Fuel supply device for engine and engine system

Abstract

The invention provides a fuel supply device for an engine and an engine system, which can easily obtain an exhaust effect. A fuel supply device (1) for an engine (2) is provided with an exhaust pipe (7) and a pressure fluctuation suppression unit (8). The exhaust pipe (7) branches from a branching point of a fuel pipe (4) that supplies fuel (F1) from the fuel tank (3) to a fuel injection pump (5) of an engine (2), and is connected to the fuel tank (3). The pressure fluctuation suppression unit (8) is disposed in the exhaust pipe (7). The pressure fluctuation suppression unit (8) permits passage of air and fuel (F1) in the downstream direction from the branch point side toward the fuel tank (3) side. The pressure fluctuation suppression unit (8) suppresses the passage of air and allows the passage of fuel (F1) in the reverse flow direction from the fuel tank (3) side to the branch point side.

Description

Technical Field

[0001] The present disclosure relates to a fuel supply device for an engine that supplies fuel to the engine and an engine system. Background Art

[0002] As a related art, a fuel supply device for an engine that supplies fuel from a fuel tank to a fuel injection pump is known (for example, refer to Patent Document 1). The fuel supply device for the engine according to the related art has the following structure: an exhaust pipe communicating with the fuel tank is provided, and a fuel filter, a fuel injection pump, and the exhaust pipe are connected by means of a tee joint. The fuel supply device for the engine has a check valve (or a sphere constituting a check valve function) in the exhaust pipe, and exhausts the fuel pipe due to pulsation generated from the fuel injection pump. That is, the air in the fuel pipe is discharged to the fuel tank through the exhaust pipe, and the check valve prevents the air from flowing back toward the tee joint.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-291958 Summary of the Invention

[0006] However, with respect to the fuel supply device for the engine according to the above related art, sometimes a small amount of fuel passes through the check valve of the exhaust pipe together with air. In this case, the fuel accumulates as surplus fuel on the downstream side (the opposite side of the tee joint) of the check valve of the exhaust pipe. Moreover, due to pulsation generated from the fuel injection pump, the accumulated surplus fuel is extruded by air, and thus the fuel may be ejected toward the fuel tank. As a result, the exhaust effect of the exhaust pipe may not be obtained sufficiently.

[0007] An object of the present disclosure is to provide a fuel supply device for an engine and an engine system that can easily obtain an exhaust effect.

[0008] The fuel supply device for an engine according to one aspect of the present disclosure includes an exhaust pipe and a pressure fluctuation suppression unit. The exhaust pipe branches off from a branch point of a fuel pipe and is connected to a fuel tank, and the fuel pipe supplies fuel from the fuel tank to a fuel injection pump of the engine. The pressure fluctuation suppression unit is disposed in the exhaust pipe. The pressure fluctuation suppression unit allows air and the fuel to pass in a downstream direction from the branch point side toward the fuel tank side. The pressure fluctuation suppression unit suppresses the passage of the air and allows the fuel to pass in an upstream direction from the fuel tank side toward the branch point side.

[0009] An engine system according to one aspect of the present disclosure includes the fuel supply device for the engine and the engine.

[0010] Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide a fuel supply device for an engine and an engine system that can easily achieve an exhaust effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an explanatory diagram showing a schematic configuration of the engine system according to Embodiment 1.

[0013] Figure 2 It is a schematic diagram for explaining the main part of the engine system according to Embodiment 1.

[0014] Figure 3 It is a schematic perspective view showing a first structural example of the pressure fluctuation suppression unit for the engine system according to Embodiment 1.

[0015] Figure 4 It is a schematic diagram showing a second structural example of the pressure fluctuation suppression unit for the engine system according to Embodiment 1.

[0016] Figure 5 It is a schematic diagram showing a third structural example of the pressure fluctuation suppression unit for the engine system according to Embodiment 1.

[0017] Figure 6 It is a schematic cross-sectional view showing a fourth structural example and a fifth structural example of the pressure fluctuation suppression unit for the engine system according to Embodiment 1.

[0018] Figure 7 It is an explanatory diagram showing a schematic configuration of the engine system according to Embodiment 2.

[0019] Figure 8 It is an explanatory diagram showing a schematic configuration of the engine system according to Embodiment 3.

[0020] Figure 9 It is an explanatory diagram showing a schematic configuration of the engine system according to Embodiment 4.

[0021] Figure 10 It is a schematic cross-sectional perspective view of the pressure fluctuation suppression unit for the engine system according to Embodiment 4.

[0022] Figure 11 It is a schematic diagram showing an operation example of the pressure fluctuation suppression unit for the engine system according to Embodiment 4.

[0023] Figure 12 It is an explanatory diagram showing a schematic configuration of the fuel supply device of the engine according to a modification of Embodiment 4.

[0024] Description of Reference Numerals

[0025] 1, 1A, 1B, 1C, 1D, 1E, 1F... fuel supply device; 2... engine; 3... fuel tank; 4... fuel pipe; 5... fuel injection pump; 7... exhaust pipe; 8... pressure fluctuation suppression section; 10... engine system; 40... tee joint (branch point); 71... internal pipe; 81... check valve; 82... bypass path; 84... liquid accumulation section; 91... first cylinder part; 92... second cylinder part; 93... third cylinder part; 811... valve element; 812... base part; 821... recess; 822... through hole; 921... first opening (communication part); 922... second opening (communication part); 923... hole; F1... fuel; P1... upstream position; P2... downstream position. Detailed Embodiment

[0026] Next, embodiments of the present disclosure will be described with reference to the drawings. The following embodiments are examples for embodying the present disclosure, and the gist thereof does not limit the technical scope of the present disclosure. The drawings referred to in the present disclosure are all schematic diagrams, and the ratios of the sizes and thicknesses of the respective structural elements in the drawings do not necessarily reflect the actual size ratios.

[0027] (Embodiment 1)

[0028] [1] Overall Structure

[0029] First, refer to Figure 1 to describe the overall structure of the engine system 10 according to this embodiment.

[0030] As Figure 1 shown, the engine system 10 according to this embodiment includes a fuel supply device 1 (hereinafter simply referred to as "fuel supply device 1") for the engine 2 and the engine 2. The "engine" mentioned here is a heat generating mechanism that burns fuel F1 to generate mechanical energy (power), and the combustion of fuel F1 occurs inside the heat generating mechanism, including an internal combustion engine, which is a prime mover that converts thermal energy into mechanical energy using gas as the working gas. That is, the engine 2 generates power (mechanical energy) using the supplied fuel.

[0031] The engine 2 according to this embodiment is a reciprocating engine that converts the reciprocating motion of a piston into a rotational motion and outputs the rotational force as power. In particular, in this embodiment, as an example, the engine 2 is a horizontally mounted water-cooled diesel engine. The fuel F1 is a liquid fuel such as a fossil fuel (light oil or gasoline, etc.) as an example. In this embodiment, the engine 2 is driven by supplying fuel F1 (here light oil) from the fuel supply device 1.

[0032] In addition, the engine 2 of the engine system 10 is used as a power source for, for example, a work machine, a vehicle, an aircraft (such as a drone), or a ship. That is, the engine system 10 is mounted on the body of a work machine, a vehicle, an aircraft, or a ship, and generates power for the work machine, the vehicle, the aircraft, or the ship. Here, the work machine means a machine that performs various operations. As an example, it includes agricultural machines (agricultural machinery) such as harvesting machines, tractors, seeders, transplanters, spreaders, sprayers, or transplanting machines, or construction machines (construction machinery) such as backhoe excavators, wheel loaders, or conveyors, etc.

[0033] In addition, in the present embodiment, for ease of explanation, the vertical direction in the state where the engine system 10 can be used is defined as the up-down direction D1. And the Figure 1 left-right direction in is defined as the left-right direction D2. However, the main idea is not to limit the usage direction (direction during use) of the engine system 10 by the above directions.

[0034] The fuel supply device 1 includes a fuel tank 3, a fuel pipe 4, a fuel injection pump 5, and a fuel filter 6. In addition, the fuel supply device 1 according to the present embodiment further includes a three-way joint 40, an exhaust pipe 7, etc.

[0035] The fuel tank 3 is a container for storing the fuel F1. The fuel tank 3 is disposed above the engine 2. A take-out port 31 is formed in the lower part of the fuel tank 3, and the fuel F1 stored in the fuel tank 3 can be taken out from the take-out port 31.

[0036] The fuel injection pump 5 injects the fuel F1 into the engine 2 to supply the fuel F1 to the engine 2. The fuel injection pump 5 has a suction port 51. The fuel injection pump 5 is connected to a fuel injection nozzle via a high-pressure pipe, and opens and closes the fuel injection valve in accordance with the fuel injection timing to inject the fuel F1 supplied from the fuel tank 3 to the suction port 51 from the fuel injection nozzle into the engine 2.

[0037] The fuel filter 6 has a primary side port 61, a secondary side port 62, and components. The fuel filter 6 discharges the fuel F1 supplied from the primary side port 61 through the components from the secondary side port 62. The components are housed in the housing of the fuel filter 6 in a replaceable manner.

[0038] The fuel pipe 4 is a pipe for supplying the 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 the present embodiment, the fuel filter 6 is inserted in the middle of 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.

[0039] Specifically, the fuel pipe 4 has: a first pipe 41, which is on the fuel tank 3 side (upstream side) when viewed from the fuel filter 6; and a second pipe 42, which is on the fuel injection pump 5 side (downstream side) when viewed from the fuel filter 6. The first pipe 41 connects the outlet 31 of the fuel tank 3 and the primary side port 61 of the fuel filter 6. The second pipe 42 connects between the secondary side port 62 of the fuel filter 6 and the suction port 51 of the fuel injection pump 5 (by means of a tee joint 40 or the like).

[0040] More specifically, the second pipe 42 is connected to the suction port 51 of the fuel injection pump 5 by means of a tee joint 40 and a third pipe 43. That is, the fuel pipe 4 further has a third pipe 43 in addition to the first pipe 41 and the second pipe 42. The tee 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 communicate with each other inside the tee joint 40. The second pipe 42 connects the secondary side port 62 of the fuel filter 6 and the first branch pipe 401 of the tee joint 40. The third pipe 43 connects the second branch pipe 402 of the tee joint 40 and the suction port 51 of the fuel injection pump 5.

[0041] Thus, the fuel F1 discharged from the secondary side port 62 of the fuel filter 6 is sequentially supplied to the suction port 51 of the fuel injection pump 5 through the second pipe 42, the tee joint 40 (between the first branch pipe 401 - the second branch pipe 402), and the third pipe 43. 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.

[0042] In addition, in the present embodiment, the fuel tank 3 is disposed on the left side of the engine 2, and the fuel tank 3 is disposed such that the lower surface (bottom surface) of the fuel tank 3 is at least higher than the position (above) of the suction port 51 of the fuel injection pump 5. Thus, the liquid level L1 of the fuel F1 in the fuel tank 3 is at a position higher than the suction port 51 of the fuel injection pump 5, and a head pressure (atmospheric pressure) is easily obtained at the liquid level L1. Therefore, the fuel supply device 1 can supply the fuel F1 by natural fall from the fuel tank 3 without using a charging pump.

[0043] In addition, regarding the fuel supply device 1 according to the present embodiment, the third branch pipe 403 of the tee joint 40 is connected to the fuel tank 3 by means of an exhaust pipe 7. Specifically, a reduction port 32 is formed in the upper part of the fuel tank 3, and the exhaust pipe 7 connects the third branch pipe 403 of the tee joint 40 and the reduction port 32 of the fuel tank 3. Thus, the air in the fuel F1 passing through the fuel pipe 4 is returned from the reduction port 32 to the inside of the fuel tank 3 through the exhaust pipe 7.

[0044] As used in this disclosure, the term "air" means gas such as bubbles in the fuel F1, for example, air, or air containing moisture such as water vapor. That is, when such air (bubbles) is contained in the fuel F1 passing through the fuel pipe 4, the air is guided through the three-way joint 40 (between the first branch pipe 401 - the third branch pipe 403) to the exhaust pipe 7 and restored from the restoration port 32 to the fuel tank 3. As a result, the exhaust in the fuel pipe 4 can be carried out.

[0045] In addition, Figure 1 In the like, the flow of the fuel F1 in the fuel supply system is indicated by a blackened arrow, and the flow of air (bubbles) is indicated by a white arrow.

[0046] [2] Details of the fuel supply device

[0047] Next, with reference to Figures 2 to 6 The details of the fuel supply device 1 according to the present embodiment will be mainly described, mainly the structure related to the exhaust pipe 7.

[0048] As Figure 2 shown, the fuel supply device 1 according to the present embodiment further includes a pressure fluctuation suppression unit 8, a first throttle valve 11, and a second throttle valve 12.

[0049] The first pipe 41 in the fuel pipe 4 is made of, for example, a rubber hose (rubber tube). One end of the first pipe 41 is connected to the first joint 301 protruding downward from the extraction port 31 of the fuel tank 3, and the other end of the first pipe 41 is connected to the primary side port 61 formed by a joint protruding leftward from the upper part of the fuel filter 6. More specifically, the first pipe 41 is arranged based on the horizontal direction (left - right direction D2) in such a way that it extends downward from the lower surface of the fuel tank 3, and its end extends to the right along the left - right direction D2 by means of a bent portion and is connected to the fuel filter 6 from the left side.

[0050] The second pipe 42 in the fuel pipe 4 is made of, for example, a rubber hose (rubber tube). One end of the second pipe 42 is connected to the secondary side port 62 formed by a joint protruding rightward from the upper part of the fuel filter 6, and the other end of the second pipe 42 is connected to the first branch pipe 401 of the three - way joint 40. More specifically, the second pipe 42 is arranged based on the horizontal direction (left - right direction D2) in such a way that it extends to the right along the left - right direction D2 from the fuel filter 6, and its end bends obliquely upward to the right and is connected to the three - way joint 40 from the lower left obliquely.

[0051] The third pipe 43 in the fuel pipe 4 is constituted by, for example, a rubber hose (rubber tube). One end portion of the third pipe 43 is connected to the second branch pipe 402 of the three-way joint 40, and the other end portion of the third pipe 43 is connected to the suction port 51 of the fuel injection pump 5. Here, a first throttle valve 11 is disposed in the middle portion of the third pipe 43. More specifically, the third pipe 43 is disposed based on the horizontal direction (left-right direction D2) in such a manner that it extends rightward from the second branch pipe 402 of the three-way joint 40 in the left-right direction D2 and its end is connected to the fuel injection pump 5 from the left side.

[0052] The exhaust pipe 7 is constituted by, for example, a rubber hose (rubber tube). One end portion of the exhaust pipe 7 is connected to the third branch pipe 403 of the three-way joint 40, and the other end portion of the exhaust pipe 7 is connected to the second joint 302 that protrudes rightward from the reduction port 32 of the fuel tank 3. Here, a second throttle valve 12 is disposed in the middle portion of the exhaust pipe 7. More specifically, the exhaust pipe 7 is disposed based on the vertical direction (up-down direction D1) in such a manner that it extends upward from the third branch pipe 403 of the three-way joint 40 in the up-down direction D1 and its end is connected to the right side surface of the fuel tank 3 via a bent portion.

[0053] In this way, the exhaust pipe 7 branches off from the fuel pipe 4 and is connected to the fuel tank 3 (the reduction port 32 thereof). Specifically, the fuel pipe 4 branches off the exhaust pipe 7 at the three-way joint 40 which is the connection point of the second pipe 42 and the third pipe 43. In other words, the exhaust pipe 7 branches off from the branch point of the fuel pipe 4 and is connected to the fuel tank 3, and the fuel pipe 4 supplies the fuel F1 from the fuel tank 3 to the fuel injection pump 5 of the engine 2. Here, the three-way joint 40 (that is, the connection point of the second pipe 42 and the third pipe 43) is an example of the branch point of the fuel pipe 4.

[0054] The three-way joint 40 which is an example of the branch point is formed such that the first branch pipe 401 and the third branch pipe 403 are arranged in a straight line and the second branch pipe 402 is orthogonal to the first branch pipe 401 and the third branch pipe 403, and the whole is configured in an approximate T shape. Therefore, the second pipe 42 and the exhaust pipe 7 which are respectively connected to the first branch pipe 401 and the third branch pipe 403 are linearly connected. On the other hand, the third pipe 43 which is connected to the second branch pipe 402 is connected in a manner orthogonal to the second pipe 42.

[0055] More specifically, the three-way joint 40 communicates the second pipe 42 and the exhaust pipe 7 on an imaginary straight line extending obliquely upward to the right in such a manner that it rises rightward from the second pipe 42 to the exhaust pipe 7. On the other hand, the three-way joint 40 communicates the third pipe 43 with the second pipe 42 in such a manner that it extends obliquely downward to the right from this imaginary straight line.

[0056] 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. That is, 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. Thereby, the sudden flow of the fuel F1 in the three-way joint 40 is suppressed, the pulsation pressure of the fuel injection pump 5 is reduced, and it is difficult for the fuel injection pump 5 to suck air.

[0057] The second throttle valve 12 is disposed in the exhaust pipe 7 that connects the third branch pipe 403 of the three-way joint 40 and the reduction port 32 of the fuel tank 3. That is, air flows from the third branch pipe 403 of the three-way joint 40 toward the reduction port 32 of the fuel tank 3 via the second throttle valve 12. The second throttle valve 12 is disposed at a predetermined interval between the exhaust pipe 7 and the third branch pipe 403.

[0058] The pressure fluctuation suppression unit 8 is disposed in the exhaust pipe 7. The pressure fluctuation suppression unit 8 allows air to pass in the downstream direction of the exhaust pipe 7 and suppresses the passage of air in the upstream direction of the exhaust pipe 7, thereby suppressing the pressure fluctuation of the fuel pipe 4. In the present disclosure, the "downstream direction" of the exhaust pipe 7 is the direction in which the exhaust pipe 7 extends from the branch point (three-way joint 40) side toward the fuel tank 3 (reduction port 32) side. In the present disclosure, the "upstream direction" of the exhaust pipe 7 is the direction in which the exhaust pipe 7 extends from the fuel tank 3 (reduction port 32) side toward the branch point (three-way joint 40) side.

[0059] 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 (reduction port 32) side in the exhaust pipe 7 and suppresses the passage of air from the fuel tank 3 (reduction port 32) side toward the branch point (three-way joint 40) side.

[0060] If such a pressure fluctuation suppression unit 8 is not provided, the branch point (three-way joint 40) of the fuel pipe 4 and the reduction port 32 of the fuel tank 3 are communicated through the exhaust pipe 7 in both directions (downstream direction and upstream direction). Therefore, the pressure of the fuel pipe 4 (at the branch point) fluctuates 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 of the fuel pipe 4 (at the branch point) can be cut off with respect to the air pressure in the fuel tank 3. Therefore, the pressure fluctuation of the fuel pipe 4 can be suppressed.

[0061] However, with respect to the fuel supply device 1 according to the present embodiment, the pressure fluctuation suppressing unit 8 allows both air and fuel F1 to pass in the downstream direction (from the branch point side toward the fuel tank 3 side). On the other hand, the pressure fluctuation suppressing unit 8 suppresses the passage of air in the upstream direction (from the fuel tank 3 side toward the branch point side) and allows the passage of fuel F1. In short, the pressure fluctuation suppressing unit 8 includes, for example, a check valve 81, such that air passes in the downstream direction of the exhaust pipe 7 and the passage of air is suppressed in the upstream direction of the exhaust pipe 7, thereby suppressing the pressure fluctuation of the fuel pipe 4. On the other hand, the pressure fluctuation suppressing unit 8 weakens the function of the check valve 81, whereby, with respect to fuel F1, it allows passage not only in the downstream direction of the exhaust pipe 7 but also in the upstream direction of the exhaust pipe 7.

[0062] Thus, for example, even if a small amount of fuel F1 passes through the pressure fluctuation suppressing unit 8 of the exhaust pipe 7 together with air in the downstream direction, the fuel F1 can pass through the pressure fluctuation suppressing unit 8 in the upstream direction. Therefore, it is difficult for the fuel F1 to accumulate as surplus fuel on the downstream side (opposite side of the three-way joint 40) in the downstream direction of the pressure fluctuation suppressing unit 8 of the exhaust pipe 7. As a result, there is an advantage that it is easy to prevent the fuel from being ejected toward the fuel tank 3 due to the pulsation generated by the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0063] Specifically, as Figure 2 shown, the pressure fluctuation suppressing unit 8 has a check valve 81 and a bypass path 82. The check valve 81 allows the fluid (air and fuel F1) to pass in the downstream direction and blocks the fluid (air and fuel F1) from passing in the upstream direction. As viewed from the check valve 81 in the exhaust pipe 7, the bypass path 82 bypasses from the downstream position P2 and the upstream position P1 in the downstream direction. The downstream position P2 mentioned here is a position on the downstream side in the downstream direction as viewed from the check valve 81 in the exhaust pipe 7, that is, on the side of the reduction port 32 of the fuel tank 3. The upstream position P1 mentioned here is a position on the upstream side in the downstream direction as viewed from the check valve 81 in the exhaust pipe 7, that is, on the side of the branch point (three-way joint 40).

[0064] That is, the pressure fluctuation suppressing unit 8 uses the check valve 81 inserted into the exhaust pipe 7 to allow both air and fuel F1 to pass only in the downstream direction and block their passage in the upstream direction. On this basis, the bypass path 82 provided in parallel with the check valve 81 bypasses from the downstream position P2 and the upstream position P1 in the downstream direction as viewed from the check valve 81 in the exhaust pipe 7. Therefore, the fuel F1 can flow from the downstream position P2 of the check valve 81 toward the upstream position P1 through the bypass path 82. As a result, the pressure fluctuation suppressing unit 8 can achieve a structure that suppresses the passage of air and allows the passage of fuel F1 in the upstream direction (from the fuel tank 3 side toward the branch point side).

[0065] More specifically, the check valve 81 includes a base portion 812 and a valve element 811. The base portion 812 has an opening 810 on the downstream side in the downstream direction (downstream position P2 side) (refer to Figure 3 ). The valve element 811 opens and closes the opening 810 of the base portion 812. That is, with respect to the check valve 81, when the fluid flows in the exhaust pipe 7 in the downstream direction, the valve element 811 is pressed by the fluid and forms an "open state" in which the opening 810 is opened, allowing the fluid to pass through. On the other hand, with respect to the check valve 81, when the fluid flows in the exhaust pipe 7 in the upstream direction, the valve element 811 is pressed by the fluid and forms a "closed state" in which the opening 810 is closed, preventing the fluid from passing through.

[0066] In the present embodiment, in particular, the valve element 811 is a sphere that moves within the exhaust pipe 7. Moreover, the base portion 812 is arranged such that the opening 810 faces at least upward. In the present embodiment, as an example, it is integrated with the third branch pipe 403 of the three-way joint 40.

[0067] Specifically, the valve element 811 is composed of a metal ball having a diameter smaller than the inner diameter of the exhaust pipe 7 and larger than the inner diameters of the base portion 812 (third branch pipe 403) and the second throttle valve 12. Around the opening 810 of the base portion 812, an elastomer (sheet) is arranged as an example of a valve seat structure that can make the valve element 811 in close contact. As Figure 2 shown, the valve element 811 is arranged between the base portion 812 (third branch pipe 403) of the exhaust pipe 7 and the second throttle valve 12.

[0068] Thereby, the valve element 811 can move bidirectionally (downstream direction and upstream direction) within the exhaust pipe 7 between the base portion 812 (third branch pipe 403) and the second throttle valve 12. Here, the specific gravity of the valve element 811 is set to be greater than the specific gravity of the fuel F1. Moreover, normally, the valve element 811 is supported by the base portion 812 due to its own weight and forms a closed state in which the opening 810 of the base portion 812 is closed. In contrast, if the fluid (air or fuel F1) flows into the base portion 812 from the branch point (three-way joint 40) side, the valve element 811 is pressed by the fluid and moves toward the second throttle valve 12 side, thereby forming an open state in which the opening 810 of the base portion 812 is opened.

[0069] According to the structure described above, when fuel F1 is supplied, the bubbles (air) in the fuel pipe 4 move upward due to gravity through the third branch pipe 403 of the three-way joint 40, and are released from the reduction port 32 into the fuel tank 3 through the exhaust pipe 7. That is, under normal conditions, although the valve core 811, which is heavier than the fuel, is formed in a closed state that closes the opening 810, when the bubbles (air) enter the exhaust pipe 7, the valve core 811 is pressed upward by the pressure difference, allowing the bubbles (air) to pass through the check valve 81.

[0070] Regarding the check valve 81 with such a structure, the valve core 811 is formed in a closed state that closes the opening 810 due to the action of gravity. Therefore, it is possible to easily disperse the air generated in the fuel pipe 4 upward, and it is possible to prevent the air from flowing backward from the fuel tank 3 side to the branch point (three-way joint 40) side. That is, it is possible to realize a check valve structure that operates with a weak opening pressure in a manner that can efficiently exhaust air.

[0071] In the present embodiment, a bypass path 82 is also provided in parallel with the check valve 81 having such a structure. That is, as Figure 2 shown, the bypass path 82 bypasses between the downstream position P2, which is more downstream than the valve core 811 (at least when in the closed state), and the upstream position P1, which is more upstream than the opening 810 of the base portion 812. Therefore, even when the valve core 811 is in a closed state that closes the opening 810, the fuel F1 can flow from the downstream position P2 toward the upstream position P1 through the bypass path 82.

[0072] Here, the upstream position P1 is located below the downstream position P2. Therefore, air does not flow from the downstream position P2 toward the upstream position P1 through the bypass path 82. Also, regarding the fuel F1 in a gas-liquid mixed state containing a large amount of bubbles (air), it does not flow from the downstream position P2 toward the upstream position P1 through the bypass path 82. As a result, only the pure fuel F1 can flow from the downstream position P2 toward the upstream position P1 through the bypass path 82.

[0073] In addition, according to the structure of the present embodiment, useful effects can also be expected even for the state where the valve core 811 is attached to the base portion 812 (attachment 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 attached, a flow of fluid (fuel F1) is generated through the bypass path 82. Therefore, a cleaning effect on the base portion 812 can be expected by using this fluid. By cleaning the base portion 812, if the attachment is mild, its elimination can be achieved.

[0074] Also, for example, even if the check valve 81 becomes stuck due to long-term storage or the like, the engine 2 can be started by initially exhausting air through the bypass path 82. Moreover, if the engine 2 is started, the stuck matter can be naturally eliminated by the overflow pressure and the suspended fuel flowing through the bypass path 82 if it is a minor case of sticking.

[0075] Next, a specific structural example of the bypass path 82 according to the present embodiment will be described with reference to Figures 3 to 6 FIGs.

[0076] In Figure 3 the first structural example shown, at least a part of the bypass path 82 is provided in the check valve 81. That is, it is not limited to a structure in which the bypass path 82 is provided separately from the check valve 81 as shown in Figure 2 FIG. Figure 3 As shown in FIG.

[0077] a part (or all) of the bypass path 82 may be integrally formed with the check valve 81. According to this structure, the bypass path 82 can be realized without increasing the number of components. Figure 3

[0078] More specifically, in the first structural example, at least a part of the bypass path 82 is constituted by a gap generated between the base portion 812 and the valve element 811 in a state where the valve element 811 is closed. That is, as shown on the right side (closed state) of Figure 3 FIG. even in a state where the valve element 811 closes the opening 810 of the base portion 812, if a minute gap is generated around the opening 810, the fuel F1 can flow from the downstream position P2 to the upstream position P1 through this gap. Regarding this structure, since the gap between the base portion 812 and the valve element 811 is utilized, the bypass path 82 can be realized with a simpler structure.

[0079] Here, in the first structural example, the gap is constituted by a recess 821 provided in a part of the circumferential direction of the opening 810 in the base portion 812. For example, as shown on the left side (open state) of Figure 4In the second structural example shown, the check valve 81 is constituted by a sleeve 83 disposed within the exhaust pipe 7. The sleeve 83 has a base portion 812 including an opening 810 at one end in the longitudinal direction, and a throttle portion 831 at an intermediate portion in the longitudinal direction. The inner diameters of the opening 810 and the throttle portion 831 are set to be smaller than the diameter of the spherical valve element 811, and the valve element 811 is accommodated within the sleeve 83 in such a manner as to be movable between the opening 810 and the throttle portion 831.

[0080] Also in the second structural example, similar to the first structural example, at least a part of the bypass path 82 is constituted by a gap formed by a recess 821 disposed in a circumferential part of the opening 810 in the base portion 812. In the second structural example, the recess 821 is formed at two locations around the opening 810. According to this structure, the bypass path 82 can also be realized with a simple structure by utilizing the gap between the base portion 812 and the valve element 811.

[0081] In Figure 5 In the third structural example shown, the check valve 81 is provided within a sleeve 83 disposed within the exhaust pipe 7. In this example, the base portion 812 is constituted by a cylindrical member inserted into one end in the longitudinal direction of the sleeve 83, and the sleeve 83 has a throttle portion 831 at an intermediate portion in the longitudinal direction. The inner diameters of the opening 810 of the base portion 812 and the throttle portion 831 are set to be smaller than the diameter of the spherical valve element 811, and the valve element 811 is accommodated within the sleeve 83 in such a manner as to be movable between the base portion 812 (opening 810) and the throttle portion 831.

[0082] Even in the third structural example, similar to the second structural example, at least a part of the bypass path 82 is constituted by a gap formed by a recess 821 disposed in a circumferential part of the opening 810 in the base portion 812. In the third structural example, the recess 821 is formed at two locations around the opening 810. According to this structure, the bypass path 82 can also be realized with a simple structure by utilizing the gap between the base portion 812 and the valve element 811.

[0083] In Figure 6 In the fourth and fifth structural examples shown, similar to the second structural example, the check valve 81 is constituted by a sleeve 83 disposed within the exhaust pipe 7. The sleeve 83 has a base portion 812 including an opening 810 at one end in the longitudinal direction, and a throttle portion 831 at an intermediate portion in the longitudinal direction. The inner diameters of the opening 810 and the throttle portion 831 are set to be smaller than the diameter of the spherical valve element 811, and the valve element 811 is accommodated within the sleeve 83 in such a manner as to be movable between the opening 810 and the throttle portion 831.

[0084] In the fourth structural example, at least a part of the bypass path 82 is constituted by a through hole 822 formed in the base portion 812. That is, in the fourth structural example, a through hole 822 that penetrates the tube wall in the thickness direction is formed in the tube wall of the base portion 812 that is part of the sleeve 83. This through hole 822 constitutes at least a part of the bypass path 82. According to this structure, the size (cross-sectional area) of the bypass path 82 can be arbitrarily set according to the shape, size, number, and position of the through hole 822, etc. Therefore, it is easy to realize a bypass path 82 with desired characteristics.

[0085] In the fifth structural example, at least a part of the bypass path 82 is constituted by a gap generated between the inner peripheral edge of the opening 810 of the base portion 812 and the valve element 811 in a state where the valve element 811 is closed. That is, in the fifth structural example, one end portion in the length direction of the sleeve 83 is reduced in diameter by stamping or the like, thereby forming a base portion 812 having an opening 810. In this case, the opening 810 of the base portion 812 does not completely become a perfect circle and is formed into a shape with a low roundness. Therefore, a gap naturally occurs between the opening 810 with a low roundness and the valve element 811 constituted by a sphere, and thus this gap is used as the bypass path 82.

[0086] Here, it is preferable that the materials of the base portion 812 (sleeve 83) and the valve element 811 are, for example, metal or an oil-resistant resin with durability. In particular, in the case of fluororesin, it is difficult for adhesion to occur, so it is also suitable for the case where the fuel F1 is a biofuel.

[0087] [3] Modification examples

[0088] The modification examples of Embodiment 1 are listed below. The modification examples described below can be combined and applied as appropriate.

[0089] The use of the engine system 10 is not limited to a power source for construction machinery, vehicles, aircraft, or ships, etc. And the power source can be a hybrid power source including the engine 2 and a motor (electric motor), and the engine 2 can also be an engine other than a diesel engine, for example.

[0090] In addition, the first pipe 41, the second pipe 42, and the third pipe 43 of the fuel pipe 4 and the exhaust pipe 7, etc. do not necessarily all consist of rubber hoses (rubber pipes), and at least a part of them can be constituted by metal pipes, for example.

[0091] In addition, the tee joint 40 is not limited to a T-shaped one, and can also be a tee joint other than the T-shaped one.

[0092] In addition, the fuel filter 6 is not an essential structure for the fuel supply device 1 and may be appropriately omitted. The first throttle valve 11 and the second throttle valve 12 are also not essential structures for the fuel supply device 1, and at least one of the first throttle valve 11 and the second throttle valve 12 may be appropriately omitted.

[0093] (Embodiment 2)

[0094] Regarding the fuel supply device 1A according to the present embodiment, as Figure 7 shown, the structure of the pressure fluctuation suppression unit 8 is different from that of the fuel supply device 1 according to Embodiment 1. Hereinafter, the same structures as those in Embodiment 1 are denoted by common reference numerals and the description thereof is appropriately omitted. In the present embodiment, the check valve 81 (see Figure 2 ) in the exhaust pipe 7 and the second throttle valve 12 (see Figure 2 ) are omitted.

[0095] That is, in the present embodiment, as Figure 7 shown, the pressure fluctuation suppression unit 8 has a liquid accumulation unit 84. The cross-sectional area of the liquid accumulation unit 84 is larger than that of the portion of the exhaust pipe 7 other than the pressure fluctuation suppression unit 8. The liquid accumulation unit 84 is provided in the middle of the exhaust pipe 7 and functions as a buffer unit that adds capacity (volume) to the exhaust pipe 7.

[0096] According to this structure, for example, even if a small amount of fuel F1 passes through the pressure fluctuation suppression unit 8 of the exhaust pipe 7 in the downstream direction together with air, the fuel F1 is stored in the liquid accumulation unit 84. If such a pressure fluctuation suppression unit 8 is not provided, the branch point (tee joint 40) of the fuel pipe 4 and the reduction port 32 of the fuel tank 3 are connected in both directions (downstream direction and upstream direction) through the exhaust pipe 7, and thus the pressure at the branch point of the fuel pipe 4 fluctuates due to the air pressure in the fuel tank 3. On the other hand, by providing the pressure fluctuation suppression unit 8 (liquid accumulation unit 84), the pressure at the branch point of the fuel pipe 4 can be cut off from the air pressure in the fuel tank 3, and thus the pressure fluctuation of the fuel pipe 4 can be suppressed.

[0097] Moreover, since the liquid accumulation unit 84 is connected to the fuel pipe 4 (branch point) through the exhaust pipe 7, the fuel F1 can also pass through the pressure fluctuation suppression unit 8 in the upstream direction. Therefore, according to the effect of reducing the flow rate of the fuel F1 in the exhaust pipe 7 and suppressing the liquid level fluctuation of the fuel F1 in the exhaust pipe 7 due to the increase in volume, the white turbidity (gas-liquid mixing) of the fuel F1 caused by air entrainment can be suppressed. As a result, there is also an advantage that it is easy to prevent the fuel from being ejected into the fuel tank 3 due to the pulsation generated by the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0098] Further, at least a part of the liquid accumulation portion 84 is arranged at the same height as the fuel tank 3 in the vertical direction (up-and-down direction D1). In the present embodiment, as an example, the liquid accumulation portion 84 is arranged in such a manner that the entire liquid accumulation portion 84 is accommodated between the lower surface and the upper surface of the fuel tank 3. According to this structure, due to the balance between the suction and discharge of the fuel F1 by the fuel injection pump 5 and the resistance between the fuel pipe 4 and the exhaust pipe 7, the liquid level of the fuel F1 in the liquid accumulation portion 84 is stabilized at a position higher than the liquid level L1 of the fuel F1 in the fuel tank 3, and it is easy to ensure the head pressure in the fuel tank 3.

[0099] In the structure of the second embodiment, it is not necessary to omit the check valve 81 in the exhaust pipe 7, and the check valve 81 can also be provided. The structure (including the modified example) related to the second embodiment can be appropriately combined and used with various structures (including the modified example) described in the first embodiment.

[0100] (Embodiment 3)

[0101] Regarding the fuel supply device 1B according to the present embodiment, as Figure 8 shown, the arrangement of the pressure fluctuation suppressing portion 8 is different from that of the fuel supply device 1 according to the first embodiment. Hereinafter, the same structures as those in the first embodiment are denoted by common reference numerals and the description is appropriately omitted.

[0102] In the present embodiment, the exhaust pipe 7 includes an internal pipe 71 that protrudes into the fuel tank 3. The pressure fluctuation suppressing portion 8 is provided in the internal pipe 71. In Figure 8 the example, the internal pipe 71 is configured to penetrate the lower surface of the fuel tank 3 and protrude upward from the inner bottom surface of the fuel tank 3. The pressure fluctuation suppressing portion 8 is arranged in the middle portion of such an internal pipe 71.

[0103] According to this structure, the pressure fluctuation suppressing portion 8 can be provided using the space inside the fuel tank 3. Therefore, there is no need to ensure a space outside the fuel tank 3 for providing the pressure fluctuation suppressing portion 8.

[0104] In the third embodiment, the pressure fluctuation suppressing portion 8 is not limited to the structure having the check valve 81 and the bypass path 82 as in the first embodiment, and may also be a structure having the liquid accumulation portion 84 as in the second embodiment. Further, the pressure fluctuation suppressing portion 8 can be constituted by a general check valve 81 other than the bypass path 82. The structure (including the modified example) related to the third embodiment can be appropriately combined and used with various structures (including the modified example) described in the first embodiment or the second embodiment.

[0105] (Embodiment 4)

[0106] Regarding the fuel supply device 1C according to the present embodiment, as Figure 9As shown, the structure of the pressure fluctuation suppression unit 8 is different from that of the fuel supply device 1A according to the second embodiment. Hereinafter, the same structures as those in the second embodiment are denoted by common reference numerals, and the description thereof is appropriately omitted.

[0107] That is, in the present embodiment, as Figure 9 shown, the pressure fluctuation suppression unit 8 includes a first cylinder portion 91 and a second cylinder portion 92. The first cylinder portion 91 and the second cylinder portion 92 are each formed in a cylindrical shape having a length in the vertical direction D1. Specifically, the first cylinder portion 91 and the second cylinder portion 92 are each formed in a cylindrical tubular shape from, for example, metal or an oil-resistant resin having durability.

[0108] Moreover, as Figure 10 shown, the outer diameter φ2 of the second cylinder portion 92 is smaller than the inner diameter φ1 of the first cylinder portion 91, and the second cylinder portion 92 is disposed inside the first cylinder portion 91. And, in the present embodiment, with respect to the length (in the vertical direction D1), the second cylinder portion 92 is shorter than the first cylinder portion 91. That is, in the present embodiment, the pressure fluctuation suppression unit 8 has a double-tube structure in which the first cylinder portion 91 is an outer tube and the second cylinder portion 92 is an inner tube.

[0109] The pressure fluctuation suppression unit 8 having the double-tube structure is provided in the middle portion of the exhaust pipe 7, and the first cylinder portion 91 and the second cylinder portion 92 are inserted in series between the branch point (tee joint 40) connected by the exhaust pipe 7 and the reduction port 32 of the fuel tank 3. Thus, the pressure fluctuation suppression unit 8 functions as a buffer unit for adding an air damper 85 (see Figure 11 ) as an air accumulation unit to the exhaust pipe 7.

[0110] More specifically, as Figure 9 shown, the second cylinder portion 92 as the inner tube is formed in a cylindrical shape with both ends open in the length direction (vertical direction D1). The lower end side opening is the first opening 921, and the upper end side opening is the second opening 922. And, the second cylinder portion 92 has a hole 923 that opens laterally on the side surface (outer peripheral surface). The center of the hole 923 is located at a position lower than the center of the second cylinder portion 92 in the length direction (vertical direction D1). More preferably, the center, upper end, or lower end of the hole 923 is located at a position lower than the nominal lower oil level of the fuel tank 3 (the nominal lower limit of the liquid level L1 of the fuel F1). In addition, the second opening 922 is located at a position at least higher than the nominal lower oil level of the fuel tank 3.

[0111] On the other hand, the first cylinder part 91 serving as the outer cylinder is a bottomed cylindrical shape with both ends in the longitudinal direction (vertical direction D1) closed, and has an opening hole 911 that opens laterally on the side surface (outer peripheral surface). The second cylinder part 92 is combined with the first cylinder part 91 in such a way as to penetrate the bottom surface on the lower side of the first cylinder part 91. Thus, when observing the pressure fluctuation suppression part 8 from below, the first opening 921 of the second cylinder part 92 is exposed at the center of the bottom surface on the lower side of the first cylinder part 91. The second opening 922 of the second cylinder part 92 is located inside the first cylinder part 91.

[0112] Thus, the first cylinder part 91 and the second cylinder part 92 are communicated with each other by a communication part (second opening 922) that is closer to the upper side than the center in the vertical direction D1. In other words, the internal space Sp2 of the second cylinder part 92 (refer to Figure 10 ), and the gap space Sp1 between the inner peripheral surface of the first cylinder part 91 and the outer peripheral surface of the second cylinder part 92 (refer to Figure 10 ) are communicated by the second opening 922 serving as the communication part.

[0113] Moreover, the first opening 921 of the second cylinder part 92 serving as the inner cylinder is connected to the branch point (tee joint 40) via the exhaust pipe 7, and the opening hole 911 of the first cylinder part 91 serving as the outer cylinder is connected to the reduction port 32 of the fuel tank 3 via the exhaust pipe 7. Thus, the pressure fluctuation suppression part 8 having a double-tube structure sets the first opening 921 of the second cylinder part 92 as the inlet and the opening hole 911 of the first cylinder part 91 as the outlet, so that air (and a small amount of fuel F1) can pass in the downstream direction from the branch point (tee joint 40) side toward the fuel tank 3.

[0114] Figure 11 Schematically shows the state of filling air into the inside of the pressure fluctuation suppression part 8 (denoted as "filling air") and the state of discharging air from the pressure fluctuation suppression part 8 (denoted as "discharging air"). In Figure 11 , the air pressure acting on the liquid level L1 of the fuel F1 is represented by a white arrow, and the moving direction of the air is represented by a thick arrow.

[0115] For example, a small amount of fuel F1 passes through the pressure fluctuation suppression part 8 of the exhaust pipe 7 together with the air in the downstream direction, so that as Figure 11As shown in "Air filling", the fuel F1 is stored in the pressure fluctuation suppression section 8. At this time, air temporarily accumulates at a position above the liquid level L1 of the pressure fluctuation suppression section 8 to form an air damper 85. Moreover, the air from the branch point (tee joint 40) side is separated from the fuel tank 3 by the fuel F1 accumulated in the lower part of the first cylinder portion 91. In this state, the air from the branch point (tee joint 40) side continuously fills the pressure fluctuation suppression section 8 from the first opening 921 through the exhaust pipe 7, so that the pressure of the air damper 85 increases, and the liquid level L1 of the fuel F1 in the pressure fluctuation suppression section 8 gradually decreases (descends).

[0116] When the liquid level L1 of the fuel F1 in the pressure fluctuation suppression section 8 is lower than the opening hole 911 (upper end), the air damper 85 communicates with the fuel tank 3 (the restoration port 32) through the exhaust pipe 7. Therefore, the air in the air damper 85 is discharged from the opening hole 911 to the fuel tank 3 (the restoration port 32) side through the exhaust pipe 7 as shown in "Air discharging". At the same time, the fuel F1 flows into the air damper 85 from the second cylinder portion 92. Therefore, the liquid level L1 of the fuel F1 in the pressure fluctuation suppression section 8 rises. Figure 11 As shown in "Air discharging", the air in the air damper 85 is discharged from the opening hole 911 to the fuel tank 3 (the restoration port 32) side through the exhaust pipe 7. At the same time, the fuel F1 flows into the air damper 85 from the second cylinder portion 92. Therefore, the liquid level L1 of the fuel F1 in the pressure fluctuation suppression section 8 rises.

[0117] The fuel supply device 1C according to the present embodiment repeatedly performs the operations of "Air filling" and "Air discharging" as described above, so that it is possible to exhaust gas and maintain a stable supply of the fuel F1.

[0118] In summary, regarding the fuel supply device 1C according to the present embodiment, the pressure fluctuation suppression section 8 includes: a first cylinder portion 91; and a second cylinder portion 92 disposed inside the first cylinder portion 91. The exhaust pipe 7 connects the branch point (tee joint 40) and the fuel tank 3 (the restoration port 32) through both the first cylinder portion 91 and the second cylinder portion 92.

[0119] According to this structure, for example, even if a small amount of fuel F1 passes through the pressure fluctuation suppression section 8 of the exhaust pipe 7 together with air in the downstream direction, the fuel F1 is stored in the air damper 85. If such a pressure fluctuation suppression section 8 is not provided, the branch point (tee joint 40) of the fuel pipe 4 and the restoration port 32 of the fuel tank 3 are connected through the exhaust pipe 7 in both directions (downstream direction and upstream direction). Therefore, the pressure of the branch point of the fuel pipe 4 fluctuates due to the influence of the air pressure in the fuel tank 3. On the contrary, by providing the pressure fluctuation suppression section 8, the pressure of the branch point of the fuel pipe 4 can be cut off from the air pressure in the fuel tank 3. Therefore, the pressure fluctuation of the fuel pipe 4 can be suppressed.

[0120] Moreover, the fuel F1 accumulated in the pressure change suppression section 8 flows through the exhaust pipe 7 to the fuel pipe 4 (branch point). Therefore, the fuel F1 can also pass through the pressure change suppression section 8 in the reverse flow direction. Therefore, based on the effect of reducing the flow velocity of the fuel F1 in the exhaust pipe 7 and suppressing the liquid level change of the fuel F1 in the exhaust pipe 7 due to the increased volume, it is possible to suppress the white turbidity (gas-liquid mixing) of the fuel F1 caused by entrained air. As a result, there are the following advantages: it is easy to prevent the fuel from being ejected into the fuel tank 3 due to the pulsation generated by the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0121] In addition, in the present embodiment, the first cylindrical portion 91 and the second cylindrical portion 92 are connected to each other by a communication portion (second opening 922) that is closer to the upper side than the center in the vertical direction D1. The lower end portion (first opening 921) of the second cylindrical portion 92 is connected to the branch point (tee joint 40) side, and the lower end portion (opening hole 911) of the first cylindrical portion 91 is connected to the fuel tank 3 side. Thus, the air transported from the branch point (tee joint 40) side passes through 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 into the first cylindrical portion 91 from the communication portion (second opening 922). And this air can be discharged from the lower end portion (opening hole 911) of the first cylindrical portion 91 to the fuel tank 3 side through 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.

[0122] In addition, in the present embodiment, the second cylindrical portion 92 is provided with a hole 923 that connects the inside (internal space Sp2) and the outside (gap space Sp1) of the second cylindrical portion 92, different from the communication portion (second opening 922). Thus, air and fuel F1 can move between the internal space Sp2 and the gap space Sp1 through the hole 923. Therefore, there are the following advantages: it is easy to prevent the fuel from being ejected into the fuel tank 3 due to the pulsation generated by the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0123] And, when viewed from the center in the vertical direction D1 of the second cylindrical portion 92, the center of the hole 923 is located on the opposite side of the communication portion (second opening 922). That is, the center of the hole 923 is located at a position lower than the center in the vertical direction D1 of the second cylindrical portion 92. Therefore, even if the air and fuel F1 do not move to the communication portion (second opening 922) in the second cylindrical portion 92, they can move between the internal space Sp2 and the gap space Sp1 through the hole 923.

[0124] In addition, the center, upper end, or lower end of the hole 923 is located at a position lower than the nominal lower fuel level of the fuel tank 3. Therefore, even when the fuel F1 in the fuel tank 3 decreases and the liquid level L1 drops to the nominal lower fuel level, the fuel F1 in the pressure fluctuation suppressing section 8 can move between the internal space Sp2 and the clearance space Sp1 through the hole 923.

[0125] Moreover, the hole 923 is not limited to one location and may be provided at multiple locations.

[0126] In addition, in the present embodiment, as Figure 10 shown, the cross-sectional area of the clearance (clearance space Sp1) between the first cylinder portion 91 and the second cylinder portion 92 is equal to or less than the cross-sectional area of the interior (internal space Sp2) of the second cylinder portion 92. Thereby, there are advantages that it is easy to prevent the fuel from being ejected into the fuel tank 3 due to the pulsation generated by the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0127] Figure 12 Various modifications of Embodiment 4 are shown. In these modifications, the structure of the pressure fluctuation suppressing section 8 is different from that of Embodiment 4.

[0128] Regarding the fuel supply device 1D according to the first modification, the second opening 922 where the second cylinder portion 92 becomes a communicating portion communicating with the first cylinder portion 91 is not formed at the upper end of the second cylinder portion 92, but is formed on the side surface (outer peripheral surface) of the second cylinder portion 92. In this case, the internal space Sp2 of the second cylinder portion 92 and the clearance space Sp1 between the inner peripheral surface of the first cylinder portion 91 and the outer peripheral surface of the second cylinder portion 92 also communicate through the second opening 922 serving as the communicating portion. The second opening 922 is not limited to one location and may be provided at multiple locations.

[0129] Regarding the fuel supply device 1E according to the second modification, the relationship between the first cylinder portion 91 and the second cylinder portion 92 is opposite to that of Embodiment 4. Specifically, the first opening 921 is not formed at the lower end of the second cylinder portion 92, but is formed on the side surface (outer peripheral surface) of the second cylinder portion 92. Moreover, the first opening 921 constitutes the communicating portion of the second cylinder portion 92 communicating with the first cylinder portion 91 instead of the second opening 922. And the opening hole 911 of the first cylinder portion 91 is not arranged at the lower part of the first cylinder portion 91 but at the upper part thereof.

[0130] In the second modification example, the opening hole 911 of the first cylindrical portion 91 serving as the outer cylinder is connected to the branch point (tee joint 40) via the exhaust pipe 7, and the second opening 922 of the second cylindrical portion 92 serving as the inner cylinder is connected to the reduction port 32 of the fuel tank 3 via the exhaust pipe 7. Thus, with respect to the pressure fluctuation suppression portion 8 having a double-tube structure, the opening hole 911 of the first cylindrical portion 91 is set as the inlet and the second opening 922 of the second cylindrical portion 92 is set as the outlet, so that air (and a small amount of fuel F1) can pass in the downstream direction from the branch point (tee joint 40) side toward the fuel tank 3.

[0131] That is, with respect to the fuel supply device 1E according to the second modification example, the first cylindrical portion 91 and the second cylindrical portion 92 are communicated with each other by a communication portion (first opening 921) located more downward than the center in the vertical direction D1. The upper end portion of the first cylindrical portion 91 is connected to the branch point (tee joint 40) side, and the upper end portion of the second cylindrical portion 92 is connected to the fuel tank 3 side. Thus, the air transported from the branch point (tee joint 40) side passes through 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 from the upper end portion (opening hole 911) of the first cylindrical portion 91 and moves into the second cylindrical portion 92 through the communication portion (first opening 921). And this air can be discharged from the upper end portion (second opening 922) of the second cylindrical portion 92 toward the fuel tank 3 side through the internal space Sp2 of the second cylindrical portion 92.

[0132] With respect to the fuel supply device 1F according to the third modification example, the pressure fluctuation suppression portion 8 has a triple-tube structure. That is, the pressure fluctuation suppression portion 8 further has a third cylindrical portion 93 disposed outside the first cylindrical portion 91. The exhaust pipe 7 connects the branch point (tee joint 40) and the fuel tank 3 through all of the first cylindrical portion 91, the second cylindrical portion 92, and the third cylindrical portion 93. Thus, there are the following advantages: it is easy to prevent fuel from being ejected toward the fuel tank 3 due to the pulsation generated from the fuel injection pump 5, and it is easy to obtain the exhaust effect of the exhaust pipe 7.

[0133] Specifically, the inner diameter of the third cylindrical portion 93 is further 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. And in the present embodiment, with respect to the length (in the vertical direction D1), the first cylindrical portion 91 is also shorter than the third cylindrical portion 93. The third cylindrical portion 93 serving as the outermost cylinder is a bottomed cylindrical shape with both ends in the length direction (vertical direction D1) closed, and has an opening hole 931 opening upward on the upper surface (upper bottom surface). The first cylindrical portion 91 and the third cylindrical portion 93 are communicated with each other by a communication portion (opening hole 911) located more downward than the center in the vertical direction D1.

[0134] Moreover, the first opening 921 of the second cylinder part 92 is connected to the branch point (tee joint 40) by means of the exhaust pipe 7, and the opening hole 931 of the third cylinder part 93, which is the outermost cylinder, is connected to the reduction port 32 of the fuel tank 3 by means of the exhaust pipe 7. Thus, the pressure fluctuation suppression part 8 with a triple-tube structure sets the first opening 921 of the second cylinder part 92 as the inlet and the opening hole 931 of the third cylinder part 93 as the outlet, so that air (and a small amount of fuel F1) can pass through in the downstream direction from the branch point (tee joint 40) side toward the fuel tank 3.

[0135] Furthermore, the pressure fluctuation suppression part 8 is not limited to the triple-tube structure. For example, it can also be a quadruple-tube structure composed of four cylinder parts or a multi-tube structure composed of five or more cylinder parts. The structures (including modified examples) related to Embodiment 4 can be appropriately combined and adopted with various structures (including modified examples) described in Embodiment 1, Embodiment 2, or Embodiment 3.

[0136] [Supplementary Notes of the Invention]

[0137] The general situation of the invention refined from the above-mentioned embodiments is described in the supplementary notes below. In addition, each structure and each processing function described in the following supplementary notes can be selected and combined arbitrarily.

[0138] <Supplementary Note 1>

[0139] A fuel supply device for an engine, wherein,

[0140] The fuel supply device for the engine includes:

[0141] An exhaust pipe that branches off from a branch point of a fuel pipe and is connected to a fuel tank, the fuel pipe supplying fuel from the fuel tank to a fuel injection pump of the engine; and

[0142] A pressure fluctuation suppression part disposed in the exhaust pipe,

[0143] The pressure fluctuation suppression part allows air and the fuel to pass through in the downstream direction from the branch point side toward the fuel tank side, and suppresses the passage of the air in the upstream direction from the fuel tank side toward the branch point side and allows the fuel to pass through.

[0144] <Supplementary Note 2>

[0145] According to the fuel supply device for an engine described in Supplementary Note 1, wherein,

[0146] The pressure fluctuation suppression part has:

[0147] A check valve that allows fluid to pass through in the downstream direction and blocks the passage of fluid in the upstream direction; and

[0148] A bypass path that, when viewed from the check valve in the exhaust pipe, bypasses from a downstream position and an upstream position in the downstream direction.

[0149] <Supplementary Note 3>

[0150] The fuel supply device for an engine according to Supplementary Note 2, wherein

[0151] At least a part of the bypass path is provided in the check valve.

[0152] <Supplementary Note 4>

[0153] The fuel supply device for an engine according to Supplementary Note 3, wherein

[0154] The check valve includes: a base portion having an opening on the downstream side in the downstream direction; and a valve element that opens and closes the opening.

[0155] <Supplementary Note 5>

[0156] The fuel supply device for an engine according to Supplementary Note 4, wherein

[0157] At least a part of the bypass path is formed by a gap generated between the base portion and the valve element in a state where the valve element is closed.

[0158] <Supplementary Note 6>

[0159] The fuel supply device for an engine according to Supplementary Note 5, wherein

[0160] The valve element is a sphere that moves within the exhaust pipe,

[0161] The gap is formed by a recess provided in a part of the circumferential direction of the opening in the base portion.

[0162] <Supplementary Note 7>

[0163] The fuel supply device for an engine according to any one of Supplementary Notes 4 to 6, wherein

[0164] At least a part of the bypass path is formed by a through-hole formed in the base portion.

[0165] <Supplementary Note 8>

[0166] The fuel supply device for an engine according to any one of Supplementary Notes 1 to 7, wherein

[0167] The exhaust pipe includes an internal pipe that protrudes into the interior of the fuel tank,

[0168] The pressure fluctuation suppression portion is provided on the internal pipe.

[0169] <Note 9>

[0170] The fuel supply device for an engine according to any one of Notes 1 to 8, wherein,

[0171] The pressure fluctuation suppression portion has a liquid accumulation portion with a cross-sectional area larger than that of the portion other than the pressure fluctuation suppression portion in the exhaust pipe.

[0172] <Note 10>

[0173] The fuel supply device for an engine according to Note 9, wherein,

[0174] At least a part of the liquid accumulation portion is arranged at the same height as the fuel tank in the vertical direction.

[0175] <Note 11>

[0176] The fuel supply device for an engine according to any one of Notes 1 to 10, wherein,

[0177] The pressure fluctuation suppression portion has: a first cylindrical portion; and a second cylindrical portion disposed inside the first cylindrical portion,

[0178] The exhaust pipe connects the branch point and the fuel tank through both the first cylindrical portion and the second cylindrical portion.

[0179] <Note 12>

[0180] The fuel supply device for an engine according to Note 11, wherein,

[0181] The first cylindrical portion and the second cylindrical portion are connected to each other by a communication portion located above the center in the vertical direction,

[0182] The lower end portion of the second cylindrical portion is connected to the branch point side, and the lower end portion of the first cylindrical portion is connected to the fuel tank side.

[0183] <Note 13>

[0184] The fuel supply device for an engine according to Note 11, wherein,

[0185] The first cylindrical portion and the second cylindrical portion are connected to each other by a communication portion located below the center in the vertical direction,

[0186] The upper end portion of the first cylindrical portion is connected to the branch point side, and the upper end portion of the second cylindrical portion is connected to the fuel tank side.

[0187] <Note 14>

[0188] The fuel supply device for an engine according to Note 12 or 13, wherein,

[0189] The second cylindrical portion is provided with a hole that connects the inside and the outside of the second cylindrical portion, differently from the communication portion.

[0190] <Supplementary Note 15>

[0191] The fuel supply device for an engine according to Supplementary Note 14, wherein

[0192] When viewed from the center in the vertical direction of the second cylindrical portion, the center of the hole is located on the opposite side of the communication portion.

[0193] <Supplementary Note 16>

[0194] The fuel supply device for an engine according to Supplementary Note 14 or 15, wherein

[0195] The center, upper end, or lower end of the hole is located at a position lower than the nominal lower oil level of the fuel tank.

[0196] <Supplementary Note 17>

[0197] The fuel supply device for an engine according to any one of Supplementary Notes 11 to 16, wherein

[0198] The cross-sectional area of the gap between the first cylindrical portion and the second cylindrical portion is equal to or less than the cross-sectional area of the inside of the second cylindrical portion.

[0199] <Supplementary Note 18>

[0200] The fuel supply device for an engine according to any one of Supplementary Notes 11 to 17, wherein

[0201] The pressure fluctuation suppression portion further has a third cylindrical portion disposed outside the first cylindrical portion,

[0202] The exhaust 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.

[0203] <Supplementary Note 19>

[0204] An engine system, wherein

[0205] The engine system includes:

[0206] The fuel supply device for an engine according to any one of Supplementary Notes 1 to 18; and

[0207] The engine.

Claims

1. A fuel supply device for an engine, wherein, the fuel supply device for the engine comprises: an exhaust pipe that branches off from a branch point of a fuel pipe and is connected to a fuel tank, and the fuel pipe supplies fuel from the fuel tank to a fuel injection pump of the engine; and a pressure fluctuation suppression part that is disposed in the exhaust pipe, the pressure fluctuation suppression part allows air and the fuel to pass through in the downstream direction from the branch point side toward the fuel tank side, and suppresses the passage of the air and allows the fuel to pass through in the upstream direction from the fuel tank side toward the branch point side.

2. The fuel supply device for an engine according to claim 1, wherein, the pressure fluctuation suppression part has: a check valve that allows fluid to pass through in the downstream direction and blocks the passage of fluid in the upstream direction; and a bypass path that bypasses from a downstream position and an upstream position in the downstream direction as viewed from the check valve in the exhaust pipe.

3. The fuel supply device for an engine according to claim 2, wherein, at least a part of the bypass path is provided in the check valve.

4. The fuel supply device for an engine according to claim 3, wherein, the check valve includes: a base part that has an opening on the downstream side in the downstream direction; and a valve element that opens and closes the opening.

5. The fuel supply device for an engine according to claim 4, wherein, at least a part of the bypass path is formed by a gap generated between the base part and the valve element in a state where the valve element is closed.

6. The fuel supply device for an engine according to claim 5, wherein, the valve element is a sphere that moves in the exhaust pipe, and the gap is formed by a recess that is disposed in a part of the circumferential direction of the opening in the base part.

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

8. The fuel supply device for an engine according to any one of claims 1 to 6, wherein, the exhaust pipe includes an internal pipe that protrudes into the interior of the fuel tank, and the pressure fluctuation suppression part is disposed in the internal pipe.

9. The fuel supply device for an engine according to any one of claims 1 to 6, wherein, the pressure fluctuation suppression part has a liquid accumulation part with a cross-sectional area larger than that of a part other than the pressure fluctuation suppression part in the exhaust pipe.

10. The fuel supply device for an engine according to claim 9, wherein, at least a part of the liquid accumulation part is disposed at the same height as the fuel tank in the vertical direction.

11. The fuel supply device for an engine according to any one of claims 1 to 6, wherein, the pressure fluctuation suppression part has: a first cylinder part; and a second cylinder part that is disposed inside the first cylinder part, and the exhaust pipe connects the branch point and the fuel tank through both the first cylinder part and the second cylinder part.

12. The fuel supply device for an engine according to claim 11, wherein, The first cylindrical portion and the second cylindrical portion are communicated with each other by a communication portion that is closer to the upper side than the center in the vertical direction. The lower end portion of the second cylindrical portion is connected to the branch point side, and the lower end portion of the first cylindrical portion is connected to the fuel tank side.

13. The fuel supply device for an engine according to claim 11, wherein The first cylindrical portion and the second cylindrical portion are communicated with each other by a communication portion that is closer to the lower side than the center in the vertical direction. The upper end portion of the first cylindrical portion is connected to the branch point side, and the upper end portion of the second cylindrical portion is connected to the fuel tank side.

14. The fuel supply device for an engine according to claim 12, wherein The second cylindrical portion is provided with a hole that connects the inside and the outside of the second cylindrical portion, differently from the communication portion.

15. The fuel supply device for an engine according to claim 14, wherein When viewed from the center in the vertical direction of the second cylindrical portion, the center of the hole is located on the opposite side of the communication portion.

16. The fuel supply device for an engine according to claim 14, wherein The center, upper end or lower end of the hole is located at a position lower than the nominal lower oil level of the fuel tank.

17. The fuel supply device for an engine according to claim 11, wherein The cross-sectional area of the gap between the first cylindrical portion and the second cylindrical portion is less than or equal to the cross-sectional area of the inside of the second cylindrical portion.

18. The fuel supply device for an engine according to claim 11, wherein The pressure fluctuation suppressing portion further has a third cylindrical portion disposed outside the first cylindrical portion. The exhaust 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.

19. An engine system, wherein The engine system includes: The fuel supply device for an engine according to any one of claims 1 to 6; and The engine.

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