Tire

Abstract

The present application provides a small-diameter tire that can balance wet performance and fuel consumption performance. The tire (1) includes a pair of bead cores (11, 11), a carcass layer (13) disposed on the bead cores (11, 11), a belt layer (14) disposed on the radially outer side of the carcass layer (13), and a tread portion. Furthermore, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400. The groove area ratio Aa [%] of the tread portion is in the range of 0.008 ≤ Aa / OD ≤ 0.150, and in the case where a region of 48 × (OD / SW)^(1 / 5) [%] from the maximum ground contact width end on the inner side of the tire in the case of being mounted on a vehicle is defined as an inner side region of the tire of the tread portion, the groove area ratio Ai [%] of the inner side region is in the relationship of Ai < Ao with the groove area ratio Ao [%] of an outer side region of the tire that is a region other than the inner side region.

Description

Technical Field

[0001] The present invention relates to a tire, and more specifically, to a small-diameter tire capable of achieving both wet performance and fuel consumption performance. Background Art

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

[0003] Description of Related Art

[0004] Patent Documents

[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 small-diameter tire capable of achieving both wet performance and fuel consumption performance.

[0008] Means for Solving the Problems

[0009] To achieve the above object, the tire of the present invention includes a pair of bead cores, a carcass layer spanning the bead cores, a belt layer disposed radially outward of the carcass layer, and a tread portion, the tire being characterized in that the tire outer diameter OD [mm] is in a range of 200 ≤ OD ≤ 660, the total tire width SW [mm] is in a range of 100 ≤ SW ≤ 400, and a groove area ratio Aa [%] of the tread portion is in a range of 0.008 ≤ Aa / OD ≤ 0.150.

[0010] In a case where a region of 48 × (OD / SW)^(1 / 5) [%] from the maximum ground contact width end on the tire inner side when mounted on a vehicle is defined as a tire inner region of the tread portion, a groove area ratio Ai [%] of the tire inner region and a groove area ratio Ao [%] of a tire outer region which is a region other than the tire inner region satisfy a relationship of Ai < Ao.

[0011] Effects of the Invention

[0012] The tire of the present invention has the advantage of achieving both the wet performance and the fuel consumption performance of the tire. Specifically, the groove area ratio Aa [%] of the tread portion is in the above range, and the groove area ratio Ai [%] and the groove area ratio Ao [%] satisfy the relationship of Ai < Ao, whereby the wet performance and the fuel consumption performance of the tire are ensured. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the tire along the radial direction according to an embodiment of the present invention.

[0014] Figure 2 It means Figure 1 The enlarged image of the tire recorded in the document.

[0015] Figure 3 It means Figure 1 The diagram illustrates the layered structure of the belt layers in a tire as described in the document.

[0016] Figure 4 It means Figure 1 The image shows an enlarged view of the tire tread area as described in the document.

[0017] Figure 5 It means Figure 4 An enlarged view of one side of the fetal face as described in the document.

[0018] Figure 6 It means Figure 1 The enlarged view of the tire sidewall and bead portion as described in the document.

[0019] Figure 7 It means Figure 6 An enlarged view of the side wall section as described in the document.

[0020] Figure 8 This is a diagram showing an example of the tread surface of the tire.

[0021] Figure 9 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0022] Figure 10 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0023] Figure 11 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0024] Figure 12 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0025] Figure 13 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0026] Figure 14 This is a graph showing the results of performance tests on tires according to embodiments of the present invention. Detailed Implementation

[0027] 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 this embodiment. Furthermore, the constituent elements of this embodiment include elements that are replaceable while maintaining the identity of the invention, and the replacements are obvious. Moreover, the various modifications described in this embodiment can be arbitrarily combined within the scope that is obvious to those skilled in the art.

[0028] [tire]

[0029] Figure 1 This is a cross-sectional view showing the radial direction of the tire 1 according to an embodiment of the present invention. The figure shows a cross-sectional view of a single-sided region of the radial direction of the tire 1 mounted on the rim 10. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

[0030] In this diagram, the tire radial section is defined as the section cut across the tire in a plane including the tire's axis of rotation (not shown). Furthermore, the tire equatorial plane CL is defined as a plane passing through the midpoint of the tire's section width as specified by JATMA and perpendicular to the tire's axis of rotation. Additionally, the tire width direction is defined as parallel to the tire's axis of rotation, and the tire radial direction is defined as perpendicular to the tire's axis of rotation. Furthermore, point T represents the tire's contact patch, and point Ac represents the tire's maximum width position.

[0031] Tire 1 has a ring structure centered on the tire's rotation axis, and includes a pair of bead cores 11, 11, a pair of sidewall cores 12, 12, a carcass layer 13, a belt layer 14, tread rubber 15, a pair of sidewall rubbers 16, 16, a pair of rim cushioning rubbers 17, 17, and an inner liner 18 (see reference). Figure 1 ).

[0032] A pair of bead cores 11, 11 are formed by winding one or more bead wires made of steel in a loop and multiple times, and are embedded in the bead portion to form the left and right bead portions. A pair of sidewall cores 12, 12 are respectively disposed on the radial outer periphery of the tire of the pair of bead cores 11, 11 to reinforce the bead portion.

[0033] The carcass layer 13 has a single-layer structure formed by a single layer of cord or a multi-layer structure formed by stacking multiple layers of cord, and is arranged in a ring between the left and right bead cores 11, 12 to form the tire skeleton. Furthermore, the two ends of the carcass layer 13 are rolled back and secured to the outside in the tire width direction, enclosing the bead core 11 and the sidewall core 12. Additionally, the cord layers of the carcass layer 13 are formed by coating multiple carcass cords made of steel or organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) with coated rubber and then rolling them, and have a cord angle of 80 degrees or more and 100 degrees or less (defined as the angle of inclination of the length direction of the carcass cord relative to the tire circumference).

[0034] The belt layer 14 is formed by stacking multiple belt ply layers 141-144, and is arranged around the outer periphery of the carcass layer 13. Figure 1 In its composition, the belted fabric layers 141 to 144 consist of a pair of cross belts 141 and 142, a belt covering layer 143, and a pair of belt edge covering layers 144 and 144.

[0035] A pair of cross belts 141 and 142 are constructed by rolling multiple belt cords made of steel or organic fiber material with coated rubber, and have a cord angle of 15 degrees or more and 55 degrees or less in absolute value (defined as the angle of inclination of the length direction of the belt cord relative to the tire circumference). Furthermore, the pair of cross belts 141 and 142 have cord angles of opposite signs, causing the length directions of the belt cords to intersect and overlap (a so-called cross-ply structure). The pair of cross belts 141 and 142 are stacked and arranged on the radially outer side of the tire carcass layer 13.

[0036] The belt cover layer 143 and the pair of belt edge cover layers 144, 144 are constructed by coating belt cover cords made of steel or organic fiber material with coated rubber, and have cord angles of 0 degrees or more and 10 degrees or less in absolute terms. Furthermore, the belt cover layer 143 and the belt edge cover layer 144 are, for example, strips made by coating one or more belt cover cords with coated rubber, which are wound multiple times in a spiral along the tire circumference around the outer periphery of the cross belts 141, 142. In addition, the belt cover layer 143 is configured to cover the entire area of ​​the cross belts 141, 142, and the pair of belt edge cover layers 144, 144 are configured to cover the left and right edges of the cross belts 141, 142 starting from the radially outer side of the tire.

[0037] The tread rubber 15 is disposed on the radial outer periphery of the tire carcass layer 13 and the belt layer 14 to form the tread portion of the tire 1. In addition, the tread rubber 15 has a crown tread 151 and a base tread 152.

[0038] The crown tread 151 is made of a rubber material with excellent ground contact characteristics and weather resistance, covering the entire area of ​​the tire contact surface and protruding from the tread, forming the outer surface of the tread portion. Furthermore, 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 having 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.

[0039] The rubber hardness Hs was determined at a temperature of 20 °C according to JIS K6253.

[0040] Modulus (strength) is determined according to JIS K6251 (using a No. 3 dumbbell) by tensile testing at 20°C using a dumbbell-shaped test piece.

[0041] The loss tangent tanδ was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., under conditions of 60 °C, 10% shear strain, ±0.5% amplitude, and 20 Hz frequency.

[0042] The base tread 152 is made of a heat-resistant rubber material and is sandwiched between the crown tread 151 and the belt layer 14, forming the base part of the tread rubber 15. Furthermore, 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. Preferably, it 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.

[0043] Furthermore, the difference in rubber hardness, Hs_cap - Hs_ut, is in the range of 3 or more and 20 or less, preferably in the range of 5 or more and 15 or less. Furthermore, the difference in modulus, M_cap - M_ut [MPa], is in the range of 0 or more and 1.4 or less, preferably in the range of 0.1 or more and 1.0 or less. Furthermore, the difference in loss tangent, tanδ_cap - tanδ_ut, is in the range of 0 or more and 0.22 or less, preferably in the range of 0.02 or more and 0.16 or less.

[0044] A pair of sidewall rubbers 16, 16 are respectively disposed on the outer side of the tire carcass layer 13 in the tire width direction to form the left and right sidewall portions. Figure 1 In this configuration, the radially outer end of the sidewall rubber 16 is disposed on the lower layer of the tread rubber 15 and sandwiched between the end of the belt layer 14 and the carcass layer 13. However, it is not limited to this; the radially outer end of the sidewall rubber 16 may also be disposed on the outer layer of the tread rubber 15 and protrude from the tire sidewall reinforcement (illustration omitted). In this case, the pad (illustration omitted) is sandwiched between the end of the belt layer 14 and the carcass layer 13.

[0045] Furthermore, the sidewall rubber 16 has a rubber hardness Hs_sw of 48 or more and 65 or less, a modulus M_sw [MPa] of 100% elongation of 1.0 or more and 2.4 or less, and a loss tangent tanδ_sw of 0.02 or more and 0.22 or less. Preferably, it has a rubber hardness Hs_sw of 50 or more and 59 or less, a modulus M_sw [MPa] of 100% elongation of 1.2 or more and 2.2 or less, and a loss tangent tanδ_sw of 0.04 or more and 0.20 or less.

[0046] A pair of rim cushioning rubbers 17, 17 extend radially inward from the inner side of the tire's radial direction from the rolled-back portion of the left and right bead cores 11, 11 and the carcass layer 13, towards the outer side in the tire's width direction, forming the rim mating surface of the bead portion. Figure 1 In the configuration, the radially outer end of the rim buffer rubber 17 is inserted into the lower layer of the sidewall rubber 16 and is sandwiched between the sidewall rubber 16 and the carcass layer 13.

[0047] The inner liner 18 is an air-permeable layer disposed on the inner surface of the tire cavity and covering the tire carcass layer 13. It inhibits oxidation of the tire carcass layer 13 due to exposure and also prevents leakage of air filled in the tire. In addition, the inner liner 18 may be made of, for example, a rubber composition with butyl rubber as the main component, or a thermoplastic resin or a thermoplastic elastomer composition in which elastomer components are blended into a thermoplastic resin.

[0048] In addition, Figure 1In this design, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, preferably in the range of 250 [mm] ≤ OD ≤ 580 [mm]. By using this small-diameter tire, the improved load-bearing capacity described later can be significantly achieved. Furthermore, the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400, preferably in the range of 105 [mm] ≤ SW ≤ 340 [mm]. Using this small-diameter tire 1, for example, the floor of a small vehicle can be lowered to increase interior space. In addition, due to the small moment of inertia, the tire weight is also small, thus improving fuel efficiency and reducing transportation costs. Especially when this small-diameter tire is installed in the wheel hub motor of a vehicle, the load on the motor can be effectively reduced.

[0049] The tire outer diameter (OD) is measured with the tire mounted on a specified rim and subjected to a specified internal pressure, under no-load conditions.

[0050] The total tire width SW is measured as the straight-line distance between the sidewalls (including all parts such as the tread pattern and lettering on the tire sidewalls) when the tire is mounted on a specified rim, given a specified internal pressure, and is in an unloaded state.

[0051] The specified rim refers to the "applied rim" as specified by JATMA, the "design rim" as specified by TRA, or the "measuring rim" as specified by ETRTO. Furthermore, the specified internal pressure refers to the "maximum tire pressure" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "inflation pressure" as specified by ETRTO. Additionally, the specified load refers to the "maximum load capacity" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "load capacity" as specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0052] Furthermore, the total tire width SW [mm] relative to the tire outer diameter OD [mm] is in the range of 0.23≤SW / OD≤0.84, preferably in the range of 0.25≤SW / OD≤0.81.

[0053] Furthermore, 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.

[0054] [Formula 1]

[0055]

[0056] In the tire 1 described above, it is assumed that a rim 10 with a rim diameter of 5 inches or more and 16 inches or less (i.e., 125 mm or more and 407 mm or less) is used. Furthermore, the rim diameter RD (mm) relative to the tire outer diameter OD (mm) is in the range of 0.50 ≤ RD / OD ≤ 0.74, preferably in the range of 0.52 ≤ RD / OD ≤ 0.71. This lower limit ensures the rim diameter RD, and in particular ensures the mounting space for the hub motor. This upper limit ensures the tire's internal volume V, which will be described later, and ensures the tire's load capacity.

[0057] It should be noted that the inner diameter of the tire is equal to the rim diameter RD of the rim 10.

[0058] Furthermore, it is assumed that the above-described tire 1 is used under 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, while the upper limit ensures the safety of the internal pressure filling operation.

[0059] Furthermore, it is assumed that the aforementioned tire 1 is installed on a vehicle that travels at low speeds, such as a minibus. 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. Furthermore, it is assumed that the aforementioned tire 1 is installed on a vehicle with 6 to 12 wheels. Thus, the load-bearing capacity of the tire is appropriately utilized.

[0060] In addition, the tire's aspect ratio, i.e., the tire section height SH [mm] (see below) Figure 2 ) and tire section width [mm] (dimension markings omitted in the figure: in Figure 1 The ratio of the width of the tire to the total width of the tire (SW) is in the range of 0.16 or higher and 0.85 or lower, preferably in the range of 0.19 or higher and 0.82 or lower.

[0061] The tire section height SH is the distance of half the difference between the tire's outer diameter and the rim diameter. It is measured with the tire mounted on a specified rim and subjected to a specified internal pressure under no-load conditions.

[0062] Tire section width is measured as the straight-line distance between the sidewalls (excluding tread patterns, lettering, etc. on the tire sidewalls) when the tire is mounted on a specified rim, given a specified internal pressure, and is in an unloaded state.

[0063] Furthermore, the tire contact width TW relative to the total tire width SW is in the range of 0.75≤TW / SW≤0.95, preferably in the range of 0.80≤TW / SW≤0.92.

[0064] Tire contact width (TW) is measured as the maximum straight-line distance along the tire axis on the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, placed perpendicular to the flat plate in a stationary state, and subjected to a load corresponding to a specified load.

[0065] Furthermore, the tire internal volume V [m^3] relative to the tire outer diameter OD [mm] is preferably within the range of 4.0 ≤ (V / OD) × 10^6 ≤ 60, and more preferably within the range of 6.0 ≤ (V / OD) × 10^6 ≤ 50. This optimizes the tire internal volume V. Specifically, by limiting the tire internal volume as described above, the tire's load-bearing capacity is ensured. Especially in small-diameter tires, assuming their use under high internal pressure and high load, it is preferable to sufficiently ensure the tire's internal volume V. By limiting the tire's internal volume as described above, tire enlargement caused by excessively large internal volume V is suppressed.

[0066] Furthermore, the tire internal volume V[m^3] relative to the rim diameter RD[mm] is in the range of 0.5≤V×RD≤17, preferably in the range of 1.0≤V×RD≤15.

[0067] [Bead core]

[0068] exist Figure 1 As described above, the pair of bead cores 11, 11 are formed by winding one or more bead wires (not shown) made of steel in a loop and multiple loops. In addition, a pair of sidewall cores 12, 12 are respectively disposed on the radial outer periphery of the tire of the pair of bead cores 11, 11.

[0069] Furthermore, the strength Tbd [N] of a bead core 11 relative to the tire outer diameter OD [mm] is in the range of 45 ≤ Tbd / OD ≤ 120, preferably in the range of 50 ≤ Tbd / OD ≤ 110, and more preferably in the range of 60 ≤ Tbd / OD ≤ 105. Furthermore, the strength Tbd [N] of the bead core relative to the total tire width SW [mm] is in the range of 90 ≤ Tbd / SW ≤ 400, preferably in the range of 110 ≤ Tbd / SW ≤ 350. This appropriately ensures the load-bearing capacity of the bead core 11. Specifically, the lower limit mentioned above suppresses tire deformation under high loads, thereby ensuring tire wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Especially in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned tire wear resistance and rolling resistance reduction are significantly achieved. The upper limit mentioned above suppresses the reduction in rolling resistance caused by the increase in the mass of the bead core.

[0070] The strength Tbd [N] of the bead core 11 is calculated as the product of the strength [N / wire] of each bead wire and the total number of bead wires in the radial sectional view. The strength of the bead wire is determined by a tensile test at 20 [°C] according to JIS G3510.

[0071] Furthermore, the strength Tbd [N] of the preferred bead core 11 satisfies the following formula (2) relative to the tire outer diameter OD [mm], distance SWD [mm], and rim diameter RD [mm]. Wherein, B1min=0.26, B2min=10.0, B1max=2.5, B2max=99.0, preferably B1min=0.35, B2min=14.0, B1max=2.5, B2max=99.0, more preferably B1min=0.44, B2min=17.6, B1max=2.5, B2max=99.0, and even more preferably B1min=0.49, B2min=17.9, B1max=2.5, B2max=99.0. Moreover, it is preferable to use the specified tire internal pressure P [kPa], where B1min=0.0016×P and B2min=0.07×P.

[0072] [Formula 2]

[0073]

[0074] The distance SWD is twice the radial distance from the tire's axis of rotation (illustration omitted) to the tire's maximum width position Ac, which is the diameter of the tire's maximum width position Ac. It is measured with the tire mounted on a specified rim and subjected to a specified internal pressure under no-load conditions.

[0075] The maximum tire width position Ac is defined as the maximum width position of the tire section width as specified by JATMA.

[0076] Furthermore, from a radial cross-sectional view of a bead core 11, the total cross-sectional area σbd [mm^2] of the bead wires made of steel is in the range of 0.025 ≤ σbd / OD ≤ 0.075 relative to the tire outer diameter OD [mm], preferably in the range of 0.030 ≤ σbd / OD ≤ 0.065. Furthermore, the total cross-sectional area σbd [mm^2] of the bead wires is in the range of 11 ≤ σbd ≤ 36, preferably in the range of 13 ≤ σbd ≤ 33. Thus, the strength Tbd [N] of the bead core 11 is achieved.

[0077] 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 wires from the radial section perspective of the bead core 11.

[0078] For example, in Figure 1 In its configuration, the bead core 11 has a quadrilateral formed by bead wires with circular cross-sections arranged in a grid pattern (not shown). However, it is not limited to this; the bead core 11 may also have a hexagon formed by bead wires with circular cross-sections arranged in a densest filling configuration (not shown). Furthermore, any arrangement of bead wires can be used to the extent that will be obvious to those skilled in the art.

[0079] Furthermore, the total cross-sectional area σbd[mm^2] of the preferred bead wires satisfies the following formula (3) relative 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.

[0080] [Formula 3]

[0081]

[0082] Furthermore, the total cross-sectional area σbd [mm^2] of the bead wires, relative to the total number of cross-sections (i.e., the total number of turns) Nbd [wires] of the bead wires in a single bead core 11 from a radial cross-sectional perspective, is preferably in the range of 0.60 ≤ σbd / Nbd ≤ 1.20, within the range of 0.50 [mm^2 / wire] to 1.40 [mm^2 / wire]. That is, the cross-sectional area σbd' [mm^2] of a single bead wire is preferably in the range of 0.60 [mm^2 / wire] to 1.20 [mm^2 / wire].

[0083] In addition, the maximum width Wbd [mm] of a bead core 11 in the radial section view (see below) Figure 2 The total cross-sectional area σbd [mm^2] of the bead wire is preferably in the range of 0.16≤Wbd / σbd≤0.50, and more preferably in the range of 0.20≤Wbd / σbd≤0.40.

[0084] In addition, Figure 1 In this configuration, 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 using the lower limit mentioned above, the tire's deflection is reduced, thus lowering the tire's rolling resistance. By using the upper limit mentioned above, the stress acting on the tire sidewall is reduced, thus suppressing tire failure.

[0085] [Peripheral layer]

[0086] Figure 2 It means Figure 1 An enlarged view of tire 1 as described in the figure. This figure shows a unilateral region bounded by the tire's equatorial plane CL.

[0087] exist Figure 1 As described above, in the tire's configuration, the carcass layer 13 is composed of a single layer of ply fabric and is arranged in a circular shape between the left and right bead cores 11, 12. Furthermore, the two ends of the carcass layer 13 are rolled back and secured to the outside of the tire width direction in a manner that wraps around the bead core 11 and the sidewall core 12.

[0088] Furthermore, the strength Tcs [N / 50mm] of each 50mm width of the ply constituting the carcass layer 13, relative to the tire outer diameter OD [mm], is in the range of 17 ≤ Tcs / OD ≤ 120, preferably in the range of 20 ≤ Tcs / OD ≤ 120. Furthermore, the strength Tcs [N / 50mm] of the carcass layer 13, relative to the total tire width SW [mm], is in the range of 30 ≤ Tcs / SW ≤ 260, preferably in the range of 35 ≤ Tcs / SW ≤ 220. This appropriately ensures the load-bearing capacity of the carcass layer 13. Specifically, by using the above lower limits, tire deformation under high loads is suppressed, thereby ensuring the tire's wear resistance. Furthermore, it allows for use under high internal pressure, reducing the tire's rolling resistance. Especially in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned tire wear resistance and rolling resistance reduction effects are significantly achieved. The aforementioned upper limit suppresses the reduction in rolling resistance caused by the increase in the mass of the tire carcass.

[0089] The strength Tcs [N / 50mm] of the ply is calculated as follows: The ply extending across the entire inner circumference of the tire, mounted on the left and right bead cores 11, 11, is defined as the effective ply. Furthermore, the strength Tcs [N / 50mm] of each carcass cord constituting the effective ply is calculated as the product of the strength [N / cord] of each carcass cord constituting the effective ply and the number of carcass cords embedded per 50mm width on the tire's equatorial plane CL [cords / 50mm]. The strength of the carcass cord is determined by a tensile test at 20°C according to JIS L1017. For example, in a carcass cord configuration formed by twisting multiple monofilaments together, the strength of the twisted carcass cord is measured, thereby calculating the strength Tcs of the carcass layer 13. Furthermore, in the configuration where the carcass layer 13 is a multi-layer structure (illustration omitted) formed by stacking multiple effective ply layers, the aforementioned strength Tcs is defined for each of the multiple effective ply layers.

[0090] For example, in Figure 1 In its construction, the carcass layer 13 has a single-layer structure consisting of a single-layer ply (reference numerals omitted in the figures), and the ply is formed by arranging carcass cords made of steel and coated with rubber at a cord angle of 80 degrees or more and 100 degrees or less relative to the tire circumference (figures omitted). Furthermore, by having the aforementioned steel carcass cords have a cord diameter φcs (mm) in the range of 0.3 ≤ φcs ≤ 1.1 and an embedded number of cords Ecs (cords / 50 mm) in the range of 25 ≤ Ecs ≤ 80, the strength Tcs (N / 50 mm) of the carcass layer 13 is achieved. Moreover, the carcass cords are formed by twisting multiple monofilaments together, and their monofilament diameter φcss (mm) is in the range of 0.12 ≤ φcss ≤ 0.24, preferably in the range of 0.14 ≤ φcss ≤ 0.22.

[0091] Furthermore, the ply layer is not limited to the above-described configuration and can also be composed of carcass cords made of organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) coated with rubber. In this case, the strength Tcs [N / 50mm] of the carcass layer 13 is achieved by having the carcass cords made of the aforementioned organic fiber materials with a cord diameter φcs [mm] in the range of 0.6 ≤ φcs ≤ 0.9 and an embedded number Ecs [strips / 50mm] in the range of 40 ≤ Ecs ≤ 70. Furthermore, carcass cords made of high-strength organic fiber materials such as nylon, aramid, and blended materials can be used to the extent that will be obvious to those skilled in the art.

[0092] Furthermore, the carcass layer 13 may also have a multi-layer structure consisting of multiple layers, such as double-layer plywood (illustration omitted). This effectively improves the tire's load-bearing capacity.

[0093] Furthermore, the total strength TTcs [N / 50mm] of the carcass layer 13 relative to the tire outer diameter OD [mm] is preferably in the range of 400 ≤ TTcs / OD ≤ 3000, within the range of 300 ≤ TTcs / OD ≤ 3500. This ensures the overall load-bearing capacity of the carcass layer 13.

[0094] The total strength TTcs[N] of the carcass layer 13 is calculated as the sum of the strengths Tcs[N] of the effective ply layers mentioned above. Therefore, the total strength TTcs[N] of the carcass layer 13 increases with the increase of the strength Tcs[N / 50mm] of each ply layer, the number of ply layers, the perimeter of the ply layer, etc.

[0095] Furthermore, the total strength TTcs[N] of the preferred carcass layer 13 satisfies the following formula (4) relative to the tire outer diameter OD[mm] and distance SWD[mm]. Wherein, Dmin=2.2, Dmax=40, preferably Dmin=4.3, Dmax=40, more preferably Dmin=6.5, Dmax=40, and even more preferably Dmin=8.7, Dmax=40. Moreover, it is preferable to use the specified tire internal pressure P[kPa], where Dmin=0.02×P.

[0096] [Formula 4]

[0097]

[0098] In addition, Figure 1 In its configuration, the carcass layer 13 has a main body portion 131 extending along the inner surface of the tire and an up-wound portion 132 that is rolled up to the outer side in the tire width direction and extends radially along the tire, in a manner that encloses the bead core 11. Furthermore, in Figure 2 In this design, the radial height Hcs [mm] from the measuring point of the rim diameter RD to the end of the upper rolled portion 132 of the carcass ply 13, relative to the tire section height SH [mm], is within the range of 0.49 ≤ Hcs / SH ≤ 0.80, and preferably within the range of 0.55 ≤ Hcs / SH ≤ 0.75. This optimizes the radial height Hcs of the upper rolled portion 132 of the carcass ply 13. Specifically, the lower limit ensures the load capacity of the sidewall, and the upper limit suppresses the decrease in rolling resistance caused by the increase in the mass of the carcass ply.

[0099] The radial height Hcs [mm] of the upper rolled portion 132 of the carcass layer 13 is measured with the tire mounted on a specified rim and given a specified internal pressure, under no-load conditions.

[0100] For example, in Figure 2In the configuration, the radially outer end (reference numeral in the drawing is omitted) of the turn-up portion 132 of the carcass ply 13 is located in the region between the tire maximum width position Ac and the end of the belt layer 14 (point Au described later), more specifically, in the region from the tire maximum width position Ac to the radial position Au' which is 70[%] of the distance Hu described later. At this time, the contact height Hcs' [mm] between the main body portion 131 and the turn-up portion 132 of the carcass ply 13 satisfies 0.07≤Hcs' / SH relative to the tire sectional height SH [mm], and preferably satisfies 0.15≤Hcs' / SH. As a result, the load capacity of the sidewall portion is effectively improved. The upper limit of Hcs' / SH is not particularly limited, but is restricted by the relationship that the contact height Hcs' satisfies Hcs'<Hcs relative to the radial height Hcs of the turn-up portion 132 of the carcass ply 13.

[0101] The contact height Hcs' of the carcass ply 13 is the extension length in the tire radial direction of the region where the main body portion 131 and the turn-up portion 132 are in contact with each other, and is measured in a no-load state after the tire is mounted on a specified rim and inflated to a specified internal pressure.

[0102] It should be noted that the end of the turn-up portion 132 of the carcass ply 13 is not limited to the above configuration, and by providing the carcass ply 13 with a so-called low-turn-up structure, the end of the turn-up portion 132 of the carcass ply 13 may also be arranged in the region between the tire maximum width position Ac and the bead core (illustration is omitted).

[0103] [Belt Layer]

[0104] Figure 3 shows Figure 1 is an explanatory view illustrating the laminated structure of the belt layer of the tire 1 described therein. In this drawing, the thin lines attached to the respective belt plies 141 to 144 schematically show the arrangement configuration of the belt cords.

[0105] In Figure 1 the configuration, as described above, the belt layer 14 is formed by laminating a plurality of belt plies 141 to 144. Furthermore, as described in Figure 3 , these belt plies 141 to 144 are composed of a pair of crossing belts 141, 142, a belt cover layer 143, and a pair of belt edge cover layers 144, 144.

[0106] At this point, the strength Tbt [N / 50mm] of each 50mm width of the pair of cross belts 141 and 142 relative to the tire outer diameter OD [mm] is in the range of 25 ≤ Tbt / OD ≤ 250, preferably in the range of 30 ≤ Tbt / OD ≤ 230. Furthermore, the strength Tbt [N / 50mm] of the cross belts 141 and 142 relative to the total tire width SW [mm] is in the range of 45 ≤ Tbt / SW ≤ 500, preferably in the range of 50 ≤ Tbt / SW ≤ 450. This appropriately ensures the load capacity of each pair of cross belts 141 and 142. Specifically, by using the above lower limits, tire deformation under high loads is suppressed, thereby ensuring the tire's wear resistance. Furthermore, it allows for use under high internal pressure, reducing the tire's rolling resistance. Especially in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned tire wear resistance and rolling resistance reduction effects are significantly achieved. The aforementioned upper limit suppresses the reduction in rolling resistance caused by the increase in the mass of the cross belt.

[0107] The strength Tbt [N / 50mm] of the belt cord layer is calculated as follows: The belt cord layer extending over an area covering 80% of the tire contact patch width TW centered on the tire equator plane CL (i.e., the central portion of the tire contact patch area) is defined as the effective belt cord layer. Furthermore, the strength [N / cord] of each belt cord constituting the effective belt cord layer is calculated as the product of the number of belt cords embedded in every 50mm width of the aforementioned 80% tire contact patch width TW, and this product is taken as the strength Tbt [N / 50mm] of the belt cord layer. The strength of the belt cord is determined by a tensile test at 20°C according to JIS L1017. For example, in a belt cord configuration formed by twisting multiple monofilaments together, the strength of the twisted belt cord is measured, thereby calculating the strength Tbt of the belt cord layer. Furthermore, in the configuration where the belt layer 14 is formed by stacking multiple effective belt layers (see reference...) Figure 1 The strength Tbt is defined for each layer in a multilayer effective belt layer. For example, in Figure 1 In the configuration, a pair of cross belts 141, 142 and belt cover layer 143 are equivalent to the effective belt fabric layer.

[0108] For example, in Figure 3In the configuration, a pair of cross belts 141 and 142 are formed by arranging steel belt cords coated with rubber at a cord angle of 15 degrees or more and 55 degrees or less relative to the tire circumference (reference numerals omitted in the figures). Furthermore, the strength Tbt (N / 50mm) of the cross belts 141 and 142 is achieved by having a cord diameter φbt (mm) in the range of 0.50 ≤ φbt ≤ 1.80 and an embedded number of cords Ebt (cords / 50mm) in the range of 15 ≤ Ebt ≤ 60. Moreover, the cord diameter φbt (mm) and the embedded number of cords Ebt (cords / 50mm) are preferably in the ranges of 0.55 ≤ φbt ≤ 1.60 and 17 ≤ Ebt ≤ 50, and more preferably in the ranges of 0.60 ≤ φbt ≤ 1.30 and 20 ≤ Ebt ≤ 40. Furthermore, the belted cord is formed by twisting multiple monofilaments together, and the diameter of its monofilament φbts [mm] is in the range of 0.16≤φbts≤0.43, preferably in the range of 0.21≤φbts≤0.39.

[0109] Furthermore, the cross-belts 141 and 142 are not limited to the above-described configuration and can also be made of belt cords made of organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) coated with rubber. In this case, the strength Tbt [N / 50mm] of the cross-belts 141 and 142 is achieved by having the belt cords made of the aforementioned organic fiber materials with a cord diameter φbt [mm] in the range of 0.50 ≤ φbt ≤ 0.90 and an embedded number Ebt [strips / 50mm] in the range of 30 ≤ Ebt ≤ 65. In addition, belt cords made of high-strength organic fiber materials such as nylon, aramid, and blended materials can be used within the scope that is obvious to those skilled in the art.

[0110] Furthermore, the belt layer 14 may also have an additional belt (illustration omitted). This additional belt may be, for example, (1) a third cross belt, which is formed by rolling multiple belt cords made of steel or organic fiber material with coated rubber, having a cord angle of 15 degrees or more and 55 degrees or less in absolute terms, or (2) a so-called high-angle belt, which is formed by rolling multiple belt cords made of steel or organic fiber material with coated rubber, having a cord angle of 45 degrees or more and 70 degrees or less, preferably 54 degrees or more and 68 degrees in absolute terms. Furthermore, the additional belt may be positioned between (a) 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 (illustration omitted). This improves the load-bearing capacity of the belt layer 14.

[0111] Furthermore, the total strength TTbt [N] of the belt layer 14 relative to the tire outer diameter OD [mm] is in the range of 70 ≤ TTbt / OD ≤ 750, preferably in the range of 90 ≤ TTbt / OD ≤ 690, more preferably in the range of 110 ≤ TTbt / OD ≤ 690, and even more preferably in the range of 120 ≤ TTbt / OD ≤ 690. This ensures the overall load-bearing capacity of the belt layer 14. Moreover, it is preferable to use the specified tire internal pressure P [kPa], where 0.16 × P ≤ TTbt / OD.

[0112] The total strength TTbt [N] of the belt layer 14 is used as the effective belt fabric layer mentioned above (in Figure 1 The strength Tbt [N / 50mm] of the pair of cross belts 141, 142 and belt cover layer 143 is calculated as a sum of the strengths. Therefore, the total strength TTbt [N] of the belt layer 14 increases with the increase of the strength Tbt [N / 50mm] of each belt fabric layer and the number of layers of the belt fabric layer.

[0113] Furthermore, the widest of the pair of cross straps 141 and 142 (in configurations with the aforementioned additional straps, illustration omitted) is the cross strap (in Figure 3 In the middle, the width Wb1 [mm] of the cross-belt bundle 141 on the inner diameter side is relative to the narrowest cross-belt bundle (in Figure 3 In the tire, 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. Furthermore, the width Wb2 [mm] of the narrowest cross belt relative to the total tire width SW [mm] is in the range of 0.61 ≤ Wb2 / SW ≤ 0.96, preferably in the range of 0.70 ≤ Wb2 / SW ≤ 0.94. By using the above lower limit, the width of the belt ply is ensured, optimizing the distribution of ground pressure in the tire contact patch area, thereby ensuring the tire's resistance to uneven wear. By using the above upper limit, deformation of the belt ply ends during tire rolling is reduced, suppressing the separation of the peripheral rubber at the belt ply ends.

[0114] The width of the belt ply is the distance between the left and right ends of each belt ply in the direction of the tire's rotation axis. It is measured with the tire mounted on a specified rim and given a specified internal pressure under no-load conditions.

[0115] Furthermore, the widest of the pair of cross straps 141 and 142 (in configurations with the aforementioned additional straps, illustration omitted) is the cross strap (in Figure 3In the middle, 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 relative to the tire ground contact width TW [mm], preferably in the range of 0.90≤Wb1 / TW≤1.20.

[0116] For example, in Figures 1-3 In this configuration, a wide cross belt 141 is disposed at the innermost radial layer of the tire, and a narrow cross belt 142 is disposed at the radial outer edge of the wide cross belt 141. Furthermore, a belt cover layer 143 is disposed at the radial outer edge of the narrow cross belt 142, covering the entirety of both cross belts 141 and 142. Additionally, a pair of belt edge cover layers 144, 144 are spaced apart from each other and disposed at the radial outer edge of the belt cover layer 143, respectively covering the left and right edges of the pair of cross belts 141 and 142.

[0117] [Tread profile and tread thickness]

[0118] Figure 4 It means Figure 1 An enlarged view of the tread of tire 1 as described.

[0119] exist Figure 4 In this design, the tread profile drop DA [mm] at the tire contact patch T, the tire contact width TW [mm], and the tire outer diameter OD [mm] have a relationship of 0.025 ≤ TW / (DA×OD) ≤ 0.400, preferably 0.030 ≤ TW / (DA×OD) ≤ 0.300. Furthermore, the tread profile drop DA [mm] at the tire contact patch T has a relationship of 0.008 ≤ DA / TW ≤ 0.060 relative to the tire contact width TW [mm], preferably 0.013 ≤ DA / TW ≤ 0.050. This optimizes the drop angle of the tread and shoulder areas (defined by the ratio DA / (TW / 2)), appropriately ensuring the load-bearing capacity of the tread. Specifically, by using the aforementioned lower limits, the drop angle of the tread and shoulder areas is ensured, thereby suppressing the reduction in wear life caused by excessive contact pressure in the tread and shoulder areas. By using the aforementioned upper limit, the tire contact patch becomes flatter, resulting in more uniform contact pressure and thus ensuring the tire's wear resistance. This is especially beneficial for small-diameter tires, which are typically used under high internal pressure and high loads; therefore, this configuration effectively optimizes the contact pressure distribution in the tire's contact patch area.

[0120] The drop DA is the radial distance from the intersection point C1 of the tire equatorial plane CL and the tread profile in the tire radial cross-sectional view along the tire's radial direction to the tire contact patch T. It is measured with the tire mounted on a specified rim and given a specified internal pressure under no-load conditions.

[0121] The tire profile is the outline of the tire in a cross-sectional view along the tire's radial direction, measured using a laser profile measuring instrument. For example, a tire profile measuring device (Matsuo Corporation) can be used as the laser profile measuring instrument.

[0122] Furthermore, the height difference DA [mm] of the tread profile at the tire contact point T is preferably satisfied by the following formula (5) relative to the tire outer diameter OD [mm] and the total tire width SW [mm]. Wherein, Emin=3.5, Emax=17, preferably Emin=3.8, Emax=13, and even more preferably Emin=4.0, Emax=9.

[0123] [Formula 5]

[0124]

[0125] also, Figure 4 The code defines 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 ground contact width TW from the tire equatorial plane CL.

[0126] At this point, the radius of curvature TRc [mm] of the arc passing through point C1 and a pair of points C2 is in the range of 0.15 ≤ TRc / OD ≤ 15 relative to the tire outer diameter OD [mm], preferably in the range of 0.18 ≤ TRc / OD ≤ 12. Furthermore, the radius of curvature TRc [mm] of the arc is in the range of 30 ≤ TRc ≤ 3000, preferably in the range of 50 ≤ TRc ≤ 2800, and even more preferably in the range of 80 ≤ TRc ≤ 2500. This appropriately ensures the load-bearing capacity of the tread. Specifically, by using the lower limit mentioned above, the central area of ​​the tread becomes flat, making the ground pressure in the tire contact area more uniform, thereby ensuring the tire's wear resistance. By using the upper limit mentioned above, the reduction in wear life caused by excessive ground pressure in the tread and shoulder areas is suppressed. Especially in small-diameter tires, assuming their use under high internal pressure and high load, the homogenization of ground pressure under these operating conditions is effectively achieved.

[0127] The radius of curvature of an arc is measured with the tire mounted on a specified rim, subjected to a specified internal pressure, and under no-load conditions.

[0128] In addition, Figure 4In this configuration, the radius of curvature TRw [mm] of the arc passing through point C1 on the tire equatorial plane CL and the left and right tire contact points T and T' is in the range of 0.30 ≤ TRw / OD ≤ 16 relative to the tire outer diameter OD [mm], preferably in the range of 0.35 ≤ TRw / OD ≤ 11. Furthermore, the radius of curvature TRw [mm] of the arc is in the range of 150 ≤ TRw ≤ 2800, preferably in the range of 200 ≤ TRw ≤ 2500. This appropriately ensures the load-bearing capacity of the tread area. Specifically, by using the lower limit mentioned above, the entire tire contact area becomes flat, making the contact pressure uniform, thereby ensuring the tire's wear resistance. By using the upper limit mentioned above, the reduction in wear life caused by excessive contact pressure in the tread and shoulder areas is suppressed. Especially in small-diameter tires, assuming their use under high internal pressure and high load, the above configuration effectively optimizes the contact pressure distribution in the tire contact area.

[0129] Furthermore, the radius of curvature TRw [mm] of the first arc passing through points C1 and C2 is within the range of 0.50 ≤ TRw / TRc ≤ 1.00, preferably within the range of 0.60 ≤ TRw / TRc ≤ 0.95, and more preferably within the range of 0.70 ≤ TRw / TRc ≤ 0.90, relative to the radius of curvature TRw [mm] of the second arc passing through point C1 and the tire contact patch T. This optimizes the tire's contact patch shape. Specifically, the lower limit disperses the contact patch pressure in the central area of ​​the tread, thereby improving the tire's wear life. The upper limit suppresses the reduction in wear life caused by excessive contact patch pressure in the tread and shoulder areas.

[0130] also, Figure 4 The definition includes point B1 on the tire carcass layer 13 on the tire equatorial plane CL and the feet of the perpendiculars B2 and B2 of the perpendiculars from the left and right tire contact points T and T to the tire carcass layer 13.

[0131] At this point, the radius of curvature CRw of the arc passing through point B1 and the pair of points B2, B2, relative to the radius of curvature TRw of the arc passing through point C1 and the tire contact points T, T, is in the range of 0.35 ≤ CRw / TRw ≤ 1.10, preferably in the range of 0.40 ≤ CRw / TRw ≤ 1.00, and more preferably in the range of 0.45 ≤ CRw / TRw ≤ 0.92. Furthermore, the radius of curvature CRw [mm] is in the range of 100 ≤ CRw ≤ 2500, preferably in the range of 120 ≤ CRw ≤ 2200. This further optimizes the tire contact shape. Specifically, the lower limit suppresses the reduction in wear life caused by the increase in rubber thickness in the tread and shoulder areas. The upper limit ensures the wear life of the central tread area.

[0132] Figure 5It means Figure 4 An enlarged view of one side of the fetal face as described in the document.

[0133] exist Figure 1 As described above, in the configuration, the belt layer 14 has a pair of cross belts 141, 142, and the tread rubber 15 has a crown tread 151 and a base tread 152.

[0134] In addition, Figure 5 In this tire, the distance Tce [mm] from the tread profile on the tire equatorial surface CL to the outer periphery 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 0.012 ≤ Tce / OD ≤ 0.10, and more preferably 0.015 ≤ Tce / OD ≤ 0.07. Furthermore, the distance Tce [mm] is in the range of 5 ≤ Tce ≤ 25, preferably in the range of 7 ≤ Tce ≤ 20. This appropriately ensures the load-bearing capacity of the tread. Specifically, the lower limit mentioned above suppresses tire deformation under high loads, thereby ensuring tire wear resistance. Especially in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned wear resistance is significantly achieved. The upper limit mentioned above suppresses the decrease in rolling resistance caused by the increase in tread rubber mass.

[0135] The distance Tce is measured with the tire mounted on a specified rim and subjected to a specified internal pressure under no-load conditions.

[0136] The outer peripheral surface of the belted cord fabric layer is defined as the entire radially outer peripheral surface of the belted cord fabric layer, which is composed of belted cords and coated rubber.

[0137] Furthermore, the distance Tce [mm] from the tread profile on the equatorial surface CL of the tire to the outer peripheral surface of the wide cross belt 141 is preferably satisfied by the following formula (6) relative to the tire outer diameter OD [mm]. Wherein, Fmin=35, Fmax=207, preferably Fmin=42, Fmax=202.

[0138] [Formula 6]

[0139]

[0140] Furthermore, the distance Tsh [mm] from the tread profile at the tire contact point T to the outer periphery of the wide cross belt 141, relative to the distance Tce [mm] on the tire equatorial plane CL, is preferably within the range of 0.60 ≤ Tsh / Tce ≤ 1.70, more preferably within the range of 1.01 ≤ Tsh / Tce ≤ 1.55, and even more preferably within the range of 1.10 ≤ Tsh / Tce ≤ 1.50. This lower limit ensures sufficient tread thickness in the shoulder area, thus suppressing repeated tire deformation during rolling and ensuring tire wear resistance. Furthermore, the upper limit ensures sufficient tread thickness in the central area, thus suppressing tire deformation under the characteristic high load conditions of small-diameter tires and ensuring tire wear resistance.

[0141] The distance Tsh is measured with the tire mounted on a specified rim and subjected to a specified internal pressure under no-load conditions. Furthermore, when there is no wide crossbelt directly below the tire's contact patch T, the distance Tsh is measured as the distance from the tread profile to the outer periphery of the extended belt cord.

[0142] Furthermore, the distance Tsh [mm] from the tread profile at the tire contact point T to the outer periphery of the wide cross belt 141 is preferably satisfied by the distance Tce [mm] on the tire equatorial plane CL, according to 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.

[0143] [Formula 7]

[0144]

[0145] also, Figure 5 The document defines a range of width ΔTW that is 10% of the tire contact patch width TW. At this point, the ratio of the maximum value Ta to the minimum value Tb of the tread rubber 15 in any range of the tire contact patch 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 range of the tire contact patch area (particularly including the ends of the belt ply layers 141 to 144) is set to be small, thus smoothing the distribution of contact pressure in the tire width direction and improving the tire's wear resistance.

[0146] The rubber thickness of tread rubber 15 is defined as the distance from the tread profile to the inner circumferential surface of tread rubber 15 (in Figure 5In this context, denoted as , is the distance from the outer peripheral surface of the crown tread 151 to the inner peripheral surface of the base tread 152. Therefore, excluding the grooves formed on the tread tread surface, the rubber thickness of the tread rubber 15 is measured.

[0147] In addition, Figure 5 In this embodiment, the rubber thickness UTce of the base tread 152 on the tire equatorial plane CL, relative to the distance Tce on the tire equatorial plane CL, is in the range of 0.04 ≤ UTce / Tce ≤ 0.60, preferably in the range of 0.06 ≤ UTce / Tce ≤ 0.50. This optimizes the rubber thickness UTce of the base tread 152.

[0148] Furthermore, the distance Tsh at the tire contact point T, relative to the rubber thickness Tu [mm] from the end of the wide cross belt 141 to the outer periphery of the carcass layer 13, is preferably in the range of 1.50 ≤ Tsh / Tu ≤ 6.90, and more preferably in the range of 2.00 ≤ Tsh / Tu ≤ 6.50. This optimizes the profile of the carcass layer 13, thereby optimizing its tension. Specifically, the lower limit ensures the tension of the carcass layer and the tread thickness in the shoulder area, thus suppressing repeated deformation of the tire during rolling and ensuring the tire's wear resistance. The upper limit ensures the rubber thickness near the end of the belt ply, thus suppressing the separation of the peripheral rubber of the belt ply.

[0149] Rubber thickness Tu serves as the rubber component between the end of the wide cross belt 141 and the carcass layer 13 (in Figure 5 In this study, the thickness of the sidewall rubber 16 is measured. Specifically, in a cross-sectional view along the tire's radial direction, a vertical line is drawn from the end of the wide cross belt 141 to the outer surface of the carcass layer 13, and the total thickness of the rubber components along this vertical line is calculated as the rubber thickness Tu.

[0150] The outer peripheral surface of the carcass layer 13 is defined as the entire radially outer peripheral surface of the ply composed of carcass cords and coated rubber. Furthermore, when the carcass layer 13 has a multi-layer structure composed of multiple ply layers (not shown), the outer peripheral surface of the outermost ply layer constitutes the outer peripheral surface of the carcass layer 13. Additionally, when the upper roll portion 132 of the carcass layer 13 (see reference...) Figure 1 When the upper roll portion 132 exists between the end of the wide cross belt 141 and the carcass layer 13 (illustration omitted), the outer peripheral surface of the upper roll portion 132 constitutes the outer peripheral surface of the carcass layer 13.

[0151] For example, in Figure 5In this configuration, the sidewall rubber 16 is inserted between the end of the wide cross-belt bundle 141 and the carcass layer 13, thereby forming a rubber thickness Tu between the end of the wide cross-belt bundle 141 and the carcass layer 13. However, the configuration of the sidewall rubber 16 is not limited to this. For example, a pad may be inserted between the end of the wide cross-belt bundle 141 and the carcass layer 13 instead of the sidewall rubber 16 (illustration omitted). Furthermore, the inserted rubber member has a rubber hardness Hs_sp of 46 or more and 67 or less, a modulus M_sp [MPa] at 100% elongation of 1.0 or more and 3.5 or less, and a loss tangent tanδ_sp of 0.02 or more and 0.22 or less. Preferably, it has a rubber hardness Hs_sp of 48 or more and 63 or less, a modulus M_sp [MPa] at 100% elongation of 1.2 or more and 3.2 or less, and a loss tangent tanδ_sp of 0.04 or more and 0.20 or less.

[0152] In addition, Figure 1 In its configuration, the tire 1 has multiple circumferential main grooves 21a, 21b, 22a and 22b extending along the tire circumference on its tread surface (see reference). Figure 4 The main grooves 21a, 21b, 22a, and 22b are divided into annular sections (reference numerals omitted in the figures). The main grooves are defined as grooves that have the obligation to display wear indicators as specified in JATMA.

[0153] At this point, the groove depth Gd1a [mm] of the circumferential main groove 21a, which is closest to the tire equatorial plane CL among the multiple circumferential main grooves 21a, 21b, 22a, and 22b, relative to the rubber thickness Gce [mm] of the tread rubber 15, is within the range of 0.50 ≤ Gd1a / Gce ≤ 1.00, preferably within the range of 0.55 ≤ Gd1a / Gce ≤ 0.98. This ensures the tire's wear resistance. Specifically, the lower limit mentioned above disperses the ground pressure in the central area of ​​the tread, thereby improving the tire's wear life. The upper limit mentioned above ensures the rigidity of the circumferential rim and also ensures the rubber thickness from the bottom of the circumferential main grooves 21a, 21b, 22a, and 22b to the belt layer.

[0154] The circumferential main groove closest to the tire equatorial plane CL is defined as the circumferential main groove located on the tire equatorial plane CL (illustration omitted). In the case where there is no circumferential main groove on the tire equatorial plane CL (refer to...), Figure 4 ), is defined as the circumferential main groove 21a that is closest to the tire equatorial plane CL.

[0155] Furthermore, the ratio Gd1a / Gce is preferably satisfied by the tire outer diameter OD [mm] according to the following formula (8). Wherein, Hmin=0.10, Hmax=0.60, preferably Hmin=0.12, Hmax=0.50, and more preferably Hmin=0.14, Hmax=0.40.

[0156] [Formula 8]

[0157]

[0158] In addition, among the multiple circumferential main grooves 21a, 21b, 22a and 22b, the groove depth Gd1a[mm] of the circumferential main groove 21a closest to the tire equatorial plane CL is greater than the groove depths Gd1b[mm], Gd2a[mm], and Gd2b[mm] of the other circumferential main grooves 21b, 22a and 22b (Gd1b≤Gd1a, Gd2a≤Gd1a, Gd2b≤Gd1a). Specifically, when the area from the tire equatorial surface CL to the tire contact patch T is divided into two equal parts along the tire width direction, the maximum value of the groove depth Gd1a of the circumferential main groove 21a closest to the tire equatorial surface CL relative to the groove depths Gd1b, Gd2a, and Gd2b of other circumferential main grooves 21b or other circumferential main grooves 22a and 22b located on the tire contact patch T side is within the range of 1.00 times or more and 2.50 times or less, preferably within the range of 1.00 times or more and 2.00 times or less, and more preferably within the range of 1.00 times or more and 1.80 times or less. This lower limit disperses the ground pressure in the central area of ​​the tread, improving the tire's wear resistance. The upper limit suppresses uneven wear caused by an excessively large difference in ground pressure between the central area of ​​the tread and the shoulder area.

[0159] [Side profile and side thickness]

[0160] Figure 6 It means Figure 1 Enlarged view of the sidewall and bead portion of tire 1 as described in the document. Figure 7 It means Figure 6 An enlarged view of the side wall section as described in the document.

[0161] Figure 6 The innermost layer relative to belt layer 14 is defined in [the definition]. Figure 6In this context, point Au is defined as the end of the inner diameter side cross belt 141 at the same position in the tire radial direction on the side profile, and point Al is defined as the end of the inner diameter side cross belt 141 at the same position in the tire radial direction on the side profile. Furthermore, the tire radial distance Hu from the tire maximum width position Ac to point Au and the tire radial distance Hl from the tire maximum width position Ac to point Al are defined. Additionally, point Au' is defined as the side profile located at a radial position 70% of the distance Hu from the tire maximum width position Ac, and point Al' is defined as the side profile located at a radial position 70% of the distance Hl from the tire maximum width position Ac.

[0162] At this point, the sum of distance Hu [mm] and distance Hl [mm] is relative to the tire profile height SH [mm] (refer to...). Figure 2 The radial distance from the belt layer 14 to the bead core 11 is optimized within the range of 0.45 ≤ (Hu + Hl) / SH ≤ 0.90, preferably within the range of 0.50 ≤ (Hu + Hl) / SH ≤ 0.85. Specifically, the lower limit ensures the deformable area of ​​the sidewall, thereby suppressing sidewall defects (e.g., separation of the rubber component at the radially outer end of the bead core 12). The upper limit reduces the deflection of the sidewall during tire rolling, thereby reducing the rolling resistance of the tire.

[0163] Distance Hu and distance Hl are measured with the tire mounted on a specified rim and given a specified internal pressure under no-load conditions.

[0164] Furthermore, the sum of the preferred distances Hu [mm] and Hl [mm] is relative to the tire outer diameter OD ( Figure 1 Tire section height SH [mm] (refer to) Figure 2 The radius of curvature RSc[mm] of the arc passing through the maximum width position Ac, point Au' and point Al' of the tire satisfies the following formula (9). Among them, I1min=0.06, I1max=0.20, I2=0.70, preferably I1min=0.09, I1max=0.20, I2=0.65.

[0165] [Formula 9]

[0166]

[0167] The radius of curvature RSc of the arc is measured with the tire mounted on a specified rim, given a specified internal pressure, and under no-load conditions.

[0168] Furthermore, the distances Hu [mm] and Hl [mm] have a relationship of 0.30 ≤ Hu / (Hu+Hl) ≤ 0.70, and preferably a relationship of 0.35 ≤ Hu / (Hu+Hl) ≤ 0.65. This optimizes the position of the maximum tire width position Ac in the deformable region of the tire sidewall. Specifically, by using the aforementioned lower limit, stress concentration near the end of the belt ply caused by the maximum tire width position Ac being too close to the end of the belt ply 14 is mitigated, thereby suppressing the separation of the peripheral rubber. By using the aforementioned upper limit, stress concentration near the bead portion caused by the maximum tire width position Ac being too close to the end of the bead core 11 is mitigated, thereby suppressing the stress concentration near the bead portion (in the bead portion reinforcement member). Figure 6 The fault is in the tire sidewall core 12.

[0169] Furthermore, the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al' is within the range of 0.05 ≤ RSc / OD ≤ 1.70 relative to the tire's outer diameter OD [mm], preferably within the range of 0.10 ≤ RSc / OD ≤ 1.60. Additionally, 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. This optimizes the radius of curvature of the sidewall profile, thereby appropriately ensuring the load-bearing capacity of the tire sidewall. Specifically, by using the aforementioned lower limit, the amount of deflection of the tire sidewall during tire rolling is reduced, thereby reducing the tire's rolling resistance. By using the aforementioned upper limit, stress concentration caused by the flattening of the tire sidewall is suppressed, thereby improving the tire's durability. Especially in small-diameter tires, there is a tendency for the tire sidewall to experience significant stress due to use under the aforementioned high internal pressure and high load; therefore, there is also the issue of ensuring the tire's resistance to sidewall shearing. In this respect, the lower limit ensures the radius of curvature of the side profile, optimizes tire tension, thereby suppressing tire collapse and thus suppressing tire sidewall cutting. Furthermore, the upper limit suppresses tire sidewall cutting caused by excessive tension in the carcass layer 13.

[0170] Furthermore, the radius of curvature RSc [mm] of the arc is in the range of 0.50 ≤ RSc / SH ≤ 0.95 relative to the tire profile height SH [mm], preferably in the range of 0.55 ≤ RSc / SH ≤ 0.90.

[0171] Furthermore, the radius of curvature RSc[mm] of the preferred arc satisfies the following formula (10) relative to the tire outer diameter OD[mm] and the rim diameter RD[mm]. Wherein, Jmin=15, Jmax=360, preferably Jmin=20, Jmax=330, more preferably Jmin=25, Jmax=300.

[0172] [Formula 10]

[0173]

[0174] also, Figure 6 A point Bc is defined on the main body 131 of the carcass layer 13, located at the same radial position relative to the tire's maximum width position Ac. Furthermore, a point Bu' is defined on the main body 131 of the carcass layer 13, located at a radial position 70% of the aforementioned distance Hu from the tire's maximum width position Ac. Additionally, a point Bl' is defined on the main body 131 of the carcass layer 13, located at a radial position 70% of the aforementioned distance Hl from the tire's maximum width position Ac.

[0175] At this point, the radius of curvature RSc [mm] of the arc passing through the maximum tire width positions Ac, Au', and Al' is in the range of 1.10 ≤ RSc / RCc ≤ 4.00, and preferably in the range of 1.50 ≤ RSc / RCc ≤ 3.50, relative to the radius of curvature RCc [mm] of the arc passing through Bc, Bu', and Bl'. Furthermore, the radius of curvature RCc [mm] of the arc passing through Bc, Bu', and Bl' is in the range of 5 ≤ RCc ≤ 300, and preferably in the range of 10 ≤ RCc ≤ 270. Thus, the relationship between the radius of curvature RSc of the tire's side profile and the radius of curvature RCc of the side profile of the carcass layer 13 is optimized. Specifically, the lower limit ensures the radius of curvature RCc of the carcass profile and the internal volume V of the tire (described later), thereby ensuring the tire's load capacity. The upper limit ensures the total thicknesses Gu and Gl of the sidewall portion (described later), thereby ensuring the load capacity of the sidewall portion.

[0176] Furthermore, the radius of curvature RSc [mm] of the aforementioned side profile is preferably satisfied by the following formula (11) relative to the radius of curvature RCc [mm] of the aforementioned carcass profile and the tire outer diameter OD [mm]. Wherein, Kmin=1, Kmax=130, preferably Kmin=2, Kmax=100, more preferably Kmin=3, Kmax=70.

[0177] [Formula 11]

[0178]

[0179] In addition, Figure 6In this context, the total thickness Gu [mm] of the sidewall portion at 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 0.017 ≤ Gu / OD ≤ 0.070. This optimizes the total thickness Gu of the radially outer region of the sidewall portion. Specifically, by using the lower limit mentioned above, the total thickness Gu of the radially outer region of the sidewall portion is ensured, suppressing tire deformation under high loads and thus ensuring tire wear resistance. Particularly in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned reduction in tire rolling resistance is significantly achieved. By using the upper limit mentioned above, the reduction in tire rolling resistance caused by excessive total thickness Gu is suppressed.

[0180] The total thickness of the sidewall portion is measured as the distance from the sidewall profile to the inner surface of the tire on a vertical line drawn from a predetermined point on the sidewall profile to the main body 131 of the carcass layer 13.

[0181] In addition, Figure 6 In this configuration, the total thickness Gu [mm] at 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 tire width position Ac, and preferably within the range of 1.90 ≤ Gu / Gc ≤ 3.00. This optimizes the thickness distribution of the sidewall portion from the maximum tire width position Ac to the innermost layer of the belt layer 14. Specifically, the lower limit ensures the total thickness Gu in the radially outer region, suppressing tire deformation under high loads and thus ensuring tire wear resistance. The upper limit suppresses the reduction in tire rolling resistance caused by excessive total thickness Gu.

[0182] Furthermore, the total thickness Gu [mm] at point Au is preferably such that the total thickness Gc [mm] at the maximum tire width position Ac and the tire outer diameter OD [mm] satisfy the following formula (12). Wherein, Lmin=0.10, Lmax=0.70, preferably Lmin=0.14, Lmax=0.70, more preferably Lmin=0.19, Lmax=0.70.

[0183] [Formula 12]

[0184]

[0185] In addition, Figure 6In this design, the total thickness Gc [mm] of the sidewall portion at the tire's maximum width position Ac has a relationship of 0.003 ≤ Gc / OD ≤ 0.060 relative to the tire's outer diameter OD [mm], preferably 0.004 ≤ Gc / OD ≤ 0.050. This lower limit ensures the total thickness Gc at the tire's maximum width position Ac, thereby ensuring the tire's load-bearing capacity. The upper limit ensures the reduction in rolling resistance caused by thinning the total thickness Gc at the tire's maximum width position Ac.

[0186] Furthermore, the total thickness Gc[mm] at the maximum tire width position Ac is preferably satisfied by the following formula (13) relative to the tire outer diameter OD[mm]. Wherein, Mmin=70, Mmax=450, preferably Mmin=80, Mmax=400.

[0187] [Formula 13]

[0188]

[0189] Furthermore, the total thickness Gc [mm] at the maximum tire width position Ac preferably satisfies the following formula (14) relative to the tire outer diameter OD [mm] and the total tire width SW [mm]. Wherein, Nmin=0.20, Nmax=15, preferably Nmin=0.40, Nmax=15, more preferably Nmin=0.60, Nmax=12.

[0190] [Formula 14]

[0191]

[0192] Furthermore, the total thickness Gc [mm] at the maximum tire width position Ac preferably satisfies the following formula (15) relative to the radius of curvature RSc [mm] of the arc passing through the maximum tire width position Ac, point Au', and Al'. Wherein, Omin=13, Omax=260, preferably Omin=20, Omax=200.

[0193] [Formula 15]

[0194]

[0195] In addition, Figure 6In this context, the total thickness Gl [mm] of the sidewall at 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. This optimizes the total thickness Gl of the radially inner region of the sidewall. Specifically, by limiting the lower limit, the total thickness Gl of the radially inner region of the sidewall is ensured, suppressing tire deformation under high loads and thus ensuring tire wear resistance. Particularly in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned reduction in tire rolling resistance is significantly achieved. By limiting the upper limit, the reduction in tire rolling resistance caused by excessive total thickness Gl is suppressed.

[0196] In addition, Figure 6 In this context, the ratio of the total thickness Gl [mm] of the sidewall portion at point A1 to the total thickness Gc [mm] of the sidewall portion at the tire's maximum width position Ac, Gl / Gc, is preferably within the range of 1.00 ≤ Gl / Gc ≤ 7.00, and more preferably within the range of 2.00 ≤ Gl / Gc ≤ 5.00. This optimizes the thickness distribution of the sidewall portion from the tire's maximum width position Ac to the bead core 11. Specifically, the lower limit ensures a sufficient total thickness Gl in the radially inner region, suppressing tire deformation under high loads and thus ensuring the tire's wear resistance. The upper limit suppresses the reduction in tire rolling resistance caused by excessive total thickness Gl.

[0197] Furthermore, preferably, the total thickness Gl [mm] of the sidewall portion at point A1, relative to the total thickness Gc [mm] at the maximum tire width position Ac and the tire outer diameter OD [mm], satisfies the following formula (16). Wherein, Pmin=0.12, Pmax=1.00, preferably Pmin=0.15, Pmax=1.00, more preferably Pmin=0.18, Pmax=1.00.

[0198] [Formula 16]

[0199]

[0200] In addition, Figure 6 In this context, the total thickness Gl [mm] at point A1 is in the range of 0.80 ≤ Gl / Gu ≤ 5.00 relative to the total thickness Gu [mm] at point Au, and preferably in the range of 1.00 ≤ Gl / Gu ≤ 4.00. This optimizes the ratio of the total thickness Gl in the radially outer region to the total thickness Gu in the radially inner region of the tire sidewall.

[0201] Furthermore, it is preferable that the total thickness Gl [mm] at the above point Al satisfies the following formula (17) with respect to the total thickness Gu [mm] at the above point Au and the tire outer diameter OD [mm]. Here, Qmin=0.09 and Qmax=0.80, preferably Qmin=0.10 and Qmax=0.70, more preferably Qmin=0.11 and Qmax=0.50.

[0202] [Formula 17]

[0203]

[0204] Furthermore, 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 satisfy the relationship of Hsc≤Hsu<HsI, preferably satisfy the relationship of 1≤Hsu-Hsc≤18 and 2≤HsI-Hsu≤27, more preferably satisfy the relationship of 2≤Hsu-Hsc≤15 and 5≤HsI-Hsu≤23. Thereby, the relationship between the rubber hardness values of the sidewall portion is optimized.

[0205] The average rubber hardness values Hsc, Hsu, and HsI are calculated as the sum of values obtained by dividing the product of the cross-sectional length and the rubber hardness of each rubber member at each measurement point of the total thickness Gc [mm] at the tire maximum width position Ac, the total thickness Gu at point Au, and the total thickness Gl at point Al by the total thickness.

[0206] Furthermore, in Figure 7 , the distance ΔAu' [mm] in the tire width direction from the tire maximum width position Ac to point Au' is 70% of the distance Hu [mm] from the aforementioned tire maximum width position Ac, and falls within the range of 0.03≤ΔAu' / (Hu×0.70)≤0.23, preferably within the range of 0.07≤ΔAu' / (Hu×0.70)≤0.17. Thereby, the curvature of the side profile in the radially outer region is optimized. Specifically, the aforementioned lower limit suppresses the occurrence of stress concentration caused by the flattening of the sidewall portion, thus improving the durability performance of the tire. The aforementioned upper limit reduces the deflection amount of the sidewall portion when the tire rolls, thus reducing the rolling resistance of the tire. In particular, small-diameter tires tend to have large stress acting on the sidewall portion when used under the aforementioned high internal pressure and high load, so there is also a problem that the side cut resistance of the tire needs to be ensured. In this regard, the aforementioned lower limit ensures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire collapse and thus suppressing side cuts of the tire. In addition, the aforementioned upper limit suppresses side cuts of the tire caused by excessive tension of the carcass layer 13.

[0207] Furthermore, the distance ΔAl' [mm] in the tire width direction from the maximum tire width position Ac to point Al' is within the range of 0.03 ≤ ΔAl' / (Hl×0.70) ≤ 0.28, preferably within the range of 0.07 ≤ ΔAl' / (Hl×0.70) ≤ 0.20, relative to 70% of the distance Hl [mm] from the maximum tire width position Ac. This optimizes the curvature of the side profile in the radially inner region. Specifically, by using the aforementioned lower limit, stress concentration caused by flattening of the tire sidewall is suppressed, thereby improving tire durability. Particularly in small-diameter tires, the bead core 11 is strengthened in the manner described above, thus effectively suppressing stress concentration near the bead core 11. By using the aforementioned upper limit, the deflection of the tire sidewall during tire rolling is reduced, thereby reducing tire rolling resistance.

[0208] The distances ΔAu' and ΔAl' are measured with the tire mounted on a specified rim and subjected to a specified internal pressure, under no-load conditions.

[0209] Furthermore, the distance ΔAu' [mm] from the tire's maximum width position Ac to point Au' in the tire width direction preferably satisfies the following formula (18) relative to the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al'. Wherein, Rmin=0.05, Rmax=5.00, preferably Rmin=0.10, Rmax=4.50.

[0210] [Formula 18]

[0211]

[0212] In addition, Figure 7 In this context, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is within the range of 1.10 ≤ ΔBu' / ΔAu' ≤ 8.00, and preferably within the range of 1.60 ≤ ΔBu' / ΔAu' ≤ 7.50, relative to the distance ΔAu' [mm] from the tire's maximum width position to point Au'. This optimizes the relationship between the curvature of the side profile and the curvature of the tire carcass in the radially outer region. Specifically, the lower limit ensures the cut resistance of the tire sidewall. The upper limit ensures the tension of the carcass layer 13, ensuring the rigidity of the tire sidewall, thereby ensuring the tire's load capacity and durability.

[0213] In addition, Figure 7In this context, the distance ΔBl' [mm] in the tire width direction from point Bc to point Bl' is within the range of 1.80 ≤ ΔBl' / ΔAl' ≤ 11.0, and preferably within the range of 2.30 ≤ ΔBl' / ΔAl' ≤ 9.50, relative to the distance ΔAl' [mm] in the tire width direction from the maximum tire width position Ac to point Al'. This optimizes the relationship between the curvature of the side profile and the curvature of the tire carcass profile in the radially inner region. Specifically, the lower limit ensures the total thickness Gl of the tire sidewall, thereby ensuring the load-bearing capacity of the tire sidewall. The upper limit ensures the tension of the carcass layer 13, ensuring the rigidity of the tire sidewall, thereby ensuring the tire's load-bearing capacity and durability.

[0214] The distances ΔBu' and ΔBl' are measured with the tire mounted on a specified rim and subjected to a specified internal pressure under no-load conditions.

[0215] Furthermore, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' preferably satisfies the following formula (19) relative to the radius of curvature RCc [mm] of the arc passing through points Bc, Bu', and Bl'. Wherein, Smin=0.40, Smax=7.0, preferably Smin=0.50, Smax=6.0.

[0216] [Formula 19]

[0217]

[0218] In addition, Figure 7 In this configuration, the rubber thickness Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac is within the range of 0.40 ≤ Gcr / Gc ≤ 0.90 relative to the total thickness Gc [mm] at the maximum tire width position Ac. Furthermore, the rubber thickness Gcr [mm] of the sidewall rubber 16 is within the range of 1.5 ≤ Gcr, preferably within the range of 2.5 ≤ Gcr. By ensuring the lower limit mentioned above, the rubber thickness Gcr [mm] of the sidewall rubber 16 is guaranteed, thereby ensuring the load-bearing capacity of the sidewall portion.

[0219] Furthermore, the rubber thickness Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac is preferably satisfied by 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.

[0220] [Formula 20]

[0221]

[0222] In addition, Figure 7 In this configuration, the rubber thickness Gin [mm] (illustration omitted) of the inner liner 18 at the maximum tire width position Ac is in the range of 0.03 ≤ Gin / Gc ≤ 0.50 relative to the total thickness Gc [mm] at the maximum tire width position Ac, preferably in the range of 0.05 ≤ Gin / Gc ≤ 0.40. This appropriately protects the inner surface of the carcass layer 13.

[0223] As described above, the tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 mounted on the bead cores 11, 11, and a belt layer 14 disposed radially outside the carcass layer 13 (see reference). Figure 1 Furthermore, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, and the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400. Additionally, the strength Tcs [N / 50mm] of each 50 [mm] width of the ply constituting the carcass layer 13 relative to the tire outer diameter OD [mm] is in the range of 17 ≤ Tcs / OD ≤ 120.

[0224] This configuration appropriately ensures the load-bearing capacity of the carcass layer 13 in small-diameter tires, thus offering the advantage of balancing tire wear resistance and low rolling resistance. Specifically, by setting the lower limit of the ratio Tcs / OD, tire deformation under high loads is suppressed, thereby ensuring tire wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Particularly in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned tire wear resistance and rolling resistance reduction are significantly achieved. By setting the upper limit of the ratio Tcs / OD, the reduction in rolling resistance caused by the increase in the mass of the carcass layer is suppressed.

[0225] Furthermore, in this tire 1, the carcass layer 13 is constructed by coating carcass cords made of steel with coated rubber. Moreover, the cord diameter φcs [mm] of the carcass cords is in the range of 0.3 ≤ φcs ≤ 1.1, and the number of embedded carcass cords Ecs [cords / 50mm] is in the range of 25 ≤ Ecs ≤ 80. This achieves the advantage of the aforementioned strength Tcs of the carcass layer 13.

[0226] Furthermore, in this tire 1, the carcass layer 13 is constructed by coating carcass cords made of organic fibers with coated rubber. Moreover, the cord diameter φcs [mm] of the carcass cords is in the range of 0.6 ≤ φcs ≤ 0.9, and the number of embedded carcass cords Ecs [cords / 50mm] is in the range of 40 ≤ Ecs ≤ 70. This provides the advantage of achieving the aforementioned strength Tcs of the carcass layer 13.

[0227] Furthermore, in this tire 1, the carcass layer 13 has a main body portion 131 extending along the inner surface of the tire and an up-wound portion 132 that is rolled up to the outer side in the tire width direction and extends radially along the tire in a manner that encloses the bead core 11 (see reference). Figure 1 Furthermore, the radial height Hcs [mm] from the measuring point of the rim diameter RD to the end of the upper rolled portion 132 of the carcass ply 13, relative to the tire section height SH [mm], is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 (refer to...). Figure 2 Therefore, it has the advantage of optimizing the radial height Hcs of the upper rolled portion 132 of the carcass layer 13. Specifically, the lower limit ensures the load capacity of the sidewall, and the upper limit suppresses the decrease in rolling resistance caused by the increase in the mass of the carcass layer.

[0228] Furthermore, in this tire 1, the contact height Hcs' [mm] between the main body 131 and the upper rolled portion 132 of the carcass layer 13 is within the range of 0.07 ≤ Hcs' / SH relative to the tire section height SH [mm] (refer to...) Figure 2 Therefore, it has the advantage of effectively improving the load-bearing capacity of the tire sidewall.

[0229] Furthermore, in this tire 1, the distance Tsh at the tire contact point 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 circumference of the carcass layer 13 (refer to...). Figure 5 Therefore, it has the advantage of optimizing the profile of the carcass layer 13, thereby optimizing the tension of the carcass layer 13.

[0230] Furthermore, in this tire 1, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is within the range of 1.10 ≤ ΔBu' / ΔAu' ≤ 8.00 relative to the distance ΔAu' [mm] in the tire width direction from the maximum tire width position Ac to point Au' (refer to...). Figure 7 This provides the advantage of optimizing the relationship between the curvature of the side profile and the curvature of the tire carcass in the radially outer region. Specifically, the lower limit ensures the cut resistance of the tire sidewall. The upper limit ensures the tension of the carcass layer 13, ensuring the rigidity of the tire sidewall, thereby ensuring the tire's load capacity and durability.

[0231] Furthermore, in this tire 1, the distance ΔBl' [mm] in the tire width direction from point Bc to point Bl' is within the range of 1.80 ≤ ΔBl' / ΔAl' ≤ 11.0 relative to the distance ΔAl' [mm] in the tire width direction from the maximum tire width position Ac to point Al' (refer to...). Figure 7This approach offers the advantage of optimizing the relationship between the curvature of the side profile and the curvature of the tire carcass in the radially inner region. Specifically, the lower limit ensures the total thickness Gl of the tire sidewall, thereby ensuring the load-bearing capacity of the tire sidewall. The upper limit ensures the radius of curvature RCc of the tire carcass, ensuring the internal volume V of the tire, thereby ensuring the load-bearing capacity of the tire.

[0232] Furthermore, in this tire 1, the difference in tread profile height DA [mm] at the tire contact patch end T has a relationship of 0.008 ≤ DA / TW ≤ 0.060 relative to the tire contact patch width TW [mm] (refer to...). Figure 4 This design optimizes the drop angle of the tread and shoulder areas (defined by the ratio DA / (TW / 2)), thereby appropriately ensuring the load-bearing capacity of the tread. Specifically, the drop angle of the tread and shoulder areas is ensured by the aforementioned lower limit, thus suppressing the reduction in wear life caused by excessive ground contact pressure in the tread and shoulder areas. The aforementioned upper limit flattens the tire contact patch, making the ground contact pressure more uniform, thereby ensuring the tire's wear resistance. Especially in small-diameter tires, assuming their use under high internal pressure and high load, the above configuration effectively optimizes the ground contact pressure distribution in the tire contact patch area.

[0233] Furthermore, in this tire 1, the belt layer 14 has a pair of cross belts 141, 142 formed by coating rubber over steel carcass cords (see reference). Figure 1 Furthermore, the strength Tbt [N / 50mm] of each 50mm width of the pair of cross belts 141 and 142 is within the range of 25 ≤ Tbt / OD ≤ 250 relative to the tire outer diameter OD [mm]. This provides the advantage of adequately ensuring the load-bearing capacity of the cross belts 141 and 142. Specifically, the lower limit mentioned above suppresses tire deformation under high loads, thereby ensuring tire wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Particularly in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned tire wear resistance and rolling resistance reduction are significantly achieved. The upper limit mentioned above suppresses the reduction in rolling resistance caused by the increase in the mass of the cross belts.

[0234] Furthermore, in this tire 1, the strength Tbd [N] of a bead core 11 is within the range of 45 ≤ Tbd / OD ≤ 120 relative to the tire outer diameter OD [mm]. This provides the advantage of adequately ensuring the load-bearing capacity of the bead core 11. Specifically, by limiting the lower limit, tire deformation under high loads is suppressed, thereby ensuring the tire's wear resistance. Furthermore, it allows for use under high internal pressure, reducing rolling resistance. Particularly in small-diameter tires, assuming use under high internal pressure and high loads, the aforementioned wear resistance and rolling resistance reduction are significantly achieved. By limiting the upper limit, the reduction in rolling resistance caused by the increase in the mass of the bead core is suppressed.

[0235] Furthermore, in this tire 1, the bead core 11 is composed of bead wires made of steel. Moreover, the total cross-sectional area σbd [mm^2] of the bead wires is within the range of 0.025 ≤ σbd / OD ≤ 0.075 relative to the tire outer diameter OD [mm]. Therefore, it has the advantage of achieving the aforementioned strength Tbd [N] of the bead core 11.

[0236] [Tread surface]

[0237] Figure 8 This is a diagram showing an example of the tread surface of the tire. For example... Figure 8 As shown, the tread has circumferential main grooves 21a, 21b, 22a, and 22b extending along the tire's circumference. These four circumferential main grooves 21a, 21b, 22a, and 22b divide the tread into multiple annular portions 30, 31a, 31b, 32a, and 32b. Furthermore, the tread has transverse grooves 24a, 24b, 25a, and 25b. Transverse groove 24a extends along both the tire's circumferential and width directions, connecting the circumferential main grooves 21a and 22a. Transverse groove 24b extends along both the tire's circumferential and width directions, connecting the circumferential main grooves 21b and 22b. Transverse groove 25a extends from the circumferential main groove 22a outward along the tire's width direction, reaching the outer side of the contact patch T. Transverse groove 25b extends from the circumferential main groove 22b outward along the tire's width direction, reaching the outer side of the contact patch T. Figure 8 In the attached figure, the reference numeral Tss represents the tire's contact patch area. Within the contact patch area Tss, the tire's contact patch width is represented by the reference numeral TW [mm], and the tire's contact patch length is represented by the reference numeral TL.

[0238] exist Figure 8 In this context, the area extending 48 × (OD / SW)^(1 / 5) [%] from the end of the tire's maximum contact patch width on the inner side when mounted on a vehicle is defined as the inner tire tread region. The area outside the inner tire tread region is defined as the outer tire tread region.

[0239] [Tank area ratio]

[0240] In having Figure 8 In the tire 1 with the tread surface shown therein, the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400, and the groove area ratio Aa [%] of the tread portion is in the range of 0.008 ≤ Aa / OD ≤ 0.150. Further, it is preferable that the groove area ratio Ai of the tire inner region and the groove area ratio Ao [%] of the tire outer region, which is a region other than the tire inner region, satisfy the relationship of Ai < Ao. By satisfying these relationships, the vehicle can be made low-floor by reducing the outer diameter, and the interior space of the vehicle can be enlarged. In addition, since the rotational inertia is small and the weight can be reduced, fuel consumption can be significantly improved. On the premise of the above definitions of the tire inner region and the tire outer region, the relationship of groove area ratio Ai < Ao means that the groove area ratio Ao of the tire outer region, which contributes greatly to water drainage during rotation, is made larger than the groove area ratio Ai of the tire inner region. Furthermore, by enlarging the tire outer region with a large groove area ratio, rolling resistance and rotational inertia can be reduced, and fuel consumption performance can be further improved. When the total width SW is large, there is a tendency that the ground contact length becomes short, which is disadvantageous to wet performance. However, by reducing the tire inner region and enlarging the tire outer region with a large groove area ratio, deterioration of wet performance can be effectively prevented, and fuel consumption performance can be improved. When the outer diameter OD is small, by reducing the tire inner region and enlarging the tire outer region with a large groove area ratio, deterioration of wet performance can be effectively prevented, and fuel consumption performance can be improved. Moreover, by setting the relationship between the groove area ratio Aa, which is effective for wet performance, and the outer diameter OD, which is effective for fuel consumption performance, within the appropriate range of 0.008 ≤ Aa / OD ≤ 0.150, both wet performance and fuel consumption performance can be achieved.

[0241] The groove area ratio is the ratio of the total sum of the areas of grooves arranged in a predetermined region of the tread portion to the area of the region. The groove area ratio is defined by groove area / (groove area + ground contact area). The groove area refers to the opening area of the grooves on the ground contact surface. In addition, the grooves refer to circumferential grooves, fine grooves and lateral grooves (transverse grooves) in the tread portion, and do not include sipes and incisions. In addition, the ground contact area refers to the contact area between the tire and the ground contact surface. Further, the groove area and the ground contact area are measured using the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure (230 kPa), placed vertically relative to the flat plate in a stationary state, and a load corresponding to a specified load (80% of the maximum load capacity) is applied thereto.

[0242] This tire can be fitted with sound-absorbing components for noise reduction purposes, such as in mobile conference rooms, or with sensors, sealants, and thermoplastic resin liners for maintenance-free applications in transport vehicles. It also performs well in vehicles equipped with monitoring systems. Under high internal pressure, tread wear reaches its limit before the durability of the tire sidewalls and belts, making it suitable for tire retreading as well.

[0243] Preferably, the groove area ratio Ai30 in the region TReen, extending from the inner contact point T to 30% of the contact width TW, is within the range of 0 ≤ Ai30 ≤ 40, and the groove area ratio Ao30 in the region TWout, extending from the outer contact point T to 30% of the contact width TW, is within the range of 5 ≤ Ao30 ≤ 50. By ensuring that the groove area ratios Ai30 and Ao30 are within these ranges, wet-weather performance and fuel efficiency can be improved. It should be noted that the region TReen, extending from the inner contact point T to 30% of the contact width TW, must be located on the inner side of the tire. The region TWout, extending from the outer contact point T to 30% of the contact width TW, must be located on the outer side of the tire.

[0244] The preferred ratio of tank area ratio Ai30 to tank area ratio Ao30, Ai30 / Ao30, is within the range of 0.1 ≤ Ai30 / Ao30 ≤ 1. By keeping the ratio Ai30 / Ao30 within this range, wetland performance and fuel consumption performance can be improved.

[0245] The maximum groove depth Gmax [mm] of the entire tread area is preferably 0.006 ≤ Gmax / OD ≤ 0.083. Maintaining the maximum groove depth Gmax within this range improves wet performance and fuel efficiency. In particular, when the outer diameter OD is large, rotational inertia increases, leading to higher transportation costs; therefore, increasing the groove depth and reducing the tread volume is preferable. More preferably, the maximum groove depth Gmax of the entire tread area is 0.007 ≤ Gmax / OD ≤ 0.060. Even more preferably, the maximum groove depth Gmax of the entire tread area is 0.008 ≤ Gmax / OD ≤ 0.050.

[0246] Preferably, the ratio Ai / Ao of the groove area ratio Ai to the groove area ratio Ao satisfies 0.05×(OD / 650)<Ai / Ao<1. By setting the ratio Ai / Ao within this range, wetland performance and fuel consumption performance can be improved. When the outer diameter OD is small, the drainage performance is insufficient, so it is necessary to increase the groove area ratio Ao and decrease the groove area ratio Ai in the tire inner region (increase the difference between the groove area ratio Ai and the groove area ratio Ao) to compensate for the drainage performance. However, when the difference between the groove area ratio Ai and the groove area ratio Ao is excessively increased, the drainage performance during straight traveling is reduced, thus the above range is preferred. More preferably, the ratio Ai / Ao satisfies 0.10×(OD / 650)≤Ai / Ao≤0.98. Still more preferably, the ratio Ai / Ao satisfies 0.15×(OD / 650)≤Ai / Ao≤0.98.

[0247] Preferably, the ratio Gi / Go of the maximum groove depth Gi [mm] in the tire inner region to the maximum groove depth Go [mm] in the tire outer region satisfies 0.4≤Gi / Go≤1.6. By setting the ratio within the above numerical range, wetland performance and fuel consumption performance can be improved. When the difference between the maximum groove depth Go in the tire outer region and the maximum groove depth Gi in the tire inner region is too large, uneven wear is prone to occur, thus the above numerical range is preferred. The ratio Gi / Go is more preferably 0.6≤Gi / Go≤1.5, and still more preferably 0.9≤Gi / Go≤1.4. Preferably, both the maximum groove depths Go and Gi are the maximum groove depths of the circumferential main grooves. The case where the lateral grooves have the maximum groove depth instead of the circumferential main grooves is also preferably within the above numerical range.

[0248] As shown in Figure 8 , the tread portion of this example has circumferential main grooves 21a, 21b, 22a and 22b extending in the tire circumferential direction. The circumferential main grooves have a groove width of 3 mm or more. Relative to the product of the outer diameter OD and the total width SW, the projected area C [mm 2 of the circumferential main grooves preferably satisfies 0.03≤C / (SW×OD)≤1.01. By defining the range of the area of the circumferential main grooves relative to the outer diameter OD and the total width SW, wetland performance and fuel consumption performance can be further improved. The projected area C refers to the total area of the circumferential grooves over one circumference of the tire. As shown in Figure 8 , when a plurality of circumferential main grooves are provided in the tread portion, the total area obtained by summing the areas of all the circumferential main grooves is defined as the projected area C. When only one circumferential main groove is provided in the tread portion, the area of this single circumferential main groove is defined as the projected area C. It should be noted that the projected area C [mm 2 of the circumferential main grooves more preferably satisfies 0.15≤C / (SW×OD)≤0.94.

[0249] Preferably, the average number of pitches Po (Po is a natural number) within the tire contact length TL in the outer region of the tire (the outermost region of the tire) satisfies OD / 200≤Po≤OD / 50 relative to the outer diameter OD. Within this range, a larger outer diameter OD results in a longer tire contact length TL. A longer tire contact length TL allows for an increase in the number of pitches. Therefore, by satisfying this condition, drainage performance is improved. More preferably, the average number of pitches Po (Po is a natural number) within the tire contact length TL in the outermost region of the tire (the outermost region of the tire) satisfies OD / 150≤Po≤OD / 60 relative to the outer diameter OD. For example, when the outer diameter OD is 300 mm, it is preferable that the number of pitches Po is a natural number between 2 and 6. Furthermore, when the outer diameter OD is 650 mm, it is preferable that the number of pitches Po is a natural number between 4 and 13.

[0250] Here, the average pitch number refers to the average of the pitches included in the tread pattern within the contact patch length on the outer side of the tire, assuming that the number of pitches varies with tire rotation. Furthermore, when there are multiple tread patterns with different pitch numbers, the average pitch number is defined as the value obtained by averaging over each tread pattern.

[0251] Preferably, the ratio Pi / Po of the average number of tire contact points Pi within the tire contact length TL in the inner tire region to the average number of tire contact points Po within the tire contact length TL in the outer tire region satisfies 0.7 ≤ Pi / Po ≤ 1.5. By satisfying the above, wet performance and fuel consumption performance can be improved. More preferably, the ratio Pi / Po of the average number of tire contact points Pi within the tire contact length TL in the inner tire region to the average number of tire contact points Po within the tire contact length TL in the outer tire region satisfies 1.0 ≤ Pi / Po ≤ 1.4.

[0252] Example

[0253] Figures 9-14 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0254] In this performance test, various test tires were evaluated in relation to (1) wet performance and (2) fuel consumption performance (fuel consumption). In addition, as an example of a small-diameter tire, two test tire sizes were used. Specifically, a test tire of size [A] 235 / 45R10 was mounted on a rim of size 10×8, and a test tire of size [B] 145 / 80R12 was mounted on a rim of size 12×4.00B.

[0255] In the evaluation related to wet performance (1), an internal pressure of 230 kPa and a load of 4.2 kN were applied to the test tire of [A] above, and an internal pressure of 80% of the JATMA specified internal pressure and a load of 80% of the JATMA specified load were applied to the test tire of [B] above. Furthermore, a four-wheeled low-floor vehicle with the test tires mounted on all four wheels was subjected to sensory tests related to driving stability by a test driver on a test track in rainy weather. The evaluation was conducted using an index with a comparison example set as the baseline (100); a higher value indicated better wet performance.

[0256] In the evaluation related to fuel consumption performance (2), an internal pressure of 230 kPa and a load of 4.2 kN were applied to the test tires of [A] above, and an internal pressure of 80% of the specified internal pressure and a load of 80% of the specified load of JATMA were applied to the test tires of [B] above. Furthermore, a four-wheeled low-floor vehicle with test tires mounted on all four wheels was driven on a 2 km long test track. The vehicle was driven 50 times on the test track at a speed of 100 km / h, and fuel consumption (km / l) was measured. The evaluation was conducted using an index with the comparative example set as the baseline (100); a higher value indicated better fuel consumption performance.

[0257] The test tire in the embodiment has Figure 1 The described structure includes a pair of bead cores 11, 11, a carcass layer 13 composed of a single layer of plywood, a belt layer 14 composed 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 cushioning rubber 17.

[0258] For the comparative example test tire, in the test tire of Example 1, the tire outer diameter OD=531[mm], the tire total width SW=143[mm] and the tire ground contact width TW=123[mm], was assembled on a rim with a rim size of 12.

[0259] As the test results show, the test tires in the examples can balance wet performance and fuel consumption performance.

[0260] This disclosure includes the following inventions.

[0261] Invention [1]

[0262] A tire comprising: a pair of bead cores; a carcass layer mounted on the bead cores; a belt layer disposed radially outward of the carcass layer; and a tread portion, characterized in that...

[0263] The tire outer diameter OD [mm] is in the range of 200≤OD≤660.

[0264] The total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400,

[0265] The groove area ratio Aa [%] of the tread portion is in the range of 0.008 ≤ Aa / OD ≤ 0.150,

[0266] In a case where a region of 48×(OD / SW)^(1 / 5) [%] from the maximum ground contact width end on the tire inner side when mounted on a vehicle is defined as the tire inner region of the tread portion, the groove area ratio Ai [%] of the tire inner region and the groove area ratio Ao [%] of the tire outer region which is a region other than the tire inner region satisfy a relationship of Ai < Ao.

[0267] Invention [2]

[0268] The tire according to Invention [1], wherein

[0269] The groove area ratio Ai30 in the region from the ground contact end on the tire inner side of the tread portion up to 30% of the ground contact width is in the range of 0 ≤ Ai30 ≤ 40,

[0270] The groove area ratio Ao30 in the region from the ground contact end on the tire outer side of the tread portion up to 30% of the ground contact width is in the range of 5 ≤ Ao30 ≤ 50.

[0271] Invention [3]

[0272] The tire according to Invention [2], wherein

[0273] The ratio Ai30 / Ao30 of the groove area ratio Ai30 to the groove area ratio Ao30 is in the range of 0.1 ≤ Ai30 / Ao30 ≤ 1.

[0274] Invention [4]

[0275] The tire according to any one of Inventions [1] to [3], wherein

[0276] The maximum groove depth Gmax [mm] in the entire region of the tread portion satisfies 0.006 ≤ Gmax / OD ≤ 0.083.

[0277] Invention [5]

[0278] The tire according to any one of Inventions [1] to [4], wherein

[0279] The ratio Ai / Ao of the groove area ratio Ai to the groove area ratio Ao satisfies 0.05×(OD / 650) < Ai / Ao < 1.

[0280] Invention [6]

[0281] The tire according to any one of the inventions [1] to [5], wherein,

[0282] The ratio of the maximum groove depth Gi[mm] in the inner region of the tire to the maximum groove depth Go[mm] in the outer region of the tire satisfies 0.4≤Gi / Go≤1.6.

[0283] Invention [7]

[0284] The tire according to any one of the inventions [1] to [6], wherein,

[0285] The tread portion has a circumferential main groove extending along the tire circumference.

[0286] The circumferential main groove has a groove width of more than 3 mm.

[0287] The projected area C[mm] of the circumferential main groove 2 The condition 0.03 ≤ C / (SW×OD) ≤ 1.01 is satisfied.

[0288] Invention [8]

[0289] The tire according to any one of the inventions [1] to [7], wherein,

[0290] The average number of spacings Po[number] within the tire contact length in the outer region of the tire satisfies OD / 200≤Po≤OD / 50 relative to the outer diameter OD, where Po is a natural number.

[0291] Invention [9]

[0292] The tire according to any one of the inventions [1] to [8], wherein,

[0293] The ratio Pi[number] of the average number of tire contact points within the tire contact length in the inner region of the tire to the average number of tire contact points Po[number] in the tire contact length in the outer region of the tire satisfies 0.7≤Pi / Po≤1.5.

[0294] Explanation of reference numerals in the attached figures

[0295] 1: Tire; 10: Rim; 11: Bead core; 12: Sidewall core; 13: Carcass layer; 131: Main body; 132: Upper roll; 14: Belt layer; 141, 142: Cross belts; 143: Belt cover layer; 144: Belt edge cover layer; 15: Tread rubber; 151: Crown tread; 152: Base tread; 16: Sidewall rubber; 17: Rim cushioning rubber; 18: Liner; 21a, 21b, 22a, 22b: Circumferential main grooves; 24a, 24b, 25a, 25b: Transverse grooves.

Claims

1. A tire, comprising: a pair of bead cores; a carcass layer spanned between the bead cores; a belt layer arranged on the radially outer side of the carcass layer; and a tread portion, the tire being characterized in that the tire outer diameter OD [mm] is in the range of 200≤OD≤660, the total tire width SW [mm] is in the range of 100≤SW≤400, the groove area ratio Aa [%] of the tread portion is in the range of 0.008≤Aa / OD≤0.150, when a region of 48×(OD / SW)^(1 / 5) [%] from the maximum ground contact width end on the tire inner side when mounted on a vehicle is defined as the tire inner region of the tread portion, the groove area ratio Ai [%] of the tire inner region and the groove area ratio Ao [%] of the tire outer region which is a region other than the tire inner region satisfy the relationship Ai<Ao, Among the pitches included in the strip-shaped patterns within the tire ground contact length of the tire outer region, when the number of pitches included in the strip-shaped patterns within the ground contact length varies with tire rotation, the value obtained by averaging the varying number of pitches is defined as the average number of pitches; when there are a plurality of strip-shaped patterns with different numbers of pitches, the value obtained by averaging for each strip-shaped pattern is defined as the average number of pitches, in such cases, The average number of spacing Po[number] within the tire contact length in the outer region of the tire satisfies OD / 200≤Po≤OD / 50 relative to the outer diameter OD, where, Po is a natural number.

2. The tire according to claim 1, wherein the groove area ratio Ai30 in the region from the ground contact end on the tire inner side of the tread portion up to 30% of the ground contact width is in the range of 0≤Ai30≤40, the groove area ratio Ao30 in the region from the ground contact end on the tire outer side of the tread portion up to 30% of the ground contact width is in the range of 5≤Ao30≤50.

3. The tire according to claim 2, wherein the ratio Ai30 / Ao30 of the groove area ratio Ai30 to the groove area ratio Ao30 is in the range of 0.1≤Ai30 / Ao30≤1.

4. The tire according to any one of claims 1 to 3, wherein the maximum groove depth Gmax [mm] in the entire region of the tread portion satisfies 0.006≤Gmax / OD≤0.

083.

5. The tire according to any one of claims 1 to 3, wherein the ratio Ai / Ao of the groove area ratio Ai to the groove area ratio Ao satisfies 0.05×(OD / 650)<Ai / Ao<1.

6. The tire according to any one of claims 1 to 3, wherein the ratio Gi / Go of the maximum groove depth Gi [mm] of the tire inner region to the maximum groove depth Go [mm] of the tire outer region satisfies 0.4≤Gi / Go≤1.

6.

7. The tire according to any one of claims 1 to 3, wherein the tread portion has circumferential main grooves extending along the tire circumferential direction, the circumferential main grooves have a groove width of 3 mm or more, The projected area C[mm] of the circumferential main groove 2 The condition 0.03 ≤ C / (SW×OD) ≤ 1.01 is satisfied.

8. The tire according to any one of claims 1 to 3, wherein The ratio Pi[number] of the average number of tire contact points within the tire contact length in the inner region of the tire to the average number of tire contact points Po[number] in the tire contact length in the outer region of the tire satisfies 0.7≤Pi / Po≤1.5.

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