Battery mounting structure of electric vehicles

Abstract

An object of the present invention is to provide a battery mounting structure for an electric vehicle that can improve NVH performance. 【Solution means】The battery module 10 includes a plurality of cells 22 and a fixing portion 23 that fixes each of the plurality of cells 22. As the support rigidity k of the fixing portion 23 and the mass m of the cell 22, the k / m of two or more sets of cells 22 and the fixing portion 23 becomes the reference k / m. The k of the reference k / m is the value of tanδ, which is the loss factor of the fixing portion 23, as x, and the minimum value k of k max is k min = 5.184×10 9 (1 / x) 2 (1 / m) 3 , and the maximum value k of k max is k max = 482.2531x 2 m <A000009>, k min < k max When it is set as, k min ≦ k ≦ k max falls within the range. As the maximum k / m greater than the reference k / m and the minimum k / m less than the reference k / m, the variance D of (reference k / m) / (reference k / m), (maximum k / m) / (reference k / m), and (minimum k / m) / (reference k / m) is 0.2

Description

[Technical Field]

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

[0002] Conventionally, in electric vehicles where a battery module containing multiple cells housed inside a battery casing is mounted on the vehicle body, vibrations input to the vehicle body from the suspension supporting the wheels during vehicle operation cause the multiple cells inside the battery casing to vibrate individually in the vertical direction, and these vibrations are transmitted to the cabin. This results in 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 structure described in Patent Document 1 includes a pair of C-shaped side plates in the battery housing to prevent multiple cells of the battery module from vibrating vertically. Each of the pair of side plates has an upper flange portion and a lower flange portion that support the cells from both the upper and lower sides. By having the pair of C-shaped side plates restrain both the left and right sides of multiple cells together, the upper and lower flange portions suppress vertical vibration of each cell, thereby improving NVH performance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-46644 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, in the above structure, a pair of side plates with a C-shaped cross-section restrain the left and right sides of a plurality of cells collectively, so that the flange portions on the upper and lower sides suppress the vertical vibration of each cell. However, the influence on the vibration due to the resonance of each cell during vehicle running is not considered, and there is room for improvement in terms of improving NVH performance.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery mounting structure for an electric vehicle capable of improving NVH performance.

Means for Solving the Problems

[0007] In order to solve the above problems, the battery mounting structure of an electric vehicle of the present invention includes, in the battery mounting structure of an electric vehicle, a vehicle body, at least one battery module fixed to the vehicle body, and a pair of left and right front wheels rotatably attached to the left and right sides of the front portion of the vehicle body. The battery module includes a battery housing, a plurality of cells accommodated in the battery housing and arranged in series in a predetermined direction, and a plurality of fixing portions arranged in the battery housing and individually fixing the plurality of cells to the battery housing. When the support rigidity of the fixing portion is k [N / m] and the mass of the cell is m [kg], k / m of at least two sets of the cell and the fixing portion among all the sets of the cell and the fixing portion becomes the reference k / m. The k and m of the reference k / m are such that when the value of the loss factor tanδ of the fixing portion is x, and the minimum value k min of k is k min = 5.184×10 9 (1 / x) 2 (1 / m) 3 and the maximum value k max of k is k max = 482.2531x 2 m [[ID= twenty-eight ]] 5 and when k min < k max is satisfied, k is such that k min ≦ k ≦ k maxIt is set so as to fall within the range, and when the maximum k / m among the k / m of all the sets of the cells and the fixing parts, which is greater than the reference k / m, is defined as the maximum k / m, and the minimum k / m among the k / m of all the sets of the cells and the fixing parts, which is less than the reference k / m, is defined 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 characterized by 0.2 < D < 550.

[0008] In such a configuration, by utilizing the entirety of a plurality of cells within the battery module and a plurality of fixing parts that fix them to the battery housing, the NVH performance can be improved by effectively attenuating the vibration of the vehicle body in a wide frequency band. Specifically, vibration attenuation is performed as follows.

[0009] According to such a configuration, when the electric vehicle is running, the vibration wave input from a pair of left and right front wheels to the vehicle body is transmitted to the battery module fixed to the vehicle body. At that time, in the battery module, elastic waves are sequentially transmitted through the fixing parts to a plurality of four or more cells arranged in a predetermined direction.

[0010] The k / m of at least two sets of the sets of all the cells and the fixing parts is the reference k / m. For k and m of the reference k / m, as a range with a high vibration attenuation effect, when the value of the loss factor tanδ of the fixing part is x, and the minimum value k min of k is k min = 5.184×10 9 (1 / x) 2 (1 / m) 3 , the maximum value k max of k is k max = 482.2531x 2 [[ID=Z8]]m 5 k min < k max when, k is set so as to fall within the range of k F min ≦ k ≦ k max .

[0011] Also, among the k / m values of all combinations of cells and fixing parts, the k / m greater than the reference k / m is the maximum k / m, and the k / m smaller than the reference k / m is 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 defined as D, the variance D is set such that 0.2 < D < 550.

[0012] As a result, in the frequency band of vibrations input to the vehicle body during vehicle travel, dissipation and interference of vibration energy occur with respect to the vibrations transmitted in order for each series of cells in a predetermined direction. That is, a vibration damping effect by so-called meta-damping, which performs continuous vibration damping along the vibration transmission direction by utilizing the mass of four or more cells arranged in series and the loss factor or damping characteristics of the fixing parts, can be obtained.

[0013] In this way, by effectively blocking the vibrations input from the front wheels to the vehicle body using a plurality of cells and fixing parts and suppressing the transmission into the vehicle interior, it is possible to improve the NVH performance of the vehicle. As a result, it is possible to suppress the vibrations of the frequencies in the load noise band input to the vehicle body during travel.

[0014] Moreover, in the above configuration, k and m of the reference k / m are set so that the k / m of at least two combinations of cells and fixing parts is within a range with a high vibration damping effect as the reference k / m. However, there are two combinations having k / m values that deviate significantly from this reference k / m, that is, the combination of cells and fixing parts with the largest k / m greater than the reference k / m, and the combination of cells and fixing parts with the smallest k / m smaller than the reference k / m.

[0015] 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, the dispersion D is set such that 0.2 < D < 550. As a result, a dispersion in the resonance frequency occurs while obtaining a vibration damping effect among a plurality of sets of cells and fixing portions. This makes it possible to expand the frequency band (bandgap) where vibration damping occurs and vibration transmission is blocked. Consequently, by effectively damping the vibration of the vehicle body in a wide frequency band, it becomes possible to improve the NVH performance.

[0016] In the battery mounting structure of the electric vehicle described above, when x = 2 which is the value of tanδ, the minimum value k of k min is k min = 1.296×10 9 (1 / m) 3 , the maximum value k of k max is k max = 1.929×10 3 m 5 , k min < k max When set as such, it is preferable that k is set within the range of k min ≦ k ≦ k max .

[0017] <0−000195>According to such a configuration, when the value of tanδ which is the loss coefficient of the fixing portion is x = 2, the range of the support stiffness k of the fixing portion, that is, the range between k <000−039>and k <000−040>can be made the widest, and it is possible to select the support stiffness k from a wide range to suppress the vibration in the load noise band. As a result, the design freedom of the battery mounting structure is expanded.

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

[0019] With this configuration, the k / m of half of the total number of cell and fixed part sets is set to the above range, which provides a high vibration damping effect, as the reference k / m. This makes it possible to reliably improve the vibration damping effect and further improve NVH performance.

[0020] In the above-described battery mounting structure for an electric vehicle, the battery module further comprises a partition portion disposed between adjacent cells and supported by the battery housing, and the fixing portion preferably fixes the cells while sandwiched between the cells and the partition portion.

[0021] In this configuration, the fixing part can stably fix the cell while sandwiched between the cell and the partition part. This makes it possible to reliably resonate each cell with elastic waves and exert a stable vibration suppression effect. [Effects of the Invention]

[0022] As described above, the battery mounting structure for electric vehicles according to the present invention can improve NVH performance. [Brief explanation of the drawing]

[0023] [Figure 1] This is a plan view showing the overall configuration of the underside of an electric vehicle to which the battery mounting structure of an electric vehicle according to an embodiment of the present invention is applied. [Figure 2] Figure 1 is a cross-sectional diagram illustrating the internal structure of the battery module, and schematically shows different vibration models where the ratio of the support stiffness k of the fixed part to the mass m of the battery module, k / m, is k1 / m1 to k4 / m4. [Figure 3] 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 cell, 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 4]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 cell mass m (k / m), and the number of cells N, which is the number of cells corresponding to each k / m. [Figure 5] Figure 2 is a three-dimensional graph showing the range of maximum value kmax and minimum value kmin for the support stiffness k of the battery module, where m is the mass of the cell, k is the support stiffness of the support, and tanδ is the loss coefficient of the support. [Figure 6] Figure 5 is a graph showing the range of maximum value kmax and minimum value kmin for the support part when the loss coefficient tanδ = 0.4, representing the cell mass m and the support stiffness k of the support part. The graph shows the distribution of the combinations of support stiffness and cell mass included in the present invention (·) and the combinations of comparative examples (×). [Figure 7] Figure 6 is a graph showing the relationship between support stiffness / cell mass and transfer function (FRF OA), illustrating the decrease in the transfer function due to the vibration damping effect in the support stiffness and cell mass combination (·) included in the present invention. [Figure 8] Figure 5 is a graph showing the range of maximum value kmax and minimum value kmin for the support part when the loss coefficient tanδ = 1.0, representing the cell mass m and the support stiffness k of the support part. The graph shows the distribution of the combinations of support stiffness and cell mass included in the present invention (·) and the combinations of comparative examples (×). [Figure 9] Figure 8 is a graph showing the relationship between support stiffness / cell mass and transfer function (FRF OA), illustrating the reduction in the transfer function due to the vibration damping effect in the support stiffness and cell mass combination (·) included in the present invention. [Figure 10] 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 11] This is a schematic diagram illustrating the resonance phenomenon, which is a comparative example with metadamping. [Figure 12] 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 13]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 14] 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]

[0024] 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.

[0025] 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.

[0026] Specifically, as shown in Figure 1, the lower part of the vehicle comprises a body 1 integrated with a casing 20, a plurality of battery modules 10 (eight in Figure 1) mounted on the casing 20 of the 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. The battery pack 5 consists of a plurality of battery modules 10 and a casing 20 that houses the battery modules 10. The plurality of battery modules 10 are individually fixed inside the casing 20. Note that at least one battery module 10 is sufficient.

[0027] 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 (not shown) that covers the top of the battery pack 5 and forms the floor of the passenger compartment.

[0028] The casing 20 of the battery pack 5 comprises a pair of left and right side members 11 that are spaced apart from each other in the vehicle width direction Y and extend in the vehicle longitudinal direction X, a front cross member 12 that extends in the vehicle width direction Y and connects to the front ends of the pair of side members 11, and a rear cross member 13 that extends in the vehicle width direction Y and connects to the rear ends of the pair of left and right side members 11.

[0029] 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.

[0030] In this embodiment, as shown in Figure 1, two rows of eight battery modules 10 are arranged spaced apart in the vehicle width direction Y. The four battery modules 10 in each row are arranged spaced equally apart in the vehicle longitudinal direction X.

[0031] As shown in Figure 2, each battery module 10 comprises a battery housing 21, four cells 22A to 22D arranged in a predetermined direction (vehicle longitudinal X) and housed inside the battery housing 21, four sets of fixing parts 23A to 23D for securing each of the cells 22, and multiple partition parts 24 for separating adjacent cells 22A to 22D. Note that the cells 22A to 22D only need to be arranged in a predetermined direction and are not limited to the vehicle longitudinal direction.

[0032] The battery housing 21 is a hollow, roughly rectangular housing, and specifically has a front wall 21a extending in the vehicle width direction Y, a rear wall 21b extending in the vehicle width direction Y parallel to the front wall 21a on the rear side of the front wall 21a, a pair of left and right side walls 21c connecting the left and right ends of the front wall 21a and the rear wall 21b and extending in the vehicle longitudinal direction X, and a top wall and bottom wall (not shown) spaced apart in the vertical direction Z.

[0033] Cells 22A to 22D consist of secondary batteries such as lithium-ion batteries and have a plate-like or thin pouch-like shape, but may also be cylindrical. Multiple plate-like cells 22A to 22D are arranged in the vehicle's longitudinal direction X so that they are parallel to each other, that is, each extends in the vehicle width direction Y.

[0034] The partition portion 24 is a plate-like portion extending in the vehicle width direction Y, positioned between two adjacent cells 22A to 22D, and both left and right ends are fixed to the side walls 21c of the battery housing 21, respectively.

[0035] The fixing sections 23A to 23D are arranged inside the battery housing 21 and individually fix cells 22A to 22D. The fixing sections 23A to 23D shown in Figure 2 individually fix cells 22A to 22D to the battery housing 21 while sandwiched between each cell 22A to 22D and the partition section 24 (in this embodiment, as described later, they are fixed to the battery housing 21 via the partition section 24).

[0036] As the fixing parts 23A to 23D, damping adhesives made of polymer materials are used. For example, sealers or rubber-based adhesives are used, and polymer adhesives having vibration damping characteristics such as a Young's modulus of 500 MPa or less and a loss coefficient of 0.1 or more at a temperature of 20°C are used. In this embodiment, each fixing part 23A to 23D made of polymer adhesive is arranged on both the front and rear surfaces of each cell 22A to 22D, and each cell 22A to 22D is bonded to the partition part 24. In this way, each fixing part 23A to 23D fixes each cell 22A to 22D to the battery housing 21 via the partition part 24. Furthermore, additional fixing parts 23E may be arranged on both sides in the vehicle longitudinal direction X of the frontmost and rearmost partition parts 24, as shown in Figure 2.

[0037] In this embodiment, the fixing part 23 supports the cell 22 while being sandwiched between the cell 22 and the partition part 24. This allows the fixing part 23 to stably fix the cell 22. Therefore, it is possible to reliably resonate each cell 22 with elastic waves and exert a stable vibration suppression effect.

[0038] (Explanation regarding the setting of support stiffness k) In the battery mounting structure of this embodiment, as shown in Figures 1 and 2, the battery module 10 has a configuration in which a plurality of cells 22 and a plurality of fixing parts 23 that individually fix the plurality of cells 22, and the support rigidity k of the fixing part 23 is set as follows in order to increase the vibration damping effect.

[0039] First, let k [N / m] be the support rigidity of the fixed part 23, m [kg] be the mass of each cell 22, and x be the value of tanδ, which is the loss coefficient of the fixed part 23, and, Minimum value of k min k min = 5.184 × 10 9 (1 / x) 2 (1 / m) 3 , The maximum value of k max k max =482.2531x 2 m 5 , kmin <k max When that happens, k is k min ≦k≦k max It is set to the range.

[0040] In this embodiment, the conditions for the loss coefficient tanδ and support stiffness k are those for 10-60°C and 100Hz.

[0041] Figure 5 shows the mass m of the cell 22 of the battery module 10 in Figure 2, the support stiffness k of the fixing part 23, and the maximum value k of the support stiffness k in the loss coefficient tanδ of the fixing part 23. max and minimum value k min This is a 3D graph showing the range in which this occurs.

[0042] According to the graph in Figure 5, the minimum value k mentioned above is k. min and maximum value k max These represent ranges indicated by roughly conical surfaces. The minimum value k is as described above. min and maximum value k max By setting the cell mass m, support stiffness k, and loss coefficient tanδ so that they fall within a certain range, multiple cells 22 can resonate with each other and continuously dampen vibrations in response to road noise (vibration waves of approximately 100Hz (100Hz~400Hz)), which is vibration input to the vehicle body when the vehicle is in motion.

[0043] For example, Figure 6 shows the maximum value k in the graph of Figure 5 when the loss coefficient of the fixed part tanδ = 0.4. max and minimum value k min Looking at the graph of cell mass m and support stiffness k of the fixed part showing the range, the combination of support stiffness k and cell mass m included in the present invention (·) is the minimum value k in Figure 6. min The curve and maximum value k maxThe distribution falls within the range enclosed by the curve, and the comparative example combination (×) is distributed outside that range. Furthermore, looking at the graph in Figure 7 showing the relationship between support stiffness / cell mass and the transfer function (FRF OA) at road noise of 100-400 Hz, it can be seen that in the combination of support stiffness k and cell mass m included in the present invention in Figure 6 (·), the transfer function is reduced to a level lower than the level of transfer function B at which vehicle occupants can feel the vibration damping effect due to the vibration damping effect. On the other hand, in the comparative example combination (×), the level is higher than the above-mentioned level of transfer function B, and it can be seen that no vibration damping effect is obtained.

[0044] Furthermore, if the loss coefficient tanδ = 0.4 or greater, and the cell mass m is 23 kg or greater, then the support stiffness / cell mass: k / m [N / (m·kg)] is 3.0 × 10⁻⁶ 5 ~1.0×10 7 Within this range, the combination of support stiffness k and cell mass m (·) is the minimum value k shown in Figure 6. min The curve and maximum value k max Computer analysis by the inventors has confirmed that vibration damping effect is obtained when the range enclosed by the curve is reached. Furthermore, when the loss coefficient tanδ = 0.4 or higher, and the cell mass m is 47 kg or higher, the support stiffness / cell mass: k / m [N / (m·kg)] is 1.0 × 10 4 ~8.0×10 7 Within this range, the combination of support stiffness k and cell mass m (·) is the minimum value k shown in Figure 6. min The curve and maximum value k max Computer analysis by the inventors has confirmed that the vibration damping effect is obtained when the area falls within the range enclosed by the curve.

[0045] Similarly, the graph in Figure 8 (the maximum value k when the loss coefficient of the fixed part in the graph in Figure 5 is tanδ = 1.0) max and minimum value k minLooking at the graphs of cell mass m and support stiffness k of the fixed part (showing the range) and the graph in Figure 9 (a graph showing the relationship between support stiffness / cell mass and transfer function (FRF OA)), it can be seen that in the combination of support stiffness k and cell mass m included in the present invention in Figure 8 (·), the transfer function is reduced to a level lower than the level of transfer function B at which vehicle occupants can feel the vibration damping due to the vibration damping effect.

[0046] Furthermore, if the loss coefficient tanδ = 1.0 or greater, and the cell mass m is 12 kg or greater, then the support stiffness / cell mass: k / m [N / (m·kg)] is 2.5 × 10⁻⁶. 5 ~1.0×10 7 Within the range, the combination of support stiffness k and cell mass m (·) is the minimum value k in Figure 8. min The curve and maximum value k max Computer analysis by the inventors has confirmed that the vibration damping effect is obtained when the area falls within the range enclosed by the curve.

[0047] Furthermore, in the case of a low loss coefficient, for example, when the loss coefficient tanδ = 0.1 or higher, and the cell mass m is 47 kg or higher, the support stiffness / cell mass: k / m [N / (m·kg)] is 4.0 × 10 4 ~7.0×10 6 Within the range, the combination of support stiffness k, cell mass m, and loss coefficient tanδ value x is the minimum value k shown in Figure 5. min The curve and maximum value k max Computer analysis by the inventors has confirmed that the vibration damping effect is obtained when the area falls within the range enclosed by the curve.

[0048] From the above results, it can be seen that the vehicle battery mounting structure of this embodiment provides the following effects and advantages.

[0049] When the electric vehicle is running, the vibration waves input from a pair of left and right front wheels 3 into the vehicle body 1 are respectively transmitted to a plurality of battery modules 10 fixed to the vehicle body 1. At this time, in each battery module 10, elastic waves are sequentially transmitted to a plurality of cells 22 arranged in the vehicle longitudinal direction X through the fixing portions 23. In the above battery mounting structure, when the support rigidity k of the fixing portion satisfies the condition of k min ≦k≦k max within the range, the plurality of cells 22 resonate respectively, interfere with the elastic wave, and reduce the elastic wave.

[0050] In other words, in the frequency band of the vibration input to the vehicle body 1 during vehicle running, dissipation and interference of vibration energy occur with respect to the vibration sequentially transmitted to each of the cells 22 in series in the vehicle longitudinal direction X. That is, a vibration damping effect by so-called metamaterial damping (meta resonance) is obtained, in which continuous vibration damping along the vibration transmission direction is performed by utilizing the masses of two or more cells 22 arranged in series and the loss factor or damping characteristics of the fixing portions 23.

[0051] Thus, by effectively blocking the vibration input from the front wheels 3 into the vehicle body 1 by using the plurality of cells 22 and the fixing portions 23 and suppressing the transmission into the vehicle interior, it is possible to improve the NVH performance of the vehicle. Thereby, it is possible to suppress the vibration of the frequency in the load noise band input to the vehicle body 1 during running.

[0052] Here, when the value of the loss factor tanδ of the fixing portion 23 is x = 2, the minimum value k of the above support rigidity k min is k min = 1.296×10 9 (1 / m) 3 、 the maximum value k of k max is k max = 1.929×10 3 m 5 、 k min <k max When it is set as k is k min ≦k≦kmax It is preferably set within the range of.

[0053] In this configuration, when x = 2, the value of tanδ, which is the loss factor of the fixed part 23, is within the range of the support rigidity k of the fixed part 23, that is, k min and k max The range between them can be made the widest, and it is possible to select the support rigidity k from a wide range to suppress the vibration of the load noise band. As a result, the design freedom of the battery mounting structure is expanded.

[0054] (Explanation of meta-damping) In order to effectively attenuate the vibration input from the front wheel 3 to the vehicle body 1 by the multi-particle distributed vibration model of the plurality of cells 22 inside the battery module 10 shown in FIGS. 1 to 2 above, the inventors have diligently devised the support rigidity k of the fixed part 23 to cause meta-damping (meta-resonance) within each battery module 10.

[0055] Here, meta-damping means, as shown in FIG. 10, in a multi-particle distributed vibration model, generating a plurality of resonances under the condition of the same excitation frequency and blocking the vibration transmitted to the output destination (that is, generating a band gap).

[0056] For example, in a normal resonance phenomenon, as shown in FIG. 11, when continuously excited at the same frequency, the input wave resonates with the reflected wave from the output destination, and the vibration reaching the output destination is amplified.

[0057] However, in the meta-damping shown in Figure 10, even when the input wave is continuously excited at the same frequency, the input wave interferes with each set of cells 22 and fixing parts 23 (with spring constant K and damping rate C) within each battery module 10, causing vibration energy to dissipate (i.e., vibration damping), thus blocking vibrations 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 to the eight battery modules 10 through the front suspension 4, front lower arm 2, front cross member 12, and bottom wall. At this time, the multiple cells 22 within each battery module 10 and the fixing parts 23 (23A~23D) (see Figure 2) that fix them interfere with the vibration and dissipate vibration energy, so the vibration gradually decreases as it moves towards the rear X2 of the vehicle.

[0058] In order to generate the damping caused by meta-damping as described above in each battery module 10, the support rigidity k of the fixed part 23 is set as described above.

[0059] The meta-damping achieved in the battery mounting structure of this embodiment as described above controls the vibration level by a resonant structure of a metamaterial that combines local resonant elements and damping elements (specifically, the structure of the battery module 10 composed of multiple cells 22 and multiple fixed parts 23). Therefore, within the target frequency band (bandgap), vibrations are not transmitted into the cabin (inside the vehicle) due to the interaction of the above-mentioned resonant structure.

[0060] (Description of the battery module 10 with distributed k / m in this embodiment) As shown in FIG. 2, in the battery module 10 of the present embodiment, when the masses of the respective plurality of cells 22A to 22D are m1 to m4, and the support rigidities of the fixing portions 23A to 23D for fixing these cells 22A to 22D are represented by k1 to k4, k / m which is the support rigidity / mass can be represented as k1 / m1 to k4 / m4, respectively.

[0061] Hereinafter, when not distinguishing individual cells among a plurality of cells, they are simply referred to as "a plurality of cells 22" or "cells 22", and hereinafter, when not distinguishing individual fixing portions among a plurality of fixing portions, they are simply referred to as "a plurality of fixing portions 23" or "fixing portion 23".

[0062] In the present embodiment, k / m including the support rigidity k in the above range (k min ≦k≦k max ) having a high vibration damping effect is particularly set as the reference k / m.

[0063] In the battery mounting structure of the present embodiment, k / m of at least two sets (preferably, half of the total number of all sets) of the sets of all cells 22 (22A to 22D) and fixing portions 23 (23A to 23D) is the reference k / m.

[0064] Also, among k / m of all sets of cells 22 and fixing portions 23, the k / m that is larger than the reference k / m and the maximum k / m is defined as the maximum k / m. Further, among k / m of all sets of cells 22 and fixing portions 23, the k / m that is smaller than the reference k / m and the minimum k / m is defined as the minimum k / m.

[0065] 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 0.2 < D < 550.

[0066] The above-mentioned standard k / m, maximum k / m, and minimum k / m can be considered, for example, as follows: For multiple cells 22 (22A~22D) arranged in series in the longitudinal direction X of the vehicle as shown in Figure 2, the ratio k / m, which is the ratio of the mass m of each cell 22 to the support stiffness k of the fixing part 23 (23A~23D) that fixes each cell 22, is expressed as k1 / m1, k2 / m2, k3 / m3, k4 / m4, ... as shown in Figure 2 above.

[0067] These k1 / m1, k2 / m2, k3 / m3, k4 / m4, ... do not necessarily have to be the same. It is sufficient to have at least two of them within the above-mentioned standard k / m setting range that provides a high vibration damping effect, and at least one maximum k / m which is a value greater than the standard k / m, and at least one minimum k / m which is a value smaller than the standard k / m.

[0068] For example, as shown in the graph in Figure 4, if we consider a model with 22 cells, where the total number of cells N is 32, then within the above-mentioned range of k / m, if k / m is 10 5.2 The value in k / m that is slightly larger than N / (m·kg) and has the largest number of cells (16) is defined as the reference k / m. The value in k / m that is greater than the reference k / m and has the maximum number of cells (8) is defined as the maximum k / m. The value in k / m that is smaller than the reference k / m and has the minimum number of cells (8) is defined as the minimum k / m.

[0069] As described above, once the baseline k / m, maximum k / m, and minimum k / m are determined, the variance D of (baseline k / m) / (baseline k / m), (maximum k / m) / (baseline k / m), and (minimum k / m) / (baseline k / m) can be determined.

[0070] The graph in Figure 3 shows the relationship between the dispersion D on the horizontal axis and the transfer function (FRF OA) of vibrations around 100Hz to 400Hz (so-called road noise) that are input from the front wheels 3 and transmitted to the vehicle body 1 during vehicle operation, on the vertical axis.

[0071] As shown in the graph of FIG. 3, if this dispersion D is set such that 0.2 < D < 550, 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 the model without dispersion (i.e., the model where k / m is the same for all cells 22). Therefore, it can be understood that if the dispersion D regarding k / m is dispersed within the above range as in this embodiment, a vibration damping effect can be obtained in a wide frequency band (band gap).

[0072] Note that for the maximum k / m and the minimum k / m, even if they are outside the setting range of the reference k / m as long as the dispersion D is within the above setting range (0.2 < D < 550), a vibration damping effect due to meta-damping can be obtained in a wide frequency band for the entire battery pack 5 including the plurality of cells 22 and the fixing portion 23.

[0073] The support rigidity k of the fixing portion 23 may be structurally weaker than the rigidity of the battery housing 21 that houses the plurality of cells 22.

[0074] Note that when the cell 22 is of the pouch type (flat bag shape) or the square cell type (flat plate shape), the number of cells 22 mounted on the vehicle body 1 is, for example, about 100 to 200. Also, when the mass m as the resonator defined by the above meta-damping is taken as 1 unit, the number of units of the cell 22 is about 12 to 50.

[0075] Also, when the cell 22 is of the cylindrical type, the number of cells 22 mounted on the vehicle body 1 is, for example, about 2000 to 4000. Also, when the mass m as the resonator defined by the above meta-damping is taken as 1 unit, the number of units of the cell 22 is about 60 to 240.

[0076] <00004i7>Regardless of the shape of cell 22 as described above, the number of resonant units is considerably greater than the number of battery modules. Therefore, sufficient vibration reduction can be obtained through the damping characteristics of the reference cell (cell 22 which is the reference k / m). As a result, even if the upper limit of dispersion D is increased to 550, as shown in the graph in Figure 3, the reduction in the reduction effect is small.

[0077] (A comparative explanation of metadamping, dynamic vibration absorbers, and damping) Here, we will explain the differences between meta-damping, dynamic vibration absorbers, and damping as vibration reduction methods.

[0078] In meta-damping, as shown by curve C1 in the graph of Figure 12, the input elastic wave C0 (an elastic wave with peaks P1 and P2) is blocked and attenuated by interference due to the interaction between the input elastic wave C0 (an elastic wave with peaks P1 and P2) and the meta-resonator (the multi-mass point dispersion vibration model in Figure 10 above), thereby expanding the band gap BG (i.e., the frequency band in which the vibration is blocked and attenuated) and forming a single, connected, wide BG.

[0079] In a dynamic vibration absorber, the vibration of the main vibration system is damped by adding an auxiliary mass and transferring energy to the auxiliary vibration system. Specifically, in a dynamic vibration absorber, as shown by curve C2 in the graph of Figure 13, the vibration is 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 12) like that of metadamping does not occur.

[0080] 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 14, the vibration is reduced 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.

[0081] (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 range by utilizing the entirety of the multiple cells 22 in the battery module 10 and the multiple fixing parts 23 that fix them to the battery housing 21. Specifically, vibration damping is performed as follows.

[0082] In this configuration, when the electric vehicle is running, vibration waves input to the vehicle body 1 from the pair of front wheels 3 are transmitted to the battery module 10 fixed to the vehicle body 1. At that time, in the battery module 10, elastic waves are sequentially transmitted via the fixing part 23 to four or more cells 22 arranged in the vehicle's longitudinal direction X (a predetermined direction).

[0083] The k / m of at least two sets of cell 22 and fixed part 23 out of all the cell 22 and fixed part 23 sets is the reference k / m. The k and m in the reference k / m are determined by setting the value of tanδ, which is the loss coefficient of the fixed part 23, as x, within the range of high vibration damping effect, and Minimum value of k min k min = 5.184 × 10 9 (1 / x) 2 (1 / m) 3 , The maximum value of k max k max =482.2531x 2 m 5 , k min <k max When that happens, k is k min ≦k≦k max It is set to be within the range.

[0084] Also, among the k / m values of all combinations of cells 22 and fixing parts 23, the k / m that is greater than the reference k / m is defined as the maximum k / m, and the k / m that is smaller 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 defined as D, the variance D is set such that 0.2 < D < 550.

[0085] As a result, in the frequency band of vibrations input to the vehicle body 1 during vehicle travel, dissipation and interference of vibration energy occur with respect to the vibrations transmitted in order for each series of cells 22 in the vehicle longitudinal direction X (predetermined direction). That is, a vibration damping effect by so-called metamaterial damping, which performs continuous vibration damping along the vibration transmission direction, is obtained by utilizing the masses of four or more cells 22 arranged in series and the loss coefficients or attenuation characteristics of the fixing parts 23.

[0086] In this way, it is possible to improve the NVH performance of the vehicle by effectively blocking the vibrations input from the front wheels 3 to the vehicle body 1 using a plurality of cells 22 and fixing parts 23 and suppressing the transmission into the passenger compartment. As a result, it is possible to suppress the vibrations of the frequencies in the road noise band input to the vehicle body 1 during travel.

[0087] Moreover, in the above configuration, k and m of the reference k / m are set so that the k / m of at least two combinations of cells 22 and fixing parts 23 is within a range where the vibration damping effect is high as the reference k / m. However, there are two combinations having k / m values that are far from this reference k / m, that is, the combination of cells 22 and fixing parts 23 that is greater than the reference k / m and is the maximum k / m, and the combination of cells 22 and fixing parts 23 that is smaller than the reference k / m and is the minimum k / m.

[0088] 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 such that 0.2 < D < 550. As a result, a dispersion in the resonance frequency occurs while obtaining a vibration damping effect among a plurality of sets of the cells 22 and the fixing portions 23. Thereby, 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 vibration of the vehicle body 1 in a wide frequency band. <MASK><MASK><MASK>(2)<MASK>Further, in the present embodiment, when x = 2 which is the value of tanδ, <MASK>the minimum value k of k<MASK>is k<MASK>= 1.296×10<MASK>(1 / m)<MASK>and <MASK><MASK>the maximum value k of k<MASK>is k<MASK>= 1.929×10<MASK>m<MASK>and <MASK>when k<MASK>< k<MASK>it is preferable that k is set within the range of k<MASK>≦ k ≦ k<MASK>. <MASK><MASK><MASK>According to such a configuration, when the value of tanδ which is the loss coefficient of the fixing portion 23 is x = 2, the range of the support stiffness k of the fixing portion 23, that is, the range between k<MASK>and k<MASK>can be made the widest, and it is possible to select the support stiffness k from a wide range to suppress the vibration in the load noise band. As a result, the design freedom of the battery mounting structure is expanded. <MASK><MASK><MASK>(3)<MASK>Further, in the battery mounting structure of the present embodiment, k / m of half of the total number of sets of the cells 22 and the fixing portions 23 is the reference k / m. <MASK> <MASK> In this configuration, the k / m of half of the total number of cell 22 and fixed part 23 pairs is set to the above range, which provides a high vibration damping effect, as the reference k / m. This makes it possible to reliably improve the vibration damping effect and further improve NVH performance.

[0093] (4) Furthermore, in the battery mounting structure of this embodiment, the battery module 10 is positioned between adjacent cells 22 and further includes a partition supported by the battery housing 21. The fixing part 23 fixes the cell 22 in place while sandwiched between the cell 22 and the partition part 24.

[0094] In this configuration, the fixing part 23 can stably fix the cell 22 while sandwiched between the cell 22 and the partition part. This makes it possible to reliably resonate each cell 22 with elastic waves and exert a stable vibration suppression effect.

[0095] (modified version) (A) In the above embodiment, as shown in Figure 2, the fixing parts 23 (23A to 23D) made of polymer adhesive or the like bond the front and rear surfaces of each cell 22 (22A to 22D) to the adjacent partition parts 24, but the present invention is not limited thereto. The fixing parts 23 may bond one of the front and rear surfaces of each cell 22, for example, the front surface, to the adjacent partition part 24. Alternatively, the fixing parts 23 may directly fix one of the upper and lower surfaces of the cell 22 to the top or bottom plate of the battery housing 21.

[0096] (B) Furthermore, as another variation of the present invention, in a configuration in which two adjacent cells 22 in the vehicle longitudinal direction X are integrally connected by welding or bolting, the two integrated cells 22 may be treated as one large cell and their front and rear surfaces may be bonded to adjacent partition portions 24 by fixing portions 23. In such a configuration, the total mass of the two integrated cells 22 is denoted as the cell mass m, and the minimum value of the support stiffness k is k min and maximum value k maxYou just need to calculate this.

[0097] (C) In the above embodiment, the cell 22 was described using a plate-shaped or pouch-shaped cell as an example, but as a modified example of the present invention, a plurality of cylindrical cells 22 may be applied. [Explanation of symbols]

[0098] 1. Vehicle body 3 Front wheels 10 Battery Modules 21 Battery enclosure Cells 22, 22A~22D 23, 23A~23D fixed part 24 Partition section

Claims

1. In the battery mounting structure of an electric vehicle, The car body and, At least one battery module fixed to the vehicle body, The vehicle body is equipped with a pair of left and right front wheels that are rotatably mounted on both the left and right sides of the front of the vehicle body, The aforementioned battery module is Battery housing and The battery housing comprises four or more cells arranged in series in a predetermined direction, The battery housing comprises four or more fixing parts, each of which secures the plurality of cells individually to the battery housing. Equipped with, When the support rigidity of the fixed part is k [N / m] and the mass of the cell is m [kg], The k / m of at least two sets of cells and fixed parts out of all sets of cells and fixed parts becomes the reference k / m. The k and m in the above reference k / m are determined by setting the value of tanδ, which is the loss coefficient of the fixed part, to x, and Minimum value of k ｍｉｎ to, k ｍｉｎ = 5.184 × 10 ９ (1 / x) ２ (1 / m) ３ , The maximum value k of k ｍａｘ is k ｍａｘ = 482.2531x ２ m ５ , k ｍｉｎ <k ｍａｘ When that happens, k, k ｍｉｎ ≤k ≤k ｍａｘ It is set to be within the range, Among all the k / m values ​​of the cell and the fixed part set, the largest 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 cells and fixed 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 0.2 < D < 550. 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, In the case where x = 2, which is the value of tanδ, The minimum value of k ｍｉｎ to, k ｍｉｎ = 1.296 × 10 ９ (1 / m) ３ , Maximum value of k ｍａｘ to, k ｍａｘ = 1.929 × 10 ３ I understand ５ , k ｍｉｎ <k ｍａｘ When that happens, k, k ｍｉｎ ≤k ≤k ｍａｘ Set to the range A battery mounting structure for an electric vehicle characterized by the following features.

3. In the battery mounting structure for an electric vehicle according to claim 1 or 2, The k / m of half of the total number of cell and fixing part sets is set to the reference k / m. A battery mounting structure for an electric vehicle characterized by the following features.

4. In the battery mounting structure for an electric vehicle according to claim 1 or 2, The battery module further comprises a partition portion disposed between adjacent cells and supported by the battery housing, The fixing portion fixes the cell while being sandwiched between the cell and the partition portion. A battery mounting structure for an electric vehicle characterized by the following features.

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