PATENT ABSTRACT
A structure for mounting a battery onto an electric vehicle comprising: a body member, which is made from metal, forming a body of the electric vehicle a battery case, which is made from resin, containing the battery charging electric power for driving the electric vehicle; a framework member, which is made from metal, being embedded in the battery case; and a connecting member connecting between the framework member and the body member.

PATENT DESCRIPTION
BACKGROUND OF THE INVENTION 
       [0001]    (1) Field of the Invention 
         [0002]    The present invention relates to a structure for mounting a battery onto an electric vehicle. 
         [0003]    (2) Description of Related Art 
         [0004]    Structures for mounting batteries using battery frames onto electric vehicles have been known in the art. The following related documents 1 and 2 disclose examples of such a structure. Although no description about material of the battery frame is disclosed in the related documents 1 and 2, conventional battery frames are metal because the battery frames support heavy batteries. 
         [0005]    [Related Document 1] Japanese Laid-open Publication H7-69077 
         [0006]    [Related Document 2] Japanese Laid-open Publication H7-69237 
         [0007]    However, metal battery frames increase the weight of electric vehicles, and accordingly, the range of the electric vehicles becomes shorter and the drivability becomes worse. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention has been developed in consideration of this situation, and it is therefore an object of the invention to provide a structure for mounting a battery onto an electric vehicle to improve the crash-resistant capability of the battery mounted on the electric vehicle while preventing increased weight and enhancing the rigidity of the electric vehicle. 
         [0009]    For this purpose, in accordance with an aspect of the present invention, there is provided a structure for mounting the battery onto the electric vehicle comprising: a body member, which is made from metal, forming a body of the electric vehicle; a battery case, which is made from resin, including the battery containing electric power for driving the electric vehicle; a framework member, which is made from metal, being embedded in said battery case; a connecting member connecting between said framework member and said body member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
           [0011]      FIG. 1  is a top view schematically showing the entire configuration of an embodiment of the present invention; 
           [0012]      FIG. 2  is a side view schematically showing the entire configuration of the embodiment of the present invention; 
           [0013]      FIG. 3  is a top view schematically showing a battery tray in the embodiment of the present invention; 
           [0014]      FIG. 4  is a schematic perspective view mainly showing batteries in a battery case and a battery holder in the embodiment of the present invention; 
           [0015]      FIG. 5  is a schematic perspective view mainly showing metal frames built into a battery tray in the embodiment of the present invention; 
           [0016]      FIG. 6  (A) is a top view schematically showing a built-in nut in the embodiment of the present invention; 
           [0017]      FIG. 6  (B) is a side view schematically showing the same built-in nut in the embodiment of the present invention; 
           [0018]      FIG. 6  (C) is a bottom view schematically showing the same built-in nut in the embodiment of the present invention; 
           [0019]      FIG. 7  is a cross-section view schematically showing the same built-in nut in the embodiment of the present invention; 
           [0020]      FIG. 8  is a schematic perspective view showing the bottom side of the battery case in the embodiment of the present invention; 
           [0021]      FIG. 9  is a perspective view schematically showing the bottom side of the battery case in the embodiment of the present invention; 
           [0022]      FIG. 10  is a schematic view showing lateral-end supporting members and a front-end supporting member in the embodiment of the present invention; 
           [0023]      FIG. 11  is a cross-section view indicated XI-XI in  FIG. 1  schematically showing a part of the structure in the embodiment of the present invention; 
           [0024]      FIG. 12  is a cross-section view indicated XII-XII in  FIG. 1  schematically showing a part of the structure in the embodiment of the present invention; 
           [0025]      FIG. 13  is a cross-section view indicated XIII-XIII in  FIG. 1  schematically showing a part of the structure in the embodiment of the present invention; 
           [0026]      FIG. 14  is a cross-section view indicated XIV-XIV in  FIG. 1  schematically showing a part of the structure in the embodiment of the present invention; 
           [0027]      FIG. 15  is a front view schematically showing a cover plate in the embodiment of the present invention; 
           [0028]      FIG. 16  is a perspective schematic view mainly showing the cover plate in the embodiment of the present invention; 
           [0029]      FIG. 17  is a cross-section view indicated XVII-XVII in  FIG. 16  schematically showing a part of the structure in the embodiment of the present invention; 
           [0030]      FIG. 18  is a cross-section view indicated XVIII-XVIII in  FIG. 16  schematically showing a part of the structure in the embodiment of the present invention; 
           [0031]      FIG. 19  is a perspective view schematically showing a battery cover in the embodiment of the present invention; 
           [0032]      FIG. 20  is a top view schematically showing the battery cover in the embodiment of the present invention; and 
           [0033]      FIG. 21  is a schematic diagram showing the connecting structures connected by metal parts in the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The embodiment of the present invention will now be described with reference to the accompanying drawings. 
         [0035]    As shown in  FIG. 1 , side members (also called ‘body members’ or ‘first body members’)  11  and  11  are mounted on the left and right sides of an electric vehicle  10 . The side members  11  and  11  extend in the longitudinal direction of the electric vehicle  10 . 
         [0036]    Further, a battery cross member (also called ‘body member’ or ‘second body member’)  12 , which extends in the transversal direction (left-right direction) and which connects the pair of side members  11  and  11 , is also mounted in the electric vehicle  10 . 
         [0037]    The side members  11  and  11  and the battery cross member  12  are iron, and constitute a body of the electric vehicle  10 . 
         [0038]    At a position between the pair of side members  11  and  11  and rear of the battery cross member  12 , a battery case  13  is disposed. The battery case  13 , which is made from polybutylene resin including glass fibers, contains and holds batteries  20  (shown in  FIG. 4 ) inside thereof while avoiding ventilation between outside and inside by keeping the inside of battery case  13  airtight. 
         [0039]    As shown in  FIG. 2 , the battery case  13  mainly comprises a battery tray  14  and a battery cover  15 . 
         [0040]    As shown in  FIG. 3 , a front-end wall (second resin wall)  16 , a left-end wall (third resin wall)  17 , a right-end wall  18 , a rear-end wall  19 , a front partition  21 , a middle partition  22  and a rear partition  23  are fixed in the battery tray  14 . 
         [0041]    The front partition  21 , the middle partition  22  and the rear partition  23  are walls extending between the left-end wall  17  and the right-end wall  18  in the left-right direction of the battery tray  14 . 
         [0042]    The front partition  21  is disposed at the front of the middle partition  22 . The rear partition  23  is disposed at the rear of the middle partition  22 . 
         [0043]    Further, in the battery tray  14 , front-battery partitions  24 A,  24 B,  24 C and  24 D are fixed. The front-battery partitions  24 A,  24 B,  24 C and  24 D are walls extending between the front-end wall  16  and the front partition  21  in the longitudinal direction (front-rear direction). Particularly, front-battery partitions  24 A and  24 D are also called first resin walls. 
         [0044]    Furthermore, in the battery tray  14 , rear-battery partitions  27 A,  27 B,  27 C and  27 D are fixed. The rear-battery partitions  27 A,  27 B,  27 C and  27 D are walls extending between the rear-end wall  19  and the rear partition  23  in the front-rear direction. 
         [0045]    Still further, in the battery tray  14 , front reinforcing walls  25 A and  25 B and concave side walls  29  and  29  are formed. The front reinforcing walls  25 A and  25 B are walls extending between the front partition  21  and the middle partition  22  in the front-rear direction. The concave side walls  29  and  29  are walls to individually make concave portions  28 A and  28 B. 
         [0046]    Between the rear partition  23  and the middle partition  22 , middle-battery partitions  26 A and  26 B are formed which walls extend in the front-rear direction. 
         [0047]    Further, between the middle partitions  26 A and  26 B, rear reinforcing walls  31 A and  31 B are formed which walls extend in the front-rear direction. 
         [0048]    As shown in  FIG. 4 , batteries  20  are fixed securely inside the battery case  13  in such a way that after the batteries  20  are individually disposed at the correct positions on the battery tray  14 , the batteries  20  are supported by battery holders (not shown), then the battery holders are fixed to the battery tray  14  by bolts (not shown). 
         [0049]    As shown in  FIG. 5 , in the battery tray  14 , a frame set (also called ‘metal frame’)  32  is included. The frame set (framework member)  32 , which is made from iron, mainly comprises front frame set (front framework)  33  and rear frame set (rear framework)  34 . 
         [0050]    As shown in  FIG. 21 , the side members  11 , the battery cross member  12 , the metal frame  32 , the front blocks  63 A and  63 B, and the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D, which are metal parts, interconnect with each other directly or indirectly so that the rigidity of the battery case  13  is increased. 
         [0051]    The front frame set  33  includes a front-left frame  38 , a front-middle frame  36  and a front-right frame  37 . 
         [0052]    The front-left frame (third metal reinforce)  38  which is an L-shaped member integrally formed by a front-left metal portion (side portion)  38 G and a front-left-front metal portion (front portion)  38 F. 
         [0053]    The front-left metal portion  38 G is embedded in the left-end wall  17  (shown in  FIG. 3 ) of the battery tray  14 . The front-left-front metal portion  38 F is embedded in the front-end wall  16  (also shown in  FIG. 3 ) of the battery tray  14 . 
         [0054]    On a left surface of the front-left metal portion  38 G, nuts  38 A,  38 B,  38 C and  38 D are welded. On a front surface of the front-left-front metal portion  38 F, nut  38 E is welded. Further, on a rear surface of the front-left-front metal portion  38 F, nut  38 H is welded. The front-right frame (third metal reinforce)  37  which is an L-shaped member integrally formed by a front-right metal portion (side portion)  37 G and a front-right-front metal portion (front portion)  37 F. 
         [0055]    The front-right metal portion  37 G is embedded in the right-end wall  18  (shown in  FIG. 3 ) of the battery tray  14 . The front-right-front metal portion  37 F is embedded in the front-end wall  16  (also shown in  FIG. 3 ) of the battery tray  14 . 
         [0056]    On a right surface of the front-right metal portion  37 G, nuts  37 A,  37 B,  37 C and  37 D are welded. On a front surface of the front-right-front metal portion  37 F, nut  37 E is welded. Further, on a rear surface of the front-right-front metal portion  37 F, nut  37 H is welded. 
         [0057]    The front-middle frame (third front frame)  36  which is a U-shaped member integrally formed by an A-reinforce (first metal-wall reinforce)  39 A and  39 B and a B-reinforce (second metal-wall reinforce)  36 C. 
         [0058]    The B-reinforce  36 C, which is embedded in the front-end wall  16  and extends in the transversal direction, interconnects the A-reinforces  39 A and  39 B. On a front surface of the B-reinforce  36 C, nuts  36 A and  36 B are welded. Further, on a rear surface of the B-reinforce  36 C, nuts  36 D,  36 E and  36 F are welded. 
         [0059]    As shown in  FIG. 21 , the left side of the A-reinforce  39 A is embedded in the front-battery partition (first resin wall)  24 A and is disposed on the rear side of the front-A block (also called crash-proof block, first crash-proof block or connecting member)  63 A and is between imaginary lines L 1  and L 2    
         [0060]    The imaginary line L 1  extends in the transversal direction through the nut  38 E at which point the left front block  63 A and the front-left-front metal portion  38 F are connected. 
         [0061]    The imaginary line L 2  extends in the transversal direction through the nut  36 A at which point the left front block  63 A and the front-middle frame  36  are connected. 
         [0062]    The right side of the A-reinforce  39 B, which is embedded in the front-battery partition (first resin wall)  24 D and is disposed at the rear side of the front-B block (also called crash-proof block, first crash-proof block or connecting member)  63 B, is disposed between imaginary lines L 3  and L 4 . 
         [0063]    The imaginary line L 3  extends in the transversal direction through the nut  36 B at which point the right front block  63 B and the front-middle frame  36  are connected. The imaginary line L 4  extends in the transversal direction through the nut  37 E at which point the right front block  63 B and the front-right-front metal portion  37 F are connected. 
         [0064]    The front-left frame  38  is distanced from the front-middle frame  36  in gap G 1 . Likewise, the front-right frame  37  is distanced from the front-middle frame  36  in gap G 2 . 
         [0065]    The left front block  63 A is fixed to the nut  36 A welded on the B-reinforce  36 C of the front-middle frame  36  by a bolt  67 . Further, the left front block  63 A is fixed to the nut  38 E welded on the front-left-front metal portion  38 F of the front-left frame  38  by another bolt  67 . Additionally, the left front block  63 A is fixed to the battery cross member  12  by a bolt (not shown). 
         [0066]    Likewise, the right front block  63 B is fixed to the nut  36 B welded on the B-reinforce  36 C of the front-middle frame  36  by a bolt  67 . Further, the right front block  63 B is fixed to the nut  37 E welded on the front-right-front metal portion  37 F of the front-right frame  37  by another bolt  67 . Additionally, the right front block  63 B is fixed to the battery cross member  12  by a bolt (not shown). 
         [0067]    Next, the rear frame set  34  will be described in detail as follows. 
         [0068]    As shown in  FIGS. 5 and 21 , the rear frame set  34  includes a rear-lateral-left frame  41 , a rear-end-left frame  42 , a rear-end-middle frame  43 , a rear-end-right frame  44  and a rear-lateral-right frame  45 . 
         [0069]    The rear-lateral-left frame (first or second rear frame)  41  is embedded in the left-end wall  17  (shown in  FIG. 3 ). Nuts  41 A,  41 B,  41 C and  41 D are welded on a left surface of the rear-lateral-left frame  41 . 
         [0070]    Likewise, the rear-lateral-right frame (second or first rear frame)  45  is embedded in the right-end wall  18  (shown in  FIG. 3 ). Nuts  45 A,  45 B,  45 C and  45 D are welded on a right surface of the rear-lateral-right frame  45 . 
         [0071]    The rear-end-left frame  42 , the rear-end-middle frame  43  and the rear-end-right frame  44  are embedded in the rear-end wall  19  (shown in  FIG. 3 ). Nut  42 A is welded on the rear-end-left frame  42 . Nuts  43 A,  43 B and  43 C are welded on the rear-end-middle frame  43 . Nut  44 A is welded on the rear-end-right frame  44 . 
         [0072]    A gap G 3  is formed between the rear-lateral-left frame  41  and rear-end-left frame  42 . A gap G 4  is formed between the rear-end-left frame  42  and the rear-end-middle frame  43 . A gap G 5  is formed between the rear-end-middle frame  43  and rear-end-right frame  44 . Further, a gap G 6  is formed between the rear-end-right frame  44  and the rear-lateral-right frame  45 . 
         [0073]    As shown in  FIGS. 4 and 21 , in the battery case  13 , battery holders  131 - 140  hold batteries  20  individually. A set of the battery holders  131 - 135  is disposed on a forward side of the battery case  13 . Another set of the battery holders  136 - 140  is disposed at the rear of the battery case  13 . 
         [0074]    In the front set of the battery holders  131 - 135 , the left most battery holder  131  is called front-A battery holder  131 , and the battery holder  132 , which is located on the right side of the front-A battery holder  131 , is called front-B battery holder  132 . 
         [0075]    On the other side, the rightmost battery holder  135  is called front-E battery holder  135 , and the battery holder  134 , which is located on the left side of the front-E battery holder  135 , is called front-D battery holder  134 . 
         [0076]    Further, the battery holder  133 , which is located between the front-B battery holder  132  and the front-D battery holder  134 , is called front-C battery holder  133 . 
         [0077]    Likewise, in the rear set of the battery holders  136 - 140 , the leftmost battery holder  136  is called rear-A battery holder  136 , and the battery holder  137 , which is located on the right side of the rear-A battery holder  136 , is called rear-B battery holder  137 . 
         [0078]    On the other side, the rightmost battery holder  140  is called rear-E battery holder  140 , and the battery holder  139 , which is located on the left side of the rear-E battery holder  140 , is called rear-D battery holder  139 . 
         [0079]    Further, the battery holder  138 , which is located between the rear-B battery holder  137  and the rear-D battery holder  137 , is called rear-C battery holder  138 . 
         [0080]    The front-A battery holder  131  has a front sleeve  131 A communicating with the nut  38 H welded on the front-left frame  38 . 
         [0081]    Further, the front-A battery holder  131  has a rear sleeve  131 B communicating with an upper opening  52 A of a built-in nut  51 A which will be described later referring to  FIG. 6 . 
         [0082]    A bolt (not shown) is inserted into the front sleeve  131 A and is engaged with the nut  38 H. Likewise, another not-shown bolt is inserted into the rear sleeve  131 B and is engaged with the built-in nut  51 A. 
         [0083]    The front-B battery holder  132  has a front sleeve  132 A communicating with the nut  36 D welded on the front-middle frame  36 . 
         [0084]    Additionally, the front-B battery holder  132  has a rear sleeve  132 B communicating with an upper opening  52 A of a built-in nut  51 B. 
         [0085]    A bolt (not shown) is inserted into the front sleeve  132 A and is engaged with the nut  36 D. Likewise, another not-shown bolt is inserted into the rear sleeve  132 B and is engaged with the built-in nut  51 B. 
         [0086]    The front-C battery holder  133  has a front sleeve  133 A communicating with the nut  36 E welded on the front-middle frame  36 . 
         [0087]    Further, the front-C battery holder  133  has a rear sleeve  133 B communicating with an upper opening  52 A of a built-in nut  51 C. 
         [0088]    An unillustrated bolt is inserted into the front sleeve  133 A and is engaged with the nut  36 E. Likewise, another not-shown bolt is inserted into the rear sleeve  133 B and is engaged with the built-in nut  51 C. 
         [0089]    The front-D battery holder  134  has a front sleeve  134 A communicating with the nut  36 F welded on the front-middle frame  36 . 
         [0090]    Additionally, the front-D battery holder  134  has a rear sleeve  134 B communicating with an upper opening  52 A of a built-in nut  51 D. 
         [0091]    An unshown bolt is inserted into the front sleeve  134 A and is engaged with the nut  36 F. Also, another unshown bolt is inserted into the rear sleeve  134 B and is engaged with the built-in nut  51 D. 
         [0092]    The front-E battery holder  135  has a front sleeve  135 A communicating with the nut  37 H welded on the front-right frame  37 . 
         [0093]    Further, the front-E battery holder  135  has a rear sleeve  135 B communicating with an upper opening  52 A of a built-in nut  51 E. 
         [0094]    A bolt (not shown) is inserted into the front sleeve  135 A and is engaged with the nut  37 H. Further, another not-shown bolt is inserted into the rear sleeve  135 B and is engaged with the built-in nut  51 E. 
         [0095]    On the other side, the rear-A battery holder  136  has a rear sleeve  136 B communicating with the nut  42 A welded on the rear-end-left frame  42 . 
         [0096]    Additionally, the rear-A battery holder  136  has a front sleeve  136 A communicating with an upper opening  52 A of a built-in nut  51 F. 
         [0097]    An unshown bolt is inserted into the rear sleeve  136 B and is engaged with the nut  42 A. Also, another unshown bolt is inserted into the front sleeve  136 A and is engaged with the built-in nut  51 F. 
         [0098]    The rear-B battery holder  137  has a rear sleeve  137 B communicating with the nut  43 A welded onto the rear-end-middle frame  43 , and has a front sleeve  137 A communicating with an upper opening  52 A of a built-in nut  51 G. 
         [0099]    An unillustrated bolt is inserted into the rear sleeve  137 B and is engaged with the nut  43 A. Also, another unillustrated bolt is inserted into the front sleeve  137 A and is engaged with the built-in nut  51 G. 
         [0100]    The rear-C battery holder  138  has a rear sleeve  138 B communicating with the nut  43 B welded on the rear-end-middle frame  43 , and has a front sleeve  138 A 1 , which communicates with an upper opening  52 A of a built-in nut  51 H, and another front sleeve  138 A 2 , which communicates with an upper opening  52 A of a built-in nut  51 I. 
         [0101]    A bolt (not shown) is inserted into the rear sleeve  138 B and is engaged with the nut  43 B. Further, other bolts (not shown) are individually inserted into the front sleeve  138 A 1  and  138 A 2  and are engaged with the built-in nuts  51 H and  51 I. 
         [0102]    The rear-D battery holder  139  has a rear sleeve  139 B communicating with the nut  43 C welded onto the rear-end-middle frame  43 , and has a front sleeve  139 A communicating with an upper opening  52 A of a built-in nut  51 J. 
         [0103]    An unillustrated bolt is inserted into the rear sleeve  139 B and is engaged with the nut  43 C. Further, another bolt (not shown) is inserted into the front sleeve  139 A and is engaged with the built-in nuts  51 J. 
         [0104]    The rear-E battery holder  140  has a rear sleeve  140 B communicating with the nut  44 A welded on the rear-end-right frame  44 , and has a front sleeve  140 A communicating with an upper opening  52 A of a built-in nut  51 K. 
         [0105]    An unshown bolt is inserted to the rear sleeve  140 B and is engaged with the nut  44 A. Further, another not shown bolt is inserted to the front sleeve  140 A and is engaged with the built-in nuts  51 K. 
         [0106]    Each lower edge of a front set of the built-in nuts  51 A- 51 E is fixed by an unillustrated bolt to a lateral-end supporting member  61 B which will be described later. 
         [0107]    Likewise, each lower edge of a rear set of the built-in nuts  51 F- 51 K is fixed by unillustrated bolt to a C-supporting member  61 C which will also be described later. 
         [0108]    As described above, the rear-end-left frame  42  is fixed to the C-supporting member  61 C via the rear-A battery holder  136  and the built-in nut  51 F. 
         [0109]    Also, the rear-end-middle frame  43  is fixed to the C-supporting member  61 C via the rear-B battery holder  137 , the built-in  51 G, the rear-C battery holder  138 , the built-in nuts  51 H and  51 I, the rear-D battery holder  139  and the built-in bolt  51 J. 
         [0110]    Likewise, the rear-end-right frame  44  is fixed to the C-supporting member  61 C via the rear-E battery holder  140  and the built-in nut  51 K. 
         [0111]    A built-in nut  51  shown in  FIG. 6  (A), (B), (C) and  FIG. 7  is embedded in the battery tray  14 . 
         [0112]    The built-in nut  51  shown in  FIG. 6  (A), (B), (C) and  FIG. 7  is identical with each of the built-in nuts  51 A,  51 B,  51 C,  51 D,  51 E and  51 F. 
         [0113]    The iron built-in nut  51  mainly comprises an upper nut  52 , a middle stem  53  and a lower nut  54 . 
         [0114]    The upper nut  52  is a cylindrical part which extends in the vertical direction and has an upper opening  52 A which opens upwardly. Inside the upper nut  52 , a bolt groove  52 B is formed. 
         [0115]    The lower nut  54  is identical to the upper nut  52  except that the upper nut  52  is in an upside-down position. In other words, the lower nut  54  is also a cylindrical part which extends in the vertical direction and has a lower opening  54 A which opens downwardly. Inside the lower nut  54 , a bolt groove  54 B is formed. 
         [0116]    The middle stem  53  is a cylindrical part between the upper nut  52  and the lower nut  54 . On the surface of the middle stem  53 , a plurality of notches (serrated portion)  53 A are formed. 
         [0117]    Between the upper nut  52  and the middle stem  53 , an upper constriction  55 A is formed. Also, between the middle stem  53  and the lower nut  54 , a lower constriction  55 B is formed. 
         [0118]    The upper constriction  55 A and the lower constriction  55 B are cylindrical parts whose outer diameter (second diameter) D 2  is smaller than the outer diameter (first diameter) D 1  of the upper nut  52 , the lower nut  54  and the middle stem  53 . 
         [0119]    Because of the serrated portion  53 A formed on the middle stem  53 , it is possible to avoid loosening and spinning of the built-in nut  51  embedded in the battery tray  14  even if a rotational torque is inputted to the built-in nut  51  around the center axis C 51 . 
         [0120]    Further, according to the upper constriction  55 A and the lower constriction  55 B, it is possible to avoid the built-in nut  51  dropping from the battery tray  14  even if the force is inputted to the built-in nut  51  along the direction of the center axis C 51 . 
         [0121]    As shown in  FIG. 8  and  FIG. 9 , lateral-end supporting members (also called ‘supporting members’ or ‘first supporting members’)  61 A,  61 B,  61 C and  61 D are fixed to the bottom surface  14 A of the battery tray  14 . 
         [0122]    The lateral-end supporting member  61 A is disposed at the front row called an A-supporting member  61 A. The lateral-end supporting member  61 B disposed rear of the A-supporting member  61 A is called a B-supporting member  61 B. 
         [0123]    Further, the lateral-end supporting member  61 C disposed rear of the B-supporting member  61 B is called a C-supporting member  61 C. Likewise, the lateral-end supporting member  61 D disposed rear of the C-supporting member  61 C is called a D-supporting member  61 D. 
         [0124]    As shown in  FIG. 1 , each of the lateral-end supporting members  61 A,  61 B,  61 C and  61 D extends in the transversal direction connecting between the side members  11  and  11  to support the bottom surface  14 A. The lateral-end supporting members  61 A,  61 B,  61 C and  61 D are made from iron. 
         [0125]    As shown in  FIG. 8 , on the A-supporting member  61 A, front-end supporting members (also called ‘supporting members’ and ‘second supporting members’)  62 A and  62 B are fixed. Each of the front-end supporting members  62 A and  62 B is a part which extends in the longitudinal direction of the vehicle  10  and is projected forward from the front end of battery tray  14 . 
         [0126]    As shown in  FIG. 10 , the front-end supporting members  62 A and  62 B are only connected to the A-supporting member  61 A and are not connected to the B-supporting member  61 B, C-supporting member  61 C and D-supporting member  61 D (see ‘X’ in  FIG. 10 ). 
         [0127]    As shown in  FIG. 1 , the front-end supporting members  62 A and  62 B connect between the battery cross member  12  and A-supporting member  61 A via front blocks  63 A and  63 B which will be described just below. In addition, the front-end supporting members  62 A and  62 B are made from iron. 
         [0128]    On the front-end supporting members  62 A and  62 B, each of the front blocks (also called ‘crash-proof blocks’ or ‘first crash-proof blocks’)  63 A and  63 B is welded respectively. The front blocks  63 A and  63 B are fixed to the front-end wall  16  by bolts  64  (shown in  FIG. 8 ) and are fixed to the battery cross member  12  by bolts  65  (shown in  FIG. 1 ). 
         [0129]    In other words, the front blocks  63 A and  63 B are parts which individually connect between the battery cross member  12  and the A-supporting member  61 A and are disposed between the battery cross member  12  and the battery tray  14 . Further, the front blocks  63 A and  63 B are made from iron. 
         [0130]    As shown in  FIG. 1 , lateral-end supporting members (also called ‘‘crash-proof blocks’, ‘second crash-proof blocks’ or ‘connecting member)  66 A,  66 B,  66 C and  66 D are respectively welded on both ends of each of the lateral-end supporting members  61 A,  61 B,  61 C and  61 D. 
         [0131]    The lateral crash-proof block  66 A fixed on the A-supporting member  61 A is called an A-lateral crash-proof block (front second crash-proof block)  66 A. The lateral crash-proof block  66 B fixed on the B-supporting member  61 B is called a B-lateral crash-proof block (front second crash-proof block)  66 B. The lateral crash-proof block  66 C fixed on the C-supporting member  61 C is called a C-lateral crash-proof block (rear second crash-proof block)  66 C. 
         [0132]    The lateral crash-proof block  66 D fixed on the D-supporting member  61 D is called a D-lateral crash-proof block (rear second crash-proof block)  66 D. 
         [0133]    As shown in  FIG. 8 , the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D are fixed to the left-end wall  17  and the right-end wall  18  of the battery tray  14  by bolts  67 , and are fixed to the side members  11  and  11  by bolts  68 . 
         [0134]    As shown in  FIG. 2 , the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D, which connect between side member  11  and the battery case  13 , are respectively disposed between the bottom surface of the side member  11  and the lateral-end supporting members  61 A,  61 B,  61 C and  61 D. Each of the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D is made from iron and is a hollow square pillar in shape. 
         [0135]    Further, each of the A-lateral crash-proof block  66 A and the B-lateral crash-proof block  66 B is directly fixed to the side member  11 , whereas, the C-lateral crash-proof block  66 C is fixed to the side member  11  via a C-connecting block  69 C. Also, the D-lateral crash-proof block  66 D is fixed to the side member  11  via a D-connecting block  69 D. 
         [0136]    Although the side member  11  is extended from a point (shown as an arrow A in  FIG. 2 ) backwardly and upwardly, the battery tray  14  is kept in a horizontal position because the C-connecting block  69 C is interposed between the side member  11  and the C-supporting member  61 C, also the D-connecting block  69 D is interposed between side member  11  and the D-supporting member  61 D. 
         [0137]    As shown in  FIG. 11 , the A-supporting member  61 A is fixed by the bolt  68  engaged with a cap nut  11 B mounted in the reinforcing member  11 A of the side member  11 . The B-supporting member  61 B is also fixed to the side member  11  by the structure shown in  FIG. 11 , description of which is omitted in the drawings. 
         [0138]    As shown in  FIG. 12 , the C-supporting member  61 C is connected to the side member  11  via the C-connecting block  69 C. The C-connecting block  69 C is a hollow iron part in which a cap nut  11 C is mounted. The C-supporting member  61 C is fixed to the C-connecting block  69 C by the bolt  68  engaged with the cap nut  11 C. 
         [0139]    As shown in  FIG. 13 , the D-supporting member  61 D is connected to the side member  11  via the D-connecting block  69 D. The D-connecting block  69 D is a hollow iron part. The D-connecting block  69 D is fixed to the side member  11  by the bolt  68  engaged with the cap nut  11 D mounted in the side member  11 . 
         [0140]    Further, a nut  69 D 1  is welded on the bottom of the D-connecting block  69 D. The D-supporting member  61 D is fixed to the D-connecting block  69 D by a bolt  71  which engages with the nut  69 D 1 . 
         [0141]    As shown in  FIG. 9 , between the left-end wall  17  of the battery tray  14  and the side member  11  and between the right-end wall  18  of the battery tray  14  and the side member  11 , two high-voltage cables  72  are respectively disposed. The high-voltage cables  72 , which are capable of carrying about 300V, connect between the batteries  20  mounted in the battery case  13  and an inverter (also called ‘external device) not shown in the drawings. 
         [0142]    Each of the high-voltage cables  72  has a hole connector  73  connected to an electric-output socket (not shown) in the battery case  13 . 
         [0143]    At both the lateral surface of the battery tray  14  facing the side members  11  (namely, at the left-end wall  17  and the right-end wall  18 ) and the bottom surface  14 A of the battery tray  14 , dent portions  28 A and  28 B are formed. 
         [0144]    Each of the dent portions  28 A and  28 B has a concave side wall  29 , which extends parallel to the side member  11 , a concave front wall  74 , which extends from the front end of the concave side wall  29  in the lateral direction, and a concave rear wall  75 , which extends from the rear end of the concave side wall  29  in the lateral direction. 
         [0145]    Further, as shown in  FIG. 14 , casing bolt-hole portions  76 , a casing low-voltage cable hole portion  77 , a casing center-hole portion  78  and a casing high-voltage cable hole portion  79  are formed at the concave side wall  29 . 
         [0146]    A cover plate  81  shown in  FIG. 15  is fixed on the back surface of the concave side wall  29 . Cover plate  81  will be described below in detail. 
         [0147]    Each of the casing bolt-hole portions  76  shown in  FIG. 14  is a hole through which a plate fixing bolt (not shown) is engaged with a plate bolt-hole portion  82  formed on the cover plate  81 . 
         [0148]    Low-voltage cables  89  (shown in  FIG. 16 ) used for supplying about 12V electric power to electrical equipment pass through the casing low-voltage cable hole portion  77 . Further, the casing low-voltage cable hole portion  77  communicates with a plate low-voltage cable hole portion  83  formed at the cover plate  81 . 
         [0149]    The casing center hole portion  78  communicates with a venting hole  84  formed at the cover plate  81 . 
         [0150]    High-voltage cable  72  (shown in  FIG. 9 ) passes through each of the casing high-voltage cable hole portions  79  and  79 . The casing high-voltage cable hole portions  79  and  79  respectively communicate with plate high-voltage cable hole portions  85 A and  85 B formed at the cover plate  81 . 
         [0151]    Further, each concave side wall  29  is kept at a distance L 5  (shown in  FIG. 9 ) defined based on the outer diameter D 3  of the high-voltage cable  72  from the side member  11 . 
         [0152]    The greater the outer diameter D 3  (thickness) of the high-voltage cable  72 , the greater distance L 5  between the concave side wall  29  and the side member  11  becomes to permit bending of cable  72 . Conversely, the smaller outer diameter D 3 , the shorter distance L 5  may be. 
         [0153]    As shown in  FIG. 15 , the cover plate  81  is fixed to the back surface of concave side wall  29  of the battery tray  14 . The cover plate  81  is a plate made from aluminum covering the casing bolt-hole portions  76 , the casing low-voltage cable hole portion  77 , the casing center hole portion  78  and the casing high-voltage cable hole portions  79  as discussed with reference to  FIG. 14 . 
         [0154]    Aluminum is used for cover plate  81  because both rigidity and weight saving are required, and it is also necessary to avoid detachment between the cover plate  81  and battery tray  14  even if the resin material of battery tray  14  expands or contracts due to temperature variation. 
         [0155]    One point the inventors have focused attention on is that the linear expansion coefficients of the main material of the battery tray  14  which is polybutylene resin including glass fiber and the material of the cover plate  81  which is aluminum, are almost the same, and accordingly, the cover plate  81  is made from aluminum. 
         [0156]    At the cover plate  81 , the plate bolt-hole portions  82 , the plate low-voltage cable hole portion  83 , the venting hole  84  and the plate high-voltage hole portions (cable hole portions)  85 A and  85 B are formed. 
         [0157]    Each of the plate bolt-hole portions  82  is a hole in which each of the plate fixing bolts  104  shown in  FIG. 17  are engaged. 
         [0158]    The plate bolt-hole portions  82  open to the front side (near side in  FIG. 15 ) of the cover plate  81 . However, the plate bolt-hole portions  82  do not open to the back (far side in  FIG. 15 ) of the cover plate  81 . 
         [0159]    Consequently, the cover plate  81  is not penetrated by the plate bolt-hole portions  82 . 
         [0160]    In the plate low-voltage cable hole portion  83 , as shown in  FIG. 16 , a rubber cap  88  is fitted. The low-voltage cables  89  are inserted through the rubber cap  88 . 
         [0161]    The venting hole  84  is a hole for venting air from the battery case  13  when the air pressure increases in the battery case  13 . 
         [0162]    In venting hole  84 , a one-way valve (not shown) is fitted, thereby maintaining airtightness in the battery case  13 . 
         [0163]    As shown in  FIG. 15  and  FIG. 18 , each of the plate high-voltage cable hole portions  85 A and  85 B is a hole into which individual socket ends  101 A and  101 A of cable holders  101  and  101  are inserted. The plate high-voltage cable hole portions  85 A and  85 B are respectively communicated with the casing high-voltage cable hole portions  79  and  79  shown in  FIG. 14 . 
         [0164]    Into the cable holders  101  and  101 , each of the high-voltage cables  72  and  72  is individually inserted. Each of the socket ends  101 A and  101 A of the cable holders  101  and  101  has a rubber O-shaped ring  103  individually equipped to secure airtightness in the battery case  13 . 
         [0165]    The cable holders  101  and  101  are fixed to the cover plate  81  by holder fixing bolts  102  and  102 , respectively. The holder fixing bolts  102  and  102  are bolts which are individually engaged with cable holder hole portions  86 A and  86 B. 
         [0166]    The cable holder hole portions  86 A and  86 B are holes which are respectively formed adjacent to the plate high-voltage cable hole portions  85 A and  85 B. The cable holder hole portions  86 A and  86 B open to the front side of the cover plate  81  and do not open to the back side of the cover plate  81 . 
         [0167]    The inner surface of each of the plate high-voltage cable hole portions  85 A and  85 B is mirror finished so that the O-shaped ring  103  fits each of the plate high-voltage cable hole portions  85 A and  85 B without leaving a gap. 
         [0168]    Further, because of the mirror finished inner surface, it is possible to protect the O-shaped ring  103  from any damage when the O-shaped ring  103  is inserted into each of the plate high-voltage cable hole portions  85 A and  85 B. 
         [0169]    Additionally, a sealing groove  87  is formed around the outer edge of the cover plate  81 . Sealing agent (not shown) is filled into sealing groove  87  to avoid leaving a gap between the concave side wall  29  of the battery tray  14  and the cover plate  81  as shown in  FIG. 17 . 
         [0170]    As shown in  FIG. 19  and  FIG. 20 , the battery cover  13  has a front raised portion  91 , a middle raised portion  92  and a rear raised portion  93 . 
         [0171]    The front raised portion  91  is a portion which is raised near the front end of the battery cover  13 . 
         [0172]    The rear raised portion  93  is a portion which is raised near the rear end of the battery cover  13 . On the front raised portion  91 , a maintenance hole portion  94  is formed. 
         [0173]    The maintenance hole portion  94  is formed for maintaining inside the battery case  13  and is normally covered by a covering plate (not shown). 
         [0174]    The middle raised portion  92  is a portion which is raised between the front raised portion  91  and the rear raised portion  93 , however, the middle raised portion  92  is lower than the front raised portion  91  and the rear raised portion  93  in height. 
         [0175]    A flange  95 , on which cover bolt hole portions  96  are formed, is formed around the edge of the battery cover  13 . 
         [0176]    As shown in  FIG. 3 , tray bolt hole portions  105 , corresponding to the location of the cover bolt hole portions  96 , are formed on the front-end wall  16 , the left-end wall  17 , right-end wall  18 , and rear-end wall  19  of the battery tray  14  (namely, around the edge of battery tray  14 ). 
         [0177]    According to this arrangement, the cover bolt hole portions  96  and the tray bolt hole portions  105  respectively communicate with each other when the battery cover  15  is put on the battery tray  14 . Thus, it is allowed that bolts (not shown) are individually inserted into the cover bolt hole portions  96  and the tray bolt hole portions  105  to fix the battery tray  14  and the battery cover  15 . 
         [0178]    Namely, the embodiment of the present invention can provide the following effects or/and advantages. 
         [0179]    For example, if the front side of the electric vehicle  10  is crashed, the battery case  13  containing batteries  20  moves forward due to inertia. Particularly, the batteries  20  are comparatively heavy, therefore, it is impossible to omit kinetic energy of the battery case  13  when the electric vehicle  10  is crashed. 
         [0180]    However, according to the present invention in this embodiment, it is possible to avoid the battery case  13  moving forward and being crashed against the battery cross member  12  because the lateral-end supporting members  61 A,  61 B,  61 C and  61 D and the front-end supporting members  62 A and  62 B are provided. 
         [0181]    Namely, it is possible to maintain the gap (see G F  in  FIG. 1 ) between the battery case  13  and the battery cross member  12  even if the electric vehicle  10  is crashed, and therefore, it is possible to avoid damage to cables (not shown) installed in the gap G F  so that the reliability of the electric vehicle  10  is improved. 
         [0182]    The front-end supporting members  62 A and  62 B are not connected to all of the lateral-end supporting members  61 A,  61 B,  61 C and  61 D, however, the front-end supporting members  62 A and  62 B are connected to only the lateral-end supporting member  61 A which is disposed at the front row. Accordingly, it is possible to reduce the length of the front-end supporting members  62 A and  62 B, and therefore, it is possible to suppress the weight and cost of front-end supporting members  62 A and  62 B in weight and cost. 
         [0183]    Namely, it is possible to improve crash-resisting capability of the batteries  20  mounted on the electric vehicle  10  while preventing increased weight and cost. 
         [0184]    Further, the lateral-end supporting members  61 A,  61 B,  61 C and  61 D and front-end supporting members  62 A and  62 B are made from iron. In addition, the battery case  13  is made from polybutylene resin including glass fibers. According to this arrangement, it is possible to reduce the weight of the battery case  13  at a reasonably low cost in mass production. Further, it is also possible to improve the mounting stiffness of the battery case  13  in relation to the electric vehicle  10 . 
         [0185]    The battery case  13  containing the batteries  20  is robustly supported by the lateral-end supporting members  61 A,  61 B,  61 C and  61 D, and further, the front blocks  63 A and  63 B prevent collision of the battery case  13  with the battery cross member  12  if the battery case  13  moves forward due to inertia even if the front side of the vehicle  10  is crashed. 
         [0186]    Further, the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D are inserted between the side surface of the battery case  13  and the side member  11 , and accordingly, it is possible to avoid a collision of the battery case  13  with the side member  11  if the battery case  13  moves laterally due to inertia even if the lateral side of the vehicle  10  is crashed. 
         [0187]    Namely, it is possible to keep the gap (see G S  and G S  in  FIG. 1 ) between the battery case  13  and the side members  11 , therefore, it is possible to prevent damage of the high-voltage cables  72  and low-voltage cables  89  installed in the gap G S  and G S  so that the reliability of the electric vehicle  10  is improved. 
         [0188]    Additionally, the lateral-end supporting members  61 A,  61 B,  61 C and  61 D, the front-end supporting members  62 A and  62 B, the front blocks  63 A and  63 B and the battery cross member  12  are made from iron. Further, the battery case  13  is made from polybutylene resin including glass fibers. 
         [0189]    According to this arrangement, it is possible to reduce the weight of the battery case  13  at a reasonably low cost in mass production. Further, it is also possible to improve the mounting rigidity of the battery case  13  on the electric vehicle  10 . 
         [0190]    The front-end supporting members  62 A and  62 B and the battery cross member  12  are connected via the front blocks  63 A and  63 B. Further, the lateral-end supporting members  61 A,  61 B,  61 C and  61 D and the side members  11  are connected via the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D. According to this arrangement, it is possible to lower the center of gravity of the battery case  13  containing the heavy batteries  20 . 
         [0191]    Further, due to inserting the front blocks  63 A and  63 B between the battery case  13  and the battery cross member  12  and inserting the lateral-end supporting members  66 A,  66 B,  66 C and  66 D between the battery case  13  and the side members  11 , it is possible to avoid collision with the cross member  12  or the side member  11  if the battery case  13  moves due to inertia even if the vehicle  10  is crashed. 
         [0192]    Therefore, it is possible to improve the crash-resistant capability of the batteries  20  mounted on the electric vehicle  10 . 
         [0193]    Namely, if the front side of the electric vehicle  10  is crashed, it is possible to avoid collisions with the battery cross member  12  if the battery case  13  moves forward due to inertia. Likewise, if the lateral side of the electric vehicle  10  is crashed, it is possible to avoid collision with the side members  11  if the battery case  13  moves laterally due to inertia. 
         [0194]    As discussed previously with  FIG. 9 , the high-voltage cables  72  and  72  are individually inserted into the plate high-voltage cable hole portions  85 A and  85 B formed at the cover plates  81  respectively fixed on the dent portions  28 A and  28 B of the battery case  13 . Further, the high-voltage cables  72  and  72 , which are disposed between the side members  11  and the battery case  13 , are curved in an arc shape with a bending radius. 
         [0195]    Further, each of the concave side walls  29  of the dent portions  28 A and  28 B is distanced L 5 , which is defined corresponding to the outer diameter D 3  of the high-voltage cable  72 , from the side member  11 . Accordingly, it is possible to avoid damaging the high-voltage cables  72  due to bending the high-voltage cables  72  with excessively small radius and it is also possible to avoid wasting the space in the battery case  13  due to curving the high-voltage cables  72  with excessively large radius. 
         [0196]    In other words, it is possible to easily install the high-voltage cables  72  connected to the batteries  20  mounted on the electric vehicle  10  while utilizing limited space in the electric vehicle  10 . 
         [0197]    Further, the high-voltage cables  72  are connected to the batteries  20  via the hole connectors  73 , and accordingly, it is possible to secure the connection between the high-voltage cables  72  and the batteries  20  at a lower cost. 
         [0198]    Particularly, it is possible to avoid unwanted disconnection of the high-voltage cables  72  from the batteries  20  due to using the hole connectors  73  to connect between the batteries  20  and the high-voltage batteries  20  as compared with using conventional detachable connectors. 
         [0199]    Therefore, it is possible to improve the reliability of the electric vehicle  10  by preventing accidental disconnection between the high-voltage cables  72  and the batteries  20 . 
         [0200]    Further, it is possible to reduce cost and weight of the electric vehicle  10  by using the hole connectors  73  as compared with using conventional detachable connectors. 
         [0201]    Each of the high-voltage cables  72  is drawn from inside the battery case  13  through the plate high-voltage cable hole portions  85 A and  85 B formed at the aluminum cover plate  81 , and accordingly, it is possible to avoid excessively varying the inner diameter of the plate high-voltage cable hole portions  85 A and  85 B due to variation of air temperature. 
         [0202]    Further, it is possible to avoid external air flowing into the battery case  13  due to sealing by each O-shaped ring  103  between the outer surface of the high-voltage cables  72  and  72  and the inner surface of the plate high-voltage cable hole portions  85 A and  85 B. 
         [0203]    Additionally, although the plate bolt-hole portions  82  open to the front side of the cover plate  81 , the plate bolt-hole portions  82  do not open to the back side of the cover plate  81 , and accordingly, it is possible to secure the airtightness in the battery case  13  while allowing the plate fixing bolts  104 , for fixing the cover plate  81  to the battery case  13 , to be engaged with the plate bolt-hole portions  82 . 
         [0204]    As shown in  FIG. 6  and  FIG. 7 , portions whose outer diameter is locally small (second diameter D 2 ) at the built-in nut  51 , namely, the upper constriction  55 A and the lower constriction  55 B in which resin of battery tray  14  is entered. Accordingly, it is possible to avoid the built-in nut  51  dropping from the battery tray  14  even if force is vertically inputted to the built-in nut  51 . 
         [0205]    Further, due to the serrated portion  53 A formed on the middle stem  53 , it is possible to avoid spinning of the built-in nut  51  embedded in the battery tray  14  even if torque is inputted to the built-in nut  51  to rotate the built-in nut  51  around the center axis C 51 , accordingly, it is possible to surely engage the bolt (not shown) with the built-in nut  51 . 
         [0206]    If the front side of the electric vehicle  10  is impacted, the battery case  13  will exhibit forward movement due to inertia. Consequently, such an impact is exerted on the battery case  13  through the front blocks  63 A and  63 B. In this case, the front-battery partitions  24 A and  24 D, which are disposed behind the front blocks  63 A and  63 B, and the additional plates  39 A and  39 B, which are embedded in the front-battery partitions  24 A and  24 D, may absorb the impact. 
         [0207]    Therefore, it is possible to improve crash-resisting capability of the batteries  20  mounted on the electric vehicle  10  while preventing increased weight and cost. 
         [0208]    Further, it is possible to further improve the rigidity of the battery case  13  because the B-reinforce  36 C, which is embedded in the front-end wall  16  which is made from resin and forms front edge of the battery  14 , connects the pair of additional plates  39 A and  39 B. 
         [0209]    Additionally, the A-reinforces  39 A and  39 B and the B-reinforce  36 C are embedded in the battery tray  14  and consequently it is possible to keep the inside of battery case  13  airtight. 
         [0210]    Furthermore, gap G 1  is formed between the front-left frame  38  and the front-middle frame  36 , and gap G 2  is formed between the front-right frame  37  and the front-middle frame  36 . Accordingly, it is possible to adapt to design changes of the battery case  13 , and it is possible to flow resin material into a mold when the battery case  13  is formed. 
         [0211]    The left front block  63 A connects the battery cross member  12 , the front-left frame  38  and B-reinforce  36 C. Likewise, the right front block  63 B connects the battery cross member  12 , the front-right frame  37  and B-reinforce  36 C. Consequently, it is possible to improve further the rigidity of battery case  13  while preventing an increased number of parts. 
         [0212]    The iron metal frame  32 , which is embedded in the resin battery case  13  containing batteries  20 , and the side frame  11  are connected by the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D which are made from iron. Further, the iron metal frame  32  embedded in the resin battery case  13  and the battery cross member  12  are connected by the front blocks  63 A and  63 B also made from iron. According to this arrangement, it is possible to increase rigidity of the battery case  13  while reducing weight of the battery case  13 , and it is also possible to improve the crash-resisting capability of the batteries  20  mounted on the electric vehicle  10 . 
         [0213]    Further, it is possible to adapt to design changes of the battery case  13  thanks to the metal frame  32  consisting of two separate frames, the front frame set  33  and the rear frame set  34 . 
         [0214]    It is possible to keep the essential rigidity of the battery case  13  by interconnecting the front frame set  33  and the rear frame set  34  via the side member  11 . 
         [0215]    Even if the lateral side of the electric vehicle  10  is crashed, it is possible that collision of the battery case  13  with the side member  11  will be prevented by the lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D. 
         [0216]    The front frame set  33  consists of a separate front-left frame  38 , front-right frame  37  and front-middle frame  36 , so accordingly, it is possible to adapt to design changes of the battery case  13 . Further, it is possible to flow resin material into a mold when the battery case  13  is formed. 
         [0217]    The front-left frame  38  and the front-middle frame  36  are connected by the left front block  63 A fixed to the battery cross member  12 , and the front-right frame  37  and the front-middle frame  36  are connected by the right front block  63 B fixed to the battery cross member  12 . In other words, the front-left frame  38 , the front-right frame  37 , the front-middle frame  36 , the side member  11  and the battery cross member  12  are all iron parts, and are all connected. Therefore, the rigidity of battery case  13  is further enhanced. 
         [0218]    The rear frame set  34  consists of a separate rear-lateral-left frame  41 , rear-end-left frame  42 , rear-end-middle frame  43 , rear-end-right frame  44  and rear-lateral-right frame  45 , and accordingly, it is possible to adapt to design changes of the battery case  13 . Further, it is possible to flow resin material into a mold when the battery case  13  is formed. 
         [0219]    The C-supporting member  61 C and the rear-end-left frame  42  are connected by the battery holder  136 , and the C-supporting member  61 C and the rear-end-middle frame  43  are connected by the battery holders  137 ,  138  and  139 . Further, the C-supporting member  61 C and the rear-end-right frame  44  are connected by the battery holder  140 . According to these arrangements, it is possible to connect all iron parts which are the rear-lateral-left frame  41 , the rear-end-left frame  42 , the rear-end-middle frame  43 , the rear-end-right frame  44 , the rear-lateral-right frame  45  and the side member  11 , and therefore, it is possible to further improve the rigidity of battery case  13 . 
         [0220]    The present invention is not limited to the above embodiment, but covers all changes and modifications which do not constitute departures from the spirit and scope of the invention. 
         [0221]    In the above embodiment, the side member  11 , the battery cross member  12 , the metal frame  32 , the front blocks  63 A and  63 B and lateral crash-proof blocks  66 A,  66 B,  66 C and  66 D are made from iron. However, it is acceptable to make these parts with a non-iron metal (i.e. aluminum or titanium). 
         [0222]    From the invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following clams.