JP7448773B2 - pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

For example, Patent Document 1 discloses a pneumatic tire in which the tread portion is composed of undertread rubber and cap rubber having different rubber hardnesses.

Patent No. 3822324

In the tread structure, if the rubber hardness of the tread is lowered in order to improve the noise performance of reducing road noise, there is a concern that the steering stability performance will deteriorate. In addition, in height vehicles with higher ceilings than general passenger cars, there is a high requirement to prevent the vehicle from wandering, and of the steering stability, straight-line stability performance is particularly important, but on the other hand, Ride comfort performance is also considered important.

An object of the present invention is to provide a pneumatic tire that can improve rolling resistance and ride comfort while ensuring straight-line stability performance.

In order to achieve the above object, a pneumatic tire according to one aspect of the present invention includes a carcass layer, a pair of intersecting belts disposed on the radially outer side of the carcass layer, cap tread rubber, and undertread rubber. a pair of shoulder main grooves formed on the outermost side of the tread surface in the tire width direction, and at least one center main groove between the shoulder main grooves; A pneumatic tire comprising: a pair of shoulder land portions defined on the outside in the tire width direction of the shoulder main groove; and at least two center land portions defined in the shoulder main groove and the center main groove. , the average gauge Ga_ce of the undertread rubber on the tire equatorial plane or the inner center land portion closest to the tire equatorial plane, and the average gauge Ga_c of the undertread rubber on at least one other outer center land portion, Ga_ce The ground contact width W_ce on the inner center land portion and the ground contact width W_c on at least one outer center land portion have the relationship W_ce>W_c.

According to the present invention, the pneumatic tire has a ground contact width on the tire equatorial plane where the ground contact length in the tire circumferential direction is longest when the tread surface makes contact with the ground, or at the inner center land portion closest to the tire equatorial plane. Wider than the ground contact width of the tread surface on one outer center land portion. Therefore, the rigidity of the inner center land portion can be ensured. Further, in this pneumatic tire, the average gauge of the at least one outer center land portion of the undertread rubber is thicker than the average gauge of the inner center land portion. Therefore, rolling resistance, which leads to low fuel consumption, can be reduced and ride comfort performance can be improved. However, if the average gauge of the undertread rubber in the center land area is thickened, the rigidity of the land area will decrease, and there is a concern that straight running stability performance will deteriorate. Then, the average gauge of the undertread rubber is made relatively thin to ensure straight-line stability performance. On the other hand, in at least one outer center land area, the average gauge of the undertread rubber is made relatively thick to reduce input from the road surface, thereby ensuring ride comfort performance. As a result, this pneumatic tire can improve rolling resistance and ride comfort while ensuring straight-line stability performance.

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 a plan view showing the tread surface of the pneumatic tire shown in FIG. 1. FIG. FIG. 3 is an enlarged view showing the tread portion of the pneumatic tire shown in FIG. 1. FIG. FIG. 4 is an enlarged view showing the tread portion of the pneumatic tire shown in FIG. 1. FIG. FIG. 5 is an enlarged view showing the tread portion of the pneumatic tire shown in FIG. 1. FIG. FIG. 6 is a schematic diagram showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 7 is a schematic diagram showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 8 is a schematic diagram showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 9 is a schematic diagram showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 10 is a schematic diagram showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 11 is a chart showing the results of a performance test of the pneumatic tire according to the embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS Below, embodiments of a pneumatic tire according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited to this embodiment. Further, the components of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within the range obvious to 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 the present embodiment. This 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.

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). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire cross-sectional width measurement points specified in JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as a direction parallel to the tire rotation axis. The inner side in the tire width direction refers to the side facing the tire equatorial plane CL in the tire width direction, and the outer side in the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire radial direction is defined as the direction perpendicular to the tire rotation axis. The tire radially inner side refers to the side facing the tire rotation axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotation axis in the tire radial direction. Moreover, point T is the tire ground contact edge.

The pneumatic tire 1 has an annular structure centered on the tire rotation axis, and as shown in FIG. 1, includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, and a belt layer 14, tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17.

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 constitute the cores of the left and right bead portions. The pair of bead fillers 12, 12 are respectively arranged along the tire circumferential direction outside the pair of bead cores 11, 11 in the tire radial direction, and reinforce the bead portion.

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 stretched 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 rolling a plurality of carcass cords made of steel or organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with coated rubber, and has a width of 80 degrees or more and 100 degrees or less. (defined as the inclination angle of the carcass cord in the longitudinal direction with respect to the tire circumferential direction).

For example, in the configuration shown in FIG. 1, the carcass layer 13 has a single-layer structure consisting of a single carcass ply, and the wound portion 132 extends along the outer circumferential surface of the main body portion 131 and is connected to the belt layer 14. They overlap in the tire width direction. Further, the terminal end of the turned-up portion 132 of the carcass layer 13 is located on the outer side in the tire width direction than shoulder main grooves 21 and 24, which will be described later.

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is arranged around the outer periphery of the carcass layer 13. Belt plies 141 to 144 include a pair of crossing belts 141 and 142, a belt cover 143, and a belt edge cover 144.

The pair of crossed belts 141 and 142 are constructed by covering a plurality of belt cords made of steel or organic fiber material with a coated rubber and rolling them, and have a cord angle of 15 degrees or more and 55 degrees or less in absolute value. Further, the pair of crossing belts 141 and 142 have cord angles of opposite signs (defined as an inclination angle in the longitudinal direction of the belt cords with respect to the tire circumferential direction), and the longitudinal direction of the belt cords crosses 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 belt edge cover 144 are constructed by covering a belt cover cord made of steel or an organic fiber material with a coated rubber, and have a cord angle of 0 degrees or more and 10 degrees or less in absolute value. 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 to constitute a tread portion of the tire. Further, the tread rubber 15 includes a cap tread rubber 151 and an undertread rubber 152. Details of the tread rubber 15 will be described later.

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. For example, in the configuration shown in FIG. 1, the outer end of the sidewall rubber 16 in the tire radial direction is disposed below 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 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 (not shown).

The pair of rim cushion rubbers 17, 17 extend in the tire radial direction on the outside 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.

The inner liner 18 is an air permeation prevention layer disposed on the inner cavity surface of the tire to cover 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. The inner liner 18 is made of, for example, a rubber composition containing butyl rubber as a main component, a thermoplastic resin, a thermoplastic elastomer composition obtained by blending an elastomer component into the thermoplastic resin, or the like.

[Tread pattern]
FIG. 2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. 1. FIG. The figure shows a tread surface 15a of a summer tire. The tread surface 15a is the outer peripheral surface of the tread portion, that is, a surface that constitutes a tread surface (tire contact surface) that comes into contact with the road surface during running.

In addition, in the figure, the tire circumferential direction is defined as the direction around the tire rotation axis as the central axis. Further, the symbol T is the tire ground contact end. Tire contact edge T 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, the tire is placed perpendicular to the flat plate in a stationary state, and a load corresponding to the specified load is applied. is defined as the maximum axial width position of the tire. Further, the symbol TW is the tire ground contact width. 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.

The standard rim refers to a "standard rim" defined by JATMA, a "Design Rim" defined by TRA, or a "Measuring Rim" defined by 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, in the case of tires for passenger cars, the specified internal pressure is 230 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

As shown in FIG. 2, the pneumatic tire 1 has a plurality of circumferential main grooves (main grooves) 21 to 24 extending in the tire circumferential direction, and a plurality of circumferential main grooves 21 to 24 defined by the circumferential main grooves 21 to 24. Land portions 31 to 35 are provided on the tread surface 15a.

The main groove is a groove that is required to display a wear indicator as defined by JATMA, and has a groove width of 4.0 mm or more and a groove depth of 6.5 mm or more.

The groove width is measured as the distance between opposing groove walls at the groove opening in an unloaded state with the tire mounted on a specified rim and filled with a specified internal pressure. In a configuration in which the groove opening has a notch or a chamfer, the measurement point is the intersection of the extension line of the tread surface 15a and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction. The width is measured.

Groove depth is measured as the distance from the tread surface to the maximum groove depth position when the tire is mounted on a specified rim and filled with a specified internal pressure under no load. Furthermore, in a configuration in which the groove bottom has partial unevenness or sipes, the groove depth is measured excluding these.

For example, in the configuration shown in FIG. 2, the pneumatic tire 1 has an asymmetric tread pattern with the tire equatorial plane CL as a boundary. However, the present invention is not limited to this, and the pneumatic tire 1 may have, for example, a tread pattern that is horizontally symmetrical with the tire equatorial plane CL as the center, or that is approximately point symmetrical with the center point on the tire equatorial plane CL. It may have a tread pattern (not shown).

In addition, the tread pattern having the configuration shown in FIGS. 1 and 2 has two circumferential main grooves 21 and 22 in the left side area with the tire equatorial plane CL as the boundary, and has two circumferential main grooves 21 and 22 in the right side area with the tire equatorial plane CL as the boundary. It has two circumferential main grooves 23 and 24, respectively. The tread pattern is divided into five rows of land portions 31 to 35 by these circumferential main grooves 21 to 24. In the tread pattern, one land portion 33 among the land portions 31 to 35 is arranged on the tire equatorial plane CL.

Note that the tread pattern is not limited to the above configuration. For example, the tread pattern may have three or five or more circumferential main grooves (not shown). Further, in the tread pattern, the circumferential main grooves may be arranged symmetrically or asymmetrically with respect to the tire equatorial plane CL (not shown). Further, in the tread pattern, one circumferential main groove may be arranged on the tire equatorial plane CL (not shown).

In addition, among the circumferential main grooves 21 and 22 arranged in one area with the tire equatorial plane CL as a boundary, the outermost circumferential main groove 21 in the tire width direction is defined as the shoulder main groove, and the other circumferential main grooves 21 and 22 are defined as the shoulder main groove. The direction main groove 22 is defined as a center main groove. In addition, among the circumferential main grooves 23 and 24 arranged in the other region with the tire equatorial plane CL as a boundary, the outermost circumferential main groove 24 in the tire width direction is defined as the shoulder main groove, and the other circumferential main grooves 24 are defined as the shoulder main groove. The direction main groove 23 is defined as a center main groove. When there are three circumferential main grooves, the two outermost circumferential main grooves in the tire width direction are defined as shoulder main grooves, and the other circumferential main groove is defined as center main groove ( (not shown).

Moreover, the land portions 31 and 35 on the outside in the tire width direction that are defined by the shoulder main grooves 21 and 24 are defined as shoulder land portions. The shoulder land portions 31 and 35 are the outermost land portions in the tire width direction and are located on the tire ground contact edge T. The other land areas 32 to 35 are defined as the center land area.

In the configuration including four circumferential main grooves 21 to 24 as shown in FIG. 2, a pair of shoulder land portions 31 and 35 and three rows of center land portions 32 to 34 are defined. In the configuration including the four circumferential main grooves 21 to 24 as shown in FIG. The center land portion 32 defined between the groove 21 and the circumferential main groove 22, which is a center main groove adjacent to each other in the tire width direction, is defined as an outer center land portion. Furthermore, in the configuration including the four circumferential main grooves 21 to 24 as shown in FIG. A center land portion 34 defined between the groove 24 and the circumferential main groove 23, which is a center main groove adjacent to each other in the tire width direction, is defined as an outer center land portion. In addition, in a configuration including four circumferential main grooves 21 to 24 as shown in FIG. The center land portion 33 that is provided is defined as an inner center land portion.

Note that in the configuration including three circumferential main grooves, a pair of shoulder land portions and two rows of center land portions are defined. In this case, in the two rows of center land parts, the center land part on the tire equatorial plane or closest to the tire equatorial plane is defined as the inner center land part, and the other center land parts are defined as the outer center land parts. In addition, when the center land parts of two rows are equidistant from the tire equatorial plane, one center land part is defined as an inner center land part, and the other center land part is defined as an outer center land part.

Note that in the configuration including five circumferential main grooves, a pair of shoulder land portions and four rows of center land portions are defined. In the configuration including five circumferential main grooves, among the four rows of center land portions, a section is defined between the shoulder main groove and each center main groove adjacent to the shoulder main groove in the tire width direction. The center land area is defined as the outer center land area. In addition, in a configuration including five circumferential main grooves, among the four rows of center land portions, two rows of center land portions partitioned between adjacent center main grooves in the tire width direction are placed above the tire equatorial plane. Alternatively, the center land portion closest to the tire equatorial plane is defined as the inner center land portion. In addition, among the four rows of center land areas, if two rows of center land areas partitioned between adjacent center main grooves in the tire width direction are equidistant from the tire equatorial plane, one center land area is placed on the inside. The center land is defined as the center land, and the other center land is defined as the outer center land.

The shoulder land portion 31 includes a lug groove 311. The lug groove 311 opens to the tire ground contact end T at one end, and terminates at the other end within the shoulder land portion 31 without intersecting the circumferential main groove 21, which is the shoulder main groove. A plurality of lug grooves 311 are provided in the tire circumferential direction.

Here, the lug groove has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 0.55 times or more and 0.80 times or less of the groove depth of the main groove. It is in. Note that the sipe has a sipe width of 1.8 mm or less and a sipe depth of 3.0 mm or more and 7.0 mm or less. The sipes are notches formed in the tread surface 15a, and are distinguished from the lug grooves in that they have the above-mentioned sipe width and sipe depth and are closed when the tire contacts the ground.

Further, in the shoulder land portion 31, the ground contact width W_s1 of the tread surface 15a is in a range of 10% or more and 20% or less of the tire ground contact width TW. Similar to the tire ground contact width TW, the ground contact width W_s1 is determined when the tire is mounted on a specified rim and a specified internal pressure is applied, and when the tire is placed perpendicular to a flat plate in a stationary state and a load corresponding to the specified load is applied. It is measured as the maximum linear distance in the tire axial direction at the contact surface between the tread surface 15a of the shoulder land portion 31 and the flat plate.

The center land portion 32, which is the outer center land portion, includes a lug groove 321. The lug groove 321 opens into the circumferential main groove 21 which is a shoulder main groove at one end and does not intersect the circumferential main groove 22 which is a center main groove at the other end. Terminates at. A plurality of lug grooves 321 are provided in the tire circumferential direction. Further, in the center land portion 32, the ground contact width W_c1 (W_c) of the tread surface 15a is in a range of 10% or more and 20% or less of the tire ground contact width TW.

The center land portion 33, which is the inner center land portion, includes a lug groove 331. The lug groove 331 has one end that opens into the circumferential main groove 22 that is the center main groove, and the other end that does not intersect with the circumferential main groove 23 that is the center main groove but extends into the center land portion 33. and terminate. A plurality of lug grooves 331 are provided in the tire circumferential direction. Further, in the center land portion 33, the ground contact width W_ce of the tread surface 15a is in a range of 10% or more and 20% or less of the tire ground contact width TW.

The center land portion 34, which is the outer center land portion, includes a lug groove 341. The lug groove 341 opens into the circumferential main groove 23 which is the center main groove at one end, and opens into the center land portion 34 at the other end without intersecting the circumferential main groove 24 which is the shoulder main groove. and terminate. A plurality of lug grooves 341 are provided in the tire circumferential direction. Further, in the center land portion 34, the ground contact width W_c2 (W_c) of the tread surface 15a is in a range of 7% or more and 15% or less of the tire ground contact width TW.

The shoulder land portion 35 includes one circumferential narrow groove 25 . The circumferential narrow groove 25 extends in the tire circumferential direction and divides the center land portion 33 into two in the tire width direction. Here, the circumferential narrow groove has a groove width narrower than the main groove and a groove depth shallower than the main groove. The shoulder land portion 35 includes lug grooves 351 and 352. The lug groove 351 opens at one end into the circumferential main groove 24, which is a shoulder main groove, and at the other end opens into a center land which does not intersect the circumferential narrow groove 25 but is partitioned inward in the tire width direction. It terminates within the section 33. A plurality of lug grooves 351 are provided in the tire circumferential direction. The lug groove 352 has one end that does not intersect the circumferential narrow groove 25 and ends within the center land portion 33 that is partitioned outward in the tire width direction, and the other end that opens to the tire ground contact edge T. . A plurality of lug grooves 352 are provided in the tire circumferential direction. Further, in the shoulder land portion 35, the ground contact width W_s2 of the tread surface 15a is in a range of 15% or more and 25% or less of the tire ground contact width TW.

[Tread rubber]
3 to 5 are enlarged views showing the tread portion of the pneumatic tire shown in FIG. 1. FIG. 3 is an enlarged view of the entire tread portion. FIG. 4 is an enlarged view of a portion of the tread portion, showing the shoulder land portion 31 and the center land portion 32. FIG. 5 mainly shows the center land portions 32-34.

The tread rubber 15 includes a cap tread rubber 151 and an undertread rubber 152.

The cap tread rubber 151 is made of a rubber material with excellent ground contact characteristics and weather resistance, and is exposed on the tread surface 15a over the entire tire contact area and forms the outer surface of the tread portion. The cap tread rubber 151 preferably has a loss tangent (tan δ) Tac in a range of 0.10 or more and 0.30 or less. Further, it is preferable that the cap tread rubber 151 has a rubber hardness Hsc in a range of 60 or more and 70 or less.

Here, the loss tangent (tan δ) is calculated using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS-K6394, at a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 60°C. Measured under the following conditions. Further, the rubber hardness is JIS-A hardness, which is a durometer hardness measured at a temperature of 20° C. using an A type durometer in accordance with JIS K-6253.

Here, the thicknesses of the cap tread rubber 151, the undertread rubber 152, and the tread rubber 15 are also referred to as gauges. The gauges of the cap tread rubber 151, the undertread rubber 152, and the tread rubber 15 are measured on an imaginary line (normal line) perpendicular to the tangent to the tread surface 15a in a cross section in the tire meridian direction.

The cap tread rubber 151 and the undertread rubber 152 are also provided at the maximum groove depth positions of the groove bottoms of the circumferential main grooves 21 to 24. The gauges of the cap tread rubber 151 and the undertread rubber 152 provided at the maximum groove depth positions of the groove bottoms of the circumferential main grooves 21 to 24 are called groove bottom gauges. The groove bottom gauges of the circumferential main grooves 21 to 24 are measured in an unloaded state with the tire mounted on a specified rim and filled with a specified internal pressure. At this time, for example, the following measurement method is used. First, a single tire is fitted to the virtual line of the tire profile measured by a laser profiler and fixed with tape or the like. Then, the gauge to be measured is measured using a caliper or the like. Note that the laser profiler used here is a tire profile measuring device (manufactured by Matsuo Co., Ltd.).

The cap tread rubber 151 preferably has a minimum gauge Gac_m of 0.6 mm or more in the groove bottom gauge. Further, the cap tread rubber 151 preferably has a thickness of 40% or more of the total groove bottom gauge Gat_m of the tread rubber 15, which is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 at the minimum gauge Gac_m position (see FIG. 5). ).

The undertread rubber 152 is made of a rubber material that has lower hardness and better heat resistance than the cap tread rubber 151, and is sandwiched between the cap tread rubber 151 and the belt layer 14 to cover the base portion of the tread rubber 15. Configure. It is preferable that the undertread rubber 152 has a loss tangent Tau of less than 0.10. Further, it is preferable that the undertread rubber 152 has a rubber hardness Hsu in a range of 50 or more and 60 or less.

It is preferable that the loss tangent Tau of the undertread rubber 152 is smaller than the loss tangent Tac of the cap tread rubber 151 (Tac>Tau). It is preferable that the difference between the loss tangent Tac of the cap tread rubber 151 and the loss tangent Tau of the undertread rubber 152 is 0.02 or more.

Furthermore, it is preferable that the rubber hardness Hsu of the undertread rubber 152 is smaller than the rubber hardness Hsc of the cap tread rubber 151 (Hsc>Hsu). It is preferable that the difference between the rubber hardness Hsc of the cap tread rubber 151 and the Hsu of the undertread rubber 152 is 4 or more.

It is preferable that the minimum gauge Gau_m of the undertread rubber 152 in the groove bottom gauge is in the range of 0.2 mm or more and 1.0 mm or less. Further, the undertread rubber 152 is preferably 8% or more and 60% or less of the total groove bottom gauge Gat_m of the tread rubber 15, which is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 at the minimum gauge Gau_m position ( (See Figure 5).

Further, the undertread rubber 152 has an average gauge Ga_c (Ga_c1, Ga_c2) in the outer center land parts 32 and 34 of the center land parts 32 to 34 in a range of 1.5 mm or more and 4.0 mm or less (see FIG. 3). ). Further, the undertread rubber 152 has an average gauge Ga_ce in the inner center land portion 33 of the center land portions 32 to 34 in a range of 1.5 mm or more and 4.0 mm or less. Here, the average gauges Ga_c (Ga_c1, Ga_c2) and Ga_ce of the undertread rubber 152 of the center land parts 32 to 34 are 70% of the center in the tire width direction with respect to the tire width direction dimension CW of the center land parts 32 to 34, respectively. In the range CWa, the gauges at three tire radial positions at both ends a and b in the tire width direction and at the center c are determined by averaging (see FIG. 4). Note that the total average gauge Gat_c (Gat_c1, Gat_c2) and Gat_ce of the tread rubber 15, which is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 of the center land parts 32 to 34, are also the tires of the center land parts 32 to 34, respectively. In a range CWa that is 70% of the widthwise dimension CW at the center in the tire width direction, gauges at three tire radial positions at both ends a and b and in the center c in the tire width direction are determined by averaging (see FIG. 4). The total average gauge Gat_c (Gat_c1, Gat_c2), Gat_ce of the tread rubber 15 is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 from the tread surface 15a, and is not related to the lug grooves 321 to 341 (Fig. (See 3). The undertread rubber 152 has a maximum gauge position in the center land portions 32 to 34 (mainly the outer center land portions 32 and 34) of 1.6 mm outward in the tire radial direction from the groove bottom of each of the circumferential main grooves 21 to 24. It is located on the inner side in the tire radial direction than the virtual line Lw passing through the point and parallel to the profile line of the tread surface 15a (see FIG. 5).

Furthermore, the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 at the shoulder land portions 31 and 35 are in a range of 0.5 mm or more and 3.0 mm or less (see FIG. 3). Here, the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 of the shoulder land parts 31 and 35 are calculated from the open end d of the circumferential main grooves 21 and 24, which are the shoulder main grooves, to the tire ground contact end in the shoulder land parts 31 and 35, respectively. In the tire width direction dimension SW up to T, there are two points in the tire radial direction: the open end d of the circumferential main grooves 21 and 24 and the end e of the range SWa that is 20% from the open end d to the tire ground contact end T side. Find the average gauge at the position (see Figure 4). In addition, the total average gauges Gat_s1 and Gat_s2 of the tread rubber 15, which is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 of the shoulder land parts 31 and 35, are also measured in the circumferential direction which is the shoulder main groove in the shoulder land parts 31 and 35. With respect to the tire width direction dimension SW from the open end d of the main grooves 21, 24 to the tire ground contact edge T, 20% from the open end d of the circumferential main grooves 21, 24 and the open end d to the tire ground contact end T side. The gauges at two positions in the tire radial direction with the end e of the range WSa are averaged (see FIG. 4). The total average gauge Gat_s1, Gat_s2 of the tread rubber 15 is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 from the tread surface 15a, and is not related to the lug grooves 311, 351, 352 (see FIG. 3). . The undertread rubber 152 has a maximum gauge position in the shoulder land portions 31 and 35 that passes through a point 1.6 mm outward in the tire radial direction from the bottom of each of the circumferential main grooves 21 to 24 to the profile line of the tread surface 15a. It is located on the inner side in the tire radial direction than the parallel virtual line Lw (see FIG. 5).

[Features and effects]
As described above, the pneumatic tire 1 of the present embodiment includes the carcass layer 13, the pair of intersecting belts 141, 142 disposed on the radially outer side of the carcass layer 13, the cap tread rubber 151, and the undertread rubber 152. A tread rubber 15 that is laminated and arranged on the radially outer side of the cross belts 141 and 142, a pair of shoulder main grooves 21 and 24 formed on the outermost side in the tire width direction of the tread surface 15a, and a shoulder main groove 21, At least one center main groove 22, 23 between the shoulder main grooves 21, 24, a pair of shoulder land portions 31, 35 defined on the outside in the tire width direction of the shoulder main grooves 21, 24, It includes at least two center land portions (inner center land portion 33, outer center land portions 32, 34) divided into grooves 22, 23.

That is, the pneumatic tire 1 of this embodiment has four circumferential main grooves (shoulder main grooves 21, 24, center main grooves 22, 23), as shown in FIGS. 6 to 8, for example. For example, as shown in FIGS. 9 and 10, a structure in which five rows of land parts (shoulder land parts 31, 35, outer center land parts 32, 34, and inner center land parts 33) are partitioned, or Four rows of land portions (shoulder land portions 31, 35, inner center land portion 33, outer center land portion 32 (34)) having directional main grooves (shoulder main grooves 21, 24, center main groove 22 (23)). ), and for example, although not clearly shown in the drawings, this includes a configuration in which five circumferential main grooves are provided and six rows of land portions are partitioned.

As shown in FIG. 3, the pneumatic tire 1 of this embodiment has an average gauge Ga_ce of the undertread rubber 152 on the tire equatorial plane CL or in the inner center land portion 33 closest to the tire equatorial plane CL, and other The average gauge Ga_c (Ga_c1, Ga_c2) of the undertread rubber 152 in at least one outer center land portion 32, 34 has a relationship of Ga_ce<Ga_c. Furthermore, in the pneumatic tire 1 of the present embodiment, the ground contact width W_ce of the tread surface 15a on the inner center land portion 33 and the ground contact width W_c of the tread surface 15a on at least one outer center land portion 32, 34 are W_ce> It has the relationship W_c.

Therefore, in this pneumatic tire 1, the ground contact width on the tire equatorial plane CL or the inner center land portion 33 closest to the tire equatorial plane CL, where the ground contact length in the tire circumferential direction is the longest when the tread surface 15a makes contact with the ground, is different from that of other It is wider than the ground contact width of the tread surface 15a on at least one outer center land portion 32, 34. Therefore, the rigidity of the inner center land portion 33 can be ensured. Further, in this pneumatic tire 1, the average gauge of at least one outer center land portion 32, 34 of the undertread rubber 152 is thicker than the average gauge of the inner center land portion 33. Therefore, rolling resistance, which leads to low fuel consumption, can be reduced and ride comfort performance can be improved. However, if the average gauge of the undertread rubber 152 in the center land areas 32, 33, and 34 is made thicker, the rigidity of the land area decreases, and there is a concern that straight-line stability performance will decrease. In the secured inner center land portion 33, the average gauge of the undertread rubber 152 is made relatively thin to ensure straight running stability performance. On the other hand, in at least one outer center land portion 32, 34 adjacent to the inner center land portion 33, the average gauge of the undertread rubber 152 is made relatively thick to reduce input from the road surface, thereby improving ride comfort. secure. As a result, this pneumatic tire 1 can improve rolling resistance and ride comfort while ensuring straight-line stability performance.

Further, in the pneumatic tire 1 of the present embodiment, the average gauge Gat_ce of the tread rubber 15 in the inner center land portion 33 and the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 are Ga_ce/Gat_ce=0. It is preferable to have a relationship of 23±0.05 (0.18≦Ga_ce/Gat_ce≦0.28). Moreover, in the pneumatic tire 1 of the present embodiment, the average gauge Gat_c of the tread rubber 15 in at least one outer center land portion 32, 34, and the average gauge Ga_c of the undertread rubber 152 in the outer center land portion 32, 34. It is preferable that Ga_c/Gat_c=0.30±0.05 (0.25≦Ga_c/Gat_c≦0.35).

Therefore, in this pneumatic tire 1, the thickness of the undertread rubber 152 in the tread rubber 15 in the inner center land portion 33 and at least one outer center land portion 32, 34 is defined in the center land portions 32, 33, 34. This contributes to reducing rolling resistance and improving ride comfort.

Furthermore, in the pneumatic tire 1 of the present embodiment, the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 and the average gauge Ga_c of the undertread rubber 152 in at least one other outer center land portion 32, 34. It is preferable that the relationship is 0.30≦Ga_ce/Ga_c≦0.95. Moreover, in the pneumatic tire 1 of this embodiment, the ground contact width W_ce at the inner center land portion 33 and the ground contact width W_c at at least one outer center land portion 32, 34 are 1.10≦W_ce/W_c≦2. It is preferable to have a relationship of 00.

Therefore, this pneumatic tire 1 defines the relationship between the average gauge of the undertread rubber 152 between the inner center land portion 33 and at least one outer center land portion 32, 34, and the relationship between the inner center land portion 33 and at least one outer center land portion 32, 34. By defining the relationship between the ground contact width of the tread surface 15a and the outer center land portions 32 and 34, it is possible to significantly improve rolling resistance and ride comfort while ensuring straight-line running stability.

In the pneumatic tire 1 of the present embodiment, the average gauge Ga_ca of the undertread rubber 152 in the inner center land portion 33 and the average gauge Ga_c of the undertread rubber 152 in at least one outer center land portion 32, 34 are 1 The maximum gauge of each undertread rubber 152 in each center land portion 32, 33, 34 is in the range of . It is preferable to be located on the inner side in the tire radial direction than the virtual line Lw that passes through a point 1.6 mm from the tread surface and is parallel to the profile line of the tread surface.

Therefore, this pneumatic tire 1 can prevent the undertread rubber 152 of each center land portion 32, 33, 34 from being exposed to the tread surface even when the tread reaches the wear life (end of wear).

In the pneumatic tire 1 of the present embodiment, the average gauge Ga_ca of the undertread rubber 152 in the inner center land portion 33, the average gauge Ga_c of the undertread rubber 152 in at least one outer center land portion 32, 34, and the average gauge Ga_c of the undertread rubber 152 in the at least one outer center land portion 32, It is preferable that the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 in the shoulder land portions 31 and 35 have a relationship of Ga_ce>Ga_s1, Ga_ce>Ga_s2, Ga_c>Ga_s1, and Ga_c>Ga_s2. Moreover, in the pneumatic tire 1 of the present embodiment, the ground contact width W_ce of the tread surface 15a on the inner center land portion 33, the ground contact width W_c of the tread surface 15a on at least one outer center land portion 32, 34, and the ground contact width W_c of the tread surface 15a on the at least one outer center land portion 32, 34, It is preferable that the ground contact widths W_s1 and W_s2 of the tread surface 15a in the portions 31 and 35 have the following relationships: W_ce<W_s1, W_ce<W_s2, W_c<W_s1, and W_c<W_s2.

Therefore, in the average gauge of the undertread rubber 152, this pneumatic tire 1 has a low temperature by making the inner center land portion 33 and at least one outer center land portion 32, 34 thicker than each shoulder land portion 31, 35. It reduces rolling resistance, which contributes to fuel efficiency, and improves ride comfort. However, if the average gauge of the undertread rubber 152 in the center land areas 32, 33, and 34 is made thicker, the rigidity of the land area decreases, and there is a concern that straight-line stability performance will decrease. In each secured shoulder land portion 31, 35, the average gauge of the undertread rubber 152 is made relatively thin to ensure straight running stability. On the other hand, in the center land portions 32, 33, and 34, the average gauge of the undertread rubber 152 is made relatively thick to reduce input from the road surface, thereby ensuring ride comfort. As a result, this pneumatic tire 1 can significantly improve rolling resistance and ride comfort while ensuring straight-line stability performance. In addition, 0.9≦Ga_ce/Ga_s1≦1.5, 0.9≦Ga_ce/Ga_s2≦1.5, 1.3≦Ga_c/Ga_s1≦3.0, 1.3≦S_c/S_s2≦3.0, and 0.5≦W_ce/W_s1≦0.8, 0.3≦W_ce/W_s2≦0.7, 0.5≦W_c/W_s1≦0.8, 0.7≦W_c/W_s2 By having a relationship of ≦0.9, it is possible to significantly improve rolling resistance and ride comfort performance while ensuring straight-line stability performance.

Further, in the pneumatic tire 1 of the present embodiment, it is preferable that the cap tread rubber 151 has a minimum gauge Gac_m of 0.6 mm or more in the groove bottom gauge. Moreover, in the pneumatic tire 1 of this embodiment, the cap tread rubber 151 is 40% of the total groove bottom gauge Gat_m of the tread rubber 15, which is the sum of the thicknesses of the cap tread rubber 151 and the undertread rubber 152 at the minimum gauge Gac_m position. It is preferable that it is above.

Therefore, in this pneumatic tire 1, by ensuring the groove bottom gauge of the cap tread rubber 151, it is possible to suppress the occurrence of cracks in the groove bottoms of the main grooves 21, 22, 23, and 24 due to repeated strain. In addition, it is preferable that the minimum gauge Gac_m in the groove bottom gauge of the cap tread rubber 151 is 0.7 mm or more, which can further suppress the occurrence of cracks in the groove bottoms of the main grooves 21, 22, 23, and 24.

Furthermore, in the pneumatic tire 1 of this embodiment, the loss tangent Tac at 60°C of the cap tread rubber 151 and the loss tangent Tau at 60°C of the undertread rubber 152 are 1.20≦Tac/Tau≦13.0. It is preferable to have the following relationship.

That is, in this pneumatic tire 1, the loss tangent at 60° C. is smaller in the undertread rubber 152 than in the cap tread rubber 151. Therefore, by specifying the average gauge of the undertread rubber 152 with a small loss tangent at 60° C., this pneumatic tire 1 can contribute to reducing rolling resistance, which leads to low fuel consumption. In the pneumatic tire 1 of this embodiment, the loss tangent Tac at 60° C. of the cap tread rubber 151 is 0.10 or more, and the loss tangent Tau at 60° C. of the undertread rubber 152 is less than 0.10. is preferred.

Moreover, in the pneumatic tire 1 of this embodiment, it is preferable that the rubber hardness Hsc of the cap tread rubber 151 and the rubber hardness Hsu of the undertread rubber 152 have a relationship of HSc>HSu.

Therefore, by specifying the average gauge of the undertread rubber 152 having a small rubber hardness, this pneumatic tire 1 can contribute to reducing rolling resistance, which leads to low fuel consumption. In the pneumatic tire 1 of this embodiment, the rubber hardness Hsc of the cap tread rubber 151 and the rubber hardness Hsu of the undertread rubber 152 have a relationship of 1.10≦HSc/HSu≦1.80. It is preferable. Furthermore, in the pneumatic tire 1 of the present embodiment, the rubber hardness Hsc of the cap tread rubber 151 is in the range of 60 to 70, and the rubber hardness Hsu of the undertread rubber 152 is in the range of 50 to 60. is preferred.

In the example shown in FIG. 6, in the four main grooves 21, 22, 23, 24, the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 is compared to the average gauge Ga_ce of the undertread rubber in the outer center land portion 32. 152 is large, and the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 in each shoulder land portion 31 and 35 are the smallest. In addition, in the example shown in FIG. 7, in the four main grooves 21, 22, 23, 24, the undertread in each outer center land portion 32, 34 is This represents a form in which the average gauge Ga_c of the rubber 152 is large and the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 in each shoulder land portion 31 and 35 are the smallest. In the example shown in FIG. 8, the four main grooves 21, 22, 23, 24 include one shoulder land portion 31, one outer center land portion 32, inner center land portion 33, and the other outer center land portion. 34 and the other shoulder land portion 35, the average gauge of the undertread rubber 152 is larger in this order. In the example shown in FIG. 9, the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 (34) is compared to the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 (34) in the three main grooves 21, 22, 23 (24). This represents a form in which the average gauge Ga_c of the tread rubber 152 is large and the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 at each shoulder land portion 31 and 35 are the smallest. In the example shown in FIG. 10, the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 (32) is compared to the average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 (32) in the three main grooves 21 (22), 23, and 24. This represents a form in which the average gauge Ga_c of the tread rubber 152 is large and the average gauges Ga_s1 and Ga_s2 of the undertread rubber 152 at each shoulder land portion 31 and 35 are the smallest.

FIG. 11 is a chart showing the results of a performance test of the pneumatic tire according to this embodiment.

In this performance test, multiple types of test tires were evaluated in terms of rolling resistance performance, ride comfort performance, and straight-line stability performance. Furthermore, in this performance test, a test tire with a tire size of 195/65R15 91H was assembled on a rim with a rim size of 15×6J, and a JATMA specified internal pressure (230 kPa) was applied to this test tire.

In the evaluation of rolling resistance performance, a drum testing machine with a rim diameter of 1707 [mm] was used, and the rolling resistance coefficient of the test tire was calculated under the conditions of a load of 4.8 kN, an air pressure of 230 kPa, and a speed of 80 km/h in accordance with ISO 28580. It was done. This evaluation is performed by an index evaluation using the conventional example as a standard (100), and the larger the value, the smaller the rolling resistance is, and it is preferable.

For evaluation of ride comfort performance, a test vehicle (domestic height vehicle: minivan) equipped with test tires on all wheels was run on a test course on a dry road surface at a speed of 60 km/h to 100 km/h, and the test driver ran a test vehicle at the time of a lane change. Sensory evaluations were also conducted on steering performance during cornering and stability when driving straight. This evaluation is performed by an index evaluation using the conventional example as a standard (100), and the larger the value, the higher the ride comfort, which is preferable.

In evaluating the straight-line stability performance, the test vehicle was run on a test course on a dry road surface at speeds of 60 km/h to 100 km/h, and the test driver performed a sensory evaluation of the straight-line stability. This evaluation is performed by index evaluation using the conventional example as a standard (100), and the larger the value is 99 or more, the higher the straight-line stability is, and it is preferable.

The test tires of Examples 1 to 8 had the configurations shown in FIGS. 1 to 3, and had an average gauge Ga_ce of the undertread rubber 152 in the inner center land portion 33 and at least one other outer center land portion 32, 34. The average gauge Ga_c (Ga_c1, Ga_c2) of the undertread rubber 152 in has a relationship of Ga_ce<Ga_c, and the contact width W_ce of the tread surface 15a in the inner center land portion 33 and the at least one outer center land portion 32, The ground contact width W_c (W_c1, W_c2) of the tread surface 15a at 34 has a relationship of W_ce>W_c.

As shown in FIG. 9, the test tire of Example 9 has the configuration shown in FIGS. 1 to 3, does not have an outer center land portion 34, has only one center main groove 22, and has an inner center land portion. The average gauge Ga_ce of the undertread rubber 152 at 33 and the average gauge Ga_c (Ga_c1) of the undertread rubber 152 at the outer center land portion 32 have a relationship of Ga_ce<Ga_c, and the tread surface 15a at the inner center land portion 33 has a relationship of Ga_ce<Ga_c. The ground contact width W_ce and the ground contact width W_c (W_c1) of the tread surface 15a in the outer center land portion 32 have a relationship of W_ce>W_c.

In the test tire of Conventional Example 1, the average gauge of the undertread rubber 152 in all the land portions 31 to 35 was the same in the configuration shown in FIGS. 1 to 3. Furthermore, as shown in FIG. 9 in the configuration of FIGS. 1 to 3, the test tire of Conventional Example 2 did not have an outer center land portion 34, had only one center main groove 22, and had all The average gauge of the undertread rubber 152 in the land portions 31, 32, 33, and 35 is the same.

Note that the groove area ratio is expressed in the relationship of large>medium>small, and in each conventional example, comparative example, and each example, the relationship is large=large, medium=medium, and small=small.

As shown in the test results, it can be seen that the test tires of Examples 1 to 8 can improve rolling resistance performance and ride comfort performance while ensuring straight-line stability performance compared to Conventional Example 1. As shown in the test results, it can be seen that the test tire of Example 9 can improve rolling resistance performance and ride comfort performance while ensuring straight-line stability performance compared to Conventional Example 2.

1 Pneumatic tire 13 Carcass layer 141, 142 Cross belt 15 Tread rubber 15a Tread surface 151 Cap tread rubber 152 Undertread rubber 21, 24 Shoulder main groove 22, 23 Center main groove 31, 35 Shoulder land 32, 34 Outer center land Section 33 Inner center land section

Claims (6)

a carcass layer, a pair of intersecting belts disposed on the radially outer side of the carcass layer, a tread rubber formed by laminating cap tread rubber and undertread rubber and disposed on the radial outer side of the intersecting belts; a pair of shoulder main grooves formed on the outermost side in the tire width direction of the surface; at least one center main groove between the shoulder main grooves; and a pair of shoulder lands defined on the outer side of the shoulder main groove in the tire width direction. and at least two center land portions defined by the shoulder main groove and the center main groove,
The average gauge Ga_ce of the undertread rubber at the inner center land portion on the tire equatorial plane or closest to the tire equatorial plane and the average gauge Ga_c of the undertread rubber at at least one other outer center land portion are such that Ga_ce< It has the relationship Ga_c,
The ground contact width W_ce on the inner center land portion and the ground contact width W_c on at least one of the outer center land portions have a relationship of W_ce>W_c,
The loss tangent Tac of the cap tread rubber at 60°C and the loss tangent Tau of the undertread rubber at 60°C have a relationship of Tac>Tau,
The rubber hardness Hsc of the cap tread rubber and the rubber hardness Hsu of the undertread rubber have a relationship of HSc>HSu.
pneumatic tires. The average gauge Gat_ce of the tread rubber in the inner center land portion and the average gauge Ga_ce of the undertread rubber in the inner center land portion have a relationship of Ga_ce/Gat_ce=0.23±0.05,
The average gauge Gat_c of the tread rubber in at least one outer center land portion and the average gauge Ga_c of the undertread rubber in the outer center land portion have a relationship of Ga_c/Gat_c=0.30±0.05. ,
The pneumatic tire according to claim 1. The average gauge Ga_ce of the undertread rubber in the inner center land portion and the average gauge Ga_c of the undertread rubber in at least one other outer center land portion have a relationship of 0.30≦Ga_ce/Ga_c≦0.95. has
A ground contact width W_ce at the inner center land portion and a ground contact width W_c at at least one outer center land portion have a relationship of 1.10≦W_ce/W_c≦2.00.
The pneumatic tire according to claim 1 or 2. The average gauge Ga_ca of the undertread rubber in the inner center land portion and the average gauge Ga_c of the undertread rubber in at least one outer center land portion are in a range of 1.5 mm or more and 4.0 mm or less,
The maximum gauge of each of the undertread rubbers in each of the center land areas is greater than an imaginary line parallel to the profile line of the tread surface passing through a point 1.6 mm outward in the tire radial direction from the bottom of each of the main grooves. , located on the inside of the tire in the radial direction,
The pneumatic tire according to any one of claims 1 to 3. an average gauge Ga_ca of the undertread rubber in the inner center land portion; an average gauge Ga_c of the undertread rubber in at least one outer center land portion; an average gauge Ga_s1 of the undertread rubber in each shoulder land portion; Ga_s2 has a relationship of Ga_ce>Ga_s1, Ga_ce>Ga_s2, Ga_c>Ga_s1, Ga_c>Ga_s2,
A ground contact width W_ce on the inner center land portion, a ground contact width W_c on at least one of the outer center land portions, and a ground contact width W_s1, W_s2 on each of the shoulder land portions,
Having the relationships of W_ce<W_s1, W_ce<W_s2, W_c<W_s1, and W_c<W_s2,
The pneumatic tire according to any one of claims 1 to 4. The loss tangent Tac of the cap tread rubber at 60° C. and the loss tangent Tau of the undertread rubber at 60° C. have a relationship of 1.20≦Tac/Tau≦13.0.
The pneumatic tire according to any one of claims 1 to 5.

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