JP6375850B2 - Pneumatic tire - Google Patents

Description

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

  In recent years, with the improvement in vehicle performance, in dry tires, the dry performance typified by driving stability on dry road surfaces and the wet performance typified by driving stability on wet road surfaces should be improved in a balanced manner. Is strongly demanded.

  Conventionally, in a pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are formed 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 each land portion is divided. Thus, a plurality of lug grooves extending in the tire width direction are formed. In a pneumatic tire having such a tread pattern, for example, four main grooves are arranged in the tread portion, and the groove width W2 of the second main groove as viewed from the outside of the vehicle is increased in a range of 16 mm to 20 mm. On the other hand, the ratio W2 / W1 between the groove width W1 of the first main groove viewed from the vehicle outer side and the groove width W2 of the second main groove viewed from the vehicle outer side is 4.0 to 5.0, The groove area ratio Sin in the vehicle inner region is 35.2% to 38.4%, and the ratio Sin / Sout between the groove area ratio Sin in the vehicle inner region and the groove area ratio Sout in the vehicle outer region is 1.1-1. It has been proposed to improve the dry performance and wet performance as well as to improve the uneven wear resistance by setting 2 (for example, see Patent Document 1).

  However, in order to obtain excellent wet performance, it is necessary to sufficiently secure the lug groove component. As a result, not only dry performance but also uneven wear resistance and noise performance tend to be reduced. Therefore, it is difficult to improve these performances in a well-balanced manner. 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 2013-224132 A

  An object of the present invention is to provide a pneumatic tire that can improve wet performance, dry performance, uneven wear resistance, and noise performance 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 region inside the vehicle from the tire equator position of the tread portion, and extends in the tire circumferential direction in a region between the tire equator position of the tread portion and the first main groove. A second main groove is provided, a third main groove extending in the tire circumferential direction is provided in a region outside the vehicle from the tire equator position of the tread portion, and the tire is provided in a region outside the vehicle from the third main groove of the tread portion. A circumferential narrow groove extending in the circumferential direction and having a narrower groove width than the first main groove to the third main groove is provided,
A first shoulder land portion is defined on the vehicle inner side than the first main groove, a second shoulder land portion is defined on the vehicle outer side than the circumferential narrow groove, and the first main groove and the second main groove are A first center land portion is defined between the second main groove and the third main groove, and between the third main groove and the circumferential narrow groove. The third center land is divided into
A plurality of first shoulder lug grooves, one end of which reaches the grounding end inside the vehicle and the other end is closed in the first shoulder land portion, and one end reaches the grounding end outside the vehicle and the other end A plurality of second shoulder lug grooves closed within the second shoulder land portion, and a plurality of first center lug grooves whose one end communicates with the first main groove and the other end is closed within the first center land portion; A plurality of second center lug grooves having one end communicating with the second main groove and the other end closed within the second center land portion;
The groove width GW ₁ of the first main groove, the groove width GW ₂ of the second main grooves, the third main groove groove width GW ₃ of a 8Mm～18mm, the groove width GW _1, GW _2, GW ₃ The ratio of the maximum value to the minimum value is in the range of 1.0 to 1.2, and the groove width GW _{4 of the} circumferential narrow groove with respect to the minimum value of the groove widths GW ₁ , GW ₂ , GW _3. The ratio of 0.2 to 0.5,
The first shoulder lug groove, the first center lug groove and the second center lug groove are inclined with respect to the tire width direction, and the inclination directions of the first center lug groove and the second center lug groove are all The first shoulder lug groove has a direction opposite to that of the first shoulder lug groove.

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 provided in a region inside the vehicle from the tire equator position of the tread portion, and the tire equator position of the tread portion and the first main groove are A second main groove is provided in a region between the two, a third main groove is provided in a region outside the vehicle from the tire equator position of the tread portion, and a circumferential narrow groove is provided in a region outside the vehicle from the third main groove in the tread portion. The groove width GW ₁ of the first main groove, the groove width GW _{2 of} the second main groove, and the groove width GW ₃ of the third main groove are 8 mm to 18 mm, and of the groove widths GW ₁ , GW ₂ , GW ₃ The ratio of the maximum value to the minimum value is in the range of 1.0 to 1.2, and the ratio of the groove width GW ₄ of the circumferential narrow groove to the minimum value of the groove widths GW ₁ , GW ₂ , GW ₃ is 0. 2 to 0.5, and one end reaches the grounding end inside the vehicle and the other end is the first shoulder at the tread portion. A plurality of first shoulder lug grooves closed within the section, a plurality of second shoulder lug grooves having one end reaching the ground contact end on the outside of the vehicle and the other end closed within the second shoulder land section, and one end being a first main A plurality of first center lug grooves that communicate with the groove and have the other end closed in the first center land portion, and a plurality of second center lugs that have one end communicated with the second main groove and the other end closed within the second center land portion. By providing the center lug groove, the dry balance can be improved by optimizing the rigidity balance of the tread portion while maintaining good wet performance.

  In addition, the end portions of the first shoulder lug groove, the second shoulder lug groove, the first center lug groove and the second center lug groove are closed, and the corresponding land portions are not subdivided, so that uneven wear resistance is achieved. Performance and noise performance can be improved. In addition, the arrangement in which the inclination directions of the first center lug groove and the second center lug groove are both opposite to the first shoulder lug groove contributes to the improvement of the wet performance. Therefore, according to the above configuration, the wet performance represented by the steering stability on the wet road surface, the dry performance represented by the steering stability on the dry road surface, the uneven wear resistance, and the noise performance can be improved in a balanced manner. It becomes possible.

  In the present invention, the tread portion may be provided with a plurality of third center lug grooves intersecting the third main groove and having one end closed in the second center land portion and the other end closed in the third center land portion. preferable. Thereby, the wet performance can be further improved while maintaining the dry performance, uneven wear resistance, and noise performance satisfactorily.

  Similarly, it is preferable to provide a plurality of fourth center lug grooves that intersect with the circumferential narrow groove in the tread portion and have one end closed in the third center land portion and the other end closed in the second shoulder land portion. . Thereby, the wet performance can be further improved while maintaining the dry performance, uneven wear resistance, and noise performance satisfactorily.

  Of the groove widths of the first shoulder lug groove, the first center lug groove and the second center lug groove, the maximum groove width Ri is the largest of the groove widths of the second shoulder lug groove, the third center lug groove and the fourth center lug groove. It is preferably larger than the groove width Ro. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface. In particular, the ratio Ro / Ri between the maximum groove width Ri and the maximum groove width Ro is preferably in the range of 0.2 to 0.6.

  The inclination angle of the first shoulder lug groove with respect to the tire width direction is preferably 15 ° or less, and the inclination angle of the first center lug groove with respect to the tire width direction is preferably 15 ° to 50 °. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface.

  The inclination angle of the second center lug groove with respect to the tire width direction is preferably 30 ° to 60 °. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface.

  The groove area ratio in the vehicle inner region that is on the vehicle inner side than the tire equator position of the tread portion is 30% to 45%, and the groove area ratio in the vehicle outer region that is on the vehicle outer side than the tire equator position of the tread portion is It is preferably 10% to 25%. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface.

  In the tire meridian cross section, the first center land portion, the second center with respect to the center profile line consisting of the center reference arc passing through each edge point on the tread of the first center land portion, the second center land portion, and the third center land portion Curvatures of the first arc, the second arc, and the third arc that bulge the land portion and the third center land portion and define the tread shape of the first center land portion, the second center land portion, and the third center land portion, respectively. The radius is preferably smaller than the radius of curvature of the center reference arc. Thus, by expanding the first center land portion, the second center land portion, and the third center land portion, the contact pressure distribution of the first center land portion, the second center land portion, and the third center land portion is increased. By optimizing, it becomes possible to further improve the handling stability and uneven wear resistance. In particular, the bulging amount from the center profile line of the first center land portion, the second center land portion, and the third center land portion is preferably in the range of 0.1 mm to 0.5 mm.

  In addition, the first shoulder land portion bulges with respect to the first shoulder profile line formed by the first shoulder reference arc passing through the edge point on the tread of the first shoulder land portion in the tire meridian cross section and in contact with the center reference arc. The curvature radius of the first shoulder arc that defines the tread shape of the first shoulder land portion is made smaller than the curvature radius of the first shoulder reference arc, and passes through the edge point on the tread surface of the second shoulder land portion in the tire meridian section. The second shoulder land portion is bulged with respect to the second shoulder profile line composed of the second shoulder reference arc in contact with the center reference arc, and the radius of curvature of the second shoulder arc defining the tread shape of the second shoulder land portion is set to the first radius. It is preferable to be smaller than the radius of curvature of the two shoulder reference arc. In this way, by bulging the first shoulder land portion and the second shoulder land portion, the contact pressure distribution of the first shoulder land portion and the second shoulder land portion is optimized, and steering stability and uneven wear resistance are improved. Further improvements are possible. In particular, the bulge amount from the first shoulder profile line of the first shoulder land portion and the bulge amount from the second shoulder profile line of the second shoulder land portion may be in the range of 0.1 mm to 0.5 mm, respectively. preferable.

  A chamfered portion is provided in each of a vehicle inner side region that is on the vehicle inner side than the tire equator position of the tread portion and a vehicle outer side region that is on the vehicle outer side of the tire equator position of the tread portion, and the chamfered portion disposed in the vehicle inner side region is provided in the vehicle. It is preferable to make it larger than the chamfered portion disposed in the outer region. As a result, it is possible to maintain good steering stability on a dry road surface while improving the initial wet performance.

  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.

  Moreover, in this invention, the groove area ratio in a vehicle inner side area | region and a vehicle outer side area | region is a groove area ratio specified within the contact area | region of a tread part. This groove area ratio is a ratio (%) of the total area of the groove portion in each region to the total area including the land portion and the groove portion of each region. The contact area of the tread part is specified based on the contact width in the tire axial direction measured when a normal load is applied by placing the tire on a regular rim and filling the regular internal pressure vertically on a plane. Is done. The ground contact edge is the outermost position in the tire axial direction of the ground contact region. “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. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUSIOLD is TRA”. In the case of ETRTO, the maximum value described in “INFLATION PRESOURES” is “LOAD CAPACITY”. However, when the tire is a passenger car, the load corresponds to 88% of the load.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is meridian sectional drawing which shows the outline shape of the tread part in the pneumatic tire of FIG. It is an expanded view which shows the tread pattern of the conventional pneumatic tire.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 3 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 3, 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 FIG. 1, 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 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  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. 2, a first main groove 11 extending in the tire circumferential direction is formed in a region inside the vehicle from the tire equator position CL of the tread portion 1, and the tire equator position CL and the first main groove of the tread portion 1 are formed. 11 is formed with a second main groove 12 extending in the tire circumferential direction, and a third main 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 circumferential direction in which the groove width is narrower than the first main groove 11, the second main groove 12, and the third main groove 13 extends in the tire circumferential direction in a region outside the vehicle from the third main groove 13 of the tread portion 1. A narrow groove 14 is formed.

  Thus, the first shoulder land portion 21 is partitioned on the vehicle inner side than the first main groove 11, and the second shoulder land portion 22 is partitioned on the vehicle outer side than the circumferential narrow groove 14. A first center land portion 31 is defined between the second main groove 12 and a second center land portion 32 is defined between the second main groove 12 and the third main groove 13. A third center land portion 33 is defined between the direction narrow groove 14. In FIG. 2, Ein and Eout respectively indicate grounding ends on the vehicle inner side and the vehicle outer side, and the tread portion 1 forms a grounding region having a grounding width TCW.

As shown in FIG. 2, the groove width GW ₁ of the first main groove 11, the groove width GW ₂ of the second main groove 12, the groove width GW ₃ of the third main groove 13 is set within a range of 8Mm～18mm, the The ratio of the maximum value to the minimum value of the groove widths GW ₁ , GW ₂ , and GW ₃ is set in the range of 1.0 to 1.2. The ratio of the groove width GW ₄ of the circumferential narrow groove 14 to the minimum value among the groove widths GW ₁ , GW ₂ , and GW ₃ is set in the range of 0.2 to 0.5. Although the groove depth of the 1st main groove 11, the 2nd main groove 12, the 3rd main groove 13, and the circumferential direction main groove 14 is not specifically limited, For example, it sets to the range of 3.0 mm-8.0 mm Just do it.

  Further, the tread portion 1 includes a plurality of first shoulder lug grooves 41, a plurality of second shoulder lug grooves 42, a plurality of first center lug grooves 51, a plurality of second center lug grooves 52, and a plurality of pieces. The third center lug groove 53 and the plurality of fourth center lug grooves 54 are formed at intervals along the tire circumferential direction. Each of the first shoulder lug grooves 41 has a structure in which one end reaches the grounding end Ein on the vehicle inner side and the other end is closed in the first shoulder land portion 21 so as not to communicate with the first main groove 11. Have. Each of the second shoulder lug grooves 42 has a structure in which one end reaches the ground contact end Eout on the vehicle outer side and the other end is closed in the second shoulder land portion 22 so as not to communicate with the circumferential narrow groove 14. Have. Each of the first center lug grooves 51 has a structure in which one end communicates with the first main groove 11 and the other end is closed in the first center land portion 31. Each of the second center lug grooves 52 has a structure in which one end communicates with the second main groove 12 and the other end is closed in the second center land portion 32. Each of the third center lug grooves 53 intersects the third main groove 13 and has a structure in which one end is closed in the second center land portion 32 and the other end is closed in the third center land portion 33. ing. Each of the fourth center lug grooves 54 has a structure that intersects the circumferential narrow groove 14 and has one end closed in the third center land portion 33 and the other end closed in the second shoulder land portion 22. ing. In particular, the first shoulder lug groove 41, the first center lug groove 51, and the second center lug groove 52 are inclined with respect to the tire width direction, and the inclination direction of the first center lug groove 51 is relative to the first shoulder lug groove 41. The second center lug groove 52 is inclined in the opposite direction with respect to the first shoulder lug groove 41.

  The groove width and depth of the first shoulder lug groove 41, the second shoulder lug groove 42, the first center lug groove 51, the second center lug groove 52, the third center lug groove 53 and the fourth center lug groove 54 are particularly For example, the groove width may be set in a range of 2.0 mm to 9.0 mm, and the groove depth may be set in a range of 3.0 mm to 8.0 mm.

  In the pneumatic tire described above, the first main groove 11 is provided in a region inside the vehicle from the tire equator position CL of the tread portion 1, and the region between the tire equator position CL of the tread portion 1 and the first main groove 11 is provided. A second main groove 12 is provided, a third main groove 13 is provided in a region outside the vehicle from the tire equator position CL of the tread portion 1, and a circumferentially narrower region is provided in a region outside the vehicle than the third main groove 13 of the tread portion 1. In addition to providing the groove 14, the tread portion 1 has a plurality of first shoulder lug grooves 41 having one end reaching the grounding end Ein on the vehicle inner side and the other end closed in the first shoulder land portion 21, and one end on the vehicle outer side. A plurality of second shoulder lug grooves 42 having the other end closed in the second shoulder land portion 22 and one end communicating with the first main groove 11 and the other end being the first center land portion 31. Multiple first center lug grooves closed inside 1 and a plurality of second center lug grooves 52 having one end communicating with the second main groove 12 and the other end closed within the second center land portion 32, while maintaining good wet performance. The dry balance can be improved by optimizing the rigidity balance of the tread portion 1.

Here, the groove width GW ₁ of the first main groove 11, the groove width GW ₂ of the second main groove 12, the groove width GW ₃ of the third main groove 13 and 8Mm～18mm, the groove width GW _1, GW _2, The ratio of the maximum value to the minimum value of GW ₃ needs to be 1.0 to 1.2. As described above, the first main groove 11, the second main groove 12, and the third main groove 13 having the same groove widths GW ₁ , GW ₂ , and GW ₃ share the drainage in the tread portion 1 evenly, thereby improving the wet performance. Can be maintained satisfactorily, and a local rigidity reduction of the tread portion 1 can be suppressed to ensure dry performance. When the groove widths GW ₁ , GW ₂ , and GW ₃ are smaller than 8 mm, the drainage performance is lowered. Buckling is likely to occur in the tread portion 1. If the ratio of the maximum value to the minimum value of the groove widths GW ₁ , GW ₂ , and GW ₃ is greater than 1.2, it becomes difficult to achieve both wet performance and dry performance. Further, the ratio of the groove width GW ₄ of the circumferential narrow groove 14 to the minimum value among the groove widths GW ₁ , GW ₂ , and GW ₃ needs to be 0.2 to 0.5. When this ratio is less than 0.2, the wet performance is degraded. Conversely, when the ratio is greater than 0.5, the dry performance is degraded.

  Moreover, in the pneumatic tire, the first shoulder lug groove 41, the second shoulder lug groove 42, the first center lug groove 51, the second center lug groove 52, the third center lug groove 53, and the fourth center lug groove 54 are formed. Since the end portions are closed and the corresponding land portions 21, 22, 31, 32, and 33 are not subdivided, uneven wear resistance and noise performance can be improved. Further, the arrangement in which the inclination directions of the first center lug groove 51 and the second center lug groove 52 are opposite to the first shoulder lug groove 41 contributes to the improvement of the wet performance. That is, by making the inclination directions of the first center lug groove 51 and the second center lug groove 52 coincide with each other, the drainage performance in the vehicle inner region is improved, so that the wet performance can be effectively improved. In order to enhance the effect of improving the wet performance, it is desirable that the inclination angles of the first shoulder lug groove 41, the first center lug groove 51, and the second center lug groove 52 with respect to the tire width direction are sequentially decreased toward the vehicle inner side. According to the above configuration, it is possible to improve the dry performance, uneven wear resistance, and noise performance typified by the stability of driving on the wet road surface, the dry performance typified by the stability of driving on the dry road surface, and the noise performance in a balanced manner. Become.

  In the pneumatic tire, a plurality of second tires intersecting the tread portion 1 with respect to the third main groove 13 and having one end closed in the second center land portion 32 and the other end closed in the third center land portion 33. By providing the 3-center lug groove 53, it is possible to further improve the wet performance while maintaining good dry performance, uneven wear resistance and noise performance. The third center lug groove 53 serves to effectively guide water on the road surface into the third main groove 13 without excessively reducing the rigidity of the tread portion 1. Each of the third center lug grooves 53 preferably has a structure bent or curved toward one side in the tire circumferential direction.

  Similarly, a plurality of fourth center lugs intersecting the tread portion 1 with respect to the circumferential narrow groove 14 and having one end closed in the third center land portion 33 and the other end closed in the second shoulder land portion 22. By providing the groove 54, it is possible to further improve the wet performance while maintaining good dry performance, uneven wear resistance and noise performance. The fourth center lug groove 54 serves to effectively guide the water on the road surface into the circumferential narrow groove 14 without excessively reducing the rigidity of the tread portion 1. Each of the fourth center lug grooves 54 preferably has a structure bent or curved toward the other side in the tire circumferential direction.

In the pneumatic tire, as shown in FIG. 2, a distance D ₄₁ from the ground contact end Ein on the vehicle inner side to the closed end on the tire equator side of the first shoulder lug groove ₄₁ is within the ground contact region of the first shoulder land portion 21. set of the range of 50% to 80% of the width W _21, from the vehicle outer side of the ground terminal Eout a distance D ₄₂₁ and the tire width direction outside of the closed end to the tire equator side of the closed end of the second shoulder lug grooves 42 The distance D ₄₂₂ is set in the range of 1% to 50% of the width W ₂₂ in the ground contact area of the second shoulder land portion 22, and is from the first main groove 11 to the closed end of the first center lug groove 51. the distance D ₅₁ is set to a range of 50% to 80% of the width W ₃₁ of the first center land portion 31, the distance D ₅₂ from the second main groove 12 to the closed end of the second center lug grooves 52 and the second center range of 20% to 40% of the width W ₃₂ of the land portion 32 Is set, the distance D ₅₃₁ from the third main groove 13 to the tire equator side of the closed end of the third center lug groove 53 is set to 1% to 20% of the width W ₃₂ of the second center land portion 32, The distance D ₅₃₂ from the third main groove 13 to the closed end of the third center lug groove 53 on the outer side in the tire width direction is set in a range of 20% to 40% of the width W ₃₃ of the third center land portion 33, and is circumferential. The distance D ₅₄₁ from the narrow groove 14 to the closed end of the fourth center lug groove 54 on the tire equator side is set in a range of 20% to 40% of the width W ₃₃ of the third center land portion 33. The distance D ₅₄₂ from the closed center of the fourth center lug groove 54 to the outer side in the tire width direction is set in a range of 20% to 40% of the width W ₂₂ in the contact area of the second shoulder land portion 22. Thereby, wet performance, dry performance, uneven wear resistance, and noise performance can be improved in a balanced manner. That is, if the first shoulder lug groove 41, the second shoulder lug groove 42, the first center lug groove 51, the second center lug groove 52, the third center lug groove 53, and the fourth center lug groove 54 are too long, dry performance or Uneven wear resistance and noise performance deteriorate, and on the contrary, if it is too short, wet performance deteriorates.

Groove width R ₄₁ of the first shoulder lug grooves 41, the maximum value becomes what the maximum groove width Ri of the groove width R ₅₁ and groove width R ₅₂ of the second center lug grooves 52 of the first center lug groove 51, the groove width R ₄₂ 2 shoulder lug grooves 42, the case of the maximum groove width Ro what is the maximum value of the groove width R ₅₄ of the groove width R ₅₃ and fourth center lug grooves 54 of the third center lug grooves 53, The maximum groove width Ri is preferably set larger than the maximum groove width Ro. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface. Moreover, it is advantageous also in reducing the passing sound outside the vehicle. In particular, the ratio Ro / Ri between the maximum groove width Ri and the maximum groove width Ro is preferably in the range of 0.2 to 0.6, more preferably in the range of 0.3 to 0.4. When the ratio Ro / Ri is out of the above range, the effect of improving the dry performance and the wet performance at the same time decreases.

In the pneumatic tire, the inclination angle θ ₄₁ of the first shoulder lug groove 41 with respect to the tire width direction is 15 ° or less, and the inclination angle θ ₅₁ of the first center lug groove 51 with respect to the tire width direction is 15 ° to 50 °. The inclination angle θ ₅₂ of the second center lug groove 52 with respect to the tire width direction is preferably 30 ° to 60 °. As a result, the wet performance during circuit running can be improved, and good steering stability can be maintained even during high-speed turning on a dry road surface. Here, when the inclination angle θ _{41 of} the first shoulder lug groove ₄₁ is too large, the wet performance is deteriorated. Further, if the inclination angle θ _{51 of} the first center lug groove 51 or the inclination angle θ _{52 of} the second center lug groove ₅₂ is too small, the effect of improving the noise performance is reduced, and conversely if too large, the dry performance and uneven wear resistance are reduced. This will reduce the improvement effect. In particular, the inclination angle θ ₄₁ of the first shoulder lug groove 41 is 3 ° to 8 °, the inclination angle θ ₅₁ of the first center lug groove ₅₁ is 20 ° to 40 °, and the inclination of the second center lug groove 52 is The angle θ ₅₂ is preferably 40 ° to 50 °. The inclination angles θ ₄₁ , θ ₅₁ , and θ ₅₂ are straight tire width directions that connect the center positions of the groove widths at both ends in each of the first shoulder lug groove 41, the first center lug groove 51, and the second center lug groove 52. Is an inclination angle with respect to.

  The groove area ratio in the vehicle inner side region that is on the vehicle inner side than the tire equator position CL of the tread portion 1 is 30% to 45%, and in the vehicle outer side region that is on the vehicle outer side than the tire equator position CL of the tread portion 1. The groove area ratio is preferably 10% to 25%. In this way, by reducing the groove area ratio in the area outside the vehicle, the load during cornering can be firmly received, so that good steering stability is maintained even during high-speed turning on a dry road surface. be able to. In particular, the groove area ratio in the vehicle outer region is preferably in the range of 18% to 22%. Moreover, wet performance at the time of circuit driving can be improved by relatively increasing the groove area ratio in the region inside the vehicle. In particular, the groove area ratio in the vehicle inner region is preferably in the range of 36% to 42%. If the groove area ratio in each region is too small, the effect of improving the wet performance is lowered, and conversely if it is too large, the effect of improving the dry performance is lowered.

  In the pneumatic tire described above, for example, the first main shoulder land portion 21, the second shoulder land portion 22, the first center land portion 31, the second center land portion 32, and the third center land portion 33 have first main A chamfered portion can be formed along the groove 11, the second main groove 12, the third main groove 13, or the circumferential narrow groove 14. As the chamfered portion, a chamfered portion made of a flat surface or a curved surface can be adopted. In this way, when the chamfered portion is provided in the tread portion 1, the chamfered portion disposed in the vehicle inner region of the tread portion 1 may be larger than the chamfered portion disposed in the vehicle outer region. For example, in the case of a chamfered portion made of a curved surface, the radius of curvature of the chamfered portion arranged in the vehicle inner region of the tread portion 1 is made larger than the radius of curvature of the chamfered portion arranged in the vehicle outer region, and In this case, the dimension in the groove width direction of the chamfered portion arranged in the vehicle inner region of the tread portion 1 may be made larger than the dimension in the groove width direction of the chamfered portion arranged in the vehicle outer region. As a result, it is possible to maintain good steering stability on a dry road surface while improving the initial wet performance.

FIG. 3 shows the contour shape of the tread portion 1 in the pneumatic tire of the present invention. Note that FIG. 3 shows the outline shape exaggerated for easy understanding of the characteristics of the tread portion 1, and does not necessarily match the actual outline shape. In FIG. 3, the tread portion 1 includes a center reference arc (curvature radius: curvature radius) passing through the edge points P _{2 to} P ₇ on the treads of the first center land portion 31, the second center land portion 32, and the third center land portion 33. the center profile line Lc consisting rc), the first shoulder reference arc which passes through the edge points P ₁ at the tread surface of the first shoulder land portion 21 in contact with respect to the center reference arc (curvature radius: Rin) first shoulder made of have a second shoulder profile line Lout consisting: a profile line Lin, the second shoulder reference arc in contact to the center reference arc through the edge points P ₈ in the tread of the second shoulder land portion 22 (Rout curvature radius) doing. The first shoulder reference arc and the center reference arc are connected without intersecting each other at the groove width center position of the first main groove 11, and the second shoulder reference arc and the center reference arc are the groove width center of the circumferential narrow groove 14. Connected without crossing each other in position. The center reference arc, the first shoulder reference arc, and the second shoulder reference arc are all arcs having a center on the inner side in the tire radial direction. Further, when the land portion of the tread portion 1 has a chamfered portion, the edge point is specified by the intersection of the extension line of the groove wall surface and the extension line of the tread surface of the land portion in the tire meridian cross section.

In the pneumatic tire, the first center land portion 31, the second center land portion 32, and the third center land portion 33 bulge outward from the center profile line Lc in the tire radial direction, and the first center land portion 31, The curvature radii R ₃₁ , R ₃₂ , and R _{33 of} the first arc, the second arc, and the third arc that define the tread surface shapes of the second center land portion 32 and the third center land portion ₃₃ are the curvature radii Rc of the center reference arc, respectively. It is set to be smaller. In this way, the first center land portion 31, the second center land portion 32, and the third center land portion 33 are bulged, thereby the first center land portion 31, the second center land portion 32, and the third center land portion 33. It is possible to increase the contact pressure near the center in the width direction of 33, optimize the contact pressure distribution, and further improve steering stability and uneven wear resistance. In particular, the bulging amount from the center profile line Lc of the first center land portion 31, the second center land portion 32, and the third center land portion 33 is in the range of 0.1 mm to 0.5 mm, more preferably 0.2 mm. It is good to be in the range of ~ 0.3 mm. If the bulging amount is out of the above range, the contact pressure distribution is not optimized, and the effect of improving steering stability and uneven wear resistance is reduced.

In the pneumatic tire, the first shoulder land portion 21 bulges outward in the tire radial direction from the first shoulder profile line Lin, and the first shoulder arc defining the tread shape of the first shoulder land portion 21 is provided. the radius of curvature R ₂₁ is set to be smaller than the radius of curvature Lin first shoulder reference arc, the second shoulder land portion 22 bulges to the outer side in the tire radial direction than the second shoulder profile line Lout, second the second shoulder arc radius of curvature R ₂₂ is set to be smaller than the radius of curvature Rout of the second shoulder reference arc defining the tread shape of the shoulder land portion 22. By bulging the first shoulder land portion 21 and the second shoulder land portion 22 in this manner, the contact pressure near the center in the width direction of the first shoulder land portion 21 and the second shoulder land portion 22 is increased. It is possible to optimize the contact pressure distribution and further improve the handling stability and uneven wear resistance. In particular, the bulge amount of the first shoulder land portion 21 from the first shoulder profile line Lin and the bulge amount of the second shoulder land portion 22 from the second shoulder profile line Lout are each in the range of 0.1 mm to 0.5 mm. More preferably, it is in the range of 0.2 mm to 0.3 mm. If the bulging amount is out of the above range, the contact pressure distribution is not optimized, and the effect of improving steering stability and uneven wear resistance is reduced.

In a pneumatic tire having a tire size of 235 / 40R18 95Y and whose mounting direction with respect to the vehicle is designated, as shown in FIGS. 1 to 3, the tire extends in the tire circumferential direction to a region on the vehicle inner side than the tire equator position of the tread portion. 1 main groove is provided, a second main groove extending in the tire circumferential direction is provided in a region between the tire equator position of the tread portion and the first main groove, and the tire circumference is provided in a region outside the vehicle from the tire equator position of the tread portion. Provided with a third main groove extending in the direction and extending in the tire circumferential direction in a region outside the vehicle with respect to the third main groove of the tread portion and having a groove width narrower than the first main groove to the third main groove. The first shoulder land portion, the second shoulder land portion, and the first center land portion to the third center land portion are defined in the tread portion, and the first shoulder lug groove, the second shoulder lug groove, and the first are defined in the tread portion. center Ragu grooved to fourth center lug grooves, the groove width GW ₁ of the first main groove, the groove width GW ₂ of the second main groove, the groove width GW ₃ of the third main groove, the groove width of the circumferential narrow GW ₄ , First shoulder lug groove width R ₄₁ and inclination angle θ ₄₁ , second shoulder lug groove width R ₄₂ , first center lug groove width R ₅₁ and inclination angle θ ₅₁ and inclination direction (first shoulder Relation to the inclination direction of the lug groove), the groove width R ₅₂ of the second center lug groove, the inclination angle θ ₅₂ , the inclination direction (relation to the inclination direction of the first shoulder lug groove), and the groove width R ₅₃ of the third center lug groove. , Groove width R ₅₄ of the fourth center lug groove, bulge amount of the first shoulder land portion, bulge amount of the second shoulder land portion, bulge amount of the first center land portion, bulge of the second center land portion Amount, the amount of bulging of the third center land portion, the radius of curvature of the chamfered portion formed in the vehicle inner region, and formed in the vehicle outer region. The tires of Examples 1 to 8 in which the radius of curvature of the chamfered portion is set as shown in Table 1 were produced.

  For comparison, as shown in FIG. 4, the tread portion 1 is provided with three main grooves (11, 12, 13) and a circumferential narrow groove (14), and the tread portion has five rows of land portions (21, 22). , 31, 32, 33), and the tire of Conventional Example 1 was prepared in which various lug grooves (41, 42, 51, 52, 53) were provided in the tread portion. Furthermore, the tire of the comparative example 1 which has the structure described in Table 1 was prepared.

  About these test tires, dry performance (steering stability, running time), wet performance (steering stability), uneven wear resistance, and noise performance were evaluated by the following test methods, and the results are also shown in Table 1. . Each evaluation was performed under the condition that the test tire was mounted on a wheel having a rim size of 18 × 8.5 J and mounted on a rear-wheel drive vehicle with a displacement of 3000 cc, and the air pressure after warm-up was 230 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. The best time was calculated for the running time. 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.

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.

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.

Noise performance:
A driving test was conducted by a test driver on a dry road test course, and the passing sound when traveling at 80 km / h was measured. About the noise performance, the magnitude of the passing sound 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 noise performance.

  As can be seen from Table 1, the tires of Examples 1 to 8 can improve wet performance, dry performance, uneven wear resistance, and noise performance in a balanced manner in comparison with Conventional Example 1 and Comparative Example 1. It was.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11 1st main groove 12 2nd main groove 13 3rd main groove 14 Circumferential narrow groove 21 1st shoulder land part 22 2nd shoulder land part 31 1st center land part 32 1st 2 center land part 33 3rd center land part 41 1st shoulder lug groove 42 2nd shoulder lug groove 51 1st center lug groove 52 2nd center lug groove 53 3rd center lug groove 54 4th center lug groove

Claims (13)

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 region inside the vehicle from the tire equator position of the tread portion, and extends in the tire circumferential direction in a region between the tire equator position of the tread portion and the first main groove. A second main groove is provided, a third main groove extending in the tire circumferential direction is provided in a region outside the vehicle from the tire equator position of the tread portion, and the tire is provided in a region outside the vehicle from the third main groove of the tread portion. A circumferential narrow groove extending in the circumferential direction and having a narrower groove width than the first main groove to the third main groove is provided,
A first shoulder land portion is defined on the vehicle inner side than the first main groove, a second shoulder land portion is defined on the vehicle outer side than the circumferential narrow groove, and the first main groove and the second main groove are A first center land portion is defined between the second main groove and the third main groove, and between the third main groove and the circumferential narrow groove. The third center land is divided into
A plurality of first shoulder lug grooves, one end of which reaches the grounding end inside the vehicle and the other end is closed in the first shoulder land portion, and one end reaches the grounding end outside the vehicle and the other end A plurality of second shoulder lug grooves closed within the second shoulder land portion, and a plurality of first center lug grooves whose one end communicates with the first main groove and the other end is closed within the first center land portion; A plurality of second center lug grooves having one end communicating with the second main groove and the other end closed within the second center land portion;
The groove width GW ₁ of the first main groove, the groove width GW ₂ of the second main grooves, the third main groove groove width GW ₃ of a 8Mm～18mm, the groove width GW _1, GW _2, GW ₃ The ratio of the maximum value to the minimum value is in the range of 1.0 to 1.2, and the groove width GW _{4 of the} circumferential narrow groove with respect to the minimum value of the groove widths GW ₁ , GW ₂ , GW _3. The ratio of 0.2 to 0.5,
The first shoulder lug groove, the first center lug groove and the second center lug groove are inclined with respect to the tire width direction, and the inclination directions of the first center lug groove and the second center lug groove are all A pneumatic tire characterized by having a direction opposite to the first shoulder lug groove.   A plurality of third center lug grooves are provided in the tread portion so as to intersect the third main groove and have one end closed in the second center land portion and the other end closed in the third center land portion. The pneumatic tire according to claim 1.   A plurality of fourth center lug grooves are provided in the tread portion so as to intersect the circumferential narrow groove and have one end closed in the third center land portion and the other end closed in the second shoulder land portion. The pneumatic tire according to claim 2.   Of the groove widths of the first shoulder lug groove, the first center lug groove, and the second center lug groove, the maximum groove width Ri is the second shoulder lug groove, the third center lug groove, and the fourth center lug groove. The pneumatic tire according to claim 3, wherein the pneumatic tire is larger than a maximum groove width Ro.   The pneumatic tire according to claim 4, wherein a ratio Ro / Ri between the maximum groove width Ri and the maximum groove width Ro is in a range of 0.2 to 0.6.   The inclination angle of the first shoulder lug groove with respect to the tire width direction is 15 ° or less, and the inclination angle of the first center lug groove with respect to the tire width direction is 15 ° to 50 °. The pneumatic tire according to any one of 5.   The pneumatic tire according to claim 6, wherein an inclination angle of the second center lug groove with respect to a tire width direction is 30 ° to 60 °.   The groove area ratio in the vehicle inner side region that is the vehicle inner side than the tire equator position of the tread portion is 30% to 45%, and in the vehicle outer side region that is the vehicle outer side than the tire equator position of the tread portion. The pneumatic tire according to any one of claims 1 to 7, wherein a groove area ratio is 10% to 25%.   The first center land portion with respect to a center profile line consisting of a center reference arc passing through each edge point on the tread of the first center land portion, the second center land portion, and the third center land portion in a tire meridian section. A first arc that bulges the second center land portion and the third center land portion, and defines a tread surface shape of each of the first center land portion, the second center land portion, and the third center land portion, The pneumatic tire according to any one of claims 1 to 8, wherein the radius of curvature of the second arc and the third arc is smaller than the radius of curvature of the center reference arc.   The bulge amount from the center profile line of the first center land portion, the second center land portion, and the third center land portion is in a range of 0.1 mm to 0.5 mm. Pneumatic tire described in 2.   In the tire meridian cross section, the first shoulder land portion bulges with respect to a first shoulder profile line formed by a first shoulder reference arc passing through an edge point on the tread surface of the first shoulder land portion and in contact with the center reference arc. The radius of curvature of the first shoulder arc defining the tread shape of the first shoulder land portion is smaller than the curvature radius of the first shoulder reference arc, and the edge at the tread surface of the second shoulder land portion in the tire meridian section A second shoulder land portion is bulged with respect to a second shoulder profile line comprising a second shoulder reference arc passing through a point and in contact with the center reference arc to define a tread shape of the second shoulder land portion. The radius of curvature of the shoulder arc is smaller than the radius of curvature of the second shoulder reference arc. The pneumatic tire according to any one of claims 1 to 10.   The amount of bulge from the first shoulder profile line of the first shoulder land portion and the amount of bulge from the second shoulder profile line of the second shoulder land portion are in the range of 0.1 mm to 0.5 mm, respectively. The pneumatic tire according to claim 11.   A chamfered portion is provided in each of the vehicle inner side region that is on the vehicle inner side than the tire equator position of the tread portion and the vehicle outer side region that is on the vehicle outer side than the tire equator position of the tread portion, and is disposed in the vehicle inner side region. The pneumatic tire according to claim 1, wherein the chamfered portion is made larger than the chamfered portion disposed in the vehicle outer region.

Images