JP7683312B2 - tire - Google Patents

Description

The present invention relates to a tire.

Patent Document 1 below describes a tire that is specified for installation on a vehicle. The tread portion of this tire is provided with a second main groove, a first main groove, and a third main groove, in that order from the inner tread edge to the outer side of the vehicle, to provide an inner shoulder land portion, an inner crown land portion, an outer crown land portion, and an outer shoulder land portion. The outer crown land portion, the inner shoulder land portion, and the outer shoulder land portion each have a plurality of closed grooves that are closed within the land portion. Such a tire is said to exhibit excellent wet performance while maintaining dry grip performance during high-load driving on a circuit, etc.

JP 2018-167717 A

However, in recent years, there has been a demand for further improvements in dry grip performance and wet performance during high-load driving.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide a tire that can improve dry grip performance and wet performance during high-load driving.

The present invention relates to a tire having a tread portion, the tread portion having a specified orientation for mounting on a vehicle, the tread portion having 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 including 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 being divided into a first land portion located on the outer side of the outer main groove in the tire axial direction, and a second land portion, a third land portion, and a fourth land portion adjacent to the first land portion in succession, the first land portion being divided into a first land portion and a second land portion, a third land portion, and a fourth land portion adjacent to the first land portion in the tire axial direction. The width of the outer main groove is greater than the axial width of each of the second land portion, the third land portion, and the fourth land portion, 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 and a second groove wall portion inclined at a larger angle to the tread normal than the first groove wall portion, and the multiple lateral grooves and the multiple sipes are arranged such that at least one of the multiple lateral grooves and the multiple sipes intersects the tire axial line at any position on the tire circumferential direction.

In the tire according to the present invention, it is preferable that each of the plurality of lateral grooves is inclined in a first direction with respect to the tire axial direction.

In the tire according to the present invention, it is preferable that each of the plurality of sipes is inclined in the first direction.

In the tire according to the present invention, the plurality of lateral grooves preferably include a plurality of outer lateral grooves arranged in the first land portion, and the plurality of outer lateral grooves preferably 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 connecting to the outer main groove.

In the tire according to the present invention, it is desirable that each of the second outer lateral grooves is located midway in the tire circumferential direction between the first outer lateral grooves that are adjacent in the tire circumferential direction.

In the tire according to the present invention, it is desirable that the axial distance between the axially inner end of the second outer lateral groove and the outer main groove is 4% to 10% of the tread width.

In the tire according to the present invention, it is preferable that the second outer lateral groove includes a shallow groove portion and a deep groove portion that is located axially outboard of the shallow groove portion and has a greater groove depth than the shallow groove portion.

In the tire according to the present invention, it is desirable that the groove depth of the shallow groove portion is 20% to 60% of the groove depth of the outer main groove.

In the tire according to the present invention, it is preferable that the second outer lateral groove has a depth change portion in which the groove depth increases from the shallow groove portion to the deep groove portion, and that the angle of the groove bottom relative to the tread surface in a longitudinal cross-sectional view of the depth change portion is 30 to 80 degrees.

In the tire according to the present invention, it is preferable that the lateral groove includes a second lateral groove that crosses the second land portion, and that the second lateral groove is located on an extension line of the first outer lateral groove toward the inside of the vehicle.

In the tire according to the present invention, it is preferable that the lateral grooves include a fourth lateral groove arranged in the fourth land portion, and the angle of the fourth lateral groove relative to the tire axial direction is greater than the angle of the second lateral groove relative to the tire axial direction.

In the tire according to the present invention, it is preferable that the angle of the fourth lateral groove relative to the tire axial direction is greater than the angle of the outer lateral groove relative to the tire axial direction.

By adopting the above-mentioned configuration, the tire of the present invention can improve dry grip performance and wet performance during high-load driving.

FIG. 2 is a development view of a tread portion of the tire of the present embodiment. 2 is a cross-sectional view taken along line AA in FIG. 1. 1A is a cross-sectional view taken along line BB in FIG. 1, and FIG. 1B is a cross-sectional view taken along line CC in FIG. FIG. 2 is an enlarged view of a first land portion and a second land portion of FIG. 1 . 2 is a cross-sectional view taken along line D-D of FIG. 1. FIG. 2 is an enlarged view of a third land portion and a fourth land portion of FIG. 1 .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is a plan view showing an expanded tread portion 2 of a tire 1 according to an embodiment of the present invention. The present invention is used, for example, in a pneumatic tire for a passenger car that can be used for normal driving on public roads as well as high-speed driving on a circuit. However, the present invention is not limited to such a tire.

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

In the case of a pneumatic tire, the outer tread end To and the inner tread end Ti are the axially outermost contact points when the tire 1 in a normal state is loaded with a normal load and touches the ground on a flat surface with a camber angle of 0°. The "normal state" refers to a state in which the tire is mounted on a normal rim, filled to normal internal pressure, and unloaded. Unless otherwise specified, the dimensions of each part of the tire 1 in this specification are values measured in the normal state. The axial distance between the outer tread end To and the inner tread end Ti is the tread width TW.

The "genuine rim" is a rim that is determined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is a "standard rim," in the case of TRA, it is a "design rim," and in the case of ETRTO, it is a "measuring rim."

The "normal internal pressure" is the air pressure set for each tire by each standard in the standard system that includes the standard on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

The "normal load" mentioned above is the load that each standard specifies for each tire in the standard system on which the tire is based. For JATMA, it is the "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY."

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

In this embodiment, the multiple 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. These main grooves 3 divide the tread portion 2 into a first land portion 7 located on the outer side of 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 adjacent to the first land portion 7 in sequence.

The axial width Wa of the first land portion 7 is greater than the axial widths Wb, Wc, and Wd of the second land portion 8, the third land portion 9, and the fourth land portion 10, respectively. This increases the lateral rigidity of the first land portion 7, which receives the greatest lateral force during cornering, improving dry grip performance during high-load driving.

Figure 2 is a cross-sectional view of line A-A in Figure 1. Figure 2 shows a cross section of the outer main groove 3B. As shown in Figure 2, the outer main groove 3B has a groove bottom 13 and a pair of groove walls 14. The pair of groove walls 14 each include a first groove wall portion 15 extending from the groove bottom 13 outward in the tire radial direction, and a second groove wall portion 16 inclined at an angle α1 to the tread normal n1 larger than that of the first groove wall portion 15. 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. This suppresses deformation such as axial collapse of the first land portion 7 and the second land portion 8 during cornering. This improves steering stability. In addition, suppressing deformation of these land portions 7 and 8 suppresses the groove volume of the outer main groove 3B from becoming smaller, thereby demonstrating high wet performance during high-load driving. In the case of an outer main groove 3B having a groove wall 14 including a first groove wall portion 15 and a second groove wall portion 16, the groove width in this specification is the length including the second groove wall portion 16.

As shown in FIG. 1, at least one of the lateral grooves 5 and sipes 6 is arranged to intersect with the tire axial line X at any position in the tire circumferential direction. This provides a drainage effect at any position in the tire circumferential direction. This configuration also reduces the change in lateral stiffness of the tread portion 2 in the tire circumferential direction, resulting in higher dry grip performance.

To improve dry grip performance during high-load driving, the width Wa of the first land portion 7 is desirably 1.3 times or more the width Wc of the narrowest land portion, in this embodiment, the third land portion 9, more desirably 1.5 times or more, more desirably 2.1 times or less, and even more desirably 1.9 times or less.

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

The groove width W1 of the outer main groove 3B is smaller than the groove width W2 of the inner main groove 3A. Such an outer main groove 3B maintains high rigidity of the tread portion 2 on the outer side of the vehicle, which is subjected to large lateral forces during cornering, and maintains high drainage performance during straight driving. Although not particularly limited, the groove width W1 of the outer main groove 3B is preferably 0.6 times or more, more preferably 0.7 times or more, more preferably 0.9 times or less, and more preferably 0.8 times or less of the groove width W2 of the inner main groove 3A.

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 greatest, and a pair of arc portions 13B, 13B that are connected to both sides of the maximum depth portion 13A and convex toward the outside of the outer main groove 3B.

In this embodiment, the first groove wall portion 15 and the second groove wall portion 16 extend linearly inward and outward in the tire radial direction. The first groove wall portion 15 and the second groove wall portion 16 may be, for example, an arc shape having a center on the inner side of the outer main groove 3B and convex toward the outer side of the outer main groove 3B.

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

In order to improve 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 preferably 1.5 times or more, more preferably 1.8 times or more, more preferably 3.0 times or less, and even more preferably 2.7 times or less, of the groove depth d1 of the outer main groove 3B.

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 arranged closer to the inner tread edge Ti 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. This improves the drainage performance near the tire equator C, where drainage is difficult, and provides excellent wet performance. Although not particularly limited, the groove width W2a of the first inner main groove 11 is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 1.5 times or less, and more preferably 1.4 times or less of the groove width W2b of the second inner main groove 12.

Figure 3(a) is a cross-sectional view of line B-B in Figure 1. Figure 3(a) shows a cross section of the first inner main groove 11. As shown in Figure 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 edge To side, and a first inner groove wall 19 extending from the groove bottom 13 toward the inner tread edge 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 with respect to the tread normal n2 larger than that of the first groove wall portion 15. The first inner groove wall 19 is formed only by the first groove wall portion 15 without the second groove wall portion 16.

Figure 3(b) is a cross-sectional view taken along line CC in Figure 1. Figure 3(b) shows a cross section of the second inner main groove 12. As shown in Figure 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 a second groove wall portion 16.

In this manner, 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 the first groove wall portion 15 and the second groove wall portion 16. Furthermore, 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. This provides an excellent rigidity balance between the vehicle inner region and the vehicle outer region of the tread portion 2, further improving dry grip performance and wet performance during high-load driving.

The pair of groove walls 14 of the second inner main groove 12 includes a second outer groove wall 14a extending from the groove bottom 13 toward the outer tread edge To, and a second inner groove wall 14b extending from the groove bottom 13 toward the inner tread edge Ti. The angle α4 of the second outer groove wall 14a with respect to the tread normal n4 is smaller than the angle α5 of the second inner groove wall 14b with respect to the tread normal n5. The angle α4 of the second outer groove wall 14a is preferably, for example, 20 degrees to 40 degrees. The angle α5 of the second inner groove wall 14b is preferably, for example, 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)) with respect to the tread normal n3 of the first inner groove wall 19.

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. This reduces the change in stiffness of the land portions 8-10, and maintains high dry grip performance during high-load driving.

As shown in FIG. 1, each of the lateral grooves 5 is inclined in a first direction (upward to the right in FIG. 1) with respect to the tire axial direction. This allows the rotation of the tire 1 to smoothly drain water in the main grooves 3 and lateral grooves 5 toward one side in the tire axial direction.

In this embodiment, the lateral grooves 5 include a plurality of outer lateral grooves 20 arranged in the first land portion 7, a second lateral groove 21 that crosses the second land portion 8, and a fourth lateral groove 24 arranged in the fourth land portion 10. The lateral grooves 5 include, for example, a second small lateral groove 22 arranged in the second land portion 8 and having an axially outer end 22e that terminates within the second land portion 8, and a third lateral groove 23 arranged in the third land portion 9.

Figure 4 is an enlarged view of the first land portion 7 and the second land portion 8. As shown in Figure 4, the outer lateral groove 20 includes a plurality of first outer lateral grooves 25 that connect to the outer main groove 3B, and a plurality of second outer lateral grooves 26 that terminate within the first land portion 7 without connecting to the outer main groove 3B. Such first outer lateral grooves 25 can drain water within the groove to the outer main groove 3B. The second outer lateral grooves 26 suppress excessive reduction in the rigidity of the first land portion 7 near the outer main groove 3B.

The first outer lateral groove 25 crosses, for example, the first land portion 7. In this embodiment, the second outer lateral groove 26 is connected to the outer tread end To. Such first outer lateral groove 25 and second outer lateral groove 26 smoothly drain water in the grooves from the outer tread end To.

Each of the second outer lateral grooves 26 is located midway in the tire circumferential direction between the first outer lateral grooves 25, 25 adjacent in the tire circumferential direction. This equalizes the circumferential rigidity of the first land portion 7. In this specification, the "midway in the tire circumferential direction" includes not only a position that is 50% of the tire circumferential distance Ls between the first outer lateral grooves 25, 25 in the tire circumferential direction from the first outer lateral groove 25 in the tire circumferential direction, but also a position that is 40% to 60% of the distance Ls.

The axial separation distance L1 between the axially inner end 26i of the second outer lateral groove 26 and the outer main groove 3B is preferably 4% or more of the tread width TW, more preferably 6% or more, more preferably 10% or less, and even more preferably 8% or less. Since the separation distance L1 is 4% or more of the tread width TW, excessive reduction 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.

Figure 5 is a cross-sectional view taken along line D-D in Figure 1. Figure 5 shows a longitudinal section of the second outer lateral groove 26. As shown in Figures 4 and 5, the second outer lateral groove 26 includes a shallow groove portion 28 and a deep groove portion 29 that is located axially outboard of the shallow groove portion 28 and has a greater groove depth than the shallow groove portion 28. In this way, the shallow groove portion 28 is provided closer to the outer main groove 3B, so that the rigidity of the land portion near the outer main groove 3B, which tends to become weak, can be maintained high.

The second outer lateral groove 26 has a depth change section 30 in which the groove depth increases from the shallow groove section 28 to the deep groove section 29. Such a depth change section 30 reduces the rigidity step of the first land portion 7. To exert such an effect, the angle β of the groove bottom 30s of the depth change section 30 relative to the tread surface 7a is preferably 80 degrees or less, and more preferably 70 degrees or less. If the angle β is excessively small, the groove volume of the second outer lateral groove 26 may become small. For this reason, the angle β is preferably 30 degrees or more, and more preferably 45 degrees or more.

To achieve the above-mentioned effect more effectively, the groove depth d4 of the shallow groove portion 28 is preferably 20% or more of the groove depth d1 of the outer main groove 3B, more preferably 30% or more, more preferably 60% or less, and even more preferably 50% or less. The groove depth d5 of the deep groove portion 29 is 3 to 7 mm.

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

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. This maintains a small rigidity step in the first land portion 7. In this specification, the groove width being "same" includes not only a difference of 0 mm between these groove widths, but also a difference of 2 mm or less between the groove widths. 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, preferably 7% or less, and more desirably 6% or less.

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. This prevents excessive reduction in the rigidity of the first land portion 7. 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 axial outer end 5e (grooves that extend beyond the tread edge are the tread edge) and the inner end 5i of the groove centerline 5c in the tire axial direction. In this specification, the "same angle" includes cases where the difference in angle between these lateral grooves is 0 degrees, as well as within ±10 degrees.

The second lateral groove 21 is located on an extension line K of the first outer lateral groove 25 extended toward the inside of the vehicle. This allows water in the second lateral groove 21 to be smoothly discharged to the outside of the outer tread edge To via the first outer lateral groove 25. In this specification, "the second lateral groove 21 is located on the extension line K" includes a state in which the extension line K of 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, as well as a state in which the extension line K overlaps with the inner and outer openings 21a, 21b of the second lateral groove 21 in the tire axial direction.

The second small lateral groove 22 is connected to the first inner main groove 11, for example. The outer end 22e of the second small lateral groove 22 is located at the middle of the second land portion 8 in the tire axial direction. Such a second small lateral groove 22 improves drainage performance while suppressing a decrease in land portion rigidity on the outer main groove 3B side of the second land portion 8. In this specification, the "middle in the tire axial direction" includes a position axially spaced 50% of the width Wb of the second land portion 8 from the outer main groove 3B toward the tire equator C, as well as a position axially spaced 40% to 60% of the width Wb.

The second lateral groove 21 and the second small lateral groove 22 are each inclined at the same angle θ2 with respect to the tire axial direction. This prevents excessive reduction in the rigidity of the second land portion 8. In this embodiment, the angle θ2 of the second lateral groove 21 and the second small lateral groove 22 is the same as the angle θ1 of the first outer lateral groove 25 and the second outer lateral groove 26.

It is desirable that the groove width W6 of the second transverse groove 21 and the groove width W7 (maximum width) of the second small transverse groove 22 are the same. In this embodiment, the groove width W6 of the second transverse groove 21 and the groove width W7 of the second small transverse groove 22 are the same as the groove width W4 of the first outer transverse groove 25 and the groove width W5 of the second outer transverse groove 26.

Figure 6 is an enlarged view of the third land portion 9 and the fourth land portion 10 in Figure 1. As shown in Figure 6, in this embodiment, the third lateral groove 23 includes a third inner lateral groove 33 and a third outer lateral groove 34. The third inner lateral groove 33 extends, for example, from the first inner main groove 11 toward the outside in the tire axial direction and terminates in the third land portion 9. In this embodiment, the third inner lateral groove 33 has a tire circumferential length that continuously decreases toward the outside in the tire axial direction. The third outer lateral groove 34 extends, for example, from the second inner main groove 12 toward the inside in the tire axial direction and terminates in the third land portion 9. In this embodiment, the third outer lateral groove 34 has a tire circumferential length that continuously decreases toward the inside in the tire axial direction.

The axial length L5 of the third inner lateral groove 33 and the axial length L6 of the third outer lateral groove 34 are each preferably 35% or less of the width Wc of the third land portion 9, and more preferably 25% or less. This maintains a high rigidity of the third land portion 9. From the viewpoint of improving drainage performance, the length L5 of the third inner lateral groove 33 and the length L6 of the third outer lateral groove 34 are preferably 10% or more of the width Wc of the third land portion 9, and more preferably 15% or more.

In this embodiment, the angle θ3 of the fourth lateral groove 24 with respect to the tire axial direction is greater than the angle θ2 of the second lateral groove 21 (shown in FIG. 4). As a result, in the fourth land portion 10 where a relatively small lateral force acts during cornering, water in the fourth lateral groove 24 is smoothly discharged to the outside of the second inner main groove 12 or the inner tread edge Ti. In addition, during straight driving, the rigidity in the tire circumferential direction of the second land portion 8 where a relatively large ground pressure acts is maintained high. In this embodiment, the angle θ3 of the fourth lateral groove 24 is greater than the angle θ2 of the second small lateral groove 22.

In order to more effectively exert the above-mentioned effect, in this embodiment, the angle θ3 of the fourth transverse groove 24 is formed to be larger than the angle θ1 of the outer transverse groove 20 (shown in FIG. 4). The angle θ3 of the fourth transverse groove 24 is formed to be larger than, for example, the angle θ1 of the first outer transverse groove 25 and the angle θ1 of the second outer transverse groove 26.

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

The fourth lateral groove 24 includes, for example, a fourth inner lateral groove 36 and a fourth outer lateral groove 37. In this embodiment, the fourth inner lateral groove 36 extends from the second inner main groove 12 to the outside in the tire axial direction and terminates within the fourth land portion 10. In this embodiment, the fourth outer lateral groove 37 extends from the inner tread edge Ti to the inside in the tire axial direction and terminates within the fourth land portion 10.

The axially outer end 36e of the fourth inner lateral groove 36 is located axially outboard of the axially inner end 37i 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 axial direction. Such a fourth lateral groove 24 improves wet performance.

The groove width W8a of the fourth inner lateral groove 36 is preferably 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 preferably 15% or more of the width Wd of the fourth land portion 10, more preferably 20% or more, more preferably 35% or less, and even more preferably 30% or less.

The groove width W8 of the fourth transverse groove 24 is larger than the groove widths W4, W5 of the outer transverse groove 20 and the groove widths W6, W7 of the second transverse groove 21 and the second small transverse groove 22. This improves wet performance in the fourth land portion 10, and maintains high land portion rigidity in the first land portion 7 and the second land portion 8. Although not particularly limited, the groove width W8 of the fourth transverse groove 24 is preferably 1.10 times or more, more preferably 1.15 times or more, more preferably 1.30 times or less, and even more preferably 1.25 times or less of the groove width W4 of the first outer transverse groove 25.

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

As shown in Figures 4 and 6, in this embodiment, the sipes 6 include a second sipe 42 arranged in the second land portion 8, a third sipe 43 arranged in the third land portion 9, and a fourth sipe 44 arranged in the fourth land portion 10.

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 edge Ti.

The angle θ6 of the fourth sipe 44 relative to the tire axial direction is greater than the angle θ4 of the second sipe 42 relative to the tire axial direction and the angle θ5 of the third sipe 43 relative to the tire axial direction. The angle θ6 of the fourth sipe 44 is preferably 20 degrees or more, more preferably 30 degrees or more, preferably 60 degrees or less, and more preferably 45 degrees or less. The angle θ4 of the second sipe 42 and the angle θ5 of the third sipe 43 are preferably 5 degrees or more, more preferably 10 degrees or more, preferably 40 degrees or less, and more preferably 30 degrees or less.

The land-sea ratio (S/L) of the tread portion 2 of this embodiment is preferably 15% or more, more preferably 20% or more, and more preferably 35% or less, and even more preferably 30% or less. The land-sea ratio is the ratio of the sum of the tread areas of the land portions 7 to 10 (L) to the sum of the areas of the grooves at the same height as the tread (S).

As shown in FIG. 1, in this embodiment, the groove width WA of each main groove 3 is larger than the groove width WB of each lateral groove 5. In addition, the groove width WA of the main groove 3, the groove width WB of each lateral groove 5, and the width WC of each sipe 6 are constant.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above and can be modified and implemented in various ways.

Tires with the basic pattern shown in Figure 1 were prototyped based on the specifications in Table 1. Each test tire was then tested for dry grip performance and wet performance. The common specifications and test methods for each test tire are as follows:

<Dry grip performance>
Each test tire was mounted on all wheels of the following test vehicle. A 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 test driver's senses. The results are shown as a score with Comparative Example 1 being 100. The higher the value, the better the tire is, and if it is 90 or less, the tire is rejected.
Tire size: 245/40R18
Rim: 18 x 8.5J
Internal pressure (kPa): 220 (all wheels)
Vehicle: 2000cc four-wheel drive vehicle

<Wet performance>
A test driver drove the test vehicle on an asphalt road surface with a radius of 100 m, on which a puddle of 5 mm depth was placed. 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 expressed as an index, with the average lateral G value of Comparative Example 1 being set at 100. The higher the value, the better, and if it is 90 or less, the tire is rejected.
The test results are shown in Tables 1 to 4.
In each example, there are three main grooves.
Also, "A" in the table indicates a position where the second outer lateral groove is closer to the first outer lateral groove than the midpoint between the first outer lateral grooves in the tire circumferential direction.
"B" in the table indicates that the second lateral groove is located at a position deviated from the extension line of the first outer lateral groove.
"C" in the table 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 configurations in which the groove wall of the outer main groove is formed only by the first groove wall portion and no second groove wall portion is provided, and in which the second outer lateral groove is not provided with a shallow groove portion.

The test results show that the tires of the embodiment have improved dry grip performance and wet performance compared to the tires of the comparison example.

Reference Signs List 1 Tire 2 Tread portion 3A Outer main groove 5 Lateral 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 line

Claims (10)

A tire having a tread portion,
The tread portion has a specified orientation for installation on a vehicle,
The tread portion is provided with a plurality of main grooves extending continuously in a tire circumferential direction, a plurality of lateral grooves extending in an axial direction of the tire, and a plurality of sipes extending in an axial direction of the tire,
The plurality of main grooves include two inner main grooves located on a vehicle inner side of the tire equator and one outer main groove located on a vehicle outer side of the tire equator,
The tread portion is divided into a first land portion located on an outer side of the outer main groove in the tire axial direction, and a second land portion, a third land portion, and a fourth land portion adjacent to the first land portion in this order,
a width in the tire axial direction of the first land portion is greater than a width in the tire axial direction of each of the second land portion, the third land portion, and the fourth land portion;
a groove width of the outer main groove is equal to or greater than a 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 from the groove bottom toward an outer side in a tire radial direction, and a second groove wall portion inclined at an angle greater than that of the first groove wall portion with respect to a tread normal,
the plurality of lateral grooves and the plurality of sipes are arranged on a tire axial line at any position in a tire circumferential direction such that at least one of the plurality of lateral grooves and the plurality of sipes intersects the tire axial line ,
The tread portion has an outer tread end that is located on an outer side of the vehicle when the tire is 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 edge,
the lateral grooves include a second lateral groove crossing the second land portion,
The second lateral groove is located on an extension line of the first outer lateral groove toward the inside of the vehicle.
tire. The tire according to claim 1, wherein each of the plurality of lateral grooves is inclined in a first direction relative to the tire axial direction. The tire of claim 2, wherein each of the plurality of sipes is inclined in the first direction. The tire according to claim 1 , wherein each of the second outer lateral grooves is located midway in the tire circumferential direction between the first outer lateral grooves adjacent in the tire circumferential direction . The tire according to any one of claims 1 to 4, wherein an axial distance between an axially inner end of the second outer lateral groove and the outer main groove is 4% to 10% of a tread width . The tire according to claim 1 , wherein the second outer lateral groove includes a shallow groove portion and a deep groove portion that is located axially outboard of the shallow groove portion and has a greater groove depth than the shallow groove portion . The tire according to claim 6 , wherein the shallow groove portion has a groove depth of 20% to 60% of the groove depth of the outer main groove . 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,
8. The tire according to claim 6 , wherein in a vertical cross-sectional view of the depth changing portion, an angle of the groove bottom with respect to the tread surface of the depth changing portion is 30 to 80 degrees. the lateral grooves include a fourth lateral groove disposed in the fourth land portion,
The tire according to claim 1 , wherein an angle of the fourth lateral groove with respect to the tire axial direction is larger than an angle of the second lateral groove with respect to the tire axial direction . The tire according to claim 9 , wherein an angle of the fourth lateral groove with respect to the tire axial direction is larger than an angle of the outer lateral groove with respect to the tire axial direction .

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