JP2663104B2 - Air vent mechanism for engine fuel supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air vent mechanism for a fuel supply system of an engine capable of supplying an appropriate fuel even when the engine is tilted to any position.

[0002]

2. Description of the Related Art Conventionally, an air vent mechanism for a fuel supply system has an air vent hole in which a ball valve is installed above an overflow chamber, and an air vent mechanism connected to a vaporizer overflow chamber. Some fuel return pipes have a large diameter, and an air vent pipe is inserted through the return pipe so that one end of the pipe faces the upper part of the overflow chamber.

However, in the case of using the former ball valve, when the engine is tilted so that the air cleaner faces downward, the valve action is sufficiently operated by the rotational vibration regardless of the existence of the ball valve. Otherwise, fuel may flow out of the vent hole. In this case, part of the spilled fuel leaks from the air cleaner through the bypass of the vent hole, so that the fuel becomes too rich to cause engine stall, and it is difficult to restart in this state. There's a problem.

On the other hand, in the case of using the latter, which does not use a ball valve, it is necessary that the air circulation pipe does not interfere with the fuel circulation function of the return pipe in a state where the pipe is penetrated inside the return pipe. The pipe must have a small cross section and the fuel that fills the return pipe and circulates easily into the air vent pipe that opens upward due to the inclination and vibration of the engine. When the engine attitude changes frequently due to the small cross-sectional area of the pipe, the fuel and air that have entered the pipe mix together to form a bumpy bubble mass, which makes it difficult for the air to breathe smoothly. There is a problem of doing.

[0005] In order to solve such a problem,
An air vent mechanism for a fuel supply system of an engine as shown in FIG. 8 has been proposed.

That is, when the engine is operated in the upright state, the air vent pipe 38 is located above the liquid level of the fuel tank 40, so that the inside of the fuel tank 40 is maintained at the atmospheric pressure, and the engine is started. Then, the diaphragm operates in accordance with the pressure fluctuation (pulsation) inside the crankcase 32, the fuel inside the fuel tank 40 is sucked by the fuel supply pipe, and the carburetor body 2 is discharged from the fuel supply passage.
0 is sent to the fuel chamber 30 side. The fuel that overflows in the fuel chamber 30 is returned from the fuel outlet 22 to the fuel tank 40 through the return pipe 27.

[0007] By continuing such a state, the engine can be satisfactorily operated in the upright state without engine stall.

Next, when the engine is tilted so that the cylinder 33 is tilted to the left from the state shown in FIG. 8, the return pipe 27 is located above the liquid level of the fuel tank 40. Driving becomes good.

Further, when the engine is tilted so that the cylinder 33 is tilted rightward from the state shown in FIG. 8, the inside of the fuel tank 40 becomes large because the air vent pipe 38 is located above the liquid level of the fuel tank 40. The pressure is maintained at the atmospheric pressure, and the driving of the engine is improved as described above.

[0010]

As described above, according to the conventional air vent mechanism of the fuel supply system of the engine, even if the fuel tank 40 is inclined, any one of the air vent pipe 38 and the return pipe 27 can be used. Since the pressure in the space above the liquid surface in the fuel tank 40 is maintained at the atmospheric pressure by one of the pipes, normal driving can be performed without occurrence of engine stall or fuel leakage regardless of the posture of the engine. I have.

However, in such a conventional air vent mechanism for a fuel supply system of an engine, as shown in FIG. 9, when the engine is tilted so that the carburetor body 20 is located at an upper position, the fuel tank 40 is not provided. When the remaining amount of fuel in the fuel tank 40 is small, the internal pressure of the fuel tank 40 is directly applied to the carburetor body 20 via both open ends of the air vent pipe 38 and the return pipe 27, so that the open end of the air vent open pipe 37a There is a problem that fuel leakage occurs from 37d.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to reliably prevent the occurrence of fuel leakage regardless of the attitude of the engine and the remaining amount of fuel in the tank. An object of the present invention is to provide a system air vent mechanism.

[0013]

An air vent mechanism for a fuel supply system of an engine according to the present invention is formed in a substantially rectangular parallelepiped shape below a carburetor body and is detachably attached to a fuel supply port without an air vent function. A fuel tank sealed by a horizontal direction is arranged, and the internal pressure above the liquid surface in the fuel tank is maintained at the atmospheric pressure by an air vent pipe or a return pipe having an air vent function, and the inside of the fuel tank is maintained. Fuel is fed into the fuel chamber on the side of the carburetor by a fuel supply pipe, and the overflow in the fuel chamber is returned to the inside of the fuel tank via the return pipe. The opposite sides of the pipes from the fuel tank side are communicated with the branch air vent passage of the carburetor. To open to the atmosphere, extend the open end of the air vent pipe to a position in contact with or close to the fuel tank inner wall, and attach the air vent pipe to one end near the upper end in the longitudinal direction of the fuel tank, A return pipe is mounted near the other end of the upper portion in the longitudinal direction of the fuel tank.

Further, the air vent mechanism for a fuel supply system of an engine according to the present invention is characterized in that the mounting portion of the return pipe of the fuel tank is formed in a convex shape and serves as an air reservoir inside the fuel tank. And

Further, in the air vent mechanism for a fuel supply system of an engine according to the present invention, a liquid level controller for controlling a liquid level of fuel in the fuel tank is provided at a fuel supply port of the fuel tank. It is characterized by being.

[0016]

According to the air vent mechanism of the fuel supply system for an engine of the present invention, the air vent pipe and the return pipe at the upper part of the fuel tank are mounted near one end and the other end at the upper part in the longitudinal direction of the fuel tank. Of the fuel tank is extended until it comes into contact with or close to the side wall of the fuel tank, especially when the remaining amount of fuel in the fuel tank is small, so that the fuel tank is positioned so that the tip of the air vent pipe is located below. Even if it is tilted, the opening at the tip is located below the fuel level, so the internal pressure of the fuel tank does not directly affect the carburetor body via the air vent pipe. Leakage of fuel to the outside through the branch air vent passage of the vessel is prevented.

Further, in the present invention, since the mounting portion of the return pipe of the fuel tank is formed in a convex shape, the mounting portion can be an air reservoir inside the fuel tank, so that the function of the return pipe is hindered. Never.

Further, in the present invention, since the liquid level control unit for controlling the liquid level of the fuel inside the fuel tank is provided at the fuel supply port of the fuel tank, for example, the level of the fuel that overflows from the fuel supply port of the fuel tank is provided. Even when fuel is injected into the fuel tank, the injection amount is controlled by the liquid level controller, so that an air reservoir can be formed inside the fuel tank.

Therefore, even when the fuel tank is fully filled with fuel, an air pocket is surely formed inside the fuel tank, so that the fuel tank is left particularly when the outside air temperature is high, such as in summer. Even if the internal pressure of the fuel tank rises, the air reservoir works effectively, and the fuel from the return pipe due to the internal pressure of the fuel tank does not flow outside through the air vent opening pipe through the carburetor.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings described below, portions common to FIG. 8 are denoted by the same reference numerals, and redundant description will be omitted.

FIGS. 1 and 2 show an embodiment of an air vent mechanism of a fuel supply system of an engine according to the present invention. FIG. 1 shows an air vent mechanism of a fuel supply system of the engine of FIG. This shows the state in which it is seen. As shown in these figures, the carburetor body 20 is provided with a fuel inlet 21 and a fuel outlet 22.

The fuel supply pipe 2 is connected to the fuel inlet 21.
3 are connected to one end 24 thereof. Fuel supply pipe 23
Is accommodated in the fuel tank 40. A filter 2 is provided at the other end 25 of the fuel supply pipe 23.
6 are attached.

The fuel outlet 22 is connected to one end of a return pipe 27 for returning overflow fuel to the fuel tank 40. The other end of the return pipe 27 is attached to the fuel tank 40 via a holding member 28. The mounting position of the other end of the return pipe 27 is close to the cap 42 as shown in FIG.

A fuel supply passage 29 communicating with the fuel inlet 21 is formed inside the carburetor body 20. The terminal end 29 a of the fuel supply passage 29 communicates with the fuel chamber 30. The fuel sent into the fuel chamber 30 is sent from the intake port of the carburetor body 20 to the cylinder 33 provided above the crankcase 32 by the nozzle 31. The amount of fuel blown from the nozzle 31 and the amount of intake air, that is, idling, is adjusted by the adjusting screw 3
4 can be adjusted by the adjustment amount.

A diaphragm 35 pulsating in accordance with the pressure fluctuation in the crankcase 32 is provided inside the carburetor body 20. By the operation of the diaphragm 35, the fuel inside the fuel tank 40 is supplied to the fuel supply pipe 23.
And is sent from the fuel supply passage 29 to the fuel chamber 30 side. The portion that has overflowed in the fuel chamber 30 is returned from the overflow chamber 30a into the fuel tank 40 through the fuel outlet 22 and the return pipe 27.

Further, between the fuel chamber 30 and the fuel outlet 22, there is provided a wire rope-shaped wire 36a for sucking up the fuel remaining in the fuel chamber 30, and the engine is stopped. The fuel supply operation by the diaphragm 35 is stopped, and the fuel remains in the fuel chamber 30. However, the fuel in the fuel chamber 30 is sucked up by the wire 36a by capillary action and returned to the fuel outlet 22 side. The interior of the fuel chamber 30 can be emptied.

In the vicinity of the diaphragm 35, a priming pump 36 is provided. The priming pump 36 is of a manual type. Since the fuel chamber 30 is empty before the engine is started, the priming pump 36 is pushed several times so that an appropriate amount of fuel can be sent to the fuel chamber 30. Has become.

Further, an air vent passage 37 is provided inside the vaporizer main body 20. Air vent passage 37
Air vent opening pipe 37 connected to one end of
The open end 37d of a is drawn below the fuel tank 40 and is open to the atmosphere. The branch air vent passage 37 b of the air vent passage 37 has an air vent pipe 3 opened into the fuel tank 40 through a holding member 39.
8 are connected. The branch air vent passage 37c branched from the air vent passage 37 is communicated with the fuel outlet 22 through the overflow chamber 30a. As shown in FIG. 3, the mounting position of the air vent pipe 38 is disposed on the area B side of the upper surface of the fuel tank 40 separated by the center line a. Incidentally, the fuel supply pipe 23 is disposed near the center of the fuel tank 40.

Here, the tip of the air vent pipe 38 is extended to a position in contact with or close to the side wall 40a of the fuel tank 40, and the tip is further obliquely cut. As shown in FIGS. 1 and 2, the fuel tank 40 is formed in a substantially rectangular parallelepiped shape, and is disposed below the carburetor body 20 in a horizontally long shape.

A fuel supply port 41 is provided above one side of the fuel tank 40. The fuel supply port 41 is closed by a cap 42 having no air vent function. Accordingly, even when the engine is tilted such that the cap 42 is positioned below the fuel tank 40, there is no possibility that fuel leaks from the cap 42.

Next, the operation of the air vent mechanism of the fuel supply system of the engine having such a configuration will be described. In the following description of the operation of the air vent mechanism, the case where the remaining amount of fuel inside the fuel tank 40 is small will be described.

First, when the engine shown in FIGS. 1 and 2 is operated in the upright state, the priming pump 36 is pushed several times because the fuel chamber 30 is empty. Of fuel. When the engine starts, the crankcase 3
2 According to the pressure fluctuation (pulsation) inside, the diaphragm 35
Operates, the fuel inside the fuel tank 40 is sucked by the fuel supply pipe 23 and sent from the fuel supply passage 29 to the fuel chamber 30 side. The fuel that overflows in the fuel chamber 30 is returned from the fuel outlet 22 to the fuel tank 40 through the return pipe 27.

By continuing such a state, the engine can be satisfactorily operated in the upright state without engine stall.

Next, as shown in FIG. 4, when the engine is inclined such that the cylinder 33 is tilted leftward from the state of FIG. 2, the return pipe 27 is located above the liquid level of the fuel tank 40. The return pipe 27 originally has a function of returning the portion overflowed in the fuel chamber 30 from the fuel outlet 22 to the inside of the fuel tank 40. As shown in FIG. Since the branch air vent passage 37c of the air vent passage 37 is communicated via the overflow chamber 30a, the inside of the fuel tank 40 is maintained at the atmospheric pressure, and the driving of the engine is improved similarly to the above.

At this time, the air vent pipe 38
Of the fuel tank 40 is extended so as to contact or approach the side wall 40a of the fuel tank 40, so that the opening at the tip is below the liquid level of the fuel, and the internal pressure of the fuel tank 40 increases the air vent pipe 38. Does not directly affect the vaporizer main body 20 through the air vent opening pipe 37a.
No fuel leaks from the open end 37d of the fin.

Next, as shown in FIG. 5, when the engine is tilted so that the cylinder 33 is tilted rightward from the state of FIG. 2, the air vent pipe 38 is located above the liquid level of the fuel tank 40. Therefore, the inside of the fuel tank 40 is maintained at the atmospheric pressure, and the return pipe 27 acts to smoothly return the fuel overflowing from the fuel chamber 30 to the inside of the fuel tank 40, thereby improving the driving of the engine similarly to the above. . In addition, air vent pipe 38
Even if the tip of the fuel tank 40 is in contact with the side wall 40a of the fuel tank 40, the tip is cut obliquely, so that the tip opening is not blocked and the function of the air vent pipe 38 is smoothly performed. Can be demonstrated.

As described above, in this embodiment, when the air vent pipe 38 in the upper part of the fuel tank 40 is attached near one end of the upper part in the longitudinal direction of the fuel tank 40, the return pipe 27 is connected to the upper part in the longitudinal direction of the fuel tank 40. And the pipes 38, 2
7 is deflected to one side and the other side with respect to the center line a of the fuel tank 40, and the tip of the air vent pipe 38 is extended until it contacts or approaches the side wall 40a of the fuel tank 40. Even when the fuel tank 40 is tilted as shown in FIG. 4 from the state of FIG. 5 in a state where the remaining amount is small, the opening at the tip is below the liquid level of the fuel, and the internal pressure of the fuel tank 40 becomes lower. Since there is no direct effect on the carburetor body 20 via the air vent pipe 38, fuel does not leak from the open end 37d of the air vent opening pipe 37a.

In this embodiment, the return pipe 2
7 is disposed on the side of the area A separated by the center line a, and the air vent pipe 38 is disposed on the side of the area B separated by the center line a. However, the present invention is not limited to this example. When the air vent pipe 38 is disposed on the side of the area B, the air vent pipe 38 may be disposed on the side of the area A. In short, the return pipe 27 and the breather pipe 38 are connected to one end of the upper part of the fuel tank 40 with the center line a as a boundary. It may be arranged near the other end.

FIG. 6 shows another embodiment in which the structure of the fuel tank 40 is changed.
The mounting portion 43 of the return pipe 27 in which an insertion hole through which the return pipe 27 is inserted and a holding member 28 that inserts and holds the return pipe 27 is formed in a convex shape.

Since the mounting portion 43 has a convex shape as described above, even when the fuel is fully filled into the fuel tank 40 from the fuel supply port 41, the fuel is returned by the convex mounting portion 43. The open end of the pipe 27 can be positioned above the liquid level of the fuel. When the fuel is pushed up due to an increase in the internal pressure of the fuel tank 40, the carburetor body 20 is returned by the return pipe 27 or the breather pipe 38.
This eliminates the problem that fuel leaks from the air vent opening pipe 37a through the valve.

Therefore, in this embodiment, even when the fuel tank 40 is fully filled with fuel, an air reservoir is reliably formed inside the fuel tank 40, so that the outside air temperature is particularly high in summer or the like. Even if the fuel tank 40 is left as it is and the internal pressure of the fuel tank 40 rises, the air pool works effectively, and the fuel from the return pipe 27 due to the internal pressure of the fuel tank 40 flows out of the air vent opening pipe 37a through the carburetor body 20. Since it does not flow, the occurrence of fuel leakage is reliably prevented regardless of the attitude of the engine or the remaining amount of fuel in the tank.

FIG. 7 shows another embodiment in which the configuration of the fuel tank 40 shown in FIG. 6 is changed, and a cylinder as a liquid level controller is provided at a fuel supply port 41 of the fuel tank 40. 44 are provided. The cylindrical body 44 controls the liquid level of the fuel injected into the fuel tank 40. When the fuel is supplied to the fuel supply port 41 with the fuel supply port 41 facing upward, for example, at a position where the fuel overflows from the fuel supply port 41. Even so, an air reservoir can be formed around the opening end of the return pipe 27 inside the fuel tank 40 by the action of the cylinder 44.

Therefore, in this embodiment, the air reservoir can be more reliably formed inside the fuel tank 40 by the cylinder 44 serving as the liquid level controller provided at the fuel supply port 41 of the fuel tank 40. .

[0044]

As described above, according to the air vent mechanism of the fuel supply system for an engine of the present invention, the air vent pipe and the return pipe in the upper part of the fuel tank are connected to one end of the upper part in the longitudinal direction of the fuel tank. At the other end, the tip of the air vent pipe was extended until it touched or approached the side wall of the fuel tank, especially when the remaining amount of fuel in the fuel tank was small. Even if the fuel tank is tilted so that it is located below, the opening at the tip is located below the liquid level of the fuel, so that the internal pressure of the fuel tank is directly vaporized through the air vent pipe. Since there is no influence on the main body, leakage of fuel to the outside through the branch air vent passage of the vaporizer is prevented.

Further, in the present invention, since the mounting portion of the return pipe of the fuel tank is formed in a convex shape, the mounting portion can be an air reservoir inside the fuel tank, so that the function of the return pipe is hindered. Never.

Further, in the present invention, since the liquid level control unit for controlling the liquid level of the fuel inside the fuel tank is provided at the fuel supply port of the fuel tank, for example, the level of the fuel that overflows from the fuel supply port of the fuel tank is provided. Even when fuel is injected into the fuel tank, the injection amount is controlled by the liquid level controller, so that an air reservoir can be formed inside the fuel tank.

Therefore, even when the fuel tank is fully filled with fuel, an air pocket is reliably formed inside the fuel tank. Even if the internal pressure of the fuel tank rises, the air pool works effectively, and the fuel from the return pipe due to the internal pressure of the fuel tank does not flow outside through the air vent opening pipe through the carburetor. The occurrence of fuel leakage can be reliably prevented regardless of the remaining amount of fuel in the tank.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of an air vent mechanism of a fuel supply system of an engine according to the present invention.

FIG. 2 is a view showing an air vent mechanism of a fuel supply system of the engine of FIG. 1;

FIG. 3 is a plan view showing the fuel tank of FIG. 1;

FIG. 4 is a view for explaining the operation of the air vent mechanism of FIG. 1;

FIG. 5 is a view for explaining the operation of the air vent mechanism of FIG. 1;

FIG. 6 is a view showing another embodiment in which the configuration of the fuel tank in FIG. 1 is changed.

FIG. 7 is a view showing another embodiment in which the configuration of the fuel tank in FIG. 6 is changed.

FIG. 8 is a view showing an air vent mechanism of a fuel supply system of a conventional engine.

FIG. 9 is a view for explaining the operation of the air vent mechanism of FIG. 8;

[Explanation of symbols]

 Reference Signs List 20 carburetor body 23 fuel supply pipe 27 return pipe 29 fuel supply passage 30 fuel chamber 31 nozzle 35 diaphragm 37 air vent passage 37a air vent opening pipe 37b, 37c branch air vent passage 38 air vent pipe 40 fuel tank 43 mounting part

Claims (3)

(57) [Claims] 1. A fuel tank 4 having a substantially rectangular parallelepiped shape below a carburetor body 20 and hermetically sealed by a cap 42 having no air vent function detachably attached to a fuel supply port 41.
0 is disposed in a horizontally elongated shape, and the internal pressure above the liquid surface in the fuel tank 40 is maintained at the atmospheric pressure by an air vent pipe 38 or a return pipe 27 having an air vent function. Is fed into the fuel chamber 30 on the side of the carburetor body 20 by the fuel supply pipe 23, and an overflow in the fuel chamber 30 is returned to the inside of the fuel tank 40 via the return pipe 27, The respective sides of the air vent pipe 38 and the return pipe 27 opposite to the fuel tank 40 side are communicated through a branch air vent passage 37b of a carburetor and are opened to the atmosphere, and the open end of the air vent pipe 38 is closed. The air vent pipe extends to a position in contact with or close to the inner wall of the fuel tank 40. 38 attached to one end side of the longitudinal upper part of the fuel tank 40, the return pipe 27
An air vent mechanism for a fuel supply system of an engine, wherein the air tank is mounted near the other end of the fuel tank 40 in the longitudinal direction. 2. The fuel supply for an engine according to claim 1, wherein a mounting portion of the fuel tank 40 to which the return pipe 27 is attached is formed in a convex shape and serves as an air reservoir inside the fuel tank 40. System air vent mechanism. 3. A liquid level controller 44 for controlling a liquid level of fuel in the fuel tank 40 at a fuel supply port 41 of the fuel tank 40. 3. An air vent mechanism for a fuel supply system of the engine according to 2.