Patent Publication Number: US-2023158878-A1

Title: Vehicle mounted structure for battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of International Application No. PCT/JP2021/006837, filed on Feb. 24, 2021. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to an installation structure of a battery pack to a vehicle. 
     Background Information 
     CO 2  emission regulations for vehicles are being required, which is promoting the electrification of vehicles. With the electrification of vehicles, batteries that store electric power for drive motors are being mounted in vehicles. This battery is also charged with electric power regenerated by the power generation motor when the vehicle decelerates (there are occasions when the drive motor generates power). In order to achieve a sufficient driving range, it is necessary to mount a battery having a large capacity, which increases the volume of the battery as well as the weight of the battery. Large, heavy batteries tend to be mounted in the floor of the vehicle cabin, due to mounting space restrictions, as well as restrictions with regard to front-to-rear weight distribution and lowering the center of gravity. In addition, in consideration of heat generated by the battery due to charging/discharging, a cooling system may be incorporated into the battery. US Patent Application Publication No. 2017/0214008 (Patent Document 1), described below, discloses a vehicle in which a battery pack incorporating a liquid cooling system is mounted in the floor of the vehicle cabin. 
     SUMMARY 
     Impact from below may be input to a battery pack mounted in the floor of a vehicle cabin, due to unevenness of the road surface, or the like. It is necessary to protect the battery pack from impact from below. In particular, cooling pipes in which coolant circulates are installed inside a battery pack incorporating a liquid cooling system, so that it is necessary to protect the cooling pipes from impact from below. Therefore, an object of the present invention is to provide a structure for mounting a battery pack in a vehicle that can reliably protect a battery pack mounted in the floor of a vehicle cabin. 
     The present invention is characterized by providing a vehicle mounted structure of a battery pack mounted to the floor of a vehicle cabin. A plate-shaped underguard is provided below a bottom plate of a housing of the battery pack. The underguard has a shape in which upwardly protruding ribs and downwardly protruding ribs are alternately arranged. Cooling pipes provided inside (or on the surface of) the bottom plate of the housing are arranged facing the downwardly protruding ribs. The underguard is attached to the housing such that the top plate of the upwardly protruding ribs and the bottom plate of the housing are spaced apart. 
     By means of the feature described above, it is possible to provide an installation structure for mounting a battery pack in a vehicle that can reliably protect a battery pack mounted in the floor of a vehicle cabin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure. 
         FIG.  1    is an exploded perspective view of an installation structure for mounting a battery pack in a vehicle according to an embodiment. 
         FIG.  2    is a bottom surface view of a battery pack in the above-described structure. 
         FIG.  3    is a bottom surface view of the battery pack to which an underguard has been attached. 
         FIG.  4    is a cross-sectional view taken along line IV-IV in  FIG.  3   . 
         FIG.  5 A  is a cross-sectional view illustrating a process of shock absorption (initial state) by the above-described structure. 
         FIG.  5 B  is a cross-sectional view illustrating the process of shock absorption (first state) by the above-described structure. 
         FIG.  5 C  is a cross-sectional view illustrating the process of shock absorption (second state) by the above-described structure. 
         FIG.  5 D  is a cross-sectional view illustrating the process of shock absorption (third state) by the above-described structure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     An installation structure for mounting a battery pack in a vehicle according to the embodiment will be described below with reference to the drawings. 
     A battery pack  1  is mounted in a floor of a vehicle cabin. The battery pack  1  occupies almost all of the vehicle cabin floor. As shown in  FIG.  1   , the installation structure for mounting the battery pack  1  on the vehicle according to the present embodiment has, in addition to the battery pack  1 , a metal underguard  2  attached to the battery pack  1  from below, and a resin under cover  3  attached to the underguard  2  from below. 
     The battery pack  1  includes a housing  10 , an upper plate  11  that closes an upper opening of the housing  10 , a plurality of battery modules (not shown) housed inside the housing  10 , and various electronic devices (not shown) such as harnesses and control modules. A plurality of battery cells are housed inside each battery module. A bottom plate  10   b  of the housing  10  is formed by joining four extruded aluminum materials in the lateral direction of the vehicle (refer to  FIG.  2   ). The extruded materials are welded to each other at flanges  10   f  formed downwardly along the side edges thereof (refer to  FIG.  4   ). A side plate  10   s  of the housing  10  is also formed of an extruded aluminum material and is joined to the peripheral edge of the bottom plate  10   b.  The upper plate  11  is a press-molded metal plate. 
     As shown in  FIG.  2   , a plurality of brackets are attached to the peripheral edge of the housing  10 . The battery pack  1  is fixed to a vehicle body (side sill, for example) via these brackets. The battery pack  1  also functions as a structural member that improves the rigidity and strength of the vehicle body. As shown in  FIG.  4   , cooling pipes  12  are integrally formed with the bottom plate  10   b  at the time of extrusion molding, and, in the present embodiment, the cooling pipes  12  are embedded inside the bottom plate  10   b.  The cooling pipes  12  are formed so as to protrude downward from the bottom surface of the bottom plate  10   b.    FIG.  4    is a cross-sectional view taken along line IV-IV in  FIG.  3    and shows only the left side of the battery pack  1 , but the right side is formed symmetrically.  FIG.  4    shows the under cover  3 , but the under cover  3  is not shown in  FIG.  3   . 
     As shown in  FIG.  4   , four cooling pipes  12  are formed in each of the extruded materials constituting the bottom plate  10   b.  Each of the cooling pipes  12  extends in the longitudinal direction of the vehicle. The cooling pipes  12  are arranged substantially evenly in the lateral direction. By integrally forming the cooling pipes  12  (as well as the flanges  10   f ) with the bottom plate  10   b,  the strength and rigidity of the bottom plate  10   b  are improved. The upper surface of the bottom plate  10   b  is flat, which is convenient for laying the battery modules described above thereon, and is convenient for increasing the contact area between the battery modules and the bottom plate  10   b.  In this manner, by embedding the cooling pipes  12  in the bottom plate  10   b  and making the upper surface of the bottom plate  10   b  flat, heat exchange between the battery modules and the coolant flowing inside the cooling pipes  12  can be promoted. 
     As shown in  FIG.  4   , the outer sides of two extruded materials on the two sides of the four extruded materials of the bottom plate  10   b  respectively form a double bottom structure. Two cooling pipes  12  are arranged inside the double bottom structure. Coolant is circulated inside each of the cooling pipes  12 . The circulation of the coolant is controlled by a temperature control system (not shown). Temperature sensors are provided in the battery modules, and the like, and the temperature control system controls a circulation pump (not shown) such that the temperature of the battery modules will remain within an appropriate range, based on the detection results of the temperature sensors. Mounting holes  13  to which the two side edges of the underguard  2  are attached and mounting holes  14  of the under cover  3  are formed in the above-described double bottom structure portions of the bottom plate  10   b  (refer to  FIG.  2   ). 
     Each of the two central extruded materials of the four extruded materials of the bottom plate  10   b  has a bracket  15  in the center in the lateral direction thereof. The brackets  15  are also integrally formed during extrusion molding, in the same manner as the cooling pipes  12 . The brackets  15  also extend in the longitudinal direction of the vehicle. Each of the brackets  15  forms a closed cross section together with the bottom plate  10   b.  As shown in  FIG.  2   , in each of the brackets  15 , five blind nuts  16  are spaced apart from each other and fixed by means of swaging. 
     The underguard  2  is made of aluminum and is press-molded. As shown in  FIGS.  3  and  4   , the underguard  2  has a corrugated shape in which upwardly protruding ribs (beads, embosses)  20  and downwardly protruding ribs  21  are alternately arranged in the lateral direction. That is, the upwardly protruding ribs  20  and the downwardly protruding ribs  21  extend in the longitudinal direction. The cooling pipes  12  of the housing  10  are arranged facing the downwardly protruding ribs  21 . In other words, in bottom surface view (or in plan view), the cooling pipes  12  are positioned within the bounds of the downwardly protruding ribs  21 . The front end portion and the rear end portion of the underguard  2  are each bent to form a stepped portion so as to be in contact with the battery pack  1 . 
     An upper plate  20   a  of the upwardly protruding ribs  20  and the bottom surface of the bottom plate  10   b  are spaced apart from each other. A lower plate  21   a  of the downwardly protruding ribs  21  and the cooling pipes  12  are spaced apart from each other. The distance between the lower plate  21   a  and the cooling pipes  12  is greater than the distance between the upper plate  20   a  and the bottom surface of the bottom plate  10   b.  A sloped plate  22  is formed between the upper plate  20   a  and the lower plate  21   a  that are adjacent to each other. Five bulges  23  are formed on the lower plate  21   a  that opposes the above-described bracket  15  to match the positions of the blind nuts  16 . Each bulge  23  protrudes upward in a circular shape and is in contact with the bottom surface of the bracket  15 . 
     A bolt hole  23   a  is formed in the center of the bulge  23 , and a bolt  23   b,  which is a fastener, is inserted into the bolt hole  23   a  and fastened to the blind nut  16 . Mounting holes  24  are formed on both sides of the underguard  2 , and the mounting holes  24  match the mounting holes  13  formed on the bottom plate  10   b.  Resin pins  25 , which are fasteners, are attached to the mounting holes  13  and  24 . In this mariner, the underguard  2  is attached to the housing  10  by the bolts  23   b  and the resin pins  25 . In addition, mounting holes  26  of the under cover  3  are formed on the lower plate  21   a,  on which the bulges  23  are not formed. 
     The under cover  3  is made of resin, and, in the present embodiment, is composed of five parts, a front portion  3   f,  a rear portion  3   r,  a central portion  3   c,  and a pair of side portions  3   s,  as shown in  FIG.  1   . These five parts are attached to the underguard  2 , thereby forming one under cover  3 . A plurality of bulges  31  are formed on the under cover  3 . Each bulge  31  protrudes upward in a circular shape and is in contact with the bottom surface (lower plate  21   a ) of the underguard  2 . A mounting hole  31   a  (refer to  FIG.  1   ) is formed in the center of each bulge  31 . The mounting holes  31   a  match the mounting holes  14  formed on the bottom plate  10   b  or the mounting holes  26  formed on the underguard  2 . The resin pin  25 , which is a fastener, is attached to the mounting hole  31   a  and the mounting hole  14   26 . In this manner, the under cover  3  is attached to the underguard  2  by the resin pins  25 . 
     The main purpose of the under cover  3  is to protect the battery pack  1  from water, mud, and the like. On the other hand, the main purpose of the underguard  2  is to protect the battery pack  1  from impact from below. A sound-absorbing material may be attached to the upper surface of the under cover  3 . Alternatively, a resin sponge or felt may be press-molded to form the under cover  3 . The under cover  3  press-molded in this manner itself has sound-absorbing qualities. In the present embodiment, the front portion  3   f,  the rear portion  3   r,  and the side portions  3   s  are formed by means of injection molding, and the central portion  3   c  is formed by means of the above-described press-molding. 
     Next, shock absorption by the underguard  2  when impact is input to the battery pack  1  from below due to unevenness or obstacles on the road surface will be described with reference to  FIGS.  5 A- 5 D .  FIGS.  5 A- 5 D  show the portion in the vicinity of where impact was input. Although the under cover  3  is not shown in  FIGS.  5 A- 5 D , impact from below is first absorbed by the under cover  3 . Mild impact can be absorbed by elastic deformation or plastic deformation of the under cover  3 . Moderate impact that cannot be fully absorbed by the deformation of the under cover  3  is absorbed as a result of the resin pins  25  that fix the under cover  3  being pulled out or being broken. That is, the resin pins (fasteners) fixing the under cover  3  can function as fuses. 
     Severe impact that cannot be fully absorbed by the under cover  3  is absorbed by the underguard  2 . In such a case, the impact is input to the underguard  2  via the under cover  3 . As can be understood from the comparison between  FIGS.  5 A and  5 B , first, the bulges  23 , which are the fixing points of the underguard  2 , are deformed so as to be crushed, thereby absorbing impact. Because the underguard  2  of the present embodiment is made of metal, the deformation of the underguard  2  can effectively absorb the impact energy. The deformation shown in  FIG.  5 B  occurs because the bottom plate  10   b  and the upper plate  20   a  of the upwardly protruding ribs  20  are spaced apart from each other. In addition, as shown in  FIG.  5 A , the cooling pipes  12  are arranged facing the downwardly protruding ribs  21 , and because the cooling pipes  12  and the lower plate  21   a  of the downwardly protruding ribs  21  are spaced apart from each other, the underguard  2  does not come in contact with the cooling pipes  12  even in the state shown in  FIG.  5 B . 
     The deformation shown in  FIG.  5 B  continues until the upper plate  20   a  comes in contact with the bottom plate  10   b.  Subsequently, as can be understood from the comparison between  FIGS.  5 B and  5 C , the sloped plate  22  and the lower plate  21   a  of the downwardly protruding ribs  21  on the outside of the bulges  23  deform, thereby absorbing the impact. At this time, because the upper plate  20   a  is already in contact with the bottom plate  10   b,  the deformed lower plate  21   a  or the sloped plate  22  is not likely to come in contact with the cooling pipes  12 . Even if the lower plate  21   a  or the sloped plate  22  comes in contact with the cooling pipes  12 , the lower plate  21   a  or the sloped plate  22  deforms, rather than the cooling pipes  12 . As shown in  FIG.  4   , a deformation similar to this deformation can occur in the flanges  10   f,  which serve as the joint portions of the extruded materials constituting the bottom plate  10   b  (refer to  FIG.  4   ). 
     If the deformation shown in  FIG.  5 C  still cannot fully absorb the impact, as can be understood from the comparison between  FIGS.  5 C and  5 D , the impact acts on the bolt hole  23   a  of the underguard  2  and deforms (breaks) the periphery of the bolt hole  23   a.  This deformation (damage) around the bolt hole  23   a  further absorbs the impact. The probability that all of the bolt holes  23   a  will break at the same time is extremely low, which prevents the underguard  2  from falling off of the vehicle. As a result of the shock absorption by means of the deformation of the underguard  2  as shown in  FIGS.  5 A to  5 D , the bottom plate  10   b,  that is, the battery pack  1  is protected from the impact. Because the bracket  15  has a closed cross section, the bracket  15  exhibits sufficient strength and rigidity against the deformation of the underguard  2  shown in  FIGS.  5 A- 5 D . 
     Unevenness and foreign objects on the road surface may directly hit the bulges  23 . In this case, in addition to the deformation described above, it is conceivable that the head portion of the bolt  23   b  may break, or that the blind nut  16  may be pulled out and the bracket  15  damaged. Even in such a case, impact is absorbed by means of the breakage of the bolt  23   b  and the pulling out of the blind nut  16 . In the case of the blind nut  16  being pulled out, the bracket  15  will be damaged but damage of the battery pack  1  will be limited to the bracket  15 , and the function of the battery pack  1  will not be impaired. The cooling pipes  12  will also be protected by the underguard  2 . 
     Here, a case was described in which the deformation of the underguard  2  proceeds from the state shown in  FIG.  5 A  to the state shown in  FIG.  5 D . However, there are cases in which all of the impact can be absorbed in the state shown in  FIG.  5 B or  5 C . In addition, while it depends on the position where the impact is input, impact is also absorbed as a result of the resin pins  25  (fasteners), which fix the underguard  2 , being pulled out or broken. However, deformation around the bolts (fasteners)  23   b  of the underguard  2  shown in  FIGS.  5 A- 5 D  can absorb more impact than the resin pins (fasteners)  25  being pulled out or broken. 
     By means of the present embodiment, the underguard  2  is attached to the housing  10  of the battery pack  1 , with the upper plate  20   a  of the upwardly protruding ribs  20  being spaced apart from the bottom surface of the bottom plate  10   b.  As a result, as shown in  FIGS.  5 A- 5 B , due to the deformation (deformation  1 ) of the underguard  2  up to where the upper plate  20   a  comes in contact with the bottom surface of the bottom plate  10   b,  impact from below is absorbed by the deformation of the underguard  2 , thereby protecting the battery pack. 
     Here, because the cooling pipes  12  are arranged facing the downwardly protruding ribs  21  of the underguard  2 , contact between the cooling pipes  12  and the underguard  2  (downwardly protruding ribs  21 ) is prevented when the underguard  2  deforms, thereby protecting the cooling pipes  12 . That is, by means of the present embodiment, the function of the cooling system of the battery pack  1  can also be protected. (The cooling pipes  12  can also be protected by means of the modified example of the arrangement of the cooling pipes  12 , described further below.) 
     In addition, by means of the present embodiment, the cooling pipes  12  protrude downward from the bottom surface of the bottom plate  10   b,  which facilitates mounting of the battery modules inside the housing  10 , and heat exchange with the coolant inside the cooling pipes  12  can be carried out efficiently. Here, if the cooling pipes  12  protrude downward from the bottom surface of the bottom plate  10   b,  it becomes difficult to protect the cooling pipes  12  from impact from below. However, because the cooling pipes  12 , which protrude downward, are spaced apart from the lower plate  21   a  of the downwardly protruding ribs  21 , contact between the deformed underguard  2  (lower plate  21   a ) and the cooling pipes  12  can be effectively avoided. That is, even the battery pack  1  provided with the cooling pipes  12  protruding downward can be reliably protected by the underguard  2 . 
     In addition, by means of the present embodiment, the bracket  15  forming a closed cross section together with the bottom plate  10   b  protrude downward from the bottom surface of the bottom plate  10   b,  and the underguard  2  (bulges  23 ) is fixed to the bracket  15  by fasteners (bolts  23   b ). That is, the bottom plate  10   b  and the fasteners of the underguard  2  to the housing  10  (bracket  15 ) of the battery pack  1  are spaced apart from each other by the height of the downwardly protruding bracket  15 . By means of this configuration, in addition to “deformation  1 ” described above, as shown in  FIGS.  5 B- 5 D , impact from below can be absorbed by the deformation of the underguard  2  to thereby protect the battery pack, by means of the following deformations  2  and  3  of the underguard  2 . (Deformation  2 ) Deformation of the underguard  2  in the range from the upper plate  20   a  of the upwardly protruding ribs  20  to the lower plate  21   a  of the downwardly protruding ribs  21 . (Deformation  3 ) Deformation accompanied by damages in the vicinity of the fastener (bolt holes  23   a ) of the underguard  2  to the housing  10 . 
     Furthermore, by means of the present embodiment, the resin under cover  3  is attached to the bottom surface of the underguard  2 . For this reason, the battery pack  1  (and the underguard  2 ) can be protected from rain and mud, and it is also possible to insulate (or absorb) airborne sounds coming from below the floor. In addition, because impact from below can also be absorbed by means of deformation of the under cover  3 , light impact can be fully absorbed by the under cover  3  without deforming the underguard  2 . In addition, the under cover  3  is fixed to the bottom surface of the underguard  2  by fasteners (resin pins  25 ). The fasteners (resin pins  25 ) function as fuses, so that impact from below can also be absorbed by means of damage to the fasteners (resin pins  25 ). 
     The present invention is not limited to the embodiment described above. The cooling pipes  12  are arranged on the bottom surface side of the bottom plate  10   b,  but may be arranged on the upper surface side (inside the housing  10 ). The thickness of the bottom plate  10   b  may be made greater than the inner diameter of the cooling pipes  12 , and the cooling pipes  12  may be arranged inside the thickness of the bottom plate  10   b  (between the bottom surface and the upper surface of the bottom plate  10   b ). The cooling pipes  12  are embedded in the bottom plate  10   b  in the above-described embodiment, but may be separately formed and attached to the surface (bottom surface or upper surface) of the bottom plate  10   b.    
     The underguard  2  is made of metal in the above-described embodiment, but may be made of fiber-reinforced plastic (FRP). The bracket  15  extends in the longitudinal direction in the above-described embodiment, but may be provided only at the positions where the underguard  2  is attached (positions of the blind nuts  16 ). In addition, while referred to as the cooling pipes  12  in the present embodiment, coolant heated by means of electric energy at the time of a cold start can be circulated inside the cooling pipes  12  to thereby warm the battery at an early stage.