Battery mounting structure of electric vehicles

Abstract

The objective is to provide a battery mounting structure for electric vehicles that can improve NVH (noise, vibration, and harshness) performance. [Solution] The electric vehicle comprises four or more battery modules 10 and a plurality of fixing parts 21 that individually fix each of the plurality of battery modules 10 to the vehicle body 1. The plurality of battery modules 10 are arranged in series in a predetermined direction. The k / m of at least two sets of battery modules 10 and fixing parts 21 becomes the reference k / m. The reference k / m is 1.42 × 10 5 ~1.85×10 7 It is within the range of [N / (m · kg)]. When the maximum k / m that is greater than the reference k / m is taken as the maximum k / m, and the minimum k / m that is less than the reference k / m is taken as the minimum k / m, and D is the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m), then the variance D is 0.1

Description

[Technical Field]

[0001] This invention relates to a battery mounting structure for an electric vehicle. [Background technology]

[0002] Conventionally, in electric vehicles with multiple battery modules mounted on the vehicle body, the individual vibrations of these modules during vehicle operation generate noise, vibration, and harshness (roughness / unpleasantness) that affect the ride comfort inside the cabin. Therefore, improving NVH performance, which is the ability to reduce these noise, vibration, and harshness, has become a challenge for electric vehicles.

[0003] Therefore, in order to improve NVH performance, the electric vehicle described in Patent Document 1 has a configuration in which a battery unit is equipped with multiple battery modules mounted in a battery case, and the mounting rigidity of some battery modules is relatively lower than that of other battery modules.

[0004] This structure enhances the overall vibration damping of the battery unit by reducing the peak amplitude of the amplitude of certain battery modules when subjected to low-frequency vibrations in a specific low-frequency range (20-50 Hz) that occur during vehicle operation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-196429 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in the above structure, the mounting rigidity of some of the battery modules is reduced to dampen vibrations throughout the entire battery unit, but the other battery modules do not contribute to vibration damping, so there is room for improvement in NVH performance.

[0007] Furthermore, in this structure, the vibration damping effect is achieved by reducing the peak amplitude value only around specific frequencies within a narrow low-frequency band (20-50 Hz), making it difficult to improve NVH performance across the wide frequency band that occurs during vehicle operation.

[0008] This invention has been made in view of the circumstances described above, and aims to provide a battery mounting structure for an electric vehicle that can improve NVH performance. [Means for solving the problem]

[0009] To solve the aforementioned problems, the battery mounting structure for an electric vehicle of the present invention comprises a vehicle body, four or more battery modules, four or more fixing parts for individually fixing each of the multiple battery modules to the vehicle body, and a pair of left and right front wheels rotatably mounted on the vehicle body at a position forward of the multiple battery modules on the vehicle body, wherein the multiple battery modules are arranged in series in a predetermined direction, and when the support rigidity of the fixing part is k [N / m] and the mass of the battery module is m [kg], the k / m of at least two sets of the battery module and fixing part sets out of all sets of the battery module and fixing part sets becomes the reference k / m, and the reference k / m is 1.42 × 10 5 ~1.85×10 7It is within the range of [N / (m·kg)], and when the k / m of all the combinations of the battery modules and the fixing parts, which is larger than the reference k / m, is taken as the maximum k / m, and the k / m of all the combinations of the battery modules and the fixing parts, which is smaller than the reference k / m, is taken as the minimum k / m, if the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) is D, then the variance D satisfies 0.1 < D < 8. This is the feature.

[0010] In such a configuration, by utilizing the entirety of a plurality of battery modules and a plurality of fixing parts for fixing them, the vibration of the vehicle body can be effectively attenuated in a wide frequency band, thereby improving the NVH performance. Specifically, vibration attenuation is performed as follows.

[0011] In the above configuration, the vibration input from the front wheels to the vehicle body is sequentially transmitted to a plurality of four or more battery modules arranged in series in a predetermined direction through the fixing parts that fix each battery module to the vehicle body.

[0012] At least two sets of the combinations of all the battery modules and the fixing parts have a k / m equal to the reference k / m. The reference k / m is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)].

[0013] Also, when the k / m of all the combinations of the battery modules and the fixing parts, which is larger than the reference k / m, is taken as the maximum k / m, and the k / m of all the combinations of the battery modules and the fixing parts, which is smaller than the reference k / m, is taken as the minimum k / m, if the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) is D, then the variance D is set such that 0.1 < D < 8.

[0014] As a result, in the frequency band of vibrations input to the vehicle body during vehicle travel, dissipation and interference of vibration energy occur at each fixing part with respect to the vibrations transmitted in order for each of the battery modules in series in a predetermined direction. That is, a vibration damping effect by so-called meta-damping (meta-resonance) is obtained, in which continuous vibration damping along the vibration transmission direction is performed by utilizing the weights of four or more battery modules arranged in series and the loss factors or damping characteristics of their fixing parts.

[0015] In this way, by effectively blocking the vibrations input from the front wheels to the vehicle body using the aggregate of a plurality of battery modules and their fixing parts and suppressing the transmission into the vehicle interior, it is possible to improve the NVH performance of the vehicle.

[0016] Moreover, in the above configuration, the k / m of at least two sets of battery modules and fixing parts is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)] which is a reference k / m with a high vibration damping effect. However, there are two sets having a k / m far from this reference k / m, that is, a set of battery modules and fixing parts having a k / m larger than the reference k / m and being the maximum k / m, and a set of battery modules and fixing parts having a k / m smaller than the reference k / m and being the minimum k / m.

[0017] In such a configuration where k / m is dispersed, as described above, when the dispersions of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) are defined as D, the dispersion D is set to 0.1 < D < 8, so that a dispersion of the resonance frequency occurs while obtaining a vibration damping effect among a plurality of sets of battery modules and fixing parts. As a result, it becomes possible to expand the frequency band (band gap) in which vibration damping occurs and vibration transmission is blocked. As a result, it becomes possible to improve the NVH performance by effectively damping the vibrations of the vehicle body in a wide frequency band.

[0018] In the battery mounting structure of the electric vehicle described above, it is preferable that k / m of the set of the battery module and the fixing part of half of the total number of the sets of the battery module and the fixing part becomes the reference k / m.

[0019] According to such a configuration, k / m of the set of the battery module and the fixing part of half of the total number is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m · kg)] which has a high vibration damping effect as the reference k / m, so that the vibration damping effect can be surely improved and the NVH performance can be further improved.

Effect of the Invention

[0020] As described above, according to the battery mounting structure of the electric vehicle of the present invention, the NVH performance can be improved.

Brief Description of the Drawings

[0021] [Figure 1] It is a plan view showing the overall configuration of the lower part of a vehicle of an electric vehicle to which the battery mounting structure of the electric vehicle according to an embodiment of the present invention is applied. [Figure 2] It is a cross-sectional view showing a battery module and a fixing part inside the battery pack of FIG. 1. [Figure 3] It is an enlarged cross-sectional view of the fixing part of FIG. 2. [Figure 4] It is a perspective view of the battery pack and the fixing part of FIG. 2. [Figure 5] It is a multi-particle distributed type vibration model that performs meta-damping constituted by a plurality of battery modules and a plurality of fixing parts in the battery pack of FIG. 1. As an example of an embodiment of the present invention, it is a schematic view of vibration models in which k / m, which is the ratio of the support rigidity k of the fixing part to the mass m of the battery module, is different for each of k1 / m1 to k4 / m4. [Figure 6]This graph shows the relationship between the variance D and the transfer function (FRF OA) when the variance D is the ratio k / m of the support stiffness k of the fixed part in a battery mounting structure to the mass m of the battery module, and the ratio k / m is (reference k / m) of (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m). [Figure 7] This graph shows the relationship between the support rigidity k of the fixed part in the battery mounting structure of this embodiment, the ratio of the support rigidity k to the mass m of the battery module (k / m), and the number of modules N, which is the number of battery modules corresponding to each k / m. [Figure 8] This graph shows the relationship between module support stiffness / module weight and transfer function for a battery mounting structure including a battery module and fixing part that is a reference k / m according to an embodiment of the present invention, and a conventional structure that is a comparative example. [Figure 9] This is a schematic diagram illustrating the meta-damping phenomenon that we want to induce in the battery mounting structure of the present invention. [Figure 10] This is a schematic diagram illustrating the resonance phenomenon, which is a comparative example with metadamping. [Figure 11] This graph shows the relationship between frequency and transfer function to explain the shielding of elastic waves over a wide frequency range due to metadamping in the present invention. [Figure 12] This graph shows the relationship between frequency and transfer function to explain the dispersion of the resonance peak at a specific frequency in a dynamic vibration absorber, which is a comparative example with metadamping. [Figure 13] This graph shows the relationship between frequency and transfer function to illustrate how the resonance peak at a specific frequency can be reduced solely by damping, as a comparative example with metadamping. [Modes for carrying out the invention]

[0022] Hereinafter, a battery mounting structure for an electric vehicle according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0023] As shown in Figure 1, the underside of an electric vehicle, including a battery mounting structure which is one embodiment of the present invention, has a structure in which the casing 20 of the battery pack 5 is integrated with the vehicle body 1. Such a structure is one in which the battery module 10 is directly mounted on the vehicle body 1 and is called a so-called skateboard structure.

[0024] Specifically, as shown in Figures 1 and 2, the lower part of the vehicle comprises a vehicle body 1 integrated with a casing 20, a plurality of battery modules 10 (eight in Figure 1) mounted on the casing 20 of the vehicle body 1, a pair of left and right front wheels 3, a pair of left and right rear wheels 7, and a drive unit P including an electric motor that drives the pair of front wheels 3.

[0025] The battery pack 5 comprises a plurality of battery modules 10 (eight in Figure 1), a casing 20 housing the battery modules 10, and a plurality of fixing parts 21 for individually fixing each of the plurality of battery modules 10 to the casing 20.

[0026] As shown in Figures 3-4, each battery module 10 has a battery body 10b consisting of a secondary battery such as a lithium-ion battery, and a metal outer shell 10a that covers the battery body 10b.

[0027] In this invention, it is sufficient that four or more battery modules 10 are arranged in series in a predetermined direction. In the embodiment shown in Figure 1, they are arranged in series in the direction of propagation of the vibration wave input from the front wheel 3, that is, in series in the vehicle longitudinal direction X. Specifically, as shown in Figure 1, two rows of four battery modules 10 are spaced apart in the vehicle width direction Y. The four battery modules 10 in each row are spaced apart at equal intervals in the vehicle longitudinal direction X.

[0028] In this invention, it is sufficient that the battery modules 10 are "arranged in series in a predetermined direction". As a modification, they may be arranged in series in the direction of propagation of vibration waves transmitted in the vehicle width direction Y from the side sills on both sides in the vehicle width direction or the side members 11 described later, that is, four or more may be arranged in series in the vehicle width direction Y.

[0029] As shown in Figure 1, the vehicle body 1 comprises a pair of front lower arms 2, a pair of front suspensions 4 fixed to the pair of front lower arms 2 and rotatably supporting a pair of front wheels 3, a casing 20 of the battery pack 5 located on the rear X2 side of the vehicle of the pair of front lower arms 2, a pair of rear lower arms 6 located on the rear X2 side of the vehicle of the casing 20, a pair of rear suspensions 8 fixed to the pair of rear lower arms 6 and rotatably supporting a pair of rear wheels 7, and a floor plate 9 (see Figure 2) that covers the top of the battery pack 5 and constitutes the floor of the passenger compartment.

[0030] The casing 20 of the battery pack 5 comprises a pair of left and right side members 11 spaced apart from each other in the vehicle width direction Y and extending in the vehicle longitudinal direction X, a front cross member 12 extending in the vehicle width direction Y and connected to the front ends of the pair of side members 11, a rear cross member 13 extending in the vehicle width direction Y and connected to the rear ends of the pair of side members 11 that are bent inward in the vehicle width direction, three intermediate cross members 14 spaced apart from each other in the vehicle longitudinal direction X and extending in the vehicle width direction Y between the front cross member 12 and the rear cross member 13, a bottom plate 16 (see Figures 1-2) positioned below the cross members 12-14, and a top plate 17 (see Figure 2) positioned above the cross members 12-14.

[0031] The rear ends of a pair of front lower arms 2 are connected to the front cross member 12. The front ends of a pair of rear lower arms 6 are connected to the rear cross member 13.

[0032] Each of the multiple fixing parts 21 of the battery pack 5 has a configuration that individually fixes each of the multiple battery modules 10 to the casing 20.

[0033] For example, the fixing portion 21 shown in Figures 2 and 4 has a configuration that fixes the front and rear surfaces and bottom surface of each battery module 10 in the vehicle longitudinal direction X to the bottom plate 16 of the casing 20.

[0034] Each fixing part 21 can have any configuration that includes a damping material capable of damping vibrations, and various configurations are possible. For example, the fixing part 21 shown in Figures 2 to 4 includes a pair of front and rear fixing brackets 22, a pair of front and rear damping adhesives 23 (corresponding to the damping material of the present invention), an elastic damping filler 24 (corresponding to both the elastic member and the damping material of the present invention), a pair of front and rear bolts 25, and a pair of front and rear bracket support members 27. The fixing brackets 22 and bracket support members 27 can be those conventionally used to fix the battery module 10, so structural changes from the conventional structure can be minimized and the reliability of fastening the battery module 10 can be ensured.

[0035] As shown in Figure 3, the fixing bracket 22 has a cylindrical portion 22a that opens vertically and into which a bolt 25 is inserted from above, an opposing portion 22c which is a plate-shaped portion that faces the damping adhesive 23, and a pair of upper and lower arm portions 22b that connect the cylindrical portion 22a and the opposing portion 22c. The damping adhesive 23 is interposed between the outer shell 10a of the battery module 10 and the opposing portion 22c of the fixing bracket 22, and adheres the fixing bracket 22 to the front or rear surface of the outer shell 10a. The elastic damping filler 24 is placed between the bottom surface of the outer shell 10a of the battery module 10 and the bottom plate 16 of the battery pack 5, and elastically supports the battery module 10. The bracket support member 27 is fixed to the bottom plate 16 of the casing 20 inside the casing 20.

[0036] The damping adhesive 23 only needs to have the function of damping vibrations by converting vibration energy into thermal energy, and in this invention, there are no particular limitations on the material or physical properties. As the damping adhesive 23, for example, a sealer or a rubber-based adhesive can be used, which has vibration damping characteristics by having a Young's modulus of 500 MPa or less and a loss coefficient of 0.1 or more at a temperature of 20°C.

[0037] As the elastic damping filler 24, a material having elastic and vibration damping properties is used, but it is sufficient if it has at least the elasticity to function as an elastic member.

[0038] The bolt 25 fastens the fixing bracket 22 to the bracket support member 27. Specifically, the bolt 25 passes through the cylindrical portion 22a of the fixing bracket 22 and fastens to the upper female thread portion 27a of the bracket support member 27.

[0039] The configuration in which multiple fixing parts 21 of the battery pack 5 fix each of the multiple battery modules 10 to the bottom plate 16 of the casing 20 can be schematically represented by the multi-mass point dispersion type vibration model shown in Figure 9.

[0040] In other words, in the multi-mass point dispersion vibration model shown in Figure 9, multiple battery modules 10 of mass M are arranged at equal intervals in the front-rear direction X on the bottom plate 16 of the casing 20 of the battery pack 5 shown in Figures 1-4, and each battery module 10 is fixed to the bottom plate 16 by a fixing part 21. The fixing part 21 can be considered to have an elastic spring constant K and a damping rate C.

[0041] The inventors of the present invention have devised a configuration that induces meta-damping (meta-resonance) within the battery pack 5 by carefully designing the fixed part 21 in order to effectively dampen vibrations input from the front wheel 3 to the vehicle body 1 using a multi-mass point dispersion type vibration model in the battery pack 5 shown in Figure 9 above.

[0042] Here, meta-damping, as shown in Figure 9, is the process of generating multiple resonances under the same excitation frequency in a multi-mass dispersion type vibration model, thereby blocking the vibrations transmitted to the output (i.e., creating a band gap). For example, in a normal resonance phenomenon, as shown in Figure 10, if the vibration is continuously excited at the same frequency, the input wave resonates with the reflected wave from the output, causing the vibrations reaching the output to be amplified.

[0043] However, in the meta-damping shown in Figure 9, even when the input wave is continuously excited at the same frequency, the vibration energy is dissipated (i.e., vibration is damped) by the interference of the input wave with each set of battery modules 10 and fixing parts 21 (each having a mass M) and the fixing parts 21 that individually support them, thereby blocking the vibration from reaching the output destination. In other words, meta-damping continuously interferes and dampens to prevent amplification due to resonance. Looking at the vehicle body 1 as a whole in Figure 1, vibrations input from the front wheels 3 during vehicle operation are transmitted sequentially to the four battery modules 10 arranged in the longitudinal direction X of the vehicle through the front suspension 4, front lower arm 2, front cross member 12, and bottom plate 16. At this time, each battery module 10 and the fixing parts 21 that fix it (see Figure 2) interfere with the vibration and dissipate the vibration energy, so the vibration gradually decreases as it moves towards the rear X2 of the vehicle (indicated by the arrows in each battery module 10 in Figure 1 becoming smaller).

[0044] In order to generate the damping caused by metadamping described above throughout the battery pack 5 and to enable vibration damping over a wide frequency band (bandgap), in this embodiment, when the support rigidity of the fixed part 21 is k [N / m] and the mass of the battery module 10 is m [kg], the k / m for each battery module 10 and fixed part 21 pair is set as follows.

[0045] First, for at least two sets (preferably, half of the total number of all sets) of the pairs of all battery modules 10 and fixing parts 21, the k / m of the pairs of battery modules 10 and fixing parts 21 is the reference k / m. The reference k / m is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)].

[0046] When the reference k / m is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)] as described above, like the A group in the graph of FIG. 8, significant vibration damping effect is exerted by the meta-damping of the entire battery pack 5. Here, FIG. 8 is a graph showing the relationship between the module support rigidity / module weight and the transfer function for a battery mounting structure (A group) including battery modules 10 and fixing parts 21 that are the reference k / m according to an embodiment of the present invention and a conventional structure (B group) which is a comparative example (specifically, a structure having no pair of damping adhesives 23 and elastic damping fillers 24).

[0047] That is, in the A group in the graph of FIG. 8, in the frequency band of vibrations input to the vehicle body 1 during vehicle running, mainly in the frequency band of 100 to 400 Hz, for any case where the loss coefficient tanD regarding the damping performance of the fixing part 21 is 0.01 to 1.0, the transfer function significantly decreases and a significant vibration damping effect is exerted.

[0048] On the other hand, in the case of the conventional support structure of a battery module without a damping material shown in the B group of FIG. 8 as a comparative example, since the module support rigidity / module mass is larger than 1.85×10 7 and the transfer function is much larger than the transfer function of the A group, it can be seen that the vibration damping effect by meta-damping is not exerted.

[0049] The meta-damping realized by the battery mounting structure of the present embodiment as described above controls the vibration level by the resonance structure of the metamaterial that combines the local resonance element and the damping element (specifically, the overall structure of the battery pack 5 composed of the plurality of battery modules 10 and the plurality of fixing portions 21). Therefore, within the target frequency band (band gap), the vibration is not transmitted into the cabin (inside the vehicle compartment) due to the interaction of the above resonance structure.

[0050] Also, among the k / m of all combinations of the battery modules 10 and the fixing portions 21, the k / m that is greater than the reference k / m and the maximum k / m is defined as the maximum k / m. Further, among the k / m of all combinations of the battery modules 10 and the fixing portions 21, the k / m that is smaller than the reference k / m and the minimum k / m is defined as the minimum k / m.

[0051] Furthermore, let the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) be D. This variance D is set so that 0.1 < D < 8.

[0052] The above reference k / m, maximum k / m, and minimum k / m can be considered as follows, for example. For a plurality (for example, 4 or more) of battery modules 10 arranged in series in the vehicle longitudinal direction X shown in FIG. 5, the ratio of the mass m of each battery module 10 to the support rigidity k of the fixing portion 21 that fixes each battery module 10, i.e., k / m, is represented as k1 / m1, k2 / m2, k3 / m3, k4 / m4, ···, respectively.

[0053] These k1 / m1, k2 / m2, k3 / m3, k4 / m4, ··· are not necessarily the same, and it is sufficient to have at least two or more within the setting range of the above reference k / m with a high vibration damping effect. It is sufficient to have at least one maximum k / m that is a value greater than the reference k / m and a minimum k / m that is a value smaller than the reference k / m.

[0054] For example, when considering a model having eight battery modules 10 with a total number of modules N = 8, as shown in the graph of FIG. 7, within the above-mentioned setting range of the reference k / m, when k / m is 10 6 the k / m value at which the number of modules N is the largest four, which is slightly smaller than N / (m·kg), becomes the reference k / m. The k / m value that is larger than the reference k / m and is the maximum value (for two modules) becomes the maximum k / m, and the k / m value that is smaller than the reference k / m and is the minimum value (for two modules) becomes the minimum k / m.

[0055] As described above, once the reference k / m, the maximum k / m, and the minimum k / m are determined, the variance D of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) can be determined.

[0056] The graph of FIG. 6 has the horizontal axis representing the variance D and the vertical axis representing the transfer function (FRF OA) for vibrations around 100 Hz to 400 Hz (so-called road noise) input from the front wheels 3 during vehicle travel and transmitted to the vehicle body 1. It is a graph showing the relationship between these variance D and the transfer function (FRF OA).

[0057] As shown in the graph of FIG. 6, if this variance D is set such that 0.1 < D < 8, it can be seen that the transfer function (FRF OA) for vibrations around 100 Hz to 400 Hz (so-called road noise) input from the front wheels 3 during vehicle travel and transmitted to the vehicle body 1 is clearly lower than the transfer function A of a model without variance (i.e., a model in which k / m is the same for all battery modules 10). Therefore, it can be understood that if the variance D regarding k / m is dispersed within the above range as in the present embodiment, a vibration damping effect can be obtained in a wide frequency band (bandgap).

[0058] The support stiffness k of the fixing part 21 is the support stiffness of the entire fixing part 21 considering the shear stiffness of the pair of front and rear damping adhesives 23 included in the fixing part 21 and the compression stiffness of the elastic damping filler 24. The support stiffness k may be set so that the reference k / m is within the above numerical range according to the mass m of the battery module 10. Further, the reference k / m, the maximum k / m, and the minimum k / m may be set so that the dispersion D is within the above setting range.

[0059] Note that the maximum k / m and the minimum k / m can obtain the vibration damping effect by meta-damping in a wide frequency band for the entire battery pack 5 including the plurality of battery modules 10 and the fixing part 21 even if they are outside the setting range (1.42×10 5 ~1.85×10 7 [N / (m · kg)]) of the reference k / m as long as the dispersion D is within the above setting range (0.1 < D < 8).

[0060] The support stiffness k of the fixing part 21 may be structurally weaker than the stiffness of the casing 20 of the battery pack 5 that houses the plurality of battery modules 10. Therefore, the fixing part 21 may have a structure other than the structure with the damping adhesive 23 and the elastic damping filler 24 added as shown in FIGS. 3 to 4.

[0061] (Comparison explanation of meta-damping, dynamic vibration absorber, and damping) Here, as a method for reducing vibration, the differences between meta-damping, a dynamic vibration absorber, and damping will be explained.

[0062] In meta-damping, as shown by the curve C1 in the graph of FIG. 11, the input elastic wave C0 (elastic wave having peaks P1 and P2) is blocked and attenuated by the interference due to the interaction between the input elastic wave C0 and the meta-resonator (the multi-particle dispersion type vibration model in FIG. 9 above), and the band gap BG (that is, the frequency band in which vibration is blocked and attenuated) is expanded to form a wide BG that is connected together.

[0063] In dynamic vibration absorbers, the vibration of the main vibration system is damped by adding an auxiliary mass and transferring energy to the auxiliary vibration system. Specifically, in dynamic vibration absorbers, as shown by curve C2 in the graph of Figure 12, vibrations are damped by splitting the single large peak P1 of the transfer function of the input elastic wave C0 into two smaller peaks. Therefore, a wide band gap BG (see Figure 11) like that of metadamping does not occur.

[0064] Furthermore, in damping, the energy generated by vibration is dissipated by the damping material into heat or fluid resistance, thereby reducing the vibration. Specifically, in damping, as shown by curve C3 in the graph of Figure 13, the vibration is attenuated by lowering one large peak P1 in the transfer function of the input elastic wave C0. Therefore, a wide band gap BG, as seen in metadamping, does not occur.

[0065] (Features of this embodiment) (1) In the battery mounting structure of this embodiment, the NVH performance can be improved by effectively damping vibrations of the vehicle body 1 over a wide frequency band by utilizing the entirety of the multiple battery modules 10 and the multiple fixing parts 21 that secure them. Specifically, vibration damping is performed as follows.

[0066] In the above configuration, vibrations input to the vehicle body from the front wheels 3 are sequentially transmitted to four or more battery modules 10 arranged in series in the vehicle's longitudinal direction X, which is a predetermined direction, via fixing parts 21 that secure each battery module 10 to the vehicle body.

[0067] The k / m of at least two sets of battery module 10 and fixing part 21 out of all sets of battery module 10 and fixing part 21 is set as the reference k / m. The reference k / m is 1.42 × 10 5 ~1.85×10 7 It is set within the range of [N / (m·kg)].

[0068] Also, among the k / m values of all combinations of battery modules 10 and fixing parts 21, the k / m greater than the reference k / m is defined as the maximum k / m, and the k / m less than the reference k / m is defined as the minimum k / m. When the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) is D, the variance D is set such that 0.1 < D < 8.

[0069] As a result, in the frequency band of the vibration input to the vehicle body 1 during vehicle travel, for the vibration transmitted in order for each series of battery modules 10 in the vehicle longitudinal direction X (predetermined direction), dissipation and interference of vibration energy occur in each fixing part 21. That is, a vibration damping effect by so-called meta-damping (meta-resonance) is obtained, which continuously damps vibration along the vibration transmission direction by utilizing the weights of four or more battery modules 10 arranged in series and the loss coefficients or damping characteristics of their fixing parts 21.

[0070] In this way, by effectively blocking the vibration input from the front wheels 3 to the vehicle body 1 using the aggregate of a plurality of battery modules 10 and their fixing parts 21 and suppressing the transmission into the vehicle interior, it is possible to improve the NVH performance of the vehicle.

[0071] Moreover, in the above configuration, the k / m of at least two sets of battery modules 10 and fixing parts 21 is set within the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)] as the reference k / m, which has a high vibration damping effect. However, there are two sets having k / m values far from this reference k / m, that is, the set of battery modules 10 and fixing parts 21 with the maximum k / m greater than the reference k / m, and the set of battery modules 10 and fixing parts 21 with the minimum k / m less than the reference k / m.

[0072] In such a configuration where k / m is dispersed, as described above, when the dispersion of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) is defined as D, by being set such that 0.1 < D < 8, a dispersion of the resonance frequency occurs while obtaining a vibration damping effect among a plurality of sets of the battery module 10 and the fixing portion 21. Thereby, it becomes possible to expand the frequency band (bandgap) in which vibration damping occurs and vibration transmission is blocked. As a result, by effectively damping the vibration of the vehicle body 1 in a wide frequency band, it becomes possible to improve the NVH performance.

[0073] (2) Also, in the present embodiment, the k / m of half of the total number of sets of the battery module 10 and the fixing portion 21 is the reference k / m.

[0074] In this configuration, the k / m of half of the total number of sets of the battery module 10 and the fixing portion 21 is set as the reference k / m and is in the range of 1.42×10 5 ~1.85×10 7 [N / (m·kg)] where the vibration damping effect is high. Therefore, it becomes possible to surely improve the vibration damping effect and further improve the NVH performance.

[0075] (3) The battery mounting structure of the present embodiment may be configured to be able to change the maximum k / m and the minimum k / m. For example, the maximum k / m and the minimum k / m may be changed by changing the fastening force of the bolt 25 of the fixing portion 21. Alternatively, either the damping adhesive 23 or the elastic damping filler 24 of the fixing portion 21 may be replaced with one having a different elastic coefficient.

[0076] (4) Also, two battery modules 10 arranged in the vehicle width direction or the vertical direction may be rigidly coupled to each other and integrated. The number of battery modules 10 in series is not particularly limited, but a larger number results in a higher vibration damping effect due to metamaterial damping.

[0077] (5) In the battery mounting structure of this embodiment, as shown in Figure 3, the fixing part 21 has a fixing bracket 22 that can be connected to the vehicle body 1 and a damping adhesive 23. The fixing bracket 22 is attached to the battery module 10 via the damping adhesive 23. In this configuration, by simply connecting the fixing bracket 22 of the fixing part 21 to the vehicle body 1, multiple battery modules 10 can be individually fixed to the vehicle body 1 via the fixing bracket 22 and damping adhesive 23 of the fixing part 21. At the same time, vibrations transmitted from the vehicle body 1 to each battery module 10 are reliably damped via the damping adhesive 23 of the fixing part 21. Therefore, it is possible to effectively dampen vibrations transmitted to multiple battery modules 10 and effectively improve the NVH performance of the vehicle.

[0078] (6) In the battery mounting structure of this embodiment, the fixing portion 21 has an elastic damping filler 24 provided on the bottom surface of the battery module 10. With this configuration, the elastic damping filler 24 provided on the bottom surface of the battery module 10 makes it possible to configure the fixing portion 21 so that the module support rigidity / module weight is within the above numerical range, thereby making it possible to more reliably improve NVH performance. Furthermore, even when an impact load is applied to the bottom surface of the battery module 10, such as when the vehicle drives over a stone on the road surface, the elastic damping filler 24 can mitigate the impact load.

[0079] (7) In the battery mounting structure of this embodiment, multiple battery modules 10 are arranged at equal intervals in the longitudinal direction X of the vehicle. This makes it possible to effectively generate meta-damping with the multiple battery modules 10 and their corresponding fixing parts 21 as a whole, thereby improving NVH performance. [Explanation of symbols]

[0080] 1. Vehicle body 3 Front wheels 5 Battery Packs 10 Battery Modules 21 Fixed part 22 Fixing brackets 23 Damping Adhesive 24 Elastic damping filler

Claims

1. In the battery mounting structure of an electric vehicle, The car body and, Four or more battery modules, Four or more fixing points for individually securing each of the multiple battery modules to the vehicle body, A pair of left and right front wheels are rotatably mounted on the vehicle body at a position forward of the vehicle body from the plurality of battery modules, and Equipped with, The plurality of battery modules are arranged in series in a predetermined direction. When the support rigidity of the fixed part is k [N / m] and the mass of the battery module is m [kg], The k / m of at least two sets of the battery module and fixing parts out of all sets of the battery module and fixing parts becomes the reference k / m. The aforementioned standard k / m is 1.42 × 10 ５ ~1.85 x 10 ７ It is within the range of [N / (m·kg)]. Among all the k / m values ​​of the battery module and the fixing part set, the k / m that is greater than the reference k / m is defined as the maximum k / m. When the minimum k / m among all the sets of battery modules and fixing parts that is smaller than the reference k / m is defined as the minimum k / m, If D is the variance of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m), The variance D is such that 0.1 < D < 8. A battery mounting structure for an electric vehicle characterized by the following features.

2. In the battery mounting structure for an electric vehicle according to claim 1, The k / m of half of the total number of sets of battery modules and fixing parts becomes the reference k / m. A battery mounting structure for an electric vehicle characterized by the following features.

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