pneumatic tires

Abstract

To provide a pneumatic tire enabling the side rigidity thereof to be improved more than ever before.SOLUTION: A pneumatic tire comprises: a pair of beads 10 each of which has a bead core 11 and a bead filler 12 extending from the bead core 11 outward in a tire radial direction; a pair of side walls 20 each of which extends outward in the tire radial direction from each of the pair of beads 10; a tread 30 arranged between the pair of side walls 20; a carcass ply 40 bridged across the pair of beads 10; an inner side reinforcement layer 60 arranged in the inside, in the tire width direction, of the bead filler 12; and an outer side reinforcement layer 70 arranged on the outside, in a tire width direction, of the bead filler 12. The inner side reinforcement layer 60 is arranged in the inside in the tire radial direction rather than an outer end 12, in the tire radial direction, of the bead filler 12; and the outer side reinforcement layer 70 has an outside extension part 72 extending from an outer end 12d in the tire radial direction of the bead filler 12 outward in the tire radial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Generally, a pneumatic tire has a structure in which a carcass ply is stretched between a pair of beads arranged at both inner peripheral ends in the tire width direction, and is covered with tread rubber, sidewall rubber, etc. Conventionally, pneumatic tires are known in which reinforcing layers for suppressing separation by the carcass ply are respectively arranged on both sides in the tire width direction of the bead fillers constituting the beads (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 above, the reinforcing layers arranged on both sides in the tire width direction of the bead fillers are both shorter than the tire radial length of the bead fillers. Therefore, when the tire receives a lateral force, it is presumed that the so-called side rigidity that resists the lateral force becomes insufficient, and there is room for improvement.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire capable of improving side rigidity more than before.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention comprises a pair of beads having a bead core and a bead filler extending radially outward from the bead core; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; a carcass ply spanning between the pair of beads; an inner side reinforcing layer disposed on the inside of the bead filler in the tire width direction; and an outer side reinforcing layer disposed on the outside of the bead filler in the tire width direction, wherein the inner side reinforcing layer is disposed radially inward from the outer end of the bead filler in the tire radial direction, and the outer side reinforcing layer has an outer extension portion extending radially outward from the outer end of the bead filler in the tire radial direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a pneumatic tire that can improve side rigidity compared to conventional tires. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a half-cross section in the tire width direction of a pneumatic tire according to the embodiment. [Figure 2] This is a partially enlarged view of Figure 1. [Figure 3] This diagram illustrates the configuration of the outer side reinforcing layer and the inner side reinforcing layer of the tire according to the embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a half cross-section in the tire width direction of tire 1, which is a pneumatic tire according to this embodiment. Figure 2 is an enlarged view of a part of Figure 1, and is a cross-sectional view showing the portion from the bead 10 to the sidewall 20, which will be described later.

[0010] The tire 1 according to this embodiment is, for example, a pneumatic tire for a passenger car. In addition to passenger cars, the tire 1 according to this embodiment can also be used for various other vehicles such as light trucks, trucks, and buses.

[0011] The basic structure of tire 1 is symmetrical in cross-section along the tire width. Figure 1 shows a half-cross-section of the right half of tire 1, and the left half, which is not shown, has the same structure. In Figure 1, the symbol S1 represents the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and located at the center in the tire width direction.

[0012] The cross-sectional view in Figure 1 shows tire 1 mounted on a specified rim and filled to the specified internal pressure in an unloaded state. The specified rim refers to the standard rim defined by JATMA corresponding to the tire size. The specified internal pressure is, for example, 180 kPa if tire 1 is for a passenger car.

[0013] Here, the tire width direction is the direction parallel to the tire rotation axis, which is the left-right direction in Figure 1. In Figure 1, it is shown as the tire width direction X. The inside of the tire width direction is the direction approaching the tire equatorial plane S1, which is the left side of the paper in Figure 1. The outside of the tire width direction is the direction away from the tire equatorial plane S1, which is the right side of the paper in Figure 1.

[0014] Furthermore, the tire radial direction is the direction perpendicular to the tire rotation axis, and corresponds to the vertical direction in Figure 1. In Figure 1, it is shown as the tire radial direction Y. The outer side of the tire radial direction is the direction away from the tire rotation axis, and corresponds to the upper side of the paper in Figure 1. The inner side of the tire radial direction is the direction closer to the tire rotation axis, and corresponds to the lower side of the paper in Figure 1. The same applies to Figure 2.

[0015] As shown in Figure 1, the tire 1 comprises a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 positioned between the pair of sidewalls 20, a carcass ply 40 positioned across the pair of beads 10, an inner liner 50 positioned on the inner side of the carcass ply 40, and an inner side reinforcing layer 60 and an outer side reinforcing layer 70 provided on the sidewalls 20.

[0016] The bead 10 includes a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a chafing element 13, and a rim protector 15.

[0017] The bead core 11 is an annular component in which a rubber-coated metal bead wire is wound multiple times in the circumferential direction of the tire. The bead core 11 is a component that secures the air-filled tire 1 to the rim. The bead filler 12 has a tapered shape as it extends from the inside to the outside in the radial direction of the tire.

[0018] As shown in Figure 2, the bead filler 12 has an inner surface 12b on the inner side in the tire circumferential direction, an outer surface 12c on the outer side in the tire circumferential direction, a tapered outer end 12d in the tire radial direction, and an inner end 12e in the tire radial direction. Both the inner surface 12b and the outer surface 12c of the bead filler 12 curve gently so as they move outward in the tire radial direction, widening outward in the tire width direction, and converging at the outer end 12d in the tire radial direction. The inner end 12e in the tire radial direction of the bead filler 12 is in close contact with the outer end 11A in the tire radial direction of the bead core 11.

[0019] The tire width direction dimension of the tire radial inner end 12e of the bead filler 12 is smaller than the tire width direction dimension of the tire radial outer end 11A of the bead core 11. A step portion 11b is formed on the inner side in the tire width direction of the tire radial outer end 11A of the bead core 11, which faces the outer side in the tire radial direction without being covered by the tire radial inner end 12e of the bead filler 12. A step portion 11c is formed on the outer side in the tire width direction of the tire radial outer end 11A of the bead core 11, which faces the outer side in the tire radial direction without being covered by the tire radial inner end 12e of the bead filler 12.

[0020] The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is composed of, for example, rubber with a higher hardness than the surrounding rubber members.

[0021] The chafer 13 is provided on the inner side in the tire radial direction of the carcass ply 40 provided around the bead core 11. The rim protector 15 includes a rim strip rubber 14. The rim strip rubber 14 is disposed on the outer side in the tire width direction of the chafer 13 and the carcass ply 40. A top portion 14a along the tire circumferential direction is formed on the outer surface of the rim strip rubber 14. The rim strip rubber 14 contacts the inner portion of the rim on which the tire 1 is mounted. The rim protector 15 is continuously annular in the tire circumferential direction. The rim protector 15 has a function of protecting the rim from damage.

[0022] The sidewall 20 includes a sidewall rubber 21 disposed on the outer side in the tire width direction of the carcass ply 40. The sidewall rubber 21 constitutes the outer wall surface of the tire 1. The sidewall rubber 21 is the most flexible part when the tire 1 performs a cushioning action, and usually, a flexible rubber with fatigue resistance is adopted.

[0023] The tread 30 includes an endless belt 31 and a cap ply 32, and a tread rubber 33.

[0024] The belt 31 is positioned radially outward of the carcass ply 40. The cap ply 32 is positioned radially outward of the belt 31. The belt 31 is a member that reinforces the tread 30. The belt 31 in this embodiment has a two-layer structure comprising an inner belt 311 and an outer belt 312. Both the inner belt 311 and the outer belt 312 have a structure in which multiple cords, such as steel cords, are covered with rubber.

[0025] In this embodiment, the two-layer belt 31 has an inner belt 311 that is wider than the outer belt 312. Therefore, the outer end 311A ​​of the inner belt 311 in the tire width direction is located further outward in the tire width direction than the outer end 312A of the outer belt 312 in the tire width direction. By providing the belt 31, the rigidity of the tire 1 is ensured and the contact of the tread 30 with the road surface is improved. Note that the belt 31 is not limited to a two-layer structure, but may have a one-layer or three or more-layer structure.

[0026] The cap ply 32 is a component that reinforces the tread 30 together with the belt 31. The cap ply 32 has a structure in which multiple insulating organic fiber cords, such as polyamide fibers, are covered with rubber. The outer end 32A of the cap ply 32 in the tire width direction is located further outward in the tire width direction than the outer end 311A ​​of the inner belt 311 in the tire width direction. The outer end 32b of the cap ply 32 in the tire width direction covers and tightly adheres to the outer end 311b of the inner belt 311 in the tire width direction. As a result, the outer belt 312 is sandwiched between the cap ply 32 and the inner belt 311. By providing the cap ply 32, durability can be improved and road noise during driving can be reduced.

[0027] The tread rubber 33 is positioned on the radially outer side of the cap ply 32. The tread rubber 33 is a component that makes up the tread surface 331 that contacts the road surface when driving. The tread surface 331 of the tread rubber 33 is provided with a tread pattern 34, which is composed of, for example, multiple grooves. High modulus rubber 36 is positioned on the outer side of the tread rubber 33 in the tire width direction. The high modulus rubber 36 is sandwiched between the tread rubber 33 and the sidewall rubber 21 and is in close contact with the tread rubber 33 and the sidewall rubber 21. The high modulus rubber 36 is a relatively thin, strip-shaped rubber member and is made of rubber with a higher modulus (elastic modulus of rubber) than the tread rubber 33 and the sidewall rubber 21.

[0028] The carcass ply 40 constitutes the ply that forms the framework of the tire 1. The carcass ply 40 is embedded in the tire 1 in such a manner that it passes between a pair of beads 10 and through the inner side of the tire cavity of a pair of sidewalls 20 and tread 30.

[0029] The carcass ply 40 includes a plurality of carcass cords (not shown) that form the skeleton of the tire 1. The plurality of carcass cords extend, for example, along the in-plane direction along the tire width direction and are arranged in a line in the circumferential direction of the tire. These carcass cords are made of insulating organic fiber cords such as polyester or polyamide. The plurality of carcass cords are covered with rubber to form the carcass ply 40.

[0030] The carcass ply 40 has a ply body portion 401, a ply folded portion 402, and a bent portion 403. The ply body portion 401 is the portion that extends from the inner side in the tire width direction of one bead core 11, through the tread 30, to the inner side in the tire width direction of the other bead core 11. The ply folded portion 402 is the portion that extends radially outward on the outer side of the bead filler 12 in the tire width direction, by being folded back around the bead core 11 from the inner end of the ply body portion 401 in the tire radial direction. The bent portion 403 is the portion that bends in a U-shape from the ply body portion 401 around the bead core 11 and connects to the ply folded portion 402. The ply body portion 401 and the ply folded portion 402 are continuous via the bent portion 403.

[0031] The ply body portion 401 is positioned on the inner side in the tire radial direction and on the inner side in the tire width direction of the bead core 11 and bead filler 12. The ply fold portion 402 is positioned on the outer side in the tire width direction of the bead core 11 and bead filler 12. The bent portion 403 includes the innermost part in the tire radial direction of the carcass ply 40.

[0032] The carcass ply 40 of this embodiment has a two-layer structure in which a first carcass ply 410 and a second carcass ply 420 are stacked on top of each other. In the ply body portion 401, the first carcass ply 410 is positioned on the inner side of the tire cavity of the second carcass ply 420.

[0033] The second carcass ply 420 of the ply fold-over portion 402 extends from the radially inner side of the tire to partway down the sidewall 20. The radially outer end 421 of the second carcass ply 420 of the ply fold-over portion 402 overlaps with the second carcass ply 420 of the ply body portion 401 located on the sidewall 20. The radially outer end 421A of the second carcass ply 420 of the ply fold-over portion 402 is located radially outward from the radially inner end 36A of the high-modulus rubber 36.

[0034] The first carcass ply 410 of the ply fold-over portion 402 extends radially outward from the inside in the tire radial direction, beyond the radially outer end 421A of the second carcass ply 420, and further extends through the sidewall 20 to the outer end of the tread 30 in the tire width direction. The radially outer end 411 of the first carcass ply 410 of the ply fold-over portion 402 overlaps with the portion of the second carcass ply 420 of the ply body 401 that extends from the sidewall 20 to the tread 30. The radially outer end 411A of the first carcass ply 410 of the ply fold-over portion 402 is located inward in the tire width direction than the outer width direction outer end 312A of the outer belt 312.

[0035] In this embodiment, the carcass ply 40 has a two-layer structure, but the carcass ply 40 may have one layer or three or more layers. It is preferable that the carcass ply 40 is composed of two or more layers, as this sufficiently suppresses local deformation of the tire 1 near the rim mounting area.

[0036] The bead 10's chamfer 13 is positioned to surround the inner end of the carcass ply 40 in the tire radial direction, including the bent portion 403. The rim strip rubber 14 is positioned on the outer side in the tire width direction of the ply fold portion 402 and the chamfer 13 of the carcass ply 40. The outer end of the rim strip rubber 14 in the tire radial direction is covered with the sidewall rubber 21.

[0037] The inner liner 50 covers the inner surface of the tire between the pair of beads 10. Therefore, the inner liner 50 constitutes the inner wall surface of the tire 1. In the area extending from the tread 30 to the sidewall 20, the inner liner 50 covers the inner surface of the ply body 401. In the area extending from the sidewall 20 to the bead 10, the inner liner 50 covers the inner surface of the ply body 401 and the chamfer 13. The inner liner 50 is made of air-permeable rubber to prevent air from leaking out of the tire cavity.

[0038] Here, the rubber used for the bead filler 12 is one that is at least harder than the sidewall rubber 21 and the inner liner 50. The hardness of the rubber is measured using a Type A durometer in a 23°C atmosphere (durometer hardness) in accordance with JIS K6253.

[0039] For example, when using the hardness of the sidewall rubber 21 as a reference, it is preferable to use rubber with a hardness of about 1.2 to 2.3 times that of the sidewall rubber 21 for the bead filler 12. It is even more preferable to use rubber with a hardness of about 1 to 1.6 times that of the sidewall rubber 21 for the rim strip rubber 14. By using such hardness levels, it is possible to ensure a balance between the flexibility of the tire and the rigidity around the bead 10.

[0040] As shown in Figure 2, the inner side reinforcement layer 60 is positioned on the inner side of the bead filler 12 in the tire width direction. The inner side reinforcement layer 60 is an annular reinforcement layer along the tire circumferential direction. The cross-sectional shape of the inner side reinforcement layer 60 in the tire width direction extends from the inside to the outside in the tire radial direction.

[0041] The inner side reinforcement layer 60 is in close contact with the inner surface 12b of the bead filler 12, with its inner end 60a in the tire radial direction engaged with the inner stepped portion 11b of the bead filler 12. Therefore, the inner end 60a of the inner side reinforcement layer 60 in the tire radial direction is located radially outward from the outer end 11A of the bead core 11. The tire radial length L1 of the inner side reinforcement layer 60 is shorter than the tire radial length L of the bead filler 12. Therefore, the outer end 60b of the inner side reinforcement layer 60 in the tire radial direction is located radially inward from the outer end 12d of the bead filler 12. In other words, the inner side reinforcement layer 60 is positioned radially inward from the outer end 60b of the bead filler 12.

[0042] Furthermore, the inner side reinforcement layer 60 is in close contact with the second carcass ply 420 of the ply body portion 401 of the carcass ply 40. That is, the inner side reinforcement layer 60 is sandwiched between the bead filler 12 and the ply body portion 401, and is in close contact with both the bead filler 12 and the second carcass ply 420 of the ply body portion 401. As a result, the inner end 60a and outer end 60b in the tire radial direction of the inner side reinforcement layer 60 are protected by the carcass ply 40, thus preventing the inner liner 50 from being damaged by the inner side reinforcement layer 60.

[0043] Here, it is preferable that the radial outer end 12d of the bead filler 12 and the radial outer end 60b of the inner side reinforcing layer 60 do not coincide in the radial X direction for manufacturing purposes, but the radial length of the inner side reinforcing layer 60 is preferably as long as possible from the viewpoint of improving rigidity. From this viewpoint, in this embodiment, the radial length L1 of the inner side reinforcing layer 60 is preferably 60% to 90% of the radial length L of the bead filler 12, and more preferably 70% to 90%.

[0044] As shown in Figure 2, the outer side reinforcing layer 70 is positioned on the outer side of the bead filler 12 in the tire width direction. The outer side reinforcing layer 70 is an annular reinforcing layer along the tire circumferential direction. The cross-sectional shape of the outer side reinforcing layer 70 in the tire width direction extends from the inside to the outside in the tire radial direction.

[0045] The outer side reinforcing layer 70 is in close contact with the outer surface 12c of the bead filler 12, with its inner end 70a in the tire radial direction engaged with the outer stepped portion 11c of the bead filler 12. Therefore, the inner end 70a of the outer side reinforcing layer 70 in the tire radial direction is located radially outward from the outer end 11A of the bead core 11 in the tire radial direction.

[0046] The radial length L2 of the outer side reinforcement layer 70 is longer than the radial length L of the bead filler 12. The outer side reinforcement layer 70 has an inner extension portion 71 that is in close contact with the outer surface 12c of the bead filler 12 and is located radially inward, and an outer extension portion 72 that extends radially outward from the radially outer end 12d of the bead filler 12. The tip of the outer extension portion 72, i.e., the radially outer end 70b of the outer side reinforcement layer 70, is located at approximately the same position as the maximum width position W1 of the tire 1 in the tire radial direction, or between the maximum width position W1 of the tire 1 and the radially outer end 12d of the bead filler 12.

[0047] The entire outer side reinforcement layer 70, that is, the inner extension portion 71 and the outer extension portion 72, are in close contact with the second carcass ply 420 of the ply folded portion 402 of the carcass ply 40. Here, the inner extension portion 71 is sandwiched between the bead filler 12 and the ply folded portion 402, and is in close contact with both the bead filler 12 and the second carcass ply 420 of the ply folded portion 402. In other words, the inner extension portion 71, which is part of the outer side reinforcement layer 70, is sandwiched between the bead filler 12 and the ply folded portion 402.

[0048] On the other hand, the outer extension portion 72, which extends radially outward in the tire direction beyond the outer end 12d of the bead filler 12, is sandwiched between the second carcass ply 420 on the ply body portion 401 side and the second carcass ply 420 on the ply fold-over portion 402 side. In other words, the outer extension portion 72 is sandwiched between the ply body portion 401 and the ply fold-over portion 402. The outer extension portion 72 is in close contact with both the second carcass ply 420 on the ply body portion 401 side and the second carcass ply 420 on the ply fold-over portion 402 side. As a result, the outer end 70b of the outer side reinforcing layer 70 in the tire direction is prevented from forming a step on the outer surface of the sidewall 20, and a good appearance is maintained. In addition, since the outer end 70b of the outer side reinforcing layer 70 in the tire direction is protected by the carcass ply 40, damage to the inner liner 50 by the outer side reinforcing layer 70 is avoided.

[0049] In this embodiment, the tire radial length L2 of the outer side reinforcing layer 70 is preferably 110% to 170% of the tire radial length L of the bead filler 12, and more preferably 120% to 160%.

[0050] In this embodiment, the outer end 60b of the inner side reinforcement layer 60 in the tire radial direction is located inward in the tire radial direction from the outer end 12d of the bead filler 12. Similarly, the outer end 70b of the outer side reinforcement layer 70 in the tire radial direction is located outward in the tire radial direction from the outer end 12d of the bead filler 12. Thus, because the outer ends of the inner side reinforcement layer 60 and the outer side reinforcement layer 70 are offset in the tire radial direction from the outer end of the bead filler 12, stress concentration is less likely to occur. As a result, durability is improved.

[0051] As shown in Figure 2, the outer end portion 61 in the tire radial direction of the inner side reinforcement layer 60 is directed toward the outer side reinforcement layer 70. The virtual extension line 611 extending in the direction directed by this outer end portion 61 intersects the outer side reinforcement layer 70.

[0052] In this embodiment, the inner side reinforcing layer 60 and the outer side reinforcing layer 70 preferably use a metal fiber cord layer containing metal fibers. Figure 3 is a diagram showing a part of the outer side reinforcing layer 70 made of a metal fiber cord layer, and is a hypothetical diagram of the outer side reinforcing layer 70 located inside the tire 1, viewed from the outside in the tire width direction toward the inside in the tire width direction. The inner side reinforcing layer 60 is also made of a metal fiber cord layer, similar to the outer side reinforcing layer 70. Therefore, in this description, the structure of both the inner side reinforcing layer 60 and the outer side reinforcing layer 70 will be described in detail, with the outer side reinforcing layer 70 being a representative example, with reference to Figure 3.

[0053] The outer side reinforcing layer 70 is composed of multiple metal cords 81 formed by twisting together multiple metal fibers, and a topping rubber 82 that covers and integrates the multiple metal cords 81.

[0054] Multiple metal cords 81 extend at an angle with respect to the radial direction R of the tire 1 and are arranged at intervals in the circumferential direction C of the tire in an inclined state. The spacing between the multiple metal cords 81 aligned in the circumferential direction C of the tire widens as it moves outward in the radial direction of the tire.

[0055] The angle θ between the radial direction R of the tire 1 and the extending direction of the metal cords 81 of the outer side reinforcing layer 70 is preferably 10° or more and 40° or less. In this embodiment, the ply cords constituting the carcass ply 40 are arranged radially (radial direction R) from the center of the tire 1. Therefore, in this embodiment, the angle θ between the extending direction of the ply cords of the carcass ply 40 and the extending direction of the respective metal cords 81 of the inner side reinforcing layer 60 and the outer side reinforcing layer 70 is 10° or more and 40° or less. The inclination direction of the metal cords 81 of the inner side reinforcing layer 60 may be in the opposite direction to the inclination direction of the metal cords 81 of the outer side reinforcing layer 70.

[0056] In this way, by crossing the ply cords of the carcass ply 40 with the metal cords 81 of the inner side reinforcing layer 60 and the outer side reinforcing layer 70 in a side view, the rigidity of the portion where the carcass ply 40 overlaps with the inner side reinforcing layer 60 and the outer side reinforcing layer 70 can be increased.

[0057] The metal used to make up the metal cord 81 is preferably a metal cord material that is highly strong yet flexible and highly fatigue-resistant, and for example, steel cord is more preferably used. In the case of steel cord, for example, several to several dozen strands of high-carbon steel wire with a diameter of about φ0.1 to φ0.5 mm are twisted together and plated as needed to improve adhesion with rubber. In this embodiment, the metal cord 81 preferably has an outer diameter (cord diameter) of, for example, 0.5 mm or more and 1.2 mm or less.

[0058] The inner side reinforcement layer 60 and the outer side reinforcement layer 70 may be reinforcement layers in which multiple insulating organic fiber cords, such as polyamide fibers, are covered with rubber, similar to the cap ply 32.

[0059] According to the tire 1 of this embodiment, when the tire 1 is subjected to a lateral force, such as during cornering, the outer side reinforcing layer 70 strongly resists that lateral force, exhibiting sufficient side rigidity. Furthermore, when subjected to a lateral force, the inner side reinforcing layer 60 effectively suppresses the deflection of the bead filler 12, thereby also exhibiting sufficient side rigidity. Therefore, the side rigidity is significantly increased by the inner side reinforcing layer 60 and the outer side reinforcing layer 70, resulting in improved cornering performance.

[0060] As in this embodiment, when the tire radial length L1 of the inner side reinforcing layer 60 is 60% or more and 90% or less of the tire radial length L of the bead filler 12, the inner side reinforcing layer 60 is particularly preferable in suppressing the deflection of the bead filler 12.

[0061] Here, three types of analysis models were created for tires having the same configuration as in this embodiment, but with different tire radial lengths L1 of the inner side reinforcing layer 60 relative to the tire radial length L of the bead filler 12, and the stiffness characteristics of these tires were measured by simulation. For comparison, a tire without the inner side reinforcing layer 60 and with only the outer side reinforcing layer 70 was created as Model 0, and its stiffness characteristics were measured by simulation in the same manner. The results are shown in Table 1.

[0062] As shown in Table 1, tire models 1 to 3 have a ratio L1 / L (%) of the radial length L1 of the inner side reinforcement layer 60 to the radial length L of the bead filler 12 of 50%, 70%, and 80%, respectively. The characteristics measured by simulation were measured as stiffness values ​​for three types: "longitudinal stiffness," which is the resistance to loads received from the longitudinal direction during acceleration and deceleration; "lateral stiffness," which is the resistance to loads from the lateral direction; and "longitudinal stiffness," which is the resistance to longitudinal loads applied from above to below. In Table 1, the stiffness improvement rate, which shows how much the stiffness of each model 1 to 3 has improved compared to model 0 without the inner side reinforcement layer 60, is shown together with the stiffness value.

[0063] The tires of each model measured were designed to fit 19×10.0J rims (19-inch rim diameter, 10-inch rim width, flange shape: J), and the internal pressure was set to 220kPa when mounted on those rims. Furthermore, a longitudinal load of 680kg, a front-to-rear load of 204kg, and a lateral load of 204kg were applied to the tires.

[0064] [Table 1]

[0065] According to Table 1, all tires with the inner side reinforcement layer 60 showed improved rigidity, confirming the rigidity-enhancing effect of the inner side reinforcement layer 60. However, Model 1 had lower lateral rigidity and higher longitudinal rigidity than Models 2 and 3. This is because Model 1 has relatively low side rigidity against lateral forces, and there are concerns about reduced ride comfort due to its high longitudinal rigidity. Therefore, it is preferable that the tire radial length L1 of the inner side reinforcement layer 60 be 50% or more of the tire radial length L of the bead filler 12. Also, if the tire radial length L1 of the inner side reinforcement layer 60 is the same as the tire radial length L of the bead filler 12, the outer ends of both tires in the tire radial direction will be aligned, which may cause stress concentration in that area and lead to a decrease in durability. For these reasons, it can be said that the ratio L1 / L of the tire radial length L1 of the inner side reinforcement layer 60 to the tire radial length L of the bead filler 12 is preferably 60% or more and 90% or less.

[0066] The tire 1 of this embodiment provides the following effects.

[0067] (1) The tire 1 according to this embodiment comprises a pair of beads 10 having a bead core 11 and a bead filler 12 extending radially outward from the bead core 11, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a carcass ply 40 spanning between the pair of beads 10, an inner side reinforcing layer 60 disposed on the inside of the bead filler 12 in the tire width direction, and an outer side reinforcing layer 70 disposed on the outside of the bead filler 12 in the tire width direction, wherein the inner side reinforcing layer 60 is disposed radially inward from the outer end of the bead filler 12 in the tire radial direction, and the outer side reinforcing layer 70 has an outer extension portion 72 extending radially outward from the outer end of the bead filler 12 in the tire radial direction.

[0068] This makes it possible to improve side rigidity compared to conventional designs, resulting in improved cornering performance.

[0069] (2) In the tire 1 according to this embodiment, the carcass ply 40 has a ply body portion 401 that extends between the tread 30 and the inner side of the bead 10 in the tire width direction, and a ply folded portion 402 that extends radially outward on the outer side of the bead filler 12 in the tire width direction by being folded back around the bead core 11 from the inner end of the ply body portion 401 in the tire radial direction, and preferably the inner side reinforcing layer 60 is sandwiched between the bead filler 12 and the ply body portion 401, and a part of the outer side reinforcing layer 70 is sandwiched between the bead filler 12 and the ply folded portion 402.

[0070] This allows for a significant improvement in side rigidity through the cooperation of the carcass ply 40, the inner side reinforcement layer 60, and the outer side reinforcement layer 70. Furthermore, during the manufacturing of the tire 1, the inner side reinforcement layer 60 and the outer side reinforcement layer 70 can be brought into contact with the bead filler 12, making it easier to position the inner side reinforcement layer 60 and the outer side reinforcement layer 70 and simplifying the manufacturing process.

[0071] (3) In the tire 1 according to this embodiment, it is preferable that the inner end 60a of the inner side reinforcing layer 60 in the tire radial direction and the inner end 70a of the outer side reinforcing layer 70 in the tire radial direction are both located radially outward from the outer end of the bead core 11 in the tire radial direction.

[0072] This allows the deflection-suppressing effect of the bead filler 12 by the inner side reinforcing layer 60 and the outer side reinforcing layer 70 to be fully exerted without being hindered by the bead core 11, thereby accurately improving the side rigidity.

[0073] (4) In the tire 1 according to this embodiment, it is preferable that the outer extension portion 72 of the outer side reinforcing layer 70 is sandwiched between the ply body portion 401 and the ply folded portion 402.

[0074] This allows for a significant improvement in side rigidity through the cooperation of the carcass ply 40 and the outwardly extended portion 72 of the outer side reinforcing layer 70. In addition, the outwardly extended portion 72 of the outer side reinforcing layer 70 is protected by the carcass ply 40, preventing adverse effects on the outer and inner surfaces of the tire by the outwardly extended portion 72.

[0075] (5) In the tire 1 according to this embodiment, the radial length L1 of the inner side reinforcing layer 60 is preferably 60% or more and 90% or less of the radial length L of the bead filler 12.

[0076] This makes it possible to accurately obtain the effect of suppressing the deflection of the bead filler 12 by the inner side reinforcing layer 60.

[0077] (6) In the tire 1 according to this embodiment, the outer end portion 61 in the tire radial direction of the inner side reinforcing layer 60 is directed toward the outer side reinforcing layer 70, and it is preferable that the virtual extension line 611 extending in the direction directed by this outer end portion 61 intersects with the outer side reinforcing layer 70.

[0078] As a result, when subjected to strong lateral forces, the deformation of the outer side reinforcement layer 70, which would bend inward in the tire width direction, can be effectively suppressed by the inner side reinforcement layer 60, enabling a further improvement in side rigidity.

[0079] Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., made to the extent that the objectives of the present invention can be achieved are also included within the scope of the present invention.

[0080] For example, the inner side reinforcing layer 60 and the outer side reinforcing layer 70 do not necessarily have to be in close contact with the bead filler 12. For example, another rubber layer may be interposed between each of the inner side reinforcing layer 60 and the outer side reinforcing layer 70 and the bead filler 12.

[0081] The length of the outer extension 72 of the outer side reinforcing layer 70 is not limited as long as it extends radially outward from the bead filler 12. For example, it may extend from the sidewall 20 to the tread 30 instead of the ply fold-over portion 402 of the carcass ply 40. [Explanation of Symbols]

[0082] 1. Tire (pneumatic tire) 10 beads 11 Bead core 12 Bead Fillers L bead filler tire radial length 20 Sidewall 30 tread 40 Carcass Ply 60 Inner side reinforcement layer L1 Inner side reinforcement layer in the tire radial direction 61 Outer edge of the inner side reinforcement layer in the tire radial direction 70 Outer side reinforcement layer 72 Outer extension 401 Main body 402 Ply Fold-over Section 611 Virtual extension line

Claims

1. A pair of beads having a bead core and a bead filler extending radially outward from the bead core, A pair of sidewalls extending radially outward from each of the aforementioned pair of beads, A tread positioned between the pair of sidewalls, A carcass ply is stretched between the pair of beads, An inner side reinforcing layer positioned on the inner side in the tire width direction of the bead filler, The bead filler comprises an outer side reinforcing layer positioned on the outer side in the tire width direction, The inner side reinforcing layer is positioned radially inward of the outer end of the bead filler in the tire radial direction, The outer side reinforcing layer has an outer extension portion that extends radially outward from the outer end of the bead filler in the tire radial direction, A pneumatic tire in which the radial length of the outer side reinforcing layer is 110% or more and 170% or less of the radial length of the bead filler, and the radial inner end of the inner side reinforcing layer and the radial inner end of the outer side reinforcing layer are both engaged with the radial outer end of the bead core.

2. The aforementioned carcass ply is A ply body portion extending between the tread and the bead in the tire width direction, The ply body portion is folded back around the bead core from the inner end in the tire radial direction, thereby having a ply folded-back portion that extends radially outward on the outer side of the bead filler in the tire width direction, The inner side reinforcing layer is sandwiched between the bead filler and the ply body. The pneumatic tire according to claim 1, wherein a portion of the outer side reinforcing layer is sandwiched between the bead filler and the ply folded portion.

3. The pneumatic tire according to claim 1 or 2, wherein the inner end of the inner side reinforcing layer in the tire radial direction and the inner end of the outer side reinforcing layer in the tire radial direction are both located radially outward from the outer end of the bead core in the tire radial direction.

4. The pneumatic tire according to claim 2, wherein the outer extension is sandwiched between the ply body and the ply folded portion.

5. The pneumatic tire according to any one of claims 1 to 4, wherein the radial length of the inner side reinforcing layer is 60% or more and 90% or less of the radial length of the bead filler.

6. The pneumatic tire according to any one of claims 1 to 5, wherein the outer end in the tire radial direction of the inner side reinforcing layer is directed toward the outer side reinforcing layer, and a virtual extension line extending in the direction directed by the outer end intersects the outer side reinforcing layer.

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