JP2005283703A - Sound absorbing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight and inexpensive sound absorbing material capable of improving sound absorptivity at about 1 to 3 KHz without increasing the thickness. <P>SOLUTION: The sound absorbing material comprises a base material 11 which has a plurality of recesses and projections formed by profile processing on a surface of a flat plate type porous elastic foamed body made of polyurethane foam etc., and a film 21 which is extended between peak parts 15a of the projections 15 and joined with the peak parts 15a of the projections 15. The film 21 is a plastic film of 10 to 1,000 μm in thickness which is made of a polyurethane film etc., intervals of the projections 15 being preferably 5 to 200 μmm and height differences between projections and recesses being 3 to 70 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sound absorbing material.

  For example, sound absorbing materials made of felt, foam, glass wool or the like are frequently used in automobiles. In addition, a sound absorbing material for automobiles is required to be lightweight for improving fuel consumption. Furthermore, in a diesel engine vehicle, an improvement in sound absorption near 1 to 3 KHz is required.

Sound absorbing material made of a fiber material such as a conventional felt or glass wool is generally used in a weight range of ^{300g / m 2 ~1600g / m 2} . In addition, it has been proposed that a resin film is stretched on glass wool, rock wool, porous board, etc. whose surface is uneven, and stored in the outer frame material. A binder and a mold are required, and cost and labor are required. In addition, when the sound absorbing material is compressed, the projections are crushed and cannot be restored even after being released from compression, and the surface of the fiber body and the resin film come into contact with each other almost entirely, limiting the vibration of the resin film, and good sound absorption Cannot be obtained.

  Further, in a sound absorbing material made of a porous material, increasing the thickness or stretching a film over the entire surface is performed as a method for improving the sound absorbing property in the vicinity of 1 to 3 kHz. However, when the thickness is increased, there arises a problem that the weight of the sound absorbing material increases and a problem that the sound absorbing material cannot be installed in an installation place where the installation space is limited. On the other hand, when the film is stretched over the entire surface, although the sound absorbing property in the vicinity of 1 to 3 kHz can be improved by the film vibration of the film, the overall sound absorbing property tends to be lowered.

Furthermore, a resin film having a large number of convex portions filled with air on the surface is also proposed, which has been proposed to be adhered to the surface of the porous material. There is a problem that it is easy to collect and a problem that the air-filled convex portion is easily damaged during construction.
JP 2000-144968 A JP-A-7-261768

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a light-absorbing material that can improve the sound-absorbing property in the vicinity of 1 to 3 kHz without increasing the thickness, and is lightweight.

  The invention of claim 1 includes: a base material having a plurality of irregularities formed on the surface of a flat porous elastic foam; and a coating stretched between the tops of the convex parts and joined to the tops of the convex parts. Concerning the sound absorbing material.

  According to a second aspect of the present invention, in the first aspect, the irregularities of the porous elastic foam are formed by profile processing.

  A third aspect of the invention is characterized in that, in the first or second aspect, the coating film is a plastic film having a thickness of 10 to 1000 μm.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the interval between the convex portions is 5 to 200 mm.

  A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, the height difference between the convex portion and the concave portion in the substrate is 3 to 70 mm.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the thickness H2 of the concave portion position in the substrate is 1 to 20 mm.

  According to the present invention, the sound absorbing material is bonded between the base material having a plurality of uneven portions formed on the surface of the flat porous elastic foam and the top portion of the convex portion. Therefore, it is possible to improve the sound absorbing property by the film vibration of the coating, particularly the sound absorbing property in the vicinity of 1 to 3 kHz, and the sound absorbing property can be improved without increasing the thickness of the sound absorbing material. . And since the said film is joined with the top part of the convex part of a base material, the film vibration of a film can be reliably performed between convex parts, and the improvement of a sound absorption property becomes more favorable.

  Furthermore, as is well known, the profile processing according to claim 2 compresses a porous elastic foam having a flat plate shape by passing it between two rolls having an uneven surface, and the compressed porous elastic foam in the compressed state. It is a processing method that has a plurality of irregularities on the cut surface when the porous elastic foam after cutting is restored by cutting the central portion with a blade, and the plurality of irregularities can be formed without using a mold. Since it can form on the surface of a base material, an inexpensive sound-absorbing material can be obtained. In addition, since the base material is made of a porous elastic foam, depending on the installation location of the sound absorbing material, even if it may be necessary to compress the sound absorbing material once during the installation work, the convex portion collapsed by the compression, Since the restoration is performed after the compression is released, the sound absorption effect by the film vibration of the coating bonded to the top of the convex portion can be obtained even after the compression is released.

  FIG. 1 is a partially cutaway perspective view of a sound absorbing material in one embodiment of the present invention, and FIG. 2 is a perspective view of a base material in the same embodiment.

A sound absorbing material 10 shown in FIG. 1 includes a base material 11 and a coating 21. As is better understood from FIG. 2, the base material 11 is formed by forming a plurality of irregularities by profile processing on the surface of a flat porous elastic foam. The porous elastic foam is not particularly limited as long as profile processing is possible. Examples of usable porous elastic foams include flexible polyurethane foam, melamine foam, rubber sponge, and olefin foam. The porous elastic foam having a density of 15 to 40 kg / m ³ and an air flow rate of 10 to 50 cc / cm ³ / sec (JIS L 1096) has good lightness and sound absorption. preferable. However, when viewed from a single foam body, the structure of the present invention exhibits better sound absorption than conventional sound absorbing materials even outside the above range.

  The unevenness is formed by a known profile processing. In the example shown in the figure, the unevenness composed of a plurality of concave portions 13 and convex portions 15 is formed on one surface of the porous elastic foam. The unevenness may be formed on both sides of the foam.

  As for the space | interval (top part space | interval) of the said convex part 15, 5 mm-200 mm are preferable. If the thickness is less than 5 mm, the degree of freedom of the coating 21 decreases between the convex portions 15, and effective sound absorption improvement due to film vibration of the coating 21 cannot be achieved. When the thickness exceeds 200 mm, the film 21 comes into contact with the recess 13 when the film 21 is bent, and the film vibration of the film 21 is not effectively performed. For the above reasons, the interval between the convex portions 15 is preferably 5 mm to 200 mm, and more preferably 30 mm to 50 mm.

  The height difference between the convex portion 15 and the concave portion 13, that is, the height difference between the thickness H1 of the base material 11 at the position of the convex portion 15 and the thickness H2 of the base material 11 at the position of the concave portion 13, the value of H1-H2 is 3 mm to 70 mm is preferable. When the thickness is less than 3 mm, the gap between the recess 13 and the coating 21 is substantially eliminated, the degree of freedom of the coating is impaired, and good sound absorption cannot be obtained. On the other hand, if it exceeds 70 mm, the increase in thickness of the sound absorbing material 10 not only impairs the light weight of the sound absorbing material 10, but also restricts the installation location of the sound absorbing material. In addition, it is preferable that the thickness H2 of the concave portion 13 position: the convex portion position thickness H1 of the base material 11 is 1: 1.5 to 1: 4. When the ratio of the thickness H1 at the position of the convex portion 15 to the thickness H2 at the position of the concave portion 13 is less than 1.5, it is difficult to obtain good film vibration of the coating film 21, and it is larger than 1.5. In the case of, light weight becomes difficult. Furthermore, the thickness H2 at the position of the recess 13 in the substrate 11 is preferably 1 to 20 mm. If the thickness is less than 1 mm, good sound-absorbing properties cannot be obtained, and a problem that a through hole is formed at the bottom of the valley of the recess after molding is likely to occur. On the other hand, if it is thicker than 20 mm, not only the light weight of the sound absorbing material 10 is impaired, but also the location of the sound absorbing material is restricted.

  The coating 21 is made of a plastic film. The material of the plastic film is not limited, and examples thereof include polyethylene, polyurethane, polyethylene terephthalate, polyamide, and silicon. Further, the coating film 21 having a thickness of 10 to 1000 μm is preferable because it has excellent film vibration characteristics and good sound absorption.

  The coating 21 is stretched between the convex portions 15 leaving a space between the concave portions 13 and covers the surface of the base material 11 on the concave-convex side. The coating 21 and the convex portion 15 are joined at the top portion 15 a of the convex portion 15. The bonding may be performed by an adhesive, or by flame welding in which the top portion 15a of the convex portion 15 is melted by a flame and the coating film 21 is pressure-bonded to the top portion 15a of the molten convex portion 15 or other bonding. The method may be used. Moreover, as long as the said coating 21 has covered the uneven | corrugated surface of the said base material 11, the whole surface of the base material 11 may be covered with the coating film 21 by the use, and favorable sound-absorbing property is obtained also in that case. Furthermore, in that case, it can be expected that the durability of the porous elastic foam as the base material is increased by covering the base material 11 with the plastic film as the coating film.

Specific examples will be described below. The sound-absorbing material of Example 1 was profile processed with a flexible polyurethane foam (density 18 kg / m ³ , air flow 30 cc / cm ³ / sec (JIS L 1096), product number F-21, manufactured by Inoac Corporation) as a base material. Then, one having an uneven surface on one side was used. In addition, the base material in Example 1 has a convex part interval (top part interval) of 30 mm, a base material thickness H1 at the convex part position of 10 mm, a base material thickness H2 at the concave part position of 3 mm, and the convex part and concave part. The height difference of H1-H2 is 7 mm, H2: H1 is 1: 3.3, and the overall dimensions of the substrate are 10 × 300 × 300 mm. Moreover, the coating film in Example 1 was stretched between the convex parts by using a polyurethane film having a thickness of 20 μm and joining the top part of the convex part of the base material by flame welding.

  The sound-absorbing material of Example 2 uses the same flexible polyurethane foam as that of Example 1 as a base material, the interval between the convex portions (top interval) is 30 mm, the thickness H1 of the base material at the convex portion position is 10 mm, and the concave portion position. Except for the point that the thickness H2 of the base material was 5 mm, the height difference between the convex part and the concave part, the value of H1-H2 was 5 mm, and H2: H1 was 1: 2, the same as the sound absorbing material of Example 1.

  For reference, the sound absorbing materials of Comparative Examples 1 to 4 shown below were manufactured. The sound-absorbing material of Comparative Example 1 was composed only of a 10 × 300 × 300 mm fiber body (manufactured by 3M, Thinsulate, TAI-2047). The sound-absorbing material of Comparative Example 2 was composed of a single foam having the flexible polyurethane foam used in Example 1 as 10 × 300 × 300 mm. The sound-absorbing material of Comparative Example 3 has the same configuration as that of Example 1 except that the coating film is not provided in Example 1. The sound absorbing material of Comparative Example 4 was composed of a polyurethane film having a thickness of 20 μm adhered to both surfaces of the flexible polyurethane foam of Comparative Example 2 by flame welding. Table 1 shows the configuration, the spacing between the convex portions, the values of H1 and H2, the values of H1-H2, the weight, and the thickness of the sound absorbing materials of Examples 1-2 and Comparative Examples 1-4.

  Moreover, about the said Examples 1-2 and Comparative Examples 1-4, the normal incidence sound absorption coefficient (%) was measured according to JISA1405. The measurement results are as shown in FIG. As is clear from FIG. 3, the sound absorbing materials of Examples 1 and 2 have a higher degree of freedom of coating compared to the sound absorbing materials of Comparative Examples 1 to 4, and sound absorption of 1 to 3 KHz is achieved due to membrane vibration. Has improved. Further, the sound absorbing material of Example 2 has a larger thickness (H2) of the recess than the sound absorbing material of Example 1, and the peak of the sound absorption coefficient at 1 to 3 kHz is somewhat shifted to the low frequency side. Similar to the sound absorbing material of Example 1, the sound absorbing property of 3150 Hz is superior to that of Comparative Examples 1 to 4.

It is a partially cutaway perspective view of a sound absorbing material in one embodiment of the present invention. It is a perspective view of the base material in the Example. It is a graph which shows the measurement result of the normal incidence sound absorption coefficient with respect to the sound-absorbing material of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sound absorbing material 11 Base material 13 Concave part 15 Convex part 15a Top part of convex part 21 Coating H1 Thickness of base material in convex part H2 Thickness of base material in concave part position

Claims (6)

  A sound-absorbing material comprising a base material having a plurality of irregularities formed on the surface of a flat porous elastic foam, and a coating film stretched between the tops of the projections and joined to the tops of the projections.   The sound absorbing material according to claim 1, wherein the irregularities of the porous elastic foam are formed by profile processing.   The sound absorbing material according to claim 1, wherein the coating is a plastic film having a thickness of 10 to 1000 μm.   The sound absorbing material according to any one of claims 1 to 3, wherein an interval between the convex portions is 5 to 200 mm.   The sound absorbing material according to any one of claims 1 to 4, wherein a height difference between the convex portion and the concave portion in the base material is 3 to 70 mm. The sound absorbing material according to any one of claims 1 to 5, wherein a thickness H2 of the concave portion position in the base material is 1 to 20 mm.

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