JP4416929B2 - Silencer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silencer connected to an exhaust system during an internal combustion period, and more particularly to a silencer having a tail portion of a double pipe structure.
[0002]
[Prior art]
The silencer is provided with a tail portion protruding rearward of the silencer body to enhance the silencing effect. Some of the tail portions have a double pipe structure in order to further enhance the noise reduction effect and improve the appearance. In the tail part of the conventional double pipe structure, as shown in FIGS. 4A and 4B, the outer peripheral edges of the outer pipe 1 and the inner pipe 2 are welded. More specifically, in the structure of FIG. 4A, the outer pipe 1 is wound so that the peripheral edge of the outer end of the outer pipe 1 protrudes radially inward to form a curled portion 1a. It welds in the state contact | abutted by the inner periphery of the curl part 1a. In the structure of FIG. 4B, a curled portion 2a is formed by winding the inner pipe 2 so that the rear end periphery of the inner pipe 2 protrudes radially outward, and the rear end periphery of the outer pipe 1 is the curl portion 2a. It is welded in a state of being abutted against the outer periphery.
[0003]
[Problems to be solved by the invention]
In the connection structure shown in FIG. 4A, workability is poor because welding is performed from the inside of the pipes 1 and 2 with the pipes 1 and 2 being abutted against each other. Also, the appearance was bad because of the weld bead. The connection structure shown in FIG. 4B is disadvantageous in terms of cost because it is buffed after welding. Furthermore, as a common drawback of the above two connection structures, the difference in thermal expansion between the pipes 1 and 2 cannot be absorbed. Therefore, it was necessary to prevent the occurrence of cracks.
[0004]
[Means for Solving the Problems]
A first aspect of the present invention is a silencer comprising a silencer body and a tail portion of a double pipe structure that protrudes rearward from the silencer body and has an outer pipe and an inner pipe.
A first curled portion is formed around the rear end periphery of the outer pipe so as to project radially inward, and is wound around the rear end periphery of the inner pipe so as to project radially outward. A second curl portion is formed, the second curl portion is positioned closer to the silencer body side than the first curl portion, the rear surface of the second curl portion is applied to the first curl portion, and the outer peripheral surface of the second curl portion Is applied to the inner peripheral surface of the outer pipe, and the rear end of the inner pipe is supported by the rear end of the outer pipe only by these abutments.
[0005]
According to a second aspect of the present invention, in the silencer of the first aspect, an annular groove is formed between the first and second curl portions.
[0006]
According to a third aspect of the present invention, in the silencer of the first aspect, the silencer body includes a cylindrical casing and a silencer pipe that is coaxially disposed inside and passes exhaust gas, The cavity between the muffler pipe and the inner passage of the muffler pipe are connected through a large number of small holes formed in the muffler pipe,
The rear end periphery of the casing and the front end periphery of the outer pipe are welded to form an outer assembly, and the rear end periphery of the muffler pipe and the front end periphery of the inner pipe are welded to form an inner assembly. The front end periphery of the silencer pipe is welded, and the inner assembly is supported by the welded portion and the abutting portions of the first and second curl portions in a spanned state on the outer assembly. .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the silencer which makes one Embodiment of this invention is demonstrated with reference to FIGS. 1-3. As shown in FIG. 1, the silencer includes a silencer body 10 and a tail portion 20 that protrudes rearward from the silencer body 10.
[0008]
The silencer main body 10 includes a cylindrical casing 11 and a silencer pipe 12 arranged coaxially in the casing 11. The front end periphery of the casing 11 is reduced in diameter and welded to the front end periphery of the muffler pipe 12. This weld is indicated by 5 in the figure. A cavity 13 is formed between the casing 11 and the muffler pipe 12. The muffler pipe 12 has a large number of small holes 12a and 12b in regions separated from each other in the front-rear direction. The front small hole 12 a is released, and the rear small hole 12 b is covered with the sound absorbing material 14. The internal passage of the muffler pipe 12 communicates with the cavity 13 through these small holes 12a and 12b.
[0009]
The tail portion 20 includes an outer pipe 21 and an inner pipe 22 that are coaxial, and has a double pipe structure. The outer pipe 21 has a cylindrical shape with the same diameter over the entire length. The inner pipe 22 has a funnel shape in which the shape extends from the front end to the middle portion, and the middle portion to the rear end has a cylindrical shape having the same diameter. The front end periphery of the outer pipe 21 is welded to the rear end periphery of the casing 11 whose diameter has been reduced. This weld is indicated by reference numeral 6 in FIG. The front end periphery of the inner pipe 22 is welded to the rear end periphery of the muffler pipe 12. This weld is indicated by reference numeral 7 in FIG.
[0010]
2 and 3, the rear end peripheral edge of the outer pipe 21 is wound so as to project radially inward, whereby a curled portion 21a (first curled portion) having a substantially circular cross section. ) Is formed. Further, the peripheral edge of the rear end of the inner pipe 22 is wound so as to project outward in the radial direction, whereby a curled portion 22a (second curled portion) having a substantially circular cross section is formed. The curled portion 22a is disposed closer to the silencer body 10 than the curled portion 21a. Thus, the curled portions 21 a and 22 a are covered with the peripheral wall of the outer pipe 21.
[0011]
The rear surface of the curled portion 22 a of the inner pipe 22 is in contact with the curled portion 21 a of the outer pipe 21, and the outer peripheral surface of the curled portion 22 a is in contact with the inner peripheral surface of the peripheral wall of the outer pipe 21. Thereby, the rear end of the inner pipe 22 is stably supported by the rear end of the outer pipe 21 without rattling. The contact portions of the curled portions 21a and 22a are denoted by reference numeral 8 in FIGS. The peripheral edges of the rear ends of the pipes 21 and 22 are merely brought into contact with each other and are not welded. An annular groove 25 is formed between the curled portions 21a and 22a on the inner peripheral side thereof.
[0012]
The casing 10 and the outer pipe 21 are connected by the welded portion 6 to constitute an outer assembly 31 that is integrated. Further, the muffler pipe 12 and the inner pipe 22 are connected by the welded portion 7 to constitute an integral inner assembly 32. Both ends of the inner assembly 32 are supported by both ends of the outer assembly 32 that is coaxial with the welded portion 5 and the contact portion 8, and are thus supported in a spanned state.
[0013]
In the above configuration, the exhaust gas from the engine diffuses from the small hole 12b on the front side of the muffler pipe 12 to the cavity 13, returns to the small hole 12b through the sound absorbing material 15, and the exhaust sound is silenced in this process. The tail portion 20 having a double pipe structure further enhances the silencing effect.
[0014]
An annular groove 25 is formed between the curled portions 21a and 22a, and the exhaust flow is disturbed by the groove 25, so that exhaust airflow noise can be reduced.
[0015]
The peripheral edges of the rear ends of the pipes 21 and 22 are merely linked by contact of the curled portions 21a and 22a, and there is no need for welding, so that the assembly work of the silencer can be simplified, and the welded portion It is possible to omit the step of polishing the substrate, which is advantageous in terms of cost. Furthermore, since there is no weld bead, the appearance is good.
[0016]
The inner pipe 22 and the outer pipe 21 have different amounts of thermal expansion due to the temperature difference. In particular, when exhaust gas is discharged, the amount of thermal expansion of the inner pipe 22 is larger than the amount of thermal expansion of the outer pipe 21. In this case, the curled portion 22a strongly presses the curled portion 21a, so that both are elastic. It deforms and absorbs the difference in thermal expansion. When both pipes 21 and 22 are at room temperature, the elastic deformation of the curled portions 21a and 22a is almost eliminated. The curled portion 22a of the inner pipe 22 slides in the axial direction on the inner peripheral surface of the outer pipe 21 with these temperature changes.
As described above, since the difference in thermal expansion of the pipe is absorbed, a large thermal stress is not applied to the pipes 21 and 22, and cracks and the like can be prevented.
[0017]
In this embodiment, since the inner assembly 32 is connected to the outer assembly 31 only at both ends, the thermal expansion difference between the muffler pipe 12 and the casing 11 is also absorbed by the contact portion 8. Can do.
[0018]
【The invention's effect】
As described above, according to the first aspect of the present invention, the outer pipe and the inner pipe are merely linked by the contact of the first and second curled portions, and there is no need for welding. The assembly work of the silencer can be simplified, and the process of polishing the welded portion can be omitted, which is advantageous in terms of cost. Furthermore, since there is no weld bead, the appearance is good. In addition, since the difference in thermal expansion between the outer pipe and the inner pipe can also be absorbed by these curled portions, the possibility of cracking in the pipe or the like due to thermal stress can be eliminated.
According to the second aspect of the present invention, an annular groove is formed between the first and second curl portions, thereby disturbing the exhaust flow, so that exhaust airflow noise can be reduced.
According to the third aspect of the present invention, the heat between the silencer body and the outer assembly including the outer pipe, and the inner assembly including the silencer pipe and the inner pipe supported in a state of being hung inside thereof. The difference in expansion can be absorbed by the curled portion.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a silencer that constitutes an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a tail portion of the silencer.
3 is a cross-sectional view further enlarging a portion III in FIG. 2;
4A and 4B are longitudinal sectional views showing different structures of a conventional tail portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Silencer main body 11 Casing 12 Silencer pipe 12a, 12b Small hole 13 Cavity 20 Tail part 21 Outer pipe 21a First curl part 22 Inner pipe 22a Second curl part 25 Annular groove 31 Outer assembly 32 Inner assembly

Claims (3)

In a silencer comprising a silencer body and a tail portion of a double pipe structure that protrudes rearward from the silencer body and has an outer pipe and an inner pipe,
A first curled portion is formed around the rear end periphery of the outer pipe so as to project radially inward, and is wound around the rear end periphery of the inner pipe so as to project radially outward. A second curl portion is formed, the second curl portion is positioned closer to the silencer body side than the first curl portion, the rear surface of the second curl portion is applied to the first curl portion, and the outer peripheral surface of the second curl portion Is applied to the inner peripheral surface of the outer pipe, and the rear end of the inner pipe is supported by the rear end of the outer pipe only by these abutments. The silencer according to claim 1, wherein an annular groove is formed between the first and second curl portions. The silencer body includes a cylindrical casing and a silencer pipe that is coaxially arranged inside and passes exhaust gas, and a cavity between the casing and the silencer pipe, and an internal passage of the silencer pipe, It is connected through many small holes formed in the muffler pipe,
The rear end periphery of the casing and the front end periphery of the outer pipe are welded to form an outer assembly, and the rear end periphery of the muffler pipe and the front end periphery of the inner pipe are welded to form an inner assembly. The front end periphery of the silencer pipe is welded, and the inner assembly is supported by the welded portion and the abutting portions of the first and second curl portions in a spanned state on the outer assembly. The silencer according to claim 1.

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