JPS6257822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a built-in acceleration pump for a butterfly throttle type diaphragm type carburetor which utilizes the pulsating pressure in the crank chamber of a two-stroke engine when the throttle valve is fully opened.

The 2-cycle engine has a simple structure, is lightweight, and can be operated in all directions, and is equipped with a diaphragm carburetor that can also be operated in all directions, making it suitable for use in hand-held or backpack-type portable work equipment, such as chain saws, brush cutters, and pest control machines. It is widely known that it is used in blowers, etc. These portable working machines are particularly required to be compact and lightweight, and as engines have recently become faster and more powerful, there is also a trend to increase the diameter of the ventilator to accommodate the high output of carburetors. In the early stages of acceleration, the negative pressure in the ventilator is low and the suction of fuel from the nozzle is delayed, resulting in more problems than poor acceleration.

As a solution to this problem, there is an acceleration pump that introduces and uses the pulsating pressure in the crank chamber of a two-stroke engine only when the throttle valve is fully open through a horizontal through hole provided in the throttle shaft of the butterfly throttle valve. There are some models that introduce this pulsating pressure into the air chamber of a diaphragm-type accelerator pump installed in the diaphragm, and forcibly inject accelerating fuel from the high-speed fuel system through the pump action of the diaphragm. It can be installed only on the outer periphery of the vessel, and the fuel passage is long and has many twists and turns, slowing down the fuel flow and causing acceleration.
In particular, repeated acceleration tends to be defective. Also, since it is located on the outer periphery of the carburetor, it is affected by external heat and has a defect that tends to cause problems in acceleration performance due to the generation of fuel paper.

In order to solve this problem, the present invention introduces the pulsating pressure in the crank chamber of a two-stroke engine only when the throttle valve is fully opened through a horizontal through hole provided in the butterfly-shaped throttle valve shaft, and uses a stable material such as rubber built into the carburetor. Pressure is applied to the outer periphery of the formed long bag-shaped accelerator pump 25 to push out the fuel inside.
This is a long bag type accelerator pump with a built-in butterfly throttle type diaphragm type carburetor that forcibly injects fuel between the fuel metering needle valve and back bleed prevention valve of the high speed fuel system.

To explain the drawings, FIGS. 1 and 2 are longitudinal cross-sectional views for explaining the functions of an embodiment of the carburetor of the present invention. FIG. 1 shows the throttle valve when the throttle valve is fully opened during acceleration, and FIG. 2 shows the state when the throttle valve is idling. FIG. 3 is an explanatory diagram of the operation of the essential parts of the accelerator pump of the present invention.

In the figure, 1 is the diaphragm type carburetor body, 2 is the fuel pump cover, 3 is the pulsating pressure inlet for operating the fuel pump from the engine crank chamber (not shown), 4 is the fuel pump diaphragm, 5 is the fuel inlet, Reference numeral 6 denotes a fuel filter steel, which is sucked and discharged from a fuel tank (not shown) through a fuel inlet 5 during operation, and is fed under pressure to an inflow valve 7.

8 is a metering diaphragm, 9 is a female ring lever shaft, 10 is a metering lever, 11 is a metering lever spring, and 12 is a metering cover that communicates with the outside air. During operation, a constant negative pressure is maintained in the metering chamber 13 inside the metering diaphragm 8 by the metering diaphragm function.

A ventilator hole 14 and a throttle hole 15 pass through the carburetor body 1 from the front to the rear. A butterfly-shaped throttle valve 17 is fixed to the throttle valve shaft 16 which is orthogonal to the throttle hole 15.
The throttle valve hole 15 is opened and closed by driving operation.

A plurality of low-speed fuel nozzles are opened in the throttle valve hole 15 in accordance with the idling opening degree of the butterfly-shaped throttle valve 17, and fuel metered by the low-speed fuel metering needle valve 19 is spouted out, allowing idling operation and low-speed operation to be performed. I can do it.

A high-speed fuel nozzle 20 opens in the ventilate 14, and a back bleed prevention valve 21 is provided just in front of the high-speed fuel nozzle 20. During idling, the atmosphere inside the ventilate flows into the metering chamber 13 from the high-speed fuel nozzle 20.
In order to prevent the back bleed phenomenon peculiar to diaphragm type carburetors, in which the backflow flows back into the low-speed fuel nozzle 18 and causes idling to malfunction and stop, the back bleed prevention valve 21 uses a back pressure difference to prevent back flow during idling. It becomes a valve and is closed.

During high-speed operation, the suction negative pressure of the high-speed fuel nozzle 20 is high, so the back bleed prevention valve 21 opens and fuel metered by the high-speed fuel metering needle valve 22 is jetted out, allowing high-speed operation.

In the conventionally known butterfly throttle valve diaphragm carburetor constructed in this manner, the present invention provides a pulsating pressure passage 23 in the engine crank chamber as shown in FIG. A lateral through-hole 24 provided in the throttle valve shaft 16 communicates with an outer circumferential air chamber 26 of a long-bag accelerator pump 25 made of a stable material such as rubber, and the long-bag accelerator pump 2 is activated by the crank chamber pulsating pressure.
The internal fuel of No. 5 is forced out between the back bleed prevention valve 21 and the high speed fuel metering needle valve 22 and is forcibly injected from the high speed fuel injection port 20 to improve poor acceleration due to a delay in fuel suction during full throttle acceleration.

As shown in FIG. 2, during idling, the engine crank chamber pulsating pressure passage 23 is blocked by the outer periphery of the throttle valve shaft 16 and the operation of the long bag accelerator pump 25 is stopped. Defects are prevented.

FIG. 3 shows details around the long bag accelerator pump 25. The pulsating positive pressure reaching the outer air chamber 26 from the pulsating pressure passage 23 of the engine crank chamber causes the long bag accelerator pump 25 to move as shown by the dotted line in the figure. The compressed internal fuel is pushed out and acceleration lag is improved. 27
is the fixed leakage prevention ring of the long bag type accelerator pump 25,
28 is a cover for the outer peripheral air chamber 26.

Since the accelerator pump of the present invention is configured in such a small and long bag shape, it can be easily built into the carburetor main body 1, and it is unlikely to cause an increase in external size, weight, or cost. In addition, since it can be located close to the high-speed fuel nozzle 20, the acceleration fuel passage is short and simple, and the acceleration pump is also made of a material with strong stability such as rubber, so that after the acceleration fuel is discharged due to pulsating positive pressure. It quickly returns to its original shape due to pulsating negative pressure, and since the back bleed prevention valve 21 closes, only the fuel metered by the high-speed fuel metering needle valve 22 can be sucked in without drawing in air, improving acceleration lag. , especially effective in improving repetitive acceleration.

Furthermore, since the carburetor is built-in, there is little heat rise due to the latent heat of vaporization of the fuel, and vapor failure of the acceleration fuel system due to heat is unlikely to occur.It is simple and low cost, yet provides an effective and reliable acceleration function, making it suitable for industrial use. It is highly effective.

[Brief explanation of the drawing]

FIGS. 1 and 2 are functional explanatory longitudinal cross-sectional views of an embodiment of the carburetor of the present invention, with FIG. 1 showing the throttle valve fully opened when accelerating, and FIG. 2 showing the throttle valve opening at idling. FIG. 3 is an explanatory diagram of the operation of the essential parts of the accelerator pump of the present invention.

Claims (1)

[Claims] 1 A horizontal through hole 24 provided in the throttle valve shaft 16 of the butterfly throttle valve 17 for controlling the pulsating pressure in the crank chamber of a 2-cycle engine.
is introduced only when the throttle valve is fully open, and pressurizes the outer circumference of the long bag accelerator pump 25 made of a stable material such as rubber built into the carburetor, and the fuel inside the pump is transferred to the high speed fuel metering needle valve 22 and the back bleed prevention valve. This is an acceleration pump of a butterfly-shaped throttle valve type diaphragm type vaporizer that is configured to forcefully emit air between the 21 and 21.