Patent Publication Number: US-2023163398-A1

Title: Energy storage apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an energy storage device, and an energy storage apparatus including an outer case that accommodates the energy storage device. 
     BACKGROUND ART 
     Patent Document 1 discloses an energy storage apparatus that includes: a body portion that accommodates a battery unit that has a plurality of batteries; and a reinforcing structure that is mounted on the body portion. This reinforcing structure includes: support struts that project upward beyond the body portion; and a receiving member that is fixed to upper portions of the support struts. Accordingly, even when any heavy object falls on the energy storage apparatus, a load (an impact load) can be received by the reinforcing structure and hence, the deformation, the rupture, and the like of the body portion are prevented. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: WO 2016/186139 A 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the above-mentioned conventional energy storage apparatus, in preparation for a case where some object impinges on the energy storage apparatus, the reinforcing structure (a reinforcing member) is disposed on the body portion (an outer case). However, a force acts on the outer case of the energy storage apparatus not only from the outside of the outer case but also from the inside of the outer case. When a gas is discharged from the energy storage device in the outer case, a pressure in the outer case (an internal pressure) sharply rises so that the outer case receives a force (the internal pressure) from the inside. Accordingly, the outer case is deformed so as to expand outward, and as a result, there is a possibility that a damage such as cracking occurs in the outer case. When a damage occurs on the outer case, there is a possibility that an unsafe phenomenon occurs. For example, a phenomenon that a gas in the outer case is leaked through a damaged portion occurs. Therefore, how to suppress such a defect of the outer case caused by a force that the outer case receives from the inside of the outer case is a crucial task from a viewpoint of increasing a safety of the energy storage apparatus. 
     The inventors of the present invention have made the present invention by focusing on the above-mentioned task from a novel viewpoint, and it is an object of the present invention to provide an energy storage apparatus where the safety of the energy storage apparatus is enhanced. 
     Means for Solving the Problems 
     An energy storage apparatus according to an aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein rigidity of each of the pair of reinforcing walls is higher than rigidity of the connecting portion. 
     An energy storage apparatus according to another aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein the reinforcing member includes a first reinforcing member and a second reinforcing member, each of the first reinforcing member and the second reinforcing member includes two plate-shaped portions disposed opposite to each other and the connecting portion connecting the two plate-shaped portions to each other, and each of the pair of reinforcing walls is formed by making one of the two plate-shaped portions of the first reinforcing member and one of the two plate-shaped portions of the second reinforcing member overlap with each other. 
     An energy storage apparatus according to another aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein a thickness of each of the pair of reinforcing walls is larger than a thickness of the connecting portion. 
     Advantages of the Invention 
     According to the present invention, it is possible to provide an energy storage apparatus where the safety of the energy storage apparatus is enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating an external appearance of an energy storage apparatus according to an embodiment. 
         FIG.  2    is an exploded perspective view of an energy storage apparatus according to the embodiment. 
         FIG.  3    is a perspective view illustrating the configuration of a reinforcing member and the periphery thereof according to the embodiment. 
         FIG.  4    is an exploded perspective view of the reinforcing member according to the embodiment. 
         FIG.  5    is a first cross-sectional view illustrating a structural relationship between the reinforcing member and an outer case according to the embodiment. 
         FIG.  6    is a second cross-sectional view illustrating a structural relationship between the reinforcing member and the outer case according to the embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     An energy storage apparatus according to an aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein rigidity of each of the pair of reinforcing walls is higher than rigidity of the connecting portion. 
     According to this configuration, the pair of reinforcing walls is connected to each other so as to restrict the movement of the pair of reinforcing walls to the outside. Accordingly, when a wall portion of the outer case receives an external force from the inside, the expansion of the wall portion to the outside is suppressed. As a result, the occurrence of a drawback such as a damage on the outer case is suppressed. Such an advantageous effect can be obtained by the reinforcing member that is mounted on the outer case from the outside and hence, the advantageous effect described above can be acquired without changing the designing of the outer case. Furthermore, the reinforcing wall has relatively high rigidity and hence, the expansion of the wall portion of the outer case can be more reliably suppressed. Further, with respect to the connecting portion where a demand for high rigidity is not so high compared to the reinforcing wall, a thickness of the connecting portion can be reduced or the connecting portion can be made thin. That is, it is possible to effectively suppress deformation of the outer case (the expansion or bulging of the wall portion) while realizing the reduction of weight, downsizing or the like of the reinforcing member. As described above, according to the energy storage apparatus of this aspect, the safety of the energy storage apparatus can be enhanced. 
     The pair of reinforcing walls may be connected by the connecting portion disposed on each of both sides in a width direction that intersects with an opposedly facing direction of the two wall portions. 
     According to this configuration, the pair of reinforcing walls is connected to each other on both sides in the width direction and hence, the pair of reinforcing walls can exert a high restraint force on the outer case. Accordingly, an effect of suppressing the expansion of the outer case is increased, and this contributes to enhancement of safety of the energy storage apparatus. 
     The energy storage device includes a case that includes a pair of long-side surfaces opposedly facing each other, and a plurality of the energy storage devices that are arranged side by side such that the pair of long-side surfaces faces the opposedly facing direction of the two wall portions may be accommodated in the outer case. 
     In a case where a plurality of energy storage devices are accommodated in the outer case in a state where the plurality of energy storage devices are arranged side by side, when the energy storage devices each have a prismatic shape, in general, the energy storage devices are arranged such that long-side surfaces of the energy storage devices face the arrangement direction of the energy storage devices. The long-side surfaces of the prismatic energy storage device are likely to expand and hence, an array of the energy storage devices formed of the plurality of energy storage devices is likely to expand in the arrangement direction of the plurality of energy storage devices. Accordingly, it is safe to say that the two opposing wall portions are likely to expand outward by receiving an expanding force applied to two wall portions. In this regard, in the energy storage apparatus of this aspect, the reinforcing member is disposed in a posture suitable for restraining the two wall portions and hence, the expansion of the outer case can be effectively suppressed. That is, the reinforcing member is disposed so as to press the portion of the outer case which is likely to expand and hence, the safety of the energy storage apparatus is enhanced. 
     The reinforcing member includes a first reinforcing member and a second reinforcing member, each of the first reinforcing member and the second reinforcing member includes two plate-shaped portions disposed opposite to each other and the connecting portion connecting the two plate-shaped portions to each other, and each of the pair of reinforcing walls may be formed by making one of the two plate-shaped portions of the first reinforcing member and one of the two plate-shaped portions of the second reinforcing member overlap with each other. 
     According to this configuration, the reinforcing member can be configured by combining two members (first and second reinforcing members) having the same shape with each other. Accordingly, it is possible to obtain a reinforcing wall having high rigidity that is formed of two plate-shaped portions. By combining the two members such that the connecting portions of the two members face each other, it is also possible to obtain a reinforcing member which can suppress expansion of the outer case in a well-balanced manner. Accordingly, it is possible to obtain a reinforcing member which efficiently suppresses the expansion of the outer case with a simple configuration, and this contributes to the enhancement of the safety of the energy storage apparatus. 
     An energy storage apparatus according to another aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein the reinforcing member includes a first reinforcing member and a second reinforcing member, each of the first reinforcing member and the second reinforcing member includes two plate-shaped portions disposed opposite to each other and the connecting portion connecting the two plate-shaped portions to each other, and each of the pair of reinforcing walls is formed by making one of the two plate-shaped portions of the first reinforcing member and one of the two plate-shaped portions of the second reinforcing member overlap with each other. 
     According to this configuration, the pair of reinforcing walls is connected to each other so as to restrict the movement of the pair of reinforcing walls to the outside and hence, the expansion of the wall portion of the outer case to the outside is suppressed. As a result, the occurrence of a damage or the like on the outer case is suppressed. The reinforcing member can be configured by combining two members (first and second reinforcing members) having the same shape with each other. Accordingly, it is possible to obtain a reinforcing wall having high rigidity that is formed of two plate-shaped portions. By combining the two members such that the connecting portions of the two members face each other, it is also possible to obtain a reinforcing member which can suppress expansion of the outer case in a well-balanced manner. Accordingly, it is possible to obtain a reinforcing member which efficiently suppresses the expansion of the outer case with a simple configuration. As described above, according to the energy storage apparatus of this aspect, the safety of the energy storage apparatus can be enhanced. 
     An energy storage apparatus according to another aspect of the present invention includes: an outer case that accommodates an energy storage device; and a reinforcing member including a pair of reinforcing walls disposed so as to sandwich two wall portions of the outer case from an outside of the outer case, the two wall portions opposedly facing each other, and a connecting portion that connects the pair of reinforcing walls to each other, wherein a thickness of each of the pair of reinforcing walls is larger than a thickness of the connecting portion. 
     According to this configuration, the pair of reinforcing walls is connected to each other so as to restrict the movement of the pair of reinforcing walls to the outside. Accordingly, when a wall portion of the outer case receives an external force from the inside, the expansion of the wall portion to the outside is suppressed. As a result, the occurrence of a drawback such as a damage on the outer case is suppressed. Such an advantageous effect can be obtained by the reinforcing member that is mounted on the outer case from the outside and hence, the advantageous effect described above can be acquired without changing the designing of the outer case. Further, the reinforcing wall has relatively large thickness and hence, the expansion of the wall portion of the outer case can be more reliably suppressed. Further, with respect to the connecting portion where a demand for large thickness is not so high compared to the reinforcing wall, the connecting portion can be formed with a relatively thin wall thickness. That is, it is possible to effectively suppress deformation of the outer case (the expansion or bulging of the wall portion) while realizing the reduction of weight, downsizing or the like of the reinforcing member. As described above, according to the energy storage apparatus of this aspect, the safety of the energy storage apparatus can be enhanced. 
     Hereinafter, the energy storage apparatus according to the embodiment (including modifications of the embodiment) of the present invention is described with reference to the drawings. All embodiments described hereinafter are a comprehensive example or a specific example. In the following embodiment, numerical values, shapes, materials, constituent elements, arrangement positions and connection modes of the constituent elements, and the like are provided as examples, and are not intended to limit the present invention. In the respective drawings, sizes and the like are not strictly illustrated. 
     In the following description and drawings, an arrangement direction along which a plurality of energy storage devices are arranged, a direction in which a pair of long-side surfaces of a case of an energy storage device are opposite to each other, or a thickness direction of the case is defined as an X-axis direction. A direction along which electrode terminals of one energy storage device are arranged or a direction in which a pair of short-side surfaces of the case of the energy storage device are opposite to each other is defined as a Y-axis direction. An arrangement direction of a body portion and a lid body in an outer case of the energy storage apparatus, an arrangement direction of the energy storage devices and bus bars, or a vertical direction is defined as a Z axis direction. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect with each other (orthogonal to each other in the embodiment and the modifications of the embodiment described later). A case is also considered where the Z-axis direction is not the vertical direction depending on a use mode. However, in the description made hereinafter, for the sake of convenience of the description, the description is made by assuming the Z-axis direction as the vertical direction. 
     In the embodiments described later, in some cases, the expressions indicating the relative directions or the relative postures such as parallel or orthogonal are used. However, these expressions also include a case where constituent elements of the energy storage apparatus do not take such directions or postures in strict meaning of the terms. A state where two directions are parallel to each other means not only a state where these two directions are completely parallel to each other but also a state where these two directions are substantially parallel to each other, that is, a state where these two directions are parallel to each other with slight difference of about a few percent. In the description made hereinafter, an X-axis direction positive side indicates an arrow direction side of the X-axis, and an X-axis direction negative side indicates a side opposite to the X-axis direction positive side. The same goes for the Y-axis direction and the Z-axis direction. 
     EMBODIMENT 
     [1. Description of Overall Configuration of Energy Storage Apparatus] 
     First, the overall configuration of an energy storage apparatus  1  according to the embodiment will be described with reference to  FIG.  1    and  FIG.  2   .  FIG.  1    is a perspective view illustrating an external appearance of the energy storage apparatus  1  according to the embodiment.  FIG.  2    is an exploded perspective view of the energy storage apparatus  1  according to the embodiment. 
     The energy storage apparatus  1  is an apparatus into which electricity can be charged from the outside and from which electricity can be discharged to the outside. In this embodiment, the energy storage apparatus  1  has an approximately rectangular parallelepiped shape. The energy storage apparatus  1  may be a battery module (assembled battery) used in an electricity storage application, a power source application, or the like. To be more specific, the energy storage apparatus  1  may be used as a battery or the like for driving a mobile body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agriculture machine, a construction machine, or a railway vehicle for an electric railway, or may be used as a battery for starting an engine of the mobile body. As the above-described automobile, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a gasoline automobile are exemplified. As the above-described railway vehicle for an electric railway, an electric train, a monorail, and a linear motor car are exemplified. The energy storage apparatus  1  can also be used as a stationary battery or the like used as a home-use battery, a generator, or the like. 
     As illustrated in  FIG.  1    and  FIG.  2   , the energy storage apparatus  1  includes a plurality of energy storage devices  20 , an outer case  10  that accommodates the plurality of energy storage devices  20 , and a reinforcing member  100  mounted on the outer case  10 . In this embodiment, eight energy storage devices  20  are accommodated in the outer case  10 . The number of energy storage devices  20  included in the energy storage apparatus  1  is not limited to 8. It is sufficient for the energy storage apparatus  1  to include one or more energy storage devices  20 . In this embodiment, one energy storage device array  24  is formed of the plurality of energy storage devices  20  arranged side by side in the X axis direction. The energy storage device array  24  may include a spacer, an insulating film, and the like not illustrated in the drawings. 
     The outer case  10  includes a body portion  12  which accommodates the energy storage device array  24  and a lid body  11 , and a bus bar plate  17  is disposed between the energy storage device array  24  accommodated in the body portion  12  and the lid body  11 . A plurality of bus bars  33  are held on the bus bar plate  17 , and the plurality of bus bars  33  are covered with bus bar covers  70  and  75 . A connection unit  80  including a control circuit and the like is disposed between the bus bar plate  17  and the lid body  11 . 
     The outer case  10  is a case (module case) having a rectangular shape (box shape) that forms an outer profile of the energy storage apparatus  1 . That is, the outer case  10  is a member that fixes the energy storage device array  24 , the bus bar plate  17 , and the like at predetermined positions, and protects these constitutional elements from an impact or the like. For example, the outer case  10  is made of an insulating member such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), a polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene/perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), an ABS resin, or a composite material of the above-mentioned materials, or metal to which insulation coating is applied. 
     The lid body  11  included in the outer case  10  is a rectangular member which closes an opening portion  15  of the body portion  12 , and includes an external terminal  91  on a positive electrode side and an external terminal  92  on a negative electrode side. The external terminals  91  and  92  are electrically connected to the plurality of energy storage devices  20  via the connection unit  80  and the bus bars  33 . The energy storage apparatus  1  charges electricity from the outside and discharges electricity to the outside via the external terminals  91 ,  92 . The external terminals  91 ,  92  are respectively formed of a conductive member made of metal such as aluminum, or an aluminum alloy. 
     The lid body  11  is provided with a ventilation chamber (not illustrated in the drawing) through which gas moving from one of the inside and the outside of the outer case  10  to the other passes, and an exhaust tube  90  that communicates the inside of the ventilation chamber with the outside of the outer case  10 . The gas inside the outer case  10  is discharged to the outside of the outer case  10  through the ventilation chamber and the exhaust tube  90 . More specifically, in the ventilation chamber, a valve member that is opened when a pressure (internal pressure) inside the outer case  10  increases to a predetermined value is disposed. Accordingly, in a normal state, even when foreign matter such as water or dust flows into the ventilation chamber through the exhaust tube  90 , the inflow of the foreign matter into the inside of the outer case  10  is substantially prevented by the valve member. When the gas is discharged from the energy storage device  20  and the internal pressure of the outer case  10  becomes equal to or higher than the predetermined value, the valve member is brought into an open state, and the gas inside the outer case  10  is discharged from the exhaust tube  90  to the outside of the outer case  10  through the ventilation chamber. 
     The body portion  12  of the outer case  10  is a bottomed rectangular cylindrical housing (housing) in which the opening portion  15  for accommodating the energy storage device array  24  is formed. In a state where the opening portion  15  is closed by the lid body  11 , a peripheral edge of the opening portion  15  and the lid body  11  are joined to each other by thermal welding. Accordingly, airtightness in the opening portion  15  is secured. 
     The energy storage device  20  is a secondary battery (battery cell) that can charge electricity and discharge electricity. More specifically, the energy storage device  20  is a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery. The energy storage device  20  has a flat rectangular parallelepiped shape (prismatic shape). In this embodiment, eight pieces of energy storage devices  20  are arranged side by side in the X-axis direction as described above. 
     In this embodiment, the energy storage device  20  includes the case  21  made of metal. The case  21  is a prismatic case having a pair of long-side surfaces  21   a  facing each other and a pair of short-side surfaces  21   b  facing each other. An electrode assembly, a current collector, an electrolyte solution, and the like are accommodated in the case  21 . In this embodiment, the plurality of energy storage devices  20  are arranged in a row in the X axis direction in a posture where the long-side surfaces  21   a  are directed in the X axis direction (a posture where the short-side surfaces  21   b  are parallel to the X axis direction). 
     Electrode terminals  22  (a positive electrode terminal and a negative electrode terminal) made of metal and electrically connected to the electrode assembly in the inside of the case  21  are provided on the lid plate  21   c  of the case  21 . The lid plate  21   c  of the case  21  is further provided with a gas release valve  23  for releasing the gas inside the case  21  to the outside. The gas release valve  23  has a function of releasing the gas inside the case  21  to the outside of the case  21  by releasing an internal pressure (by opening the valve) when the internal pressure of the case  21  increases due to vaporization of the electrolyte solution inside the case  21 . The gas release valve  23  having such a function is provided to each of the plurality of energy storage devices  20 . In this embodiment, as illustrated in  FIG.  2   , each of the plurality of energy storage devices  20  is arranged in a posture where the gas release valve  23  faces the Z-axis direction positive side. 
     The energy storage device  20  is not limited to a nonaqueous electrolyte secondary battery. The energy storage device  20  may be a secondary battery other than the non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage device  20  may be a primary battery that allows a user to use stored electricity even when the user does not charge the energy storage device  20 . In this embodiment, the energy storage device  20  having the rectangular parallelepiped shape (prismatic shape) is illustrated. However, the shape of the energy storage device  20  is not limited to the rectangular parallelepiped shape. The energy storage device  20  may have a polygonal columnar shape other than the rectangular parallelepiped shape, a circular columnar shape, an elliptical columnar shape, or the like. Further, a laminate-type energy storage device may be provided to the energy storage apparatus  1  as the energy storage device  20 . 
     The bus bar  33  is a rectangular plate-like member which is disposed on at least two energy storage devices  20  in a state where the bus bar  33  is held by the bus bar plate  17 , and the bus bar  33  electrically connects the electrode terminals  22  of at least these two energy storage devices  20  to each other. A material for forming the bus bar  33  is not particularly limited, and the bus bar  33  may be formed of metal such as aluminum, an aluminum alloy, copper, a copper alloy, or stainless steel or a combination thereof, or a conductive member other than metal. In the embodiment, using five bus bars  33 , four sets of energy storage device groups are formed where two energy storage devices  20  are connected with each other in parallel in each energy storage device group. Then, four sets of energy storage device groups are connected in series. The mode of electrical connection of the eight energy storage devices  20  is not particularly limited, and all of the eight energy storage devices  20  may be connected in series by seven bus bars. 
     The connection unit  80  is a unit that includes a plurality of bus bars, a control board, and the like, and electrically connects the energy storage device array  24  and the external terminals  91  and  92  to each other. The control board that the connection unit  80  includes has a plurality of electric components. Using this plurality of electric components, a detection circuit that detects a state of each energy storage device  20 , a control circuit that controls charging and discharging of the energy storage devices  20 , and the like are formed. In this embodiment, the connection unit  80  is fixed to the bus bar plate  17 . 
     The bus bar plate  17  is a resin-made member that holds the bus bars  33 . In this embodiment, the bus bar plate  17  is a member that holds the plurality of bus bars  33 , the connection unit  80 , and other wirings and the like (not illustrated in the drawing), and can perform positional restriction and the like of these members. A plurality of bus bar opening portions  17   a  are formed in the bus bar plate  17 . The plurality of bus bar opening portions  17   a  are provided for respectively holding the plurality of bus bars  33 . Apart of each of the plurality of bus bars  33  is exposed to a side where the plurality of energy storage devices  20  are disposed through the corresponding bus bar opening portion  17   a.    
     In the middle of the bus bar plate  17  in the Y axis direction, a path forming portion  19  extending in the X axis direction and protruding toward the Z axis direction positive side is provided along the arrangement of the gas release valves  23  of the plurality of energy storage devices  20 . The path forming portion  19  covers all of the gas release valves  23  from the Z-axis direction positive side. As illustrated in  FIG.  2   , a path outlet  18  is provided at end portions of the path forming portion  19  in a longitudinal direction of the path forming portion  19 , on both sides of an X-axis direction positive side and an X-axis direction negative side. Accordingly, the gas released from the energy storage device  20  mainly passes through the path outlet  18  and is discharged to the outside of the outer case  10  through the above-mentioned ventilation chamber and the above-mentioned exhaust tube  90 . The bus bar plate  17  configured as described above is fixed to the body portion  12  of the outer case  10  by a predetermined method such as adhesion or thermal welding. 
     Each of the bus bar covers  70  and  75  is a resin-made member covering the plurality of bus bars  33  from above, and plays a role of electrically insulating the plurality of bus bars  33  and the connection unit  80  from each other. 
     The reinforcing member  100  is a member which reinforces the outer case  10 . In the present embodiment, the reinforcing member  100  is disposed so as to surround the outer case  10 , and when the outer case  10  intends to expand due to an increase of an internal pressure, the expansion can be suppressed by the reinforcing member  100 . As illustrated in  FIG.  1    and  FIG.  2   , a plurality of restricting members  200  are fixed to the reinforcing member  100  according to the present embodiment, and these restricting members  200  mainly have a function of pressing the lid body  11 . Each of the plurality of restricting members  200  is fixed to the reinforcing member  100  by welding or fastening with a bolt or a rivet. In the present embodiment, three restricting members  200  are fixed to the reinforcing member  100 , and in order to distinguish these three restricting members  200 , reference signs ( 210 ,  220 ,  230 ) different from each other are given to the three restricting members  200  as illustrated in  FIG.  2   . In the description made hereinafter, the matter described for the “restricting member  200 ” is applied to each of the restricting members  210 ,  220 , and  230 . Hereinafter, the configuration of the reinforcing member  100  and the periphery thereof will be further described with reference to  FIG.  3    to  FIG.  6   . 
     [2. Configuration of Reinforcing Member and Periphery Thereof] 
       FIG.  3    is a perspective view illustrating the configuration of the reinforcing member  100  and the periphery thereof according to the embodiment.  FIG.  3    illustrates a state where the reinforcing member  100  and spacers  151  and  152  are separated from the outer case  10 .  FIG.  4    is an exploded perspective view of the reinforcing member  100  according to the embodiment.  FIG.  5    is a first cross-sectional view illustrating a structural relationship between the reinforcing member  100  and the outer case  10  according to the embodiment. In  FIG.  5   , a transverse cross section (a cross section parallel to an XY plane) at a middle portion in the vertical direction (Z-axis direction) of the energy storage apparatus  1  is simply illustrated, and each energy storage device  20  is illustrated not in a cross-sectional view but in a plan view. The illustration of the restricting member  200  and the spacers  151  and  152  is omitted.  FIG.  6    is a second cross-sectional view illustrating a structural relationship between the reinforcing member  100  and the outer case  10  according to the embodiment.  FIG.  6    illustrates an end portion on an X-axis direction negative side in a VI-VI cross section in  FIG.  5   . 
     As illustrated in  FIG.  3   , the reinforcing member  100  is an annular member as viewed in a plan view (when viewed from a Z-axis direction positive side) and is formed along four wall portions  13  of the outer case  10 . Specifically, the reinforcing member  100  includes a pair of reinforcing walls  101  disposed so as to sandwich the two wall portions  13  facing each other from the outside, and a connecting portion  102  connecting the pair of reinforcing walls  101  to each other. In the present embodiment, as illustrated in  FIG.  3   , the four wall portions  13  that the outer case  10  includes are distinguished into a pair of wall portions  13   a  forming the short-side surfaces of the outer case  10  and a pair of wall portions  13   b  forming the long-side surfaces of the outer case  10 . In this case, it can be expressed that the pair of reinforcing walls  101  is disposed so as to sandwich two wall portions  13   a  facing each other from the outside. 
     The reinforcing member  100  is a member made of metal such as iron or an aluminum alloy, and as illustrated in  FIG.  3   , is fixed to the outer case  10  in a state where the spacers  151  and  152  are interposed between the reinforcing member  100  and the outer case  10 . The spacers  151  and  152  are members made of mica or a resin, and are members which protect the outer case  10  from the reinforcing member  100  having higher rigidity than the outer case  10  and electrically insulate the outer case  10  and the reinforcing member  100  from each other. As such a member, a mica molded article, or a resin having an electrical insulation property such as PP, PC, or PE is adopted in the same manner as the outer case  10 . The material for forming the spacers  151  and  152  such as a resin may contain a material for improving strength, durability, heat resistance, or the like, such as glass fiber. 
     In the present embodiment, as illustrated in  FIG.  4    and  FIG.  5   , the reinforcing member  100  is configured by combining a first reinforcing member  110  and a second reinforcing member  120 . Specifically, each of the two reinforcing walls  101  of the reinforcing member  100  is configured by overlapping a plate-shaped portion  111  of the first reinforcing member  110  and a plate-shaped portion  121  of the second reinforcing member  120 . One of the two connecting portions  102  of the reinforcing member  100  is a portion connecting the two plate-shaped portions  111  of the first reinforcing member  110 , and the other is a portion connecting the two plate-shaped portions  111  of the second reinforcing member  120 . In this manner, the reinforcing member  100  formed of the first reinforcing member  110  and the second reinforcing member  120  is fixed to the outer case  10  by the following procedure. 
     First, the first reinforcing member  110  and the second reinforcing member  120  are disposed at positions illustrated in  FIG.  5    with respect to the outer case  10 . Thereafter, the first reinforcing member  110  and the second reinforcing member  120  are pressurized from both sides in the Y axis direction, and the plate-shaped portion  111  and the plate-shaped portion  121  overlapped with each other in the X axis direction are joined to each other by spot welding or the like while maintaining such a pressed state. Accordingly, the outer case  10  is brought into a state where the outer case  10  is appropriately fastened by the reinforcing member  100 , and the reinforcing member  100  is brought into a state where the reinforcing member  100  is substantially fixed to the outer case  10 . 
     Such an attachment operation of the reinforcing member  100  is performed in a state where the energy storage device array  24 , the connection unit  80  and the like are accommodated in the outer case  10  and the lid body  11  is joined to the opening portion  15  of the body portion  12 . At the time of attachment operation of the reinforcing member  100 , positions of the first reinforcing member  110  and the second reinforcing member  120  in the vertical direction (Z-axis direction) can be positioned by ribs  13   e  (see  FIG.  3    and  FIG.  6   ) provided on an outer surface of the wall portion  13  of the body portion  12 . A method of joining the plate-shaped portion  111  and the plate-shaped portion  121  is not limited to welding, and fastening using a bolt or a rivet may be adopted as the joining method. 
     As described above, in the reinforcing member  100  according to the present embodiment, each of the pair of reinforcing walls  101  disposed opposite to each other is configured by overlapping and joining the plate-shaped portions  111  and  121 . Accordingly, the rigidity of the reinforcing wall  101  is higher than that of the connecting portion  102  that is a single plate-shaped portion. From the viewpoint of thickness, a thickness of the reinforcing wall  101  is larger than a thickness of the connecting portion  102 . With such a configuration, it is possible to enhance effectiveness of a function of suppressing an expansion of the outer case  10  realized by the reinforcing walls  101  while exerting a restraining function by the connecting portion  102  with respect to the two reinforcing walls  101 . 
     As described above, the energy storage apparatus  1  according to the present embodiment includes the outer case  10  that accommodates the energy storage devices  20  and the reinforcing member  100 . The reinforcing member  100  includes the pair of reinforcing walls  101  disposed so as to sandwich the two wall portions  13  (wall portions  13   a ) of the outer case  10  facing each other from the outside, and the connecting portion  102  connecting the pair of reinforcing walls  101  to each other. The rigidity of each of the pair of reinforcing walls  101  is higher than the rigidity of the connecting portion  102 . 
     According to this configuration, the pair of reinforcing walls  101  is connected to each other so as to restrict the movement of the pair of reinforcing walls  101  to the outside. With such a configuration, the expansion of the wall portions  13   a  to the outside, when the wall portions  13   a  of the outer case  10  receives a force (an internal pressure of the outer case  10  or a pressing force attributed to an expansion of one or more energy storage devices  20 ) from the inside, can be suppressed. As a result, the occurrence of a drawback such as a damage on the outer case  10  is suppressed. When the valve of the energy storage device  20  in the outer case  10  is opened so that a gas is released from the outer case  10 , an internal pressure of the outer case  10  in a gastight state or in a substantially gastight state is rapidly increased. In this case, there may be a case where the release of the gas from the exhaust tube  90  does not catch up with the increase of the internal pressure, and the internal pressure of the outer case  10  increases or the internal pressure is maintained at a high level. In this case, it is conceivable that a damage such as cracking occurs in the resin-made outer case  10 , and the gas leaks out from the damaged portion. That is, there is a possibility that the gas leaks from an unexpected place of the outer case  10 , and that may cause a problem on safety. However, in the energy storage apparatus  1  according to this embodiment, the expansion of the outer case  10  is suppressed by the reinforcing member  100  fixed to the outer case  10  and hence, a possibility that a damage such as cracking occurs in the outer case  10  is reduced. Such an advantageous effect can be obtained by the reinforcing member  100  that is attached to the outer case  10  from the outside and hence, the above-mentioned advantageous effect can be obtained without changing the designing of the outer case  10 . 
     Further, the reinforcing wall  101  has the relatively high rigidity and hence, the expansion of the wall portion  13  of the outer case  10  can be more reliably suppressed. Further, with respect to the connecting member  102  where a demand for high rigidity is not so high compared to the reinforcing wall  101 , a thickness of the connecting member  102  can be reduced or the connecting member  102  is thinned. As illustrated in  FIG.  3   , the connecting portion  102  may be light-weighted by forming four thinned portions (opening portions). That is, in the energy storage apparatus  1  of this embodiment, it is possible to effectively suppress the deformation of the outer case  10  (the expansion of the wall portion  13 ) while realizing the reduction of weight, downsizing or the like of the reinforcing member  100 . As described above, according to the energy storage apparatus  1  of the present embodiment, the safety of the energy storage apparatus  1  can be enhanced. 
     The comparison in rigidity between the reinforcing wall  101  and the connecting portion  102  is performed by comparing values in bending rigidity between the reinforcing wall  101  and the connecting portion  102 . The bending rigidity of the reinforcing wall  101  means a bending rigidity in an arrangement direction (X axis direction) of the reinforcing wall  101  and the outer case  10 . The bending rigidity of the connecting portion  102  means a bending rigidity in an arrangement direction (Y axis direction) of the connecting portion  102  and the outer case  10 . Specifically, in the reinforcing member  100 , the pair of reinforcing walls  101  and the connecting portion  102  are cut at the connecting portion, and the pair of reinforcing walls  101  and the connecting portion  102  are separated from each other. Thereafter, the bending rigidity of the pair of reinforcing walls  102  and the bending rigidity of the connecting portion  102  are measured, and measured bending rigidity values are compared with each other. As described in the present embodiment, such a difference in rigidity may be realized by the difference in cross-sectional shape (cross-sectional secondary moment) between the reinforcing wall  101  and the connecting portion  102 , the difference in material between the reinforcing wall  101  and the connecting portion  102 , or the like, besides the difference in thickness between the reinforcing wall  101  and the connecting portion  102 . 
     In the present embodiment, the pair of reinforcing walls  101  are connected to each other by the connecting portion  102  disposed on both sides in a width direction (Y-axis direction) that intersects with an opposedly facing direction of the two wall portions  13 . 
     As described above, in the present embodiment, the pair of reinforcing walls  101  is brought into a posture parallel to the YZ plane respectively and is connected to each other on both sides in the Y axis direction and hence, the pair of reinforcing walls  101  can exert a high restraining force with respect to the outer case  10 . With such a configuration, an effect of suppressing the expansion of the outer case  10  is enhanced, and this contributes to the enhancement of the safety of the energy storage apparatus  1 . 
     In the present embodiment, as illustrated in  FIG.  2   , the plurality of energy storage devices  20  arranged side by side in an opposedly facing direction of the two wall portions  13  (wall portions  13   a ) are accommodated in the outer case  10 . 
     To be more specific, in the outer case  10 , each of the plurality of energy storage devices  20  is a prismatic energy storage device  20 , and is disposed such that the long-side surfaces  21   a  (see  FIG.  2   ) are directed in the arrangement direction of the energy storage devices  20 . In the prismatic energy storage device  20 , the long-side surfaces  21   a  are likely to expand and hence, the energy storage device array  24  formed of the plurality of energy storage devices  20  is likely to expand in the arrangement direction of the plurality of energy storage devices  20 . Accordingly, it can be said that the two opposedly facing wall portions  13   a  are likely to expand outward by receiving the expansion of the energy storage device array  24 . In this regard, in the energy storage apparatus  1  of the present embodiment, the reinforcing member  100  is disposed in a posture suitable for restraining the two wall portions  13   a  and hence, the expansion of the outer case  10  can be effectively suppressed. That is, the reinforcing member  100  is disposed so as to press the portion of the outer case  10  that is likely to expand. With such a configuration, the safety of the energy storage apparatus  1  is enhanced. 
     In the present embodiment, the reinforcing member  100  includes the first reinforcing member  110  and the second reinforcing member  120 . Each of the first reinforcing member  110  and the second reinforcing member  120  includes the two plate-shaped portions  111  or  121  disposed opposite to each other and the connecting portion  102  connecting the two plate-shaped portions  111  or  121  to each other. Each of the pair of reinforcing walls  101  is configured by overlapping one of the two plate-shaped portions  111  of the first reinforcing member  110  and one of the two plate-shaped portions  121  of the second reinforcing member  120 . 
     According to such a configuration, the reinforcing member  100  can be configured by combining two members (first and second reinforcing members  120 ) having the same shape with each other. Accordingly, it is possible to obtain a reinforcing wall  101  having high rigidity that is formed of the two plate-shaped portions  111 ,  121 . By combining the two members such that the connecting portions  102  of the two members face each other, it is also possible to obtain the reinforcing member  100  that can suppress the expansion of the outer case  10  in a well-balanced manner. Accordingly, it is possible to obtain the reinforcing member  100  that efficiently suppresses the expansion of the outer case  10  with the simple configuration, and this contributes to the enhancement of the safety of the energy storage apparatus  1 . 
     The configuration of the energy storage apparatus  1  according to the present embodiment can also be described as follows. That is, the energy storage apparatus  1  includes: the outer case  10  that accommodates the energy storage devices  20 ; and the reinforcing member  100  that includes the pair of reinforcing walls  101  and the connecting portions  102 . The pair of reinforcing walls  101  is disposed so as to sandwich the two wall portions  13  (wall portions  13   a ) of the outer case  10  opposedly facing each other from the outside. The connecting portion  102  connects the pair of reinforcing walls  101  to each other. The reinforcing member  100  includes the first reinforcing member  110  and the second reinforcing member  120 , and the first reinforcing member  110  includes the two plate-shaped portions  111  disposed opposite to each other and the connecting portion  102  that connects the two plate-shaped portions  111  to each other. The second reinforcing member  120  includes the two plate-shaped portions  121  disposed opposite to each other and the connecting portion  102  that connects the two plate-shaped portions  121  to each other. Each of the pair of reinforcing walls  101  is configured by overlapping one of the two plate-shaped portions  111  of the first reinforcing member  110  and one of the two plate-shaped portions  121  of the second reinforcing member  120 . 
     According to this configuration, the pair of reinforcing walls  101  is connected to each other so as to restrict the movement of the pair of reinforcing walls  101  to the outside and hence, the expansion of the wall portion  13   a  of the outer case  10  to the outside is suppressed. As a result, the occurrence of a damage or the like on the outer case  10  is suppressed. The reinforcing member  100  can be configured by combining two members (first and second reinforcing members  120 ) having the same shape with each other. Accordingly, it is possible to obtain a reinforcing wall  101  having high rigidity that is formed of the two plate-shaped portions  111 ,  121 . By combining the first reinforcing member  110  and the second reinforcing member  120  such that the connecting portions  102  of the first and second reinforcing members  110 ,  120  face each other, it is also possible to obtain the reinforcing member  100  that can suppress the expansion of the outer case  10  in a well-balanced manner. Accordingly, it is possible to obtain the reinforcing member  100  that efficiently suppresses the expansion of the outer case  10  with a simple configuration. Therefore, according to the energy storage apparatus  1  of the present embodiment, the safety of the energy storage apparatus  1  can be enhanced. 
     The configuration of the energy storage apparatus  1  according to the present embodiment can also be described as follows. That is, the energy storage apparatus  1  includes the outer case  10  that accommodates the energy storage devices  20  and the reinforcing member  100 . The reinforcing member  100  includes the pair of reinforcing walls  101  disposed so as to sandwich the two wall portions  13  (wall portions  13   a ) of the outer case  10  facing each other from the outside, and the connecting portion  102  connecting the pair of reinforcing walls  101  to each other. The thickness of each of the pair of reinforcing walls  101  is larger than the thickness of the connecting portion  102 . 
     According to this configuration, the pair of reinforcing walls  101  is connected to each other so as to restrict the movement of the pair of reinforcing walls  101  to the outside. Accordingly, when the wall portions  13   a  of the outer case  10  receive an external force from the inside, the expansion of the wall portions  13   a  to the outside is suppressed. As a result, the occurrence of a drawback such as a damage on the outer case  10  is suppressed. Such an advantageous effect can be obtained by the reinforcing member  100  that is attached to the outer case  10  from the outside and hence, the above-mentioned advantageous effect can be obtained without changing the designing of the outer case  10 . Further, the reinforcing wall  101  has the relatively large thickness and hence, the expansion of the wall portion  13  of the outer case  10  can be more reliably suppressed. Further, with respect to the connecting portion  102  where a demand for large thickness is not so high compared to the reinforcing wall  101 , the connecting portion  102  can be formed with a relatively thin wall thickness. That is, it is possible to effectively suppress the deformation of the outer case  10  (the expansion of the wall portion  13 ) while realizing the reduction of weight, downsizing or the like of the reinforcing member  100 . Therefore, according to the energy storage apparatus  1  of the present embodiment, the safety of the energy storage apparatus  1  can be enhanced. 
     The thickness of the reinforcing wall  101  is a width of the reinforcing wall  101  in the direction in which the pair of reinforcing walls  101  is arranged. The thickness of the reinforcing wall  101  is a width, in the arrangement direction, of main portions excluding protrusions protruding in the arrangement direction, through holes penetrating the reinforcing wall  101  in the arrangement direction, recessed portions recessed in the arrangement direction, and the like. In a case where there exists distribution or unevenness in the thickness of the reinforcing wall  101  as viewed in the direction that the reinforcing wall  101  is arranged, an average value, a most frequent value, or the like of the thickness may be adopted as the thickness of the reinforcing wall  101 . 
     In the present embodiment, the reinforcing wall  101  thicker than the connecting portion  102  is formed by overlapping the plate-shaped portions  111  and  121 . However, the reinforcing wall  101  may be formed of a single member. A reinforcing member  100  having a reinforcing wall  101  thicker than a connecting portion  102  may be manufactured by using a metal plate in which a thick portion and a thin portion are formed by press working. 
     In the present embodiment, more specifically, as shown in  FIG.  6   , the lid body  11  and the body portion  12  of the outer case  10  are joined to each other at a joint portion  14  positioned at a peripheral edge of the opening portion  15  (see  FIG.  2   ) of the outer case  10 . For example, the joint portion  14  that is a portion where the lid body  11  and the main body portion  12  are joined to each other is formed by thermal welding. In this configuration, when an internal pressure of the outer case  10  increases, the internal pressure acts on the wall portion  13   a  in  FIG.  6    in a direction that an upper end of the wall portion  13   a  falls outward. Accordingly, stress is likely to concentrate on the joint portion  14 , and as a result, there is a possibility that a part of the joint portion  14  is damaged so that a gas filled in the inside of the outer case  10  leaks out from the part of the joint portion  14 . However, in the energy storage apparatus  1  according to this embodiment, as illustrated in  FIG.  6   , the reinforcing member  100  having the relatively high rigidity is disposed at a position where the reinforcing member  100  presses the wall portion  13   a  from the outside. With such a configuration, the deformation of the wall portion  13   a  to the outside is suppressed. As a result, a damage such as cracking of the joint portion  14 , that is a portion where a damage due to deformation of the wall portion  13   a  to the outside is likely to occur, is suppressed. 
     Further, in the present embodiment, as illustrated in  FIG.  6   , the restricting member  200  is disposed outside the reinforcing member  100 . The restricting member  200  includes a contact portion  201  that is brought into contact with the upper surface of the lid body  11  and a fixing portion  202  fixed to the reinforcing member  100 . The fixing portion  202  is joined to the outer surface of the reinforcing wall  101  of the reinforcing member  100  by welding or the like. Accordingly, the restricting member  200  functions as a member that increases the rigidity of the reinforcing wall  101  or a member that increases the thickness of the reinforcing wall  101 . That is, the fixing portion  202  of the restricting member  200  can enhance the reinforcing function by the reinforcing member  100 . 
     The fixing portion  202  of the restricting member  200  further has a portion that is brought into contact with a peripheral wall portion  11   b  of the lid body  11  from the outside. Accordingly, when the combination of the wall portion  13   a  that is a part of the body portion  12  and the peripheral wall portion  11   b  of the lid body  11  is defined as the wall portion  16  of the outer case  10 , and the restricting member  200  fixed to the reinforcing member  100  by welding or the like is defined as a part of the reinforcing member  100 , the following can be said. The reinforcing member  100  includes the pair of reinforcing walls  101  disposed so as to sandwich the two wall portions  16  of the outer case  10  opposedly facing each other from the outside, and the connecting portion  102  connecting the pair of reinforcing walls  101  to each other. That is, the restricting member  200  that forms a part of the reinforcing member  100  can function as a member that suppresses the deformation, to the outside, of the peripheral wall portion  11   b  of the lid body  11  that forms a part of the wall portion  16  of the outer case  10 . To be more specific, the deformation of the peripheral wall portion  11   b  of the lid body  11  caused by the deformation of the wall portion  13   a  of the body portion  12  to the outside (the lower end of the peripheral wall portion  11   b  is inclined to open outward) is suppressed by the restricting member  200  that forms a portion of the reinforcing member  100 . As described above, according to the reinforcing member  100  of the present embodiment, the expansion of the wall portion  16  formed of the body portion  12  and the lid body  11  can be suppressed, and as a result, the safety of the energy storage apparatus  1  is enhanced. 
     (Modification) 
     The energy storage apparatus according to the present invention has been described above based on the embodiment. However, the present invention is not limited to the above-mentioned embodiment. Modes obtained by applying various modifications made by those skilled in the art to the above-mentioned embodiments are also included in the scope of the present invention without departing from the gist of the present invention. 
     The two connecting portions  102  included in the reinforcing member  100  are not necessarily disposed in an opposedly facing manner. The reinforcing member  100  may have a connecting portion  102  that connects end portions of the pair of reinforcing walls  101  on the Y-axis direction negative side to each other, and a connecting portion  102  that connects end portions of the pair of reinforcing walls  101  on the Z-axis direction negative side to each other. The number of the connecting portions  102  included in the reinforcing member  100  may be 1 or 3 or more. That is, it is sufficient for the connecting portion  102  to connect the pair of reinforcing walls  101  to each other so as to restrain the pair of reinforcing walls  101  disposed opposite to each other in the X axis direction in the X axis direction, and the shape, the number, the arrangement position, and the like of the connecting portion  102  are not particularly limited. 
     The reinforcing member  100  is not necessarily formed of the combination of the first reinforcing member  110  and the second reinforcing member  120 . After the connecting portion  102  and the reinforcing wall  101  are manufactured as separate members, the connecting portion  102  and the reinforcing wall  101  may be connected to each other by welding, fastening, or the like. That is, provided that the energy storage apparatus  1  includes the pair of reinforcing walls  101  and at least one connecting portion  102  connecting the pair of reinforcing walls  101  to each other, and the rigidity of the reinforcing wall  101  is higher than the rigidity of the connecting portion  102 , the number, the shape, and the like of the members constituting the reinforcing member  100  are not particularly limited. In this supplementary term, “provided that the rigidity of the reinforcing wall  101  is higher than the rigidity of the connecting portion  102 ,” may be read as “when the thickness of the reinforcing wall  101  is larger than the thickness of the connecting portion  102 ”. In any case, the deformation of the outer case  10  (expansion of the wall portion  13 ) can be effectively suppressed by the reinforcing member  100 . Accordingly, the safety of the energy storage apparatus  1  is enhanced. 
     Each of the reinforcing member  100  and the restricting member  200  is not necessarily made of metal. Each of the reinforcing member  100  and the restricting member  200  may be formed of a non-metallic material having high rigidity such as fiber-reinforced plastic. 
     The energy storage apparatus  1  may not include the restricting member  200 . The energy storage apparatus  1  includes at least the reinforcing member  100  as the member for reinforcing the outer case  10  and hence, it is possible to enhance the safety of the energy storage apparatus  1  as described above. 
     The configurations that are formed by arbitrarily combining the above-described plurality of constituent elements also fall within the scope of the present invention. 
     Industrial Applicability 
     The present invention is applicable to an energy storage apparatus that includes energy storage devices such as lithium ion secondary batteries or the like. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
         
           
               1 : energy storage apparatus 
               10 : outer case  11 : lid body  11   b : peripheral wall portion 
               12 : body portion  13 ,  13   a ,  13   b ,  16 : wall portion 
               13   e : rib 
               14 : joint portion  15 : opening portion 
               20 : energy storage device 
               21 : case 
               21   a : long-side surface 
               100 : reinforcing member 
               101 : reinforcing wall 
               102 : connecting portion 
               110 : first reinforcing member 
               111 ,  121 : plate-shaped portion  120 : second reinforcing member 
               200 ,  210 ,  220 ,  230 : restricting member 
               201 : contact portion 
               202 : fixing portion