Tire

Abstract

To provide a tire improved in dry grip performance and wet performance at the time of high-load running.SOLUTION: A tire 1 has a tread part 2. The tread part 2 is sectioned into a first land part 7 positioned outside an outer main groove 3B, and a second land part 8, a third land part 9 and a fourth land part 10 which are sequentially arranged adjacent to the first land part 7. A width Wa of the first land part 7 is larger than widths Wb, Wc and Wd of the second land part 8, the third land part 9 and the fourth land part 10. A groove width W2 of the outer main groove 3B is equal to or more than a groove depth of the outer main groove 3B. A groove wall of the outer main groove 3B includes a first groove wall part extending from a groove bottom and a second groove wall part inclining at an angle larger than that of the first groove wall part. On a tire axial direction line X at an arbitrary position in a tire circumferential direction, at least one of a plurality of lateral grooves 5 and at least one of a plurality of sipes 6 cross the tire axial direction line X.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below describes a tire with a specified mounting direction on a vehicle. In the tread portion of this tire, a second main groove, a first main groove, and a third main groove are provided in order from the inner tread end to the outside of the vehicle, whereby an inner shoulder land portion, an inner crown land portion, an outer crown land portion, and an outer shoulder land portion are provided. And, a plurality of closed grooves closed within the land portion are provided in the outer crown land portion, the inner shoulder land portion, and the outer shoulder land portion, respectively. Such a tire is said to exhibit excellent wet performance while maintaining dry grip performance during high-load running such as on a circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in recent years, it has been desired to further improve the dry grip performance and wet performance during high-load running.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a tire capable of improving dry grip performance and wet performance during high-load running.

Means for Solving the Problems

[0006] The present invention relates to a tire having a tread portion, wherein the tread portion has a specified mounting direction on a vehicle, and the tread portion is provided with a plurality of main grooves continuously extending in the tire circumferential direction, a plurality of lateral grooves extending in the tire axial direction, and a plurality of sipes extending in the tire axial direction. The plurality of main grooves include two inner main grooves located on the vehicle inner side of the tire equator and one outer main groove located on the vehicle outer side of the tire equator. The tread portion is divided into a first land portion located on the outer side in the tire axial direction of the outer main groove, a second land portion, a third land portion, and a fourth land portion that are sequentially adjacent to the first land portion. The width of the first land portion in the tire axial direction is larger than the widths of the second land portion, the third land portion, and the fourth land portion in the tire axial direction, respectively. The groove width of the outer main groove is equal to or greater than the groove depth of the outer main groove. The outer main groove has a groove bottom and a pair of groove walls, and each of the pair of groove walls includes a first groove wall portion extending radially outward from the groove bottom in the tire radius direction and a second groove wall portion inclined at an angle larger than that with respect to the tread normal line than the first groove wall portion. The plurality of lateral grooves and the plurality of sipes are arranged such that at least one of the plurality of lateral grooves and the plurality of sipes intersects the tire axial line at an arbitrary position in the tire circumferential direction.

[0007] It is desirable that each of the plurality of lateral grooves of the tire according to the present invention is inclined in a first direction with respect to the tire axial direction.

[0008] It is desirable that each of the plurality of sipes of the tire according to the present invention is inclined in the first direction.

[0009] It is desirable that the plurality of lateral grooves of the tire according to the present invention include a plurality of outer lateral grooves arranged in the first land portion, and the plurality of outer lateral grooves include a plurality of first outer lateral grooves connected to the outer main groove and a plurality of second outer lateral grooves that terminate within the first land portion without being connected to the outer main groove.

[0010] It is desirable that each of the plurality of second outer lateral grooves is located at the circumferential middle between the first outer lateral grooves adjacent in the tire circumferential direction.

[0011] It is desirable that the distance in the tire axial direction between the inner end in the tire axial direction of the second outer lateral groove and the outer main groove of the tire according to the present invention is 4% to 10% of the tread width.

[0012] It is desirable that the second outer lateral groove of the tire according to the present invention includes a shallow groove portion and a deep groove portion that is located axially outside the shallow groove portion and has a greater groove depth than the shallow groove portion.

[0013] It is desirable that the groove depth of the shallow groove portion of the tire according to the present invention is 20% to 60% of the groove depth of the outer main groove.

[0014] It is desirable that the second outer lateral groove of the tire according to the present invention has a depth change portion in which the groove depth increases from the shallow groove portion toward the deep groove portion, and in a longitudinal sectional view of the depth change portion, the angle of the depth change portion with respect to the tread of the groove bottom is 30 to 80 degrees.

[0015] It is desirable that the lateral groove of the tire according to the present invention includes a second lateral groove that crosses the second land portion, and the second lateral groove is located on an extension line obtained by extending the first outer lateral groove inward of the vehicle.

[0016] It is desirable that the lateral groove of the tire according to the present invention includes a fourth lateral groove disposed in the fourth land portion, and the angle of the fourth lateral groove with respect to the tire axial direction is greater than the angle of the second lateral groove with respect to the tire axial direction.

[0017] It is desirable that the angle of the fourth lateral groove with respect to the tire axial direction is greater than the angle of the outer lateral groove with respect to the tire axial direction.

Advantages of the Invention

[0018] By adopting the above configuration, the tire of the present invention can improve the dry grip performance and wet performance during high-load running.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a developed tread portion 2 of a tire 1 according to an embodiment of the present invention. The present invention is used, for example, for a pneumatic tire for a passenger car that can be driven not only on ordinary roads but also at high speeds on a circuit. However, the present invention is not limited to such tires.

[0021] The direction of mounting the tread portion 2 on the vehicle is specified. As a result, the tread portion 2 has an outer tread end To located on the outer side of the vehicle when the tire 1 is mounted on the vehicle, and an inner tread end Ti located on the inner side of the vehicle when the tire 1 is mounted on the vehicle.

[0022] The outer tread end To and the inner tread end Ti are the outermost grounding positions in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire is grounded on a plane at a camber angle of 0°. The “normal state” means that the tire is rim-mounted on a normal rim, filled with a normal internal pressure, and is in a non-loaded state. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in the above normal state. Further, the separation distance in the tire axial direction between the outer tread end To and the inner tread end Ti is the tread width TW.

[0023] The "regular rim" is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in JATMA, it is the "standard rim"; in TRA, it is the "Design Rim"; and in ETRTO, it is the "Measuring Rim".

[0024] The "regular internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In JATMA, it is the "maximum air pressure"; in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in ETRTO, it is the "INFLATION PRESSURE".

[0025] The "regular load" is the load defined for each tire in a standard system including the standards on which the tire is based. In JATMA, it is the "maximum load capacity"; in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in ETRTO, it is the "LOAD CAPACITY".

[0026] In the tread portion 2 of the present embodiment, a plurality of main grooves 3 continuously extending in the tire circumferential direction, a plurality of lateral grooves 5 extending in the tire axial direction, and a plurality of sipes 6 extending in the tire axial direction are provided. In this specification, the sipe 6 is formed in a cut shape with a width of less than 1.5 mm. The main groove 3 and the lateral groove 5 are formed in a groove shape with a groove width of 1.5 mm or more in this specification.

[0027] In the present embodiment, the plurality of main grooves 3 include two inner main grooves 3A located on the vehicle inner side of the tire equator C and one outer main groove 3B located on the vehicle outer side of the tire equator C. By these main grooves 3, the tread portion 2 is divided into a first land portion 7 located on the outer side in the tire axial direction of the outer main groove 3B, and a second land portion 8, a third land portion 9, and a fourth land portion 10 sequentially adjacent to the first land portion 7.

[0028] The tire axial width Wa of the first land portion 7 is formed to be larger than the respective tire axial widths Wb, Wc, and Wd of the second land portion 8, the third land portion 9, and the fourth land portion 10. Thereby, since the lateral rigidity of the first land portion 7 where the largest lateral force acts during turning running is increased, the dry grip performance during high-load running is improved.

[0029] FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 2 shows a cross-section of the outer main groove 3B. As shown in FIG. 2, the outer main groove 3B has a groove bottom 13 and a pair of groove walls 14. And the pair of groove walls 14 each include a first groove wall portion 15 extending radially outward in the tire radius direction from the groove bottom 13 and a second groove wall portion 16 inclined at an angle α1 larger than that with respect to the tread normal n1 than the first groove wall portion 15. Further, the groove width W1 of the outer main groove 3B is equal to or greater than the groove depth d1 of the outer main groove 3B. Thereby, during turning running, axial collapse and other deformations of the tire in the first land portion 7 and the second land portion 8 are suppressed. For this reason, the handling stability performance is improved. Further, since the deformation of these land portions 7 and 8 is suppressed, it is suppressed that the groove volume of the outer main groove 3B becomes small, so that high wet performance during high-load running is exhibited. When having a groove wall 14 including a first groove wall portion 15 and a second groove wall portion 16 like the outer main groove 3B, the groove width is, in this specification, the length including the second groove wall portion 16.

[0030] As shown in FIG. 1, at least one of the plurality of lateral grooves 5 and the plurality of sipes 6 is arranged to intersect the tire axial line X at an arbitrary position in the tire circumferential direction on the tire axial line X. Thereby, a drainage effect is obtained at an arbitrary position in the tire circumferential direction. Further, with such a configuration, the change in the lateral rigidity of the tread portion 2 in the tire circumferential direction becomes small, so that higher dry grip performance can be obtained.

[0031] In order to enhance the dry grip performance during high-load running, the width Wa of the first land portion 7 is desirably 1.3 times or more, more desirably 1.5 times or more, desirably 2.1 times or less, and more desirably 1.9 times or less of the width Wc of the land portion having the smallest width, which is the third land portion 9 in this embodiment.

[0032] The inner main groove 3A and the outer main groove 3B extend linearly along the tire circumferential direction, for example. Such inner main groove 3A and outer main groove 3B help to smoothly flow the water in the groove. The inner main groove 3A and the outer main groove 3B may extend in a zigzag shape or a wavy shape, for example.

[0033] The groove width W1 of the outer main groove 3B is formed smaller than each of the groove widths W2 of the inner main groove 3A. Such outer main groove 3B maintains a high rigidity of the tread portion 2 on the outer side of the vehicle where a large lateral force acts during turning running, and maintains a high drainage performance during straight running. Although not particularly limited, the groove width W1 of the outer main groove 3B is desirably 0.6 times or more, more desirably 0.7 times or more, desirably 0.9 or less, and more desirably 0.8 times or less of each of the groove widths W2 of the inner main groove 3A.

[0034] As shown in FIG. 2, the groove bottom 13 of the outer main groove 3B includes, for example, a maximum depth portion 13A where the groove depth is maximum, and a pair of arc portions 13B, 13B that are connected to both sides of the maximum depth portion 13A and are convex toward the outside of the outer main groove 3B.

[0035] In the present embodiment, the first groove wall portion 15 and the second groove wall portion 16 extend linearly inside and outside in the tire radial direction. The first groove wall portion 15 and the second groove wall portion 16 may be, for example, arc-shaped with a center inside the outer main groove 3B and convex toward the outside of the outer main groove 3B.

[0036] Although not particularly limited, the length W3 in the groove width direction of the second groove wall portion 16 is desirably 10% or more, more desirably 15% or more, desirably 30% or less, and more desirably 25% or less of the groove width W1 of the outer main groove 3B. The angle α1 of the second groove wall portion 16 is desirably 40 degrees or more, more desirably 50 degrees or more, desirably 75 degrees or less, and more desirably 70 degrees or less. The angle α1 is the angle of the second groove wall portion 16 with respect to the tread normal line n1 located on the outer end 16e in the tire radial direction of the second groove wall portion 16. The tread normal line n1 is the normal line to the tread surface of the land portion.

[0037] In order to enhance the wet performance while maintaining high rigidity of the first land portion 7 and the second land portion 8, the groove width W1 of the outer main groove 3B is desirably 1.5 times or more, more desirably 1.8 times or more, desirably 3.0 times or less, and more desirably 2.7 times or less of the groove depth d1 of the outer main groove 3B.

[0038] As shown in FIG. 1, the inner main groove 3A includes, for example, a first inner main groove 11 adjacent to the tire equator C, and a second inner main groove 12 disposed closer to the inner tread end Ti side than the first inner main groove 11. The groove width W2a of the first inner main groove 11 is larger than the groove width W2b of the second inner main groove 12. Thereby, the drainage performance in the vicinity of the tire equator C where drainage is difficult is enhanced, and excellent wet performance is exhibited. Although not particularly limited, the groove width W2a of the first inner main groove 11 is desirably 1.1 times or more, more desirably 1.2 times or more, desirably 1.5 times or less, and more desirably 1.4 times or less of the groove width W2b of the second inner main groove 12.

[0039] FIG. 3(a) is a cross-sectional view taken along line B-B of FIG. 1. In FIG. 3(a), the cross-section of the first inner main groove 11 is shown. As shown in FIG. 3(a), the groove wall 14 of the first inner main groove 11 includes a first outer groove wall 18 extending from the groove bottom 13 toward the outer tread end To side, and a first inner groove wall 19 extending from the groove bottom 13 toward the inner tread end Ti side. The first outer groove wall 18 includes a first groove wall portion 15 connected to the groove bottom 13, and a second groove wall portion 16 inclined at an angle α2 larger than that with respect to the tread normal n2 than the first groove wall portion 15. The first inner groove wall 19 is formed only by the first groove wall portion 15 without having the second groove wall portion 16.

[0040] FIG. 3(b) is a cross-sectional view taken along line C-C of FIG. 1. In FIG. 3(b), the cross-section of the second inner main groove 12 is shown. As shown in FIG. 3(b), the first inner main groove 11 includes a pair of groove walls 14 extending from the groove bottom 13. Each of the pair of groove walls 14 is formed only by the first groove wall portion 15 without having the second groove wall portion 16.

[0041] Thus, in this embodiment, the pair of groove walls 14 of the outer main groove 3B and the first outer groove wall 18 of the first inner main groove 11 include a first groove wall portion 15 and a second groove wall portion 16. Also, the first inner groove wall 19 of the first inner main groove 11 and the pair of groove walls 14 of the second inner main groove 12 are formed only by the first groove wall portion 15. Thereby, since the rigidity balance between the vehicle inner region and the vehicle outer region of the tread portion 2 is excellent, the dry grip performance and the wet performance during high load running are further improved.

[0042] The pair of groove walls 14 of the second inner main groove 12 include a second outer groove wall 14a extending from the groove bottom 13 toward the outer tread end To side and a second inner groove wall 14b extending from the groove bottom 13 toward the inner tread end Ti side. And the angle α4 of the second outer groove wall 14a with respect to the tread normal line n4 is formed smaller than the angle α5 of the second inner groove wall 14b with respect to the tread normal line n5. The angle α4 of the second outer groove wall 14a is preferably, for example, from 20 degrees to 40 degrees. The angle α5 of the second inner groove wall 14b is preferably, for example, from 30 degrees to 50 degrees. The angle α5 of the second inner groove wall 14b is preferably, for example, the same as the angle α3 (shown in FIG. 3(a)) of the first inner groove wall 19 with respect to the tread normal line n3.

[0043] In this embodiment, the groove width W2a of the first inner main groove 11 is equal to or greater than the groove depth d2a of the first inner main groove 11. In this embodiment, the groove width W2b of the second inner main groove 12 is equal to or greater than the groove depth d2b of the second inner main groove 12. Thereby, the change in the rigidity of each land portion 8 - 10 is reduced, and the dry grip performance during high load running is maintained high.

[0044] As shown in FIG. 1, each of the lateral grooves 5 is inclined in a first direction (in FIG. 1, upward to the right) with respect to the tire axis direction. Thereby, by utilizing the rotation of the tire 1, the water in the main groove 3 and the lateral grooves 5 is smoothly discharged toward one side in the tire axis direction.

[0045] In this embodiment, the lateral grooves 5 include a plurality of outer lateral grooves 20 disposed in the first land portion 7, a second lateral groove 21 crossing the second land portion 8, and a fourth lateral groove 24 disposed in the fourth land portion 10. The lateral grooves 5 include, for example, a second small lateral groove 22 disposed in the second land portion 8 and having an outer end 22e in the tire axial direction terminating within the second land portion 8, and a third lateral groove 23 disposed in the third land portion 9.

[0046] FIG. 4 is an enlarged view of the first land portion 7 and the second land portion 8. As shown in FIG. 4, the outer lateral grooves 20 include a plurality of first outer lateral grooves 25 connected to the outer main groove 3B and a plurality of second outer lateral grooves 26 terminating within the first land portion 7 without being connected to the outer main groove 3B. Such first outer lateral grooves 25 can discharge the water in the grooves to the outer main groove 3B. The second outer lateral grooves 26 suppress an excessive decrease in the rigidity of the first land portion 7 near the outer main groove 3B.

[0047] The first outer lateral grooves 25 cross, for example, the first land portion 7. In this embodiment, the second outer lateral grooves 26 are connected to the outer tread end To. Such first outer lateral grooves 25 and second outer lateral grooves 26 smoothly discharge the water in the grooves from the outer tread end To.

[0048] Each of the second outer lateral grooves 26 is located in the middle in the tire circumferential direction between the first outer lateral grooves 25, 25 adjacent in the tire circumferential direction. Thereby, the rigidity of the first land portion 7 in the tire circumferential direction is equalized. The "middle in the tire circumferential direction" herein includes, of course, a position separated by 50% of the separation distance Ls in the tire circumferential direction from the first outer lateral groove 25 in the tire circumferential direction, and also includes a position separated by 40% to 60% of the separation distance Ls.

[0049] The separation distance L1 in the tire axial direction between the inner end 26i in the tire axial direction of the second outer lateral groove 26 and the outer main groove 3B is desirably 4% or more, more desirably 6% or more, desirably 10% or less, and more desirably 8% or less of the tread width TW. Since the separation distance L1 is 4% or more of the tread width TW, an excessive decrease in the rigidity of the first land portion 7 is suppressed. Since the separation distance L1 is 10% or less of the tread width TW, wet performance is exhibited.

[0050] FIG. 5 is a cross-sectional view taken along line D-D of FIG. 1. FIG. 5 shows a longitudinal section of the second outer lateral groove 26. As shown in FIGS. 4 and 5, the second outer lateral groove 26 includes a shallow groove portion 28 and a deep groove portion 29 that is located on the outer side in the tire axial direction of the shallow groove portion 28 and has a greater groove depth than the shallow groove portion 28. In this way, since the shallow groove portion 28 is provided on the side closer to the outer main groove 3B, the land rigidity in the vicinity of the outer main groove 3B, where the rigidity is likely to be small, can be maintained high.

[0051] The second outer lateral groove 26 has a depth change portion 30 in which the groove depth increases from the shallow groove portion 28 toward the deep groove portion 29. Such a depth change portion 30 alleviates the rigidity step of the first land portion 7. In order to exhibit such an effect, the angle β of the groove bottom 30s of the depth change portion 30 with respect to the tread surface 7a is desirably 80 degrees or less, and more desirably 70 degrees or less. If the angle β is excessively small, the groove volume of the second outer lateral groove 26 may become small. Therefore, the angle β is desirably 30 degrees or more, and more desirably 45 degrees or more.

[0052] In order to more effectively exhibit the above-described action, the groove depth d4 of the shallow groove portion 28 is desirably 20% or more, more desirably 30% or more, desirably 60% or less, and more desirably 50% or less of the groove depth d1 of the outer main groove 3B. Also, the groove depth d5 of the deep groove portion 29 is 3 to 7 mm.

[0053] As shown in FIG. 4, the length L3 in the tire axial direction of the shallow groove portion 28 is desirably 20% or more, more desirably 25% or more, desirably 40% or less, and more desirably 35% or less of the length L2 in the tire axial direction of the second outer lateral groove 26.

[0054] It is desirable that the groove width W4 of the first outer lateral groove 25 is the same as the groove width W5 of the second outer lateral groove 26. Thereby, the rigidity step of the first land portion 7 is maintained small. In this specification, "the same" in terms of the groove widths means that not only the difference between these groove widths is 0 mm, but also embodiments where the difference between the groove widths is 2 mm or less are included. The groove width W5 of the second outer lateral groove 26 is desirably 2% or more of the tread width TW, more desirably 3% or more, desirably 7% or less, and more desirably 6% or less.

[0055] The first outer lateral groove 25 and the second outer lateral groove 26 are each inclined at the same angle θ1 with respect to the tire axial direction. Thereby, an excessive decrease in the rigidity of the first land portion 7 is suppressed. In this specification, the angle θa of each lateral groove 5 is the angle of a virtual straight line 5n (shown in FIG. 6) that connects the outer end 5e (for a groove extending beyond the tread end, it is the tread end) and the inner end 5i of the groove center line 5c in the tire axial direction by a straight line. In this specification, the "same angle" means that not only the difference between the angles of these lateral grooves is 0 degrees, but also cases within ±10 degrees are included.

[0056] The second lateral groove 21 is located on an extension line K obtained by extending the first outer lateral groove 25 toward the vehicle inner side. Thereby, the water in the second lateral groove 21 is smoothly discharged to the outside of the outer tread end To through the first outer lateral groove 25. "The second lateral groove 21 is located on the extension line K" means that in this specification, not only the case where the extension line K obtained by extending the groove center line 25c of the first outer lateral groove 25 overlaps with the groove center line 21c of the second lateral groove 21, but also the case where it overlaps with the inner and outer openings 21a, 21b of the second lateral groove 21 in the tire axial direction is included.

[0057] The second small lateral groove 22 is connected to, for example, the first inner main groove 11. Further, the outer end 22e of the second small lateral groove 22 is located at the middle in the tire axial direction of the second land portion 8. Such a second small lateral groove 22 enhances the drainage performance while suppressing a decrease in the land rigidity on the outer main groove 3B side of the second land portion 8. The "middle in the tire axial direction" means that in this specification, it is of course the position separated by 50% of the width Wb of the second land portion 8 in the tire axial direction from the outer main groove 3B toward the tire equator C side, and also includes the position separated by 40% to 60% of the width Wb in the tire axial direction.

[0058] The second circumferential groove 21 and the second minor circumferential groove 22 are each inclined at the same angle θ2 with respect to the tire axial direction. Thereby, an excessive decrease in the rigidity of the second land portion 8 is suppressed. In the present embodiment, the angles θ2 of the second circumferential groove 21 and the second minor circumferential groove 22 are the same as the angle θ1 of the first outer circumferential groove 25 and the second outer circumferential groove 26.

[0059] It is desirable that the groove width W6 of the second circumferential groove 21 and the groove width W7 (maximum width) of the second minor circumferential groove 22 are the same. In the present embodiment, the groove width W6 of the second circumferential groove 21 and the groove width W7 of the second minor circumferential groove 22 are the same as the groove width W4 of the first outer circumferential groove 25 and the groove width W5 of the second outer circumferential groove 26.

[0060] FIG. 6 is an enlarged view of the third land portion 9 and the fourth land portion 10 in FIG. 1. As shown in FIG. 6, in the present embodiment, the third circumferential groove 23 includes a third inner circumferential groove 33 and a third outer circumferential groove 34. The third inner circumferential groove 33 extends, for example, outward in the tire axial direction from the first inner main groove 11 and terminates within the third land portion 9. In the present embodiment, the length of the third inner circumferential groove 33 in the tire circumferential direction continuously decreases outward in the tire axial direction. The third outer circumferential groove 34 extends, for example, inward in the tire axial direction from the second inner main groove 12 and terminates within the third land portion 9. In the present embodiment, the length of the third outer circumferential groove 34 in the tire circumferential direction continuously decreases inward in the tire axial direction.

[0061] It is desirable that the length L5 in the tire axial direction of the third inner circumferential groove 33 and the length L6 in the tire axial direction of the third outer circumferential groove 34 are each 35% or less, more desirably 25% or less, of the width Wc of the third land portion 9. Thereby, the rigidity of the third land portion 9 is maintained high. From the viewpoint of enhancing drainage performance, the length L5 of the third inner circumferential groove 33 and the length L6 of the third outer circumferential groove 34 are desirably 10% or more, desirably 15% or more, of the width Wc of the third land portion 9.

[0062] In the present embodiment, the angle θ3 of the fourth lateral groove 24 with respect to the tire axial direction is formed larger than the angle θ2 of the second lateral groove 21 (shown in FIG. 4). Thereby, during turning travel, in the fourth land portion 10 where a relatively small lateral force acts, the water in the fourth lateral groove 24 is smoothly discharged to the outside of the second inner main groove 12 or the outer side of the inner tread end Ti. Further, during straight running, the rigidity in the tire circumferential direction of the second land portion 8 where a relatively large ground pressure acts is maintained high. In the present embodiment, the angle θ3 of the fourth lateral groove 24 is formed larger than the angle θ2 of the second small lateral groove 22.

[0063] In order to more effectively exhibit the above-described action, in the present embodiment, the angle θ3 of the fourth lateral groove 24 is formed larger than the angle θ1 of the outer lateral groove 20 (shown in FIG. 4). The angle θ3 of the fourth lateral groove 24 is formed larger than the angle θ1 of, for example, the first outer lateral groove 25 and the angle θ1 of the second outer lateral groove 26.

[0064] Although not particularly limited, the angle θ3 of the fourth lateral groove 24 is desirably 20 degrees or more, more desirably 30 degrees or more, desirably 60 degrees or less, and more desirably 45 degrees or less. The angle θ1 of the outer lateral groove 20, the angle θ2 of the second lateral groove 21, and the angle θ2 of the second small lateral groove 22 are desirably 5 degrees or more, more desirably 10 degrees or more, desirably 40 degrees or less, and more desirably 30 degrees or less.

[0065] The fourth lateral groove 24 includes, for example, a fourth inner lateral groove 36 and a fourth outer lateral groove 37. In the present embodiment, the fourth inner lateral groove 36 extends outward in the tire axial direction from the second inner main groove 12 and terminates within the fourth land portion 10. In the present embodiment, the fourth outer lateral groove 37 extends inward in the tire axial direction from the inner tread end Ti and terminates within the fourth land portion 10.

[0066] The outer end 36e in the tire axial direction of the fourth inner lateral groove 36 is located outside in the tire axial direction than the inner end 37i in the tire axial direction of the fourth outer lateral groove 37. In other words, the fourth inner lateral groove 36 and the fourth outer lateral groove 37 overlap in the tire axial direction. Such a fourth lateral groove 24 enhances wet performance.

[0067] It is desirable that the groove width W8a of the fourth inner lateral groove 36 is the same as the groove width W8b of the fourth outer lateral groove 37. Such a fourth lateral groove 24 reduces the change in rigidity of the fourth land portion 10. The groove width W8 of the fourth lateral groove 24 is desirably 15% or more, more desirably 20% or more, desirably 35% or less, and more desirably 30% or less of the width Wd of the fourth land portion 10.

[0068] The groove width W8 of the fourth lateral groove 24 is formed to be larger than the groove widths W4, W5 of the outer lateral grooves 20, and the groove widths W6, W7 of the second lateral groove 21 and the second small lateral groove 22. Thereby, in the fourth land portion 10, the wet performance is enhanced, and in the first land portion 7 and the second land portion 8, the rigidities of these land portions are maintained high. Although not particularly limited, the groove width W8 of the fourth lateral groove 24 is desirably 1.10 times or more, more desirably 1.15 times or more, desirably 1.30 times or less, and more desirably 1.25 times or less of the groove width W4 of the first outer lateral groove 25.

[0069] As shown in FIG. 1, each of the sipes 6 is inclined in the first direction. Such sipes 6 further enhance the wet performance.

[0070] As shown in FIGS. 4 and 6, in this embodiment, the sipes 6 include a second sipe 42 disposed in the second land portion 8, a third sipe 43 disposed in the third land portion 9, and a fourth sipe 44 disposed in the fourth land portion 10.

[0071] In this embodiment, the second sipe 42 connects the second small lateral groove 22 and the outer main groove 3B. In this embodiment, the third sipe 43 connects the third inner lateral groove 33 and the third outer lateral groove 34. In this embodiment, the fourth sipe 44 connects the fourth inner lateral groove 36 and the inner tread end Ti.

[0072] The angle θ6 of the fourth sip 44 with respect to the tire axial direction is formed to be larger than the angle θ4 of the second sip 42 with respect to the tire axial direction and the angle θ5 of the third sip 43 with respect to the tire axial direction. The angle θ6 of the fourth sip 44 is desirably 20 degrees or more, more desirably 30 degrees or more, desirably 60 degrees or less, and more desirably 45 degrees or less. The angle θ4 of the second sip 42 and the angle θ5 of the third sip 43 are desirably 5 degrees or more, more desirably 10 degrees or more, desirably 40 degrees or less, and more desirably 30 degrees or less.

[0073] The land-to-groove ratio (S / L) of the tread portion 2 of the present embodiment is desirably 15% or more, more desirably 20% or more, desirably 35% or less, and more desirably 30% or less. The land-to-groove ratio is the ratio of the total area (L) of the tread surfaces of each land portion 7 - 10 and the total area (S) of the grooves at the same height position as the tread surface.

[0074] As shown in FIG. 1, in the present embodiment, the groove width WA of each main groove 3 is formed to be larger than the groove width WB of each lateral groove 5. Also, the groove width WA of the main groove 3, the groove width WB of each lateral groove 5, and the width WC of each sip 6 are constant.

[0075] As described above, although one embodiment of the present invention has been described in detail, the present invention is not limited to the above specific embodiment and can be implemented in various forms.

Example

[0076] A tire having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. Then, the dry grip performance and wet performance of each test tire were tested. The common specifications of each test tire and the test method are as follows.

[0077] <Dry grip performance> Each test tire was mounted on all the wheels of the following test vehicle. The test driver drove the test vehicle at high speed on a test course with a dry asphalt road surface. The dry grip performance based on the stability and operability at this time was evaluated by the sensory evaluation of the test driver. The results are shown in scores with Comparative Example 1 set as 100. The larger the numerical value, the better. If the value is 90 or less, the tire fails. Tire size: 245 / 40R18 Rim: 18×8.5J Inner pressure (kPa): 220 (all wheels) Vehicle: Four-wheel drive vehicle with a displacement of 2000 cc

[0078] <Wet performance> The test driver drove the above test vehicle on an asphalt road surface with a radius of 100 m where there was a 5-mm-deep puddle. Then, the lateral acceleration of the front wheels at this time was measured. The lateral acceleration is the average lateral G of the front wheels at a speed of 55 - 80 km / h. The results are shown in an index with the value of the average lateral G of Comparative Example 1 set as 100. The larger the numerical value, the better. If the value is 90 or less, the tire fails. The test results are shown in Tables 1 - 4. In each example, there are three main grooves. Also, in the table, "A" indicates that the second outer lateral groove is closer to the first outer lateral groove than the middle position in the tire circumferential direction between the first outer lateral grooves. In the table, "B" indicates that the second lateral groove is at a position deviating from the extension line of the first outer lateral groove. In the table, "C" indicates that the second lateral groove is located on the extension line of the first outer lateral groove. Comparative Example 1 and Comparative Example 2 are modes where the groove wall of the outer main groove is formed only by the first groove wall part and the second groove wall part is not provided, and in the second outer lateral groove, no shallow groove part is provided.

[0079]

Table 1

[0080]

Table 2

[0081]

Table 3

[0082]

Table 4

[0083] As a result of the test, it is understood that the tire of the example has improved dry grip performance and wet performance compared to the tire of the comparative example.

Explanation of Signs

[0084] 1 Tire 2 Tread portion 3A Outer main groove 5 Cross groove 6 Sipe 7 First land portion 8 Second land portion 9 Third land portion 10 Fourth land portion 13 Groove bottom 14 Groove wall 15 First groove wall portion 16 Second groove wall portion X Tire axial direction line

Claims

1. A tire having a tread portion, wherein the tread portion has a specified mounting direction on the vehicle, the tread portion is provided with a plurality of main grooves extending continuously in the tire circumferential direction, a plurality of lateral grooves extending in the tire axial direction, and a plurality of sipes extending in the tire axial direction, the plurality of main grooves include two inner main grooves located on the inner side of the vehicle relative to the tire equator and one outer main groove located on the outer side of the vehicle relative to the tire equator, the tread portion is divided into a first land portion located on the outer side in the tire axial direction of the outer main groove, and a second land portion, a third land portion, and a fourth land portion sequentially adjacent to the first land portion, the width of the first land portion in the tire axial direction is larger than the width of each of the second land portion, the third land portion, and the fourth land portion in the tire axial direction, the groove width of the outer main groove is equal to or greater than the groove depth of the outer main groove, the outer main groove has a groove bottom and a pair of groove walls, each of the pair of groove walls includes a first groove wall portion extending radially outward from the groove bottom in the tire radius direction and a second groove wall portion inclined at an angle greater than that with respect to the tread normal line than the first groove wall portion, the plurality of lateral grooves and the plurality of sipes are arranged such that at least one of the plurality of lateral grooves and the plurality of sipes intersects the tire axial direction line on the tire axial direction line at an arbitrary position in the tire circumferential direction, the tread portion has an outer tread end located on the outer side of the vehicle when mounted on the vehicle, the plurality of lateral grooves include a plurality of outer lateral grooves arranged in the first land portion, the plurality of outer lateral grooves include a plurality of first outer lateral grooves connected to the outer main groove and a plurality of second outer lateral grooves terminating within the first land portion without being connected to the outer main groove, the first outer main groove is connected to the outer tread end, the lateral grooves include a second lateral groove crossing the second land portion, the second lateral groove is located on an extension line obtained by extending the first outer lateral groove inward of the vehicle, a tire.

2. The tire according to claim 1, wherein each of the plurality of lateral grooves is inclined in a first direction with respect to the tire axial direction.

3. The tire according to claim 2, wherein each of the plurality of sipes is inclined in the first direction.

4. The tire according to any one of claims 1 to 3, wherein each of the plurality of second outer lateral grooves is located at the middle in the tire circumferential direction between the first outer lateral grooves adjacent in the tire circumferential direction.

5. The separation distance in the tire axial direction between the inner end in the tire axial direction of the second outer lateral groove and the outer main groove is 4% to 10% of the tread width. The tire according to any one of Claims 1 to 4.

6. The second outer lateral groove includes a shallow groove portion and a deep groove portion that is located axially outside the tire of the shallow groove portion and has a greater groove depth than the shallow groove portion. The tire according to any one of Claims 1 to 5.

7. The groove depth of the shallow groove portion is 20% to 60% of the groove depth of the outer main groove. The tire according to Claim 6.

8. The second outer lateral groove has a depth change portion in which the groove depth increases from the shallow groove portion toward the deep groove portion. In a longitudinal cross-sectional view of the depth change portion, the angle of the depth change portion with respect to the tread surface of the groove bottom is 30 to 80 degrees. The tire according to Claim 6 or 7.

9. The lateral groove includes a fourth lateral groove disposed in the fourth land portion. The angle of the fourth lateral groove with respect to the tire axial direction is greater than the angle of the second lateral groove with respect to the tire axial direction. The tire according to any one of Claims 1 to 8.

10. The angle of the fourth lateral groove with respect to the tire axial direction is greater than the angle of the outer lateral groove with respect to the tire axial direction. The tire according to Claim 9.

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