JPH01250691A - Duct structure - Google Patents

Abstract

PURPOSE:To prevent the lowering of efficiency of filling intake air in a combustion chamber by forming a duct to be substantially elliptical in section by rubber or synthetic resin, and forming a pair of confronting projection-like support portions on the opposite inner surfaces of the duct which have large radius of curvature. CONSTITUTION:An intake duct 11 made of rubber or synthetic resin is bent and substantially elliptical in cross-section. A pair of projection-like support portions 13, 14 are integrally formed substantially in the center of opposite upper and lower inner surfaces 11a, 11b of a bent portion 12, that have large radius of curvature. The projection-like support portions 13, 14 are plate-like and the respective forward end portions 13a, 14a thereof are confronted with each other at a designated space S therebetween. One of the forward end portions is recessed and the other thereof is projected. Accordingly, deformation of the duct is regulated by the forward end portions so as to ensure a satisfactory sectional area of a passage for intake air.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a duct structure used, for example, in an intake system of an internal combustion engine for an automobile.

As is well known in the art, in an internal combustion engine for an automobile, an air intake duct 3 integrally formed of rubber or synthetic resin is provided between an engine body 1 and an air cleaner 2, as shown in FIG. It is arranged.

By the way, this intake duct 3 is likely to be crushed inward and deformed because a large suction negative pressure is generated inside the intake duct 3 during engine operation. Therefore, the flow resistance of the intake air increases (and the efficiency of filling the intake air into the combustion chamber decreases).

Therefore, in the conventional intake duct structure, for example, as shown in FIG.
Efforts have been made to increase the rigidity and prevent easy crushing and deformation (see, for example, Japanese Utility Model Application Publication No. 62-69695).
.

On the other hand, as another crushing deformation prevention means, for example, as shown in FIG. 5, a spiral coil spring 5 is attached to the inner peripheral surface 3b of the intake duct 3 to increase the rigidity of the intake duct 3. are also provided.

However, the former intake duct structure described above is a problem to be solved by the invention.
Since the protrusions 4 are simply formed on the outer circumferential surface 3a, a sufficient soaking prevention effect cannot necessarily be obtained, and the quality of the appearance also deteriorates.

In addition, in the latter conventional example, the installation work of the coil spring 5 into the intake duct 3 is complicated, and
There is a problem that the coil spring 5 must be manufactured separately from the coil spring 5, which deteriorates manufacturing workability.

Means for Solving the Problems The present invention was devised in view of the problems of the conventional duct structure described above. It is characterized in that a pair of protruding support portions are formed on opposing inner surfaces having a large radius, with both tip portions facing each other with a certain gap spaced between them.

According to the present invention having the above configuration, when the opposing portions of the duct with a large radius of curvature are immersed inward and deformed by a predetermined amount due to the large suction negative pressure generated in the duct, for example, the tips of the surface support portions are moved against each other. This contact prevents further crushing and deformation.

EXAMPLES Hereinafter, examples of the present invention will be described in detail based on the drawings. still,
The following embodiment shows a case where the present invention is applied to an intake duct of an internal combustion engine, similar to the above-mentioned conventional example.

FIGS. 1A and 1B show a first embodiment of the present invention. That is, the intake duct 11 made of rubber or synthetic resin is three-dimensionally bent as a whole, and has a substantially elliptical cross section extending from side to side, and is approximately midway in the longitudinal direction. A pair of protruding support portions 13 and 14 are integrally formed on the upper and lower opposing inner surfaces 11a and 11b of the bending portion 12 having a large radius of curvature. This surface support part 1
3° 14 is formed into an elongated plate shape bent along the axial direction of the bent portion 12, and the tip portions 13a of each other
, 14a face each other with a predetermined gap S therebetween. Also,
The upper tip 13a has a concave edge, while the lower tip 14a has a convex edge.

Therefore, according to the intake duct 11 of this embodiment, when large negative suction pressure is generated in the intake duct 11 during low engine load, etc., the left and right portions 15 and 16, which have high rigidity, do not collapse and deform, but the radius of curvature When the large upper and lower parts of
, 14a come into contact with the concave-convex fitted state, and prevent further inward deformation. Therefore, a sufficient cross-sectional area of the passage of the intake duct 1-11 is ensured, and an amount of intake air corresponding to the amount required by the engine can be supplied to the combustion chamber.

Moreover, due to the contact of the surface supports 13.14,
The intake air is on both sides 13b of the support part 13.14.

Since the air is smoothly guided in the downstream direction along the bending portion 14b, intake air drift at the bent portion 12 is prevented, and rapid flow is achieved through effective rectification.

In addition, when the suction negative pressure in the intake duct becomes relatively small, such as when the engine is under medium or high load, the tips 13a and 14a of both the support parts 13 and 14 are separated by reaction force, forming a gap S. Inside, there is a single, large passageway with a large cross-sectional area. Therefore, intake resistance is sufficiently reduced and a large intake flow rate can be ensured. As a result, the filling efficiency of intake air is improved, and the output can be improved.

FIGS. 2(A) and 2(B) show a second embodiment of the present invention,
In this embodiment, a pair of upper and lower support portions 1 are provided on both sides of the bent portion 12 of the intake duct 11 on the upper and lower opposing inner surfaces 11a and llb.
3, 14, 13.14 are integrally formed. Therefore, reliable contact between the upper and lower support parts 13, 14, 13.14 can be obtained, and crushing deformation can be more reliably prevented.

In addition, the rectifying action of intake air becomes more effective. Note that the other configurations are the same as in the first embodiment.

Further, in each of the above embodiments, the tip portion 1 of each support portion 13.14 is
Since 3a and 14a are formed in an uneven shape, reliable contact positioning can be obtained. Furthermore, since nothing is formed on the outer peripheral surface of the intake duct 11,
The quality of the appearance is improved.

In each of the above embodiments, each of the support parts 13 and 14 is formed at one location of the bent part I2 and is elongated (formed) along the axial direction, but is not limited to this, and can be formed at a straight part as appropriate. In addition, it is also possible to form a short protrusion.

Furthermore, the present invention is not limited to intake ducts, but can also be applied to ducts that communicate with other equipment.

Effects of the Invention As is clear from the above explanation, according to the duct structure according to the present invention, when a portion of the intake duct with a large radius of curvature deforms slightly inward by a predetermined amount, the tips of both support portions deform. Contact directly and reliably restricts further deformation. Therefore, a sufficient passage cross-sectional area of the intake duct can be ensured.

In addition, there is no need to install a coil spring inside the intake duct or manufacture it separately as in the past, and each support part can be formed integrally when molding the intake duct, so the complicated installation work can be completely eliminated. Work becomes extremely easy. Further, since the outer circumferential surface of the duct does not have any irregularities, the appearance quality is good.

[Brief explanation of the drawing]

FIG. 1(A) is a perspective view of an intake duct showing a first embodiment of the duct structure according to the present invention, and FIG. 1(B) is an I of FIG. 1(A).
- 1 line sectional view, Figure 2 (A) is a perspective view of an intake duct showing the second embodiment of the present invention, Figure 2 (B) is a -
■ Line sectional view, Figure 3 is a schematic diagram showing the intake system of an internal combustion engine,
Figure 4 is a partially enlarged perspective view showing the conventional duct structure;
The figure is a partially enlarged sectional view showing the other side of the conventional device. 11...Intake duct, lla, llb...Opposing inner surface, 13.14-...Support part, 13a, 14a-...
Tip, S... gap. Figure 1 (A) Figure 2 (A) Figure 3 Figure 5

Claims (1)

[Claims] (1) A duct made of rubber or synthetic resin is formed to have a substantially elliptical cross section, and a pair of protruding support portions are formed on opposing inner surfaces of the duct with a large radius of curvature, with both ends facing each other with a certain gap in between. The duct structure is characterized by: