulting in a high fuel supply pressure, which in turn allows for a sufficient fuel injection amount.

[0053] Figure 6 shows an example of the temporal changes in pilot pressure PP, main pressure MP, valve stroke, and inrush current IP when transitioning from a state where only the pilot valve 82 is open to a state where the main valve 83 is also open. In the figure, the dashed line represents the inrush current IP, the dashed line shows the change in pilot pressure PP, the dashed line shows the change in main pressure MP, and the solid line shows the stroke of each valve 82 and 83 in the opening direction. In the figure, PV represents the period when only the pilot valve 82 is open, and MV represents the period when the main valve 83 is open.

[0054] -Effects of the embodiment- As described above, in this embodiment, the shut-off valve 6 installed in the fuel supply pipe 52 is equipped with a pilot valve 82 and a main valve 83, making it possible to switch between opening only the pilot valve 82 by relatively reducing the electromagnetic force of the electromagnetic solenoid 71 and opening the main valve 83 by relatively increasing the electromagnetic force of the electromagnetic solenoid 71. In other words, it is possible to change the supplied fuel pressure in at least two stages: a state in which the supplied fuel pressure is relatively low and a state in which the supplied fuel pressure is relatively high. For this reason, the supplied fuel pressure can be varied without increasing the number of times the valves 82 and 83 are driven to open and close, and a fuel supply amount suitable for the engine's operating state can be obtained.

[0055] Furthermore, in this embodiment, when the engine body 2 is stopped and the valves 82 and 83 are closed, the sealing materials 82d and 83f effectively prevent hydrogen gas leakage (leakage of hydrogen gas toward the combustion chamber). Generally, injectors 54 are metal seals and therefore may not provide sufficient fuel leak prevention performance. However, even in such situations, the shut-off valve 6 can prevent hydrogen gas leakage, thus effectively preventing hydrogen gas leakage from the fuel supply system 5 toward the engine body 2 when the engine body 2 is stopped. In addition, since the shut-off valve 6 is located in the middle of the fuel supply piping 52 and closer to the delivery pipe 53, the volume of the space between the shut-off valve 6 and the injector 54 is relatively small. Therefore, when the engine body 2 is stopped, after closing the valves 82 and 83 of the shut-off valve 6, the engine body 2 is continued to run and the hydrogen gas present in this space is consumed. This reduces the amount of hydrogen gas consumed when the engine body 2 is stopped, while also reducing the amount of hydrogen gas leakage after the engine body 2 is stopped.

[0056] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments described above, and all modifications and applications are possible within the scope of the claims and equivalents thereof.

[0057] For example, the above embodiment described the application of the present invention to a system equipped with a four-cylinder hydrogen engine mounted on a vehicle. However, the present invention is not limited to this and can also be applied to gas engines used in applications other than vehicles. Furthermore, the number of cylinders is not limited to four, nor is the fuel limited to hydrogen gas.

[0058] Furthermore, in the above embodiment, a pressure reducing valve 55 was used as a pressure reducing means installed in the fuel supply pipe 52, but the invention is not limited to this, and a pump or the like may be used instead. [Industrial applicability]

[0059] The present invention is applicable as a fuel supply device to be installed in a hydrogen engine. [Explanation of symbols]

[0060] 2…Engine body (internal combustion engine) 5…Fuel supply system (fuel supply device) 51…Hydrogen storage tank (high-pressure tank) 52…Fuel supply piping 52a…Upstream fuel supply piping 52b…Downstream fuel supply piping 54...Injector (fuel injection valve) 55...Pressure reducing valve (pressure reducing means) 6...Shut-off valve (pressure variable device) 71...Electromagnetic solenoid 81a...Fuel introduction space 81b…Fuel outlet space 82…Pilot valve 82d…Second seal material 82e…Pin 82g...Tip section 83...Main valve 83a...Tip section 83b...Pilot valve insertion section 83c...Fuel passage 83f...First seal material 83g…Pin insertion hole

Claims

1. A fuel supply device that, after reducing the pressure of fuel in a high-pressure tank using a depressurization means, supplies this fuel to the fuel injection valve of an internal combustion engine via a fuel supply pipe, The fuel supply piping is equipped with a pressure variable device that varies the pressure of the fuel supplied to the fuel injection valve. The aforementioned pressure variable device is A pilot valve that opens due to the electromagnetic force generated by energizing a built-in electromagnetic solenoid, and in the open state supplies the fuel toward the fuel injection valve, The system includes a main valve that opens in conjunction with the movement of the pilot valve when an electromagnetic force greater than the electromagnetic force required to open the pilot valve is generated from the electromagnetic solenoid, and in this open state, increases the amount of fuel supplied to the fuel injector compared to when only the pilot valve is open. Furthermore, the variable pressure device includes a fuel introduction space connected to an upstream fuel supply pipe connected to the high-pressure tank, and a fuel outlet space connected to a downstream fuel supply pipe extending toward the fuel injection valve. The main valve includes a pilot valve insertion portion into which the tip of the pilot valve is inserted, and a fuel passage whose one end communicates with the space inside the pilot valve insertion portion and whose other end communicates with the fuel outlet space. The pilot valve insertion portion has a through hole formed therein that penetrates radially through the pilot valve insertion portion and connects the fuel introduction space with the space inside the pilot valve insertion portion. When the main valve is closed, the tip of the main valve abuts against the opening edge of the fuel outlet space, thereby blocking the fuel inlet space from the fuel outlet space. When the pilot valve is in the closed position, the tip of the pilot valve inserted into the pilot valve insertion section abuts against the opening edge of the fuel passage of the main valve, thereby blocking the space inside the pilot valve insertion section from the fuel passage. A pin insertion hole is provided on the base end side of the main valve, which is on the side of movement in the valve opening direction of the main valve, rather than the position where the through hole is formed in the pilot valve insertion portion of the main valve, extending in a direction perpendicular to the direction of movement of the pilot valve. A pin is inserted into the tip of the pilot valve, which is inserted through the pin insertion hole. The inner diameter dimension of the pin insertion hole in the direction of movement is set to be larger than the outer diameter dimension of the pin in the direction of movement, and when both the main valve and the pilot valve are in the closed state, a predetermined amount of space is provided between the outer surface of the pin that faces the direction of movement of the pilot valve due to energization of the electromagnetic solenoid and the inner surface of the pin insertion hole that faces the outer surface. The main valve is configured such that when the pilot valve moves beyond a predetermined amount in the valve-opening direction, the pin contacts the inner surface of the pin insertion hole, thereby receiving an operating force in the valve-opening direction from the pilot valve and starting to open. The casing that movably supports the main valve is provided with a support portion that contacts the outer surface of the pilot valve insertion portion. A fuel supply device for an internal combustion engine, characterized in that the length of the support portion in the direction along the movement direction of the main valve is set to cover the outer opening of the pin insertion hole at the position where the main valve is closed and the position where it is open, and to not close the through hole of the pilot valve insertion portion at the position where the main valve is closed.

2. In the fuel supply device for an internal combustion engine according to Claim 1, A fuel supply device for an internal combustion engine, characterized in that the tip of the main valve and the tip of the pilot valve are both provided with a rubber sealing material.

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