Vehicle floor panel structure

Abstract

To provide a floor panel structure that can provide reduced road noise and improved riding comfort in a compatible manner and can reduce time and effort required for material development.SOLUTION: A floor panel structure includes: an upper surface part; a lower surface part located below the upper surface part; and an intermediate layer part located between the upper surface part and the lower surface part. The intermediate layer part is configured, by vertically stacking a plurality of layers including damping layers each having a viscoelasticity and packed layers each having a loss coefficient smaller than that of the damping layer. The loss coefficient of the packed layer is set to be 10% or more and below 100% of the loss coefficient of the damping layer. A proportion of volume of the packed layers account for in the intermediate layer part is set to be larger than the proportion of volume of the damping layers account for in the intermediate layer part, and the damping layers are disposed both in a top layer and a bottom layer of the intermediate layer part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to the structure of a floor panel installed in a vehicle. [Background technology]

[0002] Various studies have been conducted to improve passenger comfort.

[0003] For example, Patent Document 1 discloses a structure in which a panel member used as a partition between the engine compartment and the cabin has a sound-insulating effect in order to improve the quietness inside the cabin. Specifically, Patent Document 1 discloses a hollow double-wall structure in which an inner wall and an outer wall are joined together such that a space is partitioned between them, and a damping material is filled in this space. With this structure, vibrations applied to the panel member from the engine compartment side can be dampened, and the transmission of noise from the engine compartment to the cabin side can be suppressed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-24873 [Overview of the project] [Problems that the invention aims to solve]

[0005] In addition to the bulkheads mentioned above, the panel members that make up the cabin walls include floor panels that form the bottom of the cabin. The floor panels also need to suppress so-called road noise, which is noise transmitted from outside the cabin into the cabin. Therefore, it is conceivable to apply the structure of Patent Document 1 to the floor panels to make the physical properties of the damping material capable of damping vibrations that are perceived as road noise. However, since seats on which occupants sit are provided on the floor panels, the floor panels also need to reduce vibrations that affect ride comfort. The vibrations that affect ride comfort are membrane vibrations that occur in the floor panels, and the frequency of these membrane vibrations and the frequency of vibrations that occupants perceive as road noise are different from each other. Specifically, the frequency of membrane vibrations in the floor panels is lower than the frequency of vibrations that are perceived as road noise. Therefore, simply applying the structure of Patent Document 1 to the floor panels to make the physical properties of the damping material as described above will reduce road noise, but will not improve ride comfort.

[0006] Here, if the physical properties of the damping material used above are such that they can dampen vibrations perceived as road noise and reduce membrane vibrations of the floor panel, it is possible to achieve both reduced road noise and improved ride comfort. However, developing such a material is time-consuming. In particular, the detailed frequencies of each vibration and the required degree of road noise reduction and ride comfort improvement differ depending on the vehicle type, so developing an appropriate material for each case requires considerable effort.

[0007] This invention has been made in view of the circumstances described above, and aims to realize a floor panel that can achieve both a reduction in road noise and an improvement in ride comfort, while also reducing the effort required for material development. [Means for solving the problem]

[0008] To solve the aforementioned problems, the present invention provides a vehicle floor panel structure comprising: an upper portion constituting the bottom surface of the vehicle cabin; a lower portion located below the upper portion; and an intermediate layer portion located between the upper portion and the lower portion, wherein the intermediate layer portion is constructed by stacking a plurality of layers in the vertical direction, each layer including a viscoelastic damping layer and a filling layer having a smaller loss coefficient than the damping layer, the loss coefficient of the filling layer being 10% or more and less than 100% of the loss coefficient of the damping layer, the proportion of the volume occupied by the filling layer in the intermediate layer portion being greater than the proportion of the volume occupied by the damping layer in the intermediate layer portion, and the damping layer being arranged in both the uppermost and lowermost layers of the intermediate layer portion (Claim 1).

[0009] According to the present invention, since a damping layer having viscoelastic properties and a high loss coefficient is provided in the intermediate layer, the vibration of the floor panel can be dampened by the intermediate layer. Moreover, since the damping layer is arranged in the uppermost and lowermost layers of the intermediate layer, which are adjacent to the upper and lower surfaces respectively, vibrations from the upper and lower surfaces can be directly transmitted to the damping layer, so that vibrations from the upper and lower surfaces can be effectively dampened by this damping layer.

[0010] Furthermore, a packing layer with a low loss coefficient is provided in the intermediate layer. Therefore, the packing layer vibrates in a phase-shifted manner in response to the film vibrations of the upper and lower surfaces, thereby reducing the amplitude and vibration energy of the film vibrations of the upper and lower surfaces.

[0011] Furthermore, by providing the packing layer in the intermediate layer with a higher volume ratio than the damping layer, the vibration energy of the membrane vibration can be further reduced. Additionally, by positioning the packing layer between the damping layers located in the uppermost and lowermost layers, the membrane vibrations of the upper and lower surfaces are transmitted to the packing layer via the easily deformable damping layer, thereby increasing the phase shift of the packing layer relative to the membrane vibrations of the upper and lower surfaces. Consequently, the vibration energy of the membrane vibrations of the upper and lower surfaces can be effectively reduced by the packing layer.

[0012] Furthermore, the inventors of this invention have diligently studied the physical properties of the damping layer and the filling layer, as well as the reduction margin for membrane vibration in the upper and lower surfaces. As a result, they have found that if the loss coefficient of the filling layer is set to 10% or more and less than 100% of the loss coefficient of the damping layer, the above-mentioned membrane vibration can be significantly reduced compared to the case where the intermediate layer is constructed using only the materials constituting the damping layer. Thus, according to the present invention, by setting the loss coefficient of the filling layer to 10% or more and less than 100% of the loss coefficient of the damping layer, the membrane vibration in the upper and lower surfaces can be reliably reduced, thereby reliably improving ride comfort.

[0013] Thus, according to the present invention, it is possible to reduce road noise by damping vibrations of the floor panel that are perceived as road noise, and to improve ride comfort by keeping the membrane vibrations of the floor panel to a minimum.

[0014] Furthermore, according to the present invention, even when the frequency of vibrations applied to the floor panel changes due to changes in vehicle type, etc., or when the desired degree of road noise reduction and ride comfort improvement changes, it becomes possible to achieve an appropriate balance between road noise reduction and ride comfort improvement by adjusting the number, thickness, and ratio of damping layers and filling layers. Therefore, compared to the case where the intermediate layer is composed of a single viscoelastic damping member and the physical properties of this damping member are adjusted to obtain an appropriate balance between road noise reduction and ride comfort improvement, the effort required for adjustment can be reduced. Accordingly, according to the present invention, it is possible to realize a floor panel that can achieve both road noise reduction and ride comfort improvement, while also reducing the effort required for material development.

[0015] In the above configuration, preferably, the density of the packed layer is 100% or less of the density of the damping layer (Claim 2).

[0016] According to the inventors' findings, by reducing the density of the filling layer to 100% or less of the density of the damping layer, the reduction in membrane vibration at the upper and lower surfaces becomes larger. Therefore, with the above configuration, ride comfort can be more reliably improved.

[0017] In the above configuration, preferably, the intermediate layer portion has the damping layer sandwiched between the two filling layers on the inner side in the vertical direction from the uppermost layer and the lowermost layer of the intermediate layer portion (Claim 3).

[0018] According to this configuration, a damping layer with a high density is arranged not only in the uppermost layer and the lowermost layer but also near the center in the vertical direction of the intermediate layer portion. Therefore, while making the volume ratio of the damping layer smaller than the volume ratio of the filling layer, the weight on the inner side in the vertical direction of the intermediate layer portion and the moment of inertia of the intermediate layer portion can be increased, and the phase shift between the intermediate layer portion and the filling layer with respect to the upper surface portion and the lower surface portion can be increased. Accordingly, the film vibration between the upper surface portion and the lower surface portion can be more reliably reduced.

[0019] In the above configuration, preferably, the elastic modulus of the filling layer is 200 times or more the elastic modulus of the damping layer (Claim 4).

[0020] According to the findings of the inventors of the present application, by making the elastic modulus of the filling layer 200 times or more the elastic modulus of the damping layer, the reduction cost of the film vibration between the upper surface portion and the lower surface portion is significantly increased. Therefore, according to the above configuration, the riding comfort can be made more reliably good.

[0021] In the above configuration, preferably, the elastic modulus of the filling layer is 600 times or less the elastic modulus of the damping layer (Claim 5).

[0022] According to the findings of the inventors of the present application, by making the elastic modulus of the filling layer 600 times or less the elastic modulus of the damping layer, the reduction cost of the film vibration between the upper surface portion and the lower surface portion can be surely increased. Therefore, according to the above configuration, the riding comfort can be made more reliably good.

[0023] In the above configuration, preferably, the intermediate layer portion is configured by laminating 10 layers of the damping layer and the filling layer in the vertical direction, and the second layer from the top and the second layer from the bottom of the intermediate layer portion are the filling layers (Claim 6).

[0024] In this configuration, the damping layers positioned at the top and bottom are sandwiched between the top or bottom surface and the filling layer, thereby increasing the strain of these damping layers and enhancing the vibration damping effect of the damping layers. [Effects of the Invention]

[0025] As described above, the vehicle floor panel structure of the present invention makes it possible to achieve both a reduction in road noise and an improvement in ride comfort, while also reducing the effort required for material development. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic top view showing the structure of a vehicle according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic perspective view of floor panel 1. [Figure 3] Figure 3 is a schematic diagram showing the cross-sectional structure of floor panel 1. [Figure 4] Figure 4 shows the layer pattern of the floor panels. [Figure 5] Figure 5 is a graph showing the results of the mode attenuation ratios investigated for multiple floor panel patterns. [Figure 6] Figure 6 is a graph showing the results of floor vibration reduction measurements for multiple floor panel patterns. [Figure 7] Figure 7 is a graph showing the relationship between internal mass and floor vibration reduction for several floor panel patterns. [Figure 8] Figure 8 is a graph showing the relationship between the ratio of elastic moduli between the damping layer and the filling layer and the floor vibration reduction capacity. [Figure 9] Figure 9 is a graph showing the relationship between the density ratio of the damping layer and the filling layer and the floor vibration reduction capacity. [Figure 10] Figure 10 illustrates the procedure for calculating the equivalent modulus of elasticity of an object composed of multiple layers. [Modes for carrying out the invention]

[0027] Figure 1 is a schematic top view showing the structure of a vehicle to which the floor panel structure of the present invention is applied. Figure 2 is a schematic perspective view of the floor panel 1. The floor panel 1 is a plate-shaped member as a whole. The floor panel 1 is installed on the vehicle V such that its upper surface constitutes the bottom surface of the cabin of the vehicle V, and its lower surface constitutes the lower surface of the vehicle body V0 of the vehicle V. In the example of Figure 1, the floor panel 1 has a substantially rectangular shape extending in a predetermined direction. In the example of Figure 1, two floor panels 1 are installed side by side in the vehicle width direction on the vehicle V, each extending in the longitudinal direction of the vehicle V. A seat (not shown) is placed on top of each floor panel 1, and a support part V1 for supporting the seat is arranged above the floor panel 1.

[0028] Figure 3 is a schematic diagram showing the cross-sectional structure of the floor panel 1. The floor panel 1 has an upper surface portion 10 that constitutes the upper surface of the floor panel 1, a lower surface portion 20 that constitutes the lower surface of the floor panel 1, an intermediate layer portion 40 positioned between them, and a wall portion 30 that connects the upper surface portion 10 and the lower surface portion 20 so as to surround the outer periphery of the intermediate layer portion 40.

[0029] The lower portion 20 constitutes the underside of the vehicle body V0. In other words, the lower portion 20 functions as a so-called under cover. The upper portion 10 constitutes the upper surface of the cabin of the vehicle V. In other words, the upper portion 10 functions as a so-called floor mat. In this embodiment, the upper portion 10 and the lower portion 20 are each made of resin panel members.

[0030] The intermediate layer 40 is composed of multiple layers stacked vertically, each including a damping layer 50 and a filling layer 60 with different physical properties than the damping layer 50. Specifically, the damping layer 50 is made of a material having predetermined physical properties formed in layers, and the filling layer 60 is made of a material having different physical properties than the material constituting the damping layer 50 formed in layers. In the intermediate layer 40, these layers are arranged stacked vertically.

[0031] In this embodiment, as shown in Figure 3, a total of 10 layers of damping layers 50 and filling layers 60 are stacked. Hereinafter, these 10 layers will be referred to as the 1st layer S1, 2nd layer S2, 3rd layer S3, 4th layer S4, 5th layer S5, 6th layer S6, 7th layer S7, 8th layer S8, 9th layer S9, and 10th layer S10, respectively, from top to bottom.

[0032] In this embodiment, the first layer S1, the uppermost layer of the intermediate layer 40, the fourth layer S4, the seventh layer S7, and the tenth layer, the lowermost layer of the intermediate layer 40, are the damping layers 50, and the remaining six layers are the filling layers 60.

[0033] In this embodiment, the volumes of each packing layer 60 and each damping layer 50 are set to be approximately the same. More specifically, the thickness and area (cross-sectional area in the direction perpendicular to the vertical direction) of each packing layer 60 and each damping layer 50 are set to be the same value. As a result, the volume ratio of the packing layer 60 to the intermediate layer 40 is 60%, and the volume ratio of the damping layer 50 to the intermediate layer 40 is 40%. The intermediate layer 40 is configured such that the volume ratio of the packing layer 60 to the intermediate layer 40 is greater than the volume ratio of the damping layer 50 to the intermediate layer 40.

[0034] The damping layer 50 has viscoelastic properties. For example, an acrylic-based viscoelastic material is used as the damping layer 50.

[0035] The loss coefficient of the filling layer 60 is smaller than that of the damping layer 50, and the loss coefficient of the filling layer 60 is less than 100% of the loss coefficient of the damping layer 50. Furthermore, the loss coefficient of the filling layer 60 is set to a value of 10% or more of the loss coefficient of the damping layer 50. For example, a material with a loss coefficient of 1.0 is used as the damping layer 50, and a material with a loss coefficient of 0.1, which is 10% of the loss coefficient of the damping layer 50, is used as the filling layer 60. For example, a urethane-based rigid foam filler with a loss coefficient set as described above is used as the filling layer 60.

[0036] The elastic modulus of the filling layer 60 is set to be at least 200 times and no more than 600 times the elastic modulus of the damping layer 50. For example, if the damping layer 50 has an elastic modulus of 1.5 MPa, the filling layer 60 may have an elastic modulus of 800 MPa, which is about 600 times the elastic modulus of the damping layer 50.

[0037] Furthermore, the density of the packed bed 60 is set to be 100% or less of the density of the damping bed 50. For example, if the density of the damping bed 50 is 1.0 × 10⁻⁶ -6 (Kg / mm 3 A material of the following type is used, and the density of the packed bed 60 is 5.8 × 10 -7 (Kg / mm 3 ) and a material with a density of about 60% of the damping layer 50 is used.

[0038] As described above, in the above embodiment, a damping layer 50 having viscoelastic properties and a high loss coefficient is provided in the intermediate layer 40 of the floor panel 1. Therefore, the vibration of the floor panel 1, which is recognized as road noise, can be dampened by the intermediate layer 40, thereby reducing road noise. Moreover, in the above embodiment, the damping layer 50 is arranged in the uppermost layer (first layer S1) and the lowest layer (second layer S2) of the intermediate layer 40, and a filling layer 60 is arranged in the second layer S2, which is the second layer from the top of the intermediate layer 40, and the ninth layer S9, which is the second layer from the bottom. Therefore, the vibration of the floor panel 1 can be effectively dampened by the intermediate layer 40.

[0039] Furthermore, in the above embodiment, a filling layer 60 is provided in the intermediate layer 40 of the floor panel 1, with a loss coefficient set to a relatively low value, less than 100% of the loss coefficient of the damping layer 50. Therefore, it is possible to make the filling layer 60 vibrate in response to the membrane vibrations of the upper surface 10 and lower surface 20, thereby creating a phase shift between the vibration of the filling layer 60 and the membrane vibrations of the upper surface 10 and lower surface 20. Consequently, the amplitude and vibration energy of the membrane vibrations of the upper surface 10 and lower surface 20 can be reduced, improving ride comfort. Specifically, the occupants' feet rest on the floor panel 1. Also, as described above, a seat is positioned above the floor panel 1. Therefore, if the floor panel 1 vibrates significantly, this is transmitted to the occupants, reducing ride comfort. Conversely, if the amplitude and vibration energy of the membrane vibrations of the upper surface 10 and lower surface 20 are reduced, the ride comfort felt by the occupants will improve. In particular, in the above embodiment, the volume ratio of the packed layer 60 to the intermediate layer 40 is greater than the volume ratio of the damping layer 50 to the intermediate layer 40. Therefore, the packed layer 60 can reliably reduce membrane vibrations in the upper surface 10 and the lower surface 20.

[0040] Furthermore, in the above embodiment, damping layers 50 are arranged in the uppermost layer (first layer S1) and the lowermost layer (second layer S2) of the intermediate layer 40, the density of the filling layer 60 is set to 100% or less of the density of the damping layer 50, and the damping layer 50 is provided in a position sandwiched between the two filling layers 60, vertically inward from the first layer S1 and the tenth layer S10 of the intermediate layer 40. In addition, in the above embodiment, the elastic modulus of the filling layer 60 is set to 200 times or more and 600 times or less of the elastic modulus of the damping layer 50, and the loss coefficient of the filling layer 60 is set to a value of 10% or more (and less than 100%) of the loss coefficient of the damping layer 50. As a result, the intermediate layer 40 can reliably reduce membrane vibrations of the upper surface 10 and the lower surface 20, thereby reliably improving ride comfort.

[0041] Furthermore, according to the above embodiment, even when the frequency of vibrations applied to the floor panel changes due to changes in vehicle type, etc., or when the desired degree of road noise reduction and ride comfort improvement changes, the road noise reduction effect and ride comfort improvement effect can be achieved to an appropriate degree by adjusting the number, thickness, and ratio of the damping layer 50 and the filling layer 60. Therefore, compared to the case where the intermediate layer is composed of a single viscoelastic damping member and the physical properties of this damping member are adjusted to appropriately obtain both the road noise reduction effect and the ride comfort improvement effect, the effort required for material development can be reduced.

[0042] The details of the road noise reduction and ride comfort improvement effects described above will be explained using Figures 4 to 10.

[0043] The inventors of the present invention investigated the effect of improving ride comfort on multiple floor panels, each having a different layer pattern for the intermediate layer. Figure 4 shows the layer pattern of each floor panel investigated. In other words, it is a schematic representation of the intermediate layer of each floor panel. The intermediate layer of each floor panel shown in Figure 4 is composed of a total of 10 layers, similar to the embodiment described above. The volume of each layer is also the same as in the embodiment described above. In addition, in each floor panel shown in Figure 4, the volume of the damping layer 50 in the intermediate layer 40 is 40%, and the volume of the filling layer 60 in the intermediate layer 40 is 60%.

[0044] The pattern shown in Figure 4(P1) is the same as the pattern in the above embodiment. That is, in the pattern shown in Figure 4(P1), the uppermost layer S1, the fourth layer S4, the seventh layer S7, and the bottommost layer S10 of the intermediate layer 40 are composed of damping layers 50, and the remaining second layer S2, third layer S3, fifth layer S5, sixth layer S6, eighth layer S8, and ninth layer S9 are composed of filling layers 60. Hereafter, a floor panel according to the above embodiment, in which the layer pattern is the pattern of Figure 4(P1), will be referred to as the first panel.

[0045] In the pattern shown in Figure 4 (P2), the first layer S1, the fifth layer S5, the sixth layer S6, and the tenth layer S10 are composed of damping layers 50, while the remaining second to fourth layers S4 and seventh to ninth layers S7 are composed of filling layers 60. Hereafter, a floor panel with the layer pattern shown in Figure 4 (P2) will be referred to as the second panel.

[0046] In the pattern shown in Figure 4 (P3), the first layer S1, the third layer S3, the eighth layer S8, and the tenth layer S10 are composed of damping layers 50, while the remaining second layer S2, fourth to seventh layers S7, and ninth layer S9 are composed of filling layers 60. Hereafter, a floor panel with the layer pattern shown in Figure 4 (P3) will be referred to as the third panel.

[0047] In the pattern shown in Figure 4 (P4), the first layer S1, the second layer S2, the ninth layer S9, and the tenth layer S10 are composed of damping layers 50, while the remaining third layer S3 to eighth layer S8 are composed of packing layers 60. Hereafter, a floor panel with the layer pattern shown in Figure 4 (P4) will be referred to as the fourth panel.

[0048] In the pattern shown in Figure 4 (P5), the second layer S2, the third layer S3, the eighth layer S8, and the ninth layer S9 are composed of damping layers 50, while the remaining first layer S1, fourth to seventh layers S7, and tenth layer S10 are composed of filling layers 60. Hereafter, a floor panel with the layer pattern shown in Figure 4 (P5) will be referred to as the fifth panel.

[0049] In the pattern shown in Figure 4 (P6), the third layer S3, the fourth layer S4, the seventh layer S7, and the eighth layer S8 are composed of damping layers 50, while the remaining first layer S1, second layer S2, fifth layer S5, sixth layer S6, ninth layer S9, and tenth layer S10 are composed of filling layers 60. Hereafter, a floor panel whose layer pattern is the same as the pattern in Figure 4 (P6) will be referred to as the sixth panel.

[0050] In the pattern shown in Figure 4 (P7), the fourth layer S4 to the seventh layer S7 are composed of damping layers 50, while the remaining first layer S1 to the third layer S3, and the eighth layer S8 to the tenth layer S10 are composed of packing layers 60. Hereafter, a floor panel whose layer pattern is the same as that of Figure 4 (P7) will be referred to as the seventh panel.

[0051] In the pattern shown in Figure 4 (P8), the first layer S1 to the fourth layer S4 are composed of damping layers 50, and the remaining fifth layer S5 to the tenth layer S10 are composed of packing layers 60. Hereafter, a floor panel whose layer pattern is the same as the pattern in Figure 4 (P8) will be referred to as the eighth panel.

[0052] In the pattern shown in Figure 4 (P9), the 7th layer S7 to the 10th layer S10 are composed of damping layers 50, and the remaining 1st layer S1 to the 6th layer S6 are composed of packing layers 60. Hereafter, a floor panel whose layer pattern is the same as the pattern in Figure 4 (P9) will be referred to as the 9th panel.

[0053] Figure 5 is a graph showing the results of investigating the mode damping ratio for the nine floor panel patterns described above. Note that the results shown in Figure 5 and the graphs in Figures 6 and 7 (described later) are based on the damping layer 50 having an elastic modulus of 1.5 (MPa) and a density of 1.0 × 10⁻⁶. -7 (Kg / mm 3 ), the viscoelastic material has a loss factor of 1.0, and the packed layer 60 has an elastic modulus of 800 (MPa) and a density of 5.8 × 10 -7 (Kg / mm 3 ), and the results are for when a foaming filler with a loss coefficient of 0.1 is used. In other words, the results shown in the graph of Figure 5 are for when the loss coefficient of the packed layer 60 is 10% of the loss coefficient of the damping layer 50, the elastic modulus of the packed layer 60 is about 600 times that of the damping layer 50, and the density of the packed layer 60 is about 60% of the density of the damping layer 50.

[0054] As shown in Figure 5, the mode damping ratios of the first panel (P1) to the fourth panel (P4), in which damping layers 50 are placed on the uppermost layer S1 and the lowermost layer S10 of the intermediate layer 40, are higher than the mode damping ratios of the fifth panel (P5) to the ninth panel (P9), in which a filling layer 60 is placed on at least one of the first layer S1 and the tenth layer S10.

[0055] Furthermore, the mode attenuation ratios of the first panel (P1) to the third panel (P3), in which the second layer S2 (second from the top) and the ninth layer S9 (second from the bottom) of the intermediate layer 40 are higher than those of the fourth panel (P4), in which the attenuation layer 50 is placed in the second layer S2 and the ninth layer S9.

[0056] In contrast, the floor panel 1 according to the above embodiment is composed of the same pattern as the first panel (P1), and in the floor panel 1 according to the above embodiment, damping layers 50 are arranged in the first layer S1 and the tenth layer S10, and filling layers 60 are arranged in the second layer S2 and the ninth layer S9. Therefore, according to the above embodiment, a floor panel 1 with a high mode damping ratio is realized, and vibrations transmitted from outside the cabin via the upper surface portion 10 and the lower surface portion 20 that are recognized as road noise can be effectively dampened.

[0057] Here, the reason why the mode damping ratio is high in the first panel (P1) to the fourth panel (P4), where the damping layer 50 is placed in the first layer S1 and the tenth layer S10, is thought to be because the damping layer 50 is placed in the first layer S1 and the tenth layer S10, which are in direct contact with the upper surface 10 and the lower surface 20, thereby directly transmitting the vibration energy of the upper surface 10 and the lower surface 20 to the damping layer 50 and effectively accumulating it in the damping layer 50 as strain energy.

[0058] Furthermore, the reason why the mode damping ratio of the first panel (P1) to the third panel (P3), in which the packing layer 60 is placed in the second layer S2 and the ninth layer S9, is higher than that of the fourth panel (P4), in which the damping layer 50 is also placed in the second layer S2 and the ninth layer S9, is thought to be because, in the first panel (P1) to the third panel (P3), the damping layer 50 placed in the first layer S1 and the tenth layer S10 is sandwiched between the upper surface portion 10 or the lower surface portion 20 and the packing layer 60, thereby promoting the strain of the damping layer 50 and increasing the strain energy accumulated in the damping layer 50.

[0059] Figure 6 is a graph showing the results of a study investigating the effect of the nine floor panel patterns described above on improving ride comfort.

[0060] Specifically, the inventors of this invention conducted simulations in which vibrations within the range of 50Hz to 200Hz, which are known to have a significant impact on ride comfort, were applied to each pattern of floor panel, and the inertance of each floor panel when the above vibrations were applied was calculated. Similarly, simulations were also conducted in which the above vibrations were applied to a hollow panel member, that is, a member consisting only of the upper surface 10, lower surface 20, and wall surface 30, excluding the intermediate layer 40 from the floor panel, and the inertance of this member was calculated as a reference value. Then, by comparing the inertance of each floor panel with the reference value, the reduction rate of the inertance of each floor panel relative to the reference value was calculated as an index representing the effect of improving ride comfort performance. Specifically, the floor vibration reduction (%) was calculated by subtracting the inertance of each floor panel from the reference value and dividing the result by the reference value. In other words, if the inertance of a floor panel of a predetermined pattern is set to A1 and the baseline value to A0, the floor vibration reduction (%) is calculated as follows: Floor vibration reduction (%) = (A0 - A1) / A0 × 100. The vertical axis of the graph in Figure 6 represents the floor vibration reduction (%) calculated in this way. Note that the higher the floor vibration reduction, the greater the vibration reduction effect and the better the ride comfort.

[0061] As shown in Figure 6, the floor vibration reduction of the first panel (P1) to the fourth panel (P4), in which damping layers 50 are placed on the first layer S1 and the tenth layer S10, is higher than that of the fifth panel (P5) to the ninth panel (P9), in which a filling layer 60 is placed on at least one of the first layer S1 and the tenth layer S10. In particular, the floor vibration reduction of the first panel (P1) to the fourth panel (P4) is higher than 5%, which is significantly higher than that of the hollow panel member obtained by removing the intermediate layer 40 from the floor panel.

[0062] In contrast, the floor panel 1 according to the above embodiment is composed of the same pattern as the first panel (P1), and in the floor panel 1 according to the above embodiment, the damping layer 50 is arranged in the first layer S1 and the tenth layer S10. Therefore, according to the above embodiment, the floor vibration reduction amount can be significantly increased. In other words, the membrane vibration of the upper surface 10 and the lower surface 20 can be significantly reduced, and the ride comfort can be improved.

[0063] Here, the floor vibration reduction capacity of the first panel (P1) to the fourth panel (P4), in which damping layers 50 are placed in the first layer S1 and the tenth layer S10, is higher than that of the other panels (P5 to P9), in which a filling layer 60 is placed in at least one of the first layer S1 and the tenth layer S10, and this is thought to be due to the following reasons.

[0064] In a configuration where damping layers 50 are placed on the first layer S1 and the tenth layer S10, vibrations applied to the upper surface 10 and the lower surface 20 are transmitted to the entire packing layer 60 via the damping layers 50, which are prone to deformation due to their high loss coefficient. As a result, a phase shift occurs in the vibrations applied to the upper surface 10 and the lower surface 20 as they are transmitted to the packing layer 60, and the phase shift of the packing layer 60 relative to the upper surface 10 and the lower surface 20 becomes large. Consequently, in a configuration where damping layers 50 are placed on the first layer S1 and the tenth layer S10, the floor vibration reduction capacity is high.

[0065] Furthermore, in the configuration where damping layers 50 are placed in the first layer S1 and the tenth layer S10, the entire intermediate layer 40 functions as a region that extends from the damping layer 50 positioned closest to the upper surface 10 to the damping layer 50 positioned closest to the lower surface 20, and transmits vibrations of the upper surface 10 and lower surface 20 to the packing layer 60 with a phase difference (hereinafter, as appropriate, referred to as the phase lag region). As a result, in the configuration where damping layers 50 are placed in the first layer S1 and the tenth layer S10, the volume, mass, and consequently the moment of inertia of the phase lag region become larger. Therefore, in this configuration, the phase difference of the phase lag region and the packing layer 60 contained therein with respect to the upper surface 10 and lower surface 20 becomes larger, and the floor vibration reduction capacity increases.

[0066] Figure 7 is a graph of Figure 6 organized by the mass of the phase lag region described above. Specifically, the graph in Figure 7 has the mass of the phase lag region on the horizontal axis and the floor vibration reduction amount on the vertical axis, plotting the values ​​for the first panel (P1) to the ninth panel (P9). As is clear from Figure 7, there is a high correlation between the mass of the phase lag region and the floor vibration reduction amount, and as mentioned above, it can be said that the floor vibration reduction amount is higher when the mass of the phase lag region is large. Note that in Figure 7, the eighth panel (P8) and the ninth panel (P9) are shown as having the same phase lag region mass as the seventh panel (P7).

[0067] Furthermore, as shown in the graph in Figure 5, the floor vibration reduction of the first panel (P1) to the third panel (P3), in which the damping layer 50 is provided in a position sandwiched between two filling layers 60 in the vertical direction inward of the first layer S1 and the tenth layer S10 of the intermediate layer 40, is higher than that of the fourth panel (P4), which does not have a damping layer 50 sandwiched between two filling layers 60 in the vertical direction inward of the first layer S1 and the tenth layer S10 of the intermediate layer 40. Specifically, in the first panel (P1), the damping layer 50 located in the fourth layer S4 is sandwiched between the filling layers 60 located in the third layer S3 and the fifth layer S5, and the damping layer 50 located in the seventh layer S7 is sandwiched between the filling layers 60 located in the sixth layer S6 and the eighth layer S8. Furthermore, in the second panel (P2), the damping layer 50 located in the fifth layer S5 and the sixth layer S6 is sandwiched between the packed layer 60 located in the fourth layer S4 and the seventh layer S7. In the third panel (P3), the damping layer 50 located in the third layer S3 is sandwiched between the packed layer 60 located in the second layer S2 and the fourth layer S4, and the damping layer 50 located in the eighth layer S8 is sandwiched between the packed layer 60 located in the seventh layer S7 and the ninth layer S9. On the other hand, in the fourth panel (P4), the packed layer 60 is continuously arranged from the third layer S3 to the eighth layer S8, and there is no damping layer 50 sandwiched between two packed layers 60.

[0068] The reason why the floor vibration reduction capacity is high in the first panel (P1) to the third panel (P3) is thought to be because the inclusion of a relatively dense damping layer 50 in the phase-shift region increases the weight and moment of inertia of the phase-shift region, resulting in a larger phase shift relative to the upper surface 10 and lower surface 20 of the filling layer 60 included in the phase-shift region.

[0069] In contrast, the floor panel 1 according to the above embodiment is composed of the same pattern as the first panel (P1), and a damping layer 50 is provided in the vertical direction inward from the first layer S1 and the tenth layer S10 of the intermediate layer 40, sandwiched between two filling layers 60. Furthermore, the density of the filling layer 60 is set to 100% or less of the density of the damping layer 50, so that the density of the damping layer 50 is equal to or greater than the density of the filling layer 60. Therefore, according to the above embodiment, the floor vibration reduction amount can be reliably increased, and the ride comfort can be improved.

[0070] Furthermore, the inventors of the present invention investigated the relationship between the ratio of the elastic moduli of the damping layer 50 and the filling layer 60 and the floor vibration reduction capacity, and the relationship between the ratio of the densities of the damping layer 50 and the filling layer 60 and the floor vibration reduction capacity. Figures 8 and 9 are graphs showing the results of this investigation. Specifically, the inventors of the present invention performed simulations on floor panels in which the ratio of the elastic moduli and density ratios of the damping layer 50 and the filling layer 60 were changed in various ways, and investigated the floor vibration reduction capacity of each floor panel. In the graph of Figure 8, the horizontal axis is the elastic moduli ratio, which is the ratio of the elastic moduli of the filling layer 60 to the elastic moduli of the damping layer 50, and the vertical axis is the floor vibration reduction capacity described above. In the graph of Figure 9, the horizontal axis is the density ratio, which is the ratio of the density of the filling layer 60 to the density of the damping layer 50, and the vertical axis is the floor vibration reduction capacity described above. In addition, the graphs in Figures 8 and 9 show the results when the equivalent elastic moduli and average density of the intermediate layer 40 are kept constant and the elastic moduli ratio and density ratio are changed.

[0071] Here, the average density is the average value of the densities of the intermediate layer 40, which is the total weight of the intermediate layer 40 divided by the total volume.

[0072] Furthermore, the equivalent modulus of elasticity is a value corresponding to the overall modulus of elasticity of the intermediate layer 40, and is calculated based on the respective moduli of elasticity of the damping layer 50 and the filling layer 60, as well as the respective dimensions of the damping layer 50 and the filling layer 60.

[0073] FIG. 10 is a diagram for explaining a procedure for calculating the equivalent elastic modulus of an object composed of a plurality of layers. Here, as shown in FIG. 10, an example of calculating the equivalent elastic modulus of an object composed of three layers made of substances with different elastic moduli and different thicknesses while having the same cross-sectional area (the area of a plane orthogonal to the thickness direction) will be described. Hereinafter, each layer of the object B in FIG. 10 will be referred to as the first layer D1, the second layer D2, and the third layer D3 in order from the top. In the example of FIG. 10, the equivalent elastic modulus E of the object B is calculated by the following formula (1). E = √(αE T2 + βE H2 ) ··· (1) In formula (1), α and β are coefficients whose sum of α and β is 1. E T is a value corresponding to the longitudinal elastic coefficient of the object B, and is calculated using the following formula (2) by regarding the three layers as three springs connected in series. E H is a value corresponding to the transverse elastic coefficient of the object B, and is calculated by the following formula (3) by regarding the three layers as three springs connected in parallel. E T = E1E2E3(L1 + L2 + L3) / (E1E2L3 + E2E3L1 + E1E3L2) ··· (2) E H =(E1L1 + E2L2 + E3L3) / (L1 + L2 + L3) ··· (3) E1, E2, and E3 are the elastic moduli of the first layer D1, the second layer D2, and the third layer D3, respectively. Also, as shown in FIG. 10, L1, L2, and L3 are the thickness dimensions of the first layer D1, the second layer D2, and the third layer D3, respectively.

[0074] In FIG. 8, for each density ratio, the relationship between the elastic modulus ratio and the floor vibration reduction cost is represented by a line. The five lines X1 to X5 in the graph of FIG. 8 represent the above relationship of floor panels with different density ratios. In FIG. 9, for each elastic modulus ratio, the relationship between the density ratio and the floor vibration reduction cost is represented by a line. The five lines X10 to X14 in the graph of FIG. 9 represent the above relationship of floor panels with different elastic modulus ratios.

[0075] As shown in Figure 8, for all density ratios, the floor vibration reduction increases as the elastic modulus increases from 1. Furthermore, for all density ratios, the floor vibration reduction becomes significantly larger when the elastic modulus exceeds 200. However, when the elastic modulus exceeds 600, the floor vibration reduction hardly changes even if the elastic modulus is increased further. In other words, there is almost no effect obtained by increasing the elastic modulus above 600. Therefore, it can be said that if the elastic modulus is set to be between 200 and 600, that is, if the elastic modulus of the filling layer 60 is between 200 and 600 times the elastic modulus of the damping layer 50, a high floor vibration reduction can be reliably obtained.

[0076] In contrast, in the above embodiment, the elastic modulus of the filling layer 60 is set to be 200 times or more the elastic modulus of the damping layer 50. Therefore, a higher floor vibration reduction can be obtained more reliably, and ride comfort can be improved more reliably.

[0077] Furthermore, as shown in Figure 9, for all elastic modulus ratios, the floor vibration reduction amount increases as the density ratio decreases. When the density ratio is 1 or less, the increase in the floor vibration reduction amount relative to the change in density ratio becomes small, and the floor vibration reduction amount is maintained at a high value. From this, it can be said that if the density ratio is 1 or less, that is, if the density of the packed layer 60 is 1 or less than the density of the damping layer 50, a high floor vibration reduction amount can be reliably obtained.

[0078] In contrast, in the above embodiment, the density of the filling layer 60 is set to 100% or less of the density of the damping layer 50, that is, 1 time or less. Therefore, a higher floor vibration reduction can be obtained more reliably, and ride comfort can be improved more reliably.

[0079] In addition to the above-mentioned survey results, the inventors of this application have found that when the loss coefficient of the filling layer 60 is reduced to less than 10%, the vibration damping effect of the filling layer 60 decreases, resulting in a significantly lower floor vibration reduction compared to floor panels with a loss coefficient of 10% or more for the filling layer 60.

[0080] In contrast, in the above embodiment, the density of the filling layer 60 is set to 100% or less of the density of the damping layer 50, that is, 1 time or less. Therefore, a higher floor vibration reduction can be obtained more reliably, and ride comfort can be improved more reliably.

[0081] (modified version) In the above embodiment, the case where the volume ratio of the filling layer 60 to the intermediate layer 40 is 60% was described. However, as described above, ride comfort performance can be improved by making the volume ratio of the filling layer 60 greater than the volume ratio of the damping layer 50. Therefore, the volume ratio of the filling layer 60 to the intermediate layer 40 can be appropriately changed within a range of 50% or more.

[0082] In the above embodiment, a case was described in which damping layers 50 are arranged in the fourth layer S4 and the seventh layer S7, thereby realizing a configuration in which the intermediate layer 40 has a damping layer sandwiched between two packing layers, located vertically inward from the uppermost layer (first layer S1) and the lowest layer (tenth layer S10). However, the arrangement for realizing this configuration is not limited to this.

[0083] For example, the above configuration may be realized by arranging the damping layer 50 in the fifth layer S5 and the sixth layer S6, as in the second panel (P2). Alternatively, the above configuration may be realized by arranging the damping layer 50 in the third layer S3 and the eighth layer S8, as in the third panel (P3).

[0084] Furthermore, as described above, the ride comfort is improved by arranging the damping layer 50 on both the uppermost layer (first layer S1) and the lowest layer (second layer S2) of the intermediate layer 40. Therefore, the intermediate layer 40 may be configured without a damping layer sandwiched between two filling layers in the vertical direction inward from the uppermost layer (first layer S1) and the lowest layer (tenth layer S10).

[0085] For example, the packed layers 60 may be arranged continuously from the third layer S3 to the eighth layer S8, as in the fourth panel (P4).

[0086] However, as described above, if the intermediate layer 40 is configured to have a damping layer sandwiched between two filling layers located vertically inward from the uppermost layer (first layer S1) and the lowest layer (tenth layer S10), the ride comfort can be improved more reliably.

[0087] Furthermore, although the above embodiment described a case where the density of the filling layer 60 is 100% or less of the density of the damping layer 50, the relationship between these densities is not limited to this. However, as described above, if the density of the filling layer 60 is 100% or less of the density of the damping layer 50, a good ride comfort can be reliably achieved.

[0088] Furthermore, in the above embodiment, the case in which the elastic modulus of the filling layer 60 is 200% or more of the elastic modulus of the damping layer 50 was described, but the relationship between these elastic moduli is not limited to this. However, as described above, if the elastic modulus of the filling layer 60 is 200% or more of the elastic modulus of the damping layer 50, a good ride comfort can be reliably achieved.

[0089] Furthermore, although the above embodiment described a case in which the intermediate layer 40 is composed of 10 layers, the total number of layers in the intermediate layer 40 is not limited to this. [Explanation of symbols]

[0090] 1 Floor Panel 10 Top part 20 Bottom part 30 Wall section 40 Middle Class 50 Damping Layer 60 Filled bed

Claims

1. The upper part that forms the bottom surface of the vehicle's cabin, A lower portion located below the upper portion, It comprises an intermediate layer located between the upper portion and the lower portion, The aforementioned intermediate layer is composed of multiple layers stacked vertically, each including a viscoelastic damping layer and a packing layer having a lower loss coefficient than the damping layer. The loss coefficient of the packing layer is 10% or more and less than 100% of the loss coefficient of the damping layer. The proportion of the volume occupied by the packing layer in the intermediate layer is set to be greater than the proportion of the volume occupied by the damping layer in the intermediate layer. A vehicle floor panel structure characterized in that the damping layer is arranged in both the uppermost and lowermost layers of the intermediate layer.

2. In the vehicle floor panel structure described in claim 1, A vehicle floor panel structure characterized in that the density of the filling layer is 100% or less of the density of the damping layer.

3. In the vehicle floor panel structure described in claim 2, A vehicle floor panel structure characterized in that the intermediate layer has the damping layer sandwiched between two of the filling layers, located vertically inward from the uppermost and lowermost layers of the intermediate layer.

4. In the vehicle floor panel structure described in claim 1, A vehicle floor panel structure characterized in that the elastic modulus of the filling layer is 200 times or more the elastic modulus of the damping layer.

5. In the vehicle floor panel structure described in claim 4, A vehicle floor panel structure characterized in that the elastic modulus of the filling layer is 600 times or less the elastic modulus of the damping layer.

6. In the vehicle floor panel structure described in claim 1, The floor panel structure for a vehicle is characterized in that the intermediate layer is composed of 10 layers of the damping layer and the filling layer stacked in the vertical direction, and the second layer from the top and the second layer from the bottom of the intermediate layer are the filling layers.

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