Fuel supply device for engine and engine system

Abstract

To provide a fuel supply device for an engine and an engine system, each enabling air bleeding effect to be easily obtained.SOLUTION: A fuel supply device 1 for an engine 2 comprises an air bleeding piping 7 and a pressure fluctuation suppression portion 8. The air bleeding piping 7 branches from a branching point on a fuel piping 4 which supplies fuel F1 from a fuel tank 3 to a fuel injection pump 5 of the engine 2 and is connected to the fuel tank 3. The pressure fluctuation suppression portion 8 is disposed in the air bleeding piping 7. The pressure fluctuation suppression portion 8 allows air and the fuel F1 to pass through in a forward direction from the branching point toward the fuel tank 3. The pressure fluctuation suppression portion 8 inhibits passage of the air in a reverse direction from the fuel tank 3 toward the branching point, while allowing the fuel F1 to pass through.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an engine fuel supply device and an engine system that supplies fuel to an engine. [Background technology]

[0002] As a related art, there is known a fuel supply device for an engine that supplies fuel from a fuel tank to a fuel injection pump (see, for example, Patent Document 1). The engine fuel supply device according to the related art is equipped with an air vent pipe that communicates with the fuel tank, and is configured such that a fuel filter, a fuel injection pump, and the air vent pipe are connected via a three-way joint. This engine fuel supply device has a check valve (or a sphere that functions as a check valve) in the air vent pipe, and bleeds air from the fuel pipe using pulsation generated by the fuel injection pump. In other words, air in the fuel pipe is discharged to the fuel tank through the air vent pipe, and the check valve prevents the air from flowing back toward the three-way joint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-291958 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the engine fuel supply device according to the above-described related art, a small amount of fuel may pass through the check valve in the air vent pipe along with air, and in this case, fuel may accumulate as excess fuel downstream of the check valve in the air vent pipe (the side opposite the three-way joint). Pulsation generated by the fuel injection pump then pushes out the accumulated excess fuel, which may result in fuel being sprayed into the fuel tank. As a result, the air vent pipe may not be able to fully bleed air.

[0005] An object of the present disclosure is to provide an engine fuel supply device and an engine system that can easily achieve an air bleeding effect. [Means for solving the problem]

[0006] A fuel supply device for an engine according to one aspect of the present disclosure includes an air bleed pipe and a pressure fluctuation suppression unit. The air bleed pipe branches off from a branch point in a fuel pipe that supplies fuel from a fuel tank to a fuel injection pump of the engine and is connected to the fuel tank. The pressure fluctuation suppression unit is disposed in the air bleed pipe. The pressure fluctuation suppression unit allows air and the fuel to pass in a forward direction from the branch point toward the fuel tank. The pressure fluctuation suppression unit suppresses the passage of the air and allows the fuel to pass in a reverse direction from the fuel tank toward the branch point.

[0007] An engine system according to one aspect of the present disclosure includes a fuel supply device for the engine and the engine. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an engine fuel supply device and an engine system that can easily achieve an air bleeding effect. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of an engine system according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating a main part of the engine system according to the first embodiment. [Figure 3] FIG. 3 is a schematic perspective view showing a first configuration example of a pressure fluctuation suppressor used in the engine system according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a second configuration example of the pressure fluctuation suppressor used in the engine system according to the first embodiment. [Figure 5]FIG. 5 is a schematic diagram showing a third configuration example of the pressure fluctuation suppressor used in the engine system according to the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a fourth configuration example and a fifth configuration example of the pressure fluctuation suppressor used in the engine system according to the first embodiment. [Figure 7] FIG. 7 is an explanatory diagram showing a schematic configuration of an engine system according to the second embodiment. [Figure 8] FIG. 8 is an explanatory diagram showing a schematic configuration of an engine system according to the third embodiment. [Figure 9] FIG. 9 is an explanatory diagram showing a schematic configuration of an engine system according to the fourth embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional perspective view of a pressure fluctuation suppressor used in an engine system according to the fourth embodiment. [Figure 11] FIG. 11 is a schematic diagram showing an example of the operation of the pressure fluctuation suppressor used in the engine system according to the fourth embodiment. [Figure 12] FIG. 12 is an explanatory diagram showing a schematic configuration of a fuel supply device for an engine according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The following embodiments are examples that embody the present disclosure and are not intended to limit the technical scope of the present disclosure. All drawings referred to in this disclosure are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0011] (Embodiment 1) [1] Overall structure First, the overall configuration of an engine system 10 according to this embodiment will be described with reference to FIG.

[0012] As shown in Fig. 1, an engine system 10 according to this embodiment includes a fuel supply device 1 for an engine 2 (hereinafter simply referred to as "fuel supply device 1") and the engine 2. The "engine" here is a heat engine that burns a fuel F1 to generate mechanical energy (power), and includes an internal combustion engine that is a prime mover that converts thermal energy into mechanical energy by burning the fuel F1 inside the engine and using combustion gas as working gas. In other words, the engine 2 generates power (mechanical energy) using the fuel that is supplied.

[0013] The engine 2 according to this embodiment is a reciprocating engine that converts the reciprocating motion of a piston into rotational motion and outputs rotational force as power. In particular, in this embodiment, the engine 2 is, for example, a horizontal water-cooled diesel engine. The fuel F1 is, for example, a liquid fuel such as a fossil fuel (diesel, gasoline, etc.). In this embodiment, the engine 2 is driven by the fuel F1 (diesel in this case) supplied from the fuel supply device 1.

[0014] Furthermore, the engine system 10 (engine 2) is used as a power source for, for example, a work machine, a vehicle, an aerial vehicle (such as a drone), or a ship. In other words, the engine system 10 is mounted on the body of the work machine, vehicle, aerial vehicle, or a ship, and generates power for the work machine, vehicle, aerial vehicle, or a ship. Here, the work machine refers to, for example, a machine that performs various tasks, and includes, as examples, agricultural machines (farm machines) such as harvesters, tractors, seed sowers, rice transplanters, spreaders, sprayers, or transplanters, or construction machines (construction machines) such as backhoes, wheel loaders, or carriers.

[0015] In this embodiment, for convenience of explanation, the vertical direction when the engine system 10 is in a usable state is defined as the up-down direction D1. Furthermore, the left-right direction in Fig. 1 is defined as the left-right direction D2. However, these directions are not intended to limit the direction in which the engine system 10 is used (the direction during use).

[0016] The fuel supply device 1 includes a fuel tank 3, a fuel pipe 4, a fuel injection pump 5, and a fuel filter 6. The fuel supply device 1 according to this embodiment further includes a three-way joint 40, an air bleed pipe 7, and the like.

[0017] The fuel tank 3 is a container that stores the fuel F1. The fuel tank 3 is disposed above the engine 2. An outlet 31 is formed at the bottom of the fuel tank 3, and the fuel F1 stored in the fuel tank 3 can be taken out through the outlet 31.

[0018] The fuel injection pump 5 supplies the fuel F1 to the engine 2 by injecting the fuel F1 into the inside of the engine 2. The fuel injection pump 5 has an intake port 51. The fuel injection pump 5 is connected to a fuel injection nozzle via a high-pressure pipe, and by opening and closing a fuel injection valve in accordance with the fuel injection timing, the fuel F1 supplied from the fuel tank 3 to the intake port 51 is injected into the inside of the engine 2 from the fuel injection nozzle.

[0019] The fuel filter 6 has a primary port 61, a secondary port 62, and an element. The fuel filter 6 discharges fuel F1 supplied from the primary port 61 through the element and from the secondary port 62. The element is accommodated in a case of the fuel filter 6 in a replaceable manner.

[0020] The fuel pipe 4 is a pipe for supplying fuel F1 from the fuel tank 3 to the fuel injection pump 5. Therefore, the fuel pipe 4 connects the fuel tank 3 and the fuel injection pump 5. In this embodiment, a fuel filter 6 is inserted midway in the fuel pipe 4 that connects the fuel tank 3 and the fuel injection pump 5. Therefore, the fuel F1 is supplied from the fuel tank 3 to the fuel injection pump 5 through the fuel filter 6.

[0021] Specifically, the fuel pipe 4 has a first pipe 41 on the fuel tank 3 side (upstream side) as viewed from the fuel filter 6, and a second pipe 42 on the fuel injection pump 5 side (downstream side) as viewed from the fuel filter 6. The first pipe 41 connects the outlet 31 of the fuel tank 3 to a primary side port 61 of the fuel filter 6. The second pipe 42 connects the secondary side port 62 of the fuel filter 6 to a suction port 51 of the fuel injection pump 5 (via a three-way joint 40 or the like).

[0022] More specifically, the second pipe 42 is connected to the suction port 51 of the fuel injection pump 5 via the three-way joint 40 and the third pipe 43. That is, the fuel pipe 4 has the third pipe 43 in addition to the first pipe 41 and the second pipe 42. The three-way joint 40 has a first branch pipe 401, a second branch pipe 402, and a third branch pipe 403, and the first branch pipe 401, the second branch pipe 402, and the third branch pipe 403 are communicated with each other inside the three-way joint 40. The second pipe 42 connects the secondary side port 62 of the fuel filter 6 to the first branch pipe 401 of the three-way joint 40. The third pipe 43 connects the second branch pipe 402 of the three-way joint 40 to the suction port 51 of the fuel injection pump 5.

[0023] As a result, the fuel F1 discharged from the secondary port 62 of the fuel filter 6 passes through the second pipe 42, the three-way joint 40 (between the first branch pipe 401 and the second branch pipe 402), and the third pipe 43 in this order, and is supplied to the suction port 51 of the fuel injection pump 5. Therefore, the fuel F1 in the fuel tank 3 is supplied from the fuel tank 3 to the fuel injection pump 5 through the fuel filter 6.

[0024] In this embodiment, the fuel tank 3 is disposed to the left of the engine 2, and is disposed so that the lower surface (bottom surface) of the fuel tank 3 is at a position higher (above) than at least the suction port 51 of the fuel injection pump 5. As a result, the liquid level L1 of the fuel F1 in the fuel tank 3 is higher than the suction port 51 of the fuel injection pump 5, and head pressure (atmospheric pressure) is easily obtained at the liquid level L1. Therefore, the fuel supply device 1 can supply the fuel F1 by gravity falling from the fuel tank 3 without using a feed pump.

[0025] Furthermore, in the fuel supply device 1 according to this embodiment, the third branch pipe 403 of the three-way joint 40 is connected to the fuel tank 3 via the air vent pipe 7. Specifically, a return port 32 is formed in the upper part of the fuel tank 3, and the air vent pipe 7 connects the third branch pipe 403 of the three-way joint 40 to the return port 32 of the fuel tank 3. As a result, air in the fuel F1 passing through the fuel pipe 4 is returned from the return port 32 through the air vent pipe 7 into the fuel tank 3.

[0026] In this disclosure, "air" refers to gas such as bubbles in the fuel F1, and is, for example, air or air containing moisture such as water vapor. In other words, when such air (air bubbles) is contained in the fuel F1 passing through the fuel pipe 4, the air is guided to the air vent pipe 7 through the three-way joint 40 (between the first branch pipe 401 and the third branch pipe 403) and returned to the fuel tank 3 through the return port 32. As a result, air can be vented from inside the fuel pipe 4.

[0027] In addition, in FIG. 1 and other figures, the flow of fuel F1 in the fuel supply system is indicated by solid arrows, and the flow of air (air bubbles) is indicated by hollow arrows.

[0028] [2] Details of the fuel supply system Next, the details of the fuel supply device 1 according to this embodiment, mainly the configuration related to the air vent pipe 7, will be described with reference to FIGS.

[0029] As shown in FIG. 2, the fuel supply device 1 according to this embodiment further includes a pressure fluctuation suppressor 8, a first throttle valve 11, and a second throttle valve 12.

[0030] The first pipe 41 of the fuel pipe 4 is made of, for example, a rubber hose (rubber tube). One end of the first pipe 41 is connected to a first joint 301 that protrudes downward from the outlet 31 of the fuel tank 3, and the other end of the first pipe 41 is connected to a primary side port 61 that is made of a joint that protrudes leftward from the top of the fuel filter 6. More specifically, the first pipe 41 is disposed basically in the horizontal direction (left-right direction D2) so as to extend downward from the bottom surface of the fuel tank 3 and then extend rightward along the left-right direction D2 via a curved portion to be connected to the fuel filter 6 from the left.

[0031] The second pipe 42 of the fuel pipe 4 is made of, for example, a rubber hose (rubber tube). One end of the second pipe 42 is connected to a secondary port 62 made of a joint protruding rightward from an upper portion of the fuel filter 6, and the other end of the second pipe 42 is connected to a first branch pipe 401 of the three-way joint 40. More specifically, the second pipe 42 is disposed basically in the horizontal direction (left-right direction D2) so as to extend rightward from the fuel filter 6, and then curve diagonally upward and to connect to the three-way joint 40 from diagonally downward and to the left.

[0032] The third pipe 43 of the fuel pipe 4 is made of, for example, a rubber hose (rubber tube). One end of the third pipe 43 is connected to the second branch pipe 402 of the three-way joint 40, and the other end of the third pipe 43 is connected to the suction port 51 of the fuel injection pump 5. A first throttle valve 11 is disposed midway within the third pipe 43. More specifically, the third pipe 43 is disposed basically in the horizontal direction (left-right direction D2) so that it extends rightward from the second branch pipe 402 of the three-way joint 40 along the left-right direction D2 and is connected to the fuel injection pump 5 from the left.

[0033] The air vent pipe 7 is made of, for example, a rubber hose (rubber tube). One end of the air vent pipe 7 is connected to the third branch pipe 403 of the three-way joint 40, and the other end of the air vent pipe 7 is connected to the second joint 302 that protrudes rightward from the return port 32 of the fuel tank 3. A second throttle valve 12 is disposed midway within the air vent pipe 7. More specifically, the air vent pipe 7 extends upward from the third branch pipe 403 of the three-way joint 40 in the vertical direction D1, and is disposed vertically (in the vertical direction D1) so that its end is connected to the right side surface of the fuel tank 3 from the right side via a curved portion.

[0034] In this way, the air vent pipe 7 branches off from the fuel pipe 4 at the three-way joint 40 and is connected to the fuel tank 3 (the return port 32 thereof). Specifically, the fuel pipe 4 branches off to the air vent pipe 7 at the three-way joint 40, which is the connection point between the second pipe 42 and the third pipe 43. In other words, the air vent pipe 7 branches off from a branch point in the fuel pipe 4 that supplies fuel F1 from the fuel tank 3 to the fuel injection pump 5 of the engine 2, and is connected to the fuel tank 3. Here, the three-way joint 40 (i.e., the connection point between the second pipe 42 and the third pipe 43) is an example of a branch point in the fuel pipe 4.

[0035] Three-way joint 40, which is an example of a branch point, is configured in a generally T-shape, with first branch pipe 401 and third branch pipe 403 aligned in a straight line and second branch pipe 402 perpendicular to first branch pipe 401 and third branch pipe 403. Therefore, second pipe 42 and air vent pipe 7, which are connected to first branch pipe 401 and third branch pipe 403, respectively, are linearly connected. On the other hand, third pipe 43, which is connected to second branch pipe 402, is connected perpendicular to second pipe 42.

[0036] More specifically, the three-way joint 40 connects the second pipe 42 and the air vent pipe 7 on an imaginary straight line that extends diagonally upward and to the right from the second pipe 42 to the air vent pipe 7. On the other hand, the three-way joint 40 connects the third pipe 43 to the second pipe 42 so as to extend diagonally downward and to the right from the imaginary straight line.

[0037] The first throttle valve 11 is disposed in the third pipe 43 that connects the second branch pipe 402 of the three-way joint 40 and the suction port 51 of the fuel injection pump 5. In other words, the fuel F1 flows from the second branch pipe 402 of the three-way joint 40 toward the suction port 51 of the fuel injection pump 5 via the first throttle valve 11. This suppresses a sudden flow of the fuel F1 in the three-way joint 40, reduces the pulsating pressure of the fuel injection pump 5, and makes it less likely that the fuel injection pump 5 will suck in air.

[0038] The second throttle valve 12 is disposed in the air vent pipe 7 that connects the third branch pipe 403 of the three-way joint 40 and the return port 32 of the fuel tank 3. In other words, air flows from the third branch pipe 403 of the three-way joint 40 toward the return port 32 of the fuel tank 3 via the second throttle valve 12. The second throttle valve 12 is disposed in the air vent pipe 7 with a predetermined distance between it and the third branch pipe 403.

[0039] The pressure fluctuation suppression unit 8 is disposed in the air vent pipe 7. The pressure fluctuation suppression unit 8 suppresses pressure fluctuations in the fuel pipe 4 by allowing air to pass in the forward direction of the air vent pipe 7 while suppressing air from passing in the reverse direction of the air vent pipe 7. In this disclosure, the "forward direction" of the air vent pipe 7 refers to the direction from the branch point (three-way joint 40) side of the air vent pipe 7 toward the fuel tank 3 (return port 32) side. In this disclosure, the "reverse direction" of the air vent pipe 7 refers to the direction from the fuel tank 3 (return port 32) side of the air vent pipe 7 toward the branch point (three-way joint 40) side.

[0040] That is, the pressure fluctuation suppression unit 8 allows air to pass from the branch point (three-way joint 40) side to the fuel tank 3 (return port 32) side within the air vent pipe 7, while suppressing the passage of air from the fuel tank 3 (return port 32) side toward the branch point (three-way joint 40) side.

[0041] Without such a pressure fluctuation suppression unit 8, the branch point (three-way joint 40) in the fuel pipe 4 and the return port 32 of the fuel tank 3 would be in bidirectional communication (forward and reverse directions) through the air vent pipe 7, causing the pressure in the fuel pipe 4 (at its branch point) to fluctuate due to the air pressure in the fuel tank 3. In contrast, by providing the pressure fluctuation suppression unit 8, the pressure in the fuel pipe 4 (at its branch point) can be separated from the air pressure in the fuel tank 3, making it possible to suppress pressure fluctuations in the fuel pipe 4.

[0042] In the fuel supply device 1 according to this embodiment, the pressure fluctuation suppression unit 8 allows both air and fuel F1 to pass in the forward direction (from the branch point side toward the fuel tank 3 side). On the other hand, the pressure fluctuation suppression unit 8 suppresses the passage of air but allows the passage of fuel F1 in the reverse direction (from the fuel tank 3 side toward the branch point side). In short, the pressure fluctuation suppression unit 8 includes, for example, a check valve 81, which allows air to pass in the forward direction through the air vent pipe 7 while suppressing the passage of air in the reverse direction through the air vent pipe 7, thereby suppressing pressure fluctuations in the fuel pipe 4. On the other hand, the pressure fluctuation suppression unit 8 intentionally weakens the action of the check valve 81, thereby allowing the fuel F1 to pass not only in the forward direction through the air vent pipe 7 but also in the reverse direction through the air vent pipe 7.

[0043] As a result, even if a small amount of fuel F1 passes through the pressure fluctuation suppression section 8 of the air vent pipe 7 in the forward direction together with air, the fuel F1 can also pass through the pressure fluctuation suppression section 8 in the reverse direction. Therefore, the fuel F1 is less likely to accumulate as surplus fuel on the downstream side of the pressure fluctuation suppression section 8 in the forward direction of the air vent pipe 7 (the side opposite to the three-way joint 40). As a result, there is an advantage in that it is easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and the air vent pipe 7 is more likely to have an effective air bleeding effect.

[0044] Specifically, as shown in Fig. 2, the pressure fluctuation suppression unit 8 has a check valve 81 and a bypass path 82. The check valve 81 allows fluid (air and fuel F1) to pass in the forward direction while preventing fluid (air and fuel F1) from passing in the reverse direction. The bypass path 82 bypasses a downstream position P2 and an upstream position P1 in the forward direction as viewed from the check valve 81 in the air vent pipe 7. The downstream position P2 here is the position on the downstream side in the forward direction as viewed from the check valve 81 in the air vent pipe 7, that is, the position on the side of the return port 32 of the fuel tank 3. The upstream position P1 here is the position on the upstream side in the forward direction as viewed from the check valve 81 in the air vent pipe 7, that is, the position on the side of the branch point (three-way joint 40).

[0045] That is, the pressure fluctuation suppression unit 8 allows both air and fuel F1 to pass only in the forward direction, and prevents them from passing in the reverse direction, by using the check valve 81 inserted in the air vent pipe 7. Furthermore, a bypass path 82 provided in parallel to the check valve 81 bypasses a downstream position P2 and an upstream position P1 in the forward direction as seen from the check valve 81 in the air vent pipe 7. Therefore, the fuel F1 can flow from the downstream position P2 of the check valve 81 toward the upstream position P1 via the bypass path 82. As a result, the pressure fluctuation suppression unit 8 can achieve a configuration that suppresses the passage of air and allows the passage of fuel F1 in the reverse direction (from the fuel tank 3 side toward the branch point side).

[0046] More specifically, the check valve 81 includes a base portion 812 and a valve element 811. The base portion 812 has an opening 810 (see FIG. 3) on the downstream side in the forward direction (toward downstream position P2). The valve element 811 opens and closes the opening 810 of the base portion 812. In other words, when a fluid flows in the forward direction through the air vent pipe 7, the check valve 81 is brought into an "open state" in which the valve element 811 is pushed by the fluid to open the opening 810, thereby allowing the fluid to pass. On the other hand, when a fluid flows in the reverse direction through the air vent pipe 7, the check valve 81 is brought into a "closed state" in which the valve element 811 is pushed by the fluid to close the opening 810, thereby preventing the passage of the fluid.

[0047] In particular, in this embodiment, the valve element 811 is a sphere that moves inside the air vent pipe 7. The base portion 812 is disposed so that the opening 810 faces at least upward, and in this embodiment, as an example, it is integrated with the third branch pipe 403 of the three-way joint 40.

[0048] Specifically, the valve element 811 is made of a metal ball having a diameter smaller than the inner diameter of the air vent pipe 7 and larger than the inner diameters of the seat portion 812 (third branch pipe 403) and the second throttle valve 12. An elastic body (sheet material), which is an example of a valve seat structure that can tightly fit the valve element 811, is arranged around the opening 810 in the seat portion 812. As shown in FIG. 2, the valve element 811 is arranged in the air vent pipe 7 between the seat portion 812 (third branch pipe 403) and the second throttle valve 12.

[0049] This allows the valve element 811 to move in both directions (forward and reverse directions) within the air vent pipe 7 between the seat portion 812 (third branch pipe 403) and the second throttle valve 12. The specific gravity of the valve element 811 is set to be greater than the specific gravity of the fuel F1. Normally, the valve element 811 is supported by the seat portion 812 due to its own weight, and is in a closed state in which it closes the opening 810 of the seat portion 812. On the other hand, when a fluid (air or fuel F1) flows into the seat portion 812 from the branch point (three-way joint 40) side, the valve element 811 is pushed by the fluid and moves toward the second throttle valve 12, and enters an open state in which it opens the opening 810 of the seat portion 812.

[0050] With the configuration described above, when fuel F1 is being supplied, air bubbles in the fuel pipe 4 move upward by gravity through the third branch pipe 403 of the three-way joint 40, and are released into the fuel tank 3 from the return port 32 through the air vent pipe 7. In other words, normally, the valve element 811, which has a specific gravity greater than that of the fuel, is in a closed state blocking the opening 810, but when air bubbles enter the air vent pipe 7, the pressure difference pushes the valve element 811 upward, allowing the air bubbles to pass through the check valve 81.

[0051] In check valve 81 configured as described above, gravity causes valve element 811 to close opening 810, making it possible to easily release air generated in fuel pipe 4 upward while preventing air from flowing back from fuel tank 3 toward branch point (three-way joint 40). In other words, a check valve structure can be realized that operates with a slight cracking pressure to efficiently bleed air.

[0052] In this embodiment, a bypass path 82 is further provided in parallel with the check valve 81 having such a configuration. That is, as shown in Fig. 2, the bypass path 82 bypasses between a downstream position P2 that is downstream of the valve element 811 (at least when in a closed state) and an upstream position P1 that is upstream of the opening 810 of the base portion 812. Therefore, even when the valve element 811 is in a closed state in which it closes the opening 810, the fuel F1 can flow from the downstream position P2 to the upstream position P1 through the bypass path 82.

[0053] Here, because the upstream position P1 is located lower than the downstream position P2, air does not flow from the downstream position P2 to the upstream position P1 through the bypass path 82. Furthermore, the fuel F1 in a gas-liquid mixed state containing a large amount of air bubbles also does not flow from the downstream position P2 to the upstream position P1 through the bypass path 82. As a result, only pure fuel F1 can flow from the downstream position P2 to the upstream position P1 through the bypass path 82.

[0054] Furthermore, the configuration of this embodiment can be expected to have a useful effect even when the valve element 811 is stuck to the seat portion 812 (sticking of the check valve 81). That is, by providing the bypass path 82 near the check valve 81, even when the check valve 81 is stuck, a flow of fluid (fuel F1) is generated through the bypass path 82, and the fluid can be expected to have a cleaning effect on the seat portion 812. By cleaning the seat portion 812, it is possible to resolve minor sticking.

[0055] Furthermore, even if the check valve 81 is stuck due to, for example, long-term storage, it is possible to start the engine 2 by performing initial air bleeding through the bypass path 82. Once the engine 2 starts, spill pressure and spill fuel flowing through the bypass path 82 can naturally resolve any minor sticking.

[0056] Next, a specific configuration example of the bypass path 82 according to this embodiment will be described with reference to FIGS.

[0057] In a first configuration example shown in Fig. 3, at least a part of the bypass path 82 is provided in the check valve 81. In other words, the configuration is not limited to one in which the bypass path 82 is provided separately from the check valve 81 as shown in Fig. 2, but part (or all) of the bypass path 82 may be formed integrally with the check valve 81 as shown in Fig. 3. According to this configuration, the bypass path 82 can be realized without increasing the number of parts.

[0058] More specifically, in the first configuration example, at least a portion of the bypass path 82 is made up of a gap that occurs between the seat portion 812 and the valve element 811 when the valve element 811 is in a closed state. That is, even when the valve element 811 closes the opening 810 of the seat portion 812 as shown on the right side of FIG. 3 (closed state), if there is even a small gap around the opening 810, the fuel F1 can flow from the downstream position P2 to the upstream position P1 through the gap. In this configuration, the gap between the seat portion 812 and the valve element 811 is used, so the bypass path 82 can be realized with a simpler configuration.

[0059] Here, in the first configuration example, the gap is configured by a recess 821 arranged in seat portion 812 at a portion in the circumferential direction of opening 810. Recess 821 is formed, for example, by cutting out one location on seat portion 812 around opening 810, as shown on the left side of FIG. 3 (open state). With such a cutout recess 821, even when valve body 811 closes opening 810 of seat portion 812, a gap is formed around opening 810, and this gap forms at least a portion of bypass path 82. With this configuration, the size (cross-sectional area) of bypass path 82 can be set as desired by changing the shape, size, number, position, etc. of recess 821, making it easy to realize bypass path 82 with desired characteristics.

[0060] 4, the check valve 81 is configured as a sleeve 83 placed inside the air vent pipe 7. The sleeve 83 has a base portion 812 including an opening 810 at one end in the longitudinal direction, and has a throttle portion 831 at a middle position in the longitudinal direction. The inner diameters of the opening 810 and the throttle portion 831 are set smaller than the diameter of the spherical valve element 811, and the valve element 811 is housed inside the sleeve 83 so as to be movable between the opening 810 and the throttle portion 831.

[0061] In the second configuration example, as in the first configuration example, at least a portion of bypass path 82 is made up of a gap formed by recessed portions 821 arranged in seat portion 812 at a portion of the circumferential direction of opening 810. In the second configuration example, recessed portions 821 are formed in two locations around opening 810. In this configuration as well, bypass path 82 can be realized with a simple configuration by utilizing the gap between seat portion 812 and valve body 811.

[0062] 5, the check valve 81 is provided in a sleeve 83 that is arranged in the air vent pipe 7. In this example, the base portion 812 is made of a tubular member that is inserted into one longitudinal end of the sleeve 83, and the sleeve 83 has a throttle portion 831 in a longitudinal intermediate position. The inner diameters of the opening 810 and the throttle portion 831 of the base portion 812 are set smaller than the diameter of the spherical valve element 811, and the valve element 811 is housed in the sleeve 83 so as to be movable between the base portion 812 (opening 810) and the throttle portion 831.

[0063] In the third configuration example, as in the second configuration example, at least a portion of bypass path 82 is made up of a gap formed by recesses 821 that are arranged in seat portion 812 at a portion of the circumferential direction of opening 810. In the third configuration example, recesses 821 are formed in two locations around opening 810. In this configuration as well, bypass path 82 can be realized with a simple configuration by utilizing the gap between seat portion 812 and valve body 811.

[0064] 6, similarly to the second configuration example, the check valve 81 is configured by a sleeve 83 disposed in the air vent pipe 7. The sleeve 83 has a base portion 812 including an opening 810 at one longitudinal end, and a throttle portion 831 at a longitudinal intermediate position. The inner diameters of the opening 810 and the throttle portion 831 are set smaller than the diameter of the spherical valve element 811, and the valve element 811 is accommodated in the sleeve 83 so as to be movable between the opening 810 and the throttle portion 831.

[0065] In the fourth configuration example, at least a portion of the bypass path 82 is made up of a through hole 822 formed in the base portion 812. That is, in the fourth configuration example, a through hole 822 is formed in the pipe wall of the base portion 812, which is part of the sleeve 83, so as to penetrate the pipe wall in the thickness direction. This through hole 822 constitutes at least a portion of the bypass path 82. According to this configuration, the size (cross-sectional area) of the bypass path 82 can be set arbitrarily by changing the shape, size, number, position, etc. of the through holes 822, making it easy to realize a bypass path 82 with desired characteristics.

[0066] In the fifth configuration example, at least a portion of the bypass path 82 is formed by a gap that occurs between the inner peripheral edge of the opening 810 in the seat portion 812 and the valve element 811 when the valve element 811 is closed. That is, in the fifth configuration example, one longitudinal end of the sleeve 83 is reduced in diameter by press working or the like to form the seat portion 812 having the opening 810. In this case, the opening 810 in the seat portion 812 is not a perfect circle, but has a shape with low circularity. Therefore, a gap naturally occurs between the opening 810 with low circularity and the spherical valve element 811, and this gap is used as the bypass path 82.

[0067] Here, the material of the seat portion 812 (sleeve 83) and the valve body 811 is preferably, for example, metal or a durable oil-resistant resin. In particular, fluororesin is less likely to stick, and is therefore suitable even when the fuel F1 is a biofuel.

[0068] [3] Variation Below, we will list some modified examples of embodiment 1. The modified examples explained below can be applied in appropriate combinations.

[0069] The application of the engine system 10 is not limited to a power source for a work machine, a vehicle, an aircraft, a ship, etc. Furthermore, the power source may be a hybrid power source including the engine 2 and a motor (electric motor), and the engine 2 may be, for example, an engine other than a diesel engine.

[0070] Furthermore, it is not essential that the first pipe 41, the second pipe 42, the third pipe 43, and the air vent pipe 7 in the fuel pipe 4 are all made of rubber hoses (rubber pipes), and at least some of these may be made of, for example, metal pipes.

[0071] Furthermore, the three-way joint 40 is not limited to a T-shape, and may be a three-way joint other than a T-shape.

[0072] Furthermore, the fuel filter 6 is not an essential component of the fuel supply device 1 and may be omitted as appropriate. The first throttle valve 11 and the second throttle valve 12 are also not essential components of the fuel supply device 1 and at least one of the first throttle valve 11 and the second throttle valve 12 may be omitted as appropriate.

[0073] (Embodiment 2) As shown in Fig. 7, the fuel supply device 1A according to this embodiment differs from the fuel supply device 1 according to the first embodiment in the configuration of the pressure fluctuation suppression unit 8. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals and descriptions thereof will be omitted as appropriate. In this embodiment, the check valve 81 (see Fig. 2) and the second throttle valve 12 (see Fig. 2) in the air bleed pipe 7 are omitted.

[0074] 7, the pressure fluctuation suppression section 8 has a liquid reservoir section 84. The liquid reservoir section 84 has a larger cross-sectional area than the other portions of the air vent pipe 7 other than the pressure fluctuation suppression section 8. The liquid reservoir section 84 is provided midway through the air vent pipe 7, and functions as a buffer that adds capacity (volume) to the air vent pipe 7.

[0075] According to this configuration, even if a small amount of fuel F1 passes through the pressure fluctuation suppression unit 8 of the air vent pipe 7 in the forward direction together with air, the fuel F1 is stored in the liquid reservoir 84. Without such a pressure fluctuation suppression unit 8, the branch point (three-way joint 40) in the fuel pipe 4 and the return port 32 of the fuel tank 3 would be connected in both directions (forward and reverse) through the air vent pipe 7, and the pressure in the fuel pipe 4 (at its branch point) would fluctuate due to the influence of the air pressure in the fuel tank 3. In contrast, by providing the pressure fluctuation suppression unit 8 (liquid reservoir 84), the pressure in the fuel pipe 4 (at its branch point) can be separated from the air pressure in the fuel tank 3, making it possible to suppress pressure fluctuations in the fuel pipe 4.

[0076] Furthermore, since the liquid reservoir section 84 is connected to (the branch point of) the fuel pipe 4 through the air vent pipe 7, the fuel F1 can also pass through the pressure fluctuation suppression section 8 in the reverse direction. Therefore, due to the effects of reducing the flow velocity of the fuel F1 in the air vent pipe 7 and suppressing fluctuations in the liquid level of the fuel F1 in the air vent pipe 7 due to the increased volume, it is possible to suppress clouding of the fuel F1 (gas-liquid mixture) caused by air entrainment. As a result, there is an advantage in that it becomes easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and the air bleeding effect of the air vent pipe 7 can be easily obtained.

[0077] Furthermore, at least a portion of the liquid reservoir 84 is disposed at the same height as the fuel tank 3 in the vertical direction (up-down direction D1). In the present embodiment, as an example, the liquid reservoir 84 is disposed so that the entire liquid reservoir 84 is contained between the lower and upper surfaces of the fuel tank 3. With this configuration, due to a balance between the suction and discharge of the fuel F1 in the fuel injection pump 5 and the resistance between the fuel pipe 4 and the air vent pipe 7, the liquid level of the fuel F1 in the liquid reservoir 84 is stabilized at a position higher than the liquid level L1 of the fuel F1 in the fuel tank 3, making it easier to ensure head pressure in the fuel tank 3.

[0078] In the configuration of embodiment 2, it is not essential to omit the check valve 81 in the air vent pipe 7, and a check valve 81 may also be provided. The configuration of embodiment 2 (including modified examples) can be adopted in appropriate combination with the various configurations (including modified examples) described in embodiment 1.

[0079] (Embodiment 3) 8, the fuel supply device 1B according to this embodiment differs from the fuel supply device 1 according to embodiment 1 in the arrangement of the pressure fluctuation suppression unit 8. Hereinafter, the same components as those in embodiment 1 will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0080] In this embodiment, the air vent pipe 7 includes an internal pipe 71 that protrudes into the interior of the fuel tank 3. The pressure fluctuation suppression unit 8 is provided in the internal pipe 71. In the example of FIG. 8 , the internal pipe 71 is configured to penetrate the bottom surface of the fuel tank 3 and protrude upward from the inner bottom surface of the fuel tank 3. The pressure fluctuation suppression unit 8 is disposed in the middle of such internal pipe 71.

[0081] According to this configuration, the pressure fluctuation suppressor 8 can be installed using the space inside the fuel tank 3, so there is no need to secure space outside the fuel tank 3 for installing the pressure fluctuation suppressor 8.

[0082] In the third embodiment, the pressure fluctuation suppression unit 8 is not limited to a configuration including a check valve 81 and a bypass path 82 as in the first embodiment, but may also be a configuration including a liquid reservoir 84 as in the second embodiment. Furthermore, the pressure fluctuation suppression unit 8 may be configured with a general check valve 81 excluding the bypass path 82. The configuration according to the third embodiment (including modifications) can be adopted in appropriate combination with the various configurations (including modifications) described in the first or second embodiment.

[0083] (Embodiment 4) 9, the fuel supply device 1C according to this embodiment differs from the fuel supply device 1A according to the second embodiment in the configuration of the pressure fluctuation suppression unit 8. Hereinafter, the same configuration as in the second embodiment will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0084] 9, the pressure fluctuation suppressing unit 8 has a first cylindrical portion 91 and a second cylindrical portion 92. Each of the first cylindrical portion 91 and the second cylindrical portion 92 is formed in a cylindrical shape having a length along the up-down direction D1. Specifically, each of the first cylindrical portion 91 and the second cylindrical portion 92 is formed in a cylindrical tubular shape from, for example, metal or a durable oil-resistant resin.

[0085] 10, the outer diameter φ2 of the second cylindrical portion 92 is smaller than the inner diameter φ1 of the first cylindrical portion 91, and the second cylindrical portion 92 is disposed inside the first cylindrical portion 91. Furthermore, in this embodiment, the length (in the up-down direction D1) of the second cylindrical portion 92 is also shorter than that of the first cylindrical portion 91. In other words, in this embodiment, the pressure fluctuation suppression portion 8 has a double-tube structure in which the first cylindrical portion 91 is an outer tube and the second cylindrical portion 92 is an inner tube.

[0086] The pressure fluctuation suppression unit 8 with a double pipe structure is provided midway through the air vent pipe 7, and a first cylindrical portion 91 and a second cylindrical portion 92 are inserted in series between a branch point (three-way joint 40) connected by the air vent pipe 7 and the return port 32 of the fuel tank 3. In this way, the pressure fluctuation suppression unit 8 functions as a buffer that adds an air damper 85 (see FIG. 11) as an air reservoir to the air vent pipe 7.

[0087] 9, the second cylindrical portion 92 serving as an inner cylinder has a cylindrical shape with both ends in the longitudinal direction (vertical direction D1) open, with the opening at the lower end being a first opening 921 and the opening at the upper end being a second opening 922. Furthermore, the second cylindrical portion 92 has a hole 923 on its side surface (outer peripheral surface) that opens laterally. The center of the hole 923 is located below the center of the second cylindrical portion 92 in the longitudinal direction (vertical direction D1). More preferably, the center, upper end, or lower end of the hole 923 is located below the nominal lower limit oil level of the fuel tank 3 (the nominal lower limit of the liquid level L1 of the fuel F1). Furthermore, the second opening 922 is located at least above the nominal lower limit oil level of the fuel tank 3.

[0088] On the other hand, the first cylindrical portion 91 serving as an outer cylinder is cylindrical with both ends in the longitudinal direction (vertical direction D1) closed and with a bottom, and has an opening hole 911 on its side surface (outer peripheral surface) that opens laterally. The second cylindrical portion 92 is combined with the first cylindrical portion 91 so as to penetrate the lower bottom surface of the first cylindrical portion 91. As a result, when the pressure fluctuation suppressing unit 8 is viewed from below, a first opening 921 of the second cylindrical portion 92 is exposed at the center of the lower bottom surface of the first cylindrical portion 91. The second opening 922 of the second cylindrical portion 92 is located inside the first cylindrical portion 91.

[0089] As a result, the first cylindrical portion 91 and the second cylindrical portion 92 are connected to each other at a communication portion (second opening 922) above the center in the up-down direction D1. In other words, the internal space Sp2 (see FIG. 10) of the second cylindrical portion 92 and the gap space Sp1 (see FIG. 10) between the inner peripheral surface of the first cylindrical portion 91 and the outer peripheral surface of the second cylindrical portion 92 are connected to each other at the second opening 922 serving as a communication portion.

[0090] A first opening 921 of the second cylindrical portion 92 serving as an inner cylinder is connected to the branch point (three-way joint 40) via the air vent pipe 7, and an opening hole 911 of the first cylindrical portion 91 serving as an outer cylinder is connected to the return port 32 of the fuel tank 3 via the air vent pipe 7. This allows the pressure fluctuation suppression unit 8 having a double-pipe structure to pass air (and a small amount of fuel F1) in the forward direction from the branch point (three-way joint 40) side toward the fuel tank 3, with the first opening 921 of the second cylindrical portion 92 as an inlet and the opening hole 911 of the first cylindrical portion 91 as an outlet.

[0091] 11 schematically shows a state in which air is filled inside the pressure fluctuation suppression unit 8 (denoted as "air filling"), and a state in which air is discharged (denoted as "air discharge") from the pressure fluctuation suppression unit 8. In FIG. 11, the air pressure acting on the liquid level L1 of the fuel F1 is indicated by a hollow arrow, and the direction of air movement is indicated by a thick arrow.

[0092] For example, when a small amount of fuel F1 passes forward through the pressure fluctuation suppression unit 8 of the air vent pipe 7 together with air, the fuel F1 is stored in the pressure fluctuation suppression unit 8, as shown by "Air Charging" in FIG. 11 . At this time, air temporarily accumulates above the liquid level L1 in the pressure fluctuation suppression unit 8, forming an air damper 85. The air from the branch point (three-way joint 40) side is separated from the fuel tank 3 by the fuel F1 accumulated in the lower part of the first cylindrical portion 91. In this state, air from the branch point (three-way joint 40) side continues to fill the pressure fluctuation suppression unit 8 from the first opening 921 through the air vent pipe 7, causing the pressure of the air damper 85 to increase, and the liquid level L1 of the fuel F1 in the pressure fluctuation suppression unit 8 to gradually decrease (drop).

[0093] When the liquid level L1 of the fuel F1 in the pressure fluctuation suppression unit 8 falls below (the upper end of) the opening hole 911, the air damper 85 communicates with (the return port 32 of) the fuel tank 3 through the air vent pipe 7, and therefore the air in the air damper 85 is discharged from the opening hole 911 through the air vent pipe 7 to (the return port 32 of) the fuel tank 3, as shown by "air discharge" in Fig. 11. At the same time, the fuel F1 flows into the air damper 85 from the second cylindrical portion 92, and the liquid level L1 of the fuel F1 in the pressure fluctuation suppression unit 8 rises.

[0094] The fuel supply device 1C according to this embodiment repeats the above-described "air filling" and "air discharging" operations to remove air and maintain a stable supply of fuel F1.

[0095] In short, in the fuel supply device 1C according to this embodiment, the pressure fluctuation suppression unit 8 has a first cylindrical portion 91 and a second cylindrical portion 92 disposed inside the first cylindrical portion 91. The air vent pipe 7 passes through both the first cylindrical portion 91 and the second cylindrical portion 92 to connect the branch point (the three-way joint 40) and the fuel tank 3 (the return port 32).

[0096] According to this configuration, even if a small amount of fuel F1 passes through the pressure fluctuation suppression unit 8 of the air vent pipe 7 in the forward direction together with air, the fuel F1 is stored in the air damper 85. Without such a pressure fluctuation suppression unit 8, the branch point (three-way joint 40) in the fuel pipe 4 and the return port 32 of the fuel tank 3 would be connected in both directions (forward and reverse directions) through the air vent pipe 7, and the pressure in the fuel pipe 4 (at its branch point) would fluctuate due to the influence of the air pressure in the fuel tank 3. In contrast, by providing the pressure fluctuation suppression unit 8, the pressure in the fuel pipe 4 (at its branch point) can be separated from the air pressure in the fuel tank 3, making it possible to suppress pressure fluctuations in the fuel pipe 4.

[0097] Furthermore, the fuel F1 accumulated in the pressure fluctuation suppression unit 8 is communicated with (the branching point of) the fuel pipe 4 through the air vent pipe 7, and therefore the fuel F1 can also pass through the pressure fluctuation suppression unit 8 in the reverse direction. Therefore, due to the effects of reducing the flow velocity of the fuel F1 in the air vent pipe 7 and suppressing fluctuations in the liquid level of the fuel F1 in the air vent pipe 7 due to the increase in volume, it is possible to suppress clouding of the fuel F1 (gas-liquid mixture) due to air entrainment. As a result, there is an advantage in that it becomes easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and the air venting effect of the air vent pipe 7 can be easily obtained.

[0098] In this embodiment, the first cylindrical portion 91 and the second cylindrical portion 92 are connected to each other through a communication portion (second opening 922) located above the center of the vertical direction D1. The lower end portion (first opening 921) of the second cylindrical portion 92 is connected to the branch point (three-way joint 40), and the lower end portion (opening 911) of the first cylindrical portion 91 is connected to the fuel tank 3. As a result, air sent from the branch point (three-way joint 40) passes from the lower end portion (first opening 921) of the second cylindrical portion 92 through the internal space Sp2 of the second cylindrical portion 92 and moves from the communication portion (second opening 922) into the first cylindrical portion 91. Furthermore, the air passes through a gap space Sp1 between the inner circumferential surface of the first cylindrical portion 91 and the outer circumferential surface of the second cylindrical portion 92, and can be discharged from the lower end portion (opening 911) of the first cylindrical portion 91 to the fuel tank 3.

[0099] Furthermore, in this embodiment, the second cylindrical portion 92 is provided with a hole 923 that connects the interior (internal space Sp2) and the exterior (gap space Sp1) of the second cylindrical portion 92, in addition to the communication portion (second opening 922). This allows air and fuel F1 to move between the internal space Sp2 and the gap space Sp1 through the hole 923. This has the advantage that it is easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and it is easier to obtain the air bleeding effect of the air bleeding pipe 7.

[0100] Furthermore, the center of the hole 923 is located on the opposite side of the communication portion (second opening 922) when viewed from the center of the second cylindrical portion 92 in the vertical direction D1. In other words, the center of the hole 923 is located below the center of the second cylindrical portion 92 in the vertical direction D1. Therefore, the air and fuel F1 can move between the internal space Sp2 and the gap space Sp1 through the hole 923 without moving inside the second cylindrical portion 92 to the communication portion (second opening 922).

[0101] Furthermore, the center, upper end, or lower end of the hole 923 is located below the nominal lower limit oil level of the fuel tank 3. Therefore, even if the fuel F1 in the fuel tank 3 decreases and the liquid level L1 drops to the nominal lower limit oil level, the fuel F1 in the pressure fluctuation suppression unit 8 can move between the internal space Sp2 and the gap space Sp1 through the hole 923.

[0102] Furthermore, the hole 923 is not limited to being provided in one place, but may be provided in multiple places.

[0103] 10, in this embodiment, the cross-sectional area of the gap (gap space Sp1) between the first cylindrical portion 91 and the second cylindrical portion 92 is equal to or smaller than the cross-sectional area of the interior (internal space Sp2) of the second cylindrical portion 92. This has the advantage that it is easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and the air bleeding effect of the air bleeding pipe 7 is easier to obtain.

[0104] 12 shows various modifications of the fourth embodiment. In these modifications, the configuration of the pressure fluctuation suppressor 8 differs from that of the fourth embodiment.

[0105] In the fuel supply device 1D according to the first modified example, a second opening 922, which serves as a communication portion between the second cylindrical portion 92 and the first cylindrical portion 91, is formed in the side surface (outer peripheral surface) of the second cylindrical portion 92, rather than at the upper end of the second cylindrical portion 92. Even in this case, the internal space Sp2 of the second cylindrical portion 92 communicates with the gap space Sp1 between the inner peripheral surface of the first cylindrical portion 91 and the outer peripheral surface of the second cylindrical portion 92 through the second opening 922 serving as a communication portion. The second opening 922 is not limited to being provided in one location, and may be provided in multiple locations.

[0106] In a fuel supply device 1E according to the second modification, the relationship between a first cylindrical portion 91 and a second cylindrical portion 92 is reversed from that in the fourth embodiment. Specifically, in the second cylindrical portion 92, a first opening 921 is formed on a side surface (outer peripheral surface) of the second cylindrical portion 92, rather than on a lower end of the second cylindrical portion 92. The first opening 921 constitutes a communication portion between the second cylindrical portion 92 and the first cylindrical portion 91, instead of the second opening 922. Furthermore, the opening hole 911 of the first cylindrical portion 91 is disposed in an upper portion of the first cylindrical portion 91, rather than in a lower portion thereof.

[0107] In the second modified example, the opening 911 of the first cylindrical portion 91 serving as the outer cylinder is connected to the branch point (three-way joint 40) via the air vent pipe 7, and the second opening 922 of the second cylindrical portion 92 serving as the inner cylinder is connected to the return port 32 of the fuel tank 3 via the air vent pipe 7. This allows the pressure fluctuation suppression unit 8 having a double-pipe structure to pass air (and a small amount of fuel F1) in the forward direction from the branch point (three-way joint 40) side toward the fuel tank 3, with the opening 911 of the first cylindrical portion 91 as an inlet and the second opening 922 of the second cylindrical portion 92 as an outlet.

[0108] That is, in the fuel supply device 1E according to the second modification, the first cylindrical portion 91 and the second cylindrical portion 92 are connected to each other through a communication portion (first opening 921) below the center in the up-down direction D1. The upper end of the first cylindrical portion 91 is connected to the branch point (three-way joint 40), and the upper end of the second cylindrical portion 92 is connected to the fuel tank 3. As a result, air sent from the branch point (three-way joint 40) passes from the upper end (opening 911) of the first cylindrical portion 91 through a clearance space Sp1 between the inner circumferential surface of the first cylindrical portion 91 and the outer circumferential surface of the second cylindrical portion 92, and moves from the communication portion (first opening 921) into the second cylindrical portion 92. Furthermore, the air passes through an internal space Sp2 of the second cylindrical portion 92 and can be discharged from the upper end (second opening 922) of the second cylindrical portion 92 to the fuel tank 3 side.

[0109] In the fuel supply device 1F according to the third modified example, the pressure fluctuation suppression section 8 has a triple-pipe structure. That is, the pressure fluctuation suppression section 8 further includes a third cylindrical section 93 that is disposed outside the first cylindrical section 91. The air vent pipe 7 connects the branch point (three-way joint 40) and the fuel tank 3 through all of the first cylindrical section 91, the second cylindrical section 92, and the third cylindrical section 93. This has the advantage of making it easier to prevent fuel from being sprayed into the fuel tank 3 due to pulsation generated by the fuel injection pump 5, and making it easier to obtain the air bleeding effect of the air vent pipe 7.

[0110] Specifically, the inner diameter of the third cylindrical portion 93 is larger than the outer diameter of the first cylindrical portion 91, and the first cylindrical portion 91 is disposed inside the third cylindrical portion 93. Furthermore, in this embodiment, the length (in the vertical direction D1) of the first cylindrical portion 91 is also shorter than that of the third cylindrical portion 93. The third cylindrical portion 93, which serves as the outermost cylinder, is tubular with a bottom and closed ends in the longitudinal direction (in the vertical direction D1), and has an opening 931 on its top surface (upper bottom surface) that opens upward. The first cylindrical portion 91 and the third cylindrical portion 93 are connected to each other by a communication portion (opening 911) below the center in the vertical direction D1.

[0111] The first opening 921 of the second cylindrical portion 92 is connected to the branch point (three-way joint 40) via the air vent pipe 7, and the opening hole 931 of the third cylindrical portion 93, which serves as the outermost cylinder, is connected to the return port 32 of the fuel tank 3 via the air vent pipe 7. This allows the pressure fluctuation suppression unit 8 with a triple-pipe structure to pass air (and a small amount of fuel F1) in the forward direction from the branch point (three-way joint 40) side toward the fuel tank 3, with the first opening 921 of the second cylindrical portion 92 as an inlet and the opening hole 931 of the third cylindrical portion 93 as an outlet.

[0112] Furthermore, the pressure fluctuation suppression unit 8 is not limited to a triple-pipe structure, and may be, for example, a quadruple-pipe structure combining four tubular sections, or a multiple-pipe structure combining five or more tubular sections. The configuration according to the fourth embodiment (including modifications) can be adopted in appropriate combination with the various configurations (including modifications) described in the first, second, or third embodiment.

[0113] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0114] <Appendix 1> an air vent pipe that branches off from a branch point in a fuel pipe that supplies fuel from a fuel tank to a fuel injection pump of an engine and is connected to the fuel tank; a pressure fluctuation suppression unit disposed in the air vent pipe, The pressure fluctuation suppression unit is In a forward direction from the branch point side toward the fuel tank side, air and the fuel are allowed to pass through, In the reverse direction from the fuel tank side toward the branch point side, the passage of the air is suppressed and the passage of the fuel is allowed. Engine fuel supply system.

[0115] <Appendix 2> The pressure fluctuation suppression unit is a check valve that allows the fluid to pass in the forward direction while preventing the fluid from passing in the reverse direction; a bypass path that bypasses a downstream position and an upstream position in the forward direction as seen from the check valve in the air vent pipe, 2. A fuel supply system for an engine as described in appendix 1.

[0116] <Appendix 3> At least a portion of the bypass path is provided in the check valve. 10. A fuel supply system for an engine as described in appendix 2.

[0117] <Appendix 4> The check valve includes a base portion having an opening on the downstream side in the forward direction, and a valve body that opens and closes the opening. 4. A fuel supply system for an engine as described in appendix 3.

[0118] <Appendix 5> At least a portion of the bypass path is formed by a gap that is generated between the base portion and the valve body when the valve body is closed. 5. A fuel supply system for an engine according to claim 4.

[0119] <Appendix 6> The valve body is a sphere that moves within the air vent pipe, The gap is formed by a recessed portion disposed in a portion of the pedestal portion in the circumferential direction of the opening. 6. A fuel supply system for an engine according to claim 5.

[0120] <Appendix 7> At least a part of the bypass path is formed by a through hole formed in the base portion. A fuel supply device for an engine according to any one of appendixes 4 to 6.

[0121] <Appendix 8> the front air vent pipe includes an internal pipe protruding into the interior of the fuel tank, The pressure fluctuation suppression unit is provided in the internal piping. A fuel supply device for an engine according to any one of appendices 1 to 7.

[0122] <Appendix 9> the pressure fluctuation suppression unit has a liquid reservoir portion having a cross-sectional area larger than that of a portion of the air vent pipe other than the pressure fluctuation suppression unit. A fuel supply device for an engine according to any one of appendices 1 to 8.

[0123] <Appendix 10> At least a portion of the liquid reservoir is disposed at the same height as the fuel tank in the vertical direction. 10. A fuel supply system for an engine according to claim 9.

[0124] <Appendix 11> the pressure fluctuation suppression portion has a first cylindrical portion and a second cylindrical portion disposed inside the first cylindrical portion, the air vent pipe connects the branch point and the fuel tank through both the first cylindrical portion and the second cylindrical portion. A fuel supply device for an engine according to any one of appendices 1 to 10.

[0125] <Appendix 12> the first cylindrical portion and the second cylindrical portion are connected to each other at a communication portion located above the center in the up-down direction, a lower end of the second cylindrical portion connected to the branch point side, and a lower end of the first cylindrical portion connected to the fuel tank side; 12. A fuel supply system for an engine according to claim 11.

[0126] <Appendix 13> The first cylindrical portion and the second cylindrical portion are connected to each other at a communication portion below the center in the up-down direction, An upper end of the first cylindrical portion is connected to the branch point side, and an upper end of the second cylindrical portion is connected to the fuel tank side. 12. A fuel supply system for an engine according to claim 11.

[0127] <Appendix 14> The second cylindrical portion has a hole that connects the inside and the outside of the second cylindrical portion, separate from the communication portion. 14. A fuel supply device for an engine according to claim 12 or 13.

[0128] <Appendix 15> The center of the hole is located on the opposite side of the communicating portion when viewed from the center of the second cylindrical portion in the vertical direction. 15. A fuel supply system for an engine according to claim 14.

[0129] <Appendix 16> The center, upper end, or lower end of the hole is located below the nominal lower limit oil level of the fuel tank. 16. A fuel supply device for an engine according to claim 14 or 15.

[0130] <Appendix 17> The cross-sectional area of the gap between the first cylindrical portion and the second cylindrical portion is equal to or smaller than the cross-sectional area of the inside of the second cylindrical portion. A fuel supply device for an engine according to any one of appendixes 11 to 16.

[0131] <Appendix 18> the pressure fluctuation suppression portion further includes a third cylindrical portion disposed outside the first cylindrical portion, the air vent pipe connects the branch point and the fuel tank through all of the first cylindrical portion, the second cylindrical portion, and the third cylindrical portion. A fuel supply device for an engine according to any one of appendices 11 to 17.

[0132] <Appendix 19> A fuel supply device for an engine according to any one of appendices 1 to 18; The engine. Engine system. [Explanation of symbols]

[0133] 1,1A,1B,1C,1D,1E,1F Fuel supply device 2 engines 3 fuel tanks 4 Fuel piping 5 Fuel injection pump 7 Air vent piping 8 Pressure fluctuation suppression section 10 Engine System 40 Three-way joint (branch point) 71 Internal piping 81 Check valve 82 Bypass Route 84 Liquid reservoir 91 First cylinder part 92 Second cylinder part 93 Third cylinder part 811 Valve body 812 Base 821 recess 822 Through hole 921 1st opening (communication part) 922 2nd opening (communication part) 923 holes F1 fuel P1 upstream position P2 downstream position

Claims

1. an air vent pipe that branches off from a branch point in a fuel pipe that supplies fuel from a fuel tank to a fuel injection pump of an engine and is connected to the fuel tank; a pressure fluctuation suppression unit disposed in the air vent pipe, The pressure fluctuation suppression unit is In a forward direction from the branch point side toward the fuel tank side, air and the fuel are allowed to pass through, In the reverse direction from the fuel tank side toward the branch point side, the passage of the air is suppressed and the passage of the fuel is allowed. Engine fuel supply system.

2. The pressure fluctuation suppression unit is a check valve that allows the fluid to pass in the forward direction while preventing the fluid from passing in the reverse direction; a bypass path that bypasses a downstream position and an upstream position in the forward direction as seen from the check valve in the air vent pipe, 2. The engine fuel supply system according to claim 1.

3. At least a portion of the bypass path is provided in the check valve.

3. The engine fuel supply system according to claim 2.

4. The check valve includes a base portion having an opening on the downstream side in the forward direction, and a valve body that opens and closes the opening.

4. The engine fuel supply system according to claim 3.

5. At least a portion of the bypass path is formed by a gap that is generated between the base portion and the valve body when the valve body is closed.

5. The engine fuel supply system according to claim 4.

6. The valve body is a sphere that moves within the air vent pipe, The gap is formed by a recessed portion disposed in a portion of the pedestal portion in the circumferential direction of the opening.

6. A fuel supply system for an engine according to claim 5.

7. At least a part of the bypass path is formed by a through hole formed in the base portion. The fuel supply device for an engine according to any one of claims 4 to 6.

8. the front air vent pipe includes an internal pipe protruding into the interior of the fuel tank, The pressure fluctuation suppression unit is provided in the internal piping. The fuel supply device for an engine according to any one of claims 1 to 6.

9. the pressure fluctuation suppression unit has a liquid reservoir portion having a cross-sectional area larger than that of a portion of the air vent pipe other than the pressure fluctuation suppression unit. The fuel supply device for an engine according to any one of claims 1 to 6.

10. At least a portion of the liquid reservoir is disposed at the same height as the fuel tank in the vertical direction.

10. The engine fuel supply system according to claim 9.

11. the pressure fluctuation suppression portion includes a first cylindrical portion and a second cylindrical portion disposed inside the first cylindrical portion, the air bleed pipe connects the branch point and the fuel tank through both the first cylindrical portion and the second cylindrical portion. The fuel supply device for an engine according to any one of claims 1 to 6.

12. the first cylindrical portion and the second cylindrical portion are connected to each other at a communication portion located above the center in the up-down direction, a lower end of the second cylindrical portion connected to the branch point side, and a lower end of the first cylindrical portion connected to the fuel tank side; 12. A fuel supply system for an engine according to claim 11.

13. the first cylindrical portion and the second cylindrical portion are connected to each other at a communication portion located below the center in the up-down direction, an upper end of the first cylindrical portion connected to the branch point side, and an upper end of the second cylindrical portion connected to the fuel tank side; 12. A fuel supply system for an engine according to claim 11.

14. the second cylindrical portion includes a hole connecting the inside and the outside of the second cylindrical portion, separate from the communication portion; 13. A fuel supply system for an engine according to claim 12.

15. the center of the hole is located on the opposite side of the communicating portion as viewed from the center of the second cylindrical portion in the vertical direction.

15. A fuel supply system for an engine according to claim 14.

16. The center, upper end, or lower end of the hole is located below the nominal lower limit oil level of the fuel tank.

15. A fuel supply system for an engine according to claim 14.

17. a cross-sectional area of the gap between the first cylindrical portion and the second cylindrical portion is equal to or smaller than a cross-sectional area of the inside of the second cylindrical portion; 12. A fuel supply system for an engine according to claim 11.

18. the pressure fluctuation suppression portion further includes a third cylindrical portion disposed outside the first cylindrical portion, the air bleed pipe connects the branch point and the fuel tank through all of the first cylindrical portion, the second cylindrical portion, and the third cylindrical portion.

12. A fuel supply system for an engine according to claim 11.

19. A fuel supply device for an engine according to any one of claims 1 to 6; The engine. Engine system.

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