Sound-absorbing member

Abstract

This sound-absorbing member is disposed at a portion facing a space and absorbs sound propagating through the space. The sound-absorbing member comprises a nonwoven fabric layer and a skin layer. The nonwoven fabric layer is made of a thermoplastic resin and is formed by thermoforming. The skin layer is layered on the nonwoven fabric layer so as to face the space, and has a plurality of through-holes that each penetrate in the thickness direction and are arranged in a mutually dispersed manner.

Description

Sound-absorbing member

[0001] The present invention relates to a sound-absorbing member.

[0002] In buildings and vehicles, sound-absorbing members may be provided to reduce noise in the space. In particular, in the passenger compartment of a vehicle, sounds from the power train and wheels are transmitted. Therefore, in a vehicle, it is required to reduce the noise in the passenger compartment.

[0003] Patent Document 1 discloses a sound-absorbing member having a structure in which a perforated layer and a porous layer are laminated. The perforated layer is formed of a resin material or a woven fabric and has a plurality of through holes penetrating in the thickness direction. The porous layer is formed of a polymer material or a non-woven fabric and has a plurality of holes provided so as to be continuous with the through holes of the perforated layer. In Patent Document 1, it is said that sound can be absorbed in the frequency range of 200 to 300 Hz by a Helmholtz resonator constituted by a combination of the through holes of the perforated layer and the holes of the porous layer continuous with the through holes.

[0004] However, when trying to absorb low-frequency sounds or high sound pressure sounds, it is necessary to increase the thickness of the sound-absorbing member. The same applies to the sound-absorbing member proposed in Patent Document 1 above.

[0005] If the thickness of the sound-absorbing member is increased, there are disadvantages such as restrictions on the layout of the space where the sound-absorbing member is arranged and an increase in weight. In particular, an increase in the weight of a component in a vehicle is considered difficult to be tolerated in order to reduce the environmental load.

[0006] Japanese Patent Application Laid-Open No. 2018-141839

[0007] The present invention has been made to solve the above problems, and an object thereof is to provide a sound-absorbing member having high sound absorption while suppressing an increase in size and weight.

[0008] A sound-absorbing member according to one aspect of the present invention is a member that is placed in a portion facing a space and absorbs sound propagating through the space. The sound-absorbing member according to this aspect comprises a nonwoven fabric layer and a surface layer. The nonwoven fabric layer is made of a thermoplastic resin and is formed by thermoforming. The surface layer is laminated to the nonwoven fabric layer so as to face the space and is a layer having a plurality of through holes that penetrate in the thickness direction and are dispersed among each other.

[0009] This is a schematic diagram showing the structure of a vehicle equipped with a sound-absorbing member according to an embodiment. This is a cross-sectional view showing the structure of the sound-absorbing member according to an embodiment. This is a diagram for explaining the sound absorption mechanism by the sound-absorbing member according to this embodiment. This is a diagram showing an interior member according to a comparative example. This is a cross-sectional view showing the structure of the sound-absorbing member according to Modification 1. This is a cross-sectional view showing the structure of the sound-absorbing member according to Modification 2. This is a cross-sectional view showing the structure of the sound-absorbing member according to Modification 3. This is a plan view showing the structure of the sound-absorbing member according to Modification 4. This is a plan view showing the structure of the sound-absorbing member according to Modification 5. This is a plan view showing the structure of the sound-absorbing member according to Modification 6. This is a plan view showing the structure of the sound-absorbing member according to Modification 7. This is a cross-sectional view showing the structure of the sound-absorbing member according to Modification 8.

[0010] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are illustrative examples of the present invention, and the present invention is not limited to these embodiments except for its essential configuration.

[0011] [Embodiment] 1. Structure of the vehicle 1 equipped with the sound-absorbing member 20 The structure of the vehicle 1 equipped with the sound-absorbing member 20 according to this embodiment will be described with reference to Figure 1.

[0012] As shown in Figure 1, the vehicle 1 has a passenger compartment 1a in the middle of the front-to-rear direction. In the vehicle 1, there is a power unit room 1b in front of the passenger compartment 1a. In addition, there is a rear cargo compartment 1c at the rear of the passenger compartment 1a, which is a space for loading luggage.

[0013] A seat 17 for the occupant is located inside the passenger compartment 1a. The passenger compartment 1a is separated from the power unit room 1b in front by a dash panel 14, the lower part is separated by a floor panel 15, and the upper part is separated by a roof panel 16.

[0014] The power unit room 1b houses a power unit 11 for driving the vehicle 1. The power unit 11 is a power unit such as an engine or an electric motor, or a hybrid power unit combining an engine and an electric motor.

[0015] Vehicle 1 has wheels 12 at the front and rear. Vehicle 1 has wheelhouse panels 13 that are provided to partition the space between the wheelhouses that house the wheels 12 and the space inside the vehicle 1 (passenger compartment 1a, power unit room 1b, rear cargo compartment 1c). The front wheelhouse panel 13 is partially located within the space inside the power unit room 1b, and the remainder is located inside the passenger compartment 1a, beyond the dash panel 14. The rear wheelhouse panel 13 is located inside the rear cargo compartment 1c.

[0016] In this embodiment, sound-absorbing members 20 are provided on the floor panel 15, roof panel 16, and dash panel 14 at the locations facing the passenger compartment 1a. In addition, in vehicle 1, sound-absorbing members 20 are also provided on the back of the seat 17. Furthermore, sound-absorbing members 20 are provided on the power unit room 1b side of the front wheelhouse panel 13 and on the rear cargo compartment 1c side of the rear wheelhouse panel 13. Each sound-absorbing member 20 is fixed to the target area by adhesive, resin rivets, or sewing.

[0017] 2. Structure of the sound-absorbing members 20 The structure of the sound-absorbing members 20 installed in various locations on the vehicle 1 will be explained using Figure 2. In all figures referred to in the following explanation, including Figure 2, "IN" indicates the side of the space (inside the passenger compartment 1a) and "OUT" indicates the outside (outside the passenger compartment 1a).

[0018] As shown in Figure 2, the sound-absorbing member 20 comprises a surface layer 21 and a nonwoven fabric layer 22 laminated on the outside of the surface layer 21. In the sound-absorbing member 20 according to this embodiment, as an example, the entire inner surface of the nonwoven fabric layer 22 is covered with the surface layer 21.

[0019] The surface layer 21 is a sheet-like layer formed from, for example, cloth, leather, or resin (such as nylon or polyester). The surface layer 21 has a plurality of through holes 21a that penetrate in the thickness direction.

[0020] Multiple through-holes 21a in the epidermal layer 21 are dispersed in a direction perpendicular to the thickness direction. Each through-hole 21a is formed such that the layer surface 22a of the underlying nonwoven fabric layer 22 is exposed at the bottom.

[0021] The nonwoven fabric layer 22 is joined to the skin layer 21 at its surface 22a. Various methods can be used to join the skin layer 21 and the nonwoven fabric layer 22, such as using an adhesive or using heat welding.

[0022] The nonwoven fabric layer 22 is made of a thermoplastic resin and is formed by thermoforming. In this embodiment, the thermoplastic resin used to form the nonwoven fabric layer 22 can be, for example, polyester, nylon, high-melting-point PP (high-melting-point polypropylene), etc. Furthermore, non-thermoplastic fibers such as rayon may be mixed into the nonwoven fabric layer 22 made of the aforementioned thermoplastic resin to the extent that the objectives of the present invention are achieved.

[0023] A specific method for forming the nonwoven fabric layer 22 involves placing the thermoplastic resin material inside a press mold and heating it to a predetermined temperature. Here, the "predetermined temperature" is set considering the density of the nonwoven fabric layer 22 to be formed. That is, a higher heating temperature will form a nonwoven fabric layer 22 with a higher density, while a lower heating temperature will form a nonwoven fabric layer 22 with a lower density.

[0024] 3. Sound Absorption Mechanism by Sound Absorbing Member 20 The sound absorption mechanism by the sound absorbing member 20 according to this embodiment will be explained using Figures 3A and 3B. Figure 3A shows the case when airborne sound is incident on the sound absorbing member 20 according to this embodiment, and Figure 3B shows the case when airborne sound is incident on the interior member 920 according to a comparative example.

[0025] As shown in Figure 3B, the interior member 920 of the comparative example is formed by laminating a surface layer 921 and a nonwoven fabric layer 922, similar to the sound-absorbing member 20 according to the present embodiment. However, unlike the sound-absorbing member 20 according to the present embodiment, the interior member 920 of the comparative example does not have through holes in the surface layer 921.

[0026] In the case of the comparative example's interior component 920, when airborne sound is incident from the space (passenger compartment, power unit room, rear cargo compartment) side (arrow A1), since there are no through holes in the surface layer 921, almost all of the sound is reflected back to the space side (arrow A5). As a result, in a vehicle equipped with the comparative example's interior component 920, sound resonates in the passenger compartment and other areas, impairing in-vehicle comfort.

[0027] In contrast, as shown in Figure 3A, when airborne sound is incident on the sound-absorbing member 20 according to this embodiment from the side of the space (passenger compartment 1a, power unit room 1b, rear cargo compartment 1c) (arrow A1), a portion is reflected back to the space (arrow A2), and the remainder enters the through-hole 21a of the surface layer 21 (arrow A3). The airborne sound A3 that enters the through-hole 21a is then propagated from the bottom of the through-hole 21a to the nonwoven fabric layer 22 (arrow A4). Within the nonwoven fabric layer 22, the energy of the airborne sound is converted into thermal energy by vibration due to friction with the surrounding walls, and is absorbed and dissipated. In addition, since a portion of the incident sound is absorbed by the surface, the reflected sound can be reduced relative to the incident sound. Therefore, in a vehicle 1 equipped with the sound-absorbing member 20 according to this embodiment, sound resonance in the passenger compartment 1a, etc., is suppressed.

[0028] 4. Effects The sound-absorbing member 20 according to this embodiment comprises a surface layer 21 having a plurality of through holes 21a, and a nonwoven fabric layer 22 arranged on the side opposite to the space (vehicle compartment 1a, power unit room 1b, rear cargo compartment 1c) relative to the surface layer 21. Therefore, when airborne sound is incident on the surface of the surface layer 21 of the sound-absorbing member 20, some of it is reflected by the surface layer toward the space (arrow A2 in Figure 3A), but the remainder is propagated through the through holes 21a to the nonwoven fabric layer 22 (arrow A3 in Figure 3A). The energy of the airborne sound that enters the nonwoven fabric layer 22 (sound energy) is converted into thermal energy and dissipated by interference with the fibers of the nonwoven fabric layer 22.

[0029] Furthermore, in the sound-absorbing member 20, the nonwoven fabric layer 22 is made of thermoplastic resin and formed by thermoforming, so the density can be set appropriately depending on the installation location. Specifically, the nonwoven fabric layer 22 formed by thermoforming can be made low-density by lowering the molding temperature, thereby increasing the sound absorption of airborne sound. Conversely, if thermoforming is performed at a high temperature, the density can be increased, making it possible to prevent sound energy that has entered the nonwoven fabric layer 22 from being radiated back into the space. Therefore, by adjusting the heating temperature when forming the nonwoven fabric layer 22, the properties can be appropriately adjusted according to the installation location.

[0030] Furthermore, the nonwoven fabric layer 22, which is made of thermoplastic resin and formed by thermoforming, can be processed into various shapes depending on the press mold used during thermoforming. Therefore, the sound-absorbing member 20 can be shaped to suit the location where it is to be installed, without having to join multiple parts together.

[0031] As described above, the sound-absorbing member 20 according to this embodiment has high sound absorption properties while suppressing increases in size and weight.

[0032] In this embodiment, sound-absorbing members 20 are provided in the areas of the floor panel 15, roof panel 16, and dash panel 14 that face the passenger compartment 1a, the back of the seat 17, the power unit room 1b side of the front wheelhouse panel 13, and the rear cargo compartment 1c side of the rear wheelhouse panel 13.

[0033] However, the locations where the sound-absorbing members 20 are placed are not limited to the locations mentioned above. Furthermore, it is not necessary to place the sound-absorbing members 20 in all of the above locations; they can be placed in only some of the locations.

[0034] [Modification 1] The structure of the sound-absorbing member 120 according to Modification 1 will be explained with reference to Figure 4A.

[0035] As shown in Figure 4A, the sound-absorbing member 120 according to this modified example differs from the above embodiment in that the surface facing the space has an uneven structure in which convex portions 120a and concave portions 120b are alternately continuous.

[0036] In this modified example, the sound-absorbing member 120 has a substantially uniform thickness, and the surface of the lower nonwoven fabric layer 122 on the side of the surface layer 121 has an uneven shape.

[0037] In this modified example, the sound-absorbing member 120 has a surface layer 121 made of the same material as the surface layer 21 in the above embodiment, and has a plurality of through holes 121a that are dispersed in the same way as the surface layer 21. The nonwoven fabric layer 122 is made of a thermoplastic resin, similar to the nonwoven fabric layer 22 in the above embodiment, and is formed by thermoforming.

[0038] In the sound-absorbing member 120 having the structure described above, the surface layer 121 has a plurality of through holes 121a, and the nonwoven fabric layer 122 is made of thermoplastic resin and is formed by thermoforming, so the same effects as in the above embodiment can be obtained.

[0039] Further, in the sound absorption member 120 according to this modified example, since the surface on the side facing the space (the passenger compartment 1a, the power unit room 1b, and the rear cargo compartment 1c in FIG. 1) is formed in an uneven shape, the airborne sound incident on the surface of the sound absorption member 120 (the surface of the skin layer 121) collides with each other due to the unevenness of the surface and is canceled out. Therefore, in the sound absorption member 120, in addition to the absorption and dissipation of sound energy in the non-woven fabric layer 122, higher sound absorption can be achieved by the cancellation of sound on the surface.

[0040] In this modified example, the thickness of the skin layer 121 is made uniform, but it is not limited to this. For example, the thickness of the non-woven fabric layer 222 may be made uniform as in the above embodiment, and the thickness of the skin layer 121 may be configured such that thick portions and thin portions are continuous for each location.

[0041] [Modified Example 2] The structure of the sound absorption member 220 according to Modified Example 2 will be described using FIG. 4B. In FIG. 4B, the same reference numerals are given to the members having the same structure as in the above embodiment. And hereinafter, overlapping explanations will be omitted.

[0042] The sound absorption member 220 according to this modified example is different from the above embodiment in that the density in the non-woven fabric layer 222 is not uniform in the thickness direction. Specifically, the non-woven fabric layer 222 of the sound absorption member 220 is formed such that the density gradually increases from the side of the skin layer 21 toward the opposite side (arrow B2), and the density gradually decreases from the side opposite to the space toward the side of the skin layer 21 (arrow B1).

[0043] The density adjustment in the non-woven fabric layer 222 can be performed by adjusting the heating temperature during thermoforming. Specifically, for the portion where a high density is to be achieved in the non-woven fabric layer 222, the heating temperature during thermoforming is increased, and conversely, for the portion where a low density is to be achieved, the heating temperature during thermoforming is decreased.

[0044] The sound absorption member 220 according to this modified example has the same configuration as the above embodiment except that the density of the non-woven fabric layer 222 is different in the thickness direction. Therefore, the sound absorption member 220 can obtain the same effects as the above embodiment.

[0045] Also, in the sound-absorbing member 220 according to this modification, as described above, since the density of the non-woven fabric layer 220 is configured to increase from the space side toward the opposite side, the high-density portion on the side opposite to the skin layer 21 serves as a lid for sound. Therefore, in the sound-absorbing member 220, the airborne sound that has entered the non-woven fabric layer 222 through the through-holes 21a of the skin layer 21 can be trapped within the non-woven fabric layer 222.

[0046] Also, in the sound-absorbing member 220 according to this modification, since the density of the portion of the non-woven fabric layer 222 on the side of the skin layer 21 is lowered, airborne sound is favorably incident on the non-woven fabric layer 222 through the through-holes 21a, and high sound absorption can be maintained.

[0047] Therefore, the sound-absorbing member 220 according to this modification is effective in realizing sound insulation while maintaining high sound absorption.

[0048] Note that the configuration of the sound-absorbing member 220 according to this modification can also be combined with the configuration of the sound-absorbing member 120 according to the first modification.

[0049] [Modification 3] The structure of the sound-absorbing member 320 according to Modification 3 will be described with reference to FIG. 5. In FIG. 5, members having the same structure as in the above-described embodiment are denoted by the same reference numerals. And hereinafter, overlapping descriptions will be omitted.

[0050] The sound-absorbing member 320 according to this modification is different from the above-described embodiment in that it has a plurality of constituent layers 323 to 325 in which the non-woven fabric layer 322 is laminated. Also, the plurality of constituent layers 323 to 325 constituting the non-woven fabric layer 322 are formed such that the basis weight increases in order from the side of the skin layer 21 in the lamination direction toward the opposite side, and thus it is different from the second modification in that the density increases from the side of the skin layer 21 toward the opposite side.

[0051] Each of the constituent layers 323 to 325 constituting the non-woven fabric layer 322 is made of a thermoplastic resin and is formed by thermoforming. The joining between the constituent layers 323 to 325 is made, for example, by heat welding.

[0052] The sound-absorbing member 320 according to this modified example has the same configuration as the embodiment described above, except for the differences mentioned above, and therefore can achieve the same effects as the embodiment described above. Furthermore, in the sound-absorbing member 320, a difference in density is provided between the surface layer 21 side and the opposite side by the basis weight of the multiple constituent layers 323 to 325, so the molding method is simpler than that of the modified example 2, and it can achieve the same effects as the modified example 2.

[0053] In this modified example, the sound-absorbing member 320 is constructed with a nonwoven fabric layer 322 made up of a combination of three constituent layers 323 to 325. However, the number of constituent layers that make up the nonwoven fabric layer is not limited to this. For example, the nonwoven fabric layer may be made up of two constituent layers, or it may be made up of four or more constituent layers.

[0054] Furthermore, the configuration of the sound-absorbing member 320 according to this modified example can be combined with the configuration of the sound-absorbing member 120 according to the above modified example 1.

[0055] [Modification 4] The structure of the sound-absorbing member 420 according to Modification 4 will be explained with reference to Figure 6A. In Figure 6A, only the surface layer 421 is shown, and the nonwoven fabric layer is omitted from the illustration. However, the sound-absorbing member 420 according to this modification has a nonwoven fabric layer having the same structure as the embodiment described above. Furthermore, the surface layer 421 in the sound-absorbing member 420 is formed using the same material as the surface layer 21 in the embodiment described above.

[0056] As shown in Figure 6A, when the sound-absorbing member 420 is viewed from above from the side of the space (the passenger compartment 1a, power unit room 1b, and rear cargo compartment 1c in Figure 1), the surface layer 421 has a region where the through holes 421a are relatively densely clustered (region C1) and a region where the through holes 421a are relatively scattered (region C2).

[0057] The sound-absorbing member 420 according to this modified example differs from the above embodiment in that the arrangement of through-holes 421a in the surface layer 421 is not uniform, and it has densely packed C1 regions and scattered C2 regions, but the other configurations are the same. Therefore, the sound-absorbing member 420 according to this modified example can obtain the same effects as the above embodiment.

[0058] Furthermore, in the sound-absorbing member 420 according to this modified example, if the C1 region, where through holes 421a are densely concentrated, is arranged in the area where sound absorption is to be enhanced, it is suitable for achieving high sound absorption.

[0059] In this modified example, the sound-absorbing member 420 has two distinct regions (region C1 and region C2) in the distribution of through-holes 421a in the surface layer 421, but it is not limited to this. For example, it may have three or more regions with different distribution densities of through-holes.

[0060] Furthermore, the configuration of the sound-absorbing member 420 according to this modified example can be combined with the configurations of the sound-absorbing members 120, 220, and 320 according to the above modified examples 1 to 3.

[0061] [Modification 5] The structure of the sound-absorbing member 520 according to Modification 5 will be explained with reference to Figure 6B. In Figure 6B, only the surface layer 521 is shown, and the nonwoven fabric layer is omitted from the illustration. However, the sound-absorbing member 520 according to this modification has a nonwoven fabric layer having the same structure as the embodiment described above. Furthermore, the surface layer 521 in the sound-absorbing member 520 is formed using the same material as the surface layer 21 in the embodiment described above.

[0062] As shown in Figure 6B, when the sound-absorbing member 520 is viewed from above from the side of the space (the passenger compartment 1a, power unit room 1b, and rear cargo compartment 1c in Figure 1), the surface layer 521 has a plurality of through holes 521a, 521b, which consist of through holes 521b with a relatively large hole size and through holes 521a with a relatively small hole size. In other words, the surface layer 521 of the sound-absorbing member 520 has a first through hole 521a and a second through hole 521b which has a larger hole size (opening size) than the first through hole 521a.

[0063] The sound-absorbing member 520 according to this modified example differs from the above embodiment in that it has a surface layer 521 having a larger through-hole 521b and a smaller through-hole 521a, rather than having only one type of through-hole of the same size. However, the other configurations are the same. Therefore, the sound-absorbing member 520 according to this modified example can obtain the same effects as the above embodiment.

[0064] Furthermore, in the sound-absorbing member 520 according to this modified example, it is preferable to arrange through holes 521b with a larger hole size in the areas where sound absorption is to be enhanced, in order to achieve high sound absorption.

[0065] Furthermore, the sound-absorbing member 520 is suitable for absorbing sound energy of multiple frequencies by using multiple sizes (two sizes in this modified example) for the through-holes 521a and 521b. That is, by arranging through-holes 521a and 521b with sizes corresponding to the wavelength of the incident sound energy at each location, sound energy can be effectively absorbed and dissipated.

[0066] In this modified example, the sound-absorbing member 520 has through holes 521a and 521b in the surface layer 521, but the size of the through holes is not limited to two sizes. For example, it can be three or more sizes.

[0067] Furthermore, the configuration of the sound-absorbing member 520 according to this modified example can be combined with the configurations of the sound-absorbing members 120, 220, 320, and 420 according to the above modified examples 1 to 4.

[0068] [Modification 6] The structure of the sound-absorbing member 620 according to Modification 6 will be explained with reference to Figure 7A. In Figure 7A, only the surface layer 621 is shown, and the nonwoven fabric layer is omitted from the illustration. However, the sound-absorbing member 620 according to this modification has a nonwoven fabric layer having the same structure as the embodiment described above. Furthermore, the surface layer 621 in the sound-absorbing member 620 is formed using the same material as the surface layer 21 in the embodiment described above.

[0069] As shown in Figure 7A, when the sound-absorbing member 620 is viewed from above from the side of the space (the passenger compartment 1a, power unit room 1b, and rear cargo compartment 1c in Figure 1), the through-holes 621a of the surface layer 621 have an oval (or elliptical) shape.

[0070] The sound-absorbing member 620 according to this modified example differs from the embodiment described above in that the shape of the through-hole 621a in the surface layer 621 is oval rather than circular, but the other configurations are the same. Therefore, the sound-absorbing member 620 according to this modified example can obtain the same effects as the embodiment described above.

[0071] As shown in Figure 7A, in this modified example, the sound-absorbing member 620 has oval-shaped holes in all the through-holes 621a provided in the surface layer 621, but it is not limited to this. For example, it may be configured so that circular through-holes and oval or elliptical through-holes are mixed together.

[0072] Furthermore, the configuration of the sound-absorbing member 620 according to this modified example can be combined with the configurations of the sound-absorbing members 120, 220, 320, 420, and 520 according to the above modified examples 1 to 5.

[0073] [Modification 7] The structure of the sound-absorbing member 720 according to Modification 7 will be explained with reference to Figure 7B. In Figure 7B, only the surface layer 721 is shown, and the nonwoven fabric layer is omitted from the illustration. However, the sound-absorbing member 720 according to this modification has a nonwoven fabric layer having the same structure as the embodiment described above. Furthermore, the surface layer 721 in the sound-absorbing member 720 is formed using the same material as the surface layer 21 in the embodiment described above.

[0074] As shown in Figure 7B, when the sound-absorbing member 720 is viewed from above from the side of the space (vehicle compartment 1a, power unit room 1b, and rear cargo compartment 1c in Figure 1), the through-holes 721a of the surface layer 721 have a polygonal shape (in this modified example, a hexagonal shape).

[0075] The sound-absorbing member 720 according to this modified example differs from the above embodiment in that the shape of the through-hole 721a in the surface layer 721 is polygonal rather than circular, but the other configurations are the same. Therefore, the sound-absorbing member 720 according to this modified example can obtain the same effects as the above embodiment.

[0076] As shown in Figure 7B, in the sound-absorbing member 720 according to this modified example, all the through-holes 721a in the surface layer 721 are polygonal in shape, but the invention is not limited to this. For example, in addition to the through-holes 721a having a polygonal shape, circular through-holes, oval-shaped or elliptical through-holes may also be present.

[0077] Furthermore, the configuration of the sound-absorbing member 720 according to this modified example can be combined with the configurations of the sound-absorbing members 120, 220, 320, 420, 520, and 620 according to the above modified examples 1 to 6.

[0078] [Modification 8] The structure of the sound-absorbing member 820 according to Modification 8 will be explained with reference to Figure 8.

[0079] As shown in Figure 8, the sound-absorbing member 820 according to this modified example differs from the above embodiment in that the thickness of the nonwoven fabric layer 822 is not uniform and has different portions 822a and 822b.

[0080] In this modified example, the sound-absorbing member 820 has a substantially uniform thickness in its surface layer 821.

[0081] In this modified example, the sound-absorbing member 820 has a surface layer 821 made of the same material as the surface layer 21 in the above embodiment, and has a plurality of through holes 821a distributed similarly to the surface layer 21. The nonwoven fabric layer 822 is made of a thermoplastic resin, similar to the nonwoven fabric layer 22 in the above embodiment, and is formed by thermoforming.

[0082] As shown in Figure 8, in the modified sound-absorbing member 820, the nonwoven fabric layer 822 has a thick portion 822a with a relatively greater thickness (thickness T1), a thin portion 822b with a relatively greater thickness (thickness T2), and a connecting portion 822c that smoothly connects the thick portion 822a and the thin portion 822b. Note that the connecting portion 822c in the nonwoven fabric layer 822 is not necessarily required, and depending on the location where it is to be installed, a step may be created at the boundary between the thick portion 822a and the thin portion 822b.

[0083] The sound-absorbing member 820 according to this modified example differs from the above embodiment in that the nonwoven fabric layer 822 has a thick portion 822a and a thin portion 822b, but the other configurations are the same. Therefore, the sound-absorbing member 820 according to this modified example can obtain the same effects as the above embodiment.

[0084] Furthermore, in the modified sound-absorbing member 820, a configuration is adopted in which the nonwoven fabric layer 822 has a thick portion 822a and a thin portion 822b, so that high sound absorption can be achieved while suppressing an increase in overall size and weight. That is, in the sound-absorbing member 820, if the thick portion 822a is placed in the area where sound absorption is to be enhanced, and the thin portion 822b is placed in the other areas, high sound absorption can be achieved while suppressing an increase in overall size (size in the thickness direction) and weight.

[0085] Furthermore, the configuration of the sound-absorbing member 820 according to this modified example can be combined with the configurations of the sound-absorbing members 120, 220, 320, 420, 520, 620, and 720 according to the above modified examples 1 to 7.

[0086] [Other Modifications] In the above embodiments and modifications 1 to 7, sound-absorbing members 20, 120, 220, 320, 420, 520, 620, 720, and 820 installed on the vehicle 1 were used as examples, but the application of the sound-absorbing members according to the present invention is not limited to vehicles. For example, they can also be installed on houses or outdoor walls.

[0087] Furthermore, in the above embodiments and modifications 1 to 7, the bottoms of the through holes 21a, 121a, 421a, 521a, 521b, 621a, 721a, and 821a in the epidermal layers 21, 121, 421, 521, 621, 721, and 821a are aligned with the surface of the nonwoven fabric layers 22, 122, 222, 322, and 822. However, in the present invention, it is also possible to adopt a configuration in which holes are provided in the nonwoven fabric layers so as to connect to the through holes in the epidermal layers.

[0088] [Summary] A sound-absorbing member according to one aspect of the present invention is a member that is placed in a portion facing a space and absorbs sound propagating through the space. The sound-absorbing member according to this aspect comprises a nonwoven fabric layer and a skin layer. The nonwoven fabric layer is made of a thermoplastic resin and is formed by thermoforming. The skin layer is laminated to the nonwoven fabric layer so as to face the space and is a layer having a plurality of through holes that penetrate in the thickness direction and are dispersed among each other.

[0089] The sound-absorbing member according to the above embodiment comprises a nonwoven fabric layer made of thermoplastic resin and formed by thermoforming, and a surface layer laminated on the nonwoven fabric layer and having a plurality of through holes. Therefore, when airborne sound is incident on the sound-absorbing member, some of it is reflected back into the space by the surface layer, but the remainder is transmitted to the nonwoven fabric layer through the through holes. The energy of the airborne sound (sound energy) that enters the nonwoven fabric layer is converted into thermal energy and dissipated by interference with the fibers of the nonwoven fabric layer.

[0090] Furthermore, in the sound-absorbing member according to the above embodiment, the nonwoven fabric layer is made of thermoplastic resin and formed by thermoforming, so the density can be set appropriately according to the installation location. That is, the nonwoven fabric layer formed by thermoforming can be made low in density by lowering the temperature during molding, thereby increasing the sound absorption of airborne sound. Conversely, if thermoforming is performed at a high temperature, the density can be increased, making it possible to prevent sound energy that has entered the nonwoven fabric layer from being radiated back into the space. Therefore, by adjusting the heating temperature when forming the nonwoven fabric layer, the properties can be appropriately adjusted according to the installation location.

[0091] Furthermore, the nonwoven fabric layer, which is made of thermoplastic resin and formed by thermoforming, can be processed into various shapes depending on the press mold used during thermoforming. Therefore, in the sound-absorbing member according to the above embodiment, it is possible to create a shape that suits the location where it is to be installed without joining multiple parts.

[0092] In the sound-absorbing member according to the above embodiment, the surface facing the space may be formed with an uneven shape.

[0093] In the sound-absorbing member according to the above embodiment, the surface facing the space is formed with an uneven shape. Therefore, airborne sound incident on the surface of the sound-absorbing member according to the above embodiment is canceled out by the sound waves colliding with each other due to the uneven surface. Thus, in the sound-absorbing member according to the above embodiment, higher sound absorption can be achieved not only by the absorption and dissipation of sound energy in the nonwoven fabric layer, but also by the cancellation of sound waves on the surface.

[0094] In the sound-absorbing member according to the above embodiment, the nonwoven fabric layer may have a thick portion that is relatively thick and a thin portion that is relatively thin.

[0095] In the sound-absorbing member according to the above embodiment, the nonwoven fabric layer has a thick portion and a thin portion. In a sound-absorbing member with such a configuration, the thick portion can be placed in areas where sound absorption is to be enhanced, and the thin portion can be placed in other areas. By adopting such a configuration, the sound-absorbing member according to the above embodiment can achieve high sound absorption while suppressing an increase in overall size and weight.

[0096] In the sound-absorbing member according to the above embodiment, the nonwoven fabric layer may be formed such that its density gradually increases from the side of the surface layer toward the opposite side in the thickness direction.

[0097] In the sound-absorbing member according to the above embodiment, the density of the nonwoven fabric layer is not uniform in the thickness direction, but is formed so that it gradually increases from the surface layer side toward the opposite side. Therefore, in a sound-absorbing member having a nonwoven fabric layer with the above configuration, the high-density portion of the nonwoven fabric layer opposite to the surface layer acts as a lid for sound energy, and sound energy that has entered the nonwoven fabric layer through the perforations of the surface layer can be contained within the nonwoven fabric layer. Thus, in the sound-absorbing member according to the above embodiment, sound energy that has entered the nonwoven fabric layer through the perforations of the surface layer is prevented from leaking out to the outside of the member, and thus has sound insulation properties in addition to sound absorption.

[0098] In the sound-absorbing member according to the above embodiment, the nonwoven fabric layer may have a plurality of laminated constituent layers. In this case, each of the plurality of constituent layers may be formed such that the density increases sequentially from the side of the surface layer to the opposite side in the thickness direction of the nonwoven fabric layer.

[0099] In the sound-absorbing member according to the above embodiment, the nonwoven fabric layer is composed of multiple laminated constituent layers. The density of each constituent layer is formed such that it increases sequentially from the surface layer side toward the opposite side. Therefore, in a sound-absorbing member having a nonwoven fabric layer with the above configuration, the constituent layer on the opposite side of the nonwoven fabric layer from the surface layer (the high-density constituent layer) acts as a lid for sound energy, trapping the sound energy that has entered the nonwoven fabric layer through the perforations of the surface layer. Thus, in the sound-absorbing member according to the above embodiment, the leakage of sound energy that has entered the nonwoven fabric layer through the perforations of the surface layer to the outside of the member is suppressed, and in addition to sound absorption, it also has sound insulation properties.

[0100] In the sound-absorbing member according to the above embodiment, the surface layer may have a region in which the through holes are relatively densely clustered and a region in which the through holes are relatively scattered, in a direction perpendicular to the thickness direction of the surface layer.

[0101] In the sound-absorbing member according to the above embodiment, the through-holes in the surface layer are not uniformly distributed, but rather have densely packed regions and scattered regions. In a sound-absorbing member having a surface layer with such a configuration, it is suitable for achieving high sound absorption if the regions with densely packed through-holes are placed in the areas where sound absorption is to be enhanced.

[0102] In the sound-absorbing member according to the above embodiment, the plurality of through holes in the surface layer may include through holes with a relatively large size and through holes with a relatively small size.

[0103] In the sound-absorbing member according to the above embodiment, the multiple through-holes in the surface layer do not all have the same hole size, but rather include through-holes with a larger hole size and through-holes with a smaller hole size. In a sound-absorbing member having a surface layer with such a configuration, it is suitable for achieving high sound absorption by arranging through-holes with a larger hole size in the areas where sound absorption is to be enhanced.

[0104] Furthermore, the sound-absorbing member according to the above embodiment is suitable for absorbing sound energy of multiple frequencies by using multiple sizes for the through-holes. That is, by arranging through-holes with sizes corresponding to the wavelength of the incident sound energy at each location, sound energy can be effectively absorbed and dissipated.

[0105] As described above, the sound-absorbing members according to each of the above embodiments have high sound absorption properties while suppressing increases in size and weight.

Claims

1. A sound-absorbing member that is placed on a portion facing a space and absorbs sound propagating through the space, comprising: a nonwoven fabric layer made of thermoplastic resin and formed by thermoforming; and a surface layer laminated to the nonwoven fabric layer so as to face the space, each having multiple through-holes that penetrate in the thickness direction and are dispersed among each other.

2. The sound-absorbing member according to claim 1, wherein the surface facing the space is formed in an uneven shape.

3. The sound-absorbing member according to claim 1, wherein the nonwoven fabric layer has a thick portion that is relatively thick and a thin portion that is relatively thin.

4. The sound-absorbing member according to any one of claims 1 to 3, wherein the nonwoven fabric layer is formed such that its density gradually increases from the side of the surface layer to the opposite side in the thickness direction.

5. The sound-absorbing member according to any one of claims 1 to 3, wherein the nonwoven fabric layer has a plurality of laminated constituent layers, and each of the plurality of constituent layers is formed such that the density increases sequentially from the side of the surface layer to the opposite side in the thickness direction of the nonwoven fabric layer.

6. The sound-absorbing member according to any one of claims 1 to 3, wherein the surface layer has, in a direction perpendicular to the thickness direction of the surface layer, a region in which the through holes are relatively densely clustered and a region in which the through holes are relatively scattered.

7. The sound-absorbing member according to any one of claims 1 to 3, wherein the plurality of through holes in the surface layer include through holes with a relatively large size and through holes with a relatively small size.

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