JPH11351065A - Fuel control valve for carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent such a variation in fuel discharge as caused by a mounting operation of an operation limiting cover on the head of a fuel control valve or by an engine vibration. SOLUTION: A carburetor body 20 is formed with a tapped hole 25a and a fuel passage hole with a bore smaller than that of the tapped hole 25a, both extending inwardly in this order coaxially. A fuel control valve 2 is, on the other hand, formed with a threaded stem 4 adapted to mesh with the tapped hole 25a and a point needle 3 adapted to fit into the fuel passage hole, both provided in this order from the side of its head 7 to the point. The fuel passage hole is formed in its internal surface with an axial discharge control groove 53 that shallows gradually from upperstream to downstream or along a flow of fuel. The fitting length of the point needle 3 in the fuel passage hole can be changed to control the passage area of the fuel passage hole accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel regulating valve for a carburetor of a small internal combustion engine mainly mounted on a power saw, a brush cutter and the like.

[0002]

2. Description of the Related Art Along with the regulation of exhaust gas components in a small internal combustion engine, the fuel flow rate of a carburetor is adjusted in advance in a factory for manufacturing an internal combustion engine, and a driver is provided with a fuel flow rate adjusted in advance in the factory. The fuel adjustment valve cannot be adjusted in the direction exceeding the direction.

For example, in a fuel control valve in a carburetor disclosed in Japanese Patent Application Laid-Open No. 6-102093, an operation restricting lid is provided on the head of the fuel control valve in order to prevent the fuel control valve from turning in the fuel increasing direction. Is attached. However, in the above-described fuel adjusting valve, when the operation restricting lid is attached to the head of the fuel adjusting valve, although the coil spring that suppresses the movement of the fuel adjusting valve is mounted, the rotational position of the fuel adjusting valve may be out of order. is there. In other words, there is a problem in that after the adjustment operation of the fuel adjustment valve is completed, the fuel adjustment valve is returned by the back gap of the threaded portion (backlash) by the force of the coil spring, and the fuel flow rate changes.

Accordingly, the applicant of the present application has filed Japanese Patent Application No. 7-1456.
No. 77 proposed a new fuel regulating valve. According to the above-described fuel control valve, there is no change in the fuel flow rate due to the back gap of the screw portion, but when the operation restriction lid is fitted to the head of the fuel control valve,
The tip needle of the fuel control valve may be eccentric by the amount of play between the screw hole of the carburetor body and the screw shaft of the fuel control valve. In other words, the screw shaft portion of the fuel adjustment valve is screwed into the through hole of the detent ring while screwing itself, so that there is no play between the fuel adjustment valve and the detent ring, but the carburetor body has Since the screw hole and the screw shaft of the fuel regulating valve are formed by machining, the play between the screw hole and the screw shaft cannot be completely eliminated.

If there is play between the screw hole of the carburetor body and the screw shaft of the fuel control valve, when the operation restricting lid is fitted to the head of the fuel control valve, the fuel control valve is connected to the screw shaft. Incline with the screwed part with the detent ring as a fulcrum. As a result, the tip needle portion of the fuel regulating valve is eccentric with respect to the fuel passage hole of the carburetor body, and the fuel flow rate changes. Therefore, fine adjustment must be performed again after the operation restricting lid is attached. If the processing accuracy of the screw hole and the screw shaft is increased, the play between the screw hole and the screw shaft can be reduced, but the improvement of the processing accuracy increases the cost.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to prevent a change in the fuel flow rate when the operation limiting lid is mounted on the head of the fuel regulating valve or due to vibration of the engine. , A fuel regulating valve in a carburetor.

[0007]

In order to solve the above-mentioned problems, according to the structure of the present invention, a screw hole extending inward and a fuel passage hole having a smaller diameter than the screw hole are coaxially provided in the carburetor body.
The fuel regulating valve is provided with a screw shaft portion that is screwed into the screw hole in order from the head to the tip and a tip needle portion that fits into the fuel passage hole, and the area of the fuel passage hole is adjusted by the tip needle portion. In the fuel regulating valve in the carburetor,
An axial flow rate adjusting groove which gradually becomes shallower from the upstream side to the downstream side of the fuel flow is provided on the inner peripheral surface of the fuel passage hole.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the flow rate of a fuel passage hole is adjusted by adjusting the length (dimension in the axial direction) of the tip end of a fuel regulating valve fitted into the fuel passage hole of a carburetor body. The cross-sectional area of the gap between the groove and the tip needle, that is, the fuel flow rate is adjusted.

The tip end of the cylindrical fuel regulating valve has
Since it is press-fitted or fitted into the fuel passage hole with a circular cross section without any gap, when fitting the operation restriction lid to the head of the fuel adjustment valve,
The tip needle portion of the fuel regulating valve does not move axially or radially with respect to the fuel passage hole, and the preset fuel flow does not change.

[0010]

FIG. 1 is a left side sectional view showing a mounted state of a fuel adjusting valve in a carburetor according to the present invention, and FIG. 2 is a front view thereof. As shown in FIG. 1, the carburetor body 20 has an intake passage 21 extending in a direction perpendicular to the plane of the drawing at a central portion, and a fuel chamber 24 formed at a lower end wall.
The fuel nozzle 40 is mounted in the through hole 22 connecting the fuel nozzles. The fuel nozzle 40 is provided with an annular groove 43 and a radial passage 42 on the peripheral wall of the cup-shaped main body, and a valve body 41 formed of a known disk is disposed at the upper end of the main body, and is locked at the upper end of the main body. The retaining ring 40a having a plurality of leg pieces is configured so that the valve body 41 does not come out upward.

The fuel regulating valve 2 is screwed and supported in a screw hole 25 a orthogonal to the through hole 22. The carburetor body 20 is provided with a stepped cylindrical portion 2 on the projecting wall portion 20a projecting sideways in order from the outer end to the inner side.
9, a screw hole 25a, a fuel passage hole 25, and a small-diameter fuel passage hole 23a are formed coaxially. The tip needle portion 3 of the fuel regulating valve 2 is projected into the fuel passage hole 23a, and the passage 23 orthogonal to the fuel passage hole 25 from the fuel chamber 24, the fuel passage hole 2
5. The flow rate of fuel supplied to the intake passage 21 via a sleeve 51, a fuel passage hole 23a, an annular groove 43, and a passage 42, which will be described later, is adjusted. A plurality of positioning pins 26 are integrally formed on the lower wall surface of the vaporizer main body 20 and fitted into positioning holes (not shown) of the lower wall plate. The fuel chamber 24 is defined by a diaphragm sandwiched between the carburetor body 20 and the above-described lower wall plate. However, such a configuration is well known and is not directly related to the gist of the present invention and will not be described further.

The stepped cylindrical portion 29 has a small-diameter cylindrical portion 29a inside the step portion 28 and a large-diameter cylindrical portion 29 outside the step portion 28.
b, a step-stop ring 9 to be described later abuts on the step portion 28, and an operation limiting cover for restricting the adjusting operation of the head 7 and the fuel adjusting valve 2 on the large-diameter cylindrical portion 29b. 10 are accommodated. The fuel regulating valve 2 has a flange 6 and a serration shaft 7b formed on a head 7, and a groove 7a for engaging a tool (driver) on an end face of the head 7.

The cup-shaped operation limiting lid 10 has a cylindrical portion 12 in which the flange 6 is fitted, and a serration hole 13 in which the serration shaft 7b is fitted, and a circular hole 15 through which a tool is inserted into the right end wall and a diameter. Direction grooves 16 are formed. The inner peripheral wall of the large-diameter cylindrical portion 29b has a groove width of the side wall 30a and the side wall 3.
0b (see FIG. 2) in the axial limiting groove 30
Is formed, and a metal holding plate 19 is fitted and fixed to the opening end wall of the large-diameter cylindrical portion 29b.

As shown in FIG. 2 with a lattice pattern, the substantially oval holding plate 19 has two circular openings 19a through which the operation restricting lid 10 can be inserted.
9a is provided with a notch 19b at the edge. The width (dimension in the circumferential direction) of the notch 19b is substantially equal to the ridge 14 of the operation restriction lid 10, and the holding plate 19 partially covers the end of the restriction groove 30 of the large-diameter cylindrical portion 29b. A recess 31 having the same outer shape as the holding plate 19 is formed at the opening edge of the large-diameter cylindrical portion 29b so that the holding plate 19 does not protrude from the protruding wall portion 20a. The holding plate 19 is firmly fitted in the recess 31 so that it cannot be easily removed.

The fuel control valve 2 is composed of a high-speed fuel control valve and a low-speed fuel control valve arranged in parallel to each other, and has a large-diameter cylindrical portion 29b for accommodating the operation restricting lid 10 mounted on each fuel control valve 2.
Are connected to each other at the peripheral wall portions. Accordingly, the detent ring 9 made of a relatively soft synthetic resin is also integrated, and provided with two through holes 9a. The through holes 9a are not threaded. The detent ring 9 is a small-diameter cylindrical portion 29 of the vaporizer main body 20.
a and into the large-diameter cylindrical portion 29b.

As shown in FIG. 1, according to the present invention, when the operation restricting lid 10 is mounted on the head 7 of the fuel regulating valve 2 or the vibration of the engine does not cause a change in the fuel flow rate. A screw hole 25a extending inward in the carburetor body 20 and a fuel passage hole 23a having a smaller diameter than the screw hole 25a are provided coaxially, while the screw hole 25a is sequentially formed in the fuel regulating valve 2 from the head 7 to the tip.
A screw shaft portion 4 screwed into the fuel passage hole 23a and a tip needle portion 3 fitted into the fuel passage hole 23a are provided, and a flow rate adjusting groove 53 is provided on the inner peripheral surface of the fuel passage hole 23a.

As shown in FIGS. 3 and 4, in practice, the fuel passage hole 23a is formed at the base end of the fuel passage hole 23a for convenience of processing.
A sleeve 51 having a fuel passage hole 52 having substantially the same diameter as the fuel passage hole 23a is fitted into the cylindrical portion 55, and an inner peripheral surface of the sleeve 51 is provided from the upstream side of the fuel flow. An axial flow rate adjusting groove 53 is provided which becomes gradually shallower (downward from the base end of the sleeve 51) to the downstream side. Preferably, a plurality of axial flow control grooves 53 are provided at equal intervals in the circumferential direction. The flow rate adjusting groove 53 is not limited to a rectangular cross section, but may be a triangular cross section or a circular arc cross section.

The fuel regulating valve 2 is assembled as follows. First, after the sleeve 51 is press-fitted into the cylindrical portion 55, a tool is engaged with the groove 7a of the head 7 of the fuel control valve 2, and the screw shaft portion 4 of the fuel control valve 2 is inserted into the screw hole 25a of the carburetor body 20. At the same time, the large-diameter screw shaft portion 5 is screwed into the through hole 9a of the detent ring 9 while cutting a screw groove. At the same time, while measuring the fuel flow rate, the length (axial dimension) of the distal end needle portion 3 of the fuel regulating valve 2 fitted into the fuel passage hole 52 of the sleeve 51 is adjusted so as to adjust the fuel passage hole 52. The cross-sectional area (passage area) of the gap between the flow rate adjusting groove 53 and the tip needle section 3, that is, the fuel flow rate is adjusted. Finally,
The serration hole 13 of the operation limiting lid 10 is fitted to the serration shaft 7b of the head 7 of the fuel adjusting valve 2 so that the fuel adjusting valve 2 cannot be loosened (rotated in the fuel increasing direction).

The operation restricting lid 10 is connected to the opening 19 a of the holding plate 19.
When it is pushed into the inside of the large-diameter cylindrical portion 29b, the ridge 14 of the operation restricting lid 10 is engaged with the restriction groove 30 of the large-diameter cylindrical portion 29b through the notch 19b of the holding plate 19. Operation restriction lid 10
When mounting the shaft, the friction of the threaded portion of the large diameter screw shaft portion 5 of the fuel adjusting valve 2 with the through hole 9a of the detent ring 9 and the friction of the fitting portion of the tip needle portion 3 with the fuel passage hole 52 Prevents the fuel control valve 2 from rotating. Since the operation restricting lid 10 is inserted into the large-diameter cylindrical portion 29b and does not protrude to the outside from the projecting wall portion 20a, it is difficult to forcibly remove the operation restricting lid 10.

When the driver adjusts the fuel flow rate of the carburetor, the tool is engaged with the groove 16 of the operation limiting lid 10. The ridge 14 of the operation restriction lid 10 is connected to one side wall 30 of the restriction groove 30.
2, the fuel regulating valve 2 can rotate clockwise (fuel decreasing direction) but cannot rotate counterclockwise (fuel increasing direction) in FIG. As a result, the fuel flow rate of the carburetor cannot be adjusted to a value exceeding the maximum allowable fuel flow rate preset at the time of shipment from the factory, so that operation that violates the exhaust gas regulation of the engine can be prevented. .

According to the present invention, the distal end needle portion 3 of the cylindrical fuel control valve 2 is press-fitted or fitted into the fuel passage hole 52 having a circular cross section without any gap.
When the operation restricting lid 10 is externally fitted, the tip needle portion 3 of the fuel regulating valve 2 does not move in the axial direction or the radial direction with respect to the fuel passage hole 52, and the preset fuel flow rate changes. Not even. Further, since the fuel adjusting valve 2 supports the screw shaft portion 4 and the tip needle portion 3 on the carburetor body 20,
The tip needle portion 3 receives the fuel passage hole 52 under the vibration of the engine.
And the fuel flow rate does not change.

[0022]

As described above, according to the present invention, a screw hole extending inward in the carburetor body and a fuel passage hole having a smaller diameter than the screw hole are provided coaxially, and the fuel regulating valve is provided from the head to the tip. A fuel adjusting valve in a carburetor in which a screw shaft portion screwed into the screw hole and a tip needle portion fitted into the fuel passage hole in order are provided, and the area of the fuel passage hole is adjusted by the tip needle portion. Since the inner peripheral surface of the fuel passage hole is provided with an axial flow rate adjusting groove which gradually becomes shallower from the upstream side to the downstream side of the fuel flow, when the operation limiting lid is attached or when the engine is subjected to vibration, The tip needle portion of the fuel regulating valve is eccentric with respect to the fuel passage hole of the carburetor body, and the fuel flow does not change.

Since the fuel flow rate is stable even when the threaded portion between the fuel control valve and the carburetor body is short, the fuel control valve can be made shorter than before, the protruding portion from the carburetor is shortened, and assembly to the carburetor is achieved. Workability is improved.

Since the threaded portion of the fuel regulating valve may be short,
When machining is simplified, and the amount of protrusion of the fuel regulating valve from the carburetor is shorter than before, the carburetor can be made smaller as a whole, and it is necessary to mount the carburetor in a narrow mounting space like a power saw. Is advantageous.

[Brief description of the drawings]

FIG. 1 is a left side sectional view showing a fuel regulating valve in a carburetor according to the present invention.

FIG. 2 is a front view showing a main part of the fuel regulating valve.

FIG. 3 is a front view of a sleeve provided with a flow rate adjusting groove in the fuel adjusting valve.

FIG. 4 is a left side sectional view of the sleeve.

[Explanation of symbols]

2: Fuel adjustment valve 3: Tip needle part 4: Screw shaft part
5: Large diameter screw shaft 6: Flange 7: Head 7a:
Groove 7b: Serration shaft 9: Detent ring 10: Operation limiting lid 12: Cylindrical part 13: Serration hole 14:
Ridge 16: Groove 19: Holding plate 19a: Opening 19b: Notch 20: Vaporizer main body 21: Intake passage 23a: Fuel passage hole 2
4: fuel chamber 25: fuel passage hole 25a: screw hole 29: stepped cylindrical portion 29a: small-diameter cylindrical portion 29b: large-diameter cylindrical portion 30: limiting groove 30a, 30b: side wall 31: hollow 40: fuel nozzle 40a: retaining ring 41: valve element 43: annular groove 5
1: sleeve 52: fuel passage hole 53: flow rate adjusting groove
54: Conical part 55: Cylindrical part

Claims (2)

[Claims] 1. A screw hole extending inward in the carburetor body and a fuel passage hole having a smaller diameter than the screw hole are coaxially provided, and the fuel adjusting valve is screwed into the screw hole in order from the head to the tip. A fuel regulating valve for a carburetor having a screw shaft portion and a tip needle portion fitted into the fuel passage hole, wherein the tip needle portion adjusts the area of the fuel passage hole. A fuel regulating valve in a carburetor, characterized in that an axial flow regulating groove that gradually becomes shallower from the upstream side to the downstream side of the fuel flow is provided on the surface. 2. The fuel injection valve according to claim 1, wherein a tip portion of the fuel adjustment valve has a right cylindrical shape, a portion of the tip needle portion is fitted in the fuel passage hole, and a tip of the tip needle portion is located at an intermediate portion of the flow rate adjustment groove. The fuel regulating valve in a carburetor according to claim 1, wherein the fuel regulating valve is located.