Abstract:
The present invention provides a drum or rotor wheel hub having a cast hub having a machined pilot in a flange portion and a machined pilot in a cylindrical portion, and a cast portion which separates the cylindrical pilot from the flange pilot, whereby a machined radii is not incorporated in the pilot construction.

Description:
PRIORITY  
       [0001]     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/555,575, filed Mar. 22, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates, generally, to vehicle wheel assemblies used in vehicles such as trucks, buses and trailers, and more particularly, to pilot constructions on such vehicle hubs.  
       BACKGROUND OF THE INVENTION  
       [0003]     The prior art includes wheel hubs for vehicles, including medium and heavy-duty trucks, trailers and buses. In one embodiment, the hubs include a stud pilot construction. Studs are passed through a flange of the hub and may be used for centering the brake drum and wheels which are mounted on the hub. In some prior art systems, the studs are used for centering only one of the wheel and drum, typically the wheel.  
         [0004]     U.S. Pat. No. 5,739,684 C1 issued to Burns and is assigned to the assignee of the present invention. Burns shows a prior art hub with a drum and wheel pilot arrangement. The hub is typically cast or forged and then machined to form a plurality of drum pilots which engage the corresponding pilot on the brake drum, and to form a plurality of wheel pilots which each engage the corresponding pilot on the wheel or wheels. The bolts used to mount the brake drum and wheel are not used to center the drum and wheels, rather the hub pilots are used to center the drum and wheels with respect to the hub. Typically the hub is machined with the drum pilot having a radius which is larger than the radius of the wheel pilot. Pairs of wheel pilots and drum pilots may be longitudinally aligned with one another and form a continuous machined surface having two right angles, the first separating the wheel pilot and the drum pilot. The second right angle separating the drum pilot from the hub flange. In any event, each pilot is associated with at least one right angle.  
         [0005]     As suggested before, the right angles in the pilot construction are formed by a machining process. The prior art pilot construction incorporates a machined radius into the part. The machined radii introduce stress risers in the area of the pilots. The stress risers decreases fatigue life of the hub. The stress risers can be compensated by strengthening the hub such as by increasing the thickness of the cylindrical wall of the hub.  
         [0006]     Industry trends and recent developments in hub technology have lead to lighter hub construction. Unfortunately, the light weight hub construction impacts adversely on the stress risers associated with the pilot construction.  
         [0007]     It is desirable to provide a hub pilot construction which is not associated with a decreased fatigue life. It is also desirable to provide a pilot construction which does not produce stress risers in the area of the pilot construction. It is further desirable to provide a hub construction which does not have the associated stress risers and which is light weight. It is further desirable to provide a casting where pilots are used at the junction where a flange is joined to a cylindrical body and without producing stress risers.  
       SUMMARY OF THE INVENTION  
       [0008]     It is an object of the present invention to provide a casting where pilots are used at the junction where a flange is joined to a cylindrical body, without reducing the fatigue life.  
         [0009]     It is an object of the present invention to provide a hub having an increased fatigue life.  
         [0010]     It is a further object of the present invention to provide a hub which eliminates the stress risers and is light weight.  
         [0011]     It is still a further object of the present invention to provide a lightweight hub having drum and wheel pilots but without reducing the fatigue life of the hub.  
         [0012]     The invention includes the design of a hub such that the wheel and drum pilots do not have a machined radii where these pilots interface with the hub body, hub flange or both.  
         [0013]     The present invention therefore provides in one embodiment, a wheel hub comprising a cast hub having a machined pilot in a flange portion and a machined pilot in a cylindrical portion, and a cast portion which separates the cylindrical pilot from the flange pilot, whereby a machined radii is not incorporated in the pilot construction.  
         [0014]     The present invention further provides in another embodiment, a method of manufacturing a wheel hub, comprising casting a hub, machining a pilot in a flange portion, machining a pilot in a cylindrical portion, leaving a cast portion between the flange pilot and the cylindrical portion, whereby machined radii are not incorporated in the pilot construction. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a perspective view of the inboard side of a prior art.  
         [0016]      FIG. 2  is a cross sectional view of a wheel assembly with the prior art hub of  FIG. 1 .  
         [0017]      FIG. 3  is an enlarged view of detail A of the prior art hub of  FIG. 2 .  
         [0018]      FIG. 4  is a close up view of the outboard side of the prior art hub of  FIG. 1 .  
         [0019]      FIG. 5  is a perspective view of the outboard side of the hub of the present invention.  
         [0020]      FIG. 6  is a partial cross sectional view of the hub of  FIG. 5 , showing a detailed view of the brake drum pilot of the present invention.  
         [0021]      FIG. 7  is another partial cross sectional view of the hub of  FIG. 5 , showing a detailed view of the wheel pilot of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     A prior art hub is shown in  FIG. 1  and generally designated at  10 . The term hub is used throughout the application and should be understood as referring to a hub of transportation vehicles, for example, the hubs of trucks, buses and trailers. Referring to  FIGS. 1 and 2 , the hub  10  includes a generally cylindrical body  12 , which includes an outboard extension  14  and an inboard extension  16 . The cylindrical body  12  defines a substantially cylindrical interior passageway  18  which includes bearing cups  20  which are adapted to engage roller bearing  22  to rotatably mount the hub to the vehicle axle  24  or other suspension component of the vehicle.  
         [0023]     The hub  10  also includes a mounting flange  26  extending radially from the cylindrical body  12 . The radially extending mounting flange  26  assists in defining the inboard section  16  and outboard section  14  of the hub  10 . Equidistantly spaced openings  28  are formed in the mounting flange  26  and are adapted to receive wheel mounting studs  30  for mounting a brake drum  32  to the inboard section  16  of the hub  10  and for mounting a wheel and tire assembly  34  to the outboard section  14  of the hub  10 .  
         [0024]     Referring to  FIGS. 1-3 , the brake drum  32  includes a generally cylindrical portion  36  and a mounting portion or flange  38 . The mounting flange includes equidistantly spaced openings  40  adapted to receive the wheel mounting studs  30  for mounting the brake drum as noted above. The mounting flange further forms a cylindrical opening is which is defined by an annular surface or pilot  42 . The wheel and tire assembly  34  includes an inboard wheel  44  and an outboard wheel  46 . Both the inboard wheel and outboard wheel include a mounting flange  48  having equidistantly spaced openings  50  adapted to receive the wheel mounting studs  30  for mounting the wheel and tire assembly as noted above. The inboard wheel and outboard wheel also each include a circular opening defined by an annular surface or pilot  52 .  FIG. 3  shows that the hub includes a drum pilot  54  adjacent the mounting flange  26  and on the side of the outboard section. The drum pilot  54  is engaged with the drum, specifically, with the pilot  42  of the drum. The hub further includes a wheel pilot  56  which extends from the drum pilot in a direction away from the mounting flange  26  and towards the outboard section  16 . The wheel pilot  56  is engaged with the pilot  52  of each of the wheels. Such an arrangement provides a hub piloted disc wheel system as appreciated by those skilled in the art. This is in contrast to a stud piloted disc wheel arrangement. While the present invention finds utility particularly in the hub piloted disc wheel arrangement, the stud piloted disc wheel arrangement also benefits from the present invention. The hub shown includes pulse teeth for an anti-lock brake system. However, the present invention is not limited to hubs for an ABS system. In addition, a two wheel system is shown in the drawings. However, the present invention is not limited to a two wheel system.  
         [0025]      FIG. 4  is a close up view of the outboard side of the prior art hub of  FIG. 1 . The outboard extension and the mounting flange are shown. A plurality of brake drum pilots  54  and wheel pilots  56  are shown. The hub  10  is generally formed as a casting or forging and is made from a ferrous material preferably ductile iron or cast steel. Alternatively, other ferrous materials such as steel forging or austempered ductile iron may be used in forming the hub. The bearing cups bores, sealing bores and openings  28  are machined and drilled to their proper dimensions in a manner well-known in the art. The outside surface  60  ( FIG. 1 ) of the inboard portion  16  of the hub  10  is not required to be machined for the invention to work in its intended manner. However, the outside surface  60  of the inboard section  16  may be machined for cosmetic purposes.  
         [0026]     The mounting flange  26  is machined leaving a machined surface  62 . A plurality of small protrusion  64  and large protrusions  66  of the outboard section are also machined during the process of machining the mounting flange  26  and form machined surface extensions  68 . The brake drum pilots  54  are also machined in the large and small protrusions. The brake drum pilots and respective machined surface extension  68  form a generally right angle at a transition area  70 . The transition area  70  provides a machined radius. The large protrusions are further machined and form the wheel pilots  56  and a corresponding ridge surface  72 . The wheel pilots  56  and ridge surface  72  form a generally right angle at a transition area  74 . The transition area  74  provides a machined radius. It is appreciated that the machining process leaves the small protrusions  64  with the drum pilot  54  and a corresponding transition area  70 , and leaves the large protrusions  66  with a drum pilot  54  and wheel pilot  56  and two corresponding transition areas  70 ,  74 .  
         [0027]     In the event the hub is to be configured for an ABS system, a plurality of radially extending grooves  80  are formed in the annular end face  82  of the inboard portion  16  of the hub  10  forming a series of radially extending pulse teeth  84 . The grooves  80  and the corresponding pulse teeth  84  are machined, preferably by using super abrasive machining (“SAM”) or an abrasive cutter. Alternatively, milling, broaching, laser cutting or other methods of removing metal may be utilized to form the grooves  80 .  
         [0028]     Referring to  FIG. 5 , a perspective view of the outboard side of the hub  100  of the present invention is shown. The mounting flange  110  and outboard section  112  are readily apparent. The mounting flange includes a machined surface  114 . The machined surface of the mounting flange and the cylindrical body  116  are joined by a bridge portion  118 . A plurality of protrusions  120  extend upwardly from the bridge portion. A brake drum pilot  122  is machined in the upwardly extending protrusion. A cast surface or area  124  is shown between the drum pilot  122  and the mounting flange machined surface  114 . Protrusions  126  extending from the outboard section are shown to be machined to form a wheel pilot  128  with a cast surface or area  130  between the wheel pilot  128  and the machined surface  114  of the mounting flange. The embodiment of  FIG. 5  shows the wheel pilots  128  radially spaced apart from the drum pilots  122 .  
         [0029]      FIG. 6  is a partial cross sectional view of the hub of  FIG. 5 , showing a detailed view of the brake drum pilot  122  of the present invention. It can be seen that the drum pilot  122  is separated from the machined surface  114  of the mounting flange by a cast surface or area  124 . A wheel pilot  128  is also shown. However,  FIG. 7  is another partial cross sectional view of the hub  100  of  FIG. 5 , showing a better detailed view of the wheel pilot  128  of the present invention. The cross sectional view of  FIG. 7  is slightly rotated in comparison to the view of  FIG. 6 . It can be seen that the wheel pilot  128  is separated from the machined surface  114  of the mounting flange by a cast surface or area  130 . Referring back to  FIG. 5 , it can be seen that the wheel pilot  128  and the drum pilot  122  are separated by a cast surface or area  132 .  
         [0030]     The invention includes a method as suggested from the foregoing, wherein a hub is provided. The hub is machined to provide the drum pilot and machined surface spaced apart from one another by a surface which has not been machined. The hub is machined to provide the wheel pilot and machined surface spaced apart from one another by a surface which has not been machined. The hub is machined so that there is no transition area with a machined radius.