JP2000238157A - Sound absorber structure - Google Patents

Abstract

(57) [Summary] [Purpose] Without increasing the thickness and weight per unit area of conventional sound absorbing materials,
Provided is a sound absorbing structure that absorbs sound in a high frequency range and contributes to improving quietness in a vehicle cabin. [Constitution] A sound absorbing structure in which an ultrafine fiber thin film is arranged in front of a rigid body with respect to the sound incident direction via a porous medium,
In this sound absorbing material, a sound absorbing structure in which the ultrafine fiber thin film is formed of a nonwoven fabric of a melt blown method, and a sound absorbing structure in which the ultrafine fiber thin film is formed of a spunbond nonwoven fabric of split fibers, a woven fabric, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing structure, and more particularly to a sound absorbing structure suitable for being disposed in an automobile room or an engine room.

[0002]

2. Description of the Related Art A running noise of a vehicle causes a friction noise (road noise) between a tire and a road surface, an engine noise, a wind noise of a vehicle body, and the like, and enters a vehicle interior through a vehicle body panel. Conventionally, to reduce these noises, cotton felt,
A large number of fibrous sound-absorbing materials such as synthetic felts are used to fill gaps between interior materials and vehicle body panels.

[0003] In order to enhance the quietness in a vehicle cabin, a sound absorbing material is required to have a high sound absorbing property with respect to noise in a frequency range of 1 to 5 kHz which is particularly annoying to human ears.

[0004] It is known that a sound absorbing material can effectively absorb sound when it is disposed in a portion where vibration of sound reflected by a rigid body is large, such as an interior material or a panel. The frequency of the sound vibration is 1 kHz because the distance from the rigid body is large at a quarter of the wavelength.
In order to effectively absorb the sound exceeding the above, a sound absorbing material having a thickness of about 90 mm is required. However, the frequency is 1 kHz in the vehicle cabin due to securing space, interior design restrictions, etc.
In many cases, it is not possible to set a sound-absorbing material having a thickness sufficient to absorb sounds exceeding the maximum. It is also known that increasing the weight of the sound absorbing material works advantageously. However, due to the design of the vehicle, it is not possible to improve the sound absorbing property by limiting the weight without limitation.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a frequency of 1 to 5 kHz which is particularly annoying to human ears without increasing the thickness and the weight per unit area of conventional sound absorbing materials. Provided is a sound absorber structure that absorbs noise in a frequency range and contributes to improving quietness in a vehicle cabin.

[0006]

Means for Solving the Problems According to the present invention, there is provided a sound absorbing structure in which an ultrafine fiber thin film is arranged via a porous medium in front of a rigid body with respect to a sound incident direction.
The sound absorbing material has a sound absorbing structure in which the ultrafine fiber thin film is formed of a nonwoven fabric manufactured by a melt blown method, and a sound absorbing structure in which the ultrafine fiber thin film is formed of a nonwoven fabric or woven fabric of split fibers.

[0007]

The sound absorbing body structure of the present invention has a
An ultrafine fiber thin film, a porous medium, and a rigid body are arranged in this order. The ultrafine fiber thin film is disposed on the surface of the sound absorbing material where the vibration of sound increases, and effectively absorbs noise of 1 kHz or more.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. As shown in FIG. 1, a sound absorbing structure 10 of the present invention
Is arranged in the order of the ultrafine fiber thin film 11, the porous medium 12, and the rigid body 13 when viewed from the noise incident direction.

(Ultrafine fiber thin film) The ultrafine fiber thin film of the present invention is obtained by splitting a split fiber manufactured by a melt blown method or an split fiber manufactured by a spunbond method by an external force (such as a water needle) or heat treatment. It can be formed by making the fibers into a non-woven fabric by needling. Thickness is about 0.1-1mm, weight per area 10-100g
/ M ² . In the case of the melt blown method, the average diameter of the constituent fibers is 2 μm or less, and in the case of the non-woven fabric of the split fibers, each split fiber is preferably as thin as 1 and more preferably 1 denier or less.

An example of a split fiber will be described with reference to FIG. 2A and 2B show cross-sectional structures of different types of split fibers. The type (a) surrounds a core of polyethylene fiber (diameter: 12 μ = equivalent to 1.5 denier) in the center and a polyester resin fiber (diameter: 5 μ =
(Equivalent to 0.25 denier).
The type (b) is a fiber (3.5 denier in total) in which polyester-based fibers and polypropylene-based fibers are alternately arranged so as to divide a circle into eight. These fibers are spun together and constitute a single fiber macroscopically. However, they are easily formed by external force such as a water needle or heat treatment (because the thermal expansion coefficients of the components are different). And converted into a plurality of smaller diameter fibers.

(Porous Medium) It is important for the porous medium to maintain the thickness of the gap between the rigid body and the ultrafine fiber thin film, and felt and the like are suitable. In this case, there is no designation for the fiber material, fiber diameter and thickness. Other than felts, urethane and bubble cushioning materials are also suitable as porous media. (Rigid body) It is a rigid wall body without air permeability, and actually corresponds to a (resin) substrate surface of an interior material of an automobile. (Lamination method) The ultrafine fiber thin film and the porous medium can be laminated by adhesion or needle punching. The rigid body and the porous medium are laminated by bonding or fusion. Further, the fine fibers as described above are scattered in a tuft form on a felt (porous medium) and needled toward the felt direction, so that the felt fibers and the fine fibers are entangled. A thin film can also be formed.

[0012]

(Example 1) A nonwoven fabric (fiber type polyester, average fiber diameter 2
μ, basis weight 50 g / ² , thickness 0.55 mm) and a porous medium (polyester fiber felt (1.5 denier 90% + 4 denier 10%)) with a basis weight 200 g / ² ,
(Thickness 10 mm) was used. The ultrafine fiber thin film and the porous medium are laminated by needling. (Example 2) Nonwoven fabric (polyethylene fiber (equivalent to a fiber diameter of 6μ = 0.24 denier) obtained by subjecting a spunbonded nonwoven fabric of split fibers to a water needle treatment as an ultrafine fiber thin film,
Using a polyester fiber (fiber diameter 5μ = 0.24 denier equivalent), a porous medium (polyester fiber felt (1.5 denier 90% + 4 denier 10%), basis weight 200 g / m ² , thickness 10 mm) was used. Using. The ultrafine fiber thin film and the porous medium are laminated by needling.

Comparative Example 1 Single-layer, homogeneous polyester fiber felt (1.5 denier 90% + 4 denier 10
%), A basis weight of 200 g / m ² and a thickness of 10 mm.
The felt of this comparative example is made of the same material as the porous media of Examples 1 and 2, and has the same basis weight. (Comparative Example 2) Single layer, homogeneous polyester fiber felt (1.5 denier 90% + 4 denier 10%), basis weight 400 g / m ² , thickness 10 mm. The felt of this comparative example is the same material as the porous media of Examples 1 and 2,
The basis weight is set to be twice as large. (Evaluation) The sound absorption coefficient of each of the sound absorbing structures of the examples and the comparative examples was measured by the two-microphone method (ISO / DIS 10534-2) (back air layer: 0 mm). FIG. 3 shows the measurement results of the sound absorption coefficient at each frequency. By comparing the example of the present invention with the comparative example, the example in which the ultrafine fiber thin film was laminated on the porous medium was not only compared with Comparative Example 1 having almost the same basis weight but also Comparative Example 2 having a high basis weight (particularly, (In the frequency range above 1 kHz).

[0014]

According to the sound-absorbing structure of the present invention, noise of 1 kHz or more, which is particularly annoying to human ears, is absorbed without increasing the thickness and the basis weight of the sound-absorbing material, and the quietness in the vehicle interior is improved. be able to. The sound absorber structure of the present invention is:
It is suitable for being placed in the interior of an automobile or in an engine room of an automobile, and can be used widely in combination with various kinds of automobile interior materials such as a headliner and luggage trim.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sound absorber structure according to the present invention.

FIG. 2 shows sectional views of various split fibers.

FIG. 3 shows the evaluation results of sound absorbing properties.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sound absorber structure 11 Ultrafine fiber thin film 12 Porous medium 13 Rigid body

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G10K 11/16 F16M 1/00 C 11/162 G10K 11/16 D // F16M 1/00 A F term (reference) 3D023 BA02 BA03 BB21 BB30 BC00 BD21 BE03 BE04 BE20 4F100 AK41 AT00A BA03 BA07 BA10A BA10C DG06C DG11C DG15B DG15C DJ00B EC09 GB33 JH01 JK12A JM02C 4L047 AA21 AB02 AB03 AB08 BA04 BA22 A

Claims (3)

[Claims] 1. A sound absorber structure comprising a microfiber thin film disposed in front of a rigid body with respect to a noise incident direction via a porous medium. 2. The sound absorber structure according to claim 1, wherein the ultrafine fiber thin film is constituted by a nonwoven fabric produced by a melt blown method. 3. The sound absorbing structure according to claim 1, wherein the ultrafine fiber thin film is formed of a nonwoven fabric or woven fabric of split fibers.