Abstract:
An outside gasket for insulating a cover from an external terminal to be fixed thereto is readily fixed to the cover irrespective of a simple structure. A battery includes: a battery case which contains a power generating element therein and whose top surface is opened; a cover which closes the top surface; at which an external terminal exposed to the outside is disposed at the outer surface of the cover via an outside gasket, the cover having an engagement portion which expands outward and is formed into a shape except a circle, and the outside gasket having a recess to be engaged to the engagement portion.

Description:
The present application is based on and claims priority from Japanese patent application No. 2010-276204, filed on Dec. 10, 2010, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery featured by a sealing structure at a connection portion of an external terminal, that is, a structure of an outside gasket. 
     2. Description of the Related Art 
     There has been conventionally known, as a battery, a configuration in which a riveted terminal is fixed to a cover plate via an outer insulating/preventing plate (see, for example, JP-A-2003-157812). The outer insulating/preventing plate has a square recess formed at the outer surface thereof and a projection having a through hole at an inner surface on an opposite side thereof. A flange for the riveted terminal is held in the square recess, and further, a current collecting rivet for the riveted terminal is inserted into the through hole. The current collecting rivet is caulked via the cover plate, the insulating/preventing plate, and a current connector, to thus secure these members. 
     However, the conventional battery includes the outer insulating plate which is merely brought into contact with the upper surface of a flat cover but does not include any structure for restricting movement in a rotational direction. Therefore, the outer insulating plate may be positionally deviated in the rotational direction when the riveted terminal is fixed, thereby making assembly work cumbersome. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a battery configured such that an outside gasket for insulating a cover from an external terminal to be fixed thereto is readily fixed to the cover irrespective of a simple structure. 
     According to a first aspect of the invention, a battery includes: a battery case which contains a power generating element therein and whose top surface is opened; a cover which closes the top surface; at which an external terminal exposed to the outside is disposed at the outer surface of the cover via an outside gasket, the cover having an engagement portion which expands outward and is formed into a shape except a circle, and 
     the outside gasket having a recess to be engaged to the engagement portion. 
     When the external terminal is fixed to the cover, the recess of the outside gasket is engaged to the engagement portion formed at the cover, thereby preventing positional deviation in a rotational direction. Consequently, it is possible to efficiently fix the external terminal. 
     According to a second aspect of the invention, a battery includes: a battery case which contains a power generating element therein and whose top surface is opened; a cover which closes the opening, the cover having a current collector to be connected to the power generating element via an inside gasket and having an external terminal exposed to the outside fixed via an outside gasket, the cover has: a through hole and an engagement portion which expands outward and is formed into a shape except a circle, the external terminal has a shaft and plate portion at the other end of the shaft, the external terminal being caulked at one end of the shaft through the outside gasket, the cover, the inside gasket, and the current collector; and the outside gasket having a recess to be engaged to the engagement portion and a tubular portion which is inserted into the through hole formed in the cover, is fitted to the shaft of the external terminal, and is fitted to a through hole formed in the inside gasket. 
     In the outside gasket, the engagement portion formed at the cover is located in the recess, thereby preventing the positional deviation in the rotational direction. Consequently, when the cover, the inside gasket, and the current collector are assembled via the shaft of the external terminal, followed by securely caulking, the workability can be enhanced without any need of taking care of the positional deviation of the outside gasket. 
     The outside gasket may include the recess and another recess, to which the plate portion of the external terminal is arranged, by dividing a frame member via a partition. 
     Since the plate portion of the external terminal is arranged in the recess, the external terminal is not positionally deviated by securely caulking. Further, even if the rotational power is operated to the external terminal as the opposed end of the shaft is the plate portion, the rotation of the external terminal is prevented. 
     The cover may have a lock portion formed at the outer surface thereof, and the outside gasket may have a tongue piece extending along the cover formed therein, the tongue piece having a locked portion to be locked to the lock portion in the state in which the outside gasket is engaged to the engagement portion in the cover. 
     With this configuration, the outside gasket can be prevented from being positionally deviated in the rotational direction by locking the locked portion of the tongue piece to the lock portion in the cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a perspective view showing a battery in accordance with the present embodiment; 
         FIG. 2  is a front cross-sectional view showing the battery in accordance with the present embodiment; 
         FIG. 3  is a perspective view showing a cover shown in  FIG. 1 , as viewed from the top; 
         FIG. 4  is an exploded perspective view showing the cover shown in  FIG. 3 ; 
         FIG. 5  is a perspective view showing the cover, as viewed from the bottom and cross-sectional views showing the cover, as viewed in partly enlargement; 
         FIG. 6  is an exploded perspective view shown in  FIG. 5 ; and 
         FIGS. 7A and 7B  are cross-sectional views illustrating fabrication processes for a negative electrode terminal shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment according to the present invention will be described with reference to the attached drawings. In the following description, the terms indicating specific directions or positions (including, for example, “above,” “below,” “side,” and “end”) are used, as required. Here, the use of the terms is directed to facilitating the understanding of the invention referring to the drawings, and therefore, the meanings of the terms should not restrict the technical scope of the present invention. Moreover, the following description is merely an essential example, and therefore, should not intend to restrict the present invention and its application or usage. 
       FIG. 1  shows a nonaqueous electrolytic secondary battery. The nonaqueous electrolytic secondary battery contains a power generating element  2  inside of a battery case  1 , and is sealed with a cover  3 , as shown in  FIG. 2 . Here, the battery case  1  and the cover  3  constitute an envelope member. 
     The battery case  1  is formed into a rectangular parallelepiped shape opened at the upper surface thereof, and is made of aluminum or an aluminum alloy, etc. 
     In the power generating element  2 , a separator  6  made of a porous resin film is interposed between a negative electrode  4  including a copper foil and a positive electrode  5  including an aluminum foil, like the prior art, although its details will not be shown. All of these members are formed into a belt shape, and further, the negative electrode  4  and the positive electrode  5  are flat wound in such a manner as to be contained inside of the battery case  1  in the state in which they are positionally deviated oppositely with respect to the separator  6  in a widthwise direction. As described later, a negative electrode current collector  18  is connected to the negative electrode  4  via a clip  7  whereas a positive electrode current collector  19  is connected to the positive electrode  5  via another clip  7 . 
     As shown in  FIGS. 3 to 6 , the cover  3  is made of a metallic elongated plate formed into a rectangular shape, as viewed on plane. A substantially elliptic opening  8  having a step from the upside is formed at the center of the cover  3 . A safety valve  9  made of a synthetic resin is engaged to the opening  8 . A substantially H-shaped thin portion is formed at the safety valve  9 . The thin portion is torn in the case of an abnormal increase in inner pressure, so that pressure can be decreased. 
     A small-diameter liquid injection hole  10  is formed at one end of the cover  3 , and it is designed to be closed via a plug  11  after liquid injection. 
     An engagement portion  12 , which is formed into a substantially rectangular shape, as viewed on plane, and expands upward, is formed at the lower surface at each of both ends of the cover  3 . In the engagement portion  12 , a shallow guide recess  12   b  is formed around a engaged recess  12   a  at the lower surface except one side. Moreover, a through hole  12   c  is formed at the center of a ceiling constituting the engaged recess  12   a . An external terminal  14  and a current collector  13  are adapted to fit to the engaged recess  12  and the guide recess  12   b  via a lower gasket  15  and an upper gasket  16 , respectively. 
     Lock projections  17  projecting upward from two portions in the widthwise direction are formed in the vicinity of the inside of each of the engagement portion  12  in the cover  3 . Each of the lock projections  17  is formed into a bottomed tubular shape at the same time when the cover  3  is pressed. The upper gasket  15 , described later, is locked to the lock projections  17 , to be thus positioned in a rotational direction. 
     The current collectors  13  include the negative current collector  18  made of copper and the positive current collector  19  made of aluminum. In the current collector  13 , a connection receiver  20  and legs  21  extending from both sides of the connection receiver  20  are formed by pressing a metallic elongated plate material. The connection receiver  20  is constituted of a fitting portion  22  to be engaged to the recess formed at the cover  3  and a mount portion  23  continuous to the fitting portion  22 . The fitting portion  22  is formed into a planar shape, and has a through hole  22   a  at the center thereof and a guide edge  24  extending in a vertical direction at the circumferential edge except one side continuous to the mount portion  23 . The side of the mount portion  23  functions as a continuous portion  25  extending further beyond the guide edge  24 , and thus, reaches the mount portion  23 . The guide edge  24  and the continuous portion  25  satisfactorily enhance the rigidity of the connection receiver  20  in the current collector  13 . 
     The legs  21  extend in the vertical direction from both side edges of the mount portion  23  along both side surfaces of the power generating element  2 . The legs  21  are connected to the positive electrode  5  or the negative electrode  4  in the power generating element  2  via the clip  7 . Positional deviation can be prevented since the clip  7  is held between the inner surfaces, opposite to each other, of the battery case  1 . 
     The external terminals  14  include a negative electrode external terminal  28  and a positive electrode external terminal  29 . The external terminal  14  includes a flat plate  30  and a shaft  31  extending downward from the center at a lower surface thereof. To a surface (an exposed surface) of the flat plate  30  is welded a bus bar, not shown. 
     As shown in  FIG. 7 , the negative electrode external terminal  28  is formed of an aluminum plate  32  formed into a rectangular shape, as viewed on plane, and a copper rivet  33 . That is to say, a shaft  33   a  of the rivet  33  is inserted into a through hole  32   a  formed at the center of the aluminum plate  32 , and then, a flange  33   b  is press-engaged into the through hole  32   a  by pressing. The dimension of an inner diameter of the through hole  32   a  formed at the plate  32  is slightly greater than that of an outer diameter of the shaft  33   a  of the rivet  33  and sufficiently smaller than that of an outer diameter of the flange  33   b . As a consequence, the flange  33   b  presses and enlarges the through hole  32   a  by press-fitting, to be thus turned to a press-engaged state, and further, the press-enlarged portion is brought into press-contact with the shaft  33   a , to be thus integrated therewith. Moreover, a circular recess  33   c  is formed at the center of the tip surface of the shaft  33   a  in the rivet  33 . The shaft  33   a  is inserted into the respective through holes of the upper gasket  15 , the engagement portion  12  of the cover  3 , the lower gasket  16 , and the negative electrode current collector  18  in a later-described manner, and then, the recess  33   c  is pressed and enlarged while holding the members therein, followed by securely caulking. 
     The upper gasket  15  is made of a synthetic resin, wherein the inner space of a frame formed into a rectangular shape, as viewed on plane, is divided into an upper terminal holding recess  37  and a lower containing recess  38  via a partition  36 . Tongue pieces  39  extend sideways from one of sides constituting a lower opening edge. A tubular portion  36   a  extending downward from the ceiling is formed at the center of the partition  36 . The tubular portion  36   a  is engaged to a through hole  40   a  formed at the lower gasket  16  through the through hole  12   c  formed at the engagement portion  12 . A lock hole  39   a  is formed in each of the two tongue pieces  39 , and thus, is engaged to the lock projection  17  formed in the cover  3 . The upper gasket  15  conforms to the engagement portion  12  in the cover  3  formed into the rectangular shape, as viewed on plane, and therefore, it can be prevented from being positionally deviated in the rotational direction only by its placement on the engagement portion  12 . In addition, the insertion of the lock projection  17  into the lock hole  39   a  can securely prevent any positional deviation in the rotational direction. 
     The lower gasket  16  is a plate formed into a rectangular shape, as viewed on plane, and further, is made of a synthetic resin having a through hole  16   a  at the center thereof. The lower gaskets  16  on the negative electrode side and the positive electrode side are slightly different from each other in shape. 
     A lower gasket  16 A on the negative electrode side includes an expanded portion  40  to be contained inside of the engaged recess  12   a  formed at the engagement portion  12  in the cover  3  and a flat portion  41  continuous to the expanded portion  40 . The expanded portion  40  is formed into a shape in conformity with the inner surface of the engaged recess  12   a  of the engagement portion  12  except one side thereof, and further, the through hole  40   a  is formed at the center thereof. The flat portion  41  is arranged to the guide recess  12   b  of the engagement portion  12 . The lower gasket  16 A on the negative electrode side is contained from below inside of the engaged recess  12   a  constituting the engagement portion  12  in the cover  3 , and thus, is held between the cover  3  and the negative electrode current collector  18 . In this held state, the lower gasket  16 A aims at the insulation between the negative electrode current collector  18  and the cover  3 , and further, seals the through hole  12   c  formed in the engagement portion  12  in the cover  3  together with the upper gasket  15 . 
     On the other hand, a lower gasket  16 B on the positive electrode side is formed into a flat shape, and further, has a through hole  16   a  at the center thereof, and thus, is contained inside of the engaged recess  12   a  constituting the engagement portion  12 . The lower gasket  16 B on the positive electrode side seals the through hole  12   c  formed in the engagement portion  12  in the cover  3  together with the upper gasket  15 . 
     With the battery having the above-described configuration, the positional deviation in the rotational direction can be prevented only by locating the containing recess  38  of the upper gasket  15  at the engagement portion  12  in the cover  3 . Consequently, when the shaft  31  of the external terminal  14  is inserted into the respective through holes of the upper gasket  15 , the cover  3 , the lower gasket  16 , and the current collector  13 , followed by securely caulking, the upper gasket  15  can be prevented from being positionally deviated. Thus, it is possible to enhance workability of a series of assembling work. 
     Incidentally, the present invention is not limited to the configuration described in the embodiment, and it may be variously modified. 
     For example, the upper gasket  15  is not limited to the rectangular shape, as viewed on plane, but it may be formed into various shapes, for example, a polygon such as a triangle and a pentagon or more, and an ellipse other than a circle, as viewed on plane. In summary, the upper gasket  15  may be configured in any manners as long as the positional deviation in the rotational direction can be prevented when it is attached. In some case, the upper gasket  15  may not conform to the shape of the engagement portion  12  in the cover  3 . 
     Additionally, although the battery case  1  is formed into the rectangular parallelepiped shape, the engagement portion  12  in the cover  3  and the upper gasket  15  such configured as described above can be adopted even if the battery case  1  may be formed into other shapes such as a cylindrical shape. 
     Thus, the structure of the external terminal  14  for the battery according to the present invention may be applied to various batteries such as a lithium ion battery and a lead storage battery, etc. 
     According to the present invention, the engagement portion formed into a shape other than a circle, as viewed on plane, is formed in the cover, and further, the recess formed at the outside gasket is engaged to the engagement portion. Thus, when the external terminal and the like are fixed, the workability can be enhanced without any positional deviation of the outside gasket.