Tire

Abstract

To provide a tire that can exert excellent braking performance on a dry road surface while maintaining on-ice performance.SOLUTION: The present invention pertains to a tire including a tread portion 2. The tread portion 2 includes a first shoulder circumferential groove 5 and a first shoulder land portion 11. Shoulder lateral grooves 15 disposed in the first shoulder land portion 11 include a plurality of outer shoulder lateral grooves 16 and a plurality of inner shoulder lateral grooves 17. Each of the plurality of outer shoulder lateral grooves 16 includes: a minimum portion 21 having a minimum groove width; and a maximum portion 22 disposed on a radially inward of the minimum portion 21 and having a groove width larger than the minimum portion. Each of the plurality of inner shoulder lateral grooves 17 has a groove width continuously decreasing from an opening portion 17a to a groove bottom portion 17b or a groove width constant from the opening portion 17a to the groove bottom portion 17b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Patent Document 1 below proposes a tire having a groove on the tread surface extending in the tire axial direction. The groove includes an opening formed on the tread surface, a minimum portion having a locally smallest groove width on the radially inner side of the opening, and a maximum portion having a locally largest groove width on the radially inner side of the minimum portion. The groove improves the uneven wear resistance and grip performance of the tire in a well-balanced manner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-188850 A Summary of the Invention [Problem to be solved by the invention]

[0004] The tire can exhibit excellent braking performance, particularly on dry roads, because the grooves improve grip performance. However, the grooves have a problem in that they do not exhibit sufficient friction on ice.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can exhibit excellent braking performance on dry road surfaces while maintaining performance on ice. [Means for solving the problem]

[0006] The present invention relates to a tire having a tread portion, the tread portion including a first tread edge and a second tread edge, a plurality of circumferential grooves extending continuously in a tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions divided into the plurality of circumferential grooves, the plurality of circumferential grooves including a first shoulder circumferential groove provided closest to the first tread edge, the plurality of land portions including a first shoulder land portion including the first tread edge, the first shoulder land portion being provided with a plurality of shoulder lateral grooves extending in a tire axial direction, the shoulder lateral groove including a plurality of outer shoulder lateral grooves communicating with the first tread edge, and a plurality of inner shoulder lateral grooves communicating with a shoulder circumferential groove, the plurality of outer shoulder lateral grooves and the plurality of inner shoulder lateral grooves each including an opening formed in a tread surface of the first shoulder land portion and a groove bottom, the plurality of outer shoulder lateral grooves each including a minimum portion disposed between the opening and the groove bottom and having a minimum groove width, and a maximum portion disposed radially inward of the minimum portion and having a groove width greater than that of the minimum portion, and the plurality of inner shoulder lateral grooves each have a groove width that is continuously smaller from the opening to the groove bottom or a constant groove width from the opening to the groove bottom. Effect of the Invention

[0007] By adopting the above-mentioned configuration, the tire of the present invention can exhibit excellent braking performance on dry road surfaces while maintaining performance on ice. [Brief description of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a first shoulder land portion of FIG. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Diagram 5]FIG. 3 is an enlarged view of the outer crown block and the inner crown block of FIG. 2. [Figure 6] 6 is a cross-sectional view taken along line CC in FIG. 5. [Figure 7] FIG. 3 is a cross-sectional view taken along line DD in FIG. [Figure 8] 6 is a cross-sectional view taken along line EE in FIG. 5. [Figure 9] FIG. 2 is an enlarged view of a first crown land portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are described to include the features of the present invention, but may include exaggerated expressions or expressions different from the dimensional ratios of the actual structure in order to facilitate understanding of the present invention. In addition, the same or common elements are given the same reference numerals throughout the embodiments, and duplicated explanations are omitted. FIG. 1 is a development view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. As shown in FIG. 1, the tire 1 of the present invention is preferably used as, for example, a pneumatic tire for heavy loads. However, the present invention is not limited to such an application.

[0010] The tread portion 2 includes a first tread edge T1 and a second tread edge T2, a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between them, and a plurality of land portions 4 divided by the plurality of circumferential grooves 3.

[0011] The first tread end T1 and the second tread end T2 each correspond to the ends of the contact patch when 90% of the normal load is applied to the tire 1 in a normal state and the tread portion 2 is brought into contact with a flat surface at a camber angle of 0°.

[0012] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal condition means a standard use condition according to the intended use of the tire, in which the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0013] A "genuine rim" is a rim that is defined 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 called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0014] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0015] In the case of pneumatic tires for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system that includes the standard on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of tires for which various standards are not established, the "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0016] In the tire 1 of this embodiment, the region on the first tread edge T1 side of the tire equator C and the region on the second tread edge T2 side of the tire equator C have substantially the same configuration. More specifically, the tread portion 2 of the tire 1 of this embodiment is configured in a pattern that is point-symmetric with respect to a point on the tire equator C. Therefore, the mounting orientation of the tire 1 of this embodiment on a vehicle is not specified.

[0017] The circumferential grooves 3 include a first shoulder circumferential groove 5, a second shoulder circumferential groove 6, and a crown circumferential groove 7. The first shoulder circumferential groove 5 is provided between the first tread edge T1 and the tire equator C. As a result, the first shoulder circumferential groove 5 is provided closest to the first tread edge T1 among the multiple circumferential grooves 3. The second shoulder circumferential groove 6 is provided between the second tread edge T2 and the tire equator C. As a result, the second shoulder circumferential groove 6 is provided closest to the second tread edge T2 among the multiple circumferential grooves 3. The crown circumferential groove 7 is provided between the first shoulder circumferential groove 5 and the second shoulder circumferential groove 6. In the tire 1 of this embodiment, the tread portion 2 is divided into four land portions 4 by these three circumferential grooves 3. Note that the present invention is not limited to such an embodiment.

[0018] Each circumferential groove 3 extends, for example, in a zigzag pattern in the tire circumferential direction. A groove width W1 of each circumferential groove 3 is, for example, at least 3 mm or more, and desirably 2.5% to 5.0% of the tread width TW. A depth of each circumferential groove 3 is, for example, 10 to 25 mm. The tread width TW corresponds to the axial distance of the tire from the first tread edge T1 to the second tread edge T2 in the normal state.

[0019] The crown circumferential groove 7 is provided, for example, on the tire equator C. The distance L1 in the tire axial direction from the tire equator C to the groove center line of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is, for example, 20% to 35% of the tread width TW. However, the arrangement of the circumferential grooves 3 is not limited to this range.

[0020] The multiple land portions 4 include a first shoulder land portion 11, a second shoulder land portion 12, a first crown land portion 13, and a second crown land portion 14. The first shoulder land portion 11 is sectioned on the tire axially outer side of the first shoulder circumferential groove 5, and includes a first tread edge T1. The second shoulder land portion 12 is sectioned on the tire axially outer side of the second shoulder circumferential groove 6, and includes a second tread edge T2. The first crown land portion 13 is sectioned between the first shoulder circumferential groove 5 and the crown circumferential groove 7. The second crown land portion 14 is sectioned between the second shoulder circumferential groove 6 and the crown circumferential groove 7. The second shoulder land portion 12 has substantially the same configuration as the first shoulder land portion 11. Moreover, the second crown land portion 14 has substantially the same configuration as the first crown land portion 13. Therefore, in this specification, a description of the second shoulder land portion 12 and the second crown land portion 14 is omitted.

[0021] Fig. 2 shows an enlarged view of the first shoulder land portion 11. As shown in Fig. 2, the first shoulder land portion 11 is provided with a plurality of shoulder lateral grooves 15 extending in the tire axial direction. The shoulder lateral grooves 15 include a plurality of outer shoulder lateral grooves 16 communicating with the first tread edge T1 and a plurality of inner shoulder lateral grooves 17 communicating with the first shoulder circumferential groove 5.

[0022] Fig. 3 shows a cross-sectional view taken along line AA in Fig. 2. Fig. 4 shows a cross-sectional view taken along line BB in Fig. 2. As shown in Fig. 3, the outer shoulder lateral groove 16 includes an opening 16a formed in the tread surface 11s of the first shoulder land portion 11 and a groove bottom 16b. As shown in Fig. 4, the inner shoulder lateral groove 17 also includes an opening 17a formed in the tread surface 11s of the first shoulder land portion 11 and a groove bottom 17b.

[0023] As shown in Fig. 3, the outer shoulder lateral groove 16 includes a minimum portion 21 and a maximum portion 22. The minimum portion 21 is disposed between the opening 16a and the groove bottom 16b, and has a minimum groove width. The maximum portion 22 is disposed radially inward of the minimum portion 21, and has a larger groove width than the minimum portion 21. In this specification, the groove width means the distance between two groove walls facing each other in a groove cross section, in a direction parallel to the tread surface of the land portion. The groove width in a plan view of the tread means the distance between two groove edges of the groove.

[0024] As shown in Fig. 4, the inner shoulder lateral groove 17 has a groove width that is continuously reduced from the opening 17a to the groove bottom 17b, or the groove width is constant from the opening 17a to the groove bottom 17b. Due to the above-mentioned characteristics, the tire 1 of the present invention can exhibit excellent braking performance on dry roads while maintaining performance on ice. The reason is as follows.

[0025] As shown in Fig. 2, during braking, a large ground pressure acts on the outer shoulder lateral groove 16 that communicates with the first tread edge T1. For this reason, the outer shoulder lateral groove 16 has a large effect on braking performance on dry roads. As shown in Fig. 3, in the present invention, the outer shoulder lateral groove 16 includes a minimum portion 21 and a maximum portion 22, so that a part or all of the area between the opening 16a and the minimum portion 21 comes into contact with the ground during braking, thereby increasing the contact area during braking. This improves braking performance on dry roads.

[0026] On the other hand, when traveling on ice, the inner shoulder lateral groove 17 connected to the first shoulder circumferential groove 5 (shown in FIG. 2) exerts a large frictional force on ice at the corner with the first shoulder circumferential groove 5. Also, the inner shoulder lateral groove 17 has a groove width that is continuously smaller from the opening 17a to the groove bottom 17b, or the groove width is constant from the opening 17a to the groove bottom 17b, so that it can exert a high frictional force at its edge portion. Therefore, it is possible to maintain the performance on ice. Due to these actions, the tire 1 of the present invention can exert excellent braking performance on dry roads while maintaining the performance on ice.

[0027] A more detailed configuration of this embodiment will be described below. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. Furthermore, even if any one of the configurations described below is applied alone to the tire 1 of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0028] As shown in FIG. 2, the outer shoulder lateral groove 16 and the inner shoulder lateral groove 17 have a groove width of at least 3.0 mm or more, which is different from sipes described later. The outer shoulder lateral grooves 16 and the inner shoulder lateral grooves 17 are alternately provided in the tire circumferential direction. In this embodiment, the outer shoulder lateral grooves 16 and the inner shoulder lateral grooves 17 are provided at the same pitch. Specifically, the one-pitch length P1 of the outer shoulder lateral groove 16 in the tire circumferential direction is 100% to 150% of the maximum width W2 in the tire axial direction of the first shoulder land portion 11. The one-pitch length of the inner shoulder lateral groove 17 is the same. This improves the braking performance on dry road surfaces (hereinafter simply referred to as "braking performance") and the performance on ice in a well-balanced manner. The one-pitch length P1 means the minimum distance in the tire circumferential direction between the groove center lines of two lateral grooves adjacent in the tire circumferential direction.

[0029] It is desirable that the outer shoulder lateral groove 16 and the inner shoulder lateral groove 17 are provided without overlapping in the tire axial direction. This configuration includes not only a mode in which a virtual area obtained by extending the outer shoulder lateral groove 16 in parallel to the tire circumferential direction does not overlap the inner shoulder lateral groove 17 at all, but also a mode in which the overlap length in the tire axial direction between the virtual area and the inner shoulder lateral groove 17 is 10% or less of the width W2 of the first shoulder land portion 11.

[0030] The outer shoulder lateral groove 16 and the inner shoulder lateral groove 17 are arranged at an angle of, for example, 30° or less, preferably 15° or less, relative to the tire axial direction. The outer shoulder lateral groove 16 in this embodiment extends parallel to the tire axial direction. The angle θ1 of the inner shoulder lateral groove 17 relative to the tire axial direction is larger than the angle of the outer shoulder lateral groove 16 relative to the tire axial direction (0° in this embodiment), and is, for example, 3 to 8°. However, the present invention is not limited to this embodiment.

[0031] It is preferable that the outer shoulder lateral groove 16 is terminated in the first shoulder land portion 11 without reaching the first shoulder circumferential groove 5. The axial length of the outer shoulder lateral groove 16 is 40% to 60% of the width W2 of the first shoulder land portion 11. In addition, the outer shoulder lateral groove 16 includes a constant width portion 23 extending in the axial direction of the tire with a constant groove width in a plan view of the tread, and a widened width portion 24 disposed between the constant width portion 23 and the first tread edge T1. The widened width portion 24 has a groove width that is widened toward the first tread edge T1 side. In addition, the widened width portion 24 is configured to have a depth greater than that of the constant width portion 23. In this embodiment, the constant width portion 23 of the outer shoulder lateral groove 16 has a cross-sectional shape shown in FIG. 3.

[0032] As shown in Fig. 3, the outer shoulder lateral groove 16 has two groove walls 16w that are symmetrically arranged with respect to each other. However, the present invention is not limited to this embodiment. The groove width W3 of the opening 16a of the outer shoulder lateral groove 16 is, for example, 5.0 to 10.0 mm. In a preferred embodiment, the groove width W3 of the opening 16a is larger than the groove width W4 (shown in Fig. 4) at the opening 17a of the inner shoulder lateral groove 17, and specifically, is 130% to 170% of the groove width W4. This improves braking performance and performance on ice in a well-balanced manner.

[0033] Between the opening 16a and the minimum portion 21, the groove wall 16wa of the outer shoulder lateral groove 16 is configured as a flat surface or a smoothly curved surface. Further, the maximum angle θ2 of the groove wall 16wa of the outer shoulder lateral groove 16 with respect to the tire normal, at a portion radially outboard of the minimum portion 21, is 40 to 60°. Further, the distance L2 in the tire radial direction from the opening 16a to the minimum portion 21 is 15% to 25% of the total depth d1 of the outer shoulder lateral groove 16. As a result, during braking, the groove wall is more likely to come into contact with the ground between the opening 16a and the minimum portion 21, reliably improving braking performance.

[0034] The groove width W5 at the minimum portion 21 of the outer shoulder lateral groove 16 is, for example, preferably 35% or more, more preferably 40% or more, and preferably 55% or less, more preferably 50% or less of the groove width W3 at the opening 16a. The groove width W5 at the minimum portion 21 of the outer shoulder lateral groove 16 is preferably smaller than the groove width W4 at the opening 17a of the inner shoulder lateral groove 17. The groove width W5 at the minimum portion 21 is, for example, 2.5 to 4.5 mm. This improves the braking performance and the performance on ice in a well-balanced manner. Particularly, in this embodiment, the groove width W3 of the outer shoulder lateral groove 16 is larger than the groove width W4 (shown in FIG. 4) of the inner shoulder lateral groove 17, and the groove width W5 at the minimum portion 21 is smaller than the groove width W4. Therefore, the wear progresses uniformly at the openings of these lateral grooves, and uneven wear can be suppressed.

[0035] In this embodiment, the minimum portion 21 is configured by connecting the groove wall 16wa radially outward of the minimum portion 21 and the groove wall 16wb radially inward of the minimum portion 21 via a smooth curved surface 26. The curvature radius R1 of the curved surface 26 is, for example, 2 to 4 mm. The angle θ3 between the groove wall 16wa radially outward of the minimum portion 21 and the groove wall 16wb radially inward of the minimum portion 21 is, for example, 120 to 130°. This ensures the above-mentioned effects, and also reduces the load during braking, which can be expected to improve uneven wear resistance.

[0036] Between the minimum portion 21 and the maximum portion 22, the groove wall 16wb of the outer shoulder lateral groove 16 is configured to be flat. The maximum angle θ4 of the groove wall between the minimum portion 21 and the maximum portion 22 with respect to the tire normal is smaller than the angle θ2, and is, for example, 3 to 8°. This makes it possible to prevent snow and ice pieces from clogging the groove.

[0037] Additionally, in the outer shoulder lateral groove 16, the distance L3 in the tire radial direction from the minimum portion 21 to the maximum portion 22 is 65% to 85% of the total depth d1 of the outer shoulder lateral groove 16. As a result, the distance L3 is greater than the distance L2 in the tire radial direction from the opening 16a to the minimum portion 21. Specifically, the distance L3 is 3.0 to 4.0 times the distance L2. As a result, braking performance, performance on ice, and uneven wear resistance are improved in a well-balanced manner.

[0038] The distance L4 in the tire radial direction from the maximum portion 22 to the lowest position of the groove bottom 16b is 3% to 10% of the total depth d1 of the outer shoulder lateral groove 16. The ratio L3 / L4 of the distance L3 to the distance L4 is preferably 10 to 15. As a result, the distance L4 is smaller than the distance L2 from the opening 16a to the minimum portion 21. This makes it easier for the groove wall 16wa to come into contact with the ground, ensuring the above-mentioned effects.

[0039] From the same viewpoint, it is preferable that the groove width W6 at the maximum portion 22 of the outer shoulder lateral groove 16 is smaller than the groove width W3 at the opening 16a of the outer shoulder lateral groove 16. Specifically, the groove width W6 at the maximum portion 22 is 60% to 75% of the groove width W3 at the opening 16a. Also, it is preferable that the groove width W6 at the maximum portion 22 is 1.5 to 1.7 times the groove width W5 at the minimum portion 21.

[0040] The groove bottom 16b includes, for example, a planar bottom surface 27 extending parallel to the tread surface 11s of the first shoulder land portion 11. In this embodiment, the planar groove wall 16wb and the bottom surface 27 are connected via a curved surface 28. In a preferred embodiment, the curvature radius R2 of the curved surface 28 formed on the groove bottom 16b is smaller than the curvature radius R1 of the curved surface 26 formed on the minimum portion 21. Specifically, the curvature radius R2 is set to 0.5 to 1.5 mm. The groove bottom 16b including such a curved surface 28 makes it easier for the groove wall 16wb to deform in the groove opening and closing direction, and can further suppress clogging of the groove with snow and ice pieces.

[0041] 2, it is preferable that the inner shoulder lateral groove 17 terminates within the first shoulder land portion 11 without reaching the first tread edge T1. The axial length of the inner shoulder lateral groove 17 is 40% to 60% of the width W2 of the first shoulder land portion 11. Moreover, the inner shoulder lateral groove 17 extends in the axial direction of the tire with a constant groove width over its entirety in a plan view of the tread.

[0042] As shown in Fig. 4, the inner shoulder lateral groove 17 has two groove walls 17w that are symmetrically arranged with respect to each other. However, the present invention is not limited to this embodiment. The groove width W4 of the opening 17a of the inner shoulder lateral groove 17 is, for example, 4.5 to 6.0 mm. The maximum angle of the groove wall 17w of the inner shoulder lateral groove 17 with respect to the tire normal is 5° or less. This allows the edge portion of the inner shoulder lateral groove 17 to provide a large frictional force on ice.

[0043] The total depth d2 of the inner shoulder lateral groove 17 is 90% to 110% of the total depth d1 (shown in FIG. 3) of the outer shoulder lateral groove 16, and in a preferred embodiment, these total depths are the same. This makes the rigidity of the first shoulder land portion 11 uniform, and suppresses uneven wear thereof.

[0044] In the inboard shoulder lateral groove 17, a bottom surface 29 of the groove bottom 17b and a groove wall 17w are connected via a curved surface 30. The radius of curvature R3 of the curved surface 30 is larger than the radius of curvature R2 (shown in FIG. 3) of the curved surface 28 of the groove bottom 16b of the outboard shoulder lateral groove 16. Specifically, the radius of curvature R3 is preferably set to 1.5 to 2.5 mm. This suppresses stress concentration at the groove bottom 17b and prevents damage to the groove bottom 17b.

[0045] As shown in FIG. 2, the first shoulder land portion 11 of this embodiment is provided with a plurality of shoulder longitudinal sipes 31 extending in the tire circumferential direction. In this specification, the term "sipe" means a cut having a small width, and in the sipe main body, the distance between the two inner walls is less than 1.5 mm. In addition, the sipe main body means a portion in which the two inner walls extend in the tire radial direction substantially parallel to each other. "Substantially parallel" means an aspect in which the angle between the two sipe walls is 10° or less. In this way, when ground pressure is applied to the land portion, the two inner walls in the sipe main body portion come into contact with each other, and the rigidity of the land portion can be increased. In addition, as described later, the sipe may be opened through a chamfered portion. In addition, the sipe may be provided with a widened bottom portion whose width is expanded at the bottom portion. In addition, in this specification, since the sipe is defined as described above, a cut with a distance between the two inner walls of 1.5 mm or more is treated as a groove.

[0046] The shoulder longitudinal sipes 31 are arranged, for example, in a central region when the tread surface 11s of the first shoulder land portion 11 is divided into three equal parts in the axial direction of the tire. The shoulder longitudinal sipes 31 are connected to the ends of the outer shoulder lateral grooves 16 on the side of the first shoulder circumferential groove 5. The shoulder longitudinal sipes 31 are connected to the ends of the inner shoulder lateral grooves 17 on the side of the first tread edge T1. The shoulder longitudinal sipes 31 extend linearly in parallel to the tire circumferential direction. Such shoulder longitudinal sipes 31 can provide a large frictional force in the axial direction of the tire when traveling on ice.

[0047] The first shoulder land portion 11 of the present embodiment includes a plurality of outer shoulder blocks 32 and a plurality of inner shoulder blocks 33. The outer shoulder blocks 32 are provided axially outward of the shoulder longitudinal sipes 31 and are separated between the two outer shoulder lateral grooves 16. The inner shoulder blocks 33 are provided axially inward of the shoulder longitudinal sipes 31 and are separated between the two inner shoulder lateral grooves 17.

[0048] 5 shows an enlarged view of the outer shoulder block 32 and the inner shoulder block 33. As shown in FIG. 5, these blocks are provided with a plurality of shoulder sipes 35. These shoulder sipes 35 cross the tread surface of the block in the tire axial direction. That is, the shoulder sipes 35 provided on the outer shoulder block 32 extend from the first tread edge T1 to the end of the shoulder longitudinal sipe 31 or the inner shoulder lateral groove 17 (shown in FIG. 2). The shoulder sipes 35 provided on the inner shoulder block 33 extend from the first shoulder circumferential groove 5 (shown in FIG. 2) to the shoulder longitudinal sipe 31. Such shoulder sipes 35 are useful for improving traction performance when traveling on ice.

[0049] In a preferred embodiment, the number N1 of shoulder sipes 35 provided on one outer shoulder block 32 is greater than the number N2 of shoulder sipes 35 provided on one inner shoulder block 33. However, the number N1 is preferably 150% or less of the number N2. This makes the wear of the outer shoulder block 32 and the inner shoulder block 33 progress uniformly, improving uneven wear resistance.

[0050] The shoulder sipe 35 includes, for example, two straight portions 41 extending linearly and a zigzag portion 42 extending zigzag between them. In this embodiment, the longitudinal ends of the shoulder sipe 35 are configured as the straight portions 41. In such a shoulder sipe 35, the sipe walls facing each other mesh with each other in the zigzag portions 42 to improve the rigidity of the land portions, while the presence of the straight portions 41 can suppress uneven wear at the ends of the sipes.

[0051] The shoulder sipes 35 include first shoulder sipes 36 and second shoulder sipes 37 having various different cross-sectional shapes. The first shoulder sipes 36 extend from the first tread edge T1 or the first shoulder circumferential groove 5 (shown in FIG. 2) to the shoulder longitudinal sipes 31. The second shoulder sipes 37 are provided in the outer shoulder block 32 and extend from the first tread edge T1 to the end of the inner shoulder lateral groove 17 (shown in FIG. 2).

[0052] FIG. 6 shows a cross-sectional view of the first shoulder sipe 36 of FIG. 5 taken along line CC. As shown in FIG. 6, the first shoulder sipe 36 includes a chamfered portion 36b that opens to the tread surface of the land portion with a width larger than that of the sipe main body portion 36a. The first shoulder sipe 36 has the above-mentioned chamfered portion 36b formed by bending only one of the sipe walls into a rectangular shape. The first shoulder sipe 36 also includes a widened bottom portion 36c whose width is expanded at the bottom. Such a first shoulder sipe 36 exhibits excellent water absorption performance and is useful for further improving wet performance and performance on ice.

[0053] The total depth d3 of the first shoulder sipes 36 is preferably smaller than the total depth d1 (shown in FIG. 3) of the outer shoulder lateral grooves 16, and more preferably 70% to 85% of the total depth d1, thereby improving the braking performance and the performance on ice in a well-balanced manner.

[0054] 7 shows a cross-sectional view of the second shoulder sipe 37 taken along line EE. As shown in FIG. 7, the second shoulder sipe 37 includes a chamfered portion 37b that opens to the tread surface of the land portion with a width greater than that of the sipe main body portion 37a. The second shoulder sipe 37 has two sipe walls that are both bent into a rectangular shape to form the chamfered portion 37b. The second shoulder sipe 37 also includes a widened bottom portion 37c whose width is increased at the bottom. Such a second shoulder sipe 37 can further improve wet performance and performance on ice.

[0055] The total depth d4 of the second shoulder sipes 37 is preferably smaller than the total depth d1 (shown in FIG. 3) of the outer shoulder lateral grooves 16, and more preferably 70% to 85% of the total depth d1. In this embodiment, the total depth d4 of the second shoulder sipes 37 is set to be the same as the total depth d3 of the first shoulder sipes 36. This suppresses uneven wear of the first shoulder land portion 11 (shown in FIG. 2).

[0056] FIG. 8 shows a cross-sectional view of the EE line in FIG. 5 as a cross-sectional view along the length of the shoulder sipe 35. In FIG. 8, the ridge lines dividing the unevenness formed in the sipe wall 35w are conceptually shown by two-dot chain lines. As shown in FIG. 7, in the straight line portion 41 of the shoulder sipe 35 of this embodiment, the sipe wall 35w is configured to be flat over the entire depth direction of the sipe, except for the portion forming the widening bottom portion. On the other hand, the zigzag portion 42 includes a first wall portion 42a in which the sipe wall 35w is uneven, and a second wall portion 42b that is connected to the inner side of the first wall portion 42a in the tire radial direction and in which the sipe wall 35w is substantially flat. The tire radial length L5 of the first wall portion 42a is greater than the tire radial distance L2 (shown in FIG. 3) from the tread surface 11s of the first shoulder land portion 11 to the minimum portion 21 of the outer shoulder lateral groove 16. Specifically, the length L5 is 2.5 to 3.5 times the distance L2. Such a first shoulder sipe 36 can exhibit the effect of maintaining the rigidity of the land portion in the zigzag portion 42 while maintaining excellent water absorption.

[0057] 5, the inner shoulder block 33 of this embodiment is provided with a plurality of short sipes 44. These short sipes 44 extend in the tire circumferential direction from the inner shoulder lateral groove 17 and terminate within the inner shoulder block 33 without communicating with the shoulder sipes 35. Such short sipes 44 facilitate appropriate deformation of the periphery of the groove edge of the inner shoulder lateral groove 17 and can suppress localized lifting of the contact patch around the groove edge during braking.

[0058] 9 shows an enlarged view of the first crown land portion 13. As shown in FIG. 9, the first crown land portion 13 is provided with a plurality of outer crown lateral grooves 46 and a plurality of inner crown lateral grooves 47. The outer crown lateral grooves 46 extend, for example, from the first shoulder circumferential groove 5 in the tire axial direction and terminate within the first crown land portion 13 without communicating with the crown circumferential groove 7. The inner crown lateral grooves 47 extend, for example, from the crown circumferential groove 7 in the tire axial direction and terminate within the first crown land portion 13 without communicating with the first shoulder circumferential groove 5. The outer crown lateral grooves 46 and the inner crown lateral grooves 47 can be applied with the configuration of the cross-sectional shape of the inner shoulder lateral groove 17 described above.

[0059] The first crown land portion 13 is provided with a plurality of crown longitudinal narrow grooves 48. For example, the crown longitudinal narrow grooves 48 extend in a zigzag shape from the end of the outer crown lateral groove 46 to the end of the inner crown lateral groove 47. Such crown longitudinal narrow grooves 48 are useful for improving cornering performance on ice.

[0060] The first crown land portion 13 includes a plurality of outer crown blocks 51 and a plurality of inner crown blocks 52. The outer crown blocks 51 are provided axially outward of the crown longitudinal narrow groove 48 and are separated between the two outer crown lateral grooves 46. The inner crown blocks 52 are provided axially inward of the crown longitudinal narrow groove 48 and are separated between the two inner crown lateral grooves 47.

[0061] The outer crown block 51 and the inner crown block 52 are provided with a plurality of crown sipes 53. The crown sipes 53 may have the same configuration as the first shoulder sipes 36 described above.

[0062] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects.

[0063] [Note] The present invention includes the following aspects.

[0064] [Invention 1] A tire having a tread portion, The tread portion includes a first tread edge and a second tread edge, a plurality of circumferential grooves extending continuously in a tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions divided by the plurality of circumferential grooves, The plurality of circumferential grooves include a first shoulder circumferential groove provided closest to the first tread end, The plurality of land portions include a first shoulder land portion including the first tread edge, The first shoulder land portion is provided with a plurality of shoulder lateral grooves extending in the tire axial direction, the shoulder lateral grooves include a plurality of outer shoulder lateral grooves communicating with the first tread edge and a plurality of inner shoulder lateral grooves communicating with the first shoulder circumferential groove, each of the plurality of outer shoulder lateral grooves and the plurality of inner shoulder lateral grooves includes an opening portion formed in a tread surface of the first shoulder land portion and a groove bottom portion; each of the outer shoulder lateral grooves includes a minimum portion that is disposed between the opening and the groove bottom and has a minimum groove width, and a maximum portion that is disposed radially inward of the minimum portion and has a groove width larger than that of the minimum portion, Each of the plurality of inner shoulder lateral grooves has a groove width that is continuously reduced from the opening to the groove bottom, or has a groove width that is constant from the opening to the groove bottom. tire. [Invention 2] The tire according to claim 1, wherein the groove width of the outer shoulder lateral groove at the minimum portion is smaller than the groove width of the inner shoulder lateral groove at the opening portion. [Invention 3] The tire according to the first or second aspect of the present invention, wherein a groove width at the opening of the outer shoulder lateral groove is greater than a groove width at the opening of the inner shoulder lateral groove. [Invention 4] The tire according to any one of claims 1 to 3, wherein the outer shoulder lateral groove and the inner shoulder lateral groove are provided without overlapping with each other in the tire axial direction. [Invention 5] The tire according to any one of claims 1 to 4, wherein the outer shoulder lateral groove is discontinued within the first shoulder land portion without reaching the first shoulder circumferential groove. [Invention 6] The tire according to any one of claims 1 to 5, wherein the inner shoulder lateral groove is discontinued within the first shoulder land portion without reaching the first tread edge. [Invention 7] The tire according to any one of claims 1 to 6, wherein in the outer shoulder lateral groove, the distance in the tire radial direction from the minimum portion to the maximum portion is greater than the distance in the tire radial direction from the opening to the minimum portion. [Invention 8] The tire according to any one of claims 1 to 7, wherein the maximum angle of the groove wall of the outer shoulder lateral groove with respect to the normal to the tire, radially outboard of the minimum portion, is 40 to 60°. [The present invention 9] The tire according to any one of claims 1 to 8, wherein the maximum angle of the groove wall of the inner shoulder lateral groove with respect to the tire normal is 5° or less. [The present invention 10] The tire according to any one of claims 1 to 9, wherein the outer shoulder lateral groove has a groove width of 2.5 to 4.5 mm at the narrowest portion. [Explanation of symbols]

[0065] 2 Tread section 3 Circumferential groove 4 Land 5 First shoulder circumferential groove 11 First Shoulder Land Section 15 Shoulder groove 16 Outer shoulder groove 17 Inner shoulder groove 21 Minimal part 22 Maximum part T1 First tread edge T2 Second tread edge

Claims

1. A tire having a tread portion, the tread portion includes a first tread edge and a second tread edge, a plurality of circumferential grooves extending continuously in a tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions divided by the plurality of circumferential grooves, The plurality of circumferential grooves include a first shoulder circumferential groove provided closest to the first tread end, the plurality of land portions include a first shoulder land portion including the first tread edge, The first shoulder land portion is provided with a plurality of shoulder lateral grooves extending in the tire axial direction, the shoulder lateral grooves include a plurality of outer shoulder lateral grooves communicating with the first tread edge and a plurality of inner shoulder lateral grooves communicating with the first shoulder circumferential groove, each of the plurality of outer shoulder lateral grooves and the plurality of inner shoulder lateral grooves includes an opening portion formed in a tread surface of the first shoulder land portion and a groove bottom portion; each of the outer shoulder lateral grooves includes a minimum portion that is disposed between the opening and the groove bottom and has a minimum groove width, and a maximum portion that is disposed radially inward of the minimum portion and has a groove width larger than that of the minimum portion, Each of the plurality of inner shoulder lateral grooves has a groove width that is continuously reduced from the opening to the groove bottom, or has a groove width that is constant from the opening to the groove bottom. tire.

2. The tire according to claim 1 , wherein a groove width at the minimum portion of the outer shoulder lateral groove is smaller than a groove width at the opening portion of the inner shoulder lateral groove.

3. The tire according to claim 1 or 2, wherein a groove width at the opening of the outer shoulder lateral groove is greater than a groove width at the opening of the inner shoulder lateral groove.

4. The tire according to claim 1 or 2, wherein the outer shoulder lateral groove and the inner shoulder lateral groove are provided without overlapping with each other in the tire axial direction.

5. The tire according to claim 1 or 2, wherein the outer shoulder lateral groove is discontinued within the first shoulder land portion without reaching the first shoulder circumferential groove.

6. The tire according to claim 1 or 2, wherein the inner shoulder lateral groove is discontinued within the first shoulder land portion without reaching the first tread edge.

7. The tire according to claim 1 or 2, wherein in the outer shoulder lateral groove, a distance in the tire radial direction from the minimum portion to the maximum portion is greater than a distance in the tire radial direction from the opening portion to the minimum portion.

8. 3. The tire according to claim 1, wherein a maximum angle of a groove wall of the outer shoulder lateral groove with respect to a normal to the tire, on an outer side of the minimum portion in the tire radial direction, is 40 to 60 degrees.

9. 3. The tire according to claim 1, wherein the maximum angle of the groove wall of the inner shoulder lateral groove with respect to the tire normal is 5° or less.

10. 3. The tire according to claim 1, wherein the outer shoulder lateral groove has a groove width of 2.5 to 4.5 mm at the narrowest portion.

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