Abstract:
A brake rotor including a rotor body made of a first material. The rotor body includes a central hub portion and a substantially annular disc portion extending from the central hub portion. The disc portion includes an inner disc surface and an outer disc surface. The brake rotor also includes an inner braking ring and an outer braking ring made of a second material. The inner and outer braking rings are fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the respective inner and outer disc surfaces. The brake rotor includes projections extending from at least one of the inner and outer disc surfaces to support thereon the respective one of the inner braking ring and the outer braking ring. The projections are generally configured in elongated diamond-like shapes oriented along an axis extending radially outwardly from the central hub portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to braking components, and more particularly to brake rotors.  
           [0002]    Brake rotors are important components of disc brake systems used in overland vehicles. Generally, brake rotors include a braking surface that is frictionally engaged by brake pads mounted on calipers. The size, weight, and other attributes of brake rotors are highly variable. Brake rotors must be designed to provide adequate braking forces to a vehicle when the vehicle is fully loaded. In addition, brake rotors must be designed with an acceptable service life. A passenger vehicle, for example, typically utilizes relatively large and heavy brake rotors to provide the service life and braking forces required by such a vehicle.  
           [0003]    Commonly used brake rotors are often manufactured from a cast iron, which has generally acceptable hardness and wear resistance properties. However, cast iron has a relatively high material density compared to other materials and a relatively low thermal conductivity. As a consequence, cast iron brake rotors are often unnecessarily heavy, and can not dissipate heat as efficiently as brakes made from other materials. Even under common driving conditions, poor heat dissipation can result in decreased brake performance. In high-performance and racing applications, poor heat dissipation is unacceptable.  
           [0004]    From an energy standpoint, a relatively large amount of energy is required to accelerate the large, heavy, cast iron brake rotors that are found in most passenger vehicles. Also, relatively large braking forces are required to decelerate such rotors. The weight of the rotors also increases the overall weight of the vehicle. Generally, excess weight negatively impacts handling and fuel economy.  
           [0005]    While it is known to replace cast iron with aluminum in brake rotors to decrease weight and increase heat dissipation, in most designs the weight reduction actually achieved is relatively insignificant and the complexity of manufacturing is increased to an unacceptable level.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, there is a need for lighter and better performing brake rotors that can be manufactured with a relatively simple process. In one aspect, the invention provides a brake rotor generally including a rotor body made of a first material having a central hub portion and a substantially annular disc portion extending from the central hub portion. The disc portion includes an inner disc surface and an outer disc surface. The brake rotor also generally includes an inner braking ring made of a second material, the inner braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the inner disc surface, and an outer braking ring made of a second material, the outer braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the outer disc surface. A plurality of projections extend from at least one of the inner disc surface and the outer disc surface to support thereon the respective one of the inner braking ring and the outer braking ring. The projections are generally configured in elongated diamond-like shapes oriented along an axis extending radially outwardly from the central hub portion.  
           [0007]    In another aspect, the invention provides a brake rotor generally including a rotor body made of a first material and having a central hub portion and a substantially annular disc portion extending from the central hub portion. The disc portion includes an inner disc surface and an outer disc surface. The brake rotor also generally includes an inner braking ring made of a second material, the inner braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the inner disc surface, and an outer braking ring made of a second material, the outer braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the outer disc surface. A plurality of projections extend from at least one of the inner disc surface and the outer disc surface to support thereon the respective one of the inner braking ring and the outer braking ring. A combination of two adjacent projections, the respective disc surface, and the respective braking ring form a converging-diverging nozzle to accelerate a cooling airflow past the respective disc surface and the respective braking ring.  
           [0008]    In yet another aspect, the invention provides a brake rotor generally including a rotor body made of a first material and having a central hub portion and a substantially annular disc portion extending from the central hub portion. The disc portion includes an inner disc surface and an outer disc surface. The brake rotor also generally includes an inner braking ring made of a second material, the inner braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the inner disc surface, and an outer braking ring made of a second material, the outer braking ring being fastened to the rotor body in an orientation substantially parallel with the disc portion and spaced from the outer disc surface. A plurality of elongated projections extend from at least one of the inner disc surface and the outer disc surface to support thereon the respective one of the inner braking ring and the outer braking ring. The projections are arranged in at least two radially spaced circular rows about the disc portion. The projections in any particular row are radially misaligned with the projections in any adjacent row.  
           [0009]    In a further aspect, the invention provides a method of manufacturing a brake rotor. The method generally includes forming a rotor body to have a hub portion and a disc portion extending from the hub portion, the disc portion having a first side and a second side. The method also generally includes configuring the first side of the disc portion with a plurality of support columellae. The support columellae on the first side of the disc portion partially defining cooling passageways through the brake rotor. Further, the method generally includes fastening a braking ring to the first side of the disc portion of the rotor body such that the braking ring is supported by the support columellae. The cooling passageways are defined by the disc portion of the rotor body, the support columellae, and the braking ring.  
           [0010]    In another aspect, the invention provides a brake rotor generally including a rotor body made of a first material and including a central hub portion having a central axis and a disc portion extending from the central hub portion. The disc portion includes a first surface and a second surface. The first surface of the disc portion has a plurality of columellae arranged in concentric rings coaxial to the central axis. The second surface of the disc portion has a plurality of columellae arranged in concentric rings coaxial to the central axis. The brake rotor also generally includes a first braking ring made of a second material, the first braking ring sized and shaped to be connected to the rotor body in an orientation substantially parallel with the disc portion, spaced from the first disc surface, and supported by the plurality of columellae of the first surface, and a second braking ring made of a second material, the second braking ring sized and shaped to be connected to the rotor body in an orientation substantially parallel with the disc portion, spaced from the second disc surface, and supported by the plurality of columellae of the second surface.  
           [0011]    In yet another aspect, the invention provides a brake rotor body generally including a hub portion having a central axis and a disc portion extending from the central hub portion. The disc portion includes a first surface and a second surface. The first surface of the disc portion has a first plurality of columellae arranged in a first ring coaxial to the central axis and a second plurality of columellae arranged in a second ring coaxial to the central axis. The second surface of the disc portion has a first plurality of columellae arranged in first ring coaxial to the central axis and a second plurality of columellae arranged in a second ring coaxial to the central axis.  
           [0012]    Further features and aspects of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    In the drawings:  
         [0014]    [0014]FIG. 1 is an exploded perspective view of a brake rotor embodying aspects of the invention.  
         [0015]    [0015]FIG. 2 is an exploded reverse perspective view of the brake rotor of FIG. 1.  
         [0016]    [0016]FIG. 3 is a top view of the assembled brake rotor of FIG. 1, illustrating a partial cutaway of an outer braking ring. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Before embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of the examples set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of applications and in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected,” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting, and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
         [0018]    With reference to FIGS. 1-3, an exemplary brake rotor  10  is shown. Generally, the brake rotor  10  includes a rotor body  14  having a central hub portion  18  and a disc portion  22 . The brake rotor  10  mounts to a vehicle&#39;s spindle (not shown) via the central hub portion  18 . The central hub portion  18  further includes spaced apertures  26  therethrough to affix wheel studs (not shown). Alternatively, if the brake rotor  10  is driven, the wheel studs may be affixed to an axle or constant velocity (“C-V”) joint, and the central hub portion  18  may be inserted upon the axle or C-V joint such that the wheel studs protrude through the spaced apertures  26 .  
         [0019]    As shown in FIGS. 1-2, an inner braking ring  30  is coupled to the rotor body  14  on one side of the disc portion  22 , and spaced a distance from an inner disc surface  34  of the disc portion  22 . An outer braking ring  38  is coupled to the rotor body  14  on the other side of the disc portion  22 , and spaced a distance from an outer disc surface  42  of the disc portion  22 . The inner and outer braking rings  30 ,  38  are coupled to the rotor body  14  such that, when the brake rotor  10  is assembled to the spindle positioned in the vehicle&#39;s wheel well, the inner braking ring  30  faces the inside of the wheel well and the outer braking ring  38  faces the outside of the wheel well. The braking rings  30 ,  38  provide respective braking surfaces  43 ,  44  that are frictionally engaged by a caliper through brake pads (not shown).  
         [0020]    As shown in FIGS. 1-2, the braking rings  30 ,  38  fasten to the rotor body  14  at locations on the rotor body  14  defining bosses  46 . The bosses  46  support the braking rings  30 ,  38  on the rotor body  14 . Bosses  46  are defined on both the inner and outer disc surfaces  34 ,  42 , and are generally arranged in two circular rows, an innermost circular row  50  and an outermost circular row  54 , concentric with the central hub portion  18 . The innermost circular row  50  is defined on the rotor body  14  at a location adjacent the central hub portion  18 , while the outermost circular row  54  is defined on the rotor body  14  at a location near the outer periphery of the disc portion  22 . In the exemplary construction of FIGS. 1-2, five bosses  46  are utilized in the innermost circular row  50  on both the inner disc surface  34  and the outer disc surface  42 , while ten bosses  46  are utilized in the outermost circular row  54  on both the inner disc surface  34  and the outer disc surface  42 . Alternatively, in another construction of the brake rotor  10 , a different number of bosses  46  may be utilized in the innermost and outermost circular rows  50 ,  54 . Depending on the intended application, and the magnitude of frictional braking forces transferred from the braking rings  30 ,  38  to the rotor body  14 , it might be desirable to utilize an increased or decreased number of bosses  46  to support and secure the braking rings  30 ,  38  to the rotor body  14 .  
         [0021]    With continued reference to FIGS. 1-2, the inner and outer braking rings  30 ,  38  are substantially identical in form in the illustrated embodiments. The braking rings  30 ,  38  include attachment tabs  58  defined around an inner perimeter surface  62  of the braking rings  30 ,  38 . The attachment tabs  58  protrude from the inner perimeter surface  62  and include apertures  66  therethrough. Fasteners  68  pass through the apertures  66  to secure the braking rings  30 ,  38  to the innermost circular row  50  of bosses  46 . The braking rings  30 ,  38  also include chamfered apertures  70  formed around a location adjacent an outer perimeter surface  74  of the braking rings  30 ,  38 . Additional fasteners  78  pass through the chamfered apertures  70  to secure the braking rings  30 ,  38  to the rotor body  14 . When the braking rings  30 ,  38  are assembled to the rotor body  14 , the chamfered apertures  70  allow the ends of the fasteners, or fastener heads  82 , that secure the braking rings  30 ,  38  to the outermost circular row  54  of bosses  46  to recess into the chamfered apertures  70 . This is done to allow the brake pads to frictionally engage the braking surfaces  43 ,  44  of the braking rings  30 ,  38  without concern of the brake pads contacting the fastener heads  82 . The fastener heads  82  are recessed into the chamfered apertures  70  to allow ample room for wear of the braking rings  30 ,  38  before replacement. As previously stated, if the rotor body  14  is formed with more or fewer bosses  46  as the exemplary construction of FIGS. 1-2, the number of attachment tabs  58  and chamfered apertures  70  will also vary accordingly.  
         [0022]    Again, with continued reference to FIGS. 1-2, the braking rings  30 ,  38  are fastened to the rotor body  14  through the bosses  46 . The innermost circular row  50  of bosses  46  include apertures  86  therethrough to allow the fasteners  68 , such as conventional nuts and bolts, rivets, or similar fasteners to pass through the braking rings  30 ,  38  and the rotor body  14  to secure the assembly together. Such fasteners  68  may be used to secure the braking rings  30 ,  38  to the innermost circular row  50  of bosses  46  because the brake pads are not in contact with the braking rings  30 ,  38  at the attachment tabs  58 . Further, the ends  90  of the fasteners  68 , such as the head of the bolt and the nut, may protrude from the respective braking surfaces  43 ,  44  of the braking rings  30 ,  38  in contact with the brake pads. Alternatively, in another construction of the brake rotor (not shown), chamfered apertures may also be used in the attachment tabs  58  to provide a recess for the ends  90  of the fasteners  68 , such that the ends  90  of the fasteners  68  do not protrude from the respective braking surfaces  43 ,  44  of the braking rings  30 ,  38  in contact with the brake pads.  
         [0023]    The outermost circular row  54  of bosses  46  include threaded apertures  94  to allow the fasteners  78 , such as screws or rivets, to secure the braking rings  30 ,  38  to the rotor body  14 . In the exemplary construction of the brake rotor  10  shown in FIGS. 1-2, separate sets of screws are utilized to secure the inner braking ring  30  and the outer braking ring  38  to the rotor body  14 , respectively. The screws include fastener heads  82  in the form of tapered heads matching the chamfer angle of the chamfered apertures  70  in the braking rings  30 ,  38 . As a result, the screws tightly engage the braking rings  30 ,  38 . Also, the tapered heads of the screws are recessed from the braking surfaces  43 ,  44  of the braking rings  30 ,  38  in contact with the brake pads. Alternatively, in another construction of the brake rotor (not shown), the outermost circular row  54  of bosses  46  include apertures therethrough to allow deformable fasteners, such as rivets, to secure the braking rings  30 ,  38  and the rotor body  14  together.  
         [0024]    With continued reference to FIGS. 1-2, the rotor body  14  includes multiple vane-like projections or columellae  98  (which are generically referred to herein as vanes) protruding from both inner and outer disc surfaces  34 ,  42 . As shown in the exemplary construction of FIGS. 1-2, the columellae  98  are arranged in circular rows (e.g., an innermost circular row  102 , a middle circular row  106 , and an outermost circular row  110 ) concentric with the central hub portion  18 . The columellae  98  protrude substantially the same amount from the inner and outer disc surfaces  34 ,  42  as the bosses  46  to provide additional support to the braking rings  30  and  38 .  
         [0025]    The columellae  98  define cooling air passageways  114  between the respective disc surfaces  34 ,  42  and the braking rings  30 ,  38 . The inner perimeter surface  62  of the braking rings  30 ,  38  are sized with a larger diameter than the diameter of the central hub portion  18 . As a result, when the braking rings  30 ,  38  are assembled to the rotor body  14  (see FIG. 3), an annular opening  118  is formed between the central hub portion  18  and the inner perimeter surface  62  of the outer braking ring  38  to promote a flow of cooling air through the annular opening  118  and between the outer disc surface  42  and the outer braking ring  38 . Also, the brake rotor  10  is open in the interior section of the central hub portion  18  (see FIG. 2), thus providing another annular opening (not shown) between the inner disc surface  34  and the inner braking ring  30  to promote a flow of cooling air through the annular opening between the inner disc surface  34  and the inner braking ring  30 .  
         [0026]    As shown in the exemplary airflow through the brake rotor  10  in FIG. 3, the columellae  98  arranged in the middle circular row  106  are generally configured in elongated diamond-like shapes and oriented radially on the disc portion  22 . The columellae  98  in the inner row  102  and outer row  110  are triangularly shaped. The configuration of two adjacent columellae  98  (shaped as illustrated in the drawings) accelerates the flow of air past the columellae  98 . This is the result of the columellae  98  of the middle circular row  106  approximating converging-diverging nozzles in the air passageways  114  formed between the respective disc surfaces  34 ,  42  and the braking rings  30 ,  38 . By increasing the flow of air between the respective disc surfaces  34 ,  42  and the braking rings  30 ,  38 , the brake rotor  10  is more efficiently and rapidly cooled, generally leading to increased performance and longevity of the brake rotor  10 .  
         [0027]    Further, columellae  98  arranged in the innermost circular row  102  and the outermost circular row  110  are generally configured as triangular or wedge-like shapes that are radially oriented on the disc portion  22 . The columellae  98  of the innermost circular row  102  and outermost circular row  110  are radially aligned on the disc portion  22 , while the columellae  98  of the middle circular row  106  are misaligned from the columellae  98  of the innermost circular row  102  and the outermost circular row  110 .  
         [0028]    In the exemplary construction of the brake rotor  10  shown in FIG. 3, both the configurations and the arrangement of the columellae  98  on the rotor body  14  promote “free movement” of air during rotation of the brake rotor  10  in a vehicle. During such “free movement,” air entering the annular openings  118  is allowed to flow through the brake rotor  10  in an almost unpredictable path, such that a large amount of area of the rotor body  14  is cooled by the airflow through the brake rotor  10 . Generally, however, air will flow in the paths designated by the dashed arrows P in FIG. 3. Further, the columellae  98  act as heat sinks for the braking rings  30 ,  38  since the columellae  98  are in abutting contact with the braking rings  30 ,  38 . As a result, the cooled braking rings  30 ,  38  fastened to the rotor body  14  provide increased performance over conventional, brake rotors.  
         [0029]    Preferably, the rotor body  14  is cast from aluminum or an aluminum alloy. Alternatively, the rotor body  14  may be machined from a billet material, rather than being cast from molten metal. Also, the rotor body  14  may be made of a material other than aluminum, although it is preferred to use material less dense than steel. The columellae  98  and the bosses  46  are cast with the rotor body  14 , such that relatively little finish work or machining is required to complete the rotor body  14 . In the case of the exemplary rotor body  14  in FIGS. 1-2, the apertures  86 ,  94  in the bosses may be formed during casting of the rotor body  14 . However, additional machining may be required in the bosses  46  to form threads, for example, when using threaded fasteners. In the case of the exemplary rotor body  14 , threaded fasteners  78  are used to secure the braking rings  30 ,  38  to the rotor body  14 . Therefore, a machining process is required to form the threads in the apertures  94 .  
         [0030]    Preferably, the inner and outer braking rings  30 ,  38  are stamped from sheet metal, such as steel, stainless steel, high-strength steel, or titanium. Other materials, including non-metals such as ceramics or composite materials might also be used to make the rings  30  and  38 . The attachment tabs  58  and the apertures  66  are also formed during the stamping process, which can be achieved using conventional methods and technologies such as stamping dies and stamping presses. Stamping the braking rings  30 ,  38  provides a product that requires little, if any, additional machining to achieve a final product (However, in the case of the exemplary braking rings  30 ,  38  in FIGS. 1-2, the chamfered apertures  70  may require additional machining to provide the chamfer). Another benefit of stamping is that stamping dies are re-usable. Thus, stamping the braking rings  30 ,  38  from sheet metal is highly economical and productive. Alternatively, the braking rings  30 ,  38  may be cast and/or machined from a billet material, rather than being stamped from sheet metal. Generally, the braking rings  30 ,  38  may be made of any metal harder and with a higher melting temperature than the material used to make the rotor body  14 . Assembly of the braking rings  30 ,  38  onto the rotor body  14  may be accomplished using an automated assembly process, or may be accomplished by hand.  
         [0031]    The exemplary brake rotors  10  that are illustrated and discussed dissipate heat more efficiently than conventional, cast iron brake rotors for a number of reasons. One of those reasons includes the desirable material properties of aluminum. The thermal conductivity of aluminum is about three times greater than cast iron, and the thermal diffusivity of aluminum is about four times greater than cast iron. Both of these material properties relate how well a material is able to conduct heat. As a result, the brake rotor  10  (having the aluminum rotor body) is able to dissipate the built-up heat at a higher rate than the cast iron brake rotor. Of course, the cooling passageways  114  formed between the respective braking rings  30 ,  38  also facilitate heat dissipation. As a consequence, the brake rotor  10  is generally capable of providing increased braking performance over a period of use, when compared to a cast iron brake rotor. Aluminum is also lighter in weight then cast iron. Thus, embodiments of the rotor described herein are lighter than conventional rotors.  
         [0032]    In an alternative embodiment of the invention, the rings  30  and  38  may include a plurality of apertures. As shown in FIG. 2, the ring  30  may include apertures  130  and the ring  38  may include apertures  134 . The apertures  130  and  134  enhance airflow in the passageways  114  and in combination with the passageways  114  provide enhanced airflow between the rings  30  and  38  helping to improve cooling and increase heat dissipation. The apertures  130 ,  134  are shown as circular in shape, but other shapes could be possible. Further, the apertures maybe configured in a variety of patterns.  
         [0033]    As can be seen from the above, embodiments of the invention provide an improved brake rotor. Various features of embodiments of the invention are set forth in the following claims.