Silencer

Abstract

To provide a silencer whose silence effect by vibration is improved as a silencer for a ventilation path.SOLUTION: A silencer 10 includes: a casing which is a box-shaped hollow body arranged in the middle of a ventilation path 100 and constitutes an extension part 106; and a vibration part 30 provided on an outer wall of the casing. In the vibration part 30, a plurality of vibration areas 32 which vibrate with respect to sound in the casing are separated by non-vibration areas 34 provided between the vibration areas 32, the non-vibration areas 34 can be vibrated as fixed ends and a ratio of a long side to a short side of a first virtual rectangle circumscribing the vibration area 32 in an outer surface of the vibration part 30 is greater than a ratio of the long side to the short side of a second virtual rectangle circumscribing the outer surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a muffler that muffles sound in a ventilation passage.

Background Art

[0002] Some mufflers for muffling sound in a ventilation passage are configured to provide a vibrating portion in a part of the ventilation passage, and to consume the energy of sound as mechanical energy by vibrating the vibrating portion, thereby muffling the sound. As an example of such a vibration-type muffler, there is a muffler (described as a sound-absorbing structure in Patent Document 1) described in Patent Document 1.

[0003] In Patent Document 1, an air-conditioning duct is formed by connecting a plurality of film sound absorbers that perform sound absorption by sound pressure driving. When sound is transmitted to the film sound absorber, the vibration membrane vibrates. By this vibration, sound wave energy is consumed as mechanical energy, and thus the film sound absorber performs sound absorption.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the muffler having the above configuration, since the sound is canceled by the vibration sound generated near the resonance frequency of the vibrating portion, the muffling volume increases. However, vibration muffling has a narrow applicable frequency band, and therefore it is difficult to obtain a sufficient muffling effect with a conventional muffling structure using vibration muffling.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the problems of the above prior art, and specifically, to provide a muffler for a ventilation passage with an improved muffling effect by vibration.

Means for Solving the Problem

[0007] To achieve the above object, the present invention has the following configuration. [1] A housing disposed in the middle of an air passage, and a vibration part provided on the outer wall of the housing, wherein in the vibration part, a plurality of vibration regions that vibrate with respect to the sound in the housing are separated by non-vibration regions provided between the vibration regions, and are vibratable with the non-vibration regions as fixed ends, and the ratio of the long side to the short side of a first virtual rectangle circumscribing the vibration region in the outer surface of the vibration part is larger than the ratio of the long side to the short side of a second virtual rectangle circumscribing the outer surface, a silencer. [2] The housing constitutes an expansion part in the air passage, the expansion part has an internal space whose cross-sectional size perpendicular to the extending direction of the air passage is larger than that of the part other than the expansion part in the air passage, and at least one of the plurality of side walls of the housing constitutes the vibration part, the silencer according to [1]. [3] In each of the plurality of vibration regions, the ratio of the long side to the short side of the first virtual rectangle is larger than the ratio of the long side to the short side of the second virtual rectangle, the silencer according to [1] or [2]. [4] Inside the housing, an internal air passage forming a part of the air passage extends, the internal air passage is disposed between an inlet opening and an outlet opening provided in the housing in the extending direction of the air passage, the length of the internal air passage in the extending direction is denoted as L, and for the vibration region in which the ratio of the long side to the short side of the first virtual rectangle is the largest among the plurality of vibration regions, when the length of the long side of the first virtual rectangle is denoted as La, the silencer according to any one of [1] to [3] satisfying the relationship La > L / 3. [5] In the vibration part, the non-vibration regions extend continuously along the extending direction of the air passage, in the extending 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, the silencer according to any one of [1] to [4]. [6] The thickness of the outer wall in the vibration region is the same as the thickness of the outer wall in the non-vibration region, the silencer according to any one of [1] to [5]. [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 in a state of protruding convexly toward the outside of the housing.

[10] The silencer according to [9], wherein the non-vibration region is constituted by ribs provided on the outer wall.

[11] The silencer according to [9], wherein the non-vibration region has a stepped structure formed by arranging the non-vibration region in the outer surface outside the housing more than the vibration region in the outer surface.

Advantages of the Invention

[0008] In the silencer of the present invention, the vibrating portion is divided into a plurality of vibration regions by the non-vibration region, and the ratio of the long side / short side in at least one vibration region is larger than the ratio of the long side / short side in the original vibrating portion. As a result, together with the first vibration mode, vibration modes of the second order and higher can be excited in a desired frequency band (target frequency band). As a result, a larger noise reduction amount can be obtained in the target frequency band, and the noise reduction effect by vibration noise reduction is improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 7C

Figure 8A

Figure 8B

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Mode for Carrying Out the Invention

[0010] The muffler of the present invention will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings. However, the following embodiments are merely examples given for ease of understanding of the present invention and do not limit the present invention. That is, the present invention can be changed or improved from the following embodiments without departing from the gist thereof.

[0011] In addition, the materials, shapes, etc. of each member used to implement the present invention can be arbitrarily set according to the use of the present invention and the technical level at the time of implementing the present invention. The present invention also includes equivalents thereof.

[0012] In addition, in this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In addition, in this specification, "orthogonal", "perpendicular", and "parallel" shall include the range of errors acceptable in the technical field to which the present invention pertains. For example, "orthogonal", "perpendicular", and "parallel" in this specification mean within a range of less than ±10° with respect to strict orthogonality, perpendicularity, or parallelism. Note that the error from strict orthogonality or parallelism is preferably 5° or less, and more preferably 3° or less. In addition, in this specification, the meanings of "the same", "identical", and "equal" may include the range of errors generally acceptable in the technical field to which the present invention pertains. In addition, in this specification, the meanings of "all", "any", and "every" include, in addition to the case of 100%, the range of errors generally acceptable in the technical field to which the present invention pertains. For example, cases where it is 99% or more, 95% or more, or 90% or more may be included.

[0013] In addition, "noise reduction" in the present invention is a concept that includes both the meanings of sound insulation and sound absorption. Sound insulation means shielding sound, in other words, not allowing sound to pass through. Sound absorption means reducing reflected sound, and more simply put, absorbing sound (acoustics).

[0014] In addition, hereinafter, three directions orthogonal to each other shall be referred to as "X, Y, and Z directions". Note that the X direction corresponds to the extending direction of the ventilation path 100 described later. In addition, hereinafter, the side closer to the exhaust port in the ventilation path shall be referred to as the "downstream side", and the opposite side, that is, the side closer to the air supply port, shall be referred to as the "upstream side".

[0015] [Configuration Example of Silencer for Ventilation Path of the Present Invention] The configuration of a silencer 10 according to an 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 example, for the purpose of silencing the sound propagating in a ventilation path 100 provided inside a device or a building. The ventilation path 100 is, for example, a ventilation path for ventilation or air conditioning, and is installed by laying a duct or a pipe or the like along a predetermined path. As shown in FIGS. 1, 2, and 4, the silencer 10 is installed in a state of being sandwiched between an upstream ventilation path 102 located on the upstream side of the silencer 10 and a downstream ventilation path 104 located on the downstream side of the silencer 10. The upstream ventilation path 102 and the downstream ventilation path 104 are each constituted by a hose, a pipe, or the like. Further, in the vicinity of the silencer 10, specifically, in the range adjacent to the silencer 10 on the upstream side or the downstream side of the silencer 10, the ventilation path 100 extends in a predetermined direction (X direction).

[0017] As shown in FIGS. 1 to 4, the silencer 10 includes a housing 12 as a main component. The housing 12 is a box-shaped hollow body disposed in the middle of the ventilation path 100. Further, a vibration part 30 is provided on an outer wall 14 surrounding the internal space of the housing 12. Hereinafter, each of the housing 12 and the vibration part 30 will be described in detail.

[0018] (Housing) As shown in FIGS. 1, 2, and 4, the housing 12 constitutes an expansion part 106 in the ventilation path 100. The expansion part 106 functions as a so-called expansion-type silencer, and silences the sound propagating in the ventilation path 100, specifically, by resonance (acoustic resonance) with the sound that has entered the housing 12.

[0019] As shown in FIG. 4, the expansion portion 106 has an internal space with a size of a cross-section orthogonal to the X direction (i.e., the extending direction of the ventilation passage 100) larger than that of a portion other than the expansion portion in the ventilation passage 100 (hereinafter also referred to as the general portion). That is, in the expansion portion 106, the cross-sectional area of the ventilation passage 100 is expanded with respect to the general portion. Further, as shown in FIG. 4, a housing internal ventilation passage 108 that forms a part of the ventilation passage 100 is provided inside the housing 12 forming the expansion portion 106. In the present embodiment, the housing internal ventilation passage 108 extends linearly along the X direction.

[0020] Also, as shown in FIG. 4, an inlet opening 16 is provided at one end portion of the outer wall 14 of the housing 12 in the X direction, and an outlet opening 18 is provided at the other end portion. The inlet opening 16 and the outlet opening 18 are holes penetrating the outer wall 14 in the X direction. The upstream side ventilation passage 102 is connected to the inlet opening 16, and the downstream side ventilation passage 104 is connected to the outlet opening 18. Note that 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 while being inclined with respect to the X direction.

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

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

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

[0024] Also, in the present embodiment, as can be seen from FIGS. 1 to 4, the existence ranges of the inlet opening 16 and the outlet opening 18 in the Y direction and the Z direction overlap. Here, the existence range of each opening in the Y direction and the Z direction is the range in which each opening exists in the virtual plane (YZ plane) when each opening is projected onto the virtual plane having the X direction as the normal direction. By overlapping the existence ranges of the inlet opening 16 and the outlet opening 18 in this way, the ventilation performance is improved, and air (wind) smoothly flows from the inlet opening 16 toward the outlet opening 18.

[0025] From the viewpoint of improving the ventilation performance, when the inlet opening 16 and the outlet opening 18 are of the same size, it is preferable that the existence ranges of the inlet opening 16 and the outlet opening 18 completely coincide. On the other hand, when the inlet opening 16 and the outlet opening 18 are of different sizes, it is preferable that the existence range of the smaller-sized opening is contained inside the existence range of the larger-sized opening. However, it is not limited to this, and the existence range of the inlet opening 16 and the existence range of the outlet opening 18 may partially overlap. Also, due to design constraints of the ventilation path or the like, in the Y direction and the Z direction, the existence range of the inlet opening 16 and the existence range of the outlet opening 18 may not overlap and may be separated from each other (may be displaced).

[0026] In the present embodiment, as shown in FIGS. 1 to 3, the housing 12 has a flat rectangular parallelepiped shape that is crushed in the Y direction. 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 configured, for example, by arranging six plate materials in a box shape and joining the plate materials adjacent to each other. Alternatively, when the outer wall 14 is divided into two and fragmented, each of the two fragments may be created by injection molding or blow molding or the like, and the outer wall 14 may be configured by combining the fragments.

[0027] Further, the housing 12 has a total length in the X direction, a height in the Y direction, and a width in the Z direction. Also, 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. More specifically, the ratio of the length of the longest side to the length of the shortest side in 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, specifically, a flat plate, and forms both end portions in each of the XYZ directions of the housing 12. A pair of side walls 20 forming both end portions in each direction face each other and are arranged in parallel.

[0029] The side wall 20 forming one end portion in the X direction (hereinafter, the side wall 20 at the upstream end portion) is formed with the aforementioned inlet opening 16, and the side wall 20 forming the other end portion in the X direction (hereinafter, the side wall 20 at the downstream end portion) is formed with the aforementioned outlet opening 18. The inlet opening 16 and the outlet opening 18 are each formed in the central portion in both the Y direction and the Z direction of the corresponding side wall 20.

[0030] Also, the side wall 20 forming the end portion in the Y direction is the side wall 20 having the largest surface area of its outer surface (specifically, the surface facing outward in the Y direction) among the six side walls 20. And at least one of the two side walls 20 forming the end portion in the Y direction constitutes the vibrating portion 30.

[0031] The material of the outer wall 14 is not particularly limited. For example, metal materials, resin materials, reinforced plastic materials, carbon fiber, etc. can be used as the material of the outer wall 14. Examples of metal materials include metals such as aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nickel chromium molybdenum, copper, hot-dip galvanized steel sheet (Steel Galvanized Cold Commercial: SGCC), and stainless steel, as well as alloys. Examples of resin materials include acrylic resin, polymethyl methacrylate, polycarbonate, polyamideimide, 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, triacetyl cellulose (TAC: Triacetylcellulose), polypropylene (PP: Polypropylene), polyethylene (PE: Polyethylene), polystyrene (PS: Polystyrene), ASA (Acrylate Sthrene Acrylonitrile) resin, polyvinyl chloride (PVC: Polyvinyl Chloride) resin, and PLA (Polylactic Acid) resin. Examples of reinforced plastic materials include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP). In addition, as the material of the outer wall 14, natural rubber, chloroprene rubber, butyl rubber, EPDM (ethylene propylene diene rubber), silicone rubber, and rubbers including cross-linked structures thereof can be further used.

[0032] In the present embodiment, each part of the outer wall 14 is made of the same material. However, it is not limited to this, and a part of the outer wall 14 (for example, the vibration part 30 described later) may be made of a material different from that of its peripheral part. Alternatively, a part of the outer wall 14, for example, the vibration part 30, may be made of the same type of material as its peripheral part, while being configured to have a thickness different from that of the peripheral part.

[0033] Also, in the present embodiment, from the viewpoints of ensuring the ease of forming the muffler and reducing costs, no sound-absorbing material is arranged in the housing 12, and the internal space of the housing 12 is a void space. However, it is not limited to this, and a known sound-absorbing material may be arranged in the housing 12. In this case, as the sound-absorbing material, for example, a porous sound-absorbing material, specifically, a foam, a foaming material, a non-woven fabric-based sound-absorbing material, etc. can be used. Also, for the reason of ensuring air permeability in the housing 12, in the housing 12, the sound-absorbing material is preferably arranged so as to avoid the existence ranges of the inlet opening 16 and the outlet opening 18 in the Y direction and the Z direction. To explain more clearly, in the Y direction and the Z direction, the sound-absorbing material is preferably arranged at a position outside the existence range of the inlet opening 16 and at a position outside the existence range of the outlet opening 18. Also, the sound-absorbing material may have a cylindrical shape, and in that case, the space located inside the sound-absorbing material, that is, the space inside the cylinder, preferably forms the housing internal ventilation passage 108.

[0034] (Vibration part) The vibration part 30 is provided on the housing 12 that constitutes the aforementioned expansion part 106, and is used to increase the sound attenuation amount by combining the sound attenuation effect by the expansion part 106 and the sound attenuation effect by the vibration part 30. That is, near the natural vibration frequency (resonance frequency) of the vibration part 30, the sound in the housing 12 is canceled by the vibration sound based on the vibration of the vibration part 30, and as a result, the sound attenuation amount can be increased.

[0035] The vibrating part 30 is provided on the side wall 20 of the housing 12 and is configured to vibrate in response to sound entering the housing 12. In the present embodiment, as described above, the vibrating part 30 is provided on one of the side walls 20 (hereinafter referred to as the side wall with the largest surface area) having the largest surface area among the six side walls 20. However, it is not limited to this, and it may be provided on a side wall 20 other than the side wall with the largest surface area among the six side walls 20.

[0036] In the present embodiment, the entire one side wall with the largest surface area (i.e., the side wall 20 forming one end portion of the housing 12 in the Y direction) constitutes the vibrating part 30. In this case, since the entire one side wall with the largest surface area functions as the vibrating part 30, the vibrating part 30 can easily vibrate and enhance the effect due to the natural vibration. However, it is not limited to this, and a part of one side wall with the largest surface area, specifically, a rectangular portion having an outer edge slightly inside the outer edge of the side wall may constitute the vibrating part 30. In this case, in the side wall with the largest surface area, the vibrating part 30 is preferably continuous and integrated with the peripheral portion of the vibrating part 30. Note that there may be a joint at the boundary between the vibrating part 30 and its peripheral portion, or it may have a seamless structure without a joint.

[0037] In the present embodiment, the vibrating part 30 is integrally formed of the same material as the portion of the housing 12 other than the vibrating part 30. That is, the material of the vibrating part 30 is not particularly limited, similar to the housing 12. For example, metal materials, resin materials, reinforced plastic materials, and carbon fiber can be used as the material of the outer wall 14. Among these materials, forming the vibrating part 30 using a resin material (especially a soft material) is preferable because the fundamental natural frequency and the higher natural frequency in the vibration of the vibrating part 30 are likely to be closer compared to the case of forming the vibrating part 30 using a metal material. As described above, the material of the vibrating part 30 may be different from the portion of the outer wall 14 of the housing 12 other than the vibrating part 30.

[0038] The vibrating part 30 has a rectangular shape when viewed from the Y direction orthogonal to the vibrating part 30. In other words, it has an outer surface Sg that is rectangular when viewed from the Y direction. However, the shape of the outer surface Sg of the vibrating part 30 is not limited to a rectangle, and may be a square, a circle, an ellipse, a parallelogram, a trapezoid, other quadrilaterals, or a polygon other than a quadrilateral such as a triangle.

[0039] Also, in the present embodiment, in the vibrating part 30, as shown in FIGS. 1 and 2, a plurality of vibrating regions 32 are separated by non-vibrating regions 34 provided between the vibrating regions 32. In the case shown in FIGS. 1 and 2, two vibrating regions 32 are provided, and each vibrating region 32 vibrates in response to sound entering the housing 12. At this time, the non-vibrating region 34 forms a fixed end without vibrating. That is, each of the plurality of vibrating regions 32 can vibrate with the non-vibrating region 34 as a fixed end.

[0040] The non-vibrating region 34 is harder than the vibrating region 32 in the vibrating part 30 and has a thickness greater than the thickness of the vibrating region 32 in the present embodiment. Here, the thickness of each of the vibrating region 32 and the non-vibrating region 34 is the thickness of the side wall 20 (that is, the outer wall 14) in each of the vibrating region 32 and the non-vibrating region 34. More specifically, it is the distance between the outer surface and the inner surface of the side wall with the largest area that constitutes the vibrating part 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-vibrating region 34 is provided in a state of protruding convexly toward the outside of the housing 12 (outside in the Y direction) on the side wall with the largest area of the outer wall 14. More specifically, as shown in FIGS. 1 and 5, in the present embodiment, the non-vibrating region 34 is constituted by a plate-shaped rib provided on the side wall with the largest area. Such a non-vibrating region 34 is provided in the vibrating part 30 by making the thickness of the portion corresponding to the non-vibrating region 34 larger when forming the vibrating part 30. However, it is not limited to this, and after forming the base portion of the vibrating part 30 so that the thickness of the portion is uniform, a plate-shaped member may be attached to the location corresponding to the non-vibrating region 34 on the outer surface of the base portion to form the non-vibrating region 34.

[0042] Note that the configuration of the non-vibrating region 34 is not limited to the rib structure described above, and a configuration having a stepped structure as shown in FIG. 6 may also be used. As shown in FIG. 6, this stepped structure is formed by arranging the non-vibrating region 34 (indicated by reference sign St in FIG. 6) in the outer surface Sg of the vibrating portion 30 outside the vibrating region 32 (i.e., the vibrating region surface Sv) in the outer surface Sg, specifically, outside the housing 12 in the Y direction.

[0043] The specific method of forming the stepped structure shown in FIG. 6 is not particularly limited. For example, the stepped structure may be formed by bending the portion corresponding to the non-vibrating region 34 in the side wall with the largest area constituting the vibrating portion 30 in an inverted U shape. In this case, as shown in FIG. 6, a hollow non-vibrating region 34 is formed, and the thickness t of the vibrating region 32 and the thickness t of the non-vibrating region 34 are made uniform. According to such a configuration, when providing the non-vibrating region 34, it is not necessary to make the thickness t of the portion where the non-vibrating region 34 is located in the side wall with the largest area thicker than the thickness t of other portions, and accordingly, the manufacturing cost of the muffler 10 can be suppressed.

[0044] As shown in FIGS. 1 and 2, the non-vibrating region 34 has a rectangular shape when viewed from the Y direction, more specifically, a rectangular shape with the X direction (the extending direction of the ventilation passage 100) as the longitudinal direction. That is, in the vibrating portion 30, the non-vibrating region 34 extends along the X direction and is continuously provided 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-vibrating region 34 is located at one end of the housing 12, and the other end of the non-vibrating region 34 is located at the other end of the housing 12.

[0045] Note that the direction in which the non-vibrating region 34 extends is not limited to the X direction (i.e., the extending direction of the ventilation passage 100), and as shown in FIG. 7A, it may also be the Z direction. In this case, the non-vibrating region 34 may continuously extend from one end to the other end of the side wall with the largest area in the Z direction. Further, the non-vibrating region 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] Also, as shown in FIG. 7B, a cross-shaped non-vibrating region 34 is provided on the side wall with the largest area. In other words, the non-vibrating region 34 extending in the X direction and the non-vibrating region 34 extending in the Z direction may intersect with each other. In this case, on the side wall with the largest area, four vibrating regions 32 are separated by the non-vibrating region 34. Also, as shown in FIG. 7C, the non-vibrating region 34 is provided so as to connect between a set of diagonal corners on the side wall with the largest area. In other words, the non-vibrating region 34 inclined with respect to each of the X direction and the Z direction may be provided. In this case, on the side wall with the largest area, the vibrating region 32 having a substantially triangular outer shape is separated by the non-vibrating region 34.

[0047] Each of the two vibrating regions 32 resonates with the sound in the housing 12 at its natural frequency. In the present embodiment, it can vibrate in the first vibration mode and higher-order (that is, second and higher) vibration modes. More specifically, on the outer wall 14 of the housing 12, the thickness of the side wall with the largest area constituting the vibrating portion 30 is thinner than the thickness of the other side walls 20, and the vibrating region 32 is set to a thickness that can vibrate with the non-vibrating region 34 as a fixed end.

[0048] Also, in the present embodiment, the thickness t of the vibrating region 32, that is, the thickness of the outer wall 14 of the housing 12 in the vibrating region 32, is 1 mm or more. This is because, compared with a thin vibrating region like a film material, in a vibrating region having a thickness of a certain level or more, the change in the natural frequency due to hearing ability or external force is small, and a silencer 10 with high robustness can be realized.

[0049] As shown in FIGS. 1 and 2, each of the two vibration regions 32 has a rectangular shape when viewed from the Y direction. In other words, each vibration region surface Sv (hereinafter referred to as the vibration region surface) in the outer surface Sg of the vibrating portion 30 is a rectangular surface. The vibration region surface Sv extends in the X direction (the extending direction of the air passage 100) as the longitudinal direction, and in this embodiment, it is continuous from one end to the other end of the outer surface Sg of the vibrating portion 30. 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, on the outer surface Sg of the vibrating portion 30, two rectangular vibration region surfaces Sv are provided. The two vibration region surfaces Sv have the same shape and the same area (size). However, the two vibration region surfaces Sv may have different shapes from each other, and may also have different areas from each other. Also, the number of vibration region surfaces Sv on the outer surface Sg, that is, the number of vibration regions 32 separated by the non-vibration region 34 in the vibrating portion 30, may be arbitrarily determined as long as it is 2 or more, and the arrangement position of each vibration region 32 can also be arbitrarily determined. Also, the shape of the vibration region surface Sv is not limited to a rectangle, and may be a square, a circle, an ellipse, a parallelogram, a trapezoid, other quadrilaterals, or a polygon other than a quadrilateral such as a triangle.

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

[0052] The virtual rectangle circumscribing the vibration region surface Sv or the outer surface Sg is the one with the minimum area among the virtual rectangles satisfying the following condition (1) or (2). Condition (1): When the vibration region surface Sv or the outer surface Sg is not rectangular, the vibration region surface Sv or the outer surface Sg can be arranged within the virtual rectangle in a state where the outer edge of the vibration region surface Sv or the outer surface Sg is in contact with at least three of the four sides of the virtual rectangle. Condition (2): When the vibration region surface Sv or the outer surface Sg is rectangular, the outer edge of the vibration region surface Sv or the outer surface Sg coincides and overlaps with the four sides of the virtual rectangle.

[0053] In the present embodiment, since the aspect ratio on the vibration region surface Sv is larger than the aspect ratio on the outer surface Sg, the silencing effect by the silencer 10, particularly the silencing effect in the low frequency band, can be improved.

[0054] More specifically, a silencer having the housing 12 constituting the extension part 106, that is, an extended type silencer, generally performs broadband silencing in combination with a sound absorbing material. However, from the viewpoints of constraints in forming methods such as blow molding and costs, there is a tendency to require a silencer configured without using a sound absorbing material. However, in a silencing structure using only the extension part 106 without using a sound absorbing material, as shown in FIG. 9, the sound attenuation amount decreases at a specific frequency, and the noise in that frequency band becomes a problem. FIG. 9 is an explanatory diagram of the decrease in the sound attenuation amount due to non - use of a sound absorbing material. One graph shows the sound attenuation amount when using a sound absorbing material and an extension part, and the other graph shows the sound attenuation amount when using only the extension part without using a sound absorbing material.

[0055] On the other hand, as a measure to enhance the sound absorption effect, it is conceivable to provide a vibration part 30 on the outer wall 14 of the housing 12 and combine resonance sound absorption in the extension part 106 and sound absorption by the vibration of the vibration part 30 to increase the sound absorption volume. As described above, this utilizes the fact that the sound inside the housing 12 is canceled out by the vibration sound near the resonance frequency of the vibration of the vibration part 30, resulting in an increase in the sound absorption volume. In order to effectively utilize the sound absorption by the vibration of the vibration part 30, the specifications of the vibration part 30 are set so that the effect of sound absorption by vibration can be obtained in the frequency range where the sound absorption volume decreases due to the non-use of the sound absorption material, particularly in the low-frequency band. The specifications of the vibration part 30 include the shape, size, thickness (strictly speaking, the thickness of the outer wall 14 of the housing 12 in the vibration part 30), position, and material of the vibration part 30.

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

[0057] Regarding the above points, in the present embodiment, the convex-shaped non-vibration region 34 described above is provided in the vibration part 30 to partition the plurality of vibration regions 32 by the non-vibration region 34, and the aspect ratio on the vibration region surface Sv is made larger than the aspect ratio on the outer surface Sg of the vibration part 30. The inventors have found that with such a configuration, in addition to the vibration in the primary vibration mode of the vibration region 32, the vibration in the higher-order vibration modes is excited in the frequency band where the sound absorption volume decreases due to the non-use of the sound absorption material (hereinafter, also referred to as the target frequency band).

[0058] In the muffler 10 of the present embodiment having the above configuration, as shown in FIG. 11, in the target frequency band, the sound absorption peak corresponding to the primary vibration mode and the sound absorption peak corresponding to the higher-order (specifically, second-order) vibration mode can be brought closer to each other to make the sound absorption peak broader. As a result, in the present embodiment, a higher sound absorption effect (increase in sound absorption 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 in the vibration region surface Sv increases, the natural frequencies (resonance frequencies) in the vibration modes of the second order and higher shift significantly to the lower frequency side as shown in FIG. 12 and approach the natural frequency in the primary vibration mode. Thereby, in the same frequency band, a plurality of sound absorption peaks corresponding to each of the plurality of vibration modes can be expressed. Based on this point, in the present embodiment, the aspect ratio in the vibration region surface Sv is made larger than the aspect ratio when the plurality of vibration regions 32 are not separated, that is, the aspect ratio on the outer surface Sg of the vibrating portion 30. Thereby, in the low frequency band where the sound absorption volume has decreased compared to the case where no sound absorbing material is used, a plurality of sound absorption peaks can be expressed, and the sound absorption effect can be enhanced by bringing the sound absorption peaks closer to each other.

[0060] Note that the graph shown in FIG. 12 is obtained by measuring the natural frequency when a rectangular resin plate made of ABS (Acrylonitrile Butadiene Styrene) with a thickness of 2 mm is fixed with the length of the short side being 65 mm and vibrated while changing the length of the long side. However, the graph shown in FIG. 12 is merely an example, and the variation tendency (graph) of the natural frequency in each vibration mode according to the aspect ratio may change according to the specifications of the vibrating portion.

[0061] In the present embodiment, in each of the plurality (specifically, two) of vibration regions 32 included in the vibrating portion 30, the aspect ratio on the vibration region surface Sv is larger than the aspect ratio on the outer surface Sg of the vibrating portion 30. That is, among the two vibration regions 32, the aspect ratio on the vibration region surface Sv of one vibration region 32 and the aspect ratio on the vibration region surface Sv of the other vibration region 32 are both larger than the aspect ratio on the outer surface Sg. Thereby, in the present embodiment, the above-described effects can be more effectively exhibited. However, the present invention is not limited to the above configuration, and for at least one of the plurality of vibration regions 32, it is sufficient that the aspect ratio on the vibration region surface Sv is larger than the aspect ratio on the outer surface Sg. In that case, among the plurality of vibration regions 32, a vibration region 32 having an aspect ratio on the vibration region surface Sv smaller than the aspect ratio on the outer surface Sg may be included.

[0062] Here, among the plurality of vibration regions 32, the vibration region 32 having the largest 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 denoted as La. When the plurality of vibration regions 32 have the same shape and the same size, each vibration region 32 corresponds to the specific vibration region. And in the present embodiment, the above-described 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] By satisfying the relationship shown in the above formula (1), in the present embodiment, the vibrating portion 30 (specifically, the vibration region 32) vibrates appropriately with respect to the sound in the housing 12, and as a result, the vibration of the high-order mode is appropriately excited.

[0064] More specifically, when the size of the vibration region 32, specifically, the dimensions of the vibration region surface Sv, is sufficiently small with respect to the wavelength λ of the sound, the sound pressure acts uniformly on each part of the vibration region 32, so that it is difficult to excite the vibration of the high-order mode. Therefore, the vibration region 32 needs to have an area (size) that is relatively large with respect to the wavelength λ of the sound.

[0065] On the other hand, in the muffler 10 having the housing 12 that constitutes the expansion part 106, both the antinode and node of the sound pressure in the acoustic resonance within the housing 12 exist. Therefore, it is considered that a non-uniform force acts on the vibration region 32. In the above acoustic resonance, the antinode and node of the sound pressure are separated from each other by λ / 4. Further, regarding the sound to be silenced by the muffler 10, since the shortest wavelength λ assumed corresponds to the 3 / 4λ resonance in the expansion part 106, the relationship shown in the following formula (2) is obtained. λ = 4L / 3 (2)

[0066] Based on the above, in the present embodiment, for the specific vibration region, the length La of the long side of the first virtual rectangle is set to be λ / 4 or more, that is, L / 3 (=4L / 3×1 / 4) or more. Thereby, together with the vibration of the first mode, the vibration of the higher mode of the vibration region 32 is appropriately excited.

Example

[0067] Hereinafter, the present invention will be described more specifically by way of examples. The materials, amounts used, 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 construed as being limited by the examples shown below.

[0068] (Example 1) In Example 1, a muffler having a housing that constitutes the expansion part, with a vibration part provided on the outer wall of the housing and a rib structure (non-vibration region) serving as a fixed end of vibration arranged within the vibration part was used. In the muffler of Example 1, the aspect ratio of the vibration region surface in the plurality of vibration regions separated by the rib structure is larger than the aspect ratio on the outer surface of the vibration part.

[0069] The housing of the muffler of Example 1 (hereinafter referred to as housing 12) will be described. As shown in Fig. 13, the housing 12 has a rectangular parallelepiped box shape of 150 mm × 260 mm × 62 mm and is composed of a solid material having the physical property values of an acrylic material. Specifically, the density of the housing 12 is 1180 kg / m 3 and the Young's modulus is 4.8 GPa, the Poisson's ratio is 0.35, and the loss factor is 0.0312. Also, among the side walls of the housing 12, one of the side walls with the largest outer surface area (i.e., the side wall with the largest area) constitutes the vibrating part 30, and its thickness is 1 mm. Also, the side walls other than the side wall with the largest area have a thickness of about 5 mm. The size of the outer surface of the vibrating part 30 is 140 mm × 250 mm, and its aspect ratio (specifically, the ratio of the long side to the short side of the virtual rectangle circumscribing the outer surface) is 1.79.

[0070] Also, ribs are attached to the vibrating part 30 as non-vibrating regions 34. These ribs have a thickness of about 11 mm (= 1 mm + 10 mm), extend along the long side of the side wall with the largest area, and form fixed ends during vibration. Also, each of the two vibrating regions separated by the ribs has a vibrating region area of 60 mm × 250 mm, and its aspect ratio (specifically, the ratio of the long side to the short side of the virtual rectangle circumscribing the vibrating region area) is 4.17, which is larger than the aspect ratio (= 1.79) on the outer surface of the vibrating part 30.

[0071] Then, the muffler of Example 1 was connected to a ventilation passage with an inner diameter of about 30 mm, and the sound attenuation effect on the sound propagating in the ventilation 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 vibrating portion 30 provided in the housing 12X of the silencing device, ribs as non-vibrating regions 34 extend along the short side of the side wall with the largest area, forming fixed ends during vibration. Also, each of the two vibrating regions separated by the ribs has a vibrating region area of 140 mm × 115 mm, and its aspect ratio (specifically, the ratio of the long side to the short side of the virtual rectangle circumscribing the vibrating region area) is 1.22, which is smaller than the aspect ratio (=1.79) on the outer surface of the vibrating portion 30. The configurations of the other housing 12X are common between Comparative Example 1 and Example 1.

[0073] Then, similar to Example 1, the silencer of Comparative Example 1 was connected to a ventilation passage with an inner diameter of about 30 mm, and the transmission loss for the sound propagating in the ventilation passage was calculated using commercial software COMSOL Multiphysics.

[0074] (Regarding the calculation results of the transmission loss) For each of the silencers of Example 1 and Comparative Example 1, the calculation results of the transmission loss are shown in FIG. 15. As can be seen from the figure, between Example 1 and Comparative Example 1, acoustic resonance in the expansion portion of the silencer is common, and the noise reduction volume due to λ / 2 resonance decreases near 700 Hz.

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

Explanation of symbols

[0076] 10 Silencer 12,12X housing 14 outer wall 16 inlet opening 18 outlet opening 20 side wall 30 vibrating part 32 vibration region 34 non-vibration region 100 ventilation path 102 upstream ventilation path 104 downstream ventilation path 106 expansion part 108 ventilation path inside the housing R1 first virtual rectangle R2 second virtual rectangle Sg outer surface Sv vibration region surface St fixed end face

Claims

1. A silencer comprising a housing disposed in the middle of a ventilation passage and a vibration portion provided on the outer wall of the housing, in the vibration portion, a plurality of vibration regions that vibrate in response to sound in the housing are separated by non-vibration regions provided between the vibration regions, and are capable of vibrating with the non-vibration regions as fixed ends, a silencer in which the ratio of the long side to the short side of a first virtual rectangle circumscribing the vibration region in the outer surface of the vibration portion is greater than the ratio of the long side to the short side of a second virtual rectangle circumscribing the outer surface.

2. The housing constitutes an expansion portion in the ventilation passage, the expansion portion has an internal space in which the size of a cross-section orthogonal to the extending direction of the ventilation passage is larger than that of portions of the ventilation passage other than the expansion portion, The silencer according to claim 1, wherein at least one of the plurality of side walls of the housing constitutes the vibration portion.

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

4. Inside the housing, a housing internal ventilation passage forming part of the ventilation passage extends, the housing internal ventilation passage is disposed between an inlet opening and an outlet opening provided in the housing in the extending direction of the ventilation passage, let the length of the housing internal ventilation passage in the extending direction be L, and The silencer according to claim 1, which satisfies the relationship La > L / 3 when the length of the long side of the first virtual rectangle is La for the vibration region in which the ratio of the long side to the short side of the first virtual rectangle is the largest among the plurality of vibration regions.

5. In the vibration portion, the non-vibration regions extend continuously along the extending direction of the ventilation passage, In the extending 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. The silencer according to claim 1.

6. The silencer according to claim 1, wherein the thickness of the outer wall in the vibration region is the same as the thickness of the outer wall in the non-vibration region.

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 vibration portion is made of a resin material.

9. The muffler according to claim 1, wherein the non-vibrating region is provided on the outer wall in a state of protruding convexly toward the outside of the housing.

10. The muffler according to claim 9, wherein the non-vibrating region is constituted by ribs provided on the outer wall.

11. The muffler according to claim 9, wherein the non-vibrating region has a stepped structure formed by arranging the non-vibrating region in the outer surface outside the housing more than the vibrating region in the outer surface.

Images