JP2000238588A - Sound absorbing member for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a sound absorbing material from the impact of a flying rocks as well as to restrain deterioration of the sound absorbing characteristics. SOLUTION: A sound absorbing layer 2 is covered by an elastic resin covering layer 3 having a plurality of through holes 30, with a 40% or more total hole ratio of the through holes 30, an average hole area per one hole (S) in the range of 0.2 cm2<=S<=2 cm2, and a thickness (t) in the range of 1 mm<=t<=5 mm. According to the hole configuration, entrance of sound waves into the sound absorbing layer 2 is facilitated as well as a sufficient strength of the covering layer 3 is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a sound absorbing member provided on a vehicle such as a truck to reduce noise outside the vehicle.

[0002]

2. Description of the Related Art With the increase in the number of vehicles or the number of expressways in recent years, noise generated by running vehicles has become a problem, and reduction of the noise has become an issue. Causes of noise generated by a running vehicle include engine noise, friction noise between tires and a road surface, and wind noise, and various measures are taken for each.

[0003] For example, in order to reduce noise due to engine noise, it is effective to provide an undercover or an engine cover with a sound absorbing material in the engine room. Further, in order to reduce the noise due to the engine noise and the friction noise between the tire and the road surface, a sound absorbing material is mounted on the side of the vehicle in the outflow path of the sound. However, since various parts and devices are arranged in the engine room, a mounting space for an undercover, an engine cover, and the like may not be secured. Even if these covers can be provided, there is a problem that the heat dissipation of the engine room is reduced due to an increase in the degree of sealing.

[0004] Therefore, in order to reduce the noise generated from the vehicle, it is preferable to provide a sound absorbing material on a body or a frame which has a relatively large mounting space. It is believed that the number of sound absorbing materials will increase in the future.

[0005]

As a sound absorbing material, a porous material such as urethane foam or foamed polyolefin, or a fiber assembly such as felt is generally used. However, since such a sound absorbing material is soft and has low strength, there is a problem that when the sound absorbing material is attached to a lower part of the vehicle body, the sound absorbing material is damaged by flying stones generated during traveling.

Therefore, it is conceivable to protect the sound absorbing material by covering it with a protector such as a hard resin or a steel plate. However, when the sound absorbing material is covered with the protector, the sound absorbing characteristics are significantly reduced. In addition, the protector itself may be deformed due to a flying stone, or rust may be generated due to damage of the coating film. The present invention has been made in view of such circumstances, and it is an object of the present invention to protect a sound-absorbing material from impacts such as stepping stones and to suppress a decrease in sound-absorbing characteristics.

[0007]

The sound absorbing member of the present invention which solves the above-mentioned problems is characterized in that it comprises a sound absorbing layer and a coating layer covering the sound absorbing layer, and the sound absorbing layer side is fixed to face the lower surface of the vehicle body. A member, wherein the coating layer is made of an elastic resin and has a plurality of through-holes, and the through-holes have a total porosity of 40% or more and an average opening area (S) per one piece of 0.2 cm ² ≦. S ≦
2 cm ² and the coating layer has a thickness (t) of 1 m
That is, it is formed in the range of m ≦ t ≦ 5 mm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the sound absorbing member of the present invention, sound waves such as engine sounds enter the sound absorbing layer through the through holes, and sound waves entering the holes of the sound absorbing layer are viscous resistance of the air in the holes and sound absorption. The sound energy is gradually attenuated by the vibration of the layer itself, and the sound energy is converted into heat energy to absorb sound.

[0009] By forming the opening of the coating layer as described above, sufficient strength of the coating layer can be ensured while sound waves can easily enter the sound absorbing layer, and breakage or deformation can be prevented. As the sound absorbing layer, a conventional sound absorbing material can be used, and a material formed in a predetermined shape from a porous body such as urethane foam or foamed polyolefin, or a fiber aggregate such as felt can be used.

The coating layer, which is a feature of the present invention, is formed of a resin having elasticity. As such a resin,
Examples thereof include polypropylene and polyethylene, and the thickness (t) is formed in a range of 1 mm ≦ t ≦ 5 mm. If the thickness (t) is less than 1 mm, the strength is insufficient, and the ball may be damaged by an impact such as a stepping stone. Also thickness (t)
When the thickness is more than 5 mm, resonance for a specific frequency occurs due to an increase in the mass of air inside the through-hole, and sound absorption over a wide range of frequencies may be difficult, which is not preferable. By setting the thickness (t) within this range, it is possible to reliably protect the sound absorbing layer while suppressing the occurrence of resonance.

[0011] By constituting the coating layer as described above, breakage and deformation due to impact of a flying stone or the like can be prevented. Further, since it is made of resin, there is no problem such as generation of rust due to damage of the coating film. The coating layer has a plurality of through-holes, and the total opening ratio, which is the ratio of the total opening area to the area of the coating layer, is 40% or more. It is particularly preferred that the total porosity be 50 to 70%. If the total porosity is less than 40%, the sound absorbing properties of the sound absorbing layer will deteriorate. In addition, the total aperture ratio is 7
If it exceeds 0%, the strength of the coating layer is reduced, and the coating layer is liable to be broken due to impact of stepping stones.

Further, the coating layer has an average opening area (S) per through hole in a range of 0.2 cm ² ≦ S ≦ 2 cm ² . Average opening area (S) of through hole is 0.2c
If it is smaller than m ² , the sound absorbing properties of the sound absorbing layer will be reduced, and if the average opening area (S) is larger than 2 cm ² , the strength of the coating layer will be reduced, and it will often be easy to break due to the impact of flying stones. On the other hand, when the average opening area (S) is larger than 2 cm ^2, the probability that a stepping stone collides with the internal sound absorbing layer increases, and the sound absorbing layer is likely to be damaged by the stepping stones.

That is, by forming the through holes under the above-described conditions, it is possible to prevent the presence of the coating layer from hindering the sound absorbing properties of the sound absorbing layer, and to prevent breakage or deformation due to impacts such as stepping stones. The shape of the through hole is not particularly limited, such as a circle, an ellipse, and a polygon. The sound absorbing layer and the covering layer may be simply laminated, or may be integrally joined. As a method of integrally joining, a method of mechanically joining with a clip or the like, a method of joining using an adhesive, a method of joining by welding, and the like can be adopted.

In order to fix the sound absorbing member of the present invention to the lower surface of the vehicle body, the sound absorbing layer may be directly fixed to the vehicle body, but in that case, the sound absorbing layer may be deformed. Therefore, it is preferable to fix the base material on the opposite side of the sound absorbing layer from the covering layer, and fix the sound absorbing layer to the vehicle body via the base material. And it is preferable that the periphery of the coating layer is also fixed to the base material. With this configuration, the deformation of the sound absorbing member can be more reliably prevented.

It is also preferable to form a water-repellent layer on the surface or inside the sound absorbing layer. Thus, it is possible to prevent the sound absorbing layer from being impregnated with water and the sound absorbing properties from being deteriorated.

[0016]

The present invention will now be described in more detail with reference to Test Examples and Examples.
Will be explained. (Test example) One through hole made of polyethylene resin
0.5-0.6cm opening area ^Two, Diameter 30mm, thickness
2 mm, and the total porosity is varied between 20 and 40%.
Prepare multiple types of coating layers, formed from PET fiber
The sample was laminated with the nonwoven fabric thus obtained. And normal incidence sound absorption
Rate measuring machine (“FFT Analyzer 2035” manufactured by B & K)
Was used to measure the sound absorption coefficient of the sound of each frequency. Figure the result
It is shown in FIG.

It is apparent from FIG. 1 that the higher the total aperture ratio, the higher the sound absorption coefficient.
% Is within a substantially satisfactory range. Next, the total opening ratio was fixed at 40%, and the opening area of one through-hole was 0.1%.
Using the coating layer changed at two levels of 1 and 0.3 cm ² , the sound absorption of each frequency was measured in the same manner as described above. The results are shown in FIG.

FIG. 2 shows that the sound absorbing coefficient is sufficient when the opening area is 0.3 cm ² , but the opening area is 0.1 cm 2.
² is not enough. Therefore, it is determined that the opening area of one through hole needs to be 0.2 cm ² or more. That is, according to the above test example, the average opening area of the through holes was 0.2%.
It is evident that when it is smaller than cm ² , or when the total porosity is less than 40%, the sound absorbing properties are significantly reduced.

(Embodiment) FIGS. 3 and 4 show a sound absorbing member of this embodiment. The sound absorbing member includes a base material 1, a sound absorbing layer 2 made of a fiber assembly held on the base material 1, and a coating layer 3 covering the surface of the sound absorbing layer 2. The sound absorbing member is used in such a manner that the base material 1 is fixed to the inside of the skirt portion 100 provided on both sides of the lower part of the vehicle body of the truck.

The base material 1 is formed from a hard polyethylene resin into a predetermined shape, and a bracket 10 protruding outward on the side surface.
Are provided integrally. The sound absorbing member is connected to the skirt portions 100 on both sides of the lower part of the vehicle body through the bracket 10.
Fixed to the inside surface of the The sound absorbing layer 2 is made of a non-woven fabric formed of PET fibers, and is shaped into a predetermined shape in advance.
It is sandwiched between the substrate 1 and the coating layer 3. Sound absorbing layer 2
Has a cavity 20 formed therein.

The coating layer 3 is made of polyethylene resin and has a thickness of 2 mm.
And has a plurality of through holes 30. The through holes 30 are opened in a circular shape, the average opening area (S) per piece is 0.5 cm ² , and the total opening ratio is 50%. The upper and lower ends of the coating layer 3 are welded and integrated with the base material 1, and the sound absorbing layer 2 is sandwiched and held between the base material 1 and the coating layer 3.

In this sound absorbing member, first, a base material 1, a sound absorbing layer 2, and a coating layer 3 were formed. The base material 1 was formed by press molding, the sound absorbing layer 2 was formed by shaping, and the coating layer 3 was formed by injection molding. Next, the sound absorbing layer 2 is incorporated into the covering layer 3,
The three members were integrated by laminating the base material 1 and both end portions of the coating layer 3 and performing vibration welding. Next, the sound absorbing member is provided with a skirt portion 1 extending vertically on both left and right sides of the lower part of the body of the truck.
The base material 1 is arranged inside the skirt portion 100 so as to face the inner surface of the skirt portion 100, and the bracket 10 is coupled to the skirt portion 100 by the clip 101. Thereby, the sound absorbing member is fixed to the lower part of the vehicle body of the truck.

The noise during traveling enters the sound absorbing layer 2 through the through holes 30, but is absorbed by viscous resistance inside the sound absorbing layer 2, and is prevented from escaping to the outside of the truck. Further, the through holes 30 have a sufficient opening area and the number thereof is in an appropriate range, so that the total opening ratio is also in an appropriate range. Therefore, sound waves that become noise enter the sound absorbing layer 2 smoothly, and sound energy that has entered the holes of the sound absorbing layer 2 gradually attenuates due to viscous resistance of air in the holes and vibration of the sound absorbing layer 2 itself. Then, sound energy is converted into heat energy, and the sound is absorbed. This suppresses the noise from escaping outside the vehicle.

[0024]

According to the sound absorbing member of the present invention, the sound absorbing layer can be protected from impacts such as flying stones while maintaining high sound absorbing characteristics. In addition, breakage and deformation of the coating layer itself can be prevented, and stable sound absorption characteristics can be secured for a long period of time.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between frequency and sound absorption coefficient.

FIG. 2 is a graph showing a relationship between frequency and sound absorption coefficient.

FIG. 3 is a perspective view of a main part of a sound absorbing member according to one embodiment of the present invention.

FIG. 4 is a sectional view showing a state in which the sound absorbing member according to the embodiment of the present invention is mounted on a vehicle body.

[Explanation of symbols]

1: base material 2: sound absorbing layer 3: covering layer 10: bracket 30: through hole 100: skirt portion (vehicle body)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hidetoshi Ishihara No. 1 Nagahata, Ogai, Kasuga-cho, Nishikasugai-gun, Aichi F-term (reference) 3D023 BA03 BB21 BC03 BD11 BD21 BD25 BE03 BE04 BE06 BE11 BE20 4F100 AK01B AK04 AK42 BA02 DC11B DG15 EC03 GB33 JH01 JH01A JK07B YY00B 5D061 AA06 AA22 AA25 CC11 CC15 DD01

Claims (1)

[Claims] 1. A sound absorbing member comprising a sound absorbing layer and a covering layer covering the sound absorbing layer, wherein the sound absorbing layer side is fixed to face the lower surface of the vehicle body, and the covering layer is made of an elastic resin. With a through hole of
The through holes have a total opening ratio of 40% or more, an average opening area (S) per one in the range of 0.2 cm ² ≦ S ≦ 2 cm ² , and the coating layer has a thickness (t). 1mm ≦ t ≦ 5mm
A sound absorbing member for a vehicle, wherein the sound absorbing member is formed in the range of: