Patent Publication Number: US-2022235842-A1

Title: Vibration damping band and muffler

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2021-011256 filed on Jan. 27, 2021 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a vibration damping band and a muffler. 
     Japanese Unexamined Patent Application Publication No. 2018-53794 discloses a muffler covered with a fibrous thermal insulation material. In the muffler, a thermal insulation material is arranged to have a larger density in areas of an inner tube and an outer tube that are prone to vibration than in other areas. This causes the areas having a larger density to have a relatively high stiffness, and to thereby function as a vibration damper that reduces vibration. 
     SUMMARY 
     However, the muffler disclosed in Japanese Unexamined Patent Application Publication No. 2018-53794 has a problem that vibration is not damped sufficiently and reduction in radiated noise is insufficient. 
     One aspect of the present disclosure preferably provides a vibration damping band and a muffler that reduce radiated noise appropriately. 
     An embodiment of the present disclosure is a vibration damping band to be mounted on an outer circumferential surface of a muffler main body. The vibration damping band comprises a vibration damping material and an outer panel. The vibration damping material has elasticity and is configured to be arranged on the outer circumferential surface of the muffler main body. The outer panel is arranged outside an outer lateral surface of the vibration damping material. 
     With this configuration, radiated noise generated due to vibration of the muffler main body can be suitably reduced. The reason is considered as follows. Since the vibration damping material has elasticity, a force of pulling the vibration damping material in a shearing direction by a surface of the muffler main body is generated when the muffler main body vibrates while the vibration damping band is mounted on the muffler main body. When the vibration damping material is pulled and extended, vibration energy is converted into thermal energy by internal friction of the vibration damping material. Thus, vibration is damped, and radiated noise from the muffler main body can be reduced. 
     In the vibration damping band described above, the vibration damping material may be fixed to the outer panel at least in a first fixing position and a second fixing position of the outer panel, and the vibration damping material may comprise at least a first portion fixed in the first fixing position and a second portion fixed in the second fixing position and may be extendable between the first portion and the second portion 
     With this configuration, since the vibration damping material is fixed in two positions of the outer panel spaced from each other, it is easy to form a state where the vibration damping material is extended between the two portions, that is, a state where a tension is applied to the vibration damping material. Thus, when the vibration damping band is mounted on the muffler main body, the muffler main body and the vibration damping material are easily brought into close contact with each other. This facilitates generation of a shearing stress between the muffler main body and the vibration damping material when the muffler main body vibrates. Accordingly, radiated noise can be reduced suitably. 
     In the above-described vibration damping band, a length of the vibration damping material from the first portion to the second portion may be shorter than a length from the first fixing position to the second fixing position of the outer panel. 
     With this configuration, when the outer panel is fixed along the outer circumferential surface of the muffler main body, the vibration damping material abuts the outer circumferential surface of the muffler main body. Also, a part of the vibration damping material from the first portion to the second portion is extended so as to approach a length from the first fixing position to the second fixing position of the outer panel. The vibration damping material contacts the muffler main body in a state where the vibration damping material is applied with a tension and provides a high vibration damping effect. Accordingly, radiated noise can be reduced suitably. 
     In the above-described vibration damping band, the vibration damping material may be fixed to the outer panel at least in two positions of the outer panel. With this configuration, when the muffler main body is inserted inside the vibration damping material, and thereby the vibration damping band is mounted on the muffler main body, the vibration damping material is applied with a tension. Accordingly, radiated noise can be reduced suitably. 
     The above-described vibration damping band may further comprise a swaging component. Also, the outer panel and the vibration damping material may be folded and swaged by the swaging component, and thereby the outer panel and the vibration damping material may be fixed together. This configuration allows firm fixation of the outer panel and the vibration damping material. 
     In the above-described vibration damping band, the outer panel may comprise two or more members configured to be arranged along an outer circumferential direction of the muffler main body, and the two or more members may surround the outer circumferential surface of the muffler main body. With this configuration, when the two or more members are mounted on the muffler main body, the vibration damping material is applied with a tension. Accordingly, radiated noise can be reduced suitably. 
     An embodiment of the present disclosure is a muffler that comprises a muffler main body and a vibration damping band. The vibration damping band is mounted on an outer circumferential surface of the muffler main body. Also, the vibration damping band comprises a vibration damping material and an outer panel. The vibration damping material has elasticity and is arranged on the outer circumferential surface of the muffler main body. The outer panel is arranged on an outer lateral surface of the vibration damping material. 
     With this configuration, when the vibration damping material is mounted so as to be held between the outer circumferential surface of the muffler main body and the outer panel, a tension is applied to the vibration damping material having elasticity. Accordingly, radiated noise can be reduced suitably. 
     In the above-described muffler, the muffler main body may comprise at least one separator. The vibration damping band may be provided in a position of the outer circumferential surface of the muffler main body, the position being spaced from a region in which an outer periphery of the at least one separator abuts an inner circumferential surface of the muffler main body. 
     With this configuration, the vibration damping band is arranged on a part of the muffler main body which easily vibrates. Accordingly, radiated noise can be reduced more suitably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present disclosure will be described hereinafter by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view of a muffler; 
         FIG. 2  is a schematic side view of a vibration damping band; 
         FIG. 3  is a schematic perspective view showing a state in which the vibration damping band is mounted on a muffler main body; 
         FIG. 4A  is a schematic sectional view showing the state in which the vibration damping band is mounted on the muffler main body; 
         FIG. 4B  is a schematic top view showing the state in which the vibration damping band is mounted on the muffler main body; 
         FIG. 5A  is a view of illustrating swaging between an outer panel and a vibration damping material using a swaging component; 
         FIG. 5B  is a schematic top view of the vibration damping band in a state in which the vibration damping band is swaged using the swaging component; 
         FIG. 5C  is a sectional view along a VC-VC line in  FIG. 5A ; 
         FIG. 6A  is a view illustrating fastening of the outer panel and the vibration damping material using a bolt and a nut; 
         FIG. 6B  is a schematic top view of the vibration damping band in a state in which the outer panel and the vibration damping material are fastened together using the bolt and the nut; 
         FIG. 7  is a schematic side view of a vibration damping band having an upper side portion and a lower side portion; 
         FIG. 8  is a schematic side view of a vibration damping band having only an upper side portion; 
         FIG. 9  is a schematic side view of a vibration damping band configured to be not fixed in a second fixing position; and 
         FIG. 10  is a schematic view showing a state in which two vibration damping bands are mounted on the muffler main body so as to intersect each other. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     1. Embodiment 
     1-1. Configuration 
     A muffler  1  shown in  FIG. 1  is installed in a vehicle. The muffler  1  forms a part of an exhaust flow path of exhaust gas discharged from an internal combustion engine of the vehicle. The muffler  1  comprises a muffler main body  10  and three vibration damping bands  20 .  FIG. 1  is a view prepared by superimposing a side view of the vibration damping bands  20  on a sectional view of the muffler main body  10 . 
     The muffler main body  10  comprises a casing  11 , a first separator  12 , a second separator  13 , an inlet pipe  14 , a first outlet pipe  15 , and a second outlet pipe  16 . 
     &lt;Casing&gt; 
     The casing  11  comprises therein an exhaust flow path to reduce exhaust noise. The casing  11  comprises a shell member  101 , a front lid member  102 , and a rear lid member  103 . The shell member  101  is a cylindrical member extending in a specified extending direction. The front lid member  102  and the rear lid member  103  close both end openings of the shell member  101  along the extending direction. The extending direction of the shell member  101  is an extending direction of the casing  11 . However, the extending direction is used for convenience in indicating a direction, and thus a length of the casing  11  in the extending direction may be smaller than a length between wall surfaces passing along a central axis in a cross-section orthogonal to the extending direction. 
     &lt;Separator&gt; 
     The first separator  12  and the second separator  13  are partition members to partition an internal space surrounded by an inner wall surface of the casing  11  into two or more spaces. The internal space is sectioned into two or more chambers by the first separator  12  and the second separator  13 . In the present embodiment, the internal space is sectioned into three chambers, i.e., a first chamber  31 , a second chamber  32 , and a third chamber  33  starting from a side of the rear lid member  103 . The first separator  12  and the second separator  13  each have two or more holes communicating with these chambers, and the exhaust gas is allowed to flow into other chambers through these holes. 
     &lt;Inlet Pipe&gt; 
     The inlet pipe  14  is a pipe to introduce the exhaust gas from the internal combustion engine into the casing  11 . The inlet pipe  14  is provided so as to penetrate a portion of the shell member  101  that forms the second chamber  32 . The inlet pipe  14  comprises a downstream end opened in the second chamber  32 . 
     &lt;Outlet Pipe&gt; 
     The first outlet pipe  15  and the second outlet pipe  16  are pipes to discharge the exhaust gas from the casing  11 . The exhaust gas that flows in from the inlet pipe  14  is discharged through the first outlet pipe  15  and the second outlet pipe  16 . The first outlet pipe  15  and the second outlet pipe  16  are each coupled to a not shown pipe located downstream of the muffler main body  10 . The first outlet pipe  15  is provided so as to penetrate the rear lid member  103 , the second separator  13 , and the first separator  12 . The first outlet pipe  15  comprises an upstream end opened to the third chamber  33 . The second outlet pipe  16  is provided so as to penetrate the front lid member  102 , the first separator  12 , and the second separator  13 . The second outlet pipe  16  comprises an upstream end opened to the first chamber  31 . 
     &lt;Vibration Damping Band&gt; 
     As shown in  FIGS. 2 to 4 , the vibration damping band  20  comprises an outer panel  21  and a vibration damping material  22 . 
     The outer panel  21  is a member formed of metal and having a band shape. The outer panel  21  is formed in a shape along a curved outer circumferential surface of the muffler main body  10  so as to surround the outer circumferential surface of the muffler main body  10 . The outer panel  21  is arranged outside of the vibration damping material  22 . The outer panel  21  has a generally C-shaped cross-section along a direction orthogonal to a width direction of the outer panel  21 . The width direction of the outer panel  21  here means a width direction of the aforementioned band shape. 
     The outer panel  21  comprises plate-shaped coupling pieces  23  and  24  extending outward from the first end  211  and the second end  212 , respectively, of the outer panel  21 . The coupling pieces  23  and  24  are configured to be fastened together facing each other by a bolt and a nut. 
     The vibration damping material  22  is configured to be arranged on an outer circumferential surface of the muffler main body  10 . The vibration damping material  22  is formed of an elastic member. Specifically, the vibration damping material  22  is a member extendable in response to a load applied in a pulling direction, and is elastically deformed in an extension and contraction direction. The extension and contraction direction is a longitudinal direction of the vibration damping material  22 . The vibration damping material  22  is configured not to reach an elastic limit at least in a state shown in  FIG. 3  where the vibration damping material  22  is mounted on the muffler main body  10  and extended. The vibration damping material  22  may be formed, for example, by knitting long fibers. Examples of the long fiber may include glass fiber, ceramic fiber, silica fiber, and stainless steel material. 
     The vibration damping material  22  is fixed to an inner circumferential surface of the outer panel  21  in a fixing position  25 , a second fixing position  26 , and a third fixing position  27  of the outer panel  21 . The first fixing position  25  and the third fixing position  27  are provided in vicinities of the coupling pieces  23  and  24 . The second fixing position  26  is provided opposed to the first fixing position  25  and the third fixing position  27 . Portions of the vibration damping material  22  fixed to the inner circumferential surface of the outer panel  21  in the first fixing position  25 , the second fixing position  26 , and the third fixing position  27  are referred to as “a first portion  251 ”, “a second portion  261 ”, and “a third portion  271 ”, respectively. Specifically, the vibration damping material  22  is swaged, for example, by crimping and fixed to the inner circumferential surface of the outer panel  21 . As shown in  FIG. 5 , for example, the outer panel  21  and the vibration damping material  22  are folded and swaged by a swaging component  28 , and thereby the vibration damping material  22  is fixed to the inner circumferential surface of the outer panel  21 . Note that any configuration for fixation, such as the swaging component  28 , is not shown in figures other than  FIG. 5 . 
     Returning to  FIG. 2 , the vibration damping material  22  is fixed to the outer panel  21  in a position of a chord of the outer panel  21  with a tension applied in the extension and contraction direction. The vibration damping material  22  with a tension applied in the extension and contraction direction is longer than a natural length. In this case, a length of the vibration damping material  22  from the first portion  251  to the second portion  261  is shorter than a length of the outer panel  21  from the first fixing position  25  to the second fixing position  26 . Also, a length of the vibration damping material  22  from the second portion  261  to the third portion  271  is shorter than a length of the outer panel  21  from the second fixing position  26  to the third fixing position  27 . In positions other than the first fixing position  25 , the second fixing position  26 , and the third fixing position  27 , an interspace is formed between the vibration damping material  22  and the outer panel  21 . 
     1-2. Mounting of Vibration Damping Band on Muffler Main Body 
     Here, a description will be given of one of the three vibration damping bands  20  to be mounted on the muffler main body  10 . The vibration damping band  20  is mounted on the muffler main body  10  so as to be arranged along the outer circumferential surface of the muffler main body  10 . In other words, the vibration damping band  20  is adjacent to the outer circumferential surface of the muffler main body  10  through the vibration damping material  22 . 
     First, the outer panel  21  is opened in a direction of separating the coupling pieces  23  and  24  of the outer panel  21  from each other. 
     Then, the vibration damping band  20  is put around the muffler main body  10  such that the vibration damping material  22  is brought into close contact with the muffler main body  10 . Specifically, as shown in  FIG. 1 , the vibration damping band  20  is mounted in a position on the outer circumferential surface of the muffler main body  10 , the position being spaced from regions in which outer peripheries of the first separator  12  and the second separator  13  abut an inner circumferential surface of the muffler main body  10 . More specifically, the vibration damping band  20  is mounted in a position on the outer circumferential surface of the muffler main body  10 , the position being different from regions in which outer peripheries of the first separator  12  and the second separator  13  are connected to the muffler main body  10 . 
     Subsequently, the vibration damping band  20  with the coupling pieces  23  and  24  facing each other is fixed to the muffler main body  10  using a bolt. In the present embodiment, the vibration damping material  22  is already applied with a tension before the mounting of the vibration damping band  20 . When the vibration damping band  20  is mounted on the muffler main body  10 , the vibration damping material  22  is further extended and thus is applied with a tension greater than the tension before the mounting. In this state, the vibration damping material  22  is arranged so as to abut the outer circumferential surface of the muffler main body  10 , and is held between the muffler main body  10  and the outer panel  21 . That is, the vibration damping material  22  is easily brought into close contact with the muffler main body  10 . 
     In the present embodiment, as shown in  FIG. 1 , the three vibration damping bands  20  are mounted. One of the vibration damping bands  20  is mounted between the front lid member  102  and the first separator  12 . Another one of the vibration damping bands  20  is mounted between the first separator  12  and the second separator  13 . The remaining one of the vibration damping bands  20  is mounted between the second separator  13  and the rear lid member  103 . In other words, one vibration damping band  20  is mounted for each of the chambers  31  to  33 . Each position in which the vibration damping band  20  is mounted corresponds to an amplitude antinode, at which an amplitude of the muffler main body  10  by vibration is maximum while the muffler main body  10  is vibrating. 
     1-3. Effects 
     According to the embodiment described above, the following effects are obtained: 
     (1a) In the muffler  1  of the present embodiment, the vibration damping material  22 , which is tensioned between the first portion  251  and the second portion  261  as well as between the second portion  261  and the third portion  271 , is arranged so as to be held between the outer circumferential surface of the muffler main body  10  and the outer panel  21 . With this configuration, radiated noise generated due to vibration of the muffler main body  10  can be reduced appropriately. The reason will be described below. Since the vibration damping material  22  is tensioned, when the muffler main body  10  vibrates, a force of pulling the vibration damping material  22  in a shearing direction by a surface of the muffler main body  10  is generated on the vibration damping material  22 . When the vibration damping material  22  is pulled and extended, vibration energy is converted into thermal energy by internal friction of the vibration damping material  22 . Specifically, vibration energy is converted into thermal energy by friction caused by rubbing of long fibers forming the vibration damping material  22 . Thus, vibration is damped, and radiated noise from the muffler main body  10  can be reduced. 
     The extension and contraction direction of the vibration damping material  22  coincides with the circumferential direction of the muffler main body  10 . Accordingly, in the present embodiment, the vibration damping material  22  facilitates damping of the vibration in the circumferential direction of the muffler main body  10 . 
     (1b) The length of the vibration damping material  22  from the first portion  251  to the second portion  261  extended with a specified extension force is shorter than the length of the outer panel  21  from the first fixing position  25  to the second fixing position  26 . With this configuration, when the outer panel  21  is fixed along the outer circumferential surface of the muffler main body  10 , the vibration damping material  22  abuts the outer circumferential surface of the muffler main body  10 . Also, a part of the vibration damping material  22  between the first portion  251  and the second portion  261  is extended to approach the length of the outer panel  21  from the first fixing position  25  to the second fixing position  26 . Thus, the vibration damping material  22  contacts the muffler main body  10  in a tensioned state providing a high vibration damping effect. Accordingly, radiated noise can be reduced appropriately. Also, a part of the vibration damping material  22  between the second portion  261  and the third portion  271  also achieves similar effects to those of the part between the first portion  251  and the second portion  261  as described above. 
     (1c) The vibration damping material  22  is fixed to the outer panel  21  with a tension applied between the first portion  251  and the second portion  261 . Also, the vibration damping material  22  is fixed to the outer panel  21  with a tension applied between the second portion  261  and the third portion  271 . With this configuration, the vibration damping material  22  is already tensioned before the mounting of the vibration damping band  20  on the muffler main body  10 . In other words, when the vibration damping band  20  is mounted on the muffler main body  10 , a greater tension is applied to the vibration damping material  22 . Accordingly, radiated noise can be reduced appropriately. 
     (1d) The outer panel  21  has a shape along the curved outer circumferential surface of the muffler main body  10 , and the vibration damping material  22  is fixed to the outer panel  21  in the position of a chord of the outer panel  21 . With this configuration, the outer panel  21  can hold the vibration damping material  22  with a suitable force over a wide area. Also, the vibration damping material  22  is easily tensioned, and thus can reduce radiated noise appropriately. Here, “the position of a chord of the outer panel  21 ” means the position of a chord in case of assuming the outer panel  21  to be a circular arc. 
     (1e) The vibration damping band  20  is provided in the position of the outer circumferential surface of the muffler main body  10 , the position being spaced from regions in which outer peripheries of the first separator  12  and the second separator  13  abut the inner circumferential surface of the muffler main body  10 . With this configuration, the vibration damping band  20  is arranged on a part, which easily vibrates, of the muffler main body  10 . Accordingly, radiated noise can be reduced more appropriately. 
     (1f) The vibration damping band  20  is mounted for each of the chambers  31  to  33 . With this configuration, the vibration damping band  20  can be arranged on a part, which easily vibrates, of the muffler main body  10  for each of the chambers  31  to  33 . Accordingly, radiated noise can be reduced more appropriately. 
     2. Other Embodiments 
     Although one embodiment of the present disclosure has been described above, it is to be understood that the present disclosure is not limited to the above-described embodiment but may be in various forms within the technical scope of the present disclosure. 
     (2a) In the above-described embodiment, the vibration damping material  22  is arranged on the outer panel  21  with a tension applied before the vibration damping band  20  is mounted on the muffler main body  10 . However, for example, the vibration damping material  22  may be arranged on the outer panel  21  with no tension applied. Even in this case, for example, if the length of the vibration damping material  22  from the first portion  251  to the second portion  261  when extended with a specified extension force is shorter than the length of the outer panel  21  from the first fixing position  25  to the second fixing position  26 , then the vibration damping material  22  is extended and is applied with a tension once the vibration damping band  20  is mounted on the muffler main body  10 , and a high vibration damping effect can be obtained. That is, in a state where the outer panel  21  is arranged on the muffler main body  10  through the vibration damping material  22 , the vibration damping material  22  is tensioned between the first portion  251  and the second portion  261 , and provides a high vibration damping effect. 
     (2b) Although the vibration damping material  22  is fixed to the outer panel  21  by being swaged by the swaging component  28  in the above-described embodiment, a method of fixing the vibration damping material  22  to the outer panel  21  is not limited to that. For example, as shown in  FIGS. 6A and 6B , the outer panel  21 , the vibration damping material  22 , and the muffler main body  10  may be fastened and fixed together with a bolt  29  and a nut  291 . 
     (2c) Although the vibration damping band  20  has a shape surrounding an entirety of the outer circumferential surface of the muffler main body  10  in the above-described embodiment, the shape of the vibration damping band  20  is not limited to that. For example, as shown in  FIG. 7 , the vibration damping band  20  may comprise an upper side portion  41  and a lower side portion  42 . The upper side portion  41  and the lower side portion  42  each have a sectional shape obtained by dividing a circumference of an ellipse by its long axis. The upper side portion  41  comprises plate-shaped coupling pieces  43  extending outward from respective ends of the upper side portion  41 , and the lower side portion  42  comprises plate-shaped coupling pieces  44  extending outward from respective ends of the lower side portion  42 . In this case, the coupling pieces  43  of the upper side portion  41  and the corresponding coupling pieces  44  of the lower side portion  42  are each fastened together by a bolt and a nut, and thereby the vibration damping band  20  is mounted on the muffler main body  10 . 
     Also, as shown in  FIG. 8 , the vibration damping band  20  may comprise only the upper side portion  41  without the lower side portion  42 . In this case, the muffler main body  10  comprises plate-shaped coupling pieces  45  extending outward from the muffler main body  10 . The coupling pieces  43  of the upper side portion  41  and the corresponding coupling pieces  45  of the muffler main body  10  are each fastened together by a bolt and a nut, and thereby the vibration damping band  20  is mounted on the muffler main body  10 . 
     Further, the vibration damping band  20  may be mounted along the extending direction of the muffler main body  10 , although which is not shown. 
     (2d) Although the vibration damping material  22  is fixed to the outer panel  21  in the position of the chord of the outer panel  21  in the above-described embodiment, the position of fixing the vibration damping material  22  to the outer panel  21  is not limited to that. For example, as shown in  FIG. 9 , the vibration damping material  22  may be fixed in the first fixing position  25  and the third fixing position  27 , while not being fixed in the second fixing position  26 . In this case, when the muffler main body  10  is inserted inside the vibration damping material  22  having a band shape and thereby the vibration damping band  20  is mounted on the muffler main body  10 , the vibration damping material  22  is applied with a tension. 
     (2e) Although three vibration damping bands  20  are mounted on the muffler main body  10  in the above-described embodiment, the number of the vibration damping bands  20  to be mounted is not limited to three. For example, the number of the vibration damping bands  20  may be two or less, or four or more. 
     (2f) Although one vibration damping band  20  is mounted for each of the chambers  31  to  33  in the above-described embodiment, a configuration of mounting the vibration damping bands  20  on the muffler main body  10  is not limited to that. For example, two or more vibration damping bands  20  may be mounted on the muffler main body  10  such that the two or more vibration damping bands  20  are intersecting one another. For example, as shown in  FIG. 10 , two vibration damping bands  20  may be mounted on the muffler main body  10  such that the two vibration damping bands  20  are intersecting each other. Specifically, one of the vibration damping bands  20  is mounted to pass an upper end of the first chamber  31 , a middle part of the second chamber  32 , and a lower end of the third chamber  33 . The other one of the vibration damping bands  20  is mounted to pass an upper end of the third chamber  33 , the middle part of the second chamber  32 , and a lower end of the first chamber  31 . This configuration can achieve a damping effect in a wider area with a fewer number of the vibration damping bands  20 . 
     (2g) In the above-described embodiment, the outer panel  21  is arranged along the outer circumferential surface of the muffler main body  10 . However, the outer panel  21  in its entirety does not need to be arranged along the outer circumferential surface of the muffler main body  10 . The outer panel  21  needs to be configured to hold at least a part of the vibration damping material  22  with the outer circumferential surface of the muffler main body  10  in a state where the outer panel  21  is mounted on the outer circumferential surface of the muffler main body  10 . 
     (2h) Although the outer panel  21  is fixed by a bolt and a nut in the above-described embodiment, a configuration of fixing the outer panel  21  is not limited to that. For example, the outer panel  21  may be fixed by welding. 
     (2i) In the above-described embodiment, the vibration damping material  22  is arranged to be held between the outer circumferential surface of the muffler main body  10  and the outer panel  21 , and is applied with a tension. However, the vibration damping material  22  does not need to be applied with a tension that is caused by being extended in the extension and contraction direction when being arranged to be held between the outer circumferential surface of the muffler main body  10  and the outer panel  21 . Even in this case, a damping effect can be achieved if the vibration damping material  22  is elastic. The reason is considered as follows. When the vibration damping material  22  is held between the outer circumferential surface of the muffler main body  10  and the outer panel  21 , the vibration damping material  22  is brought into a compressed state and is applied with a tension. Thus, a force of pulling the vibration damping material  22  in a shearing direction by the surface of the muffler main body  10  is generated. As a result, vibration energy is converted into thermal energy, and vibration is damped, and thus radiated noise from the muffler main body  10  can be reduced. 
     (2j) In the above-described embodiment, a configuration is exemplified in which the vibration damping material  22  extends straight from the first portion  251  to the second portion  261 , and extends straight from the second portion  261  to the third portion  271 . However, the vibration damping material  22  is not limited to this shape. For example, the vibration damping material  22  may have a meandering shape from the first portion  251  to the second portion  261 . Also, the vibration damping material  22  may have a meandering shape from the second portion  261  to the third portion  271 . 
     (2k) One or more functions performed by a single element in the above-described embodiments may be achieved by a plurality of elements, or one or more functions performed by a plurality of elements may be achieved by a single element. Also, a part of a configuration in the above-described embodiments may be omitted. Moreover, at least a part of a configuration in the above-described embodiments may be added to, or may replace, another configuration in the above-described embodiments.