Pneumatic radial tires
AssigneeBridgestone Tire Company Limited
InventorsYujiro Umezawa, Shigehisa Sano, Takao Ogino
Life of this patent
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Abstract
A pneumatic radial tire is disclosed, which comprises steel cords having a two or three layer construction represented by a designation of l+m or l+m+n as a tire reinforcement, wherein two layers at a center side of a transverse section in the steel cord have the same twisting direction but different twisting pitches. In this steel cord, m filaments constituting an outer layer are arranged so as to enter into an inside of a circumscribed circle enveloping l filaments of an inner layer at a non-contact region above a predetermined value and have a form ratio of 90-110%.
Claims3
A pneumatic radial tire comprising;
- a tire reinforcement having steel cords each having a two or three layer construction represented by a designation of l+m or l+m+n, wherein l, m and n are an integer, respectively and satisfy a relation of l<m<n and l is an integer of 2 to 5, in which two layers at a center side of a transverse section in said steel cord represented by the designation of l+m have the same twisting direction but different twisting pitches, wherein m filaments constituting an outer layer among said two layers are arranged to enter into an inside of a circumscribed circle enveloping l filaments constituting an inner layer among said two layers at such a portion that the filaments of said outer layer do not come into contact with the filaments of said inner layer, and an average value x.sub.o of a maximum value of an amount of entering a filament into the inside of the circumscribed circle per m filaments in the steel cord of a tire product satisfies the following equations:
- (-0.24k.sup.2 +0.46k)d<x.sub.O <(-0.73k.sup.2 +1.37k)d, when l is 2 (1)
- (-0.10k.sup.2 +0.24k)d<x.sub.O <(-0.31k.sup.2 +0.73k)d, when l is 3 (2)
- (-0.05k.sup.2 +0.16k)d<x.sub.O <(-0.15k.sup.2 +0.49k)d, when l is 4 (3)
- (-0.02k.sup.2 +0.12k)d<x.sub.O <(-0.06k.sup.2 +0.35k)d, when l is 5 (4),
- wherein k is a ratio of twisting pitch P.sub.1 of the filament of the inner layer to twisting pitch P.sub.2 of the filament of the outer layer and d is a filament diameter, each of the m filaments in the outer layer has a form ratio of 90% to 110%, a limit entering amount x.sub.L forms a ratio x.sub.O /x.sub.L within a range of 0.33-1.0 wherein said limit entering amount x.sub.L is represented by the following four equations:
- x.sub.L =(-0.73k.sup.2 +1.37k)d, when l is 2 (5)
- x.sub.L =(-0.31k.sup.2 +0.73k)d, when l is 3 (6)
- x.sub.L =(-0.15k.sup.2 +0.49k)d, when l is 4 (7)
- x.sub.L =(-0.06k.sup.2 +0.35k)d, when l is 5 (8)
- wherein k and d are as defined above and wherein all l and m filaments have the same filament diameter d.
In a pneumatic radial tire comprising as a tire reinforcement steel cords each having a two layer construction represented by a designation of 3+9, in which the two layers at a center side of a transverse section in said steel cord represented by the designation of 3+9 have the same twisting direction but different twisting pitches, the improvement wherein all filaments constituting the cord have the same filament diameter, and 9 filaments constituting an outer layer among said two layers are arranged so as to enter into an inside of a circumscribed circle enveloping 3 filaments constituting an inner layer among said two layers at such a portion that the filaments of said outer layer do not come into contact with the filaments of said inner layer, and an average value x.sub.o of a maximum value of an amount of entering a filament into the inside of the circumscribed circle per 9 filaments in the steel cord of a tire product satisfies the following equation:
- (-0.10k.sup.2 +0.24k)d<x.sub.o <(-0.31k.sup.2 +0.73k)d,
- wherein k is a ratio of twisting pitch P.sub.1 of the filament of the inner layer to twisting pitch P.sub.2 of the filament of the outer layer and d is a filament diameter, and a ratio of the product entering amount x.sub.o to a limit entering amount x.sub.L is within a range of 0.33-1.0, wherein said limiting entering amount x.sub.L satisfies the following equation:
- x.sub.L =(-0.31k.sup.2 +0.73k)d
- wherein k and d are as defined above and each of the 9 filaments in the outer layer has a form ratio of 90% to 110%.
Dependencies are inferred from the claim text.