CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 61/155,745, filed February 26, 2009.

BACKGROUND

[0002] The present invention relates to brake discs or "rotors" for disc-type braking systems on vehicles, and in particular motorcycles. In most traditional disc braking systems, brake rotors are attached to the hub of a wheel to be rotated with the wheel about an axis, and a stationary caliper is positioned to wrap around a radially outer edge of the rotor. In such braking systems, braking loads are transferred between the tire and the brake rotor through the wheel spokes. The caliper is actuated by pressurized fluid to selectively squeeze the rotor to slow and/or stop the rotation of the rotor and the associated wheel by friction. The friction, if not dissipated, builds up and heats the rotor. Heating a brake rotor generally has an inverse effect on the brake rotor's performance capability.

[0003] Automotive brake rotors have been developed with air channels between the braking surfaces for convective cooling. In fact, it is not uncommon for automotive brake rotors to include vanes to allow the rotor to act as a centrifugal air pump to drive the convection cooling while the rotor rotates. However, motorcycle brake rotors are substantially smaller in thickness and required to be very light weight compared to automotive brake rotors. Generally, most motorcycles also have much smaller production volumes compared to automobiles. Due to these differences, it is impractical and cost prohibitive to produce motorcycle rotors according to automotive design (e.g., including air passages for centrifugal pumping between the braking surfaces).

SUMMARY

[0004] In one aspect, the invention provides a brake rotor for a motorcycle including a pair of opposed braking surfaces spaced apart to define a rotor thickness. The brake rotor further includes a radially outer edge and a radially inner edge. A plurality of mounting features are positioned at the radially outer edge for coupling the brake rotor to a motorcycle wheel. A groove is formed in the radially outer edge. The groove is axially spaced from both of the braking surfaces. [0005] In another aspect, the invention provides a brake rotor for a motorcycle including a pair of opposed braking surfaces spaced apart to define a rotor thickness. The rotor further includes a radially outer edge and a radially inner edge. A plurality of mounting features are positioned at the radially outer edge for coupling the brake rotor to a motorcycle wheel. A pair of axially spaced apart fins are at the radially outer edge. Each of the fins includes a side surface co-extensive with one of the braking surfaces.

[0006] In yet another aspect, the invention provides a brake rotor for a motorcycle including a pair of opposed braking surfaces spaced apart to define a rotor thickness. The brake rotor further includes a radially outer edge and a radially inner edge. A plurality of mounting recesses are positioned at the radially outer edge for coupling the brake rotor to a motorcycle wheel. A first groove is formed in the radially outer edge. The first groove is axially spaced from both of the braking surfaces and has an axially measured width of about one-third of the rotor thickness. A second groove is formed in the radially inner edge. The second groove is axially spaced from both of the braking surfaces and has an axially measured width of about one-third of the rotor thickness. The first groove and the second groove have respective portions of substantially uniform radially measured depth extending along respective portions of the outer edge and the inner edge in the circumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a side view of a motorcycle including a front disc-braking system.

[0008] Fig. 2 is a front view of a brake rotor of the front disc-braking arrangement of Fig. 1.

[0009] Fig. 3 is a cross-sectional view of the brake rotor, taken along line 3-3 of Fig. 2.

[0010] Fig. 4 is a first detail view of the brake rotor taken from Fig. 2, showing an exterior recess.

[0011] Fig. 5 is a second detail view of the brake rotor taken from Fig. 2, showing a pair of interior recesses.

[0012] Fig. 6 is a cross-sectional view of the brake rotor, taken along line 6-6 of Fig. 2.

[0013] Fig. 7 is a cross-sectional view of the brake rotor, taken along line 7-7 of Fig. 6. [0014] Fig. 8A is a perspective view of an interior portion of the brake rotor of Fig. 2.

[0015] Fig. 8B is a perspective view of an exterior portion of the brake rotor of Fig. 2.

[0016] Fig. 9 is a front view of an alternate brake rotor.

[0017] Fig. 10 is a front view of an alternate brake rotor.

[0018] Fig. 11 is a detail view of the brake rotor taken from Fig. 10, showing the area surrounding a mounting location.

[0019] Fig. 12 is a perspective view of the rotor of Fig. 10.

DETAILED DESCRIPTION

[0020] Before any 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 construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

[0021] Fig. 1 illustrates a motorcycle 10 having a front disc-braking system 12 that is coupled to a front wheel 13 of the motorcycle 10. The front wheel 13 includes a rim portion 13A to which a tire 14 is coupled. A caliper 16 is coupled to a front fork 18 of the motorcycle 10 in a position that wraps around a brake rotor 20 (Figs. 2-8B). The rotor 20 is configured to be fixed to the wheel 13 to rotate therewith. The rotor 20 defines a rotational axis A that is shared with the wheel 13. The illustrated rotor 20 is particularly configured to be used in an inside-out type braking system as at 12, in which the rotor 20 is configured to be positioned adjacent the rim portion 13 A, with the caliper 16 extending around the rotor 20 from the radially inward side. U.S. Patent Nos. 6,561,298 and 6,672,419, both of which are hereby incorporated by reference, disclose inside-out braking systems and structure for mounting a rotor for such a system. As discussed in further detail below, certain features of the rotor 20 are particularly beneficial to a rotor that is used in an inside-out arrangement. However, a rotor for a disc braking arrangement having a conventional caliper position (i.e., wrapped around the radially outside edge of the rotor) can also be constructed with at least some of the features described below. Also, although the rotor 20 is illustrated as being part of the braking system 12 for the front wheel 13, a similar rotor can be configured for use with a rear wheel disc-braking system.

[0022] The rotor 20 is ring-shaped and has a radial width RW, measured between an outer edge 28 and an inner edge 52, that is less than about 25 percent of the outer radius R of the rotor 20 (as measured from the axis A to the outermost point) to create a large interior opening. This allows the caliper 16 to be positioned inside the rotor 20 and allows the rotor 20 to be coupled to the wheel 13 adjacent the rim portion 13 A. In some constructions, the radial width RW of the rotor 20 is between about 30.0 millimeters and about 50.0 millimeters. Mounting features for the rotor 20 include six recesses 24 in the outer edge 28 of the rotor 20 are used to couple the rotor 20 to the wheel with six fasteners 30 (Fig. 1). One of the recesses 24 is illustrated in the detail view of Fig. 4. The rotor 20 includes a pair of opposed braking surfaces 32A, 32B, at least portions of which are configured to be frictionally engaged by brake pads 34 (Figs. 2 and 6) that are applied to the braking surfaces 32A, 32B by the caliper 16. A plurality of apertures 36 extend through the rotor 20 perpendicular to the two braking surfaces 32A, 32B.

[0023] Channels or grooves 40 are formed in the outer edge 28 of the rotor 20. The grooves 40 extend around the entire circumference of the rotor 20, only being interrupted at each of the mounting recesses 24. Each of the grooves 40 has a depth (radially-measured) that is less than the radial width RW (i.e., the grooves 40 do not extend from the outer edge 28 to the inner edge 52 to create a passage therebetween). The grooves 40 are more than about 2.0 millimeters deep. The grooves 40 are between about 3.0 millimeters and about 6.0 millimeters deep in some constructions. The grooves 40 are about 5.0 millimeters deep in one construction. In the immediate area where the grooves 40 approach the mounting recesses 24, the groove depth may decrease gradually to zero as shown in Figs. 2, 7 and 8B. Thus, the grooves 40 are blind grooves since at least one circumferential end of each groove 40 is substantially closed.

[0024] An axially measured width W (Fig. 6) of each of the grooves 40 is about 2.0 millimeters in one construction. The width W of each of the grooves 40 can be between about 10 percent and about 70 percent of the rotor thickness (measured between the opposed braking surfaces 32A, 32B). In the illustrated construction, the width W of each of the grooves 40 is about one-third of the rotor thickness. Pairs of parallel fins 44 that extend around the circumference of the rotor 20 are axially spaced by the grooves 40 as shown in Fig. 6. Each of the fins 44 has a radial length L (Fig. 6) that is equal to the depth of the grooves 40. The groove depth (and correspondingly, the length L of the fins 44) is substantially uniform extending along a portion of the rotor 20 in the circumferential direction. In some constructions, the groove depth may be uniform around a substantially entire circumference of the rotor 20 or at least at all locations where the grooves 40 exist (e.g., all areas except those immediately adjacent the mounting recesses 24).

[0025] The thickness T of each of the fins 44 is about equal to the groove width W in the illustrated construction. Although the width W of the grooves 40 may be more or less than 2.0 millimeters, the thickness T of each of the fins 44 is always less than one-half of the total rotor thickness. The thickness T of each of the fins can be between about 15 percent and about 45 percent of the total rotor thickness.

[0026] As shown in Fig. 6, the width W of the grooves 40 is uniform substantially all the way to the bottom of the grooves 40. This particular shape, having substantially parallel interior facing groove surfaces, is effective for cooling and beneficial for manufacturability. In some constructions, the grooves 40 have an alternate shape (e.g., "V" or "wedge" shaped, among others). Alternate groove shapes, in which the side walls of the groove are not in parallel, facing relationship, may provide even greater cooling efficiency but may be less desirable for cost and manufacturability.

[0027] Additional channels or grooves 48 are formed in an inner edge 52 of the rotor 20 opposite the outer edge 28. As shown in Fig. 6, the grooves 48 in the inner edge 52 are not as deep as the grooves 40 in the outer edge 28 in the illustrated construction. In one construction, the inner grooves 48 have a depth D of about 2.0 millimeters. In other constructions, the depth D is the same as that of the grooves 40 in the outer edge 28, or the grooves 40 in the outer edge 28 can have a depth that is less than the depth D of the grooves 48 in the inner edge 52. The grooves 48 in the inner edge 52 are not in communication with the grooves 40 in the outer edge 28. Rather, the respective grooves 40, 48 are separated by a solid intermediate rotor section (Figs. 6 and 7).

[0028] Pairs of parallel fins 56 extend around the circumference of the inner edge 52 and are axially spaced by the grooves 48. The depth D of the grooves 48 (and correspondingly, the radial fin length of the fins 56) is substantially uniform extending along a portion of the rotor 20 in the circumferential direction. In some constructions, the groove depth D may be uniform around a substantially entire circumference of the rotor 20, or at least at all locations where the grooves 48 exist.

[0029] The fins 56 at the inner edge 52 are similar to the fins 44 on the outer edge 28, but have a reduced radial length corresponding to the smaller depth D of the grooves 48. The width of the grooves 48 is substantially equal to the width W of the grooves 40 such that the axial spacing between the inner fins 56 is about the same as the axial spacing between the outer fins 44.

[0030] The illustrated rotor 20 is designed such that the outer fins 44 extend radially beyond a non-finned rotor of otherwise similar design. In other words, the rotor 20 is not formed by taking an existing rotor and cutting away material from the outer edge to form the grooves 40. Rather, the fins 44 add to the overall radial dimension of the rotor 20 compared to a non- finned rotor of the same size and shape. The radial length L of the fins 44 is a significant portion of the overall radial width RW of the rotor 20. In the illustrated construction, the radial length L of the fins 44 is about 15 percent of the pad- swept radial width Wp of the rotor 20. The pad- swept radial width Wp is the designated radially measured width of the rotor 20 that is configured to be covered by and contacted by the brake pads 34. The pad-swept radial width Wp of the rotor 20 is approximately equal to the overall radial width RW minus the radial length L of the fins 44. Thus, the addition of the fins 44 to a non- finned rotor equates to about a 15 percent increase in radial width. The 15 percent increase in the radial dimension increases total surface area by about 40 percent. Outward-facing surface area (not including the facing surfaces on the inside of the grooves 40), which is most beneficial to radiant cooling, is increased by about 20 percent. This increase in surface area increases the amount of heat that can be transferred from the rotor 20 by radiant cooling. In other constructions, the radial length L of the fins 44 is between about 10 percent and about 50 percent of the pad-swept radial width Wp. The optimum radial fin length L is dependent upon cooling requirements and the thermal conductivity of the rotor material. Higher conductivity rotor materials will support greater radial fin length L, all else being equal.

[0031] In contrast to the outer fins 44, which extend the outer edge 28 of the rotor 20, the inner edge 52 is not extended further inward by the presence of the fins 56 as compared to a non- finned rotor of otherwise similar design. Rather, the inner fins 56 are formed by simply cutting the grooves 48 into the rotor 20. [0032] The outer fins 44 and the inner fins 56 provide increased surface area, promoting the primary cooling mechanism, radiant cooling, although convective cooling is also increased. The position of each of the fins 44 in the outer edge 28 makes them particularly effective at increasing the cooling capacity because the total peripheral length (circumferential direction) of the fins 44 is very large, increasing the surface area geometrically more than the percentage change in radial depth. Thus, the fins 44 are more effective than they would be on a traditional brake rotor because the rotor 20 inherently has a much larger outer circumference by being configured for an inside -out braking system. In addition, fins located on the outside of a brake rotor on a motorcycle front wheel can be readily exposed to the oncoming airflow, further increasing convective cooling.

[0033] Because the braking system 12 is of the inside-out type, the cooling capacity can be increased without weakening the caliper 16 or increasing its weight. In a traditional brake rotor, increasing the outer diameter to accommodate fins would increase the necessary throat depth of the caliper, which has to be positioned to maintain clearance between the caliper and the outer edge of the rotor. Increasing the throat depth or "reach" of the caliper makes it less stiff for a given cross-section. Increasing the cross-section to maintain stiffness results in increased weight, which is an undesirable design trait. With the ring-shaped rotor 20 configured to be positioned radially outside the caliper 16, the outer diameter can be extended with no negative effect on the strength or weight of the caliper 16.

[0034] As shown in the drawings, the rotor 20 further includes a plurality of circumferentially-spaced recesses or notches 60 formed in the inner edge 52 of the rotor 20. Two of the notches 60 are illustrated in the detail view of Fig. 5. In the illustrated construction, two notches 60 are symmetrically positioned across from each of the mounting recesses 24 on the outer edge 28. Each pair of notches 60 serves to maintain substantially constant rotor mass along the circumference by reducing the material amount of the rotor 20 across from each of a pair of radially-extending tabs 64 that flank each mounting recess 24. Equalizing the rotor mass along the circumference helps equalize rotor temperatures and avoid hot spots. The rotor 220 of Figs. 10-12 is identical to the rotor 20 of Figs. 2-8B, except that it is designed to maintain constant rotor mass at all sections along the circumference (except where the holes 236 extend through the rotor 220), whereas the rotor 20 is designed to take advantage of mass equalization in certain areas without compromising the cost and manufacturability of the rotor 20. The notches 60 also combine with the apertures 36 to sweep the entire surface of the brake pads 34. Thus, as the rotor 20 rotates relative to the caliper 16, the pads 34 encounter some type of edge on the braking surfaces 32A, 32B (i.e., the apertures 36 or the notches 60) at every radial position.

[0035] Although the mounting recesses 24 and the notches 60 are adequate in the illustrated construction, additional breaks or cross-slots in the fins 44, 56 are added in some constructions to reduce or eliminate hoop stresses, reducing the effect of thermal stresses.

[0036] The brake rotor 20 described above and illustrated in detail in Figs. 2-8B is effective to substantially increase the performance of the braking system 12 by providing greater heat dissipation ability with minimal or no increase in system weight and minimal or no sacrifice in caliper strength. Further, the brake rotor 20 can be manufactured at nearly the same cost as a non-finned rotor. For example, the addition of the fins 44, 56 and the notches 60 to an otherwise identical rotor may only increase the total manufacturing cost by about 1 percent or less. By contrast, motorcycle brake rotors that are designed with air channels for centrifugal pumping and convective cooling to emulate automotive brake rotors may cost 5 to 10 times as much as the rotor 20 or a conventional motorcycle brake rotor.

[0037] Testing on the illustrated rotor 20 has resulted in significantly lower running temperatures for a given braking test cycle and better maximum heat dissipation than heavier, more massive rotors that lack the fins 44, 56 and the notches 60 of the rotor 20.

[0038] Fig. 9 illustrates an alternate brake rotor 120 that is similar to the brake rotor 20 illustrated in Figs. 2-8B in many respects. As such, the last two digits of the reference numbers are similar where similar features are indicated. For example, the rotor 120 of Fig. 9 includes fins 144 on the outer edge 128 and a single fin 156 on the inner edge 152 that have cross-sectional profiles similar to the fins 44, 56 of the rotor 20. However, unlike the rotor 20 of Figs. 2-8B, the rotor 120 includes a radial bulge or "hump" 170 about midway between each adjacent pair of mounting recesses 124. The humps 170 increase the peripheral length of the fins 144 on the outer edge 128 without increasing the overall diameter of the rotor 120. Without the humps 170, the area between mounting locations is typically the area with the smallest radial width. The additional radial width provided by the humps 170 provides additional material at these circumferential locations to inhibit uneven heating of the rotor 120. Although the rotor 120 of Fig. 9 does not include notches on the inner edge 152 similar to the notches 60 shown in Fig. 5, such notches can be incorporated adjacent the mounting locations and/or adjacent the locations of the humps 170. Because the rotor 120 of Fig. 9 is illustrated without notches in its inner edge 152, the apertures 136 are evenly spaced around the entire circumference with no interruption at the mounting locations. Alternatives and optional configurations described above with respect to the rotor 20 of Figs. 2-8B also apply to the rotor 120 of Fig. 9.