Abstract:
An assembly according to an exemplary aspect of the present disclosure includes, among other things, a heat source, a cold plate positioned to conduct heat out of the heat source, and a heat pipe attached to the cold plate and configured to dissipate the heat from the cold plate.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to an assembly for an electrified vehicle. The assembly includes a cold plate and one or more heat pipes attached to the cold plate and configured to dissipate heat conducted through the cold plate from a heat source. 
       BACKGROUND 
       [0002]    The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle. 
         [0003]    A high voltage battery pack for powering electric machines and other electrical loads typically includes multiple battery cells. In certain conditions, such as during charging and discharging operations, heat is generated by the battery cells. This heat may need removed from the battery pack to improve battery cell capacity and life. 
       SUMMARY 
       [0004]    An assembly according to an exemplary aspect of the present disclosure includes, among other things, a heat source, a cold plate positioned to conduct heat out of the heat source, and a heat pipe attached to the cold plate and configured to dissipate the heat from the cold plate. 
         [0005]    In a further non-limiting embodiment of the foregoing assembly, the heat source is a battery cell. 
         [0006]    In a further non-limiting embodiment of either of the foregoing assemblies, the cold plate and the heat pipe are made of a similar material. 
         [0007]    In a further non-limiting embodiment of any of the foregoing assemblies, the similar material is aluminum. 
         [0008]    In a further non-limiting embodiment of any of the foregoing assemblies, a second heat pipe is attached to the cold plate at a location adjacent to the heat pipe, the second heat pipe configured to dissipate the heat. 
         [0009]    In a further non-limiting embodiment of any of the foregoing assemblies, a thermal interface material is disposed between the heat source and the cold plate. 
         [0010]    In a further non-limiting embodiment of any of the foregoing assemblies, an enclosure houses the heat source and the cold plate, and the heat pipe extends through a wall of the enclosure. 
         [0011]    In a further non-limiting embodiment of any of the foregoing assemblies, the heat pipe extends into a channel of a coolant manifold. 
         [0012]    In a further non-limiting embodiment of any of the foregoing assemblies, the heat pipe includes a condenser portion extending into the channel. 
         [0013]    In a further non-limiting embodiment of any of the foregoing assemblies, the heat pipe includes a wick and a vapor cavity disposed inside a casing. 
         [0014]    In a further non-limiting embodiment of any of the foregoing assemblies, a working fluid is configured to flow within the wick between an evaporator portion and a condenser portion of the heat pipe. 
         [0015]    In a further non-limiting embodiment of any of the foregoing assemblies, the working fluid includes liquid ammonia. 
         [0016]    A battery pack according to another exemplary aspect of the present disclosure includes, among other things, a cold plate, a battery array positioned atop the cold plate, an enclosure generally surrounding the cold plate and the battery array, a coolant manifold external to the enclosure and a heat pipe attached to the cold plate and extending into the coolant manifold. 
         [0017]    In a further non-limiting embodiment of the foregoing battery pack, a thermal interface material is disposed between the battery array and the cold plate. 
         [0018]    In a further non-limiting embodiment of either of the foregoing battery packs, the battery array includes a plurality of battery cells and a plurality of spacers disposed between the plurality of battery cells. 
         [0019]    In a further non-limiting embodiment of either of the foregoing battery packs, a thermally conductive film is wrapped around each of the plurality of battery cells. 
         [0020]    A method according to another exemplary aspect of the present disclosure includes, among other things, conducting heat into a cold plate of an assembly and dissipating the heat from the cold plate through a heat pipe that is attached to the cold plate. 
         [0021]    In a further non-limiting embodiment of the foregoing method, the heat is generated by at least one battery cell. 
         [0022]    In a further non-limiting embodiment of either of the foregoing methods, the dissipating step includes communicating the heat to a location external to the assembly and releasing at least a portion of the heat to a coolant communicated across the heat pipe. 
         [0023]    In a further non-limiting embodiment of any of the foregoing methods, the dissipating step includes evaporating and condensing a working fluid inside the heat pipe. 
         [0024]    The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
         [0025]    The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
           [0027]      FIG. 2  is a cross-sectional view of a battery assembly of an electrified vehicle. 
           [0028]      FIG. 3  is a top, cross-sectional view of a battery assembly. 
           [0029]      FIG. 4  illustrates an exemplary heat pipe. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    This disclosure details an assembly for an electrified vehicle. The assembly includes a cold plate and one or more heat pipes attached to the cold plate. In some embodiments, battery cells or other heat sources may be positioned atop the cold plate. Heat released by the heat source is conducted through the cold plate and is then dissipated by the heat pipe. In some embodiments, the heat pipe extends outside of an enclosure of the assembly and exchanges heat with a coolant within a coolant manifold. In other embodiments, the heat pipe and the cold plate are made from similar materials, such as aluminum, for example. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
         [0031]      FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12 . Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEV&#39;s and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEV&#39;s), battery electric vehicles (BEV&#39;s) and fuel cell vehicles. 
         [0032]    In one non-limiting embodiment, the powertrain  10  is a power-split powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of an engine  14  and a generator  18  (i.e., a first electric machine). The second drive system includes at least a motor  22  (i.e., a second electric machine), the generator  18 , and a battery pack  24 . In this example, the second drive system is considered an electric drive system of the powertrain  10 . The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  28  of the electrified vehicle  12 . Although a power-split configuration is shown, this disclosure extends to any hybrid or electric vehicle including full hybrids, parallel hybrids, series hybrids, mild hybrids or micro hybrids. 
         [0033]    The engine  14 , which in one embodiment is an internal combustion engine, and the generator  18  may 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, may be used to connect the engine  14  to the generator  18 . 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 . 
         [0034]    The generator  18  can be driven by the engine  14  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  18  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 . Because the generator  18  is operatively connected to the engine  14 , the speed of the engine  14  can be controlled by the generator  18 . 
         [0035]    The ring gear  32  of the power transfer unit  30  may be connected to a shaft  40 , which is connected to 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 may also be suitable. The gears  46  transfer torque from the engine  14  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 one embodiment, 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 . 
         [0036]    The motor  22  can also be 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 one embodiment, the motor  22  and the generator  18  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  18  can be employed as motors to output torque. For example, the motor  22  and the generator  18  can each output electrical power to the battery pack  24 . 
         [0037]    The battery pack  24  is an exemplary electrified vehicle battery. The battery pack  24  may be a high voltage traction battery pack that includes a plurality of battery assemblies  25  (i.e., battery arrays or groupings of battery cells) capable of outputting electrical power to operate the motor  22 , the generator  18  and/or other electrical loads of the electrified vehicle  12 . Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
         [0038]    In one non-limiting embodiment, the electrified vehicle  12  has two basic operating modes. The electrified vehicle  12  may operate in an Electric Vehicle (EV) mode where the motor  22  is used (generally without assistance from the engine  14 ) for vehicle propulsion, thereby depleting the battery pack  24  state of charge up to its maximum allowable discharging rate under certain driving patterns/cycles. The EV mode is an example of a charge depleting mode of operation for the electrified vehicle  12 . During EV mode, the state of charge of the battery pack  24  may increase in some circumstances, for example due to a period of regenerative braking. The engine  14  is generally OFF under a default EV mode but could be operated as necessary based on a vehicle system state or as permitted by the operator. 
         [0039]    The electrified vehicle  12  may additionally operate in a Hybrid (HEV) mode in which the engine  14  and the motor  22  are both used for vehicle propulsion. The HEV mode is an example of a charge sustaining mode of operation for the electrified vehicle  12 . During the HEV mode, the electrified vehicle  12  may reduce the motor  22  propulsion usage in order to maintain the state of charge of the battery pack  24  at a constant or approximately constant level by increasing the engine  14  propulsion. The electrified vehicle  12  may be operated in other operating modes in addition to the EV and HEV modes within the scope of this disclosure. 
         [0040]      FIGS. 2 and 3  illustrate a battery pack  24  that can be employed within an electrified vehicle. For example, the battery pack  24  could be part of the electrified vehicle  12  of  FIG. 1 . The battery pack  24  includes a plurality of battery cells  56  for supplying electrical power to various electrical loads of the electrified vehicle  12 . Although a specific number of battery cells  56  are depicted in  FIGS. 2-3 , the battery pack  24  could employ a fewer or a greater number of battery cells within the scope of this disclosure. In other words, this disclosure is not limited to the specific configurations shown in  FIGS. 2 and 3 . 
         [0041]    The battery cells  56  may be stacked side-by-side along a longitudinal axis A to construct a grouping of battery cells  56 , sometimes referred to as a “cell stack.” In one non-limiting embodiment, the battery cells  56  are prismatic, lithium-ion cells. However, battery cells having other geometries (cylindrical, pouch, etc.), other chemistries (nickel-metal hydride, lead-acid, etc.), or both could alternatively be utilized within the scope of this disclosure. 
         [0042]    In one non-limiting embodiment, the battery cells  56  are sandwiched between a support structure  57 , which may include end plates  58  and, optionally, spacers  60 . For example, a plurality of battery cells  56  and spacers  60  may be arranged side-by-side in an alternating fashion between the end plates  58 . The spacers  60 , which could also be referred to as separators or dividers, are thermally insulated and may be positioned at opposing ends of the stack of battery cells  56  and between adjacent battery cells  56 . The opposing end plates  58  are positioned outboard of the spacers  60 . The spacers  60  may include thermally resistant and electrically isolating plastics and/or foams that exhibit relatively high thermal insulating capabilities. The support structure  57  axially constrains the stacked battery cells  56 . The battery cells  56  and support structure  57  are together referred to as a battery array  62 . Although only a single battery array  62  is shown in  FIGS. 2-3 , the battery pack  24  could include multiple battery arrays  62 . 
         [0043]    In another non-limiting embodiment, a thermally conductive film  64  may be wrapped around each battery cell  56 . The thermally conductive films  64  facilitate thermal conduction between adjacent battery cells  56  and also electrically isolate adjacent battery cells  56  from one another. The thermally conductive films  64  may additionally establish a dielectric barrier between adjacent battery cells  56  of each battery array  62 . 
         [0044]    The battery pack  24  may be equipped with various features for thermally managing the battery cells  56 . For example, heat H may be generated and released by the battery cells  56  during charging operations, discharging operations, extreme ambient conditions, or other conditions. It is often desirable to remove the heat H from the battery pack  24  to improve capacity and life of the battery cells  56 . Although this embodiment is directed to thermally managing the battery pack  24 , the features of this disclosure may be utilized to thermally manage any high voltage electronic module, including but not limited to, battery packs, ISC modules, chargers, DCDC modules, or any other module that generates heat during operation. In one non-limiting embodiment, the battery pack  24  includes a cold plate  66 , which may alternatively be referred to as a heat exchanger plate. The battery array  62  is positioned atop the cold plate  66 . The heat H from the battery cells  56  may be conducted into the cold plate  66 . 
         [0045]    In one non-limiting embodiment, a thermal interface material  90  may be positioned between the cold plate  66  and at least a portion of the battery array  62 . The thermal interface material  90  provides a thermally conductive interface between the heat source (i.e., the battery cells  56 ) and the heat sink (i.e., the cold plate  66 ) and also fills variations between the heat source and the heat sink. 
         [0046]    One or more heat pipes  68  may be attached to the cold plate  66 . This disclosure is not limited to a specific number of heat pipes  68  and the actual number of heat pipes  68  used for any given cooling application will vary depending upon the cooling requirements of the battery pack  24 , among other factors. In addition, the heat pipes  68  shown in  FIGS. 2 and 3  are not drawn to scale. Instead, these features have been enlarged to better illustrate their various features and functions. 
         [0047]    Each heat pipe  68  may be attached to a bottom surface  70  of the cold plate  66  such that it is substantially integrated with the cold plate  66 . Other mounting locations are also contemplated within the scope of this disclosure. The heat pipes  68  may be brazed or otherwise mounted to the cold plate  66 . The heat pipes  68  and the cold plate  66  may also be made of similar materials. For example, in one non-limiting embodiment, the heat pipes  68  and the cold plate  66  are made from aluminum. Other materials may also be suitable. 
         [0048]    An enclosure  72  generally surrounds each battery array  62  and the cold plate  66  of the battery pack  24 . The enclosure  72  may be made up of one or more walls  92  that house the components of the battery pack  24 . 
         [0049]    The heat pipes  68  may protrude through at least one of the walls  92  of the enclosure  72  and extend into a coolant manifold  74 . The coolant manifold  74  may communicate a coolant C for removing heat from the heat pipes  68 . The coolant C may be a conventional type of coolant mixture such as water mixed with ethylene glycol. However, other coolants are also contemplated and could alternatively be communicated within the coolant manifold  74 . 
         [0050]    The coolant manifold  74  includes an inlet port  94  and an outlet port  96  that are both located external to the enclosure  72  (best shown in  FIG. 3 ). In this way, the potential for fluid leaks inside the enclosure  72  of the battery pack  24  is substantially eliminated. Although not shown, the coolant C exiting the outlet port  96  may be delivered to a radiator or some other heat exchanging device for cooling before being returned to the inlet port  94  in a closed loop. 
         [0051]      FIG. 4  illustrates an exemplary heat pipe  68  for use within the battery pack shown in  FIGS. 2 and 3 . The heat pipe  68  includes a casing  76 , an evaporator potion  84 , a condenser portion  86 , a wick  78  and a vapor cavity  80 . In one non-limiting embodiment, the casing  76  of the heat pipe  68  is made of aluminum. A working fluid  82 , such as liquid ammonia, is disposed inside the casing  76  and may be communicated through the wick  78 , which is porous. The working fluid  82  may evaporate into a vapor V at the evaporator portion  84  of the heat pipe  68 . As evaporation occurs, the vapor V absorbs thermal energy. The vapor V may then migrate along the vapor cavity  80  toward the condenser portion  86  of the heat pipe  68 . In the condenser portion  86 , the vapor V condenses back to fluid F and is absorbed by the wick  78 , thereby releasing thermal energy. The working fluid  82  may then flow back toward the evaporator portion  84 . 
         [0052]    Thermal management of the battery pack  24  is schematically shown in  FIGS. 2, 3 and 4  and generally occurs in the following manner. Heat H is generated and released by the battery cells  56  or some other heat source and is conducted into the cold plate  66 . The heat H conducted into the cold plate  66  is then dissipated from the battery pack  24  by the integrated heat pipes  68 . For example, as the cold plate  66  absorbs the heat H, the working fluid  82  in the evaporator portion  84  vaporizes, thereby creating a pressure gradient within the heat pipe  68 . This pressure gradient forces the vapor V to flow along the vapor cavity  80  to the cooler, condenser portion  86  that is located external to the enclosure  72  and extends into the coolant manifold  74 . The vapor V condenses in the condenser portion  86 , thereby releasing latent heat LH to the coolant C that is communicated through a channel  99  of the coolant manifold  74 . The working fluid  82  is then returned to the evaporator portion  84  by capillary forces developed in the wick  78 . Removing the heat H from the battery pack  24  in this manner maintains the battery cells  56  of the battery pack  24  within a desired operating temperature range. 
         [0053]    Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0054]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
         [0055]    The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.