Abstract:
A brake rotor for an automotive vehicle braking system is disclosed. The rotor includes a brake rotor hat portion attached to a brake rotor disk portion. The disk includes a plurality of radially extending passageways separated by a plurality of webs. The passageways have substantially constant area cross-sections for cooling the rotor and may be dimensionally symmetrical as well.

Description:
TECHNICAL FIELD 
     The present invention relates to brake rotors for automotive vehicles. 
     BACKGROUND OF THE INVENTION 
     Generally, automotive vehicle braking systems include brake rotors that are contacted by brake pads during braking to assist in slowing or stopping an automotive vehicle. It is desirable to cool the brake rotors before, during and after braking. It is known to circulate air through passageways in brake rotors to remove heat from the rotors. However, the circulation of air may be hindered by the geometry of the passageways. Additionally, the passageways may lower the desired stiffness of the rotor. Therefore, it would be desirable to provide an improved brake rotor structure that offers improved airflow through the passageways without sacrificing control over rotor rigidity. 
     SUMMARY OF THE INVENTION 
     The present invention meets the above needs by providing a brake rotor for an automotive vehicle brake system having a brake rotor hat with an annular mounting portion that includes a circular flat surface. A first set of apertures extends through the flat surface for receiving fasteners for attachment to a vehicle wheel and wheel hub. Another aperture extends through the surface for alignment with the wheel hub. The rotor hat also includes a cylindrical wall connected to the circular surface. The cylindrical wall includes a cylindrical surface, a first end and a second end. A peripheral flange having a first surface and a second surface extends radially outward from the second end of the cylindrical wall and terminates in a free edge. A plurality of webs are spaced circumferentially about and extend radially outward from the outer cylindrical surface and each of the webs has a first wall and a second wall. Each of the webs further includes a first side attached to the cylindrical wall, a second side attached to the peripheral flange, a third rounded free side and a fourth side. The first wall and the second wall of the webs are spaced so the webs increase in thickness as they extend radially outward and the first wall is generally parallel over a substantial portion of its surface to an opposing surface of a second wall of an adjacent web for at least partially defining passageways extending radially outward. An annular ring is attached to the fourth side of the webs and has a first surface, a second surface, an inner peripheral edge and an outer peripheral edge. The second surface of the annular ring is opposing and substantially parallel to the second surface of the flange. The inner edge is opposing and spaced apart from a central portion of the outer cylindrical surface of the cylindrical wall for cooperatively forming openings into the passageways with the webs. Furthermore, the openings have cross-sectional dimensions substantially similar to cross-sectional dimensions of the passageways. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features, aspects, and advantages of the invention will become apparent upon consideration of the specification and appended drawings in which: 
     FIG. 1 is a perspective view of a brake rotor; 
     FIG. 2 is a top partial cut away view of the brake rotor of FIG. 1; 
     FIG. 3 is a sectional view of the brake rotor of FIG. 1 taken along line 3—3; 
     FIG. 4 is a perspective cut away view of another brake rotor; 
     FIG. 5 is a top view of a portion of the brake rotor of FIG.  4 . 
     FIG. 6 is a sectional view of the brake rotor of FIGS. 4 and 5 taken along line 6—6. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 through 3, there is illustrated a brake rotor  10  having a cup-shaped brake rotor hat portion  12  attached to a brake rotor disk portion  14  wherein the rotor  10  is appropriate for placement in either front or rear wheels of an automotive vehicle. The brake rotor disk  14  includes a plurality of passageways  16  advantageously dimensioned to promote airflow through the passageways  16  for removing heat from the brake rotor  10  before, during or after periods of braking. 
     The brake rotor hat portion  12  is generally cylindrical with a mounting portion  18  that includes a circular flat surface  20 . A plurality of apertures  22  is defined in the flat surface  20  for receiving lugs, studs, bolts or the like, for attaching the brake rotor  10  to a wheel and a wheel hub of an automotive vehicle. Another aperture  24  for aligning with the wheel hub extends through the center of the mounting portion  18  and is concentric with the circular surface  20  of the mounting portion  18 . 
     The rotor hat portion  12  further includes a tapered wall surface  26  connected to the mounting portion  18  and adjoining a first end  28  of a cylindrical wall  30  of the hat  12 . The cylindrical wall  30  includes an outer cylindrical surface  32  extending between the first end  28  of the wall  30  and a second end  34  of the wall  30 . 
     A peripheral flange  36  of the disk  14  extends radially outward from the second end  34  of the cylindrical wall  30  of the rotor hat  12  and terminates at a free edge  38 . The flange  36  has a first surface  40  and a second surface  42  separated by a substantially uniform thickness over at least a substantial portion of its radial dimension, as the flange  36  extends radially outward. The flange  36  includes an annular channel  44  in the first surface  40  appropriate for receiving a cap (not shown) for housing a parking brake package (not shown) in a cavity  46  of the rotor  10  that is at least partially defined by an inner surface  48  of the cylindrical wall  30 . 
     The disk  14  further includes a plurality of webs  50  spaced circumferentially about and extending radially outward from the outer cylindrical surface  32  of the cylindrical wall  30 . Each of the webs  50  includes a first side  52  attached to the cylindrical wall  30  of the rotor hat portion  12 , a second side  54  attached to the peripheral flange  36 , a third rounded free side  56  and a fourth side  58 . Each of the webs  50  also includes a first wall  60  and a second wall  62  extending radially outward from the cylindrical wall  30  wherein the first wall  60  is separated from the second wall  62  by a thickness of the web  50  that increases as the web  50  extends radially outward. The first wall  60  of each web  50  is generally parallel over a substantial portion of its surface to an opposing surface of a second wall  62  of an adjacent web  50  for at least partially defining the passageways  16 . 
     The disk portion  14  includes an annular ring  64  with a first surface  66  and a second surface  68  separated by a substantially uniform thickness. The second surface  68  is attached to the fourth side  58  of the webs  50  and is substantially parallel to the second surface  42  of the flange  36 . The ring  64  includes an inner peripheral edge  70  and outer peripheral edge  72 . The inner edge  70  is spaced apart from and opposes a central portion of the outer cylindrical surface  32  of the cylindrical wall  30 . The inner edge  70 , the outer cylindrical surface  32  and the webs  50  form openings  74  providing access for the passage of air into the passageways  16 . The second surface  68  of the ring  64 , the first and second walls  60 ,  62  of the webs  50  and the second surface  42  of the flange  36  cooperatively define the passageways  16 . 
     The inner edge  70  is spaced away from the outer cylindrical surface  32  such that the openings  74  have cross-sectional dimensions that are substantially similar or substantially identical in size and shape to the cross-sectional dimensions of the passageways  16 . The cross-sectional dimensions of the openings  74  are oriented such that a cross-section of a given opening could be rotated 90° about the inner edge  70  to substantially align with the cross-sectional dimensions of the passageways  16 . Such dimensional symmetry allows any debris that may enter the openings  74  to more easily pass through the openings  74  and the passageways  16 , thus, maintaining airflow through the passageways  16 . 
     Furthermore, the passageways  16  extend radially away from the cylindrical wall  30  without dimensional rotation (i.e., a cross-section of a passageway  16  taken at a first radial distance away from the cylindrical wall  30  will be in substantially registered alignment with a cross-section taken a second further radial distance away). Such radial dimensional symmetry of the passageways  16  also assists in purging debris. 
     The rotor  10  attaches to a vehicle so that the openings  74  open away from the underbody of the vehicle or toward the normal position of a hubcap for a wheel of the vehicle. This obviates the need for a splash-guard over the openings  74  of the rotor  10 , thus, allowing greater airflow to the openings  74 . Consequently, the passageways  16  will experience greater airflow resulting in greater heat transfer away from the rotor  10 , thereby extending the useful life of the rotor  10 . 
     Now, referring to FIGS. 4 through 6, there is illustrated an alternative brake rotor  76  that is substantially identical to the brake rotor  10  of FIGS. 1 through 3 with the exception that the peripheral flange  36 , the webs  50  and the annular ring  64  have been replaced with a peripheral flange  78 , webs  80  and annular ring  82 , which cooperatively form passageways  84 . 
     The peripheral flange  78  of the rotor  10  includes a surface  86  that is angled toward the passageways  84  as the flange  78  extends radially outward, thus, increasing the thickness of the flange  78  as it extends radially outward. The annular ring  82  also includes a surface  88  that is angled toward the passageways  84  as the ring  82  extends radially outward, thus, increasing the thickness of the ring  82  as it extends radially outward. The surface  88  of the ring  82  generally opposes the surface  86  of the flange  78  and the webs  80  are generally of uniform thickness. 
     Preferably, and as shown best in FIGS. 6 and 7, the cross-sectional area of the passageways  84  is substantially radially uniform although the dimensions of the passageways  84  may be changing as they extend radially. The dimensions of the passageways  84  change according to the equation:          H   2     =       H   1              D   1                   sin                   (       ∝   1     2     )           D   2                   sin                   (       ∝   2     2     )                                  
     Wherein: 
     H 1  is a height of a rectangular cross section of one of the passageways  84  taken at a radial distance D 1  away from a radial center point  90  of the rotor  76 ; 
     H 2  is a height of a rectangular cross section of one of the passageways  84  taken at a greater or lesser radial distance D 2  away from the radial center point  90  of the rotor  76 ; 
       1  is an angle defined by three points, one, the vertex, at the radial center point  90  of the rotor  76  and the other two at intersection points wherein the opposing walls of two adjacent webs  80  intersect with the radial distance D 1  from the center point  90 ; and 
       2  is an angle defined by three points, one, the vertex, at the radial center point  90  of the rotor  76  and the other two at intersection points wherein the opposing walls of two adjacent webs  80  intersect with the radial distance D 2  from the center point  90 . 
     In alternative embodiments to the rotors shown, both the thickness of the webs, and the thickness of the flange, the annular ring or both may increase further peripherally outward to maintain constant cross-sectional area passageways. 
     Any of the rotors discussed herein may be fabricated as an integral metal part according to known techniques, or assembled from separate components. 
     It should be understood that the invention is not limited to the exact embodiment or construction, which has been illustrated and described but that various changes may be made without departing from the spirit and the scope of the invention.