Pneumatic radial tires with core-sheath steel belt cords
AssigneeBridgestone Corporation
InventorsKiyoshi Ikehara, Kiyohito Kawasaki
Life of this patent
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Abstract
A pneumatic radial tire for truck and bus comprises a carcass ply containing cords arranged substantially in a radial direction of the tire and a belt superimposed about said carcass ply and comprised of plural belt layers each containing steel cords arranged at a cord angle of 5.degree.-20.degree. with respect to an equator of the tire. In this case, the steel cord for the belt layer has a two-layer structure of a core comprised of two steel filaments and a single sheath comprised of 6-8 steel filaments and satisfies the particularly relationships on filament diameter, twisting pitch, bending rigidity, tensile strength and distance between adjoining cords.
Claims3
A pneumatic radial tire comprising a carcass ply containing cords arranged substantially in a radial direction of the tire and a belt superimposed about said carcass ply and comprised of plural belt layers each containing steel cords arranged at a cord angle of 5.degree.-20.degree. with respect to an equator of the tire, characterized in that:
- (a) said steel cord has a two-layer structure comprising a core composed of two steel filaments and a single sheath surrounding said core and composed of 7 steel filaments, in which a twisting direction of said core is the same as a twisting direction of said sheath, and satisfies the following relationships:
- 0.22.ltoreq.Dc.ltoreq.0.44 (mm),
- 0.22.ltoreq.Ds.ltoreq.0.50 (mm),
- 12.ltoreq.Ps.ltoreq.22 (mm),
- 1.0.ltoreq.Ps/Pc.ltoreq.4.0
- wherein Dc is a diameter of steel filament in the core, Pc is a twisting pitch of the core, Ds is a diameter of steel filament in the sheath and Ps is a twisting pitch of the sheath;
- (b) said steel cord has a bending rigidity B of not less than 100 kg.mm.sup.2 calculated from the following equation:
- B=1.3.times..SIGMA..sub.i B.sub.i =1.3.times..SIGMA..sub.i (.pi.D.sub.i.sup.4 /64).times.20,000
- wherein B.sub.i is a bending rigidity of each steel filament and D.sub.i is a diameter of each steel filament;
- (c) said steel cord has a breaking load S (kgf) satisfying the following relationship:
- S.gtoreq.110.times.(0.6+D)
- wherein D is a diameter of steel cord;
- (d) said steel cords are arranged so that a distance G between adjoining cords is within a range of 0.6-2.0 mm in said belt layer;
- and
- (e) said steel cord satisfies the following relationship:
- Ds/Dc.ltoreq.1.15.
Dependencies are inferred from the claim text.