JP2007256750A - Sound absorption material, method of manufacturing the same, and sound absorption panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorption material having low manufacturing costs and superior in aesthetic properties and sound absorption characteristics, and also to provide a method of manufacturing the same, and a sound absorption panel including the same. <P>SOLUTION: The sound absorption material is adopted, which comprises a metallic plate member 2 which is provided with a plurality of through-holes having a diameter of ≤200 μm along its plate thickness direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sound absorbing material, a method for manufacturing the sound absorbing material, and a sound absorbing panel.

Conventionally, porous sound absorbing materials such as glass wool and rock wool are known as sound absorbing materials. However, glass wool, rock wool, etc. generate fibers and dust, damage the surrounding environment, sound absorption characteristics deteriorate due to the influence of dust, moisture, chemicals, fat, etc., and the appearance is matte and freedom of aesthetics There is a problem that the degree is low.
Glass wool, rock wool, etc. are not usually used alone, and must be used in combination with highly breathable materials such as cloth and nets to improve the appearance or durability. There is a problem that sex is limited.

A sound absorbing panel is also known in which a through-hole is provided in a plate-shaped member made of metal, wood, plastic, or the like, and a back air layer is provided on the side opposite to the sound source of the through-hole. However, these sound-absorbing panels have a problem that the aesthetics are impaired because the diameter of the through holes is relatively large and visible with the naked eye. Further, as in the case of glass wool, rock wool, etc., it is necessary to use in combination with a material having high air permeability such as cloth or net, and this causes a problem that aesthetics are limited.
A sound absorbing panel having a through hole diameter of several hundreds of micrometers is also known (for example, Patent Document 1), but the through hole in this sound absorbing material is drilled with a drill or provided using a photolithography technique. There is a problem that the manufacturing cost is large. Further, since the aspect ratio of the through-hole increases as the plate thickness increases, there is a problem that it is difficult to manufacture a sound absorbing panel having a large plate thickness.

Furthermore, it is also considered to apply a metal porous plate formed by a known sintering method in which metal powders are loosely bonded to each other or a known foaming method in which gas is blown into molten metal and foamed to a sound absorbing material. ing.
However, in the above porous plate, although there are a large number of holes in the inside, the direction of the holes is not aligned along the thickness direction of the plate, and one or both ends of the holes are closed and penetrated. It is difficult to form holes, and burrs are easily clogged due to burrs and deformation during slicing. When slicing, the porosity does not match the aperture ratio, making it difficult to control the aperture ratio, and sound absorption There is a problem that the characteristics become unstable for each product.

Furthermore, a method of obtaining a porous metal body by mixing a metal powder and a powdered salt, heating and melting only the metal powder, and then cooling to remove only the salt is also known. However, since the porous metal body manufactured by this method has pores having a three-dimensional network structure, the orientation of the pores is not aligned along the thickness direction of the plate, and when it is sliced However, there is a problem that the porosity does not coincide with the aperture ratio, it becomes difficult to control the aperture ratio, and the sound absorption characteristics become unstable for each product.
JP 2005-173398 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a sound absorbing material that is low in manufacturing cost, excellent in aesthetics and sound absorbing characteristics, a manufacturing method thereof, and a sound absorbing panel including the sound absorbing material. And

In order to achieve the above object, the present invention employs the following configuration.
The sound-absorbing material of the present invention is made of a metal plate-like member, and the plate-like member is provided with a plurality of through holes having a diameter of 200 μm or less along the plate thickness direction.
In the sound absorbing material of the present invention, a metal powder and a through-hole forming agent powder are mixed, and then the metal powder and the through-hole forming agent powder are solidified while being stretched in one direction in a fiber shape. A bulk body is formed, and then the bulk body is sliced along a direction perpendicular to the stretching direction to form a plate-like member, and then the through-hole forming agent is removed from the plate-like member to obtain a diameter. A plurality of through holes of 200 μm or less are formed.
Moreover, in the sound-absorbing material of the present invention, it is preferable that the opening ratio of the through holes is in the range of 10% to 80%.

Next, in the method for producing a sound absorbing material of the present invention, a metal powder and a through-hole forming agent powder are mixed, and then the metal powder and the through-hole forming agent powder are respectively stretched in a fiber shape in one direction. Solidified to form a bulk body, and then slices the bulk body along the direction perpendicular to the stretching direction to form a plate-like member, and then the through-hole forming agent is formed from the plate-like member. By removing, a plurality of through holes having a diameter of 200 μm or less are provided.
Moreover, in the manufacturing method of the sound-absorbing material of the present invention, it is preferable to form the bulk body by extruding a mixture of the metal powder and the through-hole forming agent powder by a hot extrusion method. The hot extrusion method is preferably performed at a temperature lower than the temperature at which the metal powder and the through hole forming agent powder melt.
Furthermore, in the method for producing a sound absorbing material according to the present invention, the metal powder is any one of Al, Mg, Sn, and Cu, or an alloy powder mainly containing one of them, or the metal powder and the A mixed powder of alloy powder is preferable, and Al is particularly preferable.
In the method for producing a sound absorbing material of the present invention, the through hole forming agent is preferably made of a water-soluble salt, the through hole forming agent is more preferably NaCl or KCl, and NaCl is particularly preferable.

Next, the sound-absorbing panel of the present invention is characterized in that two or more sound-absorbing materials according to any one of the foregoing are disposed at a predetermined interval, and an air layer is provided between the sound-absorbing materials. To do.
In the sound absorbing panel of the present invention, the sound absorbing material according to any one of the above and a rigid body are relatively disposed at a predetermined interval, and an air layer is provided between the sound absorbing material and the rigid body. Features.
In the sound absorbing panel of the present invention, it is preferable that a porous sound absorbing material is disposed in the air layer. As the porous sound absorbing material, for example, a porous sound absorbing material such as glass wool or rock wool can be used.
In the sound absorbing panel of the present invention, it is preferable that a reinforcing member is attached to the air layer side surface of the sound absorbing material.

According to the sound absorbing material of the present invention, since a plurality of through holes of 200 μm or less are provided along the plate thickness direction of the plate-like member, the sound absorbing characteristics can be improved. Moreover, by making the diameter of the through hole 200 μm or less, the through hole is not conspicuous and the aesthetics are not impaired.
Further, according to the sound absorbing material of the present invention, the metal powder and the through-hole forming agent powder are solidified while being stretched in one direction in a fiber shape to form a bulk body, and this bulk body is perpendicular to the stretching direction. Since the through-hole is formed by removing the through-hole forming agent after being sliced into a plate shape along, there is little possibility that one end or both ends of the through-hole are closed. Thereby, it is possible to configure a sound absorbing material in which a through hole having a large aspect ratio is provided so as to extend along the thickness direction. Such a sound absorbing material has excellent sound absorbing characteristics.
Furthermore, according to the sound-absorbing material of the present invention, since the opening ratio of the through holes is in the range of 10% or more and 80% or less, instability in manufacturing and strength reduction as a panel can be avoided.

  According to the method for producing a sound absorbing material of the present invention, the metal powder and the through-hole forming agent powder are solidified while being stretched in one direction in a fiber shape to form a bulk body, and the bulk body is stretched in the stretching direction. Since the through-hole is formed by removing the through-hole forming agent after slicing into a plate shape along the vertical direction, it is unlikely that one or both ends of the through-hole will be closed, and it extends along the plate thickness direction. In addition, a sound-absorbing material having through holes with a large aspect ratio can be manufactured at low cost. Moreover, the plate thickness (length of the through hole) of the sound absorbing material can be increased. Such a sound absorbing material has excellent sound absorbing characteristics.

Furthermore, according to the sound absorbing panel of the present invention, the sound absorbing materials or the sound absorbing material and the rigid body are arranged to face each other, and an air layer is provided between the sound absorbing materials or between the sound absorbing material and the rigid body. Thus, a so-called Helmholtz resonator can be formed, and the sound absorption characteristics can be greatly improved. Moreover, since the sound absorbing material itself is excellent in aesthetics, the aesthetics of the sound absorbing panel itself can be enhanced.
Moreover, according to the sound absorbing panel of the present invention, since the porous sound absorbing material is disposed in the air layer between the sound absorbing material and the rigid body, the sound absorbing characteristics can be further improved.
Furthermore, according to the sound absorbing panel of the present invention, since the reinforcing member is attached to the surface of the sound absorbing material on the air layer side, it is possible to increase the strength of the sound absorbing material itself, thereby increasing the size of the panel surface of the sound absorbing panel. Can be.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings referred to in the following description are for explaining the sound absorbing material, the sound absorbing panel, and the method of manufacturing the sound absorbing material. The size, thickness, dimensions, etc. of each part shown in the drawings are the same as those of the actual sound absorbing material, etc. It may be different from the dimensional relationship.

"Sound absorbing material"
Hereinafter, the sound absorbing material of this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a sound absorbing material of the present embodiment, and FIG. 2 is a schematic cross-sectional view in which a part of the sound absorbing material of FIG. 1 is enlarged.

  As shown in FIG. 1, the sound absorbing material 1 of the present embodiment is made of a metal plate-like member 2 and is manufactured by a manufacturing method described later. This plate-like member 2 has one surface 2a and the other surface 2b having the largest area among the respective surfaces that are the outer surfaces of the plate-like member. The one surface 2 a and the other surface 2 b are opposed to each other along the thickness direction of the plate-like member 2. The one surface 2a and the other surface 2b are provided with a plurality of through holes 3 as shown in FIG. On the other hand, the region where the through holes 3 are not provided on the one surface 2a and the other surface 2b is a metal surface 2c.

  The material of the plate-like member 2 is preferably a metal, and is any one of Al, Mg, Sn, and Cu, or an alloy mainly composed of one of them, or a mixture of the metal and the alloy. More preferably, Al is particularly preferable.

  Further, the thickness t of the plate-like member 2 is preferably in the range of 0.5 mm to 10 mm, and more preferably in the range of 1 mm to 5 mm. The thickness t of the plate-like member 2 corresponds to the length of the through hole 3 in the plate thickness direction. If the thickness t (the length of the through hole) of the plate-like member 2 is 0.5 mm or more, it is preferable that the strength of the plate-like member 2 itself is not lowered and the sound absorption characteristics are not lowered. Further, if the thickness of the plate-like member 2 (the length of the through hole) is 10 mm or less, there is no possibility that one end or both ends of the through hole 3 will be blocked, and the sound absorption characteristics will not be deteriorated.

As shown in FIG. 2, the through hole 3 extends along the thickness direction of the plate-like member 2 and penetrates the plate-like member 2. The through hole 3 preferably has a circular shape in plan view, but may have an elliptical shape, a rectangular shape, or a polygonal shape with curved corners. Moreover, the adjacent through-holes 3 ... may be connected to each other so that a part of the through-holes whose shape in plan view is an indefinite shape may exist.
The diameter d of the through hole 3 (equivalent circular diameter of the cross-sectional area of the hole) is preferably in the range of 200 μm or less, and more preferably in the range of 50 μm or more and 200 μm or less. If it is smaller than 50 μm, it is difficult to remove the through-hole forming agent. In addition, the diameter d of the through hole 3 may be uniform or may be different for each through hole.
When the diameter of the through-hole 3 exceeds 200 μm, the through-hole 3 is easily visually recognized with the naked eye, and the aesthetic appearance of the sound absorbing material 1 is impaired.

  Further, the shape and size of the through-hole 3 in plan view are preferably constant along the thickness direction of the plate-like member 2, but the size gradually changes along the thickness direction of the plate-like member 2. Also good. That is, each of the through holes 3 shown in FIG. 2 has a constant shape and size in plan view along the thickness direction of the plate-like member 2, and the wall surface 3 a of the through hole 3 has a surface 2 a and an other surface 2 b. However, the wall surface of the through hole 3 may be a tapered surface.

  Further, the opening ratio σ of the through holes 3 is preferably in the range of 10% to 80%, and more preferably in the range of 20% to 60%. Here, the opening ratio σ of the through holes 3 is the ratio of the opening area of the through holes 3 to the area of the one surface 2a or the other surface 2b. When the opening ratio σ is 10% or more, there is no possibility that the through holes 3... Are insufficient and the sound absorption characteristics are deteriorated, and the through hole forming agent can be easily removed in the manufacturing process described later. If the aperture ratio σ is 80% or less, there is no possibility that the through holes 3 are connected to each other, and the sound absorbing material 1 has sufficient strength.

The sound absorbing material 1 is preferably arranged so that the one surface 2a or the other surface 2b faces the sound source position. The surface of the sound absorbing material 1 opposite to the sound source position is in contact with the air layer, and the air layer and the through holes 3 of the sound absorbing material 1 communicate with each other to form a so-called Helmholtz resonator, thereby obtaining sound absorbing performance. It is done.
The sound absorbing performance of the Helmholtz resonator is determined by the thickness t (length of the through hole) of the plate-like member 2, the diameter d of the through hole 3, the interval between the through holes 3, the opening ratio of the through holes 3, and the like. Therefore, what is necessary is just to set suitably in the optimal range mentioned above so that the maximum sound absorption rate may be obtained according to acoustic characteristics, such as the frequency of the sound to absorb.

Specifically, the following formula (Dah-You Maa, “Potential of microperforated panel absorber”, J. Acoust. Soc. Am., Vol. 104, No. 5, November, 1998) as the maximum sound absorption coefficient alpha ₀ represented by 1) increases, the length of the plate-like member 2 in the thickness t (through holes), by setting the diameter d and the through-hole 3 ... aperture ratio of the through-hole 3 sigma Good. Incidentally, r in the formula (1) is calculated by the equation (2), the _{k r} in equation (2) is calculated by the equation (3), k in the formula (3) in relation calculated by the equation (4) is there. In the formulas (1) to (4), t is the thickness of the plate-like member 2, d is the diameter of the through hole 3, σ is the aperture ratio of the through hole 3, and η is the viscosity of air. Ρ ₀ is the density of air, c is the speed of sound in the air, and ω is the angular frequency.

α ₀ = 4r / (1 + r) ² (1)

r = (32ηt / σρ ₀ cd ² ) k _r (2)

_{^{k r = (1 + k 2}} /32) 1/2 + (2 1/2 d / 32t) k ... (3)

k = d (ωρ ₀ / 4η) ^1/2 (4)

As described above, according to the sound absorbing material 1 of the present embodiment, since the plurality of through holes 3 of 200 μm or less are provided along the plate thickness direction of the plate-like member 2, the sound absorbing characteristics can be improved. Further, by setting the diameter of the through hole to 200 μm or less, the through holes 3 are not conspicuous and the aesthetics are not impaired.
Furthermore, according to the sound absorbing material 1 described above, since the opening ratio of the through holes 3 is in the range of 10% or more and 80% or less, more excellent sound absorbing characteristics can be exhibited.

"Sound absorbing panel"
Next, a sound absorbing panel including the above sound absorbing material will be described with reference to FIGS.
FIG. 3 is a schematic cross-sectional view showing an example of a sound absorbing panel.
The sound absorbing panel 10 shown in FIG. 3 is configured by arranging the two sound absorbing materials 1A (1) and 1B (1) to face each other with a predetermined interval therebetween. By arranging the sound absorbing materials 1A and 1B apart from each other, an air layer 11 is formed between the sound absorbing materials 1A and 1B. By providing the air layer 11 between the sound absorbing materials 1A and 1B, the through holes 3 of the sound absorbing materials 1A and 1B and the air layer 11 communicate with each other, thereby forming a so-called Helmholtz resonator. Thereby, a sound absorption characteristic can be improved significantly.

In other words, the distance m ₁ between the sound absorbing materials 1A and 1B is preferably in the range of 5 mm to 1000 mm, and more preferably in the range of 50 mm to 500 mm, as the thickness of the air layer 11. If the thickness of the air layer 11 is out of this range, good sound absorption characteristics cannot be obtained.

  In addition, since the sound absorbing panel 10 shown in FIG. 3 includes the sound absorbing materials 1A and 1B having the same configuration, either of the sound absorbing materials 1A and 1B may be arranged facing the sound source. Thereby, at the time of construction, the direction of the sound absorbing panel 10 can be freely installed regardless of the position of the sound source, and the degree of freedom of installation is increased.

Next, FIG. 4 is a cross-sectional schematic diagram showing another example of the sound absorbing panel 20.
The sound absorbing panel shown in FIG. 4 is configured by arranging the above sound absorbing material 1A and the plate-like rigid body 21 so as to face each other with a predetermined interval. By arranging the sound absorbing material 1A and the rigid body 21 apart from each other, an air layer 22 is formed between the sound absorbing material 1A and the rigid body 21, as in the case of FIG. By providing the air layer 22 between the sound absorbing material 1A and the rigid body 21, the through holes 3 of the sound absorbing material 1A and the air layer 22 are communicated to form a so-called Helmholtz resonator. Thereby, a sound absorption characteristic can be improved significantly.

Distance _{m 2} of sound-absorbing material 1A and the rigid body 21, in other words, a thickness of the air layer 22 is preferably 1000mm the range above 5 mm, more preferably 500mm or less the range of 50 mm. If the thickness of the air layer 22 is out of this range, good sound absorption characteristics cannot be obtained.

  Moreover, in the sound absorbing panel 20 shown in FIG. 4, it is preferable to arrange the sound absorbing material 1A toward the sound source side. Thereby, a sound wave is efficiently incident on the through hole 3 of the sound absorbing material 1A, and a good sound absorbing characteristic is obtained.

Next, FIG. 5 shows another example of the sound absorbing panel in a schematic cross-sectional view.
In the sound absorbing panel 30 shown in FIG. 5, the sound absorbing material 1A and the plate-like rigid body 21 are arranged to face each other with a predetermined interval, and further, the sound absorbing panel 30 is porous between the sound absorbing material 1A and the rigid body 21 (air layer 22). The sound-absorbing material 31 is arranged. By arranging the sound absorbing material 1A and the rigid body 21 apart from each other, an air layer 22 is formed between the sound absorbing material 1A and the rigid body 21, as in the case of FIGS. By providing the air layer 22 between the sound absorbing material 1A and the rigid body 21, the through holes 3 of the sound absorbing material 1A and the air layer 22 are communicated to form a so-called Helmholtz resonator. Thereby, a sound absorption characteristic can be improved significantly.
Further, the sound absorbing characteristics of the sound absorbing panel 30 can be further improved by disposing the porous sound absorbing material 31 in the air layer 22. As the porous sound absorbing material 31, for example, glass wool, rock wool, or the like can be used.

Distance _{m 3} of the sound absorbing material 1A and the rigid body 21 in the sound-absorbing panel 30, in other words, a thickness of the air layer 22 is preferably 1000mm the range above 5 mm, more preferably 500mm or less the range of 50 mm. If the thickness of the air layer 22 is out of this range, good sound absorption characteristics cannot be obtained.

  Moreover, in the sound absorbing panel 30 shown in FIG. 5, it is preferable to arrange the sound absorbing material 1A toward the sound source side, as in the case of the sound absorbing panel 20 shown in FIG. Thereby, a sound wave is efficiently incident on the through hole 3 of the sound absorbing material 1A, and a good sound absorbing characteristic is obtained.

Next, FIG. 6 shows a cross-sectional schematic diagram of another example of the sound absorbing panel.
The sound absorbing panel 40 shown in FIG. 6 has the sound absorbing material 1A and the plate-like rigid body 21 arranged to face each other with a predetermined space therebetween, and further the surface 1a on the rigid body side of the sound absorbing material 1A (the surface on the air layer 22 side). ) And a reinforcing member 41 are joined to each other. The reinforcing member 41 and the rigid body 21 may be separated from each other or may be joined. The reinforcing member 41 may be attached to either the rigid body-side surface 1a of the sound-absorbing material 1A or the surface 1b opposite to the rigid-body-side surface. It is good to attach to the surface 1a by the side of the rigid body 21 of the material 1A.

  As the reinforcing member 41, for example, a member having a gap such as a honeycomb panel made of metal such as aluminum, a cross-shaped panel, a rib or the like can be used. Thereby, there is no possibility that the through hole 3 and the air layer 22 are blocked by the reinforcing member 41.

By arranging the sound absorbing material 1A and the rigid body 21 apart from each other, an air layer 22 is formed between the sound absorbing material 1A and the rigid body 21, as in the case of FIGS. In the sound absorbing panel 40 shown in FIG. 6, the air gap of the reinforcing member 41 and the air layer 22 are communicated, and the air gap of the reinforcing member 41 is included in a part of the air layer 22.
By providing the air layer 22 between the sound absorbing material 1A and the rigid body 21, the so-called Helmholtz resonator is constituted by the through holes 3 of the sound absorbing material 1A and the air layer 22. Thereby, a sound absorption characteristic can be improved significantly.
Moreover, the strength of the sound absorbing material 1A itself can be improved by attaching the reinforcing member 41 to the sound absorbing material 1A.

In other words, the distance m ₄ between the sound absorbing material 1A and the rigid body 21 in the sound absorbing panel 40 is preferably in the range of 5 mm to 1000 mm, and more preferably in the range of 50 mm to 500 mm. If the thickness of the air layer 22 is out of this range, good sound absorption characteristics cannot be obtained.

  Moreover, in the sound absorbing panel 40 shown in FIG. 6, it is preferable to arrange the sound absorbing material 1A toward the sound source side, as in the case of the sound absorbing panels 20 and 30 shown in FIGS. Thereby, a sound wave is efficiently incident on the through hole 3 of the sound absorbing material 1A, and a good sound absorbing characteristic is obtained.

  The reinforcing member 41 may be attached not only to the sound absorbing panel 40 shown in FIG. 6 but also to each of the sound absorbing materials 1A of the sound absorbing panels 10, 20, and 30 shown in FIGS.

  Further, the porous sound absorbing material 31 may be attached not only to the sound absorbing panel 30 shown in FIG. 5 but also to the sound absorbing panels 10, 20, and 40 shown in FIGS.

  According to each of the sound absorbing panels 10 to 40 described above, the sound absorbing materials 1 </ b> A and 1 </ b> B or the sound absorbing material 1 </ b> A and the rigid body 21 are disposed to face each other, and the air layer 11 is disposed between the sound absorbing materials 1 </ b> A and 1 </ b> B or between the sound absorbing material 1 </ b> A and the rigid body 21. , 22 is provided, so-called Helmholtz resonators are constituted by the through holes 3 of the sound absorbing material and the air layers 11 and 22, and the sound absorbing characteristics can be greatly improved. Moreover, since the sound absorbing materials 1A and 1B themselves are excellent in aesthetics, the aesthetics of the sound absorbing panels 10 to 40 themselves can be enhanced.

"Manufacturing method of sound absorbing material"
Next, a method for manufacturing the sound absorbing material 1 of the present embodiment will be described.
FIG. 7 shows a flowchart of a method for manufacturing the sound absorbing material 1. As shown in FIG. 7, the manufacturing method of the sound-absorbing material 1 of the present embodiment includes a mixing step S1 in which metal powder and a through-hole forming agent powder are mixed, and a metal powder and a through-hole forming agent powder in a fibrous form. A hot extrusion step S2 in which a bulk body is formed by solidification and molding while being stretched in one direction, a slicing step S3 in which the bulk body is sliced in a plate shape along a direction perpendicular to the stretching direction, and a through hole forming agent is removed. And a through hole forming agent removing step S4 for providing a through hole.
Hereinafter, each step will be described in detail.

(Mixing step S1)
In the mixing step S1, a mixed powder is prepared by mixing the metal powder and the through-hole forming agent powder. A known mixing means may be used as the mixing means.
As the metal powder, any one of Al, Mg, Sn, and Cu, an alloy powder mainly composed of one of them, or a mixed powder of the metal powder and the alloy powder can be used. Al is particularly preferable from the viewpoints of lightness, corrosion resistance, ease of processing, material cost, and the like. In addition, as the metal powder, it is preferable to use a powder having an average particle size in the range of 30 μm to 1000 μm from the viewpoint of processing the metal powder into a fiber in the hot extrusion step S2 described later. The particle size range of the metal powder is preferably in the range of 10 μm to 2000 μm.

Next, the through-hole forming agent is preferably made of a water-soluble salt, more preferably NaCl or KCl, and particularly preferably NaCl. These through-hole forming agents have a high melting point and are processed into fibers without reacting with the metal powder in the hot extrusion step S2 described later. Moreover, these through-hole forming agents are all water-soluble, and can be easily removed in the through-hole forming agent removing step described later. In addition, the material of the through hole forming agent is not limited to those listed above, as long as it forms a fiber stretched in one direction by processing such as hot extrusion, and can be easily removed thereafter. Any thing is good.
Further, it is preferable to use a powder having an average particle diameter in the range of 50 μm to 1000 μm as the powder of the through hole forming agent. The particle size range of the through-hole forming agent powder is preferably in the range of 30 μm to 2000 μm. When the particle size of the powder is smaller than the lower limit of this range, after extrusion, the through-hole forming agent is thin, that is, the pore diameter becomes too small, and it is difficult to remove the through-hole forming agent. In addition, when the particle size of the powder is larger than the upper limit of this range, the extrusion ratio in the extrusion process must be increased, the extrusion pressure is increased, and the mold must be reinforced and the apparatus enlarged (cost is increased). Take).
The average particle size and particle size range of the metal powder and the through-hole forming agent powder are preferably the above, but are not particularly limited to this, and the diameter of the through-hole is 200 μm or less depending on the processing conditions, particularly the combination with the extrusion ratio. Any value is acceptable as long as it is within the range.

  The mixing ratio of the metal powder and the through-hole forming agent is preferably in the range of metal powder: through-hole forming agent = 90: 10 to 20:80, and particularly preferably in the range of 80:20 to 40:60. . By adjusting the mixing ratio of the metal powder and the through hole forming agent within the above range, it is possible to control the opening ratio of the through holes of the sound absorbing material. When the mixing ratio of the through-hole forming agent is reduced, sufficient through-holes are not formed, and the aperture ratio may be reduced. Further, when the mixing ratio of the through-hole forming agent is increased, it is difficult to suppress the diameter to 200 μm or less due to an increase in the diameter of the through-hole, and the opening ratio may be increased.

(Hot extrusion process S2)
Next, in the hot extrusion step S2, the mixed powder is subjected to a hot extrusion process, whereby the metal powder and the through hole forming agent powder are solidified while being stretched in one direction in a fiber shape. To form a bulk body. Regarding the conditions for hot extrusion, the extrusion ratio is preferably in the range of 3 to 500, and when Al is used as the metal powder, the extrusion temperature is preferably in the range of 300 ° C to 600 ° C. If this condition is not met, it becomes difficult to form a bulk body.
Extrusion does not need to be performed hot, and cold extrusion may be performed as long as both the metal powder and the through-hole forming agent powder are stretched into a fiber to form a bulk body.

  With this hot extrusion process, the metal powder is bonded to each other under the influence of pressure and temperature, and the bonded metal is stretched into a fiber along the extrusion direction. In addition, with respect to the powder of the through-hole forming agent, the particles are integrated with each other under the influence of pressure and temperature and are stretched into a fiber shape along the extrusion direction, or the particles themselves are fibrous along the extrusion direction. Stretched. And the metal extended | stretched to the fiber form and the through-hole formation agent are mutually integrated, and it solidifies and molds as a whole, and a bulk body is formed. In the cross section orthogonal to the extrusion direction of the bulk body, the metal stretched in the form of fibers and the through-hole forming agent are distributed in a mosaic pattern. In addition, the extending | stretching direction of the fiber in the bulk body formed by the hot extrusion process corresponds with an extrusion direction.

(Slicing step S3)
Next, in the slicing step S3, the bulk body is sliced into a plate shape along the direction perpendicular to the stretching direction (extrusion direction). FIG. 8 shows a schematic diagram of the slicing process.
FIG. 8A is a schematic cross-sectional view of the bulk body 50. In FIG. 8A, a plurality of parallel lines drawn on the cross section of the bulk body 50 are through-hole forming agents 51 extended in a fibrous form. The through hole forming agent 51 is extended in a fiber shape in the same direction as the extrusion direction.
Next, in FIG. 8B, the bulk body 50 is sliced into a plate shape along the direction perpendicular to the extrusion direction. A chain line in FIG. 8B is a line indicating a slice plane. In the present embodiment, it is preferable that the extrusion direction and the slice plane (slice direction) are perpendicular to each other. By slicing, the through-hole forming agent 51 is exposed on the slice surface, and a plate-like member 2d as shown in FIG. 8C is obtained.

(Through hole forming agent removing step S4)
Next, in the through hole forming agent removing step S4, the through hole forming agent 51 is removed from the plate member 2d to form a through hole. As the removing means, a means for eluting or volatilizing the through hole forming agent can be used. In particular, when a water-soluble salt is used as the through-hole forming agent, it is preferable to use an elution method. Specifically, the through hole forming agent 51 may be eluted from the plate-like member 2d by immersing the bulk body in water and leaving it for 1 to 24 hours.
In this way, the sound absorbing material 1 of the present embodiment is obtained.

  By the way, according to the slicing step, the sliced surface of the plate-like member 2d becomes the one surface 2a and the other surface 2b of the plate-like member 2 constituting the sound absorbing material 1. Therefore, the one surface 2a and the other surface 2b of the sound absorbing material 1 are in a relationship perpendicular to the extrusion direction. On the other hand, the through holes 3 are formed through the slicing step and the through hole forming agent removing step. Since the through holes 3 are formed by removing the through hole forming agent 51, the same direction as the extrusion direction is formed. Extends along. From the above, the through holes 3 provided in the sound absorbing material 1 have a relationship perpendicular to the one surface 2a and the other surface 2b. For this reason, when installing the manufactured sound absorbing material 1, the sound source is positioned in the extending direction of the through hole 3 by setting the surface direction of the one surface 2a or the other surface 2b of the sound absorbing material 1 toward the sound source. As a result, the sound absorbing characteristics of the sound absorbing material 1 can be effectively exhibited to the maximum.

  According to the method for producing the sound absorbing material 1 described above, the metal powder and the through-hole forming agent powder are solidified while being stretched in one direction in a fiber shape to form a bulk body, and the bulk body is perpendicular to the stretching direction. Since the through holes 3 are formed by removing the through hole forming agent after slicing in a plate shape along the direction, there is little possibility that one or both ends of the through holes 3 are closed, and along the plate thickness direction. The sound-absorbing material 1 that includes the through holes 3 that extend and have a large aspect ratio can be manufactured at low cost. Further, the thickness of the sound absorbing material 1 can be increased. Such a sound absorbing material 1 has excellent sound absorbing characteristics.

  Moreover, in the sound-absorbing material 1 manufactured by the above-described manufacturing method, the through hole 3 is formed by slicing the bulk body into a plate shape along the vertical direction of the stretching direction. There is little possibility that one end or both ends are closed, and the sound-absorbing material 1 is provided with the through holes 3 extending along the plate thickness direction and having a large aspect ratio. Such a sound absorbing material 1 has excellent sound absorbing characteristics.

Example 1
A NaCl powder (through-hole forming agent) having an average particle diameter of 420 μm and an Al powder (metal powder) having an average particle diameter of 200 μm are mixed at a volume ratio of metal powder: through-hole forming agent = 55: 45. A mixed powder was prepared.
Next, the obtained mixed powder was hot-extruded under conditions of an extrusion ratio of 6.9 and an extrusion temperature of 450 ° C. to form a cylindrical bulk body. The obtained bulk body was sliced in a direction orthogonal to the extrusion direction to obtain a plate member having a thickness of 1 mm. And the sound-absorbing material of Example 1 was manufactured by immersing this plate-like member in water for 6 hours to elute NaCl.

  When the sound absorbing material of Example 1 was observed with a scanning electron microscope, a large number of through holes having an average diameter of about 100 μm were observed. Moreover, when the opening ratio of the through hole was calculated from the mixing ratio of the through hole forming agent and the metal powder, it was 45%.

Next, the vertical sound absorption characteristics of the sound absorbing material of Example 1 were measured by the transmission function method (ISO 10534-2 compliant). Specifically, the sound absorbing material of Example 1 was disposed at one end of a hollow cylindrical acoustic tube having a length of 400 mm and an inner diameter of 40 mm, and the back air layer was 150 mm. The surface of the back air layer opposite to the sound absorbing material was a rigid body. A speaker is disposed at the other end of the acoustic tube. Further, two microphones were installed at a predetermined interval between one end and the other end of the acoustic tube. Each speaker and microphone was connected to a computing device for measurement. In this way, a measurement apparatus for normal incident sound absorption characteristics by the transfer function method (based on ISO 10534-2) was configured.
Then, a sound having a certain band from the speaker was radiated into the acoustic tube, a transmission function between two microphones provided in the tube was measured, and a normal incidence sound absorption characteristic ratio was calculated based on this transmission function.
The results are shown in FIG. FIG. 9 also shows the calculated value of the normal incidence sound absorption coefficient calculated by the above equation (1).

  As shown in FIG. 9, the measured values are in good agreement with the calculated values, indicating that excellent sound absorption characteristics are obtained.

  Further, in measuring the vertical sound absorption characteristics of the sound absorbing material of Example 1 by the transfer function method (based on ISO 10534-2), glass wool was filled in a 150 mm-thick back air layer between the sound absorbing material of Example 1 and the rigid body. Except for the above, the vertical sound absorption characteristics of the sound absorbing material of Example 1 were measured in the same manner as described above. The results are shown in FIG. FIG. 10 also shows measured values of the sound absorbing panel in FIG.

  As shown in FIG. 10, when glass wool is filled in the back air layer, the frequency band showing a sound absorption coefficient of 0.8 or more is expanded compared to the case where glass wool is not filled, and the sound absorption characteristics are increased. It can be seen that further improvements have been made. This expansion of the frequency band is considered to be due to the glass wool being filled in the air layer.

(Comparative Example 1)
The sound-absorbing material of Comparative Example 1 was manufactured by drilling a plurality of through-holes having a diameter of 200 μm with a drill on an aluminum plate having a thickness of 1 mm at a pitch of 200 μm. Each through hole was arranged in a lattice shape.
When the normal incident sound absorption coefficient was measured in the same manner as in Example 1 except that the sound absorbing material of Comparative Example 1 was used, almost the same sound absorption characteristics as in Example 1 were obtained.
However, in producing the sound absorbing material of Comparative Example 1, since the through hole was formed by drilling, it took a long time to produce the sound absorbing material.

FIG. 1 is a perspective view showing a sound absorbing material according to an embodiment of the present invention. FIG. 2 is a schematic partial sectional view of the sound absorbing material of FIG. FIG. 3 is a schematic cross-sectional view showing an example of a sound absorbing panel according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing another example of the sound absorbing panel according to the embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing another example of the sound absorbing panel according to the embodiment of the present invention. FIG. 6 is a schematic sectional view showing another example of the sound absorbing panel according to the embodiment of the present invention. FIG. 7 is a flowchart for explaining a method of manufacturing a sound absorbing material according to an embodiment of the present invention. FIG. 8 is a schematic view for explaining one step in the method for producing a sound absorbing material according to the embodiment of the present invention. FIG. 9 is a graph showing the sound absorption characteristics of the sound absorption panel of Example 1, and is a graph showing the frequency dependence of the sound absorption coefficient. FIG. 10 is a graph showing the sound absorption characteristics of the sound absorbing panel of Example 1, and is a graph showing the frequency dependence of the sound absorption rate when the back air layer is filled with glass wool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A, 1B ... Sound-absorbing material, 2, 2d ... Plate-like member, 2a ... One side (surface in which the through-hole of the plate-like member was provided), 2b ... Other side (surface in which the through-hole of the plate-like member was provided) 2c ... metal surface, 3 ... through hole, 10, 20, 30, 40 ... sound absorbing panel, 50 ... bulk body, 51 ... through hole forming agent

Claims (11)

  A sound-absorbing material comprising a metal plate-like member, wherein the plate-like member is provided with a plurality of through holes having a diameter of 200 μm or less along the plate thickness direction.   The metal powder and the through-hole forming agent powder are mixed, then the metal powder and the through-hole forming agent powder are solidified while being stretched in one direction in a fiber shape to form a bulk body, A plate-like member is formed by slicing the bulk body along a direction perpendicular to the stretching direction, and then the through-hole forming agent is removed from the plate-like member to form a plurality of through-holes having a diameter of 200 μm or less. A sound absorbing material characterized by being formed.   The sound absorbing material according to claim 1 or 2, wherein an opening ratio of the through hole is in a range of 10% to 80%.   A metal powder and a through-hole forming agent powder are mixed, and then the metal powder and the through-hole forming agent powder are solidified and formed in a fiber shape in one direction to form a bulk body, A plate-like member is formed by slicing the bulk body along a direction perpendicular to the stretching direction, and then a plurality of through-holes having a diameter of 200 μm or less are formed by removing the through-hole forming agent from the plate-like member. A method for producing a sound absorbing material, comprising: providing a sound absorbing material.   The method for producing a sound-absorbing material according to claim 4, wherein the bulk body is formed by extruding a mixture of the metal powder and the powder of the through-hole forming agent by a hot extrusion method.   The metal powder is any one of Al, Mg, Sn, and Cu, an alloy powder mainly composed of one of them, or a mixed powder of the metal powder and the alloy powder. The method for producing a sound absorbing material according to claim 4 or 5.   The method for producing a sound-absorbing material according to any one of claims 4 to 6, wherein the through-hole forming agent comprises a water-soluble salt.   A sound-absorbing panel comprising two or more sound-absorbing materials according to any one of claims 1 to 3 that are disposed relative to each other at a predetermined interval, and an air layer is provided between the sound-absorbing materials. .   The sound absorbing material according to any one of claims 1 to 3 and the rigid body are relatively arranged with a predetermined interval, and an air layer is provided between the sound absorbing material and the rigid body. Sound absorbing panel.   The sound absorbing panel according to claim 8 or 9, wherein a porous sound absorbing material is disposed in the air layer. The sound absorbing panel according to any one of claims 8 to 10, wherein a reinforcing member is attached to a surface of the sound absorbing material on the air layer side.

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