| 摘要 |
PROBLEM TO BE SOLVED: To add a high level of elongation characteristic and flexibility to a steel cord while raising the rate of use of resources other than petroleum, whereas restraining the occurrence of irregular molding and lowering of uniformity. SOLUTION: A belt-like ply 10, in which a band cord arrangement is covered with topping rubber G, is provided outside a belt layer 7 in the tire radius direction while a band layer 9 is provided having at least one piece of band ply 9A spirally wound in the tire circumferential direction. A band cord 11 is composed of steel cords 20 in which a plurality (N number) of secondary strands 13 are twisted together by upper twists while the secondary strands 13 are formed by further twisting together by intermediary twisting a plurality (M number) of first strands 12 such that a plurality (L number) of steel strands f with a strand diameter d of 0.08 to 0.20 mm are twisted together by first twists. The steel cord 20, in its load-elongation curve, have a low elasticity area Y1 from the origin to inflection point P and a high elasticity area Y2 that extends beyond the inflection point P, while the elongation of the inflection point P falls within a range of 1.2 to 6.1%, with the elongation of 2 to 7% at the time of 90 N loading. COPYRIGHT: (C)2011,JPO&INPIT |
