JP2011241550A - Track surface sound absorption structure and method of molding multi-layer sound absorption material used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a track surface sound absorption structure as a noise countermeasure for a non-ballast track by developing a sound absorption material which has a thickness that meets the construction limit on the track structure and whose sound absorption performance is 0.7 (70%) or more of reverberation room method sound absorption coefficient in a broad band.SOLUTION: The track surface sound absorption structure inhibits the reflection of the noise on the non-ballast track surface. The sound absorption material used therein is complexed by layering in the order from the incident side of acoustic energy, thermally compressing and then fusing the plural sheets of polyester fiber nonwoven cloth and a polyester fiber nonwoven cloth base material, and the sound absorption material having 0.7 (70%) or more of a reverberation room method sound absorption coefficient in 500 Hz to 2 KHz of a frequency band, is laid on the surface of the track.

Description

According to the present invention, in a non-ballast track (slab track) as a labor-saving track, rolling noise generated when a wheel rolls on a rail during train traveling and noise of auxiliary equipment are reflected on the slab track surface to reduce noise. It will be amplified.
The present invention relates to a track surface sound absorbing structure for suppressing reflection of such noise on a slab track surface, and a molding method of a multilayer sound absorbing material used therefor.

  In recent years, as a part of labor saving such as railway maintenance, not only Shinkansen railways but also conventional railways have become non-ballasted, and the number of slab tracks and elastic directly connected sleeper tracks has increased.

  In this era, the orbital structure aimed at the next generation is being studied. That is, it has a track structure that can save labor in the fastening device based on the concepts of maintenance and environmental friendliness. An example is shown in FIG. That is, the rail 1 is installed in the concrete structure 2 via the rubber plate 3 or the like, and this is a track in which the rail 1 is continuously supported by the rail holding block 4. By embedding the rail 1 in the concrete structure 2, it is expected that the amount of sound radiated from the rail 1 is reduced along the line, and the track is excellent in the environment.

On the other hand, noise generated when a train wheel rolls on the rail 1 tends to be reflected by the slab track surface and amplify the noise, which may cause problems due to environmental problems. It must also be considered that the living environment of residents is deteriorated. Therefore, laying a sound absorbing material on the track surface is indispensable for protecting the environment.
However, since the concrete member is arranged close to the head of the rail 1, when the sound absorbing material is to be laid on the raceway surface, it is necessary to keep the sound absorbing material within the building limit. For that purpose, the thickness of the sound absorbing material needs to be less than 25 mm (20 mm or less in view of safety).

  Thus, in order to realize a track surface sound absorbing structure that can be applied to all currently assumed track structures, it has been necessary to realize high sound absorbing performance with a thickness of less than 25 mm, which has been difficult in the past. In addition, although the track with the rail embedded structure has already been partly put into practical use in the tramway, when a sound absorbing material is applied to this existing track, the thickness is less than 25 mm in order to satisfy the construction limit. It is requested to do.

  For the purpose of sound absorption, as a conventional technique, there is a method in which ballast is dispersed. However, in order to improve the sound absorption performance, it is necessary to make the ballast finely divided. Nevertheless, since there is a limit to the refinement, it is difficult to secure a reverberation chamber method sound absorption rate of 0.7 (70%) or more in a wide band of 500 Hz to 2 kHz. In addition, there is a problem that if the particles are made finer, they may be scattered. Also, collecting ballasts may lead to environmental destruction, and the burden of maintenance is large and is not a means that is in current trend.

  Although application of other solid sound absorbing materials is conceivable, electricity for the signal system is flowing on the railway track, and the solid sound absorbing material laid on the track surface is required to have good electrical insulation performance. For this reason, glass wool, flexible urethane foam, or ceramics are considered as the solid sound absorbing material laid on the raceway surface.

  However, the former two have problems in weather resistance and water resistance when exposed outdoors for a long period of time, and part of the material may be peeled off from the surface and scattered around. In addition, sound absorption performance is deteriorated due to secular change, and there is a risk that the inside is also cut and deformed. Furthermore, the third ceramic system has problems in sound absorption performance, weight and cost, and is difficult to use as a practical track surface sound absorbing material.

  The present invention has been made to solve the above-described problems of the prior art, and is used for a track surface sound absorbing structure as a noise countermeasure for a non-ballast track such as a next-generation track structure or a slab track and the like. A multilayer sound-absorbing material is provided. Specifically, in order to achieve a wide track surface sound absorbing structure that satisfies the building limits of all types of track structures, the thickness of the sound absorbing material is suppressed to less than 25 mm, and the sound absorbing performance is 500 Hz to 2 kHz. The present invention provides a new molding method of a durable sound-absorbing material that has a reverberation chamber method sound absorption coefficient of 0.7 (70%) or more in a band.

  The first gist of the present invention is a track surface sound absorbing structure for suppressing the reflection of noise at the time of passing a train on a non-ballast track surface, and is a shape controlled to satisfy the building limit for various railway tracks, A sound absorbing material having a sound absorption rate of at least 20 mm in thickness and a reverberation chamber method sound absorption rate of 0.7 (70%) or more is laid on the surface of the track surface for the main frequency band of railway noise of 500 Hz to 2 kHz. It is what.

The sound absorbing material employs a multilayer sound absorbing material in which a plurality of polyester fiber non-woven fabrics and a polyester fiber non-woven fabric base material are stacked and heat-bonded from the acoustic energy incident side. The flow resistance of the non-woven fabric of the plurality of layers is 1 × 10 ^{6 to} 3 × 10 ⁶ N · sec / m ⁴ , and the flow resistance of the base material is 0.5 × 10 ^{4 to} 3.5 × 10 ⁴ N · sec / m. ⁴ is a raceway sound absorbing structure in which the flow resistance of the composite multilayer sound absorbing material is 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ⁴ .

The second gist of the present invention is a method of molding a multilayer sound absorbing material for suppressing reflection of noise when passing through a train on a non-ballast track surface, and the flow resistance is 1 × 10 ⁶ from the incident side of acoustic energy. -3 × 10 ⁶ N · sec / m ⁴ polyester fiber non-woven fabric (several sheets) and flow resistance of 0.5 × 10 ⁴ -3.5 × 10 ⁴ N · sec / m ⁴ polyester fiber non-woven fabric mother Stacked materials, formed to a thickness of 120-150% of the thickness that satisfies the building limit, sprayed hot melt material between each layer, compressed at 170-220 ° C and heat-sealed, the thickness is building A permanent distortion is applied so as not to exceed the limit, and the composite multilayer sound-absorbing material has a flow resistance of 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ⁴ and a frequency band of 500 Hz to With respect to 2 kHz, the reverberation room method sound absorption coefficient is 0.7 (70%). It is a molding method characterized by having a sound absorption coefficient of the above.

  The multilayer sound-absorbing material of the present invention is provided with excellent characteristics that exceed the conventional sound absorption performance while keeping the thickness within the specified range, and is made from a material excellent in environmental problems, recyclability, and durability. It has become. Furthermore, the sound absorbing structure using this for the raceway surface can prevent the reflection of noise on the raceway surface, and has characteristics that cannot be compared with conventional materials.

FIG. 1 is a diagram showing an outline of a next-generation orbit structure. FIG. 2 is a diagram showing the relationship between the multilayer sound absorbing material of the present invention and an incident wave as a noise source. FIG. 3 is a diagram showing the reverberation chamber method sound absorption coefficient of the multilayer sound absorbing material of the present invention. FIG. 4 is a diagram showing the sound absorption coefficient of the multilayer sound absorbing material of the present invention and the conventionally used glass wool reverberation chamber method. FIG. 5 is a graph showing the sound absorption rate of the track surface sound absorbing structure to which the multilayer sound absorbing material of the present invention is applied.

  Now, the noise (rolling sound) generated when the train including the Shinkansen is in the main band is 500 Hz to 2 kHz, and a sound absorption coefficient of 100% is required to completely eliminate reflection on the slab surface. On the contrary, if it is completely reflected on the slab surface (sound absorption rate 0%), at least noise may be amplified by 3 dB by one reflection, and if it is multiple-reflected between the vehicle side or the wall, it may be further amplified by several dB. However, if 70% is ensured as the sound absorption coefficient, it becomes 1 dB or less in one reflection and amplification by multiple reflection can be suppressed. Therefore, the purpose of the sound absorption material of the present invention is to set the sound absorption coefficient of the reverberation chamber method to 0.7 (70 In addition, a sound absorbing material having a thickness of about 20 mm and a sound absorption rate of 70% (especially 500 Hz to 800 Hz) at 500 Hz to 2 kHz is extremely high for a sound absorbing material based on the conventional idea. Since it is difficult, the present invention aims to achieve both.

  There are various types and structures of materials used for the sound absorbing material, but among these, porous materials are the most commonly used materials. Recently, there have been an increasing number of cases in which polyester fiber sound absorbing materials are applied from the viewpoints of environmental problems, recyclability, sound absorbing performance, long-term durability, and the like. This polyester fiber-based sound absorbing material has superior characteristics compared to other materials and is a high-performance sound absorbing material that is friendly to the environment. In other words, it has a relatively simple structure, excellent sound absorption performance, excellent weather resistance / durability / optimum for long-term use, recyclability has been established, and it is friendly to the global environment. have. The present invention has been developed by utilizing such characteristics and particularly aiming at sound absorption of a railway track.

  The polyester fiber-based sound absorbing material used in the present invention is preferably one obtained by a spunbond method using endless long fibers, but is not particularly limited to this, for example, a thermal bond method. , A chemical bond method, a needle punch method, a stitch bond method, or the like. Spunbond is a non-woven fabric that has been made long and dense by melt extrusion molding.

  FIG. 2 is a diagram showing the relationship between the multilayer sound-absorbing material used in the first aspect of the present invention and an incident wave as a noise source. The multilayer sound-absorbing material 20 is a two-layer polyester fiber nonwoven fabric with respect to the incident wave side. 21 and 22 (multi-layered) and a polyester fiber nonwoven fabric 23 as a base material, and hot-melt powder (not shown) between them is heat-sealed. The base material 23 is attached to the rigid wall 25.

  Now, the polyester fiber nonwoven fabrics 21 and 22 are arranged at 1/4 of the wavelength of the incident wave. The particle velocity is maximum (sound pressure 0) at this position, and the rigid wall 25 is reached. The particle velocity is designed to be 0 (maximum sound pressure).

  The base material is a non-woven fabric made from polyester fibers. Such a non-woven fabric is not a fabric formed by weaving fibers, but is simply collected and partially fused to form a solid body. In such a fiber assembly, since there is a gap between the fibers, the sound wave enters therein, and the acoustic energy of the sound wave is attenuated by the viscous resistance of air and the like as it travels. That is, the incident acoustic energy is converted into thermal energy mainly by viscous resistance in the sound absorbing structure. Thus, by using a nonwoven fabric, it is easy to process and material cost can be reduced. Further, since the air flow resistance is not woven, adjustment of the air flow resistance becomes easy. The fiber orientation of the base material may be any of lateral, longitudinal and random, but longitudinal orientation is desirable from the viewpoint of compressive strength.

  On the other hand, a two-layer polyester fiber non-woven fabric (spunbond non-woven fabric) is provided as a surface layer which is an incident surface for acoustic energy, thereby improving sound absorption performance. The surface layer is a spunbonded non-woven fabric, and attenuation of sound wave energy is amplified for the reason that a frictional resistance is generated between the spunbonded non-woven fabric and the base material. The energy of the sonic wave is greatly reduced when the attenuation is large at the location where the amplitude is large, but the location where the spunbond is placed is the location where the sound amplitude is maximum in the area where this material affects the sound, and the span is located at this position. By disposing the bond, the attenuation performance and sound absorption performance against sound waves are enhanced. Note that two types of spunbond are applied, one that has been subjected to a soaking treatment on the outside air side, and the other type that is not subjected to the soaking treatment should be used.

From this, it is important to control the flow resistance of the base material and the surface layer, and to optimally adjust the flow resistance as a multilayer sound absorbing material combining them. That is, one of the aims of the present invention is to combine the flow resistance of the multilayer sound-absorbing material (two-layer spunbond nonwoven fabric + base material) so as to fall within a specific range as much as possible near the surface layer.
For that purpose, the flow resistance of each of the constituent materials is 1 × 10 ^{6 to} 3 × 10 ⁶ N · sec / m ⁴ , and the flow resistance of the base material is 0. .5 × 10 ^{4 to} 3.5 × 10 ⁴ N · sec / m ⁴ are combined, and these are heat-sealed as a multilayer sound-absorbing material, and the overall flow resistance is 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ⁴ is adjusted so as to be contained. The multilayer sound-absorbing material thus obtained is further molded to a predetermined thickness by hot pressing to realize the sound-absorbing structure for tracks of the present invention. As a multilayer sound-absorbing material, if the lower limit value is not reached, the sound absorbing performance in the band of about 500 Hz to 800 Hz is lowered, and if this upper limit value is exceeded, the sound absorption coefficient at around 2 kHz is lowered.

The multilayer sound-absorbing material (second invention), which is the core of the orbital surface sound-absorbing structure of the present invention (second invention), has a sound absorption coefficient of 0.7 (70%) or higher in the reverberation chamber method over a wide band of 500 Hz to 2 kHz. A multilayer sound-absorbing material made of polyester fiber, and adjusted so that the overall flow resistance is 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ⁴ , and In order to finish the multilayer sound-absorbing material to a predetermined thickness, a multilayer structure having a predetermined thickness or more is first made, and this is hot-press-compressed to be permanently set and finished to a predetermined thickness.
Specifically, since a polyester fiber-based material is used, preferably, a multilayer sound-absorbing material having a thickness of 120 to 150% of a predetermined thickness is first manufactured and then compression-molded to a predetermined thickness with a hot press. Therefore, the entire sound-absorbing material is made of a polyester fiber material for ease of recyclability and the like, and many problems as a track surface sound-absorbing material are overcome. Each layer is preferably heat-sealed with a powdery hot melt.

That is, by introducing this spunbond, a high sound absorption performance at a thickness of 20 mm, which has been difficult to realize so far, was realized.
And in order to finish it to a predetermined thickness, for example, 20 mm, a composite product having a thickness of 28 to 30 mm is made, and it is further thermally compressed to finish it to a thickness of 20 mm.

(Example 1-Characteristics of multilayer sound absorbing material)
The second multilayer sound absorbing material of the present invention was molded as follows. The surface layer is composed of two layers of polyester fiber spunbond nonwoven fabric, the base material is a polyester fiber nonwoven fabric (longitudinal orientation) 28 mm thick and is composited with a surface density of 800 gr / m ² and compression molded to a predetermined thickness of 20 mm by hot pressing. The overall flow resistance was adjusted to about 4 × 10 ⁴ N · sec / m ⁴ . The surface layer has a flow resistance of about 1.5 × 10 ⁶ N · sec / m ⁴ , and the base material has a flow resistance of about 0.5 × 10 ⁴ N · sec / m ^4. Hot melt powder was sprayed and hot pressing was performed at 180 ° C.

  FIG. 3 shows the reverberation chamber method sound absorption coefficient of the obtained multilayer sound-absorbing material. In addition, it shows with the comparison with the base preform | base_material of the multilayer sound-absorbing material before compressing. As a result, even in the multilayered sound absorbing material after compression, sound absorption of 0.7 (70%) or more was achieved in the reverberation chamber method sound absorption rate over a wide band of 500 Hz to 2 kHz.

Further, it is shown in FIG. 4 in comparison with glass wool (bulk density 32 kg / m ³ ) that is most often used as a sound absorbing material. Compared to glass wool with a thickness of 50 mm, the product of the present invention exceeds the sound absorption performance of glass wool with a thickness of 20 mm, and the superiority of the product of the present invention as a track surface sound absorbing material has been proved. .

(Example 2-Features as a raceway sound absorbing structure)
As an actual application example, the multilayer sound-absorbing material of the present invention obtained in Example 1 was applied to the next-generation orbit shown in FIG. The multilayer sound-absorbing material has a thickness of 20 mm because of the construction limit. A multilayer sound-absorbing material is attached to the A to C surfaces of the next-generation track structure shown in FIG.

  The actual vehicle running test results are shown in FIG. 5 together with a non-application example of the multilayer sound absorbing material. The reduction effect is about 3 dB above 315 Hz including a wide band of 500 Hz to 2 kHz. As a result, the noise level is 95 dB before laying down to 92 dB after laying the product of the present invention, and the reduction effect of about 3 dB is obtained. The product reduces the reflection component on the raceway and proves its effectiveness.

  The present invention is as described above, and can be used in a wide range of environmental conservation fields such as the transportation field such as railways and roads, the industrial equipment and building equipment fields, and can contribute to the quietness of the environment and living space.

DESCRIPTION OF SYMBOLS 1 Rail 2 Concrete structure 3 Rubber plate 4 Holding block 20 Multi-layer sound-absorbing material 21, 22 Surface layer (polyester fiber nonwoven fabric)
23 Base material (polyester fiber nonwoven fabric)
25 Rigid wall A ~ C surface Track surface for adhering multilayer sound absorbing material

Claims (10)

A track surface sound absorbing structure for suppressing noise reflection when passing a train on a non-ballast track surface, having a shape controlled to satisfy the building limits for various railway tracks, and a main frequency band of railway noise of 500 Hz to 2 kHz. On the other hand, a track surface sound absorbing structure characterized in that a sound absorbing material having a sound absorption coefficient of at least 20 mm in thickness and having a sound absorption coefficient of 0.7 (70%) or more is laid on the surface of the track surface. 2. The track-surface sound absorbing structure according to claim 1, wherein the sound absorbing material is a multilayer sound absorbing material in which a plurality of polyester fiber non-woven fabrics and a polyester fiber non-woven fabric base material are stacked and heat-bonded to form a composite material from the incident side of acoustic energy. . The raceway sound-absorbing structure according to claim 2, wherein the polyester fiber nonwoven fabric on the incident side is obtained by a spunbond method. The raceway sound-absorbing structure according to claim 2 or 3, wherein a hot melt material is dispersed and thermally fused between the respective layers. The flow resistance of the multilayer nonwoven fabric on the sound wave incidence side is 1 × 10 ^{6 to} 3 × 10 ⁶ N · sec / m ⁴ , and the flow resistance of the base material is 0.5 × 10 ^{4 to} 3.5 × 10 ^4. The track surface according to any one of claims 2 to ⁴ , wherein N · sec / m ⁴ and the composite multilayer sound absorbing material has a flow resistance of 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ^4. Sound absorbing structure. The multilayer sound-absorbing material is formed to a thickness of 120 to 150% of the thickness that satisfies the building limit, is subjected to heat compression molding in the thickness direction, and a permanent strain is applied so that the thickness does not exceed the building limit. Item 6. The track surface sound absorbing structure according to any one of Items 1 to 5. The raceway sound-absorbing structure according to claim 6, wherein the thermal compression molding imparts permanent strain at 170 to 220 ° C. The track surface sound absorbing structure according to any one of claims 1 to 7, wherein a polyester fiber non-woven fabric is heat-sealed in a frame shape around the side surface of the heat-stressed multilayer sound absorbing material. 9. A heat-molded multilayer sound-absorbing material having a frame periphery in which two or more polyester fiber nonwoven fabrics are heat-sealed in a frame shape, and at least the outside air-side polyester fiber nonwoven fabric is subjected to a water-repellent treatment. The sound absorption structure of the raceway. A method for forming a multilayer sound absorbing material for suppressing reflection of noise at the time of passing a train on a non-ballast track surface, wherein the flow resistance is 1 × 10 ^{6 to} 3 × 10 ⁶ N · sec / sec from the incident side of acoustic energy. a plurality polyester fiber based nonwoven m ^4, flow resistance repeatedly 0.5 × ¹⁰ 4 ~3.5 × ¹⁰ 4 polyester fiber system of N · sec / ^{m 4} nonwoven preform, the thickness of which satisfies the construction gauge Formed to a thickness of 120-150%, sprayed hot melt material between each layer, compressed at 170-220 ° C. and heat-sealed to give permanent distortion so that the thickness does not exceed the building limit The combined multi-layered sound absorbing material has a flow resistance of 3.5 × 10 ^{4 to} 7 × 10 ⁴ N · sec / m ⁴ and has a reverberation chamber method sound absorption coefficient for a frequency band of 500 Hz to 2 kHz. Having a sound absorption coefficient of 0.7 (70%) or higher Molding method of the multi-layer sound-absorbing material to the butterflies.

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