JPH0110430Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications The present invention relates to a variable bench lily type vaporizer.

Prior Art A suction piston that changes a bench lily area in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter therein,
A variable bench lily type carburetor is known, which includes a metering jet provided in a fuel passage and cooperating with a needle, and in which fuel passages upstream and downstream of the metering jet are interconnected via a fuel bypass passage. (Refer to Japanese Unexamined Patent Publication No. 107851/1983).

However, in a so-called downdraft type variable bench lily type carburetor in which the intake passage of such a carburetor is almost vertical, the fuel flowing out from the metering jet flows irregularly toward the tip surface of the suction piston through the needle. Next, this fuel forms fuel droplets on the needle or the end surface of the suction piston, and the fuel droplets thus formed fall intermittently. If fuel droplets fall intermittently in this way, the air-fuel ratio will fluctuate widely during idling operation with a small amount of intake air, making it difficult to maintain stable idling operation, especially when idling operation is performed using a lean mixture. It becomes difficult to secure Therefore, in this variable bench lily type carburetor, an air bleed passage is opened on the upper wall surface of the fuel passage downstream of the fuel bypass passage which opens into the fuel passage and the fuel outlet, and air is jetted from this air bleed passage toward the upstream direction of the fuel passage. let me,
This ejected air blows off the fuel flowing over the needle. However, this variable bench lily type carburetor has a problem in that an air bleed passage must be created to blow out the fuel flowing over the needle. Furthermore, in such a variable ventilator type carburetor, when the amount of fuel flowing through the annular gap between the needle and the metering jet is small, such as during idling, the amount of fuel passing through the annular gap fluctuates irregularly, and then this fuel becomes inundated. It is difficult to ensure stable idling operation because the oil is supplied from the nozzle with regular fluctuations.

Purpose of the invention The object of the invention is to provide a variable bench lily type carburetor that has a simple structure and can ensure stable idling operation even when using a lean mixture.

Structure of the invention The structure of the invention consists of a suction piston that changes the area of the bench lily in response to the amount of intake air, a needle connected to the suction piston, and a fuel tube extending in the axial direction of the needle so that the needle can enter. A downdraft variable bench lily carburetor comprising a passage and a metering jet disposed in the fuel passage and cooperating with a needle, the fuel passage being connected to the float chamber upstream of the metering jet. The upstream and downstream fuel passages of the fuel bypass passage are connected to each other via a fuel bypass passage, and the fuel outlet of the fuel bypass passage is opened into the fuel passage toward the upstream side of the fuel passage. A fuel inlet opening toward the upstream side of the fuel passage is formed on the lower wall surface of the passage, and the fuel inlet is connected to the intake passage below the nozzle via an auxiliary fuel passage.

Embodiment Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction piston movable within the intake passage 2 in a direction perpendicular to the intake passage 2, and 4 is a suction piston. 5 is the inner wall surface of the intake passage 2, 6 is the throttle valve provided in the intake passage 2 downstream of the suction piston 3, and 7 is the carburetor float chamber. Shown respectively, suction piston 3
A bench lily portion 8 is formed between the front end surface of the intake passage and the inner wall surface 5 of the intake passage. A hollow cylindrical casing 9 is fixed to the carburetor body 1, and a guide sleeve 10 extending in the axial direction of the casing 9 inside the casing 9 is attached. A bearing 12 with a number of balls 11 is inserted into the guide sleeve 10, and the outer end of the guide sleeve 10 is closed by a blind cover 13. On the other hand, a guide rod 14 is fixed to the suction piston 3,
This guide rod 14 is inserted into the bearing 12.
It is inserted movably in the axial direction of 4. Since the suction piston 3 is thus supported by the casing 9 via the bearing 12, the suction piston 3 can move smoothly in its axial direction. The interior of the casing 9 is divided by the suction piston 3 into a negative pressure chamber 15 and an atmospheric pressure chamber 16, and a compression spring 17 is provided in the negative pressure chamber 15 to constantly press the suction piston 3 toward the bench lily portion 8.
is inserted. The negative pressure chamber 15 is connected to the bench lily section 8 through a suction hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the suction piston 3 upstream through an air hole 19 formed in the carburetor body 1. The intake passage 2 is connected to the inside of the intake passage 2.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided within this fuel passage 20. The fuel passage 20 upstream of the metering jet 21 has a fuel pipe 22 extending downward.
is connected to the float chamber 7 via the float chamber 7.
The fuel inside is sent into the fuel passage 20 via this fuel pipe 22. Furthermore, a hollow cylindrical nozzle 23 is fitted into the open end of the fuel passage 20.
Needle 4 is connected to nozzle 23 and metering jet 21
The fuel is metered by the annular gap formed between the needle 4 and the metering jet 21 and then fed into the intake passage 2 from the nozzle 23.

As shown in FIG. 1, a raised wall 24 is formed above the nozzle 23 and projects horizontally into the intake passage 2, and the flow rate is controlled between this raised wall 24 and the tip of the suction piston 3. It is done. 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 24, negative pressure is generated in the bench lily portion 8, and this negative pressure is guided into the negative pressure chamber 15 through the suction hole 18. The suction 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, so that the negative pressure inside the bench lily part 8 becomes almost constant. Moving.

Referring to FIG. 1, a fuel passage 20 upstream of the metering jet 21 and a fuel passage 20 downstream of the metering jet 21 are interconnected by a fuel bypass passage 25, within which a fuel metering jet 26 is connected. is inserted. Further, the fuel bypass passage 25 is connected to the intake passage 2 upstream of the suction piston 3 via an air bleed passage 27.
An air bleed jet 28 is inserted into this air bleed passage 27. Furthermore, an adjustment screw 29 is disposed within the fuel bypass passage 25 for adjusting the flow rate of the fuel containing the bleed air.

On the other hand, a hollow cylindrical sleeve 30 is inserted into the fuel passage 20, and a metering jet 21 is formed on the inner wall surface of the sleeve 30. The nozzle 23 has an inner diameter approximately equal to the inner diameter of the sleeve 30, and an upper notch is formed on the upper and lower outer circumferential surfaces of the nozzle 23 located inside the fuel passage 20, respectively, as shown in FIGS. 2 and 3. 31 and lower notch 3
2 is formed. The upper notch 31 and the lower notch 32 form a fuel outlet 3 in the fuel passage 20 that opens toward the upstream side of the fuel passage 20.
3 and a fuel inlet 34 are formed. The fuel outlet 33 is connected to the fuel bypass passage 25, and the fuel inlet 34 is connected to the nozzle 2 via the auxiliary fuel passage 35.
3 is connected to the intake passage 2 downstream. Nozzle 23
An auxiliary fuel inlet hole 36 is bored on the inner peripheral surface of the fuel tank.
This auxiliary fuel inlet hole 36 is aligned with the auxiliary fuel passage 35 . The inner ends 37, 38 of the nozzle 23 are rounded, and the end of the sleeve 30 facing the nozzle inner ends 37, 38 is also rounded 39. By providing the roundness in this manner, the fuel flowing out from the fuel outlet 33 can be directed to the upstream side of the fuel passage 20, and the fuel flowing along the inner wall surface of the fuel passage 20 can be directed into the fuel inlet 34. It becomes easier to send to

During engine idling operation, since the area of the annular gap formed between the needle 4 and the metering jet 21 is small, some of the fuel flows through this annular gap, and the remaining fuel flows through the fuel bypass passage 25 to the fuel outlet. 33 into the fuel passage 20
It flows out toward the upstream side of 0. At this time, the fuel flowing along the upper wall surface of the fuel passage 20 through the above-mentioned annular gap and the fuel flowing above the needle 4 are pushed back upstream and blown away by the fuel flowing out from the fuel outlet 33. These fuels are splashed onto the lower wall surface of the fuel passage 20. In this way, the fuel flowing along the upper wall surface of the fuel passage 20 and the fuel flowing above the needle 4 are pushed back upstream and blown away, so that the fuel that is not blown away at this time is caused by the fuel flowing in from the fuel outlet 33 again. Receives a blow-off effect. Therefore, the amount of fuel that passes through the fuel outlet 33 without being blown away is extremely small, and most of the fuel is thus blown off onto the lower wall surface of the fuel passage 20. The fuel splashed onto the lower wall surface of the fuel passage 20 flows into the auxiliary fuel passage 35 from the fuel inlet 34, and the fuel that could not flow into the fuel inlet 34 is captured by the auxiliary fuel inlet 36. Similarly, it flows into the auxiliary fuel passage 35. In this way, most of the fuel is sent into the auxiliary fuel passage 35 during idling. Although the fuel supplied from the metering jet 21 fluctuates irregularly, the fuel is supplied from the auxiliary fuel passage 3.
Therefore, the fuel flowing out from the auxiliary fuel passage 35 into the intake passage 2 flows continuously on the inner wall surface of the intake passage 2 and is supplied into the engine cylinder.

Effects of the invention According to the invention, fuel flows out from the fuel inlet of the fuel bypass passage toward the upstream side of the fuel passage.
The fuel flowing along the upper wall surface of the fuel passage and the fuel flowing over the needle are blown away by this spilled fuel. That is, since the fuel flowing out from the fuel bypass passage is used to blow out the fuel flowing along the upper wall surface of the fuel passage and the fuel flowing over the needle, there is no special air bleed passage for blowing out the fuel as in the conventional case. Therefore, the structure of the carburetor can be simplified. Further, by opening the fuel inlet of the auxiliary fuel passage toward the upstream side of the fuel passage, most of the fuel is sent into the auxiliary fuel passage during idling. Therefore, even if the fuel supplied from the metering jet fluctuates irregularly, this fuel forms a uniform continuous flow in the auxiliary fuel passage and is then continuously supplied into the engine cylinder without irregular fluctuations. Stable idling operation can be ensured.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a variable bench lily type carburetor according to the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a sectional view taken along the - line in FIG. 2. 3... Suction piston, 4... Needle,
20... Fuel passage, 21... Metering jet, 23
... Nozzle, 25 ... Fuel bypass passage, 27 ...
...Air bleed passage, 31, 32...Notch, 3
3...Fuel outlet, 34...Fuel inlet, 35...
...Auxiliary fuel passage, 36...Auxiliary fuel inflow hole.

Claims (1)

[Scope of utility model registration request] A suction piston that changes a bench lily area in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter therein, and the fuel passage. a down-draft variable bench lily carburetor, comprising a metering jet disposed within the float chamber and cooperating with the needle, the fuel passage being connected to the float chamber upstream of the metering jet; The upstream and downstream fuel passages are connected to each other via a fuel bypass passage, and the fuel outlet of the fuel bypass passage is opened into the fuel passage toward the upstream side of the fuel passage, and the fuel outlet is opened below the fuel outlet. A variable vent lily type carburetor in which a fuel inlet opening toward the upstream side of the fuel passage is formed on the lower wall surface of the fuel passage, and the fuel inlet is connected to the intake passage below the nozzle via an auxiliary fuel passage.