JP2004092558A - Butterfly-type throttle carburetor for use in layered scavenging internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a butterfly-type throttle carburetor for use in a layered scavenging internal combustion engine, designed to enhance startup engine performance by closing a scavenging-use air passage during engine startup, reducing air within a mixed-air passage, and supplying densely mixed air into a crank chamber. <P>SOLUTION: A butterfly-type air control valve 16 is pivot-supported at the inlet portion of an air passage channel 7 of the carburetor in a round cross sectional shape, while the outlet side of the air passage channel 7 is divided into upper and lower sections by means of a partitioning wall 8, so as to form an air passage channel having a flattened oval section 7a in the upper half, and a mixed air passage channel 11 in a round cross sectional shape at its outlet portion in the lower half. At around the outlet of the mixed air passage 11, a butterfly-shaped throttle valve 8 interlocked with the air control valve 16 is pivotally supported. The air control valve 16, which is in a total closure-possible style, is fitted at a tilted angle with the inlet portion of the air passage channel 7, while the mixed air throttle valve 9 is pivotally supported so that its aperture toward the mixed air passage11 will be opened ahead of the air control valve 16. On the air control valve 16, meanwhile, an air inlet hole 16b designed to be closed through a choke valve 24b is formed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a butterfly type throttle valve type carburetor for a stratified scavenging internal combustion engine which is substantially the same size as a conventional carburetor and has a scavenging air passage.
[0002]
[Prior art]
A butterfly-type throttle valve carburetor for a stratified scavenging internal combustion engine disclosed in Japanese Patent Application No. 2002-019967 has a carburetor body in which an air passage and an air-fuel mixture passage are vertically divided in parallel by a partition and disposed. One butterfly type air control valve is axially supported at the start end, and the upper half of the air control valve acts as an air control valve for opening and closing the air passage, and the lower half of the air control valve opens and closes the mixture passage. It is configured to work as a valve. However, in the butterfly-type throttle valve type carburetor described above, the ratio between the air amount and the fuel amount is kept almost constant irrespective of the engine speed. Cannot respond.
[0003]
Further, in the butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine disclosed in Japanese Patent Application No. 2002-019967, the gap between the upper half of the air control valve and the arc wall at the inlet of the peripheral air passage is minimized. Need to be limited. However, it is much more difficult to cut the arc wall of the air passage than to form the air passage into a cylindrical cross section, and the air control valve is designed to minimize the gap between the air passage and the air control valve. It is also difficult to incorporate.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a stratified scavenging internal combustion engine in which the scavenging air passage is closed and the air in the mixture passage is reduced at the start of the engine, and a rich mixture is supplied to the crank chamber to improve the startability when the engine is started. It is an object of the present invention to provide a butterfly type throttle valve carburetor.
[0005]
Another object of the present invention is to provide a butterfly-type throttle valve carburetor for a stratified scavenging internal combustion engine, comprising a single air control valve that closes the scavenging air passage at the start of the engine and throttles the air in the mixture passage. It is in.
[0006]
Another object of the present invention is to provide a butterfly-type throttle valve type carburetor starting apparatus for a stratified scavenging internal combustion engine which minimizes the amount of air leakage from the air control valve.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the configuration of the present invention is such that a butterfly-shaped air control valve having an intake hole in a lower half portion is axially supported at an inlet portion having a cylindrical cross section of an air passage of a carburetor body, and an air passage is provided. Is divided into upper and lower parts by a partition wall to form an air passage having a flat cross section on the upper side and a mixture passage having a circular cross section on the lower side, and the air control valve is interlocked near the outlet of the mixture passage. In a stratified scavenging throttle valve carburetor for a stratified scavenging internal combustion engine having a butterfly-shaped air-fuel mixture throttle valve axially supported, the air-control valve is attached to an inlet of the air passage so as to be capable of being fully closed, and the air-fuel mixture throttle is provided. The valve is configured to open from the closed position prior to the air control valve.
[0008]
In addition, the configuration of the present invention is characterized in that the intake port of the air control valve is closed by a separate yoke valve from the air control valve when the engine is started.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the arc-shaped wall portion in contact with the air control valve of the air passage is eliminated, the inlet portion of the air passage is machined into a cylindrical shape, and a butterfly-type air control valve that completely closes the air passage at a predetermined inclination angle is used as the air. The shaft is supported in the passage. An intake hole is provided in the lower half of the air control valve. An air passage is provided above the partition wall downstream of the air control valve in the air passage, and a mixture passage is provided below the partition wall.
[0010]
The air passage has a flat irregular cross-section so that the thickness of the vaporizer main body becomes uniform, and the mixture passage has a circular cross-section to increase the passage area and reduce the occurrence of cavities when the vaporizer main body is die-cast. . At the same time, the heat of the engine is less likely to be transmitted to the carburetor main body, and even in an engine used under a high load such as a power saw, an increase in the temperature of the carburetor is suppressed.
[0011]
In order to close the intake port of the air control valve, a hollow valve shaft that connects the chi-yoke valve to the valve shaft of the air control valve is movably extrapolated. A mixture throttle valve that opens before the air control valve is axially supported in the mixture passage. The air control valve and the air-fuel mixture throttle valve are formed in a disk shape to improve machining accuracy, minimize the amount of air leakage when fully closed, and suppress variations in carburetor performance.
[0012]
During a cold start of the engine, the air control valve acts as a chi-yoke valve, and the air-fuel mixture throttle valve is opened by a predetermined opening degree by a fast idle mechanism. Even if the chi-yoke valve is returned to the open position after the engine is started, the air-fuel mixture throttle valve is maintained at a predetermined opening degree by the fast idle mechanism, and quick warm-up is achieved.
[0013]
At the time of rapid acceleration of the engine, the opening operation of the air control valve is momentarily delayed from that of the air-fuel mixture throttle valve, so that the air-fuel mixture becomes rich and serves as an acceleration pump. In an engine such as a stratified scavenging engine in which the air-fuel mixture is set to be thin, the acceleration performance tends to deteriorate.However, the air control valve is larger than the air-fuel mixture throttle valve, Because of the negative pressure in the passage, the opening operation of the air control valve is momentarily delayed, and a rich mixture is supplied to the engine.
[0014]
【Example】
FIG. 1 is a sectional view showing a butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine according to the present invention. In the stratified scavenging engine 65, a piston 71 is inserted into a cylinder 67 to define a combustion chamber 66 above the piston 71 and a crank chamber 73 below the piston 71, respectively. The crankshaft 74 rotatably supported in the crank chamber 73 has an arm 75 integrally, and the arm 75 and the piston 71 are connected by a connecting rod 72. An exhaust port 68 that opens near the bottom dead center of the piston 71 is provided on the wall of the cylinder 67, and a scavenging passage 70 that connects the crank chamber 73 and the combustion chamber 66 is provided on the wall of the cylinder 67. An air port 78 having a check valve 76 is connected in the middle of the scavenging passage 70, and a mixture port 78 a having a check valve 77 is provided in a portion of the crank chamber 73 below the scavenging passage 70.
[0015]
The carburetor body 6 having the air passages 7, 7a and the mixture passage 11 has a pulsation for introducing the pulsating pressure of the crank chamber to the upper side of the membrane 4 by connecting the cover plate 2 with bolts 5 with the membrane 4 interposed therebetween. A fuel pump is formed by dividing the pressure chamber 3 into a pump chamber 3 a below the membrane 4. A cover plate 22 is connected to the lower end wall of the vaporizer main body 6 with a membrane 20 interposed therebetween, and a constant-pressure fuel chamber 17 is defined above the membrane 20 and an atmospheric chamber 21 is defined below the membrane 20 to supply a constant-pressure fuel. A mechanism is formed. That is, the fuel in the fuel tank (not shown) is introduced into the constant-pressure fuel chamber 17 through the inflow valve (not shown) by the above-described fuel pump, and the low-pressure fuel injection holes 13 and the high-speed fuel injection holes 14 are further discharged from the constant-pressure fuel chamber 17. Are supplied to the air-fuel mixture passage 11 respectively.
[0016]
An air-fuel mixture throttle valve 9 is supported by a valve shaft 12 in an air-fuel mixture passage 11 of the carburetor body 6, and an inlet of an air passage 7 having a larger diameter than the air-fuel mixture throttle valve 9 is provided upstream of the air-fuel mixture throttle valve 9. Is formed. A butterfly-shaped air control valve 16 is supported by a valve shaft 15 inclined to the side at a central portion of the air passage 7, preferably at a boss portion 8 a at the start end of the partition wall 8 defining the air passage 7 a and the mixture passage 11. . The upper half of the air control valve 16 opens and closes the air passage 7a, and the lower half 16a of the air control valve 16 opens and closes the mixture passage 11. Considering that the diameter of the mixture passage 11 and the diameter or passage area of the lower half of the inlet of the air passage 7 are basically the same, the diameter ratio of the mixture passage 11 to the inlet of the air passage 7 is It is desirable that the ratio be 1: 1.5 or more. In order to make the vaporizer compact, the outlet of the mixture passage 11 is arranged concentrically with the inlet of the air passage 7.
[0017]
As shown in FIG. 4, the air passage 7a is defined by a flat top wall, left and right side walls, and a bottom wall protruding upward in an arc shape. The air passage 7 a communicates the upper half of the inlet of the air passage 7 with the air port 78. The mixture passage 11 communicates the lower half of the inlet of the air passage 7 with the mixture port 78a. As shown in FIGS. 1 and 2, a plurality of low-speed fuel injection holes 13 are opened from the constant-pressure fuel chamber 17 through the low-speed fuel jet 18 and the fuel chamber 10 to the vicinity of the closed position of the mixture throttle valve 9 in the mixture passage 11. The high-speed fuel injection hole 14 projects from the constant-pressure fuel chamber 17 through the high-speed fuel jet 19 to the bench lily portion of the mixture passage 11.
[0018]
The air control valve 16 is in the closed position with a slight inclination, and the lower half 16a is connected to the air passage 7a in a state where the upper half periphery contacts the inner peripheral surface of the inlet of the air passage 7 so that air does not leak to the air passage 7a. It is attached so as to close the lower half of the entrance part. In order to prevent the air control valve 16 from sticking to the inlet of the air passage 7, the air control valve 16 is attached at an inclination angle θ (specifically, 10 to 15 °). One side of the lower half 16a of the air control valve 16 is provided with a quarter-circle intake hole 16b which is opened and closed by a chi-yoke valve 24b. One side of the air control valve 16 is superimposed on a flat notch passing through the axis of the valve shaft 15 and is connected by screws 23 (FIG. 2). On the other hand, the chi-yoke valve 24 b is formed of a quarter-circle plate slightly larger than the intake hole 16 b, and a boss 24 d having a rectangular cross section is axially moved from the hollow valve shaft 24 in which the outer end of the valve shaft 15 is rotatably inserted outside. Is fitted to the protruding piece 24a protruding outward.
[0019]
At a portion adjacent to the inner end of the boss 24d, the air control valve 16 is connected to the valve shaft 15 by a screw 23, and the screw 23 prevents the axial movement or detachment of the chi-yoke valve 24b. A return spring 44 is wound around the outer end of the hollow valve shaft 24 of the chi-yoke valve 24. One end of the return spring 44 urges the air control valve 16 to the closed position via the air control valve lever 40 to return to the closed position. The other end of the spring 44 biases the yoke valve 24b to the open position via the yoke lever 43. The intake hole 16b is set to be larger than the maximum opening area of the mixture passage 11 so that the high-speed fuel injection hole 14 is not affected by the intake hole 16b even if the mixture throttle valve 9 opens before the air control valve 16. To
[0020]
Since the valve shaft 15 of the air control valve 16 and the valve shaft 24 of the chi-yoke valve 24b are arranged concentrically, and the valve shaft 15 of the air control valve 16 penetrates the carburetor body 6 and both ends are supported by bearings, The operation of the air control valve 16 is stable, and there is no sticking to the vaporizer body 6. The air control valve 16 controls the amount of air in the air passage 7 according to the degree of opening. When the mixture throttle valve 9 is fully opened, the air control valve 16 is also fully opened. Even if the air control valve 16 does not open parallel to the inlet of the air passage 7, the diameter of the inlet of the air passage 7 is sufficiently large, so that a sufficient amount of air in the air passage 7a can be secured. Further, since the lower half 16a of the air control valve 16 protrudes from the carburetor body 6 to the outside, a sufficient amount of air in the mixture passage 11 can be secured.
[0021]
As shown in FIG. 2, an air-fuel mixture throttle valve lever 46 is connected to a left end of the valve shaft 12 of the air-fuel mixture throttle valve 9 that projects laterally from the carburetor body 6. The mixture throttle valve lever 46 is brought into contact with the tapered portion of the stop bolt 27 screwed to the support arm 29 of the carburetor body 6 by the force of a return spring 44, which will be described later. It can be adjusted arbitrarily. As shown in FIG. 4, a fast idle lever 31 is coupled to the other end of the valve shaft 12, and a bent piece 31a at the end of the fast idle lever 31 is supported by the valve shaft 15 so as to freely rotate. When engaged with the notch 43b formed at the end of the lock member, the bent piece 31a and the lock lever 43a are engaged with each other and locked.
[0022]
The air control valve lever 40 connected to the valve shaft 15 is connected to the fast idle lever 31 by a link 34. A plurality of phase change holes 32 for changing the phase relationship with the air control valve 16 are arranged on the circumference of the fast idle lever 31 of the valve shaft 12. One bent end of the link 34 is engaged with one of the phase change holes 32, and the other bent end of the link 34 is engaged with a circumferential long hole 38 provided in the air control valve lever 40. . The yoke lever 43 is connected to the hollow valve shaft 24 extrapolated to the valve shaft 15. A return spring 44 is wound around the valve shaft 24, one end of the return spring 44 is locked by the chi-yoke lever 43, and the other end of the return spring 44 is locked by the air control valve lever 40.
[0023]
The first idle lever 31 and the air control valve lever 40 are connected by a link 34, but as shown in FIG. 5, between the first idle lever 31 and the air control valve lever 40 so that the link 34 does not rattle. The tension spring 35 is stretched, and the air control valve lever 40 also moves according to the movement of the fast idle lever 31. The tension spring 35 has a sufficient force to operate the air-fuel control valve 16 with the air-fuel mixture throttle valve 9 in response to the operation of the air-fuel mixture throttle valve 9.
[0024]
Regarding the machining of the inlet portion of the air passage 7, the portion in contact with the upper half peripheral portion of the inlet portion of the air control valve 16 is ultimately more important. If the upper half of the inlet of the air passage 7 can be processed, the lower half does not have to be processed. However, in precision machining, machining the entire circumference of the air passage 7 uniformly improves the machinability. Therefore, as shown in FIG. 7, the rotation of the rotary cone-shaped rotary cutter (milling cutter) 56 having a cone angle of 2θ. The shaft 56a is tilted upward by an angle θ (the tip surface of the rotary blade 56 is tilted equal to the mounting angle at the closed position of the air control valve 16), and the rotary blade 56 is parallel to the center axis direction of the inlet of the air passage 7. While moving, the inlet portion is machined by the conical cutting portion 56b of the rotary blade 56.
[0025]
The air control valve 16 is supported by the boss 8a crossing the air passage 7 with the valve shaft 15 in a state in which the air control valve 16 is inclined by the angle θ (10 to 15 °) in the closed position. Can have a large area in the circumferential direction, and the amount of air leakage to the air passage 7a at the closed position of the air control valve 16 can be minimized. In other words, the boss 8a in contact with the valve shaft 15 can be made sufficiently large, and the amount of air leakage from the contact portion between the valve shaft 15 and the boss 8a of the precisely controlled air control valve 16 can be minimized.
[0026]
Preferably, before the air control valve 16 in the upper half of the air passage 7 is attached, the inlet of the air passage 7 is previously formed into a loose taper or conical shape by die casting (at least the inlet of the air passage 7). If a part conical surface extending toward the inlet end is provided in a portion of the upper half from the inlet end to a position immediately near the closed position of the air control valve 16), the portion to which the air control valve 16 is attached can be cut accurately. Since there is no need to perform cutting to an unrelated side, the processing time can be reduced and the life of the cutting tool can be extended.
[0027]
The air control valve 16 of the present invention acts as a chi-yoke valve for supplying a rich air-fuel mixture during a cold start of the engine. The yoke lever 43 and the lever 42 of the valve shaft 24 are urged to rotate counterclockwise by the force of the return spring 44, and the lever 42 abuts against a stop member 54 that projects laterally from the carburetor body 6. Now, when the starting rod 36 is pulled rightward from the idle position shown in FIG. 5, the lever 43 rotates clockwise. When the yoke lever 43 is rotated clockwise, the lock lever 43a is also rotated in the same direction by being pushed by the projection 43c of the yoke lever 43, and the notch 43b of the lock lever 43a engages with the bent piece 31a of the fast idle lever 31. . In this state, even if the starting rod 36 is released, the mixture throttle valve 9 shown in FIG. 6 is locked to a so-called fast idle opening in which the throttle valve 9 is slightly opened. At this time, the long hole 38 of the air control valve lever 40 still has a little room leftward. The chi-yoke valve 24b having the leak hole 24c of the chi-yoke lever 43 rotates clockwise and overlaps the air control valve lever 40 to close the intake hole 16b. When releasing the yoke operation, the lock of the mixture throttle valve 9 can be released without the excessive amount of the long hole 38 giving excessive force to the fast idle lever 31 and the link 34.
[0028]
6, the inlet of the air passage 7 communicating with the air-fuel mixture passage 11 is closed by the lower half 16a of the air control valve 16, and the air-fuel mixture throttle valve 9 is slightly opened. Therefore, a strong negative pressure is applied to the high-speed fuel injection holes 14, and a rich air-fuel mixture is supplied to the crank chamber 73 of the engine 65, so that cold start of the engine can be easily achieved. The negative pressure applied to the high-speed fuel injection hole 14 can be arbitrarily set according to the size of the intake hole 16b of the air control valve 16.
[0029]
After the start of the engine, the lock is not released even if the start rod 36 is returned to the original position, and the warm-up operation is continued. When the air-fuel mixture throttle valve lever 46 is snap-operated, that is, when the air-fuel mixture throttle valve 9 is rapidly opened and immediately closed, the air-fuel mixture throttle valve 9 rotates counterclockwise in FIG. The lock with the lock lever 43a is released, and the lock lever 43a returns to the state shown in FIG. When the snap operation is performed, the link 34 is pulled to the left, but since there is still room on the left side of the long hole 38 of the yoke lever 43, the lock between the fast idle lever 31 and the lock lever 43a is released. Then, the air-fuel mixture throttle valve 9 returns to the idle opening, the lock lever 43a returns to the position shown in FIG. 5, the air control valve 16 also returns to the original position, and the engine can continue idle operation.
[0030]
When the fast idle lever 31 is rotated counterclockwise by the trigger rod 45, that is, in the opening direction of the mixture throttle valve 9, the air control valve 16 is also rotated in the opening direction. As a result, a mixture of fuel and air is supplied from the mixture passage 11 to the crank chamber 73 of the engine 65, and air is supplied to the air port 78 of the engine 65 from the air passage 7a.
[0031]
When the air-fuel mixture throttle valve 9 is further rotated in the opening direction, the air control valve lever 40 is rotated counterclockwise by the link 34, and the air control valve lever 40, the valve shaft 15, and the air control valve 16 are integrally formed. The air passages 7 and 7a are opened counterclockwise to open the air passages, and the air flows to the middle of the scavenging passage 70, that is, to the air port 78, so that the load operation of the engine becomes possible.
[0032]
Due to the characteristics of the stratified scavenging engine, when changing the air-fuel mixture and air supply amounts, changing the phase change hole 32 of the fast idle lever 31 and engaging the left end of the link 34, when accelerating from idle operation, The timing at which the air control valve 16 opens later than the air-fuel mixture throttle valve 9 and the supply ratio of air-fuel mixture and air can be changed.
[0033]
【The invention's effect】
As described above, the present invention uses the chi-yoke valve as the starting device in the lower half of the air control valve, so that the chi-yoke valve, the valve shaft of the chi-yoke valve, etc. are not required in addition to the air control valve. A butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine can be obtained with basically the same components as those of the conventional one.
[0034]
By closing the intake port of the air control valve by a separate chiyoke valve, the air control valve acts as a chiyoke valve of the air-fuel mixture passage, and a smooth start of the engine is obtained.
[0035]
Even if the lever is returned after the engine is started, the engine is operated in the fast idle mode without returning to the idle mode, and the warm-up can be completed in a short time. After the warm-up, the operation returns to the idling operation by operating the air-fuel mixture throttle valve by a snap operation. Thereafter, the engine speed can be freely adjusted by operating the air-fuel mixture throttle valve.
[0036]
The boss of the chi-yoke valve is externally fitted to the protruding piece protruding from the hollow valve shaft to the air passage, and then the air control valve is fastened to the valve shaft with a screw, so that the head of the screw becomes a stopper and the chi-yoke valve becomes There is no escape.
[0037]
One end of a single return spring wound around the outer end of the valve shaft of the chi-yoke valve rotationally biases the air control valve to the closed position, and the other end of the return spring rotationally biases the chi-yoke valve to the open position. As a result, the number of return springs used can be reduced.
[0038]
At least the upper half of the inlet of the air passage in contact with the air control valve is inclined at the same angle as the mounting angle at the closed position of the air control valve, with the tip of the frusto-conical rotary blade inclined toward the center axis of the inlet. Since the cutting was performed on the conical surface of the rotary blade while moving, the area in the circumferential direction of the lower half of the boss supporting the air control valve can be made large, and the air flowing into the air passage at the closed position of the air control valve can be taken. Leakage can be minimized.
[0039]
By providing a partial conical surface that extends toward the inlet end at least in the upper half of the air passage inlet from the inlet end to the position near the closed position of the air control valve, the part to which the air control valve is attached can be accurately determined. The cutting time can be shortened and the life of the cutting tool can be prolonged.
[0040]
Compared to the one disclosed in Japanese Patent Application No. 2002-019967, there is no arc-shaped wall portion of the air passage, so that processing is easy, variation is small, mass production is easy, and the amount of air leakage in the air passage is minimized. it can.
[0041]
If the output is the same as that of a normal two-stroke internal combustion engine, the fuel flow rate is reduced, so that the variation in the fuel flow rate can be reduced particularly in a stratified scavenging internal combustion engine having a small displacement.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine according to the present invention.
FIG. 2 is a cross-sectional plan view of a butterfly throttle valve carburetor for the same layered scavenging internal combustion engine.
FIG. 3 is an exploded perspective view showing a relationship between a chi-yoke valve and a hollow valve shaft.
FIG. 4 is a front view of the butterfly type throttle valve carburetor for the stratified scavenging internal combustion engine.
FIG. 5 is a side view showing a fast idle mechanism of a butterfly throttle valve carburetor for a stratified scavenging internal combustion engine during idle operation of the engine.
FIG. 6 is a side view showing a fast idle mechanism of a butterfly throttle valve carburetor for a stratified scavenging internal combustion engine during a cold start of the engine.
FIG. 7 is a side cross-sectional view showing a method of processing the inlet of the air passage of the butterfly type throttle valve carburetor for the same layered scavenging internal combustion engine.
[Explanation of symbols]
3: Pulsating pressure chamber 3a: Pump chamber 4: Membrane 6: Vaporizer body 7: Air passage 7a: Air passage 8: Partition wall 8a: Boss 9: Air-fuel mixture throttle valve 11: Air-fuel mixture passage 12: Valve shaft 13: Low speed Fuel injection hole 14: High-speed fuel injection hole 15: Valve shaft 16: Air control valve 16a: Lower half 16b: Intake hole 17: Constant-pressure fuel chamber 18: Low-speed fuel jet 19: High-speed fuel jet 20: Membrane 21: Atmosphere chamber 23 : Screw 24: Valve shaft 24a: Projection piece 24b: Chiyoke valve 24c: Leak hole 24d: Boss 27: Stop bolt 29: Support arm 31: Fast idle lever 31a: Bend piece 32: Phase change hole 34: Link 35: Tension Spring 36: Starting rod 38: Slot 40: Pneumatic control valve lever 43: Cylinder lever 43a: Lock lever 43b: Notch 44: Return spring 45: Trigger rod 46: Mixing Air throttle valve lever 54: Stop member

Claims (6)

A butterfly-shaped air control valve having an intake hole in a lower half portion is axially supported at an inlet portion having a cylindrical cross section of an air passage of the carburetor main body, and an outlet side of the air passage is divided into upper and lower parts by a partition wall. Stratified scavenging in which a mixture passage having a flat cross section is formed, and a mixture passage having a circular cross section is formed on the lower side, and a butterfly-shaped mixture throttle valve that interlocks the air control valve near the outlet of the mixture passage is shaft-supported. In a butterfly type throttle valve type carburetor for an internal combustion engine, the air control valve is attached to the inlet portion of the air passage so as to be fully closed by being inclined, and the air-fuel mixture throttle valve is arranged ahead of the air control valve from a closed position. A butterfly type throttle valve type carburetor for a stratified scavenging internal combustion engine, wherein the carburetor is configured to open. 2. The butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine according to claim 1, wherein the intake port of the air control valve is closed by a chioke valve separate from the air control valve when the engine is started. The hollow valve shaft of the chi-yoke valve is extrapolated to the outer end of the valve shaft of the air control valve, and the boss of the chi-yoke valve is externally fitted to a protruding piece projecting from the hollow valve shaft to the air passage. The butterfly type carburetor according to claim 1, wherein the air control valve is connected to the valve shaft by a screw adjacent to an inner end of the boss. A return spring is wound around the outer end of the hollow valve shaft of the chi-yoke valve, one end of the return spring biases the air control valve to a closed position, and the other end of the return spring causes the chi-yoke valve to rotate. 2. A butterfly type throttle valve carburetor for a stratified scavenging internal combustion engine according to claim 1, wherein the carburetor is rotationally biased to an open position. At least the upper half of the inlet of the air passage in contact with the air control valve is inclined at the leading end surface of a frustoconical rotary blade equal to the mounting angle at the closed position of the air control valve. The butterfly type throttle valve type carburetor for a stratified scavenging internal combustion engine according to claim 1, wherein the rotary blade is cut by a conical surface of the rotary blade while moving in a central axis direction. 2. The layered structure according to claim 1, wherein at least an upper half of an inlet portion of the air passage has a partial conical surface extending toward the inlet end from a portion near the inlet end to a position near the closed position of the air control valve. 3. Butterfly type throttle valve carburetor for scavenging internal combustion engines.

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