Abstract:
A high misalignment wheel drive includes a spline drive with external crown spline for rotation around an axis of the axle shaft and a drive plate for rotation about a drive plate axis, the drive plate including an internal spline for engaging the external crown spline in a pivotable splined connection to allow the spline drive to rotationally drive the drive plate while the drive plate axis is non-aligned with respect to the axle axis by up to an angle α. First and second thrust faces are positioned with respect to the spline drive to rotate with the spline drive and define the angle α between which third and fourth thrust faces, positioned with respect to the drive plate to rotate with the drive plate and for engaging the first and second thrust faces respectively, can move.

Description:
This application claims priority to U.S. provisional patent application 61/814,607 by the present inventor entitled High Misalignment Wheel Drive and filed Apr. 22, 2013, the entirety of which, including the Appendix thereto, is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an automotive axle assembly, and particularly to a rear axle assembly for a rear drive racing automobile. 
     BACKGROUND OF THE INVENTION 
     A dependent rear axle assembly is an automotive type differential where both rear wheels are solidly connected to a housing to move up and down with the housing. In an independent or semi-independent type of rear suspension, the rear wheels can move up and down with respect to the differential housing. A floating hub is an axle housing hub to which the wheel is attached that directs the resulting force from vehicle weight and cornering forces to the axle housing. A flange type axle assembly attaches the wheel directly to the axle flange, which can result in wheel separation in the event of axle shaft failure. 
     In a typical rear wheel drive automobile having a dependent rear suspension, the axle assembly is mounted to be generally parallel to the ground and the wheels and wheels hubs are mounted perpendicularly to an axis of the axle assembly, with the wheels rotating about the same axis as the axle shaft. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a drive assembly for use with an axle assembly that allows effective and durable power transmission between a driven axle shaft and a wheel hub which rotates about a different axis than an axis of rotation of the axle shaft, or in other words, the wheel hub is oriented at other than 90° with respect to the axle shaft. 
     In one embodiment, a high misalignment wheel drive, includes: a spline drive combinable with an axle shaft for rotation around an axis of the axle shaft, the spline drive including an external crown spline; a drive plate for rotation about a drive plate axis, the drive plate including an internal spline for engaging the external crown spline in a pivotable splined connection to allow the spline drive to rotationally drive the drive plate while the drive plate axis is non-aligned with respect to the axle axis by up to an angle α, the drive plate including a mounting arrangement for mounting to a driven wheel. A first thrust face is positioned with respect to the spline drive to rotate with the spline drive. A second thrust face is positioned with respect to the first thrust face to rotate with the spline drive. A third thrust face is positioned with respect to the drive plate to rotate with the drive plate for engaging the first thrust face. A fourth thrust face is positioned with respect to the drive plate to rotate with the drive plate for engaging the second thrust face. The first thrust face and second thrust face define an angle of movement between which at least one chosen from the third thrust face and the fourth thrust face can pivot with respect to the spline drive between a position where the third thrust face engages the first thrust face, and a position where the fourth thrust face engages the first thrust face. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further objects and advantages of this invention will become more apparent and more readily appreciated from the following detailed description of the present invention, taken in conjunction with the accompanying drawings, of which: 
         FIG. 1  shows a rear elevational view of a dependent suspension axle; 
         FIG. 2  shows an end elevational view of an embodiment of the drive assembly of the present invention; 
         FIG. 3  shows a sectional view of the drive assembly of  FIG. 2  taken along section line  3 - 3 ; 
         FIG. 4  is an exploded view of the drive assembly of  FIG. 2 ; 
         FIG. 5  shows a sectional view of an embodiment of the drive assembly of the present invention; and 
         FIG. 6  shows a perspective view sectional view of the drive assembly of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upwardly”, “downwardly”, and the like, are words of convenience and are not to be construed as limiting terms. 
     In certain types of automotive racing which use a dependent rear axle housing suspension for rear wheel drive, attempts are being made to mount the wheels and wheels hubs at other than a perpendicular angle with respect to the axle housing to improve traction. That is, the wheels and wheel hubs can be mounted at a camber with respect to the axle assembly. In instances where the cars turn both left and right on the track, both left and right wheels can be given a camber, usually negative, with respect to the axle to improve traction. As is seen in  FIG. 1 , a dependent suspension axle  10  has an axis  12  which is oriented generally parallel with the ground (track)  14 . The axle  10  is shown here as a floater type axle but can be other types as well. However, hub mount  16  and wheel/tire  18  are not oriented perpendicular to the axis  12  but rotate about an axis  15  which is at an angle α with respect to axis  12 . The wheel  18  has a negative camber with respect to the axle  10 . Although the dependent suspension axle  10  can be mounted at the rear of the auto in a rear wheel drive orientation, the axle  10  can also be mounted at a front of the auto in a front wheel drive or four/all wheel drive situation. The angle α can be any desired angle but is typically a few degrees, with one preferred embodiment being approximately 3.5°, although α can be larger or smaller than this angle. Although there is a gap shown between the tire  18  and the ground  14 , this is shown just for clarity of explanation. The flexibility of the tire will conform the tire to the ground and remove the gap. 
     In other instances, such as stock car racing on oval tracks where the cars always turn in the same direction, tires of different circumferences (diameter) can be used on the rear driven axle to compensate for the corner turning radiuses that require the tire on the larger (outside) radius to travel a greater distance than the tire on the smaller (inside) radius. In this situation, the axle housing can actually be angled with respect to the track surface, so that axis  15  is parallel to the track surface  14 , while axis  12  is at the angle α with respect to the track surface  14 . To realign the orientation of the tire with respect to the track surface  14 , the larger diameter tire is given positive camber with respect to the axle housing while the smaller diameter tire is given negative camber with respect to the axle housing. In this manner, even though the axle housing is angled with respect to the track surface because of the different diameter tires, the tires can maintain a flat orientation to the track surface. In such situation, the positive camber given to the larger tire can be equal in magnitude to the negative camber given to the smaller diameter tire, although such is not required and may be different in some cases. 
     In a further aspect, the positive/negative camber situation discussed in the paragraph above can be combined with some element of camber as discussed in the paragraph preceding the paragraph immediately above, to improve traction of the tires. 
     The different tire diameters and/or the angle α can be changed for desired/improved performance depending on the car, track, length of track, banking of track, other track conditions and other factors. 
     The present invention can be used in any of these instances, where the wheel rotates about a different axis than the axis of rotation of the axle shaft, and with any type of axle assembly, including flange, floater and live, as depicted in the Appendix, as well as other types of axle assemblies. 
       FIG. 2  shows an end view of an embodiment of the drive assembly  20  of the present invention. Drive assembly  20  includes drive plate  22  having a plurality of mounting bores  24 . Drive plate  22  can be mounted to a floater hub of the type shown in the Appendix. In such a case, the floater spindle is oriented such that its axis  15  is at the angle α with respect to the axle axis  12 , with the floater hub rotating on the floater spindle about the spindle axis  15 . 
     A cap  26  is mounted to drive plate  22  with a plurality of screws  28  and with oil seal  30  maintains a liquid tight lubricant reservoir  32  in an interior of the drive plate  22 . See  FIGS. 3-4 . A threaded plug  34  is provided in the cap  26  for filling and checking lubricant. Screws  38  are sealed with O-rings  29 . An inner seal  50  is positioned on an inner side of the drive plate  22  and retained by a retaining ring  52  to seal the lubricant reservoir  32  on the inner side of the drive plate  22 . The inner seal can engage a spline drive  40 , the axle shaft  36  or another component to maintain the seal. The lubricant reservoir allows the use of oil instead of grease, which provides superior lubrication for the drive assembly and particularly the spline drive discussed below. 
       FIG. 3  shows a sectional view of the drive assembly of  FIG. 2  taken along section line  3 - 3 . An axle shaft  36  is rotationally mounted in the axle  10  to rotate about axis  12 . The axle shaft  36  includes a splined end  38  to receive a spline drive  40 . The spline drive  40  has an internal spline  42  for mating with the splined end  38  and an external crown spline  44  to mate with an internal spline  46  of drive plate  22 . Because the axle shaft  36  rotates about axis  12  but the drive plate  22  rotates about an axis  15  being at the angle α with respect to the axis  12 , accommodation must be made for this between the spline drive  40  and the internal spline  46 . To accommodate this, the external crown spline  44  is convexly radiused. In this manner, as the drive plate  22  rotates with the axle shaft  22  but about different axes, a continuous sliding motion is allowed between the spline connection of external crown spline  44  and internal spline  45  because of the radius of external crown spline  44 . As can be seen in  FIG. 3 , the connection between the external crown spline  44  and the internal spline  46  is positioned axially inwardly with respect to the drive plate  22  at the bottom of  FIG. 3  than at the top of  FIG. 3 . As the bottom portion of the drive plate  22  rotates around to the top, the engagement between the external crown spline  44  and the internal spline  46  will be sliding axially outwardly with respect to the drive plate  22  until it reaches the outward position shown at the top of  FIG. 3 . Retaining ring  48  engages axle shaft  36  to retain the spline drive  40  on the axle shaft  36  and keeps the assembly connected as one unit. The spline drive  40  is replaceable upon shearing the retaining ring  48  to allow replacement of the spline drive without requiring replacement of the axle shaft  36 . In one embodiment, the retaining ring  48  is aluminum and is positioned internally of the spline drive  40  and the spline drive can be removed by shearing the aluminum retaining ring with a press. Different shear strength materials can be used in the retaining ring  48  to change the strength of the attachment. 
     An inner thrust button  54  is rotationally fixed on the end of axle shaft  36  by retaining pins  56  engaging bores  58  in the axle shaft and bores  60  in the inner thrust button  54 . An outer thrust button  62  has bores  64  for also receiving the retaining pins  56  to be rotationally fixed to the axle shaft  36 . A retaining bolt  66  passes through center bore  68  in the outer thrust button  62  and center bore  70  in inner thrust button  54  to engage threaded bore  72  in axle shaft  36  to axially retain the thrust buttons on the axle shaft  36 . One or both of the thrust buttons includes an axially extending flanged surface  74  that creates a gap  76  between the thrust buttons. 
     A thrust plate  78  is adapted to be positioned in the gap  76  when the thrust buttons are being mounted to the axle shaft  36  by retaining bolt  66 . The thrust plate  78  has a plurality of outer bores  82  for engaging the screws  28  to rotationally fix the thrust plate  78  with respect to the drive plate  22 , although another mechanism could be used for such fixation. The thrust plate  78  includes a center bore  80  which is sufficiently large to clear the flanged surface  74  and retaining pins  56  to allow the thrust plate to rotate with respect to the thrust buttons and axle shaft  36 . 
     As is best seen in  FIG. 3 , the thrust plate  78  axially retains the axle shaft  36  while allowing the sliding movement of the spline connection (described above) as the drive plate  22  and axle shaft rotate about their different respective axes. The inner thrust button  54  has a thrust face  84  for engaging an inner thrust face  86  of thrust plate  78 . Outer thrust button  62  has a thrust face  88  for engaging outer thrust face  90  of thrust plate  78  positioned on an opposite side of thrust plate  78  from inner thrust face  86 . The thrust face  84  and inner thrust face  86  are configured to be generally aligned at one portion of the rotation circle where the splined engagement is outward-most on the drive plate  22  (the top in  FIG. 3 ) while the thrust face  88  and outer thrust face  90  are configured to be generally aligned at an opposite portion of the rotation circle where the splined engagement is inward-most on the drive plate  22  (the bottom in  FIG. 3 ). An axial clearance  92  can be provided between the dimensions of the gap  76  and the thrust faces of the thrust plate  78  as is desired to provide for clearance and thermal expansion. In one embodiment, that clearance gap  92  is approximately 0.034 inch but any desired gap can be provided. Mating angles of the thrust face pairs  84  to  86  and  88  to  90  can be set to correspond to angle α to maintain maximum thrust surface contact area. The present invention applies to any angle α or range of angles α within the range 0-90° inclusive, although angles of a will typically be within 0-10°, and more typically within 0-3.5°. 
       FIG. 5  shows an embodiment of the drive assembly.  FIG. 6  shows a perspective sectional view of the embodiment of  FIG. 5 . Here the angle α is shown at 0°, although the angle α can be any angle discussed above. 
     The cap  26  includes a centrally located threaded bore  102  into which the oil fill plug  34  can be threaded. Oil fill plug  34  can be magnetized or have a magnetic insert to collect metallic debris from the lubricating oil. An inner oil seal  106  engages the spline drive  40  to maintain an oil tight seal. The oil seal  106  is structured so that it is positioned at a shallower angle to the axle shaft  36  as compared to the oil seal shown in  FIG. 3 . This shallower angle has been found to be beneficial in maintaining the oil sealing engagement as the drive plate  22  rotates with the axle shaft  36  but about different axes to create a wobble motion of the drive plate  22  and oil seal  106  with respect to the spline drive  40 . Spline drive  40  includes an oil seal flange  108  to engage the lip of the oil seal  106 . This oil seal flange  108  provides a stronger oil seal between the oil seal  106  and the spline drive  40  and has been found to be able to maintain an effective oil seal for the reservoir  32  up to approximately 18 psi in the reservoir  32  (caused by heating of the oil and air in the reservoir  32 ). An O-ring  112  is positioned between a flange of axle shaft  36  and spline drive  40  to prevent oil leakage through the spline joint between the axle shaft  36  and the spline drive  40 . 
     Oil can be added to the reservoir  32  through the threaded bore  102 . In one approach, the axle shaft  36  is held vertically such that the bore  102  is located bottom-most with respect to the drive assembly and oil is injected into the reservoir with an injector maintaining a seal with the bore  102 . By holding open a portion of a lip of the oil seal  106 , air in the reservoir  32  is allowed to escape as oil is injected into the reservoir  32  so that the reservoir  32  is entirely filled with oil. This provides the advantage that as the drive assembly heats up during use, and it can reach 250-275° or more, there is no air in the reservoir  32  to expand and force the lubricating oil out of the reservoir between the oil seal  106  and the spline drive  40 . Once the reservoir is filled with oil  32  and all air has been removed from the reservoir  32 , the axle shaft can be inverted so that the threaded bore  102  is upward most. At this point, the oil injector can be removed, the reservoir is topped up with oil and the oil plug  34  reinstalled into the threaded bore  102 . 
     Flange  104  of outer thrust button  62  is drilled for safety wiring the bolt  66 , as is also shown in  FIGS. 3-4 . Screws  110  include externally splined heads and bores for receiving safety wire. 
     Various features of the various embodiments disclosed herein can be combined in different combinations to create new embodiments within the scope of the present invention. 
     REFERENCE NUMBERS 
     
         
           10  dependent suspension axle 
           12  axis 
           14  ground 
           15  axis 
           16  hub mount 
           18  wheel/tire 
           20  drive assembly 
           22  drive plate 
           24  mounting bores 
           26  cap 
           28  screws 
           29  O-rings 
           30  oil seal 
           32  reservoir 
           34  plug 
           36  axle shaft 
           38  splined end 
           40  spline drive 
           42  internal spline 
           44  external crown spline 
           46  internal spline 
           48  retaining ring 
           50  inner oil seal 
           52  retaining ring 
           54  inner thrust button 
           56  retaining pins 
           58  bores 
           60  bores 
           62  outer thrust button 
           64  bores 
           66  retaining bolt 
           68  center bore 
           70  center bore 
           72  threaded bore 
           74  flanged surface 
           76  gap 
           78  thrust plate 
           80  center bore 
           82  outer bore 
           84  thrust face of inner thrust button 
           86  inner thrust face of thrust plate 
           88  thrust face of outer thrust button 
           90  outer thrust face of thrust plate 
           92  axial clearance 
           102  threaded bore 
           104  drilled flange 
           106  inner oil seal 
           108  oil seal flange 
           110  screw 
           112  O-ring