1. Field of the Invention
The present invention relates to a pneumatic tire in which both end portions of a carcass ply are pinched between separated pieces of a bead core without being protruded from the bead core to an upper side in a radial direction so as to be firmly locked.
2. Description of the Related Art
In a carcass ply a constituting a frame of the pneumatic tire, as generally shown in FIG. 16A, there is employed a structure in which ply fold-back portions a2 are provided in both ends of a ply main body portion a1 extending between bead cores c and c. The ply fold-back portion a2 is extended high to an outer side in a radial direction along an outer surface of a bead apex rubber b after being folded back to an outer side from an inner side in a tire axial direction around the bead core c. Accordingly, it is possible to firmly fix both ends of the carcass ply a, it is possible to prevent the carcass cord from being slack at a time of vulcanizing so as to make a tension force to be unevenly dispersed, and it is possible to prevent a so-called blow-by that the carcass ply a comes off from the bead core c so as to be deflected therefrom, from being generated.
However, the ply fold-back portion a2 increases a tire weight in the other hand, and generates a cord breakage, a cord end loose and the like on the basis of an application of a compression stress at a time when the tire is deformed, thereby causing a bead damage.
Accordingly, in recent years, as shown in FIG. 16B, a structure in which the bead core c is separated into upper and lower sides in a radial direction, and both end portions of the carcass ply a are pinched between upper and lower core separated pieces c1 and c2 is proposed, for example, in Japanese Unexamined Patent Publication No. 11-28915.
USPTO Backgrounds
USPTO Backgrounds