Claims
- 1. A pneumatic radial tire comprising a carcass ply containing cords arranged substantially in a radial direction of the tire and a belt superimposed about said carcass ply and comprised of plural belt layers each containing steel cords arranged at a cord angle of 5.degree.-20.degree. with respect to an equator of the tire, characterized in that:
- (a) said steel cord has a two-layer structure comprising a core composed of two steel filaments and a single sheath surrounding said core and composed of 7 steel filaments, in which a twisting direction of said core is the same as a twisting direction of said sheath, and satisfies the following relationships:
- 0.22.ltoreq.Dc.ltoreq.0.44 (mm),
- 0.22.ltoreq.Ds.ltoreq.0.50 (mm),
- 12.ltoreq.Ps.ltoreq.22 (mm),
- 1.0.ltoreq.Ps/Pc.ltoreq.4.0
- wherein Dc is a diameter of steel filament in the core, Pc is a twisting pitch of the core, Ds is a diameter of steel filament in the sheath and Ps is a twisting pitch of the sheath;
- (b) said steel cord has a bending rigidity B of not less than 100 kg.mm.sup.2 calculated from the following equation:
- B=1.3.times..SIGMA..sub.i B.sub.i =1.3.times..SIGMA..sub.i (.pi.D.sub.i.sup.4 /64).times.20,000
- wherein B.sub.i is a bending rigidity of each steel filament and D.sub.i is a diameter of each steel filament;
- (c) said steel cord has a breaking load S (kgf) satisfying the following relationship:
- S.gtoreq.110.times.(0.6+D)
- wherein D is a diameter of steel cord;
- (d) said steel cords are arranged so that a distance G between adjoining cords is within a range of 0.6-2.0 mm in said belt layer; and
- (e) said steel cord satisfies the following relationship:
- Ds/Dc.ltoreq.1.15.
- 2. The pneumatic radial tire according to claim 1, wherein said steel cord is wrapped with a spiral filament in a direction opposite to the twisting direction of said sheath.
- 3. The pneumatic radial tire according to claim 1, wherein said tensile strength S satisfies the following relationship:
- S.gtoreq.130.times.(0.6+D)
Priority Claims (1)
Number |
Date |
Country |
Kind |
1-126684 |
May 1989 |
JPX |
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Parent Case Info
This is a divisional of application Ser. No. 07/525,353 filed May 18, 1990, now U.S. Pat. No. 5,311,917.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4690191 |
Kawasaki |
Sep 1987 |
|
4732197 |
Heishi et al. |
Mar 1988 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
60-169303 |
Sep 1985 |
JPX |
Non-Patent Literature Citations (2)
Entry |
Mechanics of Pneumatic Tires, ed. Samuel Clark:US Dept. of Transportation, Aug. 1981, pp. 219-220. |
"New developments in steel cords For tyres", International Polymer Science and Technology vol. 11 No. 10, 1984, pp. T153-T160. |
Divisions (1)
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Number |
Date |
Country |
Parent |
525353 |
May 1990 |
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