Abstract:
A locking washer for axles on vehicles that prevents a nut from rotational movement relative to the axle. The locking washer includes a sleeve step having central passage with a non-cylindrical section that is rotationally coupled to the axle. The non-cylindrical section may include polygonal lobes or splines that engage a matching shaped portion on the axle. The washer is engaged directly on the shaped portion of the axle instead of the threaded portion of the axle and thereby reduces manufacturing costs and steps by eliminating machining of the threaded portion. The washer being engaged on the shaped portion prevents any relative movements between the axle and the washer from disturbances such as vibration, impact, and rotation.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a locking fastener to prevent the loosening of a threaded fastener in a fastener joint. 
     BACKGROUND OF THE INVENTION 
     Locking washers are commonly used in fastening assemblies to prevent relative motion between the stem and fastened pieces, which may cause a nut to back off the stem, thereby loosening the fastened piece. 
     Vehicle wheel assemblies commonly include an axle shaft supported for rotation by a knuckle and a wheel bearing disposed between the shaft and knuckle. The assembly is commonly secured by a retaining ring. A disc for mounting a wheel for rotation with the axle shaft is then mounted on the shaft. The disc may integrate a brake rotor and hub flanges into one piece. A locking washer slides against the disc and a nut tightens the locking washer against the disc to prevent relative movement between the axle shaft and the disc, which may cause the nut to back off the axle shaft. 
     A variety of locking washers known in the art have been used with vehicle wheel assemblies to prevent nut loosening, including split washers and star washers. One problem with using star or split washers in vehicle wheel assemblies is that during operation of the vehicle, these washers may still be subject to movement. Any relative movement may cause the nut to back off, which in turn may cause the wheel to become detached while the vehicle is in motion. 
     To address these and other deficiencies associated with conventional locking washer configurations, including star or split washers, manufacturers have machined the threaded portion of the axle shaft to create a linear groove extending along its threads. The washer is provided with a spline tang extending into the groove to prevent the washer from rotating relative to the threaded shaft. A similar locking washer uses a flat portion on the inside circumference to lockingly engage a flat plane machined on the external threads. These designs prevent the nut from loosening because the washer cannot rotate around the axle shaft while being subjected to vibration, twisting, expansion, contraction, and other possible movements. However, these designs require additional machining of the threaded portion of the axle shaft. Any extra machining increases manufacturing costs and expense. Moreover, care must be taken in machining the threaded portion of the axle shaft to prevent damage to any threads. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a vehicle wheel assembly having a locking washer and axle shaft configuration that prevents rotational movement of the washer relative to the axle shaft without requiring machining of the threaded portion of the shaft. 
     The locking washer includes a generally flat outboard face against which the nut tightens. The inboard face of the washer includes an indented portion, which defines members that mate with torque transferring members on the axle shaft. The invention is further directed to a locking washer that has a step portion that allows the washer members to engage the torque transferring members of the axle shaft while securely locking the disc onto the axle shaft. 
     Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which: 
         FIG. 1  is a sectional view of a wheel end assembly according to the present invention; 
         FIG. 2  is an exploded perspective view of the wheel end assembly shown in  FIG. 1 ; 
         FIG. 3  is a partial sectional view taken along the line  3 — 3  shown in  FIG. 1 ; 
         FIG. 4  is an elevational view of the locking washer viewed from axially inward of the washer; 
         FIG. 5  is a side sectional view of the locking washer taken along the line  5 — 5  shown in  FIG. 4 ; 
         FIG. 6  is an elevational view similar to  FIG. 4  illustrating an alternative embodiment of the locking washer; and 
         FIG. 7  is an exploded sectional view of the wheel and assembly shown in FIG.  1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     I. Construction 
     A wheel end assembly  10  constructed in accordance with the preferred embodiment is illustrated in FIG.  1 . Conventionally, wheel end assemblies attach a wheel to a vehicle axle  20  and transmit torque from the engine to the wheel. To this end, the wheel end assembly  10  includes an axle support assembly  30 , a disc  50  fixed to the wheel, a locking washer  60 , and a nut  90 . The axle  20  is coupled to the engine of the car through the drive train, passes outward from the center of the car, and is supported for rotation by the axle support assembly  30 . The axle support assembly  30  includes a housing or knuckle  32  that forms a cavity within which is disposed a wheel bearing unit  40  to facilitate rotation of the axle  20  relative to the knuckle  32 . The axle support assembly  30 , wheel bearing unit  40 , and disc  50  are secured to the axle  20  by the locking washer  60  and the nut  90 , as shown in FIG.  1 . 
     In general, inner bearing rings  44  of the wheel bearing unit  40  and the disc  50  rotate with the axle  20  to drive the vehicle wheel. While a variety of axle, bearing unit, and disc configurations may be used to provide the desired rotational coupling, the illustrated embodiment of the axle  20  includes a shaped portion  22  ( FIG. 2 ) disposable within the wheel bearing unit  40  and the disc  50  and configured to rotationally couple the disc  50  to the axle  20 . Notwithstanding the variety of configurations that may be used with the present invention, it is noted that the shaped portion  22  and a cooperating central passage  52  on the disc  50  may provide a friction fit, include cooperating splines (typically twenty-eight to thirty-six splines), or polygonal lobes to rotationally interlock the shaped portion  22  with the disc  50 . It should be appreciated that while a single shaped-section  22  is described herein, separate sections of differing configurations may be used without departing from the scope of the invention defined by the appended claims. The axle  20  and inner wheel bearing rings  44  are illustrated as being frictionally coupled, but a variety of other methods may be used. The axle  20  also includes a threaded portion  24  positioned axially outward of the shaped section  22  and having threads configured to cooperate with the internal threading on the nut  90 . 
     As is best shown in  FIGS. 4 and 5 , the locking washer  60  includes an axially outer face  72 , an inner face  76 , a sleeve  78 , a central hole  74  sized to receive the axle  20 , and a shaped cavity  82  recessed axially from the inner face  76  and communicating with the central hole  74  to define a passage extending through said washer. The cylindrical and inwardly projecting washer sleeve  78  is disposable within a sleeve groove  62  formed in the disc  50  (FIG.  7 ). The shaped cavity  82  is partially defined by a non-cylindrical outer surface  84  having projections  83  configured to match the cross-sectional configuration of the shaped section  22  of the axle  20 . By this arrangement, the washer  60  is rotationally coupled to the axle shaft  20 , thereby preventing any rotational movement of the washer  60  relative to the axle shaft  20 . The outer face  72  may be scored or include other techniques known in the industry to prevent the nut  90  from rotating relative to the washer  60 . 
     While the cross-sectional configuration of the shaped cavity  82  and shaped section  22  may vary, exemplary illustrations are shown in  FIGS. 4-6 . For example,  FIGS. 4 and 5  illustrate a sleeve  78  with radially inwardly extending projections  83  in the shape of the polygonal lobes  85  that interact with similarly configured polygonal lobes  26  on the axle  20 . Another example may be seen in  FIG. 6 , where the radially inwardly extending projections in the shape of splines  88  interact with similarly configured splines on the axle  20 . The use of polygonal lobes  85  allows for ease of manufacturing the shaft  20  and the washer  60 , durability of the lobes  85  throughout the operating life, and ease of assembly in mating the shaft  20 , axle support assembly  30 , disc  50 , and washer  60 . Of course it should be easily recognized by one skilled in the art that the configuration, shape, and design of the inner shaped recess  82 , projections  83 , and outer surface  84  may be formed to interconnect with virtually any non-cylindrical shape or design of the shaped portion  22  on the axle  20 . For example, in the embodiments illustrated in  FIGS. 4-6 , the inner shaped recess  82  completely interconnects, without any gaps, with the shaped portion  22  on the axle  20 . However, the shaped recess  82  does not have to mirror the shaped portion  22  completely, but may contain only a portion that interacts with the shaped portion  22  on the axle  20  to prevent any rotational movement of the washer  60  about the axle  20 . Further, those skilled in the art will appreciate that complete multiple projections are not required for all embodiments of the invention. For example, the inner shaped recess  82  may define only one lobe  84  that interconnects with the shaped portion  22  on the axle. For many embodiments, no more than one lobe  84  may be needed to prevent rotational movement of the washer  60  relative to the axle shaft  20 . 
     The locking washer  60  may be constructed of any suitable material. In the illustrated embodiment the washer  60  is formed from heat-treated steel with a GEOMET coating applied for corrosion resistance. A GEOMET coating is a water-based chromium-free coating widely used in the auto industry to provide resistance to corrosion. Of course, it should be readily apparent that other materials such as a mild steel or aluminum may be used to form the washer. It also should be readily apparent that the coating may be zinc, black oxide, or some other corrosion-resistant material and that the washer  60  may even be formed without any coating. 
     II. Manufacturing Process 
     The manufacturing process for the axle  20 , axle support assembly  30 , wheel bearing unit  40 , disc  50 , and nut  90  are well known in the art. For axles  20  with a polygonal shaped portion  22 , conventional manufacturing processes may be used, such as counter-rotational machining. 
     The locking washer  60  may be formed by a variety of techniques well known in the art for forming washers. In the preferred embodiments, the locking washer  60  may be formed by machining but other processes may be used. When machining the washer, a blank having the size and shape of the washer may be formed. Next, the blank may be machined to form the outer groove  80 , inner shaped recess  82 , and hole  74 . Of course, one skilled in the art should recognize that there is no particular order to machine the washer  60 . Other techniques well known in the art for fasteners that are suitable for fabricating the washer  60  include stamping, powder metallurgy, and cold heading. 
     III. Assembly on a Vehicle 
     The wheel end  10  may be assembled in a manner readily apparent to those skilled in the art. For example, once the axle  20  is interconnected into the vehicle drive train (not shown) and the wheel bearing  40  is placed within the knuckle  32 , the knuckle  32  and bearing unit  40  may be slid onto the axle  20 . The knuckle  32  may then be attached to the vehicle suspension system (not shown) or the vehicle frame (not shown). Next, the disc  50  is rotationally aligned with and inserted onto the shaped axle section  22  and engaged on the lobes  26  or splines. The locking washer  60  is then placed onto the axle  20  with the projections  83  (e.g., washer lobes  85 ) aligned to engage against the shaped portion  22  and prevent rotation of the locking washer  60  relative to the axle  20 . The sleeve  78  of the washer  60  fits within the sleeve groove  62  on the disc  50 . In the illustrated embodiment the sleeve  78  is not in contact with the disc  50 , but the washer  60  contacts the disc  50  at the disc contact surface  86 . The nut  90  is then threaded onto the axle  20  and tightened so that the axle support assembly  30 , disc  50 , and locking washer  60  are all firmly held on the axle  20 . Because the locking washer  60  is engaged with the shaped portion  22  on the axle  20 , it is prevented from rotating or transferring vibrational movements from the disc  50  to the nut  90 , preventing the nut  90  from backing off. 
     The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.