Sound-absorbing materials for automobiles

Abstract

The present invention provides a sound absorbing material for automobiles that can achieve lightweight and stably obtain desired sound absorbing performance. The sound absorbing material for automobiles has a multi-layer structure, comprising a core layer (10) having tubular units (20) arranged in multiple rows and an airtight resin film layer (40) bonded to one surface of the core layer, the unit ends on one surface of the core layer having a closed surface (21) and an open end (22) separated by a row, the unit ends on the other surface of the core layer have an open end (22) in the row where the unit ends on the one surface have a closed surface, and have a closed surface (21) in the row where the unit ends on the one surface have an open end, the internal space of the unit (20) is connected to the outside through the open end (22), the Young's modulus E (MPa) of the airtight resin film layer (40) and the surface density M (g / m2) of the layer structure on the side closer to the first airtight resin film layer (40) than the core layer (10) are equal to each other. 2 ) is 0.5

Description

Technical Field

[0001] The present invention relates to a sound absorbing material for automobiles. Background Art

[0002] The structure of a car generally has an engine room in the front, a trunk room in the rear, and a car compartment in the middle. The car compartment is provided with seats such as a driver's seat, a front passenger seat, and a rear seat. In addition, in the car compartment, a front bulkhead insulator, a carpet, a floor mat, a trunk trim, and a trunk floor are provided in a manner to cover the outside of the interior parts of the car, and these parts are formed into a concave-convex shape corresponding to the shape of the car body or the design of the parts. In addition, the exterior parts under the car body are provided with a front fender lining, a rear fender lining, and a bottom cover formed into a concave-convex shape to control the air flow. Most of these parts are made of thermoplastic resin, and the material is heated and stamped using a mold in the shape of the part, and finished into a concave-convex part with multiple parts of different thicknesses.

[0003] As a recent trend in automobile development, the quietness of the car interior has received much attention. The noise transmitted to the interior of the car includes noise from the windows, noise from the tires, noise from the bottom of the car body, noise from the engine sound, noise from the motor sound, etc. Among the noises, the frequencies of 500Hz to 4000Hz are particularly considered to be harsh to the driver and passengers. In addition, in electric vehicles, the frequencies of 4000Hz to 8000Hz, which have never been harsh in the past, are also considered to be harsh to the driver and passengers because there is no engine. Therefore, the interior and exterior decorative parts of the car are required to have the function of absorbing noise in this frequency range. On the other hand, reducing fuel consumption is also important, and the weight of the interior and exterior decorative parts of the car needs to be reduced.

[0004] In addition, Japanese Patent Gazette No. 4539294 discloses that a frequency selective plate made of light metal with openings is bonded to both ends of a honeycomb core made of non-metal by an adhesive, and a fiber-reinforced substrate is bonded to the outside thereof. The frequency selective plate transmits or blocks specific frequencies.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 4539294 Summary of the invention

[0008] Problems to be solved by the invention

[0009] Since the frequency selective plate of Japanese Patent No. 4539294 is made of light metal, it is expected that the sound attenuation effect can be achieved by the friction of the air passing through the openings of the frequency selective plate, but there is no further effect. In addition, when using a component with openings, there is a problem that dirt accumulates in the openings and changes the frequency of transmission or blocking, and the desired sound absorption performance cannot be stably obtained.

[0010] Therefore, an object of the present invention is to provide a sound absorbing material for an automobile that can achieve a reduction in weight of the sound absorbing material for an automobile and can stably obtain a desired sound absorbing performance.

[0011] Means for solving problems

[0012] In order to achieve the above object, the present invention provides a multi-layered sound-absorbing material for automobiles, which comprises: a core layer having tubular units arranged in multiple rows; and a first airtight resin film layer bonded to one surface of the core layer. The Young's modulus E1 (MPa) of the first airtight resin film layer is equal to the surface density M1 (g / m 2 ) is 0.5 <E1 / M1<21。

[0013] The tubular unit may be a polygonal tubular shape such as a roughly quadrangular tubular shape or a roughly hexagonal tubular shape, or a curved tubular shape such as a roughly cylindrical shape or a roughly elliptical tubular shape. Preferably, each of the units in the core layer has a closed surface at one end and an open end at the other end, the internal space of the unit is connected to the outside through the open end of the unit, and the open ends of the unit are arranged on the two surfaces of the core layer in a manner of separating a row of adjacent units. Depending on the shape of the unit, the open end, the closed surface on one side, and the closed surface on the other side may be a polygonal shape such as a roughly quadrilateral or a roughly hexagonal shape, or a curved shape such as a roughly circular or a roughly elliptical shape.

[0014] The first airtight resin film layer may have a structure formed by stacking a plurality of materials with different Young's moduli. In this case, the Young's modulus E1 is the Young's modulus of the first airtight resin film layer as a whole. In addition, the automobile sound-absorbing material of the present invention may further include an inner surface layer on the surface of the first airtight resin film layer on the opposite side of the core layer. In this case, the surface density M1 is the combined surface density (mass per unit area) of the first airtight resin film layer and the inner surface layer. The inner surface layer is a layer facing the inner side of the car, and may be, for example, a layer composed of fibers such as non-woven fabrics, plain needles, velvet, a layer composed of foamed resins such as foamed polyurethane, foamed polyethylene, foamed nylon, or a layer composed of a combination of these.

[0015] The sound-absorbing material for an automobile of the present invention may further include a second airtight resin film layer, and the second airtight resin film layer is adhered to: the surface of the core layer on the side opposite to the surface to which the first airtight resin film layer is adhered. In this case, the relationship between the Young's modulus E2 (MPa) of the second airtight resin film layer and the surface density M2 (g / m 2 ) of the layer structure on the side of the second airtight resin film layer relative to the core layer may satisfy or not satisfy 0.5 < E2 / M2 < 21. In addition, the absolute value of the difference between E1 / M1 and E2 / M2 may be 0.8 or more. Further, the sound-absorbing material for an automobile of the present invention may further include an outer surface layer on the surface of the second airtight resin film layer on the side opposite to the core layer. In this case, the surface density M2 is the total surface density of the second airtight resin film layer and the outer surface layer. The outer surface layer is a layer facing the outer surface of the automobile, and may be, for example: a layer composed of fibers such as non-woven fabric, plain knitted fabric, and velvet; a layer composed of foamed resins such as foamed polyurethane, foamed polyethylene, and foamed nylon; or a layer formed by combining them.

[0016] In addition, the sound-absorbing material for an automobile of the present invention may further include a resin film layer having a plurality of openings, and the resin film layer is adhered to: the surface of the core layer on the side opposite to the surface to which the first airtight resin film layer is adhered.

[0017] Advantages of the Invention

[0018] Thus, the sound-absorbing material for an automobile of the present invention includes a core layer and a first airtight resin film layer. The core layer has cylindrical units arranged in multiple columns, and the first airtight resin film layer is adhered to one surface of the core layer. The relationship between the Young's modulus E1 of the first airtight resin film layer and the surface density M1 of the layer structure on the side of the first airtight resin film layer relative to the core layer is 0.5 < E1 / M1 < 21; based on this configuration, even if an airtight resin film layer that is generally considered to make no contribution to sound absorption is used, it becomes a layer that contributes to sound absorption based on the relationship between the above-mentioned core layer and the specified structure while having a Young's modulus E1 that is significantly smaller than usual relative to the surface density M1, and it is possible to obtain desired sound-absorbing performance with a peak sound absorption rate in the frequency band of 500 Hz to 8000 Hz, which is the frequency range that forms harsh noise in an automobile. Thus, based on the specified structure of the core layer and the first airtight resin film layer, not only can high rigidity be ensured while achieving weight reduction of automotive components, but also desired sound-absorbing performance can be exhibited without using components having a plurality of openings. Therefore, desired sound-absorbing performance can be stably obtained without dirt accumulating in the openings.

[0019] By configuring the first air-impermeable resin film layer to be a structure in which a plurality of materials having different Young's moduli are stacked, the Young's modulus E1 and the surface density M1 can be easily designed, and the peak value of the sound absorption rate can be easily controlled.

[0020] By further providing an inner surface layer on the surface of the first air-impermeable resin film layer opposite to the core layer, the first air-impermeable resin film layer having a smaller Young's modulus than usual can be protected and desired sound absorbing performance can be stably obtained.

[0021] Based on the configuration that the second air-impermeable resin film layer is bonded to the surface of the core layer on the opposite side to the surface to which the first air-impermeable resin film layer is bonded, and the absolute value of the ratio of the Young's modulus E2 of the second air-impermeable resin film layer to the surface density M2 of the layer structure closer to the second air-impermeable resin film layer than the core layer, that is, the difference between E2 / M2 and E1 / M1 is greater than 0.8, a sound-absorbing material for automobiles can be obtained that has two peaks of sound absorption rate in the frequency range of 500 Hz to 8000 Hz that forms harsh noise in the automobile and has excellent sound absorption performance over a wide frequency band of sound absorption frequency.

[0022] Based on the fact that the material also includes a resin film layer having a plurality of openings and the resin film layer is bonded to the surface of the core layer on the opposite side to the surface to which the first airtight resin film layer is bonded, and by pre-forming an opening pattern on the resin film layer having a plurality of openings, the degree of closure of the open end of at least one surface of the core layer can be easily adjusted and stably maintained, thereby being able to control the peak value of the sound absorption rate of the automobile sound-absorbing material, thereby being able to more easily control the above-mentioned E / M value, and being able to more easily control the peak value of the sound absorption rate of the automobile sound-absorbing material within the desired frequency band.

[0023] Each unit of the core layer has a closed surface at one end and an open end at the other end, and the internal space of the unit is connected to the outside through the open end of the unit. The open ends of the unit are arranged on the two surfaces of the core layer in a row separated by a row of adjacent units. Based on this structural configuration, it is possible to ensure that the closed surface of the core layer unit becomes the bonding surface between the first airtight resin film layer and the core layer, and the closed surface of the unit is arranged in a row separated by a row, thereby improving the adhesion between the first airtight resin film layer and the core layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a perspective view showing a process of manufacturing a core material used for a core layer in the automobile sound absorbing material of the present invention.

[0025] Figure 2 This is a schematic plan view showing a core layer of the automobile sound absorbing material of the present invention.

[0026] Figure 3 It is shown Figure 2 Schematic cross-sectional view of the core layer along line III-III.

[0027] Figure 4 This is an exploded perspective view showing one embodiment of the automobile sound absorbing material of the present invention.

[0028] Figure 5 yes Figure 4 A schematic cross-sectional view of an embodiment of a sound absorbing material for an automobile is shown.

[0029] Figure 6 This is an exploded perspective view showing another embodiment of the automobile sound absorbing material of the present invention.

[0030] Figure 7 This is a schematic cross-sectional view showing another embodiment of the automobile sound absorbing material of the present invention.

[0031] Figure 8 This is a graph showing the relationship between E1 / M1 and the sound absorption peak frequency in Examples of the automobile sound absorbing material of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, one embodiment of the automobile sound absorbing material according to the present invention will be described with reference to the accompanying drawings. In addition, the accompanying drawings are not intentionally drawn to scale unless otherwise specified.

[0033] First, the core layer common to each embodiment of the automobile sound absorbing material according to the present invention will be described. Figure 1 2 is a perspective view showing a manufacturing process of a core material that becomes the core layer. In addition, the manufacturing method of the core material is described in detail in International Publication No. 2006 / 053407, which is incorporated herein by reference as a part of the description.

[0034] like Figure 1 As shown, the core material 1 is formed by plastic deformation by thermoforming a flat sheet material using a roller (not shown) having a predetermined mold, without substantially cutting the sheet material. The material of the core material 1 can be, for example, thermoplastic resins such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and composite materials with fibers, paper, metal, etc., and thermoplastic resins are particularly preferred, but are not limited to these. In this embodiment, the case of using thermoplastic resins is described. The thickness of the sheet material is preferably in the range of 0.05 mm to 0.50 mm, for example, but is not limited to this, and the thickness of the core material 1 after thermoforming is also approximately the same.

[0035] The core material 1 has a three-dimensional structure in which the peaks 11 and the valleys 12 are alternately arranged in the width direction X orthogonal to the manufacturing direction Y. The peak 11 is composed of two side surfaces 13 and a top surface 17 therebetween, and the valley 12 is composed of two side surfaces 13 shared with adjacent peaks 11 and a bottom surface 14 therebetween. Figure 1 The case where the shape of the mountain portion 11 is a trapezoid is described below, but the present invention is not limited thereto, and the shape may be a curved shape such as a sine curve or an arcuate shape in addition to a polygonal shape such as a triangle or a rectangle.

[0036] The core material 1 has the three-dimensional structure that is continuous in the manufacturing direction Y. Figure 1 As shown, a plurality of peaks 11a, 11b, 11c, and 11d are continuously formed in the manufacturing direction Y. The valleys 12 are also continuously formed. Furthermore, the connection between the peaks 11 and the connection between the valleys 12 are achieved by alternately repeating two connection methods.

[0037] The first connection method is Figure 1 As shown in FIG. 1 , on the first folding line X1 in the width direction, the top surfaces 17b and 17c of the two adjacent mountain portions 11b and 11c are connected by the mountain portion connecting surfaces 15b and 15c of the trapezoidal shape, respectively. The mountain portion connecting surface 15 is formed at a right angle to the top surface 17. On the first folding line X1 in the width direction, the bottom surfaces 14b and 14c of the two adjacent valley portions are directly connected. The second connection method is as follows Figure 2 (and Figure 1 As shown in FIG. 1 , on the second folding line X2 in the width direction, the bottom surfaces 14a, 14b (or 14c, 14d) of two adjacent valleys are connected by trapezoidal valley connecting surfaces 16a, 16b (or 16c, 16d), respectively. The valley connecting surface 16 is formed at a right angle to the bottom surface 14. On the second folding line X2 in the width direction, the top surfaces 12a, 12b (or 12c, 12d) of two adjacent mountain portions are directly connected.

[0038] In this way, the multiple three-dimensional structures (mountains 11, valleys 12) of the core material 1 are connected by the connection area (mountain connection surface 15, valley connection surface 16), and the core layer of the automobile sound-absorbing material of the present invention is formed by folding the connection area. Specifically, the core material 1 is folded at the first folding line X1 by the mountain folding method so that the bottom surfaces 14b and 14c of the two adjacent valleys overlap each other and the angle formed by the mountain connection surfaces 15b and 15c of the two adjacent mountains is opened to 180 degrees. In addition, the core material 1 is folded at the second folding line X2 by the valley folding method so that the top surfaces 17a and 17b (or 17c and 17d) of the two adjacent mountains overlap each other and the angle formed by the valley connection surfaces 16a and 16b (or 16c and 16d) of the two adjacent valleys is closed to 180 degrees. Figure 2 and Figure 3 The core layer 10 of the automobile sound absorbing material of the present invention obtained by folding the core material 1 in this manner is shown.

[0039] like Figure 2 and Figure 3 As shown, the core layer 10 includes substantially hexagonal cylindrical units 20 arranged in a plurality of rows, and units 20A, 20C, and 20E formed by two adjacent mountain portions and units 20B and 20D formed by two adjacent valley portions are arranged in alternate rows. Figure 3 (and Figure 2 The dotted line 18 in the figure schematically shows the inner wall of the unit 20 which is the back side (inner side) of the core material and is roughly in the shape of a hexagonal cylinder.

[0040] The units 20A, 20C, and 20E formed by the mountain portions each have six unit side walls that form a substantially hexagonal cylindrical shape, and these unit side walls are formed by two top surfaces 17 and four side surfaces 13 of the unit material. In addition, these units 20A, 20C, and 20E are formed on one surface 10a ( Figure 2 (and Figure 3 The unit ends of the core layer 10 (the surface side of the core layer 10) are respectively provided with approximately hexagonal cylindrical closed surfaces 21A, 21C, and 21E for closing the unit ends, and the closed surfaces 21 on one side are respectively formed by two trapezoidal mountain connecting surfaces 15 in the unit material. In addition, these units 20A, 20C, and 20E are provided with open ends 22A, 22C, and 22E opened into a substantially hexagonal shape at the unit ends of the other surface 10b as the opposite side of the core layer 10. The internal spaces of each of the units 20A, 20C, and 20E are connected to the outside through the open ends 22A, 22C, and 22E.

[0041] The units 20B and 20D formed by the valleys also have six unit side walls that form a roughly hexagonal cylindrical shape, respectively, and these unit side walls are formed by two bottom surfaces 14 and four side surfaces 13 of the unit material. In addition, these units 20B and 20D have open ends 22B and 22D that open into a roughly hexagonal shape at the unit ends of the one surface 10a of the core layer 10. The internal spaces of each of the units 20B and 20D are connected to the outside through the open ends 22B and 22D. In addition, these units 20B and 20D have roughly hexagonal cylindrical closed surfaces 21B and 21D that close the unit ends at the unit ends of the other surface 10b of the core layer 10 as the opposite side, and these closed surfaces 21 on the other side are respectively formed by two trapezoidal valley connecting surfaces 16 of the unit material.

[0042] In this way, the core layer 10 has a side closed surface 21A, 21C, 21E formed by the mountain part of the unit material in every other row at the unit end of one surface 10a, and has another side closed surface 21B, 21D formed by the valley part of the unit material in the unit end of the other surface 10b in a row of units different from the above, but unless otherwise recorded, either one side closed surface 21 or the other side closed surface essentially performs the same function.

[0043] The overall thickness of the core layer 10 varies depending on which part of the automobile the multilayer structure is used for. Therefore, from the perspective of controlling the peak point of the sound absorption rate of the airtight resin film layer described later, the sound absorption performance of the core layer 10 itself, the strength and weight of the core layer 10, the overall thickness of the core layer 10 is preferably in the range of 3 mm to 25 mm, and more preferably in the range of 5 mm to 20 mm, but is not limited to these.

[0044] The basis weight (mass per unit area) of the core layer 10 varies depending on which part of the automobile the multilayer structure is used for, and is preferably 400 g / m 2 ~4000g / m 2 The range is more preferably 500g / m 2 ~3000g / m 2 The greater the thickness and basis weight of the core layer 10, the higher the strength of the core layer 10 is, and there is a tendency to control the peak frequency of the sound absorption rate to the low frequency side.

[0045] The basis weight of the core layer 10 can be adjusted by the spacing Pcx and Pcy (the distance between the central axes of the units) between the units 20 of the core layer 10 in addition to the material type of the core layer 10, the overall thickness of the core layer 10, and the wall thickness of the unit 20 (the thickness of the sheet). In order to make the basis weight of the core layer 10 within the above range, for example, it is preferred that the spacing Pcy between the units 20 in the manufacturing direction Y of the core, i.e., the direction in which the units 20 are adjacent to form a row, is in the range of 3 mm to 15 mm, and more preferably in the range of 4 mm to 10 mm.

[0046] Next, each embodiment of the automobile sound absorbing material according to the present invention will be described using the core layer 10 described above.

[0047] (First Embodiment)

[0048] like Figure 4 and Figure 5 As shown, the automobile sound absorbing material of the first embodiment includes: the core layer 10 described above; an airtight resin film layer 40 provided on one surface of the core layer 10; and a nonwoven fabric layer 30 further provided outside the airtight resin film layer 40 as an inner surface layer.

[0049] The material of the airtight resin film layer 40 can be, for example, a resin film such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyamide (PA), etc., but is not limited thereto. In addition, the airtight resin film layer 40 can be a structure obtained by stacking multiple layers of these different types of resins, or a structure obtained by stacking multiple layers of the same type of resin and materials with different Young's moduli.

[0050] For the Young's modulus E of the airtight resin film layer 40, since it depends on the ratio of the Young's modulus E to the surface density E described in detail later, although it is not limited by the following, it is lower than the Young's modulus used for ordinary automotive parts. For example, the upper limit of the Young's modulus E of the airtight resin film layer 40 is preferably below 1700 MPa, more preferably below 1600 MPa, and further preferably below 1500 MPa. In addition, the lower limit of the Young's modulus is preferably above 200 MPa, more preferably above 300 MPa, but is not limited to these. In addition, depending on the type of resin and the difference in the method of making the film, the Young's modulus in the direction (MD) of the flow of the molten resin of the film is different from the value of the Young's modulus in the right angle direction (TD), but the Young's modulus with a lower value should be used when calculating E / M of the present invention.

[0051] The surface density (basis weight) of the air-impermeable resin film layer 40 depends on the total surface density E of the nonwoven fabric layer 30 described in detail below. Therefore, although it is not limited to the following, it is preferred that the lower limit of the surface density of the air-impermeable resin film layer 40 is 30 g / m 2 More preferably 40 g / m 2 More preferably, 50 g / m 2 In addition, the upper limit of the surface density is preferably 500 g / m 2 Below, more preferably 300g / m 2 Below, more preferably 250g / m 2 The following, but not limited to these.

[0052] For the thickness of the airtight resin film layer 40, for example, its lower limit is preferably 0.02 mm or more, more preferably 0.03 mm or more, and further preferably 0.05 mm or more, but not limited to these. In addition, the upper limit of the thickness is preferably 0.8 mm or less, more preferably 0.7 mm or less, and further preferably 0.6 mm or less, but not limited to these.

[0053] The airtight resin film layer 40 can be bonded to the core layer 10 by heat fusion, or can be bonded to the core layer 10 by an adhesive (not shown). As the adhesive, for example, epoxy, acrylic and other adhesives can be used, but there is no particular limitation. In addition, in order to heat-fusion bond the airtight resin film layer 40 to the core layer 10 and the non-woven fabric layer 30, for example, the airtight resin film layer 40 can be made into a three-layer structure, with a central layer and two adhesive layers on the surfaces on both sides thereof. In this case, the material of the adhesive layer uses a material with a melting point lower than the melting point of the material used for the central layer. For example, by using polyamide having a melting point of 190°C to 220°C for the central layer and polyethylene having a melting point of 90°C to 130°C for the adhesive layer, the adhesive layer can be melted and firmly bonded to the core layer 10 and the nonwoven fabric layer 30 as long as the heating temperature when the air-impermeable resin film layer 40 is attached to the core layer 10 and the nonwoven fabric layer 30 and the temperature of thermoforming the automobile sound-absorbing material into a predetermined shape are set to about 150°C to 160°C. On the other hand, since the central layer does not melt, the desired sound-absorbing performance of the automobile sound-absorbing material can be obtained without significantly changing the Young's modulus of the air-impermeable resin film layer 40. In addition to polyamide, there is also polypropylene as a resin having a higher melting point than the polyethylene of the adhesive layer.

[0054] The nonwoven fabric layer 30 is preferably made of various nonwoven fabrics such as spunbond, spunlace, or needle punch using resins such as polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE), but is not limited to these.

[0055] The surface density (basis weight) of the nonwoven fabric layer 30 depends on the total surface density E of the nonwoven fabric layer 30 and the airtight resin film layer 40. Therefore, although it is not limited to the following, it is preferred that the lower limit of the surface density of the nonwoven fabric layer 30 is 10 g / m 2 More preferably 20 g / m 2 More preferably, 30 g / m 2 In addition, the upper limit of the surface density is preferably 500 g / m 2 Below, more preferably 300g / m 2 Below, more preferably 250g / m 2 The following, but not limited to these.

[0056] In this embodiment, if the Young's modulus of the airtight resin film layer 40 is set to E, and the total surface density of the airtight resin film layer 40 and the non-woven fabric layer 30 is set to M, the peak value of the sound absorption rate of the automobile sound absorbing material can be controlled to the frequency range of 500Hz to 8000Hz, which forms harsh noise in the automobile, when the value of E / M is set to the range of 0.5 to 21. Even in this frequency range (frequency band), when the peak value of the sound absorption rate is to be in the frequency band of 500Hz to 4000Hz, it is preferred to set the value of E / M to the range of 0.5 to 8; when the peak value of the sound absorption rate is to be further in the frequency band of 1000Hz to 3000Hz, it is more preferred to set the value of E / M to the range of 1.5 to 5.5. In addition, when it is desired to have a peak sound absorption rate in the frequency band of 4000 Hz to 8000 Hz, it is preferred to set the E / M value in the range of 8 to 21; when it is desired to have a peak sound absorption rate in the frequency band of 5000 Hz to 6000 Hz, it is preferred to set the E / M value in the range of 11 to 14.

[0057] Thus, according to the first embodiment, by providing an airtight resin film layer 40 on at least one surface of the core layer 10 having an open end and a closed surface separated by a row and further providing a non-woven fabric layer 30 on the outside of the airtight resin film layer 40, it is possible to achieve both lightweighting and high rigidity of the automobile sound-absorbing material, and by adjusting the ratio of the Young's modulus E of the airtight resin film layer 40 to the total surface density M of the airtight resin film layer 40 and the non-woven fabric layer 30, that is, the value of E / M, it is possible to control the peak value of the sound absorption rate of the automobile sound-absorbing material to be within a desired frequency range (frequency band).

[0058] In addition, Figure 4 and Figure 5 The figure shows a case where a non-woven fabric layer 30 is provided on the outside of the airtight resin film layer 40, but the present invention is not limited to this, and the non-woven fabric layer 30 may not be provided; by adjusting the Young's modulus E of the airtight resin film layer 40 and the surface density M of the single airtight resin film layer 40, the peak value of the sound absorption rate of the automobile sound-absorbing material can be controlled in the same way as described above.

[0059] (Second Embodiment)

[0060] like Figure 6As shown, the automobile sound absorbing material of the second embodiment comprises: the core layer 10 described above; a first airtight resin film layer 40a provided on one surface of the core layer 10; a second airtight resin film layer 40b provided on the other surface of the core layer 10; and a first nonwoven fabric layer 30a and a second nonwoven fabric layer 30b, which are further provided on the outside of the first airtight resin film layer 40a and the second airtight resin film layer 40b and serve as the inner surface layer and the outer surface layer, respectively. In addition, the same symbols (reference numerals) are given to the same structures as those in the first embodiment, and detailed descriptions thereof are omitted here.

[0061] The surfaces on both sides of the core layer 10 can be bonded with a first air-impermeable resin film layer 40a and a second air-impermeable resin film layer 40b, a first non-woven fabric layer 30a and a second non-woven fabric layer 30b having the same configuration structure (material, thickness of the resin film, manufacturing method of the non-woven fabric, basis weight, etc.), or can be bonded with a first air-impermeable resin film layer 40a and a second air-impermeable resin film layer 40b, a first non-woven fabric layer 30a and a second non-woven fabric layer 30b having different configuration structures.

[0062] In this way, when the air-impermeable resin film layer 40 is provided on both surfaces of the core layer 10, the ratio of the Young's modulus E of the air-impermeable resin film layer 40 to the surface density M of the air-impermeable resin film layer 40 and the non-woven fabric layer 30, that is, the value of E / M is adjusted on the first air-impermeable resin film layer 40a side and the second air-impermeable resin film layer 40b side. That is, the Young's modulus of the first air-impermeable resin film layer 40a is set to E1, and the surface density of the first air-impermeable resin film layer 40a and the first non-woven fabric layer 30a is set to M1, and the value of E1 / M1 is in the range of 0.5 to 21. In addition, the Young's modulus of the second air-impermeable resin film layer 40b is set to E2, and the surface density of the second air-impermeable resin film layer 40b and the second non-woven fabric layer 30b is set to M2, and the value of E2 / M2 is in the range of 0.5 to 21. It is preferred that the value of E1 / M1 is different from the value of E2 / M2, and the absolute value of the difference between E1 / M1 and E2 / M2 is preferably 0.8 or more, more preferably 2.0 or more, and further preferably 3.0 or more. In addition, the upper limit of the absolute value of the difference is preferably 5 or less, but there is no particular limitation.

[0063] According to the second embodiment, an airtight resin film layer 40 and a nonwoven fabric layer 30 are respectively provided on both surfaces of a core layer 10 with an open end and a closed surface arranged in a row, and the value of E1 / M1 on the first airtight resin film layer 40a and the value of E2 / M2 on the second airtight resin film layer 40b are both within the range of 0.5 to 21, and by further making the values ​​of both different within the range, a sound absorbing material for automobiles having two peaks of sound absorption rate in the frequency range of 500 Hz to 8000 Hz that forms harsh noise in automobiles and having excellent sound absorption performance can be obtained. In particular, by making the absolute value of the difference between the values ​​of E1 / M1 and E2 / M2 to be 0.8 or more, the frequency band of sound absorption can be expanded.

[0064] (Third Embodiment)

[0065] like Figure 7 As shown, the automobile sound absorbing material of the third embodiment comprises: the core layer 10 described above; the airtight resin film layer 40 provided on one surface of the core layer 10; the resin film layer 50 having a plurality of openings provided on the surface of the core layer 10 opposite to the airtight resin film layer 40; and the first nonwoven fabric layer 30a and the second nonwoven fabric layer 30b, which are further provided on the outside of the airtight resin film layer 40 and the resin film layer 50 and serve as the inner surface layer and the outer surface layer, respectively. In addition, the same symbols (figure marks, etc.) as those of the first embodiment and the second embodiment are marked, and detailed descriptions thereof are omitted.

[0066] The resin film layer 50 having a plurality of openings (hereinafter referred to as the opening film layer 50) has a plurality of holes 55 penetrating the layer. The holes 55 are opened in advance before being attached to the core layer 10, for example, by a hot needle or punching process (punching process using a male mold and a female mold). In order to prevent the holes from being blocked, it is preferred to have a hole shape that minimizes burrs in the holes.

[0067] The opening pattern of the holes 55 is preferably arranged in a staggered arrangement or a lattice arrangement, but there is no particular limitation. The opening rate of the perforated film layer 50 is preferably in the range of 0.2% to 5%, but there is no particular limitation. The diameter of the holes 55 is preferably in the range of 0.25 mm to 2.5 mm, and more preferably in the range of 0.3 mm to 2.0 mm.

[0068] In addition, the spacing between the holes 55 of the apertured film layer 50 is Figure 2The spacings Pcx and Pcy of the cells 20 of the core layer 10 shown in the figure do not need to be consistent; in addition, when the perforated film layer 50 is attached to the core layer 10, it is not necessary to align the holes 55 and the cells 20. This is because by randomly overlapping the positions of the holes 55 of the perforated film layer 50 and the open ends 22 of the cells 20 of the core layer 10, it is possible to appropriately ensure the connection between the inside and the outside. The spacing of the holes 55 of the perforated film layer 50 is preferably smaller than the spacing of the cells 20 of the core layer 10 in at least one direction of the X direction or the Y direction.

[0069] According to the third embodiment, even if the perforated film layer 50 is provided on the surface of the core layer 10 on the opposite side to the airtight resin film layer 40, the same effect as that of the first embodiment can be obtained. In addition, by pre-forming the perforated pattern on the perforated film layer 50, the degree of closure of the open end 22 of at least one surface of the core layer 10 can be easily adjusted and stably maintained, so that the peak value of the sound absorption rate of the automobile sound absorbing material can be controlled, thereby making it easier to control the value of E / M on the airtight resin film layer 40 side, and making it easier to control the peak value of the sound absorption rate of the automobile sound absorbing material within a desired frequency range.

[0070] Example

[0071] Next, embodiments of the present invention will be described.

[0072] As Example 1, a Figure 4 and Figure 5 The multi-layered sound absorbing material for automobiles shown in FIG. Figure 1 to Figure 3 A three-layer airtight resin film (material: polyethylene / polyamide / polyethylene; Young's modulus of the film: 300 MPa) with a thickness of 50 μm was adhered to one surface of the core layer of the structure, and a spunbond nonwoven fabric (material: polyethylene terephthalate; basis weight: 250 g / m2) was further adhered to the outside of the airtight resin film. 2 ) as the inner surface layer. The total surface density of the airtight resin film and the nonwoven fabric is 180g / m 2 Then, the multilayer structure was heated and pressurized to obtain a sound absorbing material for automobiles with interlayer adhesion.

[0073] In order to evaluate the sound absorption performance of the automobile sound absorbing material of Example 1, a cylindrical sample with a diameter of about 29 mm was taken from the automobile sound absorbing material of Example 1, and the vertical incident sound absorption rate of the sample at a frequency of 500 Hz to 6300 Hz was measured according to the method based on ISO10534-2 (JIS A1405). As a result, the peak frequency of the sound absorption rate was 1000 Hz.

[0074] The same operation as in Example 1 was carried out to prepare automobile sound absorbing materials of Examples 2 to 6 in which the materials, basis weights, thicknesses, etc. of the nonwoven fabric and the airtight resin film were changed as shown in Table 1 below, and the sound absorbing performance was measured. The results including those of Example 1 are shown in Tables 1 and Figure 8 In all the examples, a core layer made of polypropylene resin with a thickness of about 20 mm or less and a pitch Pcy between cells of about 10 mm or less was used as the core layer.

[0075] [Table 1]

[0076]

[0077] As shown in Table 1 and Figure 8 As shown in FIG. 1 , the higher the ratio of the Young's modulus E of the airtight resin film layer to the surface density M of the layer structure on the core layer, that is, the higher the value of E / M, the higher the frequency of the peak of the sound absorption rate of the automobile sound-absorbing material. It is generally believed that the airtight resin film layer does not contribute to sound absorption, but by using an airtight resin film layer having a Young's modulus E significantly smaller than usual relative to the surface density M, it is inferred that based on the relationship between the core layer and the specified structure, it becomes a contribution to sound absorption. In addition, as Figure 8 As shown, from the results of Examples 1 to 6, if the E / M value is within the range of 0.5 to 21, a sound absorbing material for automobiles having a desired sound absorbing performance having a peak of the sound absorption rate in the frequency band of 500 Hz to 8000 Hz that causes harsh noise in automobiles can be produced.

[0078] Industrial Applicability

[0079] According to the automobile sound absorbing material of the present invention, the peak value of the sound absorption rate can be controlled within the frequency range (frequency band) of 500 Hz to 8000 Hz by laminating the air-impermeable resin film layer while suppressing the weight and maintaining high rigidity. More specifically, the automobile sound absorbing material of the present invention is useful for sound absorbing cover parts of noise generating sources such as carpets, floor mats, trunk trims, trunk floors, front bulkhead insulators, and undercovers.

[0080] Description of Reference Numerals

[0081] 1: Core material

[0082] 10: Core layer

[0083] 11: Yamabe

[0084] 12: Tanibe

[0085] 13: Side face

[0086] 14: Bottom

[0087] 15: Mountain connection surface

[0088] 16: Valley connection surface

[0089] 17: Top surface

[0090] 18: Back side of core material

[0091] 19: Through hole

[0092] 20: Unit

[0093] 21: Closed surface

[0094] 22: Open end

[0095] 30: Non-woven fabric layer

[0096] 40: Airtight resin film layer

[0097] 50: Resin film layer with multiple openings

[0098] 55: Hole

Claims

1. A sound-absorbing material for automobiles, which is a multi-layered sound-absorbing material for automobiles, and the sound-absorbing material for automobiles comprises: A core layer having tubular units arranged in a plurality of rows, each of the units having a closed surface at one end and an open end at the other end, and the open ends of the units are arranged on both surfaces of the core layer in a manner of sandwiching a row of adjacent units, and the open ends are on opposite sides of the open ends of the adjacent row of units on the two surfaces; and A first air-impermeable resin film layer is bonded to one surface of the core layer, in, The closed surface of the unit of the core layer is ensured to be the bonding surface between the first air-impermeable resin film layer and the core layer, The relationship between the Young's modulus E1 of the first air-impermeable resin film layer and the areal density M1 of the layer structure on the side of the first air-impermeable resin film layer closer to the core layer than the core layer is 0.5 < E1 / M1 < 21, where the unit of the Young's modulus E1 is MPa and the unit of the areal density M1 is g / m 2 .

2. The automobile sound absorbing material according to claim 1, wherein: The first air-impermeable resin film layer has a structure in which a plurality of materials having different Young's moduli are stacked.

3. The automobile sound absorbing material according to claim 1 or 2, further comprising a second air-impermeable resin film layer bonded to a surface of the core layer opposite to a surface to which the first air-impermeable resin film layer is bonded.

4. The automobile sound absorbing material according to claim 3, wherein: The relationship between the Young's modulus E2 of the second air-impermeable resin film layer and the areal density M2 of the layer structure on the side of the second air-impermeable resin film layer closer to the core layer than the core layer is 0.5 < E2 / M2 < 21, and the absolute value of the difference between E1 / M1 and E2 / M2 is 0.8 or more, where the unit of the Young's modulus E2 is MPa and the unit of the areal density M2 is g / m 2 .

5. The automobile sound absorbing material according to claim 1 or 2, further comprising a resin film layer having a plurality of openings, wherein the resin film layer having a plurality of openings is bonded to a surface of the core layer opposite to a surface to which the first air-impermeable resin film layer is bonded.

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