JP2002039016A - Rotary throttle valve type carburettor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make fuel smoothly flow from a constant pressure chamber to a fuel supply pipe even when an engine is running by continuous accelerating and decelerating operations. SOLUTION: A throttle valve 25 having a throttle hole 26 is rotateably and elevateably inserted into a valve chamber 24 arranged so as to be perpendicular to an intake passage 28 of a carburetor body 21. A needle 2 supported by the throttle valve 25 is inserted into a fuel supply pipe 3 projecting from a constant pressure fuel chamber 43 located at a bottom portion of the carburetor body 21 toward the throttle hole 26. An intake air volume of the intake passage 28 is adjusted by turning the throttle valve 25. Fuel quantity from the fuel supply pipe 3 is adjusted by vertically moving the throttle valve 25. An accelerating pump 31 is structured by inserting a plunger 32 into a cylinder 29 arranged perpendicular to the valve chamber 24 of the carburetor body 21. The plunger 32 engages with a cam groove 61 on an external peripheral surface of the throttle valve 25 by a spring. A fuel inlet and outlet fuel inlet and outlet port of the cylinder 29 is communicated with a passage connecting the constant pressure fuel chamber 43 to a fuel injecting hole 3a at a downstream position from a check valve 4 and at an upstream position from a fuel jet 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for an internal combustion engine mounted on a portable working machine such as a brush cutter, and more particularly to a rotary throttle valve carburetor provided with an acceleration pump.

[0002]

2. Description of the Related Art In a conventional rotary throttle valve carburetor, the fuel inlet and outlet of an acceleration pump are located downstream of a fuel jet of a fuel supply pipe. The engine may stop during the continuous acceleration / deceleration operation.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a rotary throttle valve type vaporizer in which fuel flows smoothly from a constant pressure fuel chamber to a fuel supply pipe during continuous acceleration / deceleration operation of an engine. To provide equipment.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, a throttle valve having a throttle hole is rotatably and vertically movable in a cylindrical valve chamber orthogonal to an intake passage of a carburetor body. A needle supported by a throttle valve is fitted to a fuel supply pipe projecting from the constant-pressure fuel chamber at the bottom of the carburetor body to the throttle hole, and the amount of intake air in the intake path is adjusted by turning the throttle valve. In a rotary throttle valve type carburetor, which adjusts the amount of fuel from a fuel supply pipe by raising and lowering a throttle valve, a plunger is fitted to a cylinder orthogonal to the valve chamber provided in the carburetor body to constitute an acceleration pump. The plunger is engaged by a spring with a cam groove provided on the outer peripheral surface of the throttle valve, and the fuel inlet / outlet of the cylinder is connected to the fuel jet downstream of the check valve in the passage connecting the constant pressure fuel chamber and the fuel injection hole. Also connected to the passage on the upstream side And butterflies.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a rotary throttle valve type carburetor used for a small internal combustion engine, the fuel inlet / outlet of an acceleration pump is connected to a passage portion between a constant-pressure fuel chamber and a fuel jet, so that the idle position of the throttle valve is reduced. The fuel flow regulation from the first position to the fully open position is stabilized, and the setting of the fuel flow of the acceleration pump becomes easy.

[0006] The flow of fuel from the constant pressure fuel chamber to the fuel supply pipe becomes smooth, and the fuel flow does not interfere with the operation of the acceleration pump.

[0007]

1 is a front sectional view of a rotary throttle valve carburetor according to the present invention, and FIG. 2 is a plan sectional view of the rotary throttle valve carburetor. Rotary throttle valve type carburetor is carburetor body 2
One end is abutted to the intake port of the engine via a heat insulating pipe (not shown), and is fixed to the wall of the engine by bolts passing through a pair of left and right bolt insertion holes 23. The main body 21 is coupled with a lid 19 having a cylindrical portion 17 that supports an eccentric cam as a starting fuel increasing mechanism at an upper portion by a bolt 14,
A fuel pump 38, a constant-pressure fuel supply mechanism 50, and a suction pump 54 are provided at a lower portion. The main body 21 includes a cylindrical intake passage 28 (FIG. 2) extending perpendicularly to the plane of FIG. 1 and a vertical valve chamber 24 orthogonal to the intake passage 28. A throttle valve 25 is inserted into the valve chamber 24 so as to be rotatable and vertically movable. The cylindrical throttle valve 25 has a throttle hole 26 penetrating in the lateral direction.
The throttle valve lever 16 is connected to the upper end portion through the closing lid 19 through the ring 20. A seal member 18 is mounted between the shaft 15 and the upper surface of the lid 19.

A return spring 22 surrounding the shaft 15 is interposed between the lid 19 and the throttle valve 25, and has one end locked to the lid 19 and the other end locked to the throttle valve 25. Hollow shaft 15
Is screwed into the boss of the needle 2 and closed by the cap 10. The fuel jet 37 and the fuel supply pipe 3 are fitted and fixed to the bottom wall of the valve chamber 24. The needle 2 is fitted into the fuel supply pipe 3, and the opening of the fuel injection hole 3a is adjusted by raising and lowering the throttle valve 25.

A fuel pump 38 has a gasket 40a and an intermediate wall 42 connected to a lower surface of a main body 21 with a membrane 40 interposed therebetween, and a pulsating pressure chamber 39 for introducing pulsating pressure of a crank chamber of a two-stroke engine above the membrane 40. , A pump chamber 41 is defined below the membrane 40. The constant-pressure fuel supply mechanism 50 includes an intermediate wall 42.
The intermediate wall 51 is joined to the lower surface of the
A constant pressure fuel chamber 43 is provided above the air chamber 46, and an atmosphere chamber 46 is provided below the membrane 45.
Are each partitioned. A support shaft 8 is provided on the wall of the constant-pressure fuel chamber 43.
The lever 7 rotatably supported by the lever 7 is driven by the force of a spring 5 interposed between the lever 7 and the top wall of the constant-pressure fuel chamber 43.
The left end is abutted on the projecting piece at the center of the membrane 45, and the right end is engaged with the inflow valve 6.

When the membrane 40 vibrates up and down due to the pulsating pressure of the pulsating pressure chamber 39, fuel in a fuel tank (not shown) is sucked into the pump chamber 41 via a suction valve (not shown). Pump room 4
The fuel No. 1 is discharged to the constant pressure fuel chamber 43 via a discharge valve (not shown), a passage of the main body 21 and the inflow valve 6. When the constant pressure fuel chamber 43 is filled with fuel, the membrane 45 is pushed down, and the inflow valve 6 is closed as the lever 7 rotates counterclockwise.
Conversely, when the fuel in the constant pressure fuel chamber 43 becomes low, the membrane 45 is pushed up by the intake negative pressure of the constant pressure fuel chamber 43 and the atmospheric pressure of the atmosphere chamber 46, and the membrane 45 moves clockwise against the force of the spring 5 of the lever 7. The inflow valve 6 opens with the rotation. The fuel in the constant-pressure fuel chamber 43 is supplied to the check valve 4 made of a thin elastic disc, the fuel jet 37,
The air is sucked into the throttle hole 26 through the fuel supply pipe 3 and the fuel injection hole 3a, and is supplied to the engine while being mixed with the air flowing through the intake passage 28.

A suction pump 54 for replenishing fuel to the constant-pressure fuel chamber 43 before the start of the engine is provided.
To form a pump chamber 57, and a composite valve 56 integrally provided with a mushroom-shaped suction valve and a discharge valve is connected to the center wall of the pump chamber 57. When the spoiler 55 is crushed, the fuel vapor or air in the pump chamber 57 pushes open the flat crushed pipe portion of the axial center of the composite valve 56 and flows out to the passage 58, and passes through the fuel discharge pipe 59 through the fuel tank 59. Return to When the spoiler 55 is released, the pump chamber 57 becomes negative pressure, and the fuel vapor and air in the constant pressure fuel chamber 43 are pushed through the passage (not shown) to open the peripheral portion of the composite valve 56 and are sucked into the pump chamber 57.

The throttle valve lever 16 has its lower cam surface brought into contact with a follower formed of a ball supported on the lid 19 by the force of a return spring 22. Therefore, the throttle valve lever 16
Is rotated counterclockwise from the idle position a shown in FIG. 2, the throttle valve lever 16, the throttle valve 25, and the needle 2 are pushed up together by the cam mechanism, and the intake passage 2 of the throttle hole 26 is opened.
8 and the opening of the fuel injection hole 3a increases. The configuration described above is substantially the same as that of a conventional rotary throttle valve carburetor.

As shown in FIG. 2, the present invention forms a cam groove 61 on the peripheral wall at the lower end of the throttle valve 25, forms a cylinder 29 on the wall of the carburetor body 21, and attaches a plunger 32 to the cylinder 29. The acceleration pump 31 is fitted to the cam groove 61 and the rod projecting from the plunger 32 is
Are biased and engaged by the force of. The spring 33 is interposed between the plunger 32 and the stopper 34 fitted to the outer end of the cylinder 29. The fuel inlet / outlet of the cylinder 29 is connected to the passage 35.
a, through an opening provided in the gasket 40a, is connected to a portion of the passage connecting the constant pressure fuel chamber 43 and the fuel injection hole 3a downstream of the check valve 4 and upstream of the fuel jet 37.

When the throttle valve 25 in FIG. 2 is at the idle position a, the end of the plunger 32 projects into the cam groove 61. When the throttle valve 25 is rotated by the rotation angle α to the fully open position b during acceleration of the engine, the plunger 32 is pushed back by the outer peripheral surface of the throttle valve 25 against the force of the spring 33, and the spring 3
The fuel of the cylinder 29 containing the fuel tank 3 passes through the passage 35a,
The fuel is fed between the check valve 4 and the fuel jet 37 in the passage connecting the constant-pressure fuel chamber 43 and the fuel injection hole 3a.
7. The fuel is supplied to the throttle hole 26 of the throttle valve 25 via the fuel supply pipe 3 and the fuel injection hole 3a to accelerate the engine smoothly. The check valve 4 prevents the fuel from the acceleration pump 31 from returning to the constant-pressure fuel chamber 43.

Since the fuel inlet / outlet of the cylinder 29 is connected to the upstream side of the fuel jet 37, the fuel in the cylinder 29 of the acceleration pump 31 is sucked into the fuel injection hole 3a by the high intake negative pressure during high-speed operation of the engine. There is no such thing,
The fuel flow rate flowing through the fuel supply pipe 3 is stabilized, and the engine does not stop during the continuous acceleration / deceleration operation of the engine. When the throttle valve 25 is returned to the vicinity of the idle position, the plunger 32 is pushed back by the force of the spring 33, and the constant pressure fuel chamber 4
The fuel No. 3 is sucked into the cylinder 29 via the check valve 4 and the passage 35a.

In the embodiment shown in FIG. 3, the fuel inlet / outlet of the cylinder 29 is connected to a passage connecting the constant pressure fuel chamber 43 and the check valve 4. A throttle 30 is provided in a passage connecting the constant pressure fuel chamber 43 and the check valve 4. Since the fuel inlet / outlet of the cylinder 29 is connected to the upstream side of the fuel jet 37, the flow rate of fuel flowing through the fuel supply pipe 3 becomes stable even at high speed operation of the engine, so that the engine stops during continuous acceleration / deceleration operation of the engine. Nothing happens.

[0017]

According to the present invention, as described above, a throttle valve having a throttle hole is rotatably and vertically movable fitted in a cylindrical valve chamber orthogonal to an intake passage of a carburetor main body. A needle supported by a throttle valve is fitted into a fuel supply pipe projecting from the constant-pressure fuel chamber at the bottom of the throttle valve into the throttle hole, and the amount of intake air in the intake passage is adjusted by turning the throttle valve. In a rotary throttle valve type carburetor for adjusting the amount of fuel from a supply pipe, a plunger is fitted in a cylinder orthogonal to the valve chamber provided in the carburetor body to constitute an acceleration pump, and the plunger is throttled by a spring. And the fuel inlet / outlet of the cylinder was connected to a passage portion downstream of the check valve and upstream of the fuel jet of the passage connecting the constant pressure fuel chamber and the fuel injection hole. The idle position of the throttle valve Flow rate regulation to the fully open position is stable,
Even if the engine is continuously accelerated or decelerated, the engine does not stop.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a rotary throttle valve carburetor according to the present invention.

FIG. 2 is a plan sectional view of the rotary throttle valve type carburetor.

FIG. 3 is a front sectional view of a rotary throttle valve carburetor according to a partially modified embodiment of the present invention.

[Explanation of symbols]

2: Needle 3: Fuel supply pipe 3a: Fuel injection hole 4:
Check valve 5: Spring 6: Inflow valve 7: Lever 15: Shaft section 16: Throttle valve lever 17: Cylindrical section 19: Lid 2
1: vaporizer main body 22: return spring 23: bolt insertion hole 24: valve chamber 25: throttle valve 26: throttle hole 28: intake path 29: cylinder 30: throttle 31: acceleration pump 32: plunger 33: spring 34: plug 35 : Passage 35 a: Passage 37: Fuel jet 38: Fuel pump 39: Pulsating pressure chamber 40: Membrane 40 a: Gasket 41: Pump chamber 42: Intermediate wall 43: Constant pressure fuel chamber 45: Membrane 46: Atmospheric chamber 50:
Constant pressure fuel supply mechanism 51: Intermediate wall body 53: Holding plate 5
4: Suction pump 55: Spoid 56: Composite valve 5
7: Pump chamber 59: Fuel discharge pipe 61: Cam groove

Claims (3)

[Claims] 1. A throttle valve having a throttle hole is rotatably and vertically movablely fitted in a cylindrical valve chamber orthogonal to an intake passage of a carburetor body, and the throttle valve is provided from a constant pressure fuel chamber at a bottom of the carburetor body. A needle supported by a throttle valve is fitted into a fuel supply pipe projecting into the throttle hole, and the amount of intake air in the intake path is adjusted by turning the throttle valve.
In a rotary throttle valve type carburetor for adjusting the amount of fuel from a fuel supply pipe by raising and lowering a throttle valve, an acceleration pump is formed by fitting a plunger into a cylinder orthogonal to the valve chamber provided in a carburetor body, The plunger is engaged by a spring with a cam groove provided on the outer peripheral surface of the throttle valve, and the fuel inlet / outlet of the cylinder is located downstream of the check valve and upstream of the fuel jet in a passage connecting the constant pressure fuel chamber and the fuel injection hole. A rotary throttle valve type carburetor connected to a passage portion of the rotary throttle valve. 2. The fuel inlet / outlet of the cylinder is connected to a passage portion connecting the constant pressure fuel chamber and the check valve.
A rotary throttle valve type carburetor according to the above. 3. A rotary throttle valve carburetor according to claim 2, wherein a throttle is provided in a passage portion connecting said constant pressure fuel chamber and said check valve.