Patent Publication Number: US-2023158885-A1

Title: Lubricant supported electric motor assembly for compact, power dense wheel-end applications

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The subject application is a continuation of U.S. patent application Ser. No. 17/575,677 filed on Jan. 14, 2022, which claims priority to U.S. Provisional Patent Application Ser. No. 63/137,200 filed on Jan. 14, 2021, the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to electric devices, such as electric motors. More specifically, the present disclosure relates generally to a lubricant supported electric motor assembly for use in a wheel-end electric drive vehicular powertrain application. 
     BACKGROUND OF THE INVENTION 
     This section provides a general summary of background information and the comments and examples provided in this section are not necessarily prior art to the present disclosure. 
     Various drivelines in automotive, truck, and certain off-highway applications take power from a central prime mover and distribute the power to the wheels using mechanical devices such as transmissions, transaxles, propeller shafts, and live axles. These configurations work well when the prime mover can be bulky or heavy, such as, for example, various internal combustion engines (“ICE”). However, more attention is being directed towards alternative arrangements of prime movers that provide improved environmental performance, eliminate mechanical driveline components, and result in a lighter-weight vehicle with more space for passengers and payload. 
     “On wheel”, “in-wheel” or “near-wheel” motor configurations (i.e, wheel-end electric motors) are one alternative arrangement for the traditional ICE prime mover that distribute the prime mover function to each or some of the plurality of wheels via one or more electric motors disposed on, within, or proximate to the plurality of wheels. For wheel end drives packaged in a harsh wheel-end environment, robustness to shock and vibration are important. However, to meet these harsh conditions, the wheel-end electric motors often incorporate large, heavy components, and thus become heavy and bulky, resulting in electric motors that require more space than desired. In other words, to meet the requisite shock and vibration requirements, current electric motors often consume valuable space and generally are required to increase the overall mass and weight of the electric motor. Yet, in wheel-end electric drive vehicular powertrain applications, minimal package volume is an important feature and consideration. 
     In addition to smaller package volume, high torque density (per kg and per liter), higher power density, lower current requirements of power-electronics, lower cost, functional safety/fail safe and greater efficiency are additional important considerations for wheel-end electric motors. Prior art designs address some of these other considerations through the reduction of ohmic losses, improved magnetics, very high-speed motor operation, high diameter motors, and/or improvements in minimized cross-section of support structures. Yet, while these prior art wheel end electric drive configurations may be able to meet some of the requirements for wheel-end electric drive vehicular powertrain applications, the current approaches still do not adequately consider the tradeoffs of motor magnetic and electric structures with elements in the powertrain mechanical system. Accordingly, there remains a continuing need for wheel-end electric drive motors which improve performance during operation in high shock and vibration environments, while providing the lighter and smaller footprint sought, as well as addressing all of the other important considerations and needs when the electric drive motor is implemented in a wheel-end electric drive vehicular powertrain application. 
     SUMMARY OF THE INVENTION 
     The subject invention is generally directed to a lubricant supported electric motor assembly for use in a wheel-end electric drive vehicular powertrain application. The lubricant supported electric motor assembly is modular in design, and includes an electric motor module, a shifting and first stage module, and a final drive module sequentially operably interconnected with one another for producing adjustable drive torque that is ultimately conducted to a wheel of a vehicle. 
     The electric motor module includes a stator and a rotor rotatably disposed within the stator to define a gap therebetween. A lubricant is disposed in the gap for supporting the rotor relative to the stator. The rotor extends along an axis between a first rotor end and a second rotor end to present an inner rotor surface that defines an internal rotor cavity. The shifting and first stage module is disposed within the internal rotor cavity and includes a first planetary gear reducer assembly operably connected with the rotor for rotation therewith. The shifting and first stage module includes an output gear that is rotatably aligned on the axis and selectively coupleable to said first planetary gear reducer assembly for selective rotation therewith. The final drive module is disposed adjacent the shifting and first stage module and includes a second planetary gear reducer assembly operably coupled with the output gear for rotation therewith. The shifting and first stage module includes a shifting mechanism configured to establish the selective coupling between the first planetary gear assembly and the output gear to transfer adjustable torque from the shifting and first stage module to the final drive device. 
     The lubricant supported electric motor assembly results in a smaller package size, lighter weight, better torque and power density, and lower cost compared to the prior wheel-end electric drive motors. In addition, the lubricant supported electric motor assembly provides compatibility with existing suspensions, wheels and foundation brakes that allow the fitment of the lubricant supported electric motor assembly in an existing vehicle without extensive re-design work. Other advantages will be appreciated in view of the following more detailed description of the subject invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected aspects and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG.  1    is a perspective cross-sectional view of a lubricant supported electric motor assembly including a electric motor module, a shifting and first stage module and a final drive module operably interconnected to one another for producing adjustable drive torque which is ultimately conducted to a wheel of a vehicle; 
         FIG.  2    is a perspective cross-sectional view of the electric motor module; 
         FIG.  3    is a perspective cross-sectional view of a stator of the electric motor module press-fit into a surrounding motor support housing; 
         FIG.  4    is a cross-sectional perspective view of the stator illustrating a plurality of windings passing through the stator and a plurality of cooling passages disposed circumferentially along an outer portion of the stator; 
         FIG.  5    is a cross-sectional perspective view of the stator illustrating a motor housing cover attached to a first housing end of the motor support housing; 
         FIG.  6    is a cross-sectional perspective view of a rotor of the electric motor module illustrating a rotor plate and magnets secured to the rotor; 
         FIG.  7    is a cross-sectional perspective view of the electric module in an assembled condition; 
         FIG.  8    is a cross-sectional perspective view of the shifting and first stage module; 
         FIG.  9    is a cross-sectional perspective view of a portion of the shifting and first stage module illustrating a plurality of actuators and a shifting mechanism comprised of a low speed slider clutch and a high speed slider clutch concentrically arranged about an output gear; 
         FIG.  10    is a cross-sectional view of a portion of a gear housing of the shifting and first stage module illustrating the plurality of actuators including pistons slidable disposed in actuator channels; 
         FIG.  11    is a cross-sectional view of a portion of the shifting and first stage module illustrated in  FIG.  8    illustrating the plurality of actuators including a biasing member biased against the piston; 
         FIG.  12    is a cross-sectional view of a portion of the shifting and first stage module illustrated in  FIG.  8    illustrating a restrictor plate defining restrictor channels for delivering lubricant to a second lubricant bearing surface/structure extending along an outer gear housing surface; 
         FIG.  13    is a cross-sectional perspective view of a portion of the shifting and first stage module illustrated in  FIG.  8    illustrating an internal gear cavity; 
         FIG.  14    is a perspective cross-sectional end view of a portion of the shifting and first stage module illustrating the plurality of actuators interconnected with respective ones of the low and high speed slider clutches and an output shaft extending axially from the output gear; 
         FIG.  15 A  illustrates a high gear condition for the low and high speed slider clutches; 
         FIG.  15 B  illustrates a low gear condition for the low and high speed slider clutches; 
         FIG.  15 C  illustrates a neutral condition for the low and high speed slider clutches; 
         FIG.  15 D  illustrates a park condition for the low and high speed slider clutches; 
         FIG.  16    is a perspective end view of a distribution plate manifold of the shifting and first stage module; 
         FIG.  17    is a perspective cross-sectional view of a first planetary gear reducer assembly of the shifting and first stage module; 
         FIG.  18    is a perspective cross-sectional view of the shifting and first stage module illustrating the first planetary gear reducer assembly inserted into the internal gear cavity; 
         FIG.  19    is a perspective cross-sectional view of the final drive module illustrating a second planetary gear reducer assembly; 
         FIG.  20    is a perspective cross-sectional view of a planet carrier and wheel bearing of the second planetary gear reducer assembly; 
         FIG.  21    is a perspective cross-sectional view of second planet gears of the second planetary gear reducer assembly; 
         FIG.  22    is a perspective cross-sectional view illustrating a second sun gear, drive shaft and cover of the final drive module; 
         FIG.  23    is a perspective cross-sectional view illustrating the final drive module in an assembled condition; 
         FIG.  24    is a perspective cross-sectional view of the final drive module illustrating a wheel flange operably interconnected to the planet carrier; 
         FIG.  25    is a perspective cross-sectional view of the lubricant supported electric motor assembly illustrating an alternative arrangement of the final drive module; 
         FIG.  26    is a fragmentary cross-sectional view of a knuckle mounting structure; and 
         FIG.  27    is an alternative perspective view of the knuckle mounting structure. 
     
    
    
     DETAILED DESCRIPTION OF THE ENABLING EMBODIMENTS 
     Exemplary aspects of the lubricant supported electric motor assembly in accordance with the present disclosure will now be more fully described. Each of these example embodiments are provided so that this disclosure is thorough and fully conveys the scope of the inventive concepts, features and advantages to those skilled in the art. To this end, numerous specific details are set forth such as examples of specific components, devices and mechanisms associated with the lubricant supported electric motor assembly to provide a thorough understanding of each of the embodiments associated with the present disclosure. However, as will be apparent to those skilled in the art, not all specific details described herein need to be employed, the example embodiments may be embodied in many different forms, and thus should not be construed or interpreted to limit the scope of the disclosure. 
       FIGS.  1 - 25    illustrate a lubricant supported electric motor assembly  10  in accordance with an aspect of the disclosure. As best illustrated in  FIG.  1   , the lubricant supported electric motor assembly  10  is modular in design, and includes an electric motor module  12 , a shifting and first stage module  14 , and a final drive module  16  sequentially operably interconnected with one another for producing adjustable drive torque that is ultimately conducted to a wheel of a vehicle. As will be appreciated in view of the following more detailed disclosure, the modularity of the lubricant supported electric motor assembly  10  results in a design which allows for easy substitution of motor structures (as provided through the electric motor module  12 ), first stage reduction structures (as provided through the shifting and first stage module  14 ), and final reduction structures (as provided through the final drive module  16 ). This modularity advantageously allows the lubricant supported electric motor assembly  10  to accurately match a powertrain requirement by choosing the correct modules from a library of module designs. For example, in a vehicular powertrain application with a restricted speed range requirement, such as a city delivery vehicle, the shifting and first stage module  14  may not require the two-speed shift capability that will be described in more detail below. In this case, a shifting and first stage module  14  without the two-speed shift mechanism can be used, resulting in reduced weight and cost. In another powertrain application with different power and torque requirements, a different motor may be used in the electric motor module  12  to optimally match the powertrain application. Thus, the lubricant supported electric motor assembly  10  provides manufacturing and design flexibility not afforded by the prior art wheel-end electric motor assemblies. 
     As will be also be appreciated in view of the following more detailed description, as well as illustrated in the accompanying Figures, the modularity of the lubricant supported electric motor assembly  10  provides for ease of assembly, repair and replacement. More specifically, the electric motor module  12 , the shifting and first stage module  14  and the final drive module  16  can each be built as sub-assemblies and later integrated into or operably coupled with one another to build the lubricant supported electric motor assembly  10 . The various modules  12 ,  14 ,  16  may even be delivered separately, and assembled as needed, leading to more efficient assembly at an OEM. This modularity also furthers the ability for a flexible construction of a variety of wheel-end drives for different applications from the same manufacturing process. For example, replacement of the electric motor module  12  and the final drive module  16  with alternatively arranged modules instantly leads to a new device with different properties, and thus cheaper customization in terms of NRE and production. This modular structure of the lubricant supported electric motor assembly  10  also provides for easier servicing, repairability, replacement and refurbishment of the individual modules  12 ,  14 ,  16  for vehicles in the field. In other words, compared to traditional wheel-end drives, the modular structure provides better servicing with easier access to components. 
     As best illustrated in  FIGS.  1 - 2   , the electric motor module  12  includes a stator  18  extending concentrically around an axis A, and a rotor  20  extending concentrically along the axis A and movably (i.e, rotatably) disposed within the stator  18  to define a first gap  21  therebetween. The rotor  20  and the stator  18  of the electric motor module  12  produce drive torque in response to rotation of the rotor  18 , which is ultimately conducted to a wheel of a vehicle as will be described in more detail below. A lubricant  22  is disposed in the first gap  21  for presenting a first lubricant bearing surface/structure that supports the rotor  20  within the stator  18 , and provides continuous contact between these components. The lubricant  22  may therefore act as a buffer (e.g., suspension) between the stator  18  and the rotor  20  minimizing or preventing contact therebetween. In other words, the lubricant  22  is pressurized with the first gap  21  to support the rotor  20 , prevents direct contact between the stator  18  and rotor  20  and provides an electric motor module  12  which is robust to shock and vibration loading due to the presence of the lubricant  22 . 
     The electric motor module  12  includes a motor support housing  23  extending along the axis A from a first motor housing end  24  to a second motor housing end  26  and which is disposed in surrounding relationship with the stator  18  and rotor  20  for housing and isolating the motor components from an environment of the lubricant supported electric motor assembly  10 . As best illustrated in  FIG.  3   , in an arrangement, the stator  18  can be press-fit into the motor support housing  22 . However, other means of arranging the motor support housing  23  around the stator  18  and rotor  20  can be utilized without departing from the scope of the subject disclosure. 
     As best illustrated in  FIGS.  3 - 5   , the stator  18  is comprised of a stack of stator laminations which receive copper windings  28  passing therethrough. As further illustrated in  FIGS.  3 - 4   , the stator  18  defines a plurality of cooling passages  29  extending axially through the stator  18  in circumferentially spaced relationship with one another. The plurality of cooling passages  29  are disposed in fluid communication with a lubricant supply, such as the same lubricant supply which communicates to the first gap  21  between the stator  18  and rotor  20 , for conducting lubricant/oil through the stator lamination stack and conducting heat away from, and thus cooling, the stator  18 . As will be described in more detail below, a lubricant/oil distribution manifold with a variable cross section can be utilized to supply an equal flow of lubricant to all of the plurality of cooling passages  29 . A similar circular manifold can also be used to conduct the lubricant away from the stator  18  to a lubricant return system (not expressly shown). These manifolds may be part of the overall motor support structure and may also serve to conduct lubricant to bearings, gears or hydraulic actuators of the lubricant supported electric motor assembly  10 . 
     As best illustrated in  FIG.  6   , the rotor  20  of the electric motor module  12  extends between a first rotor end  30  and a second rotor end  32 , and is preferably cylindrical shaped to present a outer rotor surface  36  and an inner rotor surface  37 , each of which extend in generally parallel and radially spaced relationship to the axis A. As best illustrated in  FIGS.  2  and  6 - 7   , the inner rotor surface  37  of the rotor  20  defines an internal rotor cavity  34 . A series of magnets  38  extend circumferentially around the outer rotor surface  36  and are disposed in adjacent and facing relationship with the stator  18 . The magnets  38  can be glued to the outer rotor surface  36  or otherwise secured to the outer rotor surface  36  using mounting magnet retainers, or the like. As best illustrated in  FIGS.  1 - 2  and  6 - 7   , a rotor plate  40  being generally circular in shape is secured to the first rotor end  30  of the rotor  20  to enclose the internal rotor cavity  34  at the first motor housing end  24 . The rotor plate  40  includes a spindle  42  extending axially away from the internal rotor cavity  34  in aligned relationship about the axis A. The rotor  20  is preferably comprised of a very thin structure, and thus when the rotor plate  40  is secured to the first rotor end  30 , the resulting rotor structure  20  resembles a small paint can in both size and shape. As best illustrated in  FIGS.  1 - 2  and  7   , a motor housing cover  44  is secured to the first housing end  24  of the motor support housing  23  and is disposed adjacent the first rotor end  30  of the rotor  20  as well as the rotor plate  40 . The motor housing cover  44  includes a motor bearing  46  disposed in aligned relationship with the axis A for receiving the spindle  42  of the rotor plate  46  and mechanically rotatably supporting the rotor  20  relative to the motor housing cover  44 . In a preferred arrangement, the motor bearing  46  includes rolling elements or plain wheel bearing support, however other bearings could be utilized without departing from the scope of the subject disclosure. As will be described in more detail immediately below, the spindle  42  of the rotor plate  40  in combination with the motor bearing  46  facilitates an operable connection between the electric motor module  12  and the shifting and first stage module  14 , which are sequentially operably connected to one another. This operable connection may be stiff in torsion and radial displacement or may have defined compliances in torsion and radial displacement, the compliances of which may help control NVH or other vibration problems for the lubricant supported electric motor assembly  10 . 
     In an embodiment, the motor support housing  22  of the electric motor module  12  may also house mounting locations and wiring channels for the motor&#39;s sensors. These include, but are not limited to, motor winding temperature, motor coolant temperature, motor angular position, system vibration level, shift actuator position and hydraulic system pressure(s). 
     As best illustrated in  FIG.  1   , the shifting and first stage module  14  is assembled into and disposed within the internal rotor cavity  34  and includes a first planetary gear reducer assembly  62  operably connected with the rotor  20  for rotation therewith. As best illustrated in  FIGS.  8 - 9   , the shifting and first stage module  14  includes a gear housing  48  extending from a first gear housing end  50  to a second gear housing end  52  to define an internal gear cavity  54  and present a radially outer gear housing surface  56  extending between the first and second gear housing ends  52 ,  54 . As best illustrated in  FIG.  1   , the gear housing  48  is inserted into and placed inside of the internal rotor cavity  34  to dispose the first gear housing end  50  in adjacent relationship with the rotor plate  46  as well as the first rotor end  30  and the second gear housing end  52  in abutting and secured relationship with the second housing end  26  of the motor support housing  22 . The second gear housing end  52  of the shifting and first stage module  14  encloses an open portion of the internal motor cavity  34  of the electric motor module  12  disposed adjacent the second housing end  26  of the motor support housing  22 , to result in a structure comprised of both the electric motor module  12  and the shifting and first stage module  14 . 
     Additionally, as best illustrated in  FIG.  1   , in this nested or combined relationship, the outer gear housing surface  56  extends along an inner rotor surface  37  of the rotor  20  and presents a second lubricant bearing surface/structure for rotatably supporting the rotor  20  relative to the stator  18 . Put another way, the outer gear housing  56  is disposed in slightly spaced relationship with the inner rotor surface  37  of the rotor  20  to define a second gap  58  and the lubricant  22  is also disposed in and pressurized within this second gap  58  to provide auxiliary or additional lubricant support of the rotor  20  relative to the stator  18 . As illustrated in  FIG.  1   , this second gap  58  can taper radially outward from the second gear housing end  52  to the first gear housing end  50  such that during operation this taper pushes the lubricant  22  towards the right portion of the modules  12 ,  14  (i.e., towards the first motor housing end  24  and the first gear housing end  50 ) and into various lubricant cavities defined by the motor support housing  22 . Further, the gear housing  48  defines an annular shoulder  60  extending radially outwardly form the outer gear housing surface  56  adjacent the second gear housing end  52 , and which is disposed in abutting relationship with the second rotor end  32  of the rotor  18  for ensuring correct axial placement of the first planetary gear reducer assembly  62  and the rotor  20  relative to one another and preventing lubricant from escaping the second gap  58  adjacent this rotor  20 /shoulder  60  interface. 
     As best illustrated in  FIGS.  1  and  8   , the first planetary gear reducer assembly  62  is disposed inside of the internal gear cavity  54  adjacent the first gear housing end  50 , and is operably interconnected to the rotor plate  46  for being driven in response to rotation of the rotor plate  46  about the axis A by the rotor  20 , thus establishing the operable connection between the first planetary gear reducer assembly  62  and the rotor  20 . In an arrangement, the first planetary gear reducer assembly  62  is sun driven and includes a first sun gear  64  rotatably aligned along the axis A in abutting and operably interconnected relationship with the rotor plate  46 , preferably in opposing relationship with the spindle  42 . As further illustrated in  FIGS.  8  and  17   , the first planetary gear reducer assembly  62  includes a first planet carrier  65  rotatably supporting a plurality of first planet gears  66  arranged radially outwardly of and operably connected to the first sun gear  64 , and a first ring gear  67  is arranged concentrically around and operably connected to the first planet gears  66  for rotation about the axis A in response to rotation of the first sun gear  64 . Although described as being sun driven, the first planetary gear reducer assembly  62  could also be planet carrier driven without departing from the scope of the subject disclosure. Support for components of the first planetary gear reducer assembly  62  may be provided by self-centering gears, rolling element bearings (as shown) or plain bearings. 
     As further illustrated in  FIGS.  1 ,  8 - 9  and  14   , the shifting and first stage module  14  also includes an output gear  68  rotatably aligned along the axis A and disposed adjacent the first sun gear  64 . Similar to the planetary gear components, support for the output gear  68  may be provided by self-centering gears, rolling element bearings (as shown) or plain bearings. As will be described in more detail immediately below, the shifting and first stage module  14  includes a shifting mechanism  70  for selectively coupling the output gear  68  with the first planetary gear reducer assembly  62  and establishing selective rotation therewith. As will be described in more detail below, the shifting mechanism  70  effectuates the transferring of adjustable torque to the final drive module  16  (which as described previously is operably connected sequentially or downstream from the shifting and first stage module  14 ). As further illustrated in  FIGS.  1 ,  8 - 9  and  14   , the gear housing  48  defines a output shaft channel  72  extending along the axis A from the second gear housing end  52  to the output gear  68 . The gear housing  48  also houses or supports a output shaft bearing  74  disposed radially outside of the output shaft channel  72  next adjacent the output gear  68 . The output shaft channel  72  and the output shaft bearing  74  receive and rotatably support an output shaft  76  (See e.g.,  FIGS.  1  and  14   ) that is operably connected to the output gear  68  and extends along the axis A from the output gear  68  and axially out of or away from the second gear housing end  52  of the gear housing  48  for ultimately establishing the operable connection between the shifting and first stage module  14  to the final drive module  16 . 
     As best illustrated in  FIG.  1   , the final drive module  16  is disposed adjacent the second gear housing end  52  of the shifting and first stage module  14  as well as the second motor housing end  26  of the electric motor module  12 , and includes a second planetary gear reducer assembly  78  operably coupled with the output gear  68 . As will be described in more detail below, the second planetary gear reducer assembly  78  of the final drive module  16  transfers torque received from the shifting and first stage module  14  to a wheel of the vehicle. As best illustrated in  FIGS.  1  and  19   , the second planetary gear reducer assembly  78  includes a second sun gear  80  rotatably aligned along the axis A in operably interconnected relationship with the output shaft  76  for rotatably coupling the second sun gear  80  with the output gear  68  of the shifting and first stage module  14  and establishing the operable connection therewith. As further illustrated in  FIGS.  1  and  19 - 23   , the second planetary gear reducer assembly  78  also includes a plurality of second planet gears  82  arranged radially outwardly of and operably connected to the second sun gear  80 , and a second ring gear  84  is arranged concentrically around and operably connected to the second planet gears  82 . A planet carrier  86  rotatably supports the second planet gears  82  and is rotatable about the axis A in response to rotation of the second sun gear  80 . Support for components of the second planetary gear reducer assembly  78  is provided by a plurality of wheel bearings  88 , but may be provide by other types of bearings without departing from the scope of the subject disclosure. As further illustrated in  FIGS.  1  and  19 - 24   , the planet carrier  86  includes a wheel flange shaft  90  extending along the axis A, and a wheel flange  92  is coupled to the wheel flange shaft  90  for rotation commensurate with rotation of the planet carrier  86 . The wheel flange  92  ultimately is coupled with a wheel hub for transferring torque directly from the final drive module  16  to the vehicle&#39;s wheel. Put another way, the wheel flange shaft  90  and the wheel flange  92  establish a direct coupling of the lubricant supported electric motor assembly  10  to a wheel of a vehicle to place the lubricant supported electric motor assembly  10  in an in-wheel or on-wheel arrangement. 
     As previously mentioned, the shifting and first stage module  14  includes a shifting mechanism  70  for selectively coupling the output gear  68  with the first planetary gear reducer assembly  62  and transferring adjustable torque to the final drive module  16 . In a preferred arrangement, this shifting mechanism  70  includes at least one slider clutch  100 ,  102  which is rotatable with and axially slideable relative to the output gear  68  from a neutral position wherein the at least slider clutch  100 ,  102  is disposed in spaced and non-engaged relationship with the first planetary gear reducer assembly  62  to an engaged position wherein the at least one slider clutch  100 ,  102  is moved axially towards and into selectively coupled relationship with said first planetary gear reducer assembly  62  to establish the selective coupling between said first planetary gear reducer assembly  62  and the output gear  68 . Although the shifting mechanism  70  will be described in relation to a slider clutch, the shifting mechanism  70  could also take a number of different forms, such alternatively wet or dry plate clutches, conical synchronizers, or the like, to achieve the plurality of different functions (such as the high gear condition/function illustrated in  FIG.  15 A , the low gear condition/function illustrated in  FIG.  15 B , the neutral condition/function illustrated in  FIG.  15 C , and the park condition/function illustrated in  FIG.  15 D ) for the lubricant supported electric motor assembly  10 . Each of these functions will be explained below in association with a more detailed description of the slider clutches in the preferred embodiment of the shifting mechanism  70 . 
     As best illustrated in  FIGS.  1  and  8   , the first sun gear  64  of the first planetary gear reducer assembly  62  includes an annular sun gear flange  94  extending radially from the first sun gear  64  and disposed adjacent the output gear  68 . The sun gear flange  94  is rotatable in conjunction with the first sun gear  64 , and supported by a flange bearing  96  presented on the output gear  68  and aligned about the axis A. As further illustrated in  FIGS.  1  and  8   , the first ring gear  67  includes a concentric ring gear flange  98  extending axially from the first ring gear  67  towards the second gear housing end  52  in concentric and radially spaced relationship with the axis A. Similar to the sun gear flange  94 , the ring gear flange  98  is also rotatable about the axis A in conjunction with the first ring gear  67 . 
     The shifting mechanism  70  preferably includes a plurality of slider clutches  100 ,  102  for establishing the multiple functions (i.e., high gear, low gear, park and neutral) of the lubricant supported electric motor assembly  10 . In this preferred arrangement, and as best illustrated in  FIGS.  1 ,  8 - 9  and  14   , the plurality of slider clutches  100 ,  102  of the shifting mechanism  70  includes a high speed slider clutch  100  and a low speed slider clutch  102  concentrically and slideably arranged relative to one another, and collectively secured to the output gear  68  for rotation therewith. More specifically, the high speed slider clutch  100  is concentrically and slideably received along an outer sliding gear surface  101  of the output gear  68  for axially sliding from the neutral position (as shown in  FIG.  15 C , and in which no rotational torque is transferred from the first planetary gear reducer assembly  62  to the output gear  68 ) to the respective engaged position (as shown in  FIG.  15 A ). The low speed slider clutch  102  is also concentrically and slideably received along an outer sliding clutch surface  103  of the high speed slider clutch  100  for axially sliding from the neutral position (as shown in  FIG.  15 C ) to the respective engaged position (as shown in  FIG.  15 B ). To accomplish this arrangement, each of the low and high speed slider clutches  100 ,  102  are cylindrical or sleeve shaped, with the low speed slider clutch  102  having a larger diameter than a smaller diameter of the high speed slider clutch  100 . As will be described in more detail below, each of the high and low speed slider clutches  100 ,  102  are individually actuatable to establish selective coupling between the output gear  68  and the first planetary gear assembly  62  and transfer adjustable torque from the shifting and first stage module  14  to the final drive module  16 . For example, (1) in one instance the low and high speed slider clutches  100 ,  102  slide in unison relative to the output gear  68  towards the first gear housing end  50  (See  FIG.  15 D ), (2) in another instance only the high speed slider clutch  100  slides along the outer sliding gear surface  101  of the output gear  68  towards the first gear housing end  50 , while the low speed slider clutch  102  remains in a non-actuated position (See  FIG.  15 A ) or (3) in yet another instance only the low speed slider clutch  102  slides along the outer sliding clutch surface  103  of the high speed slider clutch  100 , while the high speed slider clutch  100  remains in a non-actuated position (See  FIG.  15 B ). After actuation, the high and low speed slider clutches  100 ,  102  retract towards the second gear housing end  52 , sliding along their respective sliding surfaces  101 ,  103  to return to the neutral, non-actuated position (as shown in  FIG.  15 C ). 
     More specifically,  FIGS.  1 ,  8  and  15 C  illustrate an arrangement in which both the high and low speed slider clutches  100 ,  102  are disposed in their neutral, non-actuated positions, and thus each are disposed in spaced and non-engaging relationship with the sun gear flange  94  and the ring gear flange  98 . In this neutral, non-actuated position for both of the low and high speed slider clutches  100 ,  102 , an operable connection is not present between the first planetary gear reducer assembly  62  and the output gear  68 , and thus no torque is transferred between these components. As such, the high and low speed slider clutches  100 ,  102  achieve the neutral function for the lubricant supported electric motor assembly  10  in this position, namely because there is no connection between the first planetary gear reducer assembly  62  and the second planetary gear reducer assembly  78 . 
     As best illustrated in  FIG.  15 A , when only the high speed slider clutch  100  is actuated and slides along the outer sliding gear surface  101  of the output gear  68  from the neutral position (shown in  FIG.  15 C ) to its respective engaged position (shown in  FIG.  15 A ), the high speed slider clutch  100  moves into overlaying and operably interconnected relationship with the sun gear flange  94 , such that rotation of the first sun gear  64  drives corresponding rotation of the high speed slider clutch  100  as well as the output gear  68  to which the high speed slider clutch  100  is operably connected. In this arrangement, the high speed slider clutch  100  establishes a high gear for the lubricant supported electric motor assembly  10 , namely because the second stage gear reducer assembly  78  is operably connected to the first sun gear  64 . 
     As best illustrated in  FIG.  15 B , when the high speed slider clutch  100  is retracted to the neutral position, and only the low speed slider clutch  102  is actuated to axially slide from the neutral position (shown in  FIG.  15 C ) to its respective engaged position (as in  FIG.  15 B ), the low speed slider clutch  102  moves into abutting and operably interconnected relationship with the ring gear flange  98 . As a result, rotation of the first ring gear  67  drives corresponding rotation of the low speed slider clutch  102  as well as the output gear  68  to which the low speed slider clutch  102  is operably connected via the high speed slider clutch  100  (i.e., because the output gear  68 , the high speed slider clutch  100 , and the low speed slider clutch  102  are concentrically arranged on another to simultaneously rotate in unison about the axis A). In this arrangement, the low speed slider clutch  102  establishes a low gear for the lubricant supported electric motor, namely because the secondary gear reducer assembly  78  is operably connected to the first stage ring gear  98 . 
     As best illustrated in  FIG.  15 D , when both the low and high speed slider clutches  100 ,  102  are actuated and moved into respective engaged conditions and respectively into operable connection with the ring gear flange  98  and the sun gear flange  94 , this establishes an operable connection of the second planetary gear reducer assembly  78  to both the first stage ring gear  98  as well as the first stage sun gear  64 , which locks the output gear  68  due to the action of the first stage planet gears  66 . In other words, actuating both the low and high speed slider clutches  100 ,  102  creates a locked condition for the lubricant supported electric motor assembly  10 , because the first stage ring and sun gears  64 ,  68  are locked up, to establish the park gear function. 
     As best illustrated in  FIGS.  1  and  8 - 15   , the shifting and first stage module  14  includes a plurality of actuators  104 ,  106  arranged about the second gear housing end  52  of the gear housing  48  in circumferentially spaced relationship to one another for each actuating the low and high speed slider clutches  100 ,  102  in accordance with the operational principles described above. In a preferred arrangement, the plurality of actuators  104 ,  106  include at least one low speed actuator  104  operably connected to the low speed slider clutch  100  and at least one high speed actuator  106  operably connected to the high speed slider clutch  102 . In a more preferred arrangement, the at least one low speed actuator  104  includes a pair of low speed actuators  104  disposed in diametrically opposed relationship to one another and each operably connected to the low speed slider clutch  100 , and the at least one high speed actuator  106  includes a pair of high speed actuators  106  disposed in diametrically opposed relationship to one another and each operably connected to the high speed slider clutch  102 . Arrangement of the pairs of low and high speed actuators  104 ,  106  in diametrically opposed relationship balances actuation of the respective slider clutch  100 ,  102  to achieve a balanced or even sliding movement—i.e., an actuation force is also applied to diametrically opposite portions of the respective slider clutch  100 ,  102  as opposed to an actuation force only applied in one location, resulting in more balanced movement of the clutches  100 ,  102 . 
     As best illustrated in  FIG.  10   , the second gear housing end  52  of the gear housing  48  defines a plurality of actuator channels  108  for receiving the at least one low and high speed actuator  104 ,  106 . As further illustrated in  FIGS.  1  and  8 - 14   , each of the at least one low and high speed actuators  104 ,  106  are comprised of a piston  110  which is slideably received in the actuator channel  108 , and a biasing member  112 , such as a Belleville spring, or the like, for biasing the piston  110  towards the second gear housing end  52  and into their neutral positions. The second gear housing end  52  defines a plurality of fluid passageways  114  each disposed in fluid communication with a respective one of the actuator channels  108  for selectively delivering hydraulic fluid or lubricant, and the associated pressure, to the actuator channels  108  to overcome the bias of the biasing member  112  and drive the pistons  110  towards the first gear housing end  52  and the clutches  100 ,  102  into their respective engaged positions. Movement of the piston  110  associated with the at least one low speed actuator  100  results in actuation of the respective low speed slider clutch  100  and movement of the piston  110  associated with the at least one high speed actuator  102  results in actuation of the high speed slider clutch  102 . When the pressure associated with the hydraulic fluid or lubricant is released from the actuator channels  108 , the biasing member  112  moves the pistons  110  back towards the first gear housing end  50 , which correspondingly pulls the respective low or high speed slider clutch  100 ,  102  back to its neutral position. As best illustrated in  FIG.  16   , the second gear housing end  52  includes an lubricant/oil distribution plate manifold  116  which defines a plurality of fluid channels  118  each disposed in fluid communication with a respective one of the fluid channels  118  for selectively delivering hydraulic fluid or lubricant  22  to the actuator channels  108  associated with the at least one low speed actuator  104  and/or the at least one high speed actuator  106 . 
     As previously discussed, the outer gear housing surface  56  of the gear housing  48  presents a second lubricant bearing surface/structure for rotatably supporting the rotor  20  relative to the stator  18 . As further illustrated in  FIG.  16   , a portion of the outer gear housing surface  56  defines a plurality of lubricant supply holes  120  disposed in circumferentially spaced relationship to one another and in fluid communication with the second gap  58  for delivering lubricant to the second gap  58  to provide auxiliary or additional lubricant support of the rotor  20  relative to the stator  18 . As best illustrated in  FIG.  12   , a restrictor plate  122  is disposed inside the gear housing  48  adjacent the second gear housing end  52 . The restrictor plate  122  defines a plurality of restrictor channels  124 , preferably rectangular or slotted in shape, for channeling and establishing restriction of the lubricant to the lubricant supply holes  120  and thus to the second gap  58  disposed along the second lubricant bearing/surface structure. As further illustrated in  FIG.  16   , the lubricant distribution plate manifold  116  also defines a lubricant supply channel  126  disposed in fluid communication with the restrictor channels  124  of the restrictor plate  122  for controlling the supply of lubricant thereto. 
     As illustrated in  FIGS.  1  and  26 - 27   , the lubricant supported electric motor assembly  10  includes a knuckle mounting structure  128  which performs a number of functions including (a) holding and supporting the electric motor module  12  and the shifting and first stage module  14 , (b) connecting the lubricant supported electric motor assembly  10  to a beam axle, (c) holding the final drive module  16  and the related wheel bearings  88  (See, e.g.,  FIG.  1   ), (d) holding a brake and parking brake, and (e) allowing oil supply connections, electric connections and parking brake cable connections. For example, as best illustrated in  FIGS.  26  and  27   , the knuckle mounting structure  128  defines a plurality of pick-up points  130  for a brake caliper, and a plurality of through-holes  132  for allowing the knuckle mounting structure to be bolted to the axle. The lubricant supported electric motor assembly  10  also deeply integrates the wheel end functions and the powertrain functions via this “multifunctional knuckle” structure  128 . 
     The lubricant supported electric motor assembly  10  described above provides a unique approach to achieving minimum weight and minimum package for use in a wheel-end drive application using a surface mounted permanent magnet motor with a distributed wave winding in conjunction with a two-speed drive system that produces high output (approximately 100 HP and 2000 ft lbs of torque), albeit with a motor support housing approximately the size of a gallon of milk. In other words, a very compact electric motor structure (SMPM with distributed wave winding, or another design with similar packaging properties) is combined with a 2-speed compact gearing to provide a wheel-end electric drive motor with smaller package size and light weight, but better torque and power density. As appreciated in view of the above disclosure, part of the drive system housed by the shifting and first stage module  14  is housed inside the electric motor module  12  in an internal rotor cavity  34  defined by the rotor  20 . Integration is made possible by the plain bearings or other forms of a very compact and low drag high diameter bearings. Note that in the lubricant supported electric motor assembly  10  described above, the torque-transmitting structures and the vehicle weight-bearing structures are combined to share capabilities. This results in shorter force paths for loads and torques, which minimizes weight and package space requirements. 
     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 regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.