Patent Publication Number: US-11376951-B2

Title: Continuously variable electric axles with on-demand energy harvesting capabilities for secondary or tag E-axles

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/487,156, entitled “CONTINUOUSLY VARIABLE ELECTRIC AXLES WITH ON-DEMAND ENERGY HARVESTING CAPABILITIES FOR SECONDARY OR TAG E-AXLES”, and filed on Aug. 20, 2019. U.S. patent application Ser. No. 16/487,156 is a U.S. National Phase of International Application No. PCT/US2018/019089, entitled “CONTINUOUSLY VARIABLE ELECTRIC AXLES WITH ON-DEMAND ENERGY HARVESTING CAPABILITIES FOR SECONDARY OR TAG E-AXLES”, and filed on Feb. 22, 2018. International Application No. PCT/US2018/019089 claims priority to U.S. Provisional Application No. 62/462,117, entitled “CONTINUOUSLY VARIABLE ELECTRIC AXLES WITH ON-DEMAND ENERGY HARVESTING CAPABILITIES FOR SECONDARY OR TAG E-AXLES”, and filed on Feb. 22, 2017. The entire contents of each of the above-listed applications are hereby incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     Hybrid vehicles are enjoying increased popularity and acceptance due in large part to the cost of fuel and greenhouse carbon emission government regulations for internal combustion engine vehicles. Such hybrid vehicles include both an internal combustion engine a˜ well as an electric motor to propel the vehicle. 
     Commercial vehicles or trailers having two or more rear axles allow such vehicles to carry greater loads when compared to vehicles and trailers having a single axle. A typical six-wheel drive arrangement for a motor vehicle includes an axle having steerable wheels at the front end of the vehicle and tandem axles at the rear of the vehicle. 
     Traditional tandem axle drivelines include 6×4 drivelines (i.e., 2 wheels on the steer axle and 4 driving wheels on tandem axles behind the steer axle) or 6×2 drivelines (i.e., 2 wheels on the steer axle and 4 wheels on the tandem axles behind the steer axle where only two wheels are on a drive axle). Any axle in the tandem axles may be a drive axle or a dead axle. When an additional axle (secondary axle) is a dead axle, it may be positioned before (a pusher axle) or after (a tag axle) a drive axle. 
     It may be useful and advantageous to have an electric tag axle with high reduction capabilities using an existing electric motor that is efficient and compact. 
     Additionally, it may be beneficial to have an electric driven axle that can provide high torque ratios and energy harvesting/energy recuperation abilities. 
     SUMMARY 
     Provided herein is an electric powertrain including a differential assembly operably coupled to a drive axle having a set of wheel coupled to the ends thereof; a planetary gear set connected to the differential assembly, the planetary gear set having a sun gear, a planet carrier supporting a plurality of planet gears, and a ring gear, wherein the planet carrier is drivingly engaged with the differential assembly; a first electric motor/generator; a second electric motor/generator; a first gear pass drivingly connected the first electric motor/generator and the ring gear; and a second gear pass drivingly connected the first electric motor/generator and the sun gear. 
     In some embodiments, the first gear pass includes a first portion connected to a first rotatable shaft and a second portion drivingly connected to a second rotatable shaft. In some embodiments, the second gear pass includes a first portion connected to a third rotatable shaft and a second portion drivingly connected to a fourth rotatable shaft. 
     In some embodiments, the electric powertrain includes a first reduction gear set positioned between the first electric motor/generator and the first gear pass. 
     In some embodiments, the electric powertrain includes a second reduction gear set positioned between the second electric motor/generator and the second gear pass. 
     In some embodiments, the electric powertrain includes a clutch positioned between the planet carrier and the differential assembly and configured to selectively engage the planet carrier and the differential assembly. 
     In some embodiments, the electric powertrain includes a third gear pass positioned between the first gear pass and the first electric motor/generator, wherein a first portion of the third gear pass is connected to the second rotatable shaft and a second portion of the third gear pass drivingly connected to an output shaft of the first electric motor/generator. 
     In some embodiments, the electric powertrain includes a fourth gear pass positioned between the third gear pass and the second electric motor/generator, wherein a first portion of the fourth gear pass is connected to the fourth rotatable shaft and a second portion of the fourth gear pass drivingly connected to an output shaft of the second electric motor/generator. 
     In some embodiments, at least one of the gear passes is an epicyclic gear set. 
     In some embodiments, the electric powertrain includes an over run clutch positioned between the ring gear and the first gear pass configured to selectively engage the ring gear and the first gear pass. 
     In some embodiments, the first and second electric motor/generators are parallel to the drive axle. 
     In some embodiments, the first and second electric motor/generators are axially adjacent to each other. In some embodiments, the first and second rotatable shafts are coaxial with drive axle. 
     In some embodiments, the electric axle includes a second clutch connected to a power take off unit and the second electric motor/generator, wherein the second clutch is configured to selectively connect the power take off unit and the electric powertrain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Novel features are set forth with particularity in the appended claims. A better understanding of the features and advantages of the embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the embodiments are utilized, and the accompanying drawings of which: 
         FIG. 1  is a schematic view of one preferred embodiment of an electric axle; 
         FIG. 2  is a schematic view of another preferred embodiment of an electric axle; 
         FIG. 3  is a schematic view of another preferred embodiment of an electric axle; 
         FIG. 4A  is a schematic view of another preferred embodiment of an electric axle; 
         FIG. 4B  is a schematic view of a tandem axle system including the electric axle depicted in  FIG. 4A ; 
         FIG. 5  is a schematic view of another preferred embodiment of an electric axle; and 
         FIG. 6  is a schematic view of another preferred embodiment of an electric axle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments. Hence, specific dimensions, directions, orientations or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. 
     Provided herein are electric powertrain configurations that may be used in hybrid and/or electric vehicles. The powertrains disclosed herein provide for an electric axle that provides high torque ratios and energy harvesting/energy recuperation abilities. 
     In some embodiments, the electric powertrains are part of electric axles which are incorporated into vehicles as tag or secondary axles in tandem or multiple axle vehicle systems. 
     It should be understood that electric or hybrid electric vehicles incorporating embodiments of the powertrains disclosed herein are capable of including a number of other additional powertrain components, such as, but not limited to, high-voltage battery pack with a battery management system or ultracapacitor, on-board charger, DC-DC converters, a variety of sensors, actuators, and controllers, among others. 
     The preferred embodiments will now be described with reference to the accompanying figures. The terminology used in the descriptions below is not to be interpreted in any limited or restrictive manner simply because it is used in conjunction with detailed descriptions of certain specific embodiments. 
     Furthermore, the embodiments include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the preferred embodiments described. 
       FIG. 1  is a schematic style view of an electric powertrain  100  according to a preferred embodiment. The electric powertrain  100  is a motor/generator driven powertrain, and may be operated in a plurality of operating modes. 
     Referring to  FIG. 1 , one preferred embodiment of an electric axle powertrain  100  includes a drivetrain  102  operably coupled to a differential assembly  104 . 
     In some embodiments, the differential assembly  104  assembly includes a common differential gear set implemented to transmit rotational power. The differential assembly  104  is operably coupled to a drive axle  106  configured to drive a set of wheels  108   a ,  108   b  on the ends thereof. 
     The differential assembly  104  is drivingly connected to a first planetary gear set  110 . The first planetary gear set  110  is provided with a ring gear  112 , a planet carrier  114 , and a sun gear  115 . The planet carrier  114  rotationally supports a plurality of planet gears that couple the sun gear  115  to the ring gear  112 . 
     In some embodiments, the differential assembly  104  is coupled directly to the planet carrier  114 . 
     The ring gear  112  is drivingly connected to a rotatable shaft  116 . Shaft  116  has a portion of a gear pass (or gear set)  118  drivingly connected thereto. Gear pass  118  drivingly connects shaft  116  with a rotatable shaft  120 . Shaft  120  has a portion of a gear pass  122  (or gear set) drivingly connected thereto. Gear pass  122  drivingly connects shaft  120  to an output of a first motor/generator  132 . 
     In some embodiments, shaft  120  extends axially, parallel to the drive axle  106 . 
     In some embodiments, shaft  120  is perpendicular to the drive axle  106  and the gear pass  118  is a right angle ring and pinion gear set. 
     The sun gear  115  is rotatably connected to a rotatable shaft  124 . Shaft  124  has a portion of a gear pass  126  (or gear set) drivingly connected thereto. Gear pass  126  drivingly connects shaft  124  to a rotatable shaft  130 . Shaft  130  has a portion of a gear pass  128  (or gear set) drivingly connected thereto. 
     In some embodiments, shaft  130  extends axially, parallel to the drive axle  106 . Gear pass  128  drivingly connects shaft  130  to an output of a second motor/generator  134 . 
     In some embodiments, shaft  124  extends axially, parallel to the drive axle  106 . 
     In some embodiments, shaft  124  is perpendicular to the drive axle and gear pass  126  is a right angle ring and pinion gear set. 
     In some embodiments, the motor/generators  132 ,  134  are capable of providing kinetic energy and converting a kinetic energy input to an electrical energy output (i.e. operate as a motor and a generator). For example, when the operator of the vehicle depresses the brake pedal the generator can covert the kinetic energy into electrical energy (i.e. regenerative braking). 
     In some embodiments, the motor/generators  132 ,  134  are connected to an energy storage device. The energy storage device can be a battery having a battery pack or a capacitor; however, it is understood that other embodiments may include other power sources including electrochemical energy conversion devices or combinations thereof including, but not limited to, an ultracapicitor or a fuel cell particularly in a fuel cell electric vehicle drivetrains (FCEV). 
     In some embodiments, the powertrain  100  is provided in a tag or secondary axle of a tandem axle or multi-axle system. 
     In some embodiments, the first and second motor/generators  132 ,  134  are positioned on radially opposite sides of the drive axle  106 . 
     In some embodiments, at least one of gear passes  118 ,  122 ,  126  or  128  are a step gear set or an epicyclic gear set. 
     In some embodiments, the first motor/generator  132  is perpendicular to the drive axle  106  and one of gear pass  122  or gear pass  118  is a right angle ring and pinion gear set. 
     In some embodiments, the second motor/generator  134  is perpendicular to the drive axle  106  and one of gear pass  128  or gear pass  126  is a right angle ring and pinion gear set. 
     In some embodiments, at least one of gear passes  118 ,  122 ,  126  or  128  are step gears or epicyclic gears. 
     The planetary gear set  110  may function as a power summation point or a power split point depending on the mode of operation of the powertrain  100 . The planetary gear set  110  functions as a power summation point of power from the motor/generators  132 ,  134  when power flows to the wheels  108   a ,  108   b  and as a power split when the motor/generators  132 ,  134  function as generators. When the power flow comes from the wheels  108   a ,  108   b , the planetary gear set  110  splits power at the carrier  114  and the kinetic energy  20  provided can be recuperated by the motor/generator(s)  132 ,  134 . 
     For any given wheel speed the first motor/generator  132  (or alternatively the second motor/generator  134 ) can operate as a motor providing power to the powertrain  100  and the second motor/generator  134  (or alternatively the second motor/generator  132 ) can operate as a generator. The generator  134  can maintain the state of charge in the battery pack or level of energy stored in the energy storage device at a sustainable or threshold level. By doing so, the energy storage device is able to provide the powertrain  100  energy for on-demand boosting if desired. If both the first and second motor/generators  132 ,  134  are operating as generators, the powertrain  100  provides a higher energy recuperation. 
     The motor  132  and generator  134  can operate at independent speeds due to the presence of the planetary gear set  110  which splits the power from the wheels with the differential assembly  104  connected to the carrier  114 . The motor/generator  132 ,  134  speeds are not limited to the wheel  108   a ,  108   b  speeds providing greater efficiency to the powertrain  100 . 
     The electric powertrain  100  can operate in multiple modes of operation providing a change in speed ratio from high to low continuously by controlling the speed of the first motor/generator  132  providing of a continuously variable electric variable axle. 
     In some embodiments, all components of the powertrain  100  are under the supervisory control of a vehicle system controller (VSC) not shown. Each powertrain component can have a separate controller under the supervisory control of the VSC. 
     In some embodiments, the powertrain  100  includes a separate battery controller (not shown) as part of a battery management system (not shown). 
     In some embodiments, the controller and/or VSC is configured to receive a number of electronic signals from sensors provided on the powertrain, vehicle, wheels, etc. The sensors optionally include temperature sensors, speed sensors, position sensors, among others. 
     In some embodiments, the controller and the VSC are configured to perform routines such as signal acquisition, signal arbitration, or other known methods for signal processing and is configured to electronically communicate to a variety of actuators and sensors. 
       FIG. 2  depicts another preferred embodiment an electric powertrain  200 . The embodiment shown in  FIG. 2  includes similar components to the powertrain  100 . Similar features of the embodiment shown in  FIG. 2  are numbered similarly in series. Different and additional features of the variation shown in  FIG. 2  are described hereinbelow and can be appreciated by one skilled in the art in view of  FIG. 1  and the other embodiments illustrated and described in this disclosure. 
     The electric axle powertrain  200  includes a drivetrain  202  operably coupled to a differential assembly  204 . 
     In some embodiments, the differential assembly  204  includes a common differential gear set implemented to transmit rotational power. 
     The differential assembly  204  is operably coupled to a drive axle  206  configured to drive a set of vehicle wheels  208   a ,  208   b  on the ends thereof. The differential assembly  204  is drivingly connected to a first planetary gear set  210 . The first planetary gear set  210  is provided with a ring gear  212 , a planet carrier  214 , and a sun gear  215 . The planet carrier  214  rotationally supports a plurality of planet gears that couple the sun gear  215  to the ring gear  212 . The ring gear  212  is drivingly connected to a rotatable shaft  216 . Shaft  216  has a 10 portion of a gear pass  218  drivingly connected thereto. Gear pass  218  drivingly connects shaft  216  with a rotatable shaft  220 . Shaft  220  has a portion of a gear pass  222  drivingly connected thereto. 
     In some embodiments, the differential assembly  204  is coupled to the planet carrier  214 . 
     In some embodiments, shaft  220  extends axially, parallel to the drive axle  206 . 
     In some embodiments, shaft  220  is perpendicular to the drive axle  206  and the gear pass  218  is a right angle ring and pinion gear set. 
     Gear pass  222  drivingly connects shaft  220  to a reduction unit  221  including a reducing gear set  223  drivingly connected to an output of a first motor/generator  232 . The sun gear  215  is rotatably connected to a rotatable shaft  224 . 
     In some embodiments, shaft  224  extends axially, parallel to the drive axle  206 . 
     Shaft  224  has a portion of a gear pass  226  drivingly connected thereto. Gear pass  226  drivingly connects shaft  224  to a rotatable shaft  230 . Shaft  230  has a portion of a gear pass  228  drivingly connected thereto. Gear pass  228  drivingly connects shaft  230  to a reduction unit  231  including a reducing gear set  233  drivingly connected to an output of a second motor/generator  234 . 
     In some embodiments, the first and second motor/generators  232 ,  234  are positioned parallel to the drive axle  206 . 
     In some embodiments, at least one of gear passes  218 ,  222 ,  226  or  228  are a step gear set or an epicyclic gear set. 
     In some embodiments, the first motor/generator  234  is perpendicular to the drive axle  206  and one of gear pass  222  or gear pass  218  is a right angle ring and pinion gear set. 
     In some embodiments, the second motor/generator  234  is perpendicular to the drive axle  206  and one of gear pass  228  or gear pass  226  is a right angle ring and pinion gear set. 
     As shown in  FIG. 2 , in some embodiments, the reducing gear set  223 , 233  are planetary gear sets that provide a primary gear reduction. 
     By providing an initial gear reduction, the planetary gear set  210  can have lower gear ratios and the gear passes  218 ,  222 ,  226 ,  228  include small diameter gears reducing the overall number of gear passes and thereby reducing the drivetrain packaging requirements. 
     In some embodiments, the reducing planetary gear sets  223 ,  233  can include a sun gear, a ring gear, and a plurality of compound planet gears rotatably mounted to a planet carrier. The sun gear can be integrally formed at one of the output shaft of the motor/generator  232 ,  234 . The ring gear is fixed to a stationary member or housing assembly. The planet carrier is drivingly connected to gear pass  222 . 
     In some embodiments, the reducing gear sets  223 ,  233  are coaxial with the outputs of the motor/generators  232 ,  234 . 
       FIG. 3  depicts another preferred embodiment of an electric powertrain  300 . The embodiment shown in  FIG. 3  includes similar components to the powertrain  100 . Similar features of the embodiment shown in  FIG. 3  are numbered similarly in series. Different and additional features of the variation shown in  FIG. 3  are described hereinbelow and can be appreciated by one skilled in the art in view of  FIG. 1  and the other embodiments illustrated and described in this disclosure. 
     The electric axle powertrain  300  includes a drivetrain  302  operably coupled to a differential assembly  304 . 
     In some embodiments, the differential assembly  304  includes a common differential gear set implemented to transmit rotational power. The differential assembly  304  is operably coupled to a drive axle  306  configured to drive a set of vehicle wheels  308   a ,  308   b  on the ends thereof. 
     The differential assembly  304  is drivingly connected to a first planetary gear set  310 . The first planetary gear set  310  is provided with a ring gear  312 , a planet carrier  314 , and a sun gear  315 . The planet carrier  314  rotationally supports a plurality of planet gears that couple the sun gear  315  to the ring gear  312 . 
     In some embodiments, the differential assembly  304  is coupled to the planet carrier  312 . 
     The ring gear  312  is drivingly connected to a rotatable shaft  316 . Shaft  316  has a portion of a gear pass  318  drivingly connected thereto. Gear pass  318  drivingly connects shaft  316  with a rotatable shaft  320 . Shaft  320  has a portion of a gear pass  322  drivingly connected thereto. 
     In some embodiments, shaft  320  extends axially, parallel to the drive axle  306 . Gear pass  322  drivingly connects shaft  320  to an output of a first motor/generator  332 . 
     The sun gear  315  is rotatably connected to a rotatable shaft  324 . Shaft  324  is drivingly connected to an output of a second motor/generator  334 . 
     In some embodiments, shaft  324  extends axially, parallel to the drive axle  306 . 
     In some embodiments, the first and second motor/generators  332 ,  334  are axially adjacent to each other and the rotatable shafts  316  and  320  are coaxial with the drive axle  306 . 
     In some embodiments, the output shafts of the first motor/generator and the second motor/generator are concentric. 
     In some embodiments, shaft  320  is transfer to the output shafts of the first and second motor/generators. 
     In some embodiments, at least one of gear passes  318 ,  322 ,  326  or  328  is a step gear set or an epicyclic gear set. 
       FIG. 4A  depicts another preferred embodiment an electric powertrain  400 . The embodiment shown in  FIG. 4A  includes similar components to the powertrain  100 . Similar features of the embodiment shown in  FIG. 4A  are numbered similarly in series. Different and additional features of the variation shown in  FIG. 4A  are described hereinbelow and can be appreciated by one skilled in the art in view of  FIG. 1  and the other embodiments illustrated and described in this disclosure. 
     The electric axle powertrain  400  includes a drivetrain  402  operably coupled to a differential assembly  404 . The differential assembly  404  is operably coupled to a drive axle  406  configured to drive a set of vehicle wheels  408   a ,  408   b  on the ends thereof. 
     In some embodiments, the differential assembly  404  includes a common differential gear set implemented to transmit rotational power. 
     The differential assembly  404  is drivingly connected to a first planetary gear set  410 . The first planetary gear set  410  is provided with a ring gear  412 , a planet carrier  414 , and a sun gear  415 . The ring gear  412  is drivingly connected to a rotatable shaft  416 . Shaft  416  has a portion of a gear pass  418  drivingly connected thereto. Gear pass  418  drivingly connects shaft  416  with a rotatable shaft  420 . Shaft  420  has a portion of a gear pass  422  drivingly connected thereto. Gear pass  422  drivingly connects shaft  420  to an output shaft  460  of a first motor/generator  432 . 
     In some embodiments, the differential assembly  404  is coupled to the planet carrier  414 . 
     The sun gear  415  is rotatably connected to a rotatable shaft  424 . Shaft  424  has a portion of a gear pass  426  drivingly connected thereto. Gear pass  426  drivingly connects shaft  424  to a rotatable shaft  430 . Shaft  430  has a portion of a gear pass  428  drivingly connected thereto. Gear pass  428  drivingly connects shaft  430  to an output shaft  462  of a second motor/generator  434 . 
     In some embodiments, shaft  424  extends axially, parallel to the drive axle  406 . 
     In some embodiments, the first and second motor/generators  432 ,  434  are positioned parallel to the drive axle  406 . 
     In some embodiments, at least one of gear passes  418 ,  422 ,  426  or  428  is a step gear set or an epicyclic gear set. 
     In some embodiments, the first motor/generator  432  is perpendicular to the drive axle  406  and one of gear pass  422  or gear pass  418  is a right angle ring and pinion gear set. 
     In some embodiments, the second motor/generator  434  is perpendicular to the drive axle  406  and one of gear pass  428  or gear pass  426  is a right angle ring and pinion gear set. 
     In some embodiments, the drivetrain  410  includes a clutch  440  that selectively connects the second motor/generator  434  to a drive shaft. The clutch  440  is in communication with the controller. 
     In some embodiments, the clutch  440  is connected to a power take off 15 unit  442 . 
       FIG. 4B  depicts the location of the clutch  440  in a tandem axle system  450  having an electric tag axle  452 , a driven axle  454  and a PTO device  442 . By connecting the drive axle  454  to a drive shaft, the drive axle  454  has electrically continuously variable functionality. If the clutch  440  is engaged, then the axle  454  becomes a dedicated hybrid transaxle. 
     When the system  450  is connected to an internal combustion engine or other power source, when clutch  440  is engaged power from the internal combustion engine us added to the power supplied by the motor/generator  434  and motor/generator  432  functions as a generator. 
     In some embodiments, clutch  440  is a dog clutch, clone clutch, wet clutch or dry clutch. 
     In some embodiments, clutch  440  is a hydraulically actuated wet clutch pack. 
     In some embodiments, a second disconnect clutch  444  is added to one of the wheels of the tag axle  452 . The electric tag axle  452  can be used to export power to a grid for a plug-in hybrid vehicle embodiment which has an onboard charger. In some embodiments, the vehicle includes an auxiliary power unit powered by the electric tag axle  452  when the vehicle is stationary and can include exportable power to grid configurations. 
       FIG. 5  depicts another preferred embodiment an electric powertrain  500 . The embodiment shown in  FIG. 5  includes similar 5 components to the powertrain  100 . Similar features of the embodiment shown in  FIG. 5  are numbered similarly in series. Different and additional features of the variation shown in  FIG. 5  are described hereinbelow and can be appreciated by one skilled in the art in view of  FIG. 1  and the other embodiments illustrated and described in this disclosure. 
     The electric powertrain  500  includes a drivetrain  502  operably coupled to a differential assembly  504 . 
     In some embodiments, the differential assembly  504  includes a common differential gear set implemented to transmit rotational power. 
     The differential assembly  504  is operably coupled to a drive axle  506  configured to drive a set of vehicle wheels  508   a ,  508   b  on the ends thereof. The differential assembly  504  is drivingly connected to a first planetary gear set  510 . The first planetary gear set  510  is provided with a ring gear  512 , a planet carrier  514 , and a sun gear  515 . 
     In some embodiments, the differential assembly  504  is selectively drivingly coupled to the planet carrier  514 . 
     A clutch  517  is positioned between the planet carrier  514  and the differential assembly  504  to selectively couple the differential assembly  504  to the carrier  514 . When the clutch  517  is disengaged, the differential assembly  504  runs in a neutral mode minimizing drag losses by disengaging the powertrain from the differential assembly  504 . 
     In some embodiments, the ring gear  512  is drivingly connected to an over run clutch  519 . The over-run clutch  519  is drivingly connected to the ring gear  512  and a shaft  516 . 
     Shaft  516  has a portion of a gear pass  518  drivingly connected thereto. Gear pass  518  drivingly connects shaft  516  with a rotatable shaft  520 . Shaft  520  has a portion of a gear pass  522  drivingly connected thereto. Gear pass  522  drivingly connects shaft  520  to an output of a first motor/generator  532 . 
     The sun gear  515  is rotatable connected to a rotatable shaft  524 . Shaft  524  has a portion of a gear pass  526  drivingly connected thereto. Gear pass 5  526  drivingly connects shaft  524  to a rotabable shaft  530 . Shaft  530  has a portion of a gear pass  528  drivingly connected thereto. Gear pass  528  drivingly connects shaft  530  to an output of a second motor/generator  534 . In some embodiments, shaft  524  extends axially, parallel to the drive axle  506 . 
     In some embodiments, the first and second motor/generators  532 ,  534  are positioned on parallel to the drive axle  506 . 
     In some embodiments, the first motor/generator  532  is perpendicular to the drive axle  506  and one of gear pass  522  or gear pass  518  is a right angle ring and pinion gear set. 
     In some embodiments, at least one of gear passes  518 ,  522 ,  526  or  528   15  is a step gear set or an epicyclic gear set. 
     In some embodiments, the second motor/generator  534  is perpendicular to the drive axle  506  and one of gear pass  528  or gear pass  526  is a right angle ring and pinion gear set. 
     The over-run clutch  519  prevents the motor/generator  532  from being back driven by the powertrain  500 . The ring gear  512  of the planetary gear set  510  can experience higher torque than the sun gear  515  because of the ring-to-sun (RTS) ratio. If the motor/generator  532  cannot produce enough torque such that torque on the ring gear  512  is not equal to the torque on the sun gear  515  multiplied by the RTS ratio, the ring gear  512  is back driven. The over-run clutch  519  is placed along the motor/generator  532  to ring gear  512  power path to prevent the ring gear  512  from back rotating. 
     In some embodiments, the over-run clutch  519  is a directional over run clutch. The directional over run clutch  519 , when energized, allows the motor/generator  532  to reverse the rotation of the output of the motor/generator  532  rotate as needed such as when the motor/generator  532  is operating in a regeneration mode. 
     A controller can control the operating mode of the powertrain  500  by at least by controlling the engagement of the over-run clutch  519  and clutch  517 . In response to a signal sent by the controller, an actuator can engage the over-run clutch  519  and/or the clutch  517 . 
       FIG. 6  depicts another preferred embodiment of an electric powertrain  600 . The embodiment shown in  FIG. 6  includes similar components to the powertrain  100 . Similar features of the embodiment shown in  FIG. 6  are numbered similarly in series. Different and additional features of the variation shown in  FIG. 6  are described hereinbelow and can be appreciated by one skilled in the art in view of  FIG. 1  and the other embodiments illustrated and described in this disclosure. 
     The electric powertrain  600  includes a drivetrain  602  operably coupled to a differential assembly  604 . The differential assembly  604  is operably coupled to a drive axle  606  configured to drive a set of vehicle wheels  608   a ,  608   b  on the ends thereof. The differential assembly  604  is drivingly connected to a first planetary gear set  610 . The first planetary gear set  610  is provided with a ring gear  612 , a planet carrier  614 , and a sun gear  614 . 
     In some embodiments, the differential assembly  604  includes a common differential gear set implemented to transmit rotational power. 
     In some embodiments, the differential assembly  604  is drivingly coupled to the planet carrier  614 . 
     The ring gear  612  is drivingly connected to a rotating shaft  616 . Shaft  616  has a portion of a gear pass  618  drivingly connected thereto. Gear pass  618  selectively drivingly connects shaft  616  with a rotatable shaft  620 . Shaft  616  has a portion of a gear pass  622  drivingly connected thereto. Gear pass  622  selectively drivingly connects shaft  616  with shaft  620 . Shaft  620  is drivingly attached to an output of a first motor/generator  632 . The sun gear  615  is rotatably connected to a rotatable shaft  624 . 
     Shaft  624  has a portion of a gear pass  626  drivingly connected thereto. Gear pass  626  selectively drivingly connects shaft  624  to a rotatable shaft  630 . Shaft  630  has a portion of a gear pass  628  drivingly connected thereto. Gear pass  628  selectively drivingly connects shaft  630  to shaft  624 . Shaft  630  is drivingly attached to an output of a second motor/generator  634 . 
     In some embodiments, shaft  624  extends axially, parallel to the drive axle  606 . 
     In some embodiments, the first and second motor/generators  632 ,  634  are positioned parallel to the drive axle  606 . 
     In some embodiments, the first motor/generator  632  is perpendicular to the drive axle and one of gear pass  622  or gear pass  618  is a right angle ring and pinion gear set. 
     In some embodiments, at least one of gear passes  618 ,  622 ,  626  or  628  is a step gear set or an epicyclic gear set. 
     In some embodiments, the second motor/generator  634  is perpendicular to the drive axle  606  and one of gear pass  628  or gear pass  626  is a right angle ring and pinion gear set. 
     The powertrain  600  is configured to be placed in at least two modes of operation, depending on a position of a selector sleeve  633 . In a first mode of operation, the powertrain  600  operates in a low speed mode operation. In a second mode of operation, the powertrain  600  operates in a high speed mode operation. 
     A controller can control the operating mode of the powertrain  600  by at least by adjusting a position of the selector sleeve  633 . To switch between the modes of operation, a selector sleeve  633  engage shafts  620  with either gear pass  622  and  618  by means of a clutching action. A shift fork  635  disposed in an annular recess formed in the selector sleeve  633  moves the selector sleeve  633  along the axis of shaft  620  into a first position, a second position, or a neutral position. In response to a signal sent by the controller, an actuator adjusts a position of the selector sleeve  633 . 
     In the first position or low mode of operation, the selector sleeve  633  is drivingly engaged with the gear pass  622  and shaft  620 . The power is transferred from the motor/generator  632  through the selector spline to gear pass  622  to shaft  616  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . 
     In the second position or high speed mode of operation, the selector sleeve  633  is drivingly engaged with gear pass  618  and shaft  620 . The power is transferred from the motor/generator  632  through the selector spline to gear pass  618 , to shaft  616  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . 
     In the neutral position, the selector sleeve  633  engages neither gear pass  622  or gear pass  618 , the selector sleeve  633  is in a neutral position. 
     The powertrain  600  is configured to be placed in multiple modes of operation, depending on a position of a selector sleeve  637 . In a first mode of operation, the powertrain  600  operates in a high speed mode operation. In a second mode of operation, the powertrain  600  operates in a low speed mode operation. In the high and low modes of operation the ratios are continuously variable within a range determined by the ratios of the gear passes and planetary gear set. 
     Similarly, the controller can control the operating mode of the powertrain  600  by at least by adjusting a position of the selector sleeve  637 . To switch between the modes of operation, a selector sleeve  637  engage shaft  630  with either gear pass  626  and  628  by means of a clutching action. A shift fork  639  disposed in an annular recess formed in the selector sleeve  637  moves the selector sleeve  637  along the axis of shaft  630  into a first position, a second position, or a neutral position. In response to a signal sent by the controller, an actuator adjusts a position of the selector sleeve  637 . 
     In the first position or low mode of operation, the selector sleeve  637  is drivingly engaged with the gear pass  626  and shaft  630 . The power is transferred from the motor/generator  634  through the selector spline to gear pass  626  to shaft  624  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . 
     In the second position or high speed mode of operation, the selector sleeve  637  is drivingly engaged with gear pass  628  and shaft  630 . The power is transferred from the motor/generator  634  through the selector spline to gear pass  628 , to shaft  624  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . 
     In the neutral position, the selector sleeve  637  engages neither gear pass  626  or gear pass  628 , the selector sleeve  637  is in a neutral position. 
     It is understood the selector sleeves  633 , 637  and shift forks  635 ,  639  may be substituted with any clutching device that permits selective engagement of a driving and a driven part. In some embodiments, a clutch can be used instead of the shift fork. The clutch can be, but is not limited to, a dog clutch, a clone clutch, a wet or dry clutch including a hydraulically actuated wet clutch pack. If a low speed range is desired the selector spline is engaged with gear pass  622 . The power is transferred from the motor/generator  632  through the selector spline to gear pass  622 , to shaft  616  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . 
     If a high speed range is desired the selector spline is engaged with gear pass  618 . The power is transferred from the motor/generator  632  through the selector spline to gear pass  618 , to shaft  616  through the planetary gear set  610  to the differential assembly  604  and, thus, to the wheels  608   a ,  608   b  through the drive axle  606 . When neither gear pass  622  nor gear pass  618  is engaged, the selector sleeve  637  is in a neutral position. 
     In some embodiments, an over run clutch (not shown) prevents the motor/generator  632  from being back driven by the powertrain  600 . The ring gear  612  of the planetary gear set  610  can experience higher torque than the sun gear  615  because of the ring-to-sun (RTS) ratio. If the motor/generator  632  cannot produce enough torque such that torque on the ring gear  612  is not equal to the torque on the sun gear  615  multiplied by the RTS ratio, the ring gear  612  is back driven. The over-run clutch  619  is placed along the motor/generator  632  to ring gear  612  power path to prevent the ring gear  614  from back rotating. 
     It should further be noted that the electric powertrains disclosed herein are optionally used as primary drive axles, second drive axles, or both. 
     It should be understood that each gear pass can include multiple gears including planetary gears. In some embodiments, at least one of the gear passes is a planetary gear set having a sun gear, ring gear and a plurality of planet gears supported by a planet carrier wherein one of the sun gear, ring rear or planet carrier can be grounded to a stationary member or housing. 
     It should be understood that additional clutches/brakes, step ratios are optionally provided to the hybrid powertrains disclosed herein to obtain varying power path characteristics. It should be noted that the connections of the electric machines to the power paths disclosed herein are provided for illustrative example and it is within a designer&#39;s means to couple the electric machines to other components of the powertrains disclosed herein. 
     It should be noted that the battery is capable of being not just a high voltage pack such as lithium ion or lead-acid batteries, but also ultracapacitors or other pneumatic/hydraulic systems such as accumulators, or other forms of energy storage systems. 
     The motor/generators described herein are capable of representing hydromotors actuated by variable displacement pumps, electric machines, pneumatic motors driven by pneumatic pumps, etc. 
     While the preferred embodiments have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the embodiments. It should be understood that various alternatives to the embodiments described herein are capable of being employed in practicing the embodiments. 
     Various embodiments as described herein are provided in the Aspects below: 
     Aspect 1. An electric powertrain comprising: a differential assembly operably coupled to a drive axle having a set of wheels coupled to the ends thereof; a planetary gear set connected to the differential assembly, the planetary gear set having a sun gear, a planet carrier supporting a plurality of planet gears, and a ring gear, wherein the planet carrier is drivingly engaged with the differential assembly; a first electric motor/generator; a second electric motor/generator; a first gear pass drivingly connected to the first electric motor/generator and the ring gear; and a second gear pass drivingly connected to the first electric motor/generator and the sun gear. 
     Aspect 2. The electric powertrain of Aspect 1, wherein a first portion of the first gear pass is connected to a first rotatable shaft and a second portion of the first gear pass is drivingly connected to a second rotatable shaft. 
     Aspect 3. The electric powertrain of one of Aspects 1-2, wherein a first portion of the second gear pass is connected to a third rotatable shaft and a second portion of the second gear pass drivingly connected to a fourth rotatable shaft. 
     Aspect 4. The electric powertrain of one of Aspects 1-3 further comprising a first reduction gear set positioned between the first electric motor/generator and the first gear pass. 
     Aspect 5. The electric powertrain of one of Aspects 1-4 further comprising a second reduction gear set positioned between the second electric motor/generator and the second gear pass. 
     Aspect 6. The electric powertrain of one of Aspects 1-5 further comprising a clutch positioned between the planet carrier and the differential assembly, wherein the clutch is configured to selectively engage the planet carrier and the differential assembly. 
     Aspect 7. The electric powertrain of one of Aspects 1-6 further comprising a third gear pass positioned between the first gear pass and the first electric motor/generator, wherein a first portion of the third gear pass is connected to the second rotatable shaft and a second portion of the third gear pass drivingly connected to an output shaft of the first electric motor/generator. 
     Aspect 8. The electric powertrain of one of Aspects 1-7 further comprising a fourth gear pass positioned between the third gear pass and the second electric motor/generator, wherein a first portion of the fourth gear pass is connected to the fourth rotatable shaft and a second portion of the fourth gear pass drivingly connected to an output shaft of the second electric motor/generator. 
     Aspect 9. The electric powertrain of one of Aspects 1-8, wherein at least one of the gear passes is an epicyclic gear set. 
     Aspect 10. The electric powertrain of one of Aspects 1-9 further comprising an over run clutch positioned between the ring gear and the first gear pass, wherein the over-run clutch is configured to selectively engage the ring gear and the first gear pass. 
     Aspect 11. The electric powertrain of one of Aspects 1-10, wherein the first and second electric motor/generators are parallel to the drive axle. 
     Aspect 12. The electric powertrain of one of Aspects 1-11, wherein the first and second electric motor/generators are axially adjacent to each other. 
     Aspect 13. The electric power train of one of Aspects 1-12, wherein the first and second rotatable shafts are coaxial with drive axle. 
     Aspect 14. An electric axle comprising the electric powertrain of one of Aspects 1-13. 
     Aspect 15. The electric axle of Aspect 14 further comprising a second clutch connected to a power take off unit and the second electric motor/generator, wherein the second clutch is configured to selectively connect the power take off unit and the electric powertrain.