Steel radial tire

Abstract

A steel cord has a core strand and an outer strand. The core strand includes three wire filaments located in a core portion and each having a same diameter, and nine wires located to enclose the three wires, twisted together with the three wire filaments, and each having a diameter smaller than that of each of the three wires. The outer strand has wires located to enclose the nine wires of the core strand, twisted in a direction reverse to the twisting direction of the core strand, and having a clearance between them.

What is claimed is: 
     
       1. A steel radial tire comprising: a tire tread;   a tire belt located in a radially inward direction of the tire tread;   a tire carcass located in a radially inward direction of the tire belt, and having a plurality of steel cords embedded in a quantity of rubber;   each of the steel cords comprising three first wires positioned to form a core strand, each of the three first wires having a first diameter;   nine second wires, respectively having a second diameter smaller than said first diameter of said first wires, positioned to enclose said first wires in said core strand, the second wires being twisted together with the three first wires in a same direction, said first diameter being 5 percent to 15 percent greater than the second diameter, the second wires having a space S2 therebetween, the space S2 being defined as a space having a shortest distance between a respective outer surface of each of two adjacent second wires, and the space S2 being 10 percent to 25 percent of a sum of a diameter of one of the second wires and the space S2;   a plurality of third wires positioned to enclose the second wires, the third wires being twisted in a direction opposite to the same twisting direction of the first and second wires; and   a space S1 between adjacent ones of the third wires, said quantity of rubber sufficiently entering the spaces S1 and S2 to achieve a strong bonding between the three first wires and the nine second wires such that the three first wires will not be pulled out while the tire is running.   
     
     
       2. The radial tire of claim 1, wherein the first wires have first diameters which are 9.5 to 15 percent greater than the second diameters of the second wires. 
     
     
       3. The radial tire of claim 2, wherein the first wires have first diameters which are 10 to 15 percent greater than the second diameters of the second wires. 
     
     
       4. The radial tire of claim 1, wherein the space S2 is 13 to 25 percent of the sum of said second diameter of the second wires and said space S2. 
     
     
       5. The radial tire of claim 1, wherein the first and second wires are twisted to have a same pitch. 
     
     
       6. The radial tire of claim 1, wherein the first diameter of each of the first wires in the core strand is in a range of 0.21 mm to 0.24 mm. 
     
     
       7. The radial tire of claim 1, wherein the second diameter of each of the second wires is 0.20+0.01 mm. 
     
     
       8. The radial tire of claim 1, wherein a diameter of each of the plurality of third wires is 0.22±0.01 mm. 
     
     
       9. The radial tire of claim 1, wherein the number of third wires is in a range of twelve to fourteen. 
     
     
       10. The radial tire of claim 1, wherein each of the first, second and third wires is plated with brass. 
     
     
       11. The radial tire of claim 1, further comprising a wrapping wire spirally wound about said plurality of third wires. 
     
     
       12. The radial tire of claim 6, wherein the first diameter of each of the first wires in the core strand is in a range of 0.21 mm to 0.23 mm.