Pneumatic tire

Abstract

To suppress uneven wear and chipping during traveling.SOLUTION: A pneumatic tire has a tread 10. The tread 10 includes a pair of shoulder regions 40 respectively provided on the outer side in a tire axial direction of a pair of shoulder main grooves 30 continuously extending in a tire circumferential direction and defined by a pair of ground contact ends E, and a center region 50 provided between the pair of shoulder main grooves 30, where a plurality of blocks are disposed in the center region 50 and the shoulder regions 40, and in a top view of the tread 10, area of the largest block having the largest area among the blocks disposed in the center region and the shoulder regions is 1.4 times or less area of the smallest block having the smallest area.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] Patent Document 1 discloses a pneumatic tire including a tread having a pair of shoulder main grooves continuously extending in the tire circumferential direction, a pair of crown main grooves continuously extending in the tire circumferential direction inside the shoulder main grooves in the tire axial direction, and a middle land portion between the crown main grooves and the shoulder main grooves. Further, Patent Document 1 discloses that the middle land portion has a first middle block having a tread area of S1 and a second middle block having a tread area of S2, and S1 / S2 is 0.9 or more and 1.1 or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, pneumatic tires have been required to suppress uneven wear and chipping during running. In particular, in off-road tires where running on rough ground is assumed, since the input from the road surface is large, it is more required to suppress uneven wear and chipping during running.

Means for Solving the Problems

[0005] The pneumatic tire of the present invention is a pneumatic tire having a tread, wherein the tread is provided on the outer side in the tire axial direction of a pair of shoulder main grooves continuously extending in the tire circumferential direction, and has a pair of shoulder regions partitioned by a pair of grounding ends and a center region provided between the pair of shoulder main grooves. A plurality of blocks are arranged in the center region and the shoulder regions. In a top view of the tread, the area of the largest block having the largest area among the blocks arranged in the center region and the shoulder regions is 1.4 times or less the area of the smallest block having the smallest area.

Advantages of the Invention

[0006] According to the pneumatic tire of the present invention, uneven wear and chipping during running can be suppressed.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, an example of an embodiment of the pneumatic tire according to the present invention will be described in detail. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. In addition, a mode formed by selectively combining the respective components of the embodiment described below is included in the present invention.

[0009] FIG. 1 is a half-sectional view of a pneumatic tire 1 according to an example of an embodiment, showing the internal structure of the tire. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10 that is a portion in contact with the road surface, a pair of sidewalls 11 disposed on both sides of the tread 10, and a pair of beads 12 disposed on the radially inner side of the sidewalls 11 in the tire diameter direction. Further, the pneumatic tire 1 includes a carcass 13 spanned between the pair of beads 12. The pneumatic tire 1 is assumed to be used off-road.

[0010] The tread 10 has a pair of shoulder main grooves 30 that continuously extend in the tire circumferential direction. Further, the tread 10 has a pair of shoulder regions 40 provided outside the shoulder main grooves 30 in the tire axial direction and partitioned by a pair of ground contact ends E, and a center region 50 provided between the pair of shoulder main grooves 30.

[0011] In this specification, the ground contact end E is defined as both ends in the tire axial direction of the region that contacts the flat road surface when a normal load is applied in a state where the unused pneumatic tire 1 is mounted on a normal rim and filled with air to reach the normal internal pressure.

[0012] Here, the "normal rim" is a rim defined by the tire standard, which is the "standard rim" in JATMA, and the "Measuring Rim" in TRA and ETRTO. The "normal internal pressure" is the "maximum air pressure" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "INFLATION PRESSURE" in ETRTO. The "normal load" is the "maximum load capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "LOAD CAPACITY" in ETRTO.

[0013] As will be described in detail later, a plurality of blocks having different shapes are arranged in the shoulder region 40 and the center region 50 of the tread 10. And, in a top view of the tread 10, among the blocks arranged in the center region 50 and the shoulder region 40, the area of the largest block with the largest area is 1.4 times or less the area of the smallest block with the smallest area. By setting the area of the largest block to 1.4 times or less the area of the smallest block, the difference in block rigidity between the blocks can be reduced, and uneven wear and chipping during running can be suppressed. Note that a block is a convex portion that is divided by main grooves, lateral grooves, and longitudinal grooves and protrudes outward in the tire diameter direction. That is, the region divided by sipes is not included in the block. Also, in this specification, a groove with a width of less than 1.5 mm is defined as a sipe. In other words, a block is a convex portion that is divided by a groove with a width of 1.5 mm or more and protrudes outward in the tire diameter direction.

[0014] The sidewall 11 is arranged on both sides of the tread 10 and is provided annularly along the tire circumferential direction. The sidewall 11 is the portion that protrudes the most outward in the tire axial direction of the pneumatic tire 1 and is gently curved so as to be convex outward in the tire axial direction. The sidewall 11 has a function of preventing damage to the carcass 13.

[0015] The bead 12 is arranged on the inner side in the tire diameter direction of the sidewall 11 and is the portion fixed to the rim of the wheel. The bead 12 has a bead core 14 and a bead filler 15. The bead core 14 is composed of a steel bead wire and is an annular member extending over the entire circumference in the tire circumferential direction and is embedded in the bead 12. The bead filler 15 has a tip-tapering shape extending outward in the tire diameter direction and is an annular rigid rubber member extending over the entire circumference in the tire circumferential direction.

[0016] The carcass 13 is spanned between a pair of beads 12 and is locked by being folded around the bead core 14. The carcass 13 is composed of at least one carcass ply. The carcass ply is formed by coating a carcass cord made of organic fibers with coating rubber. The carcass cord is arranged substantially perpendicular (for example, 80° or more and 90° or less) to the tire circumferential direction. Examples of the organic fibers used for the carcass cord include polyester fibers, rayon fibers, aramid fibers, and nylon fibers.

[0017] In the present embodiment, the carcass 13 is composed of three carcass plies 13A, 13B, and 13C. By configuring the carcass 13 with three or more carcass plies 13A, 13B, and 13C, the durability of the pneumatic tire 1 can be improved. Note that the number of carcass plies is not limited to this, and it may be one or two.

[0018] The pneumatic tire 1 further includes a belt layer 16 disposed on the outer periphery of the crown portion of the carcass 13 and a belt reinforcing layer 17 disposed on the outer periphery of the belt layer 16. That is, the belt layer 16 is disposed between the carcass 13 and the tread 10, and the belt reinforcing layer 17 is disposed between the belt layer 16 and the tread 10.

[0019] The belt layer 16 is composed of two belt plies 16A and 16B. By configuring the belt layer 16 with two belt plies 16A and 16B, it becomes easy to increase the rigidity of the tread 10. Note that the number of belt plies is not limited to this, and it may be one or three or more.

[0020] The belt plies 16A and 16B are formed by rubber-coating cords arranged in a direction inclined with respect to the tire circumferential direction. The material of the cords of the belt plies 16A and 16B is not particularly limited, and examples thereof include organic fibers such as polyester, rayon, nylon, and aramid, or metals such as steel.

[0021] Belt ply 16A is disposed on the inner side in the tire diameter direction of belt ply 16B. Also, the length of belt ply 16A in the tire axial direction is larger than the length of belt ply 16B in the tire axial direction. That is, the end portion of belt ply 16A is located on the outer side in the tire axial direction than the end portion of belt ply 16B.

[0022] The belt reinforcing layer 17 is composed of two belt reinforcing plies 17A and 17B. By configuring the belt reinforcing layer 17 with two belt reinforcing plies 17A and 17B, the restraint force of the belt layer 16 is improved, and it becomes easy to improve the durability of the pneumatic tire 1. Note that the number of belt reinforcing plies is not limited to this, and it may be one or three or more. Also, the belt reinforcing plies 17A and 17B may be cap plies that cover the entire width of the belt layer 16, or may be edge plies that cover only both ends in the tire axial direction of the belt layer 16.

[0023] The belt reinforcing plies 17A and 17B are configured by continuously winding an organic fiber cord aligned in the length direction in a spiral shape with respect to the tire circumferential direction. Examples of the organic fiber used for the belt reinforcing plies 17A and 17B include aramid fiber, polyester fiber, nylon fiber, and composite fibers composed of these fibers.

[0024] Hereinafter, with reference to FIG. 2, the tread pattern of the pneumatic tire 1 will be described in detail. FIG. 2 is a plan view of the pneumatic tire 1 (tread 10).

[0025] As shown in FIG. 2, the tread 10 is a point-symmetrical pattern that is point-symmetrical with an arbitrary point on the equator CL as the center of symmetry. Here, the equator CL is an imaginary line along the tire circumferential direction passing through the center in the tire axial direction of the tread 10.

[0026] The tread 10 has a pair of shoulder main grooves 30 that continuously extend in the tire circumferential direction. The shoulder main grooves 30 extend in a zigzag shape over the tire circumferential direction. Note that the shoulder main grooves 30 may extend linearly along the tire circumferential direction.

[0027] The groove width of the main shoulder groove 30 is preferably 3% or more of the grounding width D, and more preferably 5% or more of the grounding width D. By setting the groove width of the main shoulder groove 30 to 3% or more of the grounding width D, the drainage performance can be improved. Also, the upper limit of the groove width of the main shoulder groove 30 is, for example, 10% of the grounding width D. Therefore, the groove width of the main shoulder groove 30 is preferably 3% or more and 10% or less of the grounding width D, and more preferably 5% or more and 10% or less of the grounding width D. In this specification, the width of the groove means the width on the profile surface along the grounding surface of the tread 10 unless otherwise specified.

[0028] The depth of the main shoulder groove 30 is not particularly limited, but is, for example, 8.0 mm or more and 20.0 mm or less. In this specification, the depth of the groove means the length along the tire radial direction from the profile surface along the grounding surface of the tread 10 to the groove bottom unless otherwise specified.

[0029] The tread 10 has a pair of shoulder regions 40 provided outside the tire axial direction of the pair of main shoulder grooves 30 and partitioned by the grounding ends E, and a center region 50 provided between the pair of main shoulder grooves 30. The tire axial direction length of the center region 50 is, for example, 30% or more and 80% or less of the grounding width D. The tire axial direction length of the shoulder region 40 is 5% or more and 30% or less of the grounding width D on one side.

[0030] In the shoulder region 40, a first shoulder block 41 and a second shoulder block 42 having different shapes, and a shoulder cross groove 43 partitioning the first shoulder block 41 and the second shoulder block 42 are provided. The first shoulder block 41 and the second shoulder block 42 are alternately arranged in the tire circumferential direction via the shoulder cross groove 43.

[0031] In this embodiment, the inner end of the first shoulder block 41 in the tire axial direction is disposed inside the inner end of the second shoulder block 42 in the tire axial direction. Further, the second shoulder block 42 is formed to be slightly larger in size than the first shoulder block 41. The first shoulder block 41 and the second shoulder block 42 have a gently curved shape that slopes with respect to the tire axial direction as going toward the equator CL side.

[0032] The shoulder lateral groove 43 communicates with the shoulder main groove 30 and extends toward the ground contact end E side. The groove width of the shoulder lateral groove 43 is preferably 70% or more of the groove width of the shoulder main groove 30, and more preferably 80% or more of the groove width of the shoulder main groove 30. By setting the groove width of the shoulder lateral groove 43 to 70% or more of the groove width of the shoulder main groove 30, the drainage performance can be improved. Also, the groove width of the shoulder lateral groove 43 is preferably 110% or less of the groove width of the shoulder main groove 30, and more preferably 100% or less of the groove width of the shoulder main groove 30. By setting the groove width of the shoulder lateral groove 43 to 110% or less of the groove width of the shoulder main groove 30, the volume of the block disposed on the outer side in the tire axial direction can be increased, and as a result, the turning performance during running can be improved. Therefore, the groove width of the shoulder lateral groove 43 is preferably 70% or more and 110% or less of the groove width of the shoulder main groove 30, and more preferably 80% or more and 100% or less of the groove width of the shoulder main groove 30.

[0033] Also, the depth of the shoulder lateral groove 43 is, for example, 50% or more and 100% or less of the depth of the shoulder main groove 30. Further, the depth of the shoulder lateral groove 43 may be substantially uniform over the length direction of the shoulder lateral groove 43, or may be different in the length direction of the shoulder lateral groove 43. For example, the shoulder lateral groove 43 may have a region where the depth becomes smaller as going toward the outer side in the tire axial direction.

[0034] In the center region 50, there are provided a center block 51 which is arranged away from the shoulder main groove 30 and has a substantially polygonal shape, and a first middle block 52 and a second middle block 53 which are arranged around the center block 51. In the present embodiment, one first middle block 52 is arranged on each of both sides in the tire axial direction of the center block 51, and two second middle blocks 53 are arranged on each of both sides in the tire circumferential direction of the center block 51. That is, when the center block 51 and the first middle blocks 52 arranged on both sides in the tire axial direction of the center block 51 are taken as the first block group, and the two second middle blocks 53 are taken as the second block group, the first block group and the second block group are alternately arranged in the tire circumferential direction.

[0035] The center block 51 preferably has a substantially hexagonal shape. By making the center block 51 substantially hexagonal, it becomes easy to secure the volume of the center block 51, and the block rigidity of the center block 51 can be improved. As a result, wear and chipping of the center block 51 can be suppressed.

[0036] In addition, in the center region 50, there are provided an annular groove 54 which partitions the center block 51 and has a substantially polygonal shape, a center longitudinal groove 55 which connects adjacent annular grooves 54 in the tire circumferential direction, and two center transverse grooves 56, 57 which connect the annular groove 54 and the shoulder main groove 30.

[0037] In this embodiment, the annular groove 54, the center longitudinal groove 55, and the center transverse grooves 56 and 57 all have substantially the same groove width. The width of each groove is preferably 70% or more, and more preferably 80% or more, of the groove width of the shoulder main groove 30. By setting the width of each groove to 70% or more of the width of the shoulder main groove 30, the soil discharge performance can be improved. The upper limit of the width of each groove is, for example, 120% of the groove width of the shoulder main groove 30. Note that the groove width of the annular groove 54 may be larger than the groove widths of the center longitudinal groove 55 and the center transverse grooves 56 and 57. Also, the groove widths of the center transverse grooves 56 and 57 may be larger than the groove width of the center longitudinal groove 55.

[0038] Further, in this embodiment, the annular groove 54, the center longitudinal groove 55, and the center transverse grooves 56 and 57 all have substantially the same depth. The depth of each groove is, for example, 50% or more and 100% or less of the depth of the shoulder main groove 30.

[0039] The center longitudinal groove 55 separates the second middle blocks 53 adjacent to each other in the tire axial direction. The center longitudinal groove 55 extends along a direction inclined with respect to the tire circumferential direction. The inclination angle of the extending direction of the center longitudinal groove 55 with respect to the tire circumferential direction is, for example, 30° or more and 60° or less. Note that the center longitudinal groove 55 may extend along the tire circumferential direction.

[0040] The center transverse grooves 56 and 57 are inclined in directions opposite to each other with respect to the tire axial direction. Thereby, foreign matters such as soil, mud, and water that have entered the annular groove 54 are easily discharged efficiently, and the drainage performance and the soil discharge performance can be improved. Also, the center transverse groove 57 is disposed opposite to the shoulder transverse groove 43 via the shoulder main groove 30. Thereby, foreign matters such as soil, mud, and water are easily discharged efficiently via the shoulder transverse groove 43, and the drainage performance and the soil discharge performance can be further improved.

[0041] Here, in the top view of the tread 10, among the blocks arranged in the center region 50 and the shoulder region 40, the area of the largest block with the largest area is 1.4 times or less the area of the smallest block with the smallest area. As a result of the study by the present inventors, it has been found that by setting the area of the largest block to 1.4 times or less the area of the smallest block, the difference in block rigidity between each block can be reduced, and uneven wear and chipping during running can be suppressed. In other words, when the area of the largest block exceeds 1.4 times the area of the smallest block, uneven wear and chipping tend to occur in the smallest block with low block rigidity. Note that the area of the block described above means the area of the block in the profile plane along the ground contact surface of the tread 10.

[0042] The area of the largest block may be 1.4 times or less the area of the smallest block, but it is preferably 1.38 times or less the area of the smallest block, and more preferably 1.36 times or less the area of the smallest block. By reducing the difference between the area of the largest block and the area of the smallest block, uneven wear and chipping during running can be further suppressed. On the other hand, when the difference between the area of the largest block and the area of the smallest block becomes excessively small, the turning performance during running may decrease. Therefore, the area of the largest block is preferably 1.2 times or more the area of the smallest block.

[0043] In the present embodiment, the area of the second shoulder block 42 is the largest, and the area of the first middle block 52 is the smallest. That is, the second shoulder block 42 corresponds to the largest block, and the first middle block 52 corresponds to the smallest block.

[0044] The largest block is preferably arranged in the shoulder region 40. As described above, if the difference between the area of the largest block and the area of the smallest block is reduced, the turning performance during driving may deteriorate. By arranging the largest block in the shoulder region 40, the rigidity of the blocks arranged on the outer side in the tire axial direction increases, and the turning performance can be improved. That is, by arranging the largest block in the shoulder region 40 while making the area of the largest block 1.4 times or less the area of the smallest block, it is possible to suppress uneven wear and chipping during driving while ensuring the turning performance.

[0045] Also, the area of the center block 51 is preferably 0.85 times or more, more preferably 0.90 times or more, the area of the largest block, that is, the second shoulder block 42. Since the center block 51 is arranged at the center in the tire axial direction, uneven wear and chipping are likely to occur compared to other blocks. Therefore, by making the area of the center block 51 0.85 times or more the area of the second shoulder block 42, the rigidity of the center block 51 can be ensured, and uneven wear and chipping in the center block 51 are suppressed.

[0046] Also, the area of the center block 51 is preferably 0.98 times or less, more preferably 0.95 times or less, the area of the largest block, that is, the second shoulder block 42. By making the area of the center block 51 0.85 times or more the area of the second shoulder block 42, the volume of the blocks arranged in the shoulder region 40 can be ensured. Thereby, it is possible to suppress uneven wear and chipping during driving while ensuring the turning performance. Therefore, the area of the center block 51 is preferably 0.85 times or more and 0.98 times or less, more preferably 0.90 times or more and 0.95 times or less, the area of the largest block.

[0047] In this embodiment, as described above, blocks having two types of shapes are arranged in the shoulder region 40, and blocks having three types of shapes are arranged in the center region 50. That is, a total of five types of blocks having different shapes are arranged in the entire tread 10.

[0048] Also, as shown in FIG. 2, none of the blocks arranged in the shoulder region 40 and the center region 50 are provided with sipes and slits. In this case, the block rigidity of each block arranged in the shoulder region 40 and the center region 50 can be improved. As a result, uneven wear and chipping during driving can be suppressed. In this specification, a groove with a width of 1.5 mm or more is defined as a slit.

[0049] In addition, the corners of all the blocks arranged in the shoulder region 40 and the center region 50 have rounded shapes. Here, the radius of curvature of the rounded shape is preferably 1.0 mm or more, and more preferably 1.5 mm or more. By setting the radius of curvature of the rounded shape to 1.0 mm or more, chipping during driving can be further suppressed. Also, the radius of curvature of the rounded shape is preferably 3.0 mm or less, and more preferably 2.5 mm or less. By setting the radius of curvature of the rounded shape to 3.0 mm or less, the volume of each block can be ensured. As a result, the block rigidity of each block can be ensured. Therefore, the radius of curvature of the rounded shape is preferably 1.0 mm or more and 3.0 mm or less, and more preferably 1.5 mm or more and 2.5 mm or less.

[0050] As described above, among the blocks arranged in the shoulder region 40 and the center region 50, by setting the area of the largest block with the largest area to 1.4 times or less the area of the smallest block with the smallest area, the difference in block rigidity between the blocks can be reduced, and uneven wear and chipping during driving can be suppressed.

[0051] Note that the above embodiments can be appropriately modified without impairing the object of the present disclosure. For example, in the above embodiments, the tread 10 has a point-symmetric pattern that is point-symmetric with an arbitrary point on the equator CL as the center of symmetry, but the pattern arrangement of the tread 10 is not limited to this. For example, the tread 10 may be a line-symmetric pattern that is line-symmetric with the equator CL as the axis of symmetry. Further, the tread 10 may have a pattern other than the above point-symmetric pattern and line-symmetric pattern.

Example

[0052] Hereinafter, experimental examples will be shown, but the present invention is not limited to these experimental examples.

[0053] <Experimental Example 1> For the pneumatic tire T1 (tire size: 37X12.50R17LT, ground contact width D: 250 mm) having the tread pattern shown in FIG. 2, an FEM model divided into finite elements was created. Then, the longitudinal rigidity of each block constituting the tread was calculated by computer simulation using the FEM model. Note that the longitudinal rigidity is the rigidity that resists the longitudinal load applied from above to below to the tread. Further, in the simulation, the rigidity was calculated in a state where the tire was mounted on a specified rim and the specified internal pressure (150 kPa) was applied.

[0054] <Experimental Example 2> The tread pattern of the pneumatic tire T2 in Experimental Example 2 is shown in FIG. 3. Note that the pneumatic tire T2 in Experimental Example 2 has the same configuration as Experimental Example 1 except for the tread pattern. Further, in FIG. 3, the same reference numerals are given to the same components as those in the above embodiments.

[0055] As shown in FIG. 3, the tread 10A of Experimental Example 2 has a point-symmetrical pattern similar to the tread 10 (see FIG. 2) of Experimental Example 1, and includes a center block 51, a first middle block 52, a second middle block 53, a first shoulder block 41, and a second shoulder block 42. Note that the tread 10A of Experimental Example 2 differs from the tread 10 of Experimental Example 1 in that sipes 60 are formed in each block. Further, the tread 10A of Experimental Example 2 differs from the tread 10 of Experimental Example 1 in that slits 61, 62, and 63 that terminate inside each block are formed in the center block 51, the first middle block 52, and the second middle block 53.

[0056] Table 1 shows the areas of the upper surfaces of the respective blocks included in the treads of Experimental Example 1 and Experimental Example 2. Table 1 also shows the ratio (Smax / Smin) of the area of the largest block to the area of the smallest block, and the ratio (Scen / Smax) of the area of the center block to the area of the largest block.

[0057] [Table 1]

[0058] As shown in Table 1, for the pneumatic tire T1 of Experimental Example 1, the ratio (Smax / Smin) of the area of the largest block to the area of the smallest block is 1.4 or less, whereas for the pneumatic tire T2 of Experimental Example 2, the ratio (Smax / Smin) of the area of the largest block to the area of the smallest block exceeds 1.4.

[0059] Next, the longitudinal rigidity of each block calculated by simulation is shown in Fig. 4. In Fig. 4, the center block 51 is denoted as block number 1, the first middle block 52 as block number 2, the second middle block 53 as block number 3, the first shoulder block 41 as block number 4, and the second shoulder block 42 as block number 5. Also, in Fig. 4, the average value of the longitudinal rigidity of each block in each experimental example is denoted as 100. As a result of the study by the present inventors, a pneumatic tire with a small variation in the longitudinal rigidity of each block, that is, a small difference between the maximum value and the minimum value of the longitudinal rigidity, is a pneumatic tire in which uneven wear and chipping during running are less likely to occur.

[0060] As shown in Fig. 4, in the pneumatic tire T1 of Experimental Example 1, the variation in the longitudinal rigidity of each block is within a range of ±20% with respect to the average value. On the other hand, in the pneumatic tire T2 of Experimental Example 2, the variation in the longitudinal rigidity of each block is about ±25% with respect to the average value. From this, it can be said that by setting the ratio (Smax / Smin) of the area of the largest block to the area of the smallest block to 1.4 or less, the difference in the block rigidity of each block can be reduced. That is, by setting the ratio (Smax / Smin) of the area of the largest block to the area of the smallest block to 1.4 or less, uneven wear and chipping during running can be suppressed.

Explanation of Signs

[0061] 1 Pneumatic tire, 10 Tread, 11 Sidewall, 12 Bead, 13 Carcass, 13A, 13B, 13C Carcass ply, 14 Bead core, 15 Bead filler, 16 Belt layer, 16A, 16B Belt ply, 17 Belt reinforcing layer, 17A, 17B Belt reinforcing ply, 30 Shoulder main groove, 40 Shoulder region, 41 First shoulder block, 42 Second shoulder block, 43 Shoulder cross groove, 50 Center region, 51 Center block, 52 First middle block, 53 Second middle block, 54 Annular groove, 55 Center longitudinal groove, 56, 57 Center cross groove

Claims

1. A pneumatic tire having a tread, wherein the tread has a pair of shoulder regions respectively provided outside the tire axial direction of a pair of shoulder main grooves continuously extending in the tire circumferential direction and partitioned by a pair of grounding ends, and a center region provided between the pair of shoulder main grooves, and has a plurality of blocks are arranged in the center region and the shoulder regions, in a top view of the tread, among the blocks arranged in the center region and the shoulder regions, the area of the largest block with the largest area is 1.4 times or less the area of the smallest block with the smallest area, the pneumatic tire.

2. In the center region, a center block arranged away from the shoulder main groove and having a substantially polygonal shape, and middle blocks arranged around the center block, are provided, the pneumatic tire according to claim 1.

3. The center block has a substantially hexagonal shape, the pneumatic tire according to claim 2.

4. None of the blocks arranged in the center region and the shoulder regions are provided with sipes and slits, the pneumatic tire according to claim 1.

5. The largest block is arranged in the shoulder region, the pneumatic tire according to claim 1.

6. The area of the center block is 0.85 times or more the area of the largest block, the pneumatic tire according to claim 2.

7. In the center region, an annular groove partitioning the center block and having a substantially polygonal shape, and center longitudinal grooves connecting the adjacent annular grooves in the tire circumferential direction, and a plurality of center transverse grooves connecting the annular groove and the shoulder main groove, are provided, the pneumatic tire according to claim 2.

8. The groove width of the annular groove is 80% or more the groove width of the shoulder main groove, the pneumatic tire according to claim 7.

9. The plurality of center transverse grooves are inclined in opposite directions with respect to the tire axial direction, the pneumatic tire according to claim 7.

10. The corners of all the blocks arranged in the center region and the shoulder regions have rounded corners, the radius of curvature of the rounded corners is 1.0 mm or more and 3.0 mm or less, the pneumatic tire according to claim 1.

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