Patent Description:
A typical structure of a vehicle has an engine compartment provided at the front, a trunk compartment provided at the rear, and a passenger compartment provided in the middle thereof. The passenger compartment is provided with seats such as a driver seat, a front passenger seat, and a rear seat. In addition, the passenger compartment has a dash insulator, a floor carpet, a floor spacer, a trunk trim, and a trunk floor installed so that they cover the outside of the vehicle interior. These components are formed in uneven shapes according to shapes of vehicle bodies or designs of components. Furthermore, the exterior under a vehicle body has a front fender liner, a rear fender liner, and an undercover that is formed in an uneven shape for controlling the air flow, installed thereon. For many of these components, a thermoplastic resin is used as a material, and each of the materials is heated and press-molded by a die having the shape of the component to be finished into an uneven-shaped component having a plurality of portions with different thicknesses.

As a recent trend of vehicle development, the quietness in the interior of a vehicle is emphasized. Noise transmitted to the interior of a vehicle includes noise from the windows, noise from the tires, noise from under the vehicle body, noise from engine sounds, and noise from motor sounds. It is said that noise, particularly at frequencies of <NUM> to <NUM>, causes annoyance to drivers and passengers. Therefore, the interior and exterior components of vehicles are required to have a function of absorbing and insulating noise in these frequency bands. On the other hand, it is also important to reduce fuel consumption, and it is also required to reduce weight of interior and exterior components of vehicles.

<CIT> describes a sandwich element for a sound-absorbing inner cladding of aircraft fuselage cells, including a honeycomb-shaped core structure and cover layers applied to both sides of the core structure, in which both the cover layers each have a plurality of passages for sound transmission, in which a covering formed using a semi-permeable membrane of a plastic material is disposed on the cover layer facing to the sound, in which the semi-permeable membrane made of the plastic material includes a plurality of openings with a cross-sectional area such that the penetration of foreign bodies and/or liquids is largely prevented and sound transmission is allowed, and in which a sound absorption layer is formed on the cover layer facing away from the sound. It is described that such a configuration can provide a sandwich element having a high mechanical loading properties, a low weight, and excellent sound absorption properties.

<CIT> discloses a filler including a deformable part which can be deformed, and a non-deformable part communicated with the deformable part through a porous body. The deformable part is formed to have a hollow by a deformable part-forming member and filled with at least one deformable part filler selected from gas or liquid at its inside. The non-deformable part is formed to have a hollow by a non-deformable part-forming member and filled with a non-deformable part filler including at least a gas.

Preferred embodiments are defined in the depended claims.

The sandwich element described in the patent document is intended to facilitate sound absorption, at the sound absorbing layer, of noise incident from the direction of the core structure, and is not intended to exhibit sound insulation performance. For conventional sound-insulation material for a vehicle, materials such as expanded polystyrene (styrene foam), and urethane foam are used. Although the materials each have a low weight, they have a problem in that they are so soft that they lack rigidity.

Therefore, an object of the present invention is to provide a sound-insulation material for a vehicle having high rigidity and capable of exhibiting sufficient sound insulation performance against noise having a frequency of <NUM> to <NUM> generated in a vehicle, while maintaining a low weight of the sound-insulation material for a vehicle.

To achieve the object, the present invention provides a sound-insulation material for a vehicle having a multilayer structure according to claim <NUM>.

The tubular cell may have a polygonal tubular shape such as a substantially quadrangular tubular shape or a substantially hexagonal tubular shape, or may have a curved tubular shape such as a substantially circular tubular shape or a substantially elliptical tubular shape. It is preferable that each of the cells in the hard layer have a closed surface at one end and an open end at another end, the open ends of the cells each allow an internal space of the cell to be in communication with an outside, and the open ends of the cells be arranged on both sides of the hard layer such that rows of the open ends of the cells are in every other row. The open end, the one-side closed surface, and the other-side closed surface may have a polygonal shape such as a substantially quadrangular shape or a substantially hexagonal shape, or may have a curved shape such as a substantially circular shape or a substantially elliptical shape, according to the shape of the cell.

The static spring constant Ks of the structure consisting of the core layer and the soft layer, optionally the additional layer, and optionally the second additional layer is preferably <NUM> N/mm or more, and the ratio of the dynamic spring constant Kd to the static spring constant Ks is preferably <NUM> < Kd/Ks ≤ <NUM>.

The structure may include a film layer, a fiber layer, or a combination thereof as additional layer(s) between the hard layer and the soft layer. In that case, the dynamic spring constant Kd and the static spring constant Ks are those of a structure including a film layer, a fiber layer, or a combination thereof between the hard layer and the soft layer. A pitch Pcy between the cells in a direction in which the cells of the hard layer are adjacent to each other in a row is preferably within a range of <NUM> to <NUM>.

When a film layer is provided as an additional layer between the hard layer and the soft layer, the thickness of the film layer may be in a range of <NUM> to <NUM>. The film layer may have a plurality of apertures penetrating the film layer.

When a second additional layer is provided between the film layer and the soft layer, a static spring constant Ks of the additional layer is preferably smaller than a static spring constant Ks of the soft layer. In this case, urethane foam may be used as the material of the soft layer, the second additional layer may be a fiber layer, and a thickness of the fiber layer may be in a range of <NUM> to <NUM>.

As described above, the sound-insulation material for a vehicle is defined according to claim <NUM>. This configuration enables the sound-insulation material for a vehicle to have high rigidity while maintaining a low weight. In addition, noise with a frequency of <NUM> to <NUM> generated from a vehicle is transmitted to the vehicle interior via the vibration of air or via the vibration of an object. The noise transmitted mainly via the vibration of an object is blocked by the structure having the hard layer and the soft layer. Accordingly, the sound-insulation material for a vehicle can exhibit sufficient sound insulation performance against the noise generated in the vehicle. The ratio Kd/Ks of the dynamic spring constant to the static spring constant is called a dynamic magnification factor in the field of anti-vibration materials, and it is generally used as one of the indexes of anti-vibration performance. It is widely known that the hard layer of the present invention has conventionally been used as a core layer in vehicle-sound-absorbing materials and has a function of absorbing noise generated in vehicles. In the present invention, a flexible soft layer is adhered to such a hard core layer (hard layer), in which tubular cells are arranged in a plurality of rows. In addition, the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure consisting of the hard layer and the soft layer, is set to <NUM> or less, which is a significantly lower value than the conventional vehicle-sound-absorbing materials each using a core layer. This configuration blocks the noise transmitted mainly via the vibration of an object. Accordingly, the sound-insulation material for a vehicle can exhibit sufficient sound insulation performance against the noise generated in the vehicle.

The sound-insulation material for a vehicle is configured such that: each of the cells in the hard layer has a closed surface at one end and an open end at another end; the open ends of the cells each allow an internal space of the cell to be in communication with an outside; and the open ends of the cells are arranged on both sides of the hard layer such that rows of the open ends of the cells are in every other row. This configuration ensures that the closed surface of the cell of the hard layer serves as a surface for adhering the soft layer thereto, and arranges the closed surface of the cell in every other row, enabling the hard layer to improve adhesiveness with the soft layer.

An embodiment of a sound-insulation material for a vehicle according to the present invention is described below with reference to the accompanying drawings. Note that the drawings are not intended to be drawn to scale unless otherwise specified.

First, a hard layer common to each embodiment of the sound-insulation material for a vehicle according to the present invention is described below. <FIG> is a perspective view showing a manufacturing process of a core material to be this hard layer (also referred to as a core layer). Note that the manufacturing method of this core material is described in detail in <CIT>.

As shown in <FIG>, a flat material sheet is thermoformed by a roller (not shown) having a predetermined die to be plastically deformed substantially without cutting of the sheet, so that a core material <NUM> in the figure is formed. The material of the core material <NUM> to be used can include, for example, a thermoplastic resin such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), a composite material with fibers, paper, and metal, but it is not limited to these. In particular, a thermoplastic resin is preferable. In this embodiment, a case in which a thermoplastic resin is used is described below. The thickness of the material sheet is preferably in the range of <NUM> to <NUM>, for example, but it is not limited to this, and the thickness of the core material <NUM> after thermoforming is substantially the same.

The core material <NUM> has a three-dimensional structure in which ridge portions <NUM> and valley portions <NUM> are alternately arranged in a width direction X orthogonal to a manufacturing direction Y. The ridge portion <NUM> is configured with two side surfaces <NUM> and a top surface <NUM> between them, and the valley portion <NUM> is configured with two side surfaces <NUM> shared with the adjacent ridge portions <NUM> and a bottom surface <NUM> between them. Note that, in this embodiment, a case is described in which the shape of the ridge portion <NUM> is a trapezoid as shown in <FIG>, but the present invention is not limited to this, and in addition to polygons such as triangles or rectangles, shapes may be curved shapes such as sine curves or bow shapes.

The core material <NUM> includes the three-dimensional structure continuously in the manufacturing direction Y. That is, as shown in <FIG>, a plurality of ridge portions 11a, 11b, 11c, and 11d are continuously formed in the manufacturing direction Y. The valley portions <NUM> are also formed continuously. The connection between the ridge portions <NUM> and the connection between the valley portions <NUM> are made by alternately repeating two types of connection methods.

The first connection method is such that, as shown in <FIG>, on a first folding line X1 in the width direction, top surfaces 17b and 17c of two adjacent ridge portions 11b and 11c are connected, via trapezoidal-shaped ridge portion connecting surfaces 15b and 15c, respectively. A ridge portion connecting surface <NUM> is formed at a right angle to the top surface <NUM>. On the first folding line X1 in the width direction, bottom surfaces 14b and 14c of two adjacent valley portions are directly connected. The second connection method is such that, as shown in <FIG>, on a second folding line X2 in the width direction, bottom surfaces 14a and 14b (or 14c and 14d) of two adjacent valley portions are connected, via trapezoidal-shaped valley portion connecting surfaces 16a and 16b (or 16c and 16d), respectively. A valley portion connecting surface <NUM> is formed at a right angle to the bottom surface <NUM>. On the second folding line X2 in the width direction, top surfaces 12a and 12b (or 12c and 12d) of two adjacent ridge portions are directly connected.

Thus, the core material <NUM> has a plurality of three-dimensional structures (the ridge portions <NUM> and the valley portions <NUM>) connected via the connection regions (the ridge portion connecting surfaces <NUM> and the valley portion connecting surfaces <NUM>), and has the connection region folded to form the hard layer of the sound-insulation material for a vehicle of the present invention. Specifically, the core material <NUM> is mountain-folded along the first folding line X1 such that the bottom surfaces 14b and 14c of two adjacent valley portions contact back-to-back with each other, and the angle formed by the ridge portion connecting surfaces 15b and 15c of two adjacent ridge portions increases to <NUM> degrees. In addition, the core material <NUM> is valley-folded along the second folding line X2 such that top surfaces 17a and 17b (or 17c and 17d) of two adjacent ridge portions contact face to face with each other, and the angle between the valley portion connecting surfaces 16a and 16b (or 16c and 16d) of two adjacent valley portions decreases to <NUM> degrees. A hard layer <NUM> of the sound-insulation material for a vehicle of the present invention obtained by folding the core material <NUM> in this manner is shown in <FIG> and <FIG>.

As shown in <FIG> and <FIG>, the hard layer <NUM> includes substantially hexagonal tubular cells <NUM> arranged in a plurality of rows, and has cells 20A, 20C and 20E formed out of two adjacent ridge portions and cells 20B and 20D formed out of two adjacent valley portions, each arranged in every other row. A broken line <NUM> in <FIG> is the surface that has been the back surface of the core material, and generally indicates the inner wall of the cell <NUM> having the substantially hexagonal tubular shape.

The cells 20A, 20C, and 20E formed from the ridge portions each include six cell side walls forming the substantially hexagonal tubular shape. These cell side walls are formed out of the two top surfaces <NUM> and the four side surfaces <NUM> of the cell material. Furthermore, these cells 20A, 20C, and 20E include substantially hexagonal tubular-shaped closed surfaces 21A, 21C, and 21E, respectively, to close the cell ends at the cell ends on one surface 10a (front surface in <FIG>) of the hard layer <NUM>. Each of these closed surfaces <NUM> on one side is formed out of two trapezoidal ridge portion connecting surfaces <NUM> in the cell material. Furthermore, these cells 20A, 20C, and 20E include open ends 22A, 22C, and 22E that are opened in a substantially hexagonal shape at the cell ends on the other surface 10b which is at the opposite side of the hard layer <NUM>. The open ends 22A, 22C, and 22E allow the respective internal spaces of the cells 20A, 20C, and 20E to be in communication with the outside.

The cells 20B and 20D formed from the valley portions each also includes six cell side walls forming the substantially hexagonal tubular shape. These cell side walls are formed from two bottom surfaces <NUM> and four side surfaces <NUM> of the cell material. Furthermore, these cells 20B and 20D include open ends 22B and 22D that are opened in the substantially hexagonal shape at the cell ends on the one surface 10a of the hard layer <NUM>. The open ends 22B and 22D allow the respective internal spaces of the cells 20B and 20D to be in communication with the outside. Furthermore, these cells 20B and 20D include substantially hexagonal tubular-shaped closed surfaces 21B and 21D that close the cell ends, respectively, at the cell ends on the other surface 10b, which is at the opposite side of the hard layer <NUM>. Each of these closed surfaces <NUM> on the other side is formed out of the two trapezoidal valley portion connecting surfaces <NUM> in the cell material.

In this way, the hard layer <NUM> has the one-side closed surfaces 21A, 21C, and 21E formed out of the ridge portions of the cell material in every other row at the cell end on one surface 10a, and has the other-side closed surfaces 21B and 21D formed out of valley portions of the cell material in the different cell rows from the above at the cell ends on the other surface 10b. However, unless otherwise stated, both the closed surface <NUM> on one side and the closed surface <NUM> on the other side perform substantially the same function.

The thickness of the entire hard layer <NUM> varies depending on which component of the vehicle the multilayered structure is used for, so it is not limited to the following. However, from the viewpoint of controlling the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure consisting of the hard layer and a soft layer to be described below, the sound absorption performance of the hard layer <NUM> itself, and the strength and weight of the hard layer <NUM>, the thickness is preferably in the range of <NUM> to <NUM>, and more preferably in the range of <NUM> to <NUM>.

The basis weight (weight per unit area) of the hard layer <NUM> varies depending on which component of the vehicle the multilayered structure is used for, so it is not limited to the following. However, the basis weight is preferably in the range of <NUM>/m<NUM> to <NUM>/m<NUM>, and more preferably in the range of <NUM>/m<NUM> to <NUM>/m<NUM>. As the thickness of the hard layer <NUM> is greater and the basis weight is greater, the strength of the hard layer <NUM> generally tends to be higher.

The basis weight of the hard layer <NUM> can be adjusted by the type of material of the hard layer <NUM>, the thickness of the entire hard layer <NUM>, or the wall thickness of the cell <NUM> (thickness of the material sheet) as well as the pitches Pcx and Pcy between the cells <NUM> of the hard layer <NUM> (distance between the central axes of the cells). In order to set the basis weight of the hard layer <NUM> in the above range, for example, it is preferable that the pitch Pcy between the cells <NUM> be in the range of <NUM> to <NUM> in the direction in which the cells <NUM> are adjacent to each other to form a row, which is the core manufacturing direction Y, and it is more preferable that the pitch Pcy be in the range of <NUM> to <NUM>. In particular, in order to control the ratio Kd/Ks of the dynamic spring constant to the static spring constant, to be described below, within a predetermined range, it is still more preferable that the pitch Pcy between the cells <NUM> be within the range of <NUM> to <NUM>.

Next, individual embodiments of the sound-insulation material for a vehicle according to the present invention are described below using the hard layer <NUM> described above.

As shown in <FIG> and <FIG>, a sound-insulation material for a vehicle of a first embodiment includes a hard layer <NUM> described above, a soft layer <NUM> provided on one surface of the hard layer <NUM>, and a skin layer <NUM> provided on the other surface of the hard layer <NUM>. Note that the sound-insulation material for a vehicle of the present invention is used so that the soft layer <NUM> side is located on the side of the noise source. That is, the sound-insulation material for a vehicle of the present invention is provided on the vehicle interior side, with the soft layer <NUM> installed on a panel <NUM> side of the vehicle body.

Since the soft layer <NUM> is softer than the hard layer <NUM> (also referred to as a core layer), which has a hard nature with tubular cells arranged in a plurality of rows, it is referred to as a soft layer in this specification. The material of the soft layer <NUM> is not particularly limited if it is a material generally used for a sound insulation layer in sound-insulation material for a vehicle. However, from the viewpoint of weight reduction of the sound-insulation material for a vehicle, the material is preferably a foam of a thermoplastic resin, thermosetting resin or the like, such as urethane foam, polyethylene foam, or nylon foam. The material is also preferably fiber such as: synthetic fiber such as polyester fiber, nylon fiber or acrylic fiber; inorganic fiber such as glass wool or rock wool; and metal fiber such as aluminum fiber. The fiber is preferably felt, and the felt is preferably formed of a polyester fiber such as a low melting point polyester fiber or a material such as glass wool. In addition, the felt manufacturing method is preferably a manufacturing method such as needle punching, thermal bonding, or spunlacing. Note that the soft layer <NUM> may be a combination of foam and fiber.

The basis weight of the soft layer <NUM> is not limited to the following since it depends on the ratio Kd/Ks of a dynamic spring constant to a static spring constant to be described below, but for example, the lower limit thereof is preferably <NUM>/m<NUM> or more, and more preferably <NUM>/m<NUM> or more, and still more preferably <NUM>/m<NUM> or more. In addition, the upper limit of the basis weight is preferably <NUM>/m<NUM> or less, more preferably <NUM>/m<NUM> or less, and still more preferably <NUM>/m<NUM> or less.

The thickness of the soft layer <NUM> is not limited to the following since it depends on the ratio Kd/Ks of a dynamic spring constant to a static spring constant to be described below, but for example, the lower limit thereof is preferably <NUM> or more, more preferably <NUM> or more, and still more preferably <NUM> or more. In addition, the upper limit of the thickness is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less.

In this embodiment, a structure of the hard layer <NUM> and the soft layer <NUM> has a ratio of the dynamic spring constant Kd to the static spring constant Ks satisfying <NUM> < Kd/Ks ≤ <NUM>. The ratio Kd/Ks of the dynamic spring constant to the static spring constant is called a dynamic magnification factor in the field of anti-vibration materials and is generally used as one of the indexes of anti-vibration performance. In the present invention, the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure consisting of the hard layer <NUM> and the soft layer <NUM>, is set to <NUM> or less, which is a significantly lower value than the conventional vehicle-sound-absorbing materials each using a core layer. Noise with a frequency of <NUM> to <NUM> generated from a vehicle is transmitted to the vehicle interior via the vibration of air or via the vibration of an object. The noise transmitted mainly via the vibration of the object can be blocked by the structure having the hard layer <NUM> and the soft layer <NUM>. This makes it possible to exhibit sufficient sound insulation performance against the noise generated in the vehicle. The ratio Kd/Ks of the dynamic spring constant to the static spring constant is more preferably <NUM> or less, and still more preferably <NUM> or less. On the other hand, a too low ratio Kd/Ks of the dynamic spring constant to the static spring constant causes vibration at a low frequency, and is unsuitable for a soundproofing material for vehicles. Therefore, the lower limit of the ratio Kd/Ks needs to exceed <NUM>, and it is preferably <NUM> or more and more preferably <NUM> or more.

In particular, when the ratio Kd/Ks of the dynamic spring constant to the static spring constant is <NUM> or more, in order to maintain the shape, the static spring constant Ks, of the structure consisting of the hard layer <NUM> and the soft layer <NUM>, is preferably <NUM> N/mm or more, and more preferably <NUM> N/mm or more. The upper limit of the static spring constant Ks of the structure is not particularly limited, but it is preferably <NUM> N/mm or less, and more preferably <NUM> N/mm or less. In addition, the dynamic spring constant Kd of the structure is not particularly limited, but the lower limit thereof is preferably <NUM> N/mm or more, and more preferably <NUM> N/mm or more, and the upper limit thereof is preferably <NUM> N/mm or less, and more preferably <NUM> N/mm or less.

The ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure consisting of the hard layer <NUM> and the soft layer <NUM>, can be determined by the following method. First, each of the static spring constant Ks and the dynamic spring constant Kd, of the structure consisting of the hard layer <NUM> and the soft layer <NUM>, is measured conforming to JIS K <NUM> and JIS K <NUM>. Specifically, the static spring constant Ks (N/mm) is measured as follows: as shown in <FIG>, a sample of the structure consisting of the hard layer <NUM> and the soft layer <NUM> is compressed in a compression direction <NUM> with a load F (N) using a compression device (not shown); the displacement x (mm) of the thickness of the sample is measured at that time; as shown in <FIG>, a graph of displacement with respect to load (Ks = F/x) is created; and the static spring constant Ks is calculated from the slope of the linear region on this graph. The dynamic spring constant Kd (N/mm) is measured as follows: as shown in <FIG>, a sample of the structure consisting of the hard layer <NUM> and the soft layer <NUM> is sandwiched between mass plates <NUM> to have a predetermined mass m; the hard layer <NUM> side of this sample is placed on an accelerometer <NUM>; a vibration exciter <NUM> is placed on the soft layer <NUM> side; the vibration level is measured when the sample is vibrated over frequencies of <NUM> to <NUM> with an acceleration amplitude of <NUM>/s<NUM>; as shown in <FIG>, a graph of vibration level with respect to frequency is created; and the resonance frequency f is determined, and the dynamic spring constant Kd is calculated from the expression Kd = (2πf)<NUM> × m. Then, the ratio (Kd/Ks) is calculated using the static spring constant Ks and the dynamic spring constant Kd, which are thus calculated. The static spring constant Ks can be measured by, for example, a commercially available tensile-compression tester (AG-20kNX, manufactured by Shimadzu Corporation). The dynamic spring constant Kd can be measured by, for example, a combination of a commercially available electromagnetic vibration exciter (VG-<NUM>, manufactured by AR BROWN Co. ) and a vibration measuring device (Test. Lab, manufactured by LMS International).

The static spring constant Ks and the dynamic spring constant Kd differ depending on the configuration of the soft layer <NUM> (for example, the type of material, basis weight, thickness, and the like), and the constants are also affected by the configuration of the hard layer <NUM> to which the soft layer <NUM> is provided (for example, the material, the arrangement of cells, the thickness of the entire hard layer, the pitch of cells, the thickness of the cell wall surface, and the like). The static spring constant Ks of the soft layer <NUM> is not particularly limited, but the lower limit thereof is preferably <NUM> N/mm or more, and more preferably <NUM> N/mm or more, and the upper limit thereof is preferably <NUM> N/mm or less, and more preferably <NUM> N/mm or less.

The skin layer <NUM> is a layer that is to be a surface on the vehicle interior side when the sound-insulation material for a vehicle of this embodiment is installed on the panel <NUM> of the vehicle body. The skin layer <NUM> may be a carpet or urethane foam that is generally used as a skin layer for a sound-insulation material for a vehicle or a vehicle-sound-absorbing material. As a main material of the carpet material, for example, polyester fiber, natural fiber or the like can be used. A method used for producing the carpet can be, for example, a needle punching or the like. The surface density of the carpet is preferably in the range of <NUM> to <NUM>/m<NUM>.

According to the first embodiment, the soft layer <NUM> is provided on one surface of the hard layer <NUM> on which the open ends and the closed surfaces are arranged in every other row; the skin layer <NUM> is provided on the other surface of the hard layer <NUM>; and the ratio Kd/Ks of the dynamic spring constant to the static spring constant described above is made within the above numerical range. This configuration can increase rigidity while maintaining a low weight of the sound-insulation material for a vehicle. In addition, with respect to the noise having a frequency of <NUM> to <NUM> generated in a vehicle, this configuration can block the noise transmitted mainly via the vibration of an object to exhibit sufficient sound insulation performance.

As shown in <FIG>, a sound-insulation material for a vehicle of a second embodiment includes the hard layer <NUM> mentioned above, a soft layer <NUM> provided on one surface of the hard layer <NUM> via a film layer <NUM> as an additional layer, and a skin layer <NUM> provided on another surface of the hard layer <NUM>. Note that the same configurations as those in the first embodiment are referred to by the same reference signs, and detailed descriptions thereof are omitted here.

In the second embodiment, the film layer <NUM> is provided between the hard layer <NUM> and the soft layer <NUM>. In this case, a dynamic spring constant Kd and a static spring constant Ks are obtained by carrying out the measurement method mentioned above on the structure having the hard layer <NUM> and the soft layer <NUM> with the film layer <NUM> therebetween. From these spring constants, the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure having the hard layer <NUM> and the soft layer <NUM>, is calculated. If the ratio Kd/Ks of the dynamic spring constant to the static spring constant calculated in this way is within the predetermined numerical range described above, the same sound insulation effect as that of the first embodiment can be obtained.

The material of the film layer <NUM> to be used may be, for example, resin films such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polyamide (PA), but it is not limited to these.

The thickness of the film layer <NUM> is not particularly limited if the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure having the hard layer <NUM> and the soft layer <NUM> described above, is maintained within a predetermined range. However, for example, the lower limit of the thickness is preferably <NUM> or more, more preferably <NUM> or more, and still more preferably <NUM> or more. In addition, the upper limit of the thickness is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less.

The film layer <NUM> may be heat-welded to be adhered to the hard layer <NUM> and the soft layer <NUM>, or may be adhered thereto via an adhesive (not shown). The adhesive to be used is not particularly limited, but for example, it may be an epoxy-based or acrylic-based adhesive. In addition, in order to heat-weld the skin layer <NUM> with the hard layer <NUM> and the soft layer <NUM>, for example, the skin layer <NUM> may have a three-layer structure including a central layer and two adhesive layers located on both side surfaces thereof. In this case, the material of the adhesive layer is a material having a melting point lower than the melting point of the material used for the central layer. For example, a polyamide having a melting point of <NUM> to <NUM> is used for the central layer, and polyethylene having a melting point of <NUM> to <NUM> is used for the adhesive layer. Then, the temperature at the time of heating when the skin layer <NUM> is adhered to the hard layer <NUM> and the soft layer <NUM>, and the temperature for thermoforming into a predetermined shape of the sound-insulation material for a vehicle are set to about <NUM> to <NUM>. This configuration and process can melt only the adhesive layer without melting the central layer to enable the central layer to firmly adhere to the hard layer <NUM> and the soft layer <NUM>. A resin having a melting point higher than that of polyethylene for the adhesive layer may be a polypropylene as well as a polyamide.

The film layer <NUM> may be breathable with a plurality of apertures penetrating the film layer, or may be non-breathable without such apertures. When there are apertures, the holes are provided in advance before the film layer <NUM> is adhered to the hard layer <NUM>, for example, by a hot needle or punching (punching using a male die and a female die). In order to prevent the holes from being closed, it is preferable to have a hole shape in which burrs of the holes are minimized. The aperture pattern does not have any particular limitation, but it is preferably arranged in a staggered arrangement or a lattice arrangement. The aperture rate of the film layer <NUM> is not particularly limited, but it is preferably in the range of <NUM>% to <NUM>%. The diameter of the aperture is preferably in the range of <NUM> to <NUM>, and more preferably in the range of <NUM> to <NUM>. Note that the pitch of the apertures of the film layer <NUM> does not necessarily need to be the same as the pitches Pcx and Pcy of cells <NUM> of the hard layer <NUM> shown in <FIG>, and the apertures and the cells <NUM> do not necessarily need to be aligned when the film layer <NUM> is adhered to the hard layer <NUM>. This is because the positions of the apertures of the film layer <NUM> and open ends <NUM> of the cells <NUM> of the hard layer <NUM> randomly overlap each other to allow appropriate communication between the inside and outside. It is preferable that the pitch of the apertures of the film layer <NUM> be smaller than the pitch of the cells <NUM> of the hard layer <NUM> at least in either an X direction or a Y direction.

According to the second embodiment, a film layer <NUM> is provided between the hard layer <NUM>, on which the open ends and the closed surfaces are arranged in every other row, and the soft layer <NUM>. This makes it possible to obtain the same effect as that of the first embodiment, and the effect that the film layer <NUM> can absorb or insulate sound. In particular, providing a plurality of apertures in the film layer <NUM> enables sound absorption.

As shown in <FIG>, a sound-insulation material for a vehicle of a third embodiment includes the hard layer <NUM> mentioned above, a soft layer <NUM> provided on one surface of the hard layer <NUM> via a first film layer 80a, and a skin layer <NUM> provided on another surface of the hard layer <NUM> via a second film layer 80b. Note that the same configurations as those in the first and second embodiments are referred to by the same reference signs, and detailed descriptions thereof are omitted here.

The first and second film layers 80a and 80b to be used can have the same configuration (material, thickness, layer structure, existence or absence of apertures, and the like) as the film layer <NUM> described in the second embodiment. The first and second film layers 80a and 80b to be used may have the same configuration or may have different configurations. Also, in the third embodiment, as in the second embodiment, a dynamic spring constant Kd and a static spring constant Ks are obtained by carrying out the measurement method mentioned above on the structure having the hard layer <NUM> and the soft layer <NUM> with the first film layer 80a therebetween. From these spring constants, the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure having the hard layer <NUM> and the soft layer <NUM>, is calculated.

According to the third embodiment, the same effect as that of the second embodiment can be obtained. In addition, the second film layer 80b is provided between the skin layer <NUM> and the hard layer <NUM> on which the open ends and the closed surfaces are arranged in every other row. This makes it possible to obtain the effect that the second film layer 80b also can absorb or insulate sound.

As shown in <FIG>, a sound-insulation material for a vehicle of a fourth embodiment includes the hard layer <NUM> mentioned above, a soft layer <NUM> provided on one surface of the hard layer <NUM> with a film layer <NUM> and a fiber layer <NUM> in order therebetween as additional layers, and a skin layer <NUM> provided on another surface of the hard layer <NUM>. Note that the same configurations as those in the first and second embodiments are referred to by the same reference signs, and detailed descriptions thereof are omitted here.

In the fourth embodiment, the film layer <NUM> and the fiber layer <NUM> are provided between the hard layer <NUM> and the soft layer <NUM>. In this case, a dynamic spring constant Kd and a static spring constant Ks can be obtained by carrying out the measurement method mentioned above on the structure having the hard layer <NUM> and the soft layer <NUM> with the film layer <NUM> and the fiber layer <NUM> therebetween. From these spring constants, the ratio Kd/Ks of the dynamic spring constant to the static spring constant, of the structure having the hard layer <NUM> and the soft layer <NUM> described above, is calculated. If the ratio Kd/Ks of the dynamic spring constant to the static spring constant calculated in this way is within the predetermined numerical range described above, the same sound insulation effect as that of the first embodiment can be obtained.

The fiber layer <NUM> is not particularly limited if it maintains the ratio Kd/Ks of the dynamic spring constant to the static spring constant described above within a predetermined range. Hoverer, it is preferable to use, for example, various nonwoven fabrics such as spunbonded, spunlaced, or needle punched nonwoven fabrics using resin fibers such as polyethylene terephthalate (PET), polypropylene (PP), or polyethylene (PE). The basis weight of the fiber layer <NUM> is not particularly limited if the ratio Kd/Ks of the dynamic spring constant to the static spring constant described above is maintained within a predetermined range. However, for example, the basis weight is preferably in the range of <NUM>/m<NUM> to <NUM>/m<NUM>, more preferably in the range of <NUM>/m<NUM> to <NUM>/m<NUM>, and still more preferably in the range of <NUM>/m<NUM> to <NUM>/m<NUM>.

In particular, the static spring constant Ks of the laminated body of the film layer <NUM> and the fiber layer <NUM>, which are the additional layers, is preferably smaller than the static spring constant Ks of the soft layer <NUM> in order to make it difficult to transmit vibration. For example, the static spring constant Ks of the laminated body, which is the additional layer, is not particularly limited, but the lower limit thereof is preferably <NUM> N/mm or more, and more preferably <NUM> N/mm or more, and the upper limit of thereof is preferably <NUM> N/mm or less, and more preferably <NUM> N/mm or less.

Note that, although <FIG> shows a laminated body of the film layer <NUM> and the fiber layer <NUM>, as the additional layer, the additional layer may be only the fiber layer <NUM>. In this case, the static spring constant Ks of the fiber layer <NUM> is preferably smaller than the static spring constant Ks of the soft layer <NUM>. For example, the static spring constant Ks of the fiber layer <NUM> is not particularly limited, but the lower limit thereof is preferably <NUM> N/mm or more, and more preferably <NUM> N/mm or more, and the upper limit thereof is preferably <NUM> N/mm or less, and more preferably <NUM> N/mm or less. The material of the soft layer <NUM> to be used in this case may be urethane foam. In addition, in order to make it difficult to transmit vibration, the lower limit in the thickness of the fiber layer <NUM> in this case is preferably <NUM> or more, and more preferably <NUM> or more, and the upper limit in the thickness is preferably <NUM> or less, and more preferably <NUM> or less.

According to the fourth embodiment, the film layer <NUM> and the fiber layer <NUM> are provided between the soft layer <NUM> and the hard layer <NUM> on which the open ends and the closed surfaces are arranged in every other row. This makes it possible to obtain the same effect as that of the first embodiment, and also to obtain the effect that the film layer <NUM> and the fiber layer <NUM>, which are the additional layers, can absorb sound. In addition, when the additional layer is only the fiber layer <NUM>, the effect of further weight reduction can be obtained.

Examples and comparative examples of the present invention are described below.

As Example <NUM>, a sound-insulation material for a vehicle having a multilayer structure shown in <FIG> was produced. First, on one surface of a hard layer having the structures of <FIG> (material: polypropylene (PP) resin, pitch Pcy between cells: <NUM>, thickness of hard layer: <NUM>), a film layer (material: apertured polypropylene (PP) film, thickness: <NUM>), a fiber layer (material: PP needle punched nonwoven fabric, basis weight: <NUM>/m<NUM>), and a soft layer (material: polyurethane foam (PU), basis weight: <NUM>/m<NUM>, thickness: <NUM>) were adhered in order. Then, the static spring constant Ks of the structure having the hard layer, the film layer, the fiber layer and the soft layer was measured by a tensile-compression tester (Ag-20kNX, manufactured by Shimadzu Corporation), in which the compression terminal speed was <NUM>/min, and the compression rate was up to <NUM>%. Subsequently, a dynamic spring constant Kd was measured with a combination of an electromagnetic vibration exciter (VG-<NUM>, manufactured by AR BROWN Co. ) and a vibration measuring device (Test. Lab, manufactured by LMS International), in which the frequencies were <NUM> to <NUM>, the acceleration amplitude was <NUM>/s<NUM>, and the mass m was <NUM>. The results are shown in Table <NUM>. As shown in Table <NUM>, the static spring constant Ks was <NUM> N/mm, and the dynamic spring constant Kd was <NUM> N/mm. Therefore, the ratio Kd/Ks of the dynamic spring constant to the static spring constant was <NUM>. In addition, the static spring constant Ks of each of the fiber layer and the soft layer was measured in the same procedure as the above. The results are shown in Table <NUM>. The static spring constant Ks of the film layer was not measured here because the effect was so small that it was ignorable.

Here, a graph of the results obtained by measuring the dynamic spring constant Kd is shown in <FIG>. As shown in <FIG>, since the resonance frequency f was <NUM> in Example <NUM>, the value of Kd can be determined by substituting this measurement result and <NUM> (<NUM> N) of mass m into the expression of Kd = (2πf)<NUM> × m.

Next, insertion loss was measured for the four-layer structure of the hard layer, the film layer, the fiber layer, and the soft layer of Example <NUM>. Insertion loss is an index showing the sound insulation performance improved by attaching a sound-insulation material to a base such as a panel. Specifically, the insertion loss (ILtrim) of the structure serving as the sound-insulation material can be derived by the expression ILtrim = TLpanel-trim-TLpanel, where: TLpanel is a sound transmission loss in a state of a panel of a vehicle alone as the base; and TLpanel-trim is a sound transmission loss in a state in which the structure and the skin layer serving as a sound-insulation material are attached to the panel.

The sound transmission loss between the frequencies of <NUM> and <NUM> was measured for each of the state with the base and the state with the structure attached, and the insertion loss was determined from these measurement results based on the above expression. The result is shown in <FIG>. Here, the sound transmission loss was measured by measuring sound intensity in combination with the reverberation chamber and the anechoic chamber. The relationship between the sound transmission loss and each measured value is shown in the following expression. The size of each measurement sample was <NUM> × <NUM>.

Here, for comparison, Comparative Example <NUM> was produced in the same manner as in Example <NUM> except that expanded polystyrene (EPS) (thickness: <NUM>) was used instead of the hard layer, and the film layer and fiber layer were omitted. In Comparative Example <NUM>, the static spring constant Ks and the dynamic spring constant Kd were measured in the same manner as in Example <NUM>. The results are shown in Table <NUM> and <FIG>. Also, in Comparative Example <NUM>, the insertion loss was measured in the same manner as in Example <NUM>. The result is shown in <FIG>.

As shown in <FIG>, in Comparative Example <NUM>, because the resonance frequency f was <NUM>, the dynamic spring constant Kd was <NUM> N/mm, which was much higher than that of Example <NUM>. The static spring constant Ks was <NUM> N/mm, which was relatively close to that of Example <NUM>, but the ratio Kd/Ks of the dynamic spring constant to the static spring constant was as high a value as <NUM>. Then, as shown in <FIG>, it was confirmed that: Example <NUM>, whose ratio Kd/Ks of the dynamic spring constant to the static spring constant was <NUM>, had insertion losses that were about <NUM> dB or more higher than that of Comparative Example <NUM>, of which the ratio Kd/Ks of the dynamic spring constant to the static spring constant was <NUM> over frequencies between <NUM> and <NUM>, and exhibited excellent sound insulation performance. In addition, Comparative Example <NUM> has the structure with foamed polyurethane and expanded polystyrene, both of which are soft, and the sound-insulation material as a whole lacked rigidity. On the other hand, the hard layer used in Example <NUM> is a hard and light core layer, in which tubular cells are arranged in a plurality of rows, instead of styrene foam in Comparative Example. Therefore, the sound-insulation material as a whole can have high rigidity while maintaining low weight.

As Examples <NUM> to <NUM>, as shown in Table <NUM>, structures serving as sound-insulation materials were produced in the same manner as in Example <NUM>, except that: a hard layer had different pitch Pcy between the cells of the core; a soft layer are made of felt (material: miscellaneous fibers, basis weight: <NUM>/m<NUM>); and/or some of the hard layers and soft layers therebetween had: no film layer and/or no fiber layer; film layers made of non-breathable films without apertures; film layers with different thicknesses; and/or fiber layers with different basis weight. Then, the static spring constant Ks and the dynamic spring constant Kd of Examples <NUM> to <NUM> were measured. In addition, in Comparative Examples <NUM> and <NUM>, as shown in Table <NUM>, the static spring constant Ks and the dynamic spring constant Kd were measured in the same manner as in Example <NUM>, except that only the soft layers of Examples <NUM> and <NUM> were used as the structures. These results are shown in Table <NUM>.

As shown in Table <NUM>, even Examples <NUM> and <NUM>, each of which had neither a film layer nor a fiber layer provided between the hard layer and the soft layer, achieved ratios Kd/Ks of the dynamic spring constant to the static spring constant of <NUM> or less. In addition, Examples <NUM> to <NUM>, each of which had a different film layer, fiber layer, and/or soft layer, also achieved ratios Kd/Ks of the dynamic spring constant to the static spring constant of <NUM> or less. On the other hand, Comparative Example <NUM> which had only urethane foam had a dynamic spring constant Kd further higher than Comparative Example <NUM>, and also had a high ratio Kd/Ks of the dynamic spring constant to the static spring constant of <NUM>. Furthermore, Comparative Example <NUM>, which had only felt, had a dynamic spring constant Kd significantly lower than Comparative Examples <NUM> and <NUM>, but also had a significantly lower static spring constant Ks. As a result, the ratio Kd/Ks of the dynamic spring constant to the static spring constant was very high at <NUM>. Comparative Examples <NUM> to <NUM>, each of which had only a soft layer, each have low rigidity and a ratio Kd/Ks of the dynamic spring constant to the static spring constant exceeding <NUM>, so that the sound insulation performance between frequencies of <NUM> to <NUM> is also inferior to that of Examples.

Claim 1:
A sound-insulation material for a vehicle, having a multilayer structure, the material comprising:
a core layer (<NUM>) having tubular cells (<NUM>), the tubular cells (<NUM>) being arranged in a plurality of rows;
a soft layer (<NUM>) provided on one surface of the core layer (<NUM>), the soft layer (<NUM>) being softer than the core layer (<NUM>);
a skin layer (<NUM>) provided on the other surface of the core layer (<NUM>), the skin layer (<NUM>) being a surface on a vehicle interior side of the sound-insulation material for a vehicle;
optionally, an additional layer provided between the core layer (<NUM>) and the soft layer (<NUM>); and
optionally, a second additional layer provided between the film layer (<NUM>) and the soft layer (<NUM>), the second additional layer having a static spring constant Ks smaller than a static spring constant Ks of the soft layer (<NUM>),
the additional layer and the second additional layer being a film layer (<NUM>) or a fiber layer (<NUM>),
wherein a ratio of a dynamic spring constant Kd to a static spring constant Ks, of a structure consisting of the core layer (<NUM>), the soft layer (<NUM>), optionally the additional layer, and optionally the second additional layer is <NUM> < Kd/Ks ≤ <NUM>.