Abstract:
A retaining structure for a power supply may include top and bottom rails connected by columns, which carry loads that would otherwise be applied to the power supply. End plates may be attached to the rails to inhibit movement of the cells in directions parallel to the top and bottom rails. The rails may have a cross section configured to carry at least some of the loads applied to the battery pack. For example, at least a portion of the cross section may be configured in a shape that acts as a spring and deflects upon loading.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/430,263 filed 6 Jan. 2011, which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a retaining structure for a power supply. 
     BACKGROUND 
     Power supplies used in some applications, for example, an array of battery cells used in an electric or hybrid electric vehicle (HEV), have retention and load carrying requirements that must be met. In particular, an HEV battery pack needs to be retained in six linear directions, and at the same time is limited to a maximum load carrying capability. It is therefore desirable to have a structure that is easy to assemble and capable of transferring or carrying loads that would otherwise be felt by the battery cells. 
     SUMMARY 
     Embodiments of the invention provide a retaining structure for a power supply, such as a battery pack used in a vehicle. In at least some embodiments, top and bottom rails are connected by columns, which carry vertical loads that would otherwise be applied to the battery cells. End plates may be attached to the rails to inhibit movement of the cells in directions parallel to the top and bottom rails. The rails may have a cross section configured to carry at least some of the loads applied to the battery pack. For example, at least a portion of the cross section may be configured with a shape that acts as a spring and deflects upon loading. Embodiments of the invention provide a structure that retains individual battery cells in an array such that it acts like a stiff beam and is able to handle high loading conditions. 
     Embodiments of the invention include a power supply structure having a plurality of elongate members configured to be disposed proximate respective corners of a power supply. A pair of end plates are attached to the elongate members, and a plurality of columnar members are attached to opposing pairs of the elongate members and are configured to carry at least a portion of a load applied to the elongate members. 
     Embodiments of the invention further include a power supply structure that includes a plurality of first members configured to retain a power supply in at least four linear directions. A plurality of second members are attached to the first members and are configured to retain the power supply in at least two other directions. A plurality of columnar members are attached to opposing pairs of the first members and are configured to carry at least a portion of a load applied to the first members. 
     Embodiments of the invention also include a power supply structure having a plurality of rails configured to be disposed along a length of a power supply. A pair of end plates are attached to the rails, and a plurality of columnar members are attached to opposing pairs of the rails and configured to carry at least a portion of a load applied to the rails. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a battery pack retained by a structure in accordance with an embodiment of the invention; 
         FIGS. 2A-2C  show a number of components of a retaining structure in accordance with embodiments of the invention; 
         FIG. 3  shows a cross-sectional view of a portion of a battery pack with a retainer in accordance with embodiments of the invention; 
         FIG. 4  shows a perspective view of a battery pack retained by a structure in accordance with an embodiment of the invention; 
         FIG. 5  shows a top rail of the retaining structure shown in  FIG. 4 ; 
         FIG. 6  shows a bottom rail of the retaining structure shown in  FIG. 4 ; 
         FIG. 7  shows a cross-sectional end view of the retaining structure shown in  FIG. 4 ; and 
         FIG. 7A  shows an area of detail of the retaining structure illustrated in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
       FIG. 1  shows a power supply retaining structure  10  in accordance with an embodiment of the present invention. The power supply structure  10  is attached to and is holding together a power supply, which in this case, is made up of two arrays of battery cells  12 . The structure  10  includes first elongate members or rails  14 , columnar members or columns  16 , and second members or endplates  18 . Although  FIG. 1  shows a pair of two arrays being held together by the structure  10 , retaining structures in accordance with embodiments of the present invention may retain other types of power supplies, such as fewer than two or more than two arrays of battery cells, for example, by varying the size of the endplates. 
     The rails  14  are disposed along a length of the arrays and hold the cells  12  on the four corners, thus retaining the battery pack in four directions, specifically, along the y- and z- axes. The endplates  18  are attached to opposite ends of the rails  14  and retain the cells  12  in the other two directions, specifically, along the x-axis. The columns  16  are attached to opposing pairs of the rails  14 , proximate opposite ends  11 ,  15  (only two of which are labeled) of the columns  16 , and carry at least some of the loads that are applied on the rails, thus facilitating a transfer of force away from the cells  12 . As explained below in conjunction with  FIG. 3 , the rails  14  are configured—i.e., shaped and toleranced—in a way to have a spring effect and deform in the presence of a loading force to reduce the loads carried by the cells  12 , and to move excess loads to the columns  16 . 
     In the embodiment shown in  FIG. 1 , the rails  14  on the top and bottom of the arrays of cells  12  have the same geometric configuration; however, embodiments of the present invention may have different rails on the top and bottom. This may be warranted if a bottom side of the structure  10  is attached to a floor (not shown), and a top of the structure  10  is attached to a cover (also not shown) that has different attachment needs from the floor. Shown in  FIG. 1  are fasteners  20 , which traverse apertures in the bottom rail  14 , and fasteners  17 , which traverse apertures in the endplates  18 , to facilitate attachment to a floor. Similarly, apertures  22  shown in the top rails  14 , and apertures  19  shown in the endplates  18 , can accommodate fasteners (not shown) to attach the structure  10  to a cover. Fasteners  21  secure the endplates  18  to the rails  14  such that the endplates  18  are in a fixed position relative to the cells  12 , and the endplates  18  may apply a compressive load on the rails  14 . 
       FIGS. 2A-2C  show some of the elements of a structure like the structure  10  shown in  FIG. 1 . In  FIG. 2A , a rail  23  is shown with no columns installed. This view illustrates bosses  24  that are formed in the rail  23  to accommodate columns such as a column  25 —see  FIG. 2B . Also shown in  FIG. 2B  is a slot  26  near an end of the column  25 , which facilitates assembly and retention of the column  25  in the boss  24 .  FIG. 2B  also shows the column  25  with an aperture  28  therein. The aperture  28  may be through the column  25 , thereby making the column  25  a hollow tube. The aperture  28  may also be a blind hole, and in either case may be configured to receive a fastener, such as a machine screw, to facilitate attachment of the columns  25  to the rails  23 , and ultimately attachment of the rails  23  and columns  25  to a battery pack, such as the batteries  12  shown in  FIG. 1 . In other embodiments, a column, such as the column  25 , may itself be a long fastener configured to engage rails, such as the rail  23 . 
       FIG. 3  shows a cross section of a rail  30  retaining a battery cell  32 . The rail  30  may be part of a power supply structure, such as the retaining structure  10  shown in  FIG. 1 . A portion of a cover  34  is shown attached to the rail  30  with a fastener  36 . A seal  38  is shown on top of the rail  30 , and is configured to provide a seal between the rail  30  and the cover  34 . As described above in conjunction with the rail  14  of the structure  10 , the rail  30  is configured to transfer loads away from battery cells, such as the cell  32 . The rail  30  has a U-shaped portion  40  that will deflect in the presence of a load, such as external forces (F 1 ), (F 2 ), (F 3 ), and inertial forces (F 4 ), (F 5 ) shown in  FIG. 3 . 
     Specifically, the rail  30  deforms around at least one of the longitudinal axes  37 ,  39  of the rail  30 . This does not necessarily mean that either axis  37 ,  39  is a perfect center of rotation as the rail deforms; rather, it illustrates that the rail  30  generally deforms around a longitudinal axis or axes, as opposed to along such an axis, which would be the case for a typical beam loading condition. The deflection of the U-shaped portion  40  absorbs at least some of the energy associated with the load, and reduces the force on the battery cell  32 . An insulator  41  may optionally be used to isolate the battery cell  32  from the rail  30 . Embodiments of the present invention may have other cross-sectional configurations specifically designed to deflect in the presence of a load, thereby isolating a battery cell or cells from the full effect of a loading condition. 
       FIG. 4  shows a power supply retaining structure  42  in accordance with another embodiment of the present invention. The structure  42  is configured to retain a power supply having arrays of battery cells  43 , only a few of which are labeled for clarity. The structure  42  includes first members, which are elongate members and consist of top rails  44  and bottom rails  46 . The rails  44 ,  46  are disposed proximate corners of the cells  43  along a length of the arrays, and are attached to opposing ends of columnar members or columns  48 . Although the term “corner” often implies a vertex of straight lines or edges, it is understood that radiused or otherwise rounded edges or surfaces may be considered “corners” for purposes of this description. 
     The structure  42  also contains second members or endplates  50 , which attach to the top and bottom rails  44 ,  46 . Similar to the structure  10  illustrated in  FIG. 1 , the structure  42  is also configured to resist dislodging of the battery cells  43  in the presence of substantial inertial loads, regardless of the direction of application of the loads. The structure  42  carries, and isolates the battery cells  43  from, at least a portion of such loads. Unlike the structure  10 , where the rails  14  were the same on the top and bottom, the top and bottom rails  44 ,  46  of the structure  42  are configured differently from each other. This is illustrated and described in conjunction with  FIGS. 5 and 6 . 
       FIG. 5  shows one of the top rails  44  in detail. Specifically, the top rails  44  each include an outer member  52 , which may be made from, for example, stamped sheet metal. Providing additional strength to the rail  44  is an inner member  54 , which may be, for example, a steel bracket welded to the outer member  52 . The bracket  54 , among other things, helps the rail  44  to resist deformation along its axis  53 . The bracket  54  may include stamped bosses  55  to further resist deformation in the presence of a load. Also shown in  FIG. 5  is an insulator  56  attached to a portion of the upper rail  44 . As illustrated in more detail in  FIG. 7A , the insulator  56  helps to isolate a battery cell, such as the battery cell  43 , from a rail, which as described above may be made from an electrically conductive material such as sheet metal. The insulator  56  is similar to the insulator  41  illustrated in  FIG. 3  in conjunction with the retaining structure  10 . 
       FIG. 6  shows one of the bottom rails  46  in detail, along with support columns  48  attached thereto. The bottom rails  46  of the retaining structure  42  are also configured to provide greater strength than may be afforded by a simple metal stamping. The bottom rail  46  is made up of an outer member  58 , which, like the outer member  52  of the top rail  44 , may be made from stamped sheet metal. To provide additional strength, inner members, or brackets  60 , are welded to the outer member  58  such that they are disposed between upper and lower portions  57 ,  59  of the outer member  58 . Brackets, such as the brackets  60  may also be press fit between the upper and lower portions  57 ,  59 , an adhesive may be used to hold them in place, or they may be otherwise attached by any effective means. The brackets  60  stiffen the rail  46  and help to resist deformation around a longitudinal axis  61  of the rail  46 . Also shown in  FIG. 6  are weld nuts  62 , which are welded to the lower portion  59  of the outer member  58 . The weld nuts  62  are configured to receive threaded fasteners, which may be used, for example, to attach a portion of a floor or cover around the structure  42 . 
       FIG. 7  illustrates a cover  64  disposed around the retaining structure  42 . In  FIG. 7 , the retaining structure  42  is shown as a cross-sectional end view. In this view, only the two right-hand columns  48  of each of the side-by-side arrays are shown. This is because the columns  48  are staggered from one side of the battery array to the other side of the battery array along its length. This allows the arrays to be packed more closely together in the side-by-side relationship because corresponding columns, such as the columns  48  do not line up directly. 
     Also illustrated in  FIG. 7 , are fasteners  66 , which are used to attach the top rails  44  and the bottom rails  46  to the columns  48 . As described in detail above, with regard to the columns  16  of the retaining structure  10 , other forms of attachment between rails and columns are contemplated. Seals  68  are disposed between the cover  64  and the structure  42 . To further illustrate features of the structure  42 , an area of detail  7 A is denoted in  FIG. 7 , and is shown enlarged in  FIG. 7A . 
     As shown in  FIG. 7A , the outer member  52  of the upper rail  44  is attached to the column  48  with the fastener  66 . Disposed between the outer member  52  and the battery cell  43  is the insulator  56 . This helps to electrically isolate and provide a cushion for the battery cell  43 . The outer member  52  of the upper rail  44  is not configured as a 90° L-bracket, but rather, includes a step  70  on a flange portion  71  that allows the outer member  52  to act as a stiff spring to deflect in the face of a substantial inertial load applied to the structure  42 . With the configuration shown in  FIG. 7A , the outer member  52  can deflect in the presence of horizontal loads, vertical loads, or some combination thereof. Specifically, the outer member  52  will deform around the axis  53  under certain loading conditions. 
     As described in detail above, the bracket  54  adds strength to the upper rail  44  and keeps the outer member  52  from deflecting beyond a desired limit. In addition, the structure  42  is configured such that when it is assembled, there will be a slight gap  72  between the bracket  54  and the rail  48 . In the presence of relatively light loads, such as may be encountered during normal driving conditions, the gap  72  will be maintained, which will help to eliminate rattle and squeak issues. In the presence of a substantial load, however, portions of the structure  42 , including the outer member  52  of the top rail  44  may deflect to such an extent that contact is made between the bracket  54  and the column  48 . In these situations, which may occur in the presence of high inertial loads, such as forces (F 4 ), (F 5 ) shown in  FIG. 3 , the column  48  will help to support the bracket  54  to maintain the integrity of the structure  42 . The materials and geometric configuration of the rails  44  and the gap  72  can be chosen such that contact between the outer member  52  and the rail  44  will occur only in the presence of a predetermined load. Such a predetermined load may be a load of a predetermined magnitude and direction, thus allowing the structure  42  to be “tuned” for expected, and unexpected, loading conditions. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.