Vehicle cabin soundproofing structure

Abstract

To provide a vehicle interior soundproof structure that can improve soundproof performance in a vehicle interior as a whole.SOLUTION: A vehicle interior soundproof structure comprises a first area A1 which is an area where strength of adhesion between a non-ventilation layer 30 and a compressed fiber layer 32 is relatively weak and a second area A2 where the strength of the adhesion therebetween is relatively strong. Places, where soundproof performance in a high-frequency band (1000 Hz or higher) made more excellent by a structure 10B in the second area A2, are mixed with places, where insertion loss in a middle-frequency band (200 Hz-630 Hz) is suppressed from decreasing and soundproof performance in the middle-frequency band is improved by a structure 10A in the first area A1, so that soundproof performance in a vehicle interior as a whole can be improved.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a vehicle compartment soundproofing structure for suppressing noise from outside a vehicle compartment. [Background technology]

[0002] Conventionally, soundproofing structures are provided in the parts that divide the vehicle compartment so that noise from the outside of the vehicle or the drive unit of the vehicle is not transmitted to the inside of the vehicle compartment. As the soundproofing structure, for example, as in the automobile trim part described in the following Patent Document 1, a structure having the characteristics of a spring mass system (spring mass system), specifically, a structure in which a sound absorbing layer (decoupling layer) as a spring element, a mass element consisting of a non-breathable layer (impermeable barrier layer) and a compressed fiber layer (porous fiber layer) are laminated in order from the panel side to the inside of the panel that is the main part that divides the vehicle compartment, is often seen. Note that the automobile trim part described in Patent Document 1 aims to soundproof a frequency band between a relatively low frequency noise of 50 Hz to 500 Hz and a high frequency noise of more than 2 kHz, and it is disclosed that it is possible to exhibit high sound insulation performance in that frequency band by adjusting the Young's modulus of the porous fiber layer. In addition, the following Patent Document 2 discloses that when priority is given to sound absorption, the thickness of the porous fiber layer with the Young's modulus adjusted is made larger than when priority is given to sound insulation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-522094 [Patent Document 2] Special Publication No. 2013-521190 Summary of the Invention [Problem to be solved by the invention]

[0004] In the soundproofing structures having the configurations described in Patent Documents 1 and 2, the barrier layer and the porous fiber layer are firmly bonded to each other, and both of them function as mass elements. As described above, the soundproofing structure described in Patent Document 1 has high sound insulation properties in a relatively high frequency band and a higher frequency band. In such a configuration, a phenomenon that the sound absorbing layer as a spring element transmits relatively low frequency sounds (about 200 Hz to 500 Hz) from the main member that divides the vehicle compartment to the mass layer, that is, a so-called resonance transmission phenomenon (resonance), has conventionally occurred, and deterioration of soundproofing performance in the frequency band of 315 Hz to 630 Hz (hereinafter sometimes referred to as the "mid-frequency band") has become a problem.

[0005] The present invention has been made in consideration of such circumstances, and its objective is to provide a vehicle cabin soundproofing structure that can improve the soundproofing performance of the entire vehicle cabin by using a configuration that improves the soundproofing performance in the mid-frequency band in part of the vehicle cabin. [Means for solving the problem]

[0006] In order to solve the above problems, the vehicle compartment soundproofing structure of the present invention comprises: A vehicle cabin soundproofing structure for suppressing noise from outside a vehicle cabin, comprising: A partition member that serves as a main component for partitioning the vehicle compartment; A sound absorbing layer disposed on the indoor side of the partition member and having a large number of voids therein; A non-breathable layer arranged on the indoor side of the sound absorbing layer and made of a non-breathable material; a compressed fiber layer formed mainly of a compressed fiber aggregate, the compressed fiber layer being disposed on the indoor side of the non-breathable layer; The adhesive layer is characterized by having a first region where the adhesive strength between the air-impermeable layer and the compressed fiber layer is relatively weak, and a second region where the adhesive strength is relatively strong.

[0007] In general, the dashboard, floor, and the like of a vehicle are configured such that soundproofing materials are arranged on the interior side of partition members such as panels that are the main components that partition the vehicle cabin. When considering the soundproofing performance of a vehicle cabin, a spring-mass system model may be used. Specifically, the spring element corresponds to a part arranged on the interior side of a rigid partition member and formed of a low-density material such as uncompressed felt or foam material, and the mass element corresponds to a part formed of a high-density impermeable material provided on the interior side of the spring element, and a spring-mass system model is used. In addition, when the spring-mass system and the rigid part corresponding to the partition member are included, it has the characteristics of a hollow double wall. The soundproofing performance of the vehicle cabin is evaluated, for example, using an insertion loss, which is the difference between the sound pressure level when there is no soundproofing material (spring-mass system) and the sound pressure level when there is a soundproofing material. Generally, the compressed fiber layer is firmly bonded to the non-breathable layer. In such cases, both the non-breathable layer and the compressed fiber layer act as mass elements, causing resonance (resonant transmission phenomenon) in the mid-frequency range and reducing the insertion loss.

[0008] On the other hand, in the vehicle compartment soundproofing structure of this configuration, the adhesive strength of the compressed fiber layer to the non-breathable layer is weakened in the portion corresponding to the first region of the partition member compared to the portion corresponding to the second region. That is, in the soundproofing structure of the portion corresponding to the first region, sound is less likely to be transmitted from the non-breathable layer to the compressed fiber layer. In detail, resonance occurs between the partition member and the non-breathable layer alone, and the frequency of the resonance shifts to the high frequency side due to the reduction in the mass layer. As a result, the insertion loss in the mid-frequency band is improved in the portion corresponding to the first region compared to the portion corresponding to the second region, that is, the soundproofing performance in the mid-frequency band can be improved. Incidentally, if the adhesive strength of the compressed fiber layer to the non-breathable layer is weakened, the soundproofing performance in the high frequency band will be reduced compared to when the adhesive strength of the compressed fiber layer to the non-breathable layer is secured.

[0009] In the portion that divides the vehicle cabin, there are a region with relatively high soundproofing performance in the mid-frequency band and a region with relatively low soundproofing performance due to the structure of the partitioning member and the difference in the thickness of the sound-absorbing layer associated with the structure of the partitioning member. For example, by setting the region with relatively low soundproofing performance in the mid-frequency band as the first region and the region with relatively high soundproofing performance in the mid-frequency band as the second region, and applying the vehicle cabin soundproofing structure of this configuration, it is possible to prioritize soundproofing in the mid-frequency band in the first region while improving the soundproofing performance in the high-frequency band in the second region, thereby improving the soundproofing performance of the entire vehicle cabin. Note that in the vehicle cabin soundproofing structure of this configuration, "weakened adhesive strength" is not limited to the case where the first region is also bonded, for example, by making the second region entirely bonded while making the first region partially bonded in dots or lines, reducing the amount of adhesive applied, or changing the type of adhesive, and also includes the case where the adhesive strength is zero, that is, no adhesive is applied.

[0010] The "compressed fiber layer" in the vehicle cabin soundproofing structure of this configuration is a fiber aggregate such as felt or glass wool made of natural or synthetic fibers. For example, a so-called compressed felt can be used, which is made by thinly piling up wool fibers, applying heat and alkali to the piled fibers, squeezing and kneading them, and entangling them with each other using only the fulling properties of the wool fibers to form a cloth. It is also possible to use a porous fiber layer with an adjusted Young's modulus as described in the above-mentioned Patent Document 1.

[0011] The "sound absorbing layer" is a so-called silencer, and can be made of a fiber aggregate having many voids or a porous synthetic resin such as urethane foam. The thickness of this sound absorbing layer is preferably 3mm to 60mm. Furthermore, the "non-breathable layer" can be formed in the form of a single layer or multiple layers of film made of polyethylene, polypropylene, polyester, polyamide, ionomer resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, EVA, EVOH, EMMA, etc.

[0012] In the above configuration, the partition member is a floor panel that partitions the floor of a vehicle, the first area being a foot well portion that is the area of ​​the floor panel under the feet of a seated occupant, and the second area being at least a portion of the area excluding the foot well portion, and the sound-absorbing layer in the first area can be configured to be thicker than the sound-absorbing layer in the second area.

[0013] Unlike the portion of the vehicle soundproofing structure that is covered by a mass-bearing part such as a seat or a center console, the vehicle soundproofing structure is likely to be exposed in the footwell of an automobile. In order to improve the insertion loss of the footwell, for example, it is desirable to make the thickness of the sound absorbing layer larger than that of other portions. When the thickness of the sound absorbing layer is increased, the sound pressure level in the mid-frequency band tends to increase due to the above-mentioned resonance transmission phenomenon. The vehicle compartment soundproofing structure having this configuration is applied to the floor of such a vehicle such as an automobile or truck, and the soundproofing performance of the mid-frequency band is prioritized for the footwell portion where the sound pressure level in the mid-frequency band is high, while the soundproofing performance of the high-frequency band is ensured for the portion other than the footwell portion where the sound pressure level in the mid-frequency band is low, thereby improving the soundproofing performance of the vehicle compartment as a whole.

[0014] In the above-mentioned configuration, the breathable layer may have a weight per unit area of ​​15 gsm or more and 400 gsm or less, desirably 50 gsm or more and 200 gsm or less.

[0015] In the vehicle cabin soundproofing structure having this configuration, the basis weight of the non-air-permeable layer is limited to a relatively small value. The smaller the basis weight of the non-air-permeable layer, the more the resonance frequency (resonance transmission frequency) of the resonance transmission phenomenon shifts to the high frequency side. Therefore, with the vehicle cabin soundproofing structure having this configuration, it is possible to further improve the soundproofing performance in the mid-frequency band (especially, 315 Hz to 500 Hz).

[0016] In the above configuration, the compressed fiber layer may have a mass per unit area of ​​300 gsm or more and 1500 gsm or less, desirably 600 gsm or more and 1000 gsm or less.

[0017] In the vehicle compartment soundproofing structure having this configuration, the basis weight of the compressed fiber layer is limited, and sufficient soundproofing performance can be ensured without increasing the thickness of the compressed fiber layer.

[0018] In the above-described configuration, the first region may be configured such that the air-impermeable layer and the compressed fiber layer are not bonded to each other.

[0019] The vehicle cabin soundproofing structure having this configuration can prevent the resonance of the non-breathable layer due to the resonance transmission phenomenon from being transmitted to the compressed fiber layer, and can effectively improve the soundproofing performance in the mid-frequency range. Effect of the Invention

[0020] According to the present invention, it is possible to provide a vehicle cabin soundproofing structure capable of improving the soundproofing performance of the vehicle cabin as a whole. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view showing a floor panel of a vehicle in which a vehicle floor structure according to a first embodiment of the present invention is adopted; [Diagram 2] Plan view of the floor panel shown in Figure 1 [Diagram 3] FIG. 3 is a cross-sectional view showing a schematic floor structure in the first area shown in FIG. 2; [Figure 4] FIG. 3 is a cross-sectional view showing a schematic floor structure in the second area shown in FIG. 2 . [Diagram 5] FIG. 13 is a cross-sectional view showing a schematic diagram of a floor structure of a comparative example. [Figure 6] Spring-mass system model of the floor structure in Figures 4 and 5 [Figure 7] Spring-mass system model of the floor structure in Fig. 3 [Figure 8]Graph showing the relationship between frequency and insertion loss for each floor structure [Figure 9] Graph showing the relationship between 1 / 3 octave frequency and acoustic sensitivity in the vehicle floor structure of this embodiment and the floor structure of a comparative example. [Figure 10] A graph showing the relationship between the overall thickness of the floor structure and the resonant frequency [Figure 11] FIG. 11 is a cross-sectional view showing a schematic diagram of a vehicle floor structure in a first region according to a second embodiment of the present invention; [Figure 12] FIG. 11 is a cross-sectional view showing a schematic diagram of a vehicle floor structure in a second region according to a second embodiment of the present invention; [Figure 13] Spring-mass system model of the floor structure in Fig. 12 [Figure 14] Graph showing the relationship between frequency and insertion loss for each floor structure [Figure 15] Graph for explaining change in insertion loss when the mass per unit area of ​​the non-breathable layer is changed DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <Embodiment 1> The vehicle compartment soundproofing structure of the present invention is adopted in the structure of the floor of a vehicle (automobile), which is a vehicle, and a vehicle floor structure 10, which is an embodiment of the present invention, will be described below. The vehicle floor structure 10 is composed of a vehicle floor panel 12 shown in Figures 1 and 2, and a floor silencer 14 and a carpet 16, which are stacked on top of the vehicle floor panel 12 and will be described in detail later. The floor panel 12 is a partitioning member that is the main component that partitions the floor surface of the vehicle compartment, which is the vehicle compartment, and is made of metal, for example, and has a generally rectangular shape that is long in the front-to-rear direction of the vehicle in a plan view.

[0023] As shown in FIG. 1 and FIG. 2, the floor panel 12 has a floor tunnel 20 formed in the center of the vehicle width direction, which extends in the vehicle front-rear direction and bulges upward. In addition, the vehicle is provided with reinforcing members (two in this embodiment) extending in the vehicle width direction, and the floor panel 12 also has bulging portions 22, 23 bulging upward in a shape along the reinforcing members so that the two reinforcing members fit together. In addition, the driver's seat and the passenger's seat are arranged above the two bulging portions 22, 23 in the vehicle. In addition, the floor panel 12 has a standing wall portion 24 formed at the rear end, and the rear seat is arranged behind the standing wall portion 24 in the vehicle. In other words, in the floor panel 12, the area Aa in front of the bulging portion 22 on the front side and the area Ab between the standing wall portion 24 and the bulging portion 23 on the rear side correspond to the foot pool portion, which is the foot area of ​​a seated occupant.

[0024] In the vehicle floor structure 10 of this embodiment, a first floor structure 10A, which is the floor structure in the areas Aa, Ab that serve as the foot pools and the area Ac between the two bulging parts 22, 23, and a second floor structure 10B, which is the floor structure in a portion of the floor panel 12 other than the areas Aa, Ab, Ac (area A2 described below), are different structures. Below, the first floor structure 10A shown in Fig. 3 and the second floor structure 10B shown in Fig. 4, and the differences between the first floor structure 10A and the second floor structure 10B will be described in detail.

[0025] A floor silencer 14 is laid on the floor panel 12. The floor silencer 14 may be a fiber aggregate having many voids or a porous synthetic resin such as urethane foam. In this embodiment, the floor silencer 14 is a felt made of thermoplastic resin fibers. The floor silencer 14 is disposed on the indoor side of the floor panel 12 as a partition member, and functions as a sound absorbing layer having many voids inside. The above-mentioned foot pool areas Aa and Ab of the floor structure 10 are easily exposed, unlike the parts covered with mass parts such as seats and a center console on the floor structure 10. In order to improve the insertion loss of the foot pool areas Aa and Ab, for example, it is desirable to make the thickness of the floor silencer 14 larger than that of other parts. Therefore, the thickness of the floor silencer 14 is made larger in the parts (first floor structure 10A) corresponding to the above-mentioned foot pool areas Aa and Ab and the area Ac between the two bulging parts 22 and 23 than in other parts. That is, the thickness of the portion 14A of the floor silencer 14 corresponding to the first floor structure 10A is made larger than the thickness of the portion 14B corresponding to the second floor structure 10B. In this embodiment, the thickness of the portion 14A corresponding to the first floor structure 10A is about 20 mm, and the thickness of the portion 14B corresponding to the second floor structure 10B is about 10 mm. The thickness of the floor silencer 14 is preferably 3 mm to 60 mm in order to absorb the sound transmitted from the outside of the floor panel 12.

[0026] The vehicle floor structure 10 of this embodiment is characterized by the difference in the structure of the carpet 16 between the first floor structure 10A and the second floor structure 10B. Therefore, in evaluating the soundproofing performance of the first floor structure 10A and the second floor structure 10B, the thickness of the floor silencer in each structure is treated as being the same, and is shown as the same thickness in Figures 3 and 4.

[0027] A carpet 16 is laid on the upper side of the floor silencer 14. As shown in Figures 3 and 4, this carpet 16 is formed by laminating an air-impermeable layer 30, a compressed fiber layer 32, and a surface layer 34 in this order from the floor silencer 14 side (the outdoor side). The air-impermeable layer 30 and the compressed fiber layer 32, and the compressed fiber layer 32 and the surface layer 34 are bonded with an adhesive, respectively, to form adhesive layers 36, 38.

[0028] The non-breathable layer 30 is a film made of a non-breathable material, and is located on the indoor side of the floor silencer 14, which is a sound absorbing layer, and is intended to mainly insulate sound from the outdoor side. The non-breathable layer 30 may be formed as a single-layer or multi-layer film made of, for example, polyethylene, polypropylene, polyester, polyamide, ionomer resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, EVA, EVOH, EMMA, etc. The non-breathable layer 30 has a mass per unit area of ​​15 gsm to 400 gsm, preferably 50 gsm to 200 gsm. In this embodiment, the non-breathable layer 30 is a single-layer film made of polyethylene, and has a mass per unit area of ​​100 gsm.

[0029] The compressed fiber layer 32 is laminated on the interior side of the non-breathable layer 30 for the purpose of absorbing and insulating sound. The compressed fiber layer 32 can be, for example, a so-called compressed felt made by felting natural fibers, synthetic fibers, or a mixture of these fibers with binder fibers. The compressed felt is preferably made of recycled fiber materials such as recycled cotton, or other recycled fibers such as polyester, so-called synthetic fiber recycled material. Specifically, the compressed fiber layer 32 can be, for example, a material made by mixing a low-melting point polyester as a binder into a synthetic fiber recycled material, and then heating and forming the accumulated material into a desired mat shape by pressing. It is considered that the thicker the compressed fiber layer 32, the better the soundproofing performance. However, since the vehicle interior space is limited, it is desirable to make the thickness of the compressed fiber layer 32, in other words, the mass per unit area, small. In view of this, the mass per unit area of ​​the compressed fiber layer 32 can be set to 300 gsm or more and 1500 gsm or less, preferably 600 gsm or more and 1000 gsm or less. In this embodiment, the mass per unit area of ​​the compressed fiber layer 32 is set to 800 gsm in both the first floor structure 10A and the second floor structure 10B.

[0030] The compressed fiber layer 32 is different between the first floor structure 10A and the second floor structure 10B. Specifically, the first compressed fiber layer 32A, which is the compressed fiber layer 32 in the first floor structure 10A, is a general compressed felt manufactured by the above-mentioned method, whereas the second compressed fiber layer 32B, which is the compressed fiber layer 32 in the second floor structure 10B, has an adjusted Young's modulus and, as will be described in detail later, has improved soundproofing performance in the high frequency range (1000Hz to 8000Hz).

[0031] The surface layer 34 is not particularly limited, and various materials such as Dior surface, velour surface, plain surface, tufted carpet surface, etc. can be used. In this embodiment, Dior surface is used, and the weight per unit area is 350gsm. This surface layer 34 is the same in both the first floor structure 10A and the second floor structure 10B.

[0032] The adhesive layers 36, 38 may be formed from a liquid adhesive or a solid adhesive such as a film or tape. The adhesive layer 38 between the compressed fiber layer 32 and the skin layer 34 is bonded in the same manner in both the first floor structure 10A and the second floor structure 10B. The adhesive layer 38 is not essential and may be non-adhesive.

[0033] On the other hand, the adhesive layer 36 between the non-breathable layer 30 and the compressed fiber layer 32 has different adhesive strengths in the first floor structure 10A and the second floor structure 10B. Specifically, the first adhesive layer 36A, which is the adhesive layer 36 in the first floor structure 10A, has a lower adhesive strength than the second adhesive layer 36B, which is the adhesive layer 36 in the second floor structure 10B. Specifically, for example, the second adhesive layer 36B is fully adhesive, whereas the first adhesive layer 36A can be partially adhesive in a dot or line shape. The method for lowering the adhesive strength of the first adhesive layer 36A is not particularly limited, and for example, a method such as reducing the amount of liquid adhesive applied compared to the second adhesive layer 36B or using a different type of adhesive can be adopted.

[0034] As described above, in the present vehicle floor structure 10, the regions Aa, Ab, and Ac are the first region A1, which is a region where the adhesive strength between the non-air-permeable layer 30 and the compressed fiber layer 32 is relatively low, and the other regions except the regions Aa, Ab, and Ac are the second region A2, which is a region where the adhesive strength between the non-air-permeable layer 30 and the compressed fiber layer 32 is relatively high. In the following, the soundproofing performance of the present vehicle floor structure 10 will be described while explaining the soundproofing performance in each of the first region A1 and the second region A2, but a conventional vehicle floor structure (soundproofing structure) 100 will be used as a comparative example. Before explaining the soundproofing performance in each of the first region A1 and the second region A2, the schematic structure of the vehicle floor structure 100 of the comparative example will be described with reference to FIG. 5.

[0035] The vehicle floor structure 100 of the comparative example is composed of a floor silencer 102 and a carpet 104, similar to the vehicle floor structure 10 of this embodiment. The floor silencer 102 is similar to the floor silencer 14 of this embodiment. The carpet 104 is composed of, in order from the lower layer side (floor silencer 102 side), a backing layer (non-breathable layer) 110 made of polyethylene, a compressed fiber layer 112 made of compressed felt, and a surface layer 114 which is a Delois surface layer, and adhesive layers 116, 118 are formed between each layer by adhesive, so that the layers are firmly bonded to each other. In other words, it is similar to the second floor structure 10B in the second area A2 shown in FIG. 4.

[0036] However, the backing layer 110 of the carpet 104 has a larger mass per unit area of ​​600 gsm than the non-breathable layer 30 in this embodiment. Also, the compressed fiber layer 112 is made of compressed felt like the first compressed fiber layer 32A in this embodiment, but has a smaller mass per unit area of ​​300 gsm than the compressed fiber layer 32 in this embodiment.

[0037] The soundproofing performance of each of the first floor structure 10A, the second floor structure 10B, and the floor structure 100 of the comparative example was evaluated by carrying out an actual vehicle experiment using a taste piece and by carrying out a trial calculation using simulation software. When carrying out this simulation, a spring-mass system model shown in Fig. 6 and Fig. 7 was used. In detail, Fig. 6 shows the second floor structure 10B and the floor structure 100 of the comparative example, and Fig. 7 shows the first floor structure 10A. In addition, the evaluation of the soundproofing performance this time was carried out on a structure excluding the skin layer 34. The evaluation of the soundproofing performance of each floor structure was carried out using the insertion loss, which is the difference between the sound pressure level when there is no soundproofing material (spring-mass system) and the sound pressure level when there is a soundproofing material.

[0038] In the spring-mass model, the spring element is a part that is arranged on the indoor side of the rigid floor panel 12 and is made of a low-density material such as uncompressed felt or foam material, and in both structures, corresponds to the floor silencer 14, 102. The mass element is a part that is arranged on the indoor side of the spring element and is made of a high-density impermeable material. That is, in the second floor structure 10B, the second compressed fiber layer 32B is firmly bonded to the non-breathable layer 30 by the second adhesive layer 36B, and the non-breathable layer 30 and the second compressed fiber layer 32B correspond to the mass element. The floor structure 100 of the comparative example is also similar to the second floor structure 10B, and the backing layer 110 and the compressed fiber layer 112, which are non-breathable layers, correspond to the mass element.

[0039] As shown in FIG. 8, when comparing the insertion loss of the floor structure 100 of the comparative example with the insertion loss of the second floor structure 10B, the second floor structure 10B exhibits higher soundproofing performance in the high frequency band (1000Hz to 8000Hz) than the floor structure 100 of the comparative example due to the function of the second compressed fiber layer 32B with an adjusted Young's modulus. On the other hand, these floor structures have a hollow double-wall characteristic when including the spring mass system and the floor panel 12, which is a rigid part, and a phenomenon called a resonance transmission phenomenon (resonance) occurs between the floor panel 12 and the mass element, in which a relatively low frequency sound (about 200Hz to 500Hz) is transmitted to the mass layer. As a result, as shown in FIG. 8, the insertion loss decreases in that frequency band (hereinafter sometimes referred to as the "medium frequency band"). Incidentally, the resonance transmission frequency f, which is the frequency at which this resonance transmission phenomenon occurs, can be calculated by Equation 1. In the formula 1, m1 represents the weight per unit area of ​​the floor panel 12, m2 represents the weight per unit area of ​​the mass element, E represents the Young's modulus of the spring element (air), and d represents the thickness of the spring element. In this embodiment, the resonant transmission frequency is 469 Hz, and it can be seen from FIG. 8 that the insertion loss is the lowest.

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[0040] On the other hand, in the first floor structure 10A, the adhesion strength between the non-air-permeable layer 30 and the first compressed fiber layer 32A is weaker than that of the second floor structure 10B (close to non-adhesion), and as shown in the conceptual diagram of FIG. 7, the vibration of the non-air-permeable layer 30 is less likely to be transmitted to the first compressed fiber layer 32A. In addition, since it can be considered that almost only the non-air-permeable layer 30 corresponds to the mass element, the weight of the mass element is small, and when the resonance frequency is calculated by the formula 1, it shifts to the high frequency side from the resonance transmission frequency of the second floor structure 10B and the floor structure 100 of the comparative example. Incidentally, in this embodiment, the resonance frequency is 1389 Hz. As a result, as shown in FIG. 8, the insertion loss decreases in the high frequency band (1000 Hz to 3000 Hz), but the resonance transmission phenomenon is suppressed in the medium frequency band, and the decrease in insertion loss can be suppressed. In other words, the first floor structure 10A has a lower soundproofing performance in the high frequency range compared to the second floor structure 10B, but is able to suppress the decrease in soundproofing performance in the mid-frequency range.

[0041] The vehicle floor structure 10 of this embodiment employs a first floor structure 10A that suppresses a decrease in soundproofing performance in the mid-frequency range in the first region A1 where the floor silencer 14 is relatively thick and has excellent sound absorption in the high-frequency range, and employs a second floor structure 10B that has excellent soundproofing performance in the high-frequency range in the second region A2 where the floor silencer 14 is relatively thin. Therefore, according to this vehicle structure 10, it is possible to improve the soundproofing performance of the entire vehicle interior.

[0042] Fig. 9 shows the acoustic sensitivity near the head of an occupant seated in the rear seat of a vehicle. The solid line is for the vehicle floor structure 10 of this embodiment, and the dotted line is for the case where the floor structure 100 of the comparative example is used for the entire surface of the floor panel 12. As can be seen from Fig. 9, it was confirmed that the vehicle floor structure 10 of this embodiment has improved soundproofing performance in a wide frequency band from 250 Hz to 2000 Hz, compared to the floor structure 100 of the comparative example.

[0043] Moreover, Fig. 10 shows the relationship between the thickness of the entire floor structure and the resonant frequency when the mass per unit area (basis weight) of the non-ventilated layer is changed in the first floor structure 10A. As can be seen from Fig. 10, the smaller the basis weight of the non-ventilated layer, the more the resonant frequency shifts to the higher frequency side (upper side in Fig. 10), regardless of the thickness of the floor silencer, etc. In other words, the higher the frequency shift, the smaller the effect on the mid-frequency band can be, and therefore the less the deterioration of soundproofing performance in the mid-frequency band can be suppressed. Therefore, it is considered desirable to reduce the basis weight of the non-ventilated layer in the first floor structure 10A.

[0044] <Embodiment 2> The vehicle floor structure 200 of the second embodiment has a structure similar to that of the vehicle floor structure 10 of the first embodiment, and the same components as those of the first embodiment are designated by the same reference numerals as those of the first embodiment, and their description will be simplified or omitted. The vehicle floor structure 200 of the second embodiment is composed of a floor silencer 202 and a carpet 204, similar to the vehicle floor structure 10 of the first embodiment, but the structure of the carpet 204, more specifically, the structure in the first region A1, is different. Specifically, in the vehicle floor structure 10 of the first embodiment described above, the non-breathable layer 30 and the first compressed fiber layer 32A are bonded with a relatively weak adhesive strength in the first region A1, whereas in the vehicle floor structure 200 of the second embodiment, they are not bonded as shown in FIG. 11. That is, as shown in Fig. 12, the second floor structure 200B, which is the floor structure in the second region A2, has a second adhesive layer 36B between the non-breathable layer 30 and the second compressed fiber layer 32B, whereas as shown in Fig. 11, the first floor structure 200A, which is the floor structure in the first region A1, does not have an adhesive layer 36 between the non-breathable layer 30 and the first compressed fiber layer 32A. As a result, the vehicle floor structure 200 of this embodiment can reliably suppress the transmission of vibration from the non-breathable layer 30 to the first compressed fiber layer 32A in the first floor structure 200A, and more reliably suppress the deterioration of soundproofing performance in the mid-frequency range.

[0045] In addition, in the vehicle floor structure 200 of the second embodiment, the carpet 204 is entirely adhered to the floor silencer 202. That is, in both the first floor structure 200A and the second floor structure 200B, an adhesive layer 206 is provided between the non-breathable layer 30 and the floor silencer 202, and they are adhered to each other, as shown in Figs. 11 and 12. That is, in the second floor structure 200B, the bonding strength between the compressed fiber layer 32B and the non-breathable layer 30 is lower than the bonding strength between the non-breathable layer 30 and the floor silencer 202.

[0046] The effect of bonding the non-ventilation layer 30 and the floor silencer 14 in each of the first floor structure 200A and the second floor structure 200B will be described below. First, the second floor structure 200B will be compared with the second floor structure 10B in the first embodiment. The second floor structure 200B in the second embodiment is considered to correspond to a spring-mass system model as shown in FIG. 13. That is, as in the first embodiment, not only does resonance 210 (hereinafter sometimes referred to as "air spring resonance 210") occur due to the resonance transmission phenomenon, which is a characteristic of the hollow double wall, but also resonance 212 (hereinafter sometimes referred to as "sound absorbing layer expansion and contraction resonance 212") of the mass element (non-ventilation layer 30) occurs due to the expansion and contraction of the floor silencer 202 in the thickness direction.

[0047] The resonance frequency v of the sound absorbing layer expansion and contraction resonance 212 can be calculated by the following formula 2. In the formula 2, t represents the thickness of the floor silencer 202 which is a compressed felt, E represents the Young's modulus of the compressed felt (floor silencer 202), and ρ represents the density of air. In this embodiment, the resonance frequency is 196 Hz.

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[0048] The solid line in Fig. 14 is for the second floor structure 10B in the first embodiment, and the line connecting the rectangles in Fig. 14 is for the second floor structure 200B in the second embodiment. The above-mentioned sound absorbing layer expansion resonance 212 exists in a frequency band close to the resonance frequency of the air spring resonance 210, and an anti-resonance occurs between these two resonance frequencies, in which the phase is reversed. As a result, as shown in Fig. 14, the insertion loss is improved in the frequency band of 250Hz to 500Hz, and the soundproofing performance is improved.

[0049] Next, the effect of the first floor structure 200A will be described. In FIG. 14, the line connecting the triangles is the insertion loss of the first floor structure 200A. In addition, in FIG. 14, the line connecting the circles is the floor structure in which the non-breathable layer and the floor silencer are not bonded, as in the first floor structure 10A of the first embodiment. Furthermore, this floor structure is a structure in which the non-breathable layer 30 and the first compressed fiber layer 32A are not bonded, that is, the floor structure in this case has almost the same (more precisely, better) soundproofing performance as the first floor structure 10A of the first embodiment. Since this floor structure is a modified version of the first floor structure 10A of the first embodiment, it will be called the modified floor structure. In the first floor structure 200A of the second embodiment and the modified floor structure, as in the first floor structure 10A of the first embodiment, the resonant frequency of the air spring resonance is shifted to the high frequency side, making it possible to suppress the deterioration of the soundproofing performance in the mid-frequency band compared to the floor structure 100 of the comparative example. Furthermore, the first floor structure 200A of the second embodiment also has an anti-resonance between the resonant frequency of the air spring resonance 210 and the resonant frequency of the sound absorbing layer amplitude resonance 212. As shown in Fig. 14, the first floor structure 200A of the second embodiment has been confirmed to have an improved insertion loss in a wide frequency range (315 Hz or more) from the mid-frequency band to the high-frequency band, compared to the floor structure of the modified example, due to the synergistic effect of these factors. The same tendency was also confirmed in trial calculations using simulation software.

[0050] Next, in the second floor structure 200B of the second embodiment, the weight of the mass elements as a whole is not changed, and the weight distribution between the non-breathable layer and the compressed fiber layer is changed, and the insertion loss is compared. In detail, in addition to the second floor structure 200B of the second embodiment, which has a compressed fiber layer of 800 gsm and a non-breathable layer of 100 gsm, Comparative Example 1, which has a compressed fiber layer of 850 gsm and a non-breathable layer of 50 gsm, Comparative Example 2, which has a compressed fiber layer of 700 gsm and a non-breathable layer of 200 gsm, Comparative Example 3, which has a compressed fiber layer of 500 gsm and a non-breathable layer of 400 gsm, and Comparative Example 4, which has a compressed fiber layer of 300 gsm and a non-breathable layer of 600 gsm, are set, and the insertion loss of each is calculated by simulation software. As shown in FIG. 15, it was confirmed that the smaller the basis weight of the non-breathable layer, the lower the insertion loss in the high frequency band (1000 Hz or more), but the insertion loss in the mid-frequency band (315 Hz to 630 Hz) is improved, and the soundproofing performance in the mid-frequency band is improved. As a result, in the two-floor structure 200B, it is desirable for the mass per unit area of ​​the non-breathable layer to be 50 gsm or more and 200 gsm or less. In other words, it was confirmed that it is desirable for the non-breathable layer to have a small basis weight not only in the first floor structure 200A but also in the two-floor structure 200B.

[0051] <Other embodiments> The present invention is not limited to the above-described embodiment, and can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. For example, the following embodiments are also included within the technical scope of the present invention. (1) In the above embodiment, the skin layer is provided on the interior side of the compressed fiber layer, but the skin layer is not essential. For example, if there is a component that constitutes the design surface of the vehicle compartment, it is sufficient that the sound absorbing layer, the air impermeable layer, and the compressed fiber layer are laminated between the component and the partition member. (2) In the above embodiment, the vehicle compartment soundproofing structure of the present invention is used in the floor structure of the vehicle, but is not limited thereto. The vehicle compartment soundproofing structure of the present invention may also be used in the wall of the vehicle, the boundary with the engine room, etc. (3) Furthermore, the vehicle compartment soundproofing structure of the present invention is not limited to being provided in vehicles, but can be applied to various types of vehicles. [Explanation of symbols]

[0052] Reference Signs List 10...vehicle floor structure (vehicle compartment soundproofing structure), 10A...first floor structure, 10B...second floor structure, 12...floor panel (compartment member), 14...floor silencer (sound absorbing layer), 16...carpet, 30...non-breathable layer, 32...compressed fiber layer, 32A...first compressed fiber layer, 32B...second compressed fiber layer, 36...adhesive layer, 36A...first adhesive layer, 36B...second adhesive layer, 200...vehicle floor structure, 200A...first floor structure, 200B...second floor structure, 204...adhesive layer

[0053] Aa, Ab...area [foot reservoir], A1...first area, A2...second area

Claims

1. A vehicle cabin soundproofing structure for suppressing noise from outside a vehicle cabin, comprising: A partition member that serves as a main component for partitioning the vehicle compartment; A sound absorbing layer disposed on the indoor side of the partition member and having a large number of voids therein; A non-breathable layer arranged on the indoor side of the sound absorbing layer and made of a non-breathable material; a compressed fiber layer formed mainly of a compressed fiber aggregate, the compressed fiber layer being disposed on the indoor side of the non-breathable layer; 1. A vehicle compartment soundproofing structure comprising: a first region where the adhesive strength between said non-breathable layer and said compressed fiber layer is relatively weak; and a second region where the adhesive strength is relatively strong.

2. The partition member is a floor panel that partitions a floor of a vehicle, The first area is a foot well area that is a foot area of ​​a seated occupant on the floor panel, and the second area is at least a part of the floor panel excluding the foot well area.

2. The vehicle cabin soundproofing structure according to claim 1, wherein the sound absorbing layer in the first region has a thickness greater than that of the sound absorbing layer in the second region.

3. 3. The vehicle cabin soundproofing structure according to claim 1 or 2, wherein the non-breathable layer has a mass per unit area of ​​15 gsm or more and 400 gsm or less, preferably 50 gsm or more and 200 gsm or less.

4. 4. The vehicle cabin soundproofing structure according to claim 1, wherein the compressed fiber layer has a mass per unit area of ​​300 gsm or more and 1500 gsm or less, preferably 600 gsm or more and 1000 gsm or less.

5. 5. The vehicle compartment soundproof structure according to claim 1, wherein in the first region, the non-breathable layer and the compressed fiber layer are not bonded to each other.

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