pneumatic tires

Abstract

To provide a pneumatic tire which can suppress uneven wear of a shoulder land where a plurality of tread sipes extending in a tire axial direction are formed on a tread.SOLUTION: A pneumatic tire 1 comprises: a plurality of tread sipes 23 which are arranged on a tread 11 of a shoulder land 15A; and a plurality of lateral sipes 25 which are arranged on an outer lateral surface 12 of the shoulder land 15A. The plurality of lateral sipes 25 arranged at different positions in a tire circumferential direction TC relative to the plurality of tread sipes 23 include a pair of inner radial direction sipes 26 extending in a tire radial direction TR and a pair of outer radial direction sipes 27 in which dimension Sr1 of the inner radial direction sipe 26 in the tire radial direction TR is shorter than dimension Sr2 of the outer radial direction sipe 27 in the tire radial direction TR. The plurality of lateral sipes 25 also include circumferential sipes 28 and 29 extending in the tire circumferential direction TC which are adjacent to at least one of the pair of inner radial direction sipes 26 and the pair of outer radial direction sipes 27.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The pneumatic tire of Patent Document 1 has lateral sipes formed on the outer surface of the shoulder land located at the axially outer end of the tire, which are recessed axially inward, extend radially, and terminate at a distance from the tread, with the aim of suppressing wear at the shoulder land. Patent Document 1 also discloses a configuration in which tread sipes are provided between adjacent lateral sipes in the tire circumferential direction, recessed radially inward from the tread of the shoulder land, extend axially, and open on the outer surface of the shoulder land. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-506 Summary of the Invention [Problem to be solved by the invention]

[0004] When a shoulder land has multiple axial grooves spaced apart around the tire's circumferential direction, extending radially inward from the outer surface, and multiple tread sipes on the tread, uneven wear is likely to occur in the center between a pair of circumferentially adjacent axial grooves. This is because, when a force acts on the shoulder land while the tire is in contact with the ground, the center of the gap between a pair of axial grooves is more likely to be weakened by the tread sipes than the circumferentially outer portions, and the amount of relative displacement is greater. Therefore, the pneumatic tire of Patent Document 1 leaves room for improvement in terms of measures to prevent uneven wear at the axially outer ends of the tread.

[0005] An object of the present invention is to provide a pneumatic tire that can suppress uneven wear on shoulder land by forming a plurality of tread sipes on the tread that extend in the tire axial direction. [Means for solving the problem]

[0006] One aspect of the present invention is a tire having a tread surface at the radially outer end of the tire and an outer side surface at the axially outer end of the tire, the tread comprising: a shoulder land located at the axially outer end of the tire tread; a plurality of axial grooves provided on the shoulder land at intervals in the tire circumferential direction, recessed from the tread surface inward in the tire radial direction, extending in the tire axial direction and opening at the outer side surface; a plurality of tread sipes provided at intervals in the tire circumferential direction between a pair of axial grooves adjacent in the tire circumferential direction of the shoulder land, each recessed from the tread surface inward in the tire radial direction, extending in the tire axial direction and terminating at a position spaced apart from the outer side surface; and a plurality of lateral sipes provided on the outer side surface and recessed inward in the axial direction of the tire, the plurality of lateral sipes being arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, and the plurality of axial grooves being spaced apart from each other between the pair of axial grooves. a pair of inner radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, extending in the tire radial direction and spaced apart in the tire circumferential direction, and a pair of outer radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, and positioned closer to the axial groove than the inner radial sipes in the intervals between the pair of axial grooves, extending in the tire radial direction and spaced apart in the tire circumferential direction; and a circumferential sipe arranged adjacent to at least one of the pair of inner radial sipes and the pair of outer radial sipes, and extending in the tire circumferential direction between the adjacent pair of inner radial sipes or the pair of outer radial sipes, wherein a radial dimension of the inner radial sipes is shorter than a radial dimension of the outer radial sipes.

[0007] The inner radial sipes and the outer radial sipes are provided at different positions in the tire circumferential direction relative to the tread sipes. Therefore, compared to when the tread sipes and the radial sipes are provided at the same position in the tire circumferential direction, excessive reduction in stiffness of the shoulder land can be suppressed, and therefore, the occurrence of cracks originating from the tread sipes and the radial sipes can be suppressed.

[0008] The radial dimension of the inner radial sipe is shorter than the radial dimension of the outer radial sipe. Therefore, the rigidity of the circumferentially outer portion of the gap between a pair of axial grooves on the shoulder land can be made lower than the rigidity of the circumferentially central portion of the tire. This allows the circumferential rigidity balance to be optimized within the gap between the pair of axial grooves. Therefore, the amount of circumferential displacement of the tire when a force acts from the axially outer side to the axially inner side can be averaged, effectively suppressing uneven wear in the circumferentially central portion of the tire.

[0009] A circumferential sipe is provided adjacent to at least one of the pair of inner radial sipes and the pair of outer radial sipes, extending circumferentially between the pair of radial sipes. This suppresses the transmission of force from the outside to the inside of the area defined by the pair of radial sipes and the circumferential sipes on the outer surface of the shoulder land. This suppresses movement of the area defined by the pair of radial sipes and the circumferential sipes. As a result, uneven wear in the circumferentially central portion of the gap between the pair of axial grooves on the shoulder land, which is located in this defined area, can be effectively suppressed, and cracks at the bottoms of the tread sipes can be suppressed.

[0010] A pair of the circumferential sipes are provided adjacent to both the pair of inner radial sipes and the pair of outer radial sipes, respectively.

[0011] This configuration divides the outer surface of the shoulder land into a first region defined by a pair of inner radial sipes and a circumferential sipe, a second region defined by a pair of outer radial sipes and a circumferential sipe and located outside the first region, and a third region defined by a pair of outer radial sipes and a circumferential sipe and located outside the second region. This effectively suppresses force transmission to the circumferentially central portion of the gap between the pair of axial grooves in the first region. This effectively suppresses uneven wear in the circumferentially central portion of the gap between the pair of axial grooves.

[0012] The circumferential sipes are continuous with the adjacent inner radial sipes or the adjacent outer radial sipes.

[0013] This configuration makes it possible to more effectively suppress the transmission of force from the outside to the inside of the area defined by the pair of radial sipes and the circumferential sipe.

[0014] The circumferential sipe has a curved shape having a first portion adjacent to one of the pair of inner radial sipes or the pair of outer radial sipes, and a second portion adjacent to the other of the pair of inner radial sipes or the pair of outer radial sipes and extending in a direction different from the first portion.

[0015] This configuration allows the first and second portions of the circumferential sipe, which extend in different directions, to elastically absorb forces from different directions, thereby more effectively suppressing the transmission of forces to the circumferential center portion of the gap between the pair of axial grooves.

[0016] The first portion and the second portion are each inclined toward the tire circumferential center of the space between the pair of axial grooves from the tire radial inner end of the adjacent inner radial sipe or outer radial sipe toward the tire radial outer side, and the circumferential sipe has a shape that protrudes radially outward in the tire direction.

[0017] With this configuration, when the pneumatic tire gets stuck in a rut on the road surface, the inflection point where the first and second parts of the circumferential sipe join gets caught on the slope of the rut, improving the ability to escape from the rut.

[0018] The angle formed between the first portion and a reference line extending in the tire circumferential direction, and the angle formed between the second portion and the reference line are both greater than 0 degrees and equal to or less than 15 degrees.

[0019] With this configuration, the angle of the circumferential sipe with the inflection point as the apex becomes an obtuse angle, so that the occurrence of cracks in the circumferential sipe can be suppressed.

[0020] The inner radial sipe and the outer radial sipe each have an outer end located on the outer side in the tire radial direction and an inner end located on the inner side in the tire radial direction, and a straight line connecting the outer end of the inner radial sipe and the inner end of the inner radial sipe, and a straight line connecting the outer end of the outer radial sipe and the inner end of the outer radial sipe, each incline toward the tire circumferential center of the spacing between the pair of axial grooves as they move toward the inner side in the tire radial direction.

[0021] With this configuration, the inner radial sipes and outer radial sipes are inclined relative to the rotational direction of the pneumatic tire, thereby reducing damage originating from the inner radial sipes and outer radial sipes when coming into contact with a curb, step, etc.

[0022] The outer side surface has a chamfer at the portion in contact with the tread surface that slopes inward in the tire axial direction as it moves outward in the tire radial direction, and the tire radial outer ends of the inner radial sipes and the outer radial sipes open outward in the tire radial direction at the chamfer.

[0023] This configuration makes it possible to suppress the occurrence of cracks originating from the outer ends, which may occur when the outer ends in the tire radial direction of each of the inner radial sipes and the outer radial sipes are closed.

[0024] The tread comprises main grooves spaced apart on the inner side of the outer surface in the tire axial direction, recessed radially inward, and extending circumferentially; and a circumferential groove formed between the main groove and the outer surface, recessed radially inward, and extending circumferentially. The shoulder land comprises a rib defined by the outer surface and a sidewall of the main groove, a plurality of first blocks formed on the outer side of the rib in the tire radial direction and defined by the outer surface, the sidewall of the circumferential groove, and the sidewalls of a pair of axial grooves adjacent in the tire circumferential direction, and a plurality of second blocks formed on the outer side of the rib in the tire radial direction and defined by the sidewall of the circumferential groove, the sidewall of the main groove, and the sidewalls of a pair of axial grooves adjacent in the tire circumferential direction. The tread sipes and the side sipes are formed in the plurality of first blocks, respectively.

[0025] In the case of a shoulder land with this configuration, when a force acts from the outside to the inside in the axial direction of the tire, the rib has difficulty absorbing the force, so the impact on the first block is greater. However, because the first block has side sipes formed on it, the rigidity balance of the first block can be optimized, and uneven wear can be suppressed.

[0026] The number of the side sipes is the same as or one more than the number of the tread sipes, and is an even number of 4 or more.

[0027] In this way, since the number of side sipes is an even number of four or more, with the upper limit being one more than the number of tread sipes, the rigidity balance between a pair of axial grooves can be easily optimized. [Effects of the Invention]

[0028] In the pneumatic tire of the present invention, uneven wear of the shoulder land where a plurality of tread sipes extending in the tire axial direction are formed on the tread can be suppressed. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a perspective view showing a portion of a pneumatic tire according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing the tread pattern of the pneumatic tire of FIG. 1. [Figure 3] Enlarged view of part III in Figure 2. [Figure 4] Cross-sectional view of line IV-IV in Figure 3. [Figure 5] FIG. 3 is a side view showing a portion of the pneumatic tire of FIG. 2. [Figure 6] Enlarged view of part VI in Figure 5. [Figure 7] Cross-sectional view taken along line VII-VII in Figure 3. [Figure 8] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a modified example. [Figure 9] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a modified example. [Figure 10]FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a modified example. [Figure 11] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a modified example. [Figure 12] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a modified example. [Figure 13] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a second embodiment. [Figure 14] FIG. 7 is an enlarged view similar to FIG. 6 of a pneumatic tire according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0031] (First embodiment) 1 and 2 show a portion of a tread 10 of a pneumatic tire (hereinafter simply referred to as "tire") 1 according to a first embodiment of the present invention. The tire 1 is a heavy-duty tire in this embodiment, but may also be a tire for light trucks.

[0032] 1 and 2, a tire 1 includes a tread 10, a pair of sidewalls (not shown), and a pair of beads (not shown). The sidewalls are connected to both ends of the tread 10 in the tire axial direction TA and extend inward in the tire radial direction TR (downward in FIG. 1). The beads are connected to the inner ends of the sidewalls in the tire radial direction TR.

[0033] The tread 10 is cylindrical, extends in the tire axial direction TA, and continues endlessly in the tire circumferential direction TC. The tread 10 is defined by a tread surface 11 located at the outer end in the tire radial direction TR and a pair of outer side surfaces 12 located at the outer ends of the tire in the tire axial direction TA. The tread 10 is provided with a plurality of axial grooves 21 extending in the tire axial direction TA at intervals in the tire circumferential direction TC. In this embodiment, a plurality of side sipes 25 are provided on each of the pair of outer side surfaces 12 to suppress uneven wear in the space between pairs of axial grooves 21 adjacent in the tire circumferential direction TC.

[0034] The configuration of the tread 10 will be specifically described below.

[0035] The tread 10 is provided with a plurality of annular (endless) main grooves 14 recessed inward in the tire radial direction TR from the tread surface 11 and extending in the tire circumferential direction TC at intervals in the tire axial direction TA. Referring to Fig. 4, each main groove 14 is defined by a pair of side walls 14a facing each other in the tire axial direction TA and bottom walls 14b continuing to the inner ends of the pair of side walls 14a in the tire radial direction TR.

[0036] 2, the tread 10 has a plurality of lands 15 arranged in the tire axial direction TA by a plurality of main grooves 14. In this embodiment, four rows of lands 15 are formed by three main grooves 14, but the number of main grooves 14 and the number of lands 15 can be changed as needed.

[0037] In the following description, of the multiple lands 15, the two located at the outermost sides in the tire axial direction TA in Figure 2 will be referred to as shoulder lands 15A, and the lands other than the shoulder lands 15A located between the pair of main grooves 14 will be referred to as center lands 15B. The outer side in the tire axial direction TA means the side away from the center line CL1 that divides the tread 10 in half in the tire axial direction TA, and the inner side in the tire axial direction TA means the side closer to the center line CL1.

[0038] 2, the shoulder land 15A is defined by the outer surface 12 and the sidewall 14a of the main groove 14 closest to the outer surface 12. The center land 15B is defined by the sidewall 14a of each main groove 14 adjacent to the outer surface 12 in the tire axial direction TA. Each land 15 has one circumferential groove 20 and multiple axial grooves 21 formed therein.

[0039] 1 and 4, the circumferential grooves 20 are provided between the main grooves 14 and the outer surface 12 and between the pair of main grooves 14, recessed inward in the tire radial direction TR from the tread surface 11, and extending annularly in the tire circumferential direction TC. The circumferential groove 20 is defined by a pair of side walls 20a facing each other in the tire axial direction TA, and bottom walls 20b respectively continuing to the inner ends of the pair of side walls 20a in the tire radial direction TR.

[0040] The axial grooves 21 are recessed inward in the tire radial direction TR from the tread surface 11, extend in the tire axial direction TA, and are provided in plurality at intervals in the tire circumferential direction TC. Each axial groove 21 is defined by a pair of side walls 21a facing each other in the tire circumferential direction TC and bottom walls 21b respectively continuing to the inner ends of the pair of side walls 21a in the tire radial direction TR.

[0041] One end of each axial groove 21 in the tire axial direction TA opens at a side wall 20a of the circumferential groove 20 and is connected to the circumferential groove 20. On the outer side of the circumferential groove 20 of the shoulder land 15A in the tire axial direction TA, the other end of the axial groove 21 in the tire axial direction TA opens at the outer surface 12 and is open to the outside. On the inner side of the circumferential groove 20 of the shoulder land 15A in the tire axial direction TA and at the center land 15B, the other end of the axial groove 21 in the tire axial direction TA opens at a side wall 14a of the main groove 14 and is connected to the main groove 14.

[0042] 2 and 3, the groove width of the axial groove 21 in the tire circumferential direction TC, which is the distance between the pair of side walls 21a, is smaller than the groove width of the main groove 14 in the tire axial direction TA, which is the distance between the pair of side walls 14a. Also, the groove width of the circumferential groove 20 in the tire axial direction TA, which is the distance between the pair of side walls 20a, is smaller than the groove width of the axial groove 21.

[0043] 4, the depth of the circumferential groove 20 in the tire radial direction TR, i.e., the dimension from the tread surface 11 to the bottom wall 20b, is shallower than the depth Dr1 of the main groove 14 in the tire radial direction. The depth Dr2 of the axial groove 21 in the tire radial direction TR, i.e., the dimension from the tread surface 11 to the bottom wall 21b, is shallower than the depth Dr1 of the main groove 14. In this embodiment, the depth of the circumferential groove 20 is the same as the depth Dr2 of the axial groove 21. However, the depths of the circumferential groove 20 and the axial groove 21 may be different as long as they are shallower than the depth Dr1 of the main groove 14.

[0044] 1 and 4, each land 15 is formed with a rib 16 and a plurality of blocks 17 located outside the rib 16 in the tire radial direction TR by the main grooves 14, the circumferential grooves 20, and the axial grooves 21. For each land 15, a plurality of blocks 17 are provided at intervals in the tire circumferential direction TC, and are also provided in two rows at intervals in the tire axial direction TA.

[0045] 2, the rib 16 of the shoulder land 15A is defined by the outer surface 12 and the sidewall 14a of the main groove 14 closest to the outer surface 12. The rib 16 of the center land 15B is defined by the sidewall 14a of each of the adjacent main grooves 14.

[0046] Referring to Figures 1 and 4, two rows of blocks 18 protruding from each rib 16 are separated by a circumferential groove 20, and the multiple blocks 17 included in each block row 18 are separated by multiple axial grooves 21.

[0047] In the following description, of the two block rows 18, the one located on the outer side in the tire axial direction TA may be referred to as the outer block row 18A, and the one located on the inner side in the tire axial direction TA may be referred to as the inner block row 18B. Of the multiple blocks 17, the blocks that make up the outer block row 18A of the shoulder land 15A, i.e., the blocks (first blocks) located at the outer ends of the tread 10 in the tire axial direction TA, may be referred to as 17A, and the blocks other than 17A may be referred to as 17B (second blocks).

[0048] The block 17A is defined by the outer surface 12, the sidewalls 20a of the circumferential groove 20, and the sidewalls 21a of a pair of axial grooves 21 adjacent to each other in the tire circumferential direction TC. The block 17B is defined by the sidewalls 14a of the main groove 14, the sidewalls 20a of the circumferential groove 20, and the sidewalls 21a of a pair of axial grooves 21 adjacent to each other in the tire circumferential direction TC.

[0049] 2 and 3, the positions at which the axial grooves 21 of the outer block row 18A are formed in the tire circumferential direction TC differ from the positions at which the axial grooves 21 of the inner block row 18B are formed in the tire circumferential direction TC. As a result, the positions at which the blocks 17 of the outer block row 18A are formed and the positions at which the blocks 17 of the inner block row 18B are formed also differ from each other in the tire circumferential direction TC.

[0050] In this embodiment, the shape of the blocks 17 is rectangular when viewed from the outside in the tire radial direction TR, but this can be changed as necessary. In other words, the circumferential grooves 20 are provided linearly in the tire circumferential direction TC, but may be formed in a wavy shape with repeated concave and convex portions in the tire axial direction TA along the tire circumferential direction TC. Furthermore, the axial grooves 21 are provided linearly in the tire axial direction TA, but may be inclined with respect to a straight line (not shown) extending in the tire axial direction TA, or may be formed in a wavy shape with repeated concave and convex portions in the tire circumferential direction TC along the tire axial direction TA.

[0051] 2 to 4, each block 17 is formed with a tread sipe 23 that is recessed inward in the tire radial direction TR from the tread 11 and extends in the tire axial direction TA. The tread sipe 23 is defined by a pair of side walls 23a facing each other in the tire circumferential direction TC and a bottom wall 23b that connects to the inner ends of the pair of side walls 23a in the tire radial direction TR. Each tread sipe 23 is provided linearly along the tire axial direction TA, but may be inclined with respect to a straight line (not shown) extending in the tire axial direction TA, or may have a wavy shape with repeated concave and convex shapes in the tire circumferential direction TC along the tire axial direction TA.

[0052] A plurality of tread sipes 23, more specifically, three or more tread sipes 23 are provided at intervals in the tire circumferential direction TC between a pair of axial grooves 21 that define the block 17. In this embodiment, four tread sipes 23 are formed for a block 17 having a circumferential length of 35 mm.

[0053] The spacing between adjacent tread sipes 23 in the tire circumferential direction TC is preferably set to 5 mm or more and 8 mm or less. If the spacing between the tread sipes 23 is made too small, the rigidity of the tread 11 will be excessively reduced, while if the spacing between the tread sipes 23 is made too large, the rigidity of the tread 11 will not be sufficiently reduced, making it difficult to obtain an appropriate grip force. To prevent these inconveniences, the spacing between adjacent tread sipes 23 is preferably set within the above-specified range.

[0054] Of the tread sipes 23 formed in the block 17A, outer ends 23c located on the outer surface 12 side terminate at a position spaced apart from the ridge 13 at the outer end of the outer surface 12 in the tire radial direction TR. Of the tread sipes 23 of the block 17A, inner ends 23d located on the circumferential groove 20 side terminate at a position spaced apart from the side wall 20a of the circumferential groove 20. Of the tread sipes 23 of the block 17B, one end terminates at a position spaced apart from the side wall 20a of the circumferential groove 20, and the other end terminates at a position spaced apart from the side wall 14a of the main groove 14.

[0055] 4, the depth Dr3 of the tread sipes 23 in the tire radial direction TR, i.e., the dimension from the tread 11 to the bottom wall 23b, is shallower than both the depth Dr1 of the main groove 14 and the depth Dr2 of the axial groove 21. In this embodiment, the depth Dr3 of the tread sipes 23 is the same for all lands 15 or block rows 18, but may be different for each land 15 or block row 18.

[0056] In the case of the block 17A having the tread sipes 23 formed in this manner, when a force is applied in the contact state, uneven wear is likely to occur in the central portion in the tire circumferential direction TC of the ridge 13 between the tread 11 and the outer surface 12. In order to suppress such uneven wear on the ridge 13, a plurality of side sipes 25 are provided on the outer surface 12 of this embodiment.

[0057] The tread sipes 23 and the side sipes 25 will be specifically described below with reference to Figures 1 and 4 to 7. Figure 5 shows the tread 11 and the outer side surface 12 of the outer block row 18A of the shoulder land 15A in an expanded state.

[0058] 1 and 4, the outer surface 12 is inclined inward in the tire axial direction TA as it goes outward in the tire radial direction TR in a meridian cross section. A chamfer 12a is formed on the outer side of the outer surface 12 in the tire radial direction TR, and a continuous portion 12b is formed on the inner side in the tire radial direction TR.

[0059] The chamfer 12a is provided on the portion of the outer surface 12 that connects to the tread surface 11. In a meridian cross section, the chamfer 12a is inclined inward in the tire axial direction TA as it moves outward in the tire radial direction TR. Referring to FIG. 7, the inclination angle of the chamfer 12a with respect to a reference line RL1 extending in the tire radial direction TR is larger than the inclination angle of the main portion of the outer surface 12 (the portion between the chamfer 12a and the continuous portion 12b) with respect to the reference line RL1. The dimension of the chamfer 12a in the tire radial direction TR is smaller than the depth Dr1 of the main groove 14, the depth Dr2 of the axial grooves 21, and the depth Dr3 of the tread sipes 23.

[0060] 1 and 4, the continuous portion 12b is provided in a portion of the outer surface 12 that connects to the sidewall. The continuous portion 12b is a curved surface that contacts the sidewall on the inner side of the axial groove 21 in the tire radial direction TR in a meridian cross section.

[0061] 7, the distance Sw1 from the outer end 23c of the tread sipe 23 to the outer end of the chamfer 12a in the tire axial direction TA is set to be 1.5 times or more the dimension Sw2 of the chamfer 12a. If the ratio of the distance Sw1 to the dimension Sw2 is set too small, cracks may occur starting from the outer end 23c of the tread sipe 23. To prevent such cracks from occurring, it is preferable to set the ratio of the distance Sw1 to the dimension Sw2 to be equal to or greater than the above-mentioned value.

[0062] 5, as described above, each block 17A of this embodiment has four tread sipes 23 formed therein. If two of the tread sipes located on the inside in the tire circumferential direction TC are designated tread sipes 23A and two of the tread sipes located on the outside in the tire circumferential direction TC are designated tread sipes 23B, the block 17A can be divided in the tire circumferential direction TC into a central region 17a located between the pair of tread sipes 23A, a pair of intermediate regions 17b located between the tread sipes 23A and 23B, and an outer region 17c located on the outside of the tread sipes 23B in the tire circumferential direction TC.

[0063] 1 and 7, the side sipes 25 are formed between the chamfer 12a and the continuous portion 12b of the outer surface 12, and optimize the rigidity balance of the block 17A in the tire circumferential direction TC. The side sipes 25 include two types of four (even number) radial sipes 26, 27 and two circumferential sipes 28, 29, all of which are recessed inward from the outer surface 12 in the tire axial direction TA.

[0064] 5, two radial sipes 26 are formed in the space between a pair of axial grooves 21, closer to a center line CL2 that passes through the center of the block 17A in the tire circumferential direction TC and extends in the tire radial direction TR, and extend in the tire radial direction TR. Two radial sipes 27 are formed in the space between the pair of axial grooves 21, closer to the center line CL2 than the radial sipes 26 (i.e., closer to the axial groove 21), and extend in the tire radial direction TR. In the following description, the two sipes closer to the center line CL2 may be referred to as inner radial sipes 26, and the two sipes closer to the axial groove 21 may be referred to as outer radial sipes 27.

[0065] The circumferential sipes 28 are each connected to a pair of inner radial sipes 26, and extend in the tire circumferential direction TC between the pair of inner radial sipes 26. The circumferential sipes 29 are each connected to a pair of outer radial sipes 27, and extend in the tire circumferential direction TC between the pair of outer radial sipes 27. In the following description, the sipes connected to the inner radial sipes 26 may be referred to as inner circumferential sipes 28, and the sipes connected to the outer radial sipes 27 may be referred to as outer circumferential sipes 29.

[0066] Next, the inner radial sipes 26, the outer radial sipes 27, the inner circumferential sipes 28, and the outer circumferential sipes 29 will be specifically described in this order.

[0067] 6 and 7, a pair of inner radial sipes 26 are provided at a distance from each other in the tire circumferential direction TC and extend in the tire radial direction TR. Each inner radial sipe 26 is a groove defined by a pair of side walls 26a facing each other in the tire circumferential direction TC and bottom walls 26b connected to the inner ends of the pair of side walls 26a in the tire axial direction TA. Each inner radial sipe 26 has an outer end 26c located on the tread surface 11 side, that is, on the outer side in the tire radial direction TR, and an inner end 26d located on the sidewall side, that is, on the inner side in the tire radial direction TR.

[0068] The pair of outer radial sipes 27 are spaced apart in the tire circumferential direction TC at a greater distance than the pair of inner radial sipes 26, and extend in the tire radial direction TR. The outer radial sipes 27 are grooves defined by a pair of side walls 27a facing each other in the tire circumferential direction TC and bottom walls 27b connected to the inner ends of the pair of side walls 27a in the tire axial direction TA. The outer radial sipes 27 have an outer end 27c located on the tread surface 11 side, that is, on the outer side in the tire radial direction TR, and an inner end 27d located on the sidewall side, that is, on the inner side in the tire radial direction TR.

[0069] 1, 6, and 7, the outer ends 26c, 27c of the radial sipes 26, 27 open at the chamfer 12a and are open outward in the tire radial direction TR. More specifically, the outer ends 26c, 27c of the radial sipes 26, 27 are both located on a reference line RL2 extending in the tire circumferential direction TC. The inner ends 26d, 27d of the radial sipes 26, 27 are located outward in the tire radial direction TR from the continuous portion 12b.

[0070] As shown most clearly in FIG. 5 , the outer ends 26c, 27c of the radial sipes 26, 27 are both positioned at different positions in the tire circumferential direction TC relative to the outer ends 23c of the tread sipes 23. That is, the radial sipes 26, 27 are both positioned at different positions in the tire circumferential direction TC relative to the tread sipes 23. More specifically, the outer end 26c of the inner radial sipe 26 is positioned between the adjacent tread sipes 23A, 23B, i.e., in the middle region 17b of the block 17A. The outer end 27c of the outer radial sipe 27 is positioned outside the tread sipe 23B in the tire circumferential direction TC, i.e., in the outer region 17c of the block 17A. None of the outer ends 26c, 27c of the radial sipes 26, 27 are positioned between a pair of tread sipes 23A, i.e., in the central region 17a of the block 17A.

[0071] 6, the dimension Sr1 in the tire radial direction TR of the inner radial sipe 26 is shorter than the dimension Sr2 in the tire radial direction TR of the outer radial sipe 27. The dimension Sr1 of the inner radial sipe 26 means the distance in the tire radial direction TR from the outer end 26c to the inner end 26d of the inner radial sipe 26, and the dimension Sr2 of the outer radial sipe 27 means the distance in the tire radial direction TR from the outer end 27c to the inner end 27d of the outer radial sipe 27. Due to the difference in dimensions between the inner radial sipe 26 and the outer radial sipe 27, rigidity gradually decreases from the central region 17a to the outer region 17c of the block 17A.

[0072] The dimension Sr1 of the inner radial sipe 26 is set to be 0.25 to 0.45 times the dimension Sr2 of the outer radial sipe 27. If the dimensional ratio of the inner radial sipe 26 to the outer radial sipe 27 is made too small, the rigidity of the intermediate region 17b will not be reduced sufficiently, which may result in uneven wear in the outer region 17c. If the dimensional ratio of the inner radial sipe 26 to the outer radial sipe 27 is made too large, the rigidity of the intermediate region 17b will be reduced too much, which may result in uneven wear in the central region 17a. To prevent these inconveniences, it is preferable that the dimensional ratio of the inner radial sipe 26 to the outer radial sipe 27 be set within the above-specified range.

[0073] 6, the imaginary line (straight line) VL1 connecting the outer end 26c and inner end 26d of the inner radial sipe 26 and the imaginary line (straight line) VL2 connecting the outer end 27c and inner end 27d of the outer radial sipe 27 are each inclined in a direction approaching the center line CL2 of the block 17A as they move inward in the tire radial direction TR. In other words, the inner radial sipe 26 and the outer radial sipe 27 are each inclined toward the center in the tire circumferential direction TC between the pair of axial grooves 21 as they move inward in the tire radial direction TR.

[0074] The inclination angle θ1 of the imaginary line VL1 of the inner radial sipe 26 relative to the center line CL2 and the inclination angle θ2 of the imaginary line VL2 of the outer radial sipe 27 relative to the center line CL2 are both set to 5 degrees or greater and 15 degrees or less. If the inclination angles θ1 and θ2 of the radial sipes 26 and 27 are excessively small, the radial sipes 26 and 27 will extend along the center line CL2, making it difficult to gradually reduce the rigidity from the central region 17a to the outer region 17c of the block 17A. If the inclination angles θ1 and θ2 of the radial sipes 26 and 27 are excessively large, an overlap will occur between the short inner radial sipe 26 and the long outer radial sipe 27 as viewed from the outside in the tire radial direction TR, resulting in an excessive reduction in rigidity in the intermediate region 17b. To prevent these disadvantages, it is preferable to set the inclination angles θ1 and θ2 of the radial sipes 26 and 27 within the above-specified range. Although the inclination angles θ1, θ2 of the radial sipes 26, 27 are all the same in this embodiment, they may be different as long as they are within the above-defined range.

[0075] 6 and 7 , the inner circumferential sipe 28 is a groove defined by a pair of sidewalls 28a facing each other in the tire radial direction TR and a bottom wall 28b connected to the inner ends of the pair of sidewalls 28a in the tire axial direction TA. The inner radial sipe 28 has a left end 28c connected to one inner end 26d of the pair of inner radial sipes 26 located on the left side in FIG. 6 and a right end 28d connected to the other inner end 26d located on the right side in FIG. 6 , and extends linearly in the tire circumferential direction TC between the left end 28c and the right end 28d. In other words, the inner circumferential sipes 28 are provided adjacent to the pair of inner radial sipes 26 and extend between the pair of inner radial sipes 26 in a direction tangent to a reference line RL3 extending in the tire circumferential direction TC. However, the inner circumferential sipes 28 may be inclined at an angle between 0 and 15 degrees relative to the reference line RL3.

[0076] The outer circumferential sipes 29 are grooves defined by a pair of sidewalls 29a facing each other in the tire radial direction TR and bottom walls 29b connected to the inner ends of the pair of sidewalls 29a in the tire axial direction TA. The outer radial sipes 29 have a left end 29c connected to one inner end 27d of the pair of outer radial sipes 27, located on the left side in FIG. 6, and a right end 29d connected to the other inner end 27d, located on the right side in FIG. 6, and extend linearly in the tire circumferential direction TC between the left end 29c and the right end 29d. In other words, the outer circumferential sipes 29 are provided adjacent to the pair of outer radial sipes 27, and extend between the pair of outer radial sipes 27 in a direction tangent to a reference line RL4 extending in the tire circumferential direction TC. However, the outer circumferential sipes 29 may be inclined at an angle between 0 and 15 degrees relative to the reference line RL4.

[0077] 6 , the width of the inner radial sipe 26 in the tire circumferential direction TC is W1, the width of the outer radial sipe 27 in the tire circumferential direction TC is W2, the width of the inner circumferential sipe 28 in the tire radial direction TR is W3, and the width of the outer circumferential sipe 29 in the tire radial direction TR is W4. Here, the widths W1 and W2 in the tire circumferential direction TC do not strictly refer to the spacing between the sidewalls 26 a and the spacing between the sidewalls 27 a in the direction along the tire circumferential direction TC, but rather refer to the spacing between the sidewalls 26 a in a direction perpendicular to the sidewalls 26 a and the spacing between the sidewalls 27 a in a direction perpendicular to the sidewalls 27 a. Furthermore, the widths W3 and W4 in the tire radial direction TR do not strictly refer to the spacing between the sidewalls 28 a and the spacing between the sidewalls 29 a in the direction along the tire radial direction TR, but rather refer to the spacing between the sidewalls 28 a in a direction perpendicular to the sidewalls 28 a and the spacing between the sidewalls 29 a in a direction perpendicular to the sidewalls 29 a. The widths W1 to W4 of the sipes 26 to 29 are all set to 1.5 mm or less, more specifically, 0.3 mm or more and 1.0 mm or less, and preferably 0.6 mm or 0.8 mm.

[0078] 7, the depth in the tire axial direction TA of the inner radial sipe 26 is Da1, the depth in the tire axial direction TA of the outer radial sipe 27 is Da2, the depth in the tire axial direction TA of the inner circumferential sipe 28 is Da3, and the depth in the tire axial direction TA of the outer circumferential sipe 29 is Da4. Here, the depths Da1 to Da4 of the sipes 26 to 29 mean the distance in the tire axial direction TA from the outer surface 12 to the bottom walls 26b to 29b of the sipes 26 to 29.

[0079] In this embodiment, the widths W1 to W4 of the sipes 26 to 29 are all the same, and the depths Da1 to Da4 of the sipes 26 to 29 are also all the same. However, the widths W1 to W4 and the depths Da1 to Da4 of the sipes 26 to 29 may be different as long as they are within the respective ranges specified above. For example, the widths W1 to W4 and the depths Da1 to Da4 of the sipes 26 to 29 may be set to be the same for the inner radial sipe 26 and the inner circumferential sipe 28 and the outer radial sipe 27 and the outer circumferential sipe 29, and may be different between the inner sipes 26, 28 and the outer sipes 27, 29, or may be different between the radial sipes 26, 27 and the circumferential sipes 28, 29. In this case, it is preferable to make the widths W1 to W4 and the depths Da1 to Da4 different within a range in which the appearance (shading) of the sipes 26 to 29 appears similar.

[0080] 6 and 7, the ratio of the width W1 to the depth Da1 of the inner radial sipe 26, the ratio of the width W2 to the depth Da2 of the outer radial sipe 27, the ratio of the width W3 to the depth Da3 of the inner circumferential sipe 28, and the ratio of the width W4 to the depth Da4 of the outer circumferential sipe 29 are all set to be 0.5 to 1.0. If the ratios of the widths W1 to W4 to the depths Da1 to Da4 are made too small, the rigidity reduction of the block 17A (shoulder land 15A) will be insufficient. If the ratios of the widths W1 to W4 to the depths Da1 to Da4 are made too large, the rigidity reduction of the block 17A will be excessive. To avoid these disadvantages and obtain an appropriate rigidity reduction effect for the block 17A, it is preferable that the ratios of the widths W1 to W4 to the depths Da1 to Da4 of the sipes 26 to 29 be set within the above-specified range. In this embodiment, the ratios of the widths W1 to W4 to the depths Da1 to Da4 of the sipes 26 to 29 are all the same, but may be different between the inner sipes 26, 28 and the outer sipes 27, 29, or may be different for all the sipes 26 to 29.

[0081] 7, the depths Da1 to Da4 of the sipes 26 to 29 are set to be 0.25 to 0.75 times the dimension Sw2 of the chamfer 12a in the tire axial direction TA. If the ratio of the depths Da1 to Da4 of the sipes 26 to 29 to the dimension Sw2 of the chamfer 12a is made too small, the reduction in rigidity at the outer surface 12 of the block 17A will be insufficient. If the ratio of the depths Da1 to Da4 of the sipes 26 to 29 to the dimension Sw2 of the chamfer 12a is made too large, the resistance of the sipes 26 to 29 to external damage caused by curbs, steps, etc. will decrease. To prevent these problems, it is preferable to set the ratio of the depths Da1 to Da4 of the sipes 26 to 29 to the dimension Sw2 of the chamfer 12a within the above-specified range. In this embodiment, the ratio of the depths Da1 to Da4 of the sipes 26 to 29 to the dimension Sw2 of the chamfer 12a is the same for all, but as long as it is within the above-specified range, it may be different between the inner sipes 26, 28 and the outer sipes 27, 29, or it may be different for all sipes 26 to 29.

[0082] 6 and 7, the dimension Sr2 of the outer radial sipes 27 in the tire radial direction TR is set to be 1.25 to 1.75 times the depth Dr3 of the tread sipes 23 in the tire radial direction TR. If the ratio of the dimension Sr2 of the outer radial sipes 27 to the depth Dr3 of the tread sipes 23 is set too small, the rigidity reduction in the outer region 17c of the block 17A will be insufficient. If the ratio of the dimension Sr2 of the outer radial sipes 27 to the depth Dr3 of the tread sipes 23 is set too large, the rigidity reduction in the outer region 17c of the block 17A will be excessive. To prevent these inconveniences, it is preferable that the ratio of the dimension Sr2 of the outer radial sipes 27 to the depth Dr3 of the tread sipes 23 be set within the above-specified range.

[0083] As described above, in the tire 1 of this embodiment, the inner radial sipes 26 and the outer radial sipes 27 having different dimensions Sr1, Sr2 in the tire radial direction TR are provided on the outer surface 12 of the block 17A having the plurality of tread sipes 23. In addition, the inner circumferential sipes 28 are connected to the inner ends of the pair of inner radial sipes 26 in the tire radial direction TR, and the outer circumferential sipes 29 are connected to the inner ends of the pair of outer radial sipes 27 in the tire radial direction.

[0084] On the outer surface 12 on which these sipes 26 to 29 are formed, the space between a pair of axial grooves 21 adjacent in the tire circumferential direction TC is divided into a first region 31 defined by a pair of inner radial sipes 26 and inner circumferential sipes 28, a second region outside the first region 31 defined by a pair of outer radial sipes 27 and outer circumferential sipes 29, and a third region 33 outside the second region 32.

[0085] If there are no sipes 26 to 29 on the outer surface 12, the rigidity of the outer surface 12 of the block 17A will be lowest at the center in the tire circumferential direction TC due to the multiple tread sipes 23, and the amount of displacement due to the force acting from the outside to the inside in the tire axial direction TA will be the largest, making uneven wear more likely to occur.

[0086] In contrast, in this embodiment, in which the sipes 26-29 are provided, the rigidity of the outer surface 12 of the block 17A can be gradually reduced from the center line CL2 side of the block 17A toward the outside in the tire circumferential direction TC due to the difference in the lengths of the radial sipes 26, 27 in the tire radial direction TR. This allows the rigidity balance of the block 17A in the tire circumferential direction TC to be optimized. As a result, uneven wear in the first region 31 (central region 17a) of the block 17A can be suppressed. Furthermore, a decrease in rigidity in the central region 17a of the block 17A can be prevented from the initial to intermediate wear stages.

[0087] In particular, the shoulder land 15A of this embodiment has a configuration in which multiple blocks 17 are provided on the outer side of the rib 16 in the tire radial direction TR. In the case of such a shoulder land 15A, when a force acts from the outer side toward the inner side in the tire axial direction TA, the rib 16 has difficulty absorbing the force, and the effect on the blocks 17A is large. However, because the radial sipes 26, 27 are formed in the blocks 17A, the rigidity balance of the blocks 17A can be optimized, and uneven wear can be suppressed.

[0088] Furthermore, when the tire 1 is mounted on a steering wheel of a vehicle, it is more susceptible to lateral forces during cornering, etc., compared to when the tire is mounted on a driving wheel. The lateral forces at this time are generated not only in the tire axial direction TA but also in directions intersecting the tire axial direction TA, i.e., along the tire circumferential direction TC and along the tire radial direction TR, so the outer surface 12 is more likely to wear unevenly.

[0089] In contrast, the outer surface 12 of this embodiment is divided by the sipes 26 to 29 into a first region 31, a second region 32, and a third region 33, where the lateral force acts most strongly, and the second region 32 is divided, and the first region 31 is further divided. Therefore, it is possible to effectively prevent the force acting on the third region 33 from being transmitted to the central portion in the tire circumferential direction TC of the space between the pair of axial grooves 21 in the first region 31. Therefore, since movement of the first region 31 can be suppressed, it is possible to effectively prevent uneven wear in the central portion in the tire circumferential direction TC between the pair of axial grooves 21.

[0090] The pneumatic tire 1 configured in this manner has the following features.

[0091] The inner radial sipes 26 and the outer radial sipes 27 are provided at different positions in the tire circumferential direction TC relative to the tread sipes 23 of the tread surface 11. Therefore, compared to when the tread sipes 23 and the radial sipes 26, 27 are formed at the same positions in the tire circumferential direction TC, excessive reduction in rigidity of the shoulder land 15A can be suppressed. Therefore, the occurrence of cracks originating from the tread sipes 23 and the radial sipes 26, 27 can be suppressed.

[0092] The dimension Sr1 in the tire radial direction TR of the inner radial sipe 26 is shorter than the dimension Sr2 in the tire radial direction TR of the outer radial sipe 27. Therefore, the rigidity of the outer side in the tire circumferential direction TC between the pair of axial grooves 21 of the shoulder land 15A can be made lower than the rigidity of the central portion in the tire circumferential direction TC. This makes it possible to optimize the rigidity balance in the tire circumferential direction TC between the pair of axial grooves 21. Therefore, it is possible to average out the amount of displacement in the tire circumferential direction TC when a force acts from the outer side to the inner side in the tire axial direction TA, and to effectively suppress uneven wear in the central portion in the tire circumferential direction TC.

[0093] An inner circumferential sipe 28 is provided adjacent to the pair of inner radial sipes 26, and an outer circumferential sipe 29 is provided adjacent to the pair of outer radial sipes 27. This makes it possible to suppress the transmission of force from the outer side (third region 33) of the first region 31 or the second region 32 defined by the radial sipes 26, 27 and the circumferential sipes 28, 29 on the outer surface 12 of the shoulder land 15A to the inner side. This suppresses movement of the first region 31 or the second region 32. As a result, it is possible to effectively suppress uneven wear in the central portion in the tire circumferential direction TC of the interval between the pair of axial grooves 21 of the shoulder land 15A located in the first region 31, and also to suppress the occurrence of cracks at the bottoms of the tread sipes 23.

[0094] More specifically, the outer surface 12 of the shoulder land 15A is divided into a first region 31 defined by a pair of inner radial sipes 26 and an inner circumferential sipe 28, a second region 32 defined by a pair of outer radial sipes 27 and an outer circumferential sipe 29 and located outside the first region 31, and a third region 33 located outside the second region 32. This effectively suppresses force transmission to a central portion in the tire circumferential direction TC of the gap between a pair of axial grooves 21 within the first region 31. This effectively suppresses uneven wear in the central portion in the tire circumferential direction TC of the gap between adjacent pairs of axial grooves 21.

[0095] The inner circumferential sipes 28 are continuous with the inner radial sipes 26, and the outer circumferential sipes 29 are continuous with the outer radial sipes 27. This makes it possible to more effectively suppress the transmission of force between the pair of inner radial sipes 26.

[0096] Imaginary lines (straight lines) VL1, VL2 connecting the outer ends 26c, 27c and the inner ends 26d, 27d of the radial sipes 26, 27 are inclined inward in the tire radial direction TR toward the center line CL2 (center) in the tire circumferential direction TC between the pair of axial grooves 21. This results in an obtuse angle of inclination of the entire radial sipes 26, 27 with respect to the rotational direction of the tire 1, making it possible to suppress damage originating from the radial sipes 26, 27 when the tire comes into contact with a curb, a step, or the like.

[0097] More specifically, the inclination angles θ1, θ2 of the imaginary lines (straight lines) VL1, VL2 of the radial sipes 26, 27 are 5 degrees or more and 15 degrees or less with respect to the center line (reference line) CL2 extending in the tire radial direction TR. This makes it possible to prevent the short inner radial sipe 26 and the long outer radial sipe 27 from overlapping with each other when viewed from the outside in the tire radial direction TR. This makes it possible to prevent an excessive decrease in rigidity of the shoulder land 15A due to the overlapping of the inner radial sipe 26 and the outer radial sipe 27.

[0098] The outer ends 26c, 27c of the radial sipes 26, 27 in the tire radial direction TR are opened at the chamfer 12a, which can prevent cracks from occurring starting from the outer ends 26c, 27c, which may occur if the outer ends 26c, 27c of the radial sipes 26, 27 are closed.

[0099] The shoulder land 15A includes a rib 16, a plurality of first blocks 17A, and a plurality of second blocks 17B, and the first blocks 17A are formed with radial sipes 26, 27. In the case of such a shoulder land 15A, when a force acts from the outside to the inside in the tire axial direction TA, the rib 16 has difficulty absorbing the force, and the impact on the first blocks 17A is large. However, because the first blocks 17A have the radial sipes 26, 27, the rigidity balance of the first blocks 17A can be optimized, and uneven wear can be suppressed.

[0100] The dimension Sr2 in the tire radial direction TR of the outer radial sipe 27 is 1.25 to 1.75 times the depth Dr3 in the tire radial direction TR of the tread sipe 23. This effectively reduces the rigidity at the outer portion in the tire circumferential direction TC between the pair of axial grooves 21, thereby optimizing the rigidity balance of the shoulder land 15A and suppressing uneven wear.

[0101] The dimension Sr1 in the tire radial direction TR of the inner radial sipe 26 is 0.25 to 0.45 times the dimension Sr2 in the tire radial direction TR of the outer radial sipe 27. This makes it possible to suppress an excessive decrease in rigidity in the central portion in the tire circumferential direction TC between the pair of axial grooves 21, thereby optimizing the rigidity balance of the shoulder land 15A and suppressing uneven wear.

[0102] The distance Sw1 from the outer end 23c of the tread sipe 23 to the outer end of the chamfer 12a is 1.5 times or more the dimension Sw2 of the chamfer 12a in the tire axial direction TA, thereby suppressing the occurrence of cracks originating from the outer end 23c of the tread sipe 23.

[0103] The depths Da1, Da2 of the radial sipes 26, 27 are 0.25 to 0.75 times the dimension Sw2 of the chamfer 12a in the tire axial direction TA. This prevents a decrease in the rigidity reduction effect of the shoulder land 15A, which can occur when the depths Da1, Da2 of the radial sipes 26, 27 are made too small relative to the dimension Sw2 of the chamfer 12a, and improves the rigidity balance between the pair of axial grooves 21. Furthermore, it is possible to prevent cracks from occurring when the radial sipes 26, 27 come into contact with a curb, step, or the like, which can occur when the depths Da1, Da2 of the radial sipes 26, 27 are made too large relative to the dimension Sw2 of the chamfer 12a, thereby ensuring external damage resistance.

[0104] The ratio of the widths W1, W2 of the radial sipes 26, 27 to the depths Da1, Da2 of the radial sipes 26, 27 is 0.5 to 1.0. This prevents an insufficient reduction in rigidity of the shoulder land 15A, which may occur when the ratio of the widths W1, W2 to the depths Da1, Da2 of the radial sipes 26, 27 is excessively small. Also, it prevents an excessive reduction in rigidity of the shoulder land 15A, which may occur when the ratio of the widths W1, W2 to the depths Da1, Da2 of the radial sipes 26, 27 is excessively large.

[0105] The number of radial sipes 26, 27 is an even number, the same as the number of tread sipes 23. Therefore, the rigidity balance between the pair of axial grooves 21 can be easily optimized.

[0106] The widths W1 and W2 of the radial sipes 26 and 27 are the same, and the depths Da1 and Da2 of the radial sipes 26 and 27 are also the same, so that the appearance (shading) of the inner radial sipes 26 and the outer radial sipes 27 appears the same, thereby improving the aesthetic appearance of the tire 1.

[0107] The outer ends 26c, 27c of the radial sipes 26, 27 in the tire radial direction TR are located on a reference line RL2 extending in the tire circumferential direction TC. This allows the rigidity balance between the pair of axial grooves 21 to be easily optimized, and also allows the aesthetic appearance of the tire 1 to be improved.

[0108] Other embodiments and various modifications of the present invention will be described below, but in these descriptions, points that are not particularly mentioned are the same as those in the first embodiment. In the drawings referred to below, the same elements as those in the first embodiment are denoted by the same reference numerals.

[0109] The circumferential sipes 28, 29 may be configured as shown in Figures 8 to 11.

[0110] In the modified example shown in FIG. 8 , the circumferential sipes 28, 29 are spaced apart in the tire circumferential direction TC from the inner ends 26d, 27d of the radial sipes 26, 27, respectively. If the spacing between the circumferential sipes 28, 29 and the radial sipes 26, 27 is excessively small, the rubber therebetween may break. If the spacing between the circumferential sipes 28, 29 and the radial sipes 26, 27 is excessively large, the force of the third region 33 may be transmitted to the first region 31, causing uneven wear in the first region 31. To prevent these problems, the spacing between the circumferential sipes 28, 29 and the radial sipes 26, 27 is preferably set to 5 mm or more and 20 mm or less. However, the circumferential sipes 28, 29 may also be spaced apart inward in the tire radial direction TR from the inner ends 26d, 27d of the radial sipes 26, 27.

[0111] In the modified example shown in Fig. 9, the circumferential sipes 28, 29 are provided in the middle portions of the radial sipes 26, 27 in the tire radial direction TR. However, only one of the circumferential sipes 28, 29 may be provided in the middle portion of the corresponding radial sipes 26, 27, and the other may be provided at the inner ends 26d, 27d of the corresponding radial sipes 26, 27. Also, the circumferential sipes 28, 29 may be provided at intervals relative to the radial sipes 26, 27. Also, the circumferential sipes 28, 29 may be provided to penetrate the radial sipes 26, 27 so that the circumferential sipes 28, 29 and the radial sipes 26, 27 intersect.

[0112] In the modified example shown in Fig. 10, the circumferential sipes 28, 29 are formed in an arc shape extending around the central axis of the tire 1. The arc-shaped circumferential sipes 28, 29 may be provided at intervals relative to the radial sipes 26, 27 as in the modified example shown in Fig. 8, or may be provided in the middle portion in the tire radial direction TR as in the modified example shown in Fig. 9.

[0113] In the modified example shown in Fig. 11, the circumferential sipes 28, 29 have a bent shape with inflection points 28e, 29e when viewed from the tire axial direction TA. The bent circumferential sipes 28, 29 may be spaced apart from the radial sipes 26, 27 as in the modified example shown in Fig. 8, or may be located in the middle of the tire radial direction TR as in the modified example shown in Fig. 9.

[0114] Specifically, the inner circumferential sipe 28 of the modified example shown in FIG. 11 includes a first portion 28f connected to the inner end 26d of the left inner radial sipe 26, and a second portion 28g connected to the inner end 26d of the right inner radial sipe 26 and extending in a direction different from the first portion 28f. The first portion 28f and the second portion 28g are each inclined toward the center line CL2 of the block 17A as they extend outward in the tire radial direction TR. The groove width of the first portion 28f and the groove width of the second portion 28g in the tire circumferential direction TC are the same. In other words, the groove width of the inner circumferential sipe 28 is uniform. The point where the first portion 28f and the second portion 28g connect is an inflection point 28e. This inflection point 28e is located outward in the tire radial direction TR from the inner end 26d of the inner radial sipe 26.

[0115] The outer circumferential sipe 29 includes a first portion 29f connected to the inner end 27d of the left outer radial sipe 27, and a second portion 29g connected to the inner end 27d of the right outer radial sipe 27 and extending in a direction different from the first portion 29f. The first portion 29f and the second portion 29g are each inclined toward the center line CL2 of the block 17A as they extend outward in the tire radial direction TR. The groove width of the first portion 29f and the groove width of the second portion 29g in the tire circumferential direction TC are the same. In other words, the groove width of the outer circumferential sipe 29 is uniform. The point where the first portion 29f and the second portion 29g connect is an inflection point 29e. This inflection point 29e is located outward in the tire radial direction TR from the inner end 27d of the outer radial sipe 27.

[0116] The smaller angle θ3a formed by the reference line RL5 that passes through the inflection point 28e, which is the apex of the inner circumferential sipe 28, and extends in the tire circumferential direction TC (contacting it), and the first portion 28f, the smaller angle θ3b formed by the reference line RL5 and the second portion 28g, the smaller angle θ4a formed by the reference line RL6 that passes through the inflection point 29e, which is the apex of the outer circumferential sipe 29, and extends in the tire circumferential direction TC (contacting it), and the first portion 29f, and the smaller angle θ3b formed by the reference line RL6 and the second portion 29g are all greater than 0 degrees (excluding 0 degrees) and preferably greater than 0 degrees and less than 15 degrees. In other words, the smaller angle between the first portion 28f and the second portion 28g of the inner circumferential sipe 28 and the smaller angle between the first portion 29f and the second portion 29g of the outer circumferential sipe 29 are equal to or greater than 150 degrees and less than 180 degrees. If the angles θ3a, θ3b, θ4a, θ4b are made excessively large, the circumferential sipes 28, 29 will bend at an acute angle, making it easier for cracks to occur starting from the inflection points 28e, 29e. If the bending angles θ3a, θ3b, θ4a, and θ4b are made excessively small, the inflection points 28e and 29e will be located more inward in the tire radial direction TR than the inner ends 26d and 27d of the radial sipes 26 and 27. This means that when the tire 1 gets stuck in a rut on the road surface, the apexes of the circumferential sipes 28 and 29, which are the inflection points 28e and 29e, will not get caught on the slope of the rut. To prevent these inconveniences, it is preferable to set the bending angles θ3a, θ3b, θ4a, and θ4b of the circumferential sipes 28 and 29 within the above-specified ranges. Note that, although the bending angles θ3a, θ3b, θ4a, and θ4b of the circumferential sipes 28 and 29 are all set to the same in this embodiment, they may be different as long as they are within the above-specified ranges.

[0117] The circumferential sipes 28, 29 each have a bent shape having a first portion 28f, 29f and a second portion 28g, 29g. Therefore, the first portion 28f, 29f and the second portion 28g, 29g, which extend in different directions, can elastically absorb forces from different directions, thereby more effectively suppressing transmission of force to the central portion (first region 31) of the gap between the pair of axial grooves 21 in the tire circumferential direction TC.

[0118] The inflection points 28e, 29e, where the first portions 28f, 29f and the second portions 28g, 29g are connected, are located outward in the tire radial direction TR from the inner ends 26d, 27d in the tire radial direction TR of the adjacent radial sipes 26, 27. Therefore, when the tire 1 gets stuck in a rut on the road surface, the tops of the circumferential sipes 28, 29, which are the inflection points 28e, 29e, get caught on the slope of the rut, improving the ability to escape from the rut.

[0119] The angles θ3a, θ4a formed between the first portions 28f, 29f of the circumferential sipes 28, 29 and the reference lines RL5, RL6, and the angles θ3b, θ4b formed between the second portions 28g, 29g and the reference lines RL5, RL6 are both greater than 0 degree and not more than 15 degrees. In other words, the angles of the circumferential sipes 26, 27 with the inflection points e, 29e as their apexes are obtuse angles, which makes it possible to suppress the occurrence of cracks originating from the inflection points 28e, 29e.

[0120] In the modified example shown in FIG. 12 , a circumferential sipe 29 is provided adjacent to the outer radial sipe 27, and no adjacent circumferential sipe is provided on the inner radial sipe 26. However, it is also possible to provide a circumferential sipe 28 adjacent to the inner radial sipe 26, and not provide an adjacent circumferential sipe 29 on the outer radial sipe 27. In other words, it is sufficient that the circumferential sipe is provided adjacent to one of the pair of inner radial sipes 26 and the pair of outer radial sipes 27. Of course, in the modified examples shown in FIGS. 8 to 11 , the circumferential sipe may also be provided adjacent to only one of the pair of inner radial sipes 26 and the pair of outer radial sipes 27.

[0121] (Second embodiment) Fig. 13 shows side sipes 25 provided on the outer surface 12 of a tire according to a second embodiment. This second embodiment differs from the first embodiment in that the radial sipes 26, 27 have a curved shape with one or more inflection points 26e, 27e. The circumferential sipes 28, 29 of the second embodiment have the same configuration as the first embodiment shown in Fig. 6, but may be as shown in the modified examples shown in Figs. 8 to 11, or may be provided on only one of the radial sipes 26, 27 as shown in the modified example shown in Fig. 12.

[0122] Specifically, the radial sipes 26, 27 of the second embodiment have different tire radial direction TR dimensions, similar to the first embodiment, with the inner radial sipe 26 being shorter than the outer radial sipe 27. Therefore, the shorter inner radial sipe 26 has one inflection point 26e, and the longer outer radial sipe 27 has multiple (five) inflection points 27e. However, the numbers of inflection points 26e, 27e of the radial sipes 26, 27 can be changed as needed.

[0123] More specifically, the inner radial sipe 26 includes a first portion 26f and a second portion 26g connected to the inner end of the first portion 26f in the tire radial direction TR. The first portion 26f is inclined in a direction away from the center line CL2 of the block 17A as it moves inward in the tire radial direction TR. The second portion 26g is inclined in a direction approaching the center line CL2 of the block 17A as it moves inward in the tire radial direction TR. The inclination directions of the first portion 26f and the second portion 26g are different from the tire axial direction TA, the tire radial direction TR, and the tire circumferential direction TC. The portion where the first portion 26f and the second portion 26g join is an inflection point 26e. The groove width of the first portion 26f and the groove width of the second portion 26g in the tire circumferential direction TC are the same. In other words, the groove width of the inner radial sipe 26 is uniform.

[0124] The outer radial sipe 27 includes three first portions 27f and three second portions 27g that are connected to the inner ends of the first portions 27f in the tire radial direction TR. The first portions 27f are inclined in a direction away from the center line CL2 of the blocks 17A as they move inward in the tire radial direction TR. The second portions 27g are inclined in a direction approaching the center line CL2 of the blocks 17A as they move inward in the tire radial direction TR. The inclination directions of the first portions 27f and the second portions 27g are different from the tire axial direction TA, the tire radial direction TR, and the tire circumferential direction TC. The portion where the first portions 27f and the second portions 27g join is an inflection point 27e. The groove width of the first portions 27f and the groove width of the second portions 27g in the tire circumferential direction TC are the same. In other words, the groove width of the outer radial sipe 27 in the tire circumferential direction TC is uniform.

[0125] The angle between the first portion 26f and the second portion 26g of the inner radial sipe 26 is α, and the angle between the first portion 27f and the second portion 27g of the outer radial sipe 27 is β. Both of the angles α and β are set to be greater than or equal to 90 degrees and less than or equal to 150 degrees. If the angles α and β are set too small, the first portions 26f and 27f and the second portions 26g and 27g bend at an acute angle, making it easier for cracks to occur starting from the inflection points 26e and 27e. On the other hand, if the angles α and β are set too large, the first portions 26f and 27f and the second portions 26g and 27g approach a straight line, reducing the effect of mitigating lateral forces from different directions. To prevent these disadvantages, it is preferable to set the angles α and β within the above-specified range.

[0126] In this embodiment, the inclination angles of the first portions 26f and 27f with respect to the center line CL2 are the same, and the inclination angles of the second portions 26g and 27g with respect to the center line CL2 are also set to be the same. Therefore, the angle α of the inner radial sipe 26 and the angle β of the outer radial sipe 27 are also set to be the same. However, as long as the angles α and β are within the above-specified ranges, the inclination angles of the first portions 26f and 27f with respect to the center line CL2 may be different, the inclination angles of the second portions 26g and 27g with respect to the center line CL2 may be different, and the angles α and β may also be different.

[0127] The length La1 of the first portion 26f of the inside radial sipe 26 in the tire radial direction TR is set to be equal to or greater than the length La2 of the second portion 26g. The length Lb1 of the first portion 27f of the outside radial sipe 27 in the tire radial direction TR is set to be equal to or greater than the length Lb2 of the second portion 27g.

[0128] The length La1 of the first portion 26f of the inner radial sipe 26 is set to be equal to or greater than the length Lb1 of the first portion 27f of the outer radial sipe 27, and the length La2 of the second portion 26g of the inner radial sipe 26 is set to be equal to or greater than the length Lb2 of the second portion 27g of the outer radial sipe 27. In other words, the pitch of the inner radial sipe 26 including the first portion 26f and the second portion 26g is the same as or longer than the pitch of the outer radial sipe 27, each of which includes one first portion 27f and one second portion 27g.

[0129] The amplitude of the inner radial sipes 26 is defined by the length La1 of the first portion 26f, the length La2 of the second portion 26g, and the angle α. The amplitude of the outer radial sipes 27 is defined by the length Lb1 of the first portion 27f, the length Lb2 of the second portion 27g, and the angle β. The amplitude of the inner radial sipes 26 is set to be equal to or smaller than the amplitude of the outer radial sipes 27, i.e., the same as or smaller than the amplitude of the outer radial sipes 27.

[0130] The radial sipes 26, 27 of the second embodiment configured as described above have a curved shape with one or more inflection points 26e, 27e, and therefore can elastically absorb lateral forces from two or more different directions. Therefore, uneven wear can be effectively suppressed even when the tire 1 is mounted on a steered wheel of a vehicle.

[0131] The angles α and β formed by the first portions 26f and 27f and the second portions 26g and 27g of the radial sipes 26 and 27 are between 90 degrees and 150 degrees. This prevents cracks from occurring at the inflection points 26e and 27e, which tend to occur when the angles α and β are excessively small. Furthermore, the effect of mitigating lateral forces from different directions, which is difficult to achieve when the angles α and β are excessively large, can be reliably achieved.

[0132] (Third embodiment) 14 shows radial sipes 26, 27 and circumferential sipes 28, 29 provided on the outer surface 12 of a tire according to a third embodiment. This third embodiment differs from both the first and second embodiments in that the pair of inner radial sipes 26 have a straight shape with no bending points, and the pair of outer radial sipes 27 have a curved shape with an inflection point 27e. The configuration of the pair of inner radial sipes 26 is the same as in the first embodiment, and the configuration of the pair of outer radial sipes 27 is the same as in the second embodiment.

[0133] However, in the third embodiment, the pair of inner radial sipes 26 may be formed in a curved shape having an inflection point as in the second embodiment, and the pair of outer radial sipes 27 may be formed in a straight shape without an inflection point as in the first embodiment. In addition, the circumferential sipes 28, 29 may be formed as in the modified examples shown in Figures 8 to 11, or may be formed on only one of the radial sipes 26, 27 as in the modified example shown in Figure 12.

[0134] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0135] For example, the side sipes 25 may be composed of three or more types of radial sipes and circumferential sipes with different dimensions in the tire radial direction TR. In this case, the three or more types of radial sipes are arranged on the outer surface 12 of the block 17A so that their dimensions gradually increase from the center toward the outside in the tire circumferential direction TC. The number of tread sipes 23 may be the same as the number of radial sipes or one less. In other words, the number of radial sipes may be the same as the number of tread sipes 23 or one more than the number of tread sipes 23, as long as it is an even number of four or more. In this way, by providing an even number of radial sipes of four or more, with the upper limit being one more than the number of tread sipes 23, the rigidity balance between a pair of axial grooves 21 can be easily optimized.

[0136] The side sipes 25 may be provided on the outer surface 12 of the rib 16 without providing the blocks 17 on the shoulder land 15A. That is, in a pneumatic tire in which multiple ribs are formed by main grooves, multiple axial grooves extending inward from the outer ends of the tire in the axial direction may be provided at intervals in the tire circumferential direction in the ribs at both ends in the tire axial direction, and the side sipes 25 may be provided between adjacent axial grooves in the tire circumferential direction.

[0137] The pneumatic tire 1 is not limited to a tapered shoulder type in which the outer surface 12 is provided with a chamfer 12a, but may be a box shoulder type without a chamfer 12a.

[0138] A first aspect of the present invention is a shoulder land having a tread surface at a radially outer end of the tire and an outer surface at an axially outer end of the tire, the shoulder land being located at the axially outer end of the tread; a plurality of axial grooves provided at intervals in the tire circumferential direction on the shoulder land, recessed from the tread surface toward the tire radially inward, extending in the tire axial direction, and opening at the outer surface; a plurality of tread sipes provided at intervals in the tire circumferential direction between a pair of axial grooves adjacent in the tire circumferential direction on the shoulder land, each recessed radially inward from the tread, extending in the tire axial direction, and terminating at a position spaced apart from the outer surface; a plurality of side sipes provided on the outer surface and recessed axially inward; Equipped with The plurality of side sipes are a pair of inner radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, positioned on the tire circumferential center side of the interval between the pair of axial grooves, extending in the tire radial direction, and spaced apart in the tire circumferential direction; a pair of outer radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, extending in the tire radial direction at positions closer to the axial groove than the inner radial sipe within the interval between the pair of axial grooves, and spaced apart in the tire circumferential direction; a circumferential sipe that is provided adjacent to at least one of the pair of inner radial sipes and the pair of outer radial sipes and extends in the tire circumferential direction between the pair of adjacent inner radial sipes or the pair of outer radial sipes; Including, The present invention provides a pneumatic tire, in which the dimension of the inner radial sipe in the tire radial direction is shorter than the dimension of the outer radial sipe in the tire radial direction.

[0139] A second aspect of the present invention provides a pneumatic tire according to the first aspect, wherein the circumferential sipes are provided in pairs adjacent to both the pair of inner radial sipes and the pair of outer radial sipes, respectively.

[0140] A third aspect of the present invention provides the pneumatic tire according to the first or second aspect, wherein the circumferential sipe is continuous with the adjacent inner radial sipe or the adjacent outer radial sipe.

[0141] A fourth aspect of the present invention provides a pneumatic tire according to any one of the first to third aspects, wherein the circumferential sipes have a curved shape having a first portion adjacent to one of the pair of inner radial sipes or the pair of outer radial sipes, and a second portion adjacent to the other of the pair of inner radial sipes or the pair of outer radial sipes and extending in a direction different from the first portion.

[0142] A fifth aspect of the present invention is the first portion and the second portion are each inclined toward the tire circumferential center side of the interval between the pair of axial grooves from the tire radial direction inner end of the adjacent inner radial sipe or the adjacent outer radial sipe toward the tire radial direction outer side, There is provided a pneumatic tire according to a fourth aspect, wherein the circumferential sipes have a shape that protrudes outward in the tire radial direction.

[0143] A sixth aspect of the present invention provides a pneumatic tire according to the fourth or fifth aspect, wherein an angle formed between the first portion and a reference line extending in the tire circumferential direction, and an angle formed between the second portion and the reference line are both greater than 0 degrees and not greater than 15 degrees.

[0144] A seventh aspect of the present invention is The inner radial sipe and the outer radial sipe each have an outer end located on the outer side in the tire radial direction and an inner end located on the inner side in the tire radial direction, a straight line connecting the outer end of the inner radial sipe and the inner end of the inner radial sipe, and a straight line connecting the outer end of the outer radial sipe and the inner end of the outer radial sipe are each inclined toward a tire circumferential center side of the interval between the pair of axial grooves as they extend radially inward in the tire radial direction, The present invention provides a pneumatic tire according to any one of the first to sixth aspects.

[0145] An eighth aspect of the present invention is the outer surface has a chamfer inclined inward in the tire axial direction as it extends outward in the tire radial direction, at a portion in contact with the tread surface; The outer ends of the inner radial sipes and the outer radial sipes in the tire radial direction are chamfered to open outward in the tire radial direction. The present invention provides a pneumatic tire according to any one of the first to seventh aspects.

[0146] A ninth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The tread is main grooves provided at intervals on the inner side in the tire axial direction of the outer surface, recessed inward in the tire radial direction, and extending in the tire circumferential direction; a circumferential groove provided between the main groove and the outer surface, recessed inward in the tire radial direction, and extending in the tire circumferential direction; Equipped with The shoulder land is a rib defined by the outer surface and a sidewall of the main groove; a plurality of first blocks provided on the outer side of the rib in the tire radial direction and defined by the outer surface, a side wall of the circumferential groove, and side walls of a pair of axial grooves adjacent to each other in the tire circumferential direction; a plurality of second blocks provided on the outer side of the rib in the tire radial direction and defined by the side wall of the circumferential groove, the side wall of the main groove, and side walls of a pair of axial grooves adjacent to each other in the tire circumferential direction; and The tread sipes and the side sipes are formed in each of the plurality of first blocks. The present invention provides a pneumatic tire according to any one of the first to eighth aspects.

[0147] A tenth aspect of the present invention provides a pneumatic tire according to any one of the first to ninth aspects, wherein the number of the side sipes is the same as or one more than the number of the tread sipes, and is an even number of four or more. [Explanation of symbols]

[0148] 1 pneumatic tire 10 Tread 11 Tread 12 External surface 12a Chamfer 12b Continuous section 13 Ridge 14 Main groove 14a side wall 14b Bottom wall 15 land 15A Shoulder Land 15B Center Land 16 Ribs 17 blocks Block 17A (1st Block) Block 17B (2nd Block) 17a central area 17b Middle area 17c outer area 18 Block Row 18A Outer Block Row 18B Inner Block Row 20 Circumferential groove 20a Sidewall 20b bottom wall 21 Axial groove 21a side wall 21b Bottom wall 23, 23A, 23B Tread sipes 23a side wall 23b Bottom wall 23c outer end 23d inner edge 25 Side sipes 26 Inner radial sipes 26a side wall 26b Bottom wall 26c outer end 26d inner end 26e Inflection point 26f Part 1 26g 2nd portion 27 Outer radial sipes 27a side wall 27b Bottom wall 27c outer end 27d inner end 27e Inflection point 27f Part 1 27g 2nd portion 28 Inner circumferential sipe 28a side wall 28b Bottom wall 28c left end 28d Right end 28e Inflection point 28f Part 1 28g 2nd portion 29 Outer circumferential sipe 29a side wall 29b Bottom wall 29c left end 29d Right end 29e Inflection point 29f Part 1 29g 2nd portion 31 First area 32 Second area 33 Third area TC: Tire Circumferential Direction TA Tire axial direction TR Tire radial direction CL1 center line Dr1 Main groove depth Dr2 Axial groove depth Dr3 Tread sipe depth Sw1 Distance between tread sipes and chamfers Sw2 chamfer dimensions RL1, RL2, RL3, RL4 reference lines Sr1 Inner radial sipe dimensions Sr2 Outer radial sipe dimensions W1 Width of inner radial sipe W2 Width of outer radial sipe W3 Width of inner circumferential sipe W4 Width of outer circumferential sipe Da1 Inner radial sipe depth Da2 Depth of outer radial sipe Da3 Depth of inner circumferential sipe Da4 Depth of outer circumferential sipe

Claims

1. a shoulder land having a tread surface at a radially outer end of the tire and an outer surface at an axially outer end of the tire, the shoulder land being located at the axially outer end of the tread; a plurality of axial grooves provided at intervals in the tire circumferential direction on the shoulder land, recessed from the tread surface toward the tire radially inward, extending in the tire axial direction, and opening at the outer surface; a plurality of tread sipes provided at intervals in the tire circumferential direction between a pair of the axial grooves adjacent in the tire circumferential direction on the shoulder land, each recessed inward in the tire radial direction from the tread, extending in the tire axial direction, and terminating at a position spaced apart from the outer surface; a plurality of side sipes provided on the outer surface and recessed axially inward; Equipped with The plurality of side sipes are a pair of inner radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, positioned on the tire circumferential center side of the interval between the pair of axial grooves, extending in the tire radial direction, and spaced apart in the tire circumferential direction; a pair of outer radial sipes arranged at different positions in the tire circumferential direction with respect to the plurality of tread sipes, extending in the tire radial direction at positions closer to the axial groove than the inner radial sipe within the interval between the pair of axial grooves, and spaced apart in the tire circumferential direction; a circumferential sipe that is provided adjacent to at least one of the pair of inner radial sipes and the pair of outer radial sipes and extends in the tire circumferential direction between the pair of adjacent inner radial sipes or the pair of outer radial sipes; Including, a radial dimension of the inner radial sipes in the tire radial direction is shorter than a radial dimension of the outer radial sipes in the tire radial direction.

2. The pneumatic tire according to claim 1 , wherein a pair of the circumferential sipes are provided adjacent to both the pair of inner radial sipes and the pair of outer radial sipes, respectively.

3. The pneumatic tire according to claim 1 or 2, wherein the circumferential sipe is continuous with the adjacent inner radial sipe or the adjacent outer radial sipe.

4. 3. The pneumatic tire according to claim 1, wherein the circumferential sipe has a curved shape having a first portion adjacent to one of the pair of inner radial sipes or the pair of outer radial sipes and a second portion adjacent to the other of the pair of inner radial sipes or the pair of outer radial sipes and extending in a direction different from the first portion.

5. the first portion and the second portion are each inclined toward a tire circumferential center side of a space between the pair of axial grooves from an inner end in the tire radial direction of the adjacent inner radial sipe or the adjacent outer radial sipe toward an outer side in the tire radial direction, The pneumatic tire according to claim 4 , wherein the circumferential sipes are shaped to protrude outward in the tire radial direction.

6. The pneumatic tire according to claim 4 , wherein an angle formed between the first portion and a reference line extending in the tire circumferential direction and an angle formed between the second portion and the reference line are both greater than 0 degrees and not greater than 15 degrees.

7. The inner radial sipe and the outer radial sipe each have an outer end located on the outer side in the tire radial direction and an inner end located on the inner side in the tire radial direction, a straight line connecting the outer end of the inner radial sipe and the inner end of the inner radial sipe, and a straight line connecting the outer end of the outer radial sipe and the inner end of the outer radial sipe are each inclined toward a tire circumferential center side of the interval between the pair of axial grooves as they extend radially inward in the tire radial direction, The pneumatic tire according to claim 1 or 2.

8. the outer surface has a chamfer inclined inward in the tire axial direction as it extends outward in the tire radial direction, at a portion in contact with the tread surface; The outer ends of the inner radial sipes and the outer radial sipes in the tire radial direction are chamfered to open outward in the tire radial direction. The pneumatic tire according to claim 1 or 2.

9. The tread is main grooves provided at intervals on the inner side in the tire axial direction of the outer surface, recessed inward in the tire radial direction, and extending in the tire circumferential direction; a circumferential groove provided between the main groove and the outer surface, recessed inward in the tire radial direction, and extending in the tire circumferential direction; Equipped with The shoulder land is a rib defined by the outer surface and a sidewall of the main groove; a plurality of first blocks provided on the outer side of the rib in the tire radial direction and defined by the outer surface, a side wall of the circumferential groove, and side walls of a pair of axial grooves adjacent to each other in the tire circumferential direction; a plurality of second blocks provided on the outer side of the rib in the tire radial direction and defined by the side wall of the circumferential groove, the side wall of the main groove, and side walls of a pair of axial grooves adjacent to each other in the tire circumferential direction; and The tread sipes and the side sipes are formed in each of the plurality of first blocks. The pneumatic tire according to claim 1 or 2.

10. The pneumatic tire according to claim 1 or 2, wherein the number of the side sipes is the same as or one more than the number of the tread sipes, and is an even number of four or more.

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