JP7324427B2 - Battery unit mounting structure for electric vehicles - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery unit mounting structure for an electric vehicle including battery units that support battery modules and are mounted on a pair of floor frames.

Conventionally, in electric vehicles such as hybrid vehicles and electric vehicles, the battery that is the power source of the electric motor (for example, motor generator or motor) that drives the wheels has a large capacity, so the space below the vehicle body floor is used for the battery unit. are arranged as follows.
Generally, a battery unit is composed of a plurality of battery modules each made up of an assembly of battery cells such as lithium-ion cells, a battery case housing the plurality of battery modules, and a framework frame of the battery case.

The electric vehicle of Patent Document 1 has a battery unit supported by a pair of left and right side frames below the floor panel. a battery tray on which the plurality of battery modules are placed; a cover member covering the battery tray; and a plurality of girder members provided on the lower surface of the battery tray and extending in the vehicle width direction. is fixed to the side frame via fastening bolts.

Structures that support battery modules using members other than battery trays are also known.
The battery pack of Patent Document 2 includes a second case portion that houses a plurality of battery modules, a first case portion that covers the second case portion, and a first and second case portion that supports the first and second case portions. A center plate provided between the case portions supports the plurality of battery modules while being spaced from the bottom plate of the second case portion.

During steady running, the vibration energy generated by the wheels and the road surface is transmitted to the vehicle body strength members via the suspension members, vibrating the panel members such as the floor panel that constitute the passenger compartment. Vibrations of these panel members generate driving noise such as drumming noise and road noise.
The drumming noise is a low frequency sound of 20-50 Hz, and the road noise is a medium frequency sound of 100-400 Hz. It is sometimes called road noise including drumming noise. Driving noise such as drumming noise and road noise is reduced by adding damping materials and increasing the rigidity of the lower body.

Japanese Patent Application Laid-Open No. 2009-083601 JP 2013-129391 A

In an electric vehicle equipped with a battery unit, since the battery unit is a heavy object, there is concern that it will resonate with vehicle body vibration in a predetermined frequency band and increase running noise.
Therefore, simulation analysis by CAE (Computer Aided Engineering) was performed for the purpose of clarifying the relationship between the battery unit and running noise.
A vehicle model A (evaluation reference model) that is not equipped with a battery unit and a vehicle model B that has substantially the same specifications as the model A except for the battery unit and is equipped with a battery unit are created. The vibration of the car body at each was calculated. The battery unit has a total weight of 300 kg, and 16 battery modules of the same shape and arranged in the same posture are firmly supported. Also, as an evaluation index for vehicle body vibration, an equivalent radiation energy (ERP) corresponding to the radiated acoustic power was calculated from the displacement of each node of each model.

Analysis results will be described based on FIG.
As shown in FIG. 15, the model B equipped with the battery unit indicated by the dashed line generates low-frequency driving noise in a frequency band of about 40 Hz, and the drumming is greater than the model A not equipped with the battery unit indicated by the solid line. It was found that the noise performance deteriorated.
As a result of investigations by the inventors, it was found that the vertical behavior of the battery module, which accounts for most of the weight of the battery unit, resonates with the vertical vibration of the vehicle body-side frame and induces a low-frequency vehicle body bending motion. In other words, the higher the mounting rigidity of the battery module, the greater the tendency of the vehicle body frame to resonate. That is, it is not easy to achieve both securing of mounting rigidity of the battery module and reduction of running noise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a battery unit mounting structure and the like for an electric vehicle that can reduce traveling noise while ensuring mounting rigidity of a battery module.

A battery unit mounting structure for an electric vehicle according to claim 1 comprises a floor panel, a pair of left and right floor frames forming a closed cross section extending forward and backward in cooperation with the floor panel below the floor panel, and a battery module. a battery unit supported and attached to the pair of floor frames, the battery unit having attachment portions for the battery module and the pair of floor frames and a pair of left and right sides extending in the front-rear direction. a frame, a battery tray supported by at least the pair of side frames and forming a bottom portion of the battery unit, and a plurality of cross frames connecting between the pair of side frames; a first cross frame attached to the cross frame so as to be displaceable in the vertical direction with respect to the battery tray, the cross frame sandwiched between single-layer module housing regions for housing the battery modules in a single layer state; a second cross frame sandwiched between a layer module housing area and a two-layer module housing area housing the battery modules in two layers arranged vertically, wherein the second cross frame and the battery tray; and a closed cross section formed in cooperation with the battery tray, and a lower cross frame forming a closed cross section vertically adjacent to the battery tray in cooperation with the battery tray.

In this battery unit mounting structure for an electric vehicle, the battery unit includes the battery module, a pair of left and right side frames having mounting portions for the pair of floor frames and extending in the front-rear direction, and at least the pair of side frames. and a plurality of cross frames connecting between the pair of side frames. can be firmly connected to a pair of floor frames. Since the battery module is attached to the cross frame so as to be displaceable in the vertical direction with respect to the battery tray, the vertical movement of the battery tray supported by the side frames is separated from the vertical movement of the battery module. Directivity can be imparted, and resonance in the vertical direction between the vehicle body and the battery unit can be suppressed.
Further, in this battery unit mounting structure for an electric vehicle, the cross frame includes a first cross frame sandwiched between the single-layer module housing areas and a second cross frame sandwiched between the two-layer module housing areas. and a lower cross frame that cooperates with the battery tray to form a closed cross section formed by cooperation between the second cross frame and the battery tray and a closed cross section vertically adjacent to the battery tray with the battery tray therebetween. Therefore, it is possible to reinforce the second cross frame to which a large weight is applied without affecting the inside of the battery tray.

According to a second aspect of the invention, in the first aspect of the invention, the cross frame is configured to cooperate with the battery tray to form a closed cross section on the upper side of the battery tray, and extends vertically to form the battery module. and a fixing wall portion extending forward or rearward from the lower end of the connecting wall portion and fixed to the upper wall portion of the cross frame, the mounting bracket comprising: The battery module is connected to the battery module so that the height position of the center of gravity of the battery module and the height position of the upper wall portion of the cross frame are substantially the same height position.
According to this configuration, the mounting rigidity of the battery modules can be ensured with a simple configuration, and the vertical movement of the cross frame and the vertical movement of the battery modules can be synchronized while synchronizing the vehicle width direction movement of the cross frame and the vehicle width direction movement of the battery modules. can be separated from

The invention of claim 3 is the invention of claim 2, wherein the battery unit accommodates the battery modules such that the long axes of the battery modules are along the side frames, and a plurality of modules separated by the cross frames. It is characterized in that it has an accommodation area, and a battery module arranged in a module accommodation area sandwiching the cross frame is attached to the cross frame.
According to this configuration, the cross frame can be shared for supporting battery modules arranged in different module housing areas, and the number of cross frames can be reduced.

According to the invention of claim 4 , in the invention of claim 1 , the cross frame is formed on the side opposite to the second cross frame with respect to the first cross frame and is only between the first cross frame. A third cross frame forming a layer module accommodation area is included, and a first upper wall connection portion connecting the upper wall portion of the second cross frame to the upper wall portion of the side frame and a side wall portion of the second cross frame are connected to the above-mentioned A first side wall connecting portion that connects to the side wall portions of the side frames is integrally and continuously formed, and a second upper wall connecting portion that connects the upper wall portion of the third cross frame to the upper wall portion of the side frame and the first side wall connecting portion. A second side wall connecting portion connecting the side wall portion of the 3-cross frame to the side wall portion of the side frame is formed independently.
According to this configuration, the connecting portion between the second cross frame and the side frames to which a heavy weight is applied is strengthened, and the connecting portion between the third cross frame and the side frames to which a heavy weight is not applied is simplified. , weight reduction and productivity improvement can be achieved.

According to the invention of claim 5, in the invention of claim 2 , the module accommodation area is configured to accommodate a plurality of the battery modules, and the mounting bracket attaches the plurality of battery modules to the cross frame. is characterized by
With this configuration, the mounting bracket can be shared for supporting a plurality of battery modules, and the number of mounting brackets can be reduced.
The battery unit mounting structure for an electric vehicle according to claim 6 comprises a floor panel, a pair of left and right floor frames forming a closed cross section extending forward and backward in cooperation with the floor panel below the floor panel, and a battery module. a battery unit supported and attached to the pair of floor frames, the battery unit having attachment portions for the battery module and the pair of floor frames and a pair of left and right side frames extending in the front-rear direction. a battery tray supported by at least the pair of side frames and forming a bottom portion of the battery unit; and a plurality of cross frames connecting between the pair of side frames, wherein the battery module is connected to the battery. The cross frame is attached to the cross frame so as to be vertically displaceable with respect to the tray, and the cross frame is configured to cooperate with the battery tray to form a closed cross section on the upper side of the battery tray. A mounting bracket having a connecting wall portion connected to the module and a fixed wall portion extending forward or rearward from the lower end of the connecting wall portion and fixed to the upper wall portion of the cross frame is provided, wherein the mounting bracket is , the battery module is connected to the battery module such that the height position of the center of gravity of the battery module and the height position of the upper wall portion of the cross frame are substantially the same height position, and the battery unit is aligned with the longitudinal axis of the battery module. accommodates the battery modules along the side frames and has a plurality of module accommodation areas separated by the cross frames; a first cross frame to which a battery module is attached, the cross frame sandwiched between single-layer module housing areas that house the battery modules in a single-layer state; a second cross frame sandwiched between a two-layered two-layer module housing area arranged in two stages, wherein the second cross frame and the battery tray cooperate to form a closed cross section; It is characterized in that a lower cross frame is provided which cooperates with the battery tray to form closed cross sections vertically adjacent to each other with the battery tray interposed therebetween.

According to the battery module mounting structure for an electric vehicle of the present invention, by imparting directivity to the movement of the battery module, it is possible to reduce running noise while ensuring the mounting rigidity of the battery module.

2 is a bottom view of the electric vehicle according to the first embodiment; FIG. It is the perspective view which looked at the electric vehicle from the back side downward direction. 3 is an exploded perspective view of the battery unit; FIG. FIG. 4 is a plan view of the battery unit with the cover member and the right battery module omitted; Fig. 2 is a front perspective view of the battery unit with the cover member and the right battery module omitted; FIG. 5 is a perspective cross-sectional view of a main part of FIG. 4; FIG. 5 is a cross-sectional view taken along line VII-VII of FIG. 4; 5 is a cross-sectional view taken along line VIII-VIII of FIG. 4; FIG. FIG. 4 is a perspective view of first to third mounting brackets; FIG. 4 is an explanatory diagram of an evaluation model and frame rigidity; FIG. 4 is an explanatory diagram of module support rigidity; 4 is a graph showing the relationship between the flexural rigidity of a side frame and the flexural rigidity of a module support mechanism; FIG. 4 is an explanatory diagram of a module support mechanism; It is an analysis result about the vehicle body vibration of a present Example model and an evaluation standard model. It is an analysis result about the vehicle body vibration of a conventional model and an evaluation standard model.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing. The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its applications or uses.

Embodiment 1 of the present invention will be described below with reference to FIGS. 1 to 14. FIG.
A vehicle V according to the first embodiment is a hybrid vehicle that uses an internal combustion engine (not shown) such as a gasoline engine or a diesel engine and an electric motor (motor generator) (not shown) for driving the vehicle as drive sources.

As shown in FIGS. 1 and 2, a vehicle V includes a pair of left and right side sills 1 extending longitudinally, a floor panel 2, a pair of left and right floor frames 3 extending longitudinally, a battery unit 10, and the like. . Hereinafter, in the drawings, the direction of arrow F is defined as the front in the longitudinal direction of the vehicle body, the direction of arrow L is defined as the left in the vehicle width direction, and the direction of arrow U is defined as the upper direction in the vertical direction of the vehicle. Further, the vehicle V has a substantially bilaterally symmetrical structure.

First, the overall configuration of the vehicle V will be described.
The side sill 1 includes an outer panel having a substantially hat-shaped cross section forming a vehicle width direction outer wall portion, and an inner panel having a substantially hat-shaped cross section forming a vehicle width direction inner wall portion. It forms an elongated substantially rectangular closed cross section. A vertically extending hinge pillar is connected to the front end portion of the side sill 1, and a vertically extending rear pillar is connected to the rear end portion thereof. The vehicle V has a so-called double door structure in which the front door opens and closes around the hinge of a hinge pillar formed at the front end, and the rear door opens and closes around the hinge of the rear pillar formed at the rear end. , the center pillar is omitted.

The floor panel 2 is formed in a full-flat shape so as to span between a pair of side sills 1, and does not have a tunnel portion that bulges into the vehicle interior.
As shown in FIGS. 1, 2, and 8, the floor panel 2 includes a front panel 2a on which a seat for a front passenger (not shown) is mounted, and a front panel 2a which slopes backward upward from the rear end of the front panel 2a. It also has a rear panel 2b on which a rear seat passenger seat (not shown) is mounted.

The pair of floor frames 3 are each formed to have a substantially hat-shaped cross section, and the distance between the pair of floor frames 3 increases toward the rear. Therefore, the distance between the side sill 1 and the adjacent floor frame 3 becomes closer toward the rear. The floor frame 3 cooperates with the lower surface of the front panel 2a to form a closed cross section with a substantially rectangular cross section extending forward and backward. The rear suspension 4 is arranged behind the kick-up panel 2c and below the rear panel 2b. The suspension 4 has a pair of left and right trailing arms 4a that rotatably support wheels (not shown) at its rear end, and a pair of trailing arms 4a at both ends in the vehicle width direction. It is a torsion beam type suspension with an extending torsion beam 4b.

Next, the battery unit 10 will be explained.
As shown in FIGS. 1 to 3, the battery unit 10 is laid out in the space below the floor panel 2. As shown in FIG. The battery unit 10 includes a plurality of (for example, 16) battery modules 11 and a battery case 12 that houses the plurality of battery modules 11 . The battery module 11 that supplies electric power to the electric motor for driving the vehicle is formed into a rectangular parallelepiped battery assembly in which a plurality of rectangular parallelepiped battery cells 11a (see FIG. 8) having a standard voltage are arranged in a stack in the front-rear direction. there is The battery cell 11a is, for example, a lithium ion battery, which is a type of secondary battery.
The plurality of battery modules 11 are set to the same specifications including vertical, horizontal and height dimensions, and are housed in the battery case 12 with their longitudinal directions parallel to the front-rear direction.
The weight of this battery module 11 is, for example, approximately 14 kg, and the total weight of the battery unit 10 is, for example, approximately 300 kg.

Since the battery case 12 accommodates a high-voltage battery in which the battery modules 11 are connected in series, it is configured to ensure vibration resistance and water resistance.
As shown in FIG. 3, the battery case 12 includes a pair of left and right side frames 21, a front frame 22 that extends left and right and connects the front ends of the pair of side frames 21, and a pair of side frames that extend left and right. A rear frame 23 that connects the rear end of the frame 21, a tub-shaped battery tray 24 that is supported by each of the frames 21 to 23 and forms the bottom of the battery case 12, and a plurality of A cover member 25 made of synthetic resin and the like is provided to form a sealed space capable of accommodating the battery module 11 . The vertical bending rigidity of the side frames 21 is set to be lower than the vertical bending rigidity of the floor frame 3 .

In each of the frames 21 to 23, a substantially L-shaped lower panel and a substantially L-shaped upper panel cooperate to form a substantially rectangular closed cross section (see FIG. 7). The closed cross-sections formed by the frames 21 to 23 are connected in a ring to form a substantially square-shaped closed cross-section structure.
Each frame 21-23 is attached to the vehicle body by attachment portions 26-29.
The four pairs of left and right mounting portions 26 and the one pair of left and right mounting portions 27 extend outward in the vehicle width direction from the lower panels of the pair of side frames 21 . These mounting portions 26 and 27 are fastened and fixed to the lower wall portion of the floor frame 3 via bolts b. A pair of left and right mounting portions 28 extend forward from the lower panel of the front frame 22 . These mounting portions 28 are fastened and fixed to the lower surface of the front portion of the front panel 2a via bolts b. The mounting portion 29 extends upward from the center portion of the lower panel of the rear frame 23, and its upper end portion is fastened and fixed to a cross member (not shown) that cooperates with the rear panel 2b to form a closed cross-section that extends left and right via bolts b. It is

As shown in FIGS. 3 to 5, the battery tray 24 is firmly welded while being placed on the upper walls of the frames 21 to 23 . Therefore, the bending behavior of the battery tray 24 in the vertical direction can be regarded as substantially the same behavior as the bending behavior of the frames 21 to 23 in the vertical direction. A plate-shaped rubber member (not shown) is arranged between the battery tray 24 and the battery module 11 with a cooling pipe (not shown) interposed therebetween. Thereby, the gap between the battery tray 24 and the battery module 11 is configured to be relatively displaceable.

The battery tray 24 is divided into first to third housing areas (battery housing areas) S1 to S3 for housing the battery modules 11 by first to third cross frames 31 to 33 having substantially hat-shaped cross sections. The third and first cross frames 33, 31 define the front and rear range of the first housing area S1 corresponding to the lower front portion of the front panel 2a (front passenger seat). 32 defines the front and rear range of the second accommodation area S2 corresponding to the lower rear portion of the front panel 2a, and the second cross frame 32 and the rear frame 23 form the third accommodation area corresponding to the lower portions of the kick-up panel 2c and the rear panel 2b. It divides the range before and after the region S3. The first and second housing regions S1 and S2 each house four battery modules 11 in a single-layer state in a laterally aligned manner.

The third storage area S3 has a two-stage support mechanism 40, and has two layers in which four battery modules 11 are aligned horizontally and four battery modules 11 are aligned horizontally above these battery modules 11. 8 battery modules 11 are accommodated in the state.
As shown in FIGS. 4 to 6, the two-stage support mechanism 40 includes a substantially .pi. The upper four battery modules 11 are provided with a pair of left and right substantially T-shaped side support portions 43 that connect the left and right ends of the battery modules 11, respectively, and a bottom plate member 44 that spans the respective support portions 41 to 43. support. A pair of left and right legs of the front support portion 41 are fastened and fixed to the upper wall portion of the second cross frame 32 , and a pair of left and right legs of the rear support portion 42 are arranged above the rear support portion 35 extending to the left and right. Fastened to the wall.

As shown in FIGS. 6 and 8, the rear support portion 35 has a substantially L-shaped cross section. The rear support portion 35 has a rear end portion of the upper wall portion connected to the front wall portion of the rear frame 23 and a lower end portion of the front wall portion connected to the battery tray 24 . Together they form a closed cross-section extending left and right. Leg portions of the pair of side support portions 43 are fastened and fixed onto the battery tray 24 .

The first to third cross frames 31 to 33 cooperate with the battery tray 24 on the upper side of the battery tray 24 to form closed cross sections extending left and right. These first to third cross frames 31 to 33 are configured to have approximately the same bending rigidity in the vertical direction as the side frame 21, and are arranged at approximately equal intervals in the front-rear direction.

As shown in FIGS. 4 to 6, the first cross frame 31 includes upper wall connecting portions 31a extending outward in the vehicle width direction from both left and right ends of the upper wall portion, and left and right ends of the front wall portion and the rear wall portion. A pair of front and rear side wall connecting portions 31b extending forward and rearward from each other are formed. The upper wall connecting portion 31a is connected to the upper wall portion of the side frame 21, and the pair of side wall connecting portions 31b are connected to the inner side wall portions of the side frame 21, respectively. The upper wall connecting portion 31a and the pair of side wall connecting portions 31b are continuously formed so as to be integrally connected. The third cross frame 33 includes an upper wall connection portion 33a extending outward in the vehicle width direction from both left and right ends of the upper wall portion, and a front and rear pair of front and rear wall portions extending forward and rearward from both left and right ends of the front wall portion and the rear wall portion, respectively. side wall connecting portion 33b is formed. The upper wall connecting portion 33a is connected to the upper wall portion of the side frame 21, and the pair of side wall connecting portions 33b are connected to the inner side wall portions of the side frame 21, respectively. The upper wall connecting portion 33a and the pair of side wall connecting portions 33b are formed independently.

The second cross frame 32 includes an upper wall connecting portion 32a extending outward in the vehicle width direction from both left and right ends of the upper wall portion, and a front and rear pair extending forward and rearward from both left and right ends of the front wall portion and the rear wall portion, respectively. side wall connecting portion 32b is formed. The upper wall connecting portion 32a is connected to the upper wall portion of the side frame 21, and the pair of side wall connecting portions 32b are connected to the inner side wall portions of the side frame 21, respectively. The upper wall connecting portion 33a and the pair of side wall connecting portions 33b are continuously formed so as to be integrally connected. As shown in FIGS. 1 and 6 to 8, a lower cross frame 34 extending laterally is provided on the lower surface of the battery tray 24. As shown in FIG. The lower cross frame 34 cooperates with the battery tray 24 below the battery tray 24 to form closed cross sections that extend left and right. The closed cross section formed by the lower cross frame 34 is vertically adjacent to the closed cross section formed by the second cross frame 32 with the battery tray 24 interposed therebetween.

Each battery module 11 is attached to the first to third cross frames 31 to 33 and the rear support portion 35 via a pair of front and rear attachment brackets 51 to 53 made of sheet metal.
The vertical bending rigidity of the mounting brackets 51 to 53 is higher than the vertical bending rigidity of the battery tray 24 and higher than the vertical bending rigidity of the first to third cross frames 31 to 33 and the rear support portion 35. set to be low.

As shown in FIG. 9, the mounting brackets 51 to 53 include connecting wall portions 51a to 53a that extend vertically and are connected to the battery module 11, and fixed wall portions 51b to 51b that extend forward and backward and are fastened via fastening members. 53b, and has a substantially L-shaped cross section. Connecting wall portions 51a and 53a of the mounting bracket attached to the front side of the battery module 11 are connected to the front wall portions of the two battery modules 11 adjacent to each other via four bolts. The connecting wall portions 52a and 53a of the mounting brackets attached to the battery modules 11 are connected to the rear wall portions of the two battery modules 11 adjacent to each other via four bolts.

As shown in FIGS. 4, 5, and 8, the connecting wall portions 51a to 53a of the mounting bracket are connected to the lower battery module 11 accommodated in the first, second accommodation areas S1, S2 and the third accommodation area S3. They are supported so that the center of gravity G is positioned on an extension line L1 extending forward and backward.
Further, as shown in FIG. 8, the upper wall portions of the first to third cross frames 31 to 33 and the rear support portion 35 are formed so as to be positioned on the extension line L2 in side view. The extension line L1 and the extension line L2 are configured to be at substantially the same height position when viewed from the side.

A pair of left and right first mounting brackets 51 fixed to the third cross frame 33 and a pair of left and right second mounting brackets 52 fixed to the first cross frame 31 are arranged in the first accommodation area S1. ing. As shown in FIG. 9A, the first mounting bracket 51 is formed by pressing a 1.6 mm steel plate, for example, and includes a connecting wall portion 51a and a fixed wall portion 51b. The fixed wall portion 51b has a fastening portion 51s extending forward (in the direction opposite to the bent portion) at the left end portion, and is slightly closer to the center portion than the middle portion between the center portion and the left end portion of the fixed wall portion 51b. A positioning portion 51p extending forward is formed, and a fastening portion 51t extending forward is formed in a portion symmetrical to the positioning portion 51p with respect to the central portion of the fixed wall portion 51b.

The fixed wall portion 51b extends forward from the bent portion, and the fastening portion 51s and the fastening portion 51t are fixed to the upper wall portion of the third cross frame 33 via bolts. The connecting wall portion 51 a is supported in a cantilevered state extending from the upper wall portion of the third cross frame 33 . In addition, in the left first mounting bracket 51 corresponding to the lower side of the passenger seat, positioning is performed by the fastening portion 51s on the outside in the vehicle width direction, and fastening and fixing is performed by the positioning portion 51p on the inside in the vehicle width direction (see FIG. 4).

As shown in FIG. 9B, the second mounting bracket 52 is formed by pressing a 1.6 mm steel plate, for example, and includes a connecting wall portion 52a and a fixed wall portion 52b. The fixed wall portion 52b has a rearwardly extending fastening portion 52s formed at its right end, a rearwardly extending fastening portion 52t formed at its left end, and a rearwardly extending fastening portion 52u formed at the central portion of the fixed wall portion 52b. A positioning portion 52p extending rearward is formed in the central portion between the fastening portion 52s and the fastening portion 52u. The fixed wall portion 52b extends rearward from the bent portion, and the fastening portion 52s, the fastening portion 52t, and the fastening portion 52u are fixed to the upper wall portion of the first cross frame 31 via bolts. The connecting wall portion 52 a is supported in a cantilevered state extending from the upper wall portion of the first cross frame 31 .

A pair of left and right third mounting brackets 53 fixed to the first cross frame 31 and a pair of left and right third mounting brackets 53 fixed to the second cross frame 32 are arranged in the second accommodation area S2. ing. As shown in FIG. 9C, the right third mounting bracket 53 fixed to the first cross frame 31 is formed by pressing a steel plate of 2.0 mm, for example, and is formed by connecting the wall portion 53a and the fixing bracket 53a. and a wall portion 53b. The fixed wall portion 53b has a positioning portion 53p extending forward at the left end, a fastening portion 53s extending forward at the center portion between the center portion and the left end of the fixed wall portion 53b, and a fastening portion 53s extending forward at the left end. A fastening portion 53t extending forward is formed.

The fixed wall portion 53b extends forward from the bent portion and is fixed to the upper wall portion of the first cross frame 31 via bolts. The connecting wall portion 53a is supported in a cantilevered state projecting from the upper wall portion of the first cross frame 31 . The left third mounting bracket 53 fixed to the first cross frame 31 in a cantilevered state and the pair of right and left third mounting brackets 53 fixed to the second cross frame 32 in a cantilevered state are also arranged in the same manner. It is configured.

A pair of left and right third mounting brackets 53 fixed to the second cross frame 32 in a cantilevered state, and a pair of left and right mounted brackets fixed to the rear side support portion 35 in a cantilevered state are provided in the lower stage of the third accommodation area S3. , and the third mounting bracket 53 are arranged in the same manner as the second housing area S2. Furthermore, in the upper stage of the third accommodation area S3, a pair of left and right third mounting brackets 53 fixed to the front support portion 41 in a cantilever state and a pair of left and right mounting brackets 53 fixed to the rear support portion 42 in a cantilever state are provided. , and the third mounting bracket 53 are arranged in the same manner as in the lower stage. The first to third mounting brackets 51 to 53 have substantially the same specifications except for plate thickness, positions of fastening portions, and positions of positioning portions.

Here, the relationship between the frame rigidity and the module support rigidity will be described with respect to running noise. After creating an evaluation model for the battery case 12 of the vehicle V, the inventor conducted CAE analysis of running noise with respect to a reference noise level while changing the rigidity ratio between the frame rigidity and the module support rigidity. The frame rigidity is regarded as the vertical bending rigidity of the side frames 21 exhibiting the same behavior as the floor frame 3, and the module support rigidity is defined as the vertical bending rigidity of the third cross frame 33 and the vertical bending rigidity of the mounting bracket. It is regarded as the total stiffness with the bending stiffness of

As shown in FIG. 10( a ), the evaluation model for this analysis supports the lower four corners of each of the front and rear ends of a pair of side frames 21 . As indicated by the arrow in FIG. 10(b), a predetermined measurement load was applied from above to the maximum amplitude position of the side frame 21 when measuring the frame rigidity. Based on the above, the frame rigidity is defined as the vertical bending rigidity (N/mm) of the side frames 21 exhibiting substantially the same behavior as the floor frame 3 . In addition, since the high-rigidity two-stage support mechanism 40 that accommodates eight battery modules 11 in two layers is disposed in the third accommodation area S3, eight battery modules 11 in two rows in a single layer are arranged. The rigidity is higher than that of the first and second accommodation areas S1 and S2 that accommodate the . Therefore, in this evaluation model, the midpoint between the first and second accommodation areas S1 and S2 (connection position between the side frame 21 and the first cross frame 31), which has a large effect on the running noise of the vehicle V, is the side frame 21. corresponds to the maximum amplitude position of

The module support rigidity is defined as the vertical bending rigidity (N/mm) of the mounting bracket 51 when viewed from the front. In the first and second housing areas S1 and S2, eight single-layer battery modules 11 are supported by the first to third cross frames 31-33 via mounting brackets 51-53. Since the first to third cross frames 31 to 33 are highly rigid members compared to the mounting brackets 51 to 53, the module supporting rigidity can be regarded as the bending rigidity of the mounting bracket 51 in the vertical direction. As shown in FIG. 11(a), the connecting wall portion 51a connected to the mounting bracket 51 is supported in a cantilevered state projecting from the upper wall portion of the third cross frame 33. , the bending rigidity of the mounting bracket 51 in the vertical direction, in other words, the module supporting rigidity, is obtained using the vertical displacement amount of the connecting wall portion 51a. The same applies to the mounting brackets 52 and 53 as well.

The analysis results are shown in FIG. The horizontal axis is the frame stiffness, and the vertical axis is the module support stiffness.
As shown in FIG. 12, from this analysis result, in the region where the module support rigidity is lower than approximately 1000 N/mm, the region with good noise performance (region where the noise level is lower than the reference noise level) and the region with poor noise performance (region where the noise level is lower than the reference noise level) It was found that the boundary line of the area where the noise level is higher than the reference noise level shows linear function characteristics, and that the noise performance deteriorates in the frame rigidity area higher than the boundary line of approximately 4000 N/mm. That is, the higher the frame rigidity, the better the noise level, but the thickness of the side frame 21 increases, which poses a problem in that the weight of the vehicle body increases. In the range of approximately 1000 N/mm or less, in other words, the frame rigidity is approximately 4000 N/mm or less, and the vertical module support rigidity (vertical bending rigidity of the mounting bracket 51) is equal to the vertical bending rigidity of the side frame 21. On the other hand, it was confirmed that running noise can be improved without increasing the vehicle weight by adjusting each rigidity to a range of 25% or less.

That is, when the module support rigidity in the vertical direction is high, as indicated by the dotted line in FIG. 13, the vertical movement of the battery module 11 and the vertical movement of the side frame 21 resonate, causing running noise such as drumming noise. . On the other hand, when the vertical module support rigidity is 25% or less of the vertical bending rigidity of the side frame 21, the momentum (vibration period) of the battery module 11 increases as indicated by the dashed line in FIG. , increases independently of the momentum of the side frame 21, forming a so-called double vibration isolation mechanism (double spring).
Thereby, resonance between the vertical movement of the battery module 11 and the vertical movement of the third cross frame 33 can be avoided. The vertical movement of the third cross frame 33 (battery tray 24) connected to the side frame 21 is separated from the vertical movement of the battery module 11, and the directivity of the movement of the battery module 11 (allowing vertical movement and restricting horizontal movement) is achieved. ) suppresses resonance between the vehicle body and the battery unit 10 in the vertical direction.

As described above, in this embodiment, the fixing wall portions 51b to 53b of the mounting brackets 51 to 53 extend in the direction opposite to the battery module 11 to be fixed, and are bent from the fixing wall portions 51b to 53b. Since each of the mounting brackets 51 to 53 is fixed by each fastening portion extending in the opposite direction to the mounting brackets 51 to 53, only vertical movement of each of the mounting brackets 51 to 53 is allowed with each fastening portion as a fulcrum. Therefore, it is possible to reduce the module support rigidity consisting of the vertical bending rigidity of the cross frames and the vertical bending rigidity of the mounting brackets without the need to reduce the vertical bending rigidity of the cross frames 31-33. there is

Next, the operation and effects of the battery unit mounting structure will be described.
A simulation analysis by CAE (Computer Aided Engineering) was performed to explain the action and effect. A vehicle model A (evaluation reference model) not equipped with a battery unit and a vehicle model C of the present embodiment were created, and the vehicle body vibration in each frequency band was calculated for the models A and C, respectively. Vehicle model A and vehicle model C have substantially the same specifications except for the battery unit. Also, as an evaluation index for vehicle body vibration, equivalent radiation energy (ERP) corresponding to radiated acoustic power is calculated from the displacement of each node of each model.

FIG. 14 shows the analysis results. The horizontal axis indicates frequency, and the vertical axis indicates vehicle body vibration.
As shown in FIG. 14, it was confirmed that the vehicle body vibration of model C indicated by the dashed line is lower than that of model A indicated by the solid line in the low frequency region. In particular, model C can suppress vehicle body vibration in a frequency band around 40 Hz, which causes drumming noise, and greatly improves drumming noise performance.

According to the battery unit mounting structure according to the first embodiment, the battery unit 10 includes the battery module 11, the pair of left and right side frames 21 having mounting portions 26 and 27 for the pair of floor frames 3 and extending in the front-rear direction, Since the battery tray 24 is supported by at least one pair of side frames 21 and forms the bottom of the battery unit 10, and the first to third cross frames 31 to 33 connect between the pair of side frames 21. , the pair of side frames 21 of the battery unit 10 can be firmly connected to the pair of floor frames 3 while reducing the weight of the battery unit 10 .
Since the battery modules 10 are attached to the first to third cross frames 31 to 33 so as to be vertically displaceable with respect to the battery trays 24, the vertical movement of the battery trays 24 supported by the side frames 21 and the vertical movement of the battery modules 11 are controlled. The movement of the so-called battery module 10, which separates the battery unit 10, can have directivity, and the resonance between the vehicle body and the battery unit 10 in the vertical direction can be suppressed.

The first to third cross frames 31 to 33 are configured to cooperate with the battery tray 24 to form a closed cross section on the upper side of the battery tray 24, and extend vertically to connect to the battery modules 10. portions 51a to 53a, and fixed wall portions 51b to 53b extending from the lower ends of the connecting wall portions 51a to 53a in the direction opposite to the battery module 11 and fixed to the upper wall portions of the first to third cross frames 31 to 33. are provided, and the first to third mounting brackets 51 to 53 are positioned between the height position (L1) of the center of gravity G of the battery module 11 and the first to third cross frames 31 to 33 and the rear support portion 35 are connected to the battery module 11 so that the height positions (L2) of the upper wall portions thereof are substantially at the same height position. As a result, the mounting rigidity of the battery module 11 can be ensured with a simple structure, and the vehicle width direction motion of the first to third cross frames 31 to 33 and the vehicle width direction motion of the battery module 11 can be synchronized with each other. The vertical movement of the three cross frames 31-33 and the vertical movement of the battery module 11 can be separated.

The battery unit 10 accommodates the battery module 11 so that the long axis of the battery module 11 is along the side frame 21, and three first to third accommodation areas S1 separated by the first to third cross frames 31 to 33. , S3, and the first and second cross frames 31 and 32 are arranged in the first to third accommodation areas S1 to S3 with the first and second cross frames 31 and 32 interposed therebetween. installed. As a result, the first and second cross frames 31 and 32 can be shared for supporting the battery modules 11 arranged in the different first to third accommodation areas S1 to S3, thereby reducing the number of cross frames. can.

A first cross frame 31 sandwiched between first and second housing areas S1 and S2 for housing the battery modules 11 in a single layer state, and a second housing area S2 and the battery modules 11 are vertically arranged in two stages. A second cross frame 32 sandwiched between a third accommodation area S3 arranged in a two-layer state and a closed cross section formed by the second cross frame 32 and the battery tray 24 in cooperation with the battery tray 24 A lower cross frame 34 is provided that cooperates with the battery tray 24 to form a closed cross section that is adjacent in the vertical direction with the tray 24 interposed therebetween. As a result, the second cross frame 32 to which a heavy weight is applied can be reinforced without affecting the interior of the battery tray 24 .

The cross frame includes a third cross frame 33 formed on the side opposite to the second cross frame 32 with respect to the first cross frame 31 and forming a first accommodation area S1 only between the first cross frame 31, A first upper wall connecting portion 32 a connecting the upper wall portion of the second cross frame 32 to the upper wall portion of the side frame 21 and a first side wall connecting portion connecting the side wall portion of the second cross frame 32 to the side wall portion of the side frame 21 . The second upper wall connecting portion 33a connecting the upper wall portion 33a of the third cross frame 33 to the upper wall portion of the side frame 21 and the side wall portion of the third cross frame 33 are integrally and continuously formed with the portion 31b. A second side wall connecting portion 33b connected to the side wall portion of the side frame 21 is formed independently.
As a result, the connecting portion between the second cross frame 32 and the side frames 21 to which a heavy weight is applied is strengthened, and the connecting portion between the third cross frame 33 and the side frames 21 to which a heavy weight is not applied is simplified. Therefore, weight reduction and productivity improvement can be achieved.

The first to third housing areas S1 to S3 are configured to house a plurality of battery modules 11, and the first to third mounting brackets 51 to 53 connect the pair of left and right battery modules 11 to the first to third cross sections. Since the first to third mounting brackets 51 to 53 are attached to the frames 31 to 33, the first to third mounting brackets 51 to 53 can be shared for supporting the plurality of battery modules 11, and the number of the first to third mounting brackets 51 to 53 is reduced. be able to.

Next, a modified example in which the above embodiment is partially changed will be described.
1) In the above embodiment, an example of the battery case 12 provided with the first to third housing areas S1 to S3 and the first to third cross frames 31 to 33 was described. The battery case 12 may be provided with a single housing area and a single cross frame, as long as it permits movement and provides directivity to restrict movement in the left-right direction.

2) In the above embodiment, three types of first to third mounting brackets 51 to 53 have been described, but a single mounting bracket may also be used. In addition, although an example in which a pair of left and right mounting brackets are provided on the cross frame has been described, a single cross frame may be provided with one or three or more mounting brackets, and a single mounting bracket may be provided with one or three mounting brackets. Any of the above battery modules may be attached.

3) In the above embodiment, the height position (L1) of the center of gravity G of the battery module 11 and the height position (L2) of the upper wall portions of the first to third cross frames 31 to 33 and the rear support portion 35 are Although an example in which the connecting wall portions 51a to 53a are configured at approximately the same height has been described, at least the bottom end of the contact portion where the connecting wall portions 51a to 53a are in close contact with the battery module 11 is at approximately the same height as the center of gravity G of the battery module 11. , the effects of the present invention can be obtained. That is, in the present invention, the height position of the center of gravity of the battery module 11 is the height position of the upper wall portions of the first to third cross frames 31 to 33 and the connecting wall portions 51a to 53a are in close contact with the battery module 11. It includes a structure arranged between the lower end.

4) In the above-described embodiment, the battery module 11 is attached to the cross frames 31 to 33 and the rear support portion 35, and is vertically displaceable with respect to the battery tray 24. Although an example in which plate-like rubber members are provided has been described, at least the battery modules 11 need only be vertically displaceable, and a predetermined gap may be provided between the battery tray 24 and the battery modules 11 .

5) In addition, without departing from the spirit of the present invention, a person skilled in the art can implement the above-described embodiment in a form in which various modifications are added or in a form in which each embodiment is combined. Any modifications are also included.

2 Floor panel 3 Floor frame 10 Battery unit 11 Battery module 21 Side frame 24 Battery tray 31 First cross frame 32 Second cross frame 32a Upper wall connecting portion 32b Side wall connecting portion 33 Third cross frame 33a Upper wall connecting portion 33b Side wall connecting Part 51 First mounting bracket 52 Second mounting bracket 53 Third mounting bracket V Vehicle S1 First accommodation area S2 Second accommodation area S3 Third accommodation area

Claims (6)

A floor panel, a pair of left and right floor frames forming a closed cross section extending forward and backward in cooperation with the floor panel under the floor panel, and a battery module supported and attached to the pair of floor frames. In a battery unit mounting structure for an electric vehicle comprising a battery unit,
The battery unit includes the battery module, a pair of left and right side frames that have attachment portions for the pair of floor frames and extend in the front-rear direction, and is supported by at least the pair of side frames and supports a bottom portion of the battery unit. a battery tray to form and a plurality of cross frames connecting between the pair of side frames;
attaching the battery module to the cross frame so as to be vertically displaceable with respect to the battery tray ;
The cross frame comprises a first cross frame interposed between a single-layer module housing area for housing the battery modules in a single layer state, and two layers in which the single-layer module housing area and the battery modules are arranged vertically in two stages. and a second cross frame sandwiched between the two-layer module housing area for housing the
A lower cross frame is provided which cooperates with the battery tray to form a closed cross section formed by cooperation between the second cross frame and the battery tray and a closed cross section vertically adjacent to the battery tray with the battery tray therebetween. A battery unit mounting structure for an electric vehicle, characterized by: the cross frame is configured to cooperate with the battery tray above the battery tray to form a closed cross section;
A mounting bracket having a connecting wall portion that extends vertically and is connected to the battery module, and a fixed wall portion that extends forward or rearward from a lower end portion of the connecting wall portion and is fixed to the upper wall portion of the cross frame. provided,
3. The mounting bracket is connected to the battery module such that the height of the center of gravity of the battery module and the height of the upper wall of the cross frame are substantially the same. 2. The battery unit mounting structure for an electric vehicle according to 1. the battery unit has a plurality of module housing areas that house the battery modules such that the long axes of the battery modules are along the side frames and that are separated by the cross frames;
3. The battery unit mounting structure for an electric vehicle according to claim 2, wherein a battery module arranged in a module housing area sandwiching the cross frame is mounted on the cross frame. the cross frame includes a third cross frame formed on the opposite side of the first cross frame to the second cross frame and forming a single-layer module housing area only between the first cross frame and the third cross frame;
a first upper wall connecting portion connecting the upper wall portion of the second cross frame to the upper wall portion of the side frame; and a first side wall connecting portion connecting the side wall portion of the second cross frame to the side wall portion of the side frame. are integrally and continuously formed to connect the upper wall portion of the third cross frame to the upper wall portion of the side frame, and the side wall portion of the third cross frame to the side wall portion of the side frame. 2. The battery unit mounting structure for an electric vehicle according to claim 1, wherein the connecting second side wall connecting portion is formed independently . the module housing area is configured to house a plurality of the battery modules,
3. The battery unit mounting structure for an electric vehicle according to claim 2 , wherein the mounting bracket mounts a plurality of battery modules to the cross frame. A floor panel, a pair of left and right floor frames forming a closed cross section extending forward and backward in cooperation with the floor panel under the floor panel, and a battery module supported and attached to the pair of floor frames. In a battery unit mounting structure for an electric vehicle comprising a battery unit,
The battery unit includes the battery module, a pair of left and right side frames that have attachment portions for the pair of floor frames and extend in the front-rear direction, and is supported by at least the pair of side frames and supports a bottom portion of the battery unit. a battery tray to form and a plurality of cross frames connecting between the pair of side frames;
attaching the battery module to the cross frame so as to be vertically displaceable with respect to the battery tray;
the cross frame is configured to cooperate with the battery tray above the battery tray to form a closed cross section;
A mounting bracket having a connecting wall portion that extends vertically and is connected to the battery module, and a fixed wall portion that extends forward or rearward from a lower end portion of the connecting wall portion and is fixed to the upper wall portion of the cross frame. provided,
the mounting bracket is connected to the battery module such that the height position of the center of gravity of the battery module and the height position of the upper wall portion of the cross frame are substantially the same height position;
the battery unit has a plurality of module housing areas that house the battery modules such that the long axes of the battery modules are along the side frames and that are separated by the cross frames;
A battery module arranged in a module housing area sandwiching the cross frame is attached to the cross frame,
The cross frame comprises a first cross frame interposed between a single-layer module housing area for housing the battery modules in a single layer state, and two layers in which the single-layer module housing area and the battery modules are arranged vertically in two stages. and a second cross frame sandwiched between the two-layer module housing area for housing the
A lower cross frame is provided which cooperates with the battery tray to form a closed cross section formed by cooperation between the second cross frame and the battery tray and a closed cross section vertically adjacent to the battery tray with the battery tray therebetween. A battery unit mounting structure for an electric vehicle, characterized by: