Tire

Abstract

In the tire (1), when a point (Al) on a side profile located at the same position in the tire radial direction with respect to the radially outer end of the bead cores (11, 11) is defined, a distance (Hl) in the tire radial direction from a tire maximum width position (Ac) to the point (Al) is defined. A point Al'on the side profile at a radial position 70 [%] from the tire maximum width position Ac at a distance Hl is defined, and a point Am on the side profile at a radial position 35 [%] from the tire maximum width position Ac at a distance Hl is defined. The radius of curvature RO [mm] of an arc passing through the tire maximum width position Ac, the point Al'and the point Am when the tire is attached to a predetermined rim, a predetermined internal pressure is applied, and the tire is in an unloaded state is within the range of 0.20 < = RO / SH < = 1.20 with respect to the tire cross-sectional height SH [mm].

Description

Technical Field

[0001] The present invention relates to a tire, and more particularly to a tire capable of achieving both low rolling resistance performance and durability performance of the tire. Background Art

[0002] In recent years, small-diameter tires have been developed for installation on vehicles with lowered floors to expand the interior space of the vehicle. The small-diameter tires have a small rotational inertia and a small tire weight, and thus are expected to reduce transportation costs. On the other hand, a high load capacity is required for small-diameter tires. As a conventional tire related to this technical problem, the technology described in Patent Document 1 is known.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2020 / 122169 Summary of the invention

[0006] Problems to be solved by the invention

[0007] An object of the present invention is to provide a tire capable of achieving both low rolling resistance performance and durability performance.

[0008] Technical means of solving problems

[0009] In order to achieve the above-mentioned object, the tire of the present invention is characterized in that it has a pair of bead cores, a carcass layer mounted on the bead core, and a belt layer arranged on the radial outside of the carcass layer, and 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, points Al on the side profile at the same position in the tire radial direction relative to the radially outer end of the bead core are defined, the tire radial distance Hl from the tire maximum width position Ac to the point Al is defined, and A point Al' on the side profile located at a radial position 70[%] of the distance Hl from the maximum width position Ac of the tire defines a point Am on the side profile located at a radial position 35[%] of the distance Hl from the maximum width position Ac of the tire, and a radius of curvature RO[mm] of an arc passing through the maximum width position Ac of the tire, point Al' and point Am when the tire is mounted on a specified rim and subjected to a specified internal pressure and is in a no-load state is within the range of 0.20≤RO / SH≤1.20 relative to the tire section height SH[mm].

[0010] Effects of the Invention

[0011] The tire of the present invention optimizes the radius of curvature RO of the side profile in the radial inner region of the tire from the sidewall portion to the bead portion, thereby appropriately ensuring the load capacity of the tire. Specifically, the above-mentioned lower limit reduces the deflection of the radial inner region of the tire when the tire rolls, thereby reducing the rolling resistance of the tire. The above-mentioned upper limit alleviates the stress concentration caused by the flattening of the radial inner region of the tire, thereby improving the durability of the tire. Especially in small-diameter tires, when used under the above-mentioned high internal pressure and high load, a large stress will act on the area from the maximum width position Ac of the tire to the contact position with the rim flange portion. Due to such a tendency, the failure of the bead portion caused by the above-mentioned upper limit is effectively suppressed. As a result, it has the advantages of taking into account both the low rolling resistance performance and the durability performance of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention.

[0013] Figure 2 Yes means Figure 1 An enlarged view of the tire described in .

[0014] Figure 3 Yes means Figure 1 An explanatory diagram of the stacking structure of the belt layer of the tire described in .

[0015] Figure 4 Yes means Figure 1 An enlarged view of the tread portion of the tire described in .

[0016] Figure 5 Yes means Figure 4 An enlarged view of a single side area of ​​the tread portion described in .

[0017] Figure 6 Yes means Figure 1 An enlarged view of the sidewall and bead portions of the tire described in .

[0018] Figure 7 Yes means Figure 6 An enlarged view of the side wall portion described in .

[0019] Figure 8 Yes means Figure 6 An enlarged view of the radial inner area of ​​the tire described in .

[0020] Fig. 9 Yes means Figure 1 An explanatory diagram of the stacked structure of the carcass layer and the belt layer of the tire described in .

[0021] Fig.10 Yes means Fig. 9An explanatory diagram of an improved example of the laminated structure of the carcass layer and the belt layer described in .

[0022] Fig.11 Yes means Fig. 9 An explanatory diagram of an improved example of the laminated structure of the carcass layer and the belt layer described in .

[0023] Fig.12 This is a graph showing the results of performance tests of tires according to the embodiments of the present invention.

[0024] Fig.13 This is a graph showing the results of performance tests of tires according to the embodiments of the present invention.

[0025] Fig.14 This is a graph showing the results of performance tests of tires according to the embodiments of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the present embodiment. In addition, the constituent elements of the present embodiment include elements that are replaceable while maintaining the identity of the invention and that are obvious to replace. In addition, the multiple improved examples described in the present embodiment can be arbitrarily combined within a range that is obvious to those skilled in the art.

[0027] [tire]

[0028] Figure 1 1 is a cross-sectional view in the tire meridian direction of a tire 1 according to an embodiment of the present invention. This figure shows a cross-sectional view of a single side region in the tire radial direction of the tire 1 mounted on a rim 10. In this embodiment, a pneumatic radial tire for a passenger car is described as an example of a tire.

[0029] In this figure, the cross section in the tire meridian direction is defined as the cross section after cutting the tire on a plane including the tire rotation axis (not shown). In addition, the tire equatorial plane CL is defined as a plane passing through the midpoint of the tire section width DW specified by JATMA and perpendicular to the tire rotation axis. In addition, the tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis. In addition, point T is the tire ground contact end, and point Ac is the tire maximum width position.

[0030] The tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead cores 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 guard rubbers 17, 17, and an inner liner 18 (see Figure 1 ).

[0031] A pair of bead cores 11, 11 are formed by winding one or more bead wires made of steel in a ring shape and multiple times, and are buried in the bead portion to form a core of the left and right bead portions. A pair of bead edge cores 12, 12 are respectively arranged on the tire radial outer periphery of the pair of bead cores 11, 11 to reinforce the bead portion. In addition, the bead edge core 12 has a rubber hardness Hs_bf of 55 or more and 105 or less, a modulus M_bf [MPa] at 100 [%] elongation of 2.0 or more and 13.0 or less, and a loss tangent tanδ_bf of 0.03 or more and 0.30 or less, preferably a rubber hardness Hs_bf of 70 or more and 100 or less, a modulus M_bf [MPa] at 100 [%] elongation of 3.0 or more and 12.0 or less, and a loss tangent tanδ_bf of 0.05 or more and 0.25 or less.

[0032] The carcass layer 13 has a single-layer structure formed by a layer of carcass ply or a multi-layer structure formed by stacking multiple carcass ply layers, and is annularly erected between the left and right bead cores 11, 11 to form the skeleton of the tire. In addition, the two ends of the carcass layer 13 are rolled back in a manner to wrap the bead core 11 and the bead core 12 and are fixed to the outside in the tire width direction. In addition, the carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of inorganic fibers (e.g., steel, carbon fibers, glass fibers) or organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and has a cord angle of 80 [deg] or more and 100 [deg] or less (defined as the inclination angle of the length direction of the carcass cord relative to the circumferential direction of the tire).

[0033] The belt layer 14 is formed by stacking a plurality of belt plies 141 to 144, and is disposed around the outer periphery of the carcass layer 13. Figure 1 In the structure of , the belt plies 141 to 144 are composed of a pair of cross belts 141 , 142 , a belt cover layer 143 , and a pair of belt edge cover layers 144 , 144 .

[0034] The pair of cross belts 141, 142 is formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the length direction of the belt cord relative to the tire circumferential direction) of 15 [deg] or more and 55 [deg] or less in absolute value. In addition, the pair of cross belts 141, 142 has cord angles of opposite signs, so that the length directions of the belt cords are intersected and stacked (so-called cross ply structure). In addition, the pair of cross belts 141, 142 are stacked and arranged on the tire radial outside of the carcass layer 13.

[0035] The belt cover layer 143 and the pair of belt edge covering layers 144, 144 are formed by covering belt covering cords made of steel or organic fiber material with covering rubber, and have a cord angle of 0 [deg] or more and 10 [deg] or less in absolute value. In addition, the belt cover layer 143 and the belt edge covering layer 144 are, for example, strip-shaped profiles formed by covering one or more belt covering cords with covering rubber, and are formed by winding the strip-shaped profiles on the outer peripheral surfaces of the cross belts 141, 142 multiple times and in a spiral shape along the circumferential direction of the tire. In addition, the belt cover layer 143 is configured to cover the entire cross belt 141, 142 area, and the pair of belt edge covering layers 144, 144 are configured to cover the left and right edge portions of the cross belts 141, 142 starting from the radially outer side of the tire.

[0036] The tread rubber 15 is disposed on the tire radial direction outer periphery of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire 1. The tread rubber 15 includes a cap tread 151 and a base tread 152.

[0037] The crown tread 151 is made of a rubber material having excellent ground contact characteristics and weather resistance, and extends over the entire area of ​​the tire ground contact surface and is exposed to the tread, constituting the outer surface of the tread portion. In addition, the crown tread 151 has a rubber hardness Hs_cap of 50 or more and 80 or less, a modulus M_cap [MPa] at 100 [%] elongation of 1.0 or more and 4.0 or less, and a loss tangent tanδ_cap of 0.03 or more and 0.36 or less, preferably a rubber hardness Hs_cap of 58 or more and 76 or less, a modulus M_cap [MPa] at 100 [%] elongation of 1.5 or more and 3.2 or less, and a loss tangent tanδ_cap of 0.06 or more and 0.29 or less.

[0038] The rubber hardness Hs is measured under the temperature condition of 20 [° C.] in accordance with JIS K6253.

[0039] The modulus (breaking strength) was measured by a tensile test at a temperature of 20 [° C.] using a dumbbell-shaped test piece in accordance with JIS K6251 (using a No. 3 dumbbell).

[0040] The loss tangent tan δ was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisaku-sho, Ltd. under the conditions of a temperature of 60[°C], a shear strain of 10[%], an amplitude of ±0.5[%], and a frequency of 20[Hz].

[0041] The base tread 152 is made of a rubber material having excellent heat resistance, is sandwiched between the cap tread 151 and the belt layer 14, and constitutes the base portion of the tread rubber 15. In addition, the base tread 152 has a rubber hardness Hs_ut of 47 or more and 80 or less, a modulus M_ut [MPa] at 100 [%] elongation of 1.4 or more and 5.5 or less, and a loss tangent tanδ_ut of 0.02 or more and 0.23 or less, and preferably has a rubber hardness Hs_cap of 50 or more and 65 or less, a modulus M_ut [MPa] at 100 [%] elongation of 1.7 or more and 3.5 or less, and a loss tangent tanδ_ut of 0.03 or more and 0.10 or less.

[0042] In addition, 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. In addition, 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. In addition, 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.

[0043] The pair of sidewall rubbers 16, 16 are respectively arranged on the outer sides of the carcass layer 13 in the tire width direction to constitute left and right sidewall portions. Figure 1 In the configuration of the tire, the end of the sidewall rubber 16 on the outer side of the tire radial direction is arranged on the lower layer of the tread rubber 15 and is sandwiched between the end of the belt layer 14 and the carcass layer 13. However, the invention is not limited thereto, and the end of the sidewall rubber 16 on the outer side of the tire radial direction may also be arranged on the outer layer of the tread rubber 15 and exposed from the supporting wall portion of the tire (not shown). In this case, the belt layer insulation rubber (not shown) is sandwiched between the end of the belt layer 14 and the carcass layer 13.

[0044] In addition, the side wall rubber 16 has a rubber hardness Hs_sw of 48 to 65, a modulus M_sw [MPa] at 100 [%] elongation of 1.0 to 2.4, and a loss tangent tanδ_sw of 0.02 to 0.22, and preferably has a rubber hardness Hs_sw of 50 to 59, a modulus M_sw [MPa] at 100 [%] elongation of 1.2 to 2.2, and a loss tangent tanδ_sw of 0.04 to 0.20.

[0045] A pair of rim guard rubbers 17, 17 extend from the inner side of the tire radial direction of the left and right bead cores 11, 11 and the turned portion of the carcass layer 13 to the outer side in the tire width direction, and constitute the rim fitting surface of the bead portion. Figure 1In the configuration, the end portion of the rim guard rubber 17 on the outer side in the tire radial direction is inserted into the lower layer of the sidewall rubber 16, thereby being sandwiched and arranged between the sidewall rubber 16 and the carcass layer 13. In addition, the rim guard rubber 17 has a rubber hardness Hs_rc of 60 or more and 80 or less, a modulus Mrc [MPa] at 100 [%] elongation of 2.0 or more and 7.0 or less, and a loss tangent tanδ_rc of 0.09 or more and 0.35 or less, and preferably has a rubber hardness Hs_rc of 65 or more and 75 or less, a modulus Mrc [MPa] at 100 [%] elongation of 3.0 or more and 6.0 or less, and a loss tangent tanδ_rc of 0.11 or more and 0.30 or less.

[0046] The inner liner 18 is an airtight layer disposed on the inner cavity surface of the tire and covering the carcass layer 13, which inhibits oxidation of the carcass layer 13 due to exposure and prevents leakage of air filled in the tire. In addition, the inner liner 18 can be composed of a rubber composition with butyl rubber as a main component, or a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer component is blended in a thermoplastic resin.

[0047] In addition, Figure 1 In the embodiment, the outer diameter OD[mm] of the tire is in the range of 200≤OD≤660, preferably in the range of 250[mm]≤OD≤580[mm]. By using this small-diameter tire as an application object, the load performance improvement effect described later can be significantly obtained. In addition, the total width SW[mm] of the tire is in the range of 100≤SW≤400, preferably in the range of 105[mm]≤SW≤340[mm]. By using this small-diameter tire 1, for example, the floor of a small vehicle can be lowered to expand the space inside the vehicle. In addition, due to the small rotational inertia, the weight of the tire is also small, thereby improving fuel consumption and reducing transportation costs. In particular, when installed in a hub motor of a vehicle, the load on the motor can be effectively reduced.

[0048] The tire outer diameter OD is measured by mounting the tire on a predetermined rim and applying a predetermined internal pressure in a no-load state.

[0049] The tire overall width SW is measured as the straight-line distance between the sidewalls (including all parts such as patterns and characters on the tire side) when the tire is mounted on a specified rim and subjected to a specified internal pressure and is in an unloaded state.

[0050] The prescribed rim refers to the "application rim" prescribed by JATMA, the "design rim" prescribed by TRA, or the "measuring rim" prescribed by ETRTO. In addition, the prescribed internal pressure refers to the "maximum air pressure" prescribed by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" prescribed by TRA, or the "inflation pressures" prescribed by ETRTO. In addition, the prescribed load refers to the "maximum load capacity" prescribed by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" prescribed by TRA, or the "load capacity" prescribed by ETRTO. However, in JATMA, when the tire is a passenger car tire, the internal pressure is specified to be 180 [kPa], and the load is specified to be 88 [%] of the maximum load capacity.

[0051] Furthermore, the tire overall width SW [mm] is within the range of 0.23 ≤ SW / OD ≤ 0.84 with respect to the tire outer diameter OD [mm], and preferably within the range of 0.25 ≤ SW / OD ≤ 0.81.

[0052] In addition, the tire outer diameter OD and the tire total width SW preferably satisfy the following formula (1): wherein A1min=-0.0017, A2min=0.9, A3min=130, A1max=-0.0019, A2max=1.4, A3max=400, preferably A1min=-0.0018, A2min=0.9, A3min=160, A1max=-0.0024, A2max=1.6, A3max=362.

[0053] [Formula 1]

[0054]

[0055] In the above tire 1, it is assumed that a rim 10 having a rim diameter of 5 [inch] or more and 16 [inch] or less (i.e., 125 [mm] or more and 407 [mm] or less) is used. In addition, the rim diameter RD [mm] is in the range of 0.50 ≤ RD / OD ≤ 0.74 relative to the tire outer diameter OD [mm], preferably in the range of 0.52 ≤ RD / OD ≤ 0.71. By the above lower limit, the rim diameter RD is ensured, and in particular, the installation space for the hub motor can be ensured. By the above upper limit, the internal volume V of the tire described later is ensured, thereby ensuring the load capacity of the tire.

[0056] It should be noted that the inner diameter of the tire is equal to the rim diameter RD of the rim 10 .

[0057] In addition, it is assumed that the tire 1 is used at an internal pressure higher than the specified internal pressure, specifically 350 [kPa] or more and 1200 [kPa] or less, preferably 500 [kPa] or more and 1000 [kPa] or less. The lower limit effectively reduces the rolling resistance of the tire, and the upper limit ensures the safety of the internal pressure filling operation.

[0058] In addition, it is assumed that the tire 1 is mounted on a vehicle that travels at a low speed, such as a small shuttle bus. In addition, 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. In addition, it is assumed that the tire 1 is mounted on a vehicle with 6 to 12 wheels. In this way, the load capacity of the tire is appropriately exerted.

[0059] In addition, the aspect ratio of the tire, that is, the tire section height SH [mm] (see below) Figure 2 ) to the tire section width DW [mm] SH / DW is in the range of 0.16≤SH / DW≤0.85, preferably in the range of 0.19≤SH / DW≤0.82.

[0060] The tire section height SH is a distance equal to 1 / 2 of the difference between the tire outer diameter and the rim diameter, and is measured by mounting the tire on a specified rim and applying a specified internal pressure in a no-load state.

[0061] The tire section width DW is measured as the straight-line distance between the sidewalls (excluding patterns and letters on the tire side) when the tire is mounted on a predetermined rim, a predetermined internal pressure is applied, and the tire is in an unloaded state.

[0062] Furthermore, the tire contact patch width TW is within the range of 0.50≤TW / SW≤0.85, and preferably within the range of 0.60≤TW / SW≤0.80, relative to the tire total width SW.

[0063] The tire contact width TW is measured by the maximum straight-line distance in the tire axial direction on the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, a specified internal pressure is applied, and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to a specified load is applied.

[0064] In addition, 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. Thus, the tire internal volume V is optimized. Specifically, by the above lower limit, the tire internal volume is ensured, thereby ensuring the load capacity of the tire. In particular, in small-diameter tires, it is assumed that they are used under high internal pressure and high load, and thus it is preferred to fully ensure the tire internal volume V. By the above upper limit, the tire enlargement caused by excessive tire internal volume V is suppressed.

[0065] Furthermore, the tire internal volume V [m^3] is within the range of 0.5≤V×RD≤17, preferably within the range of 1.0≤V×RD≤15, with respect to the rim diameter RD [mm].

[0066] [Bead core and bead core]

[0067] exist Figure 1 In the tire, as described above, a pair of bead cores 11, 11 are formed by winding one or more bead wires (not shown) made of steel in an annular shape and multiple times. In addition, a pair of bead cores 12, 12 are respectively arranged on the tire radial outer periphery of a pair of bead cores 11, 11.

[0068] In addition, the strength Tbd [N] of one bead core 11 is within the range of 45 ≤ Tbd / OD ≤ 120 relative to the tire outer diameter OD [mm], preferably within the range of 50 ≤ Tbd / OD ≤ 110, and more preferably within the range of 60 ≤ Tbd / OD ≤ 105. In addition, the strength Tbd [N] of the bead core is within the range of 90 ≤ Tbd / SW ≤ 400 relative to the tire total width SW [mm], preferably within the range of 110 ≤ Tbd / SW ≤ 350. Thus, the load capacity of the bead core 11 is appropriately ensured. Specifically, by the above lower limit, the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. In addition, it can also be used under high internal pressure, reducing the rolling resistance of the tire. In particular, in small-diameter tires, it is assumed that it is used under high internal pressure and high load, thereby significantly obtaining the above-mentioned tire durability and rolling resistance reduction effect. By the above upper limit, the deterioration of rolling resistance caused by the increase in the mass of the bead core is suppressed.

[0069] The strength Tbd [N] of the bead core 11 is calculated as the product of the strength of each 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.

[0070] In addition, the strength Tbd [N] of the bead core 11 preferably satisfies the following formula (2) relative to the tire outer diameter OD [mm], the distance SWD [mm], and the rim diameter RD [mm]. Among them, 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 further preferably B1min = 0.49, B2min = 17.9, B1max = 2.5, B2max = 99.0. Moreover, it is preferred to use the specified internal pressure P [kPa] of the tire, B1min = 0.0016 × P, B2min = 0.07 × P.

[0071] [Formula 2]

[0072]

[0073] The distance SWD is twice the radial distance from the tire rotation axis (not shown) to the tire maximum width position Ac, that is, the diameter of the tire maximum width position Ac, and is measured when the tire is mounted on a specified rim and a specified internal pressure is applied and under no-load conditions.

[0074] The tire maximum width position Ac is defined as the maximum width position of the tire section width DW specified by JATMA.

[0075] Furthermore, from the perspective of the radial section of a bead core 11, the total cross-sectional area σbd [mm^2] of the bead wire made of steel is within the range of 0.025 ≤ σbd / OD ≤ 0.075 relative to the tire outer diameter OD [mm], preferably within the range of 0.030 ≤ σbd / OD ≤ 0.065. Furthermore, the total cross-sectional area σbd [mm^2] of the bead wire is within the range of 11 ≤ σbd ≤ 36, preferably within the range of 13 ≤ σbd ≤ 33. Thus, the strength Tbd [N] of the bead core 11 is achieved.

[0076] 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 from the perspective of the radial cross section of a bead core 11 .

[0077] For example, in Figure 1 In the configuration, the bead core 11 has a quadrilateral shape formed by arranging bead wires having a circular cross section in a grid shape (not shown). However, the present invention is not limited thereto, and the bead core 11 may also have a hexagon shape formed by arranging bead wires having a circular cross section in a densest packing structure (not shown). In addition, any arrangement structure of bead wires may be adopted within a range obvious to those skilled in the art.

[0078] In addition, the total cross-sectional area σbd [mm^2] of the bead wire preferably satisfies the following formula (3) with respect to the tire outer diameter OD [mm], the distance SWD [mm] and the rim diameter RD [mm]: wherein Cmin = 30, Cmax = 8, preferably Cmin = 25, Cmax = 10.

[0079] [Formula 3]

[0080] (OD*RD) / (Cmin*SWD)≤σbd≤(OD*RD) / (Cmax*SWD)…(3)

[0081] In addition, the total cross-sectional area σbd [mm^2] of the bead wire is within the range of 0.50≤σbd / Nbd≤1.40, preferably within the range of 0.60≤σbd / Nbd≤1.20, relative to the total cross-sectional number (i.e., the total number of turns) Nbd [wire] of the bead core 11 in the radial cross-sectional view. That is, the cross-sectional area σbd' [mm^2] of a single bead wire is within the range of 0.50 [mm^2 / wire] or more and 1.40 [mm^2 / wire] or less, preferably within the range of 0.60 [mm^2 / wire] or more and 1.20 [mm^2 / wire] or less.

[0082] In addition, the maximum width Wbd [mm] of a tire bead core 11 in radial cross-section (see the following) Figure 2 ) relative to the total cross-sectional area σbd [mm^2] of the tire bead wire is in the range of 0.16≤Wbd / σbd≤0.50, preferably in the range of 0.20≤Wbd / σbd≤0.40.

[0083] In addition, Figure 1 In the embodiment, the distance Dbd [mm] between the centers of gravity of a pair of bead cores 11, 11 is within the range of 0.63 ≤ Dbd / SW ≤ 0.97 relative to the total tire width SW [mm], preferably within the range of 0.65 ≤ Dbd / SW ≤ 0.95. By setting the above lower limit, the deflection of the tire is reduced, and the rolling resistance of the tire is reduced. By setting the above upper limit, the stress acting on the sidewall is reduced, and tire failure is suppressed.

[0084] In addition, Figure 2In the embodiment, the radial distance BH [mm] from the radially outer end of the bead core 11 to the radially outer end of the bead core 23, that is, the height of the bead core 23 relative to the tire section height SH [mm] is in the range of 0.10≤BH / SH≤0.40, and preferably in the range of 0.15≤BH / SH≤0.35.

[0085] The radial distance BH [mm] is measured by mounting the tire on a predetermined rim and applying a predetermined internal pressure under no-load conditions.

[0086] [Carcass layer]

[0087] Figure 2 Yes means Figure 1 This figure shows a single-side region with the tire equatorial plane CL as a boundary.

[0088] exist Figure 1 In the structure of, as described above, the carcass layer 13 is composed of a single-layer carcass ply, which is annularly arranged between the left and right bead cores 11, 11. In addition, the two ends of the carcass layer 13 are rolled back in a manner of wrapping the bead core 11 and the bead core 12 and are locked outside in the tire width direction.

[0089] In addition, the strength Tcs [N / 50mm] of the carcass cord layer constituting the carcass layer 13 per 50 [mm] width is within the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD [mm], preferably within the range of 20≤Tcs / OD≤120. In addition, the strength Tcs [N / 50mm] of the carcass layer 13 is within the range of 30≤Tcs / SW≤260 relative to the total width SW [mm] of the tire, preferably within the range of 35≤Tcs / SW≤220. This structure properly ensures the load capacity of the carcass layer 13 in a small-diameter tire, and therefore has the advantage of taking into account both the durability performance and low rolling resistance performance of the tire. Specifically, by the above-mentioned lower limit, the deformation of the tire when used under high load is suppressed, thereby ensuring the durability performance of the tire. In addition, it can also be used under high internal pressure, reducing the rolling resistance of the tire. Especially in small diameter tires, it is assumed that they are used under high internal pressure and high load, thereby significantly obtaining the above tire durability and rolling resistance reduction effect. By the above upper limit, the rolling resistance deterioration caused by the increase in the mass of the carcass layer is suppressed.

[0090] The strength Tcs [N / 50mm] of the carcass ply is calculated as follows. That is, the carcass ply that is laid on the left and right bead cores 11, 11 and extends over the entire inner circumference of the tire is defined as the effective carcass ply. Furthermore, the product of the strength of each carcass cord constituting the effective carcass ply [N / cord] and the density of the carcass cords per 50 [mm] width on the entire tire circumference and on the tire equatorial plane CL [cords / 50mm] is calculated and taken 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 structure in which a carcass cord is formed by twisting a plurality of monofilaments, the strength of the twisted carcass cord is measured to calculate the strength Tcs of the carcass layer 13. In a configuration where the carcass layer 13 has a multi-layer structure (not shown) in which a plurality of effective carcass plies are stacked, the strength Tcs is defined for each of the plurality of effective carcass plies.

[0091] For example, in Figure 1 In the structure of the tire, the carcass layer 13 has a single-layer structure consisting of a single-layer carcass ply (the reference numerals in the figure are omitted), and the carcass ply is composed of carcass cords made of steel covered with a coating rubber arranged at a cord angle of 80 [deg] or more and 100 [deg] or less relative to the tire circumferential direction (illustration omitted). In addition, by making the carcass cords made of steel have a in the range of Cord diameter within the range of The carcass layer 13 has a strength Tcs [N / 50mm] of 25 ≤ Ecs ≤ 80, preferably 50 ≤ Ecs ≤ 80. The carcass cord is formed by twisting a plurality of monofilaments, and the monofilament diameter is exist In the range of In addition, the diameter of the carcass cord Cord diameter relative to carcass cord More preferably, In addition, the carcass cord may also be composed of inorganic fibers other than steel (for example, carbon fibers, glass fibers, etc.).

[0092] In addition, the carcass ply is not limited to the above-mentioned structure, and may also be composed of carcass cords made of organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) covered with a coating rubber. In this case, by making the carcass cords made of the above-mentioned organic fiber material have Cord diameter within the range of and the density Ecs [cords / 50mm] in the range of 40≤Ecs≤70, thereby achieving the strength Tcs [N / 50mm] of the carcass layer 13. In addition, carcass cords made of high-strength organic fiber materials such as nylon, aramid, and mixed materials can be used within a range that is obvious to those skilled in the art.

[0093] The carcass layer 13 may have a multi-layer structure (not shown) in which a plurality of layers, for example, a double-layer carcass ply is stacked. This can effectively improve the load capacity of the tire.

[0094] The total strength TTcs [N] of the carcass layer 13 is within the range of 300≤TTcs / OD≤3500, preferably 400≤TTcs / OD≤3000, relative to the tire outer diameter OD [mm]. Thus, the load capacity of the entire carcass layer 13 is ensured.

[0095] The total strength TTcs[N] of the carcass layer 13 is calculated by multiplying the strength of each carcass cord [N / cord] by the total number of carcass cords [cords] in the entire carcass layer 13. Therefore, the total strength TTcs[N] of the carcass layer 13 increases with the increase in the strength Tcs[N / 50mm] of each carcass ply, the number of plies of the carcass ply, the circumference of the carcass ply, etc.

[0096] In addition, the total strength TTcs [N] of the carcass layer 13 preferably satisfies the following formula (4) with respect to the tire outer diameter OD [mm] and the distance SWD [mm]. Wherein, Dmin = 2.2, Dmax = 40, preferably Dmin = 4.3, Dmax = 40, more preferably Dmin = 6.5, Dmax = 40, and further preferably Dmin = 8.7, Dmax = 40. Furthermore, it is preferred to use the prescribed internal pressure P [kPa] of the tire, Dmin = 0.02 × P.

[0097] [Formula 4]

[0098]

[0099] In addition, Figure 1 In the structure of the tire, the carcass layer 13 has a main body 131 extending along the inner surface of the tire and a roll-up portion 132 that is rolled up to the outside in the tire width direction in a manner that wraps the bead core 11 and extends in the tire radial direction. Figure 2In this case, the radial height Hcs [mm] from the measurement point of the rim diameter RD to the end of the upper-rolled portion 132 of the carcass ply 13 with respect to the tire section height SH [mm] is in the range of 0.10 ≤ Hcs / SH ≤ 0.49, preferably in the range of 0.15 ≤ Hcs / SH ≤ 0.47. Thereby, the radial height Hcs of the upper-rolled portion 132 of the carcass ply 13 is optimized. Specifically, by the above lower limit, the load-carrying capacity of the sidewall portion is ensured, and by the above upper limit, the deterioration of the rolling resistance caused by the increase in the mass of the carcass ply is suppressed.

[0100] The radial height Hcs [mm] of the upper-rolled portion 132 of the carcass ply 13 is measured in a non-loaded state with the tire mounted on a specified rim and a specified internal pressure applied.

[0101] For example, in the Figure 2 configuration, the end portion (reference numeral omitted) on the radially outer side of the upper-rolled portion 132 of the carcass ply 13 is located in a region radially inner than the tire maximum width position Ac. More specifically, it is located in a region at the 70 [%] radial position Al' from the tire maximum width position Ac to a distance Hu described later. At this time, the contact height Hcs' [mm] between the main body portion 131 and the upper-rolled portion 132 of the carcass ply 13 with respect to the tire section height SH [mm] is in the range of 0.07 ≤ Hcs' / SH, preferably in the range of 0.10 ≤ Hcs' / SH. Thereby, the load-carrying capacity of the sidewall portion is effectively improved. The upper limit of the ratio Hcs' / SH is not particularly limited, but is restricted by the relationship that the contact height Hcs' has Hcs' < Hcs with respect to the radial height Hcs of the upper-rolled portion 132 of the carcass ply 13.

[0102] The contact height Hcs' of the carcass ply 13 is the extending length in the tire radial direction of the region where the main body portion 131 and the upper-rolled portion 132 are in contact with each other, and is measured in a non-loaded state with the tire mounted on a specified rim and a specified internal pressure applied.

[0103] It should be noted that the contact height Hcs' of the carcass ply 13 is not limited to the above structure, and the end portion of the upper-rolled portion 132 of the carcass ply 13 may be arranged in a region radially outer than the tire maximum width position Ac (not shown) by making the carcass ply 13 have a so-called high-turnup structure.

[0104] [belt ply]

[0105] Figure 3 is an explanatory view showing the laminated structure of the belt ply of the tire 1 described in Figure 1 . In this figure, the thin lines attached to each belt ply 141 to 144 schematically show the configuration of the belt cords.

[0106] exist Figure 1 In the structure of the belt layer 14, as described above, the belt layer 14 is formed by laminating a plurality of belt plies 141 to 144. Figure 3 As described above, these belt plies 141 to 144 are composed of a pair of cross belts 141 , 142 , a belt cover layer 143 , and a pair of belt edge cover layers 144 , 144 .

[0107] At this time, the strength Tbt [N / 50mm] of each of the pair of cross belts 141, 142 per 50 [mm] width is within the range of 25≤Tbt / OD≤250 relative to the tire outer diameter OD [mm], preferably within the range of 30≤Tbt / OD≤230. In addition, the strength Tbt [N / 50mm] of the cross belts 141, 142 is within the range of 45≤Tbt / SW≤500 relative to the total width SW [mm] of the tire, preferably within the range of 50≤Tbt / SW≤450. Thus, the load capacity of each of the pair of cross belts 141, 142 is properly ensured. Specifically, by the above lower limit, the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. In addition, it can also be used under high internal pressure, reducing the rolling resistance of the tire. In particular, in small-diameter tires, assuming that it is used under high internal pressure and high load, the durability of the above-mentioned tire and the effect of reducing rolling resistance are significantly obtained. By setting the upper limit described above, deterioration in rolling resistance due to an increase in the mass of the cross belt is suppressed.

[0108] The strength Tbt [N / 50mm] of the belt ply is calculated as follows. That is, the belt ply extending 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) is defined as the effective belt ply. In addition, the strength [N / belt cord] of each belt cord constituting the effective belt ply and the density [belt cord] of each 50[mm] width in the area of ​​80[%] of the tire contact width TW are calculated as the strength Tbt [N / 50mm] of the belt ply. The strength of the belt cord is measured by a tensile test at a temperature of 20[℃] in accordance with JIS K1017. For example, in a structure in which one belt cord is formed by twisting a plurality of monofilaments, the strength of the twisted belt cord is measured to calculate the strength Tbt of the belt ply. In addition, in the configuration where the belt layer 14 is formed by laminating a plurality of effective belt plies (see Figure 1 ), the above strength Tbt is defined for each layer of the multiple effective belt plies. For example, Figure 1 In the structure of , the pair of cross belts 141, 142 and the belt cover layer 143 correspond to the effective belt ply.

[0109] For example, in Figure 3 In the configuration, a pair of cross belts 141, 142 is formed by arranging steel belt cords covered with coating rubber at a cord angle (reference numerals omitted in the figure) of 15[deg] or more and 55[deg] or less relative to the tire circumferential direction. Cord diameter within the range of The cord diameter is 15 ≤ Ebt ≤ 75, and the strength Tbt [N / 50mm] of the cross belts 141 and 142 is achieved. The density Ebt [bars / 50mm] is preferably and 17≤Ebt≤50, more preferably in the range of and 20≤Ebt≤40. In addition, the belt cord is formed by twisting a plurality of monofilaments, and the monofilament diameter is exist In the range of within the range.

[0110] In addition, the cross belts 141 and 142 are not limited to the above-mentioned structure, and can also be composed of belt cords made of organic fiber materials (such as aramid, nylon, polyester, rayon, etc.) covered with coating rubber. In this case, by making the belt cords made of the above-mentioned organic fiber material have Cord diameter within the range of The strength Tbt [N / 50mm] of the cross belts 141 and 142 is achieved by keeping the density Ebt [strips / 50mm] within the range of 30≤Ebt≤65. In addition, belt cords made of organic fiber materials such as high-strength nylon, aramid, and mixed materials can be used within a range that is obvious to those skilled in the art.

[0111] In addition, the belt layer 14 may also have an additional belt (not shown). The additional belt is, for example, (1) a third cross belt, which is formed by coating a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling, and has a cord angle of 15 [deg] or more and 55 [deg] or less in absolute value, or (2) a so-called high-angle belt, which is formed by coating a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling, and may have a cord angle of 45 [deg] or more and 70 [deg] or less, preferably 54 [deg] or more and 68 [deg] or more in absolute value. In addition, the additional belt may be arranged (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 a pair of cross belts 141, 142 (not shown). As a result, the load capacity of the belt layer 14 is improved.

[0112] In addition, the total strength TTbt [N] of the belt layer 14 is within the range of 70 ≤ TTbt / OD ≤ 750 relative to the tire outer diameter OD [mm], preferably within the range of 90 ≤ TTbt / OD ≤ 690, more preferably within the range of 110 ≤ TTbt / OD ≤ 690, and further preferably within the range of 120 ≤ TTbt / OD ≤ 690. Thus, the load capacity of the entire belt layer 14 is ensured. Moreover, it is preferred to use the specified internal pressure P [kPa] of the tire, 0.16 × P ≤ TTbt / OD.

[0113] The total strength TTbt [N] of the belt layer 14 is calculated as the product of the strength of each belt cord [N / belt] and the total number of belt cords [belts] in the entire belt layer 14. Therefore, the total strength TTbt [N] of the belt layer 14 increases with the increase of the strength Tbt [N / 50mm] of each belt ply, the number of belt plies, etc.

[0114] In addition, the widest cross belt (in the pair of cross belts 141, 142 (in the configuration with the above-mentioned additional belt, the additional belt is included. The illustration is omitted) Figure 3 The width Wb1 [mm] of the cross belt 141 on the inner diameter side is relative to the narrowest cross belt (in Figure 3, the width Wb2 [mm] of the cross belt 142) on the outer diameter side is in the range of 1.00 ≤ Wb1 / Wb2 ≤ 1.40, preferably in the range of 1.10 ≤ Wb1 / Wb2 ≤ 1.35. In addition, the width Wb2 [mm] of the narrowest cross belt is in the range of 0.61 ≤ Wb2 / SW ≤ 0.96 relative to the total width SW [mm] of the tire, preferably in the range of 0.70 ≤ Wb2 / SW ≤ 0.94. By the above lower limit, the width of the belt ply is ensured, and the distribution of the ground contact pressure in the tire ground contact area is optimized, thereby ensuring the tire's resistance to uneven wear. By the above upper limit, the deformation of the ends of the belt ply when the tire rolls is reduced, and the separation of the peripheral rubber at the ends of the belt ply is suppressed.

[0115] The belt ply width 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 and a specified internal pressure applied in a no-load state.

[0116] In addition, the widest cross belt (in the pair of cross belts 141, 142 (in the configuration with the above-mentioned additional belt, the additional belt is included. The illustration is omitted) Figure 3 In the embodiment, the width Wb1 [mm] of the cross belt 141 on the inner diameter side is in the range of 0.85≤Wb1 / TW≤1.23 with respect to the tire contact width TW [mm], and preferably in the range of 0.90≤Wb1 / TW≤1.20.

[0117] For example, in Figure 1 to Figure 3 In the configuration, the wide cross belt 141 is arranged as the innermost layer in the tire radial direction, and the narrow cross belt 142 is arranged on the radial outer side of the wide cross belt 141. In addition, the belt cover layer 143 is arranged on the radial outer side of the narrow cross belt 142, covering the entire pair of cross belts 141 and 142. In addition, a pair of belt edge covering layers 144 and 144 are separated from each other and arranged on the radial outer side of the belt cover layer 143, covering the left and right edge portions of the pair of cross belts 141 and 142 respectively.

[0118] [Tread profile and tread thickness]

[0119] Figure 4 Yes means Figure 1 An enlarged view of the tread portion of the tire 1 described.

[0120] exist Figure 4In the embodiment, the drop amount DA [mm] of the tread profile at the tire contact end 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 a relationship of 0.020 ≤ TW / (DA × OD) ≤ 0.250. In addition, the drop amount DA [mm] of the tread profile at the tire contact end T has a relationship of 0.02 ≤ DA / TW ≤ 0.10 relative to the tire contact width TW [mm], preferably a relationship of 0.05 ≤ DA / TW ≤ 0.08. Thus, the drop angle of the tread shoulder area (defined by the ratio DA / (TW / 2)) is optimized, and the load capacity of the tread is appropriately ensured. Specifically, by the above lower limit, the drop angle of the tread shoulder area is ensured, thereby suppressing the reduction of wear life due to excessive contact pressure in the tread shoulder area. By the above upper limit, the tire contact area is flattened, the contact pressure becomes uniform, and the wear resistance of the tire is ensured. In particular, in a small-diameter tire, it is assumed that it is used under a high internal pressure and a high load, and thus the ground contact pressure distribution in the tire ground contact area can be effectively optimized by the above-mentioned configuration.

[0121] The drop DA is the distance in the tire radial direction from the intersection C1 of the tire equatorial plane CL and the tread profile in the tire meridian cross-sectional view to the tire ground contact edge T, and is measured when the tire is mounted on a specified rim and a specified internal pressure is applied and under no-load conditions.

[0122] The tire profile is the contour line of the tire in a cross-sectional view in the tire meridian direction, and is measured using a laser profiler. As the laser profiler, for example, a tire profile measuring device (manufactured by Matsuo Co., Ltd.) can be used.

[0123] In addition, the drop DA [mm] of the tread profile at the tire contact edge T preferably satisfies the following formula (5) relative to the tire outer diameter OD [mm] and the tire total width SW [mm]: wherein Emin = 2.5, Emax = 17, preferably Emin = 3.8, Emax = 13, and more preferably Emin = 4.0, Emax = 9.

[0124] [Formula 5]

[0125]

[0126] also, Figure 4 A point C1 on the tread profile in the tire equatorial plane CL and a pair of points C2 and C2 on the tread profile at a distance of 1 / 4 of the tire contact width TW from the tire equatorial plane CL are defined.

[0127] At this time, the radius of curvature TRc [mm] of the arc passing through the point C1 and the pair of points C2 is within the range of 0.15 ≤ TRc / OD ≤ 15, preferably within the range of 0.18 ≤ TRc / OD ≤ 12, relative to the tire outer diameter OD [mm]. In addition, the radius of curvature TRc [mm] of the arc is within the range of 30 ≤ TRc ≤ 3000, preferably within the range of 50 ≤ TRc ≤ 2800, and further preferably within the range of 80 ≤ TRc ≤ 2500. Thus, the load capacity of the tread portion is appropriately ensured. Specifically, by the above lower limit, the central area of ​​the tread portion is flattened, so that the ground contact pressure of the tire ground contact area becomes uniform, thereby ensuring the wear resistance of the tire. By the above upper limit, the reduction in wear life due to excessive ground contact pressure in the shoulder area of ​​the tread portion is suppressed. In particular, in a small-diameter tire, it is assumed that it is used under high internal pressure and high load, thereby effectively obtaining the equalization effect of the ground contact pressure under the use condition.

[0128] The radius of curvature of the arc is measured by mounting the tire on a specified rim, applying a specified internal pressure, and in a no-load state.

[0129] In addition, Figure 4 In the embodiment, the radius of curvature TRw [mm] of the circular arc passing through the point C1 of the tire equatorial plane CL and the left and right tire ground contact ends T, T is in the range of 0.30≤TRw / OD≤16 relative to the tire outer diameter OD [mm], and preferably in the range of 0.35≤TRw / OD≤11. In addition, the radius of curvature TRw [mm] of the circular arc is in the range of 150≤TRw≤2800, and preferably in the range of 200≤TRw≤2500. Thus, the load capacity of the tread portion is properly ensured. Specifically, by the above lower limit, the entire tire ground contact area is flattened, and the ground contact pressure becomes uniform, thereby ensuring the wear resistance of the tire. By the above upper limit, the reduction in wear life caused by excessive ground contact pressure in the shoulder area of ​​the tread portion is suppressed. Especially in small-diameter tires, it is assumed that they are used under high internal pressure and high load, and thus the ground contact pressure distribution in the tire ground contact area can be effectively optimized by the above configuration.

[0130] In addition, the curvature radius TRw [mm] of the first arc passing through the above-mentioned points C1 and C2 is within the range of 0.50≤TRw / TRc≤1.00 relative to the curvature radius TRw [mm] of the second arc passing through the point C1 and the tire ground contact end T, preferably within the range of 0.60≤TRw / TRc≤0.98, and more preferably within the range of 0.70≤TRw / TRc≤0.96. Thus, the ground contact shape of the tire is optimized. Specifically, by the above-mentioned lower limit, the ground contact pressure in the central area of ​​the tread is dispersed, thereby improving the wear life of the tire. By the above-mentioned upper limit, the reduction in wear life caused by excessive ground contact pressure in the shoulder area of ​​the tread is suppressed.

[0131] also, Figure 4 A point B1 on the carcass layer 13 on the tire equatorial plane CL and feet B2 and B2 of perpendicular lines extending from the left and right tire ground contact edges T and T to the carcass layer 13 are defined.

[0132] At this time, the curvature radius CRw of the arc passing through the point B1 and a pair of points B2, B2 is within the range of 0.35≤CRw / TRw≤1.60 relative to the curvature radius TRw of the arc passing through the above-mentioned point C1 and the tire ground contact ends T, T, preferably within the range of 0.45≤CRw / TRw≤1.50, and more preferably within the range of 0.55≤CRw / TRw≤1.40. In addition, the curvature radius CRw [mm] is within the range of 100≤CRw≤2500, preferably within the range of 120≤CRw≤2200. As a result, the tire ground contact shape is further optimized. Specifically, by the above-mentioned lower limit, the reduction in wear life caused by the increase in rubber thickness in the shoulder area of ​​the tread portion is suppressed. By the above-mentioned upper limit, the wear life of the central area of ​​the tread portion is ensured.

[0133] Figure 5 Yes means Figure 4 An enlarged view of a single side area of ​​the tread portion described in .

[0134] exist Figure 1 In the configuration of , as described above, the belt layer 14 has a pair of cross belts 141 , 142 , and the tread rubber 15 has a cap tread 151 and a base tread 152 .

[0135] In addition, Figure 5 In the embodiment, the distance Tce [mm] from the tread profile on the tire equatorial plane CL to the outer peripheral surface of the wide cross belt 141 has a relationship of 0.008≤Tce / OD≤0.13 relative to the tire outer diameter OD [mm], preferably has a relationship of 0.012≤Tce / OD≤0.10, and more preferably has a relationship of 0.015≤Tce / OD≤0.07. In addition, the distance Tce [mm] is in the range of 5≤Tce≤25, preferably in the range of 7≤Tce≤20. Thus, the load capacity of the tread portion is properly ensured. Specifically, by the above-mentioned lower limit, the deformation of the tire when used under high load is suppressed, thereby ensuring the wear resistance of the tire. In particular, in small-diameter tires, assuming that it is used under high internal pressure and high load, the above-mentioned wear resistance is significantly obtained. By the above-mentioned upper limit, the deterioration of rolling resistance caused by the increase in the mass of the tread rubber is suppressed.

[0136] The distance Tce is measured by mounting the tire on a predetermined rim, applying a predetermined internal pressure, and in a no-load state.

[0137] The outer peripheral surface of the belt ply is defined as the entire radially outer peripheral surface of the belt ply composed of the belt cords and the covering rubber.

[0138] Furthermore, the distance Tce [mm] from the tread profile on the tire equatorial plane CL to the outer peripheral surface of the wide cross belt 141 preferably satisfies the following formula (6) with respect to the tire outer diameter OD [mm]: wherein Fmin=35, Fmax=207, preferably Fmin=42, Fmax=202.

[0139] [Formula 6]

[0140] Fmin / (OD)∧(1 / 3)≤Tce≤Fmax / (OD)∧(1 / 3)…(6)

[0141] In addition, the distance Tsh [mm] from the tread profile at the tire ground contact end T to the outer peripheral surface of the wide cross belt 141 is within the range of 0.60 ≤ Tsh / Tce ≤ 1.70 relative to the distance Tce [mm] on the tire equatorial plane CL, preferably within the range of 0.80 ≤ Tsh / Tce ≤ 1.60, and more preferably within the range of 1.01 ≤ Tsh / Tce ≤ 1.50. By the above lower limit, the tread thickness in the shoulder area is ensured, thereby suppressing the repeated deformation of the tire when the tire rolls, thereby ensuring the wear resistance of the tire. In addition, by the above upper limit, the tread thickness in the central area is ensured, thereby suppressing the deformation of the tire when used under high loads unique to small-diameter tires, thereby ensuring the wear resistance of the tire.

[0142] The distance Tsh is measured by mounting the tire on a specified rim and applying a specified internal pressure under no-load conditions. If there is no wide cross belt directly below the tire ground contact end T, the distance Tsh is measured as the distance from the tread profile to the virtual line formed by the outer peripheral surface of the extended belt cord.

[0143] In addition, the distance Tsh [mm] from the tread profile at the tire ground contact end T to the outer peripheral surface of the wide cross belt 141 relative to the distance Tce [mm] on the tire equatorial plane CL preferably satisfies the following formula (7): wherein Gmin = 0.36, Gmax = 0.72, preferably Gmin = 0.37, Gmax = 0.71, and more preferably Gmin = 0.38, Gmax = 0.70.

[0144] [Formula 7]

[0145] Gmin*(OD)∧(1 / 7)≤Tsh / Tce≤Gmax*(OD)∧(1 / 7)…(7)

[0146] also, Figure 5An interval having a width ΔTW of 10[%] of the tire contact width TW is defined. At this time, the ratio of the maximum value Ta to the minimum value Tb of the rubber thickness of the tread rubber 15 in any interval of the tire contact area is within the range of 0[%] to 40[%], preferably within the range of 0[%] to 20[%]. In this configuration, the variation in the rubber thickness of the tread rubber 15 in any interval of the tire contact area (especially the interval including the ends of the belt carcass ply 141 to 144) is set to be smaller, so the distribution of the contact pressure in the tire width direction becomes smooth, thereby improving the wear resistance of the tire.

[0147] The rubber thickness of the tread rubber 15 is defined as the distance from the tread profile to the inner peripheral surface of the tread rubber 15 (in Figure 5 ( hereinafter referred to as “ ”, “ ” means the distance from the outer peripheral surface of the cap tread 151 to the inner peripheral surface of the base tread 152). Therefore, the rubber thickness of the tread rubber 15 is measured excluding the groove formed on the tread surface.

[0148] In addition, Figure 5 In the embodiment, the rubber thickness UTce of the base tread 152 on the tire equatorial plane CL is within the range of 0.04≤UTce / Tce≤0.60, preferably within the range of 0.06≤UTce / Tce≤0.50 relative to the distance Tce on the tire equatorial plane CL. Thus, the rubber thickness UTce of the base tread 152 is optimized.

[0149] In addition, the distance Tsh at the above-mentioned tire ground contact end T is within the range of 1.50≤Tsh / Tu≤6.90 relative to the rubber thickness Tu [mm] from the end of the wide cross belt 141 to the outer peripheral surface of the carcass layer 13, preferably within the range of 2.00≤Tsh / Tu≤6.50. As a result, the profile of the carcass layer 13 is optimized, thereby optimizing the tension of the carcass layer 13. Specifically, by the above-mentioned lower limit, the tension of the carcass layer and the tread thickness in the shoulder area are ensured, thereby suppressing the repeated deformation of the tire when the tire rolls, thereby ensuring the wear resistance of the tire. By the above-mentioned upper limit, the rubber thickness near the end of the belt cord layer is ensured, thereby suppressing the separation of the peripheral rubber of the belt cord layer.

[0150] The rubber thickness Tu is measured by inserting the rubber member between the end of the wide cross belt 141 and the carcass layer 13 (at Figure 5 Specifically, from the perspective of the cross section in the tire meridian direction, a vertical line is drawn from the end of the wide cross belt 141 down to the outer surface of the carcass layer 13, and the total thickness of the rubber components on the vertical line is calculated as the rubber thickness Tu.

[0151] The outer peripheral surface of the carcass layer 13 is defined as the entire radially outer peripheral surface of the carcass ply composed of the carcass cords and the covering rubber. In addition, when the carcass layer 13 has a multi-layer structure composed of a plurality of carcass plies (not shown), the outer peripheral surface of the outermost carcass ply constitutes the outer peripheral surface of the carcass layer 13. In addition, when the upper roll portion 132 of the carcass layer 13 (refer to Figure 1 ) exists between the end of the wide cross belt 141 and the carcass layer 13 (not shown in the figure), the outer peripheral surface of the rolled-up portion 132 constitutes the outer peripheral surface of the carcass layer 13.

[0152] For example, in Figure 5 In the configuration, the sidewall rubber 16 is inserted between the end of the wide cross belt 141 and the carcass layer 13, thereby forming a rubber thickness Tu between the end of the wide cross belt 141 and the carcass layer 13. However, the configuration of the sidewall rubber 16 is not limited thereto, and for example, a belt layer insulation rubber 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). In addition, 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.

[0153] In addition, Figure 1 In the configuration of the tire 1, the tire 1 has a plurality of circumferential main grooves 21 to 23 extending in the circumferential direction of the tire on the tread surface (see Figure 5 ) and land portions (symbols omitted in the figure) defined by these circumferential main grooves 21 to 23. The main grooves are defined as grooves having the obligation to display wear indicators as specified in JATMA.

[0154] At this time, if Figure 5 As shown, 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 within the range of 0.50 ≤ Gd1 / Gce ≤ 1.00 relative to the rubber thickness Gce [mm] of the tread rubber 15, and preferably within the range of 0.55 ≤ Gd1 / Gce ≤ 0.98. Thus, the wear resistance of the tire is ensured. Specifically, by the above lower limit, the ground contact pressure in the central area of ​​the tread portion is dispersed, thereby improving the wear life of the tire. By the above upper limit, the rigidity of the circumferential bank portion is ensured, and the rubber thickness from the groove bottom of the circumferential main groove 21 to the belt layer is ensured.

[0155] The circumferential main groove closest to the tire equatorial plane CL is defined as the circumferential main groove 21 located on the tire equatorial plane CL (see Figure 5 ), if there is no circumferential main groove on the tire equatorial plane CL (omitted from the illustration), it is defined as the circumferential main groove closest to the tire equatorial plane CL.

[0156] The ratio Gd1 / Gce preferably satisfies the following formula (8) with respect to the tire outer diameter OD [mm]: wherein Hmin=0.10, Hmax=0.60, preferably Hmin=0.12, Hmax=0.50, and more preferably Hmin=0.14, Hmax=0.40.

[0157] [Formula 8]

[0158] Hmin*250 / OD≤Gd1 / Gce≤Hmax+250 / OD…(8)

[0159] In addition, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the plurality of circumferential main grooves 21 to 23 is not less than the groove depths Gd2 [mm] and Gd3 [mm] of the other circumferential main grooves 22 and 23 (Gd2 ≤ Gd1, Gd3 ≤ Gd1). Specifically, when the area from the tire equatorial plane CL to the tire contact end T is divided into two equal parts along the tire width direction, the maximum value of the groove depth Gd1 of the circumferential main groove (the symbol in the figure is omitted) closest to the tire equatorial plane CL is within the range of 1.00 times or more and 2.50 times or less relative to the groove depths Gd2 and Gd3 of the other circumferential main grooves (the symbol in the figure is omitted) in the area on the tire contact end T side is within the range of 1.01 times or more and 2.00 times or less, and more preferably within the range of 1.05 times or more and 1.80 times or less. By the above lower limit, the ground contact pressure in the central area of ​​the tread portion is dispersed, and the wear resistance of the tire is improved. By setting the upper limit described above, uneven wear caused by an excessively large difference in ground contact pressure between the central region of the tread and the shoulder region is suppressed.

[0160] [Side profile and side thickness]

[0161] Figure 6 Yes means Figure 1 An enlarged view of the sidewall portion and the bead portion of the tire 1 described in . Figure 7 Yes means Figure 6 An enlarged view of the side wall portion described in .

[0162] Figure 6 The innermost layer relative to the belt layer 14 (in Figure 6In the figure, the point Au on the side profile at which the end of the inner diameter side cross belt 141 is located at the same position in the tire radial direction and the point Al on the side profile at which the end of the radially outer side relative to the bead core 11 is located at the same position in the tire radial direction. In addition, the distance Hu in the tire radial direction from the tire maximum width position Ac to the point Au and the distance H1 in the tire radial direction from the tire maximum width position Ac to the point Al are defined. In addition, the point Au' on the side profile at a radial position of 70[%] of the distance Hu from the tire maximum width position Ac and the point Al' on the side profile at a radial position of 70[%] of the distance H1 from the tire maximum width position Ac are defined.

[0163] At this time, the sum of the distance Hu [mm] and the distance Hl [mm] is relative to the tire section height SH [mm] (refer to Figure 2 ) is within the range of 0.45≤(Hu+Hl) / SH≤0.90, preferably within the range of 0.50≤(Hu+Hl) / SH≤0.85. Thus, the radial distance from the belt layer 14 to the bead core 11 is optimized. Specifically, by the above lower limit, the deformable area of ​​the sidewall portion is ensured, thereby suppressing the failure of the sidewall portion (for example, the separation of the rubber member at the radial outer end of the bead core 12). By the above upper limit, the deflection of the sidewall portion when the tire rolls is reduced, thereby reducing the rolling resistance of the tire.

[0164] The distance Hu and the distance H1 are measured by mounting the tire on a predetermined rim, applying a predetermined internal pressure, and in a no-load state.

[0165] In addition, the sum of the distance Hu [mm] and the distance Hl [mm] relative to the tire outer diameter OD ( Figure 1 ), tire section height SH [mm] (refer to Figure 2 ) and the curvature radius RSc [mm] of the arc passing through the tire maximum width position Ac, point Au' and point Al' preferably satisfy the following formula (9): wherein I1min = 0.06, I1max = 0.20, I2 = 0.70, preferably I1min = 0.09, I1max = 0.20, I2 = 0.65.

[0166] [Formula 9]

[0167]

[0168] The radius of curvature RSc of the arc is measured by mounting the tire on a predetermined rim and applying a predetermined internal pressure under no-load conditions.

[0169] In addition, the distance Hu [mm] and the distance Hl [mm] have a relationship of 0.30≤Hu / (Hu+Hl)≤0.70, and preferably have a relationship of 0.35≤Hu / (Hu+Hl)≤0.65. Thus, the position of the maximum width position Ac of the tire in the deformable area of ​​the sidewall portion is optimized. Specifically, by the above lower limit, the stress concentration near the end of the belt cord layer caused by the maximum width position Ac of the tire being too close to the end of the belt layer 14 is alleviated, thereby suppressing the separation of the surrounding rubber. By the above upper limit, the stress concentration near the bead portion caused by the maximum width position Ac of the tire being too close to the end of the bead core 11 is alleviated, thereby suppressing the reinforcement member of the bead portion (at Figure 6 In the figure, it is a fault of the tire bead core 12).

[0170] In addition, the radius of curvature RSc [mm] of the arc passing through the tire maximum width position Ac, point Au' and point Al' is within the range of 0.05≤RSc / OD≤1.70 relative to the tire outer diameter OD [mm], preferably within the range of 0.10≤RSc / OD≤1.60. In addition, the radius of curvature RSc [mm] of the arc is within the range of 25≤RSc≤330, preferably within the range of 30≤RSc≤300. Thus, the radius of curvature of the side profile is optimized, thereby properly ensuring the load capacity of the sidewall portion. Specifically, by the above lower limit, the deflection amount of the sidewall portion when the tire rolls is reduced, thereby reducing the rolling resistance of the tire. By the above upper limit, the stress concentration caused by the flattening of the sidewall portion is alleviated, thereby improving the durability of the tire. In particular, in small-diameter tires, when used under the above-mentioned high internal pressure and high load, a large stress will act on the sidewall portion. Due to such a tendency, there is also a problem that the side cutting resistance of the tire should be ensured. In this regard, by the above lower limit, the curvature radius of the side profile is ensured, the carcass tension is optimized, and thus the tire collapse is suppressed, thereby suppressing the side cutting of the tire. In addition, by the above upper limit, the side cutting of the tire caused by the excessive tension of the carcass layer 13 is suppressed.

[0171] Furthermore, the curvature radius RSc [mm] of the arc is within the range of 0.50≤RSc / SH≤0.99, preferably within the range of 0.55≤RSc / SH≤0.97, relative to the tire cross-section height SH [mm].

[0172] The arc curvature radius RSc [mm] preferably satisfies the following formula (10) with respect to the tire outer diameter OD [mm] and the rim diameter RD [mm]: wherein Jmin=15, Jmax=360, preferably Jmin=20, Jmax=330, and more preferably Jmin=25, Jmax=300.

[0173] [Formula 10]

[0174] Jmin*(OD / RD)∧(1 / 2)≤RSc≤Jmax+(OD / D)∧(1 / 2)…(10)

[0175] also, Figure 6 In the figure, a point Bc on the main body 131 of the carcass layer 13 located at the same position in the tire radial direction relative to the tire maximum width position Ac is defined. In addition, a point Bu' on the main body 131 of the carcass layer 13 located at a radial position of 70[%] of the above distance Hu from the tire maximum width position Ac is defined. In addition, a point Bl' on the main body 131 of the carcass layer 13 located at a radial position of 70[%] of the above distance H1 from the tire maximum width position Ac is defined.

[0176] At this time, the radius of curvature RSc [mm] of the arc passing through the maximum width position Ac of the tire, point Au' and point Al' is within the range of 1.10≤RSc / RCc≤4.00 relative to the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu' and point Bl', preferably within the range of 1.50≤RSc / RCc≤3.50. In addition, the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu' and point Bl' is within the range of 5≤RCc≤300, preferably within the range of 10≤RCc≤270. Thus, the relationship between the radius of curvature RSc of the side profile of the tire and the radius of curvature RCc of the side profile of the carcass layer 13 is optimized. Specifically, by the above lower limit, the radius of curvature RCc of the carcass profile is ensured, and the internal volume V of the tire described later is ensured, thereby ensuring the load capacity of the tire. By the above upper limit, the total thickness Gu and Gl of the sidewall portion described later are ensured, thereby ensuring the load capacity of the sidewall portion.

[0177] In addition, the curvature radius RSc [mm] of the side profile relative to the curvature radius RCc [mm] of the carcass profile and the tire outer diameter OD [mm] preferably satisfies the following formula (11): wherein Kmin=1, Kmax=130, preferably Kmin=2, Kmax=100, and more preferably Kmin=3, Kmax=70.

[0178] [Formula 11]

[0179] Kmin*(OD / RSc)∧(1 / 2)≤RCc≤Kmax*(OD / RSc)∧(1 / 2)…(11)

[0180] In addition, Figure 6, the total thickness Gu [mm] of the sidewall portion at the above point Au is within the range of 0.010 ≤ Gu / OD ≤ 0.080 relative to the tire outer diameter OD [mm], preferably within the range of 0.015 ≤ Gu / OD ≤ 0.050. Thus, the total thickness Gu of the radially outer region of the sidewall portion is optimized. Specifically, by the above lower limit, the total thickness Gu of the radially outer region of the sidewall portion is ensured, and the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. Especially in small-diameter tires, assuming that they are used under high internal pressure and high load, the above-mentioned effect of reducing the rolling resistance of the tire is significantly obtained. By the above upper limit, the deterioration of the tire rolling resistance caused by the excessive total thickness Gu is suppressed.

[0181] The total thickness of the sidewall portion is measured as the distance from the side profile to the inner surface of the tire on a vertical line drawn from a specific point on the side profile to the main body 131 of the carcass layer 13 .

[0182] In addition, Figure 6 In the above, the total thickness Gu [mm] at the point Au is within the range of 1.30 ≤ Gu / Gc ≤ 5.00 relative to the total thickness Gc [mm] of the sidewall portion at the maximum width position Ac of the tire, preferably within the range of 1.50 ≤ Gu / Gc ≤ 4.00. Thus, the thickness distribution of the sidewall portion from the maximum width position Ac of the tire to the innermost layer of the belt layer 14 is optimized. Specifically, by the above lower limit, the total thickness Gu of the radially outer region is ensured, and the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. By the above upper limit, the deterioration of the tire rolling resistance caused by the excessive total thickness Gu is suppressed.

[0183] In addition, the total thickness Gu [mm] at the above point Au preferably satisfies the following formula (12) relative to the total thickness Gc [mm] at the tire maximum width position Ac and the tire outer diameter OD [mm]: wherein Lmin = 0.10, Lmax = 0.70, preferably Lmin = 0.14, Lmax = 0.70, and more preferably Lmin = 0.19, Lmax = 0.70.

[0184] [Formula 12]

[0185] Lmin*(OD)∧(1 / 3)*Gc≤Gu≤Lmax*(OD)∧(1 / 3)*Gc…(12)

[0186] In addition, Figure 6In the embodiment, the total thickness Gc [mm] of the sidewall portion at the maximum width position Ac of the tire has a relationship of 0.003 ≤ Gc / OD ≤ 0.060 with respect to the tire outer diameter OD [mm], and preferably has a relationship of 0.004 ≤ Gc / OD ≤ 0.050. By the above lower limit, the total thickness Gc at the maximum width position Ac of the tire is ensured, thereby ensuring the load capacity of the tire. By the above upper limit, the effect of reducing the rolling resistance of the tire due to the thinning of the total thickness Gc at the maximum width position Ac of the tire is ensured.

[0187] In addition, the total thickness Gc [mm] at the tire maximum width position Ac preferably satisfies the following formula (13) with respect to the tire outer diameter OD [mm]: wherein Mmin=70, Mmax=450, preferably Mmin=80, Mmax=400.

[0188] [Formula 13]

[0189] Mmin / (OD)∧(1 / 2)≤Gc≤Mmax / (OD)∧(1 / 2)…(13)

[0190] In addition, the total thickness Gc [mm] at the maximum width position Ac of the tire preferably satisfies the following formula (14) with respect to the tire outer diameter OD [mm] and the tire total width SW [mm]: wherein Nmin = 0.20, Nmax = 15, preferably Nmin = 0.40, Nmax = 15, and more preferably Nmin = 0.60, Nmax = 12.

[0191] [Formula 14]

[0192] Nmin*(OD / SW)≤Gc≤Nmax*(OD / SW)…(14)

[0193] In addition, the total thickness Gc [mm] at the maximum tire width position Ac preferably satisfies the following formula (15) relative to the curvature radius RSc [mm] of the arc passing through the maximum tire width position Ac, point Au' and point Al': wherein Omin = 13, Omax = 260, preferably Omin = 20, Omax = 200.

[0194] [Formula 15]

[0195] Omin / (RSc)∧(1 / 2)≤Gc≤Omax / (RSc)∧(1 / 2)…(15)

[0196] In addition, Figure 6, the total thickness Gl [mm] of the sidewall portion at the above point A1 is within the range of 0.010 ≤ Gl / OD ≤ 0.150 relative to the tire outer diameter OD [mm], preferably within the range of 0.015 ≤ Gl / OD ≤ 0.100. Thus, the total thickness Gl of the radially inner region of the sidewall portion is optimized. Specifically, by the above lower limit, the total thickness Gl of the radially inner region of the sidewall portion is ensured, and the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. Especially in small-diameter tires, assuming that they are used under high internal pressure and high load, the above-mentioned effect of reducing the rolling resistance of the tire is significantly obtained. By the above upper limit, the deterioration of the tire rolling resistance caused by the excessive total thickness Gl is suppressed.

[0197] In addition, Figure 6 The ratio Gl / Gc of the total thickness Gl [mm] of the sidewall at the above point A1 to the total thickness Gc [mm] of the sidewall at the maximum width position Ac of the tire is within the range of 1.00 ≤ Gl / Gc ≤ 7.00, preferably within the range of 1.50 ≤ Gl / Gc ≤ 4.00. Thus, the thickness distribution of the sidewall from the maximum width position Ac of the tire to the bead core 11 is optimized. Specifically, by the above lower limit, the total thickness Gl of the radial inner area is ensured, and the deformation of the tire when used under high load is suppressed, thereby ensuring the durability of the tire. By the above upper limit, the deterioration of the tire rolling resistance caused by the excessive total thickness Gl is suppressed.

[0198] In addition, the total thickness Gl [mm] of the sidewall portion at the above-mentioned point A1 preferably satisfies the following formula (16) relative to the total thickness Gc [mm] at the tire maximum width position Ac and the tire outer diameter OD [mm]: wherein Pmin = 0.12, Pmax = 1.00, preferably Pmin = 0.15, Pmax = 1.00, and more preferably Pmin = 0.18, Pmax = 1.00.

[0199] [Formula 16]

[0200] Pmin*(OD)∧(1 / 3)*Gc≤Gl≤Pmax*(OD)∧(1 / 3)*Gc…(16)

[0201] In addition, Figure 6 In the embodiment, the total thickness Gl [mm] at the point A1 is within the range of 0.50 ≤ Gl / Gu ≤ 5.00 relative to the total thickness Gu [mm] at the point Au, preferably within the range of 1.00 ≤ Gl / Gu ≤ 3.00. Thus, the ratio of the total thickness Gl in the radially outer region of the sidewall portion to the total thickness Gu in the radially inner region is optimized.

[0202] In addition, the total thickness Gl [mm] at the above-mentioned point Al preferably satisfies the following formula (17) with respect to the total thickness Gu [mm] at the above-mentioned point Au and the tire outer diameter OD [mm]. Here, Qmin = 0.09, Qmax = 0.80, preferably Qmin = 0.10, Qmax = 0.70, and more preferably Qmin = 0.11, Qmax = 0.50.

[0203] [Formula 17]

[0204] Qmin*(OD)∧(1 / 3)*Gu ≤ Gl ≤ Qmax*(OD)∧(1 / 3)*Gu…(17)

[0205] In addition, in Figure 6 the average rubber hardness Hsc at the measurement position of the total thickness Gc, the average rubber hardness Hsu at the measurement position of the total thickness Gu, and the average rubber hardness HsI at the measurement point position of the total thickness Gl have the relationship of Hsc ≤ Hsu < HsI, preferably having the relationship of 1 ≤ Hsu - Hsc ≤ 18 and 2 ≤ HsI - Hsu ≤ 27, and more preferably having the relationship of 2 ≤ Hsu - Hsc ≤ 15 and 5 ≤ HsI - Hsu ≤ 23. Thereby, the relationship between the rubber hardnesses of the sidewall part is optimized.

[0206] The average rubber hardnesses Hsc, Hsu, and HsI are calculated in such a way that they are the sum of the products of the cross-sectional lengths and the rubber hardnesses of the respective rubber members at the respective measurement points of the total thickness Gc [mm] at the maximum width position Ac of the tire, the total thickness Gu at the point Au, and the total thickness Gl at the point Al, divided by the total thickness.

[0207] In addition, in Figure 7In the tire width direction, the distance ΔAu' [mm] from the maximum width position Ac of the tire to the point Au' is within the range of 0.03≤ΔAu' / (Hu×0.70)≤0.25 relative to 70% of the distance Hu [mm] from the above-mentioned maximum width position Ac of the tire, and preferably within the range of 0.07≤ΔAu' / (Hu×0.70)≤0.23. Thus, the curvature of the side profile in the radially outer area is optimized. Specifically, by the above-mentioned lower limit, the stress concentration caused by the flattening of the sidewall portion is alleviated, thereby improving the durability of the tire. By the above-mentioned upper limit, the deflection of the sidewall portion when the tire rolls is reduced, thereby reducing the rolling resistance of the tire. In particular, in small-diameter tires, when used under the above-mentioned high internal pressure and high load, a large stress will act on the sidewall portion. Due to such a tendency, there is also a problem of ensuring the tire's anti-side cutting performance. In this regard, by the above lower limit, the curvature radius of the side profile is ensured, the carcass tension is optimized, and thus the tire collapse is suppressed, thereby suppressing the side cutting of the tire. In addition, by the above upper limit, the side cutting of the tire caused by the excessive tension of the carcass layer 13 is suppressed.

[0208] In addition, the distance ΔAl' [mm] in the tire width direction from the tire maximum width position Ac to the point Al' is within the range of 0.03≤ΔAl' / (Hl×0.70)≤0.28 relative to 70% of the distance Hl [mm] from the tire maximum width position Ac, and preferably within the range of 0.07≤ΔAl' / (Hl×0.70)≤0.20. Thus, the curvature of the side profile in the radially inner area is optimized. Specifically, by the above lower limit, the stress concentration caused by the flattening of the sidewall portion is alleviated, thereby improving the durability of the tire. In particular, in small-diameter tires, since the bead core 11 is strengthened in the above manner, the stress concentration near the bead core 11 is effectively suppressed. By the above upper limit, the deflection of the sidewall portion when the tire rolls is reduced, thereby reducing the rolling resistance of the tire.

[0209] The distances ΔAu′ and ΔAl′ are measured by mounting the tire on a predetermined rim and applying a predetermined internal pressure in a no-load state.

[0210] In addition, the distance ΔAu' [mm] in the tire width direction from the tire maximum width position Ac to the point Au' preferably satisfies the following formula (18) relative to the curvature radius RSc [mm] of the arc passing through the above tire maximum width position Ac, the point Au' and the point Al': wherein Rmin = 0.05, Rmax = 5.00, preferably Rmin = 0.10, Rmax = 4.50.

[0211] [Formula 18]

[0212] Rmin*(RSc)∧(1 / 2)≤ΔAu′≤Rmax*(RSc)∧(1 / 2)…(18)

[0213] In addition, Figure 7 , the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is within the range of 1.00≤ΔBu' / ΔAu'≤7.00 relative to the distance ΔAu' [mm] in the tire width direction from the maximum tire width position to point Au', preferably within the range of 1.10≤ΔBu' / ΔAu'≤6.00. Thus, the relationship between the curvature of the side profile in the radially outer area and the curvature of the carcass profile is optimized. Specifically, by the above lower limit, the cutting resistance of the sidewall portion is ensured. By the above upper limit, the tension of the carcass layer 13 is ensured, the rigidity of the sidewall portion is ensured, and thus the load capacity and durability of the tire are ensured.

[0214] In addition, Figure 7 , the distance ΔBl' [mm] in the tire width direction from point Bc to point Bl' is within the range of 2.00≤ΔBl' / ΔAl'≤11.0 relative to the distance ΔAl' [mm] in the tire width direction from the tire maximum width position Ac to point Al', preferably within the range of 1.90≤ΔBl' / ΔAl'≤9.50. Thus, the relationship between the curvature of the side profile in the radially inner area and the curvature of the carcass profile is optimized. Specifically, by the above lower limit, the total thickness Gl of the sidewall portion is ensured, thereby ensuring the load capacity of the sidewall portion. By the above upper limit, the tension of the carcass layer 13 is ensured, the rigidity of the sidewall portion is ensured, thereby ensuring the load capacity and durability of the tire.

[0215] The distances ΔBu′ and ΔBl′ are measured by mounting the tire on a predetermined rim and applying a predetermined internal pressure in a no-load state.

[0216] In addition, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' preferably satisfies the following formula (19) relative to the curvature radius RCc [mm] of the arc passing through the above-mentioned points Bc, Bu' and Bl': wherein Smin = 0.40, Smax = 7.0, preferably Smin = 0.50, Smax = 6.0.

[0217] [Formula 19]

[0218] Smin*(RSc)∧(1 / 2)≤ΔBu′≤Smax*(RSc)∧(1 / 2)…(19)

[0219] In addition, Figure 7In the embodiment, the rubber thickness Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac is within the range of 0.35 ≤ Gcr / Gc ≤ 0.90 relative to the total thickness Gc [mm] at the maximum tire width position Ac. In addition, the rubber thickness Gcr [mm] of the sidewall rubber 16 is within the range of 1.5 ≤ Gcr, preferably within the range of 2.0 ≤ Gcr. By the above lower limit, the rubber thickness Gcr [mm] of the sidewall rubber 16 is ensured, thereby ensuring the load capacity of the sidewall portion.

[0220] In addition, the rubber thickness Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac preferably satisfies the following formula (20) relative to the total thickness Gc [mm] at the maximum tire width position Ac and the tire outer diameter OD [mm]: wherein Tmin = 80, Tmax = 0.90, preferably Tmin = 120, Tmax = 0.90.

[0221] [Formula 20]

[0222] Gc*(Tmin / OD)≤Gcr≤Gc*Tmax…(20)

[0223] In addition, Figure 7 In the embodiment, the rubber thickness Gin [mm] (not shown) of the inner liner 18 at the maximum tire width position Ac is within the range of 0.03 ≤ Gin / Gc ≤ 0.50, preferably within the range of 0.05 ≤ Gin / Gc ≤ 0.40 relative to the total thickness Gc [mm] at the maximum tire width position Ac. Thus, the inner surface of the carcass layer 13 is properly protected.

[0224] [Radial inner area of ​​the tire]

[0225] Figure 8 Yes means Figure 6 An enlarged view of the radial inner area of ​​the tire described in .

[0226] exist Figure 8 In the figure, a point Am on the side profile is defined at a radial position 35[%] of the distance H1 from the tire maximum width position Ac. Point Am corresponds to the midpoint between the tire maximum width position Ac in the tire radial direction and the point Al' on the side profile.

[0227] At this time, when the tire is mounted on a specified rim and a specified internal pressure is applied and the tire is in an unloaded state, the curvature radius RO [mm] of the arc passing through the tire maximum width position Ac, point A1' and point Am is relative to the tire section height SH [mm] (see Figure 2 ) is in the range of 0.20≤RO / SH≤1.20, preferably in the range of 0.30≤RO / SH≤1.10.

[0228] The above-mentioned structure has the advantage of optimizing the curvature radius RO of the side profile in the radial inner area of ​​the tire from the sidewall portion to the bead portion, and appropriately ensuring the tire load capacity. Specifically, the above-mentioned lower limit reduces the deflection of the radial inner area of ​​the tire when the tire rolls, thereby reducing the rolling resistance of the tire. The above-mentioned upper limit alleviates the stress concentration caused by the flattening of the radial inner area of ​​the tire, thereby improving the durability of the tire. Especially in small-diameter tires, when used under the above-mentioned high internal pressure and high load, a large stress will act on the area from the maximum width position Ac of the tire to the contact position with the rim flange portion. Due to such a tendency, the failure of the bead portion caused by the above-mentioned upper limit is effectively suppressed. As a result, the low rolling resistance performance and durability performance of the tire are taken into account.

[0229] In addition, Figure 8 In the embodiment, the radius of curvature RO [mm] of the arc is within the range of 60 ≤ RO / (SH / DW) ≤ 160 relative to the tire section width DW [mm] and the tire section height SH [mm], and preferably within the range of 70 ≤ RO / (SH / DW) ≤ 150. Thus, the radius of curvature RO [mm] of the arc is optimized relative to the aspect ratio SH / DW of the tire 1. Specifically, the deflection amount, i.e., the amount of repeated deformation, of the radial inner region of the tire during rolling is reduced by the above lower limit, thereby ensuring the durability of the tire. The stress concentration in the radial inner region of the tire is alleviated by the above upper limit, thereby improving the durability of the tire.

[0230] In addition, Figure 8 In the figure, the radius of curvature RO' [mm] of the arc is defined when the tire is mounted on a specified rim and a specified internal pressure is applied and a load of 100 [%] of the specified load is applied (dimension symbols are omitted in the figure). That is, the maximum width position Ac, point Al' and point Am of the tire in the above-mentioned no-load state are defined, and then the radius of curvature RO' [mm] of the arc passing through the three points Ac, Al' and Am (omitted in the figure) after displacement due to the application of a load of 100 [%] of the specified load is defined. At this time, the radius of curvature RO [mm] of the arc in the above-mentioned no-load state is within the range of 1.01 ≤ RO / RO' ≤ 1.60 relative to the radius of curvature RO' [mm] of the arc when 100 [%] of the specified load is applied, and preferably within the range of 1.10 ≤ RO / RO' ≤ 1.50. As a result, the radius of curvature RO' when a load of 100 [%] is applied is optimized. Specifically, the above lower limit ensures the deflection of the radial inner region of the tire when the load is applied, that is, when the load increases, thereby alleviating the stress concentration in the radial inner region of the tire. The above upper limit reduces the deflection of the radial inner region of the tire when the tire rolls, that is, the amount of repeated deformation, thereby ensuring the durability of the tire.

[0231] In addition, Figure 8 In the figure, the radius of curvature RO"[mm] of the arc is defined when the tire is mounted on a specified rim and a specified internal pressure is applied and a load of 150[%] of the specified load is applied (dimension symbols are omitted in the figure). That is, the radius of curvature RO"[mm] of the arc passing through three points Ac, Al and Am' (illustration omitted) after displacement due to the application of a load of 150[%] of the specified load is defined. At this time, the radius of curvature RO'[mm] of the arc when the above-mentioned load of 100[%] is applied is within the range of 1.01≤RO' / RO"≤1.50 relative to the radius of curvature RO"[mm] of the arc when the load of 150[%] is applied, and is preferably within the range of 1.05≤RO' / RO"≤1.40. In addition, the radius of curvature RO"[mm] of the arc when a load of 150[%] is applied is within the range of 30≤RO"≤80. As a result, the radius of curvature RO" when a load of 150[%] is applied, that is, when the load is high, is optimized. Specifically, the above lower limit ensures the deflection of the radial inner region of the tire when used under high load, thereby alleviating the stress concentration in the radial inner region of the tire. The above upper limit reduces the deflection of the radial inner region of the tire when the tire rolls, that is, the repeated deformation, thereby ensuring the durability of the tire.

[0232] In addition, Figure 8 In the above-mentioned side profile, the total thickness Gl' [mm] of the sidewall at point Al' is within the range of 1.01 ≤ Gl' / Gc ≤ 2.00, preferably within the range of 1.10 ≤ Gl' / Gc ≤ 1.90, relative to the total thickness Gc [mm] at the tire maximum width position Ac. In addition, the total thickness Gl' [mm] is within the range of 6.0 ≤ Gl' ≤ 20, preferably within the range of 7.0 ≤ Gl' ≤ 18. Thus, the thickness Gc and Gl' of the radial inner area of ​​the tire in the area from the tire maximum width position Ac to the contact position with the rim flange are optimized, thereby improving the durability of the tire.

[0233] In addition, Figure 8 In the above-mentioned side profile, the total thickness Gl' [mm] of the sidewall at point A1' is within the range of 0.40 ≤ Gl' / Gl ≤ 0.95 relative to the total thickness Gl [mm] of the sidewall at point A1, preferably within the range of 0.50 ≤ Gl' / Gl ≤ 0.90. Thus, the thickness Gl and Gl' of the bead portion in the contact area with the rim flange portion are optimized, thereby improving the durability of the tire.

[0234] In addition, Figure 8In the structure, as described above, the carcass layer 13 has a main body portion 131 extending along the inner surface of the tire and an upper roll portion 132 that is rolled up to the outside in the tire width direction in a manner that wraps the bead core 11 and extends in the tire radial direction. At this time, the rubber thickness Gr [mm] from the point Al' on the side profile to the upper roll portion 131 of the carcass layer 13 is within the range of 0.30 ≤ Gr / Gl' ≤ 0.80 relative to the total thickness Gl' [mm] of the sidewall portion at the point Al' on the side profile, and preferably within the range of 0.40 ≤ Gr / Gl' ≤ 0.70. In addition, the rubber thickness Gr [mm] is within the range of 3.0 ≤ Gr ≤ 10 [mm]. Thus, the rubber thickness at the contact position with the rim flange portion is optimized. Specifically, by the above lower limit, the rubber thickness at the contact position with the rim flange portion is ensured, thereby ensuring the durability of the tire. By the above upper limit, the deterioration of rolling resistance caused by excessive rubber thickness is suppressed.

[0235] [Carcass ply and belt ply]

[0236] Fig. 9 Yes means Figure 1 1 is an explanatory diagram of the layered structure of the carcass layer and the belt layer of the tire described in . This figure shows an enlarged view of the cross-sectional view in the meridian direction of the tire.

[0237] exist Figure 1 In the composition of Fig. 9 As shown, the carcass layer 13 is composed of a single carcass ply 13A made of a carcass cord 13cc covered with a coating rubber 13cr, and the belt layer 14 is composed of a pair of cross belts 141 and 142 made of a belt cord 14bc covered with a coating rubber 14cr. In addition, the inner liner 18 is arranged to cover the inner circumference of the carcass layer 13. However, the carcass layer 13 is not limited to the above-mentioned structure, and the carcass layer 13 can also be composed of a double carcass ply stacked (see the following description). Fig.10 ).

[0238] In addition, Fig. 9 The distance TL [mm] from the outer diameter center of the carcass cord 13cc of the carcass ply 13A (the innermost carcass ply in the structure in which the carcass ply 13 is a double-layer carcass ply (not shown)) to the inner surface of the tire is relative to the tire outer diameter OD [mm] (see Figure 1 ) is in the range of 0.001≤TL / OD≤0.009, preferably in the range of 0.002≤TL / OD≤0.008. In addition, the distance TL [mm] is relative to the tire total width SW [mm] (see Figure 1) is in the range of 0.003≤TL / SW≤0.025, preferably in the range of 0.004≤TL / SW≤0.020. By the above lower limit, air leakage is appropriately suppressed; by the above upper limit, increase in tire weight is suppressed. In addition, the distance TL [mm] is preferably 0.6≤TL.

[0239] The distance TL[mm] is based on the above two points B2 and B2 (see Figure 4 ) is calculated as the average value in the area between .

[0240] In addition, the distance TL [mm] is relative to the tire total width SW [mm], the tire outer diameter OD [mm] and the rim diameter RD [mm] (see Figure 1 ) is in the range of 1 / 80000≤TL / (SW×(OD-RD))≤1 / 3760.

[0241] In addition, Fig. 9 The distance TCSU [mm] from the center of the carcass cord 13cc of the carcass ply 13A (the innermost carcass ply in the structure in which the carcass ply 13 is a double-layer carcass ply stacked (not shown)) to the outer surface of the innermost carcass ply 13A is within the range of 0.09 ≤ TCSU / TL ≤ 1.00, preferably within the range of 0.20 ≤ TCSU / TL ≤ 0.90 relative to the distance TL [mm] from the center of the carcass cord 13cc of the innermost carcass ply 13A to the inner surface of the tire. By the above lower limit, air leakage is appropriately suppressed; by the above upper limit, the increase in tire weight is suppressed.

[0242] In addition, Fig. 9 In the embodiment, the modulus MC [MPa] of the covering rubber 13cr of the carcass ply 13A at 100 [%] elongation is within the range of MIL ≤ MC ≤ MB relative to the modulus MIL [MPa] of the inner liner 18 at 100 [%] elongation and the modulus MB [MPa] of the covering rubber 14cr of the innermost belt ply 141 of the belt layer 14 at 100 [%] elongation. In addition, the ratio MC / MIL is within the range of 1.00 ≤ MC / MIL ≤ 5.00, preferably within the range of 1.10 ≤ MC / MIL ≤ 4.50. In addition, the ratio MB / MC is within the range of 1.00 ≤ MB / MC ≤ 2.40, preferably within the range of 1.00 ≤ MB / MC ≤ 2.20. Furthermore, the modulus MC [MPa] of the covering rubber 13cr of the carcass ply 13A is within the range of 1.5 ≤ MC ≤ 12.0, preferably within the range of 2.0 ≤ MC ≤ 10.0. Thus, air leakage is appropriately suppressed and the durability of the tire is ensured.

[0243] In addition, Fig. 9The product of the thickness TC [mm] of the carcass ply 13A and the loss tangent tanδ of the covering rubber 13cr of the carcass ply 13A at 60 [°C] is in the range of 0.05≤TC×tanδ≤0.55, and more preferably in the range of 0.07≤TC×tanδ≤0.50. Thus, the heat generation of the carcass ply 13 is appropriately suppressed, and the durability of the tire is ensured.

[0244] Fig.10 Yes means Fig. 9 13 and 14. FIG. 1 is an explanatory diagram of an improved example of the laminated structure of the carcass layer 13 and the belt layer 14 described in FIG.

[0245] exist Fig. 9 In the structure of the carcass layer 13, as described above, the carcass layer 13 is composed of a single-layer carcass ply 13A. For example, it is assumed that the carcass cords 13cc of the carcass ply 13A are composed of inorganic fibers, particularly steel cords.

[0246] However, it is not limited to this. Fig.10 As shown in FIG. 1 , the carcass layer 13 may also have a structure in which two carcass plies 13A and 13B are stacked. For example, it is assumed that the carcass cords 13cc of the carcass plies 13A and 13B are composed of an organic fiber material. In this structure, the carcass ply 13B of the outermost layer of the carcass layer 13 and the belt ply of the innermost layer of the belt layer 14 (in Fig.10 The peeling force Hpp [N / 25mm] of the inner diameter side cross belt 141 per 25 [mm] width is within the range of 90≤Hpp / TCB≤300, preferably within the range of 100≤Hpp / TCB≤250, relative to the distance TCB [mm] from the outer diameter center of the carcass cord 13cc of the carcass ply 13B to the outer diameter center of the belt cord 14bc of the belt ply 141. In addition, the peeling force Hpp [N / 25mm] is within the range of 1.50≤Hpp / Ecs≤15.0, preferably within the range of 1.80≤Hpp / Ecs≤10.0, relative to the density Ecs [roots / 50mm] of the carcass cord 13cc of the carcass ply. Thus, the durability of the tire is ensured.

[0247] The peeling force Hpp [N / 25mm] is calculated by analyzing the average value of the maximum and minimum values ​​of the peak of the wavy curve obtained using a test sample having a long rectangular shape in the extending direction of the carcass cord and having a width of 25 [mm] and a length of 100 [mm] or more (preferably a length of 150 [mm] or more including a test clamping end of about 50 [mm]). In addition, the number of test samples is preferably 2 or more.

[0248] Fig.11 Yes means Fig. 9 13 and 14. FIG. 1 is an explanatory diagram of an improved example of the laminated structure of the carcass layer 13 and the belt layer 14 described in FIG.

[0249] exist Figure 1 In the structure of, as described above, the belt layer 14 is composed of a pair of cross belts 141, 142, a belt cover layer 143 and a pair of belt edge covering layers 144, 144. Fig. 9 As shown, a pair of cross belts 141 and 142 are stacked adjacent to the outer peripheral surface of the carcass layer 13 .

[0250] In contrast, Fig.11 In the configuration of , the belt layer 14 has an additional belt 145 as a third cross belt. The additional belt 145 is stacked on the outer periphery of the pair of cross belts 141 and 142.

[0251] also, Fig.11 The distance Hb between the cords of adjacent belt plies in a pair of cross belts 141, 142 and an additional belt 145 is defined in Fig.11 , the cord distance Hb1 of a pair of cross belts 141, 142 and the cord distance Hb2 of the outer diameter side cross belt 142 and the additional belt 145). At this time, the cord distance Hb_sh (omitted in the figure) at the end of at least one group of belt plies is in the range of 1.05≤Hb_sh / Hb_ce≤2.00 relative to the cord distance Hb_ce (omitted in the figure) on the tire equatorial plane CL, and preferably in the range of 1.50≤Hb_sh / Hb_ce≤1.80. Therefore, it is preferred to set the cord distance Hb larger in the central area of ​​the tread. By the above lower limit, the belt layer 14 effectively obtains the effect of suppressing the increase in the outer diameter of the tire; by the above upper limit, the durability of the belt layer is ensured. The above structure is achieved, for example, by thickening the thickness of the coating rubber of the belt ply in the central area of ​​the tread, inserting an additional rubber plate between adjacent belt plies, etc. (omitted in the figure).

[0252] [Effect]

[0253] As described above, [1] the tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 laid on the bead cores 11, 11, and a belt layer 14 arranged radially outside the carcass layer 13 (see Figure 1). In addition, 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. In addition, points Al on the side profile that are located at the same position in the tire radial direction relative to the radially outer ends of the bead cores 11, 11 are defined, a distance H1 in the tire radial direction from the tire maximum width position Ac to the point Al is defined, a point Al' on the side profile that is located at a radial position that is 70 [%] of the distance H1 from the tire maximum width position Ac is defined, and a point Am on the side profile that is located at a radial position that is 35 [%] of the distance H1 from the tire maximum width position Ac is defined (see Figure 8 ). At this time, when the tire is mounted on a specified rim and a specified internal pressure is applied and the tire is in an unloaded state, the radius of curvature RO [mm] of the arc passing through the tire maximum width position Ac, point Al' and point Am is relative to the tire section height SH [mm] (see Figure 2 ) is in the range of 0.20≤RO / SH≤1.20.

[0254] This structure has the advantage of optimizing the curvature radius RO of the side profile in the radial inner area of ​​the tire from the sidewall portion to the bead portion, thereby appropriately ensuring the load capacity of the tire. Specifically, the above-mentioned lower limit reduces the deflection of the radial inner area of ​​the tire when the tire rolls, thereby reducing the rolling resistance of the tire. The above-mentioned upper limit alleviates the stress concentration caused by the flattening of the radial inner area of ​​the tire, thereby improving the durability of the tire. Especially in small-diameter tires, when used under the above-mentioned high internal pressure and high load, a large stress will act on the area from the maximum width position Ac of the tire to the contact position with the rim flange portion. Due to such a tendency, the failure of the bead portion caused by the above-mentioned upper limit is effectively suppressed. As a result, it has the advantages of taking into account both the low rolling resistance performance and the durability performance of the tire.

[0255] [2] In the tire 1, in the tire 1 of the above [1], the radius of curvature RO [mm] (see Figure 8 ) relative to the tire section width DW [mm] (see Figure 1 ) and tire section height SH [mm] (see Figure 2 ) is within the range of 60≤RO / (SH / DW)≤150. As a result, there is an advantage that the curvature radius RO [mm] of the arc is optimized relative to the aspect ratio SH / DW of the tire 1. Specifically, the deflection amount, that is, the amount of repeated deformation, of the radial inner region of the tire during rolling is reduced by the above lower limit, thereby ensuring the durability of the tire. The stress concentration in the radial inner region of the tire is alleviated by the above upper limit, thereby improving the durability of the tire.

[0256] [3] In the tire 1, in the tire 1 of the above [1] or [2], the radius of curvature RO of the arc in the no-load state (see Figure 8 ) The radius of curvature RO' [mm] (not shown) of the arc when the tire is mounted on a specified rim and a specified internal pressure is applied and a load of 100 [%] of the specified load is applied is within the range of 1.01 ≤ RO / RO' ≤ 1.60. Thus, there is an advantage of optimizing the radius of curvature RO' when a load of 100 [%] is applied. Specifically, by means of the above lower limit, the amount of deflection of the radially inner region of the tire when a load is applied, that is, when the load increases, is ensured, thereby alleviating stress concentration in the radially inner region of the tire. By means of the above upper limit, the amount of deflection of the radially inner region of the tire when the tire rolls, that is, the amount of repeated deformation, is reduced, thereby ensuring the durability of the tire.

[0257] In addition, [4] in the tire 1, in the tire 1 of the above [3], the radius of curvature RO' [mm] (illustration omitted) of the above arc when the above 100 [%] load is applied is within the range of 1.01≤RO' / RO"≤1.50 relative to the radius of curvature RO" [mm] (illustration omitted) of the above arc when the tire 1 is mounted on a specified rim and a specified internal pressure is applied and a load of 150 [%] of the specified load is applied. Thus, there is an advantage of optimizing the radius of curvature RO" when a load of 150 [%] is applied, that is, when a high load is applied. Specifically, by means of the above lower limit, the amount of deflection of the radially inner region of the tire when used under high load is ensured, thereby alleviating stress concentration in the radially inner region of the tire. By means of the above upper limit, the amount of deflection of the radially inner region of the tire when the tire rolls, that is, the amount of repeated deformation, is reduced, thereby ensuring the durability of the tire.

[0258] [5] In the tire 1, in the tire 1 described in any one of the above [1] to [4], the strength Tcs [N / 50mm] of the carcass cord layer constituting the carcass layer 13 per 50 [mm] width is within the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD [mm]. This configuration appropriately ensures the load capacity of the carcass layer 13 in a small-diameter tire, and thus has the advantage of taking into account both the durability performance and low rolling resistance performance of the tire. Specifically, by the above lower limit, deformation of the tire when used under high load is suppressed, thereby ensuring the durability performance of the tire. In addition, it can also be used under high internal pressure, reducing the rolling resistance of the tire. In particular, in a small-diameter tire, assuming that it is used under high internal pressure and high load, the durability performance of the tire and the effect of reducing rolling resistance are significantly obtained. By the above upper limit, the deterioration of rolling resistance caused by the increase in the mass of the carcass layer is suppressed.

[0259] [6] In the tire 1, in the tire 1 described in [5] above, the carcass ply of the carcass layer 13 is formed by covering a carcass cord made of steel with a coating rubber. exist In addition, the density Ecs [lines / 50 mm] of the carcass cords is within the range of 25 ≤ Ecs ≤ 80. Thus, there is an advantage that the strength Tcs of the carcass layer 13 described above is achieved.

[0260] [7] In the tire 1 described in [6], the carcass cord is formed by twisting a plurality of monofilaments, and the monofilament diameter of the carcass cord is Cord diameter relative to carcass cord exist Thus, the strength Tcs of the carcass layer 13 is achieved.

[0261] [8] In the tire 1, in the tire 1 described in [5] above, the carcass layer 13 is formed by laminating a pair of carcass plies 13A and 13B (see Fig.10 ). In addition, a pair of carcass plies 13A, 13B are formed by covering carcass cords 13cc made of organic fiber material with a coating rubber 13cr. In addition, the cord diameter of the carcass cord 13cc is (Dimension symbols omitted) In addition, the density Ecs [lines / 50 mm] of the carcass cords 13 cc is within the range of 40≤Ecs≤70.

[0262] [9] In the tire 1 described in any one of [1] to [8] above, the total thickness Gl' [mm] of the sidewall portion at point A1' on the side profile is within the range of 1.01 ≤ Gl' / Gc ≤ 2.00 relative to the total thickness Gc [mm] at the tire maximum width position Ac (see Figure 8 ). Thus, the thickness Gc and Gl' of the inner region in the radial direction of the tire in the region from the maximum tire width position Ac to the contact position with the rim flange portion is optimized, thereby improving the durability of the tire.

[0263]

[10] In the tire 1 described in any one of [1] to [9] above, the total thickness Gl' [mm] of the sidewall portion at point A1' on the side profile is within the range of 0.4 ≤ Gl' / Gl ≤ 0.95 relative to the total thickness Gl [mm] of the sidewall portion at point A1 (see Figure 8 ). Thus, the thickness G1 and G1' of the bead portion in the contact area with the rim flange portion are optimized, thereby improving the durability of the tire.

[0264]

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

[10] , the carcass layer 13 includes a main body portion 131 extending along the inner surface of the tire and an upper roll portion 132 that is rolled up to the outside in the tire width direction and extends in the tire radial direction in a manner that wraps around the bead core 11 (see Figure 2 ). In addition, the rubber thickness Gr [mm] from the point Al' on the side profile to the roll-up portion 132 of the carcass layer 13 is within the range of 0.30 ≤ Gr / Gl' ≤ 0.80 relative to the total thickness Gl' [mm] of the sidewall portion at the point Al' on the side profile (see Figure 8 ). Thus, there is an advantage of optimizing the rubber thickness at the contact position with the rim flange. Specifically, by the above lower limit, the rubber thickness at the contact position with the rim flange is ensured, thereby ensuring the durability of the tire. By the above upper limit, the rolling resistance deterioration caused by excessive rubber thickness is suppressed.

[0265]

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

[11] , the carcass layer 13 includes a main body portion 131 extending along the inner surface of the tire and an upper roll portion 132 that is rolled up to the outside in the tire width direction and extends in the tire radial direction in a manner that wraps around the bead core 11 (see Figure 2 ). In addition, the radial height Hcs [mm] from the measurement point of the tire inner diameter to the end of the roll-up portion 132 of the carcass layer 13 is within the range of 0.10 ≤ Hcs / SH ≤ 0.49 relative to the tire section height SH [mm] (see Figure 2 ). Thus, the radial height Hcs of the roll-up portion 132 of the carcass layer 13 is optimized. Specifically, the load capacity of the sidewall portion is ensured by the above lower limit, and the rolling resistance degradation caused by the increase in the mass of the carcass layer is suppressed by the above upper limit.

[0266] Example

[0267] Figure 12 to Figure 14 This is a graph showing the results of performance tests of tires according to the embodiments of the present invention.

[0268] Using this performance test, various test tires were evaluated with respect to (1) low rolling resistance performance (fuel consumption rate) and (2) durability performance. In addition, as an example of a small-diameter tire, two test tires of different tire sizes were used. Specifically, [A] a test tire with a tire size of 235 / 45R10 was assembled on a rim with a rim size of 10, and [B] a test tire with a tire size of 145 / 80R12 was assembled on a rim with a rim size of 12×4.00B.

[0269] In the (1) evaluation related to low rolling resistance performance, an internal pressure of 80[%] of the internal pressure specified by JATMA and a load of 80[%] of the load specified by JATMA are applied to the test tire. In addition, a four-wheel low-floor vehicle with test tires installed on all wheels is driven 50 laps at a speed of 100[km / h] on a test track with a total length of 2[km]. Thereafter, the fuel consumption rate [km / l] is calculated for evaluation. The evaluation is performed by an index evaluation based on the comparative example as a reference (100). The larger the value, the smaller the fuel consumption rate, the greater the tendency to reduce rolling resistance, and the more preferred it is. In addition, if the evaluation is above 98, it can be considered that the low rolling resistance performance is appropriately ensured.

[0270] In the evaluation related to (2) durability performance, an indoor roller tester with a roller diameter of 1707 [mm] was used to apply an internal pressure of 80 [%] of the internal pressure specified by JATMA and a load of 88 [%] of the load specified by JATMA to the test tire. Then, at a driving speed of 81 [km / h], the load was increased by 13 [%] every 2 hours, and the driving distance before the tire failed was measured. Then, based on the measurement results, an index evaluation was implemented with the comparative example as the reference (100). The larger the numerical value of this evaluation, the more preferred it is.

[0271] The test tire of the embodiment has Figures 1 to 3 and Figure 8 The tire has a structure as described above, and is provided with a pair of bead cores 11, 11, a carcass layer 13 consisting of a single carcass ply, a belt layer 14 consisting of a pair of cross belts 141, 142, a belt cover layer 143 and a pair of belt edge cover layers 144, 144, a tread rubber 15, a sidewall rubber 16 and a rim guard rubber 17. In addition, the tire outer diameter OD is 531 [mm], the tire total width SW and the tire section width DW are 143 [mm], the tire section height SH is 123 [mm], and the tire inner diameter is 305 [mm].

[0272] In the test tire of the comparative example, the curvature radius RO [mm] of the arc passing through the tire maximum width position Ac, point A1′, and point Am in the test tire of Example 1 was set larger.

[0273] As shown in the test results, it can be seen that the test tires of Examples have both low rolling resistance performance and durability performance of the tire.

[0274] Description of Reference Numerals

[0275] 1: tire; 10: rim; 11: bead core; 12: bead core; 13: carcass layer; 131: main body; 132: roll-up part; 14: belt layer; 141, 142: cross belts; 143: belt cover layer; 144: belt edge covering layer; 15: tread rubber; 151: crown tread; 152: base tread; 16: sidewall rubber; 17: rim guard rubber; 18: lining; 21-23: circumferential main grooves.

Claims

1. A tire, characterized in that: A tire having a pair of bead cores, a carcass layer mounted on the bead cores, and a belt layer arranged radially outside the carcass layer. The tire outer diameter OD [mm] is within the range of 200 ≤ OD ≤ 660, The total tire width SW[mm] is within the range of 100≤SW≤400, A point Al on the side profile is defined which is located at the same position in the tire radial direction relative to the radially outer end of the tire bead core, a tire radial distance H1 from the tire maximum width position Ac to the point Al is defined, a point Al' on the side profile is defined which is located at a radial position which is 70[%] of the distance H1 from the tire maximum width position Ac, a point Am on the side profile is defined which is located at a radial position which is 35[%] of the distance H1 from the tire maximum width position Ac, and, When the tire is mounted on a specified rim and subjected to a specified internal pressure and is in an unloaded state, the curvature radius RO [mm] of the arc passing through the tire maximum width position Ac, point Al' and point Am is in the range of 0.20≤RO / SH≤1.20 relative to the tire section height SH [mm].

2. The tire according to claim 1, wherein: The curvature radius RO [mm] of the arc is in the range of 60≤RO / (SH / DW)≤150 relative to the tire section width DW [mm] and the tire section height SH [mm].

3. The tire according to claim 1, wherein: The curvature radius RO [mm] of the arc in the unloaded state is within the range of 1.01≤RO / RO'≤1.60 relative to the curvature radius RO' [mm] of the arc when the tire is mounted on a predetermined rim and a load of 100 [%] of the predetermined load is applied with a predetermined internal pressure.

4. The tire according to claim 3, wherein: The curvature radius RO' [mm] of the arc when the 100[%] load is applied is within the range of 1.01≤RO' / RO"≤1.50 relative to the curvature radius RO" [mm] of the arc when the tire is mounted on a specified rim and a load of 150[%] of the specified load is applied with a specified internal pressure.

5. The tire according to claim 1, wherein: The strength Tcs [N / 50 mm] of the carcass ply constituting the carcass layer per 50 [mm] width is within the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD [mm].

6. The tire according to claim 5, wherein: The carcass ply of the carcass layer is composed of carcass cords made of steel covered with a coating rubber. The cord diameter of the carcass cord exist within the range, and The density Ecs [cords / 50 mm] of the carcass cords is in the range of 25≤Ecs≤80.

7. The tire according to claim 6, wherein: The carcass cord is formed by twisting a plurality of monofilaments, and the monofilament diameter of the carcass cord is Cord diameter relative to the carcass cord exist within the range.

8. The tire according to claim 5, wherein: The carcass layer is formed by stacking a pair of carcass cord layers. The pair of carcass plies is formed by covering carcass cords made of organic fiber material with coating rubber. The cord diameter of the carcass cord exist within the range, and The density Ecs [cords / 50 mm] of the carcass cords is in the range of 40≤Ecs≤70.

9. The tire according to claim 1, wherein: The total thickness Gl' [mm] of the sidewall portion at the point Al' on the side profile is within the range of 1.01 ≤ Gl' / Gc ≤ 2.00 relative to the total thickness Gc [mm] at the tire maximum width position Ac.

10. The tire according to claim 1, wherein: The total thickness Gl' [mm] of the sidewall portion at the point A1' on the side profile is within the range of 0.4 ≤ Gl' / Gl ≤ 0.95 relative to the total thickness Gl [mm] of the sidewall portion at the point A1.

11. The tire according to claim 1, wherein: The carcass layer has a main body portion extending along the inner surface of the tire and a rolled-up portion rolled up to the outside in the tire width direction so as to wrap the bead core and extending in the tire radial direction, and The rubber thickness Gr [mm] from the point Al' on the side profile to the turned-up portion of the carcass layer is within the range of 0.30 ≤ Gr / Gl' ≤ 0.80 with respect to the total thickness Gl' [mm] of the sidewall portion at the point Al' on the side profile.

12. The tire according to claim 1, wherein: The carcass layer has a main body portion extending along the inner surface of the tire and a rolled-up portion rolled up to the outside in the tire width direction so as to wrap the bead core and extending in the tire radial direction, and A radial height Hcs [mm] from a measurement point of the tire inner diameter to an end of the turned-up portion of the carcass layer is within a range of 0.10≤Hcs / SH≤0.49 relative to a tire section height SH [mm].

Images