JPH0350110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The disclosed technology belongs to the technical field of ensuring smooth operation of a variable bench lily type carburetor attached to an engine mounted on an automobile.

In this invention, the suction piston advances and retreats with respect to the suction chamber attached to the bore according to the amount of intake air, thereby making the bench lily portion of the bore variable, and the suction piston has a suction chamber integrally attached to the front end of the suction piston. In order to measure the metering jet and fuel in the well, a metering needle attached to the metering needle extends from the suction piston to a rod guide that integrally extends forward from the rear of the suction chamber. This invention relates to a downdraft type variable bench lily carburetor that supports and slides a rod extending rearward, and in particular, the center of a flange portion integrally formed with a suction piston parallel to the axis of the suction piston. The line is made eccentric upward toward the air horn side with respect to the center line of the suction chamber, so that the leakage control clearance between the flange part and the lower part of the bore side of the suction chamber does not become zero, thereby preventing stagnation. This invention relates to a downdraft type variable bench lily carburetor.

<Prior Art> As is well known, the so-called variable bench lily carburetor is used as a carburetor attached to an engine installed in a vehicle such as an automobile due to various advantages such as excellent transient response, low mechanism, and compact size. It is now being used in some sports cars and even regular passenger cars.

Therefore, Japanese Patent Application No. 53-94534 (Japanese Unexamined Patent Application No. 55-23324)
A downdraft type variable bench lily carburetor 1 as shown in FIG.
A suction piston 3 that advances and retreats orthogonally to the bore 2 has a rod 4 that integrally extends rearward from the rear of the suction piston 3 and a suction chamber 5 attached to the bore 2.
The suction piston 3 is slidably supported by a rod guide 6 that integrally extends forward from the rear part of the suction piston 3, while the ring-shaped flange portion 7 of the suction piston 3 is attached to the inner surface of the suction chamber 5 by, for example, 50 mm. The suction piston 3 is provided with a uniformly small clearance on the order of microns in the circumferential direction, and the suction piston 3 has a non-sliding structure with respect to the suction chamber 5, using this clearance as a leakage control clearance.

By the way, when the engine is at idle,
When the lift amount of the head 8 of the suction piston 3 is small and the bench lily portion 11 is opened by about 7 mm, for example, when the throttle valve 9 is suddenly opened to shift to medium speed from this state, the intake manifold negative pressure reaches the mixing chamber 10 and is led out from the bench lily portion 11 to the negative pressure chamber 13 of the suction chamber 5 through the suction hole 12 of the head 8 of the suction piston 3, causing the suction piston 3 to retreat. At that time, due to a momentary delay due to the bottleneck resistance of the suction hole 12, the suction piston 3 not only fully closes due to the negative pressure of the intake manifold, but also pushes the suction piston 3 in conjunction with the application of atmospheric pressure from the air horn 14. As a result, a strong downward bending stress is applied to the rod guide 6 due to the cantilever type support, and the lower edge of the flange portion 7 near the bore 2 has zero leakage control clearance with the inner surface of the suction chamber 5. become.

Therefore, in the process of retracting the suction piston 3 and increasing the amount of lift, the above-mentioned edge slides on the inner surface of the suction chamber 5, and when this is repeated, the edge portion slides against the inner surface of the suction chamber 5. There is a drawback that there is a risk of sticking such as seizure, and in severe cases, there is also a potential drawback that the suction piston 3 may stop sliding.

In order to deal with this, it may be possible to increase the leakage control clearance, but this increases the negative pressure leakage from the negative pressure chamber 13, resulting in a problem of significant performance deterioration.

The purpose of this invention is to solve the technical problem of the downdraft type variable bench lily carburetor based on the above-mentioned conventional technology, such as the suction piston becoming stuck, and Even if a transient full closure of the suction piston occurs and bending stress is applied to the suction piston, the leakage control clearance between the flange of the suction piston and the inner surface of the suction chamber does not become zero, and the suction piston smoothly closes. It is an object of the present invention to provide an improved variable bench lily carburetor in which piston lift is effected to benefit engine technology applications in the automobile industry.

<Means for Solving the Problems> In accordance with the above-mentioned object, the structure of the present invention, which is summarized in the above-mentioned claims, is provided with a suction chamber attached to a bore drilled inside the barrel so as to be movable forward and backward. The suction piston has a metering needle integrally facing forward at the tip of its head, and integrally has a rod supported by a rod guide provided integrally facing forward from the rear of the suction chamber. Extends towards the rear,
Furthermore, the downdraft type variable bench lily carburetor has a flange portion at the rear of the suction piston that faces the inner surface of the suction chamber via a leakage control clearance, the flange portion being arranged in the axial direction of the suction piston. This is a variable bench lily carburetor whose center line along which the suction chamber extends is offset upward toward the air horn relative to the axial center line of the suction chamber.

<Function> Therefore, the suction piston is in a substantially stationary state with the downdraft type variable bench lily carburetor inhaling a constant amount of air, and then the throttle valve is suddenly opened and the negative pressure in the intake manifold is suctioned. It is led out into the negative pressure chamber of the mixing chamber through the suction hole in the head of the suction piston.
Negative pressure is delayed in leading out to the negative pressure chamber of the suction chamber through the suction hole, so negative pressure acts on the suction piston in the bore, and the suction piston momentarily fully closes and moves toward the downstream side. A bending phenomenon occurs when bending stress is applied, but the flange portion of the suction piston is eccentric because the center line along the longitudinal direction of the suction piston is eccentric toward the air horn relative to the center line of the suction chamber. As a result, the leakage control clearance on the lower side of the flange is only slightly reduced, allowing smooth sliding without sliding against the inner surface of the suction chamber, and the suction piston being able to lift. Technical measures have been taken to prevent problems such as burn-in.

<Example> Next, an example of the present invention will be described below based on the drawings from FIG. 2 onwards. In addition, in each drawing, the same reference numerals are used to describe the same parts.

In the embodiment shown in FIGS. 2 and 3, reference numeral 1' denotes an air damper type down draft variable bench lily carburetor, which includes, from downstream, a mixing chamber 10 having a throttle valve 9, a bench lily portion 11,
A barrel 15 forming a bore 2 that in turn forms an air horn 14 is provided with a suction chamber 5 on one side of the bench lily portion 11.
From inside the center of the rear end, a rod guide 6 having ball bearings 16, 16, .
is provided so as to extend toward the front.

Further, on the other side of the bench lily portion 11, there is integrally provided a float chamber 19 for storing fuel 17 and floating a float 18, and a well 21 is provided which communicates with the float chamber 19 through a suction pipe 20. , the well 21 has a main nozzle 22 for the bench lily portion 11 and a metering jet 23 inside.

The suction piston 3', which moves forward and backward in the suction chamber 5, has a metering needle 24 whose base is integrally fixed from the center of the head 8' whose front surface is inclined.
The main nozzle 2 extends concentrically toward the front.
The metering jet 23 in the well 21 is inserted into the metering jet 21, and the metering jet 23 in the well 21 is movable toward and away from the metering jet 23, so that the two cooperate to measure the fuel 17.

Further, a rod 4 integrally extends rearward from the center of the head 8' concentrically with the suction piston 3', and is inserted into the rod guide 6 via a bearing 16 to support the suction piston 3'. It can be slid forward and backward.

On the other hand, a damper spring 25 is interposed between the back surface of the head 8' and the inner rear surface of the suction chamber 5, and the suction hole 12 bored in the upper part of the head 8' is located at the bench lily part. 11 and the negative pressure chamber 13 are communicated with each other.

The flange portion 7' of the suction piston 3' is configured to form a ring-shaped leak control clearance 26 with respect to the inner surface of the suction chamber 5, which will be described in detail below. A labyrinth portion 27 is provided around the flange portion 7'.

Note that 28 is an atmospheric chamber, which communicates with the air horn 14 through a passage 29.

Therefore, when molding the suction piston 3' by die casting, the flange portion 7' is pre-aligned with the center line '-' of the head 8' which coincides with the center line of the suction chamber 5. It is designed to be eccentric toward the center line of the air horn 4, and therefore, as shown in Fig. 3, the suction chamber 5
Δr (e.g. 80 microns) on the lower side with respect to the inner surface of
On the lower side, the leak control clearance 26 of Δr' (for example, 20 microns) is made eccentric so that it is larger on the lower side and smaller on the upper side, and the overall clearance remains the same as in the conventional configuration, preventing a decrease in engine output. Make sure to do so.

In the above configuration, the engine is in an idle state after cranking, and therefore, the suction piston 3' moves to the bench lily portion 1 according to the amount of intake air.
1 is open, and the suction negative pressure led to the negative pressure chamber 13 through the suction hole 12, the atmospheric pressure in the atmospheric chamber 28, and the elastic force of the damper spring 25 are balanced, and the state is substantially stationary. It is in.

Therefore, for example, when the throttle valve 9 is suddenly opened during sudden acceleration such as sudden racing, the intake manifold negative pressure reaches the mixing chamber 10, but the negative pressure in the suction chamber 5 from the suction hole 12 There is a delay in the negative pressure being drawn into the pressure chamber 13 due to the bottleneck resistance of the suction hole 12. Therefore, suction negative pressure momentarily acts on the head 8' of the suction piston 3', and The balance of the suction piston 3' is lost, and the suction piston 3' is moved to the bench lily section 11.
fully close.

At the same time, the air horn 14 is attached to the head 8'.
As mentioned above, the atmospheric pressure from the air and the negative pressure in the mixing chamber 10 act in a push-pull manner, and as mentioned above, a bending moment acts on the suction piston 3' downstream within the bore 2, and as a result, the rod 4 is moved to the cantilever type. Since the suction chamber 5 is supported by the rod guide 6, the lower edge of the flange portion 7' near the bore 2 narrows the lower side of the leak control clearance 26 against the inner surface of the suction chamber 5. try to.

Then, at the next moment, the intake manifold negative pressure of the mixing chamber 10 is transferred to the suction hole 1.
2 into the negative pressure chamber 13 of the suction chamber 5, the suction piston 3' is lifted into a balanced state, and the bench lily portion 11
gradually opens.

In this process, the suction piston 3'
The flange portion 7' is eccentrically upward relative to the head 8', and the leakage control clearance 26 for the lower suction chamber 5 is set to be larger than that for the upper side. Even if the suction piston 3' is bent, the lower edge of the flange portion 7' on the bore 2 side will not come into contact with the inner surface of the suction chamber 5, and therefore will remain in a sliding state when lifted. As long as this occurs, there will be no galling, scraping, etc., no sticking phenomena such as seizure, and the function of the variable bench lily carburetor 1' is always guaranteed.

The above-mentioned leak control clearance 26 has little effect on the upper side when the suction piston 3' is bent downward, so it may be small and no sliding occurs.

In the embodiment shown in FIGS. 4 and 5, the flange portion 7'' is connected to the head 8' of the suction piston 3''.
As shown in FIG. 5, the rod guide 6' of the suction chamber 5' is arranged concentrically to The flange portion 7'' is eccentric and therefore has a leakage control clearance 26 of Δr on the lower side and Δr' on the upper side (Δr'<Δr) with respect to the inner surface of the suction chamber 5'. This is a mode in which the upper part is larger and the upper part is slightly eccentric, and there is substantially no difference in operation and effect from the above-mentioned embodiment.

It should be noted that the embodiments of the present invention are of course not limited to the above-mentioned embodiments, and can be applied not only to air damper type variable bench lily carburetors but also to oil damper type variable bench lily carburetors. Of course.

<Effects of the Invention> As described above, according to the present invention, in a downdraft type variable bench lily carburetor, the center of the flange portion facing the inner surface of the suction chamber of the suction piston along the axial direction of the suction piston The line is eccentrically upward toward the air horn side relative to the center line of the suction chamber, and the leak control clearance is made larger on the lower side than on the upper side, so that the leakage control clearance is larger than that on the upper side. Intake manifold negative pressure acts on the head of the suction piston, and the suction piston momentarily presses the ventilary part completely in a state where the negative pressure spread is delayed and is not sufficiently drawn out into the negative pressure chamber in the suction chamber through the suction hole of the head. Even when the piston is closed and subjected to bending deflection on the downstream side, and in that state it moves to lift, the amount of leakage control clearance to the inner surface of the suction chamber on the lower side of the flange of the suction piston must be large. Therefore, there is no sliding, smooth lifting, no galling, no sticking phenomena such as seizure, and therefore no stopping of the suction piston, always smooth operation, and setting functions. The excellent effect of being able to make full use of it is achieved.

In addition, the leak control clearance can be easily improved by simply changing the design by making the flange eccentric upward relative to the suction chamber toward the air horn. It has the advantage that there is no need to change it, and therefore the cost does not increase.

In this way, the function of a downdraft type variable bench lily carburetor can be achieved and the reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a conventional down-draft type variable bench lily carburetor, FIG. 2 and the following are explanatory views of embodiments of the present invention, and FIG. 3 is a cross-sectional view of FIG. 2, FIG. 4 is a schematic cross-sectional view of another embodiment, and FIG.
The figure is a - sectional view of FIG. 15... Barrel, 2... Bore, 5, 5'... Suction chamber, 3... Suction piston, 24... Metering needle, 6, 6'... Rod guide,
4... Rod, 26... Leak control clearance, 7', 7''... Flange section, 1', 1''... Variable bench lily carburetor, X, Y'... Center line (of flange section), X, Y (Suction chain) ) center line.

Claims (1)

[Claims] 1 A suction piston is installed in a suction chamber attached to a bore drilled inside the barrel so as to be able to move forward and backward, and has a metering needle integrally facing forward at the tip of its head, and the suction chamber A rod supported by a rod guide provided integrally toward the front from the rear of the suction chamber integrally extends rearward, and further has a flange facing the inner surface of the suction chamber through a set amount of leakage control clearance. In a down-draft type variable bench lily carburetor having a section at the rear of the suction piston, the center line of the flange section along the axial direction of the suction piston is relative to the axial center line of the suction chamber. A variable bench lily vaporizer characterized by being eccentrically upward.