JP2013079016A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of attaining both dry steering stability and snow steering stability.SOLUTION: The pneumatic tire 1 includes: a plurality of circumferential main grooves 21 extending in the tire circumferential direction; and a plurality of land portions 31, 32 defined by the circumferential main grooves 21. The land portion 31 in a center area and the land portions 32 in lateral shoulder areas have a plurality of sipes 312, 322 respectively. Further, 90 [%] or more of the sipes 312 disposed in the center area is composed of two-dimensional sipes, and 90 [%] or more of the sipes 322 disposed in the shoulder areas is composed of three-dimensional sipes. A tread portion has cap rubber and under rubber. The rubber hardness H_cap at 20 [°C] of the cap rubber and the rubber hardness H_ut at 20 [°C] of the under rubber have a relationship of H_cap<H_ut.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can achieve both dry and snow handling characteristics.

  A general winter tire has a sipe in the tread portion in order to improve the snow maneuverability of the tire. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

  In addition, in order to improve the dry maneuverability of the tire, a configuration including a tread rubber having different rubber hardnesses between the cap rubber and the under rubber is known. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 3 is known.

  In addition, in order to improve the dry maneuverability of the tire, a configuration including an under rubber having different rubber hardnesses in the tread portion center region and the shoulder region is known. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 2 is known.

JP 2010-6107 A JP 2009-262646 A JP 2000-198319 A

  An object of the present invention is to provide a pneumatic tire that can achieve both dry maneuverability and snow maneuverability.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in a tire circumferential direction and a plurality of land portions defined by the circumferential main grooves as tread portions. The left and right circumferential main grooves on the outermost side in the tire width direction are referred to as outermost circumferential main grooves, and the tread is defined by a groove center line of the left and right outermost circumferential main grooves. When the region inside the tire width direction inside is called a center region and the left and right regions outside the tire width direction are called shoulder regions, the land portion of the center region and the land portions of the left and right shoulder regions are Each sipe has a plurality of sipes, and 90% or more of the sipes arranged in the center region are composed of two-dimensional sipes, and 90% or more of the sipes arranged in the shoulder region are The cap rubber and the under rubber, and the rubber hardness H_cap of the cap rubber at 20 [° C.] and the rubber hardness H_ut of the under rubber at 20 [° C.] are H_cap. <H_ut relationship.

  In the pneumatic tire according to the present invention, the rubber hardness H_cap of the cap rubber, the rubber hardness H_ut_ce of the under rubber in the center region at 20 [° C.], and 20 [° C.] of the under rubber in the shoulder region. It is preferable that the rubber hardness H_ut_sh has a relationship of H_cap <H_ut_ce <H_ut_sh.

  In the pneumatic tire according to the present invention, rubber hardness H_cap of the cap rubber, rubber hardness H_ut_ce of the under rubber in the center region, and rubber hardness H_ut_sh of the under rubber in the shoulder region are 63 ≦ H_cap ≦ 68, It is preferable that the conditions of 70 ≦ H_ut_ce ≦ 74, 75 ≦ H_ut_sh ≦ 80, 4 ≦ H_ut_ce−H_cap ≦ 9, 3 ≦ H_ut_sh−H_ut_ce ≦ 8 are satisfied.

  In the pneumatic tire according to the present invention, it is preferable that the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region have a relationship of 1.3 ≦ D_ce / D_sh ≦ 2.0.

  In the pneumatic tire according to the present invention, it is preferable that the ground contact width W_ce in the center region and the tire ground contact width TW have a relationship of 0.45 ≦ W_ce / TW ≦ 0.55.

  In the pneumatic tire according to the present invention, the groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface is in the range of 0.25 ≦ S_ce ≦ 0.35, and the tire contact surface The total groove area ratio S_t is preferably in the range of 0.25 ≦ S_t ≦ 0.38.

  In the pneumatic tire according to the present invention, the average thickness t_ce of the under rubber in the center region and the average thickness t_sh of the under rubber in the shoulder region are 1 [mm] ≦ t_sh−t_ce ≦ 3. It is preferable to have a relationship of [mm].

  Further, in the pneumatic tire according to the present invention, the center region includes one center land portion that is divided into the left and right outermost circumferential main grooves, and the center land portion is arranged in the tire circumferential direction. A plurality of main inclined grooves and a plurality of sub inclined grooves, wherein the plurality of main inclined grooves are inclined with respect to the tire circumferential direction so as to be separated from the tire equatorial plane toward one direction of the tire circumferential direction. Each extending and communicating with either one of the left and right outermost circumferential main grooves at one end and alternately arranged in the tire circumferential direction on both sides of the tire equatorial plane. Each of the sub-inclined grooves extends while inclining with respect to the tire circumferential direction in a manner away from the tire equatorial plane in one direction of the tire circumferential direction, and intersecting with the two main inclined grooves Center Rikubu In conjunction to terminate the both ends, preferably arranged alternately toward the tire circumferential direction on both sides of the tire equatorial plane.

  In the pneumatic tire according to the present invention, since the two-dimensional sipe is arranged in the center region and the three-dimensional sipe is arranged in the left and right shoulder regions, the rigidity of the center region is set low and the rigidity of the left and right shoulder regions is set high. The Accordingly, the center region contributes to the improvement of snow handling, and the shoulder region contributes to the improvement of dry handling. Accordingly, there is an advantage that the dry maneuverability of the tire and the snow maneuverability are compatible at a high level. In addition, since the rubber hardness H_cap of the cap rubber and the rubber hardness H_ut of the under rubber have a relationship of H_cap <H_ut, there is an advantage that the snow maneuverability is improved.

FIG. 1 is a 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 a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 4 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 5 is an explanatory view illustrating a first modification of the pneumatic tire depicted in FIG. 1. FIG. 6 is an explanatory diagram illustrating a second modification of the pneumatic tire depicted in FIG. 1. FIG. 7 is an explanatory diagram showing a third modification of the pneumatic tire depicted in FIG. 1. FIG. 8 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

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

[Pneumatic tire]
FIG. 1 is a 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 a tread surface of the pneumatic tire depicted in FIG. 1. These drawings show a radial tire for a passenger car. In FIG. 1, the undertread rubber is hatched.

  The pneumatic tire 1 includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, and a pair of sidewall rubbers 16, 16. (See FIG. 1). The pair of bead cores 11 and 11 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 are disposed on the outer periphery in the tire radial direction of the pair of bead cores 11 and 11 to reinforce the bead portion. The carcass layer 13 has a single-layer structure and is bridged in a toroidal shape between the left and right bead cores 11 and 11 to constitute a tire skeleton. Further, both end portions 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. The belt layer 14 includes a pair of stacked belt plies 141 and 142, and is disposed on the outer periphery in the tire radial direction of the carcass layer 13. These belt plies 141 and 142 are formed by arranging and rolling a plurality of belt cords made of steel or organic fiber material, and cross-ply structure by inclining the belt cords in mutually different directions in the tire circumferential direction. Configure. The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions.

  In addition, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 extending in the tire circumferential direction and a plurality of land portions 31 and 32 partitioned by the circumferential main grooves 21 in a tread portion ( (See FIG. 2). The circumferential main groove refers to a circumferential groove having a groove width of 3 [mm] or more. The land portions 31 and 32 may be block rows (see FIG. 2) or ribs (not shown).

  Further, the left and right circumferential main grooves 21, 21 on the outermost side in the tire width direction are referred to as outermost circumferential main grooves. In addition, a region on the inner side in the tire width direction of the tread portion with the groove center line of the left and right outermost circumferential main grooves 21 and 21 as a boundary is referred to as a center region, and a left and right region on the outer side in the tire width direction is referred to as a shoulder region.

  For example, in this embodiment, the pneumatic tire 1 has a symmetrical tread pattern. Moreover, a pair of circumferential direction main grooves 21 and 21 are arrange | positioned left-right symmetrically in the area | region on either side which makes tire equatorial plane CL a boundary. The circumferential main grooves 21, 21 define a row of center land portions 31 and a pair of left and right shoulder land portions 32, 32. Further, these circumferential main grooves 21 and 21 are left and right outermost circumferential main grooves, and the tread portion is divided into a center region and a shoulder region. Further, the center land portion 31 and the left and right shoulder land portions 32 and 32 respectively have a plurality of lug grooves 311 and 321 extending in the tire width direction. Further, these lug grooves 311 and 321 are arranged at predetermined intervals in the tire circumferential direction. In addition, the lug groove 311 of the center land portion 31 has an open structure, and opens to the left and right edge portions of the center land portion 31 across the center land portion 31 in the tire width direction. Thereby, the center land part 31 is divided | segmented into the tire circumferential direction, and the block row | line | column is formed. On the other hand, the lug groove 321 of the shoulder land portion 32 has a semi-closed structure, opens to the edge portion of the shoulder land portion 32 at the outer end portion in the tire width direction, and the shoulder land at the inner end portion in the tire width direction. It terminates in part 32. Therefore, the shoulder land portion 32 is a rib continuous in the tire circumferential direction.

[Sipe composition and rubber hardness]
Further, in the pneumatic tire 1, the land portion 31 in the center region and the land portions 32 and 32 in the left and right shoulder regions respectively have a plurality of sipes 312 and 322 (see FIG. 2). Further, 90 [%] or more of the sipe 312 arranged in the center region is composed of a two-dimensional sipe, and 90 [%] or more of the sipe 322 disposed in the shoulder region is composed of a three-dimensional sipe.

  Here, sipe refers to a cut formed in the land. The two-dimensional sipe means a sipe having a straight sipe wall surface in a cross-sectional view perpendicular to the sipe length direction. The three-dimensional sipe refers to a sipe having a sipe wall surface that is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction. The three-dimensional sipe has an action of reinforcing the rigidity of the land portion because the meshing force of the opposing sipe wall surfaces is stronger than that of the two-dimensional sipe.

  For example, in this embodiment, the center land portion 31 and the left and right shoulder land portions 32 and 32 have a plurality of sipes 312 and 322, respectively. Further, these sipes 312 and 322 have a straight shape extending in the tire width direction, and are arranged in parallel and at predetermined intervals in the tire circumferential direction. Further, these sipes 312 and 322 have a closed structure and terminate in the land portions 31 and 32. Further, the sipes 312 of the center land portion 31 are all two-dimensional sipes, and the sipes 322 of the left and right shoulder land portions 32 and 32 are all three-dimensional sipes. Therefore, due to the difference in rigidity between the two-dimensional sipe 312 and the three-dimensional sipe 322, the rigidity of the center land portion 31 is set low and the rigidity of the left and right shoulder land portions 32, 32 is set high.

  Moreover, in this pneumatic tire 1, the tread portion includes the cap rubber 151 and the under rubber 152 (see FIG. 1). Further, the rubber hardness H_cap of the cap rubber 151 at 20 [° C.] and the rubber hardness H_ut of the under rubber 152 at 20 [° C.] have a relationship of H_cap <H_ut.

  Further, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region at 20 [° C.], and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region at 20 [° C.] are H_cap <H_ut_ce < It is preferable to have a relationship of H_ut_sh.

  In addition, rubber hardness means the JIS-A hardness based on JIS-K6263. When the cap rubber or the under rubber in the predetermined region (center region or shoulder region) is made of a plurality of rubber materials, the rubber hardness is calculated as the average rubber hardness by the following formula (1). In Equation (1), Sk represents the cross-sectional area of each rubber material in a cross-sectional view in the tire meridian direction, Hk represents the rubber hardness of each rubber material, and Sa represents a predetermined region in the cross-sectional view in the tire meridian direction. The cross-sectional area is shown.

  Rubber hardness H = (ΣSk × Hk) / Sa (k: 1, 2, 3,..., N) (1)

  For example, in this embodiment, the cap rubber 151 is made of a single rubber material constituting the center land portion 31 and the left and right shoulder land portions 32, 32, and has a single rubber hardness H_cap (see FIG. 1). The under rubber 152 includes a center under rubber 152_ce and a pair of left and right shoulder under rubbers 152_sh and 152_sh. The center under rubber 152_ce and the left and right shoulder under rubbers 152_sh and 152_sh are made of rubber materials having different rubber hardnesses. Further, the center under rubber 152_ce is disposed in the tread portion center region, and the shoulder under rubber 152_sh is disposed in the left and right tread portion shoulder regions. Further, the boundary between the center under rubber 152_ce and the left and right shoulder under rubbers 152_sh, 152_sh is located on the inner side in the tire width direction than the outermost circumferential main grooves 21, 21.

  Further, the rubber hardness H_cap of the cap rubber 151 and the rubber hardness H_ut of the under rubber 152 have a relationship of H_cap <H_ut. Here, the rubber hardness H_ut of the under rubber 152 is an average rubber hardness of the center under rubber 152_ce and the left and right shoulder under rubbers 152_sh and 152_sh, and is calculated based on the above formula (1).

  Further, the rubber hardness of the center under rubber 152_ce is set smaller than the rubber hardness of the left and right shoulder under rubbers 152_sh and 152_sh. Thereby, the rigidity of the center land part 31 is low, and the rigidity of the left and right shoulder land parts 32, 32 is set high. Further, the boundary between the center under rubber 152_ce and the left and right shoulder under rubbers 152_sh, 152_sh is disposed at a position away from the bottom of the outermost circumferential main grooves 21, 21. Therefore, the rubber hardness H_ut_ce of the under rubber 152 in the center region is calculated based on the rubber hardness of the center under rubber 152_ce, the rubber hardness of the shoulder under rubber 152_sh, and the above formula (1).

  In this pneumatic tire 1, since the two-dimensional sipe 312 is arranged in the center region and the three-dimensional sipe 322 is arranged in the left and right shoulder regions, the rigidity of the center region is set low and the rigidity of the left and right shoulder regions is set high. (See FIGS. 1 and 2). Accordingly, the center region contributes to the improvement of snow handling, and the shoulder region contributes to the improvement of dry handling. Moreover, since the rubber hardness H_cap of the cap rubber 151 and the rubber hardness H_ut of the under rubber 152 have a relationship of H_cap <H_ut, the snow handling performance is improved.

  Furthermore, since the rubber hardness H_ut_ce of the under rubber in the center region and the rubber hardness H_ut_sh of the under rubber in the shoulder region have a relationship of H_ut_ce <H_ut_sh, the rigidity of the center region is low and the rigidity of the left and right shoulder regions is set high. Is done. Therefore, the rigidity of the center region is synergistically lowered and the rigidity of the left and right shoulder regions is synergistically increased due to the relationship between the arrangement configuration of the two-dimensional sipe and the three-dimensional sipe in the center region and the shoulder region. . Thereby, dry maneuverability of the tire and snow maneuverability are compatible at a high level.

  In the configuration of FIG. 1, the boundary between the center under rubber 152_ce and the left and right shoulder under rubbers 152_sh, 152_sh is arranged at a position deviating from the bottom of the outermost circumferential main grooves 21, 21 to the inside in the tire width direction. ing. However, the present invention is not limited to this, and the boundary between the center under rubber 152_ce and the left and right shoulder under rubbers 152_sh, 152_sh may be disposed below the bottom of the outermost circumferential main grooves 21, 21, or the outermost circumferential main grooves 21 and 21 may be arranged at positions deviating from the bottom of the groove bottom to the outside in the tire width direction (not shown).

  3 and 4 are explanatory diagrams showing an example of a three-dimensional sipe. These drawings show perspective views of the wall surface of the three-dimensional sipe.

  In the three-dimensional sipe shown in FIG. 3, the sipe wall surface has a structure in which a triangular pyramid and an inverted triangular pyramid are connected in the sipe length direction. In other words, the sipe wall surface has a zigzag shape on the tread surface side and a zigzag shape on the bottom side that are shifted in pitch in the tire width direction, and unevenness that faces each other between the zigzag shapes on the tread surface side and the bottom side. Have Further, the sipe wall surface is an unevenness when viewed in the tire rotation direction among these unevennesses, between the convex bending point on the tread surface side and the concave bending point on the bottom side, the concave bending point on the tread surface side and the bottom side Between the convex bend points of the tread surface and the convex bend points on the tread surface side, and adjacent convex bend points that are adjacent to each other with ridge lines, and the ridge lines between the ridge lines in order in the tire width direction. It is formed by connecting in a plane. In addition, one sipe wall surface has an uneven surface in which convex triangular pyramids and inverted triangular pyramids are arranged alternately in the tire width direction, and the other sipe wall surface alternates between concave triangular pyramids and inverted triangular pyramids. Have uneven surfaces arranged in the tire width direction. And the sipe wall surface has the uneven | corrugated surface arrange | positioned at least at the outermost both ends of the sipe toward the outer side of a block. As such a three-dimensional sipe, for example, a technique described in Japanese Patent No. 3894743 is known.

  In the three-dimensional sipe shown in FIG. 4, the sipe wall surface has a structure in which a plurality of rectangular columns having a block shape are connected in the sipe depth direction and the sipe length direction while being inclined with respect to the sipe depth direction. In other words, the sipe wall surface has a zigzag shape on the tread surface. Further, the sipe wall surface has a bent portion that is bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block and continues in the tire width direction, and has an amplitude in the tire radial direction at the bent portion. It has a zigzag shape. In addition, while the sipe wall surface makes the tire circumferential amplitude constant, the inclination angle in the tire circumferential direction with respect to the normal direction of the tread surface is made smaller at the sipe bottom side part than the tread surface side part and bent. The amplitude of the tire in the tire radial direction is made larger at the sipe bottom side than at the tread surface side. As such a three-dimensional sipe, for example, a technique described in Japanese Patent No. 4316452 is known.

  In this pneumatic tire 1, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region are 63 ≦ H_cap ≦ 68, 70 ≦ H_ut_ce ≦. 74, 75 ≦ H_ut_sh ≦ 80, 4 ≦ H_ut_ce−H_cap ≦ 9, and 3 ≦ H_ut_sh−H_ut_ce ≦ 8 are preferably satisfied. Accordingly, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region, and the rubber hardness differences H_ut_ce−H_cap and H_ut_sh−H_ut_ce are optimized. Is done.

  In the pneumatic tire 1, it is preferable that the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region have a relationship of 1.3 ≦ D_ce / D_sh ≦ 2.0 (not shown). That is, it is preferable that the sipe density D_ce in the center region is higher than the sipe density D_sh in the shoulder region.

  The sipe density is a ratio between the sipe length and the land contact area of the land. The sipe length can be increased by, for example, making the sipe a bent shape. The sipe density can be easily adjusted by adjusting the sipe length, the number of sipes, and the like.

  As described above, in the pneumatic tire 1, the rigidity of the center land portion 31 is low due to the arrangement of the two-dimensional sipe 312 and the three-dimensional sipe 322 and the rubber hardness difference between the center under rubber 152_ce and the shoulder under rubber 152_sh. The rigidity of the left and right shoulder land portions 32, 32 is set high. Therefore, by providing the difference between the above sipe densities D_ce and D_sh, the rigidity of the center land portion 31 is further reduced, and the rigidity of the left and right shoulder land portions 32 and 32 is set to be higher.

  In the pneumatic tire 1, it is preferable that the ground contact width W_ce in the center region and the tire ground contact width TW have a relationship of 0.45 ≦ W_ce / TW ≦ 0.55 (see FIG. 2). Thereby, the ground contact width W_ce of the center region is optimized.

  For example, in this embodiment, the ground contact width W_ce of the center region matches the ground contact width of the center land portion 31, and the tire ground contact width TW is defined by the left and right tire ground contact ends T. These ratios W_ce / TW are set within the above range.

  The ground contact width W_ce and the tire ground contact width TW in the center region are loads corresponding to the specified load when the tire is mounted on the specified rim and applied with the specified internal pressure and is placed perpendicular to the flat plate in a stationary state. It is measured at the contact surface between the tire and the flat plate when added.

  Here, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed in ETRTO. The specified internal pressure means “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The specified load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  Further, in this pneumatic tire 1, the groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface is in the range of 0.25 ≦ S_ce ≦ 0.35, and the total groove area on the tire contact surface is The ratio S_t is preferably in the range of 0.25 ≦ S_t ≦ 0.38 (see FIG. 2). Thereby, the groove area ratio S_ce of the center region is optimized.

  The groove area ratio is defined as groove area / (groove area + ground area). The groove area refers to the opening area of the groove on the ground contact surface. The groove refers to a circumferential groove and a lug groove in the tread portion, and does not include sipes or kerfs. The ground contact area is the contact area between the tire and the ground contact surface. In addition, the groove area and the contact area are determined when the tire is mounted on the specified rim and applied with the specified internal pressure, and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. Measured at the contact surface between the plate and the flat plate.

  For example, in this embodiment, since the ground contact width W_ce in the center region matches the ground contact width of the center land portion 31, the ratio between the groove area of the lug groove 311 of the center land portion 31 and the ground contact area on the ground surface is the center. It is calculated as the groove area ratio S_ce within the contact width W_ce of the region. Therefore, the groove area within the ground contact width W_ce of the center region does not include the groove area of the circumferential main groove 21 but includes only the groove area of the lug groove 311. On the other hand, the total groove area on the tire ground contact surface includes the groove area of the circumferential main groove 21 and the groove areas of the lug grooves 311 and 321. Thus, the groove area ratio S_ce within the ground contact width W_ce of the center region on the ground contact surface and the total groove area ratio S_t on the tire ground contact surface are calculated and optimized to the above range.

[Modification 1]
FIG. 5 is an explanatory view illustrating a first modification of the pneumatic tire depicted in FIG. 1.

  In the configuration of FIG. 2, a pair of circumferential main grooves 21, 21 are arranged, and the tread portion is partitioned into a center region and a shoulder region with these circumferential main grooves 21, 21 as boundaries. However, the present invention is not limited to this, and three or more circumferential main grooves 21 and 22 may be arranged (see FIG. 5).

  For example, in Modification 1 of FIG. 5, the four circumferential main grooves 21 and 22 are arranged symmetrically in the left and right regions with the tire equatorial plane CL as a boundary. The circumferential main grooves 21 and 22 define three rows of center land portions 31 and a pair of left and right shoulder land portions 32 and 32. Further, the tread portion is partitioned into a center region and a shoulder region by the left and right outermost circumferential main grooves 22, 22. Each center land portion 31 has a plurality of lug grooves 311, thereby forming a block row. Each center land portion 31 and left and right shoulder land portions 32 have a plurality of sipes 312 and 322, respectively. Moreover, all the sipes 312 arrange | positioned at each center land part 31 are two-dimensional sipes, and all the sipes 322 arrange | positioned at the left and right shoulder land parts 32 are three-dimensional sipes.

  In the configuration having three or more circumferential main grooves 21, 22, the ground contact width W_ce in the center region is equal to the ground contact width W_ce1 of each center land portion 31 between the left and right outermost circumferential main grooves 22, 22. The sum of W_ce3 (W_ce = W_ce1 + W_ce2 + W_ce3) is obtained (see FIG. 5). In addition, the groove area within the contact width W_ce of the center region on the tire contact surface does not include the groove areas of the circumferential main grooves 21 and 22 but includes only the groove area of the lug grooves 311. On the other hand, the total groove area on the tire ground contact surface includes the groove areas of all the circumferential main grooves 21 and 22 and the groove areas of the lug grooves 311 and 321. Based on these, the groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface and the total groove area ratio S_t on the tire contact surface are calculated and optimized to the above range.

[Modification 2]
FIG. 6 is an explanatory diagram illustrating a second modification of the pneumatic tire depicted in FIG. 1. The figure shows a passenger car winter tire having a directional tread pattern.

  In the configuration of FIG. 2, the center land portion 31 has a lug groove 311 having an open structure, thereby forming a block row. However, the present invention is not limited to this, and the center land portion 31 may have a rib-like structure by having a semi-closed structure lug groove or a closed structure lug groove (see FIG. 6). Furthermore, the center land portion 31 may have an inclined groove.

  Moreover, in the structure of FIG. 2, the shoulder land part 32 is a rib by having the lug groove 321 of a semi-closed structure. However, the present invention is not limited thereto, and the shoulder land portion 32 may be a block row that is partitioned into a plurality of lug grooves 321 having an open structure (see FIG. 6).

  In the configuration of FIG. 2, the sipe 312 of the center land portion 31 and the sipe 322 of the shoulder land portion 32 are both closed sipes. However, the present invention is not limited to this, and the sipe of the center land portion 31 may be an open sipe or a semi-closed sipe (see FIG. 6).

  For example, in the modification 2 of FIG. 6, the pneumatic tire 1 has a directional tread pattern. Moreover, the pneumatic tire 1 has designation | designated of the rotation direction on the basis of the advancing direction of a vehicle by having designation | designated of the mounting direction of the tire with respect to a vehicle. The designation of the tire mounting direction is generally written on the sidewall portion of the tire.

  The pneumatic tire 1 includes two circumferential main grooves 21 and 21 extending in the tire circumferential direction, one center land portion 31 defined by the circumferential main grooves 21 and 21, and left and right Shoulder land portions 32 and 32 are provided. In addition, the tire equatorial plane CL is located at the center of the center land portion 31. The distance W1 from the tire equatorial plane CL to the groove center line of the circumferential main groove 21 and the distance TW / 2 from the tire equatorial plane CL to the tire ground contact edge T are 0.40 ≦ W1 / (TW / 2). ) ≦ 0.60.

  The center land portion 31 has a rib-like structure, and has a plurality of main inclined grooves 313 and a plurality of sub inclined grooves 314.

  Further, the main inclined groove 313 extends while being inclined with respect to the tire circumferential direction in a manner of being separated from the tire equatorial plane CL in one direction of the tire circumferential direction. The plurality of main inclined grooves 313 are arranged at predetermined intervals in the tire circumferential direction, and are alternately arranged in the tire circumferential direction on both sides of the tire equatorial plane CL. One end of each main inclined groove 313 (the end on the rear side with respect to the tire rotation direction) communicates with one of the left and right circumferential main grooves 21, 21. Further, the angle θ1 formed by the main inclined groove 313 and the circumferential main groove 21 at the one end is within the range of 56 [deg] ≦ θ1 ≦ 76 [deg]. Further, the other end portion (the end portion on the front side with respect to the tire rotation direction) of each main inclined groove 313 communicates with the other main inclined groove 313 beyond the tire equatorial plane CL. In addition, an angle θ2 formed by the main inclined groove 313 and the sub inclined groove 314 at the other end is in a range of 37 [deg] ≦ θ2 ≦ 57 [deg]. The plurality of main inclined grooves 313 form a zigzag central groove extending along the tire circumferential direction on the tire equatorial plane CL. Further, each main inclined groove 313 has a groove width of 2 [mm] or more and 6 [mm] or less at a portion which becomes the central groove, and a groove depth of 2 [mm] or more and 6 [mm] or less. Have

  Further, the sub-inclined groove 314 extends while being inclined with respect to the tire circumferential direction so as to be separated from the tire equatorial plane CL in one direction of the tire circumferential direction. In addition, the sub-inclined groove 314 terminates both ends in the center land portion 31 while intersecting the two main inclined grooves 313. The sub inclined groove 314 may intersect with three or more main inclined grooves 313 (not shown). Further, the plurality of sub-inclined grooves 314 are arranged at predetermined intervals in the tire circumferential direction, and are alternately arranged on both sides of the tire equatorial plane CL in the tire circumferential direction. Further, the distance W2 from the tire equatorial plane CL to the inner end in the tire width direction of the sub-inclined groove 314 and the distance TW / 2 from the tire equatorial plane CL to the tire ground contact edge T are 0.05 ≦ W2 / ( TW / 2) ≦ 0.25. Further, the distance W3 from the tire equatorial plane CL to the outer end in the tire width direction of the auxiliary inclined groove 314 and the distance TW / 2 from the tire equatorial plane CL to the tire ground contact edge T are 0.25 ≦ W3 / ( TW / 2) ≦ 0.45.

  Moreover, the left and right shoulder land portions 32 have a plurality of lug grooves 321 and circumferential narrow grooves 323, respectively.

  Each lug groove 321 communicates with the circumferential main groove 21 at one end, and extends in the tire width direction beyond the tire ground contact end T at the other end. In addition, each lug groove 321 communicates with the main inclined groove 313 with the circumferential main groove 21 therebetween (the opening to the circumferential main groove 21 is opposed).

  Further, the circumferential narrow groove 323 is a straight narrow groove extending in the tire circumferential direction. Further, the groove width of the circumferential narrow groove 323 is set within a range of 2 [mm] or more and 4 [mm] or less. Further, the groove depth of the circumferential narrow groove 323 is set within a range of 2 [mm] or more and 4 [mm] or less.

  The center land portion 31 and the left and right shoulder land portions 32 have a plurality of sipes 312 and 322, respectively. In addition, 90% or more of the sipe 312 disposed in the center land portion 31 is configured by a two-dimensional sipe, and 90% or more of the sipe 322 disposed in the shoulder land portion 32 is configured by a three-dimensional sipe. Has been. The cap rubber 151 is made of a single rubber material constituting the center land portion 31 and the left and right shoulder land portions 32, 32, and has a single rubber hardness H_cap (see FIG. 1). The under rubber 152 includes a center under rubber 152_ce and a pair of left and right shoulder under rubbers 152_sh and 152_sh. The rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152_ce in the center land portion 31, and the rubber hardness H_ut_sh of the under rubber 152_sh in the shoulder land portion 32 have a relationship of H_cap <H_ut_ce <H_ut_sh. ing.

  In the second modification of FIG. 6, the center land portion 31 includes a main inclined groove 313 and a sub inclined groove 314 extending from the vicinity of the tire equatorial plane CL toward the outer side in the tire width direction. Performance is improved. Thereby, there is an advantage that dry maneuverability and snow maneuverability are improved. Further, the sub-inclined groove 314 intersects at least two main inclined grooves 313 and terminates both ends in the center land portion 31, and the main inclined grooves 313 and the sub-inclined grooves 314 are alternately arranged in the tire circumferential direction. By being arranged, the rigidity of the tread portion is maintained. Thereby, snow maneuverability can be improved while ensuring dry maneuverability appropriately.

  In the second modification of FIG. 6, the ground contact width W_ce in the center region matches the width of the center land portion 31 partitioned into the left and right circumferential main grooves 21, 21 (see FIG. 6). Further, the groove area within the ground contact width W_ce in the center region includes the groove areas of the main inclined groove 313 and the sub inclined groove 314, and does not include the groove area of the circumferential main groove 21. On the other hand, the total groove area on the tire ground contact surface includes the groove areas of the left and right circumferential main grooves 21 and the groove areas of the main inclined grooves 313 and the sub inclined grooves 314. Based on these, the groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface and the total groove area ratio S_t on the tire contact surface are calculated and optimized to the above range.

  FIG. 7 is an explanatory diagram showing a third modification of the pneumatic tire depicted in FIG. 1.

  In the configuration of FIG. 1, the average thickness t_ce of the under rubber 152 in the center region and the average thickness t_sh of the under rubber 152 in the shoulder region are set to be substantially the same.

  However, the present invention is not limited thereto, and the average thickness t_ce of the under rubber 152 in the center region may be set larger than the average thickness t_sh of the under rubber 152 in the shoulder region (see FIG. 7). For example, in Modification 3 of FIG. 7, the shoulder under rubber 152_sh has a bulging portion 1521 that is raised in a trapezoidal shape in the shoulder region in a cross-sectional view in the tire meridian direction. Further, the relationship between the average thickness t_ce of the under rubber 152 in the center region and the average thickness t_sh of the under rubber 152 (shoulder under rubber 152_sh) in the shoulder region is 1 [mm] ≦ t_sh−t_ce ≦ 3 [mm]. have. In such a configuration, the dry maneuverability of the tire and the snow maneuverability are compatible at a higher level. For example, the thinner the average thickness t_ce of the under rubber 152 in the center region, the better the snow handling of the tire, and the thinner the average thickness t_sh of the under rubber 152 in the shoulder region, the better the dry handling of the tire. To do.

  Note that the average thicknesses t_ce and t_sh of the under rubber 152 are measured as average values of thicknesses in the normal direction relative to the tire contact surface in a cross-sectional view in the tire meridian direction.

[effect]
As described above, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 extending in the tire circumferential direction and a plurality of land portions 31 and 32 partitioned by the circumferential main grooves 21. Provided in the tread portion (see FIG. 2). The land portion 31 in the center region and the land portions 32 in the left and right shoulder regions have a plurality of sipes 312 and 322, respectively. In addition, 90% or more of the sipe 312 disposed in the center region is composed of a two-dimensional sipe, and 90% or more of the sipe 322 disposed in the shoulder region is composed of a three-dimensional sipe. Further, the tread portion has a cap rubber 151 and an under rubber 152 (see FIG. 1). Further, the rubber hardness H_cap of the cap rubber 151 at 20 [° C.] and the rubber hardness H_ut of the under rubber 152 at 20 [° C.] have a relationship of H_cap <H_ut.

  In such a configuration, since the two-dimensional sipe 312 is disposed in the center region and the three-dimensional sipe 322 is disposed in the left and right shoulder regions, the rigidity of the center region is set low and the rigidity of the left and right shoulder regions is set high (see FIG. 2). Accordingly, the center region contributes to the improvement of snow handling, and the shoulder region contributes to the improvement of dry handling. Accordingly, there is an advantage that the dry maneuverability of the tire and the snow maneuverability are compatible at a high level. In addition, since the rubber hardness H_cap of the cap rubber 151 and the rubber hardness H_ut of the under rubber 152 have a relationship of H_cap <H_ut, there is an advantage that the snow maneuverability is improved.

  Further, in the pneumatic tire 1, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region at 20 [° C.], and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region at 20 [° C.]. Have a relationship of H_cap <H_ut_ce <H_ut_sh (see FIG. 1). In such a configuration, the rigidity of the center region is set low and the rigidity of the left and right shoulder regions is set high. Therefore, the rigidity of the center region is synergistically lowered and the rigidity of the left and right shoulder regions is synergistically increased due to the relationship between the arrangement configuration of the two-dimensional sipe and the three-dimensional sipe in the center region and the shoulder region. . Accordingly, there is an advantage that the dry maneuverability of the tire and the snow maneuverability are compatible at a high level.

  In the pneumatic tire 1, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region are 63 ≦ H_cap ≦ 68, 70 ≦ H_ut_ce ≦. 74, 75 ≦ H_ut_sh ≦ 80, 4 ≦ H_ut_ce−H_cap ≦ 9, 3 ≦ H_ut_sh−H_ut_ce ≦ 8. In such a configuration, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region, and the difference between these rubber hardnesses are optimized. There is an advantage that dry maneuverability and snow maneuverability are compatible at a higher level.

  In the pneumatic tire 1, the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region have a relationship of 1.3 ≦ D_ce / D_sh ≦ 2.0. In such a configuration, since the ratio D_ce / D_sh between the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region is optimized, an advantage that the dry maneuverability and the snow maneuverability of the tire are compatible at a higher level can be achieved. There is.

  In the pneumatic tire 1, the ground contact width W_ce in the center region and the tire ground contact width TW have a relationship of 0.45 ≦ W_ce / TW ≦ 0.55 (see FIG. 2). In such a configuration, since the ground contact width W_ce of the center region is optimized, there is an advantage that the dry maneuverability and the snow maneuverability of the tire are compatible at a higher level.

  Further, in this pneumatic tire 1, the groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface is in the range of 0.25 ≦ S_ce ≦ 0.35, and the total groove area on the tire contact surface is The ratio S_t is in the range of 0.25 ≦ S_t ≦ 0.38. In such a configuration, since the groove area ratio S_ce of the center region is optimized, there is an advantage that the dry maneuverability and the snow maneuverability of the tire are compatible at a higher level.

  In the pneumatic tire 1, the average thickness t_ce of the under rubber 152 in the center region and the average thickness t_sh of the under rubber 152 in the shoulder region satisfy 1 [mm] ≦ t_sh−t_ce ≦ 3 [mm]. There is a relationship (see FIG. 7). As a result, there is an advantage that the dry maneuverability of the tire and the snow maneuverability are compatible at a higher level.

  In addition, the pneumatic tire 1 includes one center land portion 31 that is divided into left and right outermost circumferential main grooves 21 and 21 in the center region (see FIG. 6). Further, the center land portion 31 has a plurality of main inclined grooves 313 and a plurality of sub inclined grooves 314 arranged in the tire circumferential direction. Further, the plurality of main inclined grooves 313 extend while being inclined with respect to the tire circumferential direction so as to be separated from the tire equatorial plane CL in one direction of the tire circumferential direction. The plurality of main inclined grooves 313 communicate with one of the left and right outermost circumferential main grooves 21 and 21 at one end. The plurality of main inclined grooves 313 are alternately arranged on both sides of the tire equatorial plane CL in the tire circumferential direction. Further, the plurality of sub-inclined grooves 314 extend while being inclined with respect to the tire circumferential direction so as to be separated from the tire equatorial plane CL in one direction in the tire circumferential direction. Further, the plurality of sub-inclined grooves 314 terminate both ends in the center land portion 31 while intersecting the two main inclined grooves 313 and 313. A plurality of sub-inclined grooves 314 are alternately arranged in the tire circumferential direction on both sides of the tire equatorial plane CL.

  In such a configuration, the center land portion 31 includes the main inclined groove 313 and the sub inclined groove 314 extending from the vicinity of the tire equatorial plane CL toward the outer side in the tire width direction, so that the drainage performance and snow discharge performance of the tire are improved. . Thereby, there is an advantage that dry maneuverability and snow maneuverability are improved.

  FIG. 8 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, (1) dry maneuverability and (2) snow maneuverability were evaluated for a plurality of different pneumatic tires (see FIG. 8). In these performance tests, a pneumatic tire with a tire size of 235 / 45R19 was assembled on a rim with a rim size of 19 × 8J, and the pneumatic tire had an air pressure of 250 [kPa] and 85 [%] of “LOAD CAPACITY” defined by ETRTO. Is applied. As a test vehicle, a sedan type four-wheel drive vehicle having a displacement of 3.0 [L] is used.

  (1) In the evaluation relating to dry handling, a test vehicle equipped with a pneumatic tire travels on a test course having a flat circuit around 60 [km / h] to 240 [km / h]. Then, the test driver performs sensory evaluation on the steering performance at the time of lane change and cornering and the stability at the time of straight traveling. This evaluation is performed by index evaluation based on Conventional Example 1 (100), and the larger the value, the better.

  (2) In the evaluation regarding snow maneuverability, a test vehicle equipped with pneumatic tires travels at a speed of 40 [km / h] on a handling course of a snowy road test site, and a test driver performs sensory evaluation. This evaluation is performed by index evaluation based on Conventional Example 1 (100), and the larger the value, the better.

  The pneumatic tire 1 of Example 1 has the configuration described in FIGS. 1 and 2, and includes two circumferential main grooves 21, one center land portion 31, and left and right shoulder land portions 32 as a tread portion. Prepare for. Further, all the sipes 312 arranged in the center land portion 31 are made of two-dimensional sipes, and all the sipes 322 arranged in the shoulder land portion 32 are made of three-dimensional sipes. Further, the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region have a relationship of H_cap <H_ut_ce <H_ut_sh. The sipe density D_ce in the center region and the sipe density D_sh in the shoulder region have a relationship of 1.00 ≦ D_ce / D_sh.

  The pneumatic tire 1 of Examples 2 to 16 is a modification of the pneumatic tire 1 of Example 1. The pneumatic tire 1 of Example 16 has the configuration shown in FIG. 5, and includes four circumferential main grooves 21 and 22, three center land portions 31, and left and right shoulder land portions 32. Prepare for the department. Moreover, the pneumatic tire 1 of Example 17 has the configuration described in FIG. 6, and includes a main inclined groove 313 and a sub inclined groove 314 in the center land portion 31.

  The pneumatic tires of Conventional Examples 1 to 5 have the block pattern shown in FIG. 2 or a block pattern in which the number of circumferential main grooves is increased in the block pattern shown in FIG.

  As shown in the test results, in the pneumatic tires 1 of Examples 1 to 16, it can be seen that the dry and snow handling characteristics of the tire are improved as compared with the pneumatic tire of Conventional Example 1 (FIG. 8). Further, when Examples 1 to 5 are compared, the relationship among the rubber hardness H_cap of the cap rubber 151, the rubber hardness H_ut_ce of the under rubber 152 in the center region, and the rubber hardness H_ut_sh of the under rubber 152 in the shoulder region is optimized. Thus, it can be seen that the dry maneuverability of the tire and the snow maneuverability are compatible. In addition, when Examples 1 and 7 to 9 are compared, the ratio D_ce / D_sh between the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region is optimized, so that the dry operation and the snow operation of the tire are performed. It turns out that sex is compatible. In addition, when Examples 1, 10, and 11 are compared, it can be seen that, by making the ground contact width W_ce of the center region appropriate, both the dry maneuverability of the tire and the snow maneuverability are compatible. In addition, when Examples 1, 12, and 13 are compared, it can be seen that, by optimizing the groove area ratio S_ce of the center region, both the dry maneuverability of the tire and the snow maneuverability are compatible.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 21, 22 Circumferential main groove, 31 Center land part, 311 Lag groove, 312 Sipe, 313 Main inclined groove, 314 Sub-inclined groove, 32 Shoulder land part, 321 Lag groove, 322 Sipe, 323 Circumferential direction Narrow groove, 11 bead core, 12 bead filler, 13 carcass layer, 14 belt layer, 141, 142 belt ply, 15 tread rubber, 151 cap rubber, 152 under rubber, 152_ce center under rubber, 1521 bulge, 151_sh shoulder under rubber , 16 Side wall rubber

Claims (8)

A pneumatic tire including a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of land portions defined by the circumferential main grooves in a tread portion,
The left and right circumferential main grooves on the outermost side in the tire width direction are referred to as outermost circumferential main grooves, and the inner region in the tire width direction of the tread section is defined by the groove center line of the left and right outermost circumferential main grooves. Is called the center region and the left and right regions outside the tire width direction are called shoulder regions,
The land portion of the center region and the land portions of the left and right shoulder regions each have a plurality of sipes,
90% or more of the sipes arranged in the center region are composed of two-dimensional sipes, and 90% or more of the sipes disposed in the shoulder region are composed of three-dimensional sipes,
The tread portion has a cap rubber and an under rubber, and
A pneumatic tire characterized in that a rubber hardness H_cap of the cap rubber at 20 [° C.] and a rubber hardness H_ut of the under rubber at 20 [° C.] have a relationship of H_cap <H_ut.   The rubber hardness H_cap of the cap rubber, the rubber hardness H_ut_ce of the under rubber in the center region at 20 [° C.], and the rubber hardness H_ut_sh of the under rubber in the shoulder region at 20 [° C.] are H_cap <H_ut_ce < The pneumatic tire according to claim 1, having a H_ut_sh relationship.   Rubber hardness H_cap of the cap rubber, rubber hardness H_ut_ce of the under rubber in the center region, and rubber hardness H_ut_sh of the under rubber in the shoulder region are 63 ≦ H_cap ≦ 68, 70 ≦ H_ut_ce ≦ 74, 75 ≦ H_ut_sh ≦ 80. The pneumatic tire according to claim 2, wherein 4 ≦ H_ut_ce−H_cap ≦ 9 and 3 ≦ H_ut_sh−H_ut_ce ≦ 8 are satisfied.   The pneumatic tire according to claim 1, wherein the sipe density D_ce in the center region and the sipe density D_sh in the shoulder region have a relationship of 1.3 ≦ D_ce / D_sh ≦ 2.0. .   The pneumatic tire according to any one of claims 1 to 4, wherein a ground contact width W_ce in the center region and a tire ground contact width TW have a relationship of 0.45 ≦ W_ce / TW ≦ 0.55.   The groove area ratio S_ce within the contact width W_ce of the center region on the tire contact surface is in the range of 0.25 ≦ S_ce ≦ 0.35, and the total groove area ratio S_t on the tire contact surface is 0.25 ≦ S_t. The pneumatic tire according to any one of claims 1 to 5, which is in a range of ≦ 0.38.   The average thickness t_ce of the under rubber in the center region and the average thickness t_sh of the under rubber in the shoulder region have a relationship of 1 [mm] ≦ t_sh−t_ce ≦ 3 [mm]. The pneumatic tire according to any one of 6. One center land portion divided into the left and right outermost circumferential main grooves is provided in the center region, and
The center land portion has a plurality of main inclined grooves and a plurality of sub inclined grooves arranged in the tire circumferential direction,
The plurality of main inclined grooves respectively extend while being inclined with respect to the tire circumferential direction so as to be separated from the tire equatorial plane in one direction of the tire circumferential direction, and at one end, the left and right outermost grooves are extended. While communicating with either one of the outer circumferential direction main grooves respectively, alternately arranged toward the tire circumferential direction on both sides of the tire equatorial plane,
The plurality of sub-inclined grooves extend while inclining with respect to the tire circumferential direction in a manner spaced from the tire equatorial plane in one direction of the tire circumferential direction, and intersect with the two main inclined grooves. The pneumatic tire according to any one of claims 1 to 7, wherein both ends are terminated in the center land portion and are alternately arranged on both sides of the tire equatorial plane in the tire circumferential direction.

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