Abstract:
A battery module is provided in which a signal line is prevented from the influence of noise caused by an internal current output line. 
     A battery module includes: a plurality of cells  100 ; a current conduction member  34  electrically connecting electrode terminals of the plurality of cells; and a signal line  50  configured to measure capacitance of the plurality of cells, wherein the current conduction member includes a parallel section including two members which are opposite in direction of a current flowing therethrough and are arranged substantially parallel to each other, and a connection section electrically connecting the two members at one end of the parallel section, and the signal line is arranged nearly equidistant from the two members, and extends substantially parallel to the two members to approach the connection section.

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2011/006411, filed on Nov. 17, 2011, which in turn claims the benefit of Japanese Application No. 2010-266777, filed on Nov. 30, 2010, the disclosures of which Applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     The present invention relates to battery modules. 
     BACKGROUND ART 
     Battery modules including a plurality of cells accommodated in a case to be capable of outputting a predetermined voltage and capacitance are widely used as power supplies of various devices, vehicles, etc. and household power supplies. Specifically, the technique of forming blocks by connecting general-purpose secondary batteries in parallel and/or in series to be capable of outputting a predetermined voltage and capacitance and being charged, and combining the battery blocks in many ways to be applicable to various applications is beginning to be used. In the block formation technique, the performance of the batteries accommodated in the battery blocks is enhanced to reduce the size and the weight of the battery blocks themselves. Thus, the block formation technique has various advantages such as improvement of workability in assembling battery modules, and improvement of flexibility in mounting the battery modules in areas of limited space, such as a vehicle. 
     It is required for the cells included in the battery modules as described above to have substantially the same capacitance (dischargeable electric capacitance at a certain point in time). This is because if the cells exhibit variations in capacitance, certain cells are subjected to a high charge/discharge load compared to the other cells, so that the certain cells degrade earlier, which results in reduced life of the battery modules themselves. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Publication No. H07-321429 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     Prevention of the above-described variations in capacitance of the cells has not been particularly studied. In particular, when total power supply capacitance is very large, such as the case of power supplies of electric vehicles, combining a large number of cells with each other to form a battery module has been considered, but a specific method for preventing the variations in capacitance of the cells is currently under study. 
     In one of such studies, it is considered to monitor the capacitance of the cells. In order to monitor the capacitance of the cells, a signal line for the monitoring has to be provided in the battery module. 
     However, inventors of the present application found a publicly unknown problem where a current output line is disposed in the battery module, noise caused by the current output line through which a large current flows may influence the signal line, and erroneous operation may occur when the variations in capacitance of the cells are controlled based on a signal from the signal line. 
     In view of the foregoing, the present invention was devised. It is an objective of the present invention to provide a battery module in which a signal line is prevented from the influence of noise caused by a current output line in the battery module. 
     Solution to the Problem 
     A first battery module of the present invention includes: a plurality of cells; a current conduction member electrically connecting electrode terminals of the plurality of cells; and a signal line, wherein the current conduction member includes a parallel section including two members which are opposite in direction of a current flowing therethrough, and are arranged substantially parallel to each other, and a connection section electrically connecting the two members at one end of the parallel section, the signal line is arranged nearly equidistant from the two members, and is arranged substantially parallel to the two members, and one end of the signal line is arranged in a position away from the connection section in a direction toward the other end of the parallel section. 
     A second battery module of the present invention is a battery module including a plurality of cells which are columnar secondary batteries, and are accommodated in a metal case, the battery module including: a plurality of battery blocks connected to each other in series, wherein a first electrode terminal and a second electrode terminal are arranged respectively on an upper surface and a lower surface of each of the columnar cells, the battery blocks each include the plurality of cells connected to each other in parallel, where the cells are aligned with side surfaces of the cells being adjacent to each other to align the upper surfaces on a same side, and the battery blocks adjacent to each other are connected via a series connection member, the battery blocks each include a first connection member which is arranged to face the upper surfaces of the cells to electrically connect the first electrode terminals to each other, and a second connection member which is arranged to face the lower surfaces of the cells to electrically connect the second electrode terminals to each other, the plurality of battery blocks are grouped into two groups in each of which the battery blocks are arranged with the first connection members being aligned in a line, the groups are arranged to face each other, and are electrically connected to each other at ends of the two groups via a connection section on one side, a signal line is arranged nearly equidistant from the first connection members of the two groups facing each other, and one end of the signal line is arranged at a position away from the connection section in a direction toward ends of the first connection members on the other side. 
     In the above-described two configurations, the signal line does not cross a current output line of the battery module. 
     ADVANTAGES OF THE INVENTION 
     The signal line of the battery module is disposed between the two members included in the parallel section of the current conduction member, and does not cross the current output line, so that superimposition of noise on the signal line can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view schematically illustrating a configuration of a cell used in a battery block of an embodiment. 
         FIG. 2  is a cross-sectional view schematically illustrating a configuration of the battery block of the embodiment. 
         FIG. 3  is a view illustrating a configuration of a battery module of the embodiment. 
         FIG. 4  is a cross-sectional view schematically illustrating the battery module taken along the line A-A of  FIG. 3 , where the battery module is covered with a lid. 
         FIG. 5  is a view illustrating a flow of a current in the battery module. 
         FIG. 6  is a view schematically illustrating a configuration of a cell used in a battery block of another embodiment. 
         FIG. 7  is a view schematically illustrating a configuration of the battery block of the another embodiment. 
         FIG. 8  is a view illustrating a configuration of a battery module of the another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, like reference characters have been used to designate elements having substantially the same functions for the sake of brevity of description. 
     (First Embodiment) 
     &lt;Cell&gt; 
       FIG. 1  is a cross-sectional view schematically illustrating a configuration of a battery  100  used in a battery block of a first embodiment. Note that the battery used in the battery block of the present embodiment may be a battery which can also be used alone as a power supply of portable electronic devices such as lap top computers (hereinafter, batteries used in a battery block are referred to as “cells”). In this case, a high-performance general-purpose battery can be used as the cell in the battery block, and thus, performance enhancement and const reduction of the battery block can easily be made. 
     As the cell  100  used in the battery block of the present embodiment, for example, a lithium ion secondary battery in the shape of a cylindrical column as illustrated in  FIG. 1  may be used. The lithium ion secondary battery has a general configuration, and includes a safety mechanism to release gas outside the battery when the pressure in the battery is increased due to the occurrence of an internal short-circuit, or the like. Note that the cell  100  is an example of batteries useable in the present embodiment, and thus is not intended to limit batteries useable in the present embodiment. For example, rectangular lithium ion secondary batteries may be used as the cells of the present embodiment. With reference to  FIG. 1 , a specific configuration of the cell  100  will be described below. 
     As illustrated in  FIG. 1 , an electrode group  4  formed by winding a positive electrode  2  and a negative electrode  1  with a separator  3  interposed between the positive electrode  2  and the negative electrode  1  is accommodated in a cell case  7  together with a nonaqueous electrolyte. Part of the cell case  7  in which the electrode group  4  including the positive electrode  2  and the negative electrode  1  serving as power-generating elements is accommodated can be referred to as a main body section of the cell. Insulating plates  9 ,  10  are disposed above and under the electrode group  4 . The positive electrode  2  is joined to a filter  12  via a positive electrode lead  5 , and the negative electrode  1  is joined to a bottom of the cell case  7  via a negative electrode lead  6 , the bottom also serving as a negative electrode terminal (second electrode terminal). 
     The filter  12  is connected to an inner cap  13 , and a raised section of the inner cap  13  is joined to a metal valve plate  14 . Moreover, the valve plate  14  is connected to a terminal plate  8  also serving as a positive electrode terminal (first electrode terminal). The terminal plate  8 , the valve plate  14 , the inner cap  13 , and the filter  12  together seal an opening of the cell case  7  via a gasket  11 . In  FIG. 1 , the positive electrode terminal is arranged on an upper surface of the cylindrical column, and the negative electrode terminal serves as a lower surface of the cylindrical column. 
     When the pressure in the cell  100  is increased due to an internal short-circuit, or the like formed in the cell  100 , the valve body  14  expands toward the terminal plate  8 , and if the joint between the inner cap  13  and the valve body  14  is released, a current path is interrupted. When the pressure in the cell  100  further increases, the valve body  14  ruptures. Thus, gas generated in the cell  100  is released outside via a through hole  12   a  of the filter  12 , a through hole  13   a  of the inner cap  13 , the ruptured part of the valve body  14 , and an opening portion  8   a  of the terminal plate  8 . 
     Note that the safety mechanism to release the gas generated in the cell  100  to the outside is not limited to the structure illustrated in  FIG. 1 , and may have other structures. 
     &lt;Battery Block&gt; 
       FIG. 2  is a cross-sectional view schematically illustrating a configuration of a battery block  200  of the present embodiment. In the present embodiment, the battery block  200  is minimum unit of a set including multiple ones of the cell  100 , and the cells  100  in one battery block  200  are connected to each other in parallel. 
     In  FIG. 2 , a cross section of the plurality of cells  100  aligned and connected to each other in parallel is schematically illustrated (cross sections of the cells are not hatched for clarity), and the battery block  200  has a configuration in which the plurality of cells  100  are accommodated in a container  20 . 
     The main body sections of the cells  100  are inserted into cylindrical through holes formed in a cooling block  24  accommodated in the container  20 , and the cells  100  are aligned so that the main body sections of the cells  100  (side surfaces of the cylindrical columns) are adjacent to each other. Moreover, as illustrated in  FIG. 1 , each cell  100  includes the opening portion  8   a  through which the gas generated in the cell  100  is released to the outside. The cells  100  are aligned so that the opening portions  8   a  face the same direction (face upward in  FIG. 2 ) in the battery block  200 . 
     A first connection member  34  is made of a metal plate, and connects the positive electrode terminals of the cells  100  to each other. A second connection member  36  made of a metal plate is joined to the other terminals of the plurality of cells  100  (the negative electrode terminals in the present embodiment) exposed at lower openings of the through holes of the cooling block  24 , and the negative electrode terminals are connected to each other via the second connection member  36 . The first connection member  34  and the second connection member  36  are included in a current conduction member. 
     The first connection member  34  is electrically connected to a series connection member  35  disposed over an outer surface of a left side wall of the container  20 . When multiple ones of the battery block  200  are aligned, the series connection member  35  is brought into contact with and is electrically connected to an end  37  of a second connection member  36  of an adjacent battery block  200 , so that the battery blocks  200  adjacent to each other are electrically connected in series. 
     Note that a flat plate  30  is disposed in intimate contact with one end of each cell  100  (an end on a side closer to the positive electrode terminal  8  in the present embodiment), so that an accommodation section  31  is hermetically sealed with the flat plate  30 . 
     &lt;Battery Module&gt; 
       FIG. 3  is a top view schematically illustrating a battery module  300  according to the present embodiment without an upper lid of a metal case  40 . The battery module  300  includes an even number of battery blocks  200 ,  200 , . . . (six battery blocks in the present embodiment) accommodated in the case  40 . In the figure, two battery blocks  200  in the vertical direction form a pair, and three pairs are aligned in the horizontal direction. Therefore, the direction in which the three pairs are aligned, that is, the horizontal direction in the figure, is hereinafter referred to as a longitudinal direction of the battery module  300 . In other words, three battery blocks  200 ,  200 ,  200  aligned in the longitudinal direction of the battery module  300  form a group, and two groups are aligned in parallel. Moreover, the battery module  300  itself is substantially a rectangular parallelepiped. 
     As illustrated in  FIG. 3 , the first connection members  34 ,  34 ,  34  of the three battery blocks  200 ,  200 ,  200  of the upper group and the first connection members  34 ,  34 ,  34  of the three battery blocks  200 ,  200 ,  200  of the lower group face each other, and extend parallel to the longitudinal direction of the battery module  300 . 
     The first connection members  34 ,  34 ,  34  of these two groups form a parallel section of the current conduction member. Right ends of the first connection members  34 ,  34  (two members) of the pair of battery blocks  200 ,  200  on a rightmost side of the figure are electrically connected to each other via a connection section  46  disposed on the rightmost side. The pair of first connection members  34 ,  34  facing each other are arranged substantially in parallel to each other, and are opposite in direction of a current flowing therethrough. 
     Moreover, output terminals  43 ,  45  are provided on a left side surface of the battery module  300 . The term “substantially parallel” here does not mean “parallel” in a strictly mathematical sense, but may include a difference of about 10° due to design conditions or variations in assembly. Moreover, adjacent first connection members  34 ,  34 ,  34  are not connected to each other via adjacent sections thereof. However, the first connection members  34 ,  34 ,  34  of the upper group are aligned in a line, the first connection members  34 ,  34 ,  34  of the lower group are aligned in a line, and the lines are parallel to each other. Note that the lines are not necessarily parallel in a strictly mathematical sense, but may include a difference of about 10° due to design conditions or variations in assembly. 
     In  FIG. 5 , a flow of a current in the battery module  300  is schematically illustrated.  FIG. 5  is a view schematically illustrating three battery blocks  200 ,  200 ,  200  of the lower group of  FIG. 3  without the lid. The current flows from the battery block  200  on the right to the left. The flow of the current is indicated by arrows. Specifically, a current flows from the second connection member  36  facing the negative electrodes in the rightmost battery block  200  (one of the two members) through the cells  100  to the first connection member  34  facing the positive electrodes. Then, the current flows from the first connection member  34  through the series connection member  35  arranged on the left of the rightmost battery block  200  from top to bottom. A lower end of the series connection member  35  is electrically connected to the second connection member  36  of the adjacent battery block  200  on the left of the series connection member  35 . The current flows through the second connection member  36  of the battery block  200  arranged in the middle. Thereafter, the current flows likewise from the first connection member  34  through the series connection member  35  of the middle battery block  200 , and further flows through the battery block  200  on a leftmost side. 
     As illustrated in  FIG. 3 , in the battery module  300 , a current flows from a left end Y of the first connection members  34 ,  34 ,  34  of the upper group to the right, flows through the connection section  46 , and then flows from a right end X of the first connection members  34 ,  34 ,  34  of the lower group to the left. Thus, the upper group and the lower group are opposite in direction of a current flowing through the first connection members  34 ,  34 ,  34 . The first connection members  34 ,  34 ,  34  of the upper group and the first connection members  34 ,  34 ,  34  of the lower group form the parallel section, right ends of the first connection members on the rightmost side (ends of the two members) are connected to each other via the connection section  46 , and the current conduction member including the parallel section and the connection section  46  has a U-shaped structure. 
       FIG. 4  is a cross-sectional view schematically illustrating the battery module  300  taken along the line A-A of  FIG. 3 , where the battery module  300  is covered with a lid. Note that the cells  100  are not hatched. 
     Signal lines  50  extend from a left end of the battery module  300  (a left end of the parallel section) to approach the connection section  46  in the longitudinal direction, and are parallel to the first connection members  34 ,  34 . In this case also, it is not required that the signal lines  50  are parallel to the first connection members  34 ,  34  in the strict sense. The signal lines  50  extend as a collective line  48  from the left end of the battery module  300  to the outside, and a connector  49  is attached to an end of the collective line  48 . The connector  49  is connected to a control unit which is not shown. In  FIG. 3 , the signal lines  50  are hidden behind the container  20 , and are not illustrated, but extend from a left end of the case  40  to approach the connection section  46 . That is, the signal lines  50  do not reach the connection section  46 . Ends of the signal lines  50  facing the connection section  46  are arranged in a position away from the connection section  46 , and a direction away from the connection section  46  is a direction from the connection section  46  toward the left ends (the other ends) of the first connection members  34 ,  34 ,  34  included in the parallel section. 
     Through the signal lines  50 , voltage signals of the battery blocks  200  are sent to the control unit. Thus, the voltages, the capacitance, etc. of the cells  100  are measured. Therefore, if there is a cell  100  which is in an abnormal state and has a voltage or capacitance different from that of the other cells  100 , the cell  100  in the abnormal state can be located, and it is possible to notify a user or a responsible person of the battery module  300  of the occurrence of the abnormal state. 
     As illustrated in  FIG. 4 , the signal lines  50  are disposed nearly equidistant from and substantially parallel to the upper first connection member  34  and the lower first connection member  34 . Note that the cross sectional view taken along the lien A-A illustrates the pair of battery blocks  200 ,  200  in the middle, but any pair of battery blocks  200 ,  200  has the same cross-sectional view. Here, the first connection member  34  is a plate-like member, and thus the distance between the first connection member  34  and the signal lines  50  is a distance between the center in a width direction of the first connection member  34  and the signal lines  50 . A current flowing through the upper first connection member  34  and a current flowing through the lower first connection member  34  are at the same level, but flowing directions of the currents are opposite. Between the upper and lower first connection members  34 ,  34 , magnetic fluxes cancel each other due to the currents in opposite directions so that high frequencies are reduced. This reduces noise on the signal lines  50  disposed nearly equidistant from the upper and lower first connection members  34 ,  34 . Note that even when the signal lines  50  are not disposed equidistant from the upper first connection member  34  and the lower first connection member  34  in the strict sense, the noise on the signal lines  50  is reduced. 
     Moreover, the case  40  is made of metal, and is connected to ground, so that the case  40  serves as a shield, and protects the signal lines  50  from external noise. Moreover, between the adjacent members in the battery module  300 , for example, between the case  40  and the container  20 , between the container  20  and the cooling block  24 , etc., portions illustrated to be intimately in contact with each other in  FIGS. 2, 4  are formed to be intimately in contact with each other without a gap to ease entire temperature control. As described above, there is almost no gap in the battery module  300 , and thus external noise hardly enters the battery module  300 . 
     The signal lines  50  of the present embodiment are disposed between and equidistant from the upper and lower first connection members  34 ,  34  included in the parallel section serving as an output current line of the battery module  300  as described above, and thus noise is reduced. Moreover, the signal lines  50  extend only to approach the connection section  46 , and thus the output current line does not cross the signal lines  50 . Also in this aspect, the signal lines  50  are not influenced by the output current line. Moreover, the metal case  40  also serves as a shield, and thus the signal lines  50  are protected from noise in multiple ways. 
     (Second Embodiment) 
     In a second embodiment, a so-called laminated secondary battery formed by hermetically sealing a wound electrode group and a nonaqueous electrolyte with a layered film illustrated in  FIG. 6  is used as a cell  110 , a battery block  210  of  FIG. 7  includes multiple ones of the cell  110 , and a battery module  310  of  FIG. 8  includes multiple ones of the battery block  210 . Each cell  110  has a structure in which a positive electrode terminal  18  and a negative electrode terminal  17  are leads made of metal thin pieces, and both the leads protrude from an upper surface of the cell  110 . Ten such cells  110  are aligned and accommodated in a container  20 ′ so that the positive electrode terminals  18  and the negative electrode terminals  17  protrude upwardly, thereby forming the battery block  210 . In  FIG. 7 , a lid of the container  20 ′ is omitted. In a state in which the container  20 ′ is covered with the lid, the cells  110  in the container  20 ′ are connected in parallel, and a positive electrode terminal section  118  and a negative electrode terminal section  117  are provided on the lid. 
     As illustrated in  FIG. 8 , the positive electrode terminal section  118  and the negative electrode terminal section  117  are provided to different ends of the battery block  210 . In the battery module  310 , two rows of battery blocks  210  are accommodated in a case  40 ′, where the number of battery blocks  210  per row is three. The battery blocks  210 ,  210  in the row are aligned with their terminal sections having opposite polarities being adjacent to each other, and the terminal sections are electrically connected to each other via connection members  34   a ,  34   b ,  34   c ,  34   d . Moreover, ends on one side of the rows are connected to each other via a connection section  146 , and the ends on the other side of the rows are connected to output terminals  143 ,  145 . 
     In the battery module  310 , the connection members  34   a  and  34   d  in the two rows are parallel to each other and are arranged to face each other, and the connection members  34   b  and  34   c  in the two rows are parallel to each other and are arranged to face each other. The connection members  34   a  and  34   d  facing each other are opposite in direction of a current flowing therethrough, and the connection members  34   b  and  34   c  facing each other are opposite in direction of a current flowing therethrough. Signal lines  50 ,  50  are disposed nearly equidistant both from the connection members  34   a  and  34   d  facing each other and from the connection members  34   b  and  34   c  facing each other. Thus, magnetic fields generated by currents flowing through the connection member  34   a  and  34   d , and the connection members  34   b  and  34   c  cancel each other, so that superimposition of noise on electric signals sent through the signal lines  50 ,  50  is significantly reduced. 
     (Other Embodiments) 
     The embodiments described above are examples of the present invention, and are not intended to limit the present invention. The cell may be any type, and may have any structure and any shape as long as the cell is a secondary battery. The number of signal lines may be changed. The configuration and structure of the battery block are not limited to the above description. In the battery module, the number and arrangement of the battery blocks may be changed, or a temperature control member or other members may be installed in the battery module. The signal line may include a line for sending a signal representing the temperature in the battery module to the control unit. Alternatively, the signal line may include a line for sending a command signal from the control unit to the battery module. The signal line may be arranged in any positions as long as the signal line is disposed equidistant from the upper and lower first connection members. 
     INDUSTRIAL APPLICABILITY 
     As described above, the battery module according to the present invention has a structure in which noise is not superimposed on the signal line, and is useful as power supplies for mechanical products such as vehicles, household power supplies, or the like. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1  Negative Electrode 
           2  Positive Electrode 
           4  Electrode Group 
           7  Cell Case (Negative Electrode Terminal) 
           8  Terminal Plate (Positive Electrode Terminal) 
           17  Negative Electrode Terminal 
           18  Positive Electrode Terminal 
           34  First Connection Member 
           34   a  Connection Member 
           34   b  Connection Member 
           34   c  Connection Member 
           34   d  Connection Member 
           36  Second Connection Member 
           40  Case 
           40 ′ Case 
           46  Connection Section 
           50  Signal Line 
           100  Cell 
           110  Cell 
           146  Connection Section 
           200  Battery Block 
           210  Battery Block 
           300  Battery Module 
           310  Battery Module