JPS6121562Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary throttle valve type carburetor suitable for installation in a two-stroke engine used as a drive source for a chain saw or a bush cutter.

A rotary throttle valve type carburetor is provided with a cam mechanism for regulating the spiral movement of the rotary throttle valve, that is, the movement in the rotation axis direction as the throttle valve rotates. Accordingly, the effective diameter of the nozzle hole of the fuel supply mechanism provided in relation to the throttle valve is increased or decreased in accordance with the operating angle of the throttle valve.

By the way, the required change characteristics of the actual diameter of the nozzle hole with respect to the operation angle of the throttle valve described above depend on the type of internal combustion engine to which the carburetor is applied, or whether the engine is used at high altitudes where air is rare. Varies depending on usage conditions.

However, in conventional carburetors, the cam mechanism typically includes a single sloping groove formed on the outer periphery of, for example, a rotary throttle valve, and receives the throttle valve on the carburetor body to engage the groove. Since it consists of a single cam floor with a hole and a protruding hole, it is not possible to select the above-mentioned changing characteristics according to the usage conditions.

Therefore, an object of the present invention is to provide a rotary throttle valve type carburetor that can easily select the change characteristic of the effective diameter of the nozzle hole of the fuel supply mechanism with respect to the operating angle of the rotary throttle valve.

The present invention provides an operating lever coupled to a protruding end of a rotary throttle valve whose end protrudes from the carburetor body, and a portion of the carburetor body facing the lever, the portion being inclined. The present invention is characterized in that the above-mentioned change characteristics can be selected by providing a plurality of different cam surfaces and selectively attaching cam followers to portions of the lever corresponding to the respective cam surfaces.

The features of the invention will become clearer from the following description of the illustrated embodiment.

A carburetor 10 according to the present invention, as shown in FIG. 1, includes a carburetor body 12 and a rotary throttle valve 14 built into the carburetor body.

The carburetor body 12 is formed with a well-known air hole 16, one end of which communicates with an air cleaner (not shown) and the other end of which communicates with an air intake port (not shown) of an internal combustion engine. Hole 1 intersecting with hole 16 and open at one end
8 is formed.

The throttle valve 14 includes a cylindrical portion 14a accommodated in the hole 18, and a shaft portion 1 extending outward from the end of the cylindrical portion with the central axis aligned with the carburetor body 12.
4b. The throttle valve 14 has a cylindrical portion 14a and a shaft portion 14b aligned with its central axis.
A through hole 20 is formed that extends to. A well-known throttle valve 22 extending perpendicularly to the cylindrical portion 14a and aligning with the air hole 16 is formed on the cylindrical portion 14a.

A bearing member 24 that allows the shaft portion 14b of the throttle valve 14 to pass through is attached to a screw member 26 at the open end of the hole 18.
has been fixed through. The bearing member 24 forms part of the side wall of the carburetor body 12 and closes the open end of the bore 18. The bearing member 24 also allows the throttle valve 14 to move in its circumferential direction, that is, around the central axis, and in the direction of the central axis.

A nozzle tube 28 and a needle 30 are inserted into the through hole 20 of the throttle valve 14.
4 along the central axis. One end of the nozzle tube 28 is fixed to a side wall portion of the carburetor body 12 facing the bearing member 24, and the other end extends through the other end of the throttle valve 14 into the throttle hole 22 of the valve. Nozzle tube 2
8 is connected at one end to a conventionally well-known fuel supply passage (not shown), and the fuel from the fuel supply passage is passed through a nozzle hole 32 provided on the circumferential surface near the other end to a throttle hole. It erupts into 22.

The needle 30 has one end thereof connected to the throttle valve 1.
The shaft portion 14 of the throttle valve is connected to the shaft portion 14 of the throttle valve through a threaded portion 34 that allows adjustment of the relative position in the axial direction with respect to the shaft portion 14 of the throttle valve.
It is connected to b. The other end of needle 30 extends into nozzle tube 28 from the other end thereof. Therefore, by displacing the throttle valve 14 that supports the needle 30 in the direction of its central axis, the effective diameter of the nozzle hole 32 increases or decreases.

A coil spring 36 is arranged around the outer periphery of the shaft portion 14b of the throttle valve 14 in the carburetor main body 12 to surround the shaft portion. spring 3
One end of the throttle valve 6 abuts against the shoulder of the throttle valve 14, and its end 36a is locked to the throttle valve 14. Further, the other end of the spring 36 is connected to the carburetor main body 1
The end 36d of the bearing member 24 is in contact with the back surface of the bearing member 24 that forms a part of the side wall of the housing. The coil spring 36 applies a biasing force to the throttle valve 14 along its central axis due to its elasticity against compression, and applies a biasing force to the throttle valve 14 along its circumferential direction due to its elasticity against torsion. The spring force of the spring 36 holds the throttle valve 14 at the idling opening position shown in the figure.

At one end of the throttle valve 14 protruding from the side wall of the carburetor main body 12, that is, at the protruding end of the shaft portion 14b,
An operating lever 38 to which a rotational force for operating the throttle valve 14 is applied is fixed, and in relation to the lever and the portion of the carburetor body 12 facing the lever 38, that is, the surface of the bearing member 24, A cam mechanism is provided for regulating the helical movement of the throttle valve 14.

Specifically, as shown in FIG. 2, an annular convex portion 40 is formed on the surface of the bearing member 24, and portions of the surface of the convex portion facing in the diametrical direction have the same shape. A pair of inclined surfaces 42a and 42b are defined that are inclined in the circumferential direction and have different degrees of inclination. The circumferential length of each inclined surface 42a, 42b corresponds to an angular range of approximately 90 degrees from the idling opening position of the throttle valve 14 to the fully open position. Therefore, three inclined surfaces having different degrees of inclination can be defined on the surface of the convex portion 40 as required.

The respective inclined surfaces 42a, 4 of the operating lever 38
2b, there are insertion holes 46a and 43b for receiving the cam follower 44 whose cam surface is the inclined surface, as shown in FIG.
is provided. The cam follower 44 includes a shaft portion 44a and a head portion 44b connected to the shaft portion, and has a corresponding insertion hole so that the head portion engages with one of the inclined surfaces, that is, the cam surface 42a or 42b. 46a or 46b with its shaft portion 4
4a is inserted.

When the operating lever 38 is rotated, the cam follower 44 slides on a cam surface, for example, a cam surface 42a, which rotates and engages with the lever.
As a result, the throttle valve 14 is displaced along the rotation axis according to the degree of inclination defined by the cam surface 42a as the throttle valve 14 rotates.
The effective diameter of the nozzle hole 32 increases or decreases by displacement of the needle 30, which moves integrally with the nozzle hole 4, in the axial direction.

The degree of change in the effective diameter of the nozzle hole 32 with respect to the rotation of the throttle valve 14 described above depends on the degree of inclination of the cam surface 42a or 42b that engages with the cam follower 44. Therefore, cam follower 4
By selecting from the two insertion holes 46a and 46b in the mounting position 4, it is possible to select the cam surfaces 42a and 42b that cooperate with the cam follower 44 to define the spiral movement of the throttle valve 14. The change characteristic of the effective aperture of the nozzle hole 32 with respect to the rotation angle can be selected to suit the operating conditions.

In the above description, the cam surfaces 42a and 42b form the bearing member 24 that constitutes the side wall portion of the carburetor main body 12.
Although an example has been described in which the cam portion defining the cam surface is removable from the carburetor body 12 and this cam portion can be replaced with a cam portion having a different degree of inclination, various internal combustion engines can be used. This gives the vaporizer 10 greater versatility in adapting it to the following.

According to the present invention, as described above, by selecting the mounting position of the cam follower attached to the operating lever, the change characteristics of the effective diameter of the nozzle hole with respect to the operating angle of the rotary throttle valve can be easily changed. This makes it possible to properly supply fuel to the internal combustion engine, thereby improving the operating performance of the engine.

[Brief explanation of the drawing]

FIG. 1 is a partially cut away vertical sectional view of the carburetor according to the present invention, and FIG. 2 is a perspective view showing the bearing member shown in FIG. 1. 12... Carburetor body, 14... Throttle valve,
16... Air hole, 22... Throttle hole, 24...
...bearing member, 28... nozzle tube, 30...
Nozzle hole, 38...operation lever, 42a, 42b
...Cam surface, 44...Cam follower.

Claims (1)

[Scope of utility model registration request] a carburetor body having an air hole, and a generally cylindrical throttle that crosses the air hole and has one end that is a protruding end that protrudes outward from the carburetor body via a bearing member attached to the carburetor body. a rotary throttle valve that is movable in the circumferential direction and the center axis direction and has a throttle hole that can be aligned with the air hole; a nozzle tube extending into the throttle hole through the other end of the valve and having a nozzle hole for jetting fuel on its circumferential surface; a needle extending into the nozzle tube from the other end of the nozzle tube along the central axis of the valve; an operating lever coupled to the protruding end of the throttle valve; a cam mechanism for regulating the spiral movement of the throttle valve in order to make the effective diameter variable; the cam mechanism includes a plurality of cam surfaces provided facing the operating lever, each of which is connected to the bearing member; a plurality of cam surfaces formed diametrically opposite on the surface of the throttle valve and having different inclinations in the circumferential direction of the throttle valve; and selectively attached to portions of the operating lever corresponding to the cam surfaces. A rotary throttle valve type carburetor equipped with a cam follower.