JP4279624B2 - Sound attenuation bottom kit - Google Patents

Description

  The present invention relates to a multifunctional sound attenuating underbody kit applied to a vehicle exterior according to the premise of claim 1.

  The bottom of the car is basically composed of floor panels. Since that part is considered one of the most important places to enhance the quietness of the vehicle, various sound attenuating parts are used to enhance the acoustic characteristics of the vehicle.

In this technical field, in order to mainly improve the air resistance coefficient ( _Cw value) of a vehicle, it is possible to use a so-called underfloor member provided below a floor panel, for example, from Patent Document 1, Patent Document 2, and Patent Document 3. Are known. These underfloor members affect the acoustic characteristics of the vehicle, particularly the acoustic characteristics of the passenger compartment. However, these effects are merely accidental and result in both positive and negative acoustic values in the passenger compartment.
U.S. Pat.No. 5,322,340 International Publication No. 02/090172 Pamphlet European Patent No. 1 251 062

  In order to damp floor panel vibrations, asphalt material in sheet form with some fillers and additives is applied to the interior of the car. These sheets are typically heat homogenized on the floor panel using a baking oven in an automated production coating line. Not only a single layer sheet but also a sheet having a multilayer structure excellent in damping characteristics is used. In addition, these damping sheets are used in combination with interior trim materials and / or floor carpets in the passenger compartment in order to further improve the sound attenuation efficiency. The filler and the spacing material between the carpet and the damping sheet contribute to the improvement of the sound absorption characteristics inside the automobile.

Also, in this field, paints such as vinyl chloride plastisol and acrylic blastosol are applied to the outside of the vehicle bottom (including all surfaces such as under the engine of the vehicle, under the floor, wheel arch, and under the trunk floor, etc. It is known to paint by spraying. The composition of such an antirust coating is described in Patent Document 4, for example. Such a coating serves not only to prevent rust, but also to prevent damage caused by pebbles hitting the tire, which is well known as a “chipping phenomenon” during vehicle travel. For example, Patent Document 5 discloses a recently developed material having a sound insulation effect, in particular, an excellent sound absorption characteristic and a chipping prevention function at the same time.
U.S. Pat.No. 4,946,503 US Patent Publication No. 2003/0062738

It is an object of the present invention to develop an acoustically damped bottom kit that is attached to the exterior of a vehicle floor panel with an acoustically tunable (adjustable) structure that can achieve weight reduction and enhanced sound insulation effects. It is. In particular, the object of the present invention is improved sound absorption, sound insulation, body vibration damping, and additional tunability, enhanced shock or chipping protection, thermal insulation, and air resistance coefficient It is to provide a bottom kit having characteristics such as ( _Cw value) reduction. These acoustically effective means are precisely designed by experts to reduce internal noise, increase the occupant room articulation index and / or reduce vehicle exterior noise. It can be done.

This object is achieved by a sound attenuating bottom kit having the features of claim 1. In particular, the bottom kit is a sound attenuating bottom kit for external application to an automobile with a porous multilayer composite that forms a void spaced from the outer surface of the body panel, The porous multilayer composite has a total airflow resistance of 300 to 3500 MKS Rayl (= N · s / m ³ ) and a total bending rigidity of 0.005 Nm to 10.5 Nm.

  This porous multilayer composite has a porous protective scrim facing the outer surface, and may include a porous protective scrim facing the inner surface. This protective scrim can be composed of several materials, in particular non-woven materials. The porous multilayer composite can have a required rigidity by a porous layer, and the porous layer can be composed of a fiber-reinforced porous material.

The bottom kit is attached to the bottom of the vehicle body or wheel house and comprises a porous multilayer composite made of non-woven fibers. The composite is spaced from the outer surface of the bottom body panel. The composite preferably has an airflow resistance of 300 to 3500 N · s / m ³ , more preferably 300 to 3500 N · s / m ³ , particularly 1000 N · s / m ³ . The composite includes a plurality of layers made of a fibrous material, whereby the layer located outside the composite is more rigid than the layer located inside. In this composite, the innermost layer may be made of a material different from that of the outermost layer. The outermost layer can also be composed of a plastic having a higher stiffness than the innermost layer of non-woven fibrous material, which are bonded together by a suitable binder.

  The above-mentioned composite is air permeable and particularly exhibits micro-roughness. The composite according to a preferred embodiment has at least a high density acoustic insulation layer and a low density acoustic absorption layer, both layers being composed of a fibrous material or a foam material. Suitable fibers used in this composite are polyester fibers, all types of polyamide fibers, acrylic fibers, polyethylene fibers, polyolefin fibers similar to polypropylene fibers, polyvinyl chloride fibers, vinylidene fibers, polyurethane fibers, rayon, vinylon, acetate. Or natural fibers such as wood fibers, cotton, bamboo fibers, palm, wool, hemp or silk fibers, and any mixture of one or more of these .

  As binders for bonding these fibrous bodies, thermosetting resins such as phenol resin, melamine resin, alkyd resin, acrylic acid resin, or epoxy resin, polyurethane resin, vinyl chloride resin, vinyl acetate resin, ethylene vinyl Mention may be made of thermoplastic resins such as acetate copolymer resins, synthetic rubbers, certain types of hot-melt adhesives, and thermoplastic fibers having relatively low melting points such as polypropylene fibers, polyethylene fibers, polyester fibers. it can. The foam material can be PUR, PP, PE, or other suitable material.

  In an additional embodiment of the invention, in order to increase the stability and rigidity of the attachment, only a part of the area of the composite is composed of different materials having the above properties. These materials are, for example, thermoplastics and thermosetting plastics (including fiber reinforced plastics (FRP)), or metallic materials such as aluminum, stainless steel, and / or other light alloys. The rigid region and the sound absorbing material are processed so as to be integrated. For example, one method may include forming a rigid region in advance, placing it in a molding tool, and then heating and blanking the blank of sound absorbing material directly into the interior of the rigid frame.

  The above embodiment is merely an example of the kit according to the present invention, and those skilled in the art can appropriately change the above-described individual techniques according to the actual situation.

  Further techniques for forming this kit include an independent forming step preceding an independent bonding step and / or a stapling step, or first forming the acoustical absorbing material and then applying plastic material to the peripheral region of the molding tool. A molding step for forming the rigid frame.

One important aspect of the present invention is the micro-rough surface of the sound attenuation kit. This surface contributes to the improvement of the air resistance coefficient which depends on the vehicle speed, further reduction of C _w values other words, by extension contributes to fuel economy. This effect is commonly known in the art as the “shark skin effect”.

  The sound attenuating kit according to the present invention can be attached to various regions of the floor portion of the front, center, or rear of the vehicle in addition to the base panel of the vehicle. It can also be attached to the fuel tank cover. Other applications may be attached to wheel house liners and / or arcuate wheel covers to minimize primarily tire noise, pebble chipping noise and / or water splash noise.

  There is no specific limitation on the method of attaching the kit to the base, and any known fixing means can be used. For example, by using physical methods such as bolts, screws, clips, or chemical methods such as bonding, or by attaching the edges of the kit directly to a metal fixture that is pre-installed on the floor panel. Even is possible. The air gap created between the vehicle floor panel and the acoustic composite is set to be sufficient to achieve the objects of the present invention. In one alternative embodiment, the composite according to the invention comprises three layers, in particular from the outside to the inside, a layer consisting of porous carpet for protecting the inner layer from impacts from pebbles, a compressed fiber fleece (Known to those skilled in the art as “TACA”), and low density packing material, for example made of PET felt. By adding such a low density layer, a more excellent acoustic absorption effect can be obtained, and the noise level inside the vehicle can be reduced. This low density material can also be constructed from a foam material that is lightweight and has open cells.

  Advantages of the bottom kit according to the present invention include significant noise reduction in medium and high frequency ranges, considerable weight reduction of internal noise reduction means, reduction of air resistance characteristics, minimization of the need for rust prevention means Realization of the above-mentioned coating, protection against damage due to chipping of pebbles, and the realization of a simplified composite with acoustic comfort achieved by such protection, as well as brake devices, exhaust pipes, catalysts The improvement of the heat insulation capability with respect to heat radiating components, such as an apparatus, is mentioned. The main advantage is that all the characteristics mentioned above can be optimized as a single vehicle part.

  The present invention will be described in more detail with reference to the preferred embodiments described below and the accompanying drawings.

[Example 1]
As can be seen from FIG. 1, the multifunction kit 6 according to the present invention applied to the outside of the vehicle is mainly configured to have acoustic absorption characteristics. However, the kit 6 also has functions such as impact protection, sound insulation, heat insulation, and body vibration attenuation. The thickness of the multifunction kit 6 is 5 to 50 mm. This multifunction kit 6 includes a porous multilayer composite 7. The porous multilayer composite 7 is 300 to 3500 MKS Rayl (N · s / m ³ ), particularly 300 to 2500 Rayl (N · s / m ³ ), preferably 1000 Rayl (N · s / m ³ ). It has a total air resistance value, a total bending rigidity B of 0.005 Nm to 10.5 Nm, a unit area weight of 0.5 to 3 kg / m ² , and a thickness of 1 to 5 mm. The composite 7 together with the gap 4 forms a tunable multilayered sound attenuating kit. This porous multilayer composite has a porous protective scrim 1a facing the outer surface, and may include a porous protective scrim 1b facing the inner surface. This protective scrim can be composed of several materials, in particular non-woven materials. The porous multilayer composite 7 can have a required rigidity by the porous layer 3, and the porous layer 3 can be made of a fiber-reinforced porous material. The layer 3 can be manufactured by a compressed body of a fiber mat or by expanding a previously compressed fiber mat. In order to increase rigidity, the porous multilayer composite may have one or more porous rigid layers 2a, 2b made of a compressed fiber material. By appropriately adjusting the thickness, the airflow resistance and unit weight of the porous multilayer composite 7, and the depth of the gap 4, this structure is capable of both sound absorption and sound insulation against noise sources outside the vehicle. The function can be demonstrated. Here, the noise source is noise based on, for example, contact sound between a tire and a road, a driving system, exhaust, or aerodynamics. This complex can also reduce the divergence of noise to the outside, thus helping to meet the criteria according to ISO 362 {exterior test homologation test}.

FIG. 6 shows a typical incident sound field spectrum measured at the bottom (continuous line) and the acoustic absorption rate (dotted line) adjusted to have maximum performance at frequency f ₁ where most of the energy is concentrated. It is a graph. The bottom kit according to the present invention has improved acoustics compared to known plastic bottom parts to reduce energy radiating towards the floor. In particular, due to its porosity, less sound is emitted when struck by turbulent air or when vibrated for other reasons than a rigid non-porous surface. When this bottom kit is applied to a wheel house, tire noise transmitted to the inside of the vehicle and directed to the outside can be reduced. This is because it absorbs acoustic energy distributed over the entire circumference of the tire and generated in the contact area between the tire and the road surface.

[Example 2]
FIG. 2 is another embodiment of a kit according to the present invention. In this configuration, a porous acoustic material layer 9 is added between the porous multilayer composite 7 and the body panel 5. The porous acoustic material layer 9 can be made of a thermoplastic or thermosetting plastic or a porous foam. The thickness of the layer 9 is 5 mm to 25 mm, and the unit weight is 0.2 kg / m ² to 1.8 kg / m ² . This porous acoustic material may be protected by a jacket made of a thin impermeable plastic film (for example, PP, PE, etc.) or a porous protective scrim (for example, a nonwoven fabric). The porous acoustic material layer 9 may be in direct contact with the body panel 5. In that case, the depth of the gap 4 is zero. The porous material layer 9 may also be replaced by a layer of chamber absorber. In this configuration, the thickness of the porous multilayer composite 7, the porous acoustic layer 9, the protective scrim 8, the airflow resistance, and the unit weight, and the depth of the air gap 4 are adjusted appropriately, thereby making it possible to prevent the external noise source High sound absorption and sound insulation are provided.

Example 3
FIG. 3 shows another embodiment of the multifunction kit according to the present invention. In this configuration example, a porous acoustic material layer 9 is added to the gap between the porous multilayer composite 7 and the body panel 5. This additional layer can be composed of a thermoplastic or thermosetting felt or a porous foam. The additional layer has a thickness of 5 mm to 25 mm and a unit weight of 0.2 kg / m ² to 1.8 kg / m ² . The porous acoustic material may be protected by an outer cover 8a, 8b made of a thin impermeable plastic film (for example, PP, EP) or a porous protective scrim (for example, a nonwoven fabric). The porous acoustic material layer 9 is directed toward the body panel 5. Contact with the body panel 5 is ensured by a lightweight spacer 10. This lightweight spacer can be made of a porous, impervious lightweight material such as expanded polyester. Alternatively, it may be an ultralight foam having an open small hole. The thickness of the lightweight spacer can be 5 mm to 40 mm. In this embodiment, the same function as that shown in FIG. 2 can be exhibited. However, the structural damping function of the body panel 5 is further enhanced to reduce the vibration of these body panels, and thus the vehicle. It is possible to reduce noise emission to the inside of the.

4 and 5 are graphs showing a comparison of the soundproofing effects of the three samples. The soundproof sample 1 was obtained by using a polyester fiber material, and was preheated and compression-molded in a tool to have an airflow resistance of 2100 N · s / m ³ .

  In the second sample, the central portion is made of the same material and the same manufacturing method as sample 1. However, the rigid frame enclosing the outside is made of fiber reinforced plastic (FRP) by an injection molding method and then assembled.

  The soundproof sample 3 is obtained by the same material and the same manufacturing method as the sample 1 in order to obtain a high-density layer. In addition, a felt is made for the low density layer by adding a phenolic resin binder to a mixture of natural and artificial fibers. This low density layer is molded by heat compression and assembled to the high density layer.

  To produce a comparative sample, the bottom plate of the vehicle floor is painted with a vinyl chloride plastisol base coating consisting of a vinyl chloride resin mixed with DOP plasticizer, calcium carbonate, and colorants.

  The soundproof samples 1 to 3 are mounted on a solid steel plate having a thickness of 0.8 mm using bolts and nuts.

  In order to base coat the sample for comparison, the above coating is air-sprayed onto a solid steel plate, then heated and dried at 140 ° C. for 20 minutes. This gives a coating with a thickness of 1.5 mm.

  These reference samples 1 to 3 are mounted as partitions between the two chambers. Noise is generated from the speaker in one chamber, and the frequency-dependent propagation noise level is measured by the microphone in the other chamber. This measured noise level is compared with the value of the base coated comparison sample.

  The frequency-dependent sound absorption is measured using “acoustic absorption measurement by reverberation method” defined in JIS A 1406, and the bottom soundproof sample and the bottom coating comparison sample are evaluated. FIG. 4 shows the acoustic absorption characteristics of the measured samples 1 to 3 and the comparative sample in db.

  FIG. 5 shows the acoustic absorption characteristics of the measured samples 1 to 3 and the comparative sample as a percentage.

  When the measured values of the soundproof samples 1 to 3 are compared with the comparative sample, it can be seen that the soundproof characteristics are clearly improved in the audible frequency region. Furthermore, a significant improvement in the acoustic absorption characteristics in the same frequency region is also evident.

  Those skilled in the art will recognize that a marked improvement in sound attenuation characteristics is obtained by attaching the composite according to the present invention to the vehicle base. In addition, the minute roughness of the porous surface reduces the air resistance coefficient (shark skin effect), contributing to improved fuel efficiency.

  It should be noted that the present invention is not limited to the above-described embodiments, and those skilled in the art can appropriately modify the specific requirements.

It is a fragmentary sectional view which shows the basic composition of the multifunctional sound attenuation | damping bottom kit based on this invention. It is a fragmentary sectional view which shows the structure which strengthened the absorption and insulation function. It is a fragmentary sectional view which shows the structure which strengthened the structural damping function, absorption, and insulation function. It is the graph which showed the soundproof effect of what was shown in Example 1 thru | or Example 3 compared. It is the graph which showed the acoustic absorption effect of what was shown in Example 1 thru | or Example 3 compared. It is a graph which shows the adjusted incident sound field spectrum compared with a typical thing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Porous protective scrim 2a, 2b Rigid layer 3 Porous innermost layer 4 Cavity 5 Body panel 7 Porous multilayer composite 9 Porous material layer 10 Light weight spacer

Claims (12)

A multi-function sound attenuation bottom kit for application outside the automobile,
A porous multilayer composite (7) is formed which is spaced from the outer surface of a vehicle body panel (5) to form a void (4), and the porous multilayer composite (7) is 300 to 3500 N · s / m. ³ , preferably 300 to 2500 N · s / m ³ , especially 1000 N · s / m ³ , and a total bending rigidity of 0.005 Nm to 10.5 Nm Features multi-functional sound attenuation bottom kit.   The kit according to claim 1, wherein the multilayer composite (7) comprises a porous innermost layer (3) and one or two rigid layers (2a, 2b) located on the outermost side and made of porous material. A kit comprising:   3. Kit according to claim 2, characterized in that the multilayer composite (7) comprises an outwardly facing porous protective scrim (1a).   4. Kit according to claim 3, characterized in that the multilayer composite (7) comprises an inwardly facing porous protective scrim (1b).   The kit according to any one of claims 1 to 4, further comprising a porous material layer (9) inside the void (4).   6. Kit according to claim 5, characterized in that the porous material layer (9) is wrapped in a thin impermeable plastic film with a porous protective scrim.   The kit according to claim 5 or 6, further comprising a lightweight spacer (10) for pressing the porous material layer (9) against the body panel (5) of the vehicle.   The kit according to claim 7, characterized in that the lightweight spacer (10) is made of a foam or expanded polystyrene having an open small hole.   9. Kit according to claim 7 or 8, characterized in that the lightweight spacer (10) has an air chamber. The kit according to any one of claims 2 to 4, wherein the porous innermost layer is formed of a compressed body of a fiber mat, or an expanded fiber mat compressed in advance. 11. The kit according to any one of claims 2 to 4 and 10, wherein at least one of the rigid layers is made of a compressed fiber material. The kit according to claim 3 or 4, wherein the porous protective scrim layer is made of a non-woven material.

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