JPS6329866Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an accelerator pump with a built-in diaphragm type carburetor that introduces and utilizes the pulsating pressure in the crank chamber of a two-cycle engine only when the throttle valve is fully opened, and was filed by the same applicant on October 3, 1982. A part of the patent application filed on the 1st relates to the improvement of the throttle valve shaft.

The 2-cycle engine has a simple structure, is lightweight, and can be operated in all directions.It is equipped with a diaphragm carburetor that can also be operated in all directions, and can be used as a hand-held or backpack-type portable working machine, such as a chain saw, etc.
It is widely known that it is used in brush cutters, pest control machines, blowers, etc.

These types of work equipment are particularly required to be compact and lightweight, and engines are becoming increasingly high-speed and high-output in recent years, and the carburetor also tends to have a larger diameter ventilate in order to be able to handle high output. Problems such as low negative pressure in the ventilate, slowing down the suction of fuel from the nozzle, and poor acceleration are becoming more common.

In order to solve this problem, the patent application filed by the same applicant on October 3, 1982 (acceleration pump for diaphragm type carburetor) uses the pulsating pressure in the two-stroke engine crank chamber to be provided on the throttle shaft of the butterfly-shaped throttle valve. Through the side through hole, the fuel is introduced only when the throttle valve is fully open, and pressurizes the outer periphery of the long bag-shaped accelerator pump made of resilient material such as rubber built into the carburetor, and the fuel inside the pump is connected to the high-speed fuel metering needle valve to prevent back bleed. We were able to eliminate poor acceleration by using an acceleration pump with a butterfly throttle type diaphragm type carburetor that forcedly discharges air between the valve and the valve.

However, in order to ensure smooth operation, a gap of about 0.05 to 0.1 mm is required between the throttle valve shaft and the shaft hole of the carburetor body, but pulsating pressure leaks through this gap during idling, resulting in long bags. It has been discovered that because the accelerator pump operates minutely, a so-called nozzle drip phenomenon occurs in which fuel drips from the high-speed fuel nozzle, resulting in an overly rich mixture during idling, resulting in poor idling.

In order to solve this problem, the present invention provides a communication groove in the throttle valve shaft between the outer circumference of the accelerator pump and the atmospheric pressure in front of the throttle valve during idling to prevent the inflow of pulsating pressure and prevent the nozzle drip phenomenon caused by minute movements of the accelerator pump. The aim is to normalize idling.

To explain the drawings, FIGS. 1 and 2 are vertical cross-sectional views to explain the functions of the embodiment of the carburetor of the present invention. FIG. 1 shows the throttle valve when the throttle valve is fully opened and accelerated, and FIG. 2 shows the state when the throttle valve is idling. FIG. 3 is a sectional view taken along the AA arrow of the main part of the throttle valve shaft 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 from the engine crank chamber (not shown), 4 is the pump diaphragm, 5 is the fuel inlet, and 6 is the fuel steel. During operation, the fuel inlet 5 is connected to the fuel tank (not shown).
The liquid is sucked and discharged through the inflow valve 7.

8 is a metering diaphragm, 9 is a metering 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. A constant negative pressure is maintained in the metering chamber 13 inside the metering diaphragm 8 by the function of the metering diaphragm during operation.

The carburetor body 1 has a ventilate 14 and a throttle valve hole 1.
5 penetrates the front and back. A butterfly-shaped throttle valve 17 is attached to a throttle valve shaft 16 that is orthogonal to the throttle hole 15, and opens and closes the throttle valve hole 15 by operation.

A plurality of low-speed fuel nozzles 18 are opened in the throttle valve hole 15 corresponding to 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, allowing idling operation and low-speed operation.

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, atmospheric pressure air is supplied from the high-speed fuel nozzle 20 to the metering chamber 1 with a constant negative pressure.
In order to prevent the so-called back bleed phenomenon, which occurs when the fuel flows backward into the fuel nozzle 3 and flows into the low-speed fuel nozzle 18, resulting in an overly lean mixture during idling and a stop, the back bleed prevention valve 21 is a check valve due to the differential pressure between the front and rear during idling. It will be closed.

During high-speed operation, the high-speed fuel nozzle 2 is
0 suction negative pressure is high, back bleed prevention valve 21
is opened and fuel metered by the high-speed fuel metering needle valve 22 is spouted out, allowing high-speed operation.

The pulsating pressure passage 23 of the engine crank chamber is connected to the outer peripheral air chamber 26 of the long bag-shaped accelerator pump 25 made of a resilient material such as rubber, through the horizontal through hole 24 provided in the throttle valve shaft 16 when the butterfly throttle valve 17 is fully opened and accelerated. The internal fuel of the long bag accelerator pump 25 is forced out between the back bleed prevention valve 21 and the high speed fuel metering needle valve 22 by the pulsating pressure in the crank chamber, and is forcibly injected from the high speed fuel injection port 20, thereby sucking out fuel during full throttle acceleration. Improves poor acceleration due to lag.

During idling, the pulsating pressure passage 23 in the engine crank chamber is blocked by the outer periphery of the throttle valve shaft 16, as shown in FIG. In order to completely eliminate the problem of the so-called nozzle drip phenomenon in which the accelerator pump 25 operates minutely and fuel drips out from the high-speed fuel nozzle 20, the pressure between the pulsating pressure passage 23 and the atmospheric pressure in front of the butterfly throttle valve 17 is reduced during idling. Connect the communication groove 27 to the throttle valve shaft 1.
By completely stopping the operation of the long bag type accelerator pump 25 provided on the axial outer circumference of the pump 6, the idling problem caused by the nozzle drip phenomenon can be completely eliminated.

This invention was created in 1988 by the same applicant.
A part of the patent application filed on October 3rd improves the throttle valve shaft, that is, by providing a communication groove 27 on the throttle valve shaft 16 with simple and low-cost processing, the function of the long bag accelerator pump 25 when the throttle valve is fully opened is improved. The nozzle drip caused by the minute operation of the long bag accelerator pump 25 during idling is completely prevented without interfering with the operation, and normal idling and low speed operation are possible, which is highly effective industrially.

[Brief explanation of drawings]

1 and 2 are vertical cross-sectional views to explain the functions of the embodiment of the carburetor of the present invention, in which FIG. 1 shows the throttle valve fully opened when accelerating, and FIG. 2 shows the throttle valve when it is idling. FIG. 3 is a sectional view taken along arrow AA of the main part of the throttle valve shaft of the present invention.

Claims (1)

[Scope of utility model registration request] The pulsating pressure in the 2-cycle engine crank chamber is introduced into the lateral through hole 24 provided in the throttle shaft 16 of the butterfly throttle valve 17 only when the throttle valve is fully open, and is built into the carburetor using a long bag made of a stable material such as rubber. Type acceleration pump 25
The fuel inside the pump is forcibly injected between the high-speed fuel metering needle valve 22 and the back-bleed prevention valve 21, and when the throttle valve is idling, the butterfly-shaped throttle valve is This accelerator pump is a butterfly-shaped throttle valve type diaphragm type vaporizer, which communicates the atmospheric pressure at the front of 17 with the outer periphery of a long-bag type accelerator pump 25.