Patent Publication Number: US-2021194086-A1

Title: Electric vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to an electric vehicle that includes an electric motor, an engine, a battery case disposed on a lower face of a floor panel and housing battery modules for driving the electric motor, a muffler extending rearward from the engine, and a front seat and a rear seat disposed on an upper face of the floor panel. 
     BACKGROUND ART 
     An arrangement in which a battery pack disposed beneath a rear seat of an electric vehicle includes a plurality of battery modules, front battery modules are stacked vertically as two layers, a rear battery module is disposed as one layer so as to follow the inclination of a seat cushion of the rear seat, and the headroom for an occupant is ensured by disposing the rear seat at as low a position as possible is known from Patent Document 1 below. 
     RELATED ART DOCUMENTS PATENT DOCUMENTS 
     Patent Document 1: Japanese Patent No. 6086604 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     When an electric vehicle equipped with both an electric motor and an engine includes an exhaust passage member (an exhaust pipe or a muffler), disposed in the fore-and-aft direction, in a middle part in the vehicle width direction of a lower face of a vehicle body, if an attempt is made to avoid interference with the exhaust passage member, the positions of a battery pack and a rear seat become high, and there is the problem that it becomes difficult to ensure the headroom for the rear seat. 
     The present invention has been accomplished in light of the above circumstances, and it is an object thereof to ensure the headroom for a rear seat by disposing the rear seat at as low a position as possible when disposing a battery pack and the rear seat above an exhaust passage member. 
     Means for Solving the Problems 
     In order to attain the above object, according to a first aspect of the present invention, there is provided an electric vehicle comprising an electric motor, an engine, a battery case disposed on a lower face of a floor panel and housing battery modules for driving the electric motor, an exhaust passage member extending rearward from the engine, and a front seat and a rear seat disposed on an upper face of the floor panel, wherein the battery case comprises a first battery case and a second battery case, the second battery case has a smaller size than a size of the first battery case and is disposed on an upper front part of the first battery case, the second battery case is disposed below a front part of a seat cushion of the rear seat, a recess portion extending in a fore-and-aft direction and having at least part of the exhaust passage member passing therethrough is formed in a lower face of a middle part in a vehicle width direction of the first battery case, the battery modules housed in the first battery case are disposed on left and right sides of the recess portion, and the battery module housed in the second battery case is disposed so that a longitudinal direction thereof follows the vehicle width direction. 
     Further, according to a second aspect of the present invention, in addition to the first aspect, at least one of a battery control device and a junction board is disposed in a space above the recess portion in a rear part of the first battery case, and a cell voltage sensor is disposed in a space above the battery module in the rear part of the first battery case. 
     Furthermore, according to a third aspect of the present invention, in addition to the second aspect, a height of a middle part in the vehicle width direction of a rear upper face of the first battery case is smaller than a height of an upper face of the second battery case. 
     Moreover, according to a fourth aspect of the present invention, in addition to any one of the first to third aspects, a cooling medium jacket of the second battery case is formed between a case upper wall of the first battery case and a case lower wall of the second battery case. 
     Further, according to a fifth aspect of the present invention, in addition to the fourth aspect, the cooling medium jacket is defined by a lower face of the case upper wall of the first battery case and an upper face of the case lower wall of the second battery case. 
     Furthermore, according to a sixth aspect of the present invention, in addition to any one of the first to fifth aspects, a case rear wall of the second battery case is inclined from upper front toward lower rear, and wiring is disposed in a space defined between a front face of the case rear wall and a rear face of the battery module disposed in a front part of the second battery case. 
     Moreover, according to a seventh aspect of the present invention, in addition to any one of the first to sixth aspects, at least one of an upper part of the first battery case and a rear part of the second battery case comprises a beam portion extending in the vehicle width direction. 
     Further, according to an eighth aspect of the present invention, in addition to any one of the first to seventh aspects, the first battery case comprises a connector providing electrical connection between the battery modules and electrical equipment of the electric vehicle, the connector comprises a main body portion and an interface portion, and the interface portion is disposed on a front wall or a rear wall of the first battery case above the recess portion when viewed in the vehicle body fore-and-aft direction. 
     Furthermore, according to a ninth aspect of the present invention, in addition to the eighth aspect, the main body portion is disposed above the recess portion when viewed from above. 
     Moreover, according to a tenth aspect of the present invention, in addition to the ninth aspect, the interface portion is disposed on the front wall of the first battery case, the main body portion is disposed in front of a junction board disposed above the recess portion, and the junction board and the main body portion are electrically connected to each other. 
     A muffler  19  of an embodiment corresponds to the exhaust passage member of the present invention, a first battery case  31  and a second battery case  32  of the embodiment correspond to the battery case of the present invention, a second water jacket  47  of the embodiment corresponds to the cooling medium jacket of the present invention, and a low voltage connector  50  and a high voltage connector  51  of the embodiment correspond to the connector of the present invention. 
     Effects of the Invention 
     In accordance with the first aspect of the present invention, the electric vehicle includes the electric motor, the engine, the battery case disposed on the lower face of the floor panel and housing the battery modules for driving the electric motor, the exhaust passage member extending rearward from the engine, and the front seat and rear seat disposed on the upper face of the floor panel. Since the battery case includes the first battery case and the second battery case, the second battery case has a smaller size than that of the first battery case and is disposed on an upper front part of the first battery case, the second battery case is disposed below a front part of the seat cushion of the rear seat, the recess portion extending in the fore-and-aft direction and having at least part of the exhaust passage member passing therethrough is formed in a lower face of a middle part in the vehicle width direction of the first battery case, the battery modules housed in the first battery case are disposed on left and right sides of the recess portion, and the battery module housed in the second battery case is disposed so that its longitudinal direction follows the vehicle width direction, it is possible to dispose the rear seat at as low a position as possible while avoiding any interference with the battery case and while ensuring a sufficient volume for the battery case, thereby enabling the headroom for an occupant to be ensured. 
     Furthermore, in accordance with the second aspect of the present invention, since at least one of the battery control device and the junction board is disposed in a space above the recess portion in the rear part of the first battery case, and the cell voltage sensor is disposed in a space above the battery module in the rear part of the first battery case, it is possible to suppress the height of the upper face of the first battery case by positioning the battery control device or the junction board, which have relatively large vertical dimensions, in the space above the recess portion, where the battery module is not present, and by positioning the cell voltage sensor, which has relatively small vertical dimensions, in the space above the battery module. 
     Moreover, in accordance with the third aspect of the present invention, since the height of the middle part in the vehicle width direction of the rear upper face of the first battery case is smaller than the height of the upper face of the second battery case, it is possible to make it difficult for the first battery case to interfere with the rear seat. 
     Furthermore, in accordance with the fourth aspect of the present invention, since the cooling medium jacket of the second battery case is formed between the case upper wall of the first battery case and the case lower wall of the second battery case, it is possible to cool the case lower wall of the second battery case thus enhancing the effect of cooling the battery module. 
     Moreover, in accordance with the fifth aspect of the present invention, since the cooling medium jacket is defined by the lower face of the case upper wall of the first battery case and the upper face of the case lower wall of the second battery case, it is possible to form the cooling medium jacket while minimizing any increase in the number of components, and it is also possible to minimize the height of the cooling medium jacket. 
     Furthermore, in accordance with the sixth aspect of the present invention, since the case rear wall of the second battery case is inclined from the upper front toward the lower rear, and the wiring is disposed in a space defined between the front face of the case rear wall and the rear face of the battery module disposed in a front part of the second battery case, it is possible to ensure a space in the interior of the second battery case while avoiding any interference between the case rear wall and the rear seat, thereby enabling the wiring to be disposed by utilizing the space. 
     Moreover, in accordance with the seventh aspect of the present invention, since at least one of the upper part of the first battery case and the rear part of the second battery case includes the beam portion extending in the vehicle width direction, it is possible to enhance the side collision resistance by reinforcing the battery case by means of the beam part. 
     Furthermore, in accordance with the eighth aspect of the present invention, since the first battery case includes the connector providing electrical connection between the battery modules and electrical equipment of the electric vehicle, the connector includes the main body portion and the interface portion, and the interface portion is disposed on the front wall or the rear wall of the first battery case above the recess portion when viewed in the vehicle body fore-and-aft direction, it is possible to efficiently carry out the routing of wiring for electrical equipment disposed in front of or to the rear of the first battery case. 
     Moreover, in accordance with the ninth aspect of the present invention, since the main body portion is disposed above the recess portion when viewed from above, it is possible to rationally dispose the main body portion by utilizing effectively a dead space above the recess portion where no battery module is disposed. 
     Furthermore, in accordance with the tenth aspect of the present invention, since the interface portion is disposed on the front wall of the first battery case, the main body portion is disposed in front of the junction board disposed above the recess portion, and the junction board and the main body portion are electrically connected, it is possible to minimize the length of the bus bar providing a connection between the junction board and the main body portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a vehicle body of a plug-in hybrid vehicle. (first embodiment) 
         FIG. 2  is an exploded perspective view of a battery pack. (first embodiment) 
         FIG. 3  is an enlarged view of part  3  in  FIG. 1 . (first embodiment) 
         FIG. 4  is a sectional view along line  4 - 4  in  FIG. 3 . (first embodiment) 
         FIG. 5  is a view in the direction of arrow  5  in  FIG. 2 . (first embodiment) 
         FIG. 6  is a view in the direction of arrow  6  in  FIG. 2 . (first embodiment) 
         FIG. 7  is a view showing the placement of a first water jacket and a second water jacket. (first embodiment) 
         FIG. 8  is a perspective view in a state in which a first cover of a first battery case is detached. (second embodiment) 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS 
     
         
           11  Electric motor 
           12  Engine 
           14  Floor panel 
           15  Front seat 
           16  Rear seat 
           16   a  Seat cushion 
           19  Muffler (exhaust passage member) 
           31  First battery case (battery case) 
           32  Second battery case (battery case) 
           33   a  Recess portion 
           33   h  Front wall 
           34   a  Case upper wall 
           34   f  Beam portion 
           37  Battery module 
           39  Junction board 
           40  Battery control device 
           41  Cell voltage sensor 
           42   a  Case lower wall 
           43   c  Case rear wall 
           43   d  Beam portion 
           45  Battery module 
           47  Second water jacket (cooling medium jacket) 
           49  Wiring 
           50  Low voltage connector (connector) 
           50   a  Main body portion 
           50   b  Interface portion 
           51  High voltage connector (connector) 
           51   a  Interface portion 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A first embodiment of the present invention is explained below by reference to  FIG. 1  to  FIG. 7 . In the present description, the fore-and-aft direction, the left-and-right direction (vehicle width direction), and the up-and-down direction are defined with reference to an occupant seated on a driver&#39;s seat. 
     First Embodiment 
     As shown in  FIG. 1 , mounted on a vehicle body front part of a front wheel drive plug-in hybrid vehicle are an electric motor  11  for driving a front wheel, an engine  12  for driving a generator charging a battery, and a power drive unit  13  equipped with an inverter controlling the drive of the electric motor  11 . A front seat  15  and a rear seat  16  are disposed on an upper face of a floor panel  14 , and a battery pack  17  supplying power to the electric motor  11  is mounted on a lower face of the floor panel  14  beneath the rear seat  16 . An exhaust pipe  18  extends rearward from the engine  12 , and a muffler  19  provided in an intermediate part of the exhaust pipe  18  is disposed beneath the battery pack  17 . 
     As shown in  FIG. 2 , the battery pack  17  includes a lower-level first battery case  31  and an upper-level second battery case  32  superimposed on an upper front part of the first battery case  31 . The first battery case  31  includes a first case main body  33  and a first cover  34  both made of a metal by die-casting, and is formed by joining the first cover  34  to an upper face opening of the first case main body  33 . Formed in a middle part in the vehicle width direction of the first case main body  33  is a groove-shaped recess portion  33   a  having a semicircular cross section and extending in the fore-and-aft direction so as to be recessed upward, and housed within the recess portion  33   a  is part of the muffler  19  (see  FIG. 1 ). 
     As shown in  FIG. 3  to  FIG. 5  and  FIG. 7 , the first case main body  33  includes a left case bottom wall  33   b  and a right case bottom wall  33   c  that are divided to the left and right by means of the recess portion  33   a,  a left first water jacket  36 A is formed between the left case bottom wall  33   b  and a left lid member  35 A by joining the left lid member  35 A to a lower face of the left case bottom wall  33   b,  and a right first water jacket  36 B is formed between the right case bottom wall  33   c  and a right lid member  35 B by joining the right lid member  35 B to a lower face of the right case bottom wall  33   c.    
     A cooling water supply port  36   a  is formed at the front end and the inner end (right end) in the vehicle width direction of the left first water jacket  36 A, cooling water being supplied to the cooling water supply port  36   a  from a cooling water tank, which is not illustrated, and a cooling water supply passage  33   e  is formed in a left case side wall  33   d  of the first case main body  33  so as to face upward, cooling water discharged from the left end of the left first water jacket  36 A being supplied to the second battery case  32  via the cooling water supply passage  33   e.  A cooling water discharge port  36   b  is formed in the front end and the inner end (left end) in the vehicle width direction of the right first water jacket  36 B, cooling water being discharged from the cooling water discharge port  36   b  to a cooling water tank, which is not illustrated, and a cooling water discharge passage  33   g  is formed in a right case side wall  33   f  of the first case main body  33  so as to face downward, cooling water discharged from the second battery case  32  being supplied to the right end of the right first water jacket  36 B via the cooling water discharge passage  33   g.    
     Returning to  FIG. 2 , two battery modules  37  are mounted on an upper face of each of the left case bottom wall  33   b  and the right case bottom wall  33   c  of the first case main body  33 . The battery module  37 , which is a rectangular parallelepiped, is formed by layering a plurality of battery cells  38  in the longitudinal direction, and is disposed in the fore-and-aft direction so that its longitudinal direction (layering direction) follows the left and right sides of the recess portion  33   a  of the first case main body  33 . 
     A junction board  39  and a battery control device  40  are disposed on a rear upper face of the recess portion  33   a  of the first case main body  33 , and a cell voltage sensor  41  is disposed on an upper face of each of the battery modules  37  on the left and right sides of the junction board  39  and the battery control device  40 . 
     Formed in the first cover  34  covering the upper face opening of the first case main body  33  is a case upper wall  34   a  forming a bottom wall of a second water jacket  47 , which is described later, so as to extend in the vehicle width direction, and formed in opposite end parts in the vehicle width direction of the case upper wall  34   a  are left and right communication holes  34   b,    34   c  communicating with the cooling water supply passage  33   e  and the cooling water discharge passage  33   g  on the left and right sides of the first case main body  33 . A raised portion  34   d  covering the top of the junction board  39  and the battery control device  40  is formed in a middle part in the vehicle width direction of a rear part of the first cover  34 , and a raised portion  34   e  covering the top of each of the left and right cell voltage sensors  41  is formed on opposite sides of the raised portion  34   e.  Furthermore, a beam portion  34   f  having a trapezoidal cross section and protruding upward is formed in the vehicle width direction in a middle part in the fore-and-aft direction of the first cover  34 . 
     The second battery case  32  includes a second case main body  42  and a second cover  43  both made of a metal by die-casting, two battery modules  45  on the left and right having battery cells  44  layered in the vehicle width direction are disposed in the interior thereof, and a cell voltage sensor  46  is disposed on an upper face of each battery module  45 . A case lower wall  42   a  of the second case main body  42  of the second battery case  32  includes a recess portion  42   b  that is recessed upward, and a second water jacket  47  (see  FIG. 3 ,  FIG. 4 ,  FIG. 6  and  FIG. 7 ) is defined between a lower face of the recess portion  42   b  and an upper face of the case upper wall  34   a  of the first cover  34  of the first battery case  31 . 
     As shown in  FIG. 2  and inside an enlarged frame of  FIG. 3 , the outer peripheries of the second water jacket  47  and left and right communication holes  34   b,    34   c  are sealed by means of a seal member  48  held between a lower face of the case lower wall  42   a  of the second case main body  42  and the upper face of the case upper wall  34   a  of the first cover  34 . The upper face of the case upper wall  34   a  of the first cover  34  is inclined downward in going outward on the outer side of the seal member  48 . 
     As shown in  FIG. 3 , a cross section in the fore-and-aft direction of the second cover  43  includes a case front wall  43   a,  a case upper wall  43   b  and a case rear wall  43   c,  the case rear wall  43   c  being inclined from upper front toward lower rear. A space having a triangular cross section is formed between the case rear wall  43   c  and a rear face of the battery module  45  housed in the second battery case  32 , and wiring  49  is housed in this space. A beam portion  43   d  having a U-shaped cross section opening upward is formed in the vehicle width direction along the rear end of the case rear wall  43   c  of the second cover  43 . 
     As shown in  FIG. 1 , the battery pack  17  arranged as described above is mounted on the lower face of the floor panel  14  beneath the rear seat  16 . A seat cushion  16   a  of the rear seat  16  is formed so as to rise forward, a front part of the seat cushion  16   a  is disposed above the second battery case  32  of the battery pack  17 , and a rear part of the seat cushion  16   a  is disposed above a rear part of the first battery case  31  of the battery pack  17 . 
     The operation of the embodiment of the present invention having the above arrangement is now explained. 
     Since the muffler  19  provided in the exhaust pipe  18  extending rearward from the engine  12  mounted in the vehicle body front part is housed in the recess portion  33   a  extending in the fore-and-aft direction between the left case bottom wall  33   b  and the right case bottom wall  33   c  of the first case main body  33  of the lower-level first battery case  31 , it is possible to dispose the battery pack  17  at as low a position as possible while avoiding any interference with the muffler  19 , and it is thereby possible to ensure the headroom for an occupant by disposing the rear seat  16 , which is disposed above battery pack  17 , at a low position. 
     Since the four battery modules  37  housed in the first battery case  31  are disposed so that their longitudinal direction is oriented in the fore-and-aft direction so as to follow the left and right sides of the recess portion  33   a,  which bulges upward from a middle part in the vehicle width direction of the first case main body  33 , it is possible to suppress the height of the first cover  34  of the first battery case  31  by lowering the position at which the battery module  37  is mounted. On the other hand, since the two battery modules  37  of the second battery case  32  are disposed in the second case main body  42  so that their longitudinal direction is oriented in the vehicle width direction, it is possible to reduce the width in the fore-and-aft direction of the second battery case  32  and superimpose it only on a front part of the first battery case  31 . As a result, the upper face of the battery pack  17  becomes a stepped shape that rises in going forward, and it is possible, by disposing the seat cushion  16   a  of the rear seat  16  so as to follow the forward and upward inclination, to ensure the headroom for an occupant by disposing the rear seat  16  at an even lower position. 
     In particular, since the junction board  39  and the battery control device  40  of the battery pack  17  are disposed by utilizing a space above the recess portion  33   a  in the rear part of the first battery case  31 , and the cell voltage sensor  41  is disposed by utilizing a space above the battery module  37  in the rear part of the first battery case  31 , it is possible to suppress the height of the upper face of the first battery case  31  by positioning the junction board  39  and the battery control device  40 , which have relatively large vertical dimensions, in the space above the recess portion  33   a,  where the battery module  37  is not present, and by positioning the cell voltage sensor  41 , which has relatively small vertical dimensions, in the space above the battery module  37 . 
     Due to the junction board  39 , the battery control device  40  and the cell voltage sensor  41  being housed in this way, even if the height of the rear upper face of the first battery case  31  is somewhat high, since the height of the rear upper face of the first battery case  31  is lower than the height of the upper face of the second battery case  32 , there is no possibility that the first battery case  31  will interfere with the seat cushion  16   a  of the rear seat  16 . 
     Furthermore, since the case rear wall  43   c  of the second cover  43  of the second battery case  32  is inclined from the upper front toward the lower rear, and the wiring  49  is disposed in a space defined between the front face of the case rear wall  43   c  and the rear face of the battery module  45  disposed in a front part of the second battery case  32 , it is possible to ensure a space in the interior of the second battery case  32  while avoiding any interference between the case rear wall  43   c  and the seat cushion  16   a  of the rear seat  16 , thereby enabling the wiring  49  to be disposed by utilizing the space. 
     Moreover, since the first cover  34  of the first battery case  31  includes the beam portion  34   f  extending in the vehicle width direction, and the second cover  43  of the second battery case  32  includes the beam portion  43   d  extending the vehicle width direction, it is possible to enhance the side collision resistance by reinforcing the first battery case  31  and the second battery case  32  with the beam portions  34   f,    43   d.    
     Low temperature cooling water is made to circulate via the path: cooling water supply port  36   a →left first water jacket  36 A→cooling water supply passage  33   e →second water jacket  47 →cooling water discharge passage  33   g →right first water jacket  36 B→cooling water discharge port  36   b,  thus cooling the four battery modules  37  by means of the left first water jacket  36 A and the right first water jacket  36 B formed in the bottom part of the first battery case  31  and cooling the two battery modules  45  by means of the second water jacket  47  formed in the bottom part of the second battery case  32 . 
     Since the bottom wall of the first case main body  33  of the first battery case  31  is divided into the left case bottom wall  33   b  and the right case bottom wall  33   c  by means of the recess portion  33   a  housing the muffler  19 , the water jacket of the first case main body  33  is divided into two, that is, the left first water jacket  36 A and the right first water jacket  36 B, and the second water jacket  47 , which is separate from the left first water jacket  36 A and the right first water jacket  36 B, is provided on a lower face of the second case main body  42  of the second battery case  32 . 
     The battery pack  17  thus includes the three water jackets, that is, the left first water jacket  36 A, the right first water jacket  36 B and the second water jacket  47 , which are separated in the vertical and lateral directions, and since they are connected in series by means of the cooling water supply passage  33   e  provided in the left case side wall  33   d  of the first case main body  33  and the cooling water discharge passage  33   g  provided in the right case side wall  33   f , it is possible to obtain high cooling performance while minimizing the number of components by reducing the length of the cooling water passage. 
     Furthermore, since both the cooling water supply port  36   a  of the left first water jacket  36 A and the cooling water discharge port  36   b  of the right first water jacket  36 B are provided on the front face side of the first battery case  31 , it is possible to minimize the length of the cooling water passage providing a connection between the battery pack  17  and the cooling water tank, which is disposed in front of the battery pack  17 . Moreover, since the cooling water supply port  36   a  and the cooling water supply passage  33   e  are provided at opposite ends in the vehicle width direction of the left first water jacket  36 A, the cooling water discharge port  36   b  and the cooling water discharge passage  33   g  are provided at opposite ends in the vehicle width direction of the right first water jacket  36 B, and the cooling water supply passage  33   e  and the cooling water discharge passage  33   g  are provided at opposite ends in the vehicle width direction of the second water jacket  47 , it is possible to enhance the cooling performance by making cooling water flow evenly in the internal spaces of the left first water jacket  36 A, the right first water jacket  36 B and the second water jacket  47  while simplifying the routing of the cooling water passage. 
     In particular, since the upwardly recessed recess portion  42   b  is formed in the case lower wall  42   a  of the second case main body  42  of the second battery case  32 , the battery module  45  is placed on the upper face of the recess portion  42   b,  and the second water jacket  47  is formed between the lower face of the recess portion  42   b  and the upper face of the case upper wall  34   a  of the first cover  34  of the first battery case  31  joined thereto, it is possible to arrange the second water jacket  47  by utilizing the case upper wall  34   a  of the first battery case  31  and the case lower wall  42   a  of the second battery case  32 , which already exist, as they are without adding a special member. Moreover, since the second water jacket  47  is defined outside the first battery case  31  and the second battery case  32 , even if cooling water leaks from the second water jacket  47 , there is no possibility that the cooling water will enter the interior of the first battery case  31  or the second battery case  32 . 
     Furthermore, since the cooling water supply passage  33   e  providing a connection between the left first water jacket  36 A and the second water jacket  47  is formed in the left case side wall  33   d  of the first battery case  31 , and the cooling water discharge passage  33   g  providing a connection between the right first water jacket  36 B and the second water jacket  47  is formed in the right case side wall  33   f  of the first battery case  31 , not only is it possible to cut the number of components due to it being unnecessary to employ a special member such as an external pipe, but it is also possible to further reduce the number of components by encircling the second water jacket  47 , the communication hole  34   b,  and the communication hole  34   b  in common by means of the seal member  48 . Moreover, since the case upper wall  34   a  of the first cover  34  of the first battery case  31  is inclined downward in going outward on the outer side of the seal member  48  defining the outer periphery of the second water jacket  47  (see  FIG. 3 ), even if cooling water leaks from the seal member  48 , it is possible to prevent cooling water that has leaked from building up on the upper face of the case upper wall  34   a  of the first cover  34 . 
     Furthermore, since the battery module  45  housed in the second battery case  32  has the battery cells  44  layered in the vehicle width direction, it is possible to make the second battery case  32  long in the vehicle width direction, thus avoiding interference with the seat cushion  16   a  of the rear seat  16 . In this arrangement, since the second water jacket  47  of the second battery case  32  is disposed so that cooling water flows in the vehicle width direction, it is possible to efficiently cool all of the battery cells  44  of the battery module  45 . 
     A second embodiment of the present invention is now explained by reference to  FIG. 8 . 
     Second Embodiment 
     In the first embodiment, the four battery modules  37  are disposed in the interior of the first case main body  33  so that their longitudinal direction is oriented in the fore-and-aft direction, but in the second embodiment two battery modules  37  are disposed on the front side in the interior of the first case main body  33  so that their longitudinal direction is oriented in the vehicle width direction and, furthermore, four battery modules  37  are disposed on the rear side in the interior of the first case main body  33  so that their longitudinal direction is oriented in the fore-and-aft direction. These six battery modules  37  are disposed in a divided manner with three on each of opposite sides in the vehicle width direction of the recess portion  33   a  formed along the fore-and-aft direction in a middle part in the vehicle width direction of the first case main body  33 , and the junction board  39 , the battery control device  40 , a low voltage connector  50  and a high voltage connector  51  are disposed by utilizing a space above the recess portion  33   a  in which no battery module  37  is disposed. 
     That is, the junction board  39  on the lower side and the battery control device  40  on the upper side are disposed on the rear side above the recess portion  33   a  as two layers in the vertical direction. Furthermore, a main body portion  50   a  of the low voltage connector  50  is disposed on the front side above the recess portion  33   a,  and an interface portion  50   b  of the low voltage connector  50  is mounted on a front wall  33   h  above the recess portion  33   a  of the first case main body  33 . Furthermore, the high voltage connector  51  is formed from an interface portion  51   a , and the interface portion  51   a  is also mounted on the left side of the interface portion  50   b  of the low voltage connector  50  on the front wall  33   h  above the recess portion  33   a  of the first case main body  33 . 
     The junction board  39 , the main body portion  50   a  of the low voltage connector  50 , and the high voltage connector  51  are connected via bus bars  52  to  55 , the interface portion  50   b  of the low voltage connector  50  supplies low voltage current to auxiliary equipment, and the interface portion  51   a  of the high voltage connector  51  supplies high voltage current to the electric motor  11 . 
     A heat insulating plate  56  having a shape that follows the recess portion  33   a  of the first case main body  33  extends forward from the front wall  33   h,  and due to the heat insulating plate  56  being present between the exhaust pipe  18  disposed beneath the recess portion  33   a  and the interface portion  50   b  of the low voltage connector  50  and the interface portion  51   a  of the high voltage connector  51  they are protected from the heat of the exhaust pipe  18 . 
     As described above, in accordance with the second embodiment, in addition to the operational effects of the first embodiment, since the interface portions  50   b,    51   a  of the low voltage connector  50  and the high voltage connector  51  are disposed on the front wall  33   h  of the first battery case  31  above the recess portion  33   a  of the first case main body  33 , it is possible to efficiently carry out the routing of wiring for electrical equipment disposed in front of the first battery case  31 . Moreover, since the main body portion  50   a  of the low voltage connector  50  is disposed above the recess portion  33   a,  it is possible to rationally dispose the main body portion  50   a  of the low voltage connector  50  by utilizing effectively a dead space above the recess portion  33   a  where no battery module  37  is disposed. Furthermore, since the interface portions  50   b,    51   a  of the low voltage connector  50  and the high voltage connector  51  are disposed on the front wall  33   h  of the first battery case  31 , the main body portion  50   a  of the low voltage connector  50  is disposed in front of the junction board  39  disposed above the recess portion  33   a,  and the junction board  39  and the main body portion  50   a  are electrically connected to each other, it is possible to minimize the length of the bus bars  52 ,  53  providing a connection between the junction board  39  and the main body portion  50   a  of the low voltage connector  50 . 
     Embodiments of the present invention are explained above, but the present invention may be modified in a variety of ways as long as the modifications do not depart from the subject matter. 
     For example, the exhaust passage member of the present invention is not limited to the muffler  19  of the embodiments but may be the exhaust pipe  18  on the upstream side or the downstream side of the muffler  19 . 
     Furthermore, in the embodiments both the first case main body  33  of the first battery case  31  and the second cover  43  of the second battery case  32  include the beam portions  34   f ,  43   d,  but they may include at least one of the beam portions  34   f,    43   d.    
     Moreover, in the embodiments both the battery control device  40  and the junction board  39  are disposed in the space above the recess portion  33   a  in the rear part of the first battery case  31 , but at least one of the battery control device  40  and the junction board  39  may be disposed there. 
     Furthermore, in the embodiment the interface portions  50   b,    51   a  of the low voltage connector  50  and the high voltage connector  51  are provided on the front wall  33   h  of the first case main body  33 , but they may be provided on the rear wall of the first case main body  33 . 
     Moreover, the cooling medium of the present invention is not limited to the cooling water of the embodiments.