JP6426051B2 - tire - Google Patents

Description

  The present invention relates to a tire provided with a plurality of circumferential grooves and a plurality of block rows in a tread portion.

  In a tread portion of a tire used on a snowy road, generally, a plurality of block rows are divided by a plurality of circumferential grooves, and a predetermined tread pattern is formed by various grooves. Further, a tread pattern is set according to the tire performance (ice and snow performance) on a snowy and snowy road surface, and a plurality of blocks are arranged in each block row. With regard to the ice and snow performance, conventionally, there is known a tire in which an edge component in the tire width direction that affects the ice and snow performance is increased by sipes formed in each block (see Patent Document 1).

  In the conventional tire described in Patent Document 1, in order to improve wear resistance performance in addition to ice and snow performance, the width of the central land portion located on the tire equatorial plane is made wider than the widths of other land portions, The rigidity of the central land area is increased. However, in addition to the central land portion, the shoulder land portion also needs to be formed with a certain width in consideration of the wear resistance performance. Therefore, the width of the middle land between the central land and the shoulder land may be reduced, and the rigidity of the middle land may be reduced. In this case, in the middle land portion, the self-excited wear may progress due to the drag of the block, and the block may be unevenly worn (for example, heel and toe wear). Therefore, in the conventional tire, there is room for further improvement in order to achieve both the wear resistance performance and the uneven wear resistance performance.

JP, 2009-196527, A

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a tire having a plurality of block rows in a tread portion, having both ice wear resistance and uneven wear resistance while securing ice and snow performance. It is to

The present invention is divided into a tread portion by four or more circumferential grooves including two central side circumferential grooves located on both sides of the tire equatorial plane and a plurality of circumferential grooves, and two central side circumferential directions And a plurality of block rows including a central block row partitioned by grooves. Further, the tire is formed in divided grooves extending in the circumferential direction of the tire, which divide the central block row into adjacent block rows adjacent in the tire width direction, and adjacent block rows on both sides in the tire width direction of the divided grooves. And a plurality of blocks disposed adjacent to each other in order in the tire circumferential direction. A plurality of blocks on both sides in the tire width direction of the dividing groove are disposed mutually offset in the tire circumferential direction, and in the blocks adjacent in the tire width direction, the end portions in the tire circumferential direction of each block are mutually offset in the tire circumferential direction Ru is located Te. Dividing groove extends zigzag in the tire circumferential direction, between adjacent blocks in the tire width direction, Ru extending in the tire circumferential direction in a state inclined with respect to the tire width direction and the tire circumferential direction. The distance between adjacent blocks in the tire width direction is shorter than the distance between adjacent blocks in the tire circumferential direction. Each block of the plurality of blocks extends in the tire width direction while being bent a plurality of times not more than four times, and has four sipes whose both ends are closed in each block.

  According to the present invention, in a tire provided with a plurality of block rows in the tread portion, it is possible to achieve both wear resistance and uneven wear resistance while securing ice and snow performance.

It is a top view which shows the tread pattern of the tire of this embodiment. It is a top view which shows the block of a center block row. It is a schematic diagram which shows the tire which touches a road surface. It is a graph which shows the circumferential direction shear force which acts on a block at the time of tire rolling. It is a figure which shows a deformation | transformation of the block at the time of tire rolling. It is a figure showing modification of a plurality of blocks adjacent to a tire peripheral direction. It is a top view which shows the tread pattern of a conventional product. It is a top view which shows the tread pattern of a conventional product. It is a graph which shows the circumferential direction wear energy of an implementation item and a conventional item.

One embodiment of a tire of the present invention will be described with reference to the drawings.
The tire according to the present embodiment is a pneumatic tire for a vehicle (for example, a heavy load tire, a tire for a passenger car), and is formed in a known structure by a general tire structural member. That is, the tire has a pair of bead portions, a pair of sidewall portions located on the tire radius outer side of the pair of bead portions, a tread portion contacting the road surface, a pair located between the tread portion and the pair of sidewall portions It has a shoulder section. The tire also includes a pair of bead cores, a carcass disposed between the pair of bead cores, a belt disposed on the outer circumferential side of the carcass, and a tread rubber having a predetermined tread pattern.

FIG. 1 is a plan view showing the tread pattern of the tire 1 of the present embodiment, and schematically showing a part of the tread portion 2 in the tire circumferential direction S. As shown in FIG.
The tire 1 is a studless tire used on a snowy and snowy road surface, and the tread pattern of the tire 1 is a block pattern having a plurality of blocks. The tire equatorial plane 3 is located at the center of the tread portion 2 in the tire width direction H, and the shoulder portion 4 of the tire 1 is located outside the tire width direction H of the tread portion 2.

  As illustrated, the tire 1 includes a plurality of circumferential grooves 10, 11, a plurality of lateral grooves 20-22, a plurality of block rows 30, 40, 50, and a plurality of block rows 30, 40 in the tread portion 2. , 50 are provided with a plurality of blocks 31, 41, 51, respectively. The plurality of circumferential grooves 10 and 11 are main grooves (circumferential main grooves) extending in the tire circumferential direction S, and are continuously formed along the tire circumferential direction S, respectively. The tire 1 further includes four or more circumferential grooves 10 and 11 including two central circumferential grooves 10 positioned on both sides of the tire equatorial plane 3 in the tire width direction H. Here, the tire 1 is provided with four circumferential grooves 10, 11, and the plurality of circumferential grooves 10, 11 are composed of two central circumferential grooves 10 and two outer circumferential grooves 11.

  The central circumferential groove 10 is a circumferential groove disposed on the innermost side (tire equatorial plane 3 side) in the tire width direction H, and the tire equatorial plane 3 is positioned between two central circumferential grooves 10 Do. The outer circumferential groove 11 is a circumferential groove disposed on the outer side in the tire width direction H of the central circumferential groove 10, and on both sides of the tire equatorial plane 3, the central circumferential groove 10 and the shoulder portion 4 (tread Formed between the end). The plurality of lateral grooves 20 to 22 are width direction grooves (lag grooves) extending in the tire width direction H, and are formed in the block rows 30, 40, and 50, respectively. The plurality of block rows 30, 40, 50 are land portions extending along the tire circumferential direction S, and are divided into the tread portion 2 by the plurality of circumferential grooves 10, 11. The plurality of circumferential grooves 10, 11 form a plurality of block rows 30, 40, 50 including the central block row 30 in the tread portion 2.

  The plurality of block rows 30, 40, 50 are composed of one central block row 30, two intermediate block rows 40, and two shoulder block rows 50, and have a plurality of blocks 31, 41, 51, respectively. The plurality of blocks 31, 41, 51 are arranged in parallel to the block rows 30, 40, 50, respectively. The width of the plurality of block rows 30, 40, 50 is a width corresponding to the arrangement position of the circumferential grooves 10, 11 that partition each block row 30, 40, 50. Here, the width of the center block row 30 is wider than the widths of the other block rows 40 and 50, and the center block row 30 is a wide block row having the widest width in the tread portion 2. The central block row 30 is divided by two central circumferential grooves 10 and disposed between the two central circumferential grooves 10. The center block row 30 is disposed in the center region of the tread portion 2 including the tire equatorial plane 3 and is located between the two middle block rows 40. The tire equatorial plane 3 is located at the center of the center block row 30.

  The middle block row 40 is divided by the central circumferential groove 10 and the outer circumferential groove 11 and disposed between the central circumferential groove 10 and the outer circumferential groove 11. The middle block row 40 is disposed in the middle region of the tread portion 2 between the tire equatorial plane 3 and the shoulder portion 4, and is located outside the center block row 30 in the tire width direction H. The shoulder block row 50 is divided by the outer circumferential groove 11 and disposed outside the outer circumferential groove 11 in the tire width direction H. The shoulder block row 50 is disposed on the outermost side (shoulder portion 4 side) in the tire width direction H among the plurality of block rows 30, 40, 50, and the middle block row 40 is positioned on the outer side in the tire width direction H. Do.

  The plurality of lateral grooves 21 of the intermediate block row 40 are formed between the central circumferential groove 10 and the outer circumferential groove 11 and open to the central circumferential groove 10 and the outer circumferential groove 11. Further, the plurality of lateral grooves 21 are spaced apart in the tire circumferential direction S and traverse the intermediate block row 40. A plurality of blocks 41 are divided into an intermediate block row 40 of the tread portion 2 by the central circumferential groove 10, the outer circumferential groove 11, and the plurality of lateral grooves 21. The blocks 41 of the middle block row 40 are middle blocks located in the middle region of the tread portion 2, and the plurality of blocks 41 are arranged in the middle block row 40 adjacently in the tire circumferential direction S in order. The plurality of lateral grooves 21 are located between the blocks 41 adjacent in the tire circumferential direction S, respectively.

  Each block 41 of the plurality of blocks 41 has a plurality of sipes 42, 43. The plurality of sipes 42 and 43 are cuts respectively formed from the tread surface of the block 41 toward the inside of the block 41, and includes the widthwise sipes 42 and the closed sipes 43 formed in each block 41. The widthwise sipe 42 is a sipe extending in the tire width direction H in the block 41, and is disposed at the central portion of the block 41 in the tire circumferential direction S to cross the block 41. Both ends of the widthwise sipe 42 open in the central circumferential groove 10 and the outer circumferential groove 11 on both sides of the block 41.

  The closed sipe 43 is a bending sipe closed in the block 41, and extends in a zigzag in the tire width direction H while bending a plurality of times (2 to 4 times) or less. Both end portions of the closed sipes 43 do not open to the central circumferential groove 10 and the outer circumferential groove 11, and are closed in each block 41. Both wall surfaces of the closed sipe 43 are formed in a bent shape and face each other in the block 41. Here, two widthwise sipes 42 are linearly formed at the central portion of the block 41, and two closed sipes 43 are respectively formed between the widthwise sipes 42 and the lateral grooves 21.

  The plurality of lateral grooves 22 of the shoulder block row 50 are opened in the outer circumferential groove 11 and are formed from the outer circumferential groove 11 to the shoulder portion 4. Further, the plurality of lateral grooves 22 are spaced apart in the tire circumferential direction S and cross the shoulder block row 50. A plurality of blocks 51 are divided into shoulder block rows 50 by the outer circumferential grooves 11 and the plurality of lateral grooves 22. The blocks 51 of the shoulder block row 50 are shoulder blocks positioned on the shoulder portion 4 side, and the plurality of blocks 51 are arranged in the shoulder block row 50 adjacently in the tire circumferential direction S in order. The plurality of lateral grooves 22 are respectively located between the blocks 51 adjacent in the tire circumferential direction S.

  Each block 51 of the plurality of blocks 51 has a circumferential narrow groove 52 thinner than the circumferential grooves 10 and 11 and a plurality of sipes 53 and 54. The circumferential narrow groove 52 divides the block 51 into an inner portion 51A and an outer portion 51B in the tire width direction H. The plurality of sipes 53 and 54 are cuts respectively formed from the tread surface of the block 51 toward the inside of the block 51, and are composed of the widthwise sipes 53 and the closed sipes 54 formed in each block 51. The widthwise sipe 53 is a sipe extending in the tire width direction H in the inner portion 51A of the block 51, is disposed at the center of the inner portion 51A in the tire circumferential direction S, and crosses the inner portion 51A. Both end portions of the widthwise sipe 53 open in the outer circumferential groove 11 and the circumferential narrow groove 52 on both sides of the inner portion 51A.

  The closed sipe 54 is a bent sipe closed in the inner portion 51A of the block 51, and extends in a zigzag in the tire width direction H while bending a plurality of times (2 to 4 times or less) not more than four times. Both end portions of the closed sipes 54 do not open to the outer circumferential groove 11 and the circumferential narrow groove 52, and are closed in the inner portion 51 </ b> A of each block 51. Both wall surfaces of the closed sipe 54 are formed in a bent shape and face each other in the inner portion 51A. Here, two widthwise sipes 53 are linearly formed at the central portion of the inner portion 51A, and two closed sipes 54 are respectively formed between the widthwise sipes 53 and the lateral grooves 22.

  The tire 1 includes at least one dividing groove 12 which divides the central block row 30 in the tire width direction H. The dividing grooves 12 are circumferential narrow grooves (circumferential sub grooves) thinner than the circumferential grooves 10 and 11 and extend in the tire circumferential direction S in the central block row 30. The dividing groove 12 is formed between the two central circumferential grooves 10, and the dividing groove 12 divides the central block row 30 into adjacent block rows 32 adjacent in the tire width direction H. The adjacent block row 32 is a sub block row constituting the central block row 30, and the dividing groove 12 is located between two adjacent adjacent block rows 32. Here, the tire 1 has one dividing groove 12 in the central block row 30. The dividing grooves 12 are arranged in the tire equatorial plane 3 and extend in a zigzag manner in the tire circumferential direction S to divide the central block row 30 into two adjacent block rows 32.

  The plurality of lateral grooves 20 of the central block row 30 are formed in the adjacent block row 32 and open to the dividing grooves 12 and the central circumferential groove 10. Further, the plurality of lateral grooves 20 are disposed apart in the tire circumferential direction S, and traverse the adjacent block row 32. The two adjacent block rows 32 are formed between the dividing grooves 12 and the respective central circumferential grooves 10, and are arranged on both sides in the tire width direction H of the dividing grooves 12. The plurality of lateral grooves 20 are formed on both sides (one side and the other side) of the split groove 12 in the tire width direction H, and extend from the split groove 12 toward both sides in the tire width direction H. The lateral grooves 20 on one side and the other side in the tire width direction H of the dividing grooves 12 are alternately arranged along the tire circumferential direction S, and alternately open in the dividing grooves 12.

  A plurality of blocks 31 are divided into a central block row 30 of the tread portion 2 by the two central side circumferential grooves 10, the dividing grooves 12, and the plurality of lateral grooves 20. The blocks 31 of the central block row 30 are central blocks located in the central region of the tread portion 2. The plurality of blocks 31 are formed in adjacent block rows 32 on both sides of the dividing groove 12 in the tire width direction H, and arranged in each adjacent block row 32 so as to be adjacent to the tire circumferential direction S in order. The plurality of lateral grooves 20 are located between the blocks 31 adjacent in the tire circumferential direction S, respectively. Further, the plurality of blocks 31 on both sides in the tire width direction H of the dividing groove 12 are arranged mutually offset in the tire circumferential direction S. Along with this, in the blocks 31 adjacent in the tire width direction H, the end portions of the blocks 31 in the tire circumferential direction S are mutually offset in the tire circumferential direction S and arranged at different positions in the tire circumferential direction S.

FIG. 2 is a plan view showing the blocks 31 of the central block row 30, and is an enlarged view of part of the blocks 31 shown in FIG.
As shown, each block 31 of the plurality of blocks 31 has a plurality of sipes 33. The plurality of sipes 33 are cuts respectively formed from the tread surface of the block 31 toward the inside of the block 31, and from the four closed sipes 33 formed in each block 31 on both sides of the dividing groove 12 in the tire width direction H Become. The four closed sipes 33 are bending sipes closed in the block 31, and extend in a zigzag in the tire width direction H while bending a plurality of times (2 to 4 times) or less.

  Both ends of the closed sipe 33 do not open to the dividing groove 12 and the central circumferential groove 10, and are closed in each block 31. Both wall surfaces of the closed sipe 33 are formed in a bent shape and face each other in the block 31. The four closed sipes 33 are arranged in each block 31 separately in parallel in the tire circumferential direction S. The depth from the tread surface of the block 31 of each closed sipe 33 becomes deeper gradually from the central portion of each closed sipe 33 in the tire width direction H toward both ends of each closed sipe 33. The depth of the closed sipes 33 is the depth of the closed sipes 33 in the tire radial direction, and becomes deepest at both ends of the closed sipes 33 in the tire width direction H. In addition, the depth of the central portion of the closed sipe 33 is shallower than the depths of other portions of the closed sipe 33.

  The blocks 31 of the two adjacent block rows 32 are disposed on both sides of the split groove 12 in the tire width direction H, and are adjacent to each other in the tire width direction H with the split grooves 12 positioned therebetween. The dividing grooves 12 are inclined with respect to the tire width direction H and the tire circumferential direction S between the blocks 31 adjacent in the tire width direction H. Specifically, the portion 13 between the two blocks 31 of the dividing groove 12 extends in the tire circumferential direction S in a state of being inclined with respect to the tire width direction H and the tire circumferential direction S. Further, the distance F between the blocks 31 adjacent in the tire width direction H is shorter than the distance G between the blocks 31 adjacent in the tire circumferential direction S in the adjacent block row 32. That is, the width of the dividing groove 12 between the blocks 31 adjacent in the tire width direction H is narrower than the width of the lateral groove 20 between the blocks 31 adjacent in the tire circumferential direction S.

Next, the tire 1 at the time of vehicle travel will be described.
FIG. 3 is a schematic view showing the tire 1 in contact with the road surface 5 and shows the relationship between the presence or absence of the driving force of the tire 1 mounted on the vehicle and the displacement of the tread portion 2.
As illustrated, when the vehicle travels, the tire 1 rotates in the tire rotation direction and rolls on the road surface 5. The solid line in FIG. 3 shows the displacement of the tread portion 2 when there is no driving force (when the tire 1 is not rolling). The dotted line in FIG. 3 indicates the displacement of the tread portion 2 when there is a driving force (when the tire 1 is rolling).

  At the time of tire rolling, the friction between the tread portion 2 and the road surface 5 causes a difference between the displacement of the tread portion 2 and the displacement of the belt, and the tread portion 2 is deformed to fall down. In particular, when the tire 1 is a heavy load tire, the flatness of the tire 1 is high, and the rigidity of the belt is also high. As a result, the displacement difference between the tread portion 2 and the belt is increased, and the deformation of the tread portion 2 is increased. With the deformation of the tread portion 2, the contact area of the tread portion 2 decreases, and the load of the driving force per unit area of the tread portion 2 increases. As a result, the blocks of the tread portion 2 may slide on the road surface 5 and the amount of block wear may increase. In addition, at the time of kicking, the circumferential shear force of the block is increased, and the block is easily worn. In the tire 1 of the present embodiment, in the center block row 30, the circumferential shear force acting on the plurality of blocks 31 is adjusted to improve the wear resistance performance of the tire 1.

  FIG. 4 is a graph showing a circumferential shear force acting on the block at the time of tire rolling, and shows a change in the circumferential shear force at an arbitrary position of the block in contact with the road surface 5. The circumferential shear force shown in FIG. 4 is a variation of the circumferential shear force with respect to the circumferential shear force when there is no driving force, and FIG. 4 shows the circumferential shear force from stepping on to kicking out There is. Further, the solid line in FIG. 4 indicates the circumferential shear force acting on the block of the tire according to the conventional example, and the dotted line in FIG. 4 indicates the circumferential direction acting on the block 31 of the tire 1 (the tire according to the example). It shows the shear force.

  As illustrated, in the tire of the conventional example, the circumferential shear force (the amount of change) gradually increases from the time of stepping on. The total sum (integrated value) of circumferential shear forces from the time of stepping on to the time of kicking corresponds to the force that causes the vehicle to travel. However, when the contact area of the tread portion 2 decreases, the change in circumferential shear force increases, the circumferential shear force at the time of kicking increases, and the block tends to wear. On the other hand, in the block 31 of the tire 1, the circumferential shear force at the time of stepping on becomes larger than the circumferential shear force at the time of stepping on in the conventional example. As a result, the change in circumferential shear force is reduced, the circumferential shear force at the time of kicking is reduced, and the block 31 is less likely to be worn.

FIG. 5 is a view showing the deformation of the block 31 at the time of tire rolling, and schematically shows the deformation of the plurality of blocks 31 adjacent in order. The solid line in FIG. 5 shows the deformation of the block 31 when there is no driving force, and the dotted line in FIG. 5 shows the deformation of the block 31 when there is a driving force.
As illustrated, when the tire is rolling, the block 31 to be stepped on next is deformed so as to be pressed against the road surface 5 due to the increase of the shear deformation K of the block 31 that has been stepped on. The deformation L of the block 31 increases the circumferential shear force at the time of stepping on. In the tire 1, the blocks 31 adjacent to each other in the tire width direction H mainly act to increase the circumferential shear force at the time of stepping on. As a result, the circumferential shear force of the block 31 at the time of kicking is reduced, and the change in the circumferential shear force is reduced, and the occurrence of wear on the block 31 is suppressed.

FIG. 6 is a view showing a modification of the plurality of blocks 31 adjacent in the tire circumferential direction S. As shown in FIG.
As illustrated, at the time of tire rolling, the blocks 31 adjacent in the tire circumferential direction S may contact, and a force P in the tire circumferential direction S may be generated. In this case, stress may be concentrated at the predetermined position M of the block 31, and the wear resistance performance of the block 31 may be affected. On the other hand, in the tire 1, the distance F between the blocks 31 adjacent in the tire width direction H is shorter than the distance G between the blocks 31 adjacent in the tire circumferential direction S. Therefore, as compared with the blocks 31 adjacent in the tire width direction H, the contact of the blocks 31 adjacent in the tire circumferential direction S is suppressed. Thereby, the fall of the abrasion resistance performance of the block 31 is suppressed.

  Further, in the central block row 30 of the tire 1, the deformation of the block 31 is suppressed by the contact of the blocks 31 adjacent in the tire width direction H, and the circumferential shear force (in particular, the maximum circumferential shear force) is reduced. . As a result, the forced wear of the block 31 is reduced. In addition, when the forced wear is reduced in a part of the tread portion 2, the forced wear is promoted in other parts of the tread portion 2 and the self-excitation wear is reduced. Therefore, in the two middle block rows 40 adjacent to the center block row 30 in the tire width direction H, the self-excitation wear of the blocks 41 is reduced, and the occurrence of uneven wear (for example, heel and toe wear) is suppressed.

  As described above, in the tire 1 of the present embodiment, it is possible to improve the wear resistance performance and the uneven wear resistance performance by making the wear resistance performance and the uneven wear resistance performance compatible with each other. Moreover, the edge component of the block 31 can be increased by the closed sipes 33 formed in the block 31 of the central block row 30, and the ice and snow performance can be secured.

  Since the closed sipes 33 close in the block 31, the reduction in the rigidity of the block 31 can also be suppressed. Since the closed sipe 33 is bent a plurality of times not more than four times, the reduction in the rigidity of the block 31 can be reliably suppressed. Since the depth of the closed sipes 33 becomes deeper from the central portion toward both ends, even if the central portion of the closed sipes 33 disappears due to the wear of the tread portion 2, the portions on both ends of the closed sipes 33 remain. Therefore, even at the end of use of the tire 1, the ice and snow performance can be secured by the edge of the block 31 and the portions on both end sides of the closed sipe 33.

  In the same manner as the closed sipes 33, the depths of the other closed sipes 43 and 54 may be made deeper from the central portion of the closed sipes 43 and 54 in the tire width direction H toward both ends. Further, five or more circumferential grooves may be formed in the tread portion 2, and the tread portion 2 may be partitioned by five or more circumferential grooves. A plurality of dividing grooves 12 may be formed in the central block row 30 to divide the central block row 30 into a plurality of adjacent block rows 32 sequentially adjacent in the tire width direction H. In this case, the adjacent block row 32 and the lateral groove 20 are disposed between the central circumferential groove 10 and the dividing groove 12 and between the two dividing grooves 12.

(Tire test)
In order to confirm the effects of the present invention, the tire of the example (referred to as an embodiment) and two conventional tires (referred to as conventional products A and B) were produced, and their wear characteristics were evaluated. The practical product and the conventional products A and B are radial ply tires for trucks and buses of the same tire size (11R22.5). Grooves and the like were formed in the smooth tire to produce a practical product and conventional products A and B.
FIG. 7 is a plan view showing the tread pattern of the conventional product A, and FIG. 8 is a plan view showing the tread pattern of the conventional product B. As shown in FIG.

  As shown in FIG. 7, the conventional product A includes a plurality of circumferential grooves 60, a plurality of lateral grooves 61, a plurality of block rows 62, 63, 64, a plurality of blocks 65, 66, 67, and a plurality of closed A sipe 68 and a circumferential narrow groove 69 are provided. The plurality of block rows 62, 63, 64 are composed of one central block row 62, two middle block rows 63, and two shoulder block rows 64. The plurality of blocks 65, 66, 67 are divided by the plurality of circumferential grooves 60 and the plurality of lateral grooves 61, and are formed in the block rows 62, 63, 64, respectively. The blocks 67 of the shoulder block row 64 are divided by the circumferential narrow groove 69 into an inner portion 67A and an outer portion 67B in the tire width direction H. The closed sipes 68 are bending sipes, and four closed sipes 68 are formed in each block 65, 66, 67.

  As shown in FIG. 8, the conventional product B includes a plurality of circumferential grooves 70, a plurality of lateral grooves 71, a plurality of block rows 72, 73, 74, a plurality of blocks 75, 76, 77, and a plurality of sipes. 78, 79 and a circumferential narrow groove 80 are provided. The plurality of block rows 72, 73, 74 are composed of one central block row 72, two intermediate block rows 73, and two shoulder block rows 74. The plurality of blocks 75, 76, 77 are divided by the plurality of circumferential grooves 70 and the plurality of lateral grooves 71, and formed in the block rows 72, 73, 74, respectively. The blocks 77 of the shoulder block row 74 are divided by the circumferential narrow groove 80 into an inner portion 77A and an outer portion 77B in the tire width direction H.

  The plurality of sipes 78, 79 are composed of widthwise sipes 78 and closed sipes 79 formed in each block 75, 76, 77. The widthwise sipe 78 is a sipe extending in the tire width direction H, and two widthwise sipes 78 are disposed at the central portion of each block 75, 76, 77 in the tire circumferential direction S. The closed sipes 79 are bending sipes, and two closed sipes 79 are formed in each block 75, 76, 77. In the central block row 72, circumferential sipes 82, 83 are disposed between two blocks 75 adjacent in the tire width direction H.

  In the tire test, circumferential wear energy of the product and the conventional products A and B was measured under the same conditions by the wear energy measuring device, and the measurement results were compared. At that time, according to JATMA YEAR BOOK (2015, Japan Automobile Tire Association Standard), the actual product and conventional products A and B were mounted on the applicable rim, and the load and internal pressure of the actual product and conventional products A and B were adjusted. . Further, the shear force and the amount of slip applied to the blocks were measured by the wear energy measuring device, and the circumferential wear energy of each block was calculated based on the measurement results.

  The circumferential wear energy is energy in the tire circumferential direction S which causes the block to be worn, and is calculated by obtaining an integral value of shear force and slip amount in the tire circumferential direction S. In the circumferential direction, the wear energy is determined by the blocks 31, 41, 51 of the block row 30, 40, 50 of the product, the blocks 65, 66, 67 of the block row 62, 63, 64 of the conventional product A, and the blocks of the conventional product B It calculated about block 75, 76, 77 of the column 72, 73, 74, respectively.

  Table 1 shows the widths of the intermediate block rows 40, 63, 73 of the practical product and the conventional products A and B and the width ratios of the block arrays of the practical product and the conventional products A and B. The width of the middle block row 40, 63, 73 is expressed by an index where the width of the middle block row 63 of the conventional product A is 100. The width ratio of the block rows is the ratio of the width of the middle block rows 40, 63, 73 to the width of the shoulder block rows 50, 64, 74 with respect to the width of the central block rows 30, 62, 72.

  As shown in Table 1, the width of the intermediate block row 63 of the conventional product A is wider than the widths of the other intermediate block rows 40 and 73, and the width of the intermediate block row 40 of the embodiment and the intermediate block row 73 of the conventional product B The width of is the same. Further, in the conventional product A, the width of the shoulder block row 64 is the widest, and the width of the center block row 62 and the width of the middle block row 63 are the same. In the conventional product B, the width of the block row becomes wider in the order of the intermediate block row 73, the shoulder block row 74, and the central block row 72. As in the conventional product B, in the embodiment, the width of the block row becomes wider in the order of the intermediate block row 40, the shoulder block row 50, and the central block row 30.

FIG. 9 is a graph showing the circumferential wear energy of the practical product and the conventional products A and B, showing the circumferential wear energy of the blocks in each block row.
In FIG. 9, the center is the center block row 30, 62, 72, and the middle is the middle block row 40, 63, 73. Also, the shoulders are shoulder block rows 50, 64, 74. The circumferential wear energy of the shoulder block row 50, 64, 74 is the circumferential wear energy of the inner part (the inner parts 51A, 67A, 77A of the blocks 51, 67, 77) and the outer part (the blocks 51, 67, 77) The circumferential wear energy of the portions 51B, 67B, 77B).

  When the circumferential wear energy is a positive value, forced wear tends to occur, and when the circumferential wear energy is a negative value, self-excited wear tends to occur. Also, as the circumferential wear energy increases in the positive direction, forced wear tends to occur, and as the circumferential wear energy increases in the negative direction, self-excited wear tends to occur. Therefore, as the circumferential wear energy decreases (the circumferential wear energy approaches zero), forced wear or self-sustained wear is less likely to occur.

  The circumferential wear energy E1 of the implemented product is located between the circumferential wear energy EA of the conventional product A and the circumferential wear energy EB of the conventional product B, and viewed from the both circumferential wear energy EA, EB as a whole. It is getting smaller. In particular, in the blocks 41, 66, 76 of the middle block row 40, 63, 73, the circumferential wear energy E1 of the embodiment is smaller than the circumferential wear energies EA, EB of the conventional products A, B. From this, it was found that in the embodiment, the self-sustained wear can be reduced in the block 41 of the middle block row 40. Further, in the blocks 31, 65, 75 of the central block row 30, 62, 72, the circumferential wear energy E1 of the embodiment is smaller than the circumferential wear energy EB of the conventional product B, and the circumferential wear energy of the conventional product A It is about the same as EA. From this, it was found that in the embodiment, the forced abrasion can be reduced in the block 31 of the central block row 30. From the above results, it was found that in the embodiment, the wear resistance performance and the uneven wear resistance performance can be compatible.

  DESCRIPTION OF SYMBOLS 1 ... tire, 2 ... tread part, 3 ... tire equatorial plane, 4 ... shoulder part, 5 ... road surface, 10 ... central side circumferential groove, 11 ... outside circumference Direction groove, 12: split groove, 20: lateral groove, 21: lateral groove, 22: lateral groove, 30: central block row, 31: block, 32: adjacent block row, 33 ... closed sipes, 40 ... intermediate block rows, 41 ... blocks, 42 ... widthwise sipes, 43 ... closed sipes, 50 ... shoulder block rows, 51 ... blocks, 52: circumferential narrow groove, 53: widthwise sipe, 54: closed sipe, H: tire width direction, S: tire circumferential direction.

Claims (2)

Four or more circumferential grooves, including two central circumferential grooves located on both sides of the tire equatorial plane,
A plurality of block rows including a central block row divided into a tread by a plurality of circumferential grooves and divided by two central side circumferential grooves;
A tire provided with
A dividing groove extending in the tire circumferential direction, which divides the central block row into adjacent block rows adjacent in the tire width direction;
A plurality of blocks formed in adjacent block rows on both sides in the tire width direction of the dividing groove, and arranged in each adjacent block row in order adjacently in the tire circumferential direction;
A plurality of blocks on both sides in the tire width direction of the dividing groove are disposed mutually offset in the tire circumferential direction, and in the blocks adjacent in the tire width direction, the end portions in the tire circumferential direction of each block are mutually offset in the tire circumferential direction Placed
Dividing groove extends zigzag in the tire circumferential direction, between adjacent blocks in the tire width direction, extending in the tire circumferential direction in a state inclined with respect to the tire width direction and the tire circumferential direction,
The distance between adjacent blocks in the tire width direction is shorter than the distance between adjacent blocks in the tire circumferential direction,
Each block of the plurality of blocks extends in the widthwise direction of the tire while being bent a plurality of times not more than four times, and the tire has four sipes whose both ends are closed in each block. In the tire recited in claim 1,
Depth from the block tread surface of each sipe is Ri a gradually deeper toward the both end portions from the central portion in the tire width direction of the sipe, the most profoundly that the tire at both ends of the outer tire width direction of each sipe.

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