JP3356218B2 - Float vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carburetor for a general-purpose internal combustion engine,
In particular, the present invention relates to a float type carburetor having a float chamber below a horizontal intake passage.

[0002]

2. Description of the Related Art As disclosed in Japanese Utility Model Publication No. 63-41546, a float type carburetor has a column which forms a low-speed fuel passage and a high-speed fuel passage on a column projecting downward from the center of the carburetor body. And a fuel jet or a bleed pipe is disposed in the cylindrical portion, and a fuel chamber communicating with the float chamber is defined at a lower end portion of the cylindrical portion.

[0003] In the above-mentioned float type carburetor, when the engine is operated under a high load for a long time, the ambient temperature rises, the fuel in the fuel chamber is vaporized, and bubbles (fuel vapor) are generated. There is no problem if the bubbles pass through the fuel jet or low-speed fuel passage with small bubbles. However, when the amount of fuel (flow rate) flowing from the fuel chamber to the intake passage during no-load operation decreases, small bubbles stagnating in the fuel chamber collect and gradually growing. Large air bubbles may obstruct the flow of fuel required for the accelerated operation of the engine and may stop the engine.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to effectively prevent bubbles from flowing into a float chamber even if bubbles are generated in a fuel chamber, thereby preventing fuel from flowing into an intake passage. No object is to provide a float type vaporizer.

[0005]

In order to achieve the above object, according to the present invention, the periphery of the opening of the storage tank is brought into contact with the lower surface of the vaporizer main body, and the lower end of the column extending downward from the vaporizer main body is provided with the storage tank. The bottom is fastened with a bolt, and a fuel jet is screwed into a cylindrical portion that communicates the intake passage of the carburetor body with the screw hole of the column, and a fuel chamber is provided between the fuel jet of the screw hole and the bolt. One fuel inlet which communicates the bottom of the fuel chamber with the floating chamber of the storage tank, and the one which communicates the portion of the fuel chamber adjacent to the fuel jet with the floating chamber of the storage tank.
Two air outlets are provided on the support, and the fuel inlet and the air outlet are two-dimensionally parallel to each other, open tangentially to the inner peripheral wall of the fuel chamber, and the air bubbles are larger than the passage area of the fuel inlet. The outlet passage area is widened, and the entire top wall of the fuel chamber is inclined obliquely upward toward the bubble outlet.

[0006]

According to the present invention, even if air bubbles (fuel vapor) are generated in the fuel chamber inside the column protruding downward from the carburetor body, the air bubbles naturally flow out of the air bubble outlet into the float chamber, so that the air bubbles are generated. It does not stay in the fuel chamber and grow large.

[0007] The bubbles in the fuel chamber naturally flow out of the bubble outlet into the float chamber, and the fuel naturally flows out together with the bubbles, so that new fuel in the float chamber flows into the fuel chamber from the fuel inlet. Thus, a gentle flow of fuel is generated in the fuel chamber along the inner peripheral surface of the fuel chamber away from the fuel jet.

The reason why the passage area of the bubble outlet is made larger than that of the fuel inlet is to allow the fuel whose volume has been increased by the bubbles to flow out to the float chamber quickly. The reason why the fuel inlet and the bubble outlet are provided on the chi-yoke valve side is to make it easy for bubbles to flow along the inner peripheral surface of the fuel chamber when the low-speed fuel passage and the fuel jet are provided on the support.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a float type carburetor according to the present invention comprises a carburetor body 2 having a horizontal intake passage 5.
And a storage tank 14 coupled to the lower surface of the vaporizer main body 2. The intake passage 5 is formed with a bench lily 5a at an intermediate portion, and a chi-yoke valve 21 is rotatably supported by a valve shaft 20 upstream of the bench lily 5a in the intake passage 5.
The valve shaft 20 traversing the intake passage 5 is connected to the upper end with a chi-yoke lever 18. One end of a spring 19 wound around the valve shaft 20 is locked to the chi-yoke lever 18 and the lower end is locked to the carburetor body 2. Spring 19 biases the yoke valve 21 to the fully open position. A throttle valve 7 is connected to a valve shaft 4 that crosses the intake passage 5 downstream of the bench lily 5 a by a screw 6.
The valve shaft 4 is connected to the throttle valve lever 3 at the upper end.

A column 15 protruding downward from the center of the lower surface of the carburetor body 2 has an axial cylindrical portion 1 forming a high-speed fuel passage.
0 and a low-speed fuel passage 9 slightly inclined with respect to the cylindrical portion 10. Although not shown, the upper end of the low-speed fuel passage 9 is opened to a portion of the intake passage 5 adjacent to the throttle valve 7.
The cylindrical portion 10 is opened to a portion of the intake passage 5 downstream of the chi-yoke valve 21 by a passage and an air jet (not shown). Each lower end of the low-speed fuel passage 9 and the cylindrical portion 10 opens into a screw hole 30 formed in the lower end of the column 15. However, the lower end of the low-speed fuel passage 9 is closed by the stopper 9a.

The bowl-shaped storage tank 14 has an opening peripheral portion on the lower surface of the vaporizer main body 2 through the sealing member 12 and a central bottom portion on the support 1.
5 are respectively in contact with the lower end surfaces. The sealing member 17a is applied to the center bottom of the storage tank 14, and the bolt 17 is
5 is screwed into the screw hole 30, and the storage tank 14 is connected to the vaporizer main body 2. The floating chamber 16 inside the storage tank 14 is
Is accommodated. Although not shown, the float 13 is connected to the fuel valve via a known link mechanism,
The fuel valve is opened and closed so as to keep the level of fuel supplied from the fuel tank to the float chamber 16 constant.

A bleed tube 8 having a pair of upper and lower flanges 8a is fitted into the cylindrical portion 10. The bleed tube 8 is thinner than the inner diameter of the cylindrical portion 10 and has a large number of through holes 23 in the peripheral wall (FIG. 2).
Is provided. The upper end of the bleed pipe 8 protrudes to the bench lily 5 a of the intake passage 5. A passage 24 is provided below the lower flange 8 a of the bleed tube 8 and across the cylindrical portion 10 of the column 15. One end of the passage 24 communicates with the low-speed fuel passage 9 and the other end is closed by a stopper 24a.

As shown in FIG. 2, the lower end of the cylindrical portion 10 communicates with the screw hole 30, and a fuel jet 25 having a passage 25a is screwed therein. The screw hole 30 defines a fuel chamber 27 between the fuel jet 25 and the bolt 17. Fuel chamber 27
Communicates with the inside of the bleed pipe 8 through the passage 25a of the fuel jet 25. The top wall surface 30a of the fuel chamber 27 (preferably also the lower end surface of the fuel jet 25) is inclined. Prop 1
5 is provided with a fuel inlet 28 communicating with the float chamber 16 and the fuel chamber 27 on the peripheral wall adjacent to the bottom of the fuel chamber 27. The fuel chamber 27 is formed on the peripheral wall adjacent to the highest part of the top wall surface 30a.
A bubble outlet 26 is provided extending obliquely upward from the float chamber 16 to the float chamber 16.

As shown in FIG. 3, the fuel inlet 28 and the bubble outlet 26 are arranged on the peripheral wall of the fuel chamber 27 on the side of the chiyoke valve in parallel with each other in plan view. In other words, the fuel inlet 28 and the bubble outlet 26 are directed tangentially to the inner peripheral wall of the fuel chamber 27. The fuel inlet 28 and the bubble outlet 26 are provided on the chi-yoke valve side (right side in the figure) because the support 1
This is because, when the low-speed fuel passage 9 and the fuel jet 25 are provided in the fuel cell 5, air bubbles can easily flow along the inner peripheral surface of the fuel chamber 27 as shown in FIG.

Next, the operation of the float type vaporizer according to the present invention will be described. During operation of the engine, the fuel in the float chamber 16 flows into the fuel chamber 27 from the fuel inlet 28, flows into the bleed pipe 8 through the passage 25 a of the fuel jet 25, and flows through the through hole 23 of the bleed pipe 8 into the cylindrical portion 10. It mixes with air and is sucked into the intake passage 5 through the passage 24 and the low-speed fuel passage 9. At the same time, it is sucked directly from the bleed pipe 8 into the intake passage 5.

When the engine is switched from full load operation to idle operation, the ambient temperature is high and the amount of fuel sucked into the intake passage 5 is small, so that the fuel in the fuel chamber 27 is vaporized and bubbles are generated. . The air bubbles in the fuel chamber 27 are
Flows obliquely upward along the path, and eventually flows out from the bubble outlet 26 to the float chamber 16, so that the bubbles do not stagnate in the fuel chamber 27 and do not grow large. Accordingly, the flow of the fuel flowing from the fuel chamber 27 to the bleed pipe 8 through the passage 25a of the fuel jet 25 is obstructed by the large air bubbles, and problems such as malfunctioning or stopping of the engine are eliminated.

The fuel chamber 27 is a column 1 integral with the carburetor body 2.
5 has a small volume and easily generates bubbles due to the influence of the ambient temperature. However, when the bubbles flow out of the bubble outlet 26 into the large float chamber 16 as described above,
It is extinguished by cooling and partly floats above the float chamber.

[0018]

As described above, according to the present invention, the fuel inlet is provided on the peripheral wall adjacent to the bottom of the fuel chamber, and the bubble outlet is provided on the peripheral wall adjacent to the uppermost portion of the inclined top wall.
While the fuel flows into the fuel chamber from the fuel inlet and makes a half circle, the bubbles generated in the fuel chamber move diagonally upward along the ceiling wall surface and flow out smoothly from the bubble outlet to the float chamber. Further, the bubbles flow out into the cylindrical portion forming the low-speed fuel passage or the high-speed fuel passage, and there is no possibility that the flow of the fuel is obstructed.

Even if bubbles are generated in the fuel chamber, the fuel flows smoothly into the float chamber, so that new fuel in the float chamber flows into the fuel chamber instead. As a result, the temperature of the fuel chamber decreases, and the generation of bubbles occurs. Can be suppressed.

Since the air bubble outlet is machined into a column having a fuel chamber therein, the number of parts does not increase and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a float type vaporizer according to the present invention.

FIG. 2 is an enlarged front sectional view showing a main part of the float type vaporizer.

FIG. 3 is a bottom sectional view taken along line 3A-3A in FIG. 2;

[Explanation of symbols]

2: Evaporator body 5: Intake passage 8: Bleed pipe 9:
Low-speed fuel passage 10: Cylindrical part 15: Column 16: Float chamber 17: Bolt 21: Chiyoke valve 25: Fuel jet 26: Bubble outlet 27: Fuel chamber 28: Fuel inlet 30: Screw hole 30a: Top wall

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 57-69952 (JP, U) JP-B 46-7406 (JP, B1) JP-B 37-5906 (JP, Y1) JP-B 63- 41546 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 5/12 F02M 19/06

Claims (2)

(57) [Claims] 1. A peripheral portion of an opening of a storage tank is brought into contact with a lower surface of a vaporizer main body, and a bottom portion of the storage tank is fastened to a lower end of a column extending downward from the vaporizer main body by bolts. A fuel jet is screwed into a cylindrical portion communicating with the screw hole, a fuel chamber is defined between the fuel jet in the screw hole and the bolt, and a bottom portion of the fuel chamber communicates with a float chamber of the storage tank. A single fuel inlet, a bubble outlet communicating with a portion of the fuel chamber adjacent to the fuel jet and a float chamber of the storage tank are provided in the support, and the fuel inlet and the bubble outlet are parallel to each other in a plane. An opening in the tangential direction with respect to an inner peripheral wall of the fuel chamber, a passage area of the bubble outlet is larger than a passage area of the fuel inlet, and an entire upper wall of the fuel chamber is obliquely upwardly directed toward the bubble outlet. Flow characterized by being inclined to Door type carburetor. 2. The float type carburetor according to claim 1, wherein the fuel inlet and the bubble outlet are arranged on a peripheral wall of the fuel chamber on the side of the chiyoke valve.