Pneumatic tires

Abstract

To provide a pneumatic tire that improves wet performance and dry performance and is excellent in braking performance on a wet road surface and a dry road surface in particular.SOLUTION: A pneumatic tire 1 as one example according to an embodiment comprises a tread 10 which includes shoulder blocks 50 and 60, mediate blocks 70 and 80, main grooves 20 and 21 and second circumferential grooves 26 and 27. The shoulder blocks 50 and 60 and the mediate blocks 70 and 80 have sipes 51 and 71 opening to the second circumferential groove 26 and sipes 61 and 81 opening to the second circumferential groove 27 respectively. In side walls of the sipes are formed respectively inclined surfaces 52, 62, 72 and 82 inclined at a predetermined angle with respect to ground contact surfaces of the blocks, where the inclined surfaces are formed at portions which are adjacent to the second circumferential grooves 26 and 27.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a tread in which a plurality of blocks are arranged along the circumferential direction of the tire. [Background technology]

[0002] Conventionally, there is known a pneumatic tire having a tread in which a plurality of center blocks, a plurality of shoulder blocks, and a plurality of mediate blocks are arranged along the tire circumferential direction (see, for example, Patent Document 1). The tread of the tire of Patent Document 1 has a plurality of main grooves formed therein that are inclined with respect to the tire width direction. The tire of Patent Document 1 is a so-called directional tire in which the main tire rotation direction is specified. Furthermore, in the pneumatic tire of Patent Document 1, the edges of the blocks and the sipes formed in the blocks provide an edge effect on snowy and icy road surfaces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6438768 Summary of the Invention [Problem to be solved by the invention]

[0004] The pneumatic tire of Patent Document 1 aims to achieve both wet and dry performance by controlling the width, cross-sectional area, etc. of the grooves, but for example, increasing the cross-sectional area of ​​the grooves reduces the dry performance, and decreasing the cross-sectional area of ​​the grooves reduces the wet performance, making it difficult to sufficiently improve both performances.

[0005] An object of the present invention is to provide a pneumatic tire which has improved wet and dry performance, and in particular has excellent braking performance on both wet and dry road surfaces. [Means for solving the problem]

[0006] The pneumatic tire according to the present invention has a tread including a plurality of shoulder blocks arranged on both sides in the tire width direction along the tire circumferential direction, a plurality of intermediate blocks arranged along the tire circumferential direction between the tire width direction center and the shoulder blocks, main grooves formed between the shoulder blocks adjacent in the tire circumferential direction and between the intermediate blocks adjacent in the tire circumferential direction, and a circumferential groove formed between the shoulder blocks and the intermediate blocks. The shoulder blocks and the intermediate blocks each have a first sipe and a second sipe opening into the circumferential groove, and a first inclined surface and a second inclined surface inclined at a predetermined angle with respect to the block ground contact surface are formed on the sidewall of the first sipe and the sidewall of the second sipe, respectively, and the first inclined surface and the second inclined surface are formed in a portion adjacent to the circumferential groove.

[0007] According to the above configuration, the braking performance on wet and dry road surfaces is improved, and good wet and dry performances can be achieved. The slope formed on the sipe sidewall of the shoulder block and the mediate block widens the sipe width to improve drainage while ensuring the rigidity of the block, and also expands the snow pocket into which snow is caught. The sipe opens into the circumferential groove, and the slope is formed in the part of the sipe adjacent to the circumferential groove, so that water can be efficiently drained from the sipe to the circumferential groove, and the water film between the tire and the road surface can be effectively removed. In addition, the slope is formed near the block contact surface and does not significantly reduce the rigidity of the block, so that good steering stability on dry road surfaces is ensured. In other words, according to the above configuration, wet performance can be improved without deteriorating dry performance. Effect of the Invention

[0008] The pneumatic tire according to the present invention has excellent braking performance on wet and dry road surfaces, and has good wet and dry performance, and is suitable as an all-season tire. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a pneumatic tire as an example of an embodiment. [Diagram 2] 1 is a plan view of a pneumatic tire as an example of an embodiment, showing a portion of a tread. FIG. [Diagram 3] FIG. 2 is a plan view showing a schematic view of a portion of a tread. [Figure 4] FIG. 2 is an enlarged perspective view showing a left portion in the width direction of the tread. [Diagram 5] FIG. 2 is a perspective view showing a group of blocks consisting of a center block, a mediate block, and a shoulder block. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] FIG. 2 is an enlarged plan view showing a left portion in the width direction of the tread. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. In addition, the present invention includes selective combinations of the respective components of the multiple embodiments and modified examples described below.

[0011] In this specification, the terms wet road surface, snowy road surface, and dry road surface are used. A wet road surface means a road surface wet with rainwater or a road surface wet from melting snow and ice. A snowy road surface means a road surface covered with snow. A dry road surface means a dry road surface without snow and ice. In the following, for convenience of explanation, wet road surfaces and snowy road surfaces may be collectively referred to as "snow and ice road surfaces." In addition, although no particular reference is made to driving performance on frozen road surfaces (ice performance) in the following, a pneumatic tire as an example of an embodiment has good ice performance in addition to good wet performance, snow performance, and dry performance.

[0012] FIG. 1 is a perspective view of a pneumatic tire 1 according to an embodiment, and also illustrates the internal structure of the tire. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10, which is a portion that comes into contact with the road surface. The tread 10 has a tread pattern including a plurality of blocks, and is formed in an annular shape along the tire circumferential direction. The tread 10 also has a plurality of main grooves 20, 21 that are inclined with respect to the tire width direction so as to be gradually positioned rearward in the tire main rotation direction from the center in the tire width direction toward both sides in the tire width direction. The pneumatic tire 1 is a directional tire with a specified main rotation direction. The main grooves 20, 21 are formed between blocks adjacent to each other in the tire circumferential direction, and partition block groups 100, 101, which will be described later.

[0013] In this specification, the "main tire rotation direction" refers to the direction of rotation when a vehicle on which the pneumatic tire 1 is mounted moves forward. In addition, in this specification, the terms "left and right" are used for the pneumatic tire 1 and its components for convenience of explanation. The "right side" of the pneumatic tire 1 refers to the right side when the pneumatic tire 1 mounted on a vehicle is viewed from the front of the vehicle, and the "left side" refers to the left side when the pneumatic tire 1 mounted on a vehicle is viewed from the front of the vehicle. The drawings show the main tire rotation direction and arrows indicating left and right.

[0014] The tread 10 has a plurality of circumferential grooves extending in the tire circumferential direction in addition to a plurality of main grooves 20, 21. The plurality of circumferential grooves include a first circumferential groove 25 formed in the center of the tread 10 in the width direction, and second circumferential grooves 26, 27 formed on both the left and right sides of the tread 10, respectively. A third circumferential groove 28 is formed between the first circumferential groove 25 and the second circumferential groove 26, and a third circumferential groove 29 is formed between the first circumferential groove 25 and the second circumferential groove 27. The "tire width direction" and the "width direction of the tread 10" are the same direction, and hereinafter, both terms will be used as appropriate.

[0015] The tread 10 has a plurality of blocks defined by a plurality of main grooves 20, 21 and a plurality of circumferential grooves. The blocks are island-shaped land portions that rise toward the outside in the tire radial direction. The tread 10 has a plurality of center blocks 30, 40, a plurality of shoulder blocks 50, 60, and a plurality of mediate blocks 70, 80 as the blocks. The center block 30, the shoulder block 50, and the mediate block 70 are disposed on the left side of the tread 10 in the width direction, and the center block 40, the shoulder block 60, and the mediate block 80 are disposed on the right side of the tread 10 in the width direction.

[0016] In this embodiment, blocks of the same type and numbered the same are arranged in a row along the tire circumferential direction. Each row of blocks along the tire circumferential direction is composed of the same number of blocks. That is, the tread 10 has the same number of center blocks 30, 40, shoulder blocks 50, 60, and mediate blocks 70, 80.

[0017] Center blocks 30, 40 are arranged in the widthwise center of the tread 10 so as to sandwich the tire equator CL from the left and right. The tire equator CL means a line along the tire circumferential direction that passes through the tire widthwise center. The center blocks 30, 40 are divided by first circumferential grooves 25 and arranged in a staggered pattern along the tire circumferential direction (tire equator CL). Parts of the center blocks 30, 40 are located on the tire equator CL and are arranged overlapping in the tire circumferential direction.

[0018] On the left side of the tread 10 in the width direction, a center block 30, a mediate block 70, and a shoulder block 50 are arranged in series from the tire equator CL side to form one block group 100. On the right side of the tread 10 in the width direction, a center block 40, a mediate block 80, and a shoulder block 60 are arranged in series from the tire equator CL side to form one block group 101. The three blocks that make up the block group 100 are aligned in the direction in which the main groove 20 extends, and the three blocks that make up the block group 101 are aligned in the direction in which the main groove 21 extends.

[0019] As will be described in detail later, the tread 10 has a tread pattern in which the contact area (A3) of the mediate blocks 70, 80 is large and the contact area (A3) ≥ the contact area (A2) of the shoulder blocks 50, 60 is satisfied. The pneumatic tire 1 exerts high grip on snowy and icy road surfaces due to the multiple blocks, and by increasing the contact area (A3) in particular, achieves excellent driving stability on both snowy and icy road surfaces and dry road surfaces. In addition, each block is formed with sipes that enhance the edge effect on snowy and icy road surfaces. A pneumatic tire 1 having such a tread pattern is suitable, for example, for all-season tires.

[0020] The pneumatic tire 1 includes a shoulder portion 11, a sidewall portion 12, and a bead 13, which are formed in an annular shape along the tire circumferential direction, similar to the tread 10. The shoulder portion 11, the sidewall portion 12, and the bead 13 are portions that form the side surface of the pneumatic tire 1, and are provided on both the left and right sides of the pneumatic tire 1, respectively. In this embodiment, the ground contact edge E of the pneumatic tire 1 is the boundary position between the tread 10 and the shoulder portion 11. In addition, an annular side rib 14 formed on the side surface of the pneumatic tire 1 is the boundary position between the shoulder portion 11 and the sidewall portion 12.

[0021] In this specification, the ground contact ends E refer to both ends in the tire width direction of the portion that comes into contact with a flat road surface when a load of 70% of the normal load (maximum load capacity) at the normal internal pressure is applied to an unused pneumatic tire 1 mounted on a normal rim and filled with air to achieve the normal internal pressure. Similarly, the ground contact area of ​​each block of the pneumatic tire 1 refers to the area of ​​the portion that comes into contact with a flat road surface when a load of 70% of the maximum load capacity at the normal internal pressure is applied.

[0022] Here, a "regular rim" is a rim determined by the tire standard, which is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0023] The shoulder portions 11 protrude from both widthwise ends of the tread 10 outward in the tire width direction (away from the tire equator CL) and extend inward in the tire radial direction. The sidewall portions 12 extend inward in the tire radial direction from each shoulder portion 11 and are gently curved to be convex toward the outside. The beads 13 are portions fixed to the rim of the wheel and extend inward in the tire radial direction from each sidewall portion 12. The beads 13 are gently curved to be convex toward the inside and are located on the inner side of the pneumatic tire 1 in the width direction (on the tire equator CL side) than the sidewall portions 12.

[0024] As described above, FIG. 1 illustrates the internal structure of the pneumatic tire 1. The pneumatic tire 1 includes a carcass 15, which is a cord layer covered with rubber, and a tread pattern and a belt 16 arranged between the carcass 15. The carcass 15 is composed of, for example, two carcass plies, and forms a tire framework that can withstand loads, impacts, air pressure, and the like. The belt 16 is a reinforcing band stretched in the circumferential direction of the tire, and strongly tightens the carcass 15 to increase the rigidity of the tread 10. An inner liner 17, which is a rubber layer for retaining air pressure, is attached to the inner peripheral surface of the carcass 15. In addition, a bead core 18 and a bead filler 19 are arranged in the bead 13.

[0025] Fig. 2 is a plan view of the pneumatic tire 1, showing a part of the tread 10. In Fig. 2 and other figures, dot hatching is applied to the block contact surface. The block contact surface refers to the area of ​​the upper surface of each block facing outward in the tire radial direction that comes into contact with the road surface.

[0026] As shown in FIG. 2, the main grooves 20 are formed at approximately equal intervals in the tire circumferential direction and parallel to each other. Similarly, the main grooves 21 are formed at equal intervals in the tire circumferential direction and parallel to each other. The main grooves 20, 21 are arranged in a staggered manner along the tire circumferential direction. The block groups 100, 101 defined by the main grooves 20, 21 are arranged in the same manner as the main grooves 20, 21. The tread 10 has a tread pattern in which the main grooves 20 and the block groups 100 are arranged alternately in the tire circumferential direction in the left part in the width direction, and the main grooves 21 and the block groups 101 are arranged alternately in the tire circumferential direction in the right part in the width direction.

[0027] The main groove 20 and the block group 100 have a curved shape in plan view that is convex toward the rear in the tire main rotation direction. The main groove 21 and the block group 101 also have a curved shape in plan view that is convex toward the rear in the tire main rotation direction. The main grooves 20, 21 and the block groups 100, 101 are inclined in the same direction in the tire circumferential direction, and the inclination angle is larger on the tire equator CL side than on the ground contact edge E side. The inclination angle of the main grooves 20, 21 with respect to the tire width direction is, for example, 30° to 60°, or 40° to 50° on the tire equator CL side.

[0028] In the pneumatic tire 1, when the tire rotates so that the tire equator CL side of the block groups 100, 101 touches the ground first, water, snow and ice can be efficiently discharged from the tire equator CL side of the tread 10 toward the ground edge E side, and good wet and snow performance can be obtained. On the other hand, when the tire rotates in the opposite direction, the drainage and snow removal effect is not as good as in the former case. The pneumatic tire 1 is a directional tire that is mounted on a vehicle so that the direction in which the tire equator CL side of the block groups 100, 101 touches the ground first is the main rotation direction. The sidewall portion 12 is provided with an indication such as an arrow or letters indicating the main rotation direction of the tire.

[0029] The tread pattern of the tread 10 is a pattern in which the block groups 100, 101 are arranged symmetrically, for example, shifted by half a pitch in the circumferential direction of the tire with respect to a plane perpendicular to the tire's rotation axis that passes through the tire equator CL (hereinafter referred to as the "tire equatorial plane"). The shape of the block group 100 is the same as the shape of the block group 101 when it is inverted with respect to the tire equatorial plane (the same applies to the main grooves 20, 21). If the inverted block group 101 is slid in the circumferential direction of the tire, it will match the block group 100. The tread pattern of the tread 10 has a good left-right balance, which is effective in improving steering stability.

[0030] The main groove 20 is formed from a corner P4 of the right center block 40 that extends beyond the tire equator CL to the left in the tire width direction, beyond the left ground contact edge E, and extending to the left side rib 14. The main groove 20 intersects with the first circumferential groove 25 at the corner P4 of the center block 40. In this embodiment, the first circumferential groove 25 is described as being formed in a zigzag shape continuously in the tire circumferential direction. The main groove 20 gradually extends along the tire width direction from the tire equator CL side toward the ground contact edge E, and the inclination with respect to the tire width direction becomes gentle.

[0031] The width of the main groove 20 (the length in the direction perpendicular to the extension direction of the main groove 20) may be constant over the entire length, but in this embodiment, it is larger on the side of the ground contact edge E than on the side of the tire equator CL, and is maximum at or near the intersection with the second circumferential groove 26. In this case, drainage and snow removal performance is improved, and the snow column shear force that grabs and packs snow is improved, resulting in good wet and snow performance. The pneumatic tire 1 has a main groove 20 that is wider than that of a summer tire, and the ratio of the length of the main groove 20 along the tire circumferential direction to the contact surface of each block is, for example, 3:7 to 4:6.

[0032] Similarly, the main groove 21 is formed from a corner P2 of the left center block 30 that extends beyond the tire equator CL to the right in the tire width direction, beyond the right ground contact edge E, and extending to the right side rib 14. The main groove 21 intersects with the first circumferential groove 25 at the corner P2 of the center block 30. The main groove 21 gradually becomes aligned in the tire width direction from the tire equator CL side toward the ground contact edge E, and the inclination with respect to the tire width direction becomes gentler. The width of the main groove 21 is larger on the ground contact edge E side than on the tire equator CL side, and is maximum at or near the intersection with the second circumferential groove 27.

[0033] As described above, a plurality of circumferential grooves extending in the tire circumferential direction are formed in the tread 10. Each circumferential groove is narrower than the main grooves 20, 21, intersects with the main groove 20 or the main groove 21, and defines a row of blocks aligned in the tire circumferential direction. The first circumferential grooves 25 dividing the row of center blocks 30, 40 are bent in opposite directions at the intersections with the main grooves 20, 21, i.e., at the corners P2, P4 of the center blocks 30, 40, and are formed in a zigzag shape extending in the tire circumferential direction while intersecting the tire equator CL.

[0034] The second circumferential grooves 26, 27 are formed in a straight line along the tire circumferential direction without bending at the intersections with the main grooves 20, 21. By forming the second circumferential grooves 26, 27 located closest to the ground contact edge E in a straight line, good drainage performance is obtained. The second circumferential groove 26 separates the row of shoulder blocks 50 from the row of mediate blocks 70, and the second circumferential groove 27 separates the row of shoulder blocks 60 from the row of mediate blocks 80. The second circumferential grooves 26, 27 are formed wider than the other circumferential grooves, and are formed to the same depth as the main grooves 20, 21 in the portions where the protuberances 90 described later do not exist.

[0035] A raised portion 90 having a lower height than each block is provided in the second circumferential grooves 26, 27. The raised portion 90 is raised toward the outside in the tire radial direction like each block, and is formed so as to connect the lower portions of two blocks between the shoulder block 50 and the mediate block 70, and between the shoulder block 60 and the mediate block 80. As will be described in detail later, the raised portion 90 increases the rigidity of the block, for example, and contributes to improving the dry performance.

[0036] The third circumferential groove 28 is formed to divide the center block 30 and the mediate block 70 and connect the two main grooves 20. Similarly, the third circumferential groove 29 is formed to divide the center block 40 and the mediate block 80 and connect the two main grooves 21. In addition, both of the third circumferential grooves 28, 29 are inclined with respect to the tire circumferential direction so as to gradually approach the tire equator CL from the front side to the rear side in the tire main rotation direction. The third circumferential grooves 28, 29 are short grooves that cross the block groups 100, 101, and are formed in a plurality of grooves in the tire circumferential direction. In addition, the third circumferential grooves 28, 29 are formed shallower than the main grooves 20, 21.

[0037] As described above, thin sipes are formed in each block. In this embodiment, one sipe is formed in each block, and each sipe extends in a direction along the main groove 20 or the main groove 21. The sipes are thin grooves narrower than the main grooves 20, 21 and the circumferential grooves, and enhance the edge effect of catching snow and ice, thereby achieving good braking / driving performance and steering stability on snowy and icy road surfaces. The width of the sipe is, for example, 30% or less, or 20% or less, of the width of the third circumferential grooves 28, 29 in a portion where there is no slope, which will be described later.

[0038] The sipes 31, 41 of the center blocks 30, 40 and the sipes 71, 81 of the mediate blocks 70, 80 are formed over the entire longitudinal length of the ground contact surface of each block. The sipes 51, 61 of the shoulder blocks 50, 60 are formed with a length extending from the end located on the inner side in the tire width direction of each block to a ground contact end E. In addition, a slope is formed on the side wall of each sipe, inclined at a predetermined angle θ (see FIG. 6 described later) with respect to the block ground contact surface. The slope is formed at a predetermined depth from the block ground contact surface along the longitudinal direction of the sipe. The predetermined depth is, for example, 30% or less of the sipe depth.

[0039] The slope 52 formed along the sipe 51 of the shoulder block 50 has the function of effectively dispersing the ground pressure of the block, increasing the frictional force against the road surface, and improving the grip while ensuring the rigidity of the shoulder block 50. The slope 52 also widens the width of the sipe 51 to improve drainage and expands the snow pockets into which snow is trapped. The slope 52 improves braking performance on snowy and icy roads and dry roads, and contributes to improving wet performance, snow performance, and dry performance. The slope 62 formed along the sipe 61 of the shoulder block 60 also exerts the same function as the slope 52.

[0040] The slope 32 formed along the sipe 31 of the center block 30 contributes to the dispersion of ground pressure like the slope 52, but in particular improves the block's ability to grip snow and enhances traction performance on snowy roads. The slope 32 also improves drainage. The slope 42 formed along the sipe 41 of the center block 40 and the slopes 72, 82 formed along the sipes 71, 81 of the mediate blocks 70, 80, for example, perform the same function as the slope 32.

[0041] The configuration of each block will be described in detail below with reference to Figs. 2 to 4, taking three blocks constituting the block group 100 as an example. Fig. 3 is a plan view that shows a schematic diagram of the tread 10, and Fig. 4 is an enlarged perspective view of the left side portion of the tread 10 in the width direction. Figs. 5 and 6 will also be referred to as appropriate below. Fig. 5 is a view that shows the block group 100 in isolation, and Fig. 6 is a cross-sectional view taken along line AA in Fig. 5.

[0042] [Center block] 2 to 4, the center blocks 30, 40 are island-shaped raised portions formed in the center of the tread 10 in the tire width direction. The center blocks 30, 40 have a generally rectangular shape in a plan view that is elongated in the direction in which the main grooves 20, 21 extend, and the longitudinal direction of each block is inclined with respect to the tire width direction. The center blocks 30, 40 are arranged to sandwich the tire equator CL from the left and right, with a portion of the left center block 30 extending to the right beyond the tire equator CL, and a portion of the right center block 40 extending to the left beyond the tire equator CL.

[0043] The center block 30 has side walls 30a, 30b formed along the main groove 20, a side wall 30c formed at one end of the block in the longitudinal direction, and a side wall 30d formed at the other end of the block in the longitudinal direction (see FIG. 3). Similarly, the center block 40 has side walls 40a, 40b formed along the main groove 21, a side wall 40c formed at one end of the block in the longitudinal direction, and a side wall 40d formed at the other end of the block in the longitudinal direction. The side walls 30a, 40a are located in front of each block in the main rotation direction of the tire, and the side walls 30b, 40b are located in rear of each block in the main rotation direction of the tire. In other words, the side walls 30a, 40a are located on the leading side of each block, and the side walls 30b, 40b are located on the trailing side of each block.

[0044] In this embodiment, the side walls 30b, 30c of the center block 30 and the side walls 40b, 40c of the center block 40 intersect with the tire equator CL. On the other hand, the side walls 30a, 40a of each block are not disposed on the tire equator CL and do not intersect with the tire equator CL. Note that each side wall of the center blocks 30, 40 is not entirely perpendicular to the block ground contact surface, and the lower part of the side wall, particularly the part close to the groove bottom, is curved so as to spread outward from the block (the same applies to the side walls of the other blocks). In the schematic diagram of FIG. 3, the entire side wall of each block is illustrated as being perpendicular to the block ground contact surface.

[0045] The center blocks 30, 40 are arranged such that the sidewalls 30b, 40c face each other across the first circumferential groove 25, and the sidewalls 30c, 40b face each other across the first circumferential groove 25. This arrangement results in a staggered pattern in which the center blocks 30, 40 are alternately arranged along the tire equator CL. In addition, corner P2 located at the boundary between the sidewalls 30b, 30c of the center block 30 is located on an extension of the sidewall 40a of the center block 40, and corner P4 located at the boundary between the sidewalls 40b, 40c is located on an extension of the sidewall 30a.

[0046] The side walls 30a, 30b of the center block 30 are gently curved and formed substantially parallel to each other. The side wall 30d is formed along the third circumferential groove 28, faces the side wall 70c of the mediate block 70 across the third circumferential groove 28, and is formed substantially linear in plan view. Similarly, the side walls 40a, 40b of the center block 40 are gently curved and formed substantially parallel to each other. The side wall 40d is formed along the third circumferential groove 29, faces the side wall of the mediate block 80 across the third circumferential groove 29, and is formed substantially linear in plan view.

[0047] 5, the side wall 30c of the center block 30 is formed with three faces (a first face 301c, a second face 302c, and a third face 303c) whose orientations are different from one another, and there is an intersection point P5 where these three faces intersect. The first face 301c faces the side wall 40b of the center block 40 across the first circumferential groove 25, and is formed from a corner P1 located at the boundary with the side wall 30a to the center part in the short side direction of the center block 30. The second face 302c is formed from the corner P2 to the center part in the short side direction of the center block 30, and is connected to the first face 301c.

[0048] The second surface 302c is formed so as to gradually move away from the sidewall 40b of the center block 40 toward the corner P2, so that the first circumferential groove 25 gradually widens from the tire equator CL side toward the intersection with the main groove 20 (see FIG. 3). The third surface 303c is a slope connecting the block ground contact surface with the first surface 301c and the second surface 302c, and is inclined at a predetermined angle with respect to the block ground contact surface, similar to the slope 32 of the sipe 31. The sidewall 40c of the center block 40 also has three surfaces with different surface orientations.

[0049] A single sipe 31 is formed in the center block 30 along the direction in which the main groove 20 extends. The sipe 31 is formed in the center of the short side so as to bisect the ground contact surface of the center block 30 over the entire length of the ground contact surface in the longitudinal direction. The sipe 31 is formed on the side wall 30d from the block ground contact surface to the groove bottom of the third circumferential groove 28 or deeper than the groove bottom, and the sipe end 31b opens into the third circumferential groove 28. On the other hand, the sipe 31 is not formed on the side wall 30c intersecting with the tire equator CL, and the sipe end 31a does not open into the first circumferential groove 25. In this case, the edge effect and drainage effect of the sipe 31 can improve the braking performance on snowy and icy road surfaces while ensuring good braking performance on dry road surfaces.

[0050] The ground contact area (A1) of the center block 30 is the smallest among the three blocks constituting the block group 100. In this specification, the ground contact area of ​​a block means the area of ​​the portion in contact with the road surface under the above conditions, and includes the area of ​​the portion where sipes are formed. The ground contact area (A1) of the center block 30 is, for example, 20% to 35%, and more preferably 25% to 33%, when the total ground contact area of ​​the three blocks constituting the block group 100 is taken as 100%. If the ratio of the ground contact area (A1) is within this range, it becomes easy to improve the handling performance during steady driving, such as straight driving at a speed of 100 km / h or less.

[0051] The side walls of the sipes 31 are formed with slopes 32 inclined at a predetermined angle θ (see FIG. 6) with respect to the ground contact surface of the center block 30. As described above, the slopes 32 improve the traction performance on snowy road surfaces and improve drainage while ensuring the rigidity of the center block 30. The inclination angle θ of the slopes 32 is, for example, 15° to 60° or 20° to 50°, and more preferably 20° to 35° or 25° to 35°. In this case, the function of the slopes 32 is more effectively exhibited. Also, for example, during sudden braking or acceleration, the slopes 32 come into contact with the road surface, suppressing the collapse of the blocks.

[0052] In this specification, the inclination angle θ of the slope 32 with respect to the ground contact surface of the center block 30 means the angle between the block ground contact surface (block top surface) and an imaginary plane α extending from the slope 32, as shown in Fig. 6. Alternatively, the inclination angle of the slope 32 can be said to be the angle between the imaginary plane β along the ground contact surface of the center block 30 and the slope 32. This definition of the inclination angle of the slope 32 is similarly applied to the slopes of the other blocks.

[0053] The slope 32 may be formed on both the first side wall located on the front side in the tire main rotation direction and the second side wall located on the rear side in the tire main rotation direction among the side walls of the sipe 31, but is preferably formed larger on the second side wall than on the first side wall. In this embodiment, the slope 32 is formed only on the second side wall of the sipe 31 located on the rear side in the tire main rotation direction. By forming the slope 32 only on one side wall, it is possible to more highly achieve both the effect of the slope 32 and the suppression of the decrease in rigidity of the block. In addition, when the slope 32 is formed on the second side wall, the slope 32 comes into contact with the road surface during sudden braking and sudden acceleration, and it is easier to suppress the collapse of the block compared to when the slope 32 is formed on the first side wall.

[0054] In addition, the second side wall of the sipe 31 on which the slope 32 is formed is, in other words, the side wall located on the kick-out side of the side walls of the sipe 31. Alternatively, if the portion located on the front side in the main rotational direction of the tire of the center block 30 partitioned by the sipe 31 is defined as a first portion, and the portion located on the rear side in the main rotational direction of the tire is defined as a second portion, it can be said that the slope 32 is formed on the leading-in end of the second portion.

[0055] The slope 32 includes two regions (first region 32a and second region 32b) that are different from each other in planar shape (see FIG. 4). The first region 32a is a surface that is generally rectangular in planar shape that is generally parallel to the longitudinal direction of the sipe 31, and is formed with a length of 40% to 60% of the overall length of the slope 32. In contrast, the second region 32b is a surface that is generally triangular in planar shape that is inclined toward the sipe end 31b side more than the first region 32a, and the area becomes smaller toward the sipe end 31a side. By providing the second region 32b, the step formed at the end of the slope 32 can be made gentle, and stress concentration at the end of the slope 32 can be suppressed.

[0056] As shown in FIG. 6, the slope 32 is formed from the block ground surface to the middle part of the sipe 31 in the depth direction. The slope 32 is preferably formed only in the vicinity of the block ground surface. Hereinafter, the opening of the sipe in the block ground surface (block upper surface) may be referred to as the "upper opening". The sipe 31 is widened at the upper opening and its vicinity by the formation of the slope 32, but the width of the sipe 31 is not widened in the area away from the upper opening. That is, even in the part where the slope 32 of the sipe 31 is formed, the area away from the upper opening is formed with the same width as the part where the slope 32 is not present. Note that, although a 2D sipe is illustrated in FIG. 6, the sipe may be a 3D sipe.

[0057] The depth D2 of the slope 32 is, for example, 10% to 30% of the depth D1 of the sipe 31 in the first region 32a, more preferably 10% to 25% or 10% to 20%. Here, the depth of the sipe and the slope means the length from the block ground contact surface along the height direction of the block (tire radial direction). If the depth D2 is within this range, for example, the function of the slope 32 can be more effectively exhibited while ensuring the block rigidity. An example of the depth D2 of the slope 32 is 0.8 mm to 1.2 mm. In this embodiment, the depth D1 of the sipe 31 is substantially the same as the depth of the third circumferential groove 28 or is deeper than the depth of the third circumferential groove 28. The depth D1 of the sipe 31 is preferably shallower than the depth of the main groove 20.

[0058] The slope 32 is formed within a predetermined length range from the sipe end 31b located on the mediate block 70 side. The predetermined length is preferably a length that does not reach the sipe end 31a on the tire equator CL side, and the slope 32 is not formed in the vicinity of the sipe end 31a. As will be described in detail later, the slope 32 is formed with a length (length along the sipe 31) that is, for example, 30% to 50% of the longitudinal length of the contact surface of the center block 30. By controlling the length of the slope 32 within an appropriate range and precisely controlling the relationship with the length of the slopes of the other blocks, the wet performance, snow performance, and dry performance of the pneumatic tire 1 are more effectively improved.

[0059] As described above, the slope 32 widens the sipe 31 at the upper opening of the sipe 31 and its vicinity. The width W2 of the slope 32 is, for example, 1.3 to 3.5 times, more preferably 1.5 to 3 times, or 2 to 3 times, of the width W1 of the sipe 31 in the first region 32a where the slope 32 is not present (see FIG. 6). Here, the width of the slope means the length in a direction perpendicular to the direction in which the sipe extends in a plan view. If the width W2 is within this range, for example, the function of the slope 32 can be more effectively exhibited while ensuring block rigidity. An example of the width W2 is 1.5 mm to 2.5 mm. The width W1 of the sipe 31 is, for example, 5% to 35% of the width of the third circumferential groove 28.

[0060] Similarly, in the center block 40, one sipe 41 is formed along the extension direction of the main groove 21. The sipe 41 is formed over the entire longitudinal length of the block ground contact surface so as to bisect the block ground contact surface. The sipe 41 is formed on the side wall 40d from the block ground contact surface to the groove bottom of the third circumferential groove 29 or deeper than the groove bottom, and the sipe end 41b opens into the third circumferential groove 29. On the other hand, no sipe 41 is formed on the side wall 40c, and the sipe end 41a does not open into the first circumferential groove 25.

[0061] The sidewall of the sipe 41 has a slope 42 inclined at a predetermined angle with respect to the ground contact surface of the center block 40 within a predetermined length range from the sipe end 41b. The slope angle of the slope 42 is, for example, 25° to 35°, which is the same as the slope angle θ of the slope 32. The slope 42 is formed only on the second sidewall of the sidewall of the sipe 41, which is located on the rear side in the main rotational direction of the tire. In this embodiment, the shape of the center block 40 is the same as the shape of the center block 30 when it is inverted with respect to the tire equatorial plane, and if the inverted center block 30 is slid in the tire circumferential direction, it will match the center block 40.

[0062] [Shoulder block] 2 to 4, the shoulder blocks 50, 60 are island-shaped raised portions provided on both sides of the tread 10 in the tire width direction, with portions extending beyond the ground contact edge E toward the outside in the tire width direction and the inside in the tire radial direction, and the block top surfaces are greatly curved. Like the center blocks 30, 40, the shoulder blocks 50, 60 have a generally rectangular shape in a plan view that is elongated in the direction in which the main grooves 20, 21 extend, and the longitudinal direction of each block is inclined with respect to the tire width direction. On the other hand, the inclination angle of the shoulder blocks 50, 60 with respect to the tire width direction is gentler than that of the center blocks 30, 40.

[0063] The shoulder block 50 is a block larger than the center block 30 and the mediate block 70, and the length along the tire width direction is the longest among these three blocks. On the other hand, the ground contact area (A2) of the shoulder block 50 is less than or equal to the ground contact area (A3) of the mediate block 70. The ground contact area (A2) is, for example, 30% - 45%, more preferably 33% - 38%, when the total ground contact area of the three blocks constituting the block group 100 is taken as 100%. If the ratio of the ground contact area (A2) is within this range, it becomes easier to improve the handling performance during steady driving.

[0064] The ground contact area (A2) of the shoulder block 50 is larger than the ground contact area (A1) of the center block 30, and it is preferable that the ground contact area of each block satisfies the condition of A1 < A2 ≤ A3. Although it will be described in detail later, when the total of the ground contact areas (A1, A3) is 1.8 to 1.9 times the ground contact area (A2), the braking performance and the handling performance during steady driving can be more highly balanced. Also, the ratio of the length of the main groove 20 along the tire circumferential direction to the ground contact length of the shoulder block 50 is, for example, 3:7 - 4:6. The pneumatic tire 1 has a wider main groove 20 and a smaller ground contact area of the shoulder block 50 compared to a general summer tire, but high braking performance can be obtained due to the dispersion effect of the ground pressure by the slope 52.

[0065] Similarly, for the shoulder block 60, it is formed as the largest among the three blocks constituting the block group 101, but the ground contact area of the shoulder block 60 is less than or equal to the ground contact area of the mediate block 80. In this embodiment, the shape of the shoulder block 60 is the same as the shape when the shoulder block 50 is inverted with respect to the tire equatorial plane, and if the inverted shoulder block 50 is slid in the tire circumferential direction, it will coincide with the shoulder block 60.

[0066] The shoulder block 50 has sidewalls 50a, 50b formed along the main groove 20, and a sidewall 50c formed at one end of the block in the longitudinal direction (see FIGS. 3 and 4). A part of the shoulder block 50 protrudes outward in the tire width direction beyond the ground contact edge E to form a shoulder portion 11. The other end of the shoulder block 50 in the longitudinal direction opposite to the sidewall 50c is connected to a side rib 14. The sidewall 50a is located in front of the shoulder block 50 in the main tire rotation direction, and the sidewall 50b is located in the rear of the shoulder block 50 in the main tire rotation direction.

[0067] The side walls 50a, 50b are gently curved and formed substantially parallel to each other. In this embodiment, the curvature of the side walls 50a, 50b is large near the side wall 50c, and the side walls 50a, 50b have small bent portions. The side wall 50c is formed substantially linearly in a plan view, faces the side wall 70d of the mediate block 70 across the second circumferential groove 26, and is connected to the side wall 70d via a raised portion 90 formed in the groove of the second circumferential groove 26. The raised portion 90 will be described in detail later.

[0068] A single sipe 51 is formed in the shoulder block 50 along the extension direction of the main groove 20. The sipe 51 is formed in the center of the shoulder block 50 in the short side direction, from the sidewall 50c, which is the end located on the inner side in the tire width direction, along the longitudinal direction of the block, with a length exceeding the ground contact end E. The sipe 51 is formed in the sidewall 50c, for example, from the block ground contact surface to the upper surface of the raised portion 90, or is formed deeper than the upper surface of the raised portion 90 and shallower than the main groove 20. When the depth of the sipe 51 satisfies such conditions, it becomes easy to enhance the edge effect while ensuring the rigidity of the block.

[0069] The sipes 51 open to the second circumferential groove 26 and are disposed opposite to the sipe ends 71b of the sipes 71 of the mediate blocks 70 in the tire width direction across the second circumferential groove 26. In other words, the sipe ends 51a on the inner side in the tire width direction overlap with the sipe ends 71b in the tire width direction in a plan view of the tread 10. The sipes 51 are formed with a length that exceeds the ground contact end E, and the sipe ends 51b on the outer side in the tire width direction are located between the ground contact end E and the side rib 14. The height of the shoulder blocks 50 gradually decreases toward the outer side in the tire width direction, and the depth of the sipes 51 gradually decreases toward the sipe ends 51b.

[0070] The side wall of the sipe 51 is formed with a slope 52 inclined at a predetermined angle with respect to the ground contact surface of the shoulder block 50. As described above, the slope 52 ensures the rigidity of the shoulder block 50 while dispersing the ground contact pressure of the block to improve the frictional force with the road surface. Therefore, the slope 52 greatly contributes to improving the braking performance. The slope angle of the slope 52 is, for example, 15° to 60°, or 20° to 50°, more preferably 20° to 35°, or 25° to 35°, and may be substantially the same as the slope angle θ of the slope 32. In this case, the function of the slope 52 is more effectively exhibited.

[0071] The slope 52 may be formed on both the first side wall located on the front side in the tire main rotation direction and the second side wall located on the rear side in the tire main rotation direction among the side walls of the sipe 51, but is preferably formed larger on the second side wall than on the first side wall. In this embodiment, the slope 52 is formed only on the second side wall of the sipe 51 located on the rear side in the tire main rotation direction. By forming the slope 52 only on the second side wall, it is possible to more highly achieve both the effect of the slope 52 and the suppression of the decrease in rigidity of the block. In addition, for example, during sudden braking or sudden acceleration, the slope 52 comes into contact with the road surface, making it easier to suppress the collapse of the block.

[0072] The slope 52 is formed from the ground contact surface of the shoulder block 50 to a predetermined depth of the sipe 51. The slope 52 is preferably formed at the upper opening of the sipe 51 and in its vicinity. The depth of the slope 52, on the inner side in the tire width direction from the ground contact edge E, is, for example, 5% to 30% of the depth of the sipe 51, more preferably 5% to 25%, or 10% to 20%. If the depth of the slope 52 is within this range, the block rigidity can be ensured while the ground contact pressure can be effectively dispersed. An example of the depth of the slope 52 is 0.8 mm to 1.2 mm.

[0073] The inclined surface 52 may be formed to a depth equal to or greater than the inclined surface 32 of the center block 30, but in this embodiment, it is formed to be shallower than the inclined surface 32. The depth of the inclined surface 52 is, for example, 60% to 90% or 65% to 85% of the depth of the inclined surface 32. If the inclined surface 52 is formed long, the ground pressure dispersion effect of the shoulder block 50 increases, but the rigidity of the block is likely to decrease. Therefore, in this embodiment, a configuration in which the somewhat shallow inclined surface 52 is formed long is adopted, thereby achieving both ensuring block rigidity and dispersing the ground pressure to a higher degree.

[0074] The slope 52 is formed from the sipe end 51a that opens into the second circumferential groove 26 to a position beyond the ground contact end E. By forming the slope 52 over the entire length of the ground contact surface of the shoulder block 50, the effect of improving the braking performance by dispersing the ground pressure can be enhanced. In addition, by locating the end of the slope 52 outside the ground contact end E, the concentration of stress on the end of the slope 52 can be suppressed, and the durability of the block is improved. Note that, since the end of the slope 52 does not exist in the ground contact surface that is restrained by the road surface, a larger step is formed at the end of the slope 52 than in the case of the slope 32.

[0075] As described above, the slope 52 is formed in a portion adjacent to the second circumferential groove 26. The slope 52 is also formed in a position facing the slope 72 of the mediate block 70 in the tire width direction across the second circumferential groove 26. In other words, the slopes 52, 72 overlap in the tire width direction in a plan view of the tread 10. In this case, water can be efficiently drained from the sipes 51, 71 to the second circumferential groove 26, and the water film between the tire and the road surface can be effectively removed. In addition, the snow pocket that traps the snow can be efficiently enlarged, improving the snow column shear force.

[0076] The slope 52 is formed with a length that does not reach the sipe end 51b. By positioning the end of the slope 52 between the ground contact end E and the sipe end 51b, it is possible to suppress a decrease in the rigidity of the shoulder block 50 and improve the durability of the block. It is preferable that the end of the slope 52 is located near the ground contact end E in the shoulder portion 11. In addition, the rigidity of the shoulder block 50 can also be adjusted by the position of the sipe end 51b in the shoulder portion 11. For example, if the rigidity of the shoulder block 50 is too high relative to the other blocks, the sipe 51 can be extended to adjust the rigidity balance of each block.

[0077] The slope 52 is formed to have a length (length along the sipes 51) that is, for example, 30% to 60% of the longitudinal length of the block top surface. As will be described in detail later, the ratio of the length of the slope to the length of the block is greatest in the shoulder block 50 among the three blocks that make up the block group 100. Also, the length of the slope 52 along the sipes 51 is longer than the lengths of the slopes of the other two blocks along the sipes. The slope 52 of the shoulder block 50 is preferably formed long on the block ground contact surface because it contributes greatly to improving braking performance by dispersing ground pressure.

[0078] The width of the slope 52 is, for example, 1.3 to 3.5 times, more preferably 1.5 to 3 times, or 1.5 to 2.5 times, the width of the sipe 51 in the portion where the slope 52 does not exist. If the width of the slope 52 is within this range, for example, the block rigidity can be ensured while effectively dispersing the ground pressure. The slope 52 may be formed to have a width equal to or greater than that of the slope 32 of the center block 30, but in this embodiment, it is formed to be narrower than the slope 32. The width of the slope 52 is, for example, 60% to 90% or 65% to 85% of the width of the slope 32. As described above, it is preferable to form the slope 52 long on the block ground contact surface, so the depth and width of the slope 52 are made slightly smaller to more highly achieve both the block rigidity and the effect of dispersing the ground pressure.

[0079] Similarly, in the shoulder block 60, one sipe 61 is formed along the extension direction of the main groove 21. The sipe 61 is formed with a length from a sipe end 61a opening into the second circumferential groove 27, past the ground contact end E, but not reaching the side rib 14. The sipe end 61b on the outer side in the tire width direction is located between the ground contact end E and the side rib 14. The sipe end 61a is disposed opposite to the sipe end 81b of the sipe 81 of the mediate block 80 in the tire width direction, with the second circumferential groove 27 in between.

[0080] Of the side walls of the sipe 61, a second side wall located on the rear side in the main rotational direction of the tire has a slope 62 formed from a sipe end 61a opening into the second circumferential groove 27 to a position beyond the ground contact end E. The inclination angle of the slope 62 with respect to the ground contact surface of the shoulder block 60 is, for example, 25° to 35°, which is the same as the inclination angle of the slope 52. The slope 62 is formed at a position facing the slope 82 of the intermediate block 80 in the tire width direction in a plan view of the tread 10.

[0081] [Mediate Block] As shown in Figures 2 to 4, the mediate block 70 is an island-shaped raised portion provided between the center block 30 and the shoulder block 50. Similarly, the mediate block 80 is an island-shaped raised portion provided between the center block 40 and the shoulder block 60. Like the center blocks 30, 40 and the shoulder blocks 50, 60, the mediate blocks 70, 80 have a generally rectangular shape in a plan view that is elongated in the direction in which the main grooves 20, 21 extend, and the longitudinal direction of each block is inclined with respect to the tire width direction. The inclination angle of the mediate blocks 70, 80 with respect to the tire width direction is the same as or slightly gentler than the inclination angle of the center blocks 30, 40.

[0082] The mediate block 70 is larger than the center block 30 and smaller than the shoulder block 50. On the other hand, the ground contact area (A3) of the mediate block 70 is the largest among the ground contact areas of the three blocks constituting the block group 100, as described above. In addition, the ground contact area (A3) of the mediate block 70 is, for example, 33% to 45%, and more preferably 35% to 40%, when the total ground contact area of ​​the three blocks is taken as 100%. If the ratio of the ground contact area (A3) is within this range, it becomes easy to improve the handling performance during steady running.

[0083] Similarly, the contact area of ​​the mediate block 80 is the largest among the contact areas of the three blocks constituting the block group 101. In this embodiment, the shape of the mediate block 80 is the same as the shape of the mediate block 70 when it is inverted with respect to the tire equatorial plane, and if the inverted mediate block 70 is slid in the tire circumferential direction, it will match the mediate block 70.

[0084] The mediate block 70 has side walls 70a, 70b formed along the main groove 20, a side wall 70c formed along the third circumferential groove 28, and a side wall 70d formed along the second circumferential groove 26 (see Figs. 3 and 4). The side walls 70a, 70b are gently curved and extend substantially parallel to each other, and the side wall 70b is formed longer than the side wall 70a. The side wall 70a is located in front of the mediate block 70 in the main tire rotation direction, and the side wall 70b is located in the rear of the mediate block 70 in the main tire rotation direction.

[0085] The sidewall 70c is formed in a substantially linear shape in a plan view and faces the sidewall 30d of the center block 30 across the third circumferential groove 28. The sidewall 70d is formed in a substantially linear shape in a plan view and faces the sidewall 50c of the shoulder block 50 across the second circumferential groove 26. The sidewall 70d is formed along the tire circumferential direction, but the sidewall 70c is inclined so as to gradually approach the tire equator CL toward the rear in the tire main rotation direction. Therefore, the sidewalls 70c, 70d are not parallel to each other, and the sidewall 70b is longer than the sidewall 70a.

[0086] A single sipe 71 is formed in the mediate block 70 along the extension direction of the main groove 20. The sipe 71 is formed in the center of the short side so as to divide the mediate block 70 in half, over the entire length of the block in the longitudinal direction. The sipe end 71a on the inner side in the tire width direction opens into the third circumferential groove 28 and is disposed opposite the sipe end 31b of the center block 30 in the tire width direction, with the third circumferential groove 28 in between. The sipe end 71b on the outer side in the tire width direction opens into the second circumferential groove 26 and is disposed opposite the sipe end 51a of the shoulder block 50, with the second circumferential groove 26 in between.

[0087] In this embodiment, the sipes 71 are formed at the same depth over the entire longitudinal length of the mediate block 70. In the side wall 70c, the sipes 71 are formed at the same depth as the third circumferential groove 28, or are formed deeper than the third circumferential groove 28 and shallower than the main groove 20. In the side wall 70d, the sipes 71 are formed from the block ground contact surface to the upper surface of the raised portion 90 formed in the groove of the second circumferential groove 26, or are formed deeper than the upper surface of the raised portion 90 and shallower than the main groove 20. When the depth of the sipes 71 satisfies such conditions, it becomes easy to enhance the edge effect while ensuring the rigidity of the block.

[0088] The side wall of the sipe 71 is formed with a slope 72 inclined at a predetermined angle with respect to the ground contact surface of the mediate block 70. As described above, the slope 72 has the same function as the slopes 32 and 52, and while ensuring the rigidity of the block, it distributes ground pressure, improves drainage, and expands snow pockets. The slope angle of the slope 72 is, for example, 15° to 60°, or 20° to 50°, and more preferably 20° to 35°, or 25° to 35°. In this case, the function of the slope 72 is more effectively exerted. The slope angle of the slope 72 may be substantially the same as the slope angles of the slopes 32 and 52.

[0089] The slope 72 may be formed on both the first side wall located on the front side in the tire main rotation direction and the second side wall located on the rear side in the tire main rotation direction among the side walls of the sipe 71, but is preferably formed larger on the second side wall than on the first side wall. In this embodiment, the slope 72 is formed only on the second side wall of the sipe 71 located on the rear side in the tire main rotation direction. In each of the three blocks constituting the block group 100, the slope along the sipe is formed only on the second side wall. In this case, the effect of the slope and the suppression of the decrease in rigidity of the block can be more highly achieved, and the slope comes into contact with the road surface during sudden braking and sudden acceleration, making it easier to suppress the collapse of the block.

[0090] The inclined surface 72 includes two regions (first region 72a and second region 72b) having different shapes in plan view, similar to the inclined surface 32 (see FIG. 4). The first region 72a is a surface having a substantially rectangular shape in plan view that is substantially parallel to the longitudinal direction of the sipe 71, and is formed with a length exceeding 50% of the total length of the inclined surface 72, preferably 70% to 90%. In contrast, the second region 72b is a surface having a substantially triangular shape in plan view that is inclined toward the sipe end 71b side more than the first region 72a, and the area becomes smaller toward the sipe end 71a side. By providing the second region 72b, the step formed at the end of the inclined surface 72 can be made gentle, and stress concentration at the end of the inclined surface 72 can be suppressed.

[0091] The inclined surface 72 is formed from the ground contact surface of the mediate block 70 to a predetermined depth of the sipe 71. The inclined surface 72 is preferably formed at the upper opening of the sipe 71 and its vicinity. The depth of the inclined surface 72 in the first region 72a is, for example, 10% to 30% of the depth of the sipe 71, and more preferably 10% to 25%, or 10% to 20%. If the depth of the inclined surface 72 is within this range, the function of the inclined surface 72 can be more effectively exerted while ensuring block rigidity. The depth of the inclined surface 72 is, for example, substantially the same as the depth of the inclined surface 32 of the center block 30.

[0092] The slope 72 is formed within a predetermined length range from the sipe end 71b located on the shoulder block 50 side. The predetermined length is preferably a length that does not reach the sipe end 71a on the third circumferential groove 28 side, and the slope 72 is not formed in the vicinity of the sipe end 71a. The slope 72 is formed with a length (length along the sipe 71) that is, for example, 20% to 40% of the longitudinal length of the block upper surface. As will be described in detail later, the length of the slope along the sipe and the ratio of the slope length to the block length are smallest in the mediate block 70 among the three blocks constituting the block group 100.

[0093] The width of the slope 72 is, for example, 1.3 to 3.5 times, and more preferably 1.5 to 3 times, or 2 to 3 times, the width of the sipe 71 in the portion where the slope 72 is not present. If the width of the slope 72 is within this range, the function of the slope 72 can be more effectively exhibited while ensuring block rigidity. The width of the slope 72 is, for example, substantially the same as the width of the slope 32 of the center block 30. The sipe 71 may be formed to have the same width as the sipes 31, 51, or may be formed to be wider than the sipes 31, 51.

[0094] Similarly, in the mediate block 80, one sipe 81 is formed along the extension direction of the main groove 21. The sipe 81 is formed over the entire length of the mediate block 80 in the longitudinal direction so as to divide the block 80 in half. The sipe end 81a on the inner side in the tire width direction opens into the third circumferential groove 29 and is disposed opposite the sipe end 41b of the center block 40 in the tire width direction with the third circumferential groove 29 in between. The sipe end 81b on the outer side in the tire width direction opens into the second circumferential groove 27 and is disposed opposite the sipe end 61a of the shoulder block 60 with the second circumferential groove 27 in between.

[0095] Of the side walls of the sipe 81, a second side wall located on the rear side in the main rotational direction of the tire has a slope 82 formed within a predetermined length range from a sipe end 81b. The inclination angle of the slope 82 with respect to the ground contact surface of the mediate block 80 is, for example, 25° to 35°, which is the same as the inclination angle of the slope 72. The slope 82 is formed at a position facing the slope 62 of the shoulder block 60 in the tire width direction in a plan view of the tread 10.

[0096] The block groups 100 and 101 will be further described below with reference to FIGS.

[0097] As described above, the block group 100 has three blocks arranged in a row along the direction in which the main groove 20 extends, and has a gently curved shape in plan view as a whole. Like the main groove 20, the block group 100 is inclined with respect to the tire width direction so as to be gradually positioned rearward in the tire main rotation direction from the center in the tire width direction toward the outer side in the tire width direction. That is, in the three blocks constituting one block group 100, the center block 30 is disposed forward of the shoulder block 50 in the tire main rotation direction.

[0098] The block group 100 is formed with a raised portion 90 that connects the lower portions of the shoulder block 50 and the mediate block 70. By providing the raised portion 90, the rigidity of the two connected blocks can be increased, improving the dry performance. The raised portion 90 is formed only within the range between the shoulder block 50 and the mediate block 70 in the groove of the second circumferential groove 26, and is aligned in the tire width direction with the sipe ends 51a, 71b in a plan view of the tread 10. That is, the sipe ends 51a, 71b are formed in positions adjacent to the raised portion 90.

[0099] The block group 100 has a third circumferential groove 28 that divides the center block 30 and the mediate block 70, but the depth of the third circumferential groove 28 is shallower than that of the main groove 20. Therefore, it can be said that the lower parts of the center block 30 and the mediate block 70 are connected to each other by a portion that protrudes from the bottom of the main groove 20. In other words, in the block group 100, the lower parts of adjacent blocks are connected to each other via a low protruding portion. In this case, the rigidity of the block group 100 is improved, and the dry performance is improved.

[0100] The height of the upper surface of the raised portion 90 and the height of the groove bottom of the third circumferential groove 28 are, for example, approximately the same. Here, the height of the upper surface of the raised portion 90 means the length along the tire radial direction from the groove bottom to the upper surface of the main groove 20 (the same applies to the height of the groove bottom of the third circumferential groove 28). The height of the raised portion 90 is, for example, 10% to 50% or 20% to 40% of the depth of the second circumferential groove 26. When the height of the raised portion 90 is within this range, the rigidity of the block can be effectively improved without impairing the drainage performance. Note that the second circumferential groove 26 is formed to the same depth as the main groove 20 in the portion where the raised portion 90 is not present.

[0101] The block groups 100, 101 are arranged such that the sidewall 30b of the center block 30 faces the sidewall 40c of the center block 40 across the first circumferential groove 25, and the sidewall 30c faces the sidewall 40b across the first circumferential groove 25, forming a staggered pattern in which the block groups 100, 101 are alternately arranged along the tire equator CL. At least a portion of the first circumferential groove 25 is formed shallower than the main groove 20, similar to the third circumferential groove 28. For this reason, it can be said that the lower parts of the center blocks 30, 40 are connected to each other by a portion protruding from the bottom of the main groove 20.

[0102] In the block groups 100, 101, the lower parts of adjacent blocks are connected via raised portions and are formed across the left and right side ribs 14. Also, since the center block 30 is connected to two center blocks 40 adjacent in the tire circumferential direction, the lower parts of the center blocks 30, 40 are connected in the tire circumferential direction. Therefore, in the pneumatic tire 1, the center blocks 30, 40 in the center in the tire width direction and the side ribs 14 on both sides in the tire width direction function like a frame, ensuring high rigidity overall.

[0103] The contact area of ​​each block and the length of the slope formed on the sipe sidewall of each block will be further described below with reference to Fig. 7. Fig. 7 is a plan view showing a part of the tread 10, illustrating the length of each block and each slope along the tire width direction.

[0104] As shown in FIG. 7, among the three blocks constituting the block group 100, the shoulder block 50 is the largest (in terms of volume), but in terms of the contact area with the ground, the contact area (A3) of the mediate block 70 is equal to or larger than the contact area (A2) of the shoulder block 50. In this specification, the contact area of a block means the area of the portion in contact with the road surface under the above conditions, and also includes the area of the portion where the sipes are formed. In the case of the mediate block 70, the area of the entire upper surface of the block is the contact area (A3). On the other hand, in the case of the shoulder block 50, the area of the region on the upper surface of the block that is located inside the tire width direction from the grounding end E is the contact area (A2).

[0105] By making the contact area (A3) of the mediate block 70 equal to or larger than the contact area (A2) of the shoulder block 50, the handling performance during steady driving is improved. The contact area (A3) is preferably, for example, larger than the contact area (A2) and not more than 1.3 times, or not more than 1.2 times the contact area (A2). The contact area (A1) of the center block 30 is preferably smaller than the contact area (A2). The contact area (A1) is, for example, 60% - 90%, or 70% - 90% of the contact area (A2).

[0106] That is, the contact areas of the three blocks constituting the block group 100 satisfy the condition of A1 < A2 ≤ A3, and more preferably A1 < A2 < A3. In this case, it becomes easy to achieve both good braking performance and handling performance during steady driving. In this embodiment, each block constituting the block group 101 also satisfies the same condition for the contact area as in the case of the block group 100.

[0107] The total of the contact areas (A1, A3) of the center block 30 and the intermediate block 70 is preferably 1.7 to 2.0 times, more preferably 1.8 to 1.9 times, the contact area (A2) of the shoulder block 50. When this condition (A2×(1.8~1.9)=A1+A3) is satisfied, the braking performance and the handling performance during steady driving can be achieved at a higher level. When the total of the contact areas (A1, A3) is less than 1.8 times the contact area (A2), the handling performance during steady driving tends to decrease compared with the case where the above condition is satisfied. On the other hand, when the total of the contact areas (A1, A3) exceeds 1.9 times the contact area (A2), the braking performance tends to decrease compared with the case where the above condition is satisfied.

[0108] When the total of the contact areas of the three blocks constituting the block group 100 is taken as 100%, an example of the suitable contact area of each block is as follows. Contact area (A1): 25% - 32%, or 27% - 32% Contact area (A2): 33% - 38%, or 33% - 36% Contact area (A3): 35% - 40%, or 35% - 38% If the conditions of A1 < A2 ≤ A3, preferably A1 < A2 < A3, are satisfied and the ratio of the contact areas (A1~A3) is within the above range, the braking performance and the handling performance during steady driving can be achieved at a higher level.

[0109] Regarding the length of each slope, the length L along the slope 31 of the slope 32 with respect to the longitudinal length L of the upper surface of the center block 30 30 of the ratio (L 32 / L 32 ), the length L along the slope 51 of the slope 52 with respect to the longitudinal length L of the upper surface of the shoulder block 50 30 of the ratio (L 50 / L 52 ), and the length L along the slope 71 of the slope 72 with respect to the longitudinal length L of the upper surface of the intermediate block 70 52 of the ratio (L 50 ) and the length L along the slope 71 of the slope 72 with respect to the longitudinal length L of the upper surface of the intermediate block 70 70 of the ratio (L 72 / L 72 / L 70When [[ID=]] is set as L1, L2, and L3 respectively, the ratio (L2) is preferably larger than the ratio (L1) and the ratio (L3). That is, among the three blocks constituting the block group 100, the ratio (L2) of the shoulder block 50 is the largest.

[0110] In this embodiment, the ratio (L1) of the center block 30 is the second largest, and the ratio (L3) of the mediate block 70 is the smallest. That is, the pneumatic tire 1 satisfies the condition of L3 < L1 < L2. In this case, the braking performance is improved in various road surface conditions such as wet road surfaces, snow road surfaces, and dry road surfaces, and the wet performance, snow performance, and dry performance are effectively improved. On the other hand, regarding the width and depth of the inclined surface, the inclined surface 52 of the shoulder block 50 is the smallest compared to the inclined surface 32 of the center block 30 and the inclined surface 72 of the mediate block 70.

[0111] Here, the longitudinal length of the block upper surface means the longitudinal length of the block along the block upper surface. In this embodiment, it is the length along the block upper surface from the inner end in the tire width direction to the outer end in the tire width direction of the block upper surface. In FIG. 7, for the sake of clarity of the drawing, the longitudinal length of the block upper surface is illustrated by an arrow along the tire width direction. However, since the block is inclined with respect to the tire width direction and the upper surface of the shoulder block 50 is particularly curved, the length L 50 in the shoulder block 50 is longer than the illustrated length. Similarly, regarding the length along the sipe of the inclined surface, it is shown in FIG. 7. However, since the sipe is inclined with respect to the tire width direction, it is longer than the illustrated length.

[0112] The ratio of the length of the inclined surface 32 to the length of the sipe 31 of the center block 30 is substantially the same as the above ratio (L1). Also, the ratio of the length of the inclined surface 72 to the length of the sipe 71 of the mediate block 70 is substantially the same as the above ratio (L3). On the other hand, the ratio of the length of the inclined surface 52 to the length of the sipe 51 of the shoulder block 50 is 32 substantially the same as the above ratio (L2). 72 The ratio of the length of the inclined surface 72 to the length of the sipe 71 of the mediate block 70 is substantially the same as the above ratio (L3). On the other hand, the ratio of the length of the inclined surface 52 to the length of the sipe 51 of the shoulder block 50 is 52The ratio is larger than the above ratio (L2) because the sip 51 is not formed over the entire longitudinal length of the upper surface of the block, and the slope 52 is formed from the sip end 51a of the sip 51 to the vicinity of the sip end 51b.

[0113] An example of a suitable ratio of the length along the slope of the sip to the longitudinal length of the upper surface of the block along the upper surface of each block constituting the block group 100 is as follows. Ratio (L1): 30% - 50%, or 35% - 45% Ratio (L2): 30% - 60%, or 45% - 55% Ratio (L3): 20% - 40%, or 25% - 30% If the condition of L3 < L1 < L2 is satisfied and the ratios (L1 - L3) are within the above ranges, the wet performance, snow performance, and dry performance can be more effectively improved.

[0114] The length L of the slope 52 52 is preferably longer than the length L of the slope 32 32 and the length L of the slope 72. 72 Also, the length L of the slope 32 32 is preferably longer than the length L of the slope 72. 72 That is, the pneumatic tire 1 satisfies the condition of L 72 < L 32 < L 52 < L. The length L of the slope 52 52 is, for example, 2 to 4 times, or 2.5 to 3.5 times the length L of the slope 32 (the same applies to the length of the slope 52 on the ground contact surface of the block). As described above, the sip 51 and the slope 52 are formed over the entire length of the ground contact surface of the shoulder block 50.

[0115] ​​As described above, in the pneumatic tire 1 having the above configuration, the slope 52 formed on the sipe sidewall of the shoulder block 50 and the slope 72 formed on the sipe sidewall of the mediate block 70 are formed adjacent to the second circumferential groove 26 and are arranged opposite to each other in the tire width direction with the second circumferential groove 26 in between. Similarly, the slope 62 of the shoulder block 60 and the slope 82 of the mediate block 80 are formed adjacent to the second circumferential groove 27 and are arranged opposite to each other in the tire width direction with the second circumferential groove 27 in between. In this case, water can be efficiently drained from each sipe to the circumferential groove, and the water film between the tread 10 and the road surface can be effectively removed, so that the drainage performance is greatly improved. In addition, snow pockets can be efficiently enlarged.

[0116] The slopes 52, 62 of the shoulder blocks 50, 60 further ensure the rigidity of the blocks while effectively dispersing the ground pressure of the blocks. This effect of dispersing ground pressure has been proven by the present inventor. If the ground pressure can be distributed over a wide area of ​​the block contact surface, the frictional force against the road surface increases and braking performance improves. The pneumatic tire 1 has wide main grooves 20, 21 and good drainage and snow removal performance, but the contact area (A2) of the shoulder blocks 50, 60 is accordingly small. However, high braking performance can be obtained due to the effect of dispersing ground pressure by the slopes 52, 62.

[0117] Furthermore, by forming the slopes 32, 42 on the sipe side walls of the center blocks 30, 40, the sipe width can be increased to improve drainage and enlarge the snow pockets into which snow is caught while ensuring the rigidity of the blocks. The center blocks 30, 40 can firmly grip snow at the portions where the slopes 32, 42 are formed, improving traction on snowy road surfaces. In particular, by forming slopes on each block constituting the block group 100, 101 and precisely controlling the length of each slope to satisfy the above-mentioned conditions, wet performance, snow performance, and dry performance can be more effectively improved.

[0118] Moreover, by satisfying the condition that the ground contact area of each block is A1 < A2 ≤ A3, excellent handling performance can be obtained during steady driving. In particular, when the condition of A2 × (1.8 - 1.9) = A1 + A3 described above is satisfied, braking performance and handling performance during steady driving can be more highly balanced. Note that steady driving means a general driving state that is not an abnormal driving state such as suddenly turning the steering wheel during high-speed driving.

[0119] As described above, the pneumatic tire 1 is suitable for an all-season tire. In general, all-season tires emphasize wet performance and dry performance, but the pneumatic tire 1 is excellent not only in wet performance and dry performance but also in snow performance. In the present embodiment, by controlling the ground contact area of each block, the arrangement of the inclined surfaces of each block, and the dimensions in a well-balanced and accurate manner, performance suitable for an all-season tire is realized throughout the tread 10.

[0120] Note that the above-described embodiment can be appropriately modified in design without impairing the object of the present invention. For example, in the above-described embodiment, the shape of the block group 100 is the same as the shape when the block group 101 is inverted with respect to the tire equatorial plane, but the shape of one block group may be different from the inverted shape of the other block group. Alternatively, the tread pattern may be a pattern symmetric about the tire equatorial plane.

[0121] Also, in the above-described embodiment, inclined surfaces are formed on the sidewalls of the sipes of all the blocks, but inclined surfaces may not be formed on the center block. However, it is preferable that the rigidity of the blocks, the ground contact pressure, the drainage and snow removal performance, etc. are controlled in a well-balanced manner throughout the tread 10. Therefore, in order to more effectively improve wet performance, snow performance, and dry performance, it is preferable to form inclined surfaces on the sidewalls of the sipes of each block.

[0122] In addition, as long as the object of the present invention is not impaired, some blocks may not have sipes or slopes (for example, some mediate blocks may not have slopes). In the above embodiment, the ground contact area (A3) of the mediate blocks 70, 80 is larger than the ground contact area (A2) of the shoulder blocks 50, 60, but the ground contact area (A2) may be larger than the ground contact area (A3).

[0123] In the above embodiment, each block has one sipe, but each block may have two or more sipes. In the above embodiment, the drainage is improved and wet performance is improved by forming a slope on the sipe sidewall without increasing the number of sipes, but it is possible to increase the number of sipes within a range that does not impair the object of the present invention. For example, the number of sipes may be increased within a range that does not reduce block rigidity and impair dry performance. EXAMPLES

[0124] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0125] <Example 1> A pneumatic tire A1 (tire size: 205 / 55R16 91H) was manufactured having the block pattern (center block, shoulder block, mediate block, main groove, and circumferential groove) shown in Figs. 1 to 7, with slopes C, S, and M formed on the sipe sidewalls of each block. Each slope was formed only on the second sidewall located rearward in the main rotational direction of the tire, among the sipe sidewalls of each block. The shapes of the slopes C, S, and M are the same as those of the slopes shown in Figs. 1 to 7. The slopes S and M are formed at positions facing each other in the tire width direction with the circumferential groove in between.

[0126] The longitudinal length of the top surface of each block, the dimensions of the slope, etc. are as follows: The longitudinal length of the top surface of the center block L 30 :34.3mm The longitudinal length of the top surface of the shoulder block L50 :60.0mm The longitudinal length of the upper surface of the mediate block L 70 :36.8mm Sipe width W1: 0.6mm (same for other blocks) Sipe depth D1: 6mm (same for other blocks) Length L along the sipe of the center block slope C 32 :15.08mm Length of the block top surface L 30 Length of the slope L 32 Ratio of L1: 0.44 (44%) Width of slope C W2: 2mm Depth of slope C D2: 1mm Length L of the slope S of the shoulder block 52 :32.4mm Length of the block top surface L 50 Length of the slope L 52 Ratio L2: 0.54 (54%) Width of slope S: 2mm Depth of slope S: 1mm Length L of slope M of mediate block 72 : 10.4mm Length of the block top surface L 70 Length of the slope L 72 Ratio of L3: 0.28 (28%) Width of bevel M: 2mm Depth of slope M: 1mm Angle of inclination of the slope relative to the block top surface: 20°~30°

[0127] <Example 2> A pneumatic tire A2 was produced in the same manner as in Example 1, except that the inclined surface C was not formed on the sipe side wall of the center block.

[0128] <Example 3> A pneumatic tire A3 was produced in the same manner as in Example 1, except that the length of each of the inclined surfaces was changed (the ratios L1 to L3 were changed to the values ​​shown in Table 1).

[0129] <Comparative Example 1> A pneumatic tire B1 was produced in the same manner as in Example 1, except that not all of the blocks were formed with inclined surfaces.

[0130] For the pneumatic tires A1 to A3, and B1, wet braking performance (WBP) and dry braking performance (DBP) were evaluated by the following method, and the evaluation results are shown together with the ratios L1 to L3 in Table 1. The evaluation results in Table 1 are relative values ​​with the value of the pneumatic tire B1 set to 100.

[0131] [Wet braking performance (WBP) evaluation] A real vehicle (with two occupants) fitted with test tires (pneumatic tires A1-A3, B1) was driven on a wet road, and the braking distance was measured when braking force was applied at a speed of 100 km / h to activate the ABS, and the reciprocal was calculated. The results were evaluated using an index with the result of Comparative Example 1 set at 100, with a higher value indicating better wet braking performance.

[0132] [Dry braking performance (DBP) evaluation] A vehicle (with two occupants) fitted with the test tires was driven on a dry road, and the braking distance was measured when braking force was applied at a speed of 100 km / h to activate the ABS, and the reciprocal of the measured distance was calculated. The results were evaluated using an index with the result of Comparative Example 1 set at 100, with a higher index indicating better dry braking performance.

[0133] [Table 1]

[0134] As shown in Table 1, by forming the slopes S and M on the sipe sidewalls of the shoulder block and the mediate block at positions facing each other across the circumferential groove, it is possible to improve wet braking performance while maintaining dry braking performance. Also, adding the slope C to the sipe sidewall of the center block improves wet braking performance more significantly. In particular, the pneumatic tire A1 has a significantly improved wet braking performance without a decrease in dry braking performance compared to the pneumatic tire B1. [Explanation of symbols]

[0135] 1 pneumatic tire, 10 tread, 11 shoulder portion, 12 sidewall portion, 13 bead, 14 side rib, 15 carcass, 16 belt, 17 inner liner, 18 bead core, 19 bead filler, 20, 21 main groove, 25 first circumferential groove, 26, 27 second circumferential groove, 28, 29 third circumferential groove, 30, 40 center block, 30a to 30d, 40a to 40d, 50a to 50c, 70a to 70d side wall, 301c first surface, 302c second surface, 303c third surface, 31, 41, 51, 61, 71, 81 sipes, 31a, 31b, 41a, 41b, 51a, 51b, 61a, 61b, 71a, 71b, 81a, 81b Sipe end, 32, 42, 52, 62, 72, 82 slope, 32a, 72a first region, 32b, 72b second region, 50, 60 shoulder block, 70, 80 mediate block, 90 raised portion, 100, 101 block group, CL tire equator, E ground contact edge, P1, P2, P4 corner, P5 intersection

Claims

1. A plurality of shoulder blocks are arranged on both sides in a tire width direction along a tire circumferential direction; A plurality of intermediate blocks are arranged along the tire circumferential direction between a tire width direction center and the shoulder block; a main groove formed between the shoulder blocks adjacent to each other in the tire circumferential direction and between the mediate blocks adjacent to each other in the tire circumferential direction; A circumferential groove formed between the shoulder block and the mediate block; A pneumatic tire having a tread including: The shoulder block and the mediate block each have a first sipe and a second sipe that open into the circumferential groove, A first inclined surface and a second inclined surface inclined at a predetermined angle with respect to a block ground contact surface are formed on a side wall of the first sipe and a side wall of the second sipe, the first inclined surface and the second inclined surface are formed in a portion adjacent to the circumferential groove, a ratio (L1) of a length of the first inclined surface along the first sipe to a longitudinal length of an upper surface of the shoulder block is greater than a ratio (L2) of a length of the second inclined surface along the second sipe to a longitudinal length of an upper surface of the mediate block.

2. A plurality of shoulder blocks are arranged on both sides in a tire width direction along a tire circumferential direction; A plurality of intermediate blocks are arranged along the tire circumferential direction between a tire width direction center and the shoulder block; a main groove formed between the shoulder blocks adjacent to each other in the tire circumferential direction and between the mediate blocks adjacent to each other in the tire circumferential direction; A circumferential groove formed between the shoulder block and the mediate block; A pneumatic tire having a tread including: The shoulder block and the mediate block each have a first sipe and a second sipe that open into the circumferential groove, A first inclined surface and a second inclined surface inclined at a predetermined angle with respect to a block ground contact surface are formed on a side wall of the first sipe and a side wall of the second sipe, the first inclined surface and the second inclined surface are formed in a portion adjacent to the circumferential groove, a length of the first slope along the first sipe is longer than a length of the second slope along the second sipe; A pneumatic tire, wherein a width of the first slope is smaller than a width of the second slope.

3. The pneumatic tire according to claim 1 , wherein the first inclined surface and the second inclined surface are formed at positions opposing each other in a tire width direction with the circumferential groove therebetween.

4. The pneumatic tire according to any one of claims 1 to 3, wherein a raised portion is formed in the circumferential groove to connect lower portions of the shoulder block and the mediate block to each other.

5. The pneumatic tire is a tire having a designated main rotation direction, The pneumatic tire according to any one of claims 1 to 4, wherein the first inclined surface and the second inclined surface are formed larger on a second side wall that is located rearward in the main rotation direction of the tire than a first side wall that is located forward in the main rotation direction of the tire, among the side walls of the first sipe and the second sipe, respectively, or are formed only on the second side wall.

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