JP6891454B2 - tire - Google Patents

Description

The present invention relates to a tire capable of improving the uneven wear resistance of a block provided on a tread portion.

For example, Patent Document 1 below proposes a tire provided with a plurality of blocks having hexagonal treads. Each block of Patent Document 1 is provided with a crossing sipe that crosses the tread in the tire axial direction.

However, both ends of the transverse sipe of Patent Document 1 are connected to the top of the block wall protruding outward from the block. In general, since a large stress acts near the top of the block wall, the sipes of Patent Document 1 tend to cause uneven wear near the top.

Further, in Patent Document 1, the crown block and the middle block tend to wear unevenly.

As described above, the tire of Patent Document 1 has room for further improvement in improving the uneven wear resistance of the block.

Japanese Unexamined Patent Publication No. 2011-98622

The present invention has been devised in view of the above circumstances, and a main object of the present invention is to provide a tire capable of improving the uneven wear resistance of a block.

The present invention is a tire in which a tread portion is provided with a crown land portion and a middle land portion that are divided into a plurality of main grooves that extend continuously in the tire circumferential direction and are adjacent to each other. A plurality of crown blocks partitioned by a plurality of crown transverse grooves are included, and the middle land portion includes a plurality of middle blocks partitioned by a plurality of middle transverse grooves, and in a plan view of the tread portion, the crown blocks and the said Each middle block extends between the first block wall and the second block wall facing the main groove, the first end opened by the first block wall, and the second end opened by the second block wall. The first block wall and the second block wall each have a top protruding outward from the block and are curved in a V shape. In the crown block, the first end of the crossing sipe is located on the first side of the top of the first block wall in the tire circumferential direction, and the second end of the crossing sipe is the second block. The first crown block located on the second side of the top of the wall in the tire circumferential direction and the first end of the tread are located on the second side of the top of the first block wall. The second end of the crossing sipe includes a second crown block located on the first side of the top of the second block wall, and each middle block has the first end of the crossing sipe as said first. The second end of the tread is located on the second side of the top of the one block wall and the second end of the tread is located on the first side of the top of the second block wall.

In the tire of the present invention, it is desirable that the first crown block and the second crown block are alternately provided in the tire circumferential direction.

In the tire of the present invention, each of the crown blocks and each of the middle blocks has a first region and a second region partitioned on both sides of the transverse sipe in the tire circumferential direction, and the first region and the second region are defined. It is desirable that each of the tires has a closed sipe having both ends interrupted within each region.

In the tire of the present invention, the closed sipe provided in each of the middle blocks is inclined in the same direction, and the closed sipe provided in the first crown block and the closed sipe provided in the second crown block are provided. It is desirable that the closed sipe is inclined in opposite directions to each other.

In the tire of the present invention, each of the closed sipe extends in a wavy shape, and the center line of the wavy amplitude of the closed sipe provided in the crown block is arranged at the angle θ1 with respect to the tire axial direction, and the middle It is desirable that the center line of the wavy amplitude of the closed sipe provided on the block is arranged at an angle θ2 smaller than the angle θ1 with respect to the tire axial direction.

In the tire of the present invention, in each of the middle blocks, the closed sipe provided in the first region and the closed sipe provided in the second region are formed so as to overlap each other in the tire axial direction. In each crown block, it is desirable that the closed sipe provided in the first region and the closed sipe provided in the second region are formed so as not to overlap each other in the tire axial direction.

In the tire of the present invention, each of the crossing sipes has a first portion that undulates in the tire axial direction from the first end, a second portion that undulates in the tire axial direction from the second end, and the first portion. The closed sipe provided in each of the middle blocks is formed in the same block, including a third portion that is connected between the second portion and the third portion that is inclined with respect to the tire axial direction and extends linearly. The closed sipe extending along the first portion or the second portion of the transverse sipe and provided on each crown block extends along the third portion of the transverse sipe formed in the same block. Is desirable.

In the tire of the present invention, at least one of the closed sipe provided in the middle block is a region in which the first portion or the second portion of the transverse sipe of the first crown block is projected in the tire axial direction. It is desirable that they are formed at the intersections.

In a plan view of the tread portion of the tire of the present invention, each crown block and each middle block has a first block wall and a second block wall facing the main groove, and a first end and a second block opened by the first block wall. It has a crossing sipe that extends between it and the second end that opens into the block wall and is at least partially wavy. Each of the first block wall and the second block wall has a top protruding outward from the block and is curved in a V shape. A block having such a transverse sipe can appropriately relieve the stress acting on the edge of the block when it comes into contact with the road surface, and can suppress, for example, heel-and-toe wear.

In the crown block, the first end of the transverse sipe is located on the first side of the top of the first block wall in the tire circumferential direction, and the second end of the transverse sipe is located on the top of the second block wall in the tire circumferential direction. The first crown block located on the second side and the first end of the transverse sipe are located on the second side of the top of the first block wall and the second end of the transverse sipe is said above on the top of the second block wall. It includes a second crown block located on the first side. Since the arrangement of the transverse sipes is different between the first crown block and the second crown block, the parts where wear is likely to proceed are different. Therefore, when looking at the entire land portion of the crown including these blocks, it is possible to disperse the portion where wear easily progresses.

In general, the middle block receives a smaller contact pressure than the crown block, so that the wear energy is relatively small, and the progress of wear tends to be slower than that of the crown block. Based on this tendency, the inventors have conducted various experiments to arrange the crown blocks as described above, and it is better to align the arrangement of the transverse sipes arranged in each of the adjacent middle blocks. And it was found that the progress of wear of the middle block can be made uniform.

In the tire of the present invention, in each middle block, the first end of the transverse sipe is located on the second side of the top of the first block wall, and the second end of the transverse sipe is on the top of the second block wall. It is located on the first side. Each middle block having such a transverse sipe arrangement can be uniformly worn together with each of the above-mentioned crown blocks, and the uneven wear resistance of each block can be improved.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the crown land part of FIG. It is an enlarged view of the middle land part of FIG. It is an enlarged view of the 1st crown block of FIG. It is an enlarged view of the shoulder land part of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The tire 1 of the present embodiment can be used for various tires such as pneumatic tires for passenger cars and heavy loads, and non-pneumatic tires in which pressurized air is not filled inside the tires. The tire 1 of the present embodiment is suitably used as a pneumatic tire for heavy loads such as trucks and buses.

As shown in FIG. 1, the tread portion 2 of the tire 1 is provided with a land portion 10 partitioned by a plurality of main grooves 3 that extend continuously in the tire circumferential direction.

The main groove 3 includes, for example, a crown main groove 4 and a shoulder main groove 5. For example, one crown main groove 4 is provided on each side of the tire equator C. The shoulder main groove 5 is arranged, for example, on the Te side of the tread end.

In the case of a pneumatic tire, the "tread end Te" is cambered by applying a normal load to a tire 1 in a normal state in which the rim is assembled to a normal rim (not shown), the normal internal pressure is filled, and there is no load. This is the most outer contact position in the tire axial direction when the tire is grounded on a flat surface at an angle of 0 °.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The crown main groove 4 and the shoulder main groove 5 can be provided at arbitrary positions. For example, it is desirable that the center line of the crown main groove 4 is located at a distance of 0.08 to 0.15 times the tread width TW from the tire equator C. Similarly, it is desirable that the groove center line of the shoulder main groove 5 is located at a distance of 0.25 to 0.35 times the tread width TW from the tire equator C. The tread width TW is the distance in the tire axial direction between the tread ends Te and Te of the tire 1 in the normal state.

Each main groove 3 has, for example, a zigzag shape in which first inclined portions 6a and second inclined portions 6b inclined in opposite directions are alternately provided in the tire circumferential direction. It is desirable that the angle θ3 of each of the inclined portions 6a and 6b with respect to the tire circumferential direction is, for example, 5 to 15 °.

The groove width W1 of the crown main groove 4 and the groove width W2 of the shoulder main groove 5 are preferably, for example, 1.5% to 5.0% of the tread width TW. It is desirable that the groove width W2 of the shoulder main groove 5 is larger than the groove width W1 of the crown main groove 4, for example. In the case of a heavy-duty pneumatic tire, the groove depth of each main groove 3 is preferably 10 to 25 mm, for example. Each of such main grooves 3 is useful for improving wet performance and uneven wear resistance in a well-balanced manner.

The land portion 10 includes, for example, a crown land portion 11, a middle land portion 12, and a shoulder land portion 13.

The crown land portion 11 is partitioned between a pair of crown main grooves 4, 4. The middle land portion 12 is partitioned between the crown main groove 4 and the shoulder main groove 5. The shoulder land portion 13 is partitioned on the outer side of the shoulder main groove 5 in the tire axial direction. Each land portion 10 is formed as a block row in which blocks 20 partitioned by lateral grooves connecting the main grooves are arranged in the tire circumferential direction.

2 and 3 show enlarged views of the crown land portion 11 and the middle land portion 12, respectively. As shown in FIGS. 2 and 3, the crown land portion 11 includes a plurality of crown blocks 21 partitioned by a plurality of crown lateral grooves 16. The middle land portion 12 includes a plurality of middle blocks 22 partitioned by a plurality of middle lateral grooves 17.

As shown in FIG. 2, the crown lateral groove 16 extends linearly along the tire axial direction between the pair of crown main grooves 4, for example. It is desirable that the groove width W3 of the crown lateral groove 16 is larger than, for example, the groove width W1 of the crown main groove. The groove width W3 is, for example, 1.5 to 1.8 times the groove width W1.

The crown lateral groove 16 of the present embodiment is provided with, for example, a tie bar 16a having a raised groove bottom at a central portion in the tire axial direction. As a more desirable embodiment, the tie bar 16a is provided with a groove bottom sipe 16b. However, the crown lateral groove 16 is not limited to such an aspect. As used herein, the term "sipe" means a notch having a width of 1.5 mm or less and is distinguished from a groove.

As shown in FIG. 3, the middle lateral groove 17 extends at an angle θ4 of, for example, 5 to 25 ° with respect to the tire axial direction. The middle lateral groove 17 is, for example, at least partially bent. As a more desirable embodiment, the middle lateral groove 17 of the present embodiment includes a pair of the first lateral groove portion 41 and the second lateral groove portion 42. The first lateral groove portion 41 is connected to, for example, the crown main groove 4 or the shoulder main groove 5. The second lateral groove portion 42 is arranged between the first lateral groove portions 41, and is inclined at an angle larger than that of the first lateral groove portion 41 with respect to the tire axial direction, for example. As a result, during wet running, the water in the first lateral groove portion 41 is smoothly guided to the main groove side, and thus the wet performance is improved.

FIG. 4 shows an enlarged view of the first crown block 21A of FIG. 2 as a diagram for explaining the configuration of the crown block 21 and the middle block 22 of the present embodiment. As shown in FIG. 4, in the plan view of the tread portion 2, each crown block 21 and each middle block 22 has a first block wall 25a and a second block wall 25b, and a crossing sipe 30 extending between them. Have.

The first block wall 25a and the second block wall 25b extend along the main groove 3 (shown in FIG. 1), respectively. In FIG. 4, the first block wall 25a is arranged on the right side of the block 20, and the second block wall 25b is arranged on the left side of the block 20. The first block wall 25a and the second block wall 25b each have a top portion 27 protruding outward from the block and are curved in a convex V shape. The angle θ5 (shown in FIG. 2) of the block wall at the top 27 is, for example, 140 to 170 °. Due to such a block wall, the block 20 has a substantially hexagonal tread surface.

The top portion 27 is formed, for example, deviated from the central position in the tire circumferential direction of the block. As a result, each of the block walls 25a and 25b includes a long wall portion 46 and a short wall portion 47 having a length smaller in the tire circumferential direction than the long wall portion 46. In the present embodiment, in the first block wall 25a, for example, the long wall portion 46 is arranged on the first side (upper side in FIG. 3) of the top 27 in the tire circumferential direction, and the second side of the top 27 in the tire circumferential direction. A short wall portion 47 is arranged (lower side in FIG. 3). In the second block wall 25b, for example, the long wall portion 46 is arranged on the second side of the top 27 in the tire circumferential direction, and the short wall portion 47 is arranged on the first side of the top 27 in the tire circumferential direction. There is. It is desirable that the short wall portion 47 has, for example, 0.75 to 0.90 times the length of the long wall portion 46 in the tire circumferential direction. In the present embodiment, a plurality of blocks 20 having such a first block wall 25a and a second block wall 25b are provided in the tire circumferential direction.

In one block, it is desirable that the first block wall 25a and the second block wall 25b have a shape that is point-symmetrical to each other. As a result, uneven wear of the block 20 can be suppressed.

The transverse sipe 30 extends between a first end 28a opened at the first block wall 25a and a second end 28b opened at the second block wall 25b, and is at least partially wavy. The block having such a crossing sipe 30 can appropriately relieve the stress acting on the edge of the block when it comes into contact with the road surface, and can suppress, for example, heel-and-toe wear. Further, since at least a part of the crossing sipe 30 is wavy, the sipe walls facing each other mesh with each other, and the apparent rigidity of the block can be increased. Therefore, the block having such a transverse sipe 30 exhibits excellent uneven wear resistance and is also useful for reducing the rolling resistance of the tire.

As shown in FIG. 2, the crown block 21 includes a first crown block 21A and a second crown block 21B in which the arrangement of the transverse sipes 30 is different. In the present embodiment, the first crown block 21A and the second crown block 21B are alternately provided in the tire circumferential direction.

In the first crown block 21A, the first end 28a of the crossing sipe 30 is located on the first side (upper side in FIG. 2) of the top 27 of the first block wall 25a in the tire circumferential direction, and the crossing sipe 30 is the first. The two ends 28b are located on the second side (lower side in FIG. 2) of the top 27 of the second block wall 25b in the tire circumferential direction.

In the second crown block 21B, the first end 28a of the crossing sipe 30 is located on the second side of the top 27 of the first block wall 25a, and the second end 28b of the crossing sipe 30 is the top 27 of the second block wall 25b. It is located on the first side of.

Since the arrangement of the transverse sipe 30 is different between the first crown block 21A and the second crown block 21B, the portion where wear is likely to proceed is different. Therefore, when looking at the entire crown land portion 11 including these blocks, it is possible to disperse the portion where wear easily progresses.

In general, since the middle block 22 receives a contact pressure smaller than that of the crown block 21, the wear energy tends to be relatively small, and the progress of wear tends to be slower than that of the crown block 21. Based on such a tendency, the inventors should make the arrangement of the crossing sipes 30 arranged in each middle block 22 adjacent thereto in the arrangement of the crown block 21 as described above by various experiments. , It was found that the progress of wear of the crown block 21 and the middle block 22 can be made uniform.

As shown in FIG. 3, in the tire 1 of the present invention, in each middle block 22, the first end 28a of the transverse sipe 30 is located on the second side (lower side) of the top 27 of the first block wall 25a. Moreover, the second end of the transverse sipe 30 is located on the first side (upper side) of the top 27 of the second block wall 25b. Each middle block 22 having such an arrangement of the transverse sipe 30 wears uniformly together with each of the crown blocks 21 described above, and the uneven wear resistance of each block can be improved.

Further, since the first end 28a and the second end 28b of the transverse sipe 30 provided on each crown block 21 and each middle block 22 are provided at positions deviated from the top 27 of the block wall on which a large stress acts, the top Rigidity around 27 is maintained, and the uneven wear resistance of the block is enhanced.

Further, since each of the first region 26a and the second region 26b partitioned by the transverse sipe 30 includes one top of the block wall, the rigidity of each region is enhanced in a well-balanced manner.

As shown in FIG. 4, as a more desirable embodiment, the transverse sipe 30 provided in each crown block 21 and each middle block 22 is, for example, from the first portion 31 extending from the first end 28a and the second end 28b. It includes a second portion 32 that extends and a third portion 33 between them.

It is desirable that the first portion 31 and the second portion 32 each extend in a wavy shape in the tire axial direction. The first portion 31 and the second portion 32 may adopt various shapes such as a sinusoidal shape, a rectangular wavy shape, or a zigzag shape. In such a first portion 31 and a second portion 32, the rigidity of the block can be increased by strongly engaging the sipe walls facing each other, and thus the uneven wear resistance of the block is improved.

In order to further exert the above-mentioned effect, the peak-to-peak amplitude amount A1 of the first portion 31 and the second portion 32 is, for example, 0 of the maximum length L1 (shown in FIG. 2) of the block 20 in the tire circumferential direction. It is desirable that the value is 05 to 0.15 times.

It is desirable that the center lines of the amplitudes of the first portion 31 and the second portion 32 are inclined at an angle θ6 of 5 to 10 ° with respect to the tire axial direction, for example.

It is desirable that the first portion 31 and the second portion 32 of the present embodiment are formed at different positions in the tire circumferential direction, for example. Such a first portion 31 and a second portion 32 can relax the rigidity of each region partitioned by the transverse sipe 30 in the tire circumferential direction, and further reduce the stress acting on the block 20.

As a more desirable embodiment, the length of the first portion 31 in the tire axial direction is the same as the length of the second portion 32 in the tire axial direction. As a result, the block 20 is likely to be uniformly worn, and the uneven wear resistance is further improved.

The third portion 33 is inclined with respect to the tire axial direction and extends linearly, for example. The angle θ7 of the third portion 33 with respect to the tire axial direction is, for example, 40 to 60 °. Such a third portion 33, together with the first portion 31 and the second portion 32, helps reduce the stress acting on the block 20.

It is desirable that the length L3 of the third portion 33 in the tire axial direction is 0.15 to 0.30 times the maximum length L2 of the block 20 in the tire axial direction (shown in FIG. 2). As a more desirable embodiment, it is desirable that the length L3 of the third portion 33 is smaller than the length of the tie bar 16a (shown in FIG. 2) provided in the crown lateral groove 16 in the tire axial direction. Such a third portion 33 is useful for improving wet performance and uneven wear resistance in a well-balanced manner.

The tire circumferential distance L4 from the top 27 of the first block wall 25a to the first end 28a and the tire circumferential distance L5 from the top 27 to the second end 28b of the second block wall 25b are, for example, blocks. It is 0.01 to 0.40 times the maximum length L1 in the tire circumferential direction.

It is desirable that the distance L4 and the distance L5 differ depending on, for example, a block. In the first crown block 21A shown in FIG. 4, the distance L4 and the distance L5 are, for example, 0.15 to 0.25 times the maximum length L1. As a result, the position of the end of the transverse sipe 30 is appropriately separated from the top 27 and the lateral groove, so that wear starting from the end can be effectively suppressed.

As shown in FIG. 2, it is desirable that the distance L4 and the distance L5 of the second crown block 21B are smaller than those of the first crown block 21A. Specifically, in the second crown block 21B, it is desirable that the distance L4 and the distance L5 are, for example, 1.5% to 5.0% of the maximum length L1 of the block in the tire circumferential direction.

As shown in FIG. 3, in the middle block 22, the distance L4 and the distance L5 are preferably, for example, 3.0% to 6.0% of the maximum length L1 of the block in the tire circumferential direction.

As shown in FIG. 4, as a more desirable embodiment, it is desirable that the first end 28a and the second end 28b of the transverse sipe 30 are connected to the slots 37 included in the block walls 25a and 25b. The slot 37 is an inclined surface of the block walls 25a and 25b whose angle with respect to the tire radial direction is partially increased and is continuous with the tread surface. As a result, uneven wear starting from the end of the transverse sipe 30 is further suppressed.

The first region 26a and the second region 26b, which are partitioned on both sides of the transverse sipe 30 in the tire circumferential direction, are arranged on one side of the block center line 20c, respectively, and the top of the first block wall 25 or the second block wall 26, respectively. It includes a top region 34 including 27 and a non-top region 35 arranged on the other side of the block centerline 20c and having a tread area smaller than the top region 34. The block center line is a line that bisects the maximum block width in the tire axial direction and extends in the tire circumferential direction.

In the first region 26a and the second region 26b, closed sipe 38 is formed in which both ends are interrupted in each region. The closed sipe 38 can further reduce the stress acting on the block and further suppress uneven wear while suppressing excessive deformation of each region.

It is desirable that the closed sipe 38 of the present embodiment is provided, for example, in the top region 34 of the first region 26a and the second region 26b. As a result, the rigidity of the block is maintained, and the rolling resistance of the tire is reduced.

It is desirable that the closed sipe 38 extends in a wavy shape, for example. The closed sipe 38 may adopt various shapes such as a sinusoidal shape, a rectangular wavy shape, or a zigzag shape. It is desirable that the peak-to-peak amplitude amount A2 of the closed sipe 38 is smaller than, for example, the amplitude amount A1 of the first portion 31 or the second portion 32. In such a closed sipe 38, the sipe walls facing each other are appropriately engaged with each other, and deformation of each region can be suppressed.

It is desirable that the closed sipe 38 has a depth smaller than, for example, the transverse sipe 30. Specifically, the depth of the closed sipe 38 is preferably 0.20 to 0.50 times the depth of the main groove.

As shown in FIGS. 2 and 3, in the present embodiment, the closed sipe 38c provided in each crown block 21 and the closed sipe 38m provided in each middle block 22 have different configurations. There is.

As shown in FIG. 2, the closed sipe 38c provided on the crown block 21 is formed entirely in the top side region 34 without straddling the block center line (not shown), for example. The block center line is a line that bisects the maximum block width in the tire axial direction and extends in the tire circumferential direction. As a result, the decrease in rigidity of the non-top region 35 is suppressed, and the uneven wear of each region is suppressed.

The closed sipe 38c provided on the crown block 21 preferably extends along, for example, a third portion 33 of the transverse sipe 30 formed in the same block. The zigzag-shaped closed sipe 38 extending along the third portion 33 means that the center line of the amplitude of the closed sipe 38 is inclined to the same extent as the third portion 33.

It is desirable that the center line of the wavy amplitude of the closed sipe 38c is arranged at an angle θ1 of, for example, 30 to 50 ° with respect to the tire axial direction.

In each crown block 21, it is desirable that the closed sipe 38 provided in the first region 26a and the closed sipe 38 provided in the second region 26b are formed so as not to overlap each other in the tire axial direction. Such an arrangement of the closed sipe 38 can maintain the rigidity of the crown block 21 and enhance its wear resistance.

It is desirable that the closed sipe 38c provided on the first crown block 21A and the closed sipe 38c provided on the second crown block 21B are inclined in opposite directions to each other. As a result, the edges of each sipe exert frictional forces in multiple directions, which in turn enhances wet performance.

As shown in FIG. 3, the closed sipes 38 m provided in each middle block 22 are inclined in the same direction. In a preferred embodiment, the closed sipe 38m extends, for example, along a first portion 31 or a second portion 32 of a transverse sipe 30 formed in the same block. The zigzag-shaped closed sipe 38m extending along the zigzag-shaped first portion 31 or the second portion 32 means that the center line of the amplitude of the closed sipe 38m and the center of the amplitude of the first portion 31 or the second portion 32. The line means an aspect in which the line is inclined to the same degree.

It is desirable that the center line of the wavy amplitude of the closed sipe 38 m is arranged at an angle θ2 smaller than the angle θ1 with respect to the tire axial direction, for example. Specifically, it is desirable that the angle θ2 is, for example, 5 to 15 °.

In each middle block 22, it is desirable that the closed sipe 38 provided in the first region 26a and the closed sipe 38 provided in the second region 26b are formed so as to overlap each other in the tire axial direction. By combining such a middle block 22 with the arrangement of the closed sipe 38 of the crown block 21 described above, the progress of wear of each block can be made uniform.

As shown in FIG. 1, at least one of the closed sipe 38 m provided on the middle block 22 projected the first portion 31 or the second portion 32 of the transverse sipe 30 of the first crown block 21A in the tire axial direction. It is desirable that it is formed at a position where it intersects with the area. As a result, the middle block 22 and the first crown block 21A are interlocked with each other to facilitate following the road surface, and thus rolling resistance can be reduced.

In order to exert the above-mentioned effect, the formation width S1 of the closed sipe 38 in the tire circumferential direction is, for example, 5 to 10% of the maximum length L1 (shown in FIG. 2) of the first crown block 21A in the tire circumferential direction. It is desirable that the range is. Further, it is desirable that the closed sipe 38 is formed within 10% of the maximum length L1 on both sides in the tire circumferential direction from the end of the transverse sipe 30 formed in the first crown block 21A, for example.

FIG. 5 shows an enlarged view of the shoulder land portion 13 of FIG. As shown in FIG. 5, the shoulder land portion 13 includes, for example, a plurality of shoulder blocks 23 partitioned by a plurality of shoulder lateral grooves 18.

The shoulder lateral groove 18 includes, for example, a pair of first lateral groove portions 43 extending along the tire axial direction and a second lateral groove portion 44 extending inclined with respect to the tire axial direction between them. The angle θ8 of the second lateral groove 44 with respect to the tire axial direction is, for example, 25 to 35 °.

In a preferred embodiment, the groove depth of the shoulder lateral groove 18 is, for example, 0.05 to 0.25 times the groove depth of the shoulder main groove 5. As a result, the shoulder land portion 13 having high rigidity is arranged on both sides of the tread portion, and the ground contact load acting on the crown land portion 11 and the middle land portion 12 (shown in FIG. 1) is relaxed. Therefore, the uneven wear resistance of the crown land portion 11 and the middle land portion 12 is further enhanced.

The shoulder block 23 of the present embodiment has, for example, a vertically long tread surface. As a preferred embodiment, the tread of the shoulder block 23 is not provided with a sipe. Such a shoulder block 23 can exhibit excellent durability.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-mentioned specific embodiment, but is modified to various embodiments.

A heavy-duty pneumatic tire of size 11R22.5 with the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As Comparative Example 1, a tire in which the end of each crossing sipe extends from the top of the block wall was prototyped. As Comparative Example 2, a tire was prototyped in which a plurality of first crown blocks were provided in the tire circumferential direction on the land portion of the crown. In other words, in the tires of Comparative Example 2, the crossing sipes provided on the land portion of the crown are all formed in the same direction. The tires of Comparative Example 1 and Comparative Example 2 have substantially the same configuration as the tire shown in FIG. 1 except for the above configuration. The wet performance, wear resistance, presence or absence of uneven wear, and rolling resistance of the test tires were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 22.5 x 8.25
Tire internal pressure: 720kPa
Test vehicle: 10t truck, 50% of standard load capacity is loaded in front of the loading platform Tire mounting position: All wheels

<Wet performance>
Under the following conditions, the passing time when the test vehicle passed the test course with a total length of 10 m was measured. The result is displayed as an index with the passing time of Comparative Example 1 as 100. The smaller the value, the better.
Road surface: Asphalt with a water film with a thickness of 5 mm Starting method: Start with a clutch engaged at 2nd speed-1500 rpm fixed.

<Abrasion resistance>
The amount of wear of the crown block after traveling a certain distance on a dry road surface with the above test vehicle was measured. The result is displayed as an index with the wear amount of the crown block of Comparative Example 1 as 100. The smaller the value, the better the wear resistance.

<Presence or absence of uneven wear>
After traveling a certain distance on a dry road surface with the above test vehicle, it was confirmed whether there was uneven wear on the top of the block wall and heel-and-toe wear.

<Rolling resistance performance>
Rolling resistance was measured using a rolling resistance tester under the following conditions. The evaluation is displayed as an index with the value of Comparative Example 1 as 100. The smaller the value, the smaller the rolling resistance and the better.
Load: 25.01kN
Speed: 80km / h
The test results are shown in Table 1. In addition, each parameter of the Example of Table 1 is that of the 1st crown block.

As is clear from Table 1, it was confirmed that the tires of the examples suppressed uneven wear.

2 Tread part 3 Main groove 11 Crown land part 12 Middle land part 1
16 Crown lateral groove 17 Middle lateral groove 20 block 21 Crown block 22 Middle block 25a 1st block wall 25b 2nd block wall 26a 1st area 26b 2nd area 27 Top 28a 1st end 28b 2nd end 30 Crossing sipe

Claims (8)

A tire in which a tread portion is provided with a crown land portion and a middle land portion that are divided into a plurality of main grooves that extend continuously in the tire circumferential direction and are adjacent to each other.
The crown land portion includes a plurality of crown blocks partitioned by a plurality of crown transverse grooves.
The middle land portion includes a plurality of middle blocks partitioned by a plurality of middle lateral grooves.
In the plan view of the tread portion,
Each of the crown blocks and the middle blocks has a first block wall and a second block wall facing the main groove, a first end opened by the first block wall, and a second block wall opened by the second block wall. It has a transverse sipe that extends between the edges and is at least partially wavy,
The crossing sipe has a notch having a width of 1.5 mm or less.
The first block wall and the second block wall each have a top protruding outward from the block and are curved in a V shape.
The crown block is
The first end of the transverse sipe is located on the first side of the top of the first block wall in the tire circumferential direction, and the second end of the transverse sipe is the top of the second block wall. The first crown block located on the second side in the tire circumferential direction,
The first end of the transverse sipe is located on the second side of the top of the first block wall, and the second end of the transverse sipe is on the first side of the top of the second block wall. Including the second crown block located in
In each of the middle blocks, the first end of the transverse sipe is located on the second side of the top of the first block wall, and the second end of the transverse sipe is of the second block wall. A tire located on the first side of the top. The tire according to claim 1, wherein the first crown block and the second crown block are alternately provided in the tire circumferential direction. Each crown block and each middle block has a first region and a second region partitioned on both sides of the crossing sipe in the tire circumferential direction.
The tire according to claim 1 or 2, wherein closed sipes are formed in the first region and the second region, respectively, at both ends of which are interrupted in each region. The closed sipe provided in each of the middle blocks is inclined in the same direction, respectively.
The tire according to claim 3, wherein the closed sipe provided on the first crown block and the closed sipe provided on the second crown block are inclined in opposite directions to each other. Each of the closed sipes stretches in a wavy shape.
The center line of the wavy amplitude of the closed sipe provided on the crown block is arranged at the angle θ1 with respect to the tire axial direction.
The tire according to claim 3 or 4, wherein the center line of the wavy amplitude of the closed sipe provided in the middle block is arranged at an angle θ2 smaller than an angle θ1 with respect to the tire axial direction. In each of the middle blocks
The closed sipe provided in the first region and the closed sipe provided in the second region are formed so as to overlap each other in the tire axial direction.
In each of the crown blocks
The closed sipe provided in the first region and the closed sipe provided in the second region are formed according to any one of claims 3 to 5 so as not to overlap each other in the tire axial direction. Tires. Each of the crossing sipe has a first portion wavy from the first end in the tire axial direction, a second portion wavy from the second end in the tire axial direction, and the first portion and the second portion. Includes a third part that connects between the tires and extends linearly with respect to the tire axis direction.
The closed sipe provided in each of the middle blocks extends along the first or second portion of the transverse sipe formed in the same block.
The tire according to any one of claims 3 to 6, wherein the closed sipe provided in each crown block extends along the third portion of the transverse sipe formed in the same block. At least one of the closed sipe provided in the middle block is formed at a position where the first portion or the second portion of the transverse sipe of the first crown block intersects a region projected in the tire axial direction. The tire according to claim 7.

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