JPS6237948Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improved structure of a small-sized carburetor as follows.

That is, the cylindrical throttle valve 1 is provided with a low-speed fuel passage 2 and a low-speed fuel injection port 3 that opens toward the engine side, and the low-speed fuel passage 2 is provided only when the cylindrical throttle valve 1 is at a low opening.
The lower end 2b of the throttle valve 1 is inserted into the main nozzle 5a, and the fuel in the main fuel passage 5 above the main jet 6, which is installed at a position higher than the constant oil level H, flows into the low-speed fuel passage 2. The required amount of fuel is injected and supplied from the low-speed fuel nozzle 3 that opens on the engine side when the engine is running at low speed, and the end of the low-speed fuel passage 2 is injected into the throttle valve 1 from the main nozzle 5a when the opening is high. From the main nozzle 5a which is separated upward and opens wide,
In a small carburetor that supplies an appropriate amount of fuel during high-speed rotation, the lower end 2b of the low-speed fuel passage 2 is located at a low opening of the cylindrical throttle valve 1, and is located at a position higher than the constant oil level H. Main jet 6 installed in
Considering that the gap between the inner diameter of the upper main fuel passage 5 and the outer diameter of the low-speed fuel passage 2 is increased to increase the amount of bleed air mixed into the low-speed fuel passage 2, the diameter of the main injection port 5a will be increased. increases, and more fuel than is required is supplied to the engine when the cylindrical throttle valve 1 is fully opened, and negative pressure to the main nozzle 5a acts effectively when the engine changes from low speed to high speed rotation. Therefore, the gap between the inner diameter of the main fuel passage 5 and the outer diameter of the low-speed fuel passage 2 is kept to a minimum.

In such a small carburetor, since the gap between the inner diameter of the main fuel passage 5 and the outer diameter of the low-speed fuel passage 2 is limited, bleed that mixes into the fluidized fuel in the low-speed fuel passage 2 from the gap is limited. The amount of air is small and the atomization state is uneven, causing fluctuations in the amount of fuel supplied, which in turn causes variations in engine speed. For example, even if the idling speed is set to 2800rpm as shown in L1 shown in Figure 5, the rotational speed may vary from 3200rpm to 3200rpm due to rotational fluctuations.
The rotation width is approximately 2400 rpm, which is the set standard rotation speed.
It has a large fluctuation of ±400rpm compared to 2800rpm.

Therefore, the rotation speed during this operation is unstable,
The original engine performance cannot be fully demonstrated.

The present invention aims to eliminate the above-mentioned drawbacks and to achieve stability during idling rotation.

The present invention was made to achieve the above purpose.
In the above carburetor, bleed air opens between the main jet 6 provided above the oil level in the main fuel passage 5 and the lower end 2a of the low speed fuel passage 2 when the throttle valve 1 is opened at a low opening. It is characterized by the provision of a passage 7.

To explain a specific example of the present invention configured in this way, as an embodiment for causing air to flow into the low-speed fuel passage 2, the throttle valve is located in the intake passage 4 when the throttle valve is opened at a low degree, and is located in front of the intake passage 4. An upward cutaway B is formed on the front wall of the opposing cylindrical throttle valve 1 with the upper end of the lower cutaway A serving as a boundary, and the width of the upward cutaway B is smaller than the surface width of the downward cutaway A. , the upper end 2a of the low-speed fuel passage 2 provided in the cylindrical throttle valve 1 is opened to an upward cutaway B, and when the engine is idling, the throttle valve 1 opens the intake passage 2 by about 1 mm. The fuel sucked from the fuel chamber 8 by the suction negative pressure acting on the low-speed fuel nozzle 3 flows between the lower end of the low-speed fuel passage 2 inserted into the main fuel passage 5 and the high-level main jet 6. The air that flows in from the bleed air passage 7 that opens to the cylindrical throttle valve 1 is mixed in, and the air that flows in from the front of the intake passage 4 immediately before being ejected from the low-speed fuel nozzle 3 provided in the cylindrical throttle valve 1 is guided by the upward cutaway B. Since the air flowing in from the upper end of the low-speed fuel passage 2 is mixed in, the atomization state of the fuel injected from the low-speed fuel nozzle 3 becomes good, and the atomized fuel is directed downward cutaway A. Intake path 4 downstream of throttle valve 1
Since it is ejected to the top of the airflow that has entered the engine, the mixture is continuously supplied to the engine in a stable state with no uneven richness or leanness as a mixture with accelerated atomization. , conventional ±400rpm
(Fig. 5 L1) The speed was about ±150rpm.
(L2 in FIG. 5), the variation in engine rotation was reduced, and the performance of the engine using the above-mentioned small carburetor during idling operation was improved.

Further, as shown in FIG. 3, when the cylindrical throttle valve 1 is at a medium opening, the end 2b of the low-speed fuel passage 2 is separated above the main nozzle 5a, and the main nozzle 5a is opened wide and the main nozzle 5a is opened. As the negative pressure is applied, the air flow from the bleed air passage 7 opened just above the high-level main jet 6 draws the fuel from the main jet 6 upwards and injects it into the intake passage 1. In addition to the bleed effect, sufficient fuel can be supplied as the opening of the cylindrical throttle valve 1 increases, and the increase in engine speed quickly follows the operation of the throttle valve 1. We were also able to improve performance when driving other than idling.

In the above embodiment, an upward cutaway connected to a downward cutaway is formed on the front surface of the cylindrical throttle valve as a means for introducing air into the low speed fuel passage formed in the cylindrical throttle valve. Although shown as opening and connecting the upper end of the passageway to the upward cutaway, other air intake means may be used. (For example, an air intake hole connected to a low-speed fuel passage is formed in the cylindrical throttle valve 1.)

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the entire vaporizer of the present invention;
Figures 2 and 3 are longitudinal sectional views showing the operating state of the main parts of the present invention, Figure 4 is a front view of only the throttle valve, which is the main part of the present invention, and Figure 5 is a conventional carburetor and a vaporizer of the present invention. FIG. 2 is a characteristic diagram showing engine rotational fluctuations of the device. 1...Cylindrical throttle valve, 2...Low speed fuel passage, 3
...Low speed fuel nozzle, 5...Main fuel passage, 6...
Main jet, 7...Bleed air passage.

Claims (1)

[Scope of utility model registration request] A cylindrical throttle valve 1 is provided with a low-speed fuel passage 2 and a low-speed fuel nozzle 3, and when the throttle valve 1 is at a low opening, the lower end of the low-speed fuel passage 2 that protrudes below the throttle valve is a main fuel passage 5. Air intake means is inserted into the main fuel passage 5 and guides the fuel in the main fuel passage 5 into the low-speed fuel passage, and also introduces air upstream of the throttle valve 1 from the upper end of the low-speed fuel passage 2. In a carburetor, a bleed air passage opens between a main jet 6 provided above the oil level in the main fuel passage 5 and a lower end of the low-speed fuel passage 2 when the throttle valve 1 is opened at a low degree. 7. A vaporizer characterized by being provided with a.