Tire

Abstract

To provide a tire having improved dry grip performance, uneven wear resistance performance and wet performance during high-load traveling.SOLUTION: Provided is a tire 1 whose mounting direction to a vehicle is prescribed. A plurality of major grooves 3 includes an inside major groove 3A located on the side of a second tread end Ti, and an outside major groove 3B located on the side of a first tread end To. The outside major groove 3B includes a pair of groove walls and a groove bottom. The pair of groove walls includes a first groove wall part extending toward the outside of a tire radial direction from the groove bottom, and a second groove wall part 16 located outside from the first groove part in the tire radial direction, and inclined at a larger angle than the first groove wall part with respect to a tread normal. An angle θ2 with respect to the tread normal of the second groove wall part 16 is 40-75 degrees.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure 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 second tread end toward the outside of the vehicle. And, while specifying the arrangement of the first main groove to the third main groove, the groove width of the third main groove is made smaller than the groove widths of the first main groove and the second main groove. Such a tire is said to exhibit excellent wet performance while maintaining dry grip performance and uneven wear resistance during high-load driving 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, for example, during high-load driving such as circuit driving, it has been desired to further improve dry grip performance, uneven wear resistance, and wet performance.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object is to provide a tire capable of improving dry grip performance, uneven wear resistance, and wet performance during high-load driving such as circuit driving.

Means for Solving the Problems

[0006] The present disclosure relates to a tire having a tread portion with a defined mounting orientation on a vehicle. The tread portion includes a first tread end and a second tread end that are respectively located on the outer side and the inner side of the vehicle when mounted on the vehicle, and a plurality of main grooves that continuously extend in the tire circumferential direction between the first tread end and the second tread end. The plurality of main grooves include two inner main grooves whose groove center lines are located on the side of the second tread end with respect to the tire equator, and one outer main groove whose groove center line is located on the side of the first tread end with respect to the tire equator. The outer main groove includes a pair of groove walls and a groove bottom. Each of the pair of groove walls includes a first groove wall portion that extends outward in the tire radial direction from the groove bottom, and a second groove wall portion that is located on the outer side in the tire radial direction with respect to the first groove wall portion and is inclined at an angle greater than that of the first groove wall portion with respect to the tread normal. The angle θ2 of the second groove wall portion with respect to the tread normal is 40 to 75 degrees.

Advantages of the Invention

[0007] By adopting the above configuration, the tire of the present disclosure can improve the dry grip performance, uneven wear resistance performance, and wet performance during high-load running such as circuit running.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a plan view showing the tread portion 2 of a tire 1 according to an embodiment of the present disclosure developed. The tire 1 of the present disclosure is used, for example, for a pneumatic tire for a passenger car that can travel at high speed on a circuit in addition to normal driving on a public road. However, the tire 1 of the present disclosure is also used, for example, for a pneumatic tire for heavy loads or motorcycles, or a non-pneumatic tire that is not filled with compressed air inside.

[0010] The mounting direction of the tread portion 2 on the vehicle is defined. Accordingly, the tread portion 2 has a first tread end To located on the outer side of the vehicle when the tire 1 is mounted on the vehicle, and a second tread end Ti located on the inner side of the vehicle.

[0011] The first tread end To and the second 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 with a camber angle of 0°. The "normal state" means that the tire 1 is rim-mounted on a normal rim and filled with a normal internal pressure, and moreover, it is in a no-load 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 first tread end To and the second tread end Ti is the tread width TW.

[0012] The "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire 1 is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0013] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards on which Tire 1 is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0014] The "normal load" is the load defined for each tire in a standard system including the standards on which Tire 1 is based. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY".

[0015] The tread portion 2 of the present embodiment includes a plurality of main grooves 3 that continuously extend in the tire circumferential direction between a first tread end To and a second tread end Ti.

[0016] In the present embodiment, the plurality of main grooves 3 include two inner main grooves 3A whose groove center lines 3c are located on the side of the second tread end Ti with respect to the tire equator C, and one outer main groove 3B located on the side of the first tread end To with respect to the tire equator C. By these main grooves 3, the tread portion 2 is divided into a first land portion 7 located outside the outer main groove 3B in the tire axial direction, and a second land portion 8, a third land portion 9, and a fourth land portion 10 that are sequentially adjacent to the first land portion 7. Note that the groove center line 3c is a line passing through the center of the groove width.

[0017] 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 includes a pair of groove walls 13 and a groove bottom 14. Each of the pair of groove walls 13 includes a first groove wall portion 15 extending outward in the tire radial direction from the groove bottom 14, and a second groove wall portion 16 located outside the first groove wall portion 15 in the tire radial direction and inclined at an angle θ2 greater than the angle with respect to the tread normal line n of the first groove wall portion 15. The angle θ2 of the second groove wall portion 16 is 40 to 75 degrees (°). Such a second groove wall portion 16 suppresses the entrainment in which the groove edge 3e of the outer main groove 3B rolls into a tread shape and the uneven ground pressure caused by this entrainment even when a large lateral force acts, and improves the uneven wear resistance performance and dry grip performance. Further, the second groove wall portion 16 increases the lateral rigidity of the first land portion 7 and the second land portion 8 near the outer main groove 3B, etc., and suppresses the decrease in groove volume accompanying the deformation of the outer main groove 3B when receiving a lateral force. Thereby, the wet performance is improved. Furthermore, since the angle θ2 is 40 degrees or more, the entrainment and the unevenness of the ground pressure due to this entrainment are further suppressed. Since the angle θ2 is 75 degrees or less, the volumes of the first land portion 7 and the second land portion 8 are ensured and their rigidity is maintained high. From such a viewpoint, the angle θ2 is more preferably 50 degrees or more and further preferably 70 degrees or less. The tread normal line n is a normal line with respect to the virtual tread Ta obtained by filling the tread T of the land portion or the portion where the tread T is not formed by the lateral grooves 5 and the sipes 6 described later.

[0018] Although not particularly limited, the difference (θ2 - θ1) between the angle θ2 of the second groove wall portion 16 and the angle θ1 with respect to the tread normal line n of the first groove wall portion 15 is preferably 40 degrees or more, more preferably 45 degrees or more, preferably 70 degrees or less, and more preferably 65 degrees or less.

[0019] In the present embodiment, the first groove wall portion 15 and the second groove wall portion 16 are connected via a bent portion K that protrudes toward the groove center line 3c side. The bent portion K may be formed, for example, by the intersection of two straight lines or may be formed in an arc shape. In the present embodiment, the first groove wall portion 15 and the second groove wall portion 16 extend linearly.

[0020] As shown in FIG. 1, 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 wave shape, for example.

[0021] 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 an outer main groove 3B maintains the rigidity of the tread portion 2 on the outer side of the vehicle where a large lateral force acts during turning travel, and maintains high drainage performance during straight travel. 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. In the case of the main groove 3 having the second groove wall portion, the groove width is the length including the second groove wall portion in this specification.

[0022] As shown in FIG. 2, 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 travel, deformation such as the tilting of the first land portion 7 and the second land portion 8 in the tire axial direction is suppressed, so that the uneven wear resistance performance is further improved. Further, since the deformation of these land portions 7 and 8 is suppressed, a decrease in the groove volume of the outer main groove 3B is suppressed, and thus high wet performance during high-load travel is exhibited.

[0023] In order to increase the wet performance while maintaining the 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.

[0024] The groove bottom 14 of the outer main groove 3B includes, for example, a maximum depth portion 14A where the groove depth is maximum, and a pair of rising portions 14B that are connected to both sides of the maximum depth portion 14A and have an arc shape that protrudes toward the outside of the outer main groove 3B. In the present embodiment, the groove bottom 14 of the outer main groove 3B is formed in a substantially U shape. The shape of the groove bottom 14 is not limited to such a mode.

[0025] Although not particularly limited, it is desirable that the width W3 (shown in FIG. 1) of the second groove wall portion 16 of the outer main groove 3B satisfies the following formula (1) when the angle θ2 (°) of the second groove wall portion 16 of the outer main groove 3B is used. The smaller the angle θ2, the larger the width W3 is set, so that a decrease in the groove volume due to deformation of the outer main groove 3B is suppressed. In this specification, the width W3 is the length in the groove width direction of the outer main groove 3B. Note that the width W3 is preferably about 2.0 to 4.0 mm. 1×cosθ2≦W3(mm)≦7×cosθ2…(1)

[0026] The height h1 of the second groove wall portion 16 in the tire radius direction is, for example, desirably 15% or more of the groove depth d1 of the outer main groove 3B, more desirably 20% or more, desirably 35% or less, and more desirably 30% or less.

[0027] Although not particularly limited, the angle θ1 of the first groove wall portion 15 is desirably 0 degrees or more, more desirably 5 degrees or more, desirably 20 degrees or less, and more desirably 15 degrees or less.

[0028] As shown in FIG. 1, the inner main groove 3A includes, for example, a first inner main groove 11 and a second inner main groove 12 located closer to the second tread end Ti side than the first inner main groove 11. The first inner main groove 11 is, for example, the closest to the tire equator C among the main grooves 3.

[0029] 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.

[0030] The first inner main groove 11 includes a pair of groove edges 18 extending in the longitudinal direction. Each groove edge 18 includes an outer groove edge 18a located on the side of the first tread end To. The separation distance La in the tire axial direction between the outer groove edge 18a and the tire equator C is 2% or less of the tread width TW. Thereby, the above-described action is effectively exhibited. In the present embodiment, the outer groove edge 18a is located on the tire equator C.

[0031] FIG. 3(a) is a cross-sectional view taken along line B-B of FIG. 1. FIG. 3(a) shows a cross-section of the first inner main groove 11. As shown in FIG. 3(a), the first inner main groove 11 includes a pair of groove walls 20 and a groove bottom 21. The groove wall 20 of the first inner main groove 11 includes a first outer groove wall 20A located on the side of the first tread end To and a first inner groove wall 20B located on the side of the second tread end Ti. Similar to the groove bottom 14 of the outer main groove 3B, the groove bottom 21 of the first inner main groove 11 includes a maximum depth portion 21A where the groove depth is maximum and a pair of rising portions 21B that are connected to both sides of the maximum depth portion 21A and are convex in an arc shape toward the outside of the first inner main groove 11. The groove bottom 21 of the first inner main groove 11 is formed, for example, in a substantially U shape.

[0032] The first outer groove wall 20A includes a first groove wall portion 23 extending outward in the tire radial direction from the groove bottom 21 and a second groove wall portion 24 located outside the first groove wall portion 23 in the tire radial direction and inclined at an angle θ4 larger than that with respect to the tread normal n than the first groove wall portion 23. Thereby, the first outer groove wall 20A is suppressed from being involved in the rolling of the outer groove edge 18a that is continuous into a tread shape and the ground pressure from becoming non-uniform due to this involvement, and the uneven wear resistance and dry grip performance are improved.

[0033] The first inner groove wall 20B extends linearly, for example, from the groove bottom 21 to the outside in the tire radial direction. In the present embodiment, the first inner groove wall 20B extends linearly between the groove bottom 21 and the tread T.

[0034] The angle θ3 of the first groove wall portion 23 of the first outer groove wall 20A with respect to the tread normal line n is formed smaller than the angle θ5 of the first inner groove wall 20B with respect to the tread normal line n. Thereby, the volume of the second land portion 8 disposed relatively on the outer side of the vehicle is ensured. Also, on the side of the third land portion 9 of the first inner main groove 11, the groove volume can be increased. The angle θ3 of the first groove wall portion 23 of the first outer groove wall 20A is desirably 60% or more, more desirably 65% or more, desirably 90% or less, and more desirably 85% or less of the angle θ5 of the first inner groove wall 20B. The angle θ3 of the first outer groove wall 20A is desirably 25 degrees or more, more desirably 35 degrees or more, desirably 55 degrees or less, and more desirably 45 degrees or less.

[0035] Also, the angle θ3 of the first groove wall portion 23 of the first outer groove wall 20A of the first inner main groove 11 is formed larger than the angle θ1 of the first groove wall portion 15 of the outer main groove 3B. Thereby, the volume of the first land portion 7 disposed relatively on the outer side of the vehicle is ensured. Also, on the side of the second land portion 8 of the first inner main groove 11, the groove volume can be increased. The difference (θ3 - θ1) between the angle θ3 of the first groove wall portion 23 of the first outer groove wall 20A and the angle θ1 of the first groove wall portion 15 of the outer main groove 3B is desirably 15 degrees or more, more desirably 20 degrees or more, desirably 35 degrees or less, and more desirably 30 degrees or less.

[0036] The angle θ5 (°) of the first inner groove wall 20B of the first inner main groove 11 is desirably 5% or more, more desirably 10% or more, desirably 20% or less, and more desirably 10% or less of the tread width TW (mm).

[0037] The angle θ4 of the second groove wall portion 24 of the first inner main groove 11 is formed to be larger than the angle θ5 of the first inner groove wall 20B. Such a second groove wall portion 24 more effectively suppresses the entrainment that causes the tread to curl and the non-uniform ground pressure caused by this entrainment. The difference (θ4 - θ5) between the angle θ4 of the second groove wall portion 24 and the angle θ5 of the first inner groove wall 20B is desirably 10 degrees or more, more desirably 15 degrees or more, desirably 30 degrees or less, and more desirably 25 degrees or less. The angle θ4 of the second groove wall portion 24 is desirably 45 degrees or more, more desirably 55 degrees or more, desirably 75 degrees or less, and more desirably 65 degrees or less. The angle θ5 of the first inner groove wall 20B is desirably 25 degrees or more, more desirably 35 degrees or more, desirably 55 degrees or less, and more desirably 45 degrees or less.

[0038] Although not particularly limited, the height h2 of the second groove wall portion 24 in the tire radial direction is desirably 40% or more of the groove depth d2a of the first inner main groove 11, more desirably 45% or more, desirably 60% or less, and more desirably 55% or less.

[0039] FIG. 3(b) is a cross-sectional view taken along the line C-C of FIG. 1. FIG. 3(b) shows the cross-section of the second inner main groove 12. As shown in FIG. 3(b), the second inner main groove 12 includes a pair of groove walls 27 and a groove bottom 28. The groove bottom 28 includes, for example, a maximum depth portion 28A where the groove depth is maximum, and a pair of rising portions 28B, 28B that are connected to both sides of the maximum depth portion 28A and are in an arc shape convex toward the outside of the second inner main groove 12. In this embodiment, the groove bottom 28 is formed in a substantially U shape. The pair of groove walls 27 each extend linearly outward in the tire radial direction from the groove bottom 21, for example. In this embodiment, each groove wall 27 extends from the groove bottom 28 to the tread T.

[0040] Thus, in this embodiment, the pair of groove walls 13 of the outer main groove 3B and the first outer groove wall 20A of the first inner main groove 11 are formed to include the first groove wall portion and the second groove wall portion. Further, each groove wall 27 of the first inner groove wall 20B of the first inner main groove 11 and the second inner main groove 12 is formed without having the second groove wall portion. 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, the uneven wear resistance performance, and the wet performance during high load running are further improved.

[0041] The pair of groove walls 27 of the second inner main groove 12 includes a second inner groove wall 27A located on the side of the first tread end To and a second outer groove wall 27B located on the side of the second tread end Ti. And the angle θ6 of the second inner groove wall 27A with respect to the tread normal line n is formed smaller than the angle θ7 of the second outer groove wall 27B with respect to the tread normal line n. The angle θ6 of the second inner groove wall 27A is desirably 60% or more, more desirably 65% or more, desirably 90% or less, and more desirably 85% or less of the angle θ7 of the second outer groove wall 27B. The angle θ7 (°) of the second outer groove wall 27B is desirably 5% or more, more desirably 10% or more, desirably 20% or less, and more desirably 15% or less of the tread width TW (mm). The angle θ7 of the second outer groove wall 27B is desirably, for example, 30 degrees or more, more desirably 35 degrees or more, desirably 50 degrees or less, and more desirably 45 degrees or less. The angle θ7 of the second outer groove wall 27B is desirably, for example, the same as the angle θ5 of the first inner groove wall 20B of the first inner main groove 11.

[0042] The groove width W2a (shown in FIG. 1) of the first inner main groove 11 is, for example, equal to or greater than the groove depth d2a (shown in FIG. 3(a)) of the first inner main groove 11. The groove width W2b (shown in FIG. 1) of the second inner main groove 12 is, for example, 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 to 10 is reduced, and the dry grip performance during high load running is maintained high. In this embodiment, the groove width W2a of the first inner main groove 11 is larger 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 larger than the groove depth d2b of the second inner main groove 12.

[0043] As shown in FIG. 1, the width Wa in the tire axial direction of the first land portion 7 is formed to be larger than the widths Wb, Wc, and Wd in the tire axial direction of the second land portion 8, the third land portion 9, and the fourth land portion 10, respectively. 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.

[0044] 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 with the smallest width, which is the third land portion 9 in this embodiment.

[0045] In order to enhance the dry grip performance, the uneven wear resistance performance, and the wet performance in a well-balanced manner, the width Wa in the tire axial direction of the first land portion 7 is desirably 25% to 35% of the tread width TW. The width Wb in the tire axial direction of the second land portion 8 is desirably 15% to 25% of the tread width TW. Note that the width Wb of the second land portion 8 is more desirably 16% or more, even more desirably 18% or more, more desirably 24% or less, and even more desirably 22% or less of the tread width TW. The width Wc in the tire axial direction of the third land portion 9 is desirably 8% to 22% of the tread width TW. The width Wd in the tire axial direction of the fourth land portion 10 is desirably 18% to 28% of the tread width TW.

[0046] In this embodiment, the tread portion 2 is provided with a plurality of lateral grooves 5 extending in the tire axial direction and a plurality of sipes 6 extending in the tire axial direction. In this specification, the sipe 6 is formed in a cut shape with a width of less than 1.5 mm. In this specification, 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. Further, "extending in the tire axial direction" includes, in this specification, those extending at 80 degrees or less with respect to the tire axial direction.

[0047] On a tire axial line X at an arbitrary position in the tire circumferential direction, 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. Thereby, a drainage effect is obtained at an arbitrary position in the tire circumferential direction. Also, with such a configuration, in the tire circumferential direction, the change in the lateral rigidity of the tread portion 2 becomes small, so that higher dry grip performance can be obtained.

[0048] Each of the lateral grooves 5 is inclined in the same direction with respect to the tire axial direction. The lateral groove 5 is inclined, for example, in a first direction (in FIG. 1, rising to the upper right) with respect to the tire axial direction. Thereby, by utilizing the rotation of the tire 1, the water in the lateral groove 5 is smoothly discharged toward one side in the tire axial direction. Each of the sipes 6 is also inclined in the same direction with respect to the tire axial direction. The sipes 6 are each inclined, for example, in the first direction.

[0049] The angle α of each of the plurality of lateral grooves 5 and the plurality of sipes 6 with respect to the tire axial direction is desirably, for example, 5 to 60 degrees. Since the angle α is 5 degrees or more, the water in the lateral groove 5 and the sipes 6 can be smoothly discharged by utilizing the rotation of the tire 1. Since the angle α is 60 degrees or less, a decrease in the lateral rigidity of each of the land portions 7 to 10 can be suppressed. In order to effectively exhibit such an action, the angle α is more desirably 15 degrees or more and more desirably 45 degrees or less.

[0050] In the present embodiment, the lateral groove 5 includes a first lateral groove 30 arranged in the first land portion 7, a second lateral groove 31 arranged in the second land portion 8, and a fourth lateral groove 32 arranged in the fourth land portion 10. The sipes 6 include a second sipe 40 arranged in the second land portion 8, a third sipe 41 arranged in the third land portion 9, and a fourth sipe 42 arranged in the fourth land portion 10.

[0051] FIG. 4 is an enlarged plan view of the first land portion 7 and the second land portion 8. As shown in FIG. 4, the first lateral groove 30 includes a first transverse lateral groove 30A that crosses the first land portion 7 and a first interrupted lateral groove 30B that is interrupted within the first land portion 7.

[0052] The first transverse groove 30A and the first interrupted groove 30B are positioned at an equal pitch P1 in the tire circumferential direction. In this specification, the equal pitch means that the difference between the maximum value and the minimum value of the pitch includes those within 10% of the maximum value of the pitch.

[0053] The first transverse groove 30A includes an inner first portion 33A extending at the same angle α1 with respect to the tire axial direction from the outer main groove 3B, and an outer first portion 33B connected to the inner first portion 33A and extending at an angle α2 smaller than the angle with respect to the tire axial direction of the inner first portion 33A. The outer first portion 33B is connected to the first tread end To.

[0054] The first interrupted groove 30B includes an inner second portion 34A extending at the same angle α3 with respect to the tire axial direction, and an outer second portion 34B connecting the inner second portion 34A and the first tread end To. The outer second portion 34B is inclined, for example, at an angle α4 smaller than that of the inner second portion 34A.

[0055] Although not particularly limited, the length L1 of the first interrupted groove 30B in the tire axial direction is desirably 65% or more, more desirably 70% or more, desirably 85% or less, and more desirably 80% or less of the width Wa (shown in FIG. 1) of the first land portion 7.

[0056] The inner first portion 33A and the inner second portion 34A extend linearly, for example. In this embodiment, the inner first portion 33A and the inner second portion 34A extend in parallel. In this specification, the "parallel" includes not only the case where the absolute value of the difference in the angle of inclination of each is 0 degree, but also those within 10 degrees. The angle α1 of the inner first portion 33A and the angle α3 of the inner second portion 34A are desirably 10 degrees or more, more desirably 15 degrees or more, desirably 30 degrees or less, and more desirably 25 degrees or less, for example. The outer first portion 33B and the outer second portion 34B extend in parallel, for example.

[0057] The second transverse groove 31 includes a second continuous transverse groove 31A and a second discontinuous transverse groove 31B. The second continuous transverse groove 31A and the second discontinuous transverse groove 31B are alternately provided along the tire circumferential direction. The second continuous transverse groove 31A and the second discontinuous transverse groove 31B are arranged at an equal pitch P2 in the tire circumferential direction. Note that the second continuous transverse grooves 31A adjacent to each other in the tire circumferential direction are also arranged at an equal pitch P3 in the tire circumferential direction.

[0058] In the present embodiment, the second continuous transverse groove 31A crosses the second land portion 8. In the present embodiment, the second discontinuous transverse groove 31B extends from the first inner main groove 11 toward the first tread end To and terminates within the second land portion 8. The second continuous transverse groove 31A and the second discontinuous transverse groove 31B are inclined, for example, in the same direction with respect to the tire axial direction. Thereby, the rigidity step of the second land portion 8 is suppressed. In the present embodiment, the second continuous transverse groove 31A and the second discontinuous transverse groove 31B extend in parallel. The angle α5 of the second continuous transverse groove 31A with respect to the tire axial direction is, for example, desirably 10 degrees or more, more desirably 15 degrees or more, desirably 30 degrees or less, and more desirably 25 degrees or less.

[0059] The second sipe 40 is formed as a second discontinuous sipe 40A at least one end of which terminates within the second land portion 8. The second discontinuous sipe 40A connects the outer main groove 3B and the second discontinuous transverse groove 31B. The second discontinuous sipe 40A is connected to the outer end 31e in the tire axial direction of the second discontinuous transverse groove 31B. The width Wf of the second discontinuous sipe 40A is constant along the longitudinal direction.

[0060] In a plan view of the tread, the second transverse groove 31A is formed so as to completely include a virtual extension line 30c that extends the first transverse groove 30A onto the second land portion 8 along its longitudinal direction. As a result, a single virtual groove including the second transverse groove 31A and the first transverse groove 30A is formed, improving wet performance. Further, since the first transverse groove 30A and the second transverse groove 31A contact the ground at similar timings, these grooves 30A, 31A deform so as to open wide, increasing the apparent groove volume. Therefore, wet performance is further improved. In this specification, the "virtual extension line" is a line obtained by extending the groove center line of the groove or the center line of the sip. The "completely include" means, in this specification, that the virtual extension line continuously extends from the inner end to the outer end in the tire axial direction of the groove and is located above the groove.

[0061] The second transverse groove 31A extends linearly, for example. As a result, when water flows in the groove, the peeling phenomenon is suppressed and the flow resistance of the water is reduced, so that high wet performance is maintained.

[0062] In a plan view of the tread, in this embodiment, the second interrupted groove 31B is formed so as to completely include a virtual extension line 40c that extends the second interrupted sip 40A onto the second land portion 8 along its longitudinal direction.

[0063] The length L2 of the second interrupted groove 31B in the tire axial direction is desirably 40% to 60% of the width Wb of the second land portion 8. Since the length L2 of the second interrupted groove 31B is 40% or more of the width Wb of the second land portion 8, wet performance is maintained. Since the length L2 of the second interrupted groove 31B is 60% or less of the width Wb of the second land portion 8, dry grip performance is maintained. Therefore, the length L2 of the second interrupted groove 31B is more desirably 45% or more and more desirably 55% or less of the width Wb of the second land portion 8.

[0064] The groove width W7 of the second interrupted transverse groove 31B is, for example, the same as the groove width W6 of the second transverse interrupted groove 31A. Thereby, the rigidity step of the second land portion 8 is maintained small. In the present embodiment, the maximum value of the groove width W7 of the second interrupted transverse groove 31B is the same as the maximum value of the groove width W6 of the second transverse interrupted groove 31A. In this specification, the "same" includes not only the case where the difference in the groove width of each transverse groove is 0 mm, but also those in which the absolute value of these differences is within 3 mm.

[0065] The second interrupted transverse groove 31B includes, for example, a joint portion 35 that connects to the second interrupted sipe 40A. In the present embodiment, the joint portion 35 includes the outer end 31e in the tire axial direction of the second interrupted transverse groove 31B. The joint portion 35 is a portion where the groove width W7 of the second interrupted transverse groove 31B continuously decreases toward the second interrupted sipe 40A.

[0066] FIG. 5 is a cross-sectional view taken along line D-D of FIG. 1. FIG. 5 shows a longitudinal section of the second interrupted transverse groove 31B and the second interrupted sipe 40A. As shown in FIG. 5, the depth d6 of the second interrupted sipe 40A is formed smaller than the groove depth d5 of the second interrupted transverse groove 31B.

[0067] In the longitudinal section of the second interrupted transverse groove 31B, the groove bottom 35s of the joint portion 35 is formed in a convex arc shape toward the inner side in the tire radial direction. Such a joint portion 35 suppresses the rigidity step of the second land portion 8, thereby enhancing the dry grip performance and the uneven wear resistance performance. The radius of curvature R of the groove bottom 35s of the joint portion 35 is preferably 5 mm or more, more preferably 7 mm or more, preferably 12 mm or less, and more preferably 9 mm or less.

[0068] Although not particularly limited, the depth d6 of the second interrupted sipe 40A is preferably 20% or more, more preferably 35% or more, preferably 80% or less, and more preferably 65% or less of the groove depth d1 of the outer main groove 3B.

[0069] FIG. 6 is a plan view of the second land portion 8 and the third land portion 9. As shown in FIG. 6, the third sipe 41 is formed as a third transverse sipe 41A that crosses the third land portion 9.

[0070] In a plan view of the tread, the second transverse groove 31A of the second land portion 8 is formed so as to completely encompass a virtual extension line 41c obtained by extending the third transverse siped 41A along its longitudinal direction on the second land portion 8.

[0071] As shown in FIG. 1, in the present embodiment, the second transverse groove 31A and the first transverse groove 30A are formed so as to encompass a virtual extension line 41c obtained by extending the third transverse siped 41A to the first land portion 7 and the second land portion 8. Thereby, the above-described operation is more effectively exerted.

[0072] In the third land portion 9, except for the third transverse siped 41A, no transverse groove 5 and siped 6 that cross the third land portion 9 are provided. Thereby, a decrease in the land rigidity of the third land portion 9 where a large ground pressure acts during straight running is suppressed. For this reason, excellent dry grip performance is exhibited.

[0073] The third land portion 9 includes, in the present embodiment, a recess 45 that leads to the inner main groove 3A. The recess 45 includes a first recess 45A that leads to the first inner main groove 11 and a second recess 45B that leads to the second inner main groove 12. Such a recess 45 helps to increase the groove volume of the inner main groove 3A.

[0074] In the present embodiment, the third transverse siped 41A extends so as to connect the first recess 45A and the second recess 45B. Thereby, since the third transverse siped 41A and each recess 45 contact the ground at the same timing, both of them deform so as to open wide, and the apparent volume increases, so the wet performance is improved.

[0075] The recess 45 is, for example, such that the length Lb in the tire circumferential direction becomes smaller toward the intermediate position 9c in the tire axial direction of the third land portion 9. In the present embodiment, the length Lb of the recess 45 in the tire circumferential direction continuously becomes smaller toward the intermediate position 9c of the third land portion 9. In a plan view of the tread, the recess 45 is, for example, triangular. Such a recess 45 suppresses a decrease in the land rigidity of the third land portion 9. The recess 45 is not limited to such a shape.

[0076] The maximum value of the length Lb of the recess 45 is desirably 120% or more, more desirably 130% or more, desirably 160% or less, and more desirably 150% or less of the length Lc of the recess 45 in the tire axial direction. The length Lc of the recess 45 in the tire axial direction is desirably 10% or more, more desirably 15% or more, desirably 30% or less, and more desirably 25% or less of the width Wc of the third land portion 9. The depth d7 (shown in FIG. 3(b)) of the recess 45 is desirably 55% or more, more desirably 65% or more, and more desirably 100% or less of the groove depths d2a and d2b of the inner main grooves 3A. Thereby, wet performance is ensured.

[0077] FIG. 7 is a plan view of the fourth land portion 10. As shown in FIG. 7, the fourth lateral groove 32 of the fourth land portion 10 includes a fourth outer lateral groove 32A that connects to the second tread end Ti and is interrupted in the fourth land portion 10, and a fourth inner lateral groove 32B that connects to the second inner main groove 12 and is interrupted in the fourth land portion 10. The fourth sipe 42 of the fourth land portion 10 is a fourth interrupted sipe 42A that connects to the second tread end Ti and is interrupted in the fourth land portion 10. In the present embodiment, the fourth interrupted sipe 42A connects the fourth inner lateral groove 32B and the second tread end Ti.

[0078] The inner end 32i in the tire axial direction of the fourth outer circumferential groove 32A is located on the inner side in the tire axial direction than the outer end 32e in the tire axial direction of the fourth inner circumferential groove 32B. In other words, on the fourth land portion 10, an overlapping portion Y where the fourth outer circumferential groove 32A and the fourth inner circumferential groove 32B overlap in the tire axial direction is formed. Such an overlapping portion Y can effectively discharge the water film on the tread surface of the fourth land portion 10, thus improving the wet performance. In order to enhance the dry grip performance and wet performance in a well-balanced manner, the length Ld in the tire axial direction of the overlapping portion Y is desirably 3% or more of the width Wd of the fourth land portion 10, more desirably 5% or more, desirably 15% or less, and more desirably 10% or less. The inner end 32i and the outer end 32e are positions on the groove center line 32c of each of the grooves 32A and 32B.

[0079] In a tread plan view, the fourth inner circumferential groove 32B is formed so as to completely enclose a virtual extension line 42c that extends the fourth interrupted sipe 42A along its longitudinal direction on the fourth land portion 10. Thereby, since the fourth inner circumferential groove 32B and the fourth interrupted sipe 42A contact the ground at the same timing, these groove 32B and sipe 42A deform so as to open wide, and the apparent groove volume and the sipe volume increase. For this reason, the wet performance is improved.

[0080] The angle α7 of the fourth circumferential groove 32 and the fourth sipe 42 with respect to the tire axial direction is, for example, larger than the angle α6 (shown in FIG. 6) of the first circumferential groove 30, the second circumferential groove 31, the second sipe 40, and the third sipe 41 with respect to the tire axial direction. In other words, the angle α7 of the circumferential groove 5 and the sipe 6 formed on the fourth land portion 10 is larger than the angle α6 of the circumferential groove 5 and the sipe 6 formed on the first land portion 7 to the third land portion 9. Although not particularly limited, the angle α7 of the fourth circumferential groove 32 and the fourth sipe 42 is desirably 25 degrees or more, more desirably 30 degrees or more, desirably 45 degrees or less, and more desirably 40 degrees or less.

[0081] 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 sum (L) of the areas of the tread surfaces T of each land portion 7 to 10 and the sum (S) of the areas of the grooves between both tread ends To and Ti at the same height position as the tread surface T.

[0082] As described above, one embodiment of the present disclosure has been described in detail. However, the present disclosure is not limited to the above specific embodiments and can be implemented in various forms.

Example

[0083] A tire having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. Then, the dry grip performance, wet performance, uneven wear resistance performance, and drainage performance of each test tire were tested. The common specifications and test methods of each test tire are as follows.

[0084] <Dry grip performance, wet performance, uneven wear resistance 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 on a dry asphalt road surface and a test course on an asphalt road surface provided with a puddle with a water depth of 5 mm. The dry grip performance and wet performance based on the stability and operability at this time were evaluated by the sensory evaluation of the test driver. Also, after the above test, the uneven wear resistance performance based on the occurrence status of uneven wear generated in the tread portion was evaluated by the sensory evaluation of the test driver. The results are all shown in scores with Comparative Example 1 as 100. The larger the numerical value, the better. When the value is 90 or less, the tire is considered unqualified. 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 Tread width TW: 268 mm

[0085] <Drainage performance> The test driver drove the above test vehicle on an asphalt road surface with a radius of 100 m provided with a puddle of water 5 mm deep. And 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 to 80 km / h. The results are shown in an index with the value of the average lateral G of Comparative Example 1 being 100. The larger the numerical value, the better. If it is 90 or less, the tire fails. The test results are shown in Tables 1 and 2. In each table, "A" means that the second transverse groove completely encompasses the virtual extension line of the first transverse groove. "B" means that the second transverse groove does not completely encompass the virtual extension line of the first transverse groove. "C" means that each of the first transverse groove and the second transverse groove is connected to the main groove. "D" means that each of the first transverse groove and the second transverse groove is not connected to the main groove. "E" means that each of the first transverse groove and the second transverse groove extends linearly. "F" means that each of the first transverse groove and the second transverse groove extends in an arc shape. The groove widths of each main groove and each transverse groove are the same.

[0086] [Table 1]

[0087] [Table 2]

[0088] As a result of the test, it is understood that the tires of the examples have improved dry grip performance, resistance to uneven wear, drainage performance, and wet performance compared to the tires of the comparative examples.

[0089] [Appendix] This disclosure includes the following aspects.

[0090] [This Disclosure 1] A tire having a tread portion with a specified mounting orientation on a vehicle, wherein the tread portion includes a first tread end and a second tread end that are respectively located on the outer side and the inner side of the vehicle when the tire is mounted on the vehicle, and a plurality of main grooves that continuously extend in the tire circumferential direction between the first tread end and the second tread end, wherein the plurality of main grooves include two inner main grooves whose groove center lines are located on the side of the second tread end with respect to the tire equator, and one outer main groove whose groove center line is located on the side of the first tread end with respect to the tire equator, the outer main groove includes a pair of groove walls and a groove bottom, each of the pair of groove walls includes a first groove wall portion that extends outward in the tire radial direction from the groove bottom, and a second groove wall portion that is located on the outer side in the tire radial direction with respect to the first groove wall portion and is inclined at an angle larger than that of the first groove wall portion with respect to the tread normal, wherein an angle θ2 of the second groove wall portion with respect to the tread normal is 40 to 75 degrees, a tire. [Disclosure 2] The tire according to Disclosure 1, wherein a groove width of the outer main groove is equal to or greater than a groove depth of the outer main groove. [Disclosure 3] The tire according to Disclosure 1 or 2, wherein the groove width of the outer main groove is smaller than a groove width of the inner main groove. [Disclosure 4] The tire according to any one of Disclosures 1 to 3, wherein a width W3 of the second groove wall portion of the outer main groove satisfies the following formula (1) when the angle of the second groove wall portion of the outer main groove is θ2. 1×cosθ2≦W3≦7×cosθ2…(1) [Disclosure 5] The inner main groove includes a first inner main groove and a second inner main groove that is located on the side of the second tread end with respect to the first inner main groove, the first inner main groove includes a pair of groove walls and a groove bottom, the pair of groove walls of the first inner main groove includes a first outer groove wall located on the side of the first tread end, The first outer groove wall includes a first groove wall portion extending outward in the tire radial direction from the groove bottom, and a second groove wall portion located outside the first groove wall portion in the tire radial direction and inclined at an angle greater than that of the first groove wall portion with respect to the tread normal. The tire according to any one of Disclosures 1 to 4 of the present disclosure. [Disclosure 6] The pair of groove walls of the first inner main groove includes a first inner groove wall located on the side of the second tread end. The angle θ3 of the first groove wall portion of the first outer groove wall with respect to the tread normal is smaller than the angle θ5 of the first inner groove wall with respect to the tread normal. The tire according to Disclosure 5 of the present disclosure. [Disclosure 7] The second inner main groove includes a second outer groove wall located on the side of the first tread end and a second inner groove wall located on the side of the second tread end. The angle θ6 of the second outer groove wall with respect to the tread normal is smaller than the angle θ7 of the second inner groove wall with respect to the tread normal. The tire according to Disclosure 5 or 6 of the present disclosure. [Disclosure 8] The angle θ3 of the first groove wall portion of the first outer groove wall of the first inner main groove with respect to the tread normal is larger than the angle θ1 of the first groove wall portion of the outer main groove. The tire according to any one of Disclosures 5 to 7 of the present disclosure. [Disclosure 9] The tread portion further includes a plurality of transverse grooves extending in the tire axial direction and a plurality of sipes extending in the tire axial direction. The plurality of transverse grooves and the plurality of sipes are arranged such that at least one of the plurality of transverse grooves and the plurality of sipes intersects the tire axial line at an arbitrary position in the tire circumferential direction on the tire axial line. The tire according to any one of Disclosures 1 to 8 of the present disclosure. [Disclosure 10] The angle of each of the plurality of transverse grooves and the plurality of sipes with respect to the tire axial direction is 5 to 60 degrees. The tire according to Disclosure 9 of the present disclosure. [Disclosure 11] The tread portion is divided into a first land portion located outside the outer main groove in the tire axial direction, 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 25% to 35% of the tread width, the width of the second land portion in the tire axial direction is 15% to 25% of the tread width, the width of the third land portion in the tire axial direction is 8% to 22% of the tread width, the width of the fourth land portion in the tire axial direction is 18% to 28% of the tread width. The tire according to any one of Disclosures 1 to 10. [Disclosure 12] In the first land portion, a first transverse groove extending from the outer main groove toward the side of the first tread end is arranged, in the second land portion, a second transverse groove crossing the second land portion is arranged, In a tread plan view, the second transverse groove is formed so as to completely enclose a virtual extension line obtained by extending the first transverse groove along its longitudinal direction onto the second land portion. The tire according to Disclosure 11.

Explanation of Signs

[0091] 1 Tire 3A Inner main groove 3B Outer main groove 5 Transverse groove 13 Groove wall 14 Groove bottom 15 First groove wall portion 16 Second groove wall portion n Tread normal Ti Second tread end To First tread end

Claims

1. A tire having a tread portion with a defined mounting orientation on a vehicle, wherein the tread portion includes: a first tread end and a second tread end respectively located on the outer side and the inner side of the vehicle when the tire is mounted on the vehicle; and a plurality of main grooves continuously extending in the circumferential direction of the tire between the first tread end and the second tread end, wherein the plurality of main grooves include two inner main grooves whose groove center lines are located on the side of the second tread end with respect to the tire equator, and one outer main groove whose groove center line is located on the side of the first tread end with respect to the tire equator, the outer main groove includes a pair of groove walls and a groove bottom, each of the pair of groove walls includes a first groove wall portion extending outward in the radial direction of the tire from the groove bottom, and a second groove wall portion located on the outer side in the radial direction of the tire with respect to the first groove wall portion and inclined at an angle larger than that with respect to the tread normal line of the first groove wall portion, the angle θ2 of the second groove wall portion with respect to the tread normal line is 40 to 75 degrees, the tread portion is divided into a first land portion located on the outer side in the axial direction of the tire 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 axial direction of the tire is 25% to 35% of the tread width, the width of the second land portion in the axial direction of the tire is 15% to 25% of the tread width, the width of the third land portion in the axial direction of the tire is 8% to 22% of the tread width, the width of the fourth land portion in the axial direction of the tire is 18% to 28% of the tread width, a first transverse groove extending from the outer main groove toward the first tread end is disposed in the first land portion, a second transverse groove crossing the second land portion is disposed in the second land portion, in a plan view of the tread, the second transverse groove is formed so as to completely enclose a virtual extension line obtained by extending the first transverse groove along its longitudinal direction on the second land portion, a tire.

2. A tire having a tread portion with a defined mounting orientation on a vehicle, wherein the tread portion includes: a first tread end and a second tread end respectively located on the outer side and the inner side of the vehicle when the tire is mounted on the vehicle; and a plurality of main grooves continuously extending in the circumferential direction of the tire between the first tread end and the second tread end, wherein the plurality of main grooves include two inner main grooves whose groove center lines are located on the side of the second tread end with respect to the tire equator, and one outer main groove whose groove center line is located on the side of the first tread end with respect to the tire equator, The outer main groove includes a pair of groove walls and a groove bottom. Each of the pair of groove walls includes a first groove wall portion extending outward in the tire radial direction from the groove bottom, and a second groove wall portion located outside the first groove wall portion in the tire radial direction and inclined at an angle greater than that of the first groove wall portion with respect to the tread normal. The angle θ2 of the second groove wall portion with respect to the tread normal is 40 to 75 degrees. The inner main groove includes a first inner main groove and a second inner main groove located on the side of the second tread end with respect to the first inner main groove. The first inner main groove includes a pair of groove walls and a groove bottom. The pair of groove walls of the first inner main groove includes a first outer groove wall located on the side of the first tread end. The first outer groove wall includes a first groove wall portion extending outward in the tire radial direction from the groove bottom, and a second groove wall portion located outside the first groove wall portion in the tire radial direction and inclined at an angle greater than that of the first groove wall portion with respect to the tread normal. Tire.

3. The pair of groove walls of the first inner main groove includes a first inner groove wall located on the side of the second tread end. The angle θ3 of the first groove wall portion of the first outer groove wall with respect to the tread normal is smaller than the angle θ5 of the first inner groove wall with respect to the tread normal. The tire according to claim 2.

4. The second inner main groove includes a second outer groove wall located on the side of the first tread end and a second inner groove wall located on the side of the second tread end. The angle θ6 of the second outer groove wall with respect to the tread normal is smaller than the angle θ7 of the second inner groove wall with respect to the tread normal. The tire according to claim 2 or 3.

5. The angle θ3 of the first groove wall portion of the first outer groove wall of the first inner main groove with respect to the tread normal is greater than the angle θ1 of the first groove wall portion of the outer main groove. The tire according to any one of claims 2 to 4.

6. The groove width of the outer main groove is equal to or greater than the groove depth of the outer main groove. The tire according to any one of claims 1 to 5.

7. The groove width of the outer main groove is smaller than the groove width of the inner main groove. The tire according to any one of claims 1 to 6.

8. The width W3 of the second groove wall portion of the outer main groove satisfies the following formula (1) when the angle of the second groove wall portion of the outer main groove is θ2. The tire according to any one of claims 1 to 7. 1 × cosθ2 ≤ W3 ≤ 7 × cosθ2…(1)

9. The tread portion further includes a plurality of transverse grooves extending in the tire axial direction and a plurality of sipes extending in the tire axial direction. The tire according to any one of claims 1 to 8, wherein at least one of the plurality of transverse grooves and the plurality of sipes intersects the tire axial line on the tire axial line at an arbitrary position in the tire circumferential direction.

10. The tire according to claim 9, wherein an angle of each of the plurality of transverse grooves and the plurality of sipes with respect to the tire axial direction is 5 to 60 degrees.

Images