JP2003172208A - Starting device for rotary throttle valve type carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starting device for a rotary throttle valve type carburetor capable of not only increasing air but also increasing fuel in start of an engine. <P>SOLUTION: A cam shaft 30 is inserted and fitted in a cylindrical part of a projecting wall 2a formed on a cover plate 2 blocking a valve chamber of a carburetor main body 20 in such a manner that the same can rotate but can not move in an axial direction. Cam surfaces 34, 34a formed on end part circumference surfaces of the cam shaft 30 is formed to engage with a lower surface of a cam plate 8 integrated with a throttle valve lever 7. A pushing moving shaft 27 threadedly engaging with a bolt 17 capable of getting into contact with a side edge of the throttle lever 7 is inserted and fitted in a second cylindrical part of the projecting wall 2a. A thread movement mechanism moving the pushing moving shaft 27 in an axial direction by rotation of the cam shaft 30 is provided. <P>COPYRIGHT: (C)2003,JPO

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 starting mechanism of a vaporizer.

[0002]

2. Description of the Related Art In a conventional rotary throttle valve type carburetor, a cam mechanism pushes up a throttle valve lever to increase the amount of fuel in order to improve engine startability. The idle rotation may not be maintained due to lack of power.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a starting mechanism for a rotary throttle valve type carburetor which can increase not only the amount of fuel at the time of starting the engine but also the amount of air. It is in.

[0004]

In order to solve the above-mentioned problems, the structure of the present invention is such that a cam shaft is attached to a first cylindrical portion of a projecting wall formed on a cover plate that closes a valve chamber of a carburetor body. The cam surface, which is immovably and rotatably fitted and formed on the peripheral surface of the end portion of the cam shaft, is configured to be engageable with the lower surface of the cam plate integral with the throttle valve lever. A push shaft for screwing a bolt that can abut against the side edge of the throttle valve lever is fitted into the cylindrical portion,
It is characterized in that a screw mechanism for moving the push shaft in the axial direction by the rotation of the cam shaft is provided.

Further, according to the structure of the present invention, the cam shaft is fitted in the first cylindrical portion of the protruding wall formed on the cover plate closing the valve chamber of the carburetor main body so as not to be axially movable but rotatable. The cam surface formed on the peripheral surface of the end portion of the shaft is configured to be engageable with the lower surface of the cam plate integral with the throttle valve lever, and the second cylindrical portion of the projecting wall contacts the side edge of the throttle valve lever. It is characterized in that a push shaft for screwing a contactable bolt is fitted and inserted, and a screw mechanism for rotating the cam shaft by screwing of the push shaft is provided.

Further, according to the structure of the present invention, the cam shaft is fitted in the cylindrical portion of the projecting wall formed on the cover plate closing the valve chamber of the carburetor main body so as to be immovable in the axial direction and rotatable. The cam surface formed on the peripheral surface is configured to be engageable with the lower surface of the cam plate integral with the throttle valve lever, and the inclined cam surface protruding from the upper portion to the lower portion formed on the side edge of the throttle valve lever, It is characterized in that it comes into contact with a bolt screwed to the projecting wall.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in order to improve the engine startability, the amount of air is also increased when the amount of fuel is increased so that idle rotation can be maintained. For this reason, the cam shaft is immovably and rotatably fitted into the cylindrical portion of the protruding wall formed on the cover plate that closes the valve chamber of the carburetor body, and the cam formed on the peripheral surface of the end portion of the cam shaft. The surface is configured to be engageable with the lower surface of the cam plate integral with the throttle valve lever. Further, a push shaft for screwing a bolt that can come into contact with the side edge of the throttle valve lever is fitted into the second cylindrical portion of the projecting wall. The pushing shaft is moved in the axial direction by turning the cam shaft, or the cam shaft is turned by screwing the pushing shaft.

Further, a bolt is screwed into the projecting wall without providing the pushing shaft, and the inclined cam surface protruding from the upper portion to the lower portion formed on the side edge of the throttle valve lever is brought into contact with the bolt.

[0009]

1 and 2, a rotary throttle valve type carburetor equipped with a starting mechanism according to the present invention is provided on front and rear end flanges of a carburetor body 20 made of aluminum or the like through which an intake passage 18 penetrates. A pair of left and right through holes 12 are provided, an air purifier is superposed on the lower end flange of FIG. 1, and the upper end flange is connected to a wall portion surrounding the intake port of the engine through a heat insulating pipe. They are connected by a pair of bolts that pass through holes 12. In the cylindrical valve chamber orthogonal to the intake passage 18,
A throttle valve 19 having a throttle hole is fitted so as to be rotatable and movable up and down. The valve shaft 6 at the upper end of the throttle valve 19 penetrates the cover plate 2 made of synthetic resin that closes the valve chamber, and the throttle valve lever 7 is connected to the upper end of the valve shaft 6. A swivel 7 a that locks the inner cable of the remote control cable is supported at the end of the throttle valve lever 7. On the other hand, a fan-shaped cam 7b is formed at the other end of the throttle valve lever 7. The lower surface of the cam 7b is provided with a cam groove in which the depth of the groove gradually decreases in the circumferential direction, and the follower supported by the cover plate 2 engages with the above-mentioned cam groove to form a cam mechanism.

Although not shown, a fuel pump and a constant pressure fuel supply mechanism are provided at the bottom of the carburetor main body 20, and a fuel supply pipe projects from the constant pressure fuel chamber to the throttle hole of the throttle valve 19. On the other hand, the throttle valve 19 supports a needle that is inserted into the fuel supply pipe and adjusts the opening of the fuel injection hole. Therefore, when the inner cable (not shown) is pulled from the idle position shown in FIG. 1 to rotate the throttle valve lever 7 in the clockwise direction, the opening degree of the throttle hole of the throttle valve 19 with respect to the intake passage 18 increases, At the same time, the throttle valve lever 7 is pushed up by the cam mechanism, and the opening degree of the fuel injection hole of the fuel supply pipe increases.

The lid plate 2 has an inverted L shape in FIG. 1 and is superposed on the upper end surface of the carburetor body 20 together with the metal reinforcing plate 3 having the protrusions 3a, and is attached to the carburetor body 20 by a pair of bolts 4. It is concluded to. A mounting bracket (not shown) that supports the end of the outer tube is screwed and supported on the bent wall 3b formed by bending the left edge of the reinforcing plate 3 upward. The inner cable inserted through the outer tube passes through the guide projection wall 5 of the cover plate 2 and is locked to the swivel 7a.

A protruding wall 2a is integrally formed on the right side edge of the cover plate 2, an idle adjusting bolt 15 is screwed onto an upper portion of the protruding wall 2a, and a bolt 17 is attached to a cylindrical portion below the protruding wall 2a. The push shaft 27 to be screwed is supported so as not to be rotatable and slidable in the axial direction. In addition, in the cylindrical portion of the front and rear substantially central portion of the projecting wall 2a,
As shown in FIGS. 3 and 4, the cam shaft 30 provided with the starting lever 10 is fitted so as to be rotatable but immovable in the axial direction. Therefore, as shown in FIGS. 1 and 9, the pin 9a supported by the projecting wall 2a is engaged with the circumferential groove 9b provided on the cam shaft 30. The cam shaft 30 is partially formed integrally with the spiral ridge 33, and the push shaft 27 is provided with a protrusion having a groove 27 a that engages with the spiral ridge 33. Flat cam surfaces 34, 34a are formed on the peripheral surface of the end of the cam shaft 30. As shown in FIG. 3, when the starting lever 10 is upright, the cam surface 34 is integrated with the throttle valve lever 7. It projects so as not to contact the lower side of the plate 8.

As shown in FIGS. 5 and 6, a coil spring 31 is wound around the cam shaft 30, and one end of the coil spring 31 is locked to the projecting wall 2a and the other end thereof is locked to the starting lever 10.
The starting lever 10 is rotationally biased to the upright position shown in FIG. 3 by the force of the coil spring 31. An edge portion 40 projecting downward is integrally formed at a side edge of the throttle valve lever 7, the tip of the idle adjusting bolt 15 is engaged with the edge portion 40, and the pushing shaft 2
The tip of a bolt 17 screwed to 7 is configured to be engageable. However, normally, the bolt 17 does not abut the edge portion 40.

During cold starting of the engine, when the starting lever 10 is tilted from the upright state shown in FIGS. 5 and 6 to the front side (upper side in FIG. 7) as shown in FIGS. 7 and 8, the spiral protrusion 33 and the groove are formed. The push shaft 27 with which 27a engages is pushed to the left, the bolt 17 contacts the edge portion 40, and the throttle valve lever 7 is rotated in the direction of the arrow in FIG. Only the edge 40 is shown in FIG. At the same time, the cam surface 3 which is integral with the throttle valve lever 7 and projects downward from the cam plate 8
4 is switched to the cam surface 34a, and the cam surface 34a pushes up the throttle valve 19 together with the throttle valve lever 7. In this way, the opening degree of the throttle valve 19 is increased, and at the same time, the opening degree of the fuel injection hole is increased, so that a rich air-fuel mixture is supplied to the engine as the engine is cranked, and a smooth start is obtained. Particularly, when the engine is started, the air amount slightly increases, so that the warm-up operation after the start is smoothly performed. The amount of lift (lift) of the throttle valve lever 7 is determined by the height from the shaft center of the cam shaft 30 to the cam surface 34a. In addition, the edge portion 40 is fixed by the bolt 17.
The amount of rotation of the throttle valve lever 7 that is pushed is adjusted by the amount of screwing of the bolt 17 into the push shaft 27.

After the engine has been warmed up, when the throttle valve lever 7 is rotated in the clockwise direction (the direction in which the throttle valve is fully opened), the cam plate 8 rotates together with the throttle valve lever 7 and comes off the cam surface 34a. At this time, the starting lever 10 is driven by the force of the coil spring 31.
Is returned to the upright position. At the same time, the push shaft 27 in which the projection having the groove 27a engages with the spiral projection 33 of the cam shaft 30,
In FIG. 7, it is returned in the direction opposite to the arrow. The edge portion 40 is not formed at the front end portion of the throttle valve lever 7, but is formed at the rear side with respect to the rotation direction in the acceleration direction.

In the embodiment shown in FIGS. 10 to 18, a bolt 17 for rotating the throttle valve lever 7 is screwed and supported on a push shaft 37.
A cam shaft 30 for pushing up the gear 21 (see FIG. 18) that meshes with the gear 22 of the push shaft 37 to push up the throttle valve lever 7.
It is prepared for a. The idle adjusting bolt 15 is screwed onto the upper portion of the protruding wall 2a formed on the right side edge of the cover plate 2, and the push shaft 37 for screwing the bolt 17 is rotatable on the lower cylindrical portion of the protruding wall 2a. In addition, it is supported so as to be slidable in the axial direction. Further, the cam shaft 30
a is inserted so as to be rotatable and immovable in the axial direction. Therefore, as shown in FIGS. 10 and 18, the pin 9a supported by the projecting wall 2a is engaged with the circumferential groove 29b provided on the cam shaft 30a. A partial gear 21 is integrally formed at the base end of the cam shaft 30a. Flat cam surfaces 34, 34a are formed on the peripheral surface of the end of the cam shaft 30a. As shown in FIG. 15, when the starting lever 10 is upright, the cam surface 34 is integral with the throttle valve lever 7. It projects so as not to contact the lower side of the plate 8 (see FIG. 10).

As shown in FIGS. 14 and 15, a coil spring 31 is wound around the pushing shaft 37, and one end of the coil spring 31 is locked to the projecting wall 2a and the other end is locked to the starting lever 10. The force of the coil spring 31 causes the starting lever 10 to move as shown in FIG.
It is rotationally biased to the upright position shown in. An edge portion 40 projecting downward is integrally formed on a side edge of the throttle valve lever 7, a tip of the idle adjusting bolt 15 abuts on the edge portion 40, and a bolt screwed into the screw hole 23 of the push shaft 37. The tip of 17 is configured to be able to abut. However, normally, the bolt 17 does not abut the edge portion 40.

When the engine is cold started, the starting lever 10 is shown in FIG.
When it is tilted forward (upward in FIG. 16) from the upright state shown in FIGS. 4 and 15 as shown in FIGS. 16 and 17, the spiral groove 29b of the pushing shaft 37 is guided by the pin 29a and pushed to the left, The bolt 17 hits the edge portion 40, and the throttle valve lever 7 is rotated clockwise in FIG. Only edge 40 is shown in FIG. At the same time, the cam shaft 30a having the gear 21 meshing with the gear 22 is rotated and the cam plate 8 integral with the throttle valve lever 7 is rotated.
The cam surface 34 protruding downward is switched to the cam surface 34a, and the cam surface 34a pushes up the throttle valve 19 together with the throttle valve lever 7. In this way, the opening degree of the throttle valve 19 is increased, and at the same time, the opening degree of the fuel injection hole is increased, so that a rich air-fuel mixture is supplied to the engine as the engine is cranked, and a smooth start is obtained. Particularly, when the engine is started, the air amount slightly increases, so that the engine does not stop and the warm-up operation after the start is smoothly performed. The amount of lift (lift) of the throttle valve lever 7 is determined by the height from the shaft center of the cam shaft 30a to the cam surface 34a. In addition, the edge portion 40 is fixed by the bolt 17.
The amount of rotation of the throttle valve lever 7 that is pushed is adjusted by the amount of screwing of the bolt 17 into the push shaft 37.

After the engine has been warmed up, when the throttle valve lever 7 is rotated in the clockwise direction (the direction in which the throttle valve is fully open), the cam plate 8 rotates together with the throttle valve lever 7 and comes off the cam surface 34a. At this time, the starting lever 10 is driven by the force of the coil spring 31.
Is returned to the upright position. At the same time, the gear 22 of the push shaft 37
The cam shaft 30a having the gear 21 that meshes with is returned in the opposite direction.

In the embodiment shown in FIGS. 19 to 21, the bolt 17 also serving as an idle adjusting bolt is brought into contact with the cam surface 41 formed on the side edge portion of the throttle valve lever 7, and the cam shaft 30 is rotated to rotate the throttle valve. When the lever 7 is pushed up, the cam surface 41 is pushed so that the throttle valve lever 7 is slightly rotated in the acceleration direction. A cam shaft 30 having a starting lever 10 is supported by a cylindrical portion of the projecting wall 2a of the cover plate 2 so as to be rotatable and axially immovable. Therefore, the pin 9a supported by the projecting wall 2a is engaged with the circumferential groove (see FIG. 9) provided on the circumferential surface of the cam shaft 30. At the end of the cam shaft 30, a cam surface 34,
34a is formed and is projected to the lower side of the cam plate 8 formed integrally with the throttle valve lever 7. Similar to the embodiment shown in FIG. 1, one end of the coil spring 31 wound around the cam shaft 30 is locked to the projecting wall 2a and the other end is locked to the starting lever 10. A bolt 17 that also serves as an idle adjustment bolt that is screwed and supported on the protruding wall 2a has a tip on a cam surface 41 formed on a side edge portion of the throttle valve lever 7, and a return spring (not shown) that returns the throttle valve 19 to an idle position. It is urged and engaged by the force of. The cam surface 41 is formed as an inclined surface that gradually becomes higher (projects toward the bolt 17) from the upper part to the lower part.

At the position where the starting lever 10 is upright as shown in FIGS. 19 and 20, the tip of the bolt 17 engages with the upper portion of the cam surface 41 to regulate the normal idle position of the throttle valve lever 7. When the engine is cold started and the starting lever 10 is tilted,
As shown in FIG. 21, the throttle valve lever 7 is pushed up together with the cam plate 8 by the cam surface 34a of the cam shaft 30. At the same time, the lower portion of the cam surface 41 engages with the tip of the bolt 17, and the throttle valve lever 7 is rotated clockwise (acceleration direction) in FIG. Due to the increase in the fuel amount due to the rise of the throttle valve lever 7 and the increase in the air amount due to the rotation of the throttle valve lever 7, a rich air-fuel mixture is supplied to the engine, and a smooth start of the engine can be obtained. In a portable work machine in which the rotation of the engine crankshaft is transmitted to a rotary blade via a centrifugal clutch, the amount of air at the cold start of the engine is the fuel amount so that the blade does not rotate at the same time when the engine is started. Independently of, the amount is adjusted by the screwing amount of the bolt 17 into the projecting wall 2a.

[0022]

As described above, according to the present invention, not only the amount of fuel can be increased but also the amount of air can be increased during cold starting of the engine. Therefore, the startability of the engine can be improved and a stable idle after starting can be achieved. The rotation is obtained.

When the cam shaft or is rotated during cold start of the engine, the throttle valve lever is pushed up by the cam surface of the cam shaft to increase the fuel amount, and the throttle valve lever is rotated by the push shaft or the bolt. As a result, the amount of air increases and a smooth start of the engine is achieved.

[Brief description of drawings]

FIG. 1 is a plan view of a rotary throttle valve type carburetor having a starting mechanism according to a first embodiment of the present invention.

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

FIG. 3 is a side view of the rotary throttle valve type carburetor.

FIG. 4 is a side sectional view of the rotary throttle valve type carburetor.

FIG. 5 is a plan sectional view of the starting mechanism.

FIG. 6 is a side sectional view of the starting mechanism.

FIG. 7 is a plan sectional view of the starting mechanism at the time of starting operation.

FIG. 8 is a side sectional view of the starting mechanism during a starting operation.

FIG. 9 is an exploded perspective view showing a cam shaft and a pushing shaft of the starting mechanism.

FIG. 10 is a plan view of a rotary throttle valve type carburetor having a starting mechanism according to a second embodiment of the present invention.

FIG. 11 is a front view of the rotary throttle valve type carburetor.

FIG. 12 is a side view of the rotary throttle valve type carburetor.

FIG. 13 is a side sectional view of the rotary throttle valve type carburetor.

FIG. 14 is a plan sectional view of the starting mechanism.

FIG. 15 is a side sectional view of the starting mechanism.

FIG. 16 is a plan sectional view of the starting mechanism at the time of starting operation.

FIG. 17 is a side sectional view of the starting mechanism at the time of starting operation.

FIG. 18 is an exploded perspective view showing a pushing shaft and a cam shaft of the starting mechanism.

FIG. 19 is a plan view showing a starting mechanism of a rotary throttle valve type carburetor according to a third embodiment of the present invention.

FIG. 20 is a front view of the starting mechanism.

FIG. 21 is a front view of the starting mechanism at the time of starting operation.

[Explanation of symbols]

2: Lid plate 2a: Projection wall 3: Reinforcement plate 3a: Projection line 4:
Bolt 3b: Bent wall 5: Guide projection wall 6: Valve shaft 7: Throttle valve lever 7a: Swivel 7b: Cam 8: Cam plate 9a: Pin 9b:
Circumferential groove 10: Starting lever 12: Through hole 15: Idle adjusting bolt 17: Bolt 18: Intake passage 19:
Throttle valve 20: Vaporizer body 21: Gear 22: Gear
23: Screw hole 27: Pushing shaft 27a: Groove 29a: Pin 29b: Spiral groove 30: Cam shaft 30
a: cam shaft 31: coil spring 33: spiral protrusion 3
4: Cam surface 34a: Cam surface 37: Push shaft 40: Edge 41: Cam surface

Claims (6)

[Claims] 1. A cam shaft is immovably and rotatably fitted in a first cylindrical portion of a projecting wall formed on a cover plate that closes a valve chamber of a carburetor main body, and an end circumference of the cam shaft is surrounded. The cam surface formed on the surface is configured to be engageable with the lower surface of the cam plate which is integral with the throttle valve lever, and the second cylindrical portion of the projecting wall is provided with a bolt capable of contacting the side edge of the throttle valve lever. A starting mechanism for a rotary throttle valve type carburetor, comprising a screwing mechanism in which a pushing shaft to be screwed is fitted and which is moved in the axial direction by rotation of a cam shaft. 2. A cam shaft is immovably and rotatably fitted in a first cylindrical portion of a projecting wall formed on a cover plate that closes a valve chamber of a carburetor main body, and an end portion of the cam shaft is surrounded. The cam surface formed on the surface is configured to be engageable with the lower surface of the cam plate which is integral with the throttle valve lever, and the second cylindrical portion of the projecting wall is provided with a bolt capable of contacting the side edge of the throttle valve lever. A starting mechanism of a rotary throttle valve type carburetor, comprising a screwing mechanism for inserting a screwing push shaft and rotating a cam shaft by screwing the push shaft. 3. The screw mechanism according to claim 1, wherein the screw mechanism includes a spiral protrusion provided on the cam shaft and a protrusion having a groove for engaging with the spiral protrusion provided on the pushing shaft. Rotary throttle valve type carburetor starting mechanism. 4. The screw mechanism comprises a pair of gears formed on a cam shaft and a pushing shaft, which mesh with each other, a spiral groove provided on the pushing shaft, and a stationary pin which engages with the spiral groove. 1,2
The starting mechanism of the rotary throttle valve type carburetor according to 1. 5. A normal disengagement between the cam surface of the cam shaft and the cam plate of the throttle valve lever from a starting position where the cam surface of the cam shaft and the cam plate of the throttle valve lever engage. The starting mechanism of a rotary throttle valve type carburetor according to claim 1, wherein a spring for biasing the position to rotate is wound around one of the cam shaft and the push shaft. 6. A cam shaft is immovably and rotatably fitted in a cylindrical portion of a projecting wall formed on a cover plate that closes a valve chamber of a carburetor body, and is formed on an end peripheral surface of the cam shaft. The cam surface is configured to be engageable with the lower surface of the cam plate that is integral with the throttle valve lever,
A starting mechanism for a rotary throttle valve carburetor, characterized in that an inclined cam surface protruding from an upper portion to a lower portion formed on a side edge of a throttle valve lever is brought into contact with a bolt screwed to the projecting wall.