tire

Abstract

To provide a tire that can improve wear resistance and wet performance. [Solution] In this tire 1, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400. The tire 1 also has a tread rubber 15 containing a thermoplastic resin. The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to the diene rubber 100 [parts by mass]. Furthermore, the content Q [parts by mass] of the thermoplastic resin is in the range of 0.008 ≤ Q / OD ≤ 0.450 and 0.020 ≤ Q / SW ≤ 0.850 relative to the tire outer diameter OD [mm] and the tire total width SW [mm].

Description

Technical Field

[0001] The present invention relates to a tire, and more particularly to a tire capable of improving the wear resistance and wet performance of the tire.

Background Art

[0002] In recent years, small-diameter tires have been developed for vehicles 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 cost 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 the above-described small-diameter tire, since the tire contact area is small, the tire contact pressure increases, and the wear resistance and wet performance of the tire tend to deteriorate.

[0005] Therefore, the present invention has been made in view of the above, and an object thereof is to provide a tire capable of improving the wear resistance and wet performance of the tire.

Means for Solving the Problems

[0006] To achieve the above objective, the tire according to this invention comprises a pair of bead cores, a carcass layer spanning the pair of bead cores, a belt layer arranged radially outside the carcass layer, and a tread rubber arranged radially outside the belt layer. The tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400. The tire 1 also has a tire rubber composition containing a thermoplastic resin. The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to 100 [parts by mass] of diene rubber. Furthermore, the content Q [parts by mass] of the thermoplastic resin is in the range of 0.008 ≤ Q / OD ≤ 0.450 and 0.020 ≤ Q / SW ≤ 0.850 relative to the tire outer diameter OD [mm] and the tire total width SW [mm].

[0007] Furthermore, the tire according to this invention comprises a pair of bead cores, a carcass layer stretched over the bead cores, a belt layer arranged radially outside the carcass layer, and a tread rubber arranged radially outside the belt layer, wherein 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, and has a tire rubber composition containing a thermoplastic resin, wherein the content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 per 100 [parts by mass] of diene rubber, and the content Q [parts by mass] of the thermoplastic resin is in the range of 0.035 ≤ (Q × LI') / (OD × SW) ≤ 1.900 per 100 [parts by mass] of the diene rubber. [Effects of the Invention]

[0008] The tire according to this invention has the advantage that the thermoplastic resin content Q of the tire rubber composition in so-called small-diameter tires is optimized, thereby optimizing the temperature dependence of the dynamic viscoelasticity of the tire rubber composition. As a result, the temperature dependence of the dynamic viscoelasticity of the tire rubber composition is reduced, improving the tire's wear resistance and wet grip performance. Specifically, the lower limit of the above ratio ensures the tire's wear resistance and wet grip performance, and the upper limit of the above ratio suppresses the deterioration of rolling resistance caused by an excessive thermoplastic resin content Q. [Brief explanation of the drawing]

[0009] [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 a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 7] Figure 7 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 8] Figure 8 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]

[0010] 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.

[0011] [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.

[0012] 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 DW 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.

[0013] 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, and an inner liner 18 (see Figure 1).

[0014] Each pair of bead cores 11, 11 is formed by winding one or more bead wires made of steel in a ring-like and multi-layered manner, and is embedded in the bead portion to form the core of the left and right bead portions. Each pair of bead fillers 12, 12 is positioned on the outer circumference of the pair of bead cores 11, 11 in the radial direction of the tire to reinforce the bead portion. The bead filler 12 has a rubber hardness Hs_bf of 55 to 105, a modulus M_bf [MPa] of 2.0 to 13.0 at 100% elongation, and a loss tangent tanδ_bf of 0.03 to 0.30, preferably a rubber hardness Hs_bf of 70 to 100, a modulus M_bf [MPa] of 3.0 to 12.0 at 100% elongation, and a loss tangent tanδ_bf of 0.05 to 0.25.

[0015] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass ply layers stacked together, and is stretched in a toroidal manner between the left and right bead cores 11, 11 to form the tire's skeleton. The ends of the carcass layer 13 are also wrapped around the bead cores 11 and bead filler 12 and secured outward in the tire width direction. The carcass ply of the carcass layer 13 is constructed by covering multiple carcass cords made of inorganic fibers (e.g., steel, carbon fiber, glass fiber) or organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) with a coating rubber and rolling it, and has a cord angle of 80 [deg] to 100 [deg] (defined as the longitudinal inclination angle of the carcass cord with respect to the tire circumferential direction).

[0016] The belt layer 14 is made up of multiple belt plies 141 to 144 stacked together and arranged around the outer circumference of the carcass layer 13. In the configuration shown in Figure 1, the belt plies 141 to 144 consist of a pair of cross belts 141 and 142, a belt cover 143 and a pair of belt edge covers 144 and 144.

[0017] 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 a 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 of 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.

[0018] 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 a 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 cover 144 are, for example, strip materials formed by coating one or a plurality of belt cover cords with a 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.

[0019] 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.

[0020] 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.

[0021] Rubber hardness Hs is measured under temperature conditions of 20°C in accordance with JIS K6253.

[0022] 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).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] A 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 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. Furthermore, the rim cushion rubber 17 has a rubber hardness Hs_rc of 60 to 80, a modulus M_rc [MPa] of 2.0 to 7.0 when stretched to 100% and a loss tangent tanδ_rc of 0.09 to 0.35, preferably a rubber hardness Hs_rc of 65 to 75, a modulus M_rc [MPa] of 3.0 to 6.0 when stretched to 100% and a loss tangent tanδ_rc of 0.11 to 0.30.

[0029] 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.

[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], and more preferably in the range of 280 [mm] ≤ OD ≤ 570 [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], and more preferably in the range of 120 [mm] ≤ SW ≤ 320 [mm]. With such small-diameter tires 1, for example, the floor of a small vehicle can be lowered to expand the interior space. Also, 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" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO. The specified internal pressure refers to the "maximum air pressure" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or the "INFLATION PRESSURES" as defined by ETRTO. The specified load refers to the "maximum load capacity" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or the "LOAD CAPACITY" as defined by ETRTO. Furthermore, in JATMA, the specified internal pressure and specified load are also defined as "maximum air pressure" and "maximum load capacity" for passenger car tires.

[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, i.e., the ratio of the tire section height SH [mm] (see Figure 2 described later) to the tire section width DW [mm], SH / DW, is in the range of 0.16 ≤ SH / DW ≤ 0.85, and preferably in the range of 0.19 ≤ SH / DW ≤ 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 (DW) 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 0.50 ≤ TW / SW ≤ 0.85 relative to the total tire width SW, and preferably in the range of 0.60 ≤ TW / SW ≤ 0.80.

[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] [Bead core and bead filler] 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 durability 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, in small diameter tires, where use at high internal pressure and high load is expected, the above-mentioned tire durability and reduction in rolling resistance 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 [wires] in the radial cross-sectional view. The strength of the bead wire is measured by a tensile test at a temperature of 20[°C] in accordance with JIS K1017.

[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's section width DW 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. With this configuration, the load capacity of the carcass layer 13 is properly ensured in small diameter tires, which has the advantage of achieving both tire durability and low rolling resistance. Specifically, the above lower limit suppresses tire deformation when used under high load, ensuring tire durability. In addition, it becomes possible to use the tire at high internal pressure, reducing tire rolling resistance. In particular, with small-diameter tires, where high internal pressure and high loads are expected, the aforementioned tire durability and reduction in rolling resistance are significantly improved. 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 product of the strength per carcass cord [N / cord] constituting the effective carcass ply and the number of carcass cords driven in per 50 [mm] width [cords / 50mm] on the tire's equatorial plane CL is calculated as the strength Tcs [N / 50mm] of the carcass ply. The strength of the carcass cord is measured by a tensile test at a temperature of 20 [°C] in accordance with JIS K1017. For example, in a configuration where one 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 in which the carcass layer 13 has a multilayer structure (not shown) formed by stacking multiple effective carcass plies, the above-described strong Tcs 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 0.15 ≤ φcs ≤ 1.10, preferably in the range of 0.25 ≤ φcs ≤ 0.60, and a number of cords driven in Ecs [cords / 50mm] in the range of 25 ≤ Ecs ≤ 80, preferably in the range of 50 ≤ Ecs ≤ 80, thereby achieving the above-mentioned strength Tcs [N / 50mm] of the carcass layer 13. In addition, the carcass cord is made up of multiple strands twisted together, 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. Furthermore, it is even more preferable that the wire diameter φcss [mm] of the carcass cord is within the range of 0.30 ≤ φcss / φcs ≤ 0.90 relative to the cord diameter φcs [mm] of the carcass cord. Note that the carcass cord may be composed of inorganic fibers other than steel (e.g., carbon fiber, glass fiber, etc.).

[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 0.60 ≤ φcs ≤ 0.90 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] 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] of the carcass layer 13 is calculated as the product of the strength per carcass cord [N / cord] and the total number of carcass cords [cords] embedded in the entire carcass layer 13. Therefore, the total strength TTcs[N] 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 ply, and the circumference of the carcass ply.

[0072] Furthermore, it is preferable that the total strength TTcs [N] 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 up 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 0.10 ≤ Hcs / SH ≤ 0.49 with respect to the tire cross-sectional height SH [mm], preferably in the range of 0.15 ≤ Hcs / SH ≤ 0.47. This optimizes the radial height Hcs of the winding portion 132 of the carcass layer 13. Specifically, the lower limit ensures the load capacity of the tire side, and the 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] Furthermore, the carcass layer 13 may have a so-called high-turn-up structure, so that the end of the winding portion 132 of the carcass layer 13 is located in a region radially outward from the tire maximum width position Ac (not shown).

[0077] [Belt layer] Figure 3 is an explanatory diagram showing the laminated structure of the belt layer of tire 1 as described in Figure 1. In this figure, the thin lines attached to each belt ply 141 to 144 schematically show the arrangement of the belt cords.

[0078] In the configuration shown in Figure 1, as described above, the belt layer 14 is made up of multiple belt plies 141 to 144 stacked together. Furthermore, as shown in Figure 3, these belt plies 141 to 144 are composed of a pair of cross belts 141 and 142, a belt cover 143 and a pair of belt edge covers 144 and 144.

[0079] In this case, the strength Tbt [N / 50mm] per 50 [mm] width of each 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 loads, ensuring the durability of the tire. In addition, it becomes possible to use the tire at high internal pressures, reducing the rolling resistance of the tire. In particular, for small diameter tires, where use at high internal pressures and high loads is expected, the above-mentioned tire durability and reduction in rolling resistance are significantly obtained. The above upper limit suppresses the deterioration of rolling resistance caused by the increase in mass of the cross belts.

[0080] The strength Tbt [N / 50mm] of a belt ply is calculated as follows: The effective belt ply is defined as the belt ply that extends over the entire area of ​​80% of the tire contact width TW centered on the tire equatorial plane CL (i.e., the central part of the tire contact area). 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 area [cords]. The strength of the belt cord is measured by a tensile test at a temperature of 20°C in accordance with JIS K1017. 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. Furthermore, in a configuration where the belt layer 14 is made up of multiple stacked effective belt plies (see Figure 1), the above-described strong Tbt is defined for each of the multiple effective belt plies. For example, in the configuration of Figure 1, the pair of cross belts 141 and 142 and the belt cover 143 correspond to effective belt plies.

[0081] 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 ≤ 75, 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] [Tread profile and tread gauge] Figure 4 is an enlarged view showing the tread portion of tire 1 as described in Figure 1.

[0091] 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 0.015 ≤ TW / (DA × OD) ≤ 0.300, preferably 0.020 ≤ TW / (DA × OD) ≤ 0.250. Furthermore, the tread profile drop DA [mm] at the tire contact edge T has a relationship of 0.02 ≤ DA / TW ≤ 0.10 with respect to the tire contact width TW [mm], preferably 0.05 ≤ DA / TW ≤ 0.08. This optimizes the drop angle of the tread shoulder region (defined as the ratio DA / (TW / 2)), ensuring the load capacity of the tread. 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.

[0092] 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.

[0093] 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.

[0094] 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 = 2.5 and Emax = 17, preferably Emin = 3.8 and Emax = 13, and even more preferably Emin = 4.0 and Emax = 9.

[0095]

number

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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 ≤ 0.98, and more preferably in the range of 0.70 ≤ TRw / TRc ≤ 0.96, 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.

[0101] 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.

[0102] 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 ≤ 1.60, preferably in the range of 0.45 ≤ CRw / TRw ≤ 1.50, and more preferably in the range of 0.55 ≤ CRw / TRw ≤ 1.40, 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.

[0103] Figure 5 is an enlarged view showing one side of the tread area described in Figure 4.

[0104] 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.

[0105] 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 0.08 ≤ Tce / OD × 10 ≤ 1.30 with respect to the tire outer diameter OD [mm], preferably 0.12 ≤ Tce / OD × 10 ≤ 1.00, and more preferably 0.15 ≤ Tce / OD × 10 ≤ 0.70. 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.

[0106] The distance Tce is measured with the tire mounted on a specified rim, under specified internal pressure, and in an unloaded state.

[0107] 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.

[0108] 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.

[0109]

number

[0110] 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 0.50 ≤ Tsh / Tce ≤ 1.70, preferably in the range of 0.80 ≤ Tsh / Tce ≤ 1.60, and more preferably in the range of 1.01 ≤ 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.

[0111] 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.

[0112] 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.

[0113]

number

[0114] 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 value Ta to the minimum value Tb 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.

[0115] 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.

[0116] Furthermore, the rubber gauge Gce [mm] of the tread rubber 15 at the tire equatorial plane CL is in the range of 0.05 ≤ Gce / OD × 10 ≤ 0.70 with respect to the tire outer diameter OD [mm], preferably in the range of 0.10 ≤ Gce / OD × 10 ≤ 0.65, and more preferably in the range of 0.15 ≤ Gce / OD × 10 ≤ 0.60. In so-called small-diameter tires, that is, tires with a relatively small tire outer diameter OD and tire total width SW, and used under relatively large load conditions, the tire contact area is small, which increases the tire contact pressure and tends to worsen the tire's wear resistance and wet grip performance. For this reason, the rubber gauge Gce of the tread rubber 15 is set to be thick to ensure the tire's wear resistance. Specifically, the lower limit suppresses tire deformation when used under high load, ensuring the tire's wear resistance, and the upper limit suppresses the deterioration of rolling resistance caused by the increase in the mass of the tread rubber.

[0117] Furthermore, the rubber gauge Gce [mm] of the tread rubber at the tire equatorial plane is in the range of 0.15 ≤ Gce / SW × 10 ≤ 1.05 with respect to the total tire width SW [mm], preferably in the range of 0.20 ≤ Gce / SW × 10 ≤ 0.95, and more preferably in the range of 0.40 ≤ Gce / SW × 10 ≤ 0.90. In so-called small-diameter tires, that is, tires with a relatively small tire outer diameter OD and total tire width SW, and used under relatively large load conditions, the tire contact area is small, which increases the tire contact pressure and tends to worsen the tire's wear resistance and wet grip performance. For this reason, the rubber gauge Gce of the tread rubber 15 is set to be thick to ensure the tire's wear resistance. Specifically, the lower limit suppresses tire deformation when used under high load, ensuring the tire's wear resistance, and the upper limit suppresses the deterioration of rolling resistance caused by the increase in the mass of the tread rubber.

[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 ≤ 8.50, preferably in the range of 2.00 ≤ Tsh / Tu ≤ 8.00, 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 as the gauge of the rubber material (sidewall rubber 16 in Figure 5) inserted between the end of the wide cross belt 141 and the carcass layer 13. Specifically, in a cross-sectional view along the tire meridian, a perpendicular line is drawn from the end of the wide cross belt 141 to the outer surface of the carcass layer 13, and the total gauge of the rubber material along this perpendicular line is calculated as the rubber gauge Tu.

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

[0127]

number

[0128] Furthermore, 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 greater than or equal to 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 contact edge T is divided into two equal parts in the tire width direction, the groove depth Gd1 of the circumferential main groove closest to the tire equatorial plane CL (notation omitted in the figure) is in the range of 1.00 times or more and 2.50 times or less the maximum value of the groove depths Gd2 and Gd3 of the other circumferential main grooves (notation omitted in the figure) in the region on the tire contact edge T side, preferably in the range of 1.01 times or more and 2.00 times or less, and more preferably in the range of 1.05 times or more and 1.80 times or less. The above lower limit distributes the contact pressure in the center region of the tread, improving the wear resistance performance of the tire. The above upper limit suppresses uneven wear caused by an excessive difference in contact pressure between the center and shoulder areas of the tread.

[0129] [Rubber composition for tires] Tire 1 has a tire rubber composition containing a thermoplastic resin. The thermoplastic resin is a resin blended into the tire rubber composition and has a molecular weight of several hundred to several thousand, which imparts tackiness to the tire rubber composition. Such a tire rubber composition containing a thermoplastic resin is preferably used for the tread rubber 15 and sidewall rubber 16 of so-called small-diameter tires. Here, as an example, we will describe a case in which the tread rubber 15 of a small-diameter tire, more specifically the cap tread 151, is made of a tire rubber composition containing a thermoplastic resin.

[0130] In this tire rubber composition, the thermoplastic resin content Q [parts by mass] is in the range of 5 ≤ Q ≤ 120 relative to 100 [parts by mass] of diene rubber, preferably in the range of 15 ≤ Q ≤ 110, more preferably in the range of 20 ≤ Q ≤ 95, and even more preferably in the range of 35 ≤ Q ≤ 80. For example, in a configuration where the cap tread 151 is made of a tire rubber composition containing a thermoplastic resin, the lower limit ensures both wear resistance and wet grip of the tire, and the upper limit ensures the rubber hardness of the tire rubber composition and thus ensures wear resistance of the tire.

[0131] Furthermore, the thermoplastic resin content Q [parts by mass] in the tire rubber composition is in the range of 0.008 ≤ Q / OD ≤ 0.450 with respect to the tire outer diameter OD [mm], preferably in the range of 0.030 ≤ Q / OD ≤ 0.300, and more preferably in the range of 0.055 ≤ Q / OD ≤ 0.250. Also, the thermoplastic resin content Q [parts by mass] is in the range of 0.020 ≤ Q / SW ≤ 0.850 with respect to the tire total width SW [mm], preferably in the range of 0.070 ≤ Q / SW ≤ 0.750, and more preferably in the range of 0.120 ≤ Q / SW ≤ 0.700. Therefore, in so-called small-diameter tires, i.e., tires with relatively small tire outer diameter OD and tire total width SW, the lower limits of the above ratios Q / OD and Q / SW are set higher by incorporating a larger thermoplastic resin content Q compared to tires of average tire size.

[0132] In the above configuration, the thermoplastic resin content Q of the tire rubber composition for so-called small-diameter tires is optimized, thereby optimizing the temperature dependence of the dynamic viscoelasticity of the tire rubber composition. That is, small-diameter tires have a relatively small tire outer diameter OD and tire total width SW in order to reduce rolling resistance. In such small-diameter tires, the tire contact area is small, which increases the tire contact pressure and tends to worsen the tire's wear resistance and wet grip performance. Therefore, the tread rubber 15 is made of a tire rubber composition containing a thermoplastic resin, and the thermoplastic resin content Q is blended in a relatively large amount. As a result, the temperature dependence of the dynamic viscoelasticity of the tire rubber composition is reduced, and the tire's wear resistance and wet grip performance are improved. Specifically, the above lower limits of the ratio Q / OD and Q / SW ensure the tire's wear resistance and wet grip performance, and the above upper limits of the ratio Q / OD and Q / SW suppress the deterioration of rolling resistance caused by an excessive thermoplastic resin content Q.

[0133] For example, in this embodiment, as shown in Figure 1, the tire consists of a cap tread 151 and an under tread 152, each made up of laminated tread rubber 15, with the entire cap tread 151 being made from a tire rubber composition containing a thermoplastic resin. However, the embodiment is not limited to this, and at least a portion of the cap tread 151, for example, the portion exposed to the tire contact area, may be formed from a tire rubber composition containing a thermoplastic resin.

[0134] Furthermore, the thermoplastic resin content Q [parts by mass] in the tire rubber composition is in the range of 0.035 ≤ (Q × LI') / (OD × SW) ≤ 1.900, preferably in the range of 0.090 ≤ (Q × LI') / (OD × SW) ≤ 1.300, and more preferably in the range of 0.200 ≤ (Q × LI') / (OD × SW) ≤ 1.100, with respect to the tire outer diameter OD [mm], tire total width SW [mm], and load LI' [kgf] at 120% of the specified load LI. Therefore, in so-called small-diameter tires, i.e., tires having a relatively small tire outer diameter OD and tire total width SW and used under relatively large load conditions, the thermoplastic resin content Q is blended in a larger amount compared to tires of average tire size, thereby setting a higher lower limit for the above ratio (Q × LI') / (OD × SW).

[0135] In the above configuration, the thermoplastic resin content Q of the tire rubber composition for so-called small-diameter tires is optimized, thereby optimizing the temperature dependence of the dynamic viscoelasticity of the tire rubber composition. Specifically, small-diameter tires have a relatively small tire outer diameter OD and tire total width SW in order to reduce rolling resistance, and are often used under relatively large load conditions. In such small-diameter tires, the tire contact area is small, which increases the tire contact pressure, and tends to worsen the tire's wear resistance and wet grip performance. Therefore, the tread rubber 15 consists of a tire rubber composition containing a thermoplastic resin, and the thermoplastic resin content Q is blended in a relatively large amount. This reduces the temperature dependence of the dynamic viscoelasticity of the tire rubber composition, improving the tire's wear resistance and wet grip performance. Specifically, the lower limit of (Q×LI') / (OD×SW) ensures the tire's wear resistance and wet grip performance, and the upper limit of (Q×LI') / (OD×SW) suppresses the deterioration of rolling resistance caused by an excessive thermoplastic resin content Q. Furthermore, since the tire outer diameter OD and tire total width SW correlate with the tire contact area, a value correlated with the tire contact pressure can be obtained by calculating the ratio of the load LI (100% of the specified load) to the tire outer diameter OD and tire total width SW.

[0136] Furthermore, the glass transition temperature of the thermoplastic resin is in the range of 20°C to 120°C, preferably in the range of 25°C to 115°C, and more preferably in the range of 30°C to 110°C. The lower limit ensures the wet grip performance of the tire, and the upper limit suppresses the deterioration of the tire's wear resistance caused by excessive hardening of the rubber material.

[0137] The glass transition temperature of thermoplastic resins is determined by obtaining a thermogram using differential scanning calorimetry (DSC) at a heating rate of 20 °C / min, and measuring the temperature as the midpoint of the transition region in the thermogram. If the thermogram shows multiple transition regions, the midpoint of the largest transition region is defined as the glass transition temperature of the mixture.

[0138] Furthermore, the thermoplastic resin is at least one selected from the group consisting of resins comprising at least one selected from terpenes, modified terpenes, rosin, rosin esters, C5 components, C9 components, and C5C9 copolymer components, and resins in which at least a portion of the double bonds of those resins are hydrogenated. It is also preferable that the thermoplastic resin is a resin comprising at least one selected from terpenes, modified terpenes, rosin, rosin esters, C5 components, C9 components, and C5C9 copolymer components. Examples of such resins include natural resins such as terpene resins, modified terpene resins, rosin resins, and rosin ester resins, as well as synthetic resins such as petroleum resins, coal resins, phenolic resins, and xylene resins comprising C5 components and C9 components, such as C5 resins, C9 resins, and C5C9 copolymer resins.

[0139] Examples of terpene resins include α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatically modified terpene resin, and hydrogenated terpene resin. Examples of rosin resins include modified rosins such as gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleated rosin, and fumarated rosin, as well as ester derivatives of these rosins such as glycerol ester, pentaerythritol ester, methyl ester, and triethylene glycol ester, and rosin-modified phenol resin.

[0140] Examples of petroleum-based resins include aromatic hydrocarbon resins and saturated or unsaturated aliphatic hydrocarbon resins. Examples include C5 petroleum resins (aliphatic petroleum resins obtained by polymerizing fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 petroleum resins (aromatic petroleum resins obtained by polymerizing fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resins.

[0141] Furthermore, the rubber component of the tire rubber composition is a diene-based rubber, and in 100 parts by mass of the diene-based rubber, it contains 20 parts by mass or more, preferably 30 parts by mass or more and 100 parts by mass or less, more preferably 40 parts by mass or more and 100 parts by mass or less, and even more preferably 60 parts by mass or more and 100 parts by mass or less, of a specific styrene-butadiene rubber. By including a specific styrene-butadiene rubber in the rubber component of the tire rubber composition, the dispersibility of silica is improved, the tensile breaking strength is increased, the wear resistance of the tire is improved, and the loss tangent tanδ at 0°C is increased, improving the wet grip performance of the tire. The above lower limit of the amount of styrene-butadiene rubber ensures good silica dispersibility, thereby ensuring the wear resistance and wet grip performance of the tire. Note that the higher the molecular weight of the styrene-butadiene rubber, the better the wear resistance of the tire.

[0142] Furthermore, the styrene-butadiene rubber of the specific styrene-butadiene rubber is in the range of -40°C or lower, preferably between -80°C and -45°C, and more preferably between -75°C and -50°C. The above upper limit ensures an improvement in the wear resistance performance of the tire.

[0143] The glass transition temperature of styrene-butadiene rubber is determined by differential scanning calorimetry, where a thermogram is obtained at a heating rate of 20°C / min, and the temperature is measured as the midpoint of the transition region of the thermogram. Furthermore, if the diene rubber is an oil-extracted product, the glass transition temperature of the diene rubber without the oil-extracting component (oil) is measured.

[0144] Furthermore, the tire rubber composition contains a white filler in an amount of 30 parts by mass or more and less than 150 parts by mass, preferably 40 parts by mass or more and less than 150 parts by mass, and more preferably 45 parts by mass or more and less than 150 parts by mass, per 100 parts by mass of diene rubber. The above lower limit ensures the wet grip performance of the tire and also ensures a reduction in rolling resistance.

[0145] Examples of white fillers that can be used include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium dioxide, and calcium sulfate. These can be used individually or in combination of two or more. In particular, the use of silica further improves wet performance and low heat generation.

[0146] As silica, those commonly used in tire rubber compositions can be selected. For example, wet-process silica, dry-process silica, or silica surface-treated with compounds that are reactive or compatible with both silica and rubber can be used, such as carbon-silica (dual-phase filler) in which silica is supported on a carbon black surface, silane coupling agents, or polysiloxanes. Wet-process silica mainly composed of hydrated silicic acid is particularly preferred.

[0147] Furthermore, the white filler can be blended with a silane coupling agent along with silica. This improves the dispersibility of silica, further enhancing the tire's wet performance and low heat generation performance.The type of silane coupling agent is not particularly limited, but sulfur-containing silane coupling agents are preferred, such as bis-(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and VP manufactured by Evonik. Mercaptosilane compounds exemplified in Japanese Patent Publication No. 2006-249069, such as Si363, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethyl tetrasulfide You can choose from options such as lylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyltetrasulfide, 3-octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0148] Furthermore, the incorporation of fillers other than the white filler into the tire rubber composition increases the strength of the rubber composition and ensures the durability of the tire. Other fillers that can be selected include, for example, inorganic fillers such as carbon black, mica, aluminum oxide, and barium sulfate, and organic fillers such as cellulose, lecithin, lignin, and dendrimers.

[0149] Furthermore, the tire rubber composition contains 5 to 100 parts by mass, preferably 7 to 80 parts by mass, of carbon black per 100 parts by mass of diene rubber. The lower limit ensures the strength of the rubber composition and thus the durability of the tire, while the upper limit ensures low heat generation.

[0150] As carbon black, for example, furnace black, acetylene black, thermal black, channel black, and graphite carbon black can be used. Furnace black is preferred, and specific examples include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, and FEF. These carbon blacks can be used individually or in combination of two or more. Surface-treated carbon blacks obtained by chemically modifying these carbon blacks with various acid compounds may also be used.

[0151] Furthermore, the nitrogen adsorption specific surface area of ​​the carbon black is 80 [m^2 / g] or more and 250 [m^2 / g] or less, preferably 90 [m^2 / g] or more and 230 [m^2 / g] or less, and more preferably 95 [m^2 / g] or more and 220 [m^2 / g] or less. The lower limit ensures the dry grip performance and durability of the tire, and the upper limit prevents excessive heat generation.

[0152] The specific surface area for nitrogen adsorption of carbon black is calculated in accordance with JIS K6217-2.

[0153] Furthermore, the tire rubber composition contains 10 parts by mass to 30 parts by mass, preferably 15 parts by mass to 25 parts by mass, of natural rubber or isoprene-based rubber in 100 parts by mass of diene-based rubber. This improves the wear resistance of the tire. Natural rubber and isoprene-based rubber can be those known as tire rubber compositions.

[0154] [effect] As described above, [1] the tire 1 comprises a pair of bead cores 11, 11, a carcass layer 13 spanning the pair of bead cores 11, 11, a belt layer 14 positioned radially outside the carcass layer 13, and a tread rubber 15 positioned radially outside the belt layer 14. The tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400. The tire 1 also has a tire rubber composition containing a thermoplastic resin (in this embodiment, the tread rubber 15; see Figure 1). The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to the diene rubber 100 [parts by mass]. Furthermore, the thermoplastic resin content Q [parts by mass] is within the ranges of 0.008 ≤ Q / OD ≤ 0.450 and 0.020 ≤ Q / SW ≤ 0.850 with respect to the tire outer diameter OD [mm] and tire total width SW [mm].

[0155] This configuration has the advantage of optimizing the thermoplastic resin content Q of the tire rubber composition in so-called small-diameter tires, thereby optimizing the temperature dependence of the dynamic viscoelasticity of the tire rubber composition. As a result, the temperature dependence of the dynamic viscoelasticity of the tire rubber composition is reduced, improving the tire's wear resistance and wet grip performance. Specifically, the above lower limits of the ratio Q / OD and Q / SW ensure the tire's wear resistance and wet grip performance, while the above upper limits of the ratio Q / OD and Q / SW suppress the deterioration of rolling resistance caused by an excessive thermoplastic resin content Q.

[0156] Furthermore, [2] the tire 1 according to this invention comprises a pair of bead cores 21, 22, a carcass layer 13 stretched across a pair of bead cores 11, 11, a belt layer 14 arranged radially outside the carcass layer 13, and a tread rubber 15 arranged radially outside the belt layer 14. The tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the tire total width SW [mm] is in the range of 100 ≤ SW ≤ 400. The tire 1 also has a tire rubber composition containing a thermoplastic resin (in this embodiment, tread rubber 15; see Figure 1). The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to the diene rubber 100 [parts by mass]. Furthermore, the thermoplastic resin content Q [parts by mass] is within the range of 0.035 ≤ (Q × LI') / (OD × SW) ≤ 1.900 with respect to the tire outer diameter OD [mm], tire total width SW [mm], and load LI' [kgf] at 120 [%] of the specified load LI.

[0157] This configuration has the advantage of optimizing the thermoplastic resin content Q of the tire rubber composition in so-called small-diameter tires, thereby optimizing the temperature dependence of the dynamic viscoelasticity of the tire rubber composition. As a result, the temperature dependence of the dynamic viscoelasticity of the tire rubber composition is reduced, improving the tire's wear resistance and wet grip performance. Specifically, the above lower limit of (Q×LI') / (OD×SW) ensures the tire's wear resistance and wet grip performance, and the above upper limit of (Q×LI') / (OD×SW) suppresses the deterioration of rolling resistance caused by an excessive thermoplastic resin content Q.

[0158] Furthermore, [3] in this tire 1, the tread rubber 151 is made of a tire rubber composition, as described in [1] or [2] above. This has the advantage of properly obtaining the effect of improving the wear resistance and wet grip performance of the tire by the tire rubber composition containing a thermoplastic resin.

[0159] Furthermore, [4] in this tire 1, the glass transition temperature of the thermoplastic resin is in the range of 20 [°C] to 120 [°C] in any one of the above [1] to [3]. The lower limit ensures the wet grip performance of the tire, and the upper limit has the advantage of suppressing the deterioration of the tire's wear resistance caused by excessive hardening of the rubber material.

[0160] Furthermore, [5] in this tire 1, in the tire 1 described in any one of [1] to [4] above, the thermoplastic resin is at least one selected from the group consisting of a resin comprising at least one selected from terpenes, modified terpenes, rosin, rosin esters, C5 components, C9 components, and C5C9 copolymer components, and resins in which at least a portion of the double bonds of those resins are hydrogenated. This has the advantage of improving the wear resistance and wet grip performance of the tire.

[0161] Furthermore, [6] in this tire 1, in the tire 1 described in any one of [1] to [5] above, the tire rubber composition contains 20 parts by mass of styrene-butadiene rubber in 100 parts by mass of diene rubber. The inclusion of a specific styrene-butadiene rubber in the rubber component of the tire rubber composition improves the dispersibility of silica, increases the tensile breaking strength, improves the wear resistance of the tire, and increases the loss tangent tanδ at 0°C, which has the advantage of improving the wet grip performance of the tire.

[0162] Furthermore, [7] in this tire 1, the glass transition temperature of the styrene-butadiene rubber is -40 [°C] or lower, as described in [6] above. This has the advantage of ensuring improved wear resistance of the tire.

[0163] Furthermore, [8] in this tire 1, in the tire 1 described in any one of [1] to [7] above, the tire rubber composition contains 30 parts by mass or more and less than 150 parts by mass of white filler per 100 parts by mass of diene rubber. This has the advantage of ensuring the wet grip performance of the tire and ensuring a reduction in rolling resistance.

[0164] Furthermore, [9] in this tire 1, in the tire 1 described in any one of [1] to [8] above, the tire rubber composition contains 5 parts by mass to 100 parts by mass of carbon black per 100 parts by mass of diene rubber. The lower limit ensures the strength of the rubber composition and thus the durability of the tire, while the upper limit ensures low heat generation.

[0165] Furthermore,

[10] in this tire 1, in the tire 1 described in any one of [1] to [9] above, the tire rubber composition contains 10 parts by mass of natural rubber or isoprene rubber in 100 parts by mass of diene rubber. This has the advantage of improving the wear resistance of the tire.

[0166] Furthermore,

[11] in this tire 1, in the tire 1 described in any one of [1] to

[10] above, the rubber gauge Gce [mm] of the tread rubber 15 at the tire equatorial plane CL is in the range of 0.05 ≤ Gce / OD × 10 ≤ 0.70 with respect to the tire outer diameter OD [mm]. The above lower limit has the advantage of suppressing tire deformation when used under high load, thereby ensuring the wear resistance of the tire, and the above upper limit has the advantage of suppressing the deterioration of rolling resistance caused by the increase in the mass of the tread rubber.

[0167] Furthermore,

[12] in this tire 1, in the tire 1 described in any one of [1] to

[11] above, the rubber gauge Gce [mm] of the tread rubber 15 at the tire equatorial plane CL is in the range of 0.15 ≤ Gce / SW × 10 ≤ 1.05 with respect to the total tire width SW [mm]. The above lower limit has the advantage of suppressing tire deformation when used under high load, thereby ensuring the wear resistance of the tire, and the above upper limit has the advantage of suppressing the deterioration of rolling resistance caused by the increase in the mass of the tread rubber.

[0168] Furthermore,

[13] in this tire 1, in the tire 1 described in any one of [1] to

[12] above, the belt layer 14 has a pair of cross belts 141, 142 consisting of a wide cross belt (inner diameter cross belt 141 in Figure 1) and a narrow cross belt. Also, the distance Tce [mm] (see Figure 5) from the tread profile at the tire equatorial plane CL to the outer surface of the wide cross belt 141 is in the range of 0.08 ≤ Tce / OD × 10 ≤ 1.30 with respect to the tire outer diameter OD [mm] (see Figure 1).

[0169] In this configuration, the distance Tce [mm] at the tire equatorial plane CL is optimized, ensuring adequate load capacity of the tread. Specifically, the lower limit suppresses tire deformation during high-load use, ensuring tire wear resistance. This wear resistance is particularly pronounced in small-diameter tires, where high internal pressure and high load use are expected. The upper limit suppresses the deterioration of rolling resistance caused by increased tread rubber mass.

[0170] Furthermore,

[14] in this tire 1, in the tire 1 described in any one of [1] to

[12] above, the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer surface of the wide cross belt (inner diameter cross belt 141 in Figure 5) is in the range of 0.50 ≤ Tsh / Tce ≤ 1.70 with respect to the distance Tce [mm] at the tire equatorial plane CL (see Figure 5). This has the advantage of optimizing the ratio Tsh / Tce. Specifically, the above lower limit ensures the 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 the tread gauge in the center region, thereby suppressing tire deformation when used under high loads, which is characteristic of small diameter tires, and ensuring the tire's wear resistance.

[0171] Furthermore,

[15] in this tire 1, in the tire 1 described in any one of [1] to

[13] above, the distance Tsh at the tire contact edge T is in the range of 1.50 ≤ Tsh / Tu ≤ 8.50 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 (see Figure 5). This has the advantage that the profile of the carcass layer 13 is optimized and the tension of the carcass layer 13 is optimized. [Examples]

[0172] Figures 6 to 8 are charts showing the results of performance tests of tires according to embodiments of this invention.

[0173] In this performance test, several types of test tires were evaluated for (1) wear resistance, (2) wet performance, and (3) low rolling resistance. As an example of small diameter tires, two different tire sizes were used as test tires. Specifically, [A] a 145 / 80R12 test tire was mounted on a rim with a rim size of 12×4.00B, and [B] a 205 / 50R15 test tire was mounted on a rim with a rim size of 15×6J.

[0174] (1) In the evaluation of wear resistance, the test tire [A] above is subjected to an internal pressure of 240 kPa, which is 100% of the JATMA specified internal pressure, and a load of 4.41 kN, which is 120% of the JATMA specified load, while the test tire [B] above is subjected to an internal pressure of 250 kPa, which is 100% of the JATMA specified internal pressure, and a load of 6.23 kN, which is 120% of the JATMA specified load. A four-wheeled low-floor vehicle equipped with the test tires on all wheels is driven 10,000 km on a dry test course. After that, the amount of wear and the degree of uneven wear of each tire are measured and evaluated. This evaluation is performed using an index evaluation with the comparative example as the baseline (100), and a higher value is preferable.

[0175] (2) In the evaluation of wet performance (wet grip performance), the test tire [A] above is subjected to an internal pressure of 240 [kPa], which is 100% of the JATMA specified internal pressure, and a load of 4.41 [kN], which is 120% of the JATMA specified load, and the test tire [B] above is subjected to an internal pressure of 250 [kPa], which is 100% of the JATMA specified internal pressure, and a load of 6.23 [kN], which is 120% of the JATMA specified load. The test tires are then mounted on a test vehicle for performing a predetermined μ-S evaluation. The test vehicle then drives on a test course with a wet road surface, and the deceleration from 60 [km / h] to 20 [km / h] due to the operation of the ABS (Anti-lock Brake System) is measured. This evaluation is performed using an index evaluation with the comparative example as the baseline (100), and a higher value is preferable.

[0176] (3) In the evaluation of low rolling resistance performance (fuel efficiency), the test tire [A] above is subjected to an internal pressure of 240 [kPa], which is 100% of the JATMA specified internal pressure, and a load of 4.41 [kN], which is 120% of the JATMA specified load, and the test tire [B] above is subjected to an internal pressure of 250 [kPa], which is 100% of the JATMA specified internal pressure, and a load of 6.23 [kN], which is 120% 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 larger value indicates a lower fuel consumption rate and a tendency for reduced rolling resistance, which is preferable.

[0177] The test tires of the comparative examples and examples are so-called small-diameter tires and have the configuration shown in Figure 1, comprising 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. Furthermore, the entire cap tread 151 is made of a tire rubber composition containing the thermoplastic resin described above.

[0178] As the test results show, the test tire in the example demonstrates that it is possible to improve tire wear resistance and wet performance while maintaining low rolling resistance performance. [Explanation of symbols]

[0179] 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; 21-23 Circumferential main grooves

Claims

1. A tire comprising a pair of bead cores, a carcass layer spanning the pair of bead cores, a belt layer positioned radially outward of the carcass layer, and a tread rubber positioned radially outward of the belt 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 tire rubber composition includes a thermoplastic resin, The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to the diene rubber 100 [parts by mass], and A tire characterized in that the content Q [parts by mass] of the thermoplastic resin is in the range of 0.008 ≤ Q / OD ≤ 0.450 and 0.020 ≤ Q / SW ≤ 0.850 with respect to the tire outer diameter OD [mm] and the tire total width SW [mm].

2. A tire comprising a pair of bead cores, a carcass layer spanning the bead cores, a belt layer positioned radially outward of the carcass layer, and a tread rubber positioned radially outward of the belt 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 tire rubber composition includes a thermoplastic resin, The content Q [parts by mass] of the thermoplastic resin in the tire rubber composition is in the range of 5 ≤ Q ≤ 120 relative to the diene rubber 100 [parts by mass], and A tire characterized in that the content Q [parts by mass] of the thermoplastic resin is in the range of 0.035 ≤ (Q × LI') / (OD × SW) ≤ 1.900 with respect to the tire outer diameter OD [mm], the tire total width SW [mm], and the load LI' [kgf] which is 120% of the specified load LI.

3. The tire according to claim 1 or 2, wherein the tread rubber is comprised of the tire rubber composition.

4. The tire according to claim 1 or 2, wherein the glass transition temperature of the thermoplastic resin is in the range of 20°C to 120°C.

5. The tire according to claim 1 or 2, wherein the thermoplastic resin is at least one selected from the group consisting of a resin comprising at least one selected from terpenes, modified terpenes, rosin, rosin esters, C5 components, C9 components, and C5C9 copolymer components, and a resin in which at least a portion of the double bonds of such resins are hydrogenated.

6. The tire according to claim 1 or 2, wherein the tire rubber composition contains 20 parts by mass or more of styrene-butadiene rubber in 100 parts by mass of diene rubber.

7. The tire according to claim 6, wherein the glass transition temperature of the styrene-butadiene rubber is -40°C or lower.

8. The tire according to claim 1 or 2, wherein the tire rubber composition contains 30 parts by mass or more and less than 150 parts by mass of a white filler per 100 parts by mass of diene rubber.

9. The tire according to claim 1 or 2, wherein the tire rubber composition contains 5 to 100 parts by mass of carbon black per 100 parts by mass of diene rubber.

10. The tire according to claim 1 or 2, wherein the tire rubber composition comprises 10 parts by mass of natural rubber or isoprene rubber in 100 parts by mass of diene rubber.

11. The tire according to claim 1 or 2, wherein the rubber gauge Gce [mm] of the tread rubber at the tire's equatorial plane is in the range of 0.05 ≤ Gce / OD × 10 ≤ 0.70 with respect to the tire's outer diameter OD [mm].

12. The tire according to claim 1 or 2, wherein the rubber gauge Gce [mm] of the tread rubber at the tire's equatorial plane is in the range of 0.15 ≤ Gce / SW × 10 ≤ 1.05 with respect to the total tire width SW [mm].

13. The tire according to claim 1 or 2, wherein the belt layer has a pair of cross belts consisting of a wide cross belt and a narrow cross belt, and the distance Tce [mm] from the tread profile on the tire equator to the outer surface of the wide cross belt is in the range of 0.08 ≤ Tce / OD × 10 ≤ 1.30 with respect to the tire outer diameter OD [mm].

14. The tire according to claim 1, wherein the belt layer has a pair of cross belts consisting of a wide cross belt and a narrow cross belt, and the distance Tsh [mm] from the tread profile at the tire contact edge to the outer surface of the wide cross belt is in the range of 0.50 ≤ Tsh / Tce ≤ 1.70 with respect to the distance Tce [mm] at the tire equator.

15. The tire according to claim 1, wherein the belt layer has a pair of cross belts consisting of a wide cross belt and a narrow cross belt, and the distance Tsh at the tire contact end is in the range of 1.50 ≤ Tsh / Tu ≤ 8.50 with respect to the rubber gauge Tu [mm] from the end of the wide cross belt to the outer surface of the carcass layer.

Images