JPS6345563Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a variable bench lily type carburetor for an internal combustion engine, and more particularly to a variable vent lily type carburetor that controls the air-fuel ratio using air bleed.

Prior Art A variable bench lily type carburetor is a carburetor that changes the area of the vent lily in accordance with the amount of intake air, and for this purpose is equipped with a suction piston that is movable in a direction substantially perpendicular to the intake passage. A tapered metering needle is attached to the tip of the suction piston and measures the amount of fuel in cooperation with a main jet in the fuel passage. Furthermore, by bleeding air into this fuel passage, the air-fuel ratio can be precisely controlled according to the operating conditions. In order to perform air-fuel ratio control with high sensitivity using this air bleed, a part of the bleed air in a predetermined amount depending on the engine operating condition is supplied to the main jet section in the fuel passage, and the remaining amount is supplied through the branch passage. It is preferable to supply the fuel to the downstream side of the main jet, but in this way, during idling, for example, about 80% of the specified amount will be supplied to the downstream side of the main jet, and the air on this branched downstream side will be supplied to the downstream side of the main jet. The air jet disposed in the bleed passage is more susceptible to the influence of moisture in the bleed air than the air jet disposed in the air bleed passage opened in the main jet portion. As a result, when the entire carburetor and the supplied bleed air are relatively cold and humid during warm-up, the moisture turns into frost and blocks the air jet in the branch air bleed passage.
Or, if it is even colder, permanent condensation will occur and the air jet will be blocked, resulting in almost the entire amount of bleed air being supplied from the air bleed passage opened to the unblocked main jet section. . The fuel passage area of this main jet part is narrow because it measures fuel between it and the metering needle, so if a large amount of air bleeds here, it becomes difficult for fuel to pass through. In this case, the air-fuel ratio becomes leaner than the set value, and the stability of idle rotation is impaired. To avoid this, it is possible to increase the idle air-fuel ratio, but
This obviously causes a worsening of fuel efficiency. In addition, it is possible to introduce engine cooling water or to arrange other heating means near the fuel passage (JP-A-53-43134, JP-A-52-
(See Publication No. 114830). However, unless such heating means is stopped after warming up, undesirable situations such as the generation of fuel bubbles may occur.

Purpose of the invention As mentioned above, the purpose of the invention is to provide a variable bench lily type carburetor that bleeds air into the main jet section and downstream side of the main jet in the fuel passage.
The purpose of this invention is to prevent the air-fuel ratio from being diluted by blocking only one opening of an air bleed passage that is opened at a plurality of positions.

Structure of the invention The invention is equipped with a suction piston that changes the area of the bench lily in response to the amount of intake air.
A metering needle is attached to the tip of the suction piston, and a hollow cylindrical member extending coaxially with the suction piston and forming a fuel passage is disposed in front of the suction piston, and the metering needle is connected to the hollow cylinder. An air bleed passage is formed that can enter into the fuel passage to cooperate with a main jet provided inside the hollow cylindrical member and bleed air into the fuel passage. There is provided a variable bench lily type carburetor characterized in that it has a bleed hole penetrating a cylindrical wall of a main jet portion and a branch hole branched from the bleed hole and opened downstream from the main jet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a variable bench-lily carburetor according to the present invention. An intake air passage is formed in the carburetor main body 1 so that intake air flows along an arrow 2. A suction piston 4 movable in a direction perpendicular to the intake passage is provided opposite the fixed bridge 3, and a bench lily 5 is formed between the lower intake passage of the bridge 3 and the tip of the suction piston 4. Behind the suction piston 4,
A suction chamber 7 is formed by the suction casing 6 , and the suction chamber 7 communicates with the bench lily 5 through a suction hole 8 . An atmospheric chamber 9 is formed for applying atmospheric pressure to the suction piston 4, which communicates with the atmosphere by means of an atmospheric hole 10. A spring 11 is installed inside the suction chamber 7.
is arranged to connect the suction piston 4 to the bridge 3
It is biased in the direction. A piston rod 12 extends centrally from the suction piston 4 and is guided, for example along a bearing 14, in a rod guide 13 that is integral with the suction casing 6. 15
is a known throttle valve.

In such a configuration, when the engine is started, intake negative pressure is generated, this negative pressure is introduced into the suction chamber 7 through the suction hole 8, and this negative pressure overcomes the spring force of the spring 11. By moving the suction piston 4 to the left in FIG. 1, the bench lily 5 is opened. When the bench lily 5 is opened, intake air flows. When the amount of intake air increases, the negative pressure in the vent lily increases as the flow velocity increases, and therefore the negative pressure in the suction chamber 7 increases, and the amount of movement of the suction piston 4 to the left further increases. . For this reason, bench lily 5
is opened wide and the negative pressure in the vent lily decreases to a nearly constant level. Further, when the throttle valve is closed and the amount of intake air decreases, the negative pressure in the vent lily decreases, the suction piston 4 moves to the right, and the opening area of the vent lily 5 becomes smaller. Therefore, the bench lily negative pressure will increase to a substantially constant level. That is, the suction piston 4 changes the area of the vent lily in response to the amount of intake air to maintain the vent lily negative pressure at a substantially constant level.

In this way, since the vent lily negative pressure is approximately constant, the amount of fuel sucked must be measured in accordance with the amount of intake air. For this purpose, a metering needle 16 is attached to the tip of the suction piston 4 and can enter a fuel passage 17 extending coaxially with the suction piston 4. A main jet 18 is formed in the fuel passage 17, and a metering needle 16 cooperates with the main jet 18 to meter the amount of fuel to be drawn. That is, the metering needle 16 is tapered so that the diameter becomes smaller toward the tip. Therefore, when the suction piston 4 and the metering needle 16 move significantly to the left when the amount of intake air is large, The annular gap space between the main jet 18 and the metering needle 16 is increased so that a larger amount of fuel can be sucked in. In this way, the air-fuel ratio is set according to the operating conditions of the engine by the tapered shape of the metering needle. However, precise control such as during cold operation, output, or feedback control using an oxygen concentration sensor cannot be performed completely with only the taper shape of the metering needle 16, and air-fuel ratio control under such specific operating conditions cannot be performed completely. is performed by controlling the amount of air bleed.

An air bleed passage 19 is provided for such an air bleed or for an air bleed to better atomize the fuel and facilitate its mixing with air. Although it is shown as a single passage in FIG. 1, it may be a plurality of passages, and each of the plurality of passages may be provided with a valve device for increasing cold time, output, etc. It is easy to understand what can be done. The bleed air metered in this manner is supplied into the fuel passage 17.

In FIG. 1, the fuel passage 17 is formed by a hollow cylindrical member 20 and a nozzle 21. As shown in FIG. The hollow cylindrical member 20 has a hole 2 formed in the carburetor body 1.
2 and sealed with two O-rings 23. An annular space 24 is formed surrounded by the hole wall forming the hole 22, the outer peripheral surface of the hollow cylindrical member 20, and the two O-rings 23, and the aforementioned air bleed passage 19 is communicated with this annular space 24. , this annular space 24 becomes a part of the air bleed passage.

As shown in detail in FIG. 2, a bleed hole 25 is formed through the cylindrical wall of the main jet 18 of the hollow cylindrical member 20. This bleed hole 25
The main jet 18 is further branched by a branch hole 26 which intersects in a substantially T-shape at the wall forming the main jet 18 which projects inward in a flange shape. The branch hole 26 opens toward the downstream side of the main jet 18, that is, toward the nozzle 21. The number of these bleed holes 25 and branch holes 26 is not limited to one each; for example, FIG. 3 shows four bleed holes 25 and two branch holes 26, and FIG. Four holes 25 and four branch holes 26 are shown. and,
The opening cross-sectional area of these bleed holes 25 and branch holes 26 to the fuel passage is appropriately determined depending on the setting conditions for a specific engine, but generally speaking, the opening cross-sectional area of these bleed holes 25 and branch holes 26
The cross-sectional area of the opening is larger than the cross-sectional area of the opening due to the bleed hole 25.

A conventional branch hole is formed as shown by a broken line 27 in FIG.
It often occurred on the outer peripheral surface of 0. Therefore, as in the present invention, from the bleed hole 25 to the branch hole 2
Even if 6 is formed by branching, it is thought that the same problem will occur in the present invention under conditions that cause blockage due to frost or freezing as in the conventional case. However, when analyzed from conventional phenomena, such blockage that occurs in the present invention occurs at the most upstream portion of the bleed hole 25, that is, at the outer peripheral surface of the hollow cylindrical member 20. Therefore, such blockage occurs not only in the branch hole 26 but also in the bleed hole 25. Therefore, if such a blockage occurs, bleed air will no longer flow to the main jet 18, and in this state, the air-fuel ratio will become enriched rather than lean, making engine rotation unstable. Never. Since such blockage is removed as the engine warms up, it is advantageous in terms of fuel efficiency compared to the case where the air-fuel ratio is set on the rich side from the beginning.

Effects of the invention As explained above, according to the invention, only the branch hole is not blocked, so the air-fuel ratio is not further diluted than the set value, and thus an appropriate and precise air-fuel ratio can be maintained. Control is possible.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the variable bench lily type carburetor according to the present invention, Fig. 2 is a detailed view of the hollow cylindrical member forming the fuel passage of Fig. 1, and Fig. 3 is a line taken along the line - - of Fig. 2.
4 is a sectional view taken along FIG. 4, which is similar to FIG. 3 of another embodiment. DESCRIPTION OF SYMBOLS 1... Carburetor body, 4... Suction piston, 16... Metering needle, 17... Fuel passage, 18... Main jet, 19... Air bleed passage, 20... Hollow cylindrical member, 24...
Annular space, 25...bleed hole, 26...branch hole.

Claims (1)

[Scope of utility model registration request] It is equipped with a suction piston that changes the area of the bench lily in response to the amount of intake air, and a metering needle is attached to the tip of the suction piston. a hollow tubular member is disposed, the metering needle being extendable into the fuel passage for cooperation with a main jet disposed within the hollow tubular member;
Furthermore, an air bleed passage is formed to bleed air into the fuel passage, and the air bleed passage is branched from a bleed hole penetrating the cylindrical wall of the main jet portion of the hollow cylindrical member and extends downstream from the main jet. A variable bench lily type vaporizer characterized by having an open branch hole.