JPS59224450A - Variable venturi type carburetor - Google Patents

Abstract

PURPOSE:To make a carburetor stable in operation while removing frost deposited on a needle by installing a nozzle which ejects fuel to the peripheral surface of the needle of a variable venturi type carburetor. CONSTITUTION:A needle 4 installed onto the end of the throttle valve 3 of a variable venturi type carburetor is inserted into a nozzle 23. The fuel from a float chamber 7 is fed partly to the nozzle 23 through a pipe 22, and the remainder is fed to a nozzle 30 through a jet 25 by a pipe 24. The air is sucked from a nozzle 31 causig an air bleed action. The fuel from the nozzle 30 is bled by air through a passage 26 to be ejected toward peripheral surface of the needle 4 so as to blow off the frost deposited on the nozzle 23 along with a sliding movement of the needle, as a result, stable operation can be carried out without occurrence of icing.

Description

[Detailed description of the invention] Industrial applications The present invention relates to variable venturi type carburetors.

Prior art variable venturi carburetors include a needle fixed to a suction piston and extending into a fuel passage, and a metering jet disposed in the fuel passage and cooperating with the needle, the metering jet being metered by the metering jet and the needle. Fuel is supplied from the fuel passage into the intake passage of the carburetor. In order to atomize the fuel in this type of variable Hentschli type carburetor, air has conventionally been bleed into the metering jet or into the fuel passage downstream of the metering jet. However, when air bleed is performed in this way, frost is generated on the outer peripheral surface of the needle due to moisture in the air bleed, and this frost is supplied from the fuel passage into the carburetor intake passage in order to narrow the fuel flow path area. A problem arises in that the amount of fuel decreases and the air-fuel mixture supplied into the engine cylinder becomes lean.

OBJECTS OF THE INVENTION An object of the present invention is to provide a variable Hentschuri type carburetor which can prevent frost from forming on the needle and form a mixture having a constant air-fuel ratio at all times.

Structure of the Invention The structure of the present invention includes a suction piston that changes the hentschuri area in response to the amount of intake air, a needle connected to the suction piston, and a fuel passage extending in the axial direction of the needle so that the needle can enter therein. , a variable venturi carburetor comprising a metering jet disposed in a fuel passageway and cooperating with a needle, the fuel passageway being connected to a float chamber upstream of the metering jet, the fuel passageway being connected to the float chamber upstream of the metering jet and downstream of the metering jet; The fuel passages are connected to each other via a fuel bypass passage, and a nozzle extending to the vicinity of the needle is attached to an outlet of the fuel bypass passage that opens into the fuel bypass passage on the downstream side of the metering jet.

Embodiment Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction screw 1 that moves laterally within the intake passage 2, and 4 is a tip end surface of the suction piston 3. 5 is the inner wall surface of the intake passage 2, 6 is the throttle valve provided in the intake passage 2 downstream of the suction piston 3, and 7 is the carburetor float chamber. Intake passage inner wall surface 5
A henturi portion 8 is formed in between. A hollow cylindrical casing 9 is fixed to the carburetor main body 1, and a guide sleeve 10 extending in the axial direction of the casing 9 inside the casing 9 is attached. A bearing 12 having a large number of balls 11 is inserted into the guide sleeve IO, and the outer end of the guide sleeve IO is closed by a blind cover 3. On the other hand, a guide rod 14 is fixed to the suction piston 3, and the guide rod 14 is inserted into the bearing 12 so as to be movable in the axial direction of the guide rod 14.

In this way, the suction piston 3 is supported by the casing 9 via the bearing 12, so the suction piston 3
can move smoothly along its axis. The interior of the casing 9 is divided by the suction piston 3 into a negative pressure chamber 15 and an atmospheric pressure chamber 16, and a compression spring 17 is inserted into the negative pressure chamber 15 to press the suction piston 3 toward the henturi portion 8 at the time. . The negative pressure chamber 15 is connected to the hengeli part 8 through a suction hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the carburetor main body l.
Zakujo piston 3 through air hole 19 formed in
It is connected to the upstream intake passage 2.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided within this fuel passage 20. A fuel passage 20 upstream of the metering jet 21 is connected to the float chamber 7 via a downwardly extending fuel pipe 22.
The fuel in the float chamber 7 is sent into the fuel passage 20 via this fuel pipe 22. Furthermore, the intake passage inner wall surface 5
A hollow cylindrical ruzzle 23 arranged coaxially with the fuel passage 20 is fixed on the top. This nozzle 23 protrudes from the inner wall surface 5 of the intake passage into the venturi portion 8, and
The upper half of the tip of the piston 3 further protrudes from the lower half toward the suction piston 3. The needle 4 extends through the nozzle 23 as well as the metering jet 21 , and the fuel is metered by the annular gap formed between the needle 4 and the metering jet 21 before being fed from the nozzle 23 into the intake passage 2 .

1 and 2, a fuel passage 20 upstream of the metering jet 21 and a fuel passage 2 downstream of the metering jet 21 are shown.
0 are connected to each other by a fuel bypass passage 24. This fuel bypass passage 24 includes an intermediate part 24a extending in a substantially horizontal direction, an inflow passage part 24b extending from one end of the intermediate part 24a into the fuel passage 20 upstream of the metering jet 21, and a metering jet extending from the other end of the intermediate part 24a. 21 and an outflow passage section 24c extending into the fuel passage 20 downstream of the fuel passage 20, and a fuel metering jet 25 is inserted into the inflow passage section 24b. Further, a connecting portion between the inflow passage portion 24b and the intermediate portion 24a is connected to the intake passage 2 upstream of the suction piston 3 via the air bleed passage 2G and the air bleed jet 27. On the other hand, the outlet 2 of the outlet passage section 24c
8, a nozzle 29 is inserted therein. This nozzle 29 has a circular M (trapezoidal) tip that projects into the fuel passage 20, and a nozzle port 30 is formed at the top of this tip.As shown in FIG. 4. On the other hand, a plurality of 111.I air bleed holes 31 are formed on the inner peripheral surface of the metering jet 2I.
These air bleed holes 31 are connected to the intake passage 2 upstream of the suction piston 3 via an air bleed passage 32.

The intake passage 2 is located on the inner wall surface 5 of the intake passage on three sides of the nozzle 23.
A raised wall 33 is formed that projects horizontally at 1 ijJ t,;l', and between this raised wall 33 and the tip of the suction piston 3, the flow rate side (α11) is performed. ° When engine operation is started, Air flows downward in the intake passage 2. At this time, the air flow is constricted between the suction piston 3° and the raised wall 33, so negative pressure is generated in the henturi portion 8, and this negative pressure flows through the suction hole 18. It is guided into the negative pressure chamber 15 via.

The Zakujo piston 3 is arranged so that the pressure difference between the negative pressure chamber 15 and the atmospheric pressure chamber 16 becomes a substantially constant pressure determined by the spring force of the compression spring 17, that is, so that the negative pressure in the henturi part 8 becomes substantially constant. Moving.

During engine operation, a portion of the fuel flows into the fuel bypass passage 24 and flows out from the nozzle opening 30 of the nozzle 29 into the fuel passage 20, and the remaining fuel passes through the metering jet 21 to the fuel downstream of the metering jet 21. It flows into the passage 20. An air bleed passage 26 is provided for the fuel flowing within the fuel bypass passage 24.
The air is bled out, and the fuel containing air bubbles flows out from the nozzle opening 30 of the nozzle 29. On the other hand, air is also bled from the fuel flowing in the metering jet 21 through the air bleed hole 31. At this time, as shown in FIGS. 1 and 2, since the nozzle port 30 of the nozzle 29 is arranged near the outer peripheral surface of the needle 4, the fuel flowing out from the nozzle port 30 collides with the outer peripheral surface of the needle 4. As a result, frost generated on the outer peripheral surface of the needle 4 is washed away. During engine operation, the needle 4 moves according to the amount of intake air, so the fuel flowing out from the nozzle port 30 of the nozzle 29 collides with a considerable area of the outer circumferential surface of the needle 4. Frost generated on the needle 4 can be washed away over a fairly wide area of the surface.

Effects of the invention It is possible to prevent frost from adhering to and growing over a fairly wide area on the outer peripheral surface of the needle, and as a result, the flow area of the fuel passage is not narrowed, so that fuel can be sucked in proportion to the amount of intake air. It can be fed into the passageway. Therefore, the air-fuel mixture supplied into the engine cylinders will not become too lean, and stable engine operation can be ensured at all times.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a variable venturi type carburetor according to the present invention, and FIG. 2 is a partially enlarged view of FIG. 1. 3...Succidine piston, 4...Needle, 20
...fuel passage, 21...metering jet, 24...
Fuel bypass passage, 29... nozzle, 30... nozzle port.

Claims (1)

[Claims] A suction piston that changes the venturi area in response to the intake air amount, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter, and an inside of the fuel passage. a variable venturi carburetor comprising a metering jet located at and cooperating with the needle, the fuel passage being connected to the float chamber upstream of the metering jet, the fuel passage being connected to the float chamber upstream and downstream of the metering jet; The fuel passages are connected to each other via a fuel bypass passage, and the metering geso i-
A variable venturi carburetor equipped with a nozzle that extends to the vicinity of the needle at the outlet of the fuel bypass passage that opens into the fuel bypass passage on the downstream side.