JP2002235538A - Flexible tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent stress concentration while ensuring the flexibility of the whole flexible tube for an exhaust pipe. SOLUTION: The flexible tube 10 has an inner tube 15 and an outer tube 16, cylindrical parts 11 for inserting the exhaust pipe 1 are formed in both end parts, and a section between both cylindrical parts is a bellows part 12 formed like bellows. A cover 3 surrounding them and made of a wire netting is connected with the exhaust pipe to form an exhaust pipe joint. The whole length of the flexible tube is divided into a central part A and end side parts B on both sides, and a reinforcing tube 17 is nipped between the inner tube and the outer tube in the end side parts B. Consequently, the end side part has a three layer structure, the rigidity is increased, stress is flattened, and fatigue strength is improved. Since the central part has two layers, high flexibility is kept, and the thermal insulation effect is obtained by an air layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a flexible tube which is inserted in the middle of an exhaust pipe of a vehicle and suppresses transmission of engine-side vibration to a downstream exhaust pipe.

[0002]

2. Description of the Related Art A flexible tube is used as a main part of a vibration-absorbing exhaust pipe joint as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-326531. That is, as shown in FIG. 5, the end of the wire mesh cover 3 covering the entire flexible tube 50 and the end of the protector 5 are aligned with the end of the flexible tube 50 and covered, and the end of the protector 5 and the flexible tube 50 and the end of the cover 3 are spot-welded.
It is fixed by welding.

The flexible tube 50 is intended to cut off vibration from the engine side by flexing flexibly while preventing exhaust leakage, and is formed in a bellows shape so as to be expandable and contractible. The cover 3 prevents the flexible tube from being damaged by foreign matter. However, since the exhaust gas flows through the inside of the flexible tube 50, the flexible tube 50 is exposed to a high temperature, and is exposed to salt as a snow removing agent sprayed on the road through the mesh of the cover 3, so that the flexible tube 50 is in an environment that is easily corroded.

[0004] If the flexible tube 50 is made of a material having high durability in such an environment, the cost is remarkably increased. Therefore, in order to reduce the cost and further increase the flexibility, the flexible tube 50 is connected to the inner tube 52 and the outer tube. Tube 53
Has been performed. In the drawing, the inner tube 52 and the outer tube 53 are shown separated from each other for easy understanding of the structure.

[0005]

When such a flexible tube 50 is attached to an exhaust pipe and receives a shearing load while the vehicle is running, it deforms as shown in FIG. 6 (a). That is, the flexible tube 5
Although the amount of deformation in the central portion A of 0 is small, the amount of deformation in the vicinity B at both ends is large. For this reason, as shown in (b), there is a problem that stress concentration occurs at both end portions of the flexible tube 50, and the fatigue strength of the portion is reduced.

As a countermeasure against this, if the plate pressure of the inner tube 52 or the outer tube 53 is increased, the flexibility of the flexible tube is lost, and the weight and cost are increased. Accordingly, an object of the present invention is to provide a flexible tube for an exhaust pipe of a vehicle in which stress concentration is prevented while securing overall flexibility.

[0007]

For this reason, the present invention of claim 1 is a stretchable flexible tube formed by stacking at least two layers of tubes in a bellows shape, wherein Reinforcing members for increasing the rigidity at both ends are provided between the two-layer pipes. The rigidity of the end where the stress tends to concentrate is increased, and the stress is flattened.

According to a second aspect of the present invention, the reinforcing member is a reinforcing pipe sandwiched between predetermined regions on both ends of a two-layer pipe. The rigidity of the portion sandwiching the reinforcing pipe is improved.

Further, the invention according to claim 3 uses an intermediate pipe sandwiched over the entire length of a two-layer pipe as a reinforcing member, and the intermediate pipes are densely packed in a central portion, and the density gradually decreases toward both ends. It had a small hole arranged so that it might become. The rigidity is low at the central part where the small holes are dense, and the rigidity is improved at the part where the small holes are rough on both sides.

[0010] The invention of claim 4 is the invention of claim 1, 2 or 3.
An exhaust pipe joint in which a cylindrical portion is formed at both ends of the flexible tube described above, the cylindrical portion is covered on the exhaust pipe, and the end of the cover covering the flexible tube is welded to the exhaust pipe together with the end of the cylindrical portion. is there.

[0011]

Embodiments of the present invention will be described below with reference to examples. FIG. 1 is a sectional view showing a first embodiment applied to an exhaust pipe joint. Flexible tube 10
Has an inner pipe 15 and an outer pipe 16, and a cylindrical portion 11 for inserting the exhaust pipe 1 is formed at each end portion.
A bellows portion 12 formed in a bellows shape is formed between the bellows 1 and 11. The total length of the flexible tube 10 is the cylindrical portion 1
1 and approximately 3 equally divided into a central portion A and end portions B on both sides thereof. A reinforcing tube 17 is sandwiched between the inner tube 15 and the outer tube 16 at each end portion B. I have. Thus, the end portion B is a three-layer tube, and the center portion A is a two-layer tube. In the center portion A, the two-layer portion is formed such that the inner tube 15 is in close contact with the outer tube 16.

The production of the flexible tube 10 is as follows.
As shown in FIG. 2, a material pipe 20 in which a reinforcing pipe 27 is inserted into a portion corresponding to an end portion B in a two-layer pipe in which an inner straight pipe 25 and an outer straight pipe 26 having the same length are stacked, respectively. By performing bulging by injecting a liquid pressure from the inside into the material tube 20, the flexible tube 1 shown in FIG.
0 is obtained.

This flexible tube is spot-welded together with a cover 3 made of wire mesh and a protector 5 to form a vibration-absorbing exhaust pipe joint, as shown in FIG.

Thus, in this embodiment, the inner tube 15, the outer tube 16 and the reinforcing tube 17 are located near the end (end side B) of the flexible tube where a large stress has conventionally occurred when a shear load is applied. Since it has a layer structure and rigidity increases,
The stress is flattened at each portion in the longitudinal direction, and the fatigue strength against repeated shear loads is improved. On the other hand, since the central portion A is only the inner tube 15 and the outer tube 16, the flexibility of the flexible tube 10 as a whole is kept high.

FIG. 3 is a view showing a flexible tube according to a second embodiment. Flexible tube 30
Is the intermediate pipe 3 between the inner pipe 15 and the outer pipe 16 over the entire length.
7 are sandwiched to form a three-layer tube. A cylindrical portion 31 for inserting the exhaust pipe 1 is formed at each of both ends, and a bellows portion 32 formed in a bellows shape is formed between the cylindrical portions 31. The intermediate pipe 37 is provided with a large number of small holes 38, and the small holes 38 are densely packed in a central portion in the longitudinal direction of the intermediate pipe 37 so that the density gradually decreases toward the cylindrical portions 31 at both ends. Are located. No small holes are provided in the cylindrical portion 31.

The material tube 4 of the flexible tube 30
0, the inner straight pipes 25 of the same length as shown in FIG.
And an outer straight pipe 26, and an intermediate straight pipe 47 provided with the small hole 38 therebetween. This material tube 40
The flexible tube 30 shown in FIG. Although not particularly shown, the flexible tube 30 is incorporated in the exhaust pipe joint as in the previous embodiment.

According to this embodiment, the center of the flexible tube 30 is provided with small holes 38 densely in the intermediate tube 37 to ensure flexibility, and the small holes 3 near the ends.
8 with a substantial three-layer structure and increased rigidity,
Since the stress is flattened at each portion in the longitudinal direction, the fatigue strength against repeated shear loads is improved. Also,
In the central part, the inner pipe 15 and the outer pipe 16 in a number of small holes 38
A heat insulating effect is obtained by the air layer between them.

Each of the embodiments is basically based on a two-layered pipe composed of an inner pipe 15 and an outer pipe 16, and finally has a three-layered flexible structure with a reinforcing pipe 17 and an intermediate pipe 37 interposed therebetween. Although the present invention is not limited to this, the present invention is not limited to this. For example, the second layer and / or the third layer of the flexible tube having a total of four layers may be an intermediate pipe having small holes, or the second layer and the fourth layer of the total five layers may be formed. The layer can be a reinforcing tube or an intermediate tube with small holes.

Further, in the second embodiment, the shape of the small hole 38 of the intermediate pipe 37 is circular.
It can be any other shape. Further, the arrangement of the small holes 38 may be such that the density is continuously changed from the central portion to the cylindrical portion, or the small holes may be divided into a plurality of regions and the density of the small holes may be changed for each division.

[0020]

As described above, according to the present invention, in a stretchable flexible tube formed by stacking at least two layers of tubes in a bellows shape, a reinforcing member for increasing rigidity at both ends with respect to a center portion is provided. Since it is provided between the two layers of pipes, the rigidity at the end where stress tends to concentrate is increased, and the stress is flattened. This has the effect that the fatigue strength is improved by the minimum necessary reinforcing members while securing the flexibility of the flexible tube as a whole while leaving the central portion in two layers.

In particular, by sandwiching the reinforcing pipes at predetermined regions on both ends of a two-layer pipe as a reinforcing member, the structure is simple and the manufacturing is made at low cost.

Also, an intermediate pipe having a large number of small holes is sandwiched as a reinforcing member over the entire length of the two-layer pipe, and the small holes are densely packed in the center portion so that the density gradually becomes coarser toward both ends. In this case, the rigidity of the end where the stress tends to concentrate is increased, and the stress is flattened. Further, the central portion secures flexibility by dense small holes, and a heat insulating effect is obtained by the air layer of the small holes.

In addition, a cylindrical portion is formed at both ends of any of the flexible tubes, and the cylindrical portion is covered with the exhaust pipe.
Further, by welding the end of the cover covering the flexible tube and the end of the cylindrical portion to the exhaust pipe, a vibration absorbing type exhaust pipe joint having flexibility and high fatigue strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a view showing a material tube for producing a flexible tube.

FIG. 3 is a view showing a flexible tube according to a second embodiment.

FIG. 4 is a view showing a material tube for producing a flexible tube according to a second embodiment.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram showing a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust pipe 3 Cover 5 Protector 10, 30 Flexible tube 11, 31 Cylindrical part 12, 32 Bellows part 15 Inner pipe 16 Outer pipe 17 Reinforcement pipe 20, 40 Material pipe 25 Inner straight pipe 26 Outer straight pipe 27 Reinforcement pipe 37 Intermediate pipe 38 Small hole 47 Middle straight pipe

Continued on front page F term (reference) 3G004 AA01 BA04 DA01 DA14 EA03 GA06 3H104 JA07 JB02 JC04 JC08 JD03 LB05 LB38 LC04 LC05 LC08 LC15 LD02 LD06 3H111 AA03 BA01 CA47 CB03 CB04 CB24 CB28 CC17 DA15 DA26 DB11 DB20

Claims (4)

[Claims] An elastic flexible tube (10, 30) formed by stacking at least two layers of tubes (15, 16) in a bellows shape, wherein the flexible tube (10, 30) is located at both ends with respect to a central portion in the longitudinal direction. Reinforcing members for increasing rigidity (17, 37)
Is provided between the two-layer pipes. 2. The method according to claim 1, wherein the reinforcing member is formed of the two-layer pipe (15, 1).
The flexible tube according to claim 1, characterized in that it is a reinforcing tube (17) sandwiched between predetermined regions on both end sides of (6). 3. The method according to claim 1, wherein the reinforcing member comprises a tube (15,
16) an intermediate tube (37) sandwiched over the entire length of
2. The flexible pipe according to claim 1, wherein the intermediate pipe has a large number of small holes arranged in a central portion, and the small holes are arranged so that the density gradually decreases toward both ends. tube. 4. A flexible tube (10, 30) according to claim 1, 2 or 3, wherein cylindrical portions (11, 3) are provided at both ends.
1) is formed and the cylindrical portion is put on the exhaust pipe (1), and the cover (3) covering the flexible tube is welded to the exhaust pipe at the end thereof together with the end of the cylindrical portion. Features exhaust pipe fittings.