Patent Publication Number: US-2022223980-A1

Title: Bus bar plate

Description:
TECHNICAL FIELD 
     The present invention relates to a bus bar plate. 
     BACKGROUND ART 
     For example, as a power source for a vehicle or the like that requires a high output voltage, there has been known a battery module formed by electrically connecting a plurality of batteries to each other. In general, in a battery module, a plurality of batteries have been stacked, and adjacent batteries have been electrically connected via a bus bar. Further, for example, as disclosed in PTL 1, the battery module has included a bus bar plate covering a terminal placement surface of a battery stack and supporting the bus bar. By covering the terminal placement surface of the battery stack with the bus bar plate, a creepage distance between the output terminals can be ensured. The bus bar plate can also function as a support plate for supporting a voltage detection line that detects the voltage of each battery. 
     CITATION LIST 
     Patent Literature 
     PTL 1: WO 2013/161655 A 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In recent years, a number of batteries included in a power source tends to increase with the demand for higher capacity of the power source. For achieving the high capacity of the power source, it is conceivable to increase a number of battery modules, but it is more effective in terms of the cost of the power source to increase a number of stacked batteries in one battery module. That is, according to a method of increasing the number of stacked batteries in each battery module while maintaining the number of battery modules, it is possible to increase the capacity of the power source while reducing an increase in a number of components constituting the power source, thereby reducing an increase in cost. As the number of stacked batteries increases, it is naturally necessary to increase the dimensions of the bus bar plate. However, when the bus bar plate is increased in size, warpage is likely to occur particularly at an end part of the bus bar plate. When the bus bar plate is deformed due to the occurrence of warpage in the end part, adverse effects such as difficulties in ensuring the creepage distance between the output terminals and supporting the voltage detection line may occur. For this reason, there is a demand for a bus bar plate that is less likely to be warpage in the end part even when the bus bar plate is increased in size. 
     In general, batteries tend to expand or contract with use. When the number of stacked batteries increases, a dimensional variation of the battery stack increases, and a load applied to the bus bar plate increases. When an excessive load is applied to the bus bar plate, the bus bar plate may be damaged. Therefore, a bus bar plate that is less likely to be damaged even when the number of stacked batteries is increased is desired. 
     The present invention has been made in view of such a situation, and an object of the present invention is to provide a bus bar plate capable of coping with an increase in the number of stacked batteries. 
     Solution to Problem 
     One aspect of the present invention is a bus bar plate that covers a surface of a battery stack having a plurality of stacked batteries, the surface being provided with output terminals of each of the plurality of stacked batteries, and supports a bus bar electrically connecting each of the output terminals. The bus bar plate includes a plurality of plate units. Each of the plate units is disposed corresponding to one battery in the plurality of batteries or to an assembly of several batteries and has terminal openings for exposure of the output terminals provided on the corresponding battery and a coupling mechanism that couples adjacent plate units to each other. The terminal openings are provided at both ends of each of the plate units in a direction orthogonal to a stacking direction of the batteries. The coupling mechanism is located between the terminal openings arranged in the direction orthogonal to the stacking direction of the batteries and is made up of a male part disposed on a first plate unit out of the first plate unit and a second plate unit adjacent to each other, and a female part that is disposed on the second plate unit and that the male part is fitted to. The male part and the female part are fitted to each other across a gap that allows a predetermined amount of displacement of the first plate unit and the second plate unit in the stacking direction of the batteries. 
     Note that any combinations of the above-described configuration elements and configurations obtained by expressing the present invention in the form of a method, apparatus, system and the like are also effective as an aspect of the present invention. 
     Advantageous Effect of Invention 
     According to the present invention, it is possible to provide a bus bar plate capable of coping with an increase in a number of stacked batteries. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a battery module including a bus bar plate according to a first exemplary embodiment. 
         FIG. 2  is an enlarged perspective view illustrating a region including a coupling mechanism of the bus bar plate. 
         FIG. 3(A)  to (C) is view illustrating an assembly process of the battery module. 
         FIG. 4  is a perspective view of a part of a bus bar plate according to a second exemplary embodiment as viewed obliquely from above. 
         FIG. 5  is a perspective view of a part of the bus bar plate according to the second exemplary embodiment as viewed obliquely from below. 
         FIG. 6  is a perspective view of a part of a bus bar plate according to a third exemplary embodiment as viewed obliquely from above. 
         FIG. 7(A)  and (B) is view illustrating an assembly process of a battery module according to a first modified example. 
         FIG. 8(A)  is a perspective view of a second plate unit according to a second modified example as viewed from a first plate unit.  FIG. 8(B)  is a perspective view of the first plate unit according to the second modified example as viewed from a second plate unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be described on the basis of preferred exemplary embodiments with reference to the drawings. The exemplary embodiments are not intended to limit the invention but are examples, and all features described in the exemplary embodiments and combinations thereof are not necessarily essential to the invention. The same or equivalent configuration elements, members, and processing illustrated in the drawings are denoted by the same reference numerals, and a redundant description will be omitted as appropriate. The scale and shape of each part illustrated in each drawing are set for convenience in order to facilitate the description and are not limitedly interpreted unless otherwise specified. When terms such as “first” and “second” are used in the present specification or claims, unless otherwise specified, these terms do not represent any order or importance but are intended to distinguish one configuration from another configuration. In each drawing, some members, which are not important for describing the exemplary embodiment, are omitted. 
     First Exemplary Embodiment 
       FIG. 1  is an exploded perspective view of a battery module including a bus bar plate according to a first exemplary embodiment. Battery module  1  includes battery stack  2 , bus bar plate  4 , and a plurality of bus bars  6 . Battery stack  2  has a plurality of stacked batteries  8 . Each battery  8  is a rechargeable secondary battery such as a lithium-ion battery, a nickel-metal-hydride battery, or a nickel-cadmium battery. Battery  8  is a so-called prismatic battery and has exterior can  10  in a flat rectangular-parallelepiped shape. Exterior can  10  has a substantially rectangular opening on one surface, and an electrode assembly, an electrolyte, and the like are accommodated in exterior can  10  through the opening. Sealing plate  12  for sealing exterior can  10  is provided in an opening of exterior can  10 . 
     Sealing plate  12  is provided with output terminal  14  of a positive electrode near one end and output terminal  14  of a negative electrode near the other end in the longitudinal direction. The pair of output terminals  14  are electrically connected respectively to the positive electrode plate and the negative electrode plate constituting the electrode assembly. Hereinafter, output terminal  14  of the positive electrode is appropriately referred to as positive electrode terminal  14   a , and output terminal  14  of the negative electrode is appropriately referred to as negative electrode terminal  14   b . When it is not necessary to distinguish the polarity of output terminal  14 , positive electrode terminal  14   a  and negative electrode terminal  14   b  are collectively referred to as output terminal  14 . Exterior can  10 , sealing plate  12 , and output terminals  14  are electric conductors and are made of metal, for example. Sealing plate  12  and the opening of exterior can  10  are joined to each other by, for example, laser bonding. Respective output terminals  14  are inserted into through-holes (not illustrated) formed in sealing plate  12 . An insulating seal member (not illustrated) is interposed between each output terminal  14  and each through-hole. 
     In the description of the present exemplary embodiment, for convenience, sealing plate  12  is referred to as the upper surface of battery  8 , and the bottom surface of exterior can  10  disposed on the side opposite to sealing plate  12  is referred to as the lower surface of battery  8 . Battery  8  has two main surfaces that connect the upper surface and the lower surface of battery  8  to each other. The main surfaces are surfaces having the largest area out of the six surfaces of battery  8 . The main surfaces are long side surfaces connected to the long sides of the upper surface and the long sides of the lower surface. Two remaining surfaces except for the upper surface, the lower surface, and the two main surfaces are referred to as the side surfaces of battery  8 . These side surfaces are a pair of short side surfaces connected to the short sides of the upper surface and the short sides of the lower surface. 
     Further, for convenience, the surface of battery stack  2  closer to the upper-surface of battery  8  is referred as the upper surface of battery stack  2 , the surface closer to the lower-surface of battery  8  is referred as the lower surface of battery stack  2 , and the surface closer to the side surface of battery  8  is referred as the side surface of battery stack  2 . These directions and positions are defined for convenience. Therefore, for example, the portion defined as the upper surface in the present invention does not necessarily mean a portion located above the portion defined as the lower surface. 
     Sealing plate  12  is provided with a safety valve (not illustrated) between the pair of output terminals  14 . The safety valve is a mechanism for each battery  8  to eject gas inside the battery. The safety valve is configured to open and release the internal gas when the internal pressure of exterior can  10  rises to a predetermined value or more. The safety valve includes, for example, a thin part, which is provided in a part of sealing plate  12  and is thinner than the other part, and a linear groove formed on the surface of the thin part. 
     Each battery  8  has an insulating film (not illustrated). The insulating film is, for example, a cylindrical shrink tube, and is heated after exterior can  10  is inserted into the insulating film. As a result, the insulating film shrinks and covers the two main surfaces, the two side surfaces, and the bottom surface of exterior can  10 . The insulating film can prevent a short circuit between adjacent batteries  8  or between battery  8  and the end plate or a restraining member. 
     The plurality of batteries  8  are stacked at predetermined intervals with the main surfaces of adjacent batteries  8  facing each other. Note that the term “stack” means that a plurality of members are arranged in any one direction. Thus, stacking batteries  8  also includes arranging the plurality of batteries  8  horizontally. In the present exemplary embodiment, batteries  8  are stacked horizontally. Accordingly, stacking direction X of batteries  8  is a direction of extending in the horizontal direction. Hereinafter, when appropriate, a direction that is horizontal and is perpendicular to stacking direction X is referred to as horizontal direction Y, and a direction that is perpendicular to stacking direction X and horizontal direction Y is referred to as vertical direction Z. 
     Each battery  8  is disposed such that output terminals  14  are directed in the same direction. In the present exemplary embodiment, each battery  8  is disposed such that output terminals  14  are directed upward in the vertical direction. Hence the upper surface of battery stack  2  constitutes terminal placement surface  2   a  on which output terminal  14  of each battery  8  is disposed. When adjacent batteries  8  are connected in series, batteries  8  are stacked such that positive electrode terminal  14   a  of one battery  8  and negative electrode terminal  14   b  of another battery  8  are adjacent to each other. When adjacent batteries  8  are connected in parallel, positive electrode terminal  14   a  of one battery  8  and positive electrode terminal  14   a  of another battery  8  are laminated so as to be adjacent to each other. 
     Battery stack  2  has a plurality of inter-cell separators (not illustrated). The inter-cell separator is also referred to as an insulating spacer and is made of a resin sheet having an insulating property, for example. Examples of the resin used for forming the inter-cell separator include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE). The inter-cell separator is disposed between two adjacent batteries  8  to electrically insulate two batteries  8  from each other. 
     Battery stack  2  is sandwiched by a pair of end plates (not illustrated). The pair of end plates are disposed at both ends of battery stack  2  in stacking direction X of batteries  8 . The pair of end plates are adjacent to batteries  8  located at both ends in stacking direction X with external end separators (not illustrated) interposed between the end plates and batteries  8 . The external end separator can be made of the same resin material as the inter-cell separator. Each end plate is a metal sheet made of metal such as iron, stainless steel, or aluminum. By the external end separator being interposed between the end plate and battery  8 , both are insulated. 
     Battery stack  2  and the pair of end plates are restrained by a pair of restraining members (not illustrated). The pair of restraining members are also called bind bars and are long members elongated in stacking direction X of batteries  8 . The pair of restraining members are disposed in horizontal direction Y. The pair of restraining members are made of metal, for example, iron or stainless steel. 
     The plurality of batteries  8  and the plurality of inter-cell separators are alternately arranged, and these are sandwiched between the pair of end plates in stacking direction X with the external end separators interposed therebetween. In this state, both end parts of each restraining member in stacking direction X and the pair of end plates are fixed by screwing or the like, whereby the plurality of batteries  8  are fastened and restrained in stacking direction X. Accordingly, respective batteries  8  are positioned in stacking direction X. The separators, the end plates, and the restraining members have known structures, and thus, a detailed description will be omitted. 
     Bus bar plate  4  is placed on terminal placement surface  2   a  of battery stack  2 . Bus bar plate  4  is a plate-shaped member that covers terminal placement surface  2   a . Bus bar plate  4  includes a plurality of plate units  16  disposed for the plurality of batteries  8 , respectively. Bus bar plate  4  has a plate shape as a whole by the plurality of plate units  16  being coupled to each other. 
     Each plate unit  16  is made of a resin such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), or Noryl (registered trademark) resin (modified PPE). Each plate unit  16  includes body  18 , a pair of terminal openings  20 , and coupling mechanism  22 . 
     Body  18  overlaps corresponding battery  8  as viewed in a first direction in which bus bar plate  4  and battery stack  2  are disposed side by side (in vertical direction Z in the present exemplary embodiment). Body  18  has a shape roughly corresponding to the upper surface of battery  8 . Specifically, body  18  is a member having the shape of a substantially rectangular plate elongated in horizontal direction Y. 
     The pair of terminal openings  20  are openings through which the pair of output terminals  14  of corresponding battery  8  are exposed. Each plate unit  16  has a pair of terminal openings  20  at positions overlapping, in vertical direction Z, the pair of output terminals  14  of corresponding battery  8 , that is, battery  8  on which the plate unit itself is placed. The pair of terminal openings  20  are provided at both ends in the longitudinal direction of body  18  having a substantially rectangular shape. That is, terminal opening  20  is provided at both ends of each plate unit  16  in a direction orthogonal to stacking direction X of batteries  8  (in horizontal direction Yin the present exemplary embodiment). 
     Bus bar  6  is placed on each terminal opening  20 . The plurality of bus bars  6  are supported by bus bar plate  4 . Each bus bar  6  is a substantially belt-shaped metal member that electrically connects output terminals  14  of adjacent batteries  8 . One end of bus bar  6  is electrically connected to output terminal  14  of one battery  8 , and the other end is electrically connected to output terminal  14  of another battery  8 . Bus bar  6  and output terminal  14  are bonded to each other by, for example, laser bonding or ultrasonic bonding. Note that bus bars  6  may connect output terminals  14  of the same polarity of a plurality of adjacent batteries  8  in parallel to form a battery block and may further connect the battery blocks in series. 
     Coupling mechanism  22  is a mechanism that couples adjacent plate units  16  to each other and is disposed between the pair of terminal openings  20  in a direction in which the pair of terminal openings  20  are disposed side by side (in horizontal direction Yin the present exemplary embodiment). That is, coupling mechanism  22  is located between terminal openings  20  arranged in the direction orthogonal to stacking direction X of batteries  8 . Coupling mechanism  22  of the present exemplary embodiment is provided at approximately the center in the longitudinal direction of substantially rectangular body  18 . Note that each plate unit  16  has an opening (not illustrated) through which the safety valve is exposed at a position overlapping the safety valve of battery  8  in vertical direction Z. Coupling mechanism  22  is provided at a position not interfering with the opening. Coupling mechanism  22  is integrally molded with body  18 . 
       FIG. 2  is an enlarged perspective view illustrating a region including coupling mechanism  22  of bus bar plate  4 . As illustrated in  FIG. 2 , coupling mechanism  22  is made up of male part  24  and female part  26 . Male part  24  is disposed on first plate unit  16   a  out of first plate unit  16   a  and second plate unit  16   b  adjacent to each other, and female part  26  is disposed on second plate unit  16   b . Each plate unit  16  has male part  24  on one long side surface of body  18  and female part  26  on the other long side surface. Thereby, each plate unit  16  can be coupled to plate units  16  on both sides. 
     Male part  24  is a convex engagement part protruding from body  18  of first plate unit  16   a  toward second plate unit  16   b . Female part  26  is a concave engagement part provided on the surface of body  18  of second plate unit  16   b  closer to first plate unit  16   a . Male part  24  protrudes in stacking direction X, and female part  26  is recessed in stacking direction X. Male part  24  of first plate unit  16   a  is fitted to female part  26  of second plate unit  16   b , whereby first plate unit  16   a  and second plate unit  16   b  are coupled to each other. 
     Male part  24  of the present exemplary embodiment is made up of plate part  28  protruding toward second plate unit  16   b , and column part  30  disposed at the tip of plate part  28 . Plate part  28  is provided such that its thickness is directed in horizontal direction Y. Column part  30  is provided with its central axis directed in vertical direction Z and has a peripheral surface connected to the side surface of plate part  28  facing second plate unit  16   b . The diameter of column part  30  is larger than the thickness (dimension in horizontal direction Y) of plate part  28 . Female part  26  of the present exemplary embodiment is made up of plate-shaped space  32  corresponding to plate part  28  and columnar space  34  disposed at the tip of plate-shaped space  32  and corresponding to column part  30 . The thickness (dimension in horizontal direction Y) of plate-shaped space  32  is smaller than the diameter of column part  30 . Plate part  28 , column part  30 , plate-shaped space  32 , and columnar space  34  each extend from the lower end to the upper end of body  18 . 
     When first plate unit  16   a  and second plate unit  16   b  are pressed against each other with male part  24  and female part  26  aligned, column part  30  is press-fitted into plate-shaped space  32 . Then, column part  30  passes through plate-shaped space  32  and enters columnar space  34 . As a result, male part  24  is fitted to female part  26 . Displacement in a direction in which first plate unit  16   a  and second plate unit  16   b  are separated from each other is reduced by interference between column part  30  accommodated in columnar space  34  and the sidewall that defines plate-shaped space  32  in which column part  30  is also narrow. 
     Male part  24  and female part  26  are fitted to each other across gap G that allows a predetermined amount of displacement of first plate unit  16   a  and second plate unit  16   b  in stacking direction X of batteries  8 . That is, in a state where male part  24  is fitted to female part  26 , column part  30  and the peripheral surface of columnar space  34  are separated by gap G. Accordingly, the relative displacement between first plate unit  16   a  and second plate unit  16   b , particularly displacement in stacking direction X, is allowed by gap G. 
     In the vicinity of female part  26  in horizontal direction Y, it is preferable to provide cutout  36  extending substantially parallel to plate-shaped space  32  with a predetermined interval from plate-shaped space  32  in horizontal direction Y. By providing cutout  36 , the width of plate-shaped space  32  easily expands when male part  24  is fitted into female part  26 , so that male part  24  can be easily fitted into female part  26 . Note that cutouts  36  may be disposed on both sides of female part  26  or may be disposed only on one side. 
     As illustrated in  FIG. 1 , the plurality of plate units  16  have grooves  38  arranged in a line in a state of being coupled to each other outside terminal openings  20  in plate units  16 . In the present exemplary embodiment, grooves  38  are provided at both ends in the longitudinal direction of body  18  having a substantially rectangular shape. Each groove  38  is located outside terminal opening  20  in plate units  16  in horizontal direction Y and extends in stacking direction X. Thus, guide grooves  40  formed of grooves  38  of plate units  16  and extending in stacking direction X are provided at both end parts of bus bar plate  4  in horizontal direction Y. With each plate unit  16  having grooves  38 , a creepage distance between each output terminal  14  and the outside of battery module  1  can be increased. 
     By setting the positions of grooves  38  to both end parts of each plate unit  16  in horizontal direction Y, the creepage distance can be ensured more reliably. A voltage detection line and a duct structure for gas discharged from each battery  8  are provided in a central region of bus bar plate  4  in horizontal direction Y, whereby it is difficult to provide groove  38  having a height in vertical direction Z. In contrast, groove  38  can be easily provided in a region outside plate unit  16  from terminal opening  20 . 
     Guide groove  40  is used in the assembly process of battery module  1 .  FIGS. 3(A) to 3(C)  are views illustrating the assembly process of battery module  1 . First, as illustrated in  FIG. 3(A) , the plurality of plate units  16  are coupled to each other by coupling mechanism  22  to assemble bus bar plate  4 . Then, fixing rods  42  are fitted into the pair of guide grooves  40  of bus bar plate  4 . Fixing rods  42  extend from one end to the other end of bus bar plate  4  in stacking direction X. Accordingly, fixing rods  42  are fitted into respective grooves  38  of the plurality of plate units  16 . 
     Meanwhile, the plurality of batteries  8  and the inter-cell separators are alternately stacked to assemble battery stack  2 . Battery stack  2  is sandwiched between the pair of end plates and is restrained by the pair of restraining members. Then, bus bar plate  4  with fixing rods  42  fitted into guide grooves  40  is placed on terminal placement surface  2   a  of battery stack  2 . 
     As illustrated in  FIG. 3(B) , when bus bar plate  4  is placed on terminal placement surface  2   a , output terminal  14  is exposed from terminal opening  20  of each plate unit  16 . By fitting fixing rods  42  into guide grooves  40  of bus bar plate  4 , plate units  16  can be prevented from being displaced from each other at the time of placing bus bar plate  4  on terminal placement surface  2   a . This can make it easy to position terminal opening  20  of each plate unit  16  and output terminal  14  of each battery  8 . Hence it is possible to easily place bus bar plate  4  on terminal placement surface  2   a . After the placement of bus bar plate  4  on terminal placement surface  2   a , bus bar  6  is placed on terminal opening  20  of each plate unit  16 . A voltage detection line (not illustrated) is also placed on bus bar plate  4 . Thus, bus bar plate  4  also functions as a support plate of the voltage detection line. 
     As illustrated in  FIG. 3(C) , each bus bar  6  is electrically connected to output terminal  14  exposed from terminal opening  20 . In general, before bus bar  6  is connected to output terminal  14 , a voltage detection line is connected to each bus bar  6  by laser bonding or the like. After each bus bar  6  is fixed to output terminal  14 , fixing rod  42  is removed from guide groove  40 . It is thereby possible to obtain battery module  1 . After fixing rod  42  is removed from guide grooves  40 , a cover plate (not illustrated) may be placed on the upper surface of bus bar plate  4 . By placing the cover plate on bus bar plate  4 , dew condensation water, dust, and the like is prevented from being in contact with output terminal  14 , bus bar  6 , the voltage detection line, and the like of battery  8 . 
     As described above, bus bar plate  4  according to the present exemplary embodiment is a member for covering terminal placement surface  2   a  of battery stack  2  that includes the plurality of stacked batteries  8  and for supporting bus bars  6  that electrically connect output terminals  14 . Bus bar plate  4  includes a plurality of plate units  16  disposed for the plurality of batteries  8 , respectively. Each plate unit  16  includes a pair of terminal openings  20  through which a pair of output terminals  14  included in corresponding battery  8  are exposed, and coupling mechanism  22  that is disposed between the pair of terminal openings  20  and couples adjacent plate units  16  to each other. 
     Coupling mechanism  22  includes male part  24  disposed on first plate unit  16   a  out of first plate unit  16   a  and second plate unit  16   b  adjacent to each other, and female part  26  disposed on second plate unit  16   b  to which male part  24  is fitted. Male part  24  and female part  26  are fitted to each other across gap G that allows a predetermined amount of displacement of first plate unit  16   a  and second plate unit  16   b  in stacking direction X of batteries  8 . 
     By making bus bar plate  4  have a structure in which the plurality of plate units  16  are coupled to each other, that is, by dividing bus bar plate  4  into a plurality of parts, it is possible to prevent the occurrence of warpage in the end part of bus bar plate  4  as compared to a case where the bus bar plate is formed of a single plate. Therefore, according to the present exemplary embodiment, it is possible to prevent the occurrence of warpage in the end part of bus bar plate  4  while increasing the size of bus bar plate  4  in accordance with the increase in the number of stacked batteries  8 . 
     Male part  24  and female part  26  constituting coupling mechanism  22  of the present exemplary embodiment are fitted to each other across gap G that allows displacement of the plurality of plate units  16 , coupled to each other, in stacking direction X. That is, the plurality of plate units  16  are coupled to each other with a predetermined positional degree of freedom. This enables the dimensions of bus bar plate  4  to follow the dimensional variation of battery stack  2  due to the expansion or contraction of battery  8 . The size of gap G can be appropriately set on the basis of empirical knowledge of a designer or an experiment, simulation, or the like by the designer in accordance with the expansion amount, the number of stacking layers, or the like of battery  8 . 
     Therefore, even when the dimensional variation of battery stack  2  increases as the number of stacked batteries  8  increases, it is possible to avoid an excessive load applied to bus bar plate  4 . Further, with this structure, it is possible to absorb impact and vibration applied to bus bar plate  4  from the outside. Hence it is possible to reduce the possibility that bus bar plate  4  is damaged by a dimensional variation of battery stack  2 , an impact applied from the outside, or the like. Due to no need for separately providing a displacement/impact absorbing structure to prevent the breakage of bus bar plate  4 , it is possible to prevent the structure of bus bar plate  4  from being complicated and prevent the manufacturing process of bus bar plate  4  from being complicated in association with the complication of the structure. 
     Further, in the single-plate bus bar plate, when the bus bar plate is increased in size, dimensional accuracy is likely to decrease. When the dimensions of the bus bar plate do not match the dimensions of battery stack  2 , it is difficult to attach the bus bar plate to battery stack  2 . In contrast, by forming a coupling structure that allows the relative displacement of the plurality of plate units  16 , the dimensions of entire bus bar plate  4  can be freely adjusted within a predetermined range. Further, with bus bar plate  4  having been divided into the plurality of plate units  16 , the dimensions of each plate unit  16  is naturally smaller than the dimensions of entire bus bar plate  4 . Hence the dimensional accuracy of each plate unit  16  can be enhanced. Accordingly, even when bus bar plate  4  is increased in size, it is possible to avoid difficulty in attachment to battery stack  2 . 
     Moreover, with bus bar plate  4  having a structure in which the plurality of plate units  16  are coupled to each other, the size of bus bar plate  4  can be easily changed by adjusting a number of plate units  16 . It is thus possible to flexibly cope with a change in the number of stacked batteries  8 . As described above, according to the present exemplary embodiment, it is possible to provide bus bar plate  4  capable of coping with an increase in the number of stacked batteries  8 . 
     Respective plate units  16  of the present exemplary embodiment have grooves  38  arranged in a line in a state of being coupled to each other outside plate unit  16  from terminal openings  20 . This enables an increase in the creepage distance between each output terminal  14  and the outside of battery module  1 . Grooves  38  arranged in a row constitutes guide groove  40 , and fixing rod  42  is fitted into guide groove  40  in the process of assembling battery module  1 . Accordingly, at the time of placing bus bar plate  4  on battery stack  2 , the relative displacement of plate units  16  can be regulated. It is thus possible to simplify the assembly process of battery module  1 . 
     Second Exemplary Embodiment 
     A second exemplary embodiment has a configuration common to the first exemplary embodiment except for the shape of plate unit  16 . Hereinafter, the present exemplary embodiment will be described focusing on a configuration different from that of the first exemplary embodiment, and common configurations will be briefly described or not described.  FIG. 4  is a perspective view of a part of bus bar plate  4  according to the second exemplary embodiment as viewed obliquely from above.  FIG. 5  is a perspective view of a part of bus bar plate  4  according to the second exemplary embodiment as viewed obliquely from below. 
     Bus bar plate  4  includes a plurality of plate units  16 . In arbitrary first plate unit  16   a  and second plate unit  16   b  adjacent to each other, first plate unit  16   a  includes body  18  and first protrusion  44 . Body  18  is a member in the shape of a substantially rectangular plate that overlaps corresponding first battery  8   a  as viewed from a first direction in which bus bar plate  4  and battery stack  2  are disposed side by side (in vertical direction Z in the present exemplary embodiment). First protrusion  44  protrudes from body  18  toward second plate unit  16   b  and overlaps second plate unit  16   b  as viewed in the first direction. First protrusion  44  has a plate shape elongated in horizontal direction Y and is disposed such that its main surface is directed in vertical direction Z. First protrusion  44  is integrally molded with body  18 . 
     By providing first protrusion  44  on first plate unit  16   a , it is possible to prevent terminal placement surface  2   a  from being exposed from the gap between first plate unit  16   a  and second plate unit  16   b  when first plate unit  16   a  and second plate unit  16   b  are relatively displaced. It is thereby possible to more reliably ensure the creepage distance between output terminal  14  and the outside of battery module  1 . 
     On the other hand, second plate unit  16   b  includes body  18  and second protrusion  46 . Body  18  is a member in the shape of a substantially rectangular plate that overlaps corresponding second battery  8   b  as viewed in the first direction. Second protrusion  46  protrudes from body  18  toward first plate unit  16   a  and overlaps first plate unit  16   a  as viewed in the first direction. Second protrusion  46  has a plate shape elongated in horizontal direction Y and is disposed such that its main surface is directed in vertical direction Z. Second protrusion  46  is integrally molded with body  18 . 
     By providing second protrusion  46  on second plate unit  16   b , it is possible to further prevent the exposure of terminal placement surface  2   a  can be further reduced. It is thereby possible to more reliably ensure the creepage distance between output terminal  14  and the outside of battery module  1 . 
     First protrusion  44  and second protrusion  46  of the present exemplary embodiment are disposed with coupling mechanism  22  interposed therebetween in horizontal direction Y. First protrusion  44  is aligned such that its lower main surface is flush with the lower main surface of body  18 . First protrusion  44  is inserted between body  18  of second plate unit  16   b  and second battery  8   b . Second protrusion  46  is aligned such that its lower main surface is flush with the lower main surface of body  18 . Second protrusion  46  is inserted between body  18  of first plate unit  16   a  and first battery  8   a.    
     Therefore, first plate unit  16   a  and second plate unit  16   b  adjacent to each other overlap each other with first plate unit  16   a  located above and second plate unit  16   b  located below in a region on one end in horizontal direction Y and with first plate unit  16   a  located above and second plate unit  16   b  located below in a region on the other end in horizontal direction Y. It is thereby possible to prevent one of first plate unit  16   a  and second plate unit  16   b  from coming off in vertical direction Z with respect to the other. 
     Body  18  of second plate unit  16   b  has first concave part  48 , which is recessed away from second battery  8   b , on the lower surface facing terminal placement surface  2   a . First concave part  48  is disposed to overlap first protrusion  44  when viewed in stacking direction X. First concave part  48  is connected to the surface of body  18  facing first plate unit  16   a . When male part  24  of first plate unit  16   a  is fitted into female part  26  of second plate unit  16   b , first protrusion  44  is inserted into first concave part  48 . In this state, the lower surface of first protrusion  44  is exposed toward battery stack  2  to constitute a part of the lower surface of bus bar plate  4 . 
     Body  18  of first plate unit  16   a  has second concave part  50 , which is recessed away from first battery  8   a , on the lower surface facing terminal placement surface  2   a . Second concave part  50  is disposed to overlap second protrusion  46  when viewed in stacking direction X. Second concave part  50  is connected to the surface of body  18  facing second plate unit  16   b . When male part  24  of first plate unit  16   a  is fitted into female part  26  of second plate unit  16   b , second protrusion  46  is inserted into second concave part  50 . In this state, the lower surface of second protrusion  46  is exposed toward battery stack  2  to constitute a part of the lower surface of bus bar plate  4 . 
     By accommodating first protrusion  44  in first concave part  48  and accommodating second protrusion  46  in second concave part  50 , the lower surface of bus bar plate  4  facing battery stack  2  can be made flat. Accordingly, it is possible to prevent the generation of a gap between bus bar plate  4  and terminal placement surface  2   a . Hence it is possible to more reliably ensure the creepage distance between each output terminal  14  and the outside of battery module  1 . 
     Body  18  of first plate unit  16   a  has positioning projection  52  protruding toward second plate unit  16   b . Positioning projection  52  has a triangular shape when viewed in vertical direction Z and protrudes such that its width in horizontal direction Y gradually decreases as positioning projection  52  is separated from body  18 . On the other hand, body  18  of second plate unit  16   b  has positioning cutout  54  on the surface facing first plate unit  16   a . Positioning cutout  54  has a triangular shape as viewed in vertical direction Z and is recessed such that its width in horizontal direction Y gradually decreases as positioning cutout  54  is separated from first plate unit  16   a . Positioning projection  52  and positioning cutout  54  are disposed to overlap each other as viewed in stacking direction X. In the present exemplary embodiment, positioning projection  52  of first plate unit  16   a  is disposed on the upper surface of first protrusion  44 . 
     When first plate unit  16   a  and second plate unit  16   b  are coupled, positioning projection  52  is fitted into positioning cutout  54 . Thus, first plate unit  16   a  and second plate unit  16   b  can be positioned relative to each other particularly in horizontal direction Y. 
     Body  18  of second plate unit  16   b  has positioning projection  52  protruding toward first plate unit  16   a . On the other hand, body  18  of first plate unit  16   a  has positioning cutout  54  on the surface facing second plate unit  16   b . Positioning projection  52  and positioning cutout  54  are disposed to overlap each other as viewed in stacking direction X. In the present exemplary embodiment, positioning projection  52  of second plate unit  16   b  is disposed on the upper surface of second protrusion  46 . In each plate unit  16 , positioning projection  52  and positioning cutout  54  are disposed with coupling mechanism  22  interposed therebetween in horizontal direction Y. Thereby, first plate unit  16   a  and second plate unit  16   b  can be positioned more reliably. 
     Each plate unit  16  has male part  24 , first protrusion  44 , second concave part  50 , positioning projection  52 , and positioning cutout  54  on one long side surface of body  18  and has female part  26 , first concave part  48 , second protrusion  46 , positioning cutout  54 , and positioning projection  52  on the other long side surface. Thereby, each plate unit  16  can be coupled to plate units  16  on both sides. 
     Third Exemplary Embodiment 
     A third exemplary embodiment has a configuration common to the first or second exemplary embodiment except for the shape of plate unit  16 . Hereinafter, the present exemplary embodiment will be described focusing on a configuration different from those of the first and second exemplary embodiments, and common configurations will be briefly described or not described.  FIG. 6  is a perspective view of a part of bus bar plate  4  according to the third exemplary embodiment as viewed obliquely from above. 
     Bus bar plate  4  includes a plurality of plate units  16 . In any of first plate unit  16   a  and second plate unit  16   b  adjacent to each other, first plate unit  16   a  has one of position-regulating convex part  56  and position-regulating concave part  58 , which are fitted to each other, outside plate unit  16   a  from terminal opening  20  in the direction orthogonal to stacking direction X of batteries  8  (in horizontal direction Y in the present exemplary embodiment). First plate unit  16   a  has the one outside plate unit  16   a  from at least one terminal opening  20 . Second plate unit  16   b  has the other of position-regulating convex part  56  and position-regulating concave part  58  outside terminal opening  20  in plate unit  16   b  in the direction orthogonal to stacking direction X of batteries  8 . Second plate unit  16   b  has the other outside plate unit  16   b  from at least one terminal opening  20 . Position-regulating convex part  56  has a substantially plate shape, is provided with its main surface directed in vertical direction Z, and protrudes toward adjacent plate unit  16 . Position-regulating concave part  58  has a recessed shape corresponding to the shape of position-regulating convex part  56 . 
     First plate unit  16   a  according to the present exemplary embodiment has position-regulating convex part  56  on the outer side of one terminal opening  20  in plate unit  16   a  in horizontal direction Y and has position-regulating concave part  58  on the outer side of another terminal opening  20  in plate unit  16   a  in horizontal direction Y. Second plate unit  16   b  has position-regulating concave part  58  at a position overlapping position-regulating convex part  56  of first plate unit  16   a  in stacking direction X and has position-regulating convex part  56  at a position overlapping position-regulating concave part  58  of first plate unit  16   a  in stacking direction X. 
     At the time of coupling first plate unit  16   a  and second plate unit  16   b  to each other, position-regulating convex part  56  enters position-regulating concave part  58  and is fitted thereto. By disposing position-regulating convex part  56  and position-regulating concave part  58  outside terminal openings  20  in first plate unit  16   a  and second plate unit  16   b , it is possible to effectively prevent the relative rotation of first plate unit  16   a  and second plate unit  16   b  with coupling mechanism  22  as a rotation shaft. Further, by setting the positions where position-regulating convex part  56  and position-regulating concave part  58  are provided to the end parts of each plate unit  16  in horizontal direction Y, it is possible to easily ensure the installation space of each of position-regulating convex part  56  and position-regulating concave part  58 . 
     In one end part of body  18  in horizontal direction Y, each plate unit  16  has position-regulating convex part  56  on one long side surface and has position-regulating concave part  58  on the other long side surface. In the other end part of body  18  in horizontal direction Y, each plate unit  16  has position-regulating concave part  58  on one long side surface and has position-regulating convex part  56  on the other long side surface. Accordingly, position-regulating convex parts  56  of each plate unit  16  can be fitted to position-regulating concave parts  58  of plate units  16  on both sides, and position-regulating concave parts  58  of each plate unit  16  can be fitted to position-regulating convex parts  56  of plate units  16  on both sides. 
     In the present exemplary embodiment, protruding length L 1  of position-regulating convex part  56  is larger than protruding length L 2  of male part  24 . That is, the dimension of position-regulating convex part  56  in stacking direction X is larger than the dimension of male part  24  in stacking direction X, and the tip of position-regulating convex part  56  protrudes toward adjacent plate unit  16  more than the tip of male part  24 . Thus, at the time of coupling first plate unit  16   a  and second plate unit  16   b  to each other, position-regulating convex part  56  starts to enter position-regulating concave part  58  before male part  24  starts to enter female part  26 . 
     Therefore, position-regulating convex parts  56  and position-regulating concave part  58  serve as guides for determining the orientations of respective plate units  16  at the time of coupling first plate unit  16   a  and second plate unit  16   b  to each other. This can simplify the assembling process of bus bar plate  4 . It is also possible to provide both position-regulating convex part and concave parts  56  and  58  and groove  38  in each plate unit  16 . 
     Coupling mechanism  22  of the present exemplary embodiment has two sets of male part  24  and female part  26 . Specifically, first plate unit  16   a  has male part  24  and female part  26  on the surface facing second plate unit  16   b . On the other hand, second plate unit  16   b  has female part  26  and male part  24  on the surface facing first plate unit  16   a . Male part  24  of first plate unit  16   a  and female part  26  of second plate unit  16   b  are disposed to overlap each other as viewed in stacking direction X. Similarly, female part  26  of first plate unit  16   a  and male part  24  of second plate unit  16   b  are disposed to overlap each other as viewed in stacking direction X. 
     Male part  24  and female part  26  provided on first plate unit  16   a  are disposed close to each other in horizontal direction Y. Similarly, male part  24  and female part  26  provided on second plate unit  16   b  are disposed close to each other in horizontal direction Y. 
     When first plate unit  16   a  and second plate unit  16   b  are pressed against each other, male part  24  of first plate unit  16   a  and female part  26  of second plate unit  16   b  are fitted to each other. Female part  26  of first plate unit  16   a  and male part  24  of second plate unit  16   b  are fitted to each other. Thus, the plurality of plate units  16  can be coupled more firmly. Each plate unit  16  has male part  24  and female part  26  on both long side surfaces of body  18 . Thereby, each plate unit  16  can be coupled to plate units  16  on both sides. 
     Plate unit  16  according to the present exemplary embodiment has a two-fold rotationally symmetrical shape as viewed in a first direction in which bus bar plate  4  and battery stack  2  are disposed side by side (in vertical direction Z in the present exemplary embodiment). That is, each of plate units  16  has a rotationally symmetric shape about an axis that passes through an intermediate point of stacking direction X of batteries  8  and a direction orthogonal to stacking direction X and extends in the first direction. Therefore, first plate unit  16   a  and second plate unit  16   b  have the same shape, and when first plate unit  16   a  is rotated, second plate unit  16   b  is obtained. This makes it possible to prevent an increase in the number of components of bus bar plate  4  and, consequently, battery module  1 , and to simplify the assembly work. 
     This rotationally symmetric shape can be achieved by providing male part  24 , female part  26 , positioning projection  52 , positioning cutout  54 , position-regulating convex part  56 , and position-regulating concave part  58  on both surfaces of each plate unit  16  in stacking direction X of batteries  8 , providing each structure provided on one surface and each structure provided on the other surface at rotationally symmetric positions, providing first protrusion  44  provided on one surface and second protrusion  46  provided on the other surface at rotationally symmetric positions, and providing second concave part  50  provided on one surface and first concave part  48  provided on the other surface at rotationally symmetric positions. 
     The exemplary embodiments of the present invention have been described in detail above. The above-described exemplary embodiments are merely specific examples for implementing the present invention. The contents of the exemplary embodiments do not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of configuration elements can be made without departing from the spirit of the invention defined in the claims. Any new exemplary embodiment to which design change has been made has an effect of each of the combined exemplary embodiments and modified examples. In the above-described exemplary embodiments, with respect to the contents where such design changes can be made, the contents are emphasized with expressions such as “of the present exemplary embodiment” and “in the present exemplary embodiment”. However, design changes are allowed even with respect to the contents without such expressions. Any combination of configuration elements included in the exemplary embodiments is also effective as an aspect of the present invention. Hatching applied to the cross section in the drawing does not limit the material of the object to which the hatching has been applied. 
     First Modified Example 
     In the assembly process of battery module  1  described in the first exemplary embodiment, bus bar plate  4  and battery stack  2  are separately assembled, and then bus bar plate  4  is placed on battery stack  2 . However, the present disclosure is not particularly limited to this procedure.  FIGS. 7(A) and 7(B)  are views illustrating an assembly process of battery module  1  according to a first modified example. In the present modified example, as illustrated in  FIG. 7(A) , each plate unit  16  is fixed to the upper surface of each battery  8 . 
     As illustrated in  FIG. 7(B) , a plurality of batteries  8  to which plate unit  16  is fixed and the inter-cell separators are alternately stacked to assemble battery stack  2 . At this time, batteries  8  are pressed in stacking direction X, and adjacent plate units  16  are coupled to each other by coupling mechanism  22 . Thus, bus bar plate  4  is assembled simultaneously with battery stack  2 . Thereafter, bus bar  6  is placed on terminal opening  20  of each plate unit  16  and is electrically connected to output terminal  14  exposed from terminal opening  20 . A voltage detection line is also placed on bus bar plate  4  and electrically connected to bus bar  6 . It is thereby possible to obtain battery module  1 . 
     Second Modified Example 
     In the second exemplary embodiment, first protrusion  44  fits in first concave part  48  provided on the lower surface of second plate unit  16   b , and second protrusion  46  fits in second concave part  50  provided on the lower surface of first plate unit  16   a . However, the present disclosure is not particularly limited to this configuration.  FIG. 8(A)  is a perspective view of second plate unit  16   b  according to a second modified example as viewed from first plate unit  16   a .  FIG. 8(B)  is a perspective view of first plate unit  16   a  according to the second modified example as viewed from second plate unit  16   b.    
     Second plate unit  16   b  according to the present modified example includes body  18  and first hole  60  provided in the surface of body  18  facing first plate unit  16   a . First hole  60  has an opening shape corresponding to first protrusion  44  as viewed in stacking direction X. When first plate unit  16   a  and second plate unit  16   b  are coupled to each other, first protrusion  44  of first plate unit  16   a  is inserted into first hole  60 . In this state, the upper surface and the lower surface of first protrusion  44  are in contact with the top surface (inner upper surface) and the bottom surface (inner lower surface) of first hole  60 . Thus, by adopting a structure in which first protrusion  44  is inserted into first hole  60 , the creepage distance between output terminal  14  of each battery  8  and the outside of battery module  1  can be further increased. 
     Similarly, first plate unit  16   a  according to the present modified example includes body  18  and second hole  62  provided in the surface of body  18  facing second plate unit  16   b . Second hole  62  has an opening shape corresponding to second protrusion  46  as viewed in stacking direction X. When first plate unit  16   a  and second plate unit  16   b  are coupled to each other, second protrusion  46  of second plate unit  16   b  is inserted into second hole  62 . In this state, the upper surface and the lower surface of second protrusion  46  are in contact with the top surface and the bottom surface of second hole  62 . Thus, by adopting a structure in which second protrusion  46  is inserted into second hole  62 , the creepage distance between output terminal  14  of each battery  8  and the outside of battery module  1  can be further increased. 
     (Others) 
     The number of batteries  8  provided in battery module  1  is not particularly limited. The structure of each part of battery module  1  including the fastening structure of the end plate and the restraining member is not particularly limited. Batteries  8  may have a cylindrical shape or the like. 
     In the exemplary embodiments and the modified examples described above, each plate unit  16  and each battery  8  are associated on a one-to-one basis, but the present disclosure is not particularly limited to this configuration. For example, an assembly of several batteries  8  may be associated with one plate unit  16 . That is, respective plate unit  16  may be disposed for the plurality of batteries  8  on a one-to-one basis, or the plurality of batteries  8  may be divided into a plurality of assemblies each made up of some batteries  8 , and respective plate units  16  may be disposed for the respective assemblies. One plate unit  16  may be provided for one battery  8 , and another plate unit  16  may be provided for the assembly. 
     By disposing plate unit  16  for the assembly of batteries  8 , the number of plate units  16  constituting bus bar plate  4  can be reduced. For example, when first plate unit  16   a  of the first exemplary embodiment is provided for two batteries  8 , body  18  of first plate unit  16   a  has twice the dimension in stacking direction X. Further, two terminal openings  20  are disposed side by side in stacking direction X at each end part of body  18  in horizontal direction Y. 
     When first plate unit  16   a  is disposed for the first assembly of batteries  8  and second plate unit  16   b  is disposed for the second assembly of batteries  8 , body  18  of first plate unit  16   a  overlaps the first assembly, and body  18  of second plate unit  16   b  overlaps the second assembly. First protrusion  44  of first plate unit  16   a  is inserted between second plate unit  16   b  and the second assembly, and second protrusion  46  of second plate unit  16   b  is inserted between first plate unit  16   a  and the first assembly. 
     The exemplary embodiment may be specified by an item described below. 
     [Item 1] 
     Battery module  1  including: 
     battery stack  2  in which a plurality of batteries  8  are stacked; 
     bus bar  6  that electrically connects output terminals  14  of the plurality of batteries  8  to each other; and 
     bus bar plate  4  that supports bus bars  6 . 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               2 : battery stack 
               4 : bus bar plate 
               6 : bus bar 
               8 : battery 
               14 : output terminal 
               16 : plate unit 
               18 : body 
               20 : terminal opening 
               22 : coupling mechanism 
               24 : male part 
               26 : female part 
               38 : groove 
               44 : first protrusion 
               46 : second protrusion 
               56 : position-regulating convex part 
               58 : position-regulating concave part 
               60 ,  62 : hole