JPS5916521Y2 - Accelerator pump nozzle fuel leak prevention device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device that prevents fuel leakage from the accelerator pump of a carburetor, improves responsiveness during acceleration, and stabilizes the fuel flow rate in steady state.

Generally, when a carburetor accelerating device suddenly accelerates, that is, when the throttle valve is suddenly opened, the amount of incoming air increases suddenly, but since the fuel has a large mass, it does not accompany this increase.

Therefore, it is pushed out by the pressure of the pump, and the rod of the pump is linked to the throttle valve and acts at the same time as the throttle valve opens.

However, the accelerating nozzle of the carburetor is part of the choke chamber, and is installed in a location where the air flow velocity is relatively high, where fuel tends to get into the air stream when the accelerator pump is activated, or in other words, where the liquid fuel is easily atomized into mist and mixed with the air. Since there,
Even during steady operation with a constant throttle opening, negative pressure is applied to the acceleration nozzle and fuel is sucked out from the acceleration nozzle.
Extra fuel is added in addition to the fuel metered in the main jet and slow jet, and due to variations in fuel flow rate,
This is undesirable as it leads to fluctuations in engine performance and exhaust gas.

One way to prevent this excess fuel from leaking is to make the spring of the check valve stronger than the negative pressure, but the stronger the spring, the smoother the fuel supply will be when accelerating. It has the disadvantage that it cannot be used for specific purposes, resulting in poor responsiveness.

In addition, in order to prevent leakage, there is another type in which the acceleration fuel passage and the float chamber are communicated through a check valve having a control hole.

However, in this case, the negative pressure generated in the acceleration nozzle is introduced into the float chamber through the control hole of the check valve, making it difficult to maintain the float chamber at atmospheric pressure.

In particular, as the negative pressure in the acceleration nozzle increases, the pressure in the float chamber becomes even more negative.

As a result, the difference between the pressure in a part of the venturi and the pressure in the float chamber decreases, resulting in a decrease in fuel flow rate, and combustion becomes unstable, which in severe cases may result in misfire or engine stop.

However, during acceleration, fuel tries to flow out from the acceleration fuel passage to the acceleration nozzle, but since the acceleration fuel passage communicates with the float chamber through the control hole, the fuel flows through the control hole into the float chamber. Therefore, responsiveness during acceleration and acceleration fuel leakage sustainability are lacking.

This device ensures the prevention of fuel leaks, the responsiveness of the accelerator, and the fuel stability in the steady-state operating range as described above.The configuration of this device will be explained below according to the embodiment shown in the drawings. .

In the figure, A is the entire horizontal carburetor, B is its float chamber, and C is the acceleration pump chamber.

Float chamber B is a chamber that temporarily stores fuel sent out by a fuel pump, and a float 2 equipped with a needle valve 1 floats therein to keep the oil level constant.

Further, the acceleration pump chamber C is provided with a piston rod 3 and a piston 4 which are interlocked with the throttle valve by a link mechanism, and a passage 5 communicating with the float chamber B is provided with a suction check valve 6.

Furthermore, a larger diameter acceleration fuel discharge device chamber is provided in a part of the acceleration fuel supply passage 8 that communicates with the acceleration nozzle 7, and a small diameter acceleration fuel discharge device chamber that communicates with the atmosphere side of the intake passage 17 is provided in this device chamber. Small diameter hole 1 communicating with bleed hole 9 and acceleration nozzle 7 side
A valve fixing member 11 comprising 0 is installed.

The small-diameter holes 10 communicating with the bleed hole 9 communicate with each other via a small cavity 12, and the second check valve 13 is connected to the bleed hole 9 side of the cavity 12 by an elastic member 14 such as a weak spring.
It is constructed so that it is always subject to the action of

Further, a first check valve 16 is provided on the acceleration pump chamber C side of the acceleration fuel supply passage 8 via a spring 15 whose one end is connected to the valve fixing member 11 .

Reference numeral 17 denotes an intake passage, and the elastic member 14 in the cavity 12 has a weaker action strength than the spring 15 on the first check valve 16 side.

The operation of the accelerator pump nozzle fuel leak prevention device constructed as described above will be explained as follows.

If the throttle valve of the carburetor A is in a steady state of operation with a constant opening degree, the air flow rate in the intake passage 17 is extremely high, and negative pressure is generated in the acceleration nozzle 7.

On the other hand, the lower small hole 10 of the valve fixing member 11 is close to the inner end opening of the accelerating nozzle 7, and the negative pressure of the accelerating nozzle 7 immediately acts on the small cavity 12 through this small hole 10.
In order to open the check valve 13, air is sucked in from the intake passage 17, and fuel is immediately prevented from flowing out from the acceleration nozzle 7.

Note that the small hole 10 and the inner end opening of the acceleration nozzle 7 do not necessarily need to be provided in opposing positions.

However, doing so will improve responsiveness.

In this case, the first check valve 16 is hardly subjected to the negative pressure action of the accelerating nozzle 7, and is always kept closed by the action of the spring 15.

This means that the acceleration fuel supply passage 8 is blocked, and fuel leakage during steady operation with a constant throttle opening is prevented.

In this case, air is taken in from the intake passage 17 through the bleed hole 9, but the air-fuel ratio does not change due to this air, and is controlled to an appropriate air-fuel ratio by a portion of the downstream venturi.

Also, during acceleration, by stepping on the accelerator, the piston rod 3, which is interlocked with the throttle valve by the link mechanism, is pressed downward, and the acceleration piston 4 moves into the acceleration pump chamber C.
Since the fuel inside is compressed, the suction check valve 6 receives the above pressure and shuts off the passage 5 to the float chamber B.

At the same time, the acceleration fuel supply passage 8 also receives the same pressure, the first check valve 16 opens, the lower small hole 10 of the valve fixing member 11 is immediately blocked by fuel, and the second check valve 13 opens. Since the fuel is closed, the fuel will not leak from the bleed hole 9 and will be ejected from the acceleration nozzle 7 without delay.

In this case, the action strength of the spring 15 is set to be greater than that of the elastic member 14, but since the action strength of the elastic member 14 is satisfied with an extremely small action strength, the action strength of the spring 15 is set smaller than conventionally. .

For the above-mentioned reason, when the accelerator is pressed during acceleration, the fuel in the acceleration pump chamber C is compressed by the acceleration piston 4, which is activated by the link mechanism with the throttle valve, and when pressure is generated, the fuel is pumped through the spring 15, which has a relatively small acting strength. The first check valve 16 is pushed up and the liquid is ejected from the acceleration nozzle 7.

That is, the fuel supply during acceleration is carried out rapidly and continuously, and the responsiveness during acceleration is also improved.

As explained above, this invention provides a first check valve that is opened by the fuel supply pressure from the acceleration pump chamber in the middle of the acceleration fuel supply passage that communicates the acceleration pump chamber and the acceleration nozzle.
In an acceleration fuel supply device for a carburetor, which communicates with the atmosphere side of the intake passage via a second check valve that opens the upper part of the acceleration fuel supply passage above the acceleration nozzle by the negative pressure generated in the acceleration nozzle part, It has a small cavity 12, a small diameter bleed hole 9 communicating with the atmosphere side of the intake passage 17 in the upper part of the cavity, a small diameter hole 10 in the lower part of the cavity, and a small diameter hole 10 in the lower part of the cavity. A second check valve 13 that always closes the bleed hole 9 via the weak elastic member 4 and opens it by the negative pressure generated in the acceleration nozzle 7 through the lower hole 10 and the cavity 12.
The valve fixing member 11 having a valve fixing member 11 is placed in the acceleration fuel supply passage 8 above the acceleration nozzle 7, so that the lower hole 10 is close to the inner end opening of the acceleration nozzle and is blocked by the fuel pushed out when the acceleration pump is activated. Since the air pocket a between the upper part of the accelerating nozzle and the valve fixing member 11 is made smaller than the fuel collecting part at the lower part of the accelerating nozzle, the lower part of the valve fixing member 11 is fixed when not accelerating. Since the hole 10 is close to the acceleration nozzle 7, the negative pressure generated in the acceleration nozzle 7 immediately acts through the lower small diameter hole 10 into the small cavity 12 independent from the acceleration fuel supply passage 8. Since the second check valve 13 is opened to suck air from the atmospheric side of the intake passage 17 and send it to the acceleration nozzle 7, it is possible to prevent fuel from flowing out.

That is, the response sensitivity of the opening operation of the second check valve 13 during non-acceleration becomes high, and the acceleration nozzle 7 during steady driving becomes more sensitive.
This prevents unnecessary fuel from flowing out.

Further, during acceleration, the lower small hole 10 is immediately blocked by the fuel pushed out by the acceleration pump, cutting off air intake, so that fuel is immediately discharged from the acceleration nozzle 7 in response to the operation of the acceleration pump.

Therefore, good acceleration performance can also be obtained during acceleration.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional side view of a carburetor according to the present invention. 7... Acceleration nozzle, 8... Fuel supply passage, 9... Bleed hole, 6... Intake check valve, 13... ...Second check valve, 14...
...Elastic member, 15...Spring, 16.
...First check valve.

Claims (1)

[Scope of utility model registration request] A first check valve that is opened by the fuel supply pressure from the acceleration pump chamber is provided in the middle of the acceleration fuel supply passage that communicates the acceleration pump chamber and the acceleration nozzle, so that the acceleration fuel supply passage above the acceleration nozzle is provided with a first check valve that opens by the fuel supply pressure from the acceleration pump chamber. The accelerating fuel supply device for a carburetor communicates with the atmosphere side of the intake passage through a second check valve that opens when negative pressure is generated in the accelerating nozzle. A small diameter bleed hole 9 communicating with the atmosphere side of the intake passage 17 is provided in the upper part, a small diameter hole 10 is formed in the lower part of the cavity, and the bleed hole 9 is always kept in the cavity through a weak elastic member 14. to close the hole 1 at the bottom.
A valve fixing member 11 having a second check valve 3 that is opened by negative pressure generated in the acceleration nozzle 7 through the acceleration nozzle 7 and the empty chamber 12 is connected to the acceleration fuel supply passage 8 above the acceleration nozzle 7 through the hole in the lower part. 10 is close to the inner end opening of the acceleration nozzle and is fixedly installed in a position where it is likely to be blocked by extruded fuel when the acceleration pump is activated, and the air pocket a is between the upper part of the acceleration nozzle and the valve fixing member 11. A carburetor flow rate stabilizing device characterized by being smaller than the fuel reservoir at the bottom of the acceleration nozzle.