Fuel system

Abstract

To provide a fuel system that can prevent external leakage of fuel, and appropriately detect a cylinder in which fuel leakage has occurred from a connection part between a fuel injection valve and a fuel supply path.SOLUTION: A fuel system comprises: a fuel injection valve; a fuel supply path for supplying fuel to the fuel injection valve; a fuel return path for returning surplus fuel of the fuel injection valve; a leaked fuel return path of which one end is connected to a connection part between the fuel injection valve and the fuel supply path, and of which the other end is connected to the fuel return path; an inspection hole provided in the leaked fuel return path, and capable of being opened / closed by a plug member; and a check valve provided in the leaked fuel return path, and blocking a flow of fuel to the side of the connection part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to fuel systems applied to internal combustion engines. [Background technology]

[0002] For example, a common rail fuel injection system applied to a diesel engine includes a fuel pump, a common rail, and a fuel injection valve. The fuel pump draws fuel from a fuel tank, pressurizes it, and supplies it to the common rail as high-pressure fuel. The common rail maintains the high-pressure fuel supplied from the fuel pump at a predetermined pressure. The fuel injection valve injects the high-pressure fuel from the common rail into the combustion chamber of the diesel engine by opening and closing the injection valve.

[0003] The fuel injection valve is connected to a common rail via a fuel supply pipe, and is supplied with fuel, enabling it to inject high-pressure fuel into the combustion chamber. After injecting a predetermined amount of fuel, the fuel injection valve generates surplus fuel. The fuel injection valve is connected to a fuel tank via a fuel return pipe, enabling the surplus fuel to be returned to the fuel tank. The fuel supply pipe is connected with its end pressed against the fuel supply port of the fuel injection valve (metal touch). This can lead to fuel leakage at the connection between the fuel injection valve and the fuel supply pipe. To prevent this, the fuel injection valve is connected to a leaked fuel return pipe that returns fuel that leaks at the connection with the fuel supply pipe to the fuel tank. An example of such a fuel system is described in the following patent document. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent No. 2011996 [Patent Document 2] European Patent No. 1680592 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, fuel leaking from the connection between a fuel injection valve and a fuel supply pipe is returned to the fuel tank through a leaked fuel return pipe. The downstream end of the leaked fuel return pipe is connected to a fuel return pipe, and the leaked fuel is returned to the fuel tank together with excess fuel. Diesel engines are equipped with multiple fuel injection valves. Therefore, with the conventional configuration, it is difficult to identify the fuel injection valve from which the leaked fuel has occurred. To address this issue, it is possible to provide a detection hole in the leaked fuel return pipe to check for leaked fuel. However, in this case, there is a problem that if a fuel leak occurs, the leaked fuel is discharged to the outside through the detection hole.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a fuel system that prevents external fuel leakage and can properly detect a cylinder in which fuel leakage has occurred from the connection between the fuel injection valve and the fuel supply path. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the fuel system of the present disclosure comprises a fuel injection valve, a fuel supply path that supplies fuel to the fuel injection valve, a fuel return path that returns excess fuel from the fuel injection valve, a leaked fuel return path that discharges fuel that has leaked from a connection between the fuel injection valve and the fuel supply path into the fuel return path, an inspection hole that is provided in the leaked fuel return path and can be opened and closed by a plug member, and a check valve that is provided in the leaked fuel return path and prevents fuel from flowing toward the connection. [Effects of the Invention]

[0008] According to the fuel system of the present disclosure, it is possible to prevent fuel from leaking to the outside and to properly detect a cylinder in which fuel is leaking from a connection between a fuel injection valve and a fuel supply path. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a fuel system according to a first embodiment. [Figure 2]FIG. 2 is a schematic diagram illustrating a fuel leak detection device in a fuel system. [Figure 3] FIG. 3 is a schematic diagram showing a fuel leak detection device in a fuel system according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] [First embodiment] <Fuel system> FIG. 1 is a schematic diagram showing a fuel system according to a first embodiment.

[0012] 1, the fuel system 10 is mounted on a diesel engine (internal combustion engine). The fuel system 10 includes a fuel tank 11, a fuel pump 12, a common rail 13, a plurality of fuel injection valves 14, and a control device 15.

[0013] The fuel tank 11 stores a predetermined amount of fuel. The fuel tank 11 is connected to a fuel pump 12 via a fuel intake path 21. The fuel pump 12 draws fuel stored in the fuel tank 11 through the fuel intake path 21 and pressurizes it to generate high-pressure fuel. The fuel pump 12 is connected to a common rail 13 via a high-pressure fuel path 22. The common rail 13 adjusts the high-pressure fuel supplied from the fuel pump 12 to a predetermined pressure. The common rail 13 is connected to fuel injection valves 14 via multiple fuel supply paths 23 (four in the first embodiment). The fuel injection valves 14 open and close their injection valves at predetermined timings to inject the high-pressure fuel from the common rail 13 into each cylinder (combustion chamber) of the diesel engine.

[0014] The common rail 13 is connected to the fuel tank 11 via a fuel return path 24. The common rail 13 adjusts the pressure of the stored high-pressure fuel to a predetermined level, so when the high-pressure fuel rises above the predetermined pressure, surplus fuel is returned to the fuel tank 11 via the fuel return path 24. Each fuel injection valve 14 is connected to the fuel return path 24 via a fuel return path 25. The fuel injection valve 14 injects a predetermined amount of fuel according to the operating state of the diesel engine, so surplus fuel is generated. The generated surplus fuel is returned from the fuel injection valve 14 to the fuel tank 11 via the fuel return path 25 and the fuel return path 24.

[0015] The control device 15 can drive and control each fuel injection valve 14. The control device 15 drives and controls the fuel injection valves 14 in accordance with the operating state of the diesel engine, and injects a predetermined amount of fuel into the cylinder at a predetermined timing for a predetermined period of time. The common rail 13 is provided with a pressure sensor 26. The pressure sensor 26 measures the pressure of the high-pressure fuel stored in the common rail 13 and outputs the pressure to the control device 15. When the high-pressure fuel in the common rail 13 exceeds a predetermined pressure based on the measurement result of the pressure sensor 26, the control device 15 activates a pressure limiter (not shown) and returns a portion of the high-pressure fuel in the common rail 13 to the fuel tank 11 via a fuel return path 24 as surplus fuel.

[0016] <Configuration of fuel leak detection device> FIG. 2 is a schematic diagram illustrating a fuel leak detection device in a fuel system.

[0017] As shown in Fig. 2, the fuel injection valve 14 is mounted in a cylinder head 31 of a diesel engine and is capable of injecting fuel into a cylinder. The common rail 13 is connected to the fuel injection valve 14 via a fuel supply path 23. The fuel injection valve 14 is connected to a fuel return path 24 via a fuel return path 25, and the fuel return path 24 is connected to the fuel tank 11. The fuel return path 25 has a first pipe 25a and a second pipe 25b. The first pipe 25a is arranged inside the cylinder head 31, and the second pipe 25b is arranged outside the cylinder head 31. The first pipe 25a and the second pipe 25b are connected via a connector 32 fixed to the cylinder head 31.

[0018] Specifically, the fuel supply path 23 includes a first pipe 23a and a second pipe 23b. The first pipe 23a is disposed outside the cylinder head 31, and the second pipe 23b is disposed inside the cylinder head 31. The second pipe 23b is housed, for example, in a hollow portion (not shown) formed in the cylinder head 31. The second pipe 23b is fixed to the cylinder head 31 by threading a threaded portion 23c formed on the outer periphery of the second pipe 23b into a threaded portion 31a provided in the cylinder head 31. At this time, the second pipe 23b is fixed to the cylinder head 31 in a pressed state with its downstream end pressed against the side portion of the fuel injection valve 14. Therefore, the downstream end opening of the second pipe 23b communicates with a fuel supply hole formed in the side portion of the fuel injection valve 14. The first pipe 23a is connected to the end of the second pipe 23b exposed to the outside from the cylinder head 31.

[0019] The second pipe 23b constituting the fuel supply path 23 is fixed to the cylinder head 31 in a pressed state with its end pressed against the side of the fuel injection valve 14. In this case, the second pipe 23b and the fuel injection valve 14 are in metal-to-metal contact, and therefore fuel may leak from a connection C between the second pipe 23b of the fuel supply path 23 and the fuel injection valve 14. For this reason, the fuel system 10 of the first embodiment has a fuel leak detection device 40.

[0020] The fuel leak detection device 40 has a leaked fuel return path 41, an inspection hole 42, a plug member 43, and a check valve 44.

[0021] The leaked fuel return path 41 discharges fuel leaking from a connection C between the fuel injection valve 14 and the fuel supply path 23 to the fuel return paths 24, 25. That is, one end of the leaked fuel return path 41 is connected to the outside of the connection C between the fuel injection valve 14 and the fuel supply path 23, and the other end is connected to the fuel return path 25. The leaked fuel return path 41 has a first pipe 41a, a second pipe 41b, and a third pipe 41c. The first pipe 41a and the second pipe 41b are arranged inside the cylinder head 31, and the third pipe 41c is arranged outside the cylinder head 31.

[0022] One end of the first pipe 41a is connected to a connection C between the fuel injection valve 14 and the fuel supply path 23, and the other end is connected to a connector 51 fixed to the outer surface of the cylinder head 31. The second pipe 41b is connected to the first pipe 41a at one end and to an inspection hole 42 provided on the outer surface of the cylinder head 31 at the other end. The inspection hole 42 is disposed at the vertically lowest position of the first pipe 41a and the second pipe 41b serving as the leaked fuel return path 41. Therefore, when fuel leaks from the connection C between the fuel supply path 23 and the fuel injection valve 14, the leaked fuel can be discharged from the inspection hole 42 through the first pipe 41a and the second pipe 41b. The inspection hole 42 can be opened and closed by a plug member 43. When the inspection hole 42 is closed by the plug member 43, the leaked fuel is prevented from being discharged.

[0023] One end of the third pipe 41c is connected to the first pipe 41a via a connector 51, and the other end is connected to a connector 52 of the second pipe 25b of the fuel return path 25. The check valve 44 is provided in the third pipe 41c of the leaked fuel return path 41. That is, the check valve 44 is disposed outside the cylinder head 31. The check valve 44 is preferably provided at a connection portion of the third pipe 41c of the leaked fuel return path 41 with the second pipe 25b of the fuel return path 25, that is, near the connector 52. The check valve 44 allows fuel to flow from connection portion C, i.e., from the leaked fuel return path 41 to the second pipe 25b of the fuel return path 25. On the other hand, the check valve 44 prevents fuel from flowing from the second pipe 25b of the fuel return path 25 to connection portion C, that is, to the third pipe 41c of the leaked fuel return path 41.

[0024] Four fuel injection valves 14 are mounted on the cylinder head 31, and each of the fuel return paths 25 connected to the four fuel injection valves 14 is connected to the fuel return path 24, and each of the leaked fuel return paths 41 connected to each fuel injection valve 14 is connected to one of the fuel return paths 25. If the cylinder head 31 is integrated, four fuel injection valves 14 are mounted, but if the cylinder head 31 is independent for each cylinder, one fuel injection valve 14 is mounted for each cylinder.

[0025] 1, the fuel pump 12 is provided with a pressure sensor 61 that measures the pressure (discharge pressure) at which high-pressure fuel is supplied to the common rail 13 via the high-pressure fuel path 22, and an actuator 62 that controls the discharge amount to maintain this pressure constant, and outputs the detection results to the control device 15. The control device 15 is connected to an alarm 63. The alarm 63 is, for example, a speaker, a patrol lamp, a display, or the like. The control device 15 activates the alarm 63 when the actuator operation amount of the fuel pump 12 is greater than a preset operation amount. Note that a flow rate sensor may be used instead of the operation amount of the actuator 62.

[0026] <Fuel leak detection device operation> 1 and 2, when the fuel pump 12 is driven, it draws fuel stored in the fuel tank 11 through a fuel intake path 21 and pressurizes it to generate high-pressure fuel. The fuel pump 12 supplies the high-pressure fuel from a high-pressure fuel path 22 to a common rail 13, and the common rail 13 adjusts the high-pressure fuel supplied from the fuel pump 12 to a predetermined pressure. At this time, each fuel injection valve 14 returns surplus fuel from a fuel return path 25 to the fuel tank 11 via a fuel return path 24.

[0027] At this time, fuel supply path 23 is in a pressed state with the end of second pipe 23b pressed against fuel injection valve 14, which may cause fuel leakage from connection C between second pipe 23b of fuel supply path 23 and fuel injection valve 14. Fuel leak detection device 40 detects fuel leakage from connection C. Detection of fuel leakage from connection C by fuel leak detection device 40 is performed before shipping of the diesel engine or during periodic inspection of the diesel engine. However, detection may be performed at other times.

[0028] When fuel leaks from a connection C between the second pipe 23b of the fuel supply path 23 and the fuel injection valve 14, the leaked fuel flows into the first pipe 41a and also flows into the second pipe 41b in the leaked fuel return path 41. The leaked fuel that flows into the first pipe 41a flows into the third pipe 41c via the connector 51, and further flows into the fuel return path 25 via the check valve 44 and the connector 52. Therefore, the leaked fuel that leaks from the connection C is returned to the fuel tank 11 via the fuel return path 24 together with the surplus fuel flowing through the fuel return path 25, and does not leak to the outside.

[0029] Furthermore, a check valve 44 is provided in the third pipe 41c of the leaked fuel return path 41. Therefore, excess fuel flowing through the fuel return path 25 and leaked fuel that has flowed from the leaked fuel return path 41 to the fuel return path 25 do not flow back to the leaked fuel return path 41 side.

[0030] On the other hand, the leaked fuel that has flowed into the second pipe 41b reaches the inspection hole 42. However, because the inspection hole 42 is closed by the attached plug member 43, the leaked fuel does not leak to the outside through the inspection hole 42. When the fuel leak detection device 40 detects a fuel leak from the connection part C, the worker removes the plug member 43 from the inspection hole 42. At this time, if fuel is leaking from the connection part C, the leaked fuel will be discharged to the outside through the inspection hole 42. On the other hand, if fuel is not leaking from the connection part C, the leaked fuel will not be discharged to the outside through the inspection hole 42. The worker determines whether there is a fuel leak from the connection part C depending on whether or not fuel is being discharged from the inspection hole 42.

[0031] Furthermore, if fuel leaks from connection C during normal operation of the diesel engine, the consumption of high-pressure fuel stored in the common rail 13 increases, and the fuel pump 12 is required to supply a large amount of fuel to the common rail 13, increasing the discharge amount of the fuel pump 12. Therefore, the control device 15 activates an alarm 63 when the amount of operation of the actuator 62 of the fuel pump 12 exceeds a preset amount. When the alarm 63 is activated, the operator performs work to detect fuel leakage from connection C using the fuel leak detection device 40.

[0032] [Second embodiment] 3 is a schematic diagram showing a fuel leak detection device in a fuel system according to a second embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0033] As shown in FIG. 3, the fuel leakage detection device 40A includes a leaked fuel return path 41, an inspection hole 42, a plug member 43, and a check valve 44.

[0034] One end of the leaked fuel return path 41 is connected to a connection point C between the fuel injection valve 14 and the fuel supply path 23, and the other end is connected to the fuel return path 25. The check valve 44 is provided in the first pipe 41a of the leaked fuel return path 41. That is, the check valve 44 is disposed inside the cylinder head 31. The check valve 44 is preferably provided at a connection point between the first pipe 41a of the leaked fuel return path 41 and the second pipe 41b, that is, near the connector 51. The check valve 44 allows fuel to flow from the connection point C, that is, from the first pipe 41a to the second pipe 41b of the leaked fuel return path 41. On the other hand, the check valve 44 prevents fuel from flowing from the second pipe 41b of the leaked fuel return path 41 to the connection point C, that is, toward the first pipe 41a.

[0035] The operation of the fuel leak detection device 40A is similar to that of the fuel leak detection device 40 of the first embodiment, and a description thereof will be omitted.

[0036] [Effects of this embodiment] The fuel system of the first aspect includes a fuel injection valve 14, a fuel supply path 23 that supplies fuel to the fuel injection valve 14, fuel return paths 24, 25 that return excess fuel from the fuel injection valve 14, a leaked fuel return path 41 that discharges fuel that has leaked from a connection C between the fuel injection valve 14 and the fuel supply path 23 to the fuel return paths 24, 25, an inspection hole 42 provided in the leaked fuel return path 41 that can be opened and closed by a plug member 43, and a check valve 44 provided in the leaked fuel return path 41 that prevents fuel from flowing toward the connection C.

[0037] According to the fuel system of the first aspect, when fuel leaks from the connection C, the leaked fuel is discharged from the leaked fuel return path 41 to the fuel return path 25. At this time, the inspection hole 42 provided in the leaked fuel return path 41 is closed by the plug member 43, thereby preventing fuel from leaking from the inspection hole 42. Furthermore, the leaked fuel return path 41 is provided with a check valve 44, thereby preventing fuel from the fuel return path 25 from flowing back to the connection C via the leaked fuel return path 41. When the operator removes the plug member 43 from the inspection hole 42, the operator can detect fuel leakage from the connection C by checking whether fuel is being discharged from the inspection hole 42. As a result, external fuel leakage can be prevented, and the cylinder in which fuel leakage has occurred from the connection C between the fuel injection valve 14 and the fuel supply path 23 can be properly detected.

[0038] In the fuel system according to the second aspect, the check valve 44 is provided in the vicinity of the connector 52, which is the connection part of the leaked fuel return path 41 with the fuel return path 25. This makes it possible to prevent the fuel from flowing back from the fuel return path 25 to the leaked fuel return path 41, and to properly discharge the fuel that has leaked from the connection part C.

[0039] In the fuel system according to the third aspect, the inspection hole 42 is disposed at the vertically lowest position of the leaked fuel return path 41. This allows fuel leaking from the connection C to flow into the inspection hole 42 by its own weight, and the cylinder from which fuel leakage has occurred at the connection C can be properly detected.

[0040] In the fuel system according to the fourth aspect, the check valve 44 is disposed outside the cylinder head 31 to which the fuel injection valve 14 is attached. This makes it possible to improve the ease of maintenance of the check valve 44.

[0041] In the fuel system according to the fifth aspect, the check valve 44 is disposed inside the cylinder head 31 to which the fuel injection valve 14 is attached. This can improve the ease of assembly.

[0042] In the fuel system according to the sixth aspect, a plurality of fuel injection valves 14 are arranged, a plurality of fuel return paths 25 connected to the plurality of fuel injection valves 14 are connected to each other, and a plurality of leaked fuel return paths 41 connected to the plurality of fuel injection valves 14 are connected to any one of the fuel return paths 25. As a result, fuel leaking from each connection C can be made to flow from the leaked fuel return path 41 to the fuel return path 25 and properly discharged to the outside.

[0043] In the above-described embodiment, the fuel system 10 includes the fuel tank 11, the fuel pump 12, the common rail 13, the fuel injection valves 14, and the control device 15. However, the configuration of each component is not limited to that of the above-described embodiment. The arrangement and connection of each component may be set as appropriate. [Explanation of symbols]

[0044] 10 Fuel System 11 Fuel tank 12 Fuel pump 13 Common rail 14 Fuel injection valve 15 Control device 21 Fuel intake path 22 High pressure fuel line 23 Fuel supply route 24,25 Fuel return route 26 Pressure Sensor 31 Cylinder head 32 connectors 40,40A Fuel leak detection device 41 Leaked fuel return route 42 Inspection hole 43 Plug member 44 Check valve 51 Connector 52 Connector (connection part) 61 Pressure Sensor 62 Actuator 63 Alarm C Connection

Claims

1. A fuel injection valve; A common rail that stores high-pressure fuel; a fuel supply path for supplying high-pressure fuel from the common rail to the fuel injection valve; a first fuel return path that returns surplus fuel in the common rail to a fuel tank; a second fuel return path that returns surplus fuel from the fuel injection valve to the first fuel return path; a leaked fuel return path that discharges fuel leaking from a connection between the fuel injection valve and the fuel supply path to the second fuel return path; an inspection hole provided in the leaked fuel return path and capable of being opened and closed by a plug member; a check valve provided in the leaked fuel return path to prevent fuel from flowing toward the connecting portion; A fuel system comprising:

2. the check valve is provided at a connection portion of the leaked fuel return path with the second fuel return path; 10. The fuel system of claim 1.

3. The inspection hole is disposed at the lowest position in the vertical direction of the leaked fuel return path.

3. A fuel system according to claim 1 or claim 2.

4. The check valve is disposed outside a cylinder head to which the fuel injection valve is attached. A fuel system according to any one of claims 1 to 3.

5. The check valve is disposed inside a cylinder head to which the fuel injection valve is attached. A fuel system according to any one of claims 1 to 3.

6. a plurality of the fuel injection valves are arranged, the plurality of fuel return paths connected to the plurality of the fuel injection valves are connected to each other, and the plurality of leaked fuel return paths connected to the plurality of the fuel injection valves are connected to any of the plurality of second fuel return paths; A fuel system according to any one of claims 1 to 5.

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