Abstract:
The present invention provides a battery case configured by fixing a joined portion where plate sections overlap with each other using a fixation member, and two different types of sealing members are disposed at the joined portion. It is possible to ensure high sealing properties by using sealing members suitable for the respective shapes of portions of the joined portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to battery cases, and in particular, to a battery case having plate sections fixed to each other by a fixation member. 
     2. Description of the Related Art 
     JP-A-2007-200758 discloses a metal case (battery case) in which cells are stored. The metal case includes a case body (battery case body) and a cap plate (cap body) that are joined each other by screws, as well as a sealing member provided between the case body and the cap plate. Further, JP-A-2007-200758 also describes that the case body is made of a material such as iron or aluminum. In this case, as welding an aluminum material is difficult as compared to a material such as iron, a case body made of an aluminum material is often provided by jointing the material using fixation members such as rivets. 
     However, as compared to welding, forming a case body by jointing a material using fixation members is susceptible to gaps, and thus provides lower sealing functionality. Consequently, a problem of failing to ensure high sealing functionality of the case body is envisaged. Especially, in the aerospace fields, safety against leakage of organic electrolyte solutions of nonaqueous electrolyte cells (such as lithium ion cells) is highly demanded, and ensuring high sealing functionality is essential in such fields. 
     SUMMARY OF THE INVENTION 
     The present invention has been contrived in order to address the above problem, and an object of the present invention is to provide a battery case having high sealing functionality. 
     A first aspect of the present invention provides a battery case including: a joined portion where plate sections overlap with each other and are fixed by a fixation member; a first sealing member; and a second sealing member, wherein the first sealing member and the second sealing member are different from each other and are disposed at the joined portion. 
     According to the first aspect of the present invention, it is possible to ensure high sealing functionality by disposing the first sealing member and the second sealing member suitable for the respective portions of the joined portion where the plate sections overlap with each other, as compared to a case in which only one type of sealing member is used. Consequently, even in the case in which an electrolyte solution leaks from cells stored in the case, it is possible to effectively suppress leakage of the electrolyte solution from the battery case. 
     According to the first aspect of the present invention, preferably, the first sealing member is disposed between joining surfaces of the joined portion, and the second sealing member includes a paste sealing member, and is disposed so as to cover an end of the joining surface. By disposing the first sealing member between the joining surfaces and the paste second sealing member at the end of the joining surfaces, it is possible to seal the case at two positions: between the joining surfaces of the joined portion, and the end of the joining surfaces, and to improve the sealing functionality of the battery case. 
     A second aspect of the present invention provides a battery case including: a plate member being bent; notch portions each disposed at an end of a folded portion at which the plate member is bent; and a closure-sealing member covering each of the notch portions. 
     According to the second aspect of the present invention, the battery case is provided by bending the plate member, the notch portions are each disposed at the end of the folded portion, and the closure-sealing member covering each of the notch portions is provided. With such a configuration, the notch portions are covered using the closure-sealing members, and even in the case in which the electrolyte solution leaks from the cells stored in the case, it is possible to effectively suppress leakage of the electrolyte solution from the battery case. 
     According to the first and the second aspects of the present invention, a gasket sealing member can be provided at an engaging portion between the battery case body and a cap body for covering an opening of the battery case body. With such a configuration,even when the removable cap body is provided, it is possible to facilitate the sealing between the battery case body and the cap body by the gasket sealing member. Therefore, even in the case in which the electrolyte solution leaks from the cells, it is possible to suppress leakage of the electrolyte solution through a portion between the battery case body and the cap body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the invention with reference to the accompanying drawings, wherein: 
         FIG. 1  shows a perspective view illustrating a battery case according to one embodiment of the present invention; 
         FIG. 2  shows an exploded perspective view illustrating the battery case according to the embodiment; 
         FIG. 3  shows a partial cross-sectional view illustrating a joined portion of the battery case according to the embodiment; 
         FIG. 4  shows a cross-sectional view taken along line  300 - 300  in  FIG. 3 ; 
         FIG. 5  shows a perspective view illustrating an interior of a cap body of the battery case according to the embodiment; 
         FIG. 6  shows a cross-sectional view illustrating an engaging portion between the cap body and a battery case body according to the embodiment; 
         FIG. 7  shows a plan view of the battery case body according to the embodiment before bending; 
         FIG. 8  shows a perspective view for explaining a step of applying a liquid sealing member according to the embodiment; 
         FIG. 9  shows a perspective view for explaining a step of rivet-jointing according to the embodiment, 
         FIG. 10  shows a perspective view for explaining a step of covering a notch hole with a putty and a paste sealing member according to the embodiment; and 
         FIG. 11  shows a perspective view for explaining a step of applying the paste sealing member according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the present invention will now be described hereinafter with reference to the drawings. First, a battery case  100  according to the embodiment will be described with reference to  FIG. 1  to  FIG. 6 . 
     Referring to  FIG. 1  and  FIG. 2 , the battery case  100  according to the embodiment is provided with a battery case body  1  in a box shape, and a cap body  2  covering an opening  1   a  of the battery case body  1 . 
     The battery case body  1  is formed in the box shape by bending a plated material made of an aluminum alloy. It is possible to reduce the weight of the battery case  100  by using an aluminum alloy as the material of the battery case body  1 . As illustrated in  FIG. 1  and  FIG. 2 , the battery case body  1  includes a bottom section  11 , and a front section  12 , a back section  13 , and two side sections  14  that are respectively coupled to four sides of the bottom section  11 . The battery case body  1  stores twelve square-shaped lithium ion cells  200 . In addition, the front section  12 , the back section  13 , and the side sections  14  are provided with nuts  61  at positions corresponding to holes  21   b  of the cap body  2 . 
     Further, the front section  12  and the two side sections  14  of the battery case body  1  are rivet-jointed (fixed) by rivets  3 . Specifically, as illustrated in  FIG. 2 , each of the side sections  14  is provided with a plate-shaped overlap margin  141  on its end, and each end  12   b  of the front section  12  and the overlap margin  141  of the side section  14  in an overlapped state are rivet-jointed by the rivets  3 . Each rivet  3  is inserted through the holes  121  and  141   a  that are respectively provided in each end  12   b  of the front section  12  and the overlap margin  141  of the side section  14  to rivet-joint the end  12   b  of the front section  12  and the overlap margin  141  of the side section  14  (see  FIG. 4 ). In this manner, joined portions  4  are formed by joining the both ends  12   b  of the front section  12  and the overlap margins  141  of the side sections  14 . The rivets  3  are one example of a “fixation member” according to the present invention. Additionally, the front section  12 , the back section  13 , the overlap margins  141 , and overlap margins  142  are one example of “plate sections” according to the present invention. 
     Further, the overlap margins  141  are in the same shape, and, as illustrated in  FIG. 3 , each overlap margin  141  is provided so as to extend vertically from a top end to a bottom end of each side section  14  (Z direction). Moreover, a top end of each overlap margin  141  is provided so as to have a greater width in the X direction than a center of the overlap margin  141 . 
     As illustrated in  FIG. 4 , according to this embodiment, the joined portion  4  between the front section  12  and the side section  14  is provided with a liquid sealing member  41  and a paste sealing member  42 . The liquid sealing member  41  is made of a liquid material composed mainly of an olefin-based hydrocarbon having a high resistance to electrolyte solutions, and hardened into a rubber-like elastic body by volatilization of a solvent included in the sealing member. As illustrated in  FIG. 4 , the liquid sealing member  41  is provided between joining surfaces of the joined portion  4 . Specifically, the liquid sealing member  41  is provided between an inner surface  12   c  of the both ends  12   b  of the front section  12  and an outer surface  141   b  of the overlap margin  141  of the side section  14  (between the joining surfaces). Further, the liquid sealing member  41  is provided continuously between the joining surfaces of the joined portion  4  from a portion near an upper end to a portion near a lower end of the battery case body  1 . Here, the liquid sealing member  41  is one example of a “first sealing member” according to the present invention. 
     Further, the paste sealing member  42  is made of a paste material composed mainly of a silyl group-containing polymer having a high resistance to electrolyte solutions, and hardened into an elastic body by a reaction with water in the air. As illustrated in  FIG. 3  and  FIG. 4 , the paste sealing member  42  is provided so as to cover an end of the joined portion  4  across the X direction within the battery case body  1 . Specifically, as illustrated in  FIG. 4 , the paste sealing member  42  is provided so as to cover a stepped portion configured by the front section  12  and the overlap margin  141 . In  FIG. 4 , the paste sealing member  42  is provided so as to cover the entire stepped portion. However, the paste sealing member  42  can provide the effect of the present invention as long as it covers the end between the joining surfaces. Further, as illustrated in  FIG. 3 , the paste sealing member  42  is provided continuously along the shape of the end of the overlap margin  141  from the portion near the upper end to the portion near the lower end of the battery case body  1 . Here, the paste sealing member  42  is one example of a “second sealing member” according to the present invention. 
     As illustrated in  FIG. 1  to  FIG. 3 , the bottom section  11  of the battery case body  1  includes a notch hole  1   b  at each of four corners for in order to reduce stress concentration when bending the front section  12 , the back section  13 , and the two side sections  14 . Here, the notch hole  1   b  is one example of a “notch portion” according to the present invention. The notch hole  1   b  is provided with a putty  5  so as to cover the notch hole  1   b , and the putty  5  is made of a material composed mainly of an epoxy-based resin. As silyl group-containing polymers have a higher resistance to electrolyte solutions than epoxy-based resins, it is possible to suppress dissolution of the putty  5  by providing the paste sealing member  42  composed mainly of a silyl group-containing polymer so as to cover the putty  5  composed mainly of an epoxy-based resin. Here, the putty  5  is one example of a “closure-sealing member” according to the present invention. 
     The cap body  2  is made of a plate member of an aluminum alloy, which is the same material as that of the battery case body  1 . As illustrated in  FIG. 5 , the cap body  2  includes a side wall  21  provided by bending sides of the cap body  2 . The cap body  2  is also provided with an opposing wall  23  so as to face toward the side wall  21 . As illustrated in  FIG. 6 , the upper end of the battery case body  1  is inserted between the side wall  21  and the opposing wall  23  of the cap body  2 . The cap body  2  is removably attached to the battery case body  1  by screwing screws  6  with the nuts  61  of he battery case body  1  via the hole  21   b  (see  FIG. 2  and  FIG. 5 ). 
     As illustrated in  FIG. 5  to  FIG. 6 , a gasket  7  is provided between the side wall  21  and the opposing wall  23 . The gasket  7  is made of a silicon sponge having a circular cross-section, and is elastically deformable. The gasket  7  is provided so as to be sandwiched between the cap body  2  and the battery case body  1 . Specifically, upon attachment of the cap body  2  to the battery case body  1 , the gasket  7  deforms by being pressed between a portion between the side wall  21  and the opposing wall  23  of the cap body  2  and the upper end of the battery case body  1 . 
     Next, a method of manufacturing the battery case  100  according to the embodiment will be described with reference to  FIG. 1  to  FIG. 11 . 
     First, the overlap margins  141  and  142  of the plate member of an aluminum alloy illustrated in  FIG. 7  are bent inward respectively along folding lines  14   b . Then, the front section  12 , the back section  13 , and the side sections  14  are bent upward respectively along folding lines  11   a  (lines indicated by dashed lines). This results in a state as illustrated in  FIG. 8 . At this time, as notches lib in a circular arc are provided at both ends of each folding line  11   a , stress concentration due to bending of the plate member can be reduced. The notches  11   b  are portions that correspond to the notch holes  1   b  after the battery case body  1  is assembled. 
     Thereafter, the liquid sealing member  41  is provided between the joining surfaces of each of the joined portions  4  between the front section  12  and the side sections  14 . Specifically, as illustrated in  FIG. 8 , the liquid sealing member  41  is applied to an area corresponding to each of the inner surfaces  12   c  of the front section  12 . Then, the front section  12 , the back section  13 , and the side section  14  are further bent to provide a state as illustrated in  FIG. 9 . Thereafter, the rivets  3  are inserted through the holes  121  in the front section  12  and the holes  141   a  in the side sections  14 , and whereby the front section  12  is rivet-jointed with the overlap margins  141 . After the rivet-jointing, each liquid sealing member  41  is hardened into a rubber-like elastic body by volatilization of the solvent included in the sealing member. 
     In this state, the putty  5  is applied within the battery case body  1  so as to cover each of the notch holes  1   b  at the four corners of the battery case body  1 , as illustrated in  FIG. 10 . The putty  5  includes a base compound and a hardening agent, and can be hardened by mixing the base compound and the hardening agent at a predetermined proportion. Similarly, the back section  13  and the side sections  14  are rivet-jointed after application of the liquid sealing members  41 , and the putty  5  is applied so as to cover each notch portion  1   b.    
     Then, as illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 11 , the paste sealing member  42  is applied within the battery case body  1  so as to cover an end of each joined portion  4 . At this time, as illustrated in  FIG. 3  and  FIG. 11 , the paste sealing member  42  is applied continuously from an upper end to a lower end of an end along the overlap margin  141 . Further, as illustrated in  FIG. 10 , the paste sealing member  42  is applied so as to cover each of the putties  5  at the four corners of the battery case body  1  on the side of the bottom section  11 . Thereafter, each paste sealing member  42  is hardened into an elastic body by a reaction with water in the air. Similarly, the paste sealing members  42  are applied between the back section  13  and the side sections  14 , in the same manner. 
     Then, after the twelve lithium ion cells  200  are stored within the battery case body  1 , the cap body  2  is attached to the opening  1   a  of the battery case body  1  by the screws  6 . At this time, as illustrated in  FIG. 5 , the gasket  7  is fitted between the side wall  21  and the opposing wall  23  of the cap body  2 , and then the cap body  2  is attached to the battery case body  1  by the screws  6 . In this manner, the battery case  100  according to the embodiment is manufactured. 
     According to this embodiment, it is possible to ensure high sealing functionality by using the liquid sealing member  41  suitable for the shape between the joining surfaces of the joined portion  4  of the battery case body  1  and the paste sealing member  42  suitable for the shape of the ends of the joining surfaces, as compared to the case in which only one type of sealing member is used. With this, even in the case in which an electrolyte solution leaks from the lithium ion cell  200 , it is possible to effectively suppress leakage of the electrolyte solution from the battery case body  1 . 
     Further, according to this embodiment, the notch holes  1   b  for reducing stress concentration due to bending of the plate member are provided at the ends of the folding portions of the battery case body  1 , and then the putties  5  made of an epoxy-based resin are provided so as to cover the notch holes  1   b . With such a configuration, even when the notch holes  1   b  are provided, it is possible to cover the notch holes  1   b  by the putties  5 , and to ensure the sealing functionality of the battery case body  1 . 
     Moreover, according to this embodiment, the gasket  7  is provided at the engaging portion between the battery case body  1  and the cap body  2 . With such a configuration, even when the removable cap body  2  is provided, it is possible to facilitate the sealing between the battery case body  1  and the cap body  2  by the gasket  7 , and to suppress leakage of the electrolyte solution through a portion between the battery case body  1  and the cap body  2 . 
     It would be understood that the embodiment disclosed herein is in all respects exemplary and non-limiting. The present invention is defined by the scope of the appended claims, and includes any modifications made without departing from the scope of the present invention and equivalents thereto. 
     For example, while the embodiment describes the example in which the joined portion is fixed using the rivets as the fixation members, the joined portion can be fixed using the fixation members such as screws instead of the rivets in the present invention. 
     While the embodiment describes the example in which the material of the battery case body is an aluminum alloy, the battery case body can be made of a metallic material other than an aluminum alloy in the present invention. It is also possible to reduce the weight of the battery case using a magnesium alloy and the like. 
     While the embodiment describes the example in which the liquid material composed mainly of an olefin-based hydrocarbon is used for the first sealing member and the paste material composed mainly of a silyl group-containing polymer is used for the second sealing member, the materials of the sealing members are not limited to the above examples. It is possible to use a material composed mainly of, for example, a silicon-based compound or an epoxy-based compound. For the first sealing member, it is preferable to use a liquid material that can be applied in a thin layer. Further, for the first sealing member and for the second sealing member, it is preferable to use a material having a high resistance to electrolyte solutions. 
     While the embodiment describes the example in which the closure-sealing member is made of an epoxy-based resin, the closure-sealing member can be made of a material other than the epoxy-based resin. Additionally, the closure-sealing member can be one of the first sealing member and the second sealing member. 
     While the embodiment describes the example in which the battery case body in the box shape is provided by bending a single plate member, the battery case body can be provided by assembling a plurality of separate plate members in the present invention. 
     While the embodiment describes the example in which the battery case stores lithium ion cells, the battery case according to the present invention can store nonaqueous electrolyte cells other than the lithium ion cells, or nickel-metal hydride cells. 
     While the embodiment describes the example in which the first sealing member and the second sealing member are provided entirely from the portion near the upper end to the portion near the lower end of the battery case body, the first sealing member and the second sealing member can be provided only in a bottom region including the lower end in the present invention.