| 摘要 |
<p>PURPOSE:To control internal heating of a bead part and to improve durability of the bead part, by a method wherein the sectional wall thickness of the bead part is reduced, and a bead apex forms a single rubber layer having a low modulus and reduced hysteresis loss. CONSTITUTION:An apex (b), sandwiched between a carcass ply body 2 and a folded part 2', is formed in an annular structure formed in a triangle in cross section in which, with the upper part of a bead core 3 forming a base, it extends radially outwardly as the wall thickness is gradually decreased. The apex is formed by a single rubber layer made of soft rubber having 100 modulus of 10- 45kg/cm<2> and JIS hardness of 45-46 deg.. In order to prevent spreading of a cord pass, a fiber-reinforced layer 6 is firmly adhered to a carcass ply body, the cord obliquely crosses a ply cord at an angle of 40-90 deg. with the ply cord, and the fiber-reinforced layer is disposed in an annular region extending to a height h2 of an outer end in the direction of radius from the bead base, which is 1.2-3.5 times as high as a height h0 of the terminal of the folded part of the carcass from the bead base.</p> |
