JP2018161998A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can make improvement in steering stability on a dry road surface and improvement in steering stability on a wet road surface compatible.SOLUTION: In a pneumatic tire which comprises a tread part 1, a pair of side wall parts 2 and a pair of bead parts 3 and whose mounting direction to a vehicle is specified, a plurality of main grooves 11-14 extending in a tire circumferential direction are formed in the tread part 1. The main grooves 11-14 partition plural rows of ribs 21-25 in the tread part 1, and a plurality of lug grooves 31-35 extending in a tire width direction are formed in each of at least two rows of ribs 21-25. In the lug grooves 31-35, one ends open to the main grooves or ground-contact ends while the other ends terminate in the ribs. Chamfer parts 41-45 are formed in at least one edges of both edges of the lug grooves respectively. Groove widths of the lug grooves 31-35 are set to be relatively smaller outside of the vehicle than inside the vehicle, and chamfer widths of the chamfer parts 41-45 are set to be relatively larger outside the vehicle than inside the vehicle.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire having a tread portion including a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction, and more specifically, the structure of the lug groove and its chamfered portion. The present invention relates to a pneumatic tire that has been devised to achieve both improvement in handling stability on a dry road surface and improvement in handling stability on a wet road surface.

  In the pneumatic tire, a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction are formed in the tread portion. These main grooves and lug grooves greatly contribute to the drainage performance of the tread portion. Furthermore, it has been proposed to improve running performance on wet road surfaces by forming a chamfered portion at the edge of the lug groove (see, for example, Patent Documents 1 to 4).

  In the pneumatic tire having such a tread pattern, when the groove area ratio in the tread portion is increased for the purpose of further improving the running performance on the wet road surface, the rigidity of the tread portion is reduced, so that the dry road surface Driving performance will be reduced. Therefore, at present, it is difficult to improve the steering stability on the dry road surface and the steering stability on the wet road surface by simply adjusting the groove area ratio in the tread portion.

Japanese Patent Laid-Open No. 2006-159665 JP 2006-168911 A JP 2017-1583 A JP 2017-1584 A

  The object of the present invention is to improve the handling stability on the dry road surface and improve the driving stability on the wet road surface by devising the structure of the lug groove and its chamfered portion. To provide tires.

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 provided with a pair of bead portions arranged on the inner side in the tire radial direction of the tire, and a mounting direction for the vehicle is designated,
A plurality of main grooves extending in the tire circumferential direction are formed in the tread portion, and a plurality of rows of ribs are defined in the tread portion by these main grooves, and a plurality of at least two rows of ribs extending in the tire width direction are provided. Lug grooves are formed, each lug groove has one end opened to the main groove or grounding end, the other end terminates in the rib, and a chamfered portion is formed on at least one of both edges of each lug groove. The chamfer width of the chamfered portion is set to be relatively smaller in the lug groove positioned on the vehicle outer side than the lug groove positioned on the vehicle inner side, and the chamfer width of the chamfered portion is positioned on the vehicle outer side than the chamfered portion positioned on the vehicle inner side. It is characterized by being set relatively large in the part.

  In the present invention, a plurality of lug grooves extending in the tire width direction are formed in each of at least two rows, more preferably at least three rows of ribs, and one end of each lug groove is opened to the main groove or the ground contact end. By terminating the other end in the rib, the structure in which the rib is continuous along the tire circumferential direction is maintained, and the rigidity of the rib in the tire circumferential direction is increased to maintain good steering stability on the dry road surface. Can do. In addition, a chamfered portion is formed on at least one of both edges of each lug groove, and the groove width of the lug groove is set to be relatively smaller in the lug groove located on the vehicle outer side than the lug groove located on the vehicle inner side. By setting the chamfering width of the vehicle to be relatively larger at the chamfered portion located outside the vehicle than the chamfered portion located inside the vehicle, the steering stability on the dry road surface and the steering stability on the wet road surface are improved in a balanced manner. be able to. In other words, the groove width of the lug groove located on the outside of the vehicle is improved while the drainage performance is improved by effectively increasing the groove width of the lug groove located on the inside of the vehicle, while the steering stability on the wet road surface is effectively improved. By making the width relatively small, the rigidity of the rib can be increased and the steering stability on the dry road surface can be effectively improved. In addition, even when the groove width of the lug groove located on the outside of the vehicle is relatively small, the drainage performance is improved by relatively increasing the chamfer width of the chamfered portion located on the outside of the vehicle. The steering stability can be maintained well. As a result, it is possible to achieve both improvement in steering stability on a dry road surface and improvement in steering stability on a wet road surface.

  The maximum depth Y of the chamfered portion preferably satisfies the relationship of 1.0 mm ≦ Y ≦ X × 0.4 with respect to the maximum depth X of the lug groove. By appropriately setting the maximum depth Y of the chamfered portion with respect to the maximum depth X of the lug groove in this way, the steering stability on the dry road surface and the steering stability on the wet road surface can be improved in a balanced manner. it can.

  The lug grooves are preferably disposed so as to be inclined with respect to the tire width direction. By inclining the lug groove with respect to the tire width direction, the rigidity of the ribs during tire rotation can be increased and the steering stability on the dry road surface can be improved.

  The ratio A / B of the groove width A of the lug groove to the chamfer width B of the chamfered portion is set to be relatively smaller in the lug groove located on the vehicle outer side than the lug groove located on the vehicle inner side, and the minimum value of the ratio A / B Is set in the range of 0.5 to 2.0, and the maximum value of the ratio A / B is preferably set in the range of 4.0 to 10.0. By setting the ratio A / B of the groove width A of the lug groove to the chamfering width B of the chamfered portion as described above, it is possible to improve the steering stability on the dry road surface and the steering stability on the wet road surface in a balanced manner. .

  Further, the chamfered portion is preferably formed in parallel with the lug groove. By forming the chamfered portion in parallel with the lug groove, drainage performance can be effectively improved while minimizing the decrease in rib rigidity.

  In the present invention, the contact area of the tread portion is 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. Specified based on. The ground contact edge is the outermost position in the tire axial direction of the ground contact region. 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 VARIOUSIOLD” is TRA. The maximum value described in “INFLATION PRESOURS”, “INFLATION PRESOURE” in the case of ETRTO, is 180 kPa when the tire is for a passenger car. “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”. The maximum value described in “INFLATION PRESOURES” is “LOAD CAPACITY” in the case of ETRTO, but when the tire is for a passenger car, the load is equivalent 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 sectional drawing which shows the representative example of a lug groove and its chamfering part. FIG. 6 is a development view showing a modification of the tread pattern of the pneumatic tire of FIG. 1.

  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. Tc means the tire circumferential direction, and Tw means the tire width direction.

  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, four main grooves 11 to 14 extending in the tire circumferential direction are formed in the tread portion 1. By these four main grooves 11 to 14, an inner shoulder rib 21, an inner middle rib 22, a center rib 23, an outer middle rib 24, and an outer shoulder rib 25 are sequentially partitioned in the tread portion 1 from the vehicle inner side to the vehicle outer side. . A plurality of lug grooves 31 to 35 extending in the tire width direction are repeatedly formed in the ribs 21 to 25 along the tire circumferential direction.

  Each of the lug grooves 31 to 35 has one end opened to the main groove or the ground end, and the other end terminated in the rib. More specifically, one end of each lug groove 31 disposed in the inner shoulder rib 21 opens at the ground contact end inside the vehicle, while the other end terminates in the inner shoulder rib 21. One end of each lug groove 32 disposed in the inner middle rib 22 opens into the main groove 11, while the other end terminates in the inner middle rib 22. Each lug groove 33 arranged in the center rib 23 has one end opening in the main groove 12 and the other end terminating in the center rib 23. One end of each lug groove 34 disposed in the outer middle rib 24 opens into the main groove 13, while the other end terminates in the outer middle rib 24. Each lug groove 35 disposed on the outer shoulder rib 25 has one end opened to the grounding end outside the vehicle, and the other end terminated in the outer shoulder rib 25. Chamfered portions 41 to 45 are formed on at least one of both edges of the lug grooves 31 to 35 (that is, the stepping side edge and the kicking side edge), respectively. In particular, the chamfered portions 41 to 45 are preferably formed at both edges of the lug grooves 31 to 35.

  The lug groove 30 shown in FIG. 3 represents the lug grooves 31 to 35, and the chamfered portion 40 represents the chamfered portions 41 to 45. In the present invention, the lug groove 30 has a groove width A in the ground contact area of 1.5 mm or more, more preferably 1.5 mm to 4.5 mm, and the chamfered portion 40 is measured in parallel with the tread surface. The chamfer width B is set to 0.5 mm or more, more preferably in the range of 0.5 mm to 2.0 mm.

In the pneumatic tire, the groove width A of the lug groove 30 (that is, the lug grooves 31 to 35) is set to be relatively smaller on the vehicle outer side than the vehicle inner side, and the chamfered portion 40 (that is, the chamfered portions 41 to 45). The chamfer width B is set relatively larger on the vehicle outer side than on the vehicle inner side. That is, as shown in FIG. 2, the groove width A ₃₁ of the lug groove 31 in the inner shoulder rib 21, the groove width A ₃₂ of the lug groove 32 in the inner middle rib 22, the groove width A ₃₃ of the lug groove 33 in the center rib 23, Regarding the groove width A ₃₄ of the lug groove 34 in the middle rib 24 and the groove width A ₃₅ of the lug groove 35 in the outer shoulder rib 25, the relationship of A ₃₁ > A ₃₂ > A ₃₃ = A ₃₄ = A ₃₅ is established. Further, the chamfered width B ₄₁ of the chamfered portion 41 in the inner shoulder rib 21, the chamfered width B ₄₂ of the chamfered portion 42 in the inner middle rib 22, the chamfered width B ₄₃ of the chamfered portion 43 in the center rib 23, and the chamfered portion 44 in the outer middle rib 24. chamfer width B _44, the chamfer width B ₄₅ of the chamfered portion 45 in the outer shoulder rib 25, the relationship of _{B 41 <B 42 <B 43} = B 44 = B 45 is established. Although the size of the groove width A ₃₁ to A ₃₃ and the chamfer width B ₄₁ .about.B ₄₃ in rib 21 to 23 of three rows is sequentially changed, the groove width A ₃₁ in all of the ribs 21 to 25 to A The size of ₃₅ and the chamfer widths B _{41 to} B ₄₅ may be changed sequentially.

  In the pneumatic tire configured as described above, a plurality of lug grooves 31 to 35 extending in the tire width direction are formed in a plurality of rows of ribs 21 to 25, and one end of the lug grooves 31 to 35 is used as a main groove or a ground contact end. By opening the other end in the rib while opening, the structure in which the ribs 21 to 25 are continuous in the tire circumferential direction is maintained, and the rigidity of the ribs 21 to 25 in the tire circumferential direction is increased to increase the rigidity on the dry road surface. The steering stability can be maintained well. The ribs 21 to 25 as described above may be divided in the tire circumferential direction by sipes having a groove width of less than 1.5 mm. A sipe having a groove width of less than 1.5 mm does not hinder substantial continuity of the ribs 21 to 25 from the viewpoint of rigidity.

Further, in the pneumatic tire, the chamfered portions 41 to 45 are formed on at least one of both edges of the lug grooves 31 to 35, and the groove width A of the lug grooves 31 to 35 is relatively smaller on the vehicle outer side than on the vehicle inner side. By setting and setting the chamfer width B of the chamfered portions 41 to 45 relatively larger on the vehicle outer side than on the vehicle inner side, the steering stability on the dry road surface and the steering stability on the wet road surface are improved in a balanced manner. Can do. In other words, while effectively improve the steering stability on wet road surfaces to improve the drainage performance by increasing relatively groove width A ₃₁ of the lug groove 31 located on the vehicle inner side, lug located on the vehicle outer side By relatively reducing the groove widths A33 to A35 of the grooves _{33 to 35} , the rigidity of the ribs 23 to 25 can be increased, and the steering stability on the dry road surface can be effectively improved. Further, even when the groove width A ₃₃ to A ₃₅ of the lug grooves 33 to 35 which is positioned on the vehicle outer side relatively small, the chamfer width B ₄₃ .about.B ₄₅ of the chamfer 43 to 45 located on the vehicle outer side By relatively increasing the size, the drainage performance can be improved and the steering stability on the wet road surface can be maintained well. As a result, it is possible to achieve both improvement in steering stability on a dry road surface and improvement in steering stability on a wet road surface.

  In the pneumatic tire, as shown in FIG. 3, the maximum depth Y of the chamfered portion 40 satisfies the relationship of 1.0 mm ≦ Y ≦ X × 0.4 with respect to the maximum depth X of the lug groove 30. Good to be. In this way, by appropriately setting the maximum depth Y of the chamfered portion 40 with respect to the maximum depth X of the lug groove 30, the steering stability on the dry road surface and the steering stability on the wet road surface are improved in a well-balanced manner. be able to. Here, if the maximum depth Y of the chamfered portion 40 is smaller than 1 mm, the effect of improving the steering stability on the wet road surface is lowered, and conversely if it is larger than X × 0.4, the steering stability on the dry road surface is reduced. Improvement effect decreases. The maximum depth X of the lug groove 30 is preferably in the range of 2.0 mm to 7.0 mm.

  In the pneumatic tire, the lug grooves 31 to 35 are desirably arranged so as to be inclined with respect to the tire width direction. By inclining the lug grooves 31 to 35 with respect to the tire width direction, the rigidity of the ribs 21 to 25 at the time of tire rotation can be increased, and the steering stability on the dry road surface can be improved. In particular, the inclination angle of the lug grooves 31 to 35 with respect to the tire width direction is preferably in the range of 15 ° to 40 °. The inclination angles of the lug grooves 31 to 35 are the center position in the groove width direction of the grounding end of the lug grooves 31 to 35 or the opening end to the main groove and the center position in the groove width direction of the closed end of the lug grooves 31 to 35. Is an inclination angle with respect to the tire width direction of straight lines connecting each other.

In the pneumatic tire, the ratio A / B of the groove width A of the lug groove 30 (i.e., lug grooves 31 to 35) to the chamfer width B of the chamfered part 40 (i.e., chamfered parts 41 to 45) is larger than that of the vehicle inside. It is set relatively small on the outside, the minimum value of the ratio A / B is set in the range of 0.5 to 2.0, and the maximum value of the ratio A / B is set in the range of 4.0 to 10.0. ing. More specifically, the relationship of A ₃₁ / B ₄₁ > A ₃₂ / B ₄₂ > A ₃₃ / B ₄₃ = A ₃₄ / B ₄₄ = A ₃₅ / B ₄₅ is established. The values of the ratios A ₃₃ / B ₄₃ , A ₃₄ / B ₄₄ , and A ₃₅ / B ₄₅ that are the minimum values of the ratio A / B are set in the range of 0.5 to 2.0. The value of the ratio A ₃₁ / B ₄₁ that is the maximum value is set in the range of 4.0 to 10.0.

  Thus, by setting the ratio A / B of the groove width A of the lug groove 30 to the chamfer width B of the chamfered portion 40 as described above, the steering stability on the dry road surface and the steering stability on the wet road surface are balanced. Can be improved. Here, if the minimum value of the ratio A / B is smaller than 0.5, it is not possible to sufficiently secure the groove width A of the lug groove 30 on the outside of the vehicle. If it is larger than 2.0, the groove width A of the lug groove 30 is increased on the vehicle outer side, and the steering stability on the dry road surface is lowered. On the other hand, if the maximum value of the ratio A / B is smaller than 4.0, it is not possible to sufficiently secure the groove width A of the lug groove 30 inside the vehicle. If it is larger than 0.0, the groove width A of the lug groove 30 increases on the inner side of the vehicle, so that the steering stability on the dry road surface is lowered.

  Furthermore, in the pneumatic tire, the chamfered portions 41 to 45 are preferably formed in parallel to the lug grooves 31 to 35, respectively. By forming the chamfered portions 41 to 45 in parallel with the lug grooves 31 to 35, drainage performance can be effectively improved while minimizing the decrease in rigidity of the ribs 21 to 25, so that the maneuvering on the dry road surface is possible. Stability and handling stability on wet road surfaces can be improved in a well-balanced manner. In other words, if the contours of the lug grooves 31 to 35 and the contours of the chamfered portions 41 to 45 are not parallel to each other, the drainage efficiency is reduced, leading to a wasteful reduction in rigidity.

  FIG. 4 shows a modification of the tread pattern of the pneumatic tire according to the embodiment of the present invention. 4, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

In FIG. 4, the inner shoulder rib 21, inner middle rib 22, center rib 23, outer middle rib 24, and outer shoulder rib 25 are each formed with a plurality of lug grooves 31 to 35 extending in the tire width direction. Only the lug grooves 32 to 34 are provided with chamfered portions 42 to 44, respectively, and the lug grooves 31 and 35 are not provided with the aforementioned chamfered portions 41 and 45. The groove width A of the lug grooves 32 to 34 is set to be relatively smaller on the vehicle outer side than the vehicle inner side, and the chamfering width B of the chamfered portions 42 to 44 is set to be relatively larger on the vehicle outer side than the vehicle inner side. Yes. That is, the groove width A ₃₂ of the lug groove 32 in the inner middle rib 22, the groove width A ₃₃ of the lug groove 33 in the center rib 23, and the groove width A ₃₄ of the lug groove 34 in the outer middle rib 24 are A ₃₂ > A ₃₃ > A _34. The relationship is established. Further, the chamfer width B ₄₂ of the chamfered portion 42 in the inner middle rib 22, chamfer width of the chamfered portion 43 in the center rib 23 B _43, the chamfer width B ₄₄ of the chamfered portion 44 in the outer middle rib _{24, B 42 <B 43 <} B 44 The relationship is established.

  In this case as well, as in the above-described embodiment, it is possible to achieve both improvement in steering stability on a dry road surface and improvement in steering stability on a wet road surface. Thus, it is not necessary to provide the lug grooves 30 and the chamfered portions 40 on all the ribs 21 to 25 formed on the tread portion 1, and at least two rows, more preferably at least three rows of the lug grooves 30 and the chamfered portions are provided. A desired effect can be obtained by forming 40 and defining the size relationship between the groove width A and the chamfer width B.

  In the above-described embodiment, the case where four main grooves are provided in the tread portion and five rows of ribs are defined has been described. However, in the present invention, two to five main grooves extending in the tire circumferential direction are provided in the tread portion. It is preferably applied to a tread pattern provided with

In a pneumatic tire having a tire size of 245 / 45R20, a tread portion, a pair of sidewall portions, and a pair of bead portions, and a mounting direction with respect to the vehicle is designated, as shown in FIG. Four main grooves extending in the direction are formed, five rows of ribs are defined in the tread portion by these main grooves, and a plurality of lug grooves extending in the tire width direction are formed in each of the ribs. One end opens to the main groove or grounding end, the other end terminates in the rib, and a chamfered portion is formed on both edges of each lug groove, the maximum depth X of the lug groove, the maximum depth Y of the chamfered portion, Table 1 shows the groove width A (A _{31 to} A ₃₅ ) of each lug groove, the chamfer width B (B _{41 to} B ₄₅ ) of each chamfered portion, the minimum value of the ratio A / B, and the maximum value of the ratio A / B. The tire of the conventional example set to 1 and the comparative example 1 and Examples 1-6 was manufactured. In the test tire, the lug groove was disposed so as to be inclined with respect to the tire width direction, and the chamfered portion was formed in parallel with the lug groove.

  About these test tires, the steering stability on the dry road surface and the steering stability on the wet road surface were evaluated by the following test methods, and the results are also shown in Table 1.

Steering stability on dry roads:
Each test tire was assembled to a wheel with a rim size of 20 × 8.0 J and mounted on a test vehicle. The air pressure was set to 230 kPa, and a sensory evaluation was performed by a test driver when traveling on a dry road surface. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the dry road surface.

Steering stability on wet surfaces:
Each test tire was assembled on a wheel having a rim size of 20 × 8.0 J and mounted on a test vehicle. The air pressure was set to 230 kPa, and sensory evaluation was performed by a test driver when traveling on a wet road surface. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the wet road surface.

  As can be seen from Table 1, in the tires of Examples 1 to 6, the steering stability on the dry road surface and the steering stability on the wet road surface were simultaneously improved in comparison with the conventional example. On the other hand, in Comparative Example 1, since the magnitude relationship between the groove width of the lug groove and the chamfer width of the chamfered portion is reversed from that in Example 1, both the steering stability on the dry road surface and the steering stability on the wet road surface are both achieved. It was getting worse.

1 Tread portion 2 Side wall portion 3 Bead portion 11, 12, 13, 14 Main groove 21, 22, 23, 24, 25 Rib 31, 32, 33, 34, 35 Lug groove 41, 42, 43, 44, 45 Chamfer Part

Claims (6)

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 plurality of main grooves extending in the tire circumferential direction are formed in the tread portion, and a plurality of rows of ribs are defined in the tread portion by these main grooves, and a plurality of at least two rows of ribs extending in the tire width direction are provided. Lug grooves are formed, each lug groove has one end opened to the main groove or grounding end, the other end terminates in the rib, and a chamfered portion is formed on at least one of both edges of each lug groove. The chamfer width of the chamfered portion is set to be relatively smaller in the lug groove positioned on the vehicle outer side than the lug groove positioned on the vehicle inner side, and the chamfer width of the chamfered portion is positioned on the vehicle outer side than the chamfered portion positioned on the vehicle inner side. A pneumatic tire characterized in that it is set relatively large in the section.   The pneumatic tire according to claim 1, wherein the lug groove and the chamfered portion are formed in each of at least three rows of ribs.   3. The air according to claim 1, wherein the maximum depth Y of the chamfered portion satisfies a relationship of 1.0 mm ≦ Y ≦ X × 0.4 with respect to the maximum depth X of the lug groove. Enter tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the lug grooves are arranged so as to be inclined with respect to the tire width direction.   The ratio A / B of the groove width A of the lug groove to the chamfer width B of the chamfered portion is set to be relatively smaller in the lug groove located on the vehicle outer side than the lug groove located on the vehicle inner side, and the ratio A / B The minimum value is set in the range of 0.5 to 2.0, and the maximum value of the ratio A / B is set in the range of 4.0 to 10.0. The pneumatic tire according to any one of the above.   The pneumatic tire according to any one of claims 1 to 5, wherein the chamfered portion is formed in parallel with the lug groove.

Images