JP2003172207A - Starting device for rotary throttle valve type carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starting device for rotary throttle valve type carburetor capable of finely adjusting fuel increase amount and air increase amount. <P>SOLUTION: A starting shaft 16 is inserted and fitted in a boss part 2b formed as one body with a cover plate 2 blocking a valve chamber of a carburetor main body 21 and a pin 14 fixed on the boss part is engaged with a spiral groove 15 on an outer circumference surface of the starting shaft 16. A pushing bar 19 is threadedly engaged with a threaded hole 18 provided at a shifted center position of the starting shaft 16 and a tip part of the pushing bar 19 is projected downward of a throttle valve lever 9. The tip part of the pushing bar 19 is constructed in such a manner that the same can get into a contact with a lower surface of the throttle lever 9 and bump on a projecting line 9a projecting downward from a lower surface of the throttle lever 9 by rotation of the starting shaft 16. <P>COPYRIGHT: (C)2003,JPO

Description

Description: 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, a power saw, etc. The present invention relates to a rotary throttle valve type carburetor starting device that facilitates cold starting. 2. Description of the Related Art In a small general-purpose engine equipped with a centrifugal clutch equipped with a rotary throttle valve type carburetor, the amount of fuel is increased in order to improve the cold startability of the engine, and air is increased in order to maintain idle rotation. Although the amount of starting air required to maintain idling rotation was not obtained, or the amount of starting air was too high and the number of revolutions increased, the centrifugal clutch was connected and the blades rotated, causing a very dangerous situation. State. Therefore, the increase in the amount of air when the engine is started must be set so that the engine speed is slightly higher than the normal idle speed. Further, in order to change the amount of lift (lift) of the throttle valve lever, the lift lever must be reassembled. An object of the present invention, in view of the above-mentioned problems, is to provide a starting device for a rotary throttle valve type carburetor capable of finely adjusting the fuel increase and the air increase. [0004] In order to solve the above-mentioned problems, according to the present invention, a starting shaft is inserted into a boss portion integral with a lid plate for closing a valve chamber of a carburetor body. A pin fixed to the boss is engaged with a spiral groove on the outer peripheral surface of the starting shaft, a push rod is screwed into a screw hole provided at an eccentric position of the starting shaft, and a tip end of the push rod is connected to a throttle valve lever. Projecting downward, the tip of the push rod can be brought into contact with the lower surface of the throttle valve lever by rotation of the starting shaft, and can be abutted against a ridge projecting downward from the lower surface of the throttle valve lever. Features. [0005] In the present invention, the eccentric position of the starting shaft,
Screw the push rod to adjust the opening of the throttle valve. When the starting shaft is rotated, the starting shaft is screwed and moves in the axial direction, and the tip of the push rod pushes the throttle valve lever, increasing the opening of the throttle valve and increasing the amount of air. The degree of opening of the throttle valve is finely adjusted by the screwing amount of the push rod to the starting shaft, and an appropriate idle rotation without connecting the centrifugal clutch is maintained. At the same time, the tip of the push rod is located at the eccentric position of the starting shaft, contacts the lower surface of the throttle valve lever, pushes up the throttle valve lever, increases the amount of fuel, and enhances the startability of the engine. The push-up amount of the throttle valve lever is changed by exchanging the push rod with a tip having a different outer diameter. As shown in FIGS. 1 to 3, a carburetor main body 21 through which an intake passage 23 penetrates is provided with a pair of left and right through holes 2 through a heat insulating pipe.
2 is coupled to a wall surrounding the intake port of the engine by a bolt inserted into the engine. The carburetor main body 21 is provided with a vertical cylindrical valve chamber that intersects with the intake path 23, and a throttle valve having a throttle hole is fitted in the valve chamber so as to be rotatable and vertically movable.
The valve chamber is closed by a cover plate 2 made of a synthetic resin, and fastened together with an inverted L-shaped metal reinforcing plate 3 by a plurality of bolts 5. A valve shaft 7 integral with the throttle valve is connected to a throttle valve lever 9 at an upper end portion penetrating the cover plate 2. A swivel 8 is rotatably supported at an end of the throttle valve lever 9, and a fan-shaped cam portion 6 is supported in a direction opposite to the throttle valve lever 9. The left edge of the reinforcing plate 3 having the ridge 3b is bent upward to form a bent wall 3a. The end of the outer tube of the remote control cable is fixed to the bent wall 3a by a mounting bracket (not shown). The inner cable inserted into the outer tube is locked to the swivel 8 by a known means via the guide projection wall 4 integrated with the cover plate 2. An idle adjusting bolt 10 is screwed to a projecting wall 2a projecting upward from the right edge of the cover plate 2, and the throttle valve lever 9 is adjusted by the force of a return spring (not shown) as shown in FIG. It comes into contact with the bolt 10. A cam groove whose depth gradually decreases in the circumferential direction is formed on the lower surface of the plate-like cam portion 6, and a follower projecting upward from the cover plate 2 is engaged with the cam groove. Although not shown, a constant-pressure fuel supply mechanism is formed at a lower portion of the carburetor main body 21. A fuel supply pipe projects from the constant-pressure fuel chamber to a throttle hole of the throttle valve, and a needle supported by the throttle valve supplies fuel. It is inserted into the tube. In FIG. 1, when the throttle valve lever 9 is rotated clockwise, the opening degree of the throttle hole of the throttle valve with respect to the intake path 23 increases. At the same time, the needle rises together with the throttle valve by the cam mechanism, and the opening of the fuel injection hole of the fuel supply pipe increases. At the time of cold start of the engine, a cylindrical boss portion 2b is formed adjacent to the projecting wall 2a, and a starting shaft 16 having an operation lever 13 on the boss portion 2b in order to increase the amount of fuel and air. Is inserted. As shown in FIG. 4, a spiral groove 15 is formed in the starting shaft 16, and a pin 14 engaged with the spiral groove 15 is formed.
Is fixed to the boss 2b. As shown in FIG. 5, a push rod 19 is screwed into a screw hole 18 provided at an eccentric position of the starting shaft 16. The throttle valve lever 9 is opposed to the tip of the push rod 19.
An arc-shaped ridge 9a protrudes downward from the lower surface 9b. Next, the operation of the starting device for a rotary throttle valve type carburetor according to the present invention will be described. As shown in FIGS. 5 and 6, when the operation lever 13 is in the normal upright position, the push rod 19 does not abut on the lower surface 9b of the throttle valve lever 9 nor the ridge 9a. At the time of cold start of the engine, the operation lever 13 is moved in FIG.
When pushed down to the left, the push rod 1 supported by the starting shaft 16
9 moves upward and pushes up the throttle valve together with the throttle valve lever 9. Thereby, the opening degree of the fuel injection hole of the fuel supply pipe increases. At the same time, as shown in FIG. 8, the starting shaft 16 having the spiral groove 15 engaging with the pin 14 is screwed. That is, the ridge 9a is pushed leftward by the push rod 19 of the starting shaft 16, and the throttle valve lever 9 rotates slightly clockwise in FIG. Thus, an increase in the amount of fuel and an increase in the amount of air required for a cold start are achieved, and a smooth start of the engine is obtained. The amount of lift (lift) of the throttle valve lever 9 is the screw hole 1
The push rod 19 screwed to 8 can be adjusted by replacing the push rod 19 with one having a different outer diameter at the tip. The amount of rotation of the throttle valve lever 9 can be adjusted by the amount of screwing of the push rod 19 into the screw hole 18. When the throttle valve lever 9 is rotated in the acceleration direction after the start of the engine, the contact between the throttle valve lever 9 and the push rod 19 disappears, and the throttle valve lever 9 is wound around the boss portion 2b and has one end connected to the boss portion 2b.
b, the operating lever 13 is returned to the upright position by the force of a coil spring (not shown) whose other end is locked to the operating lever 13. As described above, according to the present invention, the starting shaft is inserted into the boss portion integral with the cover plate for closing the valve chamber of the carburetor body, and the spiral groove on the outer peripheral surface of the starting shaft is provided. , A pin fixed to the boss portion is engaged, a push rod is screwed into a screw hole provided at an eccentric position of the starting shaft, and a tip end of the push rod protrudes below the throttle valve lever to rotate the starting shaft. The push rod is configured to be capable of abutting against the lower surface of the throttle valve lever by movement, and to be able to abut against a ridge projecting downward from the lower surface of the throttle valve lever. The leading end of the push rod comes into contact with the lower surface of the throttle valve lever to push up the throttle valve lever, thereby increasing the amount of fuel, thereby improving the startability of the engine. The push-up amount of the throttle valve lever can be adjusted by replacing the push rod with one having a different outer diameter at the distal end of the push rod. When the starting shaft is rotated, the starting shaft is screwed and moves in the axial direction, and the tip of the push rod pushes the throttle valve lever. Therefore, the opening of the throttle valve increases, the amount of air increases, and idle rotation is reduced. Will be maintained. The degree of opening of the throttle valve is finely adjusted by the amount of screwing of the push rod with respect to the starting shaft, and proper idle rotation without connection of the centrifugal clutch is maintained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a starting device for a rotary throttle valve type carburetor according to the present invention. FIG. 2 is a front view of a starter of the rotary throttle valve carburetor. FIG. 3 is a side view of a starting device of the rotary throttle valve carburetor. FIG. 4 is a front sectional view of a starting device of the rotary throttle valve carburetor. FIG. 5 is a plan sectional view of a starting device of the rotary throttle valve type carburetor. FIG. 6 is a front sectional view of a starting device of the rotary throttle valve carburetor. FIG. 7 is a left side sectional view of a starting device of the rotary throttle valve carburetor. FIG. 8 is a front sectional view showing an operation state of a starter of the rotary throttle valve carburetor. [Description of Signs] 2: Cover plate 2a: Projecting wall 2b: Boss portion 3: Reinforcement plate 3
a: bent wall 3b: ridge 4: guide ridge 5: bolt 6: cam 7: valve stem
8: Swivel 9: Throttle valve lever 9a: Protrusion 9b:
Lower surface 10: Idle adjustment bolt 13: Operation lever
14: Pin 15: Spiral groove 16: Starting shaft 18: Screw hole 19: Push rod 21: Vaporizer body 22: Through hole 23: Intake path

Claims (1)

Claims: 1. A starting shaft is inserted into a boss portion integral with a lid plate for closing a valve chamber of a carburetor body, and the boss portion is inserted into a spiral groove on an outer peripheral surface of the starting shaft. The fixed pin is engaged, a push rod is screwed into a screw hole provided at an eccentric position of the starting shaft, a tip end of the push rod projects below a throttle valve lever, and the push rod is rotated by rotation of the starting shaft. A starting device for a rotary throttle valve type carburetor, characterized in that a tip portion is configured to be able to abut against a lower surface of a throttle valve lever and to be able to abut a ridge projecting downward from a lower surface of the throttle valve lever.