JPS627386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application) The present invention relates to a variable bench lily type carburetor, and more particularly to a carburetor that suppresses coalescence and growth of vapor bubbles generated in fuel in a fuel passage. .

(Prior Art) A variable bench lily type carburetor, for example, a horizontal needle type variable bench lily type carburetor, as shown in FIG. A suction piston 4 facing the fuel suction hole 2 and movable into the bench lily part 1 is provided with a tapered needle 5 penetrating through the throttle part 3, and the needle 5 and the throttle part 3 are connected to each other.
The amount of sucked fuel is measured by the effective cross-sectional area of the gap formed between the two. Here, the suction piston 4 moves according to the amount of intake air in the intake system, and plays the role of keeping the negative pressure in the vent lily substantially constant.

(Problems to be solved by the invention) By the way, in the conventional vaporizer of this type,
Since the upper end of the fuel passage 7, whose lower end opened into the float chamber 6, was opened into the fuel suction hole 2 on the upstream side of the constriction part 3, if the idling state continued due to high temperature, a problem could occur in the fuel. A phenomenon has occurred in which the vapor bubbles 8 remain in the fuel suction hole 2, coalesce and grow, and block the throttle part 3, causing the air-fuel mixture to gradually become thinner. Furthermore, when the vapor bubbles 8 passed through the constriction section 3, the air-fuel mixture became thinner rapidly, and hunting in the air-fuel ratio as shown in the characteristic curve A in FIG. 5 sometimes occurred. As a result of these phenomena, the stability of the engine during idling deteriorates, and in some cases, the engine stalls.

(Means for solving the problems) In order to solve the above-mentioned conventional problems, the present invention has the following features:
A constriction part is formed in a part of a fuel suction hole whose one end opens in a bench lily part, and a suction piston that is movably provided in the bench lily part and facing the fuel suction hole is provided with a taper penetrating through the inside of the constriction part. A fuel passage consisting of a thin tube with a substantially uniform cross section, one end of which opens into the float chamber, the other end of which opens directly into the inner wall of the throttle part, and a fuel suction hole located upstream of the throttle part. The main feature is that the air bleed passage is configured to open directly into the inner wall of the air bleed passage.

(Function) In the variable vent lily type carburetor configured as described above, the other end of the fuel passage is opened directly to the inner wall of the throttle part, which has the smallest passage area among the fuel suction holes and has the highest fuel flow velocity. , it is possible to prevent the above-mentioned bubbles from stagnation and to prevent their coalescence and growth. Moreover, by opening an air bleed passage in the inner wall of the fuel suction hole upstream of the throttle part,
If bleed air is introduced into this, the fuel flow velocity in the constricted portion can be further increased, and the suction effect of vapor bubbles can be further enhanced.

(Example) An example in which the present invention is applied to a horizontal needle type variable bench lily type carburetor will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 10 is a carburetor body, 11 is a bench lily portion, and 1 is a carburetor main body.
Reference numeral 2 designates a fuel suction hole whose one end opens into the bench lily portion 11, and reference numeral 13 represents a constriction portion provided in a part of the fuel suction hole 12. This constricted portion 13 is formed on a cylindrical member 14 inserted into the main body 10. 14a is O
The ring 14b is a pressure spring. 15 is a suction piston provided in the bench lily portion 11 so as to be movable forward and backward, facing the fuel suction hole 12;
The base of the suction piston 15 is housed in a suction chamber (not shown) provided on the outside of the main body 10, and is normally biased by a spring in a direction to narrow down the effective cross-sectional area of the bench lily portion 11. . The suction piston 15 moves forward and backward in accordance with the amount of intake air to keep the bench lily negative pressure approximately constant.

Reference numeral 16 denotes a tapered needle fixed to the suction piston 15, which faces the inside of the constriction part 13, and measures the fuel by being displaced within the constriction part 13 in conjunction with the suction piston 15.

A float chamber 17 is provided in the main body 10 below the fuel suction hole 12. Reference numeral 20 denotes a vertical fuel passage for guiding the fuel in the float chamber 17 into the fuel suction hole 12. The lower end 20A of the passage 20 opens near the bottom of the float chamber 17, and the upper end 20b connects the main body 10 and the fuel passage 20. It penetrates the side wall of the cylindrical member 14 and opens into the throttle section 13 . Preferably, the passageway 20 is a thin tube having a substantially uniform cross section.

On the other hand, one end of an air bleed passage 21 is opened in the inner wall of the fuel suction hole 12 on the upstream side of the throttle part 13. The other end of the air bleed passage is the main body 1
0, and bleed air is supplied from here.

With this configuration, the fuel in the float chamber 17 rises in the fuel passage 20 due to the negative pressure of the vent, is sucked into the constricted part 13 in the fuel suction hole 12, and is drawn between the needle 16 and the constricted part 13. Bench lily part 1 is measured at the annular gap formed in
It is injected within 1. Since the annular gap has a very small area, the fuel flow rate is high. Therefore, small bubbles of fuel vapor generated in the fuel passage 20 at high temperatures are sucked out from the passage 20 into the annular gap. Additionally, there is an enlarged diameter portion (dead space) between the fuel passage 20 and the annular gap.
Since there are no bubbles, there is no chance of air bubbles remaining in the middle.
Therefore, the air bubbles are sucked out to the bench lily portion through the annular gap portion without coalescing and growing.

However, at this time, bleed air is introduced into the fuel suction hole 12 from the air bleed passage 21, the fuel flow rate within the constriction part 13 is further accelerated, and the bubble suction effect is enhanced. As a result, the air-fuel ratio of the mixture supplied to the engine is kept almost constant without any hunting phenomenon or attenuation, as shown by characteristic curve B in Figure 5, and the stability of the engine during idling is ensured. Ru.

Note that, as shown in FIG. 2, the present invention provides two annular grooves 22,
3 is provided, and a narrowing portion 13 is provided in both grooves 22 and 23, respectively.
The fuel passage 20 and the air bleed passage 21 may be opened to the throttle portion 13 through a plurality of small holes 24 and 25 opening therein.

In this example, since the fuel and bleed air are introduced into the throttle part 13 through the plurality of small holes 24 and 25, the degree of mixing of the fuel with the bleed air is increased.
A uniform emulsion flow is formed, and vapor bubbles in the fuel are smoothly sucked out along with the fuel, producing the same effects as in the above embodiment.

Furthermore, as shown in FIG. 3, the present invention provides one annular groove 22' on the outside of the constricted part 13 of the cylindrical member 14, and a plurality of small holes 24' opening into the constricted part 13 in this groove 22'. may be spaced apart in the circumferential direction, and the fuel passage 20 and the air bleed passage 21 may be opened into the throttle part 13 through the plurality of small holes 24'.

In the case of this example, the small vapor bubbles generated in the passage 20 are separated from the fuel in the annular groove 22', introduced into the constriction part 13 together with bleed air, and rapidly discharged from there. It has a similar effect.

Although the embodiments have been described above, it goes without saying that the present invention can also be applied to variable bench lily type carburetors other than the horizontal needle type, that is, to carburetors in which the intake passage is arranged horizontally.

(Effects of the Invention) As described above, the present invention provides a variable bench lily type carburetor in which the other end of the fuel passage, which is made of a thin tube with a substantially uniform cross section and one end of which opens into the float chamber, is connected to the lowest end of the fuel suction hole. Since the flow path area is small and the opening is made directly into the constriction section where the fuel flow velocity is highest, it is possible to prevent the coalescence and growth of vapor bubbles generated in the fuel in the fuel passage under high temperatures, and moreover, it is possible to prevent the coalescence and growth of vapor bubbles that occur in the fuel in the fuel passage under high temperatures. Since the air bleed passage is opened in the inner wall of the fuel suction hole, the introduction of bleed air further accelerates the fuel flow velocity within the constriction part, making it extremely easy to discharge vapor bubbles, and as a result, the coalescence of vapor bubbles. This has the effect of improving the stability of the engine during idling by preventing the air-fuel ratio dilution and hunting phenomenon caused by growth.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a horizontal needle type variable bench lily type carburetor showing one embodiment of the present invention, and FIGS. 2 and 3 are longitudinal cross-sectional views of essential parts showing other embodiments of the present invention, respectively. FIG. 4 is a vertical sectional view showing a conventional horizontal needle variable bench lily type carburetor, and FIG. 5 is a diagram showing air-fuel ratio/time characteristics during idling of the conventional device and the device of the present invention. 11... Bench lily part, 12... Fuel suction hole,
13... Throttle part, 15... Suction piston,
16...needle, 17...float chamber, 20...
...Fuel passage, 21...Air bleed passage.

Claims (1)

[Claims] 1. A constriction part is formed in a part of the fuel suction hole whose one end opens in the bench lily part, and a suction piston provided opposite to the fuel suction hole and movable in the bench lily part is provided with a taper penetrating through the inside of the constriction part. A fuel passage consisting of a thin pipe with a substantially uniform cross section, one end of which opens into the float chamber, and the other end of which opens directly into the inner wall of the constriction section, and further opens the fuel passage upstream of the constriction section. A variable bench lily type vaporizer characterized by having an air bleed passage opened on the inner wall of the hole.