JPH10121597A - Sound absorption body and vehicle using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To demonstrate sound absorption superior in a wide frequency band by specifying density and thickness of a skin and the density of an inside body respectively in a sound absorption body provided with the porous inside body and the fine skin formed on the surface of the inside body. SOLUTION: In a sound absorption body provided with a porous inside body and a fine skin formed on the surface of the inside body, density of the skin is 0.15-0.6g/cm<3> , thickness of the skin is 0.01-0.2mm, and the density of the inside body is 0.015-0.075g/cm<3> . In other words, the skin is fine to some degree, and has a high density as compared with the inside body, and ventilation is suppressed, so that sound absorption is produced by film resonance in a low frequency range, the density of the skin is made slightly small, the skin is provided with, ventilation property, and sound absorption is produced by air friction of the inside body in a high frequency range. Thereby sound absorption property superior in the wide frequency band of 500-6300Hz can be demonstrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorber for reducing noise and a vehicle using the same, and more particularly, to a sound absorber having excellent sound absorbing performance in a wide frequency band of 500 to 6300 Hz. And vehicles.

[0002]

2. Description of the Related Art Hitherto, sound absorbers have been widely used in houses, railways, vehicles and the like, thereby reducing noise. As the sound absorber, various materials and structures are used in accordance with the place of use and purpose of use. For example,
For vehicles such as automobiles, fibrous materials such as felt and porous foams such as urethane foam are often used. In addition, there are various uses such as a hood insulator in the engine room, a dash insulator interposed between the engine room and the vehicle interior, a floor insulator and a headlining arranged in the vehicle interior.

[0003] Of the above materials, felt is often used. However, since felt has poor shapeability, it has a drawback that it has poor adhesion to panels and generally has poor sound absorbing and insulating performance. . Further, when the felt is used for floor carpets and the like, the unevenness due to the laid wire harness or the like may not be absorbed, and the carpet skin may be uneven and the appearance may not be good. Furthermore, since the defibrated fibers contain natural fibers, they lack stability in quality, and furthermore, have weaknesses due to weak bonding between the fibers, resulting in a lapse of time.

[0004] In order to improve such disadvantages, a sound absorber using urethane foam as a substitute material for felt has been proposed. By shaping the urethane foam and using it as a sound absorbing body, the adhesion between the sound absorbing body and the panel is improved, and the sound absorbing performance of the sound absorbing body is improved. In addition, since the sound absorber has no irregularities and is uniformly flat, the sound absorber is excellent in aesthetic appearance and has an effect of preventing deterioration over time and quality instability.

The urethane foam is a polyol,
A polyol system liquid composed of water, a catalyst, a foam stabilizer and a pigment, and an isocyanate are mixed and stirred, and the mixture is poured into a mold and molded. The urethane foam formed as described above has a dense (high-density) surface skin having a thickness of about 0.1 mm on the surface, and has a structure having a continuously foamed porous foam inside.

[0006]

Here, the sound absorption characteristics of a general porous structure are, as shown in FIG.
The sound absorption coefficient rises near 000 Hz, and at frequencies higher than 000 Hz, the sound absorption coefficient tends to gradually approach 1.0. However, the urethane foam formed by the above method shows the sound absorption characteristics as shown in FIG. 2 irrespective of the porous foam.
That is, there is a problem that the sound absorption coefficient becomes maximum near the frequency of 1000 Hz, and the sound absorption performance in a higher frequency region is not good. This is a general tendency of the conventional urethane foam, and is inferior to that of a fiber-based material such as felt if only sound absorbing performance in a high frequency region is mentioned.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a sound absorber that exhibits excellent sound absorption performance in a wide frequency band of 500 to 6300 Hz. It is to provide a vehicle using the same.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, the sound absorption mechanism caused by a porous body such as urethane foam as described above is as follows.
Clarified that it is roughly divided into low frequency region and high frequency region,
In response, the inventors have found that the above-mentioned problems can be solved by specifying the thickness and density of the skin and the density of the porous inner main body, and have completed the present invention.

That is, the sound absorber of the present invention is a sound absorber having a porous inner body and a dense skin formed on the surface of the inner body, wherein the density of the skin is 0.15 to 0.15.
0.6 g / cm ³ , a thickness of 0.01 to 0.2 mm, and a density of the inner body of 0.045 to 0.075
g / cm ³ . Further, a vehicle according to the present invention includes the above sound absorbing body.

[0010]

As described above, the present inventors have clarified that sound absorption by urethane foam has two mechanisms, a low frequency region and a high frequency region. That is, since the skin of the conventional urethane foam is dense and dense, as shown in FIG. 3, the airflow resistance of the skin is extremely higher than that of the inside of the porous body. Furthermore, as shown in FIG. 4, since the sound absorption performance changes greatly depending on the presence or absence of the skin, and the sound absorption coefficient of the urethane foam having the skin is maximized in the low frequency region, the sound absorption in the low frequency region is reduced. This is probably due to membrane resonance.

Here, the theoretical equation of the membrane resonance is given by the following equation, and it is experimentally found that the area density of the film calculated from this equation and the area density of the skin of the actually used sound absorber substantially match. ing. f = C / 2π · (ρ / ML) ^1/2 (where f is the resonance frequency, C is the speed of sound, ρ is the air density, M
Is the areal density of the film, and L is the thickness of the sound absorber.)

Further, as shown in FIG. 4, the sound absorber from which the skin is removed has a high sound absorption coefficient in a high frequency region, and shows the sound absorption characteristics of a general porous structure similar to FIG. From this, it is considered that the sound absorption in the high-frequency region is a sound absorption due to the internal air friction peculiar to the porous body. Further, as shown in FIG.
It has been found that the air permeability of the epidermis is uniquely determined by the density of the epidermis.

From the above findings, in the present invention, by suppressing the ventilation by making the skin somewhat denser and having a higher density than the inner body, sound absorption occurs due to membrane resonance in the low frequency region, and By making the density slightly lower than before, the skin has air permeability, and in the high frequency region, it absorbs sound due to the air friction of the inner body, so it has excellent sound absorption performance in a wide frequency band from 500 to 6300 Hz Can be done.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a sound absorber of the present invention will be described in detail. As described above, this sound absorber includes a dense skin and a porous inner main body. Here, the thickness of the skin is
It needs to be 0.01 to 0.2 mm. If the thickness of the epidermis is less than 0.01 mm, the film form will not be realized,
If the thickness exceeds 0.2 mm, the film becomes too rigid and does not cause film resonance. The density of the epidermis is 0.15
It needs to be 0.6 g / cm ³ . In other words,
From FIG. 5, the air flow rate at an air pressure of 0.01 kg / cm ² is:
It needs to be 100 to 300 cm ³ / cm ² · sec. The density of the skin does not occur membrane resonance too large an air permeability of less than 0.15 g / cm ^3, the sound absorbing performance of low-frequency region is significantly reduced, while the internal body exceeds 0.6 g / cm ³ This is because air does not flow and the sound absorption performance in a high frequency region is reduced.

Further, the density of the inner body is 0.045 to 0.5.
075 g / cm ³ . When the density of the inner main body is less than 0.045 g / cm ³ , the expansion ratio is too large to form a porous structure, while the expansion ratio is 0.075 g / cm ³
If it exceeds, it becomes too resinous and unsuitable as a sound absorber. In addition, the air flow rate of the inner body is 0.01 k air pressure.
g / cm ² , 350 to 2000 cm ³ / cm ² · sec
It is preferred that

The thickness of the entire sound absorbing body should be 5 to 5 so as to maintain good sound absorbing performance and not cause a problem in installation.
It is preferably about 0 mm. Further, in the sound absorbing body of the present invention, the skin and the inner body are preferably made of the same material, and it is particularly preferable that this material is urethane foam.

The sound absorber of the present invention can be suitably installed in a vehicle such as an automobile. In this case, the sound absorber is suitably used as a dash insulator, a floor insulator, or a head lining of the vehicle. be able to.

[0018]

The present invention will be described below in more detail with reference to Examples, Comparative Examples and Conventional Examples. FIG. 6 shows the sound absorption coefficient measurement.
A normal incidence sound absorption coefficient measuring device as shown in FIG. The thickness of the sample was unified at 30 mm. The air permeability was determined from the air pressure (0 to 0.1 kg / cm ² ) -air flow curve, based on the air flow (cm ³ / cm ² · se) at an air pressure of 0.01 kg / cm ^2.
c).

Example 1 Skin thickness 0.10 mm, skin density 0.51 g / cm ³ , air permeability 130 cm ³ /
cm ² · sec, the density of the inner body 0.06 g / cm ^3, by forming a polyurethane foam aeration 700cm ³ / cm ² · sec of the inner body, to obtain a sound absorbing body of this example.

Example 2 Skin thickness 0.11 mm, skin density 0.25 g / cm ³ , skin air permeability 240 cm ³ /
cm ² · sec, the density of the inner body 0.06 g / cm ^3, by forming a polyurethane foam aeration 700cm ³ / cm ² · sec of the inner body, to obtain a sound absorbing body of this example.

Example 3 Skin thickness 0.09 mm, skin density 0.36 g / cm ³ , air permeability 170 cm ³ /
cm ² · sec, the density of the inner body 0.06 g / cm ^3, by forming a polyurethane foam aeration 700cm ³ / cm ² · sec of the inner body, to obtain a sound absorbing body of this example.

Example 4 Skin thickness 0.12 mm, skin density 0.55 g / cm ³ , air permeability 110 cm ³ /
cm ² · sec, inner body density 0.075 g / cm ³ ,
A urethane foam having a flow rate of 420 cm ³ / cm ² · sec through the inner body was molded to obtain a sound absorbing body of this example.

(Example 5) Skin thickness 0.08 mm, skin density 0.24 g / cm ³ , skin air permeability 240 cm ³ /
cm ² · sec, inner body density 0.075 g / cm ³ ,
A urethane foam having a flow rate of 420 cm ³ / cm ² · sec through the inner body was molded to obtain a sound absorbing body of this example.

Example 6 Skin thickness 0.09 mm, skin density 0.31 g / cm ³ , air permeability 190 cm ³ /
cm ² · sec, density of inner body 0.045 g / cm ³ ,
A polyurethane foam having an air permeability of 1200 cm ³ / cm ² · sec through the inner main body was molded to obtain a sound absorbing body of this example.

(Example 7) The skin thickness is 0.11 mm, the skin density is 0.55 g / cm ³ , and the air permeability of the skin is 105 cm ³ /
cm ² · sec, density of inner body 0.045 g / cm ³ ,
A polyurethane foam having an air permeability of 1200 cm ³ / cm ² · sec through the inner main body was molded to obtain a sound absorbing body of this example.

(Example 8) The skin thickness is 0.05 mm, the skin density is 0.42 g / cm ³ , and the air permeability of the skin is 150 cm ³ /
cm ² · sec, the density of the inner body 0.06 g / cm ^3, by forming a polyurethane foam aeration 700cm ³ / cm ² · sec of the inner body, to obtain a sound absorbing body of this example.

(Comparative Example 1) The urethane foam of Example 1 was molded and the skin was removed to obtain a sound absorbing body of this example. The density of the inner body is 0.06 g / cm ³ , and the ventilation volume of the inner body is 700 cm ³ / cm ² · sec.

(Comparative Example 2) The urethane foam of Example 4 was molded and the skin was removed to obtain a sound absorbing body of this example. The density of the inner body is 0.075 g / cm ³ , and the ventilation volume of the inner body is 420 cm ³ / cm ² · sec.

(Comparative Example 3) The urethane foam of Example 6 was molded and the skin was removed to obtain a sound absorbing body of this example. The density of the inner body is 0.045 g / cm ³ , and the ventilation volume of the inner body is 1200 cm ³ / cm ² · sec.

(Comparative Example 4) Skin thickness 0.09 mm, skin density 0.80 g / cm ³ , skin air permeability 70 cm ³ / c
A urethane foam having m ² · sec, a density of the inner body of 0.06 g / cm ³ , and an air permeability of the inner body of 700 cm ³ / cm ² · sec was molded to obtain a sound absorbing body of this example.

(Comparative Example 5) Skin thickness 0.10 mm, skin density 0.10 g / cm ³ , air permeability of the skin 350 cm ³ /
cm ² · sec, the density of the inner body 0.06 g / cm ^3, by forming a polyurethane foam aeration 700cm ³ / cm ² · sec of the inner body, to obtain a sound absorbing body of this example.

(Conventional Example 1) Skin thickness 0.11 mm, skin density 1.09 g / cm ³ , skin air permeability 10 cm ³ / c
A urethane foam having m ² · sec, a density of the inner body of 0.06 g / cm ³ , and an air permeability of the inner body of 700 cm ³ / cm ² · sec was molded to obtain a sound absorbing body of this example.

(Conventional Example 2) Skin thickness 0.09 mm, skin density 1.01 g / cm ³ , skin air permeability 35 cm ³ / c
A urethane foam having m ² · sec, a density of the inner body of 0.075 g / cm ³ , and an air permeability of the inner body of 420 cm ³ / cm ² · sec was molded to obtain a sound absorbing body of this example.

(Conventional Example 3) Skin thickness 0.09 mm, skin density 1.05 g / cm ³ , skin air permeability 20 cm ³ / c
A urethane foam having m ² · sec, a density of the inner body of 0.045 g / cm ³ , and an air permeability of the inner body of 1200 cm ³ / cm ² · sec was molded to obtain a sound absorbing body of this example.

(Evaluation of Performance) Examples 1 to 8 and Comparative Example 1
5 to 5 and the sound absorbers obtained in Conventional Examples 1 to 3, using the device shown in FIG.
Was measured for normal incidence sound absorption coefficient. Table 1 shows the physical property data of each example, comparative example and conventional example. 7 to 20 show the measurement results of the examples, the comparative examples, and the conventional example in comparison with the conventional example 1. (The hatched portion is an improvement over the conventional example.)

[0036]

[Table 1]

7 to 14 that the various sound absorbers prepared in the embodiments have considerably improved sound absorbing performance in a high frequency region as compared with the conventional example, and have excellent sound absorbing characteristics in a wide frequency band of 500 to 6300 Hz. It was confirmed that it was a sound absorber having From FIGS. 15 to 19, the sound absorber of the comparative example which is not within the scope of the present invention has a certain degree of improvement in the sound absorption performance in the high frequency region as compared with the conventional example, but the sound absorption performance in the low frequency region is significantly reduced. It was confirmed that the performance was inferior to the sound absorbers of the examples.

[0038]

As described above, according to the present invention, the thickness and density of the skin of the sound absorbing body and the density of the porous inner body are specified.
A sound absorber exhibiting excellent sound absorption performance in a wide frequency band of 0 Hz and a vehicle using the same can be provided without increasing costs and man-hours.

[Brief description of the drawings]

FIG. 1 is a graph showing sound absorption characteristics of a general porous sound absorber.

FIG. 2 is a graph showing sound absorption characteristics of a conventional urethane foam sound absorber.

FIG. 3 is a graph showing an air permeability curve in the skin and inside of a conventional urethane foam sound absorber.

FIG. 4 is a graph showing a comparison between sound absorption characteristics of a conventional urethane foam sound absorber with and without a skin.

FIG. 5 is a graph showing the relationship between the density of the skin of urethane foam and air permeability.

FIG. 6 is a sectional view showing a normal incidence sound absorption coefficient measuring device used for performance evaluation of the sound absorbing body.

FIG. 7 is a graph showing sound absorption characteristics of the sound absorbers of Example 1 and Conventional Example 1.

FIG. 8 is a graph showing sound absorption characteristics of the sound absorbers of Example 2 and Conventional Example 1.

FIG. 9 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Example 3 and Conventional Example 1.

FIG. 10 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Example 4 and Conventional Example 1.

FIG. 11 is a graph showing sound absorbing characteristics of the sound absorbing bodies of Example 5 and Conventional Example 1.

FIG. 12 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Example 6 and Conventional Example 1.

FIG. 13 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Example 7 and Conventional Example 1.

FIG. 14 is a graph showing sound absorption characteristics of the sound absorbers of Example 8 and Conventional Example 1.

FIG. 15 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Comparative Example 1 and Conventional Example 1.

FIG. 16 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Comparative Example 2 and Conventional Example 1.

FIG. 17 is a graph showing sound absorption characteristics of the sound absorbers of Comparative Example 3 and Conventional Example 1.

FIG. 18 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Comparative Example 4 and Conventional Example 1.

FIG. 19 is a graph showing the sound absorbing characteristics of the sound absorbing bodies of Comparative Example 5 and Conventional Example 1.

FIG. 20 is a graph showing sound absorption characteristics of the sound absorbers of Conventional Examples 1, 2, and 3.

Claims (8)

[Claims] 1. A sound absorber comprising a porous inner body and a dense skin formed on the surface of the inner body, wherein the skin has a density of 0.15 to 0.6 g / cm ³ and a thickness of Is 0.01 to 0.2 mm, and the density of the inner body is 0.045 to 0.075 g / cm ³ . 2. The sound absorber according to claim 1, wherein the air permeability of the skin at an air pressure of 0.01 kg / cm ² is 100 to 300 cm ³ / cm ² · sec. 3. The air flow rate of the inner body at an air pressure of 0.01 kg / cm ² is 350 to 2000 cm ³ / cm ² · s.
The sound absorber according to claim 1, wherein the sound absorber is ec. 4. The sound absorber according to claim 1, wherein the thickness is 5 to 50 mm. 5. The sound absorber according to claim 1, wherein the skin and the inner body are made of the same material. 6. The sound absorber according to claim 5, wherein the sound absorber is made of urethane foam. 7. A vehicle comprising the sound absorber according to any one of claims 1 to 6. 8. The vehicle according to claim 7, wherein the sound absorber is used as a dash insulator, a floor insulator, and / or a headlining.