| 摘要 |
PROBLEM TO BE SOLVED: To omit the cord stranding process to suppress the manufacturing cost by neatly arranging a specified number of steel strands having a specified strand diameter without stranding to form a steel strand bundle, and burying rubber in the steel strand bundle to constitute a carcass layer. SOLUTION: A steel strand bundle 20 for reinforcing a carcass layer 2 is formed by neatly arranging 1-6, more preferably, 1-4 steel strands in parallel without stranding. The strand diameter of the steel strand is set within the range of 0.10-0.25 mm. When the strand diameter is less than 0.10 mm, the strength is insufficient, and when it exceeds 0.25 mm, the bending rigidity is suddenly increased to deteriorate the fatigue resistance. The strand diameter of the steel strand is preferably constant in the range of 0.10-0.25 mm. This reason is that the steel strand bundle 20 is apt to be partially broken by the load unevenly added to thereto when the strand diameter of the steel strand is not constant, since the steel strand bundle 20 is not stranded.
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