JPH11280558A - Rotary throttle valve type cabureter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a rotation of an engine by appropriately carrying out a control of a quantity of a fuel flow by a measuring needle inserted to a fuel nozzle at an area from an idling rotation to a medium speed rotation. SOLUTION: A fuel injection opening 17 extended in a central-axial direction is provided on a side surface of a fuel nozzle 16 and an opening portion corresponding to an absorptive quantity of an air flow by closing a portion of the fuel injection opening 17 is formed by a bar shaft portion 21 of the measuring needle 7. A quantity of a fuel flow suctioned out from the opening portion is controlled by a restricting action of a passage space between the fuel nozzle 16 and a tapered shaft portion 22.

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 type carburetor for supplying fuel to a general-purpose two-stroke engine,
More specifically, the present invention relates to a rotary throttle valve type carburetor having a function of supplying a fuel at a flow rate appropriately adjusted according to an air flow rate.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 58-101253 discloses one type of carburetor for supplying fuel to a general-purpose two-stroke engine used for portable work machines for forestry and agriculture, small vehicles and other power sources. BACKGROUND ART A rotary throttle valve type carburetor described in a gazette or the like is widely known.

In this apparatus, a cylindrical throttle valve having a throttle through-hole and a measuring needle is arranged orthogonally to an intake passage of a carburetor body, and the center axis of the throttle valve is rotated while rotating the throttle valve in accordance with an accelerator operation. By moving in the direction, the degree of overlap of the throttle hole with the intake passage is changed to control the air flow rate, and at the same time, the fuel flow rate is controlled by changing the insertion depth of the metering needle into the fuel nozzle.

As one of the means for controlling the fuel flow rate by means of a measuring needle and a fuel nozzle, as shown in FIG.
The tapered portion 55 at the tip of the measuring needle 54 is inserted into the fuel nozzle 51 provided with
3 and the tapered portion 55, the fuel injection port 5 in the high-speed rotation range.
2 and the taper portion 55 respectively. Further, as another control means, as shown in FIG. 3B, a long hole is provided in the side surface in the direction of the central axis, and a fuel nozzle 56 serving as a fuel injection port 57 has a uniform diameter rod-shaped measuring needle 5.
In some cases, the fuel injection nozzle 57 is inserted with almost no gap and the fuel injection port 57 and the measuring needle 58 overlap.

[0005]

However, the one shown in FIG. 3A shows the variation in the shape of the tapered portion 55 from the jet 53 to the fuel injection port 52 and the vibration of the measuring needle 54 accompanying the operation of the engine. As a result, the fuel adjustment becomes unstable, and the fuel flow tends to be an intermittent flow. Therefore, there is a problem that the engine rotation tends to become unstable particularly in a low / medium-speed rotation range. In addition, since the effective area of the jet 53, that is, the fuel flow rate according to the movement of the measuring needle 54, has a considerable influence on the rotation speed in the low / medium speed rotation range, the dimensional accuracy of the jet 53 and the tapered portion 55 is increased. Also have the problem that adjustment is difficult.

On the other hand, in the apparatus shown in FIG. 3B, the measuring needle 58 is inserted into the fuel nozzle 56 with almost no gap, so that the instability due to the vibration accompanying the engine operation does not occur. However, the degree of overlap between the fuel nozzle 57 and the measuring needle 58, that is, the fuel nozzle 5 exposed in front of the tip of the measuring needle 58.
Since the fuel flow rate is controlled only by the area of the opening 7, a change in the fuel flow rate in accordance with the movement of the measuring needle 58 in the low / medium speed rotation region has a considerable influence on the rotation speed, and an appropriate There is a problem that it is difficult to control.

The present invention relates to a rotary throttle valve type carburetor, that is, a cylindrical throttle valve having a throttle hole and a measuring needle arranged orthogonally to an intake passage of a carburetor body, and is arranged on a central axis of the throttle valve. And a fuel nozzle with a metering needle inserted into the throttle through-hole and controlling the air flow rate and the fuel flow rate by moving the throttle valve in the direction of its own central axis while rotating according to the accelerator operation. It is difficult to properly control the fuel flow rate in the low and medium speed range of the engine that the carburetor of the configuration has, and it is easy to make the engine rotation unstable,
It is an object of the present invention to solve the above-mentioned problem and to appropriately control the fuel flow rate by the fuel nozzle and the measuring needle.

[0008]

In order to solve the above-mentioned problems, the fuel nozzle has a slit-shaped fuel injection port extending in the center axis direction on a side surface thereof, and the measuring needle is inserted into the fuel nozzle with almost no gap. And a tapered shaft portion extending forward from the distal end thereof and having a base end having a diameter smaller than that of the rod shaft portion. The portion is closed, and the tapered shaft portion is configured to control the flow rate of fuel sucked from the opening of the fuel injection port.

The rod portion of the measuring needle that moves in the direction of the central axis integrally with the throttle valve in response to the accelerator operation changes the opening of the fuel injection port almost in proportion to the amount of intake air. At the same time, the size of the passage gap, which is the gap between the fuel nozzle and the tapered shaft portion, changes, and the fuel flow rate is appropriately controlled according to the magnitude of the throttle action. As a result, the engine can be rotated stably. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described. A carburetor body 1 has an intake passage 2 penetrating forward and backward and a valve hole 3 perpendicular to the intake passage 2 and having one end closed. A cylindrical throttle valve 4 is fitted into the valve hole 3 so as to be rotatable and movable in the direction of its own 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, a valve Axis 8
have. The nozzle insertion hole 6 is provided on the closed end side of the valve hole 3 so that the fuel nozzle 16 is inserted. Further, the valve shaft 8 is fixed to the end of the throttle valve 4 located on the open end side of the valve hole 3, penetrates through the cover body 11 of the valve hole 3, and projects outside the carburetor body 1. Further, the measuring needle 7 is pressed against the adjusting screw 9 screwed into the screw hole 8 a of the valve shaft 8 by the spring force of the pressing spring 10. The throttle valve 4 is adjustable so that the insertion depth into the fuel nozzle 16 at the idle position can be adjusted.
Is held in.

A throttle valve lever 12 which is turned by a driver's accelerator operation is fixed to the shaft end of the valve shaft 8, and a torsion coil between the throttle valve 4 and the cover body 11 has both ends fixed thereto. A valve closing spring 13 composed of a spring is inserted around the valve shaft 8. Also, the valve shaft 8 of the throttle valve 4
A flange 4a is provided at the side end, and a cam 14 is formed on a surface facing the intake passage 2, and this cam 14 contacts a pin 15 protruding from the carburetor body 1.

When the throttle valve lever 12 is turned by the 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 pin 1
The throttle valve 4 moves in the direction of its own central axis in accordance with the cam 14 contacting the cam 5, and the insertion depth of the metering needle 7 into the fuel nozzle 16 changes, so that the fuel flow sucked out from the fuel injection hole 17 opened on the side surface. Is controlled.

On the end face of the carburetor main body 1 opposite to the cover body 11, a constant fuel chamber 18 similar to a widely known membrane carburetor is provided, which is separated from the atmosphere by a diaphragm (not shown). The fuel in the constant fuel chamber 18 passes through the main fuel passage 19 and is regulated by the main jet 20 and sent to the fuel nozzle 16. A constant pressure chamber 18 for supplying fuel from a fuel tank (not shown) to the constant fuel chamber 18;
A well-known fuel pump is provided at an appropriate position on the outer surface of the carburetor body 1.

The basic configuration including the throttle valve 4, the constant fuel chamber 18, and a fuel pump (not shown) is the same as a rotary throttle valve carburetor that has been widely known.

Next, referring to FIG. 2, the measuring needle 7 is inserted into the fuel nozzle 16 with almost no gap and a rod shaft portion 21 having a uniform diameter.
And a tapered shaft portion 2 extending forward from the front end and having a smaller diameter toward the front end inserted with a gap in the fuel nozzle 16.
2 and the base end of the tapered shaft portion 22 is
It is made smaller in diameter and has a step 23 between them.

Further, the fuel injection port 17 is formed in a slit-shaped rectangle extending in the direction of the central axis from the leading edge of the fuel nozzle 16, and in the illustrated embodiment, the outlet side facing the throttle hole 5 is chamfered to enlarge the outlet. Is formed.

FIGS. 2A, 2B, and 2C show the positional relationship between the metering needle 7 and the fuel injection port 17 in the engine idle to low speed range, medium speed range, and high speed range. The area of the fuel injection port 17 that is not closed by the rod shaft 21, that is, the area of the openings 24 </ b> A, 24 </ b> B, 24 </ b> C is determined by the position of the step 23.

2A, the diameter D of the base end of the tapered shaft portion 22 in the idling or low-speed rotation range of the engine.
₀ and the tapered angle or fuel injection port 17 of the lower edge and the passage gap 16A determined by the diameter D ₁ of the tapered shaft portion 22 at the same position, i.e., the fuel flow rate is controlled by the throttling action of the gap between the tapered shaft portion 22 and the fuel nozzle 16 You. 2B, the diameter D ₀ of the base end of the tapered shaft portion 22 and the diameter D ₂ of the tapered shaft portion 22 at the same position as the lower end edge of the fuel injection port 17 are shown. The fuel flow rate is controlled by the throttle action of the passage gap 16B determined by the above.

It is apparent at first glance that the throttle action of the passage gaps 16A and 16B shown in FIGS. 2A and 2B is smaller in the latter, and the diameter D at the base end of the tapered shaft portion 22 is apparent. By appropriately setting ₀ and the taper angle, the opening 24 whose area changes almost proportionally to the opening degree of the throttle hole 5, that is, the intake air amount, from the idling rotation of the engine to the middle rotation speed range.
A, 24B, the fuel flow rate can be appropriately controlled, and the fine adjustment of the fuel flow rate can be easily performed by the adjusting screw 9.

In the high-speed rotation range of the engine shown in FIG. 2C, the step 23 moves near the upper end of the fuel injection port 17 and maximizes the opening 24C of the fuel injection port 17 to be substantially fully opened. . Further, since the small diameter portion near the tip of the tapered shaft portion 22 is located at the lower end edge of the fuel injection port 17, the passage gap
The throttle action of 6C is slight, and the fuel flow required for high-speed rotation can be secured.

The fuel injection port 17 has a slit shape extending from the front end edge of the fuel nozzle 16 and extending in the direction of the central axis. The same applies to the one described in Japanese Unexamined Patent Publication No. Sho 61-183453. In this case, the fuel injection port 1 is provided at least in the rotation range below the middle rotation range.
7 may be closed but the fuel injection port 17 may be fully opened in the high-speed rotation range, or the tapered shaft portion 22 may be made shorter than the fuel injection port 17.

[0023]

As described above, according to the present invention, the slit-shaped fuel injection port is provided on the side surface of the fuel nozzle, the opening area of the fuel injection port is changed by the rod shaft of the measuring needle, and the fuel flow rate is controlled by the tapered shaft. In this way, the fuel flow can be properly controlled, particularly in the range from idling to medium speed, and the engine rotation can be stabilized.

[Brief description of the drawings]

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

FIG. 2 is an enlarged partial view of FIG. 1, wherein (A), (B),
(C) is a longitudinal sectional view in different rotation ranges of the engine,
(D) is sectional drawing which follows the AA line of (A).

FIGS. 3A and 3B are longitudinal sectional views showing different conventional examples.

[Explanation of symbols]

1 carburetor body, 2 intake passage, 4 throttle valve, 5
Throttle hole, 7 measuring needle, 16 fuel nozzle, 1
7 fuel nozzle, 21 rod shaft, 22 taper shaft,
23 steps,

Claims (1)

[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 nozzle which is disposed on the central axis of the throttle valve and is open to the throttle through-hole and into which the metering needle is inserted, wherein the throttle valve moves in the direction of its own central axis while rotating according to an accelerator operation. In the rotary throttle valve type carburetor that controls the air flow rate and the fuel flow rate, the fuel nozzle has a slit-shaped fuel injection port extending in the center axis direction on the side surface, and the metering needle is provided with the fuel. A bar shaft portion inserted into the nozzle with almost no gap and a tapered shaft portion extending forward from the tip thereof and having a base end having a smaller diameter than the bar shaft portion, wherein the bar shaft portion is at least an engine. A part of the fuel injection port is closed in a rotation range equal to or lower than a medium speed rotation range, and the tapered shaft portion controls a flow rate of fuel sucked from an opening of the fuel injection port. Valve type Equalizer.