JP2001317350A - Double pipe for vehicle exhaust system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double pipe for a vehicle exhaust system having an excellent heat insulating property and a sound isolating property, a small reduction in exhaust gas temperature, and high productivity at a low cost. SOLUTION: A multi-layer pipe or an interlock pipe made of a very flexible and easily bent SUS material and having an irregular outer shape is employed as the inner pipe of the double pipe. The inner pipe is inserted and coupled after an outer pipe is bent, or the inner pipe is inserted and coupled into the straight outer pipe, then the outer pipe is bent by the normal method.

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 double pipe for a vehicle exhaust system used for an exhaust system of an automobile, and more particularly, to a heat shield,
The present invention relates to an inexpensive double-pipe structure excellent in sound insulation and prevention of exhaust gas temperature drop.

[0002]

2. Description of the Related Art Combustion gas from a vehicle engine is connected from an exhaust manifold to a catalytic converter and a muffler through an exhaust pipe, and is discharged from the tail pipe of the muffler to the atmosphere. Recently, due to environmental issues, lower emission of exhaust gas has been required, and it is necessary to increase the catalytic efficiency of catalytic converters.Various catalysts have been studied and developed, but it is also clear that the temperature of exhaust gas passing through the catalyst has a great effect. Become
The higher the exhaust gas temperature, the more catalytic activity, and it has become necessary to prevent the exhaust gas temperature coming out of the exhaust manifold from being lowered by the exhaust pipe. Therefore, an exhaust pipe having a double structure consisting of an outer pipe and an inner pipe has been used. However, since the distance from the vehicle engine to the soundproofing device is long and has a complicated shape, the exhaust pipe has a complicated bending. Processing is required. However, when bending a conventional double pipe consisting of an outer pipe and an inner pipe, a predetermined space is opened in the straight outer pipe and the straight inner pipe is inserted and fitted. In order to make the inner tube follow the outer tube, the outer tube and the tip of the inner tube are joined by welding or the like.Furthermore, lead or a low melting point alloy is melted between the outer tube and the inner tube, or water is filled. Since it has been bent with a rotary bender and the filler has been eluted afterwards, special equipment for filling and eluting the filler is required, and the bending cost is only expensive. In addition, it was difficult to fill and bend with good concentricity between the outer pipe and the inner pipe, and the working environment was not good. On the other hand, if the contact area between the outer pipe and the inner pipe is increased to improve the bending workability, the heat transfer from the contact section lowers the exhaust gas temperature, and there is a technical problem that the heat insulation and sound insulation effects are not recognized. there were.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inexpensive exhaust pipe having excellent heat insulation and sound insulation, a small decrease in exhaust gas temperature and good bending workability.

[0004]

A multi-layer pipe or an interlock pipe made of a SUS material having a highly flexible and easily bendable outer shape having a concave-convex shape is adopted for the inner pipe, which is capable of withstanding the temperature of the exhaust gas of a vehicle, and is made of SUS. The outer tube made of a material is subjected to a predetermined bending process or the like by a pipe bender or the like, and then the inner tube is inserted and fitted. According to such a method, the outer shape of the inner tube is inserted while sliding on the inner side of the outer tube. However, since the inner tube is formed of a multilayer tube or an interlock tube whose outer shape has an uneven shape, the outer shape is Since it only makes partial contact with the inner periphery of the pipe, it is possible to reduce the temperature decrease of the exhaust gas. Also, since the inner tube is highly flexible, if the inner tube is inserted and fitted into a straight outer tube and the outer tube is bent by a normal method, the inner tube also bends following the inner periphery of the outer tube. Will be. In this case, the bent portion only needs to be the above-mentioned inner tube having high flexibility, and the straight portion of the inner tube uses a normal SUS pipe, and the multilayer tube or the interlock tube is joined to a portion corresponding to the bent portion. You may. Here, the multilayer pipe is a spiral pipe formed by continuously forming corrugated strips as shown in FIG.
A spiral bellows tube (FIG. 4) obtained by winding up into four layers (FIG. 3) has a very flexible structure. Also, the exhaust noise reduction effect is high due to the multilayer structure. The interlock tube refers to a tube in which a member having a hook-shaped cross section is partially overlapped with an adjacent hook-like portion, and is configured to be helically expandable and contractible in the winding axis direction.

[0005]

FIG. 1 shows a case where an outer tube 1 is bent by a pipe bender and then an inner tube 2 made of a multilayer tube is inserted. Since the multilayer tube 2 has flexibility in the direction of expansion and contraction and the direction of bending, it is fitted while being in partial contact with the convex portion along the inner periphery of the outer tube. FIG. 2 shows a case where the interlock tube 11 is inserted and fitted to the inner periphery of the outer tube 10. Also in this case, the interlock tube has flexibility in the direction of expansion and contraction and in the bending direction similarly to the multilayer tube, so that it can be easily inserted even after being bent into the outer tube. Further, a double pipe in which an inner pipe joined with a normal SUS pipe is inserted into an outer pipe and fitted to an outer pipe so as to be bent so that the multilayer pipe or the interlock pipe is arranged at least at the bent portion. Is also possible.

[0006]

As described above, according to the present invention, even a vehicle system double pipe having a complicated bending shape can be easily obtained, and the outer pipe and the inner pipe are partially in contact with each other. Since most of the space is occupied by the space, the temperature reduction of the exhaust gas can be kept small by the heat insulating effect. In addition, there is no need for a conventional filler at the time of bending, and the productivity is high and the cost is low.

[Brief description of the drawings]

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

FIG. 2 shows a perspective view of a corrugated strip for making a multilayer tube.

FIG. 3 shows a state in which a corrugated strip is spirally superposed in multiple layers.

FIG. 4 shows the appearance of an inner tube composed of a multilayer tube.

FIG. 5 is a sectional view of an embodiment of the invention described in claim 2;

[Explanation of symbols]

 1, 10 ... Outer tube 2 ... Inner tube made of multilayer tube 3 ... Corrugated strip 11 ... Inner tube made of interlock tube

Claims (2)

[Claims] 1. A vehicle exhaust system comprising a vehicle exhaust system double pipe comprising an outer pipe and an inner pipe, wherein at least a bent portion of the inner pipe is a flexible multi-layer pipe having an irregular outer shape. Double tube. 2. A vehicle exhaust system double pipe comprising an outer pipe and an inner pipe, wherein at least a bent portion of the inner pipe is an interlock pipe.