Patent Publication Number: US-2006000308-A1

Title: Axle assembly with opposed electric motor carrier

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to an axle assembly that utilizes a plurality of electric motors, and more particularly to an axle configuration which locates the electric motors in an opposed arrangement to the axle.  
      There is an increasing demand for the use of hybrid electric driven and hybrid electric assisted vehicles. Hybrid electric vehicles typically utilize electric motor driven axles, which are often of a multi-axle configuration in military and specialty vehicles systems.  
      The electric motors are typically sized to meet both torque and speed requirements, which may not be the most effective for the operational requirements of such vehicles. Relatively large electric motors are often utilized to meet the torque requirements, which may result in an oversized motor for most operational conditions. Moreover, the relatively large electric motors may be difficult to package in a multi-axle vehicle configuration. Conversely, utilizing a multiple of relatively smaller electric motors may increase complexity and the difficulty of obtaining a proper gear teeth contact pattern.  
      Accordingly, it is desirable to provide a lightweight and compact electric motor driven axle configuration which allows the usage of a multiple of relatively smaller electric motors without greatly complicating obtainment of a proper gear teeth contact pattern.  
     SUMMARY OF THE INVENTION  
      The axle assembly according to the present invention includes a first and a second electric motor which drives a gearbox assembly substantially therebetween. The electric motors drive the gearbox assembly, which drives the vehicle wheels through a first and second axle shaft located along a first axis.  
      The electric motors each include an output shaft which mount a drive gear respectively thereto. Each drive gear is engaged with and drives a single hollow ring gear which drives the axle shafts. The hollow ring gear is positionally fixed within a main housing portion of a housing assembly. Electric motor housing portions are mounted to the main housing portion and each electric motor is mounted to a respective electric motor housing portion.  
      A proper gear teeth contact pattern between the drive gear and the ring gear is obtained by adjusting the electric motor housing portion relative the main housing portion. A shim plate is located between the electric motor housing portion and the main housing portion to axially adjust the drive gear relative the ring gear. To radially adjust the drive gear relative the ring gear, elongated apertures are located through the electric motor housing portion to permit the electric motor housing portion to be shifted relative the main housing portion.  
      The present invention therefore provides a lightweight and compact electric motor driven axle configuration, which allows the usage of a multiple of relatively smaller electric motors without greatly complicating obtainment of a proper gear teeth contact pattern. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
       FIG. 1  is a general perspective view of an exemplary multi-axle vehicle embodiment for use with the present invention;  
       FIG. 2  is a schematic view of an axle assembly of the present invention;  
       FIG. 3  is a sectional top view of an axle assembly of the present invention; and  
       FIG. 4  is a side view of an electric motor housing portion of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIG. 1  illustrates a schematic partial phantom view of a multi-axle vehicle  10  having a body  12  supported upon a frame  14 . The frame  14  preferably includes a pair of main longitudinal members  16 . It should be understood that although a particular vehicle arrangement is disclosed in the illustrated embodiment, other vehicles will benefit from the present invention.  
      A multiple of axle assemblies  20  each includes an axle  22  driven by one or more electric motors  24 . Each axle assembly  20  defines an axis of rotation D substantially transverse the longitudinal members  16  to drive one or more wheels  26 . The electric motors  24  are driven by a prime mover  28 , which is preferably a hybrid electric drive that powers each of the axle assemblies  20  by powering the electric motors  24 . It should be understood, however, that other prime movers such as diesel engines, gas turbines among others will also benefit from the present invention.  
      Referring to  FIG. 2 , a first and a second electric motor  24   a ,  24   b  drive a gearbox assembly  30 , which drives the wheels  26  through a first axle shaft  32   a  and a second axle shaft  32   b  ( FIG. 3 ) located along axis D and contained with a housing assembly  34 . The axle shafts  32   a ,  32   b  preferably drive each set of one or more wheels  26  through an independent suspension system  27   a ,  27   b  (illustrated schematically) however, a rigid axle arrangement will also benefit from the present invention.  
      The electric motors  24   a ,  24   b  are located along axis E, which is substantially perpendicular to axis D. The axle assembly  20  may alternatively be powered by a single electric motor to provide a relatively lighter duty axle assembly for yet another vehicle configuration without major modification to the axle assembly. It should be understood that various combinations of the axle assemblies described herein may be provided to particularly tailor an axle assembly to a particular vehicle in a modular manner.  
      Referring to  FIG. 3 , the electric motors  24   a ,  24   b  each include an output shaft  35   a ,  35   b  which mount a drive gear  36   a ,  36   b  respectively thereto. The drive gears  36   a ,  36   b  are preferably hollow pinion gears which are mounted at least partially over the output shafts  35   a ,  35   b  and are rotationally engaged therewith through splines  37  or the like. That is, the drive gears  36   a ,  36   b  at least partially telescope over the output shafts  35   a ,  35   b    
      Each drive gear  36   a ,  36   b  is engaged with and drives a single hollow ring gear  40  which drives the first axle shaft  32   a . That is, the ring gear is coaxial with axis D and the hollow ring gear  40  is rotationally engaged with the first axle shaft  32   a  through splines  41  or the like. The first axle shaft  32   a  drives the second axle shaft  32   b  through a gearbox  43  such as a differential or the like. The gearbox  43  may additionally include a speed reduction gearbox to provide a relatively lightweight and compact axle assembly, which will benefit from an electric motor of reduced size.  
      The hollow ring gear  40  is positionally fixed within a main housing portion  42  of the housing assembly  34  and mounted within a bearing  44  for rotation about axis D. That is, the hollow ring gear  40  is generally not adjustable and gear teeth contact pattern adjustment is through adjustment of the drive gear  36   a ,  36   b  relative the ring gear  40 .  
      The housing assembly  34  includes an electric motor housing portion  46   a ,  46   b  which is mounted to the main housing portion  42  through fasteners  48  such as bolts or the like. Each electric motor  24   a ,  24   b  is mounted to a respective electric motor housing portion  46   a ,  46   b . Each electric motor housing portion  46   a ,  46   b  includes a generally cylindrical pinion housing portion  50   a ,  50   b  which rotationally supports and at least partially surrounds the drive gears  36   a ,  36   b , respectively. Bearings  52   a ,  52   b  are mounted within the pinion housing portion  50   a ,  50   b  to support the drive gears  36   a ,  36   b . A retainer assembly  54   a ,  54   b  such as a nut and washer is threaded onto an end of each drive gear  36   a ,  36   b  to provide axial retention of the bearings  52   a ,  52   b  and drive gear  36   a ,  36   b  along axis E.  
      Preferably, each pinion housing portion  50   a ,  50   b  mounts an end bearing  56   a ,  56   b  which retains a pinion shaft portion  58   a ,  58   b  which extends from the end of the drive gears  36   a ,  36   b . In other words, each drive gear  36   a ,  36   b  is axial trapped but supported for rotation within the cylindrical pinion housing portion  50   a ,  50   b  between the retainer assembly  54   a ,  54   b , the bearings  52   a ,  52   b , and the end bearings  56   a ,  56   b . An electric motor housing access plate  58   a ,  58   b  is preferably located within the electric motor housing portion  46   a ,  46   b  to provide access, assembly, and maintenance to the retainer assembly  54   a ,  54   b  and the bearings  52   a ,  52   b.    
      The gear teeth contact pattern between the drive gear  36   a ,  36   b  and the ring gear  40  is obtained by adjusting the electric motor housing portion  46   a ,  46   b  relative the main housing portion  42 . Preferably, a shim plate  60  is located between the electric motor housing portion  46   a ,  46   b  and the main housing portion  42  to axially adjust the drive gear  36   a ,  36   b  relative the ring gear  40  along axis E. To radially adjust the drive gear  36   a ,  36   b  relative the ring gear  40 , elongated apertures  62  are located through the electric motor housing portion  46   a ,  46   b  ( FIG. 4 ) to receive the fasteners  48 . That is, the fasteners  48  are threaded into a threaded apertures  64  which are located in the main housing portion  42  while the elongated apertures  62  permit the electric motor housing portion  46   a ,  46   b  to be shifted relative the main housing portion  42 . Shifting of the electric motor housing portion  46   a ,  46   b  and the main housing portion  42  is accommodated by the elongated apertures  62  such that the proper gear teeth contact pattern is achieved. It should be understood that although both electric motor  24   a ,  24   b  are illustrated as mounted along common axis E, each electric motor  24   a ,  24   b  is independently positionable. Achievement of the proper gear teeth contact pattern during assembly of each the drive gear  36   a ,  36   b  may result in the electric motor  24   a ,  24   b  not being arranged along a common axis in practice.  
      Preferably, an access cover (illustrated in phantom at  66 ) is located through the main housing portion  42  to permit inspection and adjustment of the gear teeth contact pattern during assembly of the electric motor housing portion  46   a ,  46   b  and the main housing portion  42 .  
      It should be further understood that various bearing and seal locations are included within the gearbox. One of ordinary skill in the art, with the benefit of this disclosure, will consider the various bearing and seal locations to be an ordinary engineering problem such that intricate details thereof need not be fully discussed herein.  
      The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.