Fuel injection device and reciprocating internal combustion engine

Abstract

To restrain mixing of a first fuel and a second fuel, thereby allow high-precision fuel injection, and reduce harmful substances contained in exhaust gas, in a fuel injection device and a reciprocating internal combustion engine.SOLUTION: A fuel injection device 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 that of the first fuel, a fuel injection valve to which the first fuel supply path and the second fuel supply path are connected, and a piston mechanism provided between the first fuel supply path and the second fuel supply path, and comprising a piston to be moved by a differential pressure between a first supply pressure of the first fuel and a second supply pressure of the second fuel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A reciprocating internal combustion engine is equipped with a fuel injection device. The reciprocating internal combustion engine is driven by the combustion energy generated by injecting fuel into high-pressure air in a combustion chamber using the fuel injection device. In recent years, the use of carbon-free fuels that generate fewer harmful substances (such as carbon dioxide) has been considered as fuels to be used in fuel injection devices. However, some carbon-free fuels have poor ignition and combustion properties, and it has been proposed to use them in combination with fuels that have good ignition and combustion properties. An example of a fuel injection device that injects multiple types of fuel is described in Patent Document 1 below. The fuel injection device described in Patent Document 1 injects a fossil fuel as a first fuel and an alternative fuel as a second fuel in a stratified manner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-180567 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional fuel injection system, a fuel pump that pumps a first fuel is connected to a fuel injection valve via a fuel injection pipe, and an injection pump that pumps a second fuel is connected to the fuel injection valve via an injection pipe. This configuration of the conventional fuel injection system makes it easy for the first fuel and the second fuel to mix when switching fuels, which makes it difficult to precisely adjust the injection ratio of the first fuel and the second fuel.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a fuel injection device and a reciprocating internal combustion engine that enable highly accurate fuel injection by suppressing mixing of a first fuel and a second fuel, thereby reducing harmful substances contained in exhaust gas. [Means for solving the problem]

[0006] In order to achieve the above object, the fuel injection device of the present disclosure includes a first fuel supply path that supplies a first fuel having a predetermined ignition ability, a second fuel supply path that supplies a second fuel having a lower ignition ability than the first fuel, a fuel injection valve to which the first fuel supply path and the second fuel supply path are connected, and a piston mechanism that is provided between the first fuel supply path and the second fuel supply path and has a piston that moves due to a pressure difference between a first supply pressure of the first fuel and a second supply pressure of the second fuel.

[0007] A reciprocating internal combustion engine of the present disclosure includes an internal combustion engine body having a combustion chamber, and the fuel injection device according to claim 1 that injects fuel into the combustion chamber. [Effects of the Invention]

[0008] According to the fuel injection device and reciprocating internal combustion engine of the present disclosure, highly accurate fuel injection is possible by suppressing mixing of the first fuel and the second fuel, thereby reducing harmful substances contained in exhaust gas. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a marine diesel engine according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the fuel injection device of the first embodiment. [Figure 3] FIG. 3 is a time chart showing the operation of the fuel injection device. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a fuel injection device according to the second embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of a fuel injection device according to the third embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a fuel injection device according to the fourth embodiment. [Figure 7] FIG. 7 is a time chart showing the operation of the fuel injection device. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of a fuel injection device according to a fifth embodiment. [Figure 9] FIG. 9 is a time chart showing the operation of the fuel injection device. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a fuel injection device according to the sixth embodiment. [Figure 11] FIG. 11 is a time chart showing the operation of the fuel injection device. [Figure 12] FIG. 12 is a schematic diagram showing the configuration of a fuel injection device according to the seventh embodiment. [Figure 13] FIG. 13 is a time chart showing the operation of the fuel injection device. [Figure 14] FIG. 14 is a schematic diagram showing the configuration of a fuel injection device according to the eighth embodiment. [Figure 15] FIG. 15 is a schematic diagram showing the configuration of a fuel injection device according to the ninth embodiment. [Figure 16] FIG. 16 is a schematic diagram showing the configuration of a fuel injection device according to a tenth embodiment. [Figure 17] FIG. 17 is a time chart showing the operation of the fuel injection device. [Figure 18] FIG. 18 is a schematic diagram showing the configuration of a fuel injection device according to an eleventh embodiment. [Figure 19] FIG. 19 is a schematic diagram showing the configuration of a fuel injection device according to a twelfth embodiment. [Figure 20] FIG. 20 is a schematic diagram showing the configuration of a fuel injection device according to the thirteenth embodiment. [Figure 21] FIG. 21 is a schematic diagram showing the configuration of a fuel injection device according to a fourteenth embodiment. [Figure 22] FIG. 22 is a time chart showing the operation of the fuel injection device. [Figure 23] FIG. 23 is a schematic diagram showing the configuration of a fuel injection device according to a fifteenth embodiment. [Figure 24] FIG. 24 is a schematic diagram showing the configuration of a fuel injection device according to the sixteenth embodiment. [Figure 25] FIG. 25 is a schematic diagram showing a modified example of the piston mechanism. [Figure 26] FIG. 26 is a schematic diagram showing the configuration of a fuel injection device according to the seventeenth embodiment. [Figure 27] FIG. 27 is a schematic diagram showing the configuration of a fuel injection device according to an eighteenth embodiment. [Figure 28] FIG. 28 is a time chart showing the operation of the fuel injection device. [Figure 29] FIG. 29 is a schematic diagram showing the configuration of a fuel injection device according to a nineteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0011] [First embodiment] <Marine diesel engine> Fig. 1 is a schematic diagram showing a marine diesel engine according to a first embodiment. In the first embodiment, a marine diesel engine will be described as a reciprocating internal combustion engine. However, the reciprocating internal combustion engine is not limited to a marine diesel engine.

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

[0013] The marine diesel engine 10 has a diesel engine body (internal combustion engine body) 11. The diesel engine body 11 includes 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 and is disposed inside a cylinder jacket (not shown), with a cylinder cover 21 fixed to the top. The piston 13 is cylindrical and is disposed inside the cylinder liner 12 and is supported so as to be freely movable in the axial direction. The lower end of the piston 13 is connected to the upper end of a piston rod 22. Although not shown, a crankshaft is rotatably supported at the bottom of the diesel engine body 11, and the lower end of a connecting rod is rotatably connected to the crank via a crank. The diesel engine body 11 supports a crosshead so as to be freely movable in 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 inside of the scavenging trunk 14 through a plurality of scavenging ports 23. Air is supplied to the scavenging trunk 14 through an intake pipe 24.

[0016] The cylinder liner 12 has an upper space to which a cylinder cover 21 is fixed, which is partitioned by the upper surface of the piston 13, thereby forming a combustion chamber 25. The cylinder cover 21 is connected to the exhaust manifold 15 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 is driven by a valve train 27 to open and close the exhaust pipe 26. 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] The marine diesel engine 10 also 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 attached to the cylinder cover 21. The fuel injection valve 33 can inject fuel into the combustion chamber 25. The fuel supply device 31 is connected to the fuel injection valve 33 via the fuel supply path 32. The fuel supply device 31 can supply 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 position indicated by the solid line in FIG. 1), the scavenging ports 23 open and the air in the scavenging trunk 14 is introduced through the scavenging ports 23 into the combustion chamber 25. Next, when the piston 13 moves up, the piston 13 blocks communication between the scavenging ports 23 and the combustion chamber 25. At this time, the exhaust valve 16 moves up by the valve train 27, the exhaust pipe 26 is closed, and the air in the combustion chamber 25 is compressed by the movement of the piston 13. Then, when the piston 13 moves to the top dead center (the position indicated by the two-dot chain line in FIG. 1), the pressure in the combustion chamber 25 reaches a predetermined compression pressure, and the fuel injection valve 33 is actuated to inject fuel into the combustion chamber 25. Then, the air and fuel mix and burn in the combustion chamber 25, and the combustion energy moves the piston 13 down. At this time, the exhaust valve 16 moves down by the valve train 27, opening the exhaust pipe 26. Then, exhaust gas generated by the combustion is pushed out from the combustion chamber 25 through the exhaust pipe 26 into the exhaust manifold 15 and discharged.

[0019] <Configuration of fuel injection system> FIG. 2 is a schematic diagram showing the configuration of the fuel injection device of the first embodiment.

[0020] 2, fuel injection device 17 includes fuel supply device 31, fuel supply path 32, and fuel injection valve 33. Fuel supply device 31 has a first supply pump 41 and a second supply pump 42. Fuel supply path 32 has a first fuel supply path 43 and a second fuel supply path 44. Fuel injection valve 33 has a first needle valve 45 and a second needle valve 46. Fuel injection device 17 also includes a piston mechanism 47.

[0021] The fuel injection device 17 can inject a first fuel having a predetermined ignitability, and can also inject a second fuel having a lower ignitability (poorer ignitability) than the first fuel. Here, ignitability refers to the ease with which the first fuel and the second fuel can be ignited, and can also be referred to as combustibility. The first fuel is a fossil fuel (e.g., diesel fuel such as light oil or heavy oil), 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] A first fuel supply source 50 is connected to the first fuel supply path 43 at an upstream end in the supply direction of the first fuel. The first fuel supply source 50 is composed of, for example, a pressure accumulator for the first fuel and a pressure pump that pressurizes the first fuel. The first fuel supply source 50 supplies, for example, 1 MPa of first fuel to the upstream side of the first fuel supply path 43. The first supply pump 41 is connected to the first fuel supply path 43 downstream of the first fuel supply source 50. The first supply pump 41 pressurizes the first fuel on the upstream side of the first fuel supply path 43 to a predetermined pressure (for example, 80 MPa) and supplies it to the downstream side of the first fuel supply path 43.

[0023] The first 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 by a first working oil supply path 53, and a first solenoid valve 55 is provided on the first working oil supply path 53. The working fluid source 54 supplies working fluid at a predetermined pressure (e.g., 30 MPa) to the first working oil supply path 53. The first supply pump 41 functions as a booster pump, with the pressure-receiving area of ​​the plunger 52 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 in response 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 oil supply path 53. The piston 51 is actuated by the supply of working fluid, and operates the plunger 52. Then, the first supply pump 41 pressurizes the first fuel in the first fuel supply path 43. At this time, the first supply pump 41 operates by increasing the pressure of the working fluid, and therefore pressurizes the first fuel to a predetermined pressure (for example, 80 MPa).

[0025] A second fuel supply source 60 is connected to the second fuel supply path 44 at an upstream end in the supply direction of the second fuel. The second fuel supply source 60 is composed of, for example, a pressure accumulator for the second fuel and a pressure pump that pressurizes the second fuel. The second fuel supply source 60 supplies the second fuel at, for example, 10 MPa to the upstream side of the second fuel supply path 44. The second supply pump 42 is connected to the second fuel supply path 44 downstream of the second fuel supply source 60. The second supply pump 42 pressurizes the second fuel on the upstream side of the second fuel supply path 44 to a predetermined pressure (for example, 15 MPa) and supplies it to the downstream side of the second fuel supply path 44.

[0026] The second supply pump 42 has a piston 61 and a plunger 62. The piston 61 and the plunger 62 are connected to each other, and the plunger 62 is connected to the second fuel supply path 44. The piston 61 is connected to a working fluid source 54 via a second hydraulic oil supply path 63, and the second hydraulic oil supply path 63 is provided with a second solenoid valve 65. Note that the working fluid source 54 is also used as the first supply pump 41, but it may be a dedicated working fluid source. The second supply pump 42 functions as a booster pump or a decompressor pump, with the pressure-receiving area of ​​the plunger 62 set relative to the pressure-receiving area of ​​the piston 61 so as to achieve a predetermined supply pressure determined in accordance with the second fuel characteristics (e.g., saturated vapor pressure). The second solenoid valve 65 is connected to the control unit 56 and opens and closes in response to commands from the control unit 56.

[0027] When the second solenoid valve 65 is opened, the working fluid from the working fluid source 54 is supplied to the piston 61 through the second working oil supply path 63. The piston 61 is actuated by the supply of working fluid, and operates the plunger 62. Then, the second supply pump 42 pressurizes the second fuel in the second fuel supply path 44. At this time, the second supply pump 42 operates by reducing the pressurizing force of the working fluid, and therefore pressurizes the second fuel to a predetermined pressure (for example, 15 MPa).

[0028] A downstream end of first fuel supply path 43 is connected to first needle valve 45. First needle valve 45 has a valve element 45a, a biasing spring 45b, a chamber 45c, a fuel supply path 45d, and a nozzle hole 45e. First fuel supply path 43 is connected to chamber 45c. Chamber 45c is in communication with fuel supply path 45d, and fuel supply path 45d has a nozzle hole 45e formed at its tip. Valve element 45a is seated by the biasing force of biasing spring 45b, thereby blocking communication between chamber 45c and fuel supply path 45d. A predetermined first injection pressure (e.g., 40 MPa) is set in first needle valve 45. Therefore, when first fuel at a pressure higher than the first injection pressure is supplied from first fuel supply path 43 to chamber 45c, valve element 45a of first needle valve 45 rises against the biasing force of biasing spring 45b, connecting chamber 45c to fuel supply path 45d. Then, the first fuel supplied to chamber 45c flows into fuel supply path 45d and is injected from nozzle hole 45e.

[0029] The downstream end of second fuel supply path 44 is connected to second needle valve 46. Second needle valve 46 has a valve body 46a, a biasing spring 46b, a chamber 46c, a fuel supply path 46d, and a nozzle hole 46e. Second fuel supply path 44 is connected to chamber 46c. Chamber 46c communicates with fuel supply path 46d, and fuel supply path 46d has a nozzle hole 46e formed at its tip. Valve body 46a is seated by the biasing force of biasing spring 46b, thereby blocking communication between chamber 46c and fuel supply path 46d. A predetermined second injection pressure (e.g., 40 MPa) is set in second needle valve 46. Therefore, when second fuel at a pressure higher than the second injection pressure is supplied from second fuel supply path 44 to chamber 46c, valve element 46a of second needle valve 46 rises against the biasing force of biasing spring 46b, connecting chamber 46c to fuel supply path 46d. The second fuel supplied to chamber 46c then flows into fuel supply path 46d and is injected from nozzle hole 46e.

[0030] The piston mechanism 47 is provided between the first fuel supply path 43 and the second fuel supply path 44. The piston mechanism 47 has a cylindrical cylinder 71 and a columnar piston 72. The piston 72 is disposed inside the cylinder 71 and supported so as to be freely movable along the axial direction. One end of the cylinder 71 in the movement direction of the piston 72 communicates with the first fuel supply path 43, and the other end of the cylinder 71 in the movement direction of the piston 72 communicates with the second fuel supply path 44. The piston 72 has a first pressure-receiving surface 72a formed on the first fuel supply path 43 side and a second pressure-receiving surface 72b formed on the second fuel supply path 44 side. A first supply pressure from the first fuel supply path 43 acts on the first pressure-receiving surface 72a of the piston 72, and a second supply pressure from the second fuel supply path 44 acts on the second pressure-receiving surface 72b. In the piston mechanism 47, the piston 72 reciprocates due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel.

[0031] In the piston mechanism 47, the axial length of the piston 72 is shorter than the axial length of the cylinder 71. Therefore, the piston mechanism 47 is provided with a first storage section 73 on the first pressure-receiving surface 72a side that communicates with the first fuel supply path 43 and stores the first fuel, and a second storage section 74 on the second pressure-receiving surface 72b side that communicates with the second fuel supply path 44 and stores the second fuel. The piston 72 is movable within the cylinder 71, but the amount of reciprocating movement is limited by a stopper (not shown). That is, when the piston 72 moves most toward the first fuel supply path 43, a gap is formed between the first pressure-receiving surface 72a and one end of the cylinder 71, and a first storage section 73 including this gap is formed. On the other hand, when the piston 72 moves most toward the second fuel supply path 44, a gap is formed between the second pressure-receiving surface 72b and the other end of the cylinder 71, and a second storage section 74 including this gap is formed.

[0032] When second supply pump 42 is operating and first supply pump 41 is stopped, the second supply pressure of the second fuel in second fuel supply path 44 becomes higher than the first supply pressure of the first fuel in first fuel supply path 43. At this time, piston 72 of piston mechanism 47 moves toward first fuel supply path 43, and a predetermined amount of second fuel is stored in second reservoir 74. On the other hand, when first supply pump 41 is operating and second supply pump 42 is stopped, the first supply pressure of the first fuel in first fuel supply path 43 becomes higher than the second supply pressure of the second fuel in second fuel supply path 44. At this time, piston 72 of piston mechanism 47 moves toward second fuel supply path 44, and supplies the first fuel from first fuel supply path 43 to first needle valve 45 and supplies the second fuel in second reservoir 74 to second needle valve 46. First needle valve 45 injects the first fuel when the first supply pressure exceeds the first injection pressure, and second needle valve 46 injects the second fuel when the second supply pressure exceeds the second injection pressure.

[0033] A check valve 81 is provided in the first fuel supply path 43 between the connection portion of the first supply pump 41 and the connection portion of the piston mechanism 47. The check valve 81 prevents the first fuel from flowing back from the piston mechanism 47 side to the first supply pump 41 side. An opening pressure (e.g., 15 MPa) is set for the check valve 81 from the first supply pump 41 side to the piston mechanism 47 side. A check valve 87 is provided in the first fuel supply path 43 upstream of the connection portion of the first supply pump 41. The check valve 87 prevents the first fuel from flowing back from the connection portion of the first supply pump 41 side to the first fuel supply source 50 side. An opening pressure (e.g., 10 MPa) is set for the check valve 87 from the first fuel supply source 50 side to the first supply pump 41 side. Furthermore, first fuel supply path 43 is provided with return path 82 that bypasses check valves 81, 87 and first supply pump 41, and return path 82 is provided with check valve 83. When first supply pump 41 stops and the pressure downstream of check valve 81 (for example, the second supply pressure of the second fuel in second fuel supply path 44) is released by the pressure obtained by adding the spring force of check valve 83 to the pressure upstream of check valve 81, check valve 83 is released, and the first fuel in first fuel supply path 43 on the piston mechanism 47 side is returned bypassing check valve 81. Note that an opening pressure (for example, 20 MPa) is set for check valve 83 from the piston mechanism 47 side to the first supply pump 41 side.

[0034] The second fuel supply path 44 is provided with check valves 84 and 85 between the connection portion of the second supply pump 42 and the connection portion of the piston mechanism 47. The check valves 84 and 85 prevent the second fuel from flowing back from the piston mechanism 47 to the second supply pump 42. That is, the check valves 84 and 85 close when the first supply pressure is higher than the second supply pressure, thereby preventing the second fuel stored in the second reservoir 74 from flowing back to the second supply pump 42. The check valves 84 and 85 have an opening pressure (e.g., 15 MPa) set from the second supply pump 42 to the piston mechanism 47. The second fuel supply path 44 is provided with a check valve 86 between the connection portion of the second supply pump 42 and the second fuel supply source 60. The check valve 86 prevents the second fuel from flowing back from the second supply pump 42 to the second fuel supply source 60. The check valve 86 is set to an opening pressure (for example, 10 MPa) from the second fuel supply source 60 side to the second supply pump 42 side.

[0035] <Fuel injection system operation> FIG. 3 is a time chart showing the operation of the fuel injection device.

[0036] 2 and 3, the second supply pump 42 starts operating at crank angle a1. When the second supply pump 42 operates, the lift amount of the second supply pump 42 increases, and the second fuel is pressurized and supplied to the second fuel supply path 44. Then, at crank angle a2, the pressure upstream of the second needle valve 46, that is, the pressure in the second fuel supply path 44 downstream of the check valve 84, increases. At this time, the second supply pressure of the second fuel in the second fuel supply path 44 acts on the second pressure-receiving surface 72b, the lift amount of the piston 72 increases, and the piston 72 moves toward the first fuel supply path 43. Therefore, in the piston mechanism 47, the volume of the second storage portion 74 increases, and a predetermined amount of the second fuel is stored in the second storage portion 74.

[0037] Furthermore, because piston 72 moves toward first fuel supply path 43, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases at crank angle a2. Then, at crank angle a3, operation of second supply pump 42 is stopped, and the lift amount of second supply pump 42 is reduced. When second supply pump 42 is stopped, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, decreases at crank angle a4. Furthermore, when the pressure in first fuel supply path 43 increases, check valve 83 opens to return the first fuel, and the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, decreases at crank angle a4.

[0038] At crank angle a5, first supply pump 41 starts operating. When first supply pump 41 operates, the lift amount of first supply pump 41 increases, and the first fuel is pressurized and supplied to first fuel supply path 43. Then, at crank angle a6, the pressure upstream of first needle valve 45, that is, the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases. Then, the first supply pressure of the first fuel in first fuel supply path 43 acts on first pressure-receiving surface 72a, the lift amount of piston 72 decreases, and piston 72 moves toward second fuel supply path 44.

[0039] As piston 72 moves toward second fuel supply path 44, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, also increases. When the first supply pressure in first fuel supply path 43 exceeds the first injection pressure of first needle valve 45 at crank angle a7, first needle valve 45 opens and starts injecting the first fuel. Furthermore, as the pressure in second fuel supply path 44 increases, when the second supply pressure in second fuel supply path 44 exceeds the second injection pressure of second needle valve 46 at crank angle a7, second needle valve 46 opens and starts injecting the second fuel.

[0040] Thereafter, at crank angle a9, the operation of the first supply pump 41 is stopped. When the first supply pump 41 is stopped, the lift amount of the first supply pump 41 decreases, and the supply of the first fuel to the first fuel supply path 43 stops. Then, the first supply pressure of the first fuel in the first fuel supply path 43 decreases, and the movement of the piston 72 stops.

[0041] When first supply pump 41 stops, the pressure in first fuel supply path 43 upstream of check valves 81 and 83 decreases, check valve 83 opens, and the first fuel is returned. At crank angle a12, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43, decreases. At crank angle a11, the first supply pressure in first fuel supply path 43 becomes lower than the first injection pressure of first needle valve 45, causing first needle valve 45 to close and stop injecting the first fuel. When piston 72 reaches second fuel supply path 44, the supply of the second fuel to second needle valve 46 stops. At crank angle a10, the second supply pressure in second fuel supply path 44 becomes lower than the second injection pressure of second needle valve 46, causing second needle valve 46 to close and stop injecting the second fuel.

[0042] In the first embodiment, fuel injection device 17 has first needle valve 45 injecting a first fuel within a predetermined crank angle range T1, and second needle valve 46 injecting a second fuel within a predetermined crank angle range T2. In this case, the crank angle range T1 of first needle valve 45 and the crank angle range T2 of second needle valve 46 have the same fuel injection start timing but different fuel injection end timings. That is, the injection of the second fuel by second needle valve 46 ends earlier than the injection of the first fuel by first needle valve 45. However, the fuel injection start timing and end timing are not limited to those described above. The fuel injection start timing and end timing of first needle valve 45 and second needle valve 46 can be set arbitrarily. For example, by setting the second injection pressure of second needle valve 46 higher than the first injection pressure of first needle valve 45, the timing at which second needle valve 46 starts injecting the second fuel can be made later than the timing at which first needle valve 45 starts injecting the first fuel.

[0043] Therefore, the fuel injection device 17 injects the second fuel, which has poor ignition properties, while injecting the first fuel, which has good ignition properties. That is, the fuel injection device 17 reduces the injection amount of the first fuel and increases the injection amount of the second fuel. Although the second fuel has poor ignition properties, it is a carbon-free fuel that does not generate carbon dioxide, and can suppress the generation of harmful substances (such as carbon dioxide). Then, the first fuel, which has good ignition properties, is injected together with the second fuel, which has poor ignition properties. As a result, the ignition of the first fuel serves as a spark that ignites and burns the second fuel, and therefore a decrease in combustibility is suppressed.

[0044] [Second embodiment] 4 is a schematic diagram showing the configuration of a fuel injection device according to the second embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0045] 4, fuel injection device 17A includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, and piston mechanism 47A. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, and second needle valve 46 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0046] The piston mechanism 47A is provided between the first fuel supply path 43 and the second fuel supply path 44. The piston mechanism 47A has a cylindrical cylinder 71A and a columnar piston 72A. The cylinder 71A is a stepped cylinder and has a small diameter portion 91 and a large diameter portion 92. The piston 72A is a stepped piston and has a small diameter portion 93 and a large diameter portion 94. The piston 72A is disposed inside the cylinder 71A and supported so as to be movable in the axial direction. The small diameter portion 93 of the piston 72A is supported by the small diameter portion 91 of the cylinder 71A, and the large diameter portion 94 is supported by the large diameter portion 92. The piston mechanism 47A has a cylindrical space 95 formed in the axial intermediate portion between the cylinder 71A and the piston 72A. One end of a drain path 96 communicates with the space 95. When piston 72A moves, first storage section 73 and second storage section 74 are connected to space section 95, so the first fuel and second fuel flow in and mix. Drain path 96 discharges the first fuel and second fuel mixed in space section 95 to the outside and recovers them.

[0047] One end of cylinder 71A in the movement direction of piston 72A communicates with first fuel supply path 43, and the other end of piston 72A in the movement direction communicates with second fuel supply path 44. Piston 72A has a first pressure-receiving surface 72a formed on the first fuel supply path 43 side, and a second pressure-receiving surface 72b formed on the second fuel supply path 44 side. A first supply pressure of first fuel supply path 43 acts on piston 72A's first pressure-receiving surface 72a, and a second supply pressure of second fuel supply path 44 acts on second pressure-receiving surface 72b. Piston mechanism 47A reciprocates piston 72A due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel.

[0048] Piston 72A is a stepped piston, and a first pressure-receiving surface 72a is formed on the small-diameter portion 93 side, and a second pressure-receiving surface 72b is formed on the large-diameter portion 94 side. Therefore, in piston 72A, the area of ​​first pressure-receiving surface 72a is smaller than the area of ​​second pressure-receiving surface 72b. Piston mechanism 47A is provided with a first reservoir 73 communicating with first fuel supply path 43 on the first pressure-receiving surface 72a side, and a second reservoir 74 communicating with second fuel supply path 44 on the second pressure-receiving surface 72b side. In piston mechanism 47A, due to the difference in area between first pressure-receiving surface 72a and second pressure-receiving surface 72b, the first supply pressure acting on first fuel supply path 43 via first reservoir 73 becomes higher than the second supply pressure acting on second fuel supply path 44 via second reservoir 74.

[0049] The second needle valve 46 has a valve element 46a movably supported in a cylinder (not shown). A clearance for movement is provided between the outer circumferential surface of the valve element 46a and the inner circumferential surface of the cylinder, and the second fuel leaks through this clearance. It is preferable to recover the second fuel that leaks from the second needle valve 46; however, if the second fuel is ammonia, recovery is difficult because it vaporizes into a toxic gas. Therefore, a seal path 97 is provided to supply the first fuel from the first fuel supply path 43 to a sliding seal portion 46f between the valve element 46a and the cylinder. A first supply pressure of the first fuel from the first fuel supply path 43 acts on the sliding seal portion 46f via the seal path 97. Here, a second supply pressure of the second fuel from the second fuel supply path 44 acts on the valve element 46a of the second needle valve 46, but because the first supply pressure is higher than the second supply pressure, leakage of the second fuel is suppressed.

[0050] The operation of the fuel injection device 17A is almost the same as that of the fuel injection device 17 of the first embodiment, and therefore a description thereof will be omitted.

[0051] [Third embodiment] 5 is a schematic diagram showing the configuration of a fuel injection device according to a third embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0052] 5, fuel injection device 17B includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, and piston mechanism 47B. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, and second needle valve 46 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0053] The piston mechanism 47B is provided between the first fuel supply path 43 and the second fuel supply path 44. The piston mechanism 47B has a cylindrical cylinder 71 and a columnar piston 72B. The piston 72B is a rod-equipped piston and has a small-diameter rod portion 101 and a large-diameter main body portion 102. The piston 72B is disposed inside the cylinder 71 and supported so as to be movable axially. The main body portion 102 of the piston 72B is supported by the cylinder 71, and an end of the rod portion 101 extends outside the cylinder. The piston mechanism 47B has a sliding portion 103 formed between the cylinder 71 and the rod portion 101 of the piston 72B. One end of a drain path 104 is connected to the sliding portion 103. The sliding portion 103 is connected to the first reservoir 73, so that the first fuel leaks. The drain path 104 discharges and recovers the first fuel that has leaked from the sliding portion 103 to the outside. Here, because 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, the second fuel in the second fuel supply path 44 does not flow to the first fuel supply path 43 side and become mixed with the first fuel. Therefore, the first fuel recovered from the drain path 104 does not contain the second fuel, making it easier to process.

[0054] One end of the cylinder 71 in the movement direction of the piston 72B communicates with the first fuel supply path 43, and the other end of the cylinder 71 in the movement direction of the piston 72B communicates with the second fuel supply path 44. The piston 72B has a first pressure-receiving surface 72a formed on the first fuel supply path 43 side of the main body 102, and a second pressure-receiving surface 72b formed on the second fuel supply path 44 side. A first supply pressure from the first fuel supply path 43 acts on the first pressure-receiving surface 72a of the piston 72B, and a second supply pressure from the second fuel supply path 44 acts on the second pressure-receiving surface 72b. The piston mechanism 47B reciprocates the piston 72B due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel.

[0055] Piston 72B is a piston with a rod, and has a first pressure-receiving surface 72a formed on one side of body 102 and a second pressure-receiving surface 72b formed on the other side. Therefore, in piston 72B, the area of ​​first pressure-receiving surface 72a is smaller than the area of ​​second pressure-receiving surface 72b. Piston mechanism 47B is provided with a first reservoir 73 communicating with first fuel supply path 43 on the side of first pressure-receiving surface 72a, and a second reservoir 74 communicating with second fuel supply path 44 on the side of second pressure-receiving surface 72b. Due to the difference in area between first pressure-receiving surface 72a and second pressure-receiving surface 72b, in piston mechanism 47B, the first supply pressure acting on first fuel supply path 43 via first reservoir 73 becomes higher than the second supply pressure acting on second fuel supply path 44 via second reservoir 74.

[0056] A seal path 97 is provided to supply the first fuel from the first fuel supply path 43 to the sliding seal portion 46f of the valve body 46a. A first supply pressure of the first fuel from the first fuel supply path 43 acts on the seal path 97. A second supply pressure of the second fuel from the second fuel supply path 44 acts on the valve body 46a of the second needle valve 46, but because the first supply pressure is higher than the second supply pressure, leakage of the second fuel is suppressed.

[0057] The operation of the fuel injection device 17B is almost the same as that of the fuel injection device 17 of the first embodiment, and therefore a description thereof will be omitted.

[0058] [Fourth embodiment] Fig. 6 is a schematic diagram showing the configuration of a fuel injection device of the fourth embodiment, and Fig. 7 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the third embodiment described above are given the same reference numerals and detailed explanations will be omitted.

[0059] 6, fuel injection device 17C includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, piston mechanism 47B, and first flow limiter 110. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, and piston mechanism 47B are the same as those in the third embodiment, and therefore description thereof will be omitted.

[0060] First fuel supply path 43 is provided with a first flow limiter 110 that limits the supply of the first fuel between piston mechanism 47B and first needle valve 45. First flow limiter 110 has a housing 111, a valve body 112, a supply flow path 113, a discharge flow path 114, a connecting flow path 115, an orifice 116, and a compression spring 117.

[0061] The housing 111 has a hollow shape. The valve element 112 is disposed inside the housing 111 and supported so as to be movable in the axial direction (the up-and-down direction in FIG. 6 ). The supply passage 113 is provided in the upper part of the housing 111, and communicates with the downstream side of the first fuel supply passage 43, which is communicated with the piston mechanism 47B. The discharge passage 114 is provided in the lower part of the housing 111, and communicates with the upstream side of the first fuel supply passage 43, which is communicated with the first needle valve 45. The connecting passage 115 is provided inside the valve element 112. The connecting passage 115 can communicate between the supply passage 113 and the discharge passage 114. The orifice 116 is provided midway through the connecting passage 115. The compression spring 117 is disposed in the discharge passage 114 and urges the valve element 112 upward, urging it to a position where the supply passage 113 and the connecting passage 115 are communicated with each other.

[0062] In the first flow limiter 110, the first supply pressure of the first fuel in the first fuel supply path 43 acts on the upper part of the valve element 112 through the supply flow path 113. When the operation of the first supply pump 41 is stopped, the first supply pressure of the first fuel in the first fuel supply path 43 is low (for example, 20 MPa). Therefore, in the first flow limiter 110, the biasing force of the compression spring 117 pushes up the valve element 112 against the first supply pressure, and positions the valve element 112 at a position where the supply flow path 113 and the connecting flow path 115 communicate with each other. At this time, the first supply pressure of the first fuel acts on the first needle valve 45.

[0063] When first supply pump 41 is operated, the first supply pressure of the first fuel in first fuel supply path 43 becomes high (e.g., 80 MPa). The first fuel is supplied from supply flow path 113 of first flow limiter 110 through connecting flow path 115, orifice 116, and discharge flow path 114 to first needle valve 45, and the first supply pressure acts on the first fuel. When the first supply pressure exceeds the first injection pressure, first needle valve 45 injects the first fuel. At this time, the flow rate of the first fuel is restricted because the first fuel passes through orifice 116, and the pressure in supply flow path 113 increases. When the pressure of the first fuel in supply flow path 113 becomes higher than the pressure of the first fuel in discharge flow path 114, the differential pressure between the two forces valve element 112 downward against the biasing force of compression spring 117, and communication between supply flow path 113 and connecting flow path 115 is blocked. As a result, the first fuel in supply passage 113 is not supplied to first needle valve 45, the first supply pressure acting on first needle valve 45 becomes lower than the first injection pressure, and injection of the first fuel by first needle valve 45 stops.

[0064] As shown in FIGS. 6 and 7 , first, when second supply pump 42 is operated, the second fuel in second fuel supply path 44 is pressurized, and the second supply pressure of the high-pressure second fuel acts on second pressure-receiving surface 72b, moving piston 72B toward first fuel supply path 43. As a result, piston mechanism 47B stores a predetermined amount of second fuel in second reservoir 74. Next, when first supply pump 41 is operated, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases. Then, the first supply pressure of the first fuel in first fuel supply path 43 acts on first pressure-receiving surface 72a, moving piston 72B toward second fuel supply path 44. Then, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, also increases.

[0065] When the first supply pressure in first fuel supply path 43 exceeds the first injection pressure of first needle valve 45 at crank angle a21, first needle valve 45 starts injecting the first fuel. At this time, when the second supply pressure in second fuel supply path 44 exceeds the second injection pressure of second needle valve 46, second needle valve 46 starts injecting the second fuel. Then, as described above, when first flow limiter 110 is activated and the first fuel is no longer supplied to first needle valve 45, the first supply pressure becomes lower than the first injection pressure of first needle valve 45 at crank angle a22, and first needle valve 45 ends injection of the first fuel. Thereafter, when first supply pump 41 stops and piston 72B stops moving, the second supply pressure becomes lower than the second injection pressure of second needle valve 46 at crank angle a23, and second needle valve 46 ends injection of the second fuel.

[0066] In the fourth embodiment, in a fuel injection device 17C, a first needle valve 45 injects a first fuel within a predetermined crank angle range T1, and a second needle valve 46 injects a second fuel within a predetermined crank angle range T2. In this case, the fuel injection start timing is the same for crank angle range T1 of the first needle valve 45 and the crank angle range T2 of the second needle valve 46, but the fuel injection end timing is different. That is, the injection timing of the first fuel by the first needle valve 45 (crank angle range T1) is only the beginning of the injection timing of the second fuel by the second needle valve 46 (crank angle range T2).

[0067] Therefore, the fuel injection device 17C simultaneously injects the first fuel having good ignition properties and the second fuel having poor ignition properties, and when the flame ignited by the first fuel having good ignition properties becomes a spark that ignites the second fuel having poor ignition properties, the injection of the first fuel having good ignition properties is terminated. As a result, the fuel injection device 17C can reduce the injection amount of the first fuel.

[0068] [Fifth embodiment] Fig. 8 is a schematic diagram showing the configuration of a fuel injection device of the fifth embodiment, and Fig. 9 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the above-described fourth embodiment are given the same reference numerals and detailed explanations thereof will be omitted.

[0069] 8, fuel injection device 17D includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, piston mechanism 47B, first flow limiter 110, and communication path 120. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, piston mechanism 47B, and first flow limiter 110 are the same as those in the fourth embodiment, and therefore description thereof will be omitted.

[0070] First fuel supply path 43 is provided with a first flow limiter 110 that limits the supply of the first fuel between piston mechanism 47B and first needle valve 45. First flow limiter 110 has a housing 111, a valve body 112, a supply flow path 113, a discharge flow path 114, a connecting flow path 115, an orifice 116, and a compression spring 117.

[0071] The communication path 120 communicates the downstream side and upstream side of the first flow limiter 110 in the first fuel supply path 43 during the final stage of movement of the piston 72B of the piston mechanism 47B toward the second fuel supply path 44. One end of the communication path 120 communicates with the discharge flow path 114 of the first flow limiter 110, and the other end can communicate with the first storage portion 73. That is, the other end of the communication path 120 is connected to the first storage portion 73 at a position farthest from one end of the cylinder 71. In the piston mechanism 47B, the piston 72B moves from the first fuel supply path 43 side to the second fuel supply path 44 side. The other end of the communication path 120 does not communicate with the first storage portion 73 when the piston 72B is located on the first fuel supply path 43 side. The other end of communication path 120 communicates with first reservoir 73 when piston 72B moves from the first fuel supply path 43 side to the second fuel supply path 44 side and reaches the closest position to the second fuel supply path 44 side.

[0072] 8 and 9 , second supply pump 42 starts operating at crank angle a1. When second supply pump 42 operates, the lift amount of second supply pump 42 increases, and the second fuel is pressurized and supplied to second fuel supply path 44. Then, at crank angle a2, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, increases, and the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valve 81, increases. At this time, the second supply pressure of the second fuel in second fuel supply path 44 acts on second pressure-receiving surface 72b, increasing the lift amount of piston 72B and moving piston 72B toward first fuel supply path 43. As a result, in piston mechanism 47B, the volume of second storage portion 74 increases, and a predetermined amount of second fuel is stored in second storage portion 74.

[0073] Furthermore, because piston 72B moves toward first fuel supply path 43, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases at crank angle a2. Then, at crank angle a3, operation of second supply pump 42 is stopped, and the lift amount of second supply pump 42 is reduced. When second supply pump 42 is stopped, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, decreases at crank angle a4. Furthermore, when the pressure in first fuel supply path 43 increases, check valve 83 opens to return the first fuel, and the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, decreases at crank angle a4.

[0074] At crank angle a5, first supply pump 41 begins to operate. When first supply pump 41 operates, the lift amount of first supply pump 41 increases, and the first fuel is pressurized and supplied to first fuel supply path 43. Then, at crank angle a6, the pressure upstream of first flow limiter 110, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases, and the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of first flow limiter 110, increases. Then, the first supply pressure of the first fuel in first fuel supply path 43 acts on first pressure-receiving surface 72a, the lift amount of piston 72B decreases, and piston 72B moves toward second fuel supply path 44.

[0075] When piston 72B moves toward second fuel supply path 44, the pressure upstream of second needle valve 46, that is, the pressure in second fuel supply path 44 downstream of check valve 84, also increases. When the first supply pressure in first fuel supply path 43 exceeds the first injection pressure of first needle valve 45 at crank angle a7, first needle valve 45 opens and starts injecting the first fuel. When the pressure in second fuel supply path 44 increases and the second supply pressure in second fuel supply path 44 exceeds the second injection pressure of second needle valve 46 at crank angle a7, second needle valve 46 opens and starts injecting the second fuel.

[0076] At crank angle a6, when the pressure in first fuel supply path 43 increases, first flow limiter 110 begins to operate, reducing the lift amount. At crank angle a8, the pressures upstream of first flow limiter 110 and first needle valve 45 reach their maximums, after which the pressure upstream of first needle valve 45 decreases. That is, first flow limiter 110 operates, preventing the first fuel from being supplied to first needle valve 45, reducing the pressure upstream of first needle valve 45. At crank angle a9, the first supply pressure becomes lower than the first injection pressure of first needle valve 45, causing first needle valve 45 to terminate injection of the first fuel.

[0077] Piston 72B moves from the first fuel supply path 43 side to the second fuel supply path 44 side, and at crank angle a10, piston 72B reaches the position closest to second fuel supply path 44, whereby discharge flow path 114 of first flow limiter 110 and first storage 73 are connected via communication path 120. The first fuel in first storage 73 then bypasses orifice 116 (first flow limiter 110) and is supplied to first needle valve 45. This increases the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of first flow limiter 110, and increases the lift amount of first flow limiter 110. When the first supply pressure in first fuel supply path 43 exceeds the first injection pressure of first needle valve 45 at crank angle a11, first needle valve 45 opens and restarts injection of the first fuel.

[0078] Thereafter, at crank angle a12, operation of first supply pump 41 is stopped. When first supply pump 41 is stopped, the lift amount of first supply pump 41 decreases, and the supply of the first fuel to first fuel supply path 43 is stopped. As a result, the first supply pressure of the first fuel in first fuel supply path 43 decreases, and movement of piston 72B stops. When first supply pump 41 is stopped, the pressure upstream of first needle valve 45 reaches a maximum at crank angle a13. However, the pressure in first fuel supply path 43 upstream of check valves 81 and 83 decreases, check valve 83 opens, and the first fuel is returned. At crank angle a15, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43, decreases. At this time, at crank angle a14, the first supply pressure of first fuel supply path 43 becomes lower than the first injection pressure of first needle valve 45, causing first needle valve 45 to close and stop injecting the first fuel. When piston 72B reaches second fuel supply path 44, the supply of the second fuel to second needle valve 46 stops, and at crank angle a13, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44, decreases. As a result, the second supply pressure of second fuel supply path 44 becomes lower than the second injection pressure of second needle valve 46, causing second needle valve 46 to close and stop injecting the second fuel.

[0079] In the fifth embodiment, fuel injection device 17D has first needle valve 45 injecting the first fuel within predetermined crank angle ranges T11 and T12, and second needle valve 46 injecting the second fuel within predetermined crank angle range T2. That is, the injection timing of first fuel by first needle valve 45 (crank angle ranges T11 and T12) corresponds only to the beginning and end of the injection timing of second fuel by second needle valve 46 (crank angle range T2). Therefore, fuel injection device 17D simultaneously injects the first fuel with good ignition properties and the second fuel with poor ignition properties, and terminates injection of the first fuel with good ignition properties when the flame ignited by the first fuel with good ignition properties becomes the spark that ignites the second fuel with poor ignition properties. Furthermore, fuel injection device 17D injects the first fuel with good ignition properties toward the end of combustion of the second fuel with poor ignition properties, thereby completely combusting the second fuel with poor ignition properties. As a result, the fuel injection device 17D can reduce the injection amount of the first fuel and can improve the combustibility.

[0080] [Sixth embodiment] Fig. 10 is a schematic diagram showing the configuration of a fuel injection device of the sixth embodiment, and Fig. 11 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the third embodiment described above are given the same reference numerals and detailed explanations will be omitted.

[0081] 10, fuel injection device 17E includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, piston mechanism 47B, first flow limiter 130, and communication path 120. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, and piston mechanism 47B are the same as those in the third embodiment, and therefore description thereof will be omitted.

[0082] First fuel supply path 43 is provided with a first flow limiter 130 that limits the supply of the first fuel between piston mechanism 47B and first needle valve 45. First flow limiter 130 has a housing 131, a valve body 132, a supply flow path 133, a discharge flow path 134, a connecting flow path 135, a variable throttle valve (first flow limiter adjustment valve) 136, and a compression spring 137.

[0083] The housing 131 has a hollow shape. The valve element 132 is disposed inside the housing 131 and supported so as to be movable in the axial direction (the up-and-down direction in FIG. 10 ). The supply passage 133 is provided in the upper part of the housing 131 and is connected to the downstream side of the first fuel supply passage 43, which is connected to the piston mechanism 47B. The discharge passage 134 is provided in the lower part of the housing 131 and is connected to the first needle valve 45 via the first fuel supply passage 43. The connecting passage 135 is provided outside the valve element 132. The connecting passage 135 can connect the downstream side of the supply passage 133, i.e., the space downstream of the seat portion of the valve element 132, with the upstream side of the discharge passage 134. The variable throttle valve 136 is provided in the middle of the connecting passage 135. Compression spring 137 is disposed in discharge flow path 134 and biases valve element 132 upward, supporting it at a position where supply flow path 133 and connecting flow path 135 communicate with each other. Connecting flow path 135 and variable throttle valve 136 may be provided inside valve element 132. Variable throttle valve 136 is controlled by control unit 56 and is capable of adjusting the flow path area of ​​connecting flow path 135.

[0084] Communication path 120 communicates the downstream side and upstream side of first flow limiter 130 in first fuel supply path 43 at the end of movement of piston 72B of piston mechanism 47B toward second fuel supply path 44. One end of communication path 120 communicates with discharge flow path 134 of first flow limiter 130, and the other end can communicate with first reservoir 73.

[0085] In the first flow limiter 130, the first supply pressure of the first fuel in the first fuel supply path 43 acts on the upper part of the valve body 132 through the supply flow path 133. When the operation of the first supply pump 41 is stopped, the first supply pressure of the first fuel in the first fuel supply path 43 is low and is determined by the check valve 83 (for example, 20 MPa). Therefore, the first flow limiter 130 is positioned at a position where the biasing force of the compression spring 137 pushes up and seats the valve body 132 against the first supply pressure, that is, at a position where the supply flow path 133 and the connecting flow path 135 communicate with each other.

[0086] When first supply pump 41 operates, the first supply pressure of the first fuel in first fuel supply path 43 becomes high (e.g., 80 MPa). The first fuel is supplied from supply flow path 133 of first flow limiter 130 through connecting flow path 135, variable throttle valve 136, and discharge flow path 134 to first needle valve 45, and the first supply pressure acts on the first fuel. When the first supply pressure exceeds the first injection pressure, first needle valve 45 injects the first fuel. At this time, the flow rate of the first fuel is restricted because the first fuel passes through variable throttle valve 136, and the pressure in supply flow path 133 increases. When the pressure of the first fuel in supply flow path 133 becomes higher than the pressure of the first fuel in discharge flow path 134, the differential pressure between the two forces valve element 132 downward against the biasing force of compression spring 137, and communication between supply flow path 133 and connecting flow path 135 is blocked. As a result, the first fuel in supply passage 133 is not supplied to first needle valve 45, the first supply pressure acting on first needle valve 45 becomes lower than the first injection pressure, and injection of the first fuel by first needle valve 45 stops. At this time, by adjusting the opening of variable throttle valve 136 (the flow passage area of ​​connecting passage 135), it is possible to adjust the timing at which injection of the first fuel by first needle valve 45 stops.

[0087] As shown in FIGS. 10 and 11 , first, when second supply pump 42 is operated, the second fuel in second fuel supply path 44 is pressurized, and the second supply pressure of the high-pressure second fuel acts on second pressure-receiving surface 72b, moving piston 72B toward first fuel supply path 43. As a result, piston mechanism 47B stores a predetermined amount of second fuel in second reservoir 74. Next, when first supply pump 41 is operated, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases. Then, the first supply pressure of the first fuel in first fuel supply path 43 acts on first pressure-receiving surface 72a, moving piston 72B toward second fuel supply path 44. Then, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, also increases.

[0088] Then, at crank angle a21, when the first supply pressure of first fuel supply path 43 exceeds the first injection pressure of first needle valve 45, first needle valve 45 starts injecting the first fuel. At this time, when the second supply pressure of second fuel supply path 44 exceeds the second injection pressure of second needle valve 46, second needle valve 46 starts injecting the second fuel. Then, as described above, when first flow limiter 130 is activated and the first fuel is no longer supplied to first needle valve 45, at crank angle a22, the first supply pressure becomes lower than the first injection pressure of first needle valve 45, and first needle valve 45 ends injection of the first fuel.

[0089] At this time, if the opening of variable throttle valve 136 is adjusted to be large, the operation of first flow limiter 130 is delayed, and the timing at which injection of the first fuel by first needle valve 45 is stopped is delayed. On the other hand, if the opening of variable throttle valve 136 is adjusted to be small, the operation of first flow limiter 130 is advanced, and the timing at which injection of the first fuel by first needle valve 45 is stopped is advanced.

[0090] Then, at crank angle a23, when piston 72B reaches the closest position to second fuel supply path 44, communication path 120 connects discharge flow path 134 of first flow limiter 130 to first reservoir 73. The first fuel in first reservoir 73 then bypasses variable throttle valve 136 (first flow limiter 130) and is supplied to first needle valve 45. When the first supply pressure of first fuel supply path 43 exceeds the first injection pressure of first needle valve 45, first needle valve 45 resumes injection of the first fuel. When first supply pump 41 subsequently stops at crank angle a24, first needle valve 45 stops injecting the first fuel. When first supply pump 41 stops and piston 72B stops moving, second needle valve 46 terminates injection of the second fuel.

[0091] In the sixth embodiment, fuel injection device 17E has only the initial and final injection timing (crank angle ranges T11 and T12) of the first fuel by first needle valve 45 of the second fuel (crank angle range T2) by second needle valve 46. The injection end timing of the initial injection timing (crank angle range T11) of the first fuel by first needle valve 45 is adjustable. Therefore, fuel injection device 17E can improve the combustibility of the second fuel, which has poor ignition characteristics, by adjusting the injection end timing of the initial injection timing (crank angle range T11) of the first fuel in accordance with the ignition quality of the second fuel.

[0092] [Seventh embodiment] Fig. 12 is a schematic diagram showing the configuration of a fuel injection device of the seventh embodiment, and Fig. 13 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the above-mentioned fifth embodiment are given the same reference numerals and detailed explanations thereof will be omitted.

[0093] 12, fuel injection device 17F includes first supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, piston mechanism 47F, first flow limiter 110, and communication path 120. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, first needle valve 45, second needle valve 46, first flow limiter 110, and communication path 120 are the same as those in the fifth embodiment, and therefore description thereof will be omitted.

[0094] The piston mechanism 47F is substantially the same as the piston mechanism 47B of the third embodiment. That is, the piston mechanism 47F is provided between the first fuel supply path 43 and the second fuel supply path 44, and has a cylinder 71 and a piston 72B. The piston 72B has a rod portion 101 and a main body portion 102. The piston 72B has a first pressure-receiving surface 72a on the first fuel supply path 43 side of the main body portion 102, and a second pressure-receiving surface 72b on the second fuel supply path 44 side. The area of ​​the first pressure-receiving surface 72a of the piston 72B is smaller than the area of ​​the second pressure-receiving surface 72b.

[0095] In the piston mechanism 47F, the first pressure-receiving surface 72a of the piston 72B forms an inclined surface (preferably a helical shape). That is, the first pressure-receiving surface 72a is an inclined surface that is inclined relative to the radial direction of the piston 72B. The piston 72B is supported inside the cylinder 71 so as to be rotatable in the circumferential direction. A driving unit 140 is drivingly connected to the tip end of the rod portion 101 of the piston 72B. The driving of the driving unit 140 can be controlled by the control unit 56. The driving unit 140 rotates the piston 72B via the rod portion 101, and the rotation phase can be adjusted.

[0096] First fuel supply path 43 is provided with a first flow limiter 110 that limits the supply of the first fuel between piston mechanism 47F and first needle valve 45. Furthermore, communication path 120 communicates the downstream side and upstream side of first flow limiter 110 in first fuel supply path 43 at the end of the movement of piston 72B of piston mechanism 47F toward second fuel supply path 44. One end of communication path 120 is connected to discharge flow path 114 of first flow limiter 110, and the other end can be connected to first reservoir 73.

[0097] When first supply pump 41 is activated, high-pressure first fuel is supplied to first needle valve 45 through first flow limiter 110. When the first supply pressure of the first fuel exceeds the first injection pressure, first needle valve 45 injects the first fuel. When first flow limiter 110 is activated, the first fuel is not supplied to first needle valve 45, the first supply pressure acting on first needle valve 45 becomes lower than the first injection pressure, and injection of the first fuel by first needle valve 45 stops. Thereafter, when piston 72B reaches the closest position to second fuel supply path 44, communication path 120 communicates with first reservoir 73. Then, high-pressure first fuel is supplied to first needle valve 45 through communication path 120. When the first supply pressure of the first fuel exceeds the first injection pressure, first needle valve 45 again injects the first fuel. At this time, the timing at which re-injection of the first fuel by the first needle valve 45 starts can be adjusted by changing the rotational phase of piston 72B using drive unit 140 and adjusting the position of inclined first pressure-receiving surface 72a.

[0098] 12 and 13 , first, when second supply pump 42 is operated, the second fuel in second fuel supply path 44 is pressurized, and the second supply pressure of the high-pressure second fuel acts on second pressure-receiving surface 72b, moving piston 72B toward first fuel supply path 43. As a result, piston mechanism 47F stores a predetermined amount of second fuel in second storage portion 74. Next, when first supply pump 41 is operated, the pressure upstream of first needle valve 45, i.e., the pressure in first fuel supply path 43 downstream of check valves 81 and 83, increases. Then, the first supply pressure of the first fuel in first fuel supply path 43 acts on first pressure-receiving surface 72a, moving piston 72B toward second fuel supply path 44. Then, the pressure upstream of second needle valve 46, i.e., the pressure in second fuel supply path 44 downstream of check valve 84, also increases.

[0099] Then, at crank angle a21, when the first supply pressure of first fuel supply passage 43 exceeds the first injection pressure of first needle valve 45, first needle valve 45 starts injecting the first fuel. At this time, when the second supply pressure of second fuel supply passage 44 exceeds the second injection pressure of second needle valve 46, second needle valve 46 starts injecting the second fuel. Then, as described above, when first flow limiter 110 is activated and the first fuel is no longer supplied to first needle valve 45, at crank angle a22, the first supply pressure becomes lower than the first injection pressure of first needle valve 45, and first needle valve 45 ends injection of the first fuel.

[0100] Then, at crank angle a23, when piston 72B reaches the closest position to second fuel supply path 44, communication path 120 connects discharge flow path 114 of first flow limiter 110 to first reservoir 73. The first fuel in first reservoir 73 then bypasses orifice 116 (first flow limiter 110) and is supplied to first needle valve 45. When the first supply pressure of first fuel supply path 43 exceeds the first injection pressure of first needle valve 45, first needle valve 45 resumes injection of the first fuel. When first supply pump 41 subsequently stops at crank angle a24, first needle valve 45 stops injecting the first fuel. When first supply pump 41 stops and piston 72B stops moving, second needle valve 46 terminates injection of the second fuel.

[0101] At this time, if the rotational phase of piston 72B is changed and the position of inclined first pressure-receiving surface 72a is adjusted, the timing at which re-injection of the first fuel by first needle valve 45 is started can be adjusted. In other words, when the rotational phase of piston 72B is changed and the angle of first pressure-receiving surface 72a is in the position shown by the solid line in FIG. 12 , even if piston 72B reaches the closest point to second fuel supply path 44, communication path 120 does not communicate with first storage portion 73. On the other hand, when the rotational phase of piston 72B is changed and the angle of first pressure-receiving surface 72a is in the position shown by the two-dot chain line in FIG. 12 , when piston 72B reaches the closest point to second fuel supply path 44, communication path 120 communicates with first storage portion 73. Then, by changing the rotational phase of piston 72B and adjusting the angle of first pressure surface 72a between the solid line position in Figure 12 and the dashed double-dashed line position in Figure 12, it is possible to adjust the time at which communication path 120 communicates with first storage section 73 when piston 72B reaches the closest position to second fuel supply path 44.

[0102] In the seventh embodiment, fuel injection device 17F has first needle valve 45 injecting the first fuel (crank angle ranges T11 and T12) only at the beginning and end of second fuel injection (crank angle range T2) by second needle valve 46. Furthermore, the injection start timing of the final injection timing (crank angle range T12) of the first fuel by first needle valve 45 is adjustable. Therefore, fuel injection device 17E can improve the combustibility of the second fuel, which has poor ignition characteristics, by adjusting the injection start timing of the final injection timing (crank angle range T12) of the first fuel in accordance with the combustibility of the second fuel.

[0103] [Eighth embodiment] 14 is a schematic diagram showing the configuration of a fuel injection device according to an eighth embodiment. Note that members having the same functions as those in the fifth embodiment described above are given the same reference numerals, and detailed explanations thereof will be omitted.

[0104] 14, fuel injection device 17G includes fuel supply device 31, fuel supply path 32G, and fuel injection valve 33G. Fuel supply device 31 has first supply pump 41 and second supply pump 42. Fuel supply path 32G has first fuel supply path 43, second fuel supply path 44, and third fuel supply path 141. Fuel injection valve 33G has first needle valve 45, second needle valve 46, and third needle valve 142. Fuel injection device 17G also includes piston mechanism 47B, first flow limiter 110, communication path 120, and distributor valve 143. The first supply pump 41, the second supply pump 42, the first fuel supply path 43, the second fuel supply path 44, the first needle valve 45, the second needle valve 46, the piston mechanism 47B, the first flow limiter 110, and the communication path 120 are the same as those in the fifth embodiment, and therefore description thereof will be omitted.

[0105] Third fuel supply path 141 supplies the first fuel from first fuel supply path 43, bypassing piston mechanism 47B. Third needle valve 142 is connected to third fuel supply path 141. Distributor valve 143 adjusts the amount of first fuel supplied to piston mechanism 47B and the amount of first fuel supplied to third fuel supply path 141. The opening degree of distributor valve 143 is controlled by control unit 56.

[0106] That is, third fuel supply path 141 has an upstream end connected to first fuel supply path 43 between check valves 81, 83 and piston mechanism 47B. Third fuel supply path 141 has a downstream end connected to third needle valve 142. Third needle valve 142 has substantially the same configuration as first needle valve 45, and includes valve element 142a, biasing spring 142b, chamber 142c, fuel supply path 142d, and nozzle hole 142e. Third fuel supply path 141 has a downstream end connected to chamber 142c of third needle valve 142.

[0107] The distributor valve 143 is provided at a connection between the first fuel supply path 43 and the third fuel supply path 141. When the first supply pump 41 pressurizes the first fuel, the distributor valve 143 adjusts the amount of the pressurized first fuel supplied to the piston mechanism 47B through the first fuel supply path 43 and the amount of the pressurized first fuel supplied to the third fuel supply path 141.

[0108] For example, fuel injection device 17G uses distributor valve 143 to set the amount of first fuel supplied to piston mechanism 47B through first fuel supply path 43 to 100%, and to set the amount of first fuel supplied to third fuel supply path 141 to 0%. At this time, the first fuel is not supplied from third fuel supply path 141 to third needle valve 142, and therefore fuel injection device 17G of this embodiment operates in the same manner as fuel injection device 17D of the fifth embodiment.

[0109] Meanwhile, fuel injector 17G controls distributor valve 143 to set the amount of the first fuel supplied to piston mechanism 47B through first fuel supply path 43 to 0%, and to set the amount of the first fuel supplied to third fuel supply path 141 to 100%. At this time, the first fuel is not supplied from first fuel supply path 43 through piston mechanism 47B to first needle valve 45, but is supplied from third fuel supply path 141 to third needle valve 142. Therefore, fuel injector 17G injects the first fuel from third needle valve 142, does not inject the first fuel from first needle valve 45, and does not inject the second fuel from second needle valve 46.

[0110] Furthermore, fuel injector 17G controls distributor valve 143 so that 50% of the first fuel is supplied to piston mechanism 47B via first fuel supply path 43, and 50% is supplied to third fuel supply path 141. At this time, the first fuel is supplied from first fuel supply path 43 through piston mechanism 47B to first needle valve 45, and is also supplied from third fuel supply path 141 to third needle valve 142. Therefore, fuel injector 17G injects the first fuel from first needle valve 45 and third needle valve 142, and injects the second fuel from second needle valve 46.

[0111] In the eighth embodiment, the fuel injection device 17G can continuously change the ratio between the amount of the first fuel supplied to the piston mechanism 47B through the first fuel supply path 43 and the amount of the first fuel supplied to the third fuel supply path 141, using the distributor valve 143. Therefore, the fuel injection device 17G can continuously and gradually transition its operating state between an operating state in which only the first fuel is injected and an operating state in which both the first fuel and the second fuel are injected.

[0112] [Ninth embodiment] 15 is a schematic diagram showing the configuration of a fuel injection device according to a ninth embodiment. Note that members having the same functions as those in the eighth embodiment described above are given the same reference numerals and detailed description thereof will be omitted.

[0113] 15, fuel injection device 17H ​​includes fuel supply device 31, fuel supply path 32G, and fuel injection valve 33G. Fuel supply device 31 includes first supply pump 41 and second supply pump 42. Fuel supply path 32G includes first fuel supply path 43, second fuel supply path 44, and third fuel supply path 141. Fuel injection valve 33G includes first needle valve 45, second needle valve 46, and third needle valve 142. Fuel injection device 17H ​​also includes piston mechanism 47B, first flow limiter 130, communication path 120, and second flow limiter 150. First supply pump 41, second supply pump 42, first fuel supply path 43, second fuel supply path 44, third fuel supply path 141, first needle valve 45, second needle valve 46, third needle valve 142, piston mechanism 47B, first flow limiter 130, and communication path 120 are the same as those in the eighth embodiment, and therefore description thereof will be omitted.

[0114] First fuel supply path 43 is provided with a first flow limiter 130 that limits the supply of the first fuel between piston mechanism 47B and first needle valve 45. First flow limiter 130 has a housing 131, a valve body 132, a supply flow path 133, a discharge flow path 134, a connecting flow path 135, a variable throttle valve (first flow limiter adjustment valve) 136, and a compression spring 137.

[0115] Third fuel supply path 141 supplies the first fuel from first fuel supply path 43, bypassing piston mechanism 47B. Third fuel supply path 141 is connected to third needle valve 142. Third fuel supply path 141 is provided with second flow limiter 150, which limits the supply of the first fuel, between first flow limiter 130 and third needle valve 142. Second flow limiter 150 has housing 151, valve element 152, supply flow path 153, discharge flow path 154, connecting flow path 155, variable throttle valve (second flow limiter adjustment valve) 156, and compression spring 157. Second flow limiter 150 has a configuration substantially similar to first flow limiter 130. Note that second flow limiter 150 can operate independently, regardless of whether first flow limiter 130 is closed. That is, the supply flow path 133 of the first flow limiter 130 and the supply flow path 153 of the second flow limiter 150 can both be connected to the first fuel supply path 43 .

[0116] In the ninth embodiment, fuel injection device 17H ​​can adjust the amount of the first fuel injected from third needle valve 142 by adjusting the opening (flow path area) of variable throttle valve 156 in second flow limiter 150. That is, by adjusting the opening of variable throttle valve 136 in first flow limiter 130 and the opening of variable throttle valve 156 in second flow limiter 150, it is possible to continuously change the ratio between the amount of the first fuel supplied to piston mechanism 47B through first fuel supply path 43 and the amount of the first fuel supplied to third fuel supply path 141, similar to fuel injection device 17G of the eighth embodiment. Therefore, fuel injection device 17G can continuously and gradually transition between an operating state in which only the first fuel is injected and an operating state in which both the first fuel and the second fuel are injected.

[0117] [Tenth embodiment] Fig. 16 is a schematic diagram showing the configuration of a fuel injection device of the tenth embodiment, and Fig. 17 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed explanations will be omitted.

[0118] As shown in Fig. 16, the fuel injection device 17J includes a fuel supply device 31, a fuel supply path 32J, and a fuel injection valve 33J. The fuel supply device 31 includes a first supply pump 41 and a second supply pump 42. The fuel supply path 32J includes a first fuel supply path 43J and a second fuel supply path 44J. The fuel injection valve 33J includes one needle valve 160. The fuel injection device 17J also includes a piston mechanism 47. The first supply pump 41, the second supply pump 42, and the piston mechanism 47 are the same as those in the first embodiment, and therefore, description thereof will be omitted.

[0119] A downstream end of first fuel supply path 43J is connected to needle valve 160. A downstream end of second fuel supply path 44J is connected to needle valve 160. First fuel supply path 43J and second fuel supply path 44J join downstream of piston mechanism 47 and are then connected to needle valve 160. Piston mechanism 47 has a cylinder 71 and a piston 72. Piston mechanism 47 is provided between first fuel supply path 43J and second fuel supply path 44J. Piston mechanism 47 is provided with a first reservoir 73 on the first pressure-receiving surface 72a side that communicates with first fuel supply path 43J and stores the first fuel, and a second reservoir 74 on the second pressure-receiving surface 72b side that communicates with second fuel supply path 44J and stores the second fuel.

[0120] The first fuel supply path 43J has an upstream path 43a and a downstream path 43b. The second fuel supply path 44J has an upstream path 44a and a downstream path 44b. The downstream side of the upstream path 43a is connected to the first storage section 73, and the upstream side of the downstream path 43b is connected to the first storage section 73 and the downstream side is connected to the downstream path 44b. The downstream side of the upstream path 44a is connected to the second storage section 74, and the upstream side of the downstream path 44b is connected to the second storage section 74 and the downstream side is connected to the needle valve 160. That is, the downstream path 43b and the downstream path 44b join together and then communicate with the needle valve 160. The needle valve 160 has a valve body 160a, a biasing spring 160b, a chamber 160c, a fuel supply passage 160d, and a nozzle hole 160e. The needle valve 160 has substantially the same configuration as the first needle valve 45 and the second needle valve .

[0121] The piston mechanism 47 is connected to the needle valve 160 at the end of the movement of the piston 72 toward the second fuel supply path 44J. That is, the upstream end of the downstream path 43b of the first fuel supply path 43J is connected to the first storage portion 73 at a position farthest from one end of the cylinder 71. The piston mechanism 47 is configured such that the piston 72 moves from the first fuel supply path 43J side to the second fuel supply path 44J side. The upstream end of the downstream path 43b does not communicate with the first storage portion 73 when the piston 72 is located at the one end side. The other end of the downstream path 43b communicates with the first storage portion 73 when the piston 72 moves from the first fuel supply path 43J side to the second fuel supply path 44J side, becomes farthest from the one end, and reaches the closest position to the second fuel supply path 44J.

[0122] The first fuel supply path 43J is provided with a check valve 161 in the downstream path 43b disposed between the piston mechanism 47 and the needle valve 160. The check valve 161 prevents the first fuel from flowing back from the needle valve 160 toward the piston mechanism 47.

[0123] As shown in FIGS. 16 and 17 , when the second supply pump 42 is activated, the second fuel in the second fuel supply path 44J is pressurized. The second supply pressure of the high-pressure second fuel acts on the second pressure-receiving surface 72b, moving the piston 72 toward the first fuel supply path 43J. As a result, a predetermined amount of the second fuel is stored in the second storage portion 74 of the piston mechanism 47. However, in the second fuel supply path 44J, the first fuel from the previous injection remains in the downstream path 44b. At this time, the first storage portion 73 is not in communication with the downstream path 43b. Furthermore, the check valve 161 prevents the first fuel from flowing back from the needle valve 160 in the downstream path 43b toward the piston mechanism 47. Next, when the first supply pump 41 is operated, the first fuel in the upstream path 43a of the first fuel supply path 43J is pressurized, and the first supply pressure of the high-pressure first fuel acts on the first pressure-receiving surface 72a, moving the piston 72 toward the second fuel supply path 44J. As a result, the pressure in the downstream path 44b of the second fuel supply path 44J increases.

[0124] Then, at crank angle a21, when the second supply pressure of the second fuel supply path 44J exceeds the injection pressure of the needle valve 160, the needle valve 160 injects the first fuel remaining in the downstream path 44b downstream of the junction with the downstream path 43b. At crank angle a22, the needle valve 160 starts injecting the second fuel when injection of the first fuel remaining in the downstream path 44b ends. Then, at crank angle a23, when the piston 72 reaches the closest point to the second fuel supply path 44J, the needle valve 160 stops injecting the second fuel. At this time, the downstream path 43b of the first fuel supply path 43J communicates with the first reservoir 73. Then, the first fuel in the first reservoir 73 is supplied to the needle valve 160 through the downstream paths 43b and 44b, and the needle valve 160 starts injecting the first fuel again. Thereafter, when the first supply pump 41 stops at crank angle a24, the needle valve 160 stops injecting the first fuel. At this time, the first fuel remains in the downstream path 44b of the second fuel supply path 44J downstream of the junction with the downstream path 43b.

[0125] In the tenth embodiment, the fuel injection device 17J injects the first fuel in a predetermined crank angle range T11 using one needle valve 160, injects the second fuel in a predetermined crank angle range T2, and injects the first fuel in a predetermined crank angle range T12. That is, the injection timing of the first fuel (crank angle ranges T11 and T12) corresponds only to the beginning and end of the injection timing of the second fuel (crank angle range T2) using the needle valve 160. Therefore, the fuel injection device 17J injects the first fuel with good ignition properties before the second fuel with poor ignition properties, and ends injection of the first fuel with good ignition properties when the flame ignited by the first fuel with good ignition properties becomes the spark that ignites the second fuel with poor ignition properties. Furthermore, the fuel injection device 17J injects the first fuel with good ignition properties when the second fuel with poor ignition properties has finished burning, thereby completely burning the second fuel with poor ignition properties. As a result, the fuel injection device 17J can reduce the injection amount of the first fuel and improve the combustibility.

[0126] [Eleventh embodiment] 18 is a schematic diagram showing the configuration of a fuel injection device according to an eleventh embodiment. Note that members having the same functions as those in the third and tenth embodiments described above are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0127] As shown in FIG. 18, fuel injection device 17K includes fuel supply device 31, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31 includes first supply pump 41 and second supply pump 42. Fuel supply path 32J includes first fuel supply path 43J and second fuel supply path 44J. Fuel injection valve 33J includes one needle valve 160. Fuel injection device 17J also includes piston mechanism 47B. First supply pump 41, second supply pump 42, first fuel supply path 43J, second fuel supply path 44J, and needle valve 160 are the same as those in the tenth embodiment, and piston mechanism 47B is the same as those in the third embodiment, so description thereof will be omitted.

[0128] First fuel supply path 43J and second fuel supply path 44J join downstream of piston mechanism 47B and are then connected to needle valve 160. Piston mechanism 47B has a cylinder 71 and a piston 72B, and is provided between first fuel supply path 43J and second fuel supply path 44J. Piston mechanism 47B is provided with a first reservoir 73 on the first pressure-receiving surface 72a side that communicates with first fuel supply path 43J and stores the first fuel, and a second reservoir 74 on the second pressure-receiving surface 72b side that communicates with second fuel supply path 44J and stores the second fuel. In the piston mechanism 47B, 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 43J via the first storage portion 73 is higher than the second supply pressure acting on the second fuel supply path 44J via the second storage portion 74.

[0129] The piston mechanism 47B is connected to the needle valve 160 at the end of the movement of the piston 72B toward the second fuel supply path 44J. That is, the upstream end of the downstream path 43b of the first fuel supply path 43J is connected to the first storage portion 73 at a position farthest from one end of the cylinder 71. The piston mechanism 47B is connected to the first storage portion 73 when the piston 72B moves from the first fuel supply path 43J side to the second fuel supply path 44J side. The upstream end of the downstream path 43b does not communicate with the first storage portion 73 when the piston 72B is located at the one end side. The other end of the downstream path 43b communicates with the first storage portion 73 when the piston 72B moves from the first fuel supply path 43J side to the second fuel supply path 44J side, becomes farthest from the one end, and reaches the closest position to the second fuel supply path 44J. Furthermore, the seal passage 97 connects the first fuel supply passage 43J and the needle valve 160. The seal passage 97 supplies the first fuel in the first fuel supply passage 43J to the sliding seal portion 160f of the valve body 160a. The seal passage 97 is subjected to the first supply pressure of the first fuel in the first fuel supply passage 43J.

[0130] The operation of the fuel injection device 17K is substantially the same as that of the fuel injection device 17J of the tenth embodiment, and therefore a description thereof will be omitted. However, in the fuel injection device 17K of the eleventh embodiment, the piston mechanism 47B makes the first supply pressure acting on the first fuel supply path 43J higher than the second supply pressure acting on the second fuel supply path 44J. Therefore, the check valve 161 provided in the downstream path 43b is not required.

[0131] [Twelfth embodiment] 19 is a schematic diagram showing the configuration of a fuel injection device according to a twelfth embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0132] As shown in Fig. 19, fuel injection device 17L includes fuel supply device 31, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31 includes first supply pump 41 and second supply pump 42. Fuel supply path 32J includes first fuel supply path 43J and second fuel supply path 44J. Fuel injection valve 33J includes one needle valve 160. Fuel injection device 17L also includes piston mechanism 47. The first supply pump 41, second supply pump 42, first fuel supply path 43J, second fuel supply path 44J, needle valve 160, and piston mechanism 47 are the same as those in the tenth embodiment, and therefore description thereof will be omitted.

[0133] The first fuel supply path 43J is provided with a bypass path 170 that bypasses the piston mechanism 47. The bypass path 170 has an upstream end connected to the upstream path 43a and a downstream end connected to the downstream path 43b. The bypass path 170 is provided with a throttle valve (flow rate adjustment valve) 171 that adjusts the supply amount of the first fuel. The throttle valve 171 may be a variable throttle valve.

[0134] When the second supply pump 42 is operated, the piston 72 moves toward the first fuel supply path 43J, and a predetermined amount of the second fuel is stored in the second reservoir 74. When the first supply pump 41 is operated, the piston 72 moves toward the second fuel supply path 44J. When the second supply pressure of the second fuel supply path 44J exceeds the injection pressure of the needle valve 160, the needle valve 160 injects the first fuel remaining in the downstream path 44b downstream of the junction with the downstream path 43b. When the injection of the first fuel remaining in the downstream path 44b is completed, the needle valve 160 starts injecting the second fuel. At this time, the first fuel in the first fuel supply path 43J flows through the throttle valve 171 of the bypass path 170 to the downstream path 43b and is supplied to the needle valve 160. Therefore, the needle valve 160 simultaneously injects the second fuel and a small amount of the first fuel. When the piston 72 reaches the closest position to the second fuel supply path 44J, the needle valve 160 stops injecting the second fuel and restarts injecting the first fuel. After that, when the first supply pump 41 stops, the needle valve 160 stops injecting the first fuel.

[0135] In the twelfth embodiment, the fuel injection device 17L injects a small amount of the first fuel while the needle valve 160 is injecting the second fuel. Therefore, by injecting a small amount of the first fuel, which has good ignition properties, while injecting the second fuel, which has poor ignition properties, the second fuel, which has poor ignition properties, is completely combusted.

[0136] [Thirteenth embodiment] 20 is a schematic diagram showing the configuration of a fuel injection device according to a thirteenth embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0137] As shown in FIG. 20 , the fuel injection device 17M includes a fuel supply device 31, a fuel supply path 32J, and a fuel injection valve 33J. The fuel supply device 31 includes a first supply pump 41 and a second supply pump 42. The fuel supply path 32J includes a first fuel supply path 43J and a second fuel supply path 44J. The fuel injection valve 33J includes a needle valve 160. The fuel injection device 17M also includes a piston mechanism 47 and a first flow limiter 110. The first supply pump 41, the second supply pump 42, the first fuel supply path 43J, the second fuel supply path 44J, the needle valve 160, and the piston mechanism 47 are the same as those in the tenth embodiment, and the first flow limiter 110 is the same as those in the fourth embodiment, so a description thereof will be omitted.

[0138] The first fuel supply path 43J is provided with a detour path 170 that bypasses the piston mechanism 47. The detour path 170 has an upstream end connected to the upstream path 43a and a downstream end connected to the downstream path 43b. The detour path 170 is provided with a first flow limiter 110 that adjusts the supply amount of the first fuel.

[0139] When the second supply pump 42 is operated, the piston 72 moves toward the first fuel supply path 43J, and a predetermined amount of the second fuel is stored in the second reservoir 74. When the first supply pump 41 is operated, the piston 72 moves toward the second fuel supply path 44J. When the second supply pressure of the second fuel supply path 44J exceeds the injection pressure of the needle valve 160, the needle valve 160 injects the first fuel remaining in the downstream path 44b downstream of the junction with the downstream path 43b. When the injection of the first fuel remaining in the downstream path 44b is completed, the needle valve 160 starts injecting the second fuel. At this time, the first fuel in the first fuel supply path 43J flows through the first flow limiter 110 of the bypass path 170 to the downstream path 43b and is supplied to the needle valve 160. Therefore, the needle valve 160 simultaneously injects the second fuel and a small amount of the first fuel. When the piston 72 reaches the closest position to the second fuel supply path 44J, the needle valve 160 stops injecting the second fuel and restarts injecting the first fuel. After that, when the first supply pump 41 stops, the needle valve 160 stops injecting the first fuel.

[0140] In the thirteenth embodiment, the fuel injection device 17L injects a small amount of the first fuel while the needle valve 160 is injecting the second fuel. Therefore, by injecting the first fuel with good ignition properties while injecting the second fuel with poor ignition properties, the second fuel with poor ignition properties is completely combusted.

[0141] [Fourteenth embodiment] Fig. 21 is a schematic diagram showing the configuration of a fuel injection device of the fourteenth embodiment, and Fig. 22 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed explanations will be omitted.

[0142] As shown in FIG. 21 , the fuel injection device 17N includes a fuel supply device 31N, a fuel supply path 32J, and a fuel injection valve 33J. The fuel supply device 31N has a first supply pump 41 and a residual pressure adjustment valve 180. The fuel supply path 32J has a first fuel supply path 43J and a second fuel supply path 44J. The fuel injection valve 33J has one needle valve 160. The fuel injection device 17N also includes a piston mechanism 47. The first supply pump 41, the first fuel supply path 43J, the second fuel supply path 44J, and the piston mechanism 47 are the same as in the first embodiment, and the needle valve 160 is the same as in the tenth embodiment, so description thereof will be omitted.

[0143] The first supply pump 41 is similar to that in the first embodiment and pressurizes the first fuel in the first fuel supply path 43J to a predetermined pressure (e.g., 80 MPa). The first fuel supply path 43J is provided with a check valve 81 between a connection portion of the first supply pump 41 and a connection portion of the piston mechanism 47. The first fuel supply path 43J is provided with a return path 82 that bypasses the check valve 81, and the return path 82 is provided with a check valve 83. The check valve 83 functions as a pressure equalizing valve. The first fuel supply path 43J is also provided with a pressure adjustment path 181 that bypasses the check valve 81 and the return path 82 (check valve 83), and the pressure adjustment path 181 is provided with a residual pressure adjustment valve 180. The opening and closing of the residual pressure adjustment valve 180 can be controlled by the control unit 56. The residual pressure adjustment valve 180 reduces the first supply pressure of the first fuel acting on the piston mechanism 47 by discharging the first fuel in the first fuel supply path 43J downstream of the check valves 81, 83 to the first fuel supply path 43J upstream of the check valves 81, 83.

[0144] 21 and 22, when the first supply pump 41 is operated, the first supply pressure of the first fuel increases and exceeds the injection pressure in the crank angle range from crank angle a31 to crank angle a32, causing the needle valve 160 to inject the first fuel and the second fuel. When the first supply pump 41 is stopped, the first supply pressure of the first fuel decreases at crank angle a32 and remains constant up to crank angle a33. At this time, the first supply pressure of the first fuel downstream of the check valve 81 is, for example, 20 MPa, the first supply pressure of the first fuel upstream of the check valve 81 is, for example, 1 MPa, and the second supply pressure of the second fuel downstream of the check valve 85 is, for example, 15 MPa.

[0145] Residual pressure regulating valve 180 is opened in crank angle range T31 from crank angle a33 to crank angle a34. As a result, the first fuel in first fuel supply path 43J downstream of check valves 81 and 83 is discharged through pressure adjustment path 181 to first fuel supply path 43J upstream of check valves 81 and 83. Here, because the first supply pressure of piston mechanism 47 decreases relative to the second supply pressure, piston 72 moves from the second fuel supply path 44J side to the first fuel supply path 43J side, increasing the volume of second storage portion 74 and storing a predetermined amount of second fuel in second storage portion 74. Therefore, when first supply pump 41 is subsequently operated, needle valve 160 can inject the first fuel and the second fuel.

[0146] In a fuel injection device 17N of the fourteenth embodiment, a fuel supply device 31N does not have a second supply pump that pressurizes the second fuel because the fuel supply device 31N has a first supply pump 41 and a residual pressure adjustment valve 180. This simplifies the fuel supply device 31N.

[0147] [Fifteenth embodiment] 23 is a schematic diagram showing the configuration of a fuel injection device according to a fifteenth embodiment. Note that members having the same functions as those in the fifth embodiment described above are given the same reference numerals and detailed description thereof will be omitted.

[0148] 23, fuel injection device 17P includes first supply pump 41, second supply pump 42, first fuel supply path 43J, second fuel supply path 44J, first needle valve 45, second needle valve 46, piston mechanism 47B, first flow limiter 110, second flow limiter 190, and communication paths 121 and 122. First supply pump 41, second supply pump 42, first fuel supply path 43J, second fuel supply path 44J, first needle valve 45, second needle valve 46, piston mechanism 47B, and first flow limiter 110 are the same as those in the fifth embodiment, and therefore description thereof will be omitted.

[0149] First fuel supply path 43J is provided with a first flow limiter 110 and a second flow limiter 190 that limit the supply of the first fuel between piston mechanism 47B and first needle valve 45. First flow limiter 110 has a housing 111, a valve element 112, a supply flow path 113, a discharge flow path 114, a connecting flow path 115, an orifice 116, and a compression spring 117. Second flow limiter 190 has a housing 191, a valve element 192, a supply flow path 193, a discharge flow path 194, a connecting flow path 195, an orifice 196, and a compression spring 197.

[0150] Communication path 121 communicates first reservoir 73 with supply flow path 193 of second flow limiter 190 during the final stage of movement of piston 72B of piston mechanism 47B toward second fuel supply path 44J. Communication path 122 communicates discharge flow path 194 of second flow limiter 190 with a portion of first fuel supply path 43J between first flow limiter 110 and first needle valve 45. In piston mechanism 47B, piston 72B moves from the first fuel supply path 43J side to the second fuel supply path 44J side. One end of communication path 121 does not communicate with first reservoir 73 when piston 72B is located on the first fuel supply path 43J side. Furthermore, one end of the communication path 121 communicates with the first reservoir 73 when the piston 72B moves from the first fuel supply path 43J side to the second fuel supply path 44J side and reaches the closest position to the second fuel supply path 44J side.

[0151] In the fifteenth embodiment, the basic operation of fuel injection device 17P during fuel injection is the same as that of fuel injection device 17D of the fifth embodiment. However, in the fifteenth embodiment, piston 72B moves toward second fuel supply path 44J, and second flow limiter 190 is provided in the path where communication path 121 communicates with first needle valve 45, so that the injection amount of the second injection of the first fuel is also limited. Therefore, fuel injection device 17P can reduce the injection amount of the first fuel and improve combustibility. Furthermore, the injection amount of the combined fuel of the first fuel and the second fuel can be adjusted according to the operation amount of second supply pump 42.

[0152] [16th embodiment] 24 is a schematic diagram showing the configuration of a fuel injection device according to a sixteenth embodiment. Members having the same functions as those in the above-described fourteenth embodiment are given the same reference numerals, and detailed explanations thereof will be omitted.

[0153] As shown in Fig. 24, fuel injection device 17Q includes fuel supply device 31Q, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31Q has a first supply pump 41. Fuel supply path 32J has a first fuel supply path 43J and a second fuel supply path 44J. Fuel injection valve 33J has one needle valve 160. Fuel injection device 17Q also includes a piston mechanism 47B. The first supply pump 41, first fuel supply path 43J, second fuel supply path 44J, and needle valve 160 are the same as those in the fourteenth embodiment, and the piston mechanism 47B is the same as those in the third embodiment, so description thereof will be omitted.

[0154] The first supply pump 41 is similar to that in the first embodiment and pressurizes the first fuel in the first fuel supply path 43J to a predetermined pressure (e.g., 80 MPa). The first fuel supply path 43J is provided with a check valve 81 between the connection portion of the first supply pump 41 and the connection portion of the piston mechanism 47B. The first fuel supply path 43J is provided with a return path 82 that bypasses the check valve 81, and the return path 82 is provided with a check valve 83. The check valve 83 functions as a pressure equalizing valve. An opening pressure (e.g., 16 MPa) is set for the check valve 83 from the piston mechanism 47B side to the first supply pump 41 side.

[0155] A check valve 85 is provided in the second fuel supply path 44J between the second fuel supply source 60 and the connecting portion of the piston mechanism 47B. The check valve 85 prevents backflow of the second fuel from the piston mechanism 47B side to the second fuel supply source 60 side. An opening pressure (e.g., 15 MPa) from the second fuel supply source 60 side to the piston mechanism 47B side of the check valve 85 is set. In other words, the opening pressure of the check valve 85 is set lower than the opening pressure of the check valve 83 of the first fuel supply path 43J. The piston mechanism 47B has a cylinder 71 and a piston 72B. The piston 72B is a rod-equipped piston and has a rod portion 101 with a small diameter and a main body portion 102 with a large diameter. The area of ​​the first pressure-receiving surface 72a of the piston 72B is smaller than the area of ​​the second pressure-receiving surface 72b.

[0156] When the first supply pump 41 is operated, the first supply pressure of the first fuel increases and exceeds the injection pressure, causing the needle valve 160 to inject the first and second fuels. When the first supply pump 41 is stopped, the first supply pressure of the first fuel decreases. At this time, the residual pressure of the first fuel downstream of the check valve 83 is, for example, 16 MPa, and the second supply pressure of the second fuel downstream of the check valve 85 is, for example, 15 MPa. In the piston mechanism 47B, the second supply pressure (15 MPa) of the second fuel acts on the second reservoir 74, and the pressure of the first fuel in the first fuel supply path 43J is increased due to the area difference between the second pressure-receiving surface 72b and the first pressure-receiving surface 72a, and the pressure becomes equal to or exceeds the opening pressure (16 MPa) of the check valve 83. Therefore, the first fuel in the first fuel supply path 43J is returned through the check valve 83, and the piston 72B moves toward the first fuel supply path 43J.

[0157] In piston mechanism 47B, when piston 72B moves from the second fuel supply path 44J side to the first fuel supply path 43J side, the volume of second storage portion 74 increases, and a predetermined amount of second fuel is stored in second storage portion 74. At this time, the first fuel in first fuel supply path 43J is pressurized, and check valve 83 is opened to return the first fuel. Therefore, when first supply pump 41 is subsequently operated, needle valve 160 can inject the first fuel and the second fuel.

[0158] In the fuel injection device 17Q of the sixteenth embodiment, the area of ​​the first pressure-receiving surface 72a of the piston 72B on the side of the first fuel supply path 43J is reduced, so that the second fuel can flow into the second storage portion 74 by itself during the period when fuel injection is not being performed, thereby eliminating the need for the residual pressure adjustment valve 180 used in the fourteenth embodiment, thereby simplifying the fuel supply device 31N.

[0159] [Modification of piston mechanism] FIG. 25 is a schematic diagram showing a modified example of the piston mechanism.

[0160] As shown in FIG. 25, the piston mechanism 47C is provided between the first fuel supply path 43 and the second fuel supply path 44 (see FIG. 5). The piston mechanism 47C has a cylindrical cylinder 71C and a columnar piston 72C. The cylinder 71C has a rod portion 106 that extends inward (downward in FIG. 25) on the first fuel supply path 43 side (upper side in FIG. 25). The piston 72C has a main body portion 107, and a hole portion 107a is formed on the first fuel supply path 43 side (upper side in FIG. 25). The piston 72C is disposed inside the cylinder 71C and supported so as to be movable in the axial direction. The main body portion 107 of the piston 72C is supported by the cylinder 71C, and the rod portion 106 of the cylinder 71C is fitted into the hole portion 107a so as to be movable in the axial direction. In the piston mechanism 47C, a sliding portion 108 is formed between a rod portion 106 of the cylinder 71C and a hole portion 107a of the piston 72C. One end of a drain path 109 is in communication with the sliding portion 108. The sliding portion 108 is in communication with the first reservoir 73, so the first fuel leaks from the sliding portion 108. The drain path 109 discharges and recovers the first fuel that has leaked from the sliding portion 108 to the outside.

[0161] Piston 72C has a first pressure-receiving surface 72a formed on the first fuel supply path 43 side of main body 107, and a second pressure-receiving surface 72b formed on the second fuel supply path 44 side. A first supply pressure from first fuel supply path 43 acts on piston 72C's first pressure-receiving surface 72a, and a second supply pressure from second fuel supply path 44 acts on piston 72C's second pressure-receiving surface 72b. In piston mechanism 47C, piston 72C reciprocates due to the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel. In piston 72C, the area of ​​first pressure-receiving surface 72a is smaller than the area of ​​second pressure-receiving surface 72b. Piston mechanism 47C has a first reservoir 73 on the first pressure-receiving surface 72a side that communicates with first fuel supply path 43, and a second reservoir 74 on the second pressure-receiving surface 72b side that communicates with second fuel supply path 44. In piston mechanism 47C, due to the area difference between first pressure-receiving surface 72a and second pressure-receiving surface 72b, the first supply pressure acting on first fuel supply path 43 via first storage section 73 is higher than the second supply pressure acting on second fuel supply path 44 via second storage section 74.

[0162] Other configurations and operations of the piston mechanism 47C are similar to those of the piston mechanism 47B of the third embodiment, and therefore description thereof will be omitted.

[0163] [17th embodiment] 26 is a schematic diagram showing the configuration of a fuel injection device according to a seventeenth embodiment. Members having the same functions as those in the eleventh embodiment described above are given the same reference numerals, and detailed explanations thereof will be omitted.

[0164] 26, fuel injection device 17R includes fuel supply device 31, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31 has first supply pump 41 and second supply pump 42. Fuel supply path 32J has first fuel supply path 43J and second fuel supply path 44J. Fuel injection valve 33J has one needle valve 160. Fuel injection device 17R also includes piston mechanism 47B.

[0165] First fuel supply path 43J is provided with check valve 81 between the connection portion of first supply pump 41 and the connection portion of piston mechanism 47B, and with check valve 87 located upstream of the connection portion of first supply pump 41. First fuel supply path 43J is also provided with return path 82 that bypasses check valves 81, 87 and first supply pump 41, and return path 82 is provided with cut valve 88 and pressure equalizing valve 89. Cut valve 88 has a cut function linked to the operation of check valve 81, and is opened when check valve 81 is closed and closed when check valve 81 is open. Pressure equalizing valve 89 is located upstream of cut valve 88 and opens and closes so that the pressure on the upstream side and the pressure on the downstream side of first fuel supply path 43J are equalized.

[0166] First fuel supply path 43J and second fuel supply path 44J join downstream of piston mechanism 47B and are then connected to needle valve 160. Piston mechanism 47B is provided between first fuel supply path 43J and second fuel supply path 44J. Piston mechanism 47B is provided with a first reservoir 73 on the first pressure-receiving surface 72a side that communicates with first fuel supply path 43J and stores the first fuel, and a second reservoir 74 on the second pressure-receiving surface 72b side that communicates with second fuel supply path 44J and stores the second fuel. Due to the area difference between first pressure-receiving surface 72a and second pressure-receiving surface 72b, piston mechanism 47B causes the first supply pressure acting on first fuel supply path 43J via first reservoir 73 to be higher than the second supply pressure acting on second fuel supply path 44J via second reservoir 74.

[0167] The operation of the fuel injection device 17R is almost the same as that of the fuel injection device 17K of the eleventh embodiment, and therefore a description thereof will be omitted. However, the fuel injection device 17R of the seventeenth embodiment is provided with a cut valve 88 having a cut function linked to the operation of the check valve 81 in the return path 82, and therefore can appropriately supply and return the first fuel to the piston mechanism 47B.

[0168] [Eighteenth embodiment] Fig. 27 is a schematic diagram showing the configuration of a fuel injection device of the 18th embodiment, and Fig. 28 is a time chart showing the operation of the fuel injection device. Note that members having the same functions as those in the above-mentioned 16th embodiment are given the same reference numerals and detailed explanations thereof will be omitted.

[0169] 27, fuel injection device 17S includes fuel supply device 31Q, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31Q has first supply pump 41. Fuel supply path 32J has first fuel supply path 43J and second fuel supply path 44J. Fuel injection valve 33J has one needle valve 160. Fuel injection device 17S also includes piston mechanism 47S.

[0170] The first supply pump 41 is the same as in the first embodiment. In the first fuel supply path 43J, a check valve 81 is provided between the connection portion of the first supply pump 41 and the connection portion of the piston mechanism 47S, and a check valve 87 is provided upstream of the connection portion of the first supply pump 41. In addition, the first fuel supply path 43J is provided with a return path 82 that bypasses the check valves 81, 87 and the first supply pump 41, and the return path 82 is provided with a cut valve 88 and a pressure adjustment valve 211. The return path 82 is connected to the first fuel supply paths 201, 202 of the other cylinders between the cut valve 88 and the pressure adjustment valve 211. The cut valve 88 has a cut function linked to the operation of the check valve 81, and is opened when the check valve 81 is closed and closed when the check valve 81 is open. The pressure regulating valve 211 regulates the pressure in the return passage 82 in all cylinders to be equal to or higher than the pressure of the second fuel in the second fuel supply passage 44J.

[0171] Piston mechanism 47S has a cylinder 71S and a piston 72S. Piston 72S is a rod-equipped piston and has a small-diameter rod portion 101 and a main body portion 102. Piston mechanism 47S has a bulge portion 102a between rod portion 101 and main body portion 102. Meanwhile, cylinder 71S has a seat portion 102b at its upper end portion, with a reduced inner diameter. When piston 72S moves upward inside cylinder 71S, piston mechanism 47S causes bulge portion 102a to abut against seat portion 102b, thereby blocking communication between first fuel supply path 43J and first reservoir 73.

[0172] One end of cylinder 71S in the movement direction of piston 72S communicates with first fuel supply path 43J, and the other end of piston 72S in the movement direction communicates with second fuel supply path 44J. Piston 72S has a first pressure-receiving surface 72a formed on the first fuel supply path 43J side of main body 102, and a second pressure-receiving surface 72b formed on the second fuel supply path 44J side. A first supply pressure of first fuel supply path 43J acts on piston 72S's first pressure-receiving surface 72a, and a second supply pressure of second fuel supply path 44J acts on piston 72S's second pressure-receiving surface 72b. Piston mechanism 47S reciprocates piston 72S due to a pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel.

[0173] In piston 72S, the area of ​​first pressure-receiving surface 72a is smaller than the area of ​​second pressure-receiving surface 72b. Piston mechanism 47S is provided with a first reservoir 73 communicating with first fuel supply path 43J on the side of first pressure-receiving surface 72a, and a second reservoir 74 communicating with second fuel supply path 44J on the side of second pressure-receiving surface 72b. Due to the difference in area between first pressure-receiving surface 72a and second pressure-receiving surface 72b, in piston mechanism 47S, the first supply pressure acting on first fuel supply path 43J via first reservoir 73 becomes higher than the second supply pressure acting on second fuel supply path 44J via second reservoir 74.

[0174] The seal path 97 connects the first fuel supply path 43J and the needle valve 160. The seal path 97 supplies the first fuel in the first fuel supply path 43J to the sliding seal portion 160f of the valve body 160a. The first supply pressure of the first fuel in the first fuel supply path 43J acts on the seal path 97. The seal path 97 is also provided with a check valve 212 and a pressure accumulator container 213. The check valve 212 prevents the first fuel from flowing back from the needle valve 160 toward the first fuel supply path 43J. The pressure accumulator container 213 stores the first fuel when the pressure of the first fuel in the first fuel supply path 43J increases and the check valve 212 opens, and accumulates the first fuel under pressure.

[0175] 27 and 28, when the first supply pump 41 operates at crank angle a41, the first supply pressure of the first fuel in the first fuel supply path 43J increases, the first supply pressure acts on the piston 72S, the piston 72S descends, and the lift amount (upper solid line in FIG. 28) decreases. Then, the bulging portion 102a of the piston 72S separates from the seat portion 102b, and the first fuel supply path 43J communicates with the first storage portion 73. The first fuel in the first fuel supply path 43J is supplied to the first storage portion 73, and the pressure P1 (middle solid line in FIG. 28) increases (solid line in FIG. 28), the piston 72S further descends, and the second fuel in the second storage portion 74 is pressurized, and the pressure P2 (upper dotted line in FIG. 28) increases. At this time, the first fuel in the first fuel supply path 43J, whose pressure has increased, opens the check valve 212 from the seal path 97 and accumulates in the pressure accumulator vessel 213, causing the pressure P3 (two-dot chain line in FIG. 28) to rise.

[0176] From crank angle a42 to crank angle a43, the lift amount of needle valve 160 (lower solid line in FIG. 28 ) increases, and when second supply pressure P2 of the second fuel in second reservoir 74 exceeds the injection pressure of needle valve 160, needle valve 160 is opened, and the second fuel is injected from nozzle hole 160e of needle valve 160. After that, when first supply pump 41 stops, pressures P1 and P2 decrease, and from crank angle a44 to crank angle a45, the needle valve closes, and injection ends. After that, from crank angle a45 to crank angle a46, the pressure of the first fuel in first fuel supply path 43J is increased due to the area difference between second pressure-receiving surface 72b and first pressure-receiving surface 72a of piston mechanism 47S, check valve 81 closes, cut valve 88 opens, and the first fuel in first fuel supply path 43J is returned through pressure adjustment valve 211, and piston 72S moves toward first fuel supply path 43J. The pressure P3 of the first fuel accumulated in the pressure accumulator vessel 213 is always maintained at a pressure higher than the pressure of the second fuel, and is supplied to the sliding seal portion 160f of the needle valve 160, thereby maintaining the lubricity of the sliding portion of the valve body 160a and preventing the second fuel from flowing out to the drain.

[0177] In piston mechanism 47S, when piston 72S moves from the second fuel supply path 44J side to the first fuel supply path 43J side, the volume of second storage portion 74 increases, and a predetermined amount of second fuel is stored in second storage portion 74. When piston 72S reaches first fuel supply path 43J side at crank angle a46, bulging portion 102a of piston 72S abuts against seat portion 102b, and communication between first fuel supply path 43J and first storage portion 73 is blocked. Then, first fuel pressure P1 of the first fuel in first storage portion 73 (solid line in the middle of FIG. 28 ) and second pressure P2 of the second fuel in second storage portion 74 (dotted line in the middle of FIG. 28 ) are maintained slightly higher than first fuel pressure P4 of the first fuel in first fuel supply path 43J (chain line in FIG. 28 ).

[0178] In the fuel injection device 17S of the 18th embodiment, by reducing the area of ​​the first pressure-receiving surface 72a on the first fuel supply path 43J side of the piston 72B, the second fuel can flow into the second storage section 74 by itself during the period when fuel injection is not being performed, thereby simplifying the fuel supply device 31Q.

[0179] [19th embodiment] 29 is a schematic diagram showing the configuration of a fuel injection device according to a 19th embodiment. Note that members having the same functions as those in the above-described 18th embodiment are given the same reference numerals and detailed description thereof will be omitted.

[0180] 29, fuel injection device 17T includes fuel supply device 31Q, fuel supply path 32J, and fuel injection valve 33J. Fuel supply device 31Q has a first supply pump 41. Fuel supply path 32J has a first fuel supply path 43J and a second fuel supply path 44J. Fuel injection valve 33J has one needle valve 160. Fuel injection device 17Q also includes a piston mechanism 47S.

[0181] The first supply pump 41 is the same as in the first embodiment. The first fuel supply path 43J is provided with a check valve 81 between the connection portion of the first supply pump 41 and the connection portion of the piston mechanism 47S, and with a check valve 87 upstream of the connection portion of the first supply pump 41. The first fuel supply path 43J is also provided with a return path 82 that bypasses the check valves 81, 87 and the first supply pump 41, and the return path 82 is provided with a cut valve 88 and a pressure adjustment valve 211. The return path 82 is connected to the first fuel supply paths 201, 202 of the other cylinders between the cut valve 88 and the pressure adjustment valve 211. The return path 82 is also connected to a boost pump 215 via a pressurization path 214. The boost pump 215 is driven by a motor to supply the first fuel from the pressurization path 214 to the return path 82.

[0182] A check valve 85 is provided in the second fuel supply path 44J between the connection portion between the second fuel supply source 60 and the piston mechanism 47S. Furthermore, a nitrogen supply source 217 is connected to the second fuel supply path 44J between the second fuel supply source 60 and the check valve 85 via a switching valve 216. The switching valve 216 switches between the supply of the second fuel from the second fuel supply source 60 and the supply of nitrogen (N2) from the nitrogen supply source 217 to the second fuel supply path 44J. In this case, the pressure of the nitrogen from the nitrogen supply source 217 is lower than the pressure of the second fuel from the second fuel supply source 60.

[0183] Furthermore, second fuel supply path 44J is connected to drain valve 219 between piston mechanism 47S and check valve 85 via drain passage 218. The pressure-receiving area on which pressure upstream of check valve 85 in second fuel supply path 44J acts in a direction to close drain valve 219 is sufficiently larger than the pressure-receiving area on which pressure acts from drain passage 218 downstream of check valve 85 in a direction to open drain valve 219. Therefore, drain valve 219 will not open even if high pressure is applied in the opening direction while needle valve 160 is injecting the second fuel. Furthermore, when nitrogen is supplied to second fuel supply path 44J, the pressure in second fuel supply path 44J decreases and drain valve 219 opens.

[0184] When the boost pump 215 is driven, the first fuel is supplied to the pressurizing path 214 and the return path 82, and the first fuel at a pressure (e.g., 8 MPa) adjusted by the pressure regulating valve 211 is supplied to the first fuel supply path 43J. Here, when the second fuel at a predetermined pressure (e.g., 8 MPa) is supplied to the second fuel supply path 44J, the drain valve 219 closes. Then, the piston 72S moves toward the first fuel supply path 43J due to the area difference between the second pressure-receiving surface 72b and the first pressure-receiving surface 72a of the piston mechanism 47S, and a predetermined amount of the second fuel is stored in the second storage portion 74. Note that the first supply pump 41 may be operated instead of the boost pump 215.

[0185] Furthermore, with boost pump 215 and first supply pump 41 not operating, the high pressure of the first fuel is not acting on first pressure-receiving surface 72a of piston 72S in piston mechanism 47S. Here, switching valve 216 is operated to supply nitrogen from nitrogen supply source 217 to second fuel supply path 44J. The pressure of nitrogen from nitrogen supply source 217 is lower than the pressure of the second fuel in second fuel supply path 44J. Therefore, drain valve 219 is opened, and the second fuel in second storage portion 74 is discharged from drain valve 219 to the outside and cleaned. At this time, because the pressure of the first fuel in first fuel supply path 43J is still high, piston 72S moves to the dead center on the second fuel supply path 44J side, and the second fuel remaining in second storage portion 74 is pushed out. Since the pressure in first storage portion 73 is higher than the pressure in second storage portion 74, the first fuel that has leaked into second storage portion 74 through the sliding portion of piston 72S is discharged to the outside together with the second fuel. After that, when the second fuel in second storage portion 74 is discharged, pressure adjustment valve 211 is opened, and the supply of nitrogen from switching valve 216 is stopped.

[0186] In the fuel injection device 17T of the nineteenth embodiment, a nitrogen supply source 217 is connected to the second fuel supply path 44J via a switching valve 216, and a drain valve 219 is connected via a drain passage 218. Therefore, the second fuel stored in the second storage portion 74 can be discharged to the outside, and cleaning of the second storage portion 74 can be easily performed.

[0187] [Effects of this embodiment] The fuel injection device of the first aspect includes a first fuel supply path 43, 43J that supplies a first fuel having a predetermined ignition ability, a second fuel supply path 44, 44J that supplies a second fuel having a lower ignition ability than the first fuel, a fuel injection valve 33, 33G, 33J to which the first fuel supply path 43, 43J and the second fuel supply path 44, 44J are connected, and a piston mechanism 47, 47A, 47B, 47C, 47F, 47S that is provided between the first fuel supply path 43, 43J and the second fuel supply path 44, 44J and has pistons 72, 72A, 72B, 72C, 72S that move due to the pressure difference between a first supply pressure of the first fuel and a second supply pressure of the second fuel.

[0188] According to the fuel injection device of the first aspect, pistons 72, 72A, 72B, 72C, and 72S are moved by the pressure difference between the first supply pressure of the first fuel and the second supply pressure of the second fuel, thereby alternately performing a storage stroke of the second fuel and an injection stroke of the first fuel and the second fuel by fuel injection valves 33, 33G, and 33J. That is, the first fuel and the second fuel are pressurized and supplied to piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S without mixing midway. As a result, by suppressing mixing of the first fuel and the second fuel, highly accurate fuel injection is possible, thereby reducing harmful substances contained in exhaust gas.

[0189] The fuel injection device according to the second aspect is the fuel injection device according to the first aspect, further comprising: a first reservoir 73 communicating with the first fuel supply path 43, 43J to store the first fuel; and a second reservoir 74 communicating with the second fuel supply path 44, 44J to store the second fuel. As a result, when the pistons 72, 72A, 72B, 72C, 72S move from the second fuel supply path 44, 44J side to the first fuel supply path 43, 43J side, the volume of the second reservoir 74 expands, allowing the second reservoir 74 to store a predetermined amount of the second fuel to be injected in the next stroke.

[0190] The fuel injection device of the third aspect is the fuel injection device of the second aspect, further comprising: fuel injection valves 33, 33G, 33J each having a needle valve 45, 46, 142; and piston mechanisms 47, 47A, 47B, 47C, 47F, 47S, which are capable of storing a predetermined amount of second fuel in second storage section 74 when the second supply pressure is higher than the first supply pressure, and which are capable of supplying the first fuel from first fuel supply path 43, 43J to needle valve 45, 142 and supplying the second fuel in second storage section 74 to needle valve 46 when the first supply pressure is higher than the second supply pressure. As a result, the storage process of the second fuel and the injection process of the first fuel and the second fuel by the fuel injection valves 33, 33G, 33J are performed according to the differential pressure between the first supply pressure and the second supply pressure, so that the first fuel and the second fuel do not mix together midway, and the first fuel and the second fuel can be injected at the appropriate time.

[0191] A fuel injection device according to a fourth aspect is the fuel injection device according to the third aspect, further including a first supply pump 41 that pressurizes the first fuel and supplies it to the first fuel supply path 43, 43J, and a second supply pump 42 that pressurizes the second fuel and supplies it to the second fuel supply path 44, 44J, wherein the second supply pump 42 stores the second fuel in the second storage portion 74 when operated, and the first supply pump 41 supplies the first fuel from the first fuel supply path 43, 43J to the needle valve 45, 142 when operated, and supplies the second fuel in the second storage portion 74 to the needle valve 46. Thus, by alternately operating the first supply pump 41 and the second supply pump 42, a storage stroke of the second fuel and an injection stroke of the first fuel and the second fuel can be performed, and control of the first supply pump 41 and the second supply pump 42 can be simplified.

[0192] A fuel injection device according to a fifth aspect is the fuel injection device according to the fourth aspect, further comprising: a check valve 81 provided in first fuel supply path 43, 43J to prevent backflow of the first fuel toward first supply pump 41; and a return path 82 provided through which the first fuel bypasses check valve 81 and is returned to first supply pump 41 when the second supply pressure is higher than the first supply pressure. As a result, when pistons 72, 72A, 72B, 72C, 72S move from the second fuel supply path 44, 44J side to the first fuel supply path 43, 43J side to store the second fuel in second storage portion 74, the first fuel stored in first storage portion 73 is returned via return path 82, thereby enabling smooth operation of pistons 72, 72A, 72B, 72C, 72S.

[0193] A fuel injection device according to a sixth aspect is the fuel injection device according to the fourth or fifth aspect, further comprising check valves 84, 85, 86 provided in second fuel supply path 44, 44J to prevent the second fuel stored in second reservoir 74 from flowing back toward second supply pump 42 when the first supply pressure is higher than the second supply pressure. This allows the second fuel stored in second reservoir 74 by the second supply pressure to be appropriately supplied to second needle valve 46 without flowing back toward second supply pump 42.

[0194] The fuel injection device of the seventh aspect is a fuel injection device of any one of the first to sixth aspects, wherein the piston mechanism 47B, 47C, 47F, 47S has a cylinder 71, 71C, 71S provided between the first fuel supply path 43 and the second fuel supply path 44, and a piston 72B, 72C, 72S supported for movement by the cylinder 71, 71C, 71S, the cylinder 71, 71C, 71S or the piston 72B, 72C, 72S has a rod portion 101, 106, the piston 72B, 72C, 72S has a first pressure-receiving surface 72a formed at one end where the rod portion 101, 106 is located, on which a first supply pressure acts, and a second pressure-receiving surface 72b formed at the other end where a 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 becomes 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 become mixed with the first fuel, and the recovered first fuel does not contain the second fuel, making it easier to process.

[0195] A fuel injection device according to an eighth aspect is the fuel injection device according to any one of the first to seventh aspects, and further includes fuel injection valve 33 having a first needle valve 45 connected to first fuel supply path 43 and a second needle valve 46 connected to second fuel supply path 44. This allows the first fuel and the second fuel to be injected at different times, and also allows the first fuel and the second fuel to be injected simultaneously.

[0196] A fuel injection device according to a ninth aspect is the fuel injection device according to any one of the first to eighth aspects, further comprising: pistons 72A, 72B, 72C, 72S each having a first pressure-receiving surface 72a at one end in the direction of movement where a first supply pressure acts, and a second pressure-receiving surface 72b at the other end in the direction of movement where a second supply pressure acts, the area of ​​first pressure-receiving surface 72a being smaller than the area of ​​second pressure-receiving surface 72b, and a seal path 97 being provided through which the first supply pressure acts on sliding seal portion 46f of second needle valve 46. This makes it possible to suppress leakage of the second fuel from sliding seal portion 46f of second needle valve 46 and eliminates the need for recovery of the second fuel.

[0197] A fuel injection device according to a tenth aspect is the fuel injection device according to the eighth or ninth aspect, further including a first flow limiter 110, 130 that limits the supply of the first fuel in first fuel supply path 43 between piston mechanism 47, 47A, 47B, 47C, 47F, 47S and first needle valve 45. As a result, the first fuel is injected only at the beginning of the injection period of the second fuel, and the flame ignited by the first fuel, which has good ignitability, can be used as a spark to ignite the second fuel, which has poor ignitability. This ensures the ignitability of the second fuel and reduces the injection amount of the first fuel.

[0198] A fuel injection device according to an eleventh aspect is the fuel injection device according to the tenth aspect, further comprising a communication path 120 that connects the downstream side and upstream side of the first flow limiters 110, 130 in the first fuel supply path 43 at the end of the movement of the pistons 72, 72A, 72B, 72C toward the second fuel supply path 44. This allows the first fuel to be injected only at the beginning and end of the injection period of the second fuel, and the flame ignited by the first fuel with good ignition properties can be used as a spark to ignite the second fuel with poor ignition properties, and the second fuel with poor ignition properties can be completely burned.

[0199] A fuel injection device according to a twelfth aspect is the fuel injection device according to the tenth aspect, further comprising a variable throttle valve (first flow limiter adjustment valve) 136 that adjusts the operation timing of the first flow limiter 130. As a result, the variable throttle valve 136 adjusts the injection end timing of the initial injection of the first fuel, thereby making it possible to improve the combustibility of the second fuel, which has poor ignition characteristics.

[0200] A fuel injection device according to a thirteenth aspect is the fuel injection device according to any one of the tenth to twelfth aspects, and further includes a first pressure-receiving surface 72a on which a first supply pressure acts, at one end of the piston 72B in the movement direction, the first pressure-receiving surface 72a being an inclined surface inclined with respect to the radial direction of the piston 72B, and a drive unit 140 that rotates the piston 72B is provided. Thus, by rotating the inclined first pressure-receiving surface 72a, it is possible to adjust the injection start timing of the terminal injection of the first fuel and improve the combustibility of the second fuel, which has poor ignition properties.

[0201] A fuel injection device according to a fourteenth aspect is the fuel injection device according to any one of the tenth to thirteenth aspects, further including a third fuel supply path 141 that supplies the first fuel from first fuel supply path 43 bypassing piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S, and fuel injection valve 33G has a third needle valve 142 to which third fuel supply path 141 is connected, and is provided with a distributor valve 143 that adjusts the amount of the first fuel supplied to piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S and the amount of the first fuel supplied to third fuel supply path 141. Thus, distributor valve 143 supplies all of the first fuel to third fuel supply path 141 without supplying the first fuel to piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S, making it possible to inject only the first fuel without injecting the second fuel. Furthermore, by gradually changing the amount distributed by the distributor valve 143, it is possible to smoothly transition between the injection mode in which only the first fuel is injected and the injection mode in which the first fuel and the second fuel are injected.

[0202] A fuel injection device according to a fifteenth aspect is the fuel injection device according to any one of the tenth to fourteenth aspects, further comprising a third fuel supply path 141 that supplies the first fuel from the first fuel supply path 43, bypassing piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S, and a fuel injection valve 33G having a third needle valve 142 to which the third fuel supply path 141 is connected, a second flow limiter 150 that limits the supply of the first fuel is provided in the third fuel supply path 141, and a variable throttle valve (second flow limiter adjustment valve) 156 that adjusts the operation timing of the second flow limiter 150. Thus, by gradually changing the operation timing of the second flow limiter 150, a smooth transition can be made between an injection mode in which only the first fuel is injected and an injection mode in which both the first fuel and the second fuel are injected.

[0203] A fuel injection device according to a sixteenth aspect is the fuel injection device according to any one of the first to seventh aspects, further comprising: first fuel supply path (43J) and second fuel supply path (44J) joining downstream of piston mechanisms (47, 47A, 47B, 47C, 47F, 47S) and then connected to needle valve (160); piston mechanisms (47, 47A, 47B, 47C, 47F, 47S) communicate first fuel supply path (43J) with needle valve (160) at the end of movement of pistons (72, 72A, 72B, 72C) toward second fuel supply path (44J); and a check valve (161) is provided in first fuel supply path (43J) between piston mechanisms (47, 47A, 47B, 47C, 47F, 47S) and needle valve (160) to prevent backflow of the first fuel. This makes it possible to use one needle valve 160 to inject the first fuel and the second fuel at different times, and also to suppress mixing of the first fuel and the second fuel.

[0204] A fuel injection device according to a seventeenth aspect is the fuel injection device according to any one of the first to seventh aspects, further comprising: first fuel supply path (43J) and second fuel supply path (44J) joining downstream of piston mechanism (47, 47A, 47B, 47C, 47F, 47S) and then connected to needle valve (160); pistons (72, 72A, 72B, 72C, 72S) each having a first pressure-receiving surface (72a) on which a first supply pressure acts at one end in a moving direction, and a second pressure-receiving surface (72b) on which a second supply pressure acts at the other end in the moving direction, the area of ​​first pressure-receiving surface (72a) being smaller than the area of ​​second pressure-receiving surface (72b); thereby, backflow of the first fuel and the second fuel from needle valve (160) to piston mechanism (47, 47A, 47B, 47C, 47F) can be suppressed.

[0205] A fuel injection device according to an eighteenth aspect is the fuel injection device according to the sixteenth or seventeenth aspect, further comprising a bypass path 170 that bypasses piston mechanisms 47, 47A, 47B, 47C, 47F, 47S in first fuel supply path 43J, and a throttle valve (flow rate adjustment valve) 171 that adjusts the amount of first fuel supplied in bypass path 170. Thus, when injecting the second fuel having poor ignition properties, needle valve 160 injects a small amount of the first fuel having good ignition properties, thereby improving the combustibility of the second fuel having poor ignition properties.

[0206] A fuel injection device according to a nineteenth aspect is the fuel injection device according to any one of the sixteenth to eighteenth aspects, further comprising a bypass path 170 that bypasses the piston mechanisms 47, 47A, 47B, 47C, 47F, and 47S in the first fuel supply path 43J, and a first flow limiter 110 in the bypass path 170. As a result, the needle valve 160 can improve the combustibility of the second fuel having poor ignition characteristics by injecting a small amount of the first fuel having good ignition characteristics while injecting the second fuel having poor ignition characteristics.

[0207] A fuel injection device according to a twentieth aspect is the fuel injection device according to any one of the first to seventh aspects, further including a first supply pump 41 that pressurizes the first fuel and supplies it to a first fuel supply path 43, 43J, and the first fuel supply path 43, 43J is provided with a check valve 81 that prevents the first fuel from flowing back toward the first supply pump 41, and a residual pressure adjustment valve 180 that discharges the first fuel downstream of the check valve 81 to reduce the first supply pressure. Thus, by operating the first supply pump 41 and the residual pressure adjustment valve 180, a storage stroke of the second fuel and an injection stroke of the first fuel and the second fuel can be performed, and the device can be simplified by eliminating the second supply pump that pressurizes the second fuel.

[0208] A fuel injection device according to a twenty-first aspect is the fuel injection device according to any one of the first to seventh aspects, further including a first supply pump 41 that pressurizes the first fuel and supplies it to a first fuel supply path 43, 43J, the first fuel supply path 43, 43J is provided with a check valve (first check valve) 81 that prevents backflow of the first fuel toward the first supply pump 41, and the second fuel supply path 44, 44J is provided with a check valve (second check valve) 85 that prevents backflow of the second fuel toward the second fuel supply source 60, the opening pressure of the second check valve 85 being set lower than the opening pressure of the check valve 81. As a result, by operating the first supply pump 41, a storage stroke of the second fuel and an injection stroke of the first fuel and the second fuel can be performed, and the device can be simplified by eliminating the second supply pump that pressurizes the second fuel.

[0209] A fuel injection device according to a 22nd aspect is the fuel injection device according to the 21st aspect, and further includes: a bulging portion 102a provided at a base end of a rod portion 106 of piston 72S; a seat portion 102b provided in cylinder 71S on the side of first fuel supply path 43J; and when piston 72S moves toward first fuel supply path 43J, bulging portion 102a abuts against seat portion 102b, thereby blocking communication with first fuel supply path 43J. This allows communication between first fuel supply path 43J and first reservoir 73 to be appropriately established and blocked.

[0210] A fuel injection device according to a 23rd aspect is the fuel injection device according to the 21st aspect, further comprising: a nitrogen supply source (gas supply source) 217 ​​connected to second fuel supply path 44J upstream of check valve 85, the nitrogen supply source (gas supply source) supplying nitrogen (scavenging gas) at a lower pressure than the second fuel; and a drain valve 219 having a pressure receiving area on which the pressure upstream of check valve 85 acts in a closing direction that is larger than a pressure receiving area on which the pressure downstream of check valve 85 acts in an opening direction. This allows the second fuel stored in second storage section 74 to be discharged to the outside, making it easy to scavenge second storage section 74.

[0211] A reciprocating internal combustion engine according to a twenty-fourth aspect includes a diesel engine body 11 having a combustion chamber 25, and a fuel injection device 17, 17A, 17B, 17C, 17D, 17E, 17F, 17G, 17H, 17J, 17K, 17L, 17M, 17N, 17P, 17Q, 17R, 17S, 17T according to any one of the first to twenty-third aspects that injects fuel into the combustion chamber 25. This makes it possible to suppress mixing of the first fuel and the second fuel, thereby enabling highly accurate fuel injection and reducing harmful substances contained in exhaust gas. [Explanation of symbols]

[0212] 10 Marine diesel engines (reciprocating internal combustion engines) 11 Diesel engine body (internal combustion engine body) 12 Cylinder liner 13 Piston 14 Scavenging trunk 15 Exhaust manifold 16 Exhaust valve 17,17A,17B,17C,17D,17E,17F,17G,17H,17J,17K,17L,17M,17N,17P,17Q,17R,17S,17T Fuel injection device 31,31N,31Q Fuel supply system 32, 32G, 32J fuel supply route 33, 33G, 33J fuel injection valve 41 First supply pump 42 Second supply pump 43,43J First fuel supply line 44,44J Second fuel supply line 45 First needle valve 46 Second needle valve 47, 47A, 47B, 47C, 47F, 47S Piston mechanism 50 Primary fuel source 51 Piston 52 Plunger 53 First hydraulic oil supply line 54 Working fluid source 55 First solenoid valve 56 Control Unit 60 Secondary fuel source 61 Piston 62 Plunger 63 Second hydraulic oil supply line 65 Second solenoid valve 71, 71A, 71C, 71S Cylinder 72, 72A, 72B, 72C, 72S pistons 72a First pressure surface 72b Second pressure surface 73 First Reservoir 74 Second storage section 81, 83, 84, 85, 86, 87 Check valve 88 Cut valve 89 Pressure equalizing valve 82 Return Route 95 Space part 96 Drain path 101,106 Rod part 102,107 Main body 103,108 Sliding part 104,109 Drain path 110,130 First flow limiter 120, 121, 122 Communication route 136 Variable throttle valve (first flow limiter adjustment valve) 141 Third fuel supply route 142 Third needle valve 143 Distribution valve 150,190 Second flow limiter 156 Variable throttle valve (second flow limiter adjustment valve) 160 Needle valve 161 Check valve 170 Detour Route 171 Throttle valve (flow control valve) 180 Residual pressure adjustment valve 181 Pressure regulation route 211 Pressure regulating valve 212 Check valve 213 Pressure vessel 214 Pressurized path 215 Boost Pump 216 Switching valve 217 Nitrogen Sources 218 Drain passage 219 Drain valve

Claims

1. a first fuel supply path for supplying a first fuel having a predetermined ignition property; a second fuel supply path for supplying a second fuel having lower ignition ability than the first fuel; a fuel injection valve to which the first fuel supply path and the second fuel supply path are connected; a piston mechanism provided between the first fuel supply path and the second fuel supply path, the piston moving in response to a pressure difference between a first supply pressure of the first fuel and a second supply pressure of the second fuel; A fuel injection device comprising:

2. the piston mechanism has a first storage portion communicating with the first fuel supply path and storing the first fuel, and a second storage portion communicating with the second fuel supply path and storing the second fuel.

2. The fuel injection system of claim 1.

3. the fuel injection valve has a needle valve, and the piston mechanism is capable of storing a predetermined amount of the second fuel in the second storage section when the second supply pressure is higher than the first supply pressure, and is capable of supplying the first fuel from the first fuel supply path to the needle valve and supplying the second fuel in the second storage section to the needle valve when the first supply pressure is higher than the second supply pressure.

3. The fuel injection system of claim 2.

4. a first supply pump that pressurizes the first fuel and supplies it to the first fuel supply path, and a second supply pump that pressurizes the second fuel and supplies it to the second fuel supply path, wherein the second fuel is stored in the second storage unit when the second supply pump is operated, and the first fuel is supplied from the first fuel supply path to the needle valve and the second fuel in the second storage unit is supplied to the needle valve when the first supply pump is operated; 4. The fuel injection system of claim 3.

5. a check valve that prevents the first fuel from flowing back toward the first supply pump is provided in the first fuel supply path, and a return path that allows the first fuel to bypass the check valve and return to the first supply pump when the second supply pressure is higher than the first supply pressure is provided.

5. The fuel injection system of claim 4.

6. a check valve is provided in the second fuel supply path to prevent the second fuel stored in the second storage portion from flowing back toward the second supply pump when the first supply pressure is higher than the second supply pressure; 5. The fuel injection system of claim 4.

7. the piston mechanism includes a cylinder provided between the first fuel supply path and the second fuel supply path, and a piston movably supported by the cylinder, the cylinder or the piston having a rod portion, the piston having a first pressure-receiving surface on which the first supply pressure acts at one end where the rod portion is located, and a second pressure-receiving surface on which the second supply pressure acts at the other end, the area of ​​the first pressure-receiving surface being smaller than the area of ​​the second pressure-receiving surface; 2. The fuel injection system of claim 1.

8. The fuel injection valve has a first needle valve connected to the first fuel supply path and a second needle valve connected to the second fuel supply path.

2. The fuel injection system of claim 1.

9. the piston has a first pressure-receiving surface on which the first supply pressure acts at one end in the direction of movement, and a second pressure-receiving surface on which the second supply pressure acts at the other end in the direction of movement, the area of ​​the first pressure-receiving surface being smaller than the area of ​​the second pressure-receiving surface, and a seal path is provided for applying the first supply pressure to a sliding seal portion of the second needle valve.

9. The fuel injection system of claim 8.

10. a first flow limiter that limits the supply of the first fuel is provided in the first fuel supply path between the piston mechanism and the first needle valve; 9. The fuel injection system of claim 8.

11. a communication path is provided that communicates the downstream side and upstream side of the first flow limiter in the first fuel supply path at a final stage of movement of the piston toward the second fuel supply path; 11. A fuel injection system according to claim 10.

12. a first flow limiter adjustment valve is provided to adjust the operation timing of the first flow limiter; 11. A fuel injection system according to claim 10.

13. the piston has a first pressure-receiving surface formed at one end in a moving direction, on which the first supply pressure acts, the first pressure-receiving surface being an inclined surface inclined with respect to a radial direction of the piston, and a drive unit that rotates the piston is provided on the first pressure-receiving surface; 11. A fuel injection system according to claim 10.

14. a third fuel supply path is provided that supplies the first fuel from the first fuel supply path while bypassing the piston mechanism, the fuel injection valve has a third needle valve to which the third fuel supply path is connected, and the fuel injection valve is provided with a distributor valve that adjusts the supply amount of the first fuel supplied to the piston mechanism and the supply amount of the first fuel supplied to the third fuel supply path; 11. A fuel injection system according to claim 10.

15. a third fuel supply path is provided that supplies the first fuel from the first fuel supply path while bypassing the piston mechanism, the fuel injection valve has a third needle valve to which the third fuel supply path is connected, a second flow limiter that limits the supply of the first fuel is provided in the third fuel supply path, and a second flow limiter adjustment valve that adjusts the operation timing of the second flow limiter is provided.

11. A fuel injection system according to claim 10.

16. the fuel injection valve has a needle valve, the first fuel supply path and the second fuel supply path join downstream of the piston mechanism and are connected to the needle valve, the piston mechanism communicates the first fuel supply path with the needle valve at the end of movement of the piston toward the second fuel supply path, and the first fuel supply path is provided with a check valve between the piston mechanism and the needle valve to prevent backflow of the first fuel.

2. The fuel injection system of claim 1.

17. the fuel injection valve has a needle valve, the first fuel supply path and the second fuel supply path join downstream of the piston mechanism and are then connected to the needle valve, the piston has a first pressure-receiving surface on which the first supply pressure acts at one end in the moving direction, and a second pressure-receiving surface on which the second supply pressure acts at the other end in the moving direction, the area of ​​the first pressure-receiving surface being smaller than the area of ​​the second pressure-receiving surface; 2. The fuel injection system of claim 1.

18. a bypass path that bypasses the piston mechanism is provided in the first fuel supply path, and a flow rate adjustment valve that adjusts the supply amount of the first fuel is provided in the bypass path; 18. A fuel injection device according to claim 16 or claim 17.

19. a bypass path that bypasses the piston mechanism is provided in the first fuel supply path, and a flow limiter is provided in the bypass path; 18. A fuel injection device according to claim 16 or claim 17.

20. a first supply pump that pressurizes the first fuel and supplies it to the first fuel supply path, the first fuel supply path being provided with a check valve that prevents the first fuel from flowing back toward the first supply pump, and a residual pressure regulating valve that discharges the first fuel downstream of the check valve to reduce the first supply pressure; 2. The fuel injection system of claim 1.

21. a first supply pump that pressurizes the first fuel and supplies it to the first fuel supply path, the first fuel supply path is provided with a first check valve that prevents the first fuel from flowing back toward the first supply pump, and the second fuel supply path is provided with a second check valve that prevents the second fuel from flowing back toward a second fuel supply source, and an opening pressure of the second check valve is set lower than an opening pressure of the first check valve; 8. A fuel injection system according to claim 7.

22. the piston mechanism includes a bulge portion provided at a base end of the rod portion of the piston, and a seat portion provided in the cylinder on the side of the first fuel supply path, and the piston moves toward the first fuel supply path and the bulge portion abuts against the seat portion, thereby blocking communication with the first fuel supply path.

22. The fuel injection system of claim 21.

23. a gas supply source that supplies a scavenging gas having a pressure lower than that of the second fuel is connected to the second fuel supply path upstream of the second check valve, and a drain valve is provided in which a pressure-receiving area on which a pressure upstream of the second check valve acts in a closing direction is larger than a pressure-receiving area on which a pressure downstream of the second check valve acts in an opening direction.

22. The fuel injection system of claim 21.

24. an internal combustion engine body having a combustion chamber; a fuel injection device according to claim 1 for injecting fuel into the combustion chamber; A reciprocating internal combustion engine comprising:

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