JP2605532B2 - Variable venturi carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a variable venturi carburetor.

[0002]

2. Description of the Related Art A variable venturi-type carburetor automatically changes the effective cross-sectional area of a venturi according to an intake air amount of an engine.
It is almost constant regardless of the engine speed, and the fuel flow rate is
It has the characteristic that it increases or decreases sensitively according to the change in the area of the venturi. Such a mechanism improves acceleration and exerts strength in driving with a large change in the accelerator, such as a road with many curves. In addition, since the intake resistance at high speed is small, sufficient air supply can be performed during high output operation. Therefore, the variable venturi-type carburetor is suitable for a high-speed, high-power engine.

FIG. 2 shows an example of a variable venturi-type carburetor, and FIG. 3 is an enlarged view of a main part of FIG.
3 and FIG. 3, a body 1 includes a venturi 2, a float chamber 3, a fuel inlet tube 4, a main jet 5, a mix charge adjusting screw 6,
A bypass passage 7, a bypass port 7a , a bypass air jet 10, a main air jet (not shown), and the like are formed. A throttle valve 12 is disposed downstream of the bypass port 7a of the venturi 2, and a suction piston 13 is disposed upstream. The metering needle 14 provided at the center of the end face of the suction piston 13 is fitted concentrically at a small interval into the main jet 5 and the main nozzle 15.

The suction piston 13 moves to the left in the figure to a position where the negative pressure in the venturi 2 that changes according to the opening of the throttle valve 12 and the spring force of the spring 16 are balanced, and the opening area of the venturi 2 And change the main jet with the metering needle 14.
The opening area of the gate 5 is changed. Fuel flows from the float chamber 3 to the fuel inlet tube 4 → main jet 5
→ Spouts into the venturi 2 via the main nozzle 15 to be atomized, and is sucked into the intake passage and the engine (both not shown)
Supplied to

At the time of idling operation, fuel is
Float chamber 3 → Fuel inlet tube 4 → Main jet 5 → Venturi 2 (white arrow in FIG. 3), and a part of fuel in fuel inlet tube 4 is mixed fuel adjusting screw 6 tip → Bypass passage 7 → Bypass port 7a → Venturi 2 (Fig. 3
Black arrow) and a part of the fuel in the main jet 5 flows through the bypass passage 7 → the bypass port 7a → the Venturi 2 (white arrow in FIG. 3), is ejected to the Venturi 2 and is sucked into the intake passage.

[0006] As described above, the variable venturi type carburetor having a structure in which fuel is ejected from the main jet 5 even during idling operation is not a slow type or a main type independent like a normal carburetor, but a metering needle throughout idling from idling. The fuel flow rate is controlled by means of 14, and since there is no splicing of each system such as a slow system and a main system, it has a very smooth flow control characteristic. Therefore, in order not to impair the good basic characteristics, the structure is adopted in which fuel is sucked at a negative pressure upstream of the throttle valve 12 so that an excessive negative pressure is not applied to the main jet portion.

[0007]

However, in the conventional variable venturi-type carburetor, the main nozzle 15 and the bypass port 7a , which are the fuel outlets of the venturi 2, are both opened on the upstream side of the throttle valve 12. The fuel suction negative pressure during idling operation is weak, and the fuel sucked into the venturi 2 flows through the wall surface of the venturi 2 and flows out into the intake passage. For this reason, the fuel injected into the venturi 2 becomes a wall flow and is difficult to atomize, the fuel distribution to each cylinder is poor, the stability during idling operation is poor due to smoldering of the spark plug due to excessive wall flow, and the like. Futuroscope over El cut solenoid 1
In order to control the fuel by adjusting the bleed air amount according to 7, there is a problem that a run-on is generated due to a slow wall flow flowing from the venturi 2 through the intake passage after the engine is turned off.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made to improve the atomization of fuel sucked into a venturi during idling operation and to prevent instability during idling operation without impairing good basic characteristics. It is an object of the present invention to provide a variable Venturi type carburetor.

[0009]

According to the present invention, there is provided a slot provided in a venturi section.
A throttle valve and an upstream side of the throttle valve.
The main nozzle part and the downstream side of the throttle valve
The main nose having an open bypass port;
With a bypass passage that intersects the
A variable valve that ejects fuel from the bypass port during rotation
In the centuri-type carburetor, the throttle valve
And the bypass passage at an intermediate portion between the main nozzle portion and the main nozzle portion.
Form an opening to be communicated and idle the opening
An air inlet into the bypass passage during operation;
The configuration is as follows.

[0010]

When the engine is idling, the fuel in the bypass passage is ejected from a bypass port opened downstream of the throttle valve and is sucked into the intake passage. On the other hand, the opening that opens on the upstream side of the throttle valve serves as an air suction port, and a part of the air in the venturi is sucked into the intake passage together with the fuel via the bypass passage. As a result, atomization of fuel during idling operation is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The same members as those in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted. FIG. 1 shows a main part of a variable venturi-type carburetor to which the present invention is applied, and a main jet 5 provided in a hole 1 a orthogonal to a venturi 2 of a body 1.
The tip of the metering needle 14 proximal end is attached to the suction piston 13 is inserted concentrically fitted to exist a small distance, the bypass passage 7, across the hole 1a and the main nozzle 15 provided, its lower end is in communication rylene by the bypass port 9 to open the mouth under flow position of the throttle valve 12.

The bypass passage 7 is formed by an opening 8 which is opened on the side wall of the venturi 2 at an intermediate position between the throttle valve 12 and the main nozzle 15 at an upstream side of the throttle valve 12. Is communicated to. Then, the bypass passage 7, the upstream and downstream sides of the throttle valve 12 is communicated with the openings 8 and the bypass port 9.

[0013] Then, the opening 8 to idling during operation
Is an air inlet, and the bypass port 9 is a fuel outlet. That is, the opening 8 is used as an air inlet, and the air taken in from the opening 8 together with the fuel is ejected from the bypass port 9 so that the high intake pipe negative pressure in the bypass passage 7 that is conducted to the downstream side of the throttle valve 12 is reduced. A function of thinning is provided so as not to apply an excessive negative pressure to the fuel control portion such as the main jet 5 and the slow adjusting portion.

The opening 8 of the bypass passage 7 , the bypass port
The port 9 does not impair the good basic characteristics of the carburetor and prevents excessive negative pressure from being applied to the bypass passage 7 and the main jet 5 in order to promote atomization of fuel ejected from the bypass port 9. The diameter is set. For example, the hole diameter of the opening 8 is set to 4φ, and the hole diameter of the bypass port 9 is set to about 1.2φ.

The upper part of the bypass passage 7 communicates with the float chamber 3 through the mixing charge adjusting screw 6 and the fuel inlet tube 4 in the same manner as the conventional one shown in FIG. 3, and the main jet 5 is also connected to the fuel inlet tube. It communicates with the float chamber 3 via 4. Other parts are configured similarly to FIGS. 2 and 3.

The operation will be described below. During idling operation, the suction piston 13 moves to the right as shown in the figure.
The venturi 2 is slightly opened, and the metering needle 14 is in a state of deeply entering the main nozzle 15 and the main jet 5. Bypass port 9 of the bypass passage 7 is opened downstream of the slot Rubarubu 12 negative pressure directly intake pipe act to have, fuel, fuel inlet tube 4 from the float chamber 3 (FIG. 2) → main jet 5 → Bypass passage 7 (indicated by white arrow),
And the tip of the mix charge adjusting screw 6 (FIG. 2) → flows through the bypass passage 7 (shown by a black arrow), flows into the bypass passage 7, and
Issued bypass port 9 or al-injection opening to a downstream side of the sucked into the intake passage.

On the other hand, an opening 8 of the bypass passage 7 on the upstream side of the throttle valve 12 serves as an air suction port, and a part of the air in the venturi 2 is supplied from the opening 8 to the bypass passage 7 as shown by a dotted arrow. Inflow, throttle valve 1
Venturi 2 from bypass port 9 downstream of
Is sucked together with the fuel. In this way, the fuel is ejected from the bypass port 9 to the high intake pipe negative pressure section downstream of the throttle valve 12, so that atomization is promoted, and the wall flow of the fuel at the ejection section is eliminated.

[0018]

As described above, according to the present invention, atomization of fuel during idling operation is greatly improved with a very simple structure, and accordingly, fuel distribution to each cylinder is improved. At the same time, the wall flow of the fuel intake passage is reduced, so that the smoldering of the spark plug is reduced, the engine rotation fluctuation is reduced, and furthermore, the fuel flow delay into the combustion chamber immediately after the cold start of the engine, which is disadvantageous to the atomization conditions, Ovaleen stal is improved. Further, since the fuel at the time of idling passes through the bypass passage at a high flow rate, there is an excellent effect that the running out of fuel at the time of engine key-off becomes quick and the run-on is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a variable venturi-type carburetor according to the present invention.

FIG. 2 is a sectional view showing an example of a conventional variable venturi-type carburetor.

FIG. 3 is an enlarged view of a main part of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Body 2 Venturi 5 Main jet 7 Bypass passage 8 Opening 9 Bypass port 12 Throttle valve 13 Suction piston 14 Metering needle 15 Main nozzle

Claims (1)

(57) [Claims] 1. A throttle bar provided in a venturi section.
And a main nose arranged upstream of the throttle valve.
And a bypass port opening downstream of the throttle valve.
And a viper intersecting with the main nozzle portion.
Fuel passage from the bypass port during idling operation.
In the variable venturi-type carburetor to be ejected, an intermediate portion between the throttle valve and the main nozzle portion
Forming an opening communicating with the bypass passage,
The bypass passage when the opening is idling
A variable venturi-type carburetor characterized by an air intake into the interior .