Abstract:
The invention is directed to outside diameter piloting apparatus and method for concentrically aligning a disc rotor to a wheel hub. The pitch circle diameter of the annular piloting features is greater than the pitch circle diameter of the rotor mounting fasteners and the wheel studs of the hub. The outside diameter piloting feature allows a hub section profile which is smooth and continuous between the inboard side of the wheel hub up to the mounting fastener apertures. This smooth and continuous profile reduces stresses and increases the fatigue life of the wheel hub.

Description:
FIELD OF THE INVENTION 
     Present invention relates generally to an apparatus and method to pilot and or concentrically mount a disc rotor to a wheel hub. The invention relates generally to piloting surfaces formed outside the mounting fasteners on each of the hub and disc rotor to radially align the disc rotor to the wheel hub to increase the fatigue life of the wheel hub. 
     BACKGROUND OF THE INVENTION 
     The present invention is designed to minimize radial run out experienced by the attachment of an inboard disc rotor to a wheel hub for such applications as heavy truck wheel ends. Radial run out is a concern when attaching a brake rotor to a wheel hub to prevent vibration caused by disc rotor imbalance. The brake rotor must be concentrically aligned with the wheel hub prior to securing the disc rotor to the hub. Fasteners attach the disc rotor to the hub by extending through holes formed in a disc rotor mounting flange of the hub and threadably engaging a hub mounting flange on the disc rotor. Vibration may occur due to the disc rotor having an incorrect concentric alignment with the axis of the hub. 
     The method used to pilot and/or center an inboard mounted disc rotor to a wheel hub requires a machined pilot diameter of annular shape on the disc rotor that interfaces with a machined pilot diameter of annular shape on the wheel hub. Prior art pilot features are disposed between the axis of the hub and the wheel studs or generally, at a smaller pitch circle diameter than the pitch circles for either the disc rotor mounting fasteners and the wheel studs of the hub. This placement of the pilot feature formed a discontinuous section thickness of the hub body and flange by continuous or individual mounting bosses, machined undercut or small radius features form on the inboard flange region of the wheel hub. These notches and stress risers in the hub flange reduced the fatigue life of the hub. 
     Wheel hubs undergo cyclical and mean stresses that may be concentrated at an inboard flange area of the wheel hub. The stresses are particularly concentrated at discontinuous section thicknesses of the hub especially when such stress risers are formed at a pitch circle diameter equal to or less than the pitch circle diameter of the fasteners on the hub connecting the disc rotor or wheels. The stress risers formed by the prior art pilot features have a compounding effect to the cyclical and mean stresses of the wheel hub increasing the stress level at those points and reducing the fatigue life of the wheel hub. 
     It is desirable to provide a design and method of piloting the disc rotor on the wheel hub by positioning pilot features outside the pitch circle diameters of either the fasteners or studs. A benefit of such a design is to reduce the effects of fatigue on the wheel hub. It is further desirable to provide a method of piloting the disc rotor on the wheel hub where in the pilot features do not create stress risers. 
     BRIEF SUMMARY OF THE INVENTION 
     One embodiment of the present invention is directed to a piloting feature formed having the wheel hub portion on the mounting flange at a pitch circle diameter greater than the pitch circle diameter of the disc rotor fasteners and surroundingly engaging a disc rotor portion on the brake rotor. The pitch circle diameter of the piloting feature may also be greater than the pitch circle diameter of the wheel studs which are press fitted into the mounting flange of the wheel hub. The pilot feature may be a continuous boss circumscribing a pilot diameter or, alternatively may be a plurality of individual bosses formed along an outer edge of the mounting flanges having the hub portion radially outside of the disc rotor portion for concentrically piloting the hub and disc rotor during assembly. 
     In an alternative embodiment, the outside pilot feature may be formed on the mounting flange of the disc rotor hub at a pitch circle diameter greater than the pitch circle diameter of the disc rotor fasteners for surroundingly engaging the hub portion of the pilot feature outside of the wheel studs on the wheel hub. The pilot feature on the disc rotor mounting flange may be a continuous ridge circumferentially formed around the outside perimeter of the disc rotor mounting flange or may be a plurality of individual bosses formed along the outside perimeter of the disc rotor mounting flange for engaging a pilot surface on the hub mounting flange. The pilot surface on the hub may be notched into the hub mounting flange to engage the disc rotor portion and provide a smooth profile around the circumference of the assembly. 
     The placement of the pilot features at a diameter greater than the wheel stud hole diameter helps eliminates stress risers between the axis and the wheel stud holes to increase fatigue life of the hub. Forming the pilot features outside the fasteners and studs reduces the notches, machined undercuts and stress risers to provide a continuous section thickness in the hub flange between the body and the mounting holes. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a front view of a hub concentrically mounted to a disc rotor hub. 
         FIG. 2  is a perspective view of the first embodiment showing the disc rotor mounted to the hub. 
         FIG. 3  is a detail section view of the first embodiment taken at approximately  3 - 3  of  FIG. 2 . 
         FIG. 4  is an enlarged detail section view of the first embodiment showing the rotor pilot adjacent to the rotor fastener. 
         FIG. 5  is a perspective view of the second embodiment of the disc rotor pilot showing the disc rotor mounted to the hub. 
         FIG. 6  is a detail section view of the second embodiment taken at approximately  6 - 6  of  FIG. 5 . 
         FIG. 7  is an enlarged detail section view of the second embodiment showing the disc rotor pilot adjacent to the disc rotor fastener. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1  illustrates a brake rotor assembled to a wheel hub. It should be understood that drive, steer and trailer hubs are nearly identical with respect to the present invention. These assemblies comprise a hub interfacing between the vehicle axle and the wheel and a disc rotor mounted on the hub for applying a braking force. For purposes of this description, the hub portion of the assembly go will be referred to as a hub  10  and shall indicate either a drive, steer or trailer hub. Generally an inboard direction is referred to as from the wheel inward toward the hub to the disc rotor and to the center of the vehicle and the outboard direction is referred to as from the center of the vehicle outward past the disc rotor, the hub and directed toward the wheel. Inward direction refers to a radial direction toward the axis of the hub and an outward direction refers to a radial direction out from the axis of the hub. 
     Referring to  FIG. 1 , a hub  10  is illustrated concentrically attached to a disc rotor  12 . The hub  10  has a generally cylindrically shaped body  11  having an inner bore  14  for attachment to an axle (not shown) and a generally hollow interior  16  of the hub  10 . The disc rotor  12  is attached by fasteners  32  extending from the outboard side of the hub flange  18  inwardly to engage the disc rotor  12 . Wheel studs  72  extend outwardly from the hub flange  18  for securing the wheels (not shown) to the hub  10 . The disc rotor fasteners  32  and wheel studs  72  are attached to the hub  10  at a first pitch diameter from the hub axis  19 . 
     Referring to  FIG. 2 , the disc rotor flange  30  is adapted to attach to the hub flange  18  on the wheel hub  10 . The disc rotor flange  30  is attached to the hub flange  18  by the threaded disc rotor fasteners  32  extending through the hub flange  18  and threadably engaging the disc rotor flange  30 . The disc rotor flange has a series of outwardly projecting spokes  47  to engage the fasteners  32  and allow access to the wheel studs  72  at the inboard side of the hub flange. The wheel studs  72  have a head portion  73  bearing against the hub flange  18 . 
     Continuing to refer to  FIG. 2 , the concentric disc rotor pilot  49  comprises a hub portion* and a disc rotor portion*. The hub portion comprises a plurality of hub pilot bosses  50  formed circumferentially around the hub flange  18 . Each of the hub pilot bosses  50  is formed at a second pitch diameter with respect to the axis  19  of the hub  10 . The hub pilot boss  50  is formed in a radially outward position with respect to disc rotor mounting holes  44  ( FIG. 3 ). The hub pilot boss  50  extends inboard from the hub flange surface  36 . Each hub pilot boss is positioned to engage a spoke  47  on the disc rotor flange. It should be understood the hub pilot bosses  50  may be positioned to engage three or more alternating spokes  47  or alternatively, a boss  50  may be formed to correspond with and engage each spoke depending on the design characteristics. Each hub pilot boss  50  comprises a radially inward extending nub  52  for engaging an outer edge  66  of the disc rotor flange  30 . The piloting feature  49  is formed between the outer edge  66  and boss  50  for concentrically aligning the disc rotor  12  with the hub  10 . 
     Referring to  FIG. 3 , the disc rotor  12  comprises a brake engaging disc rotor  26  attached to a cylindrical rotor sleeve  28  and a disc rotor flange  30  extending outward from the sleeve  28 . The hub flange  18  as an outboard surface  34  and an inboard surface  36 . The hub flange  18  has a smooth, generally tapering inboard section  42  and a smooth hub outer surface  22 . The disc rotor mounting aperture  44  in the spoke  47  is adapted for threadably receiving the fastener  32  for securing the disc rotor  12  to the hub  10 . The disc rotor mounting aperture  44  is positioned at a first pitch diameter with respect to the axis  19  of the hub  10 . The boss  50  is positioned at second pitch diameter spaced radially outward from the first pitch diameter. The first pitch diameter is intermediate the second pitch diameter and the axis  19 . Boss  50  engages disc rotor flange  30  at outside edge  68  ( FIG. 4 ) radially outward from the disc rotor aperture  44 . Each boss  50  is formed at the second pitch diameter with respect to the hub axis  19 . The first pitch diameter is intermediate the second pitch diameter and the axis  19 . The second pitch diameter is greater than the first pitch diameter. 
     Continuing to refer to  FIG. 3 , the hub inboard section  42  further has an inboard hub flange disc rotor mounting surface  36  which is machined to be perpendicular to the axis  19 . The disc rotor flange  30  has an outboard disc rotor flange surface  62  machined to be perpendicular to the axis  19  for engagement to inboard hub flange surface  36 . The rotor flange  30  has a plurality of disc rotor apertures  46  formed at the first pitch diameter with respect to the axis  19  for alignment with disc rotor mounting holes  44 . The disc rotor flange  30  further comprises an outer disc rotor flange edge  66  having a disc rotor pilot terminating at a hub pilot  68 . Hub pilot  68  is precisely machined to the second pitch diameter for engaging the disc rotor pilot  56  to concentrically align the disc rotor  12  to the wheel hub  10 . 
     Continuing to refer to  FIG. 3 , the disc rotor  12  is attached to the hub  10  with mounting fasteners  32  shown recessed in the outboard surface of hub flange  18 . The fasteners  32  threadably engage the disc rotor flange  30  to secure the hub to the disc rotor. Inboard flange surface  36  bears against outboard disc rotor flange surface  62  to axially align the disc rotor to the hub  10 . Disc rotor pilot  56  on the hub is surroundingly engaging the disc rotor  12  in the first embodiment. It should be understood when the disc rotor  12  is attached to the hub  10 , no additional load is imparted between the disc rotor  12  and the hub  10  at the pilot feature. 
     Continuing to refer to  FIG. 3 , the detailed section view showing the interface of the hub flange  18  to the disc rotor flange  30  is illustrated showing a wheel mounting stud  72 . The wheel mounting stud  72  is pressed into the hub flange  18  at stud hole  79  formed preferably at the first pitch diameter. The wheel mounting stud  72  is held by a spline section  76  on the stud shank  78  engaging the hub flange  18 . Stud shank  78  further comprises a stud flange  80  for engaging hub flange  18 . The piloting feature  49  concentrically aligns the disc rotor  12  to the hub  10 . 
     Referring to  FIG. 4 , nub  52  on boss  50  is machined to form disc rotor pilot  56  and a pilot cavity  58 . Boss  50  extends axially inboard on tab  54  to form disc rotor pilot  56  precisely machined to the second pitch diameter for concentrically aligning the disc rotor  12  to the wheel hub  10 . The disc rotor  12  has a hub pilot  68  on the outer edge  66 . Hub pilot  68  is precision machined at the second pilot diameter outwardly from the disc rotor mounting aperture  46 . 
     Continuing to refer to  FIG. 4 , piloting feature  49  comprises a disc rotor pilot  56  surroundingly engaging rotor  12  at hub pilot  68 . The hub  12  is attached to the disc rotor  12  by rotor fastener  32  recessed into outboard surface  34  and extending through aperture  46  to threadably engage rotor flange  30  at spoke  47 . The smooth hub surface  42  extends to the hub flange surface  60  bearing against rotor flange surface  62 . Outer surface  22  on hub  10  forms the outer perimeter of the hub-disc rotor assembly. 
     Referring to  FIG. 5 , an alternative embodiment of the present invention is illustrated showing the hub  110  mounted to the disc rotor  112 . The hub  110  and disc rotor  112  are concentrically aligned by an annular disc rotor pilot  149  comprising a boss  150  formed on the disc rotor flange  130 . Boss  150  is formed at a second pitch diameter with respect to hub axis  119  in a radially outward position with respect to disc rotor fasteners  132 . The boss  150  is illustrated as a plurality of tabs  154  formed in a circumferential arrangement for surrounding the hub flange  118  and engaging hub flange  118  on the outer edge  122 . Rotor sleeve  128  supports rotor hub  130  formed into spokes  147  engaged by fasteners  132 . Rotor boss  150  on spoke  147  extends outboardly from the disc rotor  112  adjacent the outer edge  166  of disc rotor flange  130 . 
     Continuing to refer to  FIG. 5 , the hub flange  118  comprises an outer edge  122  having an outer disc rotor pilot  156  precisely channeled into the inboard flange surface  136 . When assembled, the disc rotor  112  and hub  110  are concentrically aligned by the pilots  156 ,  168 . The disc rotor  112  is piloted to a concentric position with respect to the hub  110  by the disc rotor pilot  156  surroundingly engaging the hub pilot  168 . 
     Referring to  FIG. 6 , the disc rotor flange  130  extends outwardly beyond the aperture  146  and engages the hub  110  with an axial facing hub pilot  168  for engaging the outside of the hub flange  118 . The hub pilot  168  on the disc rotor  112  is surroundingly engaging the hub  110  in the second embodiment. Hub  110  has smooth continuous, tapering inboard section  142  extending from hub body  111  to hub flange  118 . 
     Tabs  154  are outside the disc rotor pilot  156 . The disc rotor pilot  156  is formed as a channel  158  machined in the outer edge  122  to substantially align the outer edge  166  of the disc rotor flange  130  with the outer edge  122  of the hub flange  118 . The mounting fasteners  132  are extended through the hub flange to threadably engage the disc rotor flange  130  at spokes  147 . 
     Continuing to refer to  FIG. 6 , disc rotor mounting aperture  146  and the stud holes  179  may be formed at the first pitch diameter or alternatively, the disc rotor mounting apertures  146  may be formed at a pitch diameter having a different dimension from the first pitch diameter D 1  but smaller than the second pitch diameter D 2  of the pilot feature. The outer edge  122  may have a continuous disc rotor pilot  156  concentrically surrounding the hub flange  118  or may comprise a plurality of tabs  154  as shown, extending from the outer edge of the hub flange and disposed at positions to engage the hub pilot on the disc rotor  112 . 
     Referring to  FIG. 7 , the disc rotor pilot boss  150  extends in an outboard direction from the disc rotor flange surface  162  and terminates with a tab  154  having an inward positioned hub pilot  168 . Hub flange  118  is channeled at groove  158  to form the disc rotor pilot  156 . The hub pilot  168  is formed at the second pitch diameter for engaging the disc rotor pilot  156  on the hub flange  118 . After engagement at the piloting feature  149  the rotor fasteners  132  are inserted through the hub flange  134  to engage the rotor flange  130  on rotor sleeve  128 . Hub flange  134  has a continuous, tapering inboard section  142  extending to rotor fastener  132 . 
     In the first embodiment, the disc rotor flange  30  fits radially inside the disc rotor pilot  56  of the hub  10 . The pilot  49  may comprise a continuous raised boss  50  on the hub having a rotor pilot  56  which may be formed on a plurality of tabs  52  for surroundingly engaging the disc rotor  12 . The pilot  49  further comprises a hub pilot  68  on the rotor  12 . The hub pilot  68  and the rotor pilot  56  are aligned to engage each other and pilot the disc rotor to a circumferential orientation to the hub. 
     In the second embodiment, the hub mounting flange  118  fits circumferentially inside the hub pilot  168  on the disc rotor flange  130 . The disc rotor flange may have a plurality of spokes  147  extending radially outward from a position outside the first pilot diameter terminating in a tab comprising a hub pilot  168  that engages the hub at the disc rotor pilot  156 . 
     The present invention has been shown and described with reference to the foregoing exemplary embodiments. It is to be understood, however, that other forms, details, and embodiments may be made without departing from the spirit and scope of the invention which is defined in the following claims.