JP2019131150A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can make both on-ice/snow performance and uneven wear resistance compatible.SOLUTION: A circumferential narrow groove 50 extending in a tire circumferential direction with a groove width narrower than groove widths of inner lug grooves 41 between two inner circumferential main grooves 31 is formed in a center block row 21 whose both sides in a tire width direction are sectioned by the two inner circumferential main grooves 31. In the center block row 21 are formed two block rows 22 adjacent to each other through the circumferential narrow groove 50. In each block row 22, a plurality of center blocks 11 are arranged in a tire circumferential direction, and center blocks 11 that the two block rows 22 adjacent to each other through the circumferential narrow groove 50 have are arranged to be offset in the tire circumferential direction relative to the center blocks 11 that the other block rows 22 have respectively. In the center blocks 11 are formed a plurality of sipes 60 respectively. In the circumferential narrow groove 50, a connection part 55 is formed between the center blocks 11 adjacent to each other through the circumferential narrow groove 50.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  In so-called studless tires that require driving performance on ice and snow, the frictional force is increased by using flexible rubber, and the groove on the tread is devised to improve the performance on ice and snow. . For example, in the pneumatic tire described in Patent Document 1, in order to obtain high performance on ice while ensuring block rigidity, the block is provided with an open sipe and a closed sipe, and a tire is provided at the center portion in the tire width direction of the tread. A circumferential sipe extending in a zigzag shape along the equator plane is formed, and a connecting portion for connecting blocks on both sides in the tire circumferential direction is provided in a lug groove disposed between blocks adjacent in the tire circumferential direction.

  Further, in the pneumatic tire described in Patent Document 2, in order to achieve both wear resistance performance and uneven wear resistance performance while securing the performance on the snow and snow of the tire, the central block row extends to the tire in the tire circumferential direction. A division groove is formed to be divided into adjacent block rows adjacent in the width direction, and the blocks on both sides in the tire width direction of the division groove are arranged to be shifted from each other in the tire circumferential direction, and the distance between the blocks adjacent in the tire width direction Is made shorter than the distance between adjacent blocks in the tire circumferential direction, and each block is provided with a sipe that is bent a plurality of times and extends in the tire width direction so that both ends are closed in each block.

Japanese Patent No. 6138727 JP, 2006-203842, A

  Here, one of the important performances required for the studless tire is the performance on ice and snow, which is the handling stability on the road surface on ice and the road surface on snow. As means for improving the performance on ice and snow, it is a common method to improve the snow drainage performance and drainage performance and to improve the edge performance by arranging many grooves and sipes. However, when a large number of grooves and sipes are arranged, the block rigidity is lowered, so that uneven wear is likely to occur, and uneven wear resistance is likely to be reduced. For this reason, it has been very difficult to achieve both of these performances.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of achieving both snow and snow performance and uneven wear resistance.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention is the tire equator in the tire width direction across a tire equator plane among a plurality of circumferential main grooves extending in the tire circumferential direction. Among the two inner circumferential main grooves that are the circumferential main grooves disposed on both sides of the surface and a plurality of lug grooves extending in the tire width direction, between the two inner circumferential main grooves An inner lug groove that is disposed, and a central block row that is positioned between the two inner circumferential main grooves and that is partitioned on both sides in the tire width direction by the two inner circumferential main grooves. In the central block row, a circumferential narrow groove extending in the tire circumferential direction with a groove width narrower than the groove width of the inner lug groove is formed between the two inner circumferential main grooves, and the central block row Are two adjacent in the tire width direction through the circumferential narrow groove A block row is formed, and each block row includes a plurality of central blocks defined by the inner circumferential main groove, the inner lug groove, and the circumferential narrow groove arranged in the tire circumferential direction, and the circumferential direction. The central block of two block rows adjacent via a narrow groove is arranged offset in the tire circumferential direction with respect to the central block of the other block row, and the central block includes A plurality of sipes are formed, and a connecting portion is formed in the circumferential narrow groove between the central blocks adjacent to each other through the circumferential narrow groove.

  In the pneumatic tire, the central block is opposed to the plurality of central blocks included in the other block row via the circumferential narrow groove, and the central block included in the other block row. The opposite length in the tire circumferential direction is opposed to the opposite different central blocks with different lengths, and the connecting portion includes one central block and the circumferential thin portion with respect to the central block. Of the plurality of central blocks facing each other through a groove, it is preferable that the opposing length in the tire circumferential direction is formed between the central blocks that are relatively long.

  Further, in the pneumatic tire, the sipe includes an open sipe having both ends opened on both sides in the tire width direction of the central block, and a closed sipe having both ends terminating in the central block. The sipe is a three-dimensional sipe that swings in the sipe width direction with respect to the two directions of the sipe length direction and the sipe depth direction, and the depth is 50% or more of the depth of the circumferential main groove. It is preferably within the range of 70% or less.

  In the pneumatic tire, the closed sipe is disposed on both sides in the tire circumferential direction of the open sipe, and the depth of the closed sipe is in a range of 60% to 95% of the depth of the open sipe. It is preferable to be within.

  In the pneumatic tire described above, the circumferential narrow groove has a ratio between a maximum depth D1 of the circumferential narrow groove and a depth D2 at a position where the connecting portion is formed in the circumferential narrow groove ( D2 / D1) is preferably in the range of 0.6 to 0.9.

  In the pneumatic tire, the connecting portion has a ratio (LC / LB) of a length LC in the tire circumferential direction of the connecting portion to a length LB in the tire circumferential direction of the central block. It is preferably within the range of 0.6 or less.

  In the pneumatic tire, the inner lug groove has a ratio (WL / LB) of a width WL in the tire circumferential direction of the inner lug groove to a length LB in the tire circumferential direction of the central block of 0. It is preferably within the range of 15 or more and 0.3 or less.

  In the pneumatic tire, the inner lug groove has a depth in the range of 70% to 90% of the depth of the inner circumferential main groove, and the groove wall has a bent portion. It is preferable that the groove width on the groove bottom side with respect to the bent portion is narrower than the groove width of the inner lug groove on the tread surface.

  In the pneumatic tire, the inner lug groove has a ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove and the depth DL2 from the tread surface to the bent portion of 0.6 or more. It is preferably within a range of 0.9 or less.

  In the pneumatic tire, the inner lug groove has a ratio (WL2 / WL1) of the groove width WL1 at the tread surface to the groove width WL2 at the position of the bent portion is 0.3 or more and 0.5. It is preferable to be within the following range.

  In the pneumatic tire, the outer circumferential main grooves, which are the circumferential main grooves, are disposed on the outer sides in the tire width direction of the two inner circumferential main grooves, and the inner circumferential directions are adjacent to each other. Between the main groove and the outer circumferential main groove, an intermediate lug groove that is the lug groove whose both ends open to the inner circumferential main groove and the outer circumferential main groove is formed, and the inner lug groove An intermediate block row in which a plurality of intermediate blocks defined by the circumferential main groove, the outer circumferential main groove and the intermediate lug groove are arranged in the tire circumferential direction is formed, and the intermediate lug groove has a groove wall with a bent portion. Preferably, the groove width on the groove bottom side of the bent portion is narrower than the groove width of the intermediate lug groove on the tread surface.

  In the pneumatic tire, the circumferential main groove is formed with a groove wall having a bent portion, and a groove width on the groove bottom side of the bent portion is greater than that of the circumferential main groove on the tread surface. The width is preferably narrower than the groove width.

  The pneumatic tire according to the present invention has an effect that both performance on snow and snow and uneven wear resistance can be achieved.

FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment. FIG. 2 is a detailed view of part A of FIG. FIG. 3 is a detailed view of part B of FIG. 4 is a cross-sectional view taken along the line CC of FIG. 5 is a cross-sectional view taken along the line DD of FIG. 6 is a cross-sectional view taken along line FF in FIG. FIG. 7 is a modified example of the pneumatic tire according to the embodiment, and is an explanatory diagram when the center narrow groove is formed in a straight shape. FIG. 8 is a modified example of the pneumatic tire according to the embodiment, and is an explanatory diagram in the case where there is one bent portion of the inner lug groove or the intermediate lug groove. FIG. 9A is a chart showing the results of a performance evaluation test of a pneumatic tire. FIG. 9B is a chart showing the results of a performance evaluation test of a pneumatic tire. FIG. 9C is a chart showing the results of a performance evaluation test of a pneumatic tire. FIG. 9D is a chart showing the results of a performance evaluation test of a pneumatic tire. FIG. 9E is a chart showing the results of a performance evaluation test of a pneumatic tire.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be replaced by those skilled in the art and can be easily conceived, or those that are substantially the same.

[Embodiment]
In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side, and Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a circumferential direction with the rotation axis as the central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means in the tire width direction. The side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL is the center of the pneumatic tire 1 in the tire width direction. The position in the tire width direction coincides with the position in the tire width direction center line. The tire width is the width in the tire width direction between the outermost portions in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator line is a line along the tire circumferential direction of the pneumatic tire 1 on the tire equator plane CL.

  FIG. 1 is a plan view showing a tread surface 3 of a pneumatic tire 1 according to an embodiment. A pneumatic tire 1 shown in FIG. 1 is provided with a tread portion 2 at the outermost portion in the tire radial direction, and the surface of the tread portion 2, that is, a vehicle on which the pneumatic tire 1 is mounted (not shown). The portion that comes into contact with the road surface during traveling is formed as a tread surface 3. A plurality of circumferential main grooves 30 extending in the tire circumferential direction and lug grooves 40 extending in the tire width direction are formed on the tread surface 3. The tread tread 3 is divided into a plurality of blocks 10 which are land portions by the plurality of circumferential main grooves 30 and lug grooves 40.

  Specifically, four circumferential main grooves 30 are formed side by side in the tire width direction, and two inner sides arranged on both sides of the tire equatorial plane CL in the tire width direction across the tire equatorial plane CL. A circumferential main groove 31 and two outer circumferential main grooves 32 arranged one by one on the outer side in the tire width direction of each of the two inner circumferential main grooves 31 are provided. The lug groove 40 is arranged between the inner lug groove 41 disposed between the two inner circumferential main grooves 31 and between the adjacent inner circumferential main groove 31 and the outer circumferential main groove 32. An intermediate lug groove 42 provided and a shoulder lug groove 43 disposed on the outer side in the tire width direction of the outer circumferential main groove 32 are provided.

  The circumferential main groove 30 here is a longitudinal groove at least partially extending in the tire circumferential direction. Generally, the circumferential main groove 30 has a groove width of 5 mm or more, a groove depth of 10 mm or more, and a tread wear indicator (slip sign) indicating the end of wear. In the present embodiment, the circumferential main groove 30 has a groove width of 5 mm or more, a groove depth of 12 mm or more, and a tire equator line (center center) where the tire equatorial plane CL and the tread surface 3 intersect. Line). The circumferential main groove 30 may extend linearly in the tire circumferential direction, or may be provided in a wave shape or a zigzag shape. The lug groove 40 has a groove width in the range of 4 mm to 12 mm and a groove depth in the range of 6 mm to 22 mm.

  A plurality of block rows in which a plurality of blocks 10 are arranged in the tire circumferential direction are formed on the tread surface 3 by four circumferential main grooves 30. Among the block rows, the block row that is located between the two inner circumferential main grooves 31 and that is divided on both sides in the tire width direction by the two inner circumferential main grooves 31 is the central block row 21. Yes. Further, it is located between the inner circumferential main groove 31 and the outer circumferential main groove 32 adjacent to each other in the tire width direction, the inner side in the tire width direction is partitioned by the inner circumferential main groove 31, and the outer side in the tire width direction is A block row defined by the outer circumferential main grooves 32 is an intermediate block row 25. A block row that is located on the outer side in the tire width direction of the outer circumferential main groove 32 and whose inner side in the tire width direction is partitioned by the outer circumferential main groove 32 is a shoulder block row 26.

  Further, the tread surface 3 is formed with a circumferential narrow groove 50 extending in the tire circumferential direction with a groove width narrower than the groove width of the circumferential main groove 30 and the groove width of the lug groove 40. Specifically, the circumferential narrow groove 50 is disposed on the outer side in the tire width direction of the center narrow groove 51 disposed between the two inner circumferential main grooves 31 and the outer circumferential main groove 32. A shoulder narrow groove 52 is provided. That is, the center narrow groove 51 is formed in the central block row 21 located between the two inner circumferential main grooves 31, and the shoulder narrow groove 52 is located outside the outer circumferential main groove 32 in the tire width direction. The shoulder block row 26 is formed. Here, the circumferential narrow groove 50 has a groove width in the range of 1 mm to 5 mm and a groove depth in the range of 6 mm to 22 mm.

  Of the circumferential narrow grooves 50 formed as described above, the center narrow groove 51 is disposed near the center in the tire width direction between the two inner circumferential main grooves 31. In the form, at least a part of the center narrow groove 51 is located on the tire equatorial plane CL. Further, the shoulder narrow groove 52 is disposed in the vicinity of the center in the tire width direction between the outer circumferential main groove 32 and the design end E that is the outer end in the tire width direction of the tread surface 3. The design end E here refers to the outermost end in the tire width direction of the tread portion 2, and is the outermost end in the tire width direction in which a groove is formed in the tread portion 2.

  The center narrow groove 51 and the shoulder narrow groove 52 formed as described above are both bent in the tire width direction while repeatedly extending in the tire circumferential direction. That is, the center narrow groove 51 and the shoulder narrow groove 52 extend in the tire circumferential direction in a zigzag shape that repeatedly extends in the tire width direction while extending in the tire circumferential direction.

  Further, the central block row 21 and the shoulder block row 26 are further formed with block rows 22 and 27 on both sides of the circumferential narrow groove 50 in the tire width direction by the circumferential narrow grooves 50. That is, the central block row 21 is formed with two block rows 22 adjacent to each other in the tire width direction via the center narrow groove 51. Similarly, the shoulder block row 26 is formed with two block rows 27 adjacent to each other in the tire width direction via the shoulder narrow grooves 52. In the shoulder block row 26, a width direction narrow groove 58 that is a narrow groove extending in the tire width direction is formed in the block row 27 outside the shoulder narrow groove 52 in the tire width direction.

  The inner lug grooves 41 disposed between the two inner circumferential main grooves 31 are disposed on both sides of the center narrow groove 51 in the tire width direction, and one end is opened to the inner circumferential main groove 31. The other end opens into the center narrow groove 51. That is, as for the inner lug groove 41 arrange | positioned at the tire width direction both sides of the center narrow groove 51, the edge part of the tire width direction outer side both open to the inner peripheral direction main groove 31, and the edge part of the tire width direction inner side is, The center narrow groove 51 is opened. At that time, the end of the inner lug groove 41 on the inner side in the tire width direction opens to a bent portion in the center narrow groove 51 formed in a zigzag shape.

  Further, the inner lug grooves 41 disposed on both sides of the center narrow groove 51 in the tire width direction are arranged at positions in the tire circumferential direction that are different from each other between the inner lug grooves 41 on both sides of the center narrow groove 51 in the tire width direction. The inner lug grooves 41 disposed on both sides of the center narrow groove 51 in the tire width direction are alternately disposed in the tire circumferential direction. The inner lug groove 41 extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction. The inclination direction in the tire circumferential direction with respect to the tire width direction is the tire width of the center narrow groove 51. The inner lug grooves 41 on both sides are in the same direction.

  Further, the intermediate lug groove 42 disposed between the adjacent inner circumferential main groove 31 and outer circumferential main groove 32 is open at both ends to the inner circumferential main groove 31 and the outer circumferential main groove 32. ing. Specifically, the intermediate lug groove 42 has an inner end in the tire width direction that opens to the inner circumferential main groove 31 and an outer end in the tire width direction that opens to the outer circumferential main groove 32. The intermediate lug groove 42 extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction. The inclination direction in the tire circumferential direction with respect to the tire width direction is the inclination direction of the inner lug groove 41. It is in the opposite direction. In other words, the intermediate lug grooves 42 disposed on both sides of the tire equatorial plane CL in the tire width direction have the same inclination direction in the tire circumferential direction with respect to the tire width direction.

  Further, the shoulder lug grooves 43 disposed on the outer side in the tire width direction of the outer circumferential main groove 32 are disposed on both sides of the shoulder narrow groove 52 in the tire width direction. Of the shoulder lug grooves 43, the shoulder lug grooves 43 disposed on the inner side in the tire width direction of the shoulder narrow grooves 52 open to the outer circumferential main grooves 32 at the inner ends in the tire width direction, and are outside in the tire width direction. Is opened in the shoulder narrow groove 52. The shoulder lug groove 43 disposed on the outer side in the tire width direction of the shoulder narrow groove 52 has an end on the inner side in the tire width direction opened to the shoulder narrow groove 52, and an end on the outer side in the tire width direction has the design end E. It is open at. At that time, the end of the shoulder lug groove 43 that is open to the shoulder narrow groove 52 is open to the bent portion of the shoulder narrow groove 52 formed in a zigzag shape. Further, the shoulder lug grooves 43 disposed on both sides of the shoulder narrow groove 52 in the tire width direction are arranged at positions in the tire circumferential direction that are different from each other in the shoulder lug grooves 43 on both sides of the shoulder narrow groove 52 in the tire width direction. It is installed.

  Further, the width direction narrow groove 58 disposed on the outer side of the shoulder narrow groove 52 in the tire width direction is an end portion of the shoulder narrow groove 52 formed in a zigzag shape at the end portion on the inner side in the tire width direction. Opened, and the end on the outer side in the tire width direction is open at the design end E. Outside the shoulder narrow groove 52 in the tire width direction, shoulder lug grooves 43 and width direction narrow grooves 58 extending in the tire width direction are alternately arranged in the tire circumferential direction.

  The two block rows 22 included in the central block row 21 include a plurality of central blocks 11, which are blocks 10 defined by the inner circumferential main groove 31, the inner lug groove 41, and the center narrow groove 51, respectively in the tire circumferential direction. Are lined up. Further, since the inner lug grooves 41 located on both sides of the center narrow groove 51 in the tire width direction are different from each other in the tire circumferential direction, two adjacent block rows 22 via the center narrow groove 51 are associated therewith. The central block 11 included in each is offset from the central block 11 included in the other block row 22 in the tire circumferential direction. In other words, in the central block 11, the central blocks 11 each having a plurality of two adjacent block rows 22 via the center narrow groove 51 are arranged in a staggered arrangement between the block rows 22. For this reason, each central block 11 is partially overlapped in the tire width direction with respect to the two central blocks 11 included in the block row 22 different from the own block row 22.

  In the intermediate block row 25 formed between the adjacent inner circumferential main grooves 31 and outer circumferential main grooves 32, a plurality of intermediate blocks 12 are arranged side by side in the tire circumferential direction. The intermediate block 12 is a block 10 defined by an inner circumferential main groove 31, an outer circumferential main groove 32, and an intermediate lug groove 42.

  Of the two block rows 27 included in the shoulder block row 26, the block row 27 located on the inner side in the tire width direction of the shoulder narrow groove 52 includes the outer circumferential main groove 32, the shoulder lug groove 43, and the shoulder narrow groove 52. A plurality of shoulder blocks 13, which are blocks 10 partitioned by, are arranged in the tire circumferential direction. The block row 27 located on the outer side in the tire width direction of the shoulder narrow groove 52 is a plurality of shoulders that are blocks 10 defined by the shoulder lug groove 43, the width direction narrow groove 58, the shoulder narrow groove 52, and the design end E. Blocks 13 are arranged in the tire circumferential direction. Further, the shoulder blocks 13 included in the two adjacent block rows 27 via the shoulder narrow grooves 52 are arranged offset from each other in the tire circumferential direction with respect to the shoulder blocks 13 included in the other block row 27. In other words, in the shoulder block 13, the shoulder blocks 13 each having a plurality of two adjacent block rows 27 via the shoulder narrow grooves 52 are arranged in a staggered arrangement between the block rows 27.

  Each block 10 formed as described above is formed with three or more sipes 60 that extend in the tire width direction and bend repeatedly in the tire circumferential direction. Specifically, the central block 11 and the intermediate block 12 include an open sipe 61 in which both ends in the length direction of the sipe 60 open on both sides in the tire width direction of the block 10, and both ends in the length direction of the sipe 60 are in the block 10. A closed sipe 62 that terminates inside is formed. In the present embodiment, the central block 11 and the intermediate block 12 are formed with one open sipe 61 and two closed sipes 62 that are arranged one on each side of the open sipe 61 in the tire circumferential direction. Has been.

  Further, the shoulder block 13 is formed with a plurality of closed sipes 62. In this embodiment, each shoulder block 13 has three closed sipes 62 extending in the tire width direction arranged in the tire circumferential direction. It is arranged.

  Here, the sipe 60 is formed in a narrow groove shape on the tread tread surface 3, and the pneumatic tire 1 is assembled on a regular rim to form a narrow groove when no load is applied under normal internal pressure conditions. When the narrow groove is located in the part of the ground contact surface formed on the flat plate when loaded in the vertical direction on the flat plate, or when the land part where the narrow groove is formed falls, The wall surface which comprises the said fine groove, or at least one part of the site | part provided in a wall surface says what mutually contacts by deformation | transformation of a land part. The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. In this embodiment, the sipe 60 has a width in the range of 0.3 mm or more and less than 1 mm, and a depth in the range of 3 mm or more and 22 mm or less.

  FIG. 2 is a detailed view of part A of FIG. Since the central block 11 is arranged in a staggered arrangement between the block rows 22 of the central block row 21, the central block 11 included in each block row 22 of the central block row 21 has the other block row 22. The plurality of central blocks 11 are opposed to each other through the center narrow groove 51. The central block 11 facing the central block 11 of the other block row 22 via the center narrow groove 51 is opposed to the central block 11 of the other block row 22 in the tire circumferential direction. The different central blocks 11 face each other with different lengths. That is, in the present embodiment, each central block 11 is opposed to the two central blocks 11 via the center narrow groove 51, and the tire circumference of the portion facing between the opposed central blocks 11 is The length in the tire direction is different from the length in the tire circumferential direction of the portion facing the other central block 11 facing the other.

  Specifically, the edge 15 of the central block 11 defined by the center narrow groove 51 extends in the tire circumferential direction while the center narrow groove 51 is repeatedly bent in the tire width direction, so that the edge 15 of the central block 11 is also bent. doing. The edge 15 of the central block 11 is bent in a shape that is convex in a direction away from the center in the tire width direction of the central block 11, that is, a shape that is convex on the side where the center narrow groove 51 is located. The edge 15 of the central block 11 bent in this way has a length on one side and a length on the other side in the tire circumferential direction with the bent portion as a boundary, and the longer side is a long portion of the edge 15. 16, and the short side is the short portion 17 of the edge 15.

  Further, in the central block 11 included in the two adjacent block rows 22 through the center narrow groove 51, the positional relationship between the long portion 16 and the short portion 17 is opposite. For example, in the central block 11 included in one block row 22 when viewed in a predetermined tire rotation direction, when the long portion 16 is the first arrival side and the short portion 17 is the rear arrival side, the other block In the central block 11 included in the row 22, the short portion 17 is the first arrival side, and the long portion 16 is the rear arrival side.

  The central block 11 facing the two central blocks 11 via the center narrow groove 51 is opposed to one central block 11 of the two central blocks 11 facing each other. The almost entire range of the long portions 16 of the opposed central blocks 11 is opposed. In addition, the other central blocks 11 of the two central blocks 11 facing each other are partially opposed to each other in the short portions 17. Thereby, the center block 11 is the length from which the length in the tire circumferential direction differs in one center block 11 and the other center block 11 among the two center blocks 11 which oppose via the center fine groove 51. Opposing to the two central blocks 11.

  In the central narrow groove 51 that divides the two block rows 22 in the central block row 21, a connecting portion 55 is formed between the adjacent central blocks 11 through the center thin groove 51. The connecting portion 55 is formed by raising the bottom of the center narrow groove 51, that is, the connecting portion 55 is formed so that a part of the center thin groove 51 has a shallow depth. It is formed by the bottom raising part formed. The connecting portion 55 formed in the center narrow groove 51 is opposed to one central block 11 and a plurality of central blocks 11 facing the central block 11 via the center narrow groove 51 in the tire circumferential direction. It is formed between the central blocks 11 having a relatively long length. That is, the connecting portion 55 is not formed between the short portions 17 among the central blocks 11 facing each other via the center narrow groove 51, but between the long portions 16 of the facing central blocks 11. Is formed.

  FIG. 3 is a detailed view of part B of FIG. The connecting portion 55 formed in the center narrow groove 51 is formed over substantially the entire range in the length direction of the long portion 16 in the central block 11 where the long portions 16 face each other. The connecting portion 55 thus formed has a ratio (LC / LB) between the length LC of the connecting portion 55 in the tire circumferential direction and the length LB of the central block 11 in the tire circumferential direction of 0.3 or more and 0. Within the range of .6 or less. In this case, the length LB of the central block 11 in the tire circumferential direction is the distance in the tire circumferential direction between one end and the other end of the central block 11 in the tire circumferential direction. This is the maximum length of the central block 11 in the circumferential direction.

  Further, the central blocks 11 that are adjacent to each other through the center narrow groove 51 are formed so that the partial ranges of the short portions 17 at the edge 15 on the center narrow groove 51 side of both the central blocks 11 are also opposed to each other. . The central block 11 that is adjacent to each other via the center narrow groove 51 and that the partial ranges of the short portions 17 face each other is the length LD in the tire circumferential direction of the portion where the short portions 17 face each other, and the tire of the central block 11. The ratio (LD / LB) with the length LB in the circumferential direction is in the range of 0.1 to 0.3.

  Further, the inner lug groove 41 that divides both ends of the central block 11 in the tire circumferential direction is a ratio of the width WL of the inner lug groove 41 in the tire circumferential direction and the length LB of the central block 11 in the tire circumferential direction (WL / LB) is in the range of 0.15 to 0.3. The width WL in the tire circumferential direction of the inner lug groove 41 in this case is the width in the tire circumferential direction of the portion where the inner lug groove 41 is open with respect to the tread surface 3.

  4 is a cross-sectional view taken along the line CC of FIG. The center narrow groove 51 where the connecting portion 55 is formed has a ratio (D2 / D1) between the maximum depth D1 of the center thin groove 51 and the depth D2 at the position where the connecting portion 55 is formed in the center thin groove 51. However, it is in the range of 0.6 or more and 0.9 or less. That is, the center narrow groove 51 has a relationship between the maximum depth D1 at the position where the connecting portion 55 is not formed and the depth D2 from the tread surface 3 to the connecting portion 55 at the position where the connecting portion 55 is formed. However, it is in the range of 0.6 ≦ (D2 / D1) ≦ 0.9.

  Of the sipe 60 formed in the block 10, the open sipe 61 formed in the central block 11 and the intermediate block 12 swings in the sipe width direction with respect to both directions of the sipe length direction and the sipe depth direction. It is a so-called three-dimensional sipe that is a three-dimensional sipe. That is, the open sipe 61 that is a three-dimensional sipe has an amplitude in the sipe width direction in both a cross-sectional view in which the sipe length direction is a normal direction and a cross-sectional view in which the sipe depth direction is a normal direction. It has a bent sipe wall surface. Further, the open sipe 61 is bent at five or more locations on the tread surface 3 while extending in the tire width direction.

  Among the open sipes 61 formed in this way, the open sipes 61 formed in the central block 11 are open at both ends in the tire width direction at both ends in the tire width direction of the central block 11. That is, the open sipe 61 formed in the central block 11 has one end in the tire width direction opening in the center narrow groove 51 and the other end opening in the inner circumferential main groove 31. The open sipe 61 formed in the intermediate block 12 has one end in the tire width direction opening in the inner circumferential main groove 31 and the other end opening in the outer circumferential main groove 32. That is, the central block 11 and the intermediate block 12 where the open sipe 61 is formed are divided into two in the tire circumferential direction by the open sipe 61.

  The closed sipes 62 whose both ends in the tire width direction terminate in the central block 11, the intermediate block 12, and the respective blocks 10 in the shoulder block 13 extend in the tire width direction or in the tire depth direction. It is a so-called two-dimensional sipe that is a two-dimensional sipe extending straight without bending. That is, the closed sipe 62, which is a two-dimensional sipe, has a straight sipe wall surface in an arbitrary cross-sectional view (a cross-sectional view including the sipe width direction and the sipe depth direction) whose normal is the sipe length direction. doing. In the present embodiment, the closed sipe 62 is repeatedly bent in the tire circumferential direction a plurality of times while extending in the tire width direction, and has the same shape as the shape that appears on the tread tread surface 3, and the sipe bottom from the opening to the tread tread surface 3. Is formed. The closed sipe 62 is disposed on both sides of the open sipe 61 in the tire circumferential direction in the central block 11 and the intermediate block 12 where the open sipe 61 is formed.

  Of the sipe 60 formed as described above, the open sipe 61 has a depth in the range of 50% to 70% of the depth of the circumferential main groove 30. The closed sipe 62 has a depth in the range of 60% to 95% of the depth of the open sipe 61.

  5 is a cross-sectional view taken along the line DD of FIG. The inner lug groove 41 is formed with the groove wall 44 having a bent portion 45, and the groove width closer to the groove bottom 49 than the bent portion 45 is larger than the groove width WL 1 of the inner lug groove 41 on the tread surface 3. Is also narrower. Specifically, the groove wall 44 of the inner lug groove 41 includes a first bent portion 46 formed as a bent portion 45 at a portion continuous from the tread surface 3 in the groove wall 44 and a groove bottom 49 in the groove wall 44. And a second bent portion 47 formed in a continuous portion. In the groove wall 44, a portion formed from the first bent portion 46 toward the tread tread surface 3 side is formed at an angle close to the groove depth direction, and from the first bent portion 46 toward the groove bottom 49 side. The portion to be formed is formed at an angle close to the groove width direction, and the first bent portion 46 is an intersection of the portions of the groove wall 44 having different angles. In addition, a portion of the groove wall 44 that is formed from the second bent portion 47 toward the tread tread 3 side is formed at an angle close to the groove width direction and extends from the second bent portion 47 toward the groove bottom 49 side. The portion formed in this manner is formed at an angle close to the groove depth direction, and the second bent portion 47 is an intersection of the portions of the groove wall 44 having different angles.

  Further, the first bent portion 46 and the second bent portion 47 are substantially the same position in the groove depth direction, and the second bent portion 47 is more in the groove width direction than the first bent portion 46. Located inside. Therefore, a portion of the groove wall 44 between the first bent portion 46 and the second bent portion 47 is a stepped portion 48 formed at an angle close to parallel to the tread tread surface 3, and the inner lug The groove wall 44 of the groove 41 is formed in a platform shape having a stepped portion 48 substantially parallel to the tread surface 3.

  The inner lug groove 41 formed in the shape of a platform has a ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove 41 and the depth DL2 from the tread surface 3 to the bent portion 45 of 0.6 or more and 0. It is within the range of .9 or less. The inner lug groove 41 has a first bent portion 46 and a second bent portion 47 as the bent portion 45, and the tread tread 3 is between the first bent portion 46 and the second bent portion 47. Therefore, the depth DL2 from the tread tread surface 3 to the bent portion 45 is, in other words, the depth DL2 from the tread tread surface 3 to the stepped portion 48. .

  Further, the inner lug groove 41 in which the groove width on the groove bottom 49 side with respect to the bent portion 45 is narrower than the groove width WL1 on the tread tread surface 3 is the groove width WL1 on the tread tread surface 3 and the bent portion 45 The ratio (WL2 / WL1) to the groove width WL2 at the position is in the range of 0.3 to 0.5. In this case, the groove width WL2 at the position of the bent portion 45 is the groove width WL2 at the portion where the interval between the opposing groove walls 44 is narrowed by the bent portion 45, that is, the second bent portion 47. The groove width WL2 at the position of. Note that the groove width WL2 at the position of the bent portion 45 in the inner lug groove 41 or the groove width on the groove bottom 49 side of the bent portion 45 is preferably in the range of 2 mm or more and 5 mm or less.

  The intermediate lug groove 42 is also formed in a platform shape like the inner lug groove 41, the groove wall 44 is formed with a bent portion 45, and the groove width on the groove bottom 49 side of the bent portion 45 is larger. It is narrower than the groove width of the intermediate lug groove 42 on the tread surface 3. That is, the intermediate lug groove 42 also has the first bent portion 46 and the second bent portion 47 as the bent portion 45, and the tread tread surface 3 is interposed between the first bent portion 46 and the second bent portion 47. Steps 48 that are parallel to each other are formed, and the groove width WL2 at the position of the second bent portion 47 is narrower than the groove width WL1 at the tread surface 3.

  6 is a cross-sectional view taken along line FF in FIG. The inner circumferential main groove 31 is also formed with the groove wall 34 having a bent portion 35, and the groove width closer to the groove bottom 39 than the bent portion 35 is the groove width of the inner circumferential main groove 31 on the tread surface 3. The inner circumferential main groove 31 is formed like a platform like the inner lug groove 41, being narrower than the groove width. That is, the inner circumferential main groove 31 also has the first bent portion 36 and the second bent portion 37 as the bent portion 35, and the tread tread 3 between the first bent portion 36 and the second bent portion 37. A stepped portion 38 that is parallel to the groove width WM2 at the position of the second bent portion 37 is narrower than the groove width WM1 at the tread surface 3. Specifically, the inner circumferential main groove 31 has a ratio (WM2 / WM1) of the groove width WM1 at the tread tread surface 3 to the groove width WM2 at the position of the bent portion 35 is 0.3 or more and 0.7. Within the following range.

  The inner circumferential main groove 31 formed in a platform shape is a ratio of the maximum depth DM1 of the inner circumferential main groove 31 and the depth DM2 from the tread tread surface 3 to the bent portion 35, that is, the inner circumferential main groove. The ratio (DM2 / DM1) between the maximum depth DM1 of 31 and the depth DM2 from the tread tread surface 3 to the stepped portion 48 is in the range of 0.5 to 0.9.

  The inner circumferential main groove 31 has a maximum depth DM1 from the tread surface 3 to the groove bottom 39 that is deeper than a maximum depth DL1 of the inner lug groove 41, and the inner lug groove 41 has a maximum depth. DL1 is in the range of 70% to 90% of the maximum depth DM1 of the inner circumferential main groove 31.

  When the pneumatic tire 1 configured as described above is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread tread surface 3 positioned below the tread tread surface 3 contacts the road surface. When driving on a dry road surface with a vehicle equipped with pneumatic tires 1, the driving force or braking force is transmitted to the road surface or the turning force is generated mainly by the frictional force between the tread tread surface 3 and the road surface. To drive. Further, when traveling on a wet road surface, water between the tread tread surface 3 and the road surface enters the circumferential main groove 30, the lug groove 40, etc., and water between the tread tread surface 3 and the road surface in these grooves. Drive while draining. As a result, the tread tread surface 3 is easily grounded to the road surface, and the vehicle can travel by the frictional force between the tread tread surface 3 and the road surface.

  Further, when traveling on a snowy road surface, the pneumatic tire 1 compresses the snow on the road surface with the tread surface 3 and the snow on the road surface enters the circumferential main grooves 30 and the lug grooves 40, thereby Will be pressed into the groove. In this state, a driving force or a braking force is applied to the pneumatic tire 1 or a force in the tire width direction is applied by turning of the vehicle, whereby the shearing force is applied to the snow in the groove. A so-called snow column shear force is generated between the pneumatic tire 1 and snow. When traveling on a snowy road surface, resistance is generated between the pneumatic tire 1 and the road surface by the snow column shear force, so that driving force and braking force can be transmitted to the road surface. It becomes possible to run on.

  Further, when traveling on a snowy road surface or an iced road surface, the vehicle travels using the edge effect of the circumferential main groove 30, the lug groove 40, and the sipe 60. That is, when traveling on a snowy road surface or an iced road surface, the vehicle travels using resistance caused by the edge of the circumferential main groove 30, the edge of the lug groove 40, or the edge of the sipe 60 being caught on the snow surface or ice surface. Further, when traveling on an icy road surface, water on the surface of the icy road surface is absorbed by the sipe 60 and the water film between the icy road surface and the tread tread surface 3 is removed so that the icy road surface and the tread tread surface 3 come into contact with each other. It becomes easy to do. As a result, the tread tread surface 3 is increased in resistance between the road surface on ice due to frictional force and edge effect, and the traveling performance of the vehicle equipped with the pneumatic tire 1 can be ensured.

  As described above, when traveling on a snowy road surface or an iced road surface, grooves such as the circumferential main groove 30 and the lug groove 40 and the sipe 60 are important, but the performance when traveling on a snowy road surface or an iced road surface is important. When the number of grooves and sipes 60 is increased with emphasis on the performance on ice and snow, the rigidity of the block 10 tends to decrease. When the rigidity of the block 10 is lowered, the block 10 is likely to be worn, and particularly, wear at a portion having low rigidity is likely to be increased, so that uneven wear is likely to occur.

  On the other hand, the pneumatic tire 1 according to the present embodiment forms a plurality of sipes 60 in the central block 11 and forms the center narrow grooves 51 in the central block row 21 while ensuring the performance on ice and snow. The central blocks 11 included in the block row 22 defined by the narrow grooves 51 are offset from each other in the tire circumferential direction.

  As a result, when the tread surface 3 of the grounded central block 11 is separated from the road surface during rotation of the pneumatic tire 1, the central block 11 adjacent to the central block 11 is grounded via the center narrow groove 51. Since it will leave in the state which continues, when the center block 11 leaves | separates from a road surface, it can suppress leaving rapidly, slipping with respect to a road surface. For this reason, at the time of rotation of the pneumatic tire 1, it can suppress that the kicking side which is the rear arrival side in the rotation direction of the pneumatic tire 1 of the central block 11 is likely to generate wear due to sliding with respect to the road surface. The so-called heel and toe wear, which is uneven wear due to large wear on the kicking side of the block 10, can be suppressed.

  Further, since the center narrow groove 51 is formed with a connecting portion 55 between the central blocks 11 adjacent to each other via the center narrow groove 51, the center narrow groove 51 can secure the performance on ice and snow while the central block 51 is secured. 11 can be suppressed by the connecting portion 55 from becoming too low. As a result, it is possible to prevent the central block 11 from being easily worn due to the rigidity of the central block 11 being too low and causing uneven wear. As a result, both performance on snow and snow and uneven wear resistance can be achieved.

  Moreover, the connection part 55 of the center narrow groove 51 is the opposing length of a tire circumferential direction among the one central block 11 and the several central block 11 which opposes the said central block 11 via the center thin groove 51. Therefore, the rigidity of the adjacent central blocks 11 through the center narrow groove 51 can be ensured more reliably. As a result, uneven wear resistance can be ensured more reliably.

  Further, since the sipe 60 formed in the block 10 includes the three-dimensional open sipe 61 in addition to the two-dimensional closed sipe 62, the sipe 60 ensures the performance on ice and snow by the sipe 60. It is possible to suppress a decrease in rigidity of the block 10 due to the formation of. That is, the three-dimensional shape sipe 60 has a stronger meshing force between the opposite sipe wall surfaces than the two-dimensional shape sipe 60, so that the three-dimensional shape sipe 60 suppresses a decrease in rigidity of the block 10, while Performance on ice and snow can be ensured. Thereby, the partial wear of the block 10 can be suppressed more reliably.

  Moreover, since the depth of the open sipe 61 is in the range of 50% to 70% of the depth of the circumferential main groove 30, it is possible to suppress uneven wear caused by the rigidity of the block 10 becoming too low. The open sipe 61 can ensure performance on ice and snow. That is, when the depth of the open sipe 61 is less than 50% of the depth of the circumferential main groove 30, the depth of the open sipe 61 is too shallow, and thus the volume of the open sipe 61 may be too small. In addition, it may be difficult to ensure the water absorption performance in the open sipe 61. In this case, the water film between the road surface on ice and the tread surface 3 may be difficult to remove by the open sipe 61. If the depth of the open sipe 61 exceeds 70% of the depth of the circumferential main groove 30, the depth of the open sipe 61 is too deep, so that the open sipe 61 is constituted by a three-dimensional shape sipe 60. However, there is a possibility that it is difficult to suppress a decrease in rigidity of the block 10 caused by forming the sipe 60.

  On the other hand, when the depth of the open sipe 61 is in the range of 50% to 70% of the depth of the circumferential main groove 30, the decrease in rigidity of the block 10 is suppressed and the open sipe 61 Water absorption performance can be ensured. As a result, the performance on ice and snow can be ensured while suppressing uneven wear that tends to occur when the rigidity of the block 10 decreases. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  Further, since the closed sipes 62 whose both ends are terminated in the block 10 are disposed on both sides of the open sipes 61 in the tire circumferential direction, the sipes 60 are secured by the closed sipes 62 and the open sipes 61 while ensuring performance on ice and snow. The reduction in the rigidity of the block 10 due to the formation of can be more reliably suppressed. Moreover, since the depth of the closed sipe 62 is in the range of 60% to 95% of the depth of the open sipe 61, the closed sipe 62 is closed while suppressing uneven wear due to the rigidity of the block 10 becoming too low. The performance on ice and snow can be ensured by the sipe 62.

  That is, when the depth of the closed sipe 62 is less than 60% of the depth of the open sipe 61, the depth of the closed sipe 62 may be too small because the closed sipe 62 is too shallow. It may be difficult to ensure the water absorption performance of the sipe 62. In this case, the water film between the road surface on ice and the tread surface 3 may be difficult to remove by the closed sipe 62. Further, when the depth of the closed sipe 62 exceeds 95% of the depth of the open sipe 61, the depth of the closed sipe 62 is too deep, so even if both ends of the closed sipe 62 are terminated in the block 10, There is a possibility that it is difficult to suppress a decrease in rigidity of the block 10 due to the formation of the sipe 60.

  On the other hand, when the depth of the closed sipe 62 is in the range of 60% or more and 95% or less of the depth of the open sipe 61, the water absorption performance of the closed sipe 62 is suppressed while suppressing a decrease in the rigidity of the block 10. Can be secured. As a result, the performance on ice and snow can be ensured while suppressing uneven wear that tends to occur when the rigidity of the block 10 decreases. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  The center narrow groove 51 has a ratio (D2 / D1) of the maximum depth D1 of the center thin groove 51 to the depth D2 at the position where the connecting portion 55 is formed in the center thin groove 51 is 0.6. Since it is in the range of 0.9 or less, the uneven wear of the central block 11 can be suppressed while ensuring the performance on ice and snow more reliably. That is, when the ratio (D2 / D1) between the maximum depth D1 of the center narrow groove 51 and the depth D2 of the center narrow groove 51 at the position where the connecting portion 55 is formed is less than 0.6, Since the height of the connecting portion 55 is too high, the volume of the center narrow groove 51 may be too small, and the amount of snow or water that can enter the center narrow groove 51 may be reduced. In this case, it may be difficult to ensure the snow column shear force in the center narrow groove 51, or it may be difficult to ensure the drainage performance in the center narrow groove 51. When the ratio (D2 / D1) between the maximum depth D1 of the center narrow groove 51 and the depth D2 of the center narrow groove 51 at the position where the connecting portion 55 is formed exceeds 0.9, the connection Since the height of the portion 55 is too low, it may be difficult to ensure the rigidity of the central block 11 even if the connecting portion 55 is provided in the center narrow groove 51.

  In contrast, the ratio (D2 / D1) between the maximum depth D1 of the center narrow groove 51 and the depth D2 of the center narrow groove 51 at the position where the connecting portion 55 is formed is 0.6 or more and 0.9. When it is within the following range, the connecting portion 55 suppresses a decrease in rigidity of the central block 11 due to the provision of the center narrow groove 51 while ensuring the snow column shearing force and drainage performance by the center narrow groove 51. Can do. Accordingly, it is possible to more surely suppress the uneven wear that is likely to occur due to the lower rigidity of the central block 11 while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  The connecting portion 55 has a ratio (LC / LB) between the length LC of the connecting portion 55 in the tire circumferential direction and the length LB of the central block 11 in the tire circumferential direction of 0.3 to 0.6. Since it is within the range, uneven wear of the central block 11 can be suppressed while ensuring the performance on ice and snow more reliably. That is, when the ratio (LC / LB) between the length LC of the connecting portion 55 and the length LB of the central block 11 is less than 0.3, the length LC of the connecting portion 55 is too short. Even if the connecting portion 55 is provided in the narrow groove 51, it may be difficult to ensure the rigidity of the central block 11. In addition, when the ratio (LC / LB) between the length LC of the connecting portion 55 and the length LB of the central block 11 exceeds 0.6, the length LC of the connecting portion 55 is too long. The length of the portion of the groove 51 where the connecting portion 55 is not provided may be too short, and the amount of snow or water that can enter the center narrow groove 51 may be reduced. In this case, it may be difficult to ensure the snow column shear force in the center narrow groove 51, or it may be difficult to ensure the drainage performance in the center narrow groove 51.

  On the other hand, when the ratio (LC / LB) between the length LC of the connecting portion 55 and the length LB of the central block 11 is within the range of 0.3 to 0.6, the center narrow groove 51 Accordingly, the connecting portion 55 can suppress the lowering of the rigidity of the central block 11 due to the provision of the center narrow groove 51 while ensuring the snow column shear force and the drainage performance. Accordingly, it is possible to more surely suppress the uneven wear that is likely to occur due to the lower rigidity of the central block 11 while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  Further, the inner lug groove 41 has a ratio (WL / LB) of a width WL in the tire circumferential direction of the inner lug groove 41 and a length LB in the tire circumferential direction of the central block 11 of 0.15 or more and 0.3 or less. Therefore, the uneven wear of the central block 11 can be suppressed while ensuring the performance on ice and snow more reliably. That is, when the ratio (WL / LB) between the width WL of the inner lug groove 41 and the length LB of the central block 11 is less than 0.15, the width WL of the inner lug groove 41 is too narrow. There is a risk that the amount of snow or water that can enter the lug groove 41 is reduced. In this case, it may be difficult to ensure the snow column shearing force in the inner lug groove 41, or it may be difficult to ensure the drainage performance in the inner lug groove 41. If the ratio (WL / LB) between the width WL of the inner lug groove 41 and the length LB of the central block 11 exceeds 0.3, the width WL of the inner lug groove 41 is too wide. There is a possibility that the volume of the central block 11 defined by the groove 41 may be too small, and it may be difficult to ensure the rigidity of the central block 11.

  On the other hand, when the ratio (WL / LB) between the width WL of the inner lug groove 41 and the length LB of the central block 11 is in the range of 0.15 or more and 0.3 or less, the inner lug groove 41 It is possible to suppress the rigidity of the central block 11 defined by the inner lug groove 41 from becoming too low while ensuring the snow column shear force and drainage performance in the above. Accordingly, it is possible to more surely suppress the uneven wear that is likely to occur due to the lower rigidity of the central block 11 while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  Further, the inner lug groove 41 has a depth DL1 in the range of 70% or more and 90% or less of the depth DM1 of the inner circumferential main groove 31. Therefore, the inner block 11 The uneven wear can be suppressed. That is, when the depth DL1 of the inner lug groove 41 is less than 70% of the depth DM1 of the inner circumferential main groove 31, the depth DL1 of the inner lug groove 41 is too shallow, so that the inner lug groove 41 enters. There is a risk that the amount of snow or water that can be reduced. In this case, it may be difficult to ensure the snow column shearing force in the inner lug groove 41, or it may be difficult to ensure the drainage performance in the inner lug groove 41. In addition, when the depth DL1 of the inner lug groove 41 exceeds 90% of the depth DM1 of the inner circumferential main groove 31, the depth DL1 of the inner lug groove 41 is too deep, so that the inner lug groove 41 is partitioned. There is a risk that the rigidity of the central block 11 is likely to decrease.

  On the other hand, when the depth DL1 of the inner lug groove 41 is within the range of 70% or more and 90% or less of the depth DM1 of the inner circumferential main groove 31, the snow column shear force in the inner lug groove 41 or It is possible to suppress the rigidity of the central block 11 partitioned by the inner lug groove 41 from becoming too low while ensuring the drainage performance more reliably. Accordingly, it is possible to more surely suppress the uneven wear that is likely to occur due to the lower rigidity of the central block 11 while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  The inner lug groove 41 is formed with the groove wall 44 having a bent portion 45, and the groove width on the groove bottom 49 side of the bent portion 45 is the groove width of the inner lug groove 41 on the tread surface 3. Since it is narrower than WL1, the rigidity of the central block 11 partitioned by the inner lug groove 41 can be ensured while ensuring the snow column shearing force and drainage performance in the inner lug groove 41. That is, the rigidity of the inner lug groove 41 at the position closer to the inner side in the tire radial direction in the central block 11 by making the groove width closer to the groove bottom 49 than the bent portion 45 is smaller than the groove width WL1 on the tread surface 3. And the rigidity of the central block 11 can be more reliably ensured. Further, since the groove width on the tread tread surface 3 side with respect to the bent portion 45 in the inner lug groove 41 is not narrowed, the volume of the inner lug groove 41 can be secured, and the snow column shearing force and drainage performance can be secured. it can. Thereby, the uneven wear of the central block 11 can be suppressed while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  The inner lug groove 41 has a ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove 41 and the depth DL2 from the tread surface 3 to the bent portion 45 of 0.6 or more and 0.9 or less. Since it is within the range, uneven wear of the central block 11 can be suppressed while ensuring the performance on ice and snow more reliably. That is, when the ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove 41 and the depth DL2 from the tread tread surface 3 to the bent portion 45 is less than 0.6, the tread tread surface 3 to the bent portion Since the depth DL2 up to 45 is too shallow, the volume of the inner lug groove 41 may be too small, and the amount of snow or water that can enter the inner lug groove 41 may be reduced. In this case, it may be difficult to ensure the snow column shearing force in the inner lug groove 41, or it may be difficult to ensure the drainage performance in the inner lug groove 41. When the ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove 41 and the depth DL2 from the tread tread surface 3 to the bent portion 45 exceeds 0.9, the tread tread surface 3 to the bent portion 45 Since the depth DL2 is too deep, even if the bent portion 45 is formed in the inner lug groove 41 and the inner lug groove 41 is shaped like a platform, the rigidity of the central block 11 partitioned by the inner lug groove 41 is There is a risk that it will be difficult to secure effectively.

  On the other hand, the ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove 41 and the depth DL2 from the tread surface 3 to the bent portion 45 is in the range of 0.6 or more and 0.9 or less. In this case, it is possible to more reliably suppress the rigidity of the central block 11 defined by the inner lug groove 41 from becoming too low while ensuring the snow column shear force and drainage performance in the inner lug groove 41. Accordingly, it is possible to more surely suppress the uneven wear that is likely to occur due to the lower rigidity of the central block 11 while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  The inner lug groove 41 has a ratio (WL2 / WL1) between the groove width WL1 at the tread tread surface 3 and the groove width WL2 at the position of the bent portion 45 within a range of 0.3 to 0.5. Therefore, uneven wear of the central block 11 can be suppressed while suppressing the occurrence of cracks at the groove bottom 49 of the inner lug groove 41. That is, when the ratio (WL2 / WL1) between the groove width WL1 of the inner lug groove 41 on the tread tread surface 3 and the groove width WL2 at the position of the bent portion 45 is less than 0.3, the bending portion 45 However, the groove width on the groove bottom 49 side may be too narrow. In this case, when a load is applied in the vicinity of the inner lug groove 41, stress tends to concentrate on the groove bottom 49, and cracks may easily occur on the groove bottom 49. When the ratio (WL2 / WL1) between the groove width WL1 of the inner lug groove 41 on the tread tread surface 3 and the groove width WL2 at the position of the bent portion 45 exceeds 0.5, the ratio is larger than that of the bent portion 45. There is a possibility that the groove width on the groove bottom 49 side becomes too wide, and even if the inner lug groove 41 is shaped like a platform, it is effective to effectively secure the rigidity of the central block 11 partitioned by the inner lug groove 41. It can be difficult.

  On the other hand, the ratio (WL2 / WL1) between the groove width WL1 of the inner lug groove 41 at the tread tread surface 3 and the groove width WL2 at the position of the bent portion 45 is in the range of 0.3 to 0.5. In this case, the occurrence of cracks at the groove bottom 49 of the inner lug groove 41 is suppressed, and the rigidity of the center block 11 is more reliably suppressed from becoming too low, and uneven wear of the center block 11 is more reliably prevented. Can be suppressed. As a result, it is possible to more surely secure uneven wear resistance while suppressing damage to the inner lug groove 41.

  Similarly to the inner lug groove 41, the intermediate lug groove 42 is formed with a groove wall 44 having a bent portion 45, and the groove width closer to the groove bottom 49 than the bent portion 45 is the tread tread surface 3. Therefore, the rigidity of the intermediate block 12 defined by the intermediate lug groove 42 is ensured while ensuring the snow column shear force and drainage performance in the intermediate lug groove 42. be able to. Thereby, even in the vicinity of the intermediate block row 25, uneven wear of the intermediate block 12 can be suppressed while ensuring the performance on ice and snow more reliably. As a result, the performance on ice and snow and the uneven wear resistance can be achieved more reliably.

  Similarly to the inner lug groove 41, the inner circumferential main groove 31 is formed with the groove wall 34 having a bent portion 35, and the groove width closer to the groove bottom 39 than the bent portion 35 has a tread surface. 3 is narrower than the groove width WM1 of the inner circumferential main groove 31 in FIG. 3, and is partitioned by the inner circumferential main groove 31 while ensuring snow column shear force and drainage performance in the inner circumferential main groove 31. The rigidity of the block 10 can be ensured. Thereby, the uneven wear of the block 10 can be suppressed while ensuring the performance on ice and snow more reliably, and as a result, both the performance on ice and snow and the resistance to uneven wear can be more reliably achieved.

[Modification]
In the pneumatic tire 1 according to the above-described embodiment, the center narrow groove 51 and the shoulder narrow groove 52 are formed in a zigzag shape that repeatedly extends in the tire width direction while extending in the tire circumferential direction. The direction narrow groove 50 may be formed in a shape other than the zigzag shape. FIG. 7 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram when the center narrow groove 51 is formed in a straight shape. The circumferential narrow groove 50 may not be bent in the tire width direction. For example, as shown in FIG. 7, the center narrow groove 51 may be formed to extend straight in the tire circumferential direction. In this case, it is preferable that the central blocks 11 included in the block rows 22 adjacent to each other through the center narrow groove 51 are offset from each other in the tire circumferential direction with respect to the central block 11 included in the other block row 22. . That is, even when the center narrow grooves 51 are formed in a straight shape, the central blocks 11 that each of the two block rows 22 adjacent to each other via the center narrow grooves 51 have a staggered arrangement between the block rows 22. Are preferably arranged.

  Further, even when the center narrow grooves 51 are formed in a straight shape, the center blocks 11 are arranged in a staggered arrangement so that the center blocks 11 included in the adjacent block rows 22 via the center narrow grooves 51 are arranged. A part of the range in the tire circumferential direction opposes the adjacent central blocks 11 via the center narrow groove 51. The connecting portion 55 formed in the center narrow groove 51 is preferably formed in a range in which the central blocks 11 that are offset in the tire circumferential direction by being arranged in a staggered manner face each other. Even when the center narrow groove 51 is formed in a straight shape, it is possible to suppress the rigidity of the center block 11 from being too low by forming the connecting portion 55 in a range where the center blocks 11 face each other. It can suppress that it becomes easy to generate | occur | produce uneven wear resulting from the rigidity of the center block 11 becoming low too much.

  In the above-described embodiment, the central block 11 and the intermediate block 12 have one open sipe 61 and two closed sipes 62 that are disposed on both sides of the open sipe 61 in the tire circumferential direction. However, the sipes 60 may be arranged in other numbers. In the sipe 60, for example, as shown in FIG. 7, two open sipes 61 are formed in one central block 11, and one closed sipe 62 is provided on both sides of the two open sipes 61 in the tire circumferential direction. It may be arranged one by one. That is, two open sipes 61 and two closed sipes 62 may be formed in one central block 11. It is preferable that the open sipe 61 and the closed sipe 62 formed in one block 10 are appropriately set according to the size of the block 10, the position where the block 10 is disposed, and the like.

  Further, in the above-described embodiment, the inner lug groove 41 and the intermediate lug groove 42 have two bent portions 45 of the first bent portion 46 and the second bent portion 47 in one groove wall 44, and the groove wall 44. Although the stepped portion 48 is formed in the shape of a step, the inner lug groove 41 and the intermediate lug groove 42 may be formed in a shape other than the step shape.

  FIG. 8 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram when the bent portion 45 of the inner lug groove 41 and the intermediate lug groove 42 is one place. For example, as shown in FIG. 8, the inner lug groove 41 and the intermediate lug groove 42 are formed with one bent portion 45 in each groove wall 44, and the portion of the groove wall 44 closer to the groove bottom 49 than the bent portion 45 is Further, as it goes from the bent portion 45 toward the groove bottom 49 side, it may be inclined in a direction in which the distance between the opposed groove walls 44 decreases. That is, the inner lug groove 41 and the intermediate lug groove 42 are formed in a shape in which the groove width becomes narrower from the position of the bent portion 45 formed on each groove wall 44 toward the groove bottom 49 side. Also good. Even when the number of the bent portions 45 formed in the groove wall 44 is one, the groove width on the groove bottom 49 side of the bent portion 45 is narrower from the position of the bent portion 45 toward the groove bottom 49 side. This ensures the rigidity of the central block 11 and the intermediate block 12 partitioned by the inner lug groove 41 and the intermediate lug groove 42 while ensuring the snow column shearing force and drainage performance in the inner lug groove 41 and the intermediate lug groove 42. Therefore, it is possible to achieve both performance on ice and snow and uneven wear resistance.

  Similarly to this, the circumferential main groove 30 may be formed in a shape other than the platform shape. That is, the circumferential main groove 30 also has one bent portion 35 formed in each groove wall 34, and the groove width closer to the groove bottom 39 than the bent portion 35 is directed toward the groove bottom 39 from the position of the bent portion 35. It may be formed narrow.

  In the above-described embodiment, the circumferential narrow groove 50 is formed in the central block row 21 and the shoulder block row 26. However, the circumferential narrow groove 50 may be formed in a position other than this, For example, the intermediate block row 25 may be formed. In the embodiment described above, four circumferential main grooves 30 are formed, but the number of circumferential main grooves 30 may be other than four. The number of the circumferential main grooves 30 is not limited as long as the number of the circumferential main grooves 30 can partition at least the central block row 21.

[Example]
9A to 9E are tables showing results of performance evaluation tests of pneumatic tires. Hereinafter, with respect to the pneumatic tire 1 described above, the performance of the conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and the pneumatic tire of the comparative example compared with the pneumatic tire 1 according to the present invention. The evaluation test will be described. In the performance evaluation test, tests were carried out on ice / snow performance, which is the handling stability on the road surface on ice or on snow, and uneven wear resistance, which is the performance on the difficulty of uneven wear.

  In the performance evaluation test, a pneumatic tire 1 having a tire size specified by JATMA of 275 / 80R22.5 size is assembled on a rim wheel of a specified rim specified by JATMA, and the air pressure is the maximum air pressure specified by JATMA. The test was carried out by mounting on a 2-D4 test vehicle (truck).

  The evaluation method for each test item is as follows. Regarding the performance on ice and snow, a feeling evaluation is performed by a test driver when driving on a test course having an ice surface and a snow surface on a test vehicle. The example was evaluated by expressing it as an index with 100. The larger the value, the higher the handling stability on the icy and snowy roads, and the better the performance on icy and snowy.

  For uneven wear resistance, the wear amount of heel and toe wear after running 20,000 km on a test vehicle, specifically, the difference in wear amount between the kicking side and the stepping side of the central block 11 was measured. The difference between the measured wear amounts was displayed as an index with the conventional example described later as 100. The larger this value, the smaller the difference in wear amount between the kicking side and the stepping side of the central block 11, that is, the smaller the heel and toe wear, and the better the uneven wear resistance.

  A performance evaluation test compares with the pneumatic tire of the conventional example which is an example of the conventional pneumatic tire, Examples 1-28 which are the pneumatic tire 1 which concerns on this invention, and the pneumatic tire 1 which concerns on this invention. It carried out about 32 types of pneumatic tires with Comparative Examples 1-3 which are pneumatic tires. Among them, the conventional pneumatic tire has a normal arrangement in which the adjacent central blocks 11 are not offset in the tire circumferential direction via a groove extending in the tire circumferential direction, and the circumferential narrow groove is arranged in the central block row 21. 50 is not formed.

  9A to 9E, the “U-groove shape” in the shape of the inner lug groove 41, the shape of the intermediate lug groove 42, and the shape of the circumferential main groove 30 is the inner lug groove 41, the intermediate lug groove 42, The circumferential main groove 30 does not have the bent portions 45 and 35, and the groove width is gradually narrowed as the groove width is formed to be constant, or as it goes from the tread tread surface 3 side to the groove bottoms 49 and 39 side. The shape which becomes.

  Further, in Comparative Example 1, the arrangement direction of the block 10 to which the connecting portion 55 is connected is the tire circumferential direction. That is, in Comparative Example 1, the connecting portion 55 is formed in the lug groove 40 extending in the tire width direction. Is formed. Further, the comparative example 2 does not have the connecting portion 55. Further, in Comparative Example 3, although the circumferential narrow grooves 50 are formed in the central block row 21 and the connecting portions 55 are formed in the circumferential narrow grooves 50, the adjacent central blocks via the circumferential narrow grooves 50 are formed. The normal arrangement is such that 11 are not offset in the tire circumferential direction.

  In contrast, in Examples 1 to 28, which are examples of the pneumatic tire 1 according to the present invention, the circumferential narrow groove 50 is formed in the central block row 21, and the connecting portion 55 is formed in the circumferential narrow groove 50. In the zigzag arrangement, the central blocks 11 adjacent to each other through the circumferential narrow grooves 50 are offset in the tire circumferential direction. Furthermore, the pneumatic tire 1 according to Examples 1 to 29 includes the number of sipes 60 formed in each block 10, the number of open sipes 61, the bent portions of the open sipes 61, the shape of the open sipes 61, and the main circumferential direction. The depth of the open sipe 61 with respect to the depth of the groove 30, the arrangement of the closed sipe 62, the depth of the closed sipe 62 with respect to the depth of the open sipe 61, the maximum depth D1 of the circumferential narrow groove 50 and the circumferential narrow groove 50 (D2 / D1) with the depth D2 at the position where the connecting portion 55 is formed, and the ratio between the length LC of the connecting portion 55 in the tire circumferential direction and the length LB of the central block 11 in the tire circumferential direction. (LC / LB), the ratio of the width WL in the tire circumferential direction of the inner lug groove 41 to the length LB in the tire circumferential direction of the central block 11 (WL / LB), the inner circumferential direction The depth of the inner lug groove 41 with respect to the depth 31 of the main groove, the shape of the inner lug groove 41, the maximum depth DL1 of the inner lug groove 41, and the depth DL2 from the tread tread surface 3 to the bent portion 45 of the inner lug groove 41 Ratio (DL2 / DL1), the ratio (WL2 / WL1) between the groove width WL1 of the inner lug groove 41 at the position of the tread tread surface 3 and the groove width WL2 at the position of the bent portion 45 of the inner lug groove 41, intermediate The shape of the lug groove 42 and the shape of the circumferential main groove 30 are different.

  As a result of performing a performance evaluation test using these pneumatic tires 1, as shown in FIGS. 9A to 9E, the pneumatic tires 1 according to Examples 1 to 28 are compared with the conventional examples and Comparative Examples 1 to 3. Thus, it was found that both the performance on ice and snow and the uneven wear resistance can be improved. That is, the pneumatic tire 1 according to Examples 1 to 29 can achieve both snow and snow performance and uneven wear resistance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Tread tread 10 Block 11 Center block 12 Intermediate block 13 Shoulder block 15 Edge 16 Long part 17 Short part 21 Central block row 22, 27 Block row 25 Intermediate block row 26 Shoulder block row 30 Circumferential direction Main groove 31 Inner circumferential main groove 32 Outer circumferential main groove 34, 44 Groove wall 35, 45 Bent part 36, 46 First bent part 37, 47 Second bent part 38, 48 Stepped part 39, 49 Groove bottom 40 Lug groove 41 Inner lug groove 42 Intermediate lug groove 43 Shoulder lug groove 50 Circumferential narrow groove 51 Center narrow groove 55 Connection part 60 Sipe 61 Open sipe 62 Closed sipe

Claims (12)

Of the plurality of circumferential main grooves extending in the tire circumferential direction, two inner circumferential main grooves that are the circumferential main grooves disposed on both sides of the tire equator plane in the tire width direction across the tire equator plane When,
Among the plurality of lug grooves extending in the tire width direction, an inner lug groove disposed between the two inner circumferential main grooves,
A central block row located between the two inner circumferential main grooves, the both sides in the tire width direction being partitioned by the two inner circumferential main grooves;
With
In the central block row, a circumferential narrow groove extending in the tire circumferential direction with a groove width narrower than the groove width of the inner lug groove is formed between the two inner circumferential main grooves,
The central block row is formed with two block rows adjacent to each other in the tire width direction through the circumferential narrow groove,
In each block row, a plurality of central blocks defined by the inner circumferential main groove, the inner lug groove, and the circumferential narrow groove are arranged in the tire circumferential direction, and are adjacent to each other through the circumferential narrow groove. The central block of the two block rows is arranged offset in the tire circumferential direction with respect to the central block of the other block row,
Each of the central blocks is formed with a plurality of sipes,
The pneumatic tire is characterized in that a connecting portion is formed in the circumferential narrow groove between the central blocks adjacent to each other through the circumferential narrow groove. The center block is opposed to the plurality of center blocks of the other block row via the circumferential narrow groove, and is opposed to the center block of the other block row in the tire circumferential direction. Are opposed at different lengths to the opposite different central blocks,
The connecting portion has a relatively long opposing length in the tire circumferential direction among the one central block and the plurality of central blocks facing the central block via the circumferential narrow groove. The pneumatic tire according to claim 1, which is formed between the central blocks. The sipe has an open sipe whose both ends open on both sides in the tire width direction of the central block, and a closed sipe whose both ends terminate in the central block,
The open sipe is a three-dimensional sipe that swings in the sipe width direction with respect to the two directions of the sipe length direction and the sipe depth direction, and the depth is 50 times the depth of the circumferential main groove. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is within a range of not less than 70% and not more than 70%. The closed sipe is disposed on both sides in the tire circumferential direction of the open sipe,
The pneumatic tire according to claim 3, wherein a depth of the closed sipe is in a range of 60% to 95% of a depth of the open sipe.   The circumferential narrow groove has a ratio (D2 / D1) of the maximum depth D1 of the circumferential narrow groove to the depth D2 at the position where the connecting portion is formed in the circumferential narrow groove is 0. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is in a range of 6 to 0.9.   The connecting portion has a ratio (LC / LB) between a length LC of the connecting portion in the tire circumferential direction and a length LB of the central block in the tire circumferential direction within a range of 0.3 to 0.6. The pneumatic tire according to any one of claims 1 to 5.   The inner lug groove has a ratio (WL / LB) between a width WL of the inner lug groove in the tire circumferential direction and a length LB of the central block in the tire circumferential direction of 0.15 or more and 0.3 or less. The pneumatic tire according to any one of claims 1 to 6.   The inner lug groove has a depth in the range of 70% or more and 90% or less of the depth of the inner circumferential main groove, and the groove wall is formed with a bent portion, and from the bent portion. The pneumatic tire according to any one of claims 1 to 7, wherein the groove width on the groove bottom side is narrower than the groove width of the inner lug groove on the tread surface.   The inner lug groove has a ratio (DL2 / DL1) between the maximum depth DL1 of the inner lug groove and the depth DL2 from the tread tread surface to the bent portion within a range of 0.6 to 0.9. The pneumatic tire according to claim 8.   The inner lug groove has a ratio (WL2 / WL1) of a groove width WL1 at a tread tread surface and a groove width WL2 at a position of the bent portion within a range of 0.3 to 0.5. The pneumatic tire according to 8 or 9. The outer circumferential main grooves, which are the circumferential main grooves, are arranged on the outer sides in the tire width direction of the two inner circumferential main grooves,
Between the adjacent inner circumferential main groove and the outer circumferential main groove adjacent to each other, an intermediate lug groove that is the lug groove whose both ends open to the inner circumferential main groove and the outer circumferential main groove is formed. And an intermediate block row in which a plurality of intermediate blocks defined by the inner circumferential main groove, the outer circumferential main groove and the intermediate lug groove are arranged in the tire circumferential direction is formed.
The intermediate lug groove is formed such that a groove wall has a bent portion, and the groove width on the groove bottom side of the bent portion is narrower than the groove width of the intermediate lug groove on the tread surface. The pneumatic tire according to any one of 1 to 10.   The circumferential main groove is formed such that a groove wall has a bent portion, and the groove width on the groove bottom side of the bent portion is narrower than the groove width of the circumferential main groove on the tread surface. The pneumatic tire according to any one of claims 1 to 11.

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