Patent Publication Number: US-11035448-B2

Title: Multi-axis final drive assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a divisional of U.S. patent application Ser. No. 16/018,541 filed on Jun. 26, 2018, which is a divisional of U.S. patent application Ser. No. 15/334,333 filed on Oct. 26, 2016 (issued as U.S. Pat. No. 10,036,458 on Jul. 31, 2018), the entire contents of which are hereby incorporated by reference. 
    
    
     INTRODUCTION 
     The disclosure relates to a multiple-axis final drive assembly that employs an electric motor to drive a pair of opposite side wheels in a vehicle. 
     Modern motor vehicles are typically configured as either two- or all-wheel-drive. Either type of a vehicle may employ a conventional powertrain, where a single engine is used to propel the vehicle, an electric powertrain, where an electric motor is used to propel the vehicle, or a hybrid powertrain, where two or more distinct power sources, such as an internal combustion engine and an electric motor, are used to accomplish the same task. 
     An all-wheel-drive hybrid vehicle may be configured as an axle-split vehicle. In such a vehicle, independent power-sources, such as an internal combustion engine and an electric motor, are set up to independently power individual vehicle axles that are operatively connected to the respective power-sources, thus generating on-demand all-wheel-drive propulsion. In such an axle-split hybrid vehicle employing an engine and an electric motor, the electric motor may be capable of propelling the vehicle via the respective axle while the engine is shut off. 
     Each powered axle typically includes a final drive assembly with a differential that allows opposite side, i.e., left and right side, driven wheels to rotate at different speeds when the vehicle negotiates a turn. Specifically, the differential permits the driven wheel that is traveling around the outside of the turning curve to roll farther and faster than the driven wheel traveling around the inside of the turning curve, while approximately equal torque is applied to each of the driven wheels. An increase in the speed of one driven wheel is balanced by a decrease in the speed of the other driven wheel, while the average speed of the two driven wheels equals the input rotational speed of the drive shaft connecting the power-source to the differential. 
     SUMMARY 
     A final drive assembly for a vehicle drive axle has first and second axle-shafts that are configured to rotate about a common first axis. The final drive assembly includes a first gear-set configured to be operatively connected to the first axle-shaft. The final drive assembly also includes a second gear-set configured to be operatively connected to the second axle-shaft. The final drive assembly additionally includes an electric motor configured to provide an electric motor torque input to each of the first and second gear-sets and arranged on a second axis that is parallel to the first axis. 
     The final drive assembly may also include a first differential shaft operatively connected to the first gear-set and a second differential shaft operatively connected to the second gear-set. The final drive assembly may additionally include a third, differential gear-set operatively connecting the electric motor to the first and second differential shafts. 
     In the embodiment of the final drive assembly having the differential gear-set, each of the first and second gear-sets may be configured as a parallel-shaft transfer or reduction gear-set. The first parallel-shaft transfer gear-set may be operatively connected to the first differential shaft, while the second parallel-shaft transfer gear-set may be operatively connected to the second differential shaft. Each of the first and second parallel-shaft transfer gear-sets may include a respective first and second intermediate gears arranged to rotate about a third axis that is parallel to each of the first and second axes. Alternatively, each of the first and second gear-sets may be configured as a planetary or epicyclic gear-set configured to rotate about the first axis and having first, second, and third members. The first planetary gear-set may be operatively connected to the first differential shaft and the second planetary gear-set may be operatively connected to the second differential shaft. 
     Each of the first and second gear-sets may also be configured as a planetary gear-set that rotate about the first axis in the final drive assembly configured without the above differential gear-set. The final drive assembly may also include a final drive housing. In such a case, the electric motor may include a stator fixed to the final drive housing, a rotor, and an outer shaft fixed to the rotor for rotation therewith. The outer shaft may be in mesh with each of the third member of the first planetary gear-set and the third member of the second planetary gear-set. 
     The final drive assembly may additionally include an inner shaft extending through the outer shaft, in mesh with the first member of the first planetary gear-set, and operatively connected to the first member of the second planetary gear-set. 
     The inner shaft may be operatively connected to the first member of the second planetary gear-set via an idler gear. In such a case, the idler gear is configured to reverse a direction of rotation of the first member of the second planetary gear-set relative to a direction of rotation of the inner shaft. 
     The final drive assembly may additionally include an actuator configured to selectively disconnect the inner shaft from one of the first and second planetary gear-sets. 
     The first axle-shaft may be continuously connected to the second member of the first planetary gear-set and the second axle-shaft may be continuously connected to the second member of the second planetary gear-set. 
     In each of the first and second gear-sets, the first member may be a ring gear, the second member may be a planetary carrier supporting a plurality of pinion gears in mesh with the first and second members, while the third member may be a sun gear. 
     A vehicle drive axle for being mounted in a motor vehicle and employing such a final drive assembly is also disclosed. 
     The above features and advantages, and other features and advantages of the present disclosure, will be readily apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described disclosure when taken in connection with the accompanying drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a vehicle employing a hybrid electric powertrain that includes an internal combustion engine operatively connected to a first axle and a second axle employing a final drive assembly incorporating an electric motor, according to the disclosure. 
         FIG. 2  is a schematic close-up cross-sectional plan view one embodiment of the final drive assembly shown in  FIG. 1 . 
         FIG. 3  is a schematic close-up cross-sectional plan view another embodiment of the final drive assembly shown in  FIG. 1 . 
         FIG. 4  is a schematic close-up cross-sectional plan view yet another embodiment of the final drive assembly shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings in which like elements are identified with identical numerals throughout,  FIG. 1  illustrates a vehicle  10  that uses an electric motor, to be discussed in greater detail below, to drive a pair of opposite, a left and a right, side wheels. As shown, the vehicle  10  is hybrid vehicle having independent first and second power-sources that are operatively connected to respective sets of driven wheels in order to provide on-demand all-wheel-drive propulsion. The vehicle  10  may include, but not be limited to, a commercial vehicle, industrial vehicle, passenger vehicle, train or the like. As shown, the vehicle  10  is generally arranged along a longitudinal vehicle axis X. The vehicle  10  includes a first power-source shown as an internal combustion engine  12  configured to drive the vehicle via a first set of wheels, which includes a first or left-side wheel  14 - 1  and a second or right-side wheel  14 - 2 , for transmitting engine output or drive torque T 1  to a road surface  13  through a transmission assembly  16  and a first axle  18 . 
     The vehicle  10  additionally includes a second axle  20 . The second axle  20  is operatively independent from the engine  12  and the transmission  16 . The second axle  20  includes an electric motor-generator  22  that is configured to drive the vehicle  10  via a second set of wheels, which includes a first or left-side road wheel  24 - 1  and a second or right-side road wheel  24 - 2 . The electric motor-generator  22  receives its electrical energy from an energy storage device  26 . As understood by those skilled in the art, the motor-generator  22  includes a stator  22 - 1  and a rotor  22 - 2  configured to impart a motor-generator output or drive torque T 2 . According to the present disclosure, the electric motor-generator  22  is configured to drive the vehicle  10  via the drive torque T 2  independently from the engine  12  and provides the vehicle  10  with an on-demand electric axle drive. The vehicle  10  may be driven solely via the electric motor-generator  22 , i.e., in a purely electric vehicle or “EV” mode. On the other hand, when both first and second axles  18 ,  20  are driven by the respective engine  12  and the electric motor-generator  22 , the vehicle  10  is endowed with all-wheel-drive. 
     The second axle  20  includes a first axle-shaft  28 - 1  operatively connected to the left-side road wheel  24 - 1  and a second axle-shaft  28 - 2  operatively connected to the left-side road wheel  24 - 1 . Each of the first and second axle-shafts  28 - 1 ,  28 - 2  is configured to rotate about a common first axis Y 1 . As may be seen, the first axis Y 1  is arranged generally perpendicular to the longitudinal vehicle axis X. The second axle  20  also includes a final drive assembly  30  configured to transmit the drive torque T 2  to the first and second axle-shafts  28 - 1 ,  28 - 2 . The final drive assembly  30  also includes a first gear-set  32 - 1  operatively connected to the first axle-shaft  28 - 1 . The final drive assembly  30  additionally includes a second gear-set  32 - 2  operatively connected to the second axle-shaft  28 - 2 . The motor-generator  22 , being part of the final drive assembly  30  is configured to provide the drive torque T 2  input to each of the first and second gear-sets  32 - 1 ,  32 - 2 . The motor-generator  22  is arranged on a second axis Y 2  that is parallel to the first axis Y 1 . 
       FIG. 2  illustrates a final drive assembly  130 , which is a specific embodiment of the final drive assembly  30  shown in  FIG. 1 . The final drive assembly  130  may include a first differential shaft  34 - 1  operatively connected to the first gear-set  132 - 1  and a second differential shaft  34 - 2  operatively connected to the second gear-set  132 - 2 . In the embodiment of  FIG. 2 , the final drive assembly  130  may also include a third gear-set  36  configured as a differential. The differential gear-set  36  operatively connects the electric motor  22  to the first and second differential shafts  34 - 1 ,  34 - 2 . Furthermore, as shown in the final drive assembly  130 , each of the first and second gear-sets  132 - 1 ,  132 - 2  may be configured as a parallel-shaft transfer or reduction gear-set. The first parallel-shaft transfer gear-set  132 - 1  may be operatively connected to the first differential shaft  34 - 1 , while the second parallel-shaft transfer gear-set  132 - 2  may be operatively connected to the second differential shaft  34 - 2 . 
     As shown in  FIG. 2 , each of the first and second differential shafts  34 - 1 ,  34 - 2  includes respective splined ends or attached gears  38 A- 1 ,  38 A- 2 . Each of the first and second parallel-shaft transfer gear-sets  132 - 1 ,  132 - 2  includes respective first and second intermediate gears  38 B- 1 ,  38 B- 2  arranged to rotate about a third axis Y 3  that is parallel to each of the first and second axes Y 1 , Y 2 . The first and second intermediate gears  38 B- 1 ,  38 B- 2  are continuously connected to gears  38 C- 1 ,  38 C- 2 . The first and second intermediate gears  38 B- 1 ,  38 B- 2  transfer torque from the respective first and second differential shafts  34 - 1 ,  34 - 2  to the first and second axle-shafts  28 - 1 ,  28 - 2  via respective axle gear members  38 D- 1  and  38 D- 2 . 
       FIG. 3  illustrates a final drive assembly  230 , which is another specific embodiment of the final drive assembly  30  shown in  FIG. 1 . The final drive assembly  230  is similarly configured to transmit the drive torque T 2  to the first and second axle-shafts  28 - 1 ,  28 - 2 . The final drive assembly  230  includes first and second gear-sets  232 - 1 ,  232 - 2  that, like the respective first gear-sets  232 - 1 ,  232 - 2 , are operatively connected to the first and second axle-shafts  28 - 1 ,  28 - 2 . Also similar to the previously discussed final drive assembly  130  of  FIG. 2 , in the final drive assembly  230 , the motor-generator  22  arranged on the second axis Y 2  is configured to provide the drive torque T 2  input to each of the first and second gear-sets  232 - 1 ,  232 - 2 . As shown in  FIG. 3 , each of the first and second gear-sets  232 - 1 ,  232 - 2  in the final drive assembly  230  having the differential gear-set  36  may be configured as a planetary or epicyclic gear-set. As shown, each of the first and second planetary gear-sets  232 - 1 ,  232 - 2  is configured to rotate about the first axis Y 1  and have first, second, and third members  42 ,  44 , and  46 , respectively. 
     The first planetary gear-set  232 - 1  is operatively connected to the first differential shaft  34 - 1  and the second planetary gear-set  232 - 2  is operatively connected to the second differential shaft  34 - 2 . Specifically, the first differential shaft  34 - 1  is in mesh with the third member  46  of the first planetary gear-set  232 - 1  via a third parallel-shaft transfer gear-set  232 - 3 , and the second differential shaft  34 - 2  is in mesh with the third member  46  of the second planetary gear-set  232 - 2  via a fourth parallel-shaft transfer gear-set  232 - 4 . Additionally, the first axle-shaft  28 - 1  is continuously connected, i.e., for simultaneous rotation without interruption of the connection or the resultant transmission of torque, to the second member  44  of the first planetary gear-set  232 - 1 , while the second axle-shaft  28 - 2  is continuously connected to the second member  44  of the second planetary gear-set  232 - 2 . In each of the first and second gear-sets  232 - 1 ,  232 - 2 , the first member  42  may be a ring gear, the second member  44  may be a planetary carrier supporting a plurality of pinion gears  58  in mesh with the first and second members, and the third member  46  may be a sun gear, as understood by those skilled in the art. 
     According to a separate embodiment shown in  FIG. 4 , a final drive assembly  330  is disclosed that is similar to the final drive assembly embodiments  130  and  230  in being configured to transmit the drive torque T 2  to the first and second axle-shafts  28 - 1 ,  28 - 2 . The final drive assembly  330  includes first and second gear-sets  332 - 1 ,  332 - 2  that, similarly to the respective first gear-sets  332 - 1 ,  332 - 2 , are operatively connected to the first and second axle-shafts  28 - 1 ,  28 - 2 . Also analogous to the previously discussed embodiments of  FIGS. 2 and 3 , the motor-generator  22  arranged on the second axis Y 2  is configured to provide the drive torque T 2  input to each of the first and second gear-sets  332 - 1 ,  332 - 2 . The final drive assembly  330  is characterized by an absence of a separate and distinct differential gear-set  36 , such as used by the embodiments of  FIGS. 2 and 3 . The embodiment of  FIG. 4  utilizes differential rotation of a member of each of the first and second gear-sets  332 - 1 ,  332 - 2  to allow the first and second axle-shafts  28 - 1 ,  28 - 2  to rotate at different speeds, while each of the first and second gear-sets receives the drive torque T 2 . 
     Each embodiment of the contemplated embodiments of the final drive assembly  30 , i.e., final drive assemblies  130 ,  230 , and  330 , may generally include a final drive case or housing  39  configured to enclose various components disclosed and described herein. In the final drive assembly  330  shown in  FIG. 4  the stator  22 - 1  of the motor-generator  22  is fixed to the final drive housing  39 . The motor-generator  22  also includes an outer shaft  40  fixed to the rotor  22 - 2  for rotation therewith. In the final drive assembly  330 , similar to the final drive assembly  230  embodiment shown in  FIG. 3 , each of the first and second gear-sets  332 - 1 ,  332 - 2  is configured as a planetary gear-set, configured to rotate about the first axis Y 1 . Similar to the embodiment illustrated in  FIG. 3 , each of the first and second gear-sets  332 - 1 ,  332 - 2  have first, second, and third members  42 ,  44 , and  46 , respectively. The outer shaft  40  is in mesh with each of the third member  46  of the first planetary gear-set  332 - 1  and the third member of the second planetary gear-set  332 - 2 . 
     As shown in  FIG. 4 , the final drive assembly  330  also includes an inner shaft  48  extending through the outer shaft  40 . The inner shaft  48  is in mesh with the first member  42  of the first planetary gear-set  332 - 1 , and is also operatively connected to the first member  332 - 1  of the second planetary gear-set  332 - 2 . Specifically, the inner shaft  48  may be operatively connected to the first member  42  of the second planetary gear-set  332 - 2  via an idler gear  50  configured to reverse direction of rotation  52  of the first member of the second planetary gear-set relative to a direction of rotation  54  of the inner shaft  48 . 
     When the inner shaft  48  and the idler gear  50  are so connected and configured, and the first member  42  of the first planetary gear-set  332 - 1  is rotating, the second planetary gear-set  332 - 2  rotates in the opposite direction. Rotation of the first member  42  of each of the planetary gear-sets  332 - 1 ,  332 - 2  changes the speed of rotation of the axle shafts  28 - 1 ,  28 - 2 , and allows them to rotate at different speeds. The final drive assembly  330  may include an actuator  56  configured to selectively modify the operation of the inner shaft  48  and idler gear  50 . In the embodiment shown, the actuator  56  is configured to disconnect the inner shaft  48  from one of the first and second planetary gear-sets  332 - 1 ,  332 - 2 . Specifically, as shown in  FIG. 4 , the actuator  56  may be arranged in operative connection with the idler gear  50  and include a solenoid  56 A configured to shift the idler gear into meshed engagement with each of the first member  42  and the inner shaft  48 . Alternatively, the actuator  56  may be arranged in operative connection with the idler gear  50  to act as a clutch configured to impede or prevent rotation of the idler gear. 
     As shown in  FIG. 4 , the first axle-shaft  28 - 1  is continuously connected to the second member  44  of the first planetary gear-set  332 - 1 . Similarly, the second axle-shaft  28 - 2  is continuously connected to the second member  44  of the second planetary gear-set  332 - 2 . Similar to the embodiment of  FIG. 3 , in each of the first and second gear-sets  332 - 1 ,  332 - 2 , the first member  42  may be a ring gear, the second member  44  may be a planetary carrier supporting a plurality of pinion gears  58  in mesh with the first and second members, and the third member  46  may be a sun gear, as understood by those skilled in the art. 
     As shown in  FIG. 1 , the vehicle  10  also includes a programmable controller  60  configured to achieve desired propulsion of the vehicle  10  in response to command(s) from an operator of the subject vehicle. Specifically, the controller  60  may be programmed to regulate and coordinate operation of the first power-source, such as the internal combustion engine  12 , and the final drive assembly  30 . Accordingly, the controller  60  may control the operation of the motor-generator  22 , as well as the actuator  56 , to appropriately transmit drive torque T 2  to the first and second axle-shafts  28 - 1 ,  28 - 2 . To accomplish the above, the controller  64  may include a processor and tangible, non-transitory memory, which includes instructions for operation of the final drive assembly  30  programmed therein. The memory may be any recordable medium that participates in providing computer-readable data or process instructions. Such a recordable medium may take many forms, including but not limited to non-volatile media and volatile media. 
     Non-volatile media for the controller  60  may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which may constitute a main memory. Such instructions may be transmitted by one or more transmission medium, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Memory of the controller  60  may also include a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, etc. The controller  60  may be configured or equipped with other required computer hardware, such as a high-speed clock, requisite Analog-to-Digital (A/D) and/or Digital-to-Analog (D/A) circuitry, any necessary input/output circuitry and devices (I/O), as well as appropriate signal conditioning and/or buffer circuitry. Any algorithms required by the controller  60  or accessible thereby may be stored in the memory and automatically executed to provide the required functionality of the final drive assembly  30 . 
     The detailed description and the drawings or figures are supportive and descriptive of the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed disclosure have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment may be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.