Tire

Abstract

The tire (1) of the present application has a pair of bead cores (11, 11), a carcass layer (13) erected on the bead cores (11, 11), and a belt layer (14) disposed on the radially outer side of the carcass layer (13). 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. Furthermore, the breaking strength Tcs [N / 50 mm] per 50 [mm] width of the carcass ply constituting the carcass layer (13) is in the range of 17 ≤ Tcs / OD ≤ 120 with respect to the tire outer diameter OD [mm].

Description

Technical Field

[0001] This invention relates to a tire, and more specifically, to a small-diameter tire that can balance low rolling resistance and wear resistance. Background Technology

[0002] In recent years, small-diameter tires have been developed for use on vehicles with lowered floors to increase interior space. These small-diameter tires have lower rotational inertia and lighter weight, thus potentially reducing transportation costs. On the other hand, small-diameter tires require high load-bearing capacity. As a conventional tire related to this issue, the technology described in Patent Document 1 is known.

[0003] Existing technical documents

[0004] Patent documents

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

[0006] The problem that the invention aims to solve

[0007] The purpose of this invention is to provide a small-diameter tire that can balance low rolling resistance and wear resistance.

[0008] Technical means to solve the problem

[0009] To achieve the above objectives, the tire of the present invention comprises a pair of bead cores, a carcass layer mounted on the bead cores, and a belt layer disposed radially outward of the carcass layer, and is characterized in that the tire outer diameter OD [mm] is in the range of 200≤OD≤660, the tire total width SW [mm] is in the range of 100≤SW≤400, and the breaking strength Tcs [N / 50mm] of each 50 [mm] width of the carcass ply constituting the carcass layer is in the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD [mm].

[0010] Invention Effects

[0011] In the tire of this invention, the small-diameter tire can adequately ensure the load-bearing capacity of the carcass layers, thus possessing the advantage of balancing tire wear resistance and low rolling resistance. Specifically, by using the aforementioned lower limit ratio Tcs / OD, tire deformation under high loads can be suppressed, thereby ensuring tire wear resistance. Furthermore, it can be used under high internal pressure, reducing tire rolling resistance. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of the tire along the radial direction according to an embodiment of the present invention.

[0013] Figure 2 It means Figure 1 The enlarged image of the tire recorded in the document.

[0014] Figure 3 It means Figure 1 The diagram illustrates the layered structure of the belt layers in a tire as described in the document.

[0015] Figure 4 It means Figure 1 The image shows an enlarged view of the tire tread area as described in the document.

[0016] Figure 5 It means Figure 4 An enlarged view of one side of the fetal face as described in the document.

[0017] Figure 6 It means Figure 1 The enlarged view of the tire sidewall and bead portion as described in the document.

[0018] Figure 7 It means Figure 6 An enlarged view of the side wall section as described in the document.

[0019] Figure 8 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0020] Figure 9 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0021] Figure 10 This is a graph showing the results of performance tests on tires according to embodiments of the present invention. Detailed Implementation

[0022] 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 improvements described in this embodiment can be arbitrarily combined within the scope that is obvious to those skilled in the art.

[0023] [tire]

[0024] 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.

[0025] In this diagram, the tire's radial section is defined as the section cut along a plane including the tire's axis of rotation (not shown). Furthermore, the tire's equatorial plane CL is defined as a plane passing through the midpoint of the tire's cross-sectional 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. Point T represents the tire's contact patch, and point Ac represents the tire's maximum width position.

[0026] Tire 1 has a ring-shaped structure centered on the tire's axis of rotation, 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 Figure 1 ).

[0027] 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 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.

[0028] The carcass layer 13 has a single-layer structure formed by a single carcass ply or a multi-layer structure formed by stacking multiple carcass ply layers, 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 carcass ply of the carcass layer 13 is constructed 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 has 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).

[0029] 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.

[0030] A pair of cross belts 141 and 142 are constructed by coating multiple belt cords made of steel or organic fiber material with coated rubber and then rolling them, 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 with different 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 radial outer side of the tire carcass layer 13.

[0031] 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. 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.

[0032] 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. Furthermore, the tread rubber 15 has a crown tread 151 and a base tread 152.

[0033] The crown tread 151 is made of a rubber material with excellent ground contact characteristics and weather resistance, covering the entire tire contact area and protruding from the tread, thus 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.

[0034] The rubber hardness Hs is determined according to JIS K6253 at a temperature of 20°C.

[0035] Modulus (fracture strength) is determined according to JIS K6251 (using a No. 3 dumbbell) by a tensile test at 20 °C using a dumbbell-shaped specimen.

[0036] 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.

[0037] 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.

[0038] 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. Additionally, 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.

[0039] A pair of sidewall rubbers 16, 16 are respectively disposed on the outer side of the tire body 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 positioned 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 positioned on the outer layer of the tread rubber 15 and exposed in the tire sidewall reinforcement (not shown). In this case, the belt layer separator rubber (not shown) is sandwiched between the end of the belt layer 14 and the carcass layer 13.

[0040] 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.

[0041] 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 tire of the rim buffer rubber 17 is inserted into the lower layer of the sidewall rubber 16, thereby being sandwiched and disposed between the sidewall rubber 16 and the carcass layer 13.

[0042] The inner liner 18 is an air-permeable layer disposed on the inner surface of the tire cavity and covering the carcass layer 13. It inhibits oxidation of the carcass layer 13 due to exposure and also prevents leakage of air filled in the tire. Furthermore, 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 mixed.

[0043] In addition, Figure 1 In 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 reducing fuel consumption and transportation costs. In particular, if this small-diameter tire is installed on the wheel hub motor of a vehicle, the load on the motor can be effectively reduced.

[0044] The tire outer diameter (OD) is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0045] The total width of a tire (SW) is measured as the straight-line distance between the sidewalls (including all parts such as patterns and lettering on the tire sidewalls) when the tire is mounted on a specified rim, with a specified internal pressure and in an unloaded state.

[0046] The specified rim refers to the "applicable 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.

[0047] 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.

[0048] Furthermore, the tire outer diameter OD and the total tire 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.

[0049] [Formula 1]

[0050]

[0051] If the tire 1 described above is used, it is envisioned to use 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). 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 space for the hub motor. This lower limit also ensures the tire volume V, as described later, and ensures the tire's load capacity.

[0052] It should be noted that the inner diameter of the tire is equal to the rim diameter RD of the rim 10.

[0053] Furthermore, it is envisioned that the aforementioned tire 1 will be used at an internal pressure higher than the specified internal pressure, specifically, between 350 kPa and 1200 kPa, preferably between 500 kPa and 1000 kPa. The lower limit effectively reduces the rolling resistance of the tire, while the upper limit ensures the safety of the internal pressure filling operation.

[0054] Furthermore, it is envisioned that the aforementioned tire 1 is installed on a low-speed vehicle, such as a small shuttle bus. 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. It is also envisioned that the aforementioned tire 1 is installed on a vehicle with 6 to 12 wheels. This allows for appropriate utilization of the tire's load-bearing capacity.

[0055] Additionally, 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.

[0056] 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 under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0057] Tire section width is measured as the straight-line distance between the sidewalls (excluding patterns, characters, 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.

[0058] 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.

[0059] Tire contact width (TW) is measured as the maximum straight-line distance in the axial direction of the tire on the contact surface between the tire and the flat plate when the tire is mounted on a specified rim and subjected to a specified internal pressure, placed perpendicular to a flat plate in a stationary state, and subjected to a load corresponding to a specified load.

[0060] Furthermore, the tire 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 volume V. Specifically, by using the aforementioned lower limit, the tire volume can be ensured, thereby ensuring the tire's load-bearing capacity. Especially for small-diameter tires, their use under high internal pressure and high load is foreseeable; therefore, it is preferable to sufficiently ensure the tire volume V. By using the aforementioned upper limit, tire enlargement caused by excessively large tire volume V can be suppressed.

[0061] Furthermore, the tire 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.

[0062] [Bead core]

[0063] 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.

[0064] Furthermore, the breaking 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. In addition, the breaking 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 ensures adequate load-bearing capacity of the bead core 11. Specifically, by using the above lower limits, tire deformation under high loads can be suppressed, thereby ensuring tire wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction effects. The aforementioned upper limit can suppress the decrease in rolling resistance caused by the increase in the mass of the bead core.

[0065] The breaking strength Tbd [N] of the bead core 11 is calculated as the product of the breaking strength [N / bead] of each bead wire and the total number of bead wires in the radial sectional view. The breaking strength of the bead wire is determined according to JIS G3510 by a tensile test at 20 [°C].

[0066] Furthermore, the breaking strength Tbd [N] of the bead core 11, relative to the tire outer diameter OD [mm], the distance SWD [mm], and the rim diameter RD [mm], preferably satisfies the following formula (2). 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. Further, it is preferable to use the specified tire internal pressure P [kPa], with B1min=0.0016×P and B2min=0.07×P.

[0067] [Formula 2]

[0068]

[0069] The distance SWD is twice the radial distance from the tire's rotation axis (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 under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0070] The maximum tire width position Ac is defined as the maximum width position of the tire section width as specified by JATMA.

[0071] Furthermore, in a radial cross-sectional view of a bead core 11, the total cross-sectional area σbd [mm²] 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. In addition, the total cross-sectional area σbd [mm²] of the bead wires is in the range of 11 ≤ σbd ≤ 36, preferably in the range of 13 ≤ σbd ≤ 33. Thus, the breaking strength Tbd [N] of the bead core 11 can be achieved.

[0072] 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 in the radial sectional view of each bead core 11.

[0073] 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 (illustration omitted). 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 structure (illustration omitted). Furthermore, any arrangement of bead wires may be used to the extent that will be obvious to those skilled in the art.

[0074] Furthermore, the total cross-sectional area σbd[mm^2] of the bead wires is preferably satisfied by 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.

[0075] [Formula 3]

[0076]

[0077] 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 of one bead core 11 in the radial sectional view is in the range of 0.50 ≤ σbd / Nbd ≤ 1.40, preferably in the range of 0.60 ≤ σbd / Nbd ≤ 1.20. That is, the cross-sectional area σbd' [mm^2] of a single bead wire is in the range of 0.50 [mm^2 / wire] or more and 1.40 [mm^2 / wire] or less, preferably in the range of 0.60 [mm^2 / wire] or more and 1.20 [mm^2 / wire] or less.

[0078] In addition, the maximum width Wbd [mm] of a bead core 11 in a radial sectional view (see below) Figure 2 The total cross-sectional area σbd [mm^2] of the bead wire is in the range of 0.16≤Wbd / σbd≤0.50, preferably in the range of 0.20≤Wbd / σbd≤0.40.

[0079] 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, tire deflection can be reduced, thus lowering rolling resistance. By using the upper limit mentioned above, stress acting on the tire sidewall can be reduced, thus suppressing tire failure.

[0080] [Peripheral layer]

[0081] 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.

[0082] exist Figure 1 As described above, in the tire configuration, the carcass layer 13 is composed of a single layer of carcass ply, which is arranged in a ring 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 in the tire width direction in a manner that wraps around the bead core 11 and the sidewall core 12.

[0083] Furthermore, the breaking strength Tcs [N / 50mm] of each 50mm width of the carcass 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. Additionally, the breaking 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 ensures adequate load-bearing capacity of the carcass layer 13. Specifically, by meeting the aforementioned lower limits, tire deformation under high loads can be suppressed, thereby ensuring tire wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction effects. By using the aforementioned upper limit, the decrease in rolling resistance caused by the increase in the mass of the carcass layer can be suppressed.

[0084] The breaking strength Tcs [N / 50mm] of the carcass ply is calculated as follows. Specifically, the carcass 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 carcass ply. Furthermore, the breaking strength [N / ply] of each carcass cord constituting the effective carcass ply is calculated as the product of the density of the carcass cords per 50mm width on the tire's equatorial plane CL, and this product is taken as the breaking strength Tcs [N / 50mm] of the carcass ply. The breaking strength of the carcass cord is determined according to JIS L1017 by a tensile test at 20°C. For example, if a carcass cord is formed by twisting multiple monofilaments together, the breaking strength of the twisted carcass cord is measured, thereby calculating the breaking strength Tcs of the carcass ply 13. Furthermore, if the carcass layer 13 is a multi-layer structure (illustration omitted) formed by stacking multiple effective carcass plies, then the above-mentioned breaking strength Tcs is defined for each of the multiple effective carcass plies.

[0085] For example, in Figure 1In its construction, the carcass layer 13 has a single-layer structure consisting of a single-layer carcass ply (symbols omitted in the figure), and the carcass ply is composed of carcass cords made of steel and coated with rubber arranged 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 a density Ecs (roots / 50 mm) in the range of 25 ≤ Ecs ≤ 80, the breaking 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.

[0086] Furthermore, the carcass ply 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, by having the carcass cords made of the aforementioned organic fiber materials have a cord diameter φcs [mm] in the range of 0.6 ≤ φcs ≤ 0.9 and a density Ecs [roots / 50mm] in the range of 40 ≤ Ecs ≤ 70, the breaking strength Tcs [N / 50mm] of the aforementioned carcass layer 13 is achieved. Furthermore, carcass cords made of organic fiber materials such as nylon, aramid, or blended materials with high breaking strength can be used to a extent readily apparent to those skilled in the art.

[0087] Furthermore, the carcass layer 13 may also have a multi-layer structure formed by stacking multiple layers, such as double-layer carcass plies (illustration omitted). This effectively improves the tire's load-bearing capacity.

[0088] Furthermore, the total tensile 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.

[0089] The total tensile strength TTcs [N / 50mm] of the carcass layer 13 is calculated as the sum of the tensile strengths Tcs [N / 50mm] of the effective carcass ply layers. Therefore, the total tensile strength TTcs [N / 50mm] of the carcass layer 13 increases with the increase of the tensile strength Tcs [N / 50mm] of each carcass ply, the number of carcass ply layers, the circumference of the carcass ply, etc.

[0090] In addition, the total breaking strength TTcs [N / 50 mm] of the carcass layer 13 preferably satisfies the following formula (4) with respect to the outer diameter OD [mm] of the tire and the distance SWD [mm]. Here, Dmin = 2.2, Dmax = 40, preferably Dmin = 4.3, Dmax = 40, more preferably Dmin = 6.5, Dmax = 40, and further preferably Dmin = 8.7, Dmax = 40. Further, it is preferable to use the specified internal pressure P [kPa] of the tire, and Dmin = 0.02 × P.

[0091] [Formula 4]

[0092]

[0093] In addition, in Figure 1 the structure, the carcass layer 13 has a main body portion 131 extending along the inner surface of the tire and an up-rolled portion 132 that is up-rolled to the outside in the tire width direction so as to enclose the bead core 11 and extends in the tire radial direction. In addition, in Figure 2 , the radial height Hcs [mm] from the measurement point of the rim diameter RD to the end of the up-rolled portion 132 of the carcass layer 13 is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 with respect to the tire section height SH [mm], and preferably in the range of 0.55 ≤ Hcs / SH ≤ 0.75. Thereby, the radial height Hcs of the up-rolled portion 132 of the carcass layer 13 can be optimized. Specifically, through the above lower limit, the load capacity of the sidewall portion can be ensured, and through the above upper limit, the reduction of the rolling resistance due to the increase in the mass of the carcass layer can be suppressed.

[0094] The radial height Hcs [mm] of the up-rolled portion 132 of the carcass layer 13 is measured in the state of being mounted on a specified rim and given a specified internal pressure and being unloaded.

[0095] For example, in Figure 2 the structure, the radially outer end (omitted the symbol in the figure) of the up-rolled portion 132 of the carcass layer 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), and more specifically, in the region at the radial position Au' that is 70 [%] of the distance Hu described later from the tire maximum width position Ac. At this time, the contact height Hcs' [mm] between the main body portion 131 and the up-rolled portion 132 of the carcass layer 13 is in the range of 0.07 ≤ Hcs' / SH with respect to the tire section height SH [mm], and preferably in the range of 0.15 ≤ Hcs' / SH. Thereby, the load capacity of the sidewall portion can be effectively improved. The upper limit of the ratio Hcs' / SH is not particularly limited, but is restricted by the fact that the contact height Hcs' has a relationship of Hcs' < Hcs with respect to the radial height Hcs of the up-rolled portion 132 of the carcass layer 13.

[0096] The contact height Hcs' of the carcass layer 13 is the radial extension length of the area where the main body 131 and the upper roll 132 are in contact with each other. It is measured under no-load conditions while the tire is mounted on a specified rim and a specified internal pressure is applied.

[0097] It should be noted that the end of the upper rolled portion 132 of the carcass layer 13 is not limited to the above configuration. By giving the carcass layer 13 a so-called low fold structure, it can also be configured in the area between the tire's maximum width position Ac and the bead core (illustration omitted).

[0098] [Belt layer]

[0099] Figure 3 It means Figure 1 The diagram illustrates the layered structure of the belt layers of the tire 1 described herein. In this diagram, the fine lines attached to each belt ply 141 to 144 schematically show the arrangement of the belt cords.

[0100] exist Figure 1 In its configuration, as described above, the belt layer 14 is formed by stacking multiple belt fabric layers 141 to 144. Furthermore, as... Figure 3 The belted fabric layers 141-144 are composed of a pair of cross belts 141, 142, a belt covering layer 143, and a pair of belt edge covering layers 144, 144.

[0101] At this point, the breaking 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 breaking 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 ensures that the load-bearing capacity of each pair of cross belts 141 and 142 is adequately guaranteed. Specifically, by meeting the above lower limits, tire deformation under high loads can be suppressed, thereby ensuring the tire's wear resistance. Furthermore, it allows for use under high internal pressure, reducing tire rolling resistance. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction effects. The aforementioned upper limit can suppress the decrease in rolling resistance caused by the increase in the mass of the cross belt.

[0102] The breaking strength Tbt [N / 50mm] of the belt cord layer is calculated as follows. Specifically, the effective belt cord layer is defined as the area extending across 80% of the tire contact patch width TW centered on the tire equator plane CL (i.e., the central part of the tire contact patch area). Furthermore, the breaking strength [N / cord] of each belt cord constituting the effective belt cord layer is calculated as the product of the density of belt cords per 50mm width within the aforementioned 80% area of ​​the tire contact patch width TW, and this product is taken as the breaking strength Tbt [N / 50mm] of the belt cord layer. The breaking strength of the belt cord is determined according to JIS L1017 by a tensile test at 20°C. For example, if a belt cord is formed by twisting multiple monofilaments together, the breaking strength of the twisted belt cord is measured, thereby calculating the breaking strength Tbt of the belt cord layer. Additionally, if the belt layer 14 is a configuration formed by stacking multiple layers of effective belt fabric (see...), Figure 1 Then, the above-mentioned breaking strength Tbt is defined for each layer in the multi-layer effective belted fabric. 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.

[0103] For example, in Figure 3 In 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 (symbols omitted in the figure). Furthermore, by having the steel belt cords have a cord diameter φbt (mm) in the range of 0.50 ≤ φbt ≤ 1.80 and a density Ebt (roots / 50 mm) in the range of 15 ≤ Ebt ≤ 60, the breaking strength Tbt (N / 50 mm) of the cross belts 141 and 142 is achieved. Moreover, the cord diameter φbt (mm) and density Ebt (roots / 50 mm) are preferably in the ranges of 0.55 ≤ φbt ≤ 1.60 and 17 ≤ Ebt ≤ 50, 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.

[0104] 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, by having the belt cords made of the aforementioned organic fiber materials have a cord diameter φbt [mm] in the range of 0.50 ≤ φbt ≤ 0.90 and a density Ebt [roots / 50mm] in the range of 30 ≤ Ebt ≤ 65, the breaking strength Tbt [N / 50mm] of the aforementioned cross-belts 141 and 142 is achieved. In addition, belt cords made of organic fiber materials such as nylon, aramid, and blended materials with high breaking strength can be used to a extent that is obvious to those skilled in the art.

[0105] 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 and coated with 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 and coated with 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.

[0106] Furthermore, the total breaking strength TTbt [N / 50mm] of the belt layer 14 relative to the tire outer diameter OD [mm] is preferably in the range of 70 ≤ TTbt / OD ≤ 750, more 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. Further, it is preferable to use the specified tire internal pressure P [kPa], where 0.16 × P ≤ TTbt / OD.

[0107] The total breaking strength TTbtN / 50mm of the belt layer 14 is based on the above effective belt fabric layer (in Figure 1 The tensile strength Tbt [N / 50mm] of the belt layer 14 is calculated as the sum of the tensile strengths of a pair of cross belts 141, 142 and the belt cover layer 143. Therefore, the total tensile strength TTbt [N / 50mm] of the belt layer 14 increases with the increase of the tensile strength Tbt [N / 50mm] of each belt fabric layer and the number of layers of the belt fabric layer.

[0108] Additionally, the widest cross strap in a pair of cross straps 141 and 142 (which includes additional straps if the configuration includes the aforementioned additional straps; illustration omitted) is the one that is widest. 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 can be 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 can be reduced, suppressing the separation of the peripheral rubber at the belt ply ends.

[0109] 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, and is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0110] Additionally, the widest cross strap in a pair of cross straps 141 and 142 (which includes additional straps if the configuration includes the aforementioned additional straps; illustration omitted) is the one that is widest. Figure 3 In 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.

[0111] 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.

[0112] [Tread profile and tread thickness]

[0113] Figure 4 It means Figure 1 An enlarged view of the tread of tire 1 as described.

[0114] 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)) and appropriately ensures the load-bearing capacity of the tread. Specifically, by using the aforementioned lower limits, the drop angle of the tread and shoulder areas can be 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 designed for use under high internal pressure and high loads; therefore, the above configuration effectively optimizes the contact pressure distribution in the tire's contact patch area.

[0115] 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 under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0116] 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 (manufactured by Matsuo Co., Ltd.) can be used as the laser profile measuring instrument.

[0117] Furthermore, the difference in tread profile DA [mm] 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.

[0118] [Formula 5]

[0119]

[0120] 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 contact width TW from the tire equatorial plane CL.

[0121] 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 ensures adequate 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 due to excessive ground pressure in the tread and shoulder areas can be suppressed. Especially for small-diameter tires, their use under high internal pressure and high load can be anticipated, thus effectively achieving the homogenization of ground pressure under these operating conditions.

[0122] The radius of curvature of the arc is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0123] In addition, Figure 4 In 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 within the range of 0.30 ≤ TRw / OD ≤ 16 relative to the tire outer diameter OD [mm], preferably within the range of 0.35 ≤ TRw / OD ≤ 11. Furthermore, the radius of curvature TRw [mm] of the arc is within the range of 150 ≤ TRw ≤ 2800, preferably within the range of 200 ≤ TRw ≤ 2500. This ensures adequate 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 due to excessive contact pressure in the tread and shoulder areas can be suppressed. Especially for small-diameter tires, their use under high internal pressure and high load can be anticipated, thus the above configuration effectively optimizes the contact pressure distribution in the tire contact area.

[0124] 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 tire wear life. The upper limit suppresses the reduction in wear life caused by excessive contact patch pressure in the tread and shoulder areas.

[0125] 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.

[0126] 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 allows for a more optimized tire contact shape. Specifically, the lower limit mentioned above suppresses the reduction in wear life caused by the increase in rubber thickness in the tread and shoulder areas. The upper limit mentioned above ensures the wear life of the central area of ​​the tread.

[0127] Figure 5 It means Figure 4 An enlarged view of one side of the fetal face as described in the document.

[0128] 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.

[0129] In addition, Figure 5In this design, 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 within the range of 5 ≤ Tce ≤ 25, preferably within the range of 7 ≤ Tce ≤ 20. This ensures adequate load-bearing capacity of the tread. Specifically, the lower limit suppresses tire deformation under high loads, thus ensuring tire wear resistance. Especially for small-diameter tires, high internal pressure and high load use are foreseeable, resulting in significantly improved wear resistance. The upper limit suppresses the decrease in rolling resistance caused by increased tread rubber mass.

[0130] The distance Tce is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0131] 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.

[0132] Furthermore, the distance Tce [mm] from the tread profile on the tire equatorial surface CL to the outer periphery 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.

[0133] [Formula 6]

[0134]

[0135] 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.

[0136] Distance Tsh is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure. Furthermore, when there is no wide crossbelt directly below the tire's contact patch T, distance Tsh is measured as the distance from an imaginary line drawn from the tread profile to the outer periphery of the extended belt cord.

[0137] 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, preferably satisfies the following formula (7). Wherein, Gmin=0.36, Gmax=0.72, preferably Gmin=0.37, Gmax=0.71, more preferably Gmin=0.38, Gmax=0.70.

[0138] [Formula 7]

[0139]

[0140] 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.

[0141] 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 5 In this context, 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.

[0142] 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, and preferably in the range of 0.06 ≤ UTce / Tce ≤ 0.50. This optimizes the rubber thickness UTce of the base tread 152.

[0143] 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 carcass layer tension and the tread thickness in the shoulder area, thus suppressing repeated tire deformation 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.

[0144] The rubber thickness Tu is essentially a rubber component inserted between the end of the wide cross-belt layer 141 and the carcass layer 13 (in Figure 5 The thickness of the sidewall rubber (16) is used for measurement.

[0145] The outer peripheral surface of the carcass layer 13 is defined as the entire radially outer peripheral surface of the carcass ply composed of carcass cords and coated rubber. Furthermore, when the carcass layer 13 has a multi-layered structure composed of multiple carcass plies (illustration omitted), the outer peripheral surface of the outermost carcass ply constitutes the outer peripheral surface of the carcass layer 13. Additionally, when the upper roll portion 132 of the carcass layer 13 (see...) 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.

[0146] For example, in Figure 5 In this configuration, the sidewall rubber 16 is inserted between the end of the wide cross-belt 141 and the carcass layer 13, thereby forming a rubber thickness Tu between the end of the wide cross-belt 141 and the carcass layer 13. However, the configuration of the sidewall rubber 16 is not limited to this. For example, the belt layer separator rubber may be used instead of the sidewall rubber 16 to be inserted between the end of the wide cross-belt 141 and the carcass layer 13 (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.

[0147] In addition, Figure 1 In its configuration, the tire 1 has multiple circumferential main grooves 21-23 extending along the tire circumferential direction on the tread surface (see... Figure 5 ), and the annular land portion (symbols omitted in the figure) divided by these circumferential main grooves 21-23. The main groove is defined as the groove having the display obligation of the wear indicator specified by JATMA.

[0148] At this time, as Figure 5 As shown, the groove depth Gd1 [mm] of the circumferential main groove 21, which is closest to the tire equatorial plane CL among the multiple circumferential main grooves 21 to 23, is in the range of 0.50 ≤ Gd1 / Gce ≤ 1.00 relative to the rubber thickness Gce [mm] of the tread rubber 15, preferably in the range of 0.55 ≤ Gd1 / 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 the rubber thickness from the bottom of the circumferential main groove 21 to the belt layer.

[0149] The circumferential main groove closest to the tire equatorial plane CL is defined as the circumferential main groove 21 located on the tire equatorial plane CL (see [reference]). Figure 5 If there is no circumferential main groove on the tire equatorial plane CL (illustration omitted), it is defined as the circumferential main groove closest to the tire equatorial plane CL.

[0150] Furthermore, the ratio Gd1 / Gce relative to the tire outer diameter OD [mm] preferably satisfies the following formula (8). Wherein, Hmin=0.10, Hmax=0.60, preferably Hmin=0.12, Hmax=0.50, more preferably Hmin=0.14, Hmax=0.40.

[0151] [Formula 8]

[0152]

[0153] In addition, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the multiple circumferential main grooves 21 to 23 is deeper than the groove depths Gd2 [mm] and Gd3 [mm] of the other circumferential main grooves 22 and 23 (Gd2 < Gd1, Gd3 < Gd1). Specifically, when the region from the tire equatorial plane CL to the tire ground end T is bisected in the tire width direction, the groove depth Gd1 of the circumferential main groove (the symbol in the figure is omitted) closest to the tire equatorial plane CL is within a range of not less than 1.00 times and not more than 2.50 times, preferably within a range of not less than 1.00 times and not more than 2.00 times, and more preferably within a range of not less than 1.00 times and not more than 1.80 times, with respect to the maximum value of the groove depths Gd2 and Gd3 of the other circumferential main grooves (the symbol in the figure is omitted) in the region on the tire ground end T side. By the above lower limit, the ground pressure in the central region of the tread can be dispersed, thereby improving the wear resistance of the tire. By the above upper limit, uneven wear caused by an excessive ground pressure difference between the central region and the shoulder region of the tread can be suppressed.

[0154] [Side profile and side thickness]

[0155] Figure 6 To show Figure 1 an enlarged view of the sidewall portion and the bead portion of the tire 1 described in Figure 7 To show Figure 6 an enlarged view of the sidewall portion described in

[0156] Figure 6 defines points Au on the side profile at the same radial position of the end of the innermost layer of the belt layer 14 (in Figure 6 it is the inner diameter side cross belt 141) and points Al on the side profile at the same radial position of the radially outer end of the bead core 11. In addition, the distance Hu in the tire radial direction from the tire maximum width position Ac to point Au and the distance Hl in the tire radial direction from the tire maximum width position Ac to point Al are defined. In addition, points Au' on the side profile at the radial position 70[%] of the distance Hu from the tire maximum width position Ac and points Al' on the side profile at the radial position 70[%] of the distance Hl from the tire maximum width position Ac are defined.

[0157] At this time, the sum of the distance Hu [mm] and the distance Hl [mm] with respect to the tire section height SH [mm] (see Figure 2The value is preferably within the range of 0.45 ≤ (Hu + Hl) / SH ≤ 0.90, and more preferably within the range of 0.50 ≤ (Hu + Hl) / SH ≤ 0.85. This optimizes the radial distance from the belt layer 14 to the bead core 11. Specifically, the 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, thus reducing rolling resistance.

[0158] Distances Hu and Hl are measured under no-load conditions while the tire is mounted on the specified rim and subjected to the specified internal pressure.

[0159] Furthermore, the sum of distances Hu [mm] and Hl [mm] is relative to the tire outer diameter OD ( Figure 1 Tire section height SH [mm] (see) 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 is preferably satisfied by the following formula (9). Wherein, I1min=0.06, I1max=0.20, I2=0.70, preferably I1min=0.09, I1max=0.20, I2=0.65.

[0160] [Formula 9]

[0161]

[0162] The radius of curvature RSc of the arc is measured under no-load conditions while the tire is mounted on a specified rim and subjected to a specified internal pressure.

[0163] 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 allows for optimization of the position of the maximum tire width Ac in the deformable region of the tire sidewall. Specifically, the lower limit mentioned above mitigates stress concentration near the end of the belt ply caused by the maximum tire width Ac being too close to the end of the belt ply 14, thereby suppressing the separation of the surrounding rubber. The upper limit mentioned above mitigates stress concentration near the bead portion caused by the maximum tire width Ac being too close to the end of the bead core 11, thereby suppressing the stress concentration of the reinforcing member (in the bead portion)... Figure 6 The fault is in the tire sidewall core 12).

[0164] Furthermore, the radius of curvature RSc [mm] of the arc passing through the tire's maximum width position Ac, point Au', and point Al' is in the range of 0.05 ≤ RSc / OD ≤ 1.70 relative to the tire's outer diameter OD [mm], preferably in the range of 0.10 ≤ RSc / OD ≤ 1.60. Additionally, the radius of curvature RSc [mm] of the arc is in the range of 25 ≤ RSc ≤ 330, preferably in the range of 30 ≤ RSc ≤ 300. This optimizes the radius of curvature of the sidewall profile, thereby appropriately ensuring the load-bearing capacity of the tire sidewall. Specifically, the lower limit reduces the deflection of the tire sidewall during rolling, thus reducing rolling resistance. The upper limit suppresses stress concentration caused by sidewall flattening, thereby improving tire durability. Especially for small-diameter tires, there is a tendency for greater stress to be generated on the sidewall under high internal pressure and high load, therefore, ensuring the tire's resistance to sidewall shearing is also a concern. In this respect, the lower limit mentioned above ensures the radius of curvature of the side profile and optimizes tire tension, thereby suppressing tire collapse and thus inhibiting tire sidewall cutting. Furthermore, the upper limit mentioned above can suppress tire sidewall cutting caused by excessive tension in the carcass layer 13.

[0165] 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 section height SH [mm], preferably in the range of 0.55 ≤ RSc / SH ≤ 0.90.

[0166] Furthermore, the radius of curvature RSc [mm] of the arc is preferably satisfied by 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.

[0167] [Formula 10]

[0168]

[0169] 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.

[0170] 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. This optimizes 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. Specifically, by using the lower limit, the radius of curvature RCc of the carcass profile can be ensured, and the tire volume V (described later) can be ensured, thereby ensuring the tire's load capacity. By using the upper limit, the total thicknesses Gu and Gl of the sidewall portion (described later) can be ensured, thereby ensuring the load capacity of the sidewall portion.

[0171] 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.

[0172] [Formula 11]

[0173]

[0174] In addition, Figure 6 In 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. Specifically, by using the lower limit, the total thickness Gu of the radially outer region of the sidewall is ensured, suppressing tire deformation under high loads and thus ensuring tire wear resistance. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned reduction in tire rolling resistance. By using the upper limit, the reduction in tire rolling resistance caused by excessive total thickness Gu is suppressed.

[0175] The total thickness of the sidewall portion is measured as the distance from the inner surface of the tire to the sidewall profile on a vertical line drawn from a predetermined point on the sidewall profile to the main body 131 of the carcass layer 13.

[0176] In addition, Figure 6In this context, the total thickness Gu [mm] at point Au, relative to the total thickness Gc [mm] of the sidewall portion at the tire's maximum width position Ac, is within the range of 1.30 ≤ Gu / Gc ≤ 5.00, preferably within the range of 1.90 ≤ Gu / Gc ≤ 3.00. This optimizes the thickness distribution of the sidewall portion from the tire's maximum width position Ac to the innermost layer of the belt layer 14. Specifically, the lower limit ensures that the total thickness Gu in the radially outer region suppresses tire deformation under high loads, thereby ensuring the tire's wear resistance. The upper limit suppresses the reduction in tire rolling resistance caused by excessive total thickness Gu.

[0177] Furthermore, the total thickness Gu [mm] at point Au, relative to the total thickness Gc [mm] at the maximum tire width position Ac and the tire outer diameter OD [mm], preferably satisfies 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.

[0178] [Formula 12]

[0179]

[0180] In addition, Figure 6 In 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.

[0181] Furthermore, the total thickness Gc[mm] at the maximum width position Ac of the tire, relative to the tire outer diameter OD[mm], preferably satisfies the following formula (13). Wherein, Mmin=70, Mmax=450, preferably Mmin=80, Mmax=400.

[0182] [Formula 13]

[0183]

[0184] 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.

[0185] [Formula 14]

[0186]

[0187] Furthermore, the total thickness Gc [mm] at the maximum tire width position Ac, relative to the radius of curvature RSc [mm] of the arc passing through the maximum tire width position Ac, points Au' and Al', preferably satisfies the following formula (15). Wherein, Omin=13, Omax=260, preferably Omin=20, Omax=200.

[0188] [Formula 15]

[0189]

[0190] In addition, Figure 6 In 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 using 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. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned reduction in tire rolling resistance. By using the upper limit, the reduction in tire rolling resistance caused by excessive total thickness Gl is suppressed.

[0191] In addition, Figure 6 In this context, the ratio Gl / Gc 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 is within the range of 1.00 ≤ Gl / Gc ≤ 7.00, and 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, by using the lower limit, the total thickness Gl in the radially inner region can be ensured, suppressing tire deformation under high loads and thus ensuring the tire's wear resistance. By using the upper limit, the reduction in tire rolling resistance caused by excessive total thickness Gl can be suppressed.

[0192] In addition, the total thickness Gl [mm] of the sidewall portion at the above-mentioned point Al is preferably such that it satisfies the following formula (16) with respect to the total thickness Gc [mm] at the maximum width position Ac of the tire and the tire outer diameter OD [mm]. Here, Pmin = 0.12, Pmax = 1.00, preferably Pmin = 0.15, Pmax = 1.00, and more preferably Pmin = 0.18, Pmax = 1.00.

[0193] [Formula 16]

[0194]

[0195] In addition, in Figure 6 the total thickness Gl [mm] of the above-mentioned point Al is within the range of 0.80 ≤ Gl / Gu ≤ 5.00 with respect to the total thickness Gu [mm] of the above-mentioned point Au, preferably within the range of 1.00 ≤ Gl / Gu ≤ 4.00. Thereby, the ratio of the total thickness Gl in the radially outer region of the sidewall portion to the total thickness Gu in the radially inner region can be optimized.

[0196] In addition, the total thickness Gl [mm] of the above-mentioned point Al is preferably such that it satisfies the following formula (17) with respect to the total thickness Gu [mm] of the above-mentioned point Au and the tire outer diameter OD [mm]. Here, Qmin = 0.09, Qmax = 0.80, preferably Qmin = 0.10, Qmax = 0.70, and more preferably Qmin = 0.11, Qmax = 0.50.

[0197] [Formula 17]

[0198]

[0199] In addition, in Figure 6 the average rubber hardness Hsc at the measurement position of the total thickness Gc, the average rubber hardness Hsu at the measurement position of the total thickness Gu, and the average rubber hardness HsI at the measurement position of the total thickness Gl have the relationship of Hsc ≤ Hsu < HsI, preferably having the relationship of 1 ≤ Hsu - Hsc ≤ 18 and 2 ≤ HsI - Hsu ≤ 27, and more preferably having the relationship of 2 ≤ Hsu - Hsc ≤ 15 and 5 ≤ HsI - Hsu ≤ 23. Thereby, the relationship between the rubber hardnesses of the sidewall portion can be optimized.

[0200] The average rubber hardnesses Hsc, Hsu, and HsI are calculated in such a way that it is the sum of the products of the cross-sectional lengths and the rubber hardnesses of the respective rubber members at the respective measurement points of the total thickness Gc [mm] at the maximum width position Ac of the tire, the total thickness Gu at the point Au, and the total thickness Gl at the point Al, divided by the total thickness.

[0201] In addition, Figure 7 In this case, the distance ΔAu' [mm] from the tire's maximum width position Ac to point Au' in the tire width direction is within the range of 0.03 ≤ ΔAu' / (Hu×0.70) ≤ 0.23, and preferably within the range of 0.07 ≤ ΔAu' / (Hu×0.70) ≤ 0.17, relative to 70% of the distance Hu [mm] from the tire's maximum width position Ac. This optimizes the curvature of the side profile in the radially outer region. Specifically, by using the lower limit, stress concentration caused by flattening of the tire sidewall can be suppressed, thereby improving tire durability. By using the upper limit, the deflection of the tire sidewall during tire rolling can be reduced, thereby reducing rolling resistance. Especially for small-diameter tires, there is a tendency for greater stress to be generated on the tire sidewall due to use under 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 mentioned above ensures the radius of curvature of the side profile and optimizes tire tension, thereby suppressing tire collapse and thus inhibiting tire sidewall cutting. Furthermore, the upper limit mentioned above can suppress tire sidewall cutting caused by excessive tension in the carcass layer 13.

[0202] 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 can be suppressed, thereby improving tire durability. Especially for small-diameter tires, the bead core 11 can be strengthened as 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 can be reduced, thereby reducing tire rolling resistance.

[0203] The distances ΔAu' and ΔAl' are measured under no-load conditions while the tire is mounted on the specified rim and subjected to the specified internal pressure.

[0204] Furthermore, the distance ΔAu' [mm] from the tire's maximum width position Ac to point Au' in the tire width direction, 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', preferably satisfies the following formula (18). Wherein, Rmin=0.05, Rmax=5.00, preferably Rmin=0.10, Rmax=4.50.

[0205] [Formula 18]

[0206]

[0207] 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] in the tire width direction from the maximum tire 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.

[0208] In addition, Figure 7 In 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 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.

[0209] The distances ΔBu' and ΔBl' are measured under no-load conditions while the tire is mounted on the specified rim and subjected to the specified internal pressure.

[0210] 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 the aforementioned points Bc, Bu', and Bl'. Wherein, Smin=0.40, Smax=7.0, preferably Smin=0.50, Smax=6.0.

[0211] [Formula 19]

[0212]

[0213] In addition, Figure 7In 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 meeting these lower limits, the rubber thickness Gcr [mm] of the sidewall rubber 16 can be ensured, thereby ensuring the load-bearing capacity of the sidewall portion.

[0214] Furthermore, the rubber thickness Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac, relative to the total thickness Gc [mm] at the maximum tire width position Ac and the tire outer diameter OD [mm], preferably satisfies the following formula (20). Wherein, Tmin=80, Tmax=0.90, preferably Tmin=120, Tmax=0.90.

[0215] [Formula 20]

[0216]

[0217] 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 within the range of 0.03 ≤ Gin / Gc ≤ 0.50, preferably within the range of 0.05 ≤ Gin / Gc ≤ 0.40, relative to the total thickness Gc [mm] at the maximum tire width position Ac. This provides adequate protection for the inner surface of the carcass layer 13.

[0218] [Effect]

[0219] 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 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 breaking strength Tcs [N / 50mm] of each 50 [mm] width of the carcass ply constituting the carcass layer 13 relative to the tire outer diameter OD [mm] is in the range of 17 ≤ Tcs / OD ≤ 120.

[0220] With this configuration, the load-bearing capacity of the carcass layer 13 can be adequately ensured in small-diameter tires, thus achieving the advantages of balancing tire wear resistance and low rolling resistance. Specifically, by using the aforementioned lower limit ratio Tcs / OD, tire deformation under high loads can be suppressed, thereby ensuring tire wear resistance. Furthermore, it can be used under high internal pressure, reducing tire rolling resistance. Especially for small-diameter tires, their use under high internal pressure and high loads can be anticipated, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction effects. By using the aforementioned upper limit ratio Tcs / OD, the reduction in rolling resistance caused by the increase in the mass of the carcass layers can be suppressed.

[0221] Furthermore, in this tire 1, the carcass ply 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 density Ecs [cords / 50mm] of the carcass cords is in the range of 25 ≤ Ecs ≤ 80. This provides the advantage of achieving the aforementioned tensile strength Tcs of the carcass ply 13.

[0222] Furthermore, in this tire 1, the carcass ply 13 is constructed by coating carcass cords made of organic fibers with coated rubber. In addition, the cord diameter φcs [mm] of the carcass cords is in the range of 0.6 ≤ φcs ≤ 0.9, and the density Ecs [cords / 50mm] of the carcass cords is in the range of 40 ≤ Ecs ≤ 70. This provides the advantage of achieving the aforementioned tensile strength Tcs of the carcass ply 13.

[0223] 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 is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 relative to the tire section height SH [mm] (see [reference]). 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 mentioned above ensures the load capacity of the sidewall, and the upper limit mentioned above suppresses the decrease in rolling resistance caused by the increase in the mass of the carcass layer.

[0224] 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] (see [reference]). Figure 2Therefore, it has the advantage of effectively improving the load-bearing capacity of the tire sidewall.

[0225] 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 ply 13 (see [reference]). 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.

[0226] 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' (see [reference]). 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.

[0227] 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' (see [reference]). Figure 7 This 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 its load-bearing capacity. The upper limit ensures the radius of curvature RCc of the tire carcass, ensuring the tire volume V, and thus ensuring the tire's load-bearing capacity.

[0228] 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] (see [reference]). Figure 4Therefore, it has the advantage of optimizing 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, by using the aforementioned lower limit, the drop angle of the tread and shoulder areas can be ensured, thereby suppressing the reduction in wear life caused by excessive ground contact pressure in the tread and shoulder areas. By using the aforementioned upper limit, the tire contact area becomes flat, making the ground contact pressure more uniform, thereby ensuring the tire's wear resistance. Especially for small-diameter tires, their use under high internal pressure and high load can be anticipated, thus the above configuration can effectively optimize the ground contact pressure distribution of the tire contact area.

[0229] 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 [link]). Figure 1 Furthermore, the breaking 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. Especially for small-diameter tires, their use under high internal pressure and high loads is foreseeable, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction. The upper limit mentioned above suppresses the reduction in rolling resistance caused by the increase in the mass of the cross belts.

[0230] Furthermore, in this tire 1, the breaking 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 using the aforementioned lower limit, tire deformation under high loads can be suppressed, thereby ensuring the tire's wear resistance. In addition, it can be used under high internal pressure, reducing the tire's rolling resistance. Especially for small-diameter tires, their use under high internal pressure and high loads can be anticipated, thus significantly achieving the aforementioned tire wear resistance and rolling resistance reduction effects. By using the aforementioned upper limit, the reduction in rolling resistance caused by the increase in the mass of the bead core can be suppressed.

[0231] Furthermore, in this tire 1, the bead core 11 is composed of bead wires made of steel. Moreover, the total cross-sectional area σbd [mm²] 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 breaking strength Tbd [N] of the bead core 11.

[0232] Example

[0233] Figures 8 to 10 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0234] Using this performance test, various test tires were evaluated for (1) low rolling resistance performance (fuel consumption), (2) wear resistance performance, and (3) load durability performance. Furthermore, as an example of a small-diameter tire, two test tire sizes were used. Specifically, test tire [A] with a tire size of 235 / 45R10 was mounted on a rim with a rim size of 10×8, and test tire [B] with a tire size of 145 / 80R12 was mounted on a rim with a rim size of 12×4.00B.

[0235] In the evaluation related to low rolling resistance performance (1), the test tire of [A] above was subjected to an internal pressure of 230 kPa and a load of 4.2 kN, and the test tire of [B] above was subjected to an internal pressure of 80% of the JATMA specified internal pressure and a load of 80% of the JATMA specified load. In addition, a four-wheel low-floor vehicle with the test tires mounted on all wheels was driven 50 times at a speed of 100 km / h on a test track with a total length of 2 km. After that, the fuel consumption rate [km / l] was calculated and evaluated. This evaluation was carried out by an index evaluation based on a comparative example (100). The larger the value, the smaller the fuel consumption rate, the greater the tendency to reduce rolling resistance, and the more preferred.

[0236] In the evaluation of wear resistance performance (2), the test tire of [A] above was subjected to an internal pressure of 230 kPa and a load of 4.2 kN, and the test tire of [B] above was subjected to an internal pressure of 80% of the JATMA specified internal pressure and a load of 80% of the JATMA specified load. In addition, a four-wheel low-floor vehicle with the test tires mounted on all wheels was driven for 10,000 km on a dry test track. Afterwards, the wear amount and degree of uneven wear of each tire were measured and evaluated. This evaluation was carried out by an index evaluation based on a comparative example (100), with a higher value indicating better performance.

[0237] In the durability performance evaluation (3), an indoor roller testing machine with a roller diameter of 1707 mm was used. The test tire of [A] was subjected to an internal pressure of 230 kPa and a load of 4.2 kN, and the test tire of [B] was subjected to an internal pressure of 80% of the JATMA specified internal pressure and a load of 88% of the JATMA specified load. Then, at a driving speed of 81 km / h, the load was increased by 13% every 2 hours, and the driving distance before the tire failure was measured. Then, based on the measurement results, an index evaluation (100) was performed with the comparative example as the benchmark. The larger the value of this evaluation, the better the product.

[0238] 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 carcass ply, a pair of cross belts 141, 142, a belt layer 14 composed of 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.

[0239] Regarding the test tire of the comparative example, in the test tire of Example 1, the tire outer diameter OD=531[mm], the tire total width SW=143[mm], the tire ground contact width TW=123[mm], and it was assembled on a rim with a rim size of 12.

[0240] As the test results show, the test tires in the embodiment take into account the tire's low rolling resistance, wear resistance and durability.

[0241] Symbol Explanation

[0242] 1: Tires;

[0243] 10: Wheel rim;

[0244] 11: Bead core;

[0245] 12: Tire sidewall core;

[0246] 13: The body layer;

[0247] 131: Main body;

[0248] 132: Upper volume;

[0249] 14: Belt layer;

[0250] 141, 142: Cross-belt bundles;

[0251] 143: Belt cover layer;

[0252] 144: Belt edge cover layer;

[0253] 15: Tread rubber;

[0254] 151: Crown tread;

[0255] 152: Base tread;

[0256] 16: Sidewall rubber;

[0257] 17: Wheel rim cushioning rubber;

[0258] 18: Lining;

[0259] 21-23: Circumferential main channel

Claims

1. A tire, the tire comprising a pair of bead cores, a carcass layer mounted on the bead cores, and a belt layer disposed radially outward of the carcass layer, 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, and the breaking strength Tcs (N / 50mm) of each 50 (mm) width of the carcass ply constituting the carcass layer is in the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD (mm). In the cross-sectional view along the tire's radial direction, the following are defined: the tire's maximum width position Ac; a point Au on the side profile at the same radial position relative to the end of the innermost layer of the belt layer; the tire's radial distance Hu from the tire's maximum width position Ac to point Au; a point Au' on the side profile at a radial position 70% of the distance Hu from the tire's maximum width position Ac; a point Bc on the main body of the carcass layer at the same radial position relative to the tire's maximum width position Ac; and a point Bu' on the main body of the carcass layer at a radial position 70% of the distance Hu from the tire's maximum width position Ac. The tire width direction distance ΔBu' (mm) from point Bc to point Bu' is within the range of 1.10 ≤ ΔBu' / ΔAu' ≤ 8.00 relative to the tire width direction distance ΔAu' (mm) from the tire's maximum width position Ac to point Au.

2. The tire according to claim 1, wherein, The carcass ply is composed of carcass cords made of steel covered with coated rubber, and the cord diameter φcs (mm) of the carcass cords is in the range of 0.3≤φcs≤1.1, and the density Ecs (cords / 50mm) of the carcass cords is in the range of 25≤Ecs≤80.

3. The tire according to claim 1, wherein, The carcass ply is composed of carcass cords made of organic fibers covered with coated rubber, and the cord diameter φcs (mm) of the carcass cords is in the range of 0.6≤φcs≤0.9, and the density Ecs (cords / 50mm) of the carcass cords is in the range of 40≤Ecs≤70.

4. The tire according to any one of claims 1 to 3, wherein, The carcass has a main body extending along the inner surface of the tire and an upper roll portion that is rolled up to the outer side of the tire width direction and extends radially along the tire in a manner that encloses the bead core. The radial height Hcs (mm) from the measuring point of the rim diameter RD to the end of the upper roll portion is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 relative to the tire section height SH (mm).

5. The tire according to claim 4, wherein, The contact height Hcs' (mm) between the main body portion and the upper rolled portion of the tire carcass layer is within the range of 0.07 ≤ Hcs' / SH relative to the tire section height SH (mm).

6. The tire according to any one of claims 1 to 3, wherein, The belt layer has a pair of cross belts, and the distance Tsh at the tire contact point is in the range of 1.50 ≤ Tsh / Tu ≤ 6.90 relative to the rubber thickness Tu (mm) from the end of the wide cross belt in the pair of cross belts to the outer peripheral surface of the carcass layer.

7. The tire according to any one of claims 1 to 3, wherein, In the cross-sectional view along the radial direction of the tire, points A1 on the side profile at the same position in the radial direction of the tire relative to the radially outer end of the bead core are defined; the radial distance Hl from the tire's maximum width position Ac to point A1 in the tire's radial direction is defined; point A1' on the side profile at a radial position 70% of the distance Hl from the tire's maximum width position Ac; and point B1' on the main body of the carcass layer at a radial position 70% of the distance Hl from the tire's maximum width position Ac. The distance ΔBl' (mm) in the tire width direction from point B1 to point B1' is in the range of 1.80 ≤ ΔBl' / ΔAl' ≤ 11.0 relative to the distance ΔAl' (mm) in the tire width direction from the tire's maximum width position Ac to point A1'.

8. The tire according to any one of claims 1 to 3, wherein, The difference in tread profile at the tire contact point, DA (mm), has a relationship of 0.008 ≤ DA / TW ≤ 0.060 relative to the tire contact width, TW (mm).

9. The tire according to any one of claims 1 to 3, wherein, The belt layer comprises a pair of cross belts formed by coating rubber-coated steel belt cords, and... The breaking strength Tbt (N / 50mm) of each 50mm width of the pair of cross belts is in the range of 25≤Tbt / OD≤250 relative to the tire outer diameter OD (mm).

10. The tire according to any one of claims 1 to 3, wherein, The breaking strength Tbd (N) of one of the bead cores is in the range of 45 ≤ Tbd / OD ≤ 120 relative to the tire outer diameter OD (mm).

11. The tire according to claim 10, wherein, The bead core is made of steel bead wire, and the total cross-sectional area σbd (mm^2) of the bead wire is in the range of 0.025≤σbd / OD≤0.075 relative to the tire outer diameter OD (mm).

12. A tire comprising a pair of bead cores, a carcass layer mounted on the bead cores, and a belt layer disposed radially outward of the carcass layer, 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, and the breaking strength Tcs (N / 50mm) of each 50 (mm) width of the carcass ply constituting the carcass layer is in the range of 17≤Tcs / OD≤120 relative to the tire outer diameter OD (mm). In the cross-sectional view along the radial direction of the tire, the following are defined: the maximum tire width position Ac; point Al on the side profile at the same radial position relative to the radially outer end of the bead core; the radial distance Hl from the maximum tire width position Ac to point Al; point Al' on the side profile at a radial position 70% of the distance Hl from the maximum tire width position Ac; point Bc on the main body of the carcass at the same radial position relative to the maximum tire width position Ac; and point Bl' on the main body of the carcass at a radial position 70% of the distance Hl from the maximum tire width position Ac. The tire width direction distance ΔBl' (mm) from point Bc to point Bl' is within the range of 1.80 ≤ ΔBl' / ΔAl' ≤ 11.0 relative to the tire width direction distance ΔAl' (mm) from the maximum tire width position Ac to point Al'.

13. The tire according to claim 12, wherein, The carcass ply is composed of carcass cords made of steel covered with coated rubber, and the cord diameter φcs (mm) of the carcass cords is in the range of 0.3≤φcs≤1.1, and the density Ecs (cords / 50mm) of the carcass cords is in the range of 25≤Ecs≤80.

14. The tire according to claim 12, wherein, The carcass ply is composed of carcass cords made of organic fibers covered with coated rubber, and the cord diameter φcs (mm) of the carcass cords is in the range of 0.6≤φcs≤0.9, and the density Ecs (cords / 50mm) of the carcass cords is in the range of 40≤Ecs≤70.

15. The tire according to any one of claims 12 to 14, wherein, The carcass has a main body extending along the inner surface of the tire and an upper roll portion that is rolled up to the outer side of the tire width direction and extends radially along the tire in a manner that encloses the bead core. The radial height Hcs (mm) from the measuring point of the rim diameter RD to the end of the upper roll portion is in the range of 0.49 ≤ Hcs / SH ≤ 0.80 relative to the tire section height SH (mm).

16. The tire according to claim 15, wherein, The contact height Hcs' (mm) between the main body portion and the upper rolled portion of the tire carcass layer is within the range of 0.07 ≤ Hcs' / SH relative to the tire section height SH (mm).

17. The tire according to any one of claims 12 to 14, wherein, The belt layer has a pair of cross belts, and the distance Tsh at the tire contact point is in the range of 1.50 ≤ Tsh / Tu ≤ 6.90 relative to the rubber thickness Tu (mm) from the end of the wide cross belt in the pair of cross belts to the outer peripheral surface of the carcass layer.

18. The tire according to any one of claims 12 to 14, wherein, The difference in tread profile at the tire contact point, DA (mm), has a relationship of 0.008 ≤ DA / TW ≤ 0.060 relative to the tire contact width, TW (mm).

19. The tire according to any one of claims 12 to 14, wherein, The belt layer comprises a pair of cross belts formed by coating rubber-coated steel belt cords, and... The breaking strength Tbt (N / 50mm) of each 50mm width of the pair of cross belts is in the range of 25≤Tbt / OD≤250 relative to the tire outer diameter OD (mm).

20. The tire according to any one of claims 12 to 14, wherein, The breaking strength Tbd (N) of one of the bead cores is in the range of 45 ≤ Tbd / OD ≤ 120 relative to the tire outer diameter OD (mm).

21. The tire according to claim 20, wherein, The bead core is made of steel bead wire, and the total cross-sectional area σbd (mm^2) of the bead wire is in the range of 0.025 ≤ σbd / OD ≤ 0.075 relative to the tire outer diameter OD (mm).

Images