Abstract:
A power unit assembly comprises a pair of mirrored axial flux electric motors having a common axis of rotation, each axial flux motor including a rotor disposed on a rotor shaft and at least one stator disposed in operative relationship to said rotor. A common end plate is disposed between each of said pair of axial flux electric motors to provide a common mounting structure, while an output hub is operatively coupled to each rotor shaft of the pair of mirrored axial flux electric motors. Each of the pair of mirrored axial flux electric motors is operatively configured to provide independent speed and torque to each associated output hub.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/116,974, filed on Apr. 5, 2002, from which priority is claimed. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
         [0002]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates generally to a vehicle driveline support assembly and, more particularly, to a vehicle driveline support assembly incorporating a pair of electric motors wherein the driveline support, the pair of electric motors, and a pair of speed reduction transmissions are combined into a single compact power unit with two independent co-axial output shafts which may be independently controlled for speed and torque.  
           [0004]    A variety of driveline support assemblies are known in the art that utilize electric motors to power a driveline or vehicle wheel when accelerating or maintaining driveline motion, or to generate electricity from the driveline&#39;s kinetic energy when decelerating. In the past, these systems have used separate bearings for the electric motor, the driveline support and the speed reduction transmission. However, using separate bearings only adds the cost and weight of the assembly and causes the assembly to be less compact. The present invention solves this problem by reducing the number of bearings required in order to make the driveline support assembly lighter, more compact and less expensive to manufacture.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    Briefly stated, the present invention provides an assembly comprising a pair of electric motors and a pair of speed reduction transmissions within a single electric motor case and a driveline support. Each electric motor comprises a stator and a rotor, wherein the rotor is connected to a rotor shaft. A rotor support bearing rotatingly supports each rotor shaft. A driveline support supports a pair of hubs rotatably attached to the housing by a bearing. A case is attached to the housing and supports each stator and an associated speed reduction transmission. Each speed reduction transmission comprises a sun element, at least two planetary elements and an outer ring element attached to the case. Each rotor shaft is attached to a hub through an associated speed reduction transmission. Finally, each rotor shaft, speed reduction transmission, and hub are supported solely by the rotor support bearing, the driveline support bearing, and the outer ring element of the case. A shoulder portion of each rotor shaft abuts an end of the rotor support bearing such that a desired air gap is maintained between each rotor and associated stators.  
           [0006]    The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0007]    In the accompanying drawings which form part of the specification:  
         [0008]    [0008]FIG. 1 is a section view of an integral wheel bearing and axial flux motor having one stator;  
         [0009]    [0009]FIG. 2 is a perspective view of a rotor of an axial flux electric motor shown in FIG. 1;  
         [0010]    [0010]FIG. 3 is a section view of the rotor of FIG. 2 along line A-A;  
         [0011]    [0011]FIG. 4 is a perspective view of a stator of an axial flux electric motor shown in FIG. 1;  
         [0012]    [0012]FIG. 5A is a front plan view of the stator of FIG. 4, including windings and an attached case;  
         [0013]    [0013]FIG. 5B is a front plan view of the stator of FIG. 4, including an alternate simplified winding arrangement;  
         [0014]    [0014]FIG. 6 is a section view of an integral wheel bearing and axial flux motor having two stators;  
         [0015]    [0015]FIG. 7A is a section view of a pair of combined axial flux motors, each having one stator according to an embodiment of the present invention;  
         [0016]    [0016]FIG. 7B is an enlargement of section  7 B, shown in FIG. 7A;  
         [0017]    [0017]FIG. 8A is a section view of a pair of combined axial flux motors, each having two stators according to an embodiment of the present invention; and  
         [0018]    [0018]FIG. 8B is an enlargement of section  8 B, shown in FIG. 8A; 
     
    
       [0019]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.  
         [0021]    The present invention comprises an integral wheel support, planetary transmission and electric motor assembly requiring only two support bearings: a wheel support bearing and a rotor support bearing. Referring to FIG. 1, the assembly  10  comprises a wheel bearing  12  of conventional design. The wheel bearing  12  comprises a housing  14  and a hub  16 . Located between the housing  14  and the hub  16  are two rows of tapered rollers  18  that allow the hub  16  to rotate within the housing  14 . While tapered rollers are shown and preferred, other types of rollers may be used without departing from the scope of the present invention. The hub  16  may be attached to a wheel (not shown) with lugs  20 . The bearing is a package wheel bearing that has all clearances preset upon assembly.  
         [0022]    The hub  16  further defines a splined interior bore  22  for accepting a splined shaft  24 . The splined shaft  24  extends from a planetary carrier  26  of a conventional gear drive planetary transmission. The planetary carrier  26  is rotatingly attached to three planetary gears  28  by bearings  38 . The planetary gears  28  mesh with a stationary outer ring gear  32  formed on an inner surface of a planetary transmission case  30 . The planetary transmission case  30  is attached to the wheel bearing  12  by fasteners  34 . The planetary transmission case  30  further defines a vent bore  36 .  
         [0023]    A sun gear  40  meshes with all three planetary gears  28 . The sun gear  40  defines a center bore  42  for receiving a rotor shaft  44 . A key  46  prevents relative rotation of the sun gear  40  and the rotor shaft  44 . The rotor shaft  44  is rotatingly supported within a motor case  47  by a rotor bearing  48 . The rotor bearing  48  comprises two rows of tapered rollers  50  between inner races disposed on the rotor shaft  44 . Between a first shoulder  52  of the rotor shaft  44  and the sun gear  40  is located a sun gear spacer  54  which locates the sun gear  40  within the planetary gears. Between a second shoulder  56  of the rotor shaft  44  and the rotor bearing  48 , is an air gap washer  58 . By controlling the thickness of the air gap washer  58 , the axial position of the rotor shaft is manipulated and thus an air gap between a rotor  60  and stator  62  is adjusted. The stator  62  is attached to the motor case  47 , and the rotor  60  is attached to the rotor shaft  44 .  
         [0024]    Referring to FIG. 2 and FIG. 3, the rotor may be made from low carbon steel. The rotor  60  has several permanent magnets  72  attached by an acrylic adhesive, such as Loctite Multibond acrylic adhesive available from the Loctite Corporation, Rocky Hill, Conn. The magnets  72  are spaced apart by nonmetallic spacers  74 . The magnets  34  are preferably neodymium-iron-boron (Nd—Fe—B) type permanent magnets and the number of magnets determines the number of poles of the motor (i.e. if twelve magnets are adhered to the rotor, the motor has twelve poles). The magnets  72  are attached to the rotor  60  with their north-seeking faces and south-seeking faces outwardly arranged in an alternating sequence.  
         [0025]    Referring to FIG. 4, the stator  62  comprises a plurality of laminations. More specifically, the stator  62  comprises laminations of ferrous material, preferably iron, that are separated by non-conducting, non-ferrous layers to minimize losses due to eddy currents of magnetic flux within the stator  62 . The stator  40  further comprises thirty-six slides  76  defined by thirty-six grooves  78 . As shown in FIG. 5A, conductive windings  80  comprising loops of insulated copper wire are placed within the grooves  78  and around the slides  76  such that each winding  80  forms a loop surrounding two intervening grooves  78 . Another winding  80 ′ is placed within a groove  78  a portion of which surrounded by the first winding  80  and a groove  78  adjacent the first winding  80 . In this manner, windings  80  are placed within the grooves  78  of the stator  80  until every groove  78  has been fitted with a winding  80 . FIG. 5B illustrates an alternative simplified winding pattern using a reduced quantity of material.  
         [0026]    Referring back to FIG. 1, the rotor shaft  44  further comprises a rotor shaft extension  66  that extends within a bore of a resolver  68 . An end plate  64  is attached to the motor case  47  and supports the resolver  68 . A cover plate  70  covers a bore within the end plate  64  that allows access to the resolver  68  without removing the end plate  64 .  
         [0027]    The motor operates in a conventional manner for a brushless axial flux induction motor, and changing the thickness of the air gap washer  58  changes the air gap of the axial flux electric motor. The motor is controlled by a known electronic controller that adjusts the pulse width and frequency of current traveling through the wire loops of the stator in order to control the torque and speed of the motor and maintain current within motor limitations.  
         [0028]    An alternate embodiment  100  shown in FIG. 6 includes a rotor  132  having magnets  134  affixed to opposite sides of the rotor  132  by an adhesive. Adjacent magnets  134  on opposite sides of the rotor are aligned so that their opposite poles face outwardly from the rotor  132 . In addition to the stator  40  and the windings  44  is a second stator  140  and a second plurality of windings  144  wound within the second stator  140 . By adding the second stator  140  and windings  144 , the output of the axial flux motor is nearly doubled.  
         [0029]    In a compact power unit embodiment  200 , shown in FIGS. 7A and 8A, a pair of axial flux motor assemblies  10  or axial flux motor assemblies  100 , as described in detail above, are coupled together in mirrored or back-to-back alignment with a common end plate  202 . The common end plate  202  includes an axial bore  204 , shown in FIGS. 7B and 8B for supporting a pair of resolvers  68  and for receiving the rotor shaft extension  66  from each rotor shaft  44  in the compact power unit  200 . Stator cooling connections  206  are secured to each motor case  47  to carry out heat generated by the windings  80  during heavy duty cycles.  
         [0030]    The compact power unit  200  provides two identical independent output hubs  16 , having a common axis of rotation A-A, onto which a pair of drive axles or wheels (not shown) may be secured. The compact power unit  200  is suitable for mounting at an axle centerline of a vehicle to drive either directly or indirectly, a pair of vehicle wheels on opposite sides of the vehicle. Each assembly  10 ,  10  or  100 ,  100  in the compact power unit  200  is independently controllable as described above, to regulate speed and torque at each independent output hub  16 .  
         [0031]    Independent speed and torque control for opposite wheels is desirable when road surface variations at each wheel produce different coefficients of friction, as the lower wheel driving torque of the two wheels limits the effective driving torque to twice the lowest wheel torque. The application of torque in excess of the lowest wheel torque level results in spinning of the vehicle wheel. Accordingly, when driving in uneven terrain having varied surface coefficients of friction, it is highly desirable to match the driving power supplied to each individual driven wheel to different driving requirements. Driving the driven wheels of a vehicle at different speeds and individually controlling the driving torque when traveling on a slippery surface or around a curve has the distinct advantages of avoiding vehicle deformation, reducing tire wear, attaining improved traction, and enhancing vehicle dynamic stability.  
         [0032]    In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.