JP7564150B2 - Manufacturing method of silencer - Google Patents

Description

This disclosure relates to a method for manufacturing a silencer.

The muffler, which is placed in the exhaust gas flow path, is composed of a double tube with sound-absorbing material placed in the gap between the inner and outer tubes. This muffler is manufactured by filling one end of the gap with sound-absorbing material while closing the gap at the same time, and then reducing the diameter of the outer tube by spinning to close the other end of the gap (see Patent Document 1).

In this manufacturing method, in order to prevent the sound-absorbing material from protruding from the gap during spinning, the outer tube is reduced in diameter while air is sucked in from an inner tube that has holes that communicate with the gap.

JP 2019-44592 A

In the above manufacturing method, the suction force of the sound-absorbing material varies depending on the distance from the hole in the inner tube. As a result, it is not possible to sufficiently prevent the sound-absorbing material from spilling out of the gap during spinning.

One aspect of the present disclosure aims to provide a method for manufacturing a silencer that can suppress the protrusion of sound-absorbing material during spinning.

One aspect of the present disclosure is a method for manufacturing a silencer including an inner tube, an outer tube arranged to surround the outer peripheral surface of the inner tube, a gap between the inner tube and the outer tube, and a sound-absorbing material arranged in the gap. The method for manufacturing a silencer includes a step of filling the gap, the first end of which is closed, with the sound-absorbing material from a second end, and a step of reducing the diameter of the outer tube by spinning while sending gas from the second end of the gap toward the sound-absorbing material filled in the gap.

With this configuration, by sending gas from the second end toward the sound-absorbing material in the gap, the sound-absorbing material can be pressed toward the first end (i.e., the closed end) of the gap. As a result, it is possible to prevent the sound-absorbing material from protruding from the gap during spinning. In addition, it is possible to prevent the generation of an air layer where no sound-absorbing material exists, thereby improving the sound-absorbing function and reducing the size of the silencer.

In one aspect of the present disclosure, in the diameter reduction process, gas may be applied to the sound absorbing material present at least near the inner circumferential surface of the outer tube. With this configuration, the gas can press against the sound absorbing material on the radially outer side of the silencer where the centrifugal force caused by spinning is large. This promotes the effect of suppressing the protrusion of the sound absorbing material during spinning.

In one aspect of the present disclosure, in the diameter reduction process, the amount of gas per unit time sent toward the region close to the inner circumferential surface of the outer tube may be greater than the amount of gas per unit time sent toward the region close to the outer circumferential surface of the inner tube. With this configuration, the gas can be concentrated on the sound-absorbing material on the radially outer side of the silencer where the centrifugal force caused by spinning is large. This promotes the effect of suppressing the protrusion of the sound-absorbing material during spinning.

In one aspect of the present disclosure, the diameter reduction step may involve using a nozzle to send gas near the inner circumferential surface of the outer tube. With this configuration, the gas can be efficiently guided to the area where the sound-absorbing material is likely to protrude. This promotes the effect of suppressing the protrusion of the sound-absorbing material during spinning.

In one aspect of the present disclosure, the outer shape of the outer tube in a cross section perpendicular to the axial direction may be circular. In the diameter reduction process, gas may be applied to the inner peripheral surface of the outer tube that forms the gap. With this configuration, it is possible to efficiently suppress the sound absorbing material from protruding from the outer tube, where the centrifugal force on the radially outward side is large.

In one aspect of the present disclosure, the inner tube may have a communication hole that communicates with the gap. In the diameter reduction process, spinning may be performed while sucking gas from the internal space of the inner tube. With this configuration, it is possible to offset part of the centrifugal force applied to the sound-absorbing material by sucking in the gas. This promotes the effect of suppressing the protrusion of the sound-absorbing material during spinning.

FIG. 1A is a schematic central vertical cross-sectional view of a silencer in an embodiment, and FIG. 1B is a schematic cross-sectional view taken along line IB-IB in FIG. 1A. FIG. 2 is a flow diagram of a method for manufacturing a silencer according to an embodiment. 3A and 3B are schematic diagrams showing a step in the method of manufacturing the silencer of FIG. FIG. 4 is a schematic diagram showing one step in the method of manufacturing the silencer of FIG. FIG. 5 is a schematic diagram showing one step in a method for manufacturing a silencer in an embodiment different from that shown in FIG.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[1. First embodiment]
[1-1. Configuration]
<Silencer>
1A and 1B is provided in an exhaust gas flow passage of an internal combustion engine, for example. The silencer 1 includes an inner pipe 2, an outer pipe 3, a holding member 4, a gap 5, and a sound absorbing material 6.

<Inner tube>
The inner pipe 2 is a metal pipe through which exhaust gas passes. The outer shape of the inner pipe 2 in a cross section perpendicular to the axial direction (i.e., transverse cross section) is circular (specifically, a perfect circle). The inner pipe 2 has a first end 21, a second end 22, and a plurality of communication holes 23.

The first end 21 and the second end 22 are each radially connected to the outer pipe 3. The exhaust gas may flow from the first end 21 to the second end 22, or from the second end 22 to the first end 21.

The multiple communication holes 23 are through holes that connect the internal space of the inner pipe 2 (i.e., the exhaust gas flow path) with the gap 5 (i.e., the outside of the inner pipe 2). The communication holes 23 are arranged at any location along the circumferential or axial direction of the inner pipe 2. Note that the inner pipe 2 may have only one communication hole 23. The communication between the communication hole 23 and the gap 5 makes it possible to muffle noise by expanding the space using the gap 5.

<Outer tube>
The outer pipe 3 is a metal pipe arranged to surround the outer peripheral surface of the inner pipe 2, and constitutes the outer shell of the silencer 1. The outer shape of the cross section (i.e., transverse cross section) perpendicular to the axial direction of the outer pipe 3 is circular (specifically, a perfect circle). The inner diameter of the outer pipe 3 is larger than the outer diameter of the inner pipe 2.

The outer pipe 3 has a first end 31, a second end 32, and a central portion. The first end 31 is superimposed on the outer peripheral surface of the first end 21 of the inner pipe 2, and its entire circumference is joined to the first end 21 by, for example, welding. The second end 32 is superimposed on the outer peripheral surface of the second end 22 of the inner pipe 2, and its entire circumference is connected to the second end 22 via the retaining member 4.

The central portion is a portion located between the first end 31 and the second end 32 in the axial direction of the outer tube 3. The first end 31 and the second end 32 each have a smaller diameter than the central portion. The central portion has a body portion with a constant outer diameter, a first inclined portion that reduces in diameter linearly, stepwise, or curvedly from one end of the body portion toward the first end 31, and a second inclined portion that reduces in diameter linearly, stepwise, or curvedly from the other end of the body portion toward the second end 32.

<Holding member>
The holding member 4 is a ring-shaped member disposed between the second end 22 of the inner tube 2 and the second end 32 of the outer tube 3. The holding member 4 may be C-shaped with a portion of the ring cut out. The holding member 4 may also be formed by combining multiple parts that form a ring or C-shape.

The retaining member 4 is sandwiched between the outer peripheral surface of the inner tube 2 and the inner peripheral surface of the outer tube 3, and is not fixed to at least one of the inner tube 2 and the outer tube 3. The retaining member 4 slides against the inner tube 2 or the outer tube 3, thereby absorbing the difference in thermal expansion between the inner tube 2 and the outer tube 3.

The retaining member 4 is arranged along the entire circumferential direction of the outer circumferential surface of the inner tube 2 and the inner circumferential surface of the outer tube 3. In other words, the retaining member 4 is arranged so as to close the axial end of the inner tube 2 in the space between the inner tube 2 and the outer tube 3 (i.e., the gap 5). Note that the retaining member 4 does not have to completely close the gap 5.

There are no limitations on the holding member 4, so long as it can hold the sound-absorbing material 6 within the gap 5 and can slide at least relative to the inner tube 2 or the outer tube 3. A suitable example of the holding member 4 is a metal wire mesh.

<Gaps>
The gap 5 is a space provided between the inner tube 2 and the outer tube 3. The gap 5 has a first end 51 closed by the first end 21 of the inner tube 2 and the first end 31 of the outer tube 3, and a second end 52 closed by the second end 22 of the inner tube 2, the second end 32 of the outer tube 3, and the retaining member 4. The gap 5 is defined by the outer peripheral surface of the inner tube 2 and the inner peripheral surface of the outer tube 3.

<Sound absorbing material>
The sound absorbing material 6 is an aggregate of fillers having sound absorbing properties arranged in the gap 5. As the sound absorbing filler, for example, fibers such as graphite fibers are suitable.

Specifically, the sound-absorbing material 6 is disposed between the inner tube 2 and the central body portion of the outer tube 3, between the inner tube 2 and the first inclined portion of the central portion of the outer tube 3, and between the inner tube 2 and the second inclined portion of the central portion of the outer tube 3. It is preferable that the sound-absorbing material 6 is disposed with a uniform density.

<Method of manufacturing silencer>
The method for manufacturing a silencer shown in FIG. 2 includes a joining step S10, a filling step S20, and a diameter reducing step S30.

(Joining process)
In this step, as shown in FIG. 3A, the first end 21 of the inner pipe 2 and the first end 31 of the outer pipe 3 are joined together by, for example, welding.

The outer tube 3 in this process is a straight tube with one end reduced in diameter by spinning to form a first inclined section and a first end 31. The outer tube 3 is inserted into an inner tube 2 to which a retaining member 4 is fixed at the end opposite to the first end 21. The first end 21 of the inner tube 2 and the first end 31 of the outer tube 3 are joined to form a gap 5 with the first end 51 closed.

(Filling process)
In this step, as shown in FIG. 3B, the sound absorbing material 6 is filled into the gap 5 from the second end 52 (i.e., the side opposite to the first end 51).

Specifically, with the cap 12 (see FIG. 4) inserted into the second end 22 of the inner tube 2, the sound-absorbing material 6 is filled while the air inside the inner tube 2 is sucked out. When filling the sound-absorbing material 6, it is advisable to rotate the inner tube 2 and the outer tube 3 in order to fill the sound-absorbing material 6 with a relatively uniform density.

(Diameter reduction process)
In this step, as shown in FIG. 4, the outer tube 3 is reduced in diameter by spinning while gas is being fed from the second end 52 of the gap 5 toward the sound absorbing material 6 filled in the gap 5.

The outer tube 3 is spun using a known spinning device. The spinning device includes a spindle 11 attached to the first end 21 of the inner tube 2 (i.e., the first end 31 of the outer tube 3), a cap 12 inserted into the second end 22 of the inner tube 2, and a roller (not shown) positioned radially outward of the second end 32 of the outer tube 3.

The spindle 11 rotates the outer tube 3 together with the inner tube 2, for example. The tip of the spindle 11 is inserted into the internal space of the inner tube 2. A roller is pressed against the second end 32 of the outer tube 3, which is rotated by the spindle 11, from the outside in the radial direction, thereby reducing the diameter of the outer tube 3.

The spinning is performed until the outer tube 3, together with the holding member 4 previously attached to the inner tube 2, closes the second end 52 of the gap 5. This forms the second inclined portion and the second end 32 of the outer tube 3. Note that the outer tube 3 may also be spun by rotating a chuck that fixes the inner tube 2 or the outer tube 3, for example.

During spinning (specifically, from the start of rotation of the inner tube 2 and the outer tube 3 until the second end 32 of the outer tube 3 is formed), gas is sent toward the sound-absorbing material 6 by the gas supply device 13. The gas can be, for example, compressed air. The gas supply device 13 uses nozzles 13A and 13B to apply the gas to the inner surface that forms the gap 5 of the outer tube 3, thereby sending the gas near the inner surface of the rotating outer tube 3.

As a result, in this process, gas is directed at at least the sound absorbing material 6 present near the inner circumferential surface of the outer tube 3. Furthermore, in this process, gas is not substantially directed to the sound absorbing material 6 present near the outer circumferential surface of the inner tube 2. Alternatively, in this process, the amount of air near the outer circumferential surface of the inner tube 2 may be relatively smaller than the amount of air near the inner circumferential surface of the outer tube 3. For example, a stronger wind may be directed at the inner circumferential surface of the outer tube 3 than near the outer circumferential surface of the inner tube 2.

In this manner, in this process, the amount of gas per unit time sent toward the region close to the inner surface of the outer tube 3 is made greater than the amount of gas per unit time sent toward the region close to the outer surface of the inner tube 2. In other words, in this process, the amount of gas per unit area in the cross section of the gap 5 sent toward the region close to the inner surface of the outer tube 3 is made greater than the amount of gas per unit area in the cross section of the gap 5 sent toward the region close to the outer surface of the inner tube 2. In this process, both the amount of gas per unit time and the amount of gas per unit area may be adjusted.

The gas sent from the gas supply device 13 presses the sound-absorbing material 6 toward the blocked first end 51 of the gap 5. Therefore, even if the inner diameter of the outer tube 3 is large, the communication holes 23 of the inner tube 2 are offset, or the diameter of the communication holes 23 is small, the sound-absorbing material 6 can be prevented from protruding. In addition, because the sound-absorbing material 6 is compressed within the gap 5, the generation of an air layer where no sound-absorbing material 6 exists is prevented.

In this process, the second end 32 of the outer tube 3 is reduced in diameter by spinning, so it is advisable to change the orientation of the nozzles 13A and 13B accordingly. In other words, it is advisable to gradually move the tips of the nozzles 13A and 13B closer to the outer circumferential surface of the inner tube 2 in accordance with the spinning.

In FIG. 4, gas is supplied using two nozzles 13A and 13B, but since the outer tube 3 rotates, the number of nozzles may be one. Also, three or more nozzles may be arranged at equal intervals along the circumferential direction of the outer tube 3. Furthermore, the tip of the nozzle may be flared. Also, the gas supply direction may be parallel to the axial direction of the inner tube 2.

In addition, in this process, spinning is performed while sucking gas from the internal space of the inner tube 2. Specifically, gas is sucked from the internal space of the rotating inner tube 2 by the suction passage 11A provided inside the spindle 11.

The gas in the gap 5 passes through the communication hole 23 of the inner tube 2 and is discharged to the outside mainly by the spindle 11. As the gas is sucked in, the sound-absorbing material 6 is also sucked toward the outer periphery of the inner tube 2. In other words, a force that counteracts the centrifugal force caused by spinning acts on the sound-absorbing material 6. Note that a gas discharge device other than the spindle 11 may also be used.

[1-2. Effects]
According to the embodiment described above in detail, the following effects can be obtained.
(1a) By sending gas from the second end 52 toward the sound-absorbing material 6 in the gap 5, the sound-absorbing material 6 can be pressed toward the first end 51 (i.e., the closed end) of the gap 5. As a result, it is possible to suppress the sound-absorbing material 6 from protruding from the gap 5 during spinning. In addition, since it is possible to suppress the generation of an air layer where no sound-absorbing material 6 exists, it is possible to improve the sound-absorbing function and reduce the size of the silencer 1.

(1b) By blowing gas onto the sound-absorbing material 6 near the inner circumferential surface of the outer tube 3, the gas can press against the sound-absorbing material 6 on the radially outer side of the silencer 1 where the centrifugal force caused by spinning is large. This promotes the effect of suppressing the protrusion of the sound-absorbing material 6 during spinning.

(1c) By making the amount of gas sent toward the area close to the inner circumferential surface of the outer tube 3 greater than the amount of gas sent toward the area close to the outer circumferential surface of the inner tube 2, the gas can be concentrated in the sound-absorbing material 6 on the radially outer side of the silencer 1 where the centrifugal force caused by spinning is large. This promotes the effect of suppressing the protrusion of the sound-absorbing material 6 during spinning.

(1d) By using nozzles 13A and 13B to send gas near the inner circumferential surface of the outer tube 3, the gas can be efficiently guided to the area where the sound-absorbing material 6 is likely to protrude. This promotes the effect of suppressing the protrusion of the sound-absorbing material 6 during spinning.

(1e) By blowing gas onto the inner peripheral surface of the outer tube 3 that forms the gap 5, the sound-absorbing material 6 can be efficiently prevented from protruding from the outer tube 3, where the centrifugal force on the radially outward side is large.

(1f) By sucking gas from the internal space of the inner tube 2, part of the centrifugal force applied to the sound-absorbing material 6 due to the gas suction can be offset. This enhances the effect of suppressing the protrusion of the sound-absorbing material 6 during spinning.

2. Other embodiments
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(2a) In the method for manufacturing a silencer according to the above embodiment, gas does not necessarily have to be sucked from the internal space of the inner tube during the diameter reduction process. In addition, the inner tube does not necessarily have to have a communication hole.

(2b) In the method for manufacturing a silencer according to the above embodiment, the outer shapes of the cross sections of the inner and outer tubes do not necessarily have to be perfect circles. For example, the outer shapes of these cross sections may be ellipses.

(2c) In the manufacturing method of the silencer of the above embodiment, in the diameter reduction process, the gas does not necessarily have to be directed at the inner surface of the outer tube. In addition, the gas does not necessarily have to be sent by a nozzle. Furthermore, the amount of gas sent toward the area close to the inner surface of the outer tube and the amount of gas sent toward the area close to the outer surface of the inner tube may be equal.

For example, as shown in FIG. 5, the gas supply device 14 may be a fan that blows gas over the entire second end 52 of the gap 5 along the axial direction of the inner tube 2. The gas supply device 14 is configured to blow gas evenly over the entire end face of the sound-absorbing material 6.

(2d) In the manufacturing method of the muffler of the above embodiment, depending on the axial length of the muffler, the usage environment (e.g., when the exhaust gas temperature is low), etc., the muffler does not necessarily need to have a retaining member.

(2e) In the method for manufacturing a muffler according to the above embodiment, the muffler may include a separator that divides the gap into an upstream side and a downstream side in the exhaust gas flow direction. Also, only one of the gaps divided by the separator may be filled with sound-absorbing material.

Furthermore, the muffler may have two or more layers of different types of sound absorbing material. For example, during the diameter reduction process, gas may be sent to glass fiber packed on top of a sound absorbing material such as stainless wool.

(2f) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the configuration of the above embodiments may be omitted. In addition, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. All aspects included in the technical idea identified from the wording of the claims are embodiments of the present disclosure.

1... Silencer, 2... Inner tube, 3... Outer tube, 4... Holding member, 5... Gap, 6... Sound absorbing material,
11: spindle; 11A: suction passage; 12: cap; 13: gas supply device;
13A, 13B... nozzle, 14... gas supply device, 21... first end portion, 22... second end portion,
23...Communication hole, 31...First end, 32...Second end, 51...First end, 52...Second end.

Claims (7)

A method for manufacturing a silencer comprising an inner tube, an outer tube arranged to surround an outer circumferential surface of the inner tube, a gap provided between the inner tube and the outer tube, and a sound absorbing material arranged in the gap, the method comprising the steps of:
filling the gap with the sound absorbing material from a second end of the gap whose first end is closed;
a step of reducing a diameter of the outer tube by spinning while feeding gas from the second end of the gap toward the sound absorbing material filled in the gap;
Equipped with
In the step of reducing the diameter, the gas is applied to the sound-absorbing material present at least in the vicinity of an inner circumferential surface of the outer tube . A method for manufacturing the silencer according to claim 1 ,
A method for manufacturing a silencer, wherein in the diameter reducing process, the amount of gas per unit time sent toward a region close to the inner surface of the outer tube is made greater than the amount of gas per unit time sent toward a region close to the outer surface of the inner tube. A method for manufacturing a silencer according to claim 1 or 2 , comprising the steps of:
In the step of reducing the diameter, the gas is sent to the vicinity of the inner circumferential surface of the outer tube using a nozzle. A method for manufacturing the silencer according to claim 1 ,
The outer tube has a circular cross section perpendicular to the axial direction,
In the step of reducing the diameter, the gas is applied to an inner peripheral surface of the outer tube which constitutes the gap. A method for manufacturing a silencer comprising an inner tube, an outer tube arranged to surround an outer circumferential surface of the inner tube, a gap provided between the inner tube and the outer tube, and a sound absorbing material arranged in the gap, the method comprising the steps of:
filling the gap with the sound absorbing material from a second end of the gap whose first end is closed;
a step of reducing a diameter of the outer tube by spinning while feeding gas from the second end of the gap toward the sound absorbing material filled in the gap;
Equipped with
The outer tube has a circular cross section perpendicular to the axial direction,
In the step of reducing the diameter, the gas is applied to an inner peripheral surface of the outer tube which constitutes the gap . A method for manufacturing a silencer according to claim 1 or claim 5 ,
the inner tube has a communication hole communicating with the gap,
A method for manufacturing a silencer, wherein in the reducing step, the spinning is performed while sucking the gas from the internal space of the inner tube. A method for manufacturing a silencer comprising an inner tube, an outer tube arranged to surround an outer circumferential surface of the inner tube, a gap provided between the inner tube and the outer tube, and a sound absorbing material arranged in the gap, the method comprising the steps of:
filling the gap with the sound absorbing material from a second end of the gap whose first end is closed;
a step of reducing a diameter of the outer tube by spinning while a gas is being fed from the second end of the gap toward the sound absorbing material filled in the gap;
A method for manufacturing a silencer comprising the steps of:

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