Abstract:
An assembling method for a battery outer case including the steps of: molding a metal container main body with notched holes formed beforehand in its body portion for exposing terminals connected to a flat battery pack; receiving a flat battery pack in the metal container main body while fitting the terminals into the notched holes; covering the metal container main body with a metal lid; and superposing an open end portion of a metal container main body and an end portion of the metal lid with each other thereby to join them to each other by double seaming.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 11/225,828, filed Sep. 13, 2005, now allowed, and claims the benefit under 35 USC §119(a)-(d) of Japanese Application No. 2004-276250 filed Sep. 22, 2004, the entireties of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery outer case that houses a flat battery pack such as, for example, a laminate cell battery, etc., composed of a plurality of thin batteries laminated one over another. 
     2. Description of the Related Art 
     As a battery outer case in which this kind of flat battery pack is housed, there can be considered such a one as shown in  FIGS. 4A through 4F . 
     Specifically, a battery outer case  100  shown in  FIG. 4A  includes a metal container main body  102  in which a flat battery pack  101  is housed therein, and a metal lid  103  that serves to close an opening formed in the metal container main body  102 . An outwardly protruding connection flange  104  is formed at an open end of the metal container main body  102 , and a connection flange  105 , similarly protruding outwards, is formed on an end portion of the metal lid  103 , with the respective connection flanges  104 ,  105  being superposed and coupled with each other by means of spot welding or caulking. As such a caulking technique, there can be used eyelets, so-called TOX (a registered trademark of TOX PRESSOTECHNIK Co., Ltd.) joints, etc. 
     In  FIG. 4B , a metal container main body  102  is formed at its open end with a joint piece  106  extended upwards therefrom for connection, and a metal lid  101  is also formed on its outer periphery with an upwardly extending joint piece  107 , the joint pieces  106 ,  107  being superposed and coupled with each other by means of spot welding or caulking. 
     In the jointing or coupling techniques as shown in  FIG. 4A  and  FIG. 4B , however, there is the following problem. That is, in any case of spot welding and caulking joint, it is necessary for the joint pieces  106 ,  107  of the connection flanges  104 ,  105  to have their widths X 1 , Y 1  of at least 7 to 10 mm as a welding margin or a caulking margin, and hence the occupation space thereof becomes accordingly large. 
     Thus, as shown in  FIG. 4C  and  FIG. 4D , it is considered that an edge of a metal lid  103  is placed in abutment with a corresponding edge of a metal container main body  102  while eliminating the above-mentioned connection flanges and joint pieces, and abutment portions  108  of the metal lid  103  and the metal container main body  102  are joined with each other by laser welding (for example, Japanese Patent Application Laid-Open No. 2004-14125). 
     In such a case of abutment joint or connection, however, spatter generated upon welding can be easily dispersed into the inside of the container, and heat can also be transmitted to the inside of the container, so the flat battery pack  101  is liable to be damaged. In particular, in the case of a thin battery with its exterior being formed of a laminate film, the laminate layer can be damaged to induce a reduction in electrical insulation. 
       FIG. 4E  shows an example in which a metal container main body  102  and a metal lid  103  are coupled with each other by means of bolts  109 . In this example, each bolt  109  has its bolt shaft portion  109   a  inserted into a bolt hole formed in the metal lid  103 , and its bolt head  109   b  engaged with the metal lid  103 , with an end of the bolt shaft portion  109   a  being threaded into a bottom plate portion  102   a  of the metal container main body  102 . 
     In this case, however, there arises another problem. That is, the bolt head  109   b  of each bolt  109  projects from an upper surface of the metal lid  103 , so the occupation space of the entire apparatus is accordingly increased by the height of each bolt head  109   b , and at the same time, the entire weight thereof is also increased by the weight of all the bolts  109 . 
     In addition, it can be further considered that a caulking structure used in a cylindrical battery or the like is employed, as shown in  FIG. 4F . This caulking structure is such that a lid body  203  is inserted into the inner periphery of an open end portion of a metal container main body  201  through a ring-shaped gasket  202 , and is then fixedly secured to the metal container main body  201  by caulking or bending the open end portion thereof inwardly. 
     In the case of such a caulking structure, however, the gasket  202  is needed as an additional part, resulting in an increase in the number of required parts. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the problems as referred to above, and has for its object to provide a battery outer case for a flat battery pack in which the length of protrusion of joint portions between a metal container main body and a metal lid can be reduced to achieve space saving, and which is free from the influence of heat and makes it unnecessary to employ additional or extra parts such as a gasket, etc. 
     In order to achieve the above object, according to one aspect of the present invention, there is provided a battery outer case comprising: a metal container main body having at least one surface opened with a flat battery pack received therein; and a metal lid that serves to close an opening formed in the metal container main body; wherein the inside of the container is in communication with the outside thereof so as to have air permeability, and an open end periphery of the metal container main body and a lid end periphery of the metal lid are joined to each other by seaming. 
     In a first preferred form of the present invention, the flat battery pack comprises a laminate battery pack provided with an exterior member that is composed of a synthetic resin layer and a metal layer laminated one over the other. 
     In a second preferred form of the present invention, the metal container main body is provided with notched holes through which terminals connected to the flat battery pack inside the container are exposed. 
     In a third preferred form of the present invention, the metal container main body has a peripheral portion around each of the notched holes which is more rigid than the other portions thereof. 
     In a fourth preferred form of the present invention, a reinforcement bead is formed at a location near each of the notched holes in the metal container main body so as to provide high rigidity. 
     In a fifth preferred form of the present invention, the metal container main body has a turned back portion formed around each of the notched holes so as to provide high rigidity. 
     In a sixth preferred form of the present invention, the metal container main body and the metal lid have at least their inner surfaces coated with insulating layers, respectively. 
     According to another aspect of the present invention, there is provided n assembling method for a battery outer case comprising the steps of: molding a metal container main body with notched holes formed beforehand in its body portion for exposing terminals connected to a flat battery pack; receiving the flat battery pack in the metal container main body while fitting the terminals into the notched holes; covering the metal container main body with a metal lid; and superposing an open end portion of the metal container main body and an end portion of the metal lid with each other thereby to join them to each other by double seaming. 
     According to the above-mentioned first aspect of the present invention, since seam portions are constructed to be crushed toward the metal container main body, the length of protrusion of the seam portions from the metal container main body can be reduced as much as possible, so the metal container main body and the lid body can be joined to each other in a relatively small space. 
     In addition, since the seam joint between the metal container main body and the lid body can be done by seaming, there is no fear that the flat battery pack might be thermally damaged or the container might be thermally deformed, as would be caused by welding. 
     Moreover, since it is constructed such that the seam joint between the metal container main body and the metal lid is carried out by making use of part of themselves, any additional parts are not required to this end. Further, since it is also constructed such that the inside of the container is in communication with the outside thereof to have air permeability, even if gas generated in the thin batteries constituting the flat battery pack flows out to the outside of the thin batteries, the gas can escape to the outside of the container. 
     The present invention is optimal for the structure in which the flat battery pack is composed of laminate type batteries laminated one over another, as stated in the above-mentioned first preferred form of the invention. Thus, there is no influence of heat on the laminate type batteries, so it is possible to reduce the occupation space of the container itself as much as possible. As a result, the light-weight and small-size characteristics, which are major features of the laminate type batteries, are not disturbed or reduced. 
     According to the above-mentioned second preferred form of the present invention, since the metal container main body is provided with notched holes through which terminals connected to the flat battery pack are exposed, the flat battery pack can be smoothly received in the metal container main body. 
     In addition, in the case of the presence of the notched holes, the peripheral portions around the notched holes become liable to be deformed upon seaming, but such seaming can be performed without causing deformation by making the peripheral portions around the notched holes more rigid than the other portions, as stated in the above-mentioned third preferred form of the present invention, by reinforcing the peripheral portions around the notched holes by means of the reinforcement beads or the turned back portions as stated in the above-mentioned fourth or fifth preferred form of the present invention. 
     According to the above-mentioned sixth preferred form of the present invention, by coating at least the inner surfaces of the metal container main body and the metal lid with an insulating layer, it is possible to provide electrical insulation against exposed tabs of the thin batteries. Moreover, since the thin batteries themselves are laminated, insulation becomes doubled, thus making it possible to improve insulation performance. 
     Further, in case where the turned back portions are provided at the ends of the notched holes, the sections of the notched holes can be electrically insulated. 
     The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an exploded perspective view of a battery outer case according to one embodiment of the present invention. 
         FIG. 1B  is a perspective view of essential portions of the battery outer case of  FIG. 1A  when assembled. 
         FIG. 1C  is a perspective view of the battery outer case with an internal battery in  FIG. 1B  being removed. 
         FIGS. 2A through 2C  are views for explaining the function of a reinforcement bead in a seaming step. 
         FIG. 2D  is a view showing how large seam portions are. 
         FIG. 3A  is a perspective view of essential portions of a battery outer case according to another embodiment of the present invention with a thin battery assembly therein being permitted. 
         FIG. 3B  is a perspective view of essential portions of a battery outer case according to a further embodiment of the present invention with a thin battery assembly therein being permitted. 
         FIG. 3C  is an enlarged perspective view of a notched portion. 
         FIG. 3D  is a perspective view showing a state in which a terminal protrudes from a notched hole of  FIG. 3C . 
         FIG. 4A  through  FIG. 4F  show conventional battery outer cases, respectively, in which  FIG. 4A  is a cross sectional view schematically showing a container with joint flanges for spot welding or caulking;  FIG. 4B  is a cross sectional view schematically showing a container with joint pieces for spot welding or caulking;  FIG. 4C  and  FIG. 4D  are cross sectional views schematically showing the containers and lids of  FIG. 4A  and  FIG. 4B  which are joined to each other by laser welding, respectively, with the joint flanges and the joint pieces being eliminated;  FIG. 4E  is a cross sectional view schematically showing a container with a lid bolted thereto; and  FIG. 4F  is a cross sectional view of essential portions of a cylindrical battery showing a caulking structure of a lid. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now, the preferred embodiments of the present invention will be described below while referring to the accompanying drawings. 
       FIG. 1  shows a battery outer case according to one embodiment of the present invention. 
     The battery outer case, generally designated at  1 , includes a metal container main body  3  with an open upper surface and having a flat battery pack  2  housed or received therein, and a metal lid  5  that serves to close an opening  4  formed in the metal container main body  3 , an open end periphery  6  of the metal container main body  3  and a lid end periphery  7  of the metal lid  5  being joined to each other by seaming. To this end, seam portions  8  are formed at the joint portions of the open end periphery  6  of the metal container main body  3  and the lid end periphery  7 , respectively. 
     The flat battery pack  2  is constructed as follows. That is, inside a battery exterior composed of a laminate film there are laminated or stacked a plurality of serially connected laminate type batteries  21  in the form of a plurality of rectangular-shaped thin batteries, each of which is formed by sealing power generation elements each composed of a plus and a minus electrode plate and a separator laminated one over another. Thus, the laminate type batteries  21  are assembled into a vertically flat hexahedral shape as a whole, and a plus terminal  22  and a minus terminal  23  are arranged at the opposite ends of a short side of the flat hexahedral body, the plus terminal  22  and the minus terminal  23  being covered with a pair of terminal insulation resin covers  24 ,  25 . In addition, a voltage measuring connector  26  is arranged at a location between the plus terminal  22  and the minus terminal  23  for measuring the voltage of each of the laminate type batteries  21 . 
     The metal container main body  3  takes the shape of a thin box, and includes a body portion  31  of a polygonal cylindrical configuration which surrounds the flat battery pack  2 , and a bottom plate portion  32  which closes a lower end of the body portion  31  and on which a lower surface of the flat battery pack  2  is placed. The cross-sectional shape of the body portion  31  is rectangular with rounded corners, conforming to the planar shape of the flat battery pack, and includes a first side wall  31   a  and a second side wall  31   b  on a short side, and a third side wall  31   c  and a fourth side wall  31   d  on a long side. The height of the body portion  31  is set to be substantially the same as the height of the flat battery pack  2 . 
     The metal lid  5  takes the form of a thin plate-shaped configuration, and the lid end portion  7  is formed into a rectangular configuration with rounded corners, conforming to the open end portion  6  of the body portion  31 . 
     A metal material with its surface covered with an electrically insulating resin (insulating layer) is suitable as a material that constitutes the container main body  3  and the lid body  5 . For instance, an aluminum sheet with its front and back side surfaces covered with a PET resin film is preferable. For such an aluminum sheet, a 5052 AL material of a thickness of 0.5 mm is preferable, and it is also preferable that the PET resin film located on an inner side of the container be 20 microns, and that the PET resin film located on an outer side thereof be 20 microns. 
     A first and a second notched hole  91 ,  92 , from which the plus terminal  22  and the minus terminal  23  connected with the flat battery pack  2  in the container are exposed to the outside, are formed in the first side wall  31   a  of the metal container main body  3  at the left and right sides thereof at a predetermined distance apart from each other. In addition, a third notched hole  93 , from which the voltage measuring connector  26  of each of the laminate type batteries  21  constituting the flat battery pack  2  is exposed to the outside, is formed in the first side wall  31   a  of the metal container main body  3  at a location intermediate between the first and second notched holes  91 ,  92 . 
     The first and second notched holes  91 ,  92  are in the form of U shapes, respectively, conforming to the configurations of the terminal insulation resin covers  24 ,  25  that cover the plus terminal  22  and the minus terminal  23 , respectively, and includes two pairs of right and left side edge portions  91   a ,  91   b;    92   a ,  92   b  extending linearly from the upper open end portion  6  of the first side wall  31   a  toward its lower end corners near the bottom plate portion  32  in parallel with each other, and circular-arc shaped lower edge portions  91   c ,  92   c  each connecting between the lower ends of the corresponding side edge portions  91   a ,  91   b;    92   a ,  92   b.    
     The third notched hole  93  is rectangular, and includes a pair of right and left side edge portions  93   a ,  93   b  extending linearly from the upper open end portion of the first side wall  31   a  toward its lower end corners near the bottom plate portion  32  in parallel with each other, and a rectilinear lower edge portion  93   c  connecting between the lower ends of the side edge portions  93   a,    93   b . The lower edge portion  93   c  extends along the lower end corners. Also, formed in the metal lid  5  is a fifth lid-side notched hole  95  continuously extending from the third notched hole  93 . The lid-side notched hole  95  takes the form of a rectangular configuration with the same width as that of the third notched hole  93 , and extends a predetermined length from an end of the metal lid  5  in a direction perpendicular to the first side wall  31   a , so that the third notched hole  93  and the fifth notched hole  95  are combined with each other to form one notched hole. 
     A fourth notched hole  94  is formed in the second side wall  31   b  at the central location thereof. This fourth notched hole  94  extends across a lower end corner of the second side wall  31   b  to enter the bottom plate portion  32  a predetermined length. 
     Reinforcement beads  10  are formed on the first side wall  31   a  around the peripheral portions of the first notched hole  91 , the second notched hole  92  and the third notched hole  93  formed therein, and on the second side wall  92  around the peripheral portion of the fourth notched hole  94  formed therein. Thus, these first and second side walls  91 ,  92  with the reinforcement beads  10  become more rigid than the other portions without any notched hole formed therein (e.g., the third and fourth side walls  31   c ,  31   d  on the long side in this example). 
     Each of the reinforcement beads  10  is a convex row or bar of a predetermined width that protrudes from the surface of the container toward the outside thereof or a concave row or bar recessed or depressed from the surface of the container toward the outside thereof, and is of such a structure that it extends vertically in a line over the entire height of the first and second side walls  31   a ,  31   b.    
     Since the first notched hole  91  and the second notched hole  92  of the first side wall  31   a  are located adjacent to corners of high rigidity, a plurality of (e.g., three in the illustrated example) reinforcement beads  10  are arranged at predetermined peripheral intervals in a region between the first notched hole  91  and the third notched hole  93  as well as in a region between the third notched hole  93  and the second notched hole  92 . In particular, reinforcement beads  10  arranged in the immediate vicinity of the first notched hole  91 , the second notched hole  92  and the third notched hole  93  are adjoined to the side edges of the notched holes  91 ,  92 . 
     The reinforcement beads  10  on the second side wall  31   b  are provided in pluralities (e.g., two at each side in the illustrated example) in a right and a left region of the fourth central notched hole  94 . Those among the plurality of reinforcement beads  10  which are arranged adjacent to the fourth notched hole  94  are arranged in close proximity of the fourth notched hole  94 . 
     The battery outer case of the above construction is assembled as follows. 
     That is, the metal container main body  3  is first molded which has the first, second, third and fourth notched holes  91 ,  92 ,  93  and  94  formed in the first and second side walls  31   a ,  31   b  of the body portion  31  thereof, and the flat battery pack  2  is received in the metal container main body  3  thus molded. Upon receiving of the flat battery pack  2 , the insulating resin portions  24 ,  25  of the plus terminal  22  and the minus terminal  23  are fitted into the first and second notched holes  91 ,  92 , respectively. 
     Next, the metal lid  5  is placed onto the metal container main body  3  in such a manner that the lid-side notched hole  95  is aligned with the third notch hole  93 , and then the open end portion of the metal container main body  3  and the lid end portion of the metal lid  5  are superposed with each other and double seamed to form the seam portions  8 , thus completing the coupling therebetween. 
     As shown in  FIG. 2A and 2B , a seam curl portion  71  formed at the lid end portion  7  of the metal lid  5  and a seam flange portion  61  formed at the open end portion  6  of the metal container main body  3  are superposed with each other and seam joined to each other by pressing a seam roll  300  against these portions  71 ,  61  from a side thereof, but the first side wall  31   a  and the second side wall  31   b  of the metal container main body  3  are subject to an axial compression load F and a bending moment M from the seam flange portion  61 . Since the peripheral portions of the metal container main body  3  having the notches formed therein are low in rigidity, they can be easily buckling deformed under the action of the compression load F and the bending moment M, as shown in  FIG. 2C , if absence of any reinforcement beads  10 . In this embodiment, however, the flexural rigidity of the notched peripheral portions of the side wall sections are raised by the reinforcement beads  10 , so that notched peripheral portions of the first side wall section  31   a  and the second side wall section  31   b  can be prevented from deformation. 
     The dimensions of the seam portions  8  are such that they have a width a of at most 3 mm and a height b of at most 3 mm, as shown in  FIG. 2D , and hence the occupation space can be reduced as compared with conventional welding or caulking. In addition, there is caused no thermal deformation of the container and no thermal damage to the flat battery pack  2 , as will be in the case of welding. 
     Further, the first and second notches  91 ,  92  are formed beforehand, so that when the flat battery pack  2  is received in the metal container main body  3 , the terminal insulation resin covers  24 ,  25  of the plus terminal  22  and the minus terminal  23  can be fitted into the first and second notched holes  91 ,  92  from above. As a result, the flat battery pack  2  can be received smoothly in the metal container main body  3  from above the opening portion  4  thereof. 
     Moreover, in this embodiment, it is constructed such that the inside of the container in which the flat battery pack  2  is received is in communication with the outside thereof through the first through fourth notched holes  91 ,  92 ,  93  and  94  or through the seam portions  8  so as to have air permeability. Accordingly, even if gas is generated in the thin batteries that constitute the flat battery pack and the gas thus generated flows out to the outside of the thin batteries, the gas can be escaped to the outside of the container. The seam portions  8  will be of a structure having air permeability if no compound is interposed therebetween. 
     Next, another embodiment of the present invention will be described while referring to  FIGS. 3A through 3D . In the following description, only differences from the above-mentioned embodiment will be explained with the same components being identified by the same symbols while omitting an explanation thereof. 
     In  FIG. 3A , the peripheral portions around the first and second notched holes  91 ,  92  and the third notched hole  93  are bent or turned back to form upright ribs  11  in the form of turned back portions for improved rigidity without forming any reinforcement bead. 
     That is, the first and second notched holes  91 ,  92  are arranged at their one side adjacent to corners and have high rigidity at that side, so upright ribs  11  are formed at their side edges  91   b ,  92   a  opposing the third notch  93 . On the other hand, the third notch  93  is formed at its opposite side edges with upright ribs  11 . These upright ribs  11  are constructed in such a manner that they are bent or turned back in a direction to protrude outside of the container to form a U-shaped configuration, with the inner surface side of the container being exposed to the surface thereof. 
     Further,  FIG. 3B through 3D  show a further embodiment of the present invention. 
     In this embodiment, for the first and second notched holes  91 ,  92  through which terminals  22 ,  23  are exposed, at least the inner surface of the metal container main body  3  is coated with an insulating layer, and the upright ribs  11  in the form of the turned back portions are formed to extend over the right and left side edge portions  91   a ,  91   b;    92   a ,  92   b  and the circular-arc shaped lower edge portions  91   c ,  92   c , whereby electrical insulation of the plus terminal  22  and the minus terminal  23  as well as structural reinforcement can be made. With such a construction, the plus terminal  22  and the minus terminal  23  can be electrically insulated without the metal material of the metal container being exposed to the sections of the first and second notched holes  91 ,  92 , so the terminal insulation resin covers  24 ,  25  become unnecessary. 
     Although in the above embodiments, there has been shown an example of the metal container main body  3  in which the body portion  31  and the bottom plate portion  32  are integrally molded with each other, the body portion  31  and the bottom plate portion  32  may be formed separately from each other. 
     While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.