Abstract:
A bus bar module includes: a plurality of bus bar cases each housing a bus bar; a first engagement portion provided to one of the plurality of bus bar cases; a first connecting member having flexibility and connecting the plurality of bus bar cases; a plurality of insulating covers covering openings of the plurality of bus bar cases, the insulating covers including a second engagement portion to be engaged with the first engagement portion; a second connecting member having flexibility and connecting the plurality of insulating covers; and a pair of ribs provided to extend downward from an inner surface of each of the insulating covers located adjacent to each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a bus bar module, or more specifically, to a structure for engagement between resin bus bar cases which house bus bars for connecting multiple battery cells in series and resin covers which cover openings of the bus bar cases. 
         [0003]    2. Background Art 
         [0004]    A battery pack (also referred to as an assembled battery or a battery unit) formed by connecting multiple battery cells in series is used as a direct-current power source for driving an electric motor in an electric vehicle, a hybrid car or the like. As described in Japanese Patent Application Publication No. 2011-238544 (Patent Document 1), such a battery pack is fabricated by forming a battery assembly in which positive electrodes and negative electrodes of multiple battery cells alternately arranged side by side are bundled and the positive electrodes and the negative electrodes of the adjacent battery cells are connected in series by using conductive bodies called bus bars, and, if necessary, by housing the battery assembly in a housing. Then, the battery pack is put to use. 
         [0005]    The bus bars are respectively housed in box-shaped bus bar housing units (hereinafter referred to as bus bar cases) made of an insulative resin. The bus bar cases are connected in an arrangement direction of the battery cells by using U-shaped flexible connecting members. Then, a bus bar module is formed in such a way that: the columnar positive and negative electrodes of the battery cells are inserted into holes formed in the bus bars, and are fixed thereto with nuts or the like; and the bus bars and the electrode members exposed on an opening side of the bus bar cases are protected by being covered with plate-shaped insulating covers In particular, the insulating covers are formed as multiple separate covers each for a plural number of bus bar cases set appropriately in consideration of a dimensional tolerance of the battery unit. The separate insulating covers are connected to one another using flexible connecting members. Moreover, each insulating cover includes a second engagement portion to be engaged with a first engagement portion provided to a given one of the bus bar cases. The bus bar module is formed by engaging the first and second engagement portions (hereinafter referred to as a lock mechanism as appropriate) with one another. 
       SUMMARY OF THE INVENTION 
       [0006]    However, the bus bar module described in Patent Document 1 does not consider that the engagement of the lock mechanism may be released for some reason in the course of assembling a bus bar module by engaging the corresponding engagement portions of the insulating covers and the bus bar cases with one another. Specifically, there may be a case where the lock mechanism for at least one of two adjacent insulating covers is unlocked and the unlocked insulating cover is displaced relative to the corresponding bus bar case due to a deformation of the connecting member. If the insulating cover is displaced relative to the openings of the bus bar cases as described above, the columnar electrodes and the bus bars are exposed. The exposure of the columnar electrodes and the bus bars, to which a battery voltage is being applied, disturbs attachment work of the bus bar module and should therefore be avoided as much as possible. 
         [0007]    An object of the present invention is to provide a bus bar module, which is capable of preventing exposure of a columnar electrode and a bus bar, the exposure being likely to occur due to displacement of an insulating cover relative to a bus bar case in the course of assembling the bus bar module by engaging a lock mechanism for the insulating cover and the bus bar case. 
         [0008]    An aspect of the present invention is a plurality of bus bar cases made of a resin, each bus bar case configured to house a bus bar to connect a positive electrode of a battery cell and a negative electrode of an adjacent battery cell among battery cells arrayed such that the positive electrodes and the negative electrodes of the battery cells are arranged alternately; a first engagement portion provided to one of the plurality of bus bar cases; a first connecting member having flexibility and configured to connect the plurality of bus bar cases; a plurality of insulating covers made of a resin, the insulating covers configured to cover openings of the plurality of bus bar cases and including a second engagement portion to be engaged with the first engagement portion; a second connecting member having flexibility and configured to connect the plurality of insulating covers; and a pair of ribs provided to extend downward from an inner surface of each of the insulating covers located adjacent to each other while interposing the second connecting member in between, the pair of ribs configured to be in contact respectively with inner surfaces of paired walls of the corresponding bus bar case, the walls extending in a direction of arrangement of the bus bar cases and facing each other. 
         [0009]    Each of the pair of ribs may be provided at a position in the insulating cover close to the second connecting member. Each of the pair of ribs may include a reinforcing rib extending from the inner surface of the insulating cover toward a top portion of the corresponding wall of the bus bar case, and having such a length that the reinforcing rib is out of contact with the top portion. 
         [0010]    According to the present invention, it is possible to prevent exposure of the columnar electrode and the bus bar, the exposure being likely to occur due to displacement of the insulating cover relative to the bus bar case in the course of assembling the bus bar module by engaging the lock mechanism for the insulating cover and of the bus bar case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view showing an external appearance of a bus bar module according to an embodiment of the present invention. 
           [0012]      FIG. 2  is a perspective view showing inner surface sides of insulating covers of the bus bar module of  FIG. 1 . 
           [0013]      FIG. 3  is a transparent view showing ribs provided to the insulating covers according to the embodiment of the present invention. 
           [0014]      FIGS. 4A and 4B  are views of the ribs of  FIG. 3 , which are viewed from the line IV-IV in  FIG. 3 . 
           [0015]      FIGS. 5A and 5B  are views for explaining configurations of a lock mechanism for the insulating cover and of a bus bar case. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    A bus bar module according to an embodiment of the present invention will be described below with reference to the accompanying drawings. A bus bar module  1  of the embodiment of the present invention is attached to positive and negative columnar electrodes projecting from a top portion of a battery assembly (not shown), for example. In the battery assembly, positive electrodes and negative electrodes of battery cells are alternately arranged. A positive electrode of a battery cell and a negative electrode of an adjacent battery cell are connected to each other with a conductor plate called a bus bar. Thus, the multiple battery cells are connected in series. The positive electrode and the negative electrode of each battery cell in the battery assembly are located in a direction orthogonal to the arrangement direction. In other words, the electrodes of the battery cells are arranged in two rows in the arrangement direction. Accordingly, the bus bar module  1  includes two rows of bus bar case assemblies  2   a  and  2   b  located parallel to the arrangement direction of the battery assembly. Each of the bus bar case assemblies  2   a  and  2   b  includes multiple bus bar cases  3  made of a resin, each of which is configured to house the corresponding bus bar. Each two adjacent bus bar cases  3  are connected to each other with a flexible connecting member (a first connecting member)  4 . The bus bar case assemblies  2   a  and  2   b  are formed substantially into the same structure except for the respective end portions. Given this fact, the bus bar module of the embodiment will be described by using the bus bar case assembly  2   a  shown in  FIG. 1  as an example. Note that the bus bar case assembly  2   a  and the bus bar case assembly  2   b  are formed symmetrically with respect to the arrangement axis of the battery assembly. 
         [0017]    The bus bar case assembly  2   a  includes the multiple bus bar cases  3 , and the connecting members  4  each of which connects an adjacent pair of the bus bar cases  3 . The connecting members  4  are flexible. As shown in  FIG. 4A , each connecting member  4  is formed integrally with two ends of the adjacent bus bar cases  3 . The connecting member  4  includes a strip-shaped portion  4   a  formed into an inverted U-shape. The strip-shaped portion  4   a  protrudes to an upper end side of the bus bar cases  3 . However, the shape of the connecting members  4  is not limited only to this example. The connecting members  4  may adopt various structures (shapes) as long as the structures can establish the connection with such a strength that the adjacent bus bar cases  3  can change their relative positions to each other. Meanwhile, the bus bar cases  3  are provided with wire routing paths  5  located on the near side in  FIG. 1 . The wire routing paths  5  house wires for detecting voltages of the battery cells. The wire routing paths  5  are formed integrally with the respective bus bar cases  3 . Each wire routing path  5  is provided with a lid  6  which is made openable and closable. The lid  6  is connected to a side edge of the corresponding bus bar case  3  with a flexible hinge. The lid  6  is locked to a side surface of the corresponding wire routing path  5  in an attachable and detachable manner using engagement portions  7 . 
         [0018]    Three insulating covers  10  are provided in this embodiment. In the following description, these insulating covers may be occasionally referred to as insulating covers  10   a,    10   b,  and  10   c  for the sake of convenience. The insulating covers  10  cover openings of the bus bar cases  3 . Each insulating cover  10  of the embodiment is provided to cover a half of the lid  6  of each wire routing path  5 . The insulating covers  10  are formed to cover the entirety of the openings of the multiple (four or five in the illustrated example) bus bar cases  3 . Each insulating cover  10  is made of an electrically insulative resin. Each two adjacent insulating covers  10  are connected to each other with a flexible connecting member (a second connecting member)  11 . Each insulating cover  10  includes at least one second engagement portion  12  serving as a lock unit. Such a second engagement portion  12  is engaged with a corresponding first engagement portion  8  provided on one of the multiple bus bar cases  3 . Each of the insulating covers  10   a  and  10   c  is provided with two second engagement portions  12  while the insulating cover  10   b  is provided with one second engagement portion  12 . The bus bar cases  3  to be engaged with these second engagement portions  12  are provided with the first engagement portions  8  as shown in  FIGS. 5A and 5B , for example. Each second engagement portion  12  has a shape of a hole, a groove, or the like into which the corresponding first engagement portion  8  is fitted. As shown in  FIG. 5B , for instance, the second engagement portion  12  is formed into a shape of a flat plate-shaped and hollow frame. As shown in  FIG. 5B , each first engagement portion  8  is provided to protrude outward from a side wall  9  of the bus bar case  3 . The first engagement portion  8  is formed into a shape of a claw, for example. The first engagement portions  8  are provided on the bus bar cases  3  at positions corresponding to the insulating covers  10   a ,  10   b,  and  10   c.  Moreover, when the insulating covers  10   a,    10   b,  and  10   c  cover the openings of the bus bar cases  3 , the claws of the first engagement portions  8  on the bus bar cases  3  are engaged with beams of the second engagement portions  12  on the insulating covers  10 , whereby the insulating covers  10  are locked to the bus bar cases  3 . Here, the first engagement portion  8  and the second engagement portion  12  are apt to be unlocked if engagement therebetween is inadequate. Hence, the insulating covers  10  may be provided with ribs  13  as shown in  FIG. 5B . Each rib  13  is provided facing the corresponding second engagement portion  12  in such a way that the engagement portion  8  on the bus bar case  3  is nipped between the rib  13  and the second engagement portion  12 . Thus, the first engagement portion  8  and the second engagement portion  12  become less likely to be unlocked. 
         [0019]      FIG. 3  is a transparent view illustrating a state where the openings of the bus bar cases  3  are covered with the insulating covers  10 , which is viewed from an outer surface side of the insulating covers  10 . As shown in  FIG. 3 , the adjacent insulating covers  10  ( 10   a  and  10   b,  for example) are connected to each other with the flexible connecting member  11 . The connecting member  11  includes strip-shaped portions  11   a  and  11   b,  which are formed into U-shaped portions facing each other and are located between outer surfaces of opposed cover walls of the adjacent insulating covers  10 . 
         [0020]    Each of the bus bar cases  3  includes a pair of walls  3   a  and  3   b  which extend in the arrangement direction of the bus bar cases  3  and face each other. In other words, the walls  3   a  and the walls  3   b  are provided in the arrangement direction of the bus bar cases  3 , respectively. Each bus bar  21  is placed between the corresponding pair of walls  3   a  and  3   b.  As shown in  FIG. 4A , a pair of ribs  14   a  and  14   b  are provided on inner surfaces of the insulating covers  10  ( 10   a  and  10   b,  for example) that are adjacent to each other while interposing the connecting member  11  in between, and at positions of the aforementioned inner surfaces in contact with inner surfaces of the pair of walls  3   a  and  3   b.  Each of the ribs  14   a  and  14   b  is formed into a flat plate shape, and extends downward from the inner surface of the corresponding insulating cover  10  to the bus bar  21  (or a terminal  23 ). Meanwhile, each pair of ribs  14   a  and  14   b  are provided at the positions close to the connecting member  11  for connecting the adjacent insulating covers  10 . In other words, each pair of ribs  14   a  and  14   b  are provided at end portions of the corresponding insulating cover  10  to be connected to the connecting member  11 . Moreover, as shown in  FIG. 4B , each of the ribs  14   a  and  14   b  includes a reinforcing rib  15 , which projects perpendicularly from a surface of the rib (a surface facing the wall  3   a  ( 3   b )). The reinforcing rib  15  extends from the inner surface of the insulating cover  10  toward a top portion of the wall  3   a  ( 3   b ) of the bus bar case  3 . The reinforcing rib  15  has such a length that the reinforcing rib  15  can be out of contact with the top portion of the wall  3   a  ( 3   b ). Here, claws  25  for holding the bus bar  21  at a predetermined position are provided on inner surfaces of the bus bar case  3 . 
         [0021]    Procedures for assembling the bus bar module  1  will be briefly described. First, the bus bar case assemblies  2   a  and  2   b  integrally provided with the wire routing paths  5  are attached to the columnar electrodes (not shown) of the battery assembly. At this time, the columnar electrodes of the adjacent battery cells are positioned and inserted respectively into two holes  22  provided in each bus bar  21  shown in  FIG. 5A . Moreover, a voltage detection terminal  23  is brought in through a slit  24  provided in the wall  3   a  of each bus bar case  3 , and is attached to the columnar electrode that is inserted into one of the holes  22 . The terminal  23  is connected to a voltage detection wire which is routed in the wire routing paths  5 . Then, the bus bars  21  and the terminals  23  are connected to the battery cells by screwing nuts onto threads on the columnar electrodes. Subsequently, the second engagement portions  12  of the insulating covers  10  are aligned with the first engagement portions  8  of the corresponding bus bar cases  3 . Thereafter, the insulating covers  10  are attached and locked to the opening surfaces of the bus bar cases  3  sequentially from one end side of the bus bar module  1 , for example. At this time, the pair of ribs  14   a  and  14   b  provided on the inner surface of the given insulating cover  10  are positioned to come into contact with the inner surfaces of the walls  3   a  and  3   b  of the corresponding bus bar case  3 . Then, the insulating cover  10  is pushed into the bus bar case  3 . Thus, the first and second engagement portions  8  and  12  are engaged with and locked to each other. 
         [0022]    According to the embodiment of the present invention, even if the first and second engagement portions  8  and  12  as a lock mechanism for at least one of two adjacent insulating covers  10  are unlocked in the course of assembling the bus bar module  1 , the pair of ribs  14   a  and  14   b  provided on the inner surface of the relevant insulating cover  10  remain in contact with the corresponding bus bar case  3 . As a consequence, a relative position between the insulating cover  10  and the bus bar cases  3  is not displaced unless the insulating cover  10  is pulled up to a position where the pairs of ribs  14   a  and  14   b  are detached from the bus bar cases  3 . Thus, it is possible to prevent exposure of the columnar electrodes and the bus bars in the bus bar cases  3 . 
         [0023]    In other words, if at least one of the lock mechanisms for two adjacent insulating covers  10  and the corresponding bus bar cases  3  is unlocked, the unlocked insulating cover  10 , without the pairs of the ribs  14   a  and  14   b  provided, is apt to be displaced relative to the opening surfaces of the bus bar cases  3  due to a deformation of the connecting member  11 . If such displacement is significant, the columnar electrodes and bus bars in the bus bar cases  3  are exposed. The exposure of the columnar electrodes and the bus bars, to which a battery voltage is being applied, disturbs attachment work of the bus bar module. On the other hand, according to the embodiment, it is possible to avoid exposure of the columnar electrodes and the bus bars, to which the battery voltage is being applied, by restricting relative displacement between the insulating covers  10  and the opening surfaces of the bus bar cases  3 . In particular, according to the embodiment, each pair of ribs  14   a  and  14   b  are provided in the vicinity of the corresponding connecting member  11  where the displacement of the insulating cover  10  reaches a maximum. Thus, the relative displacement of the insulating cover  10  from the opening surfaces of the bus bar cases  3  can be reduced. In addition, the reinforcing ribs  15  are provided so as to reinforce the pairs of the ribs  14   a  and  14   b.  As a consequence, the pairs of ribs  14   a  and  14   b  can be made thin. 
         [0024]    Although the present invention has been described on the basis of a certain embodiment, it is obvious to those skilled in the art that the invention is not limited only to the above-described embodiment but can also be embodied in various other modes that are modified or changed within the scope of the gist of the present invention. It should be naturally understood that such modified or changed modes are also encompassed by the scope of the appended claims.