JPH063176Y2 - Variable venturi vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a variable venturi type carburetor equipped with a choke valve.

(Prior Art) First, a main part of a conventional variable Venturi type vaporizer equipped with a choke valve is schematically shown in FIGS. 9 and 10.

In FIGS. 9 and 10, 1 is the intake passage of the carburetor,
Reference numeral 2 denotes a suction piston which is arranged in the intake passage so as to be movable back and forth to form a venturi portion 3 and which changes the area of the venturi portion 3 in response to the amount of intake air.
Is a choke valve provided in the upstream intake passage 1. The front end surface of the choke valve 4 is arranged at an appropriate distance from the suction piston 2 in order to avoid interference with the suction piston 2.

(Problems to be solved by the invention) By the way, in the above-mentioned conventional variable Venturi type carburetor, even when the choke valve 4 is fully opened, the choke valve 4 and the outer peripheral surface of the suction piston 2 are relatively closed. A large gap 5 is formed. Therefore, the intake air passes through this gap 5 and the intake passage 1a of the choke valve 4 on the upper surface side.
Flow into the lower intake passage 1b from the venturi portion 3
A vortex was generated in the turbulence and the air flow was disturbed. Due to this turbulence, the lift characteristic of the suction piston becomes unstable, which makes it difficult to perform accurate air-fuel ratio control.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a variable venturi-type carburetor capable of suppressing the occurrence of air flow turbulence in the venturi portion and obtaining accurate and stable air-fuel ratio characteristics.

(Means for Solving the Problem) The present invention in accordance with the above-mentioned object is a suction device which is disposed in an intake passage so as to be movable back and forth to form a venturi portion and which changes the area of the venturi portion in response to an intake air amount. A variable pressure control device comprising a piston and an eccentric choke valve arranged in the intake passage on the upstream side of the venturi portion, and a cutout portion is provided at the lower end of the suction piston so that a part of the choke valve enters the cutout portion when fully opened. In the venturi type carburetor, the cutout portion of the suction piston (12) is located upstream of the venturi portion, and the cutout portion is formed into a flat vertical surface or a flat inclined surface inclined toward the downstream side, and the choke. The longitudinal end face (23b) of the valve is cut out linearly so that when the choke valve is fully opened, the linear end face (23b) of the choke valve is flat on the piston side. A vertical plane to contact against the slanted notch (12a), a gap between the abutment surfaces produced during full open of the valve is obtained by such a rectangle.

(Operation) According to the above configuration, when the choke valve is fully opened, the suction piston blocks the space between the upper intake passage and the lower intake passage of the choke valve, so that there is no air flow from the upper intake passage to the lower intake passage. The generation of vortices in the section is suppressed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of the present invention, and FIGS. 2 and 3 are a side view and a bottom view schematically showing an essential part of the first embodiment.

In FIG. 1, 10 is an intake passage extending in the horizontal direction, and 1
1 is a float chamber attached to the lower part of the intake passage 10,
Reference numeral 12 is a suction piston arranged in the upper center of the intake passage 10. The suction piston 12 is mounted so as to be able to move back and forth in the vertical direction, and is provided between the lower end surface facing the intake passage 10 and the inner wall surface of the intake passage 10 that faces the intake passage 10.
3 is formed. A diaphragm 14 is attached to the other end surface of the suction piston 12.
The negative pressure chamber 15 and the venturi portion 13 are communicated with each other via a suction hole 16 formed in the front end surface of the suction piston 12. Further, in the negative pressure chamber 15, the venturi portion 1
A suction spring 17 for urging the suction piston 12 in a direction to reduce the area of 3 is attached.
Further, a measuring needle 18 is attached to the end surface of the suction piston 12 facing the intake passage 10.

On the other hand, one end of the intake passage 10 has a venturi portion 13 at the bottom.
Of the main system fuel passage 19 whose other end projects into the float chamber 11, and the metering needle 18 is inserted into the main system fuel passage 19. A metering jet 20 is attached in the middle of the main fuel passage 19, and a main jet 21 is attached to the other end surface.

Next, 22 is a throttle valve provided in the downstream intake passage 10 of the venturi portion 13, and 23 is a choke valve provided in the upstream intake passage 10 of the venturi portion 13.

The choke valve 23 is connected to an auto choke mechanism (not shown) composed of bimetal, etc.
The opening is automatically set according to the engine temperature between the fully closed position shown by the two-dot chain line in the figure and the fully opened position shown by the solid line.By limiting the intake air amount, the high-concentration mixture necessary for cold start can be obtained. Supply the engine with energy. Also choke valve 2
Numeral 3 is pivotally supported by an eccentric shaft 23a, so that an eccentric moment acts in the opening direction by the intake air, so that it is held in the fully open position when the auto choke mechanism is not operating.

The choke valve 23 has a linear end face 23b formed by cutting out the end face on the long side.

A cutout portion 12a having a flat vertical surface is formed on an outer peripheral surface of the suction piston 12 facing the choke valve 23. When the choke valve 23 is opened, the cutout portion 12a is formed.
The long side end face (23b) of this enters into this flat notch 12a,
When the choke valve 23 is fully opened, the suction piston 12 blocks the space between the upper intake passage 10a and the lower intake passage 10b of the choke valve 23.

The present embodiment is configured as described above, and its operation will be described below.

After the engine is started, when the throttle valve 22 is opened and the intake air amount increases, the negative pressure of the venturi portion 13 increases,
This negative pressure is introduced into the negative pressure chamber 15 via the suction hole 16, and the negative pressure in the negative pressure chamber 15 also increases. Along with this, the suction piston 12 rises against the biasing force of the suction spring 17 and the area of the venturi portion 13 increases. At the same time, the metering needle 18 also rises, and the area of the annular gap between the metering jet 20 and the metering needle 18 increases, so that fuel commensurate with the intake air amount passes from the float chamber 11 through the main jet 21 and the main system fuel passage 19. It is sent into the intake passage 10.

However, according to this embodiment, when the choke valve 23 is fully opened, the longitudinal end surface (23b) of the choke valve 23 is in contact with the notch 12a formed in the suction piston 12, and the upper intake passage 10a of the choke valve 23 is in contact. The suction piston 12 blocks between the lower intake passage 10b and the lower intake passage 10b.
Therefore, as schematically shown in FIG. 2, there is no airflow flowing from the upper surface side intake passage 10a to the lower surface side intake passage 10b, and the generation of vortices in the venturi portion 13 can be suppressed. Therefore, the air flow is not disturbed in the venturi portion, and the lift characteristic of the suction piston 12 is stabilized.

Further, according to the present embodiment, when the choke valve 23 is opened, the tip end face enters the notch 12a, so that the total height H of the carburetor is short and the carburetor can be made compact.

Further, according to the present invention, as shown in FIG. 2, a right-angled corner portion 12b is formed in the cutout portion 12a, and a slight vortex is generated in the corner portion 12b. Therefore, as shown in FIG. It is possible to further suppress the generation of vortices by forming the notch 12a on the inclined surface that is inclined toward the downstream side so that the angle becomes different.

(Effect of the Invention) According to the present invention, when the choke valve is fully opened, the suction piston blocks the space between the upper intake passage and the lower intake passage of the choke valve. Since there is no air flow flowing into the intake passage, the generation of vortices in the venturi portion can be suppressed. Therefore, the air flow is not disturbed in the venturi portion, and the lift characteristic of the suction piston is stabilized, so that the accuracy of air-fuel ratio control can be improved.

Particularly, in the present invention, the longitudinal side end surface of the choke valve is linearly cut, the notch provided on the suction piston is positioned on the upstream side of the venturi, and the notch is inclined to a flat vertical surface or a downstream side. When the choke valve is fully opened, the linear end surface of the valve abuts a flat vertical surface or a flat inclined surface on the piston side so that a gap between both contact surfaces is generated when the valve is fully opened. Due to the rectangular shape, when the choke valve is fully opened, the valve flutters due to the forced vibration of the engine and the pulsation of the intake air accompanying it, and a gap is introduced between the both contact surfaces. Since the intake air flows in a cascading manner like this, there is no adverse effect that turbulent flow occurs because a large amount of this air flows into the central portion of the bore like a crescent-shaped gap.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIGS. 2 and 3 are side views and bottom views schematically showing essential parts of the embodiment of FIG. 1, and FIG. 4 is a notch of a suction piston. FIG. 5 is a side view schematically showing a case where the portion is formed on a slope, and FIGS. 5 and 6 are a side view and a bottom view schematically showing the conventional device. Reference numeral 10 ... Intake passage, 10a ... Choke valve upper surface side intake passage, 10b ... Choke valve lower surface side intake passage, 12 ...
Suction piston, 12a ... Notch, 13 ... Venturi, 23 ... Choke valve.

Claims (1)

[Scope of utility model registration request] 1. A suction piston, which is arranged so as to be movable back and forth in an intake passage to form a venturi portion, and which changes an area of the venturi portion in response to an intake air amount, and an intake passage upstream of the venturi portion. In the variable venturi type carburetor, which is provided with an eccentric choke valve and is provided with a notch at the lower end of the suction piston so that a part of the choke valve enters the notch when the suction piston (12) is provided. The notch of the choke valve is located on the upstream side of the venturi, and the notch is formed on a flat vertical surface or a flat slope inclined toward the downstream side, and the longitudinal end surface (23b) of the choke valve is linear. When the choke valve is fully opened, the linear end surface (23b) of the choke valve is in contact with the flat vertical surface on the piston side or the sloped notch (12a). A variable venturi-type carburetor characterized in that a gap between contact surfaces generated when the valve is fully opened is rectangular.