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EP-4737133-A1 - PNEUMATIC TIRE

EP4737133A1EP 4737133 A1EP4737133 A1EP 4737133A1EP-4737133-A1

Abstract

Provided is a pneumatic tire comprising a tread, a carcass, a reinforcing layer, and a sidewall, the tread comprising a cap tread and a base tread, the carcass comprising a carcass cord, wherein a base tread rubber and a sidewall rubber are different from each other, and wherein the following inequalities (1) and (2) are satisfied: (1) |A 2 -A 1 |>0 (2) |70°C E* B -70°C E* s |<|A 2 -A 1 |×K (provided that K is 0.70), where A 1 represents an angle at which an extending direction of carcass cord is inclined from a tire circumferential direction at the tire center line, A 2 represents an angle at which an extending direction is inclined from the tire circumferential direction at the tire maximum width position, 70°C E* B represents a complex elastic modulus at 70°C of the base tread rubber, 70°C E* S represents a complex elastic modulus at 70°C of the sidewall rubber, and K represents a constant.

Inventors

  • NAKAMURA, KENTARO
  • IMAI, Daiki

Assignees

  • Sumitomo Rubber Industries, Ltd.

Dates

Publication Date
20260506
Application Date
20251009

Claims (15)

  1. A pneumatic tire comprising a tread, a carcass, at least one reinforcing layer arranged on an outer side of the carcass in a tire radial direction, and a sidewall, the tread comprising a cap tread including a ground-contacting surface, and a base tread on an inner side of the cap tread in a tire radial direction, wherein the carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords, wherein the reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords, wherein A 1 represents an angle, in degrees, at which an extending direction of carcass cord of any of the carcass plies is inclined from a tire circumferential direction at a position on a tire center line, and A 2 represents an angle, in degrees, at which an extending direction of carcass cord of the carcass ply is inclined from the tire circumferential direction at a tire maximum width position, wherein a rubber composition constituting the base tread and a rubber composition constituting the sidewall are composed of different rubber compositions, and wherein A 1 , A 2 , 70°C E* B , 70°C E* S , and K satisfy the following inequalities (1) and (2): A 2 − A 1 > 0 70 ° C E * B − 70 ° C E * S < A 2 − A 1 × K (provided that K is 0.70, preferably 0.60), where 70°C E*s represents a complex elastic modulus, in MPa, at 70°C of the rubber composition constituting the base tread, 70°C E* S represents a complex elastic modulus, in MPa, at 70°C of the rubber composition constituting the sidewall, and K represents a constant.
  2. The pneumatic tire of claim 1, wherein, in the inequality (2), the constant K is 0.50, preferably 0.40, more preferably 0.30, further preferably 0.20, further preferably 0.10.
  3. The pneumatic tire of claim 1 or 2, wherein the rubber composition constituting the base tread comprises a rubber component, and wherein the rubber component comprises an isoprene-based rubber.
  4. The pneumatic tire of any one of claims 1 to 3, wherein the rubber composition constituting the base tread comprises a rubber component, and wherein the rubber component comprises a styrene-butadiene rubber or a butadiene rubber.
  5. The pneumatic tire of any one of claims 1 to 4, wherein the rubber composition constituting the sidewall comprises a rubber component, and wherein the rubber component comprises an isoprene-based rubber.
  6. The pneumatic tire of any one of claims 1 to 5, wherein the rubber composition constituting the sidewall comprises resin.
  7. The pneumatic tire of any one of claims 1 to 6, wherein A 1 and A RF are different, where, in at least any of the reinforcing layer plies, A RF represents an angle, in degrees, at which an extending direction of reinforcing layer cord of the reinforcing layer ply is inclined from a tire circumferential direction.
  8. The pneumatic tire of claim 7, wherein the inclination direction of A RF from the tire circumferential direction is opposite to the inclination direction of A 1 from the tire circumferential direction.
  9. The pneumatic tire of claim 7 or 8, wherein the reinforcing layer comprising the reinforcing layer ply in which the angle at which the extending direction of reinforcing layer cord is inclined from the tire circumferential direction is A RF (°) is composed of one reinforcing layer ply.
  10. The pneumatic tire of any one of claims 7 to 9, wherein the reinforcing layer ply in which the angle at which the extending direction of reinforcing layer cord is inclined from the tire circumferential direction is A RF (°) is a belt ply.
  11. The pneumatic tire of any one of claims 1 to 10, wherein the at least one reinforcing layer consists of a belt.
  12. The pneumatic tire of any one of claims 1 to 11, wherein the carcass is composed of one carcass ply.
  13. The pneumatic tire of any one of claims 1 to 12, wherein A 2 is +70° or higher and +90° or lower, preferably +75° or higher and +85° or lower, more preferably +80° or higher and +85° or lower, or -70° or lower and higher than -90°, preferably -75° or lower and -85° or higher, more preferably -80° or lower and -85° or higher.
  14. The pneumatic tire of any one of claims 1 to 13, wherein the complex elastic modulus, 70°C E*s, at 70°C of the rubber composition constituting the base tread is 7.0 or less, preferably 6.5 or less.
  15. The pneumatic tire of any one of claims 1 to 14, wherein the complex elastic modulus, 70°C E* S , at 70°C of the rubber composition constituting the sidewall is 6.5 or less.

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire. BACKGROUND OF THE INVENTION In a pneumatic tire, a carcass ply forms a skeleton. A carcass cord constituting the carcass ply is configured to distinguish between types of tires, such as a radial tire, a bias tire, and the like, depending on an extending direction thereof, and determines performances of the pneumatic tire, such as durability, rigidity, and the like. JP 2023-84469 A and WO 2021/123530 describe a pneumatic tire with carcass cords flexed by controlling the direction in which the carcass cords extend. SUMMARY OF THE INVENTION Such a pneumatic tire can be imparted with desired performances by controlling and changing an extending direction of carcass cords. However, there is a concern about deterioration in durability of the pneumatic tire due to strain concentrating on a part sandwiched between the tread part and the side part during running. It is an object of the present invention to provide a pneumatic tire comprising carcass cords whose extending direction changes for suppressing deterioration in durability. That is, the present invention relates to the following tire: a pneumatic tire comprising a tread, a carcass, at least one reinforcing layer arranged on an outer side of the carcass in a tire radial direction, and a sidewall,the tread comprising a cap tread including a ground-contacting surface, and a base tread on an inner side of the cap tread in a tire radial direction,wherein the carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords,wherein the reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords,wherein A1 represents an angle, in degrees, at which an extending direction of carcass cord of any of the carcass plies is inclined from a tire circumferential direction at a position on a tire center line, and A2 represents an angle, in degrees, at which an extending direction of carcass cord of the carcass ply is inclined from the tire circumferential direction at a tire maximum width position,wherein a rubber composition constituting the base tread and a rubber composition constituting the sidewall are composed of different rubber compositions, and wherein A1, A2, 70°C E*B, 70°C E*s, and K satisfy the following inequalities (1) and (2): A2−A1>0 70°CE*B−70°CE*S<A2−A1×K(provided that K is 0.70)where 70°C E*s represents a complex elastic modulus, in MPa, at 70°C of the rubber composition constituting the base tread, 70°C E*S represents a complex elastic modulus, in MPa, at 70°C of the rubber composition constituting the sidewall, and K represents a constant. According to the present invention, deterioration in durability of a pneumatic tire comprising carcass cords whose extending direction changes can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view passing through a tire rotation axis of a pneumatic tire relating to one embodiment of the present invention.FIG. 2 is one example of a developed view of carcass cords constituting a carcass ply of a pneumatic tire relating to one embodiment of the present invention, which represents, from the tire inner surface side, an angle formed between an extending direction of the carcass cords and a tire circumferential direction.FIG. 3 is a variation of a developed view of carcass cords constituting a carcass ply of a pneumatic tire relating to one embodiment of the present invention, which represents, from the tire inner surface side, an angle formed between an extending direction of the carcass cords and a tire circumferential direction.FIG. 4 is a schematic view representing a preferred range of an angle formed between an extending direction of a carcass cord constituting a carcass ply of a pneumatic tire relating to one embodiment of the present invention and a tire circumferential direction. DETAILED DESCRIPTION A pneumatic tire that is one embodiment of the present invention will be described below. The pneumatic tire of the present embodiment is a pneumatic tire comprising a tread, a carcass, at least one reinforcing layer arranged on an outer side of the carcass in a tire radial direction, and a sidewall, the tread comprising a cap tread including a ground-contacting surface, and a base tread on an inner side of the cap tread in a tire radial direction, wherein the carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords, wherein the reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords, wherein A1 represents an angle, in degrees, at which an extending direction of carcass cord of any of the carcass plies is inclined from a tire circumferential dire