Patent Publication Number: US-2010112428-A1

Title: Power supply apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a power supply apparatus in which a power supply element and coolant for cooling the power supply element are housed inside a power supply case. 
     2. Description of the Related Art 
     If a power supply (such as a secondary battery or a fuel cell) for driving a vehicle such as a hybrid vehicle, an electric vehicle, or a fuel cell vehicle or the like exceeds a suitable temperature, gas is produced by the cell element. Therefore, the power supply must be quickly cooled when heat is generated. 
     Japanese Patent No. 2959298 describes technology for cooling coolant. According to this technology, coolant is filled into a box-shaped container in which a plurality of unit cells are housed. This coolant is then circulated using a circulating device provided near an outer peripheral portion of the box-shaped container. 
     Also, Japanese Patent Application Publication No. 2005-19134 (JP-A-2005-19134) describes a method for circulating coolant, which has been filled inside a fuel cell container that houses a lead battery, between the inside and outside of the container using a pressure pump. 
     Also, Japanese Patent No. 2775600 describes a related cooling apparatus which includes an insulated housing and a cooler which is arranged inside this insulated housing and through which air flows. The cooler is formed by arranging a plurality of plate-shaped cooling elements parallel with each other. Battery cells to be cooled are arranged in the spaces between these parallel cooling elements. 
     Further, Japanese Patent Application Publication No. 9-266016 (JP-A-9-266016) describes a method for cooling a cylindrical cell. According to this technology, the cylindrical cell is retained by a case that contacts an outer peripheral surface of the cylindrical cell. The cylindrical cell is cooled by supplying cooling fluid through a passage that extends through the inside of the case. 
     Also, a pamphlet of International Publication 98/32186 describes a battery module in which a plurality of unit cells and fluid that has an electrical insulating property are housed inside an insulated container, and coolant is circulated between the inside and outside of the insulated container using a pump. 
     Moreover, Japanese Patent Application Publication No. 11-307139 (JP-A-11-307139) describes a battery cooling apparatus in which coolant having an electrical insulating property is filled inside a sealed container that houses a battery. A cooling conduit through which a cooling medium that cools coolant is also arranged within the sealed container. 
     However, with the structure of the technology described in Japanese Patent No. 2959298, the circulating device is provided near an outer peripheral portion of the box-shaped container so the area where circulation takes place is limited and the temperature of the coolant as a whole is not able to be made uniform. As a result, unit cells that are farther from the circulating device may not be sufficiently cooled. 
     Even if a plurality of circulating members were provided, circulation would still be insufficient in those areas where a circulating member was not provided, and the increase in the number of circulating members would increase costs. 
     In addition, with the method for forcibly circulating coolant, a circulation passage and a forced circulation pump need to be provided outside the battery container, which may increase the size of the overall apparatus. 
     SUMMARY OF THE INVENTION 
     This invention thus provides a power supply apparatus capable of suppressing variation in the temperature distribution of coolant. 
     A first aspect of the invention relates to a power supply apparatus in which a power supply element and coolant that cools the power supply element are housed in a power supply case. This power supply apparatus includes an endless belt that is arranged in the coolant, and rotating means for endlessly rotating the endless belt. 
     Here, the power supply element may be arranged in a region surrounded by the endless belt. Also, a plurality of circulation portions may be provided on the endless belt. 
     The power supply apparatus may also be provided with temperature detecting means for detecting a temperature of the coolant, and rotation controlling means for controlling rotation of the endless belt by the rotating means based on a detection result from the temperature detecting means. 
     The power supply element may be formed of a plurality of power supply bodies. In this case, the power supply element may be formed by arranging the power supply bodies parallel with each other between support members, and a bearing portion of a rotating shaft of the rotating means may be formed on the support members. 
     The power supply apparatus may also include a magnetic motor for rotating the rotating shaft from outside the power supply case. 
     According to the invention, coolant is circulated by endlessly rotating the endless belt in the coolant so variation in the temperature distribution of the coolant can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: 
         FIG. 1  is a sectional view in the Y-Z planar direction of a power supply apparatus  1  (i.e., in the length direction of a battery) according to a first example embodiment of the invention; 
         FIG. 2  is a sectional view taken along line I-I′ in  FIG. 1 ; 
         FIG. 3  is a sectional view taken along line II-II′ in  FIG. 1 ; 
         FIG. 4  is a sectional view of a rotational driving portion that rotates a rotating shaft; 
         FIG. 5  is a block diagram of a rotation control portion (i.e., rotation controlling means) that controls the rotation of an endless belt; 
         FIG. 6  is a flowchart illustrating a method for rotatably driving the endless belt; and 
         FIG. 7  is a sectional view of a power supply apparatus  1 ′ according to a second example embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, example embodiments of the invention will be described. 
     The general structure of the invention will now be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a sectional view in the Y-Z planar direction of a power supply apparatus  1  (i.e., in the length direction of a battery) according to a first example embodiment of the invention, and  FIG. 2  is a sectional view taken along line I-I′ in  FIG. 1 . 
     The power supply apparatus  1  of the invention includes a battery case (i.e., a power supply case)  11  that is filled with coolant, an assembled battery (i.e., a power supply element)  12  arranged in the coolant, and an endless belt  13  arranged in the coolant and surrounding the assembled battery  12 . The endless belt  13  is omitted in  FIG. 1 . 
     Belt drive rollers (i.e., rotating means)  17   a  to  17   d  that rotate around rotating shafts  14   a  to  14   d , respectively, are in pressure-contact with four corners of the endless belt  13  such that the endless belt  13  is able to be rotated endlessly by rotating the belt driving rollers  17   a  to  17   d.    
     Endlessly rotating the endless belt  13  circulates coolant inside the battery case  11 , thereby enabling the temperature of the coolant to be uniform (i.e., enabling variation in the temperature distribution to be suppressed). As a result, the life of the assembled battery  12  can be extended. 
     Also, arranging the endless belt  13  so that it surrounds the entire assembled battery  12  enables all of the coolant to be circulated. Thus, it is no longer necessary to provide a plurality of circulating devices to circulate all of the coolant so costs can be reduced. 
     Moreover, the circulating means (i.e., the endless belt  13 ) is arranged in the coolant so the power supply apparatus  1  can be made smaller than it can be with a structure in which the coolant is circulated by a circulation pump. 
     Next, the structure of the power supply apparatus  1  will be described in detail with reference to  FIGS. 1 to 5 .  FIG. 3  is a sectional view taken along line II-II′ in  FIG. 1 ,  FIG. 4  is a sectional view of a rotational driving portion that rotates the rotating shaft  14   a , and  FIG. 5  is a block diagram of a rotation control portion (i.e., rotation controlling means) that controls the rotation of the endless belt  13 . In  FIG. 5 , the solid line denotes a mechanical connection and the broken lines denote electrical connections. 
     As shown in  FIG. 1 , the assembled battery  12  is formed by a plurality of cylindrical cells (i.e., cylindrical power supply bodies)  123  arranged parallel with one another between a pair of cell holders (supporting members)  121  and  122  that are arranged facing one another. 
     A screw shaft portion  123   a  is arranged on one end of each cylindrical cell  123  and a screw shaft portion  123   b  is arranged on the other end of each cylindrical cell  123 . A plurality of insertion hole portions, not shown, into which the screw shaft portions  123   a  and  123   b  of each cylindrical cell  123  are inserted are formed in a matrix in the cell holders  121  and  122 . When the cylindrical cells  123  are in an assembled state, the screw shaft portions  123   a  and  123   b  protrude from the insertion hole portions to the outside of the cell holders  121  and  122 . Incidentally, the cell holders  121  and  122  are made of insulating resin. 
     When a plurality of cylindrical cells  123  are assembled together to create a battery assembly, there may be variation in the temperature of the heat produced by the cylindrical cells  123 . For example, a cylindrical cell  123  that is arranged toward the center of the battery assembly may produce heat of a higher temperature than the heat produced by a cylindrical cell  123  that is arranged toward the outside of the battery assembly. As a result, the cylindrical cell  123  toward the center may deteriorate faster than the cylindrical cell  123  toward the outside. To counteract this, variation in the temperature of the cylindrical cells  123  may be quickly suppressed by forcefully circulating coolant. 
     As shown in  FIG. 3 , a notch portion  121   a  to  121   d  is provided near each of the four corners of the cell holder  121 , and a bearing portion  18   a  to  18   d , which is indicated by hatching, is provided in each notch portion  121   a  to  121   d.    
     An R-shaped bearing surface  181   a  to  181   d  is formed on each bearing portion  18   a  to  18   d , respectively. Each bearing surface  181   a  to  181   d  rotatably supports one of the rotating shafts  14   a  to  14   d.    
     Forming the bearing portions on the cell holder  121  in this way obviates the need for independent bearing members and makes it easier to arrange the assembled battery  12  and to position a motor  15 . Incidentally, the cell holder  122  has the same structure as the cell holder  121 . 
     A bus bar  124  connects adjacent cylindrical cells  123  together in series. This bus bar  124  fits onto the screw shaft portions  123   a  and  123   b . The cylindrical cells  123  can then be fixed to the cell holders  121  and  122  by screwing fastening nuts  126  onto the screw shaft portions  123   a  and  123   b  over the bus bar  124 . 
     Next, the structure of the battery case  11  will be described in detail. As shown in  FIG. 2 , a cooling fin  19  for dissipating heat produced by the assembled battery  12  that is transmitted by the coolant, as well as a mounting bracket  21  for fixing the battery case  11  to a floor panel  22  beneath the passenger&#39;s seat, are formed on the outer peripheral surface of the battery case  11 . Incidentally, the cooling fin  19  may also be provided in plurality. 
     An open portion  21   a  that extends vertically is formed in the mounting bracket  21 . A fastening bolt  23  is inserted into this open portion  21   a  from the floor panel  22  side. 
     A tip portion of the fastening bolt  23  protrudes from the mounting bracket  21 . The power supply apparatus  1  can be fixed to the floor panel  22  by screwing a fastening nut  24  onto the fastening bolt  23  from inside the vehicle cabin. Incidentally, the battery case  11  may be made of metal or resin, for example. 
     A first temperature sensor  61  and a second temperature sensor  62  are provided on the inner peripheral surface of the battery case  11 . The first temperature sensor  61  is arranged above the assembled battery  12  and the second temperature sensor  62  is arranged below the assembled battery  12 . Here, coolant that is hot from cooling the assembled battery  12  naturally rises due to the difference in the specific gravity of the surrounding coolant. 
     Therefore, variation in the temperature of the coolant can be accurately measured by arranging the temperature sensors  61  and  62  above and below the assembled battery  12 . 
     As shown in  FIG. 5 , the first and second temperature sensors  61  and  62  are electrically connected to a battery ECU  63 . 
     The battery ECU  63  switches a motor power supply  64  on when the temperature difference of the coolant is 5° C. or more based on the temperature information output from the first and second temperature sensors  61  and  62 , and switches the motor power supply  64  off when the temperature difference of the coolant is less than 5° C. 
     Next, the structure of the endless belt  13  will be described in detail. The inside surface of the endless belt  13  faces the surface of the cylindrical cells  123  in the length direction and surrounds the assembled battery  12  in the coolant. 
     A plurality of circulation fins (i.e., circulation portions)  13   a  which extend in the direction of thickness of the belt are provided at predetermined intervals (pitches) on the outer surface of the endless belt  13 . Providing these circulation fins  13   a  promotes the circulation of the coolant. Incidentally, the circulation portions may also be formed by forming asperities (i.e., convex and concave portions) on the surface of the endless belt  13 . 
     Also, belt driving rollers  17   a  to  17   d  are in pressure-contact with the four corners of the endless belt  13  from the inside of the endless belt  13 . The belt driving rollers (i.e., rotating means)  17   a  to  17   d  are formed in cylindrical shapes, with each having a rotating shaft (i.e., rotating means)  14   a  to  14   d , respectively, at the inner radial portion. Each belt driving roller  17   a  to  17   d  rotates together as a single unit with its respective rotating shaft  14   a  to  14   d.    
     Pairs of left and right radial bearing portions  26   b  to  26   d  are provided on an inside wall portion of the battery case  11  in  FIG. 1 . The pairs of radial bearings  26   b  to  26   d  rotatably support the rotating shafts  14   b  to  14   d.    
     Next, the structure for rotating the rotating shaft  14   a  will be described with reference to  FIGS. 1 to 4 . 
     A radial bearing portion  26   a  that has the same structure as the radial bearing portions  26   b  to  26   d  is provided on an inside wall portion of the battery case  11  in the axial direction of the rotating shaft  14   a . This radial bearing portion  26   a  rotatably supports the rotating shaft  14   a.    
     Furthermore, a rotating plate accommodating portion  27  that has an accommodating space with dimensions (in the Y axis direction) greater than the thickness of the battery case  11  is provided in a wall portion of the battery case  11 , and an oil seal  31  is interposed at the boundary where the rotating plate accommodating portion  27  meets the wall portion of the battery case  11 . 
     This oil seal  31  makes it possible to reliably seal the coolant inside the battery case  11 . 
     The rotating plate accommodating portion  27  is vertically divided into two chambers, i.e., a first rotating plate accommodating portion  27   a  which is on the right side in the drawing and a second rotating plate accommodating portion  27   b  which is on the left side in the drawing, by a hat-shaped dividing wall  28 . The other end portion of the rotation shaft  14   a  extends out into the first rotating plate accommodating portion  27   a . An output shaft  15   a  of the motor (i.e., rotating means)  15  extends out into the second rotating plate accommodating portion  27   b.    
     A rotating plate  32  which is shaped like a cylinder that is closed off at one end is fixed to the other end portion of the rotating shaft  14   a . A plurality of magnets  41   a  that have a N pole on the outside and a plurality of magnets  41   b  that have an S pole on the outside are alternately arranged in the circumferential direction on the inner peripheral surface of the rotating plate  32 . 
     A disc-shaped magnet mounting plate  33  is fixed to the tip portion of the output shaft  15   a  of the motor  15 . A plurality of magnets  42   a  that have a N pole on the outside and a plurality of magnets  42   b  that have an S pole on the outside are alternately arranged in the circumferential direction on the peripheral surface of this magnet mounting plate  33 . 
     When the output shaft  15   a  of the motor  15  rotates, the magnetic action of the magnets  41   a ,  41   b ,  42   a , and  42   b  rotates the rotating shaft  14   a . Incidentally, the motor  15 , the output shaft  15   a , the magnet mounting plate  33 , the magnets  41   a ,  41   b ,  42   a , and  42   b , and the rotating plate  32  together form a magnetic motor. 
     The magnetic motor is used in this way to rotate the endless belt  13  which circulates the coolant that is sealed within the battery case  11 . 
     Here, the coolant that is filled in the battery case  11  may be material which has high specific heat, good heat conductivity, and a high boiling point, will not corrode the battery case  11  or the assembled battery  12 , and is resistant to thermal decomposition, air oxidation, and electrolysis, and the like. Moreover, an electrically insulating liquid may be used to prevent a short between electrode terminals. 
     More specifically, fluorine-containing inert liquid, for example, may be used as the coolant. Examples of a fluorinated inert fluid include Fluorinert™, Novec™ HFE (hydrofluoroether), and Novec™ 1230, all from 3M Corporation. Alternatively, a liquid other than fluorinated inert fluid (such as silicon oil) may also be used. 
     Next, a method for controlling the motor  15  will be described with reference to  FIGS. 5 and 6 .  FIG. 6  is a flowchart illustrating a method for rotatably driving the endless belt  13 . Incidentally, the routine in this flowchart is executed by the battery ECU (i.e., rotation controlling means)  63 . 
     First, the battery ECU  63  compares the temperature information output from the first and second temperature sensors  61  and  62  (step S 101 ), and then determines whether the temperature difference of the coolant is equal to or greater than 5° C. (step S 102 ). 
     If it is determined in step S 102  that the temperature difference is equal to or greater than 5° C., then the battery ECU  63  determines whether the motor power supply  64  is on (step S 103 ). If the motor power supply  64  is not on (i.e., NO in step S 103 ), the battery ECU  63  switches it on (step S 104 ). 
     When the battery ECU  63  switches the motor power supply  64  on, the output shaft  15   a  of the motor  15  rotates. As a result, the magnetic action of the magnets  41   a ,  41   b ,  42   a , and  42   b  mounted on the magnet mounting plate  33  and rotating plate  32  works to rotate the rotating shaft  14   a.    
     As shown in  FIG. 2 , the endless belt  13  that is in pressure-contact with the belt driving roller  17   a  rotates counterclockwise (i.e., in the direction of arrow G) according to the rotation of the rotating shaft  14   a . As a result, the coolant is moved along the inner peripheral wall of the battery case  11 , thus enabling the temperature of the coolant to be evened out. 
     Also, forcibly circulating coolant quickly suppresses variation in the temperature of the cylindrical cells  123  and lowers the highest temperature of the cylindrical cells  123 , thereby extending the life of the assembled battery  12 . 
     Incidentally, if it is determined in step S 103  that the motor  15  is currently being driven or the motor power supply  64  was switched on in step S 104 , the process returns to step S 101 . 
     If it is determined in step S 102  that the temperature difference is less than 5° C., the battery ECU  63  then determines whether the motor power supply  64  is on (step S 105 ). If the motor power supply  64  is on, the battery ECU  63  switches it off to stop the motor  15  (step S 106 ). Incidentally, if it was determined in step S 105  that the motor  15  is not currently being driven or the motor power supply  64  was switched off in step S 106 , the process returns to step S 101 . 
     A second example embodiment of the invention will now be described with reference to  FIG. 7  which is a sectional view of a power supply apparatus  1 ′ according to the second example embodiment. 
     The assembled battery  12  is formed by arranging cylindrical cells  123  in four rows in the direction of the Z axis (i.e., vertically) and eight rows in the direction of the X axis (i.e., horizontally). 
     A first endless belt  131  surrounds the four rows of cylindrical cells  123  on the left side and a second endless belt  132  surrounds the four rows of cylindrical cells  123  on the right side. 
     The first and second endless belts  131  and  132  are each independently driven by separate motors, i.e., the first endless belt  131  is driven by a first motor and the second endless belt  132  is driven by a second motor. These motors correspond to the motor  15  in the first example embodiment and are not shown in  FIG. 7 . 
     The first motor and the second motor are driven in opposite directions from each other. The first endless belt  131  is endlessly rotated in the counterclockwise direction by driving the first motor, and the second endless belt  132  is endlessly rotated in the clockwise direction by driving the second motor. As a result, coolant is circulated in the directions of arrows H. 
     According to the foregoing structure, coolant near the cylindrical cells  123  positioned at the center of the assembled battery  12  where a large amount of heat is produced (e.g., near the cylindrical cells  123  that are arranged in the fourth and fifth rows from the right) is able to be reliably circulated. As a result, the highest temperature of the cylindrical cells  123  can be further reduced and variation in the temperature of the cylindrical cells  123  can be further suppressed. 
     Also, providing two endless belts increases the circulation force, which enables variation in the temperature distribution among the cylindrical cells  123  to be suppressed to a greater degree than it can be with the structure of the first example embodiment. 
     The arrangement of the endless belt  13  can be modified appropriately according to the distribution of the heat produced by the assembled battery  12 . For example, the endless belt  13  may be arranged so as to surround some of the cylindrical cells  123  (such as the cylindrical cells  123  in the first and second rows). In this case, the arrangement of the endless belt  13  may be easily changed by changing the position of the rotating shaft  14 . 
     In the foregoing example embodiments, the endless belt  13  is driven based on the temperature of the coolant that cools the assembled battery  12 . Alternatively, however, the endless belt  13  may also be driven based on detection results from a temperature detection sensor that detects the temperature of coolant used to cool the engine. 
     Further, a tension roller that adjusts the tension of the endless belt  13  may also be provided. 
     In the second example embodiment, separate motors are provided for driving the first and second endless belts  131  and  132 . Alternatively, however, the first and second endless belts  131  and  132  may be driven endlessly by dividing the driving force obtained from a single motor into two using a transmitting mechanism. This reduces the number of motors which in turn lowers costs. 
     In the foregoing example embodiments, the power supply apparatus  1  is arranged on the floor panel  22  underneath the passenger&#39;s seat. Alternatively, however, the power supply apparatus  1  may be arranged in another location such as between the driver&#39;s seat and the passenger&#39;s seat, or below the rear luggage compartment. 
     Also, the invention may be applied to an electrical double layer capacitor (power supply element) or a fuel cell (power supply element). The electrical double layer capacitor is structured such that a plurality of positive and negative poles are alternately stacked together with separators in between. In this electrical double layer capacitor, aluminum foil may be used as the collector, activate carbon may be used as positive electrode active material and negative electrode active material, and a porous membrane of polyethylene may be used as the separator, for example. 
     Also, the invention may also be applied to a square battery. 
     Further, a plurality of the power supply apparatuses  1  may be arranged parallel with one another in the longitudinal direction of the vehicle. 
     The power supply apparatus described above may be used as a power supply for driving a motor in an electric vehicle (EV), a hybrid vehicle (HEV), and a fuel cell vehicle (FCV), for example. 
     While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiments are shown in various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.