JPS6224783Y2 - - 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 helical movement of the rotary throttle valve, that is, the movement in the direction of its rotation center axis as the rotary throttle valve rotates. . Due to the spiral movement of the throttle valve by this cam mechanism, the effective diameter of the nozzle hole of the fuel supply mechanism provided in association with the throttle valve is increased or decreased in accordance with the rotation angle of the throttle valve.

By the way, the required change characteristic of the actual diameter of the nozzle hole with respect to the rotational operating angle of the rotary throttle valve described above is based on the usage conditions of the internal combustion engine to which the carburetor is applied, that is, the internal combustion engine is used at high altitudes where the air is rare. It depends on whether or not it is used in a cold region.

However, in the conventional carburetor, the cam mechanism generally includes a single inclined groove formed on the outer circumferential surface of the rotary throttle valve and a hole formed in the carburetor body to receive the throttle valve. Since it consists of a single cam follower that engages with an inclined groove, it has not been possible to select the above-mentioned changes in characteristics depending on the usage conditions.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable easy selection of the change characteristic of the effective diameter of the nozzle hole of the fuel supply mechanism with respect to the rotation angle of the rotary throttle valve in a rotary throttle valve type carburetor.

The present invention relates to an operating lever fixed to a protruding end of a rotary throttle valve disposed with an end protruding from a carburetor main body, and a portion of the carburetor main body facing the operating lever. is provided with a plurality of cam surfaces extending in parallel with each other in the circumferential direction of the rotary throttle valve and each having a different inclination in the direction of extension, so that the cam follower can be displaced on the operating lever in the radial direction of the throttle valve. By positioning and adjusting the position of the cam follower, the cam follower can be selectively engaged with the plurality of cam surfaces, thereby making it possible to select the desired change characteristics described above.

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 incorporated within 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 supply port (not shown) of an internal combustion engine. A hole 18, open at one end, intersecting the air hole 16 is formed for reception.

The throttle valve 14 includes a cylindrical portion 14a accommodated in a hole 18, and a shaft portion 14b extending coaxially with the end of the cylindrical portion to the outside of the carburetor body 12.
Equipped with. A through hole 20 is formed in the throttle valve 14 and extends to the cylindrical portion 14a and the shaft portion 14b in alignment with the central axis thereof. Further, the cylindrical portion 14a has air holes 16 extending in the diametrical direction thereof.
Conventionally well-known throttle hole 22 that can be aligned with
is formed.

A bearing member 24 is fixed to the open end of the hole 18, which allows the shaft portion 14b of the throttle valve 14 to pass therethrough. Close the ends. The bearing member 24 also allows the throttle valve 14 to move in its circumferential direction, that is, to move around the central axis;
movement in the direction of the rotation center axis.

In the through hole 20 of the throttle valve 14, means for changing the effective diameter of the nozzle hole 30 provided in the nozzle tube 26, that is, a needle 28 is arranged. One end of the nozzle tube 26 is fixed to the carburetor body 12, and the other end extends into the throttle hole 22. Nozzle tube 26
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 30 provided on the circumferential surface near the other end.
and into the throttle hole 22.

The needle 28 has one end thereof connected to the throttle valve 1.
The throttle valve is connected to the shaft portion 14b of the throttle valve via a screw member 32 whose relative position relative to the throttle valve 4 in the axial direction can be adjusted. A spring 34 prevents the screw member 32 from loosening. needle 28
The other end extends from the other end of nozzle tube 26 into the nozzle tube. Therefore, needle 28
The effective diameter of the nozzle hole 30 increases or decreases by displacing the throttle valve 14 that supports the nozzle hole 30 along its rotation center axis.

A coil spring 36 is disposed around the outer periphery of the shaft portion 14b of the throttle valve 14 in the carburetor main body 12 so as to surround the shaft portion 14b. One end of the coil spring 36 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 coil spring 36 is in contact with the back surface of the bearing member 24, and the terminal 3
6b is locked to the bearing member 24. Due to its elasticity against compression, the coil spring 36
A biasing force is applied to the throttle valve 14 along its central axis, and the torsional elasticity provides a biasing force to the throttle valve 14 about the central axis. The spring force of the coil spring 36 holds the throttle valve 14 at the idling opening position shown in the figure.

Throttle valve 1 protruding from the side wall of the carburetor body
An operating lever 38 to which a rotational force for operating the throttle valve 14 is applied is fixed to one end of the shaft portion 14b, that is, the protruding end of the shaft portion 14b. A cam mechanism is provided for defining the helical movement of the throttle valve 14 in relation to the opposing part, ie, the surface of the bearing member 24 forming part of the side wall of the carburetor body 12.

That is, as shown in FIG. 2, an annular convex portion 40 is formed on the surface of the bearing member 24, and two cams extending in parallel with each other in the circumferential direction are formed on the surface of the convex portion. Surfaces 42, 42a, 42b are defined. Both cam surfaces, that is, inclined surfaces 42a,
42b is divided in the radial direction of the throttle valve 14. At the fully open angle position 44 corresponding to the fully open angle of the throttle valve 14, both inclined surfaces 42a and 42b
are at the same height standard, and at the idling opening position 46 of the throttle valve 14, the inner inclined surface 42
Both inclined surfaces 42a, 42a have different inclinations toward the opening position 46 such that the height of the outer inclined surface 42b is greater than that of the outer inclined surface 42b.

As shown in FIG. 1, the operating lever 38 is provided with a slit 48 extending in the radial direction of the throttle valve 14, and a cam follower 50 is disposed in the slit, passing through the shaft portion 50a. has been done. A spring seat 5 is provided at the protruding end of the shaft portion 50a.
2 is locked, and the spring seat and operating lever 38
A coil spring 54 surrounding the shaft portion 50a is arranged between the shaft portion 50a and the shaft portion 50a. Therefore, the cam follower 50 is movable in the direction of extension of the slit 48 with respect to the operating lever 38, and is positioned relative to the operating lever 38 by the spring force of the spring 54.

As shown in FIG. 1, with the cam follower 50 engaged with the outer inclined surface 42b, the operating lever 3
8 is operated from the idling opening position to the fully open position, the cam follower 50 slides on the inclined surface 42b from the idling opening position 46 to the fully open position 44 as the operating lever 38 rotates. do. Further, when the operating lever 38 is rotated while the cam follower 50 is moved inward in the radial direction of the throttle valve 14 and engaged with the inner inclined surface 42a, the cam follower 50 is rotated along with this rotation operation. It slides on the inclined surface 42a from the idling opening position 46 to the fully opening position 44.

Both inclined surfaces 42a and 42b are, as described above,
have different slopes. Therefore, the slit 4
By adjusting the position of the cam follower 50 in the direction of extension of the slit along the slit 8, it is possible to select the inclined surfaces 42a, 42b with which the cam follower engages. The axial displacement position of the throttle valve, that is, the change characteristic of the actual diameter of the nozzle hole 30 can be selected.

As a means for adjusting the position of the cam follower 50, as shown in FIG. An extending adjustment screw 56 is rotatably supported and can be screwed onto the cam follower 50 . A locking spring 58 surrounding the adjustment screw 56 is disposed between the cam follower 50 and the bent portion 38a, and the mounting position of the cam follower 50 can be continuously adjusted by rotating the adjustment screw 56. can.

The inclined surfaces 42a and 42b shown in FIG. 2 have the same height at the fully open position 44, and have different heights at the idling opening position.
Therefore, according to the inclined surfaces 42a and 42b shown in FIG. 2, the characteristic curve 4 as shown in FIG.
2a and 42b can be selected. The horizontal and vertical axes of the graph shown in FIG. 4 respectively indicate the rotation angle of the throttle valve 14 and the actual diameter of the nozzle hole 30,
Although the actual diameter of the nozzle hole 30 at the idling opening position 46 is the same, the actual diameter of the nozzle hole 30 at the idling opening position 46 is larger in the characteristic curve 42a than in the characteristic curve 42b. Therefore, by selecting the characteristic curve 42a in cold regions and by selecting the characteristic curve 42b in warm regions, it is possible to maintain good idling operation of the engine.

As shown in FIG. 5, in order to gradually change the height position of the inclined surface 42 at the idling opening position 46 toward the outside in the radial direction of the throttle valve 14, both the inclined surfaces by continuing in the radial direction of the throttle 14,
Desired characteristics can be obtained within the region surrounded by characteristic curves 42a and 42b shown in FIG.

Further, as shown in FIG. 6, both inclined surfaces 42a and 42 at the idling opening position 46
By making the height position of b the same and making the height positions of both inclined surfaces 42a and 42b different at the fully open position 44, the fully open position 44 is set as shown by the characteristic lines 42a and 42b in FIG. The actual diameter of the nozzle hole 30 can be changed. Characteristic curve 4
2a is suitable for driving in lowlands, characteristic curve 42
b is suitable for driving at high altitudes.

As shown in FIG. 8, both the inclined surfaces are continuous in the radial direction of the throttle valve 14, so that the height position of the inclined surface 42 at the fully open position 44 is adjusted in the radial direction of the throttle valve 14. By gradually decreasing the change outward, desired characteristics can be obtained within the region surrounded by the characteristic curves 42a and 42b shown in FIG.

Further, as shown in FIG. 9, by gradually decreasing the height of the inclined surface 44 at the idling opening position 46 and the fully opening position 44 toward the outside in the radial direction of the throttle valve 14, The actual diameter of the nozzle hole 30 at the opening positions 46 and 44 can be adjusted.

According to the present invention, as described above, by moving the mounting position of the cam follower attached to the operating lever in the radial direction of the rotary throttle valve, the cam follower can be selectively attached to a plurality of inclined surfaces with different inclinations. As a result, the change characteristic of the effective diameter of the nozzle hole with respect to the rotational operation angle of the throttle valve can be selected to be suitable for the operating condition of the engine.

Therefore, according to the present invention, with a simple configuration, fuel can be appropriately supplied to the engine to suit the operating conditions of the engine, and the operating performance of the engine can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a carburetor according to the present invention, FIG. 2 is a perspective view showing the bearing member shown in FIG. 1, and FIG. 3 is a diagram showing another embodiment of the present invention. 1, and FIG. 4 is a graph showing the characteristic curve of the vaporizer shown in FIG. 1, and FIGS. It is a drawing similar to FIG. 2 showing an example of
FIG. 7 is a graph showing a characteristic curve of the bearing member shown in FIG. 10... vaporizer, 12, 24... vaporizer body,
14...Rotary throttle valve, 38...Operation lever, 42, 42a, 42b...Cam surface, 48,
52, 54, 56, 58...positioning means.

Claims (1)

[Claims for Utility Model Registration] (1) A fuel supply mechanism provided in the carburetor body, the end of which protrudes from the carburetor body, is accommodated in the carburetor body, and an operating lever is fixed to the protruding end. A rotary throttle valve having a generally cylindrical shape and supporting means for changing the effective diameter of a nozzle hole, and a displacement of the rotary throttle valve in the direction of its rotation center axis as the rotary throttle valve rotates. and a cam mechanism for defining the
The cam mechanism includes a plurality of cam surfaces provided on a portion of the carburetor body facing the operating lever, each of which extends in the circumferential direction of the rotary throttle valve in parallel with each other, and each of which is different in the direction of extension. a cam follower attached to the operating lever; and a cam follower of the rotary throttle valve attached to the operating lever so that the cam follower can be selectively engaged with the plurality of cam surfaces. and radially adjustable positioning means. (2) The plurality of cam surfaces are continuous with each other in the radial direction of the throttle valve.
The rotary throttle valve type carburetor described in paragraph (1).