JPS59173539A - Variable venturi type carburettor - Google Patents

Abstract

PURPOSE:To stably feed fuel, by providing a fuel bypass passage bypassing a metering jet in which a needle integrally incorporated with a suction piston reciprocates, the fuel outlet port of the bypass passage being opened to the lower wall surface of a fuel passage. CONSTITUTION:There are provided a vacuum chamber 15 into which vacuum generated in the venturi section 8 in accordance with the flow rate of air flowing through an intake-air passage 2 is introduced and a suction piston 3 which is displaced in accordance with the differential pressure between the vacuum chamber 15 and an atmospheric pressure chamber 16. The amount of fuel is controlled by adjusting the inserted degree of a needle 4 which is inserted in a metering jet 21 or the annular gap between the needle 4 and the jet 21. Further, a fuel metering jet 25 is disposed in the fuel inlet passage part 24b of a fuel bypass passage 24 bypassing the metering jet 21, and as well the fuel outlet passage part 24c of the passage 24 is communicated with a fuel passage 20 downstream of the metering jet 21 through a fuel outlet port 27. Further, an air-bleed passage 28 is communicated to the intermediate part 24a of the passage 24.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable venturi carburetor for use in internal combustion engines.

Conventional technology Conventionally, in variable pliers type carburetors, in order to ensure stable engine idling operation, in addition to the main fuel system whose flow rate is controlled by the suction piston needle, there is also a fuel system that flows downstream of the throttle valve when the throttle valve opening is small. A slow fuel system is provided that sucks fuel into the intake passage by the generated negative pressure, or if a slow fuel system is not provided, the idling speed is set high. However, when a slow fuel system is provided in this way, the air-fuel ratio changes due to the opening/closing operation of the throttle valve when the main fuel supply system moves from the main fuel system to the slow fuel system, or from the slow fuel system to the main fuel system. However, this results in problems such as deterioration of vehicle drivability and deterioration of exhaust emissions.
On the other hand, if the idling speed is set high, a problem arises in that the fuel consumption rate worsens.

To solve this problem, only the main fuel passage with a metering jet that cooperates with the needle is used as a fuel supply system, and the main fuel passages upstream and downstream of the metering jet are interconnected via a fuel bypass passage. The applicant has already proposed a variable venturi type carburetor in which the fuel outlet of the fuel bypass passage is formed in the earthen wall of the main fuel passage. In this variable venturi type carburetor, most of the fuel flows through the fuel bypass passage when the amount of intake air is small, such as during idling, and the amount of fuel flowing through this fuel bypass passage is kept constant and stable. It is possible to ensure idle-link driving. Furthermore, as the amount of intake air increases, the fuel flowing through the fuel bypass passage gradually decreases, and the fuel flowing through the metering jet gradually increases, so the total fuel supplied from the main nozzle gradually increases. However, in this way, fluctuations in the air-fuel ratio when the amount of intake air increases can be suppressed.

As mentioned above, in this variable ventilator type carburetor, the fuel outlet of the fuel bypass passage is formed on the earth wall surface of the main fuel passage, and most of the fuel is drained when the amount of intake air is small, such as during idle-link operation. Since the fuel flows through the fuel bypass passage, when the amount of intake air is small, most of the fuel is supplied into the main fuel passage from above. However, when fuel is supplied into the main fuel passage from above, this fuel falls onto the needle, and then this fuel flows over the needle to the end face of the suction piston.
The liquid collects on the end face of the suction piston to form droplets, which drop intermittently.

However, when droplets fall intermittently in this way, the air-fuel ratio of the mixture supplied into the engine cylinders fluctuates when the amount of intake air is small, resulting in the problem that smooth engine operation cannot be achieved. arise.

OBJECTS OF THE INVENTION The object of the present invention is to provide a variable Penchili type carburetor that can suppress fluctuations in the air-fuel ratio when the amount of intake air is small and obtain a stable air-fuel ratio at all times regardless of the operating state of the engine. .

Structure of the Invention The structure of the present invention is such that the upstream and downstream fuel passages of the metering jet are connected to each other via a fuel bypass passage, and the fuel outlet of the fuel bypass passage is formed on the lower wall surface of the fuel passage.
The reason is that the fuel flowing out from the fuel outlet is prevented from flowing through the needle.

Embodiment Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction piston that moves laterally within the intake passage 2, and 4 is attached to the tip surface of the suction piston 3. 5 is the inner wall surface of the intake passage 2,
6 indicates a throttle valve provided in the intake passage 2 downstream of the suction piston 3; 7 indicates a carburetor float chamber;
A bench z′) portion 8 is formed between the tip end surface of the suction piston 3 and the inner wall surface 5. A hollow cylindrical casing 9 is fixed to the carburetor body 1, and a guide sleeve 1o extending in the axial direction of the casing 9 inside the casing 9 is attached.

A bearing 12 with a number of pawls 11 is inserted into the guide sleeve 10, and the outer end of the guide sleeve 1o is closed by a blind cover 13. On the other hand, suction piston 3
A guide rod 14 is fixed to the guide rod 14, and the guide rod 14 is inserted into the bearing 12 so as to be movable in the axial direction of the guide rod 14. In this way, the suction piston 3 is connected to the bearing 12.
Since the suction piston 3 is supported by the casing 9 via the casing 9, the suction piston 3 can smoothly move in one direction of its shaft. The inside of the casing 9 is divided into a negative pressure chamber 15 and an atmospheric pressure chamber 16 by the suction piston 3, and the suction piston 3 is always connected to the venturi section 8 in the negative pressure chamber 15.
A compression spring 17 is inserted which presses towards. Negative pressure chamber 1
5 is a suction hole 1 formed in the suction piston 3
The atmospheric pressure chamber 16 is connected to the intake passage 2 upstream of the suction piston 3 through an air hole 19 formed in the carburetor body 1 .

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor main body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided in the fuel passage 2o. The fuel passage 20 upstream of the metering jet 21 is connected to the float chamber 7 via a fuel tube 22 extending downward, and the fuel in the float chamber 7 is fed into the fuel passage 20 via this fuel tube 22. It will be done. Furthermore, a hollow cylindrical nozzle 23 arranged coaxially with the fuel passage 20 is fixed to the inner wall surface 5 of the intake passage. This nozzle 23 extends into the venturi portion 8 from the inner wall surface 5 of the intake passage, and the upper half of the tip of the nozzle 23 further projects toward the suction piston 3 from the lower half.

The needle 4 extends through the nozzle 23 as well as the metering jet 21, and the fuel is metered by the annular gap formed between the needle 4 and the metering jet 21 before being dispensed from the nozzle 23 into the intake passage 2.

1 and 2, a fuel passage 20 upstream of the metering jet 21 and a fuel passage 2 downstream of the metering jet 21 are shown.
0 are connected to each other by a fuel bypass passage 24.

This fuel pie A? The fuel passage 24 includes an intermediate portion 24B extending in a substantially horizontal direction, an inlet passage portion 24b extending from one end of the intermediate portion 24a into the fuel passage 20 upstream of the metering jet 21, and an inlet passage portion 24b extending from the other end of the intermediate portion 24a downstream of the metering jet 21. and an outflow passage section 24C extending into the fuel passage 20, and a fuel creation jet 25 is inserted into the inflow passage section 24b. An annular fuel outflow chamber 2 is provided around the fuel passage 20.
6 is formed, and the lower end of the outflow passage section 24c is connected to the top of the fuel outflow chamber 26.

The fuel outflow chamber 26 includes a fuel outflow port 27 that opens into the fuel passage 20 on the bottom wall surface of the nozzle 23, that is, on the bottom wall surface of the ship passage 20. So the attraction is 'Paino'? The fuel flowing inside the gas passage 24 is transferred to the fuel outflow chamber 26
The fuel then flows out from the fuel outlet 27 into the fuel passage 20 . In the embodiment shown in FIG.
is formed to extend in a direction perpendicular to the fuel passage 20. However, the fuel outlet 27 can also be formed so as to be inclined at an angle α with respect to the fuel channel 20, as shown in FIG. The connection between the intermediate B24a of the fuel bypass passage 24 and the inlet passage portion 24b is connected to the intake passage 2 upstream of the suction piston 3 via a first air bleed passage 28 and an air bleed jet 29. Further, a large number of air bleed holes 30 are formed on the inner peripheral surface of the metering jet 21, and these air bleed holes 30 are connected to the intake passage 2 upstream of the suction piston 3 via a second air bleed passage 31.
connected within.

A raised wall 32 that projects horizontally into the intake passage 2 is formed on the inner wall surface 5 of the intake passage above the nozzle 23, and flow rate control is performed between this raised wall 32 and the tip of the suction piston 3.

When engine operation is started, air flows downward in the intake passage 2. At this time, since the airflow is restricted between the suction piston 3 and the raised wall 32, negative pressure is generated in the bench portion 8, and this negative pressure is led into the square pressure chamber 15 through the suction hole 18. . The Zakujo piston 3 is arranged so that the pressure difference between the negative pressure chamber 15 and the atmospheric pressure chamber 16 becomes an almost constant pressure determined by the spring force of the compression spring 17, that is, the negative pressure inside the venturi part 8 becomes almost constant. Move to.

During engine idling, since the area of the annular gap formed between the needle 4 and the metering jet 21 is small, part of the furnace material is fed into the nozzle 23 through this annular gap, and most of the remaining fuel is consumed as fuel. The fuel flows out into the fuel passage 20 from the fuel outlet 27 via the bypass passage 24 . Air is supplied from the air bleed passage 28 into the fuel flowing in the fuel flow passage 24, and thus fuel containing air bubbles is supplied from the fuel outlet 27 into the fuel passage 20.

The fuel flowing out from the fuel outlet 27 flows along the bottom wall surface of the fuel passage 20 without contacting the needle 4, and then at the tip of the nozzle 23, some of the fuel is subjected to shear force by the air flow and becomes fine particles. The remaining fuel continuously flows down on the inner wall surface 5 of the intake passage. In this way, when the engine is idling, fuel is continuously supplied into the intake passage 2 from the tip of the nozzle 23 without adhering to the needle 4, so that fluctuations in the air-fuel ratio can be prevented.
In this way, stable engine operation can be ensured.

Further, in the embodiment shown in FIG. 3, the fuel outlet 27 is inclined toward the outlet of the nozzle 23, so that the fuel can flow out smoothly onto the inner wall surface of the nozzle 23. Fuel can be stably and continuously supplied from the tip of the nozzle 23.

When the throttle valve 6 opens and the amount of intake air increases, the suction piston 3 moves toward the negative pressure chamber 15, so that the area of the annular gap formed between the needle 4 and the metering jet 21 increases. At this time, the amount of fuel that detours through the fuel bypass passage 24 gradually decreases, and the amount of fuel that passes through the annular gap between the needle 4 and the metering jet 21 gradually increases until the nozzle 2
Since the entire fuel supplied from 3 gradually increases, the air-fuel ratio is maintained at a predetermined air-fuel ratio without fluctuation.

Effects of the invention Since fuel can be continuously supplied from the tip of the nozzle when the engine is idling, fluctuations in the air-fuel ratio can be prevented, and fluctuations in the air-fuel ratio can also be prevented when the intake air cap increases. be able to. Therefore, fluctuations in the air-fuel ratio can be prevented regardless of the operating state of the engine.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a variable venturi type vaporizer according to the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a 11ii+ section [m diagram] of another embodiment of the nozzle. 3... Suction piston, 4... Needle, 20
...Fuel passage, 21...Total noet, 24...
Fuel bypass passage, 27...fuel outflow []. Patent Applicant Toyota Motor Corporation Aisan Industries, Ltd. Patent Application Representative Patent Attorney Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Kyo Nakayama Patent Attorney Akira Yamaguchi Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A suction piston that changes the penetrating area in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending substantially horizontally in the axial direction of the needle so that the needle can enter, and the fuel a variable venturi carburetor comprising a metering jet disposed in a passageway and cooperating with the needle, the fuel passageway being connected to the float chamber upstream of the metering jet; A variable venturi carburetor, wherein the fuel passages on the downstream side are connected to each other via a fuel bypass passage, and a fuel outlet of the fuel bypass passage is formed on a lower wall surface of the fuel passage.