JP2714765B2 - Variable venturi 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, and in which a movable valve is movably disposed in a movable valve guide cylinder connected to an intake passage. The present invention relates to a variable venturi carburetor in which a venturi area formed by an intake path and a movable valve is controlled by moving the movable valve.

[0002]

2. Description of the Related Art A variable venturi carburetor comprises an intake passage penetrating a carburetor body laterally, a movable valve guide tube connected upward from an intermediate portion of the intake passage, and a movable valve guide tube. And a movable valve movably disposed in the movable valve guide cylinder, whereby a venturi area formed by the intake path and the movable valve is variably controlled. Further, a jet needle is integrally mounted on the movable valve, and the jet needle is inserted into a needle jet as a nozzle that opens at the bottom of the intake passage. Control the amount of fuel sucked into the road to an appropriate amount. On the other hand, the diameter of the intake passage from the movable valve guide cylinder toward the air cleaner (upstream side) increases in diameter toward the air cleaner, and the increase in the intake passage diameter on the air cleaner side is caused by the engine. This is performed by supplying a large amount of air toward the nozzle and effectively increasing the negative pressure at the tip opening of a nozzle (ie, a jet needle) opening to the venturi section.

[0003]

According to such a conventional variable venturi carburetor, air flowing into the carburetor from an air cleaner located upstream of the carburetor is restricted by a movable valve from an enlarged intake passage on the air cleaner side. After flowing into the formed venturi section, it is supplied to the engine via an intake passage downstream of the venturi section. Looking at the air flow from the upstream side to the downstream side in the intake passage cross section orthogonal to the moving direction of the movable valve, especially in the intake passage on the air cleaner side, the central portion of the intake passage has a longitudinal axis. Although it flows down along the line, in the outer peripheral part, it flows down obliquely toward the center along the inner peripheral wall surface of the intake path on the air cleaner side, and between the central part of the intake path and the outer peripheral part of the intake path. Since the air flow directions are different, turbulence is generated by collision of the air flows in the intake passage near the venturi section. This state is shown in FIG.
Is shown in

[0004] The turbulence in the intake passage near the venturi portion causes the flow velocity of the air flowing through the venturi portion to decrease. According to this, the tip of the nozzle opening near the venturi portion and the venturi portion is reduced. The negative pressure and the negative pressure of the low-speed fuel injection hole become small, and the air flow in the intake path including the venturi becomes unstable.
According to the above description, it becomes difficult to perform good suction of fuel from the nozzle and the low-speed fuel injection hole to the venturi portion.Furthermore, atomization of the fuel is inhibited and the intake passage including the venturi portion is located in the intake passage. It is difficult to disperse a uniform fuel. Such a problem is conspicuous when the opening area of the venturi portion is relatively small or smaller than the intermediate opening of the movable valve.

[0005] The variable venturi carburetor according to the present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an intake passage near a venturi portion particularly when the opening of the movable valve is less than the intermediate opening. By avoiding the collision of the air flow flowing through the intake passage and rectifying the flow in the direction of the longitudinal axis of the intake passage, the negative pressure at the tip of the venturi portion and the nozzle opening near the venturi portion and the negative pressure at the low-speed fuel injection hole are reduced. An object of the present invention is to suppress the decrease, and to improve the characteristics of fuel suction that is sucked into an intake passage from a nozzle and a low-speed fuel injection hole particularly in a low opening range of a movable valve. To improve atomization of fuel sucked into a suction passage from a nozzle and a low-speed fuel injection hole. Dispersing the fuel sucked into the intake passage evenly in the intake passage.
It is in.

[0006]

A variable venturi carburetor according to the present invention has a movable valve in a movable valve guide cylinder formed by connecting an intake passage through a carburetor body and being connected to an intermediate portion of the intake passage. A variable venturi vaporizer in which a vent needle area integrated with the movable valve is variably controlled by the movable valve, and a jet needle integrally attached to the movable valve is inserted and disposed in a nozzle opening in the intake path. At the bottom of the intake passage where the nozzle opens, a rectifying wall along the longitudinal direction of the intake passage from the vicinity of the air cleaner side end in the movable valve guide cylinder toward the air cleaner side end of the intake passage is provided at the bottom of the movable valve. A first aspect is that the rectifying wall is provided so as to protrude along the moving direction, and the rectifying wall is formed substantially symmetrically with a gap on both sides of a longitudinal axis of the intake passage in a cross section orthogonal to the moving direction of the movable valve. Features.

[0007] In addition to the first feature, at least the gap on the downstream side of the rectifying wall is made larger than the outer diameter of the nozzle that opens to the intake passage, and the movable valve in the state in which the movable valve is most closed in the intake passage. A second feature is that the distance is smaller than the distance formed by the air cleaner side end and the contact point with the intake path.

[0008] In addition to the first feature, the protruding height from the bottom of the intake passage at least on the downstream side of the rectifying wall is:
A third feature is that the diameter is set to be equal to or less than 1/2 of the diameter of the intake path.

Further, in addition to the first feature, a fourth straightening wall having a bottom portion is formed on the upstream side of the straightening wall so as to project further from the air cleaner side end of the intake passage toward the air cleaner. The feature of.

[0010]

According to the first feature, in the cross section of the intake passage orthogonal to the moving direction of the movable valve, the airflow flowing through the central portion of the intake passage on the air cleaner side is along the longitudinal axis of the intake passage and has a gap. The air flows along the inner peripheral wall portion of the formed opposing rectification wall, and is rectified into a flow along the longitudinal axis of the intake passage. On the other hand, the airflow flowing on the outer peripheral portion of the intake passage on the air cleaner side flows along the inner peripheral wall surface of the intake passage on the air cleaner side, and flows obliquely toward the center of the intake passage. The air collides with the outer peripheral wall of each rectifying wall from the side, and is rectified by the rectifying wall into a flow along the longitudinal axis of the intake passage. Therefore, the air flow in the venturi section where the nozzle and the low-speed fuel injection hole are opened can be rectified into the flow along the longitudinal axis of the intake path, and the reduction of the air flow rate flowing through the venturi section where the nozzle and the low-speed fuel injection hole open can be suppressed. Can be deterred.

Further, according to the second feature, in the low opening range of the movable valve, the negative pressure generated by the air flow applied to the nozzle and the low-speed fuel injection hole can be effectively increased.

According to the third feature, the negative pressure applied to the nozzle and the low-speed fuel injection hole can be effectively increased from the low opening range to the intermediate opening range of the movable valve.

According to the fourth feature, particularly, the inertia force of the air flow along the inner peripheral wall portion and the outer peripheral wall portion of the rectifying wall and along the longitudinal axis of the intake passage can be increased, and the rectifying of the air flow can be performed. The effect can be enhanced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a variable venturi type vaporizer according to the present invention will be described below with reference to FIGS.
Reference numeral 1 denotes a carburetor body in which an intake passage 2 penetrates laterally, and a movable valve guide cylinder 3 is continuously provided upward from an intermediate portion of the intake passage 2. The intake passage 2 includes an engine-side intake passage 2B (left side in FIG. 1) connected to an engine (not shown) and an air cleaner-side intake passage 2A (right side in FIG. 1) connected to an air cleaner J by a movable valve guide cylinder 3. It is divided into The diameter of the air cleaner-side intake passage 2A increases toward the air cleaner-side end 2C of the intake passage 2. Reference numeral 4 denotes a movable valve movably disposed in the movable valve guide cylinder 3;
A venturi V is formed by the bottom 4A of the movable valve 4 and the bottom 2D of the intake passage 2. As the movable valve 4 is pulled upward, the area of the venturi portion V increases. A jet needle 5 is integrally attached to the movable valve 4, and the jet needle 5 is inserted into a needle jet 7 through a nozzle 6 opened at the bottom 2 </ b> D of the intake path 2. The shape of the nozzle 6 may be cylindrical or semi-cylindrical. Reference numeral 8 denotes a low-speed fuel injection hole, which is a bypass hole that opens to the venturi portion V, and the intake passage 2 on the engine side.
A pilot outlet hole opening at B. Reference numeral 9 denotes a float chamber main body in which fuel is stored at a constant height, and the fuel in the float chamber main body 9 is a needle jet 7,
The air is sucked into the venturi portion V through the nozzle 6, and the venturi portion V and the engine-side intake passage 2 </ b> B through the low-speed fuel injection hole 8.
Sucked in. The above is a conventionally known variable venturi type vaporizer. The variable venturi type vaporizer according to the present invention has the following configuration to achieve the above object.

That is, 10 is an air cleaner side intake passage 2
A rectifying wall protruding upward from the bottom 2D of A, and the rectifying wall 10 extends from the vicinity of the air cleaner side end 3A of the movable valve guide cylinder 3 to the air cleaner side end 2C of the intake passage 2.
The clearance S extends along the longitudinal direction AA of the intake path 2 toward the right side, and furthermore, on both sides of the longitudinal axis CC of the intake path 2 in a cross section orthogonal to the moving direction BB of the movable valve 4. Are formed substantially symmetrically. In other words, the rectifying wall 10 is
At the bottom 2D of the air cleaner-side intake passage 2A, it is disposed opposite to the inner peripheral walls 10A, 10A with a gap S therebetween with the longitudinal axis CC in the cross section of the intake passage 2 therebetween. Bottom 2 of air cleaner side intake passage 2A
D projects upward with a projection height G along the moving direction of the movable valve 4.

Next, the operation will be described. With the operation of the engine, air flows from the air cleaner side end 2C of the intake passage 2 to the engine side intake passage 2B via the air cleaner side intake passage 2A and the venturi portion V. When the air flows, the air flowing in the air cleaner side intake passage 2A flows toward the venturi portion V as described below in the intake passage cross section orthogonal to the moving direction BB of the movable valve 4 (shown in FIG. 3).
That is, in the central portion of the air cleaner-side intake passage 2A, the air flows in the gap S between the inner peripheral walls 10A of the rectifying walls 10, 10 in a rectified state along the longitudinal axis CC of the intake passage 2.
At this time, the air flow along the arc-shaped inner peripheral wall surface 2E of the air cleaner side intake passage 2A is in the longitudinal axis CC direction of the intake passage 2.
Flows in an oblique direction toward the center of the rectifying wall 10, but this air flow is blocked by the outer peripheral wall 10 </ b> B of the rectifying wall 10,
Does not act in the gap S of the air cleaner side intake passage 2A.
Can form a rectified airflow along the line.

On the other hand, at the outer peripheral portion of the air cleaner-side intake passage 2A, air flows along the arc-shaped inner peripheral wall surface 2E of the air cleaner-side intake passage 2A. The flow is to flow downward obliquely toward the center of the intake path. However, this oblique air flow collides with the outer peripheral wall 10B of the rectifying wall 10, and according to this collision, the oblique air flow is forcibly converted into an air flow along the outer peripheral wall 10B of the rectifying wall 10. Since the rectifying wall 10 is formed along the longitudinal axis direction CC of the intake path 2, the air flowing through the outer peripheral portion of the air cleaner side intake path 2 </ b> A flows in the longitudinal axis direction CC of the intake path 2. The flow is rectified. The air flow flowing through the central portion and the outer peripheral portion of the air cleaner-side intake passage 2A flows down along a rectifying wall which is formed relatively long along the longitudinal axis direction CC of the intake passage 2, so that the center of the air flows. Since there is no collision between the air in the portion and the air in the outer peripheral portion, there is no turbulence in the air flow flowing into the venturi portion V, and the air in the rectified state is
Could be supplied to This airflow condition is shown in FIG. Thus, the decrease in the flow velocity of the air flowing through the venturi V can be suppressed, and the negative pressure applied to the nozzle 6 and the low-speed fuel injection hole 8 can be effectively increased. That is, it is understood from FIGS. 5 to 7 that the negative pressure applied to the low-speed fuel injection hole 8 was increased in the low opening range of the movable valve 4, and further, according to FIGS.
It is understood that the negative pressure applied to the pressure is increased.

In particular, at least the gap S1 on the downstream side of the straightening wall 10, that is, the gap S1 on the downstream straightening wall 10.
Is a gap S of the rectifying wall 10 near the air cleaner end 3A of the movable valve guide cylinder 3 and at a position close to the air cleaner end 4B of the movable valve 4. A contact point E between the air cleaner side end 4B of the movable valve 4 and the intake path 2 in a minimum opening state where the outer diameter D of the nozzle 6 opening to the intake path 2 is larger and the movable valve 4 closes the intake path 2 most. , E, (the distance F is shown in FIG. 2).
In the low opening range of the movable valve 4, a rectified air flow can be positively supplied to the nozzle 6 and the low-speed fuel injection hole 8, and more effectively applied to the nozzle 6 and the low-speed fuel injection hole 8. The negative pressure can be increased.

Further, the height G of the movable valve 4 projecting from the bottom of the intake passage 2 in the moving direction BB (upward in FIG. If the diameter H is equal to or less than 1/2 of the diameter H, the rectified air can be effectively supplied to the nozzle 6 and the low-speed fuel injection hole 8 in the low opening range of the movable valve 4. The negative pressure in the low-speed fuel injection hole 8 can be further increased.

Next, another embodiment of the present invention will be described with reference to FIGS. The same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Reference numeral 20 is connected to the rectifying wall 10 described in the first embodiment, which extends from the vicinity of the air cleaner side end 3A of the movable valve guide cylinder 3 to the air cleaner side end 2C of the intake passage 2, and the air cleaner side end of the intake passage 2 A protruding rectifying wall formed so as to protrude further toward the air cleaner J than the air cleaner 2C (further protruding rightward in FIG. 10 than the air cleaner side end 2C), and the protruding rectifying wall 20 has a bottom 21. That is, the rectifying wall P is formed by the rectifying wall 10 and the protruding rectifying wall 20 having the bottom 21, and these rectifying walls P are formed symmetrically on both sides of the longitudinal axis CC of the intake passage 2 with a gap. Further, the bottom 21 of the protruding flow regulating wall 20 is formed so as to be continuous with the inner peripheral wall surface 2E of the air cleaner side intake passage 2A between the flow regulating walls 10 and 10. In this embodiment, the needle jet 7 projects directly into the intake passage 2 and opens, and the jet needle 5 is inserted into the needle jet 7. This needle jet 7 is the same as that of the first embodiment. This corresponds to the nozzle 6.

According to the second embodiment, the length of the straightening wall P in the longitudinal direction AA is equal to the straightening wall 10 and the protruding straightening wall 20.
The length of the carburetor (the length of the intake passage 2 and the length of the intake passage 2A on the air cleaner side) is particularly reduced in terms of air intake efficiency and equipment layout. In the variable venturi carburetor for motorcycles, which tends to be
Since the air flow from A to the venturi portion V was sufficiently rectified by the long rectifying wall P in the longitudinal direction, the negative pressure applied to the low-speed fuel injection hole 8 of the nozzle (the needle jet 7 in this embodiment) is effectively reduced. It was something that could be raised. In addition, since the protruding rectifying wall 20 is disposed in the air cleaner J, there is no problem in mounting on the engine. The first and second embodiments are so-called sliding throttle valve carburetors in which a movable valve is mechanically operated by a driver, and the movable valve is operated in accordance with a negative pressure generated in an intake passage. It may be used for a so-called constant vacuum type vaporizer which automatically opens and closes.
Furthermore, the air cleaner side intake path is cut near the air cleaner side end of the movable valve guide cylinder, and an air cleaner side intake path having a rectifying wall is formed on an air funnel prepared separately from the carburetor body. A funnel may be attached to the vaporizer body. At this time, air flows into the venturi section of the carburetor body via the air cleaner-side intake passage of the air funnel. The formation and attachment of the air cleaner-side intake passage by the separate air funnel is often performed in a carburetor mounted on a competitive vehicle engine. This is because it is convenient to select the length, diameter, and shape of the intake passage in order to adapt the intake efficiency of the carburetor to each engine.

[0022]

As described above, according to the first feature of the variable venturi carburetor according to the present invention, the flow of air flowing through the central portion and the outer peripheral portion of the air cleaner side intake passage by the rectifying wall is caused in the longitudinal direction of the intake passage. Since it was possible to flow down toward the venturi section as a flow in a rectified state along the flow, the negative pressure applied to the nozzle and the low-speed fuel injection hole can be satisfactorily increased. This improves the characteristics of the fuel discharged into the road and the atomization of the fuel. According to the above description, it is possible to greatly improve the fuel supply characteristic when the movable valve is opened from the low opening state to the medium opening degree, and the fuel supply responsiveness to the opening movement of the movable valve and the fuel supply The present invention can provide a variable venturi vaporizer having excellent linearity. Further, even in the engine side intake passage, the air flow is maintained in a rectified state following the venturi portion V. According to this, the fuel sucked from the nozzles and the low-speed fuel injection holes is discharged to the engine side. In the intake passage, it is uniformly dispersed and a good atomization state is obtained, and the flammability of the engine is improved and irregular combustion of the engine occurs, or engine vibration accompanying irregular combustion occurs Can be reduced.

According to the second and third characteristics,
The air flow can be intensively rectified by the rectifying wall toward the nozzles and the low-speed fuel injection holes arranged on the longitudinal axis of the intake passage, and the negative pressure applied to the nozzles and the low-speed fuel injection holes is more effectively reduced. It was something that could be raised.

Further, according to the fourth feature, the rectification length by the rectification wall can be made sufficiently long irrespective of the length of the air cleaner side intake passage, and a rectification effect can be obtained.
In particular, the present invention is effective in a variable venturi carburetor having a relatively short intake path on the air cleaner side mounted on a motorcycle engine.

[Brief description of the drawings]

FIG. 1 is a first view of a variable venturi vaporizer according to the present invention.
The longitudinal section of an example.

FIG. 2 is a right side view of FIG.

FIG. 3 is a transverse sectional view taken along line XX of FIG. 1;

FIG. 4 is a schematic cross-sectional view showing an air flow in an intake passage in the first embodiment.

FIG. 5 is a diagram showing the relationship between the negative pressure applied to the intake passage and the negative pressure applied to the low-speed fuel injection hole when the movable valve 1/32 is opened in the variable venturi carburetor according to the present invention.

FIG. 6 is a diagram showing the relationship between the negative pressure applied to the intake passage and the negative pressure applied to the low-speed fuel injection hole when the movable valve of the variable venturi carburetor according to the present invention has the movable valve 1/16 open.

FIG. 7 is a diagram showing the relationship between the negative pressure applied to the intake passage and the negative pressure applied to the low-speed fuel injection hole when the movable valve of the variable venturi carburetor according to the present invention has the movable valve at 1/8 opening.

FIG. 8 is a diagram showing the relationship between the negative pressure applied to the intake path and the negative pressure applied to the nozzle when the movable valve 1/32 of the variable venturi carburetor according to the present invention is opened.

FIG. 9 is a graph showing the relationship between the negative pressure applied to the intake passage and the negative pressure applied to the nozzle when the movable valve of the variable venturi carburetor according to the present invention has the movable valve 1/16 open.

FIG. 10 is a longitudinal sectional view showing a second embodiment of the variable venturi carburetor according to the present invention.

FIG. 11 is a transverse sectional view taken along line YY of FIG. 10;

FIG. 12 is a schematic cross-sectional view showing the air flow of a conventional variable venturi carburetor.

[Explanation of symbols]

 Reference Signs List 2 intake path 2C air cleaner side end of intake path 2D bottom of intake path 3 movable valve guide cylinder 3A air cleaner side end of movable valve guide cylinder 4 movable valve 4B air cleaner side end of movable valve 10 rectifying wall 20 projecting rectifying wall 21 bottom

Claims (4)

(57) [Claims] An intake passage penetrates a carburetor body, and a movable valve is movably disposed in a movable valve guide cylinder formed so as to be connected to an intermediate portion of the intake passage. In a variable venturi carburetor in which the area is variably controlled and a jet needle integrally attached to the movable valve is inserted and arranged in a nozzle that opens to the intake passage, the jet needle is located at the bottom 2D of the intake passage 2 where the nozzle 6 opens. , Movable valve guide cylinder 3
From the vicinity of the air cleaner side end 3A toward the air cleaner side end 2C of the intake path 2 in the longitudinal direction A-A of the intake path 2.
Are provided along the moving direction BB of the movable valve 4 so as to protrude in the cross section orthogonal to the moving direction BB of the movable valve 4. 2. A variable venturi vaporizer characterized by being formed substantially symmetrically with a gap S on both sides of a longitudinal axis CC of the second. 2. The movable valve in a state where at least the gap S1 on the downstream side of the rectifying wall is larger than the outer diameter D of the nozzle 6 opening to the intake passage 2 and the movable valve 4 closes the intake passage 2 most. 4 air cleaner side end 4B and intake path 2
2. A variable venturi carburetor according to claim 1, wherein the distance is smaller than a distance F formed by the contact points E and E. 3. A height G of the intake passage 2 protruding from a bottom 2D of the intake passage 2 at least on the downstream side of the rectifying wall is equal to or less than の of a diameter H of the intake passage 2. Variable venturi carburetor. 4. A protruding rectifying wall 20 having a bottom portion 21 is formed on the upstream side of the rectifying wall so as to protrude further from the air cleaner side end 2C of the intake passage 2 toward the air cleaner. Item 7. A variable venturi vaporizer according to Item 1.