Abstract:
A thermistor assembly according to an exemplary aspect of the present disclosure includes, among other things, an elastomeric body, a thermistor housed at least partially inside the elastomeric body and a thermistor tip that protrudes outside of the elastomeric body.

Description:
TECHNICAL FIELD 
     This disclosure relates to a thermistor assembly. The thermistor assembly may be employed within a battery assembly of an electrified vehicle. 
     BACKGROUND 
     The need to reduce fuel consumption and emissions in automobiles and other vehicles 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 in that 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. 
     Electrified vehicle battery assemblies may be equipped with one or more battery arrays that include a plurality of battery cells. The battery cells must be reliably connected to one another in order to achieve the necessary voltage and power levels for operating the electrified vehicle. Numerous parts, including but not limited to bus bars, sense-line wiring, and sensors, are typically required to electrically connect the battery cells. 
     SUMMARY 
     A thermistor assembly according to an exemplary aspect of the present disclosure includes, among other things, an elastomeric body, a thermistor housed at least partially inside the elastomeric body and a thermistor tip that protrudes outside of the elastomeric body. 
     In a further non-limiting embodiment of the foregoing assembly, a housing at least partially encapsulates the elastomeric body. 
     In a further non-limiting embodiment of either of the foregoing assemblies, the elastomeric body is molded into the housing. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the housing is made of a material having a first modulus of elasticity and the elastomeric body is made of a material having a second modulus of elasticity that is different from the first modulus of elasticity. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the elastomeric body is made of an ethylene propylene diene monomer (EPDM). 
     In a further non-limiting embodiment of any of the foregoing assemblies, the elastomeric body is made of silicone. 
     In a further non-limiting embodiment of any of the foregoing assemblies, sense-line wiring extends from the elastomeric body. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the elastomeric body is generally T-shaped. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the elastomeric body extends between a proximal portion and a distal portion, at least one flange protruding outwardly from the elastomeric body between the proximal portion and the distal portion. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the distal portion includes laterally protruding legs. 
     A battery assembly according to another exemplary aspect of the present disclosure includes, among other things, a battery array including a plurality of battery cells and a bus bar module mounted to the battery array. At least one thermistor assembly is mounted to the bus bar module and includes an elastomeric body and a thermistor housed inside the elastomeric body. The thermistor includes a thermistor tip that protrudes from the elastomeric body and contacts at least one of the plurality of battery cells. 
     In a further non-limiting embodiment of the foregoing assembly, a housing at least partially encapsulates the elastomeric body. 
     In a further non-limiting embodiment of either of the foregoing assemblies, the housing includes a leg portion and a winged portion that extends from the leg portion. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the winged portion includes a nose and wings that extend laterally from the winged portion. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the elastomeric body is made of rubber or silicone. 
     A battery assembly according to another exemplary aspect of the present disclosure includes, among other things, a plurality of battery cells and a bus bar module positioned over the plurality of battery cells. A thermistor assembly is mounted to the bus bar module. The thermistor assembly includes an elastomeric body that is compressible between a first position and a second position to accommodate cell height variations between a first battery cell and a second battery cell of the plurality of battery cells. 
     In a further non-limiting embodiment of the foregoing assembly, a housing at least partially surrounds the elastomeric body. 
     In a further non-limiting embodiment of either of the foregoing assemblies, a thermistor is housed inside the elastomeric body. 
     In a further non-limiting embodiment of any of the foregoing assemblies, the thermistor includes a thermistor tip that extends outside of the elastomeric body and contacts the first battery cell or the second battery cell. 
     In a further non-limiting embodiment of any of the foregoing assemblies, a metallic bar is received within a central groove of the bus bar module. 
     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. 
     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 
         FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
         FIG. 2  illustrates a battery assembly of an electrified vehicle. 
         FIG. 3  illustrates a bus bar module of a battery assembly. 
         FIGS. 4A, 4B, 4C and 4D  illustrate a thermistor assembly according to a first embodiment of this disclosure. 
         FIGS. 5A and 5B  illustrate a mounting arrangement for the thermistor assembly of  FIGS. 4A-4D . 
         FIGS. 6A and 6B  illustrate another mounting arrangement for the thermistor assembly of  FIGS. 4A-4D . 
         FIG. 7  schematically illustrates the use of a thermistor assembly to accommodate cell height variations of a battery assembly. 
         FIGS. 8A, 8B and 8C  illustrate a thermistor assembly according to a second embodiment of this disclosure. 
         FIG. 9  illustrates the use of another thermistor assembly to accommodate cell height variations of a battery assembly. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure details a thermistor assembly for use within a battery assembly of an electrified vehicle. The thermistor assembly may include an elastomeric body and a thermistor housed at least partially inside the elastomeric body. The thermistor assembly includes a thermistor tip that may protrude outside of the elastomeric body. In some embodiments, a housing at least partially surrounds or encapsulates the elastomeric body. The thermistor assembly may be mounted to a bus bar module of the battery assembly using a variety of mounting arrangements. These and other features are discussed in greater detail in the paragraphs that follows. 
       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) and battery electric vehicles (BEV&#39;s). 
     In one 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 assembly  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. 
     The engine  14 , which could include 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 . 
     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 . 
     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 . 
     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 assembly  24 . 
     The battery assembly  24  is an example type of electrified vehicle battery assembly. The battery assembly  24  may include a high voltage battery pack that includes a plurality of battery arrays capable of outputting electrical power to operate the motor  22  and the generator  18 . Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
     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 assembly  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 assembly  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. 
     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 assembly  24  at a constant or approximately constant level by increasing the engine  14  propulsion usage. 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. 
       FIG. 2  illustrates a battery assembly  54  that can be incorporated into an electrified vehicle. For example, the battery assembly  54  could be employed within the electrified vehicle  12  of  FIG. 1 . The battery assembly  24  can include one or more battery arrays  56  for supplying electrical power to components of an electrified vehicle. Although a single battery array  56  is illustrated in  FIG. 2 , the battery assembly  54  could include multiple battery arrays  56  within the scope of this disclosure. In other words, this disclosure is not limited to the specific configuration shown in  FIG. 2 . 
     The battery array  56  includes a plurality of battery cells  58  stacked side-by-side and extending between opposing end plates  60  and side plates  62  to build the battery array  56 . In one embodiment, the battery cells  58  are prismatic, lithium-ion cells. However, other battery cells, including cylindrical or pouch cells, could alternatively be utilized. 
     A bus bar module  64  may be positioned over the battery array  56 . In one embodiment, the bus bar module  64  rests on top of the battery cells  58 . A bar  63  may retain the bus bar module  64  to the end plates  60  of the battery array  56 , such as by using one or more fasteners  55 . In one embodiment, the bar  63  is a metallic bar that is received within a central groove  61  of the bus bar module  64 . 
     The bus bar module  64  may accommodate a plurality of bus bars  66  that are positioned to electrically connect the battery cells  58  of the battery array  56 . The bus bars  66  may connect the battery cells  58  in either a series string or a parallel string. 
     The bus bars  66  may be connected to terminals  68  that extend from the battery cells  58 . Each bus bar  66  electrically connects adjacent terminals  68  of adjacent battery cells  58 . In one embodiment, the bus bars  66  connect adjacent terminals  68  that have opposite polarities (i.e., negative to positive or positive to negative). The bus bars  66  may be stamped, relatively thin strips of metal that are configured to conduct power generated by the battery cells  58 . Example bus bar materials include copper, brass or aluminum, although other materials having conductive properties may also be suitable. In one embodiment, the bus bars  66  are high current bus bars having relatively high amperage capacities. 
     The bus bars  66  may be mounted within pockets  70  of the bus bar module  64 . The pockets  70  may extend between walls  72  that protrude from a top surface  74  of the bus bar module  64 . The bus bars  66  may be separated from one another by arms  76  that extend from the walls  72 . In one embodiment, the bus bars  66  are welded to the bus bar module  64  using an ultrasonic welding operation that is suitable for welding dissimilar materials. 
     Referring to  FIGS. 2 and 3 , one or more thermistor assemblies  78  may also be mounted to the bus bar module  64 . Exemplary mounting arrangements are discussed in greater detail below, and the mounting locations shown in  FIGS. 2 and 3  are not intended to limit this disclosure. The battery array  56  and bus bars  66  are removed in  FIG. 3  for clarity. 
     The thermistor assemblies  78  may monitor battery conditions, such as temperatures, of one or more battery cells  58  of the battery array  56 . In one embodiment, the thermistor assemblies  78  are thermal resistors that exhibit changes in resistance in response to temperature changes of the battery cells  58 . Information pertaining to any changes in resistance responsive to changes in temperature is communicated to and processed by a control module (not shown), such as a battery electronic control module (BECM), to monitor the functionality of the battery assembly  54 , such as to avoid overcharging the battery cells  58 . 
       FIGS. 4A, 4B, 4C and 4D  illustrate an exemplary thermistor assembly  78 . In one non-limiting embodiment, the thermistor assembly  78  includes a housing  80 , an elastomeric body  82  and a thermistor  84  housed inside the elastomeric body  82  (see  FIGS. 4C and 4D ). The housing  80  may partially surround the elastomeric body  82 . Other thermistor assemblies are contemplated that eliminate the housing  80  (see, e.g., the thermistor assembly  178  of  FIGS. 8A, 8B and 8C ). 
     In this embodiment, the housing  80  acts as an outer shell of the thermistor assembly  78  and may be constructed of a plastic material. Non-limiting examples of suitable plastic materials include polypropylene and nylon. The housing  80  may extend along a longitudinal axis A (see  FIG. 4A ) and includes a leg portion  86  and a winged portion  88 . The winged portion  88  may be slightly elevated relative to the leg portion on a top  90  of the housing  80 . The winged portion  88  may include wings  92  that extend laterally from the winged portion  88  in a direction transverse to the longitudinal axis A. In another embodiment, the winged portion  88  includes a platform  94  that protrudes from the winged portion  88  at a bottom  96  of the housing  80 . 
     The elastomeric body  82  may be molded into the housing  80 , and the housing  80  could entirely or only partially encapsulate the elastomeric body  82 . In one embodiment, as best shown in  FIG. 4D , the elastomeric body  82  includes a head portion  98  and a leg portion  99  that extends from the head portion  98 . The head portion  98  and leg portion  99  may be configured in a T-shape, although other shapes and configurations are contemplated. The head portion  98  of the elastomeric body  82  may protrude out from the platform  94  of the winged portion  88  of the housing  80 . The thickness T (see  FIG. 4C ) of the portion of the elastomeric body  82  that protrudes from the housing  80  can vary depending on design specific criteria. In another embodiment, the leg portion  99  extends within both the winged portion  88  and the leg portion  86  of the housing  80 . 
     In one embodiment, the elastomeric body  82  is made of a material that includes a different modulus of elasticity than the material of the housing  80 . Non-limiting examples of elastomeric materials suitable to construct the elastomeric body  82  include rubber, ethylene propylene diene monomer (EPDM) and silicone. 
     The thermistor  84  is housed within the elastomeric body  82 . In one embodiment, the thermistor  84  includes a thermistor tip  85  that protrudes outside of the head portion  98  of the elastomeric body  82 . The thermistor  84  may be connected to sense-line wiring  87 . The sense-line wiring  87  is embedded within the housing  80  and/or the elastomeric body  82  and may extend outside of the thermistor assembly  78  to connect to a control module or some other component. 
       FIGS. 5A and 5B  illustrate a first mounting arrangement of the thermistor assembly  78 . The bus bar module  64  may include a mounting receptacle  65  for receiving the thermistor assembly  78 . The mounting receptacle  65  may be disposed at a top surface  74  of the bus bar module  64  and may include side walls  67  that extend upwardly from the top surface  74 . An end wall  69  connects between the side walls  67 , which are spaced apart from one another and arranged in parallel. 
     In one embodiment, the thermistor assembly  78  is mounted within the mounting receptacle  65  with a spring clip  71 . The spring clip  71  may extend from the end wall  69  and rest atop the winged portion  88  of the housing  80  of the thermistor assembly  78  after it is inserted into the mounting receptacle  65 . The elastomeric body  82  of the thermistor assembly  78  extends through an opening  73  (best shown in  FIG. 5B ) of the mounting receptacle  65  and contacts a battery cell  58  for accurate monitoring of temperature conditions of the battery cell  58 . The flexible, spring-like nature of the elastomeric body  82  provides consistent contact between the thermistor tip  85  and the battery cell  58  with a minimal amount of required force. 
     Another exemplary mounting arrangement is illustrated in  FIGS. 6A and 6B . In this embodiment, the mounting receptacle  65  includes lock tabs  75  instead of the spring clip feature of  FIGS. 5A and 5B . In one embodiment, the lock tabs  75  extend from opposing side walls  67  of the mounting receptacle  65  in a direction toward an end wall  69 . The thermistor assembly  78  may be mounted to the bus bar module  64  by positioning a nose  77  of the winged portion  88  of the housing  80  within a slot  79  of the mounting receptacle  65  by moving the thermistor assembly  78  in a first direction D 1 . The slot  79  may extend under the wall  69 . 
     Once the nose  77  is far enough into the slot  79  (i.e., under the wall  69 ), the thermistor assembly  78  may be moved in a second direction D 2  that is transverse to the first direction D 1  until the lock tabs  75  can be positioned over the wings  92  of the winged portion  88  of the housing  80 . The slot  79  and the lock tabs  75  substantially retain the thermistor assembly  78  within the mounting receptacle  65  such that the elastomeric body  82  remains in consistent contact with the battery cell  58 . 
       FIG. 7  illustrates a cross-sectional view through a battery assembly  54 . As illustrated, a thermistor assembly  78  can accommodate dimensional variations between adjacent battery cells  58 . For example, a first battery cell  58 A may become displaced by a distance DT from a second battery cell  58 B, causing height variations between the adjacent battery cells  58 . In such situations, the elastomeric body  82  of the thermistor assembly  78  may expand between a first position X and a second position X′ to accommodate cell height variations that may occur during assembly or operation of the battery assembly  54  in order to maintain consistent contact between the thermistor assembly  78  and the first battery cell  58 A. In another embodiment, an opposite configuration is contemplated in which the elastomeric body  82  compresses between the second position X′ and the first position X if the first battery cell  58 A is displaced to a position that is above the height of the second battery cell  58 B. 
       FIGS. 8A, 8B and 8C  illustrate another exemplary thermistor assembly  178 . In this disclosure, like reference numbers designate like elements where appropriate and reference numerals with the addition of 100 or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding original elements. 
     In this embodiment, the thermistor assembly  178  includes an elastomeric body  182  and a thermistor  184  housed inside the elastomeric body  182  (see  FIGS. 8B and 8C ). Unlike the thermistor assembly  78  described above, the thermistor assembly  178  excludes any housing that at least partially encapsulates the elastomeric body  182 . 
     In one embodiment, the elastomeric body  182  extends along a longitudinal axis A (see  FIG. 8B ) between a proximal portion  151  and a distal portion  153 . A flange  155  protrudes outwardly from the elastomeric body  182  at a location between the proximal portion  151  and the distal portion  153 . In one embodiment, the flange  155  circumscribes the elastomeric body  182 . 
     The distal portion  153  may include a pair of laterally extending legs  157 . The legs  157  extend in opposite directions from one another in a direction away from the elastomeric body  182 . In one embodiment, the legs  157  extend transverse to the longitudinal axis A. The legs  157  may be flexible between an expanded position EP and a compressed position CP (shown in phantom, see  FIG. 8B ). 
     In another embodiment, the legs  157  extend outwardly a distance D 1  from the elastomeric body  182  as measured from the longitudinal axis A of the elastomeric body  182 , and the flange  155  extends outwardly a distance D 2 . The distance D 1  may be a greater distance than the distance D 2  such that the legs  157  extend further away from the elastomeric body  182  than the flange  155 . 
     The thermistor  184  may be substantially encapsulated inside the elastomeric body  182 . In one embodiment, the elastomeric body  182  is overmolded around the thermistor  184 . The thermistor  184  may include a thermistor tip  185  that protrudes from a nose  161  of the distal portion  153 . 
     In another embodiment, as best illustrated in  FIG. 8C , a can  163  surrounds the thermistor  184 . A flange  165  of the can  163  may be mounted to the elastomeric body  182  to support the thermistor  184  inside of the elastomeric body  182 . Sense-line wiring  187  may extend from the thermistor  184  to a location outside of the thermistor assembly  178 . 
     An exemplary mounting arrangement of the thermistor assembly  178  is illustrated in  FIG. 8C , with continued reference to  FIGS. 8A and 8B . A bus bar module  164  of a battery assembly  154  may include a cut-out  145  for receiving the thermistor assembly  178 . In one embodiment, the distal portion  153  of the thermistor assembly  178  may be positioned within the cut-out  145 . As the distal portion  153  is moved further into the cut-out  145 , the legs  157  flex between the expanded position EP and the compressed position CP shown in  FIG. 8B . The legs  157  can pass through the cut-out  145  in the compressed position CP. The legs  157  extend under a surface  147 -B of the bus bar module  164  and the flange  155  extends above a surface  147 -A once the distal portion  153  has been inserted into the cut-out  145  to secure the thermistor assembly  178  to the bus bar module  164 . The thermistor tip  185  contacts a battery cell  158  in the mounted position of the thermistor assembly  178 . 
       FIG. 9  illustrates a cross-sectional view through a battery assembly  154 . As illustrated, a thermistor assembly  178  can accommodate dimensional variations between adjacent battery cells  158  of the battery assembly  154 . For example, a first battery cell  158 A may become displaced by a distance DT from a second battery cell  158 B, thereby causing height variations between the adjacent battery cells  158 . In such situations, the elastomeric body  182  of the thermistor assembly  178  may expand by moving in a first direction D 1 , or compress by moving in a second direction D 2 , to accommodate cell height variations that may occur during assembly or operation of the battery assembly  154 . In this way, the thermistor tip  185  may remain in contact with the battery cell  158 A despite any cell height variations. 
     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. 
     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. 
     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.