KR900000956Y1 - Noise preventer for vehicle - Google Patents

Abstract

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Description

Noise prevention material of car

1 is a partial cross-sectional view of an embodiment of a floor structure of a vehicle according to the prior art.

2 is a partial cross-sectional view of an embodiment of a floor structure of a vehicle according to the present invention.

3 is a partial cross-sectional view of an embodiment of a roof structure of a vehicle according to the present invention.

4a to 4c are partial cross-sectional views of yet another embodiment of a floor structure of a vehicle according to the present invention, respectively.

5 to 7 are graphs showing the relationship between sound intensity and frequency strabismus, respectively.

* Explanation of symbols for main parts of the drawings

3: an asphalt sheet 4,7 a thin sheet

5: restraint layer 6: a foam layer

8: adhesive layer

The present invention is mounted on a noise preventing material used for noise reduction in an automobile interior, in particular, a thin sheet as a component panel of an automobile, thereby reducing the replacement noise of a relatively low frequency by electric power and contributing to noise reduction in the automobile interior. It relates to a prevention material.

In general, the thin sheets constituting the vehicle body are used for bonnets, floors, front panels, ceilings, door trunks and fenders. Accordingly, countermeasures for reducing the noise inside the automobile interior have been attempted, in particular, on the body floor, the ceiling and the front panel (or the engine compartment and the interior partition). Until now, the noise preventing material has been used on a thin sheet panel of an automobile to prevent the propagation of solid sound. In such noise suppression materials, the mechanism for reducing vibration is based on the fact that the vibration energy is converted into thermal energy by shear deformation resulting from the material and structure of the noise suppression material. But. This mechanism is effective for a diffusion vibration component during the panel vibration, ie, a vibration component acting indirectly on the panel, but not only for forced or direct acting components but also for vibrations in the frequency region lower than the panel frequency. It is ineffective for.

On the other hand, the stiffness of the thin sheet panel is increased by the formation of ribs and rough machining which are considered to increase the vehicle body strength of the automobile, and as a result, the main frequency of the panel constituting the vehicle body becomes large. This tendency is particularly noticeable at the bottom and front panel.

In-vehicle noise is a combination of various noises such as sounds produced by an engine, vibrations of an engine, solid noises caused by vibrations of a tire, etc., pattern noises caused by tread shapes of tires, and wind noises when running. The inventors have conducted various researches and investigations on the nature of these noises in the automobile interior, and found that the noise level in the automobile interior is particularly high in the low frequency region of about 80-200 Hz, which is under the annoyance region. About 70% were found to be due to solid sounds, especially solids caused by engine vibrations.

The noise in the low frequency region as described above is governed by the forced vibration which is not attenuated by the conventional noise suppression material. E.g. Asphalt sheets having a noise effect have been used for the bottom of the vehicle body and the front panel, but these asphalt sheets are not effective against the forced vibrations for the reasons mentioned above.

In order to reduce such forced vibration, it is effective to use a dynamic damper. However, since the conventional dynamic damping material uses a rubber material or the like having a high spring constant as the spring member, it is difficult to apply to a low frequency region and is also unsuitable as a upholstery. In addition, since the conventional dynamic damping material has a low internal loss and strict frequency selectivity for vibration reduction, it is not only very difficult and almost impossible to match the vibration of the engine, that is, the vibration frequency that varies with the engine speed.

In addition, various materials such as felt, foam, mat, vinyl sheet, and the like have been applied to thin sheet panels constituting parts of the front panel, floor, ceiling, door, etc. The effect on sound insulation is negligible.

The present inventors have continuously studied the noise function of the dynamic damping material to improve the noise of the automobile interior. As the dynamic damping material, the composite structure of the specific foam layer and the specific restraint layer is used to reduce the noise of the automobile interior. It has been found that it can reduce the vibrations that cause. According to the present invention, a noise reduction in an automobile interior is made up of a foam layer having a static spring constant of 0.05 kg / mm / cm 2 or less, and a restraining layer bonded to the foam layer and having a weight of 0.4 g / cm 2 or more per unit area. Noise protection material is provided.

In the noise prevention material according to the present invention, the foam layer itself is easily deformed by vibration and has a high vibration energy absorption capacity, which is very flexible due to the static spring constant of 0.05 kg / mm / cm 2 or less. Because I am. In addition, by adhering the constraint layer to the foam layer, the vibration energy absorbing power of the foam layer can be further increased. That is, the noise suppression material according to the present invention forms an effective dynamic damping material in a wide vibration frequency region around a specific frequency determined by the combination of the stationary spring constant of the foam layer and the weight per unit area of the constraint layer, whereby the vibration of the panel Can control and reduce the emission of solid sound. In other words, the noise preventing material according to the present invention, as described above, has a great effect on the noise reduction of the vehicle interior in the vibration frequency range of 80-200 Hz based on the engine speed, and also has a foam layer having high vibration energy absorption. By using, the radiation from the restraint layer is very small, thus providing the effect of further reducing the noise.

As the foam layer, any form of foam in which the stationary spring constant satisfies 0.05 kg / mm / cm 2 or less may be used. For example, ordinary polyurethane foam and plastic foam such as polyvinyl chloride, polyethylene, polystyrene (these foams) Silver fillers, plasticizers, flame retardants and the like) and pressurized bodies of ordinary foams.

When the stationary spring constant of the foam layer exceeds 0.05 kg / mm / cm 2, the foam layer becomes rigid and is hardly deformed by vibration.

It is also preferable that the foam layer has a thickness of 5 to 40 mm. When the thickness is less than 5 mm, even if a flexible foam having a static spring constant of 0.05 kg / mm / cm 2 or less is used, not only is it difficult to make up for the noise reduction effect in the frequency range of 80-200 Hz, but also the foam has a predetermined thickness. Very difficult to process On the other hand, if the thickness exceeds 40 mm, the space inside the passenger compartment is actually too narrow.

As the restraint layer, any material that has a weight per unit area of 0.4 g / cm 2 or more, preferably 0.4 to 3 g / cm 2, can be used to impart restraint to the foam layer and hardly liquefy within the normal use temperature range. . When the weight per unit area of the restraint layer is less than 0.4 g / cm 2, the mass is lost, and vibrations accompanying the rotation of the engine cannot be reduced. On the other hand, if the weight per unit area exceeds 3 g / cm 2, the weight of the vehicle becomes too heavy, which adversely affects fuel consumption and other properties. In order to exhibit the noise reduction effect especially in a wide frequency range, since flexibility of a restraint layer is an important factor, it is desirable to have sufficient flexibility. Examples of the restraint layer include flexible sheets such as rubber sheets, plastic sheets, cork sheets and fibrous sheets. In addition, the thickness of the restraint layer is preferably 20 mm or less to provide sufficient flexibility and to study the filled interior of the passenger compartment.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 2 and FIG. The noise preventing material according to the present invention is a foam sheet (6), a thin sheet (4 or 7) which is bonded to the foam layer (6) and constitutes a structural panel of a vehicle such that the foam layer (6) faces the sheet sheet (4). ) And a restraint layer (5) adhered to it. In particular, when the noise protection material is applied to the ceiling panel of the car, it is good to have a structure as shown in FIG.

In addition, as shown in FIG. 4A, an asphalt sheet 3 or the like, which is usually used as the noise suppression material, may be provided between the foam layer 6 and the thin sheet sheet 4 of the noise suppression material.

The adhesion between the foam layer 6 and the restraint layer 5 is, for example, (1) a method of bonding the sheet for restraint layer to the foam layer, (2) a method of applying the emulsion for restraint layer to the foam layer, and (3) a woven fabric. The method of adhering a restraint layer to a foam layer, (4) the method of shape | molding a noise suppression material as a monolithic mold, etc. can be employ | adopted. Similarly, the adhesion between the noise suppression material and the thin sheet may include, for example, (1) a method of adhering the foam layer and the restraining layer, if necessary, to the thin sheet by heat through an adhesive sheet (FIG. 2, 4a). Degrees and 4b degrees). (2) It is carried out by any of the methods (FIG. 4C) of adhering the receptor of the restraining layer which previously enclosed the foam insect inside to a thin sheet by heating etc.

The noise preventing material according to the present invention is not only excellent in insulation and cue-handiness as an interior decoration by the sandwich structure described above, but also excellent in noise reduction effect in a car interior. In addition, when the noise preventing material according to the present invention is adhered to the ceiling panel of the vehicle, when the through-hole having an appropriate diameter is formed in the restraint layer, the sound absorption is further increased by the properties of the foam layer. The noise reduction effect in the room is increased. Furthermore, the noise preventing material according to the present invention can be widely applied to building materials, electrical equipment, and office equipment.

The following examples are examples of the present invention, but the present invention is not limited only to the following examples.

Examples 1 and 2 Comparative Examples 1 to 4 The noise preventing material shown in Table 1 below was applied to a ceiling sheet of a front wheel drive passenger car (hereinafter referred to as FF car) having a displacement of 1400 cc. Subsequently, the FF car was actually driven at an engine speed of 2,600 rpm and 3,000 rpm, and the sound level generated from the ceiling during driving was measured by an acoustic intensity measuring instrument, and the results as shown in FIGS. 5 to 7 were obtained. 5 and 7 show measurement data at an engine speed of 3,000 rpm, and FIG. 6 shows measurement data at an engine speed of 2,600 rpm. Using a loudness measurement instrument, at each of the five points in the width centerline of the FF difference, sound pressure (ure press) is measured with two adjacent microphones located close to the ceiling, and at the same time the cross spectrum of the measurement ( cross spectrum) was processed as a digital signal as a series of acoustic energy. In this case, the sound pressure is B & K. Two 1 / 2-inch microphones, product model-4165 from AS, were measured by a precision acoustic level meter, product model-2209 from B & K AS, which was then measured by Hewlett-Packard Co. The product model-5420A, a digital signal splitter, was used to obtain the sound intensity representing the sound level from the ceiling. This sound level was evaluated by the sum of the sound intensity measured at five points along the center line in the width direction of the car in the vehicle driving direction.

TABLE 1

As can be seen from Table 1 and FIGS. 5 to 7, the noise suppression material according to the present invention exhibits a significant noise reduction effect in a wide frequency range of 80 to 125 Hz.

Examples 3 to 5, Comparative Examples 1 and 5 and 6 The noise suppressing materials shown in Table 2 below were applied to the bottom of the rear wheel drive passenger car (hereinafter referred to as FR car) having a displacement of 2,000 cc and to the front panel membrane sheet. Subsequently, the FR vehicle is actually driven at an engine speed of 4,100 rpm, and the sound pressure level around the ear of the driver's seat and the center of the rear seat while driving is measured by the same precision sound level meter as used in Example 1, The results as shown in Table 2 were obtained. In this case, the FR difference shows a high noise level at 4,100 rpm (its peak is 125 Hz), so the measurement is the sound pressure level at 1/3 octave band width with a center frequency of 125 Hz.

TABLE 2

As can be seen from Table 2, when the stationary spring constant of the foam layer and the weight per unit area of the confinement layer are within the limits defined in the present invention, satisfactory noise reduction effect of the vehicle interior was obtained.

Claims (3)

A noise reduction material for automobile interior noise reduction comprising a foam layer having a stationary spring constant of 0.05 kg / mm / cm 2 or less, and a restraining layer bonded to the foam layer and having a weight of 0.49 mm or more per unit area. The noise preventing material according to claim 1, wherein the foam layer has a thickness of 5 to 40 mm. The method of claim 1. The restraint layer has a thickness of 20 mm or less.