JPH0437242Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to a carburetor, and particularly to measures to prevent foaming of fuel in a float chamber.

(Prior Art) Conventionally, as disclosed in Japanese Utility Model Application Laid-Open No. 53-69630, a fuel inlet is provided in the upper part of a float chamber to allow fuel pumped from a fuel pump to flow into the float chamber. There is no known device in which a needle valve is provided to open and close the fuel inlet port in conjunction with the float to control the flow rate of fuel flowing into the float chamber so that the fuel level in the float chamber is constant. There is.

(Problem to be solved by the invention) However, in the conventional carburetor mentioned above, the fuel pumped from the fuel pump is forced to flow into the float chamber from the fuel inlet, so when the temperature of the fuel is high such as in summer, During acceleration operation, high-temperature and high-pressure fuel is supplied from the fuel inlet to the float chamber due to an increase in the discharge pressure of the fuel pump.

On the other hand, normally, the float chamber communicates with the intake pipe through an air vent and receives the dynamic pressure of the intake air flowing through the intake pipe, so high temperature and high pressure fuel is supplied to the float chamber. When this occurs, the pressure applied to the fuel drops rapidly, causing the fuel to foam. For this reason, the foamed fuel fills the float chamber and pressurizes the liquid level of the fuel, so that the flow rate of the fuel flowing out from the float chamber becomes excessive, resulting in a problem that the air-fuel mixture becomes overbalanced.

The present invention has been made in view of this point, and an object of the present invention is to suppress foaming of fuel flowing into the float chamber.

(Means for Solving the Problems) In order to achieve the above object, the present invention allows the fuel flowing from the fuel inlet to flow into the float chamber while gradually reducing its pressure.
This suppresses foaming of fuel.

Specifically, the solution taken by the present invention includes a fuel inlet that is opened at the upper part of the float chamber and allows the fuel pumped from the fuel pump to flow into the float chamber, and the fuel inlet is opened and closed in conjunction with the float. The present invention is directed to a carburetor equipped with a needle valve to control the flow rate of fuel flowing into the float chamber, and which is separated from the main body of the float chamber in the upper space of the float chamber and communicates with the fuel inlet. The float chamber is provided with a pressure relaxation chamber that gently lowers the pressure of the fuel flowing in from the fuel inlet and causes the reduced pressure fuel to flow down into the main body portion of the float chamber.

(Function) With the above configuration, when the needle valve opens, high pressure fuel pumped from the fuel pump flows into the pressure relief chamber from the fuel inlet. Then, since the fuel pressure gradually decreases in the pressure relief chamber,
Foaming of the fuel is suppressed. Then, the fuel whose pressure has been reduced without foaming flows down from the pressure relief chamber to the main body of the float chamber.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a first embodiment of the invention. In the figure, is an intake pipe whose upstream end is connected to air cleaner A and whose downstream end is connected to an engine (not shown), and an intake passage D is formed by the intake pipe. It supplies intake air to the engine.

A float chamber 1 for storing fuel is provided on the side of the intake pipe. A fuel inlet 2 is opened in the upper part of the float chamber 1, and the fuel inlet 2 communicates with a fuel pump 4 via a fuel supply passage 3, and the fuel pumped from the fuel pump 4 is transferred to the float chamber 1. We are trying to have an inflow into the country. A float 5 is disposed within the float chamber 1, and is supported by the float chamber 5 via an arm 6 so as to swing up and down in response to fluctuations in the fuel level within the float chamber 1.

A needle valve 7 for opening and closing the fuel inlet 2 is provided below the fuel inlet 2 in a pressure relief chamber structure 1 to be described later.
9 and is arranged so as to be slidably supported in the vertical direction. The needle valve 7 has its lower end connected to the arm 6.
By touching and separating from the fuel inlet 2 in conjunction with the rocking of the float 5 to open and close the fuel inlet 2, the fuel flow rate flowing into the float chamber 1 is adjusted to the fuel level in the float chamber 1. I try to control it so that it remains constant.

Further, a downstream end of a fuel outflow passage 8 opens at the lower part of the float chamber 1, and the downstream end of the fuel outflow passage 8 communicates with a main nozzle 10 provided in the bench lily portion 9 of the intake passage D. The fuel from the float chamber 1 is caused to flow out from the main nozzle 10 to the bench lily part 9 by the negative pressure generated in the bench lily part 9 to generate an air-fuel mixture. still,
11 is an air vent that communicates the intake passage D upstream of the bench lily portion 9 with the float chamber 1 to introduce dynamic pressure into the float chamber 1 according to the intake air flow rate; 12 is a throttle valve; and 13 is a choke valve. Further, 14 is a main jet, 15 is a main air bleed, 16 is a slow port, 17 is an idle port, and 18 is an idle adjustment screw.

A bottomed cylindrical pressure relief chamber structure 19 is disposed below the fuel inlet 2 of the float chamber 1 . The fuel inlet 2 is formed in the upper wall of the pressure relief chamber structure 19, and the internal space of the pressure relief chamber structure 19 is vertically divided into two parts by a partition wall 20. An upper pressure relief chamber 21 and a lower pressure relief chamber 22 communicating with the fuel inlet 2 are defined in the upper space of the corresponding float chamber 1 . Further, as shown in FIGS. 1 and 2, a circular fitting hole for supporting the needle valve 7 is formed in the partition wall 20 and bottom wall 23 of the pressure relief chamber structure 19, and each Around the insertion hole, there are a plurality of (four each in the figure) communication holes 24, 2 through which the fuel in each pressure relief chamber 21, 22 passes downward.
4 . . . , 25 , 25 . From the communicating hole 24,
The pressure drop of the fuel flowing into the lower pressure relief chamber 22 through the lower pressure relief chamber 22 is alleviated, and the fuel is allowed to flow into the float chamber 1 through the communication holes 25, 25...

Next, to explain the operation of the above embodiment, the fuel flowing into the float chamber 1 from the fuel inlet 2 first passes through the upper pressure relief chamber 21 from the fuel inlet 2.
The fuel flows into the lower pressure relief chamber 22 and the small volume change alleviates the pressure drop of the fuel, resulting in a slight pressure drop.The fuel then flows into the lower pressure relief chamber 22 and the pressure drop is alleviated by the small volume change, resulting in a slight pressure drop. After the pressure decreases, it flows into the float chamber 1 and the pressure decreases to the internal pressure of the float chamber 1. In this way, the pressure drop in the two pressure relief chambers 21 and 22 is alleviated, so that the pressure of the fuel can be gradually reduced while flowing into the float chamber 1. Even if high-temperature and high-pressure fuel flows into the float chamber 1 from the fuel inlet 2, foaming of the fuel can be suppressed, so that a pressurizing force other than the dynamic pressure from the air vent 11 acts on the fuel liquid level in the float chamber 1. A predetermined amount of fuel can be stably flowed out from the float chamber 1 to the bench lily part 9 without any problems, and it is possible to prevent the mixture from becoming overbalanced.

FIG. 3 shows a second embodiment of the present invention, in which a partition plate 26 extending from the upper part of the float chamber 1 to below the fuel liquid level is disposed in the float chamber 1, and the partition plate 26 and the fuel liquid level are connected. Therefore, a pressure relaxation chamber 21' is defined in the upper space of the float chamber 1 corresponding to the fuel inlet 2, and the same functions and effects as in the first embodiment are achieved.

In addition, in each of the above embodiments, each pressure relief chamber 2
An open-cell foam may be disposed at 1, 22 or 21' to alleviate the pressure drop due to the flow resistance provided by the foam.

(Effect of the invention) As explained above, according to the carburetor of the invention, the fuel pumped under pressure from the fuel pump flows once into the pressure relief chamber from the fuel inlet, and the pressure is gradually reduced in the pressure relief chamber. Since the fuel is allowed to flow down into the main body of the float chamber, foaming of the fuel is suppressed regardless of the temperature and pressure of the fuel, thereby preventing unexpected pressure from acting on the fuel liquid level in the float chamber. .

Therefore, according to the present invention, a predetermined amount of fuel can be stably flowed out from the float chamber into the intake pipe, so that overbalance of the air-fuel mixture can be reliably prevented.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the invention, and FIG.
FIG. 2 is a bottom view of the pressure relief chamber structure, and FIG. 3 is a diagram corresponding to FIG. 1 showing the second embodiment. 1...Float chamber, 2...Fuel inlet, 4...
Fuel pump, 5...Float, 7...Needle valve, 21, 21', 22...Pressure relaxation chamber.

Claims (1)

[Scope of utility model registration request] A fuel inlet that is opened at the upper part of the float chamber and allows the fuel pumped from the fuel pump to flow into the float chamber, and a needle valve that opens and closes the fuel inlet in conjunction with the float, so that the fuel flows into the float chamber. The carburetor is configured to control the flow rate, and is provided in an upper space of the float chamber to be separated from the main body of the float chamber and communicated with the fuel inlet, and to control the flow rate of the fuel flowing in from the fuel inlet. A carburetor comprising a pressure relief chamber that gently lowers the pressure of the float chamber and causes the reduced fuel to flow down into the main body of the float chamber.