OPTIMIZED RAMP ANGLE ON WHEEL TO REDUCE OUTBOARD BEAD MOUNTING PRESSURE

Abstract: A tire rim (1) has a 5 DEG bead seat (3) while an inclined surface (8) nearest to the outboard flange of the rim and extending between the wheel well (4) and a bead hump (5, 6) the inclined surface has a maximum inclination alpha of less than 65 DEG , preferably in the range of 58 DEG to 62 DEG .

Description: OPTIMIZED RAMP ANGLE ON WHEEL TO REDUCE OUTBOARD BEAD MOUNTING PRESSURE Technical Field This invention relates to a rim for passenger and light truck tires. More specifically, the invention discloses a modified 5° drop center rim contour for a J(1S0) contour as defined by The Tire and Rim Association, Inc., 1998 handbook. Background of the Invention Over the years, the tubeless pneumatic tire and its associated rim have been designed to make an efficient wheel assembly. The rim provides a means to attach the wheel to the vehicle; it provides a space to locate and attach the brake assembly and finally and foremost, it provides a bead seat and rim flange designed to accept a tire and to secure that tire creating an air-tight seal between the rim and the tire. The combination of the tire and the rim flange also provides a surface to attach leaded balancing weights to reduce rim and tire vibration due to ' out of balance conditions. The rim is a most efficient mechanical structure performing all of the functions described above in one well engineered structure. The rim has evolved over the years from a cold rolled steel structure to highly engineered cast magnesium or aluminum light weight structure. The tire engineer has rarely been a significant contributor to the evolution of the rim. Radical and usually complex rims have been suggested by various tire companies to solve a difficult problem in the tire. Almost universally, these rim solutions meet with failure having very poor market acceptance. The early evolution of so-called safety tires and runflat tires all have suggested designing a special rim and tire combination. Experience dictates that the tire engineer preferably should solve his or her tire related problems within the standards already established in the United States, Europe and Japan. Within these standards, however, there are some very interesting opportunities that can greatly improve the fit relationship between the tire and the rim. In particular, tire engineers when confronted with rim diameters having a ±0.4 mm tolerance. The tire correspondingly must fit, seal, and stay secured when confronting the entire range of rim diameters. Accordingly, a tire that is mounted on a high side (D±0.4 mm) rim will have a high mounting pressure because that same tire must work on a low side (D-0.4 m) rim. Pneumatic tires of the tubeless type preferably can be mounted on a rim using a tire mounting apparatus that will seat the beads of the tire at or below 40 psi. To achieve this mounting pressure on runflat tires has been difficult. A primary problem is that the inboard side of the rim can accept a mechanical pressing of the tire bead onto the rim seat while the axially outer or outboard side must be pressurized to press the tire bead over the bead hump to seat it. The axially outer bead seat is adjacent to the well of the rim. The well is the depressed small diameter central portion or region that enables a portion of the tire's bead to slip into so that the remaining bead portion can be slipped over the rim flange. Prior art patents disclose a variety of solutions to improving the tire to rim-fit relationship. In U.S. Patent No. 4,351,382 entitled "TIRE AND WHEEL RIM ASSEMBLIES", a unique pair of abutments are disclosed that more securely lock the beads of the tire to the rim. The abutments commonly referred to as the "bead humps" have a vertical or almost vertical face adjacent to the bead, preferably in the range of 80° to 100°; while the guide face of the abutment is in the range of 30° to 60° to facilitate getting the bead over the tire wheel. The concept as disclosed may solve the retention of the tire onto the rim in the deflated state but it is doubtful a tire could be removed once mounted without damaging the bead toe portion of the tire. Furthermore, the abutment next to the rim well has the conventional inclination that is about 70° to 80° relative to the rims axis of rotation. This feature is problematic for run-flat tires because the bead tends to stick on the almost vertical face of the well. Once stuck on this vertical face, the beads will not seat. To overcome this problem of the bead sticking to the well side inclined surface, Shiozawa, et al . in U.S. Patent No. 5,139,067 teaches an inclined surface in the range of 15° to 45° relative to the axis of rotation of the tire or rim. These inventors teach that if the well side inclined surface is less than 15° or more than 45°, a resistance of the hump (10) to the bead portion B is excessively high in mounting the tire on the tire rim so that inner pressure of the tire exceeds the safety value of JATMA standard. The intersecting angle b is preferably 20° to 40°, in the embodiment shown 30°. U.S. Patent No. 5,082,041, also by Shiozawa, et al . , shows a modified bead hump with the inclined surface (11) on the well side being 30° relative to the tire's axis of rotation with the radially inner portion of the well side being presumably at the conventional 70° to 80° relative to the tire's axis. The object of the present invention is to provide a 5° drop center rim J(150) contour for 14, 15, 16, 17, 18, 19 and 20 inch rim diameters or any other passenger or light truck rim size that is within the recommended industry standard but greatly reduces mounting forces. Another object of the invention is to substantially maintain the axial distance between the rim flange on the outboard side of the rim, i.e., the one closest to the well side and the instant surface of the well. /Another objective is to maintain the axial location of both the rim flanges relative to the mounting attachments. Finally, the ability to mount the tires, particularly runflat tires well below 40 psi without compromising the retention of the deflated tire on the rim, is a primary objective. Summary of the Invention A tire rim has an axially inboard and an axially outboard end, a pair of annular flanges at both axial ends, respectively a pair of bead seats axially inwardly extending from the flanges. The rim has a reduced diameter central portion between the opposing bead seats. A bead hump is adjacent each bead seat. One inclined surface extends between the reduced diameter central portion and the bead hump nearest the annular flange located adjacent the axially outboard side. The tire rim is characterized by the combination of the one inclined surface and the bead hump having a maximum inclination i of less than 65° from a diameter D. The diameter D has ends or extremities located on the one inclined surface halfway between the bead hump and the reduced diameter central portion adjacent to the one inclined surface. At the ends or extremities of the diameter D the one inclined surface has a minimum inclination α 2 of greater than 45°. Preferably the inclination αi is between 58° and 62°, most preferably about 60°. Similarly in a preferred embodiment, α 2 is between 58° and 62°, most preferably about 60°. In a preferred embodiment i equals o 2 . The reduced diameter central portion commonly referred to is a wheel well; the wheel well is located in closer proximity to the axially outboard flange. The wheel well is spaced less than 45 mm from the axially outboard flange. Brief Description of Drawings FIGURE 1 is a cross-sectional profile of a 5° drop center rim contour for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 inch rim diameters and any dimensions there between those listed above as shown in The Tire and Rim Association, Inc. 1998 handbook. FIGURE 1A is the rim profile of the outboard side when a round hump is used. FIGURE 2 is a cross-sectional view of a rim profile according to the present invention. FIGURE 3 is an enlarged cross-sectional profile of the rim profile outboard side. FIGURE 4 is an alternative style rim contour according to The Tire and Rim Association, Inc. 1998 handbook. FIGURE 5 is an enlarged cross-sectional profile of the rim profile outboard side of the rim of FIGURE 4. FIGURE 6 is a partially cross-sectional view of a wheel assembly including the disc brake. Detailed Description of the Invention With reference to FIGURES 1 and 1A, there is shown a profile of a standard industry specified 5° drop center rim (1) for passenger vehicles. The rim (1) has a pair of axially spaced rim flanges (2) . The flanges (2) are spaced a distance (4) . Each flange extends radially outwardly from a bead seat (3); the bead seat has an inclined surface relative to the rim's axis, the inclination being 5°. Axially inward of each bead seat is a bead hump (5) or (6) . In FIGURE 1 bead hump (5) is commonly referred to as a "flat hump" while in FIGURE 1A a rounded hump (6) is shown. These humps (5) or (6) form an annular ridge that help keep the tire seated onto the bead seat by creating an obstruction to axially inward movement of the tire bead when the tire is operated without being inflated. Under normal inflated driving conditions the tire is pushed axially outwardly against the flanges (2) while the radially inner surface of the tire's bead commonly referred to as the region between the "heel" and the "toe" seals airtightly against the inclined bead seat (3) . The tire designer must design the tire bead to have a diametral interference fit with the bead seat. The radially inner portion of the tire bead is generally elastomeric and conformable to the inclined bead seat, upon assembly the bead is both deformed and compressed by the tire's bead core and the bead seat of the rim. For the deformation and compression to occur, the bead of the tire must first slide radially and axially outwardly along the inclined surface (8) and over the bead humps (5) or (6) . The industry standard rims (1) specified that the inclined surface (8) must have a minimum inclination of 10° off vertical. Typically the inclination α is about 69° or more relative to the rim's axis of rotation on the outboard side of the vehicle. Tire rims have a diametrically depressed central portion (4) that facilitates the tire mounting procedure. Those skilled in the art commonly referred to this central portion (4) as a "wheel well". The wheel well is generally and preferably located closer to the outboard side of the rim. This means that the outboard bead seat and flange are generally axially closer to the mounting holes of the rim while the inboard side of the rim seat and flange are cantilevered axially inward from the mounting holes. Ideally, the wheel well (4) has an axial width C. In the space between the wheel well (4) and the axially inboard side of the rim (1) both the brake disk caliper assembly is located as shown in FIGURE 6. The rim manufacturers try to maximize the space between the wheel well and the inboard flange. One reason why to accomplish this is the standard alternative rim as shown in FIGURE 4. As shown in the figures, the outboard rim seat and bead hump are actually cantilevered over the wheel well (4) . The thickness T is all the tire bead contacts when attempting to mount the tire onto the rim. Again, there is a high propensity for the bead portion to stick or hang up on those surfaces, due in past to the almost vertical face of the surface (8) . The modified inventive rim of FIGURE 5 shows an almost conical surface (8) extending to the bead hump and having an angle Ό ± of less than 65°, generally between 58° and 62°, most preferably about 60° relative to the axis of rotation. The radius R5 being about 0.5 mm or less. This more inclined surface is fundamentally much easier to locate the bead portion of the tire onto without providing a vertical surface to prevent slippage. As shown in the figures, the central portion (4) between the pair of radii Ri has an axial width C. In many runflat tires, air pressure sensing devices are located in this area of the rim. Such sensors typically are about 1.25 inches wide and 1.375 inches high and are accurately shaped having a circumferential length of about 4.5 inches. As shown, these devices are currently installed 180° opposite the valve stem. This method of assembly enables the mechanic changing the tire to break the bead seal at 90° and 270° relative to the valve stem. This insures the sensing device is not damaged when the tire is removed. This use of the wheel well makes it imperative that the size and location of the wheel well remain fundamentally unchanged. Nevertheless, the outboard sides inclined surface (8) can be improved without compromising the rims' simplicity or functionality. As shown in FIGURE 2, the modified inclined surface (18) has a maximum inclination αl of less than 65° from a diameter D. The diameter D passes through the rims' axis of rotation and has its extremes or end locations halfway between the bead hump radially outermost location and the reduced diameter central portion adjacent the modified inclined surface (18) . The one inclined surface (18) has a minimum inclination or 2 measured at the diameter D greater than 45°. Preferably the maximum inclination αi is between 58° and 62° most preferably 60° while the minimum inclination at the extremities of D are preferably between 58° and 62°, most preferably 60°. As shown in FIGURE 3, the intersection location of the inclined bead seat (3) and the one surface (18) is where the bead hump radius R 3 is ideally located. Preferably R 3 is about 0.25 inches or less. As can be quickly appreciated, the surface (18) being inclined at i and extended to the base of the wheel well only slightly shifts the wheel well toward the inboard side. Alternatively, at radially inward of the end location (7) of diameter D the inclination can change to almost vertical without adverse mounting consequences; in such a case, there is no shifting or shrinking of the width of the wheel well. Testing of the inventive rim (1) concept at inclinations αi equal to 60°, 45° and 30° for the surface (18) was conducted and compared to a rim having an inclined surface (8) of prior art of α equal to 69°. Test tires having a size P285/40ZR17 with a bead diameter of 17.38 inches were mounted on at 5° drop center rim having the prior art 69° inclined surface (8) and the maximum sharp diameter (ND +0.04 inches) had actual mounting pressures ranging from 74 to 38 psi. The wheel was recut and modified to have a 60° oci inclination of the modified surface (18) and the mounting pressure ranged from 38 to 24 psi. The prior art 69° inclined surface (8) average mounting pressure of 55 psi was 31 psi higher than the inventive rim having a 60° inclination, αi of the modified surface (18) which exhibited an average mounting pressure of 24 psi. A second test was conducted evaluating a minimum sharp diameter prior art rim (ND-0.04 inches) had mounting pressure range of 40 to 50 psi and an average of 45 psi. A rim was modified having a 30° i inclination the mounting pressure using similar tires ranged from 9 to 25 psi yielding a 14 psi average. A third test was conducted using a P255/45ZR17 inch tire having a 17.42 bead diameter. The rim had a maximum sharp diameter, the mounting pressure ranged from 24 to 32 psi, average 28 psi. A modified rim having a 45° i inclination along surface (18) yielded a 32 to 24 psi, 22 psi average mounting pressure range or a 6 psi lower mounting pressure than the prior art 69° inclined surface. The third test wherein the tire bead diameter is large and the rim is also large shows that the reduction in mounting pressure is of little consequence. This condition reflects when both the tires and the rim has tolerances shifted similarly. It is predicted that nominal sized rims and tire beads when mated together would yield similar favorable results. It is when the rims are maximum and the beads are of minimum tolerances that the mounting pressure becomes a most difficult. Conversely minimum sized rim and maximum sized tire beads while requiring less mounting pressure may be difficult to keep properly seated when the tire is operated without air inflation. What the test results indicate was that a minor inclination shift from 69° to 60° for i yielded results under a worst case tolerance situation that were below 40 psi consistently. A most interesting feature of the test results was that oti angles of 30° and 45°, while being predictably lower in the average mounting pressure, these inclinations required a substantial shifting of or reduction of the wheel well when compared to the 60° αi inclination. For example, a wheel well that is 2.0 inches deep having the almost vertical 69° inclination α of the surface (8) when modified by changing α to an αi of 60° is shifted axially inward 0.39 inches at full depth. Similarly at l of 45° a shift of 1.24 inches results. At i of 30° a shift of 2.7 inches results. Naturally, if the objective is to minimize the shift or the reduction of the wheel well width then the 60° αi is a superior choice. Most beneficially when ot. is initiated at the ends (7) or extremes of D then the surface radially inward of D can be vertical along surface (18). In that case, the shift of a 2.0 inch deep well would be less than 0.2 inches. While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

Claims: CLAIMS 1. A tire rim having an axially inboard end and an axially outboard end having a pair of annular flanges at both axial ends, respectively, a pair of bead seats axially inwardly extending from the flanges, a reduced diameter central portion between the opposing bead seats, a pair of bead humps, one hump being adjacent each bead seat, and one inclined surface extending between the reduced diameter central portion and the bead hump nearest the annular flange located adjacent the axially outboard side, the tire rim characterized by the combination of the one inclined surface and the bead hump having a maximum inclination oti of less than 65° from a diameter D, the extremes of the diameter D being located on the one inclined surface halfway between the bead hump and the reduced diameter central portion and the one inclined surface having a minimum inclination 2 as measured at the diameter D greater than 45°. 2. The tire rim of claim 1 wherein the maximum inclination i is in the range of 58° to 62° relative to the axis of rotation. 3. The tire rim of claim 2 wherein the maximum inclination αi is about 60° relative to the axis of rotation. 4. The tire rim of claim 2 wherein the inclination αi and 2 are substantially equal. 5. The tire rim of claim 1 wherein the central portion is a wheel well having a reduced diameter, the wheel well being axially located in closer proximity to the axially outboard flange, the wheel well being spaced less than 45.0 mm from the axially outboard flange. 6. The tire rim of claim 1 wherein 2 is in the range of 58° to 62° relative to the axis of rotation. 7. The tire rim of claim 6 wherein α 2 is about 60° relative to the axis of rotation.

Inventors: AUBE MICHAEL ALBERT, OARE THOMAS REED, AUBE, MICHAEL, ALBERT, OARE, THOMAS, REED
Applicants: AUBE MICHAEL ALBERT, GOODYEAR TIRE & RUBBER, OARE THOMAS REED, AUBE, MICHAEL, ALBERT, OARE, THOMAS, REED, THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1998
Main classification: B60B21
IPC codes: B60B21