Sound-absorbing structure, automotive interior part, and automobile

Abstract

To provide a sound absorbing structure capable of adjusting a position of a sound absorption peak, a vehicle interior component, and a vehicle.SOLUTION: A sound absorbing structure includes a porous body sheet and a laminate, where front surfaces and rear surfaces of a plurality of individual grid plates made of resin or metal are alternately arranged, in this order. The porous body sheet is fixed to the grid plate at a region facing at least a portion of grid points of the grid plate. The laminate has a fitting part in which a protrusion part provided on the front surface of the grid plate and a recess part provided on the rear surface of the grid plate are fitted to each other and which is displaceable in a direction intersecting with a lamination direction of the laminate.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a sound-absorbing structure, an interior part for a vehicle, and a vehicle.

Background Art

[0002] There are many sound sources inside a vehicle. Since quietness from noise inside and outside the vehicle is required, various sound insulation and sound absorption measures are taken in vehicles. In particular, for parts that generate large sounds such as engines, transmissions, and drive systems (inherent sound sources), dedicated sound insulation covers with excellent sound absorption and shielding performance are used. Also, since the quieting of in-vehicle noise is directly linked to the value (luxury feeling) of the vehicle, the demand for low-noise parts in vehicles is very high. For example, even inside the passenger compartment of a vehicle, cavity resonance may be induced by engine vibration, intake and exhaust sounds, road surface stimuli, etc., which may cause problems such as stuffy sounds and road noise, and measures to reduce such noise are essential. So far, various sound-absorbing parts have been used for interior parts such as roof trims in vehicle interiors, but further performance improvement is required.

[0003] Various configurations have been proposed for the sound-absorbing structure used for sound-absorbing parts (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, through the study by the inventors, it has been found that even if the technique described in Patent Document 1 is used, sufficient sound absorption performance cannot be exhibited in the frequency range of 300 Hz or less. Therefore, an object of the present invention is to provide a means that enables high sound absorption performance to be exhibited in the frequency range of 300 Hz or less.

Means for Solving the Problems

[0006] The sound absorption structure according to the present invention has, in this order, a porous sheet and a laminate in which the front and back surfaces of a plurality of lattice plates made of resin or metal are alternately arranged. The porous sheet is fixed to the lattice plate at a portion facing at least a part of the lattice points of the lattice plate. The laminate has a convex portion provided on the front surface of one of the lattice plates and a concave portion provided on the back surface of the other lattice plate fitted together, and a fitting portion displaceable in a direction intersecting the lamination direction of the laminate.

Effects of the Invention

[0007] According to the present invention, when sound is incident on the porous sheet, a portion not fixed to the lattice plate of the porous sheet is displaced in the direction of sound incidence, generating vibrations that cancel out the low-frequency components of the sound. As a result, the sound absorption performance in the low-frequency range of particularly 300 Hz or less can be improved.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention is not limited only to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from the actual ratios. In this specification, "X to Y" indicating a range means "X or more and Y or less". Also, unless otherwise specified, measurements of operations and physical properties are performed under the conditions of room temperature (20 to 25 ° C) / relative humidity 40 to 50%. In this specification, "sound absorption" means reducing reflected sound or absorbing sound (acoustics).

[0010] <First Embodiment> [Configuration of Sound Absorption Structure] FIG. 1A is an exploded perspective view showing the configuration of the sound absorption structure 1 according to the first embodiment of the present invention, and FIG. 1B shows a cross-sectional configuration along the line B-B shown in FIG. 1A. The sound absorption structure 1 has a porous sheet 10 and a laminate 20 in this order from the sound-absorbing member side. The laminate 20 includes, for example, two lattice plates (lattice plates 20A and 20B). The arrow I in FIG. 1A represents the sound-absorbing member side, that is, the direction in which sound mainly enters. In the following description, the stacking direction of the porous sheet 10 and the laminate 20 may be referred to as the Z direction, and the directions intersecting this may be referred to as the X direction and the Y direction.

[0011] This sound absorption structure 1 is preferably lightweight. From this viewpoint, the density of the entire sound absorption structure 1 is preferably 3 1 g / cm or less, more preferably 3 0.5 g / cm or less, still more preferably 3 0.3 g / cm or less, and particularly preferably 3 0.2 g / cm or less. Also, the sound absorption structure 1 is preferably thin. From this viewpoint, the overall thickness of the sound absorption structure 1 is preferably 50 mm or less, more preferably 30 mm or less, and still more preferably 20 mm or less.

[0012] (Porous sheet) The porous sheet 10 has, for example, a rectangular planar (XY plane) shape. A plurality of communication holes are provided in the porous sheet 10. There is no particular limitation on the constituent material of the porous sheet 10, and known materials can be used. For example, fibrous bodies; resin foams; porous sheets made of metal, ceramic, glass, etc. can be mentioned. Among these, resin foams are preferable because they are lightweight.

[0013] The fibrous body is not particularly limited as long as it is an aggregate of fibers having voids on its surface and inside, and any non-woven fabric such as a woven fabric or felt can be used. Also, the fibrous body may be composed of organic fibers such as resin fibers or inorganic fibers such as glass fibers.

[0014] Examples of the resin foam include polyolefin foams such as polyurethane foam (hereinafter also referred to as urethane foam), polyethylene foam, and polypropylene foam; polystyrene foam; polyamide foam; polyester foams such as polyethylene terephthalate (PET) foam and polybutylene terephthalate (PBT); (meth)acrylic foam; phenolic foam; polyvinyl chloride foam; polyimide foam; silicone resin foam; urea resin foam; melamine resin foam; ethylene propylene diene rubber (EPDM) foam; styrene butadiene rubber (SBR) foam; nitrile butadiene rubber (NBR) foam; ethylene-vinyl acetate copolymer (EVA) foam; ethylene-acrylic acid copolymer foam; ethylene-ethyl acrylate copolymer (EEA) foam; and the like. Among them, polyurethane foam is preferable from the viewpoint of sound absorption performance. Note that any of a soft foam, a semi-rigid foam, and a rigid foam can be used as these foams.

[0015] The thickness of the porous sheet 10 is not particularly limited, but from the viewpoint of the sound absorption effect, it is preferably 1 mm to 100 mm, more preferably 5 mm to 50 mm. The density of the porous sheet 10 is also not particularly limited, but it is preferably 3 kg / m 3 ~150 kg / m 3 from the viewpoint of weight reduction.

[0016] (Laminated body) The laminated body 20 that supports the porous sheet 10 has, for example, a lattice plate 20A and a lattice plate 20B in this order from the porous sheet 10 side. The lattice plates 20A and 20B have, for example, the same shape as each other. Each of the lattice plates 20A and 20B has a front surface S1 and a back surface S2 on the side opposite to the front surface S1. In the laminated body 20, the front surface S1 and the back surface S2 are alternately arranged in the lamination direction (Z direction). For example, the back surfaces S2 of the lattice plates 20A and 20B are arranged on the porous sheet 10 side (FIG. 1B). The front surface S1 and the back surface S2 are provided parallel to the porous sheet 10 and are planes parallel to the XY plane. The front surface S1 and the back surface S2 have, for example, a rectangular shape.

[0017] Figures 2A and 2B show the configurations of the front surface S1 and the back surface S2 of the grid plates 20A and 20B. Figure 2A shows the configuration of the front surface S1, and Figure 2B shows the configuration of the back surface S2. Each of the grid plates 20A and 20B has, for example, a plurality of grid points 21 and a plurality of openings 22. The openings 22 are arranged in a matrix along the X direction and the Y direction, and are holes provided so as to penetrate from the front surface S1 to the back surface S2. The openings 22 have, for example, a square planar shape. The planar shape of the openings 22 may be other shapes such as a rectangle, a hexagon, or a triangle.

[0018] It is more preferable that the plurality of openings 22 provided in each of the grid plates 20A and 20B have the same planar shape as each other and are regularly arranged on the grid plates 20A and 20B. By adopting such a configuration, the manufacturing is easy, and due to the presence of a large number of openings 22 having the same shape, the sound absorption performance for sound waves in a desired frequency range can be specifically exhibited. At this time, the ratio of the area of the openings 22 to the area of the grid plates 20A and 20B is not particularly limited.

[0019] The size of the openings 22 is not particularly limited either. For example, when the planar shape of the openings 22 is square, the length of one side thereof is, for example, 1 mm to 50 mm, preferably 2 mm to 40 mm, and more preferably 3 mm to 39 mm. By doing so, the sound absorption characteristics in the low frequency band, particularly in the frequency range of 300 Hz or less, can be improved.

[0020] Also, the area per opening 22 (opening area) is not particularly limited, but from the viewpoint of obtaining high sound absorption characteristics, it is preferably 10 mm 2 ~1500 mm 2 . When the opening area is 10 mm 2 or more, the sound absorption rate in the frequency range of 200 Hz or less can be improved. Also, when the opening area is 1500 mm 2 or less, the sound absorption rate in the frequency range of 200 to 300 Hz can be improved.

[0021] The lattice point 21 is an intersection portion of a plate portion extending in the X direction and a plate portion extending in the Y direction, and is present, for example, at the center of the four openings 22. On the lattice plate 20A disposed on the porous sheet 10 side of the laminate 20, a fixing member (fixing member 21a in FIG. 3 described later) for fixing the porous sheet 10 is provided at at least a part of the lattice point 21. In other words, the porous sheet 10 is fixed to the lattice plate 20A at a portion facing at least a part of the lattice point 21 of the lattice plate 20A, and the remaining portion is capable of vibrating in the direction in which sound is incident. Although details will be described later, this enables plate vibration to occur in the porous sheet 10 and improves the sound absorption performance in the low frequency band.

[0022] FIG. 3 shows a cross-sectional (XZ cross-sectional) structure in the vicinity of the lattice point 21 of the lattice plate 20A. A fixing member 21a is provided at the lattice point 21 of the lattice plate 20A, and the porous sheet 10 is fixed (supported) to the back surface S2 of the lattice plate 20A (laminate 20) by this fixing member 21a. The fixing member 21a may be provided over the entire lattice point 21, or may be provided at a part of the lattice point 21. The fixing member 21a may be provided at all the lattice points 21 of the lattice plate 20A, or may be provided at some of the lattice points 21. The fixing member 21a may be provided at a portion other than the lattice point 21 of the lattice plate 20A. The fixing member 21a is constituted by, for example, a double-sided tape or an adhesive. The fixing member 21a may be a fixture such as a screw and a bolt.

[0023] The lattice plates 20A and 20B have a plurality of convex portions 23 on their front surface S1 and a plurality of concave portions 24 on their back surface S2 (FIGS. 1A, 2A, and 2B). The convex portion 23 on the front surface S1 and the concave portion 24 on the back surface S2 are configured to be fitted to each other.

[0024] FIG. 4 shows a state in which the lattice plates 20A and 20B overlap, that is, the planar (XY plane) configuration of the laminate 20. The laminate 20 has a fitting portion 25 in which the convex portion 23 provided on the front surface S1 of the lattice plate 20A and the concave portion 24 provided on the back surface S2 of the lattice plate 20B are fitted, and the front surface S1 of the lattice plate 20A and the back surface S2 of the lattice plate 20B are provided in close contact with each other. In the present embodiment, this fitting portion 25 is configured to be displaceable in a direction intersecting the lamination direction of the laminate 20, specifically, within the XY plane perpendicular to the lamination direction. In other words, the position of the fitting portion 25 in the XY plane can be changed.

[0025] In the laminate 20 having this fitting portion 25, a region where the opening 22 of the lattice plate 20A and the opening 22 of the lattice plate 20B overlap (hereinafter referred to as the laminate opening 22L) is formed. Although details will be described later, in the sound absorption structure 1, by changing the position of the fitting portion 25, the size of the laminate opening 22L changes, and it becomes possible to adjust the sound absorption characteristics of the sound absorption structure 1.

[0026] The convex portion 23 has, for example, a cylindrical shape (FIGS. 1A and 1B). The concave portion 24 has a shape corresponding to this convex portion 23. Specifically, the concave portion 24 has a planar shape of a circle having approximately the same size as the planar shape of the convex portion 23 and a depth approximately the same as the height of the convex portion 23. This concave portion 24 is provided, for example, at a predetermined depth from the back surface S2. The convex portion 23 may have a prismatic shape such as a quadrangular prism, and the concave portion 24 may have a planar shape and a depth corresponding to this prismatic shape. The convex portion 23 having a cylindrical shape or a prismatic shape is easy to manufacture, and it is possible to suppress the manufacturing cost.

[0027] The number of convex portions 23 on the front surface S1 is preferably less than the number of concave portions 24 on the back surface S2 (Figs. 2A and 2B), and the convex portions 23 on the front surface S1 are arranged at positions overlapping the concave portions 24 on the back surface S2 (Fig. 1B). Thereby, all the convex portions 23 of the grid plate 20A are fitted into the concave portions 24 of the grid plate 20B, so that a gap is less likely to occur between the grid plate 20A and the grid plate 20B, and the grid plate 20A and the grid plate 20B can be brought into close contact with each other. For example, two convex portions 23 are provided on the front surface S1, and 36 concave portions 24 are provided on the back surface S2 (Figs. 2A and 2B). In the grid plates 20A and 20B, it is preferable that the back surface S2 is arranged on the porous body sheet 10 side. Thereby, a gap is less likely to occur between the grid plate 20A and the porous body sheet 10.

[0028] Preferably, a plurality of convex portions 23 are provided on the front surface S1. Thereby, a plurality of fitting portions 25 are formed between the grid plate 20A and the grid plate 20B, so that movements such as rotation of the grid plates 20A and 20B are suppressed, and the occurrence of displacement can be prevented. For example, two fitting portions 25 are formed between the grid plate 20A and the grid plate 20B (Fig. 4).

[0029] The plurality of convex portions 23 are preferably provided at positions separated from each other. For example, at least a part of the plurality of convex portions 23 is preferably arranged side by side in a direction intersecting the side direction of the outer shape of the front surface S1. For example, two convex portions 23 are arranged side by side in a direction parallel to the diagonal line of the quadrangular front surface S1 and are provided at the diagonal corner portions (Figs. 2A and 2B). Thereby, two fitting portions 25 arranged in a direction parallel to the diagonal line of the grid plates 20A and 20B are formed, so that sagging or dropping of the grid plates 20A and 20B due to their own weight can be suppressed.

[0030] The plurality of recesses 24 are provided, for example, at each of the four corner portions of the rectangular back surface S2. For example, 36 recesses 24 are provided nine by nine at each of the four corner portions of the rectangular back surface S2. The nine recesses 24 provided at the corner portion of this back surface S2 are arranged side by side at a predetermined interval in the X direction and the Y direction. In this way, by arranging a plurality of recesses 24 at a predetermined interval in a part of the back surface S2, it becomes easier to adjust the position of the fitting portion 25.

[0031] Here, by changing the recess 24 of the grid plate 20B into which the convex portion 23 of the grid plate 20A is inserted, the position of the fitting portion 25 in the XY plane can be changed. As a result, the size of the laminate opening 22L changes, and it becomes possible to adjust the sound absorption characteristics of the sound absorption structure 1. In the present embodiment, the size of the laminate opening 22L can be changed between 25% and 100% of the size of the opening 22.

[0032] The grid plates 20A and 20B are made of resin or metal. This makes it easy to adjust the Young's modulus of the grid plates 20A and 20B to a desired value, and it becomes possible to improve the sound absorption characteristics of the sound absorption structure 1.

[0033] The resin material constituting the grid plates 20A and 20B is not particularly limited, but conventionally known thermoplastic resins or thermosetting resins can be used. The grid plates 20A and 20B are preferably made of the same material. This makes it easy to manufacture the laminate 20 and can suppress the manufacturing cost.

[0034] Examples of the thermoplastic resin include polyolefin resins such as polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polypropylene, polyvinyl chloride resin, acrylic resin, methacrylic resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, ethylene-vinyl acetate resin, styrene-butadiene resin, etc. Examples of the thermosetting resin that can be used include urethane resin, melamine resin, thermosetting acrylic resin, urea resin, phenol resin, resorcinol resin, alkyl resorcinol resin, epoxy resin, thermosetting polyester, etc. In addition, resin precursors such as urethane resin prepolymer, urea resin prepolymer (initial condensate), phenol resin prepolymer (initial condensate), diallyl phthalate prepolymer, acrylic oligomer, polyvalent isocyanate, methacrylic ester monomer, diallyl phthalate monomer, etc., such as prepolymers, oligomers, and monomers that generate these resins, may be used. Among them, from the viewpoint of easy molding, thermoplastic resins are preferably used. In particular, polyolefin resins are preferred because they are lightweight, have excellent durability, and are inexpensive.

[0035] Examples of the metal material include copper, aluminum, titanium, magnesium, tungsten, iron, chromium, and alloys thereof. It is also possible to use SUS (stainless steel) or the like as the metal material.

[0036] The thicknesses of the grating plates 20A and 20B are not particularly limited. For example, they are 0.1 mm to 10 mm, preferably 0.5 mm to 5 mm. When it is 0.1 mm or more, the effects of the present invention can be more easily obtained. Also, when it is 10 mm or less, it is preferable from the viewpoint of weight reduction. The grating plates 20A and 20B, for example, have the same thickness as each other.

[0037] [Function and Effect of Sound Absorbing Structure] In the sound absorption structure 1 according to this embodiment, the porous sheet 10 is fixed to the lattice plate 20A (laminated body 20) at a portion facing at least a part of the lattice points 21 of the lattice plate 20A, and the remaining portion is capable of vibrating in the direction in which sound is incident. As a result, when sound is incident on the porous sheet 10, a plate vibration occurs in which a portion of the porous sheet 10 that is not fixed to the lattice plate 20A is displaced in the direction in which the sound is incident, canceling out the low-frequency components of the sound. As a result, since the low-frequency components of the sound are attenuated, the sound absorption structure 1 can improve the sound absorption performance in the low-frequency band. In the sound absorption structure 1, particularly, high sound absorption characteristics can be exhibited in a frequency band of 300 Hz or less (for example, 50 Hz to 300 Hz or 100 Hz to 300 Hz). Therefore, even if the porous sheet 10 and the lattice plates 20A and 20B are laminated in the reverse order from the sound-absorbing member side compared to this embodiment, it is considered that the same sound absorption effect as described above is exhibited.

[0038] In such a sound absorption structure that utilizes the plate vibration of the porous sheet, the inventors have found that the sound absorption characteristics change by changing the size of the opening of the lattice plate.

[0039] FIG. 5 is a diagram showing the relationship between the size of the opening of the lattice plate and the sound absorption characteristics. The vertical axis in FIG. 5 is the normal incidence sound absorption rate, and the horizontal axis in FIG. 5 is the frequency (Hz). The measurement of the normal incidence sound absorption rate was performed in accordance with JIS A 1405-2 (Measurement of sound absorption rate and impedance by acoustic tube - Part 2: Transfer function method). In FIG. 5, H1, H1 / 2, H1 / 4, and H2 each represent the sound absorption characteristics of a sound absorption structure having a porous sheet and a lattice plate, and the size of the opening of the lattice plate is different from each other. The openings of H1, H1 / 2, H1 / 4, and H2 are squares with a side length of 15 mm, a side length of 7.5 mm, a side length of 3.75 mm, and a side length of 30 mm, respectively. In the sound absorption structures indicated by H1, H1 / 2, H1 / 4, and H2, the lattice plate is made of polypropylene (PP). In FIG. 5, HM represents the sound absorption characteristics of a sound absorption structure having a porous sheet and a lattice plate made of SUS. The opening of this lattice plate is a square with a side length of 15 mm.

[0040] As shown in Fig. 5, in a sound absorption structure having a porous sheet and a lattice plate, the frequency band having a high sound absorption rate, that is, the position of the sound absorption peak changes according to the size of the opening of the lattice plate.

[0041] In the sound absorption structure 1 according to the present embodiment, by changing the concave portion 24 of the lattice plate 20B into which the convex portion 23 of the lattice plate 20A is inserted, the position of the fitting portion 25 in the XY plane can be changed. Thereby, the size of the laminate opening 22L changes, and the position of the sound absorption peak can be adjusted.

[0042] For example, in the sound absorption material disclosed in Patent Document 1, since the position of the sound absorption peak cannot be adjusted, in order to improve the sound absorption rate in a specific frequency band such as a low frequency band, an overall improvement in sound absorption performance is required. For example, it is possible to improve the overall sound absorption performance by increasing the thickness of the porous sheet or providing an air layer, but these methods are accompanied by an increase in the mass and volume of the sound absorption material.

[0043] Also, it is possible to selectively use lattice plates having openings of various sizes according to the position of the target sound absorption peak, but with this method, it becomes difficult to finely adjust the sound absorption peak. In addition, since lattice plates with various opening sizes are manufactured, there is a possibility of a problem with manufacturing costs.

[0044] On the other hand, in the sound absorption structure 1, as described above, the position of the sound absorption peak can be adjusted by changing the position of the fitting portion 25 of the lattice plates 20A and 20B. That is, the sound absorption rate in a specific frequency band can be improved. Therefore, it is possible to adjust the position of the sound absorption peak with a lightweight and thin configuration without accompanying an increase in mass and volume.

[0045] Also, by changing the position of the fitting portion 25, the size of the laminate opening 22L changes, so that fine adjustment (tuning) of the sound absorption peak becomes easy in mass production development. Furthermore, since parts can be shared in mass production development, it is possible to suppress manufacturing costs such as mold costs.

[0046] Further, in the sound absorption structure 1, a fitting portion 25 is formed by the convex portion 23 and the concave portion 24. Therefore, the fitting portion 25 that can be displaced with a simple configuration can be formed.

[0047] In addition, in the sound absorption structure 1, the lattice plates 20A and 20B have the same shape and are made of the same material. Therefore, mass production becomes easy, and while suppressing the manufacturing cost, it becomes possible to adjust the position of the sound absorption peak.

[0048] As described above, in the sound absorption structure 1, the laminate 20 has a fitting portion 25 that can be displaced in a direction intersecting the lamination direction. In other words, the position of the fitting portion 25 can be changed in a direction intersecting the lamination direction. As a result, the size of the laminate opening 22L formed by the lattice plates 20A and 20B changes, and the sound absorption characteristics change. Therefore, it becomes possible to adjust the position of the sound absorption peak.

[0049] Hereinafter, a modification of the lattice plates 20A and 20B (laminate 20) described in the above embodiment and other embodiments of the sound absorption structure will be described. In the following, in order to avoid duplication of description, detailed description of configurations similar to those of the sound absorption structure 1 described in the above embodiment will be omitted.

[0050] <Modification 1> FIGS. 6A and 6B show the planar configuration of the lattice plates 20A and 20B according to Modification 1, FIG. 7 shows the cross-sectional configuration along the line VII-VII shown in FIG. 6A, and FIG. 8 shows the state in which the lattice plates 20A and 20B overlap, that is, the planar configuration of the laminate 20. FIG. 6A shows the surface S1 of the lattice plates 20A and 20B, and FIG. 6B shows the configuration of the back surface S2. FIGS. 6A and 6B correspond to FIGS. 2A and 2B described in the above embodiment, and FIG. 8 corresponds to FIG. 4 described in the above embodiment.

[0051] The convex portions 23 on the surface S1 are provided, for example, at the central portion and the corner portions of the square-shaped surface S1 (FIG. 6A). This convex portion 23 has, for example, a cylindrical shape as described in the above embodiment (see FIG. 1A).

[0052] The concave portions 24 on the back surface S2 are provided at the central portion and the corner portions of the square-shaped back surface S2 (FIG. 6B). The concave portion 24 (the first concave portion) provided at the central portion has a circular planar shape. This concave portion 24 is disposed at a position overlapping with the convex portion 23 provided at the central portion of the surface S1. The concave portion 24 (the second concave portion) provided at the corner portion has an arc-shaped planar shape. This arc-shaped concave portion 24 constitutes a part of the circumference of a circle centered on the concave portion 24 provided at the central portion. The convex portion 23 is disposed at a position facing a part of this arc-shaped concave portion 24 (FIG. 7).

[0053] In the laminate 20, by inserting the two convex portions 23 provided on the surface S1 of the lattice plate 20A into the two concave portions 24 provided on the back surface S2 of the lattice plate 20B, two fitting portions 25 are formed (FIG. 8). In the laminate 20 having such lattice plates 20A and 20B, by rotating the lattice plate 20A along the arc-shaped concave portion 24, the position of one fitting portion 25 (the fitting portion 25 provided at the corner portion of the lattice plates 20A and 20B) in the XY plane can be changed. Thereby, the size of the laminate opening 22L changes continuously, and the position of the sound absorption peak can be adjusted. In this modified example, the size of the laminate opening 22L can be changed between 50% and 100% of the size of the opening 22.

[0054] Thus, also in the sound absorption structure 1 having the lattice plates 20A and 20B according to the first modified example, a fitting portion 25 that is displaceable in a direction intersecting the lamination direction is formed in the same manner as described in the above embodiment. Therefore, it becomes possible to adjust the position of the sound absorption peak.

[0055] <Second Modified Example> FIG. 9 shows a partial cross-sectional configuration of the lattice plates 20A and 20B according to Modification 2. As such, the recess 24 provided on the back surface S2 of the lattice plates 20A and 20B may be configured by a hole penetrating from the back surface S2 to the front surface S1. At this time, the recess 24 is provided at a position shifted from the convex portion 23 on the front surface S1.

[0056] The sound absorption structure 1 having the lattice plates 20A and 20B according to Modification 2 also forms a fitting portion 25 that is displaceable in a direction intersecting the stacking direction, as described in the above embodiment. Therefore, it is possible to adjust the position of the sound absorption peak.

[0057] <Second Embodiment> FIG. 10 is an exploded perspective view showing the configuration of the sound absorption structure 2 according to the second embodiment of the present invention. FIG. 10 corresponds to FIG. 1A described in the first embodiment above. The sound absorption structure 2 has a porous body sheet 10, a laminate 20, and a film 30 in this order from the sound-absorbing member side. That is, the sound absorption structure 2 is different from the sound absorption structure 1 of the first embodiment in that it has a film 30. Except for this point, the sound absorption structure 2 has the same configuration as the sound absorption structure 1 and exhibits the same effects.

[0058] The film 30 is provided to face the porous body sheet 10 with the laminate 20 in between. This film 30 is joined to the lattice plate 20B. Preferably, the film 30 is arranged so as to close the laminate opening 22L of the laminate 20. The film 30 is preferably joined to the lattice plate 20B at a portion excluding the outer periphery of the lattice plate 20B.

[0059] There is no particular limitation on the constituent material of the film 30, but those that are lightweight and have rigidity are preferred. For example, polyolefin resins such as polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polypropylene, polyethylene terephthalate resin, polyvinyl chloride resin, polystyrene resin, etc. can be preferably used.

[0060] The thickness of the film 30 is not particularly limited, but for example, it is 1 μm to 100 μm, preferably 2 μm to 50 μm. When it is within the above range, the effects of the present invention can be more easily obtained. Also, the size of the film 30 is not particularly limited, but it is preferably one that can cover the entire surface S1 of the grid plate 20B.

[0061] The porous sheet 10 of the sound absorption structure 2 has the same configuration as the porous sheet 10 described in the sound absorption structure 1.

[0062] The grid plates 20A and 20B of the sound absorption structure 2 have the same configuration as the grid plates 20A and 20B described in the sound absorption structure 1, but the opening area of the opening 22 is 10 to 225 mm 2 and more preferably so. When the opening area is 10 mm 2 or more, the sound absorption rate in the frequency range of 200 Hz or less can be improved. Also, when the opening area is 225 mm 2 or less, the sound absorption rate in the frequency range of 200 to 300 Hz can be improved.

[0063] Thus, in the sound absorption structure 2 having the film 30, in addition to the plate vibration of the porous sheet 10, the film 30 vibrates, and the sound absorption characteristics of the sound absorption structure 2 change. For example, in the sound absorption structure 2, the sound absorption rate in the frequency range of 200 to 700 Hz can be increased, and the sound absorption performance in the frequency range can be enhanced.

[0064] FIG. 11 is a diagram showing the sound absorption characteristics of a sound absorption structure having a film. The vertical axis in FIG. 11 is the normal incidence sound absorption rate, and the horizontal axis in FIG. 11 is the frequency (Hz). The measurement of the normal incidence sound absorption rate was performed in accordance with JIS A 1405-2 (Measurement of sound absorption rate and impedance by acoustic tube - Part 2: Transfer function method). In FIG. 11, HF1, HF1 / 2, HF1 / 4, and HF2.5 represent the sound absorption characteristics of sound absorption structures having a porous body sheet, a lattice plate, and a film, respectively, and the sizes of the openings of the lattice plates are different from each other. The openings of HF1, HF1 / 2, HF1 / 4, and HF2.5 are squares with a side length of 15 mm, a side length of 7.5 mm, a side length of 3.75 mm, and a side length of 37 mm, respectively. In the sound absorption structures indicated by HF1, HF1 / 2, HF1 / 4, and HF2.5, the lattice plate is made of polypropylene (PP).

[0065] By comparing FIG. 5 and FIG. 11, it can be confirmed that the sound absorption characteristics of the sound absorption structure change by providing a film in addition to the porous body sheet and the lattice plate. Also, in the sound absorption structure having a film, it can be confirmed that the position of the sound absorption peak changes according to the size of the opening of the lattice plate.

[0066] Also in the sound absorption structure 2 having such a film 30, a fitting portion 25 that can be displaced in a direction intersecting the lamination direction can be formed in the same manner as described in the first embodiment. Therefore, it becomes possible to adjust the position of the sound absorption peak.

[0067] <Application Example> The sound absorption structures 1 and 2 described in the above first embodiment and second embodiment can be suitably used for applications that absorb noise from various sound sources. Among them, the sound absorption structures 1 and 2 can be configured to be very lightweight. Since the sound absorption structures 1 and 2 can be thus lightweight, it is preferable that they be mounted on a vehicle and used. As an example of the application site, in the vehicle interior, dash insulators, dash panels, floor carpets, spacers, door trims, sound absorption structures inside door trims, sound absorption structures inside compartments, instrument panels, in-vehicle center boxes, in-vehicle upper boxes, air conditioner housings, roof trims, sound absorption structures inside roof trims, sun visors, rear seat air conditioners ducts, cooling ducts of battery cooling systems in battery-powered vehicles, cooling fans, center console trims, sound absorption structures inside consoles, parcel trims, parcel panels, seat headrests, seat backs of front seats, seat backs of rear seats, etc. can be applied. Further, in the trunk, it can be applied to trunk floor trims, trunk boards, trunk side trims, sound absorption structures inside trims, drafter covers, etc. Also, it can be applied inside the vehicle skeleton and between panels, for example, it can be applied to pillar trims and fenders. Among them, since it has excellent sound absorption performance in the frequency range of 300 Hz or less, is lightweight, and can reduce the overall thickness, it is preferably used for automotive interior parts.

[0068] The sound absorption structure of the present invention has been described above using embodiments and modification examples. However, within the scope of the technical idea of the present invention, those skilled in the art can appropriately add, modify, and omit. For example, the configurations, shapes, sizes, etc. of each part of the sound absorption structure described in the above embodiments and modification examples are examples, and other configurations, shapes, sizes, etc. may be used.

[0069] For example, in the above embodiments, etc., an example in which the laminate 20 is composed of two lattice plates (lattice plates 20A, 20B) has been described, but the laminate 20 may include three or more lattice plates. Also, the laminate 20 may include members other than lattice plates.

[0070] In addition, in the above-described embodiments and the like, an example in which two fitting portions 25 are formed between the lattice plates 20A and 20B has been described. However, one fitting portion 25 may be formed between the lattice plates 20A and 20B, or three or more fitting portions 25 may be formed.

Explanation of Reference Numerals

[0071] 1, 2 Sound absorption structure 10 Porous sheet 20 Laminate 20A, 20B Lattice plate 21 Lattice point 21a Fixing member 22 Opening 22L Laminate opening 23 Protrusion 24 Recess 25 Fitting portion 30 Film.

Claims

1. It has a porous sheet and a laminate in which the front and back surfaces of a plurality of lattice plates made of resin or metal are alternately arranged, The porous sheet is fixed to the lattice plate at a portion facing at least a part of the lattice points of the lattice plate, The laminate has a fitting portion in which a convex portion provided on the front surface of one of the lattice plates and a concave portion provided on the back surface of the other lattice plate are fitted and which is displaceable in a direction intersecting the stacking direction of the laminate, and is a sound absorption structure.

2. The sound absorption structure according to claim 1, wherein a plurality of the fitting portions are provided between one of the lattice plates and the other lattice plate.

3. The sound absorption structure according to claim 2, wherein at least a part of the plurality of fitting portions are arranged side by side in a direction intersecting the side direction of the outer shape of the lattice plate.

4. Each of the plurality of lattice plates has a rectangular planar shape, The sound absorption structure according to claim 3, wherein at least a part of the plurality of fitting portions are arranged side by side in a direction parallel to the diagonal line of the rectangle.

5. The sound absorption structure according to claim 2, wherein the concave portion includes a first concave portion and a second concave portion having an arc shape of a circle centered on the first concave portion.

6. The sound absorption structure according to any one of claims 1 to 4, wherein the number of the concave portions provided on the back surface of each of the plurality of lattice plates is larger than the number of the convex portions provided on the front surface of each of the plurality of lattice plates.

7. The sound absorption structure according to any one of claims 1 to 6, wherein the concave portion is a hole penetrating from the back surface to the front surface of the lattice plate.

8. The sound absorption structure according to any one of claims 1 to 7, further having a film facing the porous sheet with the laminate therebetween.

9. In the laminate, the back surfaces of each of the plurality of lattice plates are arranged on the porous sheet side, and the sound absorption structure according to any one of claims 1 to 8.

10. The sound absorption structure according to any one of claims 1 to 9, wherein the convex portion has a cylindrical shape or a prismatic shape.

11. An interior part for an automobile having the sound absorption structure according to any one of claims 1 to 10.

12. An automobile having the sound absorption structure according to any one of claims 1 to 10, or the interior part according to claim 11.

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