Patent Application
20070125468
The present invention is directed towards a pneumatic tire. More specifically, the present invention is directed towards a pneumatic tire with asymmetrical reinforcement in the lower sidewalls and bead regions of the tire to enhance high performance aspects of the tire.
Pneumatic tires are conventionally constructed to have a symmetrical internal construction; the symmetric being centered on the lateral center, or equatorial plane, of the tire. Laboratory studies have shown that a majority of a tire's net cornering force is generated in the area of the shoulder on the inside of the direction of turn. Roll and lateral deflection to the outside tend to lift this inside shoulder, reducing the tire's cornering capability. In many vehicles, the vehicle's suspension system compensates for the reduced cornering capability by cambering of the vehicle wheels. In cambering, the top of a wheel and tire are tilted toward the center of the radius of the turn for maximum cornering force. Through the use of high wheel camber and toe angles, car suspensions are often designed in such a way that the load carried by a tire is not equally distributed between the inner and outer side of the tire. Given the fact that both sides of a tire are generally equal, this causes an asymmetric loading of the footprint leading to a side-to-side non-uniform shape that can be detrimental to the tire performance.
The present invention is directed to a tire designed to compensate for wheel cambering and yield improved tire performance.
Disclosed herein is a pneumatic radial tire having two circumferential tire halves, with the tire comprising a carcass and a tread radially outward of the carcass. The carcass has at least one carcass reinforcing ply, opposing bead portions, and opposing sidewalls. The carcass reinforcing ply has a main portion extending between the opposing bead portions and a pair of turnup portions with each turnup portion extending from one end of the main portion. Each bead portion in the carcass has a bead core and a bead apex radially outward of each bead core with the apex located between the main portion and one turnup portion of the at least one reinforcing ply. In the tire of the invention, the apexes in each bead portion have the same radial height (HA), as measured from a bead base line (B). The tire has a bead reinforcing ply comprising carbon fiber reinforcing cords located in only one bead portion of the tire wherein the bead reinforcing ply is adjacent to the at least one carcass reinforcing ply.
In one aspect of the invention, the carbon fiber cords of the bead reinforcing ply have a denier in the range of 667 dTex to 16,000 dTex. The cords are inclined at an angle in the range of 30° to 60° relative to the circumferential direction of the tire. Additionally, the carbon fiber cords may have a TOW in the range of 6,000 to 12,000. In forming the bead reinforcing ply, the carbon fiber cords may have an end count of in the range of 10 to 30 ends per inch.
In one aspect of the invention, the bead reinforcing ply has a radially outer terminal point. The bead reinforcing ply radially outer terminal point is radially inward of the radially outer terminal point of the bead apex. Preferably, the radially outer terminal point of the bead reinforcing ply is approximately 80 to 95% of the radial height HA of the bead apex radially outer terminal point.
In different aspects of the invention, the bead reinforcing ply may be located in a variety of positions in the single bead portion. The ply may be located adjacent to the carcass reinforcing ply turnup portion, adjacent to the carcass reinforcing ply main portion, or directly adjacent to the bead apex.
In another aspect of the invention, the turnup portion of the carcass reinforcing ply in the same tire half as the bead portion having the bead reinforcing ply therein terminates at a radial height, relative to a bead base line of the tire, outward of the terminal end of the turnup portion in the opposing tread half, increasing the asymmetry of the tire construction.
In another aspect of the tire, at least one of the terminal points of the turnup portion of carcass reinforcing ply terminates at a distance HT from the maximum section width of the tire. The distance HT is in the range of 0 to 20% of the section height SH of the tire.
In another aspect of the invention, the carcass may comprise two carcass reinforcing plies. In such a tire, the terminal ends of both carcass reinforcing plies in the same tire half as the bead portion having the bead reinforcing ply therein terminate at a radial height, relative to a bead base line of the tire, outward of the terminal ends of the turnup portions in the opposing tread half.
In another aspect of the invention, the asymmetric internal construction of the tire is paired with an asymmetrical tread. For such a tire and tread combination, the tread has a plurality of transverse and circumferential grooves and one circumferentially extending tread half, due to the configuration of the transverse and circumferential grooves, has a greater stiffness in at least the circumferential direction of the tire than the opposing tread half. Preferably, the stiffer tread half is located in the same tire half as the bead portion having the bead reinforcing ply therein.
In another aspect of the combination of the asymmetric internal tire construction and asymmetrical tire tread, the tread half having a greater stiffness in at least the circumferential direction of the tire has a circumferentially continuous rib while the tread rows in the opposing tread half all have transverse grooves.
In another aspect of the invention, the tire tread may be formed of multiple rubber compounds. In such a tire, at least a portion of the tread compound in the same tire half as the bead portion having the bead reinforcing ply therein has a greater hardness property than the tread compounds located in the opposing tread half.
Definitions
The following definitions are applicable to the present disclosure and are used consistently as defined below:
“Apex” means an elastomeric filler located radially above the bead core and between the plies and the turnup ply;
“Axial” and “axially” are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire;
“Bead” or “Bead Region” means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim;
“Bead base” means the portion of the bead that forms its inside diameter;
“Bead base line (BL)” means an imaginary line, perpendicular to the equatorial plane of the tire, from the intersection of the radially extending outerside of the bead portion and the bead base;
“Bead core” means an annular hoop reinforcement in the bead region of the tire, commonly formed of steel wire, cords or cables;
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tire parallel to the Equatorial Plane (EP) and perpendicular to the axial direction;
“Design rim” means a rim having a specified configuration and width. For the purposes of this specification, the design rim and design rim widths are as specified by the industry standards in effect in the location in which the tire is made. For example, in the United States, the design rims are as specified by the Tire and Rim Association (TRA). In Europe, the rims are as specified in the European Tyre and Rim Technical Organization (ETRTO)—Standards Manual and the term design rim means the same as the standard measurement rims. In Japan, the standard organization is The Japan Automobile Tire Manufacturer's Association (JATMA);
“Equatorial plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread;
“Groove” means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zigzag manner. Circumferentially and laterally extending grooves may be sub classified as a “sipe”, “narrow,” or “main.” A “sipe” is a groove having a width in the range from about 0.2% to 0.8% of the compensated tread width, whereas a “narrow groove” has a width in the range from about 0.8% to 3% of the compensated tread width and a “main groove” has a width greater than 3% thereof. The “groove width” is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length;
“Maximum Sectional Width (SW)” is the maximum axial width of the tire as measured from one sidewall to the opposing sidewall;
“Radial” and “radially” are used to mean directions radially toward or away from the axis of rotation of the tire; and
“Tire Sectional Height (SH)” is the maximum radial height of the tire as measured from the bead base line BL.
The invention will be described by way of example and with reference to the accompanying drawings in which:
The following language is of the best presently contemplated mode or modes of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The carcass has at least one carcass reinforcing ply 12, a pair of opposing bead portions 14 and a pair of opposing sidewalls 16. The tire of
In the opposing bead portions 14, the bead apexes 24 have the same radial height HA, as measured from the bead base line BL. Located in only one bead portion 14 of the tire is a bead reinforcing ply 26. The bead reinforcing ply 26 is formed of calendered carbon fiber cords. The carbon fiber cords are inclined at an angle of 30°-60°, preferably 40°-50°, most preferably 45°, relative to the circumferential direction of the tire. Conventional chipper plies are formed of textile cords; herein carbon fiber cords provide a similar lightweight material, but have a tensile strength and breaking load strength greater than conventional textile materials.
The carbon fiber forming the carbon fiber cords in the bead reinforcing ply 26 have a denier in the range of 667 dTex to 16,000 dTex, with a preferred denier in the range of 4000 to 8000 dTex. The TOW range of the cords is 1,000 to 24,000, with a preferred range of 6,000 to 12,000. The cord has a Young's modulus of 30,000-90,000 Kpsi, with a preferred range of 30,000-40,000. The cord may have a tensile strength in the range of 400,000 to 1000,000 psi, preferably 600,000 to 740,000 psi. Additionally, the cord has a maximum elongation in the range of 1.0 to 3.0%, preferably 1.6 to 1.8%.
In forming the bead reinforcing ply 26, the end count of the carbon fiber cords, commonly referred to as ends per inch (e.p.i), is dependent upon the cord TOW. As the TOW increases, the e.p.i decreases. For the TOW range of 1,000 to 24,000, the e.p.i. ranges from 10 to 30 e.p.i. For TOW ranges of not more than 6,000, the e.p.i. is in the range of 30 to 20, with a preferred range of 27 to 21. For TOW ranges of greater than 6,000, the e.p.i. is in the range of 10 to 20, with a preferred range of 12 to 19. For three commercially available carbon fiber TOWs, the preferred e.p.i. ranges are: TOW of 6,000: 21 to 25 e.p.i.; TOW of 12,000: 15 to 20 e.p.i.; TOW of 15,000: 12 to 16 e.p.i.
In one embodiment of the invention, as illustrated, the bead reinforcing ply 26 is located within the turnup envelope and directly adjacent to the bead apex 24. The bead reinforcing ply 26 extends from the an initial point near the bead core 22 to a radially outer terminal end 28 at a radial height HR, the height HR being less than the radial height HA of the bead apex 24; preferably the bead reinforcing ply radial height HR is approximately 80 to 95% of the bead apex radial height HA. The radially inner initial point 30 of the bead reinforcing ply 26 does not have any overlap with the bead core 22, but is preferably spaced from the radially outer surface of the bead core 22 by a distance of at least 1.5 mm; preventing the end of the bead reinforcing ply 26 from being pinched between the bead core 22 and the carcass reinforcing ply 12.
In alternative constructions, the bead reinforcing ply 26 may be located a) on the axially inner side of the bead apex 24 between the bead apex 24 and the carcass ply main portion 18 (see
As the tire of the present invention is reinforced in only one bead portion 14, creating one bead portion 14 that is stiffer than the opposing bead portion 14, there is a preferential way of mounting the tire to take advantage of the asymmetrical nature of the tire. The tire preferably is mounted on a vehicle so the stiffer bead portion 14 is the outboard side O facing outwards from the vehicle with the opposing inboard side I facing the vehicle. The softer inboard sidewall and bead portion provides improved ride comfort, while the stiffer outboard sidewall and bead portion provides improved handling.
Similar to the first embodiment, the bead reinforcing ply 26 may be located in a variety of locations in the outboard side bead portion 14 in addition to the illustrated location of being axially outward of the carcass reinforcing ply turnup portion 20. The bead reinforcing ply 26 may be between the apex 24 and the carcass reinforcing ply turnup portion 20 (see
In accordance with the invention, a bead reinforcing ply 28 is located in only one bead portion 14 of the tire. Preferably, the bead reinforcing ply 26 is located between the bead apex 24 and the turnup portion 50 of the outer carcass ply 40, having a radially outer terminal end 28 at a height HR. Similar to the previous embodiments, the bead reinforcing ply 26 may be located in various locations of the bead portion 14, with the requirement that the lower terminal end 30 of the bead reinforcing ply 26 being radially outward of the bead core 22 and the radially outer end 28 of the bead reinforcing ply 26 being radially inward of the radially outer end 36 of the bead apex 24.
In the inboard tire side I, both terminal ends 46, 48 of the plies 38, 40 are radially inward of the radially outer terminal end 36 of the bead apex 24. The terminal ends 46, 48 of the plies 38, 40 are spaced by a distance HTI of at least 5% of the tire section height SH below the radially outer terminal end 36 of the bead apex 24. The inner ply terminal end 46 in the inboard tire side I may be radially inward of the outer ply terminal end 48, as illustrated in
In the inventive tire, regardless of specific embodiment, while the carcass turnup portions and the ply reinforcing in each bead portion 14 is asymmetrical, the bead apexes 24 in both bead portions 14 are identical in construction, with both apexes 24 having the same radial height. The embodiment of
Just as with the internal construction of the tire, the tread 10 of the tire may also be asymmetrical, see
The tread 10 is located between a pair of tread edges 52, 54. There are four main circumferentially extending grooves 56, 58, 60, 62. Between the first tread edge 52 and the first main groove 56 is a shoulder tread row 64. The shoulder tread row is effectively divided into two regions 64a, 64b by a narrow groove 66. The axially outer region 64a, relative to the tire equatorial plane EP, is subdivided into tread elements by a narrow width laterally extending groove 68, the regions thereby responding like tread blocks; the axially inner region 64b is subdivided by sipes 70, the region thereby responding like a tread rib.
Adjacent to the shoulder tread row 63 is a tread rib 72. The rib 72 is illustrated as having no siping or grooving, thus forming a stiff tread element. In an alternative, the rib may have limited siping or narrow grooving to provide greater flexibility to the tread rib 72.
Located on the equatorial plane EP, but not necessarily centered on the equatorial plane EP, is another tread row 74. The tread row 74 has a plurality of transverse, inclined grooves 76, forming a plurality of tread blocks 78. The grooves 76 are inclined at an angle α in the range of 85° to 65° relative to the equatorial plane EP.
Adjacent to the central tread row 74 is a tread row 80 of elongated tread blocks 82 separated by steeply inclined transverse grooves 84. The tread blocks 82 have a very long footprint pattern determined by the width of the tread row 80 and the inclination angle β of the grooves 84. The inclination angle β is in the range of 10° to 25° with one of the adjacent circumferential grooves 60, 62. The blocks 82 preferably have a circumferential length, measured between the farthest opposing corners of the block, in the range of 85-400% of the normal pressure footprint length of the tire. More details regarding this tread block configuration are provided in U.S. patent application Ser. No. 10/775,795, filed Feb. 10, 2004, which is hereby fully incorporated by reference thereto.
On the tread edge 54 is another shoulder tread row 86 divided into two regions 86a, 86b by a narrow groove 88. Both portions 86a, 86b are subdivided into individual tread elements 90, 92 by transverse grooves 94. The individual tread elements are each illustrated as having a plurality of sipes 96. By providing a plurality of transverse grooves 94 and sipes 96, the shoulder tread row 86 has a tread stiffness less than the opposing tread shoulder row 64.
As evident from the tread illustration, the tread design is asymmetrical. The selective combination of ribs, grooves, and sipes, the stiffness of the tread varies across the width of the tread. With the presence of the continuous rib 72 and the minimally siped and groove shoulder tread row 64, the tread half illustrated in the right side of
The tread stiffness may also be affected by variations in the tread rubber compound selected for the tire. If it is desired to increase, or enhance the stiffness of the outboard O tread half, the tread rubber, or even just a tread base rubber, may be selected to have a greater hardness or stiffness characteristic than the inboard I tread half. If it is desired to equalize the tread half stiffness, the inboard I tread half may be the tread portion provided with a tread rubber or tread base rubber with a greater hardness or stiffness characteristic than the outboard O tread half.
Combining the asymmetric internal construction and an asymmetric tread construction results in a tire well suited to handle the camber effects of a vehicle and provide a tire that has improved ride comfort and handling.
The tire characteristics of improved ride comfort and handling can also be achieved with the alternative treads of
In the tread of
The inclination angle of the grooves 104 and sipes 106 in the rib 72, relative to the adjacent grooves 56 or 58, is the same, but opposite direction, as the inclination angle of the grooves 98 and sipes 100 in the adjacent tread row 74. To vary the tread characteristics, the inclination angles may be in the same direction or at different angles.
