WO2024042768A1

WO2024042768A1 - Tire

Info

Publication number: WO2024042768A1
Application number: PCT/JP2023/014132
Authority: WO
Inventors: 晴香新井
Original assignee: 横浜ゴム株式会社
Priority date: 2022-08-22
Filing date: 2023-04-05
Publication date: 2024-02-29
Also published as: JP2024029653A

Abstract

In a cross-section of the tire 1 along the tire meridian direction, a point on a side profile located at the same tire-radial-direction position as an end of the innermost layer 141 of belt layers 14 is referred to as point Au. The foot of a perpendicular from point Au to a carcass layer 13 is referred to as point Iu, and the foot of a perpendicular from a tire-maximum-width position Ac to the carcass layer is referred to as point Ic. The carcass layer 13 comprises one or more carcass plies obtained by coating carcass cords 13cc with a coating rubber 13cr. In the region ranging from point Iu to point Ic, the distance TLu [mm] between the center of the carcass cords 13cc of the innermost carcass ply 13A and the inner surface of the tire, with respect to the tire outer diameter OD [mm], is in the range of 0.00010≤TLu/OD≤0.01500.

Description

tire

The present invention relates to a tire, and more particularly to a tire that can achieve both tire durability and low rolling resistance.

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

International Publication No. 2020/122169

An object of the present invention is to provide a tire that can achieve both tire durability and low rolling resistance.

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, a belt layer disposed on the radially outer side of the carcass layer, and an inner surface of the carcass layer. The tire outer diameter OD [mm] is in the range of 200≦OD≦660, the tire total width SW [mm] is in the range of 100≦SW≦400, and the tire meridian direction is In the cross-sectional view, define 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, and define the foot of the perpendicular line drawn from point Au to the carcass layer as a point. The foot of the perpendicular line drawn from the tire maximum width position Ac to the carcass layer is defined as the point Ic, and the carcass layer is made of a single layer or multiple layers of carcass ply consisting of a carcass cord coated with rubber. The distance TLu [mm] from the center of the carcass cord of the innermost layer of the carcass ply to the inner surface of the tire in the region from point Iu to point Ic is 0. It is characterized by being in the range of 00010≦TLu/OD≦0.01500.

The tire according to the present invention has the advantage that the distance from the carcass layer to the inner surface of the tire in the region from the end of the belt layer to the tire maximum width position is optimized. Specifically, the above lower limit ensures the distance TLu from the carcass layer to the inner surface of the tire in the above region where air leaks are likely to occur, and suppresses a decrease in tire durability performance and worsening of rolling resistance due to air leaks. Ru. Further, the above upper limit suppresses deterioration of rolling resistance due to an increase in tire weight. This achieves both tire durability and low rolling resistance. In particular, small-diameter tires are used under the above-mentioned high internal pressure and high load, so stress concentration tends to occur easily. Therefore, when the above configuration is adopted for a small diameter tire, the durability performance and low rolling resistance performance of the tire can be significantly improved.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. FIG. 2 is an enlarged view of the tire shown in FIG. 1. FIG. 3 is an explanatory diagram showing the laminated structure of the belt layer of the tire shown in FIG. FIG. 4 is an enlarged view showing the tread portion of the tire shown in FIG. FIG. 5 is an enlarged view showing one side region of the tread portion shown in FIG. 4. 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. 6. FIG. 8 is an explanatory diagram showing a laminated structure of a carcass layer and a belt layer of the tire shown in FIG. 1. FIG. 9 is an explanatory diagram showing a modification of the laminated structure of the carcass layer and belt layer shown in FIG. 8. FIG. 10 is an explanatory diagram showing a modification of the laminated structure of the carcass layer and belt layer shown in FIG. 8. FIG. 11 is an enlarged view showing the tire radially outer region shown in FIG. 6. FIG. FIG. 12 is an explanatory diagram showing a laminated structure of a carcass layer and an inner liner in the radially outer region of the tire shown in FIG. 11. FIG. 13 is a chart showing the results of a performance test of the tire according to the embodiment of the present invention. FIG. 14 is a chart showing the results of a performance test of the tire according to the embodiment of the present invention. FIG. 15 is a chart showing the results of a performance test of the tire according to the embodiment of the present invention.

Hereinafter, this invention will be explained in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Further, the constituent elements of this embodiment include elements that can be replaced while maintaining the identity of the invention and are obvious to be replaced. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within the range obvious to those skilled in the art.

[tire]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire 1 according to an embodiment of the present invention. 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, a cross section in the tire meridian direction is defined as a cross section when the tire is cut along a plane that includes the tire rotation axis (not shown). Further, the tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width DW defined in JATMA and is perpendicular to the tire rotation axis. Further, 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. Further, point T is the tire ground contact edge, and point Ac is the tire maximum width position.

The tire 1 has an annular structure centered around 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, and 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,

sidewall rubber

16, 16, a pair of

rim cushion rubber

17, 17, and an inner liner 18 (see FIG. 1).

The pair of

bead cores

11, 11 are formed by winding one or more bead wires made of steel in an annular shape and multiple times, and are embedded in the bead portions to form the cores of the left and right bead portions. The pair of

bead fillers

12, 12 are arranged on the outer peripheries of the pair of

bead cores

11, 11 in the tire radial direction, respectively, to reinforce the bead portions. In addition, the bead filler 12 has a rubber hardness Hs_bf of 55 or more and 105 or less, a modulus at 100 [%] elongation M_bf [MPa] of 2.0 or more and 13.0 or less, and a loss tangent of 0.03 or more and 0.30 or less. tan δ_bf, preferably a rubber hardness Hs_bf of 70 or more and 100 or less, a modulus M_bf [MPa] at elongation of 100 [%] of 3.0 or more and 12.0 or less, and a loss tangent of 0.05 or more and 0.25 or less. It has tanδ_bf.

The carcass layer 13 has a single layer structure consisting of one carcass ply or a multilayer structure consisting of a plurality of carcass plies laminated, and is spanned in a toroidal shape between the left and

right bead cores

11, 11, and is the frame of the tire. Configure. Further, both ends of the carcass layer 13 are wound back and locked outward in the tire width direction so as to wrap around the bead core 11 and bead filler 12. Further, the carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of inorganic fibers (e.g., steel, carbon fiber, glass fiber) or organic fibers (e.g., aramid, nylon, polyester, rayon, etc.) with coated rubber. The cord angle (defined as the inclination angle in the longitudinal direction of the carcass cord with respect to the tire circumferential direction) is 80 [deg] or more and 100 [deg] or less.

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is arranged to be wrapped around the outer periphery of the carcass layer 13. In the configuration of FIG. 1, belt plies 141 to 144 are composed of a pair of

intersecting belts

141, 142, a belt cover 143, and a pair of belt edge covers 144, 144.

The pair of

crossed belts

141 and 142 are constructed by rolling a plurality of belt cords made of steel or organic fibers coated with rubber, and have a cord angle of 15 [deg] or more and 55 [deg] or less in absolute value ( ) is defined as the inclination angle of the belt cord in the longitudinal direction with respect to the tire circumferential direction. Further, the pair of

crossed belts

141 and 142 have cord angles of opposite signs and are laminated with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). Further, the pair of

crossing belts

141 and 142 are stacked and arranged on the outside of the carcass layer 13 in the tire radial direction.

The belt cover 143 and the pair of belt edge covers 144, 144 are constructed by covering a belt cover cord made of steel or organic fiber material with coated rubber, and have a cord angle of 0 [deg] or more and 10 [deg] or less in absolute value. have The belt cover 143 and the belt edge cover 144 are, for example, strip materials made by covering one or more belt cover cords with coated rubber, and these strip materials are applied to the outer peripheral surfaces of the crossed

belts

141 and 142. It is constructed by wrapping it spirally multiple times in the circumferential direction of the tire. Further, a belt cover 143 is arranged to cover the entire area of the crossing

belts

141, 142, and a pair of belt edge covers 144, 144 are arranged to cover the left and right edge portions of the crossing

belts

141, 142 from the outside in the tire radial direction.

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, and constitutes the tread portion of the tire 1. Further, the tread rubber 15 includes a cap tread 151 and an undertread 152.

The cap tread 151 is made of a rubber material with excellent ground contact characteristics and weather resistance, and is exposed on the tread surface over the entire tire contact area and constitutes 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 at 100 [%] elongation M_cap [MPa] of 1.5 or more and 3.2 or less, and loss tangent of 0.06 or more and 0.29 or less. It has tanδ_cap.

Rubber hardness Hs is measured at a temperature of 20 [° C.] in accordance with JIS K6253.

The 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 a No. 3 dumbbell).

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

The undertread 152 is made of a rubber material with excellent heat resistance, is sandwiched between the cap tread 151 and the belt layer 14, and forms 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 at 100 [%] elongation M_ut [MPa] 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 a rubber hardness Hs_ut of 50 or more and 65 or less, a modulus at 100 [%] elongation M_ut [MPa] of 1.7 or more and 3.5 or less, and a loss tangent of 0.03 or more and 0.10 or less. It has tan δ_ut.

Furthermore, the difference in rubber hardness Hs_cap−Hs_ut is in the range of 3 or more and 20 or less, preferably in the range of 5 or more and 15 or less. Further, the modulus difference M_cap−M_ut [MPa] is in the range of 0 or more and 1.4 or less, preferably 0.1 or more and 1.0 or less. Further, the loss tangent difference tanδ_cap−tanδ_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 respectively arranged on the outside of the carcass layer 13 in the tire width direction, and constitute left and right sidewall portions. In the configuration of FIG. 1, the outer end of the sidewall rubber 16 in the tire radial direction is disposed below the tread rubber 15 and is sandwiched between the end of the belt layer 14 and the carcass layer 13. However, the present invention is not limited thereto, and the outer end of the sidewall rubber 16 in the tire radial direction 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. It 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. It has a tangent tan δ_sw.

A 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 left and

right bead cores

11, 11 and the rolled-up portion of the carcass layer 13, and constitute a rim fitting surface of the bead portion. In the configuration shown in FIG. 1, the outer end of the rim cushion rubber 17 in the tire radial direction is inserted into the lower layer of the sidewall rubber 16, and is sandwiched between the sidewall rubber 16 and the carcass layer 13. . In addition, the rim cushion rubber 17 has a rubber hardness Hs_rc of 60 or more and 80 or less, a modulus M_rc [MPa] at 100 [%] elongation of 2.0 or more and 7.0 or less, and a loss of 0.09 or more and 0.35 or less. It has a tangent tanδ_rc, preferably a rubber hardness Hs_rc of 65 or more and 75 or less, a modulus M_rc [MPa] at 100 [%] elongation of 3.0 or more and 6.0 or less, and a loss of 0.11 or more and 0.30 or less. It has a tangent tanδ_rc.

The inner liner 18 is an air permeation prevention layer placed on the inner cavity surface of the tire and covering the carcass layer 13, and suppresses oxidation due to exposure of the carcass layer 13, and also prevents air filled in the tire from leaking. In addition, 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 the present invention to such small-diameter tires, the effect of improving load performance, which will be described later, can be significantly achieved. Further, the tire total 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 surface of a small vehicle can be lowered to expand the interior space of the vehicle. Furthermore, since the rotational inertia is small and the tire weight is small, fuel efficiency is improved and transportation costs are reduced. Particularly when attached to an in-wheel motor of a vehicle, the load on the motor is effectively reduced.

The tire outer diameter OD is measured while the tire is mounted on a specified rim, a specified internal pressure is applied, and the tire is in an unloaded state.

Tire total width SW is measured as the straight line distance between the sidewalls (including all parts such as the pattern on the side of the tire, letters, etc.) when the tire is mounted on the specified rim, the specified internal pressure is applied, and no load is applied. be done.

The specified rim refers to the "applicable rim" specified in JATMA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. In addition, the specified internal pressure refers to the "maximum air pressure" specified in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. In addition, the specified load refers to the "maximum load capacity" specified in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "LOAD CAPACITY" specified in ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

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. within the range of

Furthermore, it is preferable that the tire outer diameter OD and the tire total 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, and A3max=362.

In the tire 1 described above, it is assumed that 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 used. Further, 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 range. With the above lower limit, the rim diameter RD can be secured, and especially the installation space for the in-wheel motor can be secured. With the above upper limit, the inner 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.

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

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

Further, the aspect ratio of the tire, that is, the ratio SH/DW of the tire cross-sectional height SH [mm] (see FIG. 2 described later) and the tire cross-sectional width DW [mm] is 0.16≦SH/DW≦0.85. It is preferably in the range of 0.19≦SH/DW≦0.82.

The tire cross-sectional height SH is a distance that is 1/2 of the difference between the tire outer diameter and the rim diameter, and is measured with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

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

Further, the tire ground contact width TW is in the range of 0.50≦TW/SW≦0.85 with respect to the tire total width SW, preferably in the range of 0.60≦TW/SW≦0.80.

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

Further, the tire internal volume V [m^3] is in the range of 4.0≦(V/OD)×10^6≦60 with respect to the tire outer diameter OD [mm], preferably 6.0≦( V/OD)×10^6≦50. Thereby, the tire internal volume V is optimized. Specifically, the above lower limit ensures the inner volume of the tire and 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 that the tire internal volume V is sufficiently secured. The above upper limit suppresses the tire from increasing in size due to the tire internal volume V becoming excessively large.

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

[Bead core and bead filler]
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 an annular manner and in multiple layers. Further, a pair of

bead fillers

12, 12 are arranged on the outer peripheries of the pair of

bead cores

11, 11 in the tire radial direction, respectively.

Further, the strength Tbd [N] of one bead core 11 is in the range of 45≦Tbd/OD≦120 with respect to the tire outer diameter OD [mm], preferably in the range of 50≦Tbd/OD≦110, More preferably, the range is 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 tire total width SW [mm]. Thereby, the load capacity of the bead core 11 is appropriately ensured. Specifically, the above lower limit suppresses tire deformation during use under high loads and ensures tire durability. In addition, it becomes possible to use the tire 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 loads, so the above-described tire durability and rolling resistance reduction effect can be significantly achieved. 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/piece] and the total number of bead wires [pieces] in a radial cross-sectional view. The strength of the bead wire is measured by a tensile test at a temperature of 20 [° C.] in accordance with JIS K1017.

Furthermore, 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]. Here, 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, even more preferably B1min=0.49, B2min=17.9 , B1max=2.5, B2max=99.0. Further, 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. It is measured as an unloaded state when applied.

The tire maximum width position Ac is defined as the maximum width position of the tire cross-sectional width DW specified 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 bead wire made of steel described above is 0.025≦σbd/OD≦ with respect to the tire outer diameter OD [mm]. It is in the range of 0.075, preferably in the range of 0.030≦σbd/OD≦0.065. Further, the total cross-sectional area σbd [mm^2] of the bead wire 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 [mm^2] of the bead wire is calculated as the sum of the cross-sectional areas of the bead wire in a radial cross-sectional view of one bead core 11.

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

Further, it is preferable that the total cross-sectional area σbd [mm^2] of the bead wire 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 wire is 0.50≦σbd/Nbd with respect to the total number of cross-sections (that is, the total number of turns) Nbd [pieces] of the bead wire of one bead core 11 in a radial cross-sectional view. It is in the range of ≦1.40, preferably in the range of 0.60≦σbd/Nbd≦1.20. That is, the cross-sectional area σbd' [mm^2] of a single bead wire is in the range of 0.50 [mm^2/piece] to 1.40 [mm^2/piece], preferably 0.60 [mm^2/piece]. mm^2/piece] or more and 1.20 [mm^2/piece] or less.

Further, the maximum width Wbd [mm] of one bead core 11 in a radial cross-sectional view (see FIG. 2 described later) is 0.16≦Wbd/σbd≦0 with respect to the total cross-sectional area σbd [mm^2] of the bead wire. .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 tire total width SW [mm]. is in the range of 0.65≦Dbd/SW≦0.95. With the above lower limit, the amount of tire deflection is reduced, and the rolling resistance of the tire is reduced. The above upper limit reduces the stress acting on the tire side portion, thereby suppressing tire failure.

In addition, in FIG. 2, the radial distance BH [mm] from the radially outer end of the bead core 11 to the radially outer end of the bead filler 23, that is, the height of the bead filler 23 is equal to the tire cross-sectional height SH [mm] is in the range of 0.10≦BH/SH≦0.40, preferably in the range of 0.15≦BH/SH≦0.35.

The radial distance BH [mm] is measured with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

[Carcass layer]
FIG. 2 is an enlarged view showing the tire 1 shown in FIG. The figure shows a region on one side with the tire equatorial plane CL as a boundary.

In the configuration of FIG. 1, as described above, the carcass layer 13 is composed of a single layer of carcass ply, and is arranged in a toroidal manner between the left and

right bead cores

11, 11. Further, both ends of the carcass layer 13 are rolled back and locked outward in the tire width direction so as to wrap around the bead core 11 and bead filler 12.

Further, the strength Tcs [N/50mm] per width 50 [mm] of the carcass ply constituting the carcass layer 13 is preferably in the range of 17≦Tcs/OD≦120 with respect to the tire outer diameter OD [mm]. is in the range of 20≦Tcs/OD≦120. Further, the strength Tcs [N/50mm] of the carcass layer 13 is in the range of 30≦Tcs/SW≦260 with respect to the tire total width SW [mm], preferably in the range of 35≦Tcs/SW≦220. . In such a configuration, since the load capacity of the carcass layer 13 is appropriately ensured in a small-diameter tire, there is an advantage that the tire has both durability performance and low rolling resistance performance. Specifically, the above lower limit suppresses tire deformation during use under high loads and ensures tire durability. In addition, it becomes possible to use the tire 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 loads, so the above-described tire durability and rolling resistance reduction effect can be significantly achieved. The above upper limit suppresses deterioration of rolling resistance due to increase in mass of the carcass layer.

The strength Tcs [N/50mm] of the carcass ply is calculated as follows. That is, the carcass ply that spans the left and right bead cores 11 and extends over the entire inner circumference of the tire is defined as an effective carcass ply. Then, the strength per carcass cord [N/piece] that constitutes an effective carcass ply and the number of carcass cords driven per width 50 [mm] around the entire circumference of the tire and on the tire equatorial plane CL [pieces/50mm] The product is calculated as the carcass ply strength Tcs [N/50mm]. The strength of the carcass cord is measured by a tensile test at a temperature of 20 [° C.] in accordance with JIS K1017. For example, in a configuration in which one carcass cord is formed by twisting a plurality of wires together, the strength of one twisted carcass cord is measured, and the strength Tcs of the carcass layer 13 is calculated. Further, in a configuration in which the carcass layer 13 has a multilayer structure (not shown) formed by laminating a plurality of effective carcass plies, the above-mentioned strength Tcs is defined for each of the plurality of effective carcass plies.

For example, in the configuration shown in FIG. 1, the carcass layer 13 has a single layer structure consisting of a single carcass ply (number omitted in the figure), and the carcass ply has a carcass cord made of steel covered with coated rubber. The cords are 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 described above has a cord diameter φcs [mm] in a range of 0.15≦φcs≦1.10, preferably in a range of 0.25≦φcs≦0.60, and a cord diameter φcs [mm] in a range of 25≦Ecs≦80. By having the driving number Ecs [pieces/50mm] in the range of , preferably in the range of 50≦Ecs≦80, the above-described strength Tcs [N/50mm] of the carcass layer 13 is realized. Further, the carcass cord is formed by twisting a plurality of wires, and the wire diameter φcss [mm] is in the range of 0.12≦φcss≦0.24, preferably 0.14≦φcss≦0. It is in the range of 22. Further, it is more preferable that the wire diameter φcss [mm] of the carcass cord is in the range of 0.30≦φcss/φcs≦0.90 with respect to the cord diameter φcs [mm] of the carcass cord. Note that the carcass cord may be made of inorganic fibers other than steel (eg, carbon fiber, glass fiber, etc.).

Furthermore, the present invention is not limited to the above, and the carcass ply may be constituted by a carcass cord made of an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) coated with coated rubber. In this case, the carcass cord made of the above-mentioned organic fiber material has a cord diameter φcs [mm] in the range of 0.60≦φcs≦0.90 and a driving number Ecs [pieces/cord] in the range 40≦Ecs≦70. 50 mm], the above-described strong Tcs of the carcass layer 13 [N/50 mm] is realized. In addition, carcass cords made of high-strength organic fiber materials such as nylon, aramid, and hybrid can be employed within the range obvious to those skilled in the art.

Furthermore, the carcass layer 13 may have a multilayer structure formed by laminating a plurality of carcass plies, for example, two layers (not shown). Thereby, the load capacity of the tire can be effectively increased.

Further, the total strength TTcs [N] of the carcass layer 13 is in the range of 300≦TTcs/OD≦3500, preferably in the range of 400≦TTcs/OD≦3000 with respect to the tire outer diameter OD [mm]. This ensures the entire load capacity of the carcass layer 13.

The total strength TTcs [N] of the carcass layer 13 is calculated as the product of the strength per carcass cord [N/cord] and the total number of carcass cords driven into the entire carcass layer 13 [number]. Therefore, the total strength TTcs [N] of the carcass layer 13 increases as the strength Tcs [N/50 mm] of each carcass ply, the number of laminated carcass plies, the circumference of the carcass ply, etc. increase.

Further, it is preferable that the total strength TTcs [N] 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, Dmax=40, preferably Dmin=4.3, Dmax=40, more preferably Dmin=6.5, Dmax=40, still more preferably Dmin=8 .7, Dmax=40. Further, it is preferable that Dmin=0.02×P using the specified tire internal pressure P [kPa].

In addition, in the configuration of FIG. 1, the carcass layer 13 includes a main body portion 131 extending along the inner surface of the tire, and a rolled-up portion extending in the tire radial direction that is rolled up outward in the tire width direction so as to wrap around the bead core 11. 132. In addition, in FIG. 2, the radial height Hcs [mm] from the measurement point of the rim diameter RD to the end of the rolled-up portion 132 of the carcass layer 13 is 0.10≦ with respect to the tire cross-sectional height SH [mm]. Hcs/SH≦0.49, preferably 0.15≦Hcs/SH≦0.47. Thereby, the radial height Hcs of the rolled up portion 132 of the carcass layer 13 is optimized. Specifically, the lower limit ensures the load capacity of the tire side portion, and the upper limit suppresses deterioration in rolling resistance due to an increase in the mass of the carcass layer.

The radial height Hcs [mm] of the rolled-up portion 132 of the carcass layer 13 is measured with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

For example, in the configuration of FIG. 2, the radially outer end (number omitted in the figure) of the rolled-up portion 132 of the carcass layer 13 is located in a region radially inward of the tire maximum width position Ac. is within the range from the tire maximum width position Ac to a radial position Al' that is 70% of the distance Hl, which will be described later. At this time, the contact height Hcs' [mm] between the main body part 131 and the rolled-up part 132 of the carcass layer 13 is in the range of 0.07≦Hcs'/SH with respect to the tire cross-sectional height SH [mm], It is preferably in the range of 0.10≦Hcs'/SH. This effectively increases the load capacity of the tire side portion. The upper limit of the ratio Hcs'/SH is not particularly limited, but is limited by the fact that the contact height Hcs' has a relationship of Hcs'<Hcs with respect to the radial height Hcs of the rolled 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 main body part 131 and the rolled-up part 132 contact each other, and when the tire is mounted on a specified rim and a specified internal pressure is applied. and is measured as a no-load condition.

Note that this is not limited to the above, and because the carcass layer 13 has a so-called high turn-up structure, even if the end of the rolled-up portion 132 of the carcass layer 13 is arranged in a region outside the tire maximum width position Ac in the tire radial direction. Good (not shown).

[Belt layer]
FIG. 3 is an explanatory diagram showing the laminated structure of the belt layers of the tire 1 shown in FIG. 1. In the figure, thin lines attached to each belt ply 141 to 144 schematically show the arrangement of the belt cords.

In the configuration of FIG. 1, as described above, the belt layer 14 is formed by laminating a plurality of belt plies 141 to 144. Further, as shown in FIG. 3, these belt plies 141 to 144 are composed of a pair of crossed

belts

141, 142, a belt cover 143, and a pair of belt edge covers 144, 144.

At this time, the strength Tbt [N/50 mm] per width 50 [mm] of each of the pair of crossed

belts

141 and 142 is in the range of 25≦Tbt/OD≦250 with respect to the tire outer diameter OD [mm]. , preferably in the range of 30≦Tbt/OD≦230. Further, the strength Tbt [N/50mm] of the crossing

belts

141 and 142 is in the range of 45≦Tbt/SW≦500 with respect to the tire total width SW [mm], preferably in the range of 50≦Tbt/SW≦450. It is in. Thereby, the load capacity of each of the pair of crossing

belts

141 and 142 is appropriately ensured. Specifically, the above lower limit suppresses tire deformation during use under high loads and ensures tire durability. In addition, it becomes possible to use the tire 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 loads, so the above-described tire durability and rolling resistance reduction effect can be significantly achieved. The above upper limit suppresses deterioration of rolling resistance due to an increase in the mass of the intersecting belt.

The strength Tbt [N/50mm] of the belt ply is calculated as follows. That is, the belt ply extending over the entire area of 80% of the tire ground contact width TW centered on the tire equatorial plane CL (that is, the central part of the tire ground contact area) is defined as an effective belt ply. Then, the strength [N/piece] per belt cord constituting the effective belt ply and the number of belt cords driven per width 50 [mm] in the area of 80 [%] of the tire ground contact width TW described above [pieces] The product is calculated as the belt ply strength Tbt [N/50mm]. The strength of the belt cord is measured by a tensile test at a temperature of 20 [° C.] in accordance with JIS K1017. For example, in a configuration in which one belt cord is formed by twisting a plurality of wires together, the strength of the one twisted belt cord is measured, and the strength Tbt of the belt ply is calculated. Further, in a structure in which the belt layer 14 is formed by laminating a plurality of effective belt plies (see FIG. 1), the above-mentioned strength Tbt is defined for each of the plurality of effective belt plies. For example, in the configuration of FIG. 1, a pair of intersecting

belts

141 and 142 and a belt cover 143 correspond to the effective belt ply.

For example, in the configuration shown in FIG. 3, a pair of crossed

belts

141 and 142 extend a steel belt cord covered with coated rubber at a cord angle of 15 degrees or more and 55 degrees or less (in the figure) with respect to the tire circumferential direction. (dimension symbol omitted). In addition, the above-mentioned steel belt cord has a cord diameter φbt [mm] in the range of 0.50≦φbt≦1.80 and a number of inserted cords Ebt [pieces/50 mm] in the range of 15≦Ebt≦75. As a result, a strong Tbt [N/50 mm] of the crossing

belts

141 and 142 is realized. Further, the cord diameter φbt [mm] and the driving number Ebt [pieces/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 preferable to be in the range of 30 and 20≦Ebt≦40. Further, the belt cord is formed by twisting a plurality of wires, and the wire diameter φbts [mm] is in the range of 0.16≦φbts≦0.43, preferably 0.21≦φbts≦0. It is in the range of 39.

Furthermore, the present invention is not limited to the above, and the crossed

belts

141 and 142 may be constituted by belt cords made of an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) coated with coated 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 a number of cords Ebt [cords/cord] in the range 30≦Ebt≦65. 50 mm], the above-mentioned strong force Tbt [N/50 mm] of the crossing

belts

141 and 142 is realized. Further, a belt cord made of a highly strong organic fiber material such as nylon, aramid, or hybrid can be employed within the range obvious to those skilled in the art.

Additionally, the belt layer 14 may include an additional belt (not shown). Such an additional belt is, for example, (1) a third cross belt, which is constructed by covering a plurality of belt cords made of steel or organic fiber material with coated rubber and rolling them, and has an absolute value of 15 [deg] or more. It has a cord angle of 55[deg] or less, or (2) it is a so-called high-angle belt, which is constructed by rolling a plurality of belt cords made of steel or organic fiber material and coated with rubber, and the absolute value The cord angle may be 45 [deg] or more and 70 [deg] or less, preferably 54 [deg] or more and 68 [deg] or less. Further, the additional belt is located between (a) the pair of crossed

belts

141, 142 and the carcass layer 13, (b) between the pair of crossed

belts

141, 142, or (c) between the pair of crossed

belts

141, 142. It may be arranged radially outward (not shown). This improves the load capacity of the belt layer 14.

Further, the total strength TTbt [N] of the belt layer 14 is in the range of 70≦TTbt/OD≦750 with respect to the tire outer diameter OD [mm], preferably in the range of 90≦TTbt/OD≦690, More preferably, the range is 110≦TTbt/OD≦690, and even more preferably, the range is 120≦TTbt/OD≦690. This ensures the entire load capacity of the belt layer 14. Furthermore, using the specified internal pressure P [kPa] of the tire, it is preferable that 0.16×P≦TTbt/OD.

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

Further, the width Wb1 [of the widest intersecting belt (in FIG. 3, the intersecting belt 141 on the inner diameter side) of the pair of intersecting belts 141 and 142 (the above-mentioned configuration includes the additional belt; not shown) mm] is in the range of 1.00≦Wb1/Wb2≦1.40 with respect to the width Wb2 [mm] of the narrowest cross belt (in FIG. 3, the cross belt 142 on the outer diameter side), and preferably It is in the range of 1.10≦Wb1/Wb2≦1.35. Further, the width Wb2 [mm] of the narrowest crossing belt is in the range of 0.61≦Wb2/SW≦0.96 with respect to the total tire width SW [mm], preferably 0.70≦Wb2/ SW is in the range of 0.94. With the above lower limit, the width of the belt ply is ensured, the ground contact pressure distribution in the tire ground contact area is optimized, and the uneven wear resistance of the tire is ensured. The above upper limit reduces distortion at the end of the belt ply during tire rolling, and suppresses separation of rubber around the end of the belt ply.

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 an unloaded state.

Further, the width Wb1 [of the widest intersecting belt (in FIG. 3, the intersecting belt 141 on the inner diameter side) of the pair of intersecting belts 141 and 142 (the above-mentioned configuration includes the additional belt; not shown) mm] is in the range of 0.85≦Wb1/TW≦1.23 with respect to the tire ground contact width TW [mm], preferably in the range of 0.90≦Wb1/TW≦1.20.

For example, in the configurations shown in FIGS. 1 to 3, a wide cross belt 141 is arranged at the innermost layer in the radial direction of the tire, and a narrow cross belt 142 is arranged on the outer side in the radial direction of the wide cross belt 141. Further, the belt cover 143 is disposed on the radially outer side of the narrow cross belt 142 and covers both of the pair of

cross belts

141 and 142 in their entirety. Further, a pair of belt edge covers 144, 144 are arranged radially outward of the belt cover 143 while being spaced apart from each other, and cover the left and right edge portions of the pair of intersecting

belts

141, 142, 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 depression amount DA [mm] of the tread profile at the tire ground contact edge T, the tire ground contact width TW [mm], and the tire outer diameter OD [mm] are 0.015≦TW/(DA×OD)≦0. 300, preferably 0.020≦TW/(DA×OD)≦0.250. Further, the depression amount DA [mm] of the tread profile at the tire ground contact edge T has a relationship of 0.01≦DA/TW≦0.10 with respect to the tire ground contact width TW [mm], preferably 0.02 The relationship is ≦DA/TW≦0.08. As a result, the depression angle (defined by the ratio DA/(TW/2)) of the shoulder region of the tread portion is optimized, and the load capacity of the tread portion is appropriately ensured. Specifically, with the above lower limit, the depression angle of the tread shoulder region is ensured, and a reduction in wear life due to excessive ground pressure in the tread shoulder region is suppressed. With the above upper limit, the tire ground contact area becomes flat, the ground contact pressure becomes uniform, and the wear resistance performance of the tire is ensured. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above configuration can effectively optimize the ground pressure distribution in the tire ground contact area.

The depression amount DA is the distance in the tire radial direction from the intersection C1 of the tire equatorial plane CL and the tread profile to the tire ground contact edge T in a cross-sectional view in the tire meridian direction, and the tire is mounted on a specified rim and a specified internal pressure is applied. It is also measured as a no-load condition.

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

Furthermore, it is preferable that the depression amount DA [mm] of the tread profile at the tire ground contact edge T satisfies the following formula (5) with respect to the tire outer diameter OD [mm] and the tire total width SW [mm]. Here, Emin=2.5 and Emax=17, preferably Emin=3.8 and Emax=13, and more preferably Emin=4.0 and Emax=9.

Further, 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 ground contact width TW from the tire equatorial plane CL are defined.

At this time, the radius of curvature TRc [mm] of the circular arc passing through the point C1 and the pair of points C2 is in the range of 0.15≦TRc/OD≦15 with respect to the tire outer diameter OD [mm], preferably 0.15≦TRc/OD≦15. It is in the range of 18≦TRc/OD≦12. Further, the radius of curvature TRc [mm] of the circular arc is in the range of 30≦TRc≦3000, preferably in the range of 50≦TRc≦2800, and more preferably in the range of 80≦TRc≦2500. Thereby, the load capacity of the tread portion is appropriately ensured. Specifically, with the above lower limit, the center region of the tread portion becomes flat, the ground contact pressure of the tire ground contact region is made uniform, and the wear resistance performance of the tire is ensured. The above upper limit suppresses a decrease in wear life caused by excessive ground contact pressure in the shoulder region of the tread. In particular, small-diameter tires are expected to be used under high internal pressure and high load, and therefore, the effect of equalizing ground pressure under such usage conditions can be effectively achieved.

The radius of curvature of the circular arc is measured with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

In addition, in FIG. 4, the radius of curvature 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 0.30≦ relative to the tire outer diameter OD [mm]. TRw/OD≦16, preferably 0.35≦TRw/OD≦11. Further, the radius of curvature TRw [mm] of the circular arc is in the range of 150≦TRw≦2800, preferably in the range of 200≦TRw≦2500. Thereby, the load capacity of the tread portion is appropriately ensured. Specifically, with the above lower limit, the entire tire ground contact area becomes flat, the ground contact pressure is made uniform, and the wear resistance performance of the tire is ensured. The above upper limit suppresses a decrease in wear life caused by excessive ground contact pressure in the shoulder region of the tread. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above configuration can effectively optimize the ground pressure distribution in the tire ground contact area.

Also, the radius of curvature TRw [mm] of the first arc passing through the points C1 and C2 described above is 0.50≦TRw/with respect to the radius of curvature TRw [mm] of the second arc passing through the point C1 and the tire contact edge T It is in the range of TRc≦1.00, preferably in the range of 0.60≦TRw/TRc≦0.98, and more preferably in the range of 0.70≦TRw/TRc≦0.96. Thereby, the ground contact shape of the tire is optimized. Specifically, the lower limit allows the ground pressure in the center region of the tread portion to be dispersed, thereby improving the wear life of the tire. The above upper limit suppresses a decrease in wear life caused by excessive ground contact pressure in the shoulder region of the tread.

In addition, in FIG. 4, a point B1 on the carcass layer 13 in the tire equatorial plane CL and legs B2, B2 of perpendicular lines drawn from the left and right tire contact edges T, T to the carcass layer 13 are defined.

At this time, the radius of curvature CRw of the circular arc passing through point B1 and the pair of points B2, B2 is 0.35≦CRw/TRw≦ with respect to the radius of curvature TRw of the circular arc passing through point C1 and the tire contact edges T, T mentioned above. 1.60, preferably 0.45≦CRw/TRw≦1.50, more preferably 0.55≦CRw/TRw≦1.40. Further, the radius of curvature CRw [mm] is in the range of 100≦CRw≦2500, preferably in the range of 120≦CRw≦2200. This makes the tire ground contact shape more appropriate. Specifically, the above lower limit suppresses a decrease in wear life caused by an increase in the rubber gauge in the shoulder region of the tread. The above upper limit ensures the wear life of the center region of the tread portion.

FIG. 5 is an enlarged view showing one side area of the tread portion shown in FIG. 4.

In the configuration of FIG. 1, as described above, the belt layer 14 has a pair of intersecting

belts

141 and 142, and the tread rubber 15 has a cap tread 151 and an undertread 152.

In addition, in FIG. 5, the distance Tce [mm] from the tread profile in 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]. .13, preferably 0.012≦Tce/OD≦0.10, more preferably 0.015≦Tce/OD≦0.07. Further, the distance Tce [mm] is in the range of 5≦Tce≦25, preferably in the range of 7≦Tce≦20. Thereby, the load capacity of the tread portion is appropriately ensured. Specifically, the above lower limit suppresses tire deformation during use under high load, 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 above-mentioned wear resistance performance can be significantly achieved. 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 when the tire is mounted on a specified rim, a specified internal pressure is applied, and there is no load.

The outer peripheral surface of the belt ply is defined as the entire radially outer peripheral surface of the belt ply consisting of the belt cord and coated rubber.

Further, it is preferable that the distance Tce [mm] from the tread profile in the tire equatorial plane CL to the outer peripheral surface of the wide cross belt 141 satisfies the following formula (6) 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 ground 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. It is preferably in the range of 0.80≦Tsh/Tce≦1.60, more preferably in the range of 1.01≦Tsh/Tce≦1.50. The above lower limit ensures the tread gauge in the shoulder region, thereby suppressing repeated deformation of the tire during tire rolling, and ensuring the wear resistance performance of the tire. Moreover, since the above upper limit ensures a tread gauge in the center region, tire deformation during use under high loads peculiar to small-diameter tires is suppressed, and the wear resistance performance of the tire is ensured.

The distance Tsh is measured when the tire is mounted on a specified rim, a specified internal pressure is applied, and there is no load. Further, when there is no wide crossing belt directly under the tire ground contact edge T, the distance Tsh is measured as the distance from the tread profile to an imaginary line that is an extension of the outer peripheral surface of the belt ply.

Further, it is preferable that the distance Tsh [mm] from the tread profile at the tire ground contact edge T to the outer peripheral surface of the wide cross belt 141 satisfies the following formula (7) with respect to the distance Tce [mm] at the tire equatorial plane CL. . Here, Gmin=0.36, Gmax=0.72, preferably Gmin=0.37, Gmax=0.71, more preferably Gmin=0.38, Gmax=0.70.

Further, in FIG. 5, a section having a width ΔTW of 10% of the tire ground contact width TW is defined. At this time, the ratio between the maximum value Ta and 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 more. In this configuration, since the amount of change in the rubber gauge of the tread rubber 15 in any section of the tire ground contact area (particularly the section including the ends of the belt plies 141 to 144) is set small, the ground contact pressure distribution in the tire width direction is smooth. This improves the wear resistance of the tire.

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

Further, in FIG. 5, the rubber gauge UTce of the undertread 152 in the tire equatorial plane CL is in the range of 0.04≦UTce/Tce≦0.60, preferably 0. It is in the range of .06≦UTce/Tce≦0.50. Thereby, the rubber gauge UTce of the undertread 152 is optimized.

Further, the distance Tsh at the tire ground contact edge T mentioned above is in the range of 1.50≦Tsh/Tu≦6.90 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. It is preferably in the range of 2.00≦Tsh/Tu≦6.50. Thereby, the profile of the carcass layer 13 is optimized and the tension of the carcass layer 13 is optimized. Specifically, the above lower limit ensures the tension of the carcass layer and the tread gauge of the shoulder region, thereby suppressing repeated deformation of the tire during tire rolling, and ensuring the wear resistance performance of the tire. Due to the above upper limit, a rubber gauge near the end of the belt ply is secured, so that separation of the rubber around the belt ply is suppressed.

The rubber gauge Tu is measured as a gauge of a rubber member (sidewall rubber 16 in FIG. 5) inserted between the end of the wide cross belt 141 and the carcass layer 13. Specifically, in a cross-sectional view in the tire meridian direction, a perpendicular line is drawn from the end of the wide cross belt 141 to the outer surface of the carcass layer 13, and the total gauge of the rubber member on this perpendicular line is calculated as the rubber gauge Tu. .

The outer peripheral surface of the carcass layer 13 is defined as the entire radially outer peripheral surface of the carcass ply made of the carcass cord and coated rubber. Further, when the carcass layer 13 has a multilayer structure consisting of a plurality of carcass plies (not shown), the outer circumferential surface of the outermost carcass ply constitutes the outer circumferential surface of the carcass layer 13. Further, when the rolled up part 132 (see FIG. 1) of the carcass layer 13 exists between the end of the wide cross belt 141 and the carcass layer 13 (not shown), the outer circumferential surface of this rolled up part 132 is This constitutes the outer peripheral surface of No. 13.

For example, in the configuration of FIG. 5, the sidewall rubber 16 is inserted between the end of the wide cross belt 141 and the carcass layer 13, and the rubber gauge Tu between the end of the wide cross belt 141 and the carcass layer 13 is is forming. However, the invention is not limited to this, and 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 at 100 [%] elongation of 1.0 or more and 3.5 or less [MPa], and a rubber hardness of 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 at 100 [%] elongation M_sp [MPa] of 1.2 or more and 3.2 or less, and a modulus M_sp [MPa] of 0.04 or more and 0.20 or less. It has a loss tangent tanδ_sp.

Further, in the configuration of FIG. 1, the tire 1 has a plurality of circumferential main grooves 21 to 23 (see FIG. 5) extending in the tire circumferential direction, and a land portion divided by these circumferential main grooves 21 to 23. (numerals omitted in the figure) are provided on the tread surface. The main groove is defined as a groove that is required to display a wear indicator as defined in 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 determined by the rubber gauge Gce[mm] of the tread rubber 15. mm] is in the range of 0.50≦Gd1/Gce≦1.00, preferably in the range of 0.55≦Gd1/Gce≦0.98. This ensures the wear resistance of the tire. Specifically, the lower limit allows the ground pressure in the center region of the tread portion to be dispersed, thereby improving the wear life of the tire. The above upper limit ensures the rigidity of the land portion and also ensures the 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) located 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.

Further, it is preferable that the ratio Gd1/Gce described above satisfies the following formula (8) with respect to the tire outer diameter OD [mm]. Here, Hmin=0.10, Hmax=0.60, preferably Hmin=0.12, Hmax=0.50, more preferably Hmin=0.14, Hmax=0.40.

Further, among the plurality of circumferential main grooves 21 to 23, the groove depth Gd1 [mm] of the circumferential main groove 21 closest to the tire equatorial plane CL is different from the groove depth Gd2 [mm] of the other circumferential

main grooves

22 and 23. mm], Gd3 [mm] or more (Gd2≦Gd1, Gd3≦Gd1). Specifically, when the area from the tire equatorial plane CL to the tire ground contact edge T is divided into two equal parts in the tire width direction, the groove depth of the circumferential main groove (number omitted in the figure) closest to the tire equatorial plane CL. The groove depth Gd1 is 1.00 times or more and 2.50 times or less the maximum value of the groove depths Gd2 and Gd3 of other circumferential main grooves (numerals omitted in the figure) in the area on the tire contact edge T side. It is preferably in the range of 1.01 times or more and 2.00 times or less, more preferably in the range of 1.05 times or more and 1.80 times or less. With the above lower limit, the ground contact pressure in the center region of the tread portion is dispersed, and the wear resistance performance of the tire is improved. The above upper limit suppresses uneven wear caused by an excessive ground contact pressure difference between the tread center region and the shoulder region.

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

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 radial cross belt 141 in FIG. 6) and a point Au on the radially 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 distance Hu in the tire radial direction from the tire maximum width position Ac to a point Au, and a distance Hl in the tire radial direction from the tire maximum width position Ac to a point Al are defined. In addition, a point Au' on the side profile is located at a radial position of 70% of the distance Hu from the tire maximum width position Ac, and a side is located at a radial position of 70% of the distance Hl from the tire maximum width position Ac. A point Al' on the profile is defined.

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 cross-sectional height SH [mm] (see Fig. 2). 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 ensures 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 of the bead filler 12). With the above upper limit, the amount of deflection of the tire side portion when the tire is rolling is reduced, and the rolling resistance of the tire is reduced.

The distance Hu and the distance Hl are measured with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

In addition, the sum of the distance Hu [mm] and the distance Hl [mm] is the tire outer diameter OD (Figure 1), the tire cross-sectional height SH [mm] (see Figure 2), the tire maximum width position Ac, the points Au' and It is preferable that the following formula (9) be satisfied for the radius of curvature RSc [mm] of the arc passing through the point Al'. 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 with the tire mounted on a specified rim, a specified internal pressure applied, and an unloaded state.

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 Thereby, the position of the tire maximum width position Ac in the deformable region of the tire side portion is optimized. Specifically, the lower limit alleviates stress concentration near the end of the belt ply caused by the tire maximum width position Ac being too close to the end of the belt layer 14, thereby suppressing separation of the surrounding rubber. Due to the above upper limit, stress concentration near the bead caused by the tire maximum 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 radius of curvature RSc [mm] of the arc passing through the tire maximum width position Ac, point Au' and 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. Further, the radius of curvature RSc [mm] of the circular 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 appropriately ensured. Specifically, the above lower limit reduces the amount of deflection of the tire side portion when the tire rolls, thereby reducing the rolling resistance of the tire. With the above upper limit, stress concentration caused by flattening of the tire side portion is alleviated, and the durability of the tire is improved. Particularly in small-diameter tires, large stress tends to act on the tire side portions due to use under the above-mentioned high internal pressure and high load, so there is also the issue of ensuring the side cut resistance of the tire. In this respect, the lower limit ensures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire collapse and suppressing tire side cuts. Furthermore, the above upper limit suppresses side cuts in the tire due to excessive tension in the carcass layer 13.

Further, the radius of curvature RSc [mm] of the circular arc is in the range of 0.50≦RSc/SH≦0.99 with respect to the tire cross-sectional height SH [mm], preferably 0.55≦RSc/SH≦0. It is in the range of .97.

Furthermore, it is preferable that the radius of curvature RSc [mm] of the circular arc satisfies the following formula (10) with respect to the tire outer diameter OD [mm] and the rim diameter RD [mm]. Here, Jmin=15, Jmax=360, preferably Jmin=20, Jmax=330, more preferably Jmin=25, Jmax=300.

Further, in FIG. 6, a point Bc on the main body portion 131 of the carcass layer 13 is defined at the same position in the tire radial direction as the tire maximum width position Ac. Further, a point Bu' on the main body portion 131 of the carcass layer 13 is defined at a radial position of 70% of the distance Hu described above from the tire maximum width position Ac. Further, a point Bl' on the main body portion 131 of the carcass layer 13 is defined at a radial position of 70% of the distance Hl described above from the tire maximum width position Ac.

At this time, the radius of curvature RSc [mm] of the arc passing through the tire maximum 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. Further, the radius of curvature RCc [mm] of the arc passing through point Bc, point Bu', and point 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 ensures the radius of curvature RCc of the carcass profile, the internal volume V of the tire described below, and the load capacity of the tire. With the above upper limit, the total gauges Gu and Gl of the tire side portion, which will be described later, are ensured, and the load capacity of the tire side portion is ensured.

Furthermore, it is preferable that the radius of curvature RSc [mm] of the side profile described above satisfies the following formula (11) with respect to the radius of curvature RCc [mm] of the carcass profile and the tire outer diameter OD [mm]. Here, Kmin=1 and Kmax=130, preferably Kmin=2 and Kmax=100, more preferably Kmin=3 and Kmax=70.

In addition, in FIG. 6, the total gauge Gu [mm] of the tire side portion at the point Au described above is preferably in the range of 0.010≦Gu/OD≦0.080 with respect to the tire outer diameter OD [mm]. is in the range of 0.015≦Gu/OD≦0.050. Thereby, the total gauge Gu of the radially outer region of the tire side portion is optimized. Specifically, the above lower limit ensures the total gauge Gu of the radially outer region of the tire side portion, suppresses tire deformation during use under high load, and ensures tire durability. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above-described effect of reducing the rolling resistance of the tire can be significantly achieved. The above upper limit suppresses deterioration of the rolling resistance of the tire due to the total gauge Gu becoming excessively large.

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

In addition, in FIG. 6, the total gauge Gu [mm] at the point Au mentioned above is 1.30≦Gu/Gc≦5.00 with respect to the total gauge Gc [mm] of the tire side part at the tire maximum width position Ac. within the range, preferably within the range of 1.50≦Gu/Gc≦4.00. Thereby, the gauge distribution in the tire side portion from the tire maximum width position Ac to the innermost layer of the belt layer 14 is optimized. Specifically, the lower limit ensures the total gauge Gu in the radially outer region, suppresses tire deformation during use under high load, and ensures tire durability. The above upper limit suppresses deterioration of the rolling resistance of the tire due to the total gauge Gu becoming excessively large.

Further, it is preferable that the total gauge Gu [mm] at the above point Au satisfies the following formula (12) with respect to the total gauge Gc [mm] at the tire maximum width position Ac and the tire outer diameter OD [mm]. Here, Lmin=0.10, Lmax=0.70, preferably Lmin=0.14, Lmax=0.70, more preferably Lmin=0.19, Lmax=0.70.

In addition, 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 has a relationship of 0.004≦Gc/OD≦0.050. With the above lower limit, the total gauge Gc at the tire maximum width position Ac is ensured, and the load capacity of the tire is ensured. The above upper limit ensures that the rolling resistance of the tire is reduced by thinning the total gauge Gc at the tire maximum width position Ac.

Furthermore, it is preferable that the total gauge Gc [mm] at the tire maximum width position Ac satisfies the following formula (13) 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 (14) with respect to the tire outer diameter OD [mm] and the tire total width SW [mm]. Here, Nmin=0.20, Nmax=15, preferably Nmin=0.40, Nmax=15, more preferably Nmin=0.60, Nmax=12.

Furthermore, the total gauge Gc [mm] at the tire maximum width position Ac is expressed by the following formula (15) for the radius of curvature RSc [mm] of the arc passing through the tire maximum width position Ac, points Au' and points Al'. It is preferable to satisfy the following. 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 above-mentioned point Al is in the range of 0.010≦Gl/OD≦0.150 with respect to the tire outer diameter OD, preferably 0.010≦Gl/OD≦0.150. 015≦Gl/OD≦0.100. As a result, the total gauge Gl in the radially inner region of the tire side portion is optimized. Specifically, the above lower limit ensures the total gauge Gl of the radially inner region of the tire side portion, suppresses tire deformation during use under high load, and ensures tire durability. In particular, small-diameter tires are expected to be used under high internal pressure and high load, so the above-described effect of reducing the rolling resistance of the tire can be significantly achieved. The above upper limit suppresses deterioration of the rolling resistance of the tire due to the total gauge Gl becoming excessively large.

In addition, in FIG. 6, the ratio Gl/Gc between the total gauge Gl [mm] of the tire side part at the above-mentioned point Al and the total gauge Gc [mm] of the tire side part at the tire maximum width position Ac is 1.00≦ Gl/Gc≦7.00, preferably 1.50≦Gl/Gc≦4.00. Thereby, the gauge distribution in the tire side portion from the tire maximum width position Ac to the bead core 11 is optimized. Specifically, the above lower limit ensures the total gauge Gl in the radially inner region, suppresses tire deformation during use under high load, and ensures tire durability. The above upper limit suppresses deterioration of the rolling resistance of the tire due to the total gauge Gl becoming excessively large.

Further, the total gauge Gl [mm] of the tire side portion at the above-mentioned point Al satisfies the following formula (16) with respect to the total gauge Gc [mm] at the tire maximum width position Ac and the tire outer diameter OD [mm]. It is preferable. Here, Pmin=0.12, Pmax=1.00, preferably Pmin=0.15, Pmax=1.00, more preferably Pmin=0.18, Pmax=1.00.

Further, in FIG. 6, the total gauge Gl [mm] at the above-mentioned point Al is preferably in the range of 0.50≦Gl/Gu≦5.00 with respect to the total gauge Gu [mm] at the above-mentioned point Au. is in the range of 1.00≦Gl/Gu≦3.00. As a result, the ratio between the total gauge Gl in the radially outer region of the tire side portion and the total gauge Gu in the radially inner region is optimized.

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

In addition, 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 point position of the total gauge Gl are as follows. Hsc≦Hsu<Hsl, preferably 1≦Hsu-Hsc≦18 and 2≦Hsl-Hsu≦27, more preferably 2≦Hsu-Hsc≦15 and 5≦Hsl-Hsu The relationship is ≦23. As a result, the relationship between the rubber hardness of the tire side portions 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 tire maximum width position Ac, the total gauge Gu at point Au, and the total gauge Gl at point Al. It is calculated as the sum of the product of rubber hardness and rubber hardness divided by the total gauge.

In addition, 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 for 70% of the distance Hu [mm] from the tire maximum width position Ac. It is in the range of .03≦ΔAu'/(Hu×0.70)≦0.25, preferably in the range of 0.07≦ΔAu′/(Hu×0.70)≦0.23. Thereby, the degree of curvature of the side profile in the radially outer region is optimized. Specifically, the above lower limit alleviates stress concentration caused by flattening of the tire side portion, and improves the durability performance of the tire. With the above upper limit, the amount of deflection of the tire side portion when the tire is rolling is reduced, and the rolling resistance of the tire is reduced. Particularly in small-diameter tires, large stress tends to act on the tire side portions due to use under the above-mentioned high internal pressure and high load, so there is also the issue of ensuring the side cut resistance of the tire. In this respect, the lower limit ensures the radius of curvature of the side profile and optimizes the carcass tension, thereby suppressing tire collapse and suppressing tire side cuts. Furthermore, the above upper limit suppresses side cuts in the tire due to excessive tension in the carcass layer 13.

Further, the distance ΔAl' [mm] in the tire width direction from the tire maximum width position Ac to the point Al' is 0.03≦ΔAl'/ for 70% of the distance Hl [mm] from the tire maximum width position Ac. It is in the range of (Hl×0.70)≦0.28, preferably in the range of 0.07≦ΔAl′/(Hl×0.70)≦0.20. Thereby, the degree of curvature of the side profile in the radially inner region is optimized. Specifically, the above lower limit alleviates stress concentration caused by flattening of the tire side portion, and improves the durability performance of the tire. Particularly in small-diameter tires, since the bead core 11 is reinforced as described above, stress concentration near the bead core 11 is effectively suppressed. With the above upper limit, the amount of deflection of the tire side portion when the tire is rolling is reduced, and the rolling resistance of the tire is reduced.

The distances ΔAu' and ΔAl' are measured when the tire is mounted on a specified rim, a specified internal pressure is applied, and there is no load.

Further, the distance ΔAu' [mm] in the tire width direction from the tire maximum width position Ac to the point Au' is the radius of curvature RSc [mm] of the arc passing through the tire maximum width position Ac, the point Au', and the point Al'. It is preferable that the following formula (18) be satisfied for . Here, Rmin=0.05 and Rmax=5.00, preferably Rmin=0.10 and Rmax=4.50.

In addition, in FIG. 7, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is 1 for the distance ΔAu' [mm] in the tire width direction from the tire maximum width position to point Au'. It is in the range of .00≦ΔBu'/ΔAu'≦7.00, preferably in the range of 1.10≦ΔBu'/ΔAu'≦6.00. 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 of the tire side portion is ensured by the above lower limit. The above upper limit ensures the tension of the carcass layer 13, the rigidity of the tire side parts, and the load capacity and durability of the tire.

In addition, in FIG. 7, the distance ΔBl' [mm] in the tire width direction from point Bc to point Bl' is relative to the distance ΔAl' [mm] in the tire width direction from the tire maximum width position Ac to point Al'. It is in the range of 2.00≦ΔBl'/ΔAl'≦11.0, preferably in the range of 1.90≦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 total gauge Gl of the tire side portion is ensured by the above lower limit, and the load capacity of the tire side portion is ensured. The above upper limit ensures the tension of the carcass layer 13, the rigidity of the tire side parts, and the load capacity and durability of the tire.

The distances ΔBu' and ΔBl' are measured when the tire is mounted on a specified rim, a specified internal pressure is applied, and there is no load.

Further, the distance ΔBu' [mm] in the tire width direction from point Bc to point Bu' is calculated using the following formula for the radius of curvature RCc [mm] of the arc passing through the points Bc, Bu', and Bl' mentioned above. It is preferable that (19) is satisfied. Here, Smin=0.40 and Smax=7.0, preferably Smin=0.50 and Smax=6.0.

In addition, in FIG. 7, the rubber gauge Gcr [mm] of the sidewall rubber 16 at the tire maximum width position Ac is 0.35≦Gcr/Gc≦0 with respect to the above-mentioned total gauge Gc [mm] at the tire maximum width position Ac. It is in the range of .90. Further, the rubber gauge Gcr [mm] of the sidewall rubber 16 is in the range of 1.5≦Gcr, preferably in the range of 2.0≦Gcr. With 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 tire maximum width position Ac is determined by the following formula (20 ) is preferably satisfied. Here, Tmin=80 and Tmax=0.90, preferably Tmin=120 and Tmax=0.90.

In addition, in FIG. 7, the rubber gauge Gin [mm] (not shown) of the inner liner 18 at the tire maximum width position Ac is 0.03≦Gin/Gc≦ with respect to the total gauge Gc [mm] at the tire maximum 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 a laminated structure of a carcass layer and a belt layer of the tire shown in FIG. 1. This figure shows an enlarged cross-sectional view in the tire meridian direction.

In the configuration of FIG. 1, as shown in FIG. 8, the carcass layer 13 consists of a single-layer carcass ply 13A formed by covering a carcass cord 13cc with a coated rubber 13cr, and the belt layer 14 consists of a belt cord 14bc coated with rubber. It is constructed by laminating a pair of crossed

belts

141 and 142 coated with 14cr. Further, an inner liner 18 is arranged to cover the inner peripheral surface of the carcass layer 13. However, the present invention is not limited to the above, and the carcass layer 13 may be constructed by laminating two carcass plies (see FIG. 9 described later).

In addition, in FIG. 8, the carcass ply 13A (the innermost carcass ply in a structure in which the carcass layer 13 is formed by laminating two carcass plies (not shown)) in the area between points B2 and B2 in FIG. The distance TL [mm] from the center of the outer diameter of the carcass cord 13cc to the inner surface of the tire is in the range of 0.00005≦TL/OD≦0.01000 with respect to the tire outer diameter OD [mm] (see Fig. 1). , preferably in the range of 0.00008≦TL/OD≦0.00900. Further, the distance TL [mm] is in the range of 0.00050≦TL/SW≦0.02500 with respect to the total tire width SW [mm] (see Fig. 1), preferably 0.00060≦TL/SW≦ It is in the range of 0.02300. The above lower limit appropriately suppresses air leakage, and the above upper limit suppresses an increase in tire weight. Moreover, it is preferable that the minimum value TL_min of the distance TL [mm] is 0.10≦TL_min. Further, the minimum value TL_min and maximum value TL_max of the distance TL [mm] in the area between points B2 and B2 in FIG. 4 have a relationship of 0.30≦TL_min/TL_max≦1.00, preferably 0. The relationship is .40≦TL_min/TL_max≦1.00. Thereby, the distance TL from the carcass cord 13cc to the inner surface of the tire is set uniformly in the above region.

The distance TL [mm] is defined at any measurement point in the area between the two points B2 and B2 (see FIG. 4) described above.

Also, the distance TL [mm] is 1/350000≦TL/(SW×(OD -RD))≦1/3760.

In addition, in FIG. 8, the carcass ply 13A at any point in the area between points B2 and B2 in FIG. The distance TCSU [mm] from the center of the carcass cord 13cc of the carcass ply to the outer surface of the innermost carcass ply 13A is equal to the distance TL [mm] from the center of the carcass cord 13cc of the innermost carcass ply 13A to the inner surface of the tire. On the other hand, it is in the range of 0.09≦TCSU/TL≦4.50, preferably in the range of 0.10≦TCSU/TL≦4.00. The above lower limit appropriately suppresses air leakage, and the above upper limit suppresses an increase in tire weight.

In addition, in FIG. 8, the modulus MC [MPa] of the coat rubber 13cr of the carcass ply 13A at 100 [%] elongation is the same as the modulus MIL [MPa] of the inner liner 18 at 100 [%] elongation and the innermost layer of the belt layer 14. The modulus MB [MPa] of the coating rubber 14cr of the belt ply 141 at 100 [%] elongation is in the range of MIL≦MC≦MB. Further, the ratio MC/MIL is in the range of 1.00≦MC/MIL≦5.00, preferably in the range of 1.10≦MC/MIL≦4.50. Further, the ratio MB/MC is in the range of 1.00≦MB/MC≦2.40, preferably in the range of 1.00≦MB/MC≦2.20. Further, the modulus MC [MPa] of the coat rubber 13cr of the carcass ply 13A 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 the durability of the tire is ensured.

In addition, in FIG. 8, the product of the thickness TC [mm] of the carcass ply 13A and the loss tangent tan δ of the coating rubber 13cr of the carcass ply 13A at 60 [°C] satisfies 0.05≦TC×tanδ≦0.55. preferably within the range of 0.07≦TC×tanδ≦0.50. Thereby, heat generation in the carcass layer 13 is appropriately suppressed, and the durability of the tire is ensured.

FIG. 9 is an explanatory diagram showing a modification of the laminated structure of the carcass layer 13 and belt layer 14 shown in FIG. 8.

In the configuration of FIG. 8, the carcass layer 13 is composed of the single layer carcass ply 13A as described above. For example, it is assumed that the carcass cord 13cc of the carcass ply 13A is made of inorganic fiber, particularly steel cord.

However, the present invention is not limited to this, and as shown in FIG. 9, the carcass layer 13 may have a structure in which two carcass plies 13A and 13B are laminated. For example, it is assumed that the carcass cords 13cc of the carcass plies 13A and 13B are made of organic fiber material. In addition, in this configuration, a peeling force Hpp [N /25mm] is in the range of 90≦Hpp/TCB≦300 with respect to the distance TCB [mm] 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. It is preferable that the range is 100≦Hpp/TCB≦250. Further, the peeling force Hpp [N/25mm] is in the range of 1.50≦Hpp/Ecs≦15.0, preferably 1.50≦Hpp/Ecs≦15.0 with respect to the number of installed carcass cords Ecs [pieces/50mm] of 13cc of carcass cords of the carcass ply. It is in the range of 80≦Hpp/Ecs≦10.0. This ensures the durability of the tire.

The peeling force Hpp [N/25mm] has a long rectangular shape in the extending direction of the carcass cord, 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 margin) is used, and it is calculated as the average value of the maximum and minimum peak values of the analyzed wavy curve. Further, it is preferable that the number of test samples is two or more.

FIG. 10 is an explanatory diagram showing a modification of the laminated structure of the carcass layer 13 and belt layer 14 shown in FIG. 8.

In the configuration of FIG. 1, as described above, the belt layer 14 is composed of a pair of intersecting

belts

141, 142, a belt cover 143, and a pair of belt edge covers 144, 144. Further, as shown in FIG. 8, a pair of

cross belts

141 and 142 are laminated adjacent to the outer peripheral surface of the carcass layer 13.

In contrast, in the configuration of FIG. 10, the belt layer 14 includes an additional belt 145, which is a third intersecting belt. The additional belt 145 is laminated around the outer periphery of the pair of intersecting

belts

141 and 142.

In FIG. 10, the distance Hb between the cords of adjacent belt plies among the pair of crossed

belts

141, 142 and the additional belt 145 (in FIG. 10, the distance Hb1 between the cords of the pair of crossed

belts

141, 142, and the outer diameter The inter-cord distance Hb2) of the side crossing belt 142 and the additional belt 145 is defined. At this time, the distance between cords 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 distance between cords Hb_ce (not shown) in the tire equatorial plane CL. It is preferably in the range of 1.50≦Hb_sh/Hb_ce≦1.80. Therefore, it is preferable that the inter-cord distance Hb is set large in the tread center region. The above lower limit allows the belt layer 14 to effectively suppress the tire outer diameter growth, and the above upper limit ensures the durability of the belt layer. The above configuration is realized, for example, by making the gauge of the coated rubber of the belt ply thicker in the center region of the tread portion, or by inserting an additional rubber sheet between adjacent belt plies (not shown).

[Tire radial outer area]
FIG. 11 is an enlarged view showing the tire radially outer region shown in FIG. 6. FIG.

In FIG. 11, a point An on the side profile located at a radial position of 35% of the distance Hu described above from the tire maximum width position Ac is defined. Point An corresponds to the midpoint between the tire maximum width position Ac in the tire radial direction and the above-mentioned point Au' on the side profile.

At this time, the radius of curvature RP [mm] of the circular arc passing through the tire maximum width position Ac, point Au', and point Am when the tire is mounted on the specified rim, the specified internal pressure is applied, and the tire is in an unloaded state is the cross section of the tire. The height SH [mm] (see FIG. 2) is in the range of 0.20≦RP/SH≦1.80, preferably in the range of 0.70≦RP/SH≦1.60. Further, the radius of curvature RP [mm] of the arc in the above-mentioned no-load state is in the range of 30≦RP≦250, preferably in the range of 50≦RP≦200.

For example, in the configuration of FIG. 11, the side profile has a single inflection in the area from the tire maximum width position Ac to the point Au near the end of the innermost layer 141 of the belt layer 14 (the area of the above-mentioned distance Hu). It has a gentle S-shape with a point (not shown), and from this inflection point, the area on the tire maximum width position Ac side is convex to the outside of the tire, and the area on the buttress side is convex to the inside of the tire. have. Further, the S-shaped inflection point is near the point Au' located at a radial position of 70% of the distance Hu. Therefore, the side profile has a substantially circular arc shape that is convex toward the outside of the tire in the area from the tire maximum width position Ac to the point Au'. Therefore, the arc defining the radius of curvature RP [mm] has a shape that is convex toward the outside of the tire.

In the above configuration, the radius of curvature RP of the side profile in the tire radial outer region from the tire side part to the buttress part is optimized, the tire's ground contact performance and durability are compatible, and the tire's load capacity is properly adjusted. Secured. Specifically, the above-mentioned lower limit of the ratio RP/SH reduces the amount of deflection of the tire radially outer region when the tire rolls, and prevents the ground contact length of the tread shoulder region from becoming excessively long. Thereby, the ground contact shape of the tire is optimized, and the ground contact performance (especially noise performance) of the tire is ensured. Furthermore, the above upper limit of the ratio RP/SH alleviates stress concentration caused by flattening of the tire's radially outer region, thereby improving tire durability. Particularly in small-diameter tires, since they are used under the above-mentioned high loads, the contact length of the shoulder region of the tread portion becomes long, and large stress tends to act on the tire side portions. Therefore, by employing the above configuration in a small diameter tire, the effect of improving the ground contact performance and durability performance of the tire can be significantly obtained.

In addition, in FIG. 11, the radius of curvature RP [mm] of the circular arc is in the range of 60≦RP/(SH/DW)≦290 with respect to the tire cross-sectional width DW [mm] and the tire cross-sectional height SH [mm]. It is preferably in the range of 150≦RP/(SH/DW)≦250. Thereby, the radius of curvature RP of the circular arc is optimized with respect to the aspect ratio SH/DW of the tire 1. Specifically, the above lower limit reduces the amount of deflection of the radially outer region of the tire when the tire rolls, thereby ensuring the ground contact performance of the tire. With the above upper limit, stress concentration in the tire radially outer region is alleviated, and the tire durability performance is improved.

In addition, in Fig. 11, the radius of curvature RP' [mm] of the circular arc when the tire is mounted on a specified rim, a specified internal pressure is applied, and a load of 100 [%] of the specified load is applied (dimension symbol in the figure). (omitted). That is, the tire maximum width position Ac, point Au', and point An are defined in the above-mentioned no-load state, and then the three points Ac, Au', and An are displaced by applying a load of 100% of the specified load. The radius of curvature RP' [mm] of a circular arc passing through (not shown) is defined. At this time, the radius of curvature RP' [mm] of the arc in the above-mentioned no-load state is 1.10≦RP/RP' with respect to the radius of curvature RP' [mm] of the arc under 100 [%] of the specified load. It is in the range of ≦2.80, preferably in the range of 1.15≦RP/RP'≦2.60. As a result, the radius of curvature RP' when applying a 100[%] load is optimized. Specifically, the above lower limit ensures the amount of deflection of the radially outer region of the tire when a load is applied, that is, when the load increases, and the stress concentration in the radially outer region of the tire is alleviated. The above upper limit reduces the amount of deflection of the radially outer region of the tire when the tire rolls, thereby ensuring the ground contact performance of the tire.

In addition, in Fig. 11, the radius of curvature RP'' [mm] of the circular arc when the tire is mounted on a specified rim, a specified internal pressure is applied, and a load of 150 [%] of the specified load is applied (dimension symbol in the figure). In other words, the radius of curvature RP'' [mm] of an arc passing through the three points Ac, Au', and An (not shown) displaced by the application of a load of 150% of the specified load is defined. At this time, the radius of curvature RP' [mm] of the arc when a load of 100 [%] is applied is the radius of curvature RP' [mm] of the arc when a load of 150 [%] of the specified load is applied. mm] is in the range of 1.01≦RP'/RP''≦1.50, preferably in the range of 1.05≦RP'/RP''≦1.30.Thereby, 150[%] The radius of curvature RP" when a load is applied, that is, when a high load is applied, is optimized. Specifically, the above lower limit ensures the amount of deflection of the radially outer region of the tire during use under high load, thereby relieving stress concentration in the radially outer region of the tire. The above upper limit reduces the amount of deflection of the tire radially outer region during tire rolling, that is, the amount of repeated deformation, and ensures the ground contact performance of the tire.

Furthermore, as described above, the belt layer 14 includes a pair of intersecting

belts

141 and 142 having cord angles of opposite signs (see FIG. 3). Further, the cord angle Bθ (Bθ1, Bθ2) of the pair of crossing

belts

141 and 142 is in the range of 15 [deg] or more and 55 [deg] or less in absolute value, preferably 15 [deg] or more and 35 [deg] or less. within the range of At this time, each of the cord angles Bθ [deg] of the pair of crossing

belts

141 and 142 is in the range of 1000≦Bθ×RP≦7700 with respect to the radius of curvature RP [mm] of the circular arc of the tire radial direction outer region. It is preferably in the range of 1200≦Bθ×RP≦7500. As a result, the product Bθ×RP is optimized. Specifically, the lower limit of the product Bθ×RP prevents the ground contact length of the tread shoulder region from becoming excessively long, and ensures the ground contact performance (especially noise performance) of the tire. The upper limit of the product Bθ×RP ensures the hoop effect of the intersecting

belts

141 and 142, and also relieves stress concentration in the tire radially outer region, improving tire durability.

FIG. 12 is an explanatory diagram showing the laminated structure of the carcass layer 13 and the inner liner 18 in the radially outer region of the tire shown in FIG. 11.

In FIG. 11, the foot of a perpendicular line drawn from a point Au on the side profile at the same position in the tire radial direction to the end of the innermost layer 141 of the belt layer 14 to the carcass layer 13 is defined as a point Iu. Further, the foot of a perpendicular line drawn from the tire maximum width position Ac to the carcass layer 13 is defined as a point Ic. As shown in FIG. 11, point Iu and point Ic correspond to the respective measurement positions of the total gauges Gu and Gc described above.

In FIG. 12, as described above, the carcass layer 13 is formed by covering the carcass cord 13cc with the coat rubber 13cr. Furthermore, in the configuration of FIG. 12, the carcass layer 13 is composed of a single layer carcass ply 13A. However, the present invention is not limited to this, and the carcass layer 13 may be composed of a plurality of carcass plies (see FIG. 9).

At this time, the innermost layer 13A of the carcass ply 13A (the innermost carcass ply in the structure in which the carcass layer 13 is formed by laminating two carcass plies (not shown)) in the region from point Iu to point Ic in FIG. The distance TLu [mm] (see Fig. 12) from the center of the carcass cord 13cc to the inner surface of the tire is 0.00010≦TLu/OD≦0.01500 with respect to the tire outer diameter OD [mm] (see Fig. 1). It is preferably in the range of 0.00015≦TLu/OD≦0.01200. Specifically, for example, in a configuration in which the inner liner 18 is made of a rubber composition containing butyl rubber as a main component, the ratio TLu/OD is in the range of 0.00090≦TLu/OD≦0.01500, preferably 0.00100. It is in the range of ≦TLu/OD≦0.01200. Further, when the inner liner 18 is made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer component into a thermoplastic resin, the ratio TLu/OD is in the range of 0.00010≦TLu/OD≦0.00200. , preferably in the range of 0.00015≦TLu/OD≦0.00100.

In the above configuration, the distance TLu from the carcass layer 13 to the inner surface of the tire in the region from the end of the belt layer 14 to the tire maximum width position Ac is optimized. Specifically, the lower limit ensures the distance TLu from the carcass layer 13 to the inner surface of the tire in the region where air leakage is likely to occur, thereby suppressing a decrease in tire durability performance and deterioration of rolling resistance due to air leakage. be done. Further, the above upper limit suppresses deterioration of rolling resistance due to an increase in tire weight. This achieves both tire durability and low rolling resistance. In particular, small-diameter tires are used under the above-mentioned high internal pressure and high load, so stress concentration tends to occur easily. Therefore, when the above configuration is adopted for a small diameter tire, the durability performance and low rolling resistance performance of the tire can be significantly improved.

Further, the minimum value TLu_min and maximum value TLu_max of the distance TLu [mm] (see FIG. 12) in the area from point Iu to point Ic in FIG. 11 have a relationship of 0.30≦TLu_min/TLu_max≦1.00. , preferably has a relationship of 0.40≦TLu_min/TLu_max≦1.00. In this configuration, since the distance TLu from the carcass cord 13cc to the inner surface of the tire is set uniformly in the above region, tire failure due to non-uniformity of the distance TLu is suppressed, and the risk of air leakage is reduced. Ru. Further, the distance TLu [mm] is in the range of 0.1≦TLu≦4.0, preferably in the range of 0.5≦TLu≦3.5. The lower limit ensures a distance TLu from the carcass cord 13cc to the inner surface of the tire, and air leakage is appropriately suppressed, and the upper limit suppresses deterioration of rolling resistance due to increase in tire weight.

For example, in the configuration of FIG. 11, TLu_min/TLu_max<1.00, and the position where the distance TLu takes the maximum value TLu_max is closer to the point Ic (that is, the tire maximum width position Ac side) than the position where the distance TLu takes the minimum value TLu_min. To position. Further, the position where the maximum value TLu_max is taken is in the region from point Ic to 35% of the distance Hu in FIG. 11 (that is, the region from point Ac to point An). Further, the position where the minimum value TLu_min is taken is in the area from the point Iu to 35% of the distance Hu in FIG. Further, the distance TLu monotonically increases from the position where the minimum value TLu_min is taken to the position where the maximum value TLu_max is taken.

Furthermore, the minimum value Ga_min (see FIG. 11) of the total gauge Ga [mm] of the tire side part in the area from point Iu to point Ic in FIG. 11, and the distance TLu' [mm] corresponding to the above distance TLu at the same position. (dimension symbols omitted in the figure) have a relationship of 0.05≦TLu'/Ga_min, preferably a relationship of 0.10≦TLu'/Ga_min (see FIG. 12). As a result, the distance TLu' from the carcass cord 13cc to the inner surface of the tire at the position where the total gauge Ga is thin is ensured, and air leakage is appropriately suppressed. In the configuration of FIG. 11, the total gauge Ga at the tire side portion becomes the minimum at the tire maximum width position Ac, and therefore the minimum value Ga_min matches the total gauge Gc. Further, the distance TLu' is measured at the tire maximum width position Ac where the total gauge Ga takes the minimum value Ga_min. Note that the upper limit of the ratio TLu'/Ga_min is not particularly limited, but is restricted by the upper limit of the distance TLu.

Moreover, the minimum value Ga_min of the total gauge Ga [mm] of the tire side part in the area from point Iu to point Ic in FIG. 11 and the distance TLu' [mm] corresponding to the above distance TLu at the same position are outside the tire. The diameter OD [mm] is in the range of 0.005≦(Ga_min+TLu')/OD≦0.040, preferably in the range of 0.006≦(Ga_min+TLu')/OD≦0.030. The above lower limit appropriately suppresses air leakage, and the above upper limit suppresses an increase in tire weight.

Moreover, the distance TLu [mm] in the region from point Iu to point Ic in FIG. 11 is 0.005 with respect to the oxygen permeability coefficient α [mm・cc/(m^2・day・mmHg)] The relationship is ≦(α^(1/2))/TLu≦1.800, preferably 0.008≦(α^(1/2))/TLu≦1.500. Further, the oxygen permeability coefficient α of the inner liner 18 is in the range of 0.0008≦α≦0.3500, and preferably in the range of 0.0010≦α≦0.3000. Thereby, while ensuring the crack resistance of the inner liner 18, it is possible to improve the internal pressure retention property against air leakage.

The oxygen permeability coefficient α is an index that indicates how much oxygen permeates through the material constituting the inner liner 18, and is based on JIS K 7126 at a relative temperature of 21 [°C] and a relative humidity of 50 [%]. measured.

Furthermore, the dynamic storage elastic modulus β [MPa] of the inner liner 18 is in the range of 1≦β≦200, and preferably in the range of 2≦β≦150. Thereby, while ensuring the crack resistance of the inner liner 18, it is possible to improve the internal pressure retention property against air leakage.

The dynamic storage elastic modulus β was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd. using a test piece cut into a rectangular shape with a width of 5 mm and a length of 60 mm, at a static strain of 5% and a dynamic strain of ±0. 1%, a frequency of 20 Hz, and a temperature of 60°C.

Additionally, in the inner liner 18, the ends of its constituent members are connected so as to overlap each other in order to suppress air leakage. At this time, the splice amount Is [mm] (not shown) of the inner liner 18 in the region from point Iu to point Ic in FIG. On the other hand, it is in the range of 0.010≦Is/OD≦0.100, preferably in the range of 0.015≦Is/OD≦0.080. Further, the splice amount Is [mm] of the inner liner 18 is in the range of 8≦Is≦20. The above lower limit appropriately suppresses air leakage, and the above upper limit suppresses deterioration of rolling resistance due to an increase in tire weight.

In addition, in FIG. 4, as described above, the legs of the perpendicular line drawn from the left and right tire ground contact ends T, T to the carcass layer 13 are defined as points B2, B2, respectively. Furthermore, the minimum value TL_min of the distance TL [mm] (see FIG. 8) from the center of the carcass cord 13cc of the innermost layer 13A of the carcass ply to the inner surface of the tire in the area between points B2 and B2 is defined.

At this time, the minimum value TLu_min of the distance TLu [mm] (see FIG. 12) in the region from point Iu to point Ic in FIG. 11 is the minimum value TLu_min of the distance TL [mm] in the region between points B2 and B2 in FIG. The value TL_min is in the range of 1.00≦TLu_min/TL_min, preferably in the range of 1.05≦TLu_min/TL_min. Therefore, the distance TLu in the region from point Iu to point Ic is set so that the distance from the carcass ply to the inner surface of the tire does not become relatively thin in the region where air leakage is likely to occur. As a result, the distance TL from the carcass ply to the inner surface of the tire in the region from point Iu to point Ic where air leakage is likely to occur is relatively secured, and air leakage is effectively suppressed.

[effect]
As explained above, [1] This 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 disposed on the radially outer side of the carcass layer 13. (See Figure 1). Further, the tire outer diameter OD [mm] is in the range of 200≦OD≦660, and the tire total width SW [mm] is in the range of 100≦SW≦400. Further, in a cross-sectional view in the tire meridian direction, a point Au on the side profile is defined at the same position in the tire radial direction with respect to the end of the innermost layer 141 of the belt layer 14. Further, the foot of the perpendicular line drawn from point Au to the carcass layer 13 is defined as point Iu, and the foot of the perpendicular line drawn from the tire maximum width position Ac to the carcass layer is defined as point Ic. Further, the carcass layer 13 is composed of a single layer (see FIG. 8) or a plurality of layers (see FIG. 9) of carcass ply, which is formed by covering a carcass cord 13cc with a coating rubber 13cr. Further, the distance TLu [mm] (see Fig. 12) from the center of the carcass cord 13cc of the innermost layer 13A of the carcass ply to the inner surface of the tire in the region from point Iu to point Ic is the tire outer diameter OD [mm] (see Fig. 1 ) is in the range of 0.00010≦TLu/OD≦0.01500.

This configuration has the advantage that the distance TLu from the carcass layer 13 to the inner surface of the tire in the region from the end of the belt layer 14 to the tire maximum width position Ac is optimized. Specifically, the lower limit ensures the distance TLu from the carcass layer 13 to the inner surface of the tire in the region where air leakage is likely to occur, thereby suppressing a decrease in tire durability performance and deterioration of rolling resistance due to air leakage. be done. Further, the above upper limit suppresses deterioration of rolling resistance due to an increase in tire weight. This achieves both tire durability and low rolling resistance. In particular, small-diameter tires are used under the above-mentioned high internal pressure and high load, so stress concentration tends to occur easily. Therefore, when the above configuration is adopted for a small diameter tire, the durability performance and low rolling resistance performance of the tire can be significantly improved.

[2] In this tire 1, in the tire 1 described in [1] above, the minimum value TLu_min and maximum value TLu_max of the distance TLu [mm] (see FIG. 12) in the area from point Iu to point Ic are , 0.30≦TLu_min/TLu_max≦1.00. In this configuration, since the distance TLu from the carcass cord 13cc to the inner surface of the tire is set uniformly in the above region, tire failure due to non-uniformity of the distance TLu is suppressed, and the risk of air leakage is reduced. It has the advantage of

[3] In this tire 1, in the tire 1 described in [1] or [2] above, the distance TLu [mm] in the region from point Iu to point Ic is 0.1≦TLu≦4. It is in the range of 0. The above lower limit has the advantage that the distance TLu from the carcass cord 13cc to the inner surface of the tire is ensured, and air leakage is appropriately suppressed, and the above upper limit suppresses deterioration of rolling resistance due to an increase in tire weight.

[4] In this tire 1, in the tire 1 according to any one of [1] to [3] above, the total gauge Ga [mm] of the tire side portion in the area from point Iu to point Ic is (see FIG. 11) and a distance TLu' [mm] corresponding to the distance TLu at the same position have a relationship of 0.05≦TLu'/Ga_min (see FIG. 12). This has the advantage that the distance TLu' from the carcass cord 13cc to the inner surface of the tire at the position where the total gauge Ga is thin is ensured, and air leakage is appropriately suppressed.

[5] In this tire 1, in the tire 1 described in any one of [1] to [4] above, the distance TLu [mm] in the region from point Iu to point Ic is It has a relationship of 0.005≦(α^(1/2))/TLu≦1.800 for the oxygen permeability coefficient α [mm·cc/(m^2·day·mmHg)]. This has the advantage of ensuring crack resistance of the inner liner 18 and improving internal pressure retention against air leakage.

[6] In this tire 1, in the tire 1 described in any one of the above [1] to [5], the splice amount Is [mm] of the inner liner 18 in the region from point Iu to point Ic is (not shown) is in the range of 0.01≦Is/OD≦0.10 with respect to the tire outer diameter OD [mm]. The above lower limit has the advantage of appropriately suppressing air leakage, and the above upper limit has the advantage of suppressing deterioration of rolling resistance due to an increase in tire weight.

[7] In this tire 1, in the tire 1 described in any one of the above [1] to [6], each of the legs of the perpendicular line drawn from the left and right tire ground contact ends T, T to the carcass layer 13 are defined as points B2 and B2 (see FIG. 4). Moreover, the minimum value TLu_min of the distance TLu [mm] (see FIG. 12) in the region from point Iu to point Ic is from the center of the carcass cord 13crc of the innermost layer 13A of the carcass ply in the region between points B2 and B2. The minimum value TL_min of the distance TL [mm] (see FIG. 8) to the inner surface of the tire is in the range of 1.00≦TLu_min/TL_min. This has the advantage that the distance TL from the carcass ply to the inner surface of the tire in the region from point Iu to point Ic where air leakage is likely to occur is relatively secured, and air leakage is effectively suppressed.

[8] In this tire 1, in the tire 1 according to any one of [1] to [7] above, the strength Tcs [N /50mm] is in the range of 17≦Tcs/OD≦120 with respect to the tire outer diameter OD [mm]. In such a configuration, since the load capacity of the carcass layer 13 is appropriately ensured in a small-diameter tire, there is an advantage that the tire has both durability performance and low rolling resistance performance. Specifically, the above lower limit suppresses tire deformation during use under high loads and ensures tire durability. In addition, it becomes possible to use the tire 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 loads, so the above-described tire durability and rolling resistance reduction effect can be significantly achieved. The above upper limit suppresses deterioration of rolling resistance due to increase in mass of the carcass layer.

[9] In this tire 1, in the tire 1 described in [8] above, the carcass ply of the carcass layer 13 is constructed by covering a carcass cord made of steel with a coated rubber. Further, the cord diameter φcs [mm] of the carcass cord is in the range of 0.15≦φcs≦1.10. Further, the number of carcass cords driven in Ecs [pieces/50 mm] is in the range of 25≦Ecs≦80. This has the advantage of realizing the strong Tcs of the carcass layer 13 described above.

[10] In this tire 1, in the tire 1 described in [9] above, the carcass cord is formed by twisting a plurality of strands, and the strand diameter φcss [mm] of the carcass cord is the same as that of the carcass cord. It is in the range of 0.30≦φcss/φcs≦0.90 with respect to the cord diameter φcs [mm] of the cord. This has the advantage of realizing the strong Tcs of the carcass layer 13 described above.

[11] In this tire 1, in the tire 1 described in [8] above, the carcass layer 13 is formed by laminating a pair of carcass plies 13A and 13B (see FIG. 9). Further, a pair of carcass plies 13A and 13B are constructed by covering a carcass cord 13cc made of an organic fiber material with a coat rubber 13cr. Further, the cord diameter φcs [mm] (dimension symbol in the figure is omitted) of the carcass cord 13cc is in the range of 0.60≦φcs≦0.90. Further, the driving number Ecs [pieces/50 mm] of the carcass cord 13cc is in the range of 40≦Ecs≦70. This has the advantage of realizing the strong Tcs of the carcass layer 13 described above.

[12] In this tire 1, in the tire 1 described in any one of [1] to [11] above, the total gauge Gu [mm] of the tire side portion at the point Au on the side profile is The outer diameter OD [mm] is in the range of 0.010≦Gu/OD≦0.080. This has the advantage of optimizing the total gauge Gu in the radially outer region of the tire side portion. Specifically, the above lower limit ensures the total gauge Gu of the radially outer region of the tire side portion, suppresses tire deformation during use under high load, and ensures tire durability. In particular, small-diameter tires are expected to be used under high internal pressure and high loads, so the above-mentioned tire durability performance can be significantly achieved. The above upper limit suppresses deterioration of the rolling resistance of the tire due to the total gauge Gu becoming excessively large.

FIGS. 13 to 15 are charts showing the results of performance tests on tires according to embodiments of the present invention.

In this performance test, multiple types of test tires were evaluated regarding (1) durability performance and (2) low rolling resistance performance (fuel consumption rate). Further, as an example of a small diameter tire, test tires of two types of tire sizes are used. Specifically, [A] a test tire with a tire size of 145/80R12 was assembled on a rim with a rim size of 12 x 4.00B, and [B] a test tire with a tire size of 235/45R10 was assembled on a rim with a rim size of 10. It will be done.

(1) In the evaluation of durability performance, an indoor drum testing machine with a drum diameter of 1707 mm was used, and the test tire was loaded with an internal pressure of 80% of the JATMA specified internal pressure and 88% of the JATMA specified load. will be granted. Then, at a running speed of 81 [km/h], the load was increased by 13 [%] every two hours, and the distance traveled until the tire failed was measured. Then, based on this measurement result, an index evaluation is performed using the comparative example as a standard (100). In this evaluation, the larger the numerical value, the better.

(2) In the evaluation regarding low rolling resistance performance, an internal pressure of 80 [%] of the JATMA specified internal pressure and a load of 80 [%] of the JATMA specified load are applied to the test tire. Furthermore, a four-wheeled 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 using the comparative example as a standard (100), and the larger the value, the lower the fuel consumption rate and the lower the rolling resistance, which is preferable. Moreover, if the evaluation is 98 or more, it can be said that low rolling resistance performance is appropriately ensured.

The test tires 1 to 29 of the examples were particularly equipped with the structures shown in FIGS. 1 to 3 and 8, and included a pair of

bead cores

11, 11, a carcass layer 13 consisting of a single carcass ply, and a pair of crossed belts. 141, 142, a belt layer 14 consisting of a belt cover 143 and a pair of belt edge covers 144, 144, tread rubber 15, sidewall rubber 16 and rim cushion rubber 17. Further, in the test tire of Example 1, the tire outer diameter OD was 531 [mm], the tire total width SW and the tire cross-sectional width DW were 143 [mm], and the tire cross-sectional height SH was 123 [mm]. The inner diameter of the tire is 305 [mm]. Further, the inner liner 18 is made of a rubber composition containing butyl rubber as a main component or a thermoplastic resin.

The test tire of the comparative example was the same as the test tire of Example 1, but the distance TLu [mm] from the center of the carcass cord 13cc of the innermost layer 13A of the carcass ply to the inner surface of the tire in the region from point Iu to point Ic (see FIG. 12) ) is set small.

As shown by the test results, it can be seen that the test tires of Examples achieve both tire durability performance and low rolling resistance performance.

1 Tire; 10 Rim; 11 Bead core; 12 Bead filler; 13 Carcass layer; 131 Main body; 132 Winding portion; 14 Belt layer; 141, 142 Cross belt; 143 Belt cover; 144 Belt edge cover; 15 Tread rubber; Tread; 152 Undertread; 16 Sidewall rubber; 17 Rim cushion rubber; 18 Inner liner; 21-23 Circumferential main groove

Claims

comprising a pair of bead cores, a carcass layer spanning the bead cores, a belt layer disposed on the radially outer side of the carcass layer, and an inner liner disposed on the inner surface of 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,
In a cross-sectional view in the tire meridian direction, 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 is defined, and a perpendicular line drawn from the point Au to the carcass layer is defined. The foot is defined as a point Iu, the foot of a perpendicular line drawn from the tire maximum width position Ac to the carcass layer is defined as a point Ic,
The carcass layer is composed of a single layer or a plurality of carcass plies formed by covering a carcass cord with a coated rubber, and
The distance TLu [mm] from the center of the carcass cord of the innermost layer of the carcass ply to the inner surface of the tire in the region from point Iu to point Ic is 0.00010≦TLu/OD with respect to the tire outer diameter OD [mm]. A tire characterized in that it is in the range of ≦0.01500.
The tire according to claim 1, wherein a minimum value TLu_min and a maximum value TLu_max of the distance TLu [mm] in the region from point Iu to point Ic have a relationship of 0.30≦TLu_min/TLu_max≦1.00.
The tire according to claim 1, wherein a distance TLu [mm] in the region from point Iu to point Ic is in a range of 0.1≦TLu≦4.0.
The minimum value Ga_min of the total gauge Ga [mm] of the tire side portion in the area from point Iu to point Ic and the distance TLu' [mm] corresponding to the distance TLu at the same position are 0.05≦TLu' The tire according to claim 1, having a relationship of /Ga_min.
The distance TLu [mm] in the region from point Iu to point Ic is 0.005≦(α^ The tire according to claim 1, having a relationship of (1/2))/TLu≦1.800.
Claim 1: The splice amount Is [mm] of the inner liner in the region from point Iu to point Ic is in a range of 0.01≦Is/OD≦0.10 with respect to tire outer diameter OD [mm]. Tires listed in.
The legs of the perpendicular line drawn from the left and right tire ground contact ends to the carcass layer are defined as points B2 and B2, and,
The minimum value TLu_min of the distance TLu [mm] in the region from point Iu to point Ic is the distance TL[ from the center of the carcass cord of the innermost layer of the carcass ply to the inner surface of the tire in the region between points B2 and B2. The tire according to claim 1, wherein the minimum value TL_min of [mm] is in the range of 1.00≦TLu_min/TL_min.
According to claim 1, the strength Tcs [N/50mm] per width 50 [mm] of the carcass ply constituting the carcass layer is in the range of 17≦Tcs/OD≦120 with respect to the tire outer diameter OD [mm]. Tires listed.
The carcass ply of the carcass layer is constructed by covering a carcass cord made of steel with a coated rubber,
The cord diameter φcs [mm] of the carcass cord is in the range of 0.15≦φcs≦1.10, and
The tire according to claim 8, wherein the number of carcass cords (Ecs/50 mm) is in the range of 25≦Ecs≦80.
The carcass cord is formed by twisting a plurality of wires, and the wire diameter φcss [mm] of the carcass cord is 0.30≦φcss/φcs with respect to the cord diameter φcs [mm] of the carcass cord. The tire according to claim 9, which is in the range ≦0.90.
The carcass layer is formed by laminating a pair of carcass plies,
The pair of carcass plies are constructed by covering a carcass cord made of organic fiber material with a coated rubber,
The cord diameter φcs [mm] of the carcass cord is in the range of 0.60≦φcs≦0.90, and
The tire according to claim 8, wherein the number of carcass cords (Ecs/50 mm) is in the range of 40≦Ecs≦70.
According to claim 1, the total gauge Gu [mm] of the tire side portion at the point Au on the side profile is in the range of 0.010≦Gu/OD≦0.080 with respect to the tire outer diameter OD [mm]. tires.