Pneumatic tire

Abstract

To provide a pneumatic tire capable of achieving both steering stability performance and durability performance while travelling at a high speed.SOLUTION: A pneumatic tire 1 has a carcass 6 and an inner liner 7 and includes: a tread part 2 extending annularly; a pair of side wall parts 3 on both sides in a tire axial direction of the tread part 2; and bead parts 4 inside a tire radial direction of the respective side wall parts 3. The carcass 6 includes at least one carcass ply 6A extending between the pair of bead parts 4 via the tread part 2 and the pair of side wall parts 3. The inner liner 7 is disposed on a tire inner cavity side of the carcass ply 6A. The carcass ply 6A arranges a plurality of carcass cords 6c. The respective carcass cords 6c have tensile force T2 equal to 55 N or less during 2% expansion and a difference (T5-T2) between tensile force T5 during 5% expansion and tensile force T2 during 2% expansion that is equal to 45 N or more.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a pneumatic tire having a carcass and an inner liner.

Background Art

[0002] Conventionally, pneumatic tires having a carcass and an inner liner are known. For example, Patent Document 1 below proposes a tire in which an organic fiber-rubber composition composite is used as a carcass ply, and the organic fiber and the rubber composition can maintain a high adhesion amount even when exposed to high temperatures.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the tire of Patent Document 1 is lightened to improve fuel efficiency, the handling stability performance during high-speed driving may decrease, or cracks may occur in the inner liner, resulting in a decrease in the durability performance during high-speed driving.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object thereof is to provide a pneumatic tire capable of achieving both handling stability performance and durability performance during high-speed driving.

Means for Solving the Problems

[0006] The present disclosure relates to a pneumatic tire having a carcass and an inner liner, comprising an annularly extending tread portion, a pair of sidewall portions on both axial sides of the tread portion in the tire axial direction, and bead portions on the inner side of each of the sidewall portions in the tire radial direction. The carcass includes at least one carcass ply extending between the pair of bead portions via the tread portion and the pair of sidewall portions. The inner liner is disposed on the tire inner cavity side of the carcass ply. A plurality of carcass cords are arranged in the carcass ply, and each of the carcass cords has a tension T2 at 2% elongation of 55 N or less and a difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation of 45 N or more.

Advantages of the Invention

[0007] By having such a carcass and inner liner, the pneumatic tire of the present disclosure can achieve both excellent handling stability and durability during high-speed driving.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. FIG. 1 shows a cross-sectional view of a tire meridian including the rotation axis of the pneumatic tire 1 in the normal state of the present embodiment. Here, the "normal state" means a no-load state in which the pneumatic tire 1 is rim-mounted on a standard rim and adjusted to a standard internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the pneumatic tire 1 are values measured in this normal state.

[0010] When there is a standard system including the standards on which the pneumatic tire 1 is based, the "regular rim" is the rim defined for each tire by such standards. For example, in the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; and in the case of ETRTO, it is the "Measuring Rim". When there is no standard system including the standards on which the pneumatic tire 1 is based, the "regular rim" is the rim with the smallest rim diameter and the smallest rim width among the rims that can be assembled with the tire and do not cause air leakage.

[0011] When there is a standard system including the standards on which the pneumatic tire 1 is based, the "regular internal pressure" is the air pressure defined for each tire by each standard. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE". When there is no standard system including the standards on which the pneumatic tire 1 is based, the "regular internal pressure" is 250 kPa for passenger car tires.

[0012] The pneumatic tire 1 of the present embodiment is preferably used as a passenger car tire. Here, the passenger car tire in this specification is a rubber pneumatic tire 1 assumed to be attached to a four-wheel running automobile and refers to one with a regular load of 1000 kg or less. Note that as a passenger car tire, as long as the regular load is 1000 kg or less, it is not particularly limited. However, from the viewpoint of suppressing excessive deformation in the tread portion, the regular load is preferably applied to a tire with a regular load of 900 kg, more preferably applied to a tire with a regular load of 750 kg, and still more preferably applied to a tire with a regular load of 700 kg.

[0013] Here, when there is a standard system including the standards on which the pneumatic tire 1 is based, the "normal load" is the load defined for each tire by each standard. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY".

[0014] Note that the pneumatic tire 1 is not limited to being a passenger car tire, and can be applied to, for example, heavy load tires, motorcycle tires, racing tires, etc.

[0015] As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a tread portion 2 extending annularly, a pair of sidewall portions 3 on both sides in the tire axial direction of the tread portion 2, and bead portions 4 on the inner sides in the tire radial direction of the respective sidewall portions 3.

[0016] The tread portion 2, for example, has an outer surface 2a that constitutes a ground contact surface that contacts the road surface during running. The sidewall portion 3 preferably extends in the tire radial direction from both sides in the tire axial direction of the tread portion 2. For example, a buttress portion is provided between the tread portion 2 and the sidewall portion 3. The bead portion 4 includes, for example, a portion that contacts the rim when assembled to the rim. The bead portion 4 preferably has an annularly extending bead core 5.

[0017] The tread portion 2 is preferably formed of at least one layer of elastomer layer. The tread portion 2 may, for example, have two or more elastomer layers laminated in the tire radial direction, or may have a plurality of elastomer layers in the tire axial direction.

[0018] Examples of the elastomer layer of the tread portion 2 include diene rubbers such as natural rubber, isoprene rubbers such as isoprene rubber, butadiene rubber, styrene-butadiene rubber, styrene-isoprene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, and butyl rubber.

[0019] In the elastomer layer of the tread portion 2, for example, circumferential grooves extending in the tire circumferential direction, lateral grooves extending in the tire axial direction, sipes with a groove width of 2 mm or less, etc. may be appropriately provided. Examples of the circumferential grooves include those extending linearly and those extending in a zigzag shape.

[0020] The profile of the outer surface 2a of the tread portion 2 is, for example, a combination of a single arc, arcs with a plurality of curvatures, or a straight line in the tire meridian cross-section. The outer surface 2a of the tread portion 2 preferably defines the tire equator position C. Here, the tire equator position C is the central position of the tread ground contact ends Te on both sides in the tire axial direction.

[0021] Further, the tread ground contact end Te is the outermost ground contact position in the tire axial direction when a normal load is applied to the properly inflated tire 1 and it is grounded on a plane with a camber angle of 0°. That is, the tread ground contact width TW between the tread ground contact ends Te is the maximum width of the ground contact surface of the inflated tire 1.

[0022] The sidewall portion 3 is preferably formed of at least one layer of an elastomer layer. The sidewall portion 3 may, for example, have two or more layers of elastomer layers laminated in the tire axial direction, or may have a plurality of elastomer layers in the tire radial direction. The elastomer layer of the sidewall portion 3 may be, for example, of the same component as the elastomer layer of the tread portion 2 or of a different component.

[0023] The profile of the outer surface 3a of the sidewall portion 3 is, for example, a combination of a single arc, arcs with a plurality of curvatures, or a straight line. Here, the outer surface 3a of the sidewall portion 3 is defined as not including partial irregularities such as decorative serrations, ribs for logo display, and protective ribs.

[0024] The outer surface 3a of the sidewall portion 3 preferably defines the tire maximum width position P. Here, the tire maximum width position P is the position where the width W in the tire axial direction is maximum. The tire maximum width position P is, for example, the center position in the tire radial direction within a certain range when the position where the width W in the tire axial direction is maximum has a certain range in the tire radial direction.

[0025] The boundary surface between the elastomer layer of the tread portion 2 and the elastomer layer of the sidewall portion 3 is, for example, such that the outer end side in the tire axial direction is located on the outer side in the tire radial direction relative to the inner end side. The boundary surface between the elastomer layer of the tread portion 2 and the elastomer layer of the sidewall portion 3 may, for example, be such that the outer end side in the tire axial direction is located on the inner side in the tire radial direction relative to the inner end side.

[0026] The pneumatic tire 1 of the present embodiment has a toroidal carcass 6 and an inner liner 7 that extend across the bead cores 5 of the pair of bead portions 4. The carcass 6 includes at least one, in this embodiment, one carcass ply 6A. Such a carcass 6 can be weight-reduced since the number of carcass plies 6A is one, and the low fuel consumption performance of the pneumatic tire 1 can be improved.

[0027] The carcass ply 6A of the present embodiment extends between the pair of bead portions 4 via the tread portion 2 and the pair of sidewall portions 3. The inner liner 7 of the present embodiment is disposed on the tire inner cavity side of the carcass ply 6A. Such an inner liner 7 can hold the compressed air filled in the tire inner cavity.

[0028] The carcass ply 6A includes, for example, a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded-back portion 6b that is continuous with the main body portion 6a and is folded back from the inner side to the outer side in the tire axial direction around the bead core 5.

[0029] Between the main body portion 6a and the folded-back portion 6b of the carcass ply 6A, for example, a bead apex 8 extending radially outward in the tire radius direction from the bead core 5 is disposed. The bead apex 8 is formed of, for example, an elastomer layer.

[0030] In the bead portion 4, for example, a bead reinforcing layer (not shown) may be provided outside the folded-back portion 6b of the carcass 6 in the tire axial direction. The bead reinforcing layer may be formed of, for example, an elastomer layer having the same components as the bead apex 8, or may be formed of an elastomer layer having different components.

[0031] In the bead portion 4, for example, a chafer (not shown) may be provided outside the folded-back portion 6b of the carcass 6 in the tire axial direction. When the bead reinforcing layer and the chafer are provided, it is desirable that the chafer be disposed outside the bead reinforcing layer in the tire axial direction.

[0032] FIG. 2 is a partial cross-sectional view of the tread portion 2 of the present embodiment, and FIG. 3 is a partial cross-sectional view of the sidewall portion 3 of the present embodiment. As shown in FIGS. 2 and 3, the carcass ply 6A is formed of, for example, an elastomer composition 6G in which a plurality of carcass cords 6c are arranged at an angle of 75 to 90° with respect to the tire circumferential direction. Here, in this specification, “A to B” indicates “A or more and B or less”.

[0033] Each of the carcass cords 6c preferably has a tension T2 at 2% elongation of 55 N or less. Since such a carcass ply 6A has a small tension T2 at 2% elongation of the carcass cord 6c and is easy to stretch, when a normal load is applied to the properly inflated tire 1 in the normal state, the carcass cord 6c can be stretched appropriately, and entry of the inner liner 7 between the carcass cords 6c can be suppressed.

[0034] Therefore, the pneumatic tire 1 of the present embodiment can suppress the occurrence of cracks in the inner liner 7 even during high-speed driving, and thus can suppress the decrease in the internal pressure during driving. As a result, the pneumatic tire 1 of the present embodiment can suppress the increase in the deformation amount of the pneumatic tire 1 during high-speed driving, and can improve the durability performance. From such a viewpoint, the tension T2 at 2% elongation of the carcass cord 6c is more preferably 50 N or less, and even more preferably 45 N or less.

[0035] Each of the carcass cords 6c preferably has a difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation of 45 N or more. Since the tension T5 at 5% elongation of the carcass cord 6c of such a carcass ply 6A is large, excessive deformation of the carcass ply 6A during high-speed driving can be suppressed. For this reason, it is considered that the pneumatic tire 1 of the present embodiment can improve the durability performance and the handling stability performance during high-speed driving.

[0036] The pneumatic tire 1 of the present embodiment has good responsiveness to steering during high-speed driving, and can improve the handling stability performance during high-speed driving. From such a viewpoint, the difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation of the carcass cord 6c is more preferably 50 N or more, and even more preferably 55 N or more.

[0037] The pneumatic tire 1 including such a carcass ply 6A can achieve both the handling stability performance and the durability performance during high-speed driving. Here, the tension T2 at 2% elongation of the carcass cord 6c corresponds to the force generated in the pneumatic tire 1 when a normal load is applied to the pneumatic tire 1 in a normal state. Further, the tension T5 at 5% elongation of the carcass cord 6c corresponds to the force generated in the pneumatic tire 1 during high-speed driving.

[0038] The carcass cord 6c preferably has a circular cross-section orthogonal to the longitudinal direction of the carcass cord 6c. Here, in this specification, circular means that the ratio of the major axis to the minor axis of the cross-section is less than 1.05.

[0039] The diameter of the carcass cord 6c is preferably 0.80 to 1.00 mm. When the diameter of the carcass cord 6c is 0.80 mm or more, it helps to improve the rigidity of the pneumatic tire 1 and can improve the handling stability performance during high-speed driving of the pneumatic tire 1. When the diameter of the carcass cord 6c is 1.00 mm or less, it helps to reduce the weight of the pneumatic tire 1 and can improve the low fuel consumption performance of the pneumatic tire 1.

[0040] The carcass ply 6A preferably has 30 to 60 carcass cords 6c arranged per ply width of 5 cm. Here, the number of carcass cords 6c arranged per ply width of 5 cm is the number arranged per ply width of 5 cm in the direction orthogonal to the longitudinal direction of the carcass cord 6c.

[0041] When the number of carcass cords 6c arranged per ply width of 5 cm is 30 or more, it helps to improve the rigidity of the pneumatic tire 1 and can improve the handling stability performance during high-speed driving of the pneumatic tire 1. From this perspective, the number of carcass cords 6c arranged is more preferably 35 or more, and even more preferably 40 or more.

[0042] When the number of carcass cords 6c arranged per ply width of 5 cm is 60 or less, it suppresses peeling due to the small interval between the carcass cords 6c and can improve the durability performance during high-speed driving of the pneumatic tire 1. From this perspective, the number of carcass cords 6c arranged is more preferably 55 or less, and even more preferably 50 or less.

[0043] As shown in FIG. 2, the tread portion 2 has, for example, at the tire equator position C, a first distance L1 which is the distance from the inner surface 6d in the tire radial direction of the carcass cord 6c located at the innermost side in the tire radial direction to the inner surface 7a of the inner liner 7. That is, the carcass cord 6c of the present embodiment is arranged such that, at the tire equator position C, the inner surface 6d in the tire radial direction of the carcass cord 6c is at a position separated from the inner surface 7a of the inner liner 7 by the first distance L1. Here, the inner surface 7a of the inner liner 7 is defined as not including minute uneven shapes generated in the manufacturing process.

[0044] The first distance L1 is preferably 0.2 mm or more. By the first distance L1 being 0.2 mm or more, the thickness of the inner liner 7 can be maintained, which helps to improve the inner liner crack resistance performance. From such a viewpoint, the first distance L1 is more preferably 0.3 mm or more.

[0045] The carcass cord 6c preferably has a value T2 / L1 obtained by dividing the tension T2 at 2% elongation by the first distance L1 of 275 N / mm or less. Such a carcass ply 6A is defined such that the tension T2 at 2% elongation is also small when the first distance L1 is small, so that when a normal load is applied to the inflated tire 1 in a normal state, it is possible to more surely suppress the inner liner 7 from entering between the carcass cords 6c.

[0046] On the other hand, when the first distance L1 is large, this carcass ply 6A is less likely to generate inner liner cracks, so it is possible to allow a relatively large tension T2 at 2% elongation, which helps to improve the handling stability performance during high-speed running of the inflated tire 1. Therefore, the inflated tire 1 of the present embodiment can achieve both the handling stability performance and the durability performance during high-speed running.

[0047] As shown in FIG. 3, the sidewall portion 3 has, for example, at the tire maximum width position P, a second distance L2 which is the distance from the outer surface 6e in the tire axial direction of the carcass cord 6c located most outward in the tire axial direction to the outer surface 3a of the sidewall portion 3. That is, the carcass cord 6c of the present embodiment is arranged such that at the tire maximum width position P, the outer surface 6e in the tire axial direction of the carcass cord 6c is positioned at a distance L2 from the outer surface 3a of the sidewall portion 3.

[0048] The second distance L2 is preferably 8.5 mm or less. By the second distance L2 being 8.5 mm or less, it helps to improve the responsiveness to steering during high-speed driving and improve the handling stability performance during high-speed driving. From such a viewpoint, the second distance L2 is more preferably 8.0 mm or less.

[0049] The carcass cord 6c preferably has a value (T5 - T2) / L2 obtained by dividing the difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation by the second distance L2 of 5.3 N / mm or more. For such a carcass ply 6A, since the tension T5 at 5% elongation is also defined to be large when the second distance L2 is large, excessive deformation of the carcass ply 6A during high-speed driving can be more reliably suppressed. Also, in this case, since a small tension T2 at 2% elongation is allowed, it helps to improve the inner liner crack resistance performance of the pneumatic tire 1.

[0050] On the other hand, for this carcass ply 6A, when the second distance L2 is small, a reaction force from the carcass 6 easily acts on the sidewall portion 3, and even if the tension T5 at 5% elongation is relatively small, it helps to improve the handling stability performance of the pneumatic tire 1 during high-speed driving. Therefore, the pneumatic tire 1 of the present embodiment can achieve both the handling stability performance and the durability performance during high-speed driving.

[0051] As shown in FIGS. 2 and 3, the carcass cord 6c of the present embodiment is a hybrid cord 9 obtained by twisting at least two types of materials. By combining materials with different moduli, such a carcass cord 6c can achieve both the handling stability performance and the durability performance during high-speed driving of the pneumatic tire 1.

[0052] The carcass cord 6c is, for example, a hybrid cord 9 obtained by twisting a first twisted yarn of polyester and a second twisted yarn of polyamide. The first twisted yarn is formed from, for example, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). The second twisted yarn is formed from, for example, nylon 66 (N66) or nylon 6 (N6). Such a carcass cord 6c helps to increase the tension T5 at 5% elongation of the first twisted yarn and helps to decrease the tension T2 at 2% elongation of the second twisted yarn.

[0053] It is desirable that the fineness of the first twisted yarn is larger than the fineness of the second twisted yarn. The fineness of the first twisted yarn is preferably 2000 dtex or more. The first twisted yarn is formed by twisting, for example, a plurality of multifilaments of 1000 to 1200 dtex. The fineness of the second twisted yarn is preferably 1600 dtex or more. The second twisted yarn is formed by twisting, for example, a plurality of multifilaments of 800 to 1000 dtex. Such a carcass cord 6c helps to achieve both the handling stability performance and the durability performance during high-speed driving of the pneumatic tire 1.

[0054] The total fineness of the carcass cord 6c is preferably 3760 dtex or more. When the total fineness of the carcass cord 6c is 3760 dtex or more, even if there is only one carcass ply 6A, it is possible to achieve both the handling stability performance and the durability performance during high-speed driving of the pneumatic tire 1. From this perspective, the total fineness of the carcass cord 6c is more preferably 40000 dtex or more.

[0055] The heat shrinkage force of carcass cord 6c at 177°C is preferably 9.0 N or less. By the heat shrinkage force of carcass cord 6c at 177°C being 9.0 N or less, it is possible to suppress the shrinkage of carcass cord 6c due to heat generation during high-speed driving, and to suppress the inner liner 7 from entering between the carcass cords 6c. From such a viewpoint, the heat shrinkage force of carcass cord 6c at 177°C is more preferably 8.5 N or less.

[0056] The elastomer composition 6G of the carcass ply 6A of the present embodiment exhibits rubber elasticity. Examples of the elastomer composition 6G of the carcass ply 6A include a rubber composition, a thermoplastic elastomer composition, and the like.

[0057] When the elastomer composition 6G of the carcass ply 6A is a rubber composition, examples of the rubber component include isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, butyl rubber, and the like. When the elastomer composition 6G of the carcass ply 6A is a thermoplastic elastomer composition, examples of the elastomer include block copolymers such as thermoplastic polyurethane, styrene-butadiene block copolymer, and styrene-ethylene-butylene-styrene block copolymer.

[0058] As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a belt layer 10 disposed on the outer side in the tire radial direction of the carcass 6, and a band layer 11 disposed on the outer side in the tire radial direction of the belt layer 10.

[0059] The belt layer 10 includes at least one sheet, preferably two or more sheets, and in the present embodiment, two belt plies 10A and 10B. The two belt plies 10A and 10B include, for example, a first belt ply 10A located on the inner side in the tire radial direction, and a second belt ply 10B located outside the first belt ply 10A. Such a belt layer 10 can increase the rigidity of the tread portion 2 and improve the handling stability performance during high-speed driving of the pneumatic tire 1.

[0060] The belt plies 10A and 10B of the belt layer 10 of the present embodiment include a belt cord (not shown) made of steel and an elastomer composition covering the belt cord. The belt cord is preferably made of a single steel wire. The belt cord may be, for example, a twisted wire formed by twisting a plurality of steel filaments.

[0061] The belt cord is arranged, for example, at an angle of 10 to 30° with respect to the tire circumferential direction. The belt cords of the first belt ply 10A and the second belt ply 10B are preferably inclined in opposite directions with respect to the tire circumferential direction. Such a belt layer 10 can enhance the rigidity of the tread portion 2 in a well-balanced manner and improve the handling stability performance during high-speed running of the pneumatic tire 1. Here, the angle of the belt cord is the angle in the pneumatic tire 1 in the normal state and can be confirmed, for example, by partially peeling the tread portion 2.

[0062] The elastomer compositions of the belt plies 10A and 10B of the present embodiment exhibit rubber elasticity. Examples of the elastomer compositions of the belt plies 10A and 10B include rubber compositions, thermoplastic elastomer compositions, and the like.

[0063] When the elastomer compositions of the belt plies 10A and 10B are rubber compositions, examples of the rubber component include isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, butyl rubber, and the like. When the elastomer compositions of the belt plies 10A and 10B are thermoplastic elastomer compositions, examples of the elastomer include block copolymers such as thermoplastic polyurethane, styrene-butadiene block copolymer, and styrene-ethylene-butylene-styrene block copolymer.

[0064] The belt cord of the present embodiment is surface-plated or ternary-plated. Examples of the plating treatment include those containing copper (Cu), zinc (Zn), etc. Examples of the ternary plating treatment include those containing copper (Cu), zinc (Zn), cobalt (Co), etc. Such a belt cord has good adhesiveness to the elastomer composition, and can generate a stress in cooperation with the elastomer composition even during high-speed running, and can improve the durability performance during high-speed running of the pneumatic tire 1.

[0065] The belt layer 11 includes at least one, and in this embodiment, one belt ply 11A. Such a belt layer 11 can enhance the restraint of the tread portion 2 even during high-speed running, and can improve the handling stability performance during high-speed running of the pneumatic tire 1.

[0066] The belt ply 11A of the present embodiment includes a belt cord arranged at an angle of 5° or less with respect to the tire circumferential direction, and an elastomer composition covering the belt cord. Here, the angle of the belt cord is the angle in the normal pneumatic tire 1, and can be confirmed, for example, by partially peeling the tread portion 2.

[0067] The belt cord is formed of, for example, metal or organic fiber. When the belt cord is metal, it is preferably formed from a single-wire steel or a twisted wire obtained by twisting a plurality of steel filaments and having a plating treatment or a ternary plating treatment on the surface. When the belt cord is organic fiber, it is preferably formed from one kind alone or a hybrid fiber of two or more kinds selected from the group consisting of polyethylene terephthalate fiber, polyethylene naphthalate fiber, nylon fiber, aramid fiber, and rayon fiber.

[0068] The elastomer composition of belt ply 11A preferably exhibits rubber elasticity, like the elastomer compositions of belt plies 10A and 10B. Examples of the elastomer composition of belt ply 11A include the same compositions as those of belt plies 10A and 10B.

[0069] As described above, the particularly preferred embodiments of the present disclosure have been described in detail. However, the present disclosure is not limited to the above-described embodiments and can be implemented in various forms.

Examples

[0070] A pneumatic tire having the basic structure shown in FIG. 1 was prototyped based on the specifications in Tables 1 and 2. Using the prototyped pneumatic tire, the handling stability performance and durability performance during high-speed driving were tested. The common specifications and test methods are as follows.

[0071] <Common Specifications> Tire size: 195 / 65R15 Constitution of carcass cords: A PET 1670 dtex / 2 B PET 2200 dtex / 2 C PET 3300 dtex / 2 D Hybrid PET 2200 dtex N66 1880 dtex E Hybrid PET 3300 dtex N66 2820 dtex

[0072] <Handling Stability Performance during High-Speed Driving> The prototyped pneumatic tire was mounted on all four wheels of a test vehicle with the air pressure adjusted to 230 kPa, and the handling stability performance when driving on a test course at a speed of 70 km / h or more was evaluated by a test driver's sensory evaluation on a 5-point scale. The same test was conducted by 20 test drivers, and their total scores were calculated. The results are represented by an index with the total score of Comparative Example 1 set to 100, and the larger the numerical value, the better the handling stability performance during high-speed driving.

[0073] <Durability Performance during High-Speed Driving> The prototype pneumatic tire was mounted on a drum tester with the air pressure adjusted to 180 kPa, and continuously driven at a speed of 120 km / h with a camber angle of 0° and a normal load applied. The presence or absence of cracks in the inner liner was checked every 2,000 km of driving distance, and the driving distance until cracks occurred was measured. The results are expressed as an index with Comparative Example 1 set to 100, and the larger the numerical value, the better the durability performance during high-speed driving.

[0074] The test results are shown in Table 1 and Table 2.

Table 1

[0075]

Table 2

[0076] As a result of the test, the pneumatic tire of the example is excellent in handling stability performance and durability performance during high-speed driving compared to the comparative example, and also has good overall performance judged by the total value of each performance. Therefore, it was confirmed that the handling stability performance and durability performance during high-speed driving can be achieved simultaneously.

[0077] [Supplementary Note] This disclosure includes the following aspects.

[0078] [This Disclosure 1] A pneumatic tire having a carcass and an inner liner, comprising an annular tread portion, a pair of sidewall portions on both sides of the tread portion in the tire axial direction, and bead portions on the inner side in the tire radial direction of each of the sidewall portions, the carcass including at least one carcass ply extending between the pair of bead portions via the tread portion and the pair of sidewall portions, the inner liner being disposed on the tire inner cavity side of the carcass ply, a plurality of carcass cords being arranged in the carcass ply, each of the carcass cords having a tension T2 at 2% elongation of 55 N or less and a difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation of 45 N or more.

[0079] [Disclosure 2] For the carcass cord, when the distance from the inner surface of the inner liner to the inner surface in the tire radial direction of the carcass cord located most inward in the tire radial direction at the tire equator position is defined as the first distance L1, the value T2 / L1 obtained by dividing the tension T2 at 2% elongation by the first distance L1 is 275 N / mm or less. The pneumatic tire according to Disclosure 1.

[0080] [Disclosure 3] For the carcass cord, when the distance from the outer surface of the sidewall portion to the outer surface in the tire axial direction of the carcass cord located most outward in the tire axial direction at the tire maximum width position is defined as the second distance L2, the value (T5 - T2) / L2 obtained by dividing the difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation by the second distance L2 is 5.3 N / mm or more. The pneumatic tire according to Disclosure 1 or 2.

[0081] [Disclosure 4] The carcass cord is a hybrid cord formed by twisting at least two types of materials. The pneumatic tire according to any one of Disclosures 1 to 3.

[0082] [Disclosure 5] The carcass cord is the hybrid cord obtained by twisting together a first twisted yarn of polyester and a second twisted yarn of polyamide, the pneumatic tire according to Disclosure 4.

[0083] [Disclosure 6] The first twisted yarn is formed from polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), the pneumatic tire according to Disclosure 5.

[0084] [Disclosure 7] The second twisted yarn is formed from nylon 66 (N66) or nylon 6 (N6), the pneumatic tire according to Disclosure 5 or 6.

[0085] [Disclosure 8] The fineness of the first twisted yarn is greater than the fineness of the second twisted yarn, the pneumatic tire according to any one of Disclosures 5 to 7.

[0086] [Disclosure 9] The total fineness of the carcass cord is 3760 dtex or more, the pneumatic tire according to any one of Disclosures 1 to 8.

[0087] [Disclosure 10] The heat shrinkage force of the carcass cord at 177 °C is 9.0 N or less, the pneumatic tire according to any one of Disclosures 1 to 9.

Explanation of Signs

[0088] 1 Pneumatic tire 2 Tread part 3 Sidewall part 4 Bead part 6 Carcass 6A Carcass ply 6c Carcass cord 7 Inner liner

Claims

1. A pneumatic tire having a carcass and an inner liner, comprising an annular tread portion, a pair of sidewall portions on both sides of the tread portion in the tire axial direction, and bead portions on the inner side of each sidewall portion in the tire radial direction, wherein the carcass includes at least one carcass ply extending between the pair of bead portions via the tread portion and the pair of sidewall portions, the inner liner is disposed on the tire inner cavity side of the carcass ply, a plurality of carcass cords are arranged in the carcass ply, each of the carcass cords has a tension T2 at 2% elongation of 45 N or less, and a difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation of 55 N or more, a pneumatic tire.

2. When the distance from the inner surface of the inner liner to the inner surface in the tire radial direction of the carcass cord located innermost in the tire radial direction at the tire equator position is defined as the first distance L1, the value T2 / L1 obtained by dividing the tension T2 at 2% elongation by the first distance L1 is 275 N / mm or less. The pneumatic tire according to claim 1.

3. When the distance from the outer surface of the sidewall portion to the outer surface in the tire axial direction of the carcass cord located outermost in the tire axial direction at the tire maximum width position is defined as the second distance L2, the value (T5 - T2) / L2 obtained by dividing the difference (T5 - T2) between the tension T5 at 5% elongation and the tension T2 at 2% elongation by the second distance L2 is 5.3 N / mm or more. The pneumatic tire according to claim 1 or 2.

4. The carcass cord is a hybrid cord formed by twisting at least two types of materials. The pneumatic tire according to any one of claims 1 to 3.

5. The carcass cord is the hybrid cord formed by twisting a first twisted yarn of polyester and a second twisted yarn of polyamide. The pneumatic tire according to claim 4.

6. The first twisted yarn is formed from polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). The pneumatic tire according to claim 5.

7. The second twisted yarn is formed from nylon 66 (N66) or nylon 6 (N6). The pneumatic tire according to claim 5 or 6.

8. The fineness of the first twisted yarn is greater than that of the second twisted yarn. The pneumatic tire according to any one of claims 5 to 7.

9. The total fineness of the carcass cord is 3760 dtex or more. The pneumatic tire according to any one of claims 1 to 8.

10. The heat shrinkage force of the carcass cord at 177 °C is 9.0 N or less. The pneumatic tire according to any one of claims 1 to 9.

11. The diameter of the carcass cord is 0.80 to 1.00 mm. The pneumatic tire according to any one of claims 1 to 10.

12. It has a belt layer arranged on the outer side in the tire radial direction of the carcass, The belt layer includes at least one belt ply, The belt ply includes a belt cord made of steel, The belt cord is surface-plated or ternary-plated. The pneumatic tire according to any one of claims 1 to 11.

13. It is used as a passenger car tire. The pneumatic tire according to any one of claims 1 to 12.

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