JP2015160469A - pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can improve wet performance, dry performance and uneven wear resistance with good balance.SOLUTION: In a pneumatic tire in which a mounting direction of the front and back sides of the tire is designated, where a distance GL1 of a first main groove 11 is set to be 6% or less of an earth-contact half width TL/2, a distance GL2 of a second main groove 12 is set to be 40%-65% of the earth-contact half width TL/2 and a distance GL3 of a sub groove is set to be 40%-65% of the earth-contact half width TL/2, are provided: a first lug groove 31, one end of which reaches a grounding end inside a vehicle and the other end of which is closed so as not to communicate with the second main groove 12; a second lug groove 32, one end of which communicates with the second main groove 12 and the other end of which is closed; a third lug groove 31, one end of which communicates with the first main groove 11 and the other end of which is closed; a plurality of fourth lug grooves 34, one ends of which communicate with the sub groove 13 and the other ends of which are closed; a fifth groove 35, one end of which communicates with the sub groove 13 and the other end of which is closed; and a sixth groove 36, one end of which reaches the grounding end outside the vehicle and the other end of which is closed so as not to communicate with the sub groove 13.

Description

  The present invention relates to a pneumatic tire in which a mounting direction with respect to a vehicle is designated, and more particularly to a pneumatic tire that can improve wet performance, dry performance, and uneven wear resistance in a well-balanced manner.

  In recent years, as the performance of vehicles has improved, dry performance represented by steering stability on dry roads and wet performance represented by steering stability on wet roads are well balanced in a high level in pneumatic tires. There is a strong demand for improvement.

  Conventionally, in a pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of rows of land portions extending in the tire circumferential direction are defined by the main grooves, and the land portions are A lug groove extending in the tire width direction is provided. For example, while providing a plurality of main grooves extending in the tire circumferential direction in the center region of the tread portion, a plurality of lug grooves extending in the tire width direction are provided in the shoulder region of the tread portion, and the end portions of these lug grooves are landed. A structure has been proposed in which the land portion is not subdivided into a plurality of blocks by closing within the portion (see, for example, Patent Document 1). In this case, since the rigidity of the tread portion is maintained, the wet performance can be improved while maintaining the dry performance.

  However, in order to obtain excellent wet performance, it is necessary to sufficiently secure the lug groove component. As a result, there is a problem that not only dry performance but also uneven wear resistance is lowered. In particular, in a severe driving environment such as circuit driving, it is required to maintain good uneven wear resistance in addition to improving wet performance and dry performance, so the conventional tread pattern is not always sufficient. .

JP 2009-113652 A

  An object of the present invention is to provide a pneumatic tire that can improve wet performance, dry performance, and uneven wear resistance in a well-balanced manner.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire comprising a pair of bead portions arranged on the inner side in the tire radial direction, the mounting direction for the vehicle is designated,
A first main groove extending in the tire circumferential direction is provided in a center region of the tread portion, and a second main groove extending in the tire circumferential direction is provided in a region inside the vehicle from the tire equator position of the tread portion, and the tire of the tread portion. A sub-groove extending in the tire circumferential direction in a region outside the vehicle from the equator position and having at least one of a groove width and a groove depth smaller than the first main groove and the second main groove;
The distance GL1 from the center position of the first main groove to the tire equator position is 6% or less of the half width TL / 2 of the tire ground contact width TL, and the distance GL2 from the center position of the second main groove to the tire equator position is the tire. 40% to 65% of the half width TL / 2 of the ground contact width TL, and the distance GL3 from the center position of the sub-groove to the tire equator position is 40% to 65% of the half width TL / 2 of the tire ground contact width TL,
A first rib is defined inside the vehicle from the second main groove, a second rib is defined between the second main groove and the first main groove, and the first main groove and the sub-groove A third rib is defined in between, and a fourth rib is defined on the vehicle outer side than the sub-groove,
The tread portion has a plurality of first lug grooves closed in the first rib so that one end reaches a ground contact end inside the vehicle and the other end is not in communication with the second main groove, and one end is A plurality of second lug grooves that communicate with the second main groove and the other end is closed in the first rib or the second rib, and one end communicates with the first main groove and the other end is within the second rib or A plurality of third lug grooves closed in the third rib, one end communicating with the sub-groove, and the other end communicating with the fourth lug groove closed in the third rib, and one end communicating with the sub-groove A plurality of fifth lug grooves whose other ends are closed in the fourth rib, and one end that reaches the grounding end outside the vehicle and the other end that is not in communication with the sub-groove. A plurality of closed sixth lug grooves are provided.

  In the present invention, in the pneumatic tire in which the mounting direction with respect to the vehicle is specified, the first main groove is disposed in the center region of the tread portion, and the second main groove is disposed in the vehicle inner region from the tire equator position of the tread portion. In addition, the sub-groove is arranged in the region outside the vehicle from the tire equator position of the tread portion, and the first lug groove to the sixth lug groove are dispersed and arranged in the tread portion, thereby maintaining good wet performance. However, the dry balance can be improved by optimizing the rigidity balance of the tread portion. In addition, since the end portions of the first lug groove to the sixth lug groove are closed and the first rib to the fourth rib are not subdivided, this greatly maintains the rigidity of each rib and suppresses uneven wear. Contribute. Therefore, according to the above configuration, it is possible to improve the wet performance represented by the steering stability on the wet road surface and the dry performance represented by the steering stability on the dry road surface and the uneven wear resistance in a balanced manner. .

  In this invention, it is preferable that a 2nd lug groove and a 3rd lug groove open toward a vehicle inner side. Thereby, the rigidity of the 2nd rib and the 3rd rib with respect to the input from the vehicle outside can be maintained, and steering stability on a dry road surface can be improved.

  The first lug groove extends across the ground contact end on the vehicle inner side to the vehicle inner end of the first rib, the sixth lug groove crosses the ground contact end on the vehicle outer side, and the vehicle outer end of the sixth lug groove. It is preferable that the part is closed in the fourth rib. Thereby, dry performance and wet performance can be improved with good balance.

  The distance RG1 from the second main groove to the closed end of the first lug groove on the tire equator side is 15% to 35% of the width RL1 in the ground contact region of the first rib, and the distance from the second main groove to the second lug groove The distance RG2 to the closed end is 30% to 65% of the width RL2 of the second rib, and the distance RG3 from the first main groove to the closed end of the third lug groove is 25% to 60% of the width RL3 of the third rib. The distance RG4 from the sub groove to the closed end of the fourth lug groove is 15% to 40% of the width RL3 of the third rib, and the distance RG5 from the sub groove to the closed end of the fifth lug groove is The distances RG6 and RG7 from the sub-groove to the closed ends on both sides of the sixth lug groove are 25% to 45% of the width RL4 in the tire contact area of the fourth rib, respectively. It is preferable. Thereby, wet performance, dry performance, and uneven wear resistance can be improved in a well-balanced manner.

  The inclination angles α1 and α6 of the first lug groove and the sixth lug groove with respect to the tire circumferential direction are 70 ° to 90 °, respectively, and the tire circumference of the second lug groove, the third lug groove, the fourth lug groove, and the fifth lug groove The inclination angles α2, α3, α4, and α5 with respect to the direction are preferably 45 ° to 80 °, respectively. Thereby, wet performance, dry performance, and uneven wear resistance can be improved in a well-balanced manner.

  The groove widths GW1 and GW2 of the first main groove and the second main groove are preferably 8 mm to 16 mm, respectively, and the groove width GW3 of the sub groove is preferably 1 mm to 2.5 mm. Thereby, dry performance and wet performance can be improved with good balance.

  The second lug groove and the third lug groove are alternately arranged along the tire circumferential direction, the third lug groove, the fourth lug groove and the fifth lug groove are alternately arranged along the tire circumferential direction, The 4 lug grooves, the fifth lug grooves, and the sixth lug grooves are preferably arranged alternately along the tire circumferential direction. By arranging the adjacent lug grooves in a staggered manner in this manner, the rigidity balance of the tread portion can be made uniform, and the dry performance and uneven wear resistance can be improved in a well-balanced manner.

  When the first lug groove, the second lug groove, the third lug groove, and the fifth lug groove open toward the vehicle inner side, the third lug groove is the first lug groove, the second lug groove, and the fifth lug groove. It is preferable to incline in the reverse direction. By inclining the third lug groove in the opposite direction to the first lug groove, the second lug groove and the fifth lug groove in this way, the rigidity balance of the tread portion is made uniform, and the dry performance and the uneven wear resistance are balanced. It can improve well.

  The groove area ratio in the region outside the vehicle from the tire equator position in the tread portion is in the range of 8% to 22%, and the groove area ratio in the region inside the vehicle from the tire equator position in the tread portion is from 22% to 40%. % Is preferable. By relatively reducing the groove area ratio in the area outside the vehicle in this way, the load during cornering can be firmly received, so the handling stability on the dry road surface is improved and the wear of the tread part is further improved. Can be suppressed. Moreover, drainage can be sufficiently ensured by relatively increasing the groove area ratio in the vehicle inner region.

  The pitch length L in the tire circumferential direction of the first lug groove to the sixth lug groove is preferably in the range of 1.5% to 3.5% of the tire outer circumferential length. Thereby, dry performance and wet performance can be improved with good balance.

  The sub-groove is preferably shallower than the fourth lug groove and the fifth lug groove. By making the sub-groove located in the region outside the vehicle shallow, it is possible to improve the steering stability on the dry road surface and to improve the uneven wear resistance.

  The first to sixth lug grooves are all curved, and the radius of curvature of the first lug groove, the second lug groove, the third lug groove, and the sixth lug groove is set to 80 mm to 360 mm, respectively. Each of the 5 lug grooves preferably has a radius of curvature of 8 mm to 40 mm. By curving each lug groove in this way, it is possible to disperse the force applied to the lug groove that is easily damaged during braking and turning, and avoid uneven wear.

  In the present invention, each dimension is measured in a state in which a tire is assembled on a regular rim and filled with a regular internal pressure. 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, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car.

  In the present invention, the tire ground contact width TL is defined as 85% of the tire cross-sectional width T measured under the measurement conditions described above. The groove area ratio is a groove area ratio in the contact area defined by the tire contact width TL. The groove area ratio is a ratio (%) of the total area of the groove portions in each region to the total area (including the land portion and the groove portion) of each region.

1 is a perspective view showing a pneumatic tire according to an embodiment of the present invention. It is a front view which shows the pneumatic tire of FIG. It is meridian sectional drawing which shows the pneumatic tire of FIG. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is an expanded view which shows the tread pattern of the pneumatic tire of a prior art example. It is an expanded view which shows the tread pattern of the pneumatic tire of a comparative example.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a pneumatic tire according to an embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the tire front and back when the vehicle is mounted is designated. 1 to 4, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted. Such a mounting direction is displayed on any part of the outer surface of the tire.

  As shown in FIGS. 1 to 3, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions that are disposed on both sides of the tread portion 1. 2 and 2 and a pair of bead portions 3 and 3 disposed on the inner side in the tire radial direction of the sidewall portions 2.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 4, a first main groove 11 extending in the tire circumferential direction is formed in the center region of the tread portion 1, and extends in the tire circumferential direction in a region on the vehicle inner side than the tire equator position CL of the tread portion 1. A second main groove 12 is formed, and a sub-groove 13 extending in the tire circumferential direction is formed in a region outside the vehicle from the tire equator position CL of the tread portion 1. The first main groove 11 and the second main groove have a maximum groove width of 2.5 mm or more when new and a groove depth of 3.5 mm or more. On the other hand, at least one of the groove width and the groove depth of the sub-groove 13 is smaller than the above definition regarding the first main groove 11 and the second main groove 12.

  When 85% of the tire cross-sectional width T (see FIG. 2) is the tire ground contact width TL, the distance GL1 from the center position of the first main groove 11 to the tire equator position CL is 6 which is a half width TL / 2 of the tire ground contact width TL. %, And the distance GL2 from the center position of the second main groove 12 to the tire equator position CL is set to 40% to 65% of the half width TL / 2 of the tire ground contact width TL, and from the center position of the sub-groove 13 The distance GL3 to the tire equator position CL is set to 40% to 65% of the half width TL / 2 of the tire ground contact width TL. Thus, the first rib 21 is defined on the vehicle inner side than the second main groove 12, and the second rib 22 is defined between the second main groove 12 and the first main groove 11. A third rib 23 is defined between the sub-groove 13 and a fourth rib 24 is defined on the vehicle outer side than the sub-groove 13.

  Further, the tread portion 1 includes a plurality of first lug grooves 31, a plurality of second lug grooves 32, a plurality of third lug grooves 33, a plurality of fourth lug grooves 34, and a plurality of fifth lugs. A groove 35 and a plurality of sixth lug grooves 36 are formed at intervals along the tire circumferential direction. Each of the first lug grooves 31 has a structure in which one end reaches the grounding end Ein inside the vehicle and the other end is closed in the first rib 21 so as not to communicate with the second main groove 12. Yes. Each of the second lug grooves 32 has a structure in which one end communicates with the second main groove 12 and the other end is closed in the second rib 22. Each of the third lug grooves has a structure in which one end communicates with the first main groove 11 and the other end is closed in the third rib 23. Each of the fourth lug grooves has a structure in which one end communicates with the sub-groove 13 and the other end is closed in the third rib 23. Each of the fifth lug grooves 35 has a structure in which one end communicates with the sub-groove 13 and the other end is closed in the fourth rib 24. Each of the sixth lug grooves 36 has a structure closed in the fourth rib 24 so that one end reaches the grounding end Eout on the vehicle outer side and the other end is not in communication with the sub-groove 13. The groove width and groove depth of the lug grooves 31 to 36 are not particularly limited. For example, the groove width is set to 3.5 mm to 8.0 mm (preferably 4.5 mm to 7.5 mm), and the groove depth is set. What is necessary is just to be 3.0 mm-7.0 mm (preferably 4.0 mm-7.0 mm).

  In the pneumatic tire described above, the first main groove 11 is disposed in the center region of the tread portion 1, the second main groove 12 is disposed in the region inside the vehicle from the tire equator position CL of the tread portion 1, and the tread portion 1. The sub-groove 13 is disposed in the region outside the vehicle from the tire equator position CL, and the lug grooves 31 to 36 are dispersed and disposed in the tread portion 1, thereby maintaining good wet performance and the tread portion 1. It is possible to improve the dry performance by optimizing the rigidity balance. In addition, since the end portions of the lug grooves 31 to 36 are closed and the ribs 21 to 24 are structured so as not to be subdivided, this greatly contributes to maintaining the rigidity of the ribs 21 to 24 and suppressing uneven wear. Therefore, according to the pneumatic tire having the tread pattern, wet performance, dry performance, and uneven wear resistance can be improved in a well-balanced manner.

  Here, when the distance GL1 from the center position of the first main groove 11 to the tire equator position CL is larger than 6% of the half width TL / 2 of the tire ground contact width TL, the wet performance is deteriorated. The distance GL1 of the first main groove 11 is preferably 3% or less of the half width TL / 2. In particular, in order to exhibit good wet performance, the first main groove 11 is desirably disposed at a position overlapping the tire equator position CL. By disposing the first main groove 11 near the tread center where the contact surface pressure is high, drainage can be efficiently performed. The first main groove 11 may be shifted to either the vehicle inner side or the vehicle outer side with respect to the tire equator position CL.

  Further, if the distance GL2 from the center position of the second main groove 12 to the tire equator position CL is smaller than 40% of the half width TL / 2 of the tire contact width TL, the rigidity of the second rib 22 is lowered, and steering stability and resistance On the contrary, if it is larger than 65%, the rigidity of the first rib 21 is lowered, and the steering stability and uneven wear resistance are deteriorated.

  Further, if the distance GL3 from the center position of the sub-groove 13 to the tire equator position CL is smaller than 40% of the half width TL / 2 of the tire ground contact width TL, the rigidity of the third rib 23 is lowered, and steering stability and uneven wear resistance are reduced. On the other hand, if it is larger than 65%, the rigidity of the fourth rib 24 is lowered, and steering stability and uneven wear resistance are deteriorated. It is preferable that the distance GL2 of the second main groove 12 and the distance GL3 of the sub-groove 13 are substantially equal.

  In the pneumatic tire, the second lug groove 32 only needs to have one end communicating with the second main groove 12, and the other end can be closed in the first rib 21 or the second rib 22. . Similarly, the third lug groove 33 only needs to have one end communicating with the first main groove 11, and the other end can be closed in the second rib 22 or the third rib 23. However, it is preferable that the second lug groove 32 and the third lug groove 33 open toward the inside of the vehicle as shown in the figure. Thereby, the rigidity of the 2nd rib 22 and the 3rd rib 23 with respect to the input from the vehicle outer side is maintained, and the steering stability on a dry road surface can be improved.

  The first lug groove 31 extends across the grounding end Ein on the vehicle inner side to the vehicle inner end of the first rib 21, and the sixth lug groove 36 crosses the grounding end Eout on the vehicle outer side, The end of the lug groove 36 on the vehicle outer side is preferably closed within the fourth rib 24. Thereby, dry performance and wet performance can be improved with good balance. That is, the first lug groove 31 on the vehicle inner side extended to the design end contributes to the improvement of the wet performance, and the sixth lug groove 36 on the outer side of the vehicle with both ends closed contributes to the improvement of the dry performance.

  In FIG. 4, the distance RG1 from the second main groove 12 to the closed end of the first lug groove 31 on the tire equator side is set to a range of 15% to 35% of the width RL1 in the ground contact region of the first rib 21. The distance RG2 from the second main groove 12 to the closed end of the second lug groove 32 is set in a range of 30% to 65% of the width RL2 of the second rib 22, and the first main groove 11 to the third lug groove 33 are set. The distance RG3 to the closed end is set in the range of 25% to 60% of the width RL3 of the third rib 23, and the distance RG4 from the sub groove 13 to the closed end of the fourth lug groove 34 is the width of the third rib 23. The distance RG5 from the sub-groove 13 to the closed end of the fifth lug groove 35 is set to a range of 15% to 40% of the width RL4 of the fourth rib 24. The distances RG6 and RG7 from the groove 13 to the closed ends on both sides of the sixth lug groove 36 are Respectively it is set in a range of 25% to 45% of the width RL4 in the fourth rib 24 of the tire contact area. Thereby, wet performance, dry performance, and uneven wear resistance can be improved in a well-balanced manner.

  Here, when the distance RG1 from the second main groove 12 to the closed end of the first lug groove 31 is smaller than 15% of the width RL1 of the first rib 21, the first lug groove 31 comes close to the second main groove 12. For this reason, rigidity is lowered and uneven wear tends to occur. On the contrary, if it is larger than 35%, drainage performance is lowered. In particular, the distance RG1 is preferably 20% to 30% of the width RL1 of the first rib 21.

  If the distance RG2 from the second main groove 12 to the closed end of the second lug groove 32 is smaller than 30% of the width RL2 of the second rib 22, the rigidity of the second rib 22 is excessively increased and the lateral force is released appropriately. Therefore, uneven wear is likely to occur. On the other hand, if it exceeds 65%, the rigidity of the second rib 22 is too low, and the steering stability on the dry road surface is lowered. In particular, the distance RG2 is preferably 40% to 55% of the width RL2 of the second rib 22.

  If the distance RG3 from the first main groove 11 to the closed end of the third lug groove 33 is smaller than 25% of the width RL3 of the third rib 23, the rigidity of the third rib 23 is excessively increased and the lateral force is appropriately released. However, if it exceeds 60%, the rigidity of the third rib 23 decreases too much, and the steering stability on the dry road surface decreases. In particular, the distance RG3 is preferably 35% to 50% of the width RL3 of the third rib 23.

  If the distance RG4 from the sub-groove 13 to the closed end of the fourth lug groove 34 is smaller than 15% of the width RL3 of the third rib 23, the rigidity of the third rib 23 is excessively increased and the lateral force can be released appropriately. Therefore, uneven wear is likely to occur. Conversely, if it exceeds 40%, the rigidity of the third rib 23 is excessively lowered, and the driving stability on the dry road surface is lowered. In particular, the distance RG4 is preferably 20% to 30% of the width RL3 of the third rib 23.

  If the distance RG5 from the sub-groove 13 to the closed end of the fifth lug groove 35 is smaller than 15% of the width RL4 of the fourth rib 24, the rigidity of the fourth rib 24 is excessively increased and the lateral force can be released appropriately. Therefore, uneven wear is likely to occur, and conversely, if it exceeds 40%, the rigidity of the fourth rib 24 is too low and the steering stability on the dry road surface is lowered. In particular, the distance RG4 is preferably 20% to 30% of the width RL4 of the fourth rib 24.

  If the distances RG6, RG7 from the sub-groove 13 to the closed ends on both sides of the sixth lug groove 36 are smaller than 25% of the width RL4 of the fourth rib 24, the wet performance during cornering is degraded, and conversely than 45%. If it is large, the handling stability on the dry road surface is lowered. In particular, the distances RG6 and RG7 are preferably 30% to 40% of the width RL4 of the fourth rib 24.

  In FIG. 4, the inclination angles α1 and α6 of the first lug groove 31 and the sixth lug groove 36 with respect to the tire circumferential direction are set in a range of 70 ° to 90 °, respectively, and the second lug groove 32, the third lug groove 33, The inclination angles α2, α3, α4, and α5 of the fourth lug groove 34 and the fifth lug groove 35 with respect to the tire circumferential direction are set in the range of 45 ° to 80 °, respectively. Thereby, wet performance, dry performance, and uneven wear resistance can be improved in a well-balanced manner. The inclination angles α1 to α6 are inclination angles with respect to the tire circumferential direction of a straight line connecting the groove width center positions at both ends in each of the first lug groove 31 to the sixth lug groove 36.

  Here, if the inclination angles α1 and α6 of the first lug groove 31 and the sixth lug groove 36 with respect to the tire circumferential direction are smaller than 70 °, the directionality at the time of rotation becomes strong, and the direction to the other direction is greater than at the time of rotation in one direction. The drainage at the time of rotation will decrease. The tread pattern specifies the mounting direction with respect to the vehicle, but does not specify the rotation direction. In particular, the inclination angles α1, α6 are preferably 75 ° to 85 °.

  If the inclination angles α2, α3, α4, α5 with respect to the tire circumferential direction of the second lug groove 32, the third lug groove 33, the fourth lug groove 34, and the fifth lug groove 35 are smaller than 45 °, the corresponding ribs 22, 23 24, the steering stability is lowered particularly when cornering on a dry road surface. Conversely, if the angle is greater than 80 °, uneven wear tends to occur during braking / driving. In particular, the inclination angles α2 to α5 are preferably 50 ° to 70 °.

  In the pneumatic tire, it is preferable that the groove widths GW1 and GW2 of the first main groove 11 and the second main groove 12 are 8 mm to 16 mm, respectively, and the groove width GW3 of the sub groove 13 is 1 mm to 2.5 mm. Thereby, dry performance and wet performance can be improved with good balance.

  Here, if the groove widths GW1 and GW2 of the first main groove 11 and the second main groove 12 are smaller than 8 mm, the drainage performance is deteriorated. Conversely, if the groove width GW1 and GW2 is larger than 16 mm, the first main groove is caused by a lateral force generated during cornering. Buckling is likely to occur in the tread portion 1 at the positions of 11 and the second main groove 12. In particular, the groove widths GW1 and GW2 are preferably 10 mm to 14 mm. The groove depths of the first main groove 11 and the second main groove 12 are preferably 5 mm to 7 mm. If the groove depth is smaller than 5 mm, the wet performance is lowered, and conversely if it is larger than 7 mm, the steering stability is lowered. In particular, the groove depths of the first main groove 11 and the second main groove 12 are preferably 5.5 mm to 6.5 mm.

  On the other hand, when the groove width GW3 of the sub-groove 13 is smaller than 1 mm, the wet performance is deteriorated. Conversely, when the groove width GW3 is larger than 2.5 mm, the steering stability is deteriorated. In particular, the groove width GW3 of the sub-groove 13 is preferably 20% to 90% of the groove depth of the first main groove 11 and the second main groove 12.

  In the pneumatic tire, the second lug grooves 32 and the third lug grooves 33 are alternately arranged along the tire circumferential direction, and the third lug grooves 33, the fourth lug grooves 34, and the fifth lug grooves 35 are tires. The fourth lug grooves, the fifth lug grooves, and the sixth lug grooves are alternately arranged along the tire circumferential direction. By arranging the adjacent lug grooves in a staggered manner in this way, the rigidity balance of the tread portion 1 can be made uniform, and as a result, the steering stability on the dry road surface can be improved and uneven wear can be avoided. .

  In addition, when the first lug groove 31, the second lug groove 32, the third lug groove 33, and the fifth lug groove 35 open toward the inside of the vehicle as illustrated, the inclination of the third lug groove 33 with respect to the tire width direction. The direction is preferably opposite to the inclination direction of the first lug groove 31, the second lug groove 32, and the fifth lug groove 35 with respect to the tire width direction. In this way, the third lug groove 33 opening in the first main groove 11 disposed in the center region of the tread portion 1 is inclined in the opposite direction to the first lug groove 31, the second lug groove 32, and the fifth lug groove 35. By doing so, the rigidity balance of the tread portion 1 can be made uniform, and as a result, steering stability on a dry road surface can be improved and uneven wear can be avoided.

  In the pneumatic tire, the groove area ratio in the region outside the vehicle from the tire equator position CL of the tread portion 1 is in the range of 8% to 22%, and the region inside the vehicle from the tire equator position CL of the tread portion 1 The groove area ratio is preferably in the range of 22% to 40%. Thus, by relatively reducing the groove area ratio in the region outside the vehicle, it is possible to firmly receive the load during cornering, so that the handling stability on the dry road surface is improved, and further, the tread portion 1 Wear can be suppressed. In particular, the groove area ratio in the vehicle outer region is preferably in the range of 12% to 20%. Moreover, drainage can be sufficiently ensured by relatively increasing the groove area ratio in the vehicle inner region. In particular, the groove area ratio in the vehicle inner region is preferably in the range of 25% to 35%.

  The pitch length L in the tire circumferential direction of the first lug groove 31 to the sixth lug groove 36 is preferably in the range of 1.5% to 3.5% of the tire outer circumferential length. Thereby, dry performance and wet performance can be improved with good balance. When the pitch length L of the first lug groove 31 to the sixth lug groove 36 is smaller than 1.5% of the tire outer peripheral length, the steering stability is lowered, and conversely, when the pitch length L is larger than 3.5%, the wet performance is lowered. . In particular, the pitch length L is preferably in the range of 2% to 3% of the tire outer peripheral length.

  The sub groove 13 is preferably shallower than the fourth lug groove 34 and the fifth lug groove 35 communicating with the sub groove 13. By making the sub-groove 13 located in the region outside the vehicle shallower, it is possible to improve steering stability on the dry road surface and reduce uneven wear and damage.

  Furthermore, the first lug groove 31 to the sixth lug groove 36 are all preferably curved. And the curvature radius RR1, RR6 of the 1st lug groove 31 and the 6th lug groove 36 which are not connected to the 1st main groove 11 or subgroove 13 extended in the tire peripheral direction, and the 1st main groove 11 or the 2nd main groove 12 The radius of curvature RR2 and RR3 of the second lug groove 32 and the third lug groove 33 that communicate with each other is 80 mm to 360 mm, respectively, and the radius of curvature RR4 and RR5 of the fourth lug groove 34 and the fifth lug groove 35 that communicate with the sub-groove 13 Is preferably 8 mm to 40 mm. By curving the lug grooves 31 to 36 in this way, it is possible to disperse the force applied to the lug grooves 31 to 36 that are easily damaged during braking and turning, and to avoid uneven wear. In particular, the curvature radii RR1, RR2, RR3, RR6 are preferably 120 mm to 240 mm, and the curvature radii RR4, RR5 are preferably 10 mm to 25 mm. In each of the lug grooves 31 to 36, a single curvature radius may be applied, or a plurality of curvature radii may be combined. In addition, curvature radius RR1-RR6 is a curvature radius of the circular arc which passes along the curve start point and curve end point which are included on the centerline of the lug grooves 31-36, and its intermediate point. When the lug grooves 31 to 36 have a bent portion, the average curvature radius of the portion excluding the bent portion is used.

  In a pneumatic tire having a tire size of 205 / 55R16 91V and designated in a vehicle mounting direction, as shown in FIGS. 1 to 4, a tread is provided with a first main groove extending in the tire circumferential direction in the center region of the tread portion. A second main groove extending in the tire circumferential direction is provided in a region inside the vehicle from the tire equator position of the tire, and a sub groove extending in the tire circumferential direction is provided in a region outside the vehicle from the tire equator position of the tread portion. The first rib to the fourth rib are divided, the first lug groove to the sixth lug groove are provided in the tread portion, the position of the first main groove [GL1 / (TL / 2) × 100%] and the groove width GW1, Position of second main groove [GL2 / (TL / 2) × 100%] and groove width GW2, position of sub-groove [GL3 / (TL / 2) × 100%] and groove width GW3, closing of first lug groove Position [RG1 / RL1 × 10 0%] and inclination angle α1, second lug groove closing position [RG2 / RL2 × 100%] and inclination angle α2, third lug groove closing position [RG3 / RL3 × 100%] and inclination angle α3, fourth Lug groove closing position [RG4 / RL3 × 100%] and inclination angle α4, fifth lug groove closing position [RG5 / RL4 × 100%] and inclination angle α5, sixth lug groove closing position [RG6 / RL4 × 100%, RG7 / RL4 × 100%] and tires of Examples 1 to 5 and Comparative Examples 1 to 4 in which the inclination angle α6 is set as shown in Tables 1 and 2, respectively.

  For comparison, as shown in FIG. 5, a plurality of main grooves (42) extending in the tire circumferential direction in the center region of the tread portion (41) and a plurality of lug grooves extending in the tire width direction in the shoulder region of the tread portion. A tire of Conventional Example 1 having (43, 44) was prepared. Further, as shown in FIG. 6, a tire of Comparative Example 5 having the same structure as Example 1 was prepared except that the sub-groove was excluded and the lug groove was not communicated with the main groove.

  In addition, although the positive value and the negative value are described as the position of the first main groove, the positive value means that the first main groove is shifted to the vehicle inner side than the tire equator position, and the negative value is the first value. This means that one main groove is shifted to the vehicle outer side than the tire equator position.

  For these test tires, dry performance (steering stability, running time), uneven wear resistance, wet performance (steering stability, hydroplaning generation speed) were evaluated by the following test methods, and the results are shown in Tables 1 and 2. It was shown together. Each evaluation was performed under the condition that the test tire was mounted on a wheel having a rim size of 16 × 7 JJ and mounted on a rear-wheel drive vehicle having a displacement of 2000 cc, and the air pressure after warm-up was 220 kPa.

Dry performance:
A driving test was conducted by a test driver on a circuit on a dry road surface, and the driving time when the circuit drove for seven laps was measured, and at the same time, the steering stability at that time was sensory evaluated. Steering stability on a dry road surface was evaluated on a 10-point scale with Conventional Example 1 being 5 points. The larger this evaluation point, the better the steering stability on the dry road surface. Regarding the running time, the best time and the average time of five laps excluding the best time and the worst time were obtained. The evaluation result of the running time is indicated by an index with the conventional example 1 as 100, using the reciprocal of the measured value. A larger index value means a shorter travel time.

Uneven wear resistance:
A running test with a test driver was performed on a circuit on a dry road surface, and after 50 km of continuous running, the degree of uneven wear occurring in the tread portion was examined. For uneven wear resistance, the degree of uneven wear was evaluated on a 10-point scale (10: excellent, 9 or 8: good, 7 or 6: acceptable, 5 or less: poor). The larger this evaluation point, the better the uneven wear resistance.

Wet performance:
A driving test was conducted by a test driver on a wet road circuit, and the steering stability at that time was sensory evaluated. Steering stability on a wet road surface was evaluated on a 10-point scale with Conventional Example 1 being 5 points. The larger this evaluation point, the better the steering stability on the wet road surface. In addition, the hydroplaning rate was measured under constant water depth conditions. The evaluation result of the hydroplaning generation speed is indicated by an index with the conventional example 1 as 100. A larger index value means higher hydroplaning generation speed.

  As can be seen from Table 1 and Table 2, the tires of Examples 1 to 5 were able to improve the wet performance, the dry performance, and the uneven wear resistance in a well-balanced manner in comparison with Conventional Example 1. On the other hand, the tires of Comparative Examples 1, 3, and 5 had poor dry performance and uneven wear resistance, but poor wet performance. In addition, the tires of Comparative Examples 2 and 4 had good wet performance but were inferior in dry performance and uneven wear resistance.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11 1st main groove 12 2nd main groove 13 Sub groove 21, 22, 23, 24 Rib 31, 32, 33, 34, 35, 36 Lug groove

Claims (12)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In a pneumatic tire with a specified mounting direction for the vehicle,
A first main groove extending in the tire circumferential direction is provided in a center region of the tread portion, and a second main groove extending in the tire circumferential direction is provided in a region inside the vehicle from the tire equator position of the tread portion, and the tire of the tread portion. A sub-groove extending in the tire circumferential direction in a region outside the vehicle from the equator position and having at least one of a groove width and a groove depth smaller than the first main groove and the second main groove;
The distance GL1 from the center position of the first main groove to the tire equator position is 6% or less of the half width TL / 2 of the tire ground contact width TL, and the distance GL2 from the center position of the second main groove to the tire equator position is the tire. 40% to 65% of the half width TL / 2 of the ground contact width TL, and the distance GL3 from the center position of the sub-groove to the tire equator position is 40% to 65% of the half width TL / 2 of the tire ground contact width TL,
A first rib is defined inside the vehicle from the second main groove, a second rib is defined between the second main groove and the first main groove, and the first main groove and the sub-groove A third rib is defined in between, and a fourth rib is defined on the vehicle outer side than the sub-groove,
The tread portion has a plurality of first lug grooves closed in the first rib so that one end reaches a ground contact end inside the vehicle and the other end is not in communication with the second main groove, and one end is A plurality of second lug grooves that communicate with the second main groove and the other end is closed in the first rib or the second rib, and one end communicates with the first main groove and the other end is within the second rib or A plurality of third lug grooves closed in the third rib, one end communicating with the sub-groove, and the other end communicating with the fourth lug groove closed in the third rib, and one end communicating with the sub-groove A plurality of fifth lug grooves whose other ends are closed in the fourth rib, and one end that reaches the grounding end outside the vehicle and the other end that is not in communication with the sub-groove. A pneumatic tire comprising a plurality of closed sixth lug grooves.   2. The pneumatic tire according to claim 1, wherein the second lug groove and the third lug groove are opened toward an inner side of the vehicle.   The first lug groove extends across the ground contact end on the vehicle inner side to the vehicle inner end of the first rib, the sixth lug groove crosses the ground contact end on the vehicle outer side, and the sixth lug groove vehicle The pneumatic tire according to claim 2, wherein an outer end portion is closed in the fourth rib.   The distance RG1 from the second main groove to the closed end on the tire equator side of the first lug groove is set to 15% to 35% of the width RL1 in the ground contact region of the first rib, and the distance from the second main groove to the above-mentioned The distance RG2 to the closed end of the second lug groove is 30% to 65% of the width RL2 of the second rib, and the distance RG3 from the first main groove to the closed end of the third lug groove is the third rib. The distance RG4 from the sub groove to the closed end of the fourth lug groove is 15% to 40% of the width RL3 of the third rib, and the fifth from the sub groove to the fifth RL3. The distance RG5 to the closed end of the lug groove is set to 15% to 40% of the width RL4 of the fourth rib, and the distances RG6 and RG7 from the sub groove to the closed ends on both sides of the sixth lug groove are set to the fourth. 25% to 45% of the width RL4 in the tire ground contact area of the rib The pneumatic tire according to claim 3, characterized in.   The inclination angles α1 and α6 of the first lug groove and the sixth lug groove with respect to the tire circumferential direction are 70 ° to 90 °, respectively, and the second lug groove, the third lug groove, the fourth lug groove, and the 5. The pneumatic tire according to claim 4, wherein the inclination angles α <b> 2, α <b> 3, α <b> 4, and α <b> 5 with respect to the tire circumferential direction of the 5 lug grooves are 45 ° to 80 °, respectively.   The groove widths GW1 and GW2 of the first main groove and the second main groove are 8 mm to 16 mm, respectively, and the groove width GW3 of the sub groove is 1 mm to 2.5 mm. The pneumatic tire according to any one of the above.   The second lug grooves and the third lug grooves are alternately arranged along the tire circumferential direction, and the third lug grooves, the fourth lug grooves, and the fifth lug grooves are alternately arranged along the tire circumferential direction. The air according to claim 1, wherein the fourth lug groove, the fifth lug groove, and the sixth lug groove are alternately arranged along a tire circumferential direction. Enter tire.   The first lug groove, the second lug groove, the third lug groove, and the fifth lug groove are opened toward the vehicle inner side, and the third lug groove is the first lug groove, the second lug groove, and The pneumatic tire according to claim 1, wherein the pneumatic tire is inclined in a direction opposite to the fifth lug groove.   The groove area ratio in the region outside the vehicle from the tire equator position of the tread portion is in the range of 8% to 22%, and the groove area ratio in the region inside the vehicle from the tire equator position of the tread portion is 22%. The pneumatic tire according to claim 1, wherein the pneumatic tire is in a range of ˜40%.   The pitch length L in the tire circumferential direction of the first lug groove to the sixth lug groove is in a range of 1.5% to 3.5% of the tire outer circumferential length. Pneumatic tire described in 2.   The pneumatic tire according to claim 1, wherein the sub-groove is shallower than the fourth lug groove and the fifth lug groove.   The first lug groove to the sixth lug groove are all curved, and the curvature radii of the first lug groove, the second lug groove, the third lug groove, and the sixth lug groove are 80 mm to 360 mm, respectively. The pneumatic tire according to any one of claims 1 to 11, wherein radii of curvature of the fourth lug groove and the fifth lug groove are 8 mm to 40 mm, respectively.

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