Abstract:
The battery of the present invention is provided with: a case having through holes; external terminals fixed in the through holes in the case in a state with part thereof protruding to the outside of the case; insulating members interposed between the case and the external terminals; flanged portions located at the peripheral edges of the through holes in the case protruding outward of the case; and reinforcing members that are disposed at the outer periphery of the flanged portions and reinforce the strength on the outer peripheral side of the flanged portions. The battery is such that the external terminals are secured in the through holes by making the flanged portions undergo plastic deformation by pressing and generating a sticking force between the external terminals and the through holes by the parts of the flanged portions that have undergone plastic deformation. The external terminals are provided with a first projection that is formed more to the outside of the case than the location receiving the sticking force due to the pressing of the flanged portion and protrudes to the outside in the radial direction from the outer peripheral surface of the external terminal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a battery, particularly to a technique of fixing an external terminal to a case. 
       BACKGROUND ART 
       [0002]    The case of the battery contains a power generating element. The external terminals (positive and negative terminals) are fixed to the outside of the case, projecting outward through the case. The external terminals are electrically connected to the power generating element, and the electric power is transmitted through the terminals between inside and outside of the battery. 
         [0003]    If the battery is a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery, the contamination of water into the battery has an influence on the battery performance, so that the high sealing property is needed. 
         [0004]    Moreover, at the fitted portions of the external terminals into the case, it is required to keep the fitting property of the terminals not to slip out from the case, the sealing property for preventing from leakage of the electrolytes contained in the case and of gases generated in the battery, and the insulating property between the terminals and the case. In short, the sufficient sealing performance between the case and the terminals is required. 
         [0005]    JP 2005-302625 A discloses a battery having an electric terminal projecting from a lid of the case, in which an insulating member is arranged between the lid and terminal and the lid is provided with a flanged portion standing out around the insulating member. The flanged portion is pressed and deformed from the direction perpendicular to the flanged portion, whereby the external terminal is press-fitted to the lid. 
         [0006]    Unfortunately, according to the use of the battery, a temperature cycle including heating and cooling is repeated, whereby the press-fitted portion may be loosened to return the former shape and the sealing property may be degraded. 
       CITATION LIST 
     Patent Literature 
       [0007]    PTL 1: JP 2005-302625 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    The objective of the present invention is to provide a battery including a case and external terminals fitted to the case with projecting therefrom, provided with high sealing property at the fitted portion between the case and terminals. 
       Technical Solutions 
       [0009]    The first embodiment of the present invention is a battery that includes: a case provided with through holes; external terminals fixed in the through holes of the case, projecting outward; insulating members interposed between the case and the external terminals; flanged portions located at the periphery of the through holes, standing out from the case; and reinforcing members located around the flanged portions to reinforce strength thereof in radial direction. The flanged portions are pressed and plastically deformed so as to generate a sticking force between the external terminals and the through holes by the plastically deformed portion, whereby the external terminals are fixed to the through holes, and each of the external terminals includes a first projection formed at outer side of the portion Where the sticking force acts, projecting radially outward from the outside of the external terminal. 
         [0010]    In the preferable embodiment, each of the external terminals includes a groove formed at the portion where the sticking force acts, and the first projection is located outer side of the groove, and each of the external terminals further includes a second projection formed at inner side of the groove, projecting radially outward from the outside of the external terminal. 
         [0011]    The first and second projections are advantageously formed continuously to the edges of the groove. 
         [0012]    In the advantageous embodiment, the battery further includes current collecting terminals connecting a power generating element and the external terminals, each of the current collecting terminals connected to the inner end of the external terminal and extending beyond the outer periphery of the external terminal, and each of the current collecting terminals holds the inside of the insulating member with the first or second projection. 
       Advantageous Effects of Invention 
       [0013]    The battery according to the present invention is provided with high sealing property at the fitted portion between the case and terminal. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  depicts a battery. 
           [0015]      FIG. 2  is an enlarged section view of a fitted portion between a case and an external terminal. 
           [0016]      FIG. 3  depicts the external terminal. 
           [0017]      FIG. 4  shows the situation where the axial force is acted on the terminal. 
           [0018]      FIG. 5  shows the situation where the radial force is acted on the terminal. 
           [0019]      FIG. 6  illustrates an alternative projection of the external terminal. 
           [0020]      FIG. 7  shows actions of the projection and a current collecting terminal where the projection of the external terminal and the current collecting terminal hold a part of the insulating member, (a) shows the case that the outer force acts on the external terminal in the axial direction, and (b) shows the case that the outer force acts on the external terminal in the radial direction. 
           [0021]      FIG. 8  depicts an alternative battery, in which the external terminal includes two projections formed at the upper and lower ends of the groove. 
           [0022]      FIG. 9  shows the action of the projections where the outer force acts on the external terminal, (a) shows the case that the outer force acts in the axial direction, and (b) shows the case that the outer force acts in the radial direction. 
           [0023]      FIG. 10  illustrates other battery, in which the external terminal includes two projections, and the projection disposed at the side of the current collecting terminal and the collecting terminal hold the part of the insulating member. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Referring to  FIG. 1 , the structure of a battery  10  as an embodiment of the present invention is explained below. The battery  10  is a lithium ion secondary battery. 
         [0025]    The battery  10  includes a power generating element  20 , a case  30  containing the power generating element  20 , two external terminals  40  projecting outward from the case  30 , and two insulating members  50  interposed between the case  30  and the terminals  40 . 
         [0026]    The power generating element  20  is an electrode body with electrolyte impregnation, which is formed by laminating or winding a positive electrode, a negative electrode and a separator. When charging or discharging the battery  10 , a chemical reaction occurs in the element  20  (in detail, the ion moves between the positive and negative electrodes via the electrolytes), and thus the electric current is generated. 
         [0027]    The case  30  is a square can, including a box  31  and a lid  32 . The box  31  has a closed-end shape and an opening at one side, and contains the element  20 . The lid  32  has a shape in accordance with the opening of the box  31 , and covers the opening of the box  31 . The lid is fixed to the box  31 . 
         [0028]    The external terminals  40  are located at the outside of the lid  32  extending outward of the battery  10 . Each of the terminals  40  is connected to the positive electrode or negative electrode of the element  20  via a current collecting terminal  45 . The external terminals  40  and the current collecting terminals  45  work as current paths for taking out the electric power from the element  20  or taking in the electric power from outside. 
         [0029]    Each of the current collecting terminals  45  is connected to the positive electrode plate or negative electrode plate of the element  20 . The material for the collecting terminal  45  may be aluminum for the positive electrode or cupper for the negative electrode. 
         [0030]    The external terminal  40  has a thread portion formed by thread rolling at the projected part from the battery  10 . if the battery  10  is actually used, the thread portion of the external terminal  40  is fixed to a bus bar or a connecting terminal of the external device. While fastening, a fastening torque and an axial force due to the bolting act on the external terminal  40 , so that the external terminal  40  is preferably made of high strength material such as steel. 
         [0031]    The external terminals  40  are fixed in the lid  32  interposed with the insulating members  50 , respectively. The insulating member  50  surrounds the external terminal  40 , thereby insulating between the case  30  and the external terminal  40 . 
         [0032]    The insulating member  50  is preferably made of material with fine high-temperature creep characteristic, or the material having the long creep property against the temperature cycle of the battery  10 , e.g. PEEK (poly (etheretherketone)), PPS (Poly Phenylene Sulfide Resin). 
         [0033]    Referring to  FIG. 2 , the fixing structure between the case  30  and the external terminal  40  is described below. 
         [0034]    As shown in  FIG. 2(   a ), the case  30  has a pair of through holes  33  through which the terminals  40  penetrate. The case is provided with flanged portions  34  projecting outward of the case each of which is formed at the periphery of the through hole  33 . 
         [0035]    The through hole  33  has a predetermined diameter and drilled in the thickness direction of the case  30 . 
         [0036]    The flanged portion  34  is formed at the edge of the hole  33  and stands out from the case  30  from inside to outside thereof, thereby formed as a thick portion. The part of the case  30  (around the hole  33 ) is plastically deformed to form the flanged portion  34 , which is formed by burring processing, deep drawing, damming, or the combination of these methods. 
         [0037]    The flanged portion  34  is surrounded by a reinforcing ring  35 . 
         [0038]    The reinforcing ring  35  is made of metal material having higher strength than the material of the ease  30  (lid  32 ), such as steel, and reinforces the flanged portion  34  against the force in the radial direction. The inner diameter of the reinforcing ring  35  is substantially same as the outer diameter of the flanged portion  34 . 
         [0039]    The insulating member  50  seals the battery  10  as well as insulates between the case  30  and the external terminal  40 . 
         [0040]    As depicted in  FIG. 2(   b ), the external terminal  40  is arranged in the through hole  33  surrounded by the insulating member  50 , and the inside portion of the projected end of the flanged portion  34  is pressed and deformed, whereby the inside part of the flanged portion  34  is extended radially inwardly. Thus, an extended portion  34   a  is formed inward in the radial direction. 
         [0041]    The flanged portion  34  is surrounded by the reinforcing ring  35  that has higher strength than the flanged portion, and therefore, the pressure during the deformation is prevented from loosening and the extended portion  34   a  is formed such that the part of the flanged portion is expanded inwardly, i.e., toward the external terminal  40 . 
         [0042]    The inwardly extended portion  34   a  compresses the insulating member  50 , thereby applying the surface pressure to the insulating member  50 . In the insulating member  50 , the area where the surface pressure from the insulating member  50  acts is elastically deformed inward, and the elastic deformation results in the surface pressure acted on the external terminal  40 . 
         [0043]    As described above, the projected end of the flanged portion  34  is pressed from the upper side and deformed by the pressing, and the extended portion  34   a  is formed inwardly, whereby the surface pressure received from the extended portion  34   a  is transmitted to the external terminal  40  via the insulating member  50 . Due to the surface pressure, the external terminal  40  is compressed and fitted in the through hole  33  of the lid  32 . 
         [0044]    The extended portion  34   a  is plastically deformed in the direction perpendicular to the pressing direction to fasten the insulating member  50  and the external terminal  40 . Therefore, among the case  30 , the insulating member  50  and the external terminal  40 , there occur strong surface pressure and friction force. As the result of that, the temperature cycle accompanied with the usage of the battery  10  does not influence on the deformation (return) of the extended portion  34   a,  thereby preventing the loosening of the fixing portion. 
         [0045]    The external terminal  40  includes a groove  41  to receive the surface pressure from the flanged portion  34 . The groove  41  is a semicircular (or the shape with edge lines such as a semioval) recess formed wholly along the outer periphery of the terminal  40 , and has a predetermined groove width. 
         [0046]    The insulating member  50  elastically deforms as above-described, so that the insulating member is partially moved into the groove  41  and sticks the edge lines of the groove  41 . Thus, the insulating member  50  is attached firmly to the terminal  40 , thereby improving the sealing property. 
         [0047]    Noted that when pressing the end of the flanged portion  34 , the lower dead end of the pressing is advantageously located substantially same as the outer edge of the groove  41 . Due to such structure, the edge line of the groove  41  is located where the plastic deformation amount of the extended portion  34   a  is the largest, and, the bonding strength between the insulating member  50  and the terminal  40  can be efficiently enhanced. 
         [0048]    As shown in  FIG. 3 , the external terminal  40  is formed with a projection  42 . The projection  42  is disposed at the outer periphery of the terminal  40  so as to project radially outwardly. The projection  42  is located upper side of the edge line of the groove  41  as the sealing point between the terminal  40  and the case  30 . In other words, the projection  42  is formed at more upper side than the portion where the pressure from the flanged portion  34  works (the lower dead end of pressing). 
         [0049]    The projection  42  is a protrusion having a semicircular section, which is formed around the terminal  40 . The projection  42  is provided above the groove  41 , and formed continuously to the upper edge line of the groove  41 . 
         [0050]    As described above, the projection  42  is located above the groove  41  as the sealing point between the terminal  40  and the insulating member  50 , and has the semicircle shape, which involves the surface (lower surface in drawing) facing inside of the groove  41  (inner side of the case  30 ). The projection  42  of the terminal  40  has effects as follows. 
         [0051]    As depicted in  FIG. 4 , when the axial force (in the vertical direction of the drawing) acts on the external terminal  40 , the insulating member  50  attaching to the terminal  40  also receives the axial force. At this time, the lower surface of the projection  42  prevents the insulating member  50  from spreading, or flowing out upward from the upper edge line of the groove  41 , thereby damming flow of the insulating member  50  around the groove  41  as the sealing point. Therefore, the insulating member  50  can avoid overcompression and keep the elasticity. As a result, the sticking force at the sealing point among the insulating member  50 , the terminal  40  and the case  30  can be maintained, and thus the sealing property can be improved. 
         [0052]    When actually using the battery  10 , the external terminal  40  is connected with the connecting terminal of the external device by bolting. During the bolting, the bolting torque and the axial force act on the bolt portion of the terminal  40 , and particularly large outer force acts in the axial direction. In this embodiment, the projection  42  of the terminal  40  prevents the insulating member  50  from deforming toward the outside by the axial force acted on the terminal  40 . 
         [0053]    As depicted in  FIG. 5 , when the radial force (in the lateral direction of the drawing) acts on the external terminal  40 , the insulating member  50  attaching to the terminal  40  also receives the radial force. Such outer force in the radial direction might make the insulating member  50  deformed and flown out in the axial direction; however the lower surface of the projection  42  prevents the insulating member  50  from spreading, or applying the reaction force to the insulating member  50 . Therefore, the insulating member  50  can avoid overcompression and keep the elasticity. As a result, the sticking force at the sealing point among the insulating member  50 , the terminal  40  and the case  30  can be maintained, and thus the sealing property can be improved. 
         [0054]    The sectional structure of the projection  42  is not limited to the semicircle. The projection may have the shape with a surface facing inside of the case  30 , such as the triangle shape shown in  FIG. 6(   a ) and the square shape shown in  FIG. 6(   b ) both of which have a flat bottom. 
         [0055]    Especially,  FIG. 6(   c ) shows the preferable structure in which the projection  42  has concave surfaces at both upper and lower surfaces, and the lower surface of the projection  42  is smoothly continued to the upper end of the groove  41 . In this case, the projection can be formed at one time by the threading for the groove  41 . In other words, the projection  42  is preferably formed at the groove  41  by rolling or the like, or provided simultaneously with the groove  41 . 
         [0056]    The projection  42  with such structure can be easily formed and the manufacturing cost for the external terminal  40  formed with the groove  41  and the projection  42  disposed at the upper end of the groove. 
         [0057]    As illustrated in  FIG. 3 , the current collecting terminal  45  includes a plate portion  46 . The plate portion  46  is disposed at the upper end of the collecting terminal  45  and connected to the lower end of the external terminal  40 . The plate portion  46  is laterally extended from the lower end of the terminal  40  beyond the inner periphery of the through hole  33 . 
         [0058]    Due to such structure, when the collecting terminal  45  is attached to the external terminal  40  and fixed to the through hole  33 , the plate portion  46  and the projection  42  hold the inside of the insulating member  50 , i.e., the contact surface between the insulating member  50  and the external terminal  40 . 
         [0059]    As described above, the plate portion  46  and the projection  42  of the collecting terminal  45  pinch the inside of the insulating member  50 , and therefore, if the outer force acts on the terminal  40  in the axial or radial direction, the projection  42  prevents the upward flow of the insulating member  50  and at the same time the plate portion  46  prevents the downward flow of the insulating member  50  (see  FIGS. 7  (( a ) and ( b ))). 
         [0060]    Accordingly, enough amount of the insulating member  50  can be secured in the sealing point, thereby maintaining the sealing property. 
         [0061]    As depicted in  FIG. 8 , the external terminal  40  advantageously includes a second projection  43  in addition to the first projection  42 . The second projection  43  is projected radially outward from the outside of the terminal  40 . The second projection  43  is located lower than the lower edge line of the groove  41  that is the sealing point between the terminal  40  and the case  30 . 
         [0062]    The second projection  43  is a protrusion having a semicircular section, which is formed around the terminal  40 . The projection  43  is provided below the groove  41 , and formed continuously to the lower edge line of the groove  41 . The structure of the second projection  43  is not limited to the semicircle as the first projection  42 , namely, the second projection  43  includes at least the surface facing inside of the groove  41  (outside of the case  30 ). For instance, the second projection  43  may be formed in the structure of the first projection  42  shown in  FIG. 6 . 
         [0063]    As above-described, the first projection  42  arranged above the groove  41  and the second projection  43  arranged below the groove  41  hold the insulating member  50  at the sealing point. If the outer force acts on the external terminal  40  in the axial direction or radial direction, the lower surface of the first projection  42  stops the upward flow of the insulating member  50  and the upper surface of the second projection  43  stops the downward flow of the insulating member  50  (see  FIGS. 9  (( a ) and ( b ))). 
         [0064]    Consequently, the insulating member  50  can be prevented from flowing out from the sealing point, thereby enhancing the sealing property of the fixing point between the case  30  and the terminal  40 . 
         [0065]      FIG. 10  depicts the more preferable embodiment, in which the external terminal  40  includes the first and second projections  42 ,  43  and the second projection  43  and the plate portion  46  of the current collecting terminal  45  pinch the insulating member  50  at the sealing point. 
         [0066]    Such embodiment can have efforts as follows; the effect of the first projection  42 , the effect of the second projection  43  and the effect of the plate portion  46  of the current collecting terminal  45 . 
       INDUSTRIAL APPLICABILITY 
       [0067]    The present invention can be applicable to a battery which takes out an external terminal from the outside of a case, and particularly to a technique of improving the sealing property in the fixing point of the external terminal and the case. 
       DESCRIPTION OF NUMERALS 
       [0068]      10 : battery,  30 : case,  40 : external terminal,  42 : projection,  43 : second projection,  45 : current collecting terminal,  46 : plate portion,  50 : insulating member