Patent Publication Number: US-9853435-B1

Title: Busbar thermal management assembly and method

Description:
TECHNICAL FIELD 
     This disclosure relates generally to a busbar for an electrified vehicle and, more particularly, to a flexible busbar having multiple layers. In some areas of the busbar, the layers are separated from each other to provide openings. 
     BACKGROUND 
     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). 
     A battery pack of an electrified vehicle can include a plurality of battery cell assemblies arranged in one or more battery arrays. Busbars can be used to distribute power to and from the battery cell assemblies, and to and from the battery pack. Some busbars are flexible busbars that include multiple individual layers stacked on top of one another. 
     SUMMARY 
     A busbar assembly, according to an exemplary aspect of the present disclosure includes, among other things, a first layer and a second layer. The second layer has a portion that contacts the first layer, and a portion that is spaced from the first layer to provide an opening between the first layer and the second layer. 
     In a further non-limiting embodiment of the foregoing busbar assembly, the first layer and the second layer extend along an axis. The portion that is spaced from the first layer is spaced radially from the first layer relative to the axis. 
     In a further non-limiting embodiment of any of the foregoing busbar assemblies, an axial section of the first layer and an axial section of the second layer each have a rectangular profile. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes an insulating coating covering the first layer and the second layer where the portion of the second layer contacts the first layer. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes a plurality of third layers. Each of the third layers has a portion that contacts another one of the third layers or the second layer. Each of the third layers having a portion that is spaced from the other third layers to provide an opening between each of the third layers and the other third layers. Each of the third layers having a portion that is spaced from the second layer to provide an opening between the third layers and the second layer. 
     In a further non-limiting embodiment of any of the foregoing busbar assemblies, the first layer and the second layer are portions of a flexible busbar assembly. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes a spacer between the first layer and the second layer. The spacer blocks the portion of the second layer that is spaced from the first layer from moving toward the first layer. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes a component secured to the first layer and the second layer. 
     In a further non-limiting embodiment of any of the foregoing busbar assemblies, the component is a relay. 
     In a further non-limiting embodiment of any of the foregoing busbar assemblies, the component is an electrified vehicle powertrain component. 
     In a further non-limiting embodiment of any of the foregoing busbar assemblies, the component is a first component secured to the first layer and the second layer at a first position. The assembly further includes a second component secured to the first layer and the second layer at a second position. The first position is between the second position and the portion that is spaced from the first layer to provide an opening. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes a fluid movement device that moves a fluid through the opening. 
     A further non-limiting embodiment of any of the foregoing busbar assemblies includes a thermal exchange plate. The portion that is spaced from the first layer is potted to the thermal exchange plate. 
     A method of managing thermal energy according to another exemplary aspect of the present disclosure includes, among other things, contacting a first layer and a second layer in a first area of a busbar, and separating, in a second area of the busbar, the first layer from the second layer to provide an opening between the first layer and the second layer. 
     Another example of the foregoing method includes moving a flow of air through the opening to cool the busbar. 
     Another example of any of the foregoing methods includes securing respective first portions of the first and second layers to a first component, and securing respective second portions of the first and second layers to a second component. 
     In another example of any of the foregoing methods, the second area is between the first portions and the second portions. 
     In another example of any of the foregoing methods, the first portions are between the second area and the second portions. 
     Another example of any of the foregoing methods includes moving a flow of air through the opening to cool the first component, the second component, or both. 
     Another example of any of the foregoing methods includes resisting closure of the opening with a spacer positioned within a portion of the opening. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       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: 
         FIG. 1  illustrates a schematic view of an example powertrain of an electrified vehicle. 
         FIG. 2  illustrates an electronic distribution system used in the powertrain of  FIG. 1 . 
         FIG. 3  illustrates a perspective view of a busbar from the electronic distribution system of  FIG. 2 . 
         FIG. 4  illustrates a side view of the busbar of  FIG. 3 . 
         FIG. 5  illustrates a section view at line  5 - 5  in  FIG. 4 . 
         FIG. 6  illustrates a section view at line  6 - 6  in  FIG. 4 . 
         FIG. 7  illustrates a side view of a portion of a busbar according to another exemplary embodiment. 
         FIG. 8  illustrates a side view of a portion of a busbar according to yet another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates generally to a busbar of an electrified vehicle. The busbar includes multiple layers. The busbar can be flexed and bent to accommodate positioning in various configurations within the electrified vehicle. In some areas, the layers of the busbar are spaced from each other to provide an opening, to facilitate an exchange of thermal energy between the busbar and the surrounding environment. 
     Referring to  FIG. 1 , a powertrain  10  of a hybrid electric vehicle (HEV) includes a battery pack  14  having a plurality of battery arrays  18 , an internal combustion engine  20 , a motor  22 , and a generator  24 . The motor  22  and the generator  24  are types of electric machines. The motor  22  and generator  24  may be separate or have the form of a combined motor-generator. 
     In this embodiment, the powertrain  10  is a power-split powertrain that employs a first drive system and a second drive system. The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  28 . The first drive system includes a combination of the engine  20  and the generator  24 . The second drive system includes at least the motor  22 , the generator  24 , and the battery pack  14 . The motor  22  and the generator  24  are portions of an electric drive system of the powertrain  10 . 
     The engine  20  and the generator  24  can be connected through a power transfer unit  30 , such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, can be used to connect the engine  20  to the generator  24 . In one non-limiting embodiment, the power transfer unit  30  is a planetary gear set that includes a ring gear  32 , a sun gear  34 , and a carrier assembly  36 . 
     The generator  24  can be driven by the engine  20  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  24  can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft  38  connected to the power transfer unit  30 . 
     The ring gear  32  of the power transfer unit  30  is connected to a shaft  40 , which is connected to the vehicle drive wheels  28  through a second power transfer unit  44 . The second power transfer unit  44  may include a gear set having a plurality of gears  46 . Other power transfer units could be used in other examples. 
     The gears  46  transfer torque from the engine  20  to a differential  48  to ultimately provide traction to the vehicle drive wheels  28 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  28 . In this example, the second power transfer unit  44  is mechanically coupled to an axle  50  through the differential  48  to distribute torque to the vehicle drive wheels  28 . 
     The motor  22  can be selectively employed to drive the vehicle drive wheels  28  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In this embodiment, the motor  22  and the generator  24  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  24  can be employed as motors to output torque. For example, the motor  22  and the generator  24  can each output electrical power to recharge cells of the battery pack  14 . 
     Referring now to  FIG. 2  with continuing reference to  FIG. 1 , an electronic distribution system  56  of the powertrain  10  is used to exchange electricity between the battery arrays  18  and a load  58 , such as the motor  22 . 
     The system  56  includes a busbar  60  that conducts electricity between a first component  64  and a second component  66 . In this example, the first component  64  is a relay, and the second component  66  is a connector, such as a connector to a wiring harness  68 . 
     The powertrain  10  includes another busbar  70  that is used to conduct electricity between a third component  74  and a fourth component  76 . In this example, the third component  74  is a relay, and the fourth component  76  is a connector, such as a connector to a wiring harness  78 . 
     Busbars could be used elsewhere within the system  56 , such as between the wiring harness  68  and the load  58 , or between the first component  64  and the battery arrays  18 . Busbars could also be used elsewhere within the powertrain  10 , in another portion of the vehicle incorporating the powertrain  10 , or for some other application. The busbar of this disclosure should not be construed as limited to busbars positioned as shown in the system  56  of  FIG. 2 . 
     It may be desirable to maintain a temperature of the first component  64 , a relay, within a particular temperature range. The components  64 ,  66 ,  74 ,  76 , the busbars  60 ,  70  and other portions of the system  56  thus may benefit from being heated or cooled. In this example, the busbar  60  is configured to facilitate heating and cooling of the busbar  60 , the first component  64 , and the second component  66 . In another example, the busbar  60  is configured to facilitate heating and cooling of just the busbar  60 , or just one of the first component  64  or the second component  66 . 
     Referring to  FIGS. 3 and 4  with continuing reference to  FIG. 2 , the busbar  60  is a flexible busbar having a plurality of layers  80 . The busbar  60  extends from a first end  84  to an opposing, second end  88 . The busbar  70  is configured similarly to the busbar  60 . 
     In this example, the first end  84  of the busbar  60  is directly connected to the first component  64 , and the second end  88  is directly connected to the second component  66 . Threaded fasteners could extend through an aperture  90  to directly connect the first end  84  to the first component  64 . The second end  88  could be clamped with the second component  66  to electrically couple the second end  88  and the second component  66 . Other examples could utilize welds or crimps to connect the busbar  60  to components. Other examples could include electrically connecting the busbar  60  to the first component  64  and the second component  66  without directly connecting the busbar  60  to the first component  64  or the second component  66 , such as through a wired connection between the busbar  60  and the first component  64  or the second component  66 . 
     The busbar  60  includes a bend  94  through all the layers  80 . Since the busbar  60  includes the bend  94 , the busbar  60  extends nonlinearly from the first end  84  to the second end  88 . 
     In other examples, the busbar  60  could include more than one bend. In still other examples, the busbar  60  could include no bends such that the busbar  60  extends linearly from the first end  84  to the second end  88 . 
     The bend  94  can be required to place the first end  84  and the second end  88  in positions appropriate for connecting to the first component  64  and the second component  66 . Bending the busbar  60  can also be required to meet packaging requirements. 
     The busbar  60  includes six layers  80  in this example. The layered structure can facilitate forming the bend  94 . The layers  80  have a rectangular axial cross-section in this example. Other examples could include layers with other axial cross-sections. 
     A first section  100  of the busbar  60  extends along a first axis A 1  from the first end  84  to the bend  94 . A second section  104  of the busbar  60  extends along a second axis A 2  from the bend  94  to the second end  88 . The first axis A 1  is transverse to the second axis A 2 . 
     Referring now to  FIGS. 5 and 6  with continuing reference to  FIGS. 3 and 4 , the first section  100  includes an area  108  wherein the layers  80  are separated from each other to provide a plurality of openings  112 . In this example, the layers  80  are spaced radially relative to the axis A 1 . Each of the layers  80  is spaced from each of the other layers  80  in this example. 
     In other examples, other numbers of the layers  80  could be spaced from each other. For example, three layers  80  that are directly contacting each other could be spaced from three other layers  80  directly contacting each other. Spacing the three layers  80  from the other three layers  80  could provide a single opening in the busbar  60 . 
     In the remaining areas of the first section  100 , the layers  80  are in direct contact with each other, such that there are no openings between the layers  80 . In the second section  104 , the layers  80  are also in direct contact with each other, such that there are no openings between the layers  80  within the second section  104 . 
     Due to the openings  112 , the area  108  includes more exposed surfaces of the layers  80  than the other portions of the busbar  60 . The exposed surfaces can facilitate thermal energy exchange between the busbar  60  and the surrounding environment. The exposed surfaces of the layers  80  act as cooling fins in this example. 
     In some examples, the busbar  60  with the area  108  having the openings  112  cools more quickly in a given environment than a busbar lacking an area where layers are separated from each other to provide openings. 
     Cooling the busbar  60  more quickly can also speed up cooling of components that are directly connected, or just thermally connected, to the busbar  60 . That is, the busbar  60 , which is cooling more quickly due to the exposed surface area, can draw heat away from the components connected to the busbar  60 . 
     In some examples, the busbar  60  with the area  108  having the openings  112  results in the first component  64  cooling more quickly in a given environment than if the first component  64  were coupled to a busbar lacking an area where layers  80  are separated from each other to provide openings. 
     In some examples, a fluid movement device  116 , such as a fan, can be positioned adjacent the area  108  to drive a flow of air through the openings  112 . Moving more air through the openings  112  can further enhance cooling. 
     In some examples, the layers  80  of the busbar  60  in the area  108  could be thermally potted to a thermal exchange plate  118  (shown in broken lines in  FIG. 5 ) separate from the busbar  60 . Fluid could move through the thermal exchange plate to exchange thermal energy with the area  108  of the busbar  60 . The thermal exchange plate option could provide increased conduction over examples relying on the flow of air. 
     In this example, the area  108  is positioned between where the busbar  60  attaches to the first component  64  and the second component  66  ( FIG. 2 ). Other examples could position the area  108  elsewhere. 
     As shown in  FIG. 7 , in another example a busbar  60   a  includes an area  108   a  with openings  112   a  positioned on a first side of a connection to a component  66   a , and the same busbar  60   a  extends from another side of the component  66   a  to electrically connect to another component  64   a . A position where the busbar  60   a  is secured to the component  66   a  is thus between the area  108   a  and a position where the busbar  60   a  is secured to the component  64   a.    
     Referring again to the busbar  60  of  FIGS. 2-6 , the layers  80  are roll formed in this example. In the area that will correspond to the area  108  when the layers  80  are stacked to form the busbar  60 , the layers  80  are formed to have a desired curve. The layers  80  that will be used on the top and bottom of the busbar  60  are formed with the most severe curve. The other layers  80  curve less, and the innermost layers  80  curve the least. Various machining process could be used to form desired curvatures in the layers  80 . 
     Other examples may form the layers  80  profiles other than curves into the layers  80  to provide a desired spacing between layers  80  in the area  108 . For example,  FIG. 8  shows an open area  108   b  with layers  80   b  bent to have a triangular profile to provide openings  112   b.    
     As shown in  FIGS. 4 and 5 , to maintain the openings  112 , the busbar  60  could be used in connection with a spacer  120 . In this example, the spacer  120  includes a plurality of fingers  124  extending from a base  128 . The fingers  124  extend into the openings  112  to block the layers  80  from moving radially toward each other. That is, the spacer  120  resists closure of the openings  112 . 
     In the example busbar  60 , some areas are covered with an insulating coating  134 , which holds the individual layers  80  together and can also prevent inadvertent contact between those areas and another structure. The areas covered by the insulating coating  134  are areas where the layers  80  are in direct contact with each other. In this example, the areas where the layers  80  are spaced from each other do not include the insulating coating  134 . In another example, the layers  80  are each individually coated with an insulating coating such that there is insulating coating between the layers  80  adjacent to each other within the area  108 . 
     In the example busbar  60 , the layers  80  are made of a single material, such as copper. In another example, portions of the layers  80  are made of a first material, like copper, and other portions of the layers  80  are made of a second different material, such as aluminum. Different materials may be used for weight reduction, for example. 
     To encourage thermal exchange, the layers  80  could include additional fins, ribs, or other features to further increase the amount of exposed surface area. 
     Features of the disclosed examples include increasing thermal energy exchange between a multilayered busbar and a surrounding environment by separating some of the layers to provide openings between the layers. The openings can further enhance thermal energy exchange if airflow is actively moved through the openings. 
     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.