Muffler

Abstract

To provide a silencer for an air passage, which has an improved effect of silencing noise caused by vibration. [Solution] The silencer 10 is a box-shaped hollow body arranged midway through an air passage 100, and includes a housing constituting an expansion section 106, and a vibration section 30 provided on the outer wall of the housing. In the vibration section 30, a plurality of vibration regions 32 that vibrate in response to sound inside the housing are separated by non-vibration regions 34 provided between the vibration regions 32, and can vibrate with the non-vibration regions 34 as fixed ends, and the ratio of the long side to the short side of a first imaginary rectangle circumscribing the vibration regions 32 on the outer surface of the vibration section 30 is greater than the ratio of the long side to the short side of a second imaginary rectangle circumscribing the outer surface.

Description

[Technical field]

[0001] The present invention relates to a silencer for reducing noise in an air passage. [Background technology]

[0002] Among mufflers that muffle sound in an air passage are those that have a vibrating part in a part of the air passage and muffle sound by consuming sound energy as mechanical energy through vibration of the vibrating part. One example of such a vibration type muffler is the muffler described in Patent Document 1 (Patent Document 1 calls it a sound absorbing structure).

[0003] In Patent Document 1, a cooling and heating duct is formed by connecting multiple membrane sound absorbers that absorb sound by sound pressure drive. When sound is transmitted to the membrane sound absorber, the membrane sound absorber vibrates its vibrating membrane. This vibration causes sound wave energy to be consumed as mechanical energy, and the membrane sound absorber absorbs sound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-116118 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the muffler having the above configuration, the sound is cancelled by the vibration sound generated near the resonant frequency of the vibrating part, so the muffling volume is large. However, the applicable frequency band of vibration muffling is narrow, so it is difficult to obtain a sufficient muffling effect with the conventional muffling structure using vibration muffling.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to solve the problems of the above-mentioned conventional technology, and specifically, to provide a silencer for an air passage that has an improved noise absorbing effect caused by vibration. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has the following configuration. [1] A silencer comprising a housing arranged midway through an air passage and a vibrating part provided on the outer wall of the housing, in which a plurality of vibration regions that vibrate in response to sound within the housing are separated by non-vibrating regions provided between the vibration regions and can vibrate with the non-vibrating regions as fixed ends, and in which the ratio of the long side to the short side of a first imaginary rectangle circumscribing the vibration regions on the outer surface of the vibrating part is greater than the ratio of the long side to the short side of a second imaginary rectangle circumscribing the outer surface. [2] The silencer described in [1], wherein the housing forms an extension portion in the air passage, the extension portion has an internal space whose cross-sectional size perpendicular to the extension direction of the air passage is larger than that of the rest of the air passage other than the extension portion, and at least one of the multiple side walls of the housing forms a vibrating portion. [3] A silencer as described in [1] or [2], wherein in each of the multiple vibration regions, the ratio of the long side to the short side of the first imaginary rectangle is greater than the ratio of the long side to the short side of the second imaginary rectangle. [4] A silencer as described in any of [1] to [3], wherein an internal air passage that forms part of the air passage extends within the housing, and the internal air passage is disposed between an inlet opening and an outlet opening provided in the housing in the extension direction of the air passage, and the length of the internal air passage in the extension direction is L, and for a vibration region among multiple vibration regions in which the ratio of the long side to the short side of the first imaginary rectangle is maximum, the length of the long side of the first imaginary rectangle is La, which satisfies the relationship La>L / 3. [5] A silencer described in any of [1] to [4], wherein in the vibrating part, the non-vibrating region extends continuously along the extension direction of the air passage, and in the extension direction, one end of the non-vibrating region and one end of the vibrating region are located at one end of the housing, and the other end of the non-vibrating region and the other end of the vibrating region are located at the other end of the housing. [6] The silencer according to any one of [1] to [5], wherein the thickness of the outer wall in the vibration region and the thickness of the outer wall in the non-vibration region are uniform. [7] The silencer according to any one of [1] to [6], wherein the thickness of the outer wall in the vibration region is 1 mm or more. [8] The silencer according to any one of [1] to [7], wherein the vibrating portion is made of a resin material. [9] The silencer according to any one of [1] to [8], wherein the non-vibration region is provided on the outer wall so as to protrude in a convex shape toward the outside of the housing.

[10] A silencer as described in [9], wherein the non-vibration area is constituted by ribs provided on the outer wall.

[11] A silencer as described in [9], wherein the non-vibration area has a step structure formed by positioning the non-vibration area in the outer surface outside the housing relative to the vibration area in the outer surface. Effect of the Invention

[0008] In the silencer of the present invention, the vibration part is divided into a plurality of vibration regions by non-vibration regions, and the ratio of the long side / short side in at least one of the vibration regions is greater than the ratio of the long side / short side in the original vibration part. This makes it possible to excite the second and subsequent vibration modes in a desired frequency band (target frequency band) along with the first vibration mode. As a result, a larger silencing volume is obtained in the target frequency band, and the silencing effect by vibration silencing is improved. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a silencer according to one embodiment of the present invention; FIG. [Diagram 2] FIG. 2 is a plan view of a silencer according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a side view of a silencer according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a JJ cross section of FIG. 3. [Diagram 5] FIG. 3 is a diagram showing a non-vibration region of a housing of a silencer according to one embodiment of the present invention, and is a diagram showing a cross section II of FIG. 2. [Figure 6] Step cross section [Figure 7A]FIG. 3 is a diagram showing a first modified example of the arrangement pattern of vibrating regions and non-vibrating regions in a housing, and corresponds to FIG. 2. [Figure 7B] 10 is a diagram showing a second modified example of the arrangement pattern of the vibrating regions and the non-vibrating regions in the housing, and corresponds to FIG. 2. FIG. [Figure 7C] 11 is a diagram showing a third modified example of the arrangement pattern of the vibrating regions and the non-vibrating regions in the housing, and corresponds to FIG. 2. FIG. [Figure 8A] FIG. 2 is an explanatory diagram of a first virtual rectangle. [Figure 8B] FIG. 11 is an explanatory diagram of a second virtual rectangle. [Figure 9] FIG. 11 is an explanatory diagram of the reduction in sound deadening caused by not using sound absorbing material. [Figure 10] 11A and 11B are diagrams relating to the noise reduction effect when vibration of a vibrating part is used. [Figure 11] FIG. 2 is a diagram showing a sound attenuation peak corresponding to a first vibration mode and a sound attenuation peak corresponding to a second vibration mode in a spectrum of sound attenuation caused by vibration of a vibrating part. [Figure 12] 10 is an explanatory diagram of the effect of the aspect ratio of the vibration region surface on the resonance frequency. FIG. [Figure 13] FIG. 2 is a perspective view showing the appearance of the silencer used in the first embodiment. [Figure 14] FIG. 2 is a perspective view showing the appearance of a silencer used in Comparative Example 1. [Figure 15] FIG. 2 is a diagram showing the silencing performance of the silencers in Example 1 and Comparative Example 1, showing the transmission loss spectrum of each silencer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The silencer of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. However, the following embodiment is merely an example given to facilitate understanding of the present invention, and is not intended to limit the present invention. In other words, the present invention may be modified or improved from the following embodiment without departing from the spirit of the present invention.

[0011] In addition, the material and shape of each member used to implement the present invention can be arbitrarily set depending on the application of the present invention and the state of the art at the time of implementing the present invention. Furthermore, the present invention includes equivalents thereof.

[0012] In addition, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower limit and upper limit. In this specification, "orthogonal," "vertical," and "parallel" include the range of error permitted in the technical field to which the present invention pertains. For example, in this specification, "orthogonal," "vertical," and "parallel" mean being within a range of less than ±10° from strictly orthogonal, vertical, or parallel. The error from strictly orthogonal or parallel is preferably 5° or less, and more preferably 3° or less. In addition, in this specification, the meanings of "same," "identical," and "equal" may include a generally acceptable range of error in the technical field to which the present invention belongs. In addition, in this specification, the meanings of "all," "any," and "all" include not only 100% but also the range of error generally accepted in the technical field to which the present invention pertains, and may include, for example, 99% or more, 95% or more, or 90% or more.

[0013] In addition, in the present invention, "sound deadening" is a concept including both sound insulation and sound absorption. Sound insulation means blocking sound, in other words, not allowing sound to pass through. Sound absorption means reducing reflected sound, or more simply, absorbing sound (acoustics).

[0014] In the following description, the three mutually orthogonal directions will be referred to as “X, Y, and Z directions.” The X direction corresponds to the extension direction of an air passage 100, which will be described later. In the following description, the side of the air passage closer to the exhaust port will be referred to as the "downstream side," and the opposite side, i.e., the side closer to the intake port, will be referred to as the "upstream side."

[0015] [Examples of the configuration of the silencer for air passages of the present invention] The configuration of a silencer 10 according to one embodiment of the present invention (hereinafter, referred to as this embodiment) will be described with reference to Figs. 1 to 7C.

[0016] The silencer 10 is used for the purpose of muffling sound propagating in an air passage 100 provided in, for example, equipment or a building. The air passage 100 is, for example, an air passage for ventilation or air conditioning, and is installed by laying a duct or a pipe or the like in a predetermined path. As shown in Figs. 1, 2 and 4, the silencer 10 is installed in a state sandwiched between an upstream air passage 102 located on the upstream side of the silencer 10 and a downstream air passage 104 located on the downstream side of the silencer 10. The upstream air passage 102 and the downstream air passage 104 are each formed of a hose or a pipe or the like. In addition, in the vicinity of the silencer 10, specifically, in a range adjacent to the silencer 10 on the upstream side or downstream side of the silencer 10, the air passage 100 extends in a predetermined direction (X direction).

[0017] 1 to 4, the silencer 10 includes a housing 12 as a main component. The housing 12 is a box-shaped hollow body disposed midway along the air passage 100. A vibrating section 30 is provided on an outer wall 14 surrounding the internal space of the housing 12. The housing 12 and the vibrating section 30 will be described in detail below.

[0018] (Housing) 1, 2, and 4, the housing 12 constitutes an expansion section 106 in the air passage 100. The expansion section 106 functions as a so-called expansion type silencer, and silences sound propagating through the air passage 100, specifically, sound that has entered the housing 12, by resonating with the sound (acoustic resonance).

[0019] As shown in Fig. 4, the extension section 106 has an internal space whose cross-sectional size perpendicular to the X direction (i.e., the extension direction of the air passage 100) is larger than that of the portion of the air passage 100 other than the extension section (hereinafter also referred to as the general section). That is, in the extension section 106, the cross-sectional area of ​​the air passage 100 is expanded relative to the general section. Also, as shown in Fig. 4, an internal housing air passage 108 that forms part of the air passage 100 is provided inside the housing 12 that forms the extension section 106, and in this embodiment, the internal housing air passage 108 extends linearly along the X direction.

[0020] 4, an inlet opening 16 is provided at one end in the X direction of an outer wall 14 of the housing 12, and an outlet opening 18 is provided at the other end. The inlet opening 16 and the outlet opening 18 are holes penetrating the outer wall 14 in the X direction, and an upstream air passage 102 is connected to the inlet opening 16, and a downstream air passage 104 is connected to the outlet opening 18. Each of the inlet opening 16 and the outlet opening 18 may penetrate the outer wall 14 of the housing 12 parallel to the X direction, or may penetrate the outer wall 14 at an angle with respect to the X direction.

[0021] The housing internal air passage 108 is disposed between the inlet opening 16 and the outlet opening 18 in the X direction, and communicates with the general part through the inlet opening 16 and the outlet opening 18. That is, the air (wind) that flows into the housing 12 through the inlet opening 16 flows downstream through the housing internal air passage 108, and is then discharged to the outside of the housing 12 through the outlet opening 18.

[0022] Here, the length of the internal housing air passage 108 extending in the X direction, more specifically, the distance in the X direction from the boundary position between the inlet opening 16 and the internal housing air passage 108 to the boundary position between the outlet opening 18 and the internal housing air passage 108, is defined as the "length of the internal housing air passage 108." Note that in Fig. 4, the length of the internal housing air passage 108 is indicated by the symbol L, and hereinafter will also be referred to as the length L of the internal housing air passage 108.

[0023] The shape (contour shape) of each of the inlet opening 16 and the outlet opening 18 is not particularly limited, and may be, for example, a circle, an ellipse, a polygon such as a triangle or a rectangle, or an irregular shape. Furthermore, the size of each of the inlet opening 16 and the outlet opening 18 may be the same or different.

[0024] 1 to 4, in this embodiment, the range of the inlet opening 16 and the range of the outlet opening 18 overlap in the Y and Z directions. Here, the range of the openings in the Y and Z directions is the range in which each opening exists when each opening is projected onto a virtual plane (YZ plane) with the X direction as the normal direction. Since the range of the inlet opening 16 and the range of the outlet opening 18 overlap in this way, ventilation is improved and air (wind) flows smoothly from the inlet opening 16 to the outlet opening 18.

[0025] From the viewpoint of improving ventilation, when the inlet opening 16 and the outlet opening 18 are the same size, it is preferable that the range in which the inlet opening 16 exists and the range in which the outlet opening 18 exists completely coincide with each other. On the other hand, when the inlet opening 16 and the outlet opening 18 are different sizes, it is preferable that the range of the smaller opening is contained inside the range of the larger opening. However, this is not limited, and the range of the inlet opening 16 and the range of the outlet opening 18 may partially overlap. Furthermore, due to design constraints of the air passage, the range of the inlet opening 16 and the range of the outlet opening 18 may not overlap and may be separated from each other (shifted) in the Y direction and the Z direction.

[0026] In this embodiment, the housing 12 has a flattened rectangular parallelepiped shape that is crushed in the Y direction, as shown in Figs. 1 to 3. In other words, the outer wall 14 of the housing 12 has six side walls 20 (corresponding to a plurality of side walls). The outer wall 14 may be formed, for example, by arranging six plate materials in a box shape and joining adjacent plate materials together. Alternatively, when the outer wall 14 is divided into two pieces, each of the two pieces may be produced by injection molding, blow molding, or the like, and the pieces may be combined to form the outer wall 14.

[0027] Furthermore, the housing 12 has a total length in the X direction, a height in the Y direction, and a width in the Z direction. Furthermore, the width (length in the Z direction) of the housing 12 is longer than the height (length in the Y direction) of the housing 12. To explain in more detail, the ratio of the length of the longest side of the contour line to the length of the shortest side of the contour line when the housing 12 is viewed from the X direction is 1.2 or more. Here, the shortest side corresponds to the height of the housing 12, and its length is equal to the length d1 in FIG. 1. The longest side corresponds to the width of the housing 12, and its length is equal to the length d2 in FIG. 1.

[0028] Each of the six side walls 20 constituting the outer wall 14 is a plate material having a thickness, more specifically a flat plate, and forms both ends in each of the X, Y and Z directions of the housing 12. A pair of side walls 20 forming both ends in each direction face each other and are arranged parallel to each other.

[0029] The sidewall 20 forming one end in the X direction (hereinafter, the sidewall 20 at the upstream end) has the inlet opening 16 described above, and the sidewall 20 forming the other end in the X direction (hereinafter, the sidewall 20 at the downstream end) has the outlet opening 18 described above. The inlet opening 16 and the outlet opening 18 are each formed in the center portion of the corresponding sidewall 20 in both the Y direction and the Z direction.

[0030] Moreover, the side wall 20 forming the end in the Y direction is the side wall 20 whose outer surface (more specifically, the surface facing outward in the Y direction) has the largest area among the six side walls 20. At least one of the two side walls 20 forming the end in the Y direction constitutes the vibration part 30.

[0031] The material of the exterior wall 14 is not particularly limited, and examples of the material that can be used for the exterior wall 14 include metal materials, resin materials, reinforced plastic materials, and carbon fiber. Examples of the metal materials include aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nichrome molybdenum, copper, hot-dip galvanized steel sheet (Steel Galvanized Cold Commercial: SGCC), and alloys such as stainless steel. Examples of the resin material include acrylic resin, polymethylmethacrylate, polycarbonate, polyamide, polyarylate, polyetherimide, polyacetal, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, ABS resin (acrylonitrile, flame-retardant ABS resin, butadiene, styrene copolymer synthetic resin), polypropylene, triacetylcellulose (TAC), polypropylene (PP), polyethylene (PE), polystyrene (PS), acrylic styrene acrylonitrile (ASA) resin, polyvinyl chloride (PVC) resin, and polylactic acid (PLA) resin. Examples of reinforced plastic materials include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP). Furthermore, as the material for the outer wall 14, rubbers including natural rubber, chloroprene rubber, butyl rubber, EPDM (ethylene propylene diene rubber), silicone rubber, and cross-linked structures of these rubbers can be further used.

[0032] In this embodiment, each portion of the outer wall 14 is made of the same material. However, without being limited thereto, a portion of the outer wall 14 (for example, the vibration section 30 described below) may be made of a material different from that of the surrounding portion. Alternatively, a portion of the outer wall 14, for example, the vibration section 30, may be made of the same material as that of the surrounding portion, but may be made to have a thickness different from that of the surrounding portion.

[0033] In addition, in this embodiment, from the viewpoint of ensuring the ease of molding of the silencer and reducing costs, no sound absorbing material is arranged in the housing 12, and the internal space of the housing 12 is an empty space. However, this is not limited to this, and a known sound absorbing material may be arranged in the housing 12. In this case, for example, a porous sound absorbing material, specifically a foam, a foam material, and a nonwoven fabric sound absorbing material, etc., can be used as the sound absorbing material. In addition, in order to ensure ventilation within the housing 12, the sound absorbing material may be arranged in the housing 12 so as to avoid the range of the inlet opening 16 and the range of the outlet opening 18 in the Y direction and the Z direction. To explain it simply, in the Y direction and the Z direction, the sound absorbing material may be arranged at a position outside the range of the inlet opening 16 and the range of the outlet opening 18. In addition, the sound absorbing material may be tubular, and in this case, the space inside the sound absorbing material, i.e., the space inside the cylinder, may form the air passage 108 inside the housing.

[0034] (Vibration part) The vibration unit 30 is provided in the housing 12 constituting the aforementioned extension unit 106, and is used to increase the amount of attenuation by combining the sound attenuation effect of the extension unit 106 with the sound attenuation effect of the vibration unit 30. In other words, near the natural frequency (resonance frequency) of the vibration unit 30, the vibration sound based on the vibration of the vibration unit 30 cancels out the sound inside the housing 12, and as a result, the amount of attenuation can be increased.

[0035] The vibration section 30 is provided on the sidewall 20 of the housing 12, and is configured to vibrate in response to sound entering the housing 12. In this embodiment, as described above, the vibration section 30 is provided on one of the six sidewalls 20 having the largest outer surface area (hereinafter, the largest-area sidewall). However, the present invention is not limited to this, and the vibration section 30 may be provided on one of the six sidewalls 20 other than the largest-area sidewall.

[0036] In this embodiment, the entirety of one of the largest-area side walls (i.e., the side wall 20 forming one end of the housing 12 in the Y direction) constitutes the vibration section 30. In this case, since the entirety of one of the largest-area side walls functions as the vibration section 30, the vibration section 30 can easily vibrate and the effect of the natural vibration can be increased. However, this is not limited to this, and a part of one of the largest-area side walls, specifically a rectangular part having an outer edge somewhat inside the outer edge of the side wall, may constitute the vibration section 30. In this case, it is preferable that the vibration section 30 is continuously integrated with the peripheral part of the vibration section 30 on the largest-area side wall. Note that there may be a seam at the boundary between the vibration section 30 and its peripheral part, or a seamless structure without a seam may be used.

[0037] In this embodiment, the vibration section 30 is formed integrally with the other parts of the housing 12 using the same material as the other parts of the housing 12. That is, the material of the vibration section 30 is not particularly limited, as is the case with the housing 12, but for example, metal materials, resin materials, reinforced plastic materials, carbon fiber, etc. can be used as the material of the outer wall 14. Among these materials, using a resin material (particularly a soft material) to form the vibration section 30 is preferable because the first-order natural frequency and the higher-order natural frequencies in the vibration of the vibration section 30 are more likely to be close to each other than when the vibration section 30 is formed using a metal material. As described above, the material of the vibration section 30 may be different from that of the other portions of the outer wall 14 of the housing 12 other than the vibration section 30.

[0038] The vibration section 30 has a rectangular shape when viewed from the Y direction perpendicular to the vibration section 30, in other words, has a rectangular outer surface Sg when viewed from the Y direction. However, the shape of the outer surface Sg of the vibration section 30 is not limited to a rectangle, and may be a square, a circle, an ellipse, a parallelepiped, a trapezoid, another quadrangle, or a polygon other than a quadrangle, such as a triangle.

[0039] In the present embodiment, as shown in Figs. 1 and 2, in the vibration section 30, a plurality of vibration regions 32 are separated by non-vibration regions 34 provided between the vibration regions 32. In the case shown in Figs. 1 and 2, two vibration regions 32 are provided, and each vibration region 32 vibrates in response to sound entering the housing 12. At this time, the non-vibration region 34 does not vibrate and serves as a fixed end. In other words, each of the plurality of vibration regions 32 can vibrate with the non-vibration region 34 as a fixed end.

[0040] The non-vibration region 34 is harder than the vibration region 32 in the vibration section 30, and in this embodiment has a thickness greater than that of the vibration region 32. Here, the thickness of each of the vibration region 32 and the non-vibration region 34 refers to the thickness of the side wall 20 (i.e., the outer wall 14) in each of the vibration region 32 and the non-vibration region 34. To explain in more detail, it is the distance between the outer surface and the inner surface of the side wall with the largest area that constitutes the vibration section 30, and is the length indicated by the symbol t in Figs. 5 and 6.

[0041] As shown in Figs. 1 and 5, the non-vibration region 34 is provided in the maximum area sidewall of the outer wall 14 in a convex shape protruding toward the outside of the housing 12 (outside in the Y direction). More specifically, as shown in Figs. 1 and 5, in this embodiment, the non-vibration region 34 is configured by a plate-shaped rib provided on the maximum area sidewall. Such a non-vibration region 34 is provided in the vibration part 30 by increasing the thickness of the part corresponding to the non-vibration region 34 when forming the vibration part 30. However, without being limited thereto, the non-vibration region 34 may be formed by, for example, shaping the part that becomes the base of the vibration part 30 so that the thickness of the part is uniform, and then attaching a plate-shaped member to the part of the outer surface of the base that corresponds to the non-vibration region 34.

[0042] The configuration of the non-vibration area 34 is not limited to the above-mentioned rib structure, and may be a step structure as shown in Fig. 6. This step structure is formed by arranging the non-vibration area 34 (indicated by the symbol St in Fig. 6) in the outer surface Sg of the vibrating part 30 on the outer side of the housing 12, more specifically, on the outer side in the Y direction, relative to the vibration area 32 (i.e., the vibration area surface Sv) in the outer surface Sg, as shown in Fig. 6.

[0043] A specific method for forming the step structure shown in Fig. 6 is not particularly limited, but for example, the step structure may be formed by bending a portion of the maximum-area sidewall constituting the vibrating part 30 that corresponds to the non-vibration region 34 into an inverted U-shape. In this case, as shown in Fig. 6, the non-vibration region 34 in a hollow state is formed, and the thickness t of the vibrating region 32 and the thickness t of the non-vibration region 34 become the same. With this configuration, when providing the non-vibration region 34, it is not necessary to make the thickness t of the portion of the maximum-area sidewall where the non-vibration region 34 is located thicker than the thickness t of the other portions, and the manufacturing cost of the silencer 10 can be reduced accordingly.

[0044] 1 and 2, the non-vibration area 34 has a rectangular shape when viewed from the Y direction, more specifically, a rectangular shape with the X direction (extension direction of the air passage 100) as the longitudinal direction. That is, in the vibration part 30, the non-vibration area 34 extends along the X direction and is provided continuously from one end to the other end of the side wall with the largest area. In other words, in the X direction, one end of the non-vibration area 34 is located at one end of the housing 12, and the other end of the non-vibration area 34 is located at the other end of the housing 12.

[0045] The direction in which the non-vibration area 34 extends is not limited to the X direction (i.e., the extension direction of the air passage 100), and may be the Z direction as shown in Fig. 7A. In this case, the non-vibration area 34 may extend continuously from one end to the other end of the maximum area side wall in the Z direction. Furthermore, the non-vibration area 34 is not limited to being continuous from one end to the other end of the housing 12 along the X direction or the Z direction, and may be provided intermittently.

[0046] 7B, a cross-shaped non-vibration region 34 is provided on the maximum-area sidewall, in other words, a non-vibration region 34 extending in the X direction and a non-vibration region 34 extending in the Z direction may be provided to intersect with each other. In this case, four vibration regions 32 are separated by the non-vibration regions 34 on the maximum-area sidewall. 7C, a non-vibration region 34 may be provided on the maximum-area sidewall so as to connect a pair of diagonal corners, in other words, a non-vibration region 34 inclined with respect to each of the X direction and the Z direction may be provided. In this case, on the maximum-area sidewall, the vibration region 32 having a substantially triangular outer shape is divided by the non-vibration region 34.

[0047] Each of the two vibration regions 32 resonates with the sound inside the housing 12 at its natural frequency, and in this embodiment, can vibrate in a primary vibration mode and a higher vibration mode (i.e., secondary and subsequent vibration modes). To explain in more detail, in the outer wall 14 of the housing 12, the thickness of the side wall with the largest area that constitutes the vibrating part 30 is thinner than the thickness of the other side walls 20, and is set to a thickness that allows the vibration region 32 to vibrate with the non-vibration region 34 as a fixed end.

[0048] In this embodiment, the thickness t of the vibration region 32, i.e., the thickness of the outer wall 14 of the housing 12 in the vibration region 32, is 1 mm or more. This is because, compared to a thin vibration region such as a membrane material, a vibration region having a certain thickness or more has a small change in natural frequency due to hearing or external force, and a silencer 10 with high robustness can be realized.

[0049] Each of the two vibration regions 32 has a rectangular shape when viewed from the Y direction, as shown in Figs. 1 and 2. In other words, each vibration region 32 (hereinafter, vibration region surface Sv) in the outer surface Sg of the vibration section 30 is a rectangular surface. The vibration region surface Sv extends with the X direction (extension direction of the air passage 100) as the longitudinal direction, and is continuous from one end to the other end of the outer surface Sg of the vibration section 30 in this embodiment. In other words, in the X direction, one end of the vibration region 32 is located at one end of the housing 12, and the other end of the vibration region 32 is located at the other end of the housing 12.

[0050] In this embodiment, two rectangular vibration area surfaces Sv are provided on the outer surface Sg of the vibrating section 30, and the two vibration area surfaces Sv have the same shape and the same area (size). However, the two vibration area surfaces Sv may have different shapes and areas. The number of vibration area surfaces Sv on the outer surface Sg, that is, the number of vibration areas 32 separated by non-vibration areas 34 in the vibrating section 30, may be determined arbitrarily as long as it is two or more, and the arrangement position of each vibration area 32 may also be determined arbitrarily. Furthermore, the shape of the vibration area surface Sv is not limited to a rectangle, but may be a square, a circle, an ellipse, a parallelepiped, a trapezoid, another quadrangle, or a polygon other than a quadrangle, such as a triangle.

[0051] In this embodiment, the aspect ratio of at least one of the two vibrating region surfaces Sv is larger than the aspect ratio of the outer surface Sg of the entire vibrating part 30 including the two vibrating regions 32 and the non-vibrating region 34. Here, the aspect ratio of the vibrating region surface Sv is the ratio (=Lt1 / Ls1) of the long side Lt1 to the short side Ls1 of the first imaginary rectangle R1 (drawn by a thick dashed line in the figure) circumscribing the vibrating region surface Sv as shown in FIG. 8A. Also, the aspect ratio of the outer surface Sg is the ratio (=Lt2 / Ls2) of the long side Lt2 to the short side Ls2 of the second imaginary rectangle R2 (drawn by a thick dashed line in the figure) circumscribing the outer surface Sg as shown in FIG. 8B.

[0052] The imaginary rectangle circumscribing the vibration region surface Sv or the outer surface Sg is the one that has the smallest area among the imaginary rectangles that satisfy the following condition (1) or (2). Condition (1): If the vibration area surface Sv or the outer surface Sg is not rectangular, the vibration area surface Sv or the outer surface Sg can be positioned within a virtual rectangle with the outer edge of the vibration area surface Sv or the outer surface Sg touching at least three of the four sides of the virtual rectangle. Condition (2): When the vibrating area surface Sv or the outer surface Sg is rectangular, the outer edges of the vibrating area surface Sv or the outer surface Sg coincide with and overlap the four sides of the imaginary rectangle.

[0053] In this embodiment, the aspect ratio of the vibration region surface Sv is larger than the aspect ratio of the outer surface Sg, so that the noise absorbing effect of the silencer 10, particularly the noise absorbing effect in the low frequency band, can be improved.

[0054] More specifically, a silencer having a housing 12 constituting the extension part 106, i.e., an extension type silencer, is generally used in combination with a sound absorbing material to mute a wide range of noise. However, due to restrictions in molding methods such as blow molding, and from the viewpoint of cost, etc., there is a tendency to demand a silencer that does not use a sound absorbing material. However, in a sound absorbing structure using only the extension part 106 without using a sound absorbing material, as shown in FIG. 9, the muffling volume decreases at a specific frequency, and noise in that frequency band becomes a problem. FIG. 9 is an explanatory diagram of the reduction in the muffling volume without using a sound absorbing material, where one graph shows the muffling volume when a sound absorbing material and an extension part are used, and the other graph shows the muffling volume when only the extension part is used without using a sound absorbing material.

[0055] On the other hand, as a measure to enhance the sound deadening effect, it is possible to provide a vibrating part 30 on the outer wall 14 of the housing 12 and increase the sound deadening volume by combining the resonance sound deadening in the expansion part 106 and the sound deadening by the vibration of the vibrating part 30. As described above, this utilizes the fact that the sound inside the housing 12 is cancelled by the vibration sound near the resonance frequency of the vibration of the vibrating part 30, so that the sound deadening volume is increased. In order to effectively utilize the sound deadening by the vibration of the vibrating part 30, the specifications of the vibrating part 30 are set so that the effect of sound deadening by vibration can be obtained at frequencies where the sound deadening volume is reduced because no sound absorbing material is used, particularly in the low frequency band. The specifications of the vibrating part 30 refer to the shape, size, thickness (strictly speaking, the thickness of the outer wall 14 of the housing 12 at the vibrating part 30), position, material, etc. of the vibrating part 30.

[0056] However, in the conventional sound deadening structure using the vibration of the vibrating part 30, the width of the frequency band to which it can be applied is narrow, and the sound deadening effect is relatively small, as shown in Fig. 10. Fig. 10 is an explanatory diagram of the sound deadening effect by the vibration of the vibrating part 30, where one graph shows the sound deadening amount when the extension part and the vibrating part are used in combination, and the other graph shows the sound deadening amount when the extension part without the vibrating part is used.

[0057] Regarding the above point, in this embodiment, the vibration section 30 is provided with the above-mentioned convex non-vibration area 34, which divides the vibration section 30 into a plurality of vibration sections 32, and the aspect ratio of the vibration section surface Sv is made larger than the aspect ratio of the outer surface Sg of the vibration section 30. The inventors have found that, with this configuration, in a frequency band in which the reduction in the amount of attenuation is reduced due to the non-use of sound absorbing material (hereinafter also referred to as a target frequency band), in addition to vibration in the first vibration mode of the vibration section 32, vibration in a higher vibration mode is excited.

[0058] In the silencer 10 of this embodiment having the above configuration, the silencer peak corresponding to the first vibration mode and the silencer peak corresponding to the higher vibration mode (specifically, the second vibration mode) can be made closer to each other in the target frequency band, making the silencer peak broader, as shown in Fig. 11. As a result, in this embodiment, a higher silencer effect (increased silencer volume) can be obtained in the target frequency band.

[0059] The above effect will be described in detail with reference to FIG. 12. As the aspect ratio of the vibration region surface Sv increases, the natural frequency (resonance frequency) in the second and subsequent vibration modes shifts significantly to the lower frequency side as shown in FIG. 12, and approaches the natural frequency in the first vibration mode. This allows multiple silencing peaks corresponding to each of the multiple vibration modes to appear in the same frequency band. In light of this, in this embodiment, the aspect ratio of the vibration region surface Sv is made larger than the aspect ratio in the case where the vibration region 32 is not divided, that is, the aspect ratio of the outer surface Sg of the vibrating part 30. This allows multiple silencing peaks to appear in the low frequency band where the silencing volume is reduced due to the absence of a sound absorbing material, and the silencing effect can be improved by bringing the silencing peaks closer to each other.

[0060] The graph shown in Fig. 12 was obtained by measuring the natural frequency when a rectangular resin plate made of ABS (Acrylonitrile Butadiene Styrene) with a thickness of 2 mm was vibrated with the short side length fixed at 65 mm and the long side length changed. However, the graph shown in Fig. 12 is merely an example, and the tendency of the natural frequency to vary (graph) in each vibration mode according to the aspect ratio may change depending on the specifications of the vibrating part.

[0061] In this embodiment, in each of the multiple (specifically, two) vibrating regions 32 included in the vibrating section 30, the aspect ratio in the vibrating region surface Sv is larger than the aspect ratio in the outer surface Sg of the vibrating section 30. In other words, the aspect ratio in the vibrating region surface Sv of one of the two vibrating regions 32 and the aspect ratio in the vibrating region surface Sv of the other vibrating region 32 are both larger than the aspect ratio in the outer surface Sg. This makes it possible to more effectively exert the above-mentioned effects in this embodiment. However, without being limited to the above configuration, it is sufficient that the aspect ratio on the vibrating region surface Sv is larger than the aspect ratio on the outer surface Sg for at least one of the multiple vibrating regions 32. In this case, the multiple vibrating regions 32 may include a vibrating region 32 whose aspect ratio on the vibrating region surface Sv is smaller than the aspect ratio on the outer surface Sg.

[0062] Here, among the multiple vibration regions 32, the vibration region 32 having the maximum aspect ratio on the vibration region surface Sv is defined as a specific vibration region, and the length of the long side of the first virtual rectangle for the specific vibration region is La. When the multiple vibration regions 32 have the same shape and the same size, each vibration region 32 corresponds to the specific vibration region. In this embodiment, the above-mentioned length La of the long side and the length L of the air passage 108 in the housing satisfy the relationship shown in the following formula (1). La>L / 3 (1)

[0063] In this embodiment, by satisfying the relationship shown in the above formula (1), the vibration part 30 (more specifically, the vibration area 32) vibrates appropriately in response to the sound within the housing 12, and as a result, vibrations in higher modes are appropriately excited.

[0064] To explain in more detail, when the size of the vibration region 32, specifically the dimensions of the vibration region surface Sv, is sufficiently small relative to the wavelength λ of the sound, the sound pressure acts uniformly on each part of the vibration region 32, making it difficult to excite vibrations in higher modes. Therefore, the vibration region 32 needs to have a relatively large area (size) relative to the wavelength λ of the sound.

[0065] On the other hand, in the silencer 10 having the housing 12 constituting the extension portion 106, both antinodes and nodes of sound pressure in acoustic resonance within the housing 12 exist, and therefore it is considered that a non-uniform force acts on the vibration region 32. In the above acoustic resonance, the antinodes and nodes of sound pressure are spaced apart by λ / 4. In addition, the shortest expected wavelength λ of the sound to be silenced by the silencer 10 corresponds to the 3 / 4λ resonance in the extension portion 106, and therefore the relationship shown in the following formula (2) is obtained. λ=4L / 3 (2)

[0066] In consideration of the above, in this embodiment, the length La of the long side of the first virtual rectangle is set to λ / 4 or more, that is, L / 3 (=4L / 3×1 / 4) or more for the specific vibration region. This allows the vibration of the first mode and the vibration of the higher mode of the vibration region 32 to be appropriately excited. EXAMPLES

[0067] The present invention will be described in more detail below with reference to examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0068] Example 1 In Example 1, a silencer was used that has a housing that constitutes an expansion section, a vibration section is provided on the outer wall of the housing, and a rib structure (non-vibration area) that serves as a fixed end of vibration is arranged inside the vibration section. In the silencer of Example 1, the aspect ratio of the vibration area surface in the multiple vibration areas separated by the rib structure is larger than the aspect ratio of the outer surface of the vibration section.

[0069] Regarding the housing (hereinafter, housing 12) of the silencer of the first embodiment, as shown in Fig. 13, the housing 12 has a rectangular box shape of 150 mm x 260 mm x 62 mm, and is made of a solid material having physical properties of acrylic material. More specifically, the density of the housing 12 is 1180 kg / m 3 The Young's modulus is 4.8 GPa, the Poisson's ratio is 0.35, and the loss factor is 0.0312. Among the side walls of the housing 12, one of the side walls having the largest outer surface area (i.e., the largest-area side wall) constitutes the vibrating section 30, and has a thickness of 1 mm. The side walls other than the largest-area side wall have a thickness of about 5 mm. The size of the outer surface of the vibrating section 30 is 140 mm x 250 mm, and the aspect ratio (more specifically, the ratio of the long side to the short side of a virtual rectangle circumscribing the outer surface) is 1.79.

[0070] In addition, a rib is attached to the vibration section 30 as a non-vibration area 34. This rib has a thickness of about 11 mm (=1 mm+10 mm), extends along the long side of the side wall with the largest area, and forms a fixed end during vibration. Each of the two vibration areas separated by the rib has a vibration area surface of 60 mm x 250 mm, and the aspect ratio (more specifically, the ratio of the long side to the short side of a virtual rectangle circumscribing the vibration area surface) is 4.17, which is larger than the aspect ratio (=1.79) of the outer surface of the vibration section 30.

[0071] Then, the silencer of Example 1 was connected to an air passage having an inner diameter of about 30 mm, and the sound absorbing effect on the sound propagating through the air passage, specifically, the transmission loss, was calculated using the commercial software COMSOL Multiphysics.

[0072] Comparative Example 1 In Comparative Example 1, as shown in Fig. 14, in the vibration part 30 provided in the housing 12X of the sound absorbing device, a rib as a non-vibration area 34 extends along the short side of the side wall with the largest area, and forms a fixed end during vibration. In addition, each of the two vibration areas separated by the rib has a vibration area surface of 140 mm x 115 mm, and the aspect ratio (more specifically, the ratio of the long side to the short side of a virtual rectangle circumscribing the vibration area surface) is 1.22, which is smaller than the aspect ratio (=1.79) of the outer surface of the vibration part 30. The other configurations of the housing 12X are common between Comparative Example 1 and Example 1.

[0073] Then, similarly to Example 1, the silencer of Comparative Example 1 was connected to an air passage having an inner diameter of about 30 mm, and the transmission loss for sound propagating through the air passage was calculated using the commercial software COMSOL Multiphysics.

[0074] (Calculation results of transmission loss) Fig. 15 shows the calculation results of the transmission loss for the silencers of Example 1 and Comparative Example 1. As can be seen from the figure, acoustic resonance in the expansion part of the silencer is common between Example 1 and Comparative Example 1, and the silencing volume due to λ / 2 resonance decreases around 700 Hz.

[0075] On the other hand, in the silencer of Example 1, as shown in Fig. 15, large silencing peaks appear near the resonance frequency (582Hz) in the first vibration mode and the second resonance frequency (637Hz). These two silencing peaks are located close to each other. As a result, in Example 1, a sufficient silencing effect was obtained. In contrast to this, in the silencer of Comparative Example 1, the two silencing peaks as in Example 1 did not appear, and therefore a sufficient silencing effect was not obtained, and the silencing effect was limited. As described above, the above-mentioned Example 1 falls within the scope of the present invention, and the effects of the present invention are clear from the results of Example 1. [Explanation of symbols]

[0076] 10 Silencer 12,12X Case 14 Exterior Wall 16 Entrance opening 18 Exit opening 20 side wall 30 Vibration section 32 Vibration area 34 Non-vibration region 100 Ventilation 102 Upstream ventilation channel 104 Downstream ventilation channel 106 Extension 108 Ventilation path inside the housing R1 First virtual rectangle R2 Second virtual rectangle Sg outer surface Sv vibration area surface St Fixed end face

Claims

1. The device includes a housing disposed midway along the air passage, and a vibration unit provided on an outer wall of the housing, In the vibration unit, a plurality of vibration regions that vibrate in response to sound within the housing are separated by non-vibration regions provided between the vibration regions, and the vibration unit is capable of vibrating with the non-vibration regions as fixed ends; A silencer, wherein a ratio of a long side to a short side of a first imaginary rectangle circumscribing the vibration region in the outer surface of the vibration part is greater than a ratio of a long side to a short side of a second imaginary rectangle circumscribing the outer surface.

2. The housing constitutes an expansion portion of the air passage, the expansion portion has an internal space having a cross-sectional size perpendicular to the extension direction of the air passage that is larger than a portion of the air passage other than the expansion portion, The silencer according to claim 1 , wherein at least one of a plurality of side walls of the housing constitutes the vibrating portion.

3. The silencer according to claim 1 , wherein in each of the plurality of vibration regions, a ratio of a long side to a short side of the first imaginary rectangle is greater than a ratio of a long side to a short side of the second imaginary rectangle.

4. An internal air passage extending within the housing and constituting a part of the air passage, the housing internal air passage is disposed between an inlet opening and an outlet opening provided in the housing in an extending direction of the air passage, The length of the internal air passage in the extension direction is L, and 2. The silencer according to claim 1, wherein, among the plurality of vibration regions, for the vibration region in which the ratio of the long side to the short side of the first virtual rectangle is maximum, when the length of the long side of the first virtual rectangle is La, the relationship La > L / 3 is satisfied.

5. In the vibration portion, the non-vibration region extends continuously along an extension direction of the air passage, The silencer according to claim 1 , wherein, in the extension direction, one end of the non-vibration region and one end of the vibration region are located at one end of the housing, and the other end of the non-vibration region and the other end of the vibration region are located at the other end of the housing.

6. The silencer according to claim 1 , wherein a thickness of the outer wall in the vibration region and a thickness of the outer wall in the non-vibration region are uniform.

7. The silencer according to claim 1 , wherein the thickness of the outer wall in the vibration region is 1 mm or more.

8. The silencer according to claim 1 , wherein the vibrating portion is made of a resin material.

9. The silencer according to claim 1 , wherein the non-vibration area is provided on the outer wall so as to protrude in a convex shape toward an outside of the housing.

10. The silencer according to claim 9 , wherein the non-vibration area is constituted by a rib provided on the outer wall.

11. The silencer according to claim 9 , wherein the non-vibration region has a step structure formed by disposing the non-vibration region in the outer surface on an outer side of the housing relative to the vibration region in the outer surface.

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