Patent Publication Number: US-2023134328-A1

Title: Electric motor and stator cooling apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Application Serial No. 17/128,281 filed Dec. 21, 2020, which is a continuation of U.S. Application Serial No. 15/820,934 filed Nov. 22, 2017 (now U.S. Pat. No. 10,879,749 issued Dec. 29, 2020). The disclosure of each of the above-referenced applications is incorporated by reference as if fully set forth in detail herein. 
    
    
     FIELD 
     The present disclosure relates to an electric motor and a stator cooling apparatus for an electric motor. 
     BACKGROUND 
     Electric motors, such as those used in vehicle drivelines, can generate heat during operation. Excess temperatures can have undesirable effects on performance and longevity of the electric motor and its associated components. As such, it can be advantageous to provide cooling to the motor to remove excess heat therefrom. While typical motor cooling methods can be sufficient for their intended uses, there continues to be a need for improved cooling of electric motors. 
     SUMMARY 
     This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present disclosure provides an electric motor can include a stator body, a rotor, a plurality of electrically conductive windings, a first end cap, and a second end cap. The stator body can be disposed about an axis and can define a plurality of fluid channels. The fluid channels can extend axially through the stator body to provide fluid communication between a first axial end of the stator body and a second axial end of the stator body. The rotor can be disposed about the axis and rotatable relative to the stator body. The plurality of electrically conductive windings can form a plurality of first winding loops and a plurality of second winding loops. The first winding loops can extend axially outward from the first axial end of the stator body. The second winding loops can extend axially outward from the second axial end of the stator body. The first end cap can be coupled to the first axial end of the stator body. The first end cap can include a first wall and a plurality of first pins. The first wall can be disposed between the first winding loops and the fluid channels. The first pins can extend from a side of the first wall that is opposite the first winding loops. The second end cap can be coupled to the second axial end of the stator body. The second end cap can include a second wall and a plurality of second pins. The second wall can be disposed between the second winding loops and the fluid channels. The second pins can extend from a side of the second wall that is opposite the second winding loops. 
     According to a further embodiment, the electric motor can further include a housing disposed about the stator body. The housing can cooperate with the stator body and the first end cap to define a first chamber in fluid communication with the fluid channels. The first pins can extend into the first chamber. The housing can cooperate with the stator body and the second end cap to define a second chamber in fluid communication with the fluid channels. The second pins can extend into the second chamber. 
     According to a further embodiment, the electric motor can further include a pump including an inlet and outlet. The inlet of the pump can be in fluid communication with the second chamber to receive fluid therefrom. The outlet of the pump can be in fluid communication with the first chamber to pump fluid thereto. 
     According to a further embodiment, the electric motor can further include a at least one shroud that includes at least one of: a first shroud disposed about the axis between the first end cap and the housing and configured to guide fluid flow from the first chamber across the first pins to the fluid channels; or a second shroud disposed about the axis between the second end cap and the housing and configured to guide fluid flow from the fluid channels across the second pins to the second chamber. 
     According to a further embodiment, the first pins can extend radially outward from the first wall. 
     According to a further embodiment, the first pins can extend radially outward of a radially inward-most part of the fluid channels. 
     According to a further embodiment, the second pins can extend radially outward from the second wall. 
     According to a further embodiment, the second pins can extend radially outward of a radially inward-most part of the fluid channels. 
     According to a further embodiment, the electric motor can further include a sensor and at least one of the first end cap or the second end cap can define a sensor bore. The sensor can be removably disposed within the sensor bore and configured to output a signal that corresponds to a temperature of the electrically conducting windings. 
     According to a further embodiment, the first and second winding loops can be encased in a thermally conductive but electrically insulating resin that contacts the first and second walls and the first and second winding loops. 
     According to a further embodiment, the first and second winding loops can extend radially outward of a radially inward-most part of the fluid channels. 
     According to a further embodiment, the first wall can include a first annular body and a second annular body coupled to the first annular body to define a first winding cavity. The first winding loops can be disposed within the first winding cavity. The first pins can extend axially from at least one of: the first annular body in a direction toward the stator body, or the second annular body in a direction away from the stator body. 
     According to a further embodiment, the first pins can extend axially in the direction toward the stator body from the first annular body and axially in the direction away from the stator body from the second annular body. 
     According to a further embodiment, the second wall can include a third annular body and a fourth annular body coupled to the third annular body to define a second winding cavity. The second winding loops can be disposed within the second winding cavity. The second pins can extend axially from at least one of: the third annular body in a direction toward the stator body, or the second annular body in a direction away from the stator body. 
     According to a further embodiment, the second pins can extend axially in the direction toward the stator body from the third annular body and axially in the direction away from the stator body from the fourth annular body. 
     In another form, the present disclosure provides an electric motor including a housing, a stator body, a rotor, a plurality of electrically conductive windings, a first end cap, and a second end cap. The stator body can be disposed about an axis. The stator body can define a plurality of fluid channels that extend axially through the stator body to provide fluid communication between a first axial end of the stator body and a second axial end of the stator body. The rotor can be disposed about the axis and rotatable relative to the stator body. The plurality of electrically conductive windings can form a plurality of first winding loops and a plurality of second winding loops. The first winding loops can extend axially outward from the first axial end of the stator body. The second winding loops can extend axially outward from the second axial end of the stator body. The first end cap can be coupled to the first axial end of the stator body. The first end cap can include a first wall and a plurality of first pins. The first end cap and the housing can define a first fluid cavity in fluid communication with the fluid channels. The first end cap can define a first winding cavity separated from the first fluid cavity by the first wall. The first winding loops can be disposed within the first winding cavity. The first pins can extend from the first wall into the first fluid cavity. The second end cap can be coupled to the second axial end of the stator body. The second end cap can include a second wall and a plurality of second pins. The second end cap and the housing can define a second fluid cavity in fluid communication with the fluid channels. The second end cap can define a second winding cavity separated from the second fluid cavity by the second wall. The second winding loops can be disposed within the second winding cavity. The second pins can extend from the second wall into the second fluid cavity. 
     According to a further embodiment, the first pins can extend radially outward from the first wall and the second pins can extend radially outward from the second wall. 
     According to a further embodiment, the first and second pins can extend radially outward of a radially inward-most part of the fluid channels. 
     According to a further embodiment, the first and second winding loops can be encased in a thermally conductive but electrically insulating resin that contacts the first and second walls and the first and second winding loops. 
     According to a further embodiment, the first and second winding loops can extend radially outward of a radially inward-most part of the fluid channels. 
     According to a further embodiment, the first wall can include a first annular body and a second annular body coupled to the first annular body to define the first winding cavity. The first pins can extend axially from at least one of: the first annular body in a direction toward the stator body, or the second annular body in a direction away from the stator body. The second wall can include a third annular body and a fourth annular body coupled to the third annular body to define the second winding cavity. The second pins can extend axially from at least one of: the third annular body in a direction toward the stator body, or the second annular body in a direction away from the stator body. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure. 
         FIG.  1    is a perspective view of a portion of an electric motor of a first construction, constructed in accordance with the teachings of the present disclosure; 
         FIG.  2    is a sectional view of a stator core of the electric motor of  FIG.  1   ; 
         FIG.  3    is a schematic sectional view of a portion of the electric motor of  FIG.  1   , schematically illustrating a cooling circuit for cooling the electric motor; 
         FIG.  4    is a perspective view of a portion of an electric motor of a second construction, constructed in accordance with the teachings of the present disclosure; 
         FIG.  5    is a schematic sectional view of a portion of the electric motor of  FIG.  4   , schematically illustrating a cooling circuit for cooling the electric motor; and 
         FIG.  6    is a perspective view of a portion of an electric motor of a third construction. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     With reference to  FIGS.  1 - 3   , an electric motor  110  of a first construction is illustrated. The electric motor  110  can include a housing  114 , a stator  118 , a rotor  122 , an output shaft  126 , a first end cap  130 , a first shroud  132 , a second end cap  134 , a second shroud  136 , and a cooling system  138 . In the example provided, the housing  114  can define a generally cylindrical cavity  142  disposed about an axis  146 . The stator  118   can be disposed about the axis  146  within the cylindrical cavity  142  and can be fixedly coupled to the housing  114  such that the stator  118  is non-rotatable relative to the housing  114 . In the example provided, an outermost cylindrical surface of the stator  118  can include one or more grooves  150  that can extend axially along the stator  118  and can mate with a spline (not specifically shown) on an interior surface of the housing  114 , though other configurations can be used. The stator  118  can be formed of a plurality of stator laminations stacked axially end to end along the axis  146 , though other configurations can be used. 
     The stator  118  can be generally annular in shape, with a first axial face or end  154  and a second axial face or end  158  opposite the first axial end  154 . The stator  118  can include an annular body  162 , a plurality of winding poles  166 , and a plurality of wire windings  170 . The annular body  162  can be fixedly coupled to the winding poles  166  to make up the stator core. The annular body  162  can define a plurality of fluid channels  174  that can be open at the first axial end  154  and the second axial end  158  and can extend axially therebetween to permit fluid communication between the first axial end  154  and the second axial end  158 . The fluid channels  174  can be disposed about the axis  146 . In the example provided, the fluid channels  174  are equally spaced apart in the circumferential direction about the axis  146 . 
     The winding poles  166  can extend radially inward from the radially inward side of the annular body  162 . The winding poles  166  can be equally spaced apart in the circumferential direction about the axis  146  to define winding slots  178  between adjacent ones of the winding poles  166 . Thus, the winding poles  166  and winding slots  178  can be radially inward of the fluid channels  174 . Electrically conductive wire can extend through the winding slots  178  and be wound about the winding poles  166  to form the wire windings  170  in a manner such that a first section of the wire windings  170  forms first winding loops  182  that extend axially outward from the first axial end  154  of the stator  118  and a second section of the wire windings  170  forms second winding loops  186  that extend axially outward from the second axial end  158  of the stator  118 . 
     The rotor  122  can be disposed about the axis  146  and can be supported for rotation relative to the stator  118 . The stator  118  can be disposed about the rotor  122  such that the rotor  122  is radially inward of the winding poles  166 . The output shaft  126  can be disposed about the axis  146  and fixedly coupled to the rotor  122  for common rotation about the axis  146 . In the example provided, the output shaft  126  can extend axially from both axial ends of the rotor  122 . While not specifically shown, the output shaft  126  can be coupled to a driveline of a vehicle for providing torque to a set of vehicle wheels. 
     The first end cap  130  can be a generally annular body and can include a first inner wall  190 , a first outer wall  194 , a first end wall  198 , and a plurality of first fins or pins  202 . In the example provided, the first end cap  130  is unitarily formed from a thermally conductive, but electrically insulating material, such as by injection molding of a plastic for example. A proximal end of the first inner wall  190  can abut the first axial end  154  of the stator  118 . The first inner wall  190  can extend axially from the first axial end  154  of the stator  118  to a distal end of the first inner wall  190 . The first inner wall  190  can be coaxial with the axis  146 . An outward facing cylindrical side of the first inner wall  190  can be disposed radially inward of the first winding loops  182  and an inward facing cylindrical side of the first inner wall  190  can be radially outward of the rotor  122 . 
     The first inner wall  190  can define a pocket  200  configured to receive a temperature sensor  204 . In the example provided, the pocket  200  extends generally axially relative to the axis  146  and is open facing axially away from the first axial end  154 . The pocket  200  can be radially inward of the first winding loops  182  and can extend axially toward the first axial end  154  such that the temperature sensor  204  therein can be in close proximity to the first winding loops  182 . For example, the temperature sensor  204  can axially overlap with the first winding loops  182 . In the example provided, the temperature sensor  204  is a thermistor, though other types of sensors can be used. Thus, pocket  200  and temperature sensor  204  can be located at a back (e.g., radially inner) plane of the first winding loops  182  such that they are away from the cooling flow, but in strong thermal conduction with the first winding loops  182  to provide accurate temperature readings of the first winding loops  182 . The temperature sensor  204  can be removably coupled to the pocket  200 , such as being threaded into the pocket  200  for example. 
     A proximal end of the first outer wall  194  can abut the first axial end  154  of the stator  118 . The first outer wall  194  can extend axially from the first axial end  154  of the stator  118  to a distal end of the first outer wall  194 . The first outer wall  194  can be coaxial with the axis  146 . In the example provided, the first outer wall  194  can be generally parallel to the first inner wall  190 . An outward facing cylindrical side of the first outer wall  194  can be disposed radially inward of the fluid channels  174  and an inward facing cylindrical side of the first outer wall  194  can be disposed radially outward of the first winding loops  182 . 
     The first end wall  198  can extend generally radially between the distal end of the first outer wall  194  and the first inner wall  190 . In the example provided, the first end wall  198  connects the distal end of the first outer wall  194  to the first inner wall  190  at a location on the first inner wall  190  that is axially between the proximal and distal ends of the first inner wall  190 . In the example provided, the first end wall  198  can be generally perpendicular to the axis  146 , though other configurations can be used. The first inner wall  190 , the first outer wall  194 , and the first end wall  198  can cooperate to define a first winding cavity  206  that is disposed annularly about the axis  146  and open toward the stator  118  and configured to receive the first winding loops  182  therein. As such, the first winding cavity  206  can be open to the slots  178  of the stator  118 . In the example provided, the first end wall  198  can include one or more first ports  210  that can be open axially through the first end wall  198 . 
     A proximal end of each first pin  202  can be fixedly coupled to the first outer wall  194  and each first pin  202  can extend radially outward from the first outer wall  194  to a distal end. In the example provided, the distal ends of the first pins  202  can be radially outward of a radially innermost part of the openings of the fluid channels  174 . In the example provided, the first pins  202  can be equally spaced in the circumferential direction about the first outer wall  194 , though other configurations can be used. In the example provided, the first outer wall  194  includes six equally spaced rows of the first pins  202  in the axial direction, though more or fewer rows can be used, or the first pins can be such that they are not arranged in ordered rows. In the example provided, some of the first pins  202  also extend axially outward (i.e., the direction away from the stator  118 ) from the first end wall  198 . In the example provided, the first pins  202  are generally cylindrical or conical in shape, but other configurations can be used, such as fins, ribs, blades, tabs, or pyramid-shapes for example. 
     The first axial end  154  of the stator  118 , the inner surface of the housing  114 , and the first outer wall  194  can cooperate to define a first chamber or fluid cavity  214  in fluid communication with the fluid channels  174 . In the example provided, the first chamber  214  is also defined by the first end wall  198  and the portion of the first inner wall  190  that is axially outward of the first end wall  198 , though other configurations can be used. Thus, the first pins  202  can extend within the first chamber  214 . In the example provided, the housing  114  defines an inlet port  218  in fluid communication with the first chamber  214 . 
     The first shroud  132  can be a hollow, generally cylindrical body disposed about the axis  146  and open at both axial ends of the first shroud  132 . The first shroud  132  can be fixedly coupled to the stator  118  or the housing  114 . The first shroud  132  can be generally between the first end cap  130  and the housing  114  to divide the first chamber  214  into an outer region and an inner region. The inner region can be open to the fluid channels  174 , i.e., in direct fluid communication with the fluid channels  174 . In other words, fluid flowing from the outer region to the fluid channels  174  must pass through the inner region. A radially inward surface of the first shroud  132  can be in close proximity to the distal ends of the first pins  202  such that fluid flowing through the inner region to the fluid channels  174  is guided across the first pins  202  and maintains a high velocity while passing between the first pins  202 . 
     The second end cap  134  can be similar to the first end cap  130  except as otherwise shown or described herein. The second end cap  134  can be a generally annular body and can include a second inner wall  222 , a second outer wall  226 , a second end wall  230 , and a plurality of second fins or pins  234 . In the example provided, the second end cap  134  is unitarily formed from a thermally conductive, but electrically insulating material, such as by injection molding of a plastic for example. A proximal end of the second inner wall  222  can abut the second axial end  158  of the stator  118 . The second inner wall  222  can extend axially from the second axial end  158  of the stator  118  to a distal end of the second inner wall  222 . The second inner wall  222  can be coaxial with the axis  146 . An outward facing cylindrical side of the second inner wall  222  can be disposed radially inward of the second winding loops  186  and an inward facing cylindrical side of the second inner wall  222  can be radially outward of the rotor  122 . 
     The second inner wall  222  can optionally define a second pocket  232  configured to receive a second temperature sensor  236 . The second pocket  232  and second temperature sensor  236  can be similar to the pocket  200  and temperature sensor  204  except as otherwise shown or described herein. In the example provided, the second pocket  232  extends generally axially relative to the axis  146  and is open facing axially away from the second axial end  158 . The second pocket  232  can be radially inward of the second winding loops  186  and can extend axially toward the second axial end  158  such that the second temperature sensor  236  therein can be in close proximity to the second winding loops  186 . For example, the second temperature sensor  236  can axially overlap with the second winding loops  186 . In the example provided, the second temperature sensor  236  is a thermistor, though other types of sensors can be used. Thus, second pocket  232  and second temperature sensor  236  can be located at a back (e.g., radially inner) plane of the second winding loops  186  such that they are away from the cooling flow, but in strong thermal conduction with the second winding loops  186  to provide accurate temperature readings of the second winding loops  186 . The second temperature sensor  236  can be removably coupled to the second pocket  232 , such as being threaded into the second pocket  232  for example. 
     A proximal end of the second outer wall  226  can abut the second axial end  158  of the stator  118 . The second outer wall  226  can extend axially from the second axial end  158  of the stator  118  to a distal end of the second outer wall  226 . The second outer wall  226  can be coaxial with the axis  146 . In the example provided, the second outer wall  226  can be generally parallel to the second inner wall  222 . An outward facing cylindrical side of the second outer wall  226  can be disposed radially inward of the fluid channels  174  and an inward facing cylindrical side of the second outer wall  226  can be disposed radially outward of the second winding loops  186 . 
     The second end wall  230  can extend generally radially between the distal end of the second outer wall  226  and the second inner wall  222 . In the example provided, the second end wall  230  connects the distal end of the second outer wall  226  to the second inner wall  222  at a location on the second inner wall  222  that is axially between the proximal and distal ends of the second inner wall  222 . In the example provided, the second end wall  230  can be generally perpendicular to the axis  146 , though other configurations can be used. The second inner wall  222 , the second outer wall  226 , and the second end wall  230  can cooperate to define a second winding cavity  238  that is disposed annularly about the axis  146  and open toward the stator  118  and configured to receive the second winding loops  186  therein. As such, the second winding cavity  238  can be open to the slots  178  of the stator  118 . In the example provided, the second end wall  230  can include one or more second ports  242  that can be open axially through the second end wall  230 . 
     A proximal end of each second pin  234  can be fixedly coupled to the second outer wall  226  and each second pin  234  can extend radially outward from the second outer wall  226  to a distal end. In the example provided, the distal ends of the second pins  234  can be radially outward of a radially innermost part of the openings of the fluid channels  174 . In the example provided, the second pins  234  can be equally spaced in the circumferential direction about the second outer wall  226 , though other configurations can be used. In the example provided, the second outer wall  226  includes six equally spaced rows of the second pins  234  in the axial direction, though more or fewer rows can be used, or the second pins can be such that they are not arranged in ordered rows. In the example provided, some of the second pins  234  also extend axially outward (i.e., the direction away from the stator  118 ) from the second end wall  230 . In the example provided, the second pins  234  are generally cylindrical or conical in shape, but other configurations can be used, such as fins, ribs, blades, tabs, or pyramid-shapes for example. 
     With additional reference to  FIG.  6   , a portion of a second end cap  134   b  is illustrated with one example of such a different configuration of the second pins  234   b . The second end cap  134   b  and second pins  234   b  can be similar to the second pins  234  ( FIGS.  1  and  3   ), except as otherwise shown or described herein. Elements of the second end cap  134   b  that are similar to elements of the second end cap  134  ( FIGS.  1  and  3   ) are indicated with similar reference numerals followed by the numeral ‘b’ and only differences are described in detail herein. In the example shown, the second pins  234   b   have a fin, rib, or blade type shape that are angled to promote uniform rotational flow around the second outer wall  226   b . In the example provided, the second pins  234   b  can extend longitudinally at an angle  610  relative to the axis  146  (e.g., relative to line  614  which is parallel to the axis  146  shown in  FIG.  3   ). This rotational flow around the second outer wall  226   b  can promote uniform flow to the outlet port  250  ( FIG.  3   ) and can increase heat absorption by the fluid. In the example provided, only the second pins  234   b  have the angled, fin/rib/blade type of pin. In an alternative configuration, not specifically shown, the first end cap  130  ( FIGS.  1  and  3   ) and not the second end cap  134  ( FIGS.  1  and  3   ) can have such angled pins to promote rotational flow. In another alternative configuration, not specifically shown, both the first end cap  130  ( FIGS.  1  and  3   ) and the second end cap  134   b  can have such angled pins to promote rotational flow. 
     Returning to the example shown in  FIGS.  1 - 3   , the second axial end  158  of the stator  118 , the inner surface of the housing  114 , and the second outer wall  226  can cooperate to define a second chamber or fluid cavity  246  in fluid communication with the fluid channels  174 . In the example provided, the second chamber  246  is also defined by the second end wall  230  and the portion of the second inner wall  222  that is axially outward of the second end wall  230 , though other configurations can be used. Thus, the second pins  234  can extend within the second chamber  246 . In the example provided, the housing  114  defines an outlet port  250  in fluid communication with the second chamber  246 . 
     The second shroud  136  can be similar to the first shroud  132 , except as otherwise shown or described herein. The second shroud  136  can be a hollow, generally cylindrical body disposed about the axis  146  and open at both axial ends of the second shroud  136 . The second shroud  136  can be fixedly coupled to the stator  118  or the housing  114 . The second shroud  136  can be generally between the second end cap  230  and the housing  114  to divide the second chamber  246  into an outer region and an inner region. The inner region can be open to the fluid channels  174 , i.e., in direct fluid communication with the fluid channels  174 . In other words, fluid flowing from the fluid channels  174  to the outer region must pass through the inner region. A radially inward surface of the second shroud  136  can be in close proximity to the distal ends of the second pins  234  such that fluid flowing through the inner region from the fluid channels  174  is guided across the second pins  234  and maintains a high velocity while passing between the second pins  234 . 
     During assembly of the motor  110 , the first end cap  130  can be fixedly mounted to the first axial end  154  of the stator  118  and the second end cap  134  can be fixedly mounted to the second axial end  158  of the stator  118 . The slots  178 , the first winding cavity  206 , and the second winding cavity  238  can then be filled with a thermally conductive, but electrically insulating resin. For example, the resin may be pumped into the first winding cavity  206  via the first ports  210  until the resin fills the first winding cavity  206 , the slots  178 , and the second winding cavity  238 . The resin may then be allowed to harden such that the hardened resin encapsulates the first winding loops  182  and the second winding loops  186 , and also contacts the first end cap  130  and the second end cap  134 . 
     Alternatively, the motor  110  may be positioned such that the axis  146  extends in a vertical direction relative to the ground and the first axial end  154  is facing upwards. In this vertical position of the motor  110 , the second ports  242  can be sealed and resin may be poured in from the top through the first ports  210  until the resin fills the second winding cavity  238 , the slots  178 , and the first winding cavity  206 . Alternatively, the second ports  242  can be open such that the resin can be pumped in from the bottom through the second ports  242  until the resin fills the second winding cavity  238 , the slots  178 , and the first winding cavity  206 . 
     The cooling system  138  can include a pump  254  and a heat exchanger  258 . The pump  254  can have an outlet coupled to the inlet port  218  for fluid communication therewith such that the pump  254  can pump fluid (e.g., dielectric cooling fluid) to the inlet port  218 . The pump  254  can have an inlet coupled to an outlet of the heat exchanger  258  for fluid communication therewith to receive fluid from the heat exchanger  258 . The heat exchanger  258  can be any suitable type of heat exchanger configured to release heat  262  to a heat sink (e.g., the atmosphere). The inlet of the heat exchanger  258  can be coupled to the outlet port  250  of the housing  114  to receive fluid therefrom. In an alternative configuration, not specifically shown, the heat exchanger  258  can be in-line between the pump  254  and the inlet port  218  (e.g., the inlet of the heat exchanger  258  can be coupled to the outlet of the pump  254 , the outlet of the heat exchanger  258  can be coupled to the inlet port  218 , and the inlet of the pump  254  can be coupled to the outlet port  250 ). 
     Thus, in operation, the pump  254  can pump cooling fluid through the cooling circuit, such that the fluid flows from the inlet port  218 , axially across the first end cap  130  and between the first pins  202  to absorb heat from the first winding loops  182  via the first pins  202 . The fluid can then flow into and through the fluid channels  174  to absorb more heat from the stator  118 . The fluid can then flow from the fluid channels  174  axially across the second end cap  134  and between the second pins  234  to absorb heat from the second winding loops  186  via the second pins  234 . The fluid can then flow through the outlet port  250  to the heat exchanger, where the heat  262  can be transferred from the fluid to a heat sink (e.g., the atmosphere). 
     With additional reference to  FIGS.  4 - 5   , an electric motor  110 ′ of a second construction is illustrated. The electric motor  110 ′ can be similar to the electric motor  110  of  FIGS.  1 - 3    except as otherwise shown or described herein. Elements shown or described herein with primed reference numerals can be similar to those shown and described above with reference to similar non-primed reference numerals except as otherwise shown or described herein. Accordingly, only differences will be described in detail herein. The electric motor  110 ′ can include a housing  114 ′, a stator  118 ′, a rotor  122 ′, an output shaft  126 ′, a first end cap  130 ′, a second end cap  134 ′ and a cooling system  138 ′. In the example provided, the housing  114 ′ can define a generally cylindrical cavity  142 ′ disposed about an axis  146 ′. The stator  118 ′ can be disposed about the axis  146 ′ within the cylindrical cavity  142 ′ and can be fixedly coupled to the housing  114 ′ such that the stator  118 ′ is non-rotatable relative to the housing  114 ′. In the example provided, an outermost cylindrical surface of the stator  118 ′ can include one or more grooves  150 ′ that can extend axially along the stator  118 ′ and can mate with a spline (not specifically shown) on an interior surface of the housing  114 ′, though other configurations can be used. The stator  118 ′ can be formed of a plurality of stator laminations stacked axially end to end along the axis  146 ′, though other configurations can be used. 
     The stator  118 ′ can be generally annular in shape, with a first axial end  154 ′ and a second axial end  158 ′ opposite the first axial end  154 ′. The stator  118 ′ can include an annular body  162 ′, a plurality of winding poles  166 ′, and a plurality of wire windings  170 ′. The annular body  162 ′ can define a plurality of fluid channels  174 ′ that can be open at the first axial end  154 ′ and the second axial end  158 ′ and can extend axially therebetween to permit fluid communication between the first axial end  154 ′ and the second axial end  158 ′. The fluid channels  174 ′ can be disposed about the axis  146 ′. In the example provided, the fluid channels  174 ′ are equally spaced apart in the circumferential direction about the axis  146 ′. 
     The winding poles  166 ′ can extend radially inward from the radially inward side of the annular body  162 ′. The winding poles  166 ′ can be equally spaced apart in the circumferential direction about the axis  146 ′ to define winding slots  178 ′ between adjacent ones of the winding poles  166 ′. Thus, the winding poles  166 ′ and winding slots  178 ′ can be radially inward of the fluid channels  174 ′. Electrically conductive wire can extend through the winding slots  178 ′ and be wound about the winding poles  166 ′ to form the wire windings  170 ′ in a manner such that a first section of the wire windings  170 ′ forms first winding loops  182 ′ that are axially outward from the first axial end  154 ′ of the stator  118 ′ and a second section of the wire windings  170 ′ forms second winding loops  186 ′ that are axially outward from the second axial end  158 ′ of the stator  118 ′. 
     The first winding loops  182 ′ can have a bend such that the first winding loops  182 ′ have a first portion that is proximate to the stator  118 ′ and extends axially outward therefrom, and a second portion that extends radially outward from the first portion. The second portion of the first winding loops  182 ′ can extend radially outward of a radially inward-most part of the fluid channels  174 ′. In the example provided, the second portion of the first winding loops  182 ′ extends radially outward of a radially outward-most part of the fluid channels  174 ′. 
     The second winding loops  186 ′ can have a bend such that the second winding loops  186 ′ have a first portion that is proximate to the stator  118 ′ and extends axially outward therefrom, and a second portion that extends radially outward from the first portion. The second portion of the second winding loops  186 ′ can extend radially outward of a radially inward-most part of the fluid channels  174 ′. In the example provided, the second portion of the second winding loops  186 ′ extends radially outward of a radially outward-most part of the fluid channels  174 ′. 
     The rotor  122 ′ can be disposed about the axis  146 ′ and can be supported for rotation relative to the stator  118 ′. The stator  118 ′ can be disposed about the rotor  122 ′ such that the rotor  122 ′ is radially inward of the winding poles  166 ′. The output shaft  126 ′ can be disposed about the axis  146 ′ and fixedly coupled to the rotor  122 ′ for common rotation about the axis  146 ′. In the example provided, the output shaft  126 ′ can extend axially from both axial ends of the rotor  122 ′. While not specifically shown, the output shaft  126 ′ can be coupled to a driveline of a vehicle for providing torque to a set of vehicle wheels. 
     The first end cap  130 ′ can be a generally annular body and can include a first inner wall  410 , a pair of first outer walls  414 ,  418 , a pair of first end walls  422 ,  426 , and a plurality of first fins or pins  430 . In the example provided, the first end cap  130 ′ is constructed of a unitarily formed first body  434  and a separate, unitarily formed second body  438  that is fixedly coupled to the first body  434  such as by plastic welding for example. The first and second bodies  434 ,  438  of the first end cap  130 ′ can be formed by any suitable means, such as by injection molding of a plastic for example. The first end cap  130 ′ can be formed from a thermally conductive, but electrically insulating material. 
     A proximal end of the first inner wall  410  can abut the first axial end  154 ′ of the stator  118 ′. The first inner wall  410  can extend generally axially from the first axial end  154 ′ of the stator  118 ′ to a distal end of the first inner wall  410 . The first inner wall  410  can be coaxial with the axis  146 ′, radially inward of the first winding loops  182 ′ and radially outward of the rotor  122 ′. A proximal end of the first outer wall  414  can abut the first axial end  154 ′ of the stator  118 ′. The first outer wall  414  can extend generally axially from the first axial end  154 ′ of the stator  118 ′ to a distal end of the first outer wall  414 . The first outer wall  414  can be coaxial with the axis  146 ′, radially outward of the first winding loops  182 ′ and the slots  178 ′, and radially inward of the fluid channels  174 ′. The distal end of the first outer wall  414  can be axially between the stator  118 ′ and the distal end of the first inner wall  410 . 
     The first end wall  422  can be annular in shape and can extend radially outward from the distal end of the first outer wall  414 . In the example provided, the first end wall  422  can extend radially outward of the radially outward-most part of the fluid channels  174 ′ and can extend radially outward of the radially outward-most cylindrical surface of the stator  118 ′. The first end wall  426  can be annular in shape and can extend radially outward from the first inner wall  410 . In the example provided, the first end wall  426  is axially between the first end wall  422  and the distal end of the first inner wall  410  such that the first inner wall  410  extends axially outward of the first end wall  426 . In the example provided, the first end wall  426  has an inner diameter that is greater than that of the first inner wall  410  and is fixedly coupled to the first inner wall  410  by a plurality of spokes  442  spaced circumferentially about the axis  146 ′ and extending between the first inner wall  410  and the first end wall  426 . The first end wall  426  can extend radially outward of the radially outward-most part of the fluid channels  174 ′ and can extend radially outward of the radially outward-most cylindrical surface of the stator  118 ′. The first outer wall  418  can extend axially between the radially outward-most parts of the first end walls  422 ,  426 . Accordingly, the first end walls  422 ,  426 , the first inner wall  410 , and the first outer walls  414 ,  418  can cooperate to define a first winding cavity  446  that is disposed annularly about the axis  146 ′ and open toward the stator  118 ′ and configured to receive the first winding loops  182 ′ therein. As such, the first winding cavity  446  can be open to the slots  178 ′ of the stator  118 ′. 
     A proximal end of each first pin  430  can be fixedly coupled to the first end wall  422  or the first end wall  426 . Each first pin  430  coupled to the first end wall  422  can extend axially inward (i.e., toward the stator  118 ′) from the first end wall  422  to a distal end. Each first pin  430  coupled to the first end wall  426  can extend axially outward (i.e., away from the stator  118 ′) from the first end wall  426  to a distal end. In the example provided, the first pins  430  can be spaced apart to permit fluid to flow between the first pins  430 . Thus, the first end cap  130 ′ can have pins extending axially toward and away from the stator  118 ′. In the example provided, the first pins  430  are generally cylindrical or conical in shape, but other configurations can be used, such as fins, ribs, blades, tabs, or pyramid-shapes for example. 
     The first axial end  154 ′ of the stator  118 ′, the inner surface of the housing  114 ′, the first outer walls  414 ,  418 , and the first end walls  422 ,  426  can cooperate to define a first chamber or fluid cavity  214 ′ in fluid communication with the fluid channels  174 ′. In the example provided, the first chamber  214 ′ is also defined by the portion of the first inner wall  410  that is axially outward of the first end wall  426 , though other configurations can be used. Thus, the first pins  430  can extend within the first chamber  214 ′. In the example provided, the housing  114 ′ defines an inlet port  218 ′ in fluid communication with the first chamber  214 ′. 
     The second end cap  134 ′ can be similar to the first end cap  130 ′ except as otherwise shown or described herein. The second end cap  134 ′ can be a generally annular body and can include a second inner wall  450 , a pair of second outer walls  454 ,  458 , a pair of second end walls  462 ,  466 , and a plurality of second fins or pins  470 . In the example provided, the second end cap  134 ′ is constructed of a unitarily formed third body  474  and a separate, unitarily formed fourth body  478  that is fixedly coupled to the third body  474  such as by plastic welding for example. The third and fourth bodies  474 ,  478  of the second end cap  134 ′ can be formed by any suitable means, such as by injection molding of a plastic for example. The second end cap  134 ′ can be formed from a thermally conductive, but electrically insulating material. 
     A proximal end of the second inner wall  450  can abut the second axial end  158 ′ of the stator  118 ′. The second inner wall  450  can extend generally axially from the second axial end  158 ′ of the stator  118 ′ to a distal end of the second inner wall  450 . The second inner wall  450  can be coaxial with the axis  146 ′, radially inward of the second winding loops  186 ′ and radially outward of the rotor  122 ′. A proximal end of the second outer wall  454  can abut the second axial end  158 ′ of the stator  118 ′. The second outer wall  454  can extend generally axially from the second axial end  158 ′ of the stator  118 ′ to a distal end of the second outer wall  454 . The second outer walls  454  can be coaxial with the axis  146 ′, radially outward of the second winding loops  186 ′ and the slots  178 ′, and radially inward of the fluid channels  174 ′. The distal end of the second outer wall  454  can be axially between the stator  118 ′ and the distal end of the second inner wall  450 . 
     The second end wall  462  can be annular in shape and can extend radially outward from the distal end of the second outer wall  454 . In the example provided, the second end wall  462  can extend radially outward of the radially outward-most part of the fluid channels  174 ′ and can extend radially outward of the radially outward-most cylindrical surface of the stator  118 ′. The second end wall  466  can be annular in shape and can extend radially outward from the second inner wall  450 . In the example provided, the second end wall  466  is axially between the second end wall  462  and the distal end of the second inner wall  450  such that the second inner wall  450  extends axially outward of the second end wall  466 . In the example provided, the second end wall  466  has an inner diameter that is greater than that of the second inner wall  450  and is fixedly coupled to the second inner wall  450  by a plurality of spokes  482  spaced circumferentially about the axis  146 ′ and extending between the second inner wall  450  and the second end wall  466 . The second end wall  466  can extend radially outward of the radially outward-most part of the fluid channels  174 ′ and can extend radially outward of the radially outward-most cylindrical surface of the stator  118 ′. The second outer wall  458  can extend axially between the radially outward-most parts of the second end walls  462 ,  466 . Accordingly, the second end walls  462 ,  466 , the second inner wall  450 , and the second outer walls  454 ,  458  can cooperate to define a second winding cavity  486  that is disposed annularly about the axis  146 ′ and open toward the stator  118 ′ and configured to receive the second winding loops  186 ′ therein. As such, the second winding cavity  486  can be open to the slots  178 ′ of the stator  118 ′. 
     A proximal end of each second pin  470  can be fixedly coupled to the second end wall  462  or the second end wall  466 . Each second pin  470  coupled to the second end wall  462  can extend axially inward (i.e., toward the stator  118 ′) from the second end wall  462  to a distal end. Each second pin  470  coupled to the second end wall  466  can extend axially outward (i.e., away from the stator  118 ′) from the second end wall  466  to a distal end. In the example provided, the second pins  470  can be spaced apart to permit fluid to flow between the second pins  470 . Thus, the second end cap  134 ′ can have pins extending axially toward and away from the stator  118 ′. In the example provided, the second pins  470  are generally cylindrical or conical in shape, but other configurations can be used, such as fins, ribs, blades, tabs, or pyramid-shapes for example. 
     While not specifically shown, the first pins  430 , and/or the second pins  470  can be constructed to promote uniform rotational flow of the fluid around the first and/or second end cap  130 ′,  134 ′, such as being fin, rib, or blade shaped and disposed at prescribed angles similar to those shown in  FIG.  6   . 
     Returning to the example provided in  FIGS.  4  and  5   , the second axial end  158 ′ of the stator  118 ′, the inner surface of the housing  114 ′, the second outer walls  454 ,  458 , and the second end walls  462 ,  466  can cooperate to define a second chamber or fluid cavity  246 ′ in fluid communication with the fluid channels  174 ′. In the example provided, the second chamber  246 ′ is also defined by the portion of the second inner wall  450  that is axially outward of the second end wall  466 , though other configurations can be used. Thus, the second pins  470  can extend within the second chamber  246 ′. In the example provided, the housing  114 ′ defines an outlet port  250 ′ in fluid communication with the second chamber  246 ′. 
     During assembly of the motor  110 ′, the first end cap  130 ′ can be fixedly mounted to the first axial end  154 ′ of the stator  118 ′ and the second end cap  134 ′ can be fixedly mounted to the second axial end  158 ′ of the stator  118 ′. The slots  178 ′, the first winding cavity  446 , and the second winding cavity  486  can then be filled with a thermally conductive, but electrically insulating resin. For example, the resin may be pumped into the first winding cavity  446  via the gaps between the spokes  442  until the resin fills the first winding cavity  446 , the slots  178 ′, and the second winding cavity  486 . The resin may then be allowed to harden such that the hardened resin encapsulates the first winding loops  182 ′ and the second winding loops  186 ′, and also contacts the first end cap  130 ′ and the second end cap  134 ′. 
     Alternatively, the motor  110 ′ may be positioned such that the axis  146 ′ extends in a vertical direction relative to the ground and the first axial end  154 ′ is facing upwards. In this vertical position of the motor  110 ′, the gaps between the spokes  482  can be sealed and resin may be poured in from the top through the gaps between the spokes  442  until the resin fills the second winding cavity  486 , the slots  178 ′, and the first winding cavity  446 . Alternatively, the gaps between the spokes  482  can be open such that the resin can be pumped in from the bottom through the gaps between the spokes  482  until the resin fills the second winding cavity  486 , the slots  178 ′, and the first winding cavity  446 . 
     The cooling system  138 ′ can include a pump  254 ′ and a heat exchanger  258 ′. The pump  254 ′ can have an outlet coupled to the inlet port  218 ′ for fluid communication therewith such that the pump  254 ′ can pump fluid (e.g., dielectric cooling fluid) to the inlet port  218 ′. The pump  254 ′ can have an inlet coupled to an outlet of the heat exchanger  258 ′ for fluid communication therewith to receive fluid from the heat exchanger  258 ′. The heat exchanger  258 ′ can be any suitable type of heat exchanger configured to release heat  262 ′ to a heat sink (e.g., the atmosphere). The inlet of the heat exchanger  258 ′ can be coupled to the outlet port  250 ′ of the housing  114 ′ to receive fluid therefrom. In an alternative configuration, not specifically shown, the heat exchanger  258 ′ can be in-line between the pump  254 ′ and the inlet port  218 ′ (e.g., the inlet of the heat exchanger  258 ′ can be coupled to the outlet of the pump  254 ′, the outlet of the heat exchanger  258 ′ can be coupled to the inlet port  218 ′, and the inlet of the pump  254 ′ can be coupled to the outlet port  250 ′). 
     Thus, in operation, the pump  254 ′ can pump cooling fluid through the cooling circuit, such that the fluid flows from the inlet port  218 ′, radially outward across the first end wall  426  and between the first pins  430  thereon to absorb heat from the first winding loops  182  via the first pins  430 . The fluid can then flow axially around the first outer wall  418  and radially inward across the first end wall  422  and between the first pins  430  thereon to absorb more heat before entering the fluid channels  174 ′. The fluid can then flow through the fluid channels  174 ′ to absorb more heat from the stator  118 ′. The fluid can then flow from the fluid channels  174 ′ radially outward across the second end wall  462  and between the second pins  470  thereon to absorb more heat. The fluid can then flow axially around the second outer wall  458  and radially inward across the second end wall  466  and between the second pins  470  thereon to absorb more heat. The fluid can then flow through the outlet port  250 ′ to the heat exchanger  258 ′, where the heat  262 ′ can be transferred from the fluid to a heat sink (e.g., the atmosphere). 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.