A PNEUMATIC RADIAL TIRE WITH HYBRID CORD REINFORCEMENT

Abstract

Pneumatic radial tire comprising a tread (4) forming the outermost layer of the tire (1) and at least one belt (5) on top of the carcass (3) forming the inner layer of the tire (1). As cap ply reinforcement layer (6) hybrid cords are applied comprising polyethylene terephthalate (PET) and nylon 6.6 multifilament yarns to provide a pneumatic radial tire having high speed durability and a low flatspot feature.

Claims

1. A pneumatic tire with hybrid cord reinforcement comprising: a tread forming the outermost layer of the tire, at least one belt on the carcass forming the inner layer of the tire, and at least one cap ply reinforcement layer, which is formed by twisting pre-twisted polyethylene terephthalate (PET) multifilament yarns and nylon yarns in Z or S direction such that they will be in reverse direction of the pre-twisting direction, wherein the twisting level of the hybrid cords is equal to pre-twisting level of yarn or it has maximum 10% difference, which is wound spirally (as strip) such that it will make an angle of 0 to 5 with the equatorial plane on the belt, and wherein the cap ply reinforcement layer the thermal shrinkage force and modulus of which are increased by stretching minimum 1% at 180-240 C., which is obtained by using hybrid cords the tensile force (LASE value) of which is minimum 8 mN/dtex at 3% elongation at 25 C. according to ASTM D855 test method, and the thermal shrinkage force of which is minimum 2 mN/dtex at 177 C. according to ASTM D855 test method.

2. The pneumatic radial tire with hybrid cord reinforcement according to claim 1, wherein at least one belt edge reinforcement layer which is provided on both sides of the cap ply reinforcement layer, and which enables to increase high speed durability by providing resistance against the increase in tire diameter.

3. The pneumatic radial tire with hybrid cord reinforcement according to claim 1, wherein at least one cap ply reinforcement layer which has hybrid cords that are formed by twisting polyethylene terephthalate (PET) multifilament yarns and nylon 6.6 multifilament yarns in Z or S direction in range of 100 to 800 twists/meter.

4. The pneumatic radial tire with hybrid cord reinforcement according to claim 3, wherein at least one cap ply reinforcement layer which has hybrid cords that are formed by twisting polyethylene terephthalate (PET) multifilament yarns and nylon 6.6 multifilament yarns preferably in twisting level of 200 to 400 twists/meter.

5. The pneumatic radial tire with hybrid cord reinforcement according to claim 1, wherein at least one cap ply reinforcement layer the width of which is equal to the width of the belt or wider than the width of the belt.

6. The pneumatic radial tire with hybrid cord reinforcement according to claim 5, wherein at least one cap ply reinforcement layer the strip width value of which is between 5 mm and 30 mm.

7. The pneumatic radial tire with hybrid cord reinforcement according to claim 6, wherein at least one cap ply reinforcement layer the strip width value of which is preferably between 8 mm and 15 mm.

8. The pneumatic radial tire with hybrid cord reinforcement according to claim 5, wherein at least one cap ply reinforcement layer wherein the number of hybrid cords in width of 10 mm varies between 5 and 20.

9. The pneumatic radial tire with hybrid cord reinforcement according to claim 5, wherein at least one cap ply reinforcement layer which has hybrid cords the linear densities of which are between 500 and 6000 dtex.

10. The pneumatic radial tire with hybrid cord reinforcement according to claim 9, wherein at least one cap ply reinforcement layer which has hybrid cords wherein the linear density of nylon 6.6 multifilament yarns is smaller than the linear density of the PET multifilament yarns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Pneumatic radial tire reinforced with hybrid cord developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

[0016] FIG. 1 is the front sectional view of the inventive radial tire.

[0017] FIG. 2 is the perspective view of hybrid cord used as cap ply reinforcement layer

[0018] FIG. 3 is the definitions of Z and S twist directions of hybrid cords present in the cap ply reinforcement layer.

[0019] The components shown in the figures are each given reference numbers as follows: [0020] 1. A pneumatic radial tire reinforced with hybrid cord [0021] 2. Tire bead ring [0022] 3. Carcass [0023] 4. Tread [0024] 5. Belt [0025] 6. Cap ply reinforcement layer [0026] 61. Hybrid cord [0027] 62. PET multifilament yarn [0028] 63. Nylon 6.6 multifilament yarn [0029] 7. Belt edge reinforcement layer

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The inventive pneumatic radial tire (1) essentially comprises at least one tread (4) forming the outermost layer of the tire (1) and at least one belt (5) on the carcass (3) forming the inner layer of the tire (1). The tire (1) is reinforced with at least one cap ply reinforcement layer (6) which is obtained by using hybrid cords (61) which are formed by twisting polyethylene terephthalate (PET) (62) and nylon 6.6 multifilament yarns (63) and the thermal shrinkage force and modulus of which are increased by applying heat-set process; therefore the high speed durability of the tire (1) is increased. The cap ply reinforcement layer (6) is between the tread (4) forming the outer layer of the tire (1) and the belt (5) formed of steel material. The cap ply reinforcement layer (6) is wound spirally on the belt (5) as strip such that it will for an angle between 0 and 5 degrees with the equatorial plane.

[0031] The heat-set process, which is a thermal process, comprises stretching hybrid cord (61) minimum 1% at 180-240 C. This process increases the tension value of the cord (61) corresponding to 3% level to minimum 8 mN/dtex at 25 C., and it increases the thermal shrinkage force above 2 mN/dtex at 177 C.

[0032] In heat-set process, the hybrid cords (61) are also provided with adhesive property with the rubber in the tire (1) by applying resorcinol formaldehyde latex (RFL) dip solution.

[0033] In the preferred embodiment of the invention, there is at least one belt edge reinforcement layer (7) wound on each side of the cap ply reinforcement layer (6) in order to support the cap ply reinforcement layer (6). Cap ply reinforcement layer (6) having hybrid cords (61) with increased thermal shrinkage force and wound on the belt (6) and the belt edge reinforcement layer (7) enable to increase high speed durability by providing resistance against the increase in diameter of the tire (1).

[0034] The hybrid cords (61) forming the cap ply reinforcement layer (6) are obtained by twisting pre-twisted PET (62) and nylon (63) yarns in Z or S direction such that they will be in reverse direction of the pre-twisting direction. The twisting level varies between 100 and 800 twists/meter, preferably 200 to 400 twists/meter. In the preferred embodiment of the invention, the twisting level of the hybrid cords (61) is equal to pre-twisting level of yarn or it has maximum 10% difference.

[0035] The width of the cap ply reinforcement layer (6) should be equal to the width of the belt (5) or it should be wider than the belt.

[0036] The width of the cap ply reinforcement layer (6) as strip which is used as wound around the belt (5) varies between 5 mm and 30 mm, preferably 8 mm to 15 mm. The number of cords (61) provided in 10 mm width of the cap ply reinforcement layer (6) can vary between 5 and 20.

[0037] The reinforcement layer (6) can exist in the tire (1) as coated with rubber or not coated with rubber. The linear densities* of the hybrid cords (61) in the cap ply reinforcement layer (6) are between 500 and 6000 dtex. In the preferred embodiment of the invention, the linear density of nylon 6.6 multifilament yarns (63) is smaller than the linear density of the PET multifilament yarns (62). In one embodiment of the invention, the linear density of nylon 6.6 yarns (63) forming the hybrid cord (61) is 1400 dtex, while the linear density of the PET yarns (62) is 1440 dtex. *The linear density is the weight of 10000 meters length of a yarn in unit of gram, and its unit value is dtex.