JPH09170424A - Muffler and its manufacturing method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To easily manufacture a silencer. SOLUTION: A thick long pipe is cut in advance to a length of an outer cylinder to form a cut pipe 20 (first step), a cassette portion 21 is inserted therein, and the cut pipe 20 is wound around the cassette portion 21. A clearance is provided between the outer periphery of the sound deadening material 4 and the cut pipe 20 (second step).
When this temporary assembly 22 is put between a pair of molds 23 and 24 and clamped, the cut pipe 20 is reduced in diameter to become the outer cylinder 2, and at the same time, the beading caulking portion 5 is integrally formed on the mold matching surface. (Third step).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer attached to an exhaust pipe of an engine of a motorcycle or the like, and a method of manufacturing the silencer.

[0002]

2. Description of the Related Art In Japanese Utility Model Laid-Open No. 4-166609, an outer cylinder is roll-formed from a flat plate portion, and an inner cylinder wound with a sound deadening material is placed inside the outer cylinder, and the diameter of the outer cylinder is changed by a jig. A method of making a muffler is shown in which the opposite edges in the axial direction are contracted and butt welded together.

[0003]

According to the above manufacturing method, a press cutting step and a rolling step for the plate material are required to form the outer cylinder, and a butt welding step is required at the time of subsequent assembly. The work constant is relatively large, the working time is long, the cost is high, and high quality control is required for the welded joint. It is also desired to improve the rigidity of the outer cylinder in order to prevent vibration of the outer cylinder, that is, ringing of the outer plate, which is caused by fluctuations in the pressure of the exhaust gas. Further, it is also desired that the front and rear cap members can be efficiently attached.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 provides an inner cylinder forming an exhaust gas passage, an outer cylinder into which the inner cylinder is inserted, and a space between these inner and outer cylinders. In a sound deadening device including a sound deadening material to be interposed, a diameter of a pipe member having a larger inner diameter than a non-assembled outer diameter which is an outer diameter of the sound deadening material in a non-compressed state is reduced in the outer cylinder. And a crimp portion is formed on the outer circumference of the outer cylinder.

The invention of claim 2 relating to the manufacturing method is
Insert the sound deadening inner body with the sound deadening material attached to the outer circumference of the inner cylinder forming the passage of the exhaust gas into the pipe member having the inner diameter larger than the non-assembled outer diameter which is the outer diameter of the non-compressed sound deadening material. Then, this pipe member is reduced in diameter so as to have a smaller diameter than the outer diameter when not assembled to form an outer cylinder, and the excess portion due to the diameter reduction of the pipe member is radially outward on the outer circumference of this outer cylinder. It is characterized in that a beading caulking portion which extends substantially the entire length in the axial direction by being projected is integrally formed.

At this time, when the cap member fitted to the end portion of the outer cylinder of the silencer is fitted to the end portion of the pipe member, the pipe member and the cap member It is also possible to perform positioning by means of a positioning portion including an annular protrusion formed on either one of the fitting portions and an annular groove formed on the other side so that this fitting portion fits.

According to the invention of claim 4, claim 2
A part of the beading caulking portion formed in (1) may be further deformed from one side surface to the other side surface.

Instead of the uneven deformation, as in the invention of claim 5, the beading caulking portion formed in claim 2 can be bent so as to fall on the outer peripheral surface of the outer cylinder.

According to a sixth aspect of the present invention, there is provided a sound deadening inner body having a sound deadening material attached to the outer periphery of an inner cylinder forming a passage for exhaust gas,
This sound deadening inner body is inserted into a pipe member having an inner diameter that is larger than the outer diameter when the sound deadening material is in a non-compressed state, and is larger than the outer diameter when the sound deadening material is not assembled. Fit the member and reduce the diameter of the pipe member so that it is smaller than the outer diameter when not assembled to form the outer cylinder, and on the outer periphery of this outer cylinder, the excess due to the diameter reduction of the pipe member is radially outward. By forming a beading caulking portion that extends substantially the entire length in the axial direction by integrally projecting to the outer cylinder, and then crimping a flange portion previously formed on the outer periphery of the fitting portion of the front and rear cap members to the outer cylinder. .

Further, in the invention of claim 7, in the invention of claim 6, the flange portion of the front and rear cap members is provided with an escape portion for avoiding a beading caulking portion of the outer cylinder, and a fitting portion of the front and rear cap members. It is characterized in that a positioning portion for the outer cylinder is provided in the.

[0011]

According to the first aspect of the present invention, since a pipe member cut from a long pipe material to a predetermined length can be used as a member for forming the outer cylinder, the conventional outer cylinder can be used. The press cutting process and the rolling process of the plate material and the butt welding process after that are unnecessary, so that the work constant and the working time can be shortened.

Further, the sound deadening material can be compressed by reducing the diameter of the pipe member, and when the caulking portion is formed on the outer circumference of the outer cylinder, the rigidity is improved by the caulking portion, and the outside caused by the pressure fluctuation of the exhaust gas or the like. Vibration of the cylinder, that is, ringing of the outer plate can be prevented.

According to the second aspect of the invention, the pipe member is reduced in diameter to form the outer cylinder, and the outer cylinder has an outer periphery,
A beading caulking portion that extends substantially the entire length in the axial direction is integrally formed by projecting an excess portion due to the diameter reduction of the pipe member outward in the radial direction.

Therefore, in addition to providing the effects of claim 1 relating to the reduced diameter outer cylinder, the assembling work with the sound deadening interior body can be performed extremely efficiently, and
At the same time as reducing the diameter, the sound deadening material is sufficiently compressed and can be firmly bonded to the sound deadening inner body.

In addition, by utilizing the surplus due to the diameter reduction, the beading caulking portion of substantially the entire axial length can be integrally formed on the outer circumference of the outer cylinder, and the long caulking portion can sufficiently improve the rigidity of the outer cylinder. Can be easily formed.

Further, as in the third aspect of the present invention, if the positioning portion composed of the annular projection and the annular groove is provided in the fitting portion of the cap member and the pipe member, the cap member is more accurate than the pipe member. And it can be positioned quickly and easily.

According to the invention of claim 4, claim 3
By partially deforming the portion of the beading caulking portion in the above from one side surface to the other side surface, the bonding strength of the beading caulking portion can be improved.

In this case, even if the beading caulking portion is bent so as to fall on the outer peripheral surface of the outer cylinder as in the fifth aspect of the invention, the bonding strength of the beading caulking portion can be similarly improved. it can.

According to the invention of claim 6, the front and rear cap members are fitted into the pipe member together with the sound deadening inner body, and after the diameter of the pipe member is reduced, a flange portion formed in advance on the outer periphery of the fitted portion of the front and rear cap members is provided. Since the outer cylinder is crimped, it is not necessary to weld the front and rear cap members that have been conventionally used to the entire circumference of the outer cylinder, and the work of fixing the cap member can be performed easily and in a short time.
Since sufficient sealing material can be applied around the fitted portions of these cap members, the sealing performance is also improved.

According to the invention of claim 7, the flange portions of the front and rear cap members are provided with the escape portions for avoiding the beading caulking portion of the outer cylinder, so that the caulking can be performed by avoiding the beading caulking portion. It is possible to prevent the sealing performance from deteriorating due to the formation of a gap between the cap member and the outer cylinder due to the caulking of the beading caulking without escaping.

Further, since the fitting portions of the front and rear cap members are provided with the positioning portions for the outer cylinder, the relief portions can be accurately positioned with respect to the beading caulking portion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a manufacturing process of a muffler according to the present invention, which is constructed as a muffler for a motorcycle engine, FIG. 2 is a schematic perspective view of a finished product, and FIG. 3 is an intermediate process. 1 is a view showing the temporary assembly cut along line 3-3 in FIG. 1, FIG. 4 is a view showing a finished product cut along line 4-4 in FIG. 2, and FIG. 5 is a detailed shape of the finished product. 2-of FIG.
It is sectional drawing which follows the 5 line.

As shown in FIGS. 2, 4 and 5, the silencer 1 has a cylindrical portion, which is a main part, of an outer cylinder 2, an inner cylinder 3 inserted inside the outer cylinder 2, a silencer 1 and an outer cylinder 2. The sound absorbing member 4 is interposed between the outer cylinder 2 and the beading caulking portion 5 that is integrally formed on the outer peripheral portion of the outer cylinder 2. The beading caulking portion 5 projects outward in the radial direction and extends in a rib shape over substantially the entire axial length. .

Front caps 6 are provided on both ends of the silencer 1.
Also, a tail cap 7 is attached, a rear portion of the exhaust pipe 8 is connected to the front cap 6, and a tail pipe 9 is supported by the tail cap 7 penetrating inward and outward.

The inside of the muffler 1 is composed of first and second separators 10 and 11, and three chambers 12, 13 and 1 are arranged in the longitudinal direction.
The first inner pipe 1 is divided into 4 and the space between the small chambers 12 and 14 is divided.
The second inner pipe 16 connects between the small chambers 13 and 14
The small chamber 13 and the outside air communicate with each other through the tail pipe 9.

A diffuser pipe 17 is provided around the tail pipe 9 in the small chamber 14, and a sound deadening material 18 such as glass wool is interposed between the diffuser pipe 17 and the tail pipe 9 inside the diffuser pipe 17, and a communication hole 9 a of the tail pipe 9 is provided. The exhaust sound in the tail pipe 9 is absorbed via the.

The inner cylinder 3 is formed of punching metal, mesh, or the like, has a large number of communication holes 19, and communicates between the interiors of the small chambers and the sound deadening member 4. The sound deadening material 4 is made of a suitable sound deadening material such as glass wool.

The silencer 4, the inner cylinder 3 and the tail pipe 9, the first separator 10 and the second pipe fitted inside the silencer 4
The separator 11, the first inner pipe 15, and the second inner pipe 16 form a sound deadening inner body.

Next, a method of manufacturing the silencer 1 will be described. In FIG. 1, first, from the long pipe member 20a to the outer cylinder 2,
The cut pipe 20 having the same length and a large inner diameter is cut to a required length (first step).

The inner diameter of the cut pipe 20 is set so that the cassette portion 21 can be inserted smoothly in the second step.
The size is larger than the outer diameter of the cassette portion 21 which will be described later when not assembled.

The cassette portion 21 is formed by adding the front cap 6 and the tail cap 7 to the sound deadening interior body and integrating them.
The tail pipe 9, the first separator 10, the second separator 11, the first inner pipe 15, and the second inner pipe 16 are assembled in advance into the inner cylinder 3, and the inner cylinder 3 is inserted.
Assemble the sound deadening material 4 around the circumference of.

At this stage, that is, the cassette portion 21
The outer diameter of the sound deadening member 4 in a state where only a small number of parts are assembled is the outer diameter of the cassette portion 21 when it is not assembled, and since the sound deadening member 4 is not compressed yet, it is larger than the inner diameter of the outer cylinder 2 when the assembly is completed, and It is smaller than the inner diameter of the cut pipe 20.

Then, the cassette portion 21 is inserted into the cut pipe 20 to form the temporary assembly 22 (second step). At this time, as is clear from FIG. 3, a clearance c between the inner diameter of the outer cylinder 2 and the outer diameter of the sound deadening member 4 is sufficient to insert the cassette portion 21 into the cut pipe 20.
Are formed.

Referring again to FIG. 1, the temporary assembly 22 is placed between a pair of dies 23 and 24 which are axially halved, and the dies 23 and 24 are arranged from the left and right as indicated by arrows B and C. Clamp the mold (3rd step). At this time, cavities corresponding to the finished product of the muffler 1 are formed in the molds 23 and 24 respectively, and a bead gap 26 is provided in a part of the mating surface 25 over substantially the entire axial length of the cut pipe 20. Has been.

Therefore, at the same time when the mold is clamped, the temporary assembly 22 is
The cut pipe 20 is reduced in diameter to become the outer cylinder 2, and the sound deadening material 4 on the inside is compressed and fixed between the inner cylinders 3.

At this time, the surplus in the circumferential direction of the cut pipe 20 is pushed into the bead gap 26 to project outward in the radial direction, and the beading caulking linearly extends to the outer circumference of the outer cylinder 2 substantially along the entire axial length. It will be Part 5.

Further, the outer cylinder 2 is caulked and fixed to the outer circumferences of the front cap 6 and the tail cap 7 by reducing the diameter so that subsequent welding can be omitted. However, they can be welded if necessary, and in this case, they are more firmly fixed.

As described above, according to the present manufacturing method, the roll forming and the butt welding for the outer cylinder, which have been conventionally required, are not necessary, so that the work constant can be reduced, and the large-diameter cut pipe 20 is used. The cassette portion 21 can be inserted smoothly, and since it is formed by crimping instead of welding, it can be manufactured quickly, so that the production efficiency can be improved.

Further, since the beading caulking portion 5 is formed in the axial direction on the outer circumference of the outer cylinder 2, the beading caulking portion 5 improves the rigidity, and the vibration of the outer cylinder caused by the pressure fluctuation of the exhaust gas, that is, It is possible to prevent ringing of the outer plate.

The invention of the present application is not limited to the above-mentioned embodiment, but can be applied in various ways. For example, as shown in FIG. 6, a beading caulking portion 5 is formed on the upper and lower sides to further improve the rigidity. be able to.

Further, the number of the beading caulking portions 5 can be set to a larger number of 3 or more, and the outer cylinder 2 is not always required.
It does not extend over substantially the entire length in the axial direction, and may be formed in a partial range in the axial direction.

7 to 12 relate to a muffler for a motorcycle according to another embodiment. However, this embodiment is different from the previous embodiment only in a few points such as the attachment of front and rear cap members, so that the description will be focused on this difference, common parts will be denoted by the same reference numerals, and redundant description will be omitted (hereinafter As well).

FIG. 7 is a view similar to FIG. 1 showing the silencer manufacturing process, FIG. 8 is a view showing a second process, FIG. 9 is a view showing a third process, and FIG. 10 is a view showing a fourth process. , FIG. 11 is Z of FIG.
FIG. 12 is an enlarged partial view in the direction of the arrow, and FIG. 12 is a view in the direction of the arrow A of FIG.

In FIG. 7, the cassette portion 21 of the second step
Differs from the previous embodiment in that the front cap 6 and the tail cap 7 are separate bodies, and the relationship between the inner diameter of the cut pipe 20 and the outer diameter of the cassette portion 21 when not assembled is the same.

Front cap 6 and tail cap 7
After the cassette portion 21 is inserted into the cut pipe 20, the cassette portion 21 is fitted into both end opening portions of the cut pipe 20, and the fitting portions 40 and 41 are provided with flange portions 42 and 43, respectively.

In the third step, the diameter of the cut pipe 20 is reduced, and this step is the same as in the previous embodiment.

In this embodiment, as the fourth step, the flange portion 4 of the front cap 6 and the tail cap 7 is further processed.
A crimping step of roll-crimping Nos. 2 and 43 from both axial sides of the outer cylinder 2 by using curl dies 30 and 31 as shown by arrows D and E is added.

In the fourth step, the front cap 6 and the tail cap 7 are fixed by caulking to the openings on both ends of the outer cylinder 2 in the axial direction, and sufficient material is preliminarily attached to the outer peripheries of the fitting portions 40, 41 prior to caulking. Good sealing performance can be obtained by applying the above sealing material.

FIG. 8 is a cross-sectional view schematically showing a state in which the front cap 6 and the tail cap 7 are fitted into the opening portions at both ends of the cut pipe 20 in the second step, and the fitting portions 40 and 41 have one of them. Flanges 42 and 43 are provided that fold back and project outward in the radial direction. The outer diameters of the outer peripheral ends of the flanges 42 and 43 are substantially equal to the outer diameter of the cassette 21 when not assembled. There is.

As shown in a partially enlarged view in the drawing, a dowel-shaped positioning protrusion 44 is formed in the fitting portion 41, and a positioning hole 45 formed in the axial end portion of the cut pipe 20.
To be fitted.

On the other hand, in the flange portion 43, a portion which is formed inward from the outer peripheral end side of the notch 46 and forms a relief portion 47 described later is formed at a position substantially symmetrical to the positioning protrusion 44. Although not shown, the fitting portion 40 side has the same structure.

FIG. 9 is a view corresponding to FIG. 8 in the third step, in which the beading caulking portion 5 formed by reducing the diameter of the cut pipe 20 is as shown in the Z arrow view in the drawing.
The inner peripheral surface of the outer cylinder 2 is in close contact with the outer peripheries of the fitting portions 40 and 41 while overlapping with the escape portion 47.

FIG. 10 is a schematic axial sectional view of the finished product formed in the fourth step.
43 are respectively crimped around the open end of the outer cylinder 2 in a curled cross section.

The enlarged portion in the figure shows the side of the flange portion 43, and by roll-caulking with the curl die 31,
The curl forming portion 32 crimps the flange portion 43 in a curl shape, leaving the relief portion 47.

As shown in FIGS. 11 and 12, the escape portion 47 is left uncrushed and the beading caulking portion 5 is left in plan view.
Forming a crimping portion 48 that wraps the end portion of the above in a substantially U-shape. Although not shown, the flange portion 42 side has the same structure.

In FIG. 10, reference numeral 49 is a front end separator, and 50 is an introduction pipe to which an exhaust pipe (not shown) is connected. The flange 42 is fitted to the maximum inner diameter of the front end separator 49, and the front end is connected. A shoulder portion formed inside the outer peripheral portion of the separator 49 is fitted to the end portion of the inner cylinder 3.

Although the inner cylinder 3 and the sound deadening material 4 are each only about half of the total length of the outer cylinder 2, even in such a case, the tail pipe 9, the first separator 10, the second separator 11, the first separator 1 Inner pipe 15, second inner pipe 1
The cassette unit 21 is composed of 6 sub-sets in advance.

Thus, according to the manufacturing method of this embodiment,
It is not necessary to weld the front and rear cap members around the outer cylinder, which is conventionally used, and the cap member (6, 6
The fixing work of 7) can be performed easily and in a short time.

In addition, since sufficient sealing material can be applied around the fitting portions 40, 41 of these cap members (6, 7) prior to the crimping work, the sealing performance is also improved.

Further, the flange portions 42, 43 of the cap member (6, 7) are provided with the escape portion 47 for avoiding the beading caulking portion 5 of the outer cylinder, so that the beading caulking portion 5 is provided.
You can avoid crimping, beading crimping part 5
Cap member (6, 7) by crimping without running away
A gap is formed between the outer cylinder 2 and the outer cylinder 2, and it is possible to prevent a situation in which the gap deteriorates the sealing performance.

Further, since the fitting portions 40, 41 of the cap members (6, 7) are provided with the positioning portions (44, 45) for the outer cylinder 2, the relief portions 47 are accurately positioned with respect to the beading caulking portion 5. Can be positioned.

FIG. 13 shows a silencer for a motorcycle having substantially the same structure as that of the previous embodiment (however, the front cap 6 and the tail cap 7 have the flange portions 42 and 43 of the previous embodiment).
(Not provided) is a view taken along the axial direction in a state before the diameter reduction of the pipe member according to the third embodiment in which the positioning structure is changed.

In FIG. 13, this positioning structure has the fitting portions 4 of the front cap 6 and the tail cap 7 respectively.
Annular projection 6 formed on the outer circumference of 0, 41 by roll processing or the like
0 and 62, and correspondingly, annular grooves 61 and 63 formed by an appropriate method on the inner circumference of the front and rear end portions of the outer cylinder 2 in the axial direction.

As is apparent from the enlarged portion in the figure, the tail cap 7 is attached to the rear end portion of the outer cylinder 2 which has not been subjected to the diameter reduction processing yet.
When is fitted, the annular projection 62 is fitted into the annular groove 63 in the most part of the circumferential direction thereof to form an annular positioning structure.

After that, if the diameter of the outer cylinder 2 is reduced, the annular projection 6
The non-fitted portion of 2 also fits in the annular groove 63, and as a result, the entire circumference of the annular protrusion 62 is positioned.

Therefore, the positioning work becomes relatively easy and quick, and the positioning becomes more accurate. The positional relationship between the annular protrusion 62 and the annular groove 63 may be reversed. The front cap 6 side is the same as the tail cap 7 side.

FIG. 14 is a view showing in principle the portion of the outer cylinder 2 in the fourth embodiment in which the joining strength of the beading caulking portion 5 formed by reducing the diameter of the outer cylinder 2 is enhanced, and is enlarged in the drawing. As is clear from the cross-section, the beading caulking portion 5 is embossed to form a recess 70 on one side and a protrusion 71 on the other side. Improves joint strength.
However, such a processing method is not limited to embossing.

Further, as another mode for enhancing the bonding strength of the beading caulking portion, there is a fifth embodiment shown in principle in FIG. FIG. 15 is a view similar to FIG. 14, and in this example, as is apparent from the enlarged cross-sectional portion in the drawing, the entire length of the beading caulking portion 5 formed by reducing the diameter is set on the outer peripheral surface of the outer cylinder 2. It is bent so that it will collapse. By bending and deforming in this manner, the bonding strength of the beading caulking portion 5 can be easily increased.

[Brief description of the drawings]

FIG. 1 is a process chart of the present invention.

FIG. 2 is a schematic perspective view of a finished product.

FIG. 3 is a view showing the temporary assembly cut along line 3-3 in FIG.

FIG. 4 is a diagram showing a completed product taken along line 4-4 in FIG.

5 is a sectional view taken along line 5-5 of FIG. 2 showing the detailed shape of the finished product.

FIG. 6 is a sectional view of a portion corresponding to FIG. 4 showing a modified example.

FIG. 7 is a diagram showing a manufacturing process of the silencer according to the second embodiment.

FIG. 8 is a diagram showing the second step.

FIG. 9 is a diagram showing the third step.

FIG. 10 is a view showing the fourth step.

11 is an enlarged partial view in the Z arrow direction of FIG.

FIG. 12 is a direction of the arrow A in FIG.

FIG. 13 is a sectional view according to a third embodiment.

FIG. 14 is a diagram showing in principle the fourth embodiment.

FIG. 15 is a view showing the principle of the fifth embodiment.

[Explanation of symbols]

1: Silencer, 2: Outer cylinder, 3: Inner cylinder, 4: Silencer, 5:
Beading caulking part 6: Front cap, 7: Tail cap, 20: Cut pipe, 21: Cassette part, 23, 24: Mold

Claims (7)

[Claims] 1. A muffler comprising an inner cylinder forming an exhaust gas passage, an outer cylinder into which the inner cylinder is inserted, and a muffling material interposed between the inner and outer cylinders. The pipe member having an inner diameter larger than the non-assembled outer diameter, which is the outer diameter of the silencer material in the uncompressed state, is formed by reducing the diameter, and the caulking portion is formed on the outer circumference of the outer cylinder. Characteristic silencer. 2. A sound deadening inner body having a sound deadening material attached to the outer circumference of an inner cylinder forming a passage for exhaust gas, the inner diameter of which is larger than the non-assembled outer diameter which is the outer diameter of the non-compressed sound deadening material. Inserted into a pipe member having, and reducing the diameter of the pipe member to a diameter smaller than the outer diameter when not assembled to form an outer cylinder, and at the outer periphery of the outer cylinder, an excess due to the diameter reduction of the pipe member is formed. A method of manufacturing a silencer, characterized in that a beading caulking portion that extends substantially the entire length in the axial direction is integrally formed by projecting outward in the radial direction. 3. The silencer comprises a cap member fitted to the end of the outer cylinder, and when the cap member is fitted to the end of the pipe member, the pipe member and the cap member are fitted together. An annular protrusion formed on either one of the joints,
The silencer manufacturing method according to claim 2, characterized in that the silencer is positioned by a positioning portion including an annular groove formed on the other side so as to be fitted. 4. The method of manufacturing a noise canceling device according to claim 2, wherein a part of the beading caulking portion is deformed in a concavo-convex manner from one side surface to the other side surface. 5. The method of manufacturing a silencer according to claim 2, wherein the beading caulking portion is bent so as to fall on the outer peripheral surface of the outer cylinder. 6. A sound deadening inner body having a sound deadening material attached to the outer periphery of an inner cylinder forming an exhaust gas passage, and the sound deadening inner body is provided with:
The silencer is inserted into a pipe member having an inner diameter larger than the outer diameter when the silencer is in a non-compressed state, and front and rear cap members are fitted to both ends in the axial direction of the pipe member to form a pipe member. The outer cylinder is formed by reducing the diameter of the outer cylinder so that it is smaller than the outer diameter when it is not assembled.
A beading caulking portion extending substantially the entire axial length is integrally formed by projecting a surplus portion due to the diameter reduction of the pipe member outward in the radial direction, and is then formed in advance on the outer periphery of the fitting portion of the front and rear cap members. A method of manufacturing a silencer, characterized in that a flange portion is crimped to the outer cylinder. 7. The front and rear cap members have flange portions provided with escape portions for avoiding beading caulking portions of the outer cylinder, and front and rear cap member fitting portions provided with positioning portions for the outer cylinder. The method for manufacturing the silencer according to claim 6.