JPH1018936A - Fuel piping structure of outboard motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide vibration control action by the elasticity of a resin, and avoid damage and failure of action due to the vibration of a fuel rail itself or an injector, by forming the fuel rail of resin. SOLUTION: Fuel raised to a predetermined injection force, is dividedly led to flow into two fuel supply passages 88, 88, led to flow from bottom to top in a feel rail 89 being a fuel passage on a right bank 30a side, and supplied in order to injectors 38 of three air cylinders (#5, #3, #1) on the right bank 30a. Also, fuel is led to flow from bottom to top in a fuel rail 89 being a fuel passage on a left bank 30b side, and supplied in order to injectors 38 of three air cylinders (#6, #4, #2) on the left bank 30b. The fuel rails 89 are formed of a resin excellent in elasticity and heat insulation propertres. Hereby, vibration control action can be obtained by the elasticity of the resin, and damage and failure of action due to the vibration of the fuel rail 89 themselves or the injectors 38, can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel piping structure for an outboard motor, and more particularly, to a four-stroke V-cycle for an outboard motor which is arranged vertically.
The present invention relates to a fuel pipe structure of a type engine.

[0002]

2. Description of the Related Art A two-cycle V-type engine has been put to practical use as an engine for an outboard motor, and a four-cycle V-type engine has been disclosed in Japanese Patent Application Laid-Open No. Hei 6-264775.

According to the prior art described in this publication, an exhaust port is provided inside each bank arranged in a V-shape in a four-stroke V-type engine for an outboard motor arranged vertically, and an exhaust port communicating with the exhaust port is provided. A compact V-type engine structure is achieved by connecting the passage to an exhaust pipe below the engine and arranging an intake port and an intake system communicating with the intake port outside each bank.

In such an outboard motor, when the engine has a structure having an injector for directly injecting fuel into an intake passage or into a cylinder, a fuel rail for supplying fuel to the injector is provided by the engine rail. Need to be fixed to The injector fixed to such a fuel rail needs to operate reliably while avoiding the influence of engine vibration as much as possible. Further, when the fuel rail is fixed to the engine, it is necessary to use a heat insulating material so that the high heat of the engine is not directly transmitted to the fuel in the fuel rail and the fuel does not evaporate.

FIG. 8 is an explanatory view showing a structure for attaching a fuel rail to an engine in an outboard motor equipped with a conventional two-cycle V-type engine. The fuel rail 800 that supplies the fuel to the injector 808 that injects the fuel into the intake passage 807 is made of a metal formed by cutting a metal material such as an aluminum alloy or iron, sheet metal, or casting. The fuel rail 800 has a mounting piece 801 attached to a boss 805 provided on a cylinder head 804 by a bolt 806 via a cylindrical insulator 802 made of a heat insulating material and an inner metal collar 803 for reinforcing the insulator 802. , Fixed to the engine.

[0006]

However, since the above-mentioned conventional fuel rail is made of metal, it has high rigidity and vibrates according to the vibration of the engine to transmit the vibration to the injector, thereby damaging the injector or the fuel rail itself. In some cases, the injector may malfunction or the injector may malfunction.
Further, the metal fuel rail is heavy and easily corroded, and the heat from the engine is transmitted through the metal collar 803 or from the surroundings to some extent regardless of the insulator 802, and the fuel inside may be evaporated. Was.
Further, since the conventional fuel rail is fixed to the engine via an insulator 802 made of a heat insulating material, the number of parts increases because the insulator 802 is required.
Assembly was cumbersome and costly.

[0007] In particular, outboard motors are required to be reduced in weight due to the special circumstances of use at sea, and corrosion by seawater must be prevented. Further, a reliable engine drive on the sea is required, and it is necessary to reliably operate the fuel system to completely prevent the occurrence of engine stall and the like, and to achieve reliable navigation.

The present invention has been made in view of the above points, and has as its object to provide an inexpensive and highly reliable fuel piping structure for an outboard motor which is lightweight and simple in structure.

[0009]

According to the present invention, there is provided a fuel pipe structure for an outboard motor equipped with an engine having an injector for injecting fuel supplied from a fuel rail. Provided is a fuel pipe structure for an outboard motor, wherein the rail is made of resin.

According to the above construction, since the fuel rail is made of a resin (synthetic resin material), its elasticity effectively absorbs engine vibration and interrupts the transmission of vibration to the injector. This prevents the injector from being damaged or malfunctioning. In addition, since the fuel rail is made of resin, the fuel rail is reduced in weight, and furthermore, since the fuel rail itself has heat insulating properties, the fuel rail is interposed with heat insulating material as in the case where the fuel rail is made of metal. There is no need to fix it, and the structure can be simplified as the heat insulating material is not required. Further, since the heat insulation of the fuel rail itself is enhanced, the vaporization of the fuel flowing inside is reliably prevented, and the reliability of the fuel supply system is enhanced. Further, since the fuel rail itself has corrosion resistance, a highly reliable product can be obtained without corrosion as in the case where the fuel rail is made of metal. Furthermore, since the fuel rail can be mass-produced by injection molding, etc., unlike the case where the fuel rail is made of metal, it does not require expensive machining such as metal material cutting, sheet metal, casting, etc. It can be provided easily and cheaply.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment,
The engine is a V-type engine.

In another preferred embodiment, the fuel rail is fixed to a boss provided on a cylinder of the engine without a heat insulating material by a mounting piece made of an integral resin provided on the fuel rail. I do.

[0013]

FIG. 1 shows a 4-cycle 6 according to an embodiment of the present invention.
FIG. 2 is a main part configuration diagram of an outboard motor equipped with a vertical cylinder V-type engine. FIGS. 2 to 4 are detailed structural diagrams of the upper part, the central part, and the lower part of the outboard motor of FIG.

The outboard motor 1 is clamped to a hull 3 at the rear of the hull via a bracket 2 and is mounted rotatably about a tilt shaft 2a by a hydraulic cylinder (not shown) or manually. The outboard motor 1 is further rotatable around the swivel shaft 4, and is mounted so as to be steerable.

The outer side of the outboard motor 1 is provided with a cowling 5 composed of an upper cowling 5a and a lower cowling 5b, which are engine housings, and an upper casing 6 below the cowling.
a and the lower casing 6b. Cowling 5
Inside, a 6-cylinder V-type engine 7 is housed in a vertical arrangement in which the axis 13 (FIG. 1) of the crankshaft 52 (FIG. 2) is arranged substantially vertically during operation. An intake passage 11, which will be described in detail later, is connected to the cylinder head 8 of each cylinder of the engine 7. FIG. 1 shows three intake passages 11 connected to one bank of three vertically arranged three cylinders in a six-cylinder V-type arrangement. Each intake passage 11 branches off from a surge tank 10, and an intake pipe 9 communicating with the outside air is connected to the surge tank 10. On the intake pipe 9, a throttle body 62 provided with a butterfly valve for adjusting the amount of intake air and the like is mounted.

A flywheel 12 is provided above the engine 7.
Are mounted coaxially with the crankshaft 52 (FIG. 2) by fastening with a nut 51. A pulley 58 (FIG. 2) is mounted below the flywheel 12 and is connected to an alternator (not shown). The upper part of the flywheel 12 is covered with a flywheel cover 57 (FIG. 2). A chain 60 for driving a valve cam is mounted on the crankshaft 52 below the pulley 58, and opens and closes an intake valve and an exhaust valve (not shown) of each cylinder in synchronization with the crankshaft 52. The chain 60 is covered with a chain cover 59.

The head 53 of the drive shaft 14 is connected and fixed to the lower side of the crankshaft 52 below the engine. A transmission mechanism 15 (FIG. 1) composed of a bevel gear, a dog clutch, and the like is attached to the lower end of the drive shaft 14. Via this transmission mechanism 15, the rotation of the engine is selected in the forward or reverse direction, and the propeller is driven. It is transmitted to the shaft 16. A propeller 17 is mounted on the rear end of the propeller shaft 16.

An exhaust passage 18 is provided from each cylinder of the engine 7.
Are provided toward the inside of the left and right banks, as described later. Each exhaust passage 18 extends vertically inside the left and right banks,
The cylinders 31 of the engine 7 communicate with each other in an exhaust collecting passage 19 formed downward along the cylinder block 31 (FIG. 5) of each cylinder.

The engine 7 is fixed to the upper surface of the upper casing 6a via an exhaust guide 20 (FIGS. 1 and 3). An oil pan 23 is attached to the lower side of the exhaust guide 20. An exhaust passage 43 is formed substantially at the center of the exhaust guide 20. The exhaust collecting passage 19 of each of the left and right banks communicates with the exhaust passage 43 of the exhaust guide 20 (FIGS. 1 and 3).
An exhaust pipe 22 is provided below the exhaust guide 20 so as to be continuous with the exhaust passage 43. The exhaust pipe 22 is disposed facing the main exhaust chamber 21 in the upper casing 6a. The exhaust gas from the engine 7 is introduced into the main exhaust chamber 21 through each exhaust passage 18, the exhaust collecting passage 19, the exhaust passage 43, and the exhaust pipe 22, and is guided further downward to form an annular space around the propeller shaft 16. And is discharged into the water from the rear end.

An oil pan 23 is provided in the upper casing 6a below the exhaust guide 20, and an oil strainer 24 is provided therein. The lower end of the crankshaft 52 (FIG. 2) (the head 53 of the drive shaft 14)
Is equipped with an oil pump 50. The oil in the oil pan 23 is sucked by the oil pump 50 via the oil strainer 24, and is pumped to the engine through the main oil passage 55 (FIGS. 1 and 2). From the main oil passage 55, a branch oil passage 56 communicating with each cylinder and the valve cam shaft is formed. The oil circulates around the camshaft and crankshaft inside the engine and around the cylinder block through these branch oil passages 56, and is returned to the oil pan 23.

Cooling water is taken in from a water inlet 25 by a cooling water pump 26 (FIGS. 1 and 4) connected to the drive shaft 14. This cooling water is guided upward as indicated by the arrow in the figure, and first cools the exhaust collecting passage 19 from below through an exhaust cooling water passage 44 formed around the exhaust collecting passage 19, From above, the main oil passage 55
After being introduced into the upper part of the oil cooling water passage 85 adjacent to and cooled down to cool the main oil passage 55, it is further introduced into the cylinder head and the cylinder block to cool around the cylinder. Thereafter, the system is divided into two systems. One system cools the periphery of the oil pan 23 and is discharged into the water, and the other system is discharged into the exhaust in the main exhaust chamber 21 through the jacket around the exhaust pipe 22. , Together with the exhaust gas, passes around the propeller shaft 16 and is discharged from the rear end into the water. By flowing the cooling water through such a path, not only the exhaust collecting passage 19 and around the cylinder but also the main oil passage 55 and the oil pan 23 can be cooled. Even if the temperature of the engine 7 becomes high, the engine oil is cooled by the cooling water after cooling the exhaust collecting passage 19,
It is kept at an appropriate temperature. If the temperature of the engine oil is lower than the temperature of the cooling water after cooling the exhaust collecting passage 19, the engine oil absorbs heat from the cooling water after cooling the exhaust collecting passage 19 and maintains the temperature at an appropriate temperature. Dripping.

The exhaust cooling water passage 44 and the oil cooling water passage 8
A pressure valve that discharges the cooling water when the pressure becomes equal to or higher than a predetermined pressure is provided in a portion of the water passage between the first and second water passages immediately after cooling the exhaust collecting passage 19. Further, at an appropriate position of such a water path of the cooling system, a thermostat that shuts off a water path including a cooling water path 85 that is in contact with the main oil path 55 when the temperature of the engine 7 falls below a predetermined temperature; And a control valve for adjusting the amount of water in accordance with the condition.

When the engine rotates, the cooling water pump directly connected to the crankshaft rotates to circulate the cooling water as described above. At this time, if the engine temperature is low, the cooling water passage is closed by the thermostat while the pump is rotating, and the pressure increases. This pressure increase is released by the pressure valve. By providing this pressure valve at the upper end of the exhaust cooling water passage 44, only the exhaust is constantly cooled even when the circulation of the cooling water in the engine is stopped by the thermostat, so that an appropriate engine operating state is maintained.

Also, by the action of the control valve,
When the thermostat is opened, a large amount of low-temperature cooling water is rapidly circulated to prevent the engine from being rapidly cooled. This control valve controls the flow rate according to the valve opening area of the thermostat and the water temperature.

In the fuel supply system of the present embodiment, a vapor separator 81 including a filter 87, a low-pressure pump 86 and a high-pressure pump is disposed on the rear side of the engine and between the left and right banks.

FIG. 5 is a horizontal cross-sectional view of a main part of the engine portion in the cowling of the embodiment, where F indicates the front side and R indicates the rear side. FIG. 6 is a rear view of the engine.
The engine 7 is composed of two banks 30a and 30b vertically arranged in a V-shape on each of the left and right sides diagonally rearward from the crankshaft 52. The cylinder head 8 of each cylinder of each bank includes a cylinder block 31. Are joined, and each cylinder block 31 is fixed to the crankcase 74. Crank case 74 that accommodates this crank shaft 52
Are assembled and fixed to the V-shaped cylinder block 31 by bolts 75 (only one is shown in the figure) provided at appropriate plural locations. A starter motor 72 for rotating the flywheel 12 at startup and a generator (alternator) 73 rotating with the crankshaft 52 on the opposite side are provided on both outer sides of the crankcase 74.
Is provided. Further, a vapor separator 81 having a high-pressure pump and a regulator is provided on the rear side of the engine and between the left and right banks 30a and 30b.

Each cylinder block 31 is formed toward the rear of a common crank chamber 32 and has a piston 34 inside.
Slides. Each piston 34 and the crankshaft 52 are connected via the connecting rod 33 at a predetermined crank phase difference angle. Each of the left and right banks 30a and 30b is provided with one common intake surge tank 10 and an intake passage 11 branched therefrom, and communicates with the intake passage 35 of each cylinder.
The injector 38 is installed in the middle of the intake passage 35 of each cylinder so as to face the intake passage 35, and an intake valve 36 is attached to an intake port at the end of the intake passage. The intake valve 36 has a cam (not shown) in which a valve lifter 77 at the upper end of the valve shaft is mounted on a cam shaft 37 that rotates in synchronization with the crank shaft 52.
By pressing against the spring 78, it slides along the valve guide 76 and opens and closes in synchronization with the rotation of the crankshaft 52.

Cylinder block 31 made of aluminum alloy
A cylinder sleeve 70 made of cast iron or the like is press-fitted into the inner surface of the cylinder for smooth sliding operation of the piston 34.

An exhaust passage 18 is formed in the cylinder head 8 of each cylinder, and an exhaust valve 39 is provided at an exhaust port at the end thereof.
Is attached. Each exhaust valve 39 is opened and closed at a predetermined timing by a cam mounted on a camshaft 40 similarly to the intake valve 36. A hole for mounting a spark plug is formed in the center of each cylinder head 8. As shown in the figure, the three exhaust passages 18 of each bank are formed inside the left and right banks 30a, 30b in the cylinder head 8 obliquely forward. An exhaust cooling water passage 44 is formed around the exhaust collecting passage 19 in which the six exhaust passages 18 of both banks are gathered. As described above, the cooling water sent from the cooling water pump 26 passes first, This exhaust passage 19 is first cooled.

As shown in FIG. 6, the exhaust collecting passage 19
At the lower end, exhaust of all six cylinders of both banks is gathered. For example, # 1 of the right bank, # 1 of the left bank
2, # 3 in the right bank, # 4 in the left bank, # in the right bank
5. The exhaust of the cylinder # 6 in the left bank merges sequentially from the top, and all the exhaust gather at the lower end. The collected exhaust gas communicates with the exhaust passage 43 of the exhaust guide 20.

As described above, one common intake surge tank 10 is provided for each of the left and right banks, and the intake passage 9 is connected to the upper center of the surge tank 10. A throttle body 62 for adjusting the amount of intake air is provided above the center of the intake passage 9.

The fuel supply system of the present embodiment includes a filter 8
7. The vapor separator 81 including the low pressure pump 86 and the high pressure pump
a, 30b. In such a fuel system, as shown in FIG. 6, fuel is introduced into a filter 87 from a tank (not shown) on the ship via a pipe 151, filtered, and then filtered through a pipe 152 to a low-pressure pump 86. Is sent to the vapor separator 81 via the pipe 153 to remove bubbles, and is sent under pressure from the two fuel supply passages 88 by a high-pressure pump. The fuel whose injection power has been increased to a predetermined injection force by the high-pressure pump flows into two fuel supply passages 88 and 88, and flows into the right bank 30a.
The fuel flows from the bottom to the top in the fuel rail 89, which is the fuel passage on the side, and supplies the fuel to the injectors 38 of the three cylinders (# 5, # 3, # 1) of the right bank in order, and the left bank 3
The fuel flows from the bottom to the top in the fuel rail 89, which is the fuel passage on the 0b side, and supplies the fuel to the injectors 38 of the three cylinders (# 6, # 4, # 2) in the left bank in order, and the return passages at the upper ends respectively. The gas is returned to the vapor separator 81 through the pipe 92 via the pressure regulator 91 through the pressure regulator 90.

From each surge tank 10, three intake passages 11 are provided in a branched manner, and are respectively connected to intake passages 35 (FIG. 5) of three cylinders vertically arranged in each bank. 3 connecting the surge tank 10 and each cylinder
In the intake passage 11, the central intake passage is expanded outward in order to equalize the intake passage length and make the combustion state in each cylinder uniform. That is, the intake passage 11 shown by the hatched section in FIG. 5 shows two upper and lower intake paths, and the outwardly extending intake passage 11 shown by the open section without hatching shows the central intake passage. With such a configuration, the length of the intake passage 11 for each cylinder becomes equal,
A uniform combustion action is obtained.

FIG. 7 is an explanatory diagram showing a state in which the fuel rail 89 of FIG. 6 is attached to the engine. As described above, the fuel rail 89 on the right side when viewed from the rear side of the engine.
Supplies fuel to the injectors 38 of the three cylinders (# 5, # 3, # 1) in the right bank, and the left fuel rail 83 connects the injectors of the three cylinders (# 6, # 4, # 2) in the left bank. 3
8 to supply fuel. Here, the injector 38 generally has a structure in which a valve opening time is controlled by a duty ratio by a drive signal current sent from the electric wiring 700, a piston inside a distal end thereof retreats, and fuel is injected into the intake passage 35. It is a target.

The two fuel rails 89 are made of a resin having excellent elasticity and heat insulation. By using the resin as described above, vibration is prevented, and fuel flowing in the fuel rail is prevented from being vaporized by high heat from the engine. As a result, highly reliable fuel supply is achieved, and injection molding and the like are achieved. It can be mass-produced inexpensively and easily with high dimensional accuracy, and is lightweight and excellent in corrosion resistance.

The fuel rail 89 is provided with a mounting piece 701 integrally formed therewith. The mounting piece 701 is mounted on a boss 702 provided on the cylinder head 8 with a bolt 703 so that the fuel rail 89 is mounted on the engine. Fix it. Since the fuel rail 89 itself is made of a resin having high elasticity and excellent heat insulating properties, vibration is prevented, and heat insulation is provided between the fuel rail and the engine as in the conventional metal fuel rail described above. There is no need to provide an insulator 802 (FIG. 8) made of a material. Accordingly, the number of parts is reduced, the assembling work is facilitated, the assembling rigidity is increased, the dimensional accuracy is improved, and the cost is reduced.

When the fuel rail is fixed to the boss of the cylinder head without passing through the insulator, the resin mounting piece 701 is protected from the bolt tightening force, or the length between the boss and the mounting piece is reduced. For adjustment,
A metal sleeve may be inserted.

In the above embodiment, the fuel fed from the vapor separator 81 is supplied to the left and right fuel rails 89.
The fuel supply system is configured as a two-system fuel supply system for supplying fuel to each injector 38 by simultaneously flowing the fuel from the bottom to the top. However, instead of such a configuration, for example, the fuel flows first from one bottom to the other within the one fuel rail. To supply fuel to each injector of one bank, and to flow continuously from the top to the bottom in the other fuel rail to supply fuel to each injector of the other bank. Of course it is good.

Further, in the above embodiment, the filter 87 of the fuel supply system, the vapor separator 81 including the low-pressure pump 86 and the high-pressure pump are disposed on the rear side of the engine and between the left and right banks 30a, 30b. However, the present invention is not limited to this. For example, it may be provided on the front side of the engine and below the throttle body 62.

Further, in the above embodiment, an outboard motor equipped with a four-cycle engine has been described. However, the fuel piping structure according to the present invention can be applied to an outboard motor equipped with a two-cycle engine. Further, the injector may be provided at a position where it is directly injected into the cylinder.

[0041]

As described above, in the present invention, since the fuel rail for supplying fuel to the injector is made of resin, a vibration damping action is obtained by its elasticity, and the fuel rail itself or the injector is damaged by vibration. And malfunctions can be avoided. In addition, the fuel rail itself has heat insulation properties to prevent fuel vaporization due to heat from the engine, and it is not necessary to fix the fuel rail to the engine via heat insulating material as in the case where the fuel rail is made of metal. Not
Since the heat insulating material is not required, the structure can be simplified,
The number of parts is reduced and the assembling work is facilitated.
Further, since the fuel rail itself is lightweight and has corrosion resistance, a highly reliable product can be obtained without being heavy and corroding unlike the case where the fuel rail is made of metal.

Further, since the fuel rail can be mass-produced by injection molding or the like, expensive processing such as metal material shaving, sheet metal, casting, etc. is not required unlike the case where the fuel rail is made of metal, and dimensional accuracy can be reduced. You can easily provide expensive products at low cost. In particular, when applied to an outboard motor, it is advantageous in terms of weight reduction of the hull and corrosion resistance against salt damage, and has achieved a reliable and reliable engine drive on the sea in terms of prevention of fuel vaporization, and the Drift accident due to engine stall etc. can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of an embodiment of an outboard motor to which the present invention is applied.

FIG. 2 is a detailed view of an upper portion of the outboard motor of FIG.

FIG. 3 is a detailed view of a central portion of the outboard motor of FIG. 1;

FIG. 4 is a detailed view of a lower portion of the outboard motor of FIG. 1;

FIG. 5 is a horizontal sectional view of a main part of the outboard motor of FIG. 1;

FIG. 6 is a rear view of an engine portion of the outboard motor of FIG. 1;

FIG. 7 is an explanatory diagram showing an example of an embodiment of a fuel piping structure for an outboard motor according to the present invention.

FIG. 8 is an explanatory view of a fuel pipe structure of a conventional outboard motor.

[Explanation of symbols]

1: outboard motor, 2: bracket, 2a: tilt shaft, 3: boat plate, 4: swivel shaft, 5: cowling, 5a: upper cowling, 5b: lower cowling, 6a: upper casing, 6b: lower casing, 7 : Engine, 8: cylinder head, 9: intake pipe, 10: surge tank, 11:
Intake passage, 12: flywheel, 13: shaft, 14: drive shaft, 15: transmission mechanism, 16: propeller shaft, 17: propeller, 18: exhaust passage, 19: exhaust collecting passage, 20: exhaust guide, 21: Main exhaust chamber, 22: exhaust pipe, 2
3: oil pan, 24: oil strainer, 26: cooling water pump, 30a, 30b: bank, 31: cylinder block, 32: crank chamber, 33: connecting rod, 34:
Piston, 35: intake passage, 36: intake valve, 37: camshaft, 38: injector, 40: camshaft, 43: exhaust passage, 44: exhaust cooling water passage, 50: oil pump, 51:
Nut, 52: crankshaft, 53: head, 55: main oil passage, 56: branch oil passage, 57: flywheel cover, 58: pulley, 59: chain cover, 6
0: chain, 62: throttle body, 70: cylinder sleeve, 72: starter motor, 73: generator,
74: crankcase, 75: bolt, 76: valve guide, 77: valve lifter, 78: spring, 81:
Vapor separator, 82:83: fuel rail, 85: oil cooling channel, 86: low pressure pump, 87: filter,
88: fuel supply path, 89: fuel rail, 90: return path, 700: electric wiring, 701: mounting piece, 702: boss, 703: bolt

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display F02M 37/00 321 B63H 21/26 K

Claims (3)

[Claims] 1. A fuel pipe structure for an outboard motor equipped with an engine having an injector for injecting fuel supplied from a fuel rail, wherein the fuel rail is made of resin. Piping structure. 2. The fuel pipe structure for an outboard motor according to claim 1, wherein the engine is a V-type engine. 3. The fuel rail according to claim 1, wherein the fuel rail is fixed to a boss provided on the cylinder of the engine by a mounting piece made of an integral resin provided on the fuel rail without interposing a heat insulating material. Outboard motor fuel piping structure.