Method of manufacturing a muffler

Abstract

The present disclosure provides a manufacturing method of a muffler capable of suppressing the escape of a sound absorbing member during spinning processing. One aspect of the present disclosure relates to a manufacturing method of a muffler provided with an inner tube, an outer tube arranged so as to surround the outer periphery of the inner tube, a gap provided between the inner tube and the outer tube, and a sound absorbing member arranged in the gap. The manufacturing method of the muffler includes a filling step of filling the sound absorbing member from a second end of the gap which is closed at a first end, and a reducing step of supplying gas to the sound absorbing member filled in the gap from the second end of the gap, and reducing the outer tube by spinning.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a muffler. Background Technology

[0002] A muffler disposed in the flow path of exhaust gas is formed of a double-layered tube, in which a sound-absorbing component is disposed in the gap between the inner and outer tubes. The muffler is manufactured by filling the sound-absorbing component with one end of the gap closed, and then using spinning to reduce the diameter of the outer tube and close the other end of the gap (see Japanese Patent Application Publication No. 2019-44592).

[0003] In this manufacturing method, in order to prevent the sound-absorbing component from escaping from the gap during spinning, air is drawn from the inner tube, which has a hole communicating with the gap, while the outer tube is reduced in diameter. Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] In the above manufacturing method, the different distances from the holes in the inner tube cause deviations in the attractive force of the sound-absorbing component. Therefore, it is impossible to sufficiently prevent the sound-absorbing component from escaping through the gaps during spinning.

[0006] Methods for solving problems

[0007] One aspect of this disclosure preferably provides a method for manufacturing a muffler that can suppress the escape of sound-absorbing components during spinning.

[0008] One aspect of this disclosure relates to a method for manufacturing a muffler, the muffler comprising: an inner tube, an outer tube disposed around the outer circumference of the inner tube, a gap disposed between the inner tube and the outer tube, and a sound-absorbing member disposed in the gap. The method for manufacturing the muffler includes: a filling step of filling the second end of a gap that is blocked at a first end with the sound-absorbing member; and a diameter reduction step of supplying gas from the second end of the gap to the sound-absorbing member filling the gap, and reducing the diameter of the outer tube by spinning.

[0009] According to the scheme described above, gas is supplied from the second end to the sound-absorbing component within the gap, thereby pushing the sound-absorbing component towards the first end (i.e., the closed end) of the gap. This prevents the sound-absorbing component from escaping from the gap during spinning. Furthermore, since the generation of an air layer without the sound-absorbing component can be suppressed, the silencing function can be improved and the muffler can be miniaturized.

[0010] In one aspect of this disclosure, during the diameter reduction process, the gas can be made to at least contact the sound-absorbing component located near the inner circumferential surface of the outer tube. According to the above-described approach, the gas can be used to push against the sound-absorbing component located radially outside the muffler, where the centrifugal force increases due to spinning. Therefore, it is possible to improve the suppression effect against the escape of the sound-absorbing component during spinning.

[0011] In one aspect of this disclosure, during the diameter reduction process, the amount of gas supplied per unit time to the region near the inner circumferential surface of the outer tube can be greater than the amount of gas supplied per unit time to the region near the outer circumferential surface of the inner tube. According to the above-described approach, the gas can be concentrated in the sound-absorbing component located radially outside the muffler where the centrifugal force increases due to spinning. Therefore, it is possible to improve the suppression effect on the escape of the sound-absorbing component during spinning.

[0012] In one aspect of this disclosure, during the diameter reduction process, a nozzle can be used to deliver gas near the inner circumferential surface of the outer tube. According to the method described above, the gas can be efficiently guided to the area where the sound-absorbing component is prone to escape. Therefore, it is possible to improve the suppression effect on the escape of the sound-absorbing component during spinning.

[0013] In one embodiment of this disclosure, the cross-sectional shape of the outer tube perpendicular to the axial direction can be circular. During the diameter reduction process, the gas can be brought into contact with the inner circumferential surface of the outer tube forming the void. According to the embodiment described above, the escape of the sound-absorbing component from the outer tube due to increased centrifugal force relative to the radially outer side can be effectively suppressed.

[0014] In one embodiment of this disclosure, the inner tube may have a communicating hole that communicates with the void. During the diameter reduction process, gas can be drawn from the internal space of the inner tube and spun. According to the embodiment described above, a portion of the centrifugal force applied to the sound-absorbing component can be offset by the attraction of the gas. Therefore, it is possible to promote the suppression effect of sound-absorbing component escaping during spunting. Attached Figure Description

[0015] Figure 1A This is a schematic central longitudinal sectional view of the muffler of the embodiment.

[0016] Figure 1B yes Figure 1A A schematic cross-sectional view at the IB-IB line.

[0017] Figure 2 This is a flowchart of the manufacturing method of the muffler according to the implementation method.

[0018] Figure 3A as well as Figure 3B It is shown Figure 2 A schematic diagram of one step in the manufacturing process of a muffler.

[0019] Figure 4 It is shown Figure 2 A schematic diagram of one step in the manufacturing process of a muffler.

[0020] Figure 5 It is shown that... Figure 4 A schematic diagram of one step in the manufacturing method of a muffler according to different implementations. Detailed Implementation

[0021] Exemplary embodiments of this disclosure will now be described with reference to the accompanying drawings.

[0022] [1. First Embodiment]

[0023] [1-1. Structure]

[0024] <Silencer>

[0025] Figure 1A as well as Figure 1B The muffler 1 shown is installed in the exhaust gas flow path of, for example, an internal combustion engine. The muffler 1 includes an inner tube 2, an outer tube 3, a retaining member 4, a gap 5, and a sound-absorbing member 6.

[0026] <Internal Management>

[0027] The inner tube 2 is a metal tube through which exhaust gas passes. The cross-section (i.e., the cross-section) of the inner tube 2 perpendicular to the axial direction is circular (specifically, a perfect circle). The inner tube 2 has a first end 21, a second end 22, and a plurality of connecting holes 23.

[0028] The first end 21 and the second end 22 are each connected to the outer pipe 3 in the radial direction. The exhaust gas can flow from the first end 21 to the second end 22 or from the second end 22 to the first end 21.

[0029] Multiple connecting holes 23 are through holes that connect the internal space of the inner tube 2 (i.e., the exhaust gas flow path) and the gap 5 (i.e., the outside of the inner tube 2). The connecting holes 23 are located at arbitrary positions along the circumference or axial direction of the inner tube 2. Alternatively, the inner tube 2 may have only one connecting hole 23. By connecting the connecting hole 23 and the gap 5, noise reduction can be achieved by utilizing the spatial expansion of the gap 5.

[0030] <Foreign Affairs Management>

[0031] The outer tube 3 is a metal tube arranged around the outer circumference of the inner tube 2, forming the outer shell of the muffler 1. The cross-section (i.e., the cross-sectional area) of the outer tube 3 perpendicular to the axial direction is circular (specifically, a perfect circle). The inner diameter of the outer tube 3 is larger than the outer diameter of the inner tube 2.

[0032] The outer tube 3 has a first end 31, a second end 32, and a central portion. The first end 31 overlaps with the outer peripheral surface of the first end 21 of the inner tube 2, and the entire circumference of the first end 31 is joined to the first end 21, for example, by welding. The second end 32 overlaps with the outer peripheral surface of the second end 22 of the inner tube 2, and the entire circumference of the second end 32 is connected to the second end 22 via a retaining member 4.

[0033] The central portion is located axially between the first end 31 and the second end 32 of the outer tube 3. Both the first end 31 and the second end 32 are reduced in diameter relative to the central portion. The central portion includes a torso, a first inclined portion, and a second inclined portion. The outer diameter of the torso is fixed. The first inclined portion is reduced in diameter from one end of the torso toward the first end 31 in a straight, stepped, or curved manner. The second inclined portion is reduced in diameter from the other end of the torso toward the second end 32 in a straight, stepped, or curved manner.

[0034] <Retaining Components>

[0035] The retaining member 4 is an annular component disposed between the second end 22 of the inner tube 2 and the second end 32 of the outer tube 3. Alternatively, the retaining member 4 may be a C-shape with a portion of the annular shape removed. Furthermore, the retaining member 4 may be composed of multiple components forming an annular or C-shape.

[0036] The retaining member 4 is sandwiched between the outer circumferential surface of the inner tube 2 and the inner circumferential surface of the outer tube 3, and the retaining member 4 is not fixed to at least one of the inner tube 2 and the outer tube 3. The difference in thermal expansion between the inner tube 2 and the outer tube 3 is absorbed by sliding the retaining member 4 relative to the inner tube 2 or the outer tube 3.

[0037] The retaining member 4 is arranged along the entire circumference of the outer circumferential surface of the inner tube 2 and the inner circumferential surface of the outer tube 3. That is, the retaining member 4 is configured to block the space (i.e., gap 5) between the inner tube 2 and the outer tube 3 at the axial end of the inner tube 2. In addition, the retaining member 4 may not completely block the gap 5.

[0038] The retaining member 4 is not particularly limited as long as it can hold the sound-absorbing member 6 within the gap 5 and can slide at least relative to the inner tube 2 or the outer tube 3. As the retaining member 4, a wire mesh made of metal is preferred, for example.

[0039] <gap>

[0040] 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 and a second end 52. The first end 51 is closed by the first end 21 of the inner tube 2 and the first end 31 of the outer tube 3, and the second end 52 is 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 circumferential surface of the inner tube 2 and the inner circumferential surface of the outer tube 3.

[0041] <Sound-absorbing components>

[0042] The sound-absorbing component 6 is an assembly of sound-absorbing filling materials disposed in the voids 5. As a sound-absorbing filling material, fibers such as glass fiber are preferred.

[0043] Specifically, sound-absorbing components 6 are disposed between the central sections of the inner tube 2 and the outer tube 3, between the first inclined sections of the central sections of the inner tube 2 and the outer tube 3, and between the second inclined sections of the central sections of the inner tube 2 and the outer tube 3. The sound-absorbing components 6 are preferably disposed at a uniform density.

[0044] <Muffler Manufacturing Method>

[0045] Figure 2 The manufacturing method of the muffler shown includes a joining process S10, a filling process S20, and a diameter reduction process S30.

[0046] (Jointing process)

[0047] In this process, such as Figure 3A As shown, for example, the first end 21 of the inner tube 2 and the first end 31 of the outer tube 3 are joined together by welding.

[0048] In this process, the outer tube 3 is formed by spinning to reduce the diameter of one end of a straight tube, thereby creating the first inclined portion and the first end 31. The outer tube 3 is inserted into the inner tube 2, wherein a retaining member 4 is fixed at the end of the inner tube 2 located on the opposite side of the first end 21. By engaging the first end 21 of the inner tube 2 and the first end 31 of the outer tube 3, a gap 5 is formed that closes the first end 51.

[0049] (Filling process)

[0050] In this process, such as Figure 3B As shown, the sound-absorbing component 6 is filled from the second end 52 of the gap 5 (i.e., the opposite side of the first end 51).

[0051] Specifically, in the end cap 12 (refer to) Figure 4 With the inner tube 2 inserted at the second end 22, the sound-absorbing component 6 is filled while air is being drawn from inside the inner tube 2. During the filling of the sound-absorbing component 6, both the inner tube 2 and the outer tube 3 can be rotated to ensure a more uniform density.

[0052] (Diameter reduction process)

[0053] In this process, such as Figure 4 As shown, gas is supplied from the second end 52 of the gap 5 to the sound-absorbing component 6 filling the gap 5, and the outer tube 3 is reduced in diameter by spinning.

[0054] The spinning of the outer tube 3 is performed using a known spinning apparatus. The spinning apparatus includes a spindle 11 mounted on the first end 21 of the inner tube 2 (i.e., the first end 31 of the outer tube 3), an end cap 12 inserted into the second end 22 of the inner tube 2, and a spinning wheel (not shown) disposed radially outside the second end 32 of the outer tube 3.

[0055] The main shaft 11, for example, causes the outer tube 3 and the inner tube 2 to rotate together. The front end of the main shaft 11 is inserted into the internal space of the inner tube 2. The rotating wheel presses against the second end 32 of the outer tube 3, which is rotating through the main shaft 11, from the radial outside, thereby reducing the diameter of the outer tube 3.

[0056] Spinning continues until the second end 52 of the gap 5 is closed by the outer tube 3 and the retaining member 4 pre-installed on the inner tube 2. This forms the second inclined portion and the second end 32 of the outer tube 3. Alternatively, spinning of the outer tube 3 can be performed, for example, by rotating a chuck that holds the inner tube 2 or the outer tube 3.

[0057] During the spinning process (specifically, from the start of rotation of the inner tube 2 and outer tube 3 until the formation of the second end 32 of the outer tube 3), gas is supplied to the sound-absorbing component 6 using the gas supply device 13. Compressed air, for example, can be used as the gas. The gas supply device 13 uses nozzles 13A and 13B to bring the gas into contact with the inner circumferential surface of the gap 5 formed in the outer tube 3, thereby supplying the gas to the vicinity of the inner circumferential surface of the rotating outer tube 3.

[0058] Therefore, in this process, the gas at least touches the sound-absorbing component 6 located near the inner circumferential surface of the outer tube 3. That is, the gas at least touches the sound-absorbing component 6 located near the inner circumferential surface of the outer tube 3. Furthermore, in this process, gas is not actually supplied to the sound-absorbing component 6 located near the outer circumferential surface of the inner tube 2. Alternatively, in this process, the airflow near the outer circumferential surface of the inner tube 2 may be relatively reduced compared to the airflow near the inner circumferential surface of the outer tube 3. For example, a stronger airflow may be applied to the inner circumferential surface of the outer tube 3 compared to the airflow near the outer circumferential surface of the inner tube 2.

[0059] As described above, in this process, the amount of gas supplied per unit time to the region near the inner circumferential surface of the outer tube 3 is greater than the amount of gas supplied per unit time to the region near the outer circumferential surface of the inner tube 2. In other words, in this process, the amount of gas per unit volume supplied to the region near the inner circumferential surface of the outer tube 3 at the cross-section of the gap 5 is greater than the amount of gas per unit volume supplied to the region near the outer circumferential surface of the inner tube 2 at the cross-section of the gap 5. In this process, both the amount of gas per unit time and the amount of gas per unit volume can also be adjusted.

[0060] The gas supplied from the gas supply device 13 causes the sound-absorbing component 6 to be pushed towards the blocked first end 51 of the gap 5. Therefore, when the inner diameter of the outer tube 3 is large, when the connecting hole 23 of the inner tube 2 is offset, and when the diameter of the connecting hole 23 is small, the escape of the sound-absorbing component 6 can be suppressed. Furthermore, since the sound-absorbing component 6 is compressed within the gap 5, the formation of an air layer where the sound-absorbing component 6 is not present can be suppressed.

[0061] In this process, since the second end 32 of the outer tube 3 is reduced in diameter by spinning, the orientation of the nozzles 13A and 13B can be changed in conjunction with the spinning process. That is, the front ends of the nozzles 13A and 13B can be moved closer to the outer circumferential surface of the inner tube 2 in conjunction with the spinning process.

[0062] In addition, Figure 4 In this configuration, two nozzles 13A and 13B are used to deliver gas. Since the outer tube 3 rotates, the number of nozzles can be one. Alternatively, three or more nozzles can be arranged at equal intervals along the circumference of the outer tube 3. Furthermore, the nozzle tips can be flared. Additionally, the gas supply direction can be parallel to the axial direction of the inner tube 2.

[0063] Furthermore, in this process, gas is drawn from the internal space of the inner tube 2 and spun. Specifically, gas is drawn from the internal space of the rotating inner tube 2 via a suction path 11A provided inside the main shaft 11.

[0064] The gas within the gap 5 passes through the connecting hole 23 of the inner tube 2 and is discharged to the outside primarily via the main shaft 11. Accompanying the gas suction, the sound-absorbing component 6 is attracted toward the outer circumferential surface of the inner tube 2. That is, a force acts on the sound-absorbing component 6 to counteract the centrifugal force generated by spinning. Alternatively, a gas discharge device other than the main shaft 11 can be used.

[0065] [1-2. Effects]

[0066] The following effects can be obtained by implementing the methods described in detail above.

[0067] (1a) Gas is supplied from the second end 52 to the sound-absorbing member 6 in the gap 5, thereby pushing the sound-absorbing member 6 toward the first end 51 (i.e., the closed end) of the gap 5. This prevents the sound-absorbing member 6 from escaping from the gap 5 during spinning. Furthermore, since the generation of an air layer without the sound-absorbing member 6 can be suppressed, the silencing function can be improved and the muffler 1 can be miniaturized.

[0068] (1b) By bringing the gas into contact with the sound-absorbing component 6 located near the inner circumferential surface of the outer tube 3, the gas can be used to push the sound-absorbing component 6, which is located radially outside the muffler 1 due to the increased centrifugal force generated by spinning. Therefore, it is possible to promote the suppression effect of the sound-absorbing component 6 escaping during spinning.

[0069] (1c) The amount of gas supplied to the region near the inner circumferential surface of the outer tube 3 is greater than the amount of gas supplied to the region near the outer circumferential surface of the inner tube 2. As a result, the gas can be concentrated on the sound-absorbing component 6 located radially outside the muffler 1, where the centrifugal force increases due to spinning. Therefore, the effect of suppressing the escape of the sound-absorbing component 6 during spinning can be improved.

[0070] (1d) Gas is delivered to the vicinity of the inner circumferential surface of the outer tube 3 using nozzles 13A and 13B, thereby efficiently guiding the gas to the area where the sound-absorbing component 6 is prone to escape. Therefore, it can promote the suppression effect of the sound-absorbing component 6 escaping during spinning.

[0071] (1e) By bringing the gas into contact with the inner circumferential surface of the outer tube 3 that forms the gap 5, the escape of the outer tube 3 due to the increased centrifugal force of the sound-absorbing component 6 relative to the radially outer side can be effectively suppressed.

[0072] (1f) Gas is drawn from the internal space of the inner tube 2, thereby offsetting part of the centrifugal force applied to the sound-absorbing component 6. Therefore, it is possible to promote the suppression effect of the sound-absorbing component 6 escaping during the spinning process.

[0073] [2. Other Implementation Methods]

[0074] The embodiments of this disclosure have been described above. However, this disclosure is not limited to the above embodiments and can be implemented in various ways.

[0075] (2a) In the method for manufacturing the silencer according to the above embodiment, it is also possible to omit the gas from the internal space of the inner tube during the diameter reduction process. Furthermore, the inner tube may not have a connecting hole.

[0076] (2b) In the manufacturing method of the muffler according to the above embodiment, the cross-sectional shape of the inner tube and the outer tube may not be a perfect circle. For example, the cross-sectional shape of the inner tube and the outer tube may be an ellipse.

[0077] (2c) In the manufacturing method of the silencer according to the above embodiment, the gas may not need to touch the inner circumferential surface of the outer tube during the diameter reduction process. Furthermore, a nozzle may not be used to deliver the gas. Additionally, the amount of gas delivered to the region near the inner circumferential surface of the outer tube may be the same as the amount of gas delivered to the region near the outer circumferential surface of the inner tube.

[0078] For example Figure 5 As shown, a fan that supplies gas along the axial direction of the inner tube 2 to the second end 52 of the gap 5 can also be used as the gas supply device 14. The gas supply device 14 is configured to make the gas evenly contact the entire end face of the sound-absorbing member 6.

[0079] (2d) In the manufacturing method of the muffler in the above embodiment, the muffler may not have a retaining member, depending on the length of the muffler in the axial direction and the operating environment (e.g., when the exhaust gas temperature is low).

[0080] (2e) In the method for manufacturing a muffler according to the above embodiment, the muffler may also include a separator that divides the gap into an upstream side in the flow direction of the exhaust gas and a downstream side in the flow direction of the exhaust gas. Furthermore, a sound-absorbing component may be filled into one side of the gap divided by the separator.

[0081] Furthermore, silencers can also have two or more layers of sound-absorbing components of different types. For example, in the diameter reduction process, gas can be supplied to glass fiber filled with sound-absorbing components such as cotton wool and stainless steel.

[0082] (2f) The functions of one constituent element in the above embodiments can be shared by multiple constituent elements, or the functions of multiple constituent elements can be integrated into one constituent element. Furthermore, a portion of the structure of the above embodiments can be omitted. At least a portion of the structure of the above embodiments can be added to the structure of other embodiments, or at least a portion of the structure of the above embodiments can be substituted with the structure of other embodiments. Additionally, all embodiments of the technical concept defined by the statements in the claims are embodiments of this disclosure.

Claims

1. A method for manufacturing a muffler, the muffler comprising: an inner tube, an outer tube disposed around the outer circumferential surface of the inner tube, a gap disposed between the inner tube and the outer tube, and a sound-absorbing member disposed in the gap, the method for manufacturing the muffler being characterized in that it includes: The filling process involves filling the sound-absorbing component from the second end of the gap that is blocked at the first end; as well as In the diameter reduction process, gas is supplied from the second end of the void to the sound-absorbing component filling the void, and the outer tube is reduced in diameter by spinning. During the diameter reduction process, the gas is made to at least come into contact with the sound-absorbing component located near the inner circumferential surface of the outer tube. In the diameter reduction process, the amount of gas delivered per unit time to the region near the inner circumferential surface of the outer tube is greater than the amount of gas delivered per unit time to the region near the outer circumferential surface of the inner tube.

2. The method for manufacturing a muffler according to claim 1, characterized in that, In the diameter reduction process, the gas is delivered near the inner circumferential surface of the outer tube using a nozzle.

3. The method for manufacturing a muffler according to claim 1, characterized in that, The outer tube has a circular cross-section perpendicular to the axial direction. In the diameter reduction process, the gas is brought into contact with the inner circumferential surface of the outer tube that forms the void.

4. The method for manufacturing a muffler according to claim 1, characterized in that, The inner tube has a communicating hole that communicates with the gap. In the diameter reduction process, the gas is drawn from the internal space of the inner tube and the spinning is performed.

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