JPH0220450Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a variable bench lily type carburetor used in an internal combustion engine.

Conventional technology A suction piston is attached so that it can move forward and backward in a direction across an intake passage formed in a carburetor body, a bench lily portion with a variable passage area is formed in front of the suction piston, and a negative pressure chamber is formed behind the suction piston. A variable bench lily type vaporizer in which a negative pressure chamber and a bench lily part are connected through a suction hole is disclosed in Japanese Patent Application Laid-Open No. 1986-
This method is known from JP-A No. 222956 and JP-A-58-107856. It has been conventional practice to equip such a variable bench lily type carburetor with an accelerator pump, and the injection nozzle of the conventional accelerator pump was
As shown in Japanese Patent No. 19630, fuel during acceleration is injected into the intake passage upstream of the bench lily. The main reason for opening the injection nozzle upstream of the bench lily is that when the injection nozzle of the accelerator pump is opened in the upstream part of the bench lily, the fuel is handled from the injection nozzle by the negative pressure of the vent lily, and the set air-fuel ratio characteristics change. That's the reason.

Problems that the invention aims to solve: Because the flow velocity of intake air is slow upstream of the bench lily, the fuel injected there is difficult to atomize, resulting in poor fuel response and mixture distribution, especially during cold acceleration. It was causing shortness of breath and sluggishness. Also, the above-mentioned problem may be improved if the fuel from the accelerator pump is injected into the bench lily section where the flow rate is high; however, if the fuel from the accelerator pump is injected into the bench lily section, the The accelerating fuel hits the tip end surface of the piston, and the fuel adheres to the piston wall surface, deteriorating the responsiveness of the fuel.

Means for Solving the Problems The present invention is characterized in that, in a variable bench lily type carburetor, the injection nozzle of the accelerator pump is directed directly downstream of the suction hole opening on the distal end surface of the suction piston. .

Embodiment In FIGS. 1 and 2, 1 is a carburetor main body;
Reference numeral 2 denotes an intake passage extending vertically downward, 3 a suction piston that moves forward and backward in a direction across the intake passage 2, 4 a needle attached to the tip surface of the suction piston 3, and 5 an inner wall surface of the intake passage 2. ,6
7 indicates a throttle valve provided in the intake passage 2 downstream of the suction piston 3, and 7 indicates a carburetor float chamber. A bench lily portion 8 is formed between the tip surface of the suction piston 3 and the inner wall surface 5 of the intake passage. Ru. 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. Guide sleeve 10
A bearing 11 is inserted inside the guide sleeve 1.
The outer end of 0 is closed by a blind lid 12. On the other hand, a guide rod 13 is fixed to the suction piston 3, and the guide rod 13 is inserted into the bearing 11 so as to be movable in the axial direction of the guide rod 13. In this way, the suction piston 3 is connected to the bearing 11.
Since the suction piston 3 is supported by the casing 9 via the casing 9, the suction piston 3 can move smoothly in its axial direction. The rear end portion 14 of the suction piston 3 has a larger diameter than the front portion due to a step, and a labyrinth 15 is formed on the outer peripheral surface of the large diameter rear end portion 14.
is formed and sealingly engages with the inner circumferential surface of the casing 9. Thus, the inside of the casing 9 is divided into a negative pressure chamber 16 and an atmospheric pressure chamber 17 by the large-diameter rear end portion 14 of the suction piston 3.
A compression spring 18 that constantly presses the suction piston 3 toward the bench lily portion 8 is inserted therein.
The negative pressure chamber 16 is connected to the bench lily part 8 through a suction hole 19 formed in the suction piston 3, and the atmospheric pressure chamber 17 is connected to the suction piston 3 upstream through an air hole 20 formed in the carburetor body 1. The intake passage 2 is connected to the inside of the intake passage 2.

The needle 4 extends coaxially with the suction piston 3 and enters a fuel passage (not shown) coaxially therewith. As is known, this fuel passage communicating with the float chamber 7 is provided with a fuel metering jet, which cooperates with the tapered needle 4 to measure the amount of fuel to be discharged. be. This fuel passage is connected to the intake passage 2 by a nozzle 30 whose upper half protrudes (the lower half is flush with the inner wall surface 5).

A fuel passage 23 extending from the acceleration pump 22 is formed at a position slightly apart from such a fuel passage, and this fuel passage 23 is connected to a horizontal passage 23 at a low level.
a, a vertical passage 23b, and a horizontal passage 23c higher than the liquid level of the float chamber 7. The horizontal passage 23c runs diagonally above the needle 4.
The injection nozzle 24 extends parallel to the intake passageway and opens into the intake passage vent lily portion 8 as an injection nozzle 24. A jet 25 is provided in the horizontal passage 23c, and a vertical bleed hole 26 is communicated between the injection nozzle 24 and the jet 25. 27 is a fuel introduction passage from the float chamber 7 to the acceleration pump 22.

As can be seen from FIG. 1, the injection nozzle 24 of the acceleration pump 22 is disposed directly downstream of the opening of the suction hole 19, facing the front end surface of the suction piston 3. The suction piston 3 in FIG. 1 is shown in cross section along the line - in FIG. 2, and it can be seen from FIG. 2 that the suction hole 19 is located diagonally above the needle 4. . However, the present invention is not limited to such a positional relationship between the needle 4 and the suction hole 19.
To explain in more detail the shape of the tip surface of the suction piston 3 in FIGS. 1 and 2, the needle 4
The central portion 31 to which is attached is slightly recessed, and the diagonally downward portion 32 from this central recessed surface 31 is a flat surface. An inclined raised surface 33 continues upward from this flat surface 32, and its uppermost crescent-shaped portion 34
becomes a flat surface again to form the most raised part, while a bridge 35 that protrudes into the intake passage 2 is formed in the carburetor body 1, and strictly speaking, the passage area of the bench lily part 8 is the same as that of the bridge. 35 and the upper edge of the flat surface 34 of the suction piston 3. The lowermost portion 36 of the suction piston 3 is inclined toward the rear of the piston. The suction hole 19 opens in the uppermost flat surface 34, and a notch 37 is formed around the opening and along the downward direction, and the injection nozzle 24 of the aforementioned acceleration pump 22 is directed toward the vertical portion of the notch 37.

The suction piston 3 responds to the amount of intake air according to the opening degree of the throttle valve 6, and when the engine load is high and the amount of intake air is large, it moves to the left in Fig. 1 to expand the area of the bench lily and increase the amount of intake air. It is well known that when the pressure is low, the engine moves to the right to reduce the area of the bench lily (Figure 1 shows the engine stopped and the bench lily is not open), thereby keeping the negative pressure in the bench lily part 8 almost constant at all times. That's what happened. During acceleration, the suction piston 3 moves to the left.
At this time, the suction piston is guided by the guide sleeve 10 and slides against the casing 9 by a labyrinth 15 provided at the large diameter rear end portion 14. Although the labyrinth 15 seals the negative pressure chamber 16 and the atmospheric pressure chamber 17, in reality some air flows from the atmospheric pressure chamber 17 to the negative pressure chamber 1.
6, and due to the rapid operation during acceleration of the suction piston 3, the negative pressure chamber 1 containing the aforementioned leaked air
6 is blown out to the bench lily portion 8 through the suction hole 19. The ejected air flows downward in the intake passage and merges with the air whose speed has been increased at the bench lily portion 8. The acceleration pump 22 is the throttle valve 6
The fuel injected from the injection nozzle 24 hits the air flow jetted from the suction hole 19, and is atomized before hitting the tip surface of the suction piston 3. Better atomization improves acceleration response and mixture distribution.
Therefore, drivability when the engine is cold is improved.
The bleed hole 26 prevents fuel from being sucked out by the negative pressure of the vent lily when the acceleration pump 22 is not operating.

Effects of the Invention As explained above, according to the present invention, atomization of acceleration fuel is promoted, and acceleration response and mixture distribution are improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a variable bench lily type carburetor according to the present invention, and FIG. 2 is a front end view of the suction piston shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Carburetor body, 2... Intake passage, 3... Suction piston, 16... Negative pressure chamber, 19... Suction hole, 22... Accelerator pump, 24... Injection nozzle.

Claims (1)

[Scope of utility model registration request] A suction piston is attached so as to be movable back and forth in a direction across an intake passage formed in the carburetor body, a bench lily portion with a variable passage area is formed in front of the suction piston, and a negative pressure chamber is formed behind the suction piston. In a variable bench lily type carburetor, the negative pressure chamber and the bench lily portion are connected to each other by a suction hole provided in a suction piston, and further includes an acceleration pump having an injection nozzle opening into the intake passage. A variable bench lily type carburetor, characterized in that a nozzle is directed directly downstream of a suction hole opening on a distal end surface of the suction piston.