Abstract:
A vehicle wheel assembly includes a vehicle wheel, a disc brake rotor, and a rotatable hub in which the rotor is securely clamped to the hub independently of the clamping of the wheel to the hub providing a desirable rigid coupling of the rotor and wheel without any physical contact between the wheel and rotor. The hub functions as an intermediate member for supporting both the rotor and the wheel while precluding direct contact therebetween to reduce any rotor deformation which might be induced by the more conventional technique of clamping of the rotor between the wheel and the hub.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to disc braking systems and more particularly to a distortion reducing technique for affixing a disc brake rotor to a rotatable wheel hub. 
     2. Description of the Related Art 
     Many motor vehicles include disc brake systems having a circular metal disc brake rotor with opposed braking surfaces that are clamped by brake pads carried by a brake caliper to exert a braking effect. The wheel hub incorporates an anti-friction wheel bearing assembly in which one race of the bearing is coupled to the vehicle suspension and the other rotationally mounts the brake rotor and wheel. Ordinarily the rotating components of the rotor, wheel and hub assembly are manufactured separately and assembled together by a plurality of bolts and lug nuts which clamp the wheel to the hub flange with a so-called hat or mounting flange portion of the rotor clamped therebetween. In order to enhance performance of the braking system it is desired to carefully and accurately control the dimensional characteristics of the rotor braking surfaces as the rotor rotates. The thickness variation of the disc and the lateral run-out or lateral deflection of the surfaces as they rotate needs to be held to minimum tolerances. The desire to control lateral run-out of braking surfaces of a disc rotor are well known and rotor manufacturing techniques have been improved to reduce such run-out. 
     For example, U.S. Pat. No. 5,988,761 teaches a wheel end hub assembly for a motor vehicle incorporating mechanical retention features which accurately and positively orient the motor vehicle brake component, such as a disc brake rotor or brake drum with respect to its wheel hub. With this approach, the machining operations for the brake component braking surfaces can be accurately based from a datum surface of the hub. The assembly incorporates a retention nut threaded onto the wheel mounting bolts which exerts a clamping force on the brake component, e.g., a rotor mounting flange, and further establishes the relative positions of the hub and brake component. In this patented arrangement, the wheel is fixed to the hub with lug nuts engaging the mounting bolts and clamping the wheel against the braking component. 
     U.S. Pat. No. 6,988,598 points out that in conventional disc brake systems, the rotor is generally rigidly attached to the wheel or hub. With this type of attachment method, the rotor run-out must be generally controlled within approximately 0.003 inches to 0.005 inches. Some racing vehicles, such as used in some classes of drag racing, utilize specialized racing aluminum wheels and the rotor must be mounted directly to such wheels. However, these wheels often do not have a mounting surface that runs true enough to mount the rotor within the permissible range of run-out without additional machining. This additional machining requires additional work time and expense and can reduce the strength of the wheel. To solve this problem, the patented device allows the rotor to slide axially during brake application assuming a new axial location not dictated by the wheel face after release of the braking pressure. This patent suggests a disc brake rotor mounting system that enables self-alignment of the rotor without the need for a precision mounting surface on the wheel. In a preferred embodiment, a generally circular wheel adapter is adapted for mounting to a surface of a hub or wheel with fasteners engaging the hub or wheel through a plurality of wheel attachment bores spaced around a circumference of the wheel adapter. The wheel adapter includes a plurality of drive pin bores spaced around its circumference through which drive pin attachment bolts can be inserted to threadingly engage a like plurality of drive pins. The drive pin attachment bolts securely fasten the drive pins to the wheel adapter. The brake rotor includes a plurality of radially aligned drive slots positioned to align with the plurality of drive pins. Alignment bushings mount between each of the rotor drive slots and a corresponding drive pin. The alignment bushings include a central channel and a pair of flanges. The raised flanges slidingly engage opposing sides of the brake rotor and axially retain each alignment bushing with respect to its corresponding drive slot. 
     In operation during braking, calipers press on the brake rotor causing torque on the brake rotor resistant to the rotation of the wheel to which the brake rotor is attached. This torque is transmitted as force through the alignment bushings to the drive pins and so on to the wheel itself. As the calipers grip on the brake rotor, any misalignment of the brake rotor will result in the calipers exerting greater force on one or the other side of the brake rotor. In such a case, once the net force on the brake rotor overcomes the resistance of the drag rings, the brake rotor will slide in or out on the drive pins until located such that the calipers exert the same force on both sides of the brake rotor. Once the braking operation subsides and the calipers no longer exert any force on the brake rotor, the brake rotor stays fixed in its new location and orientation due to the drag rings. Neither of these patented arrangements recognizes that rotor brake plate run-out can increase on the vehicle due to mounting flange distortions that occur when the wheel contacts the rotor flange as it attaches to the hub, let alone suggesting any solution to such a problem. 
     It is desirable to minimize mounting induced rotor lateral run-out along with other sources of lateral run-out. 
     SUMMARY OF THE INVENTION 
     The present invention provides solutions to these problems by fixing the rotor to the hub flange outside the wheel-to-hub flange bolted joint to reduce mounted rotor distortion induced by wheel clamp load. 
     The invention comprises, in one form thereof, a vehicle wheel assembly including a conventional vehicle wheel with a plurality of generally equiangularly spaced mounting bolt receiving apertures, a disc brake rotor having a mounting flange, and a journaled wheel hub having a generally planar wheel contact area for receiving the wheel. There is a generally planar rotor flange contact area for receiving the rotor mounting flange. The rotor flange contact area extends generally parallel to and axially spaced from the wheel contact area. The wheel contact area has a plurality of generally equiangularly spaced radially extending axially raised lobes, one for each wheel mounting bolt aperture, for receiving a corresponding wheel mounting bolt and the rotor flange contact area comprises a like plurality of recesses interleaved with the lobes for receiving generally equiangularly spaced radially inwardly extending rotor fingers each shaped to fit within a corresponding recess. 
     An advantage of the present invention is that the rotor is securely clamped to the hub independently of the clamping of the wheel to the hub providing a desirable rigid coupling of rotor to wheel without any direct physical contact between the wheel and rotor. 
     A further advantage of this invention resides in the barrel mounting of the rotor and as a result, any hub deflections occurring in this area are minimized and would not be translated into rotor brake plate lateral run out. Further, since the rotor is outboard mounted, it can be serviced or replaced without removing the hub. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a portion of a wheel mounting assembly accordingly to the prior art; 
         FIG. 2  is a cross-sectional view of a portion of a wheel mounting assembly accordingly to the present invention; 
         FIG. 3  is an isometric view of the assembly of  FIG. 2  with the wheel removed; 
         FIG. 4  is an exploded isometric view of the assembly of  FIG. 3 ; 
         FIG. 5  is an exploded isometric view similar to  FIG. 4 , but illustrating a modified form of the present invention; and 
         FIG. 6  is a cross-sectional view of a portion of the wheel mounting assembly of  FIG. 5 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several drawing views. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to  FIG. 1 , there is shown a cross-sectional view through a wheel mounting assembly  11  according to U.S. Pat. No. 5,988,761. The assembly includes hub  13 , brake rotor  15 , a cartridge type wheel bearing assembly  17  mounted to hub  13 , and wheel  19  mounted against rotor  15 . The outer race  69  of bearing assembly  17  is a unitary assembly, that forms the outer race surfaces for the sets of tapered roller bearings and includes flange  71  and bore  73  enabling it to be mounted to a suspension component of the vehicle. The wheel bearing assembly  17  may also include a toothed tone wheel which provides a signal for wheel speed sensor  75  related to wheel speed. These components are used as part of a vehicle anti-lock brake system or traction control system. Rotor  15  is spanned by caliper supported braking pads  41  and  43 . Hub  13  includes a generally cylindrical barrel section  21  and a radial protruding rotor annular mounting flange  23 . Flange  23  forms a number of wheel mounting bolt bores  25  which receive wheel mounting bolts  27 . Brake rotor  15  includes a generally circular mounting flange  29  including a plurality of bolt clearance holes  31  which are in registry with wheel mounting bolt bores  25 . Rotor mounting flange  29  defines an inboard surface  33  and an opposed outboard surface  35 . Mounting flange  29  surface  33  is clamped against the outboard surface of the mounting flange  23  of the hub  13  by nuts such as  37 . Wheel  19  is clamped against the outboard surface  35  of rotor flange  29  by nuts such as  39 . Tightening nuts  39  to secure the wheel  19  to hub  13  with the rotor flange  29  captive therebetween may induce deformation in rotor flange  29  causing undesired lateral rotor run-out as illustrated by dimension A. The clamping may also induce some radial run-out as indicated by dimension B in  FIG. 1 , however, the present invention is primarily concerned with lateral run-out. 
     In  FIGS. 2-4  analogous parts bear reference numerals one hundred greater than corresponding reference numerals of  FIG. 1 . The joined hub  113 , brake rotor  115  and wheel  119  rotate together about a common axis  153 . Rotor  115  has a mounting flange  129  with inboard  133  and outboard  135  surfaces. Inboard surface  133  is clamped against the flange of hub  113  by threaded fasteners  145  of  FIG. 3  which pass through corresponding rotor flange holes  181  ( FIG. 4 ) and threadedly engage hub apertures  183 . The hub surface  151  (best seen in  FIG. 4 ) to which the rotor face  133  is clamped is, however, quite different from the outboard surface of flange  23 . The wheel hub  113  has a generally planar wheel mounting face or contact area comprising the plurality of generally equiangularly spaced radially extending axially raised lobes  155  for receiving the wheel  119  inboard surface. The separated wheel mounting flanges allow localized wheel clamp load distortion significantly reducing the impact on the rotor. The generally planar rotor flange contact area  151  comprises the intervening recesses such as  165  and  167  for receiving the rotor mounting flange  129 .  FIG. 4  shows the rotor mounting flange  129  as a plurality (here five) of generally equiangularly spaced radially inwardly extending fingers  177  each shaped to fit within a corresponding recess between adjacent lobes. The rotor flange contact area  151  extends generally parallel to the wheel contact area and is axially spaced therefrom a distance C as shown in  FIG. 2 . In order for this clearance distance to exist, the maximum axial dimension of the fingers  177  within the corresponding recesses  165  should be less than the axial space between the wheel contact area  155  and the rotor flange contact area  151 . A typical number of wheel mounting lugs for passenger vehicles is four or five while somewhat larger pickup trucks or vans may employ eight or more. Five wheel mounting bolts  185 , one for each wheel mounting bolt aperture such as  191  are illustrated. Like numbers of lobes  155 , recesses  165 , fingers  177 , and rotor mounting bolts  145  are shown. 
       FIGS. 5 and 6  illustrate one of many possible alternate embodiments of the present invention. This embodiment may be employed when a full three hundred sixty degree support of the wheel is desired. As before, components analogous to those discussed earlier bear reference numerals one hundred greater than those previously used. Thus, a vehicle wheel  219  has mounting bolts such as  289  passing through wheel mounting bolt aperture such as  291  for fixing the wheel to a brake rotor, and journaled hub  297  with the assembly rotatable about a common axis  253 . The hub  297  again has barrel  299  and flange portions which rigidly couple the wheel and rotor for co-rotation about a that common axis and functions as an intermediate member for supporting both the rotor and the wheel while precluding direct contact therebetween. The most striking dissimilarities between  FIGS. 4 and 5  are the presence in  FIG. 5  of an extra annular ring  303  and a quite different shape of the rotor hat portions  193  and  301 . In  FIGS. 5 and 6 , the hat portion is now frustoconical tapering inwardly toward the attachment flange and its rotor flange holes such as  281 , and the surface to which the wheel  219  clamps is now composed of two separable members, the outboard surface  313  of ring  303  and the hub surfaces formed by axially raised lobes. Closer inspection reveals these lobes have two axially spaced plane surfaces or faces  307  and  309  for receiving the wheel and rotor respectively. The ring  303  rests on surface  309  while the wheel  219  engages ring surface  313  and surface  307 . Semicircular notches  311  receive the outer halves of the mounting bolts  289 . Hub face  307  is axially outboard of the second face  309  relative to the vehicle. As in the earlier embodiment, the first face  307  comprises a plurality of generally equiangularly spaced radially extending petals and the rotor includes a like plurality of generally equiangularly spaced radially inwardly extending tabs interleaved between the petals, however, only a portion of the rotor tabs lies between adjacent petals since part of each tab forms the frustoconical portion which provides the clearance for the mounting ring  303 . However, the axial extent of the petals still exceeds the thickness of the intervening rotor tabs. The ring  303  pilots onto the recess formed by the flange or petal portions  309  and lies between the hub petals or fingers so there is still a gap or separation  305  between the rotor flange and the wheel  219  similar to distance or space C in  FIG. 2 . As before, a first plurality of wheel mounting bolt  289  and lug fasteners couple the wheel to the hub  297  and second plurality of fasteners  283  rigidly couple the hub and rotor. 
     Thus, while a preferred embodiment has been disclosed, numerous modifications will occur to those of ordinary skill in this art. Accordingly, the scope of the present invention is to be measured by the scope of the claims which follow.