JP2021091366A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire configured so that rolling resistance of the tire can be reduced during travelling under a low temperature atmosphere while suppressing variation in fuel consumption performance of the tire due to change in atmospheric temperature.SOLUTION: A pneumatic tire 1 comprises: a pair of bead fillers 12 and 12 arranged outside in a radial direction of bead cores 11 and 11; a carcass layer 13 hung across the bead cores 11 and 11; a belt layer 14 arranged outside in the radial direction of the carcass layer 13; a tread rubber 15 constituted of a cap tread 151 and an under tread 152 and arranged outside in the radial direction of the belt layer 14; and a pair of side wall rubbers 16 and 16 arranged outside in a tire width direction of the carcass layer 13. A tanδ value T20_ut at 20[°C] and a tanδ value T60_ut at 60[°C] of the under tread 152 satisfy a condition as shown by relational expressions: 0.50≤T20_ut/T60_ut≤1.55 and T20_ut≤0.15.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of reducing the rolling resistance of the tire during traveling in a low temperature atmosphere while suppressing fluctuations in the fuel efficiency of the tire due to a change in atmospheric temperature. ..

Focusing on the fact that the tire temperature of a conventional pneumatic tire is about 60 [° C] when running in a room temperature atmosphere, the tan δ value (loss tangent) of the tread rubber at 60 [° C] should be set low. This reduces the rolling resistance of the tire. At the same time, the wet performance of the tire is ensured by setting a high tan δ value of the tread rubber (particularly the cap rubber constituting the tire contact patch) at 0 [° C.].

However, the above configuration has a problem that the rolling resistance of the tire during traveling in a low temperature atmosphere is deteriorated. As a conventional pneumatic tire for such a problem, the technique described in Patent Document 1 is known.

Japanese Patent No. 5998310

On the other hand, when the atmospheric temperature during running changes due to seasonal changes or the like, the rolling resistance of the tire also changes. Therefore, there is a problem that the fuel efficiency of the tire fluctuates due to the change in the atmospheric temperature.

Therefore, the present invention has been made in view of the above, and it is possible to reduce the rolling resistance of the tire during running in a low temperature atmosphere while suppressing the fluctuation of the fuel efficiency performance of the tire due to the change in the atmospheric temperature. The purpose is to provide pneumatic tires.

In order to achieve the above object, the pneumatic tire according to the present invention includes a pair of bead cores, a pair of bead fillers arranged radially outside the bead core, a carcass layer bridged over the bead core, and the carcass. A belt layer arranged on the radial outer side of the layer, a tread rubber composed of a cap tread and an under tread and arranged on the radial outer side of the belt layer, and a pair of tread rubbers arranged on the tire width outer side of the carcass layer. A pneumatic tire including a sidewall rubber and a pair of rim cushion rubbers arranged radially inside the pair of bead cores, at tan δ values T20_ut and 60 [° C.] of the under tread at 20 [° C.]. The tanδ value T60_ut satisfies the conditions of 0.50 ≦ T20_ut / T60_ut ≦ 1.55 and T20_ut ≦ 0.15.

In the pneumatic tire according to the present invention, (1) the ratio T20 / T60 of the tan δ value T20 at 20 [° C.] and the tan δ value T60 at 60 [° C.] of the under tread is optimized, so that the rolling resistance in a low temperature atmosphere is optimized. The difference between the rolling resistance and the rolling resistance in a normal temperature atmosphere can be reduced. Further, (2) When the tan δ value T20 at 20 [° C.] of the under tread is in the above range, the rolling resistance in a low temperature atmosphere is reduced. This has the advantage of reducing the rolling resistance of the tire during traveling in a low temperature atmosphere while suppressing fluctuations in the fuel efficiency of the tire due to changes in the atmospheric temperature.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a bead portion of the pneumatic tire shown in FIG. FIG. 3 is an enlarged view showing a tread portion of the pneumatic tire shown in FIG. FIG. 4 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include those that are replaceable and self-explanatory while maintaining the identity of the invention. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

[Pneumatic tires]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. Further, the figure shows a radial tire for a passenger car as an example of a pneumatic tire.

In the figure, the cross section in the tire meridian direction is defined as the cross section when the tire is cut on a plane including the tire rotation axis (not shown). Further, the tire equatorial plane CL is defined as a plane that passes through the midpoint of the measurement point of the tire cross-sectional width defined by JATTA 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, the point P is the tire maximum width position.

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

The pair of bead cores 11 and 11 are formed by winding one or a plurality of bead wires made of steel in an annular shape and in a plurality of manners, and are embedded in the bead portions to form cores of the left and right bead portions. The pair of bead fillers 12 and 12 are arranged on the outer periphery of the pair of bead cores 11 and 11 in the tire radial direction to reinforce the bead portion.

The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. To configure. Further, both ends of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. Further, the carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with coated rubber and rolling them. It has a cord angle of 100 [deg] or less (defined as an inclination angle of the carcass cord in the longitudinal direction with respect to the tire circumferential direction).

In the configuration of FIG. 1, the carcass layer 13 has a single layer structure composed of a single carcass ply. However, the present invention is not limited to this, and the carcass layer 13 may have a multilayer structure in which two or more carcass plies are laminated (not shown).

Further, in the configuration of FIG. 1, the carcass layer 13 has a structure continuous in the tire width direction, intersects the tire equatorial plane CL, and extends to the left and right regions of the tire. However, the present invention is not limited to this, and the carcass layer 13 may have a structure (so-called carcass division structure) in which the carcass layer 13 is composed of a pair of left and right carcass plies, has a divided portion in the tread portion, and is separated in the tire width direction. abridgement).

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is arranged so as to be hung around the outer circumference of the carcass layer 13. The belt plies 141 to 144 include a pair of intersecting belts 141 and 142, and a belt cover 143 and a belt edge cover 144.

The pair of crossing belts 141 and 142 are formed by coating a plurality of belt cords made of steel or an organic fiber material with coated rubber and rolling them, and have a cord angle of 15 [deg] or more and 55 [deg] or less in absolute value. Have. Further, the pair of crossing belts 141 and 142 have cord angles having different signs (defined as inclination angles in the longitudinal direction of the belt cord with respect to the tire circumferential direction), and the longitudinal directions of the belt cords intersect each other. (So-called cross-ply structure). Further, the pair of crossing belts 141 and 142 are laminated and arranged on the outer side of the carcass layer 13 in the tire radial direction.

The belt cover 143 and the belt edge cover 144 are formed by coating a belt cover cord made of steel or an organic fiber material with a coated rubber, and have a cord angle of 0 [deg] or more and 10 [deg] or less in absolute value. Further, the belt cover 143 and the belt edge cover 144 are strip materials formed by coating one or a plurality of belt cover cords with coated rubber, and the strip materials are applied to the outer peripheral surfaces of the cross belts 141 and 142. It is configured by winding it in a spiral shape multiple times in the tire circumferential direction. Further, the belt cover 143 is arranged so as to cover the entire area of the crossing belts 141 and 142, and the pair of belt edge covers 144 and 144 are arranged so as to cover the left and right edge portions of the crossing belts 141 and 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 to form a tread portion of the tire. Further, the tread rubber 15 includes a cap tread 151 and an under tread 152. The cap tread 151 is made of a rubber material having excellent ground contact characteristics and weather resistance, and is exposed to the tread surface over the entire area of the tire ground contact surface to form the outer surface of the tread portion. The under tread 152 is made of a rubber material having higher heat resistance than the cap tread 151, and is sandwiched and arranged between the cap tread 151 and the belt layer 14 to form a base portion of the tread rubber 15.

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

The pair of rim cushion rubbers 17 and 17 extend from the inside in the tire radial direction to the outside in the tire width direction of the rewinding portions of the left and right bead cores 11 and 11 and the carcass layer 13 to form a rim fitting surface of the bead portion. For example, in the configuration of FIG. 1, the outer end portion 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. ing.

The inner liner 18 is an air permeation prevention layer that is arranged on the inner surface of the tire and covers the carcass layer 13, suppresses oxidation due to exposure of the carcass layer 13, and prevents leakage of air filled in the tire. Further, the inner liner 18 is composed of, for example, a rubber composition containing butyl rubber as a main component, a thermoplastic resin, a thermoplastic elastomer composition in which an elastomer component is blended in the thermoplastic resin, and the like.

[Characteristics of tire rubber member]
In the pneumatic tire 1, each rubber member constituting the tire casing has the following configuration in order to reduce rolling resistance in a normal temperature atmosphere and a low temperature atmosphere while ensuring the wet performance of the tire.

First, the tan δ value T0_ct at 0 [° C.] and the tan δ value T60_ct at 60 [° C.] of the cap tread 151 have a relationship of 2.00 ≦ T0_ct / T60_ct ≦ 4.38, and 3.00 ≦ T0_ct / T60_ct ≦. It is preferable to have a relationship of 4.35, and it is more preferable to have a relationship of 3.10 ≦ T0_ct / T60_ct ≦ 4.31. As a result, the temperature dependence of the fuel efficiency performance of the tire can be reduced while improving the wet performance of the tire.

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

The tan δ value at 0 [° C.] is an index related to tire performance when traveling on a wet road surface. Further, the tan δ value at 20 [° C.] is an index assuming the tire temperature during running at an atmospheric temperature of about 10 [° C.], and the tan δ value at 60 [° C.] is an atmospheric temperature of about 25 [° C.]. It is an index that assumes the tire temperature when driving in. Further, the ratio of these tan δ values is an index of the temperature dependence of the rubber member.

Further, the tan δ value T20_ct at 20 [° C.] and the tan δ value T60_ct at 60 [° C.] of the cap tread 151 have a relationship of 1.60 ≦ T20_ct / T60_ct ≦ 1.90, and 1.70 ≦ T20_ct / T60_ct ≦. It is preferable to have a relationship of 1.80. As a result, the difference between the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere is reduced, and the temperature dependence of the fuel efficiency performance of the tire is reduced.

Further, the tan δ value T0_ct at 0 [° C.] of the cap tread 151 is in the range of T0_ct ≦ 0.75. Further, the tan δ value T20_ct of the cap tread at 20 [° C.] is in the range of T20_ct ≦ 0.48. Further, the tan δ value T60_ct of the cap tread at 60 [° C.] is in the range of T60_ct ≦ 0.38. As a result, rolling resistance in a low temperature atmosphere and a high temperature atmosphere is reduced while improving the wet performance of the tire. The lower limits of T0_ct, T20_ct and T60_ct are not particularly limited and are preferably closer to 0, but are restricted by the above ratio conditions.

Further, the rubber hardness Hs_ct of the cap tread 151 at 20 [° C.] is in the range of 50 ≦ Hs_ct ≦ 75. Further, the modulus of the cap tread 151 when stretched by 100 [%] is in the range of 1.0 [MPa] ≤ E'_ct ≤ 3.5 [MPa].

Rubber hardness is measured according to JIS K6253.

The modulus 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).

Further, the tan δ value T20 at 20 [° C.] and the tan δ value T60 at 60 [° C.] of the rubber member other than the cap tread 151 constituting the tire casing have a relationship of 0.50 ≦ T20 / T60 ≦ 2.00. , 0.65 ≦ T20 / T60 ≦ 1.55, and more preferably 0.80 ≦ T20 / T60 ≦ 1.50.

Specifically, as the rubber member, at least one of the bead filler 12, the under tread 152 of the tread rubber 15, the sidewall rubber 16 and the rim cushion rubber 17 satisfies the above conditions. Detailed conditions for these rubber members will be described later. Further, for example, the bead wire coated rubber of the bead core 11, the carcass cord coated rubber of the carcass layer 13, and the belt cord coated rubber of the belt layer 14 may satisfy the above conditions.

In the above configuration, the ratio T20 / T60 of the tan δ value T20 at 20 [° C.] and the tan δ value T60 at 60 [° C.] of the rubber member is optimized, so that the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere are optimized. The difference with can be reduced. As a result, fluctuations in the fuel efficiency of the tire due to changes in the atmospheric temperature (for example, seasonal changes) can be suppressed.

Further, the tan δ value T20 of the rubber member at 20 [° C.] is preferably in the range of T20 ≦ 0.22 and preferably in the range of T20 ≦ 0.15. Further, the tan δ value T60 of the rubber member at 60 [° C.] is in the range of T60 ≦ 0.17. The lower limit of T20 and T60 is not particularly limited and is preferably closer to 0, but is restricted by the above ratio conditions. This reduces rolling resistance in a low temperature atmosphere.

[Characteristics of bead filler]
Further, the tan δ value T20_bf at 20 [° C.] and the tan δ value T60_bf at 60 [° C.] of the bead filler 12 have a relationship of 0.90 ≦ T20_bf / T60_bf ≦ 1.05, and 0.91 ≦ T20_bf / T60_bf ≦. It is preferable to have a relationship of 1.04, and more preferably to have a relationship of 0.92 ≦ T20_bf / T60_bf ≦ 1.03. As a result, the difference between the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere can be reduced.

Further, the tan δ value T20_bf of the bead filler 12 at 20 [° C.] is preferably in the range of T20_bf ≦ 0.18, preferably in the range of T20_bf ≦ 0.17, and preferably in the range of T20_bf ≦ 0.16. More preferred. Further, the tan δ value T60_bf of the bead filler 12 at 60 [° C.] is in the range of T60_bf ≦ 0.20. This reduces rolling resistance in low temperature and high temperature atmospheres. The lower limits of T20_bf and T60_bf are not particularly limited and are preferably closer to 0, but are restricted by the above ratio conditions.

Further, the tan δ value T20_bf at 20 [° C.] of the bead filler 12 has a relationship of T20_ct × T20_bf ≦ 0.040 with respect to the tan δ value T20_ct at 20 [° C.] of the cap tread 151, and T20_ct × T20_bf ≦ 0. It is preferable to have a relationship of 039. As a result, rolling resistance in a low temperature atmosphere can be appropriately reduced.

Further, the tan δ value T60_bf at 60 [° C.] of the bead filler 12 has a relationship of T60_ct × T60_bf ≦ 0.030 with respect to the tan δ value T60_ct at 60 [° C.] of the cap tread 151, and T60_ct × T60_bf ≦ 0. It is preferable to have a relationship of 028, and more preferably to have a relationship of T60_ct × T60_bf ≦ 0.026. As a result, the rolling resistance in a normal temperature atmosphere is optimized.

Further, the ratio T20_bf / T60_bf of the bead filler 12 to the tan δ value T20_bf at 20 [° C.] and the tan δ value T60_bf at 60 [° C.] is the tan δ value T20_ct at 20 [° C.] and tan δ at 60 [° C.] of the cap tread 151. It has a relationship of 0.40 ≦ (T20_bf / T60_bf) / (T20_ct / T60_ct) ≦ 0.60 with respect to the ratio T20_ct / T60_ct with the value T60_ct, and 0.45 ≦ (T20_bf / T60_bf) / (T20_ct / T60_ct). ) ≤ 0.55. In such a configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set smaller than that of the rubber member located on the rim fitting surface side, so that the deformation and vibration of the rubber member during tire rolling are caused by the tire contact patch. Efficiently decays from to the rim mating surface. As a result, the energy consumption of the tire as a whole is reduced regardless of the atmospheric temperature during traveling, and the rolling resistance of the tire is reduced.

Further, the rubber hardness Hs_bf of the bead filler 12 at 20 [° C.] is in the range of 70 ≦ Hs_bf ≦ 97. Further, the modulus of the bead filler 12 when stretched at 100 [%] is in the range of 1.0 [MPa] ≤ E'_bf ≤ 13.0 [MPa].

Further, the rubber hardness Hs_bf of the bead filler 12 at 20 [° C.] has a relationship of 25 ≦ Hs_bf−Hs_ct ≦ 30 with respect to the rubber hardness Hs_ct of the cap tread 151 at 20 [° C.]. In such a configuration, the relationship between the rubber hardness of the bead filler 12 and the cap tread 151 is optimized, and the transmission efficiency and responsiveness of the steering force from the bead portion to the tire contact patch are improved. As a result, the steering stability performance of the tire is improved.

FIG. 2 is an enlarged view showing a bead portion of the pneumatic tire 1 shown in FIG. In the figure, the region A1 from the top surface of the bead core 11 to the distance of the cross-sectional height H1 of the bead core 11 is defined.

At this time, the maximum gauge Ga_bf of the bead filler 12 in the region A1 and the tan δ value T20_bf of the bead filler 12 at 20 [° C.] have a relationship of Ga_bf × T20_bf ≦ 0.90, and Ga_bf × T20_bf ≦ 0.80. It is preferable to have the relationship of. Further, the maximum gauge Ga_bf of the bead filler 12 has a relationship of 0.90 ≦ Ga_bf / W1 ≦ 1.10. With respect to the maximum width W1 of the bead core 11. As a result, the energy consumption of the bead filler 12 when the tire rolls is reduced, and the rolling resistance in a low temperature atmosphere can be reduced.

The maximum gauge Ga_bf of the bead filler 12 is measured as the maximum thickness in the tire width direction when the tire is mounted on a specified rim to apply a specified internal pressure and a no-load state is applied.

The specified rim means a "standard rim" specified by JATMA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The specified internal pressure means the "maximum air pressure" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. The specified load means the "maximum load capacity" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATTA, in the case of a passenger car tire, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity at the specified internal pressure.

Further, in FIG. 1, the height H2 of the bead filler 12 has a relationship of 0.15 ≦ H2 / SH ≦ 0.21 with respect to the tire cross-sectional height SH, and 0.18 ≦ H2 / SH ≦ 0. It is more preferable to have a relationship of 20. Further, at this time, the winding height H3 of the carcass layer 13 preferably has a relationship of 0.15 ≦ H3 / SH with respect to the tire cross-sectional height SH, and has a relationship of 0.17 ≦ H3 / SH. Is more preferable, and it is further preferable to have a relationship of 0.19 ≦ H3 / SH.

The height H2 of the bead filler 12 is measured as the extending length of the bead filler 12 in the tire radial direction.

The hoisting height H3 of the carcass layer 13 is measured as the distance in the tire radial direction from the innermost point in the radial direction of the bead core 11 to the outermost point in the radial direction of the hoisting portion of the carcass layer 13.

[Characteristics of under tread]
Further, the tan δ value T20_ut at 20 [° C.] and the tan δ value T60_ut at 60 [° C.] of the under tread 152 have a relationship of 0.50 ≦ T20_ut / T60_ut ≦ 1.55, and 0.75 ≦ T20_ut / T60_ut ≦. It is preferable to have a relationship of 1.50, and more preferably to have a relationship of 0.80 ≦ T20_ut / T60_ut ≦ 1.45. As a result, the difference between the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere can be reduced.

Further, the tan δ value T20_ut of the under tread 152 at 20 [° C.] is preferably in the range of T20_ut ≦ 0.15 and preferably in the range of T20_ut ≦ 0.07. Further, it is preferable that the tan δ value T60_ut of the under tread 152 at 60 [° C.] is in the range of T60_ut ≦ 0.30 and in the range of T60_ut ≦ 0.15. This reduces rolling resistance in low temperature and high temperature atmospheres. The lower limits of T20_ut and T60_ut are not particularly limited and are preferably closer to 0, but are restricted by the above ratio conditions.

Further, the tan δ value T20_ut at 20 [° C.] of the under tread 152 has a relationship of T0_ct × T20_ut ≦ 0.050 with respect to the tan δ value T0_ct at 0 [° C.] of the cap tread 151, and T0_ct × T20_ut ≦ 0. It is preferable to have a relationship of 050. As a result, rolling resistance in a low temperature atmosphere can be appropriately reduced.

Regarding the product of the tan δ values, according to the temperature distribution inside the tire when the tire rolls, the temperature of the cap tread 151 in contact with the road surface tends to be lower than the temperature of the under tread 152. Therefore, by using the tan δ value at a relatively low temperature for the cap tread 151, the influence of the tan δ value on the rolling resistance in a low temperature atmosphere can be appropriately evaluated.

Further, the tan δ value T60_ut at 60 [° C.] of the under tread 152 has a relationship of T40_ct × T60_ut ≦ 0.024 with respect to the tan δ value T40_ct at 40 [° C.] of the cap tread 151, and T40_ct × T60_ut ≦ 0. It is preferable to have a relationship of 020, and more preferably to have a relationship of T40_ct × T60_ut ≦ 0.015. As a result, rolling resistance in a high temperature atmosphere can be appropriately reduced.

Further, the ratio T20_ut / T60_ut of the under tread 152 to the tan δ value T20_ut at 20 [° C] and the tan δ value T60_ut at 60 [° C] is the tan δ value T20_ct at 20 [° C] of the cap tread 151 and tan δ at 60 [° C]. It has a relationship of 0.75 ≦ (T20_ut / T60_ut) / (T20_ct / T60_ct) ≦ 1.00 with respect to the ratio T20_ct / T60_ct with the value T60_ct, and 0.78 ≦ (T20_ut / T60_ut) / (T20_ct / T60_ct). ) ≤ 0.95.

In the above configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set smaller than that of the rubber member located on the rim fitting surface side, so that the deformation and vibration of the rubber member during tire rolling are caused by the tire contact. Efficiently damps from the ground towards the rim mating surface. As a result, the energy consumption of the tire as a whole is reduced regardless of the atmospheric temperature during traveling, and the rolling resistance of the tire is reduced.

Further, the rubber hardness Hs_ut of the under tread 152 at 20 [° C.] is in the range of 55 ≦ Hs_ut ≦ 65. Further, the modulus of the undertread 152 at 100 [%] extension is in the range of 1.5 [MPa] ≤ E'_ut ≤ 3.0 [MPa].

Further, the rubber hardness Hs_ut of the under tread 152 at 20 [° C.] has a relationship of 1 ≦ Hs_ct-Hs_ut ≦ 10 with respect to the rubber hardness Hs_ct of the cap tread 151, and a relationship of 3 ≦ Hs_ct-Hs_ut ≦ 8. It is preferable to have a relationship of 4 ≦ Hs_ct−Hs_ut ≦ 7. In such a configuration, since the cap tread 151 is harder than the under tread 152, the steering stability of the tire is improved, the road surface followability of the under tread 152 is improved, and the wet performance of the tire is improved.

Further, in FIG. 1, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridian direction have a relationship of 0.11 ≦ S_ut / (S_ct + S_ut) ≦ 0.50 and are 0. It is preferable to have a relationship of .13 ≦ S_ut / (S_ct + S_ut) ≦ 0.45, and it is preferable to have a relationship of 0.15 ≦ S_ut / (S_ct + S_ut) ≦ 0.40. By the above lower limit, the volume of the under tread 152 having a relatively small tan δ value is secured, and the above-mentioned rolling resistance reducing action is ensured. There is an advantage that the rolling resistance of the tire is reduced. With the above upper limit, the volume of the hard cap tread 151 is secured, and the above-mentioned effect of improving the steering stability performance of the tire is ensured.

The cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 are calculated as average values over the entire circumference of the tire.

Further, in FIG. 1, the maximum width Wb2 of the widest crossing belt 141, the maximum width Wct of the cap tread 151, and the maximum width Wut of the undertread 152 among the crossing belts 141 and 142 constituting the belt layer 14 are 15 [mm]. ] ≤Wct-Wb2≤30 [mm] and Wb2 <Wut <Wct. With the above upper limit, the maximum width Wb2 of the cross belt 142 is secured, and the rolling resistance of the tire is reduced. Further, the durability of the tire is ensured by the above-mentioned magnitude relation Wb2 <Wut <Wct.

The maximum width Wb2 of the cross belt 142, the maximum width Wct of the cap tread 151, and the maximum width Wut of the under tread 152 are measured as a no-load state while applying a specified internal pressure by mounting the tire on a specified rim.

FIG. 3 is an enlarged view showing a tread portion of the pneumatic tire 1 shown in FIG. In the figure, a virtual line L1 that passes through the end of the widest crossing belt 141 among the crossing belts 141 and 142 constituting the belt layer 14 and is perpendicular to the carcass layer 13 is defined.

At this time, the gauge Ga_ct of the cap tread 151 and the gauge Ga_ut of the under tread 152 on the virtual line L1 have a relationship of 0.20 ≦ Ga_ut / Ga_ct ≦ 0.40. By the above lower limit, the volume of the under tread 152 having a relatively small tan δ value is secured, and the above-mentioned rolling resistance reducing action is ensured. With the above upper limit, the volume of the hard cap tread 151 is secured, and the above-mentioned effect of improving the steering stability performance of the tire is ensured.

Further, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridional direction and the tan δ value T0_ct of the cap tread 151 at 0 [° C.] are 0.20 ≦ {S_ct / (S_ct + S_ut). )} × T0_ct ≦ 0.60, and 0.30 ≦ {S_ct / (S_ct + S_ut)} × T0_ct ≦ 0.58. By the above lower limit, the volume of the cap tread 151 is secured, and the above-mentioned effect of improving the steering stability performance of the tire is ensured. With the above upper limit, deterioration of rolling resistance due to an excessive volume or tan δ value of the cap tread 151 is suppressed.

Further, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridian direction and the tan δ value T20_ut of the under tread at 20 [° C.] are 0.01 ≦ {S_ut / (S_ct + S_ut). } It is preferable that the condition of × T20_ut ≦ 0.60 is satisfied and the condition of 0.01 ≦ {S_ut / (S_ct + S_ut)} × T20_ut ≦ 0.05 is satisfied. By the above upper limit, the road surface followability of the under tread 152 is ensured, the above-mentioned effect of improving the wet performance of the tire is ensured, and the tire maneuvering due to the excessive volume of the relatively soft under tread 152 is ensured. Deterioration of stability performance is suppressed.

[Characteristics of sidewall rubber]
Further, the tan δ value T20_sw at 20 [° C.] and the tan δ value T60_sw at 60 [° C.] of the sidewall rubber 16 have a relationship of 0.50 ≦ T20_sw / T60_sw ≦ 1.50, and 0.75 ≦ T20_sw / T60_sw. It is preferable to have a relationship of ≦ 1.45, and more preferably to have a relationship of 0.80 ≦ T20_sw / T60_sw ≦ 1.40. As a result, the difference between the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere can be reduced.

Further, the tan δ value T20_sw at 20 [° C.] of the sidewall rubber 16 is preferably in the range of T20_sw ≦ 0.11 and preferably in the range of T20_sw ≦ 0.10. Further, the tan δ value T60_sw at 60 [° C.] of the sidewall rubber 16 is in the range of T60_sw ≦ 0.22. This reduces rolling resistance in low temperature and high temperature atmospheres. The lower limits of T20_sw and T60_sw are not particularly limited and are preferably closer to 0, but are restricted by the above ratio conditions.

Further, the tan δ value T20_sw at 20 [° C.] of the sidewall rubber 16 has a relationship of T0_ct × T20_sw ≦ 0.070 with respect to the tan δ value T0_ct at 0 [° C.] of the cap tread 151, and T0_ct × T20_sw ≦ 0. It is preferable to have a relationship of .65, and more preferably to have a relationship of T0_ct × T20_sw ≦ 0.60. As a result, rolling resistance in a low temperature atmosphere can be appropriately reduced.

Regarding the product of the tan δ values, according to the temperature distribution inside the tire when the tire rolls, the temperature of the cap tread 151 in contact with the road surface tends to be lower than the temperature of the sidewall rubber 16. Therefore, by using the tan δ value at a relatively low temperature for the cap tread 151, the influence of the tan δ value on the rolling resistance in a low temperature atmosphere can be appropriately evaluated.

Further, the tan δ value T60_sw at 60 [° C.] of the sidewall rubber 16 has a relationship of T40_ct × T60_sw ≦ 0.024 with respect to the tan δ value T40_ct at 40 [° C.] of the cap tread 151, and T40_ct × T60_sw ≦ 0. It is preferable to have a relationship of .21, and it is more preferable to have a relationship of T40_ct × T60_sw ≦ 0.18. As a result, rolling resistance in a high temperature atmosphere can be appropriately reduced.

Further, the ratio T20_sw / T60_sw of the sidewall rubber 16 between the tan δ value T20_sw at 20 [° C.] and the tan δ value T60_sw at 60 [° C.] is the tan δ value T20_ct and 60 [° C.] of the cap tread 151 at 20 [° C.]. There is a relationship of 0.70 ≦ (T20_sw / T60_sw) / (T20_ct / T60_ct) ≦ 0.90 with respect to the ratio T20_ct / T60_ct with the tan δ value T60_ct, and 0.75 ≦ (T20_sw / T60_sw) / (T20_ct /). It is preferable to have a relationship of T60_ct) ≦ 0.85. In such a configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set smaller than that of the rubber member located on the rim fitting surface side, so that the deformation and vibration of the rubber member during tire rolling are caused by the tire contact patch. Efficiently decays from to the rim mating surface. As a result, the energy consumption of the tire as a whole is reduced regardless of the atmospheric temperature during traveling, and the rolling resistance of the tire is reduced.

Further, the ratio T20_sw / T60_sw of the sidewall rubber 16 to the tan δ value T20_sw at 20 [° C.] and the tan δ value T60_sw at 60 [° C.] is the tan δ value T20_bf and 60 [° C.] of the bead filler 12 at 20 [° C.]. It has a relationship of 0.62 ≦ (T20_bf / T60_bf) / (T20_sw / T60_sw) ≦ 0.72 with respect to the ratio T20_bf / T60_bf with the tan δ value T60_bf, and 1.40 ≦ (T20_sw / T60_sw) / (T20_bf / It is preferable to have a relationship of T60_bf) ≦ 1.60. This reduces the rolling resistance of the tire.

Further, the ratio T20_sw / T60_sw of the sidewall rubber 16 to the tan δ value T20_sw at 20 [° C.] and the tan δ value T60_sw at 60 [° C.] is the tan δ value T20_ut and 60 [° C.] of the under tread 152 at 20 [° C.]. It has a relationship of 0.90 ≦ (T20_ut / T60_ut) / (T20_ut / T60_ut) ≦ 1.10 with respect to the ratio T20_ut / T60_ut with the tan δ value T60_ut, and 0.95 ≦ (T20_sw / T60_sw) / (T20_ut /). It is preferable to have a relationship of T60_ut) ≦ 1.05. This reduces the rolling resistance of the tire.

Further, the rubber hardness Hs_sw of the sidewall rubber 16 at 20 [° C.] is in the range of 50 ≦ Hs_sw ≦ 60. Further, the modulus of the sidewall rubber 16 when stretched by 100 [%] is in the range of 1.0 [MPa] ≤ E'_sw ≤ 2.5 [MPa].

Further, the rubber hardness Hs_sw of the sidewall rubber 16 at 20 [° C.] has a relationship of 1 ≦ Hs_ct−Hs_sw ≦ 10 with respect to the rubber hardness Hs_ct of the cap tread 151 at 20 [° C.], and 3 ≦ Hs_ct. It is preferable to have a relationship of −Hs_sw ≦ 8, and it is more preferable to have a relationship of 4 ≦ Hs_ct −Hs_sw ≦ 7. In such a configuration, the relationship between the rubber hardness of the sidewall rubber 16 and the cap tread 151 is optimized, and the transmission efficiency and responsiveness of the steering force from the rim fitting surface to the tire contact patch are improved. As a result, the steering stability performance of the tire is improved.

Further, the rubber hardness Hs_sw of the sidewall rubber 16 at 20 [° C.] has a relationship of 35≤Hs_bf-Hs_sw≤40 with respect to the rubber hardness Hs_bf of the bead filler 12 at 20 [° C.], and 36≤Hs_bf. It is preferable to have a relationship of −Hs_sw ≦ 39. As a result, the steering stability performance of the tire is improved.

Further, in FIG. 1, a region A2 of 50 [%] of the tire cross-sectional height centered on the tire maximum width position P is defined.

At this time, the minimum thickness Ga_sw of the sidewall rubber 16 in the region A2 (see FIG. 2) and the tan δ value T20_sw at 20 [° C.] of the sidewall rubber 16 have a relationship of Ga_sw × T20_sw ≦ 0.25. , Ga_sw × T20_sw ≦ 0.23, and more preferably Ga_sw × T20_sw ≦ 0.21. As a result, the energy consumption of the sidewall rubber 16 when the tire rolls is reduced, and the rolling resistance in a low temperature atmosphere can be reduced. Further, the minimum thickness Ga_sw of the sidewall rubber 16 is in the range of 1.5 [mm] ≤ Ga_sw ≤ 3.5 [mm].

Further, the overlap amount La between the tread rubber 15 (specifically, at least one of the cap tread 151 and the under tread 152) and the sidewall rubber 16 is in the range of 30 [mm] ≤ La ≤ 60 [mm]. is there. The above lower limit suppresses the separation of the tread rubber, and the above upper limit suppresses the increase in rolling resistance due to excessive distortion of the shoulder portion when the tire rolls.

The overlap amount La is measured as a length along the inner peripheral surface of the tire.

[Characteristics of rim cushion rubber]
Further, the tan δ value T20_rc at 20 [° C.] and the tan δ value T60_rc at 60 [° C.] of the rim cushion rubber 17 have a relationship of 0.70 ≦ T20_rc / T60_rc ≦ 1.30, and 0.80 ≦ T20_rc / T60_rc. It is preferable to have a relationship of ≦ 1.25, and more preferably to have a relationship of 0.90 ≦ T20_rc / T60_rc ≦ 1.20. As a result, the difference between the rolling resistance in a low temperature atmosphere and the rolling resistance in a normal temperature atmosphere can be reduced.

Further, the tan δ value T20_rc of the rim cushion rubber 17 at 20 [° C.] is preferably in the range of T20_rc ≦ 0.22, preferably in the range of T20_rc ≦ 21, and more preferably in the range of T20_rc ≦ 21. Further, the tan δ value T60_rc of the rim cushion rubber 17 at 60 [° C.] is in the range of T60_rc ≦ 0.31. This reduces rolling resistance in low temperature and high temperature atmospheres. The lower limits of T20_rc and T60_rc are not particularly limited and are preferably closer to 0, but are restricted by the above ratio conditions.

Further, the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 has a relationship of T20_ct × T20_rc ≦ 0.070 with respect to the tan δ value T20_ct at 20 [° C.] of the cap tread 151, and T20_ct × T20_rc ≦ 0. It is preferable to have a relationship of .060. The above product is an index of rolling resistance in a low temperature atmosphere.

Further, the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 has a relationship of T20_bf × T20_rc ≦ 0.050 with respect to the tan δ value T20_bf at 20 [° C.] of the bead filler 12, and T20_bf × T20_rc ≦ 0. It is preferable to have a relationship of .040. As a result, rolling resistance in a low temperature atmosphere can be appropriately reduced.

Further, the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 has a relationship of T20_ct × T20_sw ≦ 0.06 with respect to the tan δ value T20_sw at 60 [° C.] of the sidewall rubber 16, and T20_ct × T20_sw ≦ It is preferable to have a relationship of 0.05. The above product is an index of rolling resistance in a low temperature atmosphere.

Further, the tan δ value T60_rc at 60 [° C.] of the rim cushion rubber 17 has a relationship of T60_ct × T60_rc ≦ 0.030 with respect to the tan δ value T60_ct at 60 [° C.] of the cap tread 151, and T60_ct × T60_rc ≦ 0. It is preferable to have a relationship of .27, and more preferably to have a relationship of T60_ct × T60_rc ≦ 0.25. As a result, rolling resistance in a high temperature atmosphere can be appropriately reduced.

Further, the tan δ value T60_rc at 60 [° C.] of the rim cushion rubber 17 has a relationship of T60_bf × T60_rc ≦ 0.040 with respect to the tan δ value T60_bf at 60 [° C.] of the bead filler 12, and T60_bf × T60_rc ≦ 0. It is preferable to have a relationship of .030. As a result, rolling resistance in a high temperature atmosphere can be appropriately reduced.

Further, the tan δ value T60_rc at 60 [° C.] of the rim cushion rubber 17 has a relationship of T60_sw × T60_rc ≦ 0.030 with respect to the tan δ value T60_sw at 60 [° C.] of the sidewall rubber 16, and T60_sw × T60_rc ≦ It is preferable to have a relationship of 0.020. The above product is an index of rolling resistance in a low temperature atmosphere.

Further, the ratio T20_rc / T60_rc of the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 to the tan δ value T60_rc at 60 [° C.] is the tan δ value T20_ct and 60 [° C.] of the cap tread 151 at 20 [° C.]. There is a relationship of 0.55 ≦ (T20_rc / T60_rc) / (T20_ct / T60_ct) ≦ 0.85 with respect to the ratio T20_ct / T60_ct with the tan δ value T60_ct, and 0.65 ≦ (T20_rc / T60_rc) / (T20_ct / It is preferable to have a relationship of T60_ct) ≦ 0.75.

In the above configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set smaller than that of the rubber member located on the rim fitting surface side, so that the deformation and vibration of the rubber member during tire rolling are caused by the tire contact. Efficiently damps from the ground towards the rim mating surface. As a result, the energy consumption of the tire as a whole is reduced regardless of the atmospheric temperature during traveling, and the rolling resistance of the tire is reduced.

Further, the ratio T20_rc / T60_rc of the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 to the tan δ value T60_rc at 60 [° C.] is the tan δ value T20_bf and 60 [° C.] of the bead filler 12 at 20 [° C.]. It has a relationship of 1.00 ≦ (T20_rc / T60_rc) / (T20_bf / T60_bf) ≦ 1.40 with respect to the ratio T20_bf / T60_bf with the tanδ value T60_bf, and 1.02 ≦ (T20_rc / T60_rc) / (T20_bf / It is preferable to have a relationship of T60_bf) ≦ 1.38, and more preferably to have a relationship of 1.04 ≦ (T20_rc / T60_rc) / (T20_bf / T60_bf) ≦ 1.36.

In the above configuration, the rubber members forming from the tire side portion to the bead portion have the same temperature dependence, so that the deformation and vibration of the rubber member during tire rolling are directed from the tire contact patch to the rim fitting surface. Efficiently attenuates. As a result, the energy consumption of the tire as a whole is reduced regardless of the atmospheric temperature during traveling, and the rolling resistance of the tire is reduced.

Further, the ratio T20_rc / T60_rc of the tan δ value T20_rc at 20 [° C.] of the rim cushion rubber 17 to the tan δ value T60_rc at 60 [° C.] is the tan δ value T20_sw and 60 [° C.] at 20 [° C.] of the sidewall rubber 16. There is a relationship of 0.85 ≦ (T20_rc / T60_rc) / (T20_sw / T60_sw) ≦ 1.15 with respect to the ratio T20_sw / T60_sw with the tan δ value T60_sw, and 0.85 ≦ (T20_rc / T60_rc) / (T20_sw). / T60_sw) ≦ 1.00 is preferable. This reduces the rolling resistance of the tire.

Further, the rubber hardness Hs_rc of the rim cushion rubber 17 at 20 [° C.] is in the range of 65 ≦ Hs_rc ≦ 75. Further, the modulus of the rim cushion rubber 17 when stretched by 100 [%] is in the range of 3.5 [MPa] ≤ E'_rc ≤ 6.0 [MPa].

Further, the rubber hardness Hs_rc of the rim cushion rubber 17 at 20 [° C.] has a relationship of 7 ≦ Hs_rc-Hs_ct ≦ 11 with respect to the rubber hardness Hs_ct of the cap tread 151 at 20 [° C.], and 8 ≦ Hs_rc. It is preferable to have a relationship of -Hs_ct ≦ 10. In such a configuration, the relationship between the rubber hardness of the rim cushion rubber 17 and the cap tread 151 is optimized, and the transmission efficiency and responsiveness of the steering force from the rim fitting surface to the tire contact patch are improved. As a result, the steering stability performance of the tire is improved.

Further, the rubber hardness Hs_rc of the rim cushion rubber 17 at 20 [° C.] has a relationship of 18 ≦ Hs_bf-Hs_rc ≦ 21 with respect to the rubber hardness Hs_bf of the bead filler 12 at 20 [° C.], and 19 ≦ Hs_bf. It is preferable to have a relationship of -Hs_rc ≦ 21. In such a configuration, the relationship between the rubber hardness of the bead filler 12 and the rim cushion rubber 17 adjacent to each other in the tire width direction is optimized, and the bead portion is continuously deformed in the tire width direction when the vehicle turns. As a result, the steering stability performance of the tire is improved.

Further, the rubber hardness Hs_rc of the rim cushion rubber 17 at 20 [° C.] has a relationship of 17 ≦ Hs_rc-Hs_sw ≦ 20 with respect to the rubber hardness Hs_sw of the sidewall rubber 16 at 20 [° C.], and 18 ≦ It is preferable to have a relationship of Hs_rc-Hs_sw ≦ 19. In such a configuration, the relationship between the rubber hardness of the sidewall rubber 16 and the rim cushion rubber 17 constituting the tire side portion from the bead portion is optimized, and the tire side portion is continuously deformed in the tire width direction when the vehicle turns. Become a target. As a result, the steering stability performance of the tire is improved.

Further, in FIG. 2, a virtual line L2 parallel to the tire rotation axis at a distance of the cross-sectional height H1 of the bead core 11 from the top surface of the bead core 11 is defined.

At this time, the gauge Ga_rc of the rim cushion rubber 17 on the virtual line L2 and the tan δ value T20_rc of the rim cushion rubber 17 at 20 [° C.] have a relationship of Ga_rc × T20_rc ≦ 0.80, and Ga_rc × T20_rc ≦ It is preferable to have a relationship of 0.70. Further, the gauge Ga_rc of the rim cushion rubber 17 is in the range of 3.5 [mm] ≤ Ga_rc ≤ 4.5 [mm]. As a result, the energy consumption of the rim cushion rubber 17 when the tire rolls is reduced, and the rolling resistance in a low temperature atmosphere can be reduced.

[effect]
As described above, the pneumatic tire 1 is bridged over a pair of bead cores 11 and 11, a pair of bead fillers 12 and 12 arranged radially outside the bead cores 11 and 11, and bead cores 11 and 13. The carcass layer 13, the belt layer 14 arranged on the radial outer side of the carcass layer 13, the tread rubber 15 composed of the cap tread 151 and the under tread 152 and arranged on the radial outer side of the belt layer 14, and the carcass layer. A pair of sidewall rubbers 16 and 16 arranged on the outer side in the tire width direction of the tire 13 and a pair of rim cushion rubbers 17 and 17 arranged on the inner side in the radial direction of the bead cores 11 and 11 are provided (see FIG. 1). Further, the tan δ value T20_ut at 20 [° C.] and the tan δ value T60_ut at 60 [° C.] of the under tread 152 satisfy the conditions of 0.50 ≦ T20_ut / T60_ut ≦ 1.55 and T20_ut ≦ 0.15.

In such a configuration, (1) the ratio T20 / T60 of the tan δ value T20 at 20 [° C.] and the tan δ value T60 at 60 [° C.] of the under tread 152 is optimized, so that rolling resistance in a low temperature atmosphere and a normal temperature atmosphere The difference from the rolling resistance can be reduced. Further, (2) When the tan δ value T20 of the under tread 152 at 20 [° C.] is in the above range, the rolling resistance in a low temperature atmosphere is reduced. This has the advantage of reducing the rolling resistance of the tire during traveling in a low temperature atmosphere while suppressing fluctuations in the fuel efficiency of the tire due to changes in the atmospheric temperature.

Further, in the pneumatic tire 1, the tan δ value T20_ut at 20 [° C.] of the under tread 152 has a relationship of T0_ct × T20_ut ≦ 0.050 with respect to the tan δ value T0_ct at 0 [° C.] of the cap tread 151. This has the advantage that the rolling resistance in a low temperature atmosphere can be appropriately reduced.

Further, in the pneumatic tire 1, the tan δ value T60_ut at 60 [° C.] of the under tread 152 has a relationship of T40_ct × T60_ut ≦ 0.024 with respect to the tan δ value T40_ct at 40 [° C.] of the cap tread 151. This has the advantage that the rolling resistance in a high temperature atmosphere can be appropriately reduced.

Further, in this pneumatic tire 1, the ratio T20_ut / T60_ut of the tan δ value T20_ut at 20 [° C.] of the under tread 152 to the tan δ value T60_ut at 60 [° C.] is the tan δ value T20_ct at 20 [° C.] of the cap tread 151. It has a relationship of 0.70 ≦ (T20_ut / T60_ut) / (T20_ct / T60_ct) ≦ 0.90 with respect to the ratio T20_ct / T60_ct with the tan δ value T60_ct at 60 [° C.]. In such a configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set to be smaller than that of the rubber member located on the tire inner surface side, so that deformation and vibration of the rubber member during tire rolling are caused from the tire contact patch to the rim. Efficiently damps towards the mating surface. This has the advantage that the energy consumption of the tire as a whole is reduced and the rolling resistance of the tire is reduced regardless of the atmospheric temperature during traveling.

Further, the ratio T20_ut / T60_ut of the under tread 152 to the tan δ value T20_ut at 20 [° C.] and the tan δ value T60_ut at 60 [° C.] is the tan δ value T20_sw and 60 [° C.] at 20 [° C.] of the sidewall rubber 16. It has a relationship of 0.90 ≦ (T20_sw / T60_sw) / (T20_ut / T60_ut) ≦ 1.10 with respect to the ratio T20_sw / T60_sw with the tanδ value T60_sw. In such a configuration, the tan δ ratio of the rubber member located on the tire contact patch side is set to be smaller than that of the rubber member located on the tire inner surface side, so that deformation and vibration of the rubber member during tire rolling are caused from the tire contact patch to the rim. Efficiently damps towards the mating surface. This has the advantage that the energy consumption of the tire as a whole is reduced and the rolling resistance of the tire is reduced regardless of the atmospheric temperature during traveling.

Further, in the pneumatic tire 1, the rubber hardness Hs_ut of the under tread 152 at 20 [° C.] has a relationship of 1 ≦ Hs_ct−Hs_ut ≦ 10 with respect to the rubber hardness Hs_ct of the cap tread 151 at 20 [° C.]. Have. In such a configuration, since the cap tread 151 is harder than the under tread 152, there is an advantage that the steering stability of the tire is improved, the road surface followability of the under tread 152 is improved, and the wet performance of the tire is improved.

Further, in the pneumatic tire 1, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridian direction have a relationship of 0.11 ≦ S_ut / (S_ct + S_ut) ≦ 0.50. .. The above lower limit has the advantage that the volume of the under tread 152 having a relatively small tan δ value is secured, and the rolling resistance of the tire is reduced. With the above upper limit, the volume of the hard cap tread 151 is secured, and there is an advantage that the above-mentioned effect of improving the steering stability performance of the tire is ensured.

Further, in the pneumatic tire 1, the maximum width Wb2 of the widest crossing belt 141 among the crossing belts 141 and 142 constituting the belt layer 14, the maximum width Wct of the cap tread 151, and the maximum width Wut of the under tread 152 (FIG. 1) satisfies the conditions of 15 [mm] ≤ Wct-Wb2 ≤ 30 [mm] and Wb2 <Wut <Wct. The lower limit of the difference Wct-Wb2 has an advantage that the separation of the tread rubber 15 is suppressed, and the upper limit has an advantage that the maximum width Wb2 of the cross belt 142 is secured and the rolling resistance of the tire is reduced. Further, there is an advantage that the durability of the tire is ensured by the above-mentioned magnitude relation Wb2 <Wut <Wct.

Further, in the pneumatic tire 1, in a cross-sectional view in the tire meridian direction, a virtual line passing through the end of the widest crossing belt 141 among the crossing belts 141 and 142 constituting the belt layer 14 and perpendicular to the carcass layer 13. L1 is defined (see FIG. 3), and the gauge Ga_ct of the cap tread 151 and the gauge Ga_ut of the undertread 152 on the virtual line L1 have a relationship of 0.20 ≦ Ga_ut / Ga_ct ≦ 0.35. With the above lower limit, there is an advantage that the volume of the under tread 152 having a relatively small tan δ value is secured, and the above-mentioned rolling resistance reducing action is ensured. With the above upper limit, the volume of the hard cap tread 151 is secured, and there is an advantage that the above-mentioned effect of improving the steering stability performance of the tire is secured.

Further, in the pneumatic tire 1, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridian direction and the tan δ value T0_ct of the cap tread 151 at 0 [° C.] are 0. The condition of 20 ≦ {S_ct / (S_ct + S_ut)} × T0_ct ≦ 0.60 is satisfied. With the above lower limit, the volume of the cap tread 151 is secured, and there is an advantage that the above-mentioned effect of improving the steering stability performance of the tire is ensured. The above upper limit has an advantage that deterioration of rolling resistance due to an excessive volume or tan δ value of the cap tread 151 is suppressed.

Further, in the pneumatic tire 1, the cross-sectional area S_ct of the cap tread 151 and the cross-sectional area S_ut of the under tread 152 in the cross-sectional view in the tire meridian direction and the tan δ value T20_ut of the under tread 152 at 20 [° C.] are 0. The condition of 01 ≦ {S_ut / (S_ct + S_ut)} × T20_ut ≦ 0.60 is satisfied. With the above lower limit, there is an advantage that the volume of the under tread 152 having a relatively small tan δ value is secured, and the above-mentioned rolling resistance reducing action is ensured. The above upper limit has the advantage that the road surface followability of the under tread 152 is ensured and the effect of improving the wet performance of the tire is ensured, and the volume of the relatively soft under tread 152 becomes excessive. There is an advantage that deterioration of steering stability performance of tires is suppressed.

Further, in the pneumatic tire 1, the tan δ value T0_ct at 0 [° C.] and the tan δ value T60_ct at 60 [° C.] of the cap tread 151 have a relationship of 2.00 ≦ T0_ct / T60_ct ≦ 4.38. This has the advantage that the temperature dependence of the fuel efficiency performance of the tire can be reduced while improving the wet performance of the tire.

Further, in the pneumatic tire 1, the tan δ value T0_ct at 0 [° C.] of the cap tread 151 is in the range of T0_ct ≦ 0.75. This has the advantage of improving the wet performance of the tire.

FIG. 4 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

In this performance test, a plurality of types of test tires were evaluated for (1) rolling resistance, (2) wet performance, and (3) steering stability performance. Further, a test tire having a tire size of 195 / 65R15 is used.

(1) In the evaluation of rolling resistance, a drum tester with a drum diameter of 1707 [mm] was used, and an internal pressure of 180 [kPa] and a load of 88 [%] of the maximum load capacity specified in JATTA were applied to the test tire. Then, the rolling resistance coefficient of the test tire was measured under the condition of a speed of 80 [km / h]. The room temperature rolling resistance is a measured value at an atmospheric temperature of 25 [° C.], and the low temperature rolling resistance is a measured value at an atmospheric temperature of 10 [° C.]. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

(2) In the evaluation of wet performance, the test tires were mounted on the front and rear wheels of the test vehicle having a displacement of 1800 [cc] and a front-wheel drive vehicle, and the air pressures of the test tires were 250 [kPa] (front wheels) and 240 [kPa] ( (Rear wheel) is given. Then, the test vehicle traveled on a test course composed of an asphalt road surface having a water depth of 2 [mm], and the braking distance from a speed of 100 [km / h] was measured. Then, based on the measurement result, an index evaluation is performed using the conventional example as a reference (100). The larger the value, the more preferable this evaluation.

(3) In the evaluation of steering stability performance, the test tires were mounted on the front and rear wheels of the test vehicle having a displacement of 1800 [cc] and a front-wheel drive vehicle, and the air pressures of the test tires were 250 [kPa] (front wheels) and 240 [kPa]. (Rear wheel) is given. Then, the test vehicle travels three laps while changing lanes on a test course on a dry road surface of one lap 2 [km], and a sensory evaluation is performed by a test driver. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

The test tires of the conventional example and the embodiment have the configuration shown in FIG. 1, and each rubber member constituting the tire casing has a predetermined physical property.

As the test results show, it can be seen that in the test tires of the examples, the rolling resistance of the tires is reduced, and the wet performance and steering stability performance of the tires are improved.

1 Pneumatic tires; 11 bead cores; 12 bead fillers; 13 carcass layers; 14 belt layers; 141, 142 cross belts; 143 belt covers; 144 belt edge covers; 15 tread rubber; 151 cap treads; 152 under treads; 16 sidewalls Rubber; 17 Rim cushion rubber; 18 Inner liner

Claims (13)

A pair of bead cores, a pair of bead fillers arranged radially outside the bead core, a carcass layer spanning the bead core, a belt layer arranged radially outside the carcass layer, a cap tread, and the like. A tread rubber composed of an under tread and arranged radially outside the belt layer, a pair of sidewall rubbers arranged outside the carcass layer in the tire width direction, and a pair of bead cores arranged radially inside. Pneumatic tires with a pair of tread rubber
Air characterized in that the tan δ value T20_ut at 20 [° C.] and the tan δ value T60_ut at 60 [° C.] of the under tread satisfy the conditions of 0.50 ≦ T20_ut / T60_ut ≦ 1.55 and T20_ut ≦ 0.15. Tires with. The pneumatic tire according to claim 1, wherein the tan δ value T20_ut at 20 [° C.] of the under tread has a relationship of T0_ct × T20_ut ≦ 0.050 with respect to the tan δ value T0_ct at 0 [° C.] of the cap tread. The air-filled product according to claim 1 or 2, wherein the tan δ value T60_ut at 60 [° C.] of the under tread has a relationship of T40_ct × T60_ut ≦ 0.024 with respect to the tan δ value T40_ct at 40 [° C.] of the cap tread. tire. The ratio T20_ut / T60_ut of the under tread to the tan δ value T20_ut at 20 [° C] and the tan δ value T60_ut at 60 [° C] is the tan δ value T20_ct at 20 [° C] and the tan δ value T60_ct at 60 [° C] of the cap tread. The pneumatic tire according to any one of claims 1 to 3, which has a relationship of 0.70 ≦ (T20_ut / T60_ut) / (T20_ct / T60_ct) ≦ 0.90 with respect to T20_ct / T60_ct. The ratio T20_ut / T60_ut of the under tread to the tan δ value T20_ut at 20 [° C.] and the tan δ value T60_ut at 60 [° C.] is the tan δ value T20_sw at 20 [° C.] and the tan δ value at 60 [° C.] of the sidewall rubber. The pneumatic tire according to any one of claims 1 to 4, which has a relationship of 0.90 ≦ (T20_sw / T60_sw) / (T20_ut / T60_ut) ≦ 1.10 with respect to the ratio T20_sw / T60_sw to T60_sw. Any of claims 1 to 5, wherein the rubber hardness Hs_ut of the undertread at 20 [° C.] has a relationship of 1 ≦ Hs_ct−Hs_ut ≦ 10 with respect to the rubber hardness Hs_ct of the cap tread at 20 [° C.]. Pneumatic tires listed in one. Any one of claims 1 to 6 in which the cross-sectional area S_ct of the cap tread and the cross-sectional area S_ut of the under tread in a cross-sectional view in the tire meridian direction have a relationship of 0.11 ≦ S_ut / (S_ct + S_ut) ≦ 0.50. Pneumatic tires listed in one. The maximum width Wb2 of the widest crossing belt among the crossing belts constituting the belt layer, the maximum width Wct of the cap tread, and the maximum width Wut of the undertread are 15 [mm] ≤ Wct-Wb2 ≤ 30 [mm]. And the pneumatic tire according to any one of claims 1 to 7, which satisfies the condition of Wb2 <Wut <Wct. In the cross-sectional view in the tire meridian direction, a virtual line L1 that passes through the end of the widest crossing belt among the crossing belts constituting the belt layer and is perpendicular to the carcass layer is defined.
The air-filled device according to any one of claims 1 to 8, wherein the cap tread gauge Ga_ct and the under tread gauge Ga_ut on the virtual line L1 have a relationship of 0.20 ≦ Ga_ut / Ga_ct ≦ 0.35. tire. The cross-sectional area S_ct of the cap tread and the cross-sectional area S_ut of the under tread in the cross-sectional view in the tire meridional direction and the tan δ value T0_ct of the cap tread at 0 [° C.] are 0.20 ≦ {S_ct / (S_ct + S_ut)}. The pneumatic tire according to any one of claims 1 to 9, which satisfies the condition of × T0_ct ≦ 0.60. The cross-sectional area S_ct of the cap tread and the cross-sectional area S_ut of the under tread in the cross-sectional view in the tire meridian direction and the tan δ value T20_ut of the under tread at 20 [° C.] are 0.01 ≦ {S_ut / (S_ct + S_ut)}. The pneumatic tire according to any one of claims 1 to 10, which satisfies the condition of × T20_ut ≦ 0.60. The invention according to any one of claims 1 to 11, wherein the tan δ value T0_ct at 0 [° C.] and the tan δ value T60_ct at 60 [° C.] of the cap tread have a relationship of 2.00 ≦ T0_ct / T60_ct ≦ 4.38. Pneumatic tires. The pneumatic tire according to any one of claims 1 to 12, wherein the tan δ value T0_ct of the cap tread at 0 [° C.] is in the range of T0_ct ≦ 0.75.

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