muffler, silencer, vacuum cleaner

Abstract

To reduce noise of a flow inside a pipe. An aspect of the present disclosure relates to a sound-reducing pipe including: a pipe body having a first flow inlet and a first flow outlet for a gas, and a peripheral wall including an inner peripheral surface connecting the first flow inlet and the first flow outlet and serving to form a flow passage for the gas to flow from the first flow inlet to the first flow outlet; and a plurality of protrusions protruding from the peripheral wall, a front end of the protrusion being located inside the pipe body as compared to the inner peripheral surface located closer to the first flow inlet side than the front end of the protrusion.

Description

Technical Field

[0001] This disclosure relates to silencers and silencers for reducing noise. This application claims priority based on Japanese Patent Application No. 2023-186728, filed on October 31, 2023, the contents of which are incorporated herein by reference. Background Technology

[0002] In recent years, technologies that mimic and utilize the diverse functions of living organisms, known as biomimetics, have attracted considerable attention. Furthermore, as an example of applying this biomimetic technology to the manufacture of products such as electrical products, Natural Technology (registered trademark) is known.

[0003] Previously, as a silencer for reducing noise contained in airflow, there are known techniques for reducing noise by causing noisy airflow to flow through a duct (e.g., Patent Document 1).

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2005-220871 Summary of the Invention The technical problem to be solved by the present invention However, in the aforementioned prior art, due to the rapid flow of air inside the pipe, there is a problem of new noise generated by the eddies of the flowing air (wind).

[0005] One objective of this disclosure is to reduce noise from flow inside pipes.

[0006] Solution for solving the problem To address the aforementioned problems, one aspect of this disclosure relates to a silencer duct comprising: a duct body having a first gas inlet and a first gas outlet, and a peripheral wall including an inner peripheral surface connecting the first gas inlet and the first gas outlet and forming a flow path for gas to flow from the first gas inlet to the first gas outlet; and a plurality of protrusions protruding from the peripheral wall, the front ends of the protrusions being located inside the duct body relative to the inner peripheral surface which is closer to the first gas inlet than the front ends of the protrusions.

[0007] Invention Effects According to one aspect of this disclosure, it is possible to reduce noise flowing inside a pipe. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view showing the structure of an example of the muffler according to Embodiment 1.

[0009] Figure 2It is shown that it is mounted on Figure 1 A three-dimensional view of the silencer's duct.

[0010] Figure 3 yes Figure 2 The side view of the silencing duct shown.

[0011] Figure 4 yes Figure 1 A magnified view of region E in the middle.

[0012] Figure 5 Is Figure 2 The diagram shows a top view of any one of the multiple protrusions formed on the pipe body, viewed radially from the inside of the pipe body.

[0013] Figure 6 It is Figure 2 The silencing duct shown is a front view with the inlet side as the front view.

[0014] Figure 7 This is a perspective view showing the protrusion in the silencing pipe according to Embodiment 2.

[0015] Figure 8 It is shown in magnification Figure 7 The top view, AA section view, and BB section view of the convex part are shown.

[0016] Figure 9 This is a cross-sectional view showing the structure of an example of the muffler according to Embodiment 3.

[0017] Figure 10 This is an enlarged cross-sectional view showing a portion of a muffler pipe in two modified examples.

[0018] Figure 11 This is a schematic diagram showing the constituent elements of the vacuum cleaner according to Embodiment 4. Detailed Implementation

[0019] [Implementation Method 1] Hereinafter, one embodiment of the present disclosure will be described in detail.

[0020] (Silencer Overview) Figure 1 This is a cross-sectional view showing the structure of an example of the muffler 1 according to Embodiment 1. Furthermore, in Figure 1 The diagram not only shows the cross-section but also the structure visible from the inside of the cross-section. For example... Figure 1 As shown, the silencer 1 includes a silencer duct 10 and a housing 2. A noise source 3 is provided at one end of the silencer duct 10. The noise source 3 is a device that generates noise. The noise source 3 can be, for example, a blower that generates airflow.

[0021] The silencer duct 10 includes a duct body 11, a plurality of protrusions 112, and an inlet 13. The silencer duct 10 is used to reduce noise propagating within it. The duct body 11 has a first inlet 11A for gas to flow in, a first outlet 11B for gas to flow out, and a peripheral wall 11D. The peripheral wall 11D includes an inner peripheral surface 11C, which connects the first inlet 11A and the first outlet 11B and forms a flow path for gas to flow from the first inlet 11A to the first outlet 11B.

[0022] The inlet section 13 is connected to the first inlet 11A of the pipe body 11. The inlet section 13 has a second inlet 13A for gas to flow in and a second outlet 13B for gas to flow out. The second outlet 13B is connected to the first inlet 11A of the pipe body 11. The inlet section 13 is formed in a funnel shape, with its second outlet 13B side being narrower than its second inlet 13A side. The inlet section 13 has, for example, a frustum shape when viewed from the side, for guiding airflow into the pipe body 11.

[0023] By providing the inlet section 13, it is not only easier to introduce airflow into the pipe body 11, but also to promote sound reflection on the inner surface of the inlet section 13 and suppress sound reflection into the pipe body 11.

[0024] Multiple protrusions 112 protrude from the peripheral wall 11D of the pipe body 11. Details of the silencer pipe 10, including the protrusions 112, will be described later. Multiple through holes 111 are formed in the peripheral wall 11D of the pipe body 11. The multiple through holes 111 are arranged along the axial direction of the pipe body 11. In addition, the multiple through holes 111 are arranged along the circumferential direction of the pipe body 11.

[0025] The housing 2 is configured to surround at least a portion of the pipe body 11 of the silencing duct 10. The housing 2 is, for example, a cylindrical housing. The housing 2 may also have sound-absorbing material 21 disposed on its inner surface. The sound-absorbing material 21 is used to absorb sound. The housing 2 forms a silencing space S, which communicates with the interior of the pipe body 11 through a plurality of through holes 111. The silencing space S is a closed space located between the pipe body 11 and the housing 2, connected to the interior space (space for gas flow) of the pipe body 11 only through a plurality of through holes 111. However, the silencing space S is not limited to a closed space; for example, the housing 2 may also be a structure with an opening on the wall on the side of the first inlet 11A or the wall on the side of the first outlet 11B.

[0026] (Silencer mechanism) exist Figure 1In the diagram, arrow Y indicates the airflow direction. As shown by arrow Y, the gas flows from the first inlet 11A to the first outlet 11B inside the pipe body 11. At this time, some noise is diffracted and enters the silencing space S through the through-hole 111, disappearing thereafter. By pre-setting sound-absorbing material 21 on the inner surface of the housing 2 used for sound reflection, the sound is absorbed by the sound-absorbing material 21, thereby more effectively reducing the noise flowing inside the pipe body 11.

[0027] (Applicable to the silencer duct of a silencer) Figure 2 It is shown that it is mounted on Figure 1 A perspective view of the silencer pipe 10 of the silencer 1 shown. Figure 3 yes Figure 2 The side view of the silencer duct 10 shown. Figure 2 , Figure 3 As shown, the side of the pipe body 11 near the first flow outlet 11B is thinner than the side of the pipe body 11 near the first flow inlet 11A. More specifically, the inner diameter of the pipe body 11 gradually decreases from its upstream side to its downstream side along the airflow direction (arrow Y). The pipe body 11 has a tapered shape. The cross-section of the pipe body 11 is not limited to a circle, but can also be elliptical, etc.

[0028] By setting the pipe body 11 to this tapered shape, even without tilting the protrusion 112 at a large angle, the airflow flowing inside can collide with the protrusion 112.

[0029] The silencer duct 10 has a plurality of protrusions 112 projecting from the peripheral wall 11D of the duct body 11. The front end 112A of each protrusion 112 is located inside the duct body 11, relative to the inner peripheral surface 11C which is closer to the first inlet 11A than the front end 112A of the protrusion 112. Sometimes, the interior of the duct body 11 is also described as the side of the central axis X of the duct body 11, or the inner side of the duct body 11. The protrusions 112 may also project upstream of the airflow. In this embodiment, the protrusions 112 are configured to project from the periphery of the through hole 111 toward the interior of the through hole 111 when viewed from the opening direction of the through hole 111.

[0030] Figure 4 yes Figure 1 A magnified view of region E in the middle. Figure 4 In the diagram, straight line F1 shows the inner circumferential surface 11C of the pipe body 11 in the cross-section. Figure 4 In the diagram, straight line F2 shows a line passing through the front end 112A of one of the protrusions 112 and parallel to the axis of the pipe body 11.

[0031] like Figure 4As shown by line F1, in this embodiment, the inner circumferential surface 11C of the pipe body 11 gradually approaches the central axis X of the pipe body 11 as it travels from the upstream side to the downstream side of the airflow. Figure 4 As shown by the straight line F2, in this embodiment, this shape is used so that the front end 112A of the protrusion 112 is located inside the pipe body 11 compared to the inner circumferential surface 11C which is closer to the first inlet 11A than the front end 112A of the protrusion 112.

[0032] In this embodiment, by providing a protrusion 112 on the pipe body 11, the airflow flowing from the first inlet 11A to the first outlet 11B will collide with the protrusion 112, and the eddy currents in the airflow will be refined by the protrusion 112. As a result, noise can be reduced.

[0033] Furthermore, since the protrusion 112 has a portion that protrudes toward the first inlet 11A, the airflow flowing from the first inlet 11A to the first outlet 11B is more likely to collide with the protrusion 112.

[0034] Furthermore, the protrusion 112 is configured to protrude from the periphery of the through hole 111 toward the interior of the through hole 111 when viewed from the opening direction of the through hole 111. As a result, while refining the vortex, it is also possible to separate the air (sound) introduced into the through hole 111 from the air flowing in the pipe body 11, thereby improving the noise reduction effect in the noise reduction space S.

[0035] Figure 5 Is Figure 2 The diagram shows a top view of any one of the plurality of protrusions 112 formed on the pipe body 11, viewed radially from the pipe body 11 and from the inner side (axial side) of the pipe body 11. The radial direction of the pipe body 11 is perpendicular to the axial direction of the pipe body 11. Figure 5 The arrow in the middle indicates the direction of the airflow deflected by the protrusion 112.

[0036] like Figure 5 As shown, the protrusion 112 protrudes from the periphery of the through hole 111 near the first flow outlet 11B side toward the first flow inlet 11A side.

[0037] By adopting this structure, the airflow from the first inlet 11A to the first outlet 11B more easily collides with the protrusion 112, and the protrusion 112 can refine the vortices contained in the airflow. This makes it easier to prevent sound contained in the airflow from entering the anechoic space S located on the outer periphery of the pipe body 11 through the through-hole 111 via diffraction. Simultaneously, it also promotes the entry of sound contained in the airflow into the anechoic space S through the through-hole 111 via reflection.

[0038] Furthermore, the protrusion 112's shape 112B on one side of the pipe body 11's circumferential direction and its shape 112C on the other side of the pipe body 11's circumferential direction can also be asymmetrical relative to the axial direction of the pipe body 11.

[0039] By employing an asymmetrical shape, when the airflow collides with the asymmetrical ridge (edge) of the protrusion 112, the airflow can be deflected in different directions. Therefore, the airflow can be dispersed in various directions, generating vortices in different directions. This allows for finer vortices within the airflow. Furthermore, by making the protrusion 112 provided in the through-hole 111 asymmetrical, the diffraction direction of sound intruding into the anechoic space S through the through-hole 111 can be dispersed, thus reducing noise more effectively.

[0040] As an example, such as Figure 5 As shown, the shape 112B of the protrusion 112 on one side of the circumferential direction can be a shape that protrudes to that side, and the shape 112C of the protrusion 112 on the other side of the circumferential direction can be a shape that is recessed to that other side.

[0041] By adopting this structure, a torsional shape combining convex and concave curves is formed, which allows the airflow to swirl in different directions along each edge, while simultaneously dispersing the diffraction direction of the sound intruding into the anechoic space S, thereby more effectively achieving the effect of promoting sound cancellation.

[0042] Figure 6 It is Figure 2 The silencing duct 10 shown is a front view with the inlet 13 side as the front view. (See diagram below.) Figure 6 As shown, multiple ribs 131 extending from the second inlet 13A side to the second outlet 13B side may also be formed on the inner surface of the inlet portion 13.

[0043] When viewed from the second inlet 13A side, the multiple ribs 131 are arranged radially with the second outlet 13B as the center, and each has a portion 131A that is radially inclined in the same direction relative to the circle centered on the center of the second outlet 13B. The center of the second outlet 13B is the same as the central axis X of the pipe body 11.

[0044] Part 131A imparts a rotational component to the airflow introduced into the duct body 11. By imparting a rotational component to the airflow, reflection or diffraction in the anechoic space S can be promoted, thereby promoting noise reduction in the anechoic space S. Here, the multiple ribs 131 are curved, but they can also be straight lines extending in a radially inclined direction.

[0045] [Implementation Method 2] Other embodiments of this disclosure are described below. Furthermore, for ease of explanation, components having the same function as those described in the above embodiments are labeled with the same reference numerals, and their descriptions are omitted.

[0046] Figure 7 This is a perspective view showing the protrusion 113 in the silencing pipe according to Embodiment 2. Figure 8 It is shown in magnification Figure 7 The figures show a top view, a cross-sectional view along line AA, and a cross-sectional view along line BB of the protrusion 113. Reference numeral 801 is the top view, reference numeral 802 is the cross-sectional view along line AA, and reference numeral 803 is the cross-sectional view along line BB. This embodiment differs from Embodiment 1 only in the shape of the protrusion 113.

[0047] As shown by reference numeral 801 in the attached drawings, the protrusion 113 protrudes from the peripheral wall 11D of the pipe body 11 and from the periphery of the through hole 111 provided on the peripheral wall 11D near the first flow outlet 11B towards the first flow inlet 11A. Furthermore, as shown by reference numerals 802 and 803 in the attached drawings, the front end 113A of the protrusion 113 is configured to protrude from the inner peripheral surface 11C further inward than the inner peripheral surface 11C of the pipe body 11.

[0048] By adopting this structure, the airflow flowing in the flow path of the pipe body 11 is more likely to collide with the protrusion 113. Therefore, the vortices contained in the airflow can be refined, thereby reducing noise.

[0049] [Implementation Method 3] The following describes yet another embodiment of this disclosure. Furthermore, for ease of explanation, components having the same function as those described in the above embodiments are labeled with the same reference numerals, and their descriptions are omitted.

[0050] Figure 9 This is a cross-sectional view showing an example of the structure of the muffler 1A according to Embodiment 3. Furthermore, in Figure 9 The diagram shows not only the cross-section but also the structure visible from the inside of the cross-section. The silencer 1A includes a silencer duct 10A and a housing 2.

[0051] The silencing duct 10A includes a first group 121 and a second group 122. The first group 121 and the second group 122 are alternately arranged along the axial direction of the silencing duct 10A. The first group 121 includes a plurality of through holes 111 and a plurality of protrusions 112 arranged circumferentially. The second group 122 includes a plurality of through holes 111 and a plurality of protrusions 112 arranged circumferentially. However, the plurality of through holes 111 and protrusions 112 in the first group 121 are circumferentially offset from the plurality of through holes 111 and protrusions 112 in the second group 122. The first group 121 and the second group 122, thus circumferentially offset, can be provided throughout the entire area of ​​the duct body 11 or in a portion thereof.

[0052] With the above structure, the silencer duct 10A can effectively allow the airflow flowing through it to collide with the protrusion 112. In addition, the silencer duct 10A can effectively disperse and refine the location of the vortex.

[0053] (Modified example) Figure 10 This is an enlarged cross-sectional view showing a portion of a muffler pipe in two modified examples. Figure 10 Arrows indicate the direction of airflow deflected by the protrusion. Reference numeral 1001 represents silencing duct 10B, and reference numeral 1002 represents silencing duct 10C. The peripheral wall 11D of silencing ducts 10B and 10C may not have a through hole. Furthermore, the duct body 11 of silencing ducts 10B and 10C may not be the aforementioned tapered shape, but may be cylindrical.

[0054] As shown by reference numeral 1001 in the attached drawing, the silencing duct 10B has multiple protruding components extending from the peripheral wall 11D, namely multiple protrusions 114 protruding inward from the inner peripheral surface 11C. The protrusions 114 obliquely protrude from the inner peripheral surface 11C towards the upstream side of the airflow (the first inlet side) and towards the inner side of the duct body 11. A space is formed between the wall surface 114A on the upstream side of the protrusion 114 and the inner peripheral surface 11C. The angle between the wall surface 114A and the inner peripheral surface 11C is an acute angle. The angle between the wall surface 114B on the downstream side of the protrusion 114 and the inner peripheral surface 11C is an obtuse angle.

[0055] With this shape of the protrusion 114, the airflow will split as if bypassing the protrusion 114, and the vortex will be refined.

[0056] As shown by reference numeral 1002 in the attached drawing, the silencing duct 10C has a plurality of protruding members extending from the peripheral wall 11D, namely, a plurality of protrusions 115 protruding inward from the inner peripheral surface 11C. The protrusions 115 protrude inward from the inner peripheral surface 11C toward the duct body 11. The wall surface 115A on the upstream side (first inlet side) of the protrusion 115 may, for example, be perpendicular to the inner peripheral surface 11C. No space is formed between the wall surface 115A and the inner peripheral surface 11C. The angle between the wall surface 115B on the downstream side of the protrusion 115 and the inner peripheral surface 11C is an obtuse angle.

[0057] With the shape of the protrusion 115 protruding inward from the inner circumferential surface 11C, the airflow will be separated as if bypassing the protrusion 115, thereby enabling the vortex to be refined more appropriately.

[0058] Thus, the silencing duct can also have a structure with multiple protrusions 114, 115 protruding from the inner circumferential surface 11C of the duct body 11 toward the inner side of the duct body 11.

[0059] By providing protrusions 114 and 115 on the pipe body 11, the airflow flowing from the upstream side to the downstream side (from the first flow inlet to the first flow outlet) will collide with the protrusions 114 and 115, and the vortices contained in the airflow can be refined by the protrusions 114 and 115. Since the vortices contained in the airflow are reduced, noise can be reduced.

[0060] [Implementation Method 4] The following describes yet another embodiment of this disclosure. Furthermore, for ease of explanation, components having the same function as those described in the above embodiments are labeled with the same reference numerals, and their descriptions are omitted.

[0061] Figure 11 This is a schematic diagram showing the constituent elements of the vacuum cleaner 100 according to Embodiment 4. The vacuum cleaner 100 includes a silencer 1, a suction section 4, a removal section 5, a blower 6, and a blow-out section 7. The suction section 4 is the part that sucks in dust by airflow. The removal section 5 removes dust from the air sucked in by the suction section 4. The removal section 5 may have a filter. The blower 6 has a fan or the like that that generates airflow for blowing air. The blower 6 may be a noise source. The blow-out section 7 is the part that blows the air delivered from the blower 6 to the outside.

[0062] The silencer 1 is disposed in the flow path from the blower 6 to the blow-out section 7. The airflow flows, for example, in the order of suction section 4, removal section 5, blower 6, silencer 1, and blow-out section 7. The silencer 1 can reduce the noise generated by the suction section 4, removal section 5, or blower 6. In addition, the vacuum cleaner 100 may also be equipped with a silencer that includes the other silencer ducts mentioned above.

[0063] 〔Summarize〕 The silencing duct of aspect 1 of this disclosure includes: a duct body having a first inlet and a first outlet for gas, and a peripheral wall including an inner peripheral surface connecting the first inlet and the first outlet and forming a flow path for gas to flow from the first inlet to the first outlet; and a plurality of protrusions protruding from the peripheral wall, the front ends of the protrusions being located inside the duct body relative to the inner peripheral surface that is closer to the first inlet than the front ends of the protrusions.

[0064] In the silencing duct of aspect 2 of this disclosure, in aspect 1 above, the protrusion may protrude toward the first inlet side.

[0065] In the silencing duct according to aspect 3 of this disclosure, in aspect 1 or 2 above, the shape of the protrusion on one side of the circumferential direction and the shape of the protrusion on the other side of the circumferential direction relative to the axial direction of the duct body may be asymmetrical to each other.

[0066] In the silencing duct of aspect 4 of this disclosure, in aspect 3 above, the shape of the protrusion on one side of the circumferential direction may be a shape that protrudes to that side, and the shape of the protrusion on the other side of the circumferential direction may be a shape that is recessed to that other side.

[0067] In the silencing duct according to aspect 5 of this disclosure, in any of aspects 1 to 4 above, the protrusion can protrude from the inner circumference towards the inside of the duct body.

[0068] In the silencing duct according to aspect 6 of this disclosure, in any of aspects 1 to 5 above, a plurality of through holes may be formed on the peripheral wall, and when viewed from the opening direction of the through hole opening, the protrusion may protrude from the periphery of the through hole into the interior of the through hole.

[0069] In the silencing duct of aspect 7 of this disclosure, in aspect 6 above, the protrusion can protrude from the periphery of the through hole near the first outlet side toward the first inlet side.

[0070] In the silencing duct of aspect 8 of this disclosure, in any of aspects 1 to 7 above, the side of the duct body near the first outlet may be thinner than the side of the duct body near the first inlet.

[0071] In the silencing duct according to aspect 9 of this disclosure, in any of aspects 1 to 8 above, an inlet portion may be provided, the inlet portion having a second inlet and a second outlet for gas, and the second outlet being connected to the first inlet of the duct body, wherein the side of the inlet portion near the second outlet may be thinner than the side of the inlet portion near the second inlet.

[0072] In the silencing duct of aspect 10 of this disclosure, in aspect 9 above, a plurality of ribs extending from the second inlet side to the second outlet side may be formed on the inner surface of the inlet portion.

[0073] In the silencing duct of aspect 11 of this disclosure, in aspect 10 above, when viewed from the second inlet side, the plurality of ribs may be arranged radially around the second outlet and have portions that are radially inclined in the same direction relative to the circle centered on the center of the second outlet.

[0074] The silencer according to aspect 12 of this disclosure includes: a silencer duct as described in any one of aspects 6 to 8 above; and a housing that surrounds at least a portion of the duct body and forms a silencer space communicating with the interior of the duct body through the plurality of through holes.

[0075] The vacuum cleaner disclosed in aspect 13 includes: the silencer described in aspect 12 above; and a blower for blowing air into the gas.

[0076] Furthermore, this disclosure incorporates technical ideas focusing on the serrated structure of an owl's wings. In other words, this disclosure relates to biomimetic.

[0077] This disclosure is not limited to the above-described embodiments. Various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this disclosure.

Claims

1. A sound attenuating duct comprising, include: The pipe body has a first inlet and a first outlet for gas, and a peripheral wall, the peripheral wall including an inner peripheral surface, the inner peripheral surface connecting the first inlet and the first outlet and used to form a flow path for gas to flow from the first inlet to the first outlet; as well as Multiple protrusions that protrude from the peripheral wall, The front end of the protrusion is located inside the pipe body, relative to the inner circumferential surface which is closer to the first inlet side than the front end of the protrusion.

2. The silencing duct according to claim 1, characterized in that, The protrusion extends toward the first inlet side.

3. The silencing duct according to claim 1, characterized in that, Relative to the axial direction of the pipe body, the shape of the protrusion on one side of the circumferential direction and the shape of the protrusion on the other side of the circumferential direction are asymmetrical to each other.

4. The silencing duct according to claim 3, characterized in that, The protrusion on one side of the circumferential direction has a shape that bulges outward toward that side. The protrusion on the other side of the circumference is concave.

5. The silencing duct according to claim 1, characterized in that, The protrusion extends from the inner circumference towards the inside of the pipe body.

6. The silencing duct according to claim 1, characterized in that, Multiple through holes are formed in the peripheral wall. When viewed from the opening direction of the through hole, the protrusion extends from the periphery of the through hole into the interior of the through hole.

7. The silencing duct according to claim 6, characterized in that, The protrusion extends from the periphery of the through hole near the first outlet side toward the first inlet side.

8. The silencing duct according to claim 6, characterized in that, The side of the pipe body closer to the first flow outlet is thinner than the side of the pipe body closer to the first flow inlet.

9. The silencing duct according to claim 1, characterized in that, Also includes: The inlet section has a second gas inlet and a second gas outlet, the second gas outlet being connected to the first gas inlet of the pipe body. The side of the inlet portion closer to the second flow outlet is thinner than the side of the inlet portion closer to the second flow inlet.

10. The silencing duct according to claim 9, characterized in that, Multiple ribs are formed on the inner surface of the inlet portion, extending from the second inlet side to the second outlet side.

11. The silencing duct according to claim 10, characterized in that, When viewed from the second inlet side, the plurality of ribs are arranged radially around the second outlet and have portions that are radially inclined in the same direction relative to the circle centered on the second outlet.

12. A silencer, characterized in that, include: The silencer duct according to any one of claims 6 to 8; as well as A housing that surrounds at least a portion of the pipe body and forms a sound-absorbing space communicating with the interior of the pipe body via the plurality of through holes.

13. A vacuum cleaner, characterized in that, include: The silencer according to claim 12; as well as A blower for supplying air to the gas.

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