JP7367837B1 - Sound absorbing structure and method for manufacturing the sound absorbing structure - Google Patents

Abstract

An object of the present invention is to provide a sound-absorbing structure and a method for manufacturing the same, which can realize both low-frequency sound-absorbing properties and simplifying the manufacturing process.
SOLUTION: A sound absorbing structure 1 includes a sheet-like member 11 having an opening K, and a hollow neck portion 12 communicating with the opening K and extending to one side of the sheet-like member 11. . At least a portion of the neck portion 12 has a region F that intersects with the thickness direction D of the sheet-like member 11. The entire neck portion 12 extends only in the direction away from the sheet-like member 11 without being folded back toward the sheet-like member 11 side.
[Selection diagram] Figure 3

Description

The present disclosure relates to a sound absorbing structure and a method of manufacturing the sound absorbing structure.

Conventionally, sound absorbing structures using glass wool, urethane foam, etc. are known. Glass wool has a sound absorbing effect due to air viscosity, and urethane foam has a sound absorbing effect due to air viscosity and attenuation caused by the material. In recent years, technology has been developed in which sound-absorbing structures are placed on the tires of vehicles such as automobiles to reduce resonance noise within the tires that occurs when the vehicle is running. Generally, the sound absorption band of a sound absorption structure made of glass wool or urethane foam is, for example, a high frequency band of 1000 Hz or higher. On the other hand, the above-mentioned resonance noise within the tire that occurs when the vehicle is running is in a low frequency band of, for example, around 200 Hz to 300 Hz.

An example of a conventional sound absorbing structure that takes sound absorption characteristics in a low frequency band into consideration is the sound absorbing structure described in Patent Document 1. This conventional sound absorbing structure includes a plate-like member having a plurality of openings, and a neck portion connected to the opening so as to extend the length of the opening. The extension of the opening by the neck is located within the air space between the plate member and the opposing wall.

Japanese Patent Application Publication No. 2013-8012

In a sound absorbing structure such as that disclosed in Patent Document 1, the sound absorbing characteristics can be shifted to the lower frequency band side by increasing the extension length of the neck portion. As shown in FIG. 1 of Patent Document 1, when the neck portion extends along the thickness direction of the plate-like member, the extension length of the neck portion is equal to the thickness of the air layer between the neck portion and the wall portion. limited by. In this configuration, in order to lower the frequency of the sound absorption characteristics to a desired band, it is necessary to ensure a sufficiently large thickness of the air layer.

On the other hand, when considering attachment of the sound absorbing structure to an object, it is preferable to reduce the thickness of the sound absorbing structure itself as much as possible. Regarding this point, FIG. 4(c) of Patent Document 1 shows that by folding the neck portion in a direction crossing the thickness direction of the plate-like member, the length of the neck portion can be reduced without changing the thickness of the air layer. A lengthening configuration is disclosed. However, in such a structure, it is necessary to join a plurality of neck parts to each of the openings of the plate-shaped member, which may complicate the manufacturing process.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide a sound absorbing structure and a method for manufacturing the same, which can realize both low-frequency sound absorption characteristics and simplifying the manufacturing process.

A sound absorbing structure according to one aspect of the present disclosure includes a sheet-like member having an opening penetrating from a first surface to a second surface, and a sheet-like member that communicates with the opening and extends toward the second surface side of the sheet-like member. a hollow neck part, at least a part of the neck part has a region that intersects with the thickness direction of the sheet-like member, and the entire neck part is not folded back toward the sheet-like member side, It extends only in the direction away from the sheet-like member.

In this sound-absorbing structure, at least a portion of the neck portion has a region that intersects with the thickness direction of the sheet-like member. This makes it possible to ensure a large extension length of the neck portion without expanding the sound absorbing structure in the thickness direction of the sheet-like member. Therefore, the sound absorption characteristics can be lowered in frequency. Further, in this sound absorbing structure, the entire neck portion extends only in the direction away from the sheet-like member without being folded back toward the sheet-like member. According to this configuration, after the neck portion is integrally formed on the sheet-like member using the mold, the hollow neck portion can be formed by removing the mold. Therefore, the manufacturing process can be simplified compared to the case where the neck parts are individually joined and attached to the opening of the sheet-like member.

The neck portion may have a helical shape. In this case, by rotating the mold, the mold can be easily removed from the neck portion formed integrally with the sheet-like member. Therefore, the manufacturing process can be further simplified.

The neck portion may be embedded in a porous sound absorber. In this case, it is possible to combine the sound absorption effect of the hollow neck and the high frequency band sound absorption effect of the porous sound absorber. Therefore, the sound absorption characteristics of the sound absorption structure can be improved. Further, when attaching the sound absorbing structure to the object, a porous sound absorber can be used as a mounting member. Thereby, the ease of attaching the sound absorbing structure to the object can be improved.

A method for manufacturing a sound absorbing structure according to an embodiment of the present disclosure is a method for manufacturing the above-mentioned sound absorbing structure, which includes: a plate-shaped member having an opening penetrating from the first surface to the second surface; and a neck portion. A preparation process of preparing a mold including a pin-shaped material having a shape corresponding to the hollow part and configured to be insertable and removable into the opening; A forming step of forming an air-impermeable layer on the second surface side of the plate-like material and the surface of the pin-like material; and a peeling step of peeling off the plate-like material after removing the pin-like material from the air-impermeable layer. Be prepared.

In this method of manufacturing a sound-absorbing structure, a mold including a plate-like material and a pin-like material is used to form an air-impermeable layer on the surfaces of these materials, thereby forming a sheet-like member with an integrated neck portion. Thereafter, the pin-shaped material is removed from the non-air permeable layer and the plate-like material is peeled off, thereby obtaining a sound absorbing structure having the above-described configuration. According to this method of manufacturing a sound absorbing structure, the manufacturing process can be simplified compared to the case where the neck parts are individually joined and attached to the opening of the sheet-like member.

According to the present disclosure, it is possible to achieve both lower frequency sound absorption characteristics and simplification of the manufacturing process.

FIG. 1 is a partially cross-sectional perspective view showing an application example of a sound absorbing structure according to an embodiment of the present disclosure. FIG. 2 is a schematic plan view of the sound absorbing structure shown in FIG. 1. FIG. FIG. 2 is a schematic side view of the sound absorbing structure shown in FIG. 1. FIG. It is a flowchart which shows an example of the manufacturing method of a sound absorption structure. It is a typical side view showing a preparation process. It is a typical side view showing a formation process. It is a typical side view showing a peeling process. It is a typical sectional view of the sound absorption structure concerning a modification. It is a graph showing typical sound absorption characteristics in a low frequency band of sound absorption structures according to Examples and Comparative Examples. It is a figure showing the relationship between each parameter of a sound absorption structure and resonance frequency. (a) and (b) are typical side views showing main parts of a sound absorbing structure according to a modification. It is a typical side view which shows the principal part of the sound absorption structure based on another modification.

Hereinafter, preferred embodiments of a sound absorbing structure and a method of manufacturing the sound absorbing structure according to one aspect of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a partially sectional perspective view showing an application example of a sound absorbing structure according to an embodiment of the present disclosure. In FIG. 1, a tire 101 used for a vehicle such as an automobile is illustrated as an object P to which the sound absorbing structure 1 is attached. In the tire 101, cavity resonance may occur in which the air inside resonates due to vibrations generated when the vehicle passes through unevenness on the road surface. The frequency of sound caused by cavity resonance is typically about 250 Hz. The sound absorbing structure 1 is arranged inside the tire 101 (for example, on the inner surface 102a of the tread 102) in order to efficiently absorb low frequency band sound due to cavity resonance.

Applications of the sound absorbing structure 1 other than sound absorption of cavity resonance within the tire 101 include, for example, sound absorption of low frequency road noise by being attached to the lower part of the car body or around the wheel house, and low frequency sound absorption by being attached to the inside of the car such as the roof. Examples include sound absorption of wave sound. The sound absorbing structure 1 is not limited to vehicles, but can also be applied to the inside or housing of various home appliances and machinery, such as air conditioners, outdoor units for air conditioners, heat pumps, refrigerators, and wind power generators.

FIG. 2 is a schematic plan view of the sound absorbing structure shown in FIG. 1. FIG. 3 is a schematic side view thereof. The sound absorbing structure 1 according to this embodiment is a thin sound absorbing structure that utilizes Helmholtz resonance sound absorption. As shown in FIGS. 2 and 3, the sound-absorbing structure 1 includes a sheet-like member 11, a neck portion 12, and a porous sound-absorbing body 13.

The sheet-like member 11 is a member that serves as a base on which the neck portion 12 is provided in the sound-absorbing structure 1 . The sheet-like member 11 has a first surface 11a serving as a sound input surface and a second surface 11b on which the neck portion 12 is provided. The sheet-like member 11 has a plurality of openings K through which sound is input. In the example of FIG. 2, the plurality of openings K are arranged in a grid pattern when viewed from above on the first surface 11a of the sheet-like member 11. As shown in FIG. 3, each of the openings K is provided so as to penetrate the sheet-like member 11 in the thickness direction D from the first surface 11a to the second surface 11b of the sheet-like member 11.

The thickness T1 of the sheet-like member 11 is, for example, about 0.1 mm to 2 mm. When the thickness T1 of the sheet-like member 11 is, for example, 0.2 mm or less, the sheet-like member 11 may be a film without self-supporting properties. The sheet-like member 11 made of such a thin film is suitable when used in combination with the porous sound absorber 13 as in this embodiment. The sheet-like member 11 may have a shape other than flat. For example, at least a portion of the sheet-like member 11 may have a curved surface, or at least a portion of the sheet-like member 11 may have an uneven surface.

The cross-sectional shape of the opening K is, for example, circular. The cross-sectional shape of the opening K is not limited to a circular shape, and may be other shapes such as a triangular shape, a rectangular shape, a polygonal shape, and an elliptical shape. The inner diameter Ra of the opening K is, for example, about 1 mm to 5 mm. The aperture ratio of the sheet-like member 11 due to the openings K (the ratio of the total area of the openings K to the area of the sheet-like member 11 on the surface of the sheet-like member 11) is, for example, about 0.1% to 10%. There is.

The neck portion 12 is a hollow member that communicates with the opening K and extends toward the second surface 11b of the sheet-like member 11. In this embodiment, a neck portion 12 is provided for each of the openings K. The inner diameter and cross-sectional shape of the hollow portion S in the neck portion 12 match the inner diameter and cross-sectional shape of the opening K. By increasing the extension length L1 of the neck portion 12, the resonance frequency of the sound absorbing structure 1, which is a Helmholtz resonator, can be decreased. That is, by increasing the extension length L1 of the neck portion 12, it becomes possible to shift the sound absorption characteristics of the sound absorption structure 1 to a low frequency band.

The extension length L1 of the neck portion 12 is the length of the extension axis of the neck portion 12 from the end connected to the opening K to the tip. In this embodiment, the neck portion 12 has a spiral shape, as will be described later. The extension length L1 of the neck portion 12 corresponds to the length of the spiral formed by the neck portion 12. In this embodiment, the extension length L1 of each neck portion 12 is equal to each other.

The neck portion 12 is formed integrally with the sheet-like member 11 by forming a non-permeable layer 24 using a mold 21 (see FIG. 6), which will be described later. In this embodiment, the sheet-like member 11 and the neck portion 12 are made of a resin material such as plastic or rubber. When the sheet-like member 11 is made of plastic, the neck portion 12 is also made of plastic. When the sheet-like member 11 is made of rubber, the neck portion 12 is also made of rubber.

Examples of plastic materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), and polyurethane (PU). ), epoxy resin, phenol resin, melamine resin, etc.

Examples of rubber materials include natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), silicone rubber, Examples include urethane rubber.

The porous sound absorber 13 is a member for improving the sound absorbing properties of the sound absorbing structure 1 in cooperation with the neck portion 12. The porous sound absorber 13 is a sheet body having a shape corresponding to the sheet member 11 . The porous sound absorber 13 has a first surface 13a that is coupled to the second surface 11b of the sheet-like member 11, and a second surface 13b that is used for attaching the sound absorbing structure 1 to the object P. In this embodiment, the second surface 13b of the porous sound absorber 13 is joined to the inner surface 102a of the tread 102 using a joining means such as an adhesive, so that the sound absorbing structure 1 is attached to the inside of the tire 101. ing.

As shown in FIG. 3, the thickness T2 of the porous sound absorber 13 in the thickness direction D of the sheet-like member 11 is larger than the length L2 of the neck portion 12 in the thickness direction D of the sheet-like member 11. There is. The length L2 of the neck portion 12 in the thickness direction D is different from the extension length L1 of the neck portion 12, and is the length of the neck portion 12 in the thickness direction D from the connecting end with the opening K to the tip. be. Thereby, the neck portion 12 is in a state buried in the porous sound absorber 13. The tip of the neck portion 12 is an open end where the hollow portion S is exposed, and is located within the porous sound absorbing body 13.

The porous sound absorber 13 is formed, for example, by foam molding of a resin material such as plastic or rubber. Examples of the plastic material include polyurethane foam. Either hard polyurethane foam or soft polyurethane foam may be used. A general method can be used for producing polyurethane foam. For example, the porous sound absorber 13 can be obtained by mixing a polyol and a polyisocyanate with a foaming agent, an antifoaming agent, a catalyst, etc., filling a mold with the mixture, and foaming and curing the mixture.

Examples of the rubber material include rubber materials obtained from latex, such as natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and chloroprene rubber (CR). The porous sound absorber 13 can be obtained by foaming and solidifying these rubber materials.

The pore diameter of the porous sound absorber 13 is, for example, 1 μm or less, preferably 500 μm or less. The open porosity of the porous sound absorber 13 (the ratio of the total area of pores to the area of the porous sound absorber 13 on the surface of the porous sound absorber 13) is, for example, about 65% to 99%, preferably about 80% to 95%. It is about %. The pore diameter and open porosity can be measured using, for example, a computerized tomography (CT scan) device using X-rays. The average value of the diameters of a plurality of (for example, 100) pores extracted based on the observed image can be used to calculate the open pore diameter. To calculate the open porosity, a divided value obtained by dividing the sum of the areas of all pores extracted based on the observed image by the area of the porous sound absorber can be used.

Next, the configuration of the neck portion 12 described above will be explained in more detail.

In the sound absorbing structure 1, (A) at least a part of the neck portion 12 has a region F that intersects with the thickness direction D of the sheet-like member 11. A region F that intersects with the thickness direction D of the sheet-like member 11 is a region F in which the extending direction of the neck portion 12 does not coincide with the thickness direction D of the sheet-like member 11, and the region F intersects with the thickness direction D of the sheet-like member 11. It means that it is tilted at a larger angle. The extending direction of the neck portion 12 is an axial direction in a region where the neck portion 12 is straight, and a tangential direction in a region where the neck portion 12 is curved.

Further, in the sound absorbing structure 1, (B) the entire neck portion 12 extends only in the direction away from the sheet-like member 11 without being folded back toward the sheet-like member 11 side. This means that in the thickness direction D of the sheet-like member 11, if the direction away from the sheet-like member 11 is positive and the direction approaching the sheet-like member 11 is negative, then This means that the component in the thickness direction D of the vector in the extending direction in the neck portion 12 is always positive in the entire region from the connecting end to the tip.

In this embodiment, as a configuration that satisfies the requirements (A) and (B) above, the neck portion 12 has a spiral shape as shown in FIG. In the example of FIG. 3, the neck portion 12 has a spiral shape with a constant diameter from the base end to the distal end. As a result, the length L2 of the neck portion 12 in the thickness direction D is smaller than the thickness T2 of the porous sound absorber 13 in the thickness direction D, while the extended length L1 of the neck portion 12 is It is larger than the thickness T2 of the porous sound absorber 13 in the width direction D.

As shown in FIG. 2, the arrangement pitch H of the neck portions 12 (the distance between the centers of the spiral portions of adjacent neck portions 12, 12) is, for example, about 10 mm to 100 mm. The inner diameter Rb of the spiral portion of the neck portion 12 is, for example, about 1 mm to 5 mm. The wall thickness Rc of the neck portion 12 is, for example, about 0.1 mm to 1.0 mm. The inclination angle (the inclination angle with respect to the thickness direction D) θ of the spiral portion of the neck portion 12 is, for example, 80° to 83°. The diameter Rd of the neck portion 12 including the wall thickness is, for example, 5 mm to 10 mm.

The extension length L1 of the neck portion 12 is, for example, about 20 mm to 100 mm. The extension length L1 of the neck portion 12 is, for example, about 1.5 to 6 times the thickness T2 of the porous sound absorber 13 in the thickness direction D. The length L2 of the neck portion 12 in the thickness direction D is, for example, about 3 mm to 11 mm. The length L2 of the neck portion 12 in the thickness direction D is, for example, about 0.1 to 0.2 times the extension length L1. The length L2 of the neck portion 12 in the thickness direction D is, for example, about 0.2 to 0.9 times the thickness T2 of the porous sound absorber 13 in the thickness direction D.

In this embodiment, in response to the fact that the neck portion 12 has a spiral shape, the opening K of the sheet-like member 11 that communicates with the neck portion 12 also has a spiral shape. The inner diameter Ra of the spiral opening K matches the inner diameter Rb of the spiral portion of the neck portion 12 (see FIG. 2). In other words, the hollow portion S of the neck portion 12 and the opening K constitute one continuous spiral-shaped internal space.

Next, a method for manufacturing the sound absorbing structure 1 having the above-described configuration will be described.

FIG. 4 is a flowchart illustrating an example of a method for manufacturing a sound absorbing structure. As shown in FIG. 4, the method for manufacturing a sound absorbing structure includes a preparation process (step S01), a forming process (step S02), and a peeling process (step S03).

The preparation process is a process of preparing the mold 21. As shown in FIG. 5, the mold 21 is composed of a plate-shaped material 22 and a pin-shaped material 23. The plate-shaped material 22 is a material for imitating the sheet-like member 11, and is made of, for example, a plastic material. The plate-shaped member 22 has a first surface 22a and a second surface 22b located on the opposite side to the first surface 22a. The thickness T3 of the plate-shaped member 22 is larger than the thickness T1 of the sheet-shaped member 11 of the sound-absorbing structure 1 to be produced, for example. The plate-shaped member 22 has an opening Ks that penetrates from the first surface 22a to the second surface 22b. In this embodiment, the opening Ks has a spiral shape corresponding to the shape of the opening K of the sheet-like member 11.

The pin-shaped member 23 is a solid member for imitating the opening K of the sheet-like member 11 and the hollow portion S of the neck portion 12, and is made of, for example, a metal material. The shape of the pin-shaped member 23 is similar to the shape of the neck portion 12. That is, at least a part of the pin-shaped profile 23 has a region that intersects with the thickness direction of the plate-shaped profile 22 (a direction that coincides with the thickness direction D of the sheet-shaped member 11), and The entire structure extends only in the direction away from the plate-shaped profile 22 without being folded back toward the plate-shaped profile 22.

In this embodiment, the pin-shaped member 23 has a spiral shape corresponding to the shapes of the opening K and the neck portion 12 of the sheet-like member 11, and is screwed into the opening K of the plate-shaped member 22 so as to be insertable and removable. There is. The extension length of the pin-shaped member 23 (the length of the spiral formed by the neck portion 12) is the length of the entire spiral-shaped internal space defined by the hollow portion S and the opening K of the neck portion 12. It is about the same length as the extended length or longer.

In the preparation process, the extension length of the pin-shaped member 23 is made longer than the extension length of the spiral-shaped internal space defined by the hollow portion S and the opening K of the neck portion 12, and the length of the pin-shaped member 23 is The one end portion 23a may be made to protrude from the opening Ks of the plate-shaped member 22 to the first surface 22a. As a result, one end portion 23a of the pin-shaped material 23 can be grasped when removing the pin-shaped material 23 from the air-impermeable layer 24 in the peeling process described later. Therefore, the pin-shaped member 23 can be easily removed from the air-impermeable layer 24.

The forming step is a step of forming the non-permeable layer 24 using the mold 21. In the forming step, as shown in FIG. 6, with the pin-shaped material 23 inserted into the opening Ks of the plate-like material 22, the second surface 22b side of the plate-like material 22 in the mold 21 and the second surface thereof are An air-impermeable layer 24 is formed on the surface of the other end 23b of the pin-shaped member 23 protruding from the pin-shaped member 22b. The sheet-like member 11 is formed by the air-impermeable layer 24 formed on the second surface 22b of the plate-like material 22, and the neck portion 12 is formed by the air-impermeable layer 24 formed on the surface of the other end 23b of the pin-like material 23. It is formed.

Injection molding, in which resin is injected into a mold containing the mold 21, may be used to form the non-porous layer 24. Further, a liquid precursor such as latex or uncured resin is applied to the second surface 22b side of the plate-shaped mold material 22 and the surface of the other end portion 23b of the pin-shaped mold material 23 protruding from the second surface 22b, The non-porous layer 24 may be formed by curing this. By such a method of forming the non-permeable layer 24, the sheet-like member 11 and the neck portion 12 are integrally formed.

When forming the non-porous layer 24 by applying and curing a liquid precursor, the neck can be removed by removing the precursor adhering to the tip surface on the other end 23b side of the pin-shaped member 23 before or after curing. An open end can be formed on the same distal end surface of the portion 12. Moreover, in order to avoid adhesion of the precursor to the tip surface on the other end 23b side of the pin-shaped member 23, the pin-shaped member 23 may be a hollow member.

The peeling process is a process of peeling the mold 21 from the non-porous layer 24. Specifically, in the peeling step, as shown in FIG. 7, after the pin-shaped material 23 is removed from the air-impermeable layer 24, the plate-like material 22 is peeled from the air-impermeable layer 24. In this embodiment, as described above, the pin-shaped member 23 has a spiral shape. Therefore, by rotating the pin-shaped member 23 around the axis, the pin-shaped member 23 can be removed from the opening Ks of the plate-shaped member 22, the opening K of the sheet-like member 11, and the neck portion 12. By removing the pin-shaped member 23, one continuous spiral-shaped internal space is formed in the sheet-shaped member 11 and the neck part 12 by the hollow part S and the opening K of the neck part 12.

If the release properties of the air-impermeable layer 24 after molding with respect to the sheet-like member 11 are sufficient, the plate-like shape material 22 can be peeled off from the air-impermeable layer 24 without using any special method. If the mold releasability of the non-porous layer 24 after molding from the sheet-like member 11 is insufficient, for example, an extrusion pin for peeling may be provided on the plate-shaped material 22, and the non-porous layer 24 may be separated from the sheet using the extrusion pin. It may be forcibly peeled off from the shaped member 11. Furthermore, prior to forming the air-impermeable layer 24, a mold release agent may be applied to the plate-like mold material 22 to improve the mold release properties of the air-impermeable layer 24 after molding from the sheet-like member 11.

As explained above, in the sound absorbing structure 1, at least a portion of the neck portion 12 has a region F that intersects with the thickness direction D of the sheet-like member 11. Thereby, the extended length L1 of the neck portion 12 can be ensured to be large without expanding the sound absorbing structure 1 in the thickness direction D of the sheet-like member 11. Therefore, the sound absorption characteristics can be lowered in frequency. Further, in the sound absorbing structure 1, the entire neck portion 12 extends only in the direction away from the sheet-like member 11 without being folded back toward the sheet-like member 11 side. According to this configuration, after the neck portion 12 is integrally formed on the sheet-like member 11 using the mold 21, the hollow neck portion 12 can be formed by removing the mold 21. Therefore, compared to the case where the neck portions 12 are individually joined and attached to the openings K of the sheet-like member 11, the manufacturing process can be simplified.

In this embodiment, the neck portion 12 has a spiral shape. Thereby, by rotating the mold 21 (in this case, the pin-shaped material 23), the pin-shaped material 23 can be easily removed from the neck portion 12 formed integrally with the sheet-like member 11. Therefore, the manufacturing process can be further simplified.

In this embodiment, the neck portion 12 is embedded in the porous sound absorber 13. Thereby, the sound absorption effect of the hollow neck portion 12 and the sound absorption effect of the porous sound absorber 13 can be combined. Therefore, the sound absorption characteristics of the sound absorption structure 1 can be improved. Furthermore, when attaching the sound absorbing structure 1 to an object P such as the tire 101 shown in FIG. 1, the porous sound absorbing body 13 can be used as an attaching member. Thereby, the ease of attaching the sound absorbing structure 1 to the object P can be improved.

In addition, in the method for manufacturing a sound absorbing structure according to the present embodiment, a mold 21 having a plate-like shape material 22 and a pin-like shape material 23 is used to form an air-impermeable layer 24 on the surface of these mold materials, so that the neck portion 12 is An integrated sheet-like member 11 is formed. Thereafter, the pin-shaped material 23 is removed from the air-impermeable layer 24 and the plate-shaped material 22 is peeled off, thereby obtaining the sound absorbing structure 1 having the above-described configuration. According to this method of manufacturing a sound absorbing structure, the manufacturing process can be simplified compared to the case where the neck portions 12 are individually bonded and attached to the opening K of the sheet-like member 11.

The present disclosure is not limited to the above embodiments. For example, in the above embodiment, the porous sound absorbing body 13 is arranged on the second surface 11b side of the sheet-like member 11, and the neck portion 12 is embedded in the porous sound absorbing body 13, but the sound absorbing structure 1A shown in FIG. The arrangement of the porous sound absorber 13 may be omitted as shown in FIG. In this case, the sound absorbing structure 1A is attached to the object P via, for example, a spacer (not shown). When attached to the object P, the neck portion 12 is located within an air layer formed between the object P and the second surface 11b of the sheet-like member 11, for example.

Also in such a sound absorbing structure 1A, similarly to the sound absorbing structure 1, a large extension length L1 of the neck portion 12 is ensured without expanding the sound absorbing structure 1A in the thickness direction D of the sheet-like member 11. can do. Therefore, the sound absorption characteristics can be lowered in frequency. Further, the manufacturing process can be simplified compared to the case where the neck portions 12 are individually joined and attached to the openings K of the sheet-like member 11.

FIG. 9 is a graph showing typical sound absorption characteristics in a low frequency band of the sound absorption structures according to Examples and Comparative Examples. In FIG. 9, the horizontal axis represents frequency (Hz), and the vertical axis represents sound absorption coefficient. The sound absorbing structure according to the comparative example is a sound absorbing structure made of a conventional porous sound absorbing material (glass wool, urethane foam, etc.). Example 1 is a sound absorbing structure corresponding to the sound absorbing structure 1 shown in FIG. 3, and Example 2 is a sound absorbing structure corresponding to the sound absorbing structure 1 shown in FIG.

As shown in FIG. 9, in the sound absorption structure according to the comparative example, although the sound absorption coefficient increases slightly as the frequency becomes higher, the sound absorption coefficient near 250 Hz remains less than 0.1. In the sound absorption structure according to Example 1, a peak of sound absorption coefficient appears near 250 Hz, and the sound absorption coefficient at the peak is about 0.8. Also, in the frequency band at the foot of the peak, the sound absorption coefficient is higher than that of the sound absorption structure according to the comparative example. In the sound absorbing structure according to Example 2, similarly to the sound absorbing structure according to Example 1, a peak of sound absorption coefficient appears near 250 Hz, and the sound absorption coefficient at the peak is about 0.8. Although the sound absorption coefficient in the frequency band at the foot of the peak is smaller than that of the sound absorbing structure according to Example 1, it can be seen that sound can be selectively absorbed in the frequency band near the peak.

FIG. 10 is a diagram showing the relationship between each parameter of the sound absorbing structure and the resonance frequency. As shown in FIG. 10, here, the thickness T1 of the sheet-like member 11, the thickness T2 of the air layer (porous sound absorber 13), the arrangement pitch H of the neck portion 12, the inner diameter Rb of the neck portion 12, the neck portion wall thickness Rc of the neck part 12, diameter Rd of the neck part 12, inclination angle θ of the neck part 12, extension length L1 of the neck part 12, length L2 of the neck part 12 in the thickness direction D, and number of turns N of the neck part 12. is a parameter, and the estimated value of the resonance frequency f is calculated for three samples (structures A to C) of sound absorbing structures with different parameters.

In structures A to C, the inner diameter Rb of the neck portion 12, the diameter Rd of the neck portion 12, the extension length L1 of the neck portion 12, the thickness T2 of the air layer (porous sound absorber 13), and the number of turns N of the neck portion 12. are different from each other, and other parameters are common. From the results shown in FIG. 10, it can be seen that structures A to C all have resonance frequencies f around 200 Hz or smaller than 200 Hz. Further, it can be seen that as the extension length L1 of the neck portion 12 becomes longer, the resonance frequency f becomes lower. Even when the extension length L2 of the neck portion 12 is increased, the length L2 of the neck portion 12 in the thickness direction D can be suppressed to about 1/7 of the length L2, so that the sound absorbing structure 1 can be It can be seen that the extension length L2 of the neck portion 12 can be secured without expanding in the direction D.

In the above embodiment, the extension lengths L1 of the neck parts 12 are equal to each other, but the extension lengths L1 of the neck parts 12 may be different from each other. For example, the neck portion 12 having the first extension length L1a and the neck portion 12 having the second extension length L1b may be combined. In this case, sound absorption characteristics can be adjusted by combining neck parts 12 with different resonance frequencies. The combination of extension lengths L1 is not limited to two types, but may be three or more types.

In the embodiment described above, each of the openings K of the sheet-like member 11 is provided with the neck portion 12, but there are openings K provided with the neck portion 12 and openings K not provided with the neck portion 12. may be combined. Even in such a configuration, the sound absorption characteristics can be adjusted by combining the opening K and neck portion 12 that have different resonance frequencies.

Although the neck portion 12 has a spiral shape in the above embodiment, the shape of the neck portion 12 is not limited to this. That is, as long as the entire neck portion 12 extends only in the direction away from the sheet-like member 11 without being folded back toward the sheet-like member 11 side, a neck portion having another shape may be adopted. . For example, as in a sound absorbing structure 1B shown in FIG. 11(a), the linear neck portion 12 may be arranged to be inclined with respect to the thickness direction D of the sheet-like member 11. Alternatively, the neck portion 12 having a gently curved shape may be arranged to be inclined with respect to the thickness direction D of the sheet-like member 11, for example, as in a sound absorbing structure 1C shown in FIG. 11(b).

Also in the sound absorbing structures 1B and 1C, the extended length L1 of the neck portion 12 can be ensured to be large without expanding in the thickness direction D of the sheet-like member 11, similarly to the above embodiment. Therefore, the sound absorption characteristics can be lowered in frequency. Further, the manufacturing process can be simplified compared to the case where the neck portions 12 are individually joined and attached to the openings K of the sheet-like member 11. In the sound-absorbing structure 1B, the shape of the pin-shaped material in the mold 21 is linear, and in the peeling process, the linear pin-shaped material is pulled out from the non-porous layer 24 after molding. A neck portion 12 can be formed. In the sound absorbing structure 1C, the shape of the pin-shaped material in the mold 21 is linear, and in the peeling process, the linear pin-shaped material is pulled out from the non-porous layer 24 after molding, so that it is integrated with the sheet-like member 11. A neck portion 12 can be formed.

In the above embodiment, the sheet-like member 11 constitutes the surface on one end side in the thickness direction D, but as shown in FIG. In addition to this, a side surface intersecting the thickness direction D may be formed. In the example of FIG. 12, the sheet-like member 11 is provided so as to cover the side surface of the porous sound absorber 13, but this is the case where the porous sound absorber 13 is not provided as in the sound absorbing structure 1A described above. Alternatively, the sheet-like member 11 may constitute a side surface that intersects with the thickness direction D. According to such a configuration, the neck portion 12 or the porous sound absorbing body 13 is surrounded by the sheet-like member 11, so that these members are protected.

The gist of the present disclosure is as follows [1] to [4].
[1] A sheet-like member having an opening that penetrates from a first surface to a second surface, and a hollow neck that communicates with the opening and extends toward the second surface of the sheet-like member. , at least a part of the neck portion has a region that intersects with the thickness direction of the sheet-like member, and the entire neck portion is not folded back toward the sheet-like member side, and the neck portion is entirely covered with the sheet-like member. A sound-absorbing structure that extends only in a direction away from.
[2] The sound absorbing structure according to [1], wherein the neck portion has a spiral shape.
[3] The sound-absorbing structure according to [1] or [2], wherein the neck portion is embedded in a porous sound-absorbing body.
[4] The method for manufacturing a sound absorbing structure according to any one of [1] to [3], including a plate-shaped material having an opening penetrating from the first surface to the second surface, and a hollow portion of the neck portion. a preparation step of preparing a mold including a pin-shaped material configured to be inserted into and removed from the opening of the plate-like material in a shape corresponding to the shape of the mold; A forming step of forming a non-porous layer on the second surface side of the plate-like material and the surface of the pin-like material in the mold, and after removing the pin-like material from the non-porous layer, removing the non-porous layer from the non-porous layer. A method for manufacturing a sound absorbing structure, comprising: a peeling step of peeling off the plate-like shape material.

DESCRIPTION OF SYMBOLS 1, 1A to 1D...Sound absorbing structure, 11...Sheet member, 11a...First surface, 11b...Second surface, K...Opening part, 12...Neck part, 13...Porous sound absorbing body, 21...Molding mold, 22... Plate shaped material, 22a... First surface, 22b... Second surface, Ks... Opening, 23... Pin shaped material, 24... Non-permeable layer, F... Region.

Claims (2)

a sheet-like member having an opening penetrating from the first surface to the second surface;
a hollow neck communicating with the opening and extending toward the second surface of the sheet-like member;
At least a portion of the neck portion has a region that intersects with the thickness direction of the sheet-like member,
The entire neck portion extends only in a direction away from the sheet-like member without being folded back toward the sheet-like member ,
The neck portion has a spiral shape and is embedded in a porous sound absorbing body,
In the porous sound absorbing body, a surface intersecting the extending direction of the neck portion is an exposed surface exposed to the outside . A method for manufacturing a sound absorbing structure according to claim 1 , comprising:
A mold is prepared that includes a plate-shaped material having an opening penetrating from a first surface to a second surface, and a pin-shaped material having a shape corresponding to the hollow part of the neck portion and configured to be insertable into and removable from the opening. Preparation process and
When the pin-shaped mold material is inserted into the opening of the plate-shaped mold material, there is a non-contact between the second surface side of the plate-shaped mold material in the mold and the surface of the pin-shaped mold material that protrudes from the second surface. a formation step of forming a ventilation layer;
A method for producing a sound absorbing structure, comprising a peeling step of peeling off the plate-like shape material from the non-ventilated layer after removing the pin-like shape material from the non-ventilated layer.

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