JPS629724A - Exhaust system for internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain an exhaust pipe which is not crushed even if it is bent to a small bending diameter by setting a state that a gap between inner and outer pipes has been held by a wire gauze, filling mesh space with a fluid, executing the bending in a state that it has been solidified, and thereafter, melting and discharging it. CONSTITUTION:That which has been circularly knitted so that a difference of a recessed part 3a and a projecting part 3b of a wire gauze 3 becomes large is positioned between inner and outer pipes, and the recessed part 3a of the wire gauze 3, and the projecting part 3b are made to adhere tightly to an inner pipe outside periphery 2a and an outer pipe inside surface 2b, respectively. In a state that a gap between the inner and the outer pipes has been held by the wire gauze in this way, its mesh space is filled with a fluid, for instance, water, and in a state that it remains frozen, bending is executed. As a result, even in case of a small bending diameter, no crushing phenomenon is generated and the bending is executed easily. After the working, ice is melted and discharged. In this way, an exhaust pipe which is excellent in workability, inexpensive and light, and has performed bending to a small diameter can be obtained.

Description

[Detailed description of the invention] B. Purpose of the invention [Industrial application field] The present invention relates to an exhaust system for an internal combustion engine.

[Conventional technology]

The exhaust pipes of this type of exhaust system are hollow multi-tubes with a space between the inner and outer pipes for the purpose of suppressing the rise in surface temperature, retaining heat for exhaust gas purification, or preventing noise due to radiated sound and transmitted sound. Alternatively, multiple tubes with close contact between the inside and outside are often used.

[Problem that the invention seeks to solve]

However, in the case of hollow tubes, the gap between the inner and outer tubes must be increased in order to ensure the minimum clearance required for bending and to prevent noise caused by interference between the inner and outer tubes due to vibrations, etc. This tends to increase the size, leading to problems such as increased material costs and weight, and the inability to reduce the bending radius.

On the other hand, close-contact multiple pipes do not provide sufficient heat insulation and heat retention effects.

It is also known that a heat insulating material such as glass wool or asbestos is filled between the inner and outer tubes, but this not only increases the weight but also prevents the inner and outer tubes from being filled with the above-mentioned filler when welding the ends after bending. Welding is not possible because it interferes with the contact between the tubes or generates gas, so there are problems with strength. Another problem is that the thickness of the pipe on the side to be welded must be increased in advance.

In particular, for example, in manifolds, it is necessary to take into account interference between adjacent pipes, or bending them within a narrow space with a small radius to ensure the length of each pipe, as well as heat insulation (heat shielding) and noise. There are many problems when there is.

The present invention has been proposed in view of the above points.

Summary: Structure of the Invention [Means for Solving the Problems] The present invention provides an exhaust pipe with a multi-pipe structure, in which a wire mesh is interposed between the inner and outer pipes, and the outward protrusion of the wire mesh is connected to the inner part of the outer pipe. The same inward convex portions are brought into close contact with the outer circumferential surface of the inner tube on the circumferential surface, fluid is filled between the inner and outer tubes, the fluid is bent in a solidified state, and then the filling material is returned to a liquid state. This is an exhaust system for an internal combustion engine characterized by exhaust.

[For production]

With the above configuration, there is no sagging during bending, there is no need to make the outer tube thicker, and bending with a very small radius of a close-fitting double pipe can be achieved. The inner and outer tubes can be integrally welded to the flange or the like via a wire mesh. It is lighter than multiple pipes filled with insulation material. It has sufficient sound insulation properties due to the damper effect of the wire mesh.

〔Example〕

FIG. 1 is a sectional view showing a bent double pipe according to the present invention, in which 1 is an outer pipe, 2 is an inner pipe, and 3 is a wire mesh interposed therebetween.

The wire mesh 3 is circular knitted with a large difference between the concave portions 3a and the convex portions 3b, and is placed between the inner and outer tubes as shown in Fig. 2, and the concave portions 3
a to the outer circumference 2a of the inner tube, and the convex portion 3b to the inner surface 1a of the outer tube. Alternatively, as shown in FIG. 3, a flat knitted material 3C with a small difference in the uneven portions may be formed into a wavy shape 3d. Furthermore, it can also be knitted on the outer surface of the inner tube.

When the gap between the inner and outer tubes is maintained by a wire mesh as described above, and the mesh space is filled with a fluid such as water and then bent, the collapse phenomenon will not occur even with a small bending radius R. easily obtained. After processing, the water is dissolved and discharged.

FIG. 4 shows an example of a manifold to which the present invention is applied, and shows that it is possible to bend small diameters such as parts A and B.

For example, when the flange 4 is welded to the tube end as shown in FIG. 5(a), the inner tube 2 is also welded together through the wire mesh 3. In addition, as shown in FIG. 4(b), the 7 langes 4, the outer tube 1, the wire mesh 3, and the inner tube 2 are welded together at the same time.

C1 Effects of the Invention Due to the above structure, excellent workability can be obtained at low cost and low weight. In particular, it is characterized in that it has a small outer diameter and can be bent to a small diameter.

Although its insulation properties are slightly inferior to hollow double pipes or double pipes filled with insulation material, it has considerable heat insulation properties, and has a sound insulation effect due to the damping effect of the wire mesh.

Moreover, it is easy to weld and is strong. .

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an exhaust pipe made by bending a double pipe according to the present invention, Fig. 2 is an enlarged cross-sectional view thereof, Fig. 3 is a cross-sectional view of a wire mesh with a large difference in wave unevenness, FIG. 4 is a view from M of the manifold (7) to which the present invention is applied, and FIG. 5 is an enlarged vertical sectional view of the flange portion. 1 is an outer tube, 2 is an inner tube, 3 is a wire mesh, 3a is a concave part, and 3b is a convex part.

Claims (1)

[Claims] (1) In an exhaust pipe with a multi-tube configuration, a wire mesh is interposed between the inner and outer pipes, and the outward protrusions of the wire mesh are placed on the inner circumferential surface of the outer pipe, and the inward protrusions are placed on the outer circumferential surface of the inner tube. An exhaust system for an internal combustion engine, characterized in that the inner and outer tubes are brought into substantially close contact with each other, fluid is filled between the inner and outer tubes, the fluid is bent in a solidified state, and the filling material is returned to a liquid state and discharged.