tire

Abstract

To provide a tire of a small diameter which can improve both of puncture sealing performance and fuel consumption performance.SOLUTION: A tire 1 includes: an inner liner 18 which is positioned at the inner side of a tread part in a tire radial direction; and a sealant layer 19 which is arranged on the surface of the inner liner 18. A tire outer diameter OD[mm] is 200≤OD≤660, and a tire total width SW[mm] is 100≤SW≤400. When average thickness of the sealant layer 19 is Ta[mm] and the tire outer diameter is OD[mm], the following expression is satisfied: 250≤Ta×OD≤4000. When an average width of the sealant layer 19 is W[mm] and the tire total width is SW[mm], the following expression is satisfied: 0.55≤W / SW≤0.85.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire, and more particularly to a small-diameter tire capable of achieving both improved puncture sealing performance and fuel efficiency performance.

Background Art

[0002] In recent years, small-diameter tires have been developed for vehicles equipped with a lowered floor to expand the interior space. In such small-diameter tires, since the rotational inertia is small and the tire weight is also small, a reduction in transportation costs is expected. On the other hand, high load capacity is required for small-diameter tires. As a conventional tire related to such problems, the technique described in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In this type of small-diameter tire, since the rotational inertia is reduced and the tire mass is also reduced, a significant improvement in fuel efficiency performance can be expected. On the other hand, when the tire diameter is reduced and the load is increased, the risk of puncture increases, and the danger at the time of tire failure due to puncture also becomes very high. Therefore, high puncture sealing performance is required.

[0005] An object of the present invention is to provide a small-diameter tire capable of achieving both improved puncture sealing performance and fuel efficiency performance.

Means for Solving the Problems

[0006] To achieve the above objective, the tire according to this invention is a tire having a sealant layer in at least the inner region in the radial direction of the tread portion, wherein the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400, the average thickness Ta [mm] of the sealant layer and the tire outer diameter OD [mm] are in the range of 250 ≤ Ta × OD ≤ 4000, and the average width W [mm] of the sealant layer is in the range of 0.55 ≤ W / SW ≤ 0.85 with respect to the total tire width SW [mm]. [Effects of the Invention]

[0007] In the tire according to this invention, by defining the tire outer diameter OD and the tire total width SW, it is possible to reduce the diameter and improve fuel efficiency. Furthermore, by defining the relationship between the average thickness Ta of the sealant layer and the tire outer diameter OD, and the relationship between the average width W of the sealant layer and the tire total width SW, it is possible to improve puncture sealing performance. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of a tire in the meridian direction, showing a tire according to an embodiment of this invention. [Figure 2] Figure 2 is a magnified view of the tire shown in Figure 1. [Figure 3] Figure 3 is an explanatory diagram showing the laminated structure of the tire belt layer described in Figure 1. [Figure 4] Figure 4 is an enlarged view showing the tire tread section described in Figure 1. [Figure 5] Figure 5 is an enlarged view showing one side of the tread area described in Figure 4. [Figure 6] Figure 6 is an enlarged view showing the sidewall and bead portions of the tire described in Figure 1. [Figure 7] Figure 7 is an enlarged view of the sidewall section shown in Figure 6. [Figure 8] Figure 8 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 9] Figure 9 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 10] Figure 10 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below with reference to the drawings. However, this embodiment does not limit the present invention. Furthermore, the components of this embodiment include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the various modifications described in this embodiment can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0010] [tire] Figure 1 is a cross-sectional view of a tire 1 according to an embodiment of the present invention, taken in the tire meridian direction. The figure shows a cross-sectional view of one side region in the tire radial direction of the tire 1 mounted on the rim 10. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

[0011] In the figure, the tire meridian cross-section is defined as the cross-section obtained when the tire is cut by a plane containing the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width as defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as the direction parallel to the tire rotation axis, and the tire radial direction is defined as the direction perpendicular to the tire rotation axis. Point T is the tire contact point, and point Ac is the tire's widest point.

[0012] The tire 1 has an annular structure centered on the tire rotation axis and comprises a pair of bead cores 11, 11, a pair of bead fillers 12, 12, 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, an inner liner 18, and a sealant layer 19 (see Figure 1).

[0013] The pair of bead cores 11, 11 are formed by annularly and multiply winding one or more bead wires made of steel, and are embedded in the bead portions to constitute the cores of the left and right bead portions. The pair of bead fillers 12, 12 are respectively arranged on the outer periphery in the tire diameter direction of the pair of bead cores 11, 11 to reinforce the bead portions.

[0014] The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged in a toroidal shape between the left and right bead cores 11, 11 to constitute the skeleton of the tire. Also, both ends of the carcass layer 13 are wound back and locked to the outside in the tire width direction so as to wrap the bead core 11 and the bead filler 12. Further, the carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has a cord angle of 80° or more and 100° or less (defined as the inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction).

[0015] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is wound around and arranged on the outer periphery of the carcass layer 13. In the configuration of FIG. 1, the belt plies 141 to 144 are composed of a pair of cross belts 141, 142, a belt cover 143, and a pair of belt edge covers 144, 144.

[0016] The pair of crossed belts 141 and 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and subjecting them to rolling processing, and have a cord angle (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction) of 15° or more and 55° or less in absolute value. Also, the pair of crossed belts 141 and 142 have cord angles with opposite signs to each other, and the longitudinal directions of the belt cords cross each other and are laminated (a so-called cross-ply structure). Further, the pair of crossed belts 141 and 142 are laminated and arranged on the outer side in the tire radial direction of the carcass layer 13.

[0017] The belt cover 143 and the pair of belt edge covers 144, 144 are formed by coating a belt cover cord made of steel or organic fiber material with coating rubber, and have a cord angle of 0° or more and 10° or less in absolute value. Also, the belt cover 143 and the belt edge covers 144 are, for example, strip materials formed by coating one or a plurality of belt cover cords with coating rubber, and this strip material is wound around the outer peripheral surfaces of the crossed belts 141 and 142 a plurality of times in a spiral shape in the tire circumferential direction. Further, the belt cover 143 is arranged to cover the entire area of the crossed belts 141 and 142, and the pair of belt edge covers 144, 144 are arranged to cover the left and right edge portions of the crossed belts 141 and 142 from the outer side in the tire radial direction.

[0018] The tread rubber 15 is arranged on the outer periphery in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute the tread portion of the tire 1. Also, the tread rubber 15 includes a cap tread 151 and an under tread 152.

[0019] The cap tread 151 is made of a rubber material with excellent contact characteristics and weather resistance, and is exposed to the tread surface over the entire tire contact area, forming the outer surface of the tread portion. The cap tread 151 has a rubber hardness Hs_cap of 50 to 80, a modulus M_cap [MPa] at 100% elongation of 1.0 to 4.0, and a loss tangent tanδ_cap of 0.03 to 0.36, preferably a rubber hardness Hs_cap of 58 to 76, a modulus M_cap [MPa] at 100% elongation of 1.5 to 3.2, and a loss tangent tanδ_cap of 0.06 to 0.29.

[0020] Rubber hardness Hs is measured under temperature conditions of 20°C in accordance with JIS K6253.

[0021] The modulus (breaking strength) is measured by a tensile test at a temperature of 20°C using a dumbbell-shaped test specimen, in accordance with JIS K6251 (using a No. 3 dumbbell).

[0022] The loss tangent tanδ is measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of a temperature of 60°C, a shear strain of 10%, an amplitude of ±0.5%, and a frequency of 20Hz.

[0023] The undertread 152 is made of a rubber material with excellent heat resistance and is sandwiched between the cap tread 151 and the belt layer 14 to form the base portion of the tread rubber 15. The undertread 152 has a rubber hardness Hs_ut of 47 to 80, a modulus M_ut [MPa] of 100% elongation of 1.4 to 5.5, and a loss tangent tanδ_ut of 0.02 to 0.23, preferably a rubber hardness Hs_ut of 50 to 65, a modulus M_ut [MPa] of 100% elongation of 1.7 to 3.5, and a loss tangent tanδ_ut of 0.03 to 0.10.

[0024] Furthermore, the difference in rubber hardness Hs_cap-Hs_ut is in the range of 3 to 20, preferably in the range of 5 to 15. Also, the difference in modulus M_cap-M_ut[MPa] is in the range of 0 to 1.4, preferably in the range of 0.1 to 1.0. Furthermore, the difference in loss tangent tanδ_cap-tanδ_ut is in the range of 0 to 0.22, preferably in the range of 0.02 to 0.16.

[0025] A pair of sidewall rubbers 16, 16 are positioned on the outer side of the carcass layer 13 in the tire width direction, respectively, to form the left and right sidewall sections. In the configuration shown in Figure 1, the outer ends of the sidewall rubbers 16 in the tire radial direction are positioned in the lower layer of the tread rubber 15 and sandwiched between the end of the belt layer 14 and the carcass layer 13. However, the configuration is not limited to this; the outer ends of the sidewall rubbers 16 in the tire radial direction may also be positioned in the outer layer of the tread rubber 15 and exposed in the buttress section of the tire (not shown). In this case, a belt cushion (not shown) is sandwiched between the end of the belt layer 14 and the carcass layer 13.

[0026] Furthermore, the sidewall rubber 16 has a rubber hardness Hs_sw of 48 to 65, a modulus M_sw [MPa] of 100% elongation of 1.0 to 2.4, and a loss tangent tanδ_sw of 0.02 to 0.22, preferably a rubber hardness Hs_sw of 50 to 59, a modulus M_sw [MPa] of 100% elongation of 1.2 to 2.2, and a loss tangent tanδ_sw of 0.04 to 0.20.

[0027] The pair of rim cushion rubbers 17, 17 extend from the inside in the tire radial direction to the outside in the tire width direction of the reversal portion of the left and right bead cores 11, 11 and the carcass layer 13, forming the rim fitting surface of the bead portion. In the configuration of Figure 1, the outer end of the rim cushion rubber 17 in the tire radial direction is inserted into the lower layer of the sidewall rubber 16 and is sandwiched between the sidewall rubber 16 and the carcass layer 13.

[0028] The inner liner 18 is an air permeability-preventing layer positioned on the inner surface of the tire and covering the carcass layer 13. It suppresses oxidation of the carcass layer 13 due to exposure and prevents air from leaking out of the tire. The inner liner 18 may be composed of, for example, a rubber composition mainly composed of butyl rubber, or a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer component is blended into a thermoplastic resin.

[0029] The sealant layer 19 is provided on the inner side of the inner liner 18 in the tire radial direction within the tread portion (tread rubber 15). The sealant layer 19 is attached to the inner surface (inner surface 18A of the inner liner 18) of the tire 1 having the structure described above. For example, when a foreign object such as a nail penetrates the tread portion, the sealant material constituting the sealant layer 19 flows into the through-hole, suppressing the decrease in air pressure and enabling the tire to continue running. Details of the inner liner 18 and the sealant layer 19 will be described later.

[0030] Furthermore, in Figure 1, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, preferably in the range of 250 [mm] ≤ OD ≤ 580 [mm]. By applying such small-diameter tires, the load performance improvement effect described later can be significantly obtained. Also, the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400, preferably in the range of 105 [mm] ≤ SW ≤ 340 [mm]. With such small-diameter tires 1, for example, the floor of a small vehicle can be lowered to expand the interior space. In addition, because the rotational inertia is small and the tire weight is small, fuel efficiency is improved and transportation costs are reduced. In particular, when mounted on an in-wheel motor of a vehicle, the load on the motor is effectively reduced.

[0031] The tire outer diameter (OD) is measured when the tire is mounted on a specified rim, subjected to a specified internal pressure, and under no-load conditions.

[0032] The tire's total width SW is measured as the straight-line distance between the sidewalls (including all parts of the tire's sidewall, such as patterns and lettering) when the tire is mounted on a specified rim, subjected to specified internal pressure, and under no-load conditions.

[0033] The specified rim refers to the "applicable rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 [kPa] air pressure, and the specified load is 88 [%] of the maximum load capacity.

[0034] Furthermore, the total tire width SW [mm] is in the range of 0.23 ≤ SW / OD ≤ 0.84 relative to the tire outer diameter OD [mm], and preferably in the range of 0.25 ≤ SW / OD ≤ 0.81.

[0035] Furthermore, it is preferable that the tire outer diameter OD and the tire total width SW satisfy the following formula (1). Here, A1min = -0.0017, A2min = 0.9, A3min = 130, A1max = -0.0019, A2max = 1.4, A3max = 400, and preferably A1min = -0.0018, A2min = 0.9, A3min = 160, A1max = -0.0024, A2max = 1.6, A3max = 362.

[0036]

number

[0037] The above tire 1 is assumed to use a rim 10 having a rim diameter of 5 inches to 16 inches (i.e., 125 mm to 407 mm). Furthermore, the rim diameter RD [mm] is in the range of 0.50 ≤ RD / OD ≤ 0.74 with respect to the tire outer diameter OD [mm], preferably in the range of 0.52 ≤ RD / OD ≤ 0.71. The above lower limit ensures the rim diameter RD, and in particular, ensures the installation space for the in-wheel motor. The above upper limit ensures the tire's internal volume V, which will be described later, and ensures the tire's load capacity.

[0038] Note that the inner diameter of the tire is equal to the rim diameter RD of rim 10.

[0039] Furthermore, the above-mentioned tire 1 is intended for use at an internal pressure higher than specified, specifically between 350 kPa and 1200 kPa, preferably between 500 kPa and 1000 kPa. The lower limit effectively reduces the rolling resistance of the tire, and the upper limit ensures the safety of the internal pressure filling process.

[0040] Furthermore, the above-mentioned tire 1 is intended to be mounted on vehicles that travel at low speeds, such as small shuttle buses. The maximum speed of the vehicle is 100 km / h or less, preferably 80 km / h or less, and more preferably 60 km / h or less. The above-mentioned tire 1 is intended to be mounted on vehicles with 6 to 12 wheels. This ensures that the tire's load capacity is properly utilized.

[0041] Furthermore, the aspect ratio of the tire, that is, the ratio of the tire section height SH [mm] (see Figure 2 described later) to the tire section width [mm] (dimension symbols omitted in the figures: in Figure 1, it is the same as the total tire width SW), is in the range of 0.16 to 0.85, and preferably in the range of 0.19 to 0.82.

[0042] The tire section height SH is half the difference between the tire's outer diameter and its rim diameter, and is measured under no-load conditions with the tire mounted on a specified rim and under specified internal pressure.

[0043] The tire section width is measured as the straight-line distance between the sidewalls (excluding patterns, lettering, etc. on the tire sidewall) when the tire is mounted on a specified rim, subjected to specified internal pressure, and under no-load conditions.

[0044] Furthermore, the tire contact width TW is in the range of 0.75 ≤ TW / SW ≤ 0.95 relative to the total tire width SW, and preferably in the range of 0.80 ≤ TW / SW ≤ 0.92.

[0045] The tire contact width TW is measured as the maximum straight distance in the axial direction of the tire at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state while a load corresponding to a specified load is applied.

[0046] Furthermore, the tire internal volume V [m^3] is within the range of 4.0 ≤ (V / OD) × 10^6 ≤ 60 relative to the tire outer diameter OD [mm], and preferably within the range of 6.0 ≤ (V / OD) × 10^6 ≤ 50. This optimizes the tire internal volume V. Specifically, the above lower limit ensures the tire internal volume and thus the tire's load capacity. In particular, for small-diameter tires, where use at high internal pressure and high loads is anticipated, it is preferable to ensure a sufficient tire internal volume V. The above upper limit suppresses the need for larger tires due to an excessively large tire internal volume V.

[0047] Furthermore, the tire internal volume V [m^3] is in the range of 0.5 ≤ V × RD ≤ 17 with respect to the rim diameter RD [mm], and preferably in the range of 1.0 ≤ V × RD ≤ 15.

[0048] [Beadcore] In Figure 1, as described above, the pair of bead cores 11, 11 are formed by winding one or more bead wires (not shown) made of steel in a ring-like and multi-layered manner. In addition, the pair of bead fillers 12, 12 are arranged on the outer circumference of the pair of bead cores 11, 11 in the radial direction of the tire.

[0049] Furthermore, the strength Tbd[N] of one bead core 11 is in the range of 45≦Tbd / OD≦120 with respect to the tire outer diameter OD[mm], preferably in the range of 50≦Tbd / OD≦110, and more preferably in the range of 60≦Tbd / OD≦105. Also, the strength Tbd[N] of the bead core is in the range of 90≦Tbd / SW≦400 with respect to the total tire width SW[mm], preferably in the range of 110≦Tbd / SW≦350. This ensures that the load capacity of the bead core 11 is properly secured. Specifically, the above lower limits suppress tire deformation when used under high load, ensuring the wear resistance of the tire. In addition, it becomes possible to use the tire at high internal pressure, and the rolling resistance of the tire is reduced. In particular, for small diameter tires, where use at high internal pressure and high load is expected, the above-mentioned wear resistance and reduction of rolling resistance of the tire are significantly obtained. The above upper limit suppresses the deterioration of rolling resistance caused by the increase in mass of the bead core.

[0050] The strength Tbd[N] of the bead core 11 is calculated as the product of the strength per bead wire [N / wire] and the total number of bead wires in the radial cross-sectional view [wires]. The strength of the bead wire is JIS G3510 It is measured by a tensile test at a temperature of 20°C in accordance with the standard.

[0051] Furthermore, it is preferable that the strength Tbd[N] of the bead core 11 satisfies the following formula (2) with respect to the tire outer diameter OD[mm], distance SWD[mm], and rim diameter RD[mm]. Here, B1min=0.26, B2min=10.0, B1max=2.5, B2max=99.0, preferably B1min=0.35, B2min=14.0, B1max=2.5, B2max=99.0, more preferably B1min=0.44, B2min=17.6, B1max=2.5, B2max=99.0, and even more preferably B1min=0.49, B2min=17.9, B1max=2.5, B2max=99.0. Furthermore, it is preferable that B1min=0.0016×P and B2min=0.07×P using the specified internal pressure P[kPa] of the tire.

[0052]

number

[0053] Distance SWD is twice the radial distance from the tire rotation axis (not shown) to the tire's maximum width position Ac, i.e., the diameter of the tire at the maximum width position Ac. It is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0054] The tire's maximum width position, Ac, is defined as the position of the maximum width of the tire section as specified by JATMA.

[0055] Furthermore, in a radial cross-sectional view of one bead core 11, the total cross-sectional area σbd [mm^2] of the bead wire made of the steel described above is in the range of 0.025 ≤ σbd / OD ≤ 0.075 with respect to the tire outer diameter OD [mm], preferably in the range of 0.030 ≤ σbd / OD ≤ 0.065. Also, the total cross-sectional area σbd [mm^2] of the bead wire is in the range of 11 ≤ σbd ≤ 36, preferably in the range of 13 ≤ σbd ≤ 33. This achieves the strong Tbd [N] of the bead core 11 described above.

[0056] The total cross-sectional area σbd [mm^2] of the bead wire is calculated as the sum of the cross-sectional areas of the bead wire in a radial cross-sectional view of one bead core 11.

[0057] For example, in the configuration shown in Figure 1, the bead core 11 has a square shape formed by arranging bead wires (not shown) having a circular cross-section in a grid pattern. However, it is not limited to this, and the bead core 11 may also have a hexagon shape formed by arranging bead wires having a circular cross-section in a close-packed structure (not shown). In addition, any bead wire arrangement structure can be adopted within the scope of what is obvious to those skilled in the art.

[0058] Furthermore, it is preferable that the total cross-sectional area σbd [mm^2] of the bead wire satisfies the following formula (3) with respect to the tire outer diameter OD [mm], distance SWD [mm], and rim diameter RD [mm]. Here, Cmin = 30 and Cmax = 8, preferably Cmin = 25 and Cmax = 10.

[0059]

number

[0060] Furthermore, the total cross-sectional area σbd [mm^2] of the bead wire is in the range of 0.50 ≤ σbd / Nbd ≤ 1.40, and preferably in the range of 0.60 ≤ σbd / Nbd ≤ 1.20, with respect to the total number of cross-sections (i.e., total number of turns) Nbd [wires] of the bead wire in a radial cross-sectional view. That is, the cross-sectional area σbd' [mm^2] of a single bead wire is in the range of 0.50 [mm^2 / wire] or more and 1.40 [mm^2 / wire] or less, and preferably in the range of 0.60 [mm^2 / wire] or more and 1.20 [mm^2 / wire] or less.

[0061] Furthermore, the maximum width Wbd [mm] of one bead core 11 in a radial cross-sectional view (see Figure 2 described later) is in the range of 0.16 ≤ Wbd / σbd ≤ 0.50 with respect to the total cross-sectional area σbd [mm^2] of the bead wire, preferably in the range of 0.20 ≤ Wbd / σbd ≤ 0.40.

[0062] Furthermore, in Figure 1, the distance Dbd [mm] between the centers of gravity of the pair of bead cores 11, 11 is in the range of 0.63 ≤ Dbd / SW ≤ 0.97 with respect to the total tire width SW [mm], preferably in the range of 0.65 ≤ Dbd / SW ≤ 0.95. The lower limit reduces the amount of tire deflection, thereby reducing the rolling resistance of the tire. The upper limit reduces the stress acting on the tire sidewall, thereby suppressing tire failure.

[0063] [Carcass layer] Figure 2 is an enlarged view of tire 1 as shown in Figure 1. This figure shows one side of the tire, with the tire equatorial plane CL as the boundary.

[0064] In the configuration shown in Figure 1, as described above, the carcass layer 13 consists of a single carcass ply and is arranged in a toroidal manner between the left and right bead cores 11, 11. In addition, both ends of the carcass layer 13 are wrapped back outward in the tire width direction and secured to enclose the bead core 11 and the bead filler 12.

[0065] Furthermore, the strength Tcs [N / 50mm] per 50 [mm] width of the carcass ply constituting the carcass layer 13 is in the range of 17 ≤ Tcs / OD ≤ 120 with respect to the tire outer diameter OD [mm], preferably in the range of 20 ≤ Tcs / OD ≤ 120. Also, the strength Tcs [N / 50mm] of the carcass layer 13 is in the range of 30 ≤ Tcs / SW ≤ 260 with respect to the total tire width SW [mm], preferably in the range of 35 ≤ Tcs / SW ≤ 220. This ensures that the load capacity of the carcass layer 13 is properly secured. Specifically, the above lower limits suppress tire deformation when used under high load, ensuring the wear resistance of the tire. In addition, it becomes possible to use the tire at high internal pressure, reducing the rolling resistance of the tire. In particular, for small diameter tires, where use at high internal pressure and high load is expected, the above-mentioned wear resistance and reduction of rolling resistance of the tire are significantly obtained. The above upper limit suppresses the deterioration of rolling resistance caused by the increase in the mass of the carcass layer.

[0066] The strength Tcs [N / 50mm] of the carcass ply is calculated as follows: The carcass ply that spans the left and right bead cores 11, 11 and extends across the entire inner circumference of the tire is defined as the effective carcass ply. The strength Tcs [N / cord] per carcass cord constituting the effective carcass ply is then calculated as the product of the number of carcass cords driven in per 50 [mm] width [cords / 50mm] on the tire's equatorial plane CL and around the entire circumference of the tire. The strength of the carcass cord is JIS L The strength is measured by a tensile test at a temperature of 20°C in accordance with 1017. For example, in a configuration where a single carcass cord is made up of multiple strands twisted together, the strength of the twisted single carcass cord is measured and the strength Tcs of the carcass layer 13 is calculated. Furthermore, in a configuration where the carcass layer 13 has a multilayer structure (not shown) made up of multiple effective carcass plies stacked together, the strength Tcs described above is defined for each of the multiple effective carcass plies.

[0067] For example, in the configuration shown in Figure 1, the carcass layer 13 has a single-layer structure consisting of a single carcass ply (not shown in the figure), and the carcass ply is composed of carcass cords made of steel covered with coated rubber, arranged at a cord angle of 80 [deg] to 100 [deg] with respect to the circumferential direction of the tire (not shown). Furthermore, the above-mentioned steel carcass cords have a cord diameter φcs [mm] in the range of 0.3 ≤ φcs ≤ 1.1 and a number of cords driven in Ecs [cords / 50mm] in the range of 25 ≤ Ecs ≤ 80, thereby achieving the above-mentioned strength Tcs [N / 50mm] of the carcass layer 13. In addition, the carcass cords are made by twisting together multiple strands, and the diameter of the strands φcss [mm] is in the range of 0.12 ≤ φcss ≤ 0.24, preferably in the range of 0.14 ≤ φcss ≤ 0.22.

[0068] Furthermore, the carcass ply may be composed of a carcass cord made of organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) coated with a rubber coating. In this case, the carcass cord made of the organic fiber material has a cord diameter φcs [mm] in the range of 0.6 ≤ φcs ≤ 0.9 and a number of strands Ecs [strands / 50mm] in the range of 40 ≤ Ecs ≤ 70, thereby achieving the above-mentioned strength Tcs [N / 50mm] of the carcass layer 13. In addition, carcass cords made of high-strength organic fiber material such as nylon, aramid, or hybrids can be used within the scope of what is obvious to those skilled in the art.

[0069] Furthermore, the carcass layer 13 may have a multilayer structure consisting of multiple, for example, two layers of carcass ply (not shown). This can effectively increase the load capacity of the tire.

[0070] Furthermore, the total strength TTcs [N / 50mm] of the carcass layer 13 is in the range of 300 ≤ TTcs / OD ≤ 3500 with respect to the tire outer diameter OD [mm], preferably in the range of 400 ≤ TTcs / OD ≤ 3000. This ensures the overall load capacity of the carcass layer 13.

[0071] The total strength TTcs [N / 50mm] of the carcass layer 13 is calculated as the sum of the strength Tcs [N / 50mm] of the effective carcass plies described above. Therefore, the total strength TTcs [N / 50mm] of the carcass layer 13 increases with an increase in the strength Tcs [N / 50mm] of each carcass ply, the number of layers of carcass plies, and the circumference of the carcass plies.

[0072] Furthermore, it is preferable that the total strength TTcs [N / 50mm] of the carcass layer 13 satisfies the following formula (4) with respect to the tire outer diameter OD [mm] and distance SWD [mm]. Here, Dmin = 2.2 and Dmax = 40, preferably Dmin = 4.3 and Dmax = 40, more preferably Dmin = 6.5 and Dmax = 40, and even more preferably Dmin = 8.7 and Dmax = 40. Furthermore, it is preferable that Dmin = 0.02 × P using the specified internal pressure P [kPa] of the tire.

[0073]

number

[0074] Furthermore, in the configuration shown in Figure 1, the carcass layer 13 has a main body portion 131 that extends along the inner surface of the tire, and a winding portion 132 that is wound outward in the tire width direction so as to enclose the bead core 11 and extends in the tire radial direction. Also, in Figure 2, the radial height Hcs [mm] from the measurement point of the rim diameter RD to the end of the winding portion 132 of the carcass layer 13 is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 with respect to the tire cross-sectional height SH [mm], preferably in the range of 0.55 ≤ Hcs / SH ≤ 0.75. This optimizes the radial height Hcs of the winding portion 132 of the carcass layer 13. Specifically, the above lower limit ensures the load capacity of the tire side, and the above upper limit suppresses the deterioration of rolling resistance caused by the increase in mass of the carcass layer.

[0075] The radial height Hcs [mm] of the winding portion 132 of the carcass layer 13 is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0076] For example, in the configuration of FIG. 2, the radially outer end (reference numeral omitted in the figure) of the winding portion 132 of the carcass layer 13 is in the region between the tire maximum width position Ac and the end of the belt layer 14 (point Au to be described later), and more specifically, it is in the region up to the radial position Au' which is 70[%] of the distance Hu to be described later from the tire maximum width position Ac. At this time, the contact height Hcs' [mm] between the main body portion 131 and the winding portion 132 of the carcass layer 13 is in the range of 0.07 ≦ Hcs' / SH with respect to the tire section height SH [mm], and preferably in the range of 0.15 ≦ Hcs' / SH. Thereby, the load capacity of the tire side portion is effectively increased. The upper limit of the ratio Hcs' / SH is not particularly limited, but is restricted by the relationship Hcs' < Hcs with respect to the radial height Hcs of the winding portion 132 of the carcass layer 13.

[0077] The contact height Hcs' of the carcass layer 13 is the extending length in the tire radial direction of the region where the main body portion 131 and the winding portion 132 contact each other, and is measured in a non-loaded state while mounting the tire on a specified rim and applying a specified internal pressure.

[0078] In addition, not limited to the above, due to the carcass layer 13 having a so-called rotor turn-up structure, the end of the winding portion 132 of the carcass layer 13 may be arranged in the region between the tire maximum width position Ac and the bead core (not shown).

[0079] [Belt layer] FIG. 3 is an explanatory view showing the laminated structure of the belt layer of the tire 1 described in FIG. 1. In the figure, the thin lines attached to each belt ply 141 to 144 schematically show the arrangement configuration of the belt cords.

[0080] In the configuration of FIG. 1, as described above, the belt layer 14 is formed by laminating a plurality of belt plies 141 to 144. Further, as shown in FIG. 3, these belt plies 141 to 144 are composed of a pair of cross belts 141, 142, a belt cover 143, and a pair of belt edge covers 144, 144.

[0081] In this case, the strength Tbt [N / 50mm] per 50 [mm] width of each of the pair of cross belts 141 and 142 is in the range of 25 ≤ Tbt / OD ≤ 250 with respect to the tire outer diameter OD [mm], preferably in the range of 30 ≤ Tbt / OD ≤ 230. Furthermore, the strength Tbt [N / 50mm] of the cross belts 141 and 142 is in the range of 45 ≤ Tbt / SW ≤ 500 with respect to the total tire width SW [mm], preferably in the range of 50 ≤ Tbt / SW ≤ 450. This ensures that the load capacity of each of the pair of cross belts 141 and 142 is properly secured. Specifically, the above lower limits suppress tire deformation when used under high load, ensuring the tire's wear resistance. In addition, it becomes possible to use the tire at high internal pressure, reducing the tire's rolling resistance. In particular, with small-diameter tires, where high internal pressure and high loads are expected, the aforementioned wear resistance and reduction in rolling resistance of the tire are significantly improved. The above upper limit suppresses the deterioration of rolling resistance caused by the increase in mass of the cross belt.

[0082] The strength Tbt [N / 50mm] of the belt ply is calculated as follows: Specifically, the belt ply extending over 80% of the tire contact width TW (i.e., the central part of the tire contact area) centered on the tire equatorial plane CL is defined as the effective belt ply. The strength Tbt [N / 50mm] of the belt ply is calculated by multiplying the strength per belt cord [N / cord] constituting the effective belt ply by the number of belt cords driven in per 50mm width in the aforementioned 80% of the tire contact width TW region [cords]. The strength of the belt cord is defined in JIS standards. L It is measured by a tensile test at a temperature of 20°C in accordance with 1017. For example, in a configuration where one belt cord is made up of multiple strands twisted together, the strength of the twisted single belt cord is measured and the strength Tbt of the belt ply is calculated. Also, if the belt layer 14 has multiple effective belt In a configuration consisting of stacked plies (see Figure 1), multiple effective beltThe above-described strong Tbt is defined for each ply. For example, in the configuration of Figure 1, the pair of cross belts 141, 142 and belt cover 143 correspond to the effective belt plies.

[0083] For example, in the configuration shown in Figure 3, a pair of cross belts 141 and 142 are constructed by arranging steel belt cords covered with coated rubber at a cord angle (dimension symbols omitted in the figure) of 15 degrees to 55 degrees relative to the circumferential direction of the tire. Furthermore, the steel belt cords have a cord diameter φbt [mm] in the range of 0.50 ≤ φbt ≤ 1.80 and a number of cords Ebt [cords / 50 mm] in the range of 15 ≤ Ebt ≤ 60, thereby achieving a strong Tbt [N / 50 mm] for the cross belts 141 and 142. In addition, the cord diameter φbt [mm] and the number of cords Ebt [cords / 50 mm] are preferably in the ranges of 0.55 ≤ φbt ≤ 1.60 and 17 ≤ Ebt ≤ 50, and more preferably in the ranges of 0.60 ≤ φbt ≤ 1.30 and 20 ≤ Ebt ≤ 40. Furthermore, the belt cord is made up of multiple strands twisted together, and the diameter of the strands φbts [mm] is in the range of 0.16 ≤ φbts ≤ 0.43, preferably in the range of 0.21 ≤ φbts ≤ 0.39.

[0084] Furthermore, the cross belts 141 and 142 may also be constructed from belt cords made of organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) coated with coated rubber. In this case, the belt cord made of the organic fiber material has a cord diameter φbt [mm] in the range of 0.50 ≤ φbt ≤ 0.90 and a number of strands Ebt [strands / 50mm] in the range of 30 ≤ Ebt ≤ 65, thereby achieving the above-mentioned strength Tbt [N / 50mm] of the cross belts 141 and 142. In addition, belt cords made of high-strength organic fiber material such as nylon, aramid, or hybrids can be used within the scope of what is obvious to those skilled in the art.

[0085] Furthermore, the belt layer 14 may have an additional belt (not shown). Such an additional belt may be, for example, (1) a third cross belt, constructed by covering a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling it, and having a cord angle of 15 [deg] to 55 [deg] in absolute value, or (2) a so-called high-angle belt, constructed by covering a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling it, and having a cord angle of 45 [deg] to 70 [deg] in absolute value, preferably 54 [deg] to 68 [deg] in absolute value. The additional belt may also be positioned (a) between a pair of cross belts 141, 142 and the carcass layer 13, (b) between a pair of cross belts 141, 142, or (c) radially outside the pair of cross belts 141, 142 (not shown). This improves the load capacity of the belt layer 14.

[0086] Furthermore, the total strength TTbt [N / 50mm] of the belt layer 14 is in the range of 70 ≤ TTbt / OD ≤ 750 with respect to the tire outer diameter OD [mm], preferably in the range of 90 ≤ TTbt / OD ≤ 690, more preferably in the range of 110 ≤ TTbt / OD ≤ 690, and even more preferably in the range of 120 ≤ TTbt / OD ≤ 690. This ensures the overall load capacity of the belt layer 14. Moreover, it is preferable that 0.16 × P ≤ TTbt / OD is met using the specified internal pressure P [kPa] of the tire.

[0087] The total strength TTbt [N / 50mm] of the belt layer 14 is calculated as the sum of the strength Tbt [N / 50mm] of the effective belt plies (a pair of cross belts 141, 142 and belt cover 143 in Figure 1). Therefore, the total strength TTbt [N / 50mm] of the belt layer 14 increases with an increase in the strength Tbt [N / 50mm] of each belt ply, the number of belt plies stacked, and so on.

[0088] Furthermore, the width Wb1 [mm] of the widest cross belt (in Figure 3, the inner diameter cross belt 141) of the pair of cross belts 141 and 142 (including the additional belt in the configuration with the additional belt described above; not shown) is in the range of 1.00 ≤ Wb1 / Wb2 ≤ 1.40 relative to the width Wb2 [mm] of the narrowest cross belt (in Figure 3, the outer diameter cross belt 142), preferably in the range of 1.10 ≤ Wb1 / Wb2 ≤ 1.35. Also, the width Wb2 [mm] of the narrowest cross belt is in the range of 0.61 ≤ Wb2 / SW ≤ 0.96 relative to the total tire width SW [mm], preferably in the range of 0.70 ≤ Wb2 / SW ≤ 0.94. The above lower limits ensure the width of the belt ply, optimize the contact pressure distribution in the tire contact area, and ensure the tire's resistance to uneven wear. The above upper limit reduces distortion at the ends of the belt ply during tire rolling, and suppresses separation of the surrounding rubber at the ends of the belt ply.

[0089] The width of the belt ply is the distance between the left and right ends of each belt ply in the tire rotation axis direction, and is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0090] Furthermore, the width Wb1 [mm] of the widest crossing belt (in Figure 3, the inner diameter crossing belt 141) of the pair of crossing belts 141 and 142 (including the additional belt in the configuration with the additional belt described above; not shown) is in the range of 0.85 ≤ Wb1 / TW ≤ 1.23 with respect to the tire contact width TW [mm], preferably in the range of 0.90 ≤ Wb1 / TW ≤ 1.20.

[0091] For example, in the configurations shown in Figures 1 to 3, a wide cross belt 141 is positioned in the innermost layer in the radial direction of the tire, and a narrow cross belt 142 is positioned radially outside the wide cross belt 141. A belt cover 143 is positioned radially outside the narrow cross belt 142, covering the entirety of both the pair of cross belts 141 and 142. A pair of belt edge covers 144, 144 are positioned radially outside the belt cover 143, spaced apart from each other, covering the left and right edges of the pair of cross belts 141 and 142, respectively.

[0092] [Tread profile and tread gauge] Figure 4 is an enlarged view showing the tread portion of tire 1 as described in Figure 1.

[0093] In Figure 4, the tread profile drop DA [mm] at the tire contact edge T, the tire contact width TW [mm], and the tire outer diameter OD [mm] have a relationship of 0.025 ≤ TW / (DA × OD) ≤ 0.400, preferably 0.030 ≤ TW / (DA × OD) ≤ 0.300. Furthermore, the tread profile drop DA [mm] at the tire contact edge T has a relationship of 0.008 ≤ DA / TW ≤ 0.060 with respect to the tire contact width TW [mm], preferably 0.013 ≤ DA / TW ≤ 0.050. This optimizes the drop angle of the tread shoulder region (defined as the ratio DA / (TW / 2)), ensuring the tread's load capacity is properly maintained. Specifically, the above lower limit ensures the drop angle of the tread shoulder region, suppressing a decrease in wear life caused by excessive contact pressure in the tread shoulder region. The above upper limit ensures that the tire contact area becomes flat and the contact pressure is uniform, thereby ensuring the tire's wear resistance. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above configuration can effectively optimize the contact pressure distribution in the tire contact area.

[0094] The drop amount DA is the radial distance of the tire from the intersection point C1 of the tire's equatorial plane CL and the tread profile in a cross-sectional view along the tire's meridian direction to the tire's contact edge T. It is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0095] The tire profile is the contour line of the tire in a cross-sectional view along the tire meridian, and is measured using a laser profiler. For example, a tire profile measuring device (manufactured by Matsuo Co., Ltd.) is used as a laser profiler.

[0096] Furthermore, it is preferable that the amount of tread profile drop DA [mm] at the tire contact edge T satisfies the following formula (5) with respect to the tire outer diameter OD [mm] and tire total width SW [mm]. Here, Emin = 3.5 and Emax = 17, preferably Emin = 3.8 and Emax = 13, and even more preferably Emin = 4.0 and Emax = 9.

[0097]

number

[0098] Furthermore, in Figure 4, we define point C1 on the tread profile at the tire equatorial plane CL, and a pair of points C2, C2 on the tread profile at a distance of 1 / 4 of the tire contact width TW from the tire equatorial plane CL.

[0099] At this time, the radius of curvature TRc [mm] of the arc passing through point C1 and the pair of points C2 is in the range of 0.15 ≤ TRc / OD ≤ 15 with respect to the tire outer diameter OD [mm], preferably in the range of 0.18 ≤ TRc / OD ≤ 12. Furthermore, the radius of curvature TRc [mm] of the arc is in the range of 30 ≤ TRc ≤ 3000, preferably in the range of 50 ≤ TRc ≤ 2800, and even more preferably in the range of 80 ≤ TRc ≤ 2500. This ensures that the load capacity of the tread is properly secured. Specifically, the lower limit makes the center region of the tread flat, equalizing the contact pressure in the tire contact area and ensuring the wear resistance of the tire. The upper limit suppresses the reduction in wear life caused by excessive contact pressure in the shoulder region of the tread. In particular, small diameter tires are expected to be used under high internal pressure and high load, so the effect of equalizing the contact pressure under such usage conditions is effectively obtained.

[0100] The radius of curvature of the arc is measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0101] Furthermore, in Figure 4, the radius of curvature TRw [mm] of the arc passing through point C1 on the tire equatorial plane CL and the left and right tire contact edges T, is in the range of 0.30 ≤ TRw / OD ≤ 16 with respect to the tire outer diameter OD [mm], preferably in the range of 0.35 ≤ TRw / OD ≤ 11. Also, the radius of curvature TRw [mm] of the arc is in the range of 150 ≤ TRw ≤ 2800, preferably in the range of 200 ≤ TRw ≤ 2500. This ensures that the load capacity of the tread is properly secured. Specifically, the lower limit ensures that the entire tire contact area is flat and the contact pressure is uniform, thereby ensuring the wear resistance of the tire. The upper limit suppresses the reduction in wear life caused by excessive contact pressure in the tread shoulder area. In particular, small diameter tires are expected to be used under high internal pressure and high load, so the above configuration can effectively optimize the contact pressure distribution in the tire contact area.

[0102] Furthermore, the radius of curvature TRw [mm] of the first arc passing through points C1 and C2 is in the range of 0.50 ≤ TRw / TRc ≤ 1.00, preferably in the range of 0.60 ≤ TRw / TRc ≤ 0.95, and more preferably in the range of 0.70 ≤ TRw / TRc ≤ 0.90, relative to the radius of curvature TRw [mm] of the second arc passing through point C1 and the tire contact edge T. This optimizes the tire's contact shape. Specifically, the lower limit distributes the contact pressure in the center region of the tread, improving the tire's wear life. The upper limit suppresses the reduction in wear life caused by excessive contact pressure in the shoulder region of the tread.

[0103] Furthermore, in Figure 4, we define point B1 on the carcass layer 13 in the tire equatorial plane CL, the left and right tire contact points T, and the feet B2, B2 of the perpendiculars drawn from T to the carcass layer 13.

[0104] At this time, the radius of curvature CRw of the arc passing through point B1 and the pair of points B2, B2 is in the range of 0.35 ≤ CRw / TRw ≤ 1.10, preferably in the range of 0.40 ≤ CRw / TRw ≤ 1.00, and more preferably in the range of 0.45 ≤ CRw / TRw ≤ 0.92, with respect to the radius of curvature TRw of the arc passing through point C1 and the tire contact edges T, T. Furthermore, the radius of curvature CRw [mm] is in the range of 100 ≤ CRw ≤ 2500, preferably in the range of 120 ≤ CRw ≤ 2200. This further optimizes the tire contact shape. Specifically, the lower limit suppresses the decrease in wear life caused by the increase in rubber gauge in the tread shoulder area. The upper limit ensures the wear life in the tread center area.

[0105] Figure 5 is an enlarged view showing one side of the tread area described in Figure 4.

[0106] In the configuration shown in Figure 1, as described above, the belt layer 14 has a pair of cross belts 141 and 142, and the tread rubber 15 has a cap tread 151 and an under tread 152.

[0107] Furthermore, in Figure 5, the distance Tce [mm] from the tread profile at the tire equatorial plane CL to the outer surface of the wide cross belt 141 has a relationship of 0.008 ≤ Tce / OD ≤ 0.13 with respect to the tire outer diameter OD [mm], preferably 0.012 ≤ Tce / OD ≤ 0.10, and more preferably 0.015 ≤ Tce / OD ≤ 0.07. Also, the distance Tce [mm] is in the range of 5 ≤ Tce ≤ 25, preferably 7 ≤ Tce ≤ 20. This ensures that the load capacity of the tread portion is properly secured. Specifically, the above lower limit suppresses tire deformation when used under high load, ensuring the wear resistance of the tire. In particular, for small diameter tires, where use under high internal pressure and high load is expected, the above wear resistance is significantly improved. The above upper limit suppresses the deterioration of rolling resistance caused by the increase in the mass of the tread rubber.

[0108] The distance Tce is measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0109] The outer circumferential surface of the belt ply is defined as the radially outer circumferential surface of the entire belt ply, which consists of the belt cord and the coating rubber.

[0110] Furthermore, it is preferable that the distance Tce [mm] from the tread profile at the tire equatorial plane CL to the outer surface of the wide cross belt 141 satisfies the following formula (6) with respect to the tire outer diameter OD [mm]. Here, Fmin = 35 and Fmax = 207, preferably Fmin = 42 and Fmax = 202.

[0111]

number

[0112] Furthermore, the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer surface of the wide cross belt 141 is in the range of 0.60 ≤ Tsh / Tce ≤ 1.70, preferably in the range of 1.01 ≤ Tsh / Tce ≤ 1.55, and more preferably in the range of 1.10 ≤ Tsh / Tce ≤ 1.50, relative to the distance Tce [mm] at the tire equatorial plane CL. The above lower limit ensures a tread gauge in the shoulder region, thereby suppressing repeated deformation of the tire during tire rolling and ensuring the tire's wear resistance. Also, the above upper limit ensures a tread gauge in the center region, thereby suppressing tire deformation during high-load use, which is characteristic of small-diameter tires, and ensuring the tire's wear resistance.

[0113] Distance Tsh is measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state. Furthermore, if there is no wide cross belt directly beneath the tire contact edge T, distance Tsh is measured as the distance from the tread profile to a virtual line extending the outer circumference of the belt ply.

[0114] Furthermore, it is preferable that the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer surface of the wide cross belt 141 satisfies the following formula (7) with respect to the distance Tce [mm] at the tire equatorial plane CL. Here, Gmin = 0.36 and Gmax = 0.72, preferably Gmin = 0.37 and Gmax = 0.71, and more preferably Gmin = 0.38 and Gmax = 0.70.

[0115]

number

[0116] Furthermore, in Figure 5, a section with a width ΔTW of 10% of the tire contact width TW is defined. In this case, the ratio of the maximum and minimum values ​​of the rubber gauge of the tread rubber 15 in any section of the tire contact area is in the range of 0% to 40%, preferably in the range of 0% to 20%. With this configuration, the amount of change in the rubber gauge of the tread rubber 15 in any section of the tire contact area (particularly the section including the ends of the belt plies 141 to 144) is set to be small, so the contact pressure distribution in the tire width direction becomes smoother, and the wear resistance performance of the tire is improved.

[0117] The rubber gauge of the tread rubber 15 is defined as the distance from the tread profile to the inner surface of the tread rubber 15 (in Figure 5, the distance from the outer surface of the cap tread 151 to the inner surface of the under tread 152). Therefore, the grooves formed on the tread surface are excluded when measuring the rubber gauge of the tread rubber 15.

[0118] Furthermore, in Figure 5, the rubber gauge UTce of the undertread 152 at the tire equatorial plane CL is in the range of 0.04 ≤ UTce / Tce ≤ 0.60 with respect to the distance Tce at the tire equatorial plane CL, and preferably in the range of 0.06 ≤ UTce / Tce ≤ 0.50. This optimizes the rubber gauge UTce of the undertread 152.

[0119] Furthermore, the distance Tsh at the tire contact end T is in the range of 1.50 ≤ Tsh / Tu ≤ 6.90, preferably in the range of 2.00 ≤ Tsh / Tu ≤ 6.50, with respect to the rubber gauge Tu [mm] from the end of the wide cross belt 141 to the outer surface of the carcass layer 13. This optimizes the profile of the carcass layer 13 and optimizes the tension of the carcass layer 13. Specifically, the lower limit ensures the tension of the carcass layer and the tread gauge in the shoulder region, thereby suppressing repeated deformation of the tire during tire rolling and ensuring the tire's wear resistance. The upper limit ensures the rubber gauge near the end of the belt ply, thereby suppressing separation of the surrounding rubber of the belt ply.

[0120] The rubber gauge Tu is measured in effect as a gauge of the rubber member (sidewall rubber 16 in Figure 5) inserted between the end of the wide cross belt 141 and the carcass layer 13.

[0121] The outer circumferential surface of the carcass layer 13 is defined as the radially outer circumferential surface of the carcass ply, which consists of carcass cords and coating rubber. Furthermore, if the carcass layer 13 has a multilayer structure consisting of multiple carcass ply (not shown), the outer circumferential surface of the outermost carcass ply constitutes the outer circumferential surface of the carcass layer 13. In addition, if the winding portion 132 of the carcass layer 13 (see Figure 1) exists between the end of the wide cross belt 141 and the carcass layer 13 (not shown), the outer circumferential surface of this winding portion 132 constitutes the outer circumferential surface of the carcass layer 13.

[0122] For example, in the configuration shown in Figure 5, the sidewall rubber 16 is inserted between the end of the wide cross belt 141 and the carcass layer 13, forming a rubber gauge Tu between the end of the wide cross belt 141 and the carcass layer 13. However, this is not the only option; for example, a belt cushion may be inserted between the end of the wide cross belt 141 and the carcass layer 13 instead of the sidewall rubber 16 (not shown). Furthermore, the inserted rubber member has a rubber hardness Hs_sp of 46 to 67, a modulus M_sp [MPa] at 100% elongation of 1.0 to 3.5, and a loss tangent tanδ_sp of 0.02 to 0.22, preferably a rubber hardness Hs_sp of 48 to 63, a modulus M_sp [MPa] at 100% elongation of 1.2 to 3.2, and a loss tangent tanδ_sp of 0.04 to 0.20.

[0123] Furthermore, in the configuration shown in Figure 1, the tire 1 has a tread surface comprising a plurality of circumferential main grooves 21-23 (see Figure 5) extending in the circumferential direction of the tire, and land areas (notation omitted in the figure) partitioned by these circumferential main grooves 21-23. The main grooves are defined as grooves that have a wear indicator display requirement as stipulated by JATMA.

[0124] At this time, as shown in Figure 5, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the multiple circumferential main grooves 21 to 23 is in the range of 0.50 ≤ Gd1 / Gce ≤ 1.00 with respect to the rubber gauge Gce [mm] of the tread rubber 15, preferably in the range of 0.55 ≤ Gd1 / Gce ≤ 0.98. This ensures the wear resistance performance of the tire. Specifically, the lower limit distributes the contact pressure in the center area of ​​the tread, improving the tire's wear life. The upper limit ensures the rigidity of the ground portion, and also ensures the rubber gauge from the groove bottom of the circumferential main groove 21 to the belt layer.

[0125] The circumferential main groove closest to the tire's equatorial plane CL is defined as the circumferential main groove 21 (see Figure 5) located on the tire's equatorial plane CL. If there is no circumferential main groove on the tire's equatorial plane CL (not shown), it is defined as the circumferential main groove closest to the tire's equatorial plane CL.

[0126] Further, it is preferable that the above ratio Gd1 / Gce satisfies the following mathematical formula (8) with respect to the tire outer diameter OD [mm]. Here, Hmin = 0.10, Hmax = 0.60, preferably Hmin = 0.12, Hmax = 0.50, and more preferably Hmin = 0.14, Hmax = 0.40.

[0127]

Number

[0128] Further, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the plurality of circumferential main grooves 21 to 23 is deeper than the groove depths Gd2 [mm] and Gd3 [mm] of the other circumferential main grooves 22 and 23 (Gd2 < Gd1, Gd3 < Gd1). Specifically, when the region from the tire equatorial plane CL to the tire ground contact end T is bisected in the tire width direction, the groove depth Gd1 of the circumferential main groove (reference numerals omitted in the figure) closest to the tire equatorial plane CL is in the range of 1.00 times or more and 2.50 times or less, preferably 1.00 times or more and 2.00 times or less, and more preferably 1.00 times or more and 1.80 times or less, with respect to the maximum value of the groove depths Gd2 and Gd3 of the other circumferential main grooves (reference numerals omitted in the figure) in the region on the tire ground contact end T side. With the above lower limit, the ground contact pressure in the tread center region is dispersed, and the wear resistance performance of the tire is improved. With the above upper limit, uneven wear caused by an excessive ground contact pressure difference between the tread center region and the shoulder region is suppressed.

[0129] [Side Profile and Side Gauge] FIG. 6 is an enlarged view showing the side fall portion and the bead portion of the tire 1 described in FIG. 1. FIG. 7 is an enlarged view showing the sidewall portion described in FIG. 6.

[0130] In Figure 6, we define point Au on the side profile, which is at the same position in the tire radial direction relative to the end of the innermost layer of the belt layer 14 (in Figure 6, the inner diameter cross belt 141), and point Al on the side profile, which is at the same position in the tire radial direction relative to the radially outer end of the bead core 11. We also define the tire radial distance Hu from the tire maximum width position Ac to point Au, and the tire radial distance Hl from the tire maximum width position Ac to point Al. Furthermore, we define point Au' on the side profile, which is at a radial position 70% of the distance Hu from the tire maximum width position Ac, and point Al' on the side profile, which is at a radial position 70% of the distance Hl from the tire maximum width position Ac.

[0131] At this time, the sum of distance Hu[mm] and distance Hl[mm] is in the range of 0.45≦(Hu+Hl) / SH≦0.90 with respect to the tire cross-sectional height SH[mm] (see Figure 2), preferably in the range of 0.50≦(Hu+Hl) / SH≦0.85. This optimizes the radial distance from the belt layer 14 to the bead core 11. Specifically, the above lower limit ensures a deformable area of ​​the tire sidewall, suppressing failures of the tire sidewall (for example, separation of the rubber material at the radially outer end of the bead filler 12). The above upper limit reduces the amount of deflection of the tire sidewall during tire rolling, thereby reducing the tire's rolling resistance.

[0132] Distances Hu and Hl are measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0133] Furthermore, it is preferable that the sum of distances Hu[mm] and Hl[mm] satisfies the following formula (9) with respect to the tire outer diameter OD (Figure 1), tire section height SH[mm] (see Figure 2), and the radius of curvature RSc[mm] of the arc passing through the tire maximum width position Ac, point Au', and point Al'. Here, I1min=0.06, I1max=0.20, and I2=0.70, and preferably I1min=0.09, I1max=0.20, and I2=0.65.

[0134]

number

[0135] The radius of curvature RSc of the arc is measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0136] Furthermore, the distances Hu[mm] and Hl[mm] have a relationship of 0.30≦Hu / (Hu+Hl)≦0.70, preferably 0.35≦Hu / (Hu+Hl)≦0.65. This optimizes the position of the tire's maximum width position Ac in the deformable region of the tire sidewall. Specifically, the lower limit alleviates stress concentration near the end of the belt ply caused by the tire's maximum width position Ac being too close to the end of the belt layer 14, thereby suppressing separation of the surrounding rubber. The upper limit alleviates stress concentration near the bead portion caused by the tire's maximum width position Ac being too close to the end of the bead core 11, thereby suppressing failure of the bead portion reinforcing member (bead filler 12 in Figure 6).

[0137] Furthermore, the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al' is in the range of 0.05 ≤ RSc / OD ≤ 1.70 with respect to the tire's outer diameter OD [mm], preferably in the range of 0.10 ≤ RSc / OD ≤ 1.60. Also, the radius of curvature RSc [mm] of the arc is in the range of 25 ≤ RSc ≤ 330, preferably in the range of 30 ≤ RSc ≤ 300. This optimizes the radius of curvature of the side profile and ensures the proper load capacity of the tire sidewall. Specifically, the lower limit reduces the amount of deflection of the tire sidewall during tire rolling, thereby reducing the tire's rolling resistance. The upper limit suppresses the occurrence of stress concentration caused by the flattening of the tire sidewall, improving the tire's durability. In particular, with small-diameter tires, large stresses tend to act on the tire sidewall due to the high internal pressure and high load conditions described above, so there is also the issue of ensuring the tire's resistance to sidewall cuts. In this regard, the lower limit ensures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire deformation and preventing tire side cuts. Furthermore, the upper limit suppresses tire side cuts caused by excessive tension in the carcass layer 13.

[0138] Furthermore, the radius of curvature RSc [mm] of the arc is in the range of 0.50 ≤ RSc / SH ≤ 0.95 with respect to the tire section height SH [mm], and preferably in the range of 0.55 ≤ RSc / SH ≤ 0.90.

[0139] Furthermore, it is preferable that the radius of curvature RSc [mm] of the arc satisfies the following formula (10) with respect to the tire outer diameter OD [mm] and rim diameter RD [mm]. Here, Jmin = 15 and Jmax = 360, preferably Jmin = 20 and Jmax = 330, and more preferably Jmin = 25 and Jmax = 300.

[0140]

number

[0141] Furthermore, in Figure 6, point Bc is defined on the main body portion 131 of the carcass layer 13 at the same position in the radial direction of the tire relative to the tire's maximum width position Ac. Also, point Bu' is defined on the main body portion 131 of the carcass layer 13 at a radial position of 70% of the distance Hu described above from the tire's maximum width position Ac. Also, point Bl' is defined on the main body portion 131 of the carcass layer 13 at a radial position of 70% of the distance Hl described above from the tire's maximum width position Ac.

[0142] At this time, the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al' is in the range of 1.10 ≤ RSc / RCc ≤ 4.00, preferably in the range of 1.50 ≤ RSc / RCc ≤ 3.50, with respect to the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu', and point Bl'. Also, the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu', and point Bl' is in the range of 5 ≤ RCc ≤ 300, preferably in the range of 10 ≤ RCc ≤ 270. This optimizes the relationship between the radius of curvature RSc of the tire's side profile and the radius of curvature RCc of the carcass layer 13's side profile. Specifically, the lower limit ensures the radius of curvature RCc of the carcass profile, the internal volume V of the tire (described later) is ensured, and the load capacity of the tire is ensured. The upper limit ensures the total gauges Gu and Gl of the tire side (described later) are ensured, and the load capacity of the tire side is ensured.

[0143] Furthermore, it is preferable that the radius of curvature RSc [mm] of the side profile described above satisfies the following formula (11) with respect to the radius of curvature RCc [mm] of the carcass profile and the tire outer diameter OD [mm]. Here, Kmin = 1 and Kmax = 130, preferably Kmin = 2 and Kmax = 100, and more preferably Kmin = 3 and Kmax = 70.

[0144]

number

[0145] Furthermore, in Figure 6, the total gauge Gu [mm] of the tire sidewall at point Au is in the range of 0.010 ≤ Gu / OD ≤ 0.080 with respect to the tire outer diameter OD [mm], preferably in the range of 0.017 ≤ Gu / OD ≤ 0.070. This optimizes the total gauge Gu in the radially outer region of the tire sidewall. Specifically, the lower limit ensures the total gauge Gu in the radially outer region of the tire sidewall, suppressing tire deformation during high-load use and ensuring the tire's wear resistance. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the reduction in tire rolling resistance described above is significantly achieved. The upper limit suppresses the deterioration of tire rolling resistance caused by an excessively large total gauge Gu.

[0146] The total gauge of the tire sidewall is measured as the distance from the sidewall to the inner surface of the tire, along a perpendicular line drawn from a predetermined point on the sidewall to the main body portion 131 of the carcass layer 13.

[0147] Furthermore, in Figure 6, the total gauge Gu [mm] at point Au is in the range of 1.30 ≤ Gu / Gc ≤ 5.00 with respect to the total gauge Gc [mm] of the tire side portion at the tire's maximum width position Ac, preferably the ratio Gu / Gc is in the range of 1.90 ≤ Gu / Gc ≤ 3.00. This optimizes the gauge distribution of the tire side portion from the tire's maximum width position Ac to the innermost layer of the belt layer 14. Specifically, the lower limit ensures a sufficient total gauge Gu in the radially outer region, suppressing tire deformation during high-load use and ensuring the tire's wear resistance. The upper limit suppresses the deterioration of the tire's rolling resistance caused by an excessively large total gauge Gu.

[0148] Furthermore, it is preferable that the total gauge Gu [mm] at point Au satisfies the following formula (12) with respect to the total gauge Gc [mm] at the tire's maximum width position Ac and the tire's outer diameter OD [mm]. Here, Lmin = 0.10 and Lmax = 0.70, preferably Lmin = 0.14 and Lmax = 0.70, and more preferably Lmin = 0.19 and Lmax = 0.70.

[0149]

number

[0150] Furthermore, in Figure 6, the total gauge Gc [mm] of the tire sidewall at the tire's maximum width position Ac has a relationship of 0.003 ≤ Gc / OD ≤ 0.060 with respect to the tire's outer diameter OD [mm], preferably 0.004 ≤ Gc / OD ≤ 0.050. The lower limit ensures that the total gauge Gc at the tire's maximum width position Ac is sufficient, thereby ensuring the tire's load capacity. The upper limit ensures that the rolling resistance of the tire is reduced by thinning the total gauge Gc at the tire's maximum width position Ac.

[0151] Furthermore, it is preferable that the total gauge Gc [mm] at the tire's maximum width position Ac satisfies the following formula (13) with respect to the tire's outer diameter OD [mm]. Here, Mmin = 70 and Mmax = 450, preferably Mmin = 80 and Mmax = 400.

[0152]

number

[0153] Furthermore, it is preferable that the total gauge Gc [mm] at the tire's maximum width position Ac satisfies the following formula (14) with respect to the tire's outer diameter OD [mm] and total tire width SW [mm]. Here, Nmin = 0.20 and Nmax = 15, preferably Nmin = 0.40 and Nmax = 15, and more preferably Nmin = 0.60 and Nmax = 12.

[0154]

number

[0155] Furthermore, it is preferable that the total gauge Gc [mm] at the tire's maximum width position Ac satisfies the following formula (15) with respect to the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al'. Here, Omin = 13 and Omax = 260, preferably Omin = 20 and Omax = 200.

[0156]

number

[0157] Furthermore, in Figure 6, the total gauge Gl [mm] of the tire sidewall at point Al is in the range of 0.010 ≤ Gl / OD ≤ 0.150 with respect to the tire outer diameter OD, preferably in the range of 0.015 ≤ Gl / OD ≤ 0.100. This optimizes the total gauge Gl in the radially inner region of the tire sidewall. Specifically, the lower limit ensures the total gauge Gl in the radially inner region of the tire sidewall, suppressing tire deformation during high-load use and ensuring the tire's wear resistance. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the reduction in tire rolling resistance described above is significantly achieved. The upper limit suppresses the deterioration of tire rolling resistance caused by an excessively large total gauge Gl.

[0158] Furthermore, in Figure 6, the ratio Gl / Gc between the total gauge Gl [mm] of the tire sidewall at point Al and the total gauge Gc [mm] of the tire sidewall at the tire's maximum width position Ac is in the range of 1.00 ≤ Gl / Gc ≤ 7.00, and preferably the ratio Gu / Gc is in the range of 2.00 ≤ Gl / Gc ≤ 5.00. This optimizes the gauge distribution of the tire sidewall from the tire's maximum width position Ac to the bead core 11. Specifically, the lower limit ensures a sufficient total gauge Gl in the radially inner region, suppressing tire deformation during high-load use and ensuring the tire's wear resistance. The upper limit suppresses the deterioration of the tire's rolling resistance caused by an excessively large total gauge Gl.

[0159] Furthermore, it is preferable that the total gauge Gl [mm] of the tire side portion at point Al satisfies the following formula (16) with respect to the total gauge Gc [mm] at the tire maximum width position Ac and the tire outer diameter OD [mm]. Here, Pmin = 0.12 and Pmax = 1.00, preferably Pmin = 0.15 and Pmax = 1.00, and more preferably Pmin = 0.18 and Pmax = 1.00.

[0160]

number

[0161] Furthermore, in Figure 6, the total gauge Gl [mm] at point Al is in the range of 0.80 ≤ Gl / Gu ≤ 5.00, and preferably in the range of 1.00 ≤ Gl / Gu ≤ 4.00, relative to the total gauge Gu [mm] at point Au. This optimizes the ratio of the total gauge Gl in the radially outer region of the tire sidewall to the total gauge Gu in the radially inner region.

[0162] Further, it is preferable that the total gauge Gl [mm] at the above-mentioned point Al satisfies the following mathematical formula (17) with respect to the total gauge Gu [mm] at the above-mentioned point Au and the tire outer diameter OD [mm]. Here, Qmin = 0.09, Qmax = 0.80, preferably Qmin = 0.10, Qmax = 0.70, and more preferably Qmin = 0.11, Qmax = 0.50.

[0163]

Number

[0164] Also, in FIG. 6, the average rubber hardness Hsc at the measurement position of the total gauge Gc, the average rubber hardness Hsu at the measurement position of the total gauge Gu, and the average rubber hardness Hsl at the measurement point position of the total gauge Gl have a relationship of Hsc ≦ Hsu < Hsl, preferably a relationship of 1 ≦ Hsu - Hsc ≦ 18 and 2 ≦ Hsl - Hsu ≦ 27, and more preferably a relationship of 2 ≦ Hsu - Hsc ≦ 15 and 5 ≦ Hsl - Hsu ≦ 23. Thereby, the relationship of the rubber hardness of the tire side portion is optimized.

[0165] The average rubber hardnesses Hsc, Hsu, and Hsl are calculated as the sum of the values obtained by dividing the product of the cross-sectional length and the rubber hardness of each rubber member by the total gauge at each measurement point of the total gauge Gc [mm] at the tire maximum width position Ac, the total gauge Gu at the point Au, and the total gauge Gl at the point Al.

[0166] Furthermore, in Figure 7, the distance ΔAu' [mm] in the tire width direction from the tire's maximum width position Ac to point Au' is in the range of 0.03 ≤ ΔAu' / (Hu × 0.70) ≤ 0.23 relative to 70% of the distance Hu [mm] from the tire's maximum width position Ac, and preferably in the range of 0.07 ≤ ΔAu' / (Hu × 0.70) ≤ 0.17. This optimizes the curvature of the side profile in the radially outer region. Specifically, the lower limit suppresses the occurrence of stress concentration caused by the flattening of the tire sidewall, thereby improving the tire's durability. The upper limit reduces the amount of deflection of the tire sidewall during tire rolling, thereby reducing the tire's rolling resistance. In particular, with small-diameter tires, large stresses tend to act on the tire sidewall due to the use under high internal pressure and high load as described above, so there is also the issue of ensuring the tire's resistance to sidewall cuts. In this regard, the lower limit ensures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire deformation and preventing tire side cuts. Furthermore, the upper limit suppresses tire side cuts caused by excessive tension in the carcass layer 13.

[0167] Furthermore, the distance ΔAl'[mm] in the tire width direction from the tire's maximum width position Ac to point Al' is in the range of 0.03≦ΔAl' / (Hl×0.70)≦0.28 relative to 70% of the distance Hl[mm] from the tire's maximum width position Ac, and preferably in the range of 0.07≦ΔAl' / (Hl×0.70)≦0.20. This optimizes the curvature of the side profile in the radially inner region. Specifically, the above lower limit suppresses the occurrence of stress concentration caused by the flattening of the tire sidewall, thereby improving the tire's durability. Especially in small-diameter tires, since the bead core 11 is reinforced as described above, stress concentration near the bead core 11 is effectively suppressed. The above upper limit reduces the amount of deflection of the tire sidewall during tire rolling, thereby reducing the tire's rolling resistance.

[0168] The distances ΔAu' and ΔAl' are measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0169] Furthermore, it is preferable that the distance ΔAu' [mm] in the tire width direction from the tire maximum width position Ac to point Au' satisfies the following formula (18) with respect to the radius of curvature RSc [mm] of the arc passing through the tire maximum width position Ac, point Au', and point Al' described above. Here, Rmin = 0.05 and Rmax = 5.00, preferably Rmin = 0.10 and Rmax = 4.50.

[0170]

number

[0171] Furthermore, in Figure 7, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is in the range of 1.10 ≤ ΔBu' / ΔAu' ≤ 8.00, preferably in the range of 1.60 ≤ ΔBu' / ΔAu' ≤ 7.50, relative to the distance ΔAu' [mm] in the tire width direction from the tire's maximum width position to point Au'. This optimizes the relationship between the curvature of the side profile and the curvature of the carcass profile in the radially outer region. Specifically, the lower limit ensures the cut resistance of the tire side. The upper limit ensures the tension of the carcass layer 13, ensuring the rigidity of the tire side, and thus ensuring the tire's load capacity and durability.

[0172] Furthermore, in Figure 7, the distance ΔBl'[mm] in the tire width direction from point Bc to point Bl' is in the range of 1.80≦ΔBl' / ΔAl'≦11.0 with respect to the distance ΔAl'[mm] in the tire width direction from the tire's maximum width position Ac to point Al', preferably in the range of 2.30≦ΔBl' / ΔAl'≦9.50. This optimizes the relationship between the curvature of the side profile and the curvature of the carcass profile in the radially inner region. Specifically, the lower limit ensures the total gauge Gl of the tire side, thereby ensuring the load capacity of the tire side. The upper limit ensures the tension of the carcass layer 13, ensuring the rigidity of the tire side, thereby ensuring the load capacity and durability of the tire.

[0173] The distances ΔBu' and ΔBl' are measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0174] Furthermore, it is preferable that the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' satisfies the following formula (19) with respect to the radius of curvature RCc [mm] of the arc passing through points Bc, Bu', and Bl' as described above. Here, Smin = 0.40 and Smax = 7.0, preferably Smin = 0.50 and Smax = 6.0.

[0175]

number

[0176] Furthermore, in Figure 7, the rubber gauge Gcr [mm] of the sidewall rubber 16 at the tire's maximum width position Ac is in the range of 0.40 ≤ Gcr / Gc ≤ 0.90 relative to the total gauge Gc [mm] at the tire's maximum width position Ac described above. Also, the rubber gauge Gcr [mm] of the sidewall rubber 16 is in the range of 1.5 ≤ Gcr, preferably in the range of 2.5 ≤ Gcr. The above lower limit ensures that the rubber gauge Gcr [mm] of the sidewall rubber 16 is maintained, thereby ensuring the load capacity of the sidewall.

[0177] Furthermore, it is preferable that the rubber gauge Gcr [mm] of the sidewall rubber 16 at the tire's maximum width position Ac satisfies the following formula (20) with respect to the total gauge Gc [mm] and tire outer diameter OD [mm] at the tire's maximum width position Ac described above. Here, Tmin = 80 and Tmax = 0.90, preferably Tmin = 120 and Tmax = 0.90.

[0178]

number

[0179] Furthermore, in Figure 7, the rubber gauge Gin [mm] (not shown) of the inner liner 18 at the tire's maximum width position Ac is in the range of 0.03 ≤ Gin / Gc ≤ 0.50, preferably in the range of 0.05 ≤ Gin / Gc ≤ 0.40, relative to the total gauge Gc [mm] at the tire's maximum width position Ac. This ensures that the inner surface of the carcass layer 13 is properly protected.

[0180] [Sealant layer and inner liner] Next, the sealant layer 19 will be described. In the small-diameter tire of the above structure, in which the tire outer diameter OD and tire total width SW are defined within the above range, the rotational inertia is reduced and the tire mass is also reduced, which can be expected to significantly improve fuel efficiency. On the other hand, reducing the diameter and increasing the load increases the risk of punctures, and the danger when a tire fails due to a puncture is also very high, so high puncture sealing performance is required. For this reason, as shown in Figure 1, the tire 1 according to this embodiment has a sealant layer 19 provided on the inner side of the inner liner 18 in the tire radial direction in the tread portion. This sealant layer 19 is formed in a sheet shape that extends in the circumferential direction of the tire and is attached to the inner surface 18A of the inner liner 18. When a foreign object such as a nail penetrates the tread portion (tread rubber 15), the sealant material constituting the sealant layer 19 flows into the through hole, suppressing the decrease in air pressure and making it possible to maintain driving.

[0181] The sealant material of the sealant layer 19 preferably contains either butyl rubber or natural rubber, or both. Generally, the rubber material used for the inner liner 18 has good compatibility with butyl rubber. For this reason, the sealant material of the sealant layer 19 preferably contains butyl rubber from the viewpoint of contact with the inner liner 18. On the other hand, since natural rubber has tougher properties than butyl rubber, even if the sealant material becomes fluid due to heat during driving, deformation of the sealant layer 19 can be suppressed. In this way, the sealant material of the sealant layer 19 can be configured to improve adhesion between the inner liner 18 and the sealant layer 19 while suppressing deformation of the sealant layer 19.

[0182] Furthermore, as shown in Figure 2, the sealant layer 19 is positioned on the inner surface of the tire (inner surface 18A of the inner liner 18) of the tread portion of the tire such that the center position Cla of the sealant layer 19 in the tire width direction is within ±10 [mm] from the tire equatorial plane CL in the tire width direction. That is, the distance Wa between the center position Cla of the sealant layer 19 in the tire width direction and the tire equatorial plane CL is within the range of ±10 [mm], preferably within the range of ±5 [mm]. As a result, the sealant layer 19 is positioned on the inner surface of the tire in the tread portion of the tire such that the center position Cla in the tire width direction is located near the tire equatorial plane CL, thereby suppressing deterioration of the tire uniformity.

[0183] The sealant layer 19 is set to an average thickness Ta of, for example, 0.5 mm to 5.0 mm. This average thickness Ta is the average value of the thickness of the sealant layer 19 attached to the inner surface 18A of the inner liner 18. Specifically, it is the average of three points: the thickness measured at two points on both sides in the tire width direction, which are 40% of the total width of the sealant layer 19, moving outward from the center position of the sealant layer 19 in the tire width direction, and the thickness measured at the center position of the sealant layer 19 in the tire width direction. In this configuration, by setting the average thickness Ta of the sealant layer 19 within the above range, it is possible to suppress the flow of the sealant material during driving while ensuring good puncture sealing performance of the tire 1. Furthermore, the processability when attaching the sealant layer 19 to the inner surface 18a of the inner liner 18 is also improved.

[0184] In Figure 1, the average thickness Ta [mm] of the sealant layer 19 and the tire outer diameter OD [mm] described above are in the range of 250 ≤ Ta × OD ≤ 4000, preferably in the range of 330 ≤ Ta × OD ≤ 3000. This makes it possible to achieve improved puncture sealing performance that matches the size of the tire 1. Specifically, in small diameter tires with an outer diameter OD defined in the above range, if Ta × OD, which is the product of the average thickness Ta of the sealant layer 19 and the tire outer diameter OD, is less than the lower limit of the specified range, the average thickness Ta of the sealant layer 19 becomes too thin. As a result, the puncture sealing performance of the tire 1 cannot be sufficiently ensured. Also, if Ta × OD, which is the product of the average thickness Ta of the sealant layer 19 and the tire outer diameter OD, exceeds the upper limit of the specified range, the average thickness Ta of the sealant layer 19 becomes too thick. As a result, the weight of the sealant layer 19 increases, and the sealant layer 19 becomes more prone to generating heat, which tends to worsen the rolling resistance of the tire 1 and reduce fuel efficiency. In this configuration, by setting Ta×OD within the above-mentioned range, it is possible to ensure the puncture sealing performance of tire 1 while suppressing a decrease in fuel efficiency.

[0185] Furthermore, the sealant layer 19 is set to an average width W of, for example, 80 mm to 300 mm. This average width W is the average value of the total width (length in the tire width direction) of the sealant layer 19 along the inner surface 18A of the inner liner 18. In this configuration, by setting the average width W of the sealant layer 19 within the above range, it is possible to appropriately cover and protect the inner surface of the tire in the tread area while suppressing the sealant layer 19 from extending excessively in the tire width direction.

[0186] The average width W [mm] of the sealant layer 19 is in the range of 0.55 ≤ W / SW ≤ 0.85 with respect to the total tire width SW [mm] described above, preferably in the range of 0.60 ≤ W / SW ≤ 0.80. This makes it possible to achieve improved puncture sealing performance that matches the size of the tire 1. Specifically, in small diameter tires with a total tire width SW defined in the above range, if the average width W of the sealant layer 19, W / SW, with respect to the total tire width SW is less than the lower limit of the specified range, the sealant layer 19 cannot sufficiently cover the inner surface of the tire in the tread area (inner surface 18A of the inner liner 18). Therefore, the puncture sealing performance of the tire 1 cannot be sufficiently ensured. Furthermore, if the average width W of the sealant layer 19, W / SW, with respect to the total tire width SW exceeds the upper limit of the specified range, the sealant material will flow toward the tire equatorial plane CL (center) side of the tread area due to the softening of the sealant material due to heat during driving and the effect of centrifugal force, causing vibration during driving. In this configuration, by setting W / SW within the range described above, it is possible to ensure the puncture sealing performance of tire 1 while suppressing vibrations during driving and improving ride comfort.

[0187] When small-diameter tires with the above-mentioned tire outer diameter OD and tire total width SW are mounted on a vehicle, the vehicle's loading space can be increased due to the smaller tire diameter, thus increasing the load capacity. When the load capacity increases, the load on the tires increases, and under such operating conditions, the tires are in a high-load state. This high-load state is when the tire is subjected to a load of approximately 120% or more of its maximum load capacity, and at this time, the tire's contact pressure and contact area increase. In this configuration, by optimally setting the average width W of the sealant layer 19 relative to the tire contact width TW under high load, sufficient puncture sealing performance can be ensured under high-load operating conditions.

[0188] The tire contact width TW under high load is measured as the maximum linear distance in the axial direction of the tire at the contact surface between the tire and the plate when the tire is mounted on a specified rim, subjected to specified internal pressure, and placed perpendicular to a plate in a stationary state, with a load corresponding to 120% of the maximum load capacity specified by JATMA. Furthermore, the load capacity of non-standard sizes can be calculated using a predetermined formula specified by JATMA.

[0189] The average width W [mm] of the sealant layer 19 is in the range of 0.80 ≤ W / TW ≤ 1.10, or more specifically, 0.85 ≤ W / TW ≤ 1.05, relative to the tire contact width TW (Figure 5) at 120% of the maximum load capacity. If W / TW is less than 0.80, the puncture sealing performance of tire 1 under high-load conditions cannot be sufficiently ensured. On the other hand, if W / TW exceeds 1.10, the sealant material flows due to softening caused by heat during driving and the effects of centrifugal force, causing vibrations during driving. In this configuration, by setting W / TW at 120% of the maximum load capacity within the above range, it is possible to ensure the puncture sealing performance of tire 1 while suppressing vibrations during driving and improving ride comfort.

[0190] Furthermore, the viscosity Vi [kPa·s] of the sealant material constituting the sealant layer 19 is set to, for example, 0.2 to 10. This viscosity Vi was measured, for example, using a rotary rheometer under the conditions of a sample shape of Φ25 [mm], thickness of 1.5 [mm], deformation amount of 0.1 [%], frequency of 1 [Hz], and temperature of 100 [℃]. In this configuration, by setting the viscosity Vi of the sealant material within the above range, it is possible to suppress gravity-induced flow of the sealant layer 19, maintain the thickness of the sealant layer 19, and ensure the puncture sealing performance of the tire 1. In addition, productivity can be improved by enabling sheet-like diffusion and spreading due to centrifugal force.

[0191] Generally, increasing tire pressure can increase load capacity, so high-pressure use is a possibility. In this high-pressure state, sealant material flows into the puncture hole, especially in the event of a puncture, making the viscosity Vi of the sealant material important. Furthermore, in small-diameter tires with the above-mentioned range of tire outer diameter OD and tire total width SW, the time required for one tire rotation is shorter, resulting in greater deformation of the puncture hole and requiring a higher viscosity Vi.

[0192] In this configuration, the viscosity Vi [kPa·s] of the sealant material and the tire outer diameter OD [mm] are in the range of 40 ≤ Vi × OD ≤ 7000, preferably in the range of 50 ≤ Vi × OD ≤ 6000. This makes it possible to improve puncture sealing performance that matches the size of tire 1 under high internal pressure usage environments. Specifically, in small diameter tires with an outer diameter OD defined in the above range, if Vi × OD, which is the product of the viscosity Vi of the sealant material and the tire outer diameter OD, is below the lower limit of the specified range, the viscosity Vi of the sealant material becomes too low. As a result, the puncture sealing performance of tire 1 cannot be sufficiently ensured, and the sealant layer 19 cannot flow due to gravity to maintain the thickness (film thickness) of the sealant layer 19. Also, if Vi × OD, which is the product of the viscosity Vi of the sealant material and the tire outer diameter OD, exceeds the upper limit of the specified range, the viscosity Vi of the sealant material becomes too high. As a result, the sealant material does not flow properly into the through hole, and the puncture sealing performance cannot be sufficiently ensured. Furthermore, the sheet-like diffusion and spreading due to centrifugal force becomes difficult, reducing productivity. In this configuration, by keeping Vi×OD within the above range, the flow of the sealant layer 19 due to gravity is suppressed, maintaining the thickness of the sealant layer 19 while ensuring the puncture sealing performance of the tire 1. Furthermore, productivity can be improved by enabling the sheet-like diffusion and spreading due to centrifugal force.

[0193] As described above, the tire 1 has a belt layer 14 consisting of a wide (maximum width) cross belt (maximum belt layer) 141 located in the innermost layer in the tire's radial direction, and a narrow (minimum width) cross belt (minimum belt layer) 142 located radially outside the cross belt 141. As shown in Figure 2, the shortest distance Lc [mm] is defined as the distance from the surface of the tread rubber 15 to the sealant layer 19 at the tire's equatorial plane CL. The shortest distance Le [mm] is defined as the distance from the surface of the tread rubber 15 to the sealant layer 19 at the end 141A of the widest cross belt 141 on a parallel plane PP parallel to the tire's equatorial plane CL. These shortest distances Lc and Le are measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0194] Here, the shortest distance Lc [mm] between the surface of the tread rubber 15 and the sealant layer 19 at the tire equatorial plane CL, and the shortest distance Le [mm] between the surface of the tread rubber 15 and the sealant layer 19 at the parallel plane PP parallel to the tire equatorial plane CL at the end 141a of the cross belt 141 of the maximum width, are in the range of 1.1 ≤ Le / Lc ≤ 2.3, preferably in the range of 1.2 ≤ Le / Lc ≤ 2.0, and more preferably in the range of 1.3 ≤ Le / Lc ≤ 1.8. If Le / Lc is below the lower limit of the specified range, the sealant material of the sealant layer 19 may flow towards the tire equatorial plane CL (center) side of the tread area where the centrifugal force is high, potentially resulting in insufficient puncture sealing in the shoulder area. Also, if Le / Lc exceeds the upper limit of the specified range, the sealant material of the sealant layer 19 may flow to the side, potentially reducing fuel efficiency. In this configuration, since Le / Lc is set within the above range, it is possible to achieve both the puncture sealing performance and fuel efficiency of tire 1.

[0195] Furthermore, as shown in Figure 5, the width L1 [mm] is defined as the distance from the tire equatorial plane CL to the end 19a of the sealant layer 19 in the tire width direction. Similarly, the width L2 [mm] is defined as the distance from the tire equatorial plane CL to the end 142a of the narrowest cross belt 142 in the tire width direction, and the width L3 [mm] is defined as the distance from the tire equatorial plane CL to the end 141a of the widest cross belt 141 in the tire width direction. These widths L1, L2, and L3 are measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no-load conditions.

[0196] Here, the width L1 of one side of the sealant layer 19 and the width L2 of one side of the minimum width cross belt 142 satisfy the range of 100[%]≦L1 / L2. Also, the width L1 of one side of the sealant layer 19 and the width L3 of one side of the maximum width cross belt 141 satisfy the range of L1 / L3≦105[%]. That is, the end 19a of the sealant layer 19 in the tire width direction lies within the region between the widthwise position of the end 142a of the minimum width cross belt 142 and the widthwise position of 105% relative to the end 141a of the maximum width cross belt 141.

[0197] If the one-sided width L1 of the sealant layer 19 is less than 100[%] of the one-sided width L2 of the cross belt 142 with the minimum width, that is, less than 100%, the puncture sealing property at the lower part of the cross belt 142 cannot be ensured sufficiently. On the other hand, if the one-sided width L1 of the sealant layer 19 is more than 105[%] of the one-sided width L3 of the cross belt 141 with the maximum width, that is, more than 105%, due to the softening of the sealant material of the sealant layer 19 caused by the heat during running and the influence of centrifugal force, the sealant material flows toward the tire equatorial plane CL (center) side of the tread part, which causes vibration during running. In this configuration, by setting the one-sided width L1 of the sealant layer 19 as described above with respect to the one-sided widths L2 and L3 of the cross belts 141 and 142, the puncture sealing property at the lower part of the belt layer 14 can be ensured sufficiently, and even when the sealant layer 19 flows during running, the vibration caused by the deviation of the sealant layer 19 can be suppressed. Note that it is preferable that the one-sided width L1 of the sealant layer 19 is narrower than the one-sided width L3 of the cross belt 141 with the maximum width, that is, L1 / L3 < 100[%]. According to this configuration, the uniformity, fuel consumption performance, and puncture sealing performance of the tire can be most suitably compatible with each other.

[0198] Next, the inner liner 18 will be described. As described above, the inner liner 18 is an air permeation prevention layer disposed on the inner cavity surface of the tire and covering the carcass layer 13. The inner liner 18 suppresses the oxidation due to the exposure of the carcass layer 13 and also prevents the leakage of the air filled in the tire.

[0199] The inner liner 18 has an oxygen permeability coefficient α [mm·cc / (m^2·day·mmHg)] at 21[°C] and 50[%] relative humidity, which is in the range of 1×10^-3≦α≦3×10^-1. This oxygen permeability coefficient α is an indicator of how much oxygen the material constituting the inner liner 18 permeates. The oxygen permeability coefficient α was measured for the inner liner 18 formed from the material described later, in accordance with JIS K 7126, at 21[°C] and 50[%] relative humidity. In addition, the inner liner 18 has a dynamic storage modulus β [MPa] at 60[°C] in the range of 1≦β≦200. The dynamic storage modulus β was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, using strips cut to a width of 5 mm and a length of 60 mm from the inner liner 18 formed of the material described later, under the conditions of static strain of 5%, dynamic strain of ±0.1%, frequency of 20 Hz, and temperature of 60°C.

[0200] In this configuration, the oxygen permeability coefficient α and dynamic storage modulus β of the inner liner 18 are set within the above-mentioned ranges, thereby improving the internal pressure retention against natural air leakage without compromising the crack resistance of the inner liner 18. Specifically, although internal pressure retention and crack resistance are conflicting properties, both can be achieved by setting the oxygen permeability coefficient α and dynamic storage modulus β within the above-mentioned ranges.

[0201] The inner liner 18 can be formed as a rubber-based air permeability barrier layer made of a material including butyl rubber, for example. Either modified butyl rubber or unmodified butyl rubber can be used as the butyl rubber. Furthermore, these modified and unmodified butyl rubbers may be mixed. This type of butyl rubber has the advantage of higher crack resistance compared to other resin compositions. Additionally, the inner liner 18, which is a rubber-based air permeability barrier layer, may contain 40 to 100 parts by mass of modified or unmodified butyl rubber and 0 to 60 parts by mass of diene rubber per 100 parts by mass of rubber component. The amount of this type of butyl rubber is preferably 50 to 100 parts by mass. By including 40 parts by mass or more of butyl rubber, sufficient internal pressure retention for the inner liner 18 can be obtained.

[0202] Furthermore, the inner liner 18 can also be formed from a material other than butyl rubber. Specifically, the inner liner 18 can be formed as a resin-based air permeability barrier layer consisting of a thermoplastic resin or a thermoplastic elastomer composition containing a thermoplastic resin and an elastomer. This thermoplastic resin is an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer. An ethylene-vinyl alcohol copolymer refers to a copolymer in which the main repeating units are ethylene units (-CH2CH2-) and vinyl alcohol units (-CH2-CH(OH)-). Ethylene-vinyl alcohol copolymers have the advantage of higher air permeability compared to other materials such as butyl rubber. For example, a sheet of ethylene-vinyl alcohol copolymer was molded from pelletized material using a 40mmφ single-screw extruder with a 200mm wide T-type die (Plastic Technology Co., Ltd.). In this case, the cylinder and die temperatures were set to the melting point of the raw material with the highest melting point + 10°C, and the material was formed into a sheet with an average thickness of 1 mm under extrusion conditions of a cooling roll temperature of 50°C and a take-up speed of 1 m / min.

[0203] Furthermore, a modified ethylene-vinyl alcohol copolymer refers to a copolymer that contains repeating units other than the ethylene unit and vinyl alcohol unit, which are the main repeating units. A modified ethylene-vinyl alcohol copolymer is preferably obtained by reacting an ethylene-vinyl alcohol copolymer with a modifying compound.

[0204] Furthermore, the inner liner 18, which is a resin-based air permeability barrier, may contain 10 to 70 parts by mass of ethylene-vinyl alcohol copolymer or modified ethylene-vinyl alcohol copolymer per 100 parts by mass of the thermoplastic elastomer composition. Preferably, the amount of this type of ethylene-vinyl alcohol copolymer or modified ethylene-vinyl alcohol copolymer is 15 to 65 parts by mass. By keeping the content of the ethylene-vinyl alcohol copolymer or modified ethylene-vinyl alcohol copolymer within the above range, sufficient internal pressure retention of the inner liner 18 can be ensured.

[0205] Furthermore, it is preferable that the thermoplastic elastomer composition has an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer as the continuous phase and the elastomer as the dispersed phase. In this case, the thermoplastic elastomer composition can be produced by melt-kneading the thermoplastic resin component and the elastomer component, for example, in a twin-screw extruder, and dispersing the elastomer component as the dispersed phase within the thermoplastic resin component that forms the continuous phase.

[0206] [effect] As described above, this tire 1 comprises an inner liner 18 positioned on the radially inner side of the tread portion and a sealant layer 19 positioned on the surface of the inner liner 18. Furthermore, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400, the average thickness Ta [mm] of the sealant layer 19 and the tire outer diameter OD [mm] are in the range of 250 ≤ Ta × OD ≤ 4000, and the average width W [mm] of the sealant layer 19 is in the range of 0.55 ≤ W / SW ≤ 0.85 relative to the tire total width SW [mm].

[0207] With this configuration, by setting the Ta×OD value within the above-mentioned range, it is possible to ensure the puncture sealing performance of tire 1 while suppressing a decrease in fuel efficiency. Furthermore, by setting the W / SW value within the above-mentioned range, it is possible to ensure the puncture sealing performance of tire 1 while suppressing vibrations during driving and improving ride comfort.

[0208] Furthermore, the average width W [mm] of the sealant layer 19 is within the range of 0.80 ≤ W / TW ≤ 1.10 relative to the tire contact width TW at 120% of the maximum load capacity. This ensures puncture sealing of the tire 1 while suppressing vibrations during driving and improving ride comfort. In particular, with small-diameter tires 1, the vehicle's loading space can be increased by reducing the tire diameter, thus increasing the load capacity. As the load capacity increases, the load on the tire 1 increases, and under such operating conditions, the tire 1 is in a high-load state, so the tire's contact pressure and contact area increase. In this configuration, by optimally setting the average width W of the sealant layer 19 relative to the tire contact width TW at high load, which is 120% of the maximum load capacity, sufficient puncture sealing can be ensured under high-load operating conditions.

[0209] Furthermore, the viscosity Vi [kPa·s] of the sealant layer 19 and the tire outer diameter OD [mm] are within the range of 40 ≤ Vi × OD ≤ 7000. This allows for maintaining the thickness of the sealant layer 19 by suppressing gravity-induced flow of the sealant layer 19, while ensuring the puncture sealing performance of the tire 1. In addition, productivity can be improved by enabling sheet-like diffusion and expansion due to centrifugal force.

[0210] Furthermore, the tread section has multiple belt layers 14, and the shortest distance Lc [mm] between the surface of the tread rubber 15 and the sealant layer 19 at the tire equatorial plane CL and the shortest distance Le [mm] between the surface of the tread rubber 15 and the sealant layer 19 at the end 141a of the widest cross belt 141 on a parallel plane PP parallel to the tire equatorial plane CL are in the range of 1.1 ≤ Le / Lc ≤ 2.3. This makes it possible to achieve both puncture sealing performance and fuel efficiency performance for the tire 1.

[0211] Furthermore, the sealant layer 19 contains butyl rubber and / or natural rubber. This improves the adhesion between the inner liner 18 and the sealant layer 19 and suppresses deformation of the sealant layer 19.

[0212] Furthermore, the sealant layer 19 is a sheet extending in the circumferential direction of the tire, and the average thickness Ta [mm] of the sealant layer 19 is in the range of 0.5 ≤ Ta ≤ 5.0. This ensures good puncture sealing performance of the tire 1 while suppressing the flow of the sealant material during driving. In addition, the processability when attaching the sealant layer 19 to the inner surface 18a of the inner liner 18 is also good.

[0213] Furthermore, the center position CLa of the sealant layer 19 in the tire width direction is positioned within a range of ±10 [mm] from the tire equatorial plane CL in the tire width direction. As a result, the sealant layer 19 is positioned on the inner surface of the tire in the tread portion such that the center position CLa in the tire width direction is located near the tire equatorial plane CL, thereby suppressing deterioration of the tire's uniformity.

[0214] Furthermore, the width L1 [mm] on one side from the tire equatorial plane CL to the widthwise end of the sealant layer 19 and the width L2 [mm] on one side from the tire equatorial plane CL to the widthwise end of the minimum width cross belt 142 satisfy the range of 100 [%] ≤ L1 / L2, and the width L1 [mm] on one side and the width L3 [mm] on one side from the tire equatorial plane CL to the widthwise end of the maximum width cross belt 141 satisfy the range of L1 / L3 ≤ 105 [%]. This ensures sufficient puncture sealing performance in the lower part of the belt layer 14, and suppresses vibrations caused by uneven distribution of the sealant layer 19 even if the sealant layer 19 flows during driving.

[0215] Furthermore, the inner liner 18 has an oxygen permeability coefficient α [mm·cc / (m²·day·mmHg)] at 21[℃] and 50[%] relative humidity within the range of 1×10^-3≦α≦3×10^-1, and a dynamic storage modulus β [MPa] at 60[℃] within the range of 1≦β≦200. This makes it possible to improve the internal pressure retention against natural air leakage without compromising the crack resistance of the inner liner 18.

[0216] Furthermore, the inner liner 18 is a rubber-based air permeability barrier made of a material containing butyl rubber, and this rubber-based air permeability barrier contains 40 to 100 parts by mass of modified or unmodified butyl rubber and 0 to 60 parts by mass of diene rubber per 100 parts by mass of rubber component. This ensures sufficient internal pressure retention for the inner liner 18. [Examples]

[0217] Figures 8 to 10 are charts showing the results of performance tests of tires according to embodiments of this invention.

[0218] In this performance test, several types of test tires were evaluated for (1) low rolling resistance performance (fuel consumption rate), (2) puncture sealing performance, and (3) internal pressure retention performance. As an example of small diameter tires, two types of test tires were used. Specifically, [A] a test tire of size 235 / 45R10 was mounted on a rim of size 10×8, and [B] a test tire of size 145 / 80R12 was mounted on a rim of size 12×4.00B.

[0219] (1) In the evaluation of low rolling resistance performance, the test tire [A] above is subjected to an internal pressure of 230 [kPa] and a load of 4.2 [kN], and the test tire [B] above is subjected to an internal pressure of 80 [%] of the JATMA specified internal pressure and a load of 80 [%] of the JATMA specified load. A four-wheeled low-floor vehicle equipped with the test tires on all wheels is driven 50 laps of a 2 [km] test course at a speed of 100 [km / h]. After that, the fuel consumption rate [km / l] is calculated and evaluated. This evaluation is performed using an index evaluation with the comparative example as the baseline (100), and a higher value indicates a lower fuel consumption rate and a tendency for reduced rolling resistance, which is preferable.

[0220] (2) In the evaluation of puncture sealing performance, a through hole (puncture hole) was made in the test tires [A] and [B] described above. Under constant temperature conditions, the test tire [A] was filled with air to an initial internal pressure of 230 [kPa], and the test tire [B] was filled with air to an initial internal pressure of 80 [%] of the JATM specified internal pressure. After that, it was confirmed whether or not air leakage occurred by measuring the air pressure. The evaluation results are shown as an index with the initial air pressure set to 100. The closer this index value is to 100, the better the puncture sealing performance. An index value of "92" or higher indicates good puncture sealing performance.

[0221] (3) In the evaluation of internal pressure retention performance, the test tire [A] above was given an initial internal pressure of 230 [kPa], and the test tire [B] above was given an initial internal pressure of 80 [%] of the JATMA specified internal pressure. The test tires [A] and [B] were left for 24 hours at a temperature of 21°C, then filled to the initial internal pressure, and the air pressure was measured periodically over 42 days. The slope of the amount of air leakage from the measured air pressure during the period from day 15 to day 42 was then calculated. The evaluation results were shown as an index using the reciprocal of the calculated amount of air leakage, with the comparative example set to 100. A larger index value indicates better internal pressure retention performance.

[0222] The test tire of the embodiment has the structure shown in Figure 1 and comprises a pair of bead cores 11, 11, a carcass layer 13 consisting of a single layer of carcass ply, a belt layer 14 consisting of a pair of cross belts 141, 142, a belt cover 143 and a pair of belt edge covers 144, 144, tread rubber 15, sidewall rubber 16 and rim cushion rubber 17, an inner liner 18 and a sealant layer 19.

[0223] The test tires of Comparative Examples 1 and 2, like the test tire of Example 1, had an outer diameter OD = 547 [mm], a total tire width SW = 143 [mm], and a tire contact width TW = 110 [mm], and were mounted on a rim of size 12 (inches). In addition, the test tires of Comparative Examples 1 and 2 differed from the test tire of Example 1 in the average thickness Ta, average width W, viscosity Vi of the sealant layer 19, the oxygen permeability coefficient α of the inner liner 18, and the dynamic storage modulus β.

[0224] As the test results show, the test tire in this example demonstrates a balance between low rolling resistance, puncture sealing performance, and internal pressure retention performance. [Explanation of Symbols]

[0225] 1 Tire; 10 Rim; 11 Bead core; 12 Bead filler; 13 Carcass layer; 131 Main body; 132 Winding section; 14 Belt layer; 141, 142 Cross belts; 143 Belt cover; 144 Belt edge cover; 15 Tread rubber; 151 Cap tread; 152 Under tread; 16 Sidewall rubber; 17 Rim cushion rubber; 18 Inner liner; 19 Sealant layer; 21-23 Circumferential main grooves

Claims

1. A tire comprising a pair of bead cores, a carcass layer spanning the bead cores, and a belt layer positioned radially outward of the carcass layer, At least the inner surface of the tread portion of the tire is provided with a sealant layer, The tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660. The total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400. The average thickness Ta [mm] of the sealant layer and the outer diameter OD [mm] of the tire are in the range of 250 ≤ Ta × OD ≤ 4000. The average width W [mm] of the sealant layer is in the range of 0.55 ≤ W / SW ≤ 0.85 with respect to the total tire width SW [mm]. The tread portion comprises a cap tread and an under tread sandwiched between the cap tread and the belt layer, wherein the difference in rubber hardness between the cap tread and the under tread, Hs_cap - Hs_ut, is in the range of 3 to 20, and the difference in loss tangent, tanδ_cap - tanδ_ut, is in the range of 0 to 0.

22. The belt layer comprises a pair of cross belts consisting of a wide cross belt and a narrow cross belt, and a belt cover positioned on the radially outer side of the pair of cross belts and covering the entire area of ​​the pair of cross belts. A tire in which the distance Tsh from the tread profile at the tire contact edge to the outer surface of the wide cross belt is in the range of 1.50 ≤ Tsh / Tu ≤ 6.90 with respect to the rubber gauge Tu [mm] from the outer edge of the belt cover in the tire width direction to the outer surface of the carcass layer.

2. The tire according to claim 1, wherein the average width W [mm] of the sealant layer is in the range of 0.80 ≤ W / TW ≤ 1.10 with respect to the tire contact width TW at 120% of the maximum load capacity.

3. The tire according to claim 1 or 2, wherein the viscosity Vi [kPa·s] of the sealant layer and the tire outer diameter OD [mm] are in the range of 40 ≤ Vi × OD ≤ 7000.

4. The tread portion has multiple belt layers, A tire according to any one of claims 1 to 3, wherein the shortest distance Lc [mm] between the surface of the tread portion and the sealant layer on the equatorial plane of the tire, and the shortest distance Le [mm] between the surface of the tread portion and the sealant layer on a parallel plane parallel to the equatorial plane of the tire at the end of the widest belt layer with the largest belt width, are in the range of 1.1 ≤ Le / Lc ≤ 2.

3.

5. The tire according to any one of claims 1 to 4, wherein the sealant layer comprises butyl rubber and / or natural rubber.

6. The sealant layer is in the form of a sheet extending in the circumferential direction of the tire. The tire according to any one of claims 1 to 5, wherein the average thickness Ta [mm] of the sealant layer is in the range of 0.5 ≤ Ta ≤ 5.

0.

7. The tire according to any one of claims 1 to 6, wherein the center position of the sealant layer in the tire width direction is located within a range of ±10 [mm] from the tire equatorial plane in the tire width direction.

8. The tread portion has multiple belt layers, Of the multiple belt layers, the layer with the smallest belt width is defined as the smallest belt layer, and the layer with the largest belt width is defined as the largest belt layer. The width L1 [mm] on one side from the tire equatorial plane to the widthwise end of the sealant layer and the width L2 [mm] on one side from the tire equatorial plane to the widthwise end of the minimum belt layer satisfy the range of 100 [%] ≤ L1 / L2, and The tire according to any one of claims 1 to 7, wherein the width L1 [mm] on one side and the width L3 [mm] from the tire equatorial plane to the widthwise end of the maximum belt layer satisfy the range L1 / L3 ≤ 105 [%].

9. It has an inner liner that covers the carcass layer spanning a pair of bead cores and on which the sealant layer is arranged, The inner liner has an oxygen permeability coefficient α [mm·cc / (m²·day·mmHg)] at 21 [°C] and a relative humidity of 50 [%] which is in the range of 1 × 10⁻³ ≤ α ≤ 3 × 10⁻¹, and a dynamic storage modulus of elasticity β [MPa] at 60 [°C] which is in the range of 1 ≤ β ≤ 200, as described in any one of claims 1 to 8.

10. The tire according to claim 9, wherein the inner liner is a rubber-based air permeability-preventing layer made of a material containing butyl rubber.

11. The tire according to claim 10, wherein the rubber-based air permeability-preventing layer comprises 40 parts by mass or more and 100 parts by mass of modified or unmodified butyl rubber and 0 parts by mass or more and 60 parts by mass of diene rubber in 100 parts by mass of the rubber component.

12. The tire according to claim 9, wherein the inner liner is a resin-based air permeability-preventing layer made of a thermoplastic resin or a thermoplastic elastomer composition containing a thermoplastic resin and an elastomer.

13. The tire according to claim 12, wherein the thermoplastic resin is an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer.

14. The tire according to claim 12 or 13, wherein the resin-based air permeability-preventing layer comprises 10 to 70 parts by mass of an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer in 100 parts by mass of the thermoplastic elastomer composition.

15. The tire according to any one of claims 12 to 14, wherein the thermoplastic elastomer composition is an ethylene-vinyl alcohol copolymer or a modified ethylene-vinyl alcohol copolymer as a continuous phase and the elastomer as a dispersed phase.

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