STEEL CORD FOR RUBBER REINFORCEMENT AND PNEUMATIC RADIAL TIRE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a steel cord for rubber reinforcement, which reduces a cord diameter as much as possible and controls a dimensional change while securing sufficient adhesiveness between cord and rubber and a pneumatic radial tire using the same. SOLUTION: The steel cord 10 useful in a belt layer 6 has a constitution that six side wires 12 having the same wire diameter as that of one helically curled core wire 11 are twisted and arranged on the outside of the core wire 11, the circumscribed circle C11 of the core wire 11 and the circumscribed circle C12 of the side wires 12 have flat structures forming elliptic shapes, respectively, the torsion direction of the core wire 11 is equal to the twisting direction of the side wires 12, the curling pitch of the core wire 11 is equal to the twisting pitch of the side wires 12, the minor diameter ds of the circumscribed circle C11 of the core wire 11 is ds>d to a wire diameter d, the minor diameter Ds of the circumscribed circle C12 of the side wires 12 is 2a