JP2000034937A - Sound absorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively absorb sound generated by an engine. SOLUTION: Aluminum foil 1 which has a plurality of small holes 2 of areas 3 mm2 or less respectively formed therein into a zigzag state and has the numerical aperture 1-30% by the small holes 2, a plate part 3 formed of a fiber mat of large gas permeability, a base part 5 molded of a same fiber mat and having a plurality of recesses 4, and a sound insulating plate 6 are stacked from the engine side in order so as to be integrated. A hollow part 7 is formed inside the fiber mat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a truck and the like for absorbing noise generated by an engine and reducing noise leaking outward.

[0002]

2. Description of the Related Art Conventionally, in vehicles such as trucks, as exemplified in JP-B-63-18010,
The noise generated by the engine is reduced by installing a sound absorbing skin material on the inner surface of the engine storage room. However, as can be read from FIG. 4 of the publication, the sound absorbing coefficient is increased particularly in a low frequency range. While you can't
Since the engine noise also significantly increases with an increase in the engine output, it has been difficult to always sufficiently prevent noise with such a device.

Further, in a vibration damping material for a vehicle disclosed in Japanese Patent Application Laid-Open No. Sho 62-165043, a melt sheet having a plurality of through-holes or bottomed holes is attached to the upper surface of a floor plate or the like. Although it has a structure in which vinyl chloride foam and felt are laminated on the melt sheet, no consideration is given to heat resistance, so it is placed close to the engine and used when receiving strong heat radiation from the engine. That is inherently impossible.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a device capable of effectively absorbing the sound generated by an engine.

[0005]

Therefore, a sound absorbing device according to the present invention comprises a metal foil having a large number of holes each having an area of 3 mm 2 or less and an opening ratio of 1 to 30%; A highly air-permeable fiber mat in which a plurality of hollow sections each having a larger cross-sectional area than the above-described hole is formed, and a sound insulating plate surrounding the engine are sequentially superposed and integrated from the engine side.

That is, even if a large number of holes are formed in the metal foil facing the engine, the area of each of the holes is relatively small, not more than 3 mm 2, and the aperture ratio of the metal foil due to the large number of holes is small. Since it is as small as 1 to 30%, heat radiation from the engine can be effectively reflected by the metal foil to suppress the heating of the sound absorbing device, while the sound generated by the engine is generated by a large number of sounds formed on the metal foil. When passing through the hole, it is squeezed and reduced, and is absorbed by the highly permeable fiber mat disposed between the metal foil and the sound insulating plate, and formed in the interior through the fiber mat. When reaching the hollow portion, it can be effectively reduced also by the resonance action in the hollow portion.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention shown in the drawings will be described by assigning the same reference numerals to the same parts. In FIG. 1, the aluminum foil 1 has a thickness of 10 to 10.
A large number of small holes 2 each having a size of 50 μ and having an area of 3 mm 2 or less are formed almost in a zigzag pattern.
The aperture ratio of the aluminum foil 1 obtained by the entire small holes 2 is 1 to
It is set to 30%.

The flat plate portion 3 is formed of a highly permeable fiber mat such as glass wool or PET non-woven fabric which is a recycled material. The base portion 5 having the entire surface is also formed of a fiber mat,
The aluminum foil 1, the flat plate portion 3, and the base portion 5 are sequentially laminated from the engine side on a steel plate or resin sound insulation plate 6 surrounding an engine (not shown) mounted on the vehicle, and
They are appropriately integrated by rivets not shown,
A large number of hollow portions 7 are formed inside the fiber mat by the flat plate portion 3 and the concave portions 4 of the base portion 5. The aluminum foil 1, the flat plate portion 3, and the base portion 5 are integrally formed by bonding or welding, and their peripheral and central portions are fixed to the sound insulating plate 6 by rivets and clips.

In the above sound absorbing device, even if a large number of small holes 2 are formed in the aluminum foil 1 facing the engine, the area of each of the small holes 2 is relatively small, not more than 3 square mm, and Since the aperture ratio of the aluminum foil 1 due to the large number of small holes 2 is as small as 1 to 30%, heat radiation from the engine is effectively reflected by the aluminum foil 1 and the heating of the sound absorbing device can be suppressed.

The sound generated by the engine is narrowed and reduced when passing through the small holes 2 of the aluminum foil 1 each having a relatively small area of 3 mm 2 or less. Is absorbed by the flat portion 3 and the fiber mat portion of the base portion 5 disposed between the first and second portions, and reaches a plurality of hollow portions 7 formed inside the fiber mat. Is also effectively reduced. In addition, since the flat part 3 is arrange | positioned inside the aluminum foil 1, it can prevent easily that the aluminum foil 1 is damaged or peeled by external force.

FIG. 2 shows the operation and effect when the total thickness of the flat plate portion 3 and the base portion 5 formed of a fiber mat is 20 mm in the above sound absorbing device. Curves a, b,
c, d, and e indicate that the aperture ratio of the small hole 2 of the aluminum foil 1 in the above sound absorbing device is 1.1%, 4.5%,
%, 18%, and 28%, the diameter of the small hole 2 is 1.5 mm, and the normal incidence sound absorption coefficient when each hollow portion 7 is filled with the fiber mat is shown. In the above embodiment, the sound absorption performance of the curve A is shown. If the area of the small holes 2 in the aluminum foil 1 is not more than 3 square mm and the aperture ratio of the small holes 2 is 1 to 30%, the normal incidence of the curve A is obtained. There was no significant change in the sound absorption coefficient.

That is, in the above embodiment, by forming a large number of hollow portions 7 inside the fiber mat,
In particular, as a result of being able to effectively absorb engine sounds in the low frequency range, it is possible to exhibit an excellent sound absorbing effect in a wide range of sounds, so that the engine noise leaking out of the vehicle can be significantly reduced, and therefore, Another advantage is that the output of the engine can be easily increased in terms of noise prevention.

In the embodiment shown in FIG. 3, an aluminum foil 1 and a flat plate portion 3 having the same structure as in the embodiment described above, and a plurality of through-holes formed by a fiber mat and having a sectional area larger than the small hole 2 are shown. A base portion 11 having a hole 10 and a flat plate portion 12 also formed of a fiber mat are sequentially superimposed from the engine side on a steel plate or resin sound insulation plate 6 surrounding an engine (not shown) mounted on a vehicle. ,
As in the case of the above-described embodiment, they are appropriately integrated and fixed to the sound insulating plate 6, and a large number of hollow portions 7 are formed by the flat plate portion 3, the through holes 10 of the base portion 11, and the flat plate portion 12. The same operation and effect as those of the above embodiment can be obtained.

[0014]

In the sound absorbing device according to the present invention, the sound generated by the engine is reduced by being squeezed when passing through a large number of holes formed in the metal foil. Absorbed by the highly permeable fiber mats arranged in the fiber mat and reduced by the resonance action in the many hollow parts formed inside the fiber mat, it has excellent sound absorption action in a wide sound range, so sound insulation There is an advantage that the noise leaking out of the board can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part in an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the embodiment.

FIG. 3 is a perspective view of a main part according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum foil 2 Small hole 3 Flat part 4 Concave part 5 Base part 6 Sound insulation plate 7 Hollow part 10 Through-hole 11 Base part 12 Flat part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02B 77/13 F02B 77/13 C G10K 11/172 G10K 11/16 E F-term (reference) 3D023 BA02 BA03 BB21 BB30 BC03 BD21 BE03 BE04 BE06 3G004 CA01 CA02 CA13 DA14 DA15 EA05 FA01 FA04 FA07 4F100 AB01A AB10 AB33A AG00 AK42 AR00C BA03 BA07 BA10A BA10C DC11A DG01 DG06B DJ10B GB32 JD02B JH01 JH10C YY00A 5D061 BB02 BB02 BB02 BB02 BB02 BB02 BB02 BB02 BB07

Claims (1)

[Claims] 1. A metal foil having a large number of holes each having an area of 3 mm 2 or less and an opening ratio of 1 to 30%, and a plurality of hollow portions each having a cross-sectional area larger than the above-mentioned holes. A sound absorbing device in which a fiber mat having high air permeability formed in the above and a sound insulating plate surrounding the engine are sequentially superimposed and integrated from the engine side.