JP3324022B2 - Sliding throttle valve carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for controlling the concentration and amount of an air-fuel mixture supplied to an engine, in which a sliding throttle valve moves in a throttle valve guide cylinder provided in connection with an intake passage. The present invention relates to a sliding throttle valve type carburetor which is freely disposed and whose venturi formed by an intake passage and a sliding throttle valve is controlled by moving the sliding throttle valve.

[0002]

2. Description of the Related Art A conventional sliding throttle valve type carburetor is shown in FIG.
7 will be described. Reference numeral 1 denotes a carburetor main body in which an intake passage 2 penetrates left and right, and a throttle valve guide cylinder 2A is continuously provided upward from an intermediate portion of the intake passage 2. Throttle valve guide cylinder 2A
A sliding throttle valve 3 is movably arranged in the inside, and the area (venturi portion) of the intake passage 2 is opened and closed by operating the sliding throttle valve 3 with an accelerator wire (not shown) by a driver. Controlled. The intake path 2 is divided by a sliding throttle valve 3 into an intake path 2B on the left air cleaner side connected to an air cleaner (not shown) and an intake path 2C on the right engine side connected to an engine (not shown). You. Reference numeral 4 denotes a needle jet of the main fuel system which opens into the intake passage 2 facing the bottom 3A of the sliding throttle valve 3, and this needle jet 4 is provided in the floating chamber 7 through the main mixing pipe 5 and the main fuel jet 6. It communicates below a certain liquid level.

[0003] A cutter 3B (CUT AWAY) is formed at the bottom 3A of the sliding throttle valve 3. The cutterway 3B is notched diagonally from the side surface 3C of the sliding throttle valve 3 on the air cleaner side toward the engine side surface 3D of the sliding throttle valve 3 and toward the bottom 3A of the sliding throttle valve 3. In other words, the cutterway 3B is a notch on the air cleaner side of the sliding throttle valve 3, and plays a role of controlling the negative pressure acting on the needle jet 4. Reference numeral 7 denotes a jet needle attached to the sliding throttle valve 3, which is inserted into a needle jet 4 which opens to the intake passage 2, and is sucked into the intake passage 2 by an annular gap formed by both members. Control the amount of main fuel used. Reference numeral 8 denotes a low-speed injection hole serving as a low-speed fuel system that opens into the intake path 2 facing the bottom of the engine-side side surface 3D of the sliding throttle valve 3. It communicates with a certain liquid level in the float chamber 7 via the jet 10. When the engine is operated, the air flowing into the intake path 2B on the air cleaner side via the air cleaner (not shown) flows toward the bottom 3A of the sliding throttle valve 3 via the cutterway 3B. The amount of air is controlled by the opening area of the venturi portion V formed by the bottom portion 3A of the sliding throttle valve 3 and the corresponding intake passage 2, and this air is supplied to the engine via the intake passage 2C on the engine side. Supplied. On the other hand, according to the air flow, a negative pressure is generated in the venturi section V, and the fuel corresponding to the negative pressure is sucked into the venturi section V from the needle jet 4 and the low-speed injection hole 8 opening in the venturi section V. The fuel is mixed into the airflow flowing through the venturi section V to form an air-fuel mixture, and this air-fuel mixture is supplied to the engine.

[0004]

According to such a conventional sliding throttle valve type carburetor, the negative pressure applied to the needle jet 4 and the low-speed injection hole 8 opening to the venturi portion V is increased, and the air flowing through the venturi portion V is increased. It has been difficult to increase the inhalation efficiency of the drug. The inability to sufficiently increase the negative pressure applied to the needle jet 4 and the low-speed injection hole 8 makes it difficult to improve the atomization characteristics of the fuel.
Engine operability, acceleration response, reduction of harmful exhaust gas components,
Furthermore, there is a problem in the setting properties of the carburetor, while the inability to increase the suction efficiency is a problem in improving the output of the engine. This is considered to be due to the following reasons. Referring to FIG. 18, which is a cross-sectional view taken along the line AA in FIG. 17, an air flow flowing in the intake passage 2B on the air cleaner side toward the engine (flows from left to right in FIG. 17). ) Is the sliding throttle valve 3
18, the air flow is diverted to the upper side B and the lower side C in FIG. Next, the air flow diverted to the side flows obliquely downward along the cutterway 3B formed in the sliding throttle valve 3, and flows into the venturi portion V. In other words, in FIG. 17, the airflow flowing along the longitudinal direction in the intake passage 2B on the air cleaner side collides with the side surface 3C on the air cleaner side of the sliding throttle valve 3, and is diverted to the horizontal side. Then, the direction changes greatly from the horizontal side flow to the downward direction D, and the cutter way 3
It flows into B. As described above, the flow direction of the air is largely changed, so that the flow velocity of the air flowing into the venturi portion V is greatly reduced, so that the generation of a high negative pressure in the venturi portion V is suppressed and the venturi portion V
, The passage of the air flow is hindered.

The present invention has been made in view of the above-mentioned problems, and increases a negative pressure generated in a venturi section V, thereby opening a needle jet 4 and a low-speed injection hole 8 opening in the venturi section V.
It is an object of the present invention to provide a sliding throttle valve type carburetor capable of effectively increasing a negative pressure applied to a gas turbine and improving suction efficiency.

[0006]

Means for Achieving the Object To achieve the above object,
According to the present invention, an intake passage penetrates a carburetor body, and the intake passage is controlled to be opened and closed by a sliding throttle valve movably arranged in a throttle valve guide cylinder, and is integrally attached to the sliding throttle valve. In a sliding throttle valve type carburetor inserted and arranged in a needle jet in which a drawn jet needle opens into an intake passage, the upstream end of the sliding throttle valve is opened on the side of the sliding throttle valve on the air cleaner side, and A first cutterway having an end directed toward the engine-side side of the sliding throttle valve and toward the bottom of the sliding throttle valve, the tangent of which crosses the bottom of the sliding throttle valve at an angle, and the upstream end has a first cutterway. And the downstream end is directed toward the engine-side side of the throttle valve and toward the bottom of the sliding throttle valve, and its tangent intersects the bottom of the sliding throttle valve at an angle smaller than the intersection angle of the first cutterway. The second cutterway and the first And Ttauei, and a connecting surface portion for continuously connecting the intersections of the second Kattauei provided, further, the first characterized in that a jet needle through the second Kattauei or connecting face portion.

According to the present invention, in addition to the first feature, the opening position of the first cutterway, which is opened on the side of the sliding throttle valve on the air cleaner side, is located above the center XX of the intake passage. The opening is a second feature.

Further, in the present invention, in addition to the first feature, a cross section of the first cutterway is formed such that a central portion thereof is formed with a recess toward the engine-side side surface of the sliding throttle valve. This is the third feature.

[0009]

According to the first feature, the airflow flowing along the air cleaner-side intake passage along the longitudinal and horizontal direction collides with the first cutterway formed on the side of the sliding throttle valve on the air cleaner side. It is converted into a flow obliquely downward toward the bottom of the sliding throttle valve. The downward airflow flows from the connection surface portion to the venturi portion via the second cutterway, and can flow into the venturi portion without greatly reducing the speed of the airflow flowing through the intake passage on the air cleaner side. . Thus, the negative pressure in the venturi can be increased, a high negative pressure can be applied to the needle jet and the low-speed injection hole, and the suction efficiency can be improved.

According to the second feature, the length of the first cutter way in the air flow direction can be made sufficiently long. According to this, the airflow from the first cutterway to the second cutterway via the connection surface can be supplied obliquely downward in a favorable rectification state, so that the negative pressure in the venturi can be effectively increased.

According to the third feature, the airflow flowing through the first cutterway flows obliquely downward along the first cutterway and also flows down toward the center of the sliding throttle valve. According to this, the airflow flowing along the first cutterway is directed toward the center of the second cutterway via the connection surface and flows into the second cutterway, and is arranged at the center of the intake path. Thus, the negative pressure applied to the needle jet and the low-speed injection hole can be more effectively increased, and the suction efficiency can be further improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a sliding throttle valve type carburetor according to the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view of the sliding throttle valve, FIG. 2 is a left side view of the sliding throttle valve of FIG. 1 viewed from the cutterway side, and FIG. 3 is a state in which the sliding throttle valve of FIG. 1 is assembled to a carburetor. FIG. 4 is a longitudinal sectional view showing FIG.
It is a cross-sectional view in the E line. The sliding throttle valve is different from the conventional sliding throttle valve carburetor shown in FIG. FIG.
The same components as those in 7 are denoted by the same reference numerals and description thereof is omitted. The sliding throttle valve 20 has a circular cross section, and has a left side formed with an air cleaner side surface 20A facing the air cleaner side intake path 2B, and a right side with the engine side intake path 2B.
An engine-side side surface 20B facing C is formed, and a bottom portion 20C facing the intake passage 2 where the needle jet 4 and the low-speed injection hole 8 are opened is formed below the side surface 20B. A first flat surface is formed from the side surface 20A on the air cleaner side to the side surface 20B on the engine side (to the right in FIG. 1) and to the bottom 20C of the sliding throttle valve 20 (to the lower side). A cutaway 20D is formed. More specifically, the first cutterway 20D forms a downward slope inclined from the side surface 20A on the air cleaner side to the bottom portion 20C of the sliding throttle valve 20, and its upstream end 20E opens to the side surface 20A on the air cleaner side. , The downstream end 20F is the bottom 20
Reach C. The tangent line FF of the first cutterway 20D intersects the bottom 20C of the sliding throttle valve 20 at an angle G.

A second cutter way 20G is formed to intersect the first cutter way 20D. The tangent line HH of the second cutter way 20G is such that the upstream end 20H of the imaginary line of the tangent line HH is the first cutter way 2H.
0D tangent line FF intersects with a virtual intersection 20J, and the downstream end 20K is the engine side surface 20 of the sliding throttle valve 20.
It forms a downward slope reaching the bottom 20C near B.
The tangent HH of the second cutterway 20G is set to an angle J smaller than the angle G at which the tangent FF of the first cutterway 20D intersects the bottom 20C with respect to the bottom 20C of the sliding throttle valve 20. Is done. An arcuate connecting surface 20L is formed at a virtual intersection 20J between the tangent FF of the first cutterway 20D and the tangent HH of the second cutterway 20G.

That is, the sliding throttle valve 20 has a first cutterway 20D, a connection surface portion 20L, and a second surface portion 20A, which extend from the side surface 20A on the air cleaner side toward the side surface 20B on the engine side and toward the bottom 20C thereof. Cutterway 2
0G are continuously formed. Further, the second cutterway 20G or the connection surface portion 20L from the inner bottom of the sliding throttle valve 20.
And a jet needle insertion hole 20M is penetrated. In this example, the jet needle insertion hole 20M was formed at the boundary between the connection surface 20L and the second cutterway 20G. The reason why the area below the jet needle insertion hole 20M is enlarged is to escape a protrusion such as a needle jet or a screen tube, and is not always necessary.

FIG. 3 shows a state in which the sliding throttle valve 20 having the above-described structure is disposed in the throttle valve guide cylinder 2A of the carburetor body 1. At this time, the side surface of the sliding throttle valve 20 on the air cleaner side is shown. 20A is disposed facing the intake passage 2B on the air cleaner side, and the engine side surface 20B is disposed on the intake passage 2B on the engine side.
The bottom 20C is disposed facing the bottom of the intake path 2 where the needle jet 4 and the low-speed injection hole 8 are open. The jet needle 7 arranged in the jet needle insertion hole 20M of the sliding throttle valve 20 is
The low-speed injection hole 8 faces the bottom 20C of the engine-side side surface 20B of the sliding throttle valve 20 and opens into the intake passage through the needle jet 4 opening through the cutterway 20G into the intake passage. .

Then, when the engine is operated,
When air flows from the intake path 2B on the air cleaner side to the intake path 2C on the engine side, the air path 2B on the air cleaner side
The horizontal airflow flowing through the inside collides with a first cutterway 20D formed on a side surface 20A of the sliding throttle valve 20 on the air cleaner side. And this first cutter way 2
The horizontal airflow that collides with 0D changes the direction of the flow along the first cutterway 20D.
Is formed as an inclined surface that forms a flat surface that descends to the right toward the bottom 20C of the sliding throttle valve 20, so that the horizontal airflow flowing through the intake passage 2B on the air cleaner side is oblique in the downward right direction. To the bottom portion 20C of the sliding throttle valve 20. Then, the airflow in the obliquely downward right direction along the first cutterway 20D flows along the connection surface portion 20L, and flows into the second cutterway 20G.

According to the above, the intake path 2 on the air cleaner side
B is the first airway 2
0D intensively rectifies the air flow obliquely downward toward the bottom 20C of the sliding throttle valve 20, and this rectified air is passed through the connection surface 20L to the second cutterway 20G.
As a result, the flow velocity of the air flow in the venturi V formed by the bottom portion 20C of the sliding throttle valve 20 and the intake passage 2 opposed thereto can be effectively increased. In particular, according to the provision of the connection surface portion 20L, the turbulence does not occur in the airflow from the first cutterway 20D to the second cutterway 20G, and the airflow can be controlled smoothly. Since the air flow velocity of the venturi V can be increased, the negative pressure of the venturi V can be increased, and the amount of air flowing through the venturi V can be effectively increased.

It is apparent from the experimental results shown in FIG. 5 that the negative pressure applied to the low-speed injection hole 8 can be increased as compared with the conventional sliding throttle valve type carburetor. According to this, it is recognized that the negative pressure could be increased at each throttle valve opening of the sliding throttle valve 20 as compared with the conventional throttle valve.

The fact that the negative pressure applied to the needle jet 4 can be increased in comparison with a conventional sliding throttle valve type carburetor is evident from the experimental results shown in FIG. According to this, it is recognized that the negative pressure could be increased at each throttle valve opening of the sliding throttle valve 20 as compared with the conventional throttle valve.

The fact that the amount of intake air flowing through the intake passage of the carburetor can be increased as compared with the conventional sliding throttle valve carburetor is clarified by the experimental results shown in FIG. According to this, it is recognized that the intake air amount could be increased at each throttle valve opening of the sliding throttle valve 20 as compared with the conventional one.

As described above, according to the fact that the negative pressure in the venturi portion V applied to the low-speed injection hole 8 and the needle jet 4 can be increased, the fuel having better atomization characteristics than the low-speed injection hole 8 and the needle jet 4 can be obtained. Can be sucked into the venturi section V, and the fuel can be uniformly mixed with the airflow flowing through the venturi section V, whereby a well-atomized uniform air-fuel mixture can be supplied to the engine. It is. Thus, the combustion state of the engine at each opening of the sliding throttle valve 20 can be satisfactorily performed, and the operability of the engine can be improved and the harmful exhaust gas component can be reduced. In addition, the fact that a good air-fuel mixture in an atomized state can be supplied to the engine means that the air-fuel mixture can be immediately supplied to the engine in response to the opening of the sliding throttle valve 20 during the acceleration operation of the engine, The acceleration responsiveness of the engine can be improved. Furthermore, since the negative pressure applied to the low-speed injection hole 8 and the needle jet 4 could be increased, the setting workability was significantly improved, and the degree of freedom for adapting to the engine was greatly increased. .

Further, according to the fact that the amount of intake air at each throttle valve opening of the sliding throttle valve 20 can be increased, the output of the engine can be improved.

Although the shape of the connection surface portion 20L in the above embodiment is formed in an arc shape, the connection surface portion 20L may be a single flat surface as shown in FIG.
Further, as shown in FIG. 9, the connection surface portion 20L may be a multi-level flat surface such as a two-level flat surface. That is, since the angle J of the tangent line HH of the second cutterway 20G is formed at an angle smaller than the angle G of the tangent line FF of the first cutterway 20D, the intersection between the two tangent lines is inevitably formed. An intersection 20J having an intersection angle is formed, and the connection surface 20L is required to suppress the occurrence of turbulence by increasing the intersection angle of the intersection 20J as much as possible.

In the second cutterway 20G, the tangent HH crossing angle J of the second cutterway 20G is equal to that of the first cutterway 2G.
Since it is set smaller than the intersection angle G of the tangent line FF of 0D, the second cutterway 20G is relatively opened to a position below the first cutterway 20D. According to the above,
The second cutterway 20G suppresses a decrease in the negative pressure of the venturi portion V. That is, the negative pressure of the venturi portion V tends to be weakened as the opening position of the second cutterway 20G with respect to the first cutterway 20D moves upward, and as described above,
The second cutter way 20G is replaced with the first cutter way 20G.
By opening at a position below D, the negative pressure in the venturi portion V can be maintained at a high negative pressure state.

The upstream end 2 of the first cutterway 20D
The opening position of the sliding throttle valve 20 in the side surface 20A on the air cleaner side of 0E is preferably above the longitudinal axis XX of the intake passage 2 shown in FIG. This is the first
The length L of the inclined surface of the cutterway 20D can be made sufficiently long, whereby the airflow flowing in the intake passage 2B on the air cleaner side can be reliably reduced obliquely along the inclined surface of the first cutterway 20D. Flow can be rectified in the direction of flow in this direction, and the air flow in this rectified state can be
L, it is possible to positively flow into the second cutterway 20G. Therefore, the above-described effect of increasing the negative pressure of the venturi section V and the improvement of the suction efficiency can be more effectively achieved.

FIG. 10 is a longitudinal sectional view showing another embodiment of the sliding throttle valve, FIG. 11 is a right side view of the sliding throttle valve of FIG. 10 viewed from the side on the air cleaner side, and FIG. LL
It is a cross-sectional view in a line. The sliding throttle valve shown in FIG. 10 and the sliding throttle valve shown in FIG. 1 are different from each other in a first cutter connection surface portion and a second cutter way. FIG.
The same reference numerals are used for the same components as those described above, and the description is omitted. That is, the first cutter 20D, the connection surface 20L, and the second cutter 20G illustrated in FIG. 1 have flat surface shapes, whereas the first cutter 20D illustrated in FIG.
The surface shapes of the cutterway 20D ', the connection surface portion 20L' and the second cutterway 20G 'are arc-shaped. This arc-shaped cutter way is well shown in FIG.
The cross section of the first cutterway 20D 'is formed in a circular arc shape having a concave portion 20N whose center portion is directed toward the engine side surface 20B of the sliding throttle valve 20 (in other words, directed rightward in FIG. 12). The deepest portion of the recess 20N is directed toward the jet needle insertion hole 20M. or,
The cross sections of the connection surface portion 20L 'and the second cutterway 20G' are also formed in an arc shape forming the concave portion 20N.

Then, by operating the engine,
When air flows from the intake path 2B on the air cleaner side to the intake path 2C on the engine side, the air path 2B on the air cleaner side
The horizontal airflow flowing through the inside collides with a first cutterway 20D 'formed on a side surface 20A of the sliding throttle valve 20 on the air cleaner side. The horizontal airflow that collides with the first cutterway 20D 'changes its direction along the first cutterway 20D'.
Since the first cutterway 20D 'is formed as an inclined surface having an arc shape that descends to the right toward the bottom portion 20C of the sliding throttle valve 20, the horizontal airflow flowing through the intake passage 2B on the air cleaner side is shifted to the right. It goes down in a diagonal direction and flows down along the center of the arc-shaped concave portion 20 </ b> N to surely go to the center of the sliding throttle valve 20. Then, the airflow in the obliquely downward right direction along the first cutterway 20D 'is
A second cutter way 20G 'via the connection surface 20L'
Flows along.

According to the above description, the intake path 2 on the air cleaner side
B, a horizontal air flow flowing through the inside of the first cutter way 20D 'is formed by the arc-shaped concave portion 20N of the first cutter way 20D'.
Is intensively rectified by the air flow obliquely downward toward the center (in other words, the center of the intake passage), and the rectified air is connected to the connection surface portion 20L 'and the second cutterway 20G'.
As a result, the flow velocity of the airflow in the venturi V formed by the bottom portion 20C of the sliding throttle valve 20 and the intake passage 2 opposed thereto can be more effectively increased. Since the air flow velocity in the venturi section V can be further increased, the negative pressure in the venturi section V can be further increased as compared with the first embodiment, and further, the air flows through the venturi section V. The amount of air can be more effectively increased as compared with the first embodiment.

FIG. 13 is a cross sectional view of a sliding throttle valve according to still another embodiment. The surface shape of the first cutter way 20D 'shown in FIG. 12 is an arc shape forming the recess 20N, whereas the first cutter way 20D' shown in FIG.
The surface of D "is formed in a conical shape having a concave portion 20N 'whose center portion is directed toward the engine side surface 20B of the sliding throttle valve 20, and the deepest corner of the conical shape is a jet needle insertion hole. Head to 20M.

According to the above, the intake path 2 on the air cleaner side
B is the first airway 2
The corners of the 0D ″ conical concave portion further intensively rectify the air flow obliquely downward toward the center of the sliding throttle valve 20, and the rectified air is connected to the connection surface portion 20L ′,
Since the gas flows into the second cutterway 20G ', the flow velocity of the air flow in the venturi V formed by the bottom portion 20C of the sliding throttle valve 20 and the intake passage 2 opposed thereto is further effectively increased. be able to. Since the air flow velocity in the venturi V can be further increased, the negative pressure in the venturi V can be further increased, and the amount of air flowing through the venturi V can be further effectively reduced. Can increase the amount.

Although the above-described sliding throttle valve has a cylindrical shape, the sliding throttle valve shown in FIG.
It may be of a long shape as shown in FIG. 15 or of a different shape having a cylindrical venturi forming portion at the center portion as shown in FIG. 16 and a blade portion extending laterally. The shape of the valve itself is not limited at all, and the first cutterway, the connection surface portion, and the second cutterway can be formed.

[0032]

As described above, according to the first feature of the sliding throttle valve carburetor according to the present invention, the airflow flowing in the intake passage on the air cleaner side is directed to the side surface of the sliding throttle valve on the air cleaner side. The first cutterway provided rectifies the airflow into a diagonally downward direction toward the bottom, and the rectified airflow flows into the second cutterway via the connection surface portion. And the negative pressure applied to the needle jet opening at the venturi portion and the low-speed injection hole can be increased, and the suction efficiency can be greatly improved.
According to the above, the mixture can be atomized well,
The combustion state of the engine can be satisfactorily performed, thereby improving the operability of the engine, reducing harmful exhaust gas components, and further improving the acceleration response and the setting workability. Further, the output performance of the engine can be improved by improving the suction efficiency.

Further, according to the second feature of the present invention, the length of the inclined surface of the first cutterway can be sufficiently set,
The effect of increasing the negative pressure of the venturi section and the improvement of the suction efficiency can be more effectively performed, and further, the reduction of the negative pressure of the venturi section due to the second cutterway is suppressed.

According to the third feature of the present invention, the air flow flowing through the first cutterway can be rectified and directed intensively toward the center of the bottom of the sliding throttle valve. The air flow velocity in the venturi can be further increased, the negative pressure in the venturi can be further increased, and the suction efficiency can be more effectively improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sliding throttle valve used in a sliding throttle valve type carburetor according to the present invention.

FIG. 2 is a left side view of a side surface of the sliding throttle valve of FIG. 1 on an air cleaner side.

FIG. 3 is a longitudinal sectional view of the sliding throttle valve type carburetor in a state where the sliding throttle valve of FIG. 1 is assembled.

FIG. 4 is a transverse sectional view taken along line EE in FIG. 3;

FIG. 5 is a diagram showing a gap between a sliding throttle valve opening and a negative pressure applied to a low-speed injection hole.

FIG. 6 is a diagram showing a relationship between the opening degree of a sliding throttle valve and a negative pressure applied to a needle jet.

FIG. 7 is a diagram showing a relationship between a sliding throttle valve opening and an intake air amount.

FIG. 8 is a longitudinal sectional view showing another embodiment of the sliding throttle valve.

9 is a left side view of the side surface on the air cleaner side of the sliding throttle valve of FIG. 8;

FIG. 10 is a longitudinal sectional view showing still another embodiment of the sliding throttle valve.

FIG. 11 is a left side view of the sliding throttle valve of FIG. 10;

FIG. 12 is a transverse sectional view taken along line LL of FIG. 10;

FIG. 13 is a cross-sectional view showing still another embodiment of the sliding throttle valve.

FIG. 14 is a simplified top plan view showing an example of the outer shape of the sliding throttle valve.

FIG. 15 is a simplified top plan view showing another example of the outer shape of the sliding throttle valve.

FIG. 16 is a simplified top plan view showing still another example of the outer shape of the sliding throttle valve.

FIG. 17 is a longitudinal sectional view showing a conventional sliding throttle valve carburetor.

18 is a transverse sectional view taken along line AA of FIG.

[Explanation of symbols]

 Reference Signs List 20 Sliding throttle valve 20A Side surface on air cleaner side 20B Side surface on engine side 20C Bottom part 20D First cutter way 20G Second cutter way 20J Intersection 20L Connection surface part 2 Intake path 7 Jet needle

Claims (3)

(57) [Claims] An intake passage penetrates a carburetor body, and the intake passage is controlled to open and close by a sliding throttle valve movably disposed in a throttle valve guide cylinder, and is integrated with the sliding throttle valve. In the sliding throttle valve type carburetor in which the fitted jet needle is inserted and arranged in the needle jet opening to the intake passage, the sliding throttle valve 20 has an upstream end on the side 20A of the sliding throttle valve 20 on the air cleaner side. The sliding throttle valve 20 is open and the downstream end is directed to the engine side surface 20 </ b> B of the sliding throttle valve 20.
0C, the first cutterway 2 whose tangent line FF intersects the bottom 20C of the sliding throttle valve 20 at an angle G.
0D, the upstream end opens into the first cutterway 20D,
The downstream end is directed toward the engine side surface 20B of the throttle valve 20 and toward the bottom 20C of the sliding throttle valve 20;
A second cutterway 20G in which −H intersects a bottom 20C of the sliding throttle valve 20 at an angle J smaller than an intersection angle G of the first cutterway 20D, and a first cutterway 2
0D and a connecting surface portion 20L that continuously connects the intersection portion 20J of the second cutterway 20G is provided, and the jet needle 7 is further arranged so as to penetrate through the second cutterway 20G or the connecting surface portion 20L. Sliding throttle valve type carburetor. 2. An opening position of the first cutterway 20D, which is opened on a side surface 20A of the sliding throttle valve 20 on the air cleaner side, is opened above a center XX of the intake path 2. The sliding throttle valve type carburetor according to claim 1. 3. A cross section of the first cutterway 20D ', the center of which is the engine side surface 2 of the sliding throttle valve 20.
2. The sliding throttle valve type carburetor according to claim 1, wherein the concave portion 20N is formed toward 0B.