JPS6242151B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in membrane valve vaporizers.

The structure of a conventional membrane valve type vaporizer is shown in FIG. In the figure, 1 is the carburetor body, 2 is the retainer spring, 3 is the jet needle, 4 is the throttle valve, 5 is the return spring, 6 is the throttle adjust screw, 7 is the float pin, 8 is the float arm, 9 is a float valve,
10 is an intake valve spring, 11 is a main diaphragm, 12 is a mixing chamber cup, 1
3 is the pump cover, 14 is the pump diaphragm,
15 is the main diaphragm cover, 16 is the main adjustment screw, 17 is the needle jet, 18 is the techler, 19 is the overflow valve, 20 is the overflow hole, 21 is the air hole, 22
is an air chamber, 23 is a diaphragm chamber, 24 is a fuel adjustment orifice, 25 is a slow air hole, 26 is a fuel inlet, 27 is an intake valve, 28 is a discharge valve, 29 is an impulse chamber, 30 is a fuel chamber, 31 is an impulse hole,
32 is a bench lily.

To explain the fuel supply system, the fuel in the fuel tank is supplied to members 13, 14, 26, 27, 28, 29,
The fuel is pumped up by a fuel pump composed of 30 and 31, enters the fuel chamber 30 through the fuel inlet 26 and the intake valve 27, is sent out from the discharge valve 28, and enters the diaphragm chamber 23 through the float valve 9. The fuel in the diaphragm chamber passes through the fuel regulating orifice 24 due to the negative intake pressure of the engine, passes through the gap between the needle jet 17 and the jet needle 3, and reaches the ventilary 32. Here it is mixed with air and supplied to the engine.

Membrane valve type carburetor fuel pump 13, 14, 26~
31 has a structure in which the pump diaphragm 14 is actuated to act as a pump by introducing the internal pressure of the crankcase of the normal engine into the impulse chamber 29, as is clear from the figure.

Next, FIG. 2 shows the relationship between the suction and delivery strokes of the pump, the engine pressure, the behavior of the main diaphragm 11, and the supplied fuel flow rate. As is clear from FIG. 2, the timing at which fuel is supplied from the pump to the diaphragm chamber (discharge stroke A) does not coincide with the intake stroke B of the engine, that is, the stroke C at which fuel is supplied to the engine from the diaphragm chamber. Therefore, the membrane valve type vaporizer has the following drawbacks.

(1) The main diaphragm 11 is lifted up by a certain amount due to the negative suction pressure B, but in addition to that, it is lifted up by the amount of the fuel flow rate C supplied to the engine in each cycle, increasing the load on the diaphragm.

(2) In the high speed rotation range, the suction negative pressure B is also high, so the amount of floating of the main diaphragm 11 (stroke and lifting force of the float arm 8) is large, and the float valve 9 is always open to supply fuel. However, when the slot valve 4 is opened at a high opening in the low speed rotation range, the suction negative pressure B
is small, so the float valve 9 is
won't open. Therefore, fuel will not be supplied.

(3) Due to negative pressure, bubbles tend to form between the float valve and the fuel pump, making the fuel supply to the engine unstable.

The purpose of the present invention is to provide a membrane valve type carburetor that eliminates the above-mentioned drawbacks, considering that securing fuel in a low speed rotation range is an important point for hot startability (full opening of the choke valve) and acceleration performance. The feature is that a fuel chamber and an intake valve and a discharge valve of the fuel chamber are formed in the fuel passage between the fuel inlet and the diaphragm chamber, and the above-mentioned valves are connected to the gas pressure in the engine crankcase. In a membrane valve type carburetor having a fuel pump operated at It is equipped with a fuel pump that opens a valve to suck in fuel.

In this case, the fuel delivery timing of the fuel pump is made to coincide with the intake stroke of the engine, thereby improving the drawbacks of the conventional system.

The present invention can be applied to a two-stroke gasoline engine with a membrane valve type carburetor.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing a membrane valve type vaporizer according to one embodiment of the present invention, and FIG. 4 is a sectional view taken along the line X--X in FIG. 3.

In the figure, 1 is the carburetor body, 3 is the jet needle, 4 is the throttle valve, 9 is the float valve, 11 is the main diaphragm, 13 is the pump cover, 14a to 14d are the pump diaphragms,
17 is a needle jet, 26 is a fuel inlet, 27
is a suction valve, 28 is a discharge valve, 29 is an impulse chamber,
30 is a fuel chamber, 31 is an impulse hole, and 33 is a pump air hole.

The fuel pump, which is a feature of this carburetor, is member 13,
Consists of 14a to 14d, 26 to 31, and 33,
The pump diaphragm includes ring-shaped flexible rubber membranes 14a and 14b and a rigid plate 14, respectively.
The rubber films 14a and 14b are baked onto the plates 14c and 14d. Also board 1
4c is provided with a suction port and a discharge port, and the suction port and discharge port are provided with a suction valve 27 and a discharge valve 28, respectively. Further, an opening 29a is provided in the center of the plate 14c.

The operation in the case of the above configuration will be described.

The function of a fuel pump is as follows, and the relationship between impulse, suction, and discharge is the exact opposite of that of conventional pumps.

In conventional fuel pumps, when the impulse is negative pressure, the intake valve opens and sucks fuel into the fuel chamber, and when the impulse is positive pressure, the discharge valve opens and discharges the fuel, but in the case of the carburetor of the present invention, When the impulse is negative pressure, the pump diaphragm 14d moves in the direction of the impulse chamber 29, so at this time the diaphragms 14a, 14
Since b is compressed, the pressure in the fuel chamber 30 increases, and the discharge valve 28 is opened to discharge fuel. Moreover, when the impulse is positive pressure, contrary to the above, the fuel chamber 30
The internal pressure becomes negative and the suction valve 27 is opened to suck in fuel.

The above case has the following effects.

Due to the action of the fuel pump described above, as shown in Figure 5, the engine's suction stroke B and the fuel pump's discharge stroke A match, resulting in a smooth flow of fuel, which is similar to that of a conventional carburetor. (1) Stopping or reducing fuel supply at low rotation speeds and high throttle valve openings, (2) Generation of air bubbles between the float valve and fuel pump, and (3) Durability due to large amplitude of the main diaphragm. It can improve sexual decline.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional membrane valve type carburetor, and Figure 2 shows the fuel flow rate, main diaphragm amplitude, suction pipe pressure, fuel pump drive pulse, crankcase pressure, cylinder A line diagram showing changes in internal pressure, FIG. 3 is a sectional view showing an embodiment of the carburetor according to the present invention, and FIG. 4 is a line taken along line X-X in FIG. 3.
5 is a diagram showing changes in fuel flow rate, main diaphragm amplitude, suction pipe pressure, fuel pump drive pulse, crankcase pressure, and cylinder pressure in the case of the carburetor shown in FIG. 3. . DESCRIPTION OF SYMBOLS 1... Carburetor body, 14a-14d... Pump diaphragm, 23... Diaphragm chamber of carburetor, 26... Fuel inlet, 27... Suction valve, 28...
...discharge valve, 29...impulse chamber, 30...fuel chamber.

Claims (1)

[Claims] 1. A membrane valve that forms a fuel chamber, an intake valve and a discharge valve for the fuel chamber in a fuel passage between a fuel inlet and a diaphragm chamber, and has a fuel pump that operates both of the valves using gas pressure in the engine crankcase. In the type carburetor, when the gas pressure is negative, the discharge valve is opened to supply fuel to the diaphragm chamber, and when the gas pressure is positive, the suction valve is opened to suck the fuel. A membrane valve vaporizer characterized by being equipped with a pump.