JPH1182174A - Rotary throttle valve type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent operability with hardly any restrictions on installation. SOLUTION: A manual starting pump 35 for introducing start-up fuel into a constant fuel chamber 22, and a manual fuel regulating needle valve 28 for regulating fuel fed from the constant fuel chamber 22 to a fuel nozzle 12 are arranged side by side at one side face part of a carburetor body 1 and manually operated from one direction while lowering the whole height of a carburetor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a rotary throttle valve carburetor for supplying fuel to a general-purpose two-stroke engine, and more particularly to a rotary throttle valve which has excellent operability and is less restricted in installation. The present invention relates to a vaporizer.

[0002]

2. Description of the Related Art Many general-purpose two-stroke engines used as driving sources for portable work machines for agriculture and forestry, small vehicles, and the like generally use a fuel pump having a diaphragm displaced by pulse pressure of an engine crankcase. A diaphragm-type constant fuel chamber that adjusts the supplied fuel to a constant pressure and sends it to the intake passage, a manual start pump that introduces the starting fuel into the constant fuel chamber, and an opening from the constant fuel chamber to the throttle hole. A manual fuel regulating needle valve for regulating the flow rate of fuel sent to the fuel nozzle.

As one type of the vaporizer, as described in Japanese Patent Application Laid-Open No. 58-101253, a cylindrical throttle valve having a throttle hole and a measuring needle is provided on the vaporizer main body. By disposing the throttle valve perpendicular to the intake passage and moving this throttle valve in the direction of its central axis while rotating according to the accelerator operation, the degree of overlap of the throttle passage with the intake passage is changed to control the air flow rate. A rotary throttle valve carburetor having a structure in which the flow rate of fuel is controlled by changing the insertion depth of a measuring needle into a fuel nozzle is known.

A fuel pump, a constant fuel chamber, and a starting pump provided in a rotary throttle valve type carburetor are provided in the carburetor main body as seen in Japanese Utility Model Laid-Open Publication No. 6-67842 because of the ease of designing the carburetor as a whole. , That is, below the bottom of the throttle valve, in the order described above.

FIG. 3 is a view schematically showing the above structure. Thick cover plates 72, 73, 74 are superimposed on the lower surface of a carburetor body 71, and a fuel pump 75 and a constant fuel chamber 76 are formed therein. In addition, a dome-shaped pump member 77a of the starting pump 77 is mounted on the lower surface of the lowermost cover plate 74.

[0006]

According to the structure shown in FIG. 3, the distance from the upper end of the valve shaft 79 extending upward from the throttle valve 78 to the upper side of the carburetor body 71 to the lower end of the pump member 77a, that is, vaporization. Since the height of the container is high and the pump member 77a is pressed down and opened by inserting a finger downward, a large space above and below required for installation and operation must be secured, and installation is greatly restricted. In some cases, it is sometimes difficult to operate the starting pump 77.

Therefore, the present invention solves the problem that the conventional rotary throttle valve type carburetor having the starting pump disposed below has a serious restriction on installation and poor operability of the starting pump. It was invented mainly for that purpose.

[0008]

That is, the present invention operates by a cylindrical throttle valve having a throttle hole and a metering needle arranged perpendicularly to an intake passage of a carburetor body, and a pulse pressure of a crankcase of an engine. A fuel pump, a constant fuel chamber for adjusting the fuel sent from the fuel pump to a constant pressure, a fuel nozzle having a metering needle opened to the throttle hole, and a fuel nozzle for supplying fuel from the constant fuel chamber to the fuel nozzle. In a rotary throttle valve carburetor having a manual fuel regulating needle valve for regulating the fuel flow to be supplied and a manual starting pump for introducing starting fuel into a constant fuel chamber, the fuel regulating needle valve and the starting pump are vaporized. It was arranged on one side of the container body.

As described above, since the starting pump is not installed below the carburetor main body, the overall height of the carburetor is reduced, and the screw shaft of the fuel adjusting needle valve protruding to the outside of the carburetor main body and the pump of the starting pump are provided. By disposing the members on one side portion, installation is less restricted. In addition, since the introduction of the starting fuel can be performed in the same one direction as the adjustment of the fuel flow rate, the operation is extremely easy, and the design of the entire layout including the engine and its accessories is also easy. .

Further, according to the present invention, in the rotary throttle valve type carburetor, the fuel pump, the fuel regulating needle valve and the starting pump are arranged on one side of the carburetor body.

In this case, only the constant fuel chamber is disposed below the carburetor main body, and the total height of the carburetor is further reduced.
Installation restrictions are further reduced.

Further, according to the present invention, in the rotary throttle valve type carburetor, a pump body having a built-in inlet check valve and an outlet check valve of a starting pump and having a pump member mounted on an outer surface thereof is provided. The fuel control needle valve was placed on the side of the carburetor body without interference.

In this way, the fuel pump and the fuel regulating needle valve can be installed independently of each other and removed for inspection and repair.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 and 2. A carburetor body 1 has an intake passage 2 penetrating forward and backward and a valve hole orthogonal to the intake passage 2 and one end of which is closed. 3
And a cylindrical throttle valve 4 is rotatably fitted into the valve hole 3 and movably in the direction of the central axis.

The throttle valve 4 has a throttle through hole 5 having a diameter substantially the same as that of the intake passage 2 perpendicular to the center axis thereof, and a nozzle insertion hole 6, a measuring needle 7 and a valve shaft 8 on the center axis. Have. The nozzle insertion hole 6 is provided at an end located on the closed end side of the valve hole 3, and the measuring needle 7 is disposed to face the nozzle insertion hole 6 and projects into the throttle hole 5, and the length of this projection is adjustable. It is fixed to the throttle valve 4.

The valve shaft 8 is integral with the throttle valve 4 and protrudes outward from the open end side of the valve hole 3 through the cover body 9 of the valve hole 3, and an accelerator lever 10 is fixed to the end thereof. I have.
A return spring 11 composed of a torsion coil spring having both ends locked to the throttle valve 4 and the cover body 9 is inserted around the valve shaft 8.

When the accelerator lever 10 is turned by a driver's accelerator operation, the throttle valve 4 rotates integrally, and the degree of overlap between the throttle passage 5 and the intake passage 2 changes, thereby controlling the intake air flow rate of the engine. At the same time, the throttle valve 4 moves in the central axis direction according to a cam mechanism (not shown), and the fuel flow rate is controlled by changing the insertion depth of the metering needle 7 into the fuel nozzle 12 inserted through the nozzle insertion hole 6. Is the same as a conventional rotary throttle valve type carburetor.

A flat plate-shaped pump body 36 of a starting pump 35 is placed on one side of a flat surface extending in a direction parallel to the intake passage 2 of the carburetor body 1 with a pump diaphragm 16 of the fuel pump 15 interposed therebetween. Have been. Fuel pump 15
Are a fuel pump chamber 17 formed of a recess formed on a side surface of the carburetor body 1 with a pump diaphragm 16 interposed therebetween, and a pulse pressure chamber 1 formed of a recess formed on an inner surface of a pump body 36.
8 and a cantilevered butterfly-shaped inlet valve 19 and outlet valve 20 formed by cutting the pump diaphragm 16.

When a pulse pressure generated in the crankcase of the engine is introduced into the pulse pressure chamber 18, the pump diaphragm 16 reciprocates, and the fuel in the fuel tank 13 is supplied to the fuel supply passage 1.
4. The fuel is sent to the fuel introduction passage 21 through the inlet valve 19, the fuel pump chamber 17, and the outlet valve 20.

The constant fuel chamber 22 is formed by a recess formed on the surface of the carburetor body 1 at the closed end side of the valve hole 3, that is, on the lower surface, and a cover body fixed to the carburetor body 1 with a diaphragm 23 interposed therebetween. It faces an atmosphere chamber 25 inside 24. The fuel introduction passage 21 is opened and closed by a fuel valve 26 that operates in accordance with the displacement of the diaphragm 23, and causes the constant fuel chamber 22 to hold a constant amount of fuel, that is, a constant pressure.

The fuel in the constant fuel chamber 22 is sent to the fuel nozzle 12 through a fuel passage 27 having a check valve 27a which closes toward the constant fuel chamber 22, and a fuel regulating needle valve 28 in the middle thereof.
Regulates the flow rate. The fuel adjusting needle valve 28 has a screw shaft 29 screwed into the carburetor main body 1 from the side on which the pump main body 36 is overlapped, and a needle-shaped valve body 30 at the tip thereof. A detent cap 32 made of synthetic resin is attached to a head 31 with a knurl having a tool engagement hole so that the cap 32 cannot be removed by press fitting.

A stopper 33 in the form of a round bar is fixedly provided on the carburetor body 1 in parallel with the fuel adjusting needle valve 28. The arm 32 a of the rotation preventing cap 32 projecting in the radial direction comes into contact with the stopper 33. The fuel adjustment needle valve 28 once adjusted and fitted with the detent cap 32 cannot be rotated more than one revolution, so that the user cannot significantly change the fuel flow rate.

The starting pump 35 has a dome-shaped pump member 37 made of an elastic material attached to the outer surface of a pump body 36, and sucks air into a starting pump chamber 38 which is an internal space thereof. Check valve 3 for discharging oil
9 and an outlet check valve 40, and two check valves 39 and 40 are provided inside the pump body 36.
The pump member 37 is air-tightly attached to the pump body 36 with its outer peripheral edge fixed by a thin plate-shaped pressing member 41 superposed on the pump body 36.

The holding member 41 and the pump body 36 are detachably fixed to the carburetor body 1 by screwing the screws 42 inserted therein into the carburetor body 1. The holding member 41 and the pump main body 36 have a large notch 43 in the lower center portion, and the fuel adjustment needle valve 28 and the stopper 33 project from the carburetor main body 1 through the notch 43, The detent cap 32 is located within the projection area of the notch 43.

For this reason, the starting pump 35 and the fuel regulating needle valve 28 are installed independently of each other, and can be detached independently of each other when performing inspection or repair. In particular, the starting pump 35 is provided with the fuel adjusting needle valve 28 and the stopper 33.
It is not necessary to machine a hole for inserting
5 can be removed without interfering with the fuel adjustment needle valve 28 or the like.

The constant fuel chamber 22 is connected to the starting pump chamber 38 via an inlet check valve 39 by a suction passage 45, and the starting pump chamber 38 is connected from the outlet check valve 40 to the fuel tank 13 by a discharge passage 44. .

Prior to starting the engine, the pump member 37
When the operation of pressing the finger with a finger to reduce the starting pump chamber 38 and then releasing the finger to expand and restore the starting pump chamber 38 is repeated, the air and the fuel vapor in the constant fuel chamber 22 are discharged to the fuel tank 13. . As a result, the fuel in the fuel tank 13 is sucked through the fuel pump 15 into the constant fuel chamber 22 that has become a negative pressure, and the fuel required for starting is filled.

In the illustrated embodiment, the fuel pump 15 is disposed on one side of the carburetor body 1, so that the overall height of the carburetor can be minimized. In some cases. Further, although a part of the fuel supply passage 14 and a part of the discharge passage 44 are formed in the pump main body 36, they may be formed in the carburetor main body 1 in some cases.

[0029]

As described above, according to the present invention, the operation of introducing the starting fuel every time the engine is started from the same direction as the minute adjustment of the fuel flow rate corresponding to the secular change of the engine performance is performed. By securing a space where these operations can be performed in one place, operability can be improved. In addition, since the overall height of the engine is reduced, installation restrictions are reduced, and the layout of the entire layout including the engine and its accessories is easily designed.

Further, by disposing the starting pump and the fuel adjusting needle valve on the same side surface without interfering with each other, installation and removal thereof can be performed independently of each other, so that assembly and disassembly are easy. Becomes

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a partial right side view of FIG.

FIG. 3 is a schematic diagram of a conventional example.

[Explanation of symbols]

1 carburetor body, 2 intake passage, 4 throttle valve, 5
Throttle hole, 7 measuring needle, 12 fuel nozzle, 1
5 fuel pump, 22 constant fuel chamber, 28 fuel adjustment needle valve, 35 starting pump, 36 pump body, 37
Pump components,

Claims (3)

[Claims] 1. A cylindrical throttle valve having a throttle through hole and a measuring needle disposed orthogonally to an intake passage of a carburetor body;
A fuel pump that is operated by a pulse pressure of an engine crankcase, a constant fuel chamber that adjusts fuel sent from the fuel pump to a constant pressure, A rotary throttle valve type including a nozzle, a manual fuel adjustment needle valve for regulating a flow rate of fuel sent from the constant fuel chamber to the fuel nozzle, and a manual starting pump for introducing starting fuel into the constant fuel chamber. A rotary throttle valve type carburetor, wherein the fuel regulating needle valve and the starting pump are arranged on one side of the carburetor body. 2. The rotary throttle valve carburetor according to claim 1, wherein the fuel pump, the fuel regulating needle valve, and the starting pump are arranged on one side portion of the carburetor body. Rotary throttle valve carburetor. 3. A rotary throttle valve type carburetor according to claim 1, wherein an inlet check valve and an outlet check valve of the starting pump are incorporated, and a pump member is mounted on an outer surface. A rotary throttle valve type carburetor, wherein the pump body is overlapped on a side surface of the carburetor body without interfering with the fuel adjusting needle valve.