JPH0472063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to agricultural or horticultural machinery,
This invention relates to an accelerator in a membrane carburetor used in small general-purpose engines such as small vehicles.

The type of carburetor that opens and closes the fuel valve according to the pressure received by the membrane to maintain almost constant fuel pressure in the fuel chamber is significantly smaller and has a simpler structure than the float type carburetor for automobile engines. Not only that, it has the feature that it can be used in any position.

By the way, such membrane type carburetors usually have a low-speed system in addition to the main system in their fuel system, but rotor-type carburetors only need to be able to supply fuel that allows the engine to operate from low to high speeds. Normally, the engine is not equipped with an acceleration system due to lack of space, etc. Therefore, when the throttle valve is opened, the exhaust valve is designed to cope with the negative pressure that increases as the amount of intake air increases. The disadvantage is that the engine speed does not increase as much as expected during sudden acceleration or under load, since only a small amount of fuel is sucked out of the main nozzle.

Therefore, like a carburetor for an automobile engine, an interlocking means for the accelerator pump and the throttle valve is provided on the part of the throttle valve shaft that protrudes outside the body, and an accelerator with a structure in which the accelerator pump is placed protruding outside the body is installed in a membrane. A vaporizer is disclosed in US Pat. No. 3,404,872.

However, when the accelerator is installed outside the carburetor body, it becomes larger, so it is often used in machines where space is extremely limited, such as lawn mowers and chainsaws, so that it does not interfere with other engine parts. Not only may it not be possible to incorporate the engine into the engine, but external dust may adhere to it and infiltrate it, causing breakdowns and wear.Furthermore, the interposition of a moving means reduces dimensional accuracy, leading to inaccurate acceleration fuel and improving engine performance. I am worried that I will not be able to achieve my goals.

The present invention solves the above-mentioned problems that occur when a membrane type carburetor is equipped with an accelerator, and provides an accelerator that is compact in shape, prevents dust from entering and adhering, and can accurately supply accelerating fuel. It was invented with the purpose of providing.

That is, the present invention includes a cam configured by a notch surface of the throttle valve shaft located inside the body of the carburetor body and a shaft circumferential surface, and a cam that is perpendicular to the throttle valve shaft and located inside the body. Fuel is delivered to the cylinder chamber from the formed cylinder chamber, a piston that contacts a cam fitted in the cylinder chamber and reciprocates to follow the rotation of the throttle valve shaft, and a fuel chamber that maintains fuel pressure almost constant. and an acceleration fuel passage formed inside the fuselage for delivering the fuel in the cylinder chamber to the main fuel passage leading from the fuel chamber to the main nozzle port. With this configuration, the above object is achieved. Ru.

Next, a specific example of the present invention will be explained based on the drawings.A fuel pump 3 is attached to one side of a body 2 having an intake passage 1, and a pressure regulating part 4 is attached to the opposite side.

The fuel pump 3 has a pump chamber 8 into which fuel is fed from a fuel inlet 5 connected to a fuel tank (not shown) through an inlet check valve 6 and an inlet passage 7, and a pulse chamber 9 into which the pulsating pressure of the engine crankcase is introduced.
and a membrane 10 that partitions these two chambers 8 and 9, and the membrane 10 is pressed and fixed to the side surface of the body 2 by a side cover 11. When the engine is operated, the pulsating pressure generated in the crankcase is introduced into the pulse chamber 9, causing the membrane 10 to reciprocate, opening the inlet check valve 6, and pressurizing the fuel sucked into the pump chamber 8 to pass the outlet passage. Open the outlet check valve 13 from 12 to the delivery passage 1
4. The fuel is fed into the fuel chamber 16 of the pressure regulating section 4 via the fuel valve 15.

The pressure regulating part 4 contacts and engages the fuel chamber 16, the atmospheric chamber 17 open to the atmosphere, a membrane 18 that partitions these two chambers 16 and 17, and the center of this membrane 18, and is connected to the fuel chamber 16. The fuel valve 15 is brought into contact with and engaged with an arm 20 which is built in and is rotatably supported by a support shaft 19, and a spring 21 acting in a direction to open the fuel valve 15 is applied to the arm 20, The membrane 18 is fixed to the body 2 by side covers 22. fuel chamber 1
6 is metered by the low-speed jet 23, passes through the low-speed fuel passage 24, and is sucked out into the intake passage 1 from the slow port 25 that opens near the side of the throttle valve 26 in the closed position. a main nozzle port 29 metered by a main jet 27 with a valve 40 and opening into the bench lily 30 through a main fuel passage 41;
The air is sucked out into the air intake path 1. The main nozzle chamber 28 and the main nozzle port 29 are formed into one nozzle body 31, and are provided with a check valve 32 that prevents air from flowing back into the fuel chamber 16 during idling.

When the fuel in the fuel chamber 16 decreases, the negative pressure increases, so the membrane 18 is drawn toward the fuel chamber 16 and the arm 20
The membrane 18 is bent toward the atmospheric chamber 17 by the fuel pressure, and the fuel valve 15 is closed. The valve is used to maintain the fuel pressure in the fuel chamber 16 almost constant, which is the same as in a conventional membrane carburetor.

The body 2 and the two side covers 11 and 22 constitute a carburetor main body 33, and a throttle valve shaft 34 to which the throttle valve 26 is fixed is rotatably supported by the body 2. A notch is formed at the shaft end of this throttle valve shaft 34, and this notch surface 35a and the arc-shaped shaft peripheral surface 35
b constitutes a cam 35, and is a cylinder chamber 3 formed inside the body 2 so as to be orthogonal to the throttle valve shaft 34.
6 is fitted with a piston 37 and a spring 39
The piston rod 38 protruding from the piston 37 is kept in constant contact with the cam 35 by the action of the spring 39. A reciprocating passage 43 branched from the downstream side of the main jet 27 of the main fuel passage 41 is opened in contact with the cylinder chamber 36, and the main fuel passage 41 and the reciprocating passage 43 are connected to the acceleration fuel passage 44.
These are formed inside the fuselage 2.

In the accelerator having the above configuration, when the throttle valve 26 is in the closed position, the piston rod 38 is in contact with the substantially horizontal notch surface 35a of the cam 35 (the second
figure). When the throttle valve 26 is opened, the piston 37 is pushed by the notch surface 35a and the shaft peripheral surface 35b, and the fuel in the cylinder chamber 36 is force-fed to the main nozzle chamber 28 via the reciprocating path 43 and the main fuel passage 43, and The air is ejected from the nozzle port 29 to the intake passage 1, and the throttle valve 2
6 is fully opened, the piston 37 reaches its maximum stroke (FIG. 3). When the throttle valve 26 closes, the piston 37 follows and moves, so that the fuel in the fuel chamber 16 is fed into the cylinder chamber 36 through the main fuel passage 41 and the reciprocating path 43 in preparation for the next acceleration operation.

In addition, due to the arrangement of each component, a part of the carburetor main body 33 may be molded to bulge out to form the cylinder chamber 36 therein.

As described above, according to the present invention, a cylinder chamber is provided inside the body of the carburetor body and a piston is fitted therein,
Accelerating fuel is generated by making the piston follow a cam made up of a notch surface located inside the body of the throttle valve shaft and the circumferential surface of the shaft, and reciprocating the piston as the throttle valve opens and closes. Since the air is injected into the intake passage during acceleration and into the cylinder chamber during deceleration, the accelerating device such as the cam, piston, and cylinder chamber is completely built into the fuselage, resulting in a compact shape that requires extremely limited space. Not only can it be incorporated into other types of machinery without interfering with other engine parts, but since there is no intrusion or adhesion of external dust, malfunctions or wear caused by dust can be eliminated. In addition, since the throttle valve shaft itself is used as a cam to bring the piston into contact with the piston, there is no drop in dimensional accuracy due to intervening separate parts such as levers, and accelerating fuel is accurately supplied in conjunction with the opening of the throttle valve, allowing for rapid acceleration. The engine rotation speed can be increased as expected during acceleration when a load is applied, and the number of parts is small, which is advantageous in terms of manufacturing and cost, and is useful for weight reduction.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a specific example of the present invention, FIG.
FIG. 3 is a partial side sectional view illustrating the operation of the accelerator. DESCRIPTION OF SYMBOLS 1...Intake path, 3...Fuel pump, 4...Pressure adjustment part, 16...Fuel chamber, 29...Main nozzle port, 34
... Throttle valve shaft, 35 ... Cam, 36 ... Cylinder chamber, 37 ... Piston, 39 ... Spring, 41 ...
Main fuel passage, 43... Reciprocating path, 44... Acceleration fuel passage.

Claims (1)

[Claims] 1. A cam formed by a notch surface of the throttle valve shaft located inside the body of the carburetor body and a shaft peripheral surface, and a cam formed inside the body so as to be perpendicular to the throttle valve shaft. A cylinder chamber, a piston that is fitted into the cylinder chamber and moves back and forth following the rotation of the throttle valve shaft in contact with the cam, and fuel is fed into the cylinder chamber from the fuel chamber that maintains fuel pressure almost constant. and an acceleration fuel passage formed inside the body for delivering the fuel in the cylinder chamber to the main fuel passage leading from the fuel chamber to the main nozzle port. .