JP2003247456A - Slidable throttle valve type carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a slidable throttle valve type carburetor which has high freedom degree of arrangement of an atmosphere passage for adjusting air intake negative pressure to act on a single fuel supply pipe, and an air control needle valve for adjusting the atmospheric pressure and a simple constitution of the atmosphere passage, and in which machine working is easily executed. <P>SOLUTION: The air on an upstream side from a Venturi part of an air intake passage 2 is supplied to the surrounding of the fuel supply pipe 4, and the air intake negative pressure to act on the fuel supply pipe 4 is changed. A fuel amount from an opening between one fuel supply pipe 4 and a needle 5 to the air intake passage 2 is controlled by integral and vertical movement of the needle 5 and a throttle valve 3. The atmosphere passage 24 for idle adjust is opened to a groove corresponding to an inclined cam face 25 to adjust an idle opening of the slide throttle valve 3 of a carburetor body 1 via the air control needle valve 21 from the upstream side from the Venturi part of the air intake passage 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding throttle valve type carburetor for a small internal combustion engine mounted on a portable work machine such as a brush cutter, and more particularly to a single fuel passage for idle operation of the engine. That is, the present invention relates to a sliding throttle valve type carburetor in which the intake negative pressure acting on a single fuel supply pipe is adjusted to adjust the fuel amount.

[0002]

2. Description of the Related Art A sliding throttle valve type carburetor has both an independent low speed fuel system and a high speed fuel system, and a single fuel system controls the fuel amount from idle to full opening of the sliding throttle valve. There are things. In the latter sliding throttle valve type carburetor, since there is no independent low-speed fuel system, it is difficult to directly adjust the fuel in idle operation. Therefore, in idle operation, the air in the upstream side of the bench lily part of the intake passage is ejected around the fuel supply pipe (fuel nozzle) via the air adjustment valve, and the intake negative pressure acting on the fuel supply pipe is adjusted by this. As a result, the amount of idle fuel is being adjusted.

As shown in FIG. 6, in the conventional sliding throttle valve type carburetor, an air adjusting valve (air adjusting needle valve) 15 is provided below the idle stop bolt 14 to change the flow rate of the atmosphere into the intake passage 2. The air is adjusted from the upstream side of the bench lily portion by the tapered tip needle of the air regulating valve 15 and then guided to the lower side of the piston type sliding throttle valve 3 of the intake passage 2. A negative pressure that balances the intake negative pressure of the engine and the atmospheric pressure of the upstream side of the sliding throttle valve 3 of the intake passage 2 acts on the fuel supply pipe 4, and the inner peripheral surface of the fuel supply pipe 4 and the sliding throttle The amount of fuel sucked into the intake passage 2 from the gap between the valve 3 and the needle 5 that is integral with the valve 3 is regulated.

Now, when the air throttle valve 15 is adjusted while the engine is rotating with the sliding throttle valve 3 in the idle position,
The intake negative pressure in the portion downstream of the sliding throttle valve 3 in the intake passage 2 is the same, but the atmospheric pressure in the portion upstream of the sliding throttle valve 3 in the intake passage 2 acts around the fuel supply pipe 4. Therefore, the intake negative pressure acting around the fuel supply pipe 4 can be weakened or strengthened. The air adjusting valve 15 is returned from the tightened position 1 to 1.5 times from the reference opening degree, and the air adjusting valve 15
The amount of atmospheric air is reduced by tightening, and the intake negative pressure acting on the fuel supply pipe 4 is increased, so that the fuel (mixture) can be adjusted to be rich. On the contrary, when the air adjusting valve 15 is loosened, the amount of air increases, the intake negative pressure acting on the fuel supply pipe 4 becomes weak, and the fuel (mixture) can be adjusted to be thin.

Since the carburetor described above does not directly adjust the fuel, the amount of change in the fuel with respect to the amount of adjustment (rotation) of the air adjusting valve 15 is gradual, and no skill is required to adjust the air adjusting valve 15. Easy to handle even for inexperienced drivers. Further, the adjustment range of the air adjusting valve 15 is only for the idle operation of the engine, and if the sliding throttle valve 3 is opened even slightly from the idle position,
Since the amount of air from the atmosphere passage passing through the air adjusting valve 15 is relatively smaller than the amount of air (intake amount) flowing below the sliding throttle valve 3 in the intake passage 2, it does not affect fuel adjustment. .

However, the structure provided with the air regulating valve 15 has the following problems. First, there is a restriction on the mounting location of the air regulating valve 15. When arranging the atmosphere passage for introducing atmospheric pressure and the air regulating valve 15 around the fuel supply pipe 4,
Since the sliding throttle valve 3 is arranged above the fuel supply pipe 4, the atmospheric passage is inevitably provided below the sliding throttle valve 3 (the bottom wall of the cylindrical portion guiding the sliding throttle valve 3). You can only open it. Further, since the atmosphere passage is located on the bottom wall of the cylindrical portion that guides the sliding throttle valve 3, it becomes difficult to machine the atmosphere passage. Since the air passage can be opened only to the bottom wall of the cylindrical portion that guides the sliding throttle valve, the air passage must be processed from the upper side to the bottom wall of the cylindrical portion.

Secondly, fuel accumulates in the air passage that opens at the bottom wall of the cylindrical portion that guides the sliding throttle valve 3, and the amount of air from the air passage easily changes. Since the air velocity is low during idle operation of the engine, the fuel discharged from the fuel supply pipe 4 may be ejected in a liquid state and flow into the opening of the atmosphere passage near the fuel supply pipe 4. A small internal combustion engine such as a portable work machine consumes a small amount of fuel, and if the fuel adheres to the air passage and the air amount is not constant, idle rotation becomes unstable. In particular, this tendency is likely to occur during idle operation for a long time, and when the portable working machine is tilted, the engine is stopped due to the fuel accumulated in the atmosphere passage (engine stall), and the working efficiency is significantly reduced.
Further, since the atmosphere passage is open near the fuel supply pipe 4, the fuel around the fuel supply pipe 4 gradually flows into the atmosphere passage after the engine is stopped, and the idle operation may not be stable during the next engine operation. is there.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to vaporize an air passage for adjusting intake negative pressure acting on a single fuel supply pipe and an air adjusting needle valve for adjusting atmospheric pressure. (EN) It is possible to provide a sliding throttle valve type carburetor which has a high degree of freedom of arrangement with respect to the main body of the device, has a simple passage structure, and is easy to machine.

[0009]

In order to solve the above-mentioned problems, the structure of the present invention is such that intake air acts on the fuel supply pipe by supplying air upstream of the bench lily portion of the intake passage to the periphery of the fuel supply pipe. For the idle adjustment of a sliding throttle valve type carburetor in which the negative pressure is changed and the amount of fuel from the gap between one fuel supply pipe and the needle is controlled by the vertical movement of the needle and throttle valve integrally The air passage of is opened from the upstream side of the bench lily part of the intake passage through the air adjusting needle valve to the groove corresponding to the inclined cam surface that adjusts the idle opening of the sliding throttle valve of the carburetor body. And

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an air adjusting needle valve as an air adjusting needle valve is arranged above or in front of an idle stop bolt for adjusting the idle position of a sliding throttle valve (upstream side portion of an intake passage). . This increases the degree of freedom in selecting the air adjustment needle valve attachment site, simplifies the processing of screw holes for screwing and supporting the air adjustment needle valve and the configuration of the atmosphere passage, and further facilitates the adjustment work of the air adjustment needle valve. Make it easy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a cylindrical portion 1a which vertically intersects an intake passage 2 having a circular cross section which penetrates a carburetor main body 1 in a direction perpendicular to the plane of the drawing is formed integrally with the carburetor main body 1. A cup-shaped or piston-type sliding throttle valve 3 is slidably fitted to the portion 1a. The sliding throttle valve 3 has a cylindrical upper half portion, and an inclined cam surface 25 is formed on the bottom wall. Further, a columnar retaining piece 3c joined to the lower end of the remote control cable 3b is fitted to the bottom wall. That is, as shown in FIG.
The cable 3b is inserted into the inside of the tubular portion from the slit 32 provided in the tubular portion, and the retaining piece 3c is provided in the hole 3 provided on the lower surface of the bottom portion.
3 is fitted and locked. A spring 3a is interposed between the upper end wall of the cylindrical portion 1a and the sliding throttle valve 3. A needle 5 protruding downward from the sliding throttle valve 3 is inserted into a fuel supply pipe (fuel nozzle) 4. The fuel supply pipe 4 is fitted and supported by the cylindrical portion 1b provided in the carburetor main body 1, its upper end is slightly projected to the bottom of the intake passage 2, and its lower end is closed. Constant pressure fuel chamber 6
Fuel is screwed into the side wall of the carburetor body 1
6 through the cylindrical portion serving as the valve chamber of the fuel adjusting needle valve 16 and the gap between the tip needle 8 of the fuel adjusting needle valve 16 and the outlet passage.
To the inside of the fuel supply pipe 4 through a radial passage provided in the fuel supply pipe 4, and is sucked into the intake passage 2 through a gap with the needle 5.

An idle stop bolt 14 that regulates the idle position of the sliding throttle valve 3 is screwed into the side wall of the carburetor body 1, and its inner end is an inclined cam surface 25 provided on the side surface of the sliding throttle valve 3.
Abutted against. Sliding throttle valve 3 and idle stop bolt 14
The relationship between and is shown in FIG.

A cover plate 7b is joined to the lower surface of the carburetor main body 1 with a membrane 7 interposed therebetween to define a constant pressure fuel chamber 6 above the membrane 7 and an atmosphere chamber 7a below the membrane 7. The right end of the lever 12 supported by the horizontal shaft 13 in the constant pressure fuel chamber 6 has a spring 12
While being pressed against the protrusion at the center of the film 7 by the force of a,
The left end of the lever 12 is locked to the lower end of an inflow valve 11 having a triangular or quadrangular cross section which is slidably supported on the ceiling wall of the constant pressure fuel chamber 6. The upper end of the inflow valve 11 forms a tapered poppet valve, and is configured to open and close the end of the passage 9 communicating with the discharge port of a fuel pump (not shown).

In the present invention, the intake negative pressure acting from the intake passage 2 on the upper end of the fuel supply pipe 4 is adjusted by adjusting the ratio of the fuel amount and the air amount at the idle position of the sliding throttle valve 3, especially the air amount. The amount of fuel sucked from the fuel supply pipe 4 to the intake passage 2 is adjusted. Therefore, the vaporizer body 1
And a screw hole 23a that is inclined almost the same as the inclined cam surface 25 is provided on the side wall of the idle stop bolt 14 above the idle stop bolt 14.
An air adjusting needle valve 21 around which a loosening spring 22 is wound is screwed into the screw hole 23a, and a tip needle 21a of the air adjusting needle valve 21 is screwed.
The air is introduced into the intake passage 2 through the gap between the passage and the groove forming the inclined cam surface 25.

As shown in FIG. 2, a valve chamber 23b and a passage 26 having a diameter smaller than that of the valve chamber 23b are formed at the tip of the screw hole 23a, and the tip needle 21a of the air regulating needle valve 21 projects into the passage 26. To be done. The passage 24 is connected to the valve chamber 23b from a portion of the intake passage 2 upstream of the sliding throttle valve 3. The air that has entered the intake passage 2, the passage 24, and the valve chamber 23b by adjusting the screwing amount of the air adjusting needle valve 21 is adjusted by the air adjusting needle valve 21, and along the groove having the passage 26 and the inclined cam surface 25. It is sucked into the intake passage 2. In this way, the intake negative pressure acting on the fuel supply pipe 4 from the lower end of the sliding throttle valve 3 of the intake passage 2 is adjusted, and the idle stop bolt 14 adjusts an appropriate amount of fuel in idle operation.

In the embodiment shown in FIG. 4, an air regulating needle valve 21 is screwed into a screw hole 23a provided substantially parallel to the idle stop bolt 14 above the idle stop bolt 14 on the side wall of the carburetor main body 1. The tip needle 21a is projected into a passage communicating with the valve chamber 23b and the passage 30. The vertical passage 30 intersects the outlet of the valve chamber 23b. The vertical passage 30 communicates with the intake passage 2 through the tip of the screw hole into which the idle stop bolt 14 is screwed and the groove having the inclined cam surface 25 of the throttle valve 3.

In the embodiment shown in FIG. 5, a screw hole 23a is provided in the side wall of the carburetor main body 1 on the upstream side of the idle stop bolt 14 and is substantially parallel to the idle stop bolt 14.
The air adjusting needle valve 21 is screwed to the outlet of the valve chamber 23b continuous with the screw hole 23a, and the tip needle 2 of the air adjusting needle valve 21 is connected to the outlet of the valve chamber 23b.
1a is projected, a passage 36 for communicating the outlet with the inner space 38 is bored from the step portion of the intake passage 2, and the starting end portion of the passage 36 is closed by a ball plug 37. A passage 40 extending obliquely from the step portion of the intake passage 2 to the valve chamber 23b is provided. In the embodiment shown in FIG. 5, the air from the intake passage 2 flows through the passage 40, the outlet of the valve chamber 23b, and the passage 3 during the idle operation of the engine.
6 into the inner space 38, and further flows into the intake passage 2 through the groove forming the inclined cam surface 25 of the sliding throttle valve 3. The amount of air flowing from the passage 40 to the intake passage 2 is adjusted depending on the screwing amount of the air adjusting needle valve 21, whereby the fuel supply pipe 4
The intake negative pressure acting on the upper end of the fuel is adjusted, and the amount of fuel sucked from the fuel supply pipe 4 is adjusted according to the intake negative pressure.

Although the embodiment of the membrane type vaporizer has been described above, the present invention is not limited to this, and can be applied to a float type vaporizer, and the fuel used for the engine is not limited to gasoline. It can also be applied to gas fuels such as, butane and propane.

[0019]

As described above, the present invention provides the air regulating needle valve above or in front of the idle stop bolt (upstream side portion of the intake passage) for adjusting the idle position of the sliding throttle valve. Therefore, there is a high degree of freedom in selecting the installation site of the air adjustment needle valve, and the configuration and processing of the screw holes and the atmosphere passage for adjusting the air adjustment needle valve are very simple, and the adjustment work of the air adjustment needle valve is also easy. become.

[Brief description of drawings]

FIG. 1 is a front sectional view of a sliding throttle valve type carburetor according to the present invention.

FIG. 2 is a cross-sectional view of the same plane.

FIG. 3 is a perspective view showing a relationship between a sliding throttle valve and an idle stop bolt.

FIG. 4 is a front sectional view of a sliding throttle valve type carburetor according to a modified embodiment of the present invention.

FIG. 5 is a plan sectional view of a sliding throttle valve type carburetor according to another modified embodiment of the present invention.

FIG. 6 is a front sectional view of a conventional sliding throttle valve carburetor.

[Explanation of symbols]

1: Vaporizer main body 1a: Cylindrical part 2: Intake passage 1b: Cylindrical part 3: Sliding throttle valve 3a: Spring 4: Fuel supply pipe 3b: Cable 5: Needle 3c: Retaining piece 6: Constant pressure fuel chamber 3d: Hole 7: Membrane 7a: Atmosphere chamber
8: Tip needle 7b: Cover plate 9: Passage 10:
Membrane fuel pump 11: Inflow valve 12: Lever 12a: Spring 14: Idle stop bolt 16: Fuel adjusting needle valve 17: Membrane 18: Shaft 21: Air adjusting needle valve
21a: Tip needle 22: Loosening spring 23: Hole
23a: screw hole 24: passage 23b: valve chamber 25: inclined cam surface 26: passage 29: ball plug 30: passage
32: slit 33: hole 36: passage 37: ball plug 38: inner space 40: passage

Claims (4)

[Claims] 1. An intake negative pressure acting on the fuel supply pipe is changed by supplying air upstream of a bench lily portion of the intake passage to the periphery of the fuel supply pipe, and the needle and the throttle valve are integrally moved up and down. In a sliding throttle valve type carburetor in which the amount of fuel from the gap between one fuel supply pipe and the needle to the intake passage is controlled,
The air passage for idle adjustment was opened from the upstream side of the bench lily part of the intake passage through the air adjustment needle valve to the groove corresponding to the inclined cam surface that adjusts the idle opening of the sliding throttle valve of the carburetor body. A sliding throttle valve type carburetor characterized in that 2. An atmosphere passage for adjusting the idle passes through the air adjusting needle valve, communicates with a screw hole into which an idle stop bolt for controlling the lowermost position of the sliding throttle valve is screwed, and a carburetor main body. 2. The sliding throttle valve type carburetor according to claim 1, wherein the sliding throttle valve type carburetor is opened to a groove corresponding to the inclined cam surface of the sliding throttle valve of the carburetor main body through a gap between the screw hole of the above and the tip portion of the idle stop bolt. . 3. The air adjusting needle valve is disposed above the idle stop bolt, and is connected to a screw hole of the idle stop bolt from an outlet passage through which a tapered tip needle of the air adjusting needle valve projects. The sliding throttle valve type carburetor according to claim 2. 4. The air regulating needle valve is disposed in front and rear parallel to the idle stop bolt, and an outlet passage of the air regulating needle valve is connected to a screw hole of the idle stop bolt.
The sliding throttle valve type carburetor according to claim 2.