JPH0545787B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a carburetor that controls the amount and concentration of air-fuel mixture supplied to an engine, and particularly relates to a so-called rotary throttle valve type carburetor in which a throttle valve rotates. It is related to vessels.

[Prior Art] The throttle valve of a carburetor is controlled by the operator's accelerator wire operation to adjust and control the amount and concentration of the air-fuel mixture supplied to the engine, and is generally a rotating type. It is broadly divided into the sliding type and the sliding type.

The present invention relates to a rotary throttle valve type carburetor using a rotary throttle valve.
62-55449 is known. According to this, the opening of the fuel control hole drilled in the fuel nozzle into the intake passage is controlled by a needle in response to the change in air volume caused by the rotation of the throttle valve. A needle is inserted into the nozzle, and as the throttle valve opens, the needle is urged upward in the figure by a spring to increase the opening of the fuel control hole into the intake tract, so that fuel is sucked into the intake tract. The amount of fuel used is increased in line with the increase in the amount of air.

The spring for biasing the needle is located in a cylindrical part provided on the shaft and passing through the opening, and is compressed between the upper end of the needle and the upper end of the nozzle.

[Problems to be Solved by the Invention] The conventional rotary throttle valve type carburetor has the following problems.

The spring, which is disposed within the cylindrical part between the upper end of the needle and the upper end of the nozzle, is bent to some extent in the compressed state, and due to this bending, the outer periphery of the spring is bent to the inner periphery of the cylindrical part. may come into contact with.

In this state, when the throttle valve is rotated, the throttle valve rotates to open and close the intake passage, and the cam surface provided on the cover causes the throttle valve to move upward in the figure.
It moves downward. According to this rotation of the throttle valve, the outer periphery of the spring receives rotational force from the contact part with the inner periphery of the cylindrical part, and the spring rotates the outer periphery of the needle while in contact with the contact part of the inner periphery of the cylindrical part. It rotates.

In other words, the contact area between the outer periphery of the spring and the inner periphery of the cylindrical portion relative to the needle changes as the throttle valve rotates.

On the other hand, when the outer periphery of the spring and the inner periphery of the cylindrical part come into contact, the spring generates a reaction force on the opposite side of the contact part, causing the needle in the nozzle to incline.

As mentioned above, since the contact area between the outer periphery of the spring and the inner periphery of the cylindrical part changes according to the rotation of the throttle valve, the inclination of the needle in the nozzle is not maintained at a constant inclination. The gap formed by the inner diameter of the nozzle and the outer periphery of the needle is not constant because it is shifted toward the engine side or toward the cleaner side. (The effective gap area does not change, but the location where the gap is formed differs.) When this gap is formed on the engine side, it is susceptible to negative pressure in the intake passage, which increases the amount of fuel that comes out. If a gap is formed on the cleaner side, it will be less likely to receive negative pressure in the intake tract, resulting in less fuel flowing out.

For these reasons, it has been difficult to accurately maintain the reproducibility of the fuel flow rate when the throttle valve is repeatedly operated.

[Means for Solving the Problems] The rotary throttle valve type carburetor of the present invention has been developed in view of the above-mentioned drawbacks, and the carburetor has excellent reproducibility of fuel when the throttle valve is repeatedly operated. In order to achieve the above object, a throttle body 15 for controlling the amount of air flowing through the intake passage of the carburetor body, and a fuel nozzle 13 that is inserted into the fuel control passage 13A of the fuel nozzle 13 that can protrude into the intake passage 11 are provided. A fuel control hole 1 arranged and drilled in the fuel nozzle 13
a needle 17 that controls the effective opening area of 3B;
A holder 18 is disposed in a holder insertion hole 15M formed in the center of the throttle body 15 and moves along the longitudinal axis of the throttle body 15 in response to rotation of the throttle body 15. The adjustment screw 19 is arranged to face the needle 17 and adjust the effective opening area of the fuel control hole 13B formed by the needle 17 and the fuel control hole 13B. In the control passage 13A, the needle 1
A needle spring 21 that presses the adjusting screw 19 is compressed.

[Function] According to the rotary throttle valve type carburetor of the present invention,
Air is supplied to the engine through a gap formed by the throttle body, while fuel is supplied through a fuel control hole formed in a fuel nozzle while being controlled by a needle.

In particular, even if the throttle body rotates, the fuel nozzle and needle do not rotate at all, so the needle spring contracted in the fuel control passage of the fuel nozzle can always be placed at a constant position.
The gap formed by the inner diameter of the fuel nozzle and the outer diameter of the needle does not change with the rotation of the throttle body, but is always at a fixed position, allowing a defined fuel supply to be carried out.

[Embodiment] Hereinafter, one embodiment of the rotary throttle valve type carburetor according to the present invention will be described with reference to FIGS. 1 and 2.

Reference numeral 10 denotes a carburetor body through which an intake passage 11 passes, and a cylindrical throttle valve guide tube 12 is bored in the middle part of the intake passage 11. This throttle valve guide cylinder 12
The lower side crosses the intake passage 11 and enters the carburetor body 10 from the bottom of the intake passage 11, and the other side opens from the upper side 10A of the carburetor body 10.

The opening side of the upper part 10A of the carburetor main body 10 of the throttle valve guide cylinder 12 is made larger in diameter than the diameter of the throttle valve guide cylinder 12 in order to accommodate a throttle valve return spring, which will be described later.

A fuel nozzle 13 is disposed protruding within the intake passage 11 at the bottom of the throttle valve guide cylinder 12, and a fuel control passage 13A is bored through the fuel nozzle 13 along its longitudinal axis. , the lower part of which is connected to the fuel flow path 14 via a fuel control jet J.

Further, the fuel control passage 13A has a fuel control hole 13.
B is bored, and preferably a long groove along the longitudinal axis of the fuel control passage 13A. Therefore, the fuel flow path 14
The fuel flowing inside flows out of the fuel nozzle 13 through the fuel control jet J, the fuel control passage 13A, and the fuel control hole 13B.

In this embodiment, the fuel control hole 13B is opened toward the engine, but its opening position is determined as appropriate depending on the setting with the engine. Reference numeral 15 denotes a throttle body rotatably disposed in the throttle valve guide cylinder 12, and has the following configuration.

That is, 15A is a shaft portion which has a fuel well hole 15B surrounding the outer periphery of the fuel nozzle 13 with a gap S and opens at least into the intake passage 11, and the outer periphery along the longitudinal axis of this shaft portion 15A. Plate-shaped throttle valve portions 15C and 15D that can control opening and closing of the intake passage 11 extend laterally.

Further, cylindrical bearing parts 15E and 15F that are fitted into the throttle valve guide cylinder 12 are provided at both upper and lower ends of the shaft part 15A which does not open into the intake passage 11, and further, the shaft part 15A which opens into the intake passage 11. Through holes 15G and 15H are formed in the fuel well 15B (gap S around the outer circumference of the fuel nozzle 13) and the intake passage 11 to communicate with each other.

The number, diameter, and position of the through holes 15G and 15H are determined by setting work with the engine.

Further, a throttle valve lever part 15J is integrally provided above the upper bearing part 15F and with a gap in the upper part 10A of the carburetor main body 10, and further above this throttle valve lever part 15J, for example, a cylindrical shape is provided. The cylindrical bodies 15K are integrally arranged. This cylinder 1
An opening recess 15L is bored at the upper end of the opening recess 15L, and the holder insertion hole 15M and the needle insertion hole 15N are connected downward in the longitudinal axis direction of the throttle body 15 and approximately on the center thereof from the bottom of the opening recess 15L. A needle fitting hole 15N located below penetrates into the fuel well 15B.

Furthermore, the opening recess 1 of the holder insertion hole 15M
The side of the opening to 5L, that is, the opening recess 15L
A control protrusion 15P that protrudes from the bottom of the
will be provided. Also, the cylindrical body 15 of the throttle body 15
A cover 16 is arranged with a gap on the sides and above K, and specifically includes an annular part 16A surrounding the side of the cylinder 15K, and an upper lid body 16B covering the top of the cylinder 15K. This upper lid body 1
The opening recess 15 of the throttle body 15 is located at the bottom of 6B.
A locking step portion 16F protruding into L is provided.

Then, the needle fitting hole 1 of the throttle body 15
A needle 17 is movably arranged in the fuel nozzle 13, and the lower part of the needle 17 is inserted into the fuel control passage 13A of the fuel nozzle 13 to control the opening area of the fuel control hole 13B with respect to the fuel well 15B. On the other hand, the upper part of the needle 17 is arranged facing the holder insertion hole 15M side.

In addition, the holder fitting hole 15 of the throttle body 15
A holder 18 is inserted into M, and a hole 18A is bored in the center of the holder 18 from the top to the bottom.
A cam portion 18B is provided from the upper side of the holder 18, and this cam portion 18B comes into contact with the control protrusion 15P of the throttle body 15.

Note that the cam portion 18B is provided in a radial direction from the center of the holder 18, and is
When P rotates about the center of the throttle body 15, the holder 18 moves up and down within the holder fitting hole 15M due to the cam profile of the cam portion 18B.

Further, reference numeral 18C is a locking protrusion provided to protrude from the holder 18, and this locking protrusion 18C is locked to a locking step 16F of the upper lid body 16. An adjustment screw 19 is screwed into the hole 18A of the holder 18, and the lower end of the adjustment screw 19 protrudes from the lower end of the holder 18 and comes into contact with the needle 17. Therefore, the longitudinal axes of the fuel nozzle 13, needle 17, throttle body 15, holder 18, and adjustment screw 19 are arranged substantially on the same straight line.

Further, a holder spring 20 is arranged approximately concentrically around the outer periphery of the adjustment screw 19, one end of which is engaged with the cover 16, and the other end of which is engaged with the holder 18. Accordingly, the cam portion 18B of the holder 18
is elastically pressed by the control protrusion 15P of the throttle body 15, and is also pressed by the locking protrusion 1 of the holder 18.
8C is pressed against the locking step 16F of the cover 16.

And 21 is a needle spring,
It is contracted in the fuel control passage 13A of the fuel nozzle 13, one end of which is engaged with the end of the needle 17 inserted into the fuel control passage 13A, and the other end is engaged with the fuel control jet J. Therefore, needle 17
is always urged upward by the spring force of this needle spring 21 and is held pressed against the lower end of the adjusting screw 19. The upper end of the needle 17 is elastically pressed against the lower end of the adjusting screw 19 by this needle spring 21. be under pressure.

Reference numeral 22 denotes a throttle valve return spring, which is arranged approximately concentrically around the outer periphery of the bearing portion 15F of the throttle body 15. One end of the throttle valve return spring 22 is locked to the throttle body 15, and the other end is locked to the throttle body 15. is secured to a stay plate 23 covering the upper side 10A of the carburetor main body 10, whereby the throttle body 15 is always biased with a force in the closing direction.

Next, its effect will be explained.

First, in order to increase the engine output from the idling state of the engine, the throttle body 15 is rotated clockwise in FIG.
15D opens the intake passage 11 and increases the amount of air flowing inside the intake passage 11.

On the other hand, when the throttle body 15 is rotated clockwise, the control protrusion 15P comes into contact with the cam part 18B of the holder 18 and moves the holder 18 upward in the figure. Since the attached adjustment screw 19 also moves upward in synchronization with the holder 18, the needle 17 moves upward by the amount of movement of the holder 18 and adjustment screw 19 due to the spring force of the needle spring 21, thereby opening the fuel control hole 13B. Fuel well hole 15
By increasing the opening for B, the amount of fuel can be increased in proportion to the increase in the amount of air.

Note that the locking protrusion 18C of the holder 18 is attached to the cover 1.
Since it comes into contact with the locking step portion 16F of No. 6, it does not rotate even when the throttle body 15 rotates.

Next, we will discuss the transition from high-speed operation to low-speed operation of the engine when the throttle body 15 is opened to a high opening degree.The throttle body 15 rotates counterclockwise in the figure, and the throttle valve parts 15C,
D can block the intake passage 11 and reduce the amount of air.

On the other hand, the holder 18 moves downward in the figure due to the contact between the cam portion 18B and the control protrusion 15P, and the adjustment screw 19 moves the needle 17 into the holder 18 against the spring force of the needle spring 21. The opening of the fuel control hole 13B to the fuel well 15B is reduced by pressing downward by the amount of movement of the fuel, thereby making it possible to reduce the amount of fuel commensurate with the reduction in the amount of air.

[Effects of the Invention] The rotary throttle valve type carburetor of the present invention provides the following effects.

When the throttle body rotates, the holder is prevented from rotating by the locking step of the cover, so the adjustment screw and needle do not rotate. Therefore, since neither the needle nor the fuel control jet, which locks both ends of the needle spring, rotates, no rotational force is applied to the needle spring.

From the above, when the needle spring is compressed by the needle, the needle spring temporarily bends and comes into contact with one side of the fuel control passage of the fuel nozzle, causing it to shift to one side with respect to the needle. Even if a force is applied, the position of this biasing force does not change due to repeated rotations of the throttle body, so the needle receives the biasing force and falls within the fuel control passage of the fuel nozzle. The position of the gap between the outer diameter of the needle and the inner diameter of the fuel control passage is formed at a constant position in the carburetor, for example on the engine side or cleaner side, and has excellent reproducibility. Accordingly, it is possible to provide a rotary throttle valve type carburetor.

By arranging the needle spring in the fuel control passage, it was possible to reduce the chamber volume in the fuel control passage, and according to this, the negative pressure applied from the fuel control hole to the intake passage causes the fuel control passage to Since the flow rate of the fuel flowing therein could be increased, it was possible to atomize the fuel and improve the negative pressure response.

[Brief explanation of the drawing]

The drawings show an embodiment of a rotary throttle valve type carburetor according to the present invention, in which FIG. 1 is a longitudinal cross-sectional view, and FIG. 2 is a cross-sectional view taken along the line of FIG. 1. 10... Carburetor main body, 12... Throttle valve guide cylinder,
13...Fuel nozzle, 13A...Fuel control passage,
13B...fuel control hole, 15...throttle body,
15A...Shaft part, 15P...Control protrusion, 16...
Cover, 17... Needle, 18... Holder,
19...Adjustment screw, J...Fuel control jet, 21...Needle spring.

Claims (1)

[Scope of Claims] 1. A throttle body 15 that controls the amount of air flowing through the intake passage 11 of the carburetor main body 10; and a throttle body 15 that is inserted into the fuel control passage 13A of the fuel nozzle 13 that can protrude into the intake passage 11 to control the amount of fuel. A needle 17 that controls the effective opening area of the fuel control hole 13B formed in the nozzle 13;
a holder 18 that moves along the longitudinal axis of the throttle body 15 in accordance with the rotation of the needle 1;
7 and formed by the needle 17 and the fuel control hole 13B.
The adjustment screw 19 adjusts the effective opening area of the fuel control passage 13A of the fuel nozzle 13.
A rotary throttle valve type carburetor in which a needle spring 21 for pressing a needle 17 against an adjusting screw 19 is compressed.