JPH0882248A - Carburetor structure - Google Patents

Abstract

(57) [Abstract] [Purpose] The structure of the VM carburetor enables good atomization even when the throttle valve is close to fully closed.
The fuel flow rate can be reduced at the time of high negative pressure during deceleration to improve fuel efficiency, and the pilot outlet for the nozzle can be easily processed. In a carburetor in which a piston valve itself of a venturi portion is opened and closed as a throttle valve via a wire by a throttle grip, an opening portion of a pilot system fuel supply passage into an intake passage 1 is
Is formed as a nozzle 10 projecting from the bottom surface 1a of the nozzle toward the center, and the plurality of pilot outlets 11 and 12 are located at least at the upper end surface and the side surface of the nozzle 10.
To open.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VM type variable venturi type carburetor which opens and closes a piston valve itself of a venturi portion as a throttle valve via a wire by a throttle grip, and particularly to a pilot outlet portion of such a carburetor. Regarding the structure.

[0002]

2. Description of the Related Art As a variable venturi type carburetor used for motorcycles, a throttle valve consisting of a butterfly valve is installed downstream of a piston valve of a venturi part, and a throttle grip is used to open and close the throttle valve via a wire. , With the CV type carburetor that automatically opens and closes according to the fluctuation of the air pressure under the piston valve due to it, without installing a throttle valve consisting of a butterfly valve in the intake passage, a wire is provided by a throttle grip through a wire. A VM type carburetor that opens and closes a piston valve of a venturi portion as a throttle valve has been widely used.

In each of these variable venturi type carburetors, in addition to the main system fuel supply passage in which fuel is sucked out through a needle jet controlled by a jet needle attached to a piston valve, fuel supply at low speed is also provided. In consideration of the above, a pilot system (slow system) fuel supply passage is provided, and a pilot outlet for sucking out the fuel from the pilot system fuel supply passage is opened in the intake passage downstream of the needle jet.

In the CV carburetor, a plurality of bypass ports are opened from the fuel supply passage to the wall surface of the intake passage near the upstream side of the pilot outlet opened to the wall surface of the intake passage, and the butterfly valve is provided in this bypass port. By making the outer peripheral edges of the disk of the throttle valve that consist of the two sides face each other, the flow of air from the bypass port into the fuel supply path (back bleed) can be changed according to the change in the opening of the throttle valve near the closed position. It has been common practice to control the outflow of fuel into the intake passage with a throttle valve.

On the other hand, in a VM carburetor, generally, as shown in FIG. 5, a pilot outlet 9 is opened in the bottom surface of the intake passage 1, and depending on the size and position of the pilot jet and pilot outlet, the pilot system fuel Only by correcting the flow rate, it is impossible to control the fuel from the pilot system fuel supply passage in accordance with the opening degree of the throttle valve (piston valve) 4.

In such a VM carburetor, a nozzle (spout cylinder) for pilot (slow) fuel is provided on the bottom wall of the intake passage (main bore) downstream of the piston valve (sliding throttle valve) (engine side). A plurality of pilot outlets (injection holes) are provided vertically on the downstream side surface (engine side) of this nozzle (spout cylinder) to project along the inner wall, and as the piston valve (throttle valve) rises, the intake passage is sequentially A VM carburetor (sliding valve type carburetor) that opens in the (bore) and can arbitrarily change the supply amount (starting and extending) of pilot system (slow system) fuel is It is conventionally known from Japanese Utility Model Publication No. 45-12652.

[0007]

By the way, in a CV carburetor having a throttle valve consisting of a butterfly valve and a bypass port, air flows from the bypass port into the fuel supply passage at an opening close to the fully closed position of the throttle valve ( Since back bleeding occurs, more air is sufficiently mixed in the fuel (primary air mixture in which air is mixed by the pilot air jet) before being sucked out into the intake passage, so that the intake air in the intake passage is Even if the flow becomes weak, atomization will be performed well.

However, in the VM carburetor, not only the conventional VM carburetor as shown in FIG. 5 but also the structure in which the flow rate of the pilot system fuel can be controlled by the conventionally known piston valve according to the above-mentioned publication. In the above, even if the fuel (primary air-fuel mixture in which air is mixed by the pilot air jet) before being sucked into the intake passage is further closed when the piston valve is close to full closure, control cannot be performed. Therefore, when the piston valve is closed and the flow of intake air in the intake passage becomes weak, there is a problem in that atomization becomes difficult to perform sufficiently.

Further, in the case where a plurality of pilot outlets are provided on the side surface of the nozzle like the conventionally known carburetor according to the above cited publication, when the carburetor is downsized, the nozzle of the pilot system fuel supply passage which faces the lower end of the piston valve. Since it is not possible to increase the height of the nozzles so much, when processing a plurality of pilot outlets on the side surface of the nozzle, the degree of freedom in position is reduced due to problems such as the processing pitch, which makes the processing difficult.

An object of the present invention is to eliminate the above-mentioned disadvantages of the conventionally known VM carburetor, and more specifically, atomize even when the throttle valve (piston valve) is close to the fully closed position. Can be carried out satisfactorily, the fuel flow rate can be reduced at the time of high negative pressure during deceleration, etc. to improve fuel efficiency, and processing for opening multiple pilot outlets to the nozzle can be performed. It is intended to provide an easy carburetor structure.

[0011]

In order to solve the above problems and to achieve the object, the present invention provides a carburetor in which the piston valve itself of the venturi portion is opened and closed as a throttle valve via a wire by a throttle grip, An opening of the pilot fuel supply passage into the intake passage is formed as a nozzle projecting from the bottom surface of the intake passage toward the center, and a plurality of pilot outlets are provided at least at the upper end surface and the side surface of the nozzle. It is characterized by being opened.

[0012]

[Operation] According to the above structure, when the throttle valve (piston valve) is close to the fully closed position, the center of the flow velocity of the intake air passes near the bottom wall of the intake passage, so The fuel (the primary air-fuel mixture in which the air is mixed by the pilot air jet) is sucked out from the pilot outlet opened on the lower side surface of the nozzle near the flow velocity center of the intake air flow.

At this time, the fuel (1
The air in the intake passage is sucked into the nozzle (back bleed) from the pilot outlet opened at the upper end surface of the nozzle in response to the suction of the (second mixture). The air taken in from the pilot outlet on the upper end surface of the nozzle is further mixed into the air-fuel mixture, and atomization is promoted.

Further, since the air is sucked into the nozzle from the pilot outlet, the flow rate of the fuel supplied from the fuel supply passage into the nozzle is reduced, so that the flow rate of the fuel is increased at the time of high load such as deceleration. Less fuel consumption improves.

When the throttle valve (piston valve) reaches an intermediate opening degree, the flow rate in the intake passage increases, and the center of the flow velocity of the intake air moves upward away from the bottom of the intake passage to move upward from the fuel supply passage. The fuel (primary air-fuel mixture) sent into the nozzle is sucked out from both the pilot outlet on the upper end face of the nozzle and the pilot outlet on the side face of the nozzle, so a sufficient amount of fuel is taken in according to the amount of intake air. It will be supplied into the passage.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a variable venturi portion of a VM carburetor according to an embodiment of the present invention. A suction chamber 2 formed so as to project upward from a top surface of an intake passage 1 has a jet needle at its tip. A piston valve 4 having a protruding portion 3 is housed in and out of the intake passage 1 via a spring 5.

The piston valve 4 has a structure as shown in FIG.
Similar to the conventional VM carburetor in which the pilot outlet 9 is directly opened on the bottom surface of the intake passage 1, the throttle grip is rotated to directly move up and down through the throttle wire to change the venturi portion. In addition to being a piston valve, it is itself a throttle valve that is opened and closed by throttle operation.

In the venturi portion of the bottom surface 1a of the intake passage facing the piston valve 4, the fuel in the main fuel supply passage measured by the main jet 6 is mixed with air from a main air jet (not shown). A needle jet 7 for supplying the air into the intake passage 1 is opened so that the jet needle 3 can move in and out according to the vertical movement of the piston valve 4 due to the change of the throttle opening.

By the way, in the venturi portion of the bottom face 1a of the intake passage of the VM carburetor facing the piston valve 4, in addition to the needle jet 7 of the main fuel supply passage,
The pilot outlet of the pilot system fuel supply path that mixes the fuel measured by the pilot jet 8 with the air from the pilot air jet to form the primary mixture and then supplies it into the intake passage is the needle jet 7 of the main system fuel supply path. It is opened downstream.

With respect to the pilot outlet of this pilot fuel supply passage, in this embodiment, as an opening of the pilot fuel supply passage into the intake passage 1, as shown in FIG. 1 and FIG. A nozzle 10 is formed so as to extend upward and project upward from the bottom surface of the intake passage 1, and a pilot outlet 11 and a pilot outlet 12 are opened at two locations on the upper end surface of the nozzle 10 and the side surface near the bottom surface of the intake passage. .

As described above, the pilot outlet 1
In the carburetor of the present embodiment in which the valves 1 and 12 are opened, as shown in FIG. 3, the opening of the throttle valve (piston valve 4) is closed to a state close to fully closed, and the lower end of the piston valve 4 and the intake passage are closed. When the center of the flow velocity of the intake air flow formed between the bottom surface 1a of the
Fuel (primary air-fuel mixture in which air is mixed by the pilot air jet) is sucked from the pilot outlet 12 on the side surface of the nozzle near the center of the flow velocity of the intake air, and the upper end surface of the nozzle 10 is opened according to the suction. The air in the intake passage is sucked from the pilot outlet 11 that has been set.

Therefore, even if the air (primary air-fuel mixture) sent into the nozzle 10 is further mixed with the air sucked from the pilot outlet 11 on the upper end face of the nozzle, the flow of intake air in the intake passage 1 is weak. Since a large amount of air is mixed in the fuel sucked from the nozzle 10, atomization is favorably performed.

Further, since the air is sucked into the nozzle 10 from the pilot outlet 11, the flow rate of the fuel supplied from the fuel supply path into the nozzle 10 is reduced, and the flow rate of the fuel is increased at the time of high load such as deceleration. Reduces fuel consumption.

Then, as shown in FIG. 4, the throttle valve (piston valve 4) is opened to the middle, and the flow of intake air formed between the lower end of the piston valve 4 and the bottom surface 1a of the intake passage. When the center of the flow velocity of is separated from the bottom surface 1a, fuel is sucked out from the pilot outlet 11 on the upper end face of the nozzle near the center of the flow velocity, and the flow rate of the intake air in the entire intake passage is increased. Fuel is also sucked out from the pilot outlet 12, and a sufficient amount of fuel corresponding to the increased amount of intake air is supplied into the intake passage.

By the way, when a plurality of pilot outlets are formed on the nozzle, the height of the nozzle cannot be increased so much due to the relationship with the piston valve when the carburetor is downsized, and the plurality of pilot outlets are formed on the side surface of the nozzle. It is difficult to machine the pilot outlet of No. 2. However, by opening the pilot outlet 11 on the upper end surface of the nozzle 10 as in this embodiment, the degree of freedom of machining the pilot outlet opening on the side surface becomes large. Processing becomes easy.

In this embodiment, only one pilot outlet 12 is formed on the side surface of the nozzle 10, but in some cases, two pilot outlets 12 are provided at different positions on the nozzle side surface together with the pilot outlet 11 on the upper end surface of the nozzle. It is also possible to form a pilot outlet of

Further, as in this embodiment, a plurality of pilot outlets 11 and 12 are provided at different positions of the nozzle 10.
The throttle valve (piston valve 4) is formed by setting the calibration jets for the pilot outlets 11 and 12, respectively.
It is also possible to control the fuel supply amount according to the opening degree of the.

[0029]

According to the structure of the carburetor of the present invention as described above, in the VM carburetor, the fuel supply amount can be controlled according to the opening degree of the throttle valve (piston valve), and Atomization can be performed better, the fuel flow rate can be reduced at high negative pressure during deceleration, etc. to improve fuel efficiency, and moreover, it is easy to process multiple pilot outlets for nozzles. Becomes

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing an embodiment of the structure of a carburetor of the present invention.

FIG. 2 is an enlarged cross-sectional view of an essential part showing the vicinity of a pilot outlet of the embodiment shown in FIG.

FIG. 3 is an enlarged cross-sectional explanatory view of the main part near the pilot outlet showing the flow of air and fuel (primary air-fuel mixture) when the throttle valve (piston valve) in the embodiment shown in FIG. .

FIG. 4 is an enlarged cross-sectional explanatory view of a main portion near a pilot outlet showing a flow of air and fuel (primary air-fuel mixture) at an intermediate opening of a throttle valve (piston valve) in the embodiment shown in FIG.

FIG. 5 is an explanatory diagram showing an outline of a conventional VM carburetor.

[Explanation of symbols]

 1 intake passage 4 piston valve (throttle valve) 10 nozzle 11 pilot outlet 12 pilot outlet

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[Procedure amendment]

[Submission date] June 19, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

FIG. 1 shows a variable venturi portion of a VM carburetor according to an embodiment of the present invention, which is a valve accommodating portion 2 formed so as to project upward from a top surface of an intake passage 1.
A piston valve 4 having a jet needle 3 protruding from the tip thereof is housed in and out of the intake passage 1 via a spring 5.

Claims (1)

[Claims] 1. In a carburetor in which a piston valve itself of a venturi portion is opened and closed as a throttle valve via a wire by a throttle grip, an opening of a pilot fuel supply passage into an intake passage is centered from a bottom surface of the intake passage. It is formed as a nozzle protruding toward, and is located on at least the upper end surface and the side surface of this nozzle,
A carburetor structure characterized by having multiple pilot outlets open.