Patent Publication Number: US-2023134810-A1

Title: Cap plate welding assembly for electric vehicle secondary battery

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2021-0145411 filed on Oct. 28, 2021, which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a cap plate welding assembly for an electric vehicle secondary battery and, more particularly, to a cap plate welding assembly for an electric vehicle secondary battery that is capable of dramatically improving driving performance of an electric vehicle in such a manner that lengths of cap plates mounted on an upper part of a battery pack casing for electric vehicle secondary batteries are welded to each other to increase a width the cap plates, so that the width of the casing in which battery cells are accommodated is increased, thereby increasing a capacity of the battery cells and the secondary battery. 
     2. Description of the Related Art 
     In a conventional lithium polymer battery for an electric vehicle, a size of a casing in which a plurality of battery cells are accommodated is formed to be small, so there is a problem in that a size of the plurality of battery cells is unable to be increased, so a capacity of the battery cells is reduced. 
     In addition, in a conventional secondary battery for an electric vehicle, in order to increase a capacity of a casing in which a plurality of battery cells are accommodated, a length of a cap plate is increased rather than a width of the cap plate mounted on an upper part of the casing. As a result, when assembling a module, due to an increase in a volume of the battery cells, there is a problem in that a size of the module and the number of the battery cells inserted therein are reduced. 
     In addition, since the secondary battery for the electric vehicle is installed in the lower part of an electric vehicle, when the current battery cell structure in a square shape is applied, there is a problem in that the height of the electric vehicle may increase. 
     In addition, a shape, size, and capacity of a casing in which a plurality of battery cells is accommodated is standardized in a conventional secondary battery for an electric vehicle, so there is a problem in that it is difficult to improve the energy density value for increasing the mileage of the electric vehicle. 
     In addition, in a conventional press forming process, there are problems in that, not only is it difficult to manage a degree of flatness of a cap plate, which is a key to quality of parts, but also, when welding between a cap plate and a casing, productivity of the process is reduced due to excessive generation of welding sparks, and concerns of occurrence of fluid leak exist due to occurrence of pinholes due to poor welding. 
     The foregoing is intended merely to aid in the understanding of the background of the present disclosure and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art. 
     Documents of Related Art 
     Patent Document 
     (Patent Document 1) KR 10-1212552 
     SUMMARY 
     Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and the present disclosure is intended to provide a cap plate welding assembly for an electric vehicle secondary battery that is capable of dramatically improving driving performance of an electric vehicle in such a manner that lengths of two cap plates mounted on an upper part of a battery pack casing for electric vehicle secondary batteries are welded to each other to increase a width of a cap plate, so that the width of the casing in which battery cells are accommodated is increased, thereby increasing a capacity of the battery cells and the secondary battery. 
     In order to achieve the above objective, according to one aspect of the present disclosure, there may be provided a cap plate welding assembly  10  for an electric vehicle secondary battery provided with an anode part  51  and a cathode part  61  fixedly inserted on an upper surface thereof and coupled to an upper part of a battery pack casing  5  for the electric vehicle secondary battery, the cap plate welding assembly  10  for an electric vehicle secondary battery, including: an anode part cap plate  20  formed long in left and right directions in a shape of a square plate material; and a cathode part cap plate  30  formed in the same size as the anode part cap plate  20  and having one side surface thereof coupled by welding to an opposite side surface of the anode part cap plate  20 , wherein the anode part cap plate  20  is provided with first horizontal planes  21  formed long in the left and right directions on a front surface and a rear surface thereof, respectively, and first vertical planes  22  perpendicular to the first horizontal planes  21  and formed in front and rear directions on a left side surface and a right side surface thereof, respectively, the cathode part cap plate  30  is provided with second horizontal planes  31  having the same shape and size as the first horizontal planes  21  and formed long in the left and right directions on a front surface and a rear surface thereof, respectively, and second vertical planes  32  having the same shape and size as the first vertical planes  22  and formed in the front and rear directions on a left side surface and a right side surface thereof, respectively, and the first vertical planes  22  include one first vertical plane coupled by welding to associated one second vertical plane of the second vertical planes  32 , the associated one second vertical plane being opposite to the one first vertical plane. 
     In addition, the anode part cap plate  20  may be provided with a first seating part  23 , on which a lower portion of the anode part  51  may be seated, and which may be recessed to be formed on a right side of an upper surface thereof, the cathode part cap plate  30  may be provided with a second seating part  33 , on which a lower portion of the cathode part  61  may be seated, and which may be recessed to be formed on a left side of an upper surface thereof, and coupling by welding may be performed between the first vertical plane  22  most distant from the first seating part  23  of the anode part cap plate  20  and the second vertical plane  32  most distant from the second seating part  33  of the cathode part cap plate  30 . 
     In addition, the coupling by welding may include: tack welding for temporarily fixing the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22 ; and main welding performed in earnest after the tack welding, wherein, in the tack welding, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  are temporarily welded by conduction welding. 
     In addition, in the tack welding, a welding point  40  may be formed on an upper portion of the one first vertical plane  22  and an upper portion of the associated one second vertical plane  32  opposite to the one first vertical plane  22 , the welding point  40  may include: a first welding point  41  formed at one upper end of the one first vertical plane  22  and one upper end of the associated one second vertical plane  32  opposite to the one first vertical plane  22 ; and a second welding point  42  formed at an opposite upper end of the one first vertical plane  22  and an opposite upper end of the associated one second vertical plane  32  opposite to the one first vertical plane  22 , wherein, in the main welding, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  may be coupled by welding to each other by the conduction welding from the first welding point  41  to the second welding point  42 . 
     In addition, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  may be coupled by melting by a laser beam illuminated in a direction of gravity from a laser welding machine. 
     As described above, in a cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure, two cap plates mounted on an upper part of a battery pack casing for the electric vehicle secondary battery are put together and lengths of the cap plates can be welded to each other to increase a width of a cap combining the two cap plates, thereby allowing a width of the casing to be increased. As a result, in the cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure, it is possible to increase a capacity of battery cells accommodated in the casing, thereby increasing a capacity of a secondary battery. Accordingly, there can be provided an effect of dramatically improving driving performance of an electric vehicle. 
     In addition, the cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure increases the width rather than the length of the cap plate so that there can be provided an effect of not only improving assembling of the module and reducing an area occupied by the battery cells but also increasing the capacity of the battery cells. 
     In addition, the cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure can lower the height of the casing accommodating a plurality of the battery cells, thereby providing an effect of reducing the height of an electric vehicle. 
     In addition, the cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure can efficiently cope with a breaking pressure thanks to an improvement of the strength of a welding part when a battery cell is defective or a high pressure is generated for the battery cells, thereby having an effect of ensuring safety with respect to an explosion of the battery cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objectives, features, and other advantages of the present disclosure will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a configuration diagram of a cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure; 
         FIG.  2    is a plan view of an anode part cap plate shown in  FIG.  1   ; 
         FIG.  3    is a front sectional view of the anode part cap plate shown in  FIG.  2   ; 
         FIG.  4    is a plan view of a cathode part cap plate shown in  FIG.  1   ; and 
         FIG.  5    is a front sectional view of the cathode part cap plate shown in  FIG.  4   . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings in order to describe in detail enough that a person of ordinary skill in the art to which the present disclosure pertains may easily implement the technical idea of the present disclosure. 
     However, the following examples are merely examples to help the understanding of the present disclosure, thereby not reducing or limiting the scope of the present disclosure. In addition, the present disclosure may be embodied in several different forms and is not limited to the embodiments described herein. 
     The cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure is provided with an anode part  51  and a cathode part  61  fixedly inserted to an upper surface thereof, and the cap plate welding assembly  10  is coupled to an upper part of a battery pack casing  5  for a secondary battery. 
       FIG.  1    is a configuration diagram of a cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure. 
     With reference to  FIG.  1   , the cap plate welding assembly for an electric vehicle secondary battery according to the present disclosure includes an anode part cap plate  20  and a cathode part cap plate  30 . 
     First, the anode part cap plate  20  is formed long in left and right directions in a shape of a square plate material. In this case, the anode part cap plate  20  is formed of an aluminum material. 
     In addition, the cathode part cap plate  30  is formed in the same size as the anode part cap plate  20  and having one side surface thereof coupled by welding to an opposite side surface of the anode part cap plate  20 . In this case, the cathode part cap plate  30  is formed of an aluminum material. 
       FIG.  2    is a plan view of an anode part cap plate  20  shown in  FIG.  1   , and  FIG.  3    is a front sectional view of the anode part cap plate  20  shown in  FIG.  2   . 
     With reference to  FIGS.  1  to  3   , first horizontal planes  21  are formed long in left and right directions on a front surface and a rear surface of the anode part cap plate  20 , respectively, and on a left side surface and a right side surface of the anode part cap plate  20 , first vertical planes  22  perpendicular to the first horizontal planes  21  are formed in front and rear directions, respectively. 
     At this time, a length in the left and right directions of the first horizontal planes  21  is formed to be longer than a length in front and rear directions of the first vertical planes  22 , and a length in a vertical direction of the first horizontal planes  21  is formed to be equal to a length of the vertical direction of the first vertical planes  22 . 
     In addition, on an upper right side of an upper surface the anode part cap plate  20 , a first seating part  23 , on which a lower portion of the anode part  51  (not shown) is seated, is recessed to be formed. 
       FIG.  4    is a plan view of a cathode part cap plate shown in  FIG.  1   , and  FIG.  5    is a front sectional view of the cathode part cap plate shown in  FIG.  4   . 
     With reference to  FIGS.  1 ,  4  and  5   , on a front surface and a rear surface of the cathode part cap plate  30 , second horizontal planes  31  having the same shapes and sizes as the first horizontal planes  21  are formed long in the left and right directions, respectively, and on a left side surface and a right side surface of the cathode part cap plate  30 , second vertical planes  32  having the same shapes and sizes as the first vertical planes  22  and being perpendicular to the second horizontal planes  31  are formed in the front and rear directions, respectively. 
     In addition, on a left side of an upper surface of the cathode part cap plate  30 , a second seating part  33 , on which a lower portion of the cathode part  61  (not shown) is seated. 
     In addition, one first vertical plane of the first vertical planes  22  is coupled by welding to associated one second vertical plane, opposite to the one first vertical plane, of the second vertical planes  32 . 
     Specifically, coupling by welding is performed between the first vertical plane  22  most distant from a first seating part  23  of the anode part cap plate  20  and the second vertical planes  32  most distant from the second seating part  33  of the cathode part cap plate  30 . 
     In addition, the coupling by welding of the anode part cap plate  20  and the cathode part cap plate  30  includes tack welding and main welding. 
     First, the tack welding is a welding method performed to temporarily fix the anode part cap plate  20  and the cathode part cap plate  30 . 
     Specifically, in the tack welding, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  are temporarily welded by conduction welding. In this case, the conduction welding refers to a laser welding method by heat conduction applied when the base material is a thin plate or an output of the laser beam is small. 
     When welded by general welding, a hole such as a pinhole and the like may be generated at a welding part between base metals, or a phenomenon of bending of the base metal may occur. However, when welded by conduction welding, the welding part between the base materials is hardly overheated, so that pinholes or bending of the base materials hardly appear. 
     Specifically, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  are coupled by melting by a laser beam illuminated in a direction of gravity from a laser welding machine. 
     In addition, in the tack welding, a welding point  40  is formed on an upper portion of the one first vertical plane  22  and an upper portion of the associated one second vertical plane  32  opposite to the one first vertical plane  22 . 
     At this time, the welding point  40  includes a first welding point  41  and a second welding point  42 . 
     First, the first welding point  41  is formed at one upper end of the one first vertical plane  22  and one upper end of the associated one second vertical plane  32  opposite to the one first vertical plane  22 . 
     In addition, the second welding point  42  is formed at an opposite upper end of the one first vertical plane  22  and an opposite upper end of the associated one second vertical plane  32  opposite to the one first vertical plane  22 . 
     In addition, the main welding means a welding method that is performed in earnest after the tack welding. 
     Specifically, in the main welding, the one first vertical plane  22  and the associated one second vertical plane  32  opposite to the one first vertical plane  22  are coupled by welding to each other by the conduction welding from the first welding point  41  to the second welding point  42 . 
     Meanwhile, after the anode part cap plate  20  and the cathode part cap plate  30  are coupled by welding together, a leak test and a tensile strength test are performed. 
     First, the leak test means a test for checking whether a fluid leaks from a welding part of the cap plate welding assembly  10  for an electric vehicle secondary battery. 
     In addition, the tensile strength test refers to a test for pulling the welded assembly to a preset reference load and then for obtaining the tensile strength of the welded part of the welded assembly from the reference load and the deformed shape of the welded assembly. 
     Meanwhile, on a center of an upper surface of the first seating part  23  of the anode part cap plate  20 , a first through hole  24 , into which a first bolt  52  (not shown) configured to fix the anode part  51  is inserted by passing through, is formed by passing through, and on opposite sides of the upper surface of the first seating part  23 , a first coupling hole  25 , to which a lower portion of the anode part  51  is fixedly coupled, is recessed to be formed. 
     In addition, on a left side of the upper surface of the anode part cap plate  20 , a first upper insertion hole  26  recessed to be formed, and on a lower surface of the first upper insertion hole  26 , a first lower insertion hole  27  is formed by passing through. 
     In addition, on the center of the upper surface of the cathode part cap plate  30 , a fixing hole  36  is recessed to be formed. 
     In addition, on a center of an upper surface of the second seating part  33  of the cathode part cap plate  30 , a second through hole  34 , into which a second bolt  62  (not shown) configured to fix the cathode part  61  is inserted by passing through, is formed by passing through, and on opposite sides of the upper surface of the second seating part  33 , a second coupling hole  35 , to which a second protrusion portion of the cathode part  61  is fixedly coupled, is recessed to be formed. 
     In the cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure, two cap plates mounted on an upper part of a battery pack casing  5  for the electric vehicle secondary battery are put together and lengths of the cap plates may be welded to each other to increase a width of a cap combining the two cap plates, thereby allowing a width of the casing  5  to be increased. As a result, in the cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure, it is possible to increase a capacity of battery cells accommodated in the casing  5 , thereby increasing a capacity of a secondary battery. Accordingly, there may be provided an effect of dramatically improving driving performance of an electric vehicle. 
     In addition, the cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure increases the width rather than the length of the cap plate so that there may be provided an effect of not only improving assembling of the module and reducing an area occupied by the battery cells but also increasing the capacity of the battery cells. 
     In addition, the cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure may lower the height of the casing  5  accommodating a plurality of the battery cells, thereby providing an effect of reducing the height of an electric vehicle. 
     In addition, the cap plate welding assembly  10  for an electric vehicle secondary battery according to the present disclosure may efficiently cope with a breaking pressure thanks to an improvement of the strength of the welding part when a battery cell is defective or a high pressure is generated for the battery cells, thereby having an effect of ensuring safety with respect to an explosion of the battery cell. 
     As described above, the present disclosure has a main technical idea to provide the side structure of a battery pack for an automotive secondary battery, and the embodiment described above with reference to the drawings is only one embodiment. In addition, the true scope of the present disclosure is based on the claims but will also extend to even equivalent embodiments that may exist in various ways.