Patent Application
20240181812
The technology relates to a tire and particularly relates to a tire having a small diameter that allows improving wear performance while maintaining fuel economy performance.
A tire having a small diameter to be mounted on a vehicle in which a floor is lowered to expand a vehicle interior space has recently been developed. In such a tire having a small diameter, since rotational inertia is small and a tire weight is also small, a reduction in transportation cost is expected. On the other hand, the tire having a small diameter is required to have a high load capacity. Technology described in International Patent Application Publication No. WO 2020/122169 is a known tire in the related art associated with such a problem.
The technology provides a tire having a small diameter that allows improving wear performance while maintaining fuel economy performance.
A tire according to the technology may include a tread portion, a pair of bead cores, a carcass layer, and a belt layer. The tread portion may include a tread rubber including a cap tread and an undertread. The carcass layer may be extended across the bead cores. The belt layer may be disposed on an outer side of the carcass layer in a radial direction. A tire outer diameter OD (mm) may be in a range 200≤OD≤660. A total tire width SW (mm) may be in a range 100≤SW≤400. A strength at break TB_cap (MPa) of the cap tread may be in a range 12≤TB_cap≤35. A relationship between an amount of change between a ground contact area CA80 at 80% of a maximum load capacity and a ground contact area CA120 at 120% of the maximum load capacity and the tire outer diameter OD may satisfy 0.0004×OD≤{(CA120−CA80)/CA80}≤0.0030×OD.
The tire according to an embodiment of the present technology exhibits an effect that allows improving wear performance while maintaining fuel economy performance.
Embodiments of the technology will be described in detail below with reference to the drawings. Note that the technology is not limited to the embodiments. Additionally, constituents of the embodiments include constituents that are substitutable and are obviously substitutes while maintaining consistency with the embodiments of the technology. Additionally, a plurality of modified examples described in the embodiments can be combined in a discretionary manner within the scope apparent to one skilled in the art.
In the same drawing, a cross-section in the tire meridian direction is defined as a cross-section of the tire taken along a plane that includes a tire rotation axis (not illustrated). Additionally, a tire equatorial plane CL is defined as a plane that passes through a midpoint of a tire cross-sectional width specified by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA) and that is perpendicular to the tire rotation axis. Additionally, a tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis. Additionally, a point T is a tire ground contact edge, and a point Ac is a tire maximum width position.
The tire 1 includes an annular structure with the tire rotation axis serving as the center, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, a pair of rim cushion rubbers 17, 17, and an innerliner 18 (see
The pair of bead cores 11, 11 include one or a plurality of bead wires that are made of steel and made by being wound annularly multiple times, embedded in bead portions 4, 4, and constitute cores of the left and right bead portions 4, 4. The pair of bead fillers 12, 12 are respectively disposed on an outer circumference of the pair of bead cores 11, 11 in the tire radial direction and reinforce the bead portions 4, 4.
The carcass layer 13 has a single layer structure including one carcass ply or a multilayer structure including a plurality of carcass plies layered, extends in a toroidal shape between the left and right bead cores 11, 11, and constitutes the backbone of the tire. Both end portions of the carcass layer 13 are turned back toward outer sides in the tire width direction and fixed to wrap the bead cores 11 and the bead fillers 12. Moreover, the carcass ply of the carcass layer 13 is made by covering a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) with a coating rubber and performing a rolling process on the carcass cords, and has a cord angle (defined as an inclination angle in a longitudinal direction of the carcass cords with respect to a tire circumferential direction) of 80 degrees or more and 100 degrees or less.
The belt layer 14 is made of a plurality of belt plies 141 to 144 being layered and is disposed around an outer circumference of the carcass layer 13. In the configuration of
The pair of cross belts 141, 142 are constituted by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and by performing a rolling process on the belt cords and have a cord angle (defined as an inclination angle in a longitudinal direction of the belt cords with respect to the tire circumferential direction) of 15 degrees or more and 55 degrees or less as an absolute value. Additionally, the pair of cross belts 141, 142 have a cord angle having mutually opposite signs and are layered by making the belt cords mutually intersect in the longitudinal direction of the belt cords (a so-called crossply structure). Furthermore, the pair of cross belts 141, 142 are disposed in a layered manner on an outer side in the tire radial direction of the carcass layer 13.
The belt cover 143 and the pair of belt edge covers 144, 144 are made by covering belt cover cords made of steel or an organic fiber material with a coating rubber and have a cord angle of 0 degrees or more and 10 degrees or less as an absolute value. Additionally, for example, a strip material is formed of one or a plurality of belt cover cords covered with coating rubber, and the belt cover 143 and the belt edge covers 144 are made by winding this strip material multiple times and in a spiral-like manner in the tire circumferential direction around outer circumferential surfaces of the cross belts 141, 142. Additionally, the belt cover 143 is disposed completely covering the cross belts 141, 142, and the pair of belt edge covers 144, 144 are disposed covering the left and right edge portions of the cross belts 141, 142 from the outer side in the tire radial direction.
The tread rubber 15 is disposed on an outer periphery in the tire radial direction of the carcass layer 13 and the belt layer 14 and constitutes a tread portion 2 of the tire 1. Additionally, the tread rubber 15 includes a cap tread 151 and an undertread 152.
The cap tread 151 is made of a rubber material that is excellent in ground contact characteristics and weather resistance, and the cap tread 151 is exposed in a tread surface all across a tire ground contact surface, and constitutes an outer surface of the tread portion 2. The cap 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 tan δ_cap of 0.03 or more and 0.36 or less and preferably has the rubber hardness Hs_cap of 58 or more and 76 or less, the modulus M_cap (MPa) at 100% elongation of 1.5 or more and 3.2 or less, and the loss tangent tan δ_cap of 0.06 or more and 0.29 or less.
The rubber hardness Hs is measured in accordance with JIS (Japanese Industrial Standard) K6253 at a temperature condition of 20° C.
The modulus is measured by a tensile test at a temperature of 20° C. with a dumbbell-shaped test piece in accordance with JIS K6251 (using a number 3 dumbbell).
The loss tangent tan δ is measured by using a viscoelasticity spectrometer available from Toyo Seiki Seisaku-sho Ltd. at a temperature of 60° C., a shear strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz.
The undertread 152 is made of a rubber material excellent in heat resistance, is disposed by being sandwiched between the cap tread 151 and the belt layer 14, and constitutes a base portion of the tread rubber 15. The undertread 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 tan δ_ut of 0.02 or more and 0.23 or less and preferably has the rubber hardness Hs_ut of 50 or more and 65 or less, the modulus M_ut (MPa) at 100% elongation of 1.7 or more and 3.5 or less, and the loss tangent tan δ_ut of 0.03 or more and 0.10 or less.
In the cap tread 151 and the undertread 152, a difference in the rubber hardness Hs_cap−Hs_ut is in the range of 3 or more and 20 or less and preferably in the range of 5 or more and 15 or less. A difference in modulus M_cap−M_ut (MPa) is in the range of 0 or more and 1.4 or less and preferably in the range of 0.1 or more and 1.0 or less. A difference in loss tangent tan δ_cap−tan δ_ut is in the range of 0 or more and 0.22 or less and preferably in the range of 0.02 or more and 0.16 or less.
Further, in the tread portion 2, the relationship between tan δ_ut of the undertread 152 at the temperature condition of 60° C. and tan δ_cap of the cap tread 151 at the temperature condition of 60° C. satisfies 0.1×tan δ_cap≤tan δ_ut≤4.5× tan δ_cap. The relationship between tan δ_ut of the undertread 152 at the temperature condition of 60° C. and tan δ_cap of the cap tread 151 at the temperature condition of 60° C. preferably satisfies 0.2×tan δ_cap≤tan δ_ut≤3.6× tan δ_cap, and more preferably satisfies 0.3× tan δ_cap≤tan δ_ut≤3.3× tan δ_cap.
Specifically, tan δ_cap of the cap tread 151 at the temperature condition of 60° C. is in the range of 0.05 or more and 0.35 or less, preferably in the range of 0.08 or more and 0.30 or less, and more preferably in the range of 0.10 or more and 0.25 or less. The undertread 152 has tan δ_ut at the temperature condition of 60° C. is in the range of 0.03 or more and 0.27 or less, preferably in the range of 0.04 or more and 0.25 or less, and more preferably in the range of 0.05 or more and 0.23 or less.
The pair of sidewall rubbers 16, 16 are each disposed on an outer side of the carcass layer 13 in the tire width direction and constitute left and right sidewall portions. In the configuration of
The sidewall rubber 16 has a rubber hardness Hs_sw of 48 or more and 65 or less, a modulus M_sw (MPa) at 100% elongation of 1.0 or more and 2.4 or less, and a loss tangent tan δ_sw of 0.02 or more and 0.22 or less and preferably the rubber hardness Hs_sw of 50 or more and 59 or less, the modulus M_sw (MPa) at 100% elongation of 1.2 or more and 2.2 or less, and the loss tangent tan δ_sw of 0.04 or more and 0.20 or less.
The pair of rim cushion rubbers 17, 17 extend from an inner side in the tire radial direction of the left and right bead cores 11, 11 and turned back portions of the carcass layer 13 toward the outer side in the tire width direction, and constitute rim fitting surfaces of the bead portions 4 to which the rim 10 is fitted. In the configuration of
The innerliner 18 is an air penetration preventing layer disposed on the tire inner surface and covering the carcass layer 13, suppresses oxidation caused by exposure of the carcass layer 13, and prevents a leakage of the air inflated in the tire 1. Additionally, the innerliner 18 may be made of, for example, a rubber composition containing butyl rubber as a main component, or may be made of a thermoplastic resin or a thermoplastic elastomer composition containing an elastomer component blended with a thermoplastic resin or the like.
In
The tire outer diameter OD is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The total tire width SW is measured as a linear distance (including all portions such as letters and patterns on the tire side surface) between the sidewalls when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
“Specified rim” refers to an “applicable rim” defined by the Japan Automobile Tire Manufacturers Association Inc. (JATMA), a “Design Rim” defined by the Tire and Rim Association, Inc. (TRA), or a “Measuring Rim” defined by the European Tyre and Rim Technical Organisation (ETRTO). Additionally, the specified internal pressure refers to a “maximum air pressure” specified by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. Additionally, the specified load refers to a “maximum load capacity” specified by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “LOAD CAPACITY” specified by ETRTO. However, in the case of JATMA, for a tire for a passenger vehicle, the specified internal pressure is an air pressure of 180 kPa, and the specified load is 88% of the maximum load capacity.
The total tire width SW (mm) is in the range 0.23≤SW/OD≤0.84 and preferably in the range 0.25≤SW/OD≤0.81 with respect to the tire outer diameter OD (mm).
The tire outer diameter OD and the total tire width SW preferably satisfy the following mathematical formula (1). Here, A1 min=−0.0017, A2 min=0.9, A3 min=130, A1 max=−0.0019, A2 max=1.4, and A3 max=400 and preferably A1 min=−0.0018, A2 min=0.9, A3 min=160, A1 max=−0.0024, A2 max=1.6, and A3 max=362.
A1 min*SW∧2+A2 min*SW+A3 min≤OD≤A1 max*SW∧2+A2 max*SW+A3 max (1)
In the tire 1, the use of the rim 10 having a rim diameter of 5 inches or more and 16 inches or less (in other words, 125 mm or more and 407 mm or less) is assumed. A rim diameter RD (mm) is in the range 0.50≤RD/OD≤0.74 and preferably in the range 0.52≤RD/OD≤0.71 with respect to the tire outer diameter OD (mm). The lower limit can ensure the rim diameter RD and in particular, ensure an installation space for the in-wheel motor. The upper limit ensures an internal volume V of the tire described later and ensures the load capacity of the tire.
Note that the tire inner diameter is equal to the rim diameter RD of the rim 10.
The use of the tire 1 at an internal pressure higher than a specified internal pressure, specifically, an internal pressure of 350 kPa or more and 1200 kPa or less and preferably 500 kPa or more and 1000 kPa or less is assumed. The lower limit effectively reduces the rolling resistance of the tire, and the upper limit ensures safety of internal pressure inflation work.
The tire 1 is assumed to be mounted on a vehicle traveling at a low speed, 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.
The tires 1 are assumed to be mounted on a vehicle having 6 to 12 wheels. As a result, the load capacity of the tire is appropriately exhibited.
An aspect ratio of the tire, in other words, a ratio between a tire cross-sectional height SH (mm) (see
The tire cross-sectional height SH is a distance equal to half of a difference between a tire outer diameter and a rim diameter, and is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The tire cross-sectional width is measured as a linear distance between sidewalls (excluding patterns, letters, and the like on the tire side surface) when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
In addition, a tire ground contact width TW is in the range 0.75≤TW/SW≤0.95 and preferably in the range 0.80≤TW/SW≤0.92 with respect to the total tire width SW.
The tire ground contact width TW is measured as a maximum linear distance in a tire axial direction in a contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure, placed perpendicular to the flat plate in a static state, and subjected to a load corresponding to a specified load.
The tire internal volume V (m{circumflex over ( )}3) is in the range 4.0≤(V/OD)×10{circumflex over ( )}6≤60 and preferably in the range 6.0≤(V/OD)×10{circumflex over ( )}6≤50 with respect to the tire outer diameter OD (mm). This makes the tire internal volume V appropriate. Specifically, the lower limit ensures the tire internal volume and ensures the load capacity of the tire. In particular, since the tire having a small diameter is assumed to be used under a high internal pressure and a high load, the tire internal volume V is preferably sufficiently ensured. The upperlimit suppresses the increase in size of the tire caused by the excessive tire internal volume V.
The tire internal volume V (m{circumflex over ( )}3) referred to herein is a volume of a space defined by a tire inner surface 5 and the specified rim when the tire 1 is mounted on the specified rim. The tire internal volume V (m{circumflex over ( )}3) is calculated based on, for example, a shape measured by CT scanning when the tire 1 is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. Note that the tire internal volume V (m{circumflex over ( )}3) may be calculated based on the shape of the tire inner surface 5 when the tire 1 is cut in a cross-section in the tire meridian direction.
The tire internal volume V (m{circumflex over ( )}3) is in the range 0.5≤V×RD≤17 and preferably in the range 1.0≤V×RD≤15 with respect to the rim diameter RD (mm).
In
A tensile strength Tbd (N) of one bead core 11 is in the range 45≤Tbd/OD≤120, preferably in the range 50≤Tbd/OD≤110, and more preferably in the range 60≤Tbd/OD≤105 with respect to the tire outer diameter OD (mm). The tensile strength Tbd (N) of the bead core is in the range 90≤Tbd/SW≤400 and preferably in the range 110≤Tbd/SW≤350 with respect to the total tire width SW (mm). As a result, the load capacity of the bead core 11 is appropriately ensured. Specifically, the lower limit suppresses tire deformation during use under a high load and ensures the wear resistance performance of the tire. Additionally, use under a high internal pressure is possible, and the rolling resistance of the tire is reduced. In particular, the use of the tire having a small diameter under a high internal pressure and a high load is assumed, and therefore the wear resistance performance and the reduction effect of the rolling resistance of the tire described above are significantly obtained. The upper limit suppresses the deterioration of the rolling resistance caused by the increase in the weight of the bead core.
The tensile strength Tbd (N) of the bead core 11 is calculated as a product of the tensile strength (N/piece) per bead wire and the total number of bead wires (piece) in the radial cross-sectional view. The tensile strength of the bead wire is measured by a tensile test at a temperature of 20° C. in accordance with JIS K1017.
The tensile strength Tbd (N) of the bead core 11 preferably satisfies the following mathematical formula (2) with respect to the tire outer diameter OD (mm), a distance SWD (mm), and the rim diameter RD (mm). Here, B1 min=0.26, B2 min=10.0, B1 max=2.5, and B2 max=99.0, preferably B1 min=0.35, B2 min=14.0, B1 max=2.5, and B2 max=99.0, more preferably B1 min=0.44, B2 min=17.6, B1 max=2.5, and B2 max=99.0, and even more preferably B1 min=0.49, B2 min=17.9, B1 max=2.5, and B2 max=99.0. Further, B1 min=0.0016×P and B2 min=0.07× P are preferable with the use of a specified internal pressure P (kPa) of the tire.
B1 min*{(OD/2)∧2−(SWD/2)∧2}+B2 min*RD≤Tbd≤B1 max*{(OD/2)∧2−(SWD/2)∧2}+B2 max*RD (2)
The distance SWD is a distance twice a radial distance from the tire rotation axis (not illustrated) to a tire maximum width position Ac, in other words, a diameter of the tire maximum width position Ac and is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The tire maximum width position Ac is defined as the maximum width position of the tire cross-sectional width defined by JATMA.
In a radial cross-sectional view of one bead core 11, a total cross-sectional area σbd (mm{circumflex over ( )}2){circumflex over ( )}2) of the bead wire made of the steel described above is in the range 0.025≤σbd/OD≤0.075 and preferably in the range 0.030≤σbd/OD≤0.065 with respect to the tire outer diameter OD (mm). The total cross-sectional area σbd (mm{circumflex over ( )}2) of the bead wire is in the range 11≤σbd≤36 and preferably in the range 13≤σbd≤33. As a result, the above-described tensile strength Tbd (N) of the bead core 11 is achieved.
The total cross-sectional area σbd (mm{circumflex over ( )}2) of the bead wire is calculated as the sum of the cross-sectional areas of the bead wires in the radial cross-sectional view of one bead core 11.
For example, in the configuration of
The total cross-sectional area σbd (mm{circumflex over ( )}2) of the bead wire preferably satisfies the following mathematical formula (3) with respect to the tire outer diameter OD (mm), the distance SWD (mm), and the rim diameter RD (mm). Here, Cmin=30 and Cmax=8 and preferably Cmin=25 and Cmax=10.
(OD*RD)/(C min*SWD)≤σbd≤(OD*RD)/(C max*SWD) (3)
The total cross-sectional area σbd (mm{circumflex over ( )}2) of the bead wire is in the range 0.50≤σbd/Nbd≤1.40 and preferably in the range 0.60≤σbd/Nbd≤1.20 with respect to the total cross-sectional area (in other words, the total number of windings) Nbd (piece) of the bead wires of one bead core 11 in the radial cross-sectional view. In other words, a cross-sectional area σbd′ (mm{circumflex over ( )}2) of a single bead wire is in the range 0.50 mm{circumflex over ( )}2/piece or more and 1.40 mm{circumflex over ( )}2/piece or less and preferably in the range 0.60 mm{circumflex over ( )}2/piece or more and 1.20 mm{circumflex over ( )}2/piece or less.
A maximum width Wbd (mm) (see
In
In the configuration of
The tensile strength Tcs (N/50 mm) per a width of 50 mm of the carcass ply constituting the carcass layer 13 is in the range 17≤Tcs/OD≤120 and preferably in the range 20≤Tcs/OD≤120 with respect to the tire outer diameter OD (mm). The tensile strength Tcs (N/50 mm) of the carcass layer 13 is in the range 30≤Tcs/SW≤260 and preferably in the range 35≤Tcs/SW≤220 with respect to the total tire width SW (mm). As a result, the load capacity of the carcass layer 13 is appropriately ensured. Specifically, the lower limit suppresses tire deformation during use under a high load and ensures the wear resistance performance of the tire. Additionally, use under a high internal pressure is possible, and the rolling resistance of the tire is reduced. In particular, the use of the tire having a small diameter under a high internal pressure and a high load is assumed, and therefore the wear resistance performance and the reduction effect of the rolling resistance of the tire described above are significantly obtained. The upper limit suppresses the deterioration of the rolling resistance caused by the increase in the weight of the carcass layer.
The tensile strength Tcs (N/50 mm) of the carcass ply is calculated as follows. In other words, the carcass ply extending between the left and right bead cores 11, 11 and extending over the entire region of the tire inner circumference is defined as an effective carcass ply. The product of the tensile strength (N/piece) per carcass cord constituting the effective carcass ply and the number of insertions (piece/50 mm) of the carcass cords per the width of 50 mm on the tire equatorial plane CL over the entire circumference of the tire is calculated as the tensile strength Tcs (N/50 mm) of the carcass ply. The tensile strength of the carcass cord is measured by a tensile test at a temperature of 20° C. in accordance with JIS K1017. For example, in a configuration in which one carcass cord is formed by intertwining, for example, a plurality of wire strands, the tensile strength of the intertwined one carcass cord is measured, and the tensile strength Tcs of the carcass layer 13 is calculated. In a configuration in which the carcass layer 13 has a multilayer structure (not illustrated) formed by layering a plurality of the effective carcass plies, the above-described tensile strength Tcs is defined for each of the plurality of effective carcass plies.
For example, in the configuration of
The configuration is not limited to the configuration, and the carcass ply may be constituted by a carcass cord made of an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) covered with a coating rubber. In this case, the carcass cord made of the organic fiber material has the cord diameter φcs (mm) in the range 0.6≤φcs≤0.9 and the number of insertions Ecs (piece/50 mm) in the range 40≤Ecs≤70, whereby the above-described tensile strength Tcs (N/50 mm) of the carcass layer 13 is achieved. In addition, the carcass cord made of the high-tensile strength organic fiber material, such as nylon, aramid, and hybrid, can be employed within the scope of obviousness by one skilled in the art.
The carcass layer 13 may have a multilayer structure formed by layering a plurality of carcass plies, for example, two layers (not illustrated). Accordingly, the load capacity of the tire can be effectively enhanced.
A total tensile strength TTcs (N/50 mm) of the carcass layer 13 is in the range 300≤TTcs/OD≤3500 and preferably in the range 400≤TTcs/OD≤3000 with respect to the tire outer diameter OD (mm). As a result, the load capacity of the entire carcass layer 13 is ensured.
The total tensile strength TTcs (N/50 mm) of the carcass layer 13 is calculated as the sum of the tensile strengths Tcs (N/50 mm) of the effective carcass plies described above. Therefore, the total tensile strength TTcs (N/50 mm) of the carcass layer 13 increases with an increase in the tensile strength Tcs (N/50 mm) of each carcass ply, the number of layered carcass plies, a circumferential length of the carcass ply, and the like.
The total tensile strength TTcs (N/50 mm) of the carcass layer 13 preferably satisfies the following mathematical formula (4) with respect to the tire outer diameter OD (mm) and the distance SWD (mm). Here, Dmin=2.2 and Dmax=40, preferably Dmin=4.3 and Dmax=40, more preferably D min=6.5 and Dmax=40, and even more preferably Dmin=8.7 and Dmax=40. Further, Dmin=0.02× P is preferable with the use of a specified internal pressure P (kPa) of the tire.
D min*{(OD/2)∧2−(SWD/2)∧2}≤TTcs≤D max*{(OD/2)∧2−(SWD/2)∧2} (4)
In the configuration of
The radial height Hcs (mm) of the turned-up portion 132 of the carcass layer 13 is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
For example, in the configuration of
The contact height Hcs′ of the carcass layer 13 is an extension length in the tire radial direction of a region in which the body portion 131 and the turned-up portion 132 are in contact with one another and is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The configuration is not limited to the configuration, and by the carcass layer 13 having a so-called low turn-up structure, the end portion of the turned-up portion 132 of the carcass layer 13 may be disposed in a region between the tire maximum width position Ac and the bead core (not illustrated).
In the configuration of
At this time, the tensile strength Tbt (N/50 mm) per the width of 50 mm of each of the pair of cross belts 141, 142 is in the range 25≤Tbt/OD≤250 and preferably in the range 30≤Tbt/OD≤230 with respect to the tire outer diameter OD (mm). The tensile strength Tbt (N/50 mm) of the cross belts 141, 142 is in the range 45≤Tbt/SW≤500 and preferably in the range 50≤Tbt/SW≤450 with respect to the total tire width SW (mm). As a result, the respective load capacities of the pair of cross belts 141, 142 are appropriately ensured. Specifically, the lower limit suppresses tire deformation during use under a high load and ensures the wear resistance performance of the tire. Additionally, use under a high internal pressure is possible, and the rolling resistance of the tire is reduced. In particular, the use of the tire having a small diameter under a high internal pressure and a high load is assumed, and therefore the wear resistance performance and the reduction effect of the rolling resistance of the tire described above are significantly obtained. The upper limit suppresses the deterioration of the rolling resistance caused by the increase in the weight of the cross belt.
The tensile strength Tbt (N/50 mm) of the belt ply is calculated as follows. In other words, a belt ply extending over the entire region of 80% of the tire ground contact width TW centered on the tire equatorial plane CL (in other words, the central portion of the tire ground contact region) is defined as an effective belt ply. The product of the tensile strength (N/piece) per belt cord constituting the effective belt ply and the number of insertions (piece) of the belt cords per the width of 50 mm in the region of 80% of the tire ground contact width TW described above is calculated as the tensile strength Tbt (N/50 mm) of the belt ply. The tensile strength of the belt cord is measured by a tensile test at a temperature of 20° C. in accordance with JIS K1017. For example, in a configuration in which one belt cord is formed by intertwining, for example, a plurality of wire strands, the tensile strength of the intertwined one belt cord is measured, and the tensile strength Tbt of the belt cord is calculated. In a configuration in which the belt layer 14 is formed by layering a plurality of the effective carcass plies (see
For example, in the configuration of
The configuration is not limited to the configuration, and the cross belts 141, 142 may be constituted by belt cords made of an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) covered with a coating rubber. In this case, the belt cord made of the organic fiber material has the cord diameter φbt (mm) in the range 0.50≤φbt≤0.90 and the number of insertions Ebt (piece/50 mm) in the range 30≤Ebt≤65, whereby the above-described tensile strength Tbt (N/50 mm) of the cross belts 141, 142 is achieved. The belt cords made of the high-tensile strength organic fiber material, such as nylon, aramid, and hybrid, can be employed within the scope of obviousness by one skilled in the art.
The belt layer 14 may include a supplemental belt (not illustrated). The supplemental belt may be, for example, (1) a third cross belt constituted by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and performing a rolling process and having a cord angle of 15 degrees or more and 55 degrees or less as an absolute value, or (2) a so-called large-angle belt constituted by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and performing a rolling process and having a cord angle of 45 degrees or more and 70 degrees or less as and preferably 54 degrees or more and 68 degrees or less as an absolute value. The supplemental belt may be disposed (a) between the pair of cross belts 141, 142 and the carcass layer 13, (b) between the pair of cross belts 141, 142, or (c) the outer side of the pair of cross belts 141, 142 in the radial direction (not illustrated). As a result, the load capacity of the belt layer 14 is improved.
Further, a total tensile strength TTbt (N/50 mm) of the belt layer 14 is in the range 70≤TTbt/OD≤750, preferably in the range 90≤TTbt/OD≤690, more preferably in the range 110≤TTbt/OD≤690, and further preferably in the range 120≤TTbt/OD≤690 with respect to the tire outer diameter OD (mm). As a result, the load capacity of the entire belt layer 14 is ensured. Further, 0.16×P≤TTbt/OD is preferable with the use of a specified internal pressure P (kPa) of the tire.
The total tensile strength TTbt (N/50 mm) of the belt layer 14 is calculated as the sum of the tensile strengths Tbt (N/50 mm) of the effective belt plies (the pair of cross belts 141, 142 and the belt cover 143 in
Among the pair of cross belts 141, 142 (the supplemental belt is included in the configuration including the supplemental belt described above (not illustrated)), a width Wb1 (mm) of the widest cross belt (the cross belt 141 on the radially inner side in
The width of a belt ply is the distance in the direction of the tire rotation axis between the left and right end portions of each belt ply, measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
Among the pair of cross belts 141, 142 (the supplemental belt is included in the configuration including the supplemental belt described above (not illustrated)), the width Wb1 (mm) of the widest cross belt (the cross belt 141 on the radially inner side in
For example, in the configurations of
In
The amount of depression DA is the distance in the tire radial direction from the intersection point C1 between the tire equatorial plane CL and the tread profile in the cross-sectional view in the tire meridian direction to the tire ground contact edge T, and is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The tire profile is a contour line of the tire in a cross-sectional view along the tire meridian direction, and is measured using a laser profiler. The laser profiler used may be, for example, a tire profile measuring device (available from Matsuo Co., Ltd.).
The amount of depression DA (mm) of the tread profile at the tire ground contact edge T preferably satisfies the following mathematical formula (5) with respect to the tire outer diameter OD (mm) and the total tire width SW (mm). Here, Emin=3.5 and Emax=17, preferably Emin=3.8 and Emax=13, and more preferably Emin=4.0 and Emax=9.
E min*(SW/OD)∧(¼)≤DA≤E max*(SW/OD)∧(¼) (5)
At this time, a radius of curvature TRc (mm) of an arc passing through the point C1 and the pair of points C2 is in the range 0.15≤TRc/OD≤15 and preferably in the range 0.18≤TRc/OD≤12 with respect to the tire outer diameter OD (mm). The radius of curvature TRc (mm) of the arc is in the range 30≤TRc≤3000, preferably in the range 50≤TRc≤2800, and more preferably in the range 80≤TRc≤2500. As a result, the load capacity of the tread portion 2 is appropriately ensured. Specifically, the lower limit flattens the tread portion center region, uniforms the ground contact pressure of the tire ground contact region, and ensures the wear resistance performance of the tire. The upper limit suppresses a decrease in wear life caused by an excessive ground contact pressure of the tread portion shoulder region. In particular, since the tire having a small diameter is assumed to be used under a high internal pressure and a high load, a uniform effect of the ground contact pressure under such a use condition can be effectively obtained.
The radius of curvature of the arc is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
In
The radius of curvature TRw (mm) of a first arc passing through the points C1 and C2 described above is in the range 0.50≤TRw/TRc≤1.00, preferably in the range 0.60≤TRw/TRc≤0.95, and more preferably in the range 0.70≤TRw/TRc≤0.90 with respect to the radius of curvature TRw (mm) of a second arc passing through the point C 1 and the tire ground contact edge T. This makes a contact patch shape of the tire appropriate. Specifically, the lower limit disperses the ground contact pressure of the tread portion center region and improves the wear life of the tire. The upper limit suppresses a decrease in wear life caused by an excessive ground contact pressure of the tread portion shoulder region.
In
At this time, a radius of curvature CRw of an arc passing through the point B1 and the pair of points B2 and B2 is in the range 0.35≤CRw/TRw≤1.10, preferably in the range 0.40≤CRw/TRw≤1.00, and more preferably in the range 0.45≤CRw/TRw≤0.92 with respect to the radius of curvature TRw of the arc passing through the point C1 and the tire ground contact edges T and T described above. The radius of curvature CRw (mm) is in the range 100≤CRw≤2500 and preferably in the range 120≤CRw≤2200. This makes the contact patch shape of the tire more appropriate. Specifically, the lower limit suppresses a decrease in wear life caused by an increase in rubber gauge in the tread portion shoulder region. The upper limit ensures the wear life in the tread portion center region.
In the configuration of
In
The distance Tce is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The outer circumferential surface of the belt ply is defined as a circumferential surface on the outer side in the radial direction of the entire belt ply formed of the belt cords and the coating rubber.
The distance Tce (mm) from the tread profile on the tire equatorial plane CL to the outer circumferential surface of the wide cross belt 141 preferably satisfies the following mathematical formula (6) with respect to the tire outer diameter OD (mm). Here, Fmin=35 and Fmax=207 and preferably Fmin=42 and Fmax=202.
F min/(OD)∧(⅓)≤Tce≤F max/(OD)∧(⅓) (6)
A distance Tsh (mm) from the tread profile at the tire ground contact edge T to the outer circumferential surface of the wide cross belt 141 is in the range 0.60≤Tsh/Tce≤1.70, preferably in the range 1.01≤Tsh/Tce≤1.55, and more preferably in the range 1.10≤Tsh/Tce≤1.50 with respect to the distance Tce (mm) in the tire equatorial plane CL. The lower limit ensures the tread gauge in the shoulder region, and therefore repeated deformation of the tire during rolling of the tire is suppressed, and the wear resistance performance of the tire is ensured. The upper limit ensures the tread gauge in the center region, and therefore the tire deformation during use under a high load peculiar to the tire having a small diameter is suppressed, and the wear resistance performance of the tire is ensured.
The distance Tsh is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. When a wide cross belt is not present immediately below the tire ground contact edge T, the distance is measured as a distance of an imaginary line of the distance Tsh extending from the outer circumferential surface of the belt ply from the tread profile.
The distance Tsh (mm) from the tread profile to the outer circumferential surface of the wide cross belt 141 in the tire ground contact edge T preferably satisfies the following mathematical formula (7) with respect to the distance Tce (mm) in the tire equatorial plane CL. Here, Gmin=0.36 and Gmax=0.72, preferably Gmin=0.37 and Gmax=0.71, and more preferably Gmin=0.38 and Gmax=0.70.
G min*(OD)∧( 1/7)≤Tsh/Tce≤G max*(OD)∧( 1/7) (7)
In
The rubber gauge of the tread rubber 15 is defined as a distance from the tread profile to the inner circumferential surface of the tread rubber 15 (in
In
The above-described distance Tsh in the tire ground contact edge T is in the range 1.50≤Tsh/Tu≤6.90 and preferably in the range 2.00≤Tsh/Tu≤6.50 with respect to a rubber gauge Tu (mm) from the end portion of the wide cross belt 141 to the outer circumferential surface of the carcass layer 13. This makes the profile of the carcass layer 13 appropriate and tension of the carcass layer 13 appropriate. Specifically, the lower limit ensures the tension of the carcass layer and the tread gauge in the shoulder region, and therefore repeated deformation of the tire during rolling of the tire is suppressed, and the wear resistance performance of the tire is ensured. The upper limit ensures the rubber gauge at or near the end portion of the belt ply, and therefore separation of the peripheral rubber of the belt ply is suppressed.
The rubber gauge Tu is substantially measured as a gauge of a rubber member (the sidewall rubber 16 in
The outer circumferential surface of the carcass layer 13 is defined as a circumferential surface on the outer side in the radial direction of the entire carcass ply formed of the carcass cords and the coating rubber. When the carcass layer 13 has a multilayer structure formed of a plurality of carcass plies (not illustrated), the outer circumferential surface of the carcass ply of the outermost layer constitutes the outer circumferential surface of the carcass layer 13. When the turned-up portion 132 (see
For example, in the configuration of
In the configuration of
At this time, as illustrated in
The circumferential main groove closest to the tire equatorial plane CL is defined as the circumferential main groove 21 (see
The ratio Gd1/Gce described above preferably satisfies the following mathematical formula (8) with respect to the tire outer diameter OD (mm). Here, Hmin=0.10 and Hmax=0.60, preferably Hmin=0.12 and Hmax=0.50, and more preferably Hmin=0.14 and Hmax=0.40.
H min*250/OD≤Gd1/Gce≤H max+250/OD (8)
A groove depth Gd1 (mm) of the circumferential main groove 21 closest to the tire equatorial plane CL among the plurality of circumferential main grooves 21 to 23 is deeper than groove depths Gd2 (mm), Gd3 (mm) of the other circumferential main grooves 22, 23 (Gd2<Gd1, Gd3<Gd1). Specifically, when a region from the tire equatorial plane CL to the tire ground contact edge T is bisected in the tire width direction, the groove depth Gd1 of the circumferential main groove (reference sign omitted in drawings) closest to the tire equatorial plane CL is in the range of 1.00 times or more and 2.50 times or less, preferably in the range of 1.00 times or more and 2.00 times or less, and more preferably in the range of 1.00 times or more and 1.80 times or less with respect to the maximum values of the groove depths Gd2, Gd3 of the other circumferential main grooves (reference sign omitted in drawings) in the region on the tire ground contact edge T side. The lower limit disperses the ground contact pressure of the tread portion center region and improves the wear resistance performance of the tire. The upper limit suppresses uneven wear caused by the excessive ground contact pressure difference between the tread portion center region and the shoulder region.
In
At this time, the sum of the distance Hu (mm) and the distance Hl (mm) is in the range 0.45≤(Hu+Hl)/SH≤0.90 and preferably in the range 0.50≤(Hu+Hl)/SH≤0.85 with respect to the tire cross-sectional height SH (mm) (see
The distance Hu and the distance Hl are measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The sum of the distance Hu (mm) and the distance Hl (mm) preferably satisfies the following mathematical formula (9) with respect to tire outer diameter OD (
I1 min*(OD/RSc)∧(½)≤(Hu+Hl)/SH≤I2+I1 max*(RSc/OD)∧(½) (9)
The radius of curvature RSc of the arc is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The distance Hu (mm) and the distance Hl (mm) have the relationship 0.30≤Hu/(Hu+Hl)≤0.70 and preferably have the relationship 0.35≤Hu/(Hu+Hl)≤0.65. This makes the position of the tire maximum width position Ac in the deformable region of the tire side portion 3 appropriate. Specifically, the lower limit alleviates stress concentration at ornear the end portion of the belt ply caused by the tire maximum width position Ac being excessively close to the end portion of the belt layer 14 and suppresses the separation of the peripheral rubber. The upper limit alleviates stress concentration at or near the bead portion 4 caused by the tire maximum width position Ac being excessively close to the end portion of the bead core 11 and suppresses a failure of a reinforcing member (the bead filler 12 in
The radius of curvature RSc (mm) of the arc passing through the tire maximum width position Ac, the point Au′, and the point Al′ is in the range 0.05≤RSc/OD≤1.70 and preferably in the range 0.10≤RSc/OD≤1.60 with respect to the tire outer diameter OD (mm). The radius of curvature RSc (mm) of the arc is in the range 25≤RSc≤330 and preferably in the range 30≤RSc≤300. This makes the radius of curvature of the side profile appropriate and appropriately ensures the load capacity of the tire side portion 3. Specifically, the lower limit reduces the amount of deflection of the tire side portion 3 during rolling of the tire and reduces the rolling resistance of the tire. The upper limit suppresses stress concentration caused by the tire side portion 3 becoming flat and improves the durability performance of the tire. In particular, in the tire having a small diameter, since large stress tends to act on the tire side portion 3 due to the use under the high internal pressure and the high load described above, there is also a problem that side cut resistance performance of the tire should be ensured. In this regard, the lower limit ensures the radius of curvature of the side profile, suppresses a collapse of the tire by making carcass tension appropriate, and suppresses side cut of the tire. The upper limit suppresses the side cut of the tire caused by an excessive tension of the carcass layer 13.
The radius of curvature RSc (mm) of the arc is in the range 0.50≤RSc/SH≤0.95 and preferably in the range 0.55≤RSc/SH≤0.90 with respect to the tire cross-sectional height SH (mm).
The radius of curvature RSc (mm) of the arc preferably satisfies the following mathematical formula (10) with respect to the tire outer diameter OD (mm) and the rim diameter RD (mm). Here, Jmin=15 and Jmax=360, preferably Jmin=20 and Jmax=330, and more preferably Jmin=25 and Jmax=300.
J min*(OD/RD)∧(½)≤RSc≤J max+(OD/D)∧(½) (10)
In
At this time, the radius of curvature RSc (mm) of the arc passing through the tire maximum width position Ac, the point Au′ and the point Al′ described above is in the range 1.10≤RSc/RcC≤4.00 and preferably in the range 1.50≤RSc/RcC≤3.50 with respect to the radius of curvature RcC (mm) of the arc passing through the point Bc, the point Bu′ and the point Bl′. The radius of curvature RcC (mm) of the arc passing through the point Bc, the point Bu′ and the point Bl′ is in the range 5≤RcC≤300 and preferably in the range 10≤RcC≤270. This makes the relationship between the radius of curvature RSc of the side profile of the tire and the radius of curvature RcC of the side profile of the carcass layer 13 appropriate. Specifically, the lower limit ensures the radius of curvature RcC of the carcass profile, ensures the internal volume V of the tire described later, and ensures the load capacity of the tire. The upper limit ensures the total gauges Gu and Gl of the tire side portion 3 described later and ensures the load capacity of the tire side portion 3.
The radius of curvature RSc (mm) of the side profile described above preferably satisfies the following mathematical formula (11) with respect to the radius of curvature RcC (mm) of the carcass profile and the tire outer diameter OD (mm). Here, Kmin=1 and Kmax=130, preferably Kmin=2 and Kmax=100, and more preferably Kmin=3 and Kmax=70.
K min*(OD/RSc)∧(½)≤RCc≤K max*(OD/RSc)∧(½) (11)
In
The total gauge of the tire side portion 3 is measured as a distance from the side profile to the tire inner surface on a perpendicular line drawn from a predetermined point on the side profile to the body portion 131 of the carcass layer 13.
In
The total gauge Gu (mm) at the above-described point Au preferably satisfies the following mathematical formula (12) with respect to the total gauge Gc (mm) at the tire maximum width position Ac and the tire outer diameter OD (mm). Here, Lmin=0.10 and Lmax=0.70, preferably Lmin=0.14 and Lmax=0.70, and more preferably Lmin=0.19 and Lmax=0.70.
L min*(OD)∧(⅓)*Gc≤Gu≤L max*(OD)∧(⅓)*Gc (12)
In
The total gauge Gc (mm) at the tire maximum width position Ac preferably satisfies the following mathematical formula (13) with respect to the tire outer diameter OD (mm). Here, M min=70 and M max=450 and preferably M min=80 and M max=400.
M min/(OD)∧(½)≤Gc≤M max/(OD)∧(½) (13)
The total gauge Gc (mm) at the tire maximum width position Ac preferably satisfies the following mathematical formula (14) with respect to the tire outer diameter OD (mm) and the total tire width SW (mm). Here, N min=0.20 and N max=15, preferably N min=0.40 and N max=15, and more preferably N min=0.60 and N max=12.
N min*(OD/SW)≤Gc≤N max*(OD/SW) (14)
The total gauge Gc (mm) at the tire maximum width position Ac preferably satisfies the following mathematical formula (15) with respect to the radius of curvature RSc (mm) of the arc passing through the tire maximum width position Ac, the point Au′, and the point Al′ described above. Here, O min=13 and O max=260 and preferably O min=20 and O max=200.
O min/(RSc)∧(½)≤Gc≤O max/(RSc)∧(½) (15)
In
In
The total gauge Gl (mm) of the tire side portion 3 at the above-described point Al preferably satisfies the following mathematical formula (16) with respect to the total gauge Gc (mm) at the tire maximum width position Ac and the tire outer diameter OD (mm). Here, Pmin=0.12 and Pmax=1.00, preferably Pmin=0.15 and Pmax=1.00, and more preferably Pmin=0.18 and Pmax=1.00.
P min*(OD)∧(⅓)*Gc≤G1≤P max*(OD)∧(⅓)*Gc (16)
In
The total gauge G1 (mm) at the above-described point Al preferably satisfies the following mathematical formula (17) with respect to the total gauge Gu (mm) at the above-described point Au and the tire outer diameter OD (mm). Here, Qmin=0.09 and Qmax=0.80, preferably Qmin=0.10 and Qmax=0.70, and more preferably Qmin=0.11 and Qmax=0.50.
Q min*(OD)∧(⅓)*Gu≤Gl≤Q max*(OD)∧(⅓)*Gu (17)
In
The average rubber hardnesses Hsc, Hsu, Hsl are calculated as the sum of values obtained by dividing the product of the cross-sectional lengths and the rubber hardnesses of the respective rubber members at the respective measurement points of the total gauge Gc (mm) at the tire maximum width position Ac, the total gauge Gu at the point Au, and the total gauge Gl at the point Al by the total gauge.
In
The distance ΔAl′ (mm) from the tire maximum width position Ac to the point Al′ in the tire width direction is in the range 0.03≤ΔAl′/(H1×0.70)≤0.28 and preferably in the range 0.07≤ΔAl′/(H1×0.70)≤0.20 with respect to 70% of the distance Hl (mm) from the tire maximum width position Ac. This makes the degree of curvature of the side profile in the region on the inner side in the radial direction appropriate. Specifically, the lower limit suppresses stress concentration caused by the tire side portion 3 becoming flat and improves the durability performance of the tire. In particular, in the tire having a small diameter, since the bead core 11 is reinforced as described above, the stress concentration at and near the bead core 11 is effectively suppressed. The upper limit reduces the amount of deflection of the tire side portion 3 during rolling of the tire and reduces the rolling resistance of the tire.
The distances ΔAu′ and ΔAl′ are measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The distance ΔAu′ (mm) from the tire maximum width position Acto the point Au′ in the tire width direction preferably satisfies the following mathematical formula (18) with respectto the radius of curvature RSc (mm) of the arc passing through the tire maximum width position Ac, the point Au′, and the point Al′ described above. Here, Rmin=0.05 and Rmax=5.00 and preferably Rmin=0.10 and Rmax=4.50.
R min*(RSc)∧(½)≤ΔAu′≤R max*(RSc)∧(½) (18)
In
In
The distances ΔBu′, ΔBl′ are measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.
The distance ΔBu′ (mm) from the point Bc to the point Bu′ in the tire width direction preferably satisfies the following mathematical formula (19) with respect to the radius of curvature RcC (mm) of the arc passing through the point Bc, the point Bu′, and the point Bl′ described above. Here, Smin=0.40 and Smax=7.0 and preferably Smin=0.50 and Smax=6.0.
S min*(RSc)∧(½)≤ΔBu′≤S max*(RSc)∧(½) (19)
In
The rubber gauge Gcr (mm) of the sidewall rubber 16 at the tire maximum width position Ac preferably satisfies the following mathematical formula (20) with respect to the total gauge Gc (mm) at the tire maximum width position Ac and the tire outer diameter OD (mm) described above. Here, Tmin=80 and Tmax=0.90 and preferably Tmin=120 and Tmax=0.90.
Gc*(T min/OD)≤Gcr≤Gc*T max (20)
In
In the cap tread 151 included in the tread rubber 15 constituting the tread portion 2, a natural rubber or an isoprene rubber of 40 parts by weight or more is blended, and a reinforcing filler of 40 parts by weight or more and 70 parts by weight or less is blended, per 100 parts by weight of a diene rubber. The blended amount of the natural rubber or the isoprene rubber per 100 parts by weight of the diene rubber in the cap tread 151 is preferably in the range of 50 parts by weight or more and 90 parts by weight or less. As the reinforcing filler, carbon black, silica, or the like is used, and carbon black is preferably used. The carbon black with a grade, such as ISAF or HAF, is used, and preferably the carbon black with SAF or ISAF is used.
The cap tread 151 has a strength at break TB_cap (MPa) in the range 12≤TB_cap≤35, and the relationship between the strength at break TB_cap (MPa) of the cap tread 151 and the tire outer diameter OD (mm) (see
The strength at break is determined in accordance with the measurement method of tensile strength at break specified in JIS K6251.
Further, in the cap tread 151, the relationship between a thickness H_cap (mm) of the cap tread 151 and the strength at break TB_cap of the cap tread 151 is within the range 0.14≤H_cap/TB_cap≤17.0. Specifically, the relationship between the thickness H_cap (mm) of the cap tread 151 and the strength at break TB_cap of the cap tread 151 satisfies the following mathematical formula (21).
13/TB_cap∧(¼)≤H_cap≤50/TB_cap∧(¼) (21)
When no groove is formed on the tire equatorial plane CL of the tread portion 2, the thickness H_cap (mm) of the cap tread 151 in this case is a thickness measured at the position of the tire equatorial plane CL. When a groove is formed on the tire equatorial plane CL of the tread portion 2, the thickness H_cap (mm) of the cap tread 151 is a thickness measured at a position of a land portion adjacent to the groove on the tire equatorial plane CL.
By setting the thickness H_cap (mm) of the cap tread 151 within the range of the mathematical formula (21), the deformation of the tread portion 2 at the time of contact with the ground can be suppressed while fuel economy performance is maintained, and wear performance can be improved.
The relationship between the thickness H_cap (mm) of the cap tread 151 thus measured and the strength at break TB_cap of the cap tread 151 preferably satisfies the following mathematical formula (22), and more preferably satisfies the following mathematical formula (23). Specifically, the thickness H_cap of the cap tread 151 is in the range of 5 mm or more and 20 mm or less, preferably in the range of 6 mm or more and 20 mm or less, and more preferably in the range of 7 mm or more and 18 mm or less.
15/TB_cap∧(¼)≤H_cap≤50/TB_cap∧(¼) (22)
20/TB_cap∧(¼)≤H_cap≤45/TB_cap∧(¼) (23)
Further, in the cap tread 151, the relationship between a brittle temperature T_cap (° C.) of the cap tread 151 and the thickness H_cap (mm) of the cap tread 151 satisfies the following mathematical formula (24). By setting the brittle temperature T_cap (° C.) of the cap tread 151 with respect to the thickness H_cap (mm) of the cap tread 151 within the range of the mathematical formula (24), wear performance can be improved while fuel economy performance is maintained.
−100/H_cap∧(¼)≤T_cap≤−40/H_cap∧(¼) (24)
The brittle temperature is measured by a measurement method in accordance with the low-temperature impact embrittlement test specified in JIS K6261.
The relationship between the brittle temperature T_cap (° C.) of the cap tread 151 and the thickness H_cap (mm) of the cap tread 151 measured as described above preferably satisfies the following mathematical formula (25), and more preferably satisfies the following mathematical formula (26). Specifically, the brittle temperature T_cap of the cap tread 151 is in the range of −65° C. or more and −25° C. or less, preferably in the range of −65° C. or more and −30° C. or less, and more preferably in the range of −65° C. or more and −40° C. or less.
−100/H_cap∧(¼)≤T_cap≤−60/H_cap∧(¼) (25)
−100/H_cap∧(¼)≤T_cap≤−80/H_cap∧(¼) (26)
In the cap tread 151, the relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 satisfies the following mathematical formula (27). By setting the rubber hardness Hs_cap of the cap tread 151 with respect to the thickness H_cap (mm) of the cap tread 151 within the range of the mathematical formula (27), wear performance can be improved while fuel economy performance is maintained.
65/H_cap∧(⅕)≤Hs_cap≤150/H_cap∧(⅕) (27)
The relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 preferably satisfies the following mathematical formula (28), and more preferably satisfies the following mathematical formula (29). Specifically, the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. is in the range of 50 or more and 80 or less, preferably in the range of 53 or more and 80 or less, and more preferably in the range of 56 or more and 75 or less.
75/H_cap∧(⅕)≤Hs_cap≤150/H_cap∧(⅕) (28)
80/H_cap∧(⅕)≤Hs_cap≤140/H_cap∧(⅕) (29)
Further, in the cap tread 151, the relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap (mm) of the cap tread 151 satisfies the following mathematical formula (30). When tan δ_cap of the cap tread 151 with respect to the thickness H_cap (mm) of the cap tread 151 is within the range of the mathematical formula (30), fuel economy performance can be improved.
0.08/H_cap∧(⅓)≤tan δ_cap≤0.70/H_cap∧(⅓) (30)
The relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap (mm) of the cap tread 151 preferably satisfies the following mathematical formula (31), and more preferably satisfies the following mathematical formula (32).
0.10/H_cap∧(⅓)≤tan δ_cap≤0.70/H_cap∧(⅓) (31)
0.15/H_cap∧(⅓)≤tan δ_cap≤0.65/H_cap∧(⅓) (32)
In the tire 1 in which the tread rubber 15 is configured as described above, the relationship between the amount of change between the ground contact area CA80 of the tread portion 2 at 80% of the maximum load capacity and the ground contact area CA120 of the tread portion 2 at 120% of the maximum load capacity and the tire outer diameter OD satisfies 0.0004×OD≤{(CA120−CA80)/CA80}≤0.0030×OD.
The ground contact area in this case refers to the area of the ground contact region of the tread portion 2 when the tread portion 2 is in contact with the ground, including an area of a portion in which a groove disposed in the tread portion 2 is formed. Additionally, the maximum load capacity in this case refers to a “maximum load capacity” specified by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “LOAD CAPACITY” specified by ETRTO. When the tire size is a size not described in JATMA, the maximum load capacity is calculated by a load capacity calculation formula described in JATMA.
The relationship between the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity and the tire outer diameter OD preferably satisfies 0.0005×OD≤{(CA120−CA80)/CA80}≤0.0025×OD and more preferably satisfies 0.0006×OD≤{(CA120−CA80)/CA80}≤0.0020×OD.
The relationship between the strength at break TB_cap (MPa) of the cap tread 151 and the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity satisfies the following mathematical formula (33). By setting the strength at break TB_cap (MPa) of the cap tread 151 within the range of the mathematical formula (33), wear performance can be improved even when the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity is large.
40×{(CA120−CA80)/CA80}≤TB_cap≤70×{(CA120−CA80)/CA80} (33)
The relationship between the strength at break TB_cap of the cap tread 151 and the amount of change between the ground contact area CA80 at 80% of the maximumload capacity and the ground contact area CA120 at 120% of the maximum load capacity preferably satisfies the following mathematical formula (34), and more preferably satisfies the following mathematical formula (35).
55×{(CA120−CA80)/CA80}≤TB_cap≤70×{(CA120−CA80)/CA80} (34)
60×{(CA120−CA80)/CA80}≤TB_cap≤70×{(CA120−CA80)/CA80} (35)
As described above, the tire 1 according to the present embodiment includes the pair of bead cores 11, 11, the carcass layer 13 extended across the pair of bead cores 11, 11, and the belt layer 14 disposed on the outer side of the carcass layer 13 in the radial direction (see
In such a configuration, since the strength at break TB_cap (MPa) of the cap tread 151 is appropriately ensured in the tire having a small diameter, wear performance can be improved while fuel economy performance is maintained. That is, in a case where the strength at break TB_cap of the cap tread 151 is TB_cap≤12, the strength at break TB_cap of the cap tread 151 is too low. Therefore, when the diameter of the tire 1 is reduced, wear performance is possibly difficult to be ensured. In addition, when the strength at break TB_cap of the cap tread 151 is TB_cap>35, the strength at break TB_cap of the cap tread 151 is too high, and thus it is possibly difficult to ensure fuel economy performance. On the other hand, when the strength at break TB_cap of the cap tread 151 is in the range 12≤TB_cap≤35, wear performance can be improved while fuel economy performance is maintained.
Further, in such a configuration, since the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity is appropriately maintained with respect to the tire outer diameter OD, the decrease in wear performance at a high load is suppressed and fuel economy performance can be more reliably ensured. That is, in the case of {(CA120−CA80)/CA80}<0.0004×OD, the amount of change between the ground contact area CA so at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity is too small. Therefore, the ground contact area cannot be ensured even under a high load at braking, which possibly makes it difficult to ensure braking performance. In the case of {(CA120−CA80)/CA80}>0.0030×OD, the amount of change between the ground contact area CA so at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity becomes too large. Therefore, the ground contact area becomes too large at a high load, and wear performance and fuel economy performance are possibly likely to deteriorate at a high load.
On the other hand, when the amount of change in the ground contact area satisfies 0.0004×OD≤{(CA120−CA80)/CA80}≤0.0030×OD, the wear resistance under a high load can be more reliably improved while fuel economy performance is ensured. As a result, wear performance can be improved while fuel economy performance is maintained.
In addition, in the tire 1 according to the embodiment, since the strength at break TB_cap (MPa) of the cap tread 151 is in the range of 7000/OD≤TB_cap≤19000/OD with respect to the relationship with the tire outer diameter OD (mm), wear performance can be improved while fuel economy performance is more reliably maintained. That is, when the relationship between the strength at break TB_cap of the cap tread 151 and the tire outer diameter OD satisfies TB_cap≤7000/OD, the strength at break TB_cap of the cap tread 151 is too low. Therefore, when the diameter of the tire 1 is reduced, it is possibly difficult to ensure wear performance. In addition, when the relationship between the strength at break TB_cap of the cap tread 151 and the tire outer diameter OD is TB_cap>19000/OD, the strength at break TB_cap of the cap tread 151 is too high, and therefore it is possibly difficult to ens ure fuel economy performance.
On the other hand, in the case where the relationship between the strength at break TB_cap of the cap tread 151 and the tire outer diameter OD is in the range 7000/OD≤TB_cap≤19000/OD, the strength at break TB_cap of the cap tread 151 can be appropriately ensured, and thus wear performance can be improved while fuel economy performance is more reliably maintained. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In addition, in the tire 1 according to the embodiment, the strength at break TB_cap (MPa) of the cap tread 151 satisfies 40×{(CA120−CA80)/CA80}≤TB_cap≤70×{(CA120−CA80)/CA80} with respect to the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity, and thus wear performance can be improved while fuel economy performance is more reliably maintained. That is, when the relationship between the strength at break TB_cap of the cap tread 151 and the amount of change in the ground contact area is TB_cap≤40×{(CA120−CA80)/CA80}, since the strength at break TB_cap of the cap tread 151 is too low with respect to the amount of change in the ground contact area, when the diameter of the tire 1 is reduced, it is possibly difficult to ensure wear performance. When the relationship between the strength at break TB_cap of the cap tread 151 and the amount of change in the ground contact area is TB_cap>70×{(CA120−CA80)/CA80}, the strength at break TB_cap of the cap tread 151 is too high with respect to the amount of change in the ground contact area, and therefore it is possibly difficult to ensure fuel economy performance.
On the other hand, when the relationship between the strength at break TB_cap of the cap tread 151 and the amount of change in the ground contact area is in the range 40×{(CA120−CA80)/CA80}≤TB_cap≤70×{(CA120−CA80)/CA80}, the strength at break TB_cap of the cap tread 151 can be appropriately ensured, and therefore wear performance can be improved while fuel economy performance is more reliably maintained. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In addition, in the tire 1 according to the embodiment, since the thickness H_cap (mm) of the cap tread 151 satisfies 13/TB_cap{circumflex over ( )}(¼)≤H_cap≤50/TB_cap{circumflex over ( )}(¼) with respect to the strength at break TB_cap of the cap tread 151, fuel economy performance can be improved while the decrease in wear performance is suppressed more reliably. That is, when the relationship between the thickness H_cap of the cap tread 151 and the strength at break TB_cap of the cap tread 151 is H_cap≤13/TB_cap{circumflex over ( )}(¼), the thickness H_cap of the cap tread 151 is too thin, and therefore the deformation of the tread portion 2 at the time of contact with the ground becomes too large, which possibly makes it difficult to ensure wear performance. In addition, when the relationship between the thickness H_cap of the cap tread 151 and the strength at break TB_cap of the cap tread 151 is H_cap>50/TB_cap{circumflex over ( )}(¼), the thickness H_cap of the cap tread 151 is too thick, and therefore the weight of the cap tread 151 increases and fuel economy performance is possibly likely to deteriorate.
On the other hand, when the relationship between the thickness H_cap of the cap tread 151 and the strength at break TB_cap of the cap tread 151 satisfies 13/TB_cap{circumflex over ( )}(¼)≤H_cap≤50/TB_cap{circumflex over ( )}(¼), the thickness H_cap of the cap tread 151 can be appropriately ensured. As a result, the deformation of the tread portion 2 at the time of contact with the ground can be suppressed while fuel economy performance is maintained, and wear performance can be improved. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In addition, in the tire 1 according to the embodiment, the relationship between the brittle temperature T_cap (° C.) of the cap tread 151 and the thickness H_cap (mm) of the cap tread 151 satisfies −100/H_cap{circumflex over ( )}(¼)≤T_cap≤−40/H_cap{circumflex over ( )}(¼). Therefore, fuel economy performance can be improved while the decrease in wear performance is suppressed more reliably. That is, in a case where the relationship between the brittle temperature T_cap of the cap tread 151 and the thickness H_cap of the cap tread 151 is T_cap≤−100/H_cap{circumflex over ( )}(¼), the brittle temperature T_cap of the cap tread 151 is too low. Therefore, although wear performance is improved, fuel economy performance is possibly likely to deteriorate. In addition, when the relationship between the brittle temperature T_cap of the cap tread 151 and the thickness H_cap of the cap tread 151 is T_cap>−40/H_cap{circumflex over ( )}(¼), the brittle temperature T_cap of the cap tread 151 is too high, and thus wear performance is possibly likely to deteriorate.
On the other hand, when the relationship between the brittle temperature T_cap of the cap tread 151 and the thickness H_cap of the cap tread 151 satisfies −100/H_cap{circumflex over ( )}(¼)≤T_cap≤−40/H_cap{circumflex over ( )}(¼), the brittle temperature T_cap of the cap tread 151 can be appropriately ensured, and wear performance can be improved while fuel economy performance is maintained. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In addition, in the tire 1 according to the embodiment, the relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 satisfies 65/H_cap{circumflex over ( )}(⅕)≤Hs_cap≤150/H_cap{circumflex over ( )}(⅕), and therefore fuel economy performance can be improved while the decrease in wear performance is suppressed more reliably. That is, when the relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 is Hs_cap≤65/H_cap{circumflex over ( )}(⅕), the rubber hardness Hs_cap of the cap tread 151 is too low, and therefore cornering power is possibly likely to decrease, and wear performance is possibly likely to deteriorate. Further, when the relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 is Hs_cap>150/H_cap{circumflex over ( )}(⅕), the rubber hardness Hs_cap of the cap tread 151 is too high. Therefore, although wear performance is improved, fuel economy performance is possibly likely to deteriorate.
On the other hand, when the relationship between the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C. and the thickness H_cap (mm) of the cap tread 151 satisfies 65/H_cap{circumflex over ( )}(⅕)≤Hs_cap≤150/H_cap{circumflex over ( )}(⅕), the rubber hardness Hs_cap of the cap tread 151 can be appropriately ensured, and wear performance can be improved while fuel economy performance is maintained. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
Further, in the tire 1 according to the embodiment, the relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap (mm) of the cap tread 151 satisfies 0.08/H_cap{circumflex over ( )}(⅓)≤tan δ_cap≤0.70/H_cap{circumflex over ( )}(⅓), and therefore fuel economy performance can be improved. That is, in the case where the relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap of the cap tread 151 is tan δ_cap≤0.08/H_cap{circumflex over ( )}(⅓), the weight of the cap tread 151 possibly excessively increases, and fuel economy performance possibly deteriorates. In addition, when the relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap of the cap tread 151 is tan δ_cap>0.70/H_cap{circumflex over ( )}(⅓), tan δ_cap of the cap tread 151 is too high, and therefore fuel economy performance is possibly likely to deteriorate.
On the other hand, when the relationship between tan δ_cap of the cap tread 151 at the temperature condition of 60° C. and the thickness H_cap of the cap tread 151 satisfies 0.08/H_cap{circumflex over ( )}(⅓)≤tan δ_cap≤0.70/H_cap{circumflex over ( )}(⅓), the relative relationship between tan δ_cap of the cap tread 151 and the thickness H_cap of the cap tread 151 can be appropriately ensured, and fuel economy performance can be improved. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
Further, in the tire 1 according to the embodiment, the relationship between tan δ_ut of the undertread 152 at the temperature condition of 60° C. and tan δ_cap of the cap tread 151 at the temperature condition of 60° C. satisfies 0.1×tan δ_cap≤tan δ_ut≤4.5×tan δ_cap, and therefore fuel economy performance can be improved. That is, when the relationship between tan δ_ut of the undertread 152 and tan δ_cap of the cap tread 151 is tan δ_ut≤0.1×tan δ_cap, tan δ_ut of the undertread 152 is too low. Therefore, the balance between the undertread 152 and the cap tread 151 deteriorates, and thus the improvement in fuel economy performance is possibly insufficient. When the relationship between tan δ_ut of the undertread 152 and tan δ_cap of the cap tread 151 is tan δ_ut>4.5× tan δ_cap, tan δ_ut of the undertread 152 is too high compared with tan δ_cap of the cap tread 151, and therefore fuel economy performance is possibly likely to deteriorate.
On the other hand, when the relationship between tan δ_ut of the undertread 152 and tan δ_cap of the cap tread 151 satisfies 0.1× tan δ_cap S tan δ_ut≤4.5× tan δ_cap, tan δ_ut of the undertread 152 and tan δ_cap of the cap tread 151 can be appropriately ensured, and fuel economy performance can be improved. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In addition, in the tire 1 according to the embodiment, in the cap tread 151, a natural rubber or an isoprene rubber of 40 parts by weight or more is blended, and a reinforcing filler of 40 parts by weight or more and 70 parts by weight or less is blended, per 100 parts by weight of a diene rubber, and therefore fuel economy performance can be improved while the decrease in wear performance is suppressed more reliably. That is, when the blend of the natural rubber or the isoprene rubber in the cap tread 151 is less than 40 parts by weight per 100 parts by weight of the diene rubber, the strength of the cap tread 151 is reduced and wear performance is possibly likely to deteriorate. When the blend of the reinforcing filler in the cap tread 151 is less than 40 parts by weight per 100 parts by weight of the diene rubber, the blend of the reinforcing filler is too small, and therefore the reinforcing effect is insufficient and wear performance is possibly likely to deteriorate. Further, when the blend of the reinforcing filler in the cap tread 151 is more than 70 parts by weight per 100 parts by weight of the diene rubber, the blend of the reinforcing filler is too large, and thus fuel economy performance is possibly likely to deteriorate.
On the other hand, when the cap tread 151 is composed of the blend of the natural rubber or the isoprene rubber of 40 parts by weight or more and the blend of the reinforcing filler of 40 parts by weight or more and 70 parts by weight or less per 100 parts by weight of the diene rubber, the blend of the cap tread 151 can be appropriately ensured and the wear performance of the cap tread 151 can be improved while fuel economy performance is ensured. As a result, wear performance can be improved while fuel economy performance is more reliably maintained.
In the performance tests, (1) wear performance and (2) fuel economy performance were evaluated for a plurality oftypes of test tires. As an example of the tire having a small diameter, test tires having two types of tire sizes are used. To be specific, a test tire [A] having a tire size of 235/45R10 was mounted on a rim having a rim size of 10×8, and [B] a test tire having a tire size of 145/80R12 was mounted on a rim having a rim size of 12×4.00B.
(1) In the evaluation for wear performance, an internal pressure of 230 kPa and a load of 4.2 kN were applied to the test tire [A], and an internal pressure of 80% of the specified internal pressure of JATMA and a load of 80% of the specified load of JATMA were applied to the test tire [B]. In addition, a four wheeled low-floor vehicle with the test tires mounted on all wheels travelled 10000 km on a dry road surface of a test course. Thereafter, the degree of the amount of wear of each tire was measured, and the reciprocal of the measured value was evaluated using index values with Comparative Example being assigned as the reference (100). The wear performance indicates that the larger the value of the index is, the smaller the wear is, and the better the wear performance is.
(2) In the evaluation for fuel economy performance, an internal pressure of 230 kPa and a load of 4.2 kN were applied to the test tire [A], and an internal pressure of 80% of the specified internal pressure of JATMA and a load of 80% of the specified load of JATMA were applied to the test tire [B]. In addition, a four wheeled low-floor vehicle with the test tires mounted on all wheels travelled 50 laps on a test course having a total length of 2 km at a speed of 100 km/h. Thereafter, a fuel consumption rate (km/l) was calculated, and the calculated value was evaluated using index values with Comparative Example being assigned as the reference (100). The fuel economy performance indicates that the larger the value of the index is, the smaller the amount of fuel consumption with respect to the travel distance is, and the better fuel economy performance is.
The performance test of the tire was performed on 24 types of tires including Examples 1 to 23, which were the tire 1 according to embodiments of the present technology, and a tire of Conventional Example to be compared with the tire 1 according to the embodiments of the present technology. All of the test tires include the pair of bead cores 11, 11, the carcass layer 13 formed of a single layered carcass ply, the pair of cross belts 141, 142, the belt layer 14 formed of the belt cover 143 and the pair of belt edge covers 144, 144, the tread rubber 15, the sidewall rubber 16, and the rim cushion rubber 17. Among them, in Comparative Example, the strength at break TB_cap (MPa) of the cap tread 151 is out of the range 12≤TB_cap≤35, and the relationship between the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity and the tire outer diameter OD is also out of the range 0.0004×OD≤{(CA120−CA80/CA80}≤0.0030×OD.
On the other hand, in all of Examples 1 to 23, which are examples of the tire 1 according to the embodiments of the present technology, the strength at break TB_cap (MPa) of the cap tread 151 is within the range 12≤TB_cap≤35, and the relationship between the amount of change between the ground contact area CA80 at 80% of the maximum load capacity and the ground contact area CA120 at 120% of the maximum load capacity and the tire outer diameter OD is also within the range 0.0004×OD≤{(CA120−CA80)/CA80}≤0.0030×OD. Furthermore, in the tires 1 according to Examples 1 to 23, the thickness H_cap (mm) of the cap tread 151, the brittle temperature T_cap (° C.) of the cap tread 151, the rubber hardness Hs_cap of the cap tread 151 at the temperature condition of 20° C., tan δ_cap of the cap tread 151 at the temperature condition of 60° C., and tan δ_ut of the undertread 152 at the temperature condition of 60° C. are different from one another.
As a result of the performance tests using these tires 1, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-065492 | Apr 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/010998 | 3/11/2022 | WO |
