Abstract:
An exemplary battery assembly includes, among other things, a thermal fin, a frame holding the thermal fin, and a stand-off of the frame configured to limit relative movement of the thermal fin toward a thermal exchange plate. An exemplary thermal fin positioning method, includes limiting relative movement of a thermal fin toward a thermal exchange plate using a stand-off disposed upon a battery cell assembly frame.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to maintaining clearances within a battery pack. The clearances facilitate thermal energy transfer between a thermal fin and a thermal exchange plate. 
       BACKGROUND 
       [0002]    Electrified vehicles differ from conventional motor vehicles because electrified vehicles are selectively driven using one or more electric machines powered by a battery pack. The electric machines can drive the electrified vehicles instead of, or in addition to, an internal combustion engine. Example electrified vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and battery electric vehicles (BEVs). 
         [0003]    Battery packs of electrified vehicles typically include a plurality of arrays each having individual battery cells that are periodically recharged to replenish the energy necessary to power the electric machines. Battery cells can heat up during charging and discharging, and during other stages of operation. Operating the battery cells at certain temperatures can improve the capacity and the life of the battery cells. 
       SUMMARY 
       [0004]    A battery assembly according to an exemplary aspect of the present disclosure includes, among other things, a thermal fin, a frame holding the thermal fin, and a stand-off of the frame configured to limit relative movement of the thermal fin toward a thermal exchange plate. 
         [0005]    In a further non-limiting embodiment of the foregoing assembly, the thermal fin is in-molded together with the frame. 
         [0006]    In a further non-limiting embodiment of any of the foregoing assemblies, the thermal fin extends a first distance away from a surface of the frame toward the thermal exchange plate, and the stand-off extends a second distance toward the thermal exchange plate. The second is distance greater than the first distance. The surface faces the heat exchange plate. 
         [0007]    In a further non-limiting embodiment of any of the foregoing assemblies, the assembly comprises a plate portion of the thermal fin configured to be positioned between axially adjacent electrodes within a battery pack array, and further comprises a first foot and a second foot of the thermal fin. The first foot and second foot both extend axially from the plate portion. 
         [0008]    In a further non-limiting embodiment of any of the foregoing assemblies, the first fin is positioned between a first pair of stand-offs, and the second fin is positioned between a second pair of the stand-offs. 
         [0009]    In a further non-limiting embodiment of any of the foregoing assemblies, the first foot is laterally spaced from the second foot. 
         [0010]    In a further non-limiting embodiment of any of the foregoing assemblies, the assembly includes a thermal interface material between the thermal fin and the thermal exchange plate. 
         [0011]    In a further non-limiting embodiment of any of the foregoing assemblies, the thermal interface material is a liquid. 
         [0012]    In a further non-limiting embodiment of any of the foregoing assemblies, the thermal interface material is a non-liquid. 
         [0013]    In a further non-limiting embodiment of any of the foregoing assemblies, the thermal interface material directly contacts the stand-off and the thermal fin. 
         [0014]    A thermal fin positioning method according to an exemplary aspect of the present disclosure includes, among other things, limiting relative movement of a thermal fin toward a thermal exchange plate using a stand-off disposed upon a battery cell assembly frame. 
         [0015]    In a further non-limiting embodiment of the foregoing method, the stand-off is integral with the battery frame. 
         [0016]    In a further non-limiting embodiment of any of the foregoing methods, the method includes in-molding the thermal fin with the frame. 
         [0017]    In a further non-limiting embodiment of any of the foregoing methods, the method includes contacting a thermal interface material with the thermal fin. 
         [0018]    In a further non-limiting embodiment of any of the foregoing methods, the thermal interface material is a liquid. 
         [0019]    In a further non-limiting embodiment of any of the foregoing methods, the thermal interface material is a non-liquid. 
         [0020]    In a further non-limiting embodiment of any of the foregoing methods, the method includes contacting the stand-off against the thermal exchange plate to limit movement of the thermal fin toward the thermal exchange plate. 
         [0021]    In a further non-limiting embodiment of any of the foregoing methods, the thermal fin and the stand-off extend from the frame in the same direction. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]    The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
           [0023]      FIG. 1  shows a side view of an example electric vehicle incorporating a battery pack. 
           [0024]      FIG. 2  shows a side view of an array from the battery pack of  FIG. 1 . 
           [0025]      FIG. 3  shows a partially exploded and partially sectioned view of a battery cell from the array of  FIG. 2  positioned adjacent a thermal exchange plate. 
           [0026]      FIG. 4  shows a perspective view of a thermal fin from the battery cell of  FIG. 3 . 
           [0027]      FIG. 5  shows a perspective view of a frame and thermal fin of the battery cells of  FIG. 3 . 
           [0028]      FIG. 6  shows a close-up front view of the portion of the array of  FIG. 3  showing an example stand-off. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    This disclosure relates generally to maintaining clearances within a battery pack. In particular, the disclosure is directed toward a stand-off that maintains a clearance between a thermal fin and a thermal exchange plate. Positioning the thermal fin against, or too close to, the thermal exchange plate can inhibit circulation of a thermal interface material (TIM) that is a liquid. Positioning the thermal fin against, or too close to, the thermal exchange plate can compress a TIM that is a non-liquid. 
         [0030]    Referring to  FIG. 1 , an example electrified vehicle  10  includes a battery  14 , an electric machine  18 , and a pair of vehicle drive wheels  22 . The electric machine  18  can receive electric power from the battery  14 . The electric machine  18  converts the electric power to torque that drives the wheels  22 . The illustrated battery  14  comprises a relatively high voltage traction battery in some embodiments. 
         [0031]    The exemplary vehicle  10  is an all-electric vehicle. In other examples, the electrified vehicle  10  is a hybrid electric vehicle, which can selectively drive the wheels  22  with torque provided by an internal combustion engine instead of, or in addition to, the electric machine  18 . 
         [0032]    Referring now to  FIG. 2  with continuing reference to  FIG. 1 , an array  24  of the battery  14  includes a plurality of individual battery cell assemblies  26  disposed along an axis A and sandwiched axially between endplates  30 . The battery  14  can include the array  24  and several other arrays. The array  24  is considered a module or stack in some examples. 
         [0033]    The battery cell assemblies  26  and endplates  30  are disposed adjacent to a thermal exchange plate  34 . The thermal exchange plate  34  is used to control heat levels within the battery cell assemblies  26 . 
         [0034]    Referring now to  FIGS. 3-5  with continuing reference to  FIG. 2 , a battery cell assembly  26  generally includes a frame structure  38 . Within the battery  14 , axially adjacent frame structures are compressed axially against electrode structures  40 . The frame structure  38  helps to hold the electrode structures  40 . 
         [0035]    The example frame structure  38  also holds a thermal fin  42  that extends from the frame structure  38  toward the thermal exchange plate  34 . The thermal fin  42  includes a plate portion  44  and at least one foot  46  extending axially from the plate portion  44 . The thermal fin  42  is typically a metallic material, such as aluminum. The frame structure  38 , in contrast to the thermal fin  42 , can be a polymer material. In this example, the thermal fin  46  is in-molded with the frame structure  38 . 
         [0036]    Within the battery  14 , the plate portion  44  takes on thermal energy from the electrode structures  40 . The thermal energy moves from the plate portion  44  to the at least one foot  46 . Thermal energy then passes from the at least one foot  46 , through a layer of a TIM  50  to the thermal exchange plate  34 . A temperature management fluid  54  is circulated through channels  58  within the thermal exchange plate  34 . The temperature management fluid  54  carries thermal energy from the thermal exchange plate  34  away from the thermal exchange plate  34  to cool the battery  14 . 
         [0037]    In this example, the TIM  50  is a liquid TIM. In another example, the TIM is a non-liquid TIM. The TIM  50  facilitates transfer of thermal energy between the thermal fin  42  and the thermal exchange plate  34 . 
         [0038]    The example TIM  50  is liquid. Movement and flow of the TIM  50  is compromised if the thermal fin  42  contacts, or is too close to, the thermal exchange plate  34 . The thermal energy transfer between feet  46  and the thermal exchange plate  34  can be inhibited if the movement and flow of the liquid TIM  50  is compromised. 
         [0039]    In examples where the TIM  50  is a non-liquid TIM, compression of the non-liquid TIM due to the thermal fin  42  being urged toward the thermal exchange plate  34  could compress the TIM  50  and inhibit thermal energy transfer. 
         [0040]    The thermal fin  42  can directly contact the TIM  50  whether the TIM  50  is liquid or non-liquid. Direct contact can facilitate thermal exchange. 
         [0041]    A person having skill in this art and the benefit of this disclosure would understand liquid TIMs and non-liquid TIMs. Example liquid TIMs can include substantially any liquid utilized to exchange thermal energy, such as BERGQUIST® liquid TIMs. Example non-liquid TIMs can include substantially any non liquid utilized to exchange thermal energy, such as silicon based sheet TIMs manufactured by SHIN-ETSU®. 
         [0042]    Referring now to  FIG. 6  with continuing reference to  FIGS. 2-5 , a force F can cause the at least one foot  46  of the thermal fin  42  to be urged toward the thermal exchange plate  34 . The forces F can be gravitational forces that cause some of the battery cell assemblies  26  to sag toward the thermal exchange plate  34 . The sagging reduces a clearance C between the feet  46  of the thermal fin  42  and the thermal exchange plate  34 . Binding and compressing the battery cell assemblies  26  within the array  24  could also reduce the clearance C. Assembly tolerances can also cause the clearance C to be reduced in some arrays  24  or in some areas of the array  24 . Substantially non-uniform pressures or excessive loads from hold down brackets associated with the array  24  could also reduce the clearance C in some areas of the array  24 . 
         [0043]    The example frame structure  38  incorporates stand-offs  70 , or ribs, to prevent the clearance C from being eliminated or reduced below a threshold level. Without the stand-offs  70 , the forces, assembly tolerances, or both, could result in the feet  46  of the thermal fin  42  coming undesirably close, or even contacting, the thermal exchange plate  34 . In this example, a tip portion  74  of the stand-off  70  contacts the thermal exchange plate  34  to prevent the thermal fin  42  from moving too close to the thermal exchange plate  34 . 
         [0044]    The stand-offs  70  can be can be molded together with the remaining portions of the frame structure  38  such that the stand-offs  70  are integral portions of the frame structure  38 . The stand-offs  70  could be a separate component that is secured to other portions of the frame structure  38  with a secondary operation after molding the frame structure  38 . 
         [0045]    In this example, the stand-offs  70  are not incorporated into the thermal fin  42  at least because the thermal fin  42  is a metallic material. The stand-offs  70  can directly contact the TIM  50 . 
         [0046]    A surface  80  of the frame structure  38  faces the thermal exchange plate  34 . At least a portion of the feet  46  is positioned between the surface  80  and the thermal exchange plate  34 . The thermal fin  42  extends a first distance D 1  from the surface  80 . The stand-off  70  extends from surface  80  a second distance D 2 , which is greater than the first distance D 1 . Because the stand-off  70  extends closer to the thermal exchange plate  34  than the thermal fin  42 , the stand-off  70  can contact the thermal exchange plate  34  to prevent the feet  46  from moving too close to the thermal exchange plate  34 . 
         [0047]    The example thermal fin  42  includes two feet  46 . The example frame structure  38  includes four stand-offs  70 . One of the stand-offs  70  is positioned at the longitudinal ends of each foot  46 . 
         [0048]    A space  84  between the feet  46  and the laterally inner stand-offs  70  can accommodate a strap (not shown) used to help bind the battery cell assemblies  26  axially between the endplates  30 . The strap is typically a metallic material. The stand-offs  70 , and particularly the laterally inner stand-offs  70 , prevent the strap from coming undesirably close to, or into contact with, the thermal exchange plate  34 . The perimeter of the frame structure  38  could instead, or additionally, include structures used to hold the array  24  together. 
         [0049]    Features of some of the disclosed embodiments include maintaining clearances within an array to help ensure that a liquid TIM is free to move in areas requiring thermal exchange. In some examples, the clearance ensures that liquid TIM will be positioned between a thermal fin and a thermal exchange plate. The clearance can help to avoid sloshing and buildup of a liquid TIM. 
         [0050]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.