JPH0617664B2 - Constant vacuum type vaporizer - Google Patents

Description

The present invention relates to a constant-vacuum carburetor equipped with a negative pressure operating valve that moves up and down in an intake passage by a negative pressure generated in an intake passage upstream of a throttle valve. Conventionally, such a constant vacuum type vaporizer is well known, for example, in Japanese Examined Patent Publication No. 40-12402 and Japanese Utility Model Publication No. 43-23922. By automatically adjusting the opening area of the intake passage according to the negative pressure generated in the upstream intake passage, the negative pressure (air velocity flowing through the needle jet portion) applied to the needle jet is controlled. This is to improve atomization of the air-fuel mixture sucked from the jet into the intake passage and to maintain an appropriate air-fuel mixture concentration. The negative pressure actuating valve of such a constant-vacuum carburetor generally has a cylindrical shape or a plate shape.

According to this cylindrical negative pressure operated valve, a relatively long venturi part can be formed and held by the bottom part of the negative pressure operated valve and the intake passage, so that the air flow flowing through this part is rectified and stabilized, and the venturi is stabilized. Since the negative pressure applied to the needle jet projecting and opening in the portion is also stable, the air-fuel mixture according to the negative pressure in the venturi portion can be accurately and stably sucked out from the needle jet. On the other hand, since the negative pressure operated valve is slidably arranged in the arc-shaped guide groove and the cylindrical guide groove formed in the carburetor body, when the negative pressure operated valve rises at a high opening, The arc-shaped guide groove remains on the side of the intake passage. According to this, the airflow flowing down the intake passage is over-flowed in this arc-shaped guide groove, which becomes a resistance against the inflow of air into the engine and cannot improve the intake efficiency, which leads to higher engine output. It was sometimes difficult to fit. In addition, the groove diameter of the cylindrical guide groove and the outer diameter of the negative pressure operating valve naturally have a clearance to allow sliding, but the negative pressure operating valve keeps the negative pressure in the intake passage during engine operation. The negative pressure actuating valve is sucked toward the engine side of the cylinder guide groove during the sudden deceleration of the engine, especially when the negative pressure in the intake passage becomes large. Due to the presence of the clearance in the guide groove and the negative pressure operated valve, they are locally contacted with each other without contacting the entire circumference.

Therefore, since the surface pressure at the contact portion increases, the material of the cylindrical guide groove, the negative pressure actuated valve, and the surface treatment must be carefully selected.

Further, since the negative pressure operated valve itself is guided and held by the guide groove and the cylindrical guide groove formed in the carburetor body, the outer diameter of the negative pressure operated valve must be larger than the intake passage diameter. Therefore, the total length of the carburetor body could not be shortened.

On the other hand, although the plate-type negative pressure operated valve is expected to improve the suction efficiency, the venturi part becomes an extremely short thin blade orifice, so the air flow flowing through this part becomes turbulent and is arranged near the negative pressure operated valve. The negative pressure applied to the needle jet becomes unstable, and it has a drawback that the air-fuel mixture cannot be sucked out more accurately and stably than the needle jet. Further, in particular, in a constant vacuum type carburetor that applies a rising force to the negative pressure operated valve by utilizing the negative pressure in the intake passage near the negative pressure operated valve, it flows near the negative pressure operated valve as described above. As the air flow becomes turbulent, the negative pressure becomes unstable and the lift characteristics of the negative pressure actuated valve cannot be made uniform.The jet needle integrated with the negative pressure actuated valve and the intake valve are projected and opened. The air-fuel mixture controllability by the needle jet was deteriorated. Also, if the shape of the end opening to the intake passage of the negative pressure operated valve is damaged, the shape of a part of the extremely short venturi portion will change, so the change in negative pressure will be large. The air-fuel mixture suction characteristics from the needle jet change greatly,
Negative pressure actuated valves must be manufactured with particular care.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned disadvantages, in which a negative pressure operated valve is provided with a venturi forming portion having a bottom portion having a continuous surface facing the intake passage and a side surface along the longitudinal axis direction of the venturi forming portion. It is formed by a more projecting plate-shaped guide part, and this guide part is slidably arranged in a guide groove formed in the carburetor main body, and the intake passage on the engine side from the air cleaner side surface of the plate-shaped guide part The object of the present invention is to provide a constant-vacuum vaporizer having excellent controllability of the air-fuel mixture and excellent suction efficiency by opening the center of the needle jet.

An embodiment of a constant vacuum vaporizer according to the present invention will be described below with reference to the drawings. Reference numeral 1 denotes an intake passage 2 penetrating the inside thereof, and on its engine side, a throttle valve 3 is rotatably arranged by a throttle valve shaft 4 and connected to a low-speed fuel system (not shown) corresponding to the throttle valve. The carburetor main body is provided with a bypass hole 5 and a pilot outlet hole 6 and a float chamber 8 is formed by the float main body 7 corresponding to one side of the carburetor main body 1. A float 9 and a valve seat and a float valve, which are arranged in a fuel inflow path (not shown), are arranged in the float chamber 8, and a constant liquid level X-X is always formed by their cooperative action. Ten
Is a negative pressure operated valve that is slidably guided and held by the carburetor main body 1 and moves up and down in the intake passage 2. The negative pressure operated valve 10 forms a venturi A together with the bottom of the intake passage 2. Cylindrical Venturi forming part with bottom 10E consisting of
10A and its Venturi forming part 10A longitudinal axis Y-
The venturi forming portion 10A has an outer diameter (A) smaller than the intake passage diameter (B). The outer diameter (A) is selected so that a stable Venturi negative pressure can be obtained, and the shape thereof is appropriately set. And this negative pressure operated valve 10 is especially used for the carburetor main body 1.
By arranging the plate-shaped guide portion 10B slidably in the guide groove 11 formed on the side of the intake passage 2, the inside of the intake passage 2 can be raised and lowered and the area of the intake passage 2 can be variably controlled. is there.

A partition 12 such as a diaphragm or a cylinder is integrally arranged on the upper portion of the negative pressure operating valve 10, and the partition 12 and the upper recess of the carburetor body 1 form an atmosphere chamber 13A. And the cap that covers the upper part 14
A pressure receiving chamber 13B is formed by and the atmosphere chamber 13A is communicated with the atmosphere through an atmosphere introducing passage (not shown), and the pressure receiving chamber 13B is formed.
Is, for example, the bottom of the venturi forming portion 10A of the negative pressure operated valve 10.
Negative pressure of Venturi A is introduced through a small hole 10C opened in 10E. Further, in the venturi portion A, a needle jet 16 which communicates with the main jet 15 via a main jet 15 opens below a constant liquid level in the float chamber 8, and in the needle jet 16, a jet needle 17 supported by the negative pressure operating valve 10 is provided. Is inserted, and the jet needle is moved by raising and lowering the negative pressure operating valve 10.
The gap formed by 17 and the needle jet 16 is adjusted to control the amount of air-fuel mixture sucked into the intake passage 2.

The needle jet 16 is opened to the position of the intake passage 2 with respect to the negative pressure operating valve 10 as follows.

That is, an opening from the air cleaner side surface 10D of the plate-shaped guide portion 10B of the negative pressure operated valve 10 (the right side surface of the plate-shaped guide portion 10B in FIG. 2) to the venturi portion A in the intake passage 2 on the engine side. Is. More specifically, as shown in FIG. 2, the air cleaner side surface 10 of the plate-shaped guide portion 10B is shown.
The center of the needle jet 16 is opened at the venturi portion A (on the left side in the figure) on the engine side from the line FF connecting D. In addition, 18 is one end locked to the negative pressure operating valve 10 and the other end is a cap so as to apply a downward force to the negative pressure operating valve 10.
It is a spring locked on 14.

According to the present invention, as described above, the negative pressure actuated valve 10 is provided with the venturi forming portion 10A and the plate-shaped guide portion 10 that laterally protrudes from the side surface of the venturi forming portion 10A in the longitudinal axis direction YY.
Since the guide portion is formed by B and the guide portion is slidably disposed in the guide groove 11 formed in the carburetor main body, the negative pressure operating valve 10
In the state where the intake passage 2 is opened to a high opening, only the plate-shaped guide groove 11 remains in the intake passage 2, and this guide groove 11 merely slides and guides the negative pressure operating valve 10. As long as it has a function, a thin groove width (for example, about 3 mm) is required. Therefore, even if the guide groove 11 remains in the intake passage 2, turbid flow is extremely reduced in the air flow flowing in the intake passage 2. Since the venturi forming portion 10A is further provided, the air flow flowing in from the upstream side of the intake passage 2 is smoothly rectified by the venturi forming portion 10A, so that the plate-shaped guide groove 11 and the venturi forming portion 10A synergize with each other. It is possible to obtain a constant vacuum type vaporizer with extremely high suction efficiency. Further, since the center of the needle jet 16 is opened to the venturi portion A on the engine side from the air cleaner side surface 10D of the plate-shaped guide portion 10B of the negative pressure operation valve 10, the needle that projects and opens to the venturi portion A is opened. The negative pressure acting on the jet 16 is stable, and the amount of fuel sucked into the intake passage 2 via the needle jet 16 is accurately and stably supplied. This is for the following reason. First, the Venturi section A includes the negative pressure operating valve 10
Is formed by the continuous surface provided on the bottom portion 10E of the intake passage 2 and the bottom of the intake passage 2, and has a longer distance in the flow direction of the intake passage 2 than the plate-shaped guide portion 10B. The airflow flowing through is in a rectified state. Also,
The opening area of the intake passage 2 is controlled by the venturi portion A and the plate-shaped guide portion 10B. Looking at the air flow in the intake passage 2 in the plate-shaped guide portion 10B,
The air directed downstream from the intake passage 2 on the upstream side (the right side in FIGS. 1 and 2) collides with the air cleaner side surface 10D of the plate-shaped guide portion 10B, and then the plate-shaped guide portion 1
After flowing into the bottom portion of 0B, it flows into the intake passage 2 on the downstream side of the plate-shaped guide portion 10B. That is, although the air flow in the intake passage 2 upstream of the air cleaner side surface 10D of the plate-shaped guide portion 10B flows along the longitudinal direction of the intake passage 2, the air cleaner side surface of the plate-shaped guide portion 10B. The air that has collided with 10D is deflected downward in a substantially right-angled direction, and the air that has flowed into the bottom of the plate-shaped guide portion 10B flows again along the longitudinal direction of the intake passage 2, especially the needle jet 16 The center 16 of the plate is the side surface 10D of the plate-shaped guide portion 10B on the air cleaner side.
Due to the opening in the venturi portion A on the engine side, the flow of air deflected downward by colliding with the plate-shaped guide portion 10B does not have any influence on the needle jet 16. That is, the needle jet 16 is opened to the venturi portion A that is formed by the continuous surface and the intake passage 2 and is in a stable rectifying state, and the air flow by the plate-shaped guide portion 10B is the flow along the longitudinal direction of the intake passage 2. It is the one that is affected and does not disturb the air rectification of the venturi portion A. Further, since the intake passage negative pressure of the venturi portion A is stable as described above, if the negative pressure of this portion is introduced into the pressure receiving chamber 13B, the movement of the negative pressure actuating valve 10 with respect to the negative pressure change can obtain an extremely stable lift characteristic. As described above, the amount of fuel and the amount of air flowing in the intake passage 2 are accurately and stably measured by stabilizing the intake passage negative pressure with respect to the needle jet 16 and the introduction negative pressure with respect to the pressure receiving chamber 13B. Therefore, the concentration of the air-fuel mixture supplied to the engine is accurately controlled.

In addition to the plate-shaped guide portion 10B, a venturi forming portion is also provided.
By providing 10A, even when a part of the venturi forming portion 10A is scratched during its manufacture, a sufficient venturi portion A can be formed, so that the turbulence of the air flow flowing through the venturi forming portion 10A is extremely small. It is extremely easy to manufacture as compared with a negative pressure operated valve.

As described above in detail, according to the constant vacuum carburetor of the present invention, the negative pressure actuated valve includes a venturi forming part, and a plate-like guide part protruding from a side surface along the longitudinal axis direction of the venturi forming part, The plate-shaped guide portion is slidably arranged in the guide groove formed in the carburetor body, and the needle jet opening in the intake passage is arranged on the engine side from the air cleaner side surface of the plate-shaped guide portion. Since it is opened to the Venturi part in the intake passage, the vortex flow due to the guide groove does not occur, the air flow is rectified in the venturi forming part, and the pressure fluctuation in the intake passage on the air cleaner side with respect to the needle jet is suppressed. Since the influence can be prevented and the negative pressure action on the needle jet can be properly and stably exerted, the synergistic action of these causes high inhalation efficiency and Forming a mixture controller action was boss, those capable of providing a constant vacuum type carburetor.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a constant vacuum type vaporizer according to the present invention, FIG. 2 is a transverse sectional view taken along line II-II in FIG. 1, and FIG. 3 is FIG. 1 III. It is a longitudinal cross-sectional view taken along the line III. 2 ... Intake passage 10 ... Negative pressure actuated valve 10A ... Venturi forming part 10B ... Plate-shaped guide part 10D ... Side surface of guide part 10B on air cleaner side A ... Venturi 11 ... Guide groove 16 ...... Needle jet

Claims (1)

[Claims] 1. A constant-vacuum carburetor equipped with a negative pressure operating valve that moves up and down in an intake passage by a negative pressure generated in an intake passage upstream of a throttle valve, the negative pressure operating valve facing the intake passage. It is formed by a venturi forming part having a bottom part formed of a continuous surface and a plate-like guide part projecting from a side surface along the longitudinal axis direction of the venturi forming part, and the plate-like guide part is formed in the carburetor body. A constant vacuum that is slidably arranged in the guide groove provided and the center of the needle jet that opens into the intake passage is opened from the air cleaner side side of the plate-shaped guide portion to the venturi portion in the intake passage on the engine side. Formula vaporizer.