JP4024511B2 - Rotary throttle type vaporizer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary throttle type carburetor for a small internal combustion engine mounted on a portable working machine such as a power saw or a brush cutter.
[0002]
[Prior art]
A rotary throttle type carburetor has a throttle valve lever connected to the valve shaft that protrudes from the lid plate of the carburetor body, and the opening of the throttle valve increases as the throttle valve lever rotates. Rises, the needle inserted from the throttle valve into the fuel supply pipe also rises, and the opening of the fuel injection hole increases.
[0003]
When the engine is cold started, when the start shaft having the start lever supported by the boss portion of the cover plate is rotated to obtain a rich mixture, the throttle valve lever is pushed up by the cam of the start shaft, and the fuel nozzle hole The opening increases and the amount of fuel increases.
[0004]
However, in the above-described rotary throttle type carburetor, if the dust adheres to the cover plate during long-term use, and particularly when the dust enters the boss portion supporting the start shaft and hardens together with the lubricating oil, the start shaft Will return worse. If the start shaft returns poorly, the throttle valve lever will remain pushed up even in the normal operation state after the warm-up operation, and the engine is always kept in a high speed operation state, which is dangerous.
[0005]
[Problems to be solved by the invention]
In view of the above-described problems, an object of the present invention is to provide a rotary throttle valve type carburetor that does not have a return failure of a start lever that is operated when starting an engine.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the configuration of the present invention is such that a throttle valve having a throttle hole is inserted into a cylindrical valve chamber traversing the intake passage of the carburetor body so that the throttle valve can be rotated and moved up and down, and the valve chamber is closed. A throttle valve lever is coupled to the valve shaft of the throttle valve penetrating the lid plate, a cam mechanism is provided between the throttle valve lever and the lid plate, and the throttle valve throttle is opened from the fuel chamber provided at the bottom of the carburetor body. In a rotary throttle valve type carburetor in which a needle for adjusting the opening degree of the fuel injection hole supported by the throttle valve is inserted into the fuel supply pipe protruding into the hole, the boss part integral with the lid plate is rotatably supported. A cam surface is provided at the end of the start shaft, the cam surface pushes up the throttle valve lever by the rotation of the start shaft, and a through hole is provided in the vicinity of the boss portion of the lid plate for discharging dust downward. It is characterized by.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a through hole is provided in the lower surface near the boss portion of the cover plate that supports the starting shaft, and dust accumulated on the cover plate is removed downward through the through hole.
[0008]
【Example】
FIG. 1 is a front sectional view of a rotary restrictor type carburetor according to the present invention. A pair of left and right through holes 7 are formed in the front and rear end flanges of the carburetor body 5, an air cleaner is abutted against the end flange (not shown), and the end flange 5a is connected to the engine via a heat insulating pipe. And a pair of bolts that pass through the through holes 7. The carburetor body 5 is formed with a cylindrical valve chamber 6 orthogonal to an intake passage extending in a direction perpendicular to the paper surface. The throttle valve 1 having a throttle hole 2 is fitted in the valve chamber 6 so as to be rotatable and movable up and down. Inserted. The throttle valve 1 is biased downward and rotationally biased to the idle position by the force of the spring 24 interposed between the lid plate 21 that closes the upper end of the valve chamber 6 and the throttle valve 1. The valve shaft 1a of the throttle valve 1 passes through the cover plate 21, and a throttle valve lever 22 is coupled to the upper end. A fan-shaped cam portion 22a is formed at one end of the throttle valve lever 22, and a swivel 23 that couples the inner wire of the remote control cable is rotatably supported at the other end.
[0009]
The cam mechanism includes a circumferential cam groove 22b provided on the lower surface of the cam portion 22a, and a follower 45 that protrudes upward from the cover plate 21 and engages with the cam groove 22b. A constant pressure fuel chamber 20 provided at the bottom of the carburetor body 5 is communicated with the fuel supply pipe 4 through a check valve 41 and a fuel jet 40. The fuel supply pipe 4 is fitted into a mounting hole 8 having a base end portion provided in the bottom wall of the valve chamber 6, and an upper end portion is projected into the throttle hole 2 of the throttle valve 1. A needle 3 supported at the upper center of the throttle valve 1 is fitted into the fuel supply pipe 4 so as to increase or decrease the opening of the fuel injection hole 4a.
[0010]
When the throttle valve lever 22 is rotated, the throttle valve 1 is raised while being rotated by the cam mechanism described above. Therefore, the opening degree of the throttle hole 2 of the throttle valve 1 with respect to the intake passage of the carburetor main body 5 increases, and at the same time, the needle 3 hanging from the throttle valve 1 rises, and the fuel injection hole 4a of the fuel supply pipe 4 The opening increases, and the amount of air corresponding to the opening of the throttle valve 1 and the amount of fuel corresponding to the opening of the fuel injection hole 4 a are sucked into the throttle hole 2.
[0011]
A membrane 9 is sandwiched between the lower surface of the vaporizer body 5 and the intermediate wall 10, a pulsation pressure introduction chamber 34 is formed above the membrane 9, and a pump chamber 35 is formed below the membrane 9. When the pulsation pressure of, for example, the crank chamber of the engine is introduced into the pulsation pressure introduction chamber 34, the fuel in the fuel tank has the fuel inlet pipe 25, the filter 26, and a check valve (not shown) as the membrane 9 moves up and down. The air is sucked into the pump chamber 35 through the passage, and further supplied to the constant pressure fuel chamber 20 through a passage having a check valve (not shown) and the inflow valve 28. The constant pressure fuel chamber 20 is defined above the membrane 12 sandwiched between the intermediate wall 10 and the intermediate wall 13, and an atmospheric chamber 37 is defined below the membrane 12. One end of the lever 29 supported by the shaft 27 of the intermediate wall 10 is locked to the inflow valve 28, and the other end is pressed against the central protrusion 12 a of the membrane 12 by the force of the spring 30.
[0012]
When the fuel in the constant pressure fuel chamber 20 decreases, the membrane 12 that receives the intake negative pressure and the atmospheric pressure pushes up the lever 29 against the force of the spring 30. The lever 29 rotates clockwise about the shaft 27, the inflow valve 28 is opened, and the fuel in the pump chamber 35 is supplied to the constant pressure fuel chamber 20 through the inflow valve 28. When the fuel in the constant pressure fuel chamber 20 increases, the membrane 12 is pushed down by the force of the spring 30, the lever 29 rotates counterclockwise about the shaft 27, and the inflow valve 28 is closed.
[0013]
Prior to the start of the engine, a suction pump 18 for discharging air and fuel vapor in the constant pressure fuel chamber 20 is provided on the lower surface of the intermediate wall 13. The suction pump 18 includes a spoid 17 and a composite check valve 16, and the peripheral portion of the spoid 17 is fixed to the lower surface of the intermediate wall body 13 by an annular presser plate 15, and the saddle type composite check valve 16 is an intermediate wall body. 13 is fitted into a central cylindrical outlet chamber 19. When the spoid 17 is repeatedly crushed, air or fuel vapor in the constant pressure fuel chamber 20 is sucked into the pump chamber 18a through the passage 14 by pushing the peripheral edge portion 16a of the composite check valve 16 and further flattened. The shaft tip 16b is pushed open to flow into the outlet chamber 19, and is returned to the fuel tank through a return pipe (not shown). Thus, when the constant pressure fuel chamber 20 becomes negative pressure, the fuel in the fuel tank is sucked into the pump chamber 35 through the passage having the fuel inlet pipe 25, the filter 26, and a check valve (not shown), and further the reverse (not shown). The air is sucked into the constant pressure fuel chamber 20 through the passage having the stop valve and the inflow valve 28.
[0014]
When the engine is started, a start shaft 32 having a start lever 31 is fitted into the boss portion 53 of the lid plate 21 in order to supply a rich air-fuel mixture to the engine. The pin 51 fixed to the boss portion 53 is engaged with the arcuate groove 50 of the start shaft 32, and the start shaft 32 is prevented from being pulled out. A spring 33 is interposed between the start lever 31 and the boss portion 53, and the start lever 31 is urged to rotate to the upright position by the force of the spring 33. As shown in FIG. 4, the cam 52 at the end of the starting shaft 32 includes a flat surface 52a and a flat cam surface 52b. Normally, the flat surface 52a protrudes below the throttle valve lever 22, and the throttle valve It does not contact the lower surface of the lever 22. When the start lever 31 is tilted sideways, as shown in FIG. 5, the cam surface 52 b formed at the end of the start shaft 32 comes into contact with the lower surface of the throttle valve lever 22 and pushes up the throttle valve lever 22.
[0015]
As shown in FIGS. 2 to 5, according to the present invention, the start shaft is adjacent to the contact Q between the normal cover plate 21 and the peripheral surface of the start shaft 32, on the opposite side of the start operation direction of the cover plate 21. 32 elongated through holes 54 extending in the axial direction are provided.
[0016]
Next, the operation of the rotary throttle type carburetor according to the present invention will be described. When starting the engine, when the start lever 31 is tilted and the start shaft 32 is rotated in the direction of the arrow x, the cam surface 52b at the end of the start shaft 32 comes into contact with the lower surface of the throttle valve lever 22, as shown in FIG. Push up. The needle 3 hanging from the upper center of the throttle valve 1 rises, the opening of the fuel injection hole 4a of the fuel supply pipe 4 increases, and the amount of fuel increases.
[0017]
When the throttle valve lever 22 is rotated in the direction of the arrow y in FIG. 3 after the warm-up operation is completed, the cam surface 52b at the end of the starting shaft 32 is disengaged from the side edge of the throttle valve lever 22, and the force of the spring 33 The start lever 31 is returned to the initial posture. At this time, the corner P where the peripheral surface of the starting shaft 32 intersects with the flat surface 52 a passes through the through hole 54, so that dust and oil are scraped off into the through hole 54. Therefore, dust and oil do not stick to the cover plate 21, the cam surface 52b, the lower surface of the throttle valve lever 22 and the like for a long period of time, and the return of the starting shaft 32 is not hindered.
[0018]
【The invention's effect】
As described above, the present invention inserts a throttle valve having a throttle hole into a cylindrical valve chamber crossing the intake passage of the carburetor body so as to be able to rotate and move up and down, and penetrates a lid plate that closes the valve chamber. A throttle valve lever is coupled to the valve shaft of the throttle valve, a cam mechanism is provided between the throttle valve lever and the lid plate, and the fuel protrudes from the fuel chamber provided at the bottom of the carburetor body into the throttle hole of the throttle valve In a rotary throttle valve type carburetor in which a needle for adjusting the opening of a fuel nozzle supported by a throttle valve is inserted into a supply pipe, the end of a start shaft that is rotatably supported by a boss portion integral with the lid plate A cam surface is provided in the part, the cam surface pushes up the throttle valve lever by the rotation of the starting shaft, and a through hole for discharging dust downward is provided in the vicinity of the boss part of the lid plate. Every time, the dust on the cover plate is moved to the through hole of the cover plate by the cam at the end of the starting shaft. Since the can dropped, there is no dust or oil gets stuck for a long period of time, it is not that the return of the start axis failure occurs.
[Brief description of the drawings]
FIG. 1 is a front sectional view of a rotary throttle valve type carburetor according to the present invention.
FIG. 2 is a bottom sectional view of a cover plate of the rotary throttle valve type vaporizer.
FIG. 3 is a perspective view showing a main part of the rotary throttle valve type carburetor.
FIG. 4 is a side sectional view showing a main part of the rotary throttle valve type carburetor.
FIG. 5 is a side sectional view showing a main part of the rotary throttle valve type carburetor.
[Explanation of symbols]
1: throttle valve 1a: valve shaft 2: throttle hole 3: needle 4: fuel supply pipe 4a: fuel injection hole 5: vaporizer body 6: valve chamber 9: membrane 10: intermediate wall 12: membrane 13: intermediate wall plate 16: Compound check valve 17: Spoid 18: Suction pump 18a: Pump chamber 19: Outlet chamber 20: Constant pressure fuel chamber 21: Lid plate 22: Throttle valve lever 22a: Cam portion 22b: Cam groove 23: Swivel 25: Fuel inlet Pipe 27: Shaft 28: Inflow valve 29: Lever 31: Start lever 32: Start shaft 33: Spring 34: Pulsation pressure introduction chamber 35: Pump chamber 37: Air chamber 40: Fuel jet 41: Check valve 45: Follower 50: Arc-shaped groove 51: Pin 52: Cam 52a: Flat surface 52b: Cam surface 53: Boss portion 54: Through hole

Claims (2)

A throttle valve having a throttle hole is inserted into a cylindrical valve chamber that crosses the intake passage of the carburetor body so that the throttle valve can be rotated and moved up and down, and the throttle valve passes through a lid plate that closes the valve chamber. A lever is connected, and a cam mechanism is provided between the throttle valve lever and the lid plate, and is supported by the throttle valve on a fuel supply pipe protruding from the fuel chamber provided at the bottom of the carburetor body to the throttle hole of the throttle valve. In the rotary throttle carburetor fitted with a needle for adjusting the opening of the fuel injection hole, a cam surface is provided at the end of the start shaft that is rotatably supported by the boss unit integral with the lid plate, A rotary throttle type carburetor characterized in that a cam surface pushes up a throttle valve lever by rotation of a starting shaft, and a through hole for discharging dust downward is provided in the vicinity of the boss portion of the lid plate. 2. The rotary throttle valve carburetor according to claim 1, wherein the through hole is provided at a position adjacent to a contact portion between an end of the start shaft and the lid plate.

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