Steel cords for the reinforcement of rubber articles and heavy duty pneumatic radial tires using the same

摘要

A rubber article-reinforcing steel cord includes a core (1) obtained by forming a single filament in a wavy shape, an inner sheath (3) formed by arranging 5 to 6 filaments (2) around the core, and an outer sheath (5) formed by arranging 9 to 12 filaments (4) around the inner sheath. The inner sheath (3) and said outer sheath (5) are twisted together. The diameter of each of the filaments of the inner and outer sheaths is not greater than that of the filaments of the core, 5d ≦ L ≦ 30d and 1.2 ≦ H ≦ 2.0d in which L and H are wave length and wave height of a wave shape of the waved filament of the core, respectively, and d is the diameter of the filament of the core, and a ratio p3/p2 between the twisting pitch P2 of the inner sheath (3) and the twisting pitch P3 of the outer sheath (5) is in a range of 1.4 to 2.5. A heavy duty pneumatic radial tire is also disclosed, which uses such steel cords in the belt thereof.