Abstract:
A final drive unit for a motor vehicle includes a sprocket driven by a transmission, a first planetary gear set where one of the rotational members is connected to the sprocket, a second planetary gear set where one of the rotational members is connected to the first planetary gear set, and an actuator moveable between a low range position and a high range position. The actuator is rotationally coupled to a differential. When the actuator is in the low range position, the actuator rotationally couples one of the rotational members of the second planetary gear set to the differential. When the actuator is in the high range position, the actuator rotationally couples another of the rotational members of the second planetary gear set to the differential.

Description:
FIELD 
       [0001]    The invention relates generally to a transverse dual planetary system, and more particularly to a dual planetary system arranged transversely to provide a high and low range gear ratio in a final drive system in a powertrain of a motor vehicle. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical powertrain or driveline in a motor vehicle includes a transfer case or differential connected between the drive wheels of the motor vehicle and the engine and transmission. The differential is employed to distribute power from the transmission to each of the drive wheels. A typical differential includes an input member that rotates a housing and a plurality of side gears. One of the side gears is connected to a first half axle shaft and another is connected to a second half axle shaft. Each half axle shaft in turn is connected to a drive wheel. In addition, in a three output differential, the housing of the differential may be directly connected to a shaft member to distribute power to another set of drive wheels or to a power takeoff unit. These all-wheel drive systems may include a planetary gear set disposed between the transmission and the differential in order to provide a high range gear ratio at the final drive unit. While these systems are useful for their intended purpose, there is room in the art for a final drive system that provides a low and a high range of gear ratios at the final drive unit. 
       SUMMARY 
       [0004]    A final drive unit for a motor vehicle is provided that has a transverse dual planetary system. The final drive unit includes a sprocket driven by a transmission, a first planetary gear set where one of the rotational members is connected to the sprocket, a second planetary gear set where one of the rotational members is connected to the first planetary gear set, and an actuator moveable between a low range position and a high range position. The actuator is rotationally coupled to a differential. When the actuator is in the low range position, the actuator rotationally couples one of the rotational members of the second planetary gear set to the differential. When the actuator is in the high range position, the actuator rotationally couples another of the rotational members of the second planetary gear set to the differential. 
         [0005]    For example, in one embodiment the final drive unit includes a driven member, a first planetary gear set having first, second, and third members, wherein the first member of the first planetary gear set is connected to the driven member, a second planetary gear set having first, second, and third members, wherein the first member of the second planetary gear set is connected to the first planetary gear set, and an actuator moveable between a low range position and a high range position. The actuator is rotationally coupled to the second member of the second planetary gear set when in the low range position and the actuator is rotationally coupled to the first member of the second planetary gear set when in the low range position. A differential is rotationally coupled to the actuator. 
         [0006]    In another example, the first planetary gear set and the second planetary gear set are disposed axially adjacent to each other and transverse relative to the motor vehicle. 
         [0007]    In yet another example, the third member of the first planetary gear set is rotationally fixed to a housing of the final drive unit and the third member of the second planetary gear set is rotationally fixed to the housing of the final drive unit. 
         [0008]    In yet another example, the first member of the second planetary gear set is coupled to the second member of the first planetary gear set. 
         [0009]    In yet another example, the first members are sun gear members, the second members are planet carrier members, and the third members are ring gear members. 
         [0010]    In yet another example, the actuator includes a first set of splines that rotationally interconnect with the first member of the second planetary gear set when in the high range position and a second set of splines that rotationally interconnect with the second member of the second planetary gear set when in the low range position. 
         [0011]    In yet another example, the actuator includes a third set of splines that rotationally interconnect with the differential when the actuator is in both the high range position and the low range position. 
         [0012]    In yet another example, the differential includes a differential housing that is splined to the third set of splines of the actuator and is rotationally connected to a drive shaft, and the differential is rotationally connected to a first half axle and a second half axle. 
         [0013]    Further features, examples, and aspects of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     
       DRAWINGS 
         [0014]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0015]      FIG. 1  is a schematic, cross-sectional diagram of a final drive unit of a powertrain of a motor vehicle having a transverse dual planetary system according to the principles of the present invention; and 
           [0016]      FIG. 2  is an enlarged view of the transverse dual planetary system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0018]    With reference to  FIG. 1 , a final drive unit for use in a motor vehicle is generally indicated by reference number  10 . The final drive unit  10  receives a drive torque from a transmission (not shown) in the motor vehicle and distributes the drive torque to one of a plurality of drive wheels (not shown) of the motor vehicle. The transmission is preferably a transverse front wheel drive transmission. The final drive unit  10  generally includes a driven member, such as a sprocket  12 , a dual planetary gear system  14 , and a differential  16  each rotatable about a transverse, with respect to the motor vehicle, axis  19 . The sprocket  12  has teeth or cogs  12 A on an outer circumference that is connected to the transmission by a chain or belt  13 . The chain or belt  13  transfers drive torque from the transmission to the sprocket  12 . The sprocket  12  is supported for rotation on a final drive unit housing  18  by bearings  20 . The final drive unit housing  18  supports and protects the various components of the final drive unit  10  and is preferably connected to a housing (not shown) of the transmission. The sprocket  12  has an inner circumference  12 B that is connected to and drives the dual planetary system  14 , for example by a plurality of intermeshing gear teeth. 
         [0019]    With reference to  FIG. 2  and continued reference to  FIG. 1 , the dual planetary gear system  14  includes a first planetary gear set  22  and a second planetary gear set  24 . The first planetary gear set  22  is disposed adjacent to the second planetary gear set  24  transversely with respect to the motor vehicle. The first planetary gear set  22  includes a sun gear member  22 A, a planet carrier member  22 B, and a ring gear member  22 C. The planet carrier member  22 B supports a plurality of planet gears  22 D, only one of which is shown. The planet gears  22 D are each in mesh with both the sun gear member  22 A and the ring gear member  22 C. The sun gear member  22 A is connected to the inner circumference  12 B of the sprocket  12 . The carrier member  22 B is connected to the second planetary gear set  24 . For example, the carrier member  22 B includes an axially extended annulus  26  that supports a bearing  28  on an outer circumference and has a plurality of teeth  30  formed on an inner circumference. The bearing  28  supports the planetary gear set  24  and the teeth  30  engage the planetary gear set  24 . The ring gear member  22 C is connected to the final drive unit housing  18  to prevent the ring gear member  22 C from rotating. 
         [0020]    The second planetary gear set  24  includes a sun gear member  24 A, a planet carrier member  24 B, and a ring gear member  24 C. The planet carrier member  24 B supports a plurality of planet gears  24 D, only one of which is shown. The planet gears  24 D are each in mesh with both the sun gear member  24 A and the ring gear member  24 C. The sun gear member  24 A is connected to an actuation plate or member  32 . Alternatively, the sun gear member  24 A and the actuation plate  32  may be a single, unitary member. The actuation plate  32  extends radially between the planetary gear set  24  and the differential  16 . The actuation plate  32  has a central bore  34  and a front face or axial end surface  36 . The central bore  34  includes a plurality of teeth  38  that engage the sun gear member  24 A. The front face  36  includes a plurality of splines  40  disposed proximate an outer periphery of the actuation plate  32 . The carrier member  24 B includes an axially extending annulus  42 . The annulus  42  is disposed radially outboard of the actuation plate  32  and extends axially past the actuation plate  32  to the differential  16 . Thus, the actuation plate  32  is disposed within the annulus  42  of the carrier member  24 B. A plurality of splines  44  are formed on an inner circumference of the annulus  42 . The ring gear member  24 C is connected to the final drive unit housing  18  to prevent the ring gear member  24 C from rotating. 
         [0021]    The dual planetary gear system  14  further includes a slidable output carrier or actuator  50  for placing the dual planetary gear system  14  in one of a low range mode of operation and a high range mode of operation, as will be described in greater detail below. The actuator  50  is substantially cylindrical and is disposed around the differential  16 . The actuator  50  includes a first end  52 , a send end  54  opposite the first end  52 , an outer surface  56 , and an inner surface  58 . A first set of splines  60  are formed on the first end  52  and are sized to engage the spines  40  formed on the actuation plate  32 . A second set of splines  62  are formed on the outer surface  56  and are sized to engage the splines  44  formed on the carrier member  24 B. A third set of splines  64  are formed on the inner surface  58  and engage the differential  16 . 
         [0022]    The outer surface  56  includes a circumferential slot  66  that receives, or is otherwise connected to, a shift actuator  68 . The shift actuator  68  moves the actuator  50  axially between a low range position, a neutral position, and a high range position. In the low range position, the actuator  50  is moved to the right in  FIGS. 1 and 2 , and the second set of splines  62  engage the splines  44  of the carrier member  24 B to rotationally couple the carrier member  24 B to the differential  16  while the first set of splines  60  do not engage the splines  40  of the actuation plate  32 . In the high range position, the actuator  50  is moved to the left in  FIGS. 1 and 2 , and the first set of splines  60  engage the splines  40  of the actuation plate  32  to rotationally couple the actuation plate  32 , and thus the sun gear member  24 A, with the differential while the second set of splines  62  do not engage the splines  44  of the carrier member  24 B. In the neutral position, shown in  FIGS. 1 and 2 , the actuator  50  does not engage either of the actuation plate  32  or the carrier member  24 B. 
         [0023]    The differential  16  generally includes a housing  70  that is rotatable about the transverse axis  19  of the final drive unit  10 . The housing  70  includes splines  72  on an outer surface that are in mesh with the third set of splines  64  of the actuator  50 . The housing  70  also defines a cavity  74 . A cross shaft member  76  extends radially through the cavity  74 . The cross shaft member  76  is secured to the housing  70  by one or more transverse pins  78  to prevent the cross shaft member  76  from rotating. A first bevel gear  80  and a second bevel gear  82  are secured to the cross shaft member  76 . The bevel gears  80 ,  82  are secured to the cross shaft member  76  and therefore to the differential housing  70 . A first side gear  84  and a second side gear  86  are both intermeshed with the first and second bevel gears  80 ,  82 . The first side gear  84  is coupled to and rotates a first half axle  88  and the second side gear  86  is coupled to and rotates a second half axle  90 . The first half axle  88  extends axially through the differential housing  70 , through the planetary gear sets  22 ,  24  and connects with a first drive wheel (not shown). The second half axle  90  extends axially through the differential cover  70  and connects with a second drive wheel (not shown). The differential housing  70  is connected to a drive shaft or member  92  that is concentric with the second half axle  90 . The drive shaft  92  may be connected to an all-wheel drive system, including a differential and third and fourth drive wheels, or to a power takeoff unit that drives auxiliary equipment. 
         [0024]    During operation, power or torque from the engine of the motor vehicle is transferred to the transmission and an output torque is transferred to the sprocket  12 . Rotation of the sprocket  12  rotates the sun gear member  22 A of the planetary gear set  22 . Depending on the position of the actuator  50 , the output torque is either increased or decreased through the transverse dual planetary gear system  14  and communicated to the differential  16  through the actuator  50 . Rotation of the differential housing  70  rotates the drive shaft  92 . Rotation of the differential housing  70  also rotates the cross shaft member  76  and bevel gears  80 ,  82  which in turn rotate the side gears  84 ,  86 . Rotation of the first side gear  84  rotates the first half axle  88  while rotation of the second side gear  86  rotates the second half axle  90 , thus transferring drive torque to the drive wheels. 
         [0025]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.