JP2700616B2 - Internal pressure adjustment mechanism of circulating carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating carburetor mainly used for a general-purpose engine used as a drive source of a working machine such as a brush cutter, a spreader and a duster, and a fuel tank thereof. The present invention relates to an internal pressure adjusting mechanism for a circulating carburetor.

[0002]

2. Description of the Related Art As is well known, the above-mentioned circulating carburetor supplies fuel in a fuel tank into a chamber by a fuel pump, and when the fuel level in the chamber exceeds a certain level, the fuel is discharged. The oil level is adjusted by the overflow, and the overflowed fuel returns to the fuel tank via the return pipe.

The prior art of this type of circulating carburetor includes:
For example, there is a carburetor described in Japanese Utility Model Publication No. 5-3729. As shown in FIG. 4, the carburetor 30 is provided with a breather 34a which is open to the atmosphere in a fuel cap 34 of a fuel supply port 33 of a fuel tank 32,
The fuel tank 32 is connected to the upper space of the chamber 31 in the chamber 0 by a communication path 35. Reference numeral 3 in the figure
Reference numeral 6 denotes a return pipe, and reference numeral 37 denotes a fuel pump. Conventionally, the fuel tank 32 is generally in the form of a rectangular parallelepiped or a rectangular parallelepiped, and in any case, the upper surface of the tank is formed in a nearly flat shape.

[0004]

The circulation type carburetor described in the above publication has an advantage that the internal pressure can be adjusted to the atmospheric pressure by preventing dust from entering the chamber. There is room for improvement.

[0005] That is, the general-purpose engine is mounted on the bush cutter as described above. In particular, in the case of a backpack-type bush cutter, work is often performed in an inclined state such as leaning forward. However, when the operation is performed in an inclined state (mainly in a forward leaning state), the return pipe 36 and the communication path 35 are closed with the fuel as shown in FIG. Also, the height of the oil level in the fuel tank 32 is higher than the fuel ejection nozzle 38 of the carburetor 30, and the hydraulic pressure (fuel head) acts on the fuel in the chamber 31. Then, in this state, the fuel supply pressure by the fuel pump 37 further acts in the chamber 31.
A large amount of fuel leaks from the nozzle 38 to the venturi section 30a through the main jet 39. Usually, the worker carries on the work on his / her back after starting the operation of the engine, in other words, a large amount of fuel is supplied to the engine during the operation of the engine. As a result, the rotation of the engine may become abnormal or the engine may stop.

Since a breather 34a for opening the atmosphere is opened in the fuel cap 34 of the fuel filler 33, the fuel cap 34 may be lowered depending on the arrangement of the fuel tank 32 with respect to the engine body. In some cases, fuel may leak from the breather 34a.

The present invention has been made in view of the above points, and does not malfunction or stall the engine even if the engine is greatly inclined, and can adjust the pressure in the chamber to the atmospheric pressure. It is an object of the present invention to provide an internal pressure adjusting mechanism for a circulating carburetor in which fuel does not leak even if it is inclined at a low angle and the structure is not complicated.

[0008]

In order to achieve the above object, an internal pressure adjusting mechanism of a circulating carburetor according to the present invention comprises: a) supplying fuel in a fuel tank into a chamber by a fuel pump and a fuel supply pipe; When the fuel level in this chamber exceeds a certain level, the fuel level is adjusted by overflowing the fuel, and the overflowed fuel is returned to the fuel tank via a return pipe by a circulating carburetor. Located below the carburetor
A communication path that constantly communicates the fuel tank with the upper space of the chamber and an air vent that communicates the upper space of the chamber with the atmosphere .
Fill the fuel tank with the fuel tank to which the lower end of the communication passage is connected.
In the circulating carburetor provided at a position lower than the height of the upper surface , b) the central portion of the fuel tank is raised upward.
Thereby, one on the filler opening of the upper surface of the surrounding is provided, fitted with a fuel cap sealable to the oil supply port, c) the return Pie
The lower end of the pump and the lower end of the communication passage
It is connected to the upper surface of the central portion of, d) the upper end of the communication passage before
Connected to a passage communicating with the upper space in the chamber,
Closed to the fuel in the vicinity of the communication passage in the chamber.
Where there is no opening for air release.
The upper end of the air communication pipe is always the oil level in the fuel tank.
Above the air communication pipe.
Said air vent provided near the upper end, e) in a state where the fuel until said vicinity of the fuel supply port is injected, a central portion of the fuel tank
A predetermined space is formed in each minute .

According to a second aspect of the present invention, d) even in a state where the carburetor is greatly inclined to one side together with the fuel tank, the positions of the fuel ejection nozzle and the air vent of the venturi portion of the carburetor are set to the level of the oil level in the fuel tank. It is desirable to set the capacity of the space so as to be higher than the height.

[0010] As described in claim 3, g) the fuel tank
Is rectangular when viewed from above, and when viewed from the side
And the return pipe and the connection
Formed in two stages, the upper stage 'where the lower ends of the passages are connected
The return pipe and the communication passage
Located on the upper surface of the section and almost in the center of the fuel tank
It may be.

[0011]

According to the internal pressure adjusting mechanism for a circulating carburetor of the present invention having the above configuration, the state in which the fuel tank is horizontal
To fill the fuel from the filler port to almost full (L height in Fig. 1)
With the fuel charged, close the fuel cap and start the engine
I do. Usually, the worker carries the engine after starting
Start, but with a brush cutter or duster, etc.
Because the work is often performed in the fuel tank, as shown in Fig. 2,
And the carburetor tilt according to the working posture. But,
Even if the fuel tank is fully filled with fuel,
A space V0 is formed in the space V0.
The height of the oil level in the fuel tank is kept low,
Lower chamber than fuel jet nozzle and air vent
The inside of the fuel tank is maintained at atmospheric pressure.
There is no excess fuel spouting and there is a fuel overload
Engine running out of order or stopped
I do not .

[0012] That is, when the carburetor and the fuel tank is greatly inclined to be (see Figure 2), is pre-formed spaces in a fuel tank to move to the upper side of the fuel tank, the oil level in the fuel tank is relatively Lower position. As a result, the height of the oil level is kept lower than the fuel jet nozzle of the carburetor, the communication passage or the return pipe is not blocked by the fuel, and the supply pressure by the fuel pump hardly acts in the chamber. . Therefore,
As in the case of the horizontal state of the engine, fuel is appropriately discharged from the chamber according to the magnitude of the negative pressure in the venturi section. Therefore, there is no possibility that the rotation of the engine becomes abnormal or stopped due to an excessive amount of fuel.

Normally, the fuel tank is arranged so that the position of the fueling cap is opposite to the direction in which the engine is tilted during operation (the position which becomes the upper side when the engine is tilted). Even when the position is at the lower part of the fuel tank, the fuel filler does not leak since the fuel supply port is closed by the closed cap.

Since the fuel tank needs to be formed so as to be larger than the fuel storage capacity, the fuel tank may have a seemingly useless space and a large fuel tank. The above-described disadvantages of the related art are eliminated by a simple configuration provided only in the fuel tank.

According to the internal pressure adjusting mechanism of the second aspect, the normal operation of the engine can be maintained even when the carburetor and the fuel tank are inclined by 45 °. In particular, in the case of a backpack-type work machine (such as a brush cutter), work in a state of being inclined at a large angle is common and is frequently performed.

According to the internal pressure adjusting mechanism of the third aspect, the fuel
Charge tank tilts in any direction (slope line SR / SL)
However, as shown in FIG. 3, the lower end of the return pipe or communication passage
Are not blocked with fuel. That is,
There is no problem when the passage is open, but it is
If the return pipe is open even if
The return pipe should not be completely filled with fuel.
There is space for ventilation. Therefore, the fuel tank
Atmospheric pressure always acts inside the fuel tank and fuel is supplied smoothly.
You .

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a circulation type carburetor according to an embodiment of the present invention;

FIG. 1 is a front sectional view showing a state in which the fuel tank according to the embodiment is combined with a circulation type carburetor, and FIG. 2 is an inclined state of the circulation type carburetor and the fuel tank shown in FIG. It is front sectional drawing which shows a state.

As shown in FIG. 1, a circulating carburetor 11 is integrally provided on the upper surface of the central portion of the fuel tank 1. In this example, the fuel tank 1 has a substantially circular shape as a whole when viewed from above, and has a central portion 1a protruding upward in an inverted mortar shape, and a fuel filler port 1b is provided on one of its surrounding upper surfaces. . A sealed (no breather) fuel cap 2 is removably attached to the filler port 1b. The capacity of the fuel tank 1 above the horizontal plane L (central portion 1a) is V0, and the capacity below the horizontal plane L is V1. This central part 1a
May be determined according to the type of a working machine (such as a brush cutter) to be mounted, but FIG. 2 shows a case where the fuel tank 1 and the fuel tank 1 are mounted on a backpack-type brush cutter. A state in which the carburetor 11 is inclined downward by approximately 45 ° to the side opposite to the fuel filler 1b is shown.
The positions of the fuel ejection nozzle 13 and the air vent 28b of the first venturi section 12 are set to be always higher than the height of the fuel oil level in the fuel tank 1. The amount of oil in the fuel tank 1 is maintained horizontally as shown in FIG.
The time when the injection is performed up to the position b is used as a reference.

In this embodiment, the carburetor 11 is of a piston valve type. A carburetor 11 is integrally provided with a fuel storage chamber 15 at a lower portion of a venturi portion 12, and a throttle valve 17 having a needle jet 16 fixed downward is provided at an upper portion thereof. The other end of a throttle cable 17 a having one end connected to a throttle lever (not shown) is connected to the throttle valve 17. The needle jet 16 is inserted into the fuel injection pipe 19 in the chamber 15 from the fuel injection nozzle 13 at the upper end. A main jet 20 is interposed at the lower end of the fuel discharge pipe 19. A fuel injection pipe 21 protrudes substantially at the center of the side wall of the chamber 15 in the height direction, and a fuel supply pipe 22 from the fuel tank 1 is
Are connected at one end. A fuel pump 23 is interposed in the fuel supply pipe 22, and the other end is inserted into the fuel tank 1 and a fuel filter 24 is attached. Also,
The fuel supply pipe 22 penetrates the upper wall of the fuel tank 1 and is inserted into the inside thereof, and a grommet 25 for sealing is mounted at the penetrating portion.

A weir 26a is provided at a position slightly lower than the upper end of the chamber 15, and a return passage 26 is provided downward from a position beyond the weir 26a.
The lower end of 9 is connected to the upper surface of the central portion 1a of the fuel tank 1. Further, the lower end of the communication passage 27 is connected to the upper surface of the central portion 1a, is arranged upward in parallel with the return pipe 29, and the upper end of the communication passage 27 is connected to the passage 27a communicating with the upper space in the chamber 15. . Further, an opening 28a for opening to the atmosphere is formed at an upper end near the communication passage 27 in the chamber 15 and at a position not closed by the fuel, and a ventilation pipe 28 is connected to the opening 28a. The ventilation pipe 28 is connected to the ventilation path 11a of the carburetor 11.
Air vent 2 at the upper end
A cover 28c is mounted on the upper side of 8b. The upper end of the ventilation pipe 28 may be bent downward in a U-shape,
The cover 28c can be omitted by being inserted into an air cleaner (not shown).

According to the internal pressure adjusting mechanism of the circulating carburetor of this embodiment having the above-mentioned structure, in FIG. 1, fuel is supplied from the fuel supply port 1b while the fuel tank 1 is horizontal.
Then, the fuel cap 2 is closed and the engine (not shown) is started up. Usually, the worker starts the work while carrying the engine after the start. However, since the work is often carried out in a slouched state with a brush cutter or a duster, the fuel tank 1 and the carburetor 11 work as shown in FIG. Incline according to the posture. However, since the space V0 is formed in the fuel tank 1 in a state where the fuel is maximally injected into the fuel tank 1, the height of the oil level in the fuel tank 1 is reduced by the space V0, and the height of the oil level is reduced. Saha fuel jet nozzle 1
3 and lower than the air vent 28b, the chamber 15
Since the inside is maintained at the atmospheric pressure, the fuel is not spouted excessively from the fuel jet nozzle 13, and there is no fuel overload, and the rotation of the engine does not become abnormal or the engine does not stop.

FIG. 3 shows an internal pressure adjusting mechanism of a circulating carburetor according to another embodiment of the present invention. The internal pressure adjusting mechanism of this embodiment differs from the above-described embodiment in the following points. is there. The fuel tank 1 'is rectangular when viewed from above,
The lower portion 1A 'provided with the fuel filler 1b when viewed from the side.
And a return pipe 29 and an upper section 1B 'to which the lower ends of the communication paths 27 are respectively connected. In addition, the return pipe 29 and the communication passage 27
Although it is arranged on the upper surface of B ′ and substantially at the center of the fuel tank 1 ′, this is as shown in FIG. 3 regardless of the direction (inclination lines SR and SL) of the fuel tank 1 ′. This is because at least one of the return pipe 29 and the lower end of the communication passage 27 is not blocked by the fuel. That is, the communication passage 2
When the return pipe 29 is open, even if the return pipe 29 is open, the inside of the return pipe 29 is not completely filled with the fuel, and the space through which the air can flow is provided. Because there is. As a result, the atmospheric pressure always acts inside the fuel tank 1 ', and the fuel is supplied smoothly. Note that the upper section 1B '
Is determined in the same manner as the volume V0 of the central portion 1a in the above embodiment. The other configurations and the internal pressure adjusting operation are common to the above-described embodiment, and thus description thereof is omitted, and common constituent members are shown in FIG. 3 using the same reference numerals as in the above-described embodiment.

Although the two embodiments of the present invention have been described above, the form of the fuel tanks 1 and 1 ′ is not particularly limited, and the fuel is injected into the vicinity of the fuel supply port 1 b. A predetermined space may be formed in the tanks 1 and 1 '. A plurality of ventilation pipes 28 can be provided. In this case, the lower end opening 28a and the air vent 28b are provided at a plurality of locations, or the lower end opening 28a is provided at a plurality of locations and a plurality of air vents 2 are provided.
8b can be grouped together.

[0025]

As is apparent from the above description,
The internal pressure adjusting mechanism of the circulating carburetor of the present invention has the following excellent effects.

(1) Even if the engine is greatly inclined, the rotation of the engine does not become abnormal or stall, the pressure in the chamber can be adjusted to the atmospheric pressure, and no fuel leaks in any direction.

(2) Since the fuel tank needs to be formed larger than the amount of fuel to be stored, there is a point that the fuel tank becomes slightly larger, but with a very simple configuration,
The above-mentioned disadvantages of the related art can be solved, and the manufacturing cost is hardly changed.

(3) In the internal pressure adjusting mechanism according to the second aspect of the present invention, the normal operation of the engine can be maintained even when the carburetor and the fuel tank are inclined by 45 °, and the engine is greatly operated during work such as a back-type brush cutter. This is effective for a working machine that often tilts.

(4) In the internal pressure adjusting mechanism according to the third aspect, the key
The carburettor or fuel tank is tilted in either direction
At least one of the lower ends of the return pipe or the communication passage.
Is not blocked by fuel, so it is always large in the fuel tank.
The pressure acts to supply the fuel smoothly .

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a state in which a fuel tank according to an embodiment of an internal pressure adjusting mechanism of the present invention is integrally combined with a circulation type carburetor, and shows a horizontal state.

FIG. 2 is a front sectional view showing a state in which the circulation carburetor and the fuel tank of FIG. 1 are inclined to a working posture.

FIG. 3 is a front sectional view showing a state in which a fuel tank according to another embodiment of the internal pressure adjusting mechanism of the present invention is integrally combined with a circulating carburetor.

FIG. 4 is a front sectional view showing a conventional internal pressure adjusting mechanism of a circulating carburetor, showing a horizontal state.

FIG. 5 is a front sectional view showing a state in which the circulation carburetor and the fuel tank of FIG. 4 are inclined to a working posture.

[Explanation of symbols]

 1.1 ′ Fuel tank 1a Central part 1b Filler port 1A ′ Lower part 1B ′ Upper part 2 Fuel cap 26 Return pipe 27 Communication passage

Claims (3)

(57) [Claims] 1. A fuel pump and a fuel supply pipe supply fuel in a fuel tank into a chamber, and when the fuel level of the fuel in the chamber exceeds a certain level, the fuel overflows and the fuel level rises. There is adjusted, by circulating carburetor method Back to the fuel tank via the overflow fuel is return pipe, underneath the carburetor
Comprising a vent for communicating the upper space and the atmosphere communication passage and the chamber constantly communicates the upper space of the fuel tank and the chamber placed towards the fuel
The fuel supply port of the tank is connected to the lower end of the communication passage by the fuel supply port.
In a circulating carburetor provided at a position lower than the height of the upper surface of the tank, the central portion of the fuel tank is raised upward, and
The one with the fuel supply port provided on the upper surface, attaching a sealed fuel cap to the oil supply port, the lower end of the lower end and the communicating passage of the return pipe pixel
Each is connected to the upper surface of the central part of the fuel tank, and the upper end of the communication passage communicates with the upper space in the chamber.
Near the communication passage in the chamber.
And at a position not blocked by fuel,
An air communication tube is always drilled in this opening,
Installed so that it is higher than the oil level in the fuel tank.
The air vent is installed near the upper end of the air communication pipe.
A predetermined space is formed in a central portion of the fuel tank in a state where the fuel is injected to a position near the fuel filler, and an internal pressure adjusting mechanism of the circulating carburetor. 2. Even in a state where the carburetor is greatly inclined to one side together with the fuel tank, a position of a fuel ejection nozzle and an air vent of a venturi portion of the carburetor is higher than an oil level in the fuel tank. 2. The internal pressure adjusting mechanism for a circulating carburetor according to claim 1, wherein the capacity of said space is set. 3. The fuel tank is rectangular when viewed from above.
Then, when viewed from the side, the lower portion provided with the refueling port and
The lower ends of the return pipe and the communication path are respectively
The upper part is connected to the upper part
Ip and the communication passage are on the upper surface of the upper section, and
3. The fuel tank according to claim 1, wherein the fuel tank is disposed substantially at the center of the fuel tank.
The internal pressure adjusting mechanism of the circulating carburetor described in the above.