JPS6357619B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a variable bench lily type carburetor.

PRIOR ART A variable bench lily carburetor comprises a needle fixed to a suction piston and penetrating into a fuel passage, and a metering jet disposed in the fuel passage and cooperating with the needle. A metered amount of fuel is supplied from the fuel passage into the intake passage of the carburetor. In order to atomize the fuel in this type of variable bench valve type carburetor, air has conventionally been bleed into the metering jet or into the fuel passage downstream of the metering jet. However, when such air bleed is performed, frost is generated on the outer peripheral surface of the needle due to moisture in the air bleed, and this frost is supplied from the fuel passage into the carburetor intake passage in order to narrow the fuel flow path area. A problem arises in that the amount of fuel decreases and the air-fuel mixture supplied into the engine cylinder becomes lean.

OBJECTS OF THE INVENTION An object of the present invention is to provide a variable vent lily type carburetor that can prevent frost from forming on the needle and form an air-fuel mixture having a constant air-fuel ratio at all times.

Structure of the Invention The structure of the present invention includes a suction piston that changes the area of the bench lily in response to the intake air amount, a needle connected to the suction piston, and a fuel that extends in the axial direction of the needle so that the needle can enter. a variable bench turret comprising a passageway, an air bleed passageway opening into the fuel passageway, and a metering jet provided in the fuel passageway and cooperating with the needle, the fuel passageway being connected to the float chamber upstream of the metering jet; In the type carburetor, the fuel passages on the upstream and downstream sides of the metering jet are connected to each other via a fuel bypass passage, and a nozzle extending to the vicinity of the needle is provided at the outlet of the fuel bypass passage that opens into the fuel passage on the downstream side of the metering jet. It's because it's installed.

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 a distal end surface of the suction piston 3. The attached needle, 5 indicates the inner wall surface of the intake passage 2, 6 indicates the throttle valve provided in the intake passage 2 downstream of the suction piston 3, 7 indicates the carburetor float chamber, and the tip surface of the suction piston 3. A bench lily portion 8 is formed between the intake passage inner wall surface 5 and the intake passage inner wall surface 5. Vaporizer body 1
A hollow cylindrical casing 9 is fixed to the casing 9, 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, and this guide rod 14 is connected to the bearing 12.
The guide rod 14 is inserted into the guide rod 14 so as to be movable in the axial direction. 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. Negative pressure chamber 15 is formed in suction hole 1 formed in 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 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, the intake passage inner wall surface 5
A hollow cylindrical ruzzle 23 arranged coaxially with the fuel passage 20 is fixed on the top. This ruzuru 23
protrudes from the inner wall surface 5 of the intake passage into the bench lily portion 8, and the upper half of the tip of the nozzle 23 further protrudes from the lower half toward the suction piston 3. The needle 4 extends through the nozzle 23 as well as the metering jet 21, and the fuel is metered through the annular gap formed between the needle 4 and the metering jet 21 before being supplied from the nozzle 23 into the intake passage 2.

Referring to FIGS. 1 and 2, a fuel passage 20 upstream of the metering jet 21 and a fuel passage 20 downstream of the metering jet 21 are connected to each other by a fuel bypass passage 24. As shown in FIG. This fuel bypass passage 2
Reference numeral 4 denotes an intermediate portion 24a extending substantially horizontally, 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 a fuel inflow passage portion 24b extending from the other end of the intermediate portion 24a into the fuel passage 21 downstream of the metering jet 21. An outflow passage 24c extends into the passage 20, and a fuel metering jet 25 is inserted into the inflow passage 24b. In addition, the inflow passage section 24b
The connection between the and the intermediate portion 24a is the air bleed passage 2.
6 and an air bleed jet 27 into the intake passage 2 upstream of the suction piston 3. On the other hand, a nozzle 29 is inserted into the outlet 28 of the outlet passage portion 24c. This nozzle 29 has a truncated conical tip that projects into the fuel passage 20, and a nozzle opening 30 is formed at the top of this tip. As shown in FIG.
is placed close to the outer circumferential surface of the On the other hand, a plurality of air bleed holes 31 are formed on the inner peripheral surface of the metering jet 21, and these air bleed holes 31 are connected to the intake passage 2 upstream of the suction piston 3 via an air bleed passage 32. .

On the inner wall surface 5 of the intake passage above the nozzle 23, there is a raised wall 33 that projects horizontally into the intake passage 2.
is formed, and the flow rate is controlled between this raised wall 33 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 33, 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.

During engine operation, some fuel flows through fuel bypass passage 2.
The remaining fuel flows into the fuel passage 20 through the metering jet 21 and flows into the fuel passage 20 downstream from the metering jet 21. Air is bleed from the air bleed passage 26 into the fuel flowing through the fuel bypass passage 24, and the fuel containing air bubbles flows out from the nozzle opening 30 of the nozzle 29. On the other hand, the air bleed hole 3 is also connected to the fuel flowing inside the metering jet 21.
Air is bled from 1. At this time, as shown in FIGS. 1 and 2, since the nozzle port 30 of the nozzle 29 is arranged near the outer peripheral surface of the needle 4, the fuel flowing out from the nozzle port 30 collides with the outer peripheral surface of the needle 4. As a result, frost generated on the outer peripheral surface of the needle 4 is washed away. During engine operation, the needle 4 moves according to the amount of intake air, so the fuel flowing out from the nozzle port 30 of the nozzle 29 collides with a considerable area of the outer circumferential surface of the needle 4. Frost generated on the needle 4 can be washed away over a fairly wide area of the surface.

Effects of the invention It is possible to prevent frost from adhering and growing over a fairly wide area on the outer peripheral surface of the needle, and as a result, the flow area of the fuel passage is not narrowed, so that fuel can be sucked in proportion to the amount of intake air. It can be fed into the passageway. Therefore, the air-fuel mixture supplied into the engine cylinders will not become too lean, and stable engine operation can be ensured at all times.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a variable bench lily type carburetor according to the present invention, and FIG. 2 is a partially enlarged view of FIG. 1. 3... Suction piston, 4... Needle,
20... Fuel passage, 21... Metering jet, 24
...Fuel bypass passage, 29...Nozzle, 30...
...Nozzle mouth.

Claims (1)

[Claims] 1. 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, a fuel passage extending in the axial direction of the needle so that the needle can enter, and the fuel A variable bench turret comprising: an air bleed passage opening into the passage; and a metering jet disposed within the fuel passage and cooperating with the needle, the fuel passage being connected to the float chamber upstream of the metering jet. In the type carburetor, the fuel passages on the upstream and downstream sides of the metering jet are connected to each other via a fuel bypass passage, and the fuel bypass passage outlet opening into the fuel passage on the downstream side of the metering jet is connected to the vicinity of the needle. Variable bench lily type carburetor with an extending nozzle.