JP2022153347A - tire - Google Patents

Abstract

To provide a small-diameter tire capable of having both low rolling resistance and wear resistance.SOLUTION: An outer diameter OD [mm] of a tire 1 is in a range of 200≤OD≤660 and a tire total width SW [mm] thereof is in the range of 100≤SW≤400. Besides, a belt layer 14 is prepared by laminating a pair of cross belts 141, 142 having a code different from each other and having a cord angle of 15 [deg] or more but 55 [deg] or less to a tire circumferential direction, and an additional belt 145 having the cord angle of 15 [deg] or more but 80 [deg] or less to the tire circumferential direction. Besides, a mightiness Tbt [N/50 mm] per 50 [mm] width of each of the pair of cross belts 141, 142 and additional belt 145 is in the range of 25≤Tbt/OD≤250 to the tire outer diameter OD [mm].SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a tire, and more particularly to a small-diameter tire capable of achieving both low rolling resistance performance and wear resistance performance.

In recent years, small-diameter tires have been developed to be mounted on vehicles with a lowered floor and an expanded interior space. Such a small-diameter tire is expected to reduce transportation costs because it has a small rotational inertia and a small tire weight. On the other hand, small-diameter tires are required to have a high load capacity. As a conventional tire related to such problems, the technique described in Patent Document 1 is known.

WO2020/122169

An object of the present invention is to provide a small-diameter tire capable of achieving both low rolling resistance performance and wear resistance performance.

In order to achieve the above object, a tire according to the present invention includes a pair of bead cores, a carcass layer spanning the bead cores, and a belt layer disposed radially outside the carcass layer. , the tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660, the total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400, and the belt layers have opposite signs and the tire A pair of cross belts having a cord angle of 15 [deg] or more and 55 [deg] or less with respect to the circumferential direction, and an additional belt having a cord angle of 15 [deg] or more and 80 [deg] or less with respect to the tire circumferential direction. and the strength Tbt [N / 50 mm] per width 50 [mm] of each of the pair of cross belts and the additional belt is 25 ≤ Tbt / with respect to the tire outer diameter OD [mm] It is characterized by being in the range of OD≦250.

The tire according to the present invention has the advantage that the load capacity of each of the pair of cross belts and the additional belts is appropriately ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the belt ply.

FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention taken along the tire meridian line. FIG. 2 is an enlarged view showing the tire shown in FIG. FIG. 3 is an explanatory diagram showing the lamination structure of the belt layers of the tire shown in FIG. 4 is an enlarged view showing the tread portion of the tire shown in FIG. 1. FIG. FIG. 5 is an enlarged view showing one side area of the tread shown in FIG. FIG. 6 is an enlarged view showing a side fall portion and a bead portion of the tire shown in FIG. 1; FIG. 7 is an enlarged view showing the sidewall portion shown in FIG. FIG. 8 is an explanatory diagram showing the laminated structure of the carcass layer and belt layer of the tire shown in FIG. FIG. 9 is an explanatory diagram showing Modification 1 of the tire shown in FIG. FIG. 10 is an explanatory diagram showing Modification 2 of the tire shown in FIG. FIG. 11 is a chart showing the results of performance tests of the tire according to the embodiment of the invention. FIG. 12 is a chart showing the results of performance tests of the tire according to the embodiment of the invention. FIG. 13 is a chart showing the results of performance tests of the tire according to the embodiment of the invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious to replace. Moreover, the multiple modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[tire]
FIG. 1 is a cross-sectional view of a tire 1 according to an embodiment of the invention taken along the tire meridian line. This figure shows a cross-sectional view of one side area in the tire radial direction of the tire 1 mounted on the rim 10 . In this embodiment, a pneumatic radial tire for a passenger car will be described as an example of a tire.

In the figure, the cross section in the tire meridian direction is defined as a cross section when the tire is cut along a plane including the tire rotation axis (not shown). Also, the tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis. Point T is the tire contact edge, and point Ac is the tire maximum width position.

The tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, a pair of rim cushion rubbers 17, 17, and an inner liner 18 (see FIG. 1).

A pair of bead cores 11, 11 are formed by winding one or a plurality of steel bead wires in a ring-shaped manner, and are embedded in the bead portions to constitute the cores of the left and right bead portions. The pair of bead fillers 12, 12 are arranged on the tire radial direction outer peripheries of the pair of bead cores 11, 11, respectively, to reinforce the bead portions.

The carcass layer 13 has a multi-layered structure formed by laminating two carcass plies 13A and 13B, and is toroidally spanned between the left and right bead cores 11 and 11 to constitute the frame of the tire. Further, both ends of the carcass layer 13 are wound back outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12 and are locked. The carcass plies 13A and 13B of the carcass layer 13 are formed by coating a plurality of carcass cords made of an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coating rubber and rolling them. ] or more and 100 [deg] or less (defined as the inclination angle of the longitudinal direction of the carcass cords with respect to the tire circumferential direction). In addition, the carcass layer 13 may be composed of a single-layer carcass ply (not shown). Further, the carcass plies 13A and 13B may be configured by coating a plurality of carcass cords made of steel with a coating rubber and rolling the coated rubber.

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144 and is placed around the outer circumference of the carcass layer 13 . 1, the belt plies 141-144 are composed of a pair of cross belts 141, 142, a belt cover 143, a pair of belt edge covers 144, 144, and an additional belt 145. In FIG.

The pair of cross belts 141 and 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with coat rubber and rolling the cords. , θ42 (see FIG. 3 described later. Defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction). The pair of cross belts 141 and 142 have cord angles with opposite signs, and are laminated with the longitudinal directions of the belt cords intersecting each other (so-called cross-ply structure). Also, the pair of cross belts 141 and 142 are laminated on the outer side of the carcass layer 13 in the tire radial direction.

The belt cover 143 and the pair of belt edge covers 144, 144 are configured by coating a belt cover cord made of steel or an organic fiber material with a coat rubber, and the absolute value of the cord angle θ43 is 0 [deg] or more and 10 [deg] or less. , θ44 (see FIG. 3 described later). The belt cover 143 and the belt edge cover 144 are, for example, strip materials made by coating one or more belt cover cords with a coating rubber. It is configured by spirally winding a plurality of times in the tire circumferential direction. A belt cover 143 is arranged to cover the entire area of the cross belts 141 and 142, and a pair of belt edge covers 144 and 144 are arranged to cover the left and right edge portions of the cross belts 141 and 142 from outside in the tire radial direction.

The additional belt 145 is, for example, (1) a third cross belt, which is constructed by coating a plurality of belt cords made of steel or an organic fiber material with a coat rubber and rolling the cords, and has an absolute value of 15 [deg]. It has a cord angle θ45 (see FIG. 3 described later) of 80 [deg] or less, or (2) is a so-called high-angle belt, in which a plurality of belt cords made of steel or organic fiber material are coated with coated rubber. It is formed by rolling and has a chord angle θ45 (see FIG. 9 described later) of 45 [deg] to 70 [deg] in absolute value, preferably 54 [deg] to 68 [deg]. Further, the additional belt 145 is (a) between the inner diameter side cross belt 141 and the carcass layer 13 (see FIG. 1 and FIG. 3 described later), (b) between the pair of cross belts 141 and 142 (not shown), Alternatively, (c) it is arranged radially outside the pair of cross belts 141 and 142 (see FIG. 9 described later). In these configurations, the additional belt 145 suppresses the growth of the outer diameter of the tire, improving the load capacity of the tire.

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to constitute the tread portion of the tire 1 . Also, the tread rubber 15 includes a cap tread 151 and an undertread 152 .

The cap tread 151 is made of a rubber material having excellent grounding properties and weather resistance, and is exposed on the tread surface over the entire tire ground contact surface to constitute the outer surface of the tread portion. In addition, 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 of 0.03 or more and 0.36 or less. tan δ_cap, preferably rubber hardness Hs_cap of 58 or more and 76 or less, modulus M_cap [MPa] at 100 [%] elongation of 1.5 or more and 3.2 or less and loss tangent of 0.06 or more and 0.29 or less tan δ_cap.

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

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

The loss tangent tan δ is measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of temperature 60 [° C.], shear strain 10 [%], amplitude ±0.5 [%] and frequency 20 [Hz]. Measured in

The undertread 152 is made of a rubber material having excellent heat resistance, and is sandwiched between the cap tread 151 and the belt layer 14 to constitute the base portion of the tread rubber 15 . In addition, 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 of 0.02 or more and 0.23 or less. tan δ_ut, preferably rubber hardness Hs_ut of 50 or more and 65 or less, modulus M_ut [MPa] at 100 [%] elongation of 1.7 or more and 3.5 or less and loss tangent of 0.03 or more and 0.10 or less tan δ_ut.

Further, the rubber hardness difference 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. Also, the modulus difference M_cap−M_ut [MPa] is in the range of 0 to 1.4, preferably in the range of 0.1 to 1.0. In addition, the loss tangent difference tan δ_cap−tan δ_ut is in the range of 0 or more and 0.22 or less, preferably 0.02 or more and 0.16 or less.

A pair of sidewall rubbers 16, 16 are arranged outside the carcass layer 13 in the tire width direction, respectively, and constitute left and right sidewall portions. In the configuration of FIG. 1 , the tire radially outer end of the sidewall rubber 16 is disposed under the tread rubber 15 and sandwiched between the end of the belt layer 14 and the carcass layer 13 . However, the present invention is not limited to this, and the radially outer end of the sidewall rubber 16 may be disposed on the outer layer of the tread rubber 15 and exposed to the buttress portion of the tire (not shown). In this case, a belt cushion (not shown) is sandwiched between the end of the belt layer 14 and the carcass layer 13 .

In addition, 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 of 0.02 or more and 0.22 or less. Has a tangent tan δ_sw, preferably a rubber hardness Hs_sw of 50 or more and 59 or less, a modulus M_sw [MPa] at 100 [%] elongation of 1.2 or more and 2.2 or less, and a loss of 0.04 or more and 0.20 or less has the tangent tan δ_sw.

The pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction to the outer side in the tire width direction of the turn-up portions of the left and right bead cores 11, 11 and the carcass layer 13, and constitute rim fitting surfaces of the bead portions. In the configuration of FIG. 1 , the radially outer end of the rim cushion rubber 17 is inserted into the lower layer of the sidewall rubber 16 and sandwiched between the sidewall rubber 16 and the carcass layer 13 . .

The inner liner 18 is an air permeation prevention layer that is placed on the inner cavity surface of the tire and covers the carcass layer 13, suppresses oxidation due to exposure of the carcass layer 13, and prevents leakage of air filled in the tire. The inner liner 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 obtained by blending an elastomer component into a thermoplastic resin. Also good.

Further, in FIG. 1, the tire outer diameter OD [mm] is in the range of 200≦OD≦660, preferably in the range of 250 [mm]≦OD≦580 [mm]. By applying such a small-diameter tire, the effect of improving load performance, which will be described later, is significantly obtained. Further, the total tire width SW [mm] is in the range of 100≤SW≤400, preferably in the range of 105 [mm]≤SW≤340 [mm]. With such a small-diameter tire 1, for example, the floor of a compact vehicle can be lowered to expand the interior space of the vehicle. In addition, since the rotational inertia is small and the tire weight is also small, the fuel efficiency is improved and the transportation cost is reduced. In particular, when mounted on an in-wheel motor of a vehicle, the load on the motor is effectively reduced.

The tire outer diameter OD is measured by mounting the tire on a specified rim, applying a specified internal pressure, and under no load condition.

The total tire width SW is measured as the linear distance between the sidewalls (including all parts such as patterns and letters on the tire side) when the tire is mounted on the specified rim, the specified internal pressure is applied, and the tire is in an unloaded state. be done.

The stipulated rim means the "applied rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. In addition, the prescribed internal pressure means the "maximum air pressure" prescribed by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" prescribed by TRA, or "INFLATION PRESSURES" prescribed by ETRTO. Moreover, the specified load means the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. However, according to JATMA, in the case of passenger car tires, the specified internal pressure is 180 [kPa] and the specified load is 88 [%] of the maximum load capacity.

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

Moreover, it is preferable that the tire outer diameter OD and the total tire width SW satisfy the following formula (1). Here, 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.

In the tire 1 described above, use of a rim 10 having a rim diameter of 5 [inch] or more and 16 [inch] or less (that is, 125 [mm] or more and 407 [mm] or less) is assumed. In addition, the rim diameter RD [mm] is in the range of 0.50 ≤ RD/OD ≤ 0.74 with respect to the tire outer diameter OD [mm], preferably 0.52 ≤ RD/OD ≤ 0.71. in the range. With the above lower limit, the rim diameter RD can be secured, and in particular, the installation space for the in-wheel motor can be secured. Due to the above upper limit, the internal volume V of the tire, which will be described later, is ensured, and the load capacity of the tire is ensured.

Note that the tire inner diameter is equal to the rim diameter RD of the rim 10 .

Further, the tire 1 is assumed to be used at an internal pressure higher than the regulation, specifically 350 [kPa] or more and 1200 [kPa] or less, preferably 500 [kPa] or more and 1000 [kPa] or less. The above lower limit effectively reduces the rolling resistance of the tire, and the above upper limit ensures the safety of the internal pressure filling operation.

Further, it is assumed that the tire 1 is mounted on a vehicle that runs at low speed, such as a small shuttle bus. Also, the maximum speed of the vehicle is 100 [km/h] or less, preferably 80 [km/h] or less, more preferably 60 [km/h] or less. Further, it is assumed that the tire 1 is mounted on a vehicle with 6 to 12 wheels. As a result, the load capacity of the tire is properly exhibited.

In addition, the aspect ratio of the tire, that is, the tire section height SH [mm] (see FIG. 2 described later) and the tire section width [mm] (dimension symbols omitted in the figure: the same as the total tire width SW in FIG. 1) is in the range of 0.16 or more and 0.85 or less, preferably 0.19 or more and 0.82 or less.

The tire cross-section height SH is half the difference between the tire outer diameter and the rim diameter, and is measured in a non-loaded state with the tire mounted on a specified rim and given a specified internal pressure.

The tire cross-sectional width is measured as the linear distance between the sidewalls (excluding patterns, letters, etc. on the tire side surface) when the tire is mounted on a specified rim, given a specified internal pressure, and in an unloaded state.

Further, the tire contact width TW is in the range of 0.65≦TW/SW≦0.95, preferably in the range of 0.80≦TW/SW≦0.92 with respect to the total tire width SW.

The tire contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim, the specified internal pressure is applied, the tire is placed perpendicular to the flat plate in the stationary state, and the load corresponding to the specified load is applied. measured as the maximum linear distance in the axial direction of the tire.

In addition, the tire internal volume V [m̂3] is in the range of 4.0≦(V/OD)×10̂6≦60 with respect to the tire outer diameter OD [mm], preferably 6.0≦( V/OD)×10̂6≦50. As a result, the tire internal volume V is optimized. Specifically, the above lower limit secures the internal volume of the tire, thereby securing the load capacity of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so it is preferable to ensure a sufficient tire internal volume V. Due to the above upper limit, an increase in tire size due to an excessive increase in the tire internal volume V is suppressed.

In addition, the tire internal volume V [m^3] is in the range of 0.5 ≤ V x RD ≤ 17, preferably 1.0 ≤ V x RD ≤ 15 with respect to the rim diameter RD [mm]. be.

[Bead core]
In FIG. 1, as described above, a pair of bead cores 11, 11 are formed by winding one or more bead wires (not shown) made of steel in a circular and multiple manner. A pair of bead fillers 12, 12 are arranged on the tire radial direction outer circumferences of the pair of bead cores 11, 11, respectively.

Further, the strength Tbd [N] of one bead core 11 is in the range of 45 ≤ Tbd/OD ≤ 120, preferably 50 ≤ Tbd/OD ≤ 110 with respect to the tire outer diameter OD [mm], More preferably, it is in the range of 60≤Tbd/OD≤105. Further, the strength Tbd [N] of the bead core is in the range of 90≤Tbd/SW≤400, preferably in the range of 110≤Tbd/SW≤350 with respect to the total tire width SW [mm]. Thereby, the load capacity of the bead core 11 is properly ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. In addition, the tire can be used at high internal pressure, and the rolling resistance of the tire is reduced. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the wear resistance performance and rolling resistance of the tires described above can be significantly reduced. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the bead core.

The strength Tbd [N] of the bead core 11 is calculated as the product of the strength per bead wire [N/wire] and the total number of bead wires [wire] in a radial cross-sectional view. The strength of the bead wire is measured by a tensile test at a temperature of 20[°C] according to JIS K1017.

Further, it is preferable that the strength Tbd [N] of the bead core 11 satisfies the following formula (2) with respect to the tire outer diameter OD [mm], the distance SWD [mm], and the rim diameter RD [mm]. where 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, more preferably B1min=0.49, B2min=17.9 , B1max=2.5 and B2max=99.0. Furthermore, it is preferable that B1min=0.0016×P and B2min=0.07×P using the specified internal pressure P [kPa] of the tire.

The distance SWD is twice the radial distance from the tire rotation axis (not shown) to the tire maximum width position Ac, that is, the diameter of the tire maximum width position Ac. applied and measured as unloaded.

The tire maximum width position Ac is defined as the maximum width position of the tire cross-sectional width defined by JATMA.

In addition, in a radial cross-sectional view of one bead core 11, the total cross-sectional area σbd [mm^2] of the steel bead wires described above is 0.025 ≤ σbd/OD ≤ 0.025 ≤ σbd/OD ≤ It is in the range of 0.075, preferably in the range of 0.030≤σbd/OD≤0.065. Also, the total cross-sectional area σbd [mm̂2] of the bead wires is in the range of 11≦σbd≦36, preferably in the range of 13≦σbd≦33. Thereby, the strong Tbd [N] of the bead core 11 described above is realized.

The total cross-sectional area σbd [mm̂2] of the bead wires is calculated as the sum of the cross-sectional areas of the bead wires in a radial cross-sectional view of one bead core 11 .

For example, in the configuration of FIG. 1, the bead core 11 has a square shape formed by arranging bead wires (not shown) having a circular cross section in a grid pattern. However, this is not the only option, and the bead core 11 may have a hexagonal shape formed by arranging bead wires having circular cross sections in a close-packed structure (not shown). In addition, any bead wire arrangement structure can be adopted within the scope obvious to those skilled in the art.

Moreover, it is preferable that the total cross-sectional area σbd [mm^2] of the bead wires satisfies the following 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, preferably Cmin=25 and Cmax=10.

Further, the total cross-sectional area σbd [mm^2] of the bead wires is 0.50≦σbd/Nbd with respect to the total number of cross-sections (that is, the total number of turns) Nbd [number] of the bead wires of one bead core 11 in a radial cross-sectional view. ≤1.40, preferably 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 0.60 [mm^2/wire] or more. mm^2/line] to 1.20 [mm^2/line] or less.

Further, the maximum width Wbd [mm] (see FIG. 2 described later) of one bead core 11 in a radial cross-sectional view is 0.16≦Wbd/σbd≦0 with respect to the total cross-sectional area σbd [mm^2] of the bead wires. 0.50, preferably 0.20≦Wbd/σbd≦0.40.

Further, in FIG. 1, the distance Dbd [mm] between the centers of gravity of the pair of bead cores 11, 11 is preferably in the range of 0.63≦Dbd/SW≦0.97 with respect to the total tire width SW [mm]. is in the range of 0.65≤Dbd/SW≤0.95. Due to the above lower limit, the deflection amount of the tire is reduced, and the rolling resistance of the tire is reduced. Due to the above upper limit, the stress acting on the tire side portion is reduced, and tire failure is suppressed.

[Carcass layer]
FIG. 2 is an enlarged view showing the tire 1 shown in FIG. The figure shows a one-side region bounded by the tire equatorial plane CL.

In the configuration of FIG. 1, as described above, the carcass layer 13 is composed of the two laminated carcass plies 13A and 13B, and is arranged toroidally span between the left and right bead cores 11 and 11. Further, both ends of the carcass layer 13 are wound back outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12 and are locked.

Further, the strength Tcs [N/50 mm] per width 50 [mm] of each of the carcass plies 13A and 13B constituting the carcass layer 13 is 17 ≤ Tcs/OD ≤ 120 with respect to the tire outer diameter OD [mm]. range, preferably 20≤Tcs/OD≤60. Further, the strength Tcs [N/50 mm] of the carcass layer 13 is in the range of 30 ≤ Tcs/SW ≤ 260, preferably 35 ≤ Tcs/SW ≤ 180 with respect to the total tire width SW [mm]. . Thereby, the load capacity of the carcass layer 13 is properly ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. In addition, the tire can be used at high internal pressure, and the rolling resistance of the tire is reduced. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the wear resistance performance and rolling resistance of the tires described above can be significantly reduced. The above upper limit suppresses deterioration of rolling resistance due to an increase in mass of the carcass layer.

The carcass ply strength Tcs [N/50 mm] is calculated as follows. That is, the carcass plies 13A, 13B that span the left and right bead cores 11, 11 and extend over the entire inner circumference of the tire are defined as effective carcass plies. Then, the strength [N / cord] per carcass cord constituting the effective carcass plies 13A, 13B and the number of carcass cords driven per tire perimeter and width 50 [mm] on the tire equatorial plane CL [ / 50 mm ] is calculated as the strength Tcs [N/50 mm] of the carcass ply. The strength of a carcass cord is measured by a tensile test at a temperature of 20[°C] according to JIS K1017. For example, in a configuration in which one carcass cord is formed by twisting a plurality of strands, the strength of one twisted carcass cord is measured to calculate the strength Tcs of the carcass layer 13 . In addition, as shown in FIG. 1, in a configuration in which the carcass layer 13 has a multilayer structure in which a plurality of effective carcass plies 13A and 13B are laminated, the above-described strength Tcs is defined for each of the plurality of effective carcass plies 13A and 13B. be.

For example, in the configuration of FIG. 1, the carcass layer 13 has a multi-layered structure consisting of two layers of carcass plies 13A and 13B, and the carcass plies 13A and 13B are coated with an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) (not shown). In this case, the carcass cords made of the organic fiber material have a cord diameter φcs [mm] in the range of 0.6 ≤ φcs ≤ 0.9 and the number of stranded cords Ecs [cords/string] in the range of 40 ≤ Ecs ≤ 70. 50 mm], the above-described strong Tcs [N/50 mm] of the carcass layer 13 is realized. In addition, a carcass cord made by twisting a plurality of types of organic fiber materials such as nylon and aramid can be used within the scope obvious to those skilled in the art.

Further, not limited to the above, for example, the single-layer carcass ply is arranged at a cord angle of 80 [deg] or more and 100 [deg] or less with respect to the tire circumferential direction. (not shown). Further, the carcass cord made of steel has a cord diameter φcs [mm] in the range of 0.3 ≤ φcs ≤ 1.1 and the number of driven cords Ecs [cord/50 mm] in the range of 25 ≤ Ecs ≤ 80. Thereby, the above-described strong Tcs [N/50 mm] of the carcass layer 13 is realized. Further, the carcass cord is formed by twisting a plurality of strands, and the strand diameter φcss [mm] is in the range of 0.12≦φcss≦0.24, preferably 0.14≦φcss≦0.24. 22 range.

Further, the total strength TTcs [N/50 mm] of the carcass layer 13 is in the range of 300 ≤ TTcs/OD ≤ 1900, preferably 400 ≤ TTcs/OD ≤ 1000 with respect to the tire outer diameter OD [mm]. be. This ensures the overall load capacity of the carcass layer 13 .

The total strength TTcs [N/50mm] of the carcass layer 13 is calculated as the sum of the strengths Tcs [N/50mm] of the above effective carcass plies. Therefore, the total strength TTcs [N/50 mm] of the carcass layer 13 increases as the strength Tcs [N/50 mm] of each carcass ply, the number of laminated carcass plies, the perimeter of the carcass ply, and the like increase.

Further, it is preferable that the total strength TTcs [N/50 mm] of the carcass layer 13 satisfies the following 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 Dmin = 6.5 and Dmax = 40, still more preferably Dmin = 8 .7 and Dmax=40. Furthermore, it is preferable that Dmin=0.02×P using the specified internal pressure P [kPa] of the tire.

In the configuration of FIG. 1, as shown in FIG. 2, the carcass layer 13 includes a body portion 131 extending along the inner surface of the tire, and the carcass layer 13 is wound outward in the tire width direction so as to wrap around the bead core 11, thereby increasing the tire diameter. and a winding portion 132 extending in a direction. Further, in FIG. 2, the radial height Hcs [mm] from the measurement point of the rim diameter RD to the end of the wound portion 132 of the carcass layer 13 is 0.49≦0.49 with respect to the tire section height SH [mm]. Hcs/SH≤0.80, preferably 0.55≤Hcs/SH≤0.75. Thereby, the radial height Hcs of the wound-up portion 132 of the carcass layer 13 is optimized. Specifically, the above lower limit secures the load capacity of the tire side portion, and the above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the carcass layer.

The radial height Hcs [mm] of the wound-up portion 132 of the carcass layer 13 is measured in a non-loaded state with the tire mounted on a specified rim and given a specified internal pressure. In addition, as shown in FIG. 2, in a configuration in which the carcass layer 13 is composed of two carcass plies 13A and 13B, the larger radial height Hcs [mm] is adopted.

For example, in the configuration of FIG. 2 , both of the two carcass plies 13A and 13B are wound outward in the tire width direction so as to wrap the bead core 11 . Further, the wound-up portion 132 of the carcass ply 13A on the inner diameter side covers the radially outer end (reference numerals omitted in the figure) of the wound-up portion 132 of the carcass ply 13B on the outer diameter side from the outside in the tire width direction. In addition, the radially outer end of the winding portion 132 of the carcass ply 13A on the inner diameter side (the reference numerals are omitted in the drawing) is located between the tire maximum width position Ac and the end of the belt layer 14 (point Au, which will be described later). More specifically, from the maximum tire width position Ac to a radial position Au' at 70% of the distance Hu, which will be described later, is within the region. At this time, the contact height Hcs′ [mm] between the body portion 131 and the winding 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], It is preferably in the range of 0.15≤Hcs'/SH. This effectively increases the load capacity of the tire side portion. Although the upper limit of the ratio Hcs'/SH is not particularly limited, it is restricted by having a relationship of Hcs'<Hcs between the contact height Hcs' and the radial height Hcs of the wound-up portion 132 of the carcass layer 13. .

The contact height Hcs′ of the carcass layer 13 is the extension length in the tire radial direction of the region where the body portion 131 and the winding portion 132 contact each other, and the tire is mounted on a specified rim to apply a specified internal pressure. is measured as a no-load condition.

Note that the carcass layer 13 may have a so-called low turn-up structure, so that the ends of the wound-up portions 132 of the carcass layer 13 may be arranged in a region between the tire maximum width position Ac and the bead core. (illustration omitted).

[Belt layer]
FIG. 3 is an explanatory diagram showing the lamination structure of the belt layers of the tire 1 shown in FIG. In the figure, thin lines attached to the belt plies 141 to 145 schematically show the arrangement of the belt cords.

In the configuration of FIG. 1, the belt layer 14 is formed by laminating a plurality of belt plies 141 to 145 as described above. 3, these belt plies 141 to 145 are composed of a pair of cross belts 141, 142, a belt cover 143, a pair of belt edge covers 144, 144, and an additional belt 145. As shown in FIG.

At this time, the strength Tbt [N/50 mm] per width 50 [mm] of each of the pair of cross belts 141 and 142 and the additional belt 145 is 25 ≤ Tbt/OD ≤ 250 with respect to the tire outer diameter OD [mm]. and preferably 30≤Tbt/OD≤180. Further, the strength Tbt [N/50mm] of the cross belts 141, 142 and the additional belt 145 is in the range of 45 ≤ Tbt/SW ≤ 500, preferably 50 ≤ Tbt/SW with respect to the total tire width SW [mm]. ≦300. Thereby, the respective load capacities of the pair of cross belts 141 and 142 and the additional belt 145 are appropriately ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. In addition, the tire can be used at high internal pressure, and the rolling resistance of the tire is reduced. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the wear resistance performance and rolling resistance of the tires described above can be significantly reduced. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the belt ply.

The belt ply strength Tbt [N/50 mm] is calculated as follows. That is, the effective belt ply is defined as the belt ply that extends over the entire area of 80% of the tire contact width TW centered on the tire equatorial plane CL (that is, the central portion of the tire contact area). Then, the strength [N / cord] per belt cord constituting the effective belt ply and the number of belt cords driven in per width 50 [mm] in the area of 80 [%] of the tire contact width TW [number] is calculated as the belt ply strength Tbt [N/50 mm]. The strength of the belt cord is measured by a tensile test at a temperature of 20[°C] according to JIS K1017. For example, in a configuration in which a single belt cord is formed by twisting a plurality of strands, the strength of the single twisted belt cord is measured to calculate the strength Tbt of the belt ply. In addition, in a configuration in which the belt layer 14 is formed by laminating a plurality of effective carcass plies (see FIG. 1), the strength Tbt described above is defined for each of the plurality of effective carcass plies. For example, in the configuration of FIG. 1, the pair of cross belts 141, 142, belt cover 143 and additional belt 145 correspond to effective belt plies.

For example, in the configuration of FIG. 3, the pair of cross belts 141 and 142 and the additional belt 145 are made of steel belt cords covered with a coat rubber and are 15[deg] or more and 80[deg] or less with respect to the tire circumferential direction. They are arranged at angles θ41, θ42, and θ45. In addition, the steel belt cord has a cord diameter φbt [mm] in the range of 0.50 ≤ φbt ≤ 1.80 and the number of strands Ebt [string/50 mm] in the range of 15 ≤ Ebt ≤ 60. Thus, the strength Tbt [N/50 mm] of the cross belts 141 and 142 and the additional belt 145 is realized. Also, the cord diameter φbt [mm] and the number of wires Ebt [wires/50 mm] are preferably in the ranges of 0.55≦φbt≦1.60 and 17≦Ebt≦50, and 0.60≦φbt≦1. It is more preferably in the range of 30 and 20≤Ebt≤40. Further, the belt cord is formed by twisting a plurality of strands, and the strand diameter φbts [mm] is in the range of 0.16≦φbts≦0.43, preferably 0.21≦φbts≦0.21≦φbts≦0.43. 39 range.

In addition, the cross belts 141, 142 and the additional belt 145 may be composed of belt cords made of organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) coated with coat rubber. In this case, the belt cord made of the organic fiber material has a cord diameter φbt [mm] in the range of 0.50≤φbt≤0.90 and the number of strands Ebt [string/string] in the range of 30≤Ebt≤65. 50 mm], the strength Tbt [N/50 mm] of the cross belts 141 and 142 and the additional belt 145 described above is realized. Further, belt cords made by twisting a plurality of types of organic fiber materials such as nylon and aramid, for example, can be employed within the scope obvious to those skilled in the art.

Further, the total strength TTbt [N/50 mm] of the belt layer 14 is in the range of 70 ≤ TTbt/OD ≤ 750, preferably 110 ≤ TTbt/OD ≤ 690 with respect to the tire outer diameter OD [mm]. more preferably in the range of 150≤TTbt/OD≤600, more preferably in the range of 170≤TTbt/OD≤560. Thereby, the load capacity of the entire belt layer 14 is ensured. Furthermore, it is preferable that 0.16×P≦TTbt/OD using the specified internal pressure P [kPa] of the tire.

The total strength TTbt [N/50 mm] of the belt layer 14 is the total strength Tbt [N/50 mm] of the above-described effective belt plies (the pair of cross belts 141 and 142, the belt cover 143 and the additional belt 145 in FIG. 1). Calculated. Therefore, the total strength TTbt [N/50 mm] of the belt layer 14 increases as the strength Tbt [N/50 mm] of each belt ply and the number of laminated belt plies increase.

3, the strength Tbt_min [N/50 mm] of the narrowest belt ply (the outer diameter side cross belt 142 in FIG. 3) of the pair of cross belts 141 and 142 and the additional belt 145 is 0.10 ≤ Tbt_min/TTbt ≤ 0.40, preferably 0.12 ≤ Tbt_min/TTbt ≤ 0.35, with respect to the total strength TTbt [N/50mm]. The above lower limit ensures that the additional belt 145 suppresses the growth of the outer diameter of the tire, and the above upper limit ensures that the other belt plies improve belt durability.

3, the width Wbmax [mm] of the widest belt ply among the pair of cross belts 141 and 142 and the additional belt 145 (in FIG. 3, the width Wb1 [mm] of the cross belt 141 on the inner diameter side or the additional belt 145 width Wb5 [mm]) is 1.00≦Wbmax/ with respect to the width Wbmin [mm] of the narrowest belt ply (in FIG. 3, the width Wb2 [mm] of the cross belt 142 on the outer diameter side). Wbmin≤1.40, preferably 1.10≤Wbmax/Wbmin≤1.35. In addition, the width Wbmax [mm] of the widest belt ply is the width Wbmid [mm] of the second widest belt ply (in FIG. 3, the width Wb5 [mm] of the additional belt 145 or the width of the inner cross belt 141 Wb1 [mm]) is in the range of 1.00≦Wbmax/Wbmid≦1.30. Further, the width Wbmin [mm] of the narrowest belt ply (in FIG. 3, the width Wb2 [mm] of the cross belt 142 on the outer diameter side) is 0.61≦Wbmin with respect to the total tire width SW [mm]. /SW≤0.96, preferably 0.70≤Wbmin/SW≤0.94. As a result, there is an advantage that the relationship among the widths Wb1, Wb2, Wb5 of the belt plies 141, 142, 145 is optimized. Specifically, the above lower limit secures the width of the belt ply, optimizes the ground contact pressure distribution in the tire contact area, and secures the uneven wear resistance of the tire. Due to the above upper limit, distortion of the end of the belt ply when the tire rolls is reduced, and separation of the peripheral rubber at the end of the belt ply is suppressed.

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 rotation axis, and is measured with the tire mounted on a specified rim, a specified internal pressure applied, and no load applied.

Further, it is preferable that the width Wbmax [mm] of the widest belt ply satisfies the following formula (5) with respect to the width Wbmin [mm] of the narrowest belt ply and the total tire width SW [mm]. Here Umin=10 and Umax=30, preferably Umin=11 and Umax=28.

Further, it is preferable that the width Wbmax [mm] of the widest belt ply satisfies the following formula (6) with respect to the width Wbmid [mm] of the second widest belt ply and the total tire width SW [mm]. Here, Vmin=10.0 and Vmax=26.0, preferably Vmin=10.5 and Umax=25.0, more preferably Vmin=10.5 and Umax=24.0.

Further, the width Wbmax [mm] of the widest belt ply among the pair of cross belts 141 and 142 and the additional belt 145 (in FIG. 3, the width Wb1 [mm] of the cross belt 141 on the inner diameter side or the width Wb5 [mm]) is in the range of 0.85≤Wbmax/TW≤1.23, preferably in the range of 0.90≤Wbmax/TW≤1.20 with respect to the tire contact width TW [mm].

For example, in the configuration shown in FIGS. 1 to 3, the wide cross belt 141 is arranged in the innermost layer in the tire radial direction, and the narrow cross belt 142 is arranged radially outside the wide cross belt 141 . Further, the additional belt 145 is a third cross belt having a cord angle of 15 [deg] or more and 80 [deg] or less. It has a cord angle of opposite sign to the cord angle of the belt 142 . A belt cover 143 is arranged radially outward of the additional belt 145 and covers the pair of cross belts 141 and 142 and the additional belt 145 as a whole. A pair of belt edge covers 144, 144 are arranged radially outside the belt cover 143 while being spaced apart from each other, and cover the left and right edge portions of the pair of cross belts 141, 142 and the additional belt 145, respectively. .

[Tread profile and tread gauge]
FIG. 4 is an enlarged view showing the tread portion of the tire 1 shown in FIG.

In FIG. 4, the tread profile drop amount DA [mm] at the tire contact edge T, the tire contact width TW [mm], and the tire outer diameter OD [mm] are 0.015≦TW/(DA×OD)≦0.015. 400, preferably 0.020≦TW/(DA×OD)≦0.250. Further, the tread profile drop amount DA [mm] at the tire contact edge T has a relationship of 0.008≦DA/TW≦0.090 with respect to the tire contact width TW [mm], preferably 0.013. It has a relationship of ≦DA/TW≦0.080. As a result, the sagging angle (defined by the ratio DA/(TW/2)) of the tread shoulder region is optimized, and the load capacity of the tread is properly ensured. Specifically, the above lower limit secures the sagging angle of the tread shoulder region, thereby suppressing a reduction in wear life due to excessive contact pressure in the tread shoulder region. Due to the above upper limit, the tire contact area becomes flat and the contact pressure is made uniform, thereby ensuring the wear resistance performance of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the configuration described above can effectively optimize the contact pressure distribution in the tire contact area. Further, by reinforcing the carcass strength Tcs of the carcass layer 13 and the belt strength Tbt of the belt layer 14 as described above, the ground contact pressure is prevented from becoming excessively large. On the other hand, since the tire has a round-shaped shoulder portion, heat generation in the tread portion due to rolling of the tire is suppressed, which improves durability of the tire. Rolling resistance performance is improved.

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 a cross-sectional view in the tire meridian direction to the tire contact edge T, and the tire is mounted on a specified rim and given a specified internal pressure. and measured as no-load condition.

The tire profile is the contour line of the tire in cross section along the tire meridian and is measured using a laser profiler. As the laser profiler, for example, a tire profile measuring device (manufactured by Matsuo Co., Ltd.) is used.

Further, it is preferable that the sagging amount DA [mm] of the tread profile at the tire contact edge T satisfies the following formula (7) 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, more preferably Emin=4.0 and Emax=9.

In FIG. 4, a point C1 on the tread profile at the tire equatorial plane CL and a pair of points C2, C2 on the tread profile at a distance of 1/4 of the tire contact width TW from the tire equatorial plane CL are defined.

At this time, the radius of curvature TRc [mm] of the arc passing through the point C1 and the pair of points C2 is in the range of 0.15≦TRc/OD≦12, preferably 0.15 ≤ TRc/OD ≤ 12 with respect to the tire outer diameter OD [mm]. It is in the range of 18≤TRc/OD≤8.0. Also, the radius of curvature TRc [mm] of the arc is in the range of 30≦TRc≦3000, preferably 50≦TRc≦2300, more preferably 80≦TRc≦2000. As a result, the load capacity of the tread portion is appropriately ensured. Specifically, the above lower limit flattens the center area of the tread portion, uniformizes the contact pressure of the tire contact area, and secures the wear resistance performance of the tire. The above upper limit suppresses reduction in wear life due to excessive contact pressure in the shoulder region of the tread portion. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the effect of equalizing ground contact pressure under such conditions of use can be effectively obtained.

The radius of curvature of the circular arc is measured under the condition that the tire is mounted on a specified rim, given a specified internal pressure, and in an unloaded state.

Further, in FIG. 4, the curvature radius TRw [mm] of the arc passing through the point C1 on the tire equatorial plane CL and the left and right tire ground contact edges T, T is 0.20≦0.20 with respect to the tire outer diameter OD [mm]. It is in the range of TRw/OD≦10, preferably in the range of 0.35≦TRw/OD≦8. Also, the radius of curvature TRw [mm] of the arc is in the range of 100≦TRw≦2300, preferably in the range of 150≦TRw≦2000. As a result, the load capacity of the tread portion is appropriately ensured. Specifically, at the above lower limit, the entire tire contact area becomes flat and the contact pressure is made uniform, thereby ensuring the wear resistance performance of the tire. The above upper limit suppresses reduction in wear life due to excessive contact pressure in the shoulder region of the tread portion. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the configuration described above can effectively optimize the contact pressure distribution in the tire contact area.

Further, the curvature radius TRw [mm] of the first arc passing through the points C1 and C2 is 0.55≦TRw/ It is in the range of TRc≦1.00, preferably in the range of 0.65≦TRw/TRc≦0.98, and more preferably in the range of 0.75≦TRw/TRc≦0.96. Thereby, the contact shape of the tire is optimized. Specifically, the above lower limit disperses the contact pressure in the center region of the tread portion, thereby improving the wear life of the tire. The above upper limit suppresses reduction in wear life due to excessive contact pressure in the shoulder region of the tread portion.

4, the point B1 on the carcass layer 13 on the tire equatorial plane CL and the left and right tire ground contact edges T, T to the outermost layer of the carcass layer 13 (in FIG. 4, the carcass ply 13B on the outer diameter side). Define the legs B2, B2 of the perpendicular line.

At this time, the radius of curvature CRw of the arc passing through the point B1 and the pair of points B2, B2 is 0.35≦CRw/TRw≦ relative to the radius of curvature TRw of the arc passing through the point C1 and the tire ground contact edges T, T. It is in the range of 1.45, preferably in the range of 0.40≤CRw/TRw≤1.40, more preferably in the range of 0.45≤CRw/TRw≤1.35. Also, the radius of curvature CRw [mm] is in the range of 100≦CRw≦2500, preferably in the range of 120≦CRw≦2200. As a result, the tire ground contact shape is optimized. Specifically, the above lower limit suppresses a decrease in wear life due to an increase in the rubber gauge in the shoulder region of the tread portion. The above upper limit secures the wear life of the center region of the tread portion.

FIG. 5 is an enlarged view showing one side area of the tread shown in FIG.

In the configuration of FIG. 1, belt layer 14 has a pair of cross belts 141, 142 and additional belt 145, and tread rubber 15 has cap tread 151 and undertread 152, as described above.

5, the distance Tce [mm] from the tread profile on the tire equatorial plane CL to the outer peripheral surface of the wide cross belt 141 is 0.008≦Tce/OD≦0 with respect to the tire outer diameter OD [mm]. 0.13, preferably 0.012≦Tce/OD≦0.10, more preferably 0.015≦Tce/OD≦0.07. Also, the distance Tce [mm] is in the range of 5≦Tce≦25, preferably in the range of 7≦Tce≦20. As a result, the load capacity of the tread portion is appropriately ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above-described wear resistance performance is remarkably obtained. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the tread rubber.

The distance Tce is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and in a no-load state.

The outer circumferential surface of the belt ply is defined as the overall radially outer circumferential surface of the belt ply consisting of belt cords and coat rubber.

Further, it is preferable that the distance Tce [mm] from the tread profile on the tire equatorial plane CL to the outer peripheral surface of the wide cross belt 141 satisfies the following formula (8) with respect to the tire outer diameter OD [mm]. Here, Fmin=35 and Fmax=207, preferably Fmin=42 and Fmax=202.

Further, the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer peripheral surface of the wide cross belt 141 is 0.60≦Tsh/Tce≦1.70 with respect to the distance Tce [mm] at the tire equatorial plane CL. , preferably 0.85≤Tsh/Tce≤1.55, more preferably 0.97≤Tsh/Tce≤1.50. Since the tread gauge of the shoulder region is ensured by the above lower limit, repeated deformation of the tire when the tire is rolling is suppressed, and wear resistance performance of the tire is ensured. In addition, since the tread gauge in the center region is secured by the upper limit, deformation of the tire during use under high load, which is characteristic of small-diameter tires, is suppressed, and wear resistance performance of the tire is secured.

The distance Tsh is measured under the condition that the tire is mounted on a specified rim, given a specified internal pressure, and in an unloaded state. Further, when there is no wide cross belt directly under the tire ground contact edge T, the distance Tsh is measured as the distance from the tread profile to the virtual line extending the outer peripheral surface of the belt ply.

Further, it is preferable that the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer peripheral surface of the wide cross belt 141 satisfies the following formula (9) with respect to the distance Tce [mm] at the tire equatorial plane CL. . Here, Gmin=0.36 and Gmax=0.72, preferably Gmin=0.37 and Gmax=0.71, more preferably Gmin=0.38 and Gmax=0.70.

Also, in FIG. 5, a section having a width ΔTW of 10% of the tire contact width TW is defined. At this time, the ratio between the maximum value Ta and the minimum value Tb of the rubber gauge of the tread rubber 15 in any section of the tire contact area is in the range of 0% to 40%, preferably 0%. It is in the range of 20[%] or less. With such a configuration, the amount of change in the rubber gauge of the tread rubber 15 in any section of the tire contact area (especially the section including the ends of the belt plies 141 to 144) is set small, so the contact pressure distribution in the tire width direction is smooth. As a result, the wear resistance performance of the tire is improved.

The rubber gauge of the tread rubber 15 is defined as the distance from the tread profile to the inner peripheral surface of the tread rubber 15 (the distance from the outer peripheral surface of the cap tread 151 to the inner peripheral surface of the undertread 152 in FIG. 5). Therefore, the rubber gauge of the tread rubber 15 is measured excluding the grooves formed on the tread surface.

5, the rubber gauge UTce of the undertread 152 on the tire equatorial plane CL is in the range of 0.04≦UTce/Tce≦0.60, preferably 0, with respect to the distance Tce on the tire equatorial plane CL. .06≤UTce/Tce≤0.50. Thereby, the rubber gauge UTce of the undertread 152 is optimized.

Further, the distance Tsh at the tire contact edge T described above is 1.0 mm with respect to the rubber gauge Tu [mm] from the end of the innermost layer of the belt layer 14 (wide cross belt 141 in FIG. 5) to the outer peripheral surface of the carcass layer 13 . It is in the range of 50≤Tsh/Tu≤30.0, preferably in the range of 2.00≤Tsh/Tu≤6.70. As a result, the profile of the carcass layer 13 is optimized and the tension of the carcass layer 13 is optimized. Specifically, since the tension of the carcass layer and the tread gauge of the shoulder region are ensured by the above lower limit, repeated deformation of the tire when the tire is rolling is suppressed, and the wear resistance performance of the tire is ensured. The above upper limit secures a rubber gauge near the ends of the belt ply, thereby suppressing separation of the peripheral rubber of the belt ply.

The rubber gauge Tu is substantially the gauge of the rubber member (side wall rubber 16 in FIG. 5) inserted between the end of the innermost layer (wide cross belt 141 in FIG. 5) of the belt layer 14 and the carcass layer 13. measured as

The outer peripheral surface of the carcass layer 13 is defined as the radially outer peripheral surface of the entire carcass ply consisting of carcass cords and coating rubber. Further, when the carcass layer 13 has a multi-layered structure composed of a plurality of carcass plies (see FIG. 1), the outer peripheral surface of the outermost carcass ply 13B constitutes the outer peripheral surface of the carcass layer 13 . Further, when the wound-up portion 132 (see FIG. 1) of the carcass layer 13 exists between the end portion of the innermost layer of the belt layer 14 and the carcass layer 13 (not shown), the outer peripheral surface of the wound-up portion 132 is It constitutes the outer peripheral surface of the carcass layer 13 .

For example, in the configuration shown in FIG. 5, the sidewall rubber 16 is inserted between the end of the wide cross belt 141 and the carcass layer 13 to provide a rubber gauge Tu between the end of the wide cross belt 141 and the carcass layer 13. forming. However, without being limited to this, for example, a belt cushion may be inserted between the end of the wide cross belt 141 and the carcass layer 13 instead of the sidewall rubber 16 (not shown). In addition, 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 0.02 or more and 0.22 or less. It has a loss tangent tan δ_sp, preferably 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 0.04 or more and 0.20 or less has a loss tangent tan δ_sp.

1, the tire 1 includes a plurality of circumferential main grooves 21 to 23 (see FIG. 5) extending in the tire circumferential direction, and land portions partitioned by these circumferential main grooves 21 to 23. (reference numerals omitted in the figure) are provided on the tread surface. A main groove is defined as a groove having a duty to display a wear indicator as defined by JATMA.

At this time, as shown in FIG. 5, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the plurality of circumferential main grooves 21 to 23 is the rubber gauge Gce [mm] of the tread rubber 15. mm] in the range of 0.50≦Gd1/Gce≦1.00, preferably in the range of 0.55≦Gd1/Gce≦0.98. Thereby, the wear resistance performance of the tire is ensured. Specifically, the above lower limit disperses the contact pressure in the center region of the tread portion, thereby improving the wear life of the tire. The above upper limit secures the rigidity of the land portion and secures a rubber gauge from the bottom of the circumferential main groove 21 to the belt layer.

The circumferential main groove closest to the tire equatorial plane CL is defined as the circumferential main groove 21 (see FIG. 5) on the tire equatorial plane CL, and when there is no circumferential main groove on the tire equatorial plane CL (not shown) ) is defined as the circumferential main groove closest to the tire equatorial plane CL.

Moreover, it is preferable that the ratio Gd1/Gce described above satisfies the following formula (10) 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, more preferably Hmin=0.14 and Hmax=0.40.

Further, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL among the plurality of circumferential main grooves 21 to 23 is the groove depth Gd2 [mm] of the other circumferential main grooves 22, 23 mm], deeper than Gd3 [mm] (Gd2<Gd1, Gd3<Gd1). Specifically, when the area from the tire equatorial plane CL to the tire ground contact edge T is bisected in the tire width direction, the groove depth of the circumferential main groove (reference numerals omitted in the figure) closest to the tire equatorial plane CL The depth Gd1 is 1.00 to 2.50 times the maximum value of the groove depths Gd2 and Gd3 of the other circumferential main grooves (reference numerals omitted in the drawing) in the region on the side of the tire ground contact edge T. range, preferably 1.00 times or more and 2.00 times or less, more preferably 1.00 times or more and 1.80 times or less. Due to the above lower limit, the contact pressure in the center region of the tread portion is distributed, and the wear resistance performance of the tire is improved. The above upper limit suppresses uneven wear caused by an excessive contact pressure difference between the tread center region and the shoulder region.

[Side profile and side gauge]
FIG. 6 is an enlarged view showing side fall portions and bead portions of the tire 1 shown in FIG. FIG. 7 is an enlarged view showing the sidewall portion shown in FIG.

In FIG. 6, a point Au on the side profile at the same position in the tire radial direction with respect to the end of the innermost layer of the belt layer 14 (inner diameter side cross belt 141 in FIG. 6) and a point Au on the radial outer side of the bead core 11 A point Al on the side profile at the same position in the tire radial direction with respect to the end is defined. Further, a radial distance Hu from the maximum tire width position Ac to the point Au and a radial distance Hl from the maximum tire width position Ac to the point Al are defined. In addition, a point Au' on the side profile located at a radial position of 70 [%] of the distance Hu from the tire maximum width position Ac and a side profile located at a radial position of 70 [%] of the distance Hl from the tire maximum width position Ac Define a point Al' on the profile.

At this time, the sum of the distance Hu [mm] and the distance Hl [mm] is in the range of 0.45 ≤ (Hu + Hl) / SH ≤ 0.90 with respect to the tire section height SH [mm] (see FIG. 2) Yes, preferably in the range of 0.50≦(Hu+Hl)/SH≦0.85. Thereby, the radial distance from the belt layer 14 to the bead core 11 is optimized. Specifically, the above lower limit secures a deformable region of the tire side portion, thereby suppressing failure of the tire side portion (for example, separation of the rubber member at the radially outer end portion of the bead filler 12). The above upper limit reduces the deflection amount of the tire side portion when the tire rolls, thereby reducing the rolling resistance of the tire.

The distance Hu and the distance Hl are measured in a state in which the tire is mounted on a specified rim, given a specified internal pressure, and no load is applied.

Further, the sum of the distance Hu [mm] and the distance Hl [mm] is the tire outer diameter OD (Fig. 1), the tire section height SH [mm] (see Fig. 2), the tire maximum width position Ac, the points Au' and It is preferable that the curvature radius RSc [mm] of the arc passing through the point Al′ satisfies the following formula (11). Here, I1min=0.06, I1max=0.20 and I2=0.70, preferably I1min=0.09, I1max=0.20 and I2=0.65.

The radius of curvature RSc of the circular arc is measured in a state in which the tire is mounted on a specified rim, given a specified internal pressure, and no load is applied.

Further, the distance Hu [mm] and the distance Hl [mm] have a relationship of 0.30≦Hu/(Hu+Hl)≦0.70, preferably 0.35≦Hu/(Hu+Hl)≦0.65. have a relationship. As a result, the position of the tire maximum width position Ac in the deformable region of the tire side portion is optimized. Specifically, the above lower limit alleviates the stress concentration near the ends of the belt ply caused by the maximum tire width position Ac being too close to the ends of the belt layer 14, thereby suppressing the separation of the peripheral rubber. Due to the above upper limit, the stress concentration near the bead caused by the maximum tire width position Ac being too close to the end of the bead core 11 is alleviated, and failure of the bead reinforcing member (bead filler 12 in FIG. 6) is suppressed. be done.

Further, the curvature radius RSc [mm] of the arc passing through the maximum tire width position Ac, the point Au' and the point Al' is in the range of 0.05 ≤ RSc / OD ≤ 1.70 with respect to the tire outer diameter OD [mm] and preferably in the range of 0.10≤RSc/OD≤1.60. Also, 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. As a result, the radius of curvature of the side profile is optimized, and the load capacity of the tire side portion is properly ensured. Specifically, the above lower limit reduces the deflection amount of the tire side portion when the tire rolls, thereby reducing the rolling resistance of the tire. Due to the above upper limit, the occurrence of stress concentration due to flattening of the tire side portion is suppressed, and the durability performance of the tire is improved. In particular, small-diameter tires tend to have a large stress acting on the tire side portions due to use under the above-described high internal pressure and high load, so there is also the issue of ensuring the tire's resistance to side cuts. In this regard, the above lower limit secures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire collapse and sidecutting of the tire. In addition, the above upper limit suppresses side cutting of the tire due to excessive tension of the carcass layer 13 .

Further, the radius of curvature RSc [mm] of the arc is in the range of 0.50≦RSc/SH≦0.95, preferably 0.55≦RSc/SH≦0 with respect to the tire section height SH [mm]. in the .90 range.

Moreover, it is preferable that the radius of curvature RSc [mm] of the arc satisfies the following formula (12) 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, more preferably Jmin=25 and Jmax=300.

In FIG. 6, a point Bc on the main body portion 131 of the innermost carcass ply 13A of the carcass layer 13, which is located at the same position in the tire radial direction as the tire maximum width position Ac, is defined. Also, a point Bu' on the main body portion 131 of the innermost carcass ply 13A at a radial position of 70% of the distance Hu from the maximum tire width position Ac is defined. Also, a point Bl' on the main body portion 131 of the innermost carcass ply 13A at a radial position of 70[%] of the distance Hl from the maximum tire width position Ac is defined.

At this time, the radius of curvature RSc [mm] of the arc passing through the maximum tire width position Ac, point Au' and point Al' is the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu' and point Bl'. 1.10≤RSc/RCc≤4.00, preferably 1.50≤RSc/RCc≤3.50. Also, the radius of curvature RCc [mm] of the arc passing through the points Bc, Bu' and Bl' is in the range of 5≤RCc≤300, preferably in the range of 10≤RCc≤270. Thereby, the relationship between the radius of curvature RSc of the side profile of the tire and the radius of curvature RCc of the side profile of the carcass layer 13 is optimized. Specifically, the above lower limit secures the radius of curvature RCc of the carcass profile, secures the internal volume V of the tire, which will be described later, and secures the load capacity of the tire. The above upper limit secures the total gauges Gu and Gl of the tire side portion, which will be described later, and secures the load capacity of the tire side portion.

Moreover, it is preferable that the curvature radius RSc [mm] of the side profile satisfies the following formula (13) with respect to the curvature radius 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, more preferably Kmin=3 and Kmax=70.

Further, in FIG. 6, the total gauge Gu [mm] of the tire side portion at the point Au described above is in the range of 0.010 ≤ Gu / OD ≤ 0.080 with respect to the tire outer diameter OD [mm], preferably is in the range of 0.017≤Gu/OD≤0.070. As a result, the total gauge Gu of the radially outer region of the tire side portion is optimized. Specifically, the above lower limit secures the total gauge Gu in the radially outer region of the tire side portion, suppresses deformation of the tire during use under high load, and secures the wear resistance performance of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the above-described effect of reducing tire rolling resistance can be obtained remarkably. The above upper limit suppresses deterioration in tire rolling resistance caused by an excessively large total gauge Gu.

The total gauge of the tire side portion is measured as the distance from the side profile to the inner surface of the tire on a vertical line drawn from a predetermined point on the side profile to the body portion 131 of the carcass layer 13 .

In FIG. 6, the total gauge Gu [mm] at the point Au described above is 1.20 ≤ Gu/Gc ≤ 5.00 with respect to the total gauge Gc [mm] of the tire side portion at the maximum tire width position Ac. preferably the ratio Gu/Gc is in the range of 1.30≤Gu/Gc≤3.00. As a result, the gauge distribution of the tire side portion from the tire maximum width position Ac to the innermost layer of the belt layer 14 is optimized. Specifically, the above lower limit secures the total gauge Gu in the radially outer region, suppresses deformation of the tire during use under a high load, and secures the wear resistance performance of the tire. The above upper limit suppresses deterioration in tire rolling resistance caused by an excessively large total gauge Gu.

Further, it is preferable that the total gauge Gu [mm] at the point Au described above satisfies the following formula (14) with respect to the total gauge Gc [mm] and the tire outer diameter OD [mm] at the tire maximum width position Ac. Here, Lmin=0.10 and Lmax=0.70, preferably Lmin=0.14 and Lmax=0.70, more preferably Lmin=0.19 and Lmax=0.70.

In FIG. 6, the total gauge Gc [mm] of the tire side portion at the tire maximum width position Ac has a relationship of 0.003 ≤ Gc/OD ≤ 0.060 with respect to the tire outer diameter OD [mm]. , preferably 0.004≤Gc/OD≤0.050. The above lower limit secures the total gauge Gc at the tire maximum width position Ac, thereby securing the load capacity of the tire. By setting the above upper limit, the effect of reducing the rolling resistance of the tire by thinning the total gauge Gc at the maximum tire width position Ac is ensured.

Further, it is preferable that the total gauge Gc [mm] at the tire maximum width position Ac satisfies the following formula (15) with respect to the tire outer diameter OD [mm]. Here, Mmin=70 and Mmax=450, preferably Mmin=80 and Mmax=400.

Further, it is preferable that the total gauge Gc [mm] at the tire maximum width position Ac satisfies the following formula (16) with respect to the tire outer diameter OD [mm] and the tire total width SW [mm]. Here, Nmin=0.20 and Nmax=15, preferably Nmin=0.40 and Nmax=15, more preferably Nmin=0.60 and Nmax=12.

Further, the total gauge Gc [mm] at the maximum tire width position Ac is expressed by the following formula (17) with respect to the radius of curvature RSc [mm] of the arc passing through the maximum tire width position Ac, the point Au' and the point Al'. is preferably satisfied. Here, Omin=13 and Omax=260, preferably Omin=20 and Omax=200.

Further, in FIG. 6, the total gauge Gl [mm] of the tire side portion at the point Al described above is in the range of 0.010≦Gl/OD≦0.150 with respect to the tire outer diameter OD, preferably 0.150. 015≤Gl/OD≤0.100. As a result, the total gauge Gl of the radially inner region of the tire side portion is optimized. Specifically, the above lower limit secures the total gauge Gl in the radially inner region of the tire side portion, suppresses deformation of the tire during use under a high load, and secures the wear resistance performance of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the above-described effect of reducing tire rolling resistance can be obtained remarkably. The above upper limit suppresses deterioration of tire rolling resistance caused by an excessively large total gauge Gl.

In FIG. 6, the ratio Gl/Gc between the total gauge Gl [mm] of the tire side portion at the point Al and the total gauge Gc [mm] of the tire side portion at the maximum tire width position Ac is 1.00≦ It is in the range of Gl/Gc≦7.00, preferably the ratio Gu/Gc is in the range of 2.00≦Gl/Gc≦5.00. As a result, the gauge distribution of the tire side portion from the tire maximum width position Ac to the bead core 11 is optimized. Specifically, the above lower limit secures the total gauge Gl in the radially inner region, suppresses deformation of the tire during use under a high load, and secures the wear resistance performance of the tire. The above upper limit suppresses deterioration of tire rolling resistance caused by an excessively large total gauge Gl.

Further, the total gauge Gl [mm] of the tire side portion at the point Al described above satisfies the following formula (18) with respect to the total gauge Gc [mm] and the tire outer diameter OD [mm] at the tire maximum width position Ac. is preferred. Here, Pmin=0.12 and Pmax=1.00, preferably Pmin=0.15 and Pmax=1.00, more preferably Pmin=0.18 and Pmax=1.00.

Further, in FIG. 6, the total gauge Gl [mm] at the point Al described above is in the range of 0.80 ≤ Gl / Gu ≤ 5.00 with respect to the total gauge Gu [mm] at the point Au described above, preferably is in the range of 0.85≤Gl/Gu≤4.00. As a result, the ratio between the total gauge Gl in the radially outer region and the total gauge Gu in the radially inner region of the tire side portion is optimized.

Further, it is preferable that the total gauge Gl [mm] at the point Al described above satisfies the following formula (19) with respect to the total gauge Gu [mm] and the tire outer diameter OD [mm] at the point Au described above. Here, Qmin=0.09 and Qmax=0.80, preferably Qmin=0.10 and Qmax=0.70, more preferably Qmin=0.11 and Qmax=0.50.

Also, in FIG. 6, the average rubber hardness Hsc at the measurement position of the total gauge Gc, the average rubber hardness Hsu at the measurement position of the total gauge Gu, and the average rubber hardness Hsl at the measurement position of the total gauge Gl. , Hsc≤Hsu<Hsl, preferably 1≤Hsu-Hsc≤18 and 2≤Hsl-Hsu≤27, more preferably 2≤Hsu-Hsc≤15 and 5≤Hsl- It has a relationship of Hsu≦23. As a result, the relationship between the rubber hardness of the tire side portion is optimized.

The average rubber hardness Hsc, Hsu, Hsl is the cross-sectional length of each rubber member at each measurement point of the total gauge Gc [mm] at the maximum tire width position Ac, the total gauge Gu at the point Au, and the total gauge Gl at the point Al. and rubber hardness divided by the total gauge.

Further, in FIG. 7, the distance ΔAu′ [mm] in the tire width direction from the tire maximum width position Ac to the point Au′ is 0 with respect to 70% of the distance Hu [mm] from the tire maximum width position Ac. 0.03≦ΔAu′/(Hu×0.70)≦0.23, preferably 0.07≦ΔAu′/(Hu×0.70)≦0.17. This optimizes the degree of curvature of the side profile in the radially outer region. Specifically, the above lower limit suppresses the occurrence of stress concentration due to flattening of the tire side portion, thereby improving the durability performance of the tire. The above upper limit reduces the deflection amount of the tire side portion when the tire rolls, thereby reducing the rolling resistance of the tire. In particular, small-diameter tires tend to have a large stress acting on the tire side portions due to use under the above-described high internal pressure and high load, so there is also the issue of ensuring the tire's resistance to side cuts. In this regard, the above lower limit secures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire collapse and sidecutting of the tire. In addition, the above upper limit suppresses side cutting of the tire due to excessive tension of the carcass layer 13 .

Further, the distance ΔAl′ [mm] in the tire width direction from the maximum tire width position Ac to the point Al′ is 0.03≦ΔAl′/ (Hl×0.70)≦0.28, preferably 0.07≦ΔAl′/(Hl×0.70)≦0.20. This optimizes the degree of curvature of the side profile in the radially inner region. Specifically, the above lower limit suppresses the occurrence of stress concentration due to flattening of the tire side portion, thereby improving the durability performance of the tire. Particularly in a small-diameter tire, since the bead core 11 is reinforced as described above, stress concentration in the vicinity of the bead core 11 is effectively suppressed. The above upper limit reduces the deflection amount of the tire side portion when the tire rolls, thereby reducing the rolling resistance of the tire.

The distances .DELTA.Au' and .DELTA.Al' are measured when the tire is mounted on a specified rim, given a specified internal pressure, and in a no-load state.

Further, the distance ΔAu′ [mm] in the tire width direction from the maximum tire width position Ac to the point Au′ is the radius of curvature RSc [mm] of the arc passing through the maximum tire width position Ac, the point Au′ and the point Al′. is preferably satisfied with the following formula (20). Here, Rmin=0.05 and Rmax=5.00, preferably Rmin=0.10 and Rmax=4.50.

Further, in FIG. 7, the distance ΔBu′ [mm] in the tire width direction from the point Bc to the point Bu′ is 1 with respect to the distance ΔAu′ [mm] in the tire width direction from the maximum tire width position to the point Au′. .10≤ΔBu'/ΔAu'≤8.00, preferably 1.60≤ΔBu'/ΔAu'≤7.50. This optimizes the relationship between the degree of curvature of the side profile and the degree of curvature of the carcass profile in the radially outer region. Specifically, the cut resistance performance of the tire side portion is ensured by the above lower limit. With the above upper limit, the tension of the carcass layer 13 is secured, the rigidity of the tire side portion is secured, and the load capacity and durability performance of the tire are secured.

Further, in FIG. 7, the distance ΔBl′ [mm] in the tire width direction from the point Bc to the point Bl′ is the distance ΔAl′ [mm] in the tire width direction from the maximum tire width position Ac to the point Al′. It is in the range of 1.80≤ΔBl'/ΔAl'≤11.0, preferably in the range of 2.30≤ΔBl'/ΔAl'≤9.50. This optimizes the relationship between the degree of curvature of the side profile and the degree of curvature of the carcass profile in the radially inner region. Specifically, the above lower limit secures the total gauge Gl of the tire side portion, thereby securing the load capacity of the tire side portion. With the above upper limit, the tension of the carcass layer 13 is secured, the rigidity of the tire side portion is secured, and the load capacity and durability performance of the tire are secured.

The distances .DELTA.Bu' and .DELTA.Bl' are measured under the condition that the tire is mounted on a specified rim, given a specified internal pressure, and unloaded.

Further, the distance ΔBu' [mm] in the tire width direction from the point Bc to the point Bu' is the radius of curvature RCc [mm] of the arc passing through the points Bc, Bu' and Bl' described above, and the following formula (21) is preferably satisfied. Here, Smin=0.40 and Smax=7.0, preferably Smin=0.50 and Smax=6.0.

7, the rubber gauge Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac is 0.40≦Gcr/Gc≦0 with respect to the total gauge Gc [mm] at the maximum tire width position Ac. in the .90 range. Also, the rubber gauge Gcr [mm] of the sidewall rubber 16 is in the range of 1.5≤Gcr, preferably in the range of 2.5≤Gcr. Due to the above lower limit, the rubber gauge Gcr [mm] of the sidewall rubber 16 is ensured, and the load capacity of the sidewall portion is ensured.

Further, the rubber gauge Gcr [mm] of the sidewall rubber 16 at the maximum tire width position Ac is expressed by the following formula (22 ) is preferably satisfied. Here, Tmin=80 and Tmax=0.90, preferably Tmin=120 and Tmax=0.90.

In FIG. 7, the rubber gauge Gin [mm] (not shown) of the inner liner 18 at the maximum tire width position Ac is 0.03 ≤ Gin/Gc ≤ the total gauge Gc [mm] at the maximum tire width position Ac. It is in the range of 0.50, preferably in the range of 0.05≤Gin/Gc≤0.40. Thereby, the inner surface of the carcass layer 13 is properly protected.

[Carcass ply and belt ply]
FIG. 8 is an explanatory diagram showing the laminated structure of the carcass layer and belt layer of the tire shown in FIG. The figure shows an enlarged view in a cross-sectional view in the tire meridian direction.

In the configuration of FIG. 1, as shown in FIG. 8, the carcass layer 13 is formed by laminating two layers of carcass plies 13A and 13B each having a carcass cord 13cc covered with a coating rubber 13cr, and the belt layer 14 is composed of: A pair of cross belts 141 and 142 each having a belt cord 14bc covered with a coat rubber 14cr and an additional belt 145 are laminated. An inner liner 18 is arranged to cover the inner peripheral surface of the carcass layer 13 .

In FIG. 8, the distance TL [mm] from the center of the outer diameter of the carcass cord 13cc of the innermost carcass ply (in FIG. 8, the inner diameter side carcass ply 13A) to the tire inner surface is the tire outer diameter OD [mm]. 0.001≤TL/OD≤0.009, preferably 0.002≤TL/OD≤0.008. Further, the distance TL [mm] is in the range of 0.003 ≤ TL/SW ≤ 0.025 with respect to the total tire width SW [mm] (see Fig. 1), preferably 0.004 ≤ TL/SW ≤ It is in the range of 0.020. Air leakage is appropriately suppressed by the above lower limit, and an increase in tire weight is suppressed by the above upper limit.

The distance TL [mm] is calculated as an average value in the area between the two points B2 and B2 (see FIG. 4).

Further, the distance TL [mm] is 1/80000 ≤ TL/(SW×(OD -RD)) ≤ 1/3760.

8, the distance TCSU [mm] from the center of the carcass cord 13cc of the innermost carcass ply (in FIG. 8, the inner diameter side carcass ply 13A) to the outer surface of the innermost carcass ply 13A is equal to the innermost carcass ply. The distance TL [mm] from the center of the carcass cord 13cc of the ply 13A to the inner surface of the tire is in the range of 0.09 ≤ TCSU/TL ≤ 1.00, preferably 0.10 ≤ TCSU/TL ≤ 0.90. in the range of Air leakage is appropriately suppressed by the above lower limit, and an increase in tire weight is suppressed by the above upper limit.

8, the modulus MC [MPa] of the coat rubber 13cr of the carcass plies 13A and 13B when stretched 100%, the modulus MIL [MPa] of the inner liner 18 when stretched 100%, and the modulus MIL [MPa] of the belt layer 14 With respect to the modulus MB [MPa] when the coat rubber 14cr of the innermost belt ply 141 is stretched by 100%, the range is MIL≦MC≦MB. Also, the ratio MC/MIL is in the range of 1.00≤MC/MIL≤3.00, preferably in the range of 1.10≤MC/MIL≤2.30. Also, the ratio MB/MC is in the range of 1.00≤MB/MC≤2.40, preferably in the range of 1.00≤MB/MC≤2.00. The modulus MC [MPa] of the coating rubber 13cr of the carcass plies 13A, 13B is in the range of 1.5≤MC≤12.0, preferably in the range of 2.0≤MC≤10.0. As a result, air leakage is appropriately suppressed, and durability performance of the tire is ensured.

8, the product of the thickness TC [mm] of the carcass plies 13A, 13B and the loss tangent tan δ of the coating rubber 13cr of the carcass plies 13A, 13B at 60 [° C.] is 0.08≦TC×tan δ≦ It is in the range of 0.45, preferably in the range of 0.10≦TC×tan δ≦0.40. Thereby, the heat generation of the carcass layer 13 is appropriately suppressed, and the durability performance of the tire is ensured.

Further, when the carcass cords 13cc of the carcass plies 13A and 13B are made of an organic fiber material, the cord diameter φcs [mm] of the carcass cords 13cc is the strength Tcs [N/50mm] of the carcass plies 13A and 13B, the carcass plies 13A, 13B, It is preferable that the number of layers Pcs [ply] of 13B and the total number Ncs [ply] of the carcass cords in one carcass ply 13A; 13B satisfy the following formula (23).

Further, when the carcass cords 13cc of the carcass plies 13A and 13B are made of an organic fiber material, the number Ecs [strings/50 mm] of driving the carcass cords 13cc is expressed by the following formula (24) with respect to the cord diameter φcs [mm] of the carcass cords 13cc. preferably fulfilled.

Further, when the carcass cords 13cc of the carcass plies 13A and 13B are made of steel, the cord diameter φcs [mm] of the carcass plies 13A and 13B is the strength Tcs [N/50mm] of the carcass plies 13A and 13B. It is preferable that the number of layers Pcs [ply] and the total number Ncs [ply] of the carcass cords woven into one carcass ply 13A; 13B satisfy the following formula (25).

Further, when the carcass cords 13cc of the carcass plies 13A and 13B are made of steel, the number of driving Ecs [lines/50 mm] satisfies the following formula (26) with respect to the cord diameter φcs [mm] of the carcass cords 13cc. is preferred.

In FIG. 8, when the carcass cords 13cc of the carcass plies 13A and 13B are made of an organic fiber material, the outermost carcass ply 13B of the carcass layer 13 and the innermost belt ply of the belt layer 14 (in FIG. The peeling force Hpp [N/25 mm] per width 25 [mm] with the cross belt 141) is the distance from the center of the outer diameter of the carcass cord 13cc of the carcass ply 13B to the center of the outer diameter of the belt cord 14bc of the belt ply 141. The distance TCB [mm] is in the range of 90≦Hpp/TCB≦300, preferably in the range of 100≦Hpp/TCB≦250. In addition, the peeling force Hpp [N/25 mm] is in the range of 1.50 ≤ Hpp/Ecs ≤ 15.0 with respect to the number Ecs [wires/50 mm] of the carcass cord 13cc of the carcass ply, and 1.80 ≤ It is in the range of Hpp/Ecs≦10.0. This ensures the durability of the tire.

The peel force Hpp [N/25 mm] has a rectangular shape elongated in the extending direction of the carcass cord, and has a width of 25 [mm] and a length of 100 [mm] or more (preferably about 50 [mm]). A test sample having a length of 150 [mm] or more including the test gripping allowance) is used, and it is calculated as the average value of the maximum and minimum peak values of the analyzed wavy curve. Moreover, it is preferable that the number of test samples is two or more.

In FIG. 8, when the carcass cords 13cc of the carcass plies 13A and 13B are made of steel, the outermost carcass ply 13B of the carcass layer 13 and the innermost belt ply of the belt layer 14 (inner diameter cross belt in FIG. 8) 141), the peeling force Hpp [N/25 mm] per width 25 [mm] is the distance TCB from the center of the outer diameter of the carcass cord 13cc of the carcass ply 13B to the center of the outer diameter of the belt cord 14bc of the belt ply 141. [mm] is in the range of 25≤Hpp/TCB≤215, preferably in the range of 30≤Hpp/TCB≤185. In addition, the peeling force Hpp [N/25 mm] is in the range of 0.30 ≤ Hpp/Ecs ≤ 15 and 0.60 ≤ Hpp/ It is in the range of Ecs≦7.5. This ensures the durability of the tire.

In FIG. 8, when the carcass cords 13cc of the carcass plies 13A and 13B are made of an organic fiber material, the outermost carcass ply 13B of the carcass layer 13 and the innermost belt ply of the belt layer 14 (in FIG. The peeling force Hpp [N/25 mm] per width of 25 [mm] with the cross belt 141) is from the center of the outer diameter of the carcass cord 13cc of the carcass ply 13B of the outermost layer of the carcass layer 13 to the innermost layer of the belt layer 14. The distance TCB to the center of the outer diameter of the belt cords 14bc of the belt ply 141, the cord diameter φcs [mm] of the carcass cords 13cc, and the number of driving Ecs [cords/50mm] satisfy the following formula (27). is preferred.

In FIG. 8, when the carcass cords 13cc of the carcass plies 13A and 13B are made of steel, the outermost carcass ply 13B of the carcass layer 13 and the innermost belt ply of the belt layer 14 (inner diameter cross belt in FIG. 8) 141), the peel force Hpp [N/25 mm] per width 25 [mm] of the carcass layer 13 is measured from the center of the outer diameter of the carcass cord 13cc of the outermost carcass ply 13B of the carcass layer 13 to the innermost belt ply of the belt layer 14. The distance TCB to the center of the outer diameter of the belt cord 14bc of 141, the cord diameter φcs [mm] of the carcass cord 13cc, and the number of driving Ecs [cord/50mm] preferably satisfy the following formula (28). .

8, the distance Hb between the cords of the adjacent belt plies of the pair of cross belts 141 and 142 and the additional belt 145 (in FIG. 8, the distance Hb1 between the cords of the pair of cross belts 141 and 142 and the outer diameter The inter-cord distance Hb2) of the side cross belt and the additional belt 145 is defined. At this time, the inter-cord distance Hb_sh (not shown) at the ends of at least one set of belt plies is 1.05≦Hb_sh/Hb_ce≦2.00 with respect to the inter-cord distance Hb_ce (not shown) on the tire equatorial plane CL. and preferably 1.50≦Hb_sh/Hb_ce≦1.80. Therefore, it is preferable that the cord-to-cord distance Hb is set large in the tread center region. With the above lower limit, the belt layer 14 effectively suppresses the growth of the outer diameter of the tire, and with the above upper limit, the durability of the belt layer is ensured. The above configuration is realized by, for example, a configuration in which the gauge of the coating rubber of the belt ply is thickened in the center region of the tread portion, a configuration in which an additional rubber sheet is inserted between adjacent belt plies, or the like (not shown).

[Modification 1]
FIG. 9 is an explanatory diagram showing Modification 1 of the tire 1 shown in FIG. The figure shows the laminated structure of the belt layer 14 . In the figure, the same components as those described in FIG. 3 are denoted by the same reference numerals, and descriptions thereof are omitted.

In the configuration of FIG. 1, the belt layer 14 includes a pair of cross belts 141, 142, a belt cover 143, a pair of belt edge covers 144, 144, and an additional belt 145, as described above. Moreover, the cord angles θ41 and θ42 of the cross belts 141 and 142 have opposite signs and are in the range of 15 degrees or more and 55 degrees or less in terms of absolute values.

Further, as shown in FIG. 3, an additional belt 145 is laminated radially outside the pair of cross belts 141 and 142 . Further, the cord angle θ45 of the additional belt 145 has the opposite sign to the cord angle θ42 of the adjacent cross belt 142, and has an absolute value of 15 [deg] or more and 80 [deg] or less with respect to the tire circumferential direction. in the range. Therefore, the additional belt 145 constitutes a third cross belt laminated on the pair of cross belts 141 and 142 . Further, the width Wb5 of the additional belt 145 is wider than the width Wb2 of the adjacent cross belt 142, and the width Wb2 is in the range of 1.03≦Wb5/Wb2≦1.40, preferably 1.05. ≤Wb5/Wb2≤1.25. Therefore, the ends of the additional belts 145 are offset in the tire width direction with respect to the ends of the adjacent cross belts 142 . As a result, the effect of suppressing the outer diameter growth of the tire by the additional belt is effectively obtained, and the durability of the belt layer 14 is improved.

On the other hand, in the configuration of FIG. 9, the additional belt 145 is laminated radially inside the pair of cross belts 141 and 142, and is between the inner diameter side cross belt 141 and the carcass layer 13 (see FIG. 1). To position. Further, the additional belt 145 is a so-called high-angle belt, and the cord angle θ45 of the additional belt 145 has the same sign and is larger than the cord angle θ41 of the inner diameter side cross belt 141, and is an absolute value with respect to the tire circumferential direction. It is in the range of 45 [deg] to 70 [deg], preferably 54 [deg] to 68 [deg]. Further, the width Wb5 of the additional belt 145 is in the range of 0.60≦Wb5/Wb1≦1.40, preferably 0.70≦Wb5/Wb1≦1.30 with respect to the width Wb1 of the inner diameter side cross belt 141. in the range of Therefore, the ends of the additional belts 145 are offset in the tire width direction with respect to the ends of the adjacent cross belts 141 . As a result, the effect of suppressing the outer diameter growth of the tire by the additional belt is effectively obtained, and the durability of the belt layer 14 is improved.

3 and 9, the belt cord of the additional belt 145 and the cross belt adjacent to the additional belt 145 among the pair of cross belts 141 and 142 (the outer diameter cross belt 142 in FIG. 3 and the inner diameter side cross belt 142 in FIG. 9). The angle Δθ [deg] (not shown) formed by the belt cords of the cross belt 141) is in the range of 10 [deg] ≤ Δθ [deg] ≤ 90 [deg], preferably 20 [deg] ≤ Δθ [deg]. ]≦60 [deg], more preferably 30 [deg]≦Δθ[deg]≦55 [deg]. As a result, the outer diameter growth of the tire is effectively suppressed, and the durability of the belt layer 14 is ensured.

Moreover, it is preferable that the angle Δθ formed by the cord angles described above satisfies the following formula (29) with respect to the tire outer diameter OD [mm]. Here, Wmin=30 and Wmax=330, preferably Wmin=60 and Wmax=220, more preferably Wmin=90 and Wmax=210.

Further, the smallest cord angle θmin [deg] (cord angle θ43 of the belt cover 144 in FIGS. 3 and 9) among the cord angles of the effective belt plies 141, 142, 143, and 145 constituting the belt layer 14 is the cord angle It is preferable to satisfy the following formula (30) with respect to the strength Tbt [N/50 mm] of the belt ply having the angle θmin. Here, Xmin=3 and Xmax=410, preferably Xmin=3 and Xmax=310, more preferably Xmin=30 and Xmax=310.

Also, the angle formed by the cord angle of the innermost belt ply and the cord angle of the second layer belt ply (in FIG. 3, the angle formed by the cord angles θ41 and θ42 of the pair of cross belts 141 and 142; An angle Δθ12 [deg] between the cord angle θ45 of 145 and the inner diameter side cross belt 141 is defined. Also, the angle formed by the cord angle of the second layer belt ply and the cord angle of the third layer belt ply (in FIG. An angle Δθ23 formed by the cord angles θ41 and θ42 of the pair of cross belts 141 and 142 is defined. At this time, these angles Δθ12 and Δθ23 [deg] have a relationship of 50≦Δθ12+Δθ23≦100. As a result, the outer diameter growth of the tire is effectively suppressed, and the durability of the belt layer 14 is ensured.

[Modification 2]
FIG. 10 is an explanatory diagram showing Modification 2 of tire 1 shown in FIG. In the figure, the same components as those described in FIG. 3 are denoted by the same reference numerals, and descriptions thereof are omitted.

In the configuration of FIG. 1, as described above, the carcass layer 13 is composed of a pair of carcass plies 13A and 13B made of organic fiber cords.

In contrast, in the configuration of FIG. 12, the carcass layer 13 consists of a single carcass ply of steel cord. Even with such a configuration, the load capacity and durability of the carcass layer 13 can be appropriately ensured.

[effect]
As described above, the tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 spanning the bead cores 11, 11, and a belt layer 14 arranged radially outside the carcass layer 13. (See Figure 1). Further, 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. In addition, the belt layer 14 is a pair of cross belts 141 and 142 having cord angles (θ41, θ41; see FIG. 3) of opposite signs and 15 [deg] or more and 55 [deg] or less with respect to the tire circumferential direction. , and an additional belt 145 having a cord angle (θ45; see FIG. 3) of 15 degrees or more and 80 degrees or less with respect to the tire circumferential direction. Further, the strength Tbt [N/50 mm] per width 50 [mm] of each of the pair of cross belts 141 and 142 and the additional belt 145 is 25 ≤ Tbt/OD ≤ 250 with respect to the tire outer diameter OD [mm]. in the range.

Such a configuration has the advantage that the respective load capacities of the pair of cross belts 141 and 142 and the additional belt 145 are properly ensured. Specifically, the above lower limit suppresses deformation of the tire during use under a high load, ensuring wear resistance performance of the tire. In addition, the tire can be used at high internal pressure, and the rolling resistance of the tire is reduced. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so that the wear resistance performance and rolling resistance of the tires described above can be significantly reduced. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the belt ply.

In the tire 1, the width Wbmax of the widest belt ply among the pair of cross belts 141 and 142 and the additional belt 145 (the width Wb1 of the inner diameter side cross belt 141 or the width Wb5 of the additional belt 145 in FIG. 3) is It is in the range of 1.00≦Wbmax/Wbmid≦1.30 with respect to the width Wbmid of the second widest belt ply (the width Wb2 of the outer diameter side cross belt 142 in FIG. 3). As a result, there is an advantage that the relationship among the widths Wb1, Wb2, Wb5 of the belt plies 141, 142, 145 is optimized. Specifically, the above lower limit secures the width of the belt ply, optimizes the ground contact pressure distribution in the tire contact area, and secures the uneven wear resistance of the tire. Due to the above upper limit, distortion of the end of the belt ply when the tire rolls is reduced, and separation of the peripheral rubber at the end of the belt ply is suppressed.

In the tire 1, the width Wbmax of the widest belt ply among the pair of cross belts 141 and 142 and the additional belt 145 (the width Wb1 of the inner diameter side cross belt 141 or the width Wb5 of the additional belt 145 in FIG. 3) is It is in the range of 1.00≦Wbmax/Wbmin≦1.40 with respect to the width Wbmin of the narrowest belt ply (the width Wb2 [mm] of the cross belt 142 on the outer diameter side in FIG. 3). As a result, there is an advantage that the relationship among the widths Wb1, Wb2, Wb5 of the belt plies 141, 142, 145 is optimized.

Further, in the tire 1, the width Wbmin of the narrowest belt ply among the pair of cross belts 141, 142 and the additional belt 145 (in FIG. 3, the width Wb2 [mm] of the cross belt 142 on the outer diameter side) is It is in the range of 0.61≦Wbmin/SW≦0.96 with respect to the total tire width SW (see FIG. 1). This has the advantage of optimizing the relationship of the width Wb2 of the belt ply 142 .

Further, in the tire 1, the angle between the belt cord of the additional belt 145 and the belt cord of the cross belt (the outer diameter side cross belt 142 in FIG. 3) adjacent to the additional belt 145 among the pair of cross belts 141 and 142 Δθ [deg] is in the range of 10 [deg]≦Δθ [deg]≦90 [deg]. This has the advantage of effectively suppressing the growth of the outer diameter of the tire and ensuring the durability of the belt layer 14 .

Further, in the tire 1, the inter-cord distance Hb between adjacent belt plies of the pair of cross belts 141 and 142 and the additional belt 145 (in FIG. 8, the inter-cord distance Hb1 between the pair of cross belts 141 and 142 and the outer The inter-cord distance Hb2) of the radial side cross belt and the additional belt 145 is defined. At this time, the inter-cord distance Hb_sh at the ends of at least one set of belt plies is in the range of 1.05≦Hb_sh/Hb_ce≦2.00 with respect to the inter-cord distance Hb_ce on the tire equatorial plane CL. Therefore, the cord-to-cord distance Hb is set large in the tread center region. With the above lower limit, there is an advantage that the belt layer 14 effectively suppresses the growth of the outer diameter of the tire, and with the above upper limit, the durability of the belt layer is ensured.

Further, in this tire 1, the distance Tsh [mm] from the tread profile at the tire contact edge T to the outer peripheral surface of the wide cross belt (the inner diameter side cross belt 141 in FIG. 5) is the distance Tce [mm] at the tire equatorial plane CL. ] in the range of 0.60≦Tsh/Tce≦1.70 (see FIG. 5). This has the advantage of optimizing the ratio Tsh/Tce. Specifically, since the tread gauge in the shoulder region is ensured by the above lower limit, repeated deformation of the tire during rolling of the tire is suppressed, and wear resistance performance of the tire is ensured. In addition, since the tread gauge in the center region is secured by the upper limit, deformation of the tire during use under high load, which is characteristic of small-diameter tires, is suppressed, and wear resistance performance of the tire is secured.

Further, in the tire 1, the distance Tsh at the tire contact edge T is 1.50≦Tsh/Tu≦30.0 with respect to the rubber gauge Tu [mm] from the end of the wide cross belt 141 to the outer peripheral surface of the carcass layer 13. 0 range (see FIG. 5). Thereby, there is an advantage that the profile of the carcass layer 13 is optimized and the tension of the carcass layer 13 is optimized.

Further, in this tire 1, the tread profile drop amount DA [mm] at the tire contact edge T has a relationship of 0.008 ≤ DA/TW ≤ 0.090 with respect to the tire contact width TW [mm] (Fig. 4). As a result, there is an advantage that the sagging angle (defined by the ratio DA/(TW/2)) of the tread shoulder region is optimized, and the load capacity of the tread is properly ensured. Specifically, the above lower limit secures the sagging angle of the tread shoulder region, thereby suppressing a reduction in wear life due to excessive contact pressure in the tread shoulder region. Due to the above upper limit, the tire contact area becomes flat and the contact pressure is made uniform, thereby ensuring the wear resistance performance of the tire. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the configuration described above can effectively optimize the contact pressure distribution in the tire contact area.

Also, in this tire 1, the pair of cross belts 141, 142 and the additional belt 145 are formed by coating steel cords with coat rubber. As a result, the effect of suppressing the growth of the outer diameter of the tire is effectively obtained, and there is an advantage that the durability of the belt layer 14 is improved.

In this tire 1, the carcass layer 13 is formed by laminating two layers of carcass plies 13A and 13B each formed by coating an organic fiber cord with a coating rubber. Further, the organic fiber cords of the two carcass plies 13A and 13B have a cord angle in the range of 80 [deg] to 100 [deg] with respect to the tire circumferential direction. Further, the strength Tcs [N/50 mm] per width 50 [mm] of each of the two carcass plies 13A and 13B is in the range of 17 ≤ Tcs/OD ≤ 120 with respect to the tire outer diameter OD [mm]. . With such a configuration, the load capacity of the carcass layer 13 is appropriately ensured in a small-diameter tire, so there is an advantage that the wear resistance performance and low rolling resistance performance of the tire are compatible.

In this tire 1, the carcass layer 13 is composed of a single-layer carcass ply 13 formed by coating steel cords with a coating rubber (see FIG. 10). Further, the steel cords of the carcass ply 13 have a cord angle in the range of 80 [deg] to 100 [deg] with respect to the tire circumferential direction. Further, the strength Tcs [N/50 mm] per 50 [mm] width of the carcass ply 13 is in the range of 17≦Tcs/OD≦120 with respect to the tire outer diameter OD [mm]. With such a configuration, the load capacity of the carcass layer 13 is appropriately ensured in a small-diameter tire, so there is an advantage that the wear resistance performance and low rolling resistance performance of the tire are compatible.

11 to 13 are charts showing the results of performance tests of tires according to embodiments of the present invention.

In this performance test, multiple types of test tires were evaluated for (1) low rolling resistance performance (fuel consumption rate), (2) wear resistance performance, and (3) load durability performance. As an example of small-diameter tires, test tires of two tire sizes are used. Specifically, [A] a test tire with a tire size of 235/45R10 is mounted on a rim with a rim size of 10×8, and [B] a test tire with a tire size of 145/80R12 is mounted on a rim with a rim size of 12×4.00B. be assembled.

(1) In the evaluation of low rolling resistance performance, an internal pressure of 230 [kPa] and a load of 4.2 [kN] were applied to the test tire [A] above, and the test tire [B] was subjected to JATMA An internal pressure of 80[%] of the prescribed internal pressure and a load of 80[%] of the JATMA prescribed load are applied. In addition, a four-wheel low-floor vehicle with test tires mounted on all wheels runs 50 laps on a test course with a total length of 2 [km] at a speed of 100 [km/h]. After that, the fuel consumption rate [km/l] is calculated and evaluated. This evaluation is performed by index evaluation with the comparative example as the standard (100), and the higher the numerical value, the lower the fuel consumption rate and the lower the rolling resistance, which is preferable.

(2) In the evaluation of wear resistance performance, the above [A] test tire was subjected to an internal pressure of 230 [kPa] and a load of 4.2 [kN], and the above [B] test tire was subjected to the JATMA standard An internal pressure of 80% of the internal pressure and a load of 80% of the JATMA specified load are applied. In addition, a four-wheel low-floor vehicle with test tires mounted on all wheels travels 10,000 [km] on a test course with a dry road surface. After that, the amount of wear and the degree of uneven wear of each tire are measured and evaluated. This evaluation is performed by index evaluation with the comparative example as the standard (100), and the larger the numerical value, the better.

(3) In the evaluation of durability performance, an indoor drum tester with a drum diameter of 1707 [mm] was used, and an internal pressure of 230 [kPa] and a load of 4.2 [kN] were applied to the test tire of [A] above. Also, an internal pressure of 80[%] of the JATMA specified internal pressure and a load of 88[%] of the JATMA specified load are applied to the test tire of [B] above. Then, the load is increased by 13 [%] every two hours at a running speed of 81 [km/h], and the running distance until the tire fails is measured. Then, based on this measurement result, index evaluation is performed with the comparative example as the standard (100). This evaluation is so preferable that the numerical value is large.

The test tire of the example has the structure shown in FIG. A belt layer 14 comprising a pair of belt edge covers 144, 144 and an additional belt 145, a tread rubber 15, a sidewall rubber 16 and a rim cushion rubber 17 are provided. Further, the carcass cord angle (not shown) of the carcass layer 13 is 90 [deg], and the angle of each belt ply of the belt layer 14 (see FIG. 3) is θ41=20 [deg], θ42=−20 [deg]. ], θ43=θ44=0 [deg], and θ45=20 [deg].

The test tire of the comparative example has a tire outer diameter OD of 531 [mm], a total tire width SW of 143 [mm], and a tire contact width TW of 123 [mm]. Mounted on the rim.

As can be seen from the test results, the test tires of the examples have both low rolling resistance performance, wear resistance performance and durability performance.

1 tire; 10 rim; 11 bead core; 12 bead filler; 13 carcass layer; 145 additional belt; 14bc belt cord; 14cr coated rubber; 15 tread rubber; 151 cap tread; 152 undertread; 16 sidewall rubber;

Claims (12)

A tire comprising a pair of bead cores, a carcass layer spanning the bead cores, and a belt layer arranged radially outside the carcass layer,
The tire outer diameter OD [mm] is in the range of 200 ≤ OD ≤ 660,
The total tire width SW [mm] is in the range of 100 ≤ SW ≤ 400,
The belt layers are a pair of cross belts having different signs and cord angles of 15 [deg] to 55 [deg] with respect to the tire circumferential direction, and 15 [deg] or more and 80 [deg] with respect to the tire circumferential direction. deg] and an additional belt having a cord angle of less than or equal to
The strength Tbt [N/50 mm] per width 50 [mm] of each of the pair of cross belts and the additional belt is in the range of 25 ≤ Tbt/OD ≤ 250 with respect to the tire outer diameter OD [mm] A tire characterized by The width Wbmax of the widest belt ply of the pair of cross belts and the additional belt is in the range of 1.00≤Wbmax/Wbmid≤1.30 with respect to the width Wbmid of the second widest belt ply. 1. Tire according to 1. The width Wbmax of the widest belt ply of the pair of cross belts and the additional belt is in the range of 1.00≤Wbmax/Wbmin≤1.40 with respect to the width Wbmin of the narrowest belt ply. 3. The tire according to 1 or 2. The width Wbmin of the narrowest belt ply of the pair of cross belts and the additional belt is in the range of 0.61≦Wbmin/SW≦0.96 with respect to the total tire width SW. A tire according to any one of the preceding paragraphs. The angle formed by the belt cord of the additional belt and the belt cord of the cross belt adjacent to the additional belt among the pair of cross belts is in the range of 10 [deg] or more and 90 [deg] or less. 5. Tire according to any one of 4. A distance Hb between the cords of adjacent belt plies of the pair of cross belts and the additional belt is defined, and a distance Hb_sh between the cords at the ends of at least one set of the belt plies is the distance between the cords on the tire equatorial plane. The tire according to any one of claims 1 to 5, wherein Hb_ce is in the range of 1.05≤Hb_sh/Hb_ce≤2.00. The distance Tsh [mm] from the tread profile at the tire contact edge to the outer peripheral surface of the wide cross belt is in the range of 0.60 ≤ Tsh/Tce ≤ 1.70 with respect to the distance Tce [mm] on the tire equatorial plane. A tire according to any one of claims 1-6. 2. The distance Tsh at the tire contact edge is in the range of 1.50≦Tsh/Tu≦30.0 with respect to the rubber gauge Tu [mm] from the end of the wide cross belt to the outer peripheral surface of the carcass layer. The tire according to any one of -7. The amount of sagging DA [mm] of the tread profile at the tire contact edge has a relationship of 0.008 ≤ DA/TW ≤ 0.090 with respect to the tire contact width TW [mm]. The tires described in . The tire according to any one of claims 1 to 9, wherein said pair of cross belts and said additional belts are formed by coating steel cords with coated rubber. The carcass layer is formed by laminating two layers of carcass plies formed by coating organic fiber cords with a coating rubber,
The organic fiber cords of the two-layer carcass ply have a cord angle in the range of 80 [deg] or more and 100 [deg] or less with respect to the tire circumferential direction, and
According to claim 10, the strength Tcs [N / 50 mm] per width 50 [mm] of each of the two carcass plies is in the range of 17 ≤ Tcs / OD ≤ 120 with respect to the tire outer diameter OD [mm] Tires as stated. The carcass layer consists of a single-layer carcass ply made by coating a steel cord with a coating rubber,
The steel cord of the carcass ply has a cord angle in the range of 80 [deg] or more and 100 [deg] or less with respect to the tire circumferential direction, and
11. The tire according to claim 10, wherein the strength Tcs [N/50 mm] per 50 [mm] width of the carcass ply is in the range of 17≤Tcs/OD≤120 with respect to the tire outer diameter OD [mm].

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