Patent Publication Number: US-2022231372-A1

Title: Battery module case for electric vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a battery module case for an electric vehicle and, more particularly, to a battery module case for an electric vehicle which has improved assemblability. 
     BACKGROUND ART 
     Generally, an electric vehicle means a vehicle operating using a driving force of a motor caused by energy of a battery. 
     Recently, research on a high-energy-density battery module and battery pack continues to maximize a driving range of an electric vehicle and interest in a mounting structure of a battery case mounted in an electric vehicle is increasing. Here, a conventional battery module is generally manufactured using an aluminum material and may include a body provided to have a hollow hexahedral shape with one open side to accommodate a battery and a cap covering an open part of the body. Here, since it is most economical to manufacture the body using extrusion (pullout) molding due to characteristics of the shape thereof, the body is generally manufactured using an extrusion molding method. 
     However, when a sharp protrusion protrudes and extends from an inside of the body formed through extrusion molding along a longitudinal direction due to a manufacturing defect, there is a serious problem that the battery is scratched and damaged by the protrusion when the battery is inserted into the body. 
     Meanwhile, the battery module may be manufactured by accommodating the battery inside the body and then coupling the body and the cap using a mechanical coupling method such as bolt fastening or the like or a laser welding method. 
     However, since it is necessary to further provide a component for forming a screw thread or a volume for bolt insertion into the body or the like and the cap in order to couple the battery module using a mechanical coupling method, an overall volume of the battery module increases. Accordingly, the volume of the battery module which has to be applied to an inside of the electric vehicle having a limited size increases such that space utilization is degraded. 
     Also, when the battery module is coupled using a laser welding method, due to the high cost of laser welding, economic feasibility and productivity are degraded. Particularly, a defect rate increases due to a melting error caused by an optimal output range difference for welding the body formed of aluminum materials through extrusion molding to the cap manufactured using aluminum materials through die casting such that the quality of a finally manufactured battery module is seriously degraded. 
     DISCLOSURE 
     Technical Problem 
     The present invention is directed to providing a battery module case for an electric vehicle which has improved assemblability. 
     Technical Solution 
     One aspect of the present invention provides a battery module case for an electric vehicle, in which a battery for an electric vehicle, which is provided to be applied to the electric vehicle, is accommodated. The battery module case includes a case portion formed of an aluminum material through extrusion molding and in which a hollow is formed with an internal profile corresponding to an external profile of the battery for an electric vehicle so that at least one of both ends in a longitudinal direction is opened while a press-fit protrusion is formed along an edge of the open end; and one or more cover portions formed of an aluminum material through die casting, provided to be coupled to the open end of the case portion, and in which an extending portion integrally extends and protrudes toward the case portion from a position of an edge corresponding to the press-fit protrusion to be press-fitted on the press-fit protrusion and a bifacial-close contacting groove surrounding both sides of the press-fit protrusion and brought into close contact therewith is formed to be recessed at an end of the extending portion. 
     Advantageous Effects 
     According to the present invention, the following effects are provided. 
     First, a press-fit protrusion formed in a case portion and a bifacial-close contacting groove formed in a cover portion are mutually press-fitted so that the occurrence of a welding defect between the case portion and the cover portion which are manufactured using different manufacturing methods of extrusion and die casting can be prevented in advance so that product quality and productivity can be significantly improved. 
     Second, since edges of both sides in a width direction of the bifacial-close contacting groove formed in the cover portion are shape-matched with and simultaneously surround both sides in a width direction of the press-fit protrusion formed in the case portion so that a width is reduced to be tapered toward an end, a coupling force between the case portion and the cover portion can be significantly improved regardless of repeated thermal deformation. 
     Third, since a catching and constraining protrusion and a catching and constraining groove which are provided on one side and the other side, opposing each other, among the press-fit protrusion and the bifacial-close contacting groove are mutually elastically caught and coupled, minute sliding movement of the press-fit protrusion caused by repetition of frequent thermal deformation can be restricted so as to prevent, in advance, detachment between the case portion and the cover portion even in the case of long-term use and to significantly improve the coupling force therebetween. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a battery module case for an electric vehicle according to one embodiment of the present invention. 
         FIG. 2  is an exploded perspective view illustrating the battery module case for an electric vehicle according to one embodiment of the present invention. 
         FIG. 3  is a front view illustrating a case portion of the battery module case for an electric vehicle according to one embodiment of the present invention. 
         FIG. 4  is a rear view illustrating a cover portion of the battery module case for an electric vehicle according to one embodiment of the present invention. 
         FIG. 5  is a cross-sectional view illustrating a press-fit protrusion and a bifacial-close contacting groove of the battery module case for an electric vehicle according to one embodiment of the present invention. 
         FIG. 6  is a front view illustrating a case portion of a battery module case for an electric vehicle according to a modified example of one embodiment of the present invention. 
         FIG. 7  is an exploded front view illustrating the case portion of the battery module case for an electric vehicle according to the modified example of one embodiment of the present invention. 
     
    
    
     BEST MODE FOR INVENTION 
     Exemplary embodiments of the present invention will be described below in detail with reference to the attached drawings. 
     Modes of the Invention 
     Hereinafter, a battery module case for an electric vehicle according to an exemplary embodiment of the present invention will be described in detail with reference to the drawings. 
       FIG. 1  is a perspective view illustrating a battery module case for an electric vehicle according to one embodiment of the present invention, and  FIG. 2  is an exploded perspective view illustrating the battery module case for an electric vehicle according to one embodiment of the present invention.  FIG. 3  is a front view illustrating a case portion of the battery module case for an electric vehicle according to one embodiment of the present invention, and  FIG. 4  is a rear view illustrating a cover portion of the battery module case for an electric vehicle according to one embodiment of the present invention. 
     As shown in  FIGS. 1 and 4 , a battery module case  100  for an electric vehicle according to one embodiment of the present invention includes a case portion  10  and a cover portion  20 . 
     Here, the battery module case  100  for an electric vehicle is a device provided to accommodate a battery for an electric vehicle provided to be applied to an electric vehicle driven with electrical energy as a power source. Here, the term electric vehicle may be understood as being used as a concept including a pure electric vehicle and a hybrid vehicle. 
     Meanwhile, referring to  FIGS. 1 to 3 , the case portion  10  may include a hollow with an internal profile corresponding to an external profile of the battery for an electric vehicle so that at least one side among both ends in a longitudinal direction is opened. The case portion  10  is formed of an aluminum material through extrusion (pullout) molding. 
     Here, in one embodiment of the present invention, it will be described and illustrated by way of example that the case portion  10  is provided as a hollow rectangular parallelepiped and has both ends open in a longitudinal direction and a pair of cover portions  20  are provided corresponding thereto. 
     Also, the case portion  10  includes a plurality of press-fit protrusions  11 ,  12 ,  13 , and  14  integrally protruding from a body of the case portion  10  along an edge of the open end. Here, the press-fit protrusions  11 ,  12 ,  13 , and  14  may be integrally formed in a region of the edge of the open end of the case portion  10  except a corner portion. 
     Also, the press-fit protrusions  11 ,  12 ,  13 , and  14  may be formed so that a width thereof is reduced to be tapered toward an end. Here, ends of the press-fit protrusions  11 ,  12 ,  13 , and  14  and ends of corners of the edge of the open end of the case portion  10  may be formed with a mutually continuous profile. That is, a width of the ends of the press-fit protrusions  11 ,  12 ,  13 , and  14  may be formed to be smaller than a width of the ends of the corners of the edge of the open end of the case portion  10 . 
     Also, the press-fit protrusions  11 ,  12 ,  13 , and  14  may include a first press-fit protrusion  11  formed on an upper side of the edge of the open end of the case portion  10  and a second press-fit protrusion  12  formed on a lower side of the edge of the open end of the case portion  10 . Also, the press-fit protrusions  13 ,  14 ,  13 , and  14  may include a third press-fit protrusion  13  formed on one side of the edge of the open end of the case portion  10  and a fourth press-fit protrusion  14  formed on the other side of the edge of the open end of the case portion  10 . 
     Meanwhile, referring to  FIGS. 1, 2, and 4 , one or more cover portions  20  may be provided to be coupled to the open end of the case portion  10 . Here, in one embodiment of the present invention, a pair of cover portions  20  may be provided to be coupled to both ends of the case portion  10 , respectively. The cover portion  20  is formed of an aluminum material through die casting. 
     Here, although the case portion  10  formed through extrusion molding and the cover portion  20  formed through die casting are formed of the same aluminum material, due to a difference in molding methods, there is a melting error caused by a difference in optimal output ranges of a welding device for welding. Here, the cover portion  20  may be formed to have a cap shape with one open side facing the case portion  10  and may have one open surface facing the case portion  10 . Also, an extending portion  25  (refer to  FIG. 5 ) may extend and protrude toward the case portion  10  from a position corresponding to the press-fit protrusions  11 ,  12 ,  13 , and  14  on an edge of the one surface of the cover portion  20 . 
     Also, the cover portion  20  may include bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  formed to be recessed in the edge at positions corresponding to the press-fit protrusions  11 ,  12 ,  13 , and  14  to be press-fitted on the press-fit protrusions  11 ,  12 ,  13 , and  14 . Here, the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  may be recessed at the end of the extending portion  25  (refer to  FIG. 5 ). 
     Here, the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  may be pressed against to be press-fitted on and coupled to the press-fit protrusions  11 ,  12 ,  13 , and  14  while surrounding both sides in a width direction of the press-fit protrusions. Also, the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  may be integrally formed in a region of the edge of the cover portion  20  except a corner portion. 
     Also, the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  may include a first bifacial-close contacting groove  21  formed on an upper side of the edge of the cover portion  20  and a second bifacial-close contacting groove  22  formed on a lower side of the edge of the cover portion  20 . Also, the bifacial-close contacting grooves  23 ,  24 ,  23 , and  24  may include a third bifacial-close contacting groove  23  formed on one side of the edge of the cover portion  20  and a fourth bifacial-close contacting groove  24  formed on the other side of the edge of the cover portion  20 . 
     Here, the first press-fit protrusion  11  and the first bifacial-close contacting groove  21  may be mutually press-fitted, and the second press-fit protrusion  12  and the second bifacial-close contacting groove  22  may be mutually press-fitted. In addition, the third press-fit protrusion  13  and the third bifacial-close contacting groove  23  may be mutually press-fitted, and the fourth press-fit protrusion  14  and the fourth bifacial-close contacting groove  24  may be mutually press-fitted. 
     In this way, the press-fit protrusions  11 ,  12 ,  13 , and  14  and the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  are mutually press-fitted, respectively, such that external profile of the case portion  10  and the cover portion  20  may be formed to be a substantially continuous profile. Here, the corner portion of the edge of the open end of the case portion  10  and the corner portion of the edge of the cover portion  20  may come into surface contact with each other. 
     Accordingly, unlike a conventional case in which a body and a cap are coupled through expensive laser welding, the press-fit protrusions  11 ,  12 ,  13 , and  14  formed in the case portion  10  and the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  formed in the cover portion  20  are mutually press-fitted, respectively. In this way, expensive laser welding is not required so that economic feasibility may be improved and assembling convenience and manufacturing convenience may be improved through an easy assembling structure. 
     Particularly, the occurrence of a welding defect between the case portion  10  and the cover portion  20  which are manufactured using different manufacturing methods of extrusion and die casting such that a melting error caused by an optimum output range difference for mutual welding is prevented. Accordingly, product quality and productivity may be significantly improved. 
     Meanwhile,  FIG. 5  is a cross-sectional view illustrating the press-fit protrusion and the bifacial-close contacting groove of the battery module case for an electric vehicle according to one embodiment of the present invention. Here, the press-fit protrusion  11  shown in  FIG. 5  is illustrated as an example of any one of the press-fit protrusions  11 ,  12 ,  13 , and  14  shown in  FIG. 2  and it should be understood that shapes of the respective press-fit protrusions  11 ,  12 ,  13 , and  14  are substantially the same. In addition, the bifacial-close contacting groove  21  shown in  FIG. 5  is illustrated as an example of any one of the bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  shown in  FIG. 2  and it should be understood that shapes of the respective bifacial-close contacting grooves  21 ,  22 ,  23 , and  24  are substantially the same. 
     As shown in  FIG. 5 , the press-fit protrusion  11  may be formed so that both sides in a width direction may be narrowed and reduced toward ends thereof and thus a width may be tapered. Here, the width direction means a direction from an outside portion of the case portion  10  exposed outward to an inside portion of the case portion  10  in which the battery for an electric vehicle is accommodated. That is, the press-fit protrusion  11  may be formed so that both sides in the width direction are simultaneously narrowed toward the end of the case portion  10 . 
     Here, the press-fit protrusion  11  is press-fitted into and shape-matched with the bifacial-close contacting groove  12 . To this end, a thickness of the press-fit protrusion  11  in the width direction may be slightly thicker than an inner width of the bifacial-close contacting groove  12 . That is, the width of the press-fit protrusion  11  and the inner width of the bifacial-close contacting groove  12  may be formed to substantially correspond to each other. 
     Also, the bifacial-close contacting groove  21  may be formed with an internal profile corresponding to an external profile of the press-fit protrusion  11  to be shape-matched with the press-fit protrusion  11  while surrounding both sides of the press-fit protrusion in the width direction. 
     In detail, the bifacial-close contacting groove  21  may be formed to be recessed at an end of the extending portion  25  integrally protruding from the edge of one surface of the cover portion. Here, a pair of edges  26  and  27  may be formed on both sides of the bifacial-close contacting groove  21  in the width direction to surround both sides of the press-fit protrusion  11  in the width direction and brought into close contact therewith. 
     Here, the edges  26  and  27  may integrally extend from the extending portion  25  and include a first edge  26  and a second edge  27 . Here, lengths of the first edge  26  and the second edge  27  may be formed to differ from each other. However, the lengths of the edges  26  and  27  may be formed to be equal. 
     For example, referring to  FIG. 5 , in the edges  26  and  27 , a longitudinal length of the first edge  26  formed at a position exposed outside the cover portion may be formed to smaller than a longitudinal length of the second edge  27 . In addition, the external profile of the case portion may be formed to correspond to the edges  26  and  27  so that respective ends of the edges  26  and  27  are shape-matched with the case portion of the press-fit protrusion  11  side. Also, a length of one of both sides of the press-fit protrusion  11  in the width direction which is exposed outside the case portion  10  may be smaller than a length of the other of both sides of the press-fit protrusion  11  in the width direction which is disposed inside the case portion  10 . Accordingly, both edges  26  and  27  in the width direction of the bifacial-close contacting groove  21  formed in the cover portion simultaneously surround and are shape-matched with both sides in the width direction of the press-fit protrusion  11  formed to have a tapered width toward the end of the case portion. Accordingly, since coupling is easily and firmly performed through only mutual press-fitting without additional welding, product quality and manufacturing convenience may be improved. 
     Also, regardless of repeated thermal deformation of the battery for an electric vehicle, detachment between the case portion and the cover portion may be prevented in advance so as to significantly improve a coupling force therebetween. Here, as heating occurs in the battery for an electric vehicle, the case portion and the cover portion may repeatedly thermally expand and contract. Here, the thermal expansion of the case portion having a larger contact area with the battery for an electric vehicle is greater than thermal expansion of the cover portion. Accordingly, the thermal expansion of the press-fit protrusion  11  is greater than the thermal expansion of the bifacial-close contacting groove  21 . That is, in an initial state of being thermally contracted, the press-fit protrusion  11  and the bifacial-close contacting groove  21  may be mutually press-fitted and the coupling force between the press-fit protrusion  11  and the bifacial-close contacting groove  21  may be firmly maintained even in the thermal expanded state. 
     Meanwhile, a catching and constraining protrusion  28  may protrude from an outer surface of one of the press-fit protrusion  11  and the bifacial-close contacting groove  21  and a catching and constraining groove  15  into which the catching and constraining protrusion  28  is elastically inserted to be caught and constrained may be recessed at an outer surface of the other which is opposite thereto. 
     That is, the catching and constraining protrusion  28  may be formed in any one of the press-fit protrusion  11  and the bifacial-close contacting groove  21 , and the catching and constraining groove  15  may be formed in the other of the press-fit protrusion  11  and the bifacial-close contacting groove  21  which is opposite thereto. 
     Here, in one embodiment of the present invention, it has been illustrated and described by way of example that the catching and constraining groove  15  is recessed at an outer surface facing the catching and constraining protrusion  28  to allow the catching and constraining protrusion  28  to be elastically inserted into and constrained by the press-fit protrusion  11 . 
     Also, in one embodiment of the present invention, it has been illustrated and described by way of example that the catching and constraining protrusion  28  protruding to face the press-fit protrusion  11  is formed on at least one of both edges  26  and  27  in the width direction of the bifacial-close contacting groove  21 . Here, the catching and constraining protrusion  28  may be integrally formed with a rounded outer profile on at least any one of the ends of both edges  26  and  27  of the bifacial-close contacting groove  21  in the width direction. 
     Of course, in some cases, a catching and constraining protrusion may be formed on a press-fit protrusion and a catching and constraining groove may be formed in a bifacial-close contacting groove, and this may be understood as being included in the scope of the present invention. 
     Here, the catching and constraining protrusion  28  may integrally extend and protrude from at least any one of the edges  26  and  27  in an integrally rounded shape toward the press-fit protrusion  11 . Also, a shape of a recessed profile of the catching and constraining groove  15  may be formed corresponding to the rounded external profile of the catching and constraining protrusion  27 . 
     Here, in one embodiment of the present invention, it has been illustrated and described by way of example that the catching and constraining protrusion  28  is integrally formed with an end of the second edge  27  formed to be longer than the first edge  26 . Of course, the catching and constraining protrusion  28  may be formed on the first edge  26  or may be formed on each of the first edge  26  and the second edge  27 . 
     Also, although it has been illustrated and described by way of example in one embodiment of the present invention that the catching and constraining groove  15  is formed in one surface of the press-fit protrusion  11  opposite the second edge  26  and opposite to an accommodation region of the battery for an electric vehicle, the present invention is not limited thereto. 
     Also, when the press-fit protrusion  11  and the bifacial-close contacting groove  21  are shape-matched with each other to insert the catching and constraining protrusion  28  into the catching and constraining groove  15 , the second edge  27  on which the catching and constraining protrusion  28  is formed may be temporarily elastically deformed. That is, when the press-fit protrusion  11  and the bifacial-close contacting groove  21  are shape-matched with each other, the catching and constraining protrusion  28  may come into contact with an outer surface of the press-fit protrusion  11  and the second edge  27  may be elastically deformed and then elastically restored. 
     Here, the second edge  27  may be provided to have a preset length or longer to allow the catching and constraining protrusion  28  to be elastic so that the catching and constraining protrusion  28  formed on the end of the second edge  27  is elastically inserted into the catching and constraining groove  15  to be caught and constrained. That is, since the second edge  27  is provided to have a preset length or longer to be elastically deformable, the catching and constraining protrusion  28  may be elastically inserted into the catching and constraining groove  15 . 
     Accordingly, after the battery for an electric vehicle is accommodated in the case portion, the press-fit protrusion  11  and the bifacial-close contacting groove  21  may be shape-matched with each other and the catching and constraining protrusion  28  and the catching and constraining groove  15  may be mutually caught and constrained. Accordingly, since the case portion and the cover portion may be easily coupled through only mutual press-fitting, manufacturing convenience may be significantly improved. 
     Here, the battery for an electric vehicle is repeatedly heated and cooled according to driving conditions such that the case portion accommodating the battery for an electric vehicle and the cover portion coupled thereto are thermally deformed. 
     Here, when a catching and constraining structure between the catching and constraining protrusion  28  and the catching and constraining groove  15  is not formed, the cover portion may be detached from the case portion whenever thermal deformation of the battery for an electric vehicle is repeated. Accordingly, the catching and constraining protrusion  28  formed with a rounded external profile on at least one of the ends of both edges  26  and  27  of the bifacial-close contacting groove  21  in the width direction is elastically inserted into and then restored to be constrained by the catching and constraining groove  15  formed to be recessed in the press-fit protrusion  11 . Accordingly, detachment between the case portion and the cover portion which is caused by repeated thermal deformation of the battery for an electric vehicle may be prevented in advance so as to significantly improve the coupling force therebetween. 
     As described above, the catching and constraining protrusion  28  and the catching and constraining groove  15  provided on one side and the other side, opposing each other, among the press-fit protrusion  11  and the bifacial-close contacting groove  21  are mutually and elastically caught and coupled. Accordingly, minute sliding movement of the press-fit protrusion  11  caused by repetition of frequent thermal deformation is restricted so that detachment between the case portion and the cover portion may be prevented in advance even in the case of long-term use so as to significantly improve a coupling force. 
     Meanwhile,  FIG. 6  is a front view illustrating a case portion of a battery module case for an electric vehicle according to a modified example of one embodiment of the present invention, and  FIG. 7  is an exploded front view illustrating the case portion of the battery module case for an electric vehicle according to the modified example of one embodiment of the present invention. Since basic components of the modified example of one embodiment of the present invention except a case portion  120  are the same as those of the above-described one embodiment, a detailed description of the same components will be omitted. 
     As shown in  FIGS. 6 and 7 , a battery module case  200  for an electric vehicle according to the modified example of one embodiment of the present invention includes a case portion  120  and a cover portion (not shown). 
     Here, the case portion  120  may include a first case portion  121  and a second case portion  122 . Here, the first case portion  121  are separately manufactured from the second case portion  122  and coupled to each other while a hollow may be formed with an internal profile corresponding to an external profile of the battery for an electric vehicle so that at least any one of both ends in a longitudinal direction may be opened. The first case portion  121  and the second case portion  122  may be formed of an aluminum material through extrusion molding. 
     Also, a plurality of press-fit protrusions may integrally protrude from the first case portion  121  and the second case portion  122  along edges of ends in a longitudinal direction. Here, a first press-fit protrusion may be formed on the first case portion  121 , and a second press-fit protrusion, a third press-fit protrusion, and a fourth press-fit protrusion may be formed on the second case portion  122 . Here, since the shapes of the first press-fit protrusion, the second press-fit protrusion, the third press-fit protrusion, and the fourth press-fit protrusion are the same as those according to one embodiment, a detailed description will be omitted. 
     In one embodiment of the present invention, it has been illustrated and described by way of example that an overall shape of the case portion  120  is provided as a hollow rectangular parallelepiped and both open ends in a longitudinal direction are opened. Also, the first case portion  121  and the second case portion  122  may be understood as being separately manufactured to form an upper side and a lower side of the overall case portion, respectively, and coupled to each other. 
     In detail, the first case portion  121  may be formed with an internal profile corresponding to an external profile of one side of the battery for an electric vehicle. Also, the second case portion  122  is detachably coupled to the first case portion  121  while being formed with an internal profile corresponding to an external profile of the other side of the battery for an electric vehicle. 
     Also, a shape-matching protrusion  123  may protrude from an opposite portion of one of the first case portion  121  and the second case portion  122 . Here, the opposite portion means a region in which the first case portion  121  and the second case portion  122  come into contact with each other. 
     Also, a shape-matching groove  124  may be recessed in an opposite portion of the other of the first case portion  121  and the second case portion  122  so that the shape-matching protrusion  123  is insertion-coupled thereto. Here, the shape-matching protrusion  123  and the shape-matching groove  124  may be formed to extend from respective opposite surfaces of the first case portion  121  and the second case portion  122  in a longitudinal direction. Here, although it has been illustrated and described by way of example in the modified example of one embodiment of the present invention that the shape-matching protrusion  123  is formed on the first case portion  121  and the shape-matching groove  124  is formed in the second case portion  122 , the present invention is not limited thereto. 
     In detail, the shape-matching protrusion  123  may be formed so that both sides in a width direction are narrowed to be tapered toward ends thereof. That is, the shape-matching protrusion  123  may be formed so that both sides in the width direction are simultaneously narrowed toward an end of the first case portion  121 . 
     Here, the shape-matching protrusion  123  is press-fitted into and shape-matched with the shape-matching groove  124 . To this end, a thickness of the shape-matching protrusion  123  in the width direction may be slightly thicker than an inner width of the shape-matching groove  124 . That is, the width of the shape-matching protrusion  123  and the inner width of the shape-matching groove  124  may be formed to substantially correspond to each other. 
     Also, the shape-matching groove  124  may be formed with an internal profile corresponding to an external profile of the shape-matching protrusion  123  to be shape-matched with the shape-matching protrusion  123  while surrounding both sides of the shape-matching protrusion  123  in the width direction. In detail, the shape-matching groove  124  may be formed to be recessed at the end of the second case portion  122  opposite to the shape-matching protrusion  123 . Here, a pair of shape-matching edges may be formed on both sides of the shape-matching groove  124  in the width direction to surround the both sides of the shape-matching protrusion  123  in the width direction and brought into close contact therewith. 
     Here, the respective shape-matching edges may include a first shape-matching edge and a second shape-matching edge. Here, lengths of the first shape-matching edge and the second shape-matching edge may be formed to differ from each other. However, the lengths of the respective shape-matching edges may be formed to be the same. 
     For example, referring to  FIG. 7 , among the shape-matching edges, a longitudinal length of the first shape-matching edge formed at a position exposed outside the second case portion  122  may be formed to be smaller than a longitudinal length of the second shape-matching edge. In addition, to allow ends of the shape-matching edges to be shape-matched with the first case portion  121  on a side of the shape-matching protrusion  123 , an external profile of the first case portion  121  may be formed to correspond to the shape-matching edges. Also, a length of one of both sides of the shape-matching protrusion  123  in the width direction which is exposed outside the first case portion  121  may be formed to be smaller than a length of the other of both sides of the shape-matching protrusion  123  in the width direction which is disposed inside the first case portion  121 . 
     Accordingly, the shape-matching edges on both sides in the width direction of the shape-matching groove  124  formed in the second case portion  122  simultaneously surround and are shape-matched with both sides in the width direction of the shape-matching protrusion  123  formed on the first case portion so that the width is reduced to be tapered toward the end. Accordingly, since coupling is firmly and easily performed through only mutual press-fitting without additional welding, product quality and manufacturing convenience may be improved. 
     Meanwhile, a fixing and constraining groove  124   b  may be formed to be recessed in an outer surface of the shape-matching protrusion  123  opposite a fixing and constraining protrusion  123   a  which will be described below to allow the fixing and constraining protrusion  123   a  to be elastically inserted thereinto and constrained. 
     Also, the fixing and constraining protrusion  123   a  may be integrally formed with a rounded external profile while protruding to be opposite the shape-matching protrusion  123  on at least one of the shape-matching edges on both sides in the width direction of the shape-matching groove  124 . 
     Here, the fixing and constraining protrusion  123   a  may be formed to extend and protrude from at least one of the shape-matching edges in an integrally rounded shape toward the shape-matching protrusion  123 . Also, a recessed profile of the fixing and constraining groove  124   b  may be formed to correspond to a rounded external profile of the fixing and constraining protrusion. 
     Here, in the modified example of one embodiment of the present invention, it has been illustrated and described by way of example that the fixing and constraining protrusion  123   a  is integrally formed at the end of the second shape-matching edge formed to be longer than the first shape-matching edge. Of course, the first fixing and constraining protrusion  123   a  may be formed on the first shape-matching edge or may be formed on each of the first shape-matching edge and the second shape-matching edge. Also, although it has been illustrated and described by way of example in one embodiment of the present invention that the fixing and constraining groove  124   b  is opposite the second shape-matching edge and formed in one surface of the shape-matching protrusion  123  opposite the region accommodating the battery for an electric vehicle, the present invention is not limited thereto. 
     Also, in order to insert the fixing and constraining protrusion  123   a  into the fixing and constraining groove  124   b , when the shape-matching protrusion  123  and the shape-matching groove  124  are shape-matched with each other, the second shape-matching edge on which the fixing and constraining protrusion  123   a  is formed may be temporarily elastically deformed. That is, when the shape-matching protrusion  123  and the shape-matching groove  124  are shape-matched with each other, the fixing and constraining protrusion  123   a  comes into contact with an outside of the shape-matching protrusion  123  and the second shape-matching edge may be elastically deformed and then elastically restored. Accordingly, after the battery for an electric vehicle is accommodated inside the first case portion  121  and the second case portion  122 , the shape-matching protrusion  123  and the shape-matching groove  124  may be shape-matched with each other and the fixing and constraining protrusion  123   a  and the fixing and constraining groove  124   b  may be mutually caught and constrained. 
     Also, the battery for an electric vehicle may be inserted between the first case portion  121  and the second case portion  122  which are separated from each other. Accordingly, the damage caused by scratches or the like which may occur when insertion is performed in a longitudinal direction of the case portion  120  may be prevented in advance. Here, since the battery for an electric vehicle is repeatedly heated and cooled several times according to an operating state, the first case portion  121  and the second case portion  122  which accommodate the battery for an electric vehicle are thermally deformed. 
     Here, when a catching and constraining structure between the fixing and constraining protrusion  123   a  and the fixing and constraining groove  124   b  is not formed, the second case portion  122  may be detached from the first case portion  121  due to repeated thermal deformation of the battery for an electric vehicle. 
     Accordingly, the fixing and constraining protrusion  123   a  formed with the rounded external profile on at least one of the ends of the shape-matching edges on both sides in the width direction of the shape-matching groove  124  is elastically inserted into the fixing and constraining groove  124   b  formed to be recessed in the shape-matching protrusion  123  and restored and restricted. Accordingly, the detachment between the first case portion  121  and the second case portion  122  caused by repetition of thermal deformation of the battery for an electric vehicle may be prevented in advance so as to significantly improve the coupling force therebetween. 
     In addition, since the first case portion  121  and the second case portion  122  are separately manufactured and stacked to reduce a hollow volume, space utilization may be improved and the number of products transportable at one time may increase so as to significantly improve economic feasibility. 
     Although the embodiments of the present invention have been described above, the present invention is not limited thereto and various modifications thereof may be made by one of ordinary skill in the art without departing from the scope of the present invention defined in the claims thereof and belong to the scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to the industrial field of manufacturing and using an electric vehicle by providing a battery module case for the electric vehicle.