JP2603112B2 - Fuel adjustment mechanism for diaphragm carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fuel adjusting mechanism for a diaphragm-type carburetor, particularly a diaphragm-type carburetor which allows easy passage of dust and fuel vapor and ensures a stable fuel quantity at all times. The present invention relates to a fuel adjusting mechanism of a vessel.

[Prior art] 2 mounted on portable work machines such as chain saws and brush cutters
The cycle internal combustion mechanism is provided with a diaphragm-type carburetor so that stable operation can be maintained even when the attitude of the body changes. In this diaphragm-type carburetor, the amount of fuel is adjusted according to the load conditions such as a cutter to be replaced with a portable work machine and the ambient temperature.

As shown in FIG. 3, in a diaphragm type carburetor provided with a fuel adjusting mechanism, a rotary throttle valve 20 having a slot hole 22 is fitted to a cylindrical portion 19 of a main body 17 so as to be rotatable and vertically movable. The upper end shaft part 15 of the rotary throttle valve 20 is a cylindrical part 19
A cam surface 13 provided on a lower surface of a lever 12 connected to a shaft 15 and supported by a cover plate 16 for closing the shaft is engaged with a ball 14 supported on the cover plate 16 by the force of a spring 18. A rod valve 21 screwably supported on the shaft portion 15 is projected into a slot hole 22 of the rotary throttle valve 20 and fitted to a fuel nozzle 39. When the lever 12 is remotely rotated by the trigger lever, the rotary throttle valve 20 and the rod valve 21 move up and down together, and the fuel nozzle
The opening area of the 39 fuel injection ports 39a is adjusted.

The fuel nozzle 39 has a cylindrical portion 23 provided at the center of the bottom of the cylindrical portion 19.
Is fitted and supported. A cylindrical portion extending radially from the cylindrical portion 23
38, a cylindrical portion 28, and a screw hole 29 are formed in the main body 17, and the cylindrical portion 28 is configured to be able to communicate with the constant pressure fuel chamber 35 of the fuel supply mechanism 52 via the passage 37 and the check valve 36.

In order to increase or decrease the amount of fuel from the constant pressure fuel chamber 35 to the fuel nozzle 39, a fuel adjusting needle valve 30 is screwed into the screw hole 29, and is held by a locking spring 31. Therefore, the amount of fuel is cylindrical
It is determined by the circumferential clearance between the fuel adjustment needle valve 30 and the tapered portion 30a (FIG. 4).

The fuel supply mechanism 52 including the constant-pressure fuel chamber 35 includes a constant-pressure fuel chamber 35 with the diaphragm 41 interposed between the intermediate body 52 and the cover 56.
35 and an atmosphere chamber 42 are defined. A lever 34 is supported by a support shaft 33 in the constant-pressure fuel chamber 35, and one end of the lever 34 has a diaphragm.
A needle valve type fuel inflow valve 10 supported at the other end of the lever 34 is urged by the spring
At the end of the discharge passage 9. The constant pressure fuel chamber 35 is a passage
43, a check valve 45 formed on the periphery of the mushroom valve, an inner space of the spoiler 48 of the primer pump 44, a check valve 46 formed on the shaft of the mushroom valve, and communication with the fuel tank 2 via a passage 47 It is possible. Fuel for starting the engine is supplied by the primer pump 44.

The fuel pump 51 has a diaphragm between the main body 17 and the intermediate body 55.
Pulsating pressure introduction chamber communicating with the crankcase of the engine across 25
24 and the pump room 7 are sectioned. When the diaphragm 25 vibrates up and down, the fuel in the fuel tank 2 passes through the passage 3, the check valve 5,
The air is sucked into the pump chamber 7 through the passage 6, and is further discharged from the pump chamber 7 to the constant-pressure fuel chamber 35 through the check valve 8, the passage 9 and the fuel inflow valve 10. When the fuel is filled in the constant pressure fuel chamber 35, the diaphragm 41 is lowered, the fuel inflow valve 10 is pushed up by the lever 34, and the end of the passage 9 is closed. Thus, the fuel under the constant pressure is held in the constant-pressure fuel chamber 35. As shown in FIG. 4, the amount of fuel sucked from the constant pressure fuel chamber 35 to the fuel nozzle 39 by the intake negative pressure in the throttle hole 22 is as shown in FIG.
It is determined by an annular gap 38a between the cylindrical portion 38 and the tapered portion 30a of the fuel adjusting needle valve 30.

However, in the case of a small internal combustion engine having a displacement of about 30 cc, the fuel consumption during idling and low load is extremely small. In the above-described fuel adjustment mechanism, dust or fuel vapor (bubbles) mixed in the fuel is used. Adheres to the annular gap 38a, the flow of the fuel changes, and in particular, the fuel vapor cannot pass smoothly, and the fuel amount fluctuates. Structurally, processing for obtaining concentricity between the cylindrical portion 38 and the tapered portion 30a becomes difficult, and the concentricity between the cylindrical portion 38 and the tapered portion 30a tends to be out of order. Therefore, the proportional relationship between the screwing amount and the fuel amount becomes unstable, and it becomes difficult to adjust the fuel amount.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to provide a fuel adjusting mechanism for a diaphragm-type carburetor, which has a simple structure, can easily adjust a fuel amount, and can obtain a stable fuel amount. Is to provide.

Means for Solving the Problems In order to achieve the above object, according to a configuration of the present invention, a fuel adjustment pipe is provided in a straight fuel passage connecting a constant pressure fuel chamber and a fuel nozzle, and a fuel adjustment pipe crossing the fuel passage is provided. A slit extending in the axial direction is provided on the peripheral wall on the constant pressure fuel chamber side, a circular hole is provided on the peripheral wall on the fuel nozzle side, and a fuel adjusting rod valve is inserted through the fuel adjusting pipe so as to be adjustable in the axial direction.

[Operation] The area of an opening such as a slit crossing the fuel passage is adjusted by the axial movement of the rod of the fuel adjusting rod valve.
Since the shape of the opening such as the slit is less likely to adhere to dust and the like than the conventional annular shape, a stable fuel amount can be obtained.

[Embodiment of the Invention] As shown in FIG. 1, a cylindrical portion 38 is formed in a main body 17 so as to cross a fuel passage 23a connecting a constant pressure fuel chamber 35 and a fuel nozzle 39.
And a screw hole 29 are formed, and the fuel adjusting pipe 59 is fitted into the cylindrical portion 38. The rod 30b of the fuel adjusting rod valve 30 is connected to the fuel adjusting pipe 59.
Are fitted so as to be movable in the axial direction. An axially long slit 57 is provided on the constant pressure fuel chamber side peripheral wall of the fuel adjusting pipe 59, and a circular hole 58 communicating with the fuel passage 23a is provided on the other peripheral wall portion. The slit 57 is formed by a disk-shaped cutter. It is preferable to increase the inner diameter of the fuel passage 23b on the constant pressure fuel chamber side according to the length of the slit 57.

According to the present invention, when the fuel adjusting rod valve 30 is screwed into the screw hole 29, the opening area of the slit 57 is adjusted by the rod portion 30b. Since the shape of the passage opening is almost triangular, problems such as dust and fuel vapor (bubbles) getting caught in the slit 57 are eliminated compared to the conventional annular passage opening, and a stable fuel amount is secured. Is done.

[Effect of the Invention] As described above, according to the present invention, a fuel regulating pipe is provided in a straight fuel passage connecting a constant pressure fuel chamber and a fuel nozzle, and a fuel regulating pipe which crosses the fuel passage is provided on a peripheral wall of the fuel regulating pipe on a constant pressure fuel chamber side. And a slit formed in the other peripheral wall, and a fuel adjusting rod valve is inserted through the fuel adjusting pipe so as to be movable in the axial direction, and a passage opening whose opening area is adjusted by the fuel adjusting rod valve. Is shaped like a slit or a half-moon, and the area of the passage opening is adjusted by the fuel adjustment rod valve that crosses the opening.Therefore, dust and fuel vapor pass more easily than the annular passage opening. And stable operation can be obtained even when the engine is idling or rotating at a low speed.

In the present invention, a slit and a circular hole are formed in the fuel adjusting pipe without providing a flat surface or a V-groove at the tip of the fuel adjusting needle valve. Therefore, high machining accuracy is not required, and there is no possibility that the fuel amount fluctuates due to the concentricity with the fuel passage of the fuel adjusting rod valve.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a fuel adjusting mechanism of a diaphragm type carburetor according to the present invention, FIG. 2 is a bottom view showing the relationship between the fuel adjusting pipe and a fuel adjusting rod valve, and FIG. 3 is a conventional diaphragm type carburetor. FIG. 4 is a side sectional view of the fuel adjusting mechanism of the carburetor. 28: cylindrical part, 30: fuel adjusting rod valve, 35: constant pressure fuel chamber, 38: cylindrical part, 39: fuel nozzle, 57: slit, 58: circular hole, 59: fuel adjusting pipe

Claims (1)

(57) [Claims] A straight fuel passage connecting a constant-pressure fuel chamber and a fuel nozzle is provided with a fuel adjusting pipe crossing the fuel passage, and a slit extending in an axial direction on a peripheral wall of the fuel adjusting pipe on a side of the constant-pressure fuel chamber is provided with the fuel. Circular holes are provided in the nozzle side peripheral wall, respectively,
A fuel adjusting mechanism for a diaphragm-type carburetor, wherein a fuel adjusting rod valve is inserted through the fuel adjusting pipe so as to adjust the axial movement.