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AssigneeBridgestone Tire Company Limited
InventorsMinoru Togashi, Kenshiro Kato, Shin-ichi Furuya
Estimating the term…
A pneumatic radial tire is adapted to improve or reduce the rolling resistance and simultaneously to improve the steering stability and riding comfortability against vibration during running without adversely affecting the wet performance and durability by making higher the carcass maximum width position and the carcass curvature reverse position, or enlarging the curvature of the carcass in the radially outer zone of the carcass maximum width position and simultaneously the carcass curvature reverse extent in the radially inner zone of the sidewalls so as to intentionally deviate from the naturally equilibrated configuration. A method of manufacturing a reduced rolling resistance pneumatic radial tire uses a mold for vulcanizing and forming the tire therein, which mold has a particular shape of cavity having a foot width 20-50% wider than a rim width and diverging progressively from shoulder corresponding portions to the wider foot portion of the cavity.
In a reduced rolling resistance pneumatic radial tire including a pair of annular sidewalls having at inner ends bead portions, respectively, a crown portion extending between radially outer ends of said sidewalls, a carcass of at least one ply including organic fiber cord layers and having ends extending about bead wires embedded in said bead portions with distal ends extending radially outwardly to reinforce said bead portions, said sidewalls and said crown portion, and hard rubber fillers filled in turns of said ply extending about said bead wires, the improvement comprising said carcass having, on each side of a plane including an equatorial line of the tire in a radial cross-section passing through a rotating axis of the tire, an outwardly extending configuration with a center of a radius of curvature positioned in an inside of the carcass in a radially outer zone from a carcass maximum width position to said crown portion and further having an inwardly extending configuration continuous with said outwardly extending configuration with a center of a radius of curvature positioned in an outside of said carcass in a radially inner zone from said carcass maximum width portion to said bead portion when said tire mounted on a rim is filled with an inner pressure 5% of a normal inner pressure;
In a reduced rolling resistance pneumatic radial tire including a pair of annular sidewalls having at inner ends bead portions, respectively, a crown portion extending between radially outer ends of said sidewalls, a carcass of at least one ply including organic fiber cord layers and having ends extending about bead wires embedded in said bead portions with distal ends extending radially outwardly, at least two belt layers consisting of rubber coated high modulus cords arranged at comparatively small angles with respect to a central circumferential line of the tire and intersecting with each other encircling said carcass to reinforce therewith said sidewalls and said crown portion, and hard rubber fillers filled in turns of said ply extending about said bead wires, the imporvement comprising said carcass having, on each side of a plane including an equatorial line of the tire in a radial cross-section passing through a rotating axis of the tire, a radial surface profile so selected that a ratio of radii R/R' is within a range of 0.65-0.85 and f is within a range of 5-10 mm when said tire mounted on a normal rim is filled with a normal inner pressure where R' is a radius of a standard circle passing through points B, E and C, where the point B is an intersection of the carcass and a line extending in parallel with said rotating axis and passing through a point at which a flange of said rim starts leaving the tire, the point C is an intersection of the carcass and a line extending through the point B and perpendicular to said rotating axis of the tire and the point E is an intersection of a line extending through a middle point D of a line segment BC and in parallel with said rotating axis and a line extending through a carcass maximum width point F and perpendicular to the rotating axis, and R is a radius of profile curvature of a shoulder passing through said point C, and where f is the maximum distance between an arc of said standard circle and the remaining carcass line smoothly, extending from said profile curvature of said shoulder to said point B having a single carcass curvature reverse position.
Dependencies are inferred from the claim text.