JP2002070523A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler with good appearance, low manufacturing cost, no generation of high thermal stress. SOLUTION: This muffler has a muffler body 10 and a tail part 20 projecting from the muffler body 10 to the rear direction. The tail part 20 has an outer pipe 21 and an inner pipe 22, and is formed in double pipe structure. The rear end peripheral part of the outer pipe 21 is wound so as to project to the inner side in the diameter direction to form a curl part 21a. The rear end peripheral part of the inner pipe 22 is wound so as to project to the outer side in the diameter direction to form a curl part 22a. The rear surface of the curl part 22a of the inner pipe 22 is made to butt to the curl part 21a of the outer pipe 21, and the outer peripheral surface of the curl part 22a is made to butt to the inner peripheral surface of the peripheral wall of the outer pipe 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 double pipe structure tail.

[0002]

2. Description of the Related Art A silencer has a tail portion protruding rearward of a silencer body to enhance the silencing effect. Some of the tails have a double pipe structure to further enhance the noise reduction effect and improve the appearance. In the tail portion of the conventional double pipe structure, the outer peripheral edges of the outer pipe 1 and the inner pipe 2 are welded as shown in FIGS. More specifically, in the structure of FIG. 4A, a curl portion 1a is formed by winding the outer peripheral edge of the outer pipe 1 so as to protrude radially inward.
The inner pipe 2 is welded in a state where the rear end peripheral edge of the inner pipe 2 is in contact with the inner circumference of the curled portion 1a. In the structure shown in FIG. 4B, the curl portion 2a is formed by winding the rear end peripheral edge of the inner pipe 2 so as to project radially outward.
The outer pipe 1 is welded with its rear end rim abutting against the outer periphery of the curled portion 2a.

[0003]

In the connection structure shown in FIG. 4 (A), the pipes 1 and 2 are brought into contact with each other.
Since welding was performed from the inside of No. 2, workability was poor. Also,
The appearance was poor due to the appearance of weld beads. The connection structure shown in FIG. 4B is disadvantageous in cost because buffing is performed after welding. Further, as a common drawback of the above two connecting structures, since the difference in thermal expansion between the pipes 1 and 2 cannot be absorbed, the strength of the pipes 1 and 2 and the welded parts are increased more than necessary so as to withstand the stress during thermal expansion. It was necessary to prevent the occurrence of cracks.

[0004]

According to a first aspect of the present invention, there is provided a silencer body, and a tail portion of a double pipe structure projecting rearward from the muffler body and having an outer pipe and an inner pipe. In the silencer, a first curl portion wound so as to project radially inward is formed at a rear end periphery of the outer pipe, and a first curl portion is formed to project radially outward at a rear end periphery of the inner pipe. The second curl portion is formed closer to the silencer main body than the first curl portion, the rear surface of the second curl portion is applied to the first curl portion, and the second curl portion is wound. The outer peripheral surface of the portion is in contact with 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.

According to a second aspect of the present invention, in the muffler according to the first aspect, an annular groove is formed between the first and second curls.

According to a third aspect of the present invention, in the muffler according to the first aspect, the muffler main body includes a cylindrical casing and a muffler pipe disposed coaxially therein and through which exhaust gas passes. The cavity between the casing and the sound deadening pipe and the internal passage of the sound deadening pipe are connected via a number of small holes formed in the sound deadening pipe, and the rear edge of the casing and the front edge of the outer pipe are welded to each other. To form an outer assembly, the rear end periphery of the silencer pipe and the front end periphery of the inner pipe are welded to form an inner assembly, the casing and the front end periphery of the muffler pipe are welded, The inner assembly is supported by the contact portions of the first and second curl portions in a state of being bridged over the outer assembly.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A silencer according to an embodiment of the present invention will be described below with reference to FIGS. FIG.
As shown in FIG. 1, the muffler includes a muffler main body 10 and a tail portion 20 protruding rearward from the muffler main body 10.

The silencer main body 10 includes a cylindrical casing 11 and a silencing pipe 12 disposed coaxially within the casing 11. The front end periphery of the casing 11 is reduced in diameter and welded to the front end periphery of the sound deadening pipe 12. This weld is indicated by reference numeral 5 in the figure. A cavity 13 is formed between the casing 11 and the muffling pipe 12. The sound deadening pipe 12 has a large number of small holes 12a and 12b in regions separated from each other in front and rear. The front small hole 12a is open, and the rear small hole 12b
Are covered with a sound absorbing material 14. The internal passage of the sound deadening pipe 12 communicates with the cavity 1 through these small holes 12a and 12b.
It is connected to 3.

The tail section 20 has an outer pipe 21 and an inner pipe 22 which are coaxial, and has a double pipe structure. The outer pipe 21 has a cylindrical shape having the same diameter over the entire length. The inner pipe 22 has a funnel shape whose shape extends rearward from the front end to the middle part, and has a cylindrical shape having the same diameter from the middle part to the rear end. The front edge of the outer pipe 21 is welded to the reduced diameter rear edge of the casing 11. This weld is indicated by reference numeral 6 in FIG. The front edge of the inner pipe 22 is welded to the rear edge of the sound deadening pipe 12. This weld is indicated by reference numeral 7 in FIG.

As shown in FIGS. 2 and 3, the outer peripheral edge of the outer pipe 21 is wound so as to protrude radially inward, thereby forming a curl portion 21a having a substantially circular cross section. 1 curl portion). Further, the rear end peripheral edge of the inner pipe 22 is wound so as to project radially outward, thereby forming a curl portion 22a (second curl portion) having a substantially circular cross section. The curl portion 22a is arranged closer to the muffler body 10 than the curl portion 21a. Thereby, the curled portions 21a, 22a
Is covered by the peripheral wall of the outer pipe 21.

The curled portion 22a of the inner pipe 22
The rear surface of the outer pipe 21 is in contact with a curled portion 21a of the outer pipe 21. The outer peripheral surface of the curled portion 22a is
Of the peripheral wall. Thereby, the rear end of the inner pipe 22 is stably supported by the rear end of the outer pipe 21 without rattling. These curl portions 21
The contact portions of a and 22a are indicated by reference numeral 8 in FIGS. The peripheral ends of the rear ends of the pipes 21 and 22 are only brought into contact with each other, but are not welded. Curl portions 21a, 2
Between 2a, an annular groove 25 is formed on the inner peripheral side.

The casing 10 and the outer pipe 21
Are connected to each other by a welded portion 6 to form an outer assembly 31 which is integrated. The silencing pipe 12 and the inner pipe 22 are connected by the welded portion 7 to form an integral inner assembly 32. The inner assembly 32 is supported at both ends of the outer assembly 32, which is coaxial with each other by the welded portion 5 and the contact portion 8, thereby being supported in a bridging state.

In the above configuration, the exhaust gas from the engine diffuses from the small hole 12b on the front side of the sound deadening pipe 12 to the cavity 13, returns to the small hole 12b via the sound absorbing material 15, and
In this process, the exhaust noise is muted. The tail portion 20 having the double pipe structure further enhances the noise reduction effect.

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 air flow noise can be reduced.

The peripheral edges of the rear ends of the pipes 21 and 22 are merely connected by the abutment of the curled portions 21a and 22a, and there is no need for welding, so that the operation of assembling the silencer can be simplified. Further, the step of polishing the welded portion can be omitted, which is advantageous in cost. Furthermore, since there is no welding bead, the appearance is good.

The amounts of thermal expansion of the inner pipe 22 and the outer pipe 21 differ depending on the temperature difference. In particular, when exhaust gas is discharged, the thermal expansion of the inner pipe 22 becomes larger than the thermal expansion of the outer pipe 21.
In this case, when the curl portion 22a strongly presses the curl portion 21a, they are elastically deformed to absorb a difference in thermal expansion. When the two pipes 21 and 22 are in a normal temperature state, the curl portions 21a and 22a hardly undergo elastic deformation. The curled portion 22a of the inner pipe 22 slides on the inner peripheral surface of the outer pipe 21 in the axial direction in accordance with these temperature changes. As described above, a large thermal stress is applied to the pipes 21 and
22 is not provided, and cracks and the like can be prevented.

In the present embodiment, since the inner assembly 32 is connected to the outer assembly 31 only at both ends, the difference in thermal expansion between the sound deadening pipe 12 and the casing 11 is also reduced by the contact portion 8. Can be absorbed.

[0018]

As described above, according to the first aspect of the present invention, the outer pipe and the inner pipe are
Since it is only connected by the contact of the first and second curled portions and there is no need for welding, the assembling work of the silencer can be simplified, and the step of polishing the welded portion can be omitted. Yes, it is cost effective. Furthermore, since there is no welding bead, the appearance is good. Moreover, since the difference in thermal expansion between the outer pipe and the inner pipe can be absorbed by these curled portions, it is possible to eliminate the possibility of cracks in the pipe or the like due to thermal stress. According to the second aspect of the present invention, since an annular groove is formed between the first and second curl portions and the exhaust flow is disturbed by this, the exhaust airflow noise can be reduced. According to the third aspect of the present invention, heat between the outer assembly including the muffler main body and the outer pipe and the inner assembly including the muffler pipe and the inner pipe supported in a bridging state therein are provided. 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 muffler according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a tail portion of the muffler.

FIG. 3 is a sectional view further enlarging a portion III in FIG. 2;

FIGS. 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 Silence 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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 7/08 F01N 7/08 A 7/18 7/18

Claims (3)

[Claims] 1. A muffler comprising: a muffler main body; and a tail portion having a double pipe structure protruding rearward from the muffler main body and having an outer pipe and an inner pipe, wherein a rear end peripheral edge of the outer pipe is provided. A first curl portion wound so as to protrude inward in the radial direction is formed, and a second curl portion wound so as to protrude outward in the radial direction is formed around the rear end of the inner pipe. The second curl portion is located closer to the muffler main body than the first curl portion;
The rear surface of the curl portion is applied to the first curl portion,
A silencer characterized in that the outer peripheral surface of the second curl portion is in contact with 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. 2. The muffler according to claim 1, wherein an annular groove is formed between the first and second curls. 3. The muffler main body includes a cylindrical casing and a muffler pipe disposed coaxially therein and through which exhaust gas passes, and a cavity between the casing and the muffler pipe, and a muffler pipe of the muffler pipe. An inner passage connected through a number of small holes formed in the sound deadening pipe; a rear end peripheral edge of the casing and a front end peripheral edge of the outer pipe are welded to form an outer assembly; The periphery and the front end periphery of the inner pipe are welded to form an inner assembly, the casing and the front end periphery of the sound deadening pipe are welded, and the welded portion and the abutting portion of the first and second curl portions form an inner portion. The muffler according to claim 1, wherein the assembly is supported on the outer assembly in a bridging state.