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EP-4737134-A1 - PNEUMATIC TIRE

EP4737134A1EP 4737134 A1EP4737134 A1EP 4737134A1EP-4737134-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, and the carcass comprising carcass cords, wherein a base tread rubber and a sidewall rubber are different from each other, and wherein the following inequalities are satisfied|: A 2 − A 1 > 0 ; and 70 ° C tan δ B × 70 ° C tan δs < A 2 − A 1 / K (provided that K is 500), where A 1 represents an angle at which an extending direction of a carcass cord is inclined from a tire circumferential direction at the tire center line, A 2 represents an angle at which the extending direction is inclined from the tire circumferential direction at the tire maximum width position, 70°C tan δ B represents a loss tangent at 70°C of the base tread rubber, 70°C tan δ S represents a loss tangent at 70°C of the sidewall rubber, and K represents a constant.

Inventors

  • NAKAMURA, KENTARO
  • Daiki, IMAI

Assignees

  • Sumitomo Rubber Industries Ltd.

Dates

Publication Date
20260506
Application Date
20251020

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 tan δ B , 70°C tan δ S , and K satisfy the following inequalities (1) and (2): A 2 − A 1 > 0 , 70 ° C tan δ B × 70 ° C tan δ S < A 2 − A 1 / K , (provided that K is 500, preferably 520, more preferably 550, further preferably 600, further preferably 640), where 70°C tan δ B represents a loss tangent at 70°C of the rubber composition constituting the base tread, 70°C tan δ S represents a loss tangent 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 700, preferably 800, more preferably 1000, further preferably 1500, further preferably 2000.
  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 silica.
  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 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 claim 8 or 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 loss tangent, 70°C tan δ B , at 70°C of the rubber composition constituting the base tread is 0.10 or less.
  15. The pneumatic tire of any one of claims 1 to 14, wherein the loss tangent, 70°C tan δ S , at 70°C of the rubber composition constituting the sidewall is 0.10 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 a desired performance by controlling and changing an extending direction of carcass cords. However, there is a concern that energy loss may occur due to the change in extending direction of the carcass cords during running, resulting in deterioration in fuel efficiency of the tire. It is an object of the present invention to provide a pneumatic tire comprising a carcass cord whose extending direction changes for suppressing deterioration in fuel efficiency. 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 the 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, andwherein A1, A2, 70°C tan δB, 70°C tan δS, and K satisfy the following inequalities (1) and (2): A2−A1>0, 70°CtanδB×70°CtanδS<A2−A1/K,(provided that K is 500),where 70°C tan δB represents a loss tangent at 70°C of the rubber composition constituting the base tread, 70°C tan δS represents a loss tangent at 70°C of the rubber composition constituting the sidewall, and K represents a constant. According to the present invention, deterioration in fuel efficiency 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 direction at