Abstract:
A method and associated apparatus for controlling fluid levels within an axle tube, the method comprising: (a) establishing a first predetermined level of a liquid lubricant within a transmission and an electric motor operatively coupled to the electric motor, the axle tube housing the electric motor and the transmission, where a cavity interposing a wall of the axle tube and the electric motor is occupied by the liquid lubricant reservoir at a second predetermined level; and, (b) lowering the first predetermined level of a liquid lubricant within the electric motor and the transmission by changing a gas pressure exerted upon the liquid lubricant, where changing the gas pressure exerted upon the liquid lubricant within the axle tube raises the second predetermined level of liquid lubricant within the cavity.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to managing an oil level in an axle or axle tube. 
       BACKGROUND OF THE INVENTION 
       [0002]    Oil is used as a lubricant and coolant for the components in an axle or axle tube. This coolant prevents over-heating and operates to increase the life of the components within the axle. More oil provides a larger volume to remove heat, however, it is desirable to maintain a low level of oil in rotating axle components to reduce windage loss. 
         [0003]    A separate sump volume for holding a larger volume of oil adds cost to the vehicle and potentially requires additional pumps to move the oil to this alternate location. The additional sump would also use space on the vehicle either making service more difficult to other components, or increasing the overall size of the vehicle. 
       SUMMARY 
       [0004]    The exemplary embodiments of the present disclosure include axle tubes and components for managing the level of lubricant within the axle tube. 
         [0005]    In exemplar form, there are four components that are lubricant cooled within a single axle tube. These components are two final drives (located at each end of the axle tube and referred to in the detailed description as the transmission subsections) and two motors (referred to in the detailed description as the motor subsections), located inside each end of the axle tube, and connected to the final drives. 
         [0006]    There are multiple desired lubricant levels within the axle tube. The ideal lubricant level inside the final drives is a few inches below centerline. The motors, however, will operate best if all lubricant fed into the motor is evacuated so that the motor does not contain any standing lubricant. 
         [0007]    Balancing the lowest level of lubricant that may be used in the final drives with the intent to reduce the lubricant level within the motors, the instant disclosure provides an alternate area as a sump or reservoir to maintain the volume of lubricant required for adequate lubricant circulation. In exemplary form, the annulus of empty space between the motor housing and the axle tube is used as the sump volume. This uses existing features and empty space on the axle tube, thereby eliminating addition of a separate sump. 
         [0008]    In exemplary form, a single drain hole is placed at the bottom of the motor. Additional drain holes are placed to allow lubricant to flow from the final drive into the axle tube, directly into the annulus surrounding the motor. In this exemplary configuration, these holes are through the motor mounting plate, but outside of the motor housing. The final drive is designed internally to trap lubricant in the planetary reduction where a higher level of lubricant is desired. This may be accomplished by blocking any path to the drain holes lower than a predetermined point below centerline. 
         [0009]    In order to gain the desired volume of lubricant in the sump, air pressure is supplied to the motor to create a pressure differential allowing a higher lubricant level in the annulus surrounding the motor, while keeping the level in the motor low. The air pressure can either be supplied by a standalone air pump or can be taken from a turbocharger of an engine. A hole is punched through the mount plate of the motor to connect the inside of the motor housing to the final drive. This allows air to flow into the final drive. A breather is connected to the wet sections of the axle tube to maintain minimal back pressure on the lubricant in the sump/annulus. This difference in pressure from within the motor/final drive to the wet axle tube will drive a higher level within the axle tube and a lower level in the motor and final drive. 
         [0010]    The exemplary embodiments allows for a single lubricant system to be shared between the motor and final drive. The air pressure and the internal design of the final drive the system is able to self-regulate different lubricant levels inside of the two components in order to use a common sump to satisfy the lubricant needs of both the motor and final drive. 
         [0011]    It is a first aspect of the present disclosure to provide an axle tube comprising: (a) a transmission subsection housing a transmission; (b) an electric motor having an outer housing, the electric motor at least partially encompassed by a motor tube to comprise a motor subsection, the outer housing having a drain orifice; and, (c) a liquid cavity cooperatively delineated by the outer housing and the motor tube, the liquid cavity, where the liquid cavity and an interior of the electric motor are in fluid communication via the drain orifice, where the transmission subsection and the motor subsection are mounted to one another, where the transmission subsection fluidicly communicates with the interior of the electric motor through a first orifice, where the transmission subsection fluidicly communicates with the interior of the electric motor and liquid cavity through a second orifice and, where the first Orifice is elevated above the second orifice. 
         [0012]    In a more detailed embodiment of the first aspect, the electric motor includes an air inlet orifice in communication with the interior of the electric motor and, the motor subsection includes a lubricant inlet orifice in communication with an interior of the motor subsection. In yet another more detailed embodiment, at least one of the transmission subsection and the motor subsection includes a drain orifice in fluid communication with a pump by way of a first conduit to draw out liquid and, at least one of the transmission subsection and the motor subsection includes a liquid inlet orifice in fluid communication with the pump by way of a second conduit to deliver liquid to at least one of the transmission subsection and the motor subsection. In a further detailed embodiment, the second conduit is in fluid communication with an in-line liquid filter and, the second conduit is in fluid communication with an in-line liquid radiator. In still a further detailed embodiment, the second conduit is in fluid communication with a liquid manifold, the liquid manifold divides the second conduit into a first inlet line and a second inlet line, the first inlet line is in fluid communication with an interior of the transmission subsection and, the second inlet line is in fluid communication with an interior of the motor subsection. In a more detailed embodiment, the motor subsection includes an end plate having an opening through which a motor shaft of the electric motor extends into the transmission subsection, the end plate including the first orifice and the second orifice, the first orifice is located above the opening and the second orifice is located below the opening. 
         [0013]    It is a second aspect of the present invention to provide an axle tube comprising: (a) a right side transmission subsection housing a right side transmission; (b) a left side transmission subsection housing a left side transmission; (c) a right side electric motor having a right side outer housing, the right side electric motor at least partially encompassed by a motor tube to comprise a motor subsection, the right side outer housing having a first drain orifice; (d) a left side electric motor having a left side outer housing, the left side electric motor at least partially encompassed by the motor tube to comprise part of the motor subsection, the left side outer housing having a second drain orifice; and, (e) a liquid cavity cooperatively delineated by the right side outer housing, the left side outer housing, and the motor tube, where the liquid cavity and an interior of the right side electric motor are in fluid communication via the first drain orifice, where the liquid cavity and an interior of the left side electric motor are in fluid communication via the second drain orifice, where the right side transmission subsection and the motor subsection are mounted to one another, where the left side transmission subsection and the motor subsection are mounted to one another, where the right side transmission subsection fluidicly communicates with the interior of the right side electric motor through a first opening, where the right side transmission subsection fluidicly communicates with the interior of the right side electric motor and the liquid cavity through a second opening, where the left side transmission subsection fluidicly communicates with the interior of the left side electric motor through a third opening, where the left side transmission subsection fluidicly communicates with the interior of the left side electric motor and the liquid cavity through a fourth opening and, where the first and third openings are respectively elevated above the second and fourth openings. 
         [0014]    In a more detailed embodiment of the second aspect, the right side electric motor includes an air inlet orifice in communication with the interior of the right side electric motor, the right side motor subsection includes a lubricant inlet orifice in communication with an interior of the right side motor subsection, the left side electric motor includes an air inlet orifice in communication with the interior of the left side electric motor and, the left side motor subsection includes a lubricant inlet orifice in communication with an interior of the left side motor subsection. In yet another more detailed embodiment, the right side motor subsection includes an end plate having an opening through which a motor shaft of the right side electric motor extends into the right side transmission subsection, the end plate including the first orifice and the second orifice, the first orifice is located above the opening and the second orifice is located below the opening and, the left side motor subsection includes an end plate having an opening through which a motor shaft of the left side electric motor extends into the left side transmission subsection, the end plate including the third orifice and the fourth orifice, the third orifice is located above the opening and the fourth orifice is located below the opening. 
         [0015]    It is a third aspect of the present invention to provide a method of controlling fluid levels within an axle tube, the method comprising: (a) establishing a first predetermined level of a liquid lubricant within a transmission and an electric motor operatively coupled to the electric motor, the axle tube housing the electric motor and the transmission, where a cavity interposing a wall of the axle tube and the electric motor is occupied by the liquid lubricant reservoir at a second predetermined level; and, (b) lowering the first predetermined level of a liquid lubricant within the electric motor and the transmission by changing a gas pressure exerted upon the liquid lubricant, where changing the gas pressure exerted upon the liquid lubricant within the axle tube raises the second predetermined level of liquid lubricant within the cavity. 
         [0016]    In a more detailed embodiment of the third aspect, the act of changing the gas pressure exerted upon the liquid lubricant includes forcing compressed air into the axle tube the compressed air coming from a discharge of a turbocharger. In yet another more detailed embodiment, the act of changing the gas pressure exerted upon the liquid lubricant includes forcing air into the axle tube using an air compressor. In a further detailed embodiment, the act of changing the gas pressure exerted upon the liquid lubricant includes applying suction to the cavity. In still a further detailed embodiment, the first predetermined level of the liquid lubricant is different within the transmission and the electric motor. In a more detailed embodiment, the transmission and an interior of the electric motor are in gaseous communication with one another through a first opening, the transmission and the cavity are in liquid communication with one another through a second opening and, the first predetermined level of a liquid lubricant within the electric motor prohibits gases communication between the interior of the transmission and the cavity. 
         [0017]    It is a fourth aspect of the present invention to provide a method of distributing a liquid lubricant within an axle tube, the method comprising: (a) using a cavity interposing an electric motor and a wall of the axle tube as a liquid lubricant reservoir, where the axle tube houses the electric motor and a transmission; and, (b) varying the amount of liquid lubricant within the reservoir by changing a pressure of a gas in communication with the liquid lubricant in the axle tube. 
         [0018]    In a more detailed embodiment of the fourth aspect, the method further includes (c) providing a predetermined amount of the liquid lubricant within the axle tube, (d) maintaining the predetermined amount of the liquid lubricant within the axle tube and, (e) dropping a level of liquid lubricant in at least one of the electric motor and the transmission, where varying the amount of liquid lubricant within the reservoir does not change the predetermined amount of the liquid lubricant within the axle tube. In yet another more detailed embodiment, the axle tube includes a second cavity interposing a second electric motor and the wall of the axle tube as a second liquid lubricant reservoir and, the axle tube houses the second electric motor and a second transmission. In a further detailed embodiment, the axle tube includes a dry section between the electric motor and the second electric motor and, the cavity is in fluid communication with the second cavity via a communication line. In still a further detailed embodiment, the act of changing the pressure of the gas in communication with the liquid lubricant includes applying suction to the reservoir. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an elevated perspective view, from the top, of an exemplary axle tube in accordance with the instant disclosure, shown without external fluid and electrical lines. 
           [0020]      FIG. 2  is an elevated perspective view, from the bottom, of the exemplary axle tube in  FIG. 1 . 
           [0021]      FIG. 3  is a cross-sectional view of the exemplary axle tube in  FIG. 1 . 
           [0022]      FIG. 4  is an elevated perspective view, from the top, of the exemplary dry center section of  FIG. 1 . 
           [0023]      FIG. 5  is an elevated perspective view, from the bottom, of the exemplary dry center section of  FIG. 4 . 
           [0024]      FIG. 6  is an elevated perspective view, from the front, of the exemplary dry center section of  FIG. 1  without a pair of walls and showing the pair of electric motors mounted to the dry center section. 
           [0025]      FIG. 7  is an elevated perspective view, taken from the electric motor side, of a cross-section taken with respect to the transmission subsection and the motor subsection housing to show the position of the electric motor with respect to adjacent components. 
           [0026]      FIG. 8  is an elevated perspective view, taken from the transmission side, of a cross-section taken with respect to the transmission subsection to show the position of the electric motor and tube with respect to adjacent components. 
           [0027]      FIG. 9  is a schematic diagram showing the level of lubricant within the exemplary axle tube of  FIG. 1  prior to start-up. 
           [0028]      FIG. 10  is a schematic diagram showing the level of lubricant within the exemplary axle tube of  FIG. 1  at start-up. 
           [0029]      FIG. 11  is a schematic diagram showing the level of lubricant within the exemplary axle tube of  FIG. 1  subsequent to start-up after the air pressure within the subsections is great enough to displace a greater amount of lubricant into a reserve cavity. 
           [0030]      FIG. 12  is an elevated perspective view, from the top, of an exemplary axle tube in accordance with the instant disclosure shown with external fluid lines. 
           [0031]      FIG. 13  is a magnified view of a portion of  FIG. 12 . 
           [0032]      FIG. 14  is an exemplary flow diagram for the axle tube shown in  FIG. 12 . 
           [0033]      FIG. 15  is an exemplary flow diagram for an alternate exemplary axle tube. 
           [0034]      FIG. 16  is another exemplary flow diagram for yet another alternate exemplary axle tube. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    The exemplary embodiments of the present disclosure are described and illustrated below to encompass axle tubes and methods of managing fluid levels within an axle tube. Of course, it will be apparent to those of ordinary skill in the art that the exemplary embodiments discussed below are merely examples and may be reconfigured without departing from the scope and spirit of the present disclosure. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present invention. 
         [0036]    Referencing  FIGS. 1-3 , a first exemplary axle tube  100  (shown without external fluid hoses) includes a dry center section  102  and corresponding right and left wet sections  104 ,  106  mounted to opposing ends of the dry center section. In this exemplary embodiment, each right and left wet section  104 ,  106  includes two subsections  108 ,  110 . The first subsection  108  is a motor subsection that houses the majority of an electric motor  112 . The second subsection  110  is a transmission subsection and includes transmission components  114  operatively coupled to the electric motor  112 . Both the right and left wet sections  104 ,  106  are sealed in order to retain oil concurrently lubricating and cooling the transmission components  114  and cooling the electric motor  112 . Both of the wet sections  104 ,  106  include seals that are operative to retard the inflow of water and other contaminants. 
         [0037]    Referring to  FIGS. 1-6 , the dry center section  102  comprises an enclosure formed by six rectangular walls  230 ,  232 ,  234 ,  236 ,  238 ,  240  that are mounted to one another. Each of the six walls  230 ,  232 ,  234 ,  236 ,  238 ,  240  corresponds to another of the remaining five walls so that corresponding pairs of walls are generally uniformly spaced apart and oriented in parallel. This orientation provides a box-shaped enclosure that defines a dry interior cavity  246 . 
         [0038]    The first corresponding pair of walls  230 ,  234  (right and left) each include a circular through hole  250  large enough to receive a dry portion  252  of an electric motor  112 . As will be discussed in more detail hereafter, the vast majority of the electric motor  112  is housed within the motor subsection  108 . Respective elastomeric ring seals  260  interposes an outer housing  262  of each electric motor  112  and an outside surface  264  of each wall  230 ,  234 . In particular, the elastomeric ring seal  260  has a diameter that is greater than the diameter of the through hole  250  so that the ring seal circumscribes the through hole, but is mounted to the outside surface  264  of each wall  230 ,  234 . In particular, the outside surface  264  includes a circular recess  266  that bounds the through hole  250  and provides a seat for a portion of the ring seal  260 . It should be noted that the housing  262  of each electric motor  112  is concurrently mounted to the seal ring  260 , but is not rigidly fastened to the dry center section  102 . Rather, the electric motor  112  floats with respect to the dry center section  102  because of the flexibility of the seal rings  260  interposing the walls  230 ,  234  and the housing  262  of each electric motor  112 . 
         [0039]    The second corresponding pair of walls  232 ,  236  (front and back) are coupled to the right and left walls  230 ,  234  and to the third corresponding pair of walls  238 ,  240  (top and bottom). Each front and back wall  232 ,  236  includes a plurality of orifices  270  adapted to provide a mounting location for attaching the axle tube to a vehicle frame (not shown), thereby providing support to the center of the axle tube. The top and bottom walls  238 ,  240  each include a rounded, rectangular through hole  272 . In this exemplary embodiment, the rounded, rectangular through hole  272  of the bottom wall  238  is closed off by a rounded rectangular pan  276  mounted to an exterior surface  278  thereof. In particular, the rounded rectangular pan  276  includes a plurality of orifices (not shown) adapted to receive threaded fasteners  280  that extend through the orifices and into holes of the bottom wall  240  in order to allow the pan to be coupled and uncoupled from the bottom wall. In contrast, the rounded, rectangular through hole  272  of the top wall  238  is not entirely closed off. Instead, a rounded rectangular pan  284  having a pair of elongated rectangular openings  286  is mounted to an outer surface of the top wall  238 . As with the bottom pan  276 , the top pan  284  includes a plurality of orifices (not shown) adapted to receive threaded fasteners  290  that extend through the orifices and into holes of the top wall  238  to couple and uncouple the top pan from the top wall. Extending from the top pan  284  and circumscribing the elongated rectangular openings  286  are adapter boxes  294 . Each adapter box  294  receives a high voltage subassembly (not shown) that is pre-connected and fluidicly sealed in order to establish electrical communication from outside the dry center section  102  and into communication with the electric motors  112  partially located within the dry center section. The adapter boxes  294  also provide connection locations for the air, oil and low voltage lines (not shown) that connect to the electric motors  112 . The top pan  284  also includes a plurality of secondary orifices  296  that interpose the adadapter boxes  294 . 
         [0040]    The dry portion  252  of each electric motor  112  includes numerous connections that provide electrical and fluid communication to the internal components of the electric motor and the transmission components  114 . Several electrical connections  300  are provided in order to supply electric current to the internal components. Those skilled in the art are familiar with the structure of electric motors and a corresponding detailed discussion of the internal components of each electric motor has been omitted only to further brevity. In addition to the electrical connections  300 , the dry portion  252  also includes an oil supply fitting  302  near the bottom of the dry portion for introducing oil into the interior of the electric motor  112 . And an air supply fitting  304  is also provided as part of the dry portion  252  near the top of the dry portion in order to introduce air into the interior of the electric motor  112 . 
         [0041]    Referring to  FIGS. 1 and 7 , the remainder of the electric motor  112  is housed within a tube  310  of the motor subsection  108 . The tube  310  comprises a dual ply  312 ,  314  cylinder having a series of fluid connections  316  that allow for fluid communication between the interior of the tube and an exterior of the tube. As will be discussed in more detail hereafter, the fluid connections  316  are coupled to hoses (see  FIGS. 12 and 13 ). In between the interior ply  314  of the tube  310  and the exterior of the electric motor housing  262  is a reserve cavity  318  that is used to store excess oil when the axle tube  100  is in operation. Both tube  310  plies  312 ,  314  are welded at one longitudinal end to the outside surface  264  of respective walls  230 ,  234 . 
         [0042]    Referencing  FIGS. 7 and 8 , the opposite longitudinal end of each tube  310  is welded to a circular flange  320  having a plurality of through holes. A first circumferentially outermost set of holes  322  receive fasteners in order to mount the flange  320  to a corresponding flange  360  of the transmission subsection  110 . A second inner circumferential set of holes (not shown) receive fasteners  324  in order to mount the flange  320  to an end plate  330  of the electric motor  112 . A gasket  332  interposes the flange  320  and the end plate  330  to ensure a fluid tight seal therebetween. 
         [0043]    The end plate  330  includes several holes having varying functionality. A first set of holes receive the fasteners  324  in order to mount the electric motor  112  to the flange  320 . A second set of through holes  336  provide communication across the end plate  330 . As will be discussed in more detail hereafter, these holes  336  provide a pathway for fluid (e.g., coolant/lubricant, such as oil) to flow between the interior of the transmission subsection  110  and the reserve cavity  318 . In order to manipulate the flow of fluid between the interior of the transmission subsection  110  and the reserve cavity  318 , the end plate  330  also includes a through hole  338  elevated above an output shaft  340  from the electric motor  112  and above the second set of through holes  336 . The through hole  338  is adapted to provide a pathway for fluid (e.g., air) to flow between the interior of the transmission subsection  110  and the electric motor housing  262 . In this manner, as air pressurizes the interior of the transmission subsection  110  and the interior of the electric motor housing  262 , coolant/lubricant is forced into the reserve cavity  318 . 
         [0044]    Referring to  FIGS. 9-11 , a schematic diagram shows the transmission subsection  110  and the motor subsection  108  coupled to one another and fluidicly sealed. In this manner, lubricant/coolant (e.g., oil)  400  is able to flow between the subsections  108 ,  110 , but the subsections generally maintain the same aggregate volume (subsection  108  plus subsection  110 ) of lubricant/coolant. And the amount of lubricant/coolant  400  located within either subsection  108 ,  110  changes depending upon whether the axle tube  100  is operable or not. 
         [0045]    Referencing FIGS. ( 7 - 9 ), initially, as the axle tube  100  becomes operable (upon receiving electric current to drive the electric motors  112  and an air supply, and upon being on level ground), the level of lubricant/coolant  400  within the subsections  108 ,  110  is generally the same. This universal level is the result of lubricant/coolant  400  freely flowing between the subsections through the second set of through holes  336  of the end plate  330  (see  FIGS. 7 and 8 ). More specifically, the level of lubricant/coolant  400  is the same in the transmission subsection  110 , the reserve cavity  318 , and in the internal cavity  350  of the electric motor  112 . But this universal level does not stay the same during operation of the axle tube  100 . 
         [0046]    Referring to  FIGS. 6-8  and  10 , after the axle tube  100  becomes operable (upon receiving electric current to drive the electric motors  112  and an air supply (e.g., air source  572  in  FIG. 14 ), and upon being on level ground), air is fed into the internal cavity  350  of the electric motor  112  by way of the air supply fitting  304  within the dry portion  252 . The air within the internal cavity  350  of the electric motor  112  builds in pressure based upon the air supply providing air above atmospheric pressure. In exemplary form, the air supply provides air at approximately forty pounds per square inch gauge (psig), which is reduced before it reaches the air supply fitting  304 . The air pressure within the electric motor  112  may be, for example, between 0.4-1.0 psig to overcome the head pressure within the reserve cavity  318  and force oil out of the interior of the electric motor through a drain  352  at the base of the electric motor housing  262 . Eventually, as the air drives out all or almost all of the lubricant  400  within the interior  350  of the electric motor  112 , air begins to escape through the drain  352  and into the reserve cavity  318 , where it is vented via a vent  580 . In this manner, the air pressure within the interior  350  of the electric motor  112  may be self-regulated. In addition, as the air pressure builds within the internal cavity  250 , the air escapes through the through hole  338  of the end plate  330  that is elevated above the output shaft  340 . Thus, the air pressure across the through hole  338  is relatively the same. This means that the air pressure within the internal cavity  350  of the electric motor  112  is the same as the air pressure within the transmission subsection  110 . Because of this equalization of pressure, the level of lubricant/coolant  400  across the through holes  336  is generally the same in the transmission subsection  110  and in the internal cavity  350  of the electric motor  112 . But it should also be noted that the transmission subsection  110  includes a retainer wall  354  operative to retain a predetermined level of lubricant  400  within a portion of the transmission subsection that is above the level of lubricant across the through holes  336 . And the level of lubricant within the reserve cavity  318  is also higher than the level of lubricant across the through holes  336 . 
         [0047]    Referencing  FIG. 11 , as the air pressure builds within the transmission subsection  110  and the internal cavity  350  of the electric motor  112 , the higher pressure air begins to displace the lubricant/coolant  400  within these areas. As air displaces the lubricant/coolant  400 , the corresponding level of lubricant/coolant  400  within the transmission subsection  110  and the internal cavity  350  drops and the lubricant/coolant is forced into the reserve cavity  318 , thus causing the level of lubricant/coolant to drastically increase—well above the level within the transmission subsection and the internal cavity  350  of the electric motor  112 . Eventually, the level of lubricant/coolant  400  within the transmission subsection  110  and the internal cavity  350  reaches an operating level as an equilibrium is established between the air pressure pushing on the lubricant/coolant and the pressure of the lubricant/coolant pushing back on the air. This operating level of lubricant/coolant  400  is determined, in large part, based upon the operating pressure of the air supply. However, those skilled in the art will realize that the operating level of lubricant/coolant  400  may change and, thus, the air pressure supplied by the air supply may also change to accommodate for these changes in the operating level of the lubricant/coolant. 
         [0048]    When the axle tube  100  no longer is operable (not electric current to drive the electric motors  112  and no air supply, and upon being on level ground), the level of lubricant/coolant  400  within the subsections  108 ,  110  returns to being uniform (see  FIG. 9 ). Specifically, without the air pressure forcing the lubricant/coolant  400  into the reserve cavity  318 , the pressure of the lubricant/coolant within the reserve cavity operates to displace the air and become evenly distributed among the subsections  108 ,  110 . 
         [0049]    Referencing  FIGS. 11-14 , the lubricant/coolant  400  flows through a closed loop  500  that includes the interior of the subsections  108 ,  110  and a series of interconnected conduits. Each tube  310  includes an exit orifice defined by an exit orifice fitting  502  that is positioned near the lowest arcuate location on the tube. The exit orifice fitting  502  is mounted to a rigid outlet conduit  504  that is mounted to a flexible outlet conduit  506 . In this way, the fitting  502  and conduits  504 ,  506  cooperate provide sealed flow for lubricant/coolant  400  exiting the reserve cavity  318  and flowing to the end of the outlet conduit  506 . Each end of both flexible outlet conduits  506  is coupled to a T-fitting  508  operative to consolidate the dual flows into a single flexible line  514 . This flexible line  514  is operatively coupled to a pump  516  that forces the lubricant/coolant  400  into a discharge flexible conduit  520  that carries the lubricant/coolant to be cooled and cleaned. 
         [0050]    Lubricant/coolant  400  is carried by the flexible conduit  520  and directed into a radiator  526 , which has a second fluid flowing therethrough to lower the temperature of the lubricant/coolant. After the lubricant/coolant  400  has been cooled, a radiator outlet conduit  528  conveys the lubricant/coolant to a filter  530 . The filter  530  is operative to remove contaminants from the lubricant/coolant  400  and discharge clean lubricant/coolant into a feed conduit  534 . 
         [0051]    The feed conduit  534  is coupled to a manifold  536  that operates to distribute the lubricant/coolant  400  among several input conduits  540 ,  542 . The first pair of input conduits  540  are each coupled to a rigid conduit  548  that is coupled to an entrance orifice fitting  550  that defines an entrance orifice. The entrance orifice fitting  550  is mounted to the flange  360  of the transmission subsection  110  and provides an egress point for lubricant/coolant  400  to flow into the interior of the transmission subsection. The second pair of input conduits  542  extends through the secondary orifices  296  (see  FIG. 5 ) of the top pan  284  and into communication with the oil supply fitting  302  of the electric motor  112  (see  FIG. 6 ), thereby providing an egress point for lubricant/coolant  400  to flow into the interior of the electric motor. 
         [0052]    Direct fluid communication between the motor subsections  108  is made possible by a communication line  560  that is coupled to respective outlet fittings  562  mounted to the tube  310  at locations elevated with respect to the exit orifice fittings  502 . In this manner, lubricant/coolant  400  is freely able to flow between one reserve cavity  318  (see  FIG. 7 ) to the other reserve cavity. The communication line  560  comprises two mirror image sections of rigid line (that generally retains its shape) that are coupled to a box fitting  563 . The box fitting  563  is coupled to a by-pass conduit  564  that is also coupled to the manifold  536 . In this manner, if the input conduits  540 ,  542  become damaged or blocked, the manifold recognizes the resulting pressure difference (greater or lesser) and diverts the lubricant/coolant  400  from the manifold  536  into the by-pass conduit  564 , where the lubricant/coolant is directed into the respective reserve cavities  318  using the communication line  560 . Otherwise, the by-pass conduit  564  contains stagnant lubricant/coolant  400 . And, as shown in part in  FIGS. 10 and 11 , an air supply conduit  570  provides air from an air source  572  to the air supply fitting  304  of the electric motor  112 . Exemplary air sources include, without limitation, turbochargers and air compressors. In this exemplary embodiment, it is envisioned that the axle tube  100  is included as part of a larger machine having an internal combustion engine with a turbocharger, where at least a portion of the discharged, compressed air from the turbocharger is routed through the air supply conduit  570 . It should also be noted that the tube  310  includes a vent  580  that may be operatively coupled to a vent line (not shown) in order to vent air within the reserve cavity  318  as the amount of lubricant/coolant  400  increases, and at the same time allow air into the reserve cavity as the amount of lubricant/coolant decreases. 
         [0053]    Referring to  FIGS. 15 and 16 , an additional set of schematic diagrams depict alternate closed loop flow paths  600 ,  700  for the lubricant/coolant  400 . In this first alternate closed loop  600 , the conduits and components are the same as the first closed loop  500  with the exception of providing an air source  572  or an air supply conduit  570 . In such a circumstance, the lubricant/coolant  400  within the subsections  108 ,  110  is not actively managed to direct more lubricant/coolant to the reserve cavities  318  when the electric motor  112  and transmission components are operational. 
         [0054]    The second alternate closed loop  700  includes the conduits and components of the first closed loop  500  with the exception of omitting the dry center section  102  and the communication line  560 . In this manner, lubricant/coolant  400  is fed directly into the motor subsection  108  and pulled directly from the motor subsection. Likewise, the air supply conduit is split and coupled directly to each motor subsection  108 . In this alternate embodiment, because the dry center section  102  is absent, the lubricant/coolant  400  conduits, electrical lines to the electric motors, and air supply line needs to able to withstand partial or total submerging in the lubricant/coolant. 
         [0055]    It should be noted that while the foregoing embodiment have discussed using compressed air to increase the level of lubricant/coolant  400  within the reserve cavity  318 , it is also within the scope of the disclosure to apply suction to the top of the reserve cavity to pull additional lubricant/coolant within the reserve cavity. In such a circumstance, the vent  580  may be couple to a suction line (not shown) that operates to create a low pressure area within the reserve cavity  318  to raise the level of lubricant/coolant  400 . 
         [0056]    Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.