JP2003065159A - Starting device for rotary throttle valve type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starting device not varying increase in the amount of air in the cold starting of an engine even if the number of idling revolutions is adjusted in a proper value after running-in of the engine. SOLUTION: A sleeve 33 slidable in the shaft direction is fit to a guide cylinder 35 supported in a cover plate 21 closing a valve chest of a carburetor body 5. A pin 33a passing through the circumferential wall of the sleeve 33 is engaged with a slit 34 in the shaft direction of the guide cylinder 35. A spring 26a is interposed between a first projection piece 35a projecting sideward from the guide cylinder 35 and a second projection piece 33b projecting sideward from the sleeve 33. An idle adjusting bolt 26 is passed through the second projection piece 33b and the spring 26a and screwed on the first projection piece 35a. A starting shaft 38 having a spiral groove 39 engaging with the pin 33a is fit to the sleeve 33. A flat cam surface 38b engaging with a cam plate 42 of a valve shaft 1a and a pressing rod 40 engaging with a side wall surface 44 of the valve shaft 1a are formed in the starting shaft 38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary throttle valve type carburetor for an internal combustion engine mounted on a portable working machine such as a brush cutter or a power saw, and more particularly to a rotary throttle valve for facilitating cold start of the engine. The present invention relates to a starter for a vaporizer.

[0002]

2. Description of the Related Art In a conventional rotary throttle valve carburetor, the opening and closing of a fuel injection hole of a fuel supply pipe is adjusted by raising and lowering a needle by rotating a throttle valve. However, since the frictional portion of the engine has a large resistance at low temperatures, it is difficult to start the engine, and the idle rotation is very unstable even when the engine is started. For this reason, the rotary throttle valve carburetor is provided with a starting fuel increasing mechanism that increases the fuel amount at the time of starting the engine and supplies a rich air-fuel mixture to the engine.

As shown in FIG. 9, a conventional rotary throttle valve type carburetor has front and rear end flanges 5a, 5 of a carburetor body 5.
b (see FIG. 1) is provided with a pair of left and right through holes 7, an air purifier is butted to the end flange 5a, and the end flange 5b is butted to the intake port of the engine through a heat insulating pipe. It Air purifier, vaporizer, and heat insulation pipe penetrate through hole 7 1
It is connected to the engine wall by a pair of mounting bolts.

The carburetor body 5 is provided with a cylindrical valve chamber 6 which is orthogonal to the intake passage (extending in the direction perpendicular to the plane of the drawing).
The throttle valve 1 having the throttle hole 2 is fitted in the valve chamber 6 so as to be rotatable and vertically movable. The valve shaft 1a of the throttle valve 1 penetrates a cover plate 21 that closes the valve chamber 6, and a throttle valve lever 22 is coupled to the upper end. A swivel 23 for connecting a remote control cable is rotatably supported at one end of the throttle valve lever 22.
A fan-shaped cam portion 22a is integrally provided at the other end of the throttle valve lever 22. The lower surface of the cam portion 22a is provided with a circumferential cam groove whose depth gradually decreases in the acceleration direction.
The follower supported by is engaged with the cam groove, which constitutes a cam mechanism.

An intermediate wall body 10 is laminated on the lower surface of the carburetor body 5 with the membrane 9 interposed therebetween, and an intermediate wall body 13 is laminated on the lower surface of the intermediate wall body 10 with the membrane 12 interposed therebetween.
To the lower surface of the above, a pressing plate 15 is connected with a spid 17 constituting a manual suction pump 18. When the pulsating pressure of the crank chamber of the engine is introduced into the upper chamber defined by the membrane 9,
The membrane 9 vibrates up and down, fuel in a fuel tank (not shown) is sucked into the pump chamber below the membrane 9 through the fuel inlet pipe 25, the filter and the suction valve, and further the discharge valve and the inflow valve 28.
Is discharged to the constant pressure fuel chamber 20 above the membrane 12.

A lever is supported in the constant pressure fuel chamber 20 by a shaft 27, the left end of the lever is biased and engaged with the central projection of the membrane 12 by the force of a spring, and the right end of the lever is engaged with the lower end of the inflow valve 28. It A constant level of fuel is stored in the constant pressure fuel chamber 20 by the inflow valve 28 that opens and closes according to the vertical displacement of the membrane 12. The lower chamber of the membrane 12 is open to the atmosphere. The fuel in the constant pressure fuel chamber 20 passes through the check valve and the fuel jet, and is sucked into the fuel injection hole of the fuel supply pipe 4 protruding into the throttle hole 2 and the throttle hole 2. The throttle valve 1 shown in FIG. 9 is at the fully open position,
The throttle hole 2 and the intake passage substantially coincide with each other in the axial direction. Throttle valve 1
The needle 3 projecting downward from is inserted into the fuel supply pipe 4.

When the throttle valve lever 22 is rotated in the acceleration direction against the force of the return spring, the opening degree of the throttle hole 2 with respect to the intake passage is increased, and at the same time, the needle 3 is raised by the above-mentioned cam mechanism to inject fuel. The opening of the hole increases.

Prior to starting the engine, the constant pressure fuel chamber 20
The suction pump 18 for discharging the air and fuel vapor of
A mushroom-shaped composite check valve 16 having an intake valve and a discharge valve is supported inside the spoid 17. The fuel vapor in the constant pressure fuel chamber 20 pushes the umbrella portion of the composite check valve 16 through the passage 14 and opens it into the inside of the void 17, and further presses the flat cut provided at the upper end of the shaft portion of the composite check valve 16. Open and return tube 19
(See FIG. 1) and returned to the fuel tank. at the same time,
Fresh fuel in the fuel tank is sucked into the constant pressure fuel chamber 20 through the fuel inlet pipe 25, the fuel pump 8 and the inflow valve 28.

The starting shaft 32 is inserted into a guide cylinder 53 formed integrally with the cover plate 21, and the starting shaft 32 is driven by the starting lever 31.
Is rotated, the cam surface 52 formed at the end of the starting shaft 32 is rotated.
Pushes up the throttle valve lever 22 to increase the fuel amount. The pin 51 engages with the arcuate groove of the starting shaft 32 to prevent the starting shaft 32 from coming off.

In a small general-purpose engine with a centrifugal clutch equipped with the rotary throttle valve type carburetor described above, when the air amount is increased above the normal idle speed, the centrifugal clutch is connected and the blade of the portable working machine operates. , Very dangerous. Therefore, the increase in the air amount at the time of starting the engine must be set so that the engine speed becomes slightly higher than the normal idle speed.

However, the idle speed of the engine becomes higher than the value set at the time of factory shipment after the running-in operation of the engine. At this time, if the idle speed is adjusted to an appropriate value by the idle adjustment bolt, the amount of air at the time of starting the engine by the starting fuel increase mechanism will be changed.

[0012]

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to cold start the engine even if the idle speed (throttle valve opening) is adjusted to an appropriate value after the engine is running in. It is an object of the present invention to provide a starting device for a rotary throttle valve type carburetor, which prevents the fuel amount from changing at any time.

[0013]

In order to solve the above-mentioned problems, the structure of the present invention is such that an axially slidable sleeve is fitted into a guide tube supported by a cover plate that closes the valve chamber of the carburetor body,
A pin that penetrates the sleeve is engaged with a slit in the axial direction of the guide tube, and a first projecting piece that projects laterally from the guide tube and a second projecting piece that projects laterally from the sleeve. A spring is interposed therebetween, the idle adjusting bolt penetrates the second projecting piece and the spring and is screwed into the first projecting piece, and the starting shaft having a spiral groove for engaging with the pin is fitted into the sleeve. A flat cam surface that engages with a cam plate provided on the valve shaft and a push rod that engages with a side wall surface provided on the valve shaft are formed at an end portion of the starting shaft.

Further, according to the structure of the present invention, the starting shaft is screwed into the boss portion formed on the cover plate for closing the valve chamber of the carburetor main body, and the cam surface is formed at the end of the starting shaft. A push rod is screwed on the, and a ridge is formed on the lower surface of the throttle valve lever connected to the valve shaft of the throttle valve, and the throttle valve lever is pushed up by the cam surface accompanying the rotation of the starting shaft, It is characterized in that the throttle valve lever is rotated by pushing the ridge by axial movement.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a starter for a rotary throttle valve type carburetor, in order to facilitate a cold start of an engine, it is possible to increase the amount of air and fuel at the same time. Depending on idle speed (throttle valve opening)
Even if is adjusted to an appropriate value, the amount of fuel at the cold start of the engine should not change.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, a rotary throttle valve type carburetor according to the present invention is provided with an air purifier and a heat insulating pipe on front and rear end flanges 5a and 5b of a carburetor main body 5 through which an intake passage traverses. They are butted together and connected to the engine wall by a pair of left and right mounting bolts. An intermediate wall body 10 forming a fuel pump is joined to the lower surface of the carburetor body 5 with a membrane 9 interposed therebetween.
An intermediate wall body 13 for partitioning the constant pressure fuel chamber is connected to the lower surface of the intermediate wall body 13 with the membrane 12 sandwiched between them, and the peripheral surface of the spoid 17 constituting the suction pump 18 is attached to the lower surface of the intermediate wall body 13 with the pressing plate 15.
Are combined by. The fuel in the fuel tank is the fuel inlet pipe 25.
Is supplied to the constant pressure fuel chamber through the fuel pump, and when the suction pump 18 is operated, fuel vapor in the constant pressure fuel chamber is returned from the return pipe 19 to the fuel tank. The other configuration is shown in FIG.
This is the same as the conventional one described in.

A cover plate 21 is superposed on the upper surface of the carburetor main body 5 and fixed to a bolt 24. A throttle valve lever 22 having a fan-shaped cam portion 22a is coupled to the upper end of the valve shaft 1a of the throttle valve 1 which penetrates the cover plate 21 and projects upward. A swivel 23 for connecting a remote control cable is supported on the throttle valve lever 22 and normally abuts against an idle adjusting bolt 26 by the force of a return spring (not shown).

An axial slit 34 is provided above the shaft hole 35b of the guide cylinder 35 which is connected to the cover plate 21 or is formed integrally with the cover plate 21, and a protrusion protruding laterally from the guide cylinder 35. The piece 35a is provided with a screw hole into which the idle adjusting bolt 26 is screwed. The sleeve 3 is attached to the guide tube 35.
3 is fitted and the pin 33a penetrating the peripheral wall of the sleeve 33 is engaged with the slit 34. The idle adjustment bolt 26 penetrates the protrusion 33b and the spring 26a, and
Is screwed onto. The throttle valve lever 22 is brought into contact with the tip of the idle adjustment bolt 26 by the force of the return spring, and the idle position of the throttle valve lever 22 is regulated.

As shown in FIGS. 3 and 5, the sleeve 33 is fitted with the starting shaft 38 having the starting lever 31. A cam 38a having a flat cam surface 38b at the end of the starting shaft 38.
Is provided, and a push rod 40 is further provided at the tip axis.
Further, the starting shaft 38 is provided with a spiral groove 39 that engages with the pin 33a protruding into the sleeve 33.

As described above, the sleeve 33 is fitted in the stationary guide tube 35, and the starting shaft 38 is fitted in the sleeve 33 so that the pin 33a of the sleeve 33 is engaged with the spiral groove 39. One end of the spring 43 wound around the base end portion of the starting shaft 38 is locked in the groove 43a of the sleeve 33, the other end of the spring 43 is locked in the starting lever 31, and the starting lever 31 moves the spring 4
The force of 3 normally biases diagonally downward. At this time, as shown in FIG. 4, a plane orthogonal to the cam surface 38 b of the cam 38 a has a gap with the lower surface of the throttle valve lever 22. On the other hand, as shown in FIG. 3, on the valve shaft 1a of the throttle valve 1, a cam plate 42 is provided between the throttle valve lever 22 and the cam portion 22a.
And a flat side wall surface 44 is provided below the cam plate 42.

Next, the operation of the starting device for the rotary throttle valve type carburetor according to the present invention will be described. Normally, the starting lever 31 is biased by a force of a spring 43 to a position that is directed obliquely downward. At the time of cold starting of the engine, when the starting lever 31 is rotated clockwise and tilted obliquely upward as shown in FIG. 2, the flat cam surface 38b engages with the lower surface of the cam plate 42 and pushes up the throttle valve lever 22. Therefore, the opening degree of the fuel injection hole increases.
At the same time, the starter shaft 38 moves in the axial direction (direction of arrow y) due to the engagement between the spiral groove 39 of the starter shaft 38 and the pin 33a, and the side wall surface 44 of the valve shaft 1a is pushed by the push rod 40, so that in FIG. Since the throttle valve lever 22 is rotated counterclockwise, the opening degree of the throttle hole of the fuel supply pipe increases. Thus
Since the throttle valve is raised and rotated by the rotation of the starting lever 31, the air amount is increased at the same time as the fuel amount is increased, so that the engine can be smoothly started.

After the engine is warmed up, when the throttle valve lever 22 is rotated in the counterclockwise direction (the direction in which the throttle valve is fully opened), the throttle valve lever 22 is pushed up by the normal cam mechanism and the cam surface 3
Since it is separated from 8b, the starting shaft 38 having the cam 38a is returned to its original position by the force of the spring 43.

In the present invention, the starting shaft 38 rotated by the starting lever 31 is provided with the cam surface 38b and the push rod 40, and the cam surface 38b can be engaged with the cam plate 42 integral with the valve shaft 1a. Side wall surface 44 formed integrally with the valve shaft 1a
Therefore, an appropriate starting operation can be obtained by processing the height of the cam surface 38b from the axial center and the axial dimension of the push rod 40 so as to match the starting characteristics of the engine. Further, the amount of fuel and the amount of air can be adjusted separately, so processing is easy.

When the idle speed is adjusted according to the operating history and operating environment of the engine, if the idle adjusting bolt 26 is loosened, the throttle valve lever 22 is rotated in the deceleration direction and only the air amount is reduced. 33 and the starting shaft 38 retreat in the axial direction, the push rod 40 of the starting shaft 38 and the valve shaft 1a
Does not change relative distance to the side wall surface 44. Therefore,
The amount of increase in fuel and air when the starting lever 31 is rotated clockwise (direction of arrow x) during cold start is almost the same as that before adjustment of the idle speed. Strictly speaking, the air-fuel ratio becomes richer as the air amount is reduced by adjusting the idle speed.

In the embodiment shown in FIGS. 6 to 8, when the starting shaft 58 supported by the guide cylinder 21b integral with the cover plate 21 is rotated,
Due to the cam surface 58a at the end of the starting shaft 58, the throttle valve lever 2
2 is pushed up, and at the same time, the push rod 5 screwed onto the starting shaft 58.
5, the projecting wall 22b of the throttle valve lever 22 is pushed and rotated.

A lid plate 21 for closing the valve chamber of the carburetor main body 5
Is fixed by a plurality of bolts 24, and a throttle valve lever 22 is coupled to the upper end of the valve shaft 1a penetrating the cover plate 21. As shown in FIG. 8, the valve shaft 1a is covered with the dustproof boot 1b. A swivel 23 is provided at the end of the throttle valve lever 22.
Is supported, and a cam portion 22a is integrally formed at the other end portion, and the cam portion 22a is provided with a cam groove that engages with a follower 54 protruding from the cover plate 21. As shown in FIGS. 6 and 7, the lower surface 22c of the throttle valve lever 22 is provided with a protruding wall 22b protruding downward. On the protruding wall 21 a protruding upward from the side edge portion of the cover plate 21, the idle adjusting bolt 26
Are screwed together. A boss portion or a guide cylinder 21b is integrally formed adjacent to the protruding wall 21a, and a starting shaft 58 having a starting lever 59 is fitted into the guide cylinder 21b. A spiral groove 57 is provided on the outer peripheral surface of the starting shaft 58, and a guide pin 56 that engages with the spiral groove 57 is fixed to the guide cylinder 21b. Starting axis 58
A push rod 55 is screwed into a screw hole 60 provided at the axis of the push rod 55, and the tip of the push rod 55 can come into contact with the protruding wall 22b. A flat cam surface 58a engageable with the lower surface 22c of the throttle valve lever 22 is formed at the end of the starting shaft 58. Other configurations are shown in FIG.
This is the same as the conventional example shown in FIG.

The starting lever 59 is normally in a substantially upright position. At this time, the cam surface 58a is separated from the lower surface 22c of the throttle valve lever 22, and the push rod 55 is close to the projecting wall 22b but does not abut. When the starting lever 59 is tilted, the spiral groove 57 of the starting shaft 58 is guided by the guide pin 56 and screwed. At this time, the starting shaft 58 moves to the left simultaneously with the rotation, and
As shown in, the cam surface 58a abuts the lower surface 22c of the throttle valve lever 22 and pushes up the throttle valve lever 22. At the same time, the push rod 55 hits the protruding wall 22b, and the throttle valve lever 22
Rotate clockwise.

As described above, when the throttle valve lever 22 is pushed up by the cam surface 58a, the opening of the fuel injection hole of the fuel supply pipe is increased and the amount of fuel is increased. At the same time, when the throttle valve lever 22 is rotated by the push rod 55, the opening degree of the throttle hole of the throttle valve is increased and the amount of air is increased. The amount of lift (lift) of the throttle valve lever 22 is determined by the dimension from the shaft center of the starting shaft 58 to the cam surface 58a. Throttle valve lever 22
The rotation amount of is adjusted by the screwing amount of the push rod 55 into the screw hole 60 of the starting shaft 58. According to the present invention, not only the amount of fuel at the time of cold starting of the engine but also the amount of air can be independently adjusted, so that stable idle rotation can be obtained after the engine is started. In particular, in the case of an engine equipped with a centrifugal clutch, it is possible to avoid the risk that the idle rotation speed becomes too high and the centrifugal clutch is connected and the blade unexpectedly rotates.

[0029]

As described above, according to the present invention, the sleeve slidable in the axial direction is inserted into the guide cylinder supported by the cover plate closing the valve chamber of the carburetor body, and the pin penetrating the sleeve is guided by the guide. A spring is interposed between a first projecting piece that projects laterally from the guide tube and a second projecting piece that projects laterally from the sleeve, which engages with a slit in the axial direction of the cylinder. The adjusting bolt penetrates the second projecting piece and the spring and is screwed into the first projecting piece, and a starting shaft having a spiral groove that engages with the pin is fitted and inserted into the sleeve, and the end of the starting shaft is provided with the adjusting shaft. Since the flat cam surface that engages with the cam plate provided on the valve shaft and the push rod that engages with the side wall surface provided on the valve shaft are formed, when the starting lever is rotated during cold starting of the engine, The cam surface of the starting shaft pushes up the valve shaft to increase the amount of fuel, and the pushing rod of the starting shaft rotates the valve shaft. Air amount is increased, and the smooth start of the engine can be obtained.

When the idle adjusting bolt is loosened in order to adjust the idle speed to an appropriate value according to the operation history of the engine, the throttle valve lever is rotated in the deceleration direction and only the air amount is reduced. At the same time, the sleeve and the starting shaft retract in the axial direction, and the relative distance between the push rod of the starting shaft and the side wall surface of the valve shaft does not change. Therefore, when the start lever during cold start is operated, the fuel amount is the same as that before the idle speed adjustment, but the amount of air is reduced by the amount that the throttle valve opening is reduced compared to before the idle speed adjustment. Is reduced, and the engine speed after starting becomes an appropriate value.

Further, a starting shaft is screwed onto a boss formed on a cover plate for closing the valve chamber of the carburetor main body, a cam surface is formed at an end of the starting shaft, and a push rod is screwed onto the starting shaft. Then, a protrusion is formed on the lower surface of the throttle valve lever coupled to the valve shaft of the throttle valve, and the throttle valve lever is pushed up by the cam surface accompanying the rotation of the starting shaft, and the protrusion is caused by the axial movement of the starting shaft. Even if the throttle valve lever is rotated by pushing the line, the same effect can be obtained.

[Brief description of drawings]

FIG. 1 is a front view of a rotary throttle valve type carburetor equipped with a starting device according to the present invention.

FIG. 2 is a plan view of the rotary throttle valve type carburetor.

FIG. 3 is an enlarged plan view showing a main part of the rotary throttle valve type carburetor.

FIG. 4 is a front view showing a normal relationship between a throttle valve lever and a cam of the rotary throttle valve type carburetor.

FIG. 5 is an exploded plan view showing the starting device of the rotary throttle valve type carburetor.

FIG. 6 is a front sectional view of a rotary throttle valve type carburetor equipped with a starting device according to a second embodiment of the present invention.

FIG. 7 is a plan sectional view of the rotary throttle valve type carburetor.

FIG. 8 is a side sectional view of the rotary throttle valve type carburetor.

FIG. 9 is a side sectional view of a conventional rotary throttle valve carburetor.

[Explanation of symbols]

1: Throttle valve 1a: Valve shaft 2: Throttle hole 3: Needle
4: Fuel supply pipe 5: Vaporizer body 6: Valve chamber 8: Fuel pump 9: Membrane 10: Intermediate wall body 12: Membrane 13: Intermediate wall body 16: Combined check valve 17: Spid 18: Suction pump 19: Return Pipe 20: Constant pressure fuel chamber 21: Lid plate 21a: Projection wall 21b: Guide cylinder 22: Throttle valve lever 22a: Cam part 22b: Projection wall 22c: Lower surface 2
3: Swivel 25: Fuel inlet pipe 26: Idle adjusting bolt 28: Inflow valve 31: Starting lever 32: Starting shaft 33: Sleeve 33a: Pin 33b: Projection piece 3
4: Slit 35: Guide tube 35a: Projection piece 35b:
Shaft hole 38: Starting shaft 38a: Cam 38b: Cam surface
39: spiral groove 40: push rod 41: cam plate 42: cam plate 43: spring 43a: groove 44: side wall surface 51: pin 52: cam surface 54: follower 55: push rod 5
6: Guide pin 57: Spiral groove 58: Starting shaft 58a:
Cam surface 59: Starting lever 60: Screw hole

Claims (3)

[Claims] 1. A sleeve slidable in an axial direction is fitted into a guide cylinder supported by a cover plate for closing a valve chamber of a carburetor body, and a pin penetrating the sleeve is engaged with a slit in the axial direction of the guide cylinder. And a spring is interposed between the first projecting piece projecting laterally from the guide tube and the second projecting piece projecting laterally from the sleeve, and the idle adjusting bolt is provided with the second projecting piece. A starting shaft having a spiral groove that engages with the pin and is screwed into the first projecting piece through the spring, and a cam plate provided on the valve shaft at the end of the starting shaft. A starting device for a rotary throttle valve carburetor, characterized in that a flat cam surface for engagement and a push rod for engagement with a side wall surface provided on the valve shaft are formed. 2. From a starting position where the cam surface of the starting shaft and the cam plate of the valve shaft engage, to a normal position where the cam surface of the starting shaft and the cam plate of the valve shaft disengage. The starting device for a rotary throttle valve carburetor according to claim 1, wherein a spring that urges rotation is wound around the starting shaft. 3. A starting shaft is screwed to a boss formed on a cover plate that closes the valve chamber of the carburetor main body, a cam surface is formed at an end of the starting shaft, and a push rod is screwed to the starting shaft. Then, a protrusion is formed on the lower surface of the throttle valve lever coupled to the valve shaft of the throttle valve, and the throttle valve lever is pushed up by the cam surface accompanying the rotation of the starting shaft, and the protrusion is caused by the axial movement of the starting shaft. A starting device for a rotary throttle valve carburetor, characterized in that a throttle valve lever is rotated by pushing a strip.