tire

Abstract

To provide a tire that can improve durability of a bead part while preventing a rim from slipping.SOLUTION: The tire is provided with: bead cores 21 respectively provided on a pair of bead parts 20 arranged at both sides of a tire equatorial plane CL in a tire width direction; a carcass layer 6 having a carcass main body part 6a and a turn-up part 6b; rim cushion rubbers 40 arranged inside in a tire radial direction of the bead cores 21 in the bead parts 20; and elastic reinforcement layers 60 arranged, to be folded back from inside in the tire width direction of the bead cores 21 toward outside in the tire width direction thereof, at positions on opposite surfaces of surfaces on which the bead cores 21 are positioned in the carcass layer 6. A thickness Tr of the elastic reinforcement layer 60 is in a range of 1.5 mm or more and 5.0 mm or less. A modulus at 100% elongation of the elastic enforcement layer 60 is in a range of 5 times or more and 25 times or less a modulus at 100% elongation of the rim cushion rubber 40.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] A tire mounted on a vehicle is mounted on a rim wheel by fitting a bead portion, which has a bead core, which is an annular member formed by bundling multiple bead wires, onto the rim of the rim wheel. Because the bead portion is the part that fits onto the rim wheel, it is prone to being subjected to large loads when the vehicle is running. For this reason, some conventional tires have a reinforcing layer disposed in the bead portion for the purpose of ensuring durability, etc. For example, in the pneumatic tires described in Patent Documents 1 to 4, a reinforcing layer is disposed on the radially outer side of the bead core in the bead portion and on the widthwise outer side of the carcass layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-300921 [Patent Document 2] Japanese Patent Application Publication No. 10-35231 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-51479 [Patent Document 4] Japanese Patent Application Publication No. 2023-5149 Summary of the Invention [Problem to be solved by the invention]

[0004] One type of failure that can occur in a bead portion is a break in a carcass cord on the turnup side, which is the portion of the carcass layer that is wound up in the bead portion. Carcass cord breakage is likely to occur, for example, when a chafer having cords made of a metal or resin material is used as a reinforcing layer arranged along the carcass layer. That is, in the bead portion, the chafer is arranged with the angle of the chafer cords inclined relative to the carcass cords. Therefore, the carcass cords bend, i.e., a wave is generated along the inclination of the chafer cords pressed against the carcass layer, and large compressive stress is generated at the location where the wave is generated, which makes the carcass cords more likely to break.

[0005] One possible approach to preventing carcass cord breakage due to carcass cord waves is to not place chafers in the bead portion, but not placing chafers in the bead portion makes it difficult to ensure the rigidity of the bead portion. When a vehicle is running, rotational torque is transmitted between the bead portion and the rim wheel due to driving force and braking force. If the rigidity of the bead portion is reduced by not placing chafers in the bead portion, the tightening force of the bead portion relative to the rim wheel is likely to decrease. In this way, if the tightening force of the bead portion relative to the rim wheel is reduced, rim slippage, which is slippage between the bead portion and the rim wheel when rotational torque is applied, is more likely to occur. For this reason, it has been extremely difficult to improve the durability of the bead portion without causing rim slippage.

[0006] The present invention has been made in view of the above, and has an object to provide a tire that can improve the durability of the bead portion while suppressing rim slippage. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the objects, the tire of the present invention comprises a carcass layer having a pair of bead portions arranged on either side of the tire equatorial plane in the tire width direction, a bead core provided in each of the pair of bead portions, a carcass main portion arranged between the pair of bead portions, and a turn-up portion formed continuously from the carcass main portion and folded back from the inner side of the bead core in the tire width direction to the outer side in the tire width direction, a rim cushion rubber arranged on the inner side of the bead core in the tire radial direction in the bead portion, and an elastic reinforcing layer folded back from the inner side of the bead core in the tire width direction to the outer side in the tire width direction on a position on the side of the carcass layer opposite to the side on which the bead core is located, wherein the thickness of the elastic reinforcing layer is in the range of 1.5 mm to 5.0 mm, and the modulus of the elastic reinforcing layer at 100% elongation is in the range of 5 to 25 times the modulus of the rim cushion rubber at 100% elongation. [Effects of the Invention]

[0008] The tire according to the present invention has an effect of being able to improve the durability of the bead portion while suppressing rim slippage. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a meridian cross-sectional view showing a main part of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a detailed view of a region on one side of the tire equatorial plane CL in the tire width direction in FIG. [Figure 3] FIG. 3 is a detailed view of part A in FIG. [Figure 4A] FIG. 4A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 4B] FIG. 4B is a chart showing the results of a performance evaluation test of a pneumatic tire. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a tire according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0011] [Embodiment] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0012] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotational axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the portions located outermost in the tire width direction, that is, the distance in the tire width direction between the portions farthest from the tire equatorial plane CL. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian cross section refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

[0013] FIG. 1 is a meridian cross-sectional view showing a main portion of a pneumatic tire 1 according to an embodiment. FIG. 2 is a detailed view of a region on one side of the tire equatorial plane CL in the tire width direction in FIG. 1. The pneumatic tire 1 according to this embodiment is a heavy-duty radial tire that is mounted on heavy-duty vehicles such as dump trucks and loaders, and more specifically, is a radial tire for construction vehicles called an OR tire (Off the Road Tire). When viewed in meridian cross-section, the pneumatic tire 1 according to this embodiment shown in FIGS. 1 and 2 has a tread portion 2 disposed at the outermost portion in the tire radial direction, and the tread portion 2 is made of tread rubber 2a, which is a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is traveling, is formed as a tread contact surface 3.

[0014] A plurality of grooves, such as circumferential grooves extending in the tire circumferential direction and lug grooves extending in the tire width direction, are formed on the tread contact surface 3 of the tread portion 2, and a plurality of land portions are defined and formed in the tread portion 2 by these grooves.

[0015] Both ends of the tread portion 2 in the tire width direction are formed as shoulder portions 4, and sidewall portions 5 are arranged from the shoulder portions 4 to predetermined positions on the inner side in the tire radial direction. In other words, the sidewall portions 5 are arranged at two locations on both sides of the pneumatic tire 1 in the tire width direction. The sidewall portions 5 are made of a sidewall rubber 5a which is a rubber composition.

[0016] Furthermore, bead portions 20 are located on the tire radially inward side of each sidewall portion 5, and like the sidewall portions 5, the bead portions 20 are arranged at two locations on both sides of the tire equatorial plane CL. That is, a pair of bead portions 20 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Each of the pair of bead portions 20 is provided with a bead core 21, and a bead filler 50 is arranged on the tire radially outer side of each bead core 21. The bead core 21 is formed by winding a bead wire, which is a steel wire, into a ring shape. The bead filler 50 is a rubber material arranged in a space formed by folding back the tire width direction end of the carcass layer 6 (described later) at the position of the bead core 21 toward the tire width direction outer side. The bead filler 50 also includes a lower filler 51 arranged in contact with the outer peripheral surface of the bead core 21 and an upper filler 52 arranged at a position closer to the tire radially outer side than the lower filler 51.

[0017] The bead portion 20 is configured so that it can be mounted on a rim wheel having a specified rim radius of 5° taper. That is, the pneumatic tire 1 according to this embodiment can be mounted on a specified rim radius in which the portion that fits with the bead portion 20 is inclined at an inclination angle of 5°±1° relative to the rotation axis of the rim wheel, inclining in a direction toward the outside in the tire radial direction as it moves from the inside to the outside in the tire width direction. The specified rim radius refers to the "applicable rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO.

[0018] A belt layer 7 is disposed on the tire radially inner side of the tread portion 2. The belt layer 7 has a multi-layer structure in which three or more belt plies are laminated, and in a typical OR tire, four to eight belt plies are laminated. In this embodiment, the belt layer 7 is formed by laminating four belt plies 7a, 7b, 7c, and 7d. The belt plies 7a, 7b, 7c, and 7d constituting the belt layer 7 are formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them. The belt plies 7a, 7b, 7c, and 7d have different inclination angles in the tire width direction with respect to the tire circumferential direction, and are laminated with the inclination directions of the belt cords crossing each other, forming a so-called cross-ply structure. This increases the structural strength of the belt layer 7.

[0019] A carcass layer 6 containing the cords of the radial ply is continuously provided on the tire radially inner side of the belt layer 7 and on the tire equatorial plane CL side of the sidewall portion 5. This carcass layer 6 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of a laminate of multiple carcass plies, and is toroidally spanned between bead cores 21 located on both sides in the tire width direction to form the tire skeleton. More specifically, the carcass layer 6 spans between a pair of bead portions 20, and is disposed from one bead portion 20 to the other of the pair of bead portions 20 located on both sides in the tire width direction. The carcass layer 6 is also folded back at the bead portion 20 from the tire widthwise inner side of the bead core 21, passing through the tire radially inner side of the bead core 21, to the tire widthwise outer side so as to enclose the bead core 21 and the bead filler 50. That is, the carcass layer 6 is folded back around the bead core 21 in the bead portion 20 from the inner side of the bead core 21 in the tire width direction to the outer side of the bead core 21 in the tire width direction.

[0020] For this reason, the carcass layer 6 has a carcass main body portion 6a disposed between the pair of bead portions 20, and a turnup portion 6b formed continuously from the carcass main body portion 6a and folded back from the inner side in the tire width direction of the bead core 21 to the outer side in the tire width direction. The carcass main body portion 6a here is a portion formed in the carcass layer 6 between the inner sides in the tire width direction of the pair of bead cores 21, and the turnup portion 6b is a portion formed continuously from the carcass main body portion 6a on the inner side in the tire width direction of the bead core 21, passing through the inner side in the tire radial direction of the bead core 21 and folded back to the outer side in the tire width direction. The bead filler 50 is disposed on the inner side in the tire width direction of the turnup portion 6b, which is a portion of the carcass layer 6 folded back to the outer side in the tire width direction of the bead core 21, and on the outer side in the tire radial direction of the bead core 21.

[0021] The turned-up portion 6b of the carcass layer 6 has its radially outer end 6ba located at the same position as the tire maximum width position WP in the tire radial direction, or located radially outward of the tire maximum width position WP. In this embodiment, the turned-up portion 6b of the carcass layer 6 has its radially outer end 6ba located radially outward of the tire maximum width position WP. In this case, the tire maximum width position WP refers to the maximum position of the tire section width. The tire section width is measured under the conditions of mounting the tire on a specified rim, applying a specified internal pressure, and applying a load of 0 kN.

[0022] The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO.

[0023] The carcass ply of the carcass layer 6 arranged as above is formed by coating a plurality of carcass cords, which are cord members made of steel or organic fiber material such as aramid, nylon, polyester, rayon, etc., with a coating rubber, which is a rubber member, and rolling the coated cords. The carcass layer 6 also has a carcass angle, which is the inclination angle of the carcass cords relative to the tire circumferential direction, of 85° to 95°.

[0024] Furthermore, an inner liner 8 is formed along the carcass layer 6 on the inner side of the carcass layer 6 or on the inner side of the carcass layer 6 in the pneumatic tire 1 .

[0025] 3 is a detailed view of portion A in FIG. 2. An elastic reinforcing layer 60 that reinforces the carcass layer 6 is disposed in the portion of the carcass layer 6 that is folded back around the bead core 21. The elastic reinforcing layer 60 is a sheet-like member made of an elastic material that does not have cords. The elastic reinforcing layer 60 is disposed in the bead portion 20, overlapping the carcass layer 6 on the outside of the carcass layer 6 at the folded back portion of the carcass layer 6, and is disposed continuously in the tire circumferential direction, folded back around the bead core 21 from the inner side to the outer side in the tire width direction, similar to the carcass layer 6. In other words, the elastic reinforcing layer 60 is disposed by being folded back from the inner side in the tire width direction of the bead core 21 to the outer side in the tire width direction at a position on the side of the carcass layer 6 opposite the side on which the bead core 21 is located.

[0026] Therefore, the elastic reinforcing layer 60 is located on the inner side in the tire width direction of the carcass layer 6 in a portion where the carcass layer 6 is located on the inner side in the tire width direction of the bead core 21, on the inner side in the tire radial direction of the carcass layer 6 in a portion where the carcass layer 6 is located on the inner side in the tire radial direction of the bead core 21, and on the outer side in the tire width direction of the carcass layer 6 in a portion where the carcass layer 6 is located on the outer side in the tire width direction of the bead core 21. In other words, the elastic reinforcing layer 60 arranged by being folded back around the bead core 21 has a turned-up portion 61 which is a portion located on the outer side in the tire width direction of the bead core 21 and a turned-up portion 62 which is a portion located on the inner side in the tire width direction of the bead core 21, the turned-up portion 61 is located on the outer side in the tire width direction of the turn-up portion 6b of the carcass layer 6, and the turned-up portion 62 is located on the inner side in the tire width direction of the carcass main body portion 6a of the carcass layer 6.

[0027] The elastic reinforcing layer 60 formed in this sheet shape and arranged along the carcass layer 6 in the bead portion 20 has a thickness Tr in the range of 1.5 mm to 5.0 mm. The thickness Tr of the elastic reinforcing layer 60 is preferably in the range of 2.0 mm to 3.5 mm.

[0028] Furthermore, the relationship between the height Hb in the tire radial direction from the rim diameter reference position BL to the tire radially outer end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 in the tire meridian cross section, and the flange height Ha, is within a range of 0.5≦Hb / Ha≦1.5. The relationship between the height Hc in the tire radial direction from the rim diameter reference position BL to the tire radially outer end 62a of the turned-up portion 62 of the elastic reinforcing layer 60 in the tire meridian cross section, and the flange height Ha, is within a range of 0.4≦Hc / Ha≦1.7.

[0029] In this case, the rim diameter reference position BL is the tire axial line passing through the rim diameter defined by the standard, i.e., the tire axial line passing through the rim diameter defined by the JATMA, TRA, or ETRTO standard. Also, the flange height Ha is the tire radial height of the rim flange of the specified rim R at the outermost part in the tire radial direction, i.e., the rim flange height of the specified rim R that complies with the JATMA, TRA, or ETRTO standard.

[0030] In addition, the height Hb from the rim diameter reference position BL to the end 61a of the rolled-up portion 61 in the elastic reinforcing layer 60 and the height Hc from the rim diameter reference position BL to the end 62a of the rolled-up portion 62 in the elastic reinforcing layer 60 are the heights in the tire radial direction when the pneumatic tire 1 is mounted on a specified rim R, filled to the normal internal pressure, and in an unloaded state with no load applied to the pneumatic tire 1.

[0031] The elastic reinforcing layer 60 disposed in the bead portion 20 is a rubber composition obtained by crosslinking with an organic peroxide a composition (product name: ZSC2395, manufactured by Zeon Corporation) in which zinc polymethacrylate is highly dispersed in hydrogenated NBR. Specifically, the elastic reinforcing layer 60 uses a rubber composition obtained by crosslinking with an organic peroxide a composition in which a metal salt of acrylic acid or methacrylic acid is dispersed in an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less. Note that the highly saturated rubber is a rubber in which the hydrogenation rate of the double bonds between carbon atoms is 70% or more.

[0032] Specifically, a rubber composition containing 100 parts by weight of rubber in total, including 40 parts by weight or more of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less, 10 to 120 parts by weight of a metal salt of acrylic acid or methacrylic acid, and 0.3 to 10 parts by weight of an organic peroxide as a cross-linking agent, can be used for the elastic reinforcing layer 60. Of course, various compounding agents commonly used in the rubber industry, such as reinforcing agents, cross-linking aids, plasticizers, and stabilizers, can be added to the rubber composition as needed.

[0033] Ethylenically unsaturated nitrile-conjugated diene highly saturated rubbers include copolymers of ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile with conjugated dienes such as 1,3-butadiene, isoprene, and 1,3-pentadiene, as well as multicomponent polymers of the above two monomers with copolymerizable monomers such as vinyl aromatic compounds, (meth)acrylic acid, alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, and cyanoalkyl (meth)acrylates. Specific examples include acrylonitrile-butadiene copolymer rubber, acrylonitrile-isoprene copolymer rubber, acrylonitrile-butadiene-isoprene copolymer rubber, acrylonitrile-butadiene-acrylate copolymer rubber, and acrylonitrile-butadiene-acrylate-methacrylic acid copolymer rubber. Hydrogenated NBR is particularly preferred. Metal salts of acrylic acid or methacrylic acid include zinc polymethacrylate.

[0034] Examples of organic peroxides include dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-mono(t-butylperoxy)hexane.

[0035] The elastic reinforcing layer 60 made of these materials has a breaking strength in the range of 10 MPa to 50 MPa, and preferably has a breaking strength in the range of 10 MPa to 40 MPa. The elastic reinforcing layer 60 also has a breaking elongation of 150% or more, and preferably has a breaking elongation in the range of 150% to 500%.

[0036] Furthermore, the elastic reinforcing layer 60 is covered with an adhesive layer to ensure adhesion to the surrounding members adjacent to the elastic reinforcing layer 60 .

[0037] In this case, the adhesive layer may be made of a rubber composition containing 100 parts by weight of rubber in total, including 50 to 85 parts by weight of at least one diene rubber selected from natural rubber, polyisoprene rubber, polybutadiene rubber, and conjugated diene-aromatic vinyl copolymer rubber, and 15 to 50 parts by weight of an ethylenically unsaturated nitrile-conjugated diene highly saturated rubber having a conjugated diene unit content of 30% by weight or less, and blended with 10 to 60 parts by weight of zinc methacrylate, 0.3 to 10 parts by weight of an organic peroxide, and 5 to 50 parts by weight of a co-crosslinking agent that has an acrylic group, a methacrylic group, or an allyl group and is liquid at room temperature.

[0038] Furthermore, a buffer rubber layer 41 is sandwiched and disposed between the turned-up portion 6b of the carcass layer 6 and the turned-up portion 61 of the elastic reinforcing layer 60. The buffer rubber layer 41 is disposed not only in the portion between the turned-up portion 6b and the elastic reinforcing layer 60, but also in a region radially outward of the elastic reinforcing layer 60 in the tire meridian cross section. In other words, the buffer rubber layer 41 is disposed between the turned-up portion 6b of the carcass layer 6 and the elastic reinforcing layer 60 within the range in the tire radial direction in which the elastic reinforcing layer 60 is disposed, and is also disposed along the turned-up portion 6b of the carcass layer 6 into a region radially outward of the elastic reinforcing layer 60.

[0039] The relationship between the tire radial height Hd of the cushioning rubber layer 41 from the rim diameter reference position BL to the tire radially inner end 41a of the cushioning rubber layer 41 and the flange height Ha is within the range of 0.2≦Hd / Ha≦0.5, and more preferably within the range of 0.3≦Hd / Ha≦0.4.

[0040] Because the cushioning rubber layer 41 is disposed between the carcass layer 6 and the elastic reinforcing layer 60, the carcass layer 6 and the elastic reinforcing layer 60 are spaced apart in the area where the cushioning rubber layer 41 is disposed. In this portion where the carcass layer 6 and the elastic reinforcing layer 60 are separated from each other, for example, the distance Ga between the radially outer end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b of the carcass layer 6 is within a range of 1.0 mm to 10.0 mm. The distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b of the carcass layer 6 is preferably within a range of 3.0 mm to 7.0 mm.

[0041] Furthermore, a rim cushion rubber 40 is arranged in the bead portion 20 on the radially inner side of the bead core 21. The rim cushion rubber 40 is arranged on the outer side of the buffer rubber layer 41. Like the buffer rubber layer 41, the rim cushion rubber 40 is arranged from the inner side of the bead core 21 in the tire width direction to the inner side in the tire radial direction and then to the outer side in the tire width direction, and is provided continuously in the tire circumferential direction. The rim cushion rubber 40 arranged in this manner forms the contact surface of the bead portion 20 with the flange of the specified rim R.

[0042] The rim cushion rubber 40 and the elastic reinforcing layer 60 arranged in this manner have different physical properties. For example, the elastic reinforcing layer 60 has a modulus Mr at 100% elongation in the range of 19.0 MPa to 93.0 MPa, and the rim cushion rubber 40 has a modulus Mc at 100% elongation in the range of 3.2 MPa to 4.2 MPa. The modulus at 100% elongation is a value measured in accordance with JIS K6250.

[0043] Furthermore, the modulus Mr of the elastic reinforcement layer 60 at 100% elongation is in the range of 5 to 25 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, and it is preferable that the modulus Mr of the elastic reinforcement layer 60 at 100% elongation is in the range of 10 to 20 times the modulus Mc of the rim cushion rubber 40 at 100% elongation.

[0044] Furthermore, the buffer rubber layer 41, which is disposed between the carcass layer 6 and the elastic reinforcing layer 60, has a modulus Mb at 100% elongation in the range of 1.9 MPa to 3.0 MPa. The modulus Mb of the buffer rubber layer 41 at 100% elongation is in the range of 0.5 to 0.8 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, and it is preferable that the modulus Mb of the buffer rubber layer 41 at 100% elongation is in the range of 0.6 to 0.7 times the modulus Mc of the rim cushion rubber 40 at 100% elongation.

[0045] The bead core 21, which is formed by winding the bead wire in a ring shape, has a substantially hexagonal shape when viewed in a tire meridian cross section. Specifically, the bead core 21 has an inner peripheral surface and an outer peripheral surface that are substantially parallel to each other when viewed as a whole, and has corners that protrude in the tire width direction at both ends in the tire width direction, forming a substantially hexagonal shape.

[0046] In this case, the inner peripheral surface of the bead core 21 refers to a surface defined by an imaginary straight line tangent to portions of the bead wires that are lined up in a row at a position on the inner side of the bead core 21 in the tire radial direction and that constitute the surface of the bead core 21, when viewed in a tire meridian cross section. Similarly, the outer peripheral surface of the bead core 21 refers to a surface defined by an imaginary straight line tangent to portions of the bead wires that are lined up in a row at a position on the outer side of the bead core 21 in the tire radial direction and that constitute the surface of the bead core 21, when viewed in a tire meridian cross section of the pneumatic tire 1.

[0047] The bead portion 20 also has a bead base portion 30, which is the inner peripheral surface of the bead portion 20 and is a fitting portion when the pneumatic tire 1 according to this embodiment is mounted on a specified rim R. The bead base portion 30 is inclined with respect to the tire rotation axis in a direction that widens outward in the tire radial direction from the side where a bead toe 31, which is the inner end in the tire width direction, is located, toward the side where a bead heel 32, which is the outer end in the tire width direction, is located.

[0048] When mounting the pneumatic tire 1 configured as above on a vehicle, first, the bead base portion 30 is fitted to the specified rim R of the rim wheel to mount the pneumatic tire 1 on the specified rim R, and the pneumatic tire 1 is assembled to the rim wheel. After the pneumatic tire 1 is assembled to the rim, it is inflated, and the rim-assembled and inflated pneumatic tire 1 is mounted on the vehicle. The pneumatic tire 1 according to this embodiment is used as a pneumatic tire 1 for a construction vehicle, for example, to be mounted on a construction vehicle such as a wheel loader.

[0049] When a vehicle equipped with a pneumatic tire 1 travels, the pneumatic tire 1 rotates with the lower part of the tread surface 3 in contact with the road surface. The vehicle travels by transmitting driving force and braking force to the road surface and generating turning force due to the frictional force between the tread surface 3 and the road surface.

[0050] When a vehicle equipped with pneumatic tire 1 is running, the frictional force generated between the road surface and the tread contact surface 3 of pneumatic tire 1 enables the vehicle to run, but when the vehicle is running, loads act in various directions on each part of pneumatic tire 1. The loads acting on pneumatic tire 1 are borne by the pressure of the air filled inside, the carcass layer 6 provided as the skeleton of pneumatic tire 1, and the like.

[0051] For example, a load acting in the tire radial direction between the tread portion 2 and the bead portions 20 due to the weight of the vehicle or unevenness of the road surface is received mainly by the pressure of the air filled inside the pneumatic tire 1, and by the sidewall portions 5 and the like being deflected. In particular, the pneumatic tire 1 according to this embodiment is mounted on a large vehicle and used under conditions of high load, so the sidewall portions 5, the carcass layer 6, and further the bead portions 20, which are portions of the pneumatic tire 1 where the rim wheel fits, are subjected to extremely large loads.

[0052] In the bead portion 20, the carcass layer 6 is folded back around the bead core 21, so when a large load acts on the bead portion 20, the load acting on the bead portion 20 acts on the carcass layer 6. That is, because the rim wheel is fitted to the bead portion 20, the load acting from the rim wheel acts on the carcass layer 6 located in the bead portion 20. When a large load acts from the rim wheel on the carcass layer 6 located in the bead portion 20, there is a risk that the carcass layer 6 will suffer a failure, such as a broken carcass cord.

[0053] One method for preventing breakdown of the carcass layer 6 located in the bead portion 20 is, for example, to place a chafer having cords made of metal or resin material along the carcass layer 6. By placing such a chafer in the bead portion 20, the carcass layer 6 can be protected from the large load acting on the bead portion 20 from the rim wheel, making it possible to prevent breakdown of the carcass layer 6.

[0054] Furthermore, when chafers are arranged in the bead portions 20 along the carcass layer 6, the chafers can increase the rigidity of the bead portions 20. This increases the fastening force of the bead portions 20 against the rim wheel that fits into the bead portions 20, making it possible to suppress rim slippage between the bead portions 20 and the rim wheel, and allowing a large rotational torque to be transmitted between the bead portions 20 and the rim wheel when the vehicle is running.

[0055] However, when a chafer having cords made of metal or resin material is arranged along the carcass layer 6, the chafer is arranged so as to be pressed against the carcass layer 6, which may cause the carcass cords in the carcass layer 6 to bend along the chafer cords, resulting in waves in the carcass cords. If waves occur in the carcass cords of the carcass layer 6, compressive stress occurs in the carcass layer 6 at the locations where the waves occur in the carcass cords, which may also cause breakdowns such as breakage of the carcass cords. On the other hand, if a chafer is not arranged in the bead portion 20 to prevent such waves in the carcass cords, it becomes difficult to protect the carcass layer 6 and to increase the rigidity of the bead portion 20, which may increase the risk of rim slippage.

[0056] In contrast, in the pneumatic tire 1 according to this embodiment, an elastic reinforcing layer 60 is arranged in the bead portion 20, folded back from the inner side in the tire width direction to the outer side in the tire width direction of the bead core 21. This prevents waves from being generated in the carcass cords of the carcass layer 6, which would cause the carcass cords to break, and allows the elastic reinforcing layer 60 to increase the rigidity of the bead portion 20 and suppress rim slippage.

[0057] Furthermore, since the thickness Tr of the elastic reinforcement layer 60 is within the range of 1.5 mm to 5.0 mm, it is possible to suppress rim slippage while suppressing peeling between the elastic reinforcement layer 60 and surrounding components. In other words, if the thickness Tr of the elastic reinforcement layer 60 is less than 1.5 mm, the thickness Tr of the elastic reinforcement layer 60 is too thin, making it difficult to increase the rigidity of the bead portion 20 even if the elastic reinforcement layer 60 is disposed in the bead portion 20. In this case, it becomes difficult to increase the tightening force of the bead portion 20 against the rim wheel, making it difficult to suppress rim slippage between the bead portion 20 and the rim wheel. Furthermore, if the thickness Tr of the elastic reinforcement layer 60 is greater than 5.0 mm, the thickness Tr of the elastic reinforcement layer 60 is too thick, which may result in the elastic reinforcement layer 60 becoming too rigid, and there is a risk of peeling occurring easily due to the difference in rigidity between the elastic reinforcement layer 60 and surrounding components.

[0058] In contrast, when the thickness Tr of the elastic reinforcement layer 60 is within the range of 1.5 mm or more and 5.0 mm or less, peeling between the elastic reinforcement layer 60 and the surrounding materials can be suppressed, while the elastic reinforcement layer 60 can increase the rigidity of the bead portion 20 and suppress rim slippage.

[0059] Furthermore, because the modulus Mr of the elastic reinforcement layer 60 at 100% elongation is in the range of 5 to 25 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, it is possible to suppress rim slippage while preventing peeling of the elastic reinforcement layer 60. In other words, if the modulus Mr of the elastic reinforcement layer 60 at 100% elongation is less than 5 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, the modulus Mr of the elastic reinforcement layer 60 is too low, which may make it difficult to ensure the reinforcing effect of the elastic reinforcement layer 60 on the bead portion 20. In this case, it becomes difficult to increase the rigidity of the bead portion 20 and increase the tightening force of the bead portion 20 against the rim wheel, which may make it difficult to suppress rim slippage. Furthermore, if the modulus Mr of the elastic reinforcing layer 60 at 100% elongation is greater than 25 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, the modulus Mr of the elastic reinforcing layer 60 is too high, and there is a risk that the rigidity of the elastic reinforcing layer 60 will be too high. In this case, there is a risk that peeling will easily occur between the elastic reinforcing layer 60 and the members surrounding the elastic reinforcing layer 60 when the pneumatic tire 1 deforms.

[0060] In contrast, when the modulus Mr of the elastic reinforcing layer 60 at 100% elongation is in the range of 5 to 25 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, peeling of the elastic reinforcing layer 60 is suppressed while the elastic reinforcing layer 60 increases the rigidity of the bead portion 20, thereby suppressing rim slippage. As a result, the durability of the bead portion 20 can be improved while suppressing rim slippage.

[0061] Furthermore, the relationship between the height Hb from the rim diameter reference position BL to the end 61a of the rolled-up portion 61 and the flange height Ha of the elastic reinforcement layer 60 is within the range of 0.5≦Hb / Ha≦1.5, and the relationship between the height Hc from the rim diameter reference position BL to the end 62a of the rolled-up portion 62 and the flange height Ha is within the range of 0.4≦Hc / Ha≦1.7, so that edge separation of the elastic reinforcement layer 60 can be suppressed while rim slippage can be suppressed.

[0062] In other words, if the relationship between the height Hb from the rim diameter reference position BL to the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the flange height Ha is Hb / Ha<0.5, the height Hb of the turned-up portion 61 of the elastic reinforcing layer 60 may be too low. Similarly, if the relationship between the height Hc from the rim diameter reference position BL to the end 62a of the turned-up portion 62 of the elastic reinforcing layer 60 and the flange height Ha is Hc / Ha<0.4, the height Hc of the turned-up portion 62 of the elastic reinforcing layer 60 may be too low. In these cases, it becomes difficult to ensure the reinforcing effect of the elastic reinforcing layer 60 on the bead portion 20, and it becomes difficult to increase the rigidity of the bead portion 20 and increase the tightening force of the bead portion 20 against the rim wheel, which may make it difficult to suppress rim slippage.

[0063] Furthermore, when the relationship between the height Hb from the rim diameter reference position BL to the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the flange height Ha is Hb / Ha > 1.5, there is a risk that the height Hb of the turned-up portion 61 of the elastic reinforcing layer 60 is too high. Similarly, when the relationship between the height Hc from the rim diameter reference position BL to the end 62a of the turned-up portion 62 of the elastic reinforcing layer 60 and the flange height Ha is Hc / Ha > 1.7, there is a risk that the height Hc of the turned-up portion 62 of the elastic reinforcing layer 60 is too high. In these cases, when the pneumatic tire 1 deforms, peeling of the elastic reinforcing layer 60 is likely to occur near the end 61a of the turned-up portion 61 or near the end 62a of the turned-up portion 62, and edge separation is likely to occur.

[0064] In contrast, when the relationship between the height Hb from the rim diameter reference position BL to the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the flange height Ha is within the range of 0.5≦Hb / Ha≦1.5, and the relationship between the height Hc from the rim diameter reference position BL to the end 62a of the turned-up portion 62 of the elastic reinforcing layer 60 and the flange height Ha is within the range of 0.4≦Hc / Ha≦1.7, edge separation of the elastic reinforcing layer 60 is suppressed while the rigidity of the bead portion 20 is increased by the elastic reinforcing layer 60, thereby suppressing rim slippage. As a result, the durability of the bead portion 20 can be improved while suppressing rim slippage.

[0065] Furthermore, because the buffer rubber layer 41 is disposed between the turned-up portion 6b of the carcass layer 6 and the elastic reinforcing layer 60, it is possible to mitigate the difference in the way that the turned-up portion 6b and the elastic reinforcing layer 60 deform, thereby reducing strain and preventing peeling of the elastic reinforcing layer 60. Furthermore, the modulus Mb of the buffer rubber layer 41 at 100% elongation is in the range of 0.5 to 0.8 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, ensuring the rigidity of the bead portion 20 and preventing rim slippage, as well as preventing peeling of the elastic reinforcing layer 60.

[0066] In other words, if the modulus Mb of the buffer rubber layer 41 at 100% elongation is less than 0.5 of the modulus Mc of the rim cushion rubber 40 at 100% elongation, the modulus Mb of the buffer rubber layer 41 will be too low, making it difficult to ensure the rigidity of the bead portion 20 and potentially making it difficult to prevent rim slippage. Also, if the modulus Mb of the buffer rubber layer 41 at 100% elongation is more than 0.8 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, the modulus Mc of the rim cushion rubber 40 will be too large, making it difficult to alleviate strain between the turned-up portion 6b of the carcass layer 6 and the elastic reinforcing layer 60. In this case, it will be difficult to reduce strain between the turned-up portion 6b and the elastic reinforcing layer 60 when the pneumatic tire 1 deforms, making it difficult to prevent peeling of the elastic reinforcing layer 60.

[0067] In contrast, if the modulus Mb of the buffer rubber layer 41 at 100% elongation is within the range of 0.5 to 0.8 times the modulus Mc of the rim cushion rubber 40 at 100% elongation, the rigidity of the bead portion 20 is ensured, preventing rim slippage and preventing peeling of the elastic reinforcing layer 60. As a result, the durability of the bead portion 20 can be improved while preventing rim slippage.

[0068] Furthermore, because the distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 on the outer side in the tire radial direction and the turned-up portion 6b is within the range of 1.0 mm to 10.0 mm, the thickness of the cushioning rubber layer 41 can be appropriately set, and peeling of the elastic reinforcing layer 60 can be more reliably suppressed. In other words, if the distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b is less than 1.0 mm, the cushioning rubber layer 41 disposed between the elastic reinforcing layer 60 and the turned-up portion 6b may become too thin. In this case, even if the cushioning rubber layer 41 is disposed between the elastic reinforcing layer 60 and the turned-up portion 6b, it may be difficult for the cushioning rubber layer 41 to reduce strain between the turned-up portion 6b and the elastic reinforcing layer 60, and peeling of the elastic reinforcing layer 60 may be difficult to suppress. Furthermore, if the distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b is greater than 10.0 mm, the buffer rubber layer 41 disposed between the elastic reinforcing layer 60 and the turned-up portion 6b may become too thick. In this case, due to the thickness of the buffer rubber layer 41, the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 is disposed closer to the surface of the pneumatic tire 1, which increases distortion near the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60, and may make edge separation more likely to occur.

[0069] In contrast, when the distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b is within the range of 1.0 mm to 10.0 mm, the thickness of the cushioning rubber layer 41 can be made appropriate while preventing the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 from coming too close to the surface of the pneumatic tire 1. As a result, peeling of the elastic reinforcing layer 60 can be more reliably prevented, and the durability of the bead portion 20 can be improved.

[0070] Furthermore, the relationship between the flange height Ha and the height Hd of the cushioning rubber layer 41 in the tire radial direction from the rim diameter reference position BL to the tire radially inner end 41a of the cushioning rubber layer 41 is within the range of 0.2≦Hd / Ha≦0.5. Therefore, by appropriately positioning the cushioning rubber layer 41 between the elastic reinforcing layer 60 and the turn-up portion 6b, peeling of the elastic reinforcing layer 60 can be more reliably suppressed. In other words, if the relationship between the flange height Ha and the height Hd of the cushioning rubber layer 41 in the tire radial direction from the rim diameter reference position BL to the tire radially inner end 41a of the cushioning rubber layer 41 is Hd / Ha<0.2, there is a risk that the cushioning rubber layer 41 will extend too far inward in the tire radial direction and intrude into the tire radially inner side of the bead core 21. In this case, there is a risk that edge separation will be more likely to occur near the tire radially inner end 41a of the cushioning rubber layer 41. Furthermore, if the relationship between the flange height Ha and the height Hd in the tire radial direction from the rim diameter reference position BL to the tire radially inner end 41a of the cushioning rubber layer 41 is Hd / Ha>0.5, there is a risk that a small amount of the cushioning rubber layer 41 will get into between the turned-up portion 6b of the carcass layer 6 and the elastic reinforcing layer 60. In this case, even if the cushioning rubber layer 41 is disposed between the elastic reinforcing layer 60 and the turned-up portion 6b, it will be difficult for the cushioning rubber layer 41 to reduce strain between the turned-up portion 6b and the elastic reinforcing layer 60, and there is a risk that it will be difficult to prevent peeling of the elastic reinforcing layer 60.

[0071] In contrast, when the relationship between the flange height Ha and the tire radial height Hd from the rim diameter reference position BL to the tire radially inner end 41a of the cushioning rubber layer 41 is within the range of 0.2≦Hd / Ha≦0.5, the cushioning rubber layer 41 can be appropriately positioned between the elastic reinforcing layer 60 and the turned-up portion 6b, and strain between the turned-up portion 6b and the elastic reinforcing layer 60 can be reduced by the cushioning rubber layer 41. As a result, peeling of the elastic reinforcing layer 60 can be more reliably suppressed, and the durability of the bead portion 20 can be improved.

[0072] Furthermore, the elastic reinforcing layer 60 uses a rubber composition obtained by crosslinking, with an organic peroxide, a composition in which a metal salt of acrylic acid or methacrylic acid is dispersed in an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less, and therefore peeling of the elastic reinforcing layer 60 can be suppressed. As a result, the durability of the bead portion 20 can be improved.

[0073] Furthermore, because the elastic reinforcing layer 60 is covered with the adhesive layer, it is possible to ensure adhesion between the elastic reinforcing layer 60 and the surrounding members adjacent to the elastic reinforcing layer 60, and it is possible to more reliably prevent peeling of the elastic reinforcing layer 60. As a result, it is possible to more reliably improve the durability of the bead portion 20.

[0074] Furthermore, the radially outer end 6ba of the turnup portion 6b of the carcass layer 6 is located at the same position in the tire radial direction as the tire maximum width position WP or further outward in the tire radial direction than the tire maximum width position WP, which prevents the end 6ba of the turnup portion 6b of the carcass layer 6 from peeling off due to a load acting on the bead portion 20. As a result, edge separation of the carcass layer 6 in the bead portion 20 can be prevented, and the durability of the bead portion 20 can be improved.

[0075] Furthermore, because the pneumatic tire 1 according to the embodiment is a tire mounted on a heavy-duty vehicle, failure of the bead portion 20 can be suppressed even under conditions in which a large load is applied to the pneumatic tire 1, and even when a large rotational torque acts between the bead portion 20 and the rim wheel, the rotational torque can be transmitted without causing rim slippage due to the tightening force of the bead portion 20. As a result, the durability of the bead portion 20 can be improved while suppressing rim slippage.

[0076] In the above-described embodiment, the pneumatic tire 1 has been described as an example of a tire according to the present invention, but the tire according to the present invention may be a tire other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without being filled with gas.

[0077] [Example] 4A and 4B are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the above-mentioned pneumatic tire 1 for a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire for comparison with the pneumatic tire 1 according to the present invention will be described below. The performance evaluation tests included tests on durability test running time, cord breakage in the turnup portion of the carcass layer, bead portion durability test running time, and rim slip resistance.

[0078] The performance evaluation test was carried out by using a pneumatic tire 1 having a nominal tire size of 1800R33 as the test tire, mounting this test tire on a rim wheel conforming to the TRA standard, and adjusting the air pressure to the air pressure specified by the TRA standard.

[0079] Among the evaluation methods for each test item, the durability test running time was evaluated by conducting a running test using an indoor drum testing machine with a load set to 120% of the maximum load specified by the TRA and a speed of 10 km / h, and evaluating the running time until the test tire was destroyed. The durability test running time was evaluated using an index with the conventional example described below set to 100, and the higher the index, the longer the time until the test tire was destroyed, indicating better performance in terms of durability test running time.

[0080] Further, regarding cord breakage in the turn-up portion of the carcass layer, the turn-up portion of the carcass layer of the test tire after the durability test running time was observed to confirm whether or not breakage of the carcass cord occurred in the turn-up portion.

[0081] The bead portion durability test running time was evaluated by buffing the tread portion to remove the tread rubber, then conducting a running test using an indoor drum testing machine at a load of 150% of the maximum load specified by the TRA and a speed of 10 km / h, and measuring the running time until the bead portion of the test tire was destroyed. In other words, while the durability test running time evaluation test evaluates the time until any part of the test tire, including the bead, is destroyed, the bead portion durability test running time evaluation test evaluates the time until the bead portion is destroyed by removing the tread rubber in advance to prevent the tread portion from being destroyed before the bead portion is destroyed, creating a state in which the bead portion is destroyed first. The bead portion durability test running time evaluation was performed using an index with the conventional example described below being set to 100. The higher the index, the longer the time until the bead portion is destroyed and the better the performance in terms of bead portion durability test running time.

[0082] Rim slip resistance was evaluated using a rim slip torque test. In the rim slip torque test, a relative torque was applied in the circumferential direction of the tire to the rim-mounted test tire and rim wheel while a load of 150% of the maximum load specified by the TRA was applied to the test tire and rim wheel. The torque was gradually increased while visually checking the amount of misalignment between the test tire and rim wheel, and the torque value was measured when a misalignment large enough to determine that rim slip had occurred. Rim slip resistance was expressed as an index, with the measured torque value being 100 for the conventional example described below. The higher the index, the less likely misalignment occurred between the test tire and rim wheel in the circumferential direction, indicating better rim slip resistance.

[0083] The performance evaluation tests were conducted on 23 types of pneumatic tires: a conventional pneumatic tire, which is an example of a conventional pneumatic tire; Examples 1 to 18, which are pneumatic tire 1 according to the present invention; and Comparative Examples 1 to 4, which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, the conventional pneumatic tire has a reinforcing layer disposed in the bead portion that is not an elastic reinforcing layer, but a steel chafer having cords made of a metal material. Furthermore, while the pneumatic tires of Comparative Examples 1 to 4 have an elastic reinforcing layer disposed in the bead portion, the thickness Tr of the elastic reinforcing layer is not within the range of 1.5 mm to 5.0 mm, or the modulus of the elastic reinforcing layer at 100% elongation is not within the range of 5 to 25 times the modulus of the rim cushion rubber at 100% elongation.

[0084] In contrast, in Examples 1 to 18, which are examples of the pneumatic tire 1 according to the present invention, the thickness Tr of the elastic reinforcing layer 60 is all in the range of 1.5 mm or more and 5.0 mm or less, and the modulus Mr of the elastic reinforcing layer 60 at 100% elongation is in the range of 5 times or more and 25 times or less the modulus Mc of the rim cushion rubber 40 at 100% elongation. Furthermore, the pneumatic tires 1 of Examples 1 to 18 differ in the ratio Hb / Ha of the height Hb of the turned-up portion 61 of the elastic reinforcing layer 60 to the flange height Ha, the ratio Hc / Ha of the height Hc of the turned-up portion 62 of the elastic reinforcing layer 60 to the flange height Ha, the ratio of the modulus Mb of the cushion rubber layer 41 at 100% elongation to the modulus Mc of the rim cushion rubber 40 at 100% elongation, the distance Ga between the end 61a of the turned-up portion 61 of the elastic reinforcing layer 60 and the turned-up portion 6b of the carcass layer 6, the ratio Hd / Ha of the height Hd of the end 41a on the radially inner side of the tire of the cushion rubber layer 41 to the flange height Ha, and whether or not the elastic reinforcing layer 60 is covered with an adhesive layer.

[0085] 4A and 4B, performance evaluation tests were conducted using these pneumatic tires 1. As a result, it was found that the pneumatic tires 1 according to Examples 1 to 18 were able to exhibit performance equal to or better than the conventional example and comparative example in terms of durability test running time, bead portion durability test running time, and rim slippage resistance, without causing cord breakage in the turn-up portion 6b of the carcass layer 6. In other words, the pneumatic tires 1 according to Examples 1 to 18 were able to improve the durability of the bead portion 20 while suppressing rim slippage.

[0086] The present disclosure includes the following inventions. Invention[1] a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core provided in each of the pair of bead portions; a carcass layer including a carcass main body portion disposed between the pair of bead portions and a turn-up portion formed continuously from the carcass main body portion and folded back from the inner side in the tire width direction of the bead core to the outer side in the tire width direction; a rim cushion rubber disposed on the inner side of the bead core in the bead portion in the tire radial direction; an elastic reinforcing layer that is folded back from the inner side in the tire width direction to the outer side in the tire width direction of the bead core at a position on a surface side of the carcass layer opposite to a surface on which the bead core is located; Equipped with The elastic reinforcing layer has a thickness in the range of 1.5 mm or more and 5.0 mm or less, A tire characterized in that the modulus of the elastic reinforcing layer at 100% elongation is in the range of 5 to 25 times the modulus of the rim cushion rubber at 100% elongation. Invention[2] The elastic reinforcing layer is a relationship between a height Hb in the tire radial direction from a rim diameter reference position to an outer end in the tire radial direction of a portion of the elastic reinforcing layer located outer in the tire width direction of the bead core and a flange height Ha is within a range of 0.5≦Hb / Ha≦1.5, The tire according to the invention [1], wherein the relationship between the height Hc in the tire radial direction from the rim diameter reference position to the outer end in the tire radial direction of the portion of the elastic reinforcing layer located on the inner side in the tire width direction of the bead core and the flange height Ha is within the range of 0.4≦Hc / Ha≦1.7. Invention[3] a cushioning rubber layer is disposed between the turnup portion of the carcass layer and the elastic reinforcing layer; A tire according to invention [1] or invention [2], wherein the modulus of the buffer rubber layer at 100% elongation is in the range of 0.5 to 0.8 times the modulus of the rim cushion rubber at 100% elongation. Invention[4] The tire according to the invention [3], wherein the distance between the radially outer end of the part of the elastic reinforcing layer located on the outer side of the bead core in the tire width direction and the turn-up portion is within the range of 1.0 mm or more and 10.0 mm or less. Invention[5] A tire according to invention [3] or invention [4], wherein the relationship between the height Hd in the tire radial direction from the rim diameter reference position to the tire radially inner end of the cushioning rubber layer and the flange height Ha is within the range of 0.2≦Hd / Ha≦0.5. Invention[6] The tire according to any one of Inventions [1] to [5], wherein the elastic reinforcing layer is formed by crosslinking a composition in which a metal salt of acrylic acid or methacrylic acid is dispersed in an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less with an organic peroxide. Invention[7] The tire according to any one of the inventions [1] to [6], wherein the elastic reinforcing layer is covered with an adhesive layer. Invention[8] A tire according to any one of inventions [1] to [7], wherein the radially outer end of the turnup portion of the carcass layer is positioned at the same position as the tire's maximum width position in the tire radial direction, or is positioned radially outward of the tire's maximum width position. Invention[9] The tire according to any one of Inventions [1] to [8], wherein the tire is a tire to be mounted on a heavy-duty vehicle. [Explanation of symbols]

[0087] 1 pneumatic tire 2 Tread section 2a Tread rubber 3 Tread contact surface 4 Shoulder section 5 Sidewall 5a Sidewall Rubber 6 carcass layers 6a Carcass main body 6b Turnup section 7 Belt Layer 7a, 7b, 7c, 7d Belt plies 8 Inner liner 20 Bead section 21 Bead core 30 Bead base part 31 Bead Toe 32 Bead Heel 40 Rim cushion rubber 41 Cushioning rubber layer 50 Bead Filler 51 Lower Filler 52 Upper Filler 60 Elastic reinforcement layer 61 Winding section 62 Rolling section

Claims

1. a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core provided in each of the pair of bead portions; a carcass layer including a carcass main body portion disposed between the pair of bead portions and a turn-up portion formed continuously from the carcass main body portion and folded back from the inner side in the tire width direction of the bead core to the outer side in the tire width direction; a rim cushion rubber disposed on the inner side of the bead core in the bead portion in the tire radial direction; an elastic reinforcing layer that is folded back from the inner side in the tire width direction to the outer side in the tire width direction of the bead core at a position on a surface side of the carcass layer opposite to a surface on which the bead core is located; Equipped with The elastic reinforcing layer has a thickness in the range of 1.5 mm or more and 5.0 mm or less, A tire characterized in that the modulus of the elastic reinforcing layer at 100% elongation is in the range of 5 to 25 times the modulus of the rim cushion rubber at 100% elongation.

2. The elastic reinforcing layer is a relationship between a height Hb in the tire radial direction from a rim diameter reference position to an outer end in the tire radial direction of a portion of the elastic reinforcing layer located outer in the tire width direction of the bead core and a flange height Ha is within a range of 0.5≦Hb / Ha≦1.5, 2. The tire according to claim 1, wherein a relationship between a height Hc in the tire radial direction from the rim diameter reference position to an outer end in the tire radial direction of a portion of the elastic reinforcing layer located on the inner side in the tire width direction of the bead core and the flange height Ha is within a range of 0.4≦Hc / Ha≦1.

7.

3. a cushioning rubber layer is disposed between the turnup portion of the carcass layer and the elastic reinforcing layer; 2. The tire according to claim 1, wherein the modulus of the buffer rubber layer at 100% elongation is in the range of 0.5 to 0.8 times the modulus of the rim cushion rubber at 100% elongation.

4. The tire according to claim 3, wherein a distance between an outer end in the tire radial direction of a portion of the elastic reinforcing layer located on the outer side of the bead core in the tire width direction and the turn-up portion is within a range of 1.0 mm to 10.0 mm.

5. 4. The tire according to claim 3, wherein the relationship between the height Hd in the tire radial direction from the rim diameter reference position to the tire radially inner end of the cushioning rubber layer and the flange height Ha is within the range of 0.2≦Hd / Ha≦0.

5.

6. 2. The tire according to claim 1, wherein the elastic reinforcing layer is formed by crosslinking a composition in which a metal salt of acrylic acid or methacrylic acid is dispersed in an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less with an organic peroxide.

7. The tire according to claim 1 , wherein the elastic reinforcing layer is covered with an adhesive layer.

8. 2. The tire according to claim 1, wherein the turnup portion of the carcass layer has an outer end in the tire radial direction that is located at the same position as a tire maximum width position in the tire radial direction or located outer in the tire radial direction than the tire maximum width position.

9. 2. The tire according to claim 1, wherein the tire is a tire to be mounted on a heavy-duty vehicle.

Images