Pneumatic tire

Abstract

To provide a pneumatic tire which suppresses increase in heel-and-toe wear while suppressing generation of shoulder drop wear.SOLUTION: A pneumatic tire 1 comprises: a shoulder land 20 of which at least a tire axil direction outer end is partitioned in a tire circumferential direction; a first recess 31 at a center in a tire circumferential direction of a shoulder outside surface 22; a second recess 32 of the shoulder outside surface 22 that is shallower than the first recess 31 on one side in the tire circumferential direction with respect to the first recess 31; and a third recess 33 of the shoulder outside surface 22 that is shallower than the first recess 31 on the other side in the tire circumferential direction with respect to the first recess 31. Outer diameter ends 31a, 32a, 33a of the first to third recesses 31, 32, 33 are positioned in a first tire radial direction range X1 up to 3.0 mm on a tire radial direction inner side from a chamfer 25 when the shoulder land 20 has the chamfer 25, or from the tire axial direction outer end of a shoulder ground plane 21 when the shoulder land 20 does not have a chamfer.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses a pneumatic tire in which a groove extending in the tire circumferential direction is provided on the buttress surface of the pneumatic tire. By forming the groove on the buttress surface, the rigidity of the tread near the ground contact edge can be reduced, improving ground contact near the ground contact edge, thereby suppressing the occurrence of uneven wear, specifically uneven wear in which the axially outer side of the shoulder land wears faster than the remaining part (hereinafter referred to as shoulder drop wear on the shoulder land). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-001617 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a groove is formed on the outer surface of the axially outer side of the shoulder land, which is defined at least at the axially outer end in the circumferential direction of the tire, the rigidity of the shoulder land at both circumferential ends of the tire is likely to be excessively reduced, which may result in increased heel-and-toe wear.

[0005] An object of the present invention is to provide a pneumatic tire that can suppress the occurrence of shoulder drop wear on the shoulder land while suppressing an increase in heel-and-toe wear. [Means for solving the problem]

[0006] One aspect of the present invention is A shoulder land is located at an end of the tread on an outer side in the tire axial direction, and at least an outer end of the shoulder land is defined in the tire circumferential direction. A first recess is recessed axially inward at a center in the circumferential direction of the tire on an outer surface on an axially outer side of the shoulder land; a second recess located on one side of the outer surface of the shoulder land in the tire circumferential direction with respect to the first recess, recessed axially inward, and shallower than the first recess; a third recess located on the other side of the outer surface of the shoulder land in the tire circumferential direction relative to the first recess, recessed axially inward, and shallower than the first recess; Equipped with The present invention provides a pneumatic tire, in which the radially outer ends of the first depression, the second depression, and the third depression are located within a radially inward range of up to 3.0 mm from a chamfer at the axially outer end of the contact surface of the shoulder land when the shoulder land has a chamfer, or from the axially outer end of the contact surface of the shoulder land when the shoulder land does not have the chamfer.

[0007] According to one aspect of the present invention, the first, second, and third recesses located near the ground contact surface of the shoulder land can reduce the rigidity of the axially outer end of the shoulder land. For example, when the pneumatic tire is mounted on a steering shaft and steering is performed, the shoulder land is easily deformed not only at the axially outer end but also at the axially inner part in order to match the road surface. In this case, the load that tends to concentrate at the axially outer end of the shoulder land is easily distributed to the remaining part, and the occurrence of shoulder drop wear of the shoulder land is suppressed.

[0008] Furthermore, because the second and third recesses are shallower than the first recess, excessive decrease in stiffness at both ends of the shoulder land in the tire circumferential direction is suppressed. As a result, an increase in the amount of slippage when the shoulder land contacts the road surface (also called stepping on) and when it leaves the road surface (also called kicking off) during the rolling of the pneumatic tire is suppressed, and an increase in heel-and-toe wear is suppressed.

[0009] Therefore, the first recess, the second recess, and the third recess can suppress the occurrence of shoulder drop wear on the shoulder land while suppressing an increase in heel-and-toe wear. [Brief description of the drawings]

[0010] [Figure 1] 1 is a meridian cross-sectional view of a pneumatic tire according to a first embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] Enlarged view of area Z in Figure 1. [Figure 4] Cross section of the shoulder land along line IV in Figure 3 . [Diagram 5] FIG. 11 is a cross-sectional view of a shoulder land according to a first modified example. [Figure 6] FIG. 11 is a cross-sectional view of a shoulder land according to a second modified example. [Figure 7] FIG. 13 is a cross-sectional view of a shoulder land according to a third modified example. [Figure 8] FIG. 13 is a cross-sectional view of a shoulder land according to the fourth modified example. [Figure 9] FIG. 13 is a cross-sectional view of a shoulder land according to the fifth modified example. [Figure 10] 5 is a cross-sectional view similar to FIG. 3 of a pneumatic tire according to a second embodiment. [Figure 11] 7 is a cross-sectional view similar to FIG. 3 of a pneumatic tire according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following description is essentially merely illustrative and is not intended to limit the present invention, its applications, or its uses. The drawings are schematic, and the ratios of dimensions, etc., differ from the actual ones.

[0012] [First embodiment] 1 is a cross-sectional view in the meridian direction of a pneumatic tire 1 according to a first embodiment of the present invention, and only one side with respect to a tire equator line CL is shown. The pneumatic tire 1 is configured as a tire for trucks, buses, or light trucks, and may be a heavy-duty pneumatic tire. In this specification, with respect to the tire axial direction, the direction toward the tire equator line CL is referred to as the tire axial inner side, and the direction away from the tire equator line CL is referred to as the tire axial outer side.

[0013] The pneumatic tire 1 includes a tread 2, a pair of sidewalls 3 extending radially inward from both axial ends of the tread 2, and a pair of beads 4 each continuing to the radially inward side of the pair of sidewalls 3.

[0014] A bead core 5 and a bead filler 6 connected to the outer side in the tire radial direction are embedded in the bead 4. The bead core 5 is formed by covering an annular bundle of bead wires made of steel wires wound multiple times with rubber. The cross-sectional shape of the bead core 5 is formed into a polygonal shape so that the bead core radial outer end surface 5a extending in the tire axial direction is located at the outer end in the tire radial direction. The bead filler 6 is made of hard rubber extending in an annular shape along the bead core radial outer end surface 5a, and the cross-sectional shape in the meridian direction is formed into a triangular shape that narrows in the tire axial direction toward the outer side in the tire radial direction.

[0015] A carcass ply 7 is laid across the tread 2 and sidewall 3 between a pair of bead cores 5. The carcass ply 7 is folded back from the inner surface side of the tire to the outer surface side of the tire around the bead cores 5. An inner liner 8 for retaining air pressure is provided on the inner surface side of the carcass ply 7.

[0016] A belt layer 10 is provided on the tire radial inner side of the tread 2. The belt layer 10 includes a first belt 11, a second belt 12, a third belt 13, and a fourth belt 14. The first belt 11 is laminated on the carcass ply 7 on the tire radial outer side. The second belt 12 is laminated on the first belt 11 on the tire radial outer side. The third belt 13 is laminated on the second belt 12 on the tire radial outer side. The fourth belt 14 is laminated on the third belt 13 on the tire radial outer side. Each of the first belt 11, the second belt 12, the third belt 13, and the fourth belt 14 is configured by covering a plurality of tire cords that are aligned parallel to the tire circumferential direction or at a predetermined inclination angle with a topping rubber. For example, a steel cord is used as the tire cord.

[0017] In this embodiment, the second belt 12 of the belt layer 10 constitutes a wide belt that is the widest in the tire axial direction. That is, the outer end point of the second belt 12 located most outward in the tire axial direction constitutes the belt end 10A of the belt layer 10 located most outward in the tire axial direction.

[0018] A plurality of circumferential grooves 15 extending in the circumferential direction of the tire are formed in the tread 2. The circumferential grooves 15 divide the tread 2 into a plurality of lands 16 in the axial direction of the tire. The lands 16 include shoulder lands 20 located at the ends on the outer side in the axial direction of the tire.

[0019] Fig. 2 is an enlarged perspective view showing the periphery of the shoulder land 20. In Fig. 2, the tire circumferential direction is a straight line extending in the left-right direction. As shown in Fig. 2, the shoulder land 20 is configured in a block shape partitioned in the tire circumferential direction by widthwise grooves 17 extending in the tire axial direction.

[0020] The shoulder land 20 has a shoulder contact surface 21 located at the outer diameter side end in the tire radial direction, and a shoulder outer side surface 22 extending inward in the tire radial direction from the outer edge in the tire axial direction of the shoulder contact surface 21. In this specification, the shoulder outer side surface 22 means the outer side surface extending inward in the tire radial direction from the outer edge in the tire axial direction of the shoulder contact surface 21 to the tire maximum width position M (see FIG. 1), and is also called a buttress surface.

[0021] The entire shoulder contact surface 21 comes into contact with the ground when the pneumatic tire 1 rolls. A plurality of sipes 23 extending in the tire axial direction are cut into the shoulder contact surface 21 on the inner side in the tire radial direction. In this embodiment, three sipes 23 are formed.

[0022] The shoulder outer surface 22 is formed with a base surface 24 extending in the tire radial direction and continuing smoothly to the maximum width position, a chamfer 25 connecting the shoulder ground contact surface 21 and the base surface 24 in a chamfered manner, and a recess 30 recessed toward the inside of the tire with respect to the base surface 24.

[0023] The recess 30 includes a first recess 31 recessed axially inward from the base surface 24 at the center of the shoulder land 20 in the tire circumferential direction, a second recess 32 located on one side TC1 of the first recess 31 in the tire circumferential direction and recessed axially from the base surface 24, and a third recess 33 located on the other side TC2 of the first recess 31 in the tire circumferential direction and recessed axially from the base surface 24. The first to third recesses 31 to 33 extend in an arc shape in the tire radial direction in a meridian cross section, and the meridian cross section shapes at any tire circumferential position are all equal. In other words, the recesses 30 have the same depth in the tire circumferential direction.

[0024] In this embodiment, the recesses 30 are adjacent to each other in the tire circumferential direction. The second recess 32, the first recess 31, and the third recess 33 are continuous in this order in the tire circumferential direction, and there is no basic surface 24 between them. In other words, the shoulder outer side surface 22 does not have a basic surface 24 in the tire radial range where the recess 30 is located, and has a basic surface 24 only on the tire radial direction outer side and tire radial direction inner side of the recess 30.

[0025] The tire radially outer ends of the recesses 30 are at the same tire radial position, and are located radially inward of the chamfer 25. The tire radially inner ends of the recesses 30 are at the same tire radial position.

[0026] The tire circumferential length W1 of the first recess 31 is set to be equal to or greater than ¼ and equal to or less than ⅓ of the tire circumferential length W0 of the shoulder land 20. In other words, the total length of the tire circumferential lengths W2 and W3 of the second recess 32 and the third recess 33 is set to be equal to or greater than ⅔ and equal to or less than ¾ of the tire circumferential length W0 of the shoulder land 20. In this embodiment, the first recess 31, the second recess 32, and the third recess 33 are configured to have the same size in the tire circumferential direction, but they may be different from each other.

[0027] FIG. 3 is an enlarged view of a portion Z in FIG. 1, showing an enlarged view of the periphery of the recess 30. Specifically, FIG. 3 is a meridian cross-sectional view of the first recess 31. As shown in FIG. 3, in this embodiment, the bottom surface 30d of each recess 30 located on the inner side in the tire axial direction is formed by a single arc having a constant radius of curvature in the meridian cross-section. The radius of curvature R1 of the bottom surface 31d of the first recess 31 is set to, for example, 5.0 mm or more and 40.0 mm or less. The radius of curvature R2 of each of the bottom surface 32d of the second recess 32 and the bottom surface 33d of the third recess 33 is larger than the radius of curvature R1 of the first recess 31, and is set to, for example, 10.0 mm or more and 80.0 mm or less.

[0028] The outer diameter end 31a of the first recess 31 on the outer side in the tire radial direction is located in a first tire radial direction range X1 that is 3.0 mm inward in the tire radial direction from the chamfer inner diameter end 25a on the inner side in the tire radial direction of the chamfer 25. The inner diameter end 31b of the first recess 31 on the inner side in the tire radial direction is located in a second tire radial direction range X2 that is 10.0 mm outward and inward in the tire radial direction from the belt end 10A as the center. Similarly, the outer diameter ends 32a, 33a of the second recess 32 and the third recess 33 are located in the first tire radial direction range X1 and the inner diameter ends 32b, 33b of the second recess 32 and the third recess 33 are located in the second tire radial direction range X2.

[0029] The depth D1 of the first depression 31 is deeper than both the depth D2 of the second depression 32 and the depth D3 of the third depression 33. Here, the depth of each depression 30 means the maximum distance when the distance of each position on the bottom surface 30d to a virtual reference line L0 connecting the outer diameter end 30a and the inner diameter end 30b in a meridian cross section is measured in a direction perpendicular to the virtual reference line L0. The position on the bottom surface 30d at which the depth (i.e., the distance from the virtual reference line L0) is maximum is referred to as the deepest position.

[0030] The depth D1 of the first recess 31 is set to, for example, 1.0 mm or more and 5.0 mm or less at the deepest position 31c on the bottom surface 31d. The depth D2 of the second recess 32 and the depth D3 of the third recess are shallower than the depth D1 of the first recess 31 and are set to, for example, 0.5 mm or more and 3.0 mm or less at the deepest position 32c on the bottom surface 32d and the deepest position 33c on the bottom surface 33d, respectively.

[0031] The shoulder outer surface 22 has an outer surface belt distance maximum position 22a where the distance to the belt end 10A is maximum, and an outer surface belt distance minimum position 22b where the distance to the belt end 10A is minimum. In this embodiment, the outer surface belt distance maximum position 22a is the outer end in the tire radial direction of the shoulder outer surface 22 (in this embodiment, the surface removal radial end 25b of the chamfer 25). The distance between the outer surface belt distance maximum position 22a and the belt end 10A is referred to as the outer surface maximum distance A. The distance between the outer surface belt distance minimum position 22b and the belt end 10A is referred to as the outer surface minimum distance C.

[0032] The first recess 31 has a bottom belt distance minimum position 31e where the distance to the belt end 10A is minimum on the bottom surface 31d. The distance between the bottom belt distance minimum position 31e and the belt end 10A is referred to as the bottom minimum distance B. In this embodiment, the position, size, and shape of the first recess 31 are set so that B / A, which is the ratio of the bottom minimum distance B to the outer surface maximum distance A, is 0.3 to 0.8. The bottom minimum distance B is set to 8.0 mm or more to ensure the thickness at the belt end 10A. The bottom minimum distance B is smaller than the outer surface minimum distance C.

[0033] Table 1 shows a CAE analysis of the strain energy density at the belt end 10A and the minimum bottom distance B. In the CAE analysis, the strain energy density at the belt end 10A when the minimum bottom distance B is changed by changing the size of the recess 30 is shown by an index, assuming that the strain energy density at the belt end 10A when the recess 30 is not formed is 100. The CAE analysis conditions were an air pressure of 600 kPa and a load of 13.7 kN applied to a pneumatic tire with a tire size of 205 / 80R17.5.

[0034] As can be seen from the analysis results, when the minimum bottom distance B is 8.0 mm or more, the strain energy density at the belt end 10A saturates at approximately 120, whereas when it is less than 8.0 mm, the stress at the belt end 10A gradually increases with the decrease in thickness. Therefore, if the minimum bottom distance B is 8.0 mm or more, the strain energy at the belt end 10A does not increase excessively. Therefore, in this embodiment, the position, size, and shape of the first recess 31 are set so that the minimum bottom distance B is 8.0 mm or more.

[0035] [Table 1]

[0036] In a meridian cross section, when a straight line connecting the belt end 10A and the outer surface belt distance maximum position 22a (the chamfered radial end 25b of the chamfer 25) is defined as a first virtual line L1, and a straight line connecting the belt end 10A and the bottom surface belt distance minimum position 31e is defined as a second virtual line L2, the angle θ between the first virtual line L1 and the second virtual line L2 is set to be greater than or equal to 20 degrees and less than or equal to 60 degrees.

[0037] Fig. 4 is a cross-sectional view of the shoulder land 20 taken along line IV-IV in Fig. 3 in a direction perpendicular to the tire radial direction. As shown in Fig. 4, the tire circumferential positions of the sipes 23 correspond to the tire circumferential center positions of the first to third recesses 31 to 33. In other words, the sipes 23 are located at positions different from the boundary position between the first recess 31 and the second recess 32 and the boundary position between the first recess 31 and the third recess 33 in the tire circumferential direction.

[0038] Corners R36 are provided at the boundary positions between the first depression 31 and the second depression 32, and at the boundary positions between the first depression 31 and the third depression 33. The radius of the corners R is set to, for example, 0.5 mm or more and 2.0 mm or less.

[0039] The pneumatic tire 1 according to the present embodiment provides the following effects.

[0040] (1) A pneumatic tire 1 is A shoulder land 20 is located at an end of the tread 2 on the outer side in the tire axial direction, and at least the outer end of the shoulder land 20 is defined in the tire circumferential direction. A first recess 31 recessed axially inward in a center of a shoulder outer surface 22 on an axially outer side of the shoulder land 20 in a tire circumferential center, a second recess 32 that is located on one side TC1 of the shoulder outer surface 22 in the tire circumferential direction with respect to the first recess 31, recessed toward the inside in the tire axial direction, and shallower than the first recess 31; A third recess 33 is located on the other side TC2 of the shoulder outer surface 22 in the tire circumferential direction with respect to the first recess 31, is recessed toward the inside in the tire axial direction, and is shallower than the first recess 31. Equipped with The outer diameter ends 31a, 32a, 33a, which are the radially outer ends of the first recess 31, the second recess 32, and the third recess 33, are located in a first tire radial range X1 that is 3.0 mm radially inward from the radially inner end of the chamfer 25 when the shoulder land 20 has a chamfer 25 at the axially outer end of the shoulder contact surface 21, or 3.0 mm radially inward from the axially outer end of the shoulder contact surface 21 when the shoulder land 20 does not have a chamfer.

[0041] As a result, the first recess 31, the second recess 32, and the third recess 33 are located near the shoulder ground contact surface 21, so that the rigidity of the axially outer end of the shoulder land 20 can be effectively reduced. For example, when the pneumatic tire 1 is mounted on a steering shaft and steering is performed, the shoulder land 20 is likely to deform not only at the axially outer end but also at the axially inner portion in order to match the road surface. In this case, the load that tends to concentrate at the axially outer end of the shoulder land 20 is likely to be distributed to the remaining portion, and the occurrence of shoulder drop wear at the axially outer end of the tire is suppressed.

[0042] Furthermore, since the second recess 32 and the third recess 33 are shallower than the first recess 31, excessive decrease in rigidity at both ends in the tire circumferential direction of the shoulder land 20 is suppressed. As a result, when the shoulder land 20 contacts the road surface (also called stepping on) and leaves the road surface (also called kicking off) during the rolling of the pneumatic tire 1, excessive deformation of the step-in side region and the kick-off side region is suppressed, thereby suppressing an increase in the amount of slip in the regions, and thus suppressing an increase in heel-and-toe wear.

[0043] Therefore, the first recess 31, the second recess 32, and the third recess 33 can suppress the occurrence of shoulder drop wear of the shoulder land 20 while suppressing an increase in heel-and-toe wear.

[0044] (2) The tire further includes a belt layer 10 located on the radially inner side of the tread 2, A bottom minimum distance B between the belt end 10A of the belt layer 10 located axially outermost in the tire and the first recess 31 may be 8.0 mm or more.

[0045] According to this configuration, the minimum bottom distance B between the belt end 10A and the bottom surface 31d of the first recess 31 is 8.0 mm or more, so that the thickness between the belt end 10A and the first recess 31 can be secured, thereby suppressing stress concentration at the belt end 10A. Therefore, separation failure at the belt end 10A can be suppressed.

[0046] (3) The tire further includes a belt layer 10 located on the radially inner side of the tread 2, The position located on the shoulder outer surface 22 and the distance from the belt end 10A located at the outermost position in the tire axial direction of the belt layer 10 is the largest as the outer surface belt distance maximum position 22a, and the position located on the bottom surface 31d of the first recess 31 and the distance from the belt end 10A is the smallest as the bottom surface belt distance minimum position 31e. The angle θ between a first virtual line L1 connecting the belt end 10A and the outer surface belt distance maximum point 22a and a second virtual line L2 connecting the belt end 10A and the bottom surface belt distance minimum point 31e may be 20 degrees or more and 60 degrees or less.

[0047] According to this configuration, since the angle between the first virtual line L1 and the second virtual line L2 is 20 degrees or more and 60 degrees or less, the first recess 31 is positioned in a location suitable for achieving both improving the heat dissipation of the belt end 10A via the first recess 31 and suppressing deterioration of ride comfort performance caused by an excessive decrease in rigidity of the shoulder land 20 due to the first recess 31.

[0048] If the angle θ between the first virtual line L1 and the second virtual line L2 is less than 20 degrees, the first recess 31 is likely to be located on the outer side in the tire radial direction, and therefore is likely to be far away from the belt end 10A, and the improvement in heat dissipation is likely to be insufficient.If the angle θ between the first virtual line L1 and the second virtual line L2 exceeds 60 degrees, the first recess 31 is likely to be located on the inner side in the tire radial direction, and therefore the rigidity of the shoulder land 20 in the inner part in the tire radial direction is likely to be excessively reduced, and the ride comfort is likely to deteriorate.

[0049] (4) The tire further includes a belt layer 10 located on the radially inner side of the tread 2, The bottom minimum distance B, which is the minimum distance between the belt end 10A located axially outermost of the belt layer 10 and the first recess 31, may be smaller than the outer surface minimum distance C, which is the minimum distance between the belt end 10A and the shoulder outer surface 22.

[0050] According to this configuration, heat dissipation from the belt end 10A via the first recess 31 can be easily ensured.

[0051] (5) The tire further includes a belt layer 10 located on the radially inner side of the tread 2, The first depression 31, the second depression 32, and the third depression 33 may have inner diameter ends 31b, 32, and 33b, which are the ends that are radially inward in the tire direction, located in a second tire radial range X2 that ranges from a position 10.0 mm radially inward in the tire direction centered on the belt end 10A that is located axially outermost of the belt layer 10 to a position 10.0 mm radially outward in the tire direction from the center.

[0052] According to this configuration, it is easy to position the first recess 31, the second recess 32, and the third recess 33 in correspondence with the belt end 10A in the vicinity of the outer side in the tire axial direction, and it is easy to ensure heat dissipation from the belt end 10A via the first recess 31, the second recess 32, and the third recess 33.

[0053] (6) The first recess 31 may have a length W1 in the tire circumferential direction that is greater than or equal to ¼ and less than or equal to ⅓ of the length W0 of the shoulder land 20 in the tire circumferential direction.

[0054] According to this configuration, the first recess 31 is located on the shoulder outer surface 22 with an appropriate circumferential size, so that the above-mentioned functions and effects can be easily exhibited appropriately. If the length W1 of the first recess 31 in the circumferential direction of the tire is less than 1 / 4 of the length W0 of the shoulder land 20 in the circumferential direction of the tire, the reduction in stiffness of the shoulder land 20 by the first recess 31 is likely to be insufficient, and heat dissipation from the belt end 10A via the first recess 31 is likely to be insufficient. If the length W1 of the first recess 31 in the circumferential direction of the tire exceeds 1 / 3 of the length W0 of the shoulder land 20 in the circumferential direction of the tire, stiffness at both ends of the shoulder land 20 in the circumferential direction of the tire is likely to be excessively reduced, in which case it is difficult to suppress an increase in heel-and-toe wear.

[0055] (7) The shoulder land 20 has a sipe 23 extending radially inward from the shoulder contact surface 21, The position of the sipe 23 in the tire circumferential direction may be shifted from the boundary position between the first recess 31 and the second recess 32 and the boundary position between the first recess 31 and the third recess 33.

[0056] According to this configuration, the sipes 23 are arranged in a region between the first recess 31 and the second recess 32 or the third recess 33, which are different in depth, and avoid a region where stress is likely to concentrate due to a large difference in rigidity. As a result, the occurrence of uneven wear (e.g., step wear) at the position where the sipes 23 are formed is suppressed.

[0057] (First Modification) In the above embodiment, the depth D2 of the second recess 32 and the depth D3 of the third recess 33 are the same depth and shallower than the depth D1 of the first recess 31, but this is not limited to the above. As shown in Fig. 5, the depth D3 of the third recess 33 located on the other circumferential side TC2 of the tire may be shallower than the depth D2 of the second recess 32 located on one circumferential side TC1 of the tire.

[0058] For example, when the rotation direction of the pneumatic tire 1 is set so that one side TC1 is located on the leading side and the other side TC2 is located on the trailing side, the third recess 33 located on the trailing side is made relatively shallow, thereby increasing the rigidity of the trailing side of the shoulder land 20 and reducing the amount of slippage in the trailing side region at the time of trailing. This reduces the amount of wear in the trailing side region of the shoulder land 20 caused by the amount of slippage at the time of trailing, making it easier to suppress the occurrence of heel-and-toe wear.

[0059] (Second Modification) In the above embodiment, the case where each recess 30 has a constant depth in the tire circumferential direction has been described as an example, but this is not limited thereto. As shown in Fig. 6, a slope 38 may be provided on the outer side of each recess 30 in the tire circumferential direction, the depth of which gradually increases toward the inner side in the tire circumferential direction and continuing to the constant depth portion. Here, in this specification, with respect to the tire circumferential direction, the inner side in the tire circumferential direction means the direction toward the center of the shoulder land 20 in the tire circumferential direction, and the outer side in the tire circumferential direction means the direction away from the center of the shoulder land 20 in the tire circumferential direction.

[0060] This configuration makes it easy to ensure the rigidity of both ends of the shoulder land 20 in the tire circumferential direction, and makes it easy to suppress the occurrence of heel-and-toe wear. Furthermore, it makes it easy to suppress a sudden change in rigidity between the first recess 31 and the second recess 32 or the third recess 33, and makes it easy to make the shoulder contact surface 21 deform smoothly from the center to both ends in the tire circumferential direction.

[0061] (Third Modification) In the second modified example, the slope 38 is configured to extend linearly in the cross section shown in FIG. 6. However, it may also be configured to extend in an arc shape as shown in FIG.

[0062] (Fourth Modification) In the above embodiment, the case where the recesses 30 are provided around the shoulder land 20 in the tire circumferential direction has been described as an example, but the present invention is not limited to this. As shown in Fig. 8, no recesses may be formed between the recesses 30, and on the outer side in the tire circumferential direction of the second recess 32 (the opposite side to the first recess 31), and on the outer side in the tire circumferential direction of the third recess 33 (the opposite side to the first recess), and the basic surface 24 may remain. The remaining basic surface 24 has a thickness in the tire circumferential direction of at least 2.0 mm.

[0063] (Fifth Modification) In the above embodiment, the recess 30 is configured with three recesses including the first recess 31, the second recess 32, and the third recess 33, but is not limited to this. As shown in Fig. 9, the recess 30 may be configured with five recesses. Even in this case, the recesses located on both sides in the tire circumferential direction may be shallower than the recess located in the center.

[0064] [Second embodiment] FIG. 10 is a meridian cross-sectional view similar to FIG. 3, showing the periphery of the depression 30 of the pneumatic tire 40 according to the second embodiment. The pneumatic tire 40 differs from the pneumatic tire 1 according to the first embodiment in that it does not have the chamfer 25. In this case, each depression 30 may be formed so that the outer diameter end 30a of each depression 30 is located in a first tire radial direction range X1 that is 3.0 mm inward in the tire radial direction from the outer end of the shoulder outer side surface 22 in the tire radial direction (which is also the outer end of the shoulder ground contact surface 21 in the tire axial direction). Note that it is preferable to provide the depression 30 on the inner side in the tire radial direction than the inner diameter end 25b of the chamfer 25, since this can delay the time when wear reaches the depression 30 during wear, and therefore it is preferable to easily maintain the effect of suppressing shoulder drop wear of the shoulder land by the depression 30.

[0065] [Third embodiment] Fig. 11 is a meridian cross-sectional view similar to Fig. 3, showing the periphery of a recess 30 in a pneumatic tire 50 according to a third embodiment. The pneumatic tire 50 differs from the pneumatic tire 1 according to the first embodiment in that a bottom surface 30d is formed of a plurality of arcs.

[0066] Specifically, the bottom surface 30d is composed of a first arc 30e located on the outer side in the tire radial direction and having a radius of curvature R11 in a meridian cross section, and a second arc 30f continuing to the inner side in the tire radial direction of the first arc 30e and having a radius of curvature R12 smaller than the radius of curvature R11. That is, the bottom surface 30d is composed of two arcs with different radii of curvature, and the radius of curvature of the arc located closer to the inner side in the tire radial direction is smaller.

[0067] As a result, since the portion with the small radius of curvature is located on the inner side in the tire radial direction, if the tire radial direction position of the inner end in the tire radial direction is the same, it is easy to configure the recess 30 deeper on the inner side in the tire radial direction. Therefore, even when the pneumatic tire 50 wears, it is easy to ensure the depth of the recess 30, and it is easy to maintain the effect of the recess 30 in suppressing shoulder drop wear of the shoulder land.

[0068] The pneumatic tire according to the present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0069] In the above embodiment, the outer diameter end 30a and the inner diameter end 30b of each recess 30 are in the same tire radial position, but the present invention is not limited to this. That is, the outer diameter end 31a and the inner diameter end 31b of the first recess 31 may be in a different tire radial position from the outer diameter end 32a and the inner diameter end 32b of the second recess 32 and the outer diameter end 33a and the inner diameter end 33b of the third recess 33. From the viewpoint of suppressing an increase in heel-and-toe wear, it is preferable to make the first recess 31 larger in the tire radial direction than the second recess 32 and the third recess 33 so that the rigidity of both ends in the tire circumferential direction of the shoulder land is not excessively reduced. For example, the tire radial positions of the outer diameter ends 31a-33a of the first to third recesses 31-33 may be aligned, and the inner diameter end 31b may be positioned radially inward of the inner diameter ends 32b, 33b.

[0070] In the above embodiment, the shoulder land 20 is configured in a block shape divided in the tire circumferential direction by the widthwise grooves 17 extending in the tire axial direction, but this is not limited to this. The shoulder land 20 may be configured in a rib shape divided in the tire circumferential direction at least at the axially outer end by lug grooves instead of the widthwise grooves 17. The above-mentioned effects of the present invention are more likely to be exhibited in a block pattern, which is more likely to cause heel-and-toe wear, than in a rib pattern.

[0071] [Note] The pneumatic tire according to the present invention provides the following aspects.

[0072] [Aspect 1] A shoulder land is located at an end of the tread on an outer side in the tire axial direction, and at least an outer end of the shoulder land is defined in the tire circumferential direction. A first recess is recessed axially inward at a center in the circumferential direction of the tire on an outer surface on an axially outer side of the shoulder land; a second recess located on one side of the outer surface of the shoulder land in the tire circumferential direction with respect to the first recess, recessed axially inward, and shallower than the first recess; a third recess located on the other side of the outer surface of the shoulder land in the tire circumferential direction relative to the first recess, recessed axially inward, and shallower than the first recess; Equipped with a tire radially outer end of each of the first depression, the second depression, and the third depression, which is the tire radially outer end, is located within a tire radial range of up to 3.0 mm inward in the tire radial direction from a chamfer at the axially outer end of the contact surface of the shoulder land if the shoulder land has a chamfer at the axially outer end of the contact surface of the shoulder land, or from the axially outer end of the contact surface of the shoulder land if the shoulder land does not have the chamfer.

[0073] [Aspect 2] The tire further includes a belt located on the radially inner side of the tread, The minimum distance between the belt end located axially outermost of the belt and the first recess is 8.0 mm or more. 2. The pneumatic tire according to claim 1.

[0074] [Aspect 3] The tire further includes a belt located on the radially inner side of the tread, A position located on the outer surface of the shoulder land and having the greatest distance from the belt end located axially outermost of the belt is defined as a belt distance maximum position, and a point located on the bottom surface of the first recess and having the smallest distance from the belt is defined as a belt distance minimum position. an angle between a first virtual line connecting the belt end and the maximum belt distance position and a second virtual line connecting the belt end and the minimum belt distance position is 20 degrees or more and 60 degrees or less; 3. The pneumatic tire according to claim 1 or 2.

[0075] [Aspect 4] The tire further includes a belt located on the radially inner side of the tread, The minimum distance between the belt end located axially outermost of the belt and the first recess is smaller than the minimum distance between the belt end and an outer surface of the shoulder land. The pneumatic tire according to any one of aspects 1 to 3.

[0076] [Aspect 5] The tire further includes a belt located on the radially inner side of the tread, The first recess, the second recess, and the third recess have inner diameter ends, which are ends on the inner side in the tire radial direction, located in a tire radial direction range ranging from a position 10.0 mm inward in the tire radial direction from a belt end of the belt that is located axially outermost in the tire, to a position 10.0 mm outward in the tire radial direction from the center. The pneumatic tire according to any one of the first to fourth aspects.

[0077] [Aspect 6] The first recess has a circumferential length that is equal to or greater than ¼ and equal to or less than ⅓ of the circumferential length of the shoulder land. The pneumatic tire according to any one of the first to fifth aspects.

[0078] [Aspect 7] The shoulder land has a sipe extending radially inward from the ground contact surface, The sipe is positioned in a tire circumferential direction away from between the first recess and the second recess and away from between the first recess and the third recess. The pneumatic tire according to any one of the first to sixth aspects.

[0079] [Aspect 8] each of the first depression, the second depression, and the third depression has a bottom surface formed by a plurality of circular arcs in a meridian cross section; The plurality of circular arcs have a smaller radius of curvature toward the inner side in the tire radial direction. The pneumatic tire according to any one of the first to seventh aspects.

Claims

1. A shoulder land is located at an end of the tread on an outer side in the tire axial direction, and at least an outer end of the shoulder land is defined in the tire circumferential direction. a first recess that is recessed axially inward at a center in the circumferential direction of the tire on an outer surface on an axially outer side of the shoulder land; a second recess located on one side of the outer surface of the shoulder land in the tire circumferential direction with respect to the first recess, recessed axially inward, and shallower than the first recess; a third recess, which is located on the other side of the outer surface of the shoulder land in the tire circumferential direction with respect to the first recess, is recessed axially inward, and is shallower than the first recess; Equipped with a first recess, a second recess, and a third recess, each of which has an outer diameter end that is an outer end in the tire radial direction, the outer diameter end being located within a tire radial range of up to 3.0 mm inward in the tire radial direction from a chamfer at an axially outer end of the contact surface of the shoulder land if the shoulder land has a chamfer at the axially outer end of the contact surface of the shoulder land if the shoulder land does not have the chamfer.

2. The tire further includes a belt located on the radially inner side of the tread, The minimum distance between the belt end located axially outermost of the belt and the first recess is 8.0 mm or more. The pneumatic tire according to claim 1.

3. The tire further includes a belt located on the radially inner side of the tread, A position located on the outer surface of the shoulder land and having the greatest distance from the belt end located axially outermost of the belt is defined as a belt distance maximum position, and a point located on the bottom surface of the first recess and having the smallest distance from the belt is defined as a belt distance minimum position. an angle between a first virtual line connecting the belt end and the maximum belt distance position and a second virtual line connecting the belt end and the minimum belt distance position is equal to or greater than 20 degrees and equal to or less than 60 degrees; The pneumatic tire according to claim 1 or 2.

4. The tire further includes a belt located on the radially inner side of the tread, a minimum distance between a belt end of the belt located axially outermost in the tire and the first recess is smaller than a minimum distance between the belt end and an outer surface of the shoulder land; The pneumatic tire according to claim 1 or 2.

5. The tire further includes a belt located on the radially inner side of the tread, The first recess, the second recess, and the third recess have inner diameter ends, which are ends on the inner side in the tire radial direction, located in a tire radial direction range ranging from a position 10.0 mm inward in the tire radial direction from a belt end of the belt that is located on the outermost side in the tire axial direction to a position 10.0 mm outward in the tire radial direction from the center. The pneumatic tire according to claim 1 or 2.

6. The first recess has a circumferential length that is equal to or greater than ¼ and equal to or less than ⅓ of the circumferential length of the shoulder land. The pneumatic tire according to claim 1 or 2.

7. The shoulder land has a sipe extending radially inward from the ground contact surface, The sipe is positioned in a tire circumferential direction away from between the first recess and the second recess and away from between the first recess and the third recess. The pneumatic tire according to claim 1 or 2.

8. each of the first depression, the second depression, and the third depression has a bottom surface formed by a plurality of circular arcs in a meridian cross section; The plurality of circular arcs have a smaller radius of curvature toward the inner side in the tire radial direction. The pneumatic tire according to claim 1 or 2.

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