JP7439657B2 - Silencer - Google Patents

Description

The present invention relates to a silencer.

BACKGROUND ART Silencers that reduce noise propagating through passages in ducts have been known.
Patent Document 1 describes a cylindrical silencer pipe with a bottom provided in the middle of a duct. Note that in Patent Document 1, the duct is called a "pipe line" and the muffler pipe is called a "side branch." In Patent Document 1, the length of the muffling tube is set to λ/4 with respect to the wavelength λ of the noise to be muffled, thereby reducing the noise at the wavelength λ.

Patent Document 1 proposes a configuration in which a bending portion is provided in the middle of the muffling tube to suppress the amount of protrusion of the muffling tube from the duct. Furthermore, a configuration has been proposed in which a plurality of bent portions are provided in the middle of the muffler tube to suppress the amount of protrusion of the muffler tube, and the muffler tube is lengthened to further reduce low-frequency noise.

JP2016-29269A

However, in the configuration of Patent Document 1 mentioned above, since the frequency to be muted is determined according to the length of the muffling tube, there is a problem that the frequency band in which the muffling effect can be obtained is narrow. In order to muffle broadband noise using the configuration of Patent Document 1, it is conceivable to install a plurality of muffling pipes of different lengths in a duct. However, if this is done, the space required to install a plurality of muffling pipes in the duct will increase.

In view of the above-mentioned points, an object of the present invention is to provide a muffler capable of suppressing an increase in installation space and improving noise reduction characteristics.

In order to achieve the above object, the invention according to claim 1 provides a silencer provided in a duct (2) in which a passageway (3) having an opening on both sides or one side is formed, the silencer communicating with the passageway in the duct. A case (4) forming a space (6), one or more partition plates (5, 5a to 5d) provided in the space within the case , and a partition plate provided at the boundary between the space within the case and the passage within the duct. It includes a boundary layer (8) that partitions the space inside the case and the passage inside the duct and ensures ventilation between the space inside the case and the passage inside the duct . At least one of the partition plates is one inner wall of the case that faces across a virtual plane (VS) that is perpendicular to the interface (BS) between the space inside the case and the passage inside the duct and that includes the center of the space inside the case. By being located at a distance from the inner wall of the other case, multiple paths are formed in the space within the case for the sound waves incident on the space within the case to propagate from the passage in the duct via the boundary layer. has been done.

As a result, a plurality of paths are formed through which the sound waves incident from the passage in the duct propagate in the space within the case, so it is possible to widen the band of the sound waves propagating through the plurality of paths. Therefore, the noise in the duct is muffled in a wide band due to the interference between the sound waves that propagate through the plurality of paths and are emitted back into the duct and the sound waves that travel through the passage in the duct. Therefore, this muffler can improve the noise reduction characteristic by widening the silencing characteristic against the noise of the passage in the duct.
Further, by providing one or more partition plates in the space inside the case, it is possible to lengthen the propagation path of the sound waves formed inside the case without increasing the size of the case. Therefore, this muffler can suppress an increase in installation space and can also improve noise reduction characteristics by further reducing low-frequency noise.

Note that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence between the component etc. and specific components etc. described in the embodiments to be described later.

FIG. 1 is a perspective view of a silencer according to a first embodiment and a duct in which the silencer is installed. 2 is a sectional view taken along the YZ plane in FIG. 1. FIG. 3 is a sectional view taken along line III-III in FIG. 2. FIG. FIG. 3 is an analytical diagram showing particle velocity vectors in the silencer according to the first embodiment. It is a schematic diagram showing the propagation path of the sound wave in the silencer concerning a 1st embodiment. It is a sectional view of a silencer concerning a 2nd embodiment and a duct in which the silencer is installed. It is a sectional view of a silencer concerning a 3rd embodiment, and a duct in which the silencer is installed. It is a sectional view of a silencer concerning a 4th embodiment, and a duct in which the silencer is installed. FIG. 7 is an analytical diagram showing vectors of particle velocity in a silencer according to a fourth embodiment. It is a schematic diagram showing the propagation path of the sound wave in the silencer concerning a 4th embodiment. It is a sectional view of the part corresponding to Drawing 3 in a silencer concerning a 5th embodiment. It is a sectional view of a silencer concerning a 6th embodiment, and a duct in which the silencer is installed. 13 is a sectional view taken along line XIII-XIII in FIG. 12. FIG. It is a sectional view of a silencer concerning a 7th embodiment, and a duct in which the silencer is installed. 15 is a sectional view taken along line XV-XV in FIG. 14. FIG. FIG. 12 is an analytical diagram showing particle velocity vectors in a silencer according to a seventh embodiment. It is a schematic diagram which shows the propagation path of the sound wave in the silencer based on 7th Embodiment. It is a schematic diagram which shows the propagation path of the sound wave in the silencer based on 7th Embodiment. It is a sectional view of a silencer concerning an 8th embodiment, and a duct in which the silencer is installed. 20 is a cross-sectional view taken along line XX-XX in FIG. 19. FIG. It is a sectional view of a silencer concerning a 9th embodiment, and a duct in which the silencer is installed. It is a graph which analyzed the relationship between frequency and noise reduction amount about 9th Embodiment and the comparative example 1 (configuration equivalent to 4th Embodiment) with respect to it. FIG. 7 is a schematic diagram showing a state in which air flows through a duct in Comparative Example 1 (configuration corresponding to the fourth embodiment). It is a perspective view of the muffler concerning a 10th embodiment, and the duct in which the muffler is installed. 24 is a sectional view taken along the YZ plane in FIG. 23. FIG. FIG. 12 is an analytical diagram showing particle velocity vectors in a silencer according to a tenth embodiment. It is a schematic diagram showing the propagation path of the sound wave in the silencer concerning a 10th embodiment. FIG. 7 is a schematic diagram showing a propagation path of a sound wave in Comparative Example 2 (a configuration corresponding to an example of a silencer shown in Patent Document 1) with respect to the tenth embodiment. 10 is a graph analyzing the relationship between frequency and noise reduction amount for the tenth embodiment and Comparative Example 2 thereto. It is a graph which analyzed the relationship between frequency and noise reduction amount about 10th Embodiment and 9th Embodiment. It is a sectional view of a silencer concerning an 11th embodiment and a duct in which the silencer is installed. FIG. 7 is a cross-sectional view of Comparative Example 3 with respect to the eleventh embodiment. 11 is a graph analyzing the relationship between frequency and noise reduction amount for the eleventh embodiment and Comparative Example 3 thereto. FIG. 7 is a sectional view showing a location where a silencer according to a twelfth embodiment is installed in a vehicle air conditioning unit. It is a sectional view of a silencer concerning a 13th embodiment and a duct in which the silencer is installed. It is a sectional view of a silencer concerning a 14th embodiment and a duct in which the silencer is installed.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, in the description of a plurality of embodiments, parts that are the same or equivalent to each other are given the same reference numerals, and the description thereof will be omitted.

Note that each drawing shows three-dimensional coordinates based on the X-axis, Y-axis, and Z-axis that are orthogonal to each other. In the following description, a direction parallel to the X axis will be referred to as an X direction, a direction parallel to the Y axis will be referred to as a Y direction, and a direction parallel to the Z axis will be referred to as a Z direction. Note that X, Y, and Z are used for explanation, and do not limit the state in which the silencer, duct, etc. are installed.

(First embodiment)
A first embodiment will be described with reference to the drawings. As shown in FIGS. 1 to 3, a muffler 1 according to the first embodiment is provided in a duct 2 and is used to reduce noise propagating through a passage 3 formed within the duct.

The duct 2 has an opening of a passage 3 on both sides or one side in the X direction, and a noise source (not shown) is disposed on one opening side of the passage 3. Note that the shape, size, etc. of the duct 2 shown in FIGS. 1 to 3 are simplified for the purpose of explanation. That is, the shape, size, etc. of the duct 2 can be set arbitrarily. The duct 2 may be, for example, an air conditioning case of a vehicle air conditioning unit, a blowout duct connected to the air conditioning case, or an exhaust pipe of an internal combustion engine. Note that when an air conditioning case or a blowout duct is used as the duct 2, the fan and motor become noise sources.

As shown in FIGS. 1 to 3, the silencer 1 includes a case 4 and a partition plate 5.
The case 4 is provided on the outer wall of the duct 2. The case 4 is provided so as to protrude from the outer wall of the duct 2 in the Y direction. The case 4 forms a space 6 inside thereof. A space 6 within the case communicates with a passage 3 within the duct.

Note that the shape, size, etc. of the case 4 shown in FIGS. 1 to 3 are simplified for the purpose of explanation. In other words, the shape, size, etc. of the case 4 can be arbitrarily set depending on the desired silencing characteristics (that is, the frequency of the noise to be silenced) or the constraints of the installation space.

In the following description, the boundary between the space 6 inside the case and the passage 3 inside the duct will be referred to as a "boundary surface BS." In FIG. 2, the boundary surface BS is indicated by a chain line with the symbol BS. Further, in FIG. 2, a virtual plane VS that is perpendicular to the boundary surface BS and that includes the center of the space 6 within the case is shown by a chain double-dashed line with the symbol VS. In the first embodiment, nothing is provided on the boundary surface BS. Note that, as described in the seventh embodiment below, the boundary surface BS may be provided with a boundary layer made of a breathable material such as a perforated panel or a nonwoven fabric.

Furthermore, in the following description, a portion of the inner wall of the case 4 located at a position facing the boundary surface BS may be referred to as a "case ceiling 4a."

The partition plate 5 is provided in a space 6 within the case. The partition plate 5 is provided so that the surface facing the plate thickness direction is along the boundary surface BS. Note that "along the boundary surface BS" includes not only a state parallel to the boundary surface BS but also a state inclined with respect to the boundary surface BS. In addition, it can also be said that the partition plate 5 is provided so that the surface facing the plate thickness direction intersects with the virtual plane VS perpendicular to the boundary surface BS.

As shown in FIG. 3, the partition plate 5 is located at a position away from at least a portion of the case inner walls 4b to 4e located in a plane parallel to the interface BS between the space 6 in the case and the passage 3 in the duct. It is provided. Specifically, both ends of the partition plate 5 in the X direction are connected to inner walls 4d and 4e of the case 4 in the X direction. Further, the length L1 of the partition plate 5 in the Z direction is shorter than the length L2 of the space 6 in the case in the Z direction. Therefore, as shown in FIGS. 2 and 3, both ends of the partition plate 5 in the Z direction are provided at positions away from the inner wall of the case 4 in the Z direction. In other words, the partition plate 5 is provided at a position away from one case inner wall 4b and the other case inner wall 4c that face each other across the virtual plane VS. Therefore, gaps are formed between both ends of the partition plate 5 in the Z direction and the inner walls 4b and 4c of the case 4 in the Z direction. Thereby, a plurality of paths are formed in the space 6 inside the case, including one gap and the other gap that face each other across the virtual plane VS, through which the sound waves incident from the passage 3 in the duct propagate. Note that in the following description, the path through which the sound waves propagate may be simply referred to as the "propagation path." Furthermore, in this specification, the term "gap" refers to a part of a propagation path, and includes a structure filled with a porous material as in the eleventh embodiment described below.

FIG. 4 is an analytical diagram showing particle velocity vectors. Note that the analysis in FIG. 4 relates to a configuration in which a boundary layer is provided at the boundary between the space 6 in the case and the passage 3 in the duct in addition to the configuration described in the first embodiment. From this analysis result, it is possible to read the propagation path of the sound wave.

FIG. 5 is a diagram schematically showing a part of the propagation path of a sound wave based on the analysis result of FIG. 4. As shown by arrow SW1 in FIG. 5, a part of the sound waves that entered the space 6 in the case from the passage 3 in the duct pass through one gap in the Z direction from the area on the duct 2 side with respect to the partition plate 5. Proceed to the area closer to the case ceiling 4a than the partition plate 5. Further, as shown by arrow SW2, another part of the sound waves that entered the space 6 in the case from the passage 3 in the duct passes through the other gap in the Z direction from the area closer to the duct 2 than the partition plate 5. , proceed to the area closer to the case ceiling 4a than the partition plate 5. In this way, a plurality of propagation paths are formed in the space 6 within the case by the partition plate 5. Therefore, it is possible to widen the frequency band of sound waves propagating in the space 6 inside the case by using a plurality of propagation paths. Further, by increasing the length of the plurality of propagation paths, it is possible to make the sound waves propagating in the space 6 inside the case low frequency. The noise inside the duct can be muffled by the interference between the sound waves that propagate along the plurality of paths and are emitted back into the duct 2 and the sound waves that travel through the passage 3 inside the duct.

The silencer 1 of the first embodiment described above has the following effects.
In the first embodiment, the partition plate 5 provided in the space 6 inside the case has one case inner wall 4b and the other case inner wall 4b facing each other across a virtual plane VS that is perpendicular to the boundary surface BS and includes the center of the space 6 inside the case. It is provided at a position away from both of the case inner walls 4c.
As a result, a plurality of propagation paths are formed in the space 6 within the case, so it is possible to widen the band of sound waves propagating through the plurality of propagation paths. Therefore, the noise in the duct is muffled in a wide band due to the interference between the sound waves that propagate through the plurality of propagation paths and are emitted to the duct 2 again, and the sound waves that travel through the passage 3 in the duct. Therefore, this muffler 1 can improve the noise reduction characteristic by widening the silencing characteristic against the noise of the passage 3 in the duct.

Further, in this muffler 1, by providing the partition plate 5 in the space 6 inside the case, it is possible to lengthen the propagation path of the sound waves formed inside the case without increasing the size of the case 4. Therefore, this muffler 1 can suppress an increase in the space required for installation and can improve noise reduction characteristics by further reducing low-frequency noise.

(Second embodiment)
A second embodiment will be described. The second embodiment differs from the first embodiment in that the configuration of the partition plate 5 is changed, and other aspects are the same as the first embodiment, so only the different parts from the first embodiment will be described.

As shown in FIG. 6, in the silencer 1 of the second embodiment, the length L1 of the partition plate 5 in the Z direction is set longer than that described in the first embodiment. Specifically, the length L1 of the partition plate 5 in the Z direction is set to be more than half the length L2 of the space 6 in the case in the Z direction. It can also be said that the area of the partition plate 5 is set to be more than half the area of the space 6 inside the case when viewed from the Y direction. Note that the length L1 of the partition plate 5 in the Z direction is set according to the target silencing characteristics (that is, the frequency of the noise to be silenced).

In the second embodiment described above, by increasing the length L1 of the partition plate 5 in the Z direction, it is possible to extend the sound propagation path and further reduce low-frequency noise.

(Third embodiment)
A third embodiment will be described. The third embodiment is also different from the first embodiment etc. in the configuration of the partition plate 5, and is otherwise the same as the first embodiment etc., so only the different parts from the first embodiment etc. explain.

As shown in FIG. 7, the silencer 1 of the third embodiment includes a plurality of partition plates 5a to 5d. The plurality of partition plates 5a to 5d are arranged at a predetermined distance from each other in the Y direction. In the following explanation, among the plurality of partition plates 5a to 5d, the partition plate placed on the case ceiling 4a side will be referred to as the "first partition plate 5a", and the partition plate placed on the boundary surface BS side will be referred to as the "second partition plate 5a". It is called "partition plate 5b". Furthermore, among the partition plates 5c and 5d arranged between the first partition plate 5a and the second partition plate 5b, the partition plate arranged on one side in the Z direction is called a "third partition plate 5c", and the Z The partition plate disposed on the other side of the direction is referred to as a "fourth partition plate 5d."

The length of the first partition plate 5a and the second partition plate 5b in the Z direction is shorter than the length of the space 6 inside the case in the Z direction. Both ends of the first partition plate 5a and the second partition plate 5b in the Z direction are provided at positions away from the inner walls 4b and 4c of the case 4 in the Z direction. In other words, the first partition plate 5a and the second partition plate 5b are provided at positions away from both one case inner wall 4b and the other case inner wall 4c that face each other with the virtual plane VS in between. Therefore, gaps are formed between both ends of the first partition plate 5a in the Z direction and the inner walls 4b and 4c of the case 4 in the Z direction. Further, gaps are also formed between both ends of the second partition plate 5b in the Z direction and the inner walls 4b and 4c of the case 4 in the Z direction.

The third partition plate 5c has one end in the Z direction connected to the case inner wall 4b. The other end of the fourth partition plate 5d in the Z direction is connected to the case inner wall 4c. The third partition plate 5c and the fourth partition plate 5d are located at positions corresponding to gaps formed between the first partition plate 5a and the second partition plate 5b and the case inner walls 4b and 4c (i.e., when viewed from the Y direction). , are provided at positions overlapping the gaps formed between the first partition plate 5a and the second partition plate 5b and the case inner walls 4b and 4c). By arranging the plurality of partition plates 5a to 5d in this manner, it is possible to lengthen the plurality of propagation paths formed in the space 6 within the case.

The silencer 1 of the third embodiment described above has a wide-band silencing characteristic for the noise in the passage 3 in the duct by forming a plurality of propagation paths in the space 6 in the case using the plurality of partition plates 5a to 5d. can be converted into
Furthermore, the silencer 1 can further reduce low-frequency noise by lengthening the propagation path of the sound waves formed inside the case using the plurality of partition plates 5a to 5d.

(Fourth embodiment)
A fourth embodiment will be described. In the fourth embodiment, the configuration of the partition plate 5 is changed from the third embodiment, and other aspects are the same as the third embodiment, so only the different parts from the third embodiment etc. will be explained. .

As shown in FIG. 8, the silencer 1 of the fourth embodiment also includes a plurality of partition plates 5a to 5d. Gaps are formed between both ends of the first partition plate 5a in the Z direction and the inner walls 4b and 4c of the case 4 in the Z direction, and gaps are formed between both ends of the second partition plate 5b in the Z direction and the case inner walls 4b and 4c. There are also gaps between them. The third partition plate 5c and the fourth partition plate 5d are provided at positions corresponding to gaps formed between the first partition plate 5a and the second partition plate 5b and the case inner walls 4b and 4c. Furthermore, in the fourth embodiment, when viewed from the Y direction, a portion of the first partition plate 5a and the second partition plate 5b is arranged so as to overlap a portion of the third partition plate 5c and the fourth partition plate 5d. has been done. Therefore, by arranging the plurality of partition plates 5a to 5d like this, it is possible to make the plurality of propagation paths formed in the space 6 within the case longer.

FIG. 9 is an analytical diagram showing particle velocity vectors. Note that the analysis in FIG. 9 relates to a configuration in which a boundary layer is provided at the boundary between the space 6 in the case and the passage 3 in the duct in addition to the configuration described in the fourth embodiment. From this analysis result, it is possible to read the propagation path of the sound wave.

FIG. 10 is a diagram schematically showing a part of the propagation path of a sound wave based on the analysis results of FIG. 9. As shown by the arrow SW3 in FIG. 10, a part of the sound waves that entered the space 6 in the case from the passage 3 in the duct are transmitted from the area on the duct 2 side than the second partition plate 5b to the Z of the second partition plate 5b. One passes through one gap in the Z direction and advances to the area between the first partition plate 5a and the second partition plate 5b, and the other passes through one gap in the Z direction of the first partition plate 5a and reaches the case ceiling 4a. Some of them advance to the area between the first partition plate 5a.
Further, as shown by arrow SW4, the other part of the sound waves that entered the space 6 in the case from the passage 3 in the duct is transferred from the area on the duct 2 side from the second partition plate 5b to the second partition plate 5b. One passes through the other gap in the Z direction and advances to the area between the first partition plate 5a and the second partition plate 5b, and the other passes from there through the other gap in the Z direction of the first partition plate 5a and reaches the case ceiling 4a. There is something that advances to the area between and the first partition plate 5a.

In this way, since a plurality of propagation paths are formed in the space 6 inside the case by the plurality of first partition plates 5a to 5d, it is possible to widen the frequency band of sound waves propagating in the space 6 inside the case. be. In addition, by arranging the plurality of first partition plates 5a to 5d so as to partially overlap when viewed from the Y direction, the length of the plurality of propagation paths is made longer, and the sound waves propagating through the space 6 inside the case are It is possible to use a lower frequency. The noise inside the duct can be muffled by the interference between the sound waves that propagate through the plurality of paths and are emitted back into the duct 2 and the sound waves that travel through the passage 3 inside the duct.

The muffler 1 of the fourth embodiment described above can widen the silencing characteristic for noise in the passage 3 in the duct by forming a plurality of propagation paths in the space 6 in the case.
Moreover, this muffler 1 can further reduce low-frequency noise by lengthening the propagation path of the sound waves formed within the case.

(Fifth embodiment)
A fifth embodiment will be described. The fifth embodiment differs from the first embodiment because the configuration of the partition plate 5 is changed from the silencer 1 described in the first embodiment, and other aspects are the same as the first embodiment. Only parts will be explained.

FIG. 11 is a cross-sectional view of a portion of the silencer 1 according to the fifth embodiment, which corresponds to the portion shown in FIG. 3 of the first embodiment. As shown in FIG. 11, in the fifth embodiment, both ends of the partition plate 5 in the Z direction are connected to inner walls 4b and 4c of the case 4 in the Z direction. Further, the length of the partition plate 5 in the X direction is shorter than the length of the space 6 in the case in the X direction. Therefore, both ends of the partition plate 5 in the X direction are provided at positions away from one inner wall 4d and the other inner wall 4e of the case 4 in the X direction. Therefore, gaps are formed between both ends of the partition plate 5 in the X direction and the inner walls 4d and 4e of the case 4 in the X direction. As a result, a plurality of propagation paths are formed in the space 6 within the case.

The fifth embodiment described above can also provide the same effects as the first embodiment. That is, the noise reduction effect does not change depending on the direction in which the partition plate 5 and the inner wall of the case are connected.

(Sixth embodiment)
A sixth embodiment will be described. The sixth embodiment differs from the silencer 1 described in the first embodiment etc. in that the configuration of the partition plate 5 is changed, and other aspects are the same as in the first embodiment etc., so the sixth embodiment is different from the first embodiment. Only the different parts will be explained.

As shown in FIGS. 12 and 13, the silencer 1 of the sixth embodiment includes a connection member 7 that connects the case ceiling 4a and the partition plate 5. The partition plate 5 is supported by the connecting member 7 in the space 6 inside the case. Therefore, the partition plate 5 is provided at a position away from the inner wall of the case 4 in the Z direction and the inner wall in the X direction.

Specifically, as shown in FIG. 13, the length L1 of the partition plate 5 in the Z direction is shorter than the length L2 of the space 6 in the case in the Z direction. Therefore, both ends of the partition plate 5 in the Z direction are provided at positions apart from the inner walls 4b, 4c of the case 4 in the Z direction. Therefore, gaps are formed between both ends of the partition plate 5 in the Z direction and the inner walls 4b and 4c of the case 4 in the Z direction. Moreover, the length L3 of the partition plate 5 in the X direction is shorter than the length L4 of the space 6 in the case in the X direction. Therefore, both ends of the partition plate 5 in the X direction are provided at positions away from the inner walls 4d and 4e of the case 4 in the X direction. Therefore, gaps are also formed between both ends of the partition plate 5 in the X direction and the inner walls 4d and 4e of the case 4 in the X direction. Therefore, in the sixth embodiment, a gap is formed between the partition plate 5 and the inner wall of the case over the entire circumference. As a result, a plurality of propagation paths are formed in the space 6 within the case.

As exemplified by arrows SW5 and SW6 in FIG. There are things that proceed like this. In this way, a plurality of propagation paths are formed in the space 6 within the case by the partition plate 5. Therefore, in the sixth embodiment, by making the lengths of the plurality of propagation paths different, it is possible to widen the frequency band of the sound waves propagating in the space 6 within the case.

The silencer 1 of the sixth embodiment described above can also widen the silencing characteristic for noise in the passage 3 in the duct by forming a plurality of propagation paths in the space 6 within the case.

(Seventh embodiment)
A seventh embodiment will be described. The seventh embodiment differs from the silencer 1 described in the first embodiment in the structure of the partition plate 5, and is otherwise the same as the first embodiment. Only the different parts will be explained.

As shown in FIGS. 14 and 15, in the seventh embodiment, the partition plate 5 is located on the case inner walls 4b to 4e located in a plane direction parallel to the interface BS between the space 6 in the case and the passage 3 in the duct. is located at a location away from at least a portion of the Specifically, the partition plate 5 is provided at a position away from one inner wall 4b of the case 4 in the Z direction. Further, the partition plate 5 is connected to the other inner wall 4c of the case 4 in the Z direction, and is also connected to both inner walls 4d and 4e of the case 4 in the X direction. Therefore, a gap is formed only between one end of the partition plate 5 in the Z direction and one inner wall 4b of the case 4 in the Z direction. Even with such a configuration, a plurality of paths are formed in the space 6 within the case through which the sound waves incident from the passage 3 in the duct propagate.

FIG. 16 is an analytical diagram showing particle velocity vectors. From this analysis result, it is possible to read the propagation path of the sound wave.

FIG. 17 is a diagram schematically showing a part of the propagation path of a sound wave based on the analysis result of FIG. 16. As illustrated by arrow SW7 in FIG. 17, a part of the sound waves that entered the space 6 in the case from the passage 3 in the duct are transmitted from a region relatively close to one inner wall 4b of the case 4 in the Z direction to the partition between the case and the case. It passes through the gap with the plate 5 and advances to the area closer to the case ceiling 4a than the partition plate 5. In addition, as shown by arrow SW8, another part of the sound waves that entered the space 6 in the case from the passage 3 in the duct is transmitted from an area relatively close to the other inner wall 4c in the Z direction of the case 4 to the partition between the case and the case. It passes through the gap with the plate 5 and advances to the area closer to the case ceiling 4a than the partition plate 5. In this way, a plurality of propagation paths are formed in the space 6 within the case by the partition plate 5.

Furthermore, as schematically shown by arrows SW9 and SW10 in FIG. There are some that move along the side of 5. In this way, a plurality of propagation paths are formed in the space 6 within the case by the partition plate 5.

As described above, also in the configuration of the seventh embodiment, by forming a plurality of propagation paths within the case, it is possible to widen the frequency band of sound waves propagating in the space 6 within the case. Further, by increasing the length of the plurality of propagation paths, it is possible to make the sound waves propagating in the space 6 inside the case low frequency. The noise inside the duct can be muffled by the interference between the sound waves that propagate along the plurality of paths and are emitted back into the duct 2 and the sound waves that travel through the passage 3 inside the duct.

In the seventh embodiment described above, the partition plate 5 is provided at a position away from only one inner wall 4b of the case 4 in the Z direction, but the partition plate 5 is not limited thereto. It is sufficient that it is provided at a position away from at least a portion of the case inner walls 4b to 4e. That is, the partition plate 5 may be separated only from the other inner wall 4c of the case 4 in the Z direction. Alternatively, the partition plate 5 may be separated from only one inner wall 4d of the case 4 in the X direction. Alternatively, the partition plate 5 may be separated only from the other inner wall 4e of the case 4 in the X direction.

(Eighth embodiment)
An eighth embodiment will be described. The eighth embodiment differs from the silencer 1 described in the first embodiment in the configuration of the partition plate 5, and is otherwise the same as the first embodiment. Only the different parts will be explained.

As shown in FIGS. 19 and 20, in the eighth embodiment, the partition plate 5 is provided at a position away from both inner walls 4b and 4c of the case 4 in the Z direction, and is provided at a position away from one inner wall of the case 4 in the X direction. It is also located away from 4d. Further, the partition plate 5 is connected to the other inner wall 4e of the case 4 in the X direction. Therefore, a gap is formed between both ends of the partition plate 5 in the Z direction and both inner walls 4b and 4c of the case 4 in the Z direction, and a gap is formed between one end of the partition plate 5 in the X direction and the case 4 in the X direction. A gap is formed between the inner wall 4d and one inner wall 4d. Thereby, a plurality of paths are formed in the space 6 within the case through which the sound waves incident from the passage 3 within the duct propagate.

Even in the configuration of the eighth embodiment, the same effects as those of the first embodiment and the like described above can be achieved.

(Ninth embodiment)
A ninth embodiment will be described. The ninth embodiment adds a boundary layer to the silencer 1 described in the fourth embodiment etc., and is otherwise the same as the fourth embodiment, so only the different parts from the fourth embodiment will be described. do.

As shown in FIG. 21, the muffler 1 of the ninth embodiment includes a boundary layer 8 at the boundary between the space 6 in the case and the passage 3 in the duct. The boundary layer 8 partitions the space 6 inside the case and the passage 3 inside the duct, and also ensures ventilation between the space 6 inside the case and the passage 3 inside the duct. As the boundary layer 8, a breathable material can be employed, for example a perforated panel or a non-woven fabric. By balancing the acoustic impedance of the boundary layer 8 and the acoustic impedance of the space 6 inside the case, it is possible to widen the band or lower the frequency of the silencing characteristic.

The graph shown in FIG. 22 is an analysis of the relationship between the frequency and the amount of noise reduction (that is, the silencing characteristics) for an example of the ninth embodiment and a first comparative example thereof. Note that an example of the ninth embodiment employs a perforated panel as the boundary layer 8. On the other hand, the first comparative example for the ninth embodiment is a configuration in which the boundary layer 8 is removed from the configuration of the ninth embodiment, that is, the configuration is similar to the fourth embodiment described above.

In the graph of FIG. 22, the solid line A1 shows the sound deadening characteristic according to the configuration of the ninth embodiment, and the broken line B1 shows the sound deadening characteristic according to the first comparative example. The frequency of the peak value of the solid line A1 is lower than the frequency of the peak value of the broken line B1. Further, the frequency range indicated by arrow A2 for the solid line A1 is wider than the frequency range indicated by arrow B2 for the broken line B1. In this way, by including the boundary layer 8, the muffler 1 of the ninth embodiment can have a broader band or lower frequency muffling characteristic compared to the first comparative example.

Next, FIG. 23 shows how gas flows through the passage 3 in the duct in a first comparative example to the ninth embodiment (that is, a configuration similar to the fourth embodiment).

When gas flows through the passage 3 within the duct, the airflow may enter the space 6 within the case, causing noise. Further, as shown by arrow AE in FIG. 23, noise may also be generated when the airflow flowing through the passage 3 in the duct hits the inner wall of the case 4 and the airflow is disturbed. In this way, when gas flows through the passage 3 in the duct, by providing the case 4 on the wall of the duct 2, new noise that is different from the noise source (not shown) placed on one opening side of the duct 2 can be generated. This may occur.

On the other hand, in the silencer 1 of the ninth embodiment shown in FIG. 21, the boundary layer 8 can prevent the airflow flowing through the passage 3 in the duct from entering the space 6 in the case. Further, the boundary layer 8 can prevent the airflow flowing through the passage 3 in the duct from hitting the inner wall of the case 4 . Therefore, in the silencer 1 of the ninth embodiment, even when gas flows through the passage 3 in the duct, the boundary layer 8 prevents new noise from being generated by providing the case 4 on the wall of the duct 2. The reduction effect can be further improved.

(10th embodiment)
A tenth embodiment will be described. The tenth embodiment differs from the ninth embodiment because the configuration of the partition plate 5 is changed from the silencer 1 described in the ninth embodiment, and other aspects are the same as the ninth embodiment. Only parts will be explained.

As shown in FIGS. 24 and 25, the silencer 1 of the tenth embodiment includes the first to third partition plates 5a to 5c described in the fourth embodiment, and includes the fourth partition plate 5d. do not have. Therefore, in the tenth embodiment, the plurality of partition plates 5a to 5c have a total area of the parts arranged on one side across the virtual plane VS that is perpendicular to the boundary surface BS and that includes the center of the space 6 in the case. , are arranged so that the total area of the parts arranged on the other side is asymmetrical . By arranging the plurality of partition plates 5a to 5c in this manner, it is possible to make the lengths of the plurality of propagation paths formed in the space 6 within the case significantly different.

FIG. 26 is an analytical diagram showing particle velocity vectors in the configuration of the tenth embodiment. From this analysis result, it is possible to read the propagation path of the sound wave.

FIG. 27 is a diagram schematically showing a part of the propagation path of a sound wave based on the analysis result of FIG. 26. As shown by arrow SW11 in FIG. 27, a part of the sound waves that have entered the space 6 in the case from the passage 3 in the duct are transmitted from the region on the duct 2 side than the second partition plate 5b to the Z of the second partition plate 5b. One passes through one gap in the Z direction and advances to the area between the first partition plate 5a and the second partition plate 5b, and the other passes through one gap in the Z direction of the first partition plate 5a and reaches the case ceiling 4a. Some of them advance to the area between the first partition plate 5a.
In addition, as shown by arrow SW12, the other part of the sound waves that entered the space 6 in the case from the passage 3 in the duct is transferred from the area on the duct 2 side from the second partition plate 5b to the second partition plate 5b. One passes through the other gap in the Z direction and advances to the area between the first partition plate 5a and the second partition plate 5b, and the other passes through the other gap in the Z direction of the first partition plate 5a and advances to the area between the case ceiling 4a and the second partition plate 5a. 1 and the area between the partition plate 5a. Of these, the propagation path shown by arrow SW11 that goes to the area between the case ceiling 4a and the first partition plate 5a is the propagation path shown by arrow SW12 that goes between the case ceiling 4a and the first partition plate 5a. The areas in between are longer than those that advance.

In this manner, in the tenth embodiment, by asymmetrically arranging the plurality of partition plates 5a to 5c with the virtual surface VS in between, the length of the propagation path formed on one side of the virtual surface VS is different from the length of the propagation path formed on one side with the virtual surface VS in between. The lengths of the propagation paths formed on the sides are different. Therefore, it is possible to make the sound waves propagating through the plurality of propagation paths formed in the space 6 inside the case wider. Therefore, this muffler 1 can provide a wider range of muffling characteristics for the noise of the passage 3 in the duct.

Here, as a second comparative example with respect to the tenth embodiment, FIG. 28 shows a silencer pipe 10 having a cylindrical shape with a bottom. The muffling pipe 10 shown in FIG. 28 corresponds to an example of the configuration disclosed in Patent Document 1 mentioned above. A bent portion 11 is provided in the middle of the muffler pipe 10, and a protrusion amount H2 of the muffler pipe 10 protruding from the duct 2 is suppressed. It is assumed that the amount of protrusion H2 of the muffling tube 10 of the second comparative example shown in FIG. 28 is the same as the amount of protrusion H1 of the case 4 of the muffler 1 of the tenth embodiment shown in FIG. 25.

As shown by arrows SW13 and SW14 in FIG. 28, the sound waves that enter the muffler tube 10 from the duct 2 are reflected at the deep part of the muffler tube 10, and are emitted into the duct 2 through the muffler tube 10 again. The noise inside the duct is muffled by the interference between the sound waves emitted from the muffling tube 10 into the duct 2 and the sound waves traveling through the passage 3 inside the duct. However, in the configuration of the second comparative example, the frequency at which the sound is muffled is determined depending on the length of the muffler tube 10, so there is a problem that the frequency band in which the sound muffling effect can be obtained is narrow.

The graph shown in FIG. 29 is an analysis of the relationship between the frequency and the amount of noise reduction (that is, the silencing characteristics) for the tenth embodiment and the second comparative example.
In the graph of FIG. 29, the solid line C1 shows the sound deadening characteristic according to the configuration of the tenth embodiment, and the broken line D1 shows the sound deadening characteristic according to the second comparative example. The frequency of the peak value of the solid line C1 is lower than the frequency of the peak value of the broken line D1. Further, the frequency range indicated by the arrow C2 for the solid line C1 is much wider than the frequency range indicated by the arrow D2 for the broken line D1. In this way, the silencer 1 of the tenth embodiment has different lengths of the plurality of propagation paths formed in the space 6 within the case, and furthermore, by increasing the length of the plurality of propagation paths. , it is possible to widen the band and lower the frequency of the silencing characteristic compared to the second comparative example.

Moreover, the graph shown in FIG. 30 is an analysis of the silencing characteristics (that is, the relationship between the frequency and the amount of noise reduction) for the tenth embodiment and the ninth embodiment.
In the graph of FIG. 30, the solid line C1 represents the silencing characteristic according to the configuration of the tenth embodiment, and the broken line A1 represents the silencing characteristic according to the configuration of the ninth embodiment. The frequency of the peak value of the solid line C1 is higher than the frequency of the peak value of the broken line A1, but the frequency range shown by the arrow C2 for the solid line C1 is much higher than the frequency range shown by the arrow A2 for the broken line A1. It is spacious. In this way, the muffler 1 of the tenth embodiment is different from the muffler 1 of the ninth embodiment by making the lengths of the plurality of propagation paths formed in the space 6 in the case more different. It is possible to make the silencing characteristics wider.

In addition, regarding the configuration of the tenth embodiment, if the length of the plurality of propagation paths is increased by increasing the number of partition plates 5 or extending the length of the partition plates 5, the silencing characteristics can be made lower in frequency. It is possible to do so.

In the tenth embodiment described above, the plurality of partition plates 5a to 5c provided in the silencer 1 are arranged on one side with the virtual plane VS perpendicular to the boundary surface BS and including the center of the space 6 in the case. The arrangement is such that the total area of the parts on the other side and the total area of the parts on the other side are asymmetrical .
As a result, the propagation path of the sound wave formed in the space 6 inside the case is such that the length of the propagation path formed on one side of the virtual surface VS is different from the length of the propagation path formed on the other side. becomes. Therefore, it is possible to make the sound waves propagating through the plurality of propagation paths formed in the space 6 inside the case wider. Therefore, the muffler 1 of the tenth embodiment can provide a wider range of muffling characteristics for the noise of the passage 3 in the duct.

(Eleventh embodiment)
An eleventh embodiment will be described. The eleventh embodiment differs from the silencer 1 described in the tenth embodiment in the structure inside the case, and is otherwise the same as the tenth embodiment, so there are no differences from the tenth embodiment. I will only explain about.

As shown in FIG. 31, in the silencer 1 of the eleventh embodiment, a space 6 within the case is filled with a porous material 9 having air permeability. As the porous material 9, for example, urethane or glass wool is used. Depending on the acoustic impedance of the porous material 9, it is possible to widen the band or lower the frequency of the sound deadening characteristic.

In the eleventh embodiment, by filling the space 6 in the case with the porous material 9, a structure for fixing the partition plate 5 is not required, and the structure of the silencer 1 can be simplified.

On the other hand, if the partition plate 5 is fixed to the inner wall of the case 4, the porous material 9 filled in the space 6 inside the case is prevented from shifting (that is, shifting or moving), so it can be used for a long period of time. It is possible to suppress the deterioration of the silencing characteristics due to

Here, FIG. 32 shows a third comparative example with respect to the eleventh embodiment. The silencer 1 of the third comparative example is one in which only a porous material 9 is filled in a space 6 within a case, and the partition plate 5 is not provided.

The graph shown in FIG. 33 is an analysis of the relationship between the frequency and the amount of noise reduction (that is, the silencing characteristics) for the configuration of the eleventh embodiment and the third comparative example thereto.
In the graph of FIG. 33, the solid line F indicates the silencing characteristic according to the configuration of the eleventh embodiment, and the broken line G indicates the silencing characteristic according to the third comparative example. At frequencies below about 650 Hz, the amount of noise reduction indicated by the solid line F is larger than the amount of noise reduction indicated by the broken line G. As described above, the silencer 1 of the eleventh embodiment has the porous material 9 and the partition plate 5 in the space 6 in the case, thereby improving the low frequency sound absorption characteristics compared to the third comparative example. It is possible.

(12th embodiment)
A twelfth embodiment will be described. The twelfth embodiment describes a form in which a silencer 1 is installed in a vehicle air conditioning unit.

As shown in FIG. 34, the vehicle air conditioning unit 20 includes an air conditioning case 21, an evaporator 22, a heater core 23, an air mix door 24, a blow-off opening door 25, and the like.
The air conditioning case 21 is a member corresponding to the duct 2 described in the first to eleventh embodiments. The air conditioning case 21 forms the outer shell of the air conditioning unit 20. A passage 3 through which air flows is formed inside the air conditioning case 21. In addition, in FIG. 34, the flow direction of the air in the passage 3 is shown by a white arrow. Further, the air conditioning case 21 has a plurality of blowout openings 26 on the downstream side of the passage 3 in the air flow direction for blowing out air to a predetermined area within the vehicle interior. A blowout duct (not shown) may be connected to the blowout opening 26 .

Inside the air conditioning case 21, an evaporator 22, a heater core 23, an air mix door 24, a blow-off opening door 25, and the like are provided.

The evaporator 22 is a heat exchanger for cooling the air flowing through the passage 3. The evaporator 22 constitutes a part of a refrigeration cycle (not shown). The evaporator 22 exchanges heat between the refrigerant flowing therein and the air passing through the evaporator 22, evaporating the refrigerant and cooling the air.

The heater core 23 is a heat exchanger for heating the air flowing through the passage 3. The heater core 23 exchanges heat between the engine cooling water or high-pressure refrigerant flowing therein and the air passing through the heater core 23, and heats the air with the heat of the engine cooling water or high-pressure refrigerant.

An air mix door 24 is provided between the evaporator 22 and the heater core 23 in the passage 3 within the air conditioning case. The air mix door 24 adjusts the ratio of air that bypasses the heater core 23 after passing through the evaporator 22 and air that passes through the heater core 23 after passing through the evaporator 22.

The blow-off opening door 25 is provided in each of the plurality of blow-off openings 26, and adjusts the opening area of the blow-off opening 261.

The muffler 1 of the twelfth embodiment is provided outside or inside the air conditioning case 21 in order to reduce noise propagating through the passage 3 inside the air conditioning case 21. In FIG. 34, locations where it is preferable to install the silencer 1 in the air conditioning case 21 are illustratively shown by broken lines P1 to P3. Note that one or more silencers 1 may be installed in the air conditioning case 21. By installing the silencer 1 in the air conditioning case 21, it is possible to reduce the noise emitted from the air conditioner into the vehicle interior, and improve air conditioning performance (that is, passenger comfort).

Although not shown, the silencer 1 may be installed in a blow-off duct connected to the blow-off opening 26 of the air conditioning case 21. Even in this case, the noise emitted from the air conditioner into the vehicle interior can be reduced, and the air conditioning performance can be improved, as described above.

(13th embodiment)
A thirteenth embodiment will be described. The thirteenth embodiment differs from the first embodiment etc. in that the method of installing the silencer 1 in the duct 2 is changed, and the other aspects are the same as in the first embodiment etc. Only the different parts will be explained.

As shown in FIG. 35, in the silencer 1 of the thirteenth embodiment, a part of the case 4 on the boundary layer 8 side enters the passage 3 in the duct, and a part of the case 4 on the ceiling side enters the duct 2. It protrudes from the outer wall in the Y direction. Even in the configuration of the thirteenth embodiment, the same effects as those of the first to twelfth embodiments described above can be achieved.

(14th embodiment)
A fourteenth embodiment will be described. The fourteenth embodiment also differs from the first embodiment etc. in that the method of installing the silencer 1 in the duct 2 is changed, and the other aspects are the same as in the first embodiment etc. Only the different parts will be explained.

As shown in FIG. 36, in the silencer 1 of the fourteenth embodiment, the entire case 4 enters the passage 3 in the duct. Even in the configuration of the fourteenth embodiment, the same effects as those of the first to thirteenth embodiments described above can be achieved.

(Other embodiments)
(1) In each of the embodiments described above, the silencer 1 has been described as having one to four partition plates 5, 5a to 5d, but the number of partition plates 5 is not limited to this and may be set arbitrarily. is possible. Further, the partition plate 5 can have any shape, and may have a flat or curved surface.

(2) In each of the embodiments described above, the silencer 1 has been described as having a rectangular parallelepiped or cubic case 4, but the case 4 is not limited to this, and the case 4 can have any shape. Further, the wall of the case 4 may be a flat surface or a curved surface.

The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims. Furthermore, the embodiments described above are not unrelated to each other, and can be combined as appropriate, except in cases where combination is clearly impossible. Furthermore, in each of the above embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is specifically stated that they are essential or where they are clearly considered essential in principle. stomach. In addition, in each of the above embodiments, when numerical values such as the number, numerical value, amount, range, etc. of the constituent elements of the embodiment are mentioned, when it is clearly stated that it is essential, or when it is clearly limited to a specific number in principle. It is not limited to that specific number, except in cases where In addition, in each of the above embodiments, when referring to the shape, positional relationship, etc. of constituent elements, etc., the shape, It is not limited to positional relationships, etc.

(summary)
According to the first aspect shown in some or all of the above-described embodiments, a silencer provided in a duct in which a passageway having openings on both sides or one side is formed has a space communicating with the passageway in the duct. The device includes a case to be formed and one or more partition plates provided in a space within the case. At least one of the partition plates is provided at a position away from at least a portion of the inner wall of the case, which is located in a plane direction parallel to the interface between the space within the case and the passage within the duct.

According to the second aspect, at least one of the partition plates is perpendicular to the interface between the space inside the case and the passage inside the duct, and is opposite to the other across a virtual plane that includes the center of the space inside the case. It is provided at a position away from the inner wall of the case and the inner wall of the other case.

According to a third aspect, the muffler further includes a boundary layer provided at the boundary between the space within the case and the passage within the duct. The boundary layer partitions the space inside the case and the passage inside the duct, and also ensures ventilation between the space inside the case and the passage inside the duct.
As a result, by adjusting the material and thickness of the boundary layer, the size of the vents included in the boundary layer, etc., it is possible to make the sound deadening characteristics wider or lower in frequency.
Furthermore, when gas flows through the passage within the duct, the boundary layer prevents the airflow from entering the space within the case. Further, the boundary layer prevents the airflow flowing through the passage in the duct from hitting the inner wall of the case and causing disturbance of the airflow. Therefore, this muffler can improve the noise reduction effect by preventing the generation of new noise due to the provision of the case using the boundary layer.

According to the fourth aspect, the passage within the duct is configured to allow gas to flow.
Thereby, the boundary layer can prevent the airflow flowing through the passage within the duct from entering the space within the case. Further, the boundary layer can prevent the airflow flowing through the passage in the duct from hitting the inner wall of the case and causing disturbance of the airflow. Therefore, this muffler can improve the noise reduction effect even when gas flows through the passage in the duct.

According to the fifth aspect, the plurality of partition plates include a predetermined partition plate and other partition plates. The predetermined partition plate and other partition plates are arranged at a predetermined distance from each other in a direction perpendicular to the interface between the space within the case and the passage within the duct. Furthermore, the predetermined partition plate and the other partition plate are arranged at positions corresponding to the gaps between the predetermined partition plate and the inner wall of the case. Further, the predetermined partition plate and the other partition plates are arranged so that a part of the predetermined partition plate and a part of the other partition plate overlap when viewed from a direction perpendicular to the boundary surface.
This makes it possible to lengthen the propagation path of sound waves formed within the case without increasing the size of the case. Therefore, this muffler can suppress an increase in installation space and can also improve noise reduction characteristics by further reducing low-frequency noise.

According to the sixth aspect, the plurality of partition plates are arranged on one side across a virtual plane that is perpendicular to the interface between the space inside the case and the passage inside the duct and includes the center of the space inside the case. They are arranged so that the total area of the parts and the total area of the parts arranged on the other side are asymmetrical .
As a result, the length of the propagation path of the sound wave formed in the space inside the case is different from the length of the propagation path formed on one side of the virtual plane to the length of the propagation path formed on the other side. . Therefore, it is possible to make the sound waves propagating through the plurality of propagation paths formed in the space inside the case wider in band. Therefore, this muffler can provide a wider range of muffling characteristics for the noise of the passage in the duct.

According to the seventh aspect, the space within the case is filled with a porous material having air permeability.
Thereby, by selecting the material of the porous material, it is possible to widen the band or lower the frequency of the sound deadening characteristic.
Furthermore, by filling the space within the case with the porous material, a structure for fixing the partition plate is not required, and the structure of the silencer can be simplified.
On the other hand, if the partition plate is fixed to the inner wall of the case, the position of the porous material filled in the space inside the case is prevented, so changes in the sound deadening characteristics due to long-term use can be suppressed.

1 Silencer 2 Duct 3 Passage 4 Cases 4a to 4e Case inner walls 5, 5a to 5d Partition plate 6 Space BS Boundary surface VS Virtual surface

Claims (5)

A silencer provided in a duct (2) in which a passage (3) having an opening on both sides or one side is formed,
a case (4) forming a space (6) communicating with the passage in the duct;
one or more partition plates (5, 5a to 5d) provided in the space within the case;
Provided at the boundary between the space in the case and the passage in the duct, partitions the space in the case and the passage in the duct, and improves the ventilation between the space in the case and the passage in the duct. a boundary layer (8) for securing ;
At least one of the partition plates faces across a virtual plane (VS) that is perpendicular to the interface (BS) between the space inside the case and the passage inside the duct and includes the center of the space inside the case. and the other case inner wall, so that the sound waves that have entered the space within the case from the passage within the duct via the boundary layer are prevented from entering the space within the case. A silencer with multiple propagation paths . The muffler according to claim 1 , wherein the passage in the duct is configured to allow gas to flow. The plurality of partition plates include predetermined partition plates (5a, 5b) and other partition plates (5c, 5d), and the predetermined partition plates and the other partition plates are arranged in the case. The other partition plate is arranged at a predetermined distance in a direction (Y) perpendicular to the interface between the space and the passage in the duct, and is located at a position corresponding to the gap between the predetermined partition plate and the inner wall of the case. according to claim 1 or 2 , wherein a portion of the predetermined partition plate and a portion of the other partition plate overlap when viewed from a direction perpendicular to the boundary surface. silencer. The plurality of partition plates (5a to 5c) are arranged on one side across a virtual plane that is perpendicular to the interface between the space in the case and the passage in the duct and that includes the center of the space in the case. 4. The silencer according to claim 3 , wherein the total area of the portions located on the other side is asymmetrical to the total area of the portions placed on the other side. The muffler according to any one of claims 1 to 4 , wherein the space within the case is filled with a porous material (9) having air permeability.

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