Abstract:
The adjustment of axial free play between the ends of a wheel bearing assembly and a wheel hub and spindle nut of the wheel assembly is achieved by first over-tightening the spindle nut against the wheel hub; secondly, identifying by an indicator gauge between the wheel hub and spindle nut the amount of axial travel of the over-tightened hub on the spindle; thirdly, loosening the spindle nut until an indicator between the hub and spindle nut substantially matches a specified amount of linear travel of the loosened hub; and finally re-tightening the spindle nut by rotating the latter the same axial amount that the hub had traveled after loosening the spindle nut.

Description:
[0001]    This application claims the benefit of Provisional application No. 60/252,326, filed Nov. 22, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to vehicle wheel bearing assemblies, and more particularly to the precise adjustment of axial free end play of the wheel hub and spindle nut at the opposite ends of the tapered bearing assembly.  
           [0003]    The magnitude of free end play at opposite ends of a bearing assembly is an important factor which determines the useful operating life of the entire system. No free end play or excessive bearing pre-load, can result in the seizing and destruction of the assembly, while too much end play, or excessive free end play, can result in shortened bearing life, scored or otherwise damaged axle components, total damage to the entire wheel and axle assembly, shortened tire life, and others.  
           [0004]    It is usual practice to establish axial free end play by tightening the spindle nut to the point of securing the wheel against any rotation, and then loosening the spindle nut to some random and non-reproducible degree to free the hub for rotation, and then to pull and push the wheel laterally, as with a long pry bar, to note the degree of wobble or end play. Readjustment of the spindle nut may be made to reduce or otherwise refine the degree of wobble, but the end result is a range of adjustments that may be acceptable to the person mounting the wheel, but unacceptable for optimum operation of the assembly.  
         SUMMARY OF THE INVENTION  
         [0005]    In its basic concept, this invention provides for the precise and reproducible establishment of zero point taper bearing adjustment by utilizing a spindle nut of known thread pitch with corresponding visibly inscribed circumferential indicia for registration with a visible index mark at the adjacent end of the spindle. Additionally, a dial indicator or other suitable linear measuring instrument, is mounted on or otherwise engages the wheel hub and its indicator adjusted to engage the visible end of the spindle. The dial then adjusted to or otherwise made note of zero. With these installations, axial movement of the spindle by a predetermined measure is known precisely, such as by a predetermined rotation of the over-tightened spindle nut noted by the circumferential indicia and index mark, and by the subsequent movement of the index mark back by a magnitude necessary to match the linear movement of the indicator dial or other instrument.  
           [0006]    It is the principal objective of this invention to provide a method for the precise and reproducible adjustment of zero end play of a vehicle wheel bearing assembly.  
           [0007]    Another important objective of this invention is the provision of apparatus by which to achieve the precise and reproducible adjustment of zero end play of a vehicle wheel bearing assembly.  
           [0008]    A further objective of this invention is to provide apparatus of the class described which is of simplified construction for economical manufacture, maintenance and repair. 
       
    
    
       [0009]    The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying drawings of a preferred embodiment.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a fragmentary vertical cross section of a conventional spindle-mounted hub having mounted thereon means for measuring and adjusting the axial free end play of the taper bearings.  
         [0011]    [0011]FIG. 2 is a front elevation of the spindle nut of FIG. 1 showing the circumferential indicia markings and associated index marker. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    [0012]FIG. 1 illustrates a conventional vehicle wheel assembly on a supporting rotary axle  10  that terminates at its outer end in a reduced diameter section, defined by flange  12 , that forms a wheel-supporting spindle  14 . The outer end portion of the spindle is provided with external threads  16  of a predetermined pitch for establishing the number of revolutions per inch of axial movement  18  of a threaded spindle nut  20  mounted for rotation on the spindle threads.  
         [0013]    The spindle  14  is arranged to support inner and outer tapered bearings  22  and  24 , respectively, which serve to support the hub  26  of a vehicle wheel  28 . The wheel is secured to hub  26  in usual manner, to allow rotation of the wheel.  
         [0014]    In accordance with this invention, the zero point determination of axle free end play and precision bearing pre-load adjustment is accomplished by measuring travel of the wheel hub  26  in relation to spindle  14 , from a known stressed zero end play position. The bearings first are over-tightened, stressing the hub and spindle assembly such that no free end play exists. Compression and stretch elasticity of all related wheel end components, including spindle  14 , hub  26 , taper bearings  22  and  24  and the bearing lubricating film, all are known constants. Stress is measured either in foot-pounds of torque or in pounds per square inch of pressure as measured between the communicating faces of spindle nut  20  and the outer bearing  24 .  
         [0015]    In this regard, it is important to note that the unit measure of torque or pressure is not linear in relation to the travel of hub  26  upon spindle  14 . The circumferential indicia  30  (FIG. 2) on spindle nut  20  are spaced apart to closely correlate to the pitch  18  of the spindle screw thread  16  and matching thread of spindle nut  20 . Index marker  32  on the visible end of the spindle  14  registers with the indicia  30  to provide for accurate reading.  
         [0016]    Indicia  30  measures axial travel of the nut  20 , and the axial distance represented by the indicia is twice the axial distance of travel of the wheel hub  26 . The axial distance of travel of hub  26  in relation to spindle  14  is measured by noting the number of indicia  30  on nut  20  in relation to index marker  32  on spindle  14 .  
         [0017]    Additionally, the axial distance of travel of the hub  26  in relation to the spindle  14  is measured by a linear mechanical or electronic instrument. The illustrated mechanical dial indicator  34  is provided with an index marker pin  36  mounted for rotation with shaft  38  secured for rotation on dial indicator housing  40 . The housing, in turn, is secured as by welding  42 , or other suitable attaching means, to bracket  44 . The bracket is secured removably to wheel hub  26 , as by screws, magnets, or other conventional means, to afford normal use of the wheel assembly after end play adjustment has been completed.  
         [0018]    The index marker shaft  38  is secured for rotation with gear  46  which meshes with a rack  48  on reciprocating plunger  50 . The plunger extends slidably through registering openings in housing  40  and bracket  44  and is spring loaded to urge it resiliently against the visible end of spindle  14 . Thus, as the linear distance between the hub  26  and spindle  14  changes the index marker pin  36  registers the change in linear dimension relative to the calibrated linear markings  52  on dial indicator  34 .  
         [0019]    Upon loosening the over-tightened spindle nut  20 , the dial indicator  34  measures the axial travel of the wheel hub  26  in relation to the spindle  14 . The axial plane of the spindle is positioned horizontally, such that compression and stretch elasticity of the over-tightened assembly, combined with the force of gravity, acts upon the hub  26 . As the nut  20  is loosened outwardly, the hub  26  travels axially outward toward the nut  20 . This travel is one-half the distance of travel of nut  20 , so as to maintain the hub centered in the saddle of the inner and outer tapered roller bearings  22  and  24 , respectively.  
         [0020]    In similar manner, the axial travel of hub  26 , as measured by the calibrated markings  52  on dial indicator  34 , is one-half the axial travel of spindle nut  20  and outer bearing  24  as the latter remains in close communication with the nut  20 . The unit measure of the indicia  30  on spindle nut  20  correlates to the screw thread pitch  18  which, for example, may be  12  threads per inch, moving the screw 0.083 inch per full revolution. The spacings between indicia markings  30  may be about two times the same unit measure of indicator  34 , or nearly 0.001 inch. In this example, the spindle nut  20  would have  42  circumferential markings  30 , each representing 0.00198 inch, closely twice the unit of measure of 0.001 inch of indicator  34 . Application of specific incremental rotational adjustment of spindle nut  20  precisely and repeatedly sets the bearings  22  and  24  to the desired axial end play and/or bearing pre-load pressure.  
         [0021]    A typical adjustment procedure involves rotating the wheel hub  26  while the spindle nut  20  is over-tightened such that the inner and outer tapered roller bearings  22  and  24  are pre-loaded. Spinning the wheel  28  permits the outer races of the bearings to work their way up the inclined planes of the tapered roller bearings. The indicator dial  34  is set to zero, and the spindle nut  20  is slowly loosened in the direction toward free axial end play, decreasing the pre-load of the over-tightened bearings. The wheel is rotated back and forth so as to assist the hub  26  in remaining centered in the bearing saddle without friction-caused axial jumps of travel. It is often experienced that the initial origin of travel is difficult to determine, and experience in this art demonstrates that the hub  26  does not begin to move in relation to spindle  14  until stretch and compression stresses relax as true axial end play approaches zero. This exact point is most difficult to discern, but a full increment of hub travel is easy to identify, such as the 0.001 inch of travel. If the dial indicator  34  immediately indicates travel, the procedure is repeated so as to be assured that adjustment is being initiated pre-stressed.  
         [0022]    The full incremental unit of measure, such as 0.001 inch, is the travel of the hub  26 , which is one-half the travel of the outer bearing  24  as the hub sits in the saddle of the bearings. The index mark  30  on the spindle  14  (or it may be an edge of a keyway or other mark), and the nut  20  typically is tightened a full indicia increment to provide a precise mechanical means of adjusting taper roller wheel bearings.  
         [0023]    To summarize, the procedure involved in this invention begins with the first step of over-tightening the spindle nut  20 , the second step of applying a measuring instrument such as dial indicator  34  to measure the axial travel of the hub  26  on the spindle  14 ; the third step of slowly loosening the spindle nut while rotating the wheel  28  until the measuring instrument  34  registers a desired unit of travel, such as 0.001 inch; and the final step of re-tightening the spindle nut  20  by utilizing the visible indicia  30  on the nut and index mark  34  to tighten the nut two times the measured increment of travel of the dial indicator  34  at the third step. At this point the axial free end play of the taper bearings is substantially zero inches. The nut  20  is secured against further rotation by a cotter pin or any other conventional procedure.  
         [0024]    It will be apparent to those skilled in the art that various changes may be made in the size, shape, type, number and arrangement of parts described hereinbefore. For example, the circumferential indicia  30  on the spindle nut  20  may be applied to the visible end of the spindle  14  and the index mark  32  applied to the spindle nut  20  as a reversal of parts. A complete workable, but less precise procedure may be followed by using only one or the other of the indicia marks  30  or dial indicator  36 . The type of dial indicator  34  illustrated may be replaced with a wide variety of linear indicators, including calipers. These and other changes may be made, as desired, without departing from the spirit of this invention and the scope of the appended claims.