pneumatic tires

Abstract

Pneumatic tires (1), comprising: a bead core (11) formed from one or more tire bead wires (111) which are wound in a ring shape and multiple times; a carcass layer (13) formed from one or more carcass layers, wherein the carcass layer (13) is folded over so that it wraps around the bead core (11) and extends over the bead core (11); a wheel rim pad rubber (17) arranged along a folded-over section (132) of the carcass layer (13) to form a rim mating surface of a bead section, wherein the bead core (11) has a predetermined wire arrangement structure formed by arranging a wire cross-section of the tire bead wire (111) in a cross-sectional view in a tire meridian direction, The following is determined in the wire arrangement structure: a tangent line L1, which touches an innermost wire layer in a tire radial direction and the innermost and outermost wire cross-sections in a tire transverse direction from one side of the rim mating surface; contact points C1, C2 on the tangent line L1; a center point Cm of the contact points C1, C2; and thicknesses G1, G2 and Gm in the tire radial direction between the contact points C1, C2 and the center point Cm and the rim mating surface. The rates of change ΔG1, ΔG2 and ΔGm of the thicknesses G1, G2 and Gm before and after rim mounting are each in a range of 10 (%) to 60 (%); wherein a layer with the largest number of wire cross-sections in the wire arrangement structure is determined as a maximum arrangement layer, the number of layers of wire cross-section on the outside of the maximum arrangement layer in the tire radial direction is greater than the number of layers of wire cross-section on the inside of the maximum arrangement layer in the tire radial direction and The number of wire cross-sections in each layer on the outside of the maximum arrangement layer decreases monotonically from the maximum arrangement layer towards the outside in the tire radial direction.

Description

Technical area

[0001] The invention relates to a pneumatic tire and, more particularly, to a pneumatic tire that can ensure rim fit of a tire while reducing tire weight. State of the art

[0002] To reduce tire weight, recent progress has been made in reducing the weight of a bead portion. A prior art pneumatic tire related to the above-mentioned need is described in Patent Document 1. Patent Document 1 reduces the weight of the tire by omitting a bead filler. Literature listPatent literature

[0003] Patent document 1: JP 2008-149 778 A Brief description of the inventionTechnical problem

[0004] However, in the above-mentioned conventional pneumatic tire, the rim fit may deteriorate due to the omission of the bead filler.

[0005] DE 39 36 231 A1 discloses a tire for use in a motor vehicle, comprising an annular bead in which an annular bead core is arranged, which contains a plurality of bead wires arranged such that an imaginary inner surface of the bead core is determined around a rotational axis of the tire. The bead wires are arranged such that the diameter of the inner surface gradually decreases from a first location on the outside of the tire to a second location on the inside of the tire opposite the first location in the direction of the rotation axis, and the bead portion is shaped such that the following requirements are met: 0.65 < So / To < 1.00 and 0.50 < Si / Ti < 0.65, where To represents the shortest distance between the bead base and the bead wires at the first location before mounting on the rim, Ti represents the shortest distance between the bead base and the bead wire at the second location before mounting on the rim,So is the shortest distance between the outer peripheral surface of the rim and the bead wire located at the first position after the tire has been mounted on the rim and before inflation, Si is the shortest distance between the outer peripheral surface of the rim and the bead wire located at the second position after the tire has been mounted on the rim and before inflation, and the shortest distances To, Ti, So and Si are measured in the radial direction of the tire.

[0006] US 4 258 775 A discloses a pneumatic radial tire having a central annular tread, two sidewalls extending from the ends of the tread, and bead portions containing bead wires, and further comprising a radial fiber cord carcass extending between the bead portions and having the ends folded around and secured to the bead portions, and a belt layer having a plurality of metal cord layers over the carcass in the tread, wherein the metal cord layers have cords at angles of 65° to 80° to radial planes including a rotational axis of the tire, and wherein the cords cross each other from layer to layer, the tire having at least one pair of rubber-coated cushioning layers positioned between the ends of the metal cord layers in the belt layer and axially spaced from each other, and having cords,which are arranged in directions of substantially 90° to the radial planes, with one end of the damping layer extending slightly beyond the end of the belt layer.

[0007] JP S63-149207 A discloses a tire with bead sections, and JP 2002-200905 A discloses a tire with a turned-up carcass layer. Relevant prior art regarding an additional cushion rubber layer between the bead core and the rim cushion rubber can be found in US 5 107 915 A.

[0008] An object of the present invention is to provide a pneumatic tire that ensures the rim fit of the tire while reducing the weight of the tire. Solution to the problem

[0009] To achieve the above-mentioned object, a pneumatic tire according to the invention includes: a bead core formed from one or more bead wires wound in a ring-like and multiple manner; a carcass layer formed from one or more carcass plies, the carcass layer being turned over to wrap the bead core and extending over the bead core;and a rim cushion rubber arranged along a turned-up portion of the carcass layer to form a rim fitting surface of a bead portion. The bead core has a predetermined wire arrangement structure formed by arranging a wire cross-section of the bead wire in a cross-sectional view in the tire meridian direction, wherein the following are defined in the wire arrangement structure: a tangent line L1 contacting, from a side of the rim fitting surface, a wire layer innermost in a tire radial direction and innermost and outermost cross-sections in a tire transverse direction; contact points C1, C2 on the tangent line of the line L1, a center point Cm of the contact points C1, C2;and thicknesses G1, G2, and Gm in the tire radial direction between the contact points C1, C2 and the center point Cm and the rim mating surface, and wherein change rates ΔG1, ΔG2, and ΔGm of the thicknesses G1, G2, and Gm before and after rim mounting are each in a range of 10 (%) to 60 (%). A layer having a largest number of wire cross-sections in the wire arrangement structure is determined as a maximum arrangement layer. The number of layers of the wire cross-section on the outer side of the maximum arrangement layer in the tire radial direction is greater than the number of layers of the wire cross-section on the inner side of the maximum arrangement layer in the tire radial direction, and the number of wire cross-sections in each layer on the outer side of the maximum arrangement layer in the tire radial direction decreases monotonically from the maximum arrangement layer toward the outer side in the tire radial direction. Advantageous effects of the invention

[0010] In the pneumatic tire according to the present invention, the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion of the bead portion can be advantageously adjusted. That is, the above-mentioned lower limit ensures the rim fitting pressure to ensure the rim fitting of the tire. Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim handling during installation due to excessive rim fitting pressure. Brief description of the drawings Fig. 1 is a cross-sectional view in a tire meridian direction illustrating a pneumatic tire according to an embodiment of the invention. Fig. 2 is a cross-sectional view showing a bead portion of the Fig. 1 pneumatic tire. Fig. 3 is an enlarged view showing a rim fitting portion of the Fig. 2 illustrated bead section. Fig. 4 is an explanatory view showing a wire arrangement structure of a Fig. 3 illustrated bead core. Fig. 5 is an explanatory view illustrating a rim fitting portion of a bead portion of a tire after rim mounting. Fig. 6 is an explanatory view showing the Fig. 3 illustrated rim fitting section. Fig. 7 is an explanatory view showing the Fig. 3 illustrated rim fitting section. Fig. 8 is an explanatory view of a modified example of the Fig. 4 illustrated bead core. Fig. 9 is an explanatory view of a modified example of the Fig. 4 illustrated bead core. Fig. 10 is an explanatory view of a modified example of the Fig. 4 illustrated bead core. Fig. 11 is an explanatory view of a modified example of the Fig. 4 illustrated bead core. Fig. 12 is an explanatory view of a modified example of the Fig. 4 illustrated bead core. Fig. 13 is an explanatory view of a modified example of the Fig. 2 illustrated bead core. Fig. 14 is an explanatory view of a wire arrangement structure of the Fig. 13 illustrated bead core. Fig. 15 is an explanatory view of a modified example of the Fig. 14 illustrated bead core. Fig. 16 is an enlarged view showing a tire side portion of the tire shown in Fig. 1 illustrated pneumatic tire. Fig. 17 is an explanatory view of a modified example of the Fig. 2 illustrated bead section. Fig. 18 is a table showing the results of performance tests of pneumatic tires according to embodiments of the invention. Fig. 19 is an explanatory view illustrating a bead core of a test tire according to a prior art example. Description of embodiments

[0011] Embodiments of the invention will be described in detail below with reference to the drawings. However, the invention is not limited to these embodiments. Furthermore, components of the embodiments include elements that are interchangeable while maintaining consistency with the invention, as well as obviously interchangeable elements. Furthermore, the modified examples described in the embodiments can be combined as needed within the scope obvious to a person skilled in the art. pneumatic tires

[0012] Fig. Figure 1 is a cross-sectional view in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the invention. The same drawing illustrates a cross-sectional view of a half-section in the tire radial direction. Likewise, the same drawing illustrates a radial tire for a passenger car as an example of a pneumatic tire.

[0013] Referring to the same drawing, "cross-section in a tire meridian direction" refers to a cross-section of the tire taken along a plane including the tire rotation axis (not shown). Reference symbol CL denotes the equatorial plane of the tire and refers to a plane perpendicular to the tire rotation axis, passing through the center of the tire in the direction of the tire rotation axis. "Tire transverse direction" refers to the direction parallel to the tire rotation axis. "Tire radial direction" refers to the direction perpendicular to the tire rotation axis.

[0014] A pneumatic tire 1 has a ring structure around the tire rotation axis and includes a pair of bead cores 11, 11, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, a pair of rim cushion rubbers 17, 17 and an inner liner 18 (see Fig. 1).

[0015] The pair of bead cores 11, 11 is formed by annularly and multiply winding one or more bead wires made of steel, and is embedded in corresponding bead portions to form cores of the left and right bead portions.

[0016] The carcass layer 13 has a single-layer structure consisting of a single carcass ply or a multi-layer structure consisting of a plurality of laminated carcass plies, and extends between the left and right bead cores 11, 11 in a toroidal shape, thereby forming the support structure for the tire. Furthermore, both end portions of the carcass layer 13 are bent outward in the tire transverse direction to wrap around the bead cores 11 and are fixed.The carcass ply of the carcass layer 13 is constructed by coating a plurality of carcass cords made of steel or an organic fiber material such as aramid, nylon, polyester, rayon, and the like with coating rubber and rolling the coated carcass cords, and has a carcass angle (defined as the inclination angle of the carcass cords in the longitudinal direction with respect to the tire circumferential direction) in a range of 80 (degrees) to 90 (degrees) in absolute value. In the embodiment shown in FIG. Fig. In the configuration illustrated in Figure 1, the carcass layer 13 has a single-layer structure formed from a single carcass ply. However, the carcass layer 13 may have a multi-layer structure formed from a plurality of laminated carcass plies.

[0017] The belt layer 14 is formed by laminating a pair of cross belts 141, 142, a belt cover 143, and a pair of belt edge covers 144, and is wound around the outer periphery of the carcass layer 13. The pair of cross belts 141, 142 are manufactured by performing a rolling process on belt cords made of steel or an organic fiber material covered with coating rubber. The cross belts 141, 142 have a belt angle in an absolute value within a range of 20 (degrees) to 55 (degrees). In addition, the pair of cross belts 141, 142 have belt angles of opposite signs (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction) and are laid so that the longitudinal directions of the belt cords cross each other (i.e., cross-ply structure).The belt cover 143 and the pair of belt edge covers 144 are configured by coating a belt cover made of steel or an organic fiber material with a coating of rubber, and the cross belts have a belt angle in a range of 0 (degrees) to 10 (degrees) as an absolute value. Further, for example, the belt cover 143 and the pair of belt edge covers 144 are each configured by winding a strip material formed by coating one or more belt cover cords with a coating of rubber in a spiral and multiple manner around the outer peripheral surfaces of the cross belts 141, 142 in the tire circumferential direction.

[0018] The tread rubber 15 is arranged outwardly of the carcass layer 13 and the belt layer 14 in the tire radial direction, forming a tread portion. The pair of sidewall rubbers 16, 16 are arranged outwardly of the carcass layer 13 in the tire transverse direction, forming left and right sidewall portions. The pair of rim cushion rubbers 17, 17 are arranged inwardly of the left and right bead cores 11, 11 and the turned-up portions of the carcass layer 13 in the tire inner radial direction, forming the rim mating surfaces of the bead portions.

[0019] The inner liner 18 is an air permeation prevention layer disposed on the tire cavity surface and covering the carcass layer 13, thereby suppressing oxidation caused by exposure of the carcass layer 13 and preventing leakage of air filled in the tire. Furthermore, the inner liner 18 is made of, for example, a rubber composition containing butyl rubber as a main component, a thermoplastic resin, a thermoplastic elastomer composition prepared by blending an elastomer component with a thermoplastic resin, and the like. The inner liner 18 is adhered to the carcass layer 13 via a bonding rubber (not illustrated). Fillerless bead structure

[0020] Fig. 2 is a cross-sectional view showing the bead portion of the Fig. 1. This figure is a cross-sectional view in the tire meridian direction showing the bead portion of the tire in the state before rim mounting.

[0021] As in Fig. As illustrated in FIG. 2, the carcass layer 13 is folded outward in the tire transverse direction so as to wrap around the bead cores 11 and is fixed. In this case, a folded portion 132 of the carcass layer 13 contacts a body part 131 to form a closed region X surrounding the bead core 11. Furthermore, the closed region X continues over the entire tire circumference to form an annular closed space surrounding the bead core 11.

[0022] The closed area X is defined as an area enclosed by the carcass ply of the carcass layer 13 in the tire meridian direction in the cross-sectional view. Specifically, the area enclosed by the surface of the coating rubber of the carcass ply is defined as the closed area X.

[0023] Also in the Fig. 2, the carcass layer 13 is composed of a monolayer carcass ply, and the self-contact of the carcass ply forms the closed region X. On the other hand, in the configuration in which the carcass layer 13 is formed of a plurality of laminated carcass plies (not illustrated), mutual contact of different carcass plies may form the closed region X. For example, although not shown, it is assumed that the carcass layer 13 has a two-layer structure formed by laminating the first and second carcass plies, that a turned-up part of the first carcass ply ends at the center of a height H1 in the tire radial direction of the bead core 11, without a body part (see Fig. 2), and a bent portion of the second carcass ply extends to the radially outer side of the bead core 11 and contacts the body part of the first carcass ply (not illustrated).

[0024] In this case, the rubber occupancy ratio in the closed region X is preferably 15 (%) or less, more preferably 10 (%) or less, and even more preferably 5 (%) or less. Accordingly, the rubber occupancy ratio in the closed region X surrounded by the body part 131 and the turned-up portion 132 of the carcass layer 13, that is, the rubber volume around the bead core 11, is set very small. Accordingly, the purpose of reducing the weight of the tire by omitting the bead filler is achieved. Note that the lower limit of the rubber occupancy ratio is not particularly limited, but is preferably 0.1 (%) or more. Accordingly, the amount of insulating rubber of the bead cores 11 is properly secured.

[0025] The rubber coverage ratio is calculated as the ratio (%) of the cross-sectional area of ​​the rubber material in the closed region X to the total cross-sectional area of ​​the closed region X in the cross-sectional view in the tire meridian direction.

[0026] For example, in the Fig. 2, the turned-up portion 132 of the carcass layer 13 is turned over to contact the body part 131 without the bead filler being included in the closed region X. Furthermore, the carcass ply of the carcass layer 13 is wound along the outer peripheral side of the bead core 11. Thus, only the components of the bead core 11 are present in the closed region X. The components of the bead core 11 include bead wires 111, an insulating rubber, a bead cap, and winding turns.

[0027] It should be noted that the bead filler is a reinforcing rubber that fills a triangular gap between the bead core and the body part and the turned-up portion of the carcass ply. It is arranged to increase the rigidity of the bead portion. The bead filler generally has a triangular cross-section and a rubber hardness in a range of 65 to 99.

[0028] The rubber hardness is measured according to JIS K 6253.

[0029] Additionally, in the above-mentioned configurations which do not contain a bead filler, as in Fig. 2, the turned-up portion 132 of the carcass layer 13 is preferably fixed in surface contact with the body part 131 of the carcass layer 13. Furthermore, a height H2 in the tire radial direction of the contact portion between the body part 131 and the turned-up portion 132 of the carcass layer 13 and a height H1 in the tire radial direction of the bead core 11 preferably have a ratio of 0.80 ≤ H2 / H1 ≤ 3.00, and more preferably a ratio of 1.20 ≤ H2 / H1 ≤ 2.50. Accordingly, the height H2 in the tire radial direction of the self-contacting portion of the carcass layer 13 is made appropriate. In other words, the above-mentioned lower limit allows the turned-up portion 132 to stably come into contact with the body part 131 to improve the durability of the bead portion. In addition, the upper limit suppresses an increase in the weight of the tire due to an excessive amount of the turned-up portion 132.

[0030] The tire radial height H1 of the bead core is measured as a maximum height in the tire radial direction in the wire arrangement structure of the bead core, from the tire radially innermost layer and the tire transversely inner end of the tire radially outermost cross section to the tire radially outermost layer and the tire radially outermost end of the tire transversely outermost wire cross section.

[0031] The height H2 in the tire radial direction of the self-contacting portion of the carcass layer is measured as a maximum length of the contact portion between the body part and the turned-up portion of the carcass layer in the tire radial direction.

[0032] Additionally, in the configuration described above, as in Fig. 2, one end (reference numeral is omitted in the figure) of the turned-up portion 132 of the carcass layer 13 preferably contacts the body part 131 of the carcass layer 13. In such a configuration, compared to the configuration in which the end of the turned-up portion 132 is spaced apart from the body part 131 (not illustrated), stress concentration at the end of the turned-up portion 132 is alleviated. Accordingly, separation of the circumferential rubber from the end of the turned-up portion 132 is suppressed.

[0033] Furthermore, for an actual length La2 (symbols for unit measurements are omitted in the figure) of the contact portion between the body part 131 and the turned-up portion 132 of the carcass layer 13 and a circumferential length La1 (symbols for unit measurements are omitted in the figure) of the closed region X, it is preferable that the relationship is 0.30 ≤ La2 / La1 ≤ 2.00, and more preferably that the relationship is 0.37 ≤ La2 / La1 ≤ 1.80. Accordingly, the actual length La2 of the self-contacting portion of the carcass layer 13 is made appropriate. That is, the above-mentioned lower limit appropriately ensures the spring characteristics of the carcass layer 13, the steering stability on dry road surfaces, and the durability of the bead portion. Furthermore, the upper limit suppresses an increase in the weight of the tire due to an excessive amount of the turned-up portion 132.

[0034] The circumferential length La1 of the closed region X is measured as a circumferential length of the surface of the carcass ply which is the boundary line of the closed region X in a cross-sectional view in the tire meridian direction.

[0035] The actual length La2 of the contact portion is measured as a circumferential length of the self-contacting portion between the body part and the turned-up portion of the carcass layer in a cross-sectional view in the tire meridian direction.

[0036] It should be noted that in the Fig. 2, as described above, the pneumatic tire 1 does not include a bead filler. However, such a limitation is not provided, and the pneumatic tire 1 may include the bead filler or other reinforcing rubber between the body part and the turned-up portion of the carcass layer (see Fig. 17 as described below). External reinforcement rubber

[0037] As in Fig. 2, the pneumatic tire 1 includes the outer reinforcing rubbers 19 in addition to the sidewall rubbers 16 and the rim cushion rubbers 17 described above.

[0038] The sidewall rubber 16 is arranged on both outer sides of the carcass layer 13 in the tire transverse direction and forms sidewall sections of the tire. In addition, the rubber hardness of the sidewall rubber 16 ranges from 40 to 70. Furthermore, the elongation at break of the sidewall rubber 16 ranges from 400 (%) to 650 (%).

[0039] The elongation at break is measured according to JIS K6251.

[0040] As described above, the rim cushion rubber 17 is arranged to cover an inner side of the bead core 11 and the turned-up portion 132 of the carcass layer 13 in the tire radial direction to form a rim mating surface of the bead portion. Furthermore, the rubber hardness of the rim cushion rubber 17 is in a range of 50 to 80. Furthermore, the elongation at break of the rim cushion rubber 17 is in a range of 150 (%) to 450 (%).

[0041] The outer reinforcing rubber 19 is arranged between the turned-up portion 132 of the carcass layer 13 and the wheel rim cushion rubber 17 (see Fig. 2). In such a configuration, especially in the configuration without bead fillers, the spring characteristics of the bead portions are enhanced by the outer reinforcing rubbers 19, thereby improving the steering stability on dry roads and the durability of the bead portion.

[0042] In addition, the rubber hardness of the outer reinforcing rubbers 19 is preferably in a range of 65 to 105, and more preferably in a range of 70 to 100. Accordingly, the above-mentioned effects of the outer reinforcing rubbers 19 are suitably ensured.

[0043] In addition, the rubber hardness of the outer reinforcing rubbers 19 is higher than the rubber hardness of the sidewall rubber 16 and the rim cushion rubber 17. More specifically, a difference ΔHs_SW between the rubber hardness of the sidewall rubber 16 and the rubber hardness of the outer reinforcing rubbers 19 is preferably 7 or more, and more preferably 12 or more. In addition, a difference ΔHs_RC between the rubber hardness of the rim cushion rubber 17 and the rubber hardness of the outer reinforcing rubber 19 is preferably 3 or more, and more preferably 7 or more. Accordingly, the reinforcing effect of the spring characteristics of the bead portions caused by the outer reinforcing rubbers 19 is appropriately exhibited. Note that the lower limit of the rubber hardness difference ΔHs_SW is limited by the lower limit of the rubber hardness of the outer reinforcing rubbers 19 described above.

[0044] In addition, the elongation at break of the outer reinforcing rubber 19 is preferably in a range of 50 (%) to 400 (%), and more preferably in a range of 70 (%) to 350 (%).

[0045] For example, in the Fig. 2, the rim cushion rubber 17 extends over the entire range from a bead toe Bt to a bead base Bb to form a rim mating surface with respect to a bead seat 101 of the rim 10. Furthermore, the rim cushion rubber 17 extends from the bead base Bb to the tire radially outer side along the turned-up portion 132 of the carcass layer 13 to form the mating surface with a flange 102 of the rim 10. Furthermore, a tire radially outer end of the rim cushion rubber 17 is interposed between the carcass layer 13 and the sidewall rubber 16, and extends further to the tire radially outer side than the end of the turned-up portion 132 of the carcass layer 13 and the flange 102 of the rim 10. Furthermore, the bead portion may include a chafer (not illustrated).

[0046] Note that the rim cushion rubber 17 preferably extends at least in a range from a bead heel Bh to a central portion (a center point Cm as described later) in the tire radially innermost layer of the bead core 11. Accordingly, the durability of the rim fitting portion of the bead portion is properly ensured.

[0047] In addition, the outer reinforcing rubber 19 is as in the configuration in Fig. 2 illustrates a tire radial direction long and located between the turned-up portion 132 of the carcass layer 13 and the rim cushion rubber 17. Furthermore, the inner end of the outer reinforcing rubber 19 in the tire radial direction overlaps the bead core 11 in the tire radial direction. Furthermore, the outer reinforcing rubber 19 extends further to the tire radial direction outer side than the end of the turned-up portion 132 of the carcass layer 13 and is located between the body part 131 of the carcass layer 13 and the sidewall rubber 16. Furthermore, the outer reinforcing rubber 19 covers the end of the turned-up portion 132 of the carcass layer 13 from the tire transverse direction outer side. In addition, the outer reinforcing rubber 19 is adjacent to the turned-up portion 132 of the carcass layer 13 over the entire area of ​​the contact portion between the body portion 131 and the turned-up portion 132 of the carcass layer 13.As a result, the spring characteristics of the bead portion are appropriately enhanced by the outer reinforcing rubber 19, thereby improving dry-road steering stability and the durability of the bead portions. Furthermore, since the rubber hardness of the outer reinforcing rubber 19 is higher than the rubber hardness of the sidewall rubber 16 and the rim cushion rubber 17, the distribution of rubber hardness near the end of the turned-up portion 132 of the carcass layer 13 decreases from the end of the carcass layer 13 toward the surface of the tire side portion. Consequently, stress generated near the end of the carcass layer 13 is alleviated to suppress the separation of the circumferential rubber.

[0048] In addition, a height H3 in the tire radial direction from a measuring point on the inner tire diameter RD to an outer end of the outer reinforcing rubber 19 in the tire radial direction and a tire cross-sectional height SH (see Fig. 1) preferably has a ratio of 0.10 ≤ H3 / SH ≤ 0.60, and more preferably a ratio of 0.15 ≤ H3 / SH ≤ 0.50. Accordingly, the height H3 of the outer reinforcing rubber 19 in the tire radial direction is made appropriate. That is, the above-mentioned lower limit appropriately enhances the spring characteristics of the bead portion with the outer reinforcing rubber 19, thereby improving the steering stability on dry road surfaces and the durability of the bead portion. Furthermore, the upper limit suppresses an increase in the weight of the tire due to an excessive amount of the outer reinforcing rubber 19.

[0049] The tire inner diameter RD is equal to the rim diameter of a specified rim.

[0050] The tire radial height H3 is measured when the tire is mounted on the specified rim, inflated to the specified internal pressure, and in an unloaded state. Specifically, this height is calculated as the difference between the diameter of the outer end of the reinforcing rubber 19 in the tire radial direction and the tire inner diameter RD.

[0051] The section height SH of the tire is a distance equal to half the difference between the tire outer diameter and the rim diameter and is measured when the tire is mounted on a given rim, inflated to a given internal pressure and in an unloaded condition.

[0052] "Specified rim" refers to an applicable rim as defined by the Japan Automobile Tire Manufacturers Association Inc. (JATMA), a design rim as defined by the Tire and Rim Association, Inc. (TRA), or a measuring rim as defined by the European Tire and Rim Technical Organization (ETRTO). In addition, "specified internal pressure" refers to a maximum air pressure as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, and "INFLATION PRESSURES" as defined by ETRTO.Furthermore, "specified load" refers to a "maximum load capacity" as defined by JATMA, the maximum value in "tire load limits at various cold inflation pressures" as defined by TRA, or "load capacity" as defined by ETRTO. However, in the case of JATMA, the specified internal pressure for a passenger car tire is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0053] In addition, preferably, a height H4 in the tire radial direction from the end of the turned-up portion 132 of the carcass layer 13 to the outer end of the outer reinforcing rubber 19 in the tire radial direction and the height H2 in the tire radial direction of the contact portion between the body part 131 and the turned-up portion 132 of the carcass layer 13 have a ratio of 0.10 ≤ H4 / H2, and more preferably a ratio of 0.30 ≤ H4 / H2. Consequently, dry-road steering stability and bead portion durability are improved. Note that the upper limit of the ratio H4 / H2 is limited by the upper limit of the above-described ratio H3 / SH.

[0054] Furthermore, an overlap amount H5 of the outer reinforcing rubber 19 and the bead core 11 in the tire radial direction and the height H1 of the bead core 11 in the tire radial direction preferably have a relationship of 0.05 ≤ H5 / H1 ≤ 1.00, and more preferably a relationship of 0.10 ≤ H5 / H1 ≤ 1.00. In addition, the overlap amount H5 is preferably in a range of 5.0 (mm) ≤ H5. Accordingly, the overlap amount H5 of the outer reinforcing rubber 19 and the bead core 11 is made appropriate. In particular, the above-mentioned lower limit ensures the overlap amount H5, thereby suppressing rubber separation at the inner end of the outer reinforcing rubber 19 in the tire radial direction.

[0055] The overlap amount H5 is measured when the tire is mounted on a specified rim, inflated to the specified internal pressure and in an unloaded state.

[0056] It should be noted that, without being limited to the above, the outer reinforcing rubbers 19 may be arranged on the outer side of the bead core 11 (not illustrated) as viewed in the tire radial direction.

[0057] In addition, a length T1 of a perpendicular line drawn from the end of the turned-up portion 132 of the carcass layer 13 to the outer surface of the tire side portion and a thickness T2 of the outer reinforcing rubber 19 on the perpendicular line preferably have a ratio of 0.10 ≤ T2 / T1 ≤ 0.90, and more preferably a ratio of 0.20 ≤ T2 / T1 ≤ 0.80. Accordingly, the thickness T2 of the outer reinforcing rubber 19 is made appropriate. That is, the above-mentioned lower limit appropriately enhances the spring characteristics of the bead portion with the outer reinforcing rubber 19, thereby improving the steering stability on dry road surfaces and the durability of the bead portion. Furthermore, the upper limit suppresses an increase in the weight of the tire due to an excessive amount of the outer reinforcing rubber 19.

[0058] In addition, in the configuration using the outer reinforcing rubber 19 instead of the bead filler as described above, a numerical value K determined by a mathematical expression (1) below preferably satisfies 0.17 ≤ K, and more preferably 0.20 ≤ K. Accordingly, the function of the outer reinforcing rubber 19 is properly ensured. In the mathematical expression (1), W is a tire inner width (mm), I is a tire inner diameter (inch), and B is a total cross-sectional area of ​​the bead wire in the bead core (mm 2 ).

[0059] Mathematical Formula 1 K=W43×I23100×B2 Rate of change of the rim fitting section

[0060] In the configurations described above without bead filler, the stiffness of the bead sections is reduced, and the rim fitting pressure of the bead sections tends to decrease. Therefore, in the Fig. 2, in order to ensure the rim fit of the tire, the bead core 11 has the following configuration.

[0061] Fig. 3 is an enlarged view showing the rim fitting portion of the Fig. 2 illustrated bead section. Fig. 4 is an explanatory view showing the wire arrangement structure of the Fig. 3 illustrated bead core. Fig. Figure 5 is an explanatory view illustrating the rim fitting portion of the bead portion of a tire after rim mounting. Among these figures, Fig. 3 the rim fitting section before rim assembly, and Fig. 5 shows the rim fitting section after rim assembly. Fig. 4 is a cross-sectional view of the uncured bead core 11 in the radial direction as a single component.

[0062] At Fig. 2, the rim mating surface of the bead portion includes the bead base Bb, the bead toe Bt, and the bead heel Bh, and has a uniform contour in the tire circumferential direction. The bead base Bb is a flat area formed on the inner side of the bead portion in the tire radial direction and constitutes a contact surface with the bead seat 101 of the rim. The bead toe Bt is a tip of the bead portion having an L-shape or a V-shape in a cross-sectional view in the tire meridian direction and is located on the innermost side of the rim mating surface in the tire transverse direction. The bead heel Bh is a curved portion connecting a wall surface of the tire side portion to the bead base Bb.

[0063] The condition of the tire before rim mounting (see Fig. 2 and Fig. 3) is defined as a state in which the tire is attached to the rim such that the positions of the left and right bead portions correspond to the measurement points of the rim width and rim diameter of the specified rim, with the tire rotation shaft horizontal and the tire itself upright. Such a tire shape is closest to the tire shape in a tire vulcanization mold, that is, the natural tire shape before inflation.

[0064] Furthermore, the condition of the tire after rim mounting (see Fig. 5) Defined as a state in which the tire is mounted on the specified rim, inflated to the specified internal pressure, and in an unloaded state. In the tire's state after rim mounting, the rim mating surface of the bead portion fits into the rim 10 of the wheel, thereby holding the tire. In this case, the bead base Bb of the rim mating surface is pressed against the bead seat 101 of the rim 10 and brought into surface contact therewith, thereby sealing the mating portion between the bead portion and the rim 10 to ensure airtightness within the tire. In addition, the bead heel Bh is arranged at the connecting portion between the bead seat 101 and the flange 102, and an outer portion of the rim fitting surface as the bead heel Bh abuts against the flange 102 of the rim 10 to hold the bead portion from the outer side in the tire transverse direction.

[0065] As in Fig. As illustrated in Figure 4, the bead core 11 has a predetermined wire arrangement structure obtained by arranging the wire cross sections of the bead wires 111 in a cross-sectional view in a tire meridian direction. The wire arrangement structure will be described below.

[0066] Here, a tangent line L1 is determined which connects, from one side of the rim mating surface, the innermost layer of the bead core 11 in the tire radial direction and the innermost and outermost wire cross sections in the tire transverse direction in the wire arrangement structure in a cross-sectional view of the tire before rim mounting in the tire meridian direction (see Fig. 3). The contact points C1 and C2 on the tangent line L1 for the wire cross-sections and a center point Cm of the contact points C1, C2 are determined. The thicknesses G1, G2 and Gm of the contact points C1, C2 and the center point Cm up to the rim mating surface in the tire radial direction are also determined. More specifically, in a cross-sectional view in the tire meridian direction, the intersection points P1, P2 and Pm of straight lines passing through the contact points C1, C2 and the center point Cm and the bead base Bb are plotted, and the distances between the contact points C1, C2 and the center point Cm and the intersection points P1, P2 and Pm are measured as the thicknesses G1, G2 and Gm, respectively.

[0067] Similarly, the thicknesses G1', G2' and Gm' of the rim fitting portion in the state of the tire after rim mounting (see Fig. 5) is determined.

[0068] In this case, the change rates ΔG1, ΔG2, and ΔGm of the thicknesses G1, G2, and Gm of the rim fitting portion before and after rim mounting are preferably in a range of 10 (%) to 60 (%), more preferably in a range of 15 (%) to 50 (%), even more preferably in a range of 20 (%) to 45 (%), and most preferably in a range of 25 (%) to 40 (%). Thus, the change rates ΔG1, ΔG2, and ΔGm of the thicknesses G1, G2, and Gm become larger in the closed region X compared to the conventional tire construction with a high rubber occupancy ratio (especially in the tire constructions with bead fillers having the same cross-section of the bead core or more). As a result, the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion of the bead portion are adjusted appropriately. That is, the above-mentioned lower limit ensures the rim fitting pressure to ensure the tire's rim fit.In addition, the above-mentioned upper limit suppresses the deterioration of the handling during tire rim installation due to excessive rim fitting pressure.

[0069] The change rate ΔGi is determined as ΔGi = (Gi - Gi') / Gi × 100 using the thicknesses Gi and Gi' before and after rim mounting at a given measuring point. For example, the change rate ΔG1 is determined as ΔG1 = (G1 - G1') / G1 × 100 using the thickness G1 before rim mounting G1 (see Fig. 3) and the thickness G1' after rim assembly (see Fig. 5) is calculated.

[0070] The above-mentioned change rates ΔG1, ΔG2 and ΔGm of the rim fitting portion are determined, for example, by the configuration of the cushion rubber layer 20 (see Fig. 6) and the configuration of the cone angles of the bead base Bb (see Fig. 7) as described below.

[0071] In addition, the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion preferably satisfy a condition of |ΔGm - ΔG2| < |ΔG1 - ΔGm|. Accordingly, the difference between the change rate |ΔG1 - ΔGm| on the bead toe Bt side is set larger than the difference between the change rate |ΔGm - ΔG2| on the bead heel Bh side. Specifically, the change rates ΔG1, ΔG2, and ΔGm satisfy a relationship of 20 (%) ≤ |(ΔG1 - ΔGm) / (ΔGm - ΔG2)| ≤ 450 (%), and more preferably 30 (%) ≤ |(ΔG1 - ΔGm) / (ΔGm - ΔG2)|. ≤ 300 (%). Therefore, the relationship between the change rates ΔG1, ΔG2, and ΔGm of the rim fit section is made appropriate. That is, the above-mentioned lower limit improves the tire's rim fit. Furthermore, the above-mentioned upper limit improves the tire's handling during rim installation.

[0072] Furthermore, the change rates ΔG1, ΔG2, and ΔGm of the thicknesses G1, G2, and Gm of the rim fitting portion preferably have a relationship of ΔG2 < ΔGm < ΔG1. In other words, the change rates ΔG1, ΔG2, and ΔGm increase toward the bead toe Bt. As a result, the rim fitting of the tire is improved.

[0073] In addition, the thicknesses G1, G2 and Gm of the rim fitting portion of the tire in the state before rim mounting in the Fig. 3, a relationship of G2 < Gm < G1 is established. In other words, the thicknesses G1, G2, and Gm of the rim fitting portion increase toward the bead toe Bt. Accordingly, the relationship between the change rates ΔG1, ΔG2, and ΔGm is made appropriate. Furthermore, in a tire for a passenger car, the thickness G1 is preferably in a range of G1 ≤ 8.0 (mm), and more preferably in the range of G1 ≤ 6.0 (mm). In addition, the thickness G2 is preferably in a range of 1.0 (mm) ≤ G2, and more preferably in a range of 2.0 (mm) ≤ G2. Accordingly, the rubber volume in the rim fitting portion on the inner side of the bead core 11 in the radial direction is made appropriate.

[0074] In addition, a width Wc2 (mm) from the innermost layer of the bead core 11 in the wire arrangement structure (see Fig. 4) the rate of change ΔGm (%) of the center point Cm, and the tire inner diameter RD in inches (see Fig. 2) preferably a ratio of 1.0 (% mm / inch) ≤ Wc2 × ΔGm / RD ≤ 50 (% mm / inch), more preferably a ratio of 2.0 (% mm / inch) ≤ Wc2 × ΔGm / RD ≤ 40 (% mm / inch), and more preferably a ratio of 5.0 (% mm / inch) ≤ Wc2 × ΔGm / RD ≤ 30 (% mm / inch). Accordingly, the relationship between the width Wc2 of the innermost layer of the bead core 11 and the change rate ΔGm is made appropriate. That is, the above-mentioned lower limit ensures the rim fit of the tire. In addition, the above-mentioned upper limit improves the tire's handleability during rim mounting.

[0075] As in the Fig. 4, the width Wc2 is measured from the innermost layer of the wire arrangement structure as the maximum width including the innermost and outermost wire cross sections in the tire transverse direction.

[0076] In addition, the width Wc2 of the innermost layer in the wire array structure is preferably in a range of 3.0 (mm) ≤ Wc2 ≤ 10.0 (mm), and more preferably in a range of 4.5 (mm) ≤ Wc2 ≤ 9.6 (mm). Wire arrangement structure of the bead core

[0077] As in Fig. As shown in Figure 4, the bead core 11 is formed by winding bead wires 111 in a ring-like and multiple manner and has a predetermined wire arrangement structure in a cross-sectional view in the tire meridian direction. The wire arrangement structure is determined by the arrangement of the wire cross-sections of the bead wires 111. Furthermore, the wire arrangement structure consists of a plurality of laminated layers in the tire radial direction, and these layers are formed of a plurality of wire cross-sections aligned in a row in the tire transverse direction. Furthermore, the innermost layer of the wire arrangement structure is substantially parallel to the rim fitting surface of the bead portion and faces the bead seat 101 of the rim 10 while the tire fits into the rim (see Fig. 3).

[0078] In the manufacturing process of the bead core 11, a core forming jig (not illustrated) is used, and one or more bead wires 111 are wound around the core forming jig in a predetermined wire arrangement structure to form the unvulcanized bead core 11. Then, the formed bead core 11 is pre-vulcanized before a vulcanization molding step of a green tire. Note that no such limitation is intended, and the pre-vulcanization of the bead core 11 may be omitted, and the unvulcanized bead core 11 may be incorporated into the green tire to perform the vulcanization molding step of the green tire.

[0079] In addition, the bead wire 111 includes a wire strand and an insulating rubber covering the wire strand (not illustrated). Furthermore, the strand is made of steel. Furthermore, the insulating rubber is preferably made of a rubber composition with a Mooney viscosity of 70 (M) or more. The Mooney viscosity is calculated according to JIS K6300-1: 2013.

[0080] In addition, the Fig. 2, as described above, the turned-up portion 132 of the carcass layer 13 surrounds the body portion 131 of the carcass layer 13 to form the closed portion X surrounding the bead core 11. In addition, the rubber occupancy ratio in the closed portion X is set to be small, which reduces the weight of the bead portion. In this case, in order to improve the durability of the bead portion, the generation of the void in the closed portion X is preferably suppressed.

[0081] Thus, as in Fig. 4, the wire arrangement structure of the bead core 11 has a wedge shape that protrudes toward the outside in the tire radial direction. More specifically, a layer in which the number of wire cross sections of the wire arrangement structure is the largest (in the Fig. 4, the second layer from the innermost layer), determined as the maximum arrangement layer. In this case, the number of layers of the wire cross-sections on the outside of the maximum arrangement layer in the tire radial direction (3 in Fig. 4) greater than the number of layers of the wire cross-section on the inner side of the maximum arrangement layer in the tire radial direction (1 in Fig. 4). In addition, the number of wire cross-sections in each layer on the outer side of the maximum arrangement layer in the tire radial direction decreases monotonically from the maximum arrangement layer toward the outer side in the tire radial direction. Furthermore, the number of layers of wire cross-sections is preferably in a range of 4 to 6. Preferably, the number of wire cross-sections in the maximum arrangement layer of the wire arrangement structure is 4 or 5, and the number of wire cross-sections in the outermost layer in the tire radial direction is 1 or 2.

[0082] Furthermore, in the closest-packed structure, the wire cross-sections are arranged in the outer side region of the maximum arrangement layer in the tire radial direction. The term "closest-packed structure" refers to the state in which centers of three adjacent wire cross-sections form a substantially regular triangle in a cross-sectional view in the tire meridian direction. In such a closest-packed structure, compared to the lattice arrangement structure in which rows of wire cross-sections are orthogonal to each other in the longitudinal and width directions, the arrangement density of the wire cross-sections of the bead core 11 increases, which improves the fracture strength of the bead core 11. Note that in the above-mentioned closest-packed state, all sets of adjacent wire cross-sections need not be in contact with each other, and some sets may be spaced apart with a small gap (not illustrated).

[0083] In a configuration such as that shown in Fig. 3, the body part 131 and the turned-up portion 132 of the carcass layer 13 extend toward the outer side in the tire radial direction along the wedge shape of the wire arrangement structure while abutting against the left and right sides of the bead core 11 in the tire transverse direction, and transition into the Y-shape and contact with each other. Consequently, a gap between the joining portion of the body part 131 and the turned-up portion 132 of the carcass layer 13 and an upper portion (so-called bead crown) on the outer side of the bead core 11 in the tire radial direction becomes smaller, which improves the durability of the bead portion. In particular, the above-mentioned structure not including a bead filler can advantageously reduce the rubber occupancy ratio in the closed region X.In addition, since the folded portion 132 can bend at an obtuse angle at the joining portion with the body part 131, the amount of deflection of the folded portion 132 is reduced, which is an improvement in the durability of the bead portion.

[0084] Furthermore, the number of wire cross sections in the innermost layer in the tire radial direction in the wire arrangement structure is 3 or 4, and is preferably equal to or smaller than the number of wire cross sections in the maximum arrangement layer.

[0085] In addition, as described in the Fig. 4, the arrangement angles θ1, θ2 at corner portions of the wire cross section on the inner side in the tire radial direction and on the inner and outer sides in the tire transverse direction in the wire arrangement structure are determined. The arrangement angles θ1, θ2 are in a range of 80 (degrees) ≤ θ1 and 80 (degrees) ≤ θ2. That is, the arrangement angles θ1, θ2 of the wire cross section are substantially right angles or obtuse angles, respectively. In addition, as shown in Fig. As illustrated in FIG. 4, the arrangement angles θ1, θ2 of the wire cross sections are preferably within a range of 100 (degrees) ≤ θ1 ≤ 150 (degrees) and 100 (degrees) ≤ θ2 ≤ 150 (degrees). Consequently, disruption of the wire arrangement structure during tire vulcanization is suppressed, which improves the tire's rim fit and the durability of the bead portion. Furthermore, when the arrangement angles θ1, θ2 of the wire cross sections each form an obtuse angle, the carcass ply can be turned over along the corner portion of the bead core 11 on the inner side in the tire radial direction, and the rubber occupancy ratio in the closed region X can further reduce the weight of the bead portion.

[0086] The arrangement angles θ1, θ2 are each measured as an angle formed by a line connecting the centers of the three wire cross-sections, which represents the corner section in the wire arrangement structure.

[0087] In addition, the Fig. 4, a maximum width Wc1 and a maximum height Hc1 of the bead core 11, and a total cross-sectional area S of the bead wires 111 of the bead core 11 preferably have a ratio of 1.20 ≤ Wc1 × Hc1 / S ≤ 5.00, more preferably a ratio of 1.50 ≤ Wc1 × Hc1 / S ≤ 4.50, and even more preferably a ratio of 1.80 ≤ Wc1 × Hc1 / S ≤ 4.00. Accordingly, the wire arrangement structure of the bead core 11 is made appropriate. That is, the above-mentioned lower limit ensures the number of wire cross-sections and the rim fit of the tire. In addition, the above-mentioned upper limit reduces the weight of the bead core 11.

[0088] It should be noted that the total cross-sectional area S of the bead wires does not include the cross-sectional area of ​​the insulating rubber.

[0089] Furthermore, the total cross-sectional area S of the bead wires 111 is preferably in a range of 5 (mm 2 ) ≤ S ≤ 35 (mm 2), more preferably in a range of 6 (mm 2 ) ≤ S ≤ 32 (mm 2 ), and even more preferably in a range of 7 (mm 2 ) ≤ S ≤ 28 (mm 2 ). Consequently, the total cross-sectional area S of the bead wires 111 is made appropriate. Specifically, the above-mentioned lower limit ensures the total cross-sectional area S of the bead wires 111 to ensure the rim fit of the tire. Furthermore, the above-mentioned upper limit reduces the weight of the bead core 11.

[0090] In addition, the outer diameter ϕ of the bead wire 111 (see Fig. 4) Preferably, the outer diameter ϕ of the bead wire 111 is within a range of 0.8 (mm) ≤ ϕ ≤ 1.5 (mm), more preferably, the outer diameter ϕ of the bead wire 111 is within a range of 0.9 (mm) ≤ ϕ ≤ 1.4 (mm), and even more preferably, the outer diameter ϕ of the bead wire 111 is made appropriate. Specifically, the above-mentioned lower limit ensures the outer diameter ϕ of the bead wire 111 to ensure the rim fit of the tire. Furthermore, the above-mentioned upper limit reduces the weight of the bead core 11.

[0091] In addition, the Fig. 4, a height Hc2 of the tangent line L1 of the innermost layer in the wire arrangement structure to the maximum width position of the bead core 11, and the maximum height Hc1 of the bead core 11 preferably has a ratio of 1.10 ≤ (Hc1 - Hc2) / Hc2 ≤ 2.80, more preferably a ratio of 1.30 ≤ (Hc1 - Hc2) / Hc2 ≤ 2.50, and even more preferably a ratio of 1.50 ≤ (Hc1 - Hc2) / Hc2 ≤ 2.30. Accordingly, the wire arrangement structure of the bead core 11 is made suitable.

[0092] The maximum height Hc1 of the bead core is measured as the maximum height of the bead core relative to the tangent line L1.

[0093] The height Hc2 of the maximum width position of the bead core is measured as the distance between the tangent line L1 and an imaginary line connecting the centers of the wire cross-sections constituting the maximum arrangement layer. In the configuration where the wire arrangement structure includes a plurality of maximum arrangement layers, the height Hc2 of the maximum width position is measured using the maximum arrangement layer on the outermost side in the tire radial direction.

[0094] For example, in the Fig. In the configuration illustrated in Figure 4, the number of layers of the wire cross-sections is 5, and the number of wire cross-sections is set to 3-4-3-2-1 in the order from the innermost layer in the tire radial direction. Thus, the number of wire cross-sections in the maximum arrangement layer is 4. In addition, the number of layers of the wire cross-section on the outer side of the maximum arrangement layer in the tire radial direction is 3, and the number of layers of the wire cross-section on the inner side of the maximum arrangement layer in the tire radial direction is 1. Consequently, the maximum arrangement layer is asymmetrical in the tire radial direction and is biased toward the inner side in the tire radial direction from the center of the wire arrangement structure in the tire radial direction. Furthermore, the wire arrangement structure on the outer side of the maximum arrangement layer in the tire radial direction has a long structure.In addition, the number of wire cross-sections in each layer decreases gradually from the maximum arrangement layer toward the outer side in the tire radial direction. All wire cross-sections are also arranged in the most densely packed structure. Thus, the arrangement angles θ1 and θ2 of the wire cross-sections at the left and right corner portions in the wire arrangement structure in the tire radial direction are each approximately 135 (degrees) (more precisely, in a range of 130 (degrees) to 140 (degrees)). In addition, the maximum arrangement layer of the wire cross-section is not the innermost layer in the tire radial direction. In addition, the number of wire cross-sections in each layer increases sequentially from the innermost layer to the maximum arrangement layer. This optimizes the wire arrangement structure.

[0095] In addition, the Fig. 3, a distance Hg in the tire radial direction from the outer end of the bead core 11 in the tire radial direction to the contact portion between the body part 131 and the turned-up portion 132 of the carcass layer 13, and the outer diameter φ of the bead wire 111 preferably has a ratio of Hg / φ ≤ 7.0, and more preferably a ratio of Hg / φ ≤ 3.0. Accordingly, the rigidity around the bead core 11 is improved. Note that in the case of Hg=0, the lower limit of the ratio of Hg / φ is 0 ≤ Hg / φ. Thickness of the rim fitting section

[0096] Fig. 6 is an explanatory view showing the Fig. 3. This figure illustrates the rim fitting section in the state before rim assembly. In this figure, the same components as in Fig. 3, the same reference numerals are used for the components illustrated, and explanations for them are omitted.

[0097] In Fig. 6, as described above, the thickness G2 in the tire radial direction is determined from the contact point C2 between the tangent line L1 on the innermost layer of the wire arrangement structure and the outermost wire cross-section in the tire transverse direction to the rim mating surface. In this case, the thickness G2 and the outer diameter ϕ of the bead wire 111 (see Fig. 4) Preferably, the ratio G2 of the rim fitting portion is 1.3 ≤ G2 / ϕ ≤ 9.5, and more preferably, the ratio G2 of the rim fitting portion is 1.8 ≤ G2 / ϕ ≤ 5.5. Accordingly, the thickness G2 of the rim fitting portion is made appropriate. That is, the above-mentioned lower limit ensures the thickness G2 of the rim fitting portion to ensure the rim fit of the tire. Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim handling during assembly due to an excessively large thickness G2 of the rim fitting portion.

[0098] In addition, Fig. 6, an intersection point Q between a straight line passing through the contact point C2 of the bead core 11 and parallel to the tire transverse direction and an outer wall surface of the rim fitting portion is determined in the tire transverse direction. Furthermore, the thickness W is determined from the contact point C2 of the bead core 11 to the point Q of the rim fitting surface in the tire transverse direction. In this case, the outer diameter ϕ of the thickness Wh and the bead wire 111 (see Fig. 4) Preferably, the thickness Wh of the rim fitting portion is 2.0 ≤ Wh / ϕ ≤ 15.0, and more preferably, the thickness Wh of the rim fitting portion is 2.5 ≤ Wh / ϕ ≤ 10.0. Accordingly, the thickness Wh of the rim fitting portion is made appropriate. That is, the above-mentioned lower limit ensures the thickness Wh of the rim fitting portion to ensure the rim fitting portion of the tire and the durability of the rim fitting portion. Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim handling during assembly due to an excessive thickness Wh of the rim fitting portion.

[0099] Additionally, as in Fig. As shown in FIG. 6, the cushion rubber layer 20 is interposed between the innermost layer of the bead core 11 and the rim cushion rubber 17. The cushion rubber layer 20 is a member having a lower rubber hardness than the rim cushion rubber 17, and includes, for example, the inner liner 18, a bonding rubber (not illustrated) bonding the inner liner 18 to the carcass layer 13, and so on, and does not include a carcass ply. In addition, the cushion rubber layer 20 may be integrated with the inner liner 18 and the bonding rubber, or it may be separate from the inner liner and the bonding rubber (not illustrated). Furthermore, the cushion rubber layer 20 may be made of the same rubber material as the inner liner 18 and the bonding rubber, or of different rubber materials (not illustrated).Furthermore, the cushion rubber layer 20 preferably extends transversely in the tire transverse direction in the range from the contact point C1 to the center point Cm of the bead core 11, preferably from the contact point C1 to the contact point C2. In such a configuration, the cushion rubber layer 20 is disposed between the innermost layer of the bead core 11 and the rim mating surface of the bead portion, thereby increasing the change rates ΔG1, ΔG2, and ΔGm of the rim mating portion to improve the rim mating of the tire. Furthermore, the contact pressure of the rim mating surface against the rim 10 is made uniform.

[0100] In addition, the rubber hardness of the cushion rubber layer 20 is lower than the rubber hardness of the rim cushion rubber 17, preferably by 5 or more, and more preferably by 8 or more. Accordingly, the effect of increasing the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion is appropriately obtained.

[0101] For example, in the Fig. 6, in a cross-sectional view taken in the tire meridian direction, the cushion rubber layer 20 extends from the tire cavity surface to the outer side of the tire in the tire transverse direction along the turned-up portion 132 of the carcass layer 13, and is sandwiched between the bead core 11 and the rim cushion rubber 17. Further, the cushion rubber layer 20 extends beyond the center point Cm in the innermost layer of the bead core 11 to the outermost contact point C2. In addition, an outer end of the cushion rubber layer 20 in the tire transverse direction terminates at the inner side of the tangent line L1 of the bead core 11 in the tire radial direction. Accordingly, the end of the cushion rubber layer 20 does not extend to the outer side surface of the bead core 11 in the tire transverse direction.As a result, the change rates ΔG1, ΔG2 and ΔGm between the bead core 11 and the rim mating surface (particularly the bead base of Bb) are effectively increased, while the rigidity between the bead core 11 and the flange 102 of the rim 10 (see . Fig. 2) is appropriately ensured. However, no such limitation is provided, and the outer end of the cushion rubber layer 20 in the tire transverse direction may extend further to the outer side in the tire radial direction from the tangent line L1 of the bead core 11.

[0102] In addition, Fig. 6, the thicknesses Tc1, Tc2 of the cushion rubber layer 20 between the measurement points C1, P1; C2, P2 of the thicknesses G1, G2 of the rim fitting portion, the ratio Tc2 < Tc1. In other words, the thickness Tc1 of the cushion rubber layer 20 on the bead toe Bt side is preferably greater than the thickness Tc2 of the cushion rubber layer 20 on the bead heel Bh side. Accordingly, the change rate ΔG1 of the rim fitting portion on the bead toe Bt side is greater than the change rate ΔG2 of the rim fitting portion on the bead heel Bh side (ΔG2 < ΔG1), resulting in an improvement in the rim fitting of the tire.

[0103] In addition, as described above, the ratio of the change rates ΔG1, ΔG2 and ΔGm of the rim fitting portion can be adjusted by adjusting the ratio between the thicknesses of the cushion rubber layer 20 between the measuring points C1, P1; C2, P2; Cm, Pm of the thicknesses G1, G2 and Gm of the rim fitting portion.

[0104] Furthermore, an average value of the thicknesses of the cushion rubber layer 20 in the range from the contact point C1 to the contact point C2 in the tire transverse direction is preferably in a range of 0.3 (mm) to 3.0 (mm). Accordingly, the average thickness of the cushion rubber layer 20 is appropriately designed. In other words, the effect of the cushion rubber layer 20 in increasing the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion is appropriately obtained by the above-mentioned lower limit. Furthermore, the upper limit suppresses a decrease in the rigidity of the rim fitting portion of the tire due to an excessive amount of the cushion rubber layer 20.

[0105] In addition, Fig. 6, the thickness G1 of the rim fitting portion on the bead toe Bt side and the thickness Tc1 of the cushion rubber layer 20 preferably have a ratio of 0.03 ≤ Tc1 / G1 ≤ 0.95, and more preferably a ratio of 0.05 ≤ Tc1 / G1 ≤ 0.85. Accordingly, the average thickness of the cushion rubber layer 20 is appropriately designed. That is, the above-mentioned lower limit appropriately ensures the effect of the cushion rubber layer 20 and increases the change rate ΔG1 of the rim fitting portion. In addition, the above-mentioned upper limit ensures the thickness G1 of the rim cushion rubber 17 to ensure the rim fit of the tire.

[0106] In addition, on the tire cavity side, the cushion rubber layer 20 extends from the measuring point on the outside of the bead core 11 in the tire radial direction with the height H1 (see Fig. 2) toward the outside in the tire radial direction preferably over 5 (mm) or more. Shape of the rim mating surface

[0107] Fig. 7 is an explanatory view showing the Fig. 3. This figure illustrates the rim fitting section in the state before rim assembly. In this figure, the same components as in Fig. 3, the same reference numerals are used for the components illustrated, and explanations for them are omitted.

[0108] As in the Fig. 7, a line tangential to the rim mating surface at the intersection point P2 is determined as an extension line L2 of the bead base Bb in a cross-sectional view before rim mounting in the tire meridian direction.

[0109] In this case, an inclination angle α of the extension line L2 of the bead base Bb with respect to the tangent line L1 of the bead core 11 is preferably in a range of 3 (degrees) ≤ α ≤ 15 (degrees), and more preferably in the range of 6 (degrees) ≤ α ≤ 12 (degrees).

[0110] Furthermore, the inclination angle α (degrees) of the extension line L2 from the bead base Bb, the change rate ΔGm (%) of the rim fitting portion, and a nominal tire width WA (dimensionless) preferably have a relationship of 0 (% degrees) ≤ ΔGm × α / WA ≤ 7 (% degrees), and more preferably a relationship of 0.5 (% degrees) ≤ ΔGm × α / WA ≤ 5.0 (% degrees). Accordingly, the ratio ΔGm × α / WA indicating the rim fitting of the tire is made appropriate. In other words, in general, as the nominal tire width WA is larger, the rim fitting of the tire is lower. In addition, as the bead base inclination angle α and the change rate ΔGm of the edge fit portion increase, the fitting pressure against the rim increases to improve the tire's rim fit. Therefore, the above-mentioned lower limit increases the ratio ΔGm × α / WA to improve the tire's rim fit.Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim's assembly processability due to excessive rim fitting pressure. Note that in the case of inclination angle α = 0 (degrees), the inclination angle is ΔGm × α / WA = 0.

[0111] In addition, as described in the Fig. 7 illustrates, in a cross-sectional view in the tire meridian direction, when the bead base Bb has a shape formed by connecting two types of linear portions having different inclination angles to each other (so-called two-stage conical shape), an extension line L2 of the linear portion on the bead heel Bh side of the bead base Bb of the rim mating surface and an extension line L3 of the linear portion on the bead toe Bt side are determined.

[0112] In this case, the inclination angles α, β of the extension lines L2 and L3 of the bead base Bb with respect to the tangent line L1 of the bead core 11 preferably have a relationship of 0 ≤ β / α ≤ 5.0, and more preferably a relationship of 1.8 ≤ β / α ≤ 4.0. Accordingly, the two-stage tapered shape of the bead base Bb is made appropriate. That is, by the above-mentioned lower limit, the effect of improving the rim fit of the tire due to the two-stage tapered shape is appropriately achieved. In addition, the above-mentioned upper limit suppresses the occurrence of a vulcanization defect in the bead base Bb.

[0113] In addition, Fig. 7 an intersection point R of the two types of linear sections of the bead base Bb is determined.

[0114] In this case, a distance Lr from the bead toe Bt to the intersection point R in the tire transverse direction and a distance Lm from the bead toe Bt to the center point Cm in the tire transverse direction preferably have a relationship of 0.50 ≤ Lr / Lm ≤ 4.0, and more preferably a relationship of 0.70 ≤ Lr / Lm ≤ 3.3. Accordingly, the position of the intersection point R is made appropriate, suitably achieving the effect of improving the rim fit of the tire due to the two-stage tapered shape.

[0115] In addition, the Fig. 7 illustrated configuration of the arrangement angles θ1 (see Fig. 4) The wire cross-section at the corner portion on the inner side in the tire radial direction and on the inner side in the tire transverse direction in the wire arrangement structure of the bead core 11 ranges from 130 (degrees) to 140 (degrees). Furthermore, the two types of linear portions of the bead base Bb are connected to each other and form a smooth arc protruding toward the outer side in the tire radial direction. Furthermore, the intersection point R is positioned between the contact point C1 and the center point Cm of the bead core 11.

[0116] In Fig. 7, a distance Dt in the tire radial direction and a distance Wt in the tire transverse direction from the contact point C1 of the bead core 11 to the bead toe Bt are determined. In this case, the distances Dt, Wt, and the thickness G1 from the contact point C1 to the rim mating surface in the tire radial direction preferably have a relationship of 7 (degrees) ≤ arctan {(Dt - G1) / Wt} ≤ 30 (degrees), and more preferably a relationship of 9 (degrees) ≤ arctan {(Dt - G1) / Wt} ≤ 25 (degrees). Accordingly, a gradient of the rim mating surface from the bead core 11 to the bead toe Bt with respect to the tire axial direction is made appropriate. That is, the above-mentioned lower limit ensures the gradient of the rim mating surface to ensure the rim mating of the tire. In addition, the above upper limit suppresses the decrease in the handling ability of the tire rim during assembly caused by an excessive gradient of the rim mating surface.

[0117] The distances Dt, Wt from the contact point C1 to the bead toe Bt are measured in the state before rim mounting. Modified examples

[0118] Fig. 8 to 12 are explanatory views of modified examples of the Fig. 4. These figures are cross-sectional views of the uncured bead core 11 in the radial direction as a single component.

[0119] In the Fig. In the configuration shown in Figure 4, the tangent line L1 to the innermost layer of the bead core 11 is parallel to the tire transverse direction. Therefore, an inclination angle X formed by the tangent line L1 with the tire transverse direction is X = 0 (degrees).

[0120] However, no such limitation is intended, and as in Fig. 8, the bead core 11 is inclined with respect to the tire transverse direction. More specifically, the bead core 11 may be inclined toward the inside on the side of the bead toe Bt in (see Fig. 3) be inclined in the tire radial direction. In such a configuration, the tangent line L1 of the innermost layer of the bead core 11 approaches parallel to the bead base Bb of the rim mating surface. In this case, the inclination angle X of the tangent line L1 with respect to the tire transverse direction is preferably within a range of -10 (degrees) ≤ X ≤ 30 (degrees). Note that the range of the relative inclination angle α of the extension line L2 of the bead base Bb with respect to the tangent line L1 of the bead core 11 is as described above.

[0121] In addition, in the Fig. 4, as described above, the number of wire cross-sections in the order from the innermost layer in the tire radial direction is set to 3 - 4 - 3 - 2 - 1. Therefore, the number of layers of wire cross-sections is 5, and the number of cross-sections in the outermost layer in the tire radial direction is 1.

[0122] In contrast, in the Fig. 9, the number of layers of wire cross-sections is 4, and the number of wire cross-sections is set to 3 - 4 - 3 - 2 in the order from the innermost layer in the tire radial direction. In the configuration shown in Fig. In the configuration illustrated in Figure 10, the number of wire cross-sections is 6, and the number of wire cross-sections is set to 3 - 4 - 5 - 4 - 3 - 2 in the order from the innermost layer in the tire radial direction. As described above, the number of layers of the wire cross-section can be 4 or 6. In addition, the number of wire cross-sections of the outermost layer in the tire radial direction can be 2. In this case, the number of layers of the wire cross-sections on the outer side of the maximum arrangement layer in the tire radial direction (2 in Fig. 9 and Fig. 3 in Fig. 10) greater than the number of layers of the wire cross-sections on the inner side of the maximum arrangement layer in the tire radial direction (1 in Fig. 9 and Fig. 2 in Fig. 10). In addition, the number of wire cross-sections in each layer decreases step by step from the maximum arrangement layer toward the outer side in the tire radial direction.

[0123] In addition, in the Fig. In the configuration illustrated in Figure 4, the number of wire cross-sections in the innermost layer in the tire radial direction is smaller than the number of wire cross-sections in the maximum arrangement layer (the second layer from the innermost layer). Therefore, all the wire cross-sections constituting the wire arrangement structure are arranged in the most densely packed structure. Therefore, the arrangement angles θ1, θ2 of the wire cross-sections at the corner portions on the inner side in the tire radial direction and on the inner and outer sides in the tire transverse direction in the wire arrangement structure are each in a range of 130 (degrees) to 140 (degrees).

[0124] In contrast, in the Fig. 11 and Fig. In the configuration illustrated in Figure 12, the number of layers of wire cross-sections is 5, and the number of wire cross-sections is set to 4 - 4 - 3 - 2 - 1 in the order from the innermost layer in the tire radial direction. Thus, the number of wire cross-sections in the innermost layer is the same as the number of wire cross-sections in the maximum arrangement layer. In addition, in the configuration shown in Fig. 11, the arrangement angles θ1 of the wire cross section at the corner portion on the inner side in the tire radial direction and on the inner side in the tire transverse direction in the wire arrangement structure are acute angles and range from 55 (degrees) to 65 (degrees). On the other hand, the arrangement angle θ2 of the wire cross section at the corner portion on the outer side in the tire transverse direction is obtuse angles and range from 130 (degrees) to 140 (degrees). In addition, in the Fig. 12, the arrangement angles θ1, θ2 of the wire cross sections at the left and right corner portions on the inner side in the tire radial direction in the wire arrangement structure are each substantially rectangular and are in a range of 85 (degrees) to 95 (degrees). In this manner, at least the arrangement angle θ2 of the wire cross section at the corner portion on the outer side in the tire transverse direction is preferably a substantially right angle or an obtuse angle. In the configuration shown in Fig. In the configuration illustrated in Figure 12, the wire cross-sections are arranged in a lattice on the inner side in the tire radial direction of the maximum arrangement layer. Thus, it is sufficient that the wire cross-section with the most densely packed structure is arranged at least in each layer on the outer side of the maximum arrangement layer in the tire radial direction.

[0125] Fig. 13 is an explanatory view of a modified example of the Fig. 2. This figure is the cross-sectional view in the tire meridian direction showing the bead portion of the tire in the state before rim mounting. Fig. 14 is an explanatory view showing a wire arrangement structure of the Fig. 13 illustrated bead core 11. Fig. 15 is an explanatory view showing a modified example of the Fig. 14. Among these figures are Fig. 14 and Fig. 15 Radial cross-sectional views illustrating the uncured bead core 11 as a single component.

[0126] In the Fig. 2, the number of wire cross-sections is set to 3 - 4 - 3 - 2 - 1 in the order from the innermost layer in the tire radial direction (see Fig. 4). Consequently, the arrangement structure of the wire cross-sections has a wedge shape that tapers towards the outer side in the tire radial direction.

[0127] In contrast, in the Fig. 13 illustrated configuration as in Fig. 14 illustrates the number of layers of the wire cross sections 5, and the number of wire cross sections is set to 3-4-5-4-3 in the order from the innermost layer in the tire radial direction. Thus, the arrangement structure of the wire cross sections may have a hexagonal shape and may be symmetrical with respect to the maximum arrangement layer in a height direction.

[0128] In the Fig. In the configuration shown in Figure 15, the number of layers of the wire cross-section is 3, and the number of wire cross-sections is set to 5-5-5 in the order from the innermost layer in the tire radial direction. In this way, the arrangement structure of the wire cross-sections may have a quadrangular shape. Thickness of the tire sidewall

[0129] Fig. 16 is an enlarged view showing a tire side portion of the tire shown in Fig. 1. This figure is an enlarged cross-sectional view in the tire meridian direction at a maximum tire width position A.

[0130] At Fig. 13, a total thickness K1 on the tire side portion at a maximum width position A is preferably in a range of 2.5 (mm) ≤ K1 ≤ 6.5, and more preferably 3.0 (mm) ≤ K1 ≤ 6.0 (mm). Accordingly, the total thickness K1 of the tire side portion is appropriately designed. Specifically, the above-mentioned lower limit ensures the total thickness K1 of the tire side portion to ensure the rolling resistance of the tire. Furthermore, the above-mentioned upper limit ensures a reduction in the weight of the tire.

[0131] The total thickness K1 of the tire side portion is measured as the distance between the tire inner surface and the tire outer surface at the maximum tire width position A in a cross-sectional view in the tire meridian direction.

[0132] Furthermore, a thickness K2 of the sidewall rubber 16 at the maximum width position A is preferably in a range of 0.3 (mm) ≤ K2 ≤ 3.0 (mm), and more preferably in a range of 0.5 (mm) ≤ K2 ≤ 2.5 (mm). Accordingly, the thickness K2 of the sidewall rubber 16 is appropriately designed. Specifically, the above-mentioned lower limit ensures the thickness K2 of the sidewall rubber 16 to ensure the cut resistance of the tire side portion. Furthermore, the above-mentioned upper limit ensures a reduction in the weight of the tire. Configuration with bead filler

[0133] Fig. 17 is a cross-sectional view of a modified example of the Fig. 2. This figure is a cross-sectional view in the tire meridian direction showing the bead portion of the tire in the state before rim mounting.

[0134] In the Fig. 2, as described above, the pneumatic tire 1 does not include a bead filler. Specifically, the rubber occupancy ratio in the closed area X surrounded by the body part 131 and the turned-up portion 132 of the carcass layer 13 is set small, which reduces the weight of the tire. Furthermore, the outer reinforcing rubber 19 is interposed between the turned-up portion 132 of the carcass layer 13 and the rim cushion rubber 17, enhancing the spring characteristics of the bead portion. In addition, the turned-up portion 132 of the carcass layer 13 is locked to the body part 131 by self-contact, and the height H2 in the tire radial direction of the self-contact portion is set to be within a predetermined range to improve the durability of the bead portion.

[0135] In contrast, in the Fig. 17, the pneumatic tire 1 is equipped with a bead filler 12. Furthermore, the bead filler 12 is arranged between the body portion 131 and the turned-up portion 132 of the carcass layer 13. In addition, the turned-up portion 132 of the carcass layer 13 is locked to the body portion 131 by self-contact to form the closed region X. Therefore, the rubber occupancy ratio in the closed region X is set to be much larger than in the configuration shown in Fig. 2. In addition, since the spring characteristics of the bead portion are ensured by the bead filler 12, the outer reinforcing rubber 19 is Fig. 2 omitted. Effects

[0136] As described above, the pneumatic tire 1 includes the bead cores 11 formed by winding one or more bead wires 111 in a ring-like and multiple manner, the carcass layer 13 formed of one or more carcass plies and turned up to be wound around the bead cores 11 and extending between the bead cores 11, and the rim cushion rubbers 17 arranged along the turned-up portions 132 of the carcass layer 13 to form rim fitting surfaces of the bead portions (see Fig. 1 and Fig. 2). In addition, in a cross-sectional view in the tire meridian direction, the bead core 11 has a predetermined wire arrangement structure formed by arranging the wire cross sections of the bead wires 111 (see Fig. 4). In addition, the following are determined in the wire arrangement structure: the tangent line L1, which, from the rim mating surface side, contacts the innermost layer in the tire radial direction and the wire cross-sections on the innermost side and the outermost side in the tire transverse direction; the contact points C1, C2 of the tangent line L1 with respect to the wire cross-sections on the innermost side and the outermost side; the center point Cm of the contact points C1, C2; and the thicknesses G1, G2 and Gm of the contact points C1, C2 and the center point Cm to the rim mating surface in the tire radial direction, respectively (see Fig. 3). In this case, the change rates ΔG1, ΔG2, and ΔGm of the thicknesses G1, G2, and Gm before and after rim installation are in the range of 10 (%) to 60 (%), respectively.

[0137] In such a configuration, the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion of the bead portion are made appropriate. That is, the above-mentioned lower limit ensures the rim fitting pressure to ensure the rim fitting of the tire. This effect is particularly advantageous in the structure that does not contain a bead filler (see Fig. 2). In addition, the above-mentioned upper limit suppresses the deterioration of the tire rim's handling during installation due to excessive rim fitting pressure.

[0138] Furthermore, in the pneumatic tire 1, the turned-up portion 132 of the carcass layer 13 contacts the body portion 131 of the carcass layer 13 to form the closed portion X which surrounds the bead core 11 (see Fig. 2). Furthermore, the rubber coverage density in the closed region X is 15 (%) or less in a cross-sectional view taken in the tire meridian direction. In such a configuration, the rubber coverage ratio in the closed region X surrounded by the body part 131 and the turned-up portion 132 of the carcass layer 13, that is, the rubber volume around the bead core 11, is very low. Accordingly, the bead filler can be omitted to reduce the weight of the tire.

[0139] In the pneumatic tire 1, between the distance Dt in the tire radial direction and the distance Wt in the tire transverse direction from the contact point C1 to the bead toe Bt, and the thickness G1 in the tire radial direction from the contact point C1 to the rim mating surface, there is a relationship of 7 (degrees) ≤ arctan {(Dt - G1) / Wt} ≤ 30 (degrees) (see Fig. 7). Accordingly, it is advantageous to appropriately set a gradient of the rim mating surface with respect to the tire axial direction from the bead core 11 to the bead toe Bt. That is, the above-mentioned lower limit ensures the gradient of the rim mating surface to ensure the rim fit of the tire. Furthermore, the above-mentioned upper limit suppresses the decrease in the handling of the tire rim during assembly caused by a sharp gradient of the rim mating surface.

[0140] In addition, in the pneumatic tire 1, there is a gap between the thickness G2 of the contact point C2 and the rim mating surface in the tire radial direction (see Fig. 3) and the outer diameter ϕ of the bead wire 111 (see Fig. 4) A ratio of 1.3 ≤ G2 / ϕ ≤ 9.5. This can advantageously make the thickness G2 of the rim fitting portion suitable. That is, the above-mentioned lower limit ensures the thickness G2 of the rim fitting portion to ensure the tire's rim fit. Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim's handling during assembly due to an excessive thickness G2 of the rim fitting portion.

[0141] In addition, in the pneumatic tire 1, there is a gap between the thickness Wh in the tire transverse direction from the contact point C2 to the rim mating surface (see Fig. 6), and the outer diameter ϕ of the bead wire 111 (see Fig. 4) A ratio of 2.0 ≤ Wh / ϕ ≤ 15.0. This can advantageously make the thickness Wh of the rim fitting portion suitable. That is, the above-mentioned lower limit ensures the thickness Wh of the rim fitting portion to ensure the rim fit of the tire. Furthermore, the above-mentioned upper limit suppresses the deterioration of the tire rim handling during assembly caused by a large thickness Wh of the rim fitting portion.

[0142] Furthermore, the change rates ΔG1, ΔG2, and ΔGm in the pneumatic tire 1 satisfy the condition |ΔGm - ΔG2| < |ΔG1 - ΔGm|. Accordingly, the relationship between the change rates ΔG1, ΔG2, and ΔGm of the rim fitting portion is advantageously made appropriate to improve the rim fitting of the tire.

[0143] Furthermore, the change rates ΔG1, ΔG2, and ΔGm in the pneumatic tire 1 have a relationship of ΔG2 < ΔGm < ΔG1. In such a configuration, the change rates ΔG1, ΔG2, and ΔGm increase toward the bead toe Bt. This can advantageously improve the tire's rim fit.

[0144] In addition, the pneumatic tire 1 is provided with the cushion rubber layer 20 which has a lower rubber hardness than the rim cushion rubber 17 and which is inserted between the innermost layer of the bead core 11 and the rim cushion rubber 17 (see Fig. 2). In such a configuration, the cushion rubber layer 20 is disposed between the bead core 11 and the rim mating surface, thereby increasing the change rates ΔG1, ΔG2, and ΔGm of the rim mating portion and uniforming the contact pressure of the rim mating surface against the rim 10 to improve the rim fitting.

[0145] Furthermore, in the pneumatic tire 1, the cushion rubber layer 20 extends at least from the contact point C1 of the bead core 11 to the center point Cm in the tire transverse direction (see Fig. 3). Accordingly, the effect of improving the rim fit due to the cushion rubber layer 20 can be effectively obtained.

[0146] In addition, in the pneumatic tire 1, the thicknesses Tc1, Tc2 of the cushion rubber layer 20 between the measuring points C1, P1; C2, P2 and the thicknesses G1, G2 of the rim fitting portion have the relationship Tc2 < Tc1 (see Fig. 6). Consequently, the change rate ΔG1 of the rim fitting portion on the bead toe side Bt is greater than the change rate ΔG2 of the rim fitting portion on the bead heel side Bh (ΔG2 < ΔG1), which advantageously improves the rim fitting of the tire.

[0147] In addition, in the pneumatic tire 1, the thickness G1 of the rim fitting portion and the thickness Tc1 of the cushion rubber layer 20 between the measurement points of the thickness G1 have the relationship 0.03 ≤ Tc1 / G1 ≤ 0.95 (see Fig. 6). Accordingly, the average thickness of the cushion rubber layer 20 is appropriately designed. That is, the above-mentioned lower limit appropriately ensures the effect of the cushion rubber layer 20 and increases the change rate ΔG1 of the rim fit portion. Furthermore, the above-mentioned upper limit ensures the thickness G1 of the rim cushion rubber 17 to ensure the rim fit of the tire.

[0148] In addition, in the pneumatic tire 1, the height Hc2 from the tangent line L1 to the maximum width position of the bead core 11 and the maximum height Hc1 of the bead core 11 have a relationship of 1.10 ≤ (Hc1 - Hc2) / Hc2 ≤ 2.80 (see Fig. 4). Accordingly, the wire arrangement structure of the bead core 11 is advantageously made suitable.

[0149] Furthermore, in the pneumatic tire 1, the arrangement angle θ2 of the wire cross section at a corner portion on the inner side in the tire radial direction and on the outer side in the tire transverse direction in the wire arrangement structure is in a range of 80 (degrees) ≤ θ2 ( Fig. 4). Consequently, disruption of the wire arrangement structure during tire vulcanization is suppressed to advantageously improve the tire's rim fit.

[0150] In addition, the pneumatic tire 1 further includes the outer reinforcing rubbers 19 each disposed between the turned-up portion 132 of the carcass layer 13 and the rim cushion rubber 17 (see Fig. 2). In such a configuration, especially in the above-mentioned configuration without bead filler, the spring characteristics of the bead portions are enhanced by the outer reinforcing rubbers 19, thereby improving the steering stability on dry roads and the durability of the bead portions.

[0151] In addition, in the pneumatic tire 1, the layer having the largest number of wire cross sections in the wire arrangement structure (the second layer from the innermost layer in Fig. 4) is determined as the maximum arrangement layer. In this case, the number of layers of wire cross-sections on the outside of the maximum arrangement layer in the tire radial direction (3 in Fig. 4) greater than the number of layers of the wire cross-section on the inner side of the maximum arrangement layer in the tire radial direction (1 in Fig. 4). In addition, the number of wire cross-sections in each layer on the outside of the maximum arrangement layer in the tire radial direction decreases monotonically from the maximum arrangement layer towards the outside in the tire radial direction (see Fig. 4). As a result, the gap between the joining portion of the body part 131 and the turned-up portion 132 of the carcass layer 13 and the upper portion (the so-called bead crown) on the outer side of the bead core 11 in the tire radial direction becomes smaller, which advantageously improves the durability of the bead portion. In particular, the above-mentioned structure containing no bead filler can advantageously reduce the rubber occupancy ratio in the closed region X. In addition, since the turned-up portion 132 can bend at an obtuse angle at the joining portion with the body part 131, the amount of deflection of the turned-up portion 132 is reduced, which advantageously improves the durability of the bead portion. Example

[0152] Fig. 18 is a table showing results of performance tests of pneumatic tires according to embodiments of the invention. Fig. 19 is an explanatory view illustrating a bead core of a test tire according to a prior art example.

[0153] In the performance tests, a variety of test tires with a tire size of 205 / 55R16 were evaluated for (1) tire dimensions and (2) rim fit.

[0154] (1) The tire mass is calculated as the average of the masses of five test tires with the same structure. The measurement results are expressed as index values ​​and evaluated using the prior art example as the reference value (100). Smaller numerical values ​​for this evaluation indicate that the test tires are lighter, and if the index value is 99 or less, the tire weight can be reduced.

[0155] (2) In the rim fit evaluation, the test tires were mounted on rims with a rim size of 16 × 6.5 J, and an air pressure of 230 (kPa) and a prescribed load of JATMA were applied to the test tires. The test tires were mounted on an SUV (Sport Utility Vehicle) with an engine displacement of 2000 (cc), which was the test vehicle. Then, when the test vehicle completed a predetermined driving route, while gradually reducing the air pressure in the test tire and causing air leakage, the air pressure at that time was measured. The measurement results are expressed as index values ​​and evaluated by determining the prior art example as the reference value (100). In this evaluation, higher numerical values ​​are preferable.

[0156] The test tires in Examples 1 to 13 have the structure that does not contain bead filler (see Fig. 1 and Fig. 2), thereby reducing the weight of the tire. In addition, the thicknesses G1, Gm, and G2 of the rim fitting portion in the state before rim installation have a relationship of G2 < Gm < G1.

[0157] When testing the tires in the prior art example, the bead core 11 in the Fig. 1 and Fig. 2 shown configuration in Fig. 18, and the outer reinforcing rubber 19 is made of the same material as the material of the wheel rim cushion rubber 17, which is to be integrated into the wheel rim cushion rubber 17. In the test tires in Comparative Examples 1 and 2, in the Fig. 1 and Fig. 2, the insulating rubber of the bead core 11 is increased to increase the rubber occupancy ratio in the closed area X.

[0158] As can be seen from the test results, the rim fit of the tire in the test tires of Examples 1 to 13 can be improved while reducing the tire weight. List of reference symbols 1 pneumatic tire 11 Bead core 111 Tire bead wire 12 bead fillers 13 carcass layers 131 body part 132 Turned section 14 Belt layer 141, 142 Cross belt 143 Belt cover 144 Belt edge cover 15 Tread rubber 16 sidewall rubber 17 Wheel rim cushion rubber 18 Inner core 19 External reinforcement rubber 10 rim 101 Bead seat 102 flange

Claims

[1] Pneumatic tyre (1), comprising: a bead core (11) formed from one or more tire bead wires (111) which are annular and wound multiple times; a carcass layer (13) formed from one or more carcass plies, the carcass layer (13) being turned over so as to wrap around the bead core (11) and extend over the bead core (11); a rim cushion rubber (17) arranged along a turned-up portion (132) of the carcass layer (13) to form a rim mating surface of a bead portion, wherein the bead core (11) has a predetermined wire arrangement structure formed by arranging a wire cross section of the tire bead wire (111) in a cross-sectional view in a tire meridian direction, the following is determined in the wire arrangement structure: a tangent line L1 contacting an innermost wire layer in a tire radial direction and the innermost and outermost wire cross sections in a tire transverse direction from one side of the rim mating surface; contact points C1, C2 on the tangent line L1; a center point Cm of the contact points C1, C2; and thicknesses G1, G2 and Gm in the tire radial direction between the contact points C1, C2 and the center point Cm and the rim mating surface, The change rates ΔG1, ΔG2 and ΔGm of the thicknesses G1, G2 and Gm before and after rim mounting are each in a range of 10 (%) to 60 (%); where a layer having a largest number of wire cross-sections in the wire arrangement structure is determined as a maximum arrangement layer, the number of layers of the wire cross-section on the outer side of the maximum arrangement layer in the tire radial direction is greater than the number of layers of the wire cross-section on the inner side of the maximum arrangement layer in the tire radial direction and the number of wire cross-sections in each layer on the outside of the maximum arrangement layer in the tire radial direction decreases monotonically from the maximum arrangement layer towards the outside in the tire radial direction. [2] Pneumatic tire (1) according to claim 1, wherein the bent portion of the carcass layer (13) contacts a body part (131) of the carcass layer (13) to form a closed region (X) around the bead core (11) in a cross-sectional view in the tire meridian direction, and a rubber coverage ratio in the closed region (X) is 15 (%) or less, wherein the rubber coverage ratio in the cross-sectional view in the tire meridian direction is calculated as the ratio of the cross-sectional area of ​​the rubber material in the closed region (X) to the total cross-sectional area of ​​the closed region (X). [3] A pneumatic tire (1) according to claim 1 or 2, wherein a distance Dt in the tire radial direction and a distance Wt in the tire transverse direction from the contact point C1 to a bead toe (Bt), and the thickness G1 in the tire radial direction from the contact point C1 to the rim mating surface satisfy a relationship of 7 (degrees) ≤ arctan {(Dt - G1) / Wt} ≤ 30 (degrees). [4] A pneumatic tire (1) according to any one of claims 1 to 3, wherein the thickness G2 in the tire radial direction from the contact point C2 to the rim mating surface and an outer diameter φ of the bead wire (111) satisfy a relationship of 1.3 ≤ G2 / φ ≤ 9.

5. [5] A pneumatic tire (1) according to any one of claims 1 to 4, wherein a thickness Wh in the tire transverse direction from the contact point C2 to the rim mating surface and an outer diameter φ of the bead wire (111) satisfy a relationship of 2.0 ≤ Wh / φ ≤ 15.

0. [6] A pneumatic tire (1) according to any one of claims 1 to 5, wherein the change rates ΔG1, ΔG2 and ΔGm satisfy a condition |ΔGm - ΔG2| < |ΔG1 - ΔGm|. [7] A pneumatic tire (1) according to claim 6, wherein the change rates ΔG1, ΔG2 and ΔGm satisfy a relationship ΔG2 < ΔGm < ΔG1. [8] A pneumatic tire according to any one of claims 1 to 7, further comprising a cushion rubber layer (20) having a lower rubber hardness than the rim cushion rubber (17), wherein the cushion rubber layer (20) is interposed between the innermost wire layer of the bead core (11) in the tire radial direction and the rim cushion rubber (17). [9] A pneumatic tire according to claim 8, wherein the cushion rubber layer (20) extends at least from the contact point C1 to the center Cm of the bead core (11) in the tire transverse direction. [10] A pneumatic tire (1) according to claim 8 or 9, wherein at the contact points C1, C2, the thicknesses Tc1, Tc2 of the cushion rubber layer (20) between the measuring points C1, P1; C2, P2 of the thicknesses G1, G2 of the rim fitting portion each satisfy a relationship Tc2 < Tc1. [11] A pneumatic tire (1) according to any one of claims 8 to 10, wherein at the contact point C1, the thickness G1 of the rim fitting portion and a thickness Tc1 of the cushion rubber layer (20) between measuring points of the thickness G1 satisfy a relationship of 0.03 ≤ Tc1 / G1 ≤ 0.

95. [12] A pneumatic tire (1) according to any one of claims 1 to 11, wherein a height Hc2 from the tangent line L1 to a maximum width position of the bead core (11) and a maximum height Hc1 of the bead core (11) satisfy a relationship of 1.10 ≤ (Hc1 - Hc2) / Hc2 ≤ 2.

80. [13] The pneumatic tire (1) according to any one of claims 1 to 12, wherein an arrangement angle θ2 of the wire cross section at a corner portion on an inner side in the tire radial direction and on an outer side in the tire transverse direction in the wire arrangement structure is in a range of 80 (degrees) ≤ θ2. [14] Pneumatic tire (1) according to one of claims 1 to 13, further comprising: an outer reinforcing rubber (19) having a higher rubber hardness than the wheel rim cushion rubber (17), wherein the outer reinforcing rubber (19) is inserted between the turned-up layer (132) of the carcass layer (13) and the wheel rim cushion rubber (17).

Images