JP2000314312A - Exhaust pipe connecting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely connect exhaust pipes firmly, and to prevent a leakage of exhaust gas from a connected part. SOLUTION: An outside diameter d1 of a first exhaust pipe 15 is larger than an inside diameter d2 of a second exhaust pipe 26 at a normal temperature. The end outer surface of the first exhaust pipe 15 is engaged with an end inner surface of the second exhaust pipe 26, by heating an end of the second exhaust pipe 26 to increase the internal diameter from d2 to d2' (such that d2'>d1>d2). After the outer surface of the engaged parts of the first and the second exhaust pipes 15, 26 is rolling caulked, when the second exhaust pipe 26 is cooled and the internal diameter is heat contracted, the initial external diameter d1 of the first exhaust pipe 15 decreases to d", and the initial internal diameter d2 of the second exhaust pipe 26 on which the first exhaust pipe 15 applies a tensile stress increases to d", thereby closely attaching the engaged parts of the first and the second exhaust pipes 15, 26, resulting in a firm connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exhaust pipe in which the inner circumference of the end of a second exhaust pipe having an inner diameter smaller than the outer diameter of the first exhaust pipe is fitted to and joined to the outer circumference of the end of the first exhaust pipe. The present invention relates to a pipe connecting structure.

[0002]

2. Description of the Related Art An exhaust gas purifying catalyst and a muffler are provided at an intermediate portion of an exhaust pipe for guiding exhaust gas of an engine.
The exhaust pipe divided into a plurality of parts needs to be connected to the inlet and the outlet of the exhaust gas purifying catalyst and the muffler. Conventionally,
Welding was commonly used to join such exhaust pipes.

On the other hand, a method of connecting an exhaust pipe without using welding has been proposed in Japanese Patent Application Laid-Open No. H11-36859. In this device, an outlet pipe and a tail tube of a muffler constituting a part of an exhaust pipe are connected by a ridge lock process while sandwiching a rear end plate.

[0004]

FIG. 7 (A)
As shown in the figure, the rear end plate 02 of the muffler 01
When the outer periphery of the end of the tail tube 04 is fitted to the inner periphery of the end of the inner pipe 03 projecting from the outer tube and joined by welding 05, the exhaust gas flowing from the muffler 01 to the tail tube 04 via the inner pipe 03 flows through the tail tube 04. Since it collides with the step 06 on the end face and disturbs the flow,
There is a problem that the exhaust resistance increases and causes a reduction in engine output and noise.

To solve such a problem, FIG.
As shown in (B), the inner periphery of the end of the tail tube 04 is fitted to the outer periphery of the end of the outlet pipe 07 protruding from the rear end plate 02 of the muffler 01, and welding 05
However, if welding 05 is to be performed, welding torch 08 needs to act on the welding portion from the rear end plate 02 side of muffler 01. Becomes difficult.

On the other hand, Japanese Unexamined Patent Publication No.
No. 9 does not cause the above problem because ridge lock processing is performed instead of welding. However, in order to prevent leakage of exhaust gas from the joint portion of the outlet pipe and the tail tube, an outlet is provided. Since a large number of annular biting grooves are formed on the outer peripheral surface of the tail tube that contacts the inner peripheral surface of the pipe, there is a problem that the number of processing steps increases and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and enables an exhaust pipe to be firmly joined without using welding, and also reliably prevents exhaust gas from leaking from a joint. It is an object of the present invention to provide a coupling structure of an exhaust pipe capable of performing the above.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, an inner diameter smaller than an outer diameter of the first exhaust pipe is provided on an outer periphery of an end of the first exhaust pipe. In the exhaust pipe coupling structure in which the inner circumference of the end of the second exhaust pipe is fitted and coupled, the inner circumference of the end of the second exhaust pipe is heated and thermally expanded. Is fitted to the outer periphery of the end of the first exhaust pipe, and the fitting portion of the first and second exhaust pipes is plastically worked and integrally connected to each other.

According to the above construction, the end of the second exhaust pipe is heated and thermally expanded, so that the inner circumference of the end of the second exhaust pipe having a small inner diameter is changed to the outer circumference of the end of the first exhaust pipe having a large outer diameter. When the end of the second exhaust pipe cools and shrinks, the fitting portions of the first and second exhaust pipes come into close contact with no gap and the leakage of exhaust gas is reliably prevented. . And first,
By plastically processing the fitting portion of the second exhaust pipe, the fitting portion can be more firmly connected and the disengagement can be reliably prevented. Thus, since the first and second exhaust pipes can be connected without using welding, not only the processing time can be shortened as compared with welding, but also deterioration of the material due to welding can be prevented.

According to the second aspect of the present invention,
In addition to the configuration of the first aspect, there is proposed an exhaust pipe coupling structure in which the first exhaust pipe is an outlet pipe protruding from an end wall of the muffler and guiding exhaust gas to the second exhaust pipe.

In order to prevent the exhaust gas flowing from the first exhaust pipe projecting from the end wall of the muffler from flowing into the second exhaust pipe from being disturbed by the step on the end face of the second exhaust pipe, the end of the first exhaust pipe is required. It is necessary to fit the inner circumference of the end of the second exhaust pipe by fitting it to the outer circumference. In this case, even if an attempt is made to join the first and second exhaust pipes by welding, the welding torch cannot act on the stepped portion of the end face of the second exhaust pipe due to interference with the end wall of the muffler. 2 It becomes difficult to weld the exhaust pipe. On the other hand, according to the above configuration, since it is not necessary to use a welding torch, even if the first exhaust pipe is an outlet pipe protruding from the end wall of the muffler, the first exhaust pipe is not obstructed by the end wall of the muffler. , A second exhaust pipe can be coupled. In addition, since the inner circumference of the end of the second exhaust pipe on the downstream side is fitted to the outer circumference of the end of the first exhaust pipe on the upstream side, the exhaust gas flowing from the first exhaust pipe side to the second exhaust pipe side is discharged from the second exhaust pipe. The flow is prevented from being disturbed by colliding with the stepped portion of the end face.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a muffler, and FIG.
FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, and FIG. 4 is an explanatory view of a process of connecting the exhaust pipe.

First, the structure of the muffler M will be described with reference to FIGS.

An outer shell of a muffler M provided in an exhaust system of an automobile engine has a shell 11 having an elliptical cross section and a caulking connection so as to close a front opening and a rear opening of the shell 11. And an elliptical front end plate 12 and a rear end plate 13. At a position eccentric from the center of the front end plate 12 and the rear end plate 13, an inlet pipe 14 and an outlet pipe 15, each of which is a short cylindrical body having a circular cross-section and integrally projecting from the plates 12, 13, are formed. The exhaust gas flows from the inlet pipe 14 into the muffler M in the direction of arrow a, and flows out of the outlet pipe 15 in the direction of arrow b. The outlet pipe 15 forms a first exhaust pipe of the present invention, and the rear end plate 13 forms an end wall of the present invention.

Inlet pipe 14 arranged coaxially
An inner pipe 1 made of a punching metal having a large number of small holes is provided on the inner periphery of the outlet pipe 15.
The outer peripheries of both ends of 6 are fitted and welded. Inner plates 17 formed in a disk shape in a state in which its has an opening 17 ₁ is fitted to the outer periphery of the inner pipe 16 are welded so as to form a gap between the inner surface of front end plate 12. Similarly, the inner plate 18 which is formed in a disk shape, with its and the opening 18 ₁ is fitted to the outer periphery of the inner pipe 16, is welded to form a gap between the inner surface of the rear end plate 13 You. Both ends of an outer pipe 19 formed in a cylindrical shape with a circular cross section by punching metal having a large number of small holes are welded to the outer periphery of the pair of inner plates 17 and 18.

The space between the front end plate 12 and the inner plate 17 is filled with an insulator 20 made of silica mat, and the space between the rear end plate 13 and the inner plate 18 is filled with an insulator 21 made of silica mat. Is done.
The outer circumference of the outer pipe 19 is made of stainless wool 2
2, and an insulator 23 made of silica mat is wound around the outer periphery of the stainless steel wool 22. The outer peripheral surface of the insulator 23 and the shell 1
A pair of spaces sandwiched between the inner peripheral surface 1 and the inner peripheral surface 1 are filled with insulators 24 and 25 made of glass wool.

A tail tube 26 constituting a second exhaust pipe of the present invention is connected to an outlet pipe 15 (first exhaust pipe) provided on the outlet side of the muffler M. Welding is not used for the connection between the outlet pipe 15 and the tail tube 26, and a connection method using both shrink fitting and caulking is adopted. Hereinafter, a processing step of connecting the outlet pipe 15 and the tail tube 26 will be described with reference to FIG.

As shown in FIG. 4A, the outer diameter d ₁ of the outlet pipe 15 is equal to that of the tail tube 26 at normal temperature.
Is formed to be larger than the inner diameter d ₂ (d ₁ >
d ₂ ) Therefore, the inner circumference of the end of the tail tube 26 cannot be fitted to the outer circumference of the end of the outlet pipe 15. When the end of the tail tube 26 is heated by a method such as high frequency heating, as shown in FIG. 4 (B), the inner diameter of the tail tube 26 is increased from d ₂ to d ₂ 'due to thermal expansion,
The inner diameter d ₂ ′ of the tail tube 26 after expansion is slightly larger than the outer diameter d ₁ of the outlet pipe 15 (d ₁
<D ₂ '). In this state, as shown in FIG.
A tail tube 2 is provided around the end of the outlet pipe 15.
6 can be fitted to the inner periphery.

Subsequently, as shown in FIG. 4D, the outer periphery of the fitting portion between the outlet pipe 15 and the tail tube 26 is rolled and caulked when the tail tube 26 is hot before it is cooled. When the tail tube 26 is cooled in this state, the inner diameter is changed from d ₂ ′ at the time of heating to d ₂ at the time of normal temperature.
₂ during the heat shrinkage process, the inner circumference of the end of the tail tube 26 closely adheres to the outer circumference of the end of the outlet pipe 15 without any gap by a strong surface pressure, and the outer diameter of the outlet pipe 15 and the inner diameter of the tail tube 26 are reduced. At this time, the outer diameter of the outlet pipe 15 that receives a compressive load from the tail tube 26 decreases from d ₁ to d ″, and the outer diameter of the tail tube 26 that receives a tensile load from the outlet pipe 15 The inner diameter increases from the initial d ₂ to d ″ (d ₁ > d ″> d ₂ ).

As described above, the outlet pipe 15 and the tail tube 26 are fitted by shrink fitting, and the fitting portion is fixed by rolling caulking, so that the outlet pipe 15 and tail tube 26 are fixed so that exhaust gas does not leak. Not only can it be tightly contacted without a gap, but also the outlet pipe 15 and the tail tube 26 can be securely prevented from coming off due to a tensile load in the axial direction, thereby enabling a firm connection without play.
Further, since the inner circumference of the end of the tail tube 26 is fitted to the outer circumference of the end of the outlet pipe 15, exhaust gas flowing from the outlet pipe 15 to the tail tube 26 does not collide with the step on the end face of the tail tube 26. In addition, it is possible to avoid an increase in exhaust gas flow resistance and contribute to an improvement in engine output and a reduction in noise.

Further, since the above-mentioned processing step does not include welding, the welding torch is used for the rear end plate 1 of the muffler M.
Not only is there no danger of workability being reduced due to interference with No. 3, but also the work time is shortened as compared to welding, which can contribute to cost reduction. Further, since the material does not deteriorate due to the heat of welding, it is not necessary to increase the thickness of the material for securing the strength, which can contribute to a reduction in weight.

In particular, when a titanium-based material is used for the exhaust pipe, not only welding is difficult, but also the springback is large, so that the plastic workability is reduced. A further weight saving is achieved by being able to be used.

Next, another embodiment of the present invention will be described with reference to FIGS. In the first embodiment, rolling caulking is employed as the plastic working after the fitting of the outlet pipe 15 and the tail tube 26. However, in the second embodiment shown in FIG. 5, the fitting of the outlet pipe 15 and the tail tube 26 is performed. In a third embodiment shown in FIG. 6, a fitting portion of the outlet pipe 15 and the tail tube 26 is pressed with a mold to form a groove. It is plastically deformed and fixed. According to the second and third embodiments, the same operation and effect as those of the first embodiment can be obtained.

Although the embodiments of the present invention have been described in detail above, various design changes can be made in the present invention without departing from the gist thereof.

For example, in the embodiment, the outlet pipe 1
Although the connection of the tail tube 5 and the tail tube 26 has been illustrated, the present invention can be applied to the connection of any other exhaust pipe of the present invention. The first and second exhaust pipes can be subjected to other arbitrary plastic processing such as ridge lock processing.

[0027]

As described above, according to the first aspect of the present invention, by heating the end of the second exhaust pipe and thermally expanding the same, the inner circumference of the end of the second exhaust pipe having a small inner diameter is reduced. Can be fitted to the outer periphery of the end of the first exhaust pipe having a large outer diameter,
When the end of the second exhaust pipe cools and shrinks, the fitting portions of the first and second exhaust pipes come into close contact with one another without any gap, and leakage of exhaust gas is reliably prevented. Then, by plastically processing the fitting portions of the first and second exhaust pipes, the fitting portions can be more firmly connected to each other, thereby securely preventing the fitting portions from coming off. Thus, since the first and second exhaust pipes can be connected without using welding, not only the processing time can be shortened as compared with welding, but also deterioration of the material due to welding can be prevented.

According to the invention described in claim 2,
Even if the first exhaust pipe is an outlet pipe protruding from the end wall of the muffler, there is no need to weld the first and second exhaust pipes, so that the welding torch interferes with the end wall of the muffler and the welding operation is hindered. Therefore, the first and second exhaust pipes can be connected without any trouble. Moreover, the first on the upstream side
Since the inner circumference of the end of the second exhaust pipe on the downstream side is fitted to the outer circumference of the end of the exhaust pipe, the exhaust gas flowing from the first exhaust pipe to the second exhaust pipe flows to the step on the end face of the second exhaust pipe. The flow is prevented from being disturbed by collision.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an automobile muffler.

FIG. 2 is a view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is an explanatory diagram of an exhaust pipe joining process.

FIG. 5 is a view showing a connection part of an exhaust pipe according to a second embodiment of the present invention.

FIG. 6 is a view showing a connection part of an exhaust pipe according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a problem of a conventional example.

[Explanation of symbols]

 M Muffler 13 Rear end plate (end wall) 15 Outlet pipe (first exhaust pipe) 26 Tail tube (second exhaust pipe)

Claims (2)

[Claims] The first exhaust pipe (15) has a first exhaust pipe (15) on its outer periphery.
An exhaust pipe coupling structure in which an inner periphery of an end of a second exhaust pipe (26) having an inner diameter (d ₂ ) smaller than an outer diameter (d ₁ ) of the exhaust pipe (15) is fitted and coupled, In a state where the end of the pipe (26) is heated and thermally expanded, the inner periphery of the end of the second exhaust pipe (26) is passed through the first exhaust pipe (1).
5) An exhaust pipe coupling structure which is fitted to the outer periphery of the end and is formed by plastically processing the coupling portions of the first and second exhaust pipes (15, 26) to be integrally coupled. 2. The second exhaust pipe (26) protruding from an end wall (13) of the muffler (M).
2. An outlet pipe for guiding exhaust gas to the exhaust pipe.
3. The exhaust pipe coupling structure according to 1.