Patent Publication Number: US-2021167443-A1

Title: Battery module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2019/029816, filed on Jul. 30, 2019, which in turn claims the benefit of Japanese Patent Application No. 2018-144115, filed on Jul. 31, 2018, and Japanese Patent Application No. 2018-144116, filed on Jul. 31, 2018, the entire disclosures of which applications are incorporated by reference herein. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present disclosure relates to a battery module. 
     Description of the Related Art 
     For example, as a power source that requires a high output voltage, such as for a vehicle, a battery module having a battery assembly in which a plurality of batteries are connected in series has been known. Regarding such a battery module, Patent Literature 1 discloses a battery module including a cooling plate having a refrigerant flow path and a plurality of batteries conductively coupled to the surface of the cooling plate. 
     In order to suppress the variation in the charge/discharge amount of each battery and maintain the performance of the battery module, it is desirable to uniformly cool each battery in a battery assembly. On the other hand, in the cooling plate, a temperature boundary layer may develop along the flow of the refrigerant. The temperature boundary layer is a resistance element of heat exchange. Therefore, when the temperature boundary layer develops, the refrigerant on the surface side of the refrigerant flow is exclusively used for heat exchange. For this reason, the cooling efficiency of the batteries decreases toward the downstream side of the refrigerant flow, and it is difficult to uniformly cool the plurality of batteries. 
     On the other hand, in Patent Literature 1, the development of the temperature boundary layer is suppressed by providing a plurality of portions having a large flow path cross-sectional area in the refrigerant flow path and repeatedly increasing or decreasing the flow rate of the refrigerant. As a result, the cooling efficiency in a direction in which the refrigerant flows is made uniform, and the plurality of batteries are cooled uniformly. 
     Patent Literature 1: JP 2013-16351 A 
     In the above-mentioned battery module, since the refrigerant flow path is provided with the portions having a large flow path cross-sectional area, the cooling plate tends to be increased in size. For example, when the large cross-sectional area portions have a shape that extends in the direction in which the adjacent flow paths are aligned, the distance between the adjacent flow paths becomes large, and the area of the cooling plate becomes large. Further, when the large cross-sectional area portions have a shape that extends in the stacking direction of the cooling plate and the batteries, the thickness of the cooling plate becomes large. When the cooling plate is increased in size, the battery module is increased in size. 
     SUMMARY OF THE INVENTION 
     The present disclosure has been made in view of such a situation, and an object of the present invention is to provide a technique for making cooling of a battery assembly uniform while avoiding an increase in size of a battery module. 
     One aspect of the present disclosure is a battery module. The battery module includes an assembly of a plurality of batteries and a cooling member arranged so as to be heat exchangeable with the assembly. The cooling member is provided with a mixing portion in which refrigerant flows and the flowing refrigerant is mixed. 
     Any combination of the above components and these obtained by converting the expressions of the present disclosure between methods, devices, systems, etc. are also effective as aspects of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which: 
         FIG. 1  is a perspective view of a battery module according to a first embodiment. 
         FIG. 2  is a perspective view of an assembly. 
         FIG. 3  is a perspective view of a battery. 
         FIG. 4  is an end view schematically illustrating the structure of a cooling member. 
         FIG. 5  is an end view schematically illustrating the structure of the cooling member. 
         FIG. 6  is a plan view schematically illustrating the structure of the battery module. 
         FIG. 7  is a perspective view of a battery module according to a second embodiment. 
         FIG. 8  is a perspective view of an assembly. 
         FIG. 9  is a perspective view of a battery. 
         FIG. 10  is an end view schematically illustrating the structure of a cooling member. 
         FIG. 11  is an end view schematically illustrating the structure of the cooling member. 
         FIG. 12A  is a cross-sectional view schematically illustrating the structure of the cooling member.  FIG. 12B  is a schematic view for explaining the operation of fine flow paths. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present disclosure will be described based on preferred embodiments with reference to the drawings. The embodiments are not intended to limit the present disclosure, but are exemplary, and all features and combinations thereof described in the embodiments are not necessarily essential to the present disclosure. The same or equivalent components, members, and processes illustrated in each drawing are denoted by the same reference numerals, and duplicated description will be appropriately omitted. 
     In addition, the scale and shape of each part illustrated in each figure are set for convenience in order to facilitate explanation, and are not limitedly interpreted unless otherwise specified. In addition, when terms such as “first” and “second” are used in the present specification or claims, these terms do not represent any order or importance unless otherwise specified, and are used to distinguish a certain configuration from other configurations. Further, in each drawing, some of the members that are not important for explaining the embodiment are omitted. 
     First Embodiment 
       FIG. 1  is a perspective view of a battery module according to a first embodiment.  FIG. 2  is a perspective view of an assembly.  FIG. 3  is a perspective view of a battery. In  FIG. 1 , only a part of a cooling member is illustrated. Further, in  FIG. 2 , illustration of a cover member is omitted. The battery module  1  includes an assembly  2  and a cooling member  4 . 
     The assembly  2  has a structure in which a plurality of batteries  6  are assembled. The assembly  2  of the present embodiment takes the form of a battery group in which a plurality of flat batteries  6  are stacked. The assembly  2  includes a plurality of batteries  6 , a plurality of separators  8 , a pair of end plates  10 , and a pair of restraining members  12 . Although only one battery group is illustrated in  FIG. 1 , the assembly  2  of the present embodiment includes a plurality of battery groups  3  (see  FIG. 6 ). 
     Each battery  6  is a rechargeable secondary battery such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery. The battery  6  is a so-called square battery, and has a flat rectangular parallelepiped outer can  14 . A substantially rectangular opening (not shown) is provided on one surface of the outer can  14 , and an electrode body, an electrolytic solution, or the like is accommodated in the outer can  14  through this opening. A sealing plate  16  for sealing the outer can  14  is provided at the opening of the outer can  14 . The sealing plate  16  is, for example, a rectangular plate. 
     The sealing plate  16  is provided with a positive electrode output terminal  18  near one end in the longitudinal direction and a negative electrode output terminal  18  near the other end. The pair of output terminals  18  are electrically connected to a positive electrode plate and a negative electrode plate constituting the electrode body, respectively. Hereinafter, as appropriate, the positive electrode output terminal  18  will be referred to as a positive electrode terminal  18   a , and the negative electrode output terminal  18  will be referred to as a negative electrode terminal  18   b . Further, when it is not necessary to distinguish the polarity of the output terminal  18 , the positive electrode terminal  18   a  and the negative electrode terminal  18   b  are collectively referred to as output terminals  18 . The outer can  14  and the sealing plate  16  are conductors, for example, made of metal. For example, the outer can  14  and the sealing plate  16  are made of aluminum, iron, stainless steel, or the like. The sealing plate  16  and the opening of the outer can  14  are joined by, for example, a laser. Each of the pair of output terminals  18  is inserted into a through hole (not shown) formed in the sealing plate  16 . An insulating sealing member (not shown) is interposed between each of the pair of output terminals  18  and each through hole. 
     In the description of the present embodiment, for convenience, the surface on the side where the sealing plate  16  is provided is the upper surface of the battery  6 , and the surface on the opposite side (the bottom surface of the outer can  14 ) is the bottom surface of the battery  6 . Further, the battery  6  has four side surfaces connecting the upper surface and the bottom surface. Two of the four side surfaces are a pair of long side surfaces connected to the long sides of the top and bottom. The long side surfaces are the surfaces having the largest area among the six surfaces of the battery  6 . The remaining two side surfaces, excluding the two long side surfaces, are a pair of short side surfaces connected to the short sides of the top and bottom. Further, in the assembly  2 , the surface on the upper surface side of the battery  6  is the upper surface of the assembly  2 , the surface on the bottom surface side of the battery  6  is the bottom surface of the assembly  2 , and the surfaces on the short side surface sides of the battery  6  are the side surfaces of the assembly  2 . Further, the upper surface side of the assembly  2  is an upper side in the vertical direction, and the bottom surface side of the assembly  2  is a lower side in the vertical direction. These directions and positions are defined for convenience. Therefore, for example, it does not mean that the portion defined as the upper surface in the present disclosure is always located above the portion defined as the bottom surface. 
     A safety valve  20  is provided between the pair of output terminals  18  on the sealing plate  16 . The safety valve  20  is structured to open when the internal pressure of the outer can  14  rises above a predetermined value to release the gas inside. The safety valve  20  of each battery  6  is connected to a gas duct (not shown), and the gas inside the battery is discharged from the safety valve  20  to the gas duct. The safety valve  20  may be formed by, for example, a thin-walled portion provided in a part of the sealing plate  16  and thinner than the other portion, and a linear groove formed on the surface of the thin-walled portion. In this configuration, when the internal pressure of the outer can  14  rises, the thin-walled portion is torn from the groove to open the valve. 
     Further, the plurality of batteries  6  are arranged side by side at predetermined intervals so that the long side surfaces of the adjacent batteries  6  face each other. In the present embodiment, the direction in which the plurality of batteries  6  are aligned is the direction X. Further, the output terminals  18  of each battery  6  are arranged so as to face the same direction. In the present embodiment, the output terminals  18  of each battery  6  are arranged so as to face the upper side in the vertical direction for convenience. The output terminals  18  of each battery  6  may be arranged so as to face different directions. The two adjacent batteries  6  are stacked so that the positive electrode terminal  18   a  of one battery  6  and the negative electrode terminal  18   b  of the other battery  6  are adjacent to each other. The positive electrode terminal  18   a  and the negative electrode terminal  18   b  are electrically connected via a bus bar (not shown). The output terminals  18  having the same polarity in the plurality of adjacent batteries  6  may be connected in parallel by a bus bar to form a battery block, and the battery blocks may be connected in series. 
     The separator  8  is also called an insulating spacer, and is made of, for example, a resin having an insulating property. The separator  8  is arranged between the two adjacent batteries  6  to electrically insulate the two batteries  6 . Further, the separator  8  is further arranged between the battery  6  and the end plate  10  to insulate the battery  6  and the end plate  10 . Examples of the resin constituting the separator  8  include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and NORYL (registered trademark) resin (modified PPE). 
     Further, a part of the separator  8  extends in the direction X and covers the upper surface of the battery  6 . As a result, it is possible to secure a creepage distance between the adjacent batteries  6  or between the battery  6  and the end plate  10 . Further, the separator  8  has openings at positions corresponding to the output terminals  18  and the safety valve  20  so that each of them is exposed. 
     The plurality of batteries  6  and the plurality of separators  8  arranged side by side are sandwiched between the pair of end plates  10 . The pair of end plates  10  are arranged so as to be adjacent to the batteries  6  located at both ends in the direction X via the separators  8 . The end plate  10  is made of, for example, a metal plate. Screw holes (not shown) into which screws  22  are screwed are provided on the surface of the end plate  10  facing the long side surface of the battery  6 . 
     The pair of restraining members  12  are also called bind bars, and are elongated members whose longitudinal direction is the direction X. The pair of restraining members  12  are arranged so as to face each other in the direction Y orthogonal to the direction X and parallel to the longitudinal direction of the sealing plate. The plurality of batteries  6 , the plurality of separators  8 , and the pair of end plates  10  are interposed between the pair of restraining members  12 . Each restraining member  12  has a rectangular flat surface portion  12   a  extending parallel to the short side surface of the battery  6 , and four eaves portions  12   b  protruding from end sides of the flat surface portion  12   a  toward the battery  6 . The two eaves portions  12   b  facing each other in the direction X are provided with through holes (not shown) through which the screws  22  are inserted. The flat surface portion  12   a  is provided with an opening portion  12   c  that exposes the short side surfaces of the batteries  6 . 
     The plurality of batteries  6  and the plurality of separators  8  are sandwiched in the direction Y by the pair of restraining members  12  under a state where these are alternately arranged and sandwiched in the direction X by the pair of end plates  10 . Each restraining member  12  is aligned so that the through holes of the restraining member  12  overlaps with the screw holes of the end plate  10 . Then, the screws  22  are inserted into the through holes and screwed into the screw holes. By engaging the pair of restraining members  12  with the pair of end plates  10  in this way, the plurality of batteries  6  are restrained. 
     The plurality of batteries  6  are tightened in the direction X by the restraining members  12 , so that the plurality of batteries  6  are positioned in the direction X. Further, the bottom surfaces of the plurality of batteries  6  abut on the lower eaves portions  12   b  of the restraining members  12  via the separators  8 , and the upper surfaces of the plurality of batteries  6  abut on the upper eaves portions  12   b  of the restraining members  12  via the separator  8 , so that the plurality of batteries  6  are positioned in the up-down direction. As an example, after these positionings are completed, the bus bar is attached to the output terminals  18  of each battery  6 , and the output terminals  18  are electrically connected. 
     The upper surface of the assembly  2  is covered with a cover member  24 . The cover member  24  prevents the contact of condensed water, dust, etc. with the output terminals  18 , the bus bar, the safety valves  20 , etc. of the batteries  6 . The cover member  24  is made of, for example, a resin having an insulating property. The cover member  24  is fixed to the upper surface of the assembly  2  by a well-known fixing structure (not shown) including screws and a well-known locking mechanism. 
     The cooling member  4  is arranged so as to be heat exchangeable with the assembly  2 , and cools each battery  6 . The cooling member  4  of the present embodiment is a plate-shaped cooling plate, and the assembly  2  is placed on the long side surface (or main surface) thereof. The assembly  2  is placed on the cooling member  4  so that the bottom surface faces the cooling member  4  side. At this time, the bottom surface of the battery  6  is thermally connected to the cooling member  4  via the eaves portions  12   b  of the restraining members  12 . In order to further improve the heat exchange efficiency between the battery  6  and the cooling member  4 , a resin sheet or the like having good thermal conductivity may be interposed between the portion of the bottom surface of the battery  6  that is exposed without being covered by the eaves portions  12   b  and the cooling member  4 . Alternatively, the entire bottom surface of the battery  6  and the cooling member  4  may be brought into abutment on each other via the above-mentioned resin sheet without providing the eaves portions  12   b  located on the bottom surface side of the battery  6 . In this case, the cooling member  4  takes on the function of the eaves portions  12   b  located on the bottom surface side of the battery  6 . 
     The cooling member  4  includes a plate-shaped portion  26  and a hollow portion  27  arranged inside the plate-shaped portion  26  through which the refrigerant flows. The hollow portion  27  includes a plurality of flow paths  28  arranged so as to extend in the direction X. Further, the plurality of flow paths  28  are arranged at predetermined intervals in the direction Y. A refrigerant supply path (not shown) is connected to one end of the hollow portion  27  in the direction X, and a refrigerant discharge path (not shown) is connected to the other end. Therefore, one end side of the hollow portion  27  is upstream of the refrigerant flow, and the other end side is downstream of the refrigerant flow. 
     The cooling member  4  of the present embodiment is a flat plate-shaped pipe. The plate-shaped portion  26  includes a first plate portion  26   a  facing the assembly  2  and a second plate portion  26   b  the side opposite to the first plate portion  26   a . The first plate portion  26   a  and the second plate portion  26   b  face each other with a predetermined gap. The hollow portion  27  is arranged in the gap between the first plate portion  26   a  and the second plate portion  26   b . Such a cooling member  4  can be formed by combining conventionally known methods such as extrusion molding. 
     The cooling member  4  may be formed by joining the first plate portion  26   a  and the second plate portion  26   b , which are separate bodies from each other. For example, by joining a plate material having a groove having the shape of the hollow portion  27  and a plate material without a groove by brazing or the like, the cooling member  4  including the hollow portion  27  between the first plate portion  26   a  and the second plate portion  26   b  can be obtained. In this case, the cooling member  4  can be easily manufactured as compared with the case where the hollow portion  27  is formed by hollowing out a solid plate material or the case where the hollow portion  27  is formed by extrusion molding. 
     The plate-shaped portion  26  is made of a material having high thermal conductivity such as aluminum. The assembly  2  is placed on the plate-shaped portion  26 , for example, via the above-mentioned resin sheet having an insulating property and thermal conductivity. Each battery  6  exchanges heat with refrigerant such as water or ethylene glycol flowing through the flow paths  28  via the resin sheet and the plate-shaped portion  26 . As a result, each battery  6  is cooled. The plate-shaped portion  26  has an insertion portion  38  into which a fastening member  36  such as a screw is inserted at a predetermined position (see  FIG. 5 ). The assembly  2  and the cooling member  4  are fixed to each other by inserting the fastening member  36  through the insertion portion  38 . The insertion portion  38  is arranged in a floating island shape in a merging portion  30  described later. The fastening member  36  may be used not only for fixing the assembly  2  and the cooling member  4 , but also for fixing the cooling member  4  to a module case. 
     Subsequently, the structure of the cooling member  4  will be described in more detail.  FIG. 4  is an end view schematically illustrating the structure of the cooling member  4 . In  FIG. 4 , the end face of the cooling member  4  cut along the plane extending in the direction X and the direction Y, that is, the XY plane is illustrated.  FIG. 5  is an end view schematically illustrating the structure of the cooling member  4 . In  FIG. 5 , the end face of the cooling member  4  cut along the plane extending in the direction Y and the direction Z (the direction in which the assembly  2  and the cooling member  4  are aligned), that is, the YZ plane is illustrated. In  FIGS. 4 and 5 , only a part of the cooling member  4  is illustrated. Further, in  FIG. 5 , the illustration of the assembly  2  is simplified. 
     The cooling member  4  is provided with a mixing portion in which the refrigerant flows and the flowing refrigerant is mixed. More specifically, the hollow portion  27  of the cooling member  4  includes branch portions  29  each including the plurality of flow paths  28 , and the merging portions  30  which are each a space where the plurality of flow paths  28  are merged. At each branch portion  29 , the plurality of flow paths  28  extend in direction X and are arranged in the direction Y at predetermined intervals. The hollow portion  27  of the present embodiment includes the plurality of branch portions  29  arranged from the upstream side to the downstream side of the refrigerant flow, and the merging portions  30  are each interposed between the two adjacent branch portions  29 . That is, the plurality of merging portions  30  are arranged at predetermined intervals in the extending direction of the flow paths  28 . Each merging portion  30  extends in a direction intersecting the extending direction of the flow paths  28  (the direction Y in the present embodiment) and intersects each flow path  28 . The refrigerant flowing from each flow path  28  is mixed at the merging portion  30 . Therefore, the merging portion  30  functions as the mixing portion. The cooling member  4  of the present embodiment can also be regarded as including the plurality of flow paths  28  extending from one end side to the other end side in the direction X, and the merging portions  30  each connecting the adjacent flow paths  28  in the middle of each flow path  28 . 
     In each flow path  28  on the upstream side of the merging portion  30 , there are refrigerant located on the wall surface side of the flow path  28  and having been subjected to heat exchange with the assembly  2  and refrigerant located on the center side of the flow path  28  and not having been subjected to heat exchange with the assembly  2 . When these refrigerants reach the merging portion  30 , they are mixed together with refrigerants that have flowed in from the other flow paths  28 . As a result, the temperature of the entire refrigerant becomes uniform. The refrigerant mixed in the merging portion  30  is diverted to each flow path  28  located on the downstream side of the merging portion  30 . 
     By mixing the refrigerants at the merging portion  30  in this way, development of a temperature boundary layer in the refrigerant is suppressed. By suppressing the development of the temperature boundary layer, the temperature deviation of the cooling member  4 , particularly the temperature deviation in the direction in which the refrigerant flows can be reduced, and therefore the temperature deviation in each battery  6  can be reduced. 
     The contact area between the refrigerant and the plate-shaped portion  26  is smaller at the merging portion  30  than at the region where the plurality of flow paths  28  extend. Therefore, the cooling member  4  has a reduced heat exchange efficiency with the assembly  2  at the merging portion  30 . Therefore, it is preferable that the merging portions  30  are arranged in a small number on the upstream side of the flow paths  28  and in a large number on the downstream side. As a result, on the upstream side where the refrigerant temperature in the cross-sectional direction of the flow path (the direction in which the cross section parallel to the YZ plane extends) is low as a whole, and heat exchange between the assembly  2  and the refrigerant is smoothly performed, it is possible to suppress a decrease in cooling efficiency due to a decrease in contact area between the refrigerant and the plate-shaped portion  26 . On the other hand, on the downstream side where the refrigerant temperature in the cross-sectional direction of the flow path tends to increase as a whole and the heat exchange tends to be hindered, the number of times the refrigerant is mixed at the merging portion  30  is increased so that the relatively high temperature refrigerant located on the wall surface side of the flow path  28  and the relatively low temperature refrigerant located on the center side of the flow path  28  are positively mixed. As a result, the refrigerant temperature is averaged between the wall surface side and the center side of the flow path  28 , and overheating of the refrigerant on the wall surface side of the flow path  28  is suppressed. As a result, heat exchange between the assembly  2  and the refrigerant can be promoted. 
     The merging portion  30  includes at least one flow blocking portion  32  that disturbs the flow of the refrigerant. The flow blocking portion  32  includes a side wall extending from one plate portion of the first plate portion  26   a  and the second plate portion  26   b  toward the other plate portion within the merging portion  30 . The side wall forming the flow blocking portion  32  has a collision surface on which the refrigerant flowing through the merging portion  30  hits. The collision surface extends in a direction intersecting the direction from an inlet  30   a  to an outlet  30   b  of the refrigerant (the direction X in the present embodiment) in the merging portion  30 . The collision surface preferably has a curved surface shape. Further, the flow blocking portion  32  may be cylindrical or columnar, and in this case, the side wall is formed by the peripheral surface of the flow blocking portion  32 . The refrigerant that has flowed from each flow path  28  into the merging portion  30  hits the flow blocking portion  32  to promote mixing. As a result, the development of the temperature boundary layer can be further suppressed. 
     In the present embodiment, some of the flow blocking portions  32  are each formed by a columnar boss  34  that protrudes in the direction Z at the merging portion  30  and extends from the first plate portion  26   a  to the second plate portion  26   b . Therefore, the peripheral surface of the boss  34  corresponds to the side wall of the flow blocking portion  32 . Further, the region of the peripheral surface of the boss  34  facing the inlet  30   a  side of the merging portion  30  corresponds to a curved collision surface extending in the direction intersecting the direction X. 
     In addition, some of the other flow blocking portions  32  are each formed by a cylindrical insertion portion  38  into which the fastening member  36  is inserted. The insertion portion  38  is a recess provided in the second plate portion  26   b  and protruding toward the first plate portion  26   a . The insertion portion  38  may be provided in the first plate portion  26   a  and protrude toward the second plate portion  26   b . That is, the flow blocking portion  32  can be formed by a recess provided in one plate portion and protruding toward the other plate portion. In this case, the peripheral surface of the insertion portion  38  corresponds to the side wall of the flow blocking portion  32 . Further, the region of the peripheral surface of the insertion portion  38  facing the inlet  30   a  of the merging portion  30  corresponds to a curved collision surface extending in the direction intersecting the direction X. 
     Since the flow blocking portion  32  has a curved collision surface, the refrigerant that hits the collision surface can be smoothly flowed to the downstream side of the flow blocking portion  32 . Further, by forming the wall surface of the flow blocking portion  32  with the peripheral surface of the boss  34  or the insertion portion  38 , it is possible to form a refrigerant flow flowing to the back side of the flow blocking portion  32 , and the refrigerant can be more agitated. 
     The insertion portion  38  has a bottomed tubular shape, and has a bottom portion  38   a  connected to the other plate portion, that is, the first plate portion  26   a  in the present embodiment. The bottom portion  38   a  is joined to the other plate portion by, for example, brazing. The cooling member  4  has a through hole  40  that penetrates the bottom portion  38   a  and the other plate portion. The fastening member  36  is inserted through the through hole  40 . With this configuration, the flow blocking portion  32  can have a function of fixing the cooling member  4  to the assembly  2  or a function of fixing the cooling member  4  to the module case. When the assembly  2  is fixed to the cooling member  4  by fastening the fastening member  36  to the insertion portion  38 , the fastening member  36  is connected to, for example, the end plate  10  or the restraining member  12 . 
     In the present embodiment, the plurality of flow blocking portions  32  are arranged at predetermined intervals along the direction intersecting the direction from the inlet  30   a  to the outlet  30   b  of the refrigerant in the merging portion  30 , in other words, along the extending direction of the merging portion  30 . As a result, the refrigerant flowing from each flow path  28  into the merging portion  30  can be mixed more evenly. 
     The flow blocking portion  32  blocks the flow of the refrigerant. Therefore, it is preferable that the flow blocking portions  32  are provided in a small number in the merging portion  30  arranged on the upstream side of the refrigerant flow and in a large number in the merging portion  30  arranged on the downstream side. As a result, it is possible to prevent the flow of the refrigerant from being blocked on the upstream side where the refrigerant temperature in the cross-sectional direction of the flow path is low as a whole and the heat exchange between the assembly  2  and the refrigerant smoothly occurs. On the other hand, on the downstream side where the refrigerant temperature in the cross-sectional direction of the flow path tends to increase as a whole and the heat exchange tends to be hindered, the refrigerant is mixed more, and the refrigerant temperature is averaged through mixing of the relatively high temperature refrigerant and the relatively low temperature refrigerant, so that the heat exchange between the assembly  2  and the refrigerant can be promoted. 
     The flow blocking portion  32  may be arranged on the upstream side in the merging portion  30 , may be arranged on the middle flow side, or may be arranged on the downstream side. Further, in the plurality of merging portions  30  arranged in the upstream-downstream direction of the flow paths  28 , the flow blocking portions  32  may be arranged so as to shift in the direction intersecting the upstream-downstream direction. For example, the flow blocking portions  32  are arranged in a staggered pattern on the XY plane. As a result, the refrigerant can be mixed more uniformly in the entire cooling member  4 . 
     Further, at least some of the merging portions  30  are arranged as follows.  FIG. 6  is a plan view schematically illustrating the structure of the battery module  1 . In  FIG. 6 , only a part of the battery module  1  is illustrated, and the illustration of the assembly  2  is simplified. 
     That is, at least a part of the merging portion  30  is provided at a position that does not overlap with the battery  6  when viewed from the direction in which the assembly  2  and the cooling member  4  are aligned (the direction Z in the present embodiment). As the position that does not overlap with the battery  6 , in other words, the position that avoids the battery  6 , there are given a position that overlaps with a gap A between the adjacent battery groups  3 , a position that overlaps with the end plate  10 , and a position that overlaps with the restraining member  12 , when viewed from the direction in which the assembly  2  and the cooling member  4  are aligned. In the present embodiment, the merging portions  30  are mainly provided at the positions that overlap with the gap A between the adjacent battery groups  3  and the position that overlaps with the end plate  10 . 
     As described above, the cooling member  4  has a reduced heat exchange efficiency with the assembly  2  at the merging portion  30 . Therefore, by separating the merging portions  30  from the batteries  6  which are the main heat generating sources, it is possible to suppress a decrease in the cooling efficiency of the assembly  2 . 
     As described above, the battery module  1  according to the present embodiment includes the assembly  2  of the plurality of batteries  6  and the cooling member  4  arranged so as to be heat exchangeable with the assembly  2 . The cooling member  4  has the hollow portion  27  through which the refrigerant flows. The hollow portion  27  includes the branch portions  29  each including the plurality of flow paths  28 , and the merging portions  30  which are each a space where the plurality of flow paths are merged. 
     As described above, in the present embodiment, the merging portions  30  are provided in the middle of the flow paths  28 , and the development of the temperature boundary layer is suppressed by mixing the refrigerant in the merging portions  30 . Therefore, unlike the case where large cross-sectional area portions are provided in the flow path as in the conventional battery module, it is possible to avoid an increase in the size of the flow path. Therefore, according to the present embodiment, it is possible to make the cooling of the assembly  2  uniform while avoiding the increase in size of the battery module  1 . Further, the uniform cooling of the assembly  2  can suppress the deterioration of the performance of the battery module  1 . Further, as compared with the conventional case where the flow velocity of the refrigerant is increased or decreased to suppress the development of the temperature boundary layer, the development of the temperature boundary layer can be efficiently suppressed with a simpler structure. 
     Further, at least a part of the merging portion  30  is provided at a position that does not overlap with the battery  6  when viewed from the direction in which the assembly  2  and the cooling member  4  are aligned. Further, the merging portion  30  is provided at a position that overlaps with the gap between the adjacent battery groups  3 , the end plate  10 , or the restraining members  12  when viewed from the direction in which the assembly  2  and the cooling member  4  are aligned. As a result, the influence of the decrease in heat exchange efficiency in the merging portion  30  on the battery  6  can be reduced, so that the cooling efficiency of the assembly  2  can be further improved. 
     Further, the merging portion  30  includes the flow blocking portion  32  that disturbs the flow of the refrigerant. As a result, the development of the temperature boundary layer can be further suppressed, so that the assembly  2  can be cooled more uniformly. Further, the flow blocking portions  32  include, for example, the insertion portion  38  for the fastening member  36  for fixing the assembly  2  and the cooling member  4 . In this way, by allowing the fastening structure of the assembly  2  and the cooling member  4  or the fastening structure of the cooling member  4  and the module case to function as the flow blocking portion  32 , the structure can be simplified and downsized as compared with a cooling member provided with a fastening mechanism with another member outside the hollow portion  27 . Therefore, the structure of the battery module  1  can be simplified. 
     Further, the cooling member  4  of the present embodiment is a flat plate-shaped pipe, and includes the first plate portion  26   a  facing the assembly  2  and the second plate portion  26   b  on the side opposite to the first plate portion  26   a . The flow blocking portion  32  includes the side wall extending from one plate portion toward the other plate portion within the merging portion  30 . The side wall has the collision surface on which the refrigerant flowing through the merging portion  30  hits. The collision surface extends in the direction intersecting the direction from the inlet  30   a  to the outlet  30   b  of the refrigerant in the merging portion  30 . Further, the collision surface has a curved surface shape. Further, the flow blocking portion  32  is cylindrical or columnar, and the side wall is formed by the peripheral surface of the flow blocking portion  32 . 
     Further, the plurality of flow blocking portions  32  are arranged at predetermined intervals along the direction intersecting the direction from the inlet  30   a  to the outlet  30   b  of the refrigerant in the merging portion  30 . Further, some of the flow blocking portions  32  are each a recess provided in one plate portion of the first plate portion and the second plate portion and protruding toward the other plate portion. According to this configuration, it is considered that the formation of the flow blocking portion becomes easier as compared with a flow blocking portion formed by a pillar or a protrusion filled with a metal material inside. In addition, the weight of the flow blocking portion can be reduced, and therefore the weight of the battery module  1  can be reduced. 
     The recess has a bottomed tubular shape, and the bottom portion  38   a  is connected to the other plate portion. The cooling member  4  has the through hole  40  that penetrates the bottom portion  38   a  and the other plate portion. Further, the first plate portion  26   a  and the second plate portion  26   b  face each other with a predetermined gap, and the hollow portion  27  is arranged in the gap between the two plate portions. Further, the hollow portion  27  includes the plurality of branch portions  29  arranged from the upstream side to the downstream side of the refrigerant flow, and the merging portions  30  are each interposed between two adjacent branch portions  29 . 
     The embodiment of the present disclosure has been described in detail above. The above-described embodiment merely shows a specific example in carrying out the present disclosure. The content of the embodiment does not limit the technical scope of the present disclosure, and many designs such as modification, addition, and deletion of components can be made without departing from the ideas of the present disclosure defined in the claims. A new embodiment with the design change has the effects of the combined embodiment and the modification. In the above-described embodiment, the contents that can be changed in design are emphasized by adding notations such as “of the present embodiment” or “in the present embodiment”, but design changes are allowed even in contents without such notations. Any combination of the above components is also effective as an aspect of the present disclosure. The hatching attached to the cross section of the drawing does not limit the material to which the hatching is attached. 
     In the first embodiment, the battery  6  is a square battery, but the shape of the battery  6  is not particularly limited and may be cylindrical or the like. Further, the numbers of the batteries  6  and the battery groups  3  included in the assembly  2  are not particularly limited. The flow paths  28  extend along the direction X, but the direction is not particularly limited. Further, the assembly  2  and the cooling member  4  may be held in direct abutment on each other. The structure of each part of the assembly  2  including the shape of the separator  8  and the fastening structure between the end plate  10  and the restraining member  12  is not particularly limited. Further, all of the plurality of flow paths  28  may not be merged at the merging portion  30 . If at least two flow paths  28  are connected at the merging portion  30 , the development of the temperature boundary layer can be suppressed in these two flow paths  28 . 
     Second Embodiment 
       FIG. 7  is a perspective view of a battery module according to a second embodiment.  FIG. 8  is a perspective view of an assembly.  FIG. 9  is a perspective view of a battery. In  FIG. 7 , only a part of a cooling member is illustrated. Further, in  FIG. 8 , illustration of a cover member is omitted. The battery module  1  includes an assembly  2  and a cooling member  4 . 
     The assembly  2  has a structure in which a plurality of batteries  6  are assembled. The assembly  2  of the present embodiment takes the form of a battery group in which a plurality of flat batteries  6  are stacked. The assembly  2  includes a plurality of batteries  6 , a plurality of separators  8 , a pair of end plates  10 , and a pair of restraining members  12 . 
     Each battery  6  is a rechargeable secondary battery such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery. The battery  6  is a so-called square battery, and has a flat rectangular parallelepiped outer can  14 . A substantially rectangular opening (not shown) is provided on one surface of the outer can  14 , and an electrode body, an electrolytic solution, or the like is accommodated in the outer can  14  through this opening. A sealing plate  16  for sealing the outer can  14  is provided at the opening of the outer can  14 . The sealing plate  16  is, for example, a rectangular plate. 
     The sealing plate  16  is provided with a positive electrode output terminal  18  near one end in the longitudinal direction and a negative electrode output terminal  18  near the other end. The pair of output terminals  18  are electrically connected to a positive electrode plate and a negative electrode plate constituting the electrode body, respectively. Hereinafter, as appropriate, the positive electrode output terminal  18  will be referred to as a positive electrode terminal  18   a , and the negative electrode output terminal  18  will be referred to as a negative electrode terminal  18   b . Further, when it is not necessary to distinguish the polarity of the output terminal  18 , the positive electrode terminal  18   a  and the negative electrode terminal  18   b  are collectively referred to as output terminals  18 . The outer can  14  and the sealing plate  16  are conductors, for example, made of metal. For example, the outer can  14  and the sealing plate  16  are made of aluminum, iron, stainless steel, or the like. The sealing plate  16  and the opening of the outer can  14  are joined by, for example, a laser. Each of the pair of output terminals  18  is inserted into a through hole (not shown) formed in the sealing plate  16 . An insulating sealing member (not shown) is interposed between each of the pair of output terminals  18  and each through hole. 
     In the description of the present embodiment, for convenience, the surface on the side where the sealing plate  16  is provided is the upper surface of the battery  6 , and the surface on the opposite side (the bottom surface of the outer can  14 ) is the bottom surface of the battery  6 . Further, the battery  6  has four side surfaces connecting the upper surface and the bottom surface. Two of the four side surfaces are a pair of long side surfaces connected to the long sides of the top and bottom. The long side surfaces are the surfaces having the largest area among the six surfaces of the battery  6 . The remaining two side surfaces, excluding the two long side surfaces, are a pair of short side surfaces connected to the short sides of the top and bottom. Further, in the assembly  2 , the surface on the upper surface side of the battery  6  is the upper surface of the assembly  2 , the surface on the bottom surface side of the battery  6  is the bottom surface of the assembly  2 , and the surfaces on the short side surface sides of the battery  6  are the side surfaces of the assembly  2 . Further, the upper surface side of the assembly  2  is an upper side in the vertical direction, and the bottom surface side of the assembly  2  is a lower side in the vertical direction. These directions and positions are defined for convenience. Therefore, for example, it does not mean that the portion defined as the upper surface in the present disclosure is always located above the portion defined as the bottom surface. 
     A safety valve  20  is provided between the pair of output terminals  18  on the sealing plate  16 . The safety valve  20  is structured to open when the internal pressure of the outer can  14  rises above a predetermined value to release the gas inside. The safety valve  20  of each battery  6  is connected to a gas duct (not shown), and the gas inside the battery is discharged from the safety valve  20  to the gas duct. The safety valve  20  may be formed by, for example, a thin-walled portion provided in a part of the sealing plate  16  and thinner than the other portion, and a linear groove formed on the surface of the thin-walled portion. In this configuration, when the internal pressure of the outer can  14  rises, the thin-walled portion is torn from the groove to open the valve. 
     Further, the plurality of batteries  6  are arranged side by side at predetermined intervals so that the long side surfaces of the adjacent batteries  6  face each other. In the present embodiment, the direction in which the plurality of batteries  6  are aligned is the direction X. Further, the output terminals  18  of each battery  6  are arranged so as to face the same direction. In the present embodiment, the output terminals  18  of each battery  6  are arranged so as to face the upper side in the vertical direction for convenience. The output terminals  18  of each battery  6  may be arranged so as to face different directions. The two adjacent batteries  6  are stacked so that the positive electrode terminal  18   a  of one battery  6  and the negative electrode terminal  18   b  of the other battery  6  are adjacent to each other. The positive electrode terminal  18   a  and the negative electrode terminal  18   b  are electrically connected via a bus bar (not shown). The output terminals  18  having the same polarity in the plurality of adjacent batteries  6  may be connected in parallel by a bus bar to form a battery block, and the battery blocks may be connected in series. 
     The separator  8  is also called an insulating spacer, and is made of, for example, a resin having an insulating property. The separator  8  is arranged between the two adjacent batteries  6  to electrically insulate the two batteries  6 . Further, the separator  8  is further arranged between the battery  6  and the end plate  10  to insulate the battery  6  and the end plate  10 . Examples of the resin constituting the separator  8  include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and NORYL (registered trademark) resin (modified PPE). 
     Further, a part of the separator  8  extends in the direction X and covers the upper surface of the battery  6 . As a result, it is possible to secure a creepage distance between the adjacent batteries  6  or between the battery  6  and the end plate  10 . Further, the separator  8  has openings at positions corresponding to the output terminals  18  and the safety valve  20  so that each of them is exposed. 
     The plurality of batteries  6  and the plurality of separators  8  arranged side by side are sandwiched between the pair of end plates  10 . The pair of end plates  10  are arranged so as to be adjacent to the batteries  6  located at both ends in the direction X via the separators  8 . The end plate  10  is made of, for example, a metal plate. Screw holes (not shown) into which screws  22  are screwed are provided on the surface of the end plate  10  facing the long side surface of the battery  6 . 
     The pair of restraining members  12  are also called bind bars, and are elongated members whose longitudinal direction is the direction X. The pair of restraining members  12  are arranged so as to face each other in the direction Y orthogonal to the direction X and parallel to the longitudinal direction of the sealing plate. The plurality of batteries  6 , the plurality of separators  8 , and the pair of end plates  10  are interposed between the pair of restraining members  12 . Each restraining member  12  has a rectangular flat surface portion  12   a  extending parallel to the short side surface of the battery  6 , and four eaves portions  12   b  protruding from end sides of the flat surface portion  12   a  toward the battery  6 . The two eaves portions  12   b  facing each other in the direction X are provided with through holes (not shown) through which the screws  22  are inserted. The flat surface portion  12   a  is provided with an opening portion  12   c  that exposes the short side surfaces of the batteries  6 . 
     The plurality of batteries  6  and the plurality of separators  8  are sandwiched in the direction Y by the pair of restraining members  12  under a state where these are alternately arranged and sandwiched in the direction X by the pair of end plates  10 . Each restraining member  12  is aligned so that the through holes of the restraining member  12  overlaps with the screw holes of the end plate  10 . Then, the screws  22  are inserted into the through holes and screwed into the screw holes. By engaging the pair of restraining members  12  with the pair of end plates  10  in this way, the plurality of batteries  6  are restrained. 
     The plurality of batteries  6  are tightened in the direction X by the restraining members  12 , so that the plurality of batteries  6  are positioned in the direction X. Further, the bottom surfaces of the plurality of batteries  6  abut on the lower eaves portions  12   b  of the restraining members  12  via the separators  8 , and the upper surfaces of the plurality of batteries  6  abut on the upper eaves portions  12   b  of the restraining members  12  via the separator  8 , so that the plurality of batteries  6  are positioned in the up-down direction. As an example, after these positionings are completed, the bus bar is attached to the output terminals  18  of each battery  6 , and the output terminals  18  are electrically connected. 
     The upper surface of the assembly  2  is covered with a cover member  24 . The cover member  24  prevents the contact of condensed water, dust, etc. with the output terminals  18 , the bus bar, the safety valves  20 , etc. of the batteries  6 . The cover member  24  is made of, for example, a resin having an insulating property. The cover member  24  is fixed to the upper surface of the assembly  2  by a well-known fixing structure (not shown) including screws and a well-known locking mechanism. 
     The cooling member  4  is arranged so as to be heat exchangeable with the assembly  2 , and cools each battery  6 . The cooling member  4  of the present embodiment is a plate-shaped cooling plate, and the assembly  2  is placed on the long side surface (or main surface) thereof. The assembly  2  is placed on the cooling member  4  so that the bottom surface faces the cooling member  4  side. At this time, the bottom surface of the battery  6  is thermally connected to the cooling member  4  via the eaves portions  12   b  of the restraining members  12 . In order to further improve the heat exchange efficiency between the battery  6  and the cooling member  4 , a resin sheet or the like having good thermal conductivity may be interposed between the portion of the bottom surface of the battery  6  that is exposed without being covered by the eaves portions  12   b  and the cooling member  4 . Alternatively, the entire bottom surface of the battery  6  and the cooling member  4  may be brought into abutment on each other via the above-mentioned resin sheet without providing the eaves portions  12   b  located on the bottom surface side of the battery  6 . In this case, the cooling member  4  takes on the function of the eaves portions  12   b  located on the bottom surface side of the battery  6 . 
     The cooling member  4  includes a hollow plate-shaped portion  26  and a flow path  28  arranged inside the plate-shaped portion  26  through which the refrigerant flows. In the present embodiment, one flow path  28  is provided inside the plate-shaped portion  26 . The flow path  28  is arranged so as to extend in the direction X. A refrigerant supply path (not shown) is connected to one end of the flow path  28  in the direction X, and a refrigerant discharge path (not shown) is connected to the other end. Therefore, one end side of the flow path  28  is upstream of the refrigerant flow, and the other end side is downstream of the refrigerant flow. The cooling member  4  may include a plurality of flow paths  28 . In this case, the plurality of flow paths  28  each extend in the direction X and are arranged in the horizontal direction Y. 
     That is, the cooling member  4  of the present embodiment is a flat plate-shaped pipe. The plate-shaped portion  26  includes a first plate portion  26   a  facing the assembly  2  and a second plate portion  26   b  the side opposite to the first plate portion  26   a . The first plate portion  26   a  and the second plate portion  26   b  face each other with a predetermined gap. The flow path  28  is arranged in this gap. Such a cooling member  4  can be formed by combining conventionally known methods such as extrusion molding. 
     The cooling member  4  may be formed by joining the first plate portion  26   a  and the second plate portion  26   b , which are separate bodies from each other. For example, by joining a first plate material having outer walls erected on both end sides in the direction Y and a second plate material having protruding portions  132  described later on the main surface by brazing or the like, the cooling member  4  including the flow path  28  between the first plate portion  26   a  and the second plate portion  26   b  can be obtained. The joining positions between the first plate material and the second plate material are, for example, positions where the tips of the outer walls and the end sides of the second plate material come into contact with each other. In this case, the cooling member  4  can be easily manufactured as compared with the case where the flow path  28  is formed by hollowing out a solid plate material or the case of performing extrusion molding. The outer walls and the protruding portions  132  may be provided on the same plate material. 
     The plate-shaped portion  26  is made of a material having high thermal conductivity such as aluminum. The assembly  2  is placed on the plate-shaped portion  26 , for example, via the above-mentioned resin sheet having an insulating property and thermal conductivity. Each battery  6  exchanges heat with refrigerant such as water or ethylene glycol flowing through the flow paths  28  via the resin sheet and the plate-shaped portion  26 . As a result, each battery  6  is cooled. The plate-shaped portion  26  has an insertion portion  144  into which a fastening member  142  such as a screw is inserted at a predetermined position (see  FIG. 12(A) ). The assembly  2  and the cooling member  4  are fixed to each other by inserting the fastening member  142  through the insertion portion  144 . The insertion portion  144  is arranged in a floating island shape in the flow path  28 . The fastening member  142  may be used not only for fixing the assembly  2  and the cooling member  4 , but also for fixing the cooling member  4  to a module case. Further, the insertion portion  144  is preferably provided at a position that does not overlap with the battery  6  when viewed from the direction Z in which the assembly  2  and the cooling member  4  are aligned. Further, when the assembly  2  is fixed to the cooling member  4  by fastening the fastening member  142  to the insertion portion  144 , the fastening member  142  is connected to, for example, the end plate  10  or the restraining member  12 . 
     Subsequently, the structure of the cooling member  4  will be described in more detail.  FIG. 10  is an end view schematically illustrating the structure of the cooling member  4 . In  FIG. 10 , the end face of the cooling member  4  cut along the plane extending in the direction X and the direction Z (the upper surface-bottom surface direction of the battery  6 ), that is, the XZ plane is illustrated. Further, only a part of the cooling member  4  is illustrated, and the illustration of the assembly  2  is simplified. 
     The cooling member  4  includes mixing portions  130  arranged in the middle of the flow path  28 . The mixing portions  130  disturb the flow of at least part of the refrigerant to generate refrigerant flows in a direction approaching or separating from the assembly  2  in the direction Z in which the assembly  2  and the cooling member  4  are aligned. In the following, the flow of the refrigerant from the upstream side to the downstream side of the flow path  28  will be referred to as a main flow S, and the flow of the refrigerant in the direction of approaching/separating from the assembly  2  will be referred to as a turbulent flow S 1 . 
     The mixing portions  130  of the present embodiment are each formed by the protruding portion  132  arranged on a first wall surface  28   a  located on the assembly  2  side of the inner wall surfaces of the flow path  28 . The first wall surface  28   a  is a surface that defines the flow path  28  in the surface of the first plate portion  26   a . The protruding portion  132  protrudes from the first wall surface  28   a  toward the center side of the flow path  28 , that is, in the direction separating from the assembly  2 . Therefore, when the main flow S of the refrigerant hits the protruding portion  132 , part of the main flow S becomes the turbulent flow S 1  traveling in the direction separating from the assembly  2 . In other words, the main flow S of the refrigerant travels downstream in the flow path  28 , and part of the flow is changed in direction to the up-down direction by the protruding portion  132 . 
     Thus, refrigerant located on the first wall surface  28   a  side and having been subjected to heat exchange with the assembly  2  and refrigerant located on the center side of the flow path  28  and not having been subjected to heat exchange with the assembly  2  are mixed. As a result, the development of the temperature boundary layer is suppressed. By suppressing the development of the temperature boundary layer, the temperature deviation of the cooling member  4 , particularly the temperature deviation in the direction in which the refrigerant flows can be reduced, and therefore the temperature deviation in each battery  6  can be reduced. 
     The cooling member  4  has a gap between the protruding portions  132  and the second wall surface  28   b  facing the first wall surface  28   a  of the inner wall surfaces of the flow path  28 . That is, the protruding portions  132  protruding from the first plate portion  26   a  do not abut on the second plate portion  26   b . As a result, it is possible to prevent the flow of the refrigerant from being blocked by the protruding portions  132  while generating the turbulent flows S 1 . The second wall surface  28   b  is a surface that defines the flow path  28  in the surface of the second plate portion  26   b.    
     As indicated by the broken line in  FIG. 10 , the protruding portion  132  may be inclined so that a front surface  132   a  facing the upstream side of the flow path  28  or the main flow S extends toward the downstream side as it approaches the tip of the protruding portion  132  in the protruding direction. As a result, it is possible to prevent the flow of the refrigerant from being blocked while generating the turbulent flows S 1 . Further, the protruding portion  132  may be inclined so that a rear surface  132   b  facing the downstream side of the flow path  28  or the main flow S extends toward the upstream side as it approaches the tip of the protruding portion  132  in the protruding direction. As a result, the refrigerant can easily flow to the corner formed by the rear surface  132   b  and the first wall surface  28   a . Therefore, the heat exchange between the assembly  2  and the refrigerant can be promoted. 
     The protruding portions  132  may be provided on the second wall surface  28   b  facing the first wall surface  28   a , that is, on the second wall surface  28   b  located on the side opposite to the assembly  2 . In this case, when the main flow S hits the protruding portion  132 , part of the main flow S becomes the turbulent flow S 1  traveling in the direction approaching the assembly  2 . Also in this case, the refrigerant located on the first wall surface  28   a  side and having been subjected to heat exchange with the assembly  2  and the refrigerant located on the center side of the flow path  28  and not having been subjected to heat exchange with the assembly  2  can be mixed. 
     The protruding portions  132  slightly block the flow of the refrigerant. Therefore, it is preferable that the protruding portions  132  are arranged in a small number on the upstream side of the main flow S and in a large number on the downstream side. As a result, it is possible to prevent the flow of the refrigerant from being blocked on the upstream side where the heat exchange between the assembly  2  and the refrigerant smoothly occurs because the refrigerant temperature is low as a whole. On the other hand, on the downstream side where the refrigerant temperature in the flow-path cross section perpendicular to the direction in which the main flow S flows tends to increase as a whole and the heat exchange tends to be hindered, the refrigerant temperature in the flow-path cross section is averaged by generating a larger number of turbulent flows S 1 . As a result, the temperature of the refrigerant on the first wall surface  28   a  side can be lowered, and the heat exchange between the assembly  2  and the refrigerant can be promoted. 
     The protruding portions  132  of the present embodiment are each formed by a part of a band-shaped member described below.  FIG. 11  is an end view schematically illustrating the structure of the cooling member  4 . In  FIG. 11 , the end face of the cooling member  4  cut along the plane extending in the direction Y and the direction Z, that is, the YZ plane is illustrated. Further, only a part of the cooling member  4  is illustrated, and the illustration of the assembly  2  is simplified. 
     The cooling member  4  has band-shaped members  134  extending in the flow path  28  in a direction intersecting the extending direction of the flow path  28  (the direction Y in the present embodiment). In the present embodiment, the plurality of band-shaped members  134  are arranged at predetermined intervals in the upstream and downstream direction of the flow path  28 . Each band-shaped member  134  has a plurality of first portions  134   a  and second portions  134   b . Each first portion  134   a  is in contact with the first wall surface  28   a  and forms the protruding portion  132 . Therefore, the protruding portion  132  of the present embodiment has an elongated shape that is long in the direction Y intersecting the flow path  28  and the direction parallel to the first wall surface  28   a . This makes it possible to agitate more refrigerant. 
     The second portion  134   b  protrudes between the adjacent first portions  134   a  toward the second wall surface  28   b  facing the first wall surface  28   a , and has a tip portion  136  which abuts on the second wall surface  28   b . The band-shaped member  134  is fixed in the flow path  28  by the first portions  134   a  abutting on the first wall surface  28   a  and the tip portions  136  of the second portion  134   b  abutting on the second wall surface  28   b . Therefore, the second portion  134   b  constitutes a support portion for fixing the protruding portion  132  in the flow path  28 . The tip portion  136  of the second portion  134   b  also functions as the protruding portion  132  protruding from the second wall surface  28   b.    
     The second portion  134   b  has a pair of side walls  138  each connecting the first portions  134   a  and the tip portion  136 . Each side wall  138  extends diagonally from the first wall surface  28   a  toward the second wall surface  28   b . That is, the side wall  138  extends so as to shift in the direction Y as it approaches the second wall surface  28   b . By inclining the side wall  138  in this way, the band-shaped member  134  easily bends in the direction in which the first portion  134   a  and the tip portion  136  approach/separate from each other. As a result, the dimensional tolerance of the band-shaped member  134  can be absorbed, and the band-shaped member  134  can be securely fixed by the flow path  28 . 
     Further, the cooling member  4  has fine flow paths  140 .  FIG. 12(A)  is a cross-sectional view schematically illustrating the structure of the cooling member  4 .  FIG. 12(B)  is a schematic view for explaining the operation of the fine flow paths  140 . In  FIG. 12(A) , a cross section of the cooling member  4  along the YZ plane is illustrated. In  FIG. 12(B) , a cross section of the cooling member  4  along the plane extending in the direction X and the direction Y, that is, the XY plane is illustrated. Further, in  FIGS. 12(A) and 12(B) , only a part of the cooling member  4  is illustrated. Further, in  FIG. 12(A) , the illustration of the assembly  2  is simplified. 
     The fine flow paths  140  are arranged in the flow path  28 . The fine flow paths  140  extend diagonally so as to shift in the direction intersecting the flow path  28 , that is, the direction intersecting the direction X and the direction parallel to the first wall surface  28   a  as they advance from the upstream side to the downstream side of the flow path  28 . In the present embodiment, the fine flow paths  140  extend diagonally so as to shift in the direction Y as they advance in the direction X. 
     The fine flow paths  140  of the present embodiment are each formed by a groove portion  148  provided in the second portion  134   b . The groove portion  148  extends so as to shift in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a  as it advances from the upstream side to the downstream side of the flow path  28 , and opens to the first wall surface  28   a  side. Specifically, the tip portion  136  of the second portion  134   b  is connected to the first portion  134   a  by the pair of side walls  138 . The pair of side walls  138  are arranged in the extending direction of the band-shaped member  134 . Further, the pair of side walls  138  extend diagonally so as to shift in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a  as they advance from the upstream side to the downstream side of the flow path  28 . That is, the side walls  138  extend so as to shift in the direction Y as they advance in the direction X. The groove portion  148  is formed by the tip portion  136  and the pair of side walls  138 . The groove portion  148  opens to the first wall surface  28   a  side. This opening is closed by the first wall surface  28   a . Therefore, the fine flow path  140  is partitioned by the tip portion  136 , the pair of side walls  138 , and the first wall surface  28   a.    
     The fine flow path  140  can change the direction of the refrigerant flow in a direction parallel to a surface  2   a  of the assembly  2  facing the cooling member  4  side, that is, a surface direction along the bottom surface of the assembly  2  or the first wall surface  28   a . The main flow S of the refrigerant travels downstream in the flow path  28 , and is changed in direction to the left-right direction by the fine flow path  140 . As a result, the flow rate of the refrigerant can be made uniform in the entire flow path  28 . As a result, the assembly  2  can be cooled more uniformly. 
     Further, the cooling member  4  has, for example, the cylindrical insertion portion  144  through which the fastening member  142  for fixing the assembly  2  and the cooling member  4  is inserted. The insertion portion  144  is a recess provided in the second plate portion  26   b  and protruding toward the first plate portion  26   a  in the flow path  28 . The insertion portion  144  may be provided in the first plate portion  26   a  and protrude toward the second plate portion  26   b . The insertion portion  144  has a bottomed tubular shape, and has a bottom portion  144   a  connected to the other plate portion, that is, the first plate portion  26   a  in the present embodiment. The bottom portion  144   a  is joined to the other plate portion by, for example, brazing. The cooling member  4  has a through hole  146  that penetrates the bottom portion  144   a  and the other plate portion. The fastening member  142  is inserted through the through hole  146 . 
     At least some of the second portions  134   b , in other words, the fine flow paths  140  are arranged on the downstream side of the refrigerant flow with respect to the insertion portion  144  of the fastening member  142  for fixing the assembly  2  and the cooling member  4 . The flow of the refrigerant flowing through the flow path  28  is blocked by the insertion portion  144 . On the other hand, by arranging the second portions  134   b  behind the insertion portion  144  in the direction in which the refrigerant flows, the refrigerant can be sent to the back side of the insertion portion  144  by the fine flow paths  140 . As a result, the flow rate of the refrigerant can be made uniform in the entire flow path  28 . As a result, the assembly  2  can be cooled more uniformly. 
     Further, the cooling member  4  has the plurality of fine flow paths  140 , and the two adjacent fine flow paths  140  extend so as to approach each other as they advance from the upstream side to the downstream side of the flow path  28 . As a result, the refrigerant flowing through the flow path  28  can be more agitated. Further, by arranging the insertion portion  144  on the upstream side of the two fine flow paths  140  and between the two fine flow paths  140 , the refrigerant can be sent to the back side of the insertion portion  144 . 
     The plurality of band-shaped members  134  arranged in the upstream-downstream direction of the flow path  28  may have the second portions  134   b  so that the fine flow paths  140  sift in the direction intersecting the upstream-downstream direction. For example, the flow paths  140  are arranged in a staggered pattern on the XY plane. As a result, the flow rate of the refrigerant can be made more uniform in the entire flow path  28 . 
     As described above, the battery module  1  according to the present embodiment includes the assembly  2  of the plurality of batteries  6  and the cooling member  4  arranged so as to be heat exchangeable with the assembly  2 . The cooling member  4  includes the flow path  28  through which the refrigerant flows, and the mixing portions  130  which are arranged in the middle of the flow path  28  and generate the refrigerant flows in the direction approaching or separating from the assembly  2  in the direction Z in which the assembly  2  and the cooling member  4  are aligned. 
     As described above, in the present embodiment, the mixing portions  130  are provided in the middle of the flow path  28 , that is, in the flow path  28 , and the development of the temperature boundary layer is suppressed by mixing the refrigerant by the mixing portions  130 . Therefore, unlike the case where large cross-sectional area portions are provided in the flow path as in the conventional battery module, it is possible to avoid an increase in the size of the flow path. Therefore, according to the present embodiment, it is possible to make the cooling of the assembly  2  uniform while avoiding the increase in size of the battery module  1 . Further, the uniform cooling of the assembly  2  can suppress the deterioration of the performance of the battery module  1 . 
     Further, in the battery module  1 , heat exchange between the refrigerant and the assembly  2  via the first wall surface  28   a  located on the assembly  2  side occurs preferentially over heat exchange via the other wall surfaces. Therefore, the temperature boundary layer easily develops along the first wall surface  28   a . On the other hand, in the present embodiment, the mixing portions  130  generate the refrigerant flows in the direction of approaching or separating from the assembly  2 . As a result, the development of the temperature boundary layer along the first wall surface  28   a  can be particularly suppressed. Therefore, as compared with the conventional case where the flow velocity of the refrigerant is increased or decreased to suppress the development of the temperature boundary layer, the development of the temperature boundary layer can be efficiently suppressed with a simpler structure. 
     Further, the mixing portions  130  of the present embodiment are each formed by the protruding portion  132  arranged on the first wall surface  28   a  located on the assembly  2  side of the inner wall surfaces of the flow path  28 . As a result, the development of the temperature boundary layer can be suppressed with a simpler structure. 
     Further, the cooling member  4  includes, in the flow path  28 , the band-shaped members  134  extending in the direction intersecting the flow path  28 . The band-shaped member  134  includes the plurality of first portions  134   a  which are in contact with the first wall surface  28   a  and form the protruding portions  132 , and the second portions  134   b  which each protrude between the adjacent first portions  134   a  toward the second wall surface  28   b  facing the first wall surface  28   a , and each have the tip portion  136  which abuts on the second wall surface  28   b . In this way, by providing one member with the function of the protruding portion  132  and the function of fixing the protruding portion  132  in the flow path  28 , the development of the temperature boundary layer can be suppressed with a simpler structure. 
     Further, the protruding portion  132  has an elongated shape that is long in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a . Further, the cooling member  4  has the fine flow paths  140  that extend so as to shift in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a  as they advance from the upstream side to the downstream side of the flow path  28 . The fine flow paths  140  can change the direction of the refrigerant flow in the direction parallel to the surface  2   a  of the assembly  2  facing the cooling member  4  side. As a result, the flow rate of the refrigerant can be made uniform in the entire cooling member  4 . As a result, the assembly  2  can be cooled more uniformly. 
     Further, in the second portion  134   b  of the present embodiment, the groove portion  148  that extends so as to shift in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a  as it advances from the upstream side to the downstream side of the flow path  28 , and opens to the first wall surface  28   a  side is provided, and the fine flow path  140  is formed by the groove portion  148 . Further, the second portion  134   b  includes the tip portion  136  that abuts on the second wall surface  28   b , and the pair of side walls  138  each connecting the first portion  134   a  and the tip portion  136 . The pair of side walls  138  extend so as to shift in the direction intersecting the flow path  28  and the direction parallel to the first wall surface  28   a  as they advance from the upstream side to the downstream side of the flow path  28 . The groove portion  148  is formed by the tip portion  136  and the pair of side walls  138 . 
     The fine flow path  140  provided in the second portion  134   b  is not limited to the above configuration. For example, when the second portion  134   b  is a solid pillar, a linear groove extending diagonally like the groove portion  148  is provided on the outer surface of the pillar, and a flow path partitioned by this groove and the first wall surface  28   a  or a flow path partitioned by this groove and the second wall surface  28   b  may be a fine flow path  140 . 
     Further, the cooling member  4  of the present embodiment includes the plurality of fine flow paths  140 . The two adjacent fine flow paths  140  extend so as to approach each other as they advance from the upstream side to the downstream side of the flow path  28 . Further, the second portion  134   b  includes the tip portion  136  that abuts on the second plate portion  26   b , and the pair of side walls  138  each connecting the first portion  134   a  and the tip portion  136 , and the side walls  138  extend diagonally from the first wall surface  28   a  toward the second wall surface  28   b . Further, the cooling member  4  is a flat plate-shaped pipe, and includes the first plate portion  26   a  facing the assembly  2 , the second plate portion  26   b  on the side opposite to the first plate portion  26   a , and the recess provided in one plate portion and protruding toward the other plate portion in the flow path  28 . The fine flow paths  140  are arranged on the downstream side of the refrigerant flow with respect to the recess. As a result, the flow rate of the refrigerant can be made uniform in the entire cooling member  4 . As a result, the assembly  2  can be cooled more uniformly. 
     Further, the recess has a bottomed tubular shape, and has the bottom portion  144   a  connected to the other plate portion. The cooling member  4  has a through hole  146  that penetrates the bottom portion  144   a  and the other plate portion. Further, the cooling member  4  has a gap between the protruding portions  132  and the second wall surface  28   b  facing the first wall surface  28   a  of the inner wall surfaces of the flow path  28 . Further, the cooling member  4  includes the first plate portion  26   a  and the second plate portion  26   b  which face each other with a predetermined gap, and the flow path  28  is arranged in the gap. 
     The embodiment of the present disclosure has been described in detail above. The above-described embodiment merely shows a specific example in carrying out the present disclosure. The content of the embodiment does not limit the technical scope of the present disclosure, and many designs such as modification, addition, and deletion of components can be made without departing from the ideas of the present disclosure defined in the claims. A new embodiment with the design change has the effects of the combined embodiment and the modification. In the above-described embodiment, the contents that can be changed in design are emphasized by adding notations such as “of the present embodiment” or “in the present embodiment”, but design changes are allowed even in contents without such notations. Any combination of the above components is also effective as an aspect of the present disclosure. The hatching attached to the cross section of the drawing does not limit the material to which the hatching is attached. 
     In the second embodiment, the battery  6  is a square battery, but the shape of the battery  6  is not particularly limited and may be cylindrical or the like. Further, the number of the batteries  6  included in the assembly  2  is not particularly limited. The flow paths  28  extend along the direction X, but the direction is not particularly limited. Further, the assembly  2  and the cooling member  4  may be held in direct abutment on each other. The structure of each part of the assembly  2  including the shape of the separator  8  and the fastening structure between the end plate  10  and the restraining member  12  is not particularly limited.