Fuel injection system and reciprocating internal combustion engine

Abstract

To suppress vaporization of fuel remaining in a fuel supply passage and enable highly accurate fuel injection in a fuel injection device and a reciprocation internal combustion engine.SOLUTION: A fuel injection device includes: a first fuel supply passage for supplying first fuel with predetermined ignitability; a second fuel supply passage for supplying second fuel with ignitability lower than that of the first fuel; a fuel injection valve having a needle valve to which the second fuel supply passage is connected; a piston mechanism having a piston that is provided between the first fuel supply passage and the second fuel supply passage and moves by using differential pressure between first supply pressure of the first fuel and second supply pressure of the second fuel; and a discharge valve provided in the second fuel supply passage between the needle valve and the piston mechanism to inhibit a backflow of the second fuel from the needle valve to the piston mechanism side.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a fuel injection device and a reciprocating internal combustion engine.

Background Art

[0002] A reciprocating internal combustion engine is equipped with a fuel injection device. The reciprocating internal combustion engine burns by injecting fuel into the high-pressure air in the combustion chamber by the fuel injection device and is driven by the generated combustion energy. In recent years, as a fuel applied to the fuel injection device, it has been considered to use a carbon-free fuel with a small amount of harmful substances (for example, carbon dioxide, etc.) generated. However, some carbon-free fuels have poor ignition and combustion properties, and it has been proposed to use them in combination with fuels having good ignition and combustion properties. As a fuel injection device that injects a plurality of types of fuels, for example, there is one described in Patent Document 1 below. The fuel injection device described in Patent Document 1 injects fossil fuel as the first fuel and alternative fuel as the second fuel in layers.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In conventional fuel injection systems, a fuel pump that delivers the first fuel is connected to a fuel injection valve via a fuel injection pipe, and an injection pump that delivers the second fuel is connected to the fuel injection valve via an injection pipe. In conventional fuel injection systems, when the pressure of the second fuel becomes higher than the opening pressure of the fuel injection valve, the fuel injection valve opens and the second fuel is injected. Subsequently, when the pressure of the second fuel falls below the opening pressure of the fuel injection valve, the fuel injection valve closes and the injection of the second fuel ends. At this time, the fuel injection valve becomes hot due to the combustion gases, and the heat from the fuel injection valve is transferred to the injection pipe, which may cause the second fuel remaining in the injection pipe to vaporize. Since the vaporized fuel gas is a compressible fluid, it may be difficult to properly compress and inject the second fuel, which has partially turned into gas, during the next fuel injection.

[0005] This disclosure aims to solve the aforementioned problems and to provide a fuel injection device and a reciprocating internal combustion engine that suppress the vaporization of fuel remaining in the fuel supply path, thereby enabling high-precision fuel injection. [Means for solving the problem]

[0006] A fuel injection device of the present disclosure for achieving the above objectives comprises: a first fuel supply path for supplying a first fuel having predetermined ignitability; a second fuel supply path for supplying a second fuel having lower ignitability than the first fuel; a fuel injection valve having a needle valve to which the second fuel supply path is connected; a piston mechanism provided between the first fuel supply path and the second fuel supply path and having a piston that moves due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel; and a discharge valve provided in the second fuel supply path between the needle valve and the piston mechanism to prevent backflow of the second fuel from the needle valve to the piston mechanism.

[0007] Furthermore, the reciprocating internal combustion engine of this disclosure comprises an internal combustion engine body having a combustion chamber and a fuel injection device for injecting fuel into the combustion chamber. [Effects of the Invention]

[0008] The fuel injection system and reciprocating internal combustion engine of this disclosure can suppress the vaporization of fuel remaining in the fuel supply path, thereby enabling highly accurate fuel injection. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram representing a marine diesel engine of the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing the fuel injection system of the first embodiment. [Figure 3] Figure 3 is a time chart showing the operation of the fuel injection system. [Figure 4] Figure 4 is a graph showing the relationship between temperature and saturated vapor pressure in the second fuel. [Figure 5] Figure 5 is a schematic diagram showing an example of the arrangement when the fuel injection system of the first embodiment is combined with another fuel injection system. [Figure 6] Figure 6 is a schematic diagram showing the fuel injection system of the second embodiment. [Figure 7] Figure 7 is a schematic diagram showing the fuel injection system of the third embodiment. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] [First Embodiment] <Marine Diesel Engines> Figure 1 is a schematic diagram representing a marine diesel engine of the first embodiment. In the first embodiment, a marine diesel engine is used as the reciprocating internal combustion engine for explanation. However, the reciprocating internal combustion engine is not limited to a marine diesel engine.

[0012] As shown in Figure 1, the marine diesel engine 10 is used, for example, as the main engine for ship propulsion, and is a two-stroke, one-cycle uniflow scavenging crosshead type internal combustion engine.

[0013] The marine diesel engine 10 has a diesel engine body (internal combustion engine body) 11. The diesel engine body 11 comprises a cylinder liner 12, a piston 13, a scavenging trunk 14, an exhaust manifold 15, and an exhaust valve 16.

[0014] The cylinder liner 12 is cylindrical in shape and is located inside the cylinder jacket (not shown), with the cylinder cover 21 fixed to its upper part. The piston 13 is cylindrical in shape and is located inside the cylinder liner 12, supported so as to be movable along the axial direction. The upper end of the piston rod 22 is connected to the lower end of the piston 13. Although not shown, the crankshaft is rotatably supported at the bottom of the diesel engine body 11, and the lower end of the connecting rod is rotatably connected via the crank. The diesel engine body 11 has a crosshead that is supported so as to be movable along the vertical direction, and the lower end of the piston rod 22 and the upper end of the connecting rod are rotatably connected to the crosshead.

[0015] The scavenging trunk 14 is connected to the lower part of the cylinder liner 12. The cylinder liner 12 communicates with the interior of the scavenging trunk 14 via a number of scavenging ports 23. The scavenging trunk 14 is supplied with air via an intake pipe 24.

[0016] The cylinder liner 12 forms a combustion chamber 25 when an upper space portion to which the cylinder cover 21 is fixed is partitioned by the upper surface of the piston 13. The exhaust manifold 15 is connected to the cylinder cover 21 via an exhaust pipe 26. That is, the combustion chamber 25 communicates with the exhaust manifold 15 via the exhaust pipe 26. The cylinder cover 21 is provided with an exhaust valve 16. The exhaust valve 16 can open and close the exhaust pipe 26 by being driven by a valve operating device 27. When the exhaust valve 16 opens the exhaust pipe 26, the combustion chamber 25 communicates with the exhaust manifold 15 via the exhaust pipe 26.

[0017] In addition, the marine diesel engine 10 includes a fuel injection device 17. The fuel injection device 17 has a fuel supply device 31, a fuel supply path 32, and a fuel injection valve 33. The fuel injection valve 33 is mounted on the cylinder cover 21. The fuel injection valve 33 can inject fuel into the combustion chamber 25. The fuel injection valve 33 is connected to the fuel supply device 31 via the fuel supply path 32. The fuel supply device 31 can supply the fuel stored in a fuel tank (not shown) to the fuel injection valve 33 via the fuel supply path 32.

[0018] First, when the piston 13 moves to the bottom dead center (the solid line position in FIG. 1), the scavenging port 23 opens and the air in the scavenging trunk 14 is introduced from the scavenging port 23 into the combustion chamber 25. Next, when the piston 13 rises, the communication between the scavenging port 23 and the combustion chamber 25 is blocked by the piston 13. At this time, the exhaust valve 16 rises by the valve operating device 27 and the exhaust pipe 26 is closed, and the air in the combustion chamber 25 is compressed by the rise of the piston 13. Then, when the piston 13 moves to the top dead center (the two-dot chain line position in FIG. 1), the pressure in the combustion chamber 25 reaches a predetermined compression pressure, and the fuel injection valve 33 operates to inject fuel into the combustion chamber 25. Then, air and fuel are mixed and burned in the combustion chamber 25, and the piston 13 descends by the combustion energy. At this time, the exhaust valve 16 descends by the valve operating device 27, so that the exhaust pipe 26 is opened. Then, the exhaust gas generated by combustion is pushed out from the combustion chamber 25 through the exhaust pipe 26 and discharged to the exhaust manifold 15.

[0019] <Configuration of Fuel Injection Device> FIG. 2 is a schematic configuration diagram showing a fuel injection device according to the first embodiment.

[0020] As shown in FIG. 2, the fuel injection device 17 includes a fuel supply device 31, a fuel supply passage 32, and a fuel injection valve 33. The fuel supply device 31 has a first fuel supply source 40, a supply pump 41, and a second fuel supply source 42. The fuel supply passage 32 has a first fuel supply passage 43 and a second fuel supply passage 44. The fuel injection valve 33 includes a needle valve 45 and a piston mechanism 47.

[0021] The fuel injection device 17 can inject a second fuel having a lower ignition property (worse) than the first fuel having a predetermined ignition property. Here, the ignition property refers to the ease of ignition of the first fuel and the second fuel. The first fuel is a fossil fuel (for example, light oil or heavy oil as diesel fuel), and the second fuel is, for example, ammonia, methanol, liquefied petroleum gas (LPG), etc. However, the first fuel and the second fuel are not limited to the fuels described above.

[0022] The first fuel supply passage 43 is connected to the first fuel supply source 40 and the supply pump 41 at the upstream end in the supply direction of the first fuel. The first fuel supply source 40 is composed of, for example, a pressure accumulation part of the first fuel and a pressure pump for pressurizing the first fuel. The first fuel supply source 40 supplies low-pressure first fuel to the upstream side of the first fuel supply passage 43. The supply pump 41 is connected to the first fuel supply passage 43 downstream of the first fuel supply source 40. The supply pump 41 pressurizes the first fuel upstream of the first fuel supply passage 43 to a high pressure and supplies it to the downstream side of the first fuel supply passage 43.

[0023] The supply pump 41 has a piston 51 and a plunger 52. The piston 51 and the plunger 52 are connected to each other, and the plunger 52 is connected to the first fuel supply path 43. The piston 51 is connected to a working fluid source 54 via the first working fluid supply path 53, and the first working fluid supply path 53 is equipped with a first solenoid valve 55. The working fluid source 54 supplies working fluid at a predetermined pressure to the first working fluid supply path 53. The supply pump 41 functions as a pressure booster pump because the pressure-receiving area of ​​the plunger 52 is set to be smaller than the pressure-receiving area of ​​the piston 51. The first solenoid valve 55 is connected to a control unit 56 and opens and closes according to commands from the control unit 56.

[0024] When the first solenoid valve 55 is opened, the working fluid from the working fluid source 54 is supplied to the piston 51 through the first working fluid supply path 53. The piston 51 operates in response to the supply of working fluid, and acts the plunger 52. Then, the supply pump 41 pressurizes the first fuel in the first fuel supply path 43. At this time, since the supply pump 41 operates by increasing the pressure of the working fluid, it pressurizes the first fuel to a high pressure.

[0025] The second fuel supply path 44 has a second fuel supply source 42 connected to its upstream end in the direction of second fuel supply. The second fuel supply source 42 consists of, for example, a second fuel accumulator and a pressurizing pump for pressurizing the second fuel. The second fuel supply source 42 supplies the second fuel to the upstream side of the second fuel supply path 44.

[0026] The downstream end of the second fuel supply path 44 is connected to the needle valve 45. The needle valve 45 has a valve body 45a, a biasing spring 45b, a chamber 45c, a fuel supply passage 45d, an injection hole 45e, and a sliding seal portion 45f. The second fuel supply path 44 is connected to the chamber 45c. The chamber 45c communicates with the fuel supply passage 45d, and the fuel supply passage 45d has an injection hole 45e formed at its tip. The valve body 45a is seated by the biasing force of the biasing spring 45b, thereby blocking communication between the chamber 45c and the fuel supply passage 45d. When a second fuel at a pressure higher than the second injection pressure is supplied to the chamber 45c from the second fuel supply path 44, the valve body 45a rises against the biasing force of the biasing spring 45b, and communication between the chamber 45c and the fuel supply passage 45d is established. Then, the second fuel supplied to chamber 45c flows into the fuel supply passage 45d and is injected from the nozzle 45e.

[0027] The piston mechanism 47 is provided between the first fuel supply path 43 and the second fuel supply path 44. Specifically, the first fuel supply path 43 has a first fuel supply source 40 and a supply pump 41 connected to its upstream end, and the piston mechanism 47 connected to its downstream end. The second fuel supply path 44 has an upstream path 61 and a downstream path 62. The upstream path 61 has a second fuel supply source 42 connected to its upstream end, and the piston mechanism 47 connected to its downstream end. The downstream path 62 has the piston mechanism 47 connected to its upstream end, and a needle valve 45 connected to its downstream end. The piston mechanism 47 has the downstream end of the first fuel supply path 43 connected to one end in the direction of piston movement, and the middle section of the second fuel supply path 44, that is, the downstream end of the upstream path 61 and the upstream end of the downstream path 62 connected to the other end in the direction of piston movement.

[0028] The piston mechanism 47 includes a cylindrical cylinder 71 and a cylindrical piston 72. The piston 72 is positioned inside the cylinder 71 and is supported to move freely along the axial direction. One end of the cylinder 71 in the direction of movement of the piston 72 communicates with the downstream end of the first fuel supply path 43, and the other end of the cylinder 71 in the direction of movement of the piston 72 communicates with the middle section of the second fuel supply path 44. The piston 72 is a piston with a rod, and has a small-diameter rod portion 73 and a body portion 74 with a larger diameter than the rod portion 73. The body portion 74 of the piston 72 is positioned inside the cylinder 71 and is supported to move freely along the axial direction. The rod portion 73 is integrally provided with the body portion 74 of the piston 72, and the tip of the rod portion 73 extends outside the cylinder 71.

[0029] The piston 72 has a first pressure-receiving surface 72a on the side facing the first fuel supply path 43 and a second pressure-receiving surface 72b on the side facing the second fuel supply path 44. The first supply pressure from the first fuel supply path 43 acts on the first pressure-receiving surface 72a of the piston 72, and the second supply pressure from the second fuel supply path 44 acts on the second pressure-receiving surface 72b of the piston 72. The piston mechanism 47 causes the piston 72 to reciprocate due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel.

[0030] The piston mechanism 47 has a main body 74 with an axial length shorter than the cylinder 71. Therefore, the piston mechanism 47 has a first storage section 75 on the first pressure-receiving surface 72a side and a second storage section 76 on the second pressure-receiving surface 72b side. The first storage section 75 communicates with the first fuel supply path 43 and stores the first fuel. The second storage section 76 communicates with the second fuel supply path 44 and stores the second fuel. The piston 72 is movable inside the cylinder 71, but its reciprocating movement is limited by a stopper (not shown). That is, when the piston 72 moves furthest towards the first fuel supply path 43 side, a gap is secured between the first pressure-receiving surface 72a and one end of the cylinder 71, and the first storage section 75, including this gap, is secured. On the other hand, when the piston 72 moves furthest toward the second fuel supply path 44, a gap is secured between the second pressure receiving surface 72b and the other end of the cylinder 71, and the second storage portion 76, which includes this gap, is secured.

[0031] As described above, the piston 72 is a piston with a rod, with a first pressure-receiving surface 72a formed on one side of the main body 74 and a second pressure-receiving surface 72b formed on the other side. Since the piston 72 has a rod portion 73 on one side of the main body 74, the area of ​​the first pressure-receiving surface 72a is smaller than the area of ​​the second pressure-receiving surface 72b. The piston mechanism 47 has a first storage portion 75 on the side of the first pressure-receiving surface 72a that communicates with the first fuel supply path 43, and a second storage portion 76 on the side of the second pressure-receiving surface 72b that communicates with the second fuel supply path 44. Therefore, due to the area difference between the first pressure-receiving surface 72a and the second pressure-receiving surface 72b, the first supply pressure acting on the first fuel supply path 43 via the first storage portion 75 is higher than the second supply pressure acting on the second fuel supply path 44 via the second storage portion 76.

[0032] The piston 72 has a bulge 77 between the rod portion 73 and the main body portion 74. On the other hand, the cylinder 71 has a seat portion 78 at the end facing the first fuel supply path 43, where the inner diameter is reduced. When the piston 72 moves inside the cylinder 71 toward the first fuel supply path 43, the bulge 77 comes into contact with the seat portion 78, thereby blocking communication between the first fuel supply path 43 and the first storage portion 75.

[0033] In the piston mechanism 47, a sliding portion 79 is formed between the cylinder 71 and the rod portion 73 of the piston 72. One end of the drain passage 80 communicates with the sliding portion 79. Since the first storage portion 75 communicates with the sliding portion 79, the first fuel leaks out. The drain passage 80 discharges and recovers the first fuel that leaked out at the sliding portion 79 to the outside. Here, since the pressure of the first fuel in the first fuel supply passage 43 is higher than the pressure of the second fuel in the second fuel supply passage 44, the second fuel in the second fuel supply passage 44 is prevented from flowing from the second storage portion 76 through the sliding portion of the cylinder 71 and piston 72, and from the first storage portion 75 to the first fuel supply passage 43 side and mixing with the first fuel. Therefore, the first fuel recovered from the drain passage 80 does not contain the second fuel, making processing easier.

[0034] Furthermore, the needle valve 45 is provided with a seal path 81 that suppresses the outflow of the second fuel to the drain. The seal path 81 has a first seal path 82, a second seal path 83, and a third seal path 84. The upstream end of the first seal path 82 is connected to the first fuel supply path 43, and the first fuel from the first fuel supply path 43 is supplied to it. The upstream end of the second seal path 83 is connected to the first fuel supply source 85, and the first fuel is supplied to it. The first fuel supply source 85 supplies the first fuel at a higher pressure than the second fuel supplied from the second fuel supply source 42. The downstream ends of the first seal path 82 and the second seal path 83 merge and are connected to the upstream end of the third seal path 84. The downstream end of the third seal path 84 is connected to the sliding seal portion 45f of the valve body 45a in the needle valve 45.

[0035] The first seal path 82 is provided with a check valve 86 that prevents backflow of the first fuel from the needle valve 45 to the first fuel supply path 43. The second seal path 83 is provided with a check valve 87 that prevents backflow of the first fuel from the needle valve 45 to the first fuel supply source 85. The third seal path 84 applies the pressure of the first fuel in the first fuel supply path 43 or the pressure of the first fuel in the first fuel supply source 85 to the sliding seal portion 45f of the needle valve 45. Therefore, the seal path 81 applies the pressure of the first fuel in the first fuel supply path 43 or the pressure of the first fuel in the first fuel supply source 85 to the sliding seal portion 45f of the needle valve 45, thereby maintaining the lubricity of the sliding seal portion 45f of the valve body 45a while suppressing the outflow of the second fuel to the drain.

[0036] In the piston mechanism 47, the first supply pressure of the first fuel from the first fuel supply path 43 acts on the first pressure-receiving surface 72a side of the piston 72 via the first reservoir 75, and the second supply pressure of the second fuel from the second fuel supply path 44 acts on the second pressure-receiving surface 72b side of the piston 72 via the second reservoir 76. When the supply pump 41 is stopped, the second supply pressure of the second fuel from the second fuel supply path 44 is lower than the first supply pressure of the first fuel from the first fuel supply path 43. As a result, a small amount of the first fuel from the first reservoir 75 leaks into the sliding parts of the cylinder 71 and piston 72, enabling lubrication of the sliding parts and sealing of the second fuel.

[0037] Then, in the piston mechanism 47, since the area of ​​the first pressure-receiving surface 72a is smaller than the area of ​​the second pressure-receiving surface 72b, the pressure balance acting on the piston 72 becomes upward. As a result, the piston 72 moves towards the first fuel supply path 43 in the piston mechanism 47, and a predetermined amount of second fuel is stored in the second storage section 76. On the other hand, when the supply pump 41 is activated, the first supply pressure of the first fuel in the first fuel supply path 43 increases, and becomes higher than the second supply pressure of the second fuel in the second fuel supply path 44. As a result, the piston 72 moves towards the second fuel supply path 44 in the piston mechanism 47, and the second fuel in the second storage section 76 is supplied to the needle valve 45, and the needle valve 45 injects the second fuel when the second supply pressure exceeds the second injection pressure. Furthermore, in the needle valve 45, the first fuel from the first fuel supply path 43 is supplied to the sliding seal portion 45f through the seal path 81, and a small amount of the first fuel flows to the chamber 45c side, thereby ensuring lubrication of the valve body 45a and suppressing the outflow of the second fuel to the drain.

[0038] The first fuel supply path 43 has a check valve 91 between the connection point of the supply pump 41 and the connection point of the piston mechanism 47. The check valve 91 prevents the backflow of the first fuel from the piston mechanism 47 side to the supply pump 41 side. The first fuel supply path 43 also has a check valve 92 between the connection point of the supply pump 41 and the first fuel supply source 40. The check valve 92 prevents the backflow of the first fuel from the connection point side of the supply pump 41 to the first fuel supply source 40 side. The first fuel supply path 43 also has a return path 93 that branches off from the path between the piston mechanism 47 and the check valve 91. The return path 93 bypasses the check valves 91, 92 and the supply pump 41. The return path 93 is equipped with a check valve 94. When the supply pump 41 stops, the check valve 94 releases the pressure downstream of the check valve 91 (for example, the second supply pressure of the second fuel in the second fuel supply path 44) from the pressure upstream of the check valve 91 plus the spring force of the check valve 94, and the first fuel in the first fuel supply path 43 on the piston mechanism 47 side is returned by bypassing the check valve 91.

[0039] The second fuel supply path 44 has a second fuel supply valve 111 between the connection point between the second fuel supply source 42 and the piston mechanism 47. The second fuel supply valve 111 is a solenoid valve connected to a control unit 56, and opens and closes according to commands from the control unit 56. When the second fuel supply valve 111 is opened, the second fuel is supplied from the second fuel supply source 42 to the second fuel supply path 44. The second fuel supply path 44 is also connected to a nitrogen supply source 112 via the second fuel supply valve 111. The second fuel supply valve 111 switches between supplying the second fuel from the second fuel supply source 42 and supplying nitrogen (N2) from the nitrogen supply source 112 to the second fuel supply path 44. In this case, the nitrogen pressure of the nitrogen supply source 112 is lower than the pressure of the second fuel from the second fuel supply source 42.

[0040] The fuel injection valve 33 is provided with a discharge valve 121 in the second fuel supply path 44 between the needle valve 45 and the piston mechanism 47 to prevent backflow of the second fuel from the needle valve 45 to the piston mechanism 47. Specifically, the discharge valve 121 is provided in the downstream path 62 connecting the needle valve 45 and the second storage section 76 of the piston mechanism 47.

[0041] The discharge valve 121 is a check valve in which a closing force acts on the ball due to the biasing force of a spring, closing the downstream path 62. The discharge valve 121 is opened when an opening force greater than the closing force acts on it, with the biasing force of the spring being the closing force. Preferably, the opening pressure of the discharge valve 121 is higher than the second supply pressure of the second fuel supplied from the second fuel supply source 42 to the second fuel supply path 44. The downstream path 62 in the second fuel supply path 44 is divided by the discharge valve 121 into an upstream first path 62a and a downstream second path 62b, and when the discharge valve 121 is closed, the flow of the second fuel from the second path 62b to the first path 62a is blocked.

[0042] The fuel injection valve 33 is connected to a second fuel supply path 44, which includes a first purge path 122 and a first purge valve 123. One end of the first purge path 122 is connected to a downstream path 62 between the second storage section 76 of the piston mechanism 47 and the discharge valve 121, and the other end is connected to a second fuel recovery system (not shown). The first purge valve 123 is operable by an on / off control valve (purge control unit) 124.

[0043] The first purge valve 123 includes a cylinder 123a, a piston 123b, a first port portion 123c, and a second port portion 123d. The piston 123b is supported so as to be axially movable relative to the cylinder 123a. The first port portion 123c is provided on the side of the cylinder 123a on the tip side of the piston 123b. The second port portion 123d is provided on the tip side of the cylinder 123a on the piston 123b. The first purge path 122 includes a first path 122a and a second path 122b. One end of the first path 122a is connected to the first path 62a of the downstream path 62, and the other end is connected to the second port portion 123d. One end of the second path 122b is connected to the first port portion 123c.

[0044] Furthermore, the first purge valve 123 has a cylinder 123a connected to a hydraulic fluid source 126 via a communication path 125, and an on / off control valve 124 is provided in the communication path 125. The on / off control valve 124 is a solenoid valve, and the first purge valve 123 is operated by the on / off control valve 124. That is, when the on / off control valve 124 is open, hydraulic fluid from the hydraulic fluid source 126 is supplied to the first purge valve 123 via the communication path 125, and when the on / off control valve 124 is closed, the hydraulic fluid pressure in the communication path 125 decreases.

[0045] When the piston 123b contacts the seat portion of the cylinder 123a, the first port portion 123c and the second port portion 123d of the first purge valve 123 are closed, and the first purge path 122 is closed, with the first path 122a and the second path 122b being closed. When the piston 123b moves away from the seat portion of the cylinder 123a, the first port portion 123c and the second port portion 123d of the first purge valve 123 are opened, and the first purge path 122 is opened, with the first path 122a and the second path 122b being opened. Here, when the tip of the piston 123b contacts the seat portion and closes the first purge path 122, the contact position between the tip and the seat portion becomes annular. The seat portion separates the first port portion 123c and the second port portion 123d, and when hydraulic fluid is supplied to the first purge valve 123 from the communication path 125, the piston 123b is operated.

[0046] Furthermore, the fuel injection valve 33 is provided with a second purge path 127 in the needle valve 45, and the second purge path 127 is provided with a second purge valve 128. One end of the second purge path 127 is connected to the chamber 45c of the needle valve 45, and the other end merges with the first purge path 122 and connects to a second fuel recovery system (not shown). The second purge valve 128 is operable by an on / off control valve 124, similar to the first purge valve 123.

[0047] The second purge valve 128 includes a cylinder 128a, a piston 128b, a first port portion 128c, and a second port portion 128d. The piston 128b is supported so as to be axially movable relative to the cylinder 128a. The first port portion 128c is provided on the side of the cylinder 128a on the tip side of the piston 128b. The second port portion 128d is provided on the tip side of the cylinder 128a on the piston 128b. The second purge path 127 includes a first path 127a and a second path 127b. One end of the first path 127a is connected to the chamber 45c, and the other end is connected to the second port portion 128d. One end of the second path 127b is connected to the first port portion 128c.

[0048] Furthermore, the second purge valve 128 has a cylinder 128a connected to the hydraulic fluid source 126 via a communication path 129, and an on / off control valve 124 is provided in the communication path 129. In other words, the first purge valve 123 and the second purge valve 128 are controlled to open and close by the same on / off control valve 124.

[0049] When the piston 128b contacts the seat portion of the cylinder 128a, the second purge valve 128 closes the first port portion 128c and the second port portion 128d, and the second purge path 127 closes the first path 127a and the second path 127b. When the piston 128b moves away from the seat portion of the cylinder 128a, the second purge valve 128 opens the first port portion 128c and the second port portion 128d, and the second purge path 127 opens the first path 127a and the second path 127b. Here, when the tip of the piston 128b contacts the seat portion and closes the second purge path 127, the contact position between the tip and the seat portion becomes annular. The seat portion separates the first port portion 128c and the second port portion 128d, and when hydraulic fluid (first fuel) is supplied from the communication path 129, the piston 128b of the second purge valve 128 is operated.

[0050] <Fuel injection system operation> Figure 3 is a time chart showing the operation of the fuel injection system.

[0051] As shown in Figures 2 and 3, when the supply pump 41 is activated at crank angle a1, the first supply pressure of the first fuel in the first fuel supply path 43 increases. This first supply pressure acts on the piston 72, causing the piston 72 to descend and reducing the lift amount (solid line at the top of Figure 3). As a result, the bulge portion 77 of the piston 72 separates from the seat portion 78, and the first fuel supply path 43 communicates with the first storage section 75. When the first fuel in the first fuel supply path 43 is supplied to the first storage section 75, the pressure P1 (solid line in the middle of Figure 3) increases, the piston 72 descends further, and the second fuel in the second storage section 76 is pressurized, causing the pressure P2 (dotted line at the top of Figure 3) to increase. At this time, the first fuel in the first fuel supply path 43, now under increased pressure, opens the check valve 86 from the first seal path 82, causing the seal pressure P3 (dotted line in Figure 3) of the needle valve 45 to increase.

[0052] From crank angle a2 to crank angle a3, the lift amount of the needle valve 45 increases, and when the second supply pressure P2 of the second fuel in the second storage section 76 exceeds the injection pressure of the needle valve 45, it opens and the second fuel is ejected from the injection hole 45e of the needle valve 45. Subsequently, when the supply pump 41 stops, pressures P1 and P2 decrease, and from crank angle a4 to crank angle a5, the needle valve 45 closes and injection ends. Subsequently, from crank angle a5 to crank angle a6, the first fuel in the first fuel supply path 43 is pressurized due to the area difference between the second pressure receiving surface 72b and the first pressure receiving surface 72a in the piston mechanism 47, the check valve 91 closes and the check valve 94 opens, and the fuel is returned by the return path 93, while the piston mechanism 47 moves the piston 72 towards the first fuel supply path 43. Furthermore, the sealing pressure P3 of the needle valve 45 is always maintained at a pressure higher than the pressure of the second fuel, and by supplying this pressure to the sliding seal portion 45f of the needle valve 45, the lubrication of the sliding seal portion 45f of the needle valve 45 is maintained while suppressing the outflow of the second fuel into the drain.

[0053] In the piston mechanism 47, when the piston 72 moves from the second fuel supply path 44 to the first fuel supply path 43, the volume of the second storage section 76 increases, and a predetermined amount of second fuel is stored in the second storage section 76. At crank angle a6, when the piston 72 reaches the first fuel supply path 43, the bulge portion 77 of the piston 72 comes into contact with the seat portion 78, and communication between the first fuel supply path 43 and the first storage section 75 is cut off. As a result, the first supply pressure P1 of the first fuel in the first storage section 75 (solid line in the middle of Figure 3) and the pressure P2 of the second fuel in the second storage section 76 (dotted line in the middle of Figure 3) are maintained to be slightly higher than the first fuel pressure P4 of the first fuel in the first fuel supply path 43 (dotted line in Figure 3).

[0054] Incidentally, when the second fuel supply valve 111 is opened, the second fuel from the second fuel supply source 42 is supplied to the second storage section 76 of the piston mechanism 47 through the second fuel supply path 44. When the piston 72 of the piston mechanism 47 descends, the second fuel in the second storage section 76 is pressurized and its pressure rises. When this pressure exceeds the opening pressure of the discharge valve 121, the second fuel is supplied to the needle valve 45. When the injection of the second fuel by the needle valve 45 ends, the pressure of the second fuel in the downstream path 62 of the second fuel supply path 44 decreases, but the pressure of the second fuel in the second path 62b partitioned by the discharge valve 121 becomes the second supply pressure of the second fuel plus the opening pressure of the discharge valve 121. In other words, the downstream pressure P5 of the discharge valve 121 is maintained higher than the pressure P2 of the second storage section 76. Therefore, the second fuel in the second path 62b in the downstream path 62 is kept in a liquid state with vaporization suppressed.

[0055] Figure 4 is a graph showing the relationship between temperature and saturated vapor pressure in the second fuel. Note that Figure 4 uses ammonia as the second fuel for explanation.

[0056] Figure 4 is a graph showing the change in saturated vapor pressure of the second fuel when its temperature rises, with the upper part of the solid line representing the liquid state and the lower part representing the gaseous state. This shows that the more the pressure of the second fuel is increased, or the more the pressure drop is suppressed, the higher the saturation temperature also rises, meaning that vaporization can be suppressed. In this embodiment, a discharge valve 121 is provided in the downstream path 62. Therefore, the discharge valve 121 partitions the second path 62b, which suppresses the pressure drop of the second fuel in the second path 62b, suppresses the vaporization of the second fuel in the second path 62b, and maintains the liquid state.

[0057] Furthermore, when the second fuel is injected, the needle valve 45 allows the high-pressure first fuel from the first fuel supply path 43 to act on the sliding seal portion 45f through the first seal path 82 and the third seal path 84. On the other hand, when the second fuel is not injected, the needle valve 45 allows the high-pressure first fuel from the first fuel supply source 85 to act on the sliding seal portion 45f through the second seal path 83 and the third seal path 84. As a result, the outflow of the second fuel to the drain can be suppressed while maintaining the lubricity of the sliding seal portion 45f of the valve body 45a.

[0058] Furthermore, the needle valve 45 blocks communication between the chamber 45c and the fuel supply passage 45d by the valve body 45a being seated on the seat portion by the biasing force of the biasing spring 45b. If the seat portion of the needle valve 45 becomes faulty or damaged, there is a risk that combustion gas (second fuel) from the combustion chamber may enter the second fuel supply passage 44 through the needle valve 45. Even in this case, since a discharge valve 121 is provided in the downstream passage 62, the combustion gas (second fuel) from the combustion chamber is prevented from entering the second fuel supply passage 44 upstream of the discharge valve 121, and is also prevented from entering the seal passage 81. Moreover, since the opening pressure of the discharge valve 121 is higher than the supply pressure of the second fuel, the discharge valve 121 is not opened by the pressure of the second fuel in the second storage section 76, and the outflow of the second fuel is suppressed.

[0059] After the fuel injection valve 33 stops, it is necessary to discharge any remaining second fuel in the second fuel supply path 44 and other areas. Specifically, the first purge valve 123 and the second purge valve 128 are opened by the on / off control valve 124, and the purge gas supply valve 115 is opened, so that purge gas is supplied from the purge gas supply path 114 to the second fuel supply path 44. At this time, the second fuel supply valve 111 is in the closed state. Since the first purge valve 123 and the second purge valve 128 are open, the first purge path 122 and the second purge path 127 are opened. As a result, the purge gas supplied to the second fuel supply path 44 pushes out any remaining second fuel in the second storage section 76 and the first path 62a of the downstream path 62, and it is discharged from the first purge path 122. Furthermore, the purge gas supplied to the second fuel supply path 44 opens the discharge valve 121, pushing out the second fuel remaining in the second path 62b of the downstream path 62, and discharging it from the second purge path 127.

[0060] Figure 5 is a schematic diagram showing an example of the arrangement when the fuel injection system of the first embodiment is combined with another fuel injection system.

[0061] By the way, in the first embodiment of the fuel injection system 17, the fuel injection valve 33 is capable of injecting only the second fuel. Therefore, it is useful to combine the fuel injection system 17 of the first embodiment with another fuel injection system 18 that is capable of injecting only the first fuel. That is, as shown in Figure 5, the fuel injection system 17 comprises a fuel supply device 31, a fuel supply path 32, and a fuel injection valve 33, and the fuel injection valve 33 injects the second fuel. The fuel injection system 18 comprises a fuel supply device 18a, a fuel supply path 18b, and a fuel injection valve 18c, and the fuel injection valve 18c injects the first fuel. With this configuration, it is possible to inject only the first fuel by the fuel injection valve 18c, to inject only the second fuel by the fuel injection valve 33, and to inject both the first and second fuels by the fuel injection valve 18c and the fuel injection valve 33. Furthermore, when only the second fuel is injected by the fuel injection valve 33, the first fuel injected from the fuel injection valve 18c can be used as ignition fuel.

[0062] [Second Embodiment] Figure 6 is a schematic diagram showing the fuel injection system of the second embodiment. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0063] As shown in Figure 6, the fuel injection system 17A comprises a fuel supply device 31, a fuel supply path 32, and a fuel injection valve 33A. The fuel supply device 31 includes a first fuel supply source 40, a supply pump 41, and a second fuel supply source 42. The fuel supply path 32 includes a first fuel supply path 43 and a second fuel supply path 44. The fuel injection valve 33A comprises a needle valve 45 and a piston mechanism 47. The configuration of the discharge valve of the fuel injection valve 33A differs from the configuration of the fuel injection valve 33 of the first embodiment.

[0064] The fuel injection valve 33A is provided with a second fuel supply valve 111 and a check valve 118 in the upstream path 61 of the second fuel supply path 44. The check valve 118 has a cylinder 118a, a piston 118b, and a connecting passage 118c. The piston 118b is supported so as to be movable in the axial direction relative to the cylinder 118a. The direction of movement of the piston 118b is along the upstream path 61. The connecting passage 118c is provided inside the piston 118b. The upstream path 61 is connected to the tip and base ends of the piston 118b in the cylinder 118a. When the check valve 118 moves towards the second fuel supply valve 111 and closes, the connecting passage 118c is closed, and the upstream path 61 is blocked.

[0065] Furthermore, the fuel injection valve 33A is provided with a discharge valve 131 in the second fuel supply path 44 between the needle valve 45 and the piston mechanism 47 to prevent backflow of the second fuel from the needle valve 45 to the piston mechanism 47. Specifically, the discharge valve 131 is provided in the downstream path 62 connecting the needle valve 45 and the second storage section 76 of the piston mechanism 47.

[0066] The discharge valve 131 is a control valve operated by control hydraulic pressure (pressure of the first fuel). The discharge valve 131 can be opened and closed by an on / off control valve (discharge control unit) 132. Specifically, the hydraulic fluid supply source 133 is connected to a pressure regulating valve 135 via a supply pump 134, and the pressure regulating valve 135 is connected in parallel to an on / off valve 137 and an on / off control valve 132 via a branch path 136. The on / off control valve 132 is then connected to the discharge valve 131 via a control path 138. The pressure regulating valve 135 regulates the pressure of the first fuel from the hydraulic fluid supply source 133 to a predetermined pressure and supplies it to the on / off valve 137 and the on / off control valve 132. It is desirable, but not limited to, that the pressure be higher than the pressure of the second fuel in the second path 62b when the injection of the second fuel is completed.

[0067] The discharge valve 131 includes a cylinder 131a, a piston 131b, a first port portion 131c, a second port portion 131d, and a third port portion 131e. The piston 131b is supported so as to be axially movable relative to the cylinder 131a. The first port portion 131c is provided on the side of the piston 131b on the tip side of the cylinder 131a. The second port portion 131d is provided on the middle part of the piston 131b in the cylinder 131a. The third port portion 131e is provided on the base end of the piston 131b in the cylinder 131a. The first path 62a is connected to the tip of the piston 131b in the cylinder 131a. The second path 62b is connected to the first port portion 131c. The control path 138 is connected to the third port portion 131e.

[0068] The on / off control valve 132 controls the opening and closing of the downstream path 62 in the second fuel supply path 44 by adjusting the control hydraulic pressure (pressure of the first fuel) acting on the discharge valve 131, which is a control valve. The on / off control valve 132 has substantially the same function as, for example, the on / off control valve 124 of the first embodiment (see Figure 2). The discharge valve 131 closes the first port portion 131c and closes the downstream path 62 when a control hydraulic pressure of a predetermined pressure is applied from the on / off control valve 132. As a result, when injecting the second fuel, the discharge valve 131 opens and injection takes place when the pressure of the second fuel becomes higher than the control hydraulic pressure, and the discharge valve closes at the end of injection, so that the pressure in the second path 62b is kept higher than the pressure in the first path 62a. In the second fuel supply path 44, the downstream path 62 is divided into an upstream first path 62a and a downstream second path 62b by a discharge valve 131. When the discharge valve 131 is closed, the first path 62a and the second path 62b are blocked, preventing the flow of the second fuel from the second path 62b to the first path 62a.

[0069] The needle valve 45 is provided with a seal path 81 that suppresses the outflow of the second fuel to the drain. The seal path 81 has a first seal path 82, a second seal path 83, and a third seal path 84. The upstream end of the first seal path 82 is connected to the first fuel supply path 43, and the first fuel from the first fuel supply path 43 is supplied to it. The upstream end of the second seal path 83 is connected to the hydraulic fluid supply source 133 via an on-off valve 137 or the like, and the first fuel is supplied to it. The downstream ends of the first seal path 82 and the second seal path 83 merge and are connected to the upstream end of the third seal path 84. The downstream end of the third seal path 84 is connected to the sliding seal portion 45f of the valve body 45a in the needle valve 45.

[0070] The first seal path 82 is provided with a seal piston 141 that prevents backflow of the first fuel from the needle valve 45 to the first fuel supply path 43. The seal piston 141 has a cylinder 141a, a piston 141b, a first port portion 141c, and a second port portion 141d. The piston 141b is supported so as to be axially movable relative to the cylinder 141a. The first port portion 141c is provided on the side of the cylinder 141a on the tip side of the piston 141b. The second port portion 141d is provided on the base end side of the cylinder 141a on the piston 141b side and functions as a reservoir for the first fuel. The upstream path of the first seal path 82 has its end connected to the tip of the piston 141b in the cylinder 141a. The end of the downstream path of the first seal path 82, that is, the upstream end of the third seal path 84, is connected to the second port portion 141d. Then, when the seal piston 141 moves to the first fuel supply path 43 side and closes, the first port portion 141c is closed and the first seal path 82 is blocked.

[0071] The second seal path 83 is provided with a check valve 142 that prevents the backflow of the first fuel from the needle valve 45 to the hydraulic fluid supply source 133. The check valve 142 has a cylinder 142a, a piston 142b, and a communication passage 142c. The piston 142b is supported so as to be axially movable relative to the cylinder 142a. The communication passage 142c is provided inside the piston 142b. The upstream end of the second seal path 83 is connected to the tip of the piston 142b in the cylinder 142a. The downstream end of the second seal path 83, that is, the upstream end of the third seal path 84, is connected to the base end of the piston 142b in the cylinder 142a. When the check valve 142 moves to the on / off valve 137 side and closes, the communication passage 142c is closed and the second seal path 83 is blocked.

[0072] The third seal path 84 is connected to the confluence of the first seal path 82 and the second seal path 83, and applies the pressure of the first fuel in the first fuel supply path 43 or the pressure of the first fuel regulated by the pressure regulating valve 135 to the sliding seal portion 45f of the needle valve 45. Therefore, the seal path 81 applies the pressure of the first fuel regulated by the pressure regulating valve 135 in the first fuel supply path 43 to the sliding seal portion 45f of the needle valve 45, thereby maintaining the lubricity of the sliding seal portion 45f of the valve body 45a while suppressing the outflow of the second fuel to the drain.

[0073] The fuel injection valve 33A is provided with a purge path 151 in the second fuel supply path 44, and the purge path 151 is provided with a purge valve 152. One end of the purge path 151 is connected to the second storage section 76 of the piston mechanism 47, and the other end is connected to a second fuel recovery system (not shown). The purge valve 152 is operable by an on / off control valve (purge control unit) 132.

[0074] The purge valve 152 includes a cylinder 152a, a piston 152b, a first port portion 152c, a second port portion 152d, and a third port portion 152e. The piston 152b is supported so as to be axially movable relative to the cylinder 152a. The first port portion 152c is provided on the side of the piston 152b on the tip side of the cylinder 152a. The second port portion 152d is provided on the middle part of the piston 152b in the cylinder 152a. The third port portion 152e is provided on the base end of the piston 152b in the cylinder 152a. The purge path 151 has an upstream path leading to the second storage portion 67, the end of which is connected to the first port portion 152c, and a downstream path leading to the second fuel recovery system, the end of which is connected to the tip of the piston 152b in the cylinder 152a. The control path 139 connected to the third port portion 131e of the discharge valve 131 is connected to the third port portion 152e.

[0075] When the piston 152b contacts the seat portion of the cylinder 152a, the first port portion 152c of the purge valve 152 is closed, blocking the purge path 151. When the piston 152b moves away from the seat portion of the cylinder 152a, the first port portion 152c of the purge valve 152 is opened, and the purge path 151 is opened.

[0076] In the second embodiment, the fuel injection device 17A is provided with a discharge valve 131 in the downstream path 62 of the second fuel supply path 44, which is operated by control hydraulic pressure (pressure of the first fuel) supplied from the on / off control valve 132. Since the discharge valve 131 is operated by control hydraulic pressure, biasing members such as springs are not required, and the structure is simplified.

[0077] Furthermore, in the seal path 81, a seal piston 141 is provided in the first seal path 82, and a check valve 142 is provided in the first seal path 82. The seal piston 141 has an area ratio of 1:1 between one end and the other end of the piston 142b. That is, the area ratio is set so that when the second fuel is injected, the pressure of the first fuel in the first seal path 82 can be maintained at a higher pressure than the pressure of the second fuel in the second path 62b downstream of the discharge valve 131. When the second fuel is injected, the needle valve 45 allows the high pressure of the first fuel in the first fuel supply path 43 to act on the sliding seal portion 45f through the first seal path 82 (seal piston 141) and the third seal path 84. On the other hand, when the second fuel is not injected, the needle valve 45 allows the pressure of the first fuel, regulated by the pressure regulating valve 135, to act on the sliding seal portion 45f through the second seal path 83 (check valve 142) and the third seal path 84. At this time, the seal piston 141 moves to open and close the first seal path 82, allowing for smooth switching of the hydraulic power source to the sliding seal portion 45f. This also allows for the suppression of the outflow of the second fuel to the drain while maintaining the lubricity of the sliding seal portion 45f of the valve body 45a.

[0078] Furthermore, if the seat portion of the needle valve 45 becomes faulty or damaged, there is a risk that combustion gas from the combustion chamber may enter the first fuel supply path 43 or the second fuel supply path 44 through the needle valve 45. Even in this case, since the discharge valve 131 and the seal piston 141 are provided, the entry of combustion gas from the combustion chamber into the second fuel supply path 44 upstream of the discharge valve 131 is suppressed, as is entry into the seal path 81.

[0079] After the fuel injection valve 33A stops, it is necessary to discharge any remaining second fuel in the second fuel supply path 44 and other areas. Specifically, when the discharge valve 131 and purge valve 152 are opened by the on / off control valve 132, purge gas is supplied to the second fuel supply path 44. At this time, when the second fuel supply valve 111 is opened, the purge gas supplied to the second fuel supply path 44 pushes out any remaining second fuel in the second storage section 76 and the downstream path 62, and it is discharged from the purge path 151.

[0080] [Third Embodiment] Figure 7 is a schematic diagram showing the fuel injection system of the third embodiment. Components having the same function as those in the second embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0081] As shown in Figure 7, the fuel injection system 17B comprises a fuel supply device 31, a fuel supply path 32, and a fuel injection valve 33B. The fuel supply device 31 includes a first fuel supply source 40, a supply pump 41, and a second fuel supply source 42. The fuel supply path 32 includes a first fuel supply path 43 and a second fuel supply path 44. The fuel injection valve 33B comprises a needle valve 45 and a piston mechanism 47. The configuration of the purge mechanism of the fuel injection valve 33B differs from that of the fuel injection valve 33A in the second embodiment.

[0082] The piston mechanism 47 includes a cylinder 71 and a piston 72. The piston 72 is supported inside the cylinder 71 so as to be movable along the axial direction. The piston mechanism 47 has a first storage section 75 on the first pressure receiving surface 72a side and a second storage section 76 on the second pressure receiving surface 72b side. The first storage section 75 communicates with the first fuel supply path 43 and stores the first fuel. The second storage section 76 communicates with the second fuel supply path 44 and stores the second fuel. In the piston mechanism 47, the volume of the second storage section 76 is maximized when the piston 72 is moved furthest toward the first fuel supply path 43 side, and the volume of the first storage section 75 is maximized when the piston 72 is moved furthest toward the second fuel supply path 44 side.

[0083] In the fuel injection system 17B, one end of the purge path 151, which constitutes the purge mechanism, is connected to the second storage section 76. The fuel injection system 17B differs from the fuel injection system 17A (see Figure 6) in that the purge valve 152 (see Figure 6) is not provided in the purge path 151. Although one end of the purge path 151 is connected to the second storage section 76, the purge path 151 and the second storage section 76 communicate only when the piston 72 moves furthest toward the first fuel supply path 43 and the second storage section 76 reaches its maximum volume.

[0084] Therefore, after the fuel injection valve 33B stops, the discharge valve 131 is opened by the on / off control valve 132, and purge gas is supplied to the second fuel supply path 44. When the second fuel supply valve 111 is opened at this time, the purge gas supplied to the second fuel supply path 44 is supplied to the second storage section 76, and the pressure in the second storage section 76 increases. As the pressure in the second storage section 76 increases, the piston 72 moves towards the first fuel supply path 43. Then, when the second storage section 76 reaches its maximum volume, the purge path 151 communicates with the second storage section 76. As a result, the purge gas supplied to the second fuel supply path 44 pushes out the second fuel remaining in the second storage section 76 and the downstream path 62, and it is discharged from the purge path 151.

[0085] The fuel injection device 17B of the third embodiment is provided with a purge path 151 that communicates with the second storage section 76 when the piston moves and the second storage section (76) reaches its maximum volume. When the piston moves away from the first fuel supply path 43 and the second storage section 76 is not at its maximum volume, the second storage section 76 is not in communication with the purge path 151. Therefore, the piston 72 can properly pressurize the second fuel in the second storage section 76. On the other hand, when purge gas at a predetermined pressure is supplied from the second fuel supply path 44 to the second storage section 76, the piston 72 moves towards the first fuel supply path 43, the second storage section 76 reaches its maximum volume, and the purge path 151 communicates with the second storage section 76. Therefore, the second fuel remaining in the second fuel supply path 44 and the second storage section 76 can be properly discharged. Furthermore, the purge mechanism does not require a purge valve, thus simplifying the structure.

[0086] [Effects of this embodiment] The fuel injection device according to the first embodiment includes a first fuel supply path 43 that supplies a first fuel having predetermined ignition properties, a second fuel supply path 44 that supplies a second fuel having lower ignition properties than the first fuel, fuel injection valves 33, 33A, 33B having a needle valve 45 to which the second fuel supply path 44 is connected, a piston mechanism 47 provided between the first fuel supply path 43 and the second fuel supply path 44 and having a piston 72 that moves due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel, and discharge valves 121, 131 provided in the second fuel supply path 44 between the needle valve 45 and the piston mechanism 47 to prevent backflow of the second fuel from the needle valve 45 to the piston mechanism 47.

[0087] According to the fuel injection device of the first embodiment, the piston 72 moves due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel, thereby enabling alternating periods of storage of the second fuel and injection of the second fuel by the fuel injection valves 33, 33A, and 33B. In other words, the first fuel and the second fuel are supplied to the piston mechanism 47 under pressurization without mixing along the way. As a result, by suppressing the mixing of the first fuel and the second fuel, highly accurate fuel injection is possible, thereby reducing harmful substances contained in the exhaust gas.

[0088] Furthermore, according to the fuel injection device of the first embodiment, discharge valves 121 and 131 are provided to prevent backflow of the second fuel from the needle valve 45 to the piston mechanism 47. After the injection of the second fuel by the needle valve 45 is completed, the discharge valves 121 and 131 partition the second path 62b between the needle valve 45 and the discharge valves 121 and 131, thereby suppressing a pressure drop. As a result, the second fuel in the second path 62b in the downstream path 62 of the second fuel supply path 44 is kept in a fluid state with vaporization suppressed. Consequently, vaporization of the second fuel remaining in the second fuel supply path 44 is suppressed, enabling high-precision fuel injection.

[0089] The fuel injection system according to the second embodiment is the fuel injection system according to the first embodiment, further comprising an upstream path 61 connecting the second fuel supply source 42 and the second storage unit 76, and a downstream path 62 connecting the second storage unit 76 and the needle valve 45, with the discharge valves 121 and 131 provided in the downstream path 62. This suppresses the pressure drop in the second path 62b between the discharge valves 121 and 131 and the needle valve 45, thereby suppressing the vaporization of the second fuel.

[0090] The fuel injection system according to the third embodiment is a fuel injection system according to the first or second embodiment, and furthermore, the discharge valves 121 and 131 are check valves. This allows for a simplification of the structure.

[0091] The fuel injection system according to the fourth embodiment is a fuel injection system according to any one of the first to third embodiments, and furthermore, the opening pressure of the discharge valves 121 and 131 is higher than the second supply pressure of the second fuel supplied from the second fuel supply source 42 to the second fuel supply path 44. As a result, the discharge valve 121 is not opened by the pressure of the second fuel in the second storage section 76, and the outflow of the second fuel can be suppressed.

[0092] The fifth embodiment of the fuel injection system is a fuel injection system according to any one of the first to fourth embodiments, further comprising a discharge valve 131 which is a control valve and an on / off control valve (discharge control unit) 132 which opens and closes the second fuel supply path 44 by controlling the control hydraulic pressure acting on the discharge valve (control valve) 1312. As a result, since the discharge valve 131 is operated by the control hydraulic pressure, a biasing member such as a spring is not required, and the structure can be simplified.

[0093] The fuel injection system according to the sixth embodiment is a fuel injection system according to any one of the first to fifth embodiments, further comprising a seal path 81 for supplying a first fuel to the sliding seal portion 45f of the needle valve 45. This makes it possible to suppress the outflow of the second fuel to the drain while maintaining the lubricity of the sliding seal portion 45f of the valve body 45a in the needle valve 45.

[0094] The seventh embodiment of the fuel injection device is a fuel injection device according to the sixth embodiment, further comprising: a first seal path 82 that supplies the first fuel from the first fuel supply path 43 to the sliding seal portion 45f; and a second seal path 83 that supplies the first fuel at a higher pressure than the second fuel from the second fuel supply path 44 between the needle valve 45 and the piston mechanism 47 after the second fuel has been injected. This allows the pressure of the high-pressure first fuel to act on the sliding seal portion 45f regardless of the injection of the second fuel.

[0095] The fuel injection device according to the eighth embodiment is a fuel injection device according to the seventh embodiment, further comprising a seal piston 141 that prevents backflow of the first fuel from the needle valve 45 and is movable along the first seal path 82, and a check valve 142 that prevents backflow of the first fuel from the needle valve 45 and is provided in the second seal path 83. As a result, when the second fuel is injected, the high-pressure first fuel from the first fuel supply path 43 acts on the sliding seal portion 45f through the first seal path 82 (seal piston 141), while when the second fuel is not injected, the pressure of the first fuel regulated by the pressure regulating valve 135 acts on the sliding seal portion 45f through the second seal path 83 (check valve 142), and the seal piston 141 moves to open and close the first seal path 82, so that the hydraulic power source for the sliding seal portion 45f can be switched smoothly.

[0096] The fuel injection system according to the ninth embodiment is a fuel injection system according to any one of the first to eighth embodiments, further comprising a first purge path 122 connected to a second storage section 76 for discharging the second fuel, a first purge valve 123 for opening and closing the first purge path 122, and an on / off control valve (purge control unit) 124 for controlling the opening and closing of the first purge valve 123. As a result, the on / off control valve 124 controls the opening and closing of the first purge valve 123, thereby allowing the second fuel remaining in the second fuel supply path 44 and the second storage section 76 to be discharged to the outside.

[0097] The fuel injection system according to the tenth embodiment is a fuel injection system according to any one of the first to eighth embodiments, further comprising a second purge path 127 connected to the chamber 45c of the needle valve 45 for discharging the second fuel, a second purge valve 128 for opening and closing the second purge path 127, and an on / off control valve (purge control unit) 124 for controlling the opening and closing of the second purge valve 128. As a result, the on / off control valve 124 controls the opening and closing of the second purge valve 128, thereby allowing the second fuel remaining in the second fuel supply path 44 and the needle valve 45 to be discharged to the outside.

[0098] The fuel injection system according to the 11th embodiment is a fuel injection system according to any one of the first to eighth embodiments, and further includes a purge path 151 with one end connected to the second storage section 76 for discharging the second fuel, a purge valve 152 for opening and closing the purge path 151, and an on / off control valve (purge control unit) 132 for controlling the opening and closing of the second purge valve 128. As a result, the on / off control valve 132 controls the opening and closing of the purge valve 152, allowing the second fuel remaining in the second fuel supply path 44 and needle valve 45 to be discharged to the outside. In addition, the structure can be simplified by providing only one set of purge path 151 and purge valve 152.

[0099] The fuel injection system according to the twelfth embodiment is a fuel injection system according to any one of the first to eighth embodiments, and further has a purge path 151 connected to the second storage section 76, which discharges the second fuel when the piston 72 moves and the second storage section 76 reaches its maximum volume. As a result, when purge gas at a predetermined pressure is supplied from the second fuel supply path 44 to the second storage section 76, the piston 72 moves and the second storage section 76 reaches its maximum volume, and the purge path 151 communicates with the second storage section 76, thereby allowing the second fuel remaining in the second fuel supply path 44 and the second storage section 76 to be properly discharged. In addition, there is no need to provide a purge valve in the purge path 151, which simplifies the structure.

[0100] The fuel injection device according to the 13th embodiment is a fuel injection device according to any one of the first to 12th embodiments, further comprising a piston mechanism 47 having a cylinder 71 provided between a first fuel supply path 43 and a second fuel supply path 44, and a piston 72 movably supported by the cylinder 71, wherein the piston 72 has a first pressure-receiving surface 72a at one end on which the first supply pressure acts, and a second pressure-receiving surface 72b at the other end on which the second supply pressure acts, and the area of ​​the first pressure-receiving surface 72a is smaller than the area of ​​the second pressure-receiving surface 72b. As a result, the pressure of the first fuel in the first fuel supply path 43 is higher than the pressure of the second fuel in the second fuel supply path 44, so that the second fuel in the second fuel supply path 44 does not flow to the first fuel supply path 43 side and mix with the first fuel, and the recovered first fuel does not contain the second fuel, making processing easier.

[0101] The reciprocating internal combustion engine according to the 14th embodiment comprises a diesel engine body 11 having a combustion chamber 25, and fuel injection devices 17, 17A, 17B according to any one of the first to 17 embodiments for injecting fuel into the combustion chamber 25. This makes it possible to suppress the vaporization of the second fuel remaining in the second fuel supply path 44 and enable highly accurate fuel injection. [Explanation of symbols]

[0102] 10. Marine diesel engine (reciprocating internal combustion engine) 11. Diesel engine body (internal combustion engine body) 12 Cylinder Liners 13 pistons 14. Scavenging Trunk 15 Exhaust Manifold 16 Exhaust valve 17,17A,17B Fuel injection device 31 Fuel supply system 32 Fuel supply routes 33, 33A, 33B Fuel Injector 40 Primary fuel source 41 Supply pump 42 Secondary fuel source 43. Fuel supply route 1 44 Second Fuel Supply Route 45 Needle valve 47 Piston mechanism 51 Pistons 52 Plungers 53. First hydraulic fluid supply path 54 Working fluid source 55. First solenoid valve 56 Control Unit 61 Upstream route 62 Downstream route 71 Cylinder 72 pistons 72a First pressure-receiving surface 72b Second pressure-receiving surface 73 Rod section 74 Main body 75. First Storage Unit 76 Second Storage Unit 77 Bulge 78 Seat section 79 Sliding part 80 Drain Path 81 Seal Route 82 First seal route 83 Second seal route 84 Third seal route 85 1st fuel source 86,87 Check valve 91,92 Check valve 93 Return Route 94 Check valve 111 Second fuel supply valve 112 Nitrogen sources 121 Discharge valve (check valve) 122 First Purge Route 123. First purge valve 124 Opening / Closing Control Valve (Purge Control Unit) 125 Connecting Routes 126. Hydraulic fluid source 127 Second Purge Route 128. Second purge valve 131 Discharge valve (control valve) 132 Opening / closing control valve (discharge control unit, purge control unit) 133. Hydraulic fluid supply source 134 Supply pump 135 Pressure Regulating Valve 136 Branch Routes 137 Shut-off valve 138,139 Control paths 141 Seal Piston 142 Check valve 151 Purge Route

Claims

1. A first fuel supply path that supplies a first fuel having predetermined ignition properties, A second fuel supply path that supplies a second fuel with lower ignition properties than the first fuel, A fuel injection valve having a needle valve to which the second fuel supply path is connected, A piston mechanism provided between the first fuel supply path and the second fuel supply path, having a piston that moves due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel, A discharge valve is provided in the second fuel supply path between the needle valve and the piston mechanism to prevent backflow of the second fuel from the needle valve to the piston mechanism side, Equipped with, The needle valve is connected downstream of the piston mechanism in the second fuel supply path, and a seal path is provided for supplying the first fuel to the sliding seal portion of the needle valve. The seal path includes a first seal path that supplies the first fuel from the first fuel supply path to the sliding seal portion, and a second seal path that supplies the first fuel at a higher pressure than the second fuel from the second fuel supply path between the needle valve and the piston mechanism after the second fuel has been injected. Fuel injection device.

2. A seal piston is provided to be movable along the first seal path to prevent the backflow of the first fuel from the needle valve, and a check valve is provided in the second seal path to prevent the backflow of the first fuel from the needle valve. The fuel injection device according to claim 1.

3. A first fuel supply path that supplies a first fuel having predetermined ignition properties, A second fuel supply path that supplies a second fuel with lower ignition properties than the first fuel, A fuel injection valve having a needle valve to which the second fuel supply path is connected, A piston mechanism provided between the first fuel supply path and the second fuel supply path, having a piston that moves due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel, A discharge valve is provided in the second fuel supply path between the needle valve and the piston mechanism to prevent backflow of the second fuel from the needle valve to the piston mechanism side, Equipped with, The piston mechanism has a first storage section to which the first fuel supply path is connected, a second storage section to which the second fuel supply path is connected, a first purge path connected to the second storage section for discharging the second fuel, a first purge valve for opening and closing the first purge path, and a purge control unit for controlling the opening and closing of the first purge valve. Fuel injection device.

4. The needle valve is connected downstream of the piston mechanism in the second fuel supply path and has a second purge path connected to the chamber of the needle valve for discharging the second fuel, a second purge valve for opening and closing the second purge path, and a purge control unit for controlling the opening and closing of the second purge valve. The fuel injection device according to claim 3.

5. The piston mechanism has a first storage section to which the first fuel supply path is connected, and a second storage section to which the second fuel supply path is connected, the second fuel supply path has an upstream path connecting the second fuel supply source and the second storage section, and a downstream path connecting the second storage section and the needle valve, and the discharge valve is provided in the downstream path. A fuel injection device according to claim 1 or claim 3.

6. The aforementioned discharge valve is a check valve. A fuel injection device according to claim 1 or claim 3.

7. The opening pressure of the check valve is higher than the second supply pressure of the second fuel supplied from the second fuel supply source to the second fuel supply path. The fuel injection device according to claim 6.

8. The discharge valve is a control valve and has a discharge control unit that opens and closes the second fuel supply path by controlling the control hydraulic pressure acting on the control valve. A fuel injection device according to claim 1 or claim 3.

9. The piston mechanism has a first storage section to which the first fuel supply path is connected, and a second storage section to which the second fuel supply path is connected, and has a purge path connected to the second storage section that discharges the second fuel when the piston moves and the second storage section reaches its maximum volume. A fuel injection device according to claim 1 or claim 3.

10. The piston mechanism comprises a cylinder provided between the first fuel supply path and the second fuel supply path, and a piston movably supported in the cylinder, wherein the piston has a first pressure-receiving surface at one end on which the first supply pressure acts, and a second pressure-receiving surface at the other end on which the second supply pressure acts, and the area of ​​the first pressure-receiving surface is smaller than the area of ​​the second pressure-receiving surface. A fuel injection device according to claim 1 or claim 3.

11. An internal combustion engine body having a combustion chamber, A fuel injection device according to claim 1 or claim 3, which injects fuel into the combustion chamber, A reciprocating internal combustion engine equipped with a motor.

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