Abstract:
A drive axle assembly for driving a wheel of a vehicle includes a moveable suspension arm and a wheel spindle fixed to the suspension arm. A planetary gearset includes a sun gear, a ring gear and a carrier rotatably supporting a plurality of planet gears in meshed engagement with the sun gear and the ring gear. The carrier encompasses the wheel spindle and is drivingly connected to the wheel. An electric motor includes a rotor and a stator. The rotor drives the sun gear.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/514,064 filed on Aug. 31, 2006. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present teachings relate to a part time hybrid electric all wheel drive system and more particularly relate to a pair of compact electric wheel motor assemblies that can selectively drive a pair of wheels that are not otherwise driven by an engine. 
     BACKGROUND 
     Typically, a hybrid electric all wheel drive system includes an electric motor and an internal combustion engine. The internal combustion engine drives the front wheels and a centrally mounted electric motor couples to a rear axle to drive the rear wheels. 
     Space under a vehicle is relatively limited and the above example requires the rear axle in addition to a relatively large centrally mounted electric motor. While the above system works well in various applications, there remains room in the art for improvement. 
     SUMMARY 
     A drive axle assembly for driving a wheel of a vehicle includes a moveable suspension arm and a wheel spindle fixed to the suspension arm. A planetary gearset includes a sun gear, a ring gear and a carrier rotatably supporting a plurality of planet gears in meshed engagement with the sun gear and the ring gear. The carrier encompasses the wheel spindle and is drivingly connected to the wheel. An electric motor includes a rotor and a stator. The rotor drives the sun gear. 
     In another arrangement, a drive axle assembly for driving first and second rear wheels of a vehicle includes a rear suspension having first and second spaced apart wheel spindles respectively fixed to individually moveable first and second suspension arms. A first electric motor is fixed to the first suspension arm and is adapted to independently drive the first rear wheel. A second electric motor is fixed to the second suspension arm and is adapted to independently drive the second rear wheel. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present teachings in any way. 
         FIG. 1  is a diagram showing a vehicle with a front wheel drive configuration that can accept an electric all wheel drive system. 
         FIG. 2  is similar to  FIG. 1  and shows the rear wheels removed from the vehicle. 
         FIG. 3  is a diagram of a hybrid electric all wheel drive system constructed in accordance with the present teachings showing a pair of electric wheel motor assemblies coupled to the vehicle of  FIG. 1 . 
         FIG. 4  is a perspective view of an electric wheel motor assembly constructed in accordance with the present teachings showing an outboard side thereof. 
         FIG. 5  is similar to  FIG. 4  and shows an inboard side thereof. 
         FIG. 6  is a cross-sectional view of  FIG. 4  showing a portion of a planetary gearset operable in the electric wheel motor assembly. 
         FIG. 7  is an exploded assembly view of the electric wheel motor assembly of  FIG. 4  showing a planetary gearset, an electric motor and a brake rotor in accordance with the present teachings. 
         FIG. 8  is a partial exploded assembly of the electric wheel motor assembly of  FIG. 4  showing the planetary gearset. 
         FIG. 9  is a perspective view of the electric wheel motor assembly of  FIG. 4  showing active cooling of the electric motor with the brake rotor having vanes formed therethrough. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present teachings, their application, or uses. It should be understood that throughout the drawings, corresponding reference numerals can indicate like or corresponding parts and features. 
     With reference to  FIGS. 3 and 4 , the present teachings generally include an electric wheel motor assembly  10 . A hybrid electric all wheel drive system  12  can be implemented on a vehicle  14 . The all wheel drive system  12  can include a driver side electric wheel motor assembly  10   a  and a passenger side electric wheel motor assembly  10   b , which can be collectively referred to as the electric wheel motor assemblies  10 . Each of the electric wheel motor assemblies  10  can couple to a rear suspension  16  that can couple to a vehicle body  14   a  and/or other suitable suspension components, such as springs or shocks. Each of the electric wheel motor assemblies  10  can be selectively engaged to provide all-wheel drive on a part time basis. 
     The vehicle  14  can include an engine  18  driving front wheels  20 . The electric motor assemblies  10  can replace a conventional wheel and a wheel mounting structure (not specifically shown) that would otherwise rotatably support the rear wheels  22  and couple the rear wheels  22  to the vehicle  14 . It will be appreciated that the vehicle  14  can be equipped with the conventional wheel and wheel mounting structure and can be subsequently retrofit with the electric motor assemblies  10 . Moreover, the electric motor assemblies  10  can be provided as original equipment in lieu of the conventional wheel and wheel mounting structure. 
     With reference to  FIG. 1 , the vehicle  14  can have a front wheel drive configuration. The front wheel drive configuration includes the engine  18  that can drive the front wheels  20 . The rear wheels  22  can be coupled to the rear suspension  16  and can receive no power from the engine  18 . With reference to  FIG. 2 , the rear wheels  22  ( FIG. 1 ) can be removed from the vehicle  14  leaving portions of the rear suspension  16  exposed. With reference to  FIG. 3 , the vehicle  14  can include the retrofit or original equipment electric wheel motor assemblies  10  that can couple to the rear suspension  16 . The rear wheels  22  can couple to the electric motor assemblies  10 , respectively. 
     While the vehicle  14  is illustrated as having a front wheel drive powertrain that serves as the primary source of propulsive power and the hybrid electric all wheel drive system  12  that provides supplemental power to the rear wheels of the vehicle  14 , it will be appreciated that the all wheel drive system  12  can also be implemented so that the electric motor assemblies  10  can drive the front wheels  20 , while the rear wheels  22  can be driven by the engine  18 . The all wheel drive system  12  can also be independent of a certain type of engine in the vehicle  14  such that the engine  18  can be an internal combustion engine, a hybrid configuration, an electric motor, other suitable power sources and combinations thereof. 
     With reference to  FIGS. 4 and 5 , one of the electric motor assemblies  10  is shown that can be retrofit or can be originally assembled to a suspension component  24  that can be part of the rear suspension  16  ( FIG. 3 ). With reference to  FIG. 6 , the electric wheel motor assembly  10  can include an electric motor  26 , a planetary gearset  28  and a wheel spindle  30 . The planetary gearset  28  can include a sun gear  32 , a ring gear  34  and a plurality of planet gears  36  that can be rotatably supported on a planet carrier  38 . It will be appreciated that when a first component or an input of the planetary gearset  28  is driven and a second component of the planetary gearset  28  is held rotationless, a third component or an output of the planetary gearset  28  can spin at an output rotational velocity that is less than the input rotational velocity. The torque transmitted through the output, however, is greater than the torque received at the input. 
     In the example provided, the sun gear  32  is the input, the ring gear  34  is maintained in a stationary (non-rotating) condition, and the planet carrier  38  is the output; but it will be appreciated that other configurations are possible such that modifications are within the capabilities of one skilled in the art. The ring gear  34  can be formed onto a portion of the wheel spindle  30 , which can be fixedly coupled to the suspension component  24 . The sun gear  32  can be driven by the electric motor  26 . The planet carrier  38  can be driven by the sun gear  32  via the planet gears  36 . Upon activation of the electric motor  26 , the planetary gearset  28  can provide, for example, a gear reduction ratio of about 1:2.64. 
     With reference to  FIGS. 4 and 5 , the electric wheel motor assembly  10  can also include a brake rotor  40  that can couple to a flange portion  42  ( FIG. 7 ) of the planet carrier  38 . With reference to  FIG. 9 , a wheel rim  44  can additionally support a pneumatic rubber tire  46 . The wheel rim  44  can also couple to the flange portion  42  ( FIG. 7 ) with the brake rotor  40  disposed therebetween, as shown in  FIG. 6 . Returning to  FIGS. 4 and 5 , a caliper  48  having brake pads  50  can be mounted to the suspension component  24  and can clamp against the brake rotor  40 . The brake rotor  40  can spin relative to a housing  52  of the electric motor  26  that can also connect to the suspension component  24 . 
     The electric wheel motor assembly  10  can generally be an annular structure symmetrical about the wheel spindle  30 . For purposes of this disclosure and with reference to  FIG. 6 , the following discussion generally begins with a spindle portion  54  of the wheel spindle  30  and proceeds radially outward (upward relative to  FIG. 6 ) toward the electric motor  26 , the brake rotor  40 , etc. 
     With reference to  FIGS. 6 ,  7  and  8 , the wheel spindle  30  can include the spindle portion  54 , a spindle bridge portion  56  and a ring gear portion  58 . The spindle portion  54  can define a central axis  60  about which the brake rotor  40  and portions of the planetary gearset  28  can spin. The spindle bridge portion  56  can extend in a generally perpendicular direction between the spindle portion  54  and the ring gear portion  58 . The ring gear portion  58  can be concentric with the spindle portion  54  and can be generally parallel to the central axis  60 . The ring gear portion  58  can be associated with the planetary gearset  28  and can include a plurality of gear teeth  62  that can engage gear teeth  64  on the planet gears  36 . The wheel spindle  30  can be fixedly coupled to the suspension component  24  and, therefore, the ring gear portion  58  can remain rotation less. 
     A first wheel bearing B 1  and a second wheel bearing B 2  can be disposed between the spindle portion  54  and the planet carrier  38  to permit the planet carrier  38  to rotate about the wheel spindle  30 . The first wheel bearing B 1  can be disposed in a position that is outboard of the second wheel bearing B 2 . Outboard can refer to a direction away from the suspension component  24  to which the wheel spindle  30  is attached. Inboard can refer to a direction toward the suspension component  24 . The first wheel bearing B 1  can establish a first imaginary plane PL that can extend in a radial direction outwardly from the first wheel bearing B 1  (i.e., radially away from the spindle portion  54 ). The second wheel bearing B 2  can establish a second imaginary plane PR that can extend in a radial direction outwardly from the second wheel bearing B 2 . The first imaginary PL and the second imaginary plane PR can be generally perpendicular to the central axis  60 . 
     A sun gear bearing B 3  can be disposed between the planet carrier  38  and the sun gear  32  and can permit the sun gear  32  to rotate relative to the planet carrier  38 . The sun gear  32  of the planetary gearset  28  can also be disposed between the first imaginary plane PL and the second imaginary plane PR. Moreover, the sun gear bearing B 3  can be disposed between the first imaginary plane PL and the second imaginary plane PR of the first wheel bearing B 1  and the second wheel bearing B 2 , respectively. 
     Further, the first wheel bearing B 1  can have an outboard face B 1 O (i.e., a face farthest from the suspension component  24 ), while the second wheel bearing B 2  can have an inboard face B 2 I (i.e., a face closest to the suspension component  24 ). The outboard face B 1 O of the first wheel bearing B 1  can be associated with a third imaginary plane PLO. The inboard face B 2 I of the second wheel bearing B 2  can be associated with a fourth imaginary plane PRI. The sun gear  32 , the planet gears  36  and/or the sun gear bearing B 3  can be contained between the third imaginary plane PLO and the fourth imaginary plane PRI. 
     The planet carrier  38  can be formed from a first carrier member  100  and a second carrier member  102 . The first carrier member  100  can rotatably support the planet gears  36 . The second carrier member  102  can couple to the wheel rim  44  ( FIG. 9 ) and/or the brake rotor  40 . The first carrier member  100  can include a hub portion  104  and a flange portion  106 . The flange portion  106  can include three apertures  108 . Each of the apertures  108  can receive a pin  110  that can rotatably support one of the planet gears  36 . 
     Each planet gear  36  can have a plurality of gear teeth  64  on an outer periphery  112 . A needle bearing  114  can be disposed between each planet gear  36  and its respective pin  110 . A pair of thrust bearings  116  can be disposed on each side of each of the planet gears  36 . While three planet gears  36  are illustrated in  FIG. 7 , additional planet gears can be rotatably coupled to the flange portion  106  of the first carrier member  100 . Moreover, while straight toothed gears (e.g., spur gears) are illustrated, it will be appreciated that gears with other tooth forms (e.g., helical) and/or other suitable types of gears can be used. 
     The second carrier member  102  can include a flange portion  118  and a hub portion  120 . The hub portion  120  of the second carrier member  102  can couple to the hub portion  104  of the first carrier member  100  and can form a fixed (i.e., rotationless) connection between the first carrier member  100  and the second carrier member  102 . The flange portion  118  of the second carrier member  102  can have a plurality of threaded holes formed thereon to receive respective threaded fasteners, such as threaded studs (F) that can extend outwardly from the flange portion  118 . Whether using threaded studs (F) or threaded bolts, the brake rotor  40  and the wheel rim  44  can couple to the flange portion  118  of the second carrier member  102 . 
     The electric motor  26  can include a rotor  122  and a stator  124 . The rotor  122  of the electric motor  26  can generally include a sun gear portion  126 , a bridge portion  128 , and a magnet portion  130 . The sun gear portion  126  can be concentric with the magnet portion  130  and can be generally perpendicular to the bridge portion  128 . The bridge portion  128  can extend between and connect the sun gear portion  126  and the magnet portion  130 . The bridge portion  128  can include an annular groove  129  that can receive portions of the pins  110  that rotatably support the planet gears  36 . The sun gear portion  126  can include a plurality of gear teeth  132  and can form the sun gear  32  of the planetary gearset  28 . To that end, the sun gear portion  126  can meshingly engage with the planet gears  36 . The magnet portion  130  can extend from the bridge portion  128  and can hold one or more magnets  134  that can form an additional annular structure around the rotor that can be electrically associated with the electric motor  26 . 
     A plurality of electric windings  136  can be connected to the housing  52  of the electric motor  26  and can at least partially form the stator  124  of the electric motor  26 . The housing  52  of the electric motor  26  can be fixedly coupled to the suspension component  24  along with the wheel spindle  30  having its ring gear portion  58 . As voltage is applied to the electric motor  26 , the input torque can be delivered to the planetary gearset  28  via the sun gear portion  126  of the rotor  122 . Because the stator  124  and the ring gear portion  58  of the wheel spindle  30  are maintained in a non-rotating condition (i.e., remain rotationless) in the example provided, the electric motor can drive the planet carrier  38  via the planet gears  36 . 
     The housing  52  of the electric motor  26  can contain the plurality of electric windings  136  that can form the stator  124  of the electric motor  26 . The windings  136  can include a suitable copper wire winding pattern. The windings can remain rotationless within the housing  52  but the magnets  134  can be coupled to the magnet portion  130  of the rotor  122  and can be generally opposite the windings  136  and form an air gap therebetween. The magnets  134  of the rotor  122 , therefore, can spin relative to the windings  136 , when voltage is applied to the electric motor  26 . 
     The housing  52  of the electric motor  26  can include a first seal S 1  and a second seal S 2 . The first seal S 1  can seal the rotor  122  to the housing  52 . The second seal S 2  can seal the rotor  122  to the wheel spindle  30  at a location that can be near the spindle bridge portion  56  and the ring gear portion  58 . As such, the first seal S 1  and the second seal S 2  can provide a seal (e.g., a lubrication seal) between the planetary gearset  28  and the plurality of windings  136  of the electric motor  26 . The windings  136  can be disposed a predetermined distance away from the plurality of the magnets  134  to insure the air gap therebetween. 
     A third seal S 3  can seal the sun gear bearing B 3  to maintain the lubrication for the sun gear bearing B 3 . A fourth seal S 4  can seal the first wheel bearing S 1  to the hub portion  120  of the second carrier member  102  and to the wheel spindle  30  and, therefore, seal lubrication in the planetary gearset  28  for, among other things, the first and second wheel bearings B 1 , B 2 . 
     A plurality of cooling fins  200  can extend radially outward from the housing  52  of the electric motor  26 . The cooling fins  200  can be exposed to the environment. In this regard, the cooling fins  200  can facilitate heat removal from the electric motor  26 , as heat is dispersed into the surrounding environment. 
     In one aspect of the present teachings and with respect to  FIG. 9 , the brake rotor  40  can contain a plurality of vanes  202  that can be configured to forcefully direct air over the cooling fins  200  on the housing  52 , when the brake rotor  40  spins relative thereto. The electric motor  26  generates heat when it provides torque to drive the planetary gearset  28  and thus drive the wheel rim  44  and tire  46 . When the vehicle  14  is moving, whether there is power to the electric motor  26  or not, the rotation of the tire  46 , and thus the rotation of the brake rotor  40 , can provide forced air or active cooling to the electric motor  26 . In this regard, rotation of the brake rotor  40  can force cooling air from the vanes  202  of the brake rotor  40  over the cooling fins  200  to cool the electric motor  26 . 
     With reference to  FIG. 5 , the brake caliper  48  can be coupled to (or packaged with) the electric wheel motor assembly  10  and can provide a braking mechanism that can slow the brake rotor  40  and thus slow the vehicle  14 . The brake caliper  48  can include a parking brake assembly  300  to further provide parking brake functionality, when the vehicle  14  is on a hill or otherwise. The parking brake assembly  300  can include an arm  302  and a lever  304  that can be biased in a first position by a spring  306 . The arm  302  can hold a brake cable  308  from which an actuator line  310  can extend. The actuator line  310  can pass through the arm  302  and can be held by the lever  304 . By pulling on the actuator line  310 , e.g., via a brake lever (not shown) in the vehicle, the lever  304  can be drawn toward the arm  302  and can extend a piston (not shown) in the brake caliper  48  toward the brake rotor  40 . As the force on the brake cable is released, the lever  304  can return to an initial position away from the arm  302 , urged by the spring  306 . The parking brake assembly  300  can then release the piston (not shown) to move away from the brake rotor  40 . 
     In one aspect, the suspension component  24  to which the electric wheel motor assembly  10  can couple can be a wheel bearing mount  400  that can be coupled to a spring pocket  402 . A brace  404  can further secure the electric wheel motor assembly  10  to the wheel bearing mount  400 . A spring seat  406  can be coupled to the spring pocket  402  and can receive, for example, a spring (not shown) that can suspend the electric wheel motor assembly  10  from the vehicle  14 . A control arm  408  can couple to the spring pocket  402  and can further couple to other portions of the vehicle body  14   a  ( FIG. 3 ) via a bushing sleeve  410 . In addition, a twist beam mounting plate  412  can couple to the control arm  408 . The wheel bearing mount  400  can extend through a back cover  68  ( FIG. 7 ) of the housing  52  of the electric motor  26  and can couple to the wheel spindle  30 . It will be appreciated that the hybrid electric all wheel drive system  12  ( FIG. 3 ) need not rely on any specific vehicle suspension configuration and further need not rely on access to a transmission or exhaust tunnel. In this regard, the all wheel drive system  12  can be implemented on or with any type of suspension. 
     In accordance with one aspect of the present teachings and with reference to  FIG. 3 , the hybrid electric all wheel drive system  12  can provide a part time drive to the rear wheels  22  of the vehicle  14 . Myriad situations can benefit from drive torque delivered to the rear wheels  22 , such as, but not limited to, a situation requiring sudden acceleration. In this regard, an engine computer  500  and/or an electric all-wheel drive module  502  can detect that a driver is requesting more power. The engine computer  500  and/or the electric all-wheel drive module  502  can then activate the all wheel drive system  12  to provide additional torque to the real wheels  22 , while the engine  18  of the vehicle  14  can provide torque to the front wheels  20  via a suitable drivetrain  504 . The electric all-wheel drive module  502  can regulate power directed from a battery  508  to the driver side electric motor assembly  10   a  and/or to the passenger side electric motor assembly  10   b . In this situation, the torque from both the engine  18  and the all wheel drive system  12  can provide relatively faster acceleration time compared to torque only delivered to the front tires  20 . 
     In a stability control situation, the engine computer  500  and/or the electric all-wheel drive module  502  can detect slip from one of the vehicle wheels  20 ,  22  and can, therefore, provide torque to one or both of the rear wheels  22  to aid in the stability situation. A conventional anti-lock brake system can be employed, for example, to detect slip at each of wheels  20 ,  22 . The electric motor assemblies  10  can be controlled by a control module  512  that can be part of or included with the engine computer  500  and/or the electric all-wheel drive module  502 . The control module  512  can also be resident in other portions of the vehicle  14 . 
     A wheel spindle from a conventional rear wheel assembly can be removed from a wheel bearing mount  510 . When the conventional rear wheel assembly is removed, the brake rotor, wheel rim and brake caliper or brake drum can also be removed with the conventional assembly. The electric wheel motor assembly  10   a ,  10   b  can then be mounted to the wheel bearing mount  510 . Specifically and with reference to  FIGS. 3 ,  5  and  7 , the back cover  68  of the housing  52  can include an aperture  70  sized to receive the wheel bearing mount  400  such that the wheel bearing mount  400  can pass through the housing  52  of the electric motor  26  and couple to the wheel spindle  30 . Moreover, the brake caliper  48  can couple to a flange  72  coupled to the wheel bearing mount  400  and can clamp against the brake rotor  40  when the service brakes (not specifically shown) are engaged. 
     In accordance with one aspect of the present teachings, each of the electric wheel motor assemblies  10  can, after the gear reduction of the planetary gearset  28 , provide drive torque to each of the rear wheels  22 . In particular example provided, each electric wheel motor assemblies  10  can provide a maximum torque of about 250 foot pounds for about sixty seconds. When producing less torque, the electric wheel motor assemblies can be activated for longer periods. It will be appreciated that using the planetary gearset  28  in series with the electric motor  26  can provide the ability to reduce the size of the electric motor  26  because of the mechanical advantage of the planetary gearset  28 . Moreover, because the all wheel drive system  12  can be a part time system, and therefore not full time system, liquid cooling of the electric motor  26  may not be necessary. As such, the all wheel drive system  12  can be a completely air-cooled system. 
     While specific aspects have been described in this specification and illustrated in the drawings, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the present teachings, as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various aspects of the present teachings may be expressly contemplated herein so that one skilled in the art will appreciate from the present teachings that features, elements and/or functions of one aspect of the present teachings may be incorporated into another aspect, as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation, configuration or material to the present teachings without departing from the essential scope thereof. Therefore, it may be intended that the present teachings not be limited to the particular aspects illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the present teachings but that the scope of the present teachings will include many aspects and examples following within the foregoing description and the appended claims.