JP2014125109A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drainage performance and anti-wear performance in a well-balanced manner.SOLUTION: There is provided a pneumatic tire in which center main grooves 3A, middle main grooves 3B, shoulder main grooves 3C, center lateral grooves 4A, middle lateral grooves 4B and shoulder lateral grooves 4C are provided in a tread portion 2. The middle lateral grooves 4B and the shoulder lateral grooves 4C extend in a nearly straight line and have lateral width of 4.0 to 16.0 mm. In the groove bottoms of the middle lateral grooves 4B and the shoulder lateral grooves 4C, there are never provided tie bars T whose protruding height from the deepest groove bottom is 50% or more of the deepest groove depth of the lateral grooves. Land ratios of a center region 5A passing through both ends of a center block 5 is 1.05-1.25 times the land ratios of a middle region 6A passing through both ends of a middle block 6. The angles of the center lateral grooves 4A relative to the tire axial direction are 15-45° and larger than the angles of the middle lateral grooves 4B relative to the tire axial direction.

Description

  The present invention relates to a pneumatic tire in which drainage performance and wear resistance performance are improved in a well-balanced manner.

  There is a pneumatic tire in which a plurality of blocks are divided in a tread portion by a plurality of main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire axial direction. In recent years, for the purpose of improving the wear resistance performance of such a pneumatic tire, a tie bar raised from the deepest groove bottom of the lateral groove is provided in the lateral groove. The tie bar suppresses movement of the block in the tire circumferential direction when the tire rolls, and reduces the amount of slip generated in the block.

  However, in the pneumatic tire as described above, the groove volume of the lateral groove is reduced by the tie bar, and the drainage performance is deteriorated. Further, when the wear of the block progresses, the lateral groove is interrupted, and there is a problem that the drainage performance at the end of wear is particularly poor. As a related technique, there is Patent Document 1 below.

JP 2011-230643 A

  The present invention has been devised in view of the actual situation as described above, and improves the ratio of the land ratio of the center area of the tread portion to the land ratio of the middle area. Furthermore, the center lateral groove, the middle lateral groove, and the shoulder lateral groove are improved. The main purpose is to provide a pneumatic tire with improved drainage performance and wear resistance performance in a well-balanced manner based on improving the shape.

  According to the first aspect of the present invention, in the tread portion, one center main groove extending continuously in the tire circumferential direction on the tire equator and both sides in the tire axial direction of the center main groove in the tire circumferential direction are provided. A pair of middle main grooves extending continuously, a pair of shoulder main grooves extending continuously in the tire circumferential direction between the middle main groove and the grounding end, and between the center main groove and the middle main groove A plurality of center lateral grooves to be joined, a plurality of middle lateral grooves to be joined between the middle main groove and the shoulder main groove, and a plurality of shoulder lateral grooves to be joined between the shoulder main groove and the grounding end are provided. Thus, a pair of center block rows in which the center blocks divided by the center main groove, the middle main groove, and the center lateral groove are separated in the tire circumferential direction, the middle main groove, and the shoulder main A pair of middle blocks separated in the tire circumferential direction, and a shoulder block divided by the shoulder main groove, the ground contact end, and the shoulder lateral groove A pneumatic tire having a pair of shoulder block rows spaced in a direction, wherein the middle lateral groove and the shoulder lateral groove extend substantially linearly and have a groove width of 4.0 to 16.0 mm, The middle horizontal groove and the shoulder horizontal groove bottoms are not provided with a tie bar whose height from the deepest groove bottom is 50% or more of the deepest groove depth of each of the horizontal grooves. The land ratio of the center region, which is the region between the tire circumferential direction lines passing through both ends of the tire, is the area between the tire circumferential direction lines passing through both ends of the middle block in the tire axial direction. The center lateral groove has an angle with respect to the tire axial direction of 15 to 45 ° and larger than the angle of the middle lateral groove with respect to the tire axial direction. This is a pneumatic tire.

  According to a second aspect of the present invention, in the tread portion, a tread rubber forming a tire outer surface is disposed, and a complex elastic modulus E * of the tread rubber is 6.3 to 7.7 MPa. It is a pneumatic tire.

  In the invention according to claim 3, the center main groove extends linearly in the tire circumferential direction, and the groove width thereof is smaller than the groove width of the middle main groove. The middle main groove and the shoulder main groove are The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire extends in a zigzag shape in the tire circumferential direction and the amplitude of each groove center line is 2 mm or more.

  According to a fourth aspect of the present invention, the center lateral groove includes a first center lateral groove disposed on one side of the tire equator and a second center lateral groove disposed on the other side of the tire equator. The transverse groove and the second center transverse groove are spaced apart in the tire circumferential direction at the same pitch, and are arranged with a half pitch phase shifted in the tire circumferential direction. It is a pneumatic tire.

  According to a fifth aspect of the present invention, the middle lateral groove and the center lateral groove adjacent to the middle lateral groove are spaced apart at the same pitch in the tire circumferential direction, and are shifted by a half pitch phase in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is disposed.

  According to a sixth aspect of the present invention, the center lateral groove includes an inner groove extending linearly outward from the center main groove in the tire axial direction, and an outer groove extending linearly from the middle main groove toward the tire equator. The pneumatic tire according to any one of claims 1 to 5, wherein the inner groove portion and the outer groove portion are misaligned in the tire circumferential direction.

  According to a seventh aspect of the present invention, the tread portion has a directional pattern in which a rotational direction is specified, and the center lateral groove is inclined toward the rear arrival side in the tire rotational direction toward the outer side in the tire axial direction. The pneumatic tire according to any one of 1 to 6.

  In the pneumatic tire of the present invention, the tread portion includes a pair of center block rows in which the center blocks divided by the center main groove, the middle main groove, and the center lateral groove are separated in the tire circumferential direction, the middle main groove, and the shoulder main A pair of middle block rows in which the middle blocks divided by the grooves and the middle lateral grooves are separated in the tire circumferential direction, and a shoulder block divided by the shoulder main groove, the ground contact edge, and the shoulder lateral grooves are separated in the tire circumferential direction. It has a pair of shoulder block rows.

  The middle lateral groove and the shoulder lateral groove extend substantially linearly and have a groove width of 4.0 to 16.0 mm. Such middle lateral grooves and shoulder lateral grooves have low drainage resistance. For this reason, drainage performance improves. Moreover, high rigidity of the middle block and the shoulder block is ensured. For this reason, abrasion resistance performance improves. A tie bar having a protruding height from the deepest groove bottom of 50% or more of the deepest groove depth of each horizontal groove is not provided at the groove bottom of the middle and shoulder horizontal grooves. Thereby, the groove volume of the middle lateral groove and the shoulder lateral groove is ensured even at the end of wear. Accordingly, the drainage performance is further improved.

  The land ratio of the center region, which is the region between the tire circumferential direction lines passing through both ends of the center block in the tire axial direction, is the land ratio of the middle region, which is the region between the tire circumferential direction lines passing through both ends of the middle block in the tire axial direction. 1.05 to 1.25 times. As a result, the rigidity of the center block is ensured higher than the rigidity of the middle block, and the ground pressure generated in the center block to which a large load acts and the middle block to which a smaller load acts than the center block can be made uniform during straight traveling. . Therefore, the slip amount of the center block and the middle block due to tire rolling is reduced in a well-balanced manner, and the wear resistance performance is improved.

  The center lateral groove has an angle with respect to the tire axial direction of 15 to 45 °. Thereby, the end edge of the center block on the first arrival side disperses and relaxes the impact from the road surface at the time of ground contact. For this reason, the slip amount of the center block is reduced. Further, the angle of the center lateral groove with respect to the tire axial direction is larger than the angle of the middle lateral groove with respect to the tire axial direction. Thereby, the impact from the road surface at the time of ground contact is mitigated in a well-balanced manner at the first edge of the center block and the first edge of the middle block. For this reason, the slip amount of the center block and the middle block is made uniform, and the wear resistance is further improved. Therefore, in the pneumatic tire of the present invention, drainage performance and wear resistance performance are improved in a well-balanced manner.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is XX sectional drawing of FIG. It is an enlarged view of the left half of FIG. It is an enlarged view of the left half of FIG. It is an expanded view of the tread part of other embodiment. It is an expanded view of the tread part of other embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic tire of the present embodiment is suitably used as a heavy duty pneumatic tire for trucks and buses, for example, and has an asymmetric tread pattern in which the rotation direction R of the tire is specified. Yeah. The rotation direction R of the tire is displayed by characters or the like on a sidewall portion (not shown), for example.

  In the tread portion 2 of the tire according to the present embodiment, one center main groove 3A continuously extending in the tire circumferential direction on the tire equator C, and both sides in the tire axial direction of the center main groove 3A are continuous in the tire circumferential direction. A pair of middle main grooves 3B extending and a pair of shoulder main grooves 3C extending continuously in the tire circumferential direction between the middle main groove 3B and the ground contact Te are provided. In the present embodiment, the tread portion 2 has a plurality of center lateral grooves 4A that connect between the center main groove 3A and the middle main groove 3B, and a plurality of links that connect between the middle main groove 3B and the shoulder main groove 3C. Middle lateral groove 4B and a plurality of shoulder lateral grooves 4C connecting between the shoulder main groove 3C and the ground contact Te are provided.

  Thereby, the tread portion 2 includes a pair of center block rows 5R and middle main grooves 3B in which the center blocks 5 divided by the center main grooves 3A, the middle main grooves 3B, and the center lateral grooves 4A are separated in the tire circumferential direction. A middle block 6 divided by a shoulder main groove 3C and a middle horizontal groove 4B is divided by a pair of middle block rows 6R spaced in the tire circumferential direction, and a shoulder main groove 3C, a ground contact end Te, and a shoulder horizontal groove 4C. A pair of shoulder block rows 7R in which the shoulder blocks 7 are spaced in the tire circumferential direction are arranged.

  Here, the “ground contact end” Te is a value obtained when a normal load is loaded on a normal rim that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to a flat surface with a camber angle of 0 degrees. It is determined as the ground contact position on the outermost side in the tire axial direction. In the normal state, the distance in the tire axial direction between the ground contact ends Te and Te is determined as the tread ground contact width TW. Further, the dimensions and the like of each part of the tire are values in the normal state unless otherwise specified.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. "If it is ETRTO, it is" Measuring Rim ".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA and table for TRA. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, and “INFLATION PRESSURE” in the case of ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  Furthermore, “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “Maximum load capacity” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO. However, when the tire is for a passenger car, the normal load is a load corresponding to 88% of each load.

  As shown in FIG. 2, the tread portion 2 is provided with a tread rubber 2G forming the tire outer surface 2a. The complex elastic modulus E * of such a tread rubber 2G is preferably 6.3 to 7.7 MPa. That is, when the complex elastic modulus E * of the tread rubber 2G is less than 6.3 MPa, the slip amount of the blocks 5 to 7 at the time of tire rolling increases, and the wear amount increases. Further, heel and toe wear may occur in the blocks 5 to 7. When the complex elastic modulus E * of the tread rubber 2G exceeds 7.7 MPa, “cracking” is likely to occur at the groove bottoms of the main grooves 3A to 3C and the lateral grooves 4A to 4C, and TGC (Tread Groove Cracking) performance. May get worse. For this reason, the complex elastic modulus E * of the tread rubber 2G is more preferably 6.5 MPa or more, and more preferably 7.5 MPa or less.

  As shown in FIG. 3, the center main groove 3A of the present embodiment extends linearly in the tire circumferential direction, for example. Such center main groove 3A smoothly drains the drainage in the groove to the rear in the tire rotation direction, and ensures high rigidity in the tire circumferential direction of the center block 5 on which a large load acts during straight traveling, Improve wear resistance and uneven wear resistance.

  The middle main groove 3B extends in, for example, a zigzag shape in the tire circumferential direction. In the middle main groove 3B of the present embodiment, middle long side portions 8A and middle short side portions 8B are alternately arranged. The middle long side portion 8A has a groove center line 10a that is inclined from the ground contact end Te side toward the tire equator C side toward the tire arrival direction in the tire rotation direction. The middle short side portion 8B has a groove center line 10b inclined in the opposite direction to the groove center line 10a of the middle long side portion 8A. The inclination directions of the middle long side portion 8A and the middle short side portion 8B may be reversed.

  The groove center line 10 of the middle main groove 3B including the groove center lines 10a and 10b is the innermost point a1 in the tire axial direction of the inner groove edge 10x on the inner side in the tire axial direction of the middle main groove 3B, and the middle main groove 3B. An intermediate point s1 of the outer groove edge 10y on the outer side in the tire axial direction with the innermost point a2 in the tire axial direction, and an outermost point a3 of the inner groove edge 10x in the tire axial direction and the outer groove edge 10y in the tire axial direction. It is obtained by alternately connecting an intermediate point s2 with the outermost point a4.

  The amplitude λ1 of the groove center line 10 of the middle main groove 3B is preferably 2 mm or more, more preferably 4 mm or more. That is, if the amplitude λ1 of the middle main groove 3B is less than 2 mm, the drainage performance during turning may be deteriorated. When the amplitude λ1 of the middle main groove 3B exceeds 8 mm, drainage resistance during straight traveling increases, and drainage performance may be deteriorated. Therefore, the amplitude λ1 of the middle main groove 3B is preferably 8 mm or less, more preferably 6 mm or less. In this specification, the amplitude λ1 of the groove center line 10 of the middle main groove 3B is the distance in the tire axial direction between the intermediate point s1 and the intermediate point s2.

  The shoulder main groove 3C extends, for example, in a zigzag shape in the tire circumferential direction. In the shoulder main groove 3C of the present embodiment, the long side portions 12A and the shoulder short side portions 12B are alternately arranged. The shoulder long side portion 12A has a groove center line 13a that inclines from the ground contact end Te side toward the tire equator C side toward the tire arrival direction rearward side. The shoulder short side portion 12B has a groove center line 13b that inclines from the tire equator C side toward the ground contact end Te side toward the rear arrival side in the tire rotation direction. The inclination directions of the shoulder long side portion 12A and the shoulder short side portion 12B may be reversed.

  The groove center line 13 of the shoulder main groove 3C including the groove center lines 13a and 13b includes the innermost point a5 in the tire axial direction of the inner groove edge 13x on the tire axial direction inner side of the shoulder main groove 3C and the shoulder main groove 3C. An intermediate point s3 between the outer groove edge 13y on the outer side in the tire axial direction and the innermost point a6 in the tire axial direction, and an outermost point a7 in the tire axial direction on the inner groove edge 13x and the outer groove edge 13y in the tire axial direction. It is obtained by alternately connecting an intermediate point s4 with the outermost point a8.

  The amplitude λ2 of the groove center line 13 of the shoulder main groove 3C is preferably 2 mm or more, more preferably 4 mm or more, preferably 8 mm or less, for the same reason as the amplitude λ1 of the groove center line 10 of the middle main groove 3B. More preferably, it is 6 mm or less. The amplitude λ2 of the groove center line 13 of the shoulder main groove 3C is defined by the distance in the tire axial direction between the intermediate point s3 and the intermediate point s4.

  As shown in FIG. 2, the groove width W1 of the center main groove 3A is smaller than the groove width W2 of the middle main groove 3B. As a result, the contact pressure in the vicinity of the groove edge of the center main groove 3A of the center block 5 to which a large load acts is reduced, and the wear resistance is improved.

  In order to enhance the above-mentioned action and drainage performance in a well-balanced manner, the groove width W1 of the center main groove 3A (the groove width perpendicular to the longitudinal direction of the groove, the same applies to the other main grooves 3B and 3C). Preferably, it is 0.8% or more of the tread ground contact width TW, more preferably 1.2% or more, preferably 2.4% or less, more preferably 2.0% or less. Similarly, the groove width W2 of the middle main groove 3B is preferably 1.5% or more of the tread ground contact width TW, more preferably 1.0% or more, preferably 4.5% or less, more preferably 4. 0% or less. Further, the groove width W3 of the shoulder main groove 3C is preferably 1.0% or more, more preferably 1.5% or more, preferably 4.0% or less, more preferably 3.5% of the tread ground contact width TW. % Or less.

  From the viewpoint of securing the rigidity of each of the blocks 5 to 7 while enhancing the drainage performance, the groove depths D1 to D3 of the main grooves 3A to 3C are preferably, for example, 15 to 25 mm.

  As shown in FIG. 1, the center main groove 3 </ b> A is provided on the tire equator C. The tire axial distance L2 between the middle main groove 3B and the tire equator C is desirably 12 to 22% of the tread contact width TW. The tire axial distance L3 between the shoulder main groove 3C and the tire equator C is desirably 28 to 33% of the tread contact width TW. Thereby, the rigidity of the tire axial direction of each block 5 thru | or 7 is ensured with sufficient balance. Further, the water film between the tread portion 2 and the road surface is drained smoothly. The positions of the main grooves 3A to 3C are specified by their groove center lines. Further, as in the present embodiment, in the middle main groove 3B and the shoulder main groove 3C which are zigzag non-linear, the amplitude center line G1 of the groove center line 10 of the middle main groove 3B and the groove center line of the shoulder main groove 3C Thirteen amplitude centerlines G2 are used.

  The center lateral groove 4A is inclined toward the rear arrival side in the tire rotation direction from the tire equator C side toward the ground contact end Te side. Such a center lateral groove 4A can smoothly drain the water in the groove from the tire equator C side to the ground contact Te side by using rolling of the tire.

  As shown in FIG. 3, the angle θ1 of the center lateral groove 4A with respect to the tire axial direction is 15 to 45 °. That is, when the angle θ1 of the center lateral groove 4A is less than 15 °, the first edge 5x of the center block 5 (in FIG. 3, the lower edge of the center block 5) receives an impact from the road surface at the time of ground contact. Cannot be distributed in the tire circumferential direction. For this reason, the slip amount of the center block 5 becomes large, and the wear resistance performance and uneven wear resistance performance deteriorate. Moreover, the drainage performance at the time of straight running is deteriorated. When the angle θ1 of the center lateral groove 4A exceeds 45 °, the rigidity of the center block 5 in the tire axial direction decreases, and the wear resistance performance and uneven wear resistance performance deteriorate. The drainage performance when turning is deteriorated. For this reason, the angle θ1 of the center lateral groove 4A is preferably 20 ° or more, and preferably 40 ° or less. The angle θ1 of the center lateral groove 4A is an angle of the groove center line 14 of the center lateral groove 4A connecting the intermediate points b1 and b2 in the tire circumferential direction at the opening ends on both sides of the center lateral groove 4A (hereinafter, referred to as the middle lateral groove 4B). And the angles θ2 and θ3 of the shoulder lateral grooves 4C are defined similarly).

  As shown in FIG. 1, the center lateral groove 4A of the present embodiment includes a first center lateral groove 15A disposed on one side (left side in FIG. 1) of the tire equator C, and the other side of the tire equator C (in FIG. 1). And the second center lateral groove 15B disposed on the right side. The first center lateral grooves 15A and the second center lateral grooves 15B are spaced apart at the same pitch Pa in the tire circumferential direction. The first center lateral groove 15A and the second center lateral groove 15B are arranged with a half pitch phase shifted in the tire circumferential direction. That is, the center lateral groove 4A and the center portion of the center block 5 in the tire circumferential direction are aligned in the tire axial direction. Thus, by setting the angle θ1 of the center lateral groove 4A within the above-described range, slip in the tire axial direction in the vicinity of both ends in the tire circumferential direction of the center block 5 having small rigidity in the tire axial direction is suppressed. Therefore, wear resistance performance and uneven wear resistance performance are improved.

  As shown in FIG. 4, the center lateral groove 4A includes an inner groove portion 16A extending linearly outward from the center main groove 3A in the tire axial direction, and an outer groove portion 16B extending linearly from the middle main groove 3B to the tire equator C side. Including. The inner groove 16A and the outer groove 16B are displaced in the tire circumferential direction. For example, the tire circumferential direction distance La between the outer end 17e in the tire axial direction of the groove center line 17a of the inner groove 16A and the inner end 17i in the tire axial direction of the groove center line 17b of the outer groove 16B is the groove of the inner groove 16A. It is 13 to 23% of the width W4a. Such a center lateral groove 4A improves the drainage performance and the rigidity of the end of the center block 5 in the tire circumferential direction in a well-balanced manner.

  An outer end 17e in the tire axial direction of the groove center line 17a of the inner groove portion 16A is an outer end in the tire axial direction of the groove edges 18x and 18y of the center lateral groove 4A extending linearly from the center main groove 3A toward the outer side in the tire axial direction. Is the middle point. The inner end 17i in the tire axial direction of the groove center line 17b of the outer groove portion 16B is the inner end in the tire axial direction of the groove edges 18z and 18w of the center lateral groove 4A extending linearly from the middle main groove 3B toward the inner side in the tire axial direction. Is the middle point.

  The groove width W4 of the center lateral groove 4A (average groove width perpendicular to the groove center line 14 is the same for the middle lateral groove 4B and the shoulder lateral groove 4C) from the tire equator C side during tire rolling. From the viewpoint of smoothly draining the water in the groove toward the ground contact Te, and from the viewpoint of ensuring the rigidity of the center block 5, it is preferably 4 to 16 mm, for example.

  The middle lateral groove 4B and the shoulder lateral groove 4C extend substantially linearly. Thereby, smooth drainage from the middle main groove 3B to the vehicle outer side through the middle lateral groove 4B and the shoulder lateral groove 4C becomes possible. Further, the middle block 6 and the shoulder block 7 are secured with high rigidity. Accordingly, drainage performance and wear resistance performance are improved in a well-balanced manner.

  As shown in FIG. 4, “substantially linear” means that in the middle lateral groove 4B, the groove center line 21 of the middle lateral groove 4B on the groove edge 20x on one side in the tire circumferential direction (upper groove edge in FIG. 4). The point 20a closest to the groove 20 and the point 20b closest to the groove center line 21 on the other groove edge 20y (lower groove edge in FIG. 4) in the tire circumferential direction are perpendicular to the groove center line 21. The distance W5a is a groove that is 80% or more of the groove width W5 of the middle lateral groove 4B. Since such middle lateral grooves 4B have a low drainage resistance, high drainage performance is maintained. As in the case of the middle lateral groove 4B, the “substantially straight line” of the shoulder lateral groove 4C is a groove in which the innermost distance W6a of the shoulder lateral groove 4C is 80% or more of the groove width W6 (shown in FIG. 1) of the shoulder lateral groove 4C. It is.

  The middle lateral groove 4B is inclined toward the rear arrival side in the tire rotation direction from the tire equator C side toward the ground contact end Te side. Therefore, as in the case of the center lateral groove 4A, the water in the groove can be smoothly drained from the tire equator C side to the ground contact Te side during tire rolling. From the same viewpoint, the shoulder lateral groove 4C is also inclined toward the rear arrival side in the tire rotation direction from the tire equator C side toward the ground contact end Te side.

  The groove width W5 of the middle lateral groove 4B is 4.0 to 16.0 mm. That is, when the groove width W5 of the middle lateral groove 4B is less than 4.0 mm, the drainage performance is deteriorated. When the groove width W5 of the middle lateral groove 4B exceeds 16.0 mm, the rigidity of the middle block 6 in the tire circumferential direction is reduced and the uneven wear resistance performance is deteriorated. For this reason, the groove width W5 of the middle lateral groove 4B is preferably 4.5 mm or more, and preferably 15.5 mm or less. From the same viewpoint, the groove width W6 of the shoulder lateral groove 4C is 4.0 mm or more, preferably 4.5 mm or more, and 16.0 mm or less, preferably 15.5 mm or less.

  As shown in FIG. 3, the angle θ2 of the middle lateral groove 4B with respect to the tire axial direction is smaller than the angle θ1 of the center lateral groove 4A. During straight traveling, the center block 5 is subjected to a larger load than the middle block 6. For this reason, by defining the angle of each lateral groove 4A, 4B as described above, the edge 5x on the first arrival side of the center block 5 and the edge 6x on the first arrival side of the middle block 6 are separated from the road surface at the time of ground contact. Impact is alleviated with a good balance. Therefore, the slip amount of the center block 5 and the middle block 6 is made uniform, and the wear resistance performance is further improved.

  In order to make the slip amount of the center block 5, the middle block 6 and the shoulder block 7 uniform, it is desirable that the angle θ2 of the middle lateral groove 4B is formed larger than the angle θ3 of the shoulder lateral groove 4C with respect to the tire axial direction.

  In order to effectively exhibit the above-described action, the angle θ2 of the middle lateral groove 4B is preferably 3 ° or more, more preferably 4 ° or more, and preferably 10 ° or less, more preferably 9 ° or less. The angle θ3 of the shoulder lateral groove 4C is preferably 0.5 ° or more, more preferably 1 ° or more, and preferably 5 ° or less, more preferably 4.5 ° or less.

  As shown in FIG. 1, the pitch Pb of the middle lateral groove 4B is the same as the pitch Pa of the center lateral groove 4A. The middle lateral groove 4B and the center lateral groove 4A are arranged with a half pitch phase shifted in the tire circumferential direction. That is, the center lateral groove 4A and the middle portion of the middle block 6 in the tire circumferential direction are aligned in the tire axial direction. Further, the middle lateral groove 4B and the center portion of the center block 5 in the tire axial direction are arranged in the tire axial direction. Thereby, the slip of the edge of the center block 5 on both sides in the tire circumferential direction in the tire axial direction and the slip of the edge on both sides of the middle block 6 in the tire circumferential direction in the tire axial direction are suppressed. Therefore, the wear resistance and uneven wear resistance are further improved.

  As shown in FIG. 2, no tie bar is provided at the groove bottom of the middle lateral groove 4B of the present embodiment. Thereby, the groove volume of the middle lateral groove 4B is ensured even at the end of wear. Accordingly, the drainage performance is further improved. Note that a tie bar (shown by a broken line) T having a height H1 raised from the deepest groove bottom less than 50% of the deepest groove depth D5 of the middle horizontal groove 4B is provided at the groove bottom of the middle horizontal groove 4B. good. Such a tie bar T is less likely to greatly affect drainage performance. From the viewpoint of further improving drainage performance, no tie bar is provided on the bottom of the shoulder lateral groove 4C of the present embodiment. Similar to the case of the middle lateral groove 4B, even if a tie bar (shown by a broken line) T having a raised height H2 from the deepest groove bottom that is less than 50% of the deepest groove depth D6 of the shoulder lateral groove 4C is provided. good.

  Although not particularly limited, in order to ensure a good balance between drainage performance and the rigidity of the land portions 5, 6, and 7, the groove depths D4 and D5 of the center lateral groove 4A and the middle lateral groove 4B are, for example, 15 0.0-25.0 mm is desirable. As for groove depth D6 of shoulder lateral groove 4C, 10.0-20.0 mm is desirable, for example.

  As shown in FIG. 4, the land ratio Lc of the center region 5A is 1.05 to 1.25 times the land ratio Lm of the middle region 6A. The center region 5A is a region between tire circumferential lines 5c and 5c passing through both ends 5e and 5e of the center block 5 in the tire axial direction. The middle region 6A is a region between tire circumferential direction lines 6c and 6c passing through both ends 6e and 6e of the middle block 6 in the tire axial direction. When the land ratio Lc of the center area 5A is less than 1.05 times the land ratio Lm of the middle area 6A, or the land ratio Lc of the center area 5A is 1.25 times the land ratio Lm of the middle area 6A. When exceeding, the rigidity of the center block 5 and the rigidity of the middle block 6 cannot be ensured in a well-balanced manner, and the ground pressure during running of the center block 5 and the middle block 6 becomes uneven. For this reason, at the time of tire rolling, the difference of the slip amount of the center block 5 and the middle block 6 becomes large, and uneven wear resistance performance deteriorates.

  Each of the blocks 5 to 7 of the present embodiment is provided with a narrow groove 22 that is substantially crank-shaped in plan view and extends in the tire axial direction. Such narrow grooves 22 reduce the length in the tire circumferential direction of each of the blocks 5 to 7 and suppress the amount of slip due to rolling of the tire.

  In order to suppress the slip amount while ensuring high rigidity of each of the blocks 5 to 7, the width W7 of the narrow groove is desirably about 1.0 to 3.0 mmM. Similarly, the depth D7 (shown in FIG. 2) of the narrow groove is desirably about 1.0 to 4.0 mm.

  The center block 5, the middle block 6 and the shoulder block 7 are inclined in a substantially triangular shape at the top where each main groove 3 and each lateral groove 4 intersect and the top where each main groove 3 and narrow groove 22 intersect. A chamfered portion m cut out is provided. Such a chamfered portion m can increase the rigidity of each of the blocks 5 to 7 and suppress the occurrence of block chipping or uneven wear.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to said specific embodiment, It implements by changing into various aspects.

In order to confirm the effect of the present invention, a 11.00R20 heavy duty pneumatic tire having the basic pattern of FIG. 1 and based on the specifications of Table 1 was tested. Except for the grooves described in Table 1, the groove width and angle of each groove are as shown in FIG. The main common specifications of each tire are as follows.
Tread contact width TW: 242.4mm
Groove depth of each main groove: 21.0mm
Center lateral groove depth: 21.0mm
Middle lateral groove depth: 21.0mm
Shoulder groove depth: 14.5mm
Groove depth of narrow groove: 2.0mm
The test method is as follows.

<Drainage performance (wet brake)>
Each sample tire was mounted on all wheels of a domestic truck (2-D car, equipped with ABS brake) loaded with 8 tons under the following conditions. The test driver then ran the test vehicle on a test course on an asphalt road surface with a water depth of 0.5 to 2.0 mm and actuated a sudden brake from a speed of 65 km / h. At this time, the braking distance from the speed of 60 km / h to 20 km / h was measured. The result is the reciprocal of the braking distance, and is displayed as an index with the value of Example 1 being 100. Larger values are better, but less than 90 are ineligible.
Rims: 8.00 × 20
Internal pressure: 780 kPa
Loading conditions: 30.4kN per tire on the drive shaft
Tie bar length / length of groove center line of each lateral groove where tie bar is provided: 30% (Examples 6 and 7 and Comparative Examples 5 and 6)

<Abrasion resistance>
A test driver drove the test vehicle on a dry asphalt road surface for 10,000 km. Thereafter, the remaining amount of the center main groove and middle main groove was measured at eight locations on the tire circumference. The result is an average value of the remaining amount of the groove, and is displayed as an index with the value of Example 1 being 100. Larger numbers are better, but 90 and below are ineligible.

<Uneven wear resistance>
The difference in the wear amount of the block edges on both sides in the tire circumferential direction of the center block of each test tire used in the wear resistance performance and the difference in the wear amounts of the block edges on both sides in the tire circumferential direction of the middle block are the tires. Eight measurements were taken in the circumferential direction. The result is the reciprocal of the average value of the difference in the amount of wear, and is displayed as an index with the value of Example 1 being 100. Larger values are better, but less than 90 are ineligible.

<TGC resistance>
While spraying ozone (500 L / H) with a concentration of 50 pphm, each test tire ran on the drum tester under the following conditions. After running, cracks in the groove bottom were observed by the examiner's naked eyes. The results were displayed in a five-point method, where the tire with the largest crack was “1” and the tire with no crack was “5”. The test conditions are as follows.
Internal pressure: 780 kPa
Load: 30.4kN
Speed: 80km / h
Travel time: 400 hours Table 1 shows the test results.

  As a result of the test, it can be confirmed that each performance of the tire of the example is improved in a balanced manner as compared with the comparative example. In addition, the test was performed by changing the width of the middle lateral groove and the shoulder lateral groove within a preferable range of values, and the test result was the same.

3A Center main groove 3B Middle main groove 3C Shoulder main groove 4A Center horizontal groove 4B Middle horizontal groove 4C Shoulder horizontal groove 5 Center block 5A Center area 6 Middle block 6A Middle area R Rotation direction

Claims (7)

One center main groove extending continuously in the tire circumferential direction on the tire equator in the tread portion, a pair of middle main grooves extending continuously in the tire circumferential direction on both sides in the tire axial direction of the center main groove, A pair of shoulder main grooves extending continuously in the tire circumferential direction between the middle main groove and the ground contact end, a plurality of center lateral grooves connecting between the center main groove and the middle main groove, and the middle main groove And a plurality of middle lateral grooves that connect between the shoulder main groove and a plurality of shoulder lateral grooves that connect between the shoulder main groove and the grounding end,
A pair of center block rows in which a center block divided by the center main groove, the middle main groove, and the center lateral groove is spaced apart in the tire circumferential direction, the middle main groove, the shoulder main groove, and the middle lateral groove A pair of middle block rows in which the divided middle blocks are separated in the tire circumferential direction, and a shoulder block divided in the shoulder main groove, the ground contact end, and the shoulder lateral groove are separated in the tire circumferential direction. A pneumatic tire having a pair of shoulder block rows,
The middle lateral groove and the shoulder lateral groove extend substantially linearly and have a groove width of 4.0 to 16.0 mm.
The middle bottom groove and the shoulder bottom groove bottom are provided with a tie bar whose height from the deepest groove bottom is 50% or more of the deepest groove depth of each of the lateral grooves,
The land ratio of the center region, which is the region between the tire circumferential direction lines passing through both ends of the center block in the tire axial direction, is the middle region which is the region between the tire circumferential direction lines passing through both ends of the middle block in the tire axial direction. 1.05 to 1.25 times the land ratio,
The pneumatic tire is characterized in that the center lateral groove has an angle with respect to a tire axial direction of 15 to 45 ° and is larger than an angle of the middle lateral groove with respect to the tire axial direction. In the tread portion, a tread rubber forming an outer surface of the tire is arranged,
The pneumatic tire according to claim 1, wherein the tread rubber has a complex elastic modulus E * of 6.3 to 7.7 MPa. The center main groove extends linearly in the tire circumferential direction and its groove width is smaller than the groove width of the middle main groove,
3. The pneumatic tire according to claim 1, wherein the middle main groove and the shoulder main groove extend in a zigzag shape in the tire circumferential direction and each groove center line has an amplitude of 2 mm or more. The center lateral groove includes a first center lateral groove disposed on one side of the tire equator and a second center lateral groove disposed on the other side of the tire equator,
The first center lateral groove and the second center lateral groove are spaced apart in the tire circumferential direction at the same pitch, and are arranged with a half-pitch phase shifted in the tire circumferential direction. The pneumatic tire according to Crab.   5. The middle lateral groove and the center lateral groove adjacent to the middle lateral groove are spaced apart from each other in the tire circumferential direction at the same pitch, and are arranged with a half pitch phase shifted in the tire circumferential direction. The pneumatic tire according to any one of the above. The center lateral groove includes an inner groove extending linearly outward from the center main groove in the tire axial direction, and an outer groove extending linearly from the middle main groove toward the tire equator,
The pneumatic tire according to claim 1, wherein the inner groove portion and the outer groove portion are displaced in the tire circumferential direction. The tread portion includes a directional pattern in which a rotation direction is designated,
The pneumatic tire according to any one of claims 1 to 6, wherein the center lateral groove is inclined toward the rear arrival side in the tire rotation direction toward the outer side in the tire axial direction.

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