| 摘要 |
PURPOSE:To improve the anti-cut property of a heavy load radial tire without lowering other performances. CONSTITUTION:The cord diameters of the third ply 12C and the fourth ply 12D of a belt layer 12 consisting of four layers are made thicker than the cord diameters of the first ply 12A and the second ply 12B, and filaments constituting the steel cords of the third ply 12C and the fourth ply 12D are made to be of thick diameters, and in the case of the steel cords of the third ply 12C and the fourth ply 12D, the ratio I/A of a section secondary moment I to a sectional area A is made to be not less than 4. 5X10<-3>mm<2>. As a result, as for the belt layer 12, the bending rigidity of the outer layer side that receives local bending deformation at the time of treading on a sharp projection, is improved, so belt break at the time of treading on a sharp projection can be effectively prevented. Here, the following is embodied; I = pi/64SIGMAd<4>A = SIGMA(d/2)<2>d = steel cord filament diameter (mm). |
