Silencer manufacturing method

Abstract

The invention relates to a manufacturing method of a silencer. In order to manufacture a muffler, a first end of a first duct is disposed inside a housing. The second pipe is inserted into the first pipe from the outside of the housing, so that the second pipe is disposed inside the housing. The second pipe is inserted from a second end of the first pipe, and the second end of the first pipe is located on the opposite side of the first end of the first pipe. As described above, a muffler is manufactured in which the first duct connected to the second duct is held on the inside of the end of the housing. Through insertion, the first end of the second pipe is moved to at least a position passing through the first end of the first pipe. The second end of the second pipe is disposed on the inside of the first pipe, and the second end of the second pipe is located on the opposite side of the first end of the second pipe.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a muffler. Background Art

[0002] The silencer used in the internal combustion engine exhaust system has two pipes: one is an intake pipe for introducing exhaust gas into the housing, and the other is an exhaust pipe for discharging exhaust gas from the housing.

[0003] For example, in Japanese Unexamined Patent Application Publication No. 2021-105377, a technique is disclosed in which, with the first pipe inserted into the interior of the first end of the housing, after reducing the diameter of the second end located on the opposite side of the first end in the housing by rotary machining, the second pipe is inserted into the housing from the reduced-diameter second end. This technique can suppress pipe displacement in the muffler. Summary of the Invention

[0004] In the prior art disclosed in Japanese Unexamined Patent Application Publication No. 2021-105377, flaring is applied to the front end of the first pipe to ensure insertability when the second pipe passes through the reduced-diameter portion of the housing and is inserted into the first pipe. If this flaring is not performed, the assemblability between the two pipes may be affected.

[0005] One aspect of the present disclosure aims to improve the assemblability of pipes.

[0006] One solution of the present disclosure is a method for manufacturing a muffler, including preparing a housing and disposing a second pipe.

[0007] Preparing the housing includes preparing a housing having a central portion, a first cylindrical end portion, and a second cylindrical end portion, the first cylindrical end portion and the second cylindrical end portion being located on both sides of the central portion and being cylindrical end portions having a diameter smaller than that of the central portion. Preparing the housing includes preparing a housing in which the first pipe is inserted into the inside of the first cylindrical end portion and the first end of the first pipe is disposed inside the housing.

[0008] Disposing the second pipe includes disposing the second pipe inside the housing by inserting the second pipe into the first pipe disposed inside the housing from the outside of the housing.

[0009] Disposing the second pipe includes inserting the second pipe from the second end of the first pipe, causing the first end of the second pipe to pass at least through the first end of the first pipe, and moving the second end of the second pipe to a position disposed inside the first pipe, where the second end of the first pipe is located on the opposite side of the first end of the first pipe, and the second end of the second pipe is located on the opposite side of the first end of the second pipe.

[0010] The silencer is configured to hold the first pipe, which is already connected to the second pipe, inside the first cylindrical end portion.

[0011] According to the above manufacturing method, even if flaring or the like is not applied to the first end of the first pipe, the second pipe can be easily inserted into the first pipe. Therefore, the assemblability between the first pipe and the second pipe can be improved.

[0012] In one aspect of the present disclosure, disposing the second pipe may include: in a state where the second pipe is already connected to the first pipe, moving at least the first end of the second pipe inserted from the second end of the first pipe inside the second cylindrical end portion so that the second pipe is held inside the second cylindrical end portion.

[0013] According to the above manufacturing method, the assemblability between the housing and the second pipe can be improved.

[0014] In one aspect of the present disclosure, the housing may be formed by reducing the diameter of the first end and the second end of a cylindrical body, wherein the second end of the cylindrical body is located on the opposite side of the first end of the cylindrical body.

[0015] Preparing the housing may include: providing the first cylindrical end portion; disposing the first end of the first pipe inside the housing; and providing the second cylindrical end portion.

[0016] Providing the first cylindrical end portion may include reducing the diameter of the first end of the cylindrical body. Disposing the first end of the first pipe inside the housing may include inserting the first pipe inside the first cylindrical end portion. Providing the second cylindrical end portion may include reducing the diameter of the second end of the cylindrical body in a state where the first pipe is inserted inside the first cylindrical end portion.

[0017] Disposing the second pipe may include: in a state where the second pipe is already connected to the first pipe, moving at least the first end of the second pipe inserted from the second end of the first pipe inside the second cylindrical end portion so that the second pipe is held inside the second cylindrical end portion.

[0018] According to the above manufacturing method, even if flaring or the like is not applied to the first end of the first pipe, the second pipe can be easily inserted into the first pipe. Therefore, the assemblability among the first pipe, the second pipe, and the housing can be improved.

[0019] One aspect of the present disclosure is a manufacturing method of a silencer, which includes: connecting; providing the first cylindrical end portion; providing the second cylindrical end portion; and disposing.

[0020] The connection includes connecting the first pipe and the second pipe to each other by inserting the second pipe inside the first pipe such that the first end of the second pipe is disposed outside the first pipe and the second end of the second pipe is disposed inside the first pipe, wherein the second end of the second pipe is on the opposite side of the first end of the second pipe.

[0021] Providing the first cylindrical end portion includes providing a first cylindrical end portion having a diameter smaller than the diameter of the cylindrical body at the first end of the cylindrical body.

[0022] Providing the second cylindrical end portion includes providing a second cylindrical end portion having a diameter smaller than the diameter of the cylindrical body at the second end of the cylindrical body, wherein the second end of the cylindrical body is on the opposite side of the first end of the cylindrical body.

[0023] The arrangement includes at least partially arranging the mutually connected first pipe and second pipe inside the cylindrical body.

[0024] The arrangement includes: by inserting the second pipe connected to the first pipe from the first end of the second pipe inside the first cylindrical end portion, at least a part of the first pipe is arranged inside the first cylindrical end portion, at least a part of the second pipe is arranged inside the second cylindrical end portion, and the first end of the first pipe is arranged inside the cylindrical body.

[0025] The silencer is configured to hold the first pipe inside the first cylindrical end portion and hold the second pipe connected to the first pipe inside the second cylindrical end portion.

[0026] According to the above manufacturing method, even if no flaring process or the like is applied to the first end of the first pipe, the second pipe can be easily inserted into the first pipe. Therefore, the assemblability between the first pipe and the second pipe can be improved.

[0027] In one aspect of the present disclosure, providing the second cylindrical end portion includes providing the second cylindrical end portion and the first cylindrical end portion on substantially the same axis.

[0028] According to the above manufacturing method, when the second pipe is inserted into the second cylindrical end portion, the position where the second pipe is inserted into the second cylindrical end portion is not easily deviated. Therefore, the assemblability between the housing and the second pipe can be improved.

[0029] In one aspect of the present disclosure, providing the second cylindrical end portion includes providing the second cylindrical end portion such that the inner diameter of the portion adjacent to the second cylindrical end portion of the cylindrical body decreases as it approaches the second cylindrical end portion.

[0030] According to the above manufacturing method, when the second pipe is inserted into the second cylindrical end portion, the second pipe is easily guided to the second cylindrical end portion. Therefore, the assemblability between the housing and the second pipe can be improved.

[0031] In one aspect of the present disclosure, the second pipe may have a holding member on the outer peripheral surface of its second end. In a state before the second pipe is inserted into the first pipe, the outer diameter of the second end of the second pipe including the holding member may be greater than or equal to the inner diameter of the first pipe.

[0032] According to the above configuration, when the second pipe is inserted into the first pipe, it is possible to suppress the second pipe from damaging the inner surface of the first pipe and to hold the second pipe by the first pipe.

[0033] In one aspect of the present disclosure, the first pipe may have a main body portion and a reduced-diameter portion. The main body portion is located between the first end and the second end of the first pipe, where the second end of the first pipe is on the opposite side of the first end of the first pipe. The reduced-diameter portion is located between the main body portion and the second end of the first pipe. The inner diameter of the second end of the first pipe may be greater than the inner diameter of the main body portion. The inner diameter of the reduced-diameter portion may be formed to decrease as it approaches the main body portion.

[0034] According to the above configuration, it is easy to insert the second pipe into the first pipe. Therefore, the assemblability between the first pipe and the second pipe can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a front view of a muffler and shows a housing as a sectional view.

[0036] Figure 2 is a flowchart showing a method of manufacturing a muffler according to the first embodiment.

[0037] Figure 3A is a view for explaining the first cylindrical end forming step of the first embodiment; Figure 3B is a view for explaining the first pipe arranging step of the first embodiment; Figure 3C is a view for explaining the second cylindrical end forming step of the first embodiment.

[0038] Figure 4A and 4B is a view for explaining the second pipe arranging step of the first embodiment.

[0039] Figure 5 is a flowchart showing a method of manufacturing a muffler according to the second embodiment.

[0040] Figure 6 is a view for explaining the pipe connecting step of the second embodiment.

[0041] Figure 7A is a view for explaining the first cylindrical end forming step of the second embodiment; Figure 7BThis is a diagram for explaining the second cylindrical end forming process of the second embodiment; Figure 7C and 7D This is a diagram for explaining the connecting pipe arrangement process of the second embodiment. Detailed Embodiment

[0042] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0043] [1. First Embodiment]

[0044] [1-1. Structure of the Muffler]

[0045] Figure 1 The muffler 1 shown is installed in a vehicle such as an automobile. The muffler 1 constitutes at least a part of the flow path of the exhaust gas generated by an automotive internal combustion engine.

[0046] The muffler 1 includes a housing 10, a first pipe 20, and a second pipe 30.

[0047] The housing 10 is a cylindrical member made of metal. The housing 10 functions as an outer pipe covering the first pipe 20 and the second pipe 30.

[0048] The housing 10 has a first cylindrical end 11, a second cylindrical end 12, a central portion 13, a first inclined portion 14, and a second inclined portion 15. The inner surface of the housing 10 defines the internal space 16 of the housing 10.

[0049] The first cylindrical end 11 and the second cylindrical end 12 are located on both sides of the housing 10 centered on the central portion 13, where the central portion 13 is located at the center of the housing 10. The first cylindrical end 11 and the second cylindrical end 12 are cylindrical portions with a diameter smaller than that of the central portion 13. The exhaust gas flows into the housing 10 through the second cylindrical end 12 and flows out of the housing 10 through the first cylindrical end 11. Hereinafter, the flow path of the exhaust gas flowing inside the housing 10 will be referred to as flow path A. "Inside the housing 10" includes the space between the first pipe 20 and the housing 10, the space between the second pipe 30 and the housing 10, the inside of the first pipe 20, and the inside of the second pipe 30. "Upstream side" refers to the upstream side of flow path A. "Downstream side" refers to the downstream side of flow path A. The first cylindrical end 11 is located at a position downstream of the central portion 13. The second cylindrical end 12 is located at a position upstream of the central portion 13.

[0050] The first inclined portion 14 is adjacent to the first cylindrical end 11 in the housing 10 and is located between the first cylindrical end 11 and the central portion 13. The inner diameter of the first inclined portion 14 decreases as it approaches the first cylindrical end 11 from the central portion 13.

[0051] The second inclined portion 15 is adjacent to the second cylindrical end portion 12 in the housing 10 and is located between the second cylindrical end portion 12 and the central portion 13. The inner diameter of the second inclined portion 15 decreases as it approaches the second cylindrical end portion 12 from the central portion 13.

[0052] In the present embodiment, both the first inclined portion 14 and the second inclined portion 15 are conical. The first inclined portion 14 and the second inclined portion 15 are not limited to being conical. For example, the first inclined portion 14 and the second inclined portion 15 may be curved.

[0053] The first pipe 20 is a pipe made of metal that extends substantially linearly. The first pipe 20 is disposed on the downstream side inside the housing 10. The first pipe 20 functions as an exhaust pipe for discharging exhaust gas from the housing 10. The first pipe 20 is held inside the first cylindrical end portion 11. A part of the first pipe 20 may also be disposed outside the first cylindrical end portion 11.

[0054] The first pipe 20 includes a first main body portion 21, a first large-diameter portion 22, a first through hole 23, and a first reduced-diameter portion 24. The first main body portion 21 has a first connecting portion 21a. The first large-diameter portion 22 has a first abutting portion 22a.

[0055] The first main body portion 21 is a portion between the upstream end and the downstream end in the first pipe 20.

[0056] The first connecting portion 21a is a portion in the upstream end of the first main body 21 that is connected to the second pipe 30. The first connecting portion 21a is located inside the housing 10.

[0057] The first large-diameter portion 22 is located at the downstream end of the first pipe 20. The inner diameter of the first large-diameter portion 22 is larger than the inner diameter of the first main body portion 21.

[0058] The first abutting portion 22a is located on the outer peripheral surface of the first large-diameter portion 22. The first abutting portion 22a abuts and is fixed to the first cylindrical end portion 11. In the present embodiment, the first abutting portion 22a is press-fitted into the first cylindrical end portion 11. According to other examples, the first main body portion 21 of the first pipe 20 may be configured such that a part of it passes through the first cylindrical end portion 11 and is located outside the housing 10. In this case, the first abutting portion 22a of the first pipe 20 that abuts the first cylindrical end portion 11 may be located at a position upstream of the first large-diameter portion 22.

[0059] The first through hole 23 penetrates the first pipe 20 from the inside to the outside of the first pipe 20. The first through hole 23 is provided on the side surface of the first pipe 20. In particular, the first through hole 23 is provided in a region of the side surface of the first main body portion 21 that is located inside the housing 10. One first through hole 23 may be provided, or a plurality of first through holes 23 may be provided.

[0060] The first reduced-diameter portion 24 is located between the first main body portion 21 and the first large-diameter portion 22, and the first reduced-diameter portion 24 connects the first main body portion 21 and the first large-diameter portion 22 to each other. The inner diameter of the first reduced-diameter portion 24 decreases as it approaches the first main body portion 21. The first reduced-diameter portion 24 can be formed in a conical shape or a stepped shape.

[0061] The second pipe 30 is a pipe made of metal that extends in a substantially straight line. The second pipe 30 is disposed on the upstream side inside the housing 10. The second pipe 30 functions as an intake pipe for introducing exhaust gas into the inside of the housing 10. The second pipe 30 is held inside the second cylindrical end portion 12. A part of the second pipe 30 may also be disposed outside the second cylindrical end portion 12.

[0062] The second pipe 30 has a second connecting portion 31, a second abutting portion 32, and a through hole 33.

[0063] The second connecting portion 31 is a portion of the downstream end of the second pipe 30 that is connected to the first pipe 20. The second connecting portion 31 is located inside the housing 10. The second connecting portion 31 has a holding member 4 on its outer surface. In Figure 1 the components located inside the first pipe 20 are shown in a dashed-line perspective view. Specifically, the second connecting portion 31 and the holding member 4 are shown in a perspective view. The other Figure 4B , Figure 7C and 7D are the same.

[0064] The holding member 4 is a strip-shaped member having a certain thickness. The holding member 4 can be elastically deformed. As an example in the present embodiment, the holding member 4 is a wire mesh. The wire mesh is formed by winding wire-shaped metal that is woven or non-woven. The holding member 4 is configured to apply a radial force to the first pipe 20 and the second pipe 30 by elastic deformation between the first pipe 20 and the second pipe 30, thereby holding the first pipe 20 and the second pipe 30.

[0065] The outer diameter of the second pipe 30 is smaller than the inner diameter of the second cylindrical end portion 12 and the inner diameter of the first pipe 20. In a state before the second connecting portion 31 is inserted into the first pipe 20, the outer diameter of the second connecting portion 31 including the holding member 4 is substantially the same as or slightly larger than the inner diameter of the first pipe 20.

[0066] The second connecting portion 31 of the second pipe 30 is held inside the first connecting portion 21a of the first pipe 20. The holding member 4 is compressed between the outer peripheral surface of the second connecting portion 31 and the inner peripheral surface of the first connecting portion 21a. That is, the second pipe 30 is pressed into the first connecting portion 21a by the holding member 4 at the second connecting portion 31. The first pipe 20 and the second pipe 30 are connected to each other by the holding member 4. The second connecting portion 31 is not fixed to the first connecting portion 21a. The second pipe 30 can slide in the first pipe 20 together with the holding member 4.

[0067] The first connecting portion 21a of the first pipe 20 and the second connecting portion 31 of the second pipe 30 are the portions that connect the first pipe 20 and the second pipe 30 to each other. Both the first connecting portion 21a and the second connecting portion 31 are located inside the housing 10.

[0068] The second abutting portion 32 is a portion located on the upstream side of the second pipe 30. The second abutting portion 32 abuts against and is fixed to the second cylindrical end portion 12. Figure 1 The second abutting portion 32 shown in is located at the upstream end of the second pipe 30. However, the second abutting portion 32 may also be located at a position downstream of the upstream end of the second pipe 30. In other words, the upstream end of the second pipe 30 may be located upstream of the second cylindrical end portion 12.

[0069] The second through hole 33 penetrates the second pipe 30 from the inside to the outside of the second pipe 30. The second through hole 33 is provided on the side surface of the second pipe 30. In particular, the second through hole 33 is provided in a region on the side surface of the second pipe 30 between the second connecting portion 31 and the second abutting portion 32. One second through hole 33 may be provided, or a plurality of second through holes 33 may be provided.

[0070] Exhaust gas flows into the interior of the muffler 1 from the upstream opening of the second pipe 30. That is, the exhaust gas passes through the inside of the second abutting portion 32 and flows in the portion of the second pipe 30 located inside the housing 10. The exhaust gas flows from the inside of the second pipe 30 through the second connecting portion 31 and the first connecting portion 21a into the inside of the first pipe 20, and passes through the inside of the first abutting portion 22a and is discharged to the outside of the muffler 1 from the downstream opening of the first pipe 20.

[0071] At this time, the exhaust gas passes through the first through-hole 23 and the second through-hole 33, and flows out from the inside of the first pipe 20 and the second pipe 30 into the internal space 16 of the housing 10. Through the action of expansion, interference, etc. of the exhaust gas in this internal space 16, the muffler 1 thus exerts a sound-absorbing effect. In order to improve the sound-absorbing effect, a sound-absorbing material can be filled in the internal space 16. A sound-absorbing material can be provided on the outer peripheral surface of at least one of the first pipe 20 and the second pipe 30 and / or a pipe covering the outer peripheral surface of the first pipe 20 or the second pipe 30, etc.

[0072] [1-2. Manufacturing method of muffler]

[0073] As Figure 2 shown, the manufacturing method of the muffler 1 includes a first cylindrical end forming step S110, a first pipe arranging step S120, a second cylindrical end forming step S130, and a second pipe arranging step S140. The manufacturing method of the muffler 1 is sequentially executed in the order of the first cylindrical end forming step S110, the first pipe arranging step S120, the second cylindrical end forming step S130, and the second pipe arranging step S140. The second cylindrical end forming step S130 can also be performed before the first pipe arranging step S120. Each step will be described with reference to FIGS. 3 and 4.

[0074] [1-2-1. First cylindrical end forming step]

[0075] The housing 10 is formed by reducing the diameter of the first end and the second end located on the opposite side of the first end of the cylindrical body 10a.

[0076] As Figure 3A shown, the first cylindrical end forming step S110 is a step of forming the first cylindrical end 11 on the cylindrical body 10a. The first cylindrical end 11 is formed by reducing the diameter of the downstream end of the cylindrical body 10a. Reducing the diameter means reducing a cylindrical component in the radial direction so as to process it into a cylindrical shape with a diameter smaller than the diameter of its surroundings. Hereinafter, reducing the diameter will also be simply referred to as diameter reduction. For example, diameter reduction can be achieved by rotational machining or other machining methods such as stamping.

[0077] The diameter reduction performed for forming the first cylindrical end 11 forms a first inclined portion 14 at a portion of the cylindrical body 10a adjacent to the upstream side of the first cylindrical end 11.

[0078] [1-2-2. First pipe arranging step]

[0079] As Figure 3B and Figure 3CAs shown, the first pipe configuration step S120 is a step of disposing the first connection portion 21a of the first pipe 20 inside the cylindrical body 10a by inserting the first pipe 20 into the inside of the first cylindrical end portion 11 of the cylindrical body 10a.

[0080] The first pipe 20 enters the inside of the cylindrical body 10a from the upstream-side opening of the cylindrical body 10a and is inserted into the first cylindrical end portion 11. The first abutting portion 22a in the first pipe 20 abuts against the first cylindrical end portion 11. The first connection portion 21a is disposed inside the cylindrical body 10a.

[0081] At this time, the first abutting portion 22a can be fixed to the first cylindrical end portion 11. For example, the fixing can be achieved by at least one of press-fitting, welding, and diameter expansion. In the present embodiment, in this step, the first abutting portion 22a is press-fitted into the first cylindrical end portion 11. In addition, the first abutting portion 22a is temporarily fixed to the first cylindrical end portion 11 by spot welding around the first cylindrical end portion 11. The first abutting portion 22a can also be fixed to the first cylindrical end portion 11 in a subsequent step of this step.

[0082] [1-2-3. Second cylindrical end portion forming step]

[0083] As Figure 3C shown, the second cylindrical end portion forming step S130 is a step of forming the second cylindrical end portion 12 on the cylindrical body 10a in a state where the first pipe 20 has been inserted into the first cylindrical end portion 11. The second cylindrical end portion 12 is formed by reducing the diameter of the upstream-side end portion of the cylindrical body 10a. The second cylindrical end portion 12 and the first cylindrical end portion are formed on substantially the same axis.

[0084] By the diameter reduction for forming the second cylindrical end portion 12, a second inclined portion 15 is formed in a portion of the cylindrical body 10a adjacent to the downstream side of the second cylindrical end portion 12.

[0085] As described above, the housing 10 is obtained by forming the first cylindrical end portion 11 and the second cylindrical end portion 12 on the cylindrical body 10a.

[0086] [1-2-4. Second pipe configuration step]

[0087] As Figure 4A shown, the second pipe configuration step S140 is a step of disposing the second pipe 30 inside the housing 10 by inserting the second pipe 30 from the outside of the housing 10 into the first pipe 20, wherein the first connection portion 21a of the first pipe 20 has been disposed inside the housing 10.

[0088] With the end on the upstream side of the second pipe 30 (i.e., the end on the side where the holding member 4 is not provided) as the front end, the second pipe 30 is inserted from the end on the downstream side of the first pipe 20 (i.e., the first large-diameter portion 22) into the inside of the first pipe 20. After inserting the front end of the second pipe 30 into the first large-diameter portion 22 of the first pipe 20, the front end of the second pipe 30 is introduced into the first main body portion 21 through the first reduced-diameter portion 24. In the present embodiment, the front end of the second pipe 30 corresponds to the second abutting portion 32.

[0089] During the process of inserting the second pipe 30 into the first pipe 20, the second connecting portion 31 at the end on the downstream side of the second pipe 30 and the holding member 4 are inserted into the inside of the first pipe 20. Since the outer diameter of the second connecting portion 31 including the holding member 4 is substantially the same as or slightly larger than the inner diameter of the first pipe 20, the second pipe 30 and the holding member 4 are pressed into the first pipe 20. In the present embodiment, a rod-shaped pressing jig 5 having a diameter smaller than the inner diameter of the first pipe 20 is used to press the second pipe 30 and the holding member 4 into the first pipe 20. The pressing jig 5 can be solid or hollow. When pressing the second pipe 30, at least a part of the portion of the pressing jig 5 that abuts against the second pipe 30 presses at least a part of the thick-walled portion of the second pipe 30.

[0090] As Figure 4B shown, when the second pipe 30 is further inserted into the first pipe 20, the front end of the second pipe 30 protrudes from the outside of the first pipe 20, moves upstream in the internal space 16 of the housing 10, and is inserted into the second cylindrical end portion 12.

[0091] The second pipe 30 passes through the second cylindrical end portion 12 and moves upstream until it abuts against the receiving jig 6, where the receiving jig 6 is located outside the housing 10 and at a position upstream of the second cylindrical end portion 12. The receiving jig 6 can abut against the second cylindrical end portion 12 or be separated from the second cylindrical end portion 12. When the front end of the second pipe 30 abuts against the receiving jig 6, the second pipe arrangement process S140 ends.

[0092] After the second pipe arrangement process S140 ends, both the second connecting portion 31 and the holding member 4 are pressed into the inside of the first pipe 20. The second pipe 30 is connected to the first pipe 20 via the holding member 4 at the second connecting portion 31. In the present embodiment, the holding member 4 is pressed into the first connecting portion 21a. Therefore, the second pipe 30 is connected to the first pipe 20 at the first connecting portion 21a of the first pipe 20. The first connecting portion 21a and the second connecting portion 31 are not fixed to each other. The second pipe 30 can slide relative to the first pipe 20 via the holding member 4.

[0093] The second abutting portion 32 abuts against the second cylindrical end portion 12. The second abutting portion 32 can be fixed to the second cylindrical end portion 12. For example, the fixing can be achieved by at least one of press-fitting, welding, and diameter expansion. The second abutting portion 32 can also be fixed to the second cylindrical end portion 12 in a subsequent process of this process.

[0094] As described above, by forming the housing 10 from the cylindrical body 10a and disposing the first pipe 20 and the second pipe 30 inside the housing 10, the muffler 1 is obtained.

[0095] [1-3. Function, Effect]

[0096] According to the embodiment described above, the following functions and effects can be obtained.

[0097] (1a) In the second pipe arranging process S140, the second pipe 30 is inserted into the first pipe 20 from the end portion on the downstream side of the first pipe 20.

[0098] According to the above insertion, even if no flaring process or the like is applied to the end portion on the upstream side of the first pipe 20, the second pipe 30 can be easily inserted into the first pipe 20. Therefore, the assemblability between the first pipe 20 and the second pipe 30 can be improved.

[0099] (1b) In the second cylindrical end portion forming process S130, the second cylindrical end portion 12 and the first cylindrical end portion 11 are formed on the same axis. By reducing the diameter for forming the second cylindrical end portion 12, a second inclined portion 15 is formed at a portion adjacent to the second cylindrical end portion 12 in the cylindrical body 10a. The inner diameter of the second inclined portion 15 decreases as it approaches the second cylindrical end portion 12 from the central portion 13.

[0100] According to the above configuration of the housing 10 or the cylindrical body 10a, in the second pipe arranging process S140, the second pipe 30 is easily inserted into the second cylindrical end portion 12 under the guidance of the second inclined portion 15. Therefore, the assemblability between the second pipe 30 and the second cylindrical end portion 12 can be improved.

[0101] (1c) The second pipe 30 is inserted into the first pipe 20 from the first large-diameter portion 22 of the first pipe 20. The inner diameter of the first large-diameter portion 22 is larger than the inner diameter of the first main body portion 21. The first reduced-diameter portion 24 connects the first main body portion 21 and the first large-diameter portion 22 to each other. The inner diameter of the first reduced-diameter portion 24 is formed to decrease as it approaches the first main body portion 21.

[0102] According to the configuration of the first pipe 20 described above, in the second pipe configuration step S140, it is easy to insert the second pipe 30 into the first pipe 20 from the first large-diameter portion 22. In addition, it is easy to insert the second pipe 30 from the first large-diameter portion 22 through the first reduced-diameter portion 24 into the first main body portion 21. Therefore, the assemblability between the first pipe 20 and the second pipe 30 can be improved.

[0103] (1d) In the first pipe configuration step S120, with the first cylindrical end portion 11 already formed in the housing 10, the first pipe 20 is inserted into the interior of the housing 10.

[0104] Compared with the case where the first cylindrical end portion 11 is formed after the first pipe 20 is disposed inside the housing 10, according to the above-described process, the position of the first pipe 20 is less likely to shift. Therefore, the position shift of the first pipe 20 can be suppressed.

[0105] In addition, there is no need for a component for supporting the first pipe 20 inside the housing 10 before the first cylindrical end portion 11 is formed. Therefore, the types of components required to manufacture the muffler 1 can be reduced.

[0106] (1e) In the second pipe configuration step S140, with the second cylindrical end portion 12 already formed in the housing 10, the second pipe 30 is inserted into the interior of the housing 10.

[0107] Compared with the case where the second cylindrical end portion 12 is formed after the second pipe 30 is disposed inside the housing 10, according to the above-described process, the position of the second pipe 30 is less likely to shift. Therefore, the position shift of the second pipe 30 can be suppressed.

[0108] In addition, there is no need for a component for supporting the second pipe 30 inside the housing 10 before the second cylindrical end portion 12 is formed. Therefore, the types of components required to manufacture the muffler 1 can be reduced.

[0109] (1f) The first connecting portion 21a of the first pipe 20 and the second connecting portion 31 of the second pipe 30, which are the portions where the first pipe 20 and the second pipe 30 are connected to each other, are both located inside the housing 10. The first connecting portion 21a and the second connecting portion 31 are not fixed to each other and can slide via the holding member 4.

[0110] According to the above configuration, when the first pipe 20 and the second pipe 30 expand or contract due to the heat from the exhaust gas, they can both elongate or contract in the axial direction. Therefore, an excessive load is not applied to the first pipe 20 and the second pipe 30, and thus the occurrence of buckling can be suppressed.

[0111] (1g) The second connecting portion 31 in the second pipe 30 has a holding member 4 on its outer peripheral surface. Therefore, in the process of inserting the second pipe 30 into the first pipe 20, damage to the inner surface of the first pipe 20 by the second pipe 30 can be suppressed.

[0112] (1h) After the second pipe arrangement step S140, the first pipe 20 can be fixed to the first cylindrical end portion 11 by welding or diameter expansion, etc., and the second pipe 30 can be fixed to the second cylindrical end portion 12. Therefore, the first pipe 20 and the second pipe 30 can be fixed more firmly to the housing 10.

[0113] [1-4. Corresponding relationships between terms]

[0114] In the above embodiment, the upstream end of the first pipe 20 and the first connecting portion 21a correspond to an example of the first end of the first pipe, and the downstream end of the first pipe 20 and the first large-diameter portion 22 correspond to an example of the second end of the first pipe.

[0115] The upstream end of the second pipe 30 and the second abutting portion 32 correspond to an example of the first end of the second pipe, and the downstream end of the second pipe 30 and the second connecting portion 31 correspond to an example of the second end of the second pipe.

[0116] The downstream end of the cylindrical body 10a corresponds to an example of the first end of the cylindrical body, and the upstream end of the cylindrical body 10a corresponds to an example of the second end of the cylindrical body.

[0117] The first cylindrical end portion forming step S110 corresponds to an example of providing the first cylindrical end portion, and the first pipe arrangement step S120 corresponds to an example of arranging the first end of the first pipe inside the housing. The second cylindrical end portion forming step S130 corresponds to an example of providing the second cylindrical end portion, and the second pipe arrangement step S140 corresponds to an example of arranging the second pipe. The first cylindrical end portion forming step S110, the first pipe arrangement step S120, and the second cylindrical end portion forming step S130 correspond to an example of preparing the housing.

[0118] [2. Second Embodiment]

[0119] [2-1. Structure of the muffler]

[0120] The manufacturing method of the muffler 1 in the second embodiment is used to manufacture the same muffler 1 as in the first embodiment. The differences between the second embodiment and the first embodiment will be described below. In addition, the same reference numerals as in the first embodiment denote the same components, and refer to the previous description.

[0121] [2-2. Manufacturing method of the muffler]

[0122] As Figure 5 shown, the manufacturing method of the muffler 1 in the second embodiment includes a pipe connection step S210, a first cylindrical end formation step S220, a second cylindrical end formation step S230, and a connecting pipe arrangement step S240. The manufacturing method of the muffler 1 in the second embodiment is sequentially executed in the order of the pipe connection step S210, the first cylindrical end formation step S220, the second cylindrical end formation step S230, and the connecting pipe arrangement step S240. However, the execution order of the pipe connection step S210, the first cylindrical end formation step S220, and the second cylindrical end formation step S230 is not particularly limited and can be executed in any order. At least two of the pipe connection step S210, the first cylindrical end formation step S220, and the second cylindrical end formation step S230 can be executed in parallel. Use Figure 6 FIG. 6 and FIG. 7 to describe each step.

[0123] [2-2-1. Pipe Connection Step]

[0124] As Figure 6 shown, the pipe connection step S210 is a step of connecting the first pipe 20 and the second pipe 30 by inserting the second pipe 30 inside the first pipe 20.

[0125] With the end on the side where the holding member 4 is not provided as the front end, the second pipe 30 is inserted into the first pipe 20 from the first large-diameter portion 22 of the first pipe 20. After the front end of the second pipe 30 is inserted into the first large-diameter portion 22 of the first pipe 20, the front end of the second pipe 30 is introduced into the first main body portion 21 through the first reduced-diameter portion 24. In the present embodiment, the front end of the second pipe 30 corresponds to the second abutting portion 32.

[0126] During the insertion of the second pipe 30 into the first pipe 20, the second connecting portion 31 of the second pipe 30 and the holding member 4 are inserted into the first pipe 20. Since the outer diameter of the second connecting portion 31 including the holding member 4 is substantially the same as or slightly larger than the inner diameter of the first pipe 20, the second pipe 30 and the holding member 4 are pressed into the first pipe 20. In the embodiment, a rod-shaped pressing jig 5 having a diameter smaller than the inner diameter of the first pipe 20 is used to press the second pipe 30 and the holding member 4 into the first pipe 20.

[0127] When the second pipe 30 is further inserted into the first pipe 20, the front end of the second pipe 30 protrudes from the outside of the first pipe 20. At this time, the second connecting portion 31 of the second pipe 30 is disposed inside the first pipe 20. In the present embodiment, the second connecting portion 31 is disposed inside the first connecting portion 21a, and the first connecting portion 21a is located at the end of the first pipe 20 on the side opposite to the first large-diameter portion 22.

[0128] As described above, in the pipe connection step S210, the second abutting portion 32 in the second pipe 30 is disposed outside the first pipe 20. The second connecting portion 31 in the second pipe 30 is disposed inside the first pipe 20. The first pipe 20 and the second pipe 30 are connected to each other.

[0129] [2-2-2. First cylindrical end forming process]

[0130] As Figure 7A shown, the first cylindrical end forming process S220 is a process of providing the first cylindrical end 11 on the cylindrical body 10a.

[0131] The first cylindrical end forming process S220 is the same process as the first cylindrical end forming process S110. That is, the first cylindrical end 11 is achieved by reducing the diameter of the downstream end of the cylindrical body 10a.

[0132] By reducing the diameter for providing the first cylindrical end 11, a first inclined portion 14 is formed at a portion of the cylindrical body 10a adjacent to the upstream side of the first cylindrical end 11.

[0133] [2-2-3. Second cylindrical end forming process]

[0134] As Figure 7B shown, the second cylindrical end forming process S230 is a process of providing the second cylindrical end 12 on the cylindrical body 10a.

[0135] The second cylindrical end forming process S230 is the same process as the second cylindrical end forming process S130. That is, the second cylindrical end 12 is provided by reducing the diameter of the upstream end of the cylindrical body 10a. The second cylindrical end 12 and the first cylindrical end 11 are provided on substantially the same axis.

[0136] By reducing the diameter for providing the second cylindrical end 12, a second inclined surface 15 is formed at a portion of the cylindrical body 10a adjacent to the downstream side of the second cylindrical end 12.

[0137] As described above, the housing 10 is obtained by providing the first cylindrical end 11 and the second cylindrical end 12 on the cylindrical body 10a.

[0138] [2-2-4. Connecting Pipe Arrangement Process]

[0139] As Figure 7C shown, the connecting pipe arrangement process S240 is a process of arranging at least a part of the first pipe 20 and the second pipe 30 that have been connected to each other inside the cylindrical body 10a. In this process, the first pipe 20 and the second pipe 30 remain in the connected state without separating from each other.

[0140] With the end on the side where the holding member 4 is not provided as the front end, the second pipe 30 connected to the first pipe 20 is inserted into the inside of the cylindrical body 10a from the first cylindrical end 11. The front end of the second pipe 30 is the upstream end of the second pipe 30. In this embodiment, the front end of the second pipe 30 corresponds to the second abutting portion 32.

[0141] During the process of inserting the mutually connected first pipe 20 and second pipe 30 into the cylindrical body 10a, the upstream end of the first pipe 20 (the first connecting portion 21a in this embodiment) enters the inside of the cylindrical body 10a from the first cylindrical end 11.

[0142] As Figure 7D shown, when the second pipe 30 is further inserted into the cylindrical body 10a, the front end of the second pipe 30 is inserted into the second cylindrical end 12, and the second abutting portion 32 is arranged inside the second cylindrical end 12. In addition, the first abutting portion 22a of the first pipe 20 is arranged inside the first cylindrical end 11. The upstream end of the first pipe 20 is arranged inside the cylindrical body 10a.

[0143] At this time, the upstream end of the second pipe 30 is located inside the second cylindrical end 12. The downstream end of the second pipe 30 is located inside the cylindrical body 10a. That is to say, the second connecting member 31 and the holding member 4 are located inside the upstream end of the first pipe 20 (i.e., the first connecting member 21a), where the first pipe 20 is located inside the cylindrical body 10a. The downstream end of the first pipe 20 is located inside the first cylindrical body end 11. However, the upstream end of the second pipe 30 may also be located outside the cylindrical body 10a. The downstream end of the second pipe 30 may also be located outside the cylindrical body 10a as long as it is inside the first pipe 20. The downstream end of the first pipe 20 may also be located outside the cylindrical body 10a.

[0144] In this process or subsequent processes of this process, the first abutting portion 22a can be fixed to the first cylindrical end portion 11. The second abutting portion 32 can be fixed to the second cylindrical end portion 12. For example, the fixation can be achieved by at least one of press-fitting, welding, and diameter expansion. In this embodiment, the first abutting portion 22a is fixed by press-fitting into the first cylindrical end portion 11. The second abutting portion 32 is fixed to the second cylindrical end portion 12 in a subsequent process of this process.

[0145] As described above, by forming the housing 10 with the cylindrical body 10a and disposing the first pipe 20 and the second pipe 30 connected to each other inside the housing 10, the muffler 1 is obtained.

[0146] [2-3. Function, Effect]

[0147] According to the second embodiment described above, the same effects as the first embodiment can be obtained. In addition, according to the second embodiment, the processes of providing the first cylindrical end portion 11 and the second cylindrical end portion 12 on the cylindrical body 10a and connecting the first pipe 20 and the second pipe 30 to each other can be implemented independently of each other. Therefore, the manufacturing man-hours can be reduced.

[0148] [2-4. Corresponding Relationship between Terms]

[0149] In the above embodiment, the upstream end of the first pipe 20 and the first connecting portion 21a correspond to an example of the first end of the first pipe.

[0150] The upstream end of the second pipe 30 and the second abutting portion 32 correspond to an example of the first end of the second pipe, and the downstream end of the second pipe 30 and the second connecting portion 31 correspond to an example of the second end of the second pipe.

[0151] The downstream end of the cylindrical body 10a corresponds to an example of the first end of the cylindrical body, and the upstream end of the cylindrical body 10a corresponds to an example of the second end of the cylindrical body.

[0152] The pipe connection process S210 corresponds to an example of connecting the first pipe and the second pipe to each other, the first cylindrical end portion forming process S220 corresponds to an example of providing the first cylindrical end portion, the second cylindrical end portion forming process S230 corresponds to an example of providing the second cylindrical end portion, and the connected pipe arrangement process S240 corresponds to an example of arrangement.

[0153] [3. Other Embodiments]

[0154] The embodiments of the present disclosure have been described above. However, the content of the present disclosure is not limited to the above embodiments and can take various forms.

[0155] (3a) In the above-described embodiment, the inner peripheral surface of the first connecting portion 21a in the first pipe 20 can be reduced in diameter. The outer peripheral surface of the second connecting portion 31 in the second pipe 30 can be enlarged in diameter. According to the above configuration, the holding member 4 disposed between the inner peripheral surface of the first connecting portion 21a and the outer peripheral surface of the second connecting portion 31 is in a further compressed state. Therefore, the resistance to vibrations from a vehicle or the like can be improved at the connecting portion between the first pipe 20 and the second pipe 30.

[0156] (3b) In the above-described embodiment, the upstream end portion of the second pipe 30 can be reduced in diameter. According to the above configuration, in the second pipe arrangement step S140 or the connecting pipe arrangement step S240, it is easy to insert the second pipe 30 into the second cylindrical end portion 12.

[0157] (3c) In the above-described embodiment, the second abutting portion 32 in the second pipe 30 can be enlarged in diameter. According to the above configuration, it is easy to fix the second abutting portion 32 to the second cylindrical end portion 12.

[0158] (3d) In the above-described embodiment, the first pipe 20 is disposed at the first cylindrical end portion 11 on the downstream side of the housing 10. The second pipe 30 is disposed on the second cylindrical end portion 12 on the upstream side of the housing 10. However, the arrangement of the first pipe 20 and the second pipe 30 is not limited thereto. For example, the first pipe 20 can be disposed on the second cylindrical end portion 12 on the upstream side of the housing 10. The second pipe 30 can be disposed at the first cylindrical end portion 11 on the downstream side of the housing 10.

[0159] (3e) Both the first cylindrical end portion 11 and the second cylindrical end portion 12 are formed by reducing the diameter of the upstream end portion or the downstream end portion of the cylindrical body 10a. However, instead of reducing the diameter of the cylindrical body 10a, an independent component that has been reduced in diameter can be provided at the upstream end portion or the downstream end portion of the cylindrical body 10a by welding or the like, thereby forming the first cylindrical end portion 11 and the second cylindrical end portion 12. This independent component can function as the first cylindrical end portion 11 or the second cylindrical end portion 12.

[0160] (3f) One or more first through holes 23 are provided in the first pipe 20. One or more second through holes 33 are provided in the second pipe 30. However, in the muffler 1, it is only necessary to provide at least one of the first through holes 23 and the second through holes 33 in at least one of the first pipe 20 and the second pipe 30. For example, if the first through hole 23 is provided in the first pipe 20, the second through hole 33 may not be provided in the second pipe 30. Or, if the second through hole 33 is provided in the second pipe 30, the first through hole 23 may not be provided in the first pipe 20.

[0161] (3g) Multiple constituent elements may implement multiple functions of one constituent element in the above-described embodiments, or multiple constituent elements may implement one function of one constituent element. In addition, one constituent element may implement multiple functions of multiple constituent elements, or one constituent element may implement one function implemented by multiple constituent elements. In addition, a part of the configuration of the above-described embodiments may be omitted. In addition, at least a part of the configuration of the above-described embodiments may be added to the configuration of the above-described other embodiments, or at least a part of the configuration of the above-described embodiments may be replaced with the configuration of the above-described other embodiments, etc.

[0162] [Technical idea disclosed in this specification]

[0163] [Item 1]

[0164] A method for manufacturing a muffler, characterized by comprising the following steps:

[0165] Prepare a housing, wherein a first end of a first pipe is disposed inside the housing; and

[0166] By inserting a second pipe into the first pipe disposed inside the housing from the outside of the housing, the second pipe is disposed inside the housing, and

[0167] The housing includes:

[0168] A central portion; and

[0169] A first cylindrical end portion and a second cylindrical end portion, the first cylindrical end portion and the second cylindrical end portion are respectively located on both sides of the central portion, and are cylindrical end portions having a diameter smaller than the diameter of the central portion,

[0170] Preparing the housing includes preparing a housing in which the first pipe is inserted inside the first cylindrical end portion, and the first end of the first pipe is disposed inside the housing,

[0171] Disposing the second pipe includes: inserting the second pipe from a second end of the first pipe, and causing the first end of the second pipe to pass at least through the first end of the first pipe, and moving the second end of the second pipe to a position disposed inside the first pipe, wherein the second end of the first pipe is located on the opposite side of the first end of the first pipe, and the second end of the second pipe is located on the opposite side of the first end of the second pipe,

[0172] The muffler is configured to hold the first pipe connected to the second pipe inside the first cylindrical end portion.

[0173] [Project 2]

[0174] The manufacturing method of the muffler according to Item 1, characterized in that,

[0175] Configuring the second pipe includes: in a state where the second pipe is already connected to the first pipe, moving at least the first end of the second pipe inserted from the second end of the first pipe to the inside of the second cylindrical end portion, so that the second pipe is held inside the second cylindrical end portion.

[0176] [Project 3]

[0177] The manufacturing method of the muffler according to Item 1, characterized in that,

[0178] The housing is formed by reducing the diameters of the first end and the second end of a cylindrical body, wherein the second end of the cylindrical body is located on the opposite side of the first end of the cylindrical body.

[0179] Preparing the housing includes:

[0180] By reducing the diameter of the first end of the cylindrical body, thereby providing the first cylindrical end portion on the cylindrical body;

[0181] By inserting the first pipe into the inside of the first cylindrical end portion, thereby disposing the first end of the first pipe inside the housing; and

[0182] By reducing the diameter of the second end of the cylindrical body in a state where the first pipe is inserted into the inside of the first cylindrical end portion, thereby providing the second cylindrical end portion on the cylindrical body.

[0183] Configuring the second pipe includes: in a state where the second pipe is already connected to the first pipe, moving at least the first end of the second pipe inserted from the second end of the first pipe to the inside of the second cylindrical end portion, so that the second pipe is held inside the second cylindrical end portion.

[0184] [Project 4]

[0185] A manufacturing method of a muffler, characterized by including the following steps:

[0186] By inserting a second pipe into the inside of a first pipe, thereby disposing the first end of the second pipe outside the first pipe, and connecting the first pipe and the second pipe to each other in such a way that the second end of the second pipe is disposed inside the first pipe, wherein the second end of the second pipe is located on the opposite side of the first end of the second pipe;

[0187] A first cylindrical end portion having a diameter smaller than that of the cylindrical body is provided at the first end of the cylindrical body;

[0188] A second cylindrical end portion having a diameter smaller than that of the cylindrical body is provided at the second end of the cylindrical body, wherein the second end of the cylindrical body is located on the opposite side of the first end of the cylindrical body; and

[0189] The first pipe and the second pipe that are connected to each other are at least partially disposed inside the cylindrical body, and

[0190] The arrangement includes: by inserting the second pipe connected to the first pipe from the first end of the second pipe into the inside of the first cylindrical end portion, at least a part of the first pipe is disposed inside the first cylindrical end portion, at least a part of the second pipe is disposed inside the second cylindrical end portion, and the first end of the first pipe is disposed inside the cylindrical body,

[0191] The silencer is configured to hold the first pipe inside the first cylindrical end portion and hold the second pipe connected to the first pipe inside the second cylindrical end portion.

[0192] [Item 5]

[0193] The method for manufacturing the silencer according to Item 3 or 4, characterized in that

[0194] Providing the second cylindrical end portion includes providing the second cylindrical end portion and the first cylindrical end portion on substantially the same axis.

[0195] [Item 6]

[0196] The method for manufacturing the silencer according to any one of Items 3 to 5, characterized in that

[0197] Providing the second cylindrical end portion includes providing the second cylindrical end portion in such a manner that the inner diameter of a portion adjacent to the second cylindrical end portion of the cylindrical body decreases as it approaches the second cylindrical end portion.

[0198] [Item 7]

[0199] The method for manufacturing the silencer according to any one of Items 1 to 6, characterized in that

[0200] The second pipe has a holding member on the outer peripheral surface of the second end of the second pipe,

[0201] In a state before the second pipe is inserted into the first pipe, an outer diameter of the second end of the second pipe including the holding member is greater than or equal to an inner diameter of the first pipe.

[0202] [Item 8]

[0203] A method for manufacturing a muffler according to any one of Items 1 to 7, characterized in that

[0204] The first pipe has a main body portion and a reduced diameter portion, wherein the main body portion is located between the first end of the first pipe and the second end of the first pipe, the second end of the first pipe is located on the opposite side of the first end of the first pipe, and the reduced diameter portion is located between the main body portion and the second end of the first pipe.

[0205] An inner diameter of the second end of the first pipe is greater than an inner diameter of the main body portion.

[0206] An inner diameter of the reduced diameter portion is formed to decrease as it approaches the main body portion.

Claims

1. A method for manufacturing a muffler, characterized in that: The following steps are involved: preparing a housing, wherein the first end of the first pipe is disposed inside the housing; and The second pipe is inserted into the first pipe arranged inside the shell from the outside of the shell, so that the second pipe is arranged inside the shell, and The housing comprises: Central Division; and a first cylindrical end portion and a second cylindrical end portion, wherein the first cylindrical end portion and the second cylindrical end portion are respectively located on both sides of the central portion and are cylindrical ends having a diameter smaller than that of the central portion, Preparing the housing includes preparing the housing, wherein the first pipe is inserted into the inner side of the first cylindrical end portion, and the first end of the first pipe is arranged inside the housing, Configuring the second pipe includes: inserting the second pipe from the second end of the first pipe, allowing the first end of the second pipe to at least pass through the first end of the first pipe, and moving the second end of the second pipe to a position configured inside the first pipe, wherein the second end of the first pipe is located on the opposite side of the first end of the first pipe, and the second end of the second pipe is located on the opposite side of the first end of the second pipe, The muffler is configured to hold the first duct connected to the second duct inside the first cylindrical end portion.

2. The method for manufacturing a muffler according to claim 1, characterized in that: Arranging the second pipe includes: in a state where the second pipe is connected to the first pipe, moving the first end of the second pipe inserted from the second end of the first pipe at least to the inside of the second cylindrical end portion so that the second pipe is held inside the second cylindrical end portion.

3. The method for manufacturing a muffler according to claim 1, characterized in that: The housing is formed by reducing the diameters of a first end and a second end of a cylindrical body, wherein the second end of the cylindrical body is located on the opposite side of the first end of the cylindrical body. The preparation of the shell comprises: The first end of the cylindrical body is reduced in diameter, thereby providing the first cylindrical end portion on the cylindrical body; inserting the first pipe into the inner side of the first cylindrical end portion so as to dispose the first end of the first pipe inside the housing; and The second end of the cylindrical body is provided with the second cylindrical end by reducing the diameter of the second end of the cylindrical body in a state where the first pipe is inserted into the inner side of the first cylindrical end. Arranging the second pipe includes: in a state where the second pipe is connected to the first pipe, moving the first end of the second pipe inserted from the second end of the first pipe at least to the inside of the second cylindrical end portion so that the second pipe is held inside the second cylindrical end portion.

4. A method for manufacturing a muffler, characterized in that: The steps include: Inserting the second pipe into the inside of the first pipe so that the first end of the second pipe is arranged outside the first pipe, and connecting the first pipe and the second pipe to each other in a manner that the second end of the second pipe is arranged inside the first pipe, wherein the second end of the second pipe is located on the opposite side of the first end of the second pipe; A first cylindrical end portion having a diameter smaller than that of the cylindrical body is provided at a first end of the cylindrical body; providing a second cylindrical end portion having a diameter smaller than a diameter of the cylindrical body at a second end of the cylindrical body, wherein the second end of the cylindrical body is located on an opposite side of the first end of the cylindrical body; and The first pipe and the second pipe connected to each other are at least partially arranged inside the cylindrical body, and The arrangement includes: inserting the second pipe connected to the first pipe from the first end of the second pipe into the inside of the first cylindrical end, thereby arranging at least a portion of the first pipe inside the first cylindrical end, arranging at least a portion of the second pipe inside the second cylindrical end, and arranging the first end of the first pipe inside the cylindrical body, The silencer is configured such that the first pipe is held inside the first cylindrical end portion, and the second pipe connected to the first pipe is held inside the second cylindrical end portion.

5. The method for manufacturing a silencer according to claim 3 or 4, characterized in that: Providing the second cylindrical end portion includes arranging the second cylindrical end portion and the first cylindrical end portion substantially on the same axis.

6. The method for manufacturing a silencer according to claim 3 or 4, characterized in that: Providing the second cylindrical end portion includes providing the second cylindrical end portion in such a manner that an inner diameter of a portion adjacent to the second cylindrical end portion of the cylindrical body decreases as approaching the second cylindrical end portion.

7. The method for manufacturing a silencer according to any one of claims 1 to 4, characterized in that: The second pipe includes a holding member on an outer peripheral surface of the second end of the second pipe. In a state before the second pipe is inserted into the first pipe, an outer diameter of the second end of the second pipe including the holding member is greater than or equal to an inner diameter of the first pipe.

8. The method for manufacturing a silencer according to any one of claims 1 to 4, characterized in that: The first pipe has a main body and a reduced diameter portion, wherein the main body is located between the first end of the first pipe and the second end of the first pipe, the second end of the first pipe is located on the opposite side of the first end of the first pipe, and the reduced diameter portion is located between the main body and the second end of the first pipe. The inner diameter of the second end of the first pipe is larger than the inner diameter of the main body. The inner diameter of the reduced diameter portion is formed to decrease as approaching the main body portion.

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