Abstract:
A battery pack includes a battery assembly having a plurality of battery cells, a busbar module that includes a plurality of conductors and an insulating member which holds the conductors, a battery control unit provided at an end portion of the battery assembly in an arrangement direction of the battery cells, and an extraction conductor that connects a total electrode terminal connected to the battery assembly to a main circuit terminal of the battery control unit. The extraction conductor has a water escape portion which is located below an imaginary line connecting the total electrode terminal to the main circuit terminal, and an upper end of the water escape portion is formed at a location that is lower than a lower end of the main circuit terminal.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a battery pack, for instance, a battery pack used as a DC power source for driving an electric motor in an electric vehicle and a hybrid electric vehicle. 
       BACKGROUND ART 
       [0002]    As described in connection with Patent Literature (PTL) 1, a battery pack of this type has a battery assembly in which a plurality of battery cells are arranged in such a manner that positive electrodes and negative electrodes of the battery cells adjoin each other and serially interconnecting and bundling the positive electrodes and the negative electrodes of the adjoining battery cells by conductors referred to as busbars. The battery assembly is used while being contained in a housing as necessary. A positive electrode (hereinafter called a “total positive electrode”) and a negative electrode (hereinafter called a “total negative electrode”) of battery cells at both ends of the battery assembly work as DC outputs of the battery pack. 
         [0003]    In a battery pack, a battery control unit for controlling the battery assembly is sometimes provided at end portion of the battery assembly in a direction where the battery cells are aligned. The battery control unit has, for instance, a current sensor for detecting an electric current output from a battery pack, a precharge contactor, a main contactor, and others. The battery control unit is used while the total electrode terminals, or the total positive terminal and the total negative terminal of the battery assembly, are connected to a controller of a load by way of the battery control unit. 
       Citation List 
       [0004]    Patent Literature 
         [0005]    [PTL 1] JP-A-2009-289431 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, according to PTL 1, the total electrode terminals are positioned on an upper surface of the battery assembly, and a main circuit terminal pulled out of an interior of the battery control unit are positioned so as to be flush with the total electrode terminals. The total electrode terminals and the main circuit terminal are connected together by a linear extraction conductor having a linear shape. Therefore, there is a potential of a fluid, such as water, intruding into the battery control unit while running along the linear extrusion conductors. Specifically, there arises a problem, such as that will be described below. For instance, if a liquid, like water, that has condensed from moisture in the atmosphere for reasons of day-night air temperature difference within the busbar module containing a conductor of the battery main circuit intrudes into the battery control unit while running along the extraction conductor, the liquid will cause a failure. 
         [0007]    A problem that the present disclosure is to solve is to prevent a liquid, like water, from intruding into a battery control unit while running along an extraction conductor connected to a battery main circuit. 
       Solution to Problem 
       [0008]    In order to solve the problem, the present disclosure provides a battery pack including a battery assembly that includes a plurality of battery cells which are arranged while positive electrodes and negative electrodes of the battery cells are alternately adjoined each other; a busbar module that includes a plurality of conductors and an insulating member which holds the conductors, each of the conductor interconnecting the positive electrode and the negative electrode of each of the adjoining battery cells in the battery assembly; a battery control unit provided at an end portion of the battery assembly in a direction in which the battery cells are arranged; and an extraction conductor that connects a total electrode terminal connected to a total positive electrode or a total negative electrode of the battery assembly to a main circuit terminal of the battery control unit, wherein the extraction conductor has a water escape portion which is located below an imaginary line connecting the total electrode terminal to the main circuit terminal, and an upper end of the water escape portion is formed at a location that is lower than a lower end of the main circuit terminal. 
         [0009]    Since the present disclosure is configured as mentioned above, a fluid running along the extraction conductor, like water, falls down to the water escape portion by gravitation. However, the upper end of the water escape portion is situated below the lower end of the main circuit terminal, the fluid will not rise upwardly against gravity from the water escape portion toward the main circuit terminal of the battery control unit. As a consequence, the fluid running along the extraction conductor of the battery main circuit, like water, flows to a position that is lower than the main circuit terminal of the battery control unit, by virtue of the water escape portion of the extraction conductor. Hence, the fluid can be prevented from intruding into the battery control unit along the extraction conductor. 
         [0010]    In the present disclosure, for example, the extraction conductor has a first cutout portion which is located between the total electrode terminal and the main circuit terminal, the water escape portion has a second cutout portion so that the water escape portion is shaped in U shape, the second cutout portion being communicated with the first cut out portion, and a bottom of the second cutout portion is formed at a position lower than the lower end of the main circuit terminal. 
         [0011]    Also, for example, the total electrode terminal and the main circuit terminal are formed respectively on a side surface of the battery assembly and a side surface of the battery control unit on the same side. 
         [0012]    Also, for example, both ends of the extraction conductor are fastened respectively to the total electrode terminal and the main circuit terminal with a bolt or a nut. 
         [0013]    Also, for example, the extraction conductor is contained in a resin case, and an opening is formed in a bottom surface of the case. By this configuration, the liquid flowing downwardly after running along the extraction conductor can be discharged outside of the case. 
         [0014]    Furthermore, for example, the resin case has a rib to be held in the first cutout portion of the water escape portion. 
       Advantageous Effects of Invention 
       [0015]    The present disclosure makes it possible to prevent a liquid, like water, from intruding into a battery control unit while running along an extraction conductor connected to a battery main circuit. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a view showing a configuration of an extraction conductor that connects a total electrode terminal with a main circuit terminal of a battery control unit in a battery pack according to an embodiment of the present disclosure; 
           [0017]      FIG. 2  is a perspective view of a principal block of the battery pack shown in  FIG. 1  according to the embodiment; and 
           [0018]      FIG. 3  is a perspective external view of the entirety of the battery pack shown in  FIG. 1  according to the embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]      FIG. 3  shows a perspective structural view of a battery pack  1  of according to an embodiment of the present disclosure. The battery pack  1 , for instance, is used as a DC power supply for activating an electric motor of an electric vehicle. As illustrated, a plurality of thinly-formed battery cells  2 , like lithium batteries, are arranged as a battery assembly  3 . The plurality of battery cells  2  are alternately arranged in such a manner that positive electrodes and negative electrodes of the battery cells are adjoined each other. The positive electrodes and the negative electrodes of the adjoining battery cells  2  are connected in series by respective conductors  4  referred to as busbars. The number of serially-connected battery cells  2  of the battery assembly  3  is determined according to a desired DC voltage. The positive electrode (hereinafter called a “total positive electrode”) and the negative electrode (hereinafter called a “total negative electrode”) of the battery cells  2  disposed at both ends of the battery assembly  3  work as DC outputs of the battery pack  1 . 
         [0020]    When the number of serially-connected battery cells  2  is an odd number, the total positive electrode and the total negative electrode are situated at respective opposite sides of the battery assembly  3 . By contrast, when the number of serially-connected battery cells is an even number, the total positive electrode and the total negative electrode are situated at the same side of the battery assembly  3 . The present embodiment is an example in which the number of battery cells connected in series is an odd number. 
         [0021]    The plurality of conductors  4  that interconnect the adjoining positive and negative electrodes of the plurality of battery cells  2  are placed within a case formed from a resin member, or an insulating member, and that is formed as a busbar module  5 . Although unillustrated by the drawing, a columnar positive terminal or a columnar negative terminal projecting from a side surface of the battery cell is connected to the positive or negative electrode of each of the battery cells  2  in the present embodiment, and a screw thread is formed on an exterior surface of each of the columnar electrode terminals. A pair of holes are drilled in each of the conductors  4  in alignment with positions of the positive electrode terminal and the negative electrode terminal of the adjoining battery cells  2 . The respective electrode terminals are inserted into the corresponding holes of the conductor  4 , and nuts are screw-engaged with the respective screw threads of the respective electrode terminals, whereby the conductor  4  is fastened to the respective electrode terminals. Incidentally, the columnar electrode terminals of the total positive electrodes or the total negative electrodes of the battery cells  2  situated at both ends of the battery assembly  3  are not connected to the electrode terminals of the adjoining battery cells  2  and pulled outside by means of an extraction conductor. 
         [0022]    In the meantime, the battery pack  1  is equipped with a battery control unit  6  that is intended for controlling the battery assembly  3  and that is positioned at an end of the battery assembly  3  along a direction in which the battery cells  2  are arranged. Although unillustrated, the battery control unit  6  is formed from pieces of control equipment housed in a plastic case, for instance, a current sensor for detecting an electric current output from the battery pack  1 , a main contactor for turning on/off an output from the battery pack  1 , a precharge contactor for turning on the output from the battery pack  1  for a given period of time before turning on the main contactor; and the like. In the present embodiment, the battery control unit  6  is fastened to the total-negative-electrode-side battery cell  2  at the end of the battery assembly  3  with an end plate  7  sandwiched therebetween. The end plate  7  is a member that is situated at either end of the battery assembly  3  in order to bundle the plurality of arranged battery cells  2 . Although unillustrated, the battery assembly  3  may be contained in a housing, if needed. 
         [0023]    By reference to  FIG. 1  and  FIG. 2 , there is described a configuration of the extraction conductor, which is a characteristic part of the above-configured battery pack  1  of the present embodiment, for connecting the total negative electrode terminal to the main circuit terminal  12  of the battery control unit  6 .  FIG. 1  is a front view showing a surface of an end portion on which a total negative electrode terminal  11  is formed, where the battery control unit  6  is positioned, of the battery assembly  3  shown in  FIG. 3 . As illustrated, in the present embodiment, the total negative electrode terminal  11  connected to a total negative electrode is connected to one main circuit terminal  12  provided on the side surface of the battery control unit  6  by way of an extraction conductor  13 . In addition, an unillustrated total positive electrode terminal is connected to the other main circuit terminal  17  of the battery control unit  6  by way of a cable. 
         [0024]    The side surface of the battery assembly  3  where the total negative electrode terminal  11  is formed and the side surface of the battery control unit  6  are placed so as to become flush with each other. The total negative electrode terminal  11  connected to the total negative electrode of the battery assembly  3  corresponds to a columnar body whose outer periphery is threaded and that is provided so as to project from a side surface of the battery cell  2 . In addition, the main circuit terminal  12  of the battery control unit  6  is provided so as to project from the side surface of the battery control unit  6 , and a screw hole is drilled in a leading-end face of the main circuit terminal  12 . The total negative electrode terminal  11  and a leading end face of the main circuit terminal  12 , for instance, are positioned so as to become flush with each other. The extraction conductor  13  for connecting the total negative electrode terminal  11  to the main circuit terminal  12  is housed in a resin case  14 . An opening is formed at a position on a base plate  14   a  of the case  14  that corresponds to the total negative electrode terminal  11  and the leading end face of the main circuit terminal  12 . The extraction conductor  13  is thereby formed so as to be able to contact electrically to the total negative electrode terminal  11  and the leading-end face of the main circuit terminal  12  by way of the opening. 
         [0025]    The extraction conductor  13  is formed so as to have a straight conductor portion connecting the total negative electrode terminal  11  to the main circuit terminal  12  and a water escape portion  13   a  provided so as to be downwardly-extended from an arbitrary position on the straight conductor portion. A cutout  13   b  (first and second cutout portions) is formed in the water escape portion  13   a,  and the extraction conductor  13  including the water escape portion  13   a  is formed in a U-shape in conformance with the cutout  13   b.  A bottom of the cutout  13   b  is formed at a position that is lower than a lower end of the main circuit terminal  12 . Further, a hole into which the total negative electrode terminal  11  is to be inserted is drilled in a position at one end of the extraction conductor  13  corresponding to the total negative electrode terminal  11 . The total negative electrode terminal  11  is inserted into the hole of the extraction conductor  13 , and the total negative terminal  11  is screw-engaged with a nut  21 , thereby connecting the extraction conductor  13 . A hole into which a bolt  22  to be screw-engaged with a screw hole drilled in the main circuit terminal  12  is drilled at a position on the other end of the extraction conductor  13  corresponding to the main circuit terminal  12 . The bolt  22  is screw-engaged into the screw hole of the main circuit terminal  12 , thereby connecting the extraction conductor  13 . A terminal connected to an end of an unillustrated cable is fastened to the main circuit terminal  17  by means of the bolt  22  being screw-engaged into the screw hole of the main circuit terminal  17  by way of the bolt hole of the terminal. 
         [0026]    An outer wall  14   b  surrounding an outer circumference of the extraction conductor  13  is formed on the base plate  14   a  of the case  14 , and a portion of the outer wall  14   b  situated at a position corresponding to the bottom of the water escape portion  13   a  of the extraction conductor  13  is cut out, thereby forming an opening  14   c.  A plurality of claws  16  are provided on an inner surface side of the outer wall  14   b,  to thus hold the extraction conductor  13  mounted on the case  14 . Further, a rib  14   d  to be inserted into the cutout  13   b  of the extraction conductor  13  is formed on the base plate  14   a  in a projecting manner. Although unillustrated, engagement projections  14   e  are accordingly provided on an exterior circumference of the outer wall  14   b  in the present embodiment, whereby a cover is to be attached to the case  14 . 
         [0027]    One voltage detection terminal  24  for detecting a voltage of each of the battery cells  2  and the extraction conductor  13  are jointly fastened and connected to the total negative electrode terminal  11 . A voltage detection line  25  is pressure-bonded to the voltage detection terminal  24 , whereby the voltage detection terminal  24  is connected to an unillustrated controller of the battery pack  1 . 
         [0028]    As mentioned above, in the present embodiment, a liquid, like water, intruded into the case  14  after running along the extraction conductor  13  falls on the downwardly-extending water escape portion  13   a  by gravitation. Since a bottom of the cutout  13   b  is situated at a position lower than the lower end of the main circuit terminal  12 , the liquid will not rise from the water escape portion  13   a  toward the main circuit terminal  12  against gravity. Consequently, the liquid, such as water, intruded into the case  14  can be prevented from intruding into the battery control unit  6  while running along the extraction conductor  13 . As a consequence, a failure, which would otherwise occur as a result of a liquid, like water, intruding into the battery control unit  6 , can be prevented. 
         [0029]    According to the present embodiment, the opening  14   c  is formed in the bottom surface of the case  14 , so that the liquid falling down while running along the extraction conductor  13  can be discharged outside the case. Furthermore, in this case, the rib  14   d  conforming to the shape of the cutout  13   b  of the water escape portion  13   a  is formed so as to project from the base plate  14   a,  whereby a path along which a liquid like water will run directly to the main circuit terminal  12  along the extraction conductor  13  is blocked. Hence, intrusion of a liquid into the battery control unit  6  can be prevented without fail. 
         [0030]    Although the case  14  of the embodiment can be formed integrally with the resin case of the busbar module  5 , the busbar module  5  is not limited to this configuration. The busbar module  5  and the case  14  can be separately formed. 
         [0031]    The present application is based on Japanese Patent Application No. 2011-165126 filed on Jul. 28, 2011, the contents of which are incorporated herein by reference. 
       INDUSTRIAL APPLICABILITY 
       [0032]    By the above configuration, a battery pack in which a liquid, like water, is prevented from intruding into a battery control unit while running along an extraction conductor connected to a battery main circuit, can be achieved. 
       REFERENCE SIGNS LIST 
       [0033]      1  battery pack 
         [0034]      2  battery cell 
         [0035]      3  battery assembly 
         [0036]      4  conductor 
         [0037]      5  busbar module 
         [0038]      6  battery control unit 
         [0039]      11  total negative terminal 
         [0040]      12  main circuit terminal 
         [0041]      13  extraction conductor 
         [0042]      13   a  water escape portion 
         [0043]      13   b  cutout portion 
         [0044]      14  case 
         [0045]      14   a  base plate 
         [0046]      14   b  exterior wall 
         [0047]      14   c  opening 
         [0048]      14   d  rib 
         [0049]      14   e  engagement projection 
         [0050]      16  claw