Abstract:
A mounting system for disc brake rotors. Drive pins are mounted to a wheel hub. Alignment bushings having outer flanges are slidably held in slots in a disc brake rotor. The alignment bushings are each held by a drive pin inserted in a hole in the alignment bushing. Drag rings prevent unwanted movement between the alignment bushings and the drive pins. The drag rings can be mounted in grooves in the alignment bushings or, alternatively, in grooves on the drive pins. Retaining rings on the drive pins prevent the bushings from coming off of the drive pins.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to disc brake systems, and more particularly, to disc brake systems used in high performance or racing applications.  
         BACKGROUND OF THE INVENTION  
         [0002]    In conventional disc brake systems, the rotor is generally rigidly attached to the wheel or hub. With this type of attachment method, the rotor runout 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 runout without additional machining. This additional machining requires additional work time and expense and can reduce the strength of the wheel.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention provides a disc brake rotor mounting system that enables self-alignment of the rotor without the need for a precision mounting surface on the wheel.  
           [0004]    The system includes a wheel adapter for mounting to a surface of the wheel. A plurality of cylindrical drive pins are fastened to the wheel adapter at a common distance from an axis of the wheel adapter. A rotor includes a like number of radially aligned drive slots opening to a central portion of the rotor. Each drive slot is adapted to receive an alignment bushing that is generally D-shaped in one embodiment. Each alignment bushing includes a central channel bounded on both sides by flanges. The central channel is adapted for engaging opposing sides of the drive slot and the flanges are adapted for engaging opposing sides of the rotor in the region surrounding the drive slot to axially retain the alignment bushing to the rotor. Each alignment bushing also includes a cylindrical through-bore adapted to slidingly engage one of the cylindrical drive pins and retain the rotor to the wheel adapter.  
           [0005]    As the alignment bushings are able to axially slide on the drive pins, the rotor is able to self align itself with respect to the wheel adapter and wheel responsive to forces exerted on it by the calipers during breaking. Further, since the alignment bushings are able to slide radially in the drive slots of the rotor, the rotor can expand and contract due to temperature changes and not induce stresses in the rotor.  
           [0006]    A drag ring is also positioned between the alignment bushings and their respective drive pins to prevent unwanted axial movement or chatter of the rotor once the rotor is aligned.  
           [0007]    It is an object of the present invention to provide a system for self-aligning a wheel mounted disc brake rotor so as to have a maximum runout within a permissible range.  
           [0008]    It is also an object of the present invention to provide a system for aligning a disc brake rotor mounted to a wheel without requiring machining of the wheel surface where the rotor mounts.  
           [0009]    It is also an object of the present invention to provide a system for self aligning a wheel mounted rotor upon initial installation and setup of the brake system.  
           [0010]    It is also an object of the present invention to provide a system for self-adjusting the position and alignment of a wheel mounted disc brake rotor as the disc brake pads wear over time.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 shows an exploded view of a disc brake rotor mounting system according to one embodiment of the invention;  
         [0012]    [0012]FIG. 2 shows a top view of an alignment bushing according to one embodiment of the invention;  
         [0013]    [0013]FIG. 3 shows a top view of a disc brake rotor according to one embodiment of the invention;  
         [0014]    [0014]FIG. 4 shows a partial sectional view of a disc brake rotor mounting system according to one embodiment of the invention taken along section line A-A of FIG. 3; and  
         [0015]    [0015]FIG. 5 shows a partial sectional view of a disc brake rotor mounting system according to a second embodiment of the invention taken along section line A-A of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The present invention is directed to a system for mounting a brake rotor to a hub or wheel.  
         [0017]    [0017]FIG. 1 shows an exploded view of the disc brake mounting system according to one embodiment of the invention. In a preferred embodiment, a generally circular wheel adapter  102  is adapted for mounting to a surface of a hub or wheel (not shown) with fasteners (not shown) engaging the hub or wheel through a plurality of wheel attachment bores  104  spaced around a circumference of the wheel adapter  102 . The wheel adapter  102  also includes a plurality of drive pin bores  106  spaced around its circumference through which a like plurality of drive pin attachment bolts  108  can be inserted to threadingly engage a like plurality of drive pins  110 . The drive pin attachment bolts  108  securely fasten the drive pins  110  to the wheel adapter  102 . Each drive pin  110  is generally cylindrical and can include an enlarged base for engaging a surface of the wheel adapter  102 . In an alternate embodiment, the drive pins  110  may be directly mounted to the hub or wheel without the use of the adapter  102 .  
         [0018]    The brake rotor  112  includes a plurality of radially aligned drive slots  114  positioned to align with the plurality of drive pins  110 . In one embodiment, each drive slot  114  includes a pair of substantially straight drive surfaces  116 . In a preferred embodiment, drive slots  114  include two drive surfaces  116  that are straight and parallel to each other.  
         [0019]    Alignment bushings  118  mount between each of the rotor drive slots  114  and a corresponding drive pin  110 . Each alignment bushing  118  is shaped to mate with a corresponding drive slot  114 . In a preferred embodiment, the alignment bushings  118  are generally D-shaped. The alignment bushings  118  include a central channel  120  and a pair of flanges  122 . The raised flanges  122  slidingly engage opposing sides of the brake rotor  112  and axially retain each alignment bushing  118  with respect to its corresponding drive slot  114 . In one embodiment, the width of the central channel  120  can be wider than the thickness of the brake rotor  112  to allow some free movement of the brake rotor  112  back and forth in the central channel  120 . Alternately, the central channel  120  can be so dimensioned so as to provide a minimum static frictional force against movement of the alignment bushing  118  in or out of the drive slot  114 . In a preferred embodiment, the central channel  120  is so dimensioned that the flanges  122  prevent any substantial movement of the alignment bushings  118  and the brake rotor  112  relative to each other in the direction perpendicular to the plane of the brake rotor  112  and the drive slots  114  contained therein, while allowing free movement of the alignment bushings  118  in a direction in or out of the drive slots  114 .  
         [0020]    In a preferred embodiment, the central channel  120  includes a pair of parallel drive surfaces (shown in FIG. 2 later herein) adapted to slidingly engage parallel drive surfaces  116  of the drive slot for transmitting torque from the brake caliper (not shown), through the brake rotor  112 , to the alignment bushing  118 . Each alignment bushing  118  also includes an axial through-bore  124  for mounting over a corresponding drive pin  110 . This mounting between the drive pin  110  and the alignment bushing  118  allows the alignment bushing  118  to axially slide on the drive pin  110 , thereby allowing the axial positioning of the brake rotor  112  in the region of that drive pin  110  to change with respect to the wheel adapter  102  and the hub or wheel. In a preferred embodiment, the desired axial sliding permitted between the alignment bushing  118  and the drive pin  110  is 0.003 inches to 005 inches, although this can be altered as desired or required.  
         [0021]    In a preferred embodiment, drag ring  126  is provided to seat in a drag ring groove  128  in the bushing through-bore  124 . This embodiment is also visible in better detail in cross-section in FIG. 4. The drag ring  126  is preferably a stainless steel split ring that is sized to provide a low level friction fit between the alignment bushing  118  and the drive pin  110 . This friction fit is not so great too prevent axial movement of the rotor when necessary for alignment but prevents unwanted axial movement which can result in chatter as well as increased wear. An alternative embodiment has the drag ring  126  seated in a drag groove in the drive pin  110 , shown in cross-section in FIG. 5.  
         [0022]    A retaining ring  130  mounts in a retaining ring groove  132  on each drive pin  110  to prevent the alignment bushing  118  from disengaging from the drive pin  110 .  
         [0023]    In operation during braking, calipers press on the brake rotor  112 , causing torque on the brake rotor  112  resistant to the rotation of the wheel to which the brake rotor  112  is attached. This torque is transmitted as force through the alignment bushings  118  to the drive pins  110  and so on to the wheel itself. As the calipers grip on the brake rotor  112 , any misalignment of the brake rotor  112  will result in the calipers exerting greater force on one or the other side of the brake rotor  112 . In such a case, once the net force on the brake rotor  112  overcomes the resistance of the drag rings  126 , the brake rotor  112  will slide in or out on the drive pins  110  until located such that the calipers exert the same force on both sides of the brake rotor  112 . Once the braking operation subsides and the calipers no longer exert any force on the brake rotor  112 , the brake rotor  112  stays fixed in its new location and orientation due to the drag rings  126 .  
         [0024]    [0024]FIG. 2 shows a top view of an alignment bushing  118  according to one embodiment of the invention. As discussed in reference to FIG. 1, the alignment bushing  118 , in one embodiment, has substantially straight drive surfaces  202  located in the central channel  120 . In a preferred embodiment, the drive surfaces  202  are straight and parallel to each other. As discussed in reference to FIG. 1, in a preferred embodiment, the drive surfaces  202  slidingly engage the drive surfaces  116  of the brake rotor  112 .  
         [0025]    [0025]FIG. 3 shows a brake rotor  112  with details of the mounting for one drive slot  114 . Each drive slot  114  is provided with an end clearance  302  between the brake rotor  112  and the alignment bushing  118 . This end clearance  302  allows for expansion and contraction of the related components due to changes in temperature (such as results from the elevated temperatures resultant from braking and the subsequent reduction in temperature when braking no longer is not occurring).  
         [0026]    In a brake rotor  112  that is fixedly mounted to a hub or wheel, the fixed mountings of the brake rotor  112  resist any expansion and contraction of the brake rotor  112 , thus inducing stresses as the brake rotor  112  is unable to expand or contract at the fixed points. Furthermore, areas of a fixed brake rotor  112  away from the fixed points are not as constrained from expanding or contracting as needed as areas near the fixed points. The resultant uneven distribution of expansion and contraction results in an uneven distribution of stresses reducing the potential life of the brake rotor  112  under fixed mounting conditions:  
         [0027]    The provision of the end clearance  302  prevents the brake rotor  112  from being exposed to additional stresses due to expansion and contraction, as compared to a solidly mounted rotor  112 . The parallel drive surfaces  116  on the rotor drive slots  114  and the parallel drive surfaces  202  on the alignment bushings  118  provide substantially increased load bearing surfaces between the two components, as compared to the embodiment where the alignment bushing  118  is essentially cylindrical in cross-section in the central channel area  120 . The increased load-bearing surface reduces local stresses at the contact areas and reduces wear and the chance of failure of the components. This is especially important when using composite brake rotors  112 , such as brake rotors  112  made from carbon fiber.  
         [0028]    [0028]FIG. 4 shows a cross-sectional view of a brake rotor  112  of FIG. 3 at cut A-A. The drive pin attachment bolt  108  is shown engaging the drive pin  110 . The drag ring  126 , within a corresponding drag ring groove  128 , is shown gripping the drive pin  110 . The end clearance  302 , as discussed in reference to FIG. 3, and the flanges  122  gripping the brake rotor  112  are also visible.  
         [0029]    [0029]FIG. 5 shows a partial sectional view of a disc brake rotor mounting system according to one embodiment taken along section line A-A of FIG. 3. In this embodiment, contrasting to the embodiment shown in FIG. 4, the drag ring  126  is held in a drag ring groove  502  situated in the drive pin  110 . In operation, the drag ring  126  exerts a frictional force on the alignment bushing  118  which presents a threshold or minimum amount of force necessary to shift the alignment bushing  118  relative to the drive pin  110 . In operation, the forces exerted on the brake rotor  112  during braking easily overcome the frictional force of the drag ring  126  with the result that the act of braking causes the brake rotor  112  to self-align on the drive pins  110 .  
         [0030]    The present invention achieves all of the objectives set forth in the background section above. The system allows the rotor to be self aligning with respect to the wheel without the need for a precision wheel mounting surface. As the brake pads wear, the rotor is automatically re-positioned to the mean center distance between the two caliper linings.  
         [0031]    While various embodiments have been described in illustrating the invention, the scope of the invention is not to be considered limited thereby, but only in accordance with the following claims.