JPH0350109B2 - - Google Patents

Description

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

According to the present 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 tip of the suction piston moves forward and extends forward. In order to measure the fuel and the metering needle provided in the well, the rod is supported by a rod guide that integrally extends forward from the suction chamber so that it can slide freely. This invention relates to a suction piston structure for a variable bench lily carburetor, and in particular, the flange portion of the suction piston facing the inner surface of the suction chamber is larger than the upper side of the suction piston when the suction piston is in a horizontal position. The lower space is large, and the outer periphery is smoothly connected, so that the negative pressure leakage control clearance between the flange and the inner surface of the suction chamber is small on the upper side and large on the lower side, reducing the overall clearance. This invention relates to a suction piston structure for a variable bench lily carburetor, which can prevent sticking when the negative pressure leakage control clearance becomes zero and there is a risk of sliding occurring.

<Prior art> As is well known, the carburetor attached to the engine installed in a car has excellent transient response, has a low aircraft height,
A so-called variable bench lily carburetor is used because of various advantages such as being compact, and has recently been installed in some sports cars and also in general passenger cars.

Therefore, Japanese Patent Application No. 53-94534
Regarding the support while allowing the suction piston 3 to slide back and forth orthogonally to the bore 2 of the downdraft type variable bench lily carburetor 1 as shown in FIG. A rod 4 integrally extended rearward from the head 8 is slidably supported by a rod guide 6 integrally extended forward in a suction chamber 5 integrally attached to the bore 2. The flange portion 7 provided at the rear end of the suction piston 3 is provided with a concentric annular minute clearance of about 50 microns against the inner surface of the suction chamber 5 as a negative pressure leakage control clearance. It has a non-sliding structure.

<Problems to be Solved by the Invention> By the way, when the engine is in an idling state and the lift amount of the head 8 of the suction piston 3 is open by about 7 mm, for example, when the throttle is turned to shift from this state to medium speed. When the valve 9 is suddenly opened, the intake manifold negative pressure is applied to the mixing chamber 10 and is further applied to the suction channel from the bench lily portion 11 through the suction hole 12 provided in the axial direction to the head 8 of the suction piston 3. However, due to flow resistance through the bottleneck of the suction hole 12, there is a time delay in deriving the negative pressure. Negative pressure is applied from the mixing chamber 10 side, and not only is it fully closed for a moment, but also a push-pull action works in conjunction with atmospheric pressure from the air horn 14 on the upstream side.
Due to the cantilever support of the rod 4 against the rod guide 6, a strong downward bending stress is applied to the suction piston 3, and the negative pressure leakage control clearance at the edge of the flange portion 7 near the lower bore 2 becomes zero. , the intake manifold negative pressure spreads through the suction hole 12 into the negative pressure chamber 13 of the suction chamber 5, the suction piston 3 opens, and in the process of increasing the lift amount, the previously zero negative pressure leak is eliminated. Due to the control clearance, the lower edge of the flange portion 7 of the suction piston 3 closer to the bore 2 slides against the inner surface of the suction chamber 5, and if this is repeated, stuck phenomena such as seizure may occur. There is a drawback that there is a risk of causing
There was also a potential inconvenience that could lead to the slide stopping.

Of course, to deal with this, the annular cross section of the negative pressure leakage control clearance formed on the inner surface of the suction chamber 5, which is formed in the same perfect circular shape as the flange portion 7, which is formed in a perfect circular shape, can be made large. However, this increases negative pressure leakage from the negative pressure chamber 13 and significantly deteriorates performance.

The object of the present invention is to solve the problem of the stuck phenomenon of the suction piston of the variable bench lily carburetor based on the above-mentioned prior art, and to solve the problem of the stuck phenomenon of the suction piston of the variable bench lily carburetor based on the above-mentioned prior art. This is an excellent variable bench lily that benefits the field of engine technology application in the automobile industry by allowing smooth lift-up of the suction piston without causing any galling phenomenon even if bending deflection occurs to the downstream side of the bore. It is an object of the present invention to provide a suction piston structure for a carburetor.

<Means and operations for solving the problem> In accordance with the above-mentioned object, the structure of the present invention, which is summarized in the above-mentioned claims, is to solve the above-mentioned problem. A suction piston is provided on the suction chamber so as to be movable back and forth, has a metering needle at its tip, and integrally has a rod that is supported by a rod guide formed integrally with the suction chamber and extends rearward. This is a suction piston structure for a variable bench lily carburetor having a flange portion that forms a negative pressure leak control clearance with respect to the inner surface of the chamber, and what is the air horn when the suction piston with the negative pressure leak control clearance is in a horizontal position? The suction piston structure of the variable bench lily carburetor is such that the gap on the opposite side is made larger than that on the air horn side to form a flange, and the negative pressure leakage control clearance remains at the set amount as a whole. It is something.

<Function> Therefore, the suction piston is in a substantially stationary state with the variable bench lily carburetor inhaling a constant amount of air, and the throttle valve is then suddenly opened to change the intake manifold negative pressure and start the mixing channel. The suction piston in the bore fully closes the bench lily and the suction chamber is delayed due to the flow resistance of the suction hole in the head of the suction piston. Negative pressure acts on the suction piston, and together with atmospheric pressure from the air horn, bending stress is applied to the downstream side, causing a bending phenomenon, which causes the flange of the suction piston and the inner surface of the suction chamber to The negative pressure leak control clearance becomes close to zero, and the suction piston tries to lift up, but in this case, the negative pressure leak control clearance becomes larger on the air horn side, that is, the upper side, than on the side opposite to the air horn side, that is, the lower side. Because the flange is shaped like this, the negative pressure leakage control clearance is large on the bottom side and small on the top side, and the overall clearance remains the same as the conventional design, so the suction chamber A technical measure has been taken to ensure that the lift can be lifted up by sliding smoothly against the inner surface without any friction, and that problems such as seizure will not occur.

<Example> Next, an example of the present invention will be described below based on the drawings from FIG. 2 onwards.

Note that the same parts as in FIG. 1 will be explained using the same reference numerals.

In the illustrated embodiment, 1' is an air damper type down draft variable bench lily carburetor;
A barrel 1 having a bore 2 forming a mixing chamber 10, a bench lily portion 11, and an air horn 14 from a downstream side having a throttle valve 9 to an upstream side.
5 is integrally provided with a suction chamber 5 on one side of the bench lily portion 11, and ball bearings 16, 16, . A rod guide 6 is provided integrally extending forward.

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 back and forth in the suction chamber 5, has a metering needle 24, whose base is integrally fixed, extending forward from the center of the head 8' whose front surface is inclined at a predetermined angle. The metering jet 23 is inserted into the main nozzle 22 and moves forward and backward into the metering jet 23 in the well 21 so that the two cooperate to measure the fuel 17 and inject it from the main nozzle 22 into the mixing chamber 10. .

Further, a rod 4 integrally extends from the center of the head 8' toward the rear opposite to the metering needle 24, and is inserted into the bearing 16 of a rod guide 6 extending forward from the suction chamber 5. The suction piston 3' is supported in a cantilever manner and is slidable back and forth.

A damper spring 25 is provided between the back surface of the head 8' and the inner rear surface of the suction chamber 5.
The suction hole 12 provided in the axial direction in the upper part of the head 8' on the air horn 14 side connects the bench lily part 11 and the negative pressure chamber 13.
are communicating.

Thus, the rear flange portion 7' of the suction piston 3' forms a negative pressure leakage control clearance 26 with the inner surface of the suction chamber 5 in a ring-shaped space as will be described in detail below. Further, a labyrinth portion 27 is provided in an annular shape around the periphery of the flange portion 7'.

In addition, 28 is an atmospheric chamber, and the above-mentioned flange part 7'
The air horn 1 is formed between the air horn 1 and the barrel 15.
4 through a passage 29.

The flange portion 7' is first formed by die-casting a die-cast material with a set radius R concentric with the head 8' (as shown by the dotted line in FIG. The entire diameter is machined with
Next, it is inserted into a chuck (not shown) in a predetermined position using a jig and clamped, offset by a set amount, and the radius of R' (in terms of curvature, radius R'>
R) and lower side (opposite side from air horn 14)
As shown in Figure 5, it is connected to the upper side (air horn side) to create a smooth outer shape, and the lower side has a smaller diameter by Δr (for example, 40 microns) than the conventional flange part 7 in the set state. On the upper side, the diameter is larger by Δr′ (e.g. 20 microns) and the negative pressure leakage clearance is 2.
6, as shown in Figures 3 and 5, is formed to be larger on the lower side and smaller on the upper side, so that the average clearance amount as a whole remains the same as in the conventional configuration, and a decrease in engine output is prevented. I'll keep it.

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 formed in 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 damper spring 25 is in a substantially stationary state. be.

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 is delayed from the suction hole 12 to the negative pressure chamber 13 in the suction chamber 5 due to flow resistance due to the bottleneck of the suction hole 12. As a result, suction negative pressure toward the mixing chamber 10 momentarily acts on the head 8' of the suction piston 3', causing the suction piston 3' to become unbalanced, causing the suction piston 3' to become unbalanced. is fully closed.

At the same time, the atmospheric pressure from the air horn 14 and the negative pressure of the mixing chamber 10 act in a push-pull manner on the head 8' of the suction piston 3', and as described above, the suction piston 3' As a result, since the rod 4 is supported by the rod guide 6 in a cantilever manner, the lower edge of the flange portion 7' near the bore becomes a suction chain. The negative pressure leakage control clearance 26 with respect to the inner surface of the bar 5 tends to narrow and come into contact with the inner surface of the bar 5.

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, the suction piston 3' is lifted and the bench lily portion 11 is opened.

In this process, the suction piston 3'
The suction chamber 5 on the lower side of the flange portion 7'
As mentioned above, the negative pressure leakage control clearance 26 with respect to the inner surface of the air horn 14 is set to be larger than that on the upper side, so that the suction piston 3' bends when fully closed. However, the lower edge of the flange portion 7' of the suction piston 3' on the bore 2 side does not come into contact with the inner surface of the suction chamber 5, so that the sliding condition between the two does not change to the current state when moving to lift-up. As long as the fuel is not discharged, there will be no galling or scraping, no sticking phenomena such as seizure, and the function of the variable bench lily carburetor 1' is always guaranteed.

In addition, the above-mentioned negative pressure leak control clearance 2
As for 6, since the upper side has little influence when the suction piston 3' bends downward, it may be small, and no sliding occurs.

It goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments, and are applicable not only to air damper type variable bench lily carburetors but also to oil damper type variable bench lily carburetors. be.

<Effects of the Invention> As described above, according to the present invention, in the structure of the suction piston that opens and closes the bench lily portion of the variable bench lily carburetor, the suction piston is formed integrally with the suction piston and faces the inner surface of the suction chamber. The flange portion forms a ring-shaped negative pressure leakage control clearance between the inner surface of the suction chamber, and the flange portion has a diameter smaller on the air horn side, that is, on the upper side and larger on the lower side. As a result, the negative pressure leakage control clearance makes its lower side larger than its upper side, and the total amount of negative pressure leakage control clearance becomes the set amount as in the conventional embodiment. As a result, intake manifold negative pressure is applied to the suction piston head when the throttle valve is suddenly opened from an idle state, and is not led out into the negative pressure chamber of the suction chamber through the suction hole. In a temporary delay state, the suction piston is momentarily fully closed and subjected to bending action toward the mixing chamber side, that is, the downstream side. The side bore edges have a large negative pressure leakage control clearance, so no sliding occurs, smooth lift-up, no galling, and no sticking phenomena such as seizure. The suction piston does not stop, and always operates smoothly.
Excellent effects can be achieved that allow the setting functions to be fully utilized.

Further, the negative pressure leakage control clearance can be easily achieved by offset machining or the like during lathe cutting of the flange portion, which has the advantage of not increasing costs so much.

In this way, there is the advantage that the function of the variable bench lily vaporizer can be achieved and reliability can be increased.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional variable bench lily carburetor, Fig. 2 and the following are explanatory views of one embodiment of the present invention, Fig. 2 is an overall schematic sectional view, and Fig. 3 is a rear view of a suction piston. A perspective view, FIG. 4 is a vertical sectional view of the suction piston, and FIG. 5 is a comparative front view of the diameter of the suction piston. 1'... Variable bench lily carburetor, 5... Suction chamber, 24... Metering needle, 6... Rod guide, 4... Rod, 3'... Suction piston, 26... Negative pressure leak control clearance, 7'... Flange portion.

Claims (1)

[Claims] 1. A variable bench lily is installed in a suction chamber attached to the bore of the carburetor so as to be able to move forward and backward, has a metering needle at its tip, is supported by a rod guide formed integrally with the suction chamber, and extends rearward. In the suction piston structure of the variable bench lily carburetor, the suction piston has a flange portion that forms a set amount of negative pressure leakage control clearance with respect to the inner surface of the suction chamber. The control clearance between the suction piston on the side opposite to the air horn in a horizontal position is made larger than that on the air horn side to form a flange, and the negative pressure leakage control clearance as a whole remains at the set amount. A suction piston structure of a variable bench lily carburetor characterized by: