Fuel supply device for internal combustion engine

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 such as a gas engine, and more particularly to an improvement for making the pressure of the fuel supply variable. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1 and Patent Document 2, in a gas engine that uses gas such as hydrogen as fuel, a valve that can be opened and closed is provided in a fuel supply pipe extending from a fuel tank to a delivery pipe in a fuel supply system. Patent Document 1 discloses a configuration in which a shutoff valve that is closed when the supply of fuel (hydrogen gas) to a fuel injection valve is stopped is provided in the fuel supply pipe. Patent Document 2 discloses a configuration in which a pressure reducing valve for reducing the pressure of the fuel supplied to the fuel injection valve (hereinafter sometimes referred to as the supply fuel pressure) is provided in the fuel supply pipe. Generally, this pressure reducing valve is mechanical, and the supply fuel pressure is fixed to a constant value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-180751 A [Patent Document 2] JP 2021-139321 A Summary of the Invention [Problem to be solved by the invention]

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

[0005] As a means for satisfying this requirement, it is conceivable to provide a solenoid valve in the fuel supply pipe and adjust the supply fuel pressure by switching the solenoid valve open and closed (alternately switching between a fully open state and a fully closed state). FIG. 5(b) shows an example of the change in the supply current (excitation current for switching the solenoid valve open and closed) to the electromagnetic solenoid and the associated change in the internal pressure of the delivery pipe (hereinafter referred to as delivery pressure) when this solenoid valve is used. Specifically, FIG. 5(b) shows an example of the case where the vehicle goes from normal driving (period T1 in the figure) to a deceleration period (period T2 in the figure), then transitions to idling driving (period T3 in the figure), then passes through an acceleration period (period T4 in the figure), and returns to normal driving (period T5 in the figure).

[0006] In the case of a configuration equipped with the above-mentioned solenoid valve, during idling operation, the solenoid valve is alternately switched 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] When a solenoid valve is provided in this manner, not only does the number of times the solenoid valve is opened and closed per unit time (the number of times the fully open and fully closed states are repeated) increase, but it also becomes difficult to adjust the fuel flow rate, leaving room for improvement.

[0008] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention 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 solution of the present invention for achieving the above object is directed to a fuel supply device that reduces the pressure of fuel in a high-pressure tank by a pressure reducing means and then supplies the fuel to a fuel injection valve of an internal combustion engine through a fuel supply pipe, and the fuel supply device is characterized in that a pressure varying device that varies the pressure of the fuel supplied to the fuel injection valve is disposed in the fuel supply pipe, the pressure varying device comprising: a pilot valve that opens by an electromagnetic force generated by energizing an electromagnetic solenoid contained therein and supplies the fuel to the fuel injection valve in the open state, and a main valve that opens in conjunction with the movement of the pilot valve when the electromagnetic solenoid generates an electromagnetic force greater than the electromagnetic force that opens the pilot valve and increases the amount of fuel supplied to the fuel injection valve in the open state compared to when only the pilot valve is open.

[0010] With this feature, by controlling the energization of the electromagnetic solenoid, it is possible to switch between a relatively small amount of fuel supply to the fuel injection valve by opening only the pilot valve and a relatively large amount of fuel supply to the fuel injection valve by opening the main valve. In other words, it is possible to change the supply fuel pressure in at least two stages: a state in which the supply fuel pressure is relatively low by setting the fuel supply amount to a relatively small amount, and a state in which the supply fuel pressure is relatively high by setting the fuel supply amount to a relatively large amount. Therefore, compared to the case where the above-mentioned solenoid valve is provided, it is possible to make the supply fuel pressure variable without increasing the number of times the valve is opened and closed, and to obtain the amount of fuel supply suitable for the operating state of the internal combustion engine.

[0011] Furthermore, the main valve is configured to receive an operating force from the pilot valve in the valve opening direction and start opening when the pilot valve moves in the valve opening direction beyond a predetermined amount.

[0012] This makes it possible, by adjusting the electromagnetic force through control of the flow of electricity to a single electromagnetic solenoid, to switch between a state in which only the pilot valve is open by keeping the movement of the pilot valve below a predetermined amount, and a state in which the main valve is open by making the movement of the pilot valve exceed a predetermined amount.

[0013] More specifically, the pressure varying device includes a fuel introduction space connected to an upstream fuel supply pipe connected to the high-pressure tank and a fuel discharge space connected to a downstream fuel supply pipe extending toward the fuel injection valve, the main valve includes a fuel passage having one end connected to the fuel introduction space and the other end connected to the fuel discharge space, and a pilot valve insertion portion into which a tip of the pilot valve is inserted, and when the main valve is in a closed state, the tip of the main valve abuts against an opening edge of the fuel discharge space to block the fuel introduction space and the fuel discharge space, and when the pilot valve is in a closed state, the tip of the pilot valve inserted in the pilot valve insertion portion abuts against an opening edge of the fuel passage of the main valve to block the fuel introduction space and the fuel passage. Further, a pin insertion hole extending in a direction perpendicular to the movement direction of the pilot valve is provided in the pilot valve insertion portion of the main valve, and a pin to be inserted into the pin insertion hole is integrally provided at the tip of the pilot valve, and the inner diameter dimension of the pin insertion hole in the direction along the movement direction is set to be larger than the outer diameter dimension of the pin in the direction along the movement direction, and when the main valve and the pilot valve are both in a closed state, the predetermined amount of space is provided between the outer surface of the pin that faces the direction of movement of the pilot valve when current is applied to the electromagnetic solenoid and the inner surface of the pin insertion hole that faces the outer surface.

[0014] According to this configuration, when the main valve is in a closed state in which the tip of the main valve is in contact with the opening edge of the fuel outlet space and the pilot valve is in contact with the opening edge of the fuel passage of the main valve, the pilot valve is moved by the electromagnetic force of the electromagnetic solenoid from the closed state in which the tip of the pilot valve is in contact with the opening edge of the fuel passage of the main valve, if the amount of movement is equal to or less than a predetermined amount, the pin integrally provided at the tip of the pilot valve does not apply an operating force (an operating force in the valve opening direction for the main valve) to the inner surface of the pin insertion hole of the main valve. Therefore, only the pilot valve is opened (a state in which the fuel supply amount is made relatively small to make the supply fuel pressure relatively low). When the electromagnetic force of the electromagnetic solenoid becomes large and the amount of movement of the pilot valve exceeds a predetermined amount, the pin applies an operating force to the inner surface of the pin insertion hole, and the electromagnetic force of the electromagnetic solenoid is also transmitted to the main valve, and the main valve is opened (a state in which the fuel supply amount is made relatively large to make the supply fuel pressure relatively high). In this way, by adopting a linking structure between the pilot valve and the main valve using a pin, it is possible to switch between a state in which only the pilot valve is open and a state in which the main valve is open.

[0015] The pressure varying device includes a fuel introduction space connected to an upstream fuel supply pipe connected to the high-pressure tank and a fuel discharge space connected to a downstream fuel supply pipe extending toward the fuel injection valve, the main valve includes a fuel passage having one end connected to the fuel introduction space and the other end connected to the fuel discharge space, and a pilot valve insertion portion into which a tip of the pilot valve is inserted, and when the main valve is in a closed state, the tip of the main valve abuts against an opening edge of the fuel discharge space to block the fuel introduction space and the fuel discharge space, and when the pilot valve is in a closed state, the tip of the pilot valve inserted in the pilot valve insertion portion abuts against an opening edge of the fuel passage of the main valve to block the fuel introduction space and the fuel passage. The tip of the main valve and the tip of the pilot valve are both provided with a rubber seal.

[0016] According to this, when the internal combustion engine is stopped and each valve is in a closed state, each sealant can reliably prevent fuel leakage (fuel leakage toward the combustion chamber). For example, even in a situation where the fuel injection valve that injects fuel into the combustion chamber of the internal combustion engine does not have sufficient fuel leakage prevention performance, the pressure variable device can prevent fuel leakage, so that it is possible to reliably prevent fuel leakage from the fuel supply device toward the internal combustion engine when the internal combustion engine is stopped. Effect of the Invention

[0017] In the present invention, the pressure varying device disposed in the fuel supply pipe is provided with a pilot valve and a main valve, and it is possible to switch between opening only the pilot valve by making the electromagnetic force of the electromagnetic solenoid relatively small, and opening the main valve by making the electromagnetic force of the electromagnetic solenoid relatively large. In other words, it is possible to change the supply fuel pressure in at least two stages. Therefore, it is possible to vary the supply fuel pressure without increasing the number of times the valve is opened and closed, and to obtain the amount of fuel supply suitable for the operating state of the internal combustion engine. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing a schematic configuration of a hydrogen engine system. [Diagram 2] FIG. [Diagram 3] 3(a) is a cross-sectional view showing the periphery of each valve of a shutoff valve, in which FIG. 3(a) shows each valve in a closed state, FIG. 3(b) shows the pilot valve in an open state, and FIG. 3(c) shows the main valve in an open state. [Figure 4] 5A and 5B are diagrams for explaining valve closing and opening forces acting on each valve. [Diagram 5] 5A and 5B are diagrams showing an example of a change in excitation current to an electromagnetic solenoid and an associated change in delivery pressure, where FIG. 5A is a diagram according to an embodiment and FIG. 5B is a diagram according to the prior art. [Figure 6] FIG. 4 is a diagram showing an example of temporal changes in pilot pressure, main pressure, valve stroke, and inrush current in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described as being applied to a system equipped with a four-cylinder hydrogen engine (an internal combustion engine fueled by hydrogen gas) mounted on a vehicle.

[0020] -Overview of hydrogen engine system- First, before describing the shutoff valve (the pressure varying device in the present invention) provided in the fuel supply system, the schematic configuration of the hydrogen engine system according to this embodiment will be briefly described.

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

[0022] The engine body 2 includes four cylinders #1 to #4, and generates a rotational driving force by reciprocating movement of pistons (not shown) associated with combustion of a 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 attached to the upper end of a cylinder block 21 in the engine body 2, and spark plugs 22 (not shown) are disposed in the cylinder head so as to face the combustion chambers of each of the cylinders #1 to #4. Also, an injector (direct injection injector: fuel injection valve) 54 is disposed in each of the cylinders #1 to #4, which injects hydrogen gas (fuel) supplied from a fuel supply system 5 into the combustion chamber. A water temperature sensor 23 for detecting the temperature of engine cooling water, a crank angle sensor 24 for detecting the crank angle, and the like are disposed 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 (air) toward the combustion chambers of each of the cylinders #1 to #4. 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 are arranged on the upstream side of the intake passage 31 (upstream side of the flow of intake air). The throttle valve 37 is driven by a throttle motor 38. An intake valve (not shown) is arranged at the downstream end of an intake port formed in the cylinder head, and intake air is supplied into the combustion chamber by opening this intake valve. The configuration of the intake system 3 is not limited to this. For example, the configuration may be such that the surge tank 32 is not included.

[0024] The exhaust system 4 includes an exhaust manifold 41 and an exhaust passage 42. A catalytic converter 43 for purifying exhaust (mainly NOx in the exhaust) is disposed in the exhaust passage 42. An exhaust valve (not shown) is disposed at the upstream end of an exhaust port formed in the cylinder head, and exhaust gas is discharged from the combustion chamber when this exhaust valve is opened. 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, a fuel supply pipe 52, a delivery pipe 53, and an injector 54 for each cylinder. The hydrogen storage tank 51 is a tank for storing hydrogen under high pressure. The fuel supply pipe 52 is provided with a pressure reducing valve (pressure reducing means) 55 for reducing the pressure of hydrogen gas supplied to the delivery pipe 53, a relief valve 56 that opens when the fuel pressure inside the fuel supply pipe 52 exceeds a predetermined value, and a shutoff valve 6 for adjusting the pressure of the fuel supplied to the delivery pipe 53. Hereinafter, the fuel supply pipe 52 upstream of the shutoff valve 6 (hydrogen storage tank 51 side) will be referred to as the upstream fuel supply pipe 52a, and the fuel supply pipe 52 downstream of the shutoff valve 6 (delivery pipe 53 side) will be referred to as the downstream fuel supply pipe 52b. Further, a pressure sensor 57 for detecting the pressure of the hydrogen gas in the delivery pipe 53 and a temperature sensor 58 for detecting the temperature of the hydrogen gas in the delivery pipe 53 are disposed in the delivery pipe 53 .

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

[0027] The ECU (Electronic Control Unit) 100 is a known device that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup RAM. The CPU executes various arithmetic processing based on various control programs and maps stored in the ROM. The RAM temporarily stores the results of calculations performed by the CPU and data input from each sensor, and the backup RAM stores data that should be saved when the engine is stopped, for example.

[0028] The ECU 100 is connected to the above-mentioned water temperature sensor 23, crank angle sensor 24, air flow meter 35, intake air temperature sensor 36, pressure sensor 57, temperature sensor 58, etc. Also connected to the ECU 100 is an accelerator opening sensor 101 that outputs a detection signal corresponding to the depression amount of an accelerator pedal (not shown). Furthermore, the ECU 100 is connected to the ignition plug 22 (more specifically, an igniter), throttle motor 38, injector 54, etc.

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

[0030] -Shut-off valve configuration- Next, the shutoff valve 6, which is a characteristic component of this embodiment, will be described. Fig. 2 is a cross-sectional view of the shutoff valve 6. In the following description, the left side in Fig. 2 will be referred to as the base end side, and the right side as the tip end side. As shown in Fig. 2, the shutoff valve 6 has a drive unit 7 equipped with an electromagnetic solenoid 71 and disposed on the base end side, and a pressure adjustment unit 8 capable of adjusting the supplied fuel pressure by driving the drive unit 7 and disposed on the tip side.

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

[0032] The drive unit side casing 72 includes a casing body 73 configured by integrally assembling a plurality of members, and a spring receiving member 74 fastened with a bolt to the base end side (left side in FIG. 2) of the casing body 73.

[0033] The electromagnetic solenoid 71 includes a core 71a and a solenoid coil 71b made of a conducting wire wound around the outer periphery of the core 71a, and generates an electromagnetic force when a current is applied to the solenoid coil 71b. The magnitude of the electromagnetic force can be adjusted according to the value of the current applied to the solenoid coil 71b.

[0034] The pressure adjusting section 8 includes a pressure adjusting section side casing 81 , a pilot valve 82 and a main valve 83 .

[0035] The pressure adjusting section side casing 81 is integrally assembled to the drive section side casing 72 via the seal 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 (the upstream fuel supply pipe 52a connected to the hydrogen storage tank 51: see FIG. 1) and a fuel discharge space 81b connected to the downstream fuel supply pipe 52b (the downstream fuel supply pipe 52b extending toward the delivery pipe 53 and the injector 54). Therefore, when at least one of the pilot valve 82 and the main valve 83 is in an open state, the fuel introduction space 81a and the fuel discharge space 81b communicate with each other, and hydrogen gas supplied from the hydrogen storage tank 51 and depressurized by the pressure reducing valve 55 passes through the shutoff 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 accommodating recess 82a is formed at the base end of the pilot valve 82. A spring 82b accommodated in the spring accommodating recess 82a is compressed between the bottom surface of the spring accommodating recess 82a and the spring receiving member 74, and applies a biasing force in the valve closing direction (direction toward the tip side) to the pilot valve 82. 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 valve closing direction (direction toward the tip side) due to the biasing force of the spring 82b, whereas 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 valve opening direction (direction toward the base end side) against the biasing force of the spring 82b. The amount of movement of the pilot valve 82 in the valve opening direction is adjusted by the magnitude of the electromagnetic force, that is, the magnitude of the current passed through the solenoid coil 71b.

[0037] A tip portion 82g of the pilot valve 82 is inserted into a base end portion of the main valve 83, and is capable of moving within a predetermined movable range relative to the main valve 83. Below, the configurations of the tip portion 82g of the pilot valve 82 and the main valve 83, as well as the assembly state of these valves 82, 83 will be described.

[0038] The main valve 83 has a generally disk-shaped tip portion 83a and a pilot valve insert portion 83b extending cylindrically from the outer edge of the tip portion 83a toward the base end. The outer diameter of tip portion 82g of the pilot valve 82 generally matches the inner diameter of the pilot valve insert portion 83b, and tip portion 82g of the pilot valve 82 is inserted into the pilot valve insert portion 83b.

[0039] A fuel passage 83c extending in a direction along the axis of the main valve 83 is provided in the tip 83a of the main valve 83. One end of the fuel passage 83c (the base end of the main valve 83) is open to the space inside the pilot valve insertion part 83b, and the other end (the tip side of the main valve 83) is open to the fuel outlet space 81b. The pilot valve insertion part 83b of the main valve 83 is formed with a through hole 83d that penetrates the pilot valve insertion part 83b in the radial direction. This allows the space inside the pilot valve insertion part 83b to communicate with the fuel introduction space 81a through the through hole 83d. That is, one end of the fuel passage 83c can communicate with the fuel introduction space 81a through the through hole 83d. The fuel passage 83c and the through hole 83d serve as a passage for hydrogen gas when the pilot valve 82 is opened, as described later. Therefore, the inner diameters of the fuel passage 83c and the through hole 83d are determined according to the fuel supply pressure required when the pilot valve 82 is opened.

[0040] An annular recess 83e is formed on the end surface on the tip side of the tip portion 83a of the main valve 83, and an annular rubber first seal member 83f is attached to the recess 83e. As shown in Fig. 2 and Fig. 3(a) (a cross-sectional view showing the periphery of the valves 82, 83 of the shutoff valve 6, with the valves 82, 83 in a closed state), when the main valve 83 is in a closed state, the first seal member 83f of the main valve 83 abuts on the opening edge of the fuel discharge space 81b to separate the fuel introduction space 81a from the fuel discharge space 81b. That is, the high sealing performance of the first seal member 83f, which is accompanied by elastic deformation, separates the fuel introduction space 81a from the fuel discharge space 81b.

[0041] A recess 82c is formed in a tip end 82g of the pilot valve 82, and a cylindrical rubber second seal member 82d is attached to the recess 82c. As shown in Fig. 2 and Fig. 3(a), when the pilot valve 82 is in a closed state, the second seal member 82d of the pilot valve 82 abuts against the opening edge of the fuel passage 83c of the main valve 83, thereby isolating the space inside the pilot valve insertion portion 83b from the fuel passage 83c. In other words, the high sealing performance of the second seal member 82d, which is accompanied by elastic deformation, isolates the space inside the pilot valve insertion portion 83b from the fuel passage 83c.

[0042] Furthermore, the pilot valve insertion portion 83b of the main valve 83 has pin insertion holes 83g, 83g formed on each of the opposing surfaces. In Fig. 2, the pin insertion holes 83g, 83g are formed on the upper and lower surfaces of the pilot valve insertion portion 83b. The pin insertion hole 83g may be a circular hole or a rectangular hole. The pin insertion hole 83g may be a through hole that reaches the outer surface of the pilot valve insertion portion 83b as shown in Fig. 2, or may be a bottomed hole that does not reach the outer surface of the pilot valve insertion portion 83b.

[0043] A pin 82e extending in a direction perpendicular to the axis of the pilot valve 82 is attached to a tip 82g of the pilot valve 82. Specifically, a through hole penetrating in the radial direction is formed in the tip 82g of the pilot valve 82, and the pin 82e is inserted into the through hole. The inner diameter of the through hole and the outer diameter of the pin 82e are approximately equal. 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. Both ends of the pin 82e (portions protruding from the outer surface of the pilot valve 82) are inserted into the 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 pilot valve 82 can move relative to the main valve 83 (relative movement in the direction along the axis) by the difference between the outer diameter of the pin 82e and the inner diameter of the pin insertion hole 83g.

[0044] Specifically, when the main valve 83 and the pilot valve 82 are both in a closed state as shown in FIG. 2, a predetermined gap is provided between the surface of the outer surface of the pin 82e facing the base end side and the inner surface of the pin insertion hole 83g facing this surface. Therefore, when the pilot valve 82 moves due to the electromagnetic force of the electromagnetic solenoid 71, if the movement amount is equal to or less than the above-mentioned predetermined amount, the pin 82e does not apply an operating force (an operating force in the valve opening direction for the main valve 83) to the inner surface of the pin insertion hole 83g. Therefore, as shown in FIG. 3(b), only the pilot valve 82 opens. In this state, the flow of hydrogen gas is as shown by the arrow in the figure. That is, the hydrogen gas that flows from the upstream fuel supply pipe 52a into the fuel introduction space 81a passes through the through hole 83d, the space inside the pilot valve insertion part 83b, the fuel passage 83c, and the fuel discharge space 81b, and is discharged to the downstream fuel supply pipe 52b. As described above, the inner diameter dimensions of fuel passage 83c and through hole 83d are determined according to the supply fuel pressure required when pilot valve 82 is opened (a relatively low required pressure). Therefore, by setting the amount of fuel supplied to delivery pipe 53 at a relatively small flow rate, the supply fuel pressure is made relatively low.

[0045] On the other hand, when the electromagnetic force of the electromagnetic solenoid 71 becomes large and the movement amount of the pilot valve 82 exceeds the above-mentioned predetermined amount, the pin 82e applies an operating force to the inner surface of the pin insertion hole 83g, and the electromagnetic force of the electromagnetic solenoid 71 is also transmitted to the main valve 83. Therefore, the main valve 83 is opened (the main valve 83 is pulled up) as shown in FIG. 3(c). Before the main valve 83 opens, the pilot valve 82 is already in an open state, and the pressure difference between the fuel introduction space 81a and the fuel discharge space 81b (the pressure difference between the front and rear of the main valve 83) is small, so that the main valve 83 can be opened with a relatively small electromagnetic force. In this state, the hydrogen gas flows as shown by the arrows in the figure. That is, the hydrogen gas that flows from the upstream fuel supply pipe 52a into the fuel introduction space 81a passes through the gap formed between the main valve 83 and the pressure adjustment unit side casing 81, passes through the fuel discharge space 81b, and is discharged to the downstream fuel supply pipe 52b. In this case, the cross-sectional area of ​​the gap formed between main valve 83 and pressure regulating unit casing 81 is larger than the cross-sectional area of ​​the hydrogen gas flow path (e.g., the cross-sectional area of ​​fuel passage 83c) in the state shown in Fig. 3(b) above. Therefore, the amount of fuel supplied to delivery pipe 53 is set to a relatively large flow rate, thereby making the supply fuel pressure relatively high.

[0046] Here, the valve closing force and the valve opening force acting on each of the valves 82 and 83 will be described. Fig. 4 is a diagram for explaining these valve closing and opening forces. As shown in Fig. 4, the valve closing force acting on each of the valves 82 and 83 includes 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 introduction space 81a and the fuel discharge space 81b: the upstream-downstream differential pressure) and the upstream-downstream differential pressure acting on the main valve 83. As shown in Fig. 2, when comparing the area of ​​the main valve 83 facing the base end side with the area facing the fuel discharge space 81b, the former area is larger. Therefore, when the main valve 83 is in the closed state, a large upstream-downstream differential pressure is applied in the valve closing direction.

[0047] On the other hand, the pressure acting on the pilot valve 82 when only the pilot valve 82 is open includes the spring force and the upstream / downstream pressure difference of the pilot valve 82, and a state in which only the pilot valve 82 is open can be achieved by adjusting the electromagnetic force within the range of X in the figure. Also, when the main valve 83 is open, almost no upstream / downstream pressure difference occurs between the valves 82, 83, so the opening force is an electromagnetic force that is sufficient to open the main valve 83 against the spring 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 shutoff valve operation - Next, the operation of the shutoff valve 6 constructed as above will be described.

[0049] As described above, in a hydrogen engine, it is preferable to make the supply fuel pressure variable in order to obtain an appropriate fuel injection amount when the fuel injection amount into the combustion chamber is the maximum injection amount and when the fuel injection amount is the minimum injection amount. The shutoff valve 6 in this embodiment is adapted to make the supply fuel pressure variable by controlling the excitation current to the electromagnetic solenoid 71 to switch between a state in which only the pilot valve 82 is opened (see FIG. 3(b)) and a state in which the main valve 83 is opened (see FIG. 3(c)). For example, when the accelerator pedal depression amount detected by the accelerator pedal position sensor 101 is zero and the engine is in an idling operation state, the excitation current is made relatively low to open only the pilot valve 82 and set the supply fuel pressure low, thereby making it possible to improve the accuracy of the fuel injection amount. On the other hand, when the accelerator pedal depression amount detected by the accelerator pedal position sensor 101 is large, for example, when the engine is in a WOT state, the excitation current is made relatively high to open the main valve 83 and set the supply fuel pressure high, thereby making it possible to obtain a sufficient fuel injection amount.

[0050] Fig. 5(a) shows an example of a change in the supply current (excitation current for switching between opening and closing of the pilot valve 82 and the main valve 83) to the electromagnetic solenoid 71 of the shutoff valve 6 according to this embodiment, and an associated change in the delivery pressure. Specifically, Fig. 5(a) shows an example of a case in which, like the case of Fig. 5(b) described above, the vehicle goes from normal driving (period T1 in the figure) through a deceleration period (period T2 in the figure), then transitions to idling driving (period T3 in the figure), then passes through an acceleration period (period T4 in the figure), and returns to normal driving (period T5 in the figure).

[0051] During idling, the excitation current is made relatively low and only the pilot valve 82 is opened as shown in FIG. 3(b). As a result, fuel is supplied to the delivery pipe 53 at a relatively small flow rate, so that the fuel supply pressure is set low, and this makes it possible to improve the accuracy of the fuel injection amount. More specifically, based on the hydrogen gas pressure detected by the pressure sensor 57 disposed in the delivery pipe 53, feedback control of the excitation current is performed 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 FIG. 5(a), when only the pilot valve 82 is open and the delivery pressure reaches the upper limit of the range P1, the excitation current is made zero to close the pilot valve 82, and when the delivery pressure reaches the lower limit of the range P1, the excitation current is passed to open the pilot valve 82, and this operation is repeated.

[0052] On the other hand, during WOT, the excitation current is made relatively high to open the main valve 83 as shown in Fig. 3(c) .As a result, fuel is supplied to the delivery pipe 53 at a relatively large flow rate, and the supply fuel pressure is set high, thereby making it possible to obtain a sufficient fuel injection amount.

[0053] 6 is a diagram showing an example of temporal changes in pilot pressure PP, main pressure MP, valve stroke, and inrush current IP when transitioning from a state in which only the pilot valve 82 is open to a state in which the main valve 83 is open. In the diagram, the dashed line indicates the inrush current IP, the one-dot chain line indicates the change in pilot pressure PP, the two-dot chain line indicates the change in main pressure MP, and the solid lines indicate the stroke in the opening direction of each of the valves 82, 83. As for the stroke in the opening direction of each of the valves 82, 83, PV in the diagram indicates the period when only the pilot valve 82 is open, and MV indicates the period when the main valve 83 is open.

[0054] -Effects of the embodiment- As described above, in this embodiment, the shutoff valve 6 disposed in the fuel supply pipe 52 is provided with the pilot valve 82 and the main valve 83, and it is possible to switch between opening only the pilot valve 82 by making the electromagnetic force of the electromagnetic solenoid 71 relatively small, and opening the main valve 83 by making the electromagnetic force of the electromagnetic solenoid 71 relatively large. In other words, it is possible to change the supply fuel pressure in at least two stages, a state in which the supply fuel pressure is relatively low and a state in which the supply fuel pressure is relatively high. Therefore, it is possible to make the supply fuel pressure variable without increasing the number of times the valves 82 and 83 are opened and closed, and to obtain a fuel supply amount suitable for the operating state of the engine.

[0055] In this embodiment, when the valves 82, 83 are closed while the engine body 2 is stopped, the seal members 82d, 83f effectively prevent leakage of hydrogen gas (leakage of hydrogen gas toward the combustion chamber). Generally, the injector 54 is a metal seal, and therefore may not have sufficient fuel leak prevention performance. However, even in such a situation, the shutoff valve 6 can effectively prevent leakage of hydrogen gas from the fuel supply system 5 toward the engine body 2 while the engine body 2 is stopped. Furthermore, the shutoff valve 6 is disposed in the middle of the fuel supply pipe 52 and near the delivery pipe 53, so that the volume of the space between the shutoff valve 6 and the injector 54 is relatively small. Therefore, when the engine body 2 is stopped, after closing each valve 82, 83 of the shut-off valve 6, the engine body 2 continues to operate and the hydrogen gas present in this space is consumed, thereby reducing the amount of hydrogen gas consumed when the engine body 2 is stopped while also reducing the amount of hydrogen gas leaking after the engine body 2 is stopped.

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

[0057] For example, in the above embodiment, the present invention has been described as being applied to a system equipped with a four-cylinder hydrogen engine mounted on a vehicle. The present invention is not limited to this, and can also be applied to gas engines used for purposes other than vehicles. The number of cylinders is not limited to four. The fuel is not limited to hydrogen gas.

[0058] In the above embodiment, the pressure reducing valve 55 is used as the pressure reducing means disposed in the fuel supply pipe 52, but the present invention is not limited to this, and a pump or the like may be used. [Industrial Applicability]

[0059] The present invention is applicable as a fuel supply device provided 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 pipe 52b: downstream fuel supply pipe 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 discharge space 82... pilot valve 82d... second seal material 82e... pin 82g...Tip 83...Main valve 83a...Tip 83b: pilot valve insertion portion; 83c: fuel passage; 83f: first seal material 83g…Pin insertion hole

Claims

1. A fuel supply device that reduces the pressure of fuel in a high-pressure tank by a pressure reducing means and then supplies the fuel to a fuel injection valve of an internal combustion engine through a fuel supply pipe, a pressure varying device that varies the pressure of the fuel supplied to the fuel injection valve is disposed in the fuel supply pipe, The pressure varying device is a pilot valve that opens by an electromagnetic force generated by energizing a built-in electromagnetic solenoid and supplies the fuel to the fuel injection valve in the open state; a main valve that opens in conjunction with movement of the pilot valve when an electromagnetic force greater than the electromagnetic force at which the pilot valve opens is generated from the electromagnetic solenoid, and that, in the open state, increases the amount of fuel supplied to the fuel injection valve compared to a case in which only the pilot valve is open.

2. 2. The fuel supply system for an internal combustion engine according to claim 1, 2. A fuel supply device for an internal combustion engine, wherein when the pilot valve moves in the valve opening direction beyond a predetermined amount, the main valve receives an operating force in the valve opening direction from the pilot valve and begins opening.

3. 3. The fuel supply system for an internal combustion engine according to claim 2, the pressure varying device includes a fuel inlet 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 fuel passage having one end communicating with the fuel introduction space and the other end communicating with the fuel discharge space, and a pilot valve insertion portion into which a tip end of the pilot valve is inserted, When the main valve is in a closed state, a tip end portion of the main valve abuts against an opening edge portion of the fuel discharge space to block off the fuel introduction space and the fuel discharge space, when the pilot valve is in a closed state, the tip end of the pilot valve inserted into the pilot valve insertion portion abuts against an opening edge of the fuel passage of the main valve, thereby blocking off the fuel introduction space and the fuel passage, a pin insertion hole extending in a direction perpendicular to a moving direction of the pilot valve is provided in the pilot valve insertion portion of the main valve, a pin that is inserted into the pin insertion hole is integrally provided at the tip end of the pilot valve, a fuel supply device for an internal combustion engine, characterized in that an inner diameter dimension of the pin insertion hole in the direction along the movement direction is set to be larger than an outer diameter dimension of the pin in the direction along the movement direction, and when the main valve and the pilot valve are both in a closed state, the predetermined amount of space is provided between an outer surface of the pin that faces the direction of movement of the pilot valve when current is applied to the electromagnetic solenoid and an inner surface of the pin insertion hole that faces the outer surface.

4. 3. The fuel supply system for an internal combustion engine according to claim 1, the pressure varying device includes a fuel inlet 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 fuel passage having one end communicating with the fuel introduction space and the other end communicating with the fuel discharge space, and a pilot valve insertion portion into which a tip end of the pilot valve is inserted, When the main valve is in a closed state, a tip end portion of the main valve abuts against an opening edge portion of the fuel discharge space to block off the fuel introduction space and the fuel discharge space, when the pilot valve is in a closed state, the tip end of the pilot valve inserted into the pilot valve insertion portion abuts against an opening edge of the fuel passage of the main valve, thereby blocking off the fuel introduction space and the fuel passage, 2. A fuel supply system for an internal combustion engine, wherein said tip portion of said main valve and said tip portion of said pilot valve are both provided with a rubber seal material.

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