JP2017227787A - Sound absorbing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily put a non-through hole of a sound absorbing sheet into a shape as designed.SOLUTION: A sound absorbing sheet 1 is composed of an elastic material having a hole for sound absorption 23. One side of the sound absorbing sheet 1 in a thickness direction has a first opening 21 and a second opening 22 formed with a space between them. The hole 23 extends, inside the sound absorbing sheet 1, from the first opening 21 to the second opening 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sound absorbing sheet provided, for example, on a door panel of an automobile, and particularly belongs to the technical field of a structure having holes.

  Conventionally, for example, as disclosed in Patent Document 1, a sheet having a foamed layer is known. The sheet of Patent Document 1 has a five-layer structure, and a core layer made up of a large number of short fiber shaped bodies is provided at the center in the thickness direction, and a front side and a back side foam layer are provided on both sides of the core layer. Furthermore, a front side skin layer is provided so as to cover the front side foam layer, and a back side skin layer is provided so as to cover the back side foam layer. This five-layered sheet is a so-called core in which a thermoplastic resin is filled in a cavity between a fixed mold and a movable mold, and then the movable mold is moved away from the fixed mold while foaming the thermoplastic resin. Molded by the back. Then, by irradiating the front skin layer and the front foam layer with laser light, a non-through hole that reaches the core layer and does not reach the back skin layer is formed.

  As described above, as a method for improving the sound absorption performance of the sheet, a method of forming a large number of non-through holes or through holes in the sheet is generally known.

  Further, as a method of forming a through hole or a non-through hole in a sheet, a processing method using a blade such as a drill or a punch is known in addition to laser light irradiation.

JP 2012-106422 A JP 2009-264102 A

  By the way, when a non-through hole is formed as in the sheet of Patent Document 1, it is known that the sound absorption performance varies depending on the length of the non-through hole. In order to increase the sound absorption performance in a specific frequency band, There are cases where it is desired to increase the length of the non-through hole. Therefore, it is conceivable to increase the length of the non-through hole by increasing the thickness of the sheet, but in such a case, the sheet becomes heavy and it is difficult to dispose the sheet in a narrow place. .

  If the holes are formed obliquely with respect to the sheet as in Patent Document 2, the depth of the non-through hole can be increased without increasing the thickness of the sheet. Even if it is possible to form a hole inclined at 0 °, the depth of the hole is at most √2 times the thickness and has a limit.

  In addition, it is conceivable to maximize the length of the hole by making the hole (through hole) formed so as to penetrate the sheet, but in this way, for example, while suppressing the entry of water from the outside When there is a need to obtain a sound absorbing effect, there is a concern of water intrusion from the through hole, so that the use is limited. Furthermore, since the through hole has a different sound absorption characteristic for each frequency from the non-through hole, the through hole may not provide the desired sound absorption performance.

  The present invention has been made in view of such points, and the object of the present invention is to make the shape of the non-through hole, particularly the length of the hole, easily as designed in the sound absorbing sheet having holes. There is.

  In order to achieve the above object, in the present invention, a hole extending so as to connect two openings opened on one surface of the sheet is formed inside the sheet.

The first invention is
In the sound absorbing sheet made of an elastic material in which holes for sound absorption are formed,
A first opening and a second opening are formed at a distance from each other on the surface on one side in the thickness direction of the sound absorbing sheet,
The hole is characterized in that the inside of the sound absorbing sheet extends from the first opening to the second opening.

  According to this configuration, since the hole is formed so as to extend from the first opening formed on the one side surface of the sound absorbing sheet to the second opening, the first opening and the second opening regardless of the thickness of the sound absorbing sheet. The length of the hole is arbitrarily set according to the distance between Since the first opening and the second opening are open on one side of the sound absorbing sheet, the distance between the first opening and the second opening can be increased without increasing the thickness of the sound absorbing sheet. The length of the hole is easily increased.

According to a second invention, in the first invention,
The hole extending from the first opening to the second opening in the sound absorbing sheet does not penetrate through the surface opposite to the surface on which the first opening and the second opening are formed. Features.

  According to this configuration, it is not necessary to form an opening on the other surface of the sound absorbing sheet, so that water-stopping is ensured.

According to a third invention, in the first or second invention,
The sound absorbing sheet has a foam layer having a large number of bubbles,
The bubble is open on the inner surface of the hole.

  According to this configuration, the sound that enters the hole also enters the inside of the bubble, and the sound absorbing performance is further enhanced.

According to a fourth invention, in any one of the first to third inventions,
A solid skin layer is provided on both sides in the thickness direction of the sound absorbing sheet, and the first opening and the second opening are formed in the skin layer.

  According to this configuration, since the sound absorbing sheet is less likely to allow water to pass through due to the skin layer, it is possible to use the sound absorbing sheet in a portion where waterproofness is required.

According to a fifth invention, in any one of the first to fourth inventions,
A cross-sectional area of the hole is substantially the same from the first opening to the second opening.

  According to this configuration, it is possible to easily form a hole with, for example, a laser beam, a drill, a punch, or the like.

A sixth invention is the invention according to any one of the first to fifth aspects,
The hole is bent inside the sound absorbing sheet.

  According to this configuration, when sound entering the inside of the hole from the outside of the sound absorbing sheet is reflected by the inner surface of the hole, it is difficult to go out of the hole, so that the sound absorbing performance is further enhanced.

  According to the first invention, the first opening and the second opening are formed on the surface on one side in the thickness direction of the sound absorbing sheet made of the elastic material, and the hole is formed so as to extend from the first opening to the second opening. Thus, the length of the hole can be increased without increasing the thickness of the sound absorbing sheet, and a desired sound absorbing performance can be obtained.

  According to the second aspect of the present invention, it is not necessary to form an opening on the other surface of the sound absorbing sheet, so that water-stopping is ensured.

  According to the third aspect, since the air bubbles are opened on the inner surface of the hole, the sound absorption performance can be further enhanced.

  According to the fourth aspect, since the solid skin layers are provided on both sides in the thickness direction of the sound absorbing sheet and the first opening and the second opening are formed in one skin layer, the waterproofness of the sound absorbing sheet can be improved.

  According to the fifth aspect, since the cross-sectional area of the hole is substantially the same from the first opening to the second opening, the hole can be easily formed by laser light or the like.

  According to the sixth aspect of the invention, since the hole is bent inside the sound absorbing sheet, it is difficult for the sound that has entered the hole from the outside of the sound absorbing sheet to go out. Thereby, sound absorption performance can be improved further.

It is the perspective view which looked at the front door with which the sound-absorbing sheet which concerns on embodiment was attached from the vehicle interior side. It is a perspective view of a sound absorption sheet concerning an embodiment. It is sectional drawing in the III-III line of FIG. It is sectional drawing of the sheet | seat before forming a hole. It is sectional drawing which shows the case where the sheet | seat before forming a hole is folded and irradiated with a laser beam. It is sectional drawing of the state which expand | deployed the sheet | seat after irradiating a laser beam. It is the figure which showed a mode that a hole was formed using a hole formation tool. It is a graph which shows normal incidence sound absorption coefficient.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 is a perspective view of an automobile front door 50 to which a sound absorbing sheet 1 according to an embodiment of the present invention is attached as viewed from the vehicle interior side. The front door 50 includes a door main body portion 52 that constitutes a substantially lower half portion of the front door 50, a door frame portion 53 that constitutes a substantially upper half portion of the front door 50, and a door glass 54. . The door main body 52 is formed by joining an outer panel 52a located outside the vehicle interior of the door main body 52 and an inner panel 52b located inside the vehicle interior of the door main body 52, and the interior is hollow. It has become. The door glass 54 is supported by a window regulator (not shown) so as to be movable up and down.

  An opening 52c is formed in the inner panel 52b. The opening 52c is greatly open to the inner panel 52b. In addition, a speaker mounting hole 52d and the like are also formed in the inner panel 52b.

  The sound absorbing sheet 1 is attached to the inner panel 52b, and the opening 52c of the inner panel 52b is closed by the sound absorbing sheet 1.

  Although not shown, when the rear door is provided in the automobile, the basic configuration of the rear door is the same as that of the front door 50, and the sound absorbing sheet 1 according to the present invention can be attached to the rear door. The present invention can also be applied to an automobile without a rear door. Furthermore, the sound absorbing sheet 1 can be used by being attached to a vehicle body or an exterior member.

  The outer shape of the sound absorbing sheet 1 is set larger than the opening 52c of the inner panel 52b. Thereby, the whole opening 52c of the inner panel 52b is covered with the sound absorbing sheet 1. The sound absorbing sheet 1 preferably covers the entire opening 52c of the inner panel 52b, but the sound absorbing sheet 1 may have a shape that does not cover a part of the opening 52c. Moreover, although the thickness of the sound-absorbing sheet 1 can be set to 8 mm, for example, it is not restricted to this, For example, it can set to 4 mm or more and 15 mm or less.

  The sound absorbing sheet 1 is entirely made of an elastic material. Examples of the raw material of the sound absorbing sheet 1 include rubber, thermoplastic elastomer, or thermoplastic resin. The raw material of the sound absorbing sheet 1 is formed by extruding the raw material so as to form a sheet having a predetermined thickness. obtain. Examples of the rubber include synthetic rubbers such as ethylene / propylene / diene rubber (EPDM), chloroprene rubber (CR), styrene / butadiene rubber (SBR), and acrylonitrile / butadiene rubber (NBR). Examples of the thermoplastic elastomer include olefin (TPO) and styrene (TPS). Examples of the thermoplastic resin include polyethylene (PE), polypropylene (PP), and ethylene vinyl acetate copolymer (EVA). The raw material of the sound-absorbing sheet 1 may be only one kind of the above raw materials, or may be a raw material in which any plural kinds are mixed.

  2 and 3, the sound-absorbing sheet 1 has a three-layer structure including a front side skin layer 11, an intermediate layer 12, and a back side skin layer 13, so that the front side skin layer 11 is on the vehicle interior side. Attached to the front door 50.

  The front side skin layer 11 is located on one side (front side) in the thickness direction of the sound absorbing sheet 1. The back side skin layer 13 is located on the other side (back side) in the thickness direction of the sound absorbing sheet 1. In this embodiment, the front and the back are defined for the convenience of explanation. However, either one may be used indoors, or the relationship between the front and back may be reversed. .

  The front side skin layer 11 and the back side skin layer 13 can be set to the same thickness, or one can be made thinner than the other. Moreover, the front side skin layer 11 and the back side skin layer 13 are solids which do not have air bubbles, and have a water-stopping property which prevents liquid such as water from passing in the front and back direction. On the other hand, the intermediate layer 12 is a foamed layer having bubbles. As a form of formation of bubbles in the intermediate layer 12, for example, a continuous bubble (continuous bubble) structure in which the bubbles are continuous may be used, or some of the bubbles are continuous and other bubbles are not continuous. A bubble (semi-continuous bubble) structure may be used, or a closed cell structure in which the bubbles are not continuous may be used.

  Since the outer shape of the sound absorbing sheet 1 is set larger than the opening 2c of the inner panel 2b, the entire opening 2c of the inner panel 2b is covered with the sound absorbing sheet 1. The sound absorbing sheet 1 preferably covers the entire opening 2c of the inner panel 2b. However, the sound absorbing sheet 1 may have a shape that does not cover a part of the opening 2c. Moreover, although the thickness of the sound-absorbing sheet 1 can be set to 8 mm, for example, it is not restricted to this, For example, it can set to 4 mm or more and 15 mm or less.

  The thickness of the front side skin layer 11 and the back side skin layer 13 is set to be thinner than the thickness of the intermediate layer 12. For example, it is preferable that the thickness of the front side skin layer 11 is 1/5 or less of the thickness of the intermediate layer 12, thereby ensuring a sufficient thickness of the intermediate layer 12 in the sound absorbing sheet 1 and improving the sound absorbing performance. The thickness of the front side skin layer 11 and the back side skin layer 13 can be, for example, 0.5 mm or more and 1 mm, and the thickness of the intermediate layer 12 is, for example, about 2 mm to 14 mm, more specifically, about 6 mm to 7 mm. Can do.

  A sound absorbing hole 23 is formed in the sound absorbing sheet 1. That is, a substantially circular first opening 21 and second opening 22 are formed in the front surface skin layer (surface on one side in the thickness direction) 11 of the sound-absorbing sheet 1 with a space therebetween. As shown in the figure, a first opening 21 and a second opening 22 are paired. In this embodiment, a large number of first openings 21 and second openings 22 are formed. The hole 23 has a substantially circular cross section similar to the first opening 21 and the second opening 22. The hole 23 is formed in the intermediate layer 12 which is the inside of the sound absorbing sheet 1, and extends through the intermediate layer 12 from the first opening 21 to the second opening 22. The hole 23 communicates only with the first opening 21 and the second opening 22 so as not to reach the back side skin layer 13. Thereby, the water-stopping property of the sound-absorbing sheet 1 having the holes 23 is ensured.

  The hole 23 extends from the first opening 21 toward the back side of the sound-absorbing sheet 1 so as to approach the second opening 22 and then bends as a whole so as to extend toward the front side and reach the second opening 22. As shown in FIG. 3, the overall shape of the hole 23 is curved so that the central portion in the extending direction of the hole 23 is closest to the back-side skin layer 13. In addition, many bubbles of the intermediate layer 12 are opened on the inner surface of the hole 23. Further, the cross-sectional area of the hole 23 is substantially the same from the first opening 21 to the second opening 22.

(Method for producing sound absorbing sheet)
Next, a method for manufacturing the sound absorbing sheet 1 configured as described above will be described. First, as shown in FIG. 4, an elastic sheet 100 as a material is obtained. This elastic sheet 100 has a front side solid skin layer 101, an intermediate foam layer 102, and a back side solid skin layer 103 corresponding to the front side skin layer 11, the intermediate layer 12 and the back side skin layer 13 of the sound absorbing sheet 1, respectively. The elastic sheet 100 can be obtained by, for example, extrusion molding, but the manufacturing method of the elastic sheet 100 is not limited to this.

  Thereafter, for example, as shown in FIG. 5, the elastic sheet 100 is folded. At this time, the front side skin layer 101 of the elastic sheet 100 is positioned outside, and the back side skin layer 103 is positioned inside. As shown in the drawing, the elastic sheet 100 is folded so that there is no gap on the back side skin layer 103 side. Moreover, since it is the elastic sheet 100, in the folded state, it is elastically deformed so that it becomes thinner toward the front end side (left side in FIG. 5) of the folded portion (the bent portion and its vicinity).

  Subsequently, the laser beam L is irradiated as indicated by a virtual line in FIG. Since the irradiation apparatus of the laser beam L is a conventionally well-known apparatus, detailed description is abbreviate | omitted. The phantom line in FIG. 5 has shown the irradiation range of the laser beam L, and in this embodiment, the irradiation range of the laser beam L is separated from the front-end | tip part (left end part of FIG. 5) in the folding part of the elastic sheet 100. And is set so as not to reach the back side skin layer 103. The irradiation range of the laser light L can be arbitrarily set by a known method such as lens adjustment. Further, the output of the laser light L is set so that at least two elastic sheets 100 can be penetrated in a state where they overlap each other. That is, since it is not necessary to stop the laser beam L in the middle of the elastic sheet 100, the adjustment of the output of the laser beam L is easy. In addition, by setting the output of the laser beam L to be slightly stronger, the laser beam L can be surely penetrated even if the size of the bubbles and the degree of density of the elastic sheet 100 differ depending on the part.

  Since the irradiated laser beam L front side skin layer 101 is located outside, after baking the upper side skin layer 101 located on the upper side in FIG. 5, the intermediate layer 12 is baked, and then the lower side skin located on the lower side. Bake layer 101. What is necessary is just to irradiate the laser beam L to several places. By changing the interval between the portions irradiated with the laser light L, the interval between the adjacent holes 23 and 23 can be arbitrarily set.

  After the irradiation with the laser beam L, when it is developed as shown in FIG. 6, the trace of the irradiation with the laser beam L becomes the first opening 21, the second opening 22 and the hole 23, and the sound absorbing sheet 1 is obtained. Since the sound absorbing sheet 1 has elasticity, it restores its original shape when deployed.

  In addition, after forming the 1st opening 21, the 2nd opening 22, and the hole 23 as mentioned above, another part of the sound-absorbing sheet 1 is folded as shown in FIG. Thereby, the 1st opening 21, the 2nd opening 22, and the hole 23 can be formed also in another part. By repeating this, a large number of first openings 21, second openings 22 and holes 23 can be formed.

  In this embodiment, the folding portion of the sheet 100 is irradiated with the laser L, but other methods such as punching with a blade such as a drill or a punch are also possible.

  Furthermore, as shown in FIG. 7, a method of forming holes using a crochet-shaped hole forming tool 60 on the unfolded sheet 100 is also possible. The hole forming tool 50 may be moved in the direction of arrow A.

(Effect of embodiment)
As described above, according to this embodiment, the hole 23 is formed so as to extend from the first opening 21 formed in the front skin layer 11 of the sound absorbing sheet 1 to the second opening 22. Accordingly, the length of the hole 23 can be easily increased depending on the distance between the first opening 21 and the second opening 22 without increasing the thickness of the sound absorbing sheet 1. In addition, it is not necessary to form an opening in the back side skin layer 13 of the sound absorbing sheet 1 and the front side skin layer 11 is formed of a solid, so that water-stopping property can be secured.

  In addition, since the bubbles are opened on the inner surface of the hole 23, the sound that has entered the hole 23 also enters the inside of the bubble, and the sound absorbing performance is further enhanced.

  Further, since the hole 23 is bent inside the sound absorbing sheet 1, it is difficult for the sound that has entered the hole 23 from the outside of the sound absorbing sheet 1 to go outside and the sound that has entered the inside from the first opening 21. The sound that enters the inside through the second opening 22 collides with the inside of the hole 23. Thereby, sound absorption performance can be improved further.

  For example, when the sound absorbing sheet 1 itself is curved or the surface on one side in the thickness direction is partially raised, sound absorption is performed from the first opening 21 to the second opening 22 formed on the one surface in the thickness direction. The hole 23 extending inside the sheet 11 may be formed straight without being bent. In other cases, the hole 23 is bent, and the hole 23 is bent. The sound that enters the inside of the hole 23 from the outside becomes difficult to go outside, and the sound that enters the inside from the first opening 21 and the sound that enters the inside from the second opening 22 collide inside the hole 23, The sound absorption effect can also be enhanced.

  Next, the sound absorbing effect by the sound absorbing sheet 1 will be described with reference to FIG. The horizontal axis of the graph shown in FIG. 8 is the frequency (Hz), and becomes higher toward the right side. In addition, the vertical axis of the graph shown in FIG. 8 is the normal incident sound absorption coefficient, which increases as it goes upward.

  In the graph of FIG. 8, “present invention” is the sound absorbing sheet 1 in which the first opening 21, the second opening 22, and the hole 23 are formed as described in the above embodiment, and “unprocessed” is shown in FIG. 4. The “through hole” is a case where a through hole penetrating in the front and back direction is formed in the elastic sheet 100 shown in FIG. 4, and the “vertical non-through hole” is the elastic sheet 100 shown in FIG. 4. In addition, a hole perpendicular to the front side skin layer 11 is formed so that the hole does not reach the back side skin layer 13.

  In the case of “unprocessed”, the normal incidence sound absorption coefficient is low in the region above the frequency of 2500 Hz, and the degree of noise reduction that tends to be attached to the passenger's ear is low. In the case of the “through hole”, the normal incident sound absorption coefficient is high near the frequency of 3000 Hz, but the normal incident sound absorption coefficient is low in other regions, and the sound absorption performance is insufficient. In the case of the “vertical non-through hole”, the vertical incident sound absorption coefficient is low in the frequency range of 3500 Hz to 5000 Hz, and the sound absorption performance is low.

  On the other hand, in the case of the “present invention”, when the frequency is around 3000 Hz, it is possible to obtain a high normal incident sound absorption coefficient as in the case of the “vertical non-through hole”. Higher normal incidence sound absorption rate than in the case of “non-through-hole” and “through-hole” can be obtained, and further, in the region of 1500 Hz to 2000 Hz, higher normal incidence sound absorption rate than in the case of “through-hole” be able to. Accordingly, the sound absorbing sheet 1 in which the first opening 21, the second opening 22, and the hole 23 are formed has a high degree of noise reduction that is likely to be attached to the passenger's ear when used for vehicles. Can be improved.

(Other embodiments)
In the said embodiment, although the 1st opening 21, the 2nd opening 22, and the hole 23 are formed using the laser beam L, it is not restricted to this, For example, cutters (not shown), such as a drill and a punch, are used. The first opening 21, the second opening 22 and the hole 23 may be formed by use. That is, the elastic sheet 100 can be partially excised by pressing the blade from the same direction as the irradiation direction when the elastic sheet 100 is folded as shown in FIG. Thus, the first opening 21, the second opening 22, and the hole 23 can be formed.

  Furthermore, as shown in FIG. 7, a method of forming a hole with a crochet-shaped hole forming tool 60 in the unfolded sheet 100 is also possible.

  Moreover, although the said embodiment demonstrated the case where the sound-absorbing sheet 1 consisted of a foam material, not only this but the sound-absorbing sheet 1 may consist of a solid material.

  Moreover, the shape of the 1st opening 21 and the 2nd opening 22 may not be circular, and an ellipse and a polygon may be sufficient. Further, the cross-sectional shape of the hole 23 may be elliptical or polygonal.

  The above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the sound absorbing sheet according to the present invention can be used as a sound absorbing member for automobiles, for example.

DESCRIPTION OF SYMBOLS 1 Sound absorption sheet 11 Front side skin layer 12 Middle layer 13 Back side skin layer 21 1st opening 22 2nd opening 23 Hole

Claims (6)

In the sound absorbing sheet made of an elastic material in which holes for sound absorption are formed,
A first opening and a second opening are formed at a distance from each other on the surface on one side in the thickness direction of the sound absorbing sheet,
The sound absorbing sheet, wherein the hole extends inside the sound absorbing sheet from the first opening to the second opening. In the sound-absorbing sheet according to claim 1,
The hole extending from the first opening to the second opening in the sound absorbing sheet does not penetrate through the surface opposite to the surface on which the first opening and the second opening are formed. Characteristic sound absorbing sheet. In the sound-absorbing sheet according to claim 1 or 2,
The sound absorbing sheet has a foam layer having a large number of bubbles,
A sound-absorbing sheet, wherein the bubbles are open on an inner surface of the hole. In the sound-absorbing sheet according to any one of claims 1 to 3,
A sound absorbing sheet, characterized in that a solid skin layer is provided on both sides in the thickness direction of the sound absorbing sheet, and the first opening and the second opening are formed in the skin layer. In the sound-absorbing sheet according to any one of claims 1 to 4,
The sound absorbing sheet according to claim 1, wherein a cross-sectional area of the hole is substantially the same from the first opening to the second opening. In the sound-absorbing sheet according to any one of claims 1 to 5,
The sound absorbing sheet, wherein the hole is bent inside the sound absorbing sheet.

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