Sound absorption material and railway vehicle

Abstract

To provide a sound absorption material and railway vehicle capable of effectively absorbing low-frequency noise within a passenger compartment of a railway vehicle.SOLUTION: One embodiment of the present invention comprises: a first porous layer 60 formed using a non-combustible porous material and attached to a roof structure 4; an elastic layer 61 formed using an elastic material and laminated on the inner side of the first porous layer 60; and a second porous layer 62 formed using a non-combustible porous material and laminated on the inner side of the elastic layer 61. Because density of the second porous layer 62 is lower than that of the first porous layer 60, low-frequency sound entering from the vehicle interior side to the sound-absorbing material is more readily transmitted through the second porous layer 62 to the elastic layer 61. This enables effective absorption of the low-frequency sound through the vibration (deformation) of the elastic layer 61 and the first porous layer 60.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sound-absorbing material and a railway vehicle, and more particularly to a sound-absorbing material and a railway vehicle that can effectively absorb low-frequency noise inside a railway vehicle. [Background technology]

[0002] For example, Patent Document 1 describes a sound-absorbing material 1 including a spring portion 20 (first porous layer) that is placed on an installation surface W of equipment or the like, a first mass portion 11 (elastic layer) that is overlaid on the spring portion 20, and a second mass portion 12 (second porous layer) that is overlaid on the first mass portion 11. The spring portion 20 and the second mass portion 12 are formed using glass wool, and the first mass portion 11 is formed using rubber, a resin film, a metal material, or a combination thereof (a laminate of rubber, resin, or metal films). In this sound-absorbing material 1, the mass portions 11, 12 and the spring portion 20 resonate with noise (sound waves) that enter the second mass portion 12 from a sound source, and this resonance absorbs the noise.

[0003] The greater the mass of this type of sound-absorbing material, the higher the sound-absorbing performance. On the other hand, when installing sound-absorbing materials on railway vehicles, it is desirable for the sound-absorbing material to be lightweight due to its intended use and structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-020003 (for example, paragraphs 0037, 0038, 0051, and FIG. 12) Summary of the Invention [Problem to be solved by the invention]

[0005] Noise inside a railway vehicle is mainly noise with a frequency of 400 Hz or less (hereinafter referred to as "low-frequency noise"). However, it has been found that the above-mentioned conventional structure in which the sound-absorbing material 1 is attached to the inner wall of a railway vehicle (which was not publicly known at the time of filing this application) is unable to sufficiently absorb such low-frequency noise. This is due to the density of the spring portion 20 (32 kg / m 3 ) compared to the second mass part 12 (96 kg / m 3 ) has a high density, low frequency sound is reflected by the second mass portion 12, and the absorption of low frequency sound by the first mass portion 11 and the spring portion 20 is insufficient.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a sound-absorbing material and a railway vehicle that can effectively absorb low-frequency noise inside a railway vehicle. [Means for solving the problem]

[0007] To achieve this objective, the sound-absorbing material of the present invention is attached to the inner wall of a railway vehicle body and comprises a first porous layer formed using a non-flammable porous material, an elastic layer laminated on the inner surface of the first porous layer and formed using an elastic material, and a second porous layer laminated on the inner surface of the elastic layer and formed using a non-flammable porous material, wherein the density of the second porous layer is lower than that of the first porous layer.

[0008] The railway vehicle of the present invention has the above-described sound-absorbing material of the present invention attached to the inner wall of the car body. [Effects of the Invention]

[0009] The sound-absorbing material of claim 1 and the railway vehicle of claim 6 have the following advantages: The density of the second porous layer laminated on the inner surface side (i.e., the passenger compartment side) of the elastic layer is lower than that of the first porous layer, so that low-frequency sound incident on the sound-absorbing material from inside the vehicle is easily transmitted to the elastic layer through the second porous layer. This has the effect of effectively absorbing low-frequency sound through the vibration (deformation) of the elastic layer and the first porous layer.

[0010] The sound-absorbing material of claim 2 achieves the following effect in addition to the effect achieved by the sound-absorbing material of claim 1. Since the elastic layer is composed of a first elastic film and a second elastic film that is bonded to the first elastic film and has a different hardness from the first elastic film, the sound-absorbing characteristics of the elastic layer as a whole can be adjusted by changing the hardness of the first elastic film or the second elastic film. This has the effect of making it easy to form an elastic body with desired sound-absorbing characteristics.

[0011] The sound-absorbing material of claim 3 achieves the following effect in addition to the effect achieved by the sound-absorbing material of claim 1. Because the first porous layer is formed using glass wool and the second porous layer is formed using carbon fiber, there is an effect that the sound-absorbing material can be made lighter while ensuring its non-combustibility, compared to when the second porous layer is formed using glass wool, for example.

[0012] The sound-absorbing material of claim 4 achieves the following effect in addition to the effect achieved by the sound-absorbing material of claim 3. Because the second porous layer is thinner than the first porous layer, it is possible to ensure the thickness of the first porous layer required for absorbing low-frequency sound while preventing the overall thickness of the sound-absorbing material from increasing. This has the effect of achieving both a spacious passenger compartment and improved sound absorption of low-frequency sound by the first porous layer.

[0013] The sound-absorbing material of claim 5 has the following effect in addition to the effect of the sound-absorbing material of claim 1. Because the first porous layer, the elastic layer, and the second porous layer are not bonded to one another, it is not necessary to use adhesive when forming the sound-absorbing material. This has the effect of making it easier to ensure the non-combustibility of the sound-absorbing material. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a railway vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the railway vehicle at part II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First, the overall configuration of a railway vehicle 1 will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the railway vehicle 1 according to one embodiment of the present invention. Fig. 1 is a partial cross-sectional view of the railway vehicle 1 cut along a plane perpendicular to the rail direction (longitudinal direction of the car body). In the following description, the direction of the sleepers (width direction of the car body) perpendicular to the rail direction will be referred to as the left-right direction.

[0016] As shown in Fig. 1, a railway vehicle 1 includes an underframe 2 that extends in the fore-and-aft direction of the car body (a direction perpendicular to the plane of the paper in Fig. 1). A pair of side structures 3 rise upward from both left and right ends of the underframe 2, and the upper ends of the pair of left and right side structures 3 are connected to each other by a roof structure 4. Although not shown in the figure, end structures rise from both front-and-aft ends of the underframe 2, and the space surrounded by the underframe 2, side structures 3, roof structure 4, and end structure forms a passenger compartment 5.

[0017] Noise in the passenger compartment 5 caused by vibrations while the railway vehicle 1 is running, etc., is mainly sound with a frequency of 400 Hz or less (hereinafter referred to as "low-frequency sound"). This low-frequency sound is absorbed by sound-absorbing materials 6 attached to the surface of the roof structure 4 facing the passenger compartment 5 (in this embodiment, the surface facing the underside of the vehicle; hereinafter referred to as the "inner surface"). A plurality of sound-absorbing materials 6 are attached to the roof structure 4 in the front-to-rear and left-to-right directions, and these multiple sound-absorbing materials 6 are held in place by holders 7 provided on the inner surface of the roof structure 4.

[0018] The holder 7 has a base 70 that protrudes from the roof structure 4 toward the passenger compartment 5, and an overhanging portion 71 that protrudes in a flange-like shape from the tip of the protruding portion of the base 70 so as to be approximately perpendicular to the base 70. The sound-absorbing material 6 is attached to the roof structure 4 by inserting the edge of the sound-absorbing material 6 between the roof structure 4 and the overhanging portion 71. In other words, the sound-absorbing material 6 is not glued to the roof structure 4, but is simply held by the holder 7. However, the sound-absorbing material 6 may also be fixed to the roof structure 4 by a known joining method such as adhesive bonding or pin joining.

[0019] In addition, when the edge of the sound-absorbing material 6 is inserted between the roof structure 4 and the overhanging portion 71 (hereinafter referred to as the "inserted state of the sound-absorbing material 6"), it is preferable that the edge of the sound-absorbing material 6 is sandwiched between the roof structure 4 and the overhanging portion 71, but a configuration in which the edge of the sound-absorbing material 6 is supported only by the overhanging portion 71 (a gap is formed between the sound-absorbing material 6 and the roof structure 4) is also acceptable. Furthermore, in the inserted state of the sound-absorbing material 6, a configuration in which the edge of the sound-absorbing material 6 is supported (in contact with) the base 70 is also acceptable, or a configuration in which the edge of the sound-absorbing material 6 is not supported by the base 70 (a gap is formed between the sound-absorbing material 6 and the base 70).

[0020] Although not shown in the figure, the sound-absorbing material 6 is formed in a rectangular shape when viewed in its thickness direction (viewed from below), and the four sides of the sound-absorbing material 6 are held by holders 7. Furthermore, each sound-absorbing material 6 held by the holders 7 is covered by a ceiling panel with high sound permeability attached to the roof structure 4, but the ceiling panel is not shown in Figure 1 (the same applies to Figure 2 described later).

[0021] In this embodiment, the sound-absorbing material 6 is held by the retainers 7 (made of steel) that form the framework of the roof structure 4, but other known mounting structures using interior panels (ceiling panels) of the passenger compartment 5 or lighting devices can also be used for the mounting structure of the sound-absorbing material 6. An example of other known mounting structures is the technology described in JP 2020-093747 A. The retainers 7 are not limited to steel, and may be made of a metal material other than steel, such as aluminum, or a non-flammable resin material.

[0022] Next, the detailed configuration of the sound-absorbing material 6 will be described with reference to Fig. 2. Fig. 2 is a partially enlarged cross-sectional view of the railway vehicle 1 at part II in Fig. 1. Note that in Fig. 2, the thickness of the elastic layer 61 of the sound-absorbing material 6 is enlarged for ease of understanding.

[0023] As shown in Fig. 2, the roof structure 4 is an aluminum alloy extruded profile (a profile with a double-skin structure) in which an outer plate 40 constituting its outer surface and an inner plate 41 facing the inside of the outer plate 40 are connected in a truss shape by a plurality of connecting plates 42. A first porous layer 60 of the sound-absorbing material 6 is laminated on the inner surface (the surface facing the passenger compartment 5) of the inner plate 41 of the roof structure 4. The first porous layer 60 is a flat glass wool, and an elastic layer 61 is laminated on the inner surface of this first porous layer 60.

[0024] The elastic layer 61 is composed of a first elastic film 61a that is overlaid on the inner surface of the first porous layer 60, and a second elastic film 61b that is overlaid on the inner surface of the first elastic film 61a. Each of these elastic films 61a and 61b is made of a butyl rubber film. A second porous layer 62 is laminated on the inner surface of the elastic layer 61 (second elastic film 61b), and the second porous layer 62 is formed in a flat plate shape using a carbon fiber insulating mat material (a mat made by weaving carbon fibers).

[0025] Here, the first porous layer 60 has a density of 32 kg / m 3 However, when glass wool of a similar density was used to form the second porous layer 62, the result was that low-frequency sound could not be sufficiently absorbed. This is thought to be because low-frequency sound is absorbed mainly by the vibration (deformation) of the first porous layer 60 and the elastic layer 61, and when the density of the second porous layer 62 is increased, low-frequency sound is reflected by the second porous layer 62 (low-frequency sound is less likely to be transmitted to the elastic layer 61).

[0026] In contrast, in this embodiment, the density of the first porous layer 60 (in this embodiment, 32 kg / m 3 ), the density of the second porous layer 62 (7 kg / m 3 ) is lowered. This results in effective absorption of low-frequency sound. This is thought to be because low-frequency sound incident on the sound-absorbing material 6 from the passenger compartment 5 side is easily transmitted to the elastic layer 61 side through the second porous layer 62, and the vibration (deformation) of the elastic layer 61 and the first porous layer 60 allows effective absorption of low-frequency sound.

[0027] Therefore, in this embodiment, the second porous layer 62 is formed using carbon fiber, but the second porous layer 62 may be formed using another porous material (for example, the same glass wool as the first porous layer 60) as long as it has a lower density than the first porous layer 60. Even in such a configuration, low-frequency sound is easily transmitted through the second porous layer 62 to the elastic layer 61 side.

[0028] However, it is most preferable that the second porous layer 62 be formed using a heat insulating mat material of carbon fiber, for the reasons explained below.

[0029] First, the sound-absorbing material 6 needs to have a certain level of non-combustibility, and in order to ensure a large interior space in the passenger compartment 5, it is necessary to make the sound-absorbing material 6 thin. On the other hand, if the second porous layer 62 is formed using glass wool, for example, it is difficult to achieve both non-combustibility and thinness in the second porous layer 62. This is because, in order to form the glass wool into a relatively thin (for example, 25 mm or less) flat plate, it is necessary to add a binder (molding resin) when molding the glass wool, and such a binder reduces the non-combustibility of the glass wool.

[0030] That is, when glass wool is used for the second porous layer 62, in order to ensure the non-combustibility of the sound-absorbing material 6 (to eliminate the need to add a binder when molding the glass wool), it is necessary to increase the thickness of the second porous layer 62. As a result, it is not possible to ensure a large interior space for the passenger compartment 5.

[0031] On the other hand, a carbon fiber heat insulating mat material can be formed relatively thin (for example, 25 mm or less) without adding the above-mentioned binder. Therefore, as in this embodiment, it is preferable to use glass wool for the first porous layer 60 and carbon fiber for the second porous layer 62. This makes it possible to both impart non-combustibility to the second porous layer 62 (sound absorbing material 6) and ensure a large interior space in the passenger compartment 5 by reducing the thickness of the second porous layer 62 (sound absorbing material 6). Furthermore, by forming the second porous layer 62 to be thin, it is also possible to reduce the weight of the sound absorbing material 6.

[0032] Furthermore, in order to provide the sound-absorbing material 6 with the desired sound absorption properties while ensuring a spacious interior space for the passenger compartment 5, it is preferable that the overall thickness of the sound-absorbing material 6 be 90 mm or more and 110 mm or less. More specifically, it is preferable that the thickness of the first porous layer 60 be 65 mm or more and 80 mm or less, and the thickness of the second porous layer 62 be 15 mm or more and 35 mm or less. In this way, by making the thickness of the second porous layer 62 made of carbon fiber (25 mm in this embodiment) thinner than the thickness of the first porous layer 60 made of glass wool (75 mm in this embodiment), it is possible to prevent the overall thickness of the sound-absorbing material 6 from becoming too thick while ensuring the thickness of the first porous layer 60 required for absorbing low-frequency sounds and the thickness of the second porous layer 62 required for non-combustibility. Therefore, it is possible to ensure a spacious interior space for the passenger compartment 5.

[0033] It is preferable that the thickness of each of the elastic films 61a, 61b is 0.6 mm to 2.0 mm, and that the overall thickness of the elastic layer 61 is 2.0 mm to 6.0 mm. By forming the elastic layer 61 with such a thickness, it is possible to prevent the overall thickness of the sound-absorbing material 6 from increasing while ensuring the thickness (mass) of the elastic layer 61 required to absorb low-frequency noise. Therefore, it is possible to ensure a wide interior space in the passenger compartment 5 while effectively absorbing low-frequency noise with the sound-absorbing material 6.

[0034] The low-frequency sound absorption characteristics of the elastic layer 61 are affected not only by its thickness (mass) but also by its hardness and tensile strength. In this embodiment, the hardness of the first elastic film 61a is 57, and the hardness of the second elastic film 61b is 66, but it is preferable that the hardness of the first elastic film 61a be equal to or greater than 50 but less than 60, and that the hardness of the second elastic film 61b be equal to or greater than 60 but less than 70. The hardness of each of the elastic films 61a and 61b was measured using a durometer type A in accordance with JIS K6253-3:2023.

[0035] Furthermore, when a tensile test is performed on a dumbbell-shaped No. 1 test piece at a tensile speed of 500 mm / min in accordance with JIS K6251:2017, the first elastic film 61a preferably has a tensile strength of 6 MPa to 8 MPa (7.29 MPa in this embodiment) and an elongation at break of 300% to 500% (407% in this embodiment).The second elastic film 61b preferably has a tensile strength of 0.5 MPa to 2.0 MPa (1.04 MPa in this embodiment) and an elongation at break of 50% to 100% (70% in this embodiment).

[0036] In addition, in accordance with JIS K6268:1998, the density of the first elastic film 61a is 1.0 Mg / m 3 More than 1.4Mg / m 3 or less (in this embodiment, 1.29 Mg / m 3 ), and the density of the second elastic film 61b is preferably 1.5 Mg / m 3 More than 1.9Mg / m 3 or less (in this embodiment, 1.67 Mg / m 3 ) is preferred.

[0037] By forming each elastic membrane 61a, 61b using rubber with such physical properties and setting the thickness of each elastic membrane 61a, 61b to 0.6 mm or more and 2.0 mm or less (in this embodiment, the first elastic membrane 61a is 2.0 mm and the second elastic membrane 61b is 0.6 mm), an elastic layer 61 suitable for absorbing low-frequency sound can be formed.

[0038] Thus, in order for the sound-absorbing material 6 to absorb low-frequency sound of a desired (target) frequency, it is necessary to form the elastic layer 61 using rubber with suitable physical properties. For this reason, if the elastic layer 61 is formed from a single layer of rubber film, for example, it becomes difficult to select (manufacture) a material with the desired sound-absorbing characteristics, i.e., to absorb low-frequency sound of the desired frequency.

[0039] In contrast, in this embodiment, the elastic layer 61 is formed by adhering a first elastic film 61a and a second elastic film 61b (multiple-layer rubber film) having a different hardness from the first elastic film 61a. This makes it possible to adjust the sound absorption characteristics of the elastic layer 61 as a whole by changing the hardness and physical properties of the first elastic film 61a and the second elastic film 61b. Therefore, an elastic layer 61 with desired sound absorption characteristics can be easily formed.

[0040] In this embodiment, the first elastic membrane 61a is laminated on the roof structure 4 side, and the second elastic membrane 61b is laminated on the passenger compartment 5 side, but low-frequency sound can also be effectively absorbed by reversing the front and back of these elastic membranes 61a, 61b. Therefore, the first elastic membrane 61a may be laminated on the inner surface of the second elastic membrane 61b.

[0041] Here, for example, it is possible to integrate the layers 60 to 62 of the sound-absorbing material 6 by bonding them together with an adhesive. However, bonding with an adhesive may reduce the fire resistance of the sound-absorbing material 6 depending on the type of adhesive, and in such cases, the thickness of the second porous layer 62 (carbon fiber insulation material) must be increased.

[0042] In contrast, in this embodiment, the elastic layer 61 (first elastic film 61a) is simply stacked on the first porous layer 60 without being bonded, and the second porous layer 62 is simply stacked on the elastic layer 61 (second elastic film 61b) without being bonded. In other words, the first porous layer 60, the elastic layer 61, and the second porous layer 62 are not bonded to each other, which eliminates the need to use adhesive when forming the sound-absorbing material 6. Therefore, unlike the case where bonding is performed with an adhesive as described above, the second porous layer 62 (sound-absorbing material 6) can be formed thin while suppressing a decrease in the non-flammability of the sound-absorbing material 6 as a whole. This allows for a larger interior space in the passenger compartment 5.

[0043] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above form in any way, and it can be easily inferred that various modifications and improvements are possible within the scope that does not deviate from the spirit of the present invention.

[0044] In the above embodiment, the roof structure 4 is exemplified as the inner wall of the car body to which the sound-absorbing material 6 is attached, but the sound-absorbing material 6 may also be attached to, for example, the underframe 2 (under the floor of the passenger compartment 5), the side structure 3 or the end structure (side wall of the passenger compartment 5).

[0045] In the above embodiment, the non-flammable porous material is described as being made of glass wool for the first porous layer 60 and carbon fiber for the second porous layer 62, but this is not necessarily limited to this. For example, the first porous layer 60 may be made of a heat insulating mat material made of carbon fiber, and the second porous layer 62 may be made of glass wool.

[0046] Each of the porous layers 60, 62 may be a nonwoven fabric made of inorganic fibers such as rock wool, glass fiber, or ceramic fiber, or metal fibers (non-flammable fibers such as aluminum), or a non-woven fabric made from a combination of these fibers. Each of the porous layers 60, 62 may also be formed using a woven fabric made of non-flammable fibers such as glass cloth. That is, each of the porous layers 60, 62 may be made of other known non-flammable porous materials.

[0047] In the above embodiment, the density of the first porous layer 60 is 32 kg / m 3 and the density of the second porous layer 62 is 7 kg / m 3 However, the density of each porous layer 60, 62 can be set appropriately as long as the density of the second porous layer 62 is lower than that of the first porous layer 60. For example, the density of the first porous layer 60 is 24 kg / m 3 More than 96kg / m 3 The density of the second porous layer 62 is 4 kg / m or less. 3 More than 16kg / m 3 The following is fine.

[0048] In the above embodiment, the second porous layer 62 is thinner than the first porous layer 60, but the thickness of each porous layer 60, 62 may be the same, or the second porous layer 62 may be thicker than the first porous layer 60.

[0049] In the above embodiment, the elastic layer 61 is formed of two layers, the first elastic film 61a and the second elastic film 61b, but the elastic layer 61 may be formed of a single layer or three or more elastic films.

[0050] In the above embodiment, butyl rubber is used for the elastic layer 61 (elastic membranes 61a, 61b), but this is not necessarily limited to this. For example, the elastic layer 61 may be formed using rubber or elastomer such as silicone rubber, urethane rubber, acrylic rubber, chloroprene rubber, or fluororubber. In other words, other known materials having a predetermined elasticity may be used for the elastic layer 61. Furthermore, when the elastic layer 61 is formed from multiple elastic membranes, some or all of the elastic membranes may be formed from an elastic material different from the other elastic membranes.

[0051] In the above embodiment, the sound-absorbing material 6 is described as being composed of only three layers: the first porous layer 60, the elastic layer 61, and the second porous layer 62. However, in addition to these layers 60 to 62 (on the outer surface side of the first porous layer 60 or the inner surface side of the second porous layer 62), other sound-absorbing materials may be laminated.

[0052] In the above embodiment, the first porous layer 60, the elastic layer 61, and the second porous layer 62 are not bonded to each other, but some or all of the layers 60 to 62 may be bonded to each other. [Explanation of symbols]

[0053] 1. Railway vehicles 6. Sound-absorbing materials 60 First porous layer 61 Elastic layer 61a First Elastic Membrane 61b Second elastic membrane 62 Second porous layer

Claims

1. The railroad vehicle comprises a first porous layer attached to an inner wall of a car body and formed using a non-flammable porous material, an elastic layer laminated on the inner surface side of the first porous layer and formed using an elastic material, and a second porous layer laminated on the inner surface side of the elastic layer and formed using a non-flammable porous material, A sound-absorbing material characterized in that the density of the second porous layer is lower than that of the first porous layer.

2. 2. The sound-absorbing material according to claim 1, wherein the elastic layer comprises a first elastic film and a second elastic film bonded to the first elastic film and having a hardness different from that of the first elastic film.

3. 2. The sound-absorbing material according to claim 1, wherein the first porous layer is made of glass wool, and the second porous layer is made of carbon fiber.

4. 4. The sound absorbing material according to claim 3, wherein the second porous layer is thinner than the first porous layer.

5. 2. The sound-absorbing material according to claim 1, wherein the first porous layer, the elastic layer, and the second porous layer are not bonded to one another.

6. A railway vehicle, wherein the sound-absorbing material according to any one of claims 1 to 5 is attached to an inner wall of the car body.

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