Tire

Abstract

To provide a tire capable of exhibiting excellent on-ice performance while suppressing damage of a block.SOLUTION: The present invention relates to a tire having a tread part 2. The tread part 2 includes a plurality of blocks 9, and at least one of the plurality of blocks 9 includes at least one first transverse sipe 8. The first horizontal sipe 8 includes a body part 25 and a widening part 26. The body part 25 includes a pair of concave and convex sipe wall parts 27 extending in a wavy manner in the tire axial direction and the tire radial direction. The first transverse sipe 8 has a sipe depth which is a distance in the tire radial direction from the ground plane 9s to the inner end of the widening part 26 in the tire radial direction, and the sipe depth d2 of both end parts 8e in the tire axial direction of the first transverse sipe 8 is smaller than the sipe depth d1 of the central part 8c in the tire axial direction of the first transverse sipe 8.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 in which a plurality of sipes are provided in a block. The sipes include a first sipe in which a sipe body is formed by a sipe wall extending in a planar shape, and a second sipe in which a sipe body is formed by a sipe wall extending in a wavy shape. Further, widened portions are provided on the tire radially inner side of the sipe body portions of the first sipe and the second sipe. In this tire, even if a large circumferential shear force acts on the block in which the sipe is provided, the widened portions suppress stress concentration on the bottom portion of the sipe, and damage to the block can be suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7306163 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, tires have been provided with many sipes in the blocks in order to further improve performance on ice, but such blocks may have reduced rigidity, and therefore there is a need to suppress damage to the blocks caused by the sipes.

[0005] The present invention has been devised in view of the above-mentioned circumstances, and has as its main object to provide a tire that can exhibit excellent performance on ice while suppressing damage to the blocks. [Means for solving the problem]

[0006] The present invention is a tire having a tread portion, the tread portion including a plurality of blocks, at least one of the plurality of blocks including at least one first lateral sipe that completely crosses the ground contact surface of the block in the tire axial direction, the first lateral sipe including a main body portion extending in the tire radial direction and a widened portion that is connected to the radially inward side of the main body portion and has a width greater than that of the main body portion, the main body portion including a pair of uneven sipe wall portions that extend in a wavy manner in the tire axial direction and the tire radial direction, the first lateral sipe has a sipe depth that is the radial distance from the ground contact surface to the radially inner end of the widened portion, and the sipe depth of both ends of the first lateral sipe in the tire axial direction is smaller than the sipe depth of a central portion of the first lateral sipe in the tire axial direction. Effect of the Invention

[0007] The tire of the present invention can exhibit excellent performance on ice while suppressing damage to the blocks. [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 crown land portion of FIG. [Diagram 3] FIG. 3 is an enlarged view of the outer crown block of FIG. 2. [Figure 4] FIG. 4 is a perspective view of a sipe wall of the first horizontal sipe of FIG. 3. [Diagram 5] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 4 is a cross-sectional view taken along line BB in FIG. [Figure 7] 4 is a cross-sectional view taken along line CC in FIG. [Figure 8] FIG. 6 is an end view taken along line DD in FIG. 5. [Figure 9] 4 is a cross-sectional view taken along line EE in FIG. [Figure 10] FIG. 2 is an enlarged view of a first shoulder land portion of FIG. [Figure 11] 11 is a cross-sectional view taken along the line FF in FIG. 10. [Figure 12] 11 is a cross-sectional view taken along line GG in FIG. 10. 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. However, 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] The tread portion 2 includes a plurality of blocks 9. Hereinafter, the configuration will be described using the blocks included in the first crown land portion 13 as an example. Fig. 2 shows an enlarged view of the first crown land portion 13. As shown in Fig. 2, the first crown land portion 13 of this embodiment is provided with a plurality of outer crown lateral grooves 15, a plurality of inner crown lateral grooves 16, and a plurality of crown longitudinal sipes 17.

[0022] The outer crown lateral groove 15 extends axially inward from the first shoulder circumferential groove 5 and terminates within the first crown land portion 13. The inner crown lateral groove 16 extends axially outward from the crown circumferential groove 7 and terminates within the first crown land portion 13. The crown longitudinal sipe 17 communicates with the outer crown lateral groove 15 and the inner crown lateral groove 16. Specifically, the crown longitudinal sipe 17 communicates with an axially inner end of the outer crown lateral groove 15 and an axially outer end of the inner crown lateral groove 16.

[0023] In this specification, the term "sipe" refers to a recess having a longitudinal direction, which includes an area where two inner walls contact each other when a normal load is applied to the ground contact surface. The sipe width in the area (the distance between the two inner walls in the normal state) is less than 1.5 mm, and preferably 0.5 to 1.2 mm. The sipe may partially include an area where the two inner walls do not contact each other when a normal load is applied. For this reason, the sipe may include a chamfered portion or a widened portion, which will be described later.

[0024] The first crown land portion 13 of the present invention includes a plurality of outer crown blocks 21 and a plurality of inner crown blocks 22. The outer crown block 21 is divided into two outer crown lateral grooves 15 and a crown longitudinal sipe 17. The inner crown block 22 is divided into two inner crown lateral grooves 16 and a crown longitudinal sipe 17. Thus, the block 9 of the present invention includes at least the outer crown block 21 and the inner crown block 22. However, the present invention is not limited to such an embodiment.

[0025] Fig. 3 shows an enlarged view of an outer crown block 21 as an example of a block 9. As shown in Fig. 3, at least one of the blocks 9 includes at least one first transverse sipe 8 that completely crosses the contact surface of the block 9 in the tire axial direction. The block 9 shown in Fig. 3 has four first transverse sipes 8, but the present invention is not limited to this embodiment.

[0026] Fig. 4 shows a perspective view conceptually illustrating a sipe wall of the first transverse sipe 8. Fig. 5 shows a cross-sectional view taken along line AA in Fig. 3. Fig. 6 shows a cross-sectional view taken along line BB in Fig. 3. Fig. 7 shows a cross-sectional view taken along line CC in Fig. 3. As shown in Figs. 4 to 7, the first transverse sipe 8 includes a main body portion 25 extending in the tire radial direction (more specifically, in the sipe depth direction), and a widened portion 26 that is continuous with the main body portion 25 on the inner side in the tire radial direction and has a width greater than that of the main body portion 25. The widened portion 26 forms a bottom portion of the first transverse sipe 8.

[0027] As shown in Figures 4 and 5, the main body 25 includes a pair of concave-convex sipe wall portions 27 that extend wavy in the tire axial direction and the tire radial direction. In Figures 3 and 4, one of the pair of concave-convex sipe wall portions 27 is shown, and the other concave-convex sipe wall portion 27 is disposed opposite to the one so as to form a constant sipe width. This other concave-convex sipe wall portion 27 also has the configuration shown in Figures 4 and 5. In Figure 5, a ridge line 28 formed by bending the sipe wall is conceptually shown by a two-dot chain line.

[0028] 5 to 7, the first transverse sipes 8 have a sipe depth that is the distance in the tire radial direction from the contact surface 9s to the radially inner end of the widened portion 26. In addition, the sipe depth d2 of both end portions 8e of the first transverse sipes 8 in the tire axial direction (more specifically, in the sipe longitudinal direction) is smaller than the sipe depth d1 of the axial center portion 8c of the first transverse sipes 8. This allows the tire of the present invention to exhibit excellent on-ice performance while suppressing damage to the blocks 9. The reason for this is as follows.

[0029] As shown in FIG. 3, at least one first transverse sipe 8 is provided in the block 9. The first transverse sipe 8 provides friction in the circumferential direction of the tire when traveling on ice, and can improve performance on ice. Also, as shown in FIG. 4 and FIG. 5, the main body 25 of the first transverse sipe 8 of the present invention includes a pair of concave-convex sipe wall portions 27. When ground pressure acts on the block 9, the pair of concave-convex sipe wall portions 27 of such a main body 25 can mesh with each other to maintain the rigidity of the block 9. Therefore, the widened portion 26 can suppress stress concentration on the bottom portion of the first transverse sipe. This can suppress damage to the block 9.

[0030] 5 to 7, in the present invention, the sipe depth d2 of each of the first transverse sipes 8 at both ends 8e in the tire axial direction is smaller than the sipe depth d1 of each of the first transverse sipes 8 at the center portion 8c in the tire axial direction. This increases the rigidity of the ends of the first transverse sipes 8, and further suppresses damage to the blocks 9 originating from the ends. In addition, the center portion 8c of the first transverse sipes 8 has a sufficient depth, so that the water absorption of the sipes is not impaired, and excellent performance on ice can be achieved.

[0031] 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.

[0032] 3, a plurality of first transverse sipes 8 are provided in one block 9, and preferably two to four first transverse sipes 8 are provided. In this embodiment, two sipe pairs 10 each consisting of two adjacent first transverse sipes 8 are arranged in one block 9.

[0033] In a plan view of the tread, each first lateral sipe 8 includes, for example, a straight portion 30 extending linearly from one end or the other end in the tire axial direction, and a zigzag portion 31 extending zigzag between them. In this embodiment, the two straight portions 30 have the above-mentioned sipe depth d2. The zigzag portion 31 includes the concave-convex sipe wall portion 27 and has the above-mentioned sipe depth d1. The length of each straight portion 30 in a plan view of the tread (so-called periphery length, the same applies below) is 10% to 20% of the length of the first lateral sipe 8. The length of the zigzag portion 31 is 60% to 80% of the length of the first lateral sipe 8.

[0034] It is desirable that the first lateral sipes 8 are inclined with respect to the tire axial direction. The angle of a virtual line (not shown) connecting both ends of the first lateral sipes 8 is, for example, 5 to 15°.

[0035] As shown in Figures 6 and 7, the first transverse sipes 8 open at the ground contact surface 9s, for example, through the chamfered portion 33. In this embodiment, one sipe wall 8w extends linearly from the ground contact surface 9s, and the other sipe wall 8w is bent into a rectangular shape and connected to the ground contact surface 9s. As a result, the opening width W2 of the first transverse sipes 8 is, for example, 1.5 to 2.5 mm. Such chamfered portion 33 can improve wet performance while suppressing uneven wear around the sipes.

[0036] Moreover, the main body portion 25 extends in the tire radial direction with a constant width (meaning the distance between two sipe walls 8w) even at both ends 8e in the tire axial direction and in the region where the concave-convex sipe wall portion 27 is formed. Here, the constant width includes a mode in which the difference between the maximum width and the minimum width in the main body portion 25 is 5% or less of the maximum width, from the viewpoint of allowing for unavoidable errors in rubber products such as tires. The width W3 of the main body portion 25 is, for example, 0.4 to 0.8 mm. In such a main body portion 25, the two sipe walls 8w are tightly adhered to each other when ground pressure acts on the first lateral sipe 8, and the rigidity of the block 9 can be more effectively maintained.

[0037] The main body portion 25 is formed over the entire length of the first transverse sipe 8. Also, as shown in Figs. 4 and 5, at least one, preferably both, of the end portions 8e of the first transverse sipe 8, the main body portion 25 includes a pair of flat sipe wall portions 34 extending in a single plane. In a more preferable embodiment, the entire portion between the chamfered portion 33 and the widened portion 26 at both end portions 8e is configured as the flat sipe wall portion 34. As a result, the edge of the first transverse sipe 8 becomes straight on the side wall of the block 9, and damage around this edge is suppressed.

[0038] 8 shows an end view of the line DD in FIG. 5. As shown in FIG. 8, a pair of uneven sipe wall portions 27 in the main body portion 25 extends in the tire radial direction while maintaining the zigzag shape of the zigzag portion 31 (shown in FIG. 3) that can be observed in a plan view of the tread of the block 9. The uneven sipe wall portion 27 includes a plurality of bent portions 36 that can be observed in a cross section parallel to the ground contact surface of the block 9. The bent angle θ1 of these bent portions 36 is, for example, 110 to 130°. The bent portion 36 includes two portions that are inclined in opposite directions and directly connected to each other to form a convex portion, and no portion extending along the sipe longitudinal direction is included between the two portions. Moreover, the amplitude A1 (peak-to-peak amplitude, the same applies below) of the pair of concave-convex sipe wall portions 27 in the tire circumferential direction (more specifically, the direction perpendicular to the sipe longitudinal direction) in this cross section is 0.5 to 3.0 mm. This makes it possible to obtain the above-mentioned effects while suppressing molding defects during vulcanization molding.

[0039] From the same viewpoint, as shown in FIG. 7, the pair of concave-convex sipe wall portions 27 in the main body portion 25 extends in the sipe longitudinal direction while maintaining the zigzag shape that can be observed in the cross section of the first transverse sipe 8. The pair of concave-convex sipe wall portions 27 includes two or more bent portions 37 in the tire radial direction. The bent portion 37 has a bent angle θ2 of, for example, 130 to 150°. The bent portion 37 includes two portions that are inclined in opposite directions and directly connected to each other to form a convex portion, and no portion extending along the tire radial direction is included between the two portions. The amplitude A2 of the pair of concave-convex sipe wall portions 27 in this cross section in the tire circumferential direction (more specifically, in the direction perpendicular to the sipe depth direction) is 0.5 to 3.0 mm.

[0040] As shown in Fig. 4, it is desirable that the radially inner end of the uneven sipe wall portion 27 is located radially outward of the position of the smallest sipe depth at both end portions 8e. It is also desirable that the axial length of the uneven sipe wall portion 27 is smaller than the axial length of the center portion 8c (the length of the portion excluding both end portions 8e having a sipe depth d2 (shown in Fig. 5) described later from the first lateral sipe 8). This prevents the area of ​​the uneven sipe wall portion 27 from becoming excessively large, and the water absorption performance of the first lateral sipe 8 can be sufficiently ensured.

[0041] As shown in FIG. 5, if the difference in depth between the center 8c and both ends 8e of the first transverse sipe 8 is small, the above-mentioned effect of increasing the rigidity of both ends 8e may not be fully achieved. Conversely, if the difference in depth is excessively large, the wear of the edge of the first transverse sipe 8 may progress unevenly between the center 8c and both ends 8e, which may lead to uneven wear of the ground contact surface 9s of the block 9. Therefore, in a desirable embodiment, the difference between the maximum sipe depth at the center 8c of the first transverse sipe 8 and the minimum sipe depth at both ends 8e of the first transverse sipe 8 is 5% to 15% of the maximum depth da of the circumferential groove 3. Here, the circumferential groove 3 means the circumferential groove 3 adjacent to the block 9, and in this embodiment means the first shoulder circumferential groove 5 (shown in FIG. 1). In a more desirable embodiment, the sipe depth d1 at the center 8c of the first transverse sipe 8 is 55% to 65% of the maximum depth da of the circumferential groove 3. Further, the sipe depth d2 at both ends 8e of the first transverse sipes 8 is 45% to 55% of the maximum depth da of the circumferential groove 3. By providing the first transverse sipes 8 with such a depth, the durability and on-ice performance of the blocks 9 can be improved in a well-balanced manner.

[0042] Moreover, the sipe depth d2 at both end portions 8e of the first transverse sipes 8 is preferably 80% to 90% of the sipe depth d1 at the central portion 8c of the first transverse sipes 8. This improves the durability and on-ice performance of the blocks 9 in a well-balanced manner.

[0043] 4, 6 and 7, the widened portions 26 are formed over the entire length of the first transverse sipe 8. Also, as shown in Fig. 6 and 7, the widened portions 26 at both ends 8e of the first transverse sipe 8 are configured to have a shape smaller than the widened portion 26 at the central portion 8c of the first transverse sipe 8. The width W5 of the widened portions 26 at both ends 8e is, for example, 60% to 75% of the width W4 of the widened portion 26 at the central portion 8c.

[0044] As shown in FIG. 7, the widened portion 26 includes a first curved surface 38a and a second curved surface 38b in a communicating portion 26a that is connected to the main body portion 25 that extends with a constant width. The first curved surface 38a and the second curved surface 38b are smoothly curved in a direction away from each other toward the tire radially inward. The curvature radius r1 of the first curved surface 38a is, for example, 8 to 12 mm. The curvature radius r2 of the second curved surface 38b is smaller than the curvature radius r1, for example, 4 to 6 mm. In a desirable embodiment, the second curved surface 38b is formed on the sipe wall on the side where the chamfered portion 33 is provided.

[0045] The widened portion 26 includes a curved surface 38c between its maximum width position and the inner end. The radius of curvature r3 of the curved surface 38c is, for example, 0.4 to 0.8 mm. The curved surface 38c on the side where the chamfered portion 33 is disposed has a larger radius of curvature than the curved surface 38c on the opposite side.

[0046] FIG. 9 shows a cross-sectional view of the EE line in FIG. 3 as a diagram showing a cross section of the sipe pair 10. As shown in FIG. 9, one of the first horizontal sipes 8 included in the sipe pair 10 is arranged so that the sipe wall 8w including the chamfered portion 33 is located on the opposite side to the other first horizontal sipe 8. The other first horizontal sipe 8 is similarly arranged. As a result, the first curved surface 38a of the widened portion 26 of one of the first horizontal sipes 8 is located on the side of the other first horizontal sipe 8. Similarly, the first curved surface 38a of the widened portion 26 of the other first horizontal sipe 8 is also located on the side of the one first horizontal sipe 8. As a result, the rigidity of the root portion of the rubber piece sandwiched between the sipe pair 10 is maintained, and damage to the block can be further suppressed.

[0047] As shown in Fig. 2, the outer crown lateral groove 15 and the inner crown lateral groove 16 each extend linearly and inclined with respect to the tire axial direction. In a preferred embodiment, the inner crown lateral groove 16 is inclined in the opposite direction to the outer crown lateral groove 15 with respect to the tire axial direction. The angle of these lateral grooves with respect to the tire axial direction is, for example, 5 to 15 degrees. This provides excellent wet performance.

[0048] The crown longitudinal sipes 17 extend, for example, in a zigzag shape. The maximum depth of the crown longitudinal sipes 17 is 90% to 110% of the sipe depth d1 (shown in FIG. 5) of the central portion 8c of the first horizontal sipe 8. Such crown longitudinal sipes 17 are useful for improving the durability and wet performance of the block in a well-balanced manner.

[0049] Each of the outer crown block 21 and the inner crown block 22 is provided with a plurality of short sipes 35. The short sipes 35 extend in the tire circumferential direction from the outer crown lateral groove 15 or the inner crown lateral groove 16, and end without reaching the first lateral sipes 8. Such short sipes 35 provide frictional force in the tire axial direction during running on wet roads.

[0050] Fig. 10 shows an enlarged view of the first shoulder land portion 11 of Fig. 1. As shown in Fig. 10, the first shoulder land portion 11 of this embodiment is provided with a plurality of outer shoulder lateral grooves 45, a plurality of inner shoulder lateral grooves 46, and a plurality of shoulder longitudinal sipes 48.

[0051] The outer shoulder lateral groove 45 extends axially inward from the first tread edge T1 and terminates within the first shoulder land portion 11. The inner shoulder lateral groove 46 extends axially outward from the first shoulder circumferential groove 5 and terminates within the first shoulder land portion 11. The shoulder longitudinal sipe 48 communicates with the outer shoulder lateral groove 45 and the inner shoulder lateral groove 46. Specifically, the shoulder longitudinal sipe 48 communicates with an axially inner end of the outer shoulder lateral groove 45 and an axially outer end of the inner shoulder lateral groove 46.

[0052] The first shoulder land portion 11 of the present invention includes a plurality of outer shoulder blocks 51 and a plurality of inner shoulder blocks 52. The outer shoulder block 51 is divided into two outer shoulder lateral grooves 45 and a shoulder longitudinal sipe 48. The inner shoulder block 52 is divided into two inner shoulder lateral grooves 46 and a shoulder longitudinal sipe 48.

[0053] At least one second transverse sipe 55 that completely crosses the ground contact surfaces of the outer shoulder block 51 and the inner shoulder block 52 in the tire axial direction is provided on the outer shoulder block 51 and the inner shoulder block 52. The characteristics of the second transverse sipe 55 will be described below, but the characteristics of the first transverse sipe 8 can be applied to the second transverse sipe 55 for matters that are not described.

[0054] FIG. 11 shows a cross-sectional view of the line FF in FIG. 10 as a diagram showing the sipe wall of the second transverse sipe 55. As shown in FIG. 11, the second transverse sipe 55 includes a main body portion 56 extending in the tire radial direction, and a widened portion 57 that is connected to the tire radially inward side of the main body portion 56 and has a width larger than that of the main body portion 56. The main body portion 56 includes a pair of uneven sipe wall portions 58 that extend in a wavy manner in the tire axial direction. Unlike the first transverse sipe 8, the pair of uneven sipe wall portions 58 of the second transverse sipe 55 extend in a zigzag manner in a cross section along the ground contact surface of the block, but extend in a straight line in a cross section perpendicular to the sipe length direction. As a result, even if two sipe walls included in the second transverse sipe 55 come into contact with each other, these sipe walls slide in the tire radial direction and shear deformation, making it easier for the edges of the second transverse sipe 55 to provide frictional force in the tire circumferential direction. Therefore, wet performance is improved.

[0055] The sipe depth d4 of the second lateral sipes 55 at both ends 55e in the tire axial direction is smaller than the sipe depth d3 of the center portion 55c in the tire axial direction of the second lateral sipes 55. The sipe depth d4 of the second lateral sipes 55 at both ends 55e is, for example, 90% to 95% of the sipe depth d3 of the center portion 55c of the second lateral sipes 55. As a result, the ratio of the sipe depth d4 of the both ends to the sipe depth d3 of the center portion 55c of the second lateral sipes 55 is greater than the ratio of the sipe depth d2 of the both ends 8e to the sipe depth d1 of the center portion 8c of the first lateral sipes 8. As a result, the second lateral sipes 55 can exhibit high water absorption, improving wet performance.

[0056] 10, the inner shoulder block 52 and the outer shoulder block 51 are provided with a plurality of second transverse sipes 55. The number of second transverse sipes 55 provided on the outer shoulder block 51 is greater than the number of second transverse sipes 55 provided on the inner shoulder block 52. Specifically, the outer shoulder block 51 is provided with five second transverse sipes 55, and the inner shoulder block 52 is provided with four second transverse sipes 55.

[0057] Fig. 12 shows a cross-sectional view of line GG in Fig. 10 as a diagram illustrating the characteristics of the second transverse sipes 55 provided on the outer shoulder block 51. As shown in Fig. 12, at least one of the second transverse sipes 55 provided on the outer shoulder block 51 includes a chamfered portion 59 in which both sipe walls 55w are bent into a rectangular shape and connected to the ground contact surface. Such a second transverse sipe 55 can reliably suppress uneven wear around its edge.

[0058] As shown in Fig. 10, the second lateral sipe 55 shown in Fig. 12 is provided in the circumferential center of the outer shoulder block 51. More specifically, the second lateral sipe 55 is provided in the central region when the contact surface of the outer shoulder block 51 is divided by two imaginary straight lines extending parallel to the tire axial direction so that the contact surface is divided into three equal parts. In a more preferable embodiment, the second lateral sipe 55 communicates with the inner shoulder lateral groove 46. This can further suppress damage to the outer shoulder block 51.

[0059] 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.

[0060] [Note] The present invention includes the following aspects.

[0061] [Invention 1] A tire having a tread portion, The tread portion includes a plurality of blocks, At least one of the plurality of blocks includes at least one first lateral sipe that completely crosses the contact surface of the block in the tire axial direction, The first lateral sipe includes a main body portion extending in a tire radial direction and a widened portion that is connected to the main body portion on the inner side in the tire radial direction and has a width larger than that of the main body portion, The main body portion includes a pair of uneven sipe wall portions extending in a wavy manner in the tire axial direction and the tire radial direction, The first lateral sipe has a sipe depth that is a distance in the tire radial direction from the ground contact surface to an inner end of the widened portion in the tire radial direction, The sipe depth of the first lateral sipe at both ends in the tire axial direction is smaller than the sipe depth of the first lateral sipe at a center portion in the tire axial direction. tire. [Invention 2] The tire according to claim 1, wherein the main body portion extends in the tire radial direction with a constant width. [Invention 3] The tire according to claim 2, wherein the main body portion and the widened portion are each formed over the entire length of the first lateral sipe. [Invention 4] The tire according to claim 3, wherein at least one of the opposite ends of the first lateral sipe includes a pair of flat sipe wall portions extending in a single plane. [Invention 5] The tread portion includes a circumferential groove adjacent to the block and extending continuously in a tire circumferential direction, The tire according to any one of claims 1 to 4, wherein a difference between a maximum sipe depth of the first lateral sipe at the central portion and a minimum sipe depth of the first lateral sipe at both end portions is 5% to 15% of a maximum depth of the circumferential groove. [Invention 6] The sipe depth of the first lateral sipe at the central portion is 55% to 65% of the maximum depth of the circumferential groove, The tire according to invention 5, wherein the sipe depth of each of the first lateral sipes at both end portions is 45% to 55% of the maximum depth of the circumferential groove. [Invention 7] The tire according to any one of claims 1 to 6, wherein the pair of uneven sipe wall portions has an amplitude of 0.5 to 3.0 mm in the tire circumferential direction. [Invention 8] The tire according to any one of claims 1 to 7, wherein the pair of concave-convex sipe wall portions includes two or more bent portions in the tire radial direction. [The present invention 9] The widened portion includes a curved surface between a maximum width position and the inner end, The tire according to any one of claims 1 to 8, wherein the curved surface has a radius of curvature of 0.4 to 0.8 mm. [The present invention 10] The tire according to any one of claims 1 to 9, wherein the at least one block is provided with two to four of the first lateral sipes. [The present invention 11] an inner end of the uneven sipe wall portion in the tire radial direction is located inward in the tire radial direction from a position where the sipe depth is smallest at both ends, The tire according to any one of claims 1 to 10, wherein the length of the uneven sipe wall portion in the tire axial direction is smaller than the length of the central portion in the tire axial direction. [Explanation of symbols]

[0062] 2 Tread section 8 First horizontal sipe 8e Both ends 8c central part 9 Blocks 9s ground plane 25 Main body 26 Widening section 27 Concave and convex sipe wall d1 Depth of the center of the first horizontal sipe d2 Sipe depth at both ends of the first horizontal sipe

Claims

1. A tire having a tread portion, The tread portion includes a plurality of blocks, At least one of the plurality of blocks includes at least one first lateral sipe that completely crosses the contact surface of the block in the tire axial direction, The first lateral sipe includes a main body portion extending in a tire radial direction and a widened portion connected to the main body portion on an inner side in the tire radial direction and having a width larger than that of the main body portion, The main body portion includes a pair of uneven sipe wall portions extending in a wavy manner in the tire axial direction and the tire radial direction, The first lateral sipe has a sipe depth that is a distance in the tire radial direction from the ground contact surface to an inner end of the widened portion in the tire radial direction, A sipe depth at both ends of the first lateral sipe in the tire axial direction is smaller than a sipe depth at a center portion of the first lateral sipe in the tire axial direction. tire.

2. The tire of claim 1 , wherein the body portion extends radially of the tire with a constant width.

3. The tire according to claim 2 , wherein the main body portion and the widened portion are each formed over an entire length of the first lateral sipe.

4. The tire of claim 3 , wherein at least one of said opposite ends of said first transverse sipe, said body portion includes a pair of flat sipe wall portions extending in a single plane.

5. The tread portion includes a circumferential groove adjacent to the block and extending continuously in a tire circumferential direction, The tire according to any one of claims 1 to 4, wherein a difference between a maximum sipe depth at the central portion of the first lateral sipe and a minimum sipe depth at both ends of the first lateral sipe is 5% to 15% of a maximum depth of the circumferential groove.

6. A sipe depth of the first lateral sipe at the central portion is 55% to 65% of a maximum depth of the circumferential groove, The tire according to claim 5, wherein a sipe depth at each of the two end portions of the first lateral sipe is 45% to 55% of a maximum depth of the circumferential groove.

7. 5. The tire according to claim 1, wherein the pair of concave-convex sipe wall portions have an amplitude of 0.5 to 3.0 mm in the tire circumferential direction.

8. The tire according to claim 1 , wherein the pair of concave-convex sipe wall portions includes two or more bent portions in the tire radial direction.

9. The widened portion includes a curved surface between a maximum width position and the inner end, 5. The tire according to claim 1, wherein the radius of curvature of the curved surface is 0.4 to 0.8 mm.

10. The tire according to any one of claims 1 to 4, wherein the at least one block is provided with two to four of the first lateral sipes.

11. an inner end of the uneven sipe wall portion in the tire radial direction is located inward in the tire radial direction from a position where the sipe depth is smallest at both ends, The tire according to claim 1 , wherein an axial length of the uneven sipe wall portion is smaller than an axial length of the central portion.

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