JP7059782B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving the wet starting performance of the tire.

The heavy-duty tire has a problem that the contact area of the tire is reduced and the tire becomes slippery when the loaded vehicle is empty, and the wet starting performance of the tire deteriorates. The wet start performance is a traction performance in a low speed region on a wet road surface, particularly a traction performance when the vehicle starts from a stopped state, and is an evaluation showing that the slip ratio of the tire immediately after the start of rolling of the tire is small.

As a related conventional pneumatic tire, the technique described in Patent Document 1 is known. This document describes pneumatic tires with excellent traction on wet roads (evaluation based on measured values of the time required to accelerate from a stationary state and travel a predetermined distance. See paragraph 0036 of Reference 1). To disclose.

Japanese Unexamined Patent Publication No. 2006-111122

It is an object of the present invention to provide a pneumatic tire capable of improving the wet starting performance of the tire.

In order to achieve the above object, the pneumatic tire according to the present invention has a pair of shoulder circumferential grooves and a pair of center circumferential grooves extending in the tire circumferential direction, and the shoulder circumferential groove and the center circumferential groove. A pair of compartmentalized shoulder land areas, a pair of second land areas and a center land area, and a plurality of second lug grooves and a plurality of center lug grooves penetrating the pair of second land areas and the center land area in the tire width direction. A ground contact region R of 50 [%] of the tire ground contact width centered on the equatorial plane of the tire is defined, and the groove area ratio Ra of the ground contact region R is 0.25≤Ra≤0. The total length Lb of the projected lengths of the edges of all the grooves arranged in the ground contact region R in the tire circumferential direction in the range of 45 and the ground contact width TW'of the ground contact region R are 25 ≦ Lb /. It is characterized by having a relationship of TW'≦ 35.

The pneumatic tire according to the present invention has an advantage that the edge component in the tire circumferential direction of the groove in the ground contact region R when the vehicle is empty is optimized, and the wet starting performance of the tire is improved.

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. FIG. 3 is a plan view showing a shoulder region of the pneumatic tire shown in FIG. FIG. 4 is a plan view showing a center region of the pneumatic tire shown in FIG. FIG. 5 is a cross-sectional view of the pneumatic tire shown in FIG. 2 in the groove depth direction. FIG. 6 is a tread plan view showing a modified example of the pneumatic tire shown in FIG. 2. FIG. 7 is a plan view showing a center region of the pneumatic tire shown in FIG. FIG. 8 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention. FIG. 9 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

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

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

In the figure, the cross section in the tire meridian direction means a cross section when the tire is cut on a plane including a tire rotation axis (not shown). Further, the reference numeral CL is a tire equatorial plane, and refers to a plane that passes through the center point of the tire in the direction of the tire rotation axis and is perpendicular to the tire rotation axis. Further, the tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

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

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

The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. To configure. Further, both ends of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. Further, the carcass ply of the carcass layer 13 is composed of a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) coated with coated rubber and rolled, and has an absolute value of 80. It has a carcass angle of [deg] or more and 90 [deg] or less (defined as an inclination angle in the longitudinal direction of the carcass cord with respect to the tire circumferential direction).

The belt layer 14 is formed by laminating a high-angle belt 141, a pair of crossing belts 142 and 143, and a belt cover 144, and is arranged so as to be hung around the outer periphery of the carcass layer 13. The high-angle belt 141 is configured by covering a plurality of belt cords made of steel or organic fiber with coated rubber and rolling them, and has a belt angle of 45 [deg] or more and 70 [deg] or less in absolute value (tire circumferential direction). It is defined as the longitudinal tilt angle of the belt cord with respect to.). The pair of crossed belts 142 and 143 are formed by coating a plurality of belt cords made of steel or organic fiber with coated rubber and rolling them, and have a belt angle of 10 [deg] or more and 55 [deg] or less in absolute value. Have. Further, the pair of crossed belts 142 and 143 have belt angles having different symbols from each other, and are laminated so that the longitudinal directions of the belt cords cross each other (having a so-called cross-ply structure). The belt cover 144 is formed by coating a plurality of belt cover cords made of steel or an organic fiber material with coated rubber and rolling them, and has a belt angle of 10 [deg] or more and 55 [deg] or less in absolute value.

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the radial direction of the tire to form a tread portion of the tire. The pair of sidewall rubbers 16 and 16 are arranged on the outer sides of the carcass layer 13 in the tire width direction, respectively, to form the left and right sidewall portions. The pair of rim cushion rubbers 17 and 17 are arranged inside the left and right bead cores 11 and 11 and the rewinding portion of the carcass layer 13 in the tire radial direction, respectively, to form a rim fitting surface of the bead portion.

[Tread pattern]
FIG. 2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. The figure shows the tread pattern of all-season tires. In the figure, the tire circumferential direction means the direction around the tire rotation axis. Further, the reference numeral T is a tire contact end, and the dimension symbol TW is a tire contact width.

As shown in FIG. 2, the pneumatic tire 1 has four circumferential grooves 21 and 22 extending in the circumferential direction of the tire, and five rows of land portions 31 to 21 divided into these circumferential grooves 21 and 22. 33 is provided on the tread surface. Specifically, the left and right regions with the tire equatorial plane CL as a boundary have two circumferential grooves 21 and 22, respectively. Further, these circumferential grooves 21 and 22 are arranged symmetrically with respect to the tire equatorial plane CL. Further, one land portion 33 is arranged on the tire equatorial plane CL. Further, each of the land portions 31 to 33 has a plurality of lug grooves 311, 321, 331.

Here, of the two circumferential grooves 21 and 22 arranged in one region with the tire equatorial plane CL as a boundary, the circumferential groove 21 on the tire contact end T side is called a shoulder circumferential groove, and the tire is tired. The circumferential groove 22 on the CL side of the equatorial plane is called a center circumferential groove.

Further, the land portions 31 and 31 on the outer side in the tire width direction divided into the left and right shoulder circumferential grooves 21 and 21 are defined as the shoulder land portions. The shoulder land portion 31 is the outermost land portion in the tire width direction and is located on the tire ground contact end T. Further, the land portion 32 divided into the shoulder circumferential groove 21 and the center circumferential groove 22 is defined as the second land portion. Further, the land portion 33 divided into the left and right center circumferential grooves 22 and 22 is defined as the center land portion. The center land portion 33 is arranged on the tire equatorial plane CL. Further, the lug groove 311 arranged in the shoulder land portion 31 is defined as a shoulder lug groove, the lug groove 321 arranged in the second land portion 32 is defined as a second lug groove, and the lug groove arranged in the center land portion 33 is defined. 331 is defined as a center lug groove.

In the configuration of FIG. 2, the four circumferential grooves 21 and 22 are the main grooves. However, the present invention is not limited to this, and the left and right center circumferential grooves 22 and 22 may be the main grooves, and the left and right shoulder circumferential grooves 21 and 21 may be fine grooves. Further, in the configuration of FIG. 2, the four circumferential grooves 21 and 22 have a zigzag shape. However, the present invention is not limited to this, and some circumferential grooves, for example, the shoulder circumferential groove 21 may have a straight shape.

The main groove is a groove having an obligation to display a wear indicator specified in JATTA. Further, the lug groove is a lateral groove extending in the tire width direction, and opens when the tire touches the ground and functions as a groove. Further, the sipe described later is a notch formed in the tread tread surface, and is distinguished from a lug groove in that it is closed when the tire touches the ground.

For example, in the configuration of FIG. 2, the groove width Wg21 of the left and right shoulder circumferential grooves 21 and 21 is in the range of 4.0 [mm] ≤ Wg21 ≤ 12.0 [mm], and the groove depth Hg21 (the figure described later). 5) is in the range of 6.0 [mm] ≤ Hg21 ≤ 18.0 [mm]. Further, the groove width Wg22 of the left and right center circumferential grooves 22 and 22 is in the range of 6.0 [mm] ≤ Wg22 ≤ 15.0 [mm], and the groove depth Hg22 (see FIG. 5) is 10.0. It is in the range of [mm] ≦ Hg22 ≦ 18.0 [mm].

Further, in the configuration of FIG. 2, the lug grooves 311, 321, 331 of the land portions 31 to 33 have an open structure penetrating the land portions 31 to 33 in the tire width direction, and have a predetermined interval in the tire circumferential direction. It is arranged in. Therefore, each land portion 31 to 33 includes a plurality of blocks 312, 322, and 332 (see FIGS. 3 and 4 described later), which are partitioned by a plurality of lug grooves 311, 321, and 331.

Further, the groove width Wg31 (see FIG. 3) of the shoulder lug groove 311 is in the range of 4 [mm] ≦ Wg31 ≦ 16 [mm], and the groove depth Hg31 (see FIG. 5) is 2 [mm] ≦ Hg31 ≦ 16. It is in the range of [mm]. Further, the groove width Wg32 (see FIG. 3) of the second lug groove 321 is in the range of 4 [mm] ≦ Wg32 ≦ 9 [mm], and the groove depth Hg32 (see FIG. 5) is 2 [mm] ≦ Hg32 ≦ 16. It is in the range of [mm]. Further, the groove width Wg33 (see FIG. 4) of the center lug groove 331 is in the range of 4 [mm] ≦ Wg33 ≦ 9 [mm], and the groove depth Hg33 (see FIG. 5) is 9 [mm] ≦ Hg33 ≦ 18. It is in the range of [mm].

The groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled. In a configuration in which the land portion has a notch or a chamfered portion at the edge portion, the groove width is measured at the intersection of the tread tread and the extension line of the groove wall in a cross-sectional view with the groove length direction as the normal direction. Is measured. Further, in the configuration in which the grooves extend in a zigzag shape or a wavy shape in the tire circumferential direction, the groove width is measured as the distance between the facing groove walls.

The groove depth is measured as the maximum value of the distance from the tread tread to the groove bottom in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled. Further, in the case where the groove has a partially uneven portion or a sipe at the groove bottom, the groove depth is measured by excluding these.

The sipe width is measured as the maximum value of the opening width of the sipe on the tread surface of the land in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled.

The sipe depth is measured as the maximum value of the distance from the tread tread to the bottom of the sipe under no load with the tire mounted on the specified rim and filled with the specified internal pressure. Further, in the configuration in which the sipe has a partially uneven portion at the groove bottom, the sipe depth is measured excluding these.

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

For example, in the configuration of FIG. 2, the pneumatic tire 1 has a substantially point-symmetrical tread pattern having a center point on the tire equatorial plane CL. However, the present invention is not limited to this, and the pneumatic tire 1 may have, for example, a left-right axisymmetric tread pattern or a left-right asymmetric tread pattern centered on the tire equatorial plane CL, and may have a directionality in the tire rotation direction. It may have a tread pattern to have (not shown).

Further, in FIG. 2, the distance D1 from the tire equatorial plane CL to the groove center line of the shoulder circumferential groove 21 and the tire contact width TW have a relationship of 0.30 ≦ D1 / TW ≦ 0.35. Further, it is preferable that the distance D2 from the tire equatorial plane CL to the groove center line of the center circumferential groove 22 and the tire contact width TW have a relationship of 0.20 ≦ D2 / TW ≦ 0.30, and 0.25. It is more preferable to have a relationship of ≦ D2 / TW ≦ 0.30. Therefore, the left and right center circumferential grooves 22 and 22 are arranged in the ground contact region R when the vehicle is empty, which will be described later.

The groove center line of the circumferential main groove is defined as a straight line passing through the midpoints of the left and right measurement points of the groove width of the circumferential main groove and parallel to the tire circumferential direction.

The tire contact width is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply the specified internal pressure 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 linear distance in the tire axis direction.

The tire ground contact end is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply the specified internal pressure and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is defined as the maximum width position in the tire axial direction.

[Groove area ratio in the ground contact area when the vehicle is empty]
FIG. 3 is a plan view showing a shoulder region of the pneumatic tire shown in FIG. FIG. 4 is a plan view showing a center region of the pneumatic tire shown in FIG. In these figures, FIG. 3 shows the block rows of the shoulder land portion 31 and the second land portion 32, and FIG. 4 shows the block rows of the second land portion 32 and the center land portion 33. FIG. 5 is a cross-sectional view of the pneumatic tire shown in FIG. 2 in the groove depth direction. The figure shows a cross-sectional view along the lug grooves 311, 321, 331 of each land portion 31 to 33.

In FIG. 2, the ground contact region R of the tire ground contact half width TW'(50 [%] of the ground contact width TW) with the tire equatorial plane CL as the center line is defined. This ground contact area R corresponds to the ground contact area when the vehicle is empty, and specifically corresponds to the ground contact area when a load of 20 [%] to 30 [%] of the specified load is applied.

At this time, the groove area ratio Ra of the ground contact region R when the vehicle is empty is preferably in the range of 0.25 ≦ Ra ≦ 0.45, and preferably in the range of 0.27 ≦ Ra ≦ 0.38. By the above lower limit, the groove area ratio of the ground contact region R is secured, and the wet running performance of the tire (that is, the tire performance during running on a wet road surface, particularly the wet braking performance and the wet steering stability performance) is ensured. Further, by the above upper limit, the ground contact area of the ground contact area R is secured, and the dry performance of the tire (that is, the tire performance while traveling on a dry road surface, particularly the uneven wear resistance performance and the dry steering stability performance) is ensured. ..

The groove area ratio is defined by the groove area / (groove area + ground contact area) in a predetermined region. The groove area means the opening area of the groove on the ground plane. Further, the groove means a circumferential groove and a lug groove of the tread portion, and does not include a sipe, a calf, a notch portion and the like. The ground contact area is measured as the contact area between the tire and the road surface.

Further, the groove area ratio Rc of the center land portion 33 is preferably in the range of 0.20 ≦ Rc ≦ 0.30, and more preferably in the range of 0.25 ≦ Rc ≦ 0.30. By the above lower limit, the groove area ratio Rc of the center land portion 33 is secured, and the wet running performance of the tire is ensured. Further, by the above upper limit, the rigidity of the center land portion 33 is secured, and the dry performance of the tire is ensured.

The ground contact area ratio of the land portion is calculated as the ratio of the ground contact area of the land portion to the area of the band-shaped region whose left and right boundaries are the measurement points of the maximum ground contact width of the land portion.

Further, in the configuration of FIG. 2, the total sum of the edge components in the tire circumferential direction of the grooves arranged in the ground contact region R when the vehicle is empty is set to be relatively large. Specifically, the relationship between the total length Lb of the projected lengths of all the grooves arranged in the ground contact region R in the tire circumferential direction and the ground contact width TW'of the ground contact region R is 25≤Lb / TW'≤35. It is preferable to have a relationship of 28 ≦ Lb / TW'≦ 30. By the above lower limit, the edge component of the groove in the ground contact region R in the tire circumferential direction is secured, and the wet starting performance of the tire is ensured. Further, by the above upper limit, the decrease in the rigidity of the land portion due to the excessive groove length is suppressed, and the dry performance of the tire is ensured.

Similarly, the total sum of the edge components in the tire width direction of the grooves arranged in the ground contact region R when the vehicle is empty is set to be relatively large. Specifically, the relationship between the total La of the projected lengths of all the grooves arranged in the ground contact region R in the tire width direction and the ground contact width TW'of the ground contact region R is 60≤La / TW'≤70. It is preferable to have a relationship of 62 ≦ La / TW'≦ 70. By the above lower limit, the edge component of the groove in the ground contact region R in the tire width direction is secured, and the wet starting performance of the tire is ensured. Further, by the above upper limit, the decrease in the rigidity of the land portion due to the excessive groove length is suppressed, and the dry performance of the tire is ensured.

The projected groove length is measured as the groove length when the edges of all the grooves (excluding the sipes that block when the tire touches the ground) are projected on the tire contact patch in the tire width direction or the tire circumferential direction. To.

Further, in the configuration of FIG. 2, the groove width Wg21 of the shoulder circumferential groove 21 and the groove width Wg22 of the center circumferential groove 22 have a relationship of Wg21 <Wg22 (see FIG. 2). Therefore, the groove width Wg 22 of the center circumferential groove 22 is set to be relatively large. In such a configuration, since the left and right center circumferential grooves 22 and 22 are arranged in the ground contact region R when the vehicle is empty as described above, the groove area of the ground contact region R is secured and the wet performance of the tire is ensured. On the other hand, since the groove width Wg21 of the shoulder circumferential groove 21 is set to be relatively narrow, the rigidity of the shoulder region of the tread portion is ensured, and the braking performance of the tire is ensured. Further, the groove widths Wg21 and Wg22 preferably have a relationship of 0.55 ≦ Wg21 / Wg22 ≦ 0.75, and more preferably 0.60 ≦ Wg21 / Wg22 ≦ 0.70.

Further, the ground contact area Ac of the center land portion 33 and the ground contact areas Am1 and Am2 of the pair of second land portions 32 and 32 in the ground contact region R when the vehicle is empty have a relationship of 0.40 ≦ (Am1 + Am2) / Ac ≦ 0.60. It is preferable to have, and it is more preferable to have a relationship of 0.42 ≦ (Am1 + Am2) / Ac ≦ 0.60. Therefore, the ground contact areas Am1 and Am2 of the second land portions 32 and 32 are set to be relatively large. By the above lower limit, the contact areas Am1 and Am2 of the second land portions 32 and 32 are secured, and the dry performance of the tire is ensured. Further, by the above upper limit, uneven wear caused by excessive ground contact areas Am1 and Am2 of the second land portions 32 and 32 is suppressed. Further, it is preferable that the ground contact areas Am1 and Am2 of the left and right second land portions 32 and 32 have a relationship of 0.90 ≦ Am1 / Am2 ≦ 1.10. As a result, the contact areas on the left and right sides of the tire in the contact area R are made uniform.

Further, in the configuration of FIG. 2, a plurality of blocks 312, 322, 332 (see FIGS. 3 and 4) in which each land portion 31 to 33 is partitioned by a plurality of lug grooves 311, 321, 331 as described above. To prepare for. Here, the block 312 of the shoulder land portion 31 is defined as the shoulder block, the block 322 of the second land portion 32 is defined as the second block, and the block 332 of the center land portion 33 is defined as the center block.

At this time, it is preferable that the ground contact area Bm of the second block 322 and the ground contact area Bc of the center block 332 have a relationship of 0.55 ≦ Bm / Bc ≦ 0.75, and 0.60 ≦ Bm / Bc ≦ 0. It is more preferable to have a relationship of .70. Further, it is preferable that the ground contact area Bs of the shoulder block 312 and the ground contact area Bc of the center block 332 have a relationship of 0.50 ≦ Bs / Bc ≦ 0.60. Further, it is preferable that the ground contact area Bs of the shoulder block 312 and the ground contact area Bm of the second block 322 have a relationship of 0.90 ≦ Bs / Bm ≦ 1.10. As a result, the contact area ratio of the blocks 312, 322, and 332 of each land portion 31 to 33 is optimized, and uneven wear of the blocks is suppressed.

Further, in the configuration of FIG. 2, the pitch numbers Ns, Nm, and Nc of the blocks 312, 322, and 332 of each land portion 31 to 33 are the same, and are set in the range of 50 or more and 55 or less. However, the present invention is not limited to this, and the pitch numbers Ns, Nm, and Nc of each land portion 31 to 33 may be different (not shown).

[Additional features]
In the configuration of FIG. 2, the pneumatic tire 1 has the following additional features.

As shown in FIG. 2, the four circumferential grooves 21 and 22 have a zigzag shape having an amplitude in the tire width direction. Further, the adjacent circumferential grooves 21, 22; 22, 22; 22, 21 are arranged so that the zigzag shapes are reversed from each other. Further, the lug grooves 311, 321 and 331 of the land portions 31 to 33 open to the zigzag-shaped tops of the circumferential grooves 21 and 22. Further, the lug grooves 311, 321; 321 and 331 of the adjacent land portions 31, 32; 32, 33 alternately open in the tire circumferential direction with respect to the zigzag-shaped tops of the circumferential grooves 21, 22. As a result, the blocks 312, 322; 322, and 332 of the adjacent land portions 31, 32; 32, 33 are arranged in a staggered manner in the tire circumferential direction with the circumferential groove 21; 22 interposed therebetween. Further, the left and right edge portions of the blocks 312, 322, and 332 of the land portions 31 to 33 have a shape that is convex toward the circumferential grooves 21 and 22 along the zigzag shape of the circumferential grooves 21 and 22. Therefore, each block 312, 322, and 332 has a ground contact shape that widens toward the central portion in the tire circumferential direction.

As shown in FIG. 3, the groove width Wg31 of the shoulder lug groove 311 of the shoulder land portion 31 widens from the shoulder circumferential groove 21 toward the tire ground contact end T. As a result, the drainage property of the shoulder region of the tread portion is enhanced. On the other hand, the groove width Wg 32 of the second lug groove 321 of the second land portion 32 widens from the shoulder circumferential groove 21 toward the center circumferential groove 22 side. As a result, the groove area ratio Ra of the ground contact region R when the vehicle is empty is increased. Further, it is preferable that the ratio of the maximum value and the minimum value of the groove width Wg32 is in the range of 1.00 ≦ Wg32_max / Wg32_min ≦ 1.10.

Further, as shown in FIG. 3, the shoulder lug groove 311 and the second lug groove 321 are inclined in the same direction with each other. Further, it is preferable that the inclination angle θ1 of the shoulder lug groove 311 with respect to the tire circumferential direction is in the range of 74 [deg] ≦ θ1 ≦ 80 [deg]. Further, it is preferable that the inclination angle θ2 of the second lug groove 321 with respect to the tire circumferential direction is in the range of 73 [deg] ≦ θ2 ≦ 81 [deg].

The inclination angle of the lug groove is measured as the angle formed by the straight line connecting the left and right end portions of the lug groove and the tire circumferential direction.

Further, the shoulder block 312 is provided with a notch 313 at the edge portion on the shoulder circumferential direction groove 21 side. Further, the notch 313 is on an extension of the groove center line (not shown) of the second lug groove 321. Specifically, the notch 313 is arranged at the maximum width position of the shoulder block 312 and faces the groove opening of the second lug groove 321. Similarly, the second block 322 includes a notch 323 at the edge portion on the shoulder circumferential groove 21 side. Further, the notch portion 323 is on an extension line of the groove center line (not shown) of the shoulder lug groove 311. Specifically, the notch 323 is arranged at the maximum width position of the second block 322 and faces the groove opening of the second lug groove 321. Further, the notch 313 of the shoulder block 312 and the notch 323 of the second block 322 are arranged in a staggered manner in the tire circumferential direction. As a result, the edge component of the shoulder region of the tread portion is increased, and the wet performance of the tire is improved.

The notch is defined as a stepped recess (ie, a step) with a bottom surface parallel to the tread of the land.

Further, as shown in FIG. 5, the amount of steps from the treads of the land portions 31 and 32 to the bottom surface of the cutout portions 313 and 323 (dimension symbols omitted in the figure) is the groove depth Hg21 of the shoulder circumferential groove 21. It is preferably in the range of 25 [%] or more and 35 [%] or less. In the configuration of FIG. 5, the step amount of the cutout portions 313 and 323 is set to be the same as the groove depths Wg31 and Wg32 of the lug grooves 311 and 321.

As shown in FIG. 4, it is preferable that the center lug groove 331 of the center land portion 33 has a bending shape having a plurality of bending points. In the configuration of FIG. 4, the center lug groove 331 has a Z-shape having two bending points, and is arranged so as to intersect the tire equatorial plane CL at the intermediate extending portion of the Z-shape. Further, it is preferable that each portion of the Z-shape is inclined with respect to the tire circumferential direction. Specifically, the angle θ31 formed by the left and right extending portions of the Z-shape and the tire circumferential direction is in the range of 65 [deg] ≤ θ31 ≤ 74 [deg], and the intermediate extending portion and the tire circumferential direction It is preferable that the angle θ32 formed by the tires is in the range of 4 [deg] ≤ θ32 ≤ 9 [deg]. As a result, the projected length of the center lug groove 331 in the tire circumferential direction and the tire width direction is increased, and the wet performance of the tire is improved.

Further, in the configuration of FIG. 4, the center block 332 does not have a groove and a sipe penetrating the center block 332. Therefore, the ground contact surface of the center block 332 is not divided by a groove or a sipe, and is continuous over the entire area in the tire circumferential direction and the width direction. As a result, the rigidity of the center block 332 is ensured, and the dry performance of the tire is improved.

Further, in the configuration of FIG. 4, the shoulder block 312 and the second block 322 do not have grooves and sipes penetrating these blocks 312 and 322. As a result, the rigidity of the blocks 312 and 322 is ensured, and the dry performance of the tire is improved.

However, the present invention is not limited to this, and blocks 312, 322, and 332 may have sipes penetrating blocks 312 to 332 (not shown). Even in such a configuration, since the sipe is closed when the tire touches the ground, the rigidity of the blocks 312 to 332 is properly ensured. Further, the blocks 312 to 332 may be provided with a narrow groove or a shallow groove having a closed structure that terminates in the ground plane of the blocks 312 to 332 (not shown). Further, as will be described later, the blocks 312 to 332 may be provided with a shallow groove penetrating the blocks 312 to 332 in the tire width direction. Even with these configurations, the rigidity of the blocks 312 to 332 can be ensured.

In FIG. 5, as described above, the groove width Wg21 (see FIG. 2) of the shoulder circumferential groove 21 is narrower than the groove width Wg22 of the center circumferential groove 22 (Wg21 <Wg22), and as shown in FIG. , The groove depth Hg21 of the shoulder circumferential groove 21 is shallower than the groove depth Hg22 of the center circumferential groove 22 (Hg21 <Hg21). As a result, the groove volume of the ground contact region R (see FIG. 2) when the vehicle is empty becomes relatively large, and the wet performance of the tire is improved. In addition, the rigidity of the shoulder region of the tread portion becomes relatively large, and the dry braking performance of the tire is improved. Further, it is preferable that the groove depth Hg21 of the shoulder circumferential groove 21 and the groove depth Hg22 of the center circumferential groove 22 have a relationship of 1.00 ≦ Hg22 / Hg21 ≦ 1.20.

Further, as shown in FIG. 5, the groove depths Hg31 and Hg32 of the shoulder lug groove 311 and the second lug groove 321 are shallower than the groove depth Hg21 of the shoulder circumferential groove 21 (Hg31 <Hg21, Hg32 <Hg21). As a result, the rigidity of the shoulder region of the tread portion becomes relatively large, and the dry braking performance of the tire is improved. Further, the groove depths Hg31 and Hg32 of the shoulder lug groove 311 and the second lug groove 321 may be in the range of 25 [%] or more and 30 [%] or less with respect to the groove depth Hg21 of the shoulder circumferential groove 21. preferable.

Further, the groove depth Hg 33 of the center lug groove 331 is deeper than the groove depth Hg 32 of the second lug groove 321 (Hg32 <Hg33). As a result, the groove volume of the ground contact region R when the vehicle is empty is secured, and the wet performance of the tire is ensured. Further, it is preferable that the groove depth Hg 33 of the center lug groove 331 and the groove depth Hg 32 of the second lug groove 321 have a relationship of 2.40 ≦ Hg 33 / Hg 32 ≦ 2.90.

In the configuration of FIG. 5, the lug grooves 311, 321, and 331 of the land portions 31 to 33 have a constant groove depth. However, the present invention is not limited to this, and the lug grooves 311, 321, 331 may have a bottom upper portion at the groove opening with respect to the circumferential grooves 21 and 22 (not shown). As a result, the rigidity of the land portions 31 to 33 is increased.

[Modification example]
FIG. 6 is a tread plan view showing a modified example of the pneumatic tire shown in FIG. 2. FIG. 7 is a plan view showing a center region of the pneumatic tire shown in FIG. The figure shows a block row of the second land area 32 and the center land area 33. In these figures, the same components as those shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In the configuration of FIG. 2, the center block 332 does not have a groove and a sipe that penetrate the center block 332 in the tire circumferential direction. In such a configuration, the ground contact surface of the center block 332 is not divided in the tire width direction when the tire touches the ground, so that the rigidity of the center block 332 is ensured, which is preferable.

On the other hand, in the configurations of FIGS. 6 and 7, each of the second block 322 and the center block 332 is provided with fine grooves 324 and 333 (see FIG. 7) penetrating the blocks 322 and 332 in the tire width direction. Further, the groove widths of these fine grooves 324 and 333 are in the range of 1.0 [mm] or more and 3.0 [mm] or less, and the groove depth is 1.0 [mm] 3.0 or more [mm] or less. Is in the range of. In such a configuration, the edge component of the ground contact region R when the vehicle is empty is increased by the narrow grooves 324 and 333, and the wet starting performance of the tire is improved.

For example, in the configuration of FIG. 7, the narrow groove 324 of the second block 322 has a straight shape, is arranged at the center of the second block 322 in the tire circumferential direction, and penetrates the second block 322 in the tire width direction. .. Further, one end of the narrow groove 324 opens in the notch 323 of the second block 322, and the other end opens at the maximum width position on the center circumferential groove 22 side of the second block 322.

Further, the narrow groove 333 of the center block 332 has a bending shape having a plurality of bending points, is arranged at the center of the block 332 in the tire circumferential direction, and penetrates the center block 332 in the tire width direction. Further, each of both ends of the narrow groove 333 is opened at the maximum width position on the center circumferential direction groove 22 and 22 side of the center block 332. Specifically, the center lug groove 331 has a Z shape having two bending points, and the narrow groove 333 of the center block 332 has a zigzag shape having four bending points. Further, the zigzag shape of the fine groove 333 is substantially parallel to the first fine groove portion (reference numeral omitted in the figure) extending in the tire width direction in the tire circumferential direction (that is, the inclination angle is within the range of ± 5 [degrees]. It is formed by alternately connecting the second narrow grooves extending in). Further, the second narrow groove portion extending in the tire circumferential direction is at a distance of 20 [%] or more and 40 [%] or less of the ground contact width of the center block 332 from the maximum width position of the center block 332.

Further, as described above, the ground contact area Bc of the center block 332 and the ground contact area Bm of the second block have a relationship of 0.55 ≦ Bm / Bc ≦ 0.75. The treads of the second block 322 and the center block 332 are substantially bisected by the narrow grooves 324 and 333. Specifically, the ground contact areas Sm1 and Sm2 of the pair of treads of the second block 322 partitioned in the narrow groove 324 are in the range of 0.80 ≦ Sm1 / Sm2 ≦ 1.20, and are divided into the fine grooves 333. The ground contact areas Sc1 and Sc2 of the pair of treads of the center block 332 are in the range of 0.80 ≦ Sc1 / Sc2 ≦ 1.10. As a result, the ground contact areas of the center block 332 and the second block partitioned by the narrow grooves 324 and 333 are made uniform, and uneven wear of the blocks 322 and 332 is suppressed.

[effect]
As described above, the pneumatic tire 1 has a pair of shoulder circumferential grooves 21, 21 and a pair of center circumferential grooves 22, 22 extending in the tire circumferential direction, and a shoulder circumferential groove 21 and a center circumferential direction. A plurality of shoulder land portions 31, a pair of second land portions 32, 32 and a center land portion 33, 33, and a plurality of penetrating the pair of second land portions 32 and the center land portion 33 in the tire width direction, which are partitioned by the groove 22. A second lug groove 321 and a plurality of center lug grooves 331 are provided (see FIG. 2). Further, when defining a ground contact region R of 50 [%] of the tire ground contact width TW centered on the tire equatorial plane CL, the groove area ratio Ra of the ground contact region R is in the range of 0.25 ≦ Ra ≦ 0.45. It is in. Further, the relationship between the total length Lb of the projected lengths of the edges of all the grooves arranged in the ground contact region R in the tire circumferential direction and the ground contact width TW'of the ground contact region R is 25≤Lb / TW'≤35. Has.

In such a configuration, (1) the groove area ratio Ra of the ground contact region R when the vehicle is empty is optimized, and there is an advantage that both wet performance and dry performance of the tire are compatible. That is, by the above lower limit, the groove area ratio of the ground contact region R is secured, and the wet running performance of the tire (that is, the tire performance while running on a wet road surface, particularly the wet braking performance and the wet steering stability performance) is ensured. To. Further, by the above upper limit, the ground contact area of the ground contact area R is secured, and the dry performance of the tire (that is, the tire performance while traveling on a dry road surface, particularly the uneven wear resistance performance and the dry steering stability performance) is ensured. ..

Further, (2) the edge component (total projected length Lb) of the groove in the ground contact region R when the vehicle is empty is optimized, and there is an advantage that both wet performance and dry performance of the tire are compatible. That is, by the above lower limit, the edge component of the groove in the ground contact region R in the tire circumferential direction is secured, and the wet starting performance of the tire is ensured. Further, by the above upper limit, the decrease in the rigidity of the land portion due to the excessive groove length is suppressed, and the dry performance of the tire is ensured.

Further, in the pneumatic tire 1, the total La of the projected lengths of all the grooves arranged in the ground contact region R in the tire width direction and the ground contact width TW'(see FIG. 2) of the ground contact region R are 60. It has a relationship of ≦ La / TW'≦ 70. As a result, the edge component (total projected length La) of the groove in the ground contact region R when the vehicle is empty is optimized, and there is an advantage that both wet performance and dry performance of the tire are compatible. That is, by the above lower limit, the edge component of the groove in the ground contact region R in the tire width direction is secured, and the straight start performance on the wet road is ensured. Further, by the above upper limit, the decrease in the rigidity of the land portion due to the excessive groove length is suppressed, and the dry performance of the tire is ensured.

Further, in the pneumatic tire 1, the distance D2 from the tire equatorial plane CL to the groove center line of the center circumferential groove 22 and the tire contact width TW have a relationship of 0.20 ≦ D2 / TW ≦ 0.30. Have (see FIG. 2). This has the advantage that the position of the center circumferential groove 22 is optimized. That is, by the above lower limit, the edge component of the groove in the ground contact region R in the tire width direction is secured, and the wet starting performance of the tire is ensured. Further, by the above upper limit, the decrease in the rigidity of the land portion due to the excessive groove length is suppressed, and the dry performance of the tire is ensured.

Further, in the pneumatic tire 1, the ground contact areas Am1 and Am2 of the pair of second land portions 32 and the ground contact area Ac of the center land portion 33 in the ground contact region R are 0.40 ≦ (Am1 + Am2) / Ac ≦ 0.60. Have a relationship. This has the advantage that the ground contact areas Am1 and Am2 of the second land portion 32 are optimized. That is, by the above lower limit, the contact areas Am1 and Am2 of the second land portions 32 and 32 are secured, and the dry performance of the tire is ensured. Further, by the above upper limit, uneven wear of the second land portion 32 due to the excessive ground contact areas Am1 and Am2 of the second land portions 32 and 32 is suppressed.

Further, in the pneumatic tire 1, the groove area ratio Rc of the center land portion 33 is in the range of 0.23 ≦ Rc ≦ 0.30. This has the advantage that the groove area ratio Rc of the center land portion 33 is optimized. That is, by the above lower limit, the groove area ratio Rc of the center land portion 33 is secured, and the wet running performance of the tire is ensured. Further, by the above upper limit, the rigidity of the center land portion 33 is secured, and the dry performance of the tire is ensured.

Further, the pneumatic tire 1 includes a plurality of center blocks 332 partitioned by a plurality of center lug grooves 331 (see FIG. 3). Further, the center block 332 has an edge portion that is convex toward the groove 22 in the center circumferential direction. This has the advantage that the rigidity of the center block 332 is ensured, the dry performance of the tire is improved, and the drainage property of the center lug groove 331 is improved.

Further, in the pneumatic tire 1, the groove width Wg21 of the shoulder circumferential groove 21 and the groove width Wg22 of the center circumferential groove 22 have a relationship of Wg21 <Wg22 (see FIG. 2). In such a configuration, since the left and right center circumferential grooves 22 and 22 are arranged in the ground contact region R when the vehicle is empty, the groove area of the ground contact region R is secured and the wet performance of the tire is ensured. On the other hand, since the groove width Wg21 of the shoulder circumferential groove 21 is set to be relatively narrow, the rigidity of the shoulder region of the tread portion is ensured, and the braking performance of the tire is ensured.

Further, in the pneumatic tire 1, the groove widths Wg21 and Wg22 (see FIG. 2) described above have a relationship of 0.55 ≦ Wg21 / Wg22 ≦ 0.75. This has the advantage that the groove widths Wg21 and Wg22 of the shoulder circumferential groove 21 and the center circumferential groove 22 are optimized.

Further, the pneumatic tire 1 includes a plurality of second blocks 322 and a plurality of center blocks 332 partitioned by a plurality of second lug grooves 321 and a plurality of center lug grooves 331 (see FIG. 4). Further, the ground contact area Bm of the second block 322 and the ground contact area Bc of the center block 332 have a relationship of 0.55 ≦ Bm / Bc ≦ 0.75. This has the advantage that the ground contact area ratio of the second block 322 and the center block 332 is optimized, and uneven wear of the block is suppressed.

Further, the pneumatic tire 1 has a plurality of shoulder lug grooves 311 penetrating the shoulder land portion 31 in the tire width direction, and a plurality of shoulder blocks 312 partitioned by a plurality of shoulder lug grooves 311 and a plurality of center lug grooves 331. And a plurality of center blocks 332 (see FIGS. 3 and 4). Further, the ground contact area Bs of the shoulder block 312 and the ground contact area Bc of the center block 332 have a relationship of 0.50 ≦ Bs / Bc ≦ 0.60. As a result, the contact area ratio of the blocks 312, 322, and 332 of each land portion 31 to 33 is optimized, and uneven wear of the blocks is suppressed.

Further, the pneumatic tire 1 includes a plurality of shoulder lug grooves 311 penetrating the shoulder land portion 31 in the tire width direction, and a plurality of second blocks 322 partitioned by the plurality of second lug grooves 321 (see FIG. 3). ). Further, the second block 322 is provided with a notch 323 at the edge portion on the shoulder circumferential direction groove 21 side. Further, the notch 323 is on an extension of the groove center line of the shoulder lug groove 311. In such a configuration, the edge component of the notch 323 has an advantage that the wet performance of the tire is improved. Further, since the cutout portion 323 is on the extension line of the shoulder lug groove 311, there is an advantage that the drainage property is improved and the wet performance of the tire is further improved.

Further, the pneumatic tire 1 has a plurality of shoulder lug grooves 311 penetrating the shoulder land portion 31 in the tire width direction, and a plurality of shoulder blocks 312 partitioned by a plurality of shoulder lug grooves 311 and a plurality of second lug grooves 321. And a plurality of second blocks 322 (see FIG. 3). Further, the shoulder block 312 is provided with a notch 323 at the edge portion on the shoulder circumferential direction groove 21 side. Further, the notch 323 is on an extension of the groove center line of the second lug groove 321. In such a configuration, the edge component of the notch 323 has an advantage that the wet performance of the tire is improved. Further, since the notch 323 is on the extension line of the second lug groove 321, there is an advantage that the drainage property is improved and the wet performance of the tire is further improved.

Further, the pneumatic tire 1 includes a plurality of center blocks 332 partitioned by a plurality of center lug grooves 331 (see FIG. 4). Further, the center block 332 does not have a groove penetrating the center block 332 in the tire circumferential direction. This has the advantage that the rigidity of the center block 332 is ensured and the dry performance of the tire is improved.

Further, the pneumatic tire 1 includes a plurality of second blocks 322 partitioned by a plurality of second lug grooves 321 and a plurality of center blocks 332 partitioned by a plurality of center lug grooves 331 (FIGS. 6 and 7). reference). Further, at least one of the second block 322 and the center block 332 is provided with narrow grooves 324 and 333 penetrating the block in the tire width direction (see FIG. 7). This has the advantage that the edge component of the ground contact region R when the vehicle is empty is increased by the narrow grooves 324 and 333, and the wet starting performance of the tire is improved.

Further, in the pneumatic tire 1, the groove width of the fine grooves 324 and 333 (see FIG. 7) is in the range of 1.0 [mm] or more and 3.0 [mm] or less, and the groove depth is 1.0 [. It is in the range of mm] or more and 3.0 [mm] or less. This has the advantage that the edge action of the fine grooves 324 and 333 is properly ensured.

8 and 9 are charts showing the results of performance tests of pneumatic tires according to the embodiment of the present invention.

In this performance test, a plurality of types of test tires were evaluated for (1) wet start performance, (2) wet acceleration performance, and (3) dry steering stability performance. Further, a test tire having a tire size of 11R22.5 Y69 is assembled to the specified rim of JATTA, and the specified internal pressure of JATTA and a load of 6.2 [kN] are applied to this test tire. Further, the test tires are mounted on all the wheels of the tractor head, which is the test vehicle.

(1) In the evaluation of wet starting performance, the test vehicle accelerates the test course on the wet road surface with the full accelerator while the traction control system is turned off and the diff lock system is turned on. Then, the time from 0 [km / h] to 6 [km / h] of the traveling speed is measured, and the index evaluation is performed. This evaluation is performed by an exponential evaluation based on the conventional example (100), and the larger the value, the more preferable.

(2) In the evaluation of wet acceleration performance, the test vehicle accelerates the test course on the wet road surface with the full accelerator while the traction control system is turned off and the diff lock system is turned on. Then, the time from 6 [km / h] to 21 [km / h] of the traveling speed is measured, and the index evaluation is performed. This evaluation is performed by an exponential evaluation based on the conventional example (100), and the larger the value, the more preferable.

(3) In the evaluation of dry steering stability performance, the test vehicle runs on the test course, and a professional test driver evaluates the feeling regarding lane change performance and cornering performance. This evaluation is performed by an exponential evaluation based on the conventional example (100), and the larger the value, the more preferable.

The test tires of Examples 1-18 have the configurations of FIGS. 1 and 2. Further, the tire contact width TW is 250 [mm], and therefore the contact width TW'of the contact region R when the vehicle is empty is 125 [mm]. Further, the center circumferential groove 22 is the main groove, the groove width Wg22 thereof is 5.0 [mm], and the groove depth Hg22 thereof is 14.0 [mm]. Further, the ground contact area Bc of the center block 332 (see FIG. 4) is 13500 [mm ^ 2], and the pitch number Nc is 54.

In the test tire of the conventional example 1, the numerical value in the configuration of the first embodiment is changed.

As shown by the test results, it can be seen that the test tires of Examples 1 to 18 have both wet starting performance, wet acceleration performance and dry steering stability performance.

1 Pneumatic tire, 11 bead core, 12 bead filler, 13 carcass layer, 14 belt layer, 141 high angle belt, 142, 143 cross belt, 144 belt cover, 15 tread rubber, 16 sidewall rubber, 17 rim cushion rubber, 21 Shoulder circumferential groove, 22 center circumferential groove, 31 shoulder land, 311 shoulder lug groove, 312 shoulder block, 313 notch, 32 second land, 321 second lug groove, 322 second block, 323 notch, 324 narrow groove , 33 center land, 331 center lug groove, 332 center block, 333 narrow groove

Claims (15)

A pair of shoulder circumferential grooves and a pair of center circumferential grooves extending in the tire circumferential direction, a pair of shoulder land portions, a pair of second land portions and a center partitioned by the shoulder circumferential groove and the center circumferential groove. A pneumatic tire comprising a land portion, a plurality of second lug grooves and a plurality of center lug grooves penetrating the pair of second land portions and the center land portion in the tire width direction.
A ground contact region R of 50 [%] of the tire ground contact width centered on the tire equatorial plane is defined.
The groove area ratio Ra of the ground contact region R is in the range of 0.25 ≦ Ra ≦ 0.45, and
The total Lb of the projected lengths of the edges of all the grooves arranged in the ground contact region R in the tire circumferential direction and the ground contact width TW'of the ground contact region R have a relationship of 25≤Lb / TW'≤35. Pneumatic tires that feature that. Claim 1 in which the total La of the projected lengths of all the grooves arranged in the ground contact region R in the tire width direction and the ground contact width TW'of the ground contact region R have a relationship of 60≤La / TW'≤70. Pneumatic tires listed in. The air according to claim 1 or 2, wherein the distance D2 from the tire equatorial plane to the groove center line of the center circumferential groove and the tire contact width TW have a relationship of 0.20 ≦ D2 / TW ≦ 0.30. Tires with. Claims 1 to 3 in which the ground contact areas Am1 and Am2 of the pair of second land portions and the ground contact area Ac of the center land portion in the ground contact region R have a relationship of 0.40 ≦ (Am1 + Am2) / Ac ≦ 0.60. Pneumatic tires listed in any one. The pneumatic tire according to any one of claims 1 to 4, wherein the groove area ratio Rc of the center land portion is in the range of 0.23 ≦ Rc ≦ 0.30. A plurality of center blocks partitioned by the plurality of center lug grooves are provided, and
The pneumatic tire according to any one of claims 1 to 5, wherein the center block has an edge portion that is convex toward the groove side in the center circumferential direction. The pneumatic tire according to any one of claims 1 to 6, wherein the groove width Wg21 of the shoulder circumferential groove and the groove width Wg22 of the center circumferential groove have a relationship of Wg21 <Wg22. The pneumatic tire according to claim 7, wherein the groove widths Wg21 and Wg22 have a relationship of 0.55 ≦ Wg21 / Wg22 ≦ 0.75. A plurality of second blocks and a plurality of center blocks partitioned by the plurality of second lug grooves and the plurality of center lug grooves are provided, and the plurality of center blocks are provided.
The pneumatic tire according to any one of claims 1 to 8, wherein the ground contact area Bm of the second block and the ground contact area Bc of the center block have a relationship of 0.55 ≦ Bm / Bc ≦ 0.75. .. A plurality of shoulder lug grooves penetrating the shoulder land portion in the tire width direction, a plurality of shoulder blocks and a plurality of center blocks partitioned by the plurality of shoulder lug grooves and the plurality of center lug grooves are provided.
The pneumatic tire according to claim 9, wherein the ground contact area Bs of the shoulder block and the ground contact area Bc of the center block have a relationship of 0.50 ≦ Bs / Bc ≦ 0.60. A plurality of shoulder lug grooves penetrating the shoulder land portion in the tire width direction and a plurality of second blocks partitioned by the plurality of second lug grooves are provided, and
The second block is provided with a notch at the edge portion on the shoulder circumferential groove side.
The pneumatic tire according to any one of claims 1 to 10, wherein the notch is on an extension of the groove center line of the shoulder lug groove. A plurality of shoulder lug grooves penetrating the shoulder land portion in the tire width direction, a plurality of shoulder blocks and a plurality of second blocks partitioned by the plurality of shoulder lug grooves and the plurality of second lug grooves, and
The shoulder block is provided with a notch at the edge portion on the shoulder circumferential groove side.
The pneumatic tire according to any one of claims 1 to 11, wherein the notch is on an extension of the groove center line of the second lug groove. A plurality of center blocks partitioned by the plurality of center lug grooves are provided, and
The pneumatic tire according to any one of claims 1 to 12, wherein the center block does not have a groove penetrating the center block in the tire circumferential direction. A plurality of second blocks partitioned by the plurality of second lug grooves and a plurality of center blocks partitioned by the plurality of center lug grooves are provided, and
The pneumatic tire according to any one of claims 1 to 13, wherein at least one of the second block and the center block has a narrow groove penetrating the block in the tire width direction. The 14th aspect of the present invention, wherein the groove width of the fine groove is in the range of 1.0 [mm] or more and 3.0 [mm] or less, and the groove depth is in the range of 1.0 [mm] or more and [mm] or less. Pneumatic tires.

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