JP2003295867A - Sound absorption structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorption structure with a perforated plate arranged therein which is light in weight, highly strong, strong to impact as well, and excellent in sound absorption performance as well. <P>SOLUTION: The sound absorption structure attached to at least one of a front surface, the flank and under surface of a vehicle is provided with a sound insulating member through a porous material and/or air layer behind the following sound absorption material: A sound absorption material formed by disposing the porous material 2 having a number of fine pores communicating the front and rear on the back of the perforated plate 1 consisting of a metallic sheet of aluminum, etc., having an opening rate of ≤35%, for example, the porous material formed by compression bonding an assemblage of metallic fibers of aluminum, an aluminum alloy, a stainless steel, etc., by a method, such as rolling or the porous material formed by additionally installing net materials, such as expanded metals, to both surfaces or one surface of the assemblage of the metallic fibers and subjecting the same to compression bonding and molding. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight, durable and strong sound absorbing structure used as a noise countermeasure for a vehicle that generates noise.

[0002]

2. Description of the Related Art Conventionally, as a sound absorbing material, there are a glass wool sound absorbing material obtained by processing glass fiber into a plate shape, an inorganic porous sound absorbing material obtained by sintering ceramic particles or a cement-based material, but at a high speed. When it is used to perform sound absorption processing on the outside of a running vehicle, there is a problem in that the sound absorbing material deteriorates and is damaged by high-speed airflow, vibration, etc., and performance is degraded, and fragments are scattered. Glass wool sound absorbing materials tend to deteriorate in performance due to the scattering of fibers due to high-speed air flow, and ceramic rigid sound absorbing materials are easily cracked, and since they are heavy, there is a problem that the weight increases when mounted on a vehicle or the like. .

As a countermeasure against these problems, there is a method of protecting the surface of the porous sound absorbing material with a perforated plate or the like, but the aperture ratio of the perforated plate is set to 30 in order to prevent deterioration of the sound absorbing performance.
However, there is a problem in that the reinforcing effect is reduced when the aperture ratio is increased, and there is a concern that fibers and fragments are scattered from the holes of the perforated plate in glass fibers and ceramics.

In order to improve such a point, a sound absorbing structure shown in the following Patent Document 1 is proposed. However,
Since the body of a railroad vehicle is reflective, noise such as the noise of the pantograph and overhead lines at the top of the vehicle and the noise of the motor at the bottom of the vehicle, the noise of the friction between wheels and rails, and other road surfaces such as tunnel walls, slab tracks, and concrete when traveling at high speeds. There is a problem that amplification is caused by reciprocal reflection between the soundproof wall and the vehicle body surface, and further improvement has been desired.

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 2002-215172: Claims 1 to 5

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a perforated plate which is lightweight, has high strength, is strong against impact, and has excellent sound absorbing performance. Provided is a sound absorbing structure.

[0007]

The above problem is a sound absorbing structure mounted on at least one of the upper surface, the side surface and the lower surface of a vehicle, behind a perforated plate having an aperture ratio of 35% or less, A porous material and / or an air layer is formed behind the sound absorbing material, which has a large number of pores communicating with the front and back and has a flow resistance of air per unit area of 100 N · S / m ³ or more. This can be solved by the sound absorbing structure of the present invention, which is characterized in that the sound insulating member is provided via the. The present invention can be preferably embodied in a form in which the perforated plate is made of metal or resin, a form in which the porous material is made of metal, or a combination thereof.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the sound absorbing structure of the present invention will be described with reference to FIGS.
First, the sound absorbing structure of the present invention is a sound absorbing structure attached to at least one of an upper surface, a side surface, and a lower surface of a vehicle, and a porous material and / or air is provided behind a specific sound absorbing material described below. The feature is that a sound insulating member is provided through the layers.

The feature of the sound absorbing material 3 used in the present invention is that it is behind a perforated plate 1 having a large aperture ratio of 35% or less, for example, a metal plate made of aluminum, stainless steel, iron or the like. Has a large number of pores communicating with the front and back, and the air flow resistance per unit area is 100 N · S /
A porous material 2 having a size of m ³ or more, for example, a porous material obtained by pressure-bonding an aggregate of metal fibers such as aluminum, an aluminum alloy, and stainless steel by a method such as roll forming, expanded metal on both sides or one side of the aggregate of metal fibers, and the like. In addition, a mesh material (not shown) is attached and a porous material or the like is formed by pressure bonding.

Now, the perforated plate 1 which is a constituent member of the present invention will be described. The opening shape of the perforated plate 1 is shown in FIG.
Examples are the round hole shape shown in (A) and the long hole shape shown in (B). These perforated plates 1 are made of aluminum, stainless steel,
A metal plate made of iron or the like and perforated and provided with a large number of openings 11, a plastic, a reinforced plastic such as FRP, or a resin such as hard rubber is used. The thickness may be about 1 to 3 mm, but is not particularly limited. In addition, in FIG. 1C, the elongated hole is further lengthened to exemplify a slit-shaped extended opening shape, which is formed by arranging strip-shaped plate materials such as metal plates in parallel.

The aperture ratio is preferably 35% at maximum.
However, the maximum may be 30%. Further, in the case of a slit shape or a long hole shape, 20 to 35% is preferable, and in the case of other round hole shape, the maximum may be 25%. In addition to the above-mentioned shapes, the planar opening shape of the opening 11 may be a triangle, a quadrangle, or the like, and the cross-sectional shape of the opening 11 may be selected according to the application such as a straight hole, a tapered hole, or burring. The size of the opening 11 is not limited, but the diameter or width is preferably about 2 to 10 mm for the purpose of protecting the porous material.

The opening 11 of FIG. 1C is obtained by providing a perforated plate 1 on the surface of the porous material 2 in the form of a plurality of strip-shaped (slit) plates arranged with a predetermined gap. The individual strip-shaped (slit) plates may be connected at an appropriate interval as necessary, for example, at intervals of the following lengths or more. Further, the opening 11 shown in FIGS. 1B and 1C is used when it is necessary to secure the sound absorbing property while protecting the porous material 2 and suppress the generation of wind noise. For the purpose, it is preferable that the size of the opening is 2 to 20 mm in width, the length is 50 mm or more, and the opening ratio is 20 to 35%. Further, the longitudinal ends of the slit-shaped and long-hole-shaped openings 11 may be semicircular, triangular, quadrangular, polygonal, etc., and their cross-sectional shape may be selected depending on the application such as straight, taper, and burring. .

Although FIG. 1C shows an example in which the end of the opening 11 in the longitudinal direction is opened, if the surface of the mounting opening of the vehicle and the upper surface of the sound absorbing material are aligned when mounted on the vehicle. The end of the sound absorbing material in the longitudinal direction is closed at the opening of the vehicle. The sound absorbing material may be mounted so that the thickness of the perforated plate is floated (protruded) from the surface of the mounting opening of the vehicle so that the end portion is not closed.

Next, the porous material 2 which is a constituent member of the present invention and is arranged behind the perforated plate 1 will be described. The porous material 2 is a porous member having a large number of pores communicating with the front and back and having a sound absorbing property, and a porosity of 20 to 50.
%, The air flow resistance per unit area is 10
0 to 2000 N · S / m ³ is used. It is more preferably 600 to 1500 N · S / m ³ . The plate thickness is suitably 5 mm or less.

The material of the porous material is preferably metallic or metallic. For example, a porous material 2 obtained by pressure-bonding an aggregate of metal fibers such as aluminum, aluminum alloy, and stainless by a method such as roll forming, a mesh material such as expanded metal (not shown) on both sides or one side of the aggregate of metal fibers. , A porous material formed by pressure-bonding, a porous material 2 formed by a method such as adding an adhesive after the pressure-bonding and solidifying, a porous material 2 obtained by sintering metal particles such as aluminum or an aluminum alloy, a metal A porous material 2 in which particles are solidified with an adhesive, or a porous material 2 in which a communication hole is formed by foaming a metal such as aluminum can be preferably applied.

Among the above, in the case of the porous material 2 to which the metal fibers are pressure bonded, the plate thickness can be adjusted, and it is possible to reduce the thickness to, for example, about 1 mm. Further, since the metal fibers are intricately entangled with each other, Since peeling and scattering hardly occur, it is particularly preferable as a material to be placed inside or behind the perforated plate 1.

The following materials may be used as the other porous material 2. Sintering of ceramic particles, foams, and foams of cementitious materials. A plate-shaped body made of ceramic fibers processed with an adhesive. Thermo-compression-bonded body of plastic particles, plate-like body that is adhesively processed. Thermocompression-bonded body of plastic fiber, plate-like body that is adhesively processed.

As a joining structure of the porous material 2 and the perforated plate 1 as described above, a non-adhesive structure in which the perforated plate 1 and the porous material 2 are simply superposed is also adopted, but they are bonded by an adhesive. ,
It is preferable to bond them by a method such as heating to form a surface-adhesive structure or a surface-bonded structure. In this case, heat or an adhesive may be used together.

Further, the porous material 2 is brought into contact with the perforated plate 1 in the state of the raw material to perform processing such as molding so that the porous material 2 and the perforated plate 1 are integrally formed. May be. In order to improve the bondability between the perforated plate 1 and the porous material 2, a burring process is performed on the perforated plate 1 (see FIG. 2).
(See (3)) to form the bent burring portion 22, or a porous material may be pressed into the opening 11 of the perforated plate to form the burring portion 22 (see FIG. 2 (2)). The methods may be used in combination. Further, the perforated plate may be arranged on one surface (front surface) or both surfaces (front surface, back surface) of the porous material.

Next, the combination of the perforated plate 1 and the porous material 2 will be described. Basically, the perforated plate 1 and the porous material 2 are in a one-to-one combination, but a plurality of kinds of one may be arranged in combination with the other as in the following case. Perforated plate + Porous material + Perforated plate (see Fig. 2 (4)) Perforated plate Perforated plate + Porous material A (small flow resistance) + Porous material B (large flow resistance) (Fig. 2 (5) )) Perforated plate Perforated plate + porous material C (made of metal) + porous material D (made of glass fiber) (see FIG. 2 (5))

The sound absorbing characteristics of the sound absorbing material 3 thus obtained are as follows.
It can be adjusted by the sound absorption characteristics of the porous material 2.
Since the sound absorption characteristics of the porous material 2 are mainly determined by the air flow resistance (permeation resistance) per unit area, the porosity, and the size and shape of the pores, it depends on the selection of the material of the porous material 2 and the manufacturing conditions. Can be adjusted. For example, if the plate thickness is thin, reduce the size of the air gap, and if the plate thickness is thick, increase the size of the air gap to set the air flow resistance per unit area to a specified value. By adjusting to
It can be adjusted to the required sound absorption characteristics. In order to enhance strength and impact resistance, the perforated plate 1 is adjusted to be thicker and the hole diameter, the hole length, and the slit width dimension are adjusted to be smaller.

Next, the structure of the sound absorbing structure of the present invention will be described with reference to FIG. Basically, the structure of this sound absorbing structure is, as shown in FIG. 3 (1), from the sound source side, a sound absorbing material 3 (for example, a perforated plate + a porous material 2) + air layer 4 + sound insulation member 6 However, between the sound absorbing material and the sound insulating member, a plurality of layers of porous material and air layer, as in the following example,
It can be arranged in combination. Sound absorbing material 3 + porous material 5 + air layer 4 + sound insulation member 6 (see FIG. 3 (2)) sound absorbing material 3 + air layer 4 + porous material 5 + air layer 4 + sound insulation member 6 (see FIG. 3 (3)) Material 3 + Air layer 4 + Sound insulation member 6 + Air layer 4 +
Like the sound absorbing material 3, a double-sided sound absorbing structure in which the sound absorbing material 3 is arranged on both sides may be used.

As the sound insulating member 6, a metal such as iron or aluminum, a resin plate such as plastic, or an inorganic material such as concrete is suitable. As the porous material 5, the above-mentioned materials can be appropriately adopted. The sound absorbing material of the present invention is one in which a relatively thin porous material is arranged behind the perforated plate, and further, since it is a sound absorbing structure in which an air layer is arranged behind the perforated plate, resonance sound absorption by the perforated plate and There is a synergistic effect of converting sound waves by the porous material into heat energy and attenuating it, and high sound absorption characteristics can be obtained even if the aperture ratio of the perforated plate is relatively small.

The sound absorbing structure thus obtained is preferably used as a sound absorbing component such as an upper surface portion, a side surface portion, a lower surface portion of a vehicle body of a railway vehicle and around wheels. The vehicle body itself may be used as the sound insulation member. When the sound absorbing material is installed on the upper surface or the side surface of the vehicle body, the sound absorbing material 2 fills the opening 11 of the perforated plate 1 as shown in FIG. 2 (2) in order to prevent wind noise and improve the appearance. It is preferable to use one having a different structure and to make the perforated plate as thin as possible.

Furthermore, for wind noise, FIG.
(C) A sound absorbing material having a long hole or a slit-shaped opening 11 is used so that the long hole-shaped and slit-shaped openings 11 are attached so that their longitudinal directions are substantially parallel to the traveling direction of the vehicle. Is preferred. High-speed airflow will flow in the longitudinal direction of the slits and long holes, and the number of openings in the airflow direction will be smaller than in a simple perforated plate as shown in Fig. 1 (A), and obstacles will be reduced, so wind noise will be generated. Can be suppressed.

In order to prevent wind noise and improve the appearance,
A sound-permeable thin film may be attached to the surface of the perforated plate to smooth the surface of the vehicle body, or innumerable fine projections may be provided on the entire surface or a net may be attached. Also, when installing the sound absorbing material on the upper surface or side surface of the vehicle body,
It may be installed only in a portion that is easily affected by reflection during traveling. In order to reinforce the sound absorbing material, a lattice-like reinforcing material such as a honeycomb may be arranged in the air layer portion.

If a sound absorbing material is not attached to the surface of the vehicle body and it is made to be reflective, when the vehicle runs at high speed, friction noise between the pantograph and overhead lines on the upper body of the vehicle and motor noise of the lower body of the vehicle,
Noise such as frictional noise between wheels and rails is amplified by being reflected back and forth between tunnel walls, road surfaces such as slab tracks, soundproof walls such as concrete, and vehicle body surfaces (top, side, bottom) and propagated to the private side. Therefore, the noise in the surroundings increases, but if the surface of the vehicle body is made to absorb sound as in the present invention, the generated noise does not reciprocate and the reflected sound can be reduced. Further, it is possible to suppress the generation of wind noise due to the sound absorbing material.

[0028]

[Embodiment 1] Next, a more detailed description will be given based on Table 1 showing an embodiment of the present invention. Porous material (A) obtained by press-molding an aggregate of aluminum fibers having a fiber diameter of about 0.1 mm, made of aluminum having an aperture ratio of 70 to 80% on both sides of an aggregate of aluminum fibers having a fiber diameter of about 0.1 mm. Porous material (B) obtained by arranging the expanded metal of No. 1 and an aggregate of aluminum fibers having a fiber diameter of about 0.1 mm, and an expanded metal made of aluminum having an opening ratio of 70% is arranged on one surface of the aggregate and crimp-formed. Porous material (C),
On one surface of (D), a perforated plate having a circular hole was attached to a stainless steel plate having a thickness of 1 mm to obtain test samples No1 to No11 which are examples of the sound absorbing material used in the present invention. In addition, the test sample No. 12 under the conditions outside the scope of the present invention and the test samples No. 13 to No. 15 having a structure in which the perforated plate was not arranged were compared as comparative examples.

Regarding the sound absorbing materials of the above Examples and Comparative Examples,
The normal incidence sound absorption coefficient was measured and the impact test was performed. The normal incident sound absorption coefficient was measured by providing an air layer behind the sound absorbing material or arranging a porous material, and a typical example of the sound absorbing characteristics is shown in FIG.
Table 1 shows the peak values. In addition, the impact test,
A 50 cm square sound absorbing material for measurement was placed on the sand, and a 0.5 kg steel ball was dropped from a height of 1 m to examine whether or not the material was deformed.

According to this example, as shown by the test results in Table 1, it is found that the sound absorbing material and the sound absorbing structure of the present invention have a good sound absorbing coefficient and are excellent in impact resistance. It

[0031]

[Table 1]

[0032]

[Example 2] Aluminum porous material (B) of Example 1
And a slit plate are combined, and test samples No16 to No19, which are examples of the sound absorbing material used in the present invention, are combined with a perforated plate (oblong hole), and test samples No20 to No2 are combined.
3 in combination with a perforated plate (round hole)
Got 4. In addition, the test body No. 25 under conditions outside the scope of the present invention
Was compared as a comparative example.

With respect to the sound absorbing materials of the above Examples and Comparative Examples,
Create a test piece with a width of 1 m, a length of 1 m and a thickness of about 50 mm,
Wind noise, normal incidence sound absorption coefficient and impact test were performed.
The wind noise was compared by measuring the noise generated in the vicinity of the surface by passing a high-speed air stream over the surface of the test body. Impact test is 50
A cm-square sound absorbing material for measurement was placed on sand, and a 0.5 kg steel ball was dropped from a height of 1 m to investigate whether or not the material was deformed. Measured normal incidence sound absorption coefficient is 100 mm in diameter
A test piece of the sound absorbing material was created and measured.

According to this Example 2, as shown in the test results of Table 2 below, the sound absorbing material and the sound absorbing structure of the present invention have a good sound absorbing coefficient and are excellent in impact resistance, and It can be seen that the long holes and the slits are higher than the round holes to suppress the generation of wind noise. The sound absorbing structure of the present invention,
As described above, the surface aperture ratio is protected by a metal perforated plate with a relatively small aperture ratio of up to 35%, and the porous material placed behind it is also a crimp aggregate of metal fibers. In addition, it has a structure that is unlikely to be damaged or scattered even against high-speed airflow or impact, and it also has an appropriate sound absorption coefficient.
Since the influence of wind noise can be reduced, it is suitable as a sound absorbing material for vehicles and the like.

[0035]

[Table 2]

[0036]

Since the sound absorbing structure having the perforated plate of the present invention configured as described above, the surface thereof is reinforced by the perforated plate and is excellent in strength and impact resistance, and is in a thin plate shape. Since it is lightweight, it is easy to install, and the problem due to the increase in weight is unlikely to occur even after installation, and it has high sound absorption characteristics despite being reinforced with a perforated plate. Further, it has an excellent effect that it can be suitably used for absorbing sound from the upper surface portion, side surface portion, lower surface portion of a vehicle traveling at high speed, around wheels, and the like, noise can be significantly reduced, and the influence of wind noise is small. Therefore, the present invention has an extremely great industrial value as a sound absorbing structure in which a slit plate or a slotted plate having the problems of the related art is arranged.

[Brief description of drawings]

FIG. 1 is a perspective view (A), (B), and (C) of a main part for explaining a sound absorbing material used in the present invention.

FIG. 2 is a schematic sectional view showing a combination (1 to 5) of constituent members of the sound absorbing material used in the present invention.

FIG. 3 is a schematic sectional view showing a combination (1 to 3) of constituent members of the sound absorbing structure of the present invention.

FIG. 4 is a graph showing sound absorption characteristics of a representative example.

[Explanation of symbols]

1 Perforated Plate, 11 Openings, 2 Porous Material, 22 Burring Part, 3 Sound Absorbing Material, 4 Air Layer, 5 Porous Material, 6
Sound insulation material.

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Claims (3)

[Claims] 1. A sound absorbing structure mounted on at least one of an upper surface, a side surface and a lower surface of a vehicle, and having an opening ratio of 3.
Behind a perforated plate of 5% or less, a large number of pores communicating with the front and back are provided, and the air flow resistance per unit area is 100N.
・ Behind the sound absorbing material with a porous material of S / m ³ or more,
A sound-absorbing structure comprising a sound-insulating member provided through a porous material and / or an air layer. 2. The sound absorbing structure according to claim 1, wherein the perforated plate is made of metal or resin. 3. The porous material is made of metal.
Alternatively, the sound absorbing structure according to item 3.